Physiology&Behavior,Vol. 51, pp. 585-591, 1992
0031-9384/92 $5.00 + .00 Copyright© 1992 PergamonPressLtd.
Printed in the USA.
Thermoregulatory Responses of Rhesus Monkeys During Spaceflight FRANK
M. S U L Z M A N , * J A M E S S. F E R R A R O , ' ~ I C H A R L E S A. FULLER,~: M A R T I N C. M O O R E - E D E , § V. K L I M O V I T S K Y , ¶
V. M A G E D O V $
A N D A. M. A L P A T O V ~
*Division of Life Sciences, National Aeronautics and Space Administration, Washington, DC 20546, C'Department of Physiology, Southern Illinois University, School of Medicine, Carbondale, IL 62901-6512, ¢Department of Animal Physiology and California Primate Research Center, University of California, Davis, CA 95616-8519, §Institute for Circadian Physiology, 6 77 Beacon Street, Boston, MA 02215, and ¶Institute of Biomedical Problems, Moscow, Russia R e c e i v e d 15 J u l y 1991 SULZMAN, F. M., J. S. FERRARO, C. A. FULLER, M. C. MOORE-EDE, V. KLIMOVITSKY, V. MAGEDOV, AND A. M. ALPATOV. Thermoregulatoryresponsesof Rhesus monkeys duringspaceflight. PHYSIOL. BEHAV. 51(3) 585-591, 1992.This study examines the activity, axillary temperature (T,), and ankle skin temperature (T,~) of two male Rhesus monkeys exposed to microgravity in space. The animals were flown on a Soviet biosateUite mission (COSMOS 1514). Measurements on the flight animals, as well as synchronous flight controls, were performed in the Soviet Union. Additional control studies were performed in the United States to examine the possible role of metabolic heat production in the T~ response observed during the spaceflight. All monkeys were exposed to a 24-h light-dark cycle (LD 16:8) throughout these studies. During weightlessness, T,~ in both flight animals was lower than on earth. The largest difference (0.75 °C) occurred during the night. There was a reduction in mean heart rate and Ta during flight. This suggests a reduction in both heat loss and metabolic rate during spaceflight. Although the circadian rhythms in all variables were present during flight, some differences were noted. For example, the amplitude of the rhythms in T~kand activity were attenuated. Furthermore, the T.~ and activity rhythms did not have precise 24.0 hour periods and may have been externally desynchronized from the 24-h LD cycle. These data suggest a weakening of the coupling between the internal circadian pacemaker and the external LD synchronizer. Axillary temperature
Circadian rhythms
Macacamulatta
THE microgravity encountered during spaceflight produces a number of physiological adjustments including cephalic fluid shifts resulting from the loss of hydrostatic pressure. Humans in orbit show this fluid redistribution as facial puffiness, reduced calf girth, and a reduction in leg volume. This fluid shift has been postulated to contribute to several physiological responses including: space motion sickness, changes in fluid and electrolyte balance, and perhaps decreased muscular function (16). On Earth, recumbency has frequently been used as a model simulating this fluid shift (10,16). It is recognized that such antiorthostasis can alter both skin and core body temperature. For example, recumbency of humans during the daytime produces an elevation in skin temperature and a lowering of core temperature ( 1,8,17). Lower body-positive pressure, another groundbased model for studying fluid electrolyte balance in primates, has also been shown to influence body temperature (2). The regulation of body temperature is also altered when animals are exposed to increased gravitational fields. Hyperdynamic environments, (+G) produced via centrifugation, produce a transient hypothermia in rats (7) and monkeys (4). Hypothermia has also been observed in rats (14) and a macaque (9) exposed
Microgravity
Skin temperature
Activity
to weightlessness during spaceflight. Decreases in body temperature and thermal discomfort have also been reported by the Soviet cosmonauts during spaceflight (18). The circadian rhythm of body temperature is also influenced by altered gravitational fields (5,6). This study was conducted to study the thermoregulatory and circadian rhythm responses of primates during spaceflight. Axillary and ankle skin temperature, as well as activity, were measured in two animals during a five-day Soviet biosatellite flight (COSMOS 1514). Reductions in both temperatures were observed during weightlessness. Further, although circadian rhythms were observed in all variables, the amphtude of the skin temperature rhythm was reduced and the axillary temperature and activity rhythms demonstrated non-24-hour periods. METHODS These studies were conducted using Rhesus monkeys (Macaca mulatta), weighing 3-5 kg. Before collecting data the monkeys were extensively trained for periods of up to 9 months to accept restraint in the flight system for periods of up to 10 days.
t Requests for reprints should be addressed to James S. Ferraro.
