bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of N-methyl-d,l-aspartic acid and aspartic acid on the plasma concentration of gonadotrophins, GH and prolactin in the ewe
Authors: Downing J A , Joss J , Scaramuzzi R J 
Published: December 2004

Abstract
Aspartic acid is a neurotransmitter in the central nervous system that acts via the glutamate receptor and the analogue, N-methyl-d,l-aspartic acid (NMA) is an agonist that stimulates GnRH secretion. Under normal dietary conditions, the plasma concentration of aspartic acid in ewes is low and if increased by improved nutrition may increase the brain concentration of aspartic acid leading to increased gonadotrophin secretion. In two experiments we investigated the effects of NMA on pituitary hormone concentrations and the effects of aspartic acid on ovulation rate and pituitary hormone concentrations. The intravenous injection of NMA into cycling ewes resulted in an immediate (within 15 min) release of a pulse of LH and of GH and a prolonged (up to 1 h) suppression of prolactin secretion. There were marked differences in responsiveness to NMA between individual ewes. The intravenous infusion of aspartic acid for 5 days in the late luteal phase of the oestrous cycle did not affect ovulation rate but reduced the mean LH (P<0·05) and FSH (P<0·05) concentrations in plasma. The frequency of LH pulses also tended to be lower (P<0·1) in ewes infused with aspartic acid. It is suggested that the decrease in gonadotrophin secretion in ewes infused with aspartic acid is due to effects on the hypothalamus or the anterior pituitary gland which are not related to increased levels of ovarian feedback. These changes are likely to involve decreased GnRH secretion.
Journal of Endocrinology (1996) 149, 65–72
Inhibin-related proteins in rat prostate
Authors: Risbridger G P , Thomas T , Gurusinghe C J , McFarlane J R 
Published: December 2004

Abstract
Inhibin and activin are members of the transforming growth factor β (TGFβ) family which can regulate cell proliferation in a number of tissues. The presence of inhibins and the related proteins, activins, in the prostate has been implicated by the detection of activin type II receptors. The aim of this study was to determine whether or not immunoactive (ir) inhibin and ir-activin are present in the rat prostate and to study the acute regulation by androgens. The results showed that mRNAs for the α and β inhibin subunits were detected in rat prostate by reverse transcription-PCR together with ir-inhibin and ir-activin in prostate cytosols. The levels of ir-activin in the prostate (223 ± 44 ng/gland) were greater than the levels of ir-inhibin (6·89 ng/gland), and activin immunoreactivity was localised to the epithelial cells. The presence of these proteins and the subunit mRNAs suggests that these proteins are produced in the prostate and may have a role in prostate function. The study of the effect of androgen withdrawal on the levels of ir-activin and ir-inhibin in these tissues showed no change in the content of ir-inhibin or ir-activin (ng/g tissue) after 3 days of castration or following the administration of the cytotoxic drug ethane dimethane sulphonate (EDS), although there was a significant (P<0·01) decline in prostate weight. Fourteen days after EDS treatment, as the prostate weight fell significantly lower, the amount of ir-inhibin and ir-activin per prostate gland was significantly (P<0·01) reduced although the concentration was unaffected. These data demonstrate, for the first time, that inhibin α and β subunit mRNA and ir-inhibin and ir-activin are present in the prostate; the role of these proteins in prostate function remains to be established.
Journal of Endocrinology (1996) 149, 93–99
Functional heterogeneity of human term cytotrophoblasts revealed by differential sensitivity to extracellular Ca2+ and nucleotides
Authors: Bradbury R A , McCall M N , Brown M J , Conigrave A D 
Published: December 2004

