bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Asn87 and Asp318 mutations on ligand binding and signal transduction in the rat GnRH receptor.
Authors: Cook J. V. , Faccenda E. , Anderson L. , Couper G. G, , Eidne K. A. , Taylor P. L. 
Published: December 2008

ABSTRACT
The gonadotrophin-releasing hormone (GnRH) receptor is unlike other G-protein coupled receptors in that the highly conserved amino acids, Asp in the second transmembrane region and Asn in the seventh, are interchanged. Site-directed mutagenesis studies mutated these residues back to their normally conserved positions. Two single mutants Asn87Asp & Asp318Asn and one double mutant Asn87Asp Asp318Asn were transiently expressed in COS-1 cells and their effect on binding to GnRH and inositol phosphate production measured. The single mutant Asp318Asn had no effect on ligand binding but abolished GnRH-dependent inositol phosphate production, whereas mutations Asn87Asp and Asn87Asp Asp318Asn show a complete loss of GnRH binding and subsequent inactivation of its second messenger system.
Journal of Molecular Endocrinology
Post-transcriptional block in oxytocin gene expression within the seminiferous tubules of the bovine testis
Authors: Ungefroren H , Davidoff M , Ivell R 
Published: December 2008

Abstract
Northern blot hybridization showed that bovine and sheep testis, unlike testes from other mammals, contain moderate levels of an apparently normal oxytocin gene transcript. In situ hybridization localized this mRNA to within the seminiferous tubules, possibly in the Sertoli cells. Conflicting with this result, immunohistochemistry showed that both oxytocin and the syngeneic neurophysin I epitopes are both clearly restricted to the Leydig cells, being expressed here at a low level. Since illegitimate transcription from spurious start sites can lead to a lack of translation product, the integrity of the major ruminant testicular transcripts of the oxytocin gene was checked using differential hybridization, RNase protection and multiple polymerase chain reaction assays. All tests showed the transcripts to have a normal, translatable composition and to be transcribed from the conventional 5' initiation site. Therefore, the block in oxytocin gene expression within the tubules is probably due to a lesion at the post-transcriptional level. The low level peptide expression in the Leydig cells can probably be attributed to the presence of functional transcripts in these cells, which are below the level of significant detection for the in situ hybridization assay.
Journal of Endocrinology (1994) 140, 63–72
In vivo growth hormone gene expression in neonatal rat thymus and bone marrow
Authors: Binder G , Revskoy S , Gupta D 
Published: December 2008

Abstract
The ontogenesis of GH gene expression in the pituitary gland and immune organs of rats was studied by in vitro amplification of GH mRNA using a specific reverse transcription-polymerase chain reaction. Samples were obtained after microsurgery and total RNA extraction of fetal, neonatal and adult rat tissues. Amplification was followed by analysis using Southern blot techniques and hybridization using a specific digoxigenin-labelled GH cDNA probe. The study was started on day 15 of gestation. GH gene expression occurred in the pituitary gland on day 17. GH mRNA was found in the bone marrow and thymus of neonatal rats but not in the spleen or liver. No GH transcripts were detected in the immune organs of fetal or adult rats. The transient GH expression in rat immune organs may indicate a specific function of GH in the development of the immune system during the neonatal period.
Journal of Endocrinology (1994) 140, 137–143
Several insulin-like growth factor-I analogues and complexes of insulin-like growth factors-I and -II with insulin-like growth factor-binding protein-3 fail to mimic the effect of growth hormone upon lactation in the rat
Authors: Flint D J , Tonner E , Beattie J , Gardner M 
Published: December 2008

