LETHAL AND TERATOGENIC EFFECTS AFTER EXPOSURE TO X-RAYS AT VARIOUS TIMES OF EARLY MURINE GESTATION

Various well-defined stages during completion of the second meiotic division and early organogenesis of mouse embryos were X-irradiated with doses of 1-4 Gy (100-400 rad). The major risk was prenatal mortality with radiation sensitivity changing markedly with dependence on the developmental stage irradiated; in the case of day 1 even within hours. The surviving fetuses did show a significantly enhanced frequency of malformation on day 19 of gestation (mostly gastroschisis and some exencephalies). This was true for all stages between days 1 and 8; only sensitivity again changed considerably. The radiation doses used in this study are markedly higher than doses that can be expected from radiation diagnostics, but exposure is in a range comparable to doses that can occur in radiation therapy (e.g., Morbus Hodgkin).