title: Germinal vesicle breakdown in the Xenopus laevis oocyte: description of a transient microtubular structure.
abstract: During progesterone-induced meiotic maturation of Xenopus oocytes in vitro, 7 morphological stages were defined. Using cytological analysis, nuclear breakdown was divided into three stages. Stage 1 corresponded to basal germinal vesicle breakdown. Stage 2 was characterized by the advent and development of a fibrillar network formed by microtubules at the basal part of the nucleus. Below, a lamellar microtubule organizing center (MTOC) was present. Numerous vesicles of smooth endoplasmic reticulum were proximal to both of these structures. During its formation and modification (stages 2 and 3), the fibrillar network migrated towards the animal pole. A prometaphase 1 stage was observed before the formation of the metaphase 1 spindle.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000648:ultrastructure; D005260:Female; D008540:Meiosis / Q000187:drug effects; D008854:Microscopy, Electron; D008870:Microtubules / Q000648:ultrastructure*; D009865:Oocytes / Q000187:drug effects / Q000648:ultrastructure*; D010063:Ovum / Q000648:ultrastructure*; D011374:Progesterone / Q000494:pharmacology; D014982:Xenopus laevis / Q000502:physiology*
chemical_list: D011374:Progesterone