bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of corticosterone on circulating concentrations of corticosterone, prolactin, thyroid hormones and somatomedin C and on fattening in broilers selected for high or low fat content
Authors: Buyse J. , Decuypere E. , Sharp P. J. , Huybrechts L. M. , Kühn E. R. , Whitehead C.
Published: December 2008

Daily changes in the concentrations of plasma corticosterone, prolactin, thyroid hormones and somatomedin C were measured in 28-day-old fat and lean lines of broilers produced by selection for high and low concentrations of very low density lipoproteins (VLDL). The effects of daily injections of corticosterone on the concentrations of these hormones and on fattening were compared in the two lines. The selection procedure had no effect on the concentrations of any of the hormones. However, daily rhythms in concentrations of plasma corticosterone, tri-iodothyronine (T3) and prolactin were less often observed in the fat line than in the lean line. No differences were seen between lines in the daily rhythms in plasma thyroxine (T4) and somatomedin C. Daily injections of 2500 μg corticosterone/kg body weight, in both lines, depressed mean concentrations of plasma prolactin, T3 and somatomedin C and body weight. This dose of corticosterone also increased abdominal fat pad and liver weights expressed as a percentage of body weight. The liver and fat pad responses to 2500 μg corticosterone in both lines were greater when the steroid was injected at the end rather than towards the beginning of the 14-h daily photoperiod. There was no difference between the lines in the fattening response to corticosterone. Lower doses of 100 and 500 μg corticosterone per day did not induce fattening or affect concentrations of plasma prolactin. They did, however, depress concentrations of plasma T3. Concentrations of plasma T4 were increased in both lines treated with 2500, but not with 100 or 500 μg corticosterone, towards the beginning of the daily photoperiod. It is concluded that selection for low and high concentrations of VLDL does not affect mean levels of the hormones measured at 28 days of age or the fattening response to corticosterone. It does, however, alter the amplitude in the daily rhythm in concentrations of corticosterone, T3 and prolactin. The fattening response to corticosterone is associated with depressed concentrations of plasma prolactin, T3 and somatomedin C.

J. Endocr. (1987) 112, 229–237
The involvement of ovarian factors in maintaining the pituitary glands of female rats in a state of low LH responsiveness to LHRH
Authors: de Koning J. , Tijssen A. M. I. , van Rees G. P.
Published: December 2008

The effects of discontinuation and restoration of ovarian influences on the pituitary LH response to LHRH in vitro were investigated.

When female rat pituitary glands taken on day 2 of dioestrus were incubated with LHRH the release of LH was low during the first hour (lag phase response) and afterwards a progressive, protein synthesis-dependent increase took place (second phase response), this being the self-priming action of LHRH.

Short-term discontinuation (less than 1 day) of ovarian influences on the rat pituitary gland in vivo (ovariectomy) or in vitro (incubation in medium only) resulted in an increased LHRH-induced LH response during the lag phase.

The biphasic LH response or the self-priming action of LHRH disappeared completely after long-term discontinuation of ovarian influences on the pituitary gland, LH release being at its maximum from the start of the incubation. The biphasic response was reinstated when ovaries were implanted under the kidney capsules of ovariectomized rats. Auto-implantation of an ovary into the spleen immediately after bilateral ovariectomy did not, however, prevent the disappearance of the LHRH self-priming action. Ovarian activity responsible for the presence of the low LH response during the lag phase was thus effectively removed by the liver, but inhibin-like activity suppressing serum FSH levels remained present. Silicone elastomer implants (s.c.) containing oestradiol-17β, implanted for 4 weeks, did not reverse the loss of the biphasic LH response to LHRH.

It is concluded that liver-labile factors released by the ovaries keep the pituitary gland in a state of low responsiveness to LHRH. By giving a sufficiently high LHRH stimulus this inhibitory effect is neutralized and transition to a highly responsive state can be achieved. The ovarian factor(s) is not identical to inhibin or oestradiol-17β.

J. Endocr. (1987) 112, 265–273
A possible dual regulation of prolactin release by the serotoninergic system in rats at pro-oestrus and during late pregnancy: role of ovarian hormones
Authors: Jahn G. A. , Deis R. P.
Published: December 2008

The effect of para-chlorophenylalanine (pCPA), an inhibitor of serotonin synthesis, on prolactin release was studied in rats on the day of pro-oestrus and at the end of pregnancy (day 19). The surges of prolactin normally seen in the afternoon of pro-oestrus in intact rats and in rats ovariectomized on dioestrous day 2 and primed with oestrogen were significantly inhibited by pCPA treatment. Administration of 5-hydroxy-tryptophan reversed the inhibitory action of pCPA on prolactin release. Treatment with progesterone also completely reversed the inhibitory effect of pCPA on prolactin release in pro-oestrous rats and partially reversed it in ovariectomized oestrogen-treated rats.

Ovariectomy on day 19 of pregnancy induced a significant release of prolactin 12 and 24 h later. Administration of pCPA on day 18 of pregnancy produced a marked increase in serum concentrations of prolactin on days 19 and 20 in rats left intact or ovariectomized on day 19. Administration of 5-hydroxy-tryptophan significantly reversed this stimulatory effect of pCPA on prolactin release but did not modify the release of prolactin induced by ovariectomy. Methiothepin (1-[10,11-dihydro-8-(methylthio)  thiepin-10,41]-4-methylpiperazine maleate), a serotonin receptor blocker, also induced a significant increase in serum concentrations of prolactin on day 20 of pregnancy in rats left intact or ovariectomized on day 19. These results suggest the existence of different serotoninergic actions in the regulation of prolactin release at pro-oestrus and in late pregnancy. Serotonin facilitates the surges of serum prolactin released at pro-oestrus and in ovariectomized rats treated with oestrogen; progesterone enhances this effect. On the other hand, during late pregnancy, when progesterone tonically inhibits prolactin release, serotonin inhibits the release of prolactin.

