[Histomorphologic study of the bones of monkeys after 14-day anti-orthostatic hypokinesia]

Using a semi-automatic image analyzer MOP Videoplan, a quantitative histomorphometric investigation of sponge bone of tibial metaphyses, iliac crests and lumbar vertebrae of monkeys kept for 14 days in the head-down position (at -10 degrees) was carried out. This exposure was found to cause spongy bone reduction in all the above bones. The lowered number and activity of osteoblasts as well as the reduced amount of osteoids during the exposure give evidence that the inhibition of bone neoformation makes a significant contribution to osteopenia. The involvement of osteoclast resorption in the spongiosa reduction during head-down tilt needs further study because in our experiments the osteoclast number or acid phosphatase activity did not grow significantly.