[Tumors in animals irradiated during embryogenesis].

In experiments on 465 male and female white non-lineal rats irradiated in their embryonal (7th day--240 rats), organogenesis (14th day--105 rats) and foetal periods of embryogenesis (19th day--120 rats) with 60Co--rays in a dose of 100 r, its actual power 168 r/m, and on 73 control rats the authors have studied the frequency and terms of tumors appearance. A group comprising 219 experimental rats and 53 control animals, died during a period of 200--600 days following their birth, was analysed. Irradiation at different stages of embryogenesis would provide a statistically significant increase in the frequency of tumors and shorten the terms of their appearance. In control animals tumors arose in 16,9% (in 9 of 53 animals). Embryonal and foetal periods of embryogenesis proved to be mostly susceptible as evidenced by the yield of radiation tumors. In animals exposed to irradiation in their embryonal period tumors arose in 64,5% (in 69 of 107 rats), in the foetal period--in 62,8% (in 44 of 70 rats), and during the period of organogenesis--in 42,8% (in 18 of 42 rats). Rats exposed to irradiation in the embryonal and foetal period of embryogenesis developed tumors to the 120--180th day of the experiment, while in the organogenesis period--to the 400th day. Maximum tumor appearance was observed in the last third of the lifetime. Male rats irradiated in the period of embryogenesis developed tumors of the mammary gland and bones, females- ovarian and bone tumors, which were absent in control animals.