bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two site-specific radioimmunoassays which demonstrate the presence of proteolytically modified insulin-like growth factor-binding protein-3 in the circulation
Authors: Hughes S. C. Cwyfan , Wass J. A. H. , Holly J. M. P. 
Published: December 2008

ABSTRACT
The presence of proteolytic activity in the circulation directed against insulin-like growth factor binding protein-3 (IGFBP-3) was originally described in pregnancy but has subsequently been described in a number of catabolic and other pathological conditions. However, detection of this proteolytically modified IGFBP-3 has been demonstrated, in most cases, following separation using SDS-PAGE and this has led to speculation that its occurrence may be an artefact of the harsh conditions employed. Using two sitespecific antisera, one of which recognizes as its antigenic site a region of IGFBP-3 which is close to that of the IGF-binding domain, we have developed two radioimmunoassays which, when compared, can reveal alterations in the IGF-binding domain of IGFBP-3. The presence of IGFBP-3 modified by the circulating protease is denoted in this system by a divergence in the IGFBP-3 levels observed; this divergence has been shown to coincide with protease activity as determined by Western ligand blotting. The use of these assays has confirmed that the IGF-binding site of IGFBP-3 undergoes proteolytic modification in the circulation during a number of pathologies.
Journal of Endocrinology (1993) 137, 321–328
Protein kinase C activation and calcium mobilization decrease prolactin release from human decidual cells in early pregnancy
Authors: Kubota T. , Kamada S. , Taguchi M. , Sakamoto S. , Aso T. 
Published: December 2008

ABSTRACT
The present study was undertaken to investigate the effects of protein kinase C (PKC) activation and calcium mobilization on the release of prolactin from human decidual cells in early pregnancy. Decidua obtained from patients in early pregnancy was enzymatically dispersed and cultured with phorbol myristate acetate (PMA) and calcium ionophore A23187 in a cell culture system. Prolactin in the medium was measured by enzyme-immunoassay.
PMA, a PKC activator, dose-dependently attenuated the release of prolactin from cultured decidual cells, while a PKC inhibitor, H7, significantly (P < 0·001) diminished the effect of PMA on prolactin release. PMA had no effect on cell numbers or DNA synthesis in the decidual cells during culture. It did not significantly increase the generation of inositol phosphate in decidual cells prelabelled with myo[3H]inositol and it had no effect on intracellular calcium concentration ([Ca2 + ]i). Calcium ionophore A23187, a Ca2 +-mobilizing agent, also significantly (P<0·001) attenuated the release of prolactin and potentiated the PMA-induced suppression of prolactin release from decidual cells.
These findings suggest that activation of PKC and mobilization of Ca2+ may be involved in regulating prolactin release from human decidual cells. The PMA-induced suppression of prolactin release is not triggered by phosphoinositide hydrolysis nor by the increase in [Ca2 + ]i in decidual cells.
Journal of Endocrinology (1993) 137, 335–340
Vasoactive intestinal peptide, but not pituitary adenylate cyclase-activating peptide, modulates the responsiveness of the gonadotroph to LHRH in man
Authors: Hammond P. J. , Talbot K. , Chapman R. , Ghatei M. A. , Bloom S. R. 
Published: December 2008

ABSTRACT
Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) are hypothalamic peptides sharing considerable sequence homology which are postulated to be hypophysiotrophic releasing factors. When infused into man, PACAP has no effect on anterior pituitary hormone levels, while VIP causes a significant increase in circulating prolactin concentrations. However, PACAP has recently been shown to augment the release of LH and FSH in response to LHRH in rat anterior pituitary cell culture. In order to ascertain if either peptide has a similar effect in man, PACAP and VIP were infused at 3·6 pmol/kg per min into six healthy male volunteers, and an LHRH test was performed 30 min after the infusion was commenced. Infusion of PACAP did not alter the gonadotrophin response to LHRH significantly. However, VIP augmented the release of LH significantly, both during the infusion and for 30 min thereafter, although there was no effect on FSH release. Thus VIP, but not PACAP, potentiates the release of LH after LHRH injection in man.
Journal of Endocrinology (1993) 137, 529–532
Insulin-like growth factor-II in human fetal adrenals: regulation by ACTH, protein kinase C and growth factors
Authors: Ilvesmäki V. , Blum W. F. , Voutilainen R. 
Published: December 2008