Abstract
Lactation was suppressed in rats using a combined treatment of bromocriptine (to reduce prolactin concentrations) and a specific antiserum to rat GH administered twice daily for 2 days. When milk production had ceased, as determined by litter weight loss and the absence of milk in the stomachs of pups, attempts were made to reinitiate lactation using prolactin, GH, insulin-like growth factor-I (IGF-I) precomplexed to recombinant human IGF-binding protein-3 (hIGFBP-3) or IGF-I plus IGF-II precomplexed to hIGFBP-3. Despite the fact that all treatments except prolactin led to increases in serum IGFs and IGFBP-3, only prolactin and GH provoked the reinitiation of milk production as determined by increased litter weight gain, milk in the stomach of pups and a significant increase in the weight of the mammary glands.
Since the mammary gland has been shown to produce IGFBPs which may inhibit IGF action we also tested three IGF-I analogues, R3-IGF-I, Long-IGF-I and Long-R3-IGF-I. R3-IGF-I has a single amino acid substitution (Glu to Arg) at position 3 whereas Long-IGF-I has a 13 amino acid N-terminal extension. These modifications dramatically reduce the ability of these analogues to bind to IGFBPs although they remain active at the IGF-I receptor. Such IGF analogues would therefore be expected to be active irrespective of the production of inhibitory IGFBPs. However, none was effective in reinitiating lactation, even at doses which have been shown to be biologically effective in terms of nitrogen retention.
We therefore conclude that, despite the fact that GH induces increases in serum IGF-I, IGF-II and IGFBP-3 when administered to lactating rats, the combination of all of these factors fails to reinitiate lactation. The biological significance of these changes and the mechanism by which GH stimulates milk secretion, when there appear to be no GH receptors on mammary epithelial cells, remain unclear, although the fact that both GH and prolactin were able to prevent reductions in DNA content of the gland suggest that regulation of apoptosis may be involved.
Journal of Endocrinology (1994) 140, 211–216
Comparison of the effectiveness of various procedures for reducing or eliminating insulin-like growth factor-binding protein interference with insulin-like growth factor-I radioimmunoassays on porcine sera
Authors: Frey R S , Hathaway M R , Dayton W R 
Published: December 2008

Abstract
We have examined the efficacy of various methods for reducing the interference of insulin-like growth factor-binding proteins (IGFBPs) with insulin-like growth factor-I (IGF-I) radioimmunoassays (RIAs) run on porcine sera. Acid–ethanol (AE) extraction, AE extraction followed by cryoprecipitation, glycyl–glycine (GG) extraction, GG extraction followed by Sephadex G-50 chromatography in 1 mol acetic acid/l (GG/G-50), and Sep-Pak chromatography were analysed. To provide a range of IGF-I and IGFBP levels, sera obtained from control, hypophysectomized, diabetic and somatotrophin-treated pigs were used. Recoveries of IGF-I added to sera prior to treatments other than Sep-Pak chromatography ranged from 85 to 105% and were not significantly different. In contrast, Sep-Pak chromatography gave extremely variable recoveries. 125I-Labelled IGF-I ligand blotting showed that GG extraction followed by acid G-50 chromatography was by far the most effective method of removing or inactivating IGFBPs in porcine sera. Consequently, this procedure was used as a standard against which to compare other extraction procedures. GG extraction alone removed or inactivated low molecular weight binding proteins but appeared to have little effect on IGFBP-3. AE extraction reduced the level of IGFBP-3 but had little effect on lower molecular weight binding proteins. Even though none of the tested procedures completely removed or inactivated the binding proteins, all samples yielded IGF-I displacement curves that were parallel to that obtained for IGF-I standard. Despite yielding parallel displacement curves, sera extracted by various methods gave dramatically different apparent IGF-I levels when subjected to IGF-I RIA. IGF-I RIA of GG extracted sera yielded IGF-I values that were closest to those obtained for identical serum samples subjected to glycyl-glycine extraction followed by G-50 chromatography. For sera from control, hypophysectomized, diabetic and somatotrophin-treated pigs, the relationship of the IGF-I level in GG-extracted sera to that in GG-extracted, acid G-50 chromatographed (GG/G-50) sera was √GG=1·13√GG/G-50−0·23 (r2=0·98). Consequently, GG extraction can be used to remove IGFBP interference with IGF-I RIAs of porcine sera from normal, hypophysectomized, diabetic and somatotrophin-treated animals.
Journal of Endocrinology (1994) 140, 229–237
Normal gastric inhibitory polypeptide response to oral glucose in hypothyroidism
Authors: Hays J H , Silverman E , Potter B B , Shakir K M M 
Published: December 2008

