bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relative occupation of type-I and type-II corticosteroid receptors in rat brain following stress and dexamethasone treatment: functional implications
Authors: Reul J. M. H. M. , van den Bosch F. R. , de Kloet E. R. 
Published: December 2008

ABSTRACT
The rat brain contains two receptor systems for corticosterone: the type-I corticosterone-preferring receptor and the classical type-II glucocorticoid receptor. The two receptor populations can be distinguished in binding studies with the 'pure' synthetic glucocorticoid 11β,17β-dihydroxy-6-methyl-17α (1-propynyl)-androsta-1,4,6-trione-3-one (RU 28362). In-vitro autoradiography and quantitative image analysis showed that the type-I receptor was localized almost exclusively in the hippocampus, whereas the type-II receptor extended throughout the brain, with the highest levels in the nucleus paraventricularis, nucleus supraopticus and in the thalamic, amygdaloid, hippocampal and septal regions. Unoccupied type-I and type-II receptor sites, as measured in vitro by cytosol binding of 3H-labelled steroids, displayed a large difference in the rate of appearance after adrenalectomy. The availability of type-I receptors exhibited a marked increase, reaching maximal levels within 4–7 h, and then remained constant until 2 weeks after adrenalectomy. The availability of type-II receptors did not change considerably during the first 24 h after adrenalectomy, but displayed a large increase in capacity during the subsequent 2 weeks. After adrenocortical activation as a consequence of exposure to a novel environment, plasma concentrations of corticosterone increased to reach a peak of 811 nmol/l after 30 min and attained the basal concentration (43 nmol/l) after 240 min. During this time, occupation of type-I receptors increased from 77·8% at 0 min to 97% at 30–60 min and then declined to 84·8% after 240 min. Occupation of the type-II receptors was 28·1% at 0 min, 74·5% after 30 min and 32·8% after 240 min. Injection of dexamethasone (25 μg/100 g body wt) at 08.00 h resulted in suppression of basal plasma concentrations of corticosterone and prevented the circadian-driven rise in circulating corticosterone. Occupation of type-I receptors did not change considerably as a result of injection of dexamethasone, but occupation of type-II receptors was markedly increased till 16.00 h compared with that after injection of vehicle.
It was concluded that the type-I and type-II receptors are not only localized differently in the rat brain, but also exhibit a striking difference in occupation after manipulation of the pituitary-adrenocortical system. The data further support the concept of a type-I receptor-mediated tonic activating influence and a type-II receptor-mediated feedback action of corticosterone on brain function.
J. Endocr. (1987) 115, 459–467
INHIBIN BIOACTIVITY IN HUMAN TESTICULAR EXTRACTS
Authors: Simpson B.J.B. , Tsonis C.G. , Wu F.C.W. 
Published: December 2008

ABSTRACT
Inhibin bioactivity was measured in human testicular extracts by a sensitive sheep pituitary cell bioassay. The relationship between testicular inhibin bioactivity, daily sperm production (DSP) and plasma concentrations of FSH, LH, testosterone and oestradiol were examined. The mean level of testicular inhibin bioactivity was 4.4 ±1.3 U/g (mean ± SD) with a significantly lower value in those who received radiotherapy (3.2 ± 1.4 U/g) than in the untreated group (4.8 ± 1.1 U/g). In contrast to the rat, human testicular inhibin bioactivity was not significantly correlated to FSH or DSP. These findings suggest that inhibin may have a complex role in normal and/or pathological testicular function.
LEYDIG CELL STEROID PRODUCTION IN THE PRESENCE OF LH IS FURTHER STIMULATED BY RAT TESTICULAR FLUID, FETAL CALF SERUM AND BOVINE FOLLICULAR FLUID, BUT NOT BY RAT AND BOVINE SERUM
Authors: Melsert R. , Rammerts F.F.G. 
Published: December 2008

ABSTRACT
LH-dependent steroid production by isolated rat Leydig cells is fourfold stimulated by the addition of charcoal–stripped rat testicular fluid. Fetal calf serum and bovine follicular fluid have similar stimulatory effects. In contrast, rat and bovine serum suppress steroid production in the presence of LH in a dose–dependent manner. The results show that stimulatory and inhibitory factors can modulate Leydig cell steroidogenesis and these factors appear not to be organ or species specific.
Metabolic actions of cortisol in a macropodid marsupial Thylogale billardierii
Authors: Martin I. K. , McDonald I. R. 
Published: December 2008

