1

llrlwyl e"e -;;/' 206479

FINAL REPORT

NAG2-795

EFFECTS OF CENTRIFUGE DIAMETER & OPERATION

ON RODENT ADAPTATION TO CHRONIC

CENTRIFUGATION

PRINCIPAL INVESTIGATOR

Charles A. Fuller
Cha A. Fuller

TABLE OF CONTENTS

INTRODUCTION 3

Background & Significance 3

Centrifuge Characteristics 5

Project Description 8

METHODS 11

Subjects 11

Protocol 11

Data Collected 12

RESULTS 14

Body Mass 14

Food Consumption 18

Water Consumption 22

Neurovestibular Tests 26

Movement Analysis 27

Body Temperature 28

Activity 37

SUMMARY 47

BIBLIOGRAPHY 48

2
Charles A. Full

INTRODUCTION

Background & Significance

Gravitational Biology is concerned with the functional and structural

alterations that occur in biological systems exposed to altered gravitational

fields. These have been observed in studies using a variety of experimental

approaches, some ground-based and some in Earth-orbit [8].

The principal physical change in orbiting vehicles is the removal of

the effects of Earth gravity -- weightlessness, and understanding this

phenomenon is of critical importance to the continuing development of

gravitational biology. The environment of spacecraft also have other factors

that may modify biological function, such as solar and cosmic radiation,

forces and materials produced in the space station (noise, vibration,

environmental contaminants, etc.), illumination schedule, etc. These

secondary factors may produce separate biological effects, or modify the

effects of weightlessness. An interaction of the effects of ionizing radiation

and gravitational fields has been demonstrated in rats [2,3] and also in

plants and micro-organisms in orbiting satellites [7]. In short term orbital

experiments these extraneous factors may not significantly affect results,

however, in the protracted exposure anticipated with the space station, their

cumulative effects may seriously interfere with the research. It is of critical

importance that any influence of these extraneous factors upon biological

experiments in the space station be identified so they can be separated and

3
Charle Fuller

not be confused with the effect of weightlessness. Provision must therefore

be made for a suitable control as a part of space station experiments. Such

requirements can only be fulfilled by an on-board centrifuge operating at 1

G. If the only biologically significant factor in the space station environment is

weightlessness, the responses of on-board 1 G controls should be the same

as those exhibited by equivalent ground-based controls. The use of onboard 1 G-controls on the space station should be continued until all

variables in the space station environments are identified and determined

not to have interfering biological effects.

The Space Station centrifuge facility will also be utilized for specimen

holding so that the transition to weightlessness and return to 1 G can be

made in a controlled manner permitting careful and repeated observations

of the immediate responses to a 1 G change in the ambient acceleration

field. For this, biological material will be maintained at 1 G from launch and

provision made for its ready transfer to the Space Station environment.

Similarly, it must be arranged for materials maintained under conditions of

weightlessness to be readily transferred to the 1 G centrifuge. Animals and

plants could also be preadapted to other fields: e.g., Lunar, 0.16 G; or

Martian, 0.35 G.

Other potential uses of Space Station centrifuge include: (1)

investigation and provision of counter-measures for gravitational

deadaptation of astronauts; and (2), studies of labyrinthine function in

weightlessness. Potentially, periodic exposure to a 1 G field could prevent
b

Ch2ges k Fuller

or limit the severity of the decompensations seen in circulatory, skeletal and

muscular systems that occur with continued residence in weightlessness. t

In order to determine gravitational effects satisfactorily, it is essential

that a Space Station centrifuge be capable of providing multiple fields

between 0 and 1 G. Observations in weightlessness will establish the

nature of mass-determined biological function, that which is retained in

weightlessness. The difference between observations made at Earth gravity

and in weightlessness will establish the weight-determined biological

function, that which develops under a 1 G gravitational load. However, such

information will be based on only two points of observation, and as such it

cannot be generalized -- and if space biology is to have scientific merit it

must be amenable to generalization. Observations in at least three, and

preferably more, gravitational fields will be necessary for the development of

any generalization, such as determining the kinetics of gravitational

responses.

A multi-field capability of a space station centrifuge is also essential in

determining threshold fields for gravitational responses. It can be

demonstrated that for some biological processes an acceleration field

greater than minimum strength is required to elicit a gravitational response.

Understanding such thresholds is essential to the development of a

coherent science of gravitational biology. Understanding of thresholds for

adaptive responses will also provide information of biomedical concern. The

"permanent presence of man" in space may be jeopardized by human

5
Charles

'

inability to adapt to chronic weightlessness. Artificial inertial fields (artificial

gravity) in future spacecraft or stations may provide the required

countermeasure for our successful habitation of space. Understanding the

threshold-G for various physiological processes will be an essential

contribution in establishing the appropriate fractional-G for such

countermeasures.

