Cytophotometric determination of the relative amounts of deoxyribonucleic acid in the nuclei of blastocysts during normal and retarded implantation in the rat.

Cytophotometrics measures of DNA-Feulgen were realized in normal and delayed implantation blastocysts of the rat. During afternoon of the 5th day of progestation, blastocysts were of two types: those nuclei of which were in G1 gap and those nuclei of which were synthetising DNA. In delayed implantation, blastocyst nuclei were in G1 or G2 gap. Mitosis were rarely seen. After oestrogen injection DNA-synthesis started again. Cell kinetics before ovoimplantation is discussed.