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Information for Teachers, Including Suggestions 
on Relevance to School Curricula. 


Volume 4 
Life Sciences 

Produced by theSkylab Program and NASA's Education Programs 
Division in Cooperation with the University of Colorado 

Washington, D.C. 20546, May 1973 

For sale by the Saperlntendent of Docnmeots, U.S. QoTemment Printing Office, Washington, D.C. 20402 



Characteristically, new scientific knowledge reaches general application in classrooms years 
after it has been obtained. This long delay stems, to a large extent, from a lack of awareness 
that information is available and that it has relevance to secondary school curricula. To 
accelerate this process, the National Aeronautics and Space Administration has prepared a 
series of documents concerning Skylab experiments to apprise the educational community 
in detail of the investigations being conducted in the Skylab Program, and the types of 
information being produced. 

The objective is not to introduce the Skylab Program as a' subject in the classroom, but 
rather to make certain that the educational community is aware of the information being 
generated and that it will be available for use. Readers are urged to use these books as an 
aid in planning development of future curriculum supplement materisil to make the most 
appropriate use of this source of scientific knowledge. 

National Aeronautics and Space Administration 

Washington, B.C. 20546 

May 1973 




Skylab Experiment M071, Mineral Balance 11 

Skylab Experiment M073, Bioassay of Body Fluids 13 

Skylab Experiment M078, Bone Mineral Measurement 15 


Skylab Experiment Mill, Cytogenic Studies of the Blood 23 

Skylab Experiment M112, Man's Immunity, in vitro Aspects 25 

Skylab Experiment Ml 13, Blood Volume and Red Cell Life Span 27 

Skylab Experiment Ml 14, Red Blood Cell-Metabolism 29 

Skylab Experiment Ml 15, Special Hematologic Effect 31 


Skylab Experiment M092, Inflight Lower Body Negative Pressure (LBNP) .... 41 

Skylab Experiment M093, Vectorcardiogram 43 


Skylab Experiment Ml 71, Metabolic Activity 49 


Skylab Experiment M131, Human Vestibular Function 53 

Skylab Experiment, Sleep Monitoring 59 


Skylab Experiment SOI 5, Effects of Zero Gravity on Single Human Cells 66 

Skylab Experiment S071,Circadian Rhythm— Pocket Mice 69 

Circadian Rhythm— Vinegar Gnats 72 





The Skylab Education Program 

This year the United States' first manned scientific space station, Skylab, was launched into 
orbit to be the facility in which successive crews of astronauts can perform more than 270 
scientific investigations in a variety of fields of interest. These investigations can be divided 
into four categories: physical sciences, biomedical sciences, earth applications, and space 

The Skylab Program will produce information that will enhance present scientific knowledge 
and perhaps extend the frontiers of knowledge on subjects ranging from the nature of the 
universe to the structure of the single human cell. It is the objective of the National 
Aeronautics and Space Administration that the knowledge derived from the Skylab 
Program's investigations be made available to the educational community for applications to 
high school education at the earliest possible date. 

For this reason, the Skylab Education Program was created to assure that maximum 
educational • benefits are obtained from the Skylab effort, documentation of Skylab 
activities is adequately conducted, and understanding of scientific developments is 

This document, one of several volurnes prepared as part of the Skylab Education Program, 
has the dual purpose of (1) informing high school teachers about the scientific investigations 
performed in Skylab, and (2) enabling teachers to evaluate the educational benefits the 
Skylab Program can provide. .' 

These books will define the objectives of each experiment, describe the scientific 
background on which the experiment is based, outline the experimental procedures, and 
indicate the types of data anticipated. 

In preparing these documents an attempt has been made to illustrate relationships between 
the planned Skylab investigations and high school science topics. Concepts for classroom 
activities have been included that use specific elements of Skylab science as focal points for 
demonstrations of selected subjects. In some areas these address current curriculum topics 
by providing practical applications of relatively familiar, but sometimes abstract principles; 
in other areas the goal is to provide an introduction to phenomena rarely addressed in high 
school science curricula. 

It is the hope of the National Aeronautics and Space Administration that these volumes will 
assist the high school teacher in recognizing the educational value of the information 
resulting from the Skylab Program which is available to all who desire to make use of it. 


Readers are asked to evaluate the investigations described herein in terms of the scientific 
subjects taught in secondary schools. The related curriculum topics identified should serve 
as suggestions for the application of Skylab Program-generated information to classroom 
activities. As information becomes available from the Skylab Program, announcements will 
be distributed to members of the educational community on the NASA Educational 
Programs Division mailing list. To obtain these announcements send name, title, and full 
school mailing list (including zip code) to: 

National Aeronautics and Space Administration 

Washington, D.C. 20546 

Mail Code FE 

This volume covers a broad spectrum of scientific investigations on Skylab that have been 
designed to improve man's understanding of himself and his physiological functions and 
needs. Additionally, a small group of related studies on the biochemical and biophysical 
behavior of lower organisms and single human cells in the weightless environment of space is 
included. . , . 

So that the reader will have a better understanding of the timing, setting, and scope of the 
total scientific endeavor on Skylab, a brief description of the Skylab Program has been 


Valuable guidance was provided in the area of relevance to high school curricula by Dr. 
James R. Wailes, Professor of Science Education, School of Education, University of 
Colorado; assisted by Mr. Kenneth C. Jacknicke, Research Associate on leave from the 
University of Alberta, Edmonton, Alberta, Canada; Mr. Russel Yeany, Jr., Research 
Associate, on leave from the Armstrong School District, Pennsylvania; and Dr. Harry Herzer 
and Mr. Duane Houston, Education and Research Foundation, Oklahoma State University. 

The Skylab Program 

The Skylab orbiting space station will serve as a ^yorkshop and living quarters for astronauts 
as they perform investigations in the following broad categories: physical sciences, 
biomedical sciences, Earth applications, and space applications. 

The spacecraft will remain operational for an eight-month period, manned on three 
occasions and unmanned during intervening periods of operation. Each manned flight will 
have a crew of three different astronauts. The three flights are planned for durations of one 
month, two months, and two months, respectively. 

A summary of objectives of each of the categories of investigation follows. 

Physical Science 

Observations free of filtering and obscuring effects of the Earth's atmosphere will be 
performed to increase man's knowledge of (1) the sun and of its importance to Earth and 
mankind, and (2) the radiation and particulate environment in near-Earth space and the 
sources from which these phenomena emanate. 

Biomedical Science 

Observations under conditions different from those on Earth will be made to increase man's 
knowledge of the biological functions of living organisms, and of the capabilities of man to 
live and work for prolonged periods in the orbital environment. 

Earth Applications 

Techniques will be developed for observing from space and interpreting (1) Earth 
phenomena in the areas of £^culture, forestry, geology, geography, air and water pollution, 
land use and meteorology, and (2) the influence of man on these elements. 

Space Applications 

Techniques for adapting to and using the unique properties of space flight will be developed. 

The Skylab Spacecraft 

The Skylab cluster contains five modules (see illustration). 

1) The orbital workshop is the prime living and working area for the Skylab crews. It 
contains living and sleeping quarters, food preparation and eating areas, and personal 
hygiene equipment. It also contains the equipment for the biomedical science experiments 
and for some of the physical science and space applications experiments. Solar arrays for 
generation of electrical power are mounted outside this module. 

2) The airlock module contains the airlock throu^ which suited astronauts emerge to 
perform activities outside the cluster. It also contains equipment used to control the 
cluster's internal environment and the workshop electrical power and communications 

3) The multiple docking adapter provides the docking port for the arriving and departing 
command and service modules, and contains the control center for the telescope mount 
experiments and systems. It also houses the Earth applications experiments and materials 
science and technology experiments. 

4) The Apollo telescope mount houses a sophisticated solar observatory having eight 
telescopes observing varying wavelengths from visible, through near and far ultraviolet, to 
X-ray. It contains the gyroscopes and computers by which the flight attitude of Skylab is 
controlled. Solar arrays mounted on this module generate about half of the electrical power 
available to the cluster. 

5) The command and service module is the vehicle in which the crew travels from Earth 
to Skylab and back to Earth, and in which supplies are conveyed to Skylab, and experiment 
specimens and film are returned to Earth. 

Skylab will fly in a circular orbit about 436 kilometers (235 nautical miles) above the 
surface of the Earth, and is planned to pass over any given point within latitudes 50° north 
and 50° south of the equator every five days. In its orbital configuration, Skylab will weigh 
over 91,000 kilograms (200,000 poimds) and will contain nearly 370 cubic meters (13,000 
cubic feet) for work and living space (about the size of a three bedroom house). 

1 Apollo telescope mount 6 

2 Solar arrays 7 

3 Sleeping quarters H 

4 Personal hygiene 9 

5 Biomedical science experiment 

Figure 1 Skylab Orbiting Station 

Ward room 10 

Orbital workshop 1 1 

Experiment compartment 12 

Airlock external hatch 13 

Airlock module 
Multiple docking adapter 
Earth resources experiments 
Command and service module 

Skylab Life Science Investigations 

Major study emphasis in the Skylab Program is on life sciences as summarized in Figure 2. 

The human body incorporates a large number of interdependent body systems in 
homeostatic balance, which is essential to the })roper functioning and well being of the body 
as a whole. Therefore, the program shown in figure 2 recognizes that measurement of 
change in a single body system or function is not a final answer in itself. Ultimate answers 
require a considerable amount of cross correlation among the six principal study areas. 

The si.\ areas of scientific investigations being emphasized in Skylab appear on the left side 
of the figure. The investigative program for these areas includes measurement of individual 
events and subsequent integration of all data to establish the effects of interactions. 

The inquiring reader of this book can discover that the educational potential of the program 
of investigations discussed is not limited to the specific scientific thrust of the experiment 
but has a broader association which cuts across many elements of the high school 
curriculum. Thus, the general subject area of this book, life sciences, can provide source 
material in such diverse fields as physics, biology, and chemistry. 

Table 1 is a cross index of general curriculum elements to specific investigations within the 
Skylab Life Sciences Experiment program. 


Nfineial and Hormonal 

Hematology and 

Cardiovascular Status 

Energy Expenditure 

MO 71 Mineral Balance 

M078 Bone Mineral 

M073 Bioassy of 
Body Fluids 

M092 Lower Body 
Negative I*ressure 

M093 Vectpcardiogram 

Ml 71 Metabolic 

Mill Cytogenetic 
Studies of Blood 

Ml 12 Man's Immunity 
in vitro Aspects 

Ml 13 Blood Volume 
Red Cell Life Span 

Ml 14 Red Blood 
Ceil Metabolism 

Ml 15 Special 
Hematologic Effects 



SOI 5 Effects of Zero-g 
on Sin^e Human CeDs 

S071 arcadian Rhytiim, 
Pocket Mice " 

S072 Circadian Rhythm, 
Vinegar Gnat 

Ml 31 Human 
Vestibular Function 

Ml 33 Sleep 

Figure 2. Experimental Program 


Table 1 Related Gurriculum Topics 

^""^^-...^^^^ SUBJECT 










Calcium exchange in - 
equilibrium, analysis 
of mineral constituents, 
electrophoretic analysis 
of protein, waste proc- 
essing osmotic pressures, 
calcium replacement by 

Sr In bones 

Cyclic menus, nutrient 
parameters, food prepara- 
tion and consumption 
in a unique environment, 
dietary deficiencies, 
effect of diet in bone 
development; caloric, con- 
tent of food ■ 

X-ray techniques, mass 
measurement in zero 
gravity, radioisotopes, 

Nutrition, metabolism, - 
mineral- and hormonial bai- 
ance.'relationship-of . 
bones and blood, digestive 
tract, role of hormones, 
structure and function;of 
nephron units, bone de- 
velopment . 

Techniques of blood, 
urine, vomitus and 
fecal analysis 


Protein analysis, DNA 
and RNA analysis, blood 
analysis, enzyme struc- 
ture.-ATP cycle bonding 
in biochemical cycles, 
O2 and CO2 transport 
in blood 

Production of^serums, 
meiosis studies,-^ body 
defense against disease; 
vaccines; function of 
blood cells, cell produc- 
tion and' destruction; 
function of enzymes, ex-' -. 
amination of bone marrow 


Gas. laws, partial pres- 
sures, .equilibrium, .. 
location and.function of . 
chemoreceptors in.the 

Fluid dynamics of cardio- 
vascular system, dynamics, 
of zero gravity; mechanical. 
failures of the^circulatory 
systems; hydrostatics^ . 
aroustics,- thermal'dynamics 

Role of' gravity in cir- 
culatory system, blood 
pressure, respiration 
rate, effect of CO2 on 
respiration, hyperventi- 
1 lation,,orthostatism, 
shock integration of 

Electronics, electrodes- 
design, positive and**- 
negative feedback, 




Measurement of Oj intake- 
vs CO2 output, caloric- 
determination of nutrients, 
gas laws 

Caloric-content of'foods, »" 
determining. energy 
, requirements 

Work- output, and gas. flow 
rate determinations 

Toxic substances and 
effect-on respiration, 
vital capacity, metabo-- 
lism of plants,- breath-.. 
ing rate after exercise, . 
CO2/O2 ratio;effects on 
heart beat 

Electronics, system 

design and integration • - 
of engineering and 
scientific disciplines ' 


Electrode design, sound in-^ 
low pressure atmosphere; 
inertia, acceleration, 
spatial localization, 
fluid dynamics . 

Exercise related to touch, 
vision, smell', hearing, 
balance, taste,>motion 
sickness; sense functions- 
of brain, sleep habits,' . 
vestibular functions, . 
nerve transmission, 
electroculographic study, 

Studies of motion, - 
touch psmell, hearing 
balancevtaste, vision; 
integration ofsenses,- . 
electrochemical nature •-, 
of nerve impulses; ion c- 
transfer across a mem- ■ ■ 
- brane, ionic. potention.' 
of an axon 

System design, feedback 
servo systems, digital . 
logic, integration of ^ 
engineering and scien- 
tific disciplines, space 
station design- 


Analysis of body fluids 

Rhythmicxycles of 
temperature, bloods 
pressure, manual dex- 
terity ; drug effective- 
ness, circadian rhythm 
of mice; fruit flies, 

Drosoph ila- genetics,- 
mitosis and cell struc- 
ture, chromosome aber- 
rations, acne.Iinkage,^ 
gene mapping, blood 
d iseases 

Study design 

Section 1 



Manned Since the beginning of manned spaceflight in the United 

Spaceflight States, there has been a continuing concern regarding man's 

ability to live and operate efficiently while on extended 

flights in space. Answers to this concern can be obtained only 

through a careful quantitative assessment of the crews' 

performance and physiological well being while working in 

the space environment. The study must develop data on 

trends and rates of adjustments while providing an 

instantaneous assessment of the crewmen's status and 

performance at critical points during the flight. Equally 

important is the ability of the crew to readjust to life on 

Earth after return from orbit. Interpretation of data depends 

on comparing flight results with a data base obtained in 

ground laboratories. Such a combination of ground and 

inflight experimentation forms the basic plan for the Skylab 

biomedical program. 

Missions up to 14 days have produced changes . in the 
astronaut's body tissues and systems as expected. Although 
the vector of these changes has been in the expected 
direction, individual changes have often differed from the 
predicted value. While these earlier missions have shown that 
man's gross capabilities to operate in the space environment 
continue at or near Earth equivalence, new techniques for 
performing a given task on orbit have sometimes been 
required to reflect the unique character of the space 

The Skylab Program and the life science experiments that are 
to be performed offer an opportunity to increase man's 
knowledge of the biological and physiological functions of 
living organisms. This will be achieved by making scientific 
observations of living organisms in an environment different 
from that on Earth, and evaluating the transitional effects as 
the organism responds and hopefully adapts to these new 

Specificcdly, the Skylab biomedical experiments provide Data requirements for long 
information on man's ability to- duration spaceflight planning 

1) perforrh effectively while in near weightless flight up to 
56 days, 

2) identify natural biological cycles, 

3) identify the adequacy of or need for additional 
life-support provisions to control changes in body 
chemistry within acceptable bounds, 

4) confirm or refine the habitability design criteria for 
future long-duration manned systems. 



In addition, information will be developed to aid in 
understanding crew psychological reactions to long-duration 
confinement; evaluating the problems associated with food, 
water, and waste management; and for developing criteria for 
designing better crew-nionitoring systems for future missions. 
The Sky lab Program should provide these data at a 
sufficiently early date to affect the next major manned 

In terms of life-science reseairch, Skylab aims primarily at 
identifying and defiriing physiologic and psychologic adaptive 
changes and establishing whether these will be progressive or 
self-limiting. If progressive, they could necessitate returning a 
crew back to Earth before the scheduled time. If self-limiting, 
the crew should pass through a period of adjustment 
followed by stabilization appropriate to the new 
environment. It is well knovra that when man travels to a 
high-altitude city or works in an undersea environment for 
long periods, the body processes pass through an initial 
adjustment followed by stabilization at new levels 
appropriate to survival in the new environment. This 
transient adjustment is also expected for the Skylab crew. 
The new stable levels of accommodation are expected to be 
adequate for the normal health and function of man during 
continued orbital flight. Upon return to the terrestrial 
environment the space-stabilized levels of accommodation 
may become significant factors in the crews' well being; that 
is, the acclimatization to space which has occurred may 
require specialized assistance to help the crewmen readapt to 
Earth following long duration space flight. Based on shorter 
duration past missions, the predicted course of events is 
encouraging for these longer manned spaceflights. 

The experiments selected for Skylab reflect a synthesis of the 
observations made during previous flights. Body systems 
which have shown changes and which could present a 
problem for the crewmen have received priority in this 
continuing research. 

These studies have been organized for the purposes of this 
document in the following order: 

Section 2, Mineral and Hormonal Balance 

Section 3, Hematology and Immunology 

Section 4, Cardiovascular Status 

Section 5, Energy Expenditure 

Section 6, Neurophysiology 

Section 7, Biology 

Acclimatable and accommo- 
dative reflexes trigger transi- 
tional adjustments in body 

In each section a general introductory background is 
included. The purpose of this background is to estabhsh a 
fundamental relationship between the experimental program 
and basic classroom science. This background is oriented 
towards establishing a broad scientific link between the 
Skylab experimental program and classroom science 
curricula. Hence, this approach emphasizes the general 
scientific background of the experimental program and 
separates the Skylab technological goals from the broader 
teaching aspects. Other subsections describe the specific 
technical objectives, equipment, and expected data output 
from each experiment. 

Sedtion 2 

Mineral and 
Hormonal Balance 

Mineral Balance 

Skylab Experiment ivi071 

BioassVrOf Body Fluids 
Skylab Experiment IVlb73 

Bone Mineral Measurement 
Skylab Exjseriment M078 




In order to maintain life, an oi^anism must be able to 
coordinate a wide variety of different functions. For this 
purpose, animals, including man, have developed two 
importamt communication systems. The nervous system has 
the form of an elaborate telegraph (neural) network in which 
communications paths are reasonably well defined by 
anatomical connections which, in many cases, provide very 
specific routing of transmitted messages to discrete 
anatomicEil sites. The other communication system is the 
endocrine system consisting of many ductless glands (Figure 
2-1). In it, messages are carried in the bloodstream in the 
form of complex chemical substances (hormones) that 
interact with special cells to receive the hormone and to react 
to it in a specific way. These "target cells" may be limited to 
one particular type of cell, e.g., the gonadal cells that respond 
to the gonadotrophic hormone, or the renal tubular cells that 
respond to aldosterone. However, some hormones, such as 
insulin, act upon many different types of cells. 

Hormones— any of various 
internally secreted compounds 
formed in endocrine organs that 
affect the functions of receptive 
organs when carried to them by 
body fluids. 

^^^^BjHWH^^^^^^^^B Brain ^^^^^^^^^^^^| 
^^HSg^EBM||^^^^B^^9 Hypothalamic Nuclei ^H 
^^^^^^^^^^^^^^^^^^^ Hypophysis (Pituitary) H 

^H^^^^^B Adrenal Cortex ^M 
^^^^^^^^ Adrenal Medulla H 


^^^ Testes male) ^^^| 
^^^[ Ovaries (in female) ^^^J 

Figure 2-1 Major Endocrine Glands in Man 

Neuroendo- There are many interactions between the nervous and 
crine System endocrine systems, so that they are sometimes considered 
collectively as the neuroendocrine system. For example, 
transmission between neurones in the sympathetic nervous 
system occurs via adrenergic hormones. These hormones are 
also produced by the adrenal medulla, an organ which 
functions as an endocrine gland, but is embryologically 
derived from neural tissue. Another example of the close 
relationship between the neural and endocrine systems is the 
requirement that certain hormones be present for the normal 
development and functioning of nerve tissue. It is known, for 
instance, that lack of thyroid hormone in infancy results in 
mental retardation, and in adults in the slowing of 
conduction in the nerves. The complex systems which 
' control some physiological variables such as body water 

content are known to include both neural and endocrine 
elements. The type of action which hormones may elicit 
from target cells is shown in Table 2-1. The extent of 
interactions between the neurohormonal processes and the 
basic behavior of target cells is shown in Figure 2-2. 

Adrenergic — activated 
transmitted by epinephrine. 

