Silver staining of the postacrosomal sheath during human spermiogenesis

A cytochemical study of the nucleolus and nucleolus-related structures during human spermatogenesis

Besides the components of typical nucleoli, three other nuclear structures were identified in spermatogonia by positive silver staining: dense centers, fibrillar regions, and dense granules. There was a close relationship between the dense centers and fibrillar regions in spermatogonia and spermatocytes, whereas the dense granules, which appeared dispersed throughout the nucleoplasm of spermatogonia, became localized at the periphery of chromosomes in spermatocytes. From the beginning of spermiogenesis, these three structures then appeared in direct relationship with the dense fibrillar component of the nucleolus. At the Golgi phase, a new nuclear structure also appeared in close relationship with the dense fibrillar component. As it was morphologically similar to the fibrillar region, but not silver stained, it was designated fibrillar structure. With further spermatid development, as the dense fibrillar component gradually disappeared, a sharp increase in the number of the associated dense granules was observed; these granules then disappeared as well. In spermatids at cap phase, each fibrillar region appeared intimately associated with several fibrillar structures. In maturing spermatids, silver staining became confined to the fibrils that appeared located inside the nuclear vacuole. The nuclear vacuole also contained a dense fibrillar structure in intimate relationship with these fibrils and the peripheral condensed chromatin. Ethidium bromide-PTA, Na-tungstate and EDTA regressive staining suggest the presence of RNP in the fibrillar regions, dense granules and intravacuolar fibrils, and the presence of DNP in the fibrillar structures.

Extractions reveal specific argentophilic proteins in rat and bull sperm heads

BACKGROUND

Silver-stainability (argentophilia) of cytoplasmic structures occurring in spermatids have been localized into the organizing perinuclear theca, but the biochemical nature and structural associations of these proteins with the cytoskeletal and membranous elements are unresolved and, therefore, were the aim of the present study.

METHODS

Light and electron microscopic analysis of the silver-stainability in the rat spermatids and spermatozoa was carried out in the intact testis tissue and epididymal spermatozoa and after their chemical and mechanical extraction. Correlation of argentophilia with specific proteins of rat and bovine spermatids and spermatozoa was investigated using a recently developed technique for silver nitrate staining of proteins on nitrocellulose.

RESULTS

Sequential formation of the silver-stainable domains seemed to proceed from the argentophilic acrosomal ring. Various extractions indicated that argentophilia in the spermatids and spermatozoa was mainly associated with the perinuclear theca and to some extent to the plasma membrane. Hyamine-soluble extract from spermatozoa of rat and bull revealed only a single argentophilic protein of 130 kDa. Hyamine and SDS-soluble extracts of rat testis tissue contained an additional group of argentophilic polypeptides of lower molecular weight (115, 94, 36, 23, and 21 kDa).

CONCLUSIONS

Reduction in the number of argentophilic proteins appears to be involved in a series of changes in the cyto-architecture of developing spermatids. Tentative cytoskeletal nature of argentophilic proteins remains to be identified. Nevertheless, they may have important physical relations with the higher-order organization of the sperm head cytoskeleton and overlying membranes.