[Characteristics of trophoblast cell reproduction in the connective zone of the rat placenta. I. Determination of the degree of ploidy and the number of Barr bodies in interphase nuclei].

The degree of ploidy in the interphase nuclei was determined in the connective zone of the rat's placenta on days 13 and 14 of embryo development. On day 13, the ploidy in the majority of nuclei was 2c or 4c; on day 14, the 4c nuclei were dominating, the share of 8c nuclei increasing. The number of Barr's bodies in each nucleus of the placental connective zone tends to increase with the increase in ploidy level. This is an evidence of a "genuine polyploidy" as a mechanism of the initial polyploidization of the given cell population.