bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of α and thyrotrophin-β subunit mRNA levels by androgens in the female rat
Authors: Ahlquist J. A. O. , Franklyn J. A. , Ramsden D. B. , Sheppard M. C. 
Published: December 2008

ABSTRACT
Thyroid and steroid hormones act by similar mechanisms to influence gene expression in the anterior pituitary gland. The genes encoding the common α and TSH-β glycoprotein subunits are known to be regulated by thyroid hormones; we report here the effects of androgen administration on levels of α and TSH-β mRNA in pituitary cytoplasm in the euthyroid and hypothyroid female rat. Dihydrotestosterone (DHT) suppressed both α and TSH-β mRNAs to levels lower than those found in untreated animals; a similar reduction was seen in hypothyroid animals treated with DHT. A biphasic response of TSH-β mRNA was seen following administration of tri-iodothyronine (T3) to hypothyroid rats, with early stimulation followed by later inhibition; these changes were also evident after administration of T3 to androgen-treated animals, although mRNA levels were again suppressed. The effects of testosterone were similar to those of DHT. In contrast to the changes in mRNA levels, androgen administration did not lead to significant alterations in serum TSH concentrations or pituitary TSH content.
These results indicate that, like thyroid hormones, androgens suppress both α and TSH-β subunit mRNA levels in the female rat. Androgens, however, exert differential effects on TSH synthesis and release which contrast with those of thyroid hormones.
Influences of photoperiod on sexual behaviour, neuroendocrine steroid receptors and adenohypophysial hormone secretion and gene expression in female golden hamsters
Authors: Bittman E. L. , Hegarty C. M. , Layden M. Q. , Jonassen J. A. 
Published: December 2008

ABSTRACT
Exposure to short daylengths arrests the oestrous cycle, provokes daily gonadotrophin surges and reduces the ability of exogenous oestradiol to trigger behavioural receptivity in golden hamsters. In order to examine neuroendocrine effects of photoperiod which might underlie these responses, ovariectomized hamsters were maintained under long or short photoperiods for 54 days before treatment with cholesterol or various doses of oestradiol-17β. Short days reduced the ability of low doses of oestrogen to prime hamsters for the induction of oestrus by progesterone. Upon repetition of oestrogen priming 2 weeks later, photoperiod was without significant influence on the concentrations of nuclear oestrogen receptors or cytosolic progestin receptors in a block of tissue containing the hypothalamus and preoptic area.
Oestradiol treatment provoked significant increases in serum concentrations of LH and prolactin in the afternoon, but photoperiod did not alter the positive-feedback efficacy of this gonadal steroid hormone. Adenohypophysial LH-β subunit and prolactin mRNAs were suppressed by short days in ovariectomized hamsters not treated with oestradiol. Oestradiol decreased expression of the LH-β subunit gene in both stimulatory and inhibitory photoperiods, but increased prolactin mRNA abundance in both long and short days. Photoperiod therefore exerts pronounced steroid-independent effects on phasic LH and prolactin secretion, but regulation of adenohypophysial abundance of LH-β subunit and prolactin mRNAs by oestradiol is not markedly influenced by daylength. Photoperiodic regulation of the priming effects of oestradiol on behavioural receptivity may result from modulation of events occurring subsequent to steroid—receptor interactions, or involve changes in receptor populations not detectable by the present methods.
Effect of glucocorticoids on α1-adrenergic receptor binding in rat vascular smooth muscle
Authors: Haigh R. M. , Jones C. T. 
Published: December 2008

