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G. V. Kriel, M. J. Bryant, and M. A. Lomax


Two separate experiments were carried out to examine the effect of dietary protein intake on basal and GHstimulated plasma insulin-like growth factor-I (IGF-I) concentrations during either saline or glucose infusion into the jugular vein. In experiment 1, six castrated male lambs (27·1 ± 1·2 kg live weight (LW)) were fed a diet restricted in both metabolizable energy (ME; 0·18 MJ/kg LW per day) and nitrogen (2·0 g/kg LW per day) intakes, while in experiment 2 a further six lambs were fed a similar restricted ME intake but an increased nitrogen intake (3·0 g/kg LW per day). In both experiments glucose (experiment 1, 0·009 mmol/kg LW per min; experiment 2, 0·015 mmol/kg LW per min) or saline (0·25 ml/min) was infused for 6 days and plasma samples were obtained from the jugular vein at hourly intervals on day 4 (basal) or on days 5 and 6 after an i.v. GH challenge. In experiment 1 there was no increase in plasma IGF-I concentrations in response to the GH challenge during saline infusion, but during glucose infusion the plasma concentration of IGF-I increased to a peak after 24 h and declined over the next 20 h. Basal concentrations of IGF-I, insulin and glucose were significantly higher during glucose infusion. In experiment 2 the area under the IGF-I peak in response to the GH challenge was the same for the infusions of saline and glucose but the peak value for IGF-I was significantly higher during glucose infusion due to higher concentrations in the basal period. It is concluded that feeding a dietary intake of metabolisable energy and nitrogen which is only just sufficient to meet the requirements for maintenance of body tissues completely abolishes the increase in plasma IGF-I in response to GH challenge. Increasing the nitrogen supply in the diet or i.v. infusion of glucose re-establishes the IGF-I response to GH challenge as well as increasing basal IGF-I concentrations. The potential involvement of circulating concentrations of insulin, glucose and amino acids in the control of plasma IGF-I levels are discussed.

Journal of Endocrinology (1992) 132, 195–199

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J Bryant, E Loveman, C Cave, D Chase, and R Milne

We have evaluated the reporting of withdrawals due to adverse effects and specific adverse effects in randomised controlled trials of recombinant human GH in adults. A systematic review was carried out of randomised controlled trials of the clinical effectiveness of recombinant human GH in adults with GH deficiency in relation to impact on quality of life. Trials were identified from searching electronic databases, bibliographies of related articles and consulting experts. There was reporting of withdrawals due to adverse effects and specific adverse effects. Rates of oedema and arthralgia were reported in included trials. Seventeen randomised controlled trials, published between 1990 and 1999, met the inclusion criteria for the review. Nine trials reported data on the effectiveness of GH on quality of life in adults. Only five trials (29%) reported both withdrawals from the study because of adverse events and specific adverse events with numbers per study arm and per type. Six further trials (35%) reported either withdrawal details or specific adverse event details or partial data on specific adverse events. Six trials (35%), however, did not report information on either withdrawals or specific adverse events. Ten of the 17 studies (59%) reported the number of patients who withdrew from the study due to adverse events per study arm and type of adverse event per study arm. Seven of the 17 trials (41%) reported the number of specific adverse events per study arm and six (35%) reported the type per study arm. The reporting of adverse events in randomised controlled trials of GH is variable and not consistent across trials. It is not possible to assess the impact that adverse events may have had on unblinding patients, and therefore the extent to which the effects of GH may have been overestimated. Therefore those conducting endocrinology trials in the future need to pay attention to the reporting of withdrawals due to adverse events and specific adverse events.