Abstract
We have prepared purified cytotrophoblasts from human term placentas and examined the sensitivity of fura-2 loaded cells to the nucleotides ATP and UTP and to changes in extracellular Ca2+ concentration ([Ca2+]o). Purified cytotrophoblasts were obtained by collagenase digestion and separation according to density using selfgenerated Percoll gradients. The cytotrophoblast fraction was free of red cell and largely free of white cell contamination (as assessed by uniformly negative staining for vimentin and the failure of >90% of fura-2 loaded cells to respond to the chemotactic peptide fMet-Leu-Phe). Purified cells secreted progesterone in a linear fashion over several hours in the presence of 25-hydroxycholesterol. The cells ranged in size from approximately 7·5 to 50 μm in diameter as described previously for purified cytotrophoblasts, and an analysis of cells for sensitivity to [Ca2+]o or nucleotides suggested functional heterogeneity within the cytotrophoblast population. Small cells (7·5–10 μm) were negative for cytokeratin-8 and, after loading with fura-2, were insensitive to extracellular nucleotides but sensitive to elevations in [Ca2+]o. Medium-sized cells (12–20 μm) were largely cytokeratin-positive (70% of cells) and sensitive to both ATP and UTP but largely insensitive to [Ca2+]o. Large cells (25–50 μm) were uniformly cytokeratin-positive (100% of cells) and, after fura-2 loading, sensitive to both [Ca2+]o and extracellular ATP or UTP. We examined the likely origin of small, medium and large cytotrophoblasts using an immunomagnetic cell sorting procedure that separates villous cytotrophoblasts (which do not express major histocompatibility class I antigens) from extravillous cytotrophoblasts. This procedure resulted in the selective sedimentation of almost all medium and large cells, leading to the conclusion that the small cells were villous cytotrophoblasts whereas medium and large cells were predominantly extravillous in origin. The data suggest that small, medium and large cytotrophoblasts have distinct roles in the function of the term placenta.
Journal of Endocrinology (1996) 149, 135–144
Fluorescence-activated cell sorted rat islet cells and studies of the insulin secretory process
Authors: Josefsen K , Stenvang J P , Kindmark H , Berggren P-O , Horn T , Kjær T , Buschard K 
Published: December 2004

Abstract
Studies of individual cell types in the islets of Langerhans are complicated by the cells' functional coupling by gap junctions and paracrine interaction. Access to purified alpha and beta cells is therefore desirable. We present a simplified and optimized method for fluorescence-activated cell sorting of endocrine pancreatic rat islets. For dispersion of the islets, dispase was superior to trypsin, as the number of vital single cells was higher (1·1 ± 0·1 × 103 vs 0·6 ± 0·1 × 103/islet, P<0·05). The purity of the sorted cells was 96·7 ± 1·2% for the non-beta cells and 97·8 ± 0·6% for the beta cells (numbers in percentages of endocrine cells). In culture, isolated beta cells, non-beta cells and mixtures of beta and non-beta cells formed aggregates, but not at low temperature (4 °C) and not in medium with low serum content (2%). Finally, in pure beta cell aggregates, glucose stimulated changes in cytoplasmic free Ca2+ concentration although both glucose- and arginine-induced insulin secretion was much reduced. We conclude that alpha cells are necessary for insulin secretion but not for glucose sensing.
Journal of Endocrinology (1996) 149, 145–154
The role of pregnenolone-metabolizing enzymes in the regulation of oestradiol biosynthesis during development of the first wave dominant follicle in the cow
Authors: Carrière P D , Harvey D , Cooke G M 
Published: December 2004

Abstract
During the luteal phase in the cow, a first-wave dominant follicle grows to reach ovulatory size, but then ceases to grow, becomes no longer dominant and enters a phase of slow regression. During this growth transition, the concentration of oestradiol has been shown to decrease in follicular fluid. The objective of this study was to determine if follicular fluid oestradiol concentrations are regulated by the activity of three major steroidogenic enzymes, namely P450-aromatase (P450-arom), 3β-hydroxysteroid dehydrogenase/Δ5–Δ4 isomerase (3β-HSD) and 17α-hydroxylase C-17,20 lyase cytochrome P450 enzyme (P450–17α) measured in granulosa and theca cells isolated from individual first-wave dominant follicles. Follicle growth and state of dominance was assessed by ultrasonography and follicles were classified as growing-dominant (GD, n=6), non-growing-dominant (NGD, n=8) or non-growing-non-dominant (NGND, n=6). Mean follicular fluid concentrations of oestradiol were higher in GD than in NGD or NGND follicles (511 ± 98 versus 136 ± 16 and 20 ± 11 nmol/l respectively). Oestradiol was not correlated with P450-arom in any of the three groups. In GD follicles, oestradiol was positively correlated with pregnenolone concentration but neither was correlated with granulosa or theca 3β-HSD activity or with theca P450–17α activity. In NGD follicles, oestradiol was negatively correlated with theca 3β-HSD activity and pregnenolone was negatively correlated with granulosa 3β-HSD activity. In NGND follicles, oestradiol was positively correlated, and pregnenolone was negatively correlated with theca 3β-HSD and P450–17α activities. These studies demonstrated that pregnenolone supply is the principal regulating factor of oestradiol output during follicle dominance and during the loss of dominance but that the levels of P450–17α and 3β-HSD activity become rate-limiting when the follicle is no longer dominant.
Journal of Endocrinology (1996) 149, 233–242
Immunohistochemical localization of the glucocorticoid receptor in human fetal membranes and decidua at term and preterm delivery
Authors: Sun M , Ramirez M , Challis J R G , Gibb W 
Published: December 2004

