title: Intranuclear membranes (vesicles, lamellae, annulate lamellae) in oocytes of the ascidian, Styela partita.
abstract: Transmission electron microscope studies on developing oocytes of Styela partita that were preserved with a primary fixative of buffered glutaraldehyde and a secondary fixative of buffered osmium tetroxide have dealt with the origin, distribution, and associations of intranuclear annulate lamellae in both previtellogenic and vitellogenic oocytes. These studies (1) substantiate that, developmentally, intranuclear vesicles appear to precede differentiated intranuclear annulate lamellae although intranuclear vesicles and intranuclear annulate lamellae may coexist in the same nucleus (germinal vesicle), (2) substantiate an earlier demonstration that the inner membrane of the nuclear envelope forms blebs which could, after detachment, become intranuclear vesicles, (3) confirm that the pore-associated material of the pores in intranuclear annulate lamellae appears to be structurally identical to that of the pores in the nuclear envelope, (4) demonstrate that at certain times during oogenesis electron-dense material inside the nucleus, thought to represent nucleolar-derived material, is continuous with the pore-associated material of pores in both intranuclear annulate lamellae and the nuclear envelope, (5) propose a function for intranuclear annulate lamellae that considers the pores to play a role in processing or assembling various RNA's and proteins to become cytoplasmic polyribosomes as has recently been suggested also for the pores in the nuclear envelope as well as pores in cytoplasmic or extranuclear annulate lamellae, and (6) provide additional evidence that intranuclear annulate lamellae are not remnants of the nuclear envelope persisting after mitosis as has been described to be the case in certain other cells.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000648:ultrastructure*; D005260:Female; D007425:Intracellular Membranes / Q000648:ultrastructure*; D007448:Invertebrates / Q000648:ultrastructure; D009685:Nuclear Envelope / Q000648:ultrastructure; D009865:Oocytes / Q000648:ultrastructure*; D009866:Oogenesis; D010063:Ovum / Q000648:ultrastructure*