title: [Segregation and integration of cytoplasmic and nuclear materials during cleavage and induced fusion of blastomeres of mouse early embryos].
abstract: Mouse embryos were analyzed vitally, on fixed total and chromosome preparation at the two-cell stage and during transition to the four-cell stage, upon polyethylene glycol-induced fusion of sister blastomeres and early cleavage of thus obtained somatic hybrids. Vital staining by Rhodamine 123 showed a diffuse distribution of functionally active mitochondria with a decreasing gradient towards the periphery of blastomeres, concentration in the zone of contact between the blastomeres, and as a ring in the center. A weakly fluorescent zone inside the mitochondrial "ring" corresponded to the interphase nucleus position, as followed from vital staining by Hoechst 33258 and analysis of fixed embryos stained by lacmoid. In the course of cleavage, the mitochondria aggregated in the zone of condensed chromosomes. The topography of mitochondria reflected the barrel shape of the spindle division similar in the intact blastomeres and products of fusion and allowed us to follow segregation of the cytoplasmic and nuclear materials among the daughter cells until the mitosis completion. During formation of the fusion products, the preserved cytoplasmic boundary was visualized by the location of mitochondria, thus suggesting the absence of intense changes in the cytoplasm during fusion of the blastomeres. The movement of mitochondrial "rings" marked the centripetal translocation of the nuclei. We did not observe formation of a common "ring" or fusion of the interphase nuclei. Association of the nuclear materials took place only at the metaphase stage. Sister blastomeres of the two-cell somatic hybrids, just as those of intact embryos, entered the subsequent cleavage division asynchronously. Cytogenetic analysis confirms formation of the tetraploid embryos as a result of induced fusion of sister blastomeres.
authors.affiliation: Institute of Cytology, Russian Academy of Sciences, St.-Petersburg, Russia.
authors.forename: N A
authors.initials: NA
authors.lastname: Bogoliubova
authors.forename: G G
authors.initials: GG
authors.lastname: Sekirina
mesh_terms: D000818:Animals; D006690:Bisbenzimidazole; D001757:Blastomeres / Q000502:physiology*; D002459:Cell Fusion / Q000502:physiology; D002467:Cell Nucleus / Q000648:ultrastructure*; D020090:Chromosome Segregation; D002970:Cleavage Stage, Ovum / Q000648:ultrastructure*; D003593:Cytoplasm / Q000648:ultrastructure*; D005456:Fluorescent Dyes; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D008928:Mitochondria / Q000648:ultrastructure; D011092:Polyethylene Glycols; D020112:Rhodamine 123
chemical_list: D005456:Fluorescent Dyes; D020112:Rhodamine 123; D011092:Polyethylene Glycols; D006690:Bisbenzimidazole