ABSTRACT
Glucocorticoids are known to have marked effects on blood pressure regulation, predominantly through altering cardiovascular sensitivity to noradrenaline. However, the molecular mechanisms underlying this action remain unclear. As part of our studies into these we have measured α1-adrenergic receptor binding using the ligand [3H]prazosin in plasma membrane fractions of aortas prepared from control, adrenalectomized and dexamethasone-treated adrenalectomized rats. In controls there were 50±8 (s.e.m.; n=6) fmol α1-adrenergic receptors/mg membrane protein (Bmax) with a dissociation constant (Kd) of 0·52±0·10 nm (n=6). Adrenalectomy 8 days before tissue preparation caused a 40% decrease in Bmax and a 60% decrease in Kd. Dexamethasone replacement after adrenalectomy returned these values close to those of controls. Noradrenaline competed for the [3H]prazosin-binding sites. Computer analysis by a non-linear curve-fitting program (LIGAND) showed that noradrenaline binding was to a heterogeneous population of high- and low-affinity receptors with Kd values of 1·87±0·73 μm and 0·48±0·12 mm (n=5) respectively. Guanosine thiotriphosphate (GTP[S]) caused the conversion of high-affinity to low-affinity binding, consistent with the model of the high-affinity sites being coupled to a G protein. After adrenalectomy, noradrenaline binding was to a homogeneous population of low-affinity receptors; hence, the effect of GTP[S] was no longer apparent, suggesting that under these conditions the α1-adrenergic receptors were unable to couple to a G protein. The two-site model of binding and GTP[S] effect was returned by dexamethasone treatment. These data provide evidence that glucocorticoids not only modulate the number of α1-adrenergic receptors on vascular smooth muscle, but also cause disruptions in receptor—G protein coupling. This may be an important mechanism by which glucocorticoids exert their effect on cardiovascular sensitivity.
Vasopressin stimulates cortisol secretion and phosphoinositide catabolism in cultured bovine adrenal fasciculata/reticularis cells
Authors: Bird I. M. , Nicol M. , Williams B. C. , Walker S. W. 
Published: December 2008

ABSTRACT
Cells isolated from the zona fasciculata/reticularis (ZFR) of the bovine adrenal cortex and maintained in culture were found to secrete cortisol in response to vasopressin stimulation. The increased cortisol secretion was dose dependent, with a threshold response at 1 nm and a maximal response (1·68-fold over basal) at 0·1 μm. In cells cultured in the presence of [3H]inositol (to prelabel the membrane phosphoinositide pool), stimulation with vasopressin in the presence of LiCl (10 mm) resulted in a similar dose-dependent increase in labelling of the phosphoinositol fraction, with a maximal response (1·45-fold over basal) at 10 nm. The increased labelling of the phosphoinositol fraction was independent of extracellular Ca2+ as it was not abolished in medium with [Ca2+ ] buffered to intracellular resting levels. This suggests that vasopressin stimulation results in the activation of a phosphoinositidase C. It is probable that cortisol secretion by bovine ZFR cells in response to vasopressin is dependent upon activation of this Ca2+-independent phosphoinositidase C. However, the small magnitude of the cortisol secretory response makes it unlikely that vasopressin is a primary regulator of cortisol secretion in vivo.
The gene for the β subunit of porcine FSH: absence of consensus oestrogen-responsive element and presence of retroposons
Authors: Hirai T. , Takikawa H. , Kato Y. 
Published: December 2008

ABSTRACT
To elucidate the structure and control of expression of the porcine FSH-β subunit gene, two genomic clones were isolated and the entire gene structure was determined to the extent of 10 kb, consisting of 6 kb of the 5′-flanking region and 4 kb of the transcriptional unit. The porcine FSH-β gene consisted of three exons the same as the human and bovine genes, but the positions of both splicing sites of porcine intron-1 were unique. It is known that the synthesis of FSH is regulated by gonadal steroids, gonadotrophin-releasing hormone (GnRH) and inhibin. However, the consensus steroid-responsive element was unexpectedly absent in the 5′-flanking region of 6 kb. On the other hand, the potential binding sites for activator protein-1 (AP1) and AP2, which might be stimulated by the GnRH—protein kinase C cascade, were present at seven and five positions respectively. An imperfect cyclic AMP-responsive element was also present. Southern blot analyses, using the cDNA and genomic fragments as probes, gave smear patterns suggesting the presence of repetitive sequences in the porcine FSH-β gene. A survey of homology with the repetitive sequences revealed that short interspersed repeated sequences (SINES)-type non-viral retroposons were present with about 250 bp length repeats twice in the 5′-flanking region and once each in intron-1 and the 3′-flanking region. Other SINES-like sequences were also found in intron-1, exon-2 and exon-3. In comparison with the 5′-flanking sequences of the porcine α and LH-β genes, there were no significantly conserved regions, implying a lack of common modulation of the three subunit genes.
The use of inclusion bodies, isolated from Escherichia coli expressing corticotrophin-releasing hormone precursor, to raise specific antibodies against the neuropeptide moiety
Authors: Castro M. G. , Lowenstein P. R. , Saphier P. W. , Linton E. A. , Lowry P. J. 
Published: December 2008

