bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parathyroid hormone-related protein in milk and its correlation with bovine milk calcium
Authors: Law F. M. K. , Moate P. J. , Leaver D. D. , Diefenbach-Jagger H. , Grill V. , Ho P. W. M. , Martin T. J. 
Published: December 2008

ABSTRACT
Parathyroid hormone-related protein (PTHrP) has been shown to be present in milk of various mammals. We have assayed PTHrP in milk of various species by radioimmunoassay and estimated the molecular weights by Western blot analysis. PTHrP concentrations in bovine, ovine and human milk were 59·2±18·5, 74·1±35·0 and 36·6±20·7 μg/l (means ± s.d.) respectively, in pooled samples collected at various stages of lactation. PTHrP in mammalian milk was found to exist in two forms with molecular weights of 17·5 kDa and 21·5 kDa approximating those of PTHrP(1-108) and (1–141) respectively. In comparison, marsupial milk PTHrP appeared as a single low molecular weight form of 14·4 kDa which approximated to that of PTHrP(1–84). We performed a longitudinal study measuring the concentration of PTHrP in milk throughout lactation in cows, and found it to increase with the duration of lactation (r= 0·669, n = 91). We further examined the relationship between the concentration of PTHrP and total calcium in bovine milk, and the differences between these constituents in milk from Friesian and Jersey cows. PTHrP concentrations correlated positively with total milk calcium (r = 0·346, n = 105). The mean milk concentration of PTHrP of the Jerseys was significantly higher than that of the Friesians (52·6±5·4 μg/l compared with 41·0±4·8 μg/l, P < 0·01), as was the mean milk calcium concentration (30·5±3·0 mmol/l compared with 26·7±2·7 mmol/l, P < 0·01). We therefore postulate that production of PTHrP by the mammary gland may be associated with calcium transport from blood to milk. Also PTHrP may play a role in the development of milk fever in Jerseys which are predisposed to this condition.
Journal of Endocrinology (1991) 128, 21–26
Indirect evidence for short-loop negative feedback of insulin secretion in the rat
Authors: Ammon H. P. T. , Reiber C. , Verspohl E. J. 
Published: December 2008

ABSTRACT
Feedback inhibition of glucose-mediated insulin release has repeatedly been demonstrated in isolated pancreatic islets and in the perfused pancreas. It was the aim of the present study to determine whether inhibition occurs through a long-loop (plasma concentration of insulin) or a short-loop (local concentration) action of insulin. The perfused rat pancreas was used, with different perfusion rates and different insulin concentrations in the medium. Increasing the flow rate from 1 to either 3 or 6 ml/min gradually decreased the insulin concentration in the effluent, at stimulatory concentrations of glucose (11·1 and 16·7 mmol/l). Under the same conditions, however, the integrated amount of insulin released over a period of 30 min was significantly enhanced. When exogenous insulin (2·7 and 5·4 μmol/l) was added to the perfusion medium, insulin secretion in the presence of 11·1 or 16·7 mmol glucose/l at flow rates of 3 and 6 ml/min was diminished. This effect was most prominent with 1 1·1 mmol glucose/l and 2·7 μmol exogenous insulin/l at all flow rates (except 1 ml/min), as well as at the high perfusion flow rates with other glucose concentrations. Insulin secretion was not affected by 5·4 μmol exogenous insulin/l at 1 ml/min or by 2·7 μmol exogenous insulin/l at 3 ml/min. The data support a negative feedback inhibition of insulin secretion by secreted insulin, since insulin secretion was decreased by either adding exogenous insulin or by lowering endogenous insulin as the consequence of increased flow rates. They also suggest that the local extracellular concentration of insulin is of more importance than the plasma concentration, consistent with the concept of a short-loop feedback as already claimed for other hormones and/or neurotransmitters.
Journal of Endocrinology (1991) 128, 27–34
A renin-like enzyme in rat luteal tissue: evidence of local synthesis and its regulation during pregnancy
Authors: De Vito E. , Guardia D. C. , Cabrera R. R. 
Published: December 2008