Abstract
Although the action of gastric inhibitory polypeptide (GIP) on the β cells of the pancreas is well documented, the effect of this hormone on insulin secretion in patients who are hypothyroid has not been studied. Hypothyroid patients demonstrate increased serum immunoreactive insulin levels in response to oral glucose when compared with euthyroid subjects. We postulated that a delayed and exaggerated response of GIP could account for the hyperinsulinaemic response. Nine thyroidectomized patients (aged 44·9 ± 3·6 years) who were otherwise healthy but undergoing re-evaluation for recurrence of thyroid carcinoma, were given a 75 g oral glucose tolerance test (OGTT). These subjects were studied 6 weeks after thyroid hormone replacement had been stopped and while on hormone treatment. The serum glucose and plasma GIP responses to oral glucose were similar in the euthyroid and hypothyroid states. The serum insulin response as well as the areas under the curve for insulin following OGTT were significantly elevated (P<0·01) during hypothyroidism. Solid-phase gastric emptying times studied in six patients who were euthyroid and hypothyroid were not different (35 ± 12 versus 36 ± 14 min respectively). None of the subjects had detectable levels of serum thyroglobulin, microsomal or parietal cell antibodies. In summary, we have confirmed a hyperinsulinaemic response to an OGTT and normal solid-phase gastric emptying rates in this form of hypothyroidism. We did not find significant differences in serum glucose or GIP responses and postulate this as evidence of resistance to the effects of endogenous insulin. The mechanism of alterations in carbohydrate tolerance in the hypothyroid state continue to remain unknown.
Journal of Endocrinology (1994) 140, 309–312
Corticotrophin-releasing hormone does not inhibit growth hormone-releasing hormone-induced release of growth hormone in control subjects but is effective in patients with eating disorders
Authors: Rolla M , Andreoni A , Bellitti D , Ferdeghini M , Ghigo E , Müller E E 
Published: December 2008

Abstract
Previous studies have shown that corticotrophin-releasing hormone (CRH) inhibits GH secretion in response to GH-releasing hormone (GHRH) in normal women and men, and animal studies suggest that this effect is mediated by an increased release of somatostatin from the hypothalamus. It has been reported that there are abnormalities in the neuroendocrine regulation of the hypothalamo-pituitary-somatotrophic axis and the hypothalamo-pituitary-adrenocortical axis in patients with eating disorders. The present study therefore investigated the ability of CRH to inhibit the GH response to GHRH in eight young women with anorexia nervosa (AN) and in seven young women with eating disorders which were not otherwise specified (NOS). We also compared the effect of CRH in the patients with the response it caused in ten control women. In contrast to a previous report, combined i.v. administration of 50 μg human CRH (hCRH) and 50 μg GHRH(1–29) caused a GH response in control women which was higher, although not significantly so, than that induced by GHRH alone (area under the curve (AUC) 988·5 ±506·0 compared with 1568·4 ±795·6 (s.e.m.) ng/ml per 120 min for GHRH alone and GHRH plus hCRH respectively).
Conversely, the administration of hCRH given together with GHRH markedly inhibited the GH response induced by the latter in both AN patients (AUC 2253·0 ±385·7 compared with 1224·4 ±265·7 ng/ml per 120 min for GHRH and GHRH plus hCRH respectively; P<0·005 and NOS patients (AUC 2827·4±281·1 compared with 308·5 ± 183·4 ng/ml per 120 min for GHRH and GHRH plus hCRH respectively; P<0·0001). These results (1) refute the suggestion that there is an inhibitory influence of CRH over GH secretion under normal conditions, (2) indicate that this inhibitory influence exists in patients with eating disorders, and (3) imply that, in the latter, hypothalamic somatostatinergic function is, at least in part, preserved.
Journal of Endocrinology (1994) 140, 327–332
Characterization of two relaxin genes in the chimpanzee
Authors: Evans B A , Fu P , Tregear G W 
Published: December 2008

Abstract
Relaxin is a peptide hormone which has a variety of physiological effects on tissues of the reproductive tract as well as other organs such as the heart and brain. Whereas all non-primates so far examined have only a single relaxin gene, humans have two genes (H1 and H2, or gene 1 and gene 2). H2 relaxin is synthesized in the corpus luteum during pregnancy and is also found in the placenta and prostate, whereas expression of H1 has been very difficult to detect. We have begun a study of relaxin genes in the chimpanzee to assess whether this species may provide a suitable model in which to examine the roles of gene 1 relaxin. We find that the chimpanzee has two relaxin genes, one of which is very similar to H2. The second gene has an gene 1 type A chain but the B chain is of the gene 2 type, possibly due to a gene conversion event. The authentic chimpanzee gene 2 (Ch2) is expressed in the corpus luteum of pregnancy and in the placenta. Ch1 is not expressed in the placenta, but the mRNA can be detected by polymerase chain reaction in the corpus luteum.
Journal of Endocrinology (1994) 140, 385–392
Decreased number and size and the defective function of testicular macrophages in long-term hypophysectomized rats are reversed by treatment with human gonadotrophins
Authors: Gaytan F , Bellido C , Romero J L , Morales C , Reymundo C , Aguilar E 
Published: December 2008

