bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transferrin inhibits aromatase activity of rat granulosa cells in vitro
Authors: Li Y. D. , Zhang Z. W. , Li W. X. 
Published: December 2008

ABSTRACT
The effect of transferrin on basal and FSH-stimulated aromatase activity of granulosa cells from immature female rats treated with diethylstilboestrol (DES) was examined in vitro by a radiometric method. The basal activity of the enzyme was very low after 3 days of incubation. Treatment with FSH (20 ng/ml) resulted in a 9·6-fold increase in activity, whereas coincubation with increasing doses of transferrin (3–300 μg/ml) produced a dose-dependent inhibition of FSH-stimulated aromatase activity with a projected minimal effective dose of < 2 μg/ml. A time-course study showed that the inhibitory effect of transferrin on aromatase activity has become significant at 48 h of incubation.
The inhibitory action of transferrin on the enzyme complex was further confirmed by showing that the FSH dose–response curve was significantly suppressed by concomitant treatment with 100 μg transferrin/ml with a maximum suppression of 54·1 % at a dose of 30 ng FSH/ml.
The possibility that transferrin may act through a non-specific inhibitory effect seems unlikely, as no changes in cell number and DNA content per well were observed. In fact, protein synthesis was enhanced after treatment with transferrin. Aromatase activity, stimulated by several promoters of cyclic AMP (cAMP), such as prostaglandin E2 (PGE2), forskolin and 8-bromo-cAMP, was significantly suppressed by 100 μg transferrin/ml (36·6, 47·4 and 23·4% inhibition respectively), suggesting that the effect of transferrin on FSH action may involve a site(s) distal to cAMP generation.
These findings indicated that transferrin, present in follicular fluid, may play an important role in the regulation of granulosa cell differentiation.
Journal of Endocrinology (1991) 131, 245–250
Oral insulin in diabetic dogs
Authors: Saffran M. , Field J. B. , Peña J. , Jones R. H. , Okuda Y. 
Published: December 2008

ABSTRACT
Bovine crystalline insulin, mixed with an absorption enhancer, was loaded by hand into gelatin capsules, which were then coated with an azopolymer designed to deliver the insulin in the upper colon. In 34 experiments with 14 pancreatectomized mongrel dogs of both sexes, the coated capsules were administered orally after a pre-dose period of 1 h. The dogs had cannulae in the portal vein, hepatic vein and femoral artery and Doppler flow probes on the portal vein and hepatic artery. Insulin and food were withdrawn the day before an experiment. Responses measured were plasma glucose, plasma insulin, hepatic glucose production rate, hepatic plasma flow rate and plasma glucagon-like immunoactivity (GLI). Control experiments, with capsules without insulin, produced small changes from 'pre-dose' values. Insulin-containing capsules, without the azopolymer coating, resulted in some early changes consistent with upper gastrointestinal absorption. Single oral doses (66 to 400 nmol/kg) of insulin in completely coated capsules produced peaks of portal plasma insulin and transient decreases in plasma glucose, hepatic glucose production, hepatic plasma flow and plasma GLI. The changes usually began 1·5–2 h after administration of a single dose, and lasted for up to 3 h, but were not significantly related to the dose of insulin. Multiple oral doses of insulin, given at 1·5-h intervals, resulted in multiple peaks of plasma insulin, a continuing dose-dependent fall in plasma glucose to near-euglycaemia with the highest dose, and profound decreases in hepatic glucose production and plasma GLI. These data demonstrate that insulin absorbed from the gastrointestinal tract causes changes in glucose metabolism in the diabetic dog that are consistent with the action of insulin primarily on the liver and that repeated oral doses are necessary to correct the hyperglycaemia.
Journal of Endocrinology (1991) 131, 267–278
Regulation of testicular insulin-like growth factor-I in pubertal growth hormone-deficient male rats
Authors: Spiteri-Grech J. , Bartlett J. M. S. , Nieschlag E. 
Published: December 2008

