The effect of 5-bromodeoxyuridine on mouse embryos during neurulation in vitro

Summary Mouse embryos explanted at various stages during neurulation were cultured for 20–28 h in the presence of 25–900 g/ml of 5-bromodeoxyuridine (BUdR). BUdR strongly inhibited closure of the cranial neural tube, which was found to be stage-dependent. When mouse embryos were exposed to BUdR after development of the concave curvature in the neuroepithelium of the midbrain to the upper hindbrain regions, they became insensitive to the drug-induced open cranial neural tube. Histological observations showed that BUdR interfered with interkinetic migration and cytokinesis of the neuroepithelial cells. These cellular abnormalities were not dependent on the morphological development of the cranial neural folds. The³H-BUdR experiment confirmed that the label was mostly incorporated into the DNA fraction.Acknowledgment. This work was supported by Grant-in-Aids for scientific research No. 557469 and 58480391 from the Ministry of Education, Japan.