In Japanese quail the effect of a 90 day immobilization on the pool of
bone marrow stromal cells (CFU-f) was studied. CFU-f were determined
in femur and tibia by a tissue culture method at different times of im
mobilization. A linear decrease in the number of CFU-f both tissues wa
s found during 60 days of immobilization with a subsequent adaptation
at the low level of the pool of CFU-f The results indicate a profound
effect of hypodynamy on the bone marrow microenvironment.