Table 2-1 Hormone Elicited Control 

Altered blood flow to cells, e.g., nearly all tropic 

hormones on target glands. 

Altered membrane properties of specific cells. 

1 ) ADH: renal loop of Henle and H2 transport. 

2) Aldosterone: renal proximal tubule and Na*^ 

3) Various hormones and amino acid transport, e.g., 
178-estradial increases transport by uterus. 

4) Insulin: glucose transport; iC transport; Pi 
transport; and transport into muscles but not 

Altered rates of protein metabolism. 

1) Anabolism— increased protein synthesis e.g., 

a) GH: bone, muscle, liver 

b) TSH: thyroid; ACTH; adrenal cortex, etc. 

c) Thyroxin: many cells 

d) Cortisol: liver 

2) Catabolism — increased protein degradation 

a) Cortisol: muscle, bone 

b) Thyroxin (large doses): many cells 
Altered enzymatic activity 

1) CHO Metabolism e.g., 

a) Epinephrine: liver, muscle phosphorylase 
and glycogenolysis 

b) Insulin: muscle and glycogen synthesis 

2) Lipid metabolism 

a) Many hormones: lipolysis in adipose 

b) Insulin: antilipolysis in adipose tissue. 
Mineral, water and electrolyte metabolism 

Effects may be secondary to those listed in categories 
above, e.g., PTH and Ca** mobilization may be 
secondary to increased catabolism of bone protein, or 
altered membrane changes. 

Change in External of 
Internal Environment 

Sensory Input 

of Component 
in Plasma 


Output = Alteration in Metabolic Behavior of Target Cells 

Figure 2-2 Neurohumoral Interactive Processes Influencii^ Metabolic Activity of Specific Cells 

Referring to Figure 2-2, it is apparent that the interactions 
are many and complex and further that these actions can be 
triggered by outside environmental influences that can affect 
component concentration in the plasma, the portal 
circulation, and even the brain through sensory organ inputs. 
During the evolution of man, gravitational forces have 
unquestionably played a major role in his physiological 
development. The significance of this force in the health and 
growth of man is of uncertain limits today. 

Composition One rather interesting aspect of this is demonstrated by the 
of Bone - influence which such external forces may have on the growth 
of bone in the body. 

Bonie is a unique tissue comprising a very special body organ 
system. Living bone requires the same nutrients, controls, 
and environments as other living tissue in the body. In 
contrast, however, to other body tissue and because of its 
calcified nature, bone provides, a semipermanent biological 
record. Hence, like the growing tree, the structure of bone 
records the anomalies of its past including irregularities of 
diet, disease, and environment. 

Bone shows many levels of organization (Fig. 2-3). Typically, 
bones are composed of two basic types of material: compact 
(lamellar) bone and spongy (cancellous) bone. Compact bone 
makes up the wall of the central portion (diaphysis) as well as 
the outer shell of the flared ends (metaphysis). The interior 
of the metaphysis is composed of spongy bone which in time 
is built up of a collection of plates and bars csilled trabeculae 
(little beams). There is little difference in the bony material 
in these two types of bone although the porosity of each 
type is quite different. 

The outer surface of the bone is covered by a membrane 
-' . known as the periosteum; the inner surface is covered by a 
membrane known as the endosteum. The volume that is 
contained within the wall of the diaphysis is called the 
medullary cavity and it is filled with marrow as are the spaces 
between the trabeculae of spongy bone. Yellow marrow is 
found in the large cavities of the long bones. It consists for 
the most part of fat cells. It may be replaced by red marrow 
in anemia. Red marrow is the site for production of the 
granular leucocytes and the erythrocytes (red blood cells). 
Red marrow is found in the flat and short bones, the articular 
ends of the bones, the bones of the vertebrae, the cranial 
dipole and the ribs. Both types of marrow have a supporting 
connective tissue and numerous blood vessels. 

Cancellous— of a reticular, 
spongy, or lattice-like structure: 
used mainly of bony tissue. 

Diaphysis— the shaft of a long 

Metaphysis— the wider part at 
the extremity of the shaft of a 
long bone, adjacent to the 
epiphysical disc. 

Bone is formed by cells called osteoblasts, and destroyed or 
resorbed by other cells called osteoclasts. These two cell 
types are formed from undifferentiated mesenchyinal cells 
lying on the surface and in the spaces of the bones. When a 



-Articulates with 

• Line of Epiphyseal 

■ Articulate with 
Fetalis and Tibia 

Figure 2-3 Structiure of Human Femur 



certain stimulus is received, these mesenchymal cells begin 
functional and morphologic transitions which terminate in 
the formation of specilized osteoblasts and osteoclasts as 
appropriate to the stimulus. The deposition or mobilization 
of calcium under the influence of structural loads on the 
bone completes the growth of new adult bone. Bone cells 
(osteocytes) were originally osteoblasts which became 
included in the bone matrix. They are the living elements of 
bone tissue and their function is to maintain the chemical 
environment of the surrounding nonliving tissue. In lamellar 
bone, there Eire about 20,000 osteocytes per cubic millimeter, 
residing in the same number of lacunae (spaces) and they are 
about 10 X 15 X 25 microns in size. Osteocytes die for a 
variety of reasons; after death they are absorbed and leave 
empty lacunae behind. Human osteocytes live an average of 
25 years. 

There are a wide variety of observations that indicate that the 
growth system, whose function is to penetrate and remodel 

Osteoblast— a cell that arises 
from a fibroblast and which, as 
it matures, is associated with the 

production of bone. 


Fibroblast — a connective tissue 

Osteocytes — an osteoblast that 
has become imbedded within the 
bone matrix, which connects to 
other osteocytes to form bone. 

bone, is somehow responsive to the local state of stress; that 
is, physical loads of various kinds alter the growth rate, 
shape, and structure of bone. 

Bone Measurements of bone weight show that inactivity through 

Measurement confinement, immobilization, or paralysis causes a significant 

reduction in both the amount and quality of bone. Several 

studies of this phenomena involving patients immobilized in 

pelvic girdle and leg casts have been made. During the 

confinement period, significant levels of calcium, 

phosphorus, and nitrogen were found in urinary and fecal 

excretions. Animal experiments indicate that immobilization 

of a limb invariably leads to disuse atrophy and a reduction 

in muscle and bone weight. 

Long bones with an angulation caused by a poorly set but Angulation— the formation of a 

healed fracture have been observed in children to gradually sharp obstructive angle 

straighten. These changes and adjustments in shape require 

bone to be resorbed on the tension or minimum compression 

side and deposited on the more heavily loaded side. Thus, it 

can be observed that the bone cross section drifts in a 

direction to minimize loading eccentricity so that bone 

appears to possess a stress directed growth regulating 

mechanism which adjusts the bone architecture in response 

to external loads. 

Generally, it can be said that usage in the young growing 
skeleton leads to changes of shape and structure while in 
older, fully grown bones usage leads mainly to changes in 
structure. It is as if the growing bone would grow into a new 
pattern, determined by mechanical forces, while fully grown 
bone has become more rigid in its outer shape, but can adapt 
to changed forces by a new orientation of its internal 
structural elements. 

The skeleton diuing man's daily activities is exposed to a 
wide range of loads varying in me^itude and direction. The 
growth stimulus will therefore also vary in both intensity and 
direction. Thus, bone organization in the adult is finally 
determined by those activity patterns most frequent in the 
lifetime of the individual, superimposed, of course, on the 
genetically controlled pattern unique to the species. Activity 
patterns not characteristic of the species would therefore be 
expected to stimulate growth contrary to genetically carried 
traits, and result in a bone weakened for characteristic 
activities of the species. 

The Skylab Program affords a unique near-weightless 
environment in which to test many of the theories that have 
been advanced as to the manner in which body health and 
growth are influenced by the environment, and specifically to 
evaluate the role of mineral balance and neurohumoral 
influence on this growth. 


Mineral Bed rest immobilization studies have shown that in healthy 

Balance young adults urinary calcium increases to 2-3 times the 

control level within 5 weeks after confinement. X-ray studies 
of the bones have demonstrated demineralization as early as 
2-3 weeks after immobilization. Gemini pre- and postflight 
x-rays have suggested a similar loss of mineral from peripheral 
bones; the Gemini 7 mineral balance experiment has 
demonstrated a trend toward negative mineral balance. 
Continuous losses of calcium and nitrogen, such as those 
during long duration missions, mi^t result in impairment of 
skeletal and muscle integrity and the formation of kidney 
stones. Identification of the rates of actual deterioration will 
allow specific countermeasures to be taken on later flints, 
such as the institution of exercise routines and the 
manipulation of dietary constituents. 

The principal method of assessing the effect of a stressor on 
the biochemical integrity of the skeletal and muscular 
systems is to determine whether the stressor promotes a 
catabolic response that is greater than the anabolic 
capabilities of the tissues. The change in equilibrium may be 
reflected in an imbalance between the nutrient intake of the 
constituent in question and the output of it and/or its 
metabolites. A state of negative nitrogen or calcium balance 
is not itself detrimental unless it is of an extent and duration 
that results in compromise of the integrity of muscle or bone 
with resultant increases in susceptibility to disease or actual 
pathology. Prior to the onset of recognizable disease, 
however, minor changes in function suggesting later 
deterioration can be demonstrated. ^ 


Stressor— a stimulus, such as pain 
or fear, that disturbs or 
interferes with the normal 
physiological equilibrium of an 

Anabolism — any constructive 
process by which sample 
substances are converted into 
more complex compounds, 
constructive metabolism. 

Catabolism— any destructive 
process by which complex 
substances' are converted by 
living cells into more simple 
compounds; destructive 

The objective of this experiment is to determine the effects 
of space flight on the muscle and skeletal body systems by 
quantitative assessment of the gains and losses of biochemical 
constituents of metabolic importance. These constituents are 
water, calcium, phosphorus, magnesium, sodium, potassium, 
nitrogen, urea, hydroxy proline, creatinine and chloride. 


The Mineral Balance and Bioassay of Body Fluids experiment 
data were obtained from a detailed, daily inventory of food 
£ind water intake, of body mass, and of output of waste 
products. Waste products, feces, urine and vomitus are 
measured, processed, and stored onboard for return to E£ui;h 
with the crew, and subjected to detailed analysis. Equipment 
designed to perform the specimen and body mass 
measurement, M074 and M0172, respectively, is used to 
support this experiment. 



Experiment The performance of the Mineral Balance Investigations starts 

Investigations 21 days before flight and continues throughout the flight and 

for 18 consecutive days after return to Earth. Each day of 

the observing period, the following functions will be 

performed by the crew: 

1) Body weight (or mass) will be measured immediately 
after the first urine voiding following the sleep period. 

2) A predetermined diet will be used since the composition 
of the crewman's diet must be known and carefully 
controlled. In the preflight period, each crewman will use 
this diet to allow the 'establishment of individual 
metabolic equilibrium. Every effort will be made to make 
the diet palatable. The premeasured menu for each meal 
will be prepared and the mass of any leftover food will be 
measured and recorded. 

3) Fluid can be taken as desired, but all intake will be 
recorded. This includes fluid used for food 

4) All urine, feces, and vomitus wUl be collected pre- and 
postflight and preserved for analysis. Inflight, the amount 
of daily urine output from each crewman will be 
determined, and a measured homogeneous sample of at 
least 45 milliliters (2 for tracer method volume 
determination) taken, frozen, and stored for analysis. All 
feces and vomitus passed will be collected, the mass will 
be measured, and the specimens will be dried and stored 
for postflight analysis. 

5) Periodic blood samples will be taken and the 
concentration of selected constituents determined. 
Inflight blood samples will be processed and frozen for 
postflight analysis. 


During the Skylab Program, three crews (three men in each) 
will occupy the orbital workshop on three separate occasions. 
The initial mission will last up to 28 days and the other two 
for up to 56 days each. The Mineral Balance Experiment will 
be performed on all three missions so that by the end of the 
Skylab Program a continuous quantitative assessment of the 
muscle and skeletal body systems for nine different 
individuals will have been obtained. For each individual, a 
preflight baseline will be followed by a day-by-day profile of 
his physiological reaction to the space environment, and 
postflight, his readaptation to Earth's normal conditioris. 
Specifically, the following data on a daily basis will be 
obtained preflight, inflight and postflight: 

1) food consumption— nutritional, mineral, and caloric 

2) fluid consumption; 

3) feces— mass and concentration of biochemical 

4) urine— total voids volume and concentration of the 
biochemical constituents; 

5) vomitus— mass and concentration of the biochemical 
1 constituents; 

6) body mass. 

In addition, blood samples will be taken periodically pre-, in- 
and postflight. These samples will be analyzed to determine 
alkaline phosphates, total protein, electrophoresis pattern, 
sugar, calcium, phosphorus, magnesium, sodium, potassium, 
hydiroxyproline, chloride, and creatinine. 


Bioassyof Although many external influences contribute to the 

Body Fluids enviroriment . of the human organism as a whole, the 
environment of its basic unit, the living cell, is wholly 
internal. Since changes in extracellular fluid produce changes 
in the composition of the intracellular fluid, it is essential to 
the nonnal furiction of cells that the constancy of this fluid 
be maintained. This is achieved by the close interaction of 
several organ systems, the kidney holding a predominant role. 
The kidney, is thus viewed as an organ which not only 
removes metabolic wastes, but actually performs highly 
important homepstatic functions by adjusting plasma volume 
and compqsition. 

The necessity of elucidating the homeostatic control 
mechanisms that govern plasma volume and composition is 
evident "when one realizes the complex and, as yet, 
unexplained inteiractions of these metabolic and endocrine 
controls; Iri the changing external environment, there is a 
narirpw, margin within which man's physiological well-being 
can" be accominodated by these functions. Evidence exists to 
suggest that these- mechanisms may play a significant role in 
man's adaptation to stress, including gravity. 


Homeostatic — uniformity or 
stability in the normal body 
states of an organism. 

The objective of the Bioassay of Body Fluids Experiment is 
to evaluate the endocrinological adaptation resulting from 
exposure to the spaceflight environment for periods up to 56 
days and to readaptation to the Earth environment. 
SpecificaUy, the following elements in blood and/or urine 
will be evaluated: adrenocorticotropic hormone (ACTH), 
17-hydroxy-corticosterone. (Cortisol), angiotensin II, renin, 


aldosterone, antidiuretic hormone (ADH), epinephrine, 
norepinephrine, urine electrolytes (sodium and potassium), 
urine amd plasma osmolality, extracellular fluid volume, total 
body water, serum thyrocalcitonin parathyroid hormone, 
serum thyroxine, hydrocortisone, renin activity, total and 
fractional ketosteroids, insulin, human growth hormone, and 
thyroid stimulating hormone. 


The Mineral Balance and Bioassay of Body Fluids data is 
obtained . from a detailed, daily inventory of food and water 
intake, of body mass, and of output of waste products. Waste 
products, feces, urine, and vomitus are measured, processed, 
and stored onboard for return to Earth with the crew, and 
subjected to detailed analysis in the postflight period. 
Equipment for performing the specimen and body ' mass 
measurements, M074 and M0172, respectively, is used to 
support this experiment. 

Bioassy— determination of the 
active power of a substance by 
testing its effect in an organism. 


Experiment The experiments will be accomplished in three phases: (1) 
Investigations preflight, for 21 days, (2) inflight, and (3) postflight until 

readaptation has been established, beginning immediately 

after flight. 

The following functions will be performed each day of the 
observing period: 


1) Body weight (or mass) will be measured immediately 
after the first urine voiding following the sleep period. 

2) A predetermined diet will be used since the composition 
of the crewman's diet must be known and carefully 
controlled. In the preflight period each crewman vdll use 
this diet to establish individual metabolic equilibrium. 
Every effort will be made to make the diet palatable. The 
premeasured menu for each meal will be prepared and the 
mass of any leftover food will be measured and recorded. 

3) Fluid can be taken as desired, but all intake will be 
recorded. This includes fluid used for food 

4) All urine, feces, and vomitus will be collected pre- and 
postflight and preserved for analysis. Inflight, the amount 
of daily urine output from each crewman will be 
determined, and a nieasured homogeneous sample of at 
least 75 milliliters for bioassay of body fluids 
experiments taken, frozen, and stored for analysis! All 
feces and vomitus passed will be collected; the mass will 
be measured; the specimens will be dried and stored for 
postflight analysis. 

5) Periodic blood samples will be taken and the 
concentration of selected constituents determined. 
Inflight blood samples will be processed and frozen for 
postflight analysis. 


The Bioassay of Body Fluids Experiment will occur on all 
three missions so that by the end of the Skylab Program, a 
continuous quantitative assessment of the endocrinological 
adaptation for nine different individuals will have been 
obtained. For each individual, a preflight baseline will be 
obtained, followed by a day-by-day profile of his 
physiological reaction to the space environment, and after 
flight, his readaptation to Earth ■• normal conditions. 
Specifically, the following data on a daily basis will be 
obtained preflight, inflight, and postflight: ' 

1) Data obtained from Mineral Balance, Experiment M071 

2) Urine — concentration of the biochemical constituents Biochemical-dealing with living 
specified in the Objectives. ' matter. 

In addition, blood samples will be taken periodically pre-, in- 
and postflight and those parameters specified in the 
Objectives will be determined. 


Bone Mineral Stimulus of bone metabohsm is a function of the forces 
Measurement exerted on the bone by the attached muscles and the force 

exerted along the longitudinal axis of the skeletal system by 

gravity. Both forces are altered during complete bed rest and 

absence of gravity. Consequently, bone mineral losses have 

been associated with long-term bed rest and were anticipated 

as a potential problem for the crews of long-term space 


In both Gemini and early ApoUo flights, small but significant 
losses have been measured in astronaut bone mass. In 
contrast to the Gemini and early Apollo studies, which used a 
radiographic densitometry technique, the bone mineral 
studies performed on Apollo 14, using the gamma ray 
absorption technique, revealed no significant losses in borie 
mineral content. More data from both ground based and 
inflight studies are necessary to resolve the issue before 
committing man to extended space travel. 


The objective of the Bone Mineral Measurement experiment 
is to determine, by a photon absorptiometric technique, the 


occurrence and degree of bone mineral changes in the Skylab 
crewmen that might result from exposure to the weightless 



The Bone Mineral Measurement experiment consists of 
preflight and postflight measurement of the condition of two 
bones in each astronaut. The ground based equipment for 
this experiment is a photon scanning device in which an 

iodine-125 photon source is mounted in opposition to an Photon--a quantum of electro- 
x-ray detector.- The astronaut's limb containing the bone to magnetic radiation, 
be measured is firmly held in the required position within the 
scanning device. Foot molds and restraining equipment are 
used for accurate positioning of the subject for the scan. 


Experiment The Bone Mineral Measurement performance using the 

Investigations photon scanner starts 30 days before flight. The bones to be 

measured are the heel bone (os-calcis) in the left foot and one 

of the bones (radius) in the right forearm. (See Fig. 2-3.) 

X-rays of the heel will be made seven days before the first 

photon scanner observation. 

Preflight scans of the left os-calcis and right radius will be 
accomplished on the flight crew, backup crew, and on a 
control group 30, 14 and 3 days before the launch of the 
flight crew. 

Postflight measurements will be made on the flight crew and 
on the control group within 10 hours after splashdown and at 
the following intervals: 2 to 3 days, 5 to 10 days, and 30 to 
45 days if baseline values have not been reached in the 5- to 
10-day period. 

The measurement on recovery day should be made at the 
earliest time possible (within 10 hours) after crew recovery to 
minimize the effect of weight bearing by the os-calcis and 
maximize the data accuracy on the extent of the bone 
mineral losses under zero gravity conditions. 

Additional postflight measurements will be required if the 
flight crewmembers have not reestablished their baseline 
values by the third measurement. 


The data returned by this experiment will be the pre- and 
postflight bone density measurements of the os-calcis and 
radius of each Skylab crewmember (three from the 28-day 
mission and six from the 56-day mission) and nine control 
group members. The data will be used to determine the 
impact of the spaceflight environment on the degree and 
occurrence of the bone mineral changes. 

Section 3 

Hematology and 

Cytogenetic Studies of the Blood, 
Si<ylab Experiment Mill ( 

Man's Immunity, In Vitro Aspects, 
Sky lab Experiment M 112 

Blood Volume and Red Cell Life Span, 
Skylab Experiment Ml 13 

Red Blood Cell Metabolism, 
Skylab Experiment Ml 14 

Special Hematologic Effect, 
Skylab Experiment M115 

Hematology Hematology, the study of the form and function of blood, in 
large part is concerned with changes in the concentration of 
the functional elements of the blood. These changes can 
come about as the result of disease processes and 
environmental changes, or they may be induced as a 
purposeful experiment. 