ABSTRACT
In undisturbed pademelon wallabies (Thylogale billardierii) with indwelling jugular venous catheters, an increase in the plasma cortisol concentration from 0.25±0.05 to 1.35±0.15 (s.e.m.) μmol/l in 2 h, during i.v. infusion of cortisol at 1.0 mg/kg per h, caused no significant change in the plasma glucose concentration from the control value of 4.26±0.25 mmol/l. The rates of appearance (Ra) and metabolic clearance (MCR) of glucose, measured by steady-state isotope dilution, also did not change significantly from the control values of 14.9±0.7 μmol/kg per min and 3.52±0.19 ml/kg per min respectively. Twice-daily i.m. injections of 7 mg cortisol/kg for 7 days caused increases in plasma concentrations of cortisol, from 0.26±0.02 to 0.66±0.04 μmol/l on day 7, and glucose, from 5.1±0.1 to 7.2±0.6 mmol/l by day 5. The concentration of glycogen in the liver of wallabies fasted for 24 h increased from the control level of 1.17±0.56 to 5.92±1.14 g/100 g on day 7 (P<0.01), but mean glucose Ra and MCR did not change significantly. Plasma concentrations of α-amino nitrogen rose from 2.73±0.13 to 3.22±0.12 mmol/l on day 1 and remained at this level. Plasma concentrations of urea rose from 8.59±0.62 to 9.70±0.32 mmol/l on day 1, but then declined below the control level. Food intake and urinary excretion of nitrogen did not change in undisturbed animals. However, fasting followed by liver biopsy was accompanied by urinary excretion of nitrogen in excess of food intake, persisting until day 2 of treatment.
The transient effect of cortisol on the plasma concentration of urea and lack of effect on urinary excretion of nitrogen could be explained by urea recycling, as indicated by a low urinary urea nitrogen: total nitrogen ratio and failure to excrete more than a mean of 26% of infused urea.
It is concluded that cortisol has no short-term effect on carbohydrate metabolism in this marsupial. In the long term it can increase hepatic carbohydrate reserves through utilization of tissue amino nitrogen, the resulting urea being conserved by recycling.
J. Endocr. (1988) 116, 71–79
Induced development of ovulatory follicles during the early stages of lactation by the administration of LH in the rat
Authors: Taya K. , Sasamoto S. 
Published: December 2008

ABSTRACT
To determine whether failure of follicular maturation during the early stages of lactation in rats is due to inadequate LH stimulation, lactating rats nursing eight pups were injected twice daily for 1–3 days (days 2–5 of lactation) with various doses of ovine LH. Follicular maturation was determined by the ability of the follicles to ovulate in response to 10 IU human chorionic gonadotrophin (hCG), endogenous oestradiol-17β and inhibin production. Ovulation was not induced in control animals in response to 10 IU hCG given between days 2 and 5 of lactation. On the other hand, an injection of 10 IU hCG could induce ovulation in LH-treated animals, in which 25 and 50 μg LH per injection were given s.c. from days 2 to 5 of lactation. Concentrations of oestradiol-17β and inhibin activity in ovarian venous plasma increased progressively after the administration of LH, indicating that induced development of ovulatory follicles had occurred. Plasma concentrations of FSH declined in LH-treated animals compared with those in control animals. The decrease in plasma concentrations of FSH was not observed when lactating rats were ovariectomized before the first injection of LH, indicating that ovarian products, probably inhibin, from developing follicles may suppress the secretion of FSH from the pituitary gland. In both LH-treated and control animals, concentrations of prolactin and progesterone remained increased during the period of LH administration. The present results, therefore, suggest that the plasma levels of LH are an important determinant of follicular maturation during lactation in rats.
J. Endocr. (1988) 116, 115–122
Peripheral progesterone concentrations in the luteal-phase ewe: effects of a β-adrenergic receptor antagonist and two β2-adrenergic agonists
Authors: Wheeler A. G. , Lean J. , Walker M. 
Published: December 2008

ABSTRACT
Peripheral blood samples were collected at 10-min intervals from three conscious sheep in which ovulation had been induced 6–10 days previously using exogenous hormones. Saline was infused into a jugular vein for about 1 h, followed by the experimental drug for 1–2 h and followed by saline again for a further 2 h. The experiments were repeated following induced luteolysis and ovulation. The infusion of a β-adrenergic antagonist (propranolol) into three conscious luteal-phase ewes decreased (P<0·05) the peripheral progesterone concentration in each animal. Infusions of β2-adrenergic agonists (ritodrine and salbutamol) increased (P<0·05) the progesterone concentration in four out of eight experiments. The β-adrenergic antagonist decreased the heart rate and the β2-adrenergic agonist increased it; the arterial blood pressure and respiratory rate were unaffected. The decrease in the prosgesterone concentration in response to the β-adrenergic antagonist suggests that the normal ovarian secretion of progesterone is partly the result of sympathetic stimulation, and that the sympathetic innervation of the ovary may have a physiological role in modulating progesterone secretion.
J. Endocr. (1988) 116, 137–142
Ovarian steroids modulate the action of calcitonin in women
Authors: Pansini F. , Bergamini C. M. , Bellinazzi A. , Andreoli M. , Perri G. , Bagni B. , Mollica G. 
Published: December 2008