J. Endocr. (1987) 112, 367–374
Chromatographic characteristics of pro-opiomelanocortin-derived peptides from the rat transplantable tumour 7315a
Authors: Morano M. I. , Estivariz F. E.
Published: December 2008

Adrenocorticotrophin (ACTH) and other proopiomelanocortin (POMC)-derived peptides produced by the 7315a corticomammotrophic tumour have been poorly studied although they elicit profound hypertrophy and hyperplasia in the adrenal glands of recipient Buffalo rats. Tumour extracts were chromatographed on Sephadex G-75 and fractions monitored for POMC-derived peptides by four radioimmunoassay (RIA) systems: ACTH, α-MSH, β-lipotrophin (β-LPH)/endorphin and N-terminal POMC (N-POMC). Chromatograms were compared with those of pars distalis extracts from normal Buffalo rats. All four RIA systems detected immunoreactive material in tumour extracts. ACTH, β-LPH/ endorphin and N-POMC were present in approximately equimolar amounts (ACTH content 93·40 ± 5·27 (s.e.m.) pmol/g) whereas α-MSH was present in smaller amounts (2·83± 0·13 pmol/g). Total peptide content correlated well with tumour weight. ACTH immunoreactivity (IR) in Sephadex chromatograms was located in a large 20 000 mol. wt peak, an ACTH(1–39) peak and a smaller peak coinciding with ACTH(1–24). The latter two peaks showed biological activity consistent with ACTH(1–39) and an ACTH (1–24)-like peptide respectively. The β-LPH/endorphin RIA revealed a peak eluting at approximately 20 000 mol. wt which could not be ascribed to any known POMC peptide containing the endorphin sequence. A β-LPH-like peak, a β-endorphin-like peak and a smaller-sized peak, which contained the bulk of the β-LPH/endorphin IR, were detected; the low molecular weight peak probably representing α- or γ-endorphin. The N-POMC RIA revealed a 20 000 mol. wt peak and a wide peak which could not be completely resolved into two peaks, and which probably represented N-POMC(1–95) and (N-POMC(1–74). No 30 000 mol. wt precursor could be detected with any of the RIA systems employed. Sephadex chromatography of material released from perfused dispersed tumour cells revealed identical IR peaks with all RIA systems used. Glycosylation of tumour POMC peptides was assessed by Concanavalin A–agarose (Con A) chromatography of pooled IR peaks from Sephadex chromatograms. The 20 000 mol. wt (both IR-ACTH and IR-N-POMC) peak, IR-N-POMC(1–95) and IR-N-POMC(1–74) peaks all bound to Con A and were specifically eluted with methylglucoside. Sephadex G-75 and Con A chromatography of pooled pars distalis extracts from normal Buffalo rats were performed. They showed significant differences, compared with tumour extract chromatograms, with all the RIA systems employed. It is concluded that the 7315a tumour processes POMC in a different manner when compared with normal Buffalo rat pars distalis and that it may be used as an interesting model in which to study the processing of POMC. In addition it may shed light on the role of POMC-derived peptides, other than ACTH(1–39), on adrenal growth and function.

J. Endocr. (1987) 112, 417–425
Local production of progesterone by the corpus luteum of the marmoset monkey in response to perfusion with chorionic gonadotrophin and melatonin in vivo
Authors: Webley G. E. , Hearn J. P.
Published: December 2008

The effect of human chorionic gonadotrophin (hCG) and melatonin on the local production of progesterone by the marmoset corpus luteum was investigated in vivo using a perfusion cannula system. Progesterone secretion was measured in 10-min fractions of buffer which had been perfused through the corpus luteum at a flow rate of 70 μl/min for a maximum of 3 h in anaesthetized animals. Two corpora lutea were cannulated in each animal; one for perfusion of test material and the other for perfusion with buffer alone as a control. Perfusion with hCG (25 i.u./ml), investigated as a positive control, produced a marked stimulation of progesterone secretion which increased 10–20 min from the start of perfusion and reached a peak after 30–60 min. A stimulation of progesterone was also observed after perfusion with melatonin (860 pmol/l). The response was evident within 10–30 min of the hormone reaching the corpus luteum and was similar in magnitude to that observed for hCG. The ability of melatonin to stimulate progesterone secretion supports previous in-vitro studies and suggests an ovarian action for melatonin in the primate. The local perfusion system described may have potential uses in studies of luteal function related to aspects of infertility or regulation of fertility.

J. Endocr. (1987) 112, 449–457
The effect of thyroid hormones on growth hormone gene expression in vivo in rats
Authors: Wood D. F. , Franklyn J. A. , Docherty K. , Ramsden D. B. , Sheppard M. C.
Published: December 2008

Thyroid hormones are important regulators of GH synthesis and secretion. In this study we have made a detailed examination of the time-course of the effects of hypothyroidism and tri-iodothyronine (T3) replacement in the intact rat on GH gene expression in the anterior pituitary gland. Changes in pituitary cytoplasmic GH messenger (m)RNA levels were compared with total pituitary GH content and serum GH concentration during the development of hypothyroidism and following short-term T3 replacement in vivo. Hypothyroidism was associated with a fall in pituitary GH mRNA levels. Treatment of hypothyroid animals with T3 rapidly stimulated GH mRNA levels to values above those seen in euthyroid controls. The reduction in GH mRNA levels seen during the development of hypothyroidism was accompanied by a fall in serum GH and pituitary GH content, both of which were partially restored by T3 replacement. Thus thyroid hormone replacement in hypothyroidism rapidly stimulates GH mRNA synthesis, which is followed by the gradual restoration of pituitary GH stores and serum GH concentration.

