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In the 18.5-day flight of the Soviet biosatellite Cosmos-936 (3-22, August 1977) com-parative investigations of the physiological effects of prolonged weightlessness (20 rats) and artificial gravity of 1 g (10 rats) were carried out. Throughout the flight artificial gravity was generated by means of animal rotation in two centrifuges with a radius of 320mm. Postflight examination of animals and treatment of the flight data were performed by Soviet scientists in collaboration with the specialists from Bulgaria, Czechoslovakia, the German Democratic Republic, Hungary, Poland, Rumania, France and the U.S.A. During the flight the total motor activity of the weightless rats was higher and their body temperature was lower than those of the centrifuged animals. Postflight examination of the weightless rats showed a greater percentage of errors during maze an increase in water intake and a decrease in diuresis; a fall of the resistance of peripheral red cells; an increase in the conditionally pathogenic microflora in the mouth; a decrease of oxygen consumption, carbon dioxide production and energy expenditures; a drop in the static physical endurance; a decline in the capacity to keep balance on the rail; an increase in the latent period of the lifting reflex, etc. The centrifugal animals displayed lesser or no change of the above type. These findings together with the biochemical and morphological data give evidence that during and after flight adaptive processes in the centrifuged rats developed better.

Publisher Summary This chapter describes the physiological mechanisms of the adaptation of mammals to weightlessness and the results of animal experiments aboard earth biological satellites. Manned and animal space flights of recent years have afforded a good opportunity to study human and animal functions in weightlessness and to clarify the mechanisms of its effects. The purpose of these studies were to investigate the patterns of adaptation of higher animals to the weightless state, to study the physiological and morphobiochemical characteristics of organs and tissues of weightless animals, and to explore their readaptation to earth's gravity after exposure to zero-g. The animal studies aboard biosatellites furnished adetailed information about structural and metabolic changes in muscles and bones. These changes were similar to those seen in ground-based simulation experiments/hypokinesia and hypodynamia. This holds good promise that the changes can be reversed with the aid of specially developed exercises. From the practical point of view, it is important that the level of changes in various muscles and bones was different and closely correlated with the degree of their involvement in the antigravitational function on earth.