Abstract
The human fetal membranes and decidua may be important in the onset and/or progression of human labor by providing prostaglandins for this process. Glucocorticoids have been implicated in the regulation of prostaglandin production by these tissues but to date there is no direct evidence for glucocorticoid receptors (GRs) being present in human intrauterine tissues. The purpose of the present study was to determine, using immunohistochemistry, whether the human fetal membranes and decidua contained GRs; to determine the localization of receptors to the cytoplasm or nuclei, and to examine the content and distribution of the GRs in tissues obtained during pregnancy following preterm labor (<37 weeks) and at term prior to and following term labor. Term tissues were obtained prior to labor by elective Cesarian section (n=9) or following vaginal delivery (n=9). Tissues from 14 patients who delivered preterm but with no clinical evidence of infection were also examined. Cryostat sections were thaw-mounted onto microscope slides. The immunoreactive GRs were visualized with an Elite Vectastain ABC Kit using a polyclonal antibody prepared against a synthetic peptide corresponding to amino acids 346–367 of the human GR. At term, nuclear GRs were found in amnion epithelial cells, mesenchyme and the chorion laeve. GRs were present, but were less defined, in the decidua. A similar distribution was found in the preterm tissues. However, nuclear staining in the amnion epithelial cells, mesenchymal cells, chorion and decidua was more pronounced in tissues obtained following preterm labor. This study provides direct evidence for the presence of GRs in human fetal membranes and decidua, and suggests the possible importance of multiple cell types in the action of glucocorticoids in these tissues.
Journal of Endocrinology (1996) 149, 243–248
Some effects of a low sodium intake on the expression of P450 aldosterone synthase in the hamster adrenal cortex: immunoblotting, immunofluorescent and immuno-gold electron microscopic studies
Authors: LeHoux J G , Lefebvre A , Ducharme L , Lehoux J , Martel D , Brière N 
Published: December 2004

Abstract
In the current work we studied the effects of a low sodium intake on P450 aldosterone synthase (P450aldo) in the adrenal cortex of male hamsters by Western blotting analysis. We also investigated the zonal distribution of P450aldo with a specific antibody using immunofluorescence and immuno-gold electron microscopy.
Western blotting analysis revealed a progressive induction of P450aldo in the adrenals of hamsters kept on a low sodium diet, with two-, four- and eightfold increases after 2, 4 and 21 days on the diet.
Immunofluorescence microscopy showed that P450aldo was confined to the zona glomerulosa (ZG) cells. Electron microscopy showed P450aldo to be located in the mitochondria of ZG cells. When hamsters were maintained on a low sodium intake for 2, 11 and 21 days, P450aldo was still found only in the ZG; the ZG appeared either unchanged or sometimes slightly enlarged. Moreover, at days 11 and 21, the intensity of the immunofluorescent signal was much stronger in the ZG of hamsters on the low sodium intake than in controls. Hence, immunocytochemistry using the colloidal-gold technique showed P450aldo to be more abundant in the mitochondria of the experimental animals than in controls.
To conclude, P450aldo is present only in the ZG of hamster adrenals and sodium restriction appears to induce its expression by stimulating production within individual ZG cells rather than by stimulating a proliferation of the ZG cells.
Journal of Endocrinology (1996) 149, 341–349
Osmotic and volaemic regulation of atrial and ventricular natriuretic peptide secretion in conscious eels
Authors: Kaiya H , Takei Y 
Published: December 2004