ABSTRACT
Slow i.v. infusion of salmon calcitonin into normal women led to a transient increase in plasma concentrations of cyclic AMP and to a decrease in plasma calcium, which was maintained for at least 2 h. These responses were significantly reduced in the same patients after hysterectomy and ovariectomy. In contrast, maintenance of the ovaries at the time of surgery, or substitutive hormonal therapy, seemed to restore the sensitivity to exogenous calcitonin, suggesting a permissive role of ovarian steroids in the effect of calcitonin. The most likely explanation for this phenomenon is that these hormones influence either the number of calcitonin receptors or the coupling of the receptors to the functional unit of bone adenylate cyclase.
J. Endocr. (1988) 116,155–159
The somatotrophic axis in young steers: influence of nutritional status and oestradiol-17β on hepatic high-and low-affinity somatotrophic binding sites
Authors: Breier B. H. , Gluckman P. D. , Bass J. J. 
Published: December 2008

ABSTRACT
The binding of bovine GH (bGH) to hepatic membranes obtained from steers on either high (3% dry matter of body weight per day) or low (1% dry matter of body weight per day) planes of nutrition with or without an oestradiol-17β implant was studied (n = 5 per group). Binding studies were performed on both crude membrane homogenates and on 100 000 g microsomal membrane fractions; identical results were obtained using both preparations. In all four groups of animals, linear Scatchard plots were obtained, but following pretreatment of the membranes with MgCl2 to remove endogenously bound hormone, curvilinear plots were obtained in the groups on the high plane of nutrition. Analysis of these curves suggested the presence of a high- and low-affinity binding site, the high-affinity site being fully occupied in the absence of MgCl2 pretreatment.
The specific binding of bGH in MgCl2-pretreated crude membranes was greater (P < 0·01) in well-fed steers (14·8 ± 1·6%) than in poorly fed steers (9·8 ± 0·9%). Scatchard analysis showed this to be due to the presence of a high-affinity site (dissociation constant (Kd) = 11·6 ± 3·3 pmol/l) in the well-fed animals only. In addition, there was an increase (P < 0·01) in the affinity, but not in the capacity, of the low-affinity site (Kd = 106·4 ± 22·8 pmol/l in well-fed steers and 197·0 ± 23·8 pmol/l in poorly fed steers).
Oestradiol treatment was associated with an increase (P < 0·01) in specific binding at both planes of nutrition, but binding was higher (P < 0·01) in well-fed (24·8 ± 2·9%) than in poorly fed (15·6 ± 3·7%) steers. Scatchard analysis after MgCl2 pretreatment again showed a curvilinear plot at the high and a linear plot at the low nutritional plane. The effect of oestradiol was to increase (P < 0·001) the capacity of the high-affinity site from 1·87 ± 0·61 pmol/100 mg in the control well-fed group to 6·56 ± 1 ·2 pmol/100 mg. The capacity of the low-affinity site was increased (P < 0·01) from 20·1 ± 2·6 to 30·1 ± 3·2 pmol/100 mg in the well-fed group, with a similar change in the poorly fed group. Oestradiol had no effect on the apparent affinity of either binding site.
These studies demonstrate a heterogeneity of somatotrophic binding sites of hepatic membranes in steers. The presence of a high-affinity site is determined by nutritional status, whereas oestradiol primarily affects receptor capacity. Thus nutrition and oestradiol have independent and qualitatively different effects on somatotrophic binding. As the rate of weight gain correlated (P < 0·01) with the capacity of the high-affinity site, it is suggested that somatotrophic receptor modulation is a primary factor in the regulation of somatic growth in the ruminant.
J. Endocr. (1988) 116, 169–177
The role of protein kinase C in LHRH-induced LH and FSH release and LHRH self-priming in rat anterior pituitary glands in vitro
Authors: Johnson M. S. , Mitchell R. , Fink G. 
Published: December 2008

