bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of acetylcholine and 5-hydroxytryptamine on the secretion of corticotrophin-releasing factor-41 and arginine vasopressin from the rat hypothalamus in vitro
Authors: Hillhouse E. W. , Milton N. G. N. 
Published: December 2008

ABSTRACT
Previous studies using the isolated rat hypothalamus in vitro have shown that both acetylcholine and 5-hydroxytryptamine (5-HT) stimulate the secretion of bioactive corticotrophin-releasing factor (CRF). However, the CRF complex consists of a number of bioactive substances, and in this study we examined the effect of acetylcholine and 5-HT on the release of immunoreactive (ir)-CRF-41 and ir-arginine vasopressin (AVP) in vitro. Acetylcholine caused a dose-dependent (10 pmol–10 nmol/l) release of both neuropeptides, and the effect was partially antagonized by both atropine and hexamethonium. Nicotine (0·1–10 μmol/l) also stimulated the release of both peptides, whereas bethanacol had no effect on AVP release, but had a variable action on CRF-41 release. 5-HT caused a dose-dependent (10 pmol–1 nmol/l) stimulation of CRF-41 release without any effect on AVP release, and this effect was antagonized by cyproheptadine, suggesting the participation of specific 5-HT receptors.
Journal of Endocrinology (1989) 122, 713–718
A comparison of the seasonal hormone changes and patterns of growth, voluntary food intake and reproduction in juvenile and adult red deer (Cervus elaphus) and Père David's deer (Elaphurus davidianus) hinds
Authors: Loudon A. S. I. , Milne J. A. , Curlewis J. D. , McNeilly A. S. 
Published: December 2008

ABSTRACT
Non-domesticated seasonally breeding ungulates exhibit marked seasonal changes in metabolic rate, voluntary food intake (VFI), pelage growth and moult and hormone secretion. It is not known whether these seasonal rhythms are regulated by the same central processes which control the onset and termination of the breeding season. Here we compare two closely related deer species which have significantly different mating and calving seasons. Seasonal changes in VFI, liveweight, coat growth, plasma prolactin and tri-iodothyronine (T3), and the timing of the breeding season were examined over a 15-month period in six adult post-pubertal red and Père David's deer from January to April the following year. The timing of the seasonal changes in prolactin, T3, VFI and coat growth were all significantly advanced by 56, 23, 60 and 54 days respectively in the Père David's deer. The times of onset and termination of the breeding season of Père David's deer were also significantly advanced by 90 days, but in both species, the breeding season was of similar duration (160 ± 5 (s.e.m.) days). Changes in liveweight of adult red deer could be explained by changes in VFI rather than efficiency of utilization. This was not the case in Père David's deer and may indicate seasonal changes in the efficiency of energy utilization. In order to establish whether these species differences develop with age, we undertook a second study in which seasonal changes in VFI, growth, plasma prolactin concentrations and the timing of the onset of the breeding season were recorded for ten red deer and six Père David's deer from 6 to 18 months of age. Both species exhibited a similar decline in VFI in the first autumn of life. Subsequently, the Père David's deer exhibited an advance in the timing of the seasonal peak in VFI and prolactin (21 and 66 days respectively); puberty occurred 3 months earlier than in red deer. The earlier breeding season of the Père David's deer was associated with a significant advance in a range of seasonal endocrine and physiological parameters. These species differences may develop with age. Our data indicate that seasonal patterns of metabolism and growth may be closely linked to those mechanisms which also regulate the onset and termination of the breeding season.
Journal of Endocrinology (1989) 122, 733–745
Quantification of opioid-binding sites in the ewe hypothalamus
Authors: Yang K.-P. , Haynes N. B. , Lamming G. E. 
Published: December 2008

ABSTRACT
Opioid-binding sites were quantified in the ewe hypothalamus using [3H]diprenorphine ([3H]DIP) as the radioligand. [3H]DIP binding to hypothalamic membrane preparations was stereospecific, saturable with respect to [3H]DIP concentration, and linear with hypothalamic membrane protein content. Scatchard analysis revealed a single class of binding sites. There were no significant differences in binding site concentration or binding affinity in hypothalami from intact ewes during the breeding and non-breeding seasons, or from long-term ovariectomized ewes with and without oestradiol treatment during the breeding season. Thus, whilst ovarian steroid hormones are known to modify LH responses to opioids and their antagonists in the ewe in vivo, they do not appear to do this by modulating the numbers of hypothalamic opioid-binding sites.
Journal of Endocrinology (1989) 122, 763–767
AMPLIFICATION OF UTEROGLOBIN SECRETION BY ALTERNATING PROLACTIN-PROGESTERONE ADMINISTRATION
Authors: Daniel J. C. , June ja S. C. 
Published: December 2008