ABSTRACT
Insulin-like growth factor-II (IGF-II) may be one of the most important local growth factors in human fetal adrenals (HFAs), where its mRNA levels are upregulated by ACTH. We have investigated whether protein kinase C (PKC)-dependent mechanisms and various polypeptide growth factors participate in the regulation of IGF-II gene expression in cultured HFA cells, and whether HFA cells secrete IGF-II peptide into the culture medium. ACTH enhanced IGF-II mRNA accumulation dose- and time-dependently, maximally four- to sixfold, and this increase was inhibited dose-dependently (0·01-100 μg/l) by 12-O-tetradecanoyl phorbol-13-acetate (TPA), a PKC activator. TPA decreased basal IGF-II mRNA levels by approximately 55%. Staurosporine, a PKC inhibitor, abolished the inhibitory effects of TPA and induced accumulation of IGF-II mRNA. Dibutyryl cyclic AMP, cholera toxin and forskolin increased IGF-II mRNA accumulation as much as ACTH, and TPA inhibited these stimulations in a similar way. ACTH increased the IGF-II peptide concentration in most experiments, but this increase was modest in comparison with IGF-II mRNA changes. TPA, although it decreased IGF-II mRNA levels, tended to increase IGF-II peptide in the medium. Additions of GH, IGF-I and IGF-II to the cell culture medium also increased IGF-II mRNA accumulation. Transforming growth factor-β1 inhibited IGF-II mRNA accumulation to the same extent as TPA. Epidermal growth factor and basic fibroblast growth factor did not change IGF-II mRNA levels. Our results confirm previous reports that ACTH is an important regulator of IGF-II in human fetal adrenals, and show that IGF-II gene expression is under multifactorial control, which includes the PKC system and polypeptide growth factors.
Journal of Endocrinology (1993) 137, 533–542
In-vitro effects of insulin-like growth factor-I on gill Na+,K+-ATPase in coho salmon, Oncorhynchus kisutch
Authors: Madsen S. S. , Bern H. A. 
Published: December 2008

ABSTRACT
The effect of ovine GH (oGH) in vivo and recombinant bovine insulin-like growth factor-I (rbIGF-I) in vitro on gill Na+,K+-ATPase activity was investigated in two seasonal experiments conducted during the parr–smolt transformation period of coho salmon.
In 1991, when fish were held under a photoperiod of 12 h light: 12 h darkness, the stimulatory effect of oGH (1 μg/g) on gill Na+,K+-ATPase in vivo decreased at the time of expected parr–smolt transformation. Gill Na+,K+-ATPase from control fish was insensitive to rbIGF-I in vitro from February to June, whereas GH treatment induced sensitivity to rbIGF-I (100–1000 μg/l) in vitro in February and March, but not later in development.
In 1992, when fish were held under natural conditions, oGH (4 μg/g) stimulated gill Na+,K+-ATPase in vivo from February to July. There was, however, a pronounced developmental change in sensitivity of gill Na+,K+-ATPase to rbIGF-I in vitro. In February, gills from control fish were insensitive, but oGH treatment in vivo induced sensitivity to rbIGF-I in vitro (100–1000 μg/l). In April and May, control fish were sensitive to rbIGF-I in vitro. This sensitivity was not further potentiated by oGH treatment in vivo. In June, gills from control or oGH-treated fish were not sensitive to rbIGF-I in vitro, but in July exogenous oGH again induced gill tissue sensitivity to rbIGF-I at 1000 μg/l. Both studies showed that rbIGF-I stimulates gill Na+,K+-ATPase directly; an ability that may depend on priming by endogenous or exogenous GH. This supports the role of IGF-I as an endocrine mediator for GH action during parr–smolt transformation.
Journal of Endocrinology (1993) 138, 23–30
19-Hydroxyandrostenedione amplifies the hypertensive action of mineralocorticoids in rats
Authors: Sekihara H. , Yazaki Y. , Kojima T. 
Published: December 2008