Regardless of how these changes are precipitated, if they 
exceed relatively narrow physiological limits they will be 
accompanied by dramatic changes in the effectiveness of the 
individual even to the extent of causing death. The following 
discussion is intended to provide a brief resume of the 
functions and functional elements that form the basis for our 
present understanding of the role of blood in health and 


Every living organism, simple or complex, requires for its 
survival, the ability to exchange materials with its 
environment, extracting from the environment those 
materials which it can metabolize for its energy requirements 
and rejecting to the environment those materials which 
would poison it. In the case of single cell and other relatively 
simple organisms, the process of transmembrane diffusion 
provides an effective mechanism for satisfying this need. 
Larger, more complex (multicellular) organisms must provide 
sophisticated organ systems to accomplish this function since 
the external environment makes intimate contact with the 
organism's body only at its surface. For example, the skin 
surface of the average adult human amounts to only about 
1.7 m^ resulting in a surface to volume ratio of about 0.02 
mm' /mm^ . Furthermore, this surface is relatively impervious 
to most materials, and serves only as a means for eliminating 
excess heat and a small amount of water. Hence, the 
exchange of materials between the cells of the body and the 
external environment must be carried on by specialized 
systems such as the lung, kidney, gastrointestinal (GI) tract, 
blood, and interstitial fluid. 


These specialized systems are related as shown in the diagram 
of Figure 3-1. Reference to this diagram shows that while the 
lung, kidney, and GI tract interface with the external 
environment, they do not interface directly with the cells of 
the body. The materials upon which the body is dependent 
pass through two intermediate mechanisms, the circulatory 
system, and the interstitial fluid. The interstitial fluid, which 
bathes all cells in the body, provides a uniform environment 
from which the cells extract their material needs and to 
which they reject waste products. The circulatory system 
provides a transport mechanism that assures physical and 
chemical uniformity (within relatively narrow physiological 

Interstitial Fluid— that portion 
of the body water outside of the 
cells and outside of the plasma 


limits) of the interstitial fluid. The circulatory system so 
permeates the interstital compartment that in the heart, for 
instance, no cell is further than about 0.008 mm from a 

Vital In addition to the transport of gases, material, and waste 

Transport products, blood' has other equally vital functions. These 

Functions functions include carrying the heat generated by the cells' 

metabolic activity to the surface for easy transfer to the 
surrounding environment, and certain defense mechanisms by 
which bacteria and foreign particles are removed from the 



lli ll i m ill 


Liquids and 
^k dissolved solids 



•* J I ^ KV-VWWWM ' 

_ ..: ' Cent •: ii'Ceiill 



yi ' " SI ■ ! ■ 

1 I 17 '1 1 I'M 



O2] ■ Lungs! CO2 



External Environment 

Figure 3-1 Transport Functions of Blood 

• Interstitial fluid 



Because of the significant part which blood plays in 
maintaining a suitable environment for other tissue in the 
body essentially free of foreign matter and infectious agents, 
it is inconceivable that changes in the blood would not effect 
these other tissues. In recent times we have therefore come to 
understand that, in addition to quantity, the quality of blood 
is also significant. In order to understand how blood quality 
can vary, it is necessary to know something about the 
composition of blood. 

The blood, which fills the vascular pathways of the 
circulatory system, is a truly vmique substance. Even 
primitive man probably suspected the vital role that blood 
plays and recognized that survival from the hazards of the 
hunt and combat were in direct proportion to any loss of 
blood. We have £ilready indicated that blood performs many 
vital functions which suggests that blood is more than a 
simple fluid. Indeed if blood is examined even casusdly it can 
be seen to be composed of two phases, a fluid phase and a 
cellular phase. This can be easily demonstrated; for example, 

if a fresh sample of blood is rapidly cooled and centrifuged 
for, say, five minutes, it can be separated into a collection of 
heavy particles in the bottom of the sample tube leaving a 
clear fluid on top (supernatant). This clear fluid (about 55% 
of the sample volume) can be poured off leaving the 
separated sediment in the bottom half of the tube. The 
supernatant fluid will be noted after a short while to exhibit 
a unique property, that is, it will congeal into a jelly like 
mass. This liquid phase of the blood which is capable of 
congealing is called plasma. If fresh plasma is continuously 
stirred with a glass rod, it will be found after awhile that 
congealing will not occur. Instead, it will be noted that a pale 
yellow material (fibrin) will collect on the stirring rod. The 
remaining fluid in the tube, which will now not congeal, is 
called serum. 

Returning to the red sediment that was collected, a careful 
microscopic examination will reveal that a variety of formed 
elements (cells) have been collected. 

Cell Types Many studies of these cells have been performed and it is 

known • that the cells in the blood include a least three 
families of cell types as shown in the tabulation. 





1) Granular Polymorphonuclear Leucocytes 


a) Neutrophils 

b) Eosinophils 

c) Basophils 

2) Lymphocytes 

3) Monocytes 



Hence, it seems that whole blood consists of at least four 
functional elements: plasma, erythrocytes, leucocytes, and 

Blood Plasma The plasma has been demonstrated above to include several 

components, since fibrin could be isolated by stirring. 

_ Actually, plasma is a complex solution of electrolytes and 

proteins. The concentration of these plasma constituents 

as found in normal blood is tabulated. 




















Fibrin— a whitish insoluble 
protein that forms the essential 
portion of the blood dot. 


Function of For the specific roles of each component of plasma, the 
Plasma reader is referred to the abundant literature on hematology. 

Some of the generalizations which we can note here ascribe 
specific roles for plasma in (1) neutralizing the acid end 
products of metabolism, (2) regulation of heat loss from the 
body, (3) regulation of the proportions of water in the 
vascular and interstitial compartments, (4) prevention of 
excessive hemorrhage from wounds, and (5) immunological 
defense against invading viruses and foreign protein. 

The formed cells identified previously are also specialized 
with respect to their function in the overall role of blood. 
The erythrocytes, responsible for the transport of gases, are 
specialized with respect to form and also chemically by the 
presence of the protein hemoglobin. The special shape of 
erythrocytes, a sort of flattened sphere with a central 
depression (Figure 3-2) results in a cell having a large surface 
area to volume ratio, which improves the efficiency with 
which gases diffuse across the.cell membrane. Simultaneously 
this innovative form achieves a low viscosity for efficient 
pumping by the heart. The presence of hemoglobin in 
erythrocytes is principally responsible for the gas transport 
efficiency of blood. Analysis indicates that at sea level 
pressures the oxygen dissolved in blood would be 
approximately 3 ml per liter of plasma. Under similar 
conditions the presence of hemoglobin increases the oxygen 
concentration to approximately 200 ml. The actual manner 
by which gases are taken up by the red cells is not nearly as 
simple as this discussion may imply and the reader, is referred 
to the many good texts for an in-depth treatment of this 

Hemoglobin — the 
oxygen-carrying pigment of the 

Plasma— the fluid portion of the 
blood in which the corpuscles 
are suspended. 

2.2 microns- 

Figure 3-2 Erythrocyte 


The leucocytes, as noted previously, comprise a spectrum of 
cell types. Observations made with blood suggest that these 
cells have been specialized to remove bacteria and foreign 
particles from the blood. Other evidence suggests that the 
biilk of the activity of leucocytes, however, takes place 
outside of the vascular pathways. The leucocytes therefore 

are transient residents of the blood stream on their way to 
some location in the tissue where they may be needed to 
destroy invading bacteria or particulate matter. Leucocytes 
perform their function by a process of phagocytosis 
(ingestion and digestion). 

No one knows with any certainty the origins of each of the 
cell types nor is the exact role of each in the body's defense 
known. Some generalizations that can be made, however, are 
that the three varieties of granulocytes are transported by the 
blood to tissue sites where they disintegrate releasing active 
enzymes, (1) the neutrophils that are specifically active in 
phagocytosis of bacteria, (2) the lymphocytes that circulate 
continuously between the tissue and bloodstream and are 
active in immune responses, and (3) the monocytes that are 
circulating phagocytes active in phagocytizing nonliving 
particulate mattei^. 

The platelets are very small and can be easily overlooked in 
the blood. They are known to be cell fragments originating in 
bone marrow and tend to disintegrate readily. Platelets carry 
substantial amounts of serotonin, a vasoconstrictor which is 
active in reducing blood loss from severed vessels. 
Additionally, platelets are believed to play a significant role 
in the maintenance of the endothelial lining of the vascular 

Phagocyte —any cell that ingests 
microorganisms or other cells 
and foreign particles. 



Environmental Most of US would have little difficulty accepting the premise 
Conditions that disease can influence the form and function of blood. 

Most are even vaguely aware that the external environment, 
particularly radiation in the form of x-rays, can cause 
dysfunction of blood. Many, however, will not recognize that 
environmental changes considered to be physically tolerable 
may stress the circulatory system, including the 
hematopoietic (related to blood forming) process and the 
immunological mechanism, beyond acceptable physiological 

A commonly recognized physiological response to changed 
environmental conditions is found in the deeper and more 
rapid breathing which is experienced when we go to 
unaccustomed high altitudes. This accommodative reflex is 
the body's response to the hypoxic (low oxygen) atmosphere 
of the new environment. If this stress persists for a long 
enough period of time, compensating changes will be made in 
the functional elements of the blood; that is, the body will 
generate more erythrocytes (red blood cells) so as to increase 
the oxygen-carrying capacity of the blood. This latter change 
is an acclimatizing change which minimizes the energy 
expended in maintaining an adequate level of oxygen in the 


blood. This acclimating process, however, is not without 
penalty since the resulting "higher hematocrit" (increased red 
cell content of the blood) increases the viscosity of the blood 
and imposes added pumping loads on the heart. If large 
environmental changes of this type were permanently 
endured, serious consequences might result. It is to be 
expected, that even more subtle changes in the blood may be 
provoked by other environmental changes. Since some of 
these changes could produce irreversible damj^e to the body, 
it is essential to understand how these changes may occur and 
what physiological limits may be endured without harm. 

Hematocrit— the volume 
percentage of erythrocytes in 
whole blood 

Orbital ' flight in a spacecraft such as Skylab provides a 
laboratory having an artificially maintained atmosphere, near 
weightlessness, and nearly closed ecological environment. 
Studies conducted here may provide new information 
relating to man's ability to acclimate safely to spaceflight and 
may also provide valuable insight into the underlying 
mechanisms by which these changes are accommodated. 




The Skylab Hematology and Immunology experiments 
described on the following pages include five investigations to 
evaluate specific aspects of man's immunologic and 
hematologic systems that might be altered by or respond to 
the spaceflight environment. The biochemical functions 
investigated with these experiments include (1) cytogenetic 
damage to blood cells, (2) immune resistance to. disease, (3) 
regulation of plasma and red cell volumes, (4) metabolic 
processes of the red blood cell, and (5) physical-chemical 
aspects of red blood cell functions. 

The investigations being conducted are not meant to provide 
an all inclusive coverage of immunohematologic functions, 
but are expected to serve as sensitive indicators of 
stress-induced changes in these functions in man. Selection of 
these specific protocols has been based upon experience 
gained from previous manned spaceflight missions and 
associated ground based studies. The specific goals of these 
experiments are to determine— 

1) environmental factors responsible for the loss of red cell 
mass noted during the Gemini Program; 


2) relative roles of the 100% oxygen environment, nitrogen 
in small amounts, weightlessness, duration of exposure, 
diminished red cell production versus increased 
destruction, ambient total pressure, vibration, ambient 
temperature, and dietary factors; 

3) spaceflight factors responsible for changes in plasma 

Studies of 
the Blood 

4) influence of long-duration spaceflight on the coagulation 
process, platelet function, and vascular friability, and to 
assess the environmental factors responsible for such 

5) any alterations in inflammatory response that may occur 
as a result of long-duration spaceflight, and evaluate; 

6) extent to which spaceflight may influence mitosis (cell 
division) and/or chromosomal composition, and which 
environmental factors are responsible and what 
preventive action can be taken if such changes do occur. 



Because chromosome aberration yields in peripheral blood 
leucocytes have been found to be sensitive indicators of 
exposure to radiation, such measurements can be employed 
as in vivo dosimeters. 

In mitosis (cell reproduction), each chromosome duplicates 
itself with the duplicates being separated from each other at 
cell division. One duplicate chromosome goes into the 
nucleus of one daughter cell and the other duplicate goes into 
the nucleus of the second daughter cell. The end product of 
this process is cell division which involves several phases. 
Each phase is characterized by a particular pattern of 
chromosome behavior. It is during one of these phases (the 
metaphase) that chromosomal aberrations may be 
microscopically observed. 

Chromosome analyses were done for all of the Gemini 
missions (with the exception of Gemini VIII which was 
terminated early) under the operational medical program. 
Significant, though slight, increases in some types of 
chromosomal aberrations were seen following some of the 
missions. This effect could not be correlated with mission 
duration, extravehicular activities, isotope injection of the 
crews or other obvious flight parameters. Observations on the 
Skylab crewmembers can assist in elucidating the mechanism 
of this phenomenon. 

Measurement of the number of chromosome aberrations has 
been demonstrated by ground based studies to be a sensitive 
method of biological radiation dose estimation. Ambient 
radiation encountered during long duration missions or 
unexpected solar flare events could produce significant 
increases in aberration levels. Even if no detectable increases 
in aberration levels are observed in the Skylab missions, the 
experiment will have served the useful purpose of 
demonstrating the lack of a detectable genetic hazard 
associated with these missions. 

Metaphase — the middle stage of 
mitosis during which the 
lengthwise separation of the 
chromosomes in the equatorial 
plate occurs. 





The method of detecting chromosomal aberration will be 
visual analysis that involves counting the chromosomes, the 
number of breaks, and types where possible, and then making 
a comparison between the identifiable chromosome forms 
with groups of chrornosomes that compose the normal 
human complement. ' 

Standard statistical procedures will be used to determine if a 
significant increase ' in aberrations appears postflight. This 
analysis will include comparisons of preflight aberration 
levels in normal individuals of the general population. 
"Predicted" aberration levels for postflight samples will be 
calculated by using inflight physical dose radiation 
measurements (available from Experiment D008, Radiation 
in Spacecraft, and other sources) and existing experimentally 
determined chromosomal aberration production coefficients. 
The effects of any other operational or experimental 
procedure likely to produce chromosomal aberration (such as 
radioisotope injections) will be measured on normal control 
subjects. These control subjects will be similar in age and 
physical attributes to the crewmembers. The control subjects 
will participate in all tests and medical procedures that are 
undertaken by the flight crewmembers. Examination will be 
made of the chromosomes of the control members and the 
flight crew before initiation of preflight procedures and tests 
to detect any chromosomal aberrations already present. 

By allowing for predicted aberration yields and the yields due 
to experimental or operational procedures, any aberration 
frequency difference evident from comparisons of preflight 
and postflight samples can be ascribable to radiation or other 
space parameters. 


The objectives of this experiment are to make preflight and 
postflight determinations of chromosome aberration 
frequencies in the peripheral leucocytes of the Skylab flight 
crewmembers and to provide in vivo dosimetry. These data 
will add to the findings of other Skylab cytologic and 
metabolic experiments to determine the genetic 
consequences of long-duration space travel on man. 

Dosimetry— the accurate and 
systematic determination of 



No inflight hardware is required since the experiment uses 
blood samples taken pre- and postflight beginning one month 
befpre launch and ending three weeks after recovery. 


The leucocytes will be placed in a short-term tissue culture. 
During the first cycle of mitotic activity in the in vitro 
cultures, standard chromosome preparations of the 
leucocytes will be prepared. 

The leucocytes from the cell culture will be removed during 
metaphase and "fixed." A visual analysis will be performed 
which involves counting the chromosomes, the number bf 
breaks and types where possible, and then making a 
comparison between the identifiable chromosome forms with 
groups of chromosomes comprising the normal human 


The data from this experiment will consist of the 
chromosome aberration frequencies that appear after flight 
for nine men, three of whom will have experienced 28 days 
in Earth orbit and the rest 56 days each. An estimate of the 
radiation dose experienced by each nian will be made based 
on the number of chromosome breaks. 

in vitro 



Information on man's humoral arid cellular immimity and 
coagulation phenomena during and following exposure to 
space flight is essential before flight crews can be committed 
to extended missions. Significant alterations of the iminunity 
mechanisms will produce • prejudicial effects upon this 
inherent defense system, thei-eby seriously compromising the 
crewman's operational status. The cellular immunity system 
is exquisitely sensitive to radiation, and the coagulation 
status is affected by man's activity. 

The experimental program measures itiems which contribute 
to man's ability to combat infections and repair traumatized 
(injured) tissues after exposure to weightlessness, spacecraft 
atmosphere, sublethal ionizing radiation, the monotonous 
immunologic stimulation of a closed environment, and the 
unusual orientation and physical activity. Significant 
alterations of the extracellular or cellular 
immune-mechanisms may produce detrimental effects upon 
normal physiological functions, may result in increased 
susceptibility to infections, and conceivably can induce the 
onset of autoimmune diseases. 


Autoimmunization — the 
production in an organism of 
reactivity to its own tissues 

The objective of this experiment is to assay changes in 
humoral and cellular immunity as reflected by the 
concentrations of plasma and blood cell proteins, blastoid 
transformations, and the synthesis of ribonucleic acid (RNA), 
and deoxyribonucleic acids (DNA) by the lymphocytes 
(white cells in lymph). 



The inflight blood collection system will draw venous blood 
and centrifuge the samples for preservation. Onboard freezing 
will be used to preserve the samples during the mission and 
maintain them in a frozen state. They will be returned in the 
frozen state in a urine-return container for postflight analysis. 
This inflight blood collection system and allied facilities will 
"" be used to obtain, process, preserve, and return hematology 

samples for Experiments M071, M073, M112, M113, M114, 
and MH5. (See M115 for more details on this equipment.) 


Experiment The experiment will obtain preflight baselines, which will be 
Investigations indications of normal metabolism, from the crewmembers 

and a control group composed of three men physically 

similar to the crewmembers who will serve as controls while 

the crewmembers are in spaceflight. Inflight blood samples 

will be taken four times from each crewman during the 

28-day mission and eight times from each crewman during 

the 56-day missions. Upon recovery after the spaceflight, 

information will be again obtained from the crewmembers 

before body functions "normalize," and compared with the 

preflight baselines, inflight profiles, and with the data being 

obtained from the ground control group (GCG) to detect any 

significant deviations. An extensive battery of analyses will 

be performed using appropriate laboratory techniques to 

detect qualitative and/or quantitative changes. Periodic 

examinations will be made of the blood proteins and 

lymphocytes until the possible altered concentrations are 

likely to have stabilized. Protocols for the experiment are 

given in the section on Experiment Ml 15. 


Data will be gathered from blood samples taken preflight, 
inflight and postflight. These samples will be analyzed for the 
following constituents: 

1) total plasma proteins; 

2) plasma protein fractions (albumins, alpha globulins, beta 
globulins, gamma globulins); 

3) lymphocyte morphology; 

4) ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) 
synthesis rates in lymphocytes; 

5) kinetics of lymphocyte RNA and DNA; 

6) observation of blastoid formation; 

7) lymphocyte functional response to antigen; Antigen— a substance that 

stimulates antibodies 

8) quantification of 4.5s, 7s, and 19s. 


Volume and 


Environmental factors encountered during spaceflight may 
affect the red cell mass and plasma volume. These include 
near weightlessness, the spacecraft breathing atmosphere, and 
ionizing radiation environments. 

Weightlessness may cause a redistribution of the total blood 
volume between the arterial and venous segments and by 
reducing the quantity of blood in the limbs. In the weightless 
state, a redistribution of pulmonary blood volume may occur 
with relatively greater perfusion in the apex of the lungs. In 
this condition, ventilation and perfusion ratios might be 
expected to be similar to those produced when the subject is 
lying down in zero gravity. Results from previous missions 
suggest that these changes have not produced pathological 
changes in the blood vessels. It is not known, however, 
whether long-duration missions could predispose to changes 
including thrombosis (blood clot). Previous missions have 
also led to changes in circulating plasma volume at recovery. 
Analysis has suggested that these changes are of a magnitude 
similar to those found in bed rest. The rate at which this 
change occurs j^nd whether the plasma volume decreases or is 
augmented during the stress of reentry is unknown. It is 
believed that plasma volume changes may have conti-ibuted 
to the temporary orthostatic hypotension and to the decrease 
in exercise tolerance that crewmembers experienced soon 
after recovery. 

The site of red blood cell (RBC) production in the mature 

adult is the marrow of membranous bones (e.g., sternum and 

vertebrae). The rate of production is dependent on metabolic 

demands and the current red cell population. The rate of 

RBC production can be measured quantitatively by injection 

of a known quantity of a radioactive iron tracer. The 

radioiron, combined with globulin, is transported to other 

parts of the body. That part of the iron which reaches the 

membranous bones is incorporated into the heme portion of Heme — the nonprotein, 

hemoglobin by the bone marrow. Since not all the iron insoluble, iron protoporphyrin 

appearing in the plasma is used for erythrocyte production constituent of hemoglobin 

but is instead taken up by the iron pools of the body, a 

fraction of the injected radioiron will be unavailable for 

incorporation into developing RBCs. This can be determined 

by measuring the concentration of radioiron in the 

circulating RBC after seven days and comparing it with the 

initial concentration of radioiron in the plasma. 

Since the rate of RBC production acts with RBC loss to 
increase or decrease the total RBC mass present at a given 
time, any changes in the rates of RBC production and 
destruction will be necessarily reflected in the red cell mass. 