ABSTRACT
GH plays a major role in pubertal growth, effects mainly mediated by stimulation of insulin-like growth factor-I (IGF-I) production by the liver. However, the role of GH in the regulation of pubertal onset, spermatogenesis and fertility is still under debate. GH and FSH have, in addition, been implicated in the regulation of IGF-I production by Sertoli cells in a number of studies, although conflicting results have been reported. The interpretation of studies using GH-deficient mutant mice has been complicated by the presence of additional defects in the hypothalamic-pituitary-gonadal axis of these animals. We have therefore used GH-deficient mutant male rats with no other documented hormonal deficiencies to study the effect of GH administration on somatic and testicular development, circulating and testicular IGF-I concentrations and testicular histology.
Body weights in GH-deficient rats substituted with GH were not significantly different from untreated or GH-treated normal rats and were significantly higher than body weights in untreated dwarf rats. Similarly, circulating IGF-I concentrations in GH-treated GH-deficient rats were not significantly different from those in untreated or GH-treated normal rats but were significantly higher than circulating IGF-I concentrations in untreated dwarf rats. No differences in testicular IGF-I concentrations were observed in any of the groups studied. Testicular weights remained low in both untreated and GH-treated GH-deficient animals compared with control animals but spermatogenesis was qualitatively and quantitatively normal in all groups at the end of the observation period.
We conclude that GH does not play a major role in the regulation of testicular IGF-I production at puberty although we cannot exclude the possibility that the low but detectable levels of GH in the blood of mutant rats is sufficient to augment testicular responsiveness to gonadotrophins and therefore result in normal gonadal development.
Journal of Endocrinology (1991) 131, 279–285
The insulin-like growth factors and their binding proteins in a case of non-islet-cell tumour-associated hypoglycaemia
Authors: Cotterill A. M. , Holly J. M. P. , Davies S. C. , Coulson V. J. , Price P. A. , Wass J. A. H. 
Published: December 2008

ABSTRACT
Non-islet-cell tumours which induce hypoglycaemia are rare. Insulin-like growth factor-II (IGF-II) produced by some tumours is thought to be responsible for the hypoglycaemia and other systemic effects, despite normal or even low serum IGF-II levels. We studied a 44-year-old woman presenting with symptomatic hypoglycaemia associated with a large intraabdominal haemangiopericytoma. The serum IGF-II level was 455 μg/l when measured after acid-ethanol extraction (normal range (NR) 450–750 μg/l) and 1063 μg/l after acid chromatography (normal human serum pool 1068 μg/l). Levels of fasting plasma insulin, C-peptide, glucose and serum IGF-I levels were low before the operation (< 2 mU/l (NR <2-14), 0·23 nmol/l (NR 0-4-1-2), 3-1 mmol/l, (NR 3-7-5-9) and 002 U/ml respectively). After tumour removal, the symptoms resolved rapidly and the patient made a full recovery. Secretion of both insulin and growth hormone was suppressed before the operation in response to a 75 g glucose meal and to an infusion of 100 μg GH-releasing hormone (GHRH) respectively in comparison with studies after the operation. Serum IGF-II levels 6 weeks and 12 weeks after the operation fell to 385 μg/1 (777 μg/1; acid chromatography) and 280 μg/1 (647 μg/1; acid chromatography) and serum IGF-I levels increased to 0-35 U/ml and 0-26 U/ml. Serum before the operation and tumour extract contained chiefly a large molecular weight precursor IGF-II (molecular weight 15 000–20 000) which disappeared from the serum after the operation. The IGF-binding proteins (IGFBP-1, IGFBP-2, IGFBP-3 and IGFBP-4) were examined. The preoperation fasting serum IGFBP-1 level was lower than expected (31 μg/l (NR 20–70 μg/l)) and similar to levels at 6 weeks after the operation (33 μg/l). This was surprising given the differences in plasma insulin levels before and after the operation (< 2 mU/l versus 13 mU/l). Using Western ligand blotting techniques, serum IGFBP-3 levels were found to be low and IGFBP-2 appeared to be the dominant IGFBP before the operation. Serum IGFBP-3 levels after the operation fell further. This further decrease appeared, in part, to be due to the presence of a cation-dependent IGFBP-3-specific protease which has previously only been described in late pregnancy.
We conclude that in this subject, despite normal serum IGF-II levels, the hypoglycaemia and systemic effects on insulin and GH secretion were due to increased bioavailability of a circulating tumour-produced precursor form of IGF-II. This increased bioavailability appears to be due to alterations in the circulating levels and perhaps affinities of the IGFBPs.
Journal of Endocrinology (1991) 131, 303–311
Effect of acute and chronic administration of clonidine on hypothalamic content of growth hormone-releasing hormone and somatostatin in the rat
Authors: Gil-Ad I. , Laron Z. , Koch Y. 
Published: December 2008