ABSTRACT
We have investigated the role of protein kinase C (PKC) in LHRH-induced LH and FSH secretion and LHRH priming. Hemipituitary glands from pro-oestrous rats were incubated with agents known to affect PKC and with or without LHRH, during which time the secretion of gonadotrophins was measured. Phorbol esters and phospholipase C, activators of PKC, released LH and FSH in a concentration-dependent manner and potentiated the LHRH-induced secretion of gonadotrophins in parallel with their ability to release these hormones alone. Inhibitors of PKC had either no effect on LH release (1-(5-isoquinolinesulphonyl)-2-methylpiperazine hydrochloride) or they augmented LHRH-induced gonadotrophin release (polymyxin B and 8-(N,N-diethylamino) octyl-3,4,5-trimethoxybenzoate). Neither the activators nor the inhibitors of PKC, when present with LHRH, caused any change in LHRH priming, even though the activators alone produced a release of gonadotrophins that showed a temporal pattern similar to that produced by LHRH priming. The profiles of effects on LH and FSH secretion were always qualitatively similar. These results show that PKC may be involved in general regulation of gonadotrophin release but that it is not important in acute responses to LHRH nor in LHRH self-priming.
J. Endocr. (1988) 116, 231–239
Inhibin bioactivity and pituitary cell mitogenic activity from cultured chicken ovarian granulosa and thecal/stromal cells
Authors: Tsonis C. G. , Sharp P. J. , McNeilly A. S. 
Published: December 2008

ABSTRACT
A sensitive bioassay for inhibin based on the suppression of FSH release from cultured sheep anterior pituitary cells was used to determine whether inhibin is present in the preovulatory follicle in the domestic hen. Granulosa and thecal/stromal layers were separated from the five largest (F1–F5) yellow yolky follicles in the ovary and incubated in culture medium for 18 h. Inhibin was found predominantly in the media in which granulosa layers had been incubated. There was a progressive increase in the amount of inhibin produced per mg granulosa layer protein during the 5–6 days before ovulation.
The ovary was observed to contain a growth factor which stimulated the proliferation of ovine pituitary cells. Thecal/stromal layer-conditioned medium (ThCM) but not granulosa layer-conditioned medium had a dose- and time-dependent mitogenic effect on cultured sheep pituitary cells. The maximal mitogenic effect achieved for ThCM was four to fivefold greater than control media and was significantly higher than the maximal mitogenic effects of epidermal growth factor (250 ng/ml; 1·5 × control) and transforming growth factor-β (500 ng/ml; 1·2 × control).
It is concluded that inhibin is produced by the granulosa layers in the large yellow yolky preovulatory ovarian follices of the domestic hen. The thecal/stromal layers in these follicles produce a potent mitogenic factor, not produced by the granulosa layers, which stimulates the division of ovine anterior pituitary cells in vitro.
J. Endocr. (1988) 116, 293–299
Effect of isolation stress on concentrations of arginine vasopressin, α-melanocyte-stimulating hormone and ACTH in the pituitary venous effluent of the normal horse
Authors: Alexander S. L. , Irvine C. H. G. , Livesey J. H. , Donald R. A. 
Published: December 2008

ABSTRACT
A non-surgical, non-stressful technique was used for collection of pituitary venous blood from five conscious horses every minute for two 10-min periods before and during isolation from the herd, which caused a predictable, yet humane and physiological, emotional stress. Pituitary blood was also sampled every 5 min for two approximately 90-min periods before and after isolation, while jugular blood was sampled every 15 min throughout the experiment.
During isolation, all horses became agitated, hyperventilating and sweating. Packed red cell volume increased, as did pituitary venous concentrations of adrenaline (mean ± s.e.m. concentration before isolation, 621·5±112·3 pmol/l; peak during isolation, 2665·4 ± 869·8 pmol/l; P <0·05) and noradrenaline (before, 871·8 ± 111·8 pmol/l; peak, 2726·1 ± 547·4 pmol/l; P<0·02). Concentrations of arginine vasopressin (AVP) were higher in pituitary venous but not in jugular blood during isolation than during the preceding 10-min period (P <0·05). Although AVP secretion increased in all horses, in three of the five it rose dramatically in the first minute of isolation to 25·7 (horse 1), 13·6 (horse 4) and 145·1 (horse 5) times the level in the last sample collected before isolation. Mean pituitary venous concentrations of ACTH and α-MSH increased during isolation in the three horses which had large increases in AVP secretion, but, overall, stress did not significantly affect ACTH or α-MSH secretion. Similarly, mean jugular cortisol levels were not significantly altered by isolation. However, the magnitudes of ACTH, AVP and α-MSH responses to isolation were negatively correlated with the jugular cortisol level before isolation. The changes in pituitary venous concentrations of ACTH and AVP were synchronous under resting conditions, whether samples were collected at intervals of 1 (P <0·01) or 5 (P <0·005) min; however, this synchrony was lost during isolation. The changes in pituitary venous concentrations of ACTH and α-MSH were synchronous both at rest (P <0·025 for 1-min sampling, P <0·01 for 5-min sampling) and during isolation (P<0·01).
We conclude that isolation stress increases AVP secretion and may alter the temporal relationship between pituitary venous concentrations of AVP and ACTH. Furthermore, the magnitude of the responses of AVP, ACTH and α-MSH to isolation is significantly affected by the prevailing cortisol level.
J. Endocr. (1988) 116, 325–334
Role of calcium in the secretomotor response of the thyroid: effects of calcium ionophore A23187 on radioiodine turnover, membrane potential and fluid transport in cultured porcine thyroid cells
Authors: Manley S. W. , Rose D. S. , Huxham G. J. , Bourke J. R. 
Published: December 2008

