Polkovenko O. The peculiarities of the bone tissue osteoclastic re-sorption under the lowering of a support load

The dissertation is dedicated to studying the peculiarities of the osteoclastic resorption of mammals' bone tissue under modeled hypokinesia and microgravity (American Space station SLS-2 and biosatellite "BION-11"). With the use of histological and morphometrical methods we established that under hypokinesia the spongy bone of white rats' femora shows destructive changes in the bone tissue fs a result of an increase of the osteoclasts' num-ber and intensification of their functional activity. This is mostly expressed in the proximal metaphyses and epiphyses. In the researches employing 3Н-thymidine - labeling dynamics of the osteoclast nuclei we established that under hypokinesia there occurs an enhancement of osteoclastogenesis by way of confluence and attachment of precursor mononuclear cells. Our electron-microscopic researches showed that under hypokinesia conditions the ultrastructural changes in osteoclasts take place which confirm intensifi-cation of their functional activity. In the osteoclasts' population of proxymal metaphyses from rats' (SLS-2) femoral bones and of the iliac crest of non-human monkeys ("BІОN-11") under the microgravity we revealed the "gi-ant" osteoclasts showing a higher level of development of the zone of spe-cific functions compared to typical osteoclasts. Some morphological peculi-arities of the osteoclasts' interactions with cells in the resorptive zones were studied. As a result we established, that under the hypokinesia and micro-gravity the osteoclasts play a significant role in the bone tissue loss in zones of bone structures' adaptive remodeling. Under microgravity an increase of the osteoclasts' functional activity is more expressed than under hypokinesia.