Identification of serum GH-binding proteins in the goldfish (Carassius auratus) and comparison with mammalian GH-binding proteins.
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The present study constitutes the characterization of a specific, high-affinity GH-binding protein (GHBP) in the serum of a teleost, the goldfish (Carassius auratus). GH-binding assay and ligand blotting techniques were employed to identify GHBPs in goldfish serum and hepatocyte culture medium. The binding characteristics and apparent molecular weights (Mr) of goldfish GHBPs were also compared with those of rabbit and rat. LIGAND analysis identified a single class of high-affinity and low-capacity binding sites for iodinated recombinant carp GH (rcGH) in the goldfish serum, with an association constant (Ka) of 20.1x10(9) M-1 and a maximum binding capacity (Bmax) of 161 fmol ml-1 serum. A single class of binding sites for iodinated recombinant sea bream GH and bovine GH (bGH) was also found in goldfish serum, but with a much lower affinity than that of rcGH. The binding affinity for iodinated bGH in rabbit and rat sera was found to be similar to that reported previously. Ligand blotting revealed multiple forms of GHBPs in sera of goldfish, rabbit and rat with Mr ranging from 70 kDa to 400 kDa and 27 kDa to 240 kDa under non-reducing and reducing conditions respectively. A prominent band with Mr of 66 kDa and a minor band with Mr of 27 kDa were observed to occur in sera from all three species under reducing conditions. Iodoacetamide promoted the shedding of three GHBPs with Mr of 25, 40 and 45 kDa from the cultured goldfish hepatocytes. The appearance of all bands was completely inhibited by the presence of excess unlabeled rcGH. Our results provide clear evidence that a GHBP exists in the goldfish and indicate that more information on teleost GHBPs is needed if the physiology of growth in teleosts is to be fully understood. (+info)
Ovine chorionic somatomammotrophin (oCS) production by isolated cotyledon cells from sheep in early and mid gestation: auto-regulation by recombinant oCS.
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We report the ability of sheep placental cotyledonary cells, isolated at different periods of pregnancy (40 to 90 days) to produce ovine chorionic somatomammotrophin (oCS) in in vitro culture conditions. This oCS production increased gradually with stage of pregnancy. Endogenous oCS net production by isolated placental cells was increased, in a dose-dependent manner, by addition of recombinant oCS (roCS). This effect was not observed after addition of recombinant ovine growth hormone. The roCS effect was more potent on cells collected during early pregnancy. Specific immunoprecipitation of oCS revealed that roCS treatment was associated with an increased dose-dependent incorporation of [35S]methionine-[35S]cysteine. These findings provide evidence that oCS may act in a paracrine/autocrine manner to up-regulate its own production during early gestation. We suggest that this autoregulation may be associated with morphological and functional differentiation of the trophoblast during the growth of the placenta. (+info)
Neuropeptide Y restores appetite and alters concentrations of GH after central administration to endotoxic sheep.
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The objective of this study was to determine whether neuropeptide Y (NPY) and recombinant human interleukin-1 receptor antagonist (IL-1ra) would: first, increase food intake; secondly, decrease concentrations of GH; thirdly, reduce GHRH-induced release of GH; and fourthly, reduce changes to concentrations of IGF-I in plasma during experimental endotoxemia in sheep. Six treatments were given to six castrated male sheep in a 6x6 Latin square treatment order. Osmotic mini-pumps were implanted at 0 h and a jugular vein was cannulated. Each sheep was continuously infused with saline (0.9%) or lipopolysaccharide (LPS) (20 micrograms/kg per 24 h, s.c.) at 10 microliters/h for 72 h via the osmotic mini-pumps. Blood samples (3 ml) were collected at 15-min intervals from 24 to 33 h. At 26 h, one of three treatments (artificial cerebrospinal fluid, NPY or IL-1ra) was injected i.c.v. within 30 s (0.3 microgram/kg), then infused i.c.v. from 26 to 33 h (600 microliters/h) at 0.3 microgram/kg per h. GHRH was injected i.v. (0.075 microgram/kg) at 32 h after which blood samples were collected at 5, 10, 15, 30, 45 and 60 min. Feed intake was reduced up to 50% for 48 h in LPS-treated compared with non-LPS-treated sheep. NPY restored feed intake in LPS-treated sheep and induced hyperphagia in non-LPS-treated sheep from 24 to 48 h. In contrast, IL-1ra did not affect appetite. Injection of NPY increased concentrations of GH from 26 to 27 h, while IL-1ra had no effect. Infusion of NPY suppressed GHRH-induced release of GH. However, no treatment altered pulse secretion parameters of GH. Concentrations of IGF-I were 20% higher at 72 h in LPS-treated sheep given NPY than in sheep treated with LPS alone, and this may reflect increased appetite from 24 to 48 h. We concluded that reduced appetite during endotoxemia is due to down-regulation of an NPY-mediated mechanism. Furthermore, NPY stimulates release of GH in healthy sheep, does not reduce pulse secretion parameters of GH, but does suppress GHRH-induced release of GH in endotoxic sheep. Therefore, NPY may be an important neurotransmitter linking appetite with regulation of GH during endotoxemic and healthy states in sheep. (+info)
Measurement of biological activity of somatotropin in hypophysectomized rats.
