[Experimental study on radial ray deficiency in rat].
Radial ray deficiency were induced in WKAH/Hkm rat fetuses by maternal administration of myleran on either day 10.0, 10.5, or 11.0 of pregnancy. In radial ray deficiency, the severity of absence of the fingers was classified into three types and the degree of radial arrest was classified into four types. The degree of radial arrest was closely related to the severity of absence of the fingers. The greater the dose of myleran was given, the more severe was the radial arrest. As for the soft tissue, the more radial the muscular, nervous and vascular systems were located, the more they were severely affected. The degree of dysplasia of muscular, nervous, and arterial systems depended on the status of dysplasia of the radius. The skeletal and soft tissue anomalies in rats were the same as those in human beings, suggesting that exposure to some environmental factors at a sensitive period of embryogenesis may cause radial deficiency in humans. The critical period for radial ray deficiency is one day later than that for ulnar deficiency in rats, which may contribute to the greater frequency of radial deficiency than ulnar deficiency in humans. It was suggested that the difference of the susceptibility to the environmental factors may determine the phenotype of longitudinal ray deficiencies in embryogenesis.