bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of tactile and electrical stimuli upon release of vasoactive intestinal polypeptide in the mammalian penis
Authors: Dixson A. F. , Kendrick K. M. , Blank M. A. , Bloom S. R. 
Published: December 2008

ABSTRACT
Plasma levels of vasoactive intestinal polypeptide (VIP) in the corpora cavernosa penis and dorsal penile veins greatly exceeded those measured in the limb or caudal veins during anaesthesia in various mammals (Bennett's wallaby, Barbary sheep, cheetah, puma, sooty mangabey, pigtail macaque and chimpanzee). Tactile stimulation of the penis immediately before or during collection of blood samples resulted in an increase. In the wallaby, VIP levels (mean ± s.e.m.) in blood samples collected from the flaccid penis in the absence of tactile stimulation were very low (0·6 ± 0·5 pmol/l). A 36-fold increase in VIP occurred after manual extension of the flaccid penis (24·8 ± 3·2 pmol/l) or during manually stimulated erections (25· 1 ± 1·7 pmol/l). Electrical stimulation of erection produced no significant increase in VIP levels (2·3±0·9 pmol/l) unless accompanied by tactile stimulation (17·5±1·4 pmol/l). These studies provide the first demonstration that sensory feedback from the penis plays an important role in regulating vasoactive intestinal polypeptidergic activity. Since VIP is a potent vasodilator its release due to tactile stimuli during copulation may play a role in the maintenance of penile erection.
J. Endocr. (1984) 100, 249–252
Induction of cytosolic receptors for 1α,25-dihydroxyvitamin D3 in the immature rat uterus by oestradiol
Authors: Levy J. , Zuili I. , Yankowitz N. , Shany S. 
Published: December 2008

ABSTRACT
The role of oestradiol-17β in the induction of specific cytosolic receptors for 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) was examined in the immature rat uterus.
An acrylamide gel electrophoretic analysis was developed to separate the specific receptor for 1,25(OH)2D3 from the plasma binding protein for vitamin D3 metabolites. Employing this sensitive method the presence of receptors for 1,25(OH)2D3 in the mature rat uterus was evident. Such receptors were not found in the uterus of saline-treated immature rats. However, oestradiol administration caused an induction of these receptors in the immature rat uterus, together with a significant increase in the uterine weight, progesterone receptor level and peroxidase activity.
These results suggest a mechanism for oestradiol regulation of calcium metabolism in the uterus at times of high demand for this cation during the gestation period.
J. Endocr. (1984) 100, 265–269
Characterization of somatostatin in peripheral and portal plasma in the duck: in-vivo metabolism of somatostatin-28 and-14
Authors: Di Scala-Guenot D. , Strosser M.-T. , Mialhe P. 
Published: December 2008

ABSTRACT
A sensitive and specific radioimmunoassay without an extraction step was developed for somatostatin in duck plasma. Degradation of Tyr1-125I-labelled somatostatin-14 (S-14) averaged 2% for blood collected with EDTA and zymofren. Recovery of somatostatin-like immunoreactivity (SLI), added to the plasma, averaged 91% for S-14 and 86% for S-28. Chromatographic analysis of portal plasma on Sephadex G-25 showed three peaks: one peak coeluted with cytochrome c (mol. wt 12 500) in the void volume and was called 'big' somatostatin; of the two smaller forms, one coeluted with synthetic S-28 and the other with synthetic S-14; these were immunologically and physicochemically indistinguishable from synthetic S-28 and S-14. In peripheral plasma only the large form of somatostatin, 'big' somatostatin, was found. The mean portal plasma concentration of SLI was 4·1 ±0·41 μg/l (n = 11, range 2·8–5·1 μg/l). In peripheral plasma the SLI concentration was 1·05 ±0·45 μg/l (n = 11, range 0·84–1·2 μg/l). The metabolic clearance rate, distribution volume and calculated half-life values were 63·1 ± 14 ml/kg per min, 40·9±8·9 ml/kg and 1·06±0·19 min for S-14 compared with 45·7 ±7 ml/kg per min, 14·8 ±2·5 ml/kg and 2·14± 0·54 min for S-28. These results indicated that S-28 was cleared from plasma at a slower rate than S-14 in the duck. It was concluded that: (1) portal plasma SLI was four times higher than peripheral SLI; (2) SLI in portal plasma existed as 'big' somatostatin, S-28 and S-14, whereas in peripheral plasma it existed mainly as 'big' somatostatin; (3) invivo studies indicated that S-28 was metabolized less rapidly than S-14.
J. Endocr. (1984) 100, 329–335
Small increases in peripheral noradrenaline inhibit the milk-ejection response by means of a peripheral mechanism
Authors: Lefcourt A. M. , Akers R. M. 
Published: December 2008

