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The nucleolus and its modifications during oogenesis of Torpedo marmorata
No full textThe structural organisation of the nucleolar apparatus during oogenesis of the spotted ray Torpedo marmorata was investigated. The observations showed that unlike other cartilaginous fishes, in T. marmorata the nucleolar apparatus was always represented by one or two conspicuous nucleoli, whose organization significantly changed during oocyte development. In the smallest follicles (follicles <300 μm in diameter) the nucleolus was made up of granular and fibrillar components, and actively incorporated 3H uridine; later it becomes more and more electron‐dense so in follicles of 400 μm in diameter its components and 3H uridine incorporation were no longer evident. These results indicate that in T. marmorata the nucleolar apparatus significantly changes and undergoes a possible impairment in rRNA synthesis. After nucleolus inactivation, the synthesis of rRNA may be substained by granulos
The Fas/FasL system is a possible regulator of germ cell apoptosis in the testis of Torpedo marmorata
No full textThe role played by the Fas/FasL system in the activation of apoptosis during the spermatogenesis of the spotted ray Torpedo marmorata was investigated. By immunohistochemical and western blot techniques it was demonstrated that the Fas/FasL system is amply represented during spermatogenesis of T. marmorata and it could act both via a paracrine and autocrine route: paracrine at the level of immature and mature cysts, autocrine only in mature cysts
Cadherin in developing and maturing cysts of Torpedo marmorata testis
No full textWe investigated the presence of cadherins, Ca++ dependent cell-cell adhesion molecules, during the development and maturation of cysts in the testis of the spotted ray Torpedo marmorata. Using different anti-cadherin antibodies, we provide evidence by means of immunohistochemistry and immunoblotting that cadherins are involved in the interaction between Sertoli and germ cells. During the development and maturation of cysts, in fact, cadherins occur between Sertoli and germ cells when they begin to interact to build a cyst. Later on, the presence of cadherins between Sertoli and germ cells persists; furthermore, during the formation of spermatoblast, it is also evident at the level of indentations, arising from Sertoli cells and encompassing germ cells. Finally, the present findings strongly suggest that cadherins are also involved in the spermiogenesis as germ cells, when male gamete differentiation starts, are intensively stained, while, when spermiation is completed, the spermatozoa appear unlabeled
ALPHA AND BETA SPECTRIN DISTRIBUTION DURING THE DIFFERENTIATION OF PYRIFORM CELLS IN FOLLICLES OF LIZARD PODARCIS SICULA
No full textOogenesis in the spotted ray Torpedo marmorata
No full textInvestigation of embryos, neonates, sub-adult and adult female Torpedo marmorata showed that oogenesis is immediate. It begins very early in development and continues, in its proliferative phase after birth. In newborns, 3–4 month old, all germ cells present in the ovary have achieved diplotene stage and are surrounded by a single layer of small follicle cells (primordial follicles). Later with continued oocyte growth, the follicular epithelium (granulosa) progressively changes its organization and becomes multilayered and polymorphic with the presence of three types of cells: small, intermediate and pyriform cells. This organization lasts until the end of oocyte growth, but its activity changes significantly. Indeed, in the previtellogenic phase intermediate and pyriform-cells transfer to the oocyte mitochondria, ribosomes, vesicles, via intercellular bridges; during vitellogenesis, intermediate and pyriform cells, as well as small follicle cells, synthesize and transfer vitellogenin within the oocyte. During Torpedo oogenesis, in concomitance with the differentiation of the granulosa, the nucleolar apparatus is modified significantly: transcriptionally active in primary follicles, it becomes inactive during the subsequent stages of oocyte growth
Immunolocalization of 3beta-HSD and 17beta-HSD in the testis of the spotted ray Torpedo marmorata
No full textUsing polyclonal antibodies, we examined the localization of 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 17beta-hydroxysteroid dehydrogenase (17beta-HSD) as markers of the site of steroidogenetic activity during the spermatogenesis of Torpedo marmorata. These enzymes play a central role in the biosynthesis of steroid hormones, including androgen and oestrogen production. We demonstrated that in the spotted ray testis, Sertoli and Leydig cells, as well as spermatogonia, show a positive reaction to anti 3beta-HSD and 17beta-HSD antibodies. In particular, we demonstrated that Sertoli cells show a positive reaction to anti 3beta-HSD and 17beta-HSD antibodies in cysts containing spermatogonia and spermatozoa, while Leydig cells present a positive reaction only when they are located between cysts containing meiotic cells. This study strongly suggests that, as hypothesised in our previous study [Prisco, M., Liguoro, A., D'Onghia, B., Ricchiari, L., Andreuccetti, P., Angelini, F., 2002. Fine structure of Leydig and Sertoli cells in the testis of immature and mature spotted ray Torpedo marmorata. Mol. Reprod. Dev. 63, 192-201.], Sertoli and Leydig cells are differently involved in the hormonal control of spermatogenesis: Sertoli cells before the beginning of meiosis and after spermiation, Leydig cells only during meiosis phase. Moreover, the present paper deals with the possibility that also spermatogonia are engaged in the production of androgen hormones, as they are characterized by the presence of 3beta-HSD and 17beta-HSD enzymes, and show the ultrastructural features of steroid hormone-producing cells
Ovarian follicle cells in Torpedo marmorata synthesize vitellogenin
No full textThe pattern of vitellogenesis is similar in all non-mammalian vertebrates: the liver, under oestrogenic stimulus, synthesizes vitellogenin (VTG) that, via the maternal circulation, is delivered to the oocyte and here internalized by receptor-mediated endocytosis (Wallace, 1985: Development Biology. A comprehensive synthesis. Vol. 1 Oogenesis:127-177; Schneider, 1996: Int Rev Cytol 166:103-134; LaFleur, 1999: Encyclopedia of Reproduction Vol. 4:985-992). The contribution to vitellogenesis of different components of the ovarian follicle has also been reported in amphibians (Wallace, 1985), squamate reptiles (Ghiara and Limatola, 1980: Acta Embryol Morphol Exper 1:5-6; Andreuccetti, 1992: J Morphol 212:1-11), and recently, supporting previous reports (Chieffi and Pierantoni, 1987: Hormones and Reproduction in Fishes, Amphibians and Reptiles Single vol.:117-144), in Torpedo marmorata (Prisco et al., 2001: Perspective in comparative endocrinology: Unity and diversity Single vol.:1197-1201; Prisco et al., 2002b: Gen Comp Endocrinol 128:171-179). The present investigation, performed with immunoblotting, immunohistochemical, and in situ hybridization techniques during different stages of follicular growth in T. marmorata, shows that, as previously supposed (Prisco et al., 2002b), granulosa cells in both previtellogenic and vitellogenic phases actively synthesize VTG. This is the first time among vertebrates that the synthesis of this protein has been found to occur also within the ovarian follicle. The present data also demonstrate that the contribution of granulosa cells becomes particularly evident during vitellogenesis. Indeed, in vitellogenic follicles, small, intermediate, and pyriform-like cells cross-react with an anti-VTG antibody and are positive to a hybridization signal with a VTG mRNA probe. By contrast, in previtellogenesis only the enlarged cells, i.e., intermediate and pyriform-like cells, are involved in VTG synthesi
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