Administration of testosterone to wether lambs: effects on protein and energy metabolism and growth hormone status

Lobley, G. E.; Connell, Alexmary; Buchan, Vivien; Skene, Pat A.; Fletcher, J. M.

doi:10.1677/joe.0.1150439

Cited by 23 publications

(18 citation statements)

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“…Castration reduces and T stimulates body weight gain, nitrogen retention, and/or food intake in a number of species [73, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84]. As mentioned previously, intact male sheep exhibit increased numbers of cells expressing NPY and increased NPY mRNA during long days that are associated with increased voluntary food intake [23].…”

Section: Discussionmentioning

confidence: 99%

Neuropeptide Y Gene Expression in Male Sheep: Influence of Photoperiod and Testosterone

Dobbins

Lubbers²,

Jackson³

et al. 2004

Neuroendocrinology

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The frequency of pulsatile release of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) is high in the breeding season and low in the nonbreeding season. These alterations in the patterns of GnRH and LH release are due to an interaction of daylength and gonadal steroid negative feedback. A vast amount of data indicates that steroid-responsive neural systems may play a role in regulating seasonal changes in GnRH release. One candidate system is neuropeptide Y (NPY). To determine the independent and interactive influences of photoperiod and steroid exposure on NPY mRNA levels, we used hypothalamic tissue from four groups (n = 4 per group) of castrated male sheep that were simultaneously housed in photochambers and exposed to: (1) a 16L:8D photoperiod (LD); (2) LD and implanted with testosterone (LD + T); (3) a 10L:14D photoperiod (SD), and (4) SD + T. Circulating levels of T averaged 2.8 ± 0.2 ng/ml in implanted animals, but were undetectable in nonimplanted males. Mean LH levels were significantly reduced (p < 0.01) in the LD + T group as compared with the other groups which did not differ from each other. The silver grain area per NPY neuron in the arcuate nucleus, as assessed by in situ hybridization, was inversely related to mean LH values, with the grain area per cell being significantly greater (p < 0.05) for LD + T males than for all other groups which did not differ from each other. NPY cell numbers were not significantly different (p > 0.10) among the treatment groups. These results show that NPY mRNA expression is increased in male sheep during a LD photoperiod in a T-dependent manner. Our data are consistent with the idea that NPY is involved in the seasonal regulation of GnRH and LH release in the male sheep.

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Section: Discussionmentioning

confidence: 99%

Neuropeptide Y Gene Expression in Male Sheep: Influence of Photoperiod and Testosterone

Dobbins

Lubbers²,

Jackson³

et al. 2004

Neuroendocrinology

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“…Secondly, the increase in GH secretion at puberty may precede the onset of puberty and the associated increase in testosterone concentrations (Thompson et al 1972). Indeed, in one recent study, it has also been reported that testosterone treatment of wether lambs failed to affect plasma GH concen¬ trations (Lobley, Connell, Buchan et al 1987). The possibility exists for the stimulation of skeletal growth by testosterone to be facilitated in part or in total by an increase in receptor responsiveness to either GH or IGF-I, or both, rather than by an action at the level of the pituitary or hypothalamus.…”

Section: Introductionmentioning

confidence: 97%

Growth hormone and testosterone can independently stimulate the growth of hypophysectomized prepubertal lambs without any alteration in circulating concentrations of insulin-like growth factors

Young

Mesiano

Hintz

et al. 1989

Journal of Endocrinology

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Castrated prepubertal lambs were hypophysectomized and then treated with GH and testosterone either alone or in combination over a series of 3-week treatment periods. Hypophysectomy resulted in a rapid reduction in skeletal growth rate which could be reversed by the administration of either GH (4 IU three times a week for 3 weeks) or testosterone propionate (10 mg daily for 3 weeks). When GH or testosterone treatment was withdrawn, skeletal growth fell to the post-operative rate. Combined treatment with both GH and testosterone was no more or less effective than either hormone given singly. The order of administration did not have any effect on the growth rate. Circulating concentrations of insulin-like growth factor-I (IGF-I) were reduced by hypophysectomy, but neither GH nor testosterone treatment, alone or in combination, had any effect on IGF-I concentrations. Concentrations of IGF-II rose following hypophysectomy, and again were not affected by any of the hormonal replacement treatments. In conclusion, both GH and testosterone could stimulate skeletal growth in the hypophysectomized lamb without any alteration of circulating IGF concentrations, and testosterone can clearly stimulate skeletal growth in the complete absence of GH.

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“…Methionine is one of the major limiting amino acids for dairy cows (Han 2009;Lobley et al 1987;Girard et al 2005). The benefits of methionine supplementation include improvement in milk production and antioxidant capacity, reduction in lymphocyte apoptosis, promotion of the expression of the Bcl-2 genes of the lymphocytes, and inhibition of the Bax gene (Han 2009;Nichols et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Methionine protects against hyperthermia-induced cell injury in cultured bovine mammary epithelial cells

Han

Yang

2015

Cell Stress and Chaperones

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The aim of this study was to investigate the effects of methionine on cell proliferation, antioxidant activity, apoptosis, the expression levels of related genes (HSF-1, HSP70, Bax and Bcl-2) and the expression levels of protein (HSP70) in mammary epithelial cells, after heat treatment. Methionine (60 mg/L) increased the viability and attenuated morphological damage in hyperthermia-treated bovine mammary epithelial cells (BMECs). Additionally, methionine significantly reduced lactate dehydrogenase leakage, malondialdehyde formation, nitric oxide, and nitric oxide synthase activity. Superoxide dismutase, catalase, and glutathione peroxidase enzymatic activity was increased significantly in the presence of methionine. Bovine mammary epithelial cells also exhibited a certain amount of HSP70 reserve after methionine pretreatment for 24 h, and the expression level of the HSP70 gene and protein further increased with incubation at 42°C for 30 min. Compared to the control, the expression of HSF-1 mRNA increased, and there was a significantly reduced expression of Bax/Bcl-2 mRNA and a reduced activity of caspase-3 against heat stress. Methionine also increased survival and decreased early apoptosis of hyperthermia-treated BMECs. Thus, methionine has cytoprotective effects on hyperthermia-induced damage in BMECs.

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Administration of testosterone to wether lambs: effects on protein and energy metabolism and growth hormone status

Cited by 23 publications

References 0 publications

Neuropeptide Y Gene Expression in Male Sheep: Influence of Photoperiod and Testosterone

Neuropeptide Y Gene Expression in Male Sheep: Influence of Photoperiod and Testosterone

Growth hormone and testosterone can independently stimulate the growth of hypophysectomized prepubertal lambs without any alteration in circulating concentrations of insulin-like growth factors

Methionine protects against hyperthermia-induced cell injury in cultured bovine mammary epithelial cells

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