ABSTRACT
Hypothalamic GH-releasing hormone (GHRH) and somatostatin contents were determined in male rats at pre- and mid-pubertal stages following acute (0·15 mg/kg) or chronic (0·1 mg/kg twice daily for 7 days) administration of clonidine. Hypothalamic GHRH content increased markedly during transition from pre- to mid- and late-pubertal stages (2·05±0·17vs 3·13±0·26 and 3·46±0·20 ng/hypothalamus respectively, means ±s.e.m.). Hypothalamic GHRH content was markedly decreased 1 h after clonidine administration in mid-pubertal but not in prepubertal rats (3·67±0·23 vs 2·65±0·22 ng/hypothalamus). Hypothalamic somatostatin content, on the other hand, decreased in both age groups, although the decrease in the mid-pubertal group was more pronounced (51% and 38% respectively). In addition, the GH responsiveness to clonidine was higher at mid-puberty than at prepuberty. Determination of hypothalamic somatostatin and GHRH content in the chronic experiment 4 h after the last drug administration revealed a marked decrease in GHRH in the mid-pubertal rats and a slight decrease in the prepubertal rats (1·78±0·32 vs 3·15±0·31 and 2·01±0·30 vs 2·35±0·15 ng/hypothalamus; P < 0·005 and P<0·05 respectively) whereas somatostatin levels were not altered. It is suggested that the clonidineinduced GH secretion is modulated by a chain of events which involves primary stimulation of GHRH release resulting in increased GH secretion which, via a negative-feedback mechanism, triggers an enhancement of somatostatin release which ultimately normalizes the system. This mechanism is age-dependent and reaches full maturity only at the onset of puberty.
Journal of Endocrinology (1991) 131, 381–385
Sex differences in the ultradian pattern of plasma growth hormone concentrations in mice
Authors: MacLeod J. N. , Pampori N. A. , Shapiro B. H. 
Published: December 2008

ABSTRACT
Ultradian patterns of plasma GH concentration were determined in adult male and female mice. Serial blood samples were collected every 15 min over 8 h through surgically placed chronic indwelling right atrial catheters and assayed for GH content by an homologous radioimmunoassay. In both sexes, GH concentrations fluctuated episodically from baseline values that were often in the range of 2 μg/l which approached the limit of assay sensitivity, to peak values sometimes reaching 100 μg/l. Male mice, however, demonstrated a regular periodicity of GH peaks approximately every 2·5 h with interposed stable baseline concentrations that were significantly longer in duration than in females. The absence of extended baseline concentrations in females reduced cycle length to an average of 1·4 h and significantly increased the overall mean GH concentration. The duration, height and area of GH peaks and the average concentration between peaks were comparable in males and females. Sexual dimorphism in the ultradian patterns of serum GH concentrations have been shown in both mice and rats to regulate the expression of several sex-specific phenotypes. Comparing endogenous GH patterns in mice and rats demonstrates that males of both species have less frequent peaks than females over the same interval of time. This separation of GH peaks appears to be an essential element for the expression of masculine GH-dependent traits.
Journal of Endocrinology (1991) 131, 395–399
Testicular steroidogenesis in the testicular feminized (Tfm) mouse: loss of 17α-hydroxylase activity
Authors: Murphy L. , O'Shaughnessy P. J. 
Published: December 2008

