Ultrastructural and functional variations in the spermatid nucleolus during spermiogenesis in the mouse.
The localization, structure, and activity of the nucleolus-organizers (NORs) were studied during spermiogenesis in the mouse by light and electron microscopy procedures including NOR-silver-staining and actinomycin D treatment. After the two meiotic divisions the NORs resume their activity during the Golgi phase of spermatid differentiation (steps 1-3), and the nucleolus displays a specific 'padlock' structure containing the fibrillar components of an active nucleolus. This activity drops during the cap phase (steps 4-7) during which the nucleolus undergoes a segregation process of its components. No nucleolar structure is visible during the acrosomal and maturation phases of spermatid differentiation.
D000818:Animals; D002466:Cell Nucleolus / Q000502:physiology / Q000648:ultrastructure*; D008297:Male; D051379:Mice; D008854:Microscopy, Electron; D009697:Nucleolus Organizer Region / Q000502:physiology / Q000648:ultrastructure*; D013087:Spermatids / Q000502:physiology / Q000648:ultrastructure*; D013091:Spermatogenesis