Centrifuge Characteristics

In addition to providing an inertial field, centrifuges have other

characteristics that may, if not controlled, confuse the gravitational effects

[9]. The basic physical relationships of a centrifuge are:

a = rc0 2 ; or

G = a/g = rco2/g

where: a is the acceleration (inertial) field;

r is the radius of rotation;

co is the rotation rate (radians/time);

G is the field characteristic (the weight-to-mass ratio); and,

g is the Earth's gravitational constant.

The reciprocal relationship between radius and rotation rate allows

the same field to be developed at infinite combinations of radius and rotation

rate. Whether or not rotation rate has any effect, separate from field strength,

6
Chad Fuller,

upon long-term gravitational experiments has never been adequately

determined. In practice, the possibility of such interference has been

recognized, but avoided by providing a large diameter (usually 4-6 m) which

minimizes any separate effect of rotation. However, in the Space Station,

centrifuge diameter may be limited and any separate rotatory influence must

be identified by ground-based experiments. It is important that any

interaction between rotation rate and G-field be thoroughly explored. Such

information may provide suitable correction factors, or indicate the maximum

fields (for a given diameter) that do not develop interference from rotatory

effects.

Recent work has shown an effect of centrifuge diameter on the rate of

adaptation of feeding and drinking of squirrel monkeys (41. During chronic

centrifugation, after an initial decline, mean daily levels of feeding and

drinking returned towards precentrifugation levels. These variables adapted

towards a steady state level faster on a larger diameter centrifuge. The

amplitude of the body temperature rhythm was similarly affected.

The ratio of specimen stature ("height") to the diameter of rotation also

is important because of potential interference from "head-to-foot" Ggradients in experimental subjects. This complication also has been

recognized by investigators using centrifuges, and similarly avoided by

providing a large diameter of rotation. In a Space Station there will be

dimensional limits upon centrifuge size potentially introducing artifacts in

biological experiments. Consequently, it is imperative that ground-based
Char Her

research be initiated to identify the biological effects of head-to-foot Ggradients. Such information may provide suitable correction factors, or

indicate the maximum G-gradient that will interfere with experimentation.

The latter may limit the numbers of species (on the basis of stature)

amenable to centrifugation on the Space Station.

The movement of organisms within a rotational environment also

produce additional forces which are a function of the direction of movement

[10]. For example, any motion in the plane of rotation of the centrifuge

causes a 900 cross (Coriolis) acceleration equal to twice the relative velocity

times the angular velocity. Thus, this force, which is proportional to angular

velocity, is proportional to centrifuge diameter. Whether Coriolis forces will

be of sufficient magnitude to have an influence on the adaptation and

movement patterns of specimens such as rodents in a small diameter

centrifuge, such as that being planned for space station is unknown.

Ground based studies [1 ] indicate that there is a time-intensity

summation for gravitational effects, so that brief interruptions do not greatly

affect the results of a biological experiment. Experiments which involve a

daily 15 minute interruption in centrifugation (about 1% of a day) will yield

results similar to those from experiments in which the centrifugation is

continuous, but at 99% of the field strength. The variability in biological

response to ground-based acceleration is such that this difference should

not be detected. However, this relationship may not apply in a space station

where the suspension of centrifugation will involve weightlessness,

s
Charles . Ful er

potentially producing a disorientation that may induce separate and

significant biological effects.

Project Description

Data from spaceflight and ground based experiments have clearly

demonstrated the importance of Earth gravity to normal physiological

function in man and animals. The physiological systems that are affected by

exposure to altered gravitational environments include those responsible for

regulation of temperature homeostasis, sleep and biological rhythms.

Understanding the mechanisms of these effects and developing rational and

effective counter-measures to astronaut deconditioning in space require the

investigation of these gravity-dependent systems and functions under

conditions of -long-term weightlessness/microgravity. In order to fully

understand the nature of the interaction of biological systems and gravity, it

is necessary to make repeated observations at several field strengths

between 0 and 1 + G. A centrifuge in an orbiting spacecraft provides the only

method for studies of these gravity-dependent phenomena between

microgravity and Earth gravity. This centrifuge must be capable of

accommodating experimental subjects -- both acutely and chronically.

However, such rotational facilities are not without technical and physical

limitations, which may also prove to be severe biological limitations.

