Histogenesis of Japanese quail bone and cartilage tissues at the final stages of embryonic development in microgravity

: The article reports the results of comparative histological studies of skeleton development in 14- and 16-day Japanese quail embryos grown in space flight and in the 1-g gravity. The investigation revealed retardation of cartilage replacement by bone in the femur and tibia in space embryos as compared with their controls. Perichondral ossification metaphysis was reached by day 14 both in the space and control embryos. Destruction of cartilaginous diaphysis advanced onto the proximal and distal parts including the periphery. Tibia and femur cartilaginous cores in space embryos were destructed worse than in the controls in consequence of insufficient minerals supply. Perichondral ossification in the 16-day space and control embryos was alike close to completion spreading as far as the epiphysis. Long bones metaphysis was abundant in monomorphic cells as a growth bank existing during and 7 days post hatching. However, absence, in contrast to the controls, of osteogensis sites in long bones epiphysis, suggested retardation of chondrocytes calcification in these areas, as well as of ossification in space embryos.