Response of the very early mouse embryo to low levels of ionizing radiations.

The mouse embryo from fertilization of the egg through the second or third eleavages (1.5 days) has been exposed to from 5 to 25 r x rays, and the gross consequences in terms of embryoric death and anormalies have been determined. Any x irradiation used to the 0.5 day embryo (prior to the first cleavage) was deleterious in terms of increased embrvonic death. An exposure of 5 r raused 11% mons deaths than among the controls, and 25 r caused 38% more deaths. X irradiation exencephalia occurred in a few instances following 15 or 20 r at 0.5 day and also at 1.5 days. Thus this cerebral anomaly can be caused by x irradiation even prior to the first cleavage. Mouse embryos exposed at these very early stages are often fragmented, or the entire egg is broken up into globules; one of these conditions may show the zygotic nucleus. Funther development of . such fragmented embryos is doubtful. The ovaries of x- irradiated pregnant mice show growing follicles with a higher preponderance of degenerating bocytes, pyknotic nuclei, congealed chroruain, and vacuolated nucleoli. On the basis of this study, the question is raised as to whether any extraneous or avoidable xmore » irradiation of the human ovary should be allowed except where life is otherwise endangered- (auth)« less