For example, G-gradients are inherent in all gravitational fields. In

man on Earth there is a calculable head-to-foot G-gradient. So the problem

of G-gradients in animals on centrifuges is a quantitative, rather than

9
Char . F ler

qualitative, one. Centrifuge geometry and operation also produce several

irregularities in acceleration fields (i.e., Coriolis forces, cross-coupled

accelerations, starting and stopping accelerations, etc.). These potentially

adverse aspects of centrifugation have not been critically examined; yet,

where rotational radii must be limited, such as in the spacecraft, these

factors may interfere with research objectives and they must be considered

either during design of such centrifuges or as a factor in their experimental

usage. This program examined the influence of variable diameter

centrifuges (1.8 to 6 m) and their operation on the physiology and behavior

of rats These studies measured the responses of these rodents to

centrifugation in a constant acceleration field, but at different radii.

10
Chart A. Fuller

METHODS

In this program we compared the influence of centrifuge diameter

(1.8, 2.5 and 6.0 m) and stopping frequency (daily for one hour or weekly for

seven hours) on the physiology and behavior of the rat. The studies were

performed by measuring the responses of these rodents to centrifugation in

a fixed acceleration field, but at different radii. These experiments provide

data on the influence of: centrifuge diameter, Coriolis forces and stopping

frequency on the adaptation of rats to chronic acceleration.

Subjects: Male Sprague Dawley rats (325g) served as subjects for

these studies. All animals were maintained in an LD 12:12 cycle (12 hours

of light followed by 12 hours of darkness) and a relatively constant ambient

temperature (22-25°C) throughout all phases of the experiment. Each

animal was surgically implanted with a biotelemetry transmitter to allow the

collection of body temperature and activity data. Food and water were

available ad libitum. Animal husbandry chores were performed weekly.

Protocol: Each study consisted of: a 27 day baseline (1 G), 57 days of

the experimental condition (1,5 G, 1.05 G, or 1 G), and a 28 day

postcentrifugation period (1 G). Animal-experimenter interactions occurred

on the same weekly schedule during all portions of the protocol, animal.

During the altered gravitational environment phase of the experiment, the

centrifuges were either stopped daily for one hour (Daily) or once per week

for a 7 hour period (Weekly). Thus, the total time of 1.5G exposure per week

11
Chad e _ r

was the same for both the Daily and Weekly studies. In all, 10 groups (n = 8)

were studied; centrifuge diameters of 1.8, 2.5 m and 6.0 m were used to

generate a 1.5 G ambient force. Two additional control groups were

examined. The first was a 1 G static control group and the second was a

rotational control (SRC) group exposed to 10 rpm on the 6.0 m centrifuge

(1.05 G). Thus, the groups examined were:

1.8m - Daily & Weekly Stop

2.5m - Daily & Weekly* Stop

6.Om - Daily & Weekly Stop

SRC - Daily & Weekly Stop

Control - Daily & Weekly Stop

*Note: Equipment fdilure resulted in the experimental portion of the weekly stop at this diameter being

shortened to 29 days. However, by this time, all parameters had returned to baseline levels.

Data collected: Animals were weighed weekly (at the time of cage

changing) and measures of food and water consumption were made at this

time. While its cage was being changed, several behavioral tests that have

been used previously to test vestibular integrity [5] were performed on each

animal. Four tests of neurovestibular function were performed weekly on

each subject. These were:

Air-Righting Reflex. Rats were held 45 cm above a padded table in a

supine position and dropped. Normal rats would turn and land on their feet,

while rats with vestibular dysfunction would fail this reflex test and land on

their backs.

12
Charle uller

Contact-Righting Reflex. Rats were positioned in, a supine position

and their back in contact with the table surface. A flat sheet of Plexiglas was

placed in contact with the feet. Normal rats would turn to right themselves,

while rats with vestibular dysfunction would attempt to step or walk along the

Plexiglas sheet.

Head Movement Reflex. Animals were held in the air by the base of

the tail for 5 seconds. Normal rats would move their head ventrally in order

to climb upward. Rats with vestibular dysfunction would move their head

dorsally or attempt to spin in a circular rotation.

Elevated Platform Test. Rats were placed on a 15 x 15 cm platform

elevated 45 cm above the table. Rats were tested for the latency to step off

the platform onto the table.

As an additional measure of behavior and to allow for examination of

possible responses to Coriolis forces, 4 animals in each group were

videotaped for 50 minutes at the start of the light portion of the LID cycle.

Activity and body temperature were continuously monitored by

telemetry and these data were collected by microcomputer at 10 minute

intervals. Collecting at this frequency allowed us to examine both the

homeostatic levels of these variables and the daily, or circadian, rhythms.

These data were subjected to cosinor analysis in order to determine the

daily mean, amplitude and phase of the rhythms. ANOVA for repeated

measures was used to compare results between groups.

