Variations in the vitellogenin titre during the reproductive cycle of Rana esculenta L.
ABSTRACT 1. Vitellogenin titre has been measured by rocket immunoelectrophoresis in specimens of Rana esculenta L. caught at three different locations in southern Italy. 2. Variations in the serum level of vitellogenin are temporally related to ovarian growth during the reproductive cycle. 3. With the exception of the FL population, vitellogenin titre is low at spawning time but increases prior to ovarian recovery. 4. It eventually levels off, or undergoes a slight decline during winter, when the ovary is in a static phase. 5. The evidence presented in this study is consonant with the experimental model on hormonal control of vitellogenesis. 6. The vitellogenin patterns observed in the populations examined in this study are interpreted as due to different environmental conditions even though the hybridogenetic nature of Rana esculenta has also to be taken into account.
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ABSTRACT: We report the presence of a progesterone receptor (PR) in the brain of the female amphibian Rana esculenta and changes in the levels of this PR during the gonadal recovery phase in relation to different circulating steroid levels and steroid treatment. The highest level of the PR in the nuclear brain extract corresponded to a low level of plasma progesterone and occurred when vitellogenin synthesis was at a minimum. The lowest level was found during follicular growth, concomitant with increased plasma 17beta-estradiol and progesterone levels. The PR levels were significantly higher in ovariectomized female R. esculenta than in intact and sham-operated female frogs. Treatment with 17beta-estradiol and progesterone downregulated the frog brain PR, indicating that a possible progesterone-receptor interaction is involved in the modulation of vitellogenin.Annals of the New York Academy of Sciences 05/2009; 1163:407-9. · 4.38 Impact Factor
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ABSTRACT: Steroids secreted by the ovary, specifically estrogen and progesterone, influence the expression of behaviors associated with reproduction by interacting with a specific binding protein, or receptor, located in target cells in certain hypothalamic nuclei. The present paper reviews the progesterone receptor studies in the vertebrates brain, the progesterone receptor fluctuations throughout the reproductive cycle and suggests a role for progesterone receptors in the regulation of hypothalamic functions in amphibians. Furthermore, we report here a combined biochemical and immunohistochemical analysis of the hypothalamic progesterone receptor during the reproductive cycle of a lower vertebrate, the female amphibian anura Rana esculenta. 3H-Progesterone binding activity was found in both cytosol and nuclear extract samples. The progesterone binding moiety showed typical characteristics of a true receptor, such as high affinity, low capacity and specificity for progesterone. Further characterization was performed by using monoclonal antiserum raised against both the subunits A and B of the chicken progesterone receptor. Immunostained neurons were located mainly in two specific regions of the hypothalamus: the preoptic area and the infundibular hypothalamus. An immunoreactive band of about 67 kDa was observed using Western blotting, both in the cytosol and in the nuclear extract. Progesterone receptor levels fluctuated throughout the cycle along with plasma steroids and vitellogenin synthesis.Brain Research Reviews 12/2001; 37(1-3):172-7. · 7.82 Impact Factor
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ABSTRACT: The control mechanism of vitellogenin synthesis and/or release by the liver has been investigated in the green frog, Rana esculenta. The effects of estradiol on vitellogenin serum titres have been evaluated in adult females after hypophysectomy and/or ovariectomy and treatment with Cortisol, growth hormone (GH), and homologous pituitary suspensions. The results indicated that the estradiol-dependent vitellogenin synthesis and/or release needs a hypophysial principle (s) to be fully stimulated. Attempts to identify this substance (s) showed that it is different from Cortisol and mammalian GH.Italian Journal of Zoology - ITAL J ZOOLOGY. 01/1985; 52:343-346.