ABSTRACT
The calcium ionophore A23187 (0·1–1 μmol/l) inhibited membrane electrical polarization, uptake of 125I, fluid transport and TSH-stimulated release of radioiodine from the organic pool in follicular cultures of porcine thyroid cells. At higher concentrations (1–30 μmol/l), A23187 promoted release of radioiodine from the organic pool. Stimulation of release of radioiodine from the organic pool by veratridine (a sodium channel agonist, 0·4–1 mmol/l) and A23187 was dependent on the calcium concentration of the medium, while TSH action was independent. Incubation in medium of very low calcium concentration (0·0177 mmol/l) resulted in enhanced release from the organic pool, which was inhibited by TSH (256 μU/ml), A23187 (25 μmol/l) or veratridine (0·5 mmol/l). These data therefore do not support the hypothesis that calcium acts as a mediator of the secretomotor action of TSH, but suggest the possibility of a TSH-induced increase in intracellular calcium as a regulatory negative-feedback mechanism.
J. Endocr. (1988) 116, 373–380
RNA synthesis in the Leydig cells of the mature rat: effect of oestradiol-17β
Authors: Ronco A. M. , Pino A. M. , Valladares L. E. 
Published: December 2008

ABSTRACT
In view of the evidence that there may be an effect of high concentrations of oestradiol on testicular steroidogenic function, we have investigated the effect of this steroid on [3H]uridine incorporation into RNA by testicular cells. Our results have shown that oestradiol in vitro induced a marked dose-dependent inhibition of RNA synthesis by purified Leydig cells. The concentrations of oestradiol tested varied from 2 to 40 μmol/l; these concentrations also impaired net testosterone synthesis in vitro after human chorionic gonadotrophin (hCG) stimulation. Under the effect of oestradiol, the kinetics of [3H]nucleoside incorporation into RNA were impaired early and the inhibition of RNA synthesis was specific for oestrogenic compounds. It was concluded that, in Leydig cells, oestradiol, in addition to its known inhibitory action on the response of testosterone to hCG, triggers a more extensive response that also includes RNA synthesis in vitro.
J. Endocr. (1988) 116, 387–392
Plasma levels of neuropeptide tyrosine Y (NPY) are increased in human sepsis but are unchanged during canine endotoxin shock despite raised catecholamine concentrations
Authors: Watson J. D. , Sury M. R. J. , Corder R. , Carson R. , Bouloux P. M. , Lowry P. J. , Besser G. M. , Hinds C. J. 
Published: December 2008

ABSTRACT
Alterations in levels of adrenal vein and circulating immunoreactive neuropeptide tyrosine Y (NPY), as well as systemic catecholamine concentrations, have been investigated in the dog after endotoxin administration. Eighteen dogs were anaesthetized with α-chloralose and allowed to breathe spontaneously. Severe shock was produced by the administration of a large bolus of Escherichia coli endotoxin followed by a continuous infusion. In two further animals the left lumbar adrenal vein was cannulated and an intermittent choke allowed retrograde sampling of the adrenal effluent. The production of hypodynamic shock was associated with marked increases in systemic catecholamine concentrations but there were no consistent changes in adrenal vein or systemic immunoreactive NPY levels. In contrast, circulating concentrations of immunoreactive NPY were markedly raised above the normal range in five patients with septic shock.
J. Endocr. (1988) 116, 421–426