13
Cha Fuller

Results

The process of adapting to a hypergravity environment is typically

triphasic: there is an initial response, a period of adaptation and, finally, a

new steady-state level is achieved (6]. These experiments were designed to

allow us to examine both the acute response to 24 hours of centrifugation,

and the adaptation to the new G environment. In all variables examined,

with the exception of neurovestibular function which did not appear to be

affected by the level of G-force that was used in these experiments, there

was an immediate response followed by a rapid return back to baseline

values. Each individual variable is discussed below.

Body mass: The average weekly change in body mass is plotted in

Figures 1 (Daily Stop) and 2 (Weekly Stop). The period of 1.5 G is indicated

by the dark line on the x-axis. Onset of centrifugation resulted in a loss in

body mass that is reflected as a negative delta. There was no significant

difference between the responses at the different diameters. The SRC did

not differ from the stationary Control.

14
45

30

is

E 0

cm

is

-30

k

DAILY STOP DELTA WEIGHT

Chars

WEEK OF STUDY

WEEKLY STOP DELTA WEIGHT

45

30

1

J9

5

cn

E 0

cm

_ ,An

,.-

Fig. 2

...... IF ..... 1.8m .

--o-- 2.5m

0 6.Om

- Control

----- SRC

1

0 1 2 3 4 5 6 7 8 9 10 i'l 12 13 141 s

WEEK OF STUDY

15
Chart r

Delta body mass is plotted for the Daily and Weekly regime at each

diameter in Figure 3. At 2.5 and 6.Om the change was significantly different

Fig. 3

so

40

C

^

G

20

a

0

W

a

-20

-40

60

40

U)

20

a

JW

-20

1.8m

T

•

•

♦°s

s

Daily

........I Weekly

2.5m

Daily

• .' '••••••'•. ......... Weekly .,

♦e

-40

0 V

6.Om Daily

40

C

......••. Weekly

i •. • •.. .....

J

W

-20

-40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

WEEK OF STUDY

16
Charles r

between the Weekly and Daily stopping regimens (p < 0.01). Recovery of

weight gain took longer when the centrifuge was only stopped once per

week than when it was stopped daily. This was not the case at the smallest

diameter (1.8m). These same data for the SRC and Control are shown in

Figure 4.

Fig. 4

60

40

20

Q

0 W

-20

-40

60

40

/

U) 20

v

Q 0 I—J

W

0 -20

CONTROL Daily

+♦••+•+•. Weekly

Daily

Weekly s _

s♦

ee++e♦

♦ e

-40

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

WEEK OF STUDY

17
h^

Charles A. Fuller

Food consumption: Food intake was also decreased at the onset of

centrifugation. The average weekly food consumption is plotted in Figures 5

(Daily Stop) and 6 (Weekly Stop). The period of 1.5 G is indicated by the

dark line on the x-axis. Again, there was no significant difference between

the responses at the different diameters. The SRC did not differ from the

stationary Control. Recovery of food intake rate was achieved by the 3rd

week of centrifugation.

18
Charles Uer

DAILY STOP FOOD CONSUMPTION

225

Fig. 5

200

125

100

"T -,

- 1

1

1

...e... 2.5 m

—^— 6.Om

Control

----- SRC

2 3 4 5 6 7 S 9 10 11 1 2 1:1 1 4 1 5

Y 175 d

d

3

H

om 150

WEEK OF STUDY

WEEKLY FOOD CONSUMPTION

225

Fig. 6

200 T T T T

r T

175-'^- 1

^'^~^ .•r

^ ^ 1 T

1

E 150- t T T 1 y =

l

°f

—+-- 1.8 m

125- 

- --o. - - 2.5m

6.Om

Control

-- SRC

100

0 1 2 3 4 5 6 7 8 9 10 11 1 2 1'3 14 1 5

WEEK OF STUDY

19
200

N

C'3

150

Chad s

Weekly food consumption is plotted for the Daily and Weekly regime

at each diameter in Figure 7 and for the Control and SRC in Figure 8. i

Fig. 7

1 .8m Daily

•s ......•°. Weekly

e

^e

v e.u.uv ••eves...•°°•e

225

200

N 175

150

125

100

100

225

6.0m —e Daily

200-........ Weekly

175

N

es..eye • v^

150 • °°. • °•es.ee.e e•

...es.e..vv

125

100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 115

WEEK OF STUDY

20
C a ufler

Fig. 8

225 k

200

N 175

CO

150- ...........

-----rs••-

125

100

225

SRC

200

175- ; • .,..•• N

0 150 Daily

125 ......••. Weekly

100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

WEEK OF STUDY

21
..I

Chade ss A. Fuller

Water consumption: Water intake presents a much more irregular

pattern than body weight or food consumption. Average weekly water

consumption is plotted in Figure 9 (Daily) and Figure 10 (Weekly). Water

consumption did decrease with the onset of centrifugation, but recovery was

accomplished more quickly. Again, neither centrifuge diameter nor stopping

frequency appeared to affect this variable.