ABSTRACT
The effects of exogenous noradrenaline on the milk-ejection response were determined for nine Holstein cows. Noradrenaline was injected (0·95 nmol/kg) 15 s after the start of teat stimulation (preparation) or infused (0·13 nmol/kg per min, after bolus injection of 0·47 nmol/kg) starting 10 min before milking for 20 min. Cows were prepared (udder wash and dry) for 1 min before milking. Both injection and infusion resulted in approximately a 3·5-fold increase in peripheral noradrenaline at 1·75 min after the start of milking (baseline noradrenaline 0·83 and 0·89 nmol/l plasma; at 4 min, 2·00 and 3·00 nmol/l). Prolactin release was delayed and oxytocin release enhanced, while milk yield was decreased by 8·6% for both treatments. The maximum rate of milk flow was also depressed by treatment. In contrast, milking time increased for injection and decreased for infusion. In addition, a milk-yield-dependent change in the pattern of milk flow was seen in response to treatment. In medium-yield animals, two distinct milk-flow peaks were apparent and injection delayed the time to the second peak.
We conclude that physiologically meaningful increases in peripheral noradrenaline can inhibit milk-ejection response by means of a peripheral mechanism not involving inhibition of release of oxytocin.
J. Endocr. (1984) 100, 337–344
Gonadal steroid modulation of naloxone-induced LH secretion in the rat
Authors: Petraglia F. , Locatelli V. , Pen̄alva A. , Cocchi D. , Genazzani A. R. , Müller E. E. 
Published: December 2008

ABSTRACT
The effect of acute administration of the opioid receptor antagonist naloxone hydrochloride (5 mg/kg, s.c.) on plasma LH levels was evaluated in female and male rats 24, 36 and 48 h and 1,3 and 5 weeks after gonadectomy and in 5-week gonadectomized rats after acute or chronic (2 weeks) administration of oestradiol benzoate (OB, 10 μg/rat per day, s.c.), testosterone propionate (TP, 150 μg/rat, s.c.) or dihydrotestosterone propionate (DHT, 150 μg/rat, s.c.) respectively. Concurrent evaluation of plasma LH after administration of LH releasing hormone (LHRH, 1 μg/kg, i.p.) was performed in the same experimental groups.
In rats of both sexes, a significant rise in plasma LH after naloxone was observed in sham-operated and recently gonadectomized rats (24–48 h); in female rats 36 and 48 h after gonadectomy the rise was higher than in controls. One, 3 and 5 weeks after gonadectomy, naloxone failed to stimulate LH release in both female and male rats. In gonadectomized rats undergoing steroid replacement therapy, OB administered 72 h before testing, TP (16 and 72 h) and DHT (16 h) were the most effective in reinstituting the LH response to naloxone. Chronic administration of gonadal steroids did not restore normal LH responsiveness to naloxone. In most experimental groups, LH responses after naloxone were clearly unrelated to pituitary LH responsiveness to LHRH, which indicates that the opioid antagonist was acting via the central nervous system. In conclusion, these results demonstrate that: (1) gonadal steroids are critically important for the inhibitory effect of endogenous opioids on LH secretion to be manifested; (2) inhibition by the opiatergic system on LH secretion is more dependent on a modulatory action of gonadal steroids than on their simple presence or absence.
J. Endocr. (1984) 101, 33–39
Effects of naloxone and electroacupuncture treatment on plasma concentrations of LH in sheep
Authors: Malven P. V. , Bossut D. F. B. , Diekman M. A. 
Published: December 2008

ABSTRACT
Mature ewes were injected intravenously with the opioid antagonist naloxone (1·1 mg/kg) during the breeding season. Ewes with luteal phase concentrations of plasma progesterone responded with a significant (P <0·05) increase in plasma LH 14–23 min after naloxone injection. In contrast, non-luteal ewes with low plasma progesterone did not respond to injection of naloxone with an LH increase. Similar treatment of castrated males (wethers) with this dosage of naloxone failed to increase plasma LH. Electroacupuncture (EA) treatment of luteal phase ewes prevented the ability of exogenous naloxone to increase plasma LH. Treatment of wethers by EA decreased significantly (P <0·01) their high basal concentrations of plasma LH, but similar EA treatment of intact ewes did not change their low basal concentrations of LH.
J. Endocr. (1984) 101, 75–80
Desensitization of rat anterior pituitary gland to thyrotrophin releasing hormone
Authors: Sheppard M. C. , Shennan K. I. J. 
Published: December 2008

