Efficacy of periodic centrifugation of primates during 4-week head-down tilt

Creation of artificial force of gravity (AFG) to counteract the negative co nsequences of microgravity in manned space missions of extended duration is one of the high-priority problems of space biology and medicine. However, there are a number of especial effects of AFG (namely, structural changes i n muscles and bones, and some other system) which need implantation of elec trodes and sensors and are possible only with animals. That is why it is of particular interest to make studies with monkeys whose reactions to change d gravity bear much resemblance with human (1). The purpose of the investigation was development of a protocol of periodic gravity loads as a countermeasure against the hypokinetic syndrome in Macac a mulatta. Two series of experiments were performed. In the series, animals were split into two groups of 6 species each who were motor restrained with the head end tilted downward at 5 degrees (HDT) for 28 days. Monkeys of group-2 were periodically subjected to centrifugation (HDT+G). During the first series of experiments rotation was conducted in the +Gz direction at g-loads from 1.2 to 1.6 units for 30-40 minutes 4-5 times a week. In the second series, g-load was equal to 1.2 units and the animals were rotated 30 min. 2-3 time a week. The criterion of g-training protocol efficacy was a test +Gz run at 3 units for 30 s. during which functioning of the cardiovascular systems and its c ontrols was evaluated. The test run was performed prior to and after HDT. F ollowing HDT the animals of group HDT+G were more resistant to the test tha n their counterparts who had not been trained on the centrifuge. Data of the investigation imply that following HDT and HDT+G alike reduced the amount of total bodily fluids (by approximately 5%), the intracellular component (approximately 4%), and plasma volume (by 6-7%). Yet, there are r adical differences between the groups in the levels of reduction in extrace llular fluids (by 11% and 6.5%, respectively, P <0,05) and the interstitial component (by 11.5% and 6.5%, respectively, P <0,05 Prophylactic centrifugation during HDT was also positive to the muscular bl ood flow in lower extremities. (C) 2001 Published by Elsevier Science Ltd.