J. Endocr. (1987) 112, 459–463
The renin-angiotensinogen reaction during pregnancy and oral contraception: estimation of kinetic parameters by an autologous plasma renin assay
Authors: Daniels C. R. , Eisen V. , Slater J. D. H.
Published: December 2008

A method has been developed which allows estimation of the kinetic parameters of the plasma renin-angiotensinogen reaction from data obtained by autologous renin assays at several plasma dilutions. The quantitative aspects of the renin-angiotensin system were examined in 28 plasma samples from 23 healthy, normotensive pregnant women. They were compared with 20 women who were not pregnant, of whom 12 were taking oral contraceptives and eight were not. In the first 3 months of pregnancy, there was a sharp increase in plasma renin activity and concentration. Plasma angiotensinogen rose steadily throughout pregnancy. The higher concentrations of renin and angiotensinogen would lead to an increase in angiotensin formation with potentially adverse consequences. However, this increase may be reduced by the fall in the affinity between renin and antiotensinogen which is suggested by the present observation that the Michaelis-Menten constant (Km) attained values five to six times higher than those seen in women not taking oral contraceptives.

The smaller increases in plasma renin and angiotensinogen induced by oral contraceptives were less effectively compensated by lower affinity.

Circumstantial evidence is provided which suggests that the observed high Km values may be due to oestrogen/pregnancy-induced synthesis of an angiotensinogen with a lower affinity for renin.

J. Endocr. (1987) 112, 465–472
PRODUCTION OF INHIBIN BIOACTIVITY BY HUMAN GRANULOSA-LUTEIN CELLS: STIMULATION BY LH AND TESTOSTERONE IN VITRO
Authors: Tsonis C. G. , Hillier S. G. , Baird D. T.
Published: December 2008

Granulosa-lutein cells from human preovulatory ovarian follicles were cultured for up to 12 days to determine their capacity for production of inhibin in vitro. Using a highly sensitive sheep pituitary cell bioassay we observed time-related changes in basal inhibin production, maximal during the first 4 days of culture (48 ± 15 units/million cells every 2 days, means ± S.E.M.; n = 5 patients) falling to values five times lower by day 12. After 4-6 days of culture in the presence of human LH (hLH) inhibin production was enhanced in proportion to the hLH dose (maximum five fold at 10 ng/ml); hFSH over the same dose-range had no effect. Progesterone production in response to hLH followed a similar pattern to that of inhibin and was also unresponsive to hFSH. In the absence of exogenous aromatase substrate, basal and gonadotrophin-stimulated oestradiol production was negligible after the first 4 days. Addition of testosterone (1 μmol/l) to the culture medium increased oestrogen formation several hundredfold with no effect on progesterone production. Inhibin production was also increased by 50-100% in the presence of testosterone.

These results demonstrate that LH and testosterone stimulate the production of inhibin by granulosa-lutein cells in vitro. It is suggested that inhibin production occurs under hormonal control in the corpus luteum as well as in the preovulatory follicle in the human ovary.
Distribution and postprandial release of porcine peptide YY
Authors: Adrian T. E. , Bacarese-Hamilton A. J. , Smith H. A. , Chohan P. , Manolas K. J. , Bloom S. R.
Published: December 2008

Peptide YY (PYY), a thirty-six amino acid intestinal hormonal peptide with a tyrosine residue at each end (hence YY as Y represents tyrosine in the new peptide nomenclature), was found throughout the gastrointestinal tract of the pig. Concentrations were very low in the foregut (antrum, 3·4 ± 0·3 pmol/g; duodenum, 1·1 ± 1·5 pmol/g), higher in the distal small intestine (ileum, 100 ± 13 pmol/g) and very high in the large bowel (descending colon, 270 ± 45 pmol/g).

Peptide YY was found to circulate in plasma and concentrations rose substantially in response to eating (fasting, 138 ± 15 pmol/l; postprandial, 263 ± 21 pmol/l; P<0·001). There was a small but significant portal/arterial gradient in postprandial PYY levels.

More than 90% of the immunoreactive PYY in gut extracts eluted, on gel permeation chromatography, in an identical position to pure PYY standard, but small amounts of higher molecular weight material, possibly precursors, were detected. In contrast, plasma from fasting pigs contained a large proportion (60–70%) of these large molecular forms. These findings suggest that the putative pro-PYY may be cleared more slowly from the circulation than the 36 amino acid hormonal peptide.

The high concentrations of immunoreactive PYY in the circulation of the young pig may reflect a species difference between pig and man or may indicate an important role for PYY in the developing animal.

J. Endocr. (1987) 113, 11–14
Effects of various steroids on the thymus, spleen, ventral prostate and seminal vesicles in old orchidectomized rats
Authors: Fitzpatrick F. T. A. , Greenstein B. D.
Published: December 2008

The effects of several steroids on the regenerating thymus in ageing male rats have been studied. Rats aged from 12 to 15 months were orchidectomized and 7 days later implanted s.c. with silicone elastomer tubing containing 25 mg testosterone, 5α-dihydrotestosterone (DHT), oestradiol, progesterone or corticosterone. One group of rats received an empty implant. Thirty days later the rats were killed and the thymus, spleen, ventral prostate and seminal vesicles weighed and retained for histology. Whole blood was taken for total and differential white cell counts; plasma was prepared for radioimmunoassay of testosterone, oestradiol, progesterone and corticosterone.