ABSTRACT
We have studied the secretion of TSH and prolactin from perifused rat anterior pituitary glands in vitro in response to single pulses of thyrotrophin releasing hormone (TRH) and KCl after prior exposure to TRH. Anterior pituitary fragments were incubated in normal medium or in medium containing 28 nmol TRH/1 for 20 h before perifusion. Thyrotrophin releasing hormone (28 nmol/l), administered as a 3-min pulse, stimulated TSH and prolactin release from control tissue to a peak value four or five times that of basal. After exposure of the pituitary tissue to TRH for 20 h, the subsequent response of TSH to a 3-min pulse of TRH was, however, markedly reduced; in contrast, the prolactin response was not significantly reduced. In a similar series of experiments KCl (60 nmol/l) was administered to both control and TRH-'treated' pituitary tissue as a 3-min pulse; no significant differences in TSH responses or prolactin responses were observed. These data indicate that TRH desensitizes the pituitary thyrotroph to a subsequent TRH stimulus but has very little effect on prolactin secretion.
J. Endocr. (1984) 101, 101–105
Control of thyroglobulin secretion from the rat thyroid gland
Authors: Black E. G. , Sheppard M. C. , Hoffenberg R. 
Published: December 2008

ABSTRACT
Serum thyroglobulin (Tg), measured by radioimmunoassay, was high in 6-propylthiouracil (PTU)-treated rats but low in thyroxine (T4)-treated animals compared with euthyroid controls. Thyroid-stimulating hormone (TSH) stimulated Tg release in vitro from enzymatically dispersed normal rat thyroid cells in a dose-dependent manner. Thyroid cells prepared from T4-treated animals behaved similarly to cells from control rats, whereas in vitro basal release of Tg from thyroid cells prepared from PTU-treated animals was high and the response to TSH was lost. Our data confirm the TSH dependency of Tg release in vivo and in vitro and our system provides a means of studying the control of Tg secretion in vitro.
J. Endocr. (1984) 101, 107–111
Adrenal androgen concentrations in endometrium and plasma during the menstrual cycle
Authors: Bonney R. C. , Scanlon M. J. , Jones D. L. , Reed M. J. , James V. H. T. 
Published: December 2008

ABSTRACT
Concentrations of 5-androstene-3β, 17β-diol (androstenediol), dehydroepiandrosterone (DHA) and DHA sulphate (DHAS) were measured in endometrium and plasma from normal premenopausal and perimenopausal women (average ages 37 and 48 years respectively) at different stages of the menstrual cycle. Plasma levels did not vary with the stage of the cycle for any of the three steroids. Mean plasma levels of androstenediol ranged between 2·03 and 2·92 nmol/l for premenopausal women and 1·38 and 1·58 nmol/l for perimenopausal women while mean concentrations of DHA were 20·80–36·41 nmol/l (premenopausal women) and 13·87–19·07 nmol/l (perimenopausal women). The values for DHAS were more variable and ranged between 3·20 and 4·56 and 2·94 and 4·25 μmol/l for pre- and perimenopausal women respectively.
In premenopausal women endometrial tissue concentrations of androstenediol and DHA increased three to fourfold in the secretory phase while no increase was observed in DHAS. There was a similar increase in androstenediol but not DHA or DHAS during the secretory phase for perimenopausal women. A significant positive correlation was found for tissue androstenediol and DHA in both groups of women but the relationship between DHAS and the other androgens was significant only for perimenopausal women.
We suggest that the increase in androstenediol and DHA concentrations could be due to an increase in a receptor or binding protein, possibly progesterone dependent, present in secretory phase endometrium.
J. Endocr. (1984) 101, 181–188
Hypertrophied adrenocortical tissue of the Australian brush-tailed possum (Trichosurus vulpecula): uniformity during reproduction
Authors: Call R. N. , Janssens P. A. 
Published: December 2008

ABSTRACT
Adrenal glands from normal male and female brush-tailed possums (Trichosurus vulpecula) were weighed and sectioned to investigate reported changes in the relative size of the hypertrophied region of the cortex during the reproductive cycle. Total adrenal gland weight in normal females averaged 120 mg/kg body weight and the hypertrophied region occupied 40% of the gland volume. No significant variation was found in these figures between glands from pregnant, lactating and cyclic possums. In addition, no cyclic pattern of cellular changes was found in the hypertrophied region. These results differ from views expressed in the current literature which are based on the original description of the hypertrophied zone.
J. Endocr. (1984) 101, 263–267
Soya–a dietary source of the non-steroidal oestrogen equol in man and animals
Authors: Axelson M. , Sjövall J. , Gustafsson B. E. , Setchell K. D. R. 
Published: December 2008