22
350

300

Y

m 250

N

E

200

150

a

,,^ —^-- 1.8m Fig. 10 ---a-- 2.5m

6.0 m

",l,

T

Control

----- SRC

T T

/ ♦ / ♦ ,/ t

1

O 1 2 3 4 5 6 7 S 9 10 11 12 13 14 i!i

DAILY STOP WATER CONSUMPTION

C

t

150

Fig. 9 .n 1.8m

0... 2.5m

—0 6.0m

Control T

----- SRC

1z

♦

pp

•, 1

1

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1j

350

300

Y

3 250

E

200

WEEK OF STUDY

WEEKLY STOP WATER CONSUMPTION

WEEK OF STUDY

23
Ch r

Weekly water consumption is plotted for the Daily and Weekly regime

at each diameter in Figure 11 and for the Control and SRC in Figure 12.

Fig. 11

350

300

NJ

250

200

150

350

300

J 250

1.8m

Daily

••••• n ••. Weekly

• i

e•ee,•ee•

°♦ Ne•eee es •

♦ ^°

•>eeAe•

•°• Daily 2.5m ; ••.

• ........^ Weekly

"Oor—A

200

150

37V

300

N 250

J

200

150

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

WEEK OF STUDY

24
Charl . A. Fuller

Fig. 12

i

350

300 .....°°°' Weekly

250

200

150

350

SRC

-^ Daily

300 .°°°°°°°. Weekly

250

200- : •.••

150

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

WEEK OF STUDY

25
Ch II r

Neurovestibular tests:

Air-Righting Reflex. There were no abnormal responses to this test. `

Contact-Righting Reflex. There were no responses to this test that

indicated neurovestibular dysfunction.

Head Movement Reflex. The only abnormal responses to this test

were seen in the 1.8m diameter subjects. Over the seven week period of

centrifugation, there were a total of four abnormal responses during the

Daily Stop regime and two during the Weekly Stop regime.

Elevated Platform Test. This test produced the most "abnormal"

responses and the results are summarized in Table 1. However, given the

following: nearly one-third of the responses occurred in the three weeks of

baseline data collection, approximately one-fifth of the responses occurred

in the stationary Control group and the testers' observed that the rats were

often "sliding down the leg of the platform like a fireman," we have

concluded that these results do not indicate neurovestibular compromise.

26
C F Uer

Table 1

Week I 1.8m 12.5m I 6.Om I Control I SRC

Dly Wkly Wkly Dly Wkly Dly Wkly DI Wkl

1 - 4 - 3 3 0 1 - 1

2 - 0 - 0 0 0 1 - 0

3 - 0 2 1 1 1 3 - 0

4 3 1 0 1 0 0 1 3 0

5 2 4 0 1 0 0 0 3 0

6 1 1 1 1 1 0 0 0 0

7 1 0 0 2 0 2 0 0 0

8 1 0 - 1 0 1 0 0 0

9 0 0 - 0 2 1 0 0 0

10 0 1 - 0 1 1 0 0 0

11 0 1 - 0 1 0 0 0 0

12 0 2 0 1 0 0 0 0 0

13 0 1 2 1 2 1 0 0 0

14 0 0 0 1 0 0 0 0 0

15 0 1 - 1 0 0 - - -

We would attribute these results to the relatively low hype rgravitational force

that is being introduced.

Movement analysis: A preliminary analysis of the video records was

made examining: linearity of movements, number and direction of rotation

movements, total movement time, length of distance traveled, and pattern of

movement. This analysis of the videotapes revealed an initial (one day)

suppression of activity caused by exposure to centrifugation. However, after

activity resumed, it did not appear that any of the analyzed variables were

altered. Given the responses to the neurovestibular tests, these data were

unsurprising and further analysis of the tapes was deemed unproductive.

27
Char) Fuller

Body temperature: These data were subjected to cosinor analysis; a

cosine curve was fitted to each successive 24 hour interval of data. The

mean, amplitude and acrophase (time of peak of the cosine curve) were

determined. Each of these variables is discussed below.

Daily Mean Body Temperature: Data from days 21-49 are shown in

Figures 13 (Daily) and 14 (Weekly). This time period encompassed the last

6 days of precentrifugation and the first 22 days of 1.5G exposure. There

was an initial depression of the daily mean body temperature at the onset of

centrifugation. This depression occurred at all diameters. Recovery back to

baseline mean body temperature was generally accomplished within one

week.

28
3

37.:

U0

w 3

H

a 36.