Such changes in red cell mass can be measured. aind analyzed 
by injection of radioactive chromium (in the form of sodium 
chromate) tagged red cells. The sodiuin chrorhate diffuses 
through the cell membrane where it is converted to 
chromium chloride and, in this form, bound to hemoglobin. 
The volume of RBCs is then calculated by allowing the 
chromium-tagged cells to disperse through the circulatory 
System and measuring the extent to which the chromium has 
become diluted. The fact that chromium doesnot reenter the 
red cell makes it a good tracer for RBC mass determinations. 
Chromium incorporated into the hemoglobin structure of the 
circulating red cell also provides a means for estimating the 
rate of random cell destruction by monitoring the rate at 
which chromium disappears from the red cell mass.' 

Red Cell Life To determine selective age dependent erythrocyte 
Span destruction and mean red cell life span, carbon 14 labeled 

glycine will be injected into a superficial arm vein of each 
crewmember and control subject. The radioactively labeled 
glycine, by its incorporation into the heme portion of 
hemoglobin, labels the erythrocytes produced on that day. 
Sequential blood sampling will then give the percentage of 
labeled erythrocytes in the blood at any given time (days), 
and by plotting this data, survival and destruction curves can 
be obtained. The resultant curves can then be , analyzed 
mathematically and a mean life span for the cells determined. 
Since only a small portion of the carbon 14 is reutilized in 
erythropoiesis, it is an ideal RBC label. 

Finally, plasma volume changes can be measured by adding a 
known amount of radioiodinated human serum albumin to 
each crewmember's blood. Albumin is a major constituent of 
the plasma and is the protein most responsible for 
maintaining the osmotic pressure at the capillary membrane. 
It acts to prevent plasma fluid from leaking out of the 
capillaries into interstitial space. ^ 

E ry thropoiesis— the 
of erythrocytes 


The Skylab life support system provides a combination of 
breathing gases which because of the lower than normal 
nitrogen partial pressure will be hypobaric. The partial 
pressure of oxygen in the breathing atmosphere will be 
slightly increased at least during extravehicular activity by 
the crew. Additionally, the atmosphere will contain trace 
amounts of other gases released from onboard equipment and 
supplies; Small amounts of other gases may also be released 
as a result of the crew's metabolic activity and from bacteria 
and molds which may be present. 

Hypobaric— characterized by less 
than normal pressure or weight 


In the Gemini flight, red cell mass decreases were found that 
were generally greater than the red cell mass decreases found 
in Apollo flight crewmembers. Total pressure of the 
atmospheres in the Gemini and Apollo missions were quite 
similar while partial pressures of oxygen and nitrogen were 

different— more oxygen and no nitrogen . present in the 
Gemini missions. It is probable that there were also 
differences in the trace gases respired during the missions. 

The red cell mass differences in these previous missions were 
probably related to the above factors although other factors 
might have been important also. As an example, red. cell mass 
changes are expected as a result of changes in the amount of 
physical activity performed during the . mission. Athletic 
conditioning is associated with an increase in red cell mass. 
Conversely, red cell mass declines have been found in certain 
bed rest studies, although in the studies to date the arnount 
of blood drawn for research testing may have been a factor in 
the decreased red cell mass. 

Since a number of inflight environmental conditions have 

been found capable of affecting the total blood volume and 

its constituents, delineation of inflight effects on 

hematopoiesis is necessary in order to predict the course and Hematopoiesis— the formation of 

consequences of long duration spaceflights on future flight blood cells 



The objective of this experiment is to determine the effect of 
Earth orbital missions on plasma volume and red blood cell 
populations with particular attention paid to changes in red 
cell mass, red cell destruction rate, red cell life span, and red 
cell production rate. 


Blood samples will be collected preflight, postflight, and 
inflight, and processed in accordance with the protocol 
shown in Ml 15. 


The data to be collected in support of this experiment 
include the following variables: 

1) red cell life span; 

2) red cell production, distribution, and destruction rates; 

3) plasma volume. 


Blood Cell- 

At one time, the red blood cell was believed to be an inert 
particle composed of water and hemoglobin. We now know, 


of course, that the erythrocj^es are hving cells, doing work, 
and requiring energy just as other tissues in the body do. The 
average life span of the human red blood cell is estimated to 
be 120 days. During this period, it is estimated that the 
average erythrocyte travels 100 miles between the heart and 
the tissue that it serves. In order to remain functional, the red 
corpuscle must (1) maintain an internal environment against 
a steep ionic gradient across the cell membrane, (2) resist 
forces that try to change its characteristic bi-concave shape to 
spherical, (3) maintain active transport mechanisms that 
support the metabolic requirements of the cell. Interruption 
to these processes would render the red blood cell ineffectual 
and would be fatal in a matter of days. 

Influence of 



This experiment will assess the influence of the spaceflight 
environment on the metabolic processes of red cells. The red 
blood cell requires for its energy source a continuous supply 
of glucose. The process by which the glucose penetrates the 
red blood cell's membrane is not known; however, it is 
believed to involve an active transport process rather than 
simple diffusion. It is suspected that the membrane's 
framework, in particular the fatty (lipid) fraction of the 
framework, is functional in this process. Because the 
membrane is the dynamic component in the active transport 
process, its chemical composition and structural integrity will 
be examined by this experiment. 

Through the metabolic breakdown of glucose, particularly 
ADP (adenosine diphosphate) to ATP (adenosine 
triphosphate) energy is stored in chemical bonds. Changes in 
the glucose metabolic pathway, which may occur as a result 
of spaceflight, will be analyzed by examination of several key 
intracellular enzymes found in preflight and postflight blood 


The objective of this experiment is to determine if any 
metabolic and/or membrane changes occur in the human red 
blood cell as a result of exposure to the spaceflight 

Enzyme— organic substance 
capable of presenting chemical 
changes in organic substances by 
catalytic action, such as in 

EQUIPMENT (See M115.) 



The data that will be taken in support of this experiment will 
be the preflight, inflight, and postflight values of the 
foUowring variables: 

1) methemoglobih; 

2) reduced gluthathione; 

3) glyceraldehyde-6-phosphate dehydrogenase; 

4) pyruvate kinase; 

5) glyceraldehyde-3-phosphate dehydrogenase; 

6) phosphofructokinase; 

7) hexokinase; 

8) phosphoglyceric acid kinase; 

9) acetylcholinesterase; 

10) lipid peroxide levels; 

11) adenosinetriphosphate; 

12) 2,3-diphosphoglycerate. 






Data collected from pre-Skylab spaceflights indicate that the 
spaceflight environment may induce a loss of red blood cells 
in the crew. These earlier investigations have suggested that 
this loss may result from a self-limiting hemolysis which 
appears to be related to alterations in mean corpuscular 
volume and increased osmotic fragility. Since reticulocyte 
(an early form of the red blood cell) counts which indicate 
bone marrow activity have not revealed depression of the 
bone marrow activity due to such flights, and since 
reticulocytosis (above normal reticulocyte count) did not 
appear until the fourth day, it is likely that red cell loss 
resulted from a reduced need for red cells for the transport of 

Similar data gathered during Apollo missions provided a basis 
for comparison vdth the data derived from the Gemini 
program. Comparison of these data suggested that a causative 
factor in the reduced RBC was the Gemini atmospheric 
composition— specifically, the high oxygen concentration. 
Data obtained from the later Apollo flights have also 
indicated alteration of fluid and electrolyte balance, while 
examination of red cell electrolytes by electron probe 
analysis indicates similar shifts. 

A "bestfit" hypothesis based on these previous data would 
have it that the hyperoxic atmosphere in spacecraft (and 
possibly other environmental parameters such as 


-the liberation of 


weightlessness) induces chemical changes in the red blood cell 
membrane. These changes directly or indirectly disrupt the 
active transpoii mechanisms leading to increased osmotic 
pressures and eventual lysis (destruction) of the cell either 
through membrane swelling and rupture or through lipid 
breakdown and fragmentation. 


The objectives of this experiment are to examine critical 
physiochemical hematological parameters relative to the 
maintenance of homeostasis, and to evaluate the effects of 
spaceflight on these parameters. 


Inflight^Blood The inflight blood collection system that supports this 
Collection related series of studies is designed to collect and process 

blood samples without coagulation or contamination. The 

inflight blood collection system contains the following major 


1) syringes capable of extracting approximately 11 

milliliters of venous blood from each crewman under Venous— relating to a vein, 
sterile procedures; 

2) small blood sampling vials, into which the crewman 
places a few drops of whole blood already containing a 

3) automatic sample processors, two-chamber spring-loaded 
containers, used to process and separate the blood cells 
from the plasma by centrifugation; 

4) a two-speed centrifuge used to receive the automatic 
sample processors and separate the blood into red cells 
and plasma, and to maintain this separation in the 
weightless environment. 


The blood samples for the group of Hematology and 
Immunology Experiments will be collected in accordance 
with Figure 3-3. Specific handling and processing procedures 
will be followed to obtain the data for each of the 

Records will be maintained that include sampling times and 
the time, name, and quantity of any injections taken 
(including x-rays), plus any illness of a subject. A record will 
be maintained during the flight of the following events: flight 
duration, extravehicular activity, solar events, any abnormal 
exposure to radiation, infectious diseases, symptoms of 

Inflight blood samples 

11 ml blood 
in automatic 
sample processor 


•Fixative • 


Freeze and store ■ 


Transport to NASA MSC 


(cells + plasma) 

Experiment M071 
0.5 ml 


Experiment M073 
3.0 ml 

Angiotensin 1 . 

Experiment M112 
0.5 ml 

Plasma proteins 

Experiment Ml 13 
2.0 ml. 

Red cell life span 
Red cell mass • 

Experiment Ml 14 
4.0 ml 


Lipid peroxide levels 

Pyrovate kinase 
2, 3 diphosphoglycerate 

Experiment Ml 15 
1.0 ml 


Cellular potassium • 

Fixed sample 

Experiment Ml 15 

Cellular hemoglobin- 
Ultras tructure 


Figure 3-3 Inflight Blood Processing Flow Chart for Hematology and Immunology Series Experiment 

illness, use of medication and types of drugs used, with 
dosage and duration of usage. Also any deviation from the 
expected orbital workshop atmospheric total pressure or 
partial pressure of its constituents will be recorded. 

Blood samples will be taken inflight four times from each 
crewman during the 28-day mission and eight times from 
each crewman during the 56-day mission. 


Supporting Data in support of Experiment Mil 5 will be taken preflight 

Data and postflight only and will consist of information about the 

following variables of routine hematology: 

1) red cell count; 

2) hematocrit; 

3) hemoglobin; 

4) red cell indexes; 

5) reticulocyte count; 

6) white cell count; 

7) differential and morphology; 

8) platelet count; 

9) acid and osindtic fragilities, 
and special hematology: 

1) red cell critical volume and red cell volume distribution; 

2) hemoglobin characterization; 

3) single cell hemoglobin distribution; 

4) membrane and cellular ultrastructure; 

5) intraerythrocytic electrolytes; 

6) red cell electrophoretic mobility; 

7) red cell density separation; 

8) cellular RNA, protein distribution. 


Section 4 

Cardiovascular Status 

Lower Body Negative Pressure, 
Skylab Experiment M092 

Skylab Experiment IV1093 


The cardiovascular system, one of the vital systems of the 
body, functions as a transport media linking man's internal 
environment (the interstitial fluid surrounding all cells) with 
the three large surface areas exposed to his external 
environment (lungs, gastrointestinal tract and kidneys). In 
essence, it consists of a very large number of very small 
tubular vessels (capillaries) which permeate all regions of the 
interstitial fluid and the externally exposed areas of the 
lungs, etc. The extensive capillaries are joined by larger 
vessels (arteries and veins) to a pump (the heart), thus 
forming a closed system through which the transporting fluid 
(the blood) is kept flowing at an adequate rate. 

Blood Plow The circular nature of the blood flow is demonstrated in the 
schematic diagram of the cardiovascular system of Figure 4-1. 
The system consists of two capillary networks connected in 
series with two piimps to form a closed loop. The two 
pumps, the right and left ventricles of the heart, shown 
physically separated in the diagram, actually comprise a 
single organ. The blood leaving the right ventricle flows to 
the capillary bed of the lungs while that leaving the left 
ventricle flows to capillaries distributed throughout the rest 
I of the body. Each ventricle is preceded by a supporting 

atrium, a chamber of the heart, which acts as a receiving 
reservoir and auxiliary pump to fill the associated ventricle. 

Blood leaves the right ventricle through a single, large vessel, 
the pulmonary artery, and enters the left atrium from the 



(15 mm Hg) 


Arteries — oxygenated blood 
Veins— unoxygenated blood 
carrying carbon dioxide 

Figure 4-1 Schematic Diagram of the Circulatory System 




lungs by way of four pulmonary veins; it leaves the left 
ventricle through the large aorta, and returns from all parts of 
the body by way of two large veins, the superior and inferior 
venae cavae. All vessels carrying blood from the heart to 
capillaries are arteries, and those conveying blood from 
capillaries back to the heart are veins. The circulating blood 
volume in man is about 76 ml/kg of body weight, about 5.3 
liters in an average man weighing 70 kilograms. 

The part of the vascular system traversed by the blood in 
going from the left ventricle to the right atrium is called the 
systemic circuit. It includes the capillary beds of all parts of 
the body except the lungs. The pumping force that moves 
blood -through this circuit comes from contractions of the 
left ventricle. The large nurhber of capillary networks that 
supply the organs and tissue of the body constitute many 
circuits connected in parallel and supplied by the extensively 
branched arterial system that begins with the aorta. Blood 
leaving the capillaries enters small veins that join together to 
form larger and larger veins. This arrangement continues until 
all the systemic blood returns to the right atrium through the 
two large venae cavae. The systemic circuit contains about 
80% of the total circulating blood volume, approximately 
4240 milliliters for the 70-kilogram average man. 

The capillaries, which have very thin and permeable walls, 
exchange water and dissolved materials (including gases) with 
the interstitial fluid. This two-way passage (in and out) of 
fluid has been estimated to exceed 200 liters, per minute. 

The capillaries are very small but their number is so large that 
the total area available for diffusion is very.largfe, approaching 
100 square meters. The number of capillaries in tissue can be 
correlated with the metabolism of the tissue; for example, in 
a heart muscle where oxygen use is high, microscopic studies 
show as many as 6000 capillaries in each square millimeter of 
tissue cross section. Since many capiilaries may "close 
down," especially in the skeletal muscle except during 
exercise or work, the volume of blood present in the systemic 
capillaries is variable. It has been estimated that in an average 
adult this volume may range between 60 and 200 milliliters. 

The systemic arteries act as conduits to distribute blood to 
the systemic capillary beds. The aorta at its beginning (the 
ascending aorta) has an outer diameter of about 2.5 
centimeters and a wall thickness of nearly 2 millimeters. At 
each branch point, the cross sectional area of each branch is 
smaller than the parent vessel while the total cross sectional 
area of the branches is greater. The arteries do not contribute 
significantly by diffusion to the exchange of materials with 
the interstial fluid. The volume of blood contained within all 
the systemic arteries under normal circumstances is estimated 
to be about 20% (~one liter) of the total blood volume. 

Total Blood Volume- ~5 liters 
Volume in Systemic 
Arteries- ~i liter 


The smallest branches of the arterial system are called 
arterioles. Arterioles are different from small arteries in that 
their walls are thick in relation to their internal diameter. 
This extra wall thickness consists of circumferentially 
oriented smooth muscle fibers. The cross sectional area of the 
arteriolar lumen varies with contractions of the smooth 
muscle which are controlled by neurohumoral factors. These 
changes control resistance to blood flow in the systemic 
circuit and distribution of the blood flow to the capillary 

The veins form an extensive recovery system for conveying 
the blood returning from capillary beds to the right atrium. 
Although their walls are much thinner than those of the 
arteries, they also permit no significant diffusion of 
substances through them. The distinctive feature of the 
venous system is its large volume. The volume of blood 
contained within the veins is about 75% of the volume in the 
whole systemic circuit or about 3200 milliliters. Veins, unlike 
other vessels, are equipped with one-way valves that permit 
blood flow only toward the heart. 

Pulmonary The pulmonary circuit, which is sometimes called "the lesser 

Circuit circulation," extends from the pulmonary artery as it leaves 

the right ventricle to the pulmonary veins as they enter the 

left atrium. The pulmonary circuit carries venous blood (i.e., 

blood which has come from systemic capillaries and is 

therefore low in oxygen content and high in carbon dioxide 

content) to the lungs, where it is converted to arterial blood 

(blood which is freshly oxygenated and has had much of the 

carbon dioxide removed). The pulmonary artery is the only 

artery that carries venous blood, and the pulmonary veins are 

the only veins that carry arterial blood. The pulmonary 

circuit, like the systemic, is composed of arteries, capillaries, 

and veins, but all vessels are generally shorter and larger in 

diameter than corresponding systemic vessels. In the 

pulmonary circuit thick-walled arterioles are absent and the 

very small arteries (<100 microns in diameter) show little or 

no smooth muscle in their walls. 

In the human lungs, air is conducted via the trachea, bronchi, 

and their branches to about 300 million small air sacs or 

alveoli, which are honeycomb-like structures about 200 to 

250 microns in diameter. The pulmonary capillaries, which Micron— a millionth part of a 

are 10 to 14 microns in length, and 7 to 9 microns in meter 

diameter, extend as a dense network within the thin, 

membranous partitions separating adjacent alveoli. 

Calculations have shown the surface aiea of capilleiry wall 

exposed to the alveolar air averages to be from 50 to 70 

square meters in the average adult. The total volume of blood 

within the capillaries of the pulmonary circuit is of the order 

of 100 milliliters. 



Much of our knowledge of the dynamic characteristics of the 
cardiovascular system, and the mechanisms governing its 
response to changes in activity, environment, and disease has 
come from observations on animals, chiefly dogs. In recent 
years, great technological advances in bioinstrumentation 
have made it possible to confirm and extend these 
observations on man. It is still true, however, that many 
measurements can be made only on anesthetized animals, 
some can be made as well on unanesthetized animals but not 
on man, and some on both animals and man in the conscious 
state. Under all conditions, the method of measurement used 
will disturb, to some extent, the cardiovascular system of the 
subject, and influence the variable being measured. It is 
always important to minimize this disturbance, to assess its 
significance, and to take it into account, when possible, in 
interpreting the results. 

He mo dynamically, the circulatory parameters of most 
interest are pressures and flows in various parts of the 
cardiovascular system. Because of the rhythmical 
contractions of the heart, the input of blood into both 
pulmonary and systemic circuits is intermittent. 
Consequently, the blood flow in all the systemic arteries, the 
systemic veins close to the heart, and probably all of the 
pulmonary vessels is pulsatile rather than steady. In the 
systemic capillaries and peripheral veins, the flow is 
essentially steady because of the low-pass filtering action of 
arterial compliance and arteriolar resistance. Pressures, 
therefore, are pulsatile in all four chambers of the heart and 
in all parts of the vascular system with the exception of 
systemic capillaries and peripheral veins. 

Mechanically, the heart is a muscular organ consisting of two 
major pumping chambers, the right and left ventricles, each 
of which receives blood from a contractile antechamber, right 
and left atria, respectively. Backflow of blood from ventricle 
to atrium is prevented by the valve on the right side 
(tricuspid) and the valve on the left side (mitral). The right 
ventricle ejects blood into the pulmonary artery from which 
backflow is prevented by a semilunar pulmonary valve. 
Backflow of blood into the left ventricle from its outflow 
vessel, the aorta, is prevented by a similar semilunar aortic 




Diagram of Human Heart 



An outstanding characteristic of cardiac activity is the fact 
that the heart continues to contract rhythmically when all of 
its connections with the nervous system are severed, or even 
when it is removed completely from the body. This indicates 
that, unlike skeletal muscle, cardiac muscle is not dependent 
upon impulses coming to it from the nervous system for its 
activation. It has the property of automaticity. 

Au tomatici ty— occurring 
spontaneously, uhvoluntarily 

Normally, the rhythmically occurring stimuli responsible for 
cardiac contraction arise in the sinus node. This "built-in 
stimulator" or pacemaker of the heart has the property of 
automatically discharging rhythmical stimuli which activate 
the heart. This wave of excitation, beginning in the sinus 
node and traveling in all directions through the atrial muscle, 
is known as the cardiac impulse. It consists of electrical 
(action currents), chemical and thermal changes, and is 
followed closely by mechanical contraction. As in the case of 
a nerve impulse traveling along a nerve fiber, or in impulse 
traversing a single skeletal muscle fiber, the cardiac impulse 
also involves a progressive depolarization of cell membranes. 

Depolarization — the 
neutralizing polarity 

act of 

Contraction The normal sequence of contraction of the heart chambers 

Sequence results from the spread of the cardiac impulse. This impulse 

arises in the sinus node, located in the wall of the right 
atrium; hence this chamber contracts first. Because the rate 
of conduction of the impulse through atrial muscle is quite 
rapid, the left atrium contracts only a very short time after 
the right. Practically, the two atria contract almost 
simultaneously. The impulse is slowed down considerably, 
however, while traveling between the interatrial septum and 
the ventricular muscle mass. This is because conduction 
between atria and ventricles can only occur by way of the 

A-V (atrio-ventricular) node and "bundle" (a specialized 
conducting tissue). The only other tissue normally 
connecting auricles with ventricles is connective tissue, which 
does not have the property of conducting an impulse. This 
results in the completion of atrial contraction before 
ventricular contraction begins. During the period of 
contraction and depolarization, action currents similar to 
those in all muscles of the body can be sensed at the surface 
of the body. 


