The effects of 5-bromodeoxyuridine (BrdU) on morphogenesis of the early chick embryo

The effects of BrdU (3×10^-4 M) on morphogenesis of the chick embryo explanted at the definitive streak stage and cultured for 24 hours were studied. Compared to controls treated embryos often showed (1) an open neural tube and (2) less numerous somites. Heart development was not significantly affected by BrdU. The damage caused by BrdU was not permanent, i.e., the embryos retained the ability to undergo fairly normal morphogenesis when, after 4-5 hours of BrdU treatment, they were subcultured on a medium with excess thymidine.