ABSTRACT
Changes in the concentration of a renin-like enzyme were studied in androgenized rats in which a single luteal phase was induced by the administration of chorionic gonadotrophin. A significant increase in the luteal renin-like enzyme (RLE) concentration was found between the youngest corpora lutea (48 h old) and the oldest one studied (6 days old). The luteal RLE content varied independently of changes in plasma renin concentration. These results suggest that this enzyme was produced locally. The lack of correlation between the luteal RLE and plasma prolactin supports our previous observation that the changes in luteal renin concentration appear not to be prolactin-dependent. Furthermore, the suckling-associated hormones appear not to be related with the regulation of luteal RLE concentration, since the values were not modified in androgenized maternal rats which were suckling when compared with the controls. Changes in luteal renin concentration were also studied during pregnancy. A significant increase was found a few hours after a fertile mating which reached a peak on day 1 of pregnancy, followed by a rapid decrease to low levels throughout the remainder of the pregnancy. Because the renin-angiotensin facilitates angiogenesis, luteal renin may act as an angiogenic factor, stimulating blood vessel growth in the corpora lutea. An alternative hypothesis is that the increase in RLE could be a trigger for calcium flux redistribution and steroid biosynthesis.
Journal of Endocrinology (1991) 128, 43–49
Distribution of 125I-labelled insulin-binding sites in peripheral tissues of the normal and diabetic rat: an autoradiographic study
Authors: Thompson C. S. , Sykes R. M. , Muddle J. , Dashwood M. R. 
Published: December 2008

ABSTRACT
In-vitro autoradiography was used to demonstrate the regional distribution of 125I-labelled insulin-binding sites in the liver, kidney and heart of normal rats and rats made diabetic with streptozotocin.
The distribution of insulin-binding sites in the liver of control rats was uniformly high, while in the kidney of control rats there was weak 125I-labelled insulin binding in the medulla and dense binding in the cortex. In the hearts of control rats a high density of 125I-labelled insulin-binding sites was evident both in the atrial and ventricular muscle.
Non-ketotic diabetes mellitus caused a marked increase in 125I-labelled insulin-binding sites in both the liver and kidney with the former tissue exhibiting a time-dependent (7 to 62 days) increase. There was no apparent effect of diabetes on insulin-binding sites in the heart.
Since experimental diabetes causes (1) a decrease in circulating insulin concentration and (2) impaired insulin action at many target tissues, the increase in 125I-labelled insulin-binding sites observed in the present study may represent a compensatory 'up regulation' of insulin receptors.
Journal of Endocrinology (1991) 128, 85–89
Characterization of a factor(s) from partially purified human gonadotrophin preparations which inhibit(s) the binding of radiolabelled human LH and human chorionic gonadotrophin to Candida albicans
Authors: Bramley T. A. , Menzies G. S. , Williams R. J. , Kinsman O. S. , Adams D. J. 
Published: December 2008

ABSTRACT
We have shown previously that partially purified human chorionic gonadotrophin (hCG) preparations inhibited the specific binding of I-labelled hLH or hCG to Candida albicans membranes at much lower concentrations than did highly purified hLH or hCG preparations. We now describe the characterization and partial purification of a heat-labile glycoprotein from commercially available gonadotrophin preparations. The factor strongly inhibited LH binding to Candida membranes, but not to sheep or pig luteal LH receptors. This material had a molecular weight of 16 000–21 000 daltons, bound strongly to CM-Sepharose at physiological pH, and could be resolved completely from hCG and from epidermal growth factor-like factors present in commercial gonadotrophin preparations. Its activity was not attenuated by a range of inhibitors specific for the four major classes of proteolytic enzymes, nor did it inhibit hormone binding by causing degradation of 125 I-labelled hLH or hCG tracers. Factors which inhibited hLH binding to Candida membranes were also present in partially purified human urinary and equine serum gonadotrophin preparations and in placental extracts, but were not detected in highly purified CG of hLH preparations. The properties of this factor were similar to those described for β-core protein, a cleavage product of the β subunit of hCG which is a contaminant of commercial gonadotrophin preparations. Highly purified β-core protein inhibited 125I-labelled hLH binding to Candida membranes, but not to sheep luteal binding sites.
Preparations of hCG depleted of inhibitor activity could stimulate adenylate cyclase activity in Candida membranes almost five fold. In contrast, partially purified inhibitor preparations strongly inhibited basal adenylate cyclase activity (to 18% of control levels). These observations suggest that endogenous LH-like factors, perhaps similar to β-core proteins of hCG, may play a role in the regulation of morphogenesis in Candida species.
Journal of Endocrinology (1991) 128, 139–151
Pharmacokinetics of thyrotrophin-releasing hormone in patients in different thyroid states
Authors: Iversen E. 
Published: December 2008