ABSTRACT
Long-term ovariectomized rabbits were given injections of progesterone and prolactin in an alternating sequence (progesterone for 5 days, prolactin for 4 days and progesterone for 5 days) to test the hypothesis that each of these hormones acts to increase the other's receptor, resulting in a positive feedback process whereby prolactin augments the progesterone-dependent increase in the mRNA for the uterine protein, uteroglobin. The results of this study support the hypothesis, in that the experimental rabbits produced exceptionally large concentrations of uteroglobin.
Comparison of the effects of administration of recombinant bovine growth hormone or N-Met insulin-like growth factor-I to lactating goats
Authors: Davis S. R. , Gluckman P. D. , Hodgkinson S. C. , Farr V. C. , Breier B. H. , Burleigh B. D. 
Published: December 2008

ABSTRACT
Five goats were injected with GH (15 mg/day), three goats received systemic infusions of insulin-like growth factor (IGF)-I (43 nmol/h) and four goats received systemic infusions of physiological saline (20 ml/h) on days 4–6 of a 10-day experimental period during mid-lactation.
Milk yield increased by an average of 24% in GH-treated goats by the time of the third injection. In contrast, milk yield of IGF-I-infused goats did not differ from saline-infused animals although two of three goats did show a small increase (12%) after 36 h of IGF-I infusion.
With GH and IGF-I treatments plasma IGF-I concentrations increased similarly, reaching maxima of 100–130 nmol/l within 24 h. Plasma IGF-I concentration was relatively constant in saline-infused goats at about 50 nmol/l throughout the experiment.
Total IGF-I bound to 50 kDa and 150 kDa binding proteins in plasma was increased by GH and IGF-I treatments but, in contrast to IGF-I, GH increased the proportion of IGF-I bound to 150 kDa binding protein.
In a second experiment, four goats received systemic infusion of IGF-I (43 nmol/h) and four goats received systemic infusion of physiological saline (20 ml/h). There was no evidence that milk yield was changed during IGF-I infusion. However, when those goats which had previously received IGF-I infusions were injected with GH, milk yield increased by 30%. While the increment in plasma IGF-I concentration during IGF-I infusion was similar to that obtained in the first experiment, the IGF-I response to GH injection was much greater, plasma concentrations rising to 230 nmol/l.
The data show a lack of milk yield response in goats whose plasma IGF-I concentrations were increased by IGF-I administration. Systemic infusion of IGF-I appears to be ineffective as a means of procuring a sustained increase in milk production.
Journal of Endocrinology (1989) 123, 33–39
Regulation by oestradiol of serum levels of LH and FSH and pituitary levels of gonadotrophin-releasing hormone receptors after ovariectomy in the rat
Authors: Rosen H. , Jameel M. L. , Dee C. , Barkan A. L. 
Published: December 2008

ABSTRACT
We studied cyclic and ovariectomized, oestradiol-treated rats to investigate whether oestradiol concentrations before ovariectomy determine the dynamics of the rises in serum levels of LH and FSH, and in pituitary gonadotrophin-releasing hormone (GnRH) receptors after ovariectomy. In cyclic rats, ovariectomy on metoestrus (oestradiol = 44 pmol/l), but not at midnight of dioestrus (oestradiol =254 pmol/l) was followed by a rise in GnRH receptors 40 h later. Randomly cyclic females were ovariectomized under ether anaesthesia and treated with s.c. oestradiol implants for 2 days to provide serum levels spanning the physiological range. Exposure to lower oestradiol concentrations (48 or 74 pmol/l) resulted in significant rises in levels of LH and FSH, and in GnRH receptors earlier than exposure to higher (148 or 309 pmol/l) oestradiol levels (2 compared with 4 days). GnRH given for 24 h after removal of the implant was unable to induce a rise in GnRH receptors in any group, while LH and FSH responses to GnRH were proportional to the pretreatment levels of oestradiol. This suggests that the concentration of oestradiol before ovariectomy determines the subsequent dynamics of LH and FSH and of GnRH receptors through actions at the hypothalamic and pituitary level.
Journal of Endocrinology (1989) 123, 249–256
Relationship between insulin-like growth factor-I and low-density lipoprotein cholesterol levels in primary hypothyroidism in women
Authors: Hoogerbrugge–v.d.Linden N. , Jansen H. , Hülsmann W. C. , Birkenhäger J. C. 
Published: December 2008

