Gravity and light effects on the circadian clock of a desert beetle, Trigonoscelis gigas.

Circadian function is affected by exposure to altered ambient force environments. Under non-earth gravitational fields, both basic features of circadian rhythms and the expression of the clock responsible for these rhythms are altered. We examined the activity rhythm of the tenebrionid beetle, Trigonoscelis gigas, in conditions of microgravity (microG; spaceflight), earth's gravity (1 G) and 2 G (centrifugation). Data were recorded under a light-dark cycle (LD), constant light (LL), and constant darkness (DD). Free-running period (tau) was significantly affected by both the gravitational field and ambient light intensity. In DD, tau was longer under 2 G than under either 1 G or microG. In addition, tauLL was significantly different from tauDD under microG and 1 G, but not under 2 G.

[Sand-desert tenebrionid beetle Trigonoscelis gigas reitter: a promising biological model for space chronobiology]. / Pustynnyi zhuk-chernotelka Trigonoscelis gigas reitter: perspektivnyi bioob''ekt dlia kosmicheskoi khronobiologii.

The beetle proposed for studying has a unique feature: unusually precise and reliable circadian clock that evolved as an advanced adaptation to extreme arid environment. Consequently this clock became functionally similar to that of vertebrates, i.e. it has a narrow range of entrainment, stable free-running period, strong endogenous component of rhythm. This beetle is also using due to its high viability, good tolerance to housing and handling, small size and safety in use. Space flight experiments with beetles on BION, PHOTON satellites and on MIR orbital station proved that parameters of circadian rhythms are dependent upon gravity. Future studies will focus on electrophysiology and comparative ecology of these beetles. This biological species together with developed methods represent a new promising technology of research in gravitational chronobiology.

Circadian rhythms in Macaca mulatta monkeys during Bion 11 flight.

Circadian rhythms of primate brain temperature, head and ankle skin temperature, motor activity, and heart rate were studied during spaceflight and on the ground. In space, the circadian rhythms of all the parameters were synchronized with diurnal Zeitgebers. However, in space the brain temperature rhythm showed a significantly more delayed phase angle, which may be ascribed to an increase of the endogenous circadian period.

Thermal regulation in Macaca mulatta during space flight.

The results of studies of body temperature and thermal regulation in Macaca mulatta flown on biosatellites Bion 6-11 are presented. The effect of microgravity on deep body temperature as compared to skin temperature was investigated. In most animals, deep body temperature declined moderately and then tended to return to normal. Brain temperature/ankle temperature correlation changed. The system of thermal regulation was found to function adequately in space.

[Noncontact system of bugs motor activity recoding]. / Beskontaktnaia sistema registratsii dvigatel'noi aktivnosti zhukov.

A noncontact system for recording the motor activity of beetles is based on utilisation of infrared radiation. The system and digital PC input-output card DIO-96 were integrated into a 96-channel computerized facility to maintain, monitor and perform circadian studies of insects which was experimentally tested.

Effects of microgravity on circadian rhythms in insects.

NASA: The desert beetle Trigonoscelis gigas Reitt. was used as a biological model in studies that examined the effects of space flight on the circadian timing system. Results from studies aboard the Bion-10, Bion-11, and Photon-11 missions are reported. The control study is an ongoing Mir experiment. The studies indicate that the free-running period in beetles may be longer during space flight.^ieng

Response of insect activity rhythms to altered gravitational environments.

NASA: Researchers describe the development of the Beetle Activity Monitor (BAM), constructed to support an experiment with the desert beetle, Trigonoscelis gigas, proposed for the NASA-Mir program. The BAM tracks beetle movement via a wheel which turns as the animal moves in the cage. In addition to design features that conform to shuttle specifications and animal housing standards, it holds a maximum number of animals, allows for continuous recording of activity, and provides a controlled lighting environment. An experiment with 32 beetles collected data in 5-minute increments for animals exposed to constant darkness and 12-hour light-dark periods. Results of this experiment indicate that the light-dark cycle entrained the beetle circadian rhythm.^ieng

Primate circadian rhythms during spaceflight: results from Cosmos 2044 and 2229.

