[Effect of weightlessness on rats endocrine system development].

The histological structure of the brain and spinal cord, visual, olfactory, auditory and vestibular analysers, and endocrine organs (epiphysis, hypophysis, thyroid and parathyroid glands) were investigated in newborn rats delivered by females who had been exposed to weightlessness a half of the pregnancy period. Analysers of the flight animals did not have any marked deviations from the norm. Loci of neurone degeneration resembling porencephaly but less massive were revealed in various brain portions (cortex, hypocampus, metencephalon, spinal cord) of the infant rats developed in space flight. Endocrine studies showed accelerated differentiation of the thyroid cells secreting thyroid hormones, C-cells, and parathyroid cells in most of the infant rats of the flight group. The test animals reduced the size of epiphysis and the number of pinealocytes. Adenohypophysis was found to be smaller with altered spatial distribution of the trabecular system. The changes look quite impressive but do not threaten viability of the animals.