Murine neonate hemopoiesis following in utero total-body irradiation.

Irradiation (50-200 rad of cobalt-60 gamma rays) on day 10.5 of gestation in the mouse had the following residual effects on neonate and juvenile hemopoiesis: (a) greater damage observed in the day-15 juvenile than in the day-9 neonate; (b) greater fluctuation of peripheral blood hemogram indices from normal values in the day-15 animal than in the day-9 animal; (c) spleen cellularity affected more than bone marrow cellularity; (d) greater radiation injury reflected by bone marrow hemopoietic progenitor cells (erythroid: BFU-E and CFU-E; granulocyte-macrophage: GM-CFC; megakaryocyte: Meg-CFC), and (e) a more pronounced decrease in medulla- and spleen-erythropoietic activity with each increase in dose of irradiation.