ABSTRACT
The effect of insulin-like growth factor-I (IGF-I) on the disturbance of lipid metabolism during primary hypothyroidism was studied in 12 women with primary hypothyroidism. Significant increases in both low-density lipoprotein (LDL) cholesterol and intermediate-density lipoprotein cholesterol were seen. Lipoprotein concentrations reverted to normal after substitution with thyroxine (T4) until the euthyroid state was reached. A decrease in IGF-I of 65% (P<0·005) was seen in hypothyroid patients and this was inversely correlated (r=−0·75; P<0·01) with the concentration of LDL cholesterol. Multivariate regression analysis of LDL cholesterol against IGF-I and free T4 showed that IGF-I determines the concentration of LDL cholesterol instead of free T4.
Our data suggest that in hypothyroidism, IGF-I is a determinant of the concentration of LDL cholesterol. In addition, hypothyroidism can influence plasma lipoprotein metabolism by lowering the activity of the salt-resistant lipase (liver lipase).
Journal of Endocrinology (1989) 123, 341–345
Biphasic response in the secretion of gonadotrophin-releasing hormone in ovariectomized ewes injected with oestradiol
Authors: Caraty A. , Locatelli A. , Martin G. B. 
Published: December 2008

ABSTRACT
In ovariectomized ewes, an injection of oestrogen initially inhibits the tonic secretion of LH, and then induces a large release of LH similar to the preovulatory surge in intact ewes. The pattern of hypothalamic secretion of gonadotrophin-releasing hormone (GnRH) into the pituitary portal blood during this biphasic response to oestrogen was investigated in conscious, unrestrained, ovariectomized adult Ile-de-France ewes during the breeding season. The ewes were ovariectomized and implanted with cannulae for portal blood collection on the same day. Seven days later, portal and peripheral blood samples were collected simultaneously every 5 min for 25 h. The ewes were injected with oestradiol-17β (25 μg i.v. and 25 μg i.m.) 6·25 h after the start of sampling. GnRH and LH were measured by radioimmunoassay in portal and jugular plasma samples respectively.
A clear pulsatile pattern of LH secretion was observed before the oestradiol injection in all ewes, followed by the typical biphasic decrease (negative feedback) and increase (positive feedback) in mean concentrations. The sampling period was divided, for analysis, into pretreatment, negative feedback and positive feedback phases. Before injection with oestradiol, the GnRH pulses were clearly defined in portal blood and always synchronized with LH pulses in the peripheral circulation. The frequency was 5·9 ± 0·6 pulses/6 h (mean ± s.e.m.), and the amplitude was 31·6±7·6 pmol/l. During negative feedback, both the frequency (4·2 ± 0·5 pulses/6 h, P<0·01) and amplitude (15·2 ± 4·6 pmol/l, P<0·05) of the GnRH pulses decreased. During positive feedback, there was a large surge in the concentration of GnRH, due primarily to an increase in pulse frequency (11·0±1·3 pulses/6 h, P<0·01). A change in pulse amplitude was not detected, but there was a large increase in the basal level of GnRH (P<0·05). As a consequence of the changes in frequency and amplitude of the pulses, the mean levels of GnRH before injection with oestradiol (5·3 ± 1·0 pmol/l) differed (P<0·05) from those during negative (3·8±0·5 pmol/l) and positive (18·9±4·7 pmol/l) feedback phases.
These results show that the biphasic pattern of LH secretion induced by oestrogen injection in short-term ovariectomized ewes is caused by parallel changes in the secretion of GnRH as well as changes in pituitary responsiveness to GnRH. An abrupt increase in the frequency of GnRH pulses appears to be a key component of the positive feedback mechanism which elicits the oestradiol-induced surges of both GnRH and LH.
Journal of Endocrinology (1989) 123, 375–382
Quantitative analysis of germ cell numbers and relation to intratesticular testosterone following vitamin A-induced synchronization of spermatogenesis in the rat
Authors: Bartlett J. M. S. , Weinbauer G. F. , Nieschlag E. 
Published: December 2008

