bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chromatographic characteristics of pro-opiomelanocortin-derived peptides from the rat transplantable tumour 7315a
Authors: Morano M. I. , Estivariz F. E. 
Published: December 2008

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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