After orchidectomy only, a multilobular thymus was present, and histologically the tissue appeared healthy. In testosterone- and oestradiol-treated rats, thymus weight was reduced to about 50% of that in untreated animals. Histologically, much of the thymus taken at autopsy was fat and what remained was poorly organized and contained a much lower density of thymocytes. The total white cell count was significantly reduced in these animals, the effect appearing to be predominantly on lymphocytes. Although treatment with DHT also resulted in a lower mean thymus weight than that of orchidectomized animals, histologically the tissue appeared similar to that of the untreated castrated animals. In rats treated with DHT, the total white cell count was significantly higher than in testosterone-implanted rats. Both progesterone and corticosterone implants resulted in significantly smaller mean thymus weights, although these steroids were not as potent as testosterone or oestradiol. Corticosterone, but not progesterone, appeared to cause a significant reduction in circulating lymphocytes. Dihydrotestosterone possessed only half the potency of testosterone in restoring the weights of the accessory sex organs. Serum concentrations of testosterone in orchidectomized old rats were 0·33 ± 0·02 nmol/l and in testosterone-implanted rats 4·8 ± 0·4 nmol/l. These results raise the possibility that testosterone and oestradiol may have caused atrophy of the thymus, while DHT may have retarded regeneration of the thymus without any atrophic effect. It remains to be seen whether the different responses between testosterone and DHT, in both the thymus and accessory sex organs, are due to differences in intrinsic action or differences in the metabolism of the steroids.

J. Endocr. (1987) 113, 51–55
The occurrence of pituitary prolactin depletion–transformation in lactating rats: dependence on strain of rats, homogenization conditions and method of assay
Authors: Lawson D. M. , Haisenleder D. J. , Gala R. R. , Moy J. A.
Published: December 2008

The objectives of this study were to determine (1) whether pre-release transformation (depletion) of pituitary prolactin occurs as the result of suckling to the same extent in several strains of lactating rats, (2) the molecular nature of the transformed hormone, (3) whether the quantity of transformed (depleted) prolactin recovered is dependent upon the type of homogenization buffer used and (4) whether the method of assay influences the extent to which transformed prolactin is detected. During the course of these experiments other factors such as the methods of handling and storing pituitaries and homogenates were also found to influence the amount of prolactin recovered.

The results indicated that transformation of prolactin is a very labile event which is affected by many factors. Strain and supplier of rats was critical to the observation of suckling-induced depletion of prolactin, with Spartan- and Holtzman-derived Sprague–Dawley strains exhibiting the most consistent responses. When transformation was observed, it mattered little which buffer was used for homogenization; however, alkaline or acidic buffers extracted more prolactin than did neutral buffers. Triton X-100 also significantly enhanced the efficiency of extraction by neutral buffers. Maintaining pituitaries on dry ice immediately upon removal from the animal increased the amount of prolactin recovered, as did freezing the homogenate for 1–5 weeks before assay. The addition of the protease inhibitor, benzamidine hydrochloride, did not affect the pituitary content of prolactin. Assay of prolactin by polyacrylamide electrophoresis and densitometry yielded more prolactin than either radioimmunoassay or the Nb2 lymphoma bioassay. The molecular nature of pituitary prolactin, extracted at neutral pH, as judged by gel filtration was altered slightly but consistently by suckling, such that large molecular forms increased at the expense of the smallest molecular form.

We conclude from these studies that great care must be exercised when attempting to characterize dynamic changes in pituitary prolactin content in lactating rats. Strain and supplier of rats, methods of handling and storing pituitaries, types of buffers used for homogenization and methods of assay all influence the amount of prolactin recovered and can influence the extent to which rapid changes in pituitary prolactin are detected.

J. Endocr. (1987) 113, 71–80
Inhibition of casein and fat synthesis and α-lactalbumin secretion by progesterone in explants from bovine lactating mammary glands
Authors: Shamay A. , Zeelon E. , Ghez Z. , Cohen N. , Mackinlay A. G. , Gertler A.
Published: December 2008

The effect of progesterone on casein and fat synthesis, on α-lactalbumin secretion and on accumulation of casein mRNA was studied in explants from bovine lactating mammary glands, cultured in the presence of insulin, cortisol or prolactin. All four biological activities were inhibited down to or below the level obtained in medium without prolactin. However, inhibition was only achieved by using concentrations of progesterone exceeding by 1000-fold those required for similar effects in tissue from non-lactating animals. A similar inhibitory effect was also found using high levels of other steroids without 11β-hydroxyl, such as deoxycorticosterone and dehydroepiandrosterone, and to some extent with oestradiol-17β, but not with cortisol or corticosterone. The inhibition by progesterone did not result from a decrease in explant viability, as determined by glucose uptake.

J. Endocr. (1987) 113, 81–88
Comparison of the effects on purified Leydig cells of four hormones (oxytocin, vasopressin, opiates and LHRH) with suggested paracrine roles in the testis
Authors: Sharpe R. M. , Cooper I.
Published: December 2008

Four hormones have been identified by various authors as possible paracrine regulators of testicular Leydig cells. The aim of this study was to evaluate their effects on purified adult rat Leydig cells under various conditions in vitro, and then to assess whether comparable effects occurred in vivo.

