Search results for "Vitellogenesis"

Characterization of vitellogenins in Spilostethus pandurus (Hemiptera): Immunoelectrophoretic studies and short-term labelling experiments

1992

Abstract The haemolymph of Spilostethus pandurus contains three female-specific proteins (I, II and III) as revealed by SDS-PAGE. Antibodies prepared against them recognize three fractions (4, 5 and 6) in ovarian extracts which have similar molecular weights suggesting that I, II and III are vitellogenins. Upon injection of a 14C amino acid mixture into vitellogenic females, labelled proteins first appear in the fat body, then in the haemolymph and next in the ovarian follicles.

2002

Analysis of gonad organization and development revealed that Serranus atricauda is a functional simultaneous hermaphrodite. The ovary is classified as asynchronous. Oocyte growth is divided into five stages: stage I (primary growth stage), stage II (yolk vesicle formation), stage III (vitellogenesis), stage IV (oocyte maturation) and stage V (mature egg). The testis is of the unrestricted or lobular spermatogonial type. Spermatogenic cells include spermatogonia, primary and secondary spermatocytes, spermatids (which form cysts in the seminiferous tubules) and spermatozoa (free in the lumen). The histological structure of the gonad and sperm morphology would seem to indicate that this specie…

Control of ovarian steroidogenesis in insects: A locust neurohormone is active in vitro on blowfly ovaries

2009

0016-6480 doi: DOI: 10.1016/j.ygcen.2009.04.034; Ovarian steroidogenesis controlling insect reproduction is mainly regulated by brain gonadotropins liberated from corpora cardiaca (CC). Till now, different neurohormones have been identified in two insect groups only, locusts and mosquitoes, and it is unknown whether they could be active in other insects. In order to complete previous observations on the control of ovarian steroidogenesis in the blowfly, Phormia regina, we examined whether neuropeptides isolated from locust CC have an effect in vitro on ovarian steroidogenesis in our dipteran model. Our experiments showed that crude extracts from locust CC efficiently stimulated steroidogene…

Calcium inhibits ovarian steroidogenesis in the blowfly Phormia regina.

2002

1479-6805 0022-0795; Calcium is frequently involved in the stimulation of steroidogenesis in gonads and endocrine glands, generally in association with cAMP. However, our present observations show that it has the opposite effect in the ovary of the blowfly Phormia regina. Our in vitro experiments first showed that extracellular calcium does not play a role during the stimulation of steroidogenesis in fly ovaries; indeed steroidogenesis was activated in vitro as efficiently in a medium with or without calcium, either by pharmacological compounds mimicking cAMP signaling or by active brain extracts. When calcium was experimentally introduced into biosynthetic cells by ionophores or liberated …

Vitellogenesis inhibition in Oncopeltus fasciatus females (Heteroptera: Lygaeidae) exposed to cadmium

2005

Abstract Newly moulted females of the insect Oncopeltus fasciatus were exposed to cadmium (Cd) dissolved in the drinking water (50–400 mg l −1 Cd) for 5 days. Cd exposure delayed ovarian maturation and inhibited egg production. Exposure to Cd, moreover, decreased hemolymph levels of the two major vitellogenin polypeptides of O. fasciatus , VG1 and VG2, in a concentration-dependent way, probably by a reduction in their synthesis. The ovarian levels of VG1 and VG2 were also decreased in Cd-exposed females. It was next investigated whether Cd effects might be a consequence of the endocrine disruption of vitellogenin synthesis, which is controlled by juvenile hormone (JH). JH replacement therap…

Identification of the yolk receptor protein in oocytes of Nereis virens (Annelida, Polychaeta) and comparison with the locust vitellogenin receptor

1992

In oviparous animals large amounts of yolk proteins of extraovarian origin are accumulated by developing oocytes during vitellogenesis. The yolk protein precursors, the vitellogenins (VTG), are transported into the oocytes by receptor-mediated endocytosis. In oocytes of the polychaetous annelid, Nereis virens, the receptor protein for VTG was visualized by ligand blotting studies as a protein with an apparent molecular mass of 190 kDa under non-reducing conditions. Anti-Locusta VTG receptor antibodies recognize the Nereis VTG receptor protein. The Nereis VTG receptor protein binds Locusta and Schistocerca VTG; the VTG receptor proteins of both locust species bind the Nereis vitellin. These …