During routine daily activities, the force of gravity influences 
the distribution of blood in the cardiovascular system and, 
consequently, changes the nature of blood flow regulation. 
Thus, the function of this system is dependent upon the 
effects exerted by the Earth's gravitational pull. 

Problems Due 
to Lack of 

The effects of null or diminished gravitational forces that are 
experienced during space flight have not been fully 
elucidated by past studies. However, flight observations 
coupled with analyses of the cardiovascular system have 
indicated the following potential problem areas when the 
forces of gravity are altered. 

Cardiac Contractility— Reduction in work performed by 
antigravity muscles reduces the nutritive and waste removal 


requirements imposed upon the cardiovascular system; herice, 
the heart leads a more sedentary existence. One mechanism 
by which it can decrease its total output is to reduce the 
forcefulness of each contraction. 

Vascular Responsiveness— Alterations in the responses of the 
vascular smooth muscle, which occur with decreased 
stimulation (hormonal, nervous, mechanical) with changes 
in the contractile properties of smooth muscle cells, and with 
alterations in vessel geometry caused by change in 
intravascular volume, will result in qualitative and 
quantitative changes in the cardiovascular function. In 
particular, the vascular neural reflexes that compensate for 
drainage of intravascular fluid away from the heart when a 
man assumes an upright position in a gravitational field 
become less effective. This situation, called orthostatic 
hypotension, can develop after a few days in a weightless 
state and upon return to Earth could lead to temporary bouts 
of fainting because of inadequate brain circulation. 

Capillary Exchange— Alteration in the transcapillary pressure 
gradients or the properties of the capillary walls change the 
quantity and the composition of the fluid that moves from 
the intravascular into the extravascular spaces. 

Viscoelastic Characteristics of Vessels— Changes in vascular 
distensibility, especially that of the capacitance vessels 
•' . (located principally in the venous circulation), markedly alter 
the quantity of blood returned to the heart as well as the 
time-dependent characteristics of venous blood return, and 
thence, alter the output of the heart. 

Decreased Endocrine Activity— Depletion of vasoactive Vasoactive— exerting an effect 

hormone stores (e.g., norepinepherine) or decreases in their upon the blood vessels 

rates of synthesis effectively limit or alter the ability of the 

vascular system to respond to stress when the need arises. 

Smooth muscle responses to given concentrations of 

vasoactive hormones may also assume different patterns as 

adaptation to a new environment occurs. 

Decreased Vascularity— Both an enriched oxygen atmosphere 
and a decrease in oxygen demands of tissues associated with 
decreased work will reduce the oxygen transport 
requirements placed upon the cardiovascular system. The rate 
of oxygen diffusion through the tissue spaces to meet cellular 
oxygen needs will become lower. Thus, the diffusion paths 
can be lengthened without compromising these needs. Under 
these circumstances, tissues become less vascular through a 
relatively slow process of acclimatization. 

Shifts of Intravascular Fluid Volumes — Volume receptors that 
respond to vessel or heart chamber wall stretch are stimulated 
by shifts of fluid within the vascular spaces when 

gravitational forces are removed or decreased. Through 
neuroendocrine pathways, a diuresis is initiated and the total 
water content of the body is reduced. This results in partial 
dehydration of body tissues and reduces the capacity to 
respond to stress. 

Nonspace Related Conditions— Consideration must also be 
given to debilitating cardiovascular diseases and to other 
Earth environmental conditions not unique to weightlessness. 
The occurrences! of these are not precluded by weightlessness; 
hence, long term comprehensive longitudinal studies on flight 
crews and improved prediction models are required to 
establish probability tables to assist medical support of long 
duration missions. 

The Skylab program incorporates two experiments that 
provide information on the performance of the 
cardiovascular system in the near weightless environment of 
space. This infprmation will aid in establishing the relative 
importance of the above problems for long-duration 

Inflight Lower SKYLAB EXPERIMENT M092 

Body Negative 


Reduced orthostatic tolerance can be demonstrated by Orthostatic— pertaining to or 

provocative (stimulating) testing during weightless flight. One caused by standing erect. 

method of provocative testing involves the application of 

lower body negative pressure (subambient pressure to the 

body surface below the diaphragm). The equipment to apply 

this negative pressure is the lower body negative pressure 

device (LBNPD). Physiological indicators are heart electrical 

activity, pulse pressure, blood pressure, heart rate and limb 


The body stresses produced by LBNP on the cardiovascular 

system of a supine subject in 1-g in certain respects closely Supine— lying on the back in a 

resembles the effects produced by a normal upright posture, relaxed position 

These stresses are an effective decrease in resistance to blood 

flow to dependent portions of the body, and increase in the 

level of venous pressure in dependent veins required to return 

blood to the heart. LBNP results in pooling of blood in the 

lower body hindering its return to the heart, and therefore 

elicits a similar cardiovascular response to that experienced 

during upright posture on Earth. LBNP thus provides an 

objective means of provoking cardiovascular responses that 

can be used to determine the extent of cardiovascular 

deconditioning. The technique could conceivably serve as a 

countermeasure to deconditioning due to the near weightless 

environment, by providing periodic calibrated stresses that 

may minimize the effects of spaceflight. 




The objective of this experiment is to provide information 
concerning the time course of cardiovascular deconditioning 
during flight and to provide inflight data for predicting the 
degree of orthostatic intolerance and impairment of physical 
capacity which is expected following Earth return. 


The major components of the experiment equipment used 


1) lower body negative pressure device (LBNPD), 

2) leg volume measuring system (LVMS), 

3) blood pressure measuring system (BPMS), 

4) body temperature measuring system (BTMS) (M171 
experiment equipment), 

5) vectorcardiograph (VCG) (M093 experiment equipment). 

The LBNPD consists of a cylindrical tank with a waist seal 
that provides positive isolation of the inner volume and lower 
limbs from the ambient atmosphere. An inner crotch support 
prevents the crewman from being pulled into the device by 
the reduced internal pressure during operation'. This device 
can be evacuated to a controllable pressure of 0-50 mm Hg 
below the ambient cabin pressure. 

The LVMS senses the changes in the circumference of the leg 
at the level of the calf muscle by a capacitive type detector 
leg band. Data signals from the leg band are then conditioned 
and displayed on a console panel as percent volume change. 

The BPMS includes an inflatable arm cuff and a microphone 
for detecting the Korotkoff sounds characterizing blood flow 
using , the auscultatory method. These pressures can be 
displayed and/or recorded for transmission to the ground. 


Each of the crewmen will participate in the LBNP tests at 
approximately the same time each day, every third day 
during the mission. A LBNP test will consist of a 5-minute 
period of rest at 15 minutes of progressively decreasing 
pressure on the lower limbs until 50 mm Hg (1 psi) below 
cabin pressure is reached. This is followed by 5 minutes of 
rest. Physiologic measurements are made throughout the test 

A minimum of five measurement sessions are planned for 
each flight crew at approximate intervals as follows: selection 
of the crew, 60 days, 21 days, 10 days, and 2 days before 
launch. These data will serve as both the experimental 
control and the baseline reference for postflight data. 

Korotkoff Method — to 
determine blood pressure 

The auscultatory 
method— listening for sounds in 
the body to ascertain the 
condition of the lungs, heart, etc 

Postflight measurements will be made beginning as soon as 
possible after recovery, at recovery plus 24 hours, and at each 
24-hour interval thereafter until normal preflight values are 


The principal measurements taken during the experiment are 
as follows: 


1) pressure differential (AP across the chamber), 

2) leg circumference (correlatable with leg volume), 

3) blood pressure, 

4) internal temperature (LBNPD chamber temperature), 

5) cabin temperature (ambient temperature to the subject's 
head, shoulders, and upper torso), 

6) subject's body temperature, 

7) vectorcardio^am, 

8) heart rate. 



The excitation process in cardiac muscle is similar to that in 
skeletal muscle and in nerves. It results in a propagated 
depolarization of cell membranes described below and is 
made evident by action currents. The electrocardiogram is a 
graphic record of the action currents from the heart muscle; 

These action currents may be recorded by placing pickup 
electrodes at two locations on the surface ' of the body. At 
any instant during the cardiac cycle the heart may be 
considered as a battery with' the depolarized region of the 
heart (through which the impulse has already passed at that 
instant) acting as a negative pole, and the inactive region of 
the heart' (through which the impulse has not yet passed) 
acting as the positive pole. This Battery is immersed in an 
electrically conducting medium, the body. Consequently, 
action currents will flow, not only within the heart, but 
through all the tissues of the body, including' those at the 
surface. Hence, surface' electrodes may be used to lead off and 
irecprd these ' potential differences as an index of cardiac 
action currents. ■'" . ■■'■."'■ ' 

Vectorcardiogram— a graphic 
record of the magnitude and 
direction of the electrical forces 
of the heart 

Electrocardio- As the cardiac impulse spreads through the heart during each 
gram heart cycle, the spatial and electrical relationships between 

active and inactive regions of the hejirt are constantly 
changing, thus causing the surface potentials to change from 
moment to moment, both in magnitude and direction. Thesis 
changing potential differences between lead-off points on the 
body . surface, when graphically recorded, constitute the 
electrocardiogram. ■ . ' 


Axis of the 

The electrical condition of the heart at any instant may be 
represented by a vector whose direction indicates the 
orientation of the negative or depolarized portion of the 
heart with respect to the positive or inactive region of the 
heart at that instjant. The magnitude of this vector is 
proportional to the instantaneous potential difference 
between the positive and negative portions of the heart. This 
vector, which undergoes cyclical changes in magnitude and 
direction in space during each heart cycle, is known as the 
electrical axis of the heart. The instantaneous potential 
difference recorded between any two surface lead-off points 
is proportional to the projection of the electrical axis upon 
the line'joining these two points. 

Electrocardiogram— a graphic 
tracing of the electric current 
produced by the contraction of 
the heart muscle 


Thus, a record taken from two points on the surface of the 
body will provide information concerning the cyclical 
variations of the electrical axis of the heart. More 
information can be obtained by recording from several pairs 
of surface points than can be obtained by recording from 
only one pair. Hence, it is customary to record, in turn, from 
three pairs of lead-off points known as the three standard 
limb leads. Lead I is taken from the two arms, lead II from 
the right arm and left leg, and lead III from the left arm and 
left leg. (See Figure 4-2.) 

Standard ECG Limb Leads 



Typical ECG-Lead I (left arm-right arm) 
Legend : 



Left Arm (LA) 
Left Leg 
Left Leg 

Right Arm (RA) 
Right Arm 
Left Arm 






Right Side 


Left Side 


Left Chest 

Figure 4-2 Standard ECG Connections 


If some portion of the hcEirt is injured as the result of 
inadequate blood supply or some disease process, injury 
currents will flow. These injury currents may appear in the 
standard limb leads, but sometimes, if the injured area is 
small, or if it is located in particular regions of the heart, the 
injury current can be recorded only by applying one 
electrode to the surface of the body as close to the heart as 
possible, i.e., on the chest. Consequently, it is customary to 

record, in addition to the limb leads, two or more chest leads 
in which one electrode is placed on the chest and the other 
electrode on an arm or leg. Additional leads are often taken 
from the chest and sacral regions. 

The form of the electrocardiogram recorded from any lead is 
determined by the site of origin of the cardiac impulse, its 
pathway of spread through the heart, the position of the 
heart within the chest, and the presence or absence of injury 
currents. This is simply another way of saying that the form 
of the electrocardiogram is determined by the cyclical 
variations in direction and amplitude of the electrical axis of 
the heart and the point of attachment of the leads. 

Cardiac Impulse — the impulse or 
beat of the heart at the fifth 
intercostal space at the left side 
of the sternum 

The form of the electrocardiogram for a typical normal heart 
cycle is indicated in Figure 4-2. This curve is typical for the 
limb leads; minor variations are seen in the chest leads. The 
important characteristics of the curve are the P wave, the 
QRS complex, the S-T segment, and the T wave. Important 
time intervals are the P-R interval and the duration of the 
QRS complex. 

Reading the 
ECG Wave 

The P wave results from the activation of the auricles. The 
QRS complex results from the activation or depolarization of 
the ventricles. The S-T segment occurs during the time in 
which the ventricles are in the completely depolarized state, 
and -the T wave represents ventricular repolarization. No 
significance is attached to the U wave which is sometimes 


A specialized form of the electrocardiogram called 
vectorcardiogram (VCG) can be obtained by plotting one 
channel against the other. Figure 4-3 shows a typical 
arrangement for generation of VCGs. A cardiologist trained 
in interpretation of VCGs can tell much about the activities 
of the heart from such a display. 


Typical VCG (leaps I & V^) 

Figure 4-3 VCG Connections 


Actually experiment M093 will analyze the three channels of 
information on a computer to get the information needed. 
Among the things that can be determined by an analysis of 
yCG are the electrical orientation of the heart and its 
movements. This experiment will analyze the VCG taken on 
each of the nine astronauts who fly in Skylab both preflight, 
inflight, and postflight. VCGs obtained while the astronaut is 
at rest and at a number of exercise levels on the ergometer 
will also be analyzed. 

Ergometer — an instrument for 
measuring the force of muscular 


The objective of this experiment is to measure the 
vectorcardiographic potentials of each astronaut periodically 
throughout the mission so that flight-induced changes in 
heart function can be detected and compared with a baseline 
established preflight. 


The equipment consists of the various electrodes and wires 
for "picking up" the voltages from the astronaut's body and 
the electronics equipment for amplifying the voltages, 
protecting the astronaut from electrical shock, and 
conditioning the voltages into the three channels of 


The experiment is scheduled to- be performed every threei 
days on each astronaut. The subject crew member attaches- 
the VCG electrodes, rests on the ergometer for five minutes, 
then pedals for two minutes at a set work rate of 150 watts. ^ 
He then rests for 10 minutes. 


The data, recorded on tape to be telemetered to the nearest 
ground tracking station, consist of the three standard vector- 
cardiogram voltage signals and a heart rate channel, along with 
voice identification of the conditions of recording. 


Section 5 

Energy Expenditure 

Metabolic Activity, 
Skytab Experiment MITI 


The most basic process of living systems is production of 
energy by metabolism. The energy derived from these 
processes is used for physiological and biochemical functions, 
permitting the organism to perform work. 

When an individual is not moving or working and has not 
recently eaten, all of the energy appears as heat. During this 
condition, energy production can be directly measured by 
direct calorimetry. However, this covers only a srnall portion 
of the time when total energy measurements are required. 

Energy Energy production can also be calculated using indirect 

Production calorimetry which measures the oxygen consumed. Since 

oxygen is not stored (except for about one liter as 
oxyhemoglobin and myoglobin in the blood and tissues), its 
consumption keeps pace with immediate needs and is 
proportionate to the total energy produced. One problem 
with using only oxygen consumption as a measure of energy 
production is the fact that the energy released per mol of 
oxygen is dependent upon the food being oxidized. Although 
an estimate of 4.82 k cal/mol oxygen is accurate enough for 
most purposes, the actual values can be determined from an 
analysis of the respiratory quotient (RQ), which requires that 
carbon dioxide production (during steady state conditions) 
be measured simultaneously with oxygen consumption. 

The measurement of energy production through the use of 
indirect calorimetry has been accomplished clinically and in 
the laboratory using two general methods— closed circuit and 
open circuit. Excellent discussions of these two types of 
measurement can be found (Cpnsolazio, et al. 1963; Best and 
Taylor, 1961; Bard, 1961; Bartels, 1963.) In the closed 
system the subject rebreathes from a container of 100% 
oxygen and a carbon dioxide absorber. The oxygen 
consumption is then determined by the decrease in volume of 
the system or by the amount of oxygen added to keep the 
volume constant. If carbon dioxide production is desired, the 
carbon dioxide absorber must be weighed or analyzed, or be 
assessed by a system that determines volumes before and 
after carbon dioxide absorption. Luft (1958) has reviewed 
spirometric methods which have been used for closed circuit 
indirect calorimetry. 

The standard open circuit method of determining metabolic 
rate is based on minute volumes and gas concentrations. 
Usually only expired volume (collected in a spirometer - 
Tissot method; in a bag - Douglas method; or measured.with 
a dry gas meter with a portion of gas being saved for analysis - 
Kofranyi-Michaelis respirometer) is measured and analyzed 
for its oxygen, carbon dioxide, and nitrogen content. From 
these values it is possible to calculate inspired volume and 
therefore Vq , Vqq , and RQ. 

Calorimetry— measurements of 
the amounts of heat absorbed or 
given out 


If man is to be qualified for long duration missions, it is 
imperative that energy metabolism data be collected in flight. 
This is needed because of logistics and life, support 
requirements, as well as the possible physiological 
degradation of work performance. 

Until inflight data can be collected, it is also required that 
energy metabolism and work performance, as well as 
pulmonary function, be evaluated pre- and postflight. Should 
a physiological degradation of ability to do work be evident, 
an acceptable limit of this degradation will have to be 
established. These limits will be determined by required 
activities for the successful completion of a mission, 
considerations relating to the mechanism behind ' the 
degradation, and whether countermeasures are possible. 

Life Support The life support systems both in the spacecraft and the suits 
for EVA operations must be adequate to accommodate the 
functional work capacity (both sustained and transient 
thermal loads) of the typical astronaut. While the work 
capacity in the spacecraft is not likely to exceed that of an 
aircraft pilot in the geogravitational environment, this cannot 
be said of EVA operations, where an emergency may raise 
the metabolic level to that experienced during heavy exertion 
on Earth. Fletcher (1964) has compiled data from several 
sources (Figure 5-1), to show metabolic curves for first class 
athletes and healthy men engaged in exerting activities 
(running, rowing, cycling, etc) under normal atmospheric 
conditions. The design criteria for the life support systems 
for EVA operations should be such as to permit the levels of 
activity shown by Fletcher, thus providing for those 
emergencies which call for. these higher metabolic levels. 

EVA— extravehicular activity 

Time, lir 
0.25 1 3 5 10 

Time, min 

Metabolic Rate 
Btu " Kcal 


i 18,000 

_= 16,000-4,000 
.2 14,000-3,500 

2.0 "1 12,000-- 3,000 
I 10,000-2,560 
6 8,000-- 2,000 


1-0 S 6,000 


^ 4,000--l,000 
0.5 O 

. 2,000- 








Figure 5-1 - Maximum Sustained Work Capacity 



Metabolism has been an area of investigation from the first 
manned missions. During the Gemini Program in the mid 60s, 
a number of the medical investigations were concerned with 
metabolism. Many tests were performed to determine 
whether the crew would become fatigued doing the types of 
activities that had been planned, and whether the life suppoi^ 
system in the spacecraft and in the space suit would be able 
to meet the astronauts' requirements. During these early 
missions, it was learned that there were some significant 
problems. The astronauts became much more fatigued than 
had been expected, tasks were much harder to perform, and 
the possibility arose that under certain conditions the carbon 
dioxide levels in the space suit rose to higher than desirable 
levels. Problems with the design of equipment and the work 
regimens specified for the astronauts were discussed. These 
concerns and investigations continued into the Apollo 
Program, and still many questions remain to be answered. 

Of particular interest is the relationship between the 
metabolic requirements of certain physical tasks in space 
compared to the requirements for the same tasks on Earth. A 
common means of determining these requirements is to 
ascertain the oxygen consumption and carbon dioxide 
production of the body during the performance of the 
specified task. 

These consumption and production rates cannot be measured 
directly at the cellular level where the demand exists. 
Measuring intake and output for the body as a whole is 
considered to represent the aggregate demand for all cellular 
activity. Consumption and production are usually called 
oxygen uptake and carbon dioxide output. The former is 
determined by measuring the amount of oxygen that a 
person breathes in over a given period of time and subtracting 
from it the amount of oxygen that he breathes out over the 
same period of time. The latter is determined similarly: the 
volume of carbon dioxide breathed in over the period is 
siibtracted firom the voluine of carbon dioxide breathed out 
over that same peiriod. For certain types of exercise, the 
oxygen uptake is equal to oxygen consumption and carbon 
dioxide output is equal to carbon dioxide production. By 
properly planning an experinient, the oxygen consumption 
and carbon dioxide piroduction can be determined from the 
oxygen uptake and carbon dioxide output measurements 
(along with other supportive measurements and information). 

By doing such determinations while a subject is performing a 
measured amount of physical work, the relationship between 
metabolic activity and the physical work can be determined. 

Metabolism— the sum of all the 
physical and chemical processes 
by which living organized 
substance is produced and 


Such measurements are commonly done in the laboratory 
taking the measurements yvhUe the subject is performing 
work on a treadmill or an ergorneter, each of which is a 
means of providing known ^mounts of physical work for the 
individual to do. ' 


The objectives of this experiment are to determine if man's 
metabolic effectiveness in doing mechanical work is 
progressively altered py exposure to the space environment, 
and to evaluate the bicycle ergorneter as an exerciser for long 
duration missions. 