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J L Garibay-Tupas, R A Maaskant, F C Greenwood, and G D Bryant-Greenwood


The two human relaxin genes termed H1 and H2 are expressed in the choriodecidua and placenta and have been proposed to act via specific receptors as local modulators of collagenolysis in the fetal membranes. Such receptors have been inferred, but not demonstrated, from studies of the effect of adding exogenous relaxin to these tissues. Thus conditions were optimized for the binding of 32P-labelled human relaxin H2 to membrane-enriched particulate fractions of human fetal membranes, amnion and chorion, with adhering decidua. The membrane protein concentration was optimal at 250 μg, when incubated at 27 °C for 60 min, at pH 7·5 with Mn2+ and Mg2+ ion concentrations of 2·0 mm. Incubation of membrane particulate fractions with increasing amounts of labelled relaxin H2 suggested the presence of a single class of binding sites with an affinity constant (K a) of 2·15 nm. The binding was primarily to the chorion and decidua with very little to the amnion layer. The competition for binding of the 32P-labelled human relaxin H2 with unlabelled relaxin H2 gave an IC50 of 28 pm, while an IC50 of 60 pm and 280 pm was obtained for relaxin H1 and porcine relaxin respectively. In contrast, unlabelled guinea-pig relaxin inhibited this binding by only 10% even at a 1000-fold greater concentration than H2, and human recombinant insulin failed to inhibit even at a million-fold concentration of unlabelled relaxin H2.

Relaxins H2 and H1 can readily displace the binding of either 32P-labelled human relaxins H1 or H2 and gave very similar displacement curves. The binding affinity of relaxin H2, however, was fivefold higher than that of relaxin H1. These data provide evidence for the presence of a relaxin receptor that may preferentially bind relaxin H2.

Journal of Endocrinology (1995) 145, 441–448

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C E Bryant, A Tomlinson, J A Mitchell, C Thiemermann, and D A Willoughby


Nitric oxide produced from l-arginine by nitric oxide synthase (NOS) acts in a variety of biological processes via the stimulation of guanylyl cyclase and subsequent elevation of cGMP. Constitutive, calcium-dependent isoforms of NOS are found in endothelial cells (eNOS) and neurones (nNOS), while macrophages express an inducible, calcium-independent isoform (iNOS) in response to the action of certain cytokines or bacterial endotoxin. While the regulation of NOS by exogenous glucocorticoids and steroid hormones is well documented, the effects of endogenous steroid hormones on NOS activity, such as those released during the oestrous cycle, is unknown. Here we demonstrate, using specific antibodies for eNOS, nNOS and iNOS, the presence of NOS in the epithelium of rat fallopian tubes at pro-oestrus, late pro-oestrus, oestrus, metoestrus and dioestrus. Western blot analysis of rat fallopian tube homogenates revealed a protein band at approximately 125 kDa which was recognised by antibodies to different isoforms of NOS, but no bands at the expected molecular weights (eNOS, 140 kDa; nNOS, 160 kDa; iNOS, 135 kDa). NOS activity in fallopian tubes was measured by the conversion of l-[3H]arginine to l-[3H]citrulline. Both calcium-dependent and -independent NOS activities were present. However, in late pro-oestrus when circulating oestrogens are low, NOS activity was reduced in comparison to all other stages of the oestrous cycle. Thus we show that NOS is present in the epithelial lining of the fallopian tube and is recognised at a previously undescribed molecular weight. The changes in NOS activity in these cells during the oestrous cycle may modulate tube motility and contribute to sucessful fertility.

Journal of Endocrinology (1995) 146, 149–157

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S. C. Stansfield, P. G. Knight, N. Z. Al-Mauly, and M. J. Bryant


Prepubertal ewes can, under certain circumstances, be stimulated to ovulate by the novel introduction of a ram. The endocrine response to the presence of the ram is characterized by a rapid increase in the frequency of episodic release of LH. The purpose of this study was to investigate the effect of the presence of a ram on LH pulse frequency in vivo, gonadotrophin-releasing hormone (GnRH) and β-endorphin concentrations in the median eminence, and on the influence of the endogenous opioid peptide agonist [d-Ala2,N-Phe4,Met(0)ol5]-enkephalin (FK 33–824) on basal and depolarization-induced release of GnRH from median eminence tissue superfused in vitro. The study was performed at two prepubertal ages in August and September. In September, the introduction of a ram resulted in an increase in pulsatile release of LH, which was associated with an increase in the rate of basal release of GnRH from median eminence tissue superfused in vitro, and the development of a marked ability of FK 33–824 to suppress depolarization-induced release of GnRH. The concentration of β-endorphin in the median eminence was reduced in animals exposed to the ram at this time. In contrast, the introduction of a ram in August failed to stimulate an increase in LH pulse frequency, basal release of GnRH in vitro was not altered and FK 33–824 was ineffective in reducing depolarization-induced release of GnRH. These results suggest that the premature onset of reproductive activity induced by exposure to the ram may involve the participation of the endogenous opioid peptide system.