ABSTRACT
The dietary origin of the weak oestrogen equol (7-hydroxy-3-(4′-hydroxyphenyl)-chroman) present in human urine has been investigated using gas chromatography–mass spectrometry. Feeding experiments with different food constituents and monitoring the urinary excretion of equol revealed that soya food yields more than 0·1 mg urinary equol/g flour ingested. From this source the glucoside of daidzein (4′,7-dihydroxyisoflavone) has been isolated and identified as a precursor of equol. Both equol and daidzein were characterized as monoglucuronide conjugates in human urine and the concentration of urinary equol exceeded the concentrations of the classical oestrogens by 100- to 1000-fold after ingestion of a single meal containing soya protein. The potential biological significance of this result is discussed.
J. Endocr. (1984) 102, 49–56
5β-Reductase activity in the brain and cloacal gland of male and female embryos in the Japanese quail (Coturnix coturnix japonica)
Authors: Balthazart J. , Ottinger M. A. 
Published: December 2008

ABSTRACT
Testosterone metabolism was studied by an in-vitro technique in the brain and cloacal gland of young male and female quail at different ages ranging from 7 days of incubation to 2 days after hatching. Very active metabolism, leading almost exclusively to the production of 5β-reduced compounds, was observed. 5β-Reductase activity remained high throughout the incubation period in the hypothalamus, decreased around the time of hatching in the cerebellum and decreased progressively between days 7 and 15 of incubation in the cloacal gland. These changes could be involved in the control of sexual differentiation: the high 5β-reductase in the brain possibly protects males from being behaviourally demasculinized by their endogenous testosterone while the decreasing 5β-reductase in the cloacal gland would progressively permit the masculinization of that structure.
J. Endocr. (1984) 102, 77–81
Activity of LH receptor, LH-stimulated cyclic AMP and testosterone production in the Leydig cell of heat-acclimatized rats
Authors: Bedrak E. , Chap Z. 
Published: December 2008

ABSTRACT
Key reactions associated with the capacity of the isolated Leydig cell to synthesize testosterone were studied in male rats acclimatized to a hot environment (33–35 °C, 25–40% relative humidity) and controls (20–22 °C, 30–50% relative humidity). The results demonstrate that acclimatization to heat coincides with: (1) a lower number of human chorionic gonadotrophin (hCG) receptors (P<0·01) in the Leydig cell, (2) higher affinity of the Leydig cell for hCG (P < 0·05), (3) lower hCG-stimulated cyclic AMP production (P<0·05) by the Leydig cell and (4) lower capacity of the Leydig cell to synthesize testosterone (P<0·01) after hCG challenge. It is suggested that the major cellular alteration responsible for the decreased testosterone secretion by the Leydig cell lies distal to the step involving the binding of the trophic hormone to its receptor and that heat-acclimatization induces changes in the integrity of the various cellular membranes leading to the impeded function of adenylate cyclase and 17β-hydroxysteroid oxidoreductase.
J. Endocr. (1984) 102, 167–173
Dopamine agonist- and antagonist-induced modulation of pituitary gonadotrophin releasing hormone receptors are independent of changes in serum prolactin
Authors: Clayton R. N. , Bailey L. C. 
Published: December 2008

ABSTRACT
The effect of drug-induced hypo- and hyperprolactinaemia on pituitary gonadotrophin releasing hormone receptors (GnRH-R), serum and pituitary gonadotrophins (LH and FSH) and prolactin was investigated in intact adult male and female rats. Hypoprolactinaemia (serum prolactin <20% of control values) resulting from dopamine agonist (bromocriptine) infusion (4 mg/kg per day for 7 days) was accompanied by a 40–50% increase in GnRH-R in both male and female animals, though this was not accompanied by any major change in serum or pituitary LH and FSH. Hyperprolactinaemia (serum prolactin greater than ten times control values) induced by the dopamine receptor antagonist metoclopramide (65 mg/kg per day for 7 days) increased GnRH-R between 35 and 45% in both male and female rats without altering serum gonadotrophins. Domperidone (1 mg twice daily for 14 days) also increased GnRH-R by 50% but only in female rats. Both dopamine antagonists significantly increased pituitary prolactin content. Pituitary FSH increased in female rats treated with both metoclopramide and domperidone.
The stimulatory effects of bromocriptine and metoclopramide on GnRH-R in male rats were prevented by concurrent treatment with a GnRH antiserum, suggesting that the drug effects were mediated through alteration in endogenous GnRH secretion.
Induction of massive (serum prolactin > 2000 μg/l) hyperprolactinaemia in male and female rats with a transplantable prolactin-secreting pituitary tumour did not reduce GnRH-R concentration, although serum gonadotrophins were suppressed and pituitary gonadotrophin content was increased.
These results indicate a dissociation between serum prolactin concentrations and pituitary GnRH receptor content and indicate that dopamine agonist and antagonist agents can influence GnRH-R independently of prolactin, possibly by acting on central dopamine receptors responsible for catecholaminergic regulation of GnRH secretion.
J. Endocr. (1984) 102, 215–223
Effect of parathyroid hormone and calcitonin on the cytoplasmic spreading of isolated osteoclasts
Authors: Chambers T. J. , Athanasou N. A. , Fuller K. 
Published: December 2008

