Radiation Injury Resulting from Nuclear Labeling with Tritiated Thymidine in the Chick Embryo

Abstract

Chick embryos given tritiated thymidine in the egg are subjected to a prolonged exposure, because the isotope remains in the egg for many hours. When 2- to 3-day chick embryos were treated with 10 to 50 [mu]c of tritiated thymidine (sp. act. 1.6 or 1.9 curies per millimole) and incubation continued for 12 or more hours, cytological changes characteristic of radiation injury appeared. Prom inent among the changes observed was the appearance of numerous deoxyribonucleic acid-containing cytoplasmic bodies. Injury could be avoided and satisfactory radioautographs still obtained by diluting the thymidine-H3 100 to 500 times with unlabeled thymidine, thus reducing the specific activity to 4 to 20 uc per micromole.