Abstract
The effects of acute manipulation of plasma osmolality and blood volume on plasma atrial and ventricular natriuretic peptide (ANP and VNP) levels were examined in conscious freshwater eels, Anguilla japonica. A bolus injection of hypertonic NaCl (0·85 m and 1·7 m, 2·5 ml/kg body weight) through a catheter into the ventral aorta produced increases in plasma Na concentration and osmolality with parallel concentration-dependent, transient increases in plasma ANP and VNP levels. Plasma ANP and VNP levels also increased after injection of 1·7 m mannitol solution which produced an increase in plasma osmolality but a decrease in plasma Na concentration. However, injection of a 2·0 m solution of urea, which does not cause cellular dehydration in mammals, produced only small increases in plasma ANP and VNP levels, although plasma osmolality increased.
A bolus injection of 10 or 25 ml/kg isotonic saline supplemented with 2% dextran for colloidal osmotic pressure, which theoretically increased blood volume by 29% or 71%, produced volume-dependent, transient increases in plasma ANP and VNP levels without changes in plasma Na concentration and osmolality. Similar volume expansion with dialysed eel plasma caused greater increases than with dextran-saline. However, these increases were much smaller than those after osmotic stimuli. These results indicate that secretion of ANP and VNP is regulated by two receptor mechanisms: osmoreceptors activated by cellular dehydration, not specifically by hypernatraemia, and volume or stretch receptors activated by hypervolaemia. The relative importance of the osmoreceptive mechanism is greater in eels than in mammals where volaemic regulation dominates over osmotic regulation for ANP secretion.
Journal of Endocrinology (1996) 149, 441–447
Selective toxic effects of tamoxifen on osteoclasts: comparison with the effects of oestrogen
Authors: Arnett T R , Lindsay R , Kilb J M , Moonga B S , Spowage M , Dempster D W 
Published: December 2004

Abstract
We investigated the actions of the trans- and cis-isomers of tamoxifen on the function of neonatal rat osteoclasts in vitro. Both compounds inhibited resorption pit formation by osteoclast-containing mixed bone cell cultures incubated for 24 h on cortical bone slices. Cell counts revealed that the inhibition was closely related to a cytotoxic effect, to which osteoclasts appeared particularly sensitive. Partial inhibition of resorption was seen in the presence of 2 μm trans-tamoxifen, whereas complete abolition of resorption and osteoclast viability occurred with 10 μm trans-tamoxifen; survival of mononuclear cells was unimpaired at either concentration. Cis-tamoxifen appeared to be slightly more toxic, with significant inhibitions of osteoclast viability and thus resorption pit formation at a concentration of 2 μm, and also of mononuclear cell numbers at 10 μm. Time-lapse video observations indicated that osteoclast death occurred rapidly (within 2–3 h) following exposure to 10 μm of either trans-tamoxifen or cis-tamoxifen. The morphological appearance of the dying cells was consistent with apoptosis. These results may help to explain the anti-resorptive action of tamoxifen seen in vivo in rats and humans. In contrast, oestradiol-17β consistently exerted no significant effects on resorption pit formation by rat osteoclasts over 24 h, even at grossly supraphysiological concentrations (up to 10 μm).
Journal of Endocrinology (1996) 149, 503–508
The effect of ovarian arterial infusion of human recombinant inhibin and bovine follicular fluid on ovarian hormone secretion by ewes with an autotransplanted ovary
Authors: Campbell B K , Scaramuzzi R J 
Published: December 2004

Abstract
Recombinant human inhibin A (rhInh) or steroid-free bovine follicular fluid (bFF) were infused into the ovarian artery of anoestrous ewes with ovarian autotransplants induced to ovulate with a pulsatile regimen of GnRH applied after a 10-day pretreatment with progestagen sponges. In the period 12–24 h after sponge withdrawal ewes received ovarian arterial infusions of saline (n=6), 0·3 μg rhInh/h (n=5), 1·6 μg rhInh/h (n=5) or 25 μl bFF/h (n=4).
Controls had a normal follicular phase with an LH surge 43 ± 3 h after sponge withdrawal which resulted in ovulation (six out of six). Both doses of rhlnh increased ovarian venous inhibin concentrations in a dose-related fashion (P<0·05) but resulted in depressions (P<0·05) in FSH concentrations of similar magnitude. Both doses of rhInh acutely inhibited ovarian oestradiol and androstenedione secretion (P<0·01) but at the end of rhInh infusion oestradiol secretion was quickly re-established without a corresponding increase in FSH. LH surges were detected in five out of five and three out of five ewes infused with low and high doses of rhInh respectively, and progesterone concentrations during the subsequent luteal phase were depressed (P<0·05). Infusion of bFF had no effect on inhibin or FSH concentrations but resulted in acute inhibition (P<0·01) of ovarian oestradiol, androstenedione and inhibin secretion, a delay (P<0·05) in the time to the LH surge and a depression (P<0·05) in luteal-phase progesterone concentrations.
In conclusion, while the depression in FSH induced by rhlnh cannot be excluded as a cause for the inhibitory effects of rhInh treatment on ovarian function, such a mechanism cannot fully explain the ovarian responses obtained to rhInh infusion. These results therefore support a direct ovarian role for inhibin in the modulation of ovarian function in addition to its indirect role in controlling FSH. This conclusion is supported by the demonstration that bFF can induce similar inhibitory effects on ovarian function without changing FSH.
Journal of Endocrinology (1996) 149, 531–540
THE ROLE OF IGFBP-3 IN THE REGULATION OF IGFBP-4 PROTEOLYSIS
Authors: Donnelly M.J. , Holly J.M.P. 
Published: December 2004

