4 Laboratory (Flight Backup Subjects); Flight Simulated (to 30 days)

Primate Life Support System; Primate Physiological Sensors

The rhythmicity of activity levels, metabolism, excretion rates, thermoregulation, and cardiovascular measures persist in terrestrial laboratory conditions where environmental factors such as light, temperature, and humidity are kept in con- stant and unvarying conditions. It is believed that if these circadian processes become arrhythmic or desynchronized a deterioration of the organism can result. As the possibility of desynchronosis of the circadian rhythm and its consequences in the space environment is of great concern, this experiment was designed to study the effect of weightlessness on circadian rhythms.

A variety of parameters measured inflight were analyzed and compared to simi- larly maintained ground-control subjects in order to determine if desynchronosis occurred. Telemetry included implanted sensors for EEG, EMG, ECG, and respiration, vascular catheters to monitor venous and arterial pressures, temper- ature sensors in the brain, and general environmental parameters. Computer programs and plotting techniques were used to estimate periodicity. Due to the rapid changes in parameters recorded during the last thirty hours, only 7.5 cycles of 24-hour rhythms were used in analysis from the 8.8-day flight. Day averaging was the most common method: data obtained during the flight were interpolated to fixed 1.5-hour intervals; an average for a four-day period was obtained; and deviations were plotted to give the parameter a cyclic representation. Time displacement of two such tracings was an indication of an altered circadian rhythm.

All physiological sensors functioned well throughout the flight, and the subject displayed a define desynchronosis in some physiological processes. The pCO₂, brain and body temperatures and heart rate were well correlated and indicated a rhythm of greater than 25 hours; however arterial blood pressure remained at 24 hours. Such internal desynchronization of temperature, cardiac, and respiratory cycles from the blood pressure and the external desynchronization from the imposed 24-hour daily routine may have been detrimental to the well-being of the flight subject. The derangement of the cardiovascular system suggested as a concomitant of space flight, and the desynchronization found in the flight subject, may well have acted together to bring about its rapid deterioration. There was no evidence of this desynchronosis in any ground controls, including Biosatellite simulations lasting up to thirty days. This suggests the existence of a gravity dependent mechanism in the control of circadian rhythm.

Hahn, P.M.: Circadian Rhythms of the Macaca nemestrina Monkey in Biosatellite III. BIOSPEX: Biological Space Experiments, NASA TM-58217, 1979, p. 109.

Hahn, P.M. et al.: Circadian Rhythms of the Macaca nemestrina Monkey in Biosatellite III. Aerospace Medicine, vol. 42, 1971, pp. 295-304.

Hoshizaki, T.: Biorhythms of a Nonhuman Primate in Space. Chronobiology, Igaku Shoin (Tokyo), 1974, pp. 424-428.

Hoshizaki, T. et al.: Circadian Rhythms and Sleep/Wake Activity in the Biosatellite Monkey. Physiologist, vol. 16, 1973, pp. 202-208.

Tejada, R.I. et al.: Analysis of 10 Minutes of Physiological Data from the Biosatellite III from Lift-Off to Orbital Insertion. Aerospace Medicine, vol. 42, 1971, pp. 281-287.

¥ = publication of related ground-based study