[Head-down tilt hypokinesia in monkeys: a morphological study]

Morphological examinations of rhesus monkeys (Macaca mulatta) exposed to head-down tilt for 7 and 19 days are summarized. The major changes detected in various systems, organs and tissues are described. The changes are thought to be of different origin and caused by blood redistribution, hypokinesia per se and concomitant stress. It is emphasized that head-down tilt is one of the most adequate methods for simulating effects of zero-g in monkeys.