ABSTRACT
In view of recent reports suggesting that thyroid hormone control of TRH degradation occurs outside the central nervous system in animals, the effect of thyroid status on serum and tissue degradation of TRH in man was investigated. In six patients with hyperthyroidism and six patients with hypothyroidism, constant TRH infusions were carried out for determination of plasma clearance rate (PCR) and half-life of disappearance (t½) of TRH, with simultaneous determination of half-life of disappearance in serum in vitro (t½p). Using a kinetic model, this enabled the calculation of the half-life of disappearance in the extravascular tissue compartment (t½t). All patients were reinvestigated after they had become euthyroid. PCR, t½ and t½p were 22·1 ±3·4 ml/kg per min, 6·8±1·1 min and 17·3±6·7 min (means ± s.d.) respectively in the euthyroid patients. The t½p was slightly but significantly prolonged during hyperthyroidism. The t½ was 5·6 min in the hyperthyroid patients compared with 9·4 min in the hypothyroid patients. The calculated t½t was 6·5 min in the euthyroid patients. In the patients with untreated hyperthyroidism, t½t was significantly reduced (22·7±10·7%; mean ± s.d.), while it was considerably prolonged (41·1±24·6%) in patients with untreated hypothyroidism. The percentage reduction or prolongation of t½t was negatively correlated with the logarithm of the serum concentrations of thyroxine (r = 0·92) and tri-iodothyronine (r= 0·91) in the untreated patients. Thus, thyroid hormones induce alterations in the pharmacokinetics of TRH. This may partly be due to induction by thyroid hormones of membrane-bound pyroglutamyl aminopeptidase.
Journal of Endocrinology (1991) 128, 153–159
Influence of nutrition and bovine growth hormone (GH) on hepatic GH binding, insulin-like growth factor-I and growth of lambs
Authors: Bass J. J. , Oldham J. M. , Hodgkinson S. C. , Fowke P. J. , Sauerwein H. , Molan P. , Breier B. H. , Gluckman P. D. 
Published: December 2008

ABSTRACT
The effect on young lambs of 0·25 mg recombinant bovine GH (bGH)/kg per day on plasma concentrations of insulin-like growth factor-I (IGF-I), glucose, specific hepatic GH binding and body composition changes was examined at two levels of nutrition (lucerne pellets; 3 and 1·7% of body weight/day). Lambs on low levels of nutrition had low plasma IGF-I (P < 0·001). Plasma concentrations of IGF-I were increased by bGH treatment at both levels of nutrition, with the high nutrition group showing the greatest IGF-I response after 3 and 40 days of bGH treatment. Plasma glucose, after 40 days, was higher overall (P < 0·05) in lambs on high nutrition. bGH treatment increased plasma glucose, with the response being greater in the well-fed lambs. Specific binding of GH to liver membranes was highest in lambs on high nutrition and on bGH treatment; no significant interaction between nutrition and bGH treatment was detected, indicating that specific binding of GH was increased proportionally by bGH at both nutritional levels. The major change in body composition was the reduced level of fatness in lambs treated with bGH. There was no significant effect of bGH on body weight although bGH treatment tended to increase weight gain of well-fed lambs and decreased weight loss of poorly nourished lambs.
The results show that, although there was a significant (P < 0·05) bGH/nutrition interaction for IGF-I there was no such interaction for body weight/components or specific GH binding to the liver. The results indicate that an increase in plasma IGF-I does not necessarily result in increases in growth or changes in carcass composition.
Journal of Endocrinology (1991) 128, 181–186
Epidermal growth factor (EGF) inhibits the secretomotor response of the thyroid: effects of EGF on radioiodine turnover and fluid transport in cultured porcine thyroid cells
Authors: Bourke J. R. , Murdoch S. , Manley S. W. , Matainaho T. , Huxham G. J. , Waters M. J. 
Published: December 2008

ABSTRACT
Thyrotrophin (4-256 μU/ml) promoted an increase in the rate of release of radioiodine from the organic iodine pool of cultured porcine thyroid cells in follicular formations. This action of TSH was antagonized by low concentrations of epidermal growth factor (EGF; 0·1–5 nmol/l). The maximal effect of EGF was reached by 0·5 nmol/l. EGF (0·5–5 nmol/l) also inhibited the stimulatory effect of 8-chloro cyclic AMP (0·06–1·0 nmol/l) on radioiodine turnover. Exposure of thyroid cultures to media with a calcium concentration of 17·7 μmol/l (1% of normal) resulted in a very marked increase in the rate of release of radioiodine. The effect of TSH in low-calcium media was to inhibit the increased release of radioiodine, and EGF (0·5 nmol/l) antagonized this inhibitory effect of TSH. The calcium ionophore, A23187, stimulated radioiodine release in a dose-dependent fashion, and EGF (1·7 nmol/l) inhibited this response. Fluid transport in thyroid monolayers was stimulated by prostaglandin E2 (PGE2; 1 μmol/l). EGF (5 nmol/l) also stimulated fluid transport, but antagonized the effect of PGE2 added subsequently. It was concluded that EGF exerted acute antagonistic effects on thyroid cell responses in vitro to cyclic AMP and agents promoting accumulation of cyclic AMP in time-frames too short for these inhibitory effects to be attributable to the dedifferentiative effect of the growth factor.
Journal of Endocrinology (1991) 128, 213–218
Characterization and autoradiographical localization of oxytocin receptors within the ovine endometrium in relation to post-partum corpus luteum function
Authors: Wallace J. M. , Morgan P. J. , Helliwell R. , Aitken R. P. , Cheyne M. , Williams L. M. 
Published: December 2008