In agreement with previous findings, an LHRH agonist (LHRH-A) exerted clear-cut effects on testosterone secretion by Leydig cells both in vitro and in vivo. On its own, LHRH-A stimulated testosterone production by Leydig cells for up to 24 h in culture but inhibited testosterone production stimulated by human chorionic gonadotrophin (hCG) between 24 and 72 h of culture. In-vivo, unilateral intratesticular injection of adult rats with 1 ng LHRH-A resulted 5 h later in a significant increase in testosterone concentrations in testicular interstitial fluid (IF). Vasopressin exerted effects in vitro which were similar to those of LHRH-A. On its own, vasopressin stimulated testosterone production for up to 5 h of culture, but not thereafter, while in the presence of hCG, vasopressin inhibited testosterone production beyond 24 h of culture. The initial stimulatory effect of vasopressin on testosterone production occurred with concentrations of 1 nmol/l and higher, but the magnitude of stimulation (threefold or less) was considerably less than that induced by LHRH-A (ninefold) over the same time period. In contrast to LHRH-A, unilateral intratesticular injection of vasopressin in high doses (20 and 2 ng) had no effect on IF testosterone levels 5 h later. When Leydig cells were cultured in the presence of testicular IF, to approximate in-vivo conditions, there was marked stimulation of testosterone production, but the effects of vasopressin and LHRH-A in the presence of IF were comparable to those observed in its absence. Neither morphine nor oxytocin at concentrations of 0·1 μmol/l had any effect on testosterone production under any of the conditions of culture, and unilateral intratesticular injection of oxytocin, morphine or naloxone was without effect on the IF levels of testosterone.

It is concluded that opiates and oxytocin are probably not involved in the paracrine regulation of Leydig cells, whereas vasopressin may play such a role. However, as the stimulatory effects of vasopressin were small in relation to those of LHRH-A and were not evident in vivo, the physiological significance of the effects of vasopressin are uncertain.

J. Endocr. (1987) 113, 89–96
Concentrations of progesterone and oestradiol-17β after administration of a 3β-hydroxysteroid dehydrogenase inhibitor to sheep in late pregnancy
Authors: Taylor M. J.
Published: December 2008

An inhibitor of 3β-hydroxysteroid dehydrogenase (3β-HSD) activity was administered to sheep in late pregnancy. A rapid fall in plasma progesterone concentrations followed, associated with premature delivery by all animals 44±3 h (s.e.m.) after administration of inhibitor. A significant (about twofold) increase in plasma concentrations of oestradiol-17β was detected immediately before delivery. These results demonstrate, in contrast to previous reports, that 3β-HSD inhibitors have the capacity consistently to induce premature delivery associated with increased oestrogen release in sheep.

J. Endocr. (1987) 113, 97–101
Inhibin-like activity in Sertoli cell culture media and testicular homogenates from rats of various ages
Authors: Ultee-van Gessel A. M. , de Jong F. H.
Published: December 2008

The influence of age on testicular inhibin in untreated, neonatally hemicastrated and prenatally irradiated rats was studied using in-vivo and in-vitro experiments.

In testicular cytosols prepared from 1-, 7-, 14-, 21-, 42- and 63-day-old rats concentrations of testicular inhibin could be measured with an in-vitro bioassay method using dispersed pituitary cells. Preparations of testicular cytosols caused a dose-dependent suppression of pituitary FSH secretion, whereas no effects were found on LH secretion. Testicular content of inhibin increased gradually with age, while after 14 days of age a relatively large increase of peripheral FSH concentrations occurred in all experimental groups. Neonatal hemicastration or prenatal irradiation resulted in decreased inhibin content of the testis and increased plasma FSH levels.

The production of inhibin activity by Sertoli cells obtained from 7-, 14-, 21-, 42- and 63-day-old normal rats was measured during a 24-h incubation period on the third day of culture. The inhibin production per 106 plated Sertoli cells decreased rapidly after 14 days of age and the lowest production of inhibin was found in Sertoli cells from rats of 63 days of age. After preincubation with ovine FSH significantly larger amounts of inhibin activity were detected in spent media from 21-day-old rat testes. In contrast, suppression of inhibin production was found after preculture in the presence of testosterone at most of the ages studied.

These data from in-vivo and in-vitro experiments indicate that a reciprocal relationship exists between pituitary FSH secretion and inhibin production before the age of 21 days. This relationship supports the concept that inhibin is a physiologically important modulator of FSH secretion before puberty, while the role of the large amount of testicular inhibin present at the older ages remains to be determined.

J. Endocr. (1987) 113, 103–110
Localization of epidermal growth factor receptors in the human prostate by biochemical and immunocytochemical methods
Authors: Maddy S. Q. , Chisholm G. D. , Hawkins R. A. , Habib F. K.
Published: December 2008

The receptor for epidermal growth factor (EGF) was characterized in the particulate fraction from human benign prostatic hyperplasia (BPH) and was present in 85% of tissues analysed. The uptake of 125I-labelled EGF by BPH was dependent on both time and temperature, with maximum specific uptake achieved after incubation for 90 min at 37 °C. Binding characteristics revealed two classes of binding sites of higher (mean dissociation constant (Kd)±s.d.= 0·8 ± 0·2 nmol/l) and lower (Kd = 7·6 ±2·8 nmol/l) affinities. Competition studies demonstrated the specificity of the receptor assay since the binding of labelled EGF was abolished with excess unlabelled EGF but not with excess unlabelled human GH, human insulin, venom nerve growth factor, human FSH, human LH and human prolactin. There was a complex biphasic relationship between specific binding and protein concentration in the range 0·1–8 mg/ml. Subcellular fractionation of BPH homogenates demonstrated that the bulk of the specific binding was confined to the 800 g (crude heavy pellet) and 15 000 g (mitochondrial pellet) fractions. The 105 000 g (microsomal pellet) and the 105 000 g (cytosol fraction) exhibited low and variable binding capacities for the growth factor. The presence of EGF receptor was also confirmed by immunocytochemical staining of frozen sections from BPH using monoclonal antibody specific for EGF receptors. A positive correlation between 125I-labelled EGF binding and the intensity of staining was found. The presence of a specific EGF-binding receptor protein in human BPH tissues suggests that EGF may play a role in the pathogenesis of human BPH.