ABSTRACT
We have reported that 19-hydroxyandrostenedione (19-OH-A-dione) amplifies the sodium-retaining action of aldosterone. To evaluate whether it also amplifies the hypertensive action of small doses of aldosterone, mononephrectomized rats were given 0·5 mg aldosterone, 10 mg 19-OH-A-dione or a combination of both once a week for 19 weeks, and changes in blood pressure were evaluated. Rats were given 154 mmol NaCl/l to drink. The blood pressure of controls, rats given aldosterone alone, 19-OH-Adione alone or a combination of both in week 19 were 137±4 (s.e.m), 146±7, 147±4 and 191±8 mmHg respectively. The blood pressure of rats given the combination was significantly higher than any of the other three groups. These results indicate that 19-OH-A-dione amplifies the hypertensive action of aldosterone and may be considered a potent hypertensive agent in the presence of aldosterone. To evaluate whether 19-OH-A-dione amplifies the hypertensive action of small doses of deoxycorticosterone acetate (DOCA), another experiment was carried out in which similar rats were given 5 mg DOCA or a combination of 5 mg DOCA and 10 mg 19-OH-A-dione once a week for 8 weeks. The blood pressure of controls, rats given DOCA alone and a combination of DOCA and 19-OH-A-dione in week 8 were 139±5, 166±7 and 208±12 mmHg respectively. The blood pressure of rats given a combination of DOCA and 19-OH-A-dione was significantly higher than that of control rats or the rats given DOCA alone. These results indicate that 19-OH-A-dione can also amplify the hypertensive action of DOCA. It is concluded that 19-OH-A-dione amplifies the hypertensive action of mineralocorticoids as well as the sodium-retaining action of aldosterone.
Journal of Endocrinology (1993) 138, 31–40
Episodic and seasonal rhythms of cortisol secretion in male Eld's deer (Cervus eldi thamin)
Authors: Monfort S. L. , Brown J. L. , Wildt D. E. 
Published: December 2008

ABSTRACT
Episodic and seasonal rhythms of cortisol secretion were evaluated in six adult Eld's deer (Cervus eldi thamin) stags. Plasma cortisol was measured in serial blood samples collected via remote catheterization every 10 min for 10 h within 2 weeks of the summer solstice (21 June), autumn equinox (22 September), winter solstice (21 December) and spring equinox (20 March), and in weekly blood samples collected from sedated stags. Cortisol was secreted episodically at a rate of approximately 0·6 peaks/h. Based on quantitative peak detection analyses of each 10-h data series, no overall seasonal differences (P>0·05) were detected in the number of peaks (mean range, 5·7–6·2), maximal peak height (mean range, 30·1–40·8 nmol/l), mean peak height as per cent increase (mean range, 158–168%), mean interval between peaks (mean range, 80·1–88·6 min), mean peak width (mean range, 55·1–65·1 min) and mean peak area under the curve (mean range, 675–816 nmol/l min). Based on weekly blood sampling, spring cortisol concentrations were elevated (P<0·05) compared with summer and autumn concentrations. However, when mean cortisol concentrations derived from the 10-h quarterly data sets were analysed, no seasonal differences (P>0·05) were detected. The present study represents the first detailed confirmation of episodic cortisol secretion in any cervid. Results (1) indicate that Eld's deer stags lack a distinct seasonal rhythm of cortisol secretion and (2) clearly illustrate the need for frequent blood sampling in fully conscious individuals to ensure accurate assessment of adrenal status in cervids.
Journal of Endocrinology (1993) 138, 41–49
Growth hormone secretion in the horse: unusual pattern at birth and pulsatile secretion through to maturity
Authors: Stewart F. , Goode J. A. , Allen W. R. 
Published: December 2008

ABSTRACT
A heterologous radioimmunoassay was developed and validated for the measurement of horse GH in plasma. It utilized recombinant-derived bovine GH as the radiolabelled ligand, a guinea-pig anti-porcine GH serum as first antibody and pituitary-derived horse GH as standard. Cross-reactivites were high with all of the pituitary and recombinant-derived GH preparations tested (49–140%) and very low (<0·3%) with horse FSH, LH and prolactin. A synthetic analogue of GH-releasing factor(1–29) stimulated the expected pattern of GH release in foals.
Plasma GH concentrations in foals were low at birth (<20 ng/ml) but rose sharply to a definite and, in most cases, very large peak (18–195 ng/ml) during the first 30–40 min post partum, followed by a steady decline to basal levels again by 60–100 min post partum. GH secretion was clearly pulsatile in all older foals tested (2 weeks, 1 month and 4 months of age) and in six adults (three mares and three stallions), all bled at 15-min intervals for 7–8 h. Basal levels and pulse amplitudes were higher in foals than in adults and pulse frequency was higher in stallions than in mares (3–5 pulses/8 h vs 1–2 pulses/8 h). Pulsatile secretion was further characterized in one mare by simultaneous sampling of jugular vein and pituitary cavernous sinus blood. Peak GH concentrations in cavernous sinus blood draining the pituitary gland were more than tenfold higher than the corresponding peak concentrations in peripheral circulation. The patterns of GH release in the horse therefore appear to be similar to those reported in other species with the exception of the low values at birth followed by the dramatic rise and fall in concentrations during the first hour post partum.
Journal of Endocrinology (1993) 138, 81–89
Thyrotrophin-releasing hormone-induced growth hormone secretion in domestic fowl: concomitant stimulation of dopamine turnover in the medial basal hypothalamus
Authors: Harvey S. , Lea R. W. 
Published: December 2008