ABSTRACT
Osteoclasts, the major agents of bone resorption, were isolated from neonatal rat bone, and the cytoplasmic spreading of these cells was measured after incubation in the presence or absence of hormones or other cell types. Salmon calcitonin, which inhibits osteoclastic bone resorption, reduced spreading in a dose-dependent manner and caused significant inhibition at concentrations as low as 6·7 pg/ml. Parathyroid hormone (PTH) had no effect on the spreading of isolated osteoclasts but if osteoblasts and osteoclasts were co-cultured the addition of PTH caused a marked increase in spreading at concentrations of 0·025 i.u./ml and above. The results suggest that while calcitonin is a direct inhibitor of osteoclastic activity, PTH may stimulate osteoclasts through a primary action on osteoblasts.
J. Endocr. (1984) 102, 281–286
Production rate, metabolic clearance rate and blood concentration of progesterone in conscious and anaesthetized pregnant rats
Authors: Waddell B. J. , Bruce N. W. 
Published: December 2008

ABSTRACT
Both production rate and metabolic clearance rate (MCR) of progesterone may vary rapidly and so effect short-term changes in blood concentration of the hormone. Here, a constant infusion and sampling technique was used to estimate these three characteristics of progesterone metabolism in seven conscious and ten anaesthetized rats on day 16 of pregnancy. After steady state was achieved, four samples were collected during a 1-h period from each rat. Mean values for production rate and MCR of progesterone in conscious rats were 14·0 ±1·4 μmol/day and 63·2 ± 6·2 litres/day respectively. Both values were substantially reduced in anaesthetized rats (8.6 ±0·8 μmol/ day and 39·4± 3·4 litres/day respectively) and so blood concentration was unchanged. The production rate was positively related to the total mass of luteal tissue (common correlation coefficient, r = 0·61, P <0·05). There were no consistent changes in the three characteristics with time but variation within rats was high. The estimated coefficients of variation for production rate, MCR and blood concentration within rats were 26, 18 and 17% in conscious and 27, 20 and 23% in anaesthetized rats respectively. Short-term changes in production rate and MCR generally were in the same direction (P <0·05). This reduced variation in blood concentration which would otherwise have occurred if production rate and MCR were unrelated. The pregnant rat is clearly capable of rapid shifts in production rate, MCR and blood concentration of progesterone and the positive relationship between production rate and MCR has a homeostatic effect on blood concentration.
J. Endocr. (1984) 102, 357–363
Ovulation in the marmoset monkey: endocrinology, prediction and detection
Authors: Harlow C. R. , Hearn J. P. , Hodges J. K. 
Published: December 2008

ABSTRACT
Circulating progesterone, oestrogens and LH were measured in female marmosets (Callithrix jacchus) over the periovulatory period. Progesterone concentrations increased in all animals within 1 day of the estimated day of ovulation, confirming the usefulness of this hormone for retrospective detection of ovulation. Oestradiol-17β and LH both showed a preovulatory rise, but due to the large quantity of plasma required (oestradiol: 0·2 ml) and the length of time taken for the assay (LH: 2–3 days), measurement of these hormones is not practical for the prediction of ovulation. There were no preovulatory changes in unconjugated oestrone, but a rise in total (i.e. conjugated plus unconjugated) oestrone was used to time the collection of recently ovulated oocytes. Levels of oestrone-3-sulphate showed an increase at least 1 day before the expected day of ovulation in four out of five animals. This preovulatory rise can be measured easily by a rapid direct assay, thereby providing a practical method for predicting ovulation in this species.
J. Endocr. (1984) 103, 17–24