Ultrastructure of ependyma in brain third ventricle of the rats exposed to repeated tail-suspension. Scanning electron microscopical study.

By means of scanning electron microscopy the ultrastructure of ependyma was studied in the brain third ventricle of the rats repeatedly exposed to 14-day tail-suspension (TS). Animals were subjected to TS for 30 days, then readapted to horizontal position during 30 days and again, repeatedly subjected to TS for 14 days simultaneously with the rats which were in TS for the first time during 14 days. Repeated TS of rats, inspite of repeated redistribution of body liquid mediums in cranial direction, results in considerably less expressed destructive changes in ultrastructure of ependymocyte cilia, then after primary 14- and 30-day TS, showing much greater cerebrospinal fluid (CSF) outflow from brain ventricles into sagittal venous sinus at postponed for a long time, repeated simulation of weightlessness effects in comparison with CSF outflow at primery one.

Brain vessels in the rats exposed to primary and repeated tail-suspension. Minimization of structural changes after repeated exposure.

The aim of study was histological examination of brain vessels in the rats exposed to repeated tail-suspension (TS). The rats were subjected to 30-day TS, then readapted to horizontal position for 30 days and again exposed to 14-day TS simultaneously with the rats which were underwent to 14-day TS for the first time. 30-day TS induced in brain vessels the adaptive changes hindering the excessive blood inflow to brain--spasm and hypertrophy of muscle-elastic valves in extra- and intracerebral arteries and also the destructive changes--loss of vascular tone in extra- and intracerebral arteries, plethora in extra- and intracerebral veins, intracerebral venules and capillaries, conglutination of erythrocytes in capillaries, plasmatization of veins and capillaries and edema of brain tissue pointing out in total the increase in blood inflow to the brain and difficulty of blood outflow.

Histological study of brain in the rats exposed to 93-days' tail-suspension.

Antiorthostatic position of rats during 93-days' tail suspension induced in the brain strongly pronounced edema of nervous tissue, alteration of structure in horoid plexus, pointing out the decrease in liquor secretion by exocytosis and increase in itraventricular pressure, morphological changes in veins and capillaries, reflecting the development of plethora in veins and tendency to thrombogenesis, and also the appearance of structural signs of prolonged arterial vasoconstriction and narrowing of arterial lumen in surface arteries which be considered as an adaptive process lying the obstacles to excessive blood inflow to brain and dumping the pulse wave during prolonged antiorthostatic state.