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The behaviour of silver-positive structures during meiotic prophase of male mice
Abstract:
Air dried preparations and sections of mouse seminiferous tubules were stained with an ammoniacal silver solution to study the behaviour of silver positive structures in meiotic prophase I nuclei. The presence of RNA was investigated using specific staining techniques and RNase digestion. Pachytene nuclei showed silver precipitation at the paracentromeric region of two to six autosomal bivalents. In spermatogonia at least the chromosome nos. 12, 15, 16, 17 and 18 proved to have transcriptionally active nucleolus organizer regions. From late pachytene the Ag-positive structures migrate towards the sex vesicle. In prediffuse diplotene, when the silver spots reached the sex vesicle, a vacuole-like body appeared near the sex vesicle. At the same time significant amounts of RNA accumulate near to the sex vesicle. Finally, in diffuse diplotene a tripartite structure could be observed, composed of (a) a horseshoe-shaped structure adjacent to the sex vesicle, which contains a great deal of RNA, (b) a vacuole-like body, being enclosed by the horseshoe and (c) an Ag-positive mass, migrated from the nucleolus organizer regions. It is probable that the tripartite structure, or at least a part of it, is a large nucleolus. The significance of the structure is discussed.
Insights
Silver staining reveals a tripartite structure in mouse meiotic prophase I, likely a large nucleolus, forming near the sex vesicle. This structure contains RNA and silver-positive material from nucleolus organizer regions.
Area of Science:
- Cell Biology
- Genetics
- Reproductive Biology
Background:
- Meiotic prophase I involves complex chromosomal rearrangements.
- Nucleolus organizer regions (NORs) are crucial for ribosome biogenesis and are transcriptionally active.
- The behavior of silver-positive structures and RNA during male meiosis is not fully understood.
Purpose of the Study:
- To investigate the behavior of silver-positive structures and RNA during meiotic prophase I in mouse seminiferous tubules.
- To identify the origin and composition of a specific tripartite structure observed in diffuse diplotene.
Main Methods:
- Air-dried preparations and sections of mouse seminiferous tubules.
- Ammoniacal silver staining to visualize silver-positive structures.
- Specific RNA staining techniques and RNase digestion to detect RNA presence.
Main Results:
- Silver precipitation was observed at the paracentromeric regions of autosomal bivalents in pachytene nuclei.
- Transcriptionally active nucleolus organizer regions were identified on specific chromosomes in spermatogonia.
- Ag-positive structures migrated towards the sex vesicle, forming a tripartite structure with RNA and a vacuole-like body in diffuse diplotene.
Conclusions:
- The observed tripartite structure is likely a large nucleolus or a significant part of it.
- This structure plays a role in the events of meiotic prophase I, potentially involving RNA sequestration and nucleolar function.
- The study provides insights into the dynamic changes of nucleolar components during male gametogenesis.