[Pathogenesis of radiation-induced abnormalities of the bones and joints of white rat embryos].

After X-radiation of pregnant rats on the 10th day of pregnancy, in 50% of the fetuses studied subtotal aplasia of the tibial bone anlage and decreasing number of the metatarsus and finger phalanges anlages are observed. Radiation on the 11th day of embryogenesis does not result in anomaly formation of the thoracic and pelvic extremities. After radiation on the 12th day of embryogenesis, the most specific anomaly of the pelvic extremity is phocomelia. The thoracic extremity skeleton lesions are revealed as an ulnar type of distal ectromelia, or axial ectromelia. After radiation on the 13th--14th day, hypoplasia of the bone anlages, that make zeugopodium, autopodium, is observed. After radiation on the 13th day, a partial or total aplasia of the fibular bone anlage can take place. In all the fetuses a sharp decrease in number of the hand and foot bone anlages is observed; it is connected with a total aplasia of some of them and with fusion of the others. A specific feature for radiation lesions of the extremity skeleton is that the oppositely situated anlages of the bones do not separate from each other. This results from certain disturbances in the joint interzone formation at early stages of embryogenesis and from underdevelopment of the joint cleft. Qualitatively different radiation anomalies of the extremity skeleton development are formed as consequence of disturbances in morphogenetic processes of determination: migration, proliferation, morphogenetic cell death and differentiation.