title: Spherical bodies present within the germinal vesicle of Podarcis sicula previtellogenic oocyte derive from the temporaneous inactivation of ribosomal genes.
abstract: In the present paper we have investigated the origin of the spherical bodies (SBs) present within the germinal vesicle of about 400 microm previtellogenic oocytes in the lizard Podarcis sicula. In particular, we have attempted to clarify whether they derive from the single, large nucleolus present in early diplotenic oocyte as a consequence of ribosomal gene inactivation. We have, therefore, experimentally induced a decrease in rRNA synthesis by injecting animals with D-galactosamine or by exposing them to low temperatures. The investigations carried out have demonstrated that both treatments induce significant ultrastructural changes in the nucleolar apparatus and in particular fragmentation and the formation of SBs comparable to those observed in germinal vesicle under physiological conditions. These results indicate that the germinal vesicle of Podarcis sicula has a nucleolar apparatus that significantly changes its aspect according to its functional status and reveal that in this species, the time course of rRNA synthesis is peculiar with respect to any other vertebrate oocyte studies so far.
authors.affiliation: Department of Evolutive and Comparative Biology, University of Naples Federico II, Naples, Italy. andreucc@dgbm.unina.it
authors.forename: Ricchiari
authors.initials: R
authors.lastname: Loredana
authors.forename: Prisco
authors.initials: P
authors.lastname: Marina
authors.forename: Tammaro
authors.initials: T
authors.lastname: Stefania
authors.forename: Motta
authors.initials: M
authors.lastname: Chiara Maria
authors.forename: Pugliese
authors.initials: P
authors.lastname: Isabella
authors.forename: Andreuccetti
authors.initials: A
authors.lastname: Piero
mesh_terms: D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism / Q000648:ultrastructure*; D003080:Cold Temperature; D022162:Cytoplasmic Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D005260:Female; D005688:Galactosamine / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D008116:Lizards / Q000378:metabolism*; D008854:Microscopy, Electron; D009865:Oocytes / Q000378:metabolism* / Q000648:ultrastructure; D012335:RNA, Ribosomal / Q000378:metabolism; D012270:Ribosomes / Q000235:genetics* / Q000378:metabolism
chemical_list: D012335:RNA, Ribosomal; D005688:Galactosamine