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0031-9384/92 $5.00 + .00 Copyright© 1992 PergamonPressLtd.
Printed in the USA.
Thermoregulatory Responses of Rhesus Monkeys During Spaceflight FRANK
M. S U L Z M A N , * J A M E S S. F E R R A R O , ' ~ I C H A R L E S A. FULLER,~: M A R T I N C. M O O R E - E D E , § V. K L I M O V I T S K Y , ¶
V. M A G E D O V $
A N D A. M. A L P A T O V ~
*Division of Life Sciences, National Aeronautics and Space Administration, Washington, DC 20546, C'Department of Physiology, Southern Illinois University, School of Medicine, Carbondale, IL 62901-6512, ¢Department of Animal Physiology and California Primate Research Center, University of California, Davis, CA 95616-8519, §Institute for Circadian Physiology, 6 77 Beacon Street, Boston, MA 02215, and ¶Institute of Biomedical Problems, Moscow, Russia R e c e i v e d 15 J u l y 1991 SULZMAN, F. M., J. S. FERRARO, C. A. FULLER, M. C. MOORE-EDE, V. KLIMOVITSKY, V. MAGEDOV, AND A. M. ALPATOV. Thermoregulatoryresponsesof Rhesus monkeys duringspaceflight. PHYSIOL. BEHAV. 51(3) 585-591, 1992.This study examines the activity, axillary temperature (T,), and ankle skin temperature (T,~) of two male Rhesus monkeys exposed to microgravity in space. The animals were flown on a Soviet biosateUite mission (COSMOS 1514). Measurements on the flight animals, as well as synchronous flight controls, were performed in the Soviet Union. Additional control studies were performed in the United States to examine the possible role of metabolic heat production in the T~ response observed during the spaceflight. All monkeys were exposed to a 24-h light-dark cycle (LD 16:8) throughout these studies. During weightlessness, T,~ in both flight animals was lower than on earth. The largest difference (0.75 °C) occurred during the night. There was a reduction in mean heart rate and Ta during flight. This suggests a reduction in both heat loss and metabolic rate during spaceflight. Although the circadian rhythms in all variables were present during flight, some differences were noted. For example, the amplitude of the rhythms in T~kand activity were attenuated. Furthermore, the T.~ and activity rhythms did not have precise 24.0 hour periods and may have been externally desynchronized from the 24-h LD cycle. These data suggest a weakening of the coupling between the internal circadian pacemaker and the external LD synchronizer. Axillary temperature
Circadian rhythms
Macacamulatta
THE microgravity encountered during spaceflight produces a number of physiological adjustments including cephalic fluid shifts resulting from the loss of hydrostatic pressure. Humans in orbit show this fluid redistribution as facial puffiness, reduced calf girth, and a reduction in leg volume. This fluid shift has been postulated to contribute to several physiological responses including: space motion sickness, changes in fluid and electrolyte balance, and perhaps decreased muscular function (16). On Earth, recumbency has frequently been used as a model simulating this fluid shift (10,16). It is recognized that such antiorthostasis can alter both skin and core body temperature. For example, recumbency of humans during the daytime produces an elevation in skin temperature and a lowering of core temperature ( 1,8,17). Lower body-positive pressure, another groundbased model for studying fluid electrolyte balance in primates, has also been shown to influence body temperature (2). The regulation of body temperature is also altered when animals are exposed to increased gravitational fields. Hyperdynamic environments, (+G) produced via centrifugation, produce a transient hypothermia in rats (7) and monkeys (4). Hypothermia has also been observed in rats (14) and a macaque (9) exposed
Microgravity
Skin temperature
Activity
to weightlessness during spaceflight. Decreases in body temperature and thermal discomfort have also been reported by the Soviet cosmonauts during spaceflight (18). The circadian rhythm of body temperature is also influenced by altered gravitational fields (5,6). This study was conducted to study the thermoregulatory and circadian rhythm responses of primates during spaceflight. Axillary and ankle skin temperature, as well as activity, were measured in two animals during a five-day Soviet biosatellite flight (COSMOS 1514). Reductions in both temperatures were observed during weightlessness. Further, although circadian rhythms were observed in all variables, the amphtude of the skin temperature rhythm was reduced and the axillary temperature and activity rhythms demonstrated non-24-hour periods. METHODS These studies were conducted using Rhesus monkeys (Macaca mulatta), weighing 3-5 kg. Before collecting data the monkeys were extensively trained for periods of up to 9 months to accept restraint in the flight system for periods of up to 10 days.
t Requests for reprints should be addressed to James S. Ferraro.
585
586
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PRE-FLIGHT CONTROL (1G)
A
A
37
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uJ tr < cr ul 12.
40
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