Mechanisms of development of histological and cytochemical changes in mammals (rats) during orbital flights]

The review surveys the publications on morphological and cytological changes in different functional systems of mammals (rats) flown on board the biological satellites of the Cosmos series. The paper gives an evidence that major changes in rats during orbital flights are induced by motor deprivation resulting in distinct metabolic disorders which histologically are represented as osteoporosis of the spongy segments of the long tubular skeletal bones, their periosteocytic osteolysis and atrophic developments in skeletal muscles. The paper discusses neurotrophic nature of these changes and emphasizes the contribution of stress reactions at different flight stages, especially on return to 1 g.