[A study of the polyploid nuclei of the giant trophoblast cells of several species of rodents using phase contrast microscopy]. / Izuchenie poliploidnykh iader gigantskikh kletok trofoblasta nekotorykh vidov gryzunov s pomoshch'iu fazovokontrastnoi mikroskopii

Patterns of chromosome morphology in high polyploid trophoblast nuclei of placenta were compared in the rat, rabbit and Microtus arvalis. In the rat and rabbit placenta two types of nuclei were recognized. Some nuclei have ribbon-like chromosomes, while others display thin oligotene fibrils with paired chromomers evenly distributed throughout all karyoplasm. In the latter case, the polytenic structure of chromosomes is seen preserved only near the nucleoli. In the rat and rabbit trophoblast nuclei, the ribbon-like polytene chromosomes could be distinguished only with phase contrast microscopy. In the trophoblast nuclei of Microtus arvalis polytene chromosomes were found only at early stages of embryonic development (9 day old embryo). On later stages of cell differentiation, the chromosomes or chromosome rosetts are seen. Similarities in mechanisms of polyploidization in the high polyploid nuclei of Diptera and in trophoblast nuclei of rodents are discussed.