Abstract
Macrophages are a common cell type in the testicular interstitium of the rat and are morphologically and functionally related to Leydig cells. We investigated the number of macrophages and Leydig cells in long-term (24 weeks) hypophysectomized (LTHX) or sham-operated rats. LTHX rats showed a 76% decrease in the number of macrophages, whereas the number of Leydig cells was only slightly decreased (by 18%). The profile areas of both macrophages and Leydig cells were very much decreased (46% and 66% respectively).
Sham-operated and LTHX rats were treated with vehicle or human FSH and LH (hFSH/hLH; 75 IU/kg body weight per day) for 1 week. This treatment induced a 286% increase in the number of macrophages and a 32% increase in the number of Leydig cells in LTHX rats. The profile areas of macrophages and Leydig cells were also increased (212% and 184% respectively). About 80% of macrophages showed vacuolization of the cytoplasm. Gonadotrophin treatment did not induce changes in cell numbers in sham-operated animals but about 30% of macrophages showed large cytoplasmic vacuoles.
Vehicle- or hormone-treated LTHX rats were given a single injection of ethylene dimethane sulphonate (EDS) and killed 72 h later. Leydig cells were absent from the testicular interstitium of sham-operated rats but there were large numbers of dead Leydig cells (about 40% of the pre-existing population) in the testicular interstitium of LTHX rats 3 days after EDS treatment. Complete clearance of the testicular interstitium from EDS-killed Leydig cells was found in LTHX rats treated with hFSH/hLH. These results indicate that the decreased number and size and the defective function of testicular macrophages in LTHX rats can be restored by treatment with gonadotrophins.
Journal of Endocrinology (1994) 140, 399–407
Effect of inhibin immunoneutralization on steroidogenesis in rat ovarian follicles in vitro
Authors: Smyth C D , Gosden R G , McNeilly A S , Hillier S G 
Published: December 2008

Abstract
Inhibin is a putative gonadal paracrine factor produced by FSH-stimulated granulosa cells. To assess the paracrine function of inhibin further, preantral follicles (approx. 240 μm) with attached thecal cells were isolated mechanically from immature rat ovaries and cultured individually in vitro for 5 days in medium containing homologous serum and FSH. After 5 days, follicles had grown to preovulatory size (approx. 470 μm) with a commensurate increase in oestradiol secretion but not progesterone. Immunoneutralization of endogenous inhibin resulted in a significant decrease in oestradiol secretion and an increase in progesterone accumulation. When antiserum-treated follicles were supplemented with exogenous inhibin, oestradiol secretion was restored and progesterone accumulation was reduced. Aromatase substrate (androstenedione) levels were too low to measure, regardless of antiserum treatment. However, follicles treated with inhibin antiserum in the presence of exogenous androstenedione also exhibited oestradiol levels similar to untreated controls while progesterone accumulation remained elevated. We interpret these data as evidence that inhibin secreted by FSH-stimulated granulosa cells exerts a physiologically significant paracrine function in the follicle wall. Based on previous observations that inhibin stimulates androgen synthesis by isolated thecal/interstitial cells, it is proposed that granulosa-derived inhibin promotes thecal androgen synthesis and hence oestrogen synthesis during preovulatory follicle development. The antiserum-induced increase in progesterone accumulation is most probably explained by reduced metabolism of C21 steroid substrate to androgen in thecal/interstitial cells deprived of inhibin. It is concluded that inhibin is a physiological modulator of follicular steroidogenesis which exerts its effect at the level of thecal cell androgen synthesis.
Journal of Endocrinology (1994) 140, 437–443
Metabolism of testosterone trans-4-n-butylcyclohexyl carboxylate, a high potency androgen, in rodents and primates: in vitro studies
Authors: Monder C , Vincze I , Blye R P , lohan F 
Published: December 2008