ABSTRACT
The biological effects of insulin-like growth factors (IGFs) are mediated by cell surface receptors but their bioavailability is regulated by IGF binding proteins (IGFBPs) which bind IGF with higher affinity than the receptor. Proteolytic cleavage of the binding proteins reduces their affinity for IGF making the IGF more available to the cell receptor. In the current study we have examined the regulation of IGFBP-4 protease produced by cultured human dermal fibroblasts.
IGF-I and the analogs of IGF-I (LR3 and Des[1-3]) induced a dose dependent increase in both proliferation and IGFBP-3 production. Low concentrations of IGF-I induced a marked loss of IGFBP-4 by Western ligand blotting (WLB). This effect was confirmed by the ability of media collected from cells exposed to increasing concentrations of IGF-I to fragment recombinant IGFBP-4, an effect blocked by EDTA.
IGFBP-4 proteolysis was observed when cells were exposed to Des[1-3] (albeit at higher concentrations) but not with LR3. Both analogs bind to the IGF receptor but do not bind to IGFBP-4 and have reduced (Des[1-3]) or no (LR3) affinity for IGFBP-3. This demonstrated that neither receptor activation nor ligand binding directly to IGFBP-4 was necessary for IGF induced proteolysis. Protease activity correlated with affinity for IGFBP-3 suggesting a role for IGFBP-3 in the regulation of IGFBP-4 proteolysis. This was confirmed by the ability of excess recombinant IGFBP-3 to inhibit the IGF-I and Des[1-3] induced proteolysis of IGFBP-4. Addition of IGF-I to media from cells unexposed to IGF induced IGFBP-4 proteolysis but this was not seen with LR3 which does not bind to IGFBP-3. Fragmentation occured at higher concentrations of Des[1-3] consistent with its reduced affinity for IGFBP-3
This data suggests that IGFBP-4 proteolysis is regulated in a novel manner by IGFBP-3 which is dependent on the relative proportions of the different binding proteins and the levels of IGFs
Expression of the steroidogenic acute regulatory protein mRNA in adrenal tumors and cultured adrenal cells
Authors: Liu J , Heikkilä P , Kahri A I , Voutilainen R 
Published: December 2004

Abstract
The steroidogenic acute regulatory protein (StAR) has recently been shown to be a factor necessary for cholesterol transport into adrenal and gonadal mitochondria, which is the regulated, rate-limiting step in steroidogenesis. We show here that StAR mRNA is highly expressed in normal adult adrenals (n=9), adrenocortical adenomas (n=16), adrenal hyperplasias (n=6), adrenocortical carcinomas (n=6) and adrenals adjacent to tumor tissues (n=9). There was a good correlation between the expression of StAR and the cholesterol side-chain cleavage enzyme/20,22-desmolase (P450 scc) mRNAs both in normal (r=0·93; P<0·01) and in tumor (r=0·97; P<0·001) tissues. No StAR mRNA was detected in Northern blots of liver, kidney, breast, parathyroid or phaeochromocytoma RNAs.
In cultured adrenocortical cells, adrenocorticotropin (ACTH), (Bu)2cAMP, and cholera toxin increased StAR and P450 scc mRNA accumulation 6- to 18-fold, dose-and time-dependently. StAR (and P450 scc) mRNA increased relatively slowly in response to ACTH treatment, with the maximal increment at 24 h, while the mRNA of the early response gene c-fos peaked within 2 h. The protein kinase inhibitor H-7 inhibited basal and ACTH-induced StAR mRNA expression. Our results show that StAR mRNA is expressed at high levels in normal human adrenals and adrenocortical neoplasms. It is up-regulated in parallel with P450 scc by ACTH in adult adrenocortical cells, which suggests that ACTH is at least one of the key regulators of adrenal StAR expression.
Journal of Endocrinology (1996) 150, 43–50