J. Endocr. (1987) 115, 333–339

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Studies of the effect of mating on the release of prolactin over a 47-h period from the onset of oestrus in the ewe are presented. Surges of prolactin occurred around the time of pre-ovulatory luteinizing hormone release, and in some instances copulation appeared to result in an additional surge of prolactin secretion.

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In contrast to hypophysectomy, pituitary stalk section in the sheep on any day of the oestrous cycle permits a continued secretion of progesterone which is comparable to that of normal animals (Denamur, Martinet & Short, 1966). These authors postulated that the maintenance of the secretory ability of the corpus luteum after stalk section must be due in part to the continued release of pituitary prolactin. Measurements of plasma prolactin during the normal oestrous cycle of the sheep and after section of the stalk were carried out to verify the hypothesis, and the results are shown in Table 1.

Samples from three normal ewes (E1, E 2 and E 3) were taken daily at 07.00 h from the jugular vein. The onset of oestrus was detected by testing with vasectomized rams six times a day (06.00 h, 07.30 h, 09.00 h, 15.30 h, 17.00 h and 18.30 h). All samples were

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J. L. Whitely, P. E. Hartmann, D. L. Willcox, G. D. Bryant-Greenwood, and F. C. Greenwood


The synthetic progestagen, medroxyprogesterone acetate (MPA), was administered to sows in late pregnancy with the objective of slightly delaying the time of farrowing and thereby providing more marked associations between hormonal changes and the termination of pregnancy, and the initiation of farrowing and lactation in this species.

MPA was administered orally (140 mg, twice daily) to eight sows in late pregnancy on days 112, 113 and 114 of gestation. Parturition was then induced to occur on day 116 by injecting 200 μg cloprostenol i.m. on day 115 of gestation. The peripartum changes in the plasma concentrations of progesterone, cortisol, oestradiol-17β, relaxin, prolactin, lactose and 13,14-dihydro-15-keto prostaglandin F (PGFM) were measured in these sows together with a group of untreated sows. The gestational length for the MPA-treated sows (116·3 ± 0·3 days, mean±s.e.m.) was significantly (P<0·01) greater compared with the untreated sows (114·9 ± 0·3 days). Plasma progesterone declined earlier (P<0·05) with respect to the time of parturition in the treated sows compared with the untreated group. With respect to the timing of parturition, the time at which maximal concentrations of relaxin were attained and the timing of the subsequent decline were earlier in the MPA-treated sows. In both groups of sows, the concentration of relaxin increased before the decline in plasma progesterone. In the untreated sows, the concentration of PGFM increased either slightly before or at the same time as the decline in plasma progesterone, whereas in sows treated with MPA, progesterone concentrations began to decline before any significant increase in the plasma concentration of PGFM. The profiles of cortisol, oestradiol-17β and PGFM were similar in both groups of sows. In both groups of sows, the timing of the initial increase in the concentration of plasma prolactin coincided with a similar rise in plasma lactose (P<0·01). Plasma progesterone either declined earlier or at the same time as the rise in plasma lactose (P<0·01) in the treated group of sows only.

We conclude that since the prepartum changes in the concentration of progesterone and relaxin occurred before significant changes in the concentration of PGFM in the MPA-treated sows, the nature of the luteolytic factor and the mechanism by which it exerts its action remains obscure. The higher concentration of lactose in the mammary secretion at birth in the MPA-treated sows compared with the untreated group suggested that lactogenesis was initiated earlier with respect to parturition following MPA treatment. Furthermore, the administration of MPA to sows in late pregnancy delayed the onset of parturition but did not inhibit lactogenesis.

Journal of Endocrinology (1990) 124, 475–484