Abstract
Testosterone trans-4-n-butylcyclohexyl carboxylate releases continuous physiological levels of testosterone into the circulation of men or monkeys over a period of 8 to 10 weeks from an intramuscular depot and may, therefore, be an agent of choice for androgen replacement therapy. The purpose of this study was to investigate the metabolism of the ester and its side chain. The ester was hydrolysed by blood sera of guinea-pig, rabbit and rat, but not horse or man. It was slowly hydrolysed by rat and cynomolgus liver and the testosterone metabolites androstenedione and androstanediol were formed. Bucyclic acid (trans-4-n-butylcyclohexyl carboxylate) was slowly metabolized to two metabolites, M1 and M2, by cynomolgus liver homogenates. The acid metabolites were analysed by chromatography and mass spectrometry after reaction with diazomethylpyrene to form fluorescent pyrenyl esters. When compared with synthetic compounds using the criteria of chromatographic mobility and mass spectral analysis, the polar metabolite was identified as hydroxy-4-n-butylcyclohexyl carboxylate. The less polar metabolite could not be definitively identified.
Journal of Endocrinology (1994) 140, 465–473
Differences in the association of insulin-like growth factor-I (IGF-I) and IGF-I variants with rat, sheep, pig, human and chicken plasma-binding proteins
Authors: Lord A P D , Bastian S E P , Read L C , Walton P E , Ballard F J 
Published: December 2008

Abstract
Associations between labelled insulin-like growth factors (IGFs) and IGF-binding proteins in plasma have been compared in the rat, sheep, human, pig and chicken. The IGFs tested were recombinant human IGF-I, the truncated variant, des(1–3)IGF-I, and LR3IGF-I, an extended form that had been engineered so as to minimize interactions with IGF-binding proteins. Marked species differences were demonstrated, notably that the IGF-I variants which exhibited extremely weak binding in rat plasma bound significantly in plasma from the other species. This result was shown both by size-exclusion chromatography of labelled IGFs added to plasma, in which the extent of variant IGF-I binding decreased in the order sheep>human>pig=chicken>rat, and by competition for labelled IGF-I binding in vitro, in which the order was pig=chicken>sheep>human>rat. Notwithstanding these differences, the two IGF-I variants showed only slight between-species binding differences when tested with purified rat, sheep and human IGF-binding protein-3. Ligand blotting experiments with plasma from the five species similarly showed a consistent pattern in that IGF-I binding was much greater than des(1–3)IGF-I binding, which in turn was greater than LR3 IGF-I binding. These experiments suggest first that IGF-binding properties measured after the removal of endogenous IGFs do not always reflect the situation with untreated plasma or in vivo, and secondly, the increased potencies of des(1–3)IGF-I and LR3 IGF-I in rat growth studies that have been ascribed to higher concentrations of these peptides in the free form cannot necessarily be extended to other species.
Journal of Endocrinology (1994) 140, 475–482
Effects of hypothyroidism on the growth hormone axis in sheep
Authors: Fletcher T P , Clarke I J 
Published: December 2008

Abstract
This study examined the effect of thyroidectomy (TX) on the GH axis in sheep. The secretion of GH was monitored 10 and 77 days after TX or sham-TX when the effects on plasma GH and prolactin levels of the injection of 0·5 μg GH-releasing factor (GRF)/kg and 1 μg thyrotrophin-releasing hormone (TRH)/kg were also assessed.
There were no significant differences in GH pulse amplitude, pulse frequency, inter-pulse interval and GH secreted/h between sham-TX and TX animals at 10 or 77 days after TX.
There was no difference in the GH response to GRF injection in sham-TX sheep at any time but in TX sheep the GH response was significantly (P<0·05) attenuated 10 days after TX. After 77 days the GH response was similar to the response before TX. There was no measurable GH response to injection of TRH in sham-operated or TX sheep at any time. The prolactin response to TRH was not affected by TX or sham-TX.
These results suggest that TX in sheep does not affect GH secretion but paradoxically the response to GRF is attenuated in hypothyroid sheep in the short term. TRH causes release of prolactin but not GH in sheep.
Journal of Endocrinology (1994) 140, 495–502