Measurements Five major pieces of equipment are used for this experiment. 

1) Metabolic Analyzer determines the oxygen update for 
one minute and five minute periods; carbon dioxide 
output for one minute and five minute periods; minute 
volume, the total gas expired by the subject during a 
one-minute period; respiratory exchange ratio, the ratio 
of carbon dioxide output to oxygen uptake; and vital 
capacity, the measurement of the maximum amount of 
gas that a person expires after a full inspiration. 

2) Ergometer, a controllable workload pedal device, having a 
workload selector and tachometer. The pedals connect to 
the workload which offers mechanical resistance set to a 
desired level. The ergometer measures work rate, the 
actual work rate which the astronaut performs on the 
ergometer; revolutions per minute, the rate at which the 
astronaut pedals the ergometer; and total work 
performed during a given period. 

3) Body Temperature Measuring System electrically 
measures the temperature in the subject's mouth using an 
oral thermistor. 

4) Vectorcardiograph senses three channels of electrical 
signals from the heart and permits heart i:ate to be 

5) Blood Pressure Measuring System comprises a 
microphone and inflatable arm cuff. 


Thermistor — a special type of 
resistance thermometer that 
measures extremely small 
changes in temperature 


The metabolic activity experiment will begin 12 months 
before flight. The experiment will be repeated at one-month 
intervals from '6 months before launch and also 5 days before 
flight. Inflight the experiment will be repeated five tirhes by 

each crewman during the, 28-day flight, and eight times 
during the 56-day flight. After recovery the exercise capacity 
test will be performed oh each crewman as soon as possible 
after recovery and again after 24 hbuirs. If there are any 
significant changes in hietabolic performance during the 
course of the rhissiori, these cHanges will be followed until 
baseline levels are reached. 

Work profiles for this experiment include (1) the subject 
remains relaxed and motionless for 5 minutes, (2) he then 
pedals for five minutes with an energy output fixed at 25% of 
his preflight dietermined rnaximum capacity; (3) the work 
rate is changed to 50% of his preflight maximum capacity, 
and the subject operates the ergorheter at this rate without 
interruption for another five minutes; (6) the work irate is 
changed to 75% of the preflight determined maximum 
capacity and operated at this rate for five minutes; (7) the 
subject stops the ergometer, relaxes, and remains motionless 
for 5 minutes. 


The data retiirn from this experiment will consist of the 
profiles that occur during a prescribed exercise regime in zero 
gravity for the following variables: blood pressure, heart rate, 
vectorcardiogram, and metabolic rate. The metabolic rate is 
computed from measurements of oxygen consumption and 
carbon dioxide piroduction. The data derived from this 
experiment are recoirded on the spacecraft tape recorder and 
transmitted to ground. Manual data recording is available as a 
backup mode. Voice comments are also recorded. Motion 
picture data will be obtained using a 16mm camera. 


Section 6 


Human Vestibular Function, 
Sky lab Experiment Ml 31 

Sleep Monitoring, 
Skylab Experiment Ml 33 


pagf; btank ^ot nmm 

The physiology of the nervous system in man is complex, 
ranging from the sensing and processing of input information 
via the afferent nervous system, to the higher order 
neurological functions haying a poorly understood 
neurophysiological basis, e.g., language, learning, and states 
of consciousness. 

Two investigations being conducted oh Skylab will evaluate 
aspects of the central nervous system and the impact of 
weightlessness. The first, an experiment involving the human 
vestibular apparatus, will investigate the effects of 
weightlessness on the crewman's ability to niaintaih 
perceptual acuity and orientation in sp^ce. This experiment 
will identify changes in the normal functioning of the 
vestibular apparatus after long periods of weightlessness. 

The second investigation will use the electroencephalogram 
(EEG) in an attempt to evaluate the sleep patterns derived 
from the brainwaves in the space environment. This 
experiment should establish whether there are changes in the 
sleep quality or quantity associated with extended flights. 





Body position and movement is perceived principally by 
specialized sense organs in the inner ear, collectively termed 
the vestibular apparatus or the labyrinthine receptors. These 
organs are the otoliths and the semicircular canals. The 
otoliths are stimulated by linear accelerations (including 
gravity) and are the specialized organs for the sensofy 
perception of head tilt relative to the direction of the local 
force field. The semicircular canals sense the magnitude and 
direction of angular accelerations. The brain integrates these 
sensory data inputs to determine and maintain the body's 
posture and orientation. 

The importance of the vestibular organs in day to day 
activities Isecomes apparant if one considers their 
neuroanatomical connections to the- 

1) reticular system, dealing with alertness and attention, 

2) eye muscles, 

3) aiitonomic nervous system, dealing with regulation of 
respiration, heart rate, GI tract motility, etc, 

4) voluntary and anti-gravity body muscles, and 

5) cerebral cortex. 

Cerebral CJortex— the convoluted 
layer of gray substance that 
covers each cerebal hemisphere 


Reaction of 
Astronauts on 

Experimentally produced discrepancy between visuEil, 
vestibulai:, and tactile-kinesthetic spatial perceptions have 
been shown to cause a stressful sensory conflict which, 
depending on the individual, produceis symptoms ranging 
from disorientation to nausea and vomiting. 

Varying degrees of discomfort and disorientation have also 
been noted under conditions of near weightless spaceflight. 
During the first American orbital flight (MA-6, February 20, 
1962) Astronaut Glenn in his pilot report noted that he had 
experienced an illusion of tumbling forward after cessation of 
the initial acceleration of his vehicle and entry into the 
weightless environment. He also noted a false sensation of 
accelerating in a direction opposite to retrorocket firing 
before reentry. 

Astronaut Cooper, referring to his Mercury Flight (MA-9, 
May 15, 1963), has been quoted as having felt 
"... somewhat strange for the first few minutes. . ." after 
which he "readily adapted" and felt "completely at ease." 
Later in the mission, following a short nap, he is quoted as 
awaking "with no idea where I was and it took me several 
seconds to orient myself." He also stated that, with respect 
to sleep, "you have trouble regrouping yourself for a short 
while when you come out of it." He had an experience, 
similar to Astronaut Carpenter's on an earlier flight (MA-7, 
May -24, 1962), when the cockpit seemed to be "somewhat 
differently located in respect to myself," upon onset of the 
weightless state. He felt, during the early part of the first 
orbit, a moving forward in the seat in spite of tightly fastened 
restraint straps, and the equipinent storage kit on his right 
seemed at a different angle relative to him than when on the 
launch pad. He felt that he was sitting upright although he 
later described a feeling of hanging upside down because of 
pressures against his shoulder straps. 

The sensation of hanging upside down from their restraint 
straps was also noted by Russian Cosmonauts Yegbrov and 
Feoktistov (VOSKHOD 1, October 12, 1964) but were 
similarly brief and always disappeared upon the onset of 
reentry acceleration. Cosmonauts Gagarin (VOSTOK 1, April 
12, 1961), Titov (VOSTOK 2, August 6, 1961) and Popovich 
(VOSTOK 4, August 12, 1962) also briefly experienced this 
inversion illusion during their space flights but the 
phenomenon was reported to have had no effect on their 


A more significant feature of early Russian spaceflight 
experience was the apparent motion sickness syndrome 
reported by Titov during VOSTOK 2. After five or six orbits 
he noted symptoms of decreased appetite, giddiness, and 
nausea which were aggravated by sharp head movements and 
reduced by keeping his head still. In spite of the fact that the 

vehicle was probably rotating slowly and that repeated head 
movements comljined with anxiety and the initial inversion 
experiences could theoretically account for the problem, the 
results were interpreted, as from a direct 
"otolithic- vegetative" disorder. Subsequently, a great deal 
more investigation and training was devoted to the 
labyrinthine and proprioceptive systems in the Soviet space 
effort with somewhat ambiguous results. Symptoms as 
dramatic as Titov's were not again reported until the flights 
of Apollo 8 and 9, although temporary motion sickness was 
apparently experienced in a milder forrh by both Fedktistov 
and Yegorov. The eight Eind. fourteen days of Gemini V 
(August 21, 1965) and Gem,ini VII (December 4, 1965), 
respectively, produced no such symptoms in the four U. S. 
astronauts involved, although they experienced an increased 
gravity sensitivity during retrofire and reentry. This apparent 
form of increased vestibular sensitivity disappeared 

Labyrinth — a system 
intercommunicating systems 
canals, such as the inner ear 


Pr opri oceptive— receiving 
stimulations within the tissues of 
the body 

Finally, the nausea and vomiting that occurred during the 
Apollo 8 and 9 flights was almost certainly caused by 
vestibular system malftanctiohs. The relationship between 
these symptoms and the greater freedom of intravehicular 
movement in the Apollo CM deserves careful attention. 

Areas of In- 

Because of the inability to produce conditions of prolonged 
weightlessness on Earth, at least two major areas of vestibular 
investigation are necessary for the qualification of man in 
long duration space flight: 

1) Ensure that permanent otolithic changes attributable to 
spaceflight conditions do not occur; 

2) Ensure that temporary vestibular disturbances will hot 
occur inflight that will inteirfere with crew safety and 
mission success. 

These areas are also significant to the study of man's 
adaptation to rotating space vehicles and artificial gravity 

The experimental approach in Skylab uses a healthy^ 
well-trained subject adapted somewhat to the unusual 
vestibular stimuli he has experienced as an aviator in the 
flight phase. Control groups have been selected so as to 
include some known vestibular defectives. In one test, the 
measurement of angular acceleration threshold, a rotating 
chair device will be used to provide the subject stimuli of 
physiological character, at best unusual in a subgravity 
environment, and a test goggle to measure oculogyral illusion. 
Oculogyral illusion, the most sensitive indicator of threshold, 
is a form of apparent motion that has its genesis in the 
cupula-endolymph mechanism and may be viewed under 
many different circumstances. The test goggle used provides 





the favorable conditions of dimly lighted three-dimensional 
target viewed in darkness and fixed with respect to the 
subject. The expected apparent motion of the target is in the 
direction of accleleration. 

In another part of the experiment, provocative tests will serve 
to evaluate the subject's susceptibility to reflex vestibular 
disturbances and to motion sickness and may, in addition, 
measure his abihty to cope with such disturbances. These 
tests will measure the coriolis sickness susceptibility index 
using, again, the rotating chair but with the subject making 
standardized head motions out of the plane of rotation. 

A unique feature of this test is the method of scoring the 
investigators have developed. This highly effective method 
yields a single value, the index, enabling the investigator to 
make comparisons within and among test subjects. The level 
of severity pf acute motion sickness will, therefore, Jae 
absolutely controlled to a definite end point defined as 
Malaise IIA. (See fable 6-1). The test end point will be fixed, 
while the level of stresses required to reach that end point 
will be measured (number of sequence of head motions and 
rotational velocity). 

Table 6-1 Diagnostic Categorization of Different Levels of Severity 
of Acute Motion Sickness 


16 Points 

8 Points 

4 Points 

2 Points 

1 Point 


or retch- 


Nausea 1 

tric dis- 




Pallor II 


jective warmth 














Headache > II 


Dizziness, eyes 
closed ^ II, 
eyes open III 


Levels of Severity Identified by Total Points Scored 


Malaise A 

Malaise B 




(M IIA) 

(M IIB) 







*AOS = Ac 

Iditional qualifying symptoms I = moderate, 
I = severe or marked, II = slight. 

Epigastric— pertaining to the 

upper middle region of the. 

abdomen, located virithin the 
sternal angle 


Spatial The spatial localization experiment uses the rotating litter 

Localization chair in the static tilt and litter modes, together with the 

otolith test goggles, blindfold, and a reference sphere and 

magnetic pointer. The astronaut's capability to determine his 

orientation is tested with the chair upright as well as tilted. 

The subject is first tilted to various positions relative to the 
spacecraft with his eyes closed and is asked to indicate both 
his perceived direction of gravity and body orientation. He 
indicates this both by setting the direction of an illuminated 
line in the test goggles and by lining up a magnetic indicator 
rod on a handheld sphere. 

In the litter mode, the reference sphere and magnetic pointer . 
and blindfold are used. Tests will investigate orientation 
based upon a sensed g-vector provided by external reference 
cues and internal reference cues. The chair is converted to a 
litter and the subject attempts to align the magnetic pointer 
to an external reference while blindfolded. Settings are made 
with the litter in a horizontal position and with the litter in a 
tilted position. 


The objectives of this experiment are to acquire data to 
validate measurements of specific behavioral and 
physiological responses as influenced by vestibular activity 
under Earth gravity and in free-fall conditions. These studies 
are also expected to determine the crewman's adaptability to 
unusual vestibular conditions, and to predict habitability 
requirements for future spacecraft which may be rotated to 
generate an artificial gravity force leading to unusual coriolis 
forces. Another objective is to measure the accuracy and 
variability in the crewman's judgment of spatial coordinates 
based upon abnormal receptor cues and inadequate visual 

Coriolis Forces— a fictitious 
force used to describe motion 
(aircraft or cloud formation) 
relative to a noninertial, 
uniformly rotating frame of 


The equipment for this experiment consists of-- 

1) rotating litter chair, 

2) proximity device, 

3) blindfold, 

4) otolith test goggle (with a biteboard mounting), 

5) reference sphere with a m^netic pointer. 

The rotating litter chair is a precision motor-driven 
servocontrolled, rotating chair which can be tilted in two 
directions or converted to a litter; however, it is only rotated 
in the upright position. 


The right eyepiece of the otolith test, goggles contains a 
seif-illuminated target with pitch and roll adjustment. The 
target is a slit of light that can be rotated to indicate a roil 
position; a Break in the middle indicates the pitch position; 
and ,a secontl small break at one end indicates polarity. The 
target, the only thing visible to the subject, is illuminated by 
a radioactive source in the goggles. 

The otoiitH test goggle is fastened, to the chair so that when 
the subject .bites on a biteboard and the gogglies are properly 
adjiisted, the head wUl be held in the correct position for the 
test: .- ,. ".-,'• - ■ ■ 

THe reference sphere with magnetic pointer is a device for 
rneasuring spatial localization' using nonvisual clues. A 
magnetic pointer is held against the reference sphere and 
moved by the subject. The subject's judgments are nieasured 
by a three dimensional readout device that allows free 
translatibnal movement. 


Motion Each of. two crewinen will participate in dynamic vestibular 

Sensitivity tests consisting of motion; Sensitivity tests iising the rotation 

litter chair in the rotating nibde to cletermine susceptibility 

to coriolis forces as a function of tirrie ih. weightlessness, and 

to measure serriicircular . canal response thresholds by 

conducting oculogyral illusion (OGI) threshold tests.^ This Oculogyral— pertaining to 

sequence will be done on .5 equally spaced occasions during movement of the eye about the 

the first 28-day mission. Each test sequence requires anteroposterior axis 

approximately 30 minutes per crewman. 

Each of three crewmen will participate in spatial localization 
tests using the otolith test goggles and the rod and sphere 
device. These tests will be performed once early in the 
mission,, once in the rniddle of the mission, and once late in 
the mission. 


During motion sensitivity tests: 

1) test subject symptomatology in accordance with Figure 
6-1 for determination of tirrie course of symptom 
developrhent to the test end point; 

2) experiment data pertaining to chair velocity, direction, 
head motion characteristics, and experimental equipment 

During oculogyral illusion tests: 

1) oculogyral illusion response; 

2) stimulus characteristics— chair acceleration, velocity and 

3) experimental equipment performance data. 

During spatial localization tests: 

1) accuracy of subjects spatial localization and test 
conditions (subjects actual orientation relative to the 
space labs spatial coordinates). 

Motion picture films of the experiment performance in all 
modes will be obtained. 




One of the most dramatic and fundamental ways in which 
the behavior of a mammal can change is in its state of 
consciousness. There is a spectrum of changes from alertness 
through quiet resting to drowsiness to various kinds of sleep. 
These changes in states of consciousness affect the activity of 
the nervous system in many ways. In the last few years our 
understanding of states of consciousness has increased (and 
changed) markedly. 

One way of examining what is going on in the brain is by 

means of an EEG (electroencephalograph). The EEC is a 

recording of the electrical activity from the cerebral cortex. 

It is clear, that the EEG is not just due to action potentials in 

cells, although these probably contribute. Synaptic currents Synaptic— pertaining to the 

play the largest part. There are good correlations between the anatomical relation of one nerve 

EEG and states of consciousness. <=^" *° another 

During alert, attentive activity the EEG is "low voltage, fast" 
i.e., waves of less than 100 microwatts recorded from the 
surface of cortex with frequencies mostly greater than 15 Hz. 
When the subject is in a relaxed state, cpnscious but not 
attentive to anything, the EEG has an alpha rhythm. The 
alpha rhj^hm has a frequency of 8 Hz and amplitude of up to 
400 microwatts. As the subject becomes more drowsy, the 
frequency becomes slower. This is mixed with bursts of 
electrical activity at 10 to 14 Hz lasting a few seconds. In 
some kinds of sleep, the EEG waves are 2 to 3 Hz and about 
400 microwatts. However, in another kind of sleep, the EEG 
is low voltage, fast, almost exactly as in the alert state. AU 
mammals demonstrate this same pattern although the exact 
frequency is somewhat different from animal to animal. 

The arousal mechanism subserves attentive alert behavior and 
the associated EEG pattern. There is an anatomical site that 


governs this activity, the reticular formation of the 
mesencephalon (in the upper brain stem) and the adjacent 
posterior parts of the hypothalamus. This is sometimes called 
the reticular activating center. Electrical stimulation of this 
site causes the animal to become alert, a response that will 
last longer than the duration of the stimulus. Destruction of 
this center produces coma. Among the normal inputs to this 
center are those from all the sensory systems. A single cell in 
this center may be fired by a flash of light, a ringing bell, a 
touch on the skin, or a smell. It is polysensory. This makes 
sense in terms of the function of the center, for any kind of 
sensory stimulation, if sufficiently intense, will cause an 
animal to become alert. 

There are many aspects of arousal. The musculature increases Muscul ture— the muscular 

its tone, and the cardiovascular system is affected. With apparatus of the body, or any 

arousal the sensitivity of most aspects of sensory systems is P^* ** '* 

decreased. This may seem paradoxical, but this eliminates 

irrelevant inputs and presumably allows greater attention 

toward specific sensory inputs. There is no simple 

interpretation of the effects of arousal on the activity of the 

cerebral cortex. Some cells fire more, some less; some are 

more excitable, some are less excitable. 

There are two kinds of sleep. One kind, which we will call 
slow wave sleep, comprises about 75% of sleeping time. The 
other kind of sleep, which we will call paradoxical sleep, in 
humans comes in episodes of 10 to 20 minutes duration 
every 30 to 90 minutes and comprises about 25% of sleep. 
(Paradoxical sleep is also called rapid eye movement sleep or 
REM sleep.) Paradoxical sleep can only be reached by going 
through slow wave sleep. 

Paradoxical Paradoxical sleep is very stereotyped. It starts abruptly, it 

Sleep involves a loss of tone in muscles, except those of the face 

and eyes. The facial muscles twitch and there are rapid 

movements of the eyes. The blood pressure decreases. The 

EEG is low voltage fast frequency. If a human is awakened, 

especially during the early st^es of deep sleep, he will 

usually report a dream. If an animal is awakened as soon as 

an episode of paradoxical sleep begins, another episode of 

deep sleep cannot start again for at least 30 minutes. If 

animals are awakened whenever they begin to have an 

episode of deep sleep, because of this "refractory period," 

they can be prevented from spending much time in 

paradoxical sleep, although their total sleeping time remains 

normal. All animals, after being deprived of paradoxical 

sleep, show an increased proportion of paradoxical sleep the 

next time they sleep. 

A center for paradoxical sleep has been found in the pons 
(part of the brain stem). Stimulation of this site initiates 
paradoxical sleep; destruction of the site prevents paradoxical 

sleep. Norepinephrine, which is presumed to be a synaptic 
transmitter substance, is concentrated in these areas and 
appears to be very much involved in pciradoxical sleep. 

Slow Wave Slow wave sleep (non REM or NREM) can be initiated by 

Sleep stimulation of many parts of the brain. Many other sites 

initiate slow wave sleep if stimulated at about 8 Hz, even a 

peripheral nerve. Slow wave sleep, unlike arousal and 

paradoxical sleep, seems to require that the cerebral cortex 

be present. However, a major contribution to slow wave sleep 

comes from the medulla (part of the brain stem). Serotonin, Serotonin— a constituent of 

which is presumed to be a synaptic transmitter substance, is blood platelets 

concentrated in these areas and appears to be very much 

involved with slow wave sleep. If a barbiturate general 

anesthetic is injected into the blood going to the posterior 

brain's stem (i.e., to the pons and medulla) the animal will 

wake up. If the anesthetic is allowed to go to the more 

anterior part of the brain the animal will be anesthetized, 

which is similar to slow wave sleep in many ways. Slow wave 

sleep and alert behavior are part of a continuum. There are 

many intermediate stages. Paradoxical sleep, however, is all 

or none, with no intermediate stages. 

It would appear that there are three active mechanisms 
involved in states of consciousness. Sleep is not just the 
absence of consciousness. 