2

W

3

35.

s

Fig. 13

1r 1.8M

i

r 2.5M

i ------ 6.OM

•--- CONTROL

g ---- SRC

i

21 28 35 42 4 9

DAILY STOP - TEMPERATURE MEAN

DAY

WEEKLY STOP - TEMPERATURE MEAN

38

V 37.5

WQ

H

cr- 37

WCL

mW

0 36.5

O

m

Z

w 36

35.5

a

Fig. 14

- • --- - ---- 

1.8M

2.5M

1

i

------- CONTROL

-- _ - SRC

21 28 35 42 4'

DAY

29
V 37.5

w

= 37.0

36.5

w

CLw 36.0

N

35.5

—..— Daily

Weekly

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

38.0

00

37.1

Q 36.:

w

a- 36.1

w

1" 35.:

7 14 21 28 35 42 49 56 63 70 77 84 91 981-05

00

M 37.0

M

H

36.5

w

M 36.0

w

f-

-s Daily

Weekly

35.5

Chart r

The mean daily body temperature is plotted vs. day of the study for the

Daily and Weekly Stopping at each diameter in Figure 15.

Fig. 15

38.0 1.8M

38.0-r

6-.OM

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

DAY

30
Uj 37.0

H

< 36.5

w

CL 36.0

W

~ 35.5

Daily

Weekly

Chad Fuller

The mean daily body temperature is plotted- vs. day of-the study for the

Control and Slow Rotational Control in Figure 16.

Fig. 16

38.0

CONTROL

V 37.5 0

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

38.0

V 37.5

U'

Q 36.5 CC

W

CL 36.0

W

~ 35.5

-- Daily

Weekly

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

DAYS

Amplitude of the Body Temperature Rhythm: Onset of centrifugation

resulted in a reduction in the amplitude of the body temperature rhythm.

Rhythm amplitude gradually returned to pre-centrifugation levels. These

data are shown in Figure 17 (Daily Stopping), Figure 18 (Weekly Stopping),

Figure 19 (Daily vs. Weekly by diameter) and Figure 20 (Control and SRC).

31
Ch ler

DAILY STOP..- TEMPZRATU.RE--AMPLITU-DE----- 

1

0.8

w 0.6

D

FJ

a

a 0.4

0.2

IFig. 17

k

1.8M

2.5M

------- 6.0 M

------- CONTROL

-- - - SRC

!1 28 35 42 4i i

DAY

WEEKLY STOP - TEMPERATURE AMPLITUDE

1

0.75

W

O

0.5 J

a

a

0.25

Fig. 18 1.8M

2.5M

------ 6.0m

-----•- CONTROL

---- SRC

0

!1 28 35 42 49

DAY

32
t

I "r.11l^

f

Ch A. Fuller

Fig. 19

0.8

0.6

w

0

t- 0.4 J

CL

m

Q 0.2

0.0

1.00

0.f

w

G 0.F

H

-i 0. o.

e 0.:

0.0

0

0.7

0.6

w 0.5

0.4

H

a 0.3

a 0.2

0.1

0.0

0

7 14 21 28 35 42 49 56 63 70 77 84 91 98105

7 14 21 28 35 42 49 56 63 70 77 84 91 98105

7 14 21 28 35 42 49 56 63 70 77 84 91 98105

DAY

33
Ch^ A. Fuller

Fig. 20

0.6

0.5-#

CONTROL i"

w

i 1

0.4,`

a 0.3

Q

0.2 _Daily

Weekly

0.1

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

0.7

0,6 SRC

0.5-

0.4

H

CL 0.3,

,Q 0.2 Daily

0.1 Weekly

0.0

0 7 14 21 28 35 42 49 56 63 70 77 84 91 9 81 05

DAY

Phase of the Body Temperature Rh)dhm: The timing of the body

temperature rhythm was also altered at the onset of centrifugation, and as

did the mean and amplitude, the timing of the rhythm also recovered back to

the baseline values. These data are shown in Figures 21 (Daily Stopping),

22 (Weekly Stopping), 23 (Daily vs. Weekly for each diameter) and 24

(Control and SRC).

5

34
Chade 'filer

DAILY STOP - TEMPERATURE PHASE

40

35

in

x

x

 30

Wcn

Q

x

a

25

20

Fig. 21 1.8M

2.5M

!i ------ 6.0M

------- CONTROL i-

---- SRC

!1 28 35 42 4.

DAY

WEEKLY STOP - TEMPERATURE PHASE

45

Fig, 22 1.8M

-- 2.5M

40

------ 6.OM

CONTROL

cn 35 1 ---- SRC

x

Wcn

30

a

25

-- - - - - - - ----

20

!1 28 35 42 49

DAY

35
Charles A. Fuller

Fig. 23

40

1.8M

--- Daily

35- _ A Wsaokfu

cn

cc

z 30

w

cn

= 25

CL

20

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

45

2.5M

40 -- Daily

cn 35

Weekly

W 30

a

25- CL .