ABSTRACT
Thyrotrophin-releasing hormone (TRH) stimulates GH secretion in domestic fowl by actions at pituitary and central nervous system sites. The possibility that this central action might be mediated by hypothalamic catecholamines or indoleamines was therefore investigated. When TRH was administered into the lateral ventricles of anaesthetized fowl the concentration of 3,4-dihydroxyphenylacetic acid (DOPAC, a metabolite of dopamine (DA)) in the medial basal hypothalamus (MBH) was increased within 20 min. The concentrations of MBH noradrenaline (NA), DA, serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were, however, unaffected by the intracerebroventricular (i.c.v.) administration of TRH, although the MBH concentrations of somatostatin and TRH were concomitantly reduced. A rapid increase in DA release into MBH extracellular fluid and its metabolism to DOPAC was also observed after i.c.v. or i.v. administration of TRH, in birds in which the MBH was perfused in vivo with Ringer's solution. Microdialysate concentrations of NA, 5-HT and 5-HIAA were not, however, affected by central or peripheral injections of TRH. Diminished GH responses to i.v. TRH challenge occurred in birds pretreated with reserpine (a catecholamine depletor), α-methyl-paratyrosine (a DA synthesis inhibitor) and pimozide (a DA receptor antagonist). These results therefore provide evidence for the involvement of a hypothalamic dopaminergic pathway in the induction of GH release following the central or peripheral administration of TRH. In contrast with its inhibitory actions at peripheral sites, DA would appear to have a central stimulatory role in regulating GH release in birds.
Journal of Endocrinology (1993) 138, 225–232
Bioactive and immunoreactive variants of prolactin in milk and serum of lactating rats and their pups
Authors: Kacsóh B. , Veress Z. , Tóth B. E. , Avery L. M. , Grosvenor C. E. 
Published: December 2008

ABSTRACT
Prolactin (PRL)-like bioactivity (in Nb2 lymphoma assay) and immunoreactivity (in radioimmunoassay (RIA)) in rat milk, maternal and neonatal sera and in neonatal rat pituitary cultures were investigated. The PRL-like bioactivity in the water-soluble fraction of rat milk was high and exceeded its immunoreactivity 5·8-, 4·0- and 2·1-fold, on days 2, 12 and 22 of lactation respectively. The elevated bioactivity to immunoreactivity (B/I) ratio of PRL in milk was not due to the presence of interleukin-2 (IL-2) in milk, since the proliferation of the CTLL-2 murine T cells, which are not sensitive to PRL, was promoted by IL-2 but not by milk. Serum levels of immunoreactive PRL were low in sera of non-weaned rat pups on days 2, 12 and 22 postpartum. Similar to milk, the B/I ratio of PRL in sera of rat pups was high and decreased with time postpartum. Pituitary glands of pups obtained on days 2, 12 and 22 secreted progressively increasing amounts of PRL in vitro; the B/I ratio ranged between 1·2 and 2·1 without a significant change. The relative concentrations of size variants in milk were not proportional to those in serum of lactating rats on day 2 postpartum as assessed by Sepharcryl S-100 HR gel permeation chromatography and Nb2 bioassay or RIA. Size variants of biologically active PRL were abundant in early milk and gradually diminished as lactation progressed: a partially resolved peak representing monomeric to dimeric PRL variants (relative molecular weights ranging between 18 k and 42 k) became progressively narrower between days 2 and 22. Biologically active and immunoreactive PRLs displayed disparate elution profiles. The elution profile of PRL in sera of neonatal rats on day 2 postpartum was different from that of maternal serum or milk. The major immunological (and possibly biological) PRL-like activity eluted as two adjacent peaks at 2·2 k and 1·5 k, raising the possibility that fragments of milk-borne PRL were absorbed from the gut after partial proteolytic degradation. In contrast with PRL, GH (which is present in rat milk only in minute concentrations) did not show heterogeneity in sera of 2-day-old rat pups in gel permeation chromatography.
The present results demonstrate that the concentrations of PRL-like activity in rat milk and newborn rat serum have been grossly underestimated because levels have been measured by RIA. The high B/I ratio of PRL in milk and neonatal sera is due to the presence of PRL-related compounds. The difference between the ontogeny in the B/I ratio of serum and in-vitro secreted PRL might be related to absorption of PRL variants from milk during the early postpartum period. The data suggest that PRL might be modified by the mammary gland and the neonatal gut during its passage from the circulation of the mother to that of the neonatal rat.
Journal of Endocrinology (1993) 138, 243–257
The effect of dietary protein restriction on the secretory dynamics of 1α-hydroxycorticosterone and urea in the dogfish, Scyliorhinus canicula: a possible role for 1α-hydroxycorticosterone in sodium retention
Authors: Armour K. J. , O'Toole L. B. , Hazon N. 
Published: December 2008