The circadian timing system (CTS) coordinates an animal's physiology and behavior both internally and with the 24-h day. Previous studies have suggested that the CTS is sensitive to changes in gravity. To examine this question, the expression of the CTS in four juvenile male rhesus macaques (Macaca mulatta) were studied in space. These animals were flown on the Cosmos 2044 and 2229 missions. Activity, heart rate, and axillary and brain (Cosmos 2229) temperatures were recorded. In both flights, the subjects exhibited delays in the phasing of their temperature rhythms and a decrease in mean heart rate compared with ground control studies. These data are in support of other studies that demonstrate that the CTS is sensitive to changes in the gravitational environment. Furthermore, the data also support the concept of a multioscillator organization of the primate CTS due to the differential responses of the rhythms measured.

Impact of microgravity and hypergravity on free-running circadian rhythm of the desert beetle Trigonoscelis gigas Reitt.

Free-running circadian rhythms of locomotor activity of Tenebrionid beetles Trigonoscelis gigas Reitt., taken from the Turkmenian sand desert, were monitored in DD. The effects of microgravity --11 days in space flight aboard the Russian BION-10 "COSMOS" satellite, and of 2G hypergravity--seven days on a centrifuge, were determined. Two kinds of effects were found. In stable 2-peak records, there was a moderate decrease of tau in microgravity and an increase of tau in 2G, both of about 0.3 hr. In unstable records, alterations of gravity caused drastic deviations of tau and phi. Remarkably, two peaks of the activity rhythm, which are supposed to be controlled by separate oscillators, responded to gravity transitions in different ways. Gravity effects on the circadian system could be explained from a direct effect on the oscillator(s) itself or from a feed-back by altered locomotion to the pacemaker. Thus, for the first time the gravity dependence of a free-running circadian rhythm was proved in a combination of real space flight and centrifuge experiments.

[Human circadian rhythms and the work and rest regimen: the hypothesis of the "coiled spring"]. / Tsirkadiannye ritmy cheloveka i rezhim truda i otdykha: gipoteza "szhatoi pruzhiny".

Studies of human free-running circadian rhythms have been reviewed. The conditions of development of free-run of the circadian rhythms were considered. On the basis of these data a hypothesis of "compressed spring" was proposed. It claims that the human circadian rhythms synchronized within the 24 h day are instable and related to physiologic tension. It follows that in conditions of relative isolation (long-term space flight, submarine navigation, polar expedition), during the transition period after a trans-meridian flight, and during adaptation to a shift (especially, night) work it is advisable to arrange a work-rest schedule on the basis of a prolonged 25 h day.

Thermoregulatory responses of rhesus monkeys during spaceflight.

This study examines the activity, axillary temperature (T(ax)), and ankle skin temperature (Tsk) of two male Rhesus monkeys exposed to microgravity in space. The animals were flown on a Soviet biosatellite 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(ax) 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(ax) in both flight animals was lower than on earth. The largest difference (0.75 degree C) occurred during the night. There was a reduction in mean heart rate and Tsk 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 Tsk and activity were attenuated. Furthermore, the T(ax) 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.

Possible mechanism of microgravity impact on Carausius morosus ontogenesis.

Experiments aboard "Spacelab-D1" and "Cosmos-1887" revealed an adverse effect of space flight on Carausius morosus embryos. The main influencing factor for stick insect eggs turned out to be microgravity, while the contribution of HZE particles of cosmic radiation was relatively low. Flight experiments indicated an increased vulnerability of stick insect eggs to microgravity at intermediate stages of development, that could support the "convection" hypothesis.

Circadian rhythms in a long-term duration space flight.