20

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

40

6.OM

-- Daily

35- Weekly

N

30- ii

Ui

cn

2

25-

a

20

14 21 28 35 42 49 56 63 70 77 84 91 98105

DAYS

36
Char - ler

Fig. 24

30

CONTROL

28

JN

w,

a

CL 24 Daily

Weekly

22

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

28

SRC Daily

26

Weekly

!r

24-

w

Cn

a.

20

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

DAY

Activi : The activity data were also subjected to cosinor analysis. In

general, the response of the circadian rhythm of activity paralleled that of the

body temperature rhythm, i.e. an initial decrease in mean level and

amplitude coincided with altered phase control. These variables all returned

to baseline levels.

.Daily Mean Activity: Data from days 21-49 are shown in Figures 25

(Daily) and 26 (Weekly). As in the body temperature rhythm, at all

37
w

Charles A. F r

diameters, an initial depression of daily mean levels was followed by a

recovery back to pre-centrifugation levels.

DAILY STOP - ACTIVITY MEAN

e^

z 6

0

H

Z 4

O

U

ra

Fig. 25 1.8M

--- 2.5M

------ 6.OM

---- SRC

0-' ^- - {• -

0

21 28 35 42 49

DAY

WEEKLY STOP - ACTIVITY MEAN

60

Fig. 26

50

z

0 40

• - -- •^^ ------ H

Z

0 30

v

r 1.8M

~ 20 2.5M ha

c^ ------ 6.0 M

10 " SRC

>_1 28 35 42 4 9

DAY

38
0 30 r

N

F— 20 z

V 10

0

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

DAY

40 z

2

Charles A. Fuller

The mean daily activity at each -diameter is - shown- in Figure-27. - - - - —^

a

Fig. 27

60

z 50

2

0 40

T

30

z

v 20

10

1.8M

yy;;!

+f

Daily

Weekly

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

80

70 M Daily

z 60- Weekly

E

0 50-

z

30

0 20

r

10 NNII

50 0 7 1 4 21 28 35 42 49 56 63 70 77 84 91 98105

39
z

61

i

0

51

T

H 4'

z

v 3'

Charles

Mean daily activity for the Control and SRC groups are plotted in Fig.

28. i

Fig. 28

2500

z 2250

2

0 2000

Z 1750

M

v 1500

CONTROL

-- Daily

Weekly

1250

0 7 1 4 21 28 35 42 49 56 63 70 77 84 91 98105

70

20 -'r--r--r r—T i

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

DAY

Amplitude of the ActivityRhythm: Data from days 21-49 are shown in

Figures 29 (Daily) and 30 (Weekly). As in the body temperature rhythm, at

all diameters, an initial depression of rhythm amplitude was followed by a

recovery back to pre-centrifugation levels.

40
DAILY STOP - ACTIVITY AMPLITUDE

60

1.8M

50 2.5 M

------- 6.0 M

40 ---- SRC

Char A. ler

w

0

tom- 30

J

a.

2

a

20

10

n

9

DAY

WEEKLY STOP - ACTIVITY AMPLITUDE

40

30

WO

20 J

a

Q

10

0

9

Fig. 3,0^

r `i tt --' 1

r _ t ^ t ^ 1

r

'^--y

tt ' ^ ^ - ., 1 ,' ^ t

r ' ^ 1

i 1 t /`^ t ! t

' t o t !

2.5M ^'^w' v

------ 6.OM

---- SRC 'v

21 28 35 42 4

DAY

41
30

w

D

20

J

CL

2

< 10

Cha A. Fuller

Activity amplitude data for each diameter centrifuge are shown in Fig 31.

Fig. 31

40

1.8M

w 30

2A. D i

20 J

a

a 10 -- Daily

Weekly

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

60

50 J %2.5M

i

-Daily

w 40 --

0

H 30

J

CL 20

0

0 7 1'4 21 28 35 42 49 56 63 70 77 84 91 9810 5

40

0 7 1 4 21 28 35 42 49 56 63 70 77 84 91 98105

DAY

42
04

0

40

35

0 30

E- 25 M

CL

B 20

15

10

Charles . Fuller

Activity amplitude data for the Control and SRC groups are shown in Fig 31.

Fig. 32

2000

1500

w

0

~-1000

J

CL

2

a 500

-- Daily

Weekly

CONTROL

7 14 21 28 35 42 49 56 63 70 77 84 91 98105

d)' r ^

Ig i

3

r

Daily

Weekly

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

DAY

Phase of the Activity Rhythm: These data are shown in Figs. 33-36,

following the same pattern; i.e. Daily stop for all groups (33), Weekly stop for

all groups (34), Daily vs. Weekly for all centrifuges (35) and Daily vs. Weekly

for Control and SRC (36).

