title: Ultracytochemical localization of Na+, K+-activated ATPase in the oocytes of Heterandria formosa Agassiz, 1853 (Pisces, Poeciliidae).
abstract: Using ultracytochemical methods, this paper studies the presence of Na+, K+-activated ATPase during oocyte development in Heterandria formosa. ATPase was discovered in all four oocyte stages, but its level was highest in stages II and III in which yolk formation took place. Na+, K+-activated ATPase was found on the membranes of both the yolk vesicles and the cortical granules and on the oocyte and follicular microvilli and the primary oocyte membrane, indicating that the microvilli were the sites of substance exchange between the follicle and the oocyte.
mesh_terms: D000818:Animals; D005260:Female; D005399:Fishes / Q000033:anatomy & histology*; D007425:Intracellular Membranes / Q000201:enzymology; D008871:Microvilli / Q000201:enzymology; D009865:Oocytes / Q000201:enzymology / Q000648:ultrastructure*; D010063:Ovum / Q000648:ultrastructure*; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis*
chemical_list: D000254:Sodium-Potassium-Exchanging ATPase