[Morphological and cytofluorometric study of the giant cells of the trophoblast of the common vole].

The primary and secondary giant cells of trophoblast in placenta Microtus arvalis were studied. The giant polyploid nuclei are formed in result of series of successively proceeding endomitotic polyploidization of chromosomes. Two stages of endomitosis are described: endointerphase with the uniform net of thin chromatin threads and the stage when small round or rod-shaped paired chromosomes gather mostly under the nuclear membrane. Great number of round, oval, and complex-shaped nucleoli may be seen in nuclei during both stages of endomitosis, the number growing during polyploidization. The morphology of the chromosome-nucleolar apparatus involves peculiarities of the polyploidization mechanism in placenta Microtus arvalis trophoblast. Endomitosis occurs both in low and high-polyploid nuclei. Cytofluorometric determination of the DNA amount in nuclei polyploid nature. The degree of polyploidy of the trophoblast giant cells nuclei during terminal differentiation of placenta corresponds to 128c-512c, and some nuclei contain the DNA amount corresponding to 1024 and 2048 chromosomal sets. The cause of origin of the polyploid cells in trophoblast of rodents placenta is discussed.