ABSTRACT
The putative osmoregulatory role of the unique elasmobranch corticosteroid, 1α-hydroxycorticosterone (1α-OH-B), was investigated using dietary protein restriction as a means of limiting urea biosynthetic ability. Groups of dogfish (Scyliorhinus canicula) were adapted to either a high or a low protein diet (HPD and LPD respectively) and the secretory dynamics of urea and 1α-OH-B were determined following acclimation to normal (100%), 130% and 50% sea water.
In normal sea water, LPD fish showed significantly decreased blood production of urea compared with fish fed a HPD (P <0·05), and the plasma urea concentration required to maintain iso-osmolality was achieved only by a substantial decrease in urea clearance from the plasma. Unlike HPD fish, LPD fish in 130% sea water had no apparent ability to increase plasma urea concentration. An alternative strategy adopted by these animals was the retention of high plasma concentrations of Na+ and Cl−, which increased plasma osmolality and tended to decrease osmotic water loss. Concomitant with the increased ion concentrations, plasma 1α-OH-B concentration was also greatly elevated in LPD fish indicating that the steroid may be acting to minimize Na+ (and Cl−) excretion at osmoregulatory sites such as the rectal gland, kidney and gills.
This and a previous study have also demonstrated that 1α-OH-B concentration is elevated in 50% sea water. Decreases in plasma Na+ concentration are tolerated down to 75% sea water, whereafter Na+ is preferentially retained and further decreases in osmolality are achieved by reductions in plasma urea concentration. Increased 1α-OH-B concentration in 50% sea water corresponds to Na+ retention and regulation around a lower set point.
The results of this study are consistent with a mineralocorticoid role for 1α-OH-B in elasmobranchs, with 1α-OH-B acting preferentially to maintain plasma Na+ concentrations under certain osmotic conditions.
Journal of Endocrinology (1993) 138, 275–282
Timing of exposure to somatostatin relative to growth hormone-releasing factor dictates the rat anterior pituitary cell growth hormone response
Authors: Richardson S. B. , Twente S. 
Published: December 2008

ABSTRACT
The temporal interactions of rat GH-releasing factor (GRF) and somatostatin (SRIF) on the secretion of GH from perifused rat anterior pituitary cells have been studied. SRIF and GRF were employed at concentrations in a range close to levels reported in the hypophysial circulation of the rat.
GH secretion was inhibited by pulses of 1 nmol SRIF/1 (6 min) or 0·3 nmol SRIF/1 (6 or 20 min). No rebound GH stimulation was observed. Exposure of cells to 6-min pulses of 0·3 nmol rat GRF/1 repeated three times resulted in rapid stimulatory responses which became attenuated. Concomitant exposure to 0·3 nmol SRIF/1 during a GRF pulse resulted in transient inhibition followed by a delayed and enhanced GH response, measured as the area under the curve but not peak height, whereas continuation of SRIF after a GRF pulse abolished the GH response. Exposure to 0·3 nmol SRIF/1 prior to but not during a GRF pulse did not delay or inhibit the GH response. The area under the curve was increased under these conditions because of the lowered baseline in cells perifused with SRIF.
SRIF alters somatotroph responsivity to equimolar concentrations of rat GRF and under different temporal conditions and can inhibit, enhance or delay GH secretion.
Journal of Endocrinology (1993) 138, 369–377