J. Endocr. (1987) 113, 147–153
Preliminary investigations into the endocrine systems of subfertile cattle: location of a common lesion (rate-limiting step)
Authors: Dobson H. , Alam M. G. S.
Published: December 2008

Dairy cows with a variety of clinical conditions were investigated in an attempt to identify the cause(s) of subfertility. Sequential or simultaneous injections of 20 μg gonadotrophin-releasing hormone (GnRH), 1 mg oestradiol benzoate and 0·06 mg ACTH(1–24) into five clinical cases of ovarian follicular cysts, two cases of poor body condition and one case of lameness and into control cows revealed a failure in the LH positive-feedback response to oestradiol in all eight clinical cases, but in only two out of twelve control cows. Two of the clinical cases and the two non-responding control cows had high or rising initial progesterone concentrations which would explain the absence of response. All cows studied responded similarly to GnRH and ACTH(1–24).

It is suggested that hypothalamus-pituitary control of LH release may involve a rate-limiting step (in the oestradiol positive-feedback system) and that lesions at this point result in subfertility in a variety of clinical situations.

J. Endocr. (1987) 113, 167–171
A novel technique for measuring hypothalamic and pituitary hormone secretion rates from collection of pituitary venous effluent in the normal horse
Authors: Irvine C. H. G. , Alexander S. L.
Published: December 2008

We have described a novel technique for collecting pituitary venous effluent in the horse by placing a cannula in the intercavernous sinus close to the outlet of the pituitary veins using a venous pathway unique to equids. Cannula placement and blood collection are carried out painlessly in fully conscious, ambulatory, unstressed animals. There is no interference to hypothalamic, pituitary or target organ function. The blood collected contains readily measurable concentrations of gonadotrophin-releasing hormone, and LH concentrations which can be up to 40 times those in concurrent peripheral blood samples. Four millilitre blood samples, a quantity which permits simultaneous measurement of many hypothalamic and pituitary hormones, can be collected at 2-min intervals for several days. Intercavernous sinus blood flow can be calculated allowing secretion rates of hypothalamic and pituitary hormones to be determined for any time-period. This model is uniquely useful for investigating the normal functional characteristics of several neuroendocrine and endocrine systems.

J. Endocr. (1987) 113, 183–192
Calmodulin inhibitors and 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate do not prevent the inhibitory effect of prostaglandin F2α on cyclic AMP production in isolated rat corpora lutea
Authors: Lahav M. , Rennert H. , Sabag K. , Barzilai D.
Published: December 2008

In the rat corpus luteum, prostaglandin F2α (PGF2α) rapidly inhibits LH-induced cyclic AMP (cAMP) production when given in vivo or to isolated corpora lutea, but not to broken-cell preparations. The suggestion that increased cytosolic calcium concentration mediates PGF2α action was investigated in corpora lutea of pseudopregnancy induced in immature rats by administration of pregnant mare serum gonadotrophin (15 i.u.). Isolated 10-day-old corpora lutea were incubated for 90 min with LH (5 μg/ml), PGF2α (10 μmol/l) and other additions, and cAMP concentration in the tissue was estimated. The putative inhibitor of intracellular calcium release or action, 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8; 30 or 150 μmol/l), did not abolish the effect of PGF2α. Similarly ineffective was the combination of TMB-8 (150 μmol/l) and calcium-depleted medium (free ionized calcium concentration, 30 nmol/l). Calmodulin inhibitors of three different chemical structures were then tested. The phenothiazine trifluoperazine, at 300 as well as 30 μmol/l, did not interfere with the inhibitory effect of PGF2α on cAMP, while suppressing (at 300 μmol/l) progesterone secretion in LH-treated tissue. Furthermore, inhibition by PGF2α was not impaired by pimozide, a diphenylbutylpiperidine (25 and 50 μmol/l) nor by N-(6-aminohexyl)-5-chloro-1-naphthalene sulphonamide (W-7; 15 and 45 μmol/l). In the presence of LH alone, W-7 (45 μmol/l) inhibited and TMB-8 (30 μmol/l augmented cAMP accumulation, indicating that the luteal tissue was effectively exposed to these compounds. Thus, drugs known to inhibit calcium- and calmodulin-dependent processes in a variety of tissues did not abolish the inhibitory action of PGF2α on luteal cAMP production.