ABSTRACT
Synchronization of spermatogenesis would provide an ideal model for the investigation of stage-dependent changes in the secretion of paracrine factors. In vitamin A-deficient animals subsequently injected with vitamin A, over 80% of seminiferous tubules were synchronized within three to five stages of the seminiferous cycle. Following replenishment of vitamin A, spermatogenic stages IV–VI (35 days), VI–VIII (38 days), IX–XII (41 days), I–IV (45 days) and V–VII (48 days) were observed. Despite synchronization of spermatogenesis at all stages, spermatogenesis was markedly impaired when evaluated in a quantitative fashion. At all times evaluated, numbers of round spermatids were reduced compared with age-matched controls. Numbers of pachytene spermatocytes reached control values only after 45 days of vitamin A replenishment. Elongate spermatids were almost totally absent up to 41 days after vitamin A replenishment. Testicular and epididymal weights were also reduced, although testicular weights showed a significant recovery over the time-course of the study. Serum and pituitary concentrations of LH and FSH were raised at the commencement of the study, with serum gonadotrophins returning to control values 48 days after vitamin A replenishment. Both testicular and serum testosterone concentrations in treated animals tended to be higher than in the controls.
Although synchronization of spermatogenesis was achieved, testicular testosterone concentrations did not reflect the stage-dependent cyclical changes observed in earlier studies. Testicular concentrations of testosterone were raised throughout the period of observation with the exception of animals synchronized around stages II–IV of the spermatogenic cycle. No correlation between the most frequent stages and intratesticular testosterone was found (r = 0·06, P > 0·1). Previous observations that testosterone concentrations are selectively increased at stages VII–VIII of the spermatogenic cycle are not supported by the present study.
Journal of Endocrinology (1989) 123, 403–412
Asymmetric ovulatory response induced by a unilateral implant of atropine in the anterior hypothalamus of the cyclic rat
Authors: Cruz M. E. , Jaramillo L. P. , Domínguez R. 
Published: December 2008

ABSTRACT
The effects were analysed, on ovulation at the next oestrus, of unilaterally implanting atropine in the anterior hypothalamus of rats on each day of the oestrous cycle. Implantation on day 1 of dioestrus on either side of the anterior hypothalamus blocked ovulation. Implantation on the left side of the hypothalamus on day 2 of dioestrus blocked ovulation in all animals, whereas implantation on the right side allowed 71% of the animals to ovulate (0/4 vs 5/7; P < 0·05). Implantation at pro-oestrus on either side of the hypothalamus did not modify the rate of ovulation. When implantation was carried out on the day of oestrus on the right, none of the animals ovulated, but all ovulated when the implant was on the left (0/8 vs 8/8; P < 0·01). The results suggest the existence of a cholinergic hypothalamic lateralization in the mechanism regulating ovulation which depends on the day of the oestrous cycle.
Journal of Endocrinology (1989) 123, 437–439
Parathyroid hormone-related proteins in cultured epithelial cells
Authors: Docherty H. M. , Dixon-Lewis M. J. , Milton P. G. , Blight A. , Heath D. A. 
Published: December 2008

ABSTRACT
The distribution and molecular characteristics of parathyroid hormone-related protein (PTH-rP) in conditioned media and cell extracts of cultured human keratinocytes, and in media from a variety of both normal and transformed epithelial and non-epithelial cell cultures were studied. PTH-rP of Mr 20 000 was observed in keratinocyte-conditioned media, and a larger form, Mr 29 000, in the keratinocyte cell extract. PTH-like bioactivity was also detected in media from 12 out of 17 epithelial cell cultures, but was not present in media from 14 cell cultures of non-epithelial origin. The molecular size of the PTH-like protein present in the epithelial cell media was approximately 20 000, corresponding with the PTH-rP in keratinocyte-conditioned medium. These observations may explain why hypercalcaemia is most commonly associated with tumours of epithelial origin.
Journal of Endocrinology (1989) 123, 487–493
Aldosterone and thyroid hormone interaction on the sodium and potassium transport pathways of rat colonic epithelium
Authors: Edmonds C. J. , Willis C. L. 
Published: December 2008