ABSTRACT
Testicular feminized (Tfm) mice are totally insensitive to androgen and may be used to study the role of the androgen receptor in normal development and function. We have examined testicular and Leydig cell steroidogenesis in Tfm mice. Serum bioactive LH was high in Tfm mice but serum testosterone was low and this was associated with a severe reduction in testicular testosterone production in vitro. Examination of [3H]pregnenolone metabolism by testes of Tfm mice indicated that progesterone, rather than testosterone, was the major steroid produced. Leydig cells were isolated from normal and Tfm mice and from normal mice in which testicular descent was surgically prevented before puberty. As in whole testes, androgen production in response to human chorionic gonadotrophin was severely reduced in Leydig cells from testes of Tfm mice compared with normal or cryptorchid groups. In contrast, progesterone production by Leydig cells from testes of Tfm mice was markedly increased in comparison with other groups. Total steroid production (progesterone plus androstenedione plus testosterone), however, was only 24% of normal in Leydig cells from Tfm mice. The pattern of steroid production by Leydig cells from cryptorchid testes was similar to control, although total steroid production was reduced to about 50% (this was significantly higher than the Tfm group, P<0·05). The high progesterone/androgen ratio in testes from Tfm mice suggested that 17α-hydroxylase was depleted in these animals. To confirm this, activity of the four major steroidogenic enzymes associated with the smooth endoplasmic reticulum was measured. Activities (per testis) of 3β-hydroxysteroid dehydrogenase and 5α-reductase were normal in Tfm and cryptorchid mice but, as expected, 17α-hydroxylase activity was only 2·4% of control and 4·5% of cryptorchid testes. 17-Ketosteroid reductase activity was markedly reduced in cryptorchid testes (14·4% of control) but there was a further reduction in testes from Tfm mice to 0·1% of control. Results show that the Tfm mutation is associated with marked loss of 17α-hydroxylase and 17-ketosteroid reductase activities. This suggests that these enzymes may require receptor-mediated androgen stimulation during development to express normal activity.
Journal of Endocrinology (1991) 131, 443–449
Comparison of the galactopoietic response to pituitary-derived and recombinant-derived variants of bovine growth hormone
Authors: Eppard P. J. , Bentle L. A. , Violand B. N. , Ganguli S. , Hintz R. L. , Kung L. , Krivi G. G. , Lanza G. M. 
Published: December 2008

ABSTRACT
Two studies were designed to examine the differences in galactopoietic potency of molecular variants of pituitary- and recombinant-derived bovine GH (bGH). The recombinant bGH molecules included aminoterminal and position-127 amino acid substitutions which are representative of two of the four natural pituitary variants or of partially degraded bGH molecules. Amino-terminal variants of bGH included methionine (Met1), alanine (Ala1), serine (Ser1) or deletion of four amino acids (Δ1−4). The Δ1–4 variants were representative of degradation products previously isolated in pituitary bGH preparations. In the first study, 54 lactating Holstein cows received i.m. injections of a buffer solution (control), pituitaryderived bGH, or recombinant-derived [Met1, Leu127]-bGH, [Met1, Val127]-bGH, [Ala1, Leu127]-bGH, or [Ala1, Val127]-bGH. Cows received 25 mg bGH/day for 21 days. Substitution of the amino-terminal alanyl residue with methionine did not affect milk response. GH variants with Val127 elicited a greater milk response (8·5 kg/day) than Leu127 bGH variants (6·5 kg/day). The average milk response to the four recombinant bGH variants was 7·5 kg/day greater than controls compared with 4·4 kg/day for pituitary-derived bGH. In contrast, blood bGH concentrations were equivalent for pituitary and recombinant bGH treatments, approximately 20 μg/l more than control levels at 3 h after injection. Blood free fatty acid concentrations were increased, but insulin and glucose levels were unaffected by bGH treatment. In the second study, 54 lactating Holstein cows received i.m. injections of a buffer control solution or recombinant-derived [Met1,Leu127]-bGH, [Ser1,Leu127]-bGH, [Ser1,Val127]-bGH, [Δ1–4,Leu127]-bGH or [Δ1–4,Val127]-bGH. Cows received 25 mg bGH/day for 28 days. The milk response to full-length bGH variants was 6·6 kg/day greater than the response to the amino-terminal deletion variants (P<0·05). Substitution of valine for leucine did not affect milk response to either the deletion (Δ1–4) or full-length (Met1 or Ser1) bGH molecules. In conclusion, the lowered galactopoietic potency of pituitary bGH preparations was demonstrated, at least in part, to be due to the presence of amino-terminal amino acid deletions rather than differences in amino acid sequences of recombinant bGH. Ala1 bGH variants with valine at postiion 127 elicited a greater milk response than Leu127 variants.
Journal of Endocrinology (1992) 132, 47–56
Arachidonic acid-induced LH release is ATP-independent and insensitive to N-ethyl maleimide
Authors: Kaye P. V. , van der Merwe P. A. , Millar R. P. , Davidson J. S. 
Published: December 2008

