title: [Formation of a complex system of cytoplasmic membranes and microfilament bundles in the period of nuclear fragmentation completion of giant trophoblast polykaryocytes].
abstract: A study of the ultrastructure of the rat trophoblast giant multinuclear cells (polykaryocytes) has shown that each separating nuclear fragment is enveloped with a thick cytoplasmic area. Simultaneously, membraneous complexes are involved in the separation of small cellular territories near the nuclear fragments within the polykaryocyte. Long outgrowings of the outer nuclear membrane go inside the cytoplasm and, on branching, produce a system of flat cisternae of the smooth endoplasmic reticulum, which, in turn, participates in the formation of plasmatic membranes that are separated within small karyocytes. Flat cisternae of the smooth endoplasmic reticulum display desmosome-like structures, both in the areas separating neighbouring cells and in those directly associated with the perinuclear space of the nuclear envelope. Formation of microvilli was seen after smooth endoplasmic reticulum membranes were separated and broad lacunae were produced. Microfilament bundles, 9 nm in diameter, have been seen in the cytoplasm of separating cells. These filaments are, as a rule, connected by one end with the outer nuclear membrane, touching membranous structures of the cytoplasm with the other end. The nature and possible functional importance of these bundles are discussed.
mesh_terms: D000818:Animals; D002455:Cell Division; D002467:Cell Nucleus / Q000648:ultrastructure*; D003599:Cytoskeleton / Q000648:ultrastructure*; D005260:Female; D007425:Intracellular Membranes / Q000648:ultrastructure*; D008854:Microscopy, Electron; D011123:Polyploidy; D011247:Pregnancy; D051381:Rats; D014327:Trophoblasts / Q000648:ultrastructure*
vernacular_title: Obrazovanie slozhnoĭ sistemy tsitoplazmaticheskikh membran i puchkov mikrofilamentov v period zaversheniia fragmentatsii iader gigantskikh polkariotsitov trofoblasta.