ABSTRACT
We have expressed human pre-procorticotrophin-releasing hormone (pre-proCRH) as a fusion protein to β-galactosidase in Escherichia coli. The chimeric fusion protein was found in insoluble bacterial inclusion bodies. The inclusion bodies were isolated, purified and solubilized, and used as imunogens in rabbits to raise antibodies against the neuropeptide moiety. The antibodies generated were characterized by immunoassays and immunocytochemical techniques. The immunoassay results showed that the recombinant pre-proCRH antibodies cross-reacted with the full-length CRH precursor and several cleavage products derived from it, i.e. CRH(1–41) and CRH(36–41). They did not cross-react with the CRH antagonist CRH(9–41). Extracts of stalk median eminence from various species were also studied. The antibodies cross-reacted with extracts from ovine, bovine, human and rat tissues, exhibiting parallel displacement curves to that of synthetic rat/human CRH(1–41) used as standard. They also cross-reacted with a skin extract of the frog, a species known to contain a CRH-related peptide, i.e. sauvagine, in this tissue. The immunocytochemical studies demonstrated that the antibodies generated against recombinant human preproCRH labelled neurones in the rat paraventricular nucleus of the hypothalamus. They exhibited the same pattern of staining as that obtained with an antibody generated against synthetic CRH(1–41). The results indicate that these antibodies can recognize CRH(1–41) or CRH-related molecules in the hypothalamus in situ as well as in tissue extracts from several species. Hence, they will be useful tools in the study of the CRH biosynthetic pathway and its intracellular compartmentalization.
Depletion of islet amyloid polypeptide in the spontaneously diabetic (BB) Wistar rat
Authors: Bretherton-Watt D. , Ghatei M. A. , Legon S. , Jamal H. , Suda K. , Bloom S. R. 
Published: December 2008

ABSTRACT
Islet amyloid polypeptide (IAPP) in the pancreas of the spontaneously diabetic (BB) Wistar rat was examined by radioimmunoassay, and IAPP mRNA levels were determined by Northern blotting. IAPP-like immunoreactivity in the diabetic rat pancreas was found to be significantly depleted compared with control (non-diabetic) BB rats (85·9±5 pmol/g in control rats, n = 8, vs 8·97 ± 0·9 pmol/g in diabetic rats, n=5; mean ± s.e.m.). A similar change in insulin concentrations was found, although insulin was present in approximately 100-fold greater amounts than IAPP. Chromatography of the IAPP immunoreactivity revealed a single molecular form, corresponding to synthetic IAPP. Northern blot analysis of pancreatic RNA (n = 4) revealed that IAPP mRNA in the diabetic group was depleted to 22% of the signal intensity in the control group. Insulin mRNA was dramatically reduced to only 4% of the control group and, in contrast, somatostatin was relatively unaffected, with the diabetic group retaining 86% of signal compared with the controls.
This animal model of insulin-dependent diabetes results from severe autoimmune destruction of the β cell. The extremely low levels of both insulin and its messenger RNA are in agreement with this. These results demonstrate that this pathological state is also associated with a loss of IAPP from the pancreas. Insulin-dependent diabetes is associated with a range of metabolic disturbances. It is possible that the concomitant depletion of IAPP may be a contributory factor in exacerbating the condition.
Variable methylation of the 5′-flanking DNA of the human pro-opiomelanocortin gene
Authors: Lavender P. , Clark A. J. L. , Besser G. M. , Rees L. H. 
Published: December 2008

ABSTRACT
The pro-opiomelanocortin gene is widely expressed in human tissues, although both transcriptional initiation sites and regulation appear to be tissue specific. In order to determine how promoter and enhancer choice is effected, we have studied the methylation pattern of the gene in a number of normal tissues, tumours and cell lines. Variability of this pattern was observed in the 5′-flanking DNA, particularly at the HpaII site located at −304 bp upstream from the pituitary CAP site. This site was generally methylated in tissues likely to express the predominant extrapituitary (800 nucleotide) message, while in tissues known to express the normal pituitary (1150 nucleotide) message and longer species, a tendency towards undermethylation was observed. Although the sites at which variable methylation occurs did not correspond to established binding sites for regulatory proteins, many of these regions remain to be determined and thus it is possible that methylation may be influential in the tissue-specific regulation of this gene.
Maitotoxin increases inositol phosphates in rat anterior pituitary cells
Authors: Sortino M. A. , Delahunty T. M. , Yasumoto T. , Cronin M. J. 
Published: December 2008