ABSTRACT
The induction of ovulation in early post-partum ewes is associated with a high incidence of premature luteal regression which is independent of the suckling stimulus but dependent on the stage post partum. The aim of the present study was to determine whether oxytocin receptors are present on uterine endometrium early in the luteal phase and hence ascertain whether oxytocin-induced uterine prostaglandin F2α release is a possible mechanism involved in the premature regression of these post-partum corpora lutea. Ovarian and uterine tissues were collected on day 4 of the cycle in ewes induced to ovulate at either 21 or 35 days post partum (n = 4 per group). A further four cyclic ewes were similarly synchronized to ovulate and acted as controls. Corpora lutea from the 21-day post-partum group were significantly (P < 0·01) smaller, had a lower progesterone content and a reduced capacity to secrete progesterone in vitro than corpora lutea from 35-day post-partum or control ewes.
A highly specific oxytocin receptor ligand 125I-labelled d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH29]-vasotocin was used to localize and characterize high affinity oxytocin receptors in uterine endometrium (dissociation constant 145 pmol/l). Oxytocin receptor concentrations in endometrium from ewes induced to ovulate at 21 days post partum were on average five-fold higher (P < 0·05) than in 35-day post-partum and control groups.
Journal of Endocrinology (1991) 128, 253–260
The influence of repeated stress on the release of melanin-concentrating hormone in the rainbow trout
Authors: Green J. A. , Baker B. I. 
Published: December 2008

ABSTRACT
Melanin-concentrating hormone (MCH) is a neurohypophysial peptide that induces pigmentary pallor in teleosts and which is released when the fish are placed on a white background. An additional effect of the peptide is the depression of ACTH and hence cortisol secretion during moderate stress. The present work on rainbow trout shows that plasma MCH concentrations, while unaffected by a single stress, are raised by repeated stress (1 ml saline injected i.p. without anaesthesia) and remain high for several hours thereafter. The response to stress is observed only in white-adapted fish and not in fish kept in black-coloured tanks, when MCH release is normally low. Plasma concentrations of MCH vary diurnally but stress induces an equivalent incremental rise in plasma MCH, whether administered in the middle or towards the end of the photophase. The stress-induced rise in MCH concentrations is prevented by treatment with dexamethasone. The results support the suggestion that the modulatory effect of MCH on the hypothalamopituitary-interrenal axis of fish might be enhanced under conditions of stress.
Journal of Endocrinology (1991) 128, 261–266
Efflux of potassium ions in angiotensin II-stimulated bovine adrenocortical cells
Authors: Shepherd R. M. , Fraser R. , Nichols D. J. , Kenyon C. J. 
Published: December 2008

ABSTRACT
Angiotensin II (AII) stimulation of steroidogenesis is known to be associated with depolarization of the adrenocortical cell membrane. In these cells, membrane permeability to potassium ions governs electrical potential. The effects of All on the rate of efflux of K+ in relation to the control of aldosterone synthesis has been investigated in bovine adrenocortical cells preloaded with 43K.
In static incubations, the pattern of 43K efflux fitted a model with two exponential components with t½ values of 47·7±1·7 and 14·2±0·6 (s.e.m.) min. AII increased the efflux rate of the slow-exchange component (t½ 37·1±0·6 min) and retarded efflux from the fast-exchange component. With ouabain present to prevent reuptake of the isotope, the rate of efflux for both components was increased in unstimulated cells (t½ 28·4±1·1 and 12·0±0·7 min). AII again increased the rate of efflux from the slow component (t½ = 24·2±1·7 min, P < 0·01) and retarded efflux from the fast component. These biphasic effects were apparent in cells treated with a range of AII concentrations (0·1 nmol/l–1 μmol/l) but the point in time at which increased efflux from the slower component predominated over retardation of the slow component was earlier for cells treated with 1 μmol AII/l than for cells treated with lower concentrations.
We suggest that decreases and increases in K+ efflux caused by AII are associated with depolarization and repolarization respectively. Changes in intracellular concentrations of Ca2+ may link these events.
Journal of Endocrinology (1991) 128, 297–304
Disappearance half-life times of exogenous and growth hormone-releasing factor-stimulated endogenous growth hormone in normal rats
Authors: Chapman I. M. , Helfgott A. , Willoughby J. O. 
Published: December 2008