The blood flow and oxygen consumption of the brain is the 
same in arousal and slow wave sleep, but is increased in 
paradoxical sleep. There have been a few experiments in 
which recordings have been made from the same nerve cell 
while the animal was spontaneously awake, and then asleep. 
Some neurons fire more during sleep, some less. Most 
neurons fire more during paradoxical sleep. Therefore, the 
brain does not rest in sleep. In fact, it is most active in 
paradoxical sleep, and it is resting when it is awake. The 
common sense view and the scientific view until about 1963 
was that the function of sleep was to rest the brain. Today 
we are not certain as to what the function of sleep is, but we 
do know that it is essential to physical and psychological well 

From the beginning of the space program there has been 
considerable interest in whether the astronaut was getting 
adequate sleep. In order to answer this question NASA has 
been investigating the use of the EEG for inflight monitoring 
of sleep. These investigations include determination of the 
minimum number of brain areas from which signals that yield 
useful information are picked up, and whether an onboard 
computer can be used for performing the analysis, thus 
reducing the complexity of the telemetry system that is 
needed to return data to Earth. A preliminary approach to 


the problem was undertaken to 1965 and continues to the 
present time under the direction of the Principal Investigator 
for this experiment. 


Sleep of 

The primary goal will be to monitor the sleep status of a 
spacecraft crewmember during selected periods throughout 
an extended space mission, utilizing automatic onboard 
analysis of electroencephalogram (EEG) and 
electro-oculograph (EOG) with telemetry of results. Sleep 
profiles will thus be available in the Mission Control Center 
and may be readily evaluated in order to detect any 
alterations in sleep quantity or quality. 


The major components of the experiment equipment are: 

1) cap assembly, 

2) preamplifier and accelerometer assembly, and 

3) control panel assembly. 

The cap assembly precisely fits the astronaut's head and 
correctly positions seven electrodes, which are part of it. The 
electrodes are funnel-shaped, soft "rubbery" devices 
containing electrolyte soaked sponges. The lower portion of 
each electrode is cut off by scissors just before the crewman 
puts on the cap, thus exposing , the electrolyte for proper 
contact with the scalp. A new cap will be supplied for each 
experiment sleep period. 


Three consecutive nights of sleep recording will be required 
of the prime and backup crewmember within 60 days before 
launch, plus a one-hour session in the Principal Investigator's 


A total of 15 selected sleep periods shall be recorded during 
the first (28-day) mission, and 21 sleep periods during the 
second mission (56 days). 

Three nights of sleep recording aire desired oh postflight days 
1, 3, and 5, using the same procedures arid basic equipment. 

The procedure for this experiment is quite simple. On the 
specified nights, before retiring, the astronaut takes a cap 
assembly, cuts the tips off of the electrodes, connects the cap 
assembly to the rest of the equipment, dons the cap, and 
secures himself in the sleep restraint. After checking the 
operation of the equipment he goes to sleep in a normal 

manner. As he sleeps the equipment automatically performs 
the analyses and provides data to the telemetry system. Upon 
awaking he disconnects the equipment, throws away the cap, 
and makes any comments needed in the log and to the voice 
data system. 


1) Copies of all data tapes obtained during preflight and 
postflight baseline testing will be provided to the 
Principal Investigator for analysis. 

2) A log entry is required after each monitored sleep period, 
preflight, inflight, and postflight. This entry, made by 
voice recording, will contain information on the duration 
of sleep, quality of the sleep, and any medication used by 
the subject with 24 hours before the beginning of the 
monitored sleep period. 


Section 7 


Effects of Zero Gravity on Single Human Cells, 
Skylab Experiment SOI 5 

Circadian Rhythm-Pocket Mice, 
Skylab Experiment S071 

Circadian Rhythm-Vinegar Gnats, 
Skylab Experiment S072 


Biological Many biological processes of living organisms are periodic in 

Processes nature. The most well known of these are the circadian 

(daily) rhythms of sleep, body temperature, flower petal 

movements, etc, but there are many other biological 

oscillatory frequencies as well. These rhythms are believed to 

be evolutionary in origin and responsive to terrestrial cues 

such as light/dark cycles. During manned space travel beyond 

his evolutionary environment, temporal factors will have to 

be included as part of the provided environment to avoid 

breakdown of periodicities. Although work/rest schedules 

may be the governing input, there are basic biolo^cal 

questions related to circadian rhythms that may be of 


It is possible to divide circadian rhythm research into four Circadian— pertaining to a period 

categories: (1) occurrence and general characteristics, (2) of about 24 hours 
environmental phase-setting, (3) the basic mechanism, and 
(4) the importance of these rhythms to the organism. 

To summarize briefly: (1) from unicellular organisms to man, 
there are few biological processes that do not demonstrate 
periodicity; and (2) circadian processes have a labile temporal 
relationship wdth the environment and can be phase-set 
(entrained) with appropriate light or temperature stimuli. 

The latter two aspects, however, have • evaded scientific 
inquiry, although many investigators are attempting to 
determine the mechanism of circadian rhythms and the 
physiolo^cal consequence of their disruption. 

Circadian rhythms, rather than being direct biological 
responses to the immediate temporal environment, may serve 
a more basic role in the functioning of living systems. 
Processes must occur not only at the proper place and in 
sufficient quantity, but must also occur at the proper 
time. Thus, the circadian mechanism permits interval 
synchronization of an organism's processes and at the same 
time synchronizes the total organism to its environment. 

A review of the literature on human circadian rhythms shows 
over 50 physiological variables with significant circadian 
variations. Although this variation is only a small percentage 
of the total change for a function such as vital capacity, it 
accounts for the majority of the variation in others such as 
electrolyte excretion. The circadian changes observed are 
often caused by variations in other processes. Thus, it is not 
always possible to determine the direct relationship between 
the observed rhythm and the basic causal mechanism. 

Changes in circadian rhythms may occur during certain 
pathological conditions. In addition, there may be decreased 


psychological performance associated with changes Dysrhythmia— disturbance of 
(dysrhythmia or desynchronization) in circadian rhythms, rhythm 
This phenomena is becoming a well-known effect of rapid 
travel across several time zones. 




There are two theories regarding the basic mechanism of 
circadian rhytiims: (1) they are the result of a completely 
endogenous mechanism (biochemical or biophysical 
oscillator) with other environmental factors, such as light or 
temperature, acting as phase-setters; and (2) they represent 
an organism's response to subtle geophysical fluctuations 
(such as magnetic fields) with li^t and temperature again 
acting as phase-setters between the basic mechanism and the 

The majority of investigators subscribe to the first theory; 
however, the required critical evidence has not been 
collected. The Skylab Program offers an environment in 
which the two hypotheses can be tested, since during orbital 
flight the geophysical variations are no longer available to the 
organism on a 24-hour basis, and during interplanetary flight 
they should be completely absent or greatly distorted. 

At present, there is only suggestive evidence of detrimental 
effects due to disruption of normal rhythms in abnormal 
temporal environments. To date, it has not been possible to 
completely abolish circadian rhythms, only to perturb them. 
If the second hypothesis proves to be true, a completely new 
factor will have to be considered during long duration flights, 
i.e., the lack of a basic temporal coordination mechanism. 

Effects of 
Zero Gravity 
on Single Hu- 
man Cells 



A great deal is known about the behavior of human cells in a 
1-g environment; both normal and abnormal behavior is well 
understood. However, virtually no information exists on the 
behavior of cells in a near weightless environment. 

This experiment to study the influence of weightlessness on 
living human cells is designed to obtain information on cell 
development and propagation by using two different and 
separate methods. 

Observation of 


The first method will be through observation of two living 
cells using microscopes and cameras. These cells will be kept 
alive for the entire mission and returned alive. The cell 
behavior will be periodically recorded during the mission. 
This technique, using phase contrast microscopes (specimen 
does not have to be stained) and time-lapse photographs will 
allow postflight study of the visible portions of a cell. 

of Cells 

Examples of this will be changes in ceU size, cell division 
(mitosis), and changes in size and movement of specific 
particles in the cell (oi^aneDe). Kidney cells will be used 
because they flatten out in the specimen chamber so that the 
nucleus and other particles are easily seen under a low power 

Chemical The second method will deal with the chemical properties of 

^°P^J^'^® cells and will be conducted during periods of rapid growth 

rate. This portion of the experiment will be completed on the 

fourth and tenth days of the mission, at which time the cells 

are fixed and will be held in that condition until they are 

returned for ground analysis. 

The cell chemical study will use 24 separate embryonic lung 
cell cultures. The cells will be allowed to grow for four days 
and ten days, respectively, after the start of the mission. On 
these days various radioactive materials tliat can be 
assimilated by the cell will be introduced into sorhe of the 
specimen chambers at specific times and for specific 
durations. This will mark or label various functions of the 
cells at that psirticular time. After the cells have been labeled, 
excess radioactive material will be rinsed from the chamber 
and all of the cells preserved with a fixative that will hold 
them in that state until they are returned for ground analysis. 

The information that will be gained from this portioh of the 

experiment will be (1) the distribution of chemical 

components in the cell (histochemical), (2) the amounts and Histochemical— chemistry of 

rates of synthesis of various chemical constituents, and (3) tissues 

the ultra structure, or arrangement of the very smallest 

elements of a cell. 


This experirrient will determine effects of near weightlessness 
on living human cells in a tissue culture. 


The expeiiment package consists of two major subsystems 
both " enclosed in a single hermetically sealed package— the 
microscope-camera subsystem and the biopack subsystem. 
See Figure 7-1 for a simplified block diagram showing the 
functions of the experiment. 

The biopacks and the microscope-camera subsystems are 
contained in a hermetically sealed experiment package which 
also includes two clocks that control the automatic 
operations. The two biopacks are enclosed in another 
hermetically sealed container within the experiment package. 


Human Cell 



40X microscope- 



i 4 

20X microscope- 


Biopack 1 

Media Label Rinse Label 




Selector valve 

Specimen |||^|.3|£)|o|g|0|glfl|gl0|g| 

Biopack 2 

Clock 2 

Pressure Shell - 

Figure 7-1 Simplified Schematic of Human Cell Experiment 

The 20X and 40X power microscopes shown in Figure 7-1 
have exposure lamp assemblies that project an image down a 
light-tight tube to a mirror and film gate assembly. The image 
is reflected on the film or in a viewport for ground checkout 
when the mirror is manually rotated 90 degrees. The viewing 
mechanism is used only for ground checkout and is 
spring-loaded to prevent the mirror from being inadvertently 
left in the viewport position after ground checkout. No 
further adjustments are made in flight. 

Each camera assembly operates independently and is 
controlled by separate- internal clocks. Both cameras use 
16mm film for recording microscope images of the cells. 

The two camera asseniblies operate identically. One camera 
photographs time-lapse motion pictures of images from the 
40X magnification microscope. The second camera 
photographs im^es 'from the 20X microscope. A removable 
film pack is used to contain the 16mm film that is required 
for each camera. The two" films travel in opposite directioris, 
thereby maintaining a constant center of gravity. 

Two separate specimen chambers, one for each microscope, 
will provide a temperature-cori trolled environment in. which 
the cells can live. 

Each specimen chamber has an independent media exchange 
assembly to provide firesh nutrients to the living cells. Twice 

Time-Lapse Photography — a slow 
and continuous process at 
regular intervals 


each day (not concurrently with the photographing period) 
fresh nutrients are forced into the specimen chamber and 
waste removed. 

Each of the two specimen chambers contain two thin glass 
coverslips with a molded rubber gasket held between them. 
The specimens are attached to the inside of the coversUp 
nearest the objective lens. Two tubes are attached to the 
coversUp for supplying nutrients, and removing waste 
material from the space between the coverslips. Each 
specimen chamber has a media pump assembly. This pump 
consists of a cylinder, a piston and a lead screw. Twice daily 
the lead screw is turned one revolution to advance the piston 
a short distance into the cylinder. This action forces fresh 
media into the specimen chamber and waste media to the 
return side of the pump. 

The biopack subsystem consists of two independent 
assemblies enclosed in a sealed container inside the 
experiment package. Each assembly controls 12-ceU 
chemistry experiments and each assembly contains 12 ceD 
chambers, a motor drive assembly, a pump for providing 
fresh nutrients and removing waste from the cells, and 
provisions for lalDeling, rinsing, and fixing the cell cultures 
whenever commanded by a crewmember. 


The filming of the living cells is performed automatically. 
The crewman has to check only for the proper operation of 
the camera indicator lamp for the first 10 days. In the other 
part (chemical properties) of the experiment, the crewman 
will operate the experiment manually at the 4- and 10-day 
points to perform the radioactive fluid labeling activities. 

During the mission, the experiment package must not be 
subjected to temperatures above 95° F or below 50° F, or to 
radiation x-ray sources strong enough to damage the film. 


Time-lapse motion pictures of the cell activity, as seen 
through the 20X and 40X magnification microscope, wUl be 
made and the results of the cell chemical analyses will be 
published in study reports, possibly early in 1975. 

Rhythm ■ 
Pocket Mice 


If the stability (precision) or the period of physiological 
rhythms of small mamiiials change significantly during flight, 
then there is a strong indication' that biorhythms of animals 


on Earth are timed by some factor (or environmental force) 
which is absent or significantly altered in space. This change 
in the behavior of pocket mice, along with similar evidence 
from the vinegar gnat circadian rhythm experiment, would 
imply that weightless spaceflight alters the functioning of 
basic control mechanisms for metabolic activity. The 
maintenance of normal biological rhythms in man during 
spaceflight is important to his well-being and effectiveness in 
space. Insofar as we can assume a common response in 
mammalian function, if the pocket mice in space continue 
their terrestrial biorhythms, then we can conclude that space 
conditions impose no stress on the basic biological clock 
mechanism and, that man's performance will not be degraded 
because of rhythm disturbances. 

Body Tem- 
perature and 


The objective of this experiment is to study the circadian 
rhythms of body temperature and activity in pocket mice 
(genus, perognathus) in an environment of constant 
temperature, pressure, and total darkness, and in the absence 
of geophysical variables within a 24-hour period. 


The experiment consists of a sealed animal enclosiire coupled 
to an environmental control system. The animal enclosure 
contains six isolated mouse cages, the biotelemetry receivers, 
and monitoring detector circuitry. The environmental control 
system maintains the mice in a controlled environment of 
constant temperature, pressure, and darkness. 

The cages are cylindrical tanks with porous sealed covers and 
have an internal height of 1.5 inches and a floor area of 18 
square inches. Each cage contains food for the mice. All the 
cages receive equal ventilation from a common air supply. 
Figure 7-2 shows a cross section of the cages. The inside of 
the cage except for the fiberglass tubing is covered with a 
layer of porous material. 

The environmental control system is illustrated in Figure 7-3. 
The environmental control system tank houses a fan to 
circulate the air, a charcoal-lithium hydroxide absorption 
canister to remove carbon dioxide arid ammonia, a dew-point 
control heat exchanger, a moisture separator, and 
temperature control heater. The accessories mounted on the 
tank include an oxygen supply tank and regulators, the fluid 
pump control elements and plumbing for connecting the heat 
exchanger to an external cold plate. The entire experiment 
package is surrounded by a multilayered blanket of 
aluminized Mylar. 

A biotelemeter with a self-contained power source is 
implanted in each mouse to monitor and transmit body 

Pocket mouse- 
4 to 4V2" long 
% to 1/3 oz. 

Biotelemetry— the recording and 
measuring of certain vital 
phenomena of living organisms, 
occurring at a distance from the 
measuring device 




Mouse cage 


Air outlet 


Figure 7-2 Cross Section of Cage 

Heater _ 

To mouse - 
house, air 




Mouse ' Cage 

^llcci ^ 

Mouse ' ^ Cage 

Mouse ^ / Cage a 




Heater control 

Mous^ \ ^Cage 


Lo pressure 

Hi pressure 


Og charging 



J I Li-OH 

Gas absorption 

^ ^ ^ 


charcoal 2 typs. 



To supplemental 
cooling system 

Figure 7-3 Environmental Control System 


temperature information. The animal activity is determined 
from variations in the signal strength as the mouse changes 
position with respect to a receiving antenna in the center of 
each cage. The data acquisition and processing is done by the 
electronics data system. 


The experiment is performed during 28 days of the mission. 
Before launch, 24 pocket mice are placed in a simulated 
flight hardware environment and maintained in a constant 
environment for at least three weeks to document the "free 
running" circadian periods of body temperatures and activity 
of each mouse." Two groups of six mice are selected from the 
24 £ind placed into the two flight units following the baseline 
run. One of the flight imits is placed into the launch vehicle 
while the remaining flight unit is used as a ground control. 
The circadian rhythms of each inouse are continuously 
monitored' from launch for 28 days minirnum while 
continuously maintaining the constant intemal environment 
of the flight hard^yare. 

Additional groups (those remaining from the 24) of pocket 
mice are maintained in a constant environment at the launch 
site, and monitored simultaneously with the flight group for 
body temperature and activity. 




The measurements from this experiment are taken for the 
duration of the mission. Data will be transmitted to the 
ground data stations every 8 hours. Analyses of the data from 
the flight and ground control mice will be reported in a 
science report publishecd about a year after the mission. 



The first formal record of biological rhythms was probably 
made by the astronomer, De Mairan, who in 1729 described 
diurnally periodic leaf movements in plants held in the dark. 
The literature is now replete with evidence of diurnal 
periodicity in many forms of life at many levels of 
organization. Present day research emphasizes on one hand, 
the mechanisms of the so-called "biological clock," and on 
the other, the coupling of the clock to environmental stimuli. 
Whether control of the period of the clock is predominantly a 
physiological oi: environmental phenomenon is debatable on 
the basis of existing data. Theoretically, the study of 
biorhythms in space would permit resolution of the question 
^s to whether terrestrial stimuli indeed set the period or 
simply determine its phase. 

Periodicity — tendency to recur at 
regular intervals 

The principal evidence for external stimuli setting the period 
of the circadiari rhythm is the (1) remsirkable persistence ahd 
precision of the rhythm in organisins kept in constant 
environments apparently free of stimuU that are capable of 
entraining a self-siistainihg oscillation, and (2) the remarkable 
insehsitivity of the free running period to the level of 
temperature (temperature compensation). If the control of 
the period were truly endogenoiis (metabolic), changes in 
temperature should have produced pronounced changes in 
period in poikilothermic organisms; On the basis of these 
observations^ Dr. Frank Brown of NortHwestem University 
has postulated a precise 24-hour component in the circadian 
rhythm resulting from entraihment to some "pervasive 
geophysical force." 

Effect of Zero 
Gravity on 

Most workers, however, believe circadian periodicity to be 
primarily inherent in the organism. Recent evidence 
implicates a role of genetic structure in setting the period, 
loci having been found which can effect an aperiodicity. The 
Sky lab experiment is an effort not so. much to provide a 
definitive answer to the opposing contentions as to shed light 
on the effect bf 2ero gravity and removal from the Earth's 
immediate geophysical parameter on a precisely measured 
biological phenomenon. 

Drosophila eclosion rhythm is the best studied circadian 
system of any organism. Techniques fully developed at 
Princeton University permit the selection of a piipal 
population that would emerge in, e.g., thiree or fouir 
successive peaks of activity separated by a precise circadiari 
period. Methods of assaying the emergence of the adults in 
the weightless state and providing the environmental control 
which the experiment requires have been under study at 
Northrop Corporate Laboratories. 


Drosophila —the fruit fly, used 
extensively in experiment 


The objective of this experiment is to study the circadian 
rhythms of vinegar gnat pupae (genus, drosophila) under 
conditions of weightlessness and in the absence of 
geophysical variables within a 24-hour period associated with 
the Earth's rotation. 


The equipment consists of four pupae compartments, the 
circadian data system and power supply, and the control 

Each cylindrical scaled pupae corhpartment consists 

essentially of a control post that supports 180 pupae on a photosensor-a device sensitive 

plate, scanning lamps, photosensors, a stimulus Ught, a to light 


solution of potassium hydroxide, and environmental 
controls. The pupae plate contains 12 beds equally spaced 
around its periphery. Each bed contains 16 holes. Pupae are 
glued over 15 of the holes so that they completely obscure 
the holes; the 16th is uncovered to monitor the scanning 
light. One hundred ninety-two photosensors are mounted 
under the pupae plate, one for each hole. Twelve of these 
photosensors monitor the scanning lights. 

Each of the 12 beds has an overhead red scanning light that 
transmits through the pupae onto their individual 
photosensors. The detection system can discriminate between 
an empty pupae case and developing pupae which exhibit 
various degrees of transparency during development, but only 
after eclosion is sufficient light transmitted through the 
empty pupae case to activate the detection system. The beds 
are scanned sequentially for 0.5 seconds every 10 minutes. 

The sealed compartments are charged with air of specified 
composition to maintain the pupae throughout the 
experiment. The initial charging pressure is adjusted so that 
when the compartments are heated to their experiment level, 
the pressure will rise to sea level pressure. The carbon dioxide 
concentration and humidity in the compartments are 
controlled by a potassium hydroxide solution. The internal 
temperature is regulated to automatically supply or remove 

A white light provides a stimulus with a wavelength between 
400 to 700 nanometers to the pupae to determine the phase 
of the biological clock controlling eclosion. 