ABSTRACT
The mechanism of arachidonic acid (AA)-induced LH release was characterized using sheep pituitary cells in primary culture permeabilized with Staphylococcal α-toxin. In intact cells, exogenous AA evoked release of LH in a manner which was partially dependent on extracellular Ca2+. At similar concentrations, AA also caused cell permeabilization as monitored by efflux of [3H]2-deoxyglucose metabolites. In α-toxin-permeabilized cells where cytosolic Ca2+ was clamped at resting levels, AA retained its ability to cause LH release. Unlike the stimulation of exocytosis produced by Ca2+, phorbol ester or cyclic AMP, AA-evoked release was independent of ATP and was not inhibited by pretreatment with N-ethyl maleimide. These findings indicated that exogenous AA does not cause LH release by Ca2+ influx or mobilization or by activating protein kinase C. The results suggest that LH release induced by exogenous AA is probably due to its detergent-like properties, and does not represent true exocytosis.
Journal of Endocrinology (1992) 132, 77–82
Different effects of the antiprogesterone RU486 on progesterone secretion by the corpus luteum of rats with 4- and 5-day oestrous cycles
Authors: Sánchez-Criado J. E. , Uilenbroek J. Th. J. , Karels B. 
Published: December 2008

ABSTRACT
Administration of the antiprogesterone RU486 (2 mg/day) for 14 days to rats with a 5-day reproductive cycle resulted in an increase in both ovarian and pituitary weight in contrast with rats with a 4-day oestrous cycle. Luteal progesterone production decreased earlier in 4-day than in 5-day cyclic rats. Treatment of 5-day cyclic rats with antiprogesterone from the day of metoestrus onwards resulted in the advancement of the preovulatory prolactin surge by 24 h. Progesterone production by the corpus luteum was, however, not affected, indicating that in 5-day cyclic rats the corpora lutea are still functionally active at the time of the preovulatory surge of prolactin. They become, therefore, stimulated both in size and progesterone production. In contrast, the corpora lutea in 4-day cyclic rats are functionally inactive at the time of the preovulatory surge of prolactin, and prolactin acts luteolytically. In conclusion, the advancement of the preovulatory surge of prolactin by 24 h accounts, at least in part, for the increase in ovarian weight in 5-day cyclic rats after treatment with antiprogesterone. The results of these experiments do not agree with a direct effect of the antiprogesterone RU486 on progesterone secretion by the corpus luteum.
Journal of Endocrinology (1992) 132, 115–122
Effects of oestradiol-17β on FSH-stimulated steroidogenesis in cultured marmoset granulosa cells
Authors: Shaw H. J. , Hodges J. K. 
Published: December 2008

ABSTRACT
A role for oestradiol in ovarian follicular development is well recognized. However, a number of disparate effects have been reported for the action of oestradiol in the primate ovary. To investigate this further, we have examined the effects of oestradiol on the differentiation of granulosa cells isolated from small (0·5–1 mm) antral follicles obtained from the ovaries of prepubertal marmoset monkeys (Callithrix jacchus). Granulosa cells were co-cultured with oestradiol and human FSH (hFSH) for 48 h, or were pretreated with oestradiol for 48 h before addition of gonadotrophin for a further 48 h. Oestradiol (0·01–100 nmol/l) had no effect on basal or hFSH-stimulated progesterone accumulation and aromatase activity when the hormones were added concurrently. Furthermore, oestradiol did not influence the ability of hFSH to induce LH/human chorionic gonadotrophin (hCG) responsiveness in immature granulosa cells. The absence of synergism between oestradiol and hFSH in the induction of marmoset granulosa cell differentiation was independent of the presence of phenol red in culture medium. However, gonadotrophin-stimulated steroidogenesis was attenuated when cells were cultured in the presence of phenol red compared with in its absence; this effect was more pronounced for gonadotrophin-stimulated aromatase activity but was evident for LH/hCG-stimulated progesterone accumulation at higher doses of hCG (10 and 100 ng/ml). An effect of phenol red on basal steroidogenesis was less obvious.
In contrast, pretreatment of granulosa cells with oestradiol (0·1 μmol/l) alone for 48 h resulted in a greater steroidogenic response to hFSH (P<0·001) and dibutyryl cyclic AMP (P<0·01) treatment during a second 48-h culture period compared with cultures pretreated with dihydrotestosterone (0·1 μmol/l), hFSH (30 ng/ml) or without hormones. This stimulatory effect of oestradiol appeared to be specific in that it was antagonized (P<0·05) by the anti-oestrogen tamoxifen (1 μmol/l).
In conclusion, this study provides evidence for a stimulatory autocrine role of oestradiol in the primate ovary. However, the action of oestradiol appears not to synergize with FSH directly, but rather to increase FSH-stimulated steroidogenesis by an independent mechanism.
Journal of Endocrinology (1992) 132, 123–131