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See detailEffect of gonadal steroids on pituitary LH secretion and mediobasal hypothalamic GnRH mRNA in ferrets.
Bakker, Julie ULg; Baum, M. J.

in Journal of Reproduction and Fertility (2000), 119(2), 315-21

In vitro release and content of GnRH in mediobasal hypothalamic slices are reduced by ovariectomy of female ferrets but are not affected by castration of male ferrets in breeding condition. The aim of the ... [more ▼]

In vitro release and content of GnRH in mediobasal hypothalamic slices are reduced by ovariectomy of female ferrets but are not affected by castration of male ferrets in breeding condition. The aim of the present study was to determine whether this sex difference reflects a sexually dimorphic effect of gonadal steroids on mediobasal hypothalamic GnRH mRNA content of male and female ferrets killed 4 weeks after gonadectomy, either with or without steroid hormone replacement. This time interval exceeds the 6-10 days needed for increments in plasma LH concentrations to stabilize after gonadectomy of ferrets of both sexes. In situ hybridization using an (35)S-labelled oligoprobe complementary to the human GnRH coding region showed that the number of mediobasal hypothalamic neurones and the cellular content of GnRH mRNA did not differ significantly among groups of male and female ferrets that were either in breeding condition or that had been gonadectomized and treated with sex steroids or oil vehicle. These results indicate that gonadal hormones regulate mediobasal hypothalamic GnRH biosynthesis and release in both sexes via post-transcriptional events that may include GnRH mRNA translation or the conversion of pre-pro GnRH precursor into mature GnRH. [less ▲]

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See detailDissociation of increases in plasma insulin-like growth factor I and testosterone during the onset of puberty in bulls
Renaville, Robert ULg; Massart, Serge; Sneyers, M. et al

in Journal of Reproduction and Fertility (1996), 106(1), 79-86

The present study was conducted to examine the relationship between plasma concentrations of testosterone, insulin-like growth factor I (IGF-I) and IGF-binding proteins (IGFBPs) during puberty, in male ... [more ▼]

The present study was conducted to examine the relationship between plasma concentrations of testosterone, insulin-like growth factor I (IGF-I) and IGF-binding proteins (IGFBPs) during puberty, in male calves treated with GnRH or testosterone propionate. Twelve male Holstein calves (10 weeks old) were assigned to the control group (n = 6), the GnRH-treated group (n = 3) or the testosterone-treated group (n = 3). For 8 weeks, the GnRH-treated group received a single i.v. injection of GnRH (0.5 mu g kg(-1) body mass) each day while the testosterone-treated group received an i.m. injection of testosterone propionate (0.5 mg kg(-1) body mass) twice a day. The calves were studied until they were 200 days old. Hormone treatments were stopped one month after puberty was reached in the control group. Blood samples were collected every 30 min for 8 h every third day. Hormone concentrations were determined by radioimmunoassay. Western ligand blotting and immunoblotting, using monoclonal antibodies against IGFBP-2, and IGFBP-3, were used to characterize the IGF-binding proteins. In the control group, puberty occurred at about 120 days of age and was associated with an increase in concentrations of testosterone, IGF-I and IGFBP-3 and a decrease in concentration of IGFBP-2. In the GnRH-treated group, plasma testosterone remained low until 8 weeks after establishment of puberty in the control group (4 weeks after the end of treatment). In the testosterone-treated group, testosterone was high during the treatment period and then decreased to prepubertal values when treatment was stopped. Testosterone values increased again to reach postpubertal values 5 weeks after the end of hormone treatment. Nevertheless, independent of testosterone status, the profile of IGF-I and the IGFBPs in the GnRH- and testosterone-treated groups were parallel to that reported for the control group with the transition from prepubertal to adult values at about 120 days of age. In conclusion, concentrations of testosterone, IGF-I and IGFBP-3 increase together, but probably independently, during the onset of puberty in male calves. [less ▲]

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See detailChanges In The Hypophyseal-Gonadal Axis During The Onset Of Puberty In Young Bulls
Renaville, Robert ULg; Devolder, A.; Massart, Serge et al

in Journal of Reproduction and Fertility (1993), 99(2),

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See detailAn immunological cryo-ultrastructural study of a sequential appearance of proteins in placental binucleate cells in early pregnancy in the cow
Morgan, G.; Wooding, F. B. P.; Beckers, Jean-François ULg et al

in Journal of Reproduction and Fertility (1989), 86

Using the most sensitive immunocytochemical method available, on ultrathin frozen sections, the results in this paper demonstrate that bovine placental lactogen (bPL) is present in the earliest fetal ... [more ▼]

Using the most sensitive immunocytochemical method available, on ultrathin frozen sections, the results in this paper demonstrate that bovine placental lactogen (bPL) is present in the earliest fetal binucleate cells found at 21 days post coitum in the trophectoderm. A second protein, the SBU-3 antigen, which is absent in the early stages of pregnancy appears abruptly in the binucleate cell granules at 30 days post coitum coincident with the start of villus development. Subsequently, the granules contain both bPL and the SBU-3 antigen. This sequential production of unlike proteins indicates that the binucleate cell has different functions depending on the stage of pregnancy and has important roles to play both at implantation and in villus development. [less ▲]

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See detailElectrical and mechanical activity of the cervix in the ewe during pregnancy and parturition.
Toutain, P. L.; Garcia-Villar, R.; Hanzen, Christian ULg et al

in Journal of Reproduction and Fertility (1983), 68

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