43
Chart r

DAILY STOP - ACTIVITY PHASE

i

1.8M

Fig. 33

2.5M

r ------ 6.0 M

,

------ CONTROL

---- SRC

n

r

40

35

cn

w 30

Q

a

25

20-4-

21 28 35 42 49

DAY

WEEKLY STOP - ACTIVITY PHASE

40

Fig. 34 1.8M

2.5M

35 ------- 6.OM

: , CONTROL

N ---- SRC

2 r'

uj 30

cn

I

'l-- -^' - ice. ,•i^^^'-^^^^ "`

20-4-

21 28 35 2 4

DAY

44
3^

U)

31

w

U)

a

= 2 a

35

30

W

N

Q

CL 25

Charles A. F Iler

40

35

30

W

Cl) a

CL 25

Fig. 35

1,8M Daily

Weekly

^t

20

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

40

20

40 -7

7 14 21 28 35 42 49 56 63 70 77 84 91 981 05

20 -1 --ter– —1 1 1 a I I T—r—r--^

0 7 14 21 28 35 42 49 56 63 70 77 84 91 98105

DAY

45
k 30-

28-

cc

26-

ui Am I

W

A 

^ i ^ ^^ ^

2 ^ (n

CC.

21

U.1

cn

2 CL

Charles A. Fuller

Fig. 36

cL 24 - Daily

Weekly

22 1 1 0 7 1 4 21 28 35 42 49 56 63 70 77 84 91 98165

30

22 1 1 1 1 1 1 i I I I I 0 7 1 4 21 28 35 42 49 56 63 70 77 84 91 981 05

DAY

46
Charles . Fuller

SUMMARY

k

This study examined the responses of rats to centrifugation in a

constant acceleration field (1.5 G). Centrifuge diameter (1.8m, 2.5m or 6.0m)

and schedule of operation (Daily or weekly stop) varied between groups.

Body mass, food consumption, water consumption and neurovestibular

function were measured weekly. Body temperature and activity were

continuously monitored using telemetry. A subset of subjects were

videotaped (50 minutes per day) to allow for movement analysis.

Exposure to a hyperdynamic field of this magnitude did cause the

expected depression in the physiological variables monitored. Recovery

was accomplished within a relatively rapid time frame; all variables returned

to precentrifugation levels. In general, the magnitudes of the changes and

the rate of recovery were similar at different centrifuge diameters and

stopping frequency. There were cases, however, in which the magnitude of

the response and/or the rate of recovery to a new steady-state were altered

as a result of centrifuge diameter.

In summary, these results indicate that stopping frequency has little, if

any, effect on adaptation to chronic centrifugation. However, the angular

velocity (co), and therefore centrifuge diameter is an important consideration

in the adaptation of an organism to chronic centrifugation.

47
Charles A. Fuller

BIBLIOGRAPHY

1. Burton, R. R., and A. H. Smith, 1972. Stress and adaptation responses

to repeated acute acceleration. Am. J. Physiol. 222:1505-10.

2. Casey, H. W., et al., 1967. influence of chronic acceleration on the

effects of whole body irradiation in rats. Aerospace Med. 38:451-57.

3. Edwards, B. F., 1963. Effects of radiation and supragravitational forces

on growth. Doctoral Thesis, Emory University.

4. Fuller, C. A. , 1985. Influence of exposure to a prolonged

_ hyperdynamic field on body temperature in the squirrel monkey. The

Physiologist. 28:S157-58.

5. Ossenkopp, K., A. Prkacin and E. Hargreaves, 1990. Sodium

arsanilate-induced vestibular dysfunction in rats: Effects on open-field

behavior and spontaneous activity in the automated Digiscan

monitoring system. Pharmacol. Biochem. & Beha y. 36:875-881.

6. Oyama, J., 1971. Effect of artificial gravity on thermoregulation,

respiratory metabolism and intermediary metabolism in animals. In:

Regulatory Biology. Depressed Metabolic States. NASA TM-X-69354,

[Washington, DC], pp. 27-51.

7. Saunders, J. F., ed., 1971. The Experiments of Biosatellite II. NASA SP204 [Washington, DC].

i

48
Charles r

8. Smith, A. H., 1992. Centrifuges: their development and use in

gravitational biology. ASGSB Bulletin 5(2):33-41.

9. Smith, A. H., 1983. The role of chronic acceleration in gravitational

physiology. The Physiologist 26(6, Suppl):47-50.

10. Stone, R. W., 1973. An overview of artificial gravity. In: NASA SP -314

[Washington, DC]. p. 23-33.

49