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AIM: To develop a method for measurement of biological activity of recombinant DNA-derived somatotropin (rhGH). METHODS: The effects of varying the route, frequency and period of administration of GH, the sex of test animals on the biological responses, body weight gain (BWG), and tibial epiphyseal width (TEW), of hypophysectomized (Hypox) rats were compared, respectively. 4-d BWG, 6-d BWG, and 6-d TEW tests were carried out simultaneously in the same group of Hypox rats to determine the biopotency of GH preparations according to a parallel line bioassay (6-point assay). The final result was chosen from the test which had smaller values for the index of precision (lambda) and the average rate of fiducial limits (ARFL) than other tests. RESULTS: No significant differences in the responses between male and female rats, between sc and im, once daily and twice daily injections of bGH were found. But the BWG and TEW of Hypox rats injected with 0.045 and 0.135 IU.d-1 of bGH for 6 d were significantly greater than that for 4 d. Both 4-d BWG test and 6-d BWG test in the range from 0.020 to 0.500 IU.d-1 had values for lambda = 0.0660 and 0.1747, and for r = 0.9000 and 0.9237, respectively. Three estimates of rhGH preparation compared with the International Standard for somatotropin (IShGH), 4.6132, 3.9829, and 4.8023 IU/ampoule, were obtained separately from 4-d BWG test, 6-d BWG test and 6-d TEW test. And the result from 6-d BWG test was reported finally because it had smaller values for lambda and ARFL (0.0608 and 37.907%) than other two tests. CONCLUSION: Both BWG test and TEW test can be carried out simultaneously in the same group of Hypox rats. 6-d BWG test seemed to be more suitable for potency determination of GH preparations than 4-d BWG test and 6-d TEW test. (+info)
A decade of growth hormone treatment in girls with Turner syndrome in the UK. UK KIGS Executive Group.
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Fifteen per cent of children treated with growth hormone (GH) are receiving treatment for Turner syndrome, but few results are available on final height in the UK. In this study, data were obtained from the UK KIGS database for 485 girls with Turner syndrome who were treated from 1986, allowing an audit of practice and outcome over 10 years. Over the decade, the mean age of starting growth hormone treatment fell from 10.4 to 8.5 years and the starting dose increased from 0.55 to 0.95 IU/kg/week. The frequency of injections increased from three to six or seven/week. Some girls received suboptimal doses, which also differed depending on whether they were based on weight or surface area. To assess what height gain might be expected at final height, all 52 girls who were prepubertal at the start of treatment, which continued for four years or more, and who had reached final height or had a growth velocity < 2 cm/year were selected. Their mean gain in final height was 5.2 cm and the GH dose was 0.78 IU/kg/week over 5.8 years. Final height gain correlated significantly with duration of treatment, total dose received, and first year response, which itself related to starting dose. This audit shows a changing pattern of treatment over the past decade, which in many instances has been inadequate. When treatment starts before puberty and continues through to final height, with a dose of 30 IU/m2/week in six or seven injections, a mean increase in final height of 5 cm or more would be expected. (+info)
Growth failure and pituitary function in CHARGE and VATER associations.