The experiment is performed during the first 20 days of the 
mission. All crew operations are to be performed only upon 
direction from the ground flight controllers. 

In the circadian rhythm-vinegar gnat experiment, a 
population of 720 vinegar gnat pupae divided into 4 groups is 
placed in Earth orbit in a dormant state. When in orbit, the 
pupae are warmed to approximately 20°C to allow 
development. Sometime after the temperatures are stabilized, 
the pupae are exposed to a single 2-minute pulse of white 
light. The light pulse sets the phase of the circadian rhythms 
and establishes the baseline from which the circadian 
rhythms are determined. 

The eclosion of pupae (emerging from puparia) in each of Puparia— pupal cases formed of 
the compartments is continuously monitored until the cuticula of preceding larval 
experiment termination. instars 

In addition to the inflight pupae, an equal population of 
pupae will be housed at the laimch site. These pupae will be 

stimulated simultaneously with the fli^t group, exposed to 
the same controlled environment, and monitored for the 
same data. 

The data acquired from the experiments will be analyzed to 
determine any variance among the circadian rhythms 
observed in the flight group while in orbit and the circadian 
rhythms observed during the baseline run and those observed 
in the ground control groups. A significant digression of 
either the precision or length of the free-running circadian 
periods measured in space from those periods measured on 
Earth would constitute evidence of dependency of circadian 
organization upon conditions of spacefli^t. Conversely, 
continuance in space of the precise free-running circadian 
periods measured on the ground would constitute evidence in 
favor of the independence of circadian organization of 
spaceflight conditions, including weightlessness. 


The data from this experiment are recorded from prelaunch 
until deactivation of the experiment. Data will be transmitted 
to the ground data stations every 8 hours. Results of the 
analysis of this data will be published in a science report 
possibly early in 1975. 


Section 8 

Classroom Activities 

In preceding sections a fundamental tie has been established 
between the Skylab experimental program and the science 
that guides and disciplines man's quest for knowledge about 
himself. In this section, a few classroom activities, discussion 
topics and student experiments which the teacher maj^ 
employ to demonstrate the principles and techniques of 
scientific inquiry are suggested. These simple qualitative 
classroom activities can be coupled with more precise and 
quantitative data and aids from Skylab to enhance the 
educational process. The su^ested demonstrations that 
represent only a very small sample of those which might be 
performed, have been included only to show the scope of 
relevant experimental techniques. 


Body Mass The evolution of the mammalian skeleton has been 

significantly influenced by factors such as gravity, which is 
the primary discussion topic of this section. 

The weight of an animal is proportional to the gravitational 
attraction and. the mass of the body. The relative mass of a 
body is directly proportional to its volume. A very large 
sphere has much less surface in proportion to its volume 
than a very small sphere. If the radius of a sphere is increased, 
its surface increases by the square (A = 4nT^ ), but its volume 
increases by the cube (V = 4/37rr' ). 

The following discussion is adapted from DuBrul* 

The operation of the principle that volume of a sphere 
increases by the cube may be applied in different ways in the 
animal world. Suppose we pretend that the body of an 
animal is like a sphere and that four legs support this sphere. 
The four legs are subjected to pressure from the weight of the 
body. What is the relationship of the thickness of an animal's 
legs to volume of its body? A horse has long thin legs. A 
moose is lai^er than a horse, but its legs seem to be only a 
little thicker. An elephant is still larger, but its legs are 
enormously thicker. Now we are near the upper limit of size 
for living land animals. Not only is the proportion of legs to 
body of these three animals different, but the locomotion is 
also different. The horse has a rapid gallop; the moose a 
slower pace; the elephant a steady plod. 

The African elephant can weigh as much as 6V2 tons. With its 
bone structure this elephant is near the limit of its size, while 
still retaining its mobility. However, a whale, the largest of all 
mammals may weigh forty times as much as an elephant. The 

*DuBrul, E. Lloyd: Biomechanics of the Body, BSCS 
Pamphlet #5, January, 1963, American Institute of 
Biological Sciences, pp 2, 3 


whale's bones arie not proportionately thickened, but they 
aire strong enough because the whale is supported by water. 
Many of the dinosaurs approached whale-Uke size. How were 
they £idapted for survival? 

A discussion of one of the problems that would arise with the 
increase in size of an organism follows. 

If an organism were to double in size, could it retain the same 
structural makeup under Earth gravity conditions? By 
doubling its size, an organism would increase eight times in 
volume (weight) with .only an increase of four times in 
strength of the skeleton. (The strength of a bone is 
proportional to the diameter squared. This scaling restraint is 
discussed more fully in Physics, D.C. Heath & Company, 
i960 edition, p 45 ff, or in the 1965 edition on page 48 ff. 
Reading these pages could lead to an interesting discussion on 
evaluation of organisms under varying gravitational 

Other interesting problems that could be posed for discussion 
purposes are: 

• Are animals possessing no skeletons (invertebrates) 
subjected to the same limitations as vertebrates? 

• How much increase in size or mass would be possible 
before additional skeletal strength would be necessary if 
an organism were transferred to gravity conditions oh the 
Moon (gravity 1/6 Earth's)? 

• The leg bones of one animal are twice as strong £is those 
of another closely related animal of similar shape. What 
would you expect to be the ratios of the animals' heights 
and weights? 

The Concept Because of the problems associated with conducting 
of Cause experiments involving the use of hormones, the following 

Invitations to Inquiry are submitted for discussion topics. 
The soiirce of these Invitations is the Biology Teacher's 
Handbook (John Wiley, 1970), prepared in cooperation with 
the Biological Sciences Curriculum Study. "The teacher 
presents the background of the invitations orally and when 
necessary at the blackboard.* He then poses the problem of 
the invitation arid invites student reaction. Thereafter he 
deals with student responses as they arise, asking diagnostic 
questions which help students see what is vsrrong with poor 
answeirs, reviewing the logic that justifies good responses. 

Physics, b.C. Heath & Company, 1965 p 48 

*BSCS has developed inquiry slides which relate to there 
topics and are related to these invitations. 


Sound responses to early problems of an invitation then lead 
naturally to the next problem in the invitation and the 
procedure of diagnostic and analytical questioning 


Subject: Thyroid Action (p i08) 
Topic: Unit Causes 

'One of the easiest of complications to understand is the fact 
that we can always try to break big causes into little ones. A 
whole gland, such as the adrensQj for example, can be treated 
as a cause. We reinove it and note the consequences of 
removal. Then we interpret these consequences as indications 
of the. normal effects of the adirenal gland. There is nothing 
erroneous about such an experiinent and iriteirpretation, but 
it is certainly incomplete, for we can go ori to divide the 
gland into parts, such as mediilla and cortex, and redo bur 
experiment using one such part at a time. Later, we niay 
analyze still further. Perhaps we would, proceed by 
distinguishing different kinds of cells in the cortex and trying 
to remove one kind of cell at a time— and so on down to 

'Back of this progressive analysis of causes into finer knd 
finer parts is the idea that somewhiere we will arrive at 
irreducible unit causes, or causal elements. However, the 
possibility of such elemented causes does not mean that 
grosser, composite causes, such as whole oi^ans or tissue 
components of organs, are "wrong" or useless. On the 
contrary, they may be very useful, not only in iapplied 
biology, as in medicine, but also in research. 

'Hence, what we want to convey to students is not that one 
level of analysis is better or more "scientific" than another, 
but only that there are many levels.' (p 108) 

Invitation #17 uses this piroceilure to investigate the action of 
the thyroid gland. 


Subject: Parathyroid Action (p 116) 
Topic: Multiple Causation 

This Inyitation illustrates that a given effect may be evoked 
by what appears to be several different causes. 

'This is sometimes referred to as multiple causation, but the 
term is something of a misnomer. It si^gests that several 



genuinely different things or events can cause precisely the 
same effect. This could be the case in nature. However, the 
concept of causation underlying much biological research 
into causes includes the idea that, ultimately, if several 
instances of an effect are identical, the cause will also be 
found to be the same. 

'It follows from this concept that when we think we have a 
case of different causes leading to the same effect, we 
proceed to make finer analyses (either spatial or sequential) 
in order to find what is common to the apparently different 

"Thus, midtiple causation is a complication of enquiry at two 
levels. First, it involves the simple possibility that an event 
may have "several causes." Second, it involves the more 
abstruse notion that several causes may reeilly be one— though, 
of course, the common factor, the "true" cause may be 
located in several places or react in several different 
circumstances, or be involved in several different sequences. 

'In this Invitation we deal with "multiple causation" in its 
simplest form: the idea of the same causal source lying in 
several different locations. We do not introduce the 
complication of an underlying common cause acting in 
different circumstances or throu^ different sequences.' (p 


Subject: Control of Thyroid Secretion (p 128) 
Topic: Inhibiting Causes 

Invitations 17 and 21 have treated causal factors as being 
positive, leading to the appearance or the increase of 
something. This Invitation illustrates the fact that a causal 
factor may be negative and lead to the inhibition of 


Subject: Pituitary— Gonad Mechanisms 
Topic: Feedback Mechanisms 

'This Invitation has two major points. First, it exemplifies the 
fact that experimental tests of hypotheses cannot, as a rule, 
verify them. As a rule we can demonstrate only that the 
hypothesis is not possible or that it might be the case. Only 
when all the possible alternative hypotheses are known can 
experimental test, by eliminating all but one alternative, 
verify that one. This situation is sometimes referred to as 

"the falsif lability, but not the verifiability of hypotheses." 
The point is that we are rarely in a position to say with 
certainty that we know all the possible alternatives. 

"The second function of the Invitation is to add a last item to 
our understanding of cause-effect enquiry: the existence of 
complex 'interactions of causes, 

"The Invitation is based on a real case— the sexual cycle in the 
mammalian female. However, it refers to oi^ans and materials 
only by code letters, A, B, C, and so on. This is done for two 
reasons. First, it makes it possible to use the Invitation at any 
time, since background information is not required. Second, 
it permits us to put our emphasis on the general pattern of 
interaction, rather than on the specific case.' (p 130) 

The previous. Invitations are examples of how students can 
investigate the: 

• function of various glands, 

• relationship among gland organs and the hormones 

• feedback mechanism as a regulator of hormone secretion. 

They stress the role of critical observation and involve 
students in designing experiments, interpreting data, 
formulating hypotheses, identifying problems, and 
performing other tasks related to the investigative nature of 

of Food 

Students may determine the relative caloric content of food 
by using a standard calorimeter or the homemade one shown 
in the sketch. 

Thermometer (Celsius) 
(Do not leave in tube 
while heating.) 

Test tube (bottom 
should be approximately 
2 cm above food. 

Soft drink can - 

Diagram from BSCS Patterns and Processes 1966 p. 78 

Cover cork with 
aluminum foil 


Heart and 

When using a homemade calorimeter, satisfactory results can 
be obtained by following these procedures: 

1) Measure 2/10 gram of food to bie tested and place on the 

2J Place 10 ml of water in the test tube and record the 
temperatiire of the the water; 

3) After the initial reading, remove the thermometer from 
the test tube; . 

4) Ignite the food and place calorimeter over burning food 
with flame directly- under the test tube. Bum food to an 
ash. If flame goes out, repeat steps 1, 2, 3, and 4. 

5) Immediately measure the resulting increase of water 

Note: If water should boU, the amount of water should 
be increased in multiples of ten ; or decrease the amount 
of' food. If the water boils, most of the heat energy is 
being used as heat of vaporization of the water (540 
CEllories per gram); 

6) The caloric content: of the food is calculated as follows: 
change in teinperature (Celsius) x number of ml of water 
= calories present in the amount of food burned. 

Note: This procedure .provides a caloric content in small 
calories . (c). (c is the heat necessary to raise the 
temperature . of I'.mJ of water 1°C.) Theire is a larger 
unit, the kilocalorie or calorie with a capital G, which is 
1000 times as big as the small c calories and is the unit 
commonly used today in specifying caloric content of 

Foods that provide particularly good results include nuts, 
cereals, sugar, and dried bread. 

Students working in paii:s can gather data on heart rate and 
breathing rate Using amount of activity as a variable. One 
student can record the pulse rate and breathing rate of 
another student lying at rest, standing, after mild activity, 
and after more strenuous activity. The data gathered can be 
tabulated in the following form. 

Heart Rate 

Breathing Rate 



at rest 




Class results can be graphed on 6ach activity to illustrate 
individual differences within the class. Average results for all 
activities can be graphed to illustrate the effects of the 
amount of activity on these two body functions. 

The heart of a double pithed frog can be attached to a 
kymograph for observation of amplitude and rate of heart 
beat. (For pithing instructions, see Follansbee Harper Animal 
Behavior, BSCS Laboratory Block, D. C. Heath & Company, 

Kymograph— an instrument for 
recording variations or undula- 
tions, arterial or other 

Laboratory stand 


The heart can be cooled using iced Ringer's solution (a 
solution of salts comparable in composition to the frog's 
body fluid) to slow it down and a chemical, such as adrenalin 
(1 in 10,000), to speed up heart action. 

Physical stimulation, i.e., poking with a pin or small electrical 
stimulation, will also alter the rate. 

Lung Capacity To study the relative lung capacities, the setup shown in the 
sketch can be used. Have students, using a normal breath, 
blow into the rubber tubing and measure the amount of 
water displaced. 

After refilling the jar a second student may i:epeat the 
experiment. For comparative purposes students rhay wish to 
repeat the experiment after filling lungs to capacity and 
exhaling all the air in the lungs to displace the water. 

For more accurate volume measurements, mark the water 
level with a grease pencil, remove the jar, empty it 
completely, and with jar in upright position measure the 
amount of water necessary to fill the jar to the pencil mark. 


Open-mouth jar 

Rubber or 
plastic tubing 

Related to 

This experiment demonstrates the amount of CO2 produced 
under different levels of physical activity. 

Measure 100 ml of water and test for CO2 by adding 5 drops 
of a 1% solution of phenolphthalein. If a pink color appears 
in the water and rernains for at least fifteen seconds, it can be 
assumed there is no acid in the water. If the water remains 
clear, there is acid present and it must be neutralized before 
the amount of CO2 added can be deterrhined. To neutralize 
the water add dilute sodium hydroxide (NaOH) solution drop 
by drop until the water turns slightly pink. Be sure to count 
and record the number of drops requiired. Save the sample of 
water and use it as a control reference. 

1) Have a student lie on his back inhaling through the nose 
and exhaling through a tube which is inserted in a flask 
with 100 ml of water containing 5 drops of 
phenolphthalein for one minute. 

2) Add sodium hydroxide (NaOH) drop by drop as before 
until the pink color appears as in the control solution. 
The difference in the number of drops of NaOH required 
to color the control solution and experimental solution is 
an indication of the amount of CO2 added. 

3) For comparison pvirposes, the experiment can be 
repeated after exercising vigorously for one minute, e.g., 
deep hand bends, running in place, etc. 




4) Additional activity: have the student undergo some 
physical activity such as running up a flight of stairs. (The 
work required to run up the stairs can be calculated if so 
desired.) Then have the student breathe into the 


phenolphthalein solution for the same length of time as 
before. Note the number of drops of NaOH added to 
indicate a change. 

If phenolphthalein is not available, the same relative meas- 
sures may be obtained by blowing into limewater and com- 
paring the amount of precipitate formed when CO2 reacts 
with the calcium hydroxide to form calcium carbonate. 

Students may want to investigate some of the visual illusions 
that are discussed in most hi^ school psychology textbooks. 

Other sense investigations can also be used, i.e., have students 
make a 1-inch grid of washable ink on the palm of the hand, 
back of the hand, and on the forearm. The grid should be 
made up of 1/8-inch squares. By using 3 inch nails, some of 
which have been placed in ice water and some in hot water, 
the students can attempt to map the heat and cold receptors 
in the grids. Note: one student should place the nails for 
another student who is blindfolded. Students must take care 
not to push too hard on the nails or the pain or pressure 
receptors will be stimulated, confusing the experimental 

By compjiring the location and number of receptors in the 
three grids, students can get an indication of the more 
sensitive areas to heat and cold. 

Vestibular The student may perform experiments that provide a 

Apparatus measure of the role and function of the vestibular apparatus 

in maintaining balance and posture. In order to stress this 
body system, the student can be seated in a swivel chair and 
spun "X" number of times. The effect of this stress can be 
qualitatively observed by assignment of selected tasks such as 
walking a straight line, picking up small objects, tossing coins 
into a small bucket, etc. 


English sparrows may be captured during the winter months 
when the photoperiod is approximately nine hours. The birds 
must be sacrificed in order that the gonads may be examined. 
(A painless way to kill the birds is to dip their beaks into the 
fimiesof carbon tetrachloride. Hold the birds beak into the 
opening of a bottle of CCL4 . Students should avoid breathing 
the fumes.) 

Measure the weight and size of the gonads of a male and 
female. This serves as a control. 

The remaining birds are to be placed in covered cages with a 
light and timing device to increase the photoperiod to 13 or 
14 hours. Birds should be exposed to the lengthened 
photoperiod for three weeks. One pair should be kept under 
the 9-hour photoperiod to serve as additional control. 


At the end of the three-week period, the size of the gonads of 
the control and experimental birds may be examined. 

Circadian Circadian periods such as photoperiodicity can be 

Rhythms investigated in the laboratory or classroom. Mice can be 

placed in a cage with an activity wheel. A 24-hour recording 
device attached to the wheel can be used to record the 
number of revolutions and time of day. By using timers to 
control artificial lighting, the photoperiod can be set to cover 
a wide range of light-dark cycles. Analysis of activity 
patterns, light-dark cycles, food consumption, and body 
weight wUl reveal the influence of photoperiod. 


Section 9 

Glossary of Terms 


Aberration Any deviation from the normal number. 

Biastoid Pertaining to embryonic cell forms 

Biorhythm A biologically inherent cyclic variation or recurrence of an event or state, 

such as the sleep cycle, circadian rhythms. 

Cation An ion carrying a charge of positive electricity; therefore going to the 

negatively charged cathode. 

Chromosomal Pertaining to the body in the cell nucleus that is the bearer of genes. 

Circadian Relating to biologic variations or rhythms with a cycle of about 24 hours. 

Colchicine An alkaloid obtained from colchicum. 

Cytogenetics Study of heredity— cytology and genetics. 

Diastolic Relating to the dilation of the heart cavities, during which they fill with 


Diuresis Increased discharge of urine. 

Diurnal Pertaining to day or daylight. 

Endocrine The internal secretion of a gland. 

Endogenous Originating or produced within the organism or one of its parts. 

Epinephrine The chief hormone of the normal adrensil medulla, adrenaline. 

Erythropoiesis The formation of red blood cells. 

Exogenous Originating or produced outside. 

Friability Easily crumbled or reduced to powder. 

Globulin A simple protein found in blood, milk, muscle and seeds. 

Hematopoietic Blood forming. 

Hemolysis The alteration or destruction of red blood cells in such a manner that 

hemoglobin is liberated into the medium in which the cells are suspended. 

Hemostatic Arresting the flow of blood within the vessels. 

Histochemical Chemistry of the tissues. 

Homeostatic The state of equilibrium in the living body with respect to various 

functions and to the chemical composition of fluids and tissues. 


Homeothermic Denoting the warm blooded animals. 

Humoral Relating to the extracellular fluids of the body. 

Hyperbaric Pertaining to pressure of ambient gases greater than 1 atmosphere. 

Hypobaric Characterized by low atmospheric pressure. 

Hypodynamia Diminished power. 

Hypotension Subnormal arterial blood pressure. 

Leukocyte Any one of the white blood cells. 

Lysis Destruction, as of cells by a specific substance (lysin). 

Mesenchymal A pluripotential cell form found between the ectoderm and entoderm of 

young embryos. These cells give rise to any of the connective or 
supporting tissue. 

Microflora Microscopic forms of bacterial life. 

Mitosis The usual process of cell reproduction consisting of a sequence of 

modifications of the nucleus that result in the formation of two daughter 
cells with exactly the same chromosome and deoxyribonucleic acid 
(DNA) content as that of the original cell. 

Morphologic Relating to the science which treats of the configuration or the structure 

of animals and plants. 

Myocardium Heart muscle. 

Neutrophil A mature white blood cell in the granulocytic series. 

Oculogyria The limits of rotation of the eyeballs. 

Orthostatic Relating to or caused by the erect posture. 

Organelle One of the specialized part of a protozoan or tissue cell serving for the 

performance of some individual function. 

Osteoblastic Relating to a bone forming cell. 

Osteoclastic Relating to the activity in the absorption and removal of osseous (bony) 


Otolith Part of the vestibular apparatus (ear stone). 

Parenchymal The distinguishing tissue of a gland. 

Pathologic Diseased. 

Phagocytosis Engulfing of microorganisms, other cells, and foreign particles by 



PoikUotherinic Denoting the so-called cold blooded animals and the plants. 

Reticulocyte A young red blood cell. 

Spatial Relating to space, or a space. 

Steroid Hormone of the adrenal cortex. 

Stressor Any force which stresses the body, organ, or system. 

Systolic Relating to the rhythmical contraction of the heart. 

Venous Relating to a vein or to the veins.