Low levels of x-irradiation and the early mammalian embryo.

Abstract

Newly fertilized eggs of mice or the l-2 stage (at 24 hr) were x irradiated to low levels of 5 and 15 r, and the embryos and fetuses examined for sequelae. The percentage of early deaths and resorptions was increased over the controls to l9% among those irradiated before cleavage and to 9% among those irradiated during the first cleavage. Exencephaly (brain hernia) was found following only l5 r at both 0.5 and l.5 days post conception. Even after 5-r exposure there was some evidence of delay in the early cleavages and an increase in the percentage of early abnormals, cytologically determined. Some of the cytologic effects of x rays on the early embryo were: fragmentation, separation of blastomeres, elimination of protoplasm as blebs, elimination of one or both pronuclei, pyknosis of the nuclei, swelling, vacuolization, hyperchromaticity, and staining evidence of phase degeneration. (P.C.H.)