Thesis abstract Characterization of the nucleolar cycle and chromatoid body formation in the spermatogenesis of some vertebrate species

R.L. Peruquetti
2009 Genetics and Molecular Research  
The chromatoid body (CB) is a cytoplasmic organelle that has a function related to RNA and protein accumulation and/or storage for later germ-cell differentiation. Many theories have been postulated to explain the origins of the CB material. One of the most accepted theories indicates that CB originates from nucleolar material, in which it was fragmented during early spermatogenesis; this fragmented nucleolar material migrates to the cytoplasm. Our objectives were to: 1) monitor nucleolar
more » ... tor nucleolar material distribution by cytochemical techniques (hematoxylin-eosin, toluidine blue, modified critical electrolyte concentration for detecting RNA, silver-ion impregnation, and Feulgen reaction) and by ultrastructural analysis (transmission electron microscopy), and 2) compare nucleolar material distribution with the formation of CB in some vertebrate species: Tilapia rendalli (Teleostei, Cichlidae); Dendropsophus minutus (Amphibia, Anura); Phrynops geoffroanus (Reptilia, Testudines), and Oryctolagus cuniculus (Mammalia, Lagomorpha). We found that nucleolar fragmentation occurred during the beginning of prophase I and nucleolus reorganization occurred in the early spermatid nucleus. The area of the early spermatid nucleolus was significantly smaller than that of the spermatogonium nucleolus. Three phenomena could contribute to the difference between the spermatogonium nucleolar area and the early spermatid nucleolar area: a) modification of cell activity; b) decrease in the number of nucleolus organizer regions in the spermatids, and c) migration of fragmented nucleolar material from the nucleus to the cytoplasm. This nucleolar material will participate in the CB formation process. Ultrastructural analysis showed an accumulation of nuages, which form the CB before nucleolar fragmentation, in the spermatogonium cytoplasm of T. rendalli and D. minutus. Otherwise, the CB in P. geoffroanus and O. cuniculus is formed only in the primary spermatocyte cytoplasm, when the nucleolus was fragmented. The CB was found to be associated with mitochondrial clusters in the primary spermatocyte cytoplasm. This cytoplasmic organelle was observed in associa-
doi:10.4238/vol8-2ta017 fatcat:7hai7fvqebe55bgrtteu4vcxn4