In order to maintain cosmonaut health and performance, it is important for the work-rest schedule to follow human circadian rhythms (CR). What happens with CR in space flight? Investigations of CR in mammals revealed, that the circadian phase in flight is less stable, probably due to a displacement of the range of entrainment, resulting from internal period change (the latter was confirmed on insects). The circadian period may be a gravity-dependent parameter. If so, the basic biological requirement for the day length might be different in weightlessness. On this basis, a higher risk of desynchronosis is expected in a long-duration space flight. As a countermeasure, a non-24-hr day length could be suggested, being close to the internal circadian period (in humans about 25 hr). Taking into account a possible displacement of period in weightlessness, it seems reasonable to establish a flexible work-rest schedule, capable to follow the body temperature CR by means of biofeedback.

Biological role of gravity: hypotheses and results of experiments on "Cosmos" biosatellites.

In order to reveal the biological significance of gravity, microgravity effects have been studied at the cellular, organism and population levels. The following questions arise. Do any gravity-dependent processes exist in a cell? Is cell adaptation to weightlessness possible; if so, what role may cytoskeleton, the genetic apparatus play in it? What are the consequences of the lack of convection in weightlessness for the performance of morphogenesis? Do the integral characteristics of living beings change in weightlessness? Is there any change in "biological capacity" of space, its resistance to expansion of life? What are the direction and intensity of microgravity action as a factor of natural selection, the driving force of evolution? These problems are discussed from a theoretical point of view, and in the light of results obtained in experiments from aboard biosatellites "Cosmos".

Studies of circadian rhythms in space flight: some results and prospects.

Results of the chronobiological experiments carried out aboard the Soviet "COSMOS" biosatellites with beetles, rats and primates indicate a possibility of 1. decrease of the circadian rhythm stability in space flight, expansion of the range of phase "hunting"; 2. shift of the endogenous circadian period in microgravity. Both should result in a higher hazard of desynchronosis in space flight. In the future it is important to investigate systematically the circadian range of entrainment in microgravity, the capabilities of rhythms to adapt to different durations of the day.

Gravitational biology experiments aboard the biosatellites "COSMOS" # 1887 and # 2044.

A number of experiments have been carried out in space flight using Protozoans, cell cultures, plants, flat worms, insects and amphibians. No qualitative, strictly unfavorable effects of microgravity could be detected. Microgravity may only slightly stimulate or inhibit some biological processes.

Effects on ontogenesis of Carausius morosus hit by cosmic heavy ions.

Among the biological problems that arise in long duration spaceflights, the effects of weightlessness and ionizing radiation appear to be the two main risk factors. Eggs of the stick insect Carausius morosus were exposed to spaceflight conditions during the 12.56 day Biosatellite mission Cosmos 1887. Five different ages were used, representing different sensitivities to radiation and different capacities for regeneration. During spaceflight the eggs continued their development. Already, in the Spacelab D1 mission in 1985, it has been shown that microgravity leads to a reduced hatching rate of eggs exposed during the early steps of development. When the eggs were hit by a heavy ion, a further but not significant reduction of the hatching rate was observed. Hatching was normal for eggs which were exposed on a 1 g reference centrifuge in space. Heavy ion hits caused body anomalies. The combined action of heavy ions and microgravity resulted in an unexpectedly high rate of anomalies. In the experiment on Cosmos 1887 these results were confirmed. Studies on the embryonic development before hatching showed no major difference between flight and ground control specimen, neither in speed of development nor in morphological anomalies. Hatching therefore seems to be the critical point in insect ontogenesis.

[Free course of circadian rhythms in Trigonoscelis gigas beetles after space flight]. / Svobodnyi beg tsirkadia'lnykh ritmov u zhukov-chernotelok posle kosmicheskogo poleta.

Before and after space flight on Cosmos-1887 motor activity of Trigonoscelis gigas beetles kept in darkness was recorded. After flight 6 out of 7 beetles showed reduction of periods of free running circadian rhythms. The fact that the change was not observed in controls suggests that it can be attributed to the effects of O G. It is assumed that in space flight the biological requirements for the day duration are modified.