J. Endocr. (1987) 113, 205–212
Isolation of inhibin from ovine follicular fluid
Authors: Leversha L. J. , Robertson D. M. , de Vos F. L. , Morgan F. J. , Hearn M. T. W. , Wettenhall R. E. H. , Findlay J. K. , Burger H. G. , de Kretser D. M.
Published: December 2008

Two forms of inhibin with molecular weights of 65 000 and 30 000 (65 and 30 kD) were isolated from ovine follicular fluid using a combination of gel permeation chromatography, reversed-phase high-performance liquid chromatography and preparative polyacrylamide gel electrophoresis. The 65 kD form was partially purified approximately 315-fold whilst the 30 kD form was isolated as two isoforms (29 and 30 kD) of similar biological activity and in >95% purity (1210-fold purification and 4·2% recoveries). On reduction the 30 kD form resolved into four components of 36, 31, 20–21 and 16 kD of which the 20–21 and 16 kD components were similar to the corresponding inhibin subunits isolated from porcine and bovine follicular fluid. The 36 kD component was established as a non-reducible inhibin-like material, based on its binding to antiserum raised against bovine 58 kD inhibin. The nature of the remaining non-reducible 31 kD component is unknown. Two NH2-terminal amino acid sequences (first 13 amino acids) identified in purified 30 kD inhibin were identical to the corresponding subunit amino acid sequences of bovine 31 kD inhibin.

J. Endocr. (1987) 113, 213–221
Effects of continuous intravenous infusion of an ovine placental extract enriched in placental lactogen on plasma hormones, metabolites and metabolite biokinetics in non-pregnant sheep
Authors: Thordarson G. , McDowell G. H. , Smith S. V. , Iley S. , Forsyth I. A.
Published: December 2008

Continuous intravenous infusions of saline or of a placental extract containing ovine placental lactogen were given to three non-pregnant, non-lactating ewes over periods of 36 h, 1 week apart. During saline infusion no placental lactogen was detected in jugular vein plasma, but infusion of the placental extract raised the placental lactogen concentration from undetectable to 40-50 μg/l, similar to concentrations in ewes with one fetus on day 90 of pregnancy. By comparison with the saline control period, infusion of the placental extract consistently increased both plasma concentrations and irreversible loss of non-esterified fatty acids. Plasma concentrations of glucose and urea, but not irreversible loss of these metabolites, were consistently increased. Although the placental extract was not subjected to extensive purification, it was enriched in placental lactogen and contained no detectable contamination with insulin, prolactin or growth hormone. The results are suggestive of a role for placental lactogen in modifying metabolism and acting during pregnancy to provide nutrients for fetal metabolism.

J. Endocr. (1987) 113, 277–283
Leukotriene release by endometrium and myometrium throughout the menstrual cycle in dysmenorrhoea and menorrhagia
Authors: Rees M. C. P. , Di Marzo V. , Tippins J. R. , Morris H. R. , Turnbull A. C.
Published: December 2008

Endometrium and myometrium were collected at hysterectomy from 21 women with measured menstrual blood loss. Eight women complained of dysmenorrhoea and the remaining 13 had pain-free periods. Specimens were obtained throughout the menstrual cycle (menstrual, n = 5; follicular, n = 3; early luteal, n = 3; mid-luteal, n = 5; late luteal, n = 4). Leukotriene C4, leukotriene D4 and leukotriene E4 release were examined using a short-term incubation technique. Endometrial leukotriene release, which was always significantly greater than myometrial release, changed throughout the menstrual cycle and the highest concentrations were found during menstruation. Endometrial, but not myometrial, leukotriene concentrations were significantly higher in tissues obtained from women with a complaint of dysmenorrhoea compared with those in tissue from pain-free women. No correlation was found between leukotriene release in either endometrium or myometrium and menstrual blood loss (range 15–457 ml).

J. Endocr. (1987) 113, 291–295
Acetylcholine stimulates steroidogenesis in isolated frog adrenal gland through muscarinic receptors: evidence for a desensitization mechanism
Authors: Benyamina M. , Leboulenger F. , Lirhmann I. , Delarue C. , Feuilloley M. , Vaudry H.
Published: December 2008

The effect of cholinergic agonists on glucocorticoid and mineralocorticoid production by frog interrenal (adrenal) tissue was studied in vitro by means of continuous perifusion. Acetylcholine, at doses ranging from 1 to 100 μmol/l, stimulated both corticosterone and aldosterone output in a dose-dependent manner, with a half-maximal effective dose of 2·5 μmol/l. Corticosteroid production was also stimulated by muscarine (10 μmol/l). In contrast, neither nicotine nor nicotine bitartrate (1–100 μmol/l) enhanced corticosteroid biosynthesis. The kinetics of the response of adrenal cells to acetylcholine and muscarine were similar to those observed during angiotensin II stimulation. In particular, a significant reduction (20–40%) in the spontaneous level of corticosteroid production was recorded after the initial infusion of muscarinic agents, but no further decrease in the basal level occurred after a second cholinergic administration. The effect of acetylcholine was blocked by the muscarinic receptor antagonist atropine (10 μmol/l). These results indicate that acetylcholine can stimulate frog adrenocortical cells through muscarinic receptors. Repeated 20-min pulses of acetylcholine (50 μmol/l) or muscarine (10 μmol/l), given at one pulse per 130 min, resulted in a marked reduction in the secretory response to the second pulse. No reduction in the stimulatory effect of acetylcholine or muscarine was observed when a 6·5-h interval separated two 20-min infusions of the secretagogue. In contrast with these findings, iterative pulses of the muscarinic agonist pilocarpine (in the range 1–100 μmol/l) did not cause any desensitization.

These data show that the neurotransmitter acetylcholine can modulate frog adrenocortical function and suggest that, in addition to more conventional regulators, i.e. ACTH and angiotensin II, the cholinergic endings of the splanchnic nerve might participate in the regulation of corticosteroid secretion, at least under some physiological conditions such as neurogenic stress.