ABSTRACT
This study was performed to determine the disappearance half-life times of endogenous and exogenous rat GH in conscious normal rats and to compare these with the decay characteristics of GH at the end of spontaneous normal bursts. The endogenous half-life was determined in five rats by giving an i.v. injection of rat GH-releasing factor followed after 10 min by an i.v. injection of long-acting somatostatin analogue (octreotide) and taking blood samples for 85 min. The half-lives (mean ± s.e.m.) were 3·4±0·4 min and 13·2±1·1 min for the first and second exponential respectively as determined by bi-exponential analysis. The exogenous GH half-life was determined in ten rats by giving i.v. octreotide followed after 10 min by i.v. rat GH and sampling for 85 min. The half-lives of exogenous GH were 3·3±0·2 min and 17·5±1·4 min by bi-exponential analysis and there was no significant difference between the half-lives of endogenous and exogenous GH. The half-life of the decline of GH levels at the end of spontaneous bursts in nine rats was 14·4±0·9 min, not different from the half-life of endogenous GH, the secretion of which was terminated by octreotide. This suggests that the end of spontaneous GH bursts is marked by sudden cessation of GH release and may provide an indication of the rapidity of change in the levels of the underlying hypothalamic hormones which control GH release.
Journal of Endocrinology (1991) 128, 369–374
Effect of basal and pulsatile LH release on FSH-stimulated follicle growth in ewes chronically treated with gonadotrophin-releasing hormone agonist
Authors: Picton H. M. , McNeilly A. S. 
Published: December 2008

ABSTRACT
Ewes chronically treated with gonadotrophin-releasing hormone (GnRH) agonist were used to investigate the importance of the peripheral concentration of LH in FSH-stimulated follicular development. Twenty-four Welsh Mountain ewes were treated with two agonist implants containing 3·3 mg buserelin. During week 6 of treatment all the ewes were given a 72-h continuous infusion of ovine FSH alone (3 μg/h) or FSH with large (7·5 μg)- or small (2·5 μg) amplitude pulses of ovine LH delivered at 4-hourly intervals. The importance of baseline LH throughout the FSH infusion was evaluated in six animals which were treated with a specific antiserum against bovine LH (LH-AS) 15–20 h before the start of FSH treatment.
In the absence of LH-AS, infusion of FSH alone or with large or small pulses of LH stimulated the development of a normal number of small follicles (≤ 2·5 mm in diameter) and large follicles (> 2·5 mm in diameter). These follicles had normal diameter and steroid secretion compared with control ewes on day 8 of the luteal phase. In contrast, the animals pretreated with LH-AS developed no follicles > 2·0 mm in diameter but the number of small follicles per ewe was significantly (P < 0·05) increased.
These results support the hypothesis that FSH in the absence of pulsatile LH release stimulates preovulatory follicular development in ewes treated with GnRH agonist. The follicular response to LH pulses of different amplitude is dependent on both the stage of development of the follicle and the peripheral concentration of FSH. The endogenous basal level of LH present throughout the FSH infusion is essential for FSH to induce follicle growth beyond > 2·5 mm in diameter.
Journal of Endocrinology (1991) 128, 449–456
THE MEASUREMENT OF INSULIN-LIKE GROWTH FACTOR 1 IN SHEEP PLASMA
Authors: Bruce L.A. , Atkinson T. , Hutchinson J.S.M. , Shakespear R.A. , MacRae J.C. 
Published: December 2008

ABSTRACT
A method is described for the radioimmunoassay (RIA) of insulin-like growth factor 1 (IGF-1) in neutralised formic acid-ethanol extracts of sheep plasma. The ability of the acid-ethanol pretreatment to remove the IGF-1 binding proteins (BPs), which interfere in the assay has been examined. Comparative plasma IGF-1 concentrations determined by the method correlated closely (P<0.001) with corresponding values where BPs were removed by acid gel filtration. The method has been applied to studies in which sheep were given exogenous growth hormone and indicated that plasma IGF-1 levels respond rapidly to the onset and termination of treatment.