ABSTRACT
Maitotoxin is a potent marine poison that mobilizes calcium in most vertebrate cell types and accelerates secretion from anterior pituitary cells. It is not known whether voltage-sensitive calcium channels or other mechanisms initiate the effects of maitotoxin on anterior pituitary cells. Changes in intracellular Ca2+ levels may also be achieved by releasing internal calcium stores via inositol trisphosphate (InsP3). Indeed, maitotoxin rapidly increased inositol phosphate accumulation in a concentration-dependent manner. Calcium channel antagonists such as nifedipine and verapamil did not block this response nor did calcium-mobilizing agents (BAYk8644, A23187) mimic this effect. These data suggest that the mechanism by which maitotoxin acts at the pituitary may include the activation of an enzyme that produces the calcium-mobilizing signal InsP3.
EVIDENCE FOR A PREVIOUSLY UNIDENTIFIED UPSTREAM EXON IN THE HUMAN OESTROGEN RECEPTOR GENE.
Authors: Keaveney M. , Klug J. , Dawson M.T. , Nestor P.V. , Neilan J.G. , Forde R.C. , Gannon F. 
Published: December 2008

ABSTRACT
The presence of a previously unidentified exon upstream of the originally described human oestrogen receptor (hOR) gene is demonstrated. This is shown to be spliced to the 5′ untranslated region of the previously designated exon I. The resulting genomic structure of the human gene is thus in agreement with the structure of the mouse OR gene and highlights the conservation of an 18 amino acid upstream open-reading frame formed from the above splicing event. Taken in conjunction with previous publications this would suggest that the hOR gene is a complex transcriptional unit that contains two promoters.
Regulation by progesterone of the high-affinity state of myometrial β-adrenergic receptor and of adenylate cyclase activity in the pregnant rat
Authors: Cohen-Tannoudji J. , Vivat V. , Heilmann J. , Legrand C. , Maltier J. P. 
Published: December 2008

ABSTRACT
The effects of pregnancy or progesterone dominance on the β-adrenergic responsiveness of the uterus were studied in myometrial membranes from mid-and late-pregnant rats (day 15 and on the 16th h of day 22 of pregnancy respectively) or 24 h after administration of progesterone. Levels of the high (RH)- and low (RL)-affinity states of the β-adrenergic receptor were determined by competition experiments between 125I-labelled cyanopindolol binding and the selective β-agonist isoproterenol. The ratio KL/KH (respective dissociation constants) was determined since it also reflects the degree of formation of the high-affinity state of the β-adrenergic receptor. From day 15 to the 10th h of day 22 of pregnancy, two distinct affinity states were apparent: 80–55% RH (KH=0·31–0·21 μm) and 45–20% RL (KL=14–5 μm) with a ratio of KL/KH of 55–34. In the last 6 h before birth, β-adrenergic receptors underwent uncoupling which was paralleled by decreased responsiveness of myometrial adenylate cyclase to isoproterenol (maximum velocity (Vmax)=17±3 vs 44±3 fmol cyclic AMP/10 min per mg protein on day 15). At this stage of pregnancy, previous exposure to progesterone resulted in a 1·8-fold increase in 125I-labelled cyanopindolol-binding sites (Bmax) and the reappearance of the high-affinity state (67% RH, KH=0·19±0·04 (s.e.m.) μm, ratio KL/KH=81·1 ± 16·9). These results were reversed in the presence of the antiprogestin RU486 (100% RL, KL=24·6±4·1 μm, 41% reduction of Bmax). Moreover, after progesterone, adenylate cyclase activity was strongly stimulated by isoproterenol (Vmax=60±12 fmol cyclic AMP/10 min per mg protein vs 17±3 in controls). The data suggest (1) that progesterone may exert a permissive effect on β-adrenergic responsiveness of the pregnant rat myometrium and (2) that at term, both a desensitization mechanism involving uncoupling of β-adrenergic receptors and a decrease in activation of adenylate cyclase lead to a loss of myometrial response to β-agonists.
Predicted structure of the bovine calcitonin gene-related peptide and the carboxy-terminal flanking peptide of bovine calcitonin precursor
Authors: Collyear K. , Girgis S. I. , Saunