Cristina G Herbosa

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To test the hypothesis that mechanisms controlling the secretion of LH are modulated by glucose availability, the acute effects of glucoprivation were studied. The model was the gonadectomized male lamb raised on a limited diet of artificial milk. The approach was to monitor LH secretion before and after the administration of a competitive antagonist of(More)
Glutamate and aspartate have been hypothesized to function as neurotransmitters in the regulation of the gonadotropin-releasing hormone (GnRH) neurosecretory system. We, therefore, determined if hypothalamic stimulation of luteinizing hormone (LH) secretion in the intact prepubertal female lamb could be achieved by intravenous injection of(More)
Growth retardation induced by dietary restriction results in hypogonadotropism, and thus, puberty is delayed. The present studies determined 1) whether reduced LH secretion in the growth-retarded condition is due to a reduction in the frequency and/or in the amplitude of GnRH secretion, and 2) whether the mechanism regulating LH secretion is being actively(More)
In sheep, prenatal exposure to androgens during a critical period for sexual differentiation can masculinize tonic luteinizing hormone (LH) secretion and defeminize the LH surge. The present study investigated the possible independent control of these two modes of LH secretion, as revealed by their developmental history. Specifically, we tested the(More)
In sheep, the surge mode of gonadotropin secretion is sexually differentiated, i.e. the LH surge is present in the female, but not in the male. The present study tested the hypothesis that sexual differentiation of the LH surge mechanism reflects a sex difference in the pattern of GnRH, and that prenatal androgens abolish the surge mode of GnRH secretion.(More)
In most seasonal breeders, photoperiod influences the timing of the transition to sexual maturity. In sheep, males and females express reproductive maturity under different photoperiods. Spring-born males begin the maturational process during lengthening days (spring), whereas females do so during shortening days (autumn). We hypothesized that photoperiod(More)
In female sheep, photoperiod regulates the timing of the transition to adulthood. We tested the hypothesis that photoperiod very early in development influences the timing of the pubertal LH rise that initiates sexual maturation. The first experiment was designed to determine the influence of day length information perceived before birth by varying prenatal(More)
Photoperiod times the transition to sexual maturity in many seasonal breeders. In male and female sheep, photoperiod influences the timing of puberty differentially. Whereas in females, age at sexual maturity is highly dependent on photoperiod, puberty in males begins at the same age regardless of day length. We have determined that this sex difference is(More)
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