annaresource.blogg.se - Frog ovary parts

They progress through the meiotic cell cycle and arrest again before fertilization in the second meiotic metaphase with high activity of CSF and MSF. The fully grown frog oocytes acquire fertilization competence in the process of meiotic maturation. It was found subsequently that MPF represents a complex of cyclin B and Cdk1 kinase ( Hunt, 1989), and CSF was identified as a multicomponent system comprising the meiotic protein kinase Mos and the MAPK pathway (reviewed in Tunquist and Maller, 2003 Schmidt et al., 2006 Wu and Kornbluth, 2008). MPF was originally defined by Masui and Markert as a cytoplasmic activity from mature oocytes that causes complete maturation upon injection into immature oocytes, and CSF, as a cytoplasmic activity from unfertilized eggs that promotes metaphase arrest upon transfer to early dividing embryos. They are characterized by a low activity of the main meiotic regulators, the cytostatic factor (CSF) and maturation-promoting factor (MPF) ( Masui and Markert, 1971 Smith and Ecker, 1971). The fully grown frog oocytes are not competent for fertilization. Communication and paracrine interactions between the oocyte and somatic cells in the follicle were found to be necessary for normal ovulation. Direct contacts between the oocyte and somatic cells in the follicle are formed via terminal gap junctions connecting the oocyte and follicle cell plasma membranes ( Browne et al., 1979). At the advanced stages of growth, oocytes resting in ovarian follicles are surrounded by the follicle envelope, consisting of several layers, such as theca/epithelial layer, granulosa cell layer, and vitelline envelope.

Oocytes of most vertebrate species, including frog oocytes, reside and grow in the ovaries while arrested in the first meiotic prophase. For the purpose of comparison and generalization, we also refer extensively to ovulation in other biological species, most notoriously, in mammals. Here, we provide an overview of the major molecular and cytological events of ovulation observed in frogs, primarily in the African clawed frog Xenopus laevis, using mainly ex vivo approaches, with the focus on meiotic oocyte maturation and follicle rupture. Moreover, most of the molecular mechanisms and signaling pathways engaged in this process have been delineated using in vitro ovulation models.

Remarkably, ovulation in different species can be reproduced out-of-body with high fidelity. It refers to the entire process of ovarian follicle responses to hormonal stimulation resulting in the release of mature fertilization-competent oocytes from the follicles and ovaries. Ovulation is a unique physiological phenomenon that is essential for sexual reproduction.

2Department of Biochemistry, Saint Petersburg State University, Saint Petersburg, Russia.

1Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, Japan.

Metamorphosis takes place in tadpoles when the frog becomes lung breathing and terrestrial.Alexander A. Gametes come out through cloacal aperture.įrog's larvae are aquatic, gill breathing. In breeding season, frogs perform a false copulation: the act of amplexus so that both the sexes release huge number of gametes together in water. Eggs enter cloaca through oviducts of both sides. Eggs enter oviducal funnel to reach oviduct. In female frogs, ovaries shed the mature eggs in coelomic cavity. The sperms exit testes through ureter which is a common urinogenital duct: ureter delivers sperms in cloaca. In frogs, testes delivers sperms inside Bidder's canal running through kidney. In males, testes is not abdominal in location these are present in scrotal sac. In human special ligaments attach the gonads to body wall. In both the sexes of frog, each gonad remains attached to the kidney of same side. Similarities between human and frog's system are limited to the fact that both possess paired testes/ovary for gamete production. Reproductive system of frog is responsible for producing gametes which are released in water for fertilisation.