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Growth failure and anterior pituitary dysfunction are clinical features of the CHARGE and VATER associations. This study investigated pituitary dysfunction as a potential cause of poor growth in a series of four and three patients with the CHARGE and VATER associations, respectively, who had height standard deviation scores (SDS) less than-2. Five of the seven patients had associated subnormal growth velocity SDS. Patients were investigated with a combination of dynamic and basal endocrine tests. All patients were found to be normonatraemic and to have normal basal thyrotroph and stimulated corticotroph function. The one peripubertal patient had evidence of biochemical gonadotroph dysfunction. Although two patients had marginally low stimulated serum growth hormone responses to glucagon stimulation testing, this was associated with either normal growth velocity or normal serum insulin-like growth factor binding protein 3 (IGFBP-3) concentrations. Thus, somatotroph dysfunction could not be demonstrated unequivocally in any patient. Poor childhood linear growth in the CHARGE and VATER associations does not appear to be associated with pituitary dysfunction. (+info)
5-HT1A receptor function in normal subjects on clinical doses of fluoxetine: blunted temperature and hormone responses to ipsapirone challenge.
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Serotonergic receptors of the 5-HT1A subtype have been suggested to play a pivotal role in the mechanism of action of antidepressant drugs, including specific serotonin reuptake inhibitors (SSRIs). We examined the effect of clinical doses of the SSRI, fluoxetine, on 5-HT1A receptor function in 15 normal volunteers. Hypothermic and hormone responses to the 5-HT1A receptor agonist, ipsapirone (0.3 mg per kg, per os) were examined after two weeks of placebo and again, after the subjects had been receiving fluoxetine for four weeks. On fluoxetine, the hypothermic response to ipsapirone was significantly blunted, as were ACTH, cortisol and growth hormone release. Ipsapirone plasma levels were significantly increased by fluoxetine but a pharmacokinetic effect could not have accounted for the observed blunting of 5-HT1A receptor mediated effects. These findings confirm and extend previous observations in rodents and humans and indicate that both post-synaptic 5-HT1A receptors in the hypothalamus, which mediate hormone responses to 5-HT1A agonists, and pre-synaptic 5-HT1A receptors which (putatively) mediate the hypothermic response, are rendered subsensitive by chronic SSRI administration. Since fluoxetine did not have significant effects on mood and other psychological variables in these subjects, alterations in 5-HT1A receptor function induced by SSRIs may have psychotropic relevance only in the context of existing perturbations of serotonergic function which underlie the psychopathological states in which these drugs are therapeutically effective. (+info)
Immunohistochemical evidence that follicle-stimulating hormone and luteinizing hormone reside in separate cells in the chicken pituitary.
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As is the case in other tetrapod species, the chicken gonadotropins LH and FSH consist of a common alpha subunit and a hormone-specific beta subunit. Gonadotrophs containing LH were shown earlier to be distributed throughout both the caudal and cephalic lobes of the chicken anterior pituitary, but the cellular distribution of FSH in avian species is still uncertain. The purpose of this study was to determine the cellular distribution of FSH-containing chicken gonadotrophs by use of FSH-specific monoclonal antibodies (mAbs). Three new mAbs toward chicken FSH were proven hormone specific by immunodetection of purified hormones on dot blots and by dual-label immunohistochemistry (IHC) on sagittal sections of chicken pituitaries. A rabbit antibody was used to detect chicken LH. Results showed that LH-containing gonadotrophs were densely distributed throughout the anterior pituitary, whereas gonadotrophs containing FSH were much less numerous; in addition, while also present in both lobes, FSH-positive cells were largely absent from the outer margin of the gland. Dual-label IHC revealed that LH and FSH reside almost exclusively in separate gonadotrophs. The identity of FSH-containing cells was further confirmed through use of an antibody to the chicken alpha subunit, which showed that FSH immunoreactivity was always colocalized with the alpha subunit. Our results suggest the possibility that production and secretion of LH and FSH may be regulated differently in chickens than in most other species studied to date. (+info)