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It was hypothesized that metabolic programming of processes underlying puberty can be shifted temporally through the use of a stair-step compensatory growth model such that puberty is optimally timed to occur at 11 to 12 mo of age. Forty crossbred beef heifers were weaned at approximately 3.5 mo of age and, after a 2-wk acclimation period, were assigned(More)
In the present study, we tested the hypothesis that short-term fasting would reduce leptin gene expression, circulating leptin, and LH pulsatility in prepubertal heifers in association with a decrease in circulating concentrations of insulin and insulin-like growth factor I (IGF-I). Twelve prepubertal crossbred heifers (mean +/- SD = 315 +/- 5 kg body(More)
We have shown recently that fasting permits leptin to modulate both luteinizing hormone (LH) and insulin secretion in cows. In rodents, leptin causes divergent effects on LH and insulin release that are dose dependent. To test the hypothesis that leptin effects on LH and insulin secretion in fasted cows are dose related, we examined the effects of various(More)
Onset of puberty is characterised by a marked increase in the frequency of release of gonadotrophin-releasing hormone (GnRH) and luteinising hormone (LH). The Kiss1 gene plays a critical role in pubertal development, and its product, kisspeptin, stimulates GnRH and LH release. In the present study, we tested the hypothesis that Kiss1 gene expression in the(More)
Objectives were to (1) characterize the relationship of third-ventricle (IIIV) cerebrospinal fluid (CSF) concentrations of growth hormone-releasing hormone (GHRH) with concentrations of GH in the peripheral circulation; and (2) assess the influence of acute administration of appetite-regulating peptides leptin (anti-orexigenic) and neuropeptide Y (NPY;(More)
The onset of puberty in mammals involves an increase in the pulsatile release of GNRH and LH. The KISS1 gene is essential for pubertal development, and its product, kisspeptin, stimulates the release of LH. The objective of this study was to determine the effects of kisspeptin in the hypothalamic-adenohypophyseal-gonadal axis of prepubertal ewe lambs. Ewe(More)
In the current study, we hypothesized that diets high in linoleic acid would increase conjugated linoleic acid (CLA) tissue content, reduce adiposity and leptin production, and result in an increase in the age at puberty in heifers. Heifers were weaned and blocked by body weight (heavy, n = 10, and light, n = 10) and allocated randomly within block to(More)
Recent evidence has implicated neurokinin B (NKB) in the complex neuronal network mediating the effects of gonadal steroids on the regulation of gonadotrophin-releasing hormone (GnRH) secretion. Because the neurokinin 3 receptor (NK3R) is considered to mediate the effects of NKB at the cellular level, we determined the distribution of immunoreactive NK3R in(More)
Orphanin FQ (OFQ), also known as nociceptin, is a member of the endogenous opioid peptide family that has been functionally implicated in the control of pain, anxiety, circadian rhythms, and neuroendocrine function. In the reproductive system, endogenous opioid peptides are involved in the steroid feedback control of GnRH pulses and the induction of the(More)
Leptin plays an important role in signaling nutritional status to the central reproductive axis of mammals and appears to be at least a permissive factor in the initiation of puberty. The expression and secretion of leptin are correlated with body fat mass and are acutely affected by changes in feed intake. Moreover, circulating leptin increases during(More)