[Histomorphometry of primate's iliac bones following head-down tilting and "dry" immersion]

Histomorphometry of the iliac bone in Macaca mulatta males was performed in experiments with 30-d head-down tilting (HDT, n = 6) and 8-10-d "dry" immersion (DI, n = 6). The iliac crest was sampled two weeks before DI or a month prior to HDT, and immediately after completion of the experiments. HDT was shown to provoke osteopenia in the bone spongy manifested by losses in the volume of spongiosa, number of trabeculae, and growth of the space in-between. Osteoids were noted to gain volume and thickness, whereas the osteoclast resorption surface was not altered The iliac spongiosa deviations following DI were qualitatively similar to those after HDT but more marked as evidenced by reduction in such integral parameter as the spongy volume. Analysis of the data and their comparison with iliac bones taken from the space-flown primates suggest that DI can be viewed as another, besides HDT, ground-based model of microgravity effects on the spongy bone. Exposure in DI was less durable and yet caused qualitatively same atrophy of the iliac spongiosa as HDT though a bit more significant.