ABSTRACT
The effect of hypothyroidism on potassium adaptation (shown by increased potassium secretion in response to potassium loading) and on the action of aldosterone on potassium secretion and sodium fluxes was examined in the rat distal colon.
Potassium adaptation, particularly the response to an acute potassium load, was impaired by hypothyroidism which also considerably reduced the rise of transepithelial electrical potential difference (p.d.) of total and transcellular (active) lumen-to-plasma sodium fluxes and of potassium secretion normally produced by aldosterone. These changes were, in part, corrected by a short period (3 days) of tri-iodothyronine replacement. Moreover in aldosterone-treated hypothyroid rats, amiloride in the lumen was considerably less effective in reducing the p.d. and sodium fluxes than in aldosterone-treated normal rats.
The intracellular sodium transport pool was greater in the hypothyroid than in the normal rats (5·0± 1·1 (s.e.m.) nmol/mg dry weight compared with 2·9 ± 0·2 nmol/mg dry weight; P<0·02). Aldosterone increased the pool in the normal but not in the hypothyroid rats while amiloride had little effect on the pool in the aldosterone-treated hypothyroid rats but almost abolished it in aldosterone-treated normal rats.
Aldosterone plays a major part in the adaptation of colonic sodium and potassium transport to sodium depletion or potassium excess; these adaptations were much impaired in hypothyroid animals. The present results are consistent with a deficiency in aldosterone induction of potassium- and amiloride-sensitive sodium pathways in the apical membrane of colonic epithelial cells in hypothyroid rats, a deficiency which limits the stimulant effect of aldosterone on sodium and potassium transport.
Journal of Endocrinology (1990) 124, 47–52
Inhibition by staurosporine of TRH-induced refractoriness of inositol phospholipid hydrolysis in rat anterior pituitaries
Authors: Iriuchijima T. , Mori M. 
Published: December 2008

ABSTRACT
To clarify the mechanism(s) underlying the TRH-induced refractory state of the anterior pituitary, we evaluated rat pituitary inositol phospholipid hydrolysis in the presence of staurosporine. TRH caused a time- and dose-dependent accumulation of inositol phosphates in rat anterior pituitary slices. Pretreatment with 550 nmol TRH/l completely abolished the subsequent accumulation of inositol phosphates in response to 140 nmol TRH/l. TRH-stimulated accumulation of inositol phosphates did not occur after pretreatment with 0·2 μmol phorbol ester/l. Refractoriness of inositol phospholipid hydrolysis which was produced by pretreatment with TRH and phorbol ester was inhibited by staurosporine. The present data support the hypothesis that protein kinase C plays a profound role in TRH induction of the refractory state of inositol phospholipid hydrolysis in the anterior pituitary.
Journal of Endocrinology (1990) 124, 75–79
Central administration of corticotrophin-releasing factor in the sheep: effects on secretion of gonadotrophins, prolactin and cortisol
Authors: Naylor A. M. , Porter D. W. F. , Lincoln D. W. 
Published: December 2008

ABSTRACT
Stress interferes with the normal secretion of LH and FSH from the anterior pituitary gland and therefore exerts a deleterious effect on reproductive function. Evidence suggests that the stress-induced disruption of gonadal function is due to a central action of corticotrophin-releasing factor (CRF) to inhibit the release of LHRH into the hypophysial-portal circulation. The following studies were undertaken to investigate further the role of CRF in regulating gonadotrophin release in the sheep and to determine whether central administration of this peptide can alter the secretion of other hormones (e.g. prolactin and cortisol) known to be released under conditions of stress.
In contrast to other species, injection of CRF into the third ventricle of the sheep brain caused a dose-related stimulation of LH secretion. The pulse frequency and mean levels of LH were increased significantly following central administration of CRF. In contrast to this effect, central administration of CRF did not alter the plasma concentration of FSH but caused a marked and dose-related stimulation of prolactin and cortisol secretion. The stimulatory effect of CRF on prolactin secretion was reversed by i.v. administration of the opioid antagonist naloxone, suggesting that endogenous opioid peptides mediate the central effect of CRF on the release of prolactin, but not cortisol.
In conclusion, these data demonstrate that administration of CRF causes a dose-related stimulation of LH and prolactin release from the anterior pituitary gland and cortisol from the adrenal gland. In the case of prolactin, endogenous opioid peptides are likely to mediate this response. The observations concerning LH are the opposite of those reported for the rat and the monkey where CRF caused a prolonged inhibition of gonadotrophin secretion. This suggests that a species difference may exist or, alternatively, the stimulatory effect of CRF on LH secretion in the sheep may be similar to the increase in LH secretion reported in rats and monkeys subjected to short-term handling or restraint stress.
Journal of Endocrinology (1990) 124, 117–125