The effect of sublethal roentgen-ray irradiation on the induction process caused by transitional epithelium in connective tissue

Abstract

Guinea pigs were irradiated at different intervals after the onset of induction caused by the transplantation of transitional epithelium. A mixture of minced mucous membrane from the urinary bladder of 4 or 5 guinea pigs was transplanted homoplastically into the anterior abdominal wall of 140 guinea pigs. The results show that irradiation on the 8th-- 11th day after transplantation, when the zone of induction consists of young osteogenic tissue, leads to a severe disturbance of osteogenesis and to the total abolition of the induction effect (absorption of bone) 10 days after irradiation. The intermediate forms of transformation of the connective-tissue elements into osteogenic cells, which were observed in the grafts on the 5th day, were less sensitive. The results indicate that the time of appearance of foci of extramedullary hemopoiesis is closely related to moment of transplantation of the epithelium and not to the time of irradiation. It was also found that a definite stage of differentiation is essential for the formation of hemopoietic tissue, and that this is reached in the zone of induction from 2 to 3 weeks after transplantation of transitional epithelium. (P.C.H.)