J. Endocr. (1987) 113, 339–348
Effects of 4,4′-di-isothiocyano-2,2′-stilbene disulphonate on iodide uptake by primary cultures of turtle thyroid follicular cells
Authors: Chow S. Y. , Yen-Chow Y. C. , White H. S. , Woodbury D. M.
Published: December 2008

Iodide uptake by primary cultures of turtle thyroid follicular cells is directly proportional to the Na + concentration and is inversely proportional to the HCO3− concentration in culture medium, but is not affected by the Cl− concentration. Addition of 4,4′-di-isothiocyano-2,2′-stilbene disulphonate (DIDS; 10 μmol/l and higher doses) to medium containing different concentrations of Na+ (5–140 mmol/l), HCO3− (0–40 mmol/l) and Cl − (120 mmol/l) generally enhanced iodide uptake by the cultured cells; however, there was no significant effect in Na+-free and in low Cl− (90 mmol/l and less) medium. The inhibitory effects on iodide uptake of ouabain, frusemide and perchlorate were attenuated by DIDS which also antagonized the stimulatory effects on iodide uptake of TSH, although both DIDS and TSH increased the 125I− cell/medium ratio when they were given alone. At doses of 100 μmol/l and higher, DIDS lowered the intracellular pH of cultured cells when the pH of the medium was maintained at a constant level. It also increased the intracellular Cl − concentration, but had no effect on intracellular Na+ or K +. The input and specific resistances of cell membranes in cultured thyroid cells and in isolated thyroid slices increased (decreased conductance) after adding DIDS to the perfusion fluids. Both Na+/K+- and HCO3−-ATPase activities in homogenates of turtle thyroid tissue were inhibited by DIDS. Results from this investigation demonstrate (1) that in addition to preventing the leak of iodide from thyroid cells, DIDS may act to increase the sensitivity of the Na + -anion carrier to I− and thereby increases iodide uptake, and (2) that a HCO3−–Cl− exchange system is present in the thyroid cell membrane and appears to be linked to the transport of iodide into thyroid cells.

J. Endocr. (1987) 113, 403–412
The significance of small pulses of gonadotrophin-releasing hormone
Authors: Clarke I. J. , Cummins J. T.
Published: December 2008

A series of experiments was conducted to ascertain the significance of 'small' pulses of gonadotrophin-releasing hormone (GnRH). In the first experiment, ovariectomized hypothalamo-pituitary disconnected (HPD) ewes were given 250 ng pulses of GnRH every 2 h for 1 week, 25 ng pulses every 2 h for 24 h, 25 ng pulses hourly for 24 h and then alternating hourly pulses of 25 and 250 ng. During the 25 ng pulses, LH was not detectable in plasma and FSH concentrations declined after 2 days. Following the 25 ng pulses, the resumption of 250 ng pulses led to exaggerated LH responses (mean ± s.e.m. pulse amplitude 18·7 ± 1·7 vs 10·2 ± 1·2 μg/l in the first week). In a second experiment, ovariectomized–HPD ewes were maintained on 250 ng GnRH pulses every 2 h for 1 week and were then given three 25 ng pulses mid-way between the 250 ng pulses. Samples of blood were taken over three 250 ng pulses without 25 ng insertions and over three pulses with insertions. The insertion of 25 ng GnRH pulses did not cause LH pulses in their own right and did not alter the LH responses to the 250 ng pulses. In a third experiment, 50 ng GnRH pulses were inserted between the 250 ng GnRH pulses, as in experiment 2; these 50 ng pulses caused small LH pulses and led to a reduction in the response of the LH pulse amplitude to the 250 ng pulses. The 'small' LH pulses which occurred in response to 50 ng GnRH compensated for the reduced responses to the 250 ng pulses. Hence, the integrated area under the LH curve and between successive 250 ng pulses remained the same, irrespective of the 50 ng insertions.

From these data we conclude that 'small' GnRH pulses alone can sustain ongoing LH synthesis without release, leading to an accumulation of releasable LH, and that the insertion of 'small' GnRH pulses may modify the pattern of pituitary responsiveness to 'large' GnRH pulses.

J. Endocr. (1987) 113, 413–418
Naloxone reverses post-ejaculatory inhibition of sexual behaviour in female rats
Authors: Forsberg G. , Bednar I. , Eneroth P. , Södersten P.
Published: December 2008

Sexual receptivity was inhibited in ovariectomized rats treated with oestradiol benzoate (OB: two injections of 2 μg) and progesterone (0·5 mg) immediately after ejaculation by the male and restored after the end of the post-ejaculatory refractory period in the male. The post-ejaculatory inhibition of sexual receptivity was reversed by i.p. (5 mg), intracerebroventricular (50 μg) or intrathecal (50 μg) injection of the opioid peptide receptor antagonist naloxone. The concentration of serum β-endorphin-like immunoreactivity in ovariectomized rats treated with OB plus progesterone was unaltered by sexual interactions with males (18·3 ± 6·0 (s.e.m.), 26·4 ± 2·1 and 21·8 ± 6·1 pmol/l before sexual activity, after ejaculation and after the end of the post-ejaculatory interval) but reduced to non-detectable by hypophysectomy. Subcutaneous injection of 10 μg β-endorphin raised serum concentrations of β-endorphin-like immunoreactivity but did not affect the display of sexual behaviour. The behaviour was also unaffected by intracerebroventricular injection of 0·1, 0·2 or 1·0 μg β-endorphin or by injections of 0·25 μg β-endorphin in the periaqueductal central grey of the mesencephalon. The results show that ejaculation by male rats causes a transient inhibition of sexual receptivity in the female which may be dependent upon opioid peptide receptor mechanisms in the brain and spinal cord. It is unlikely that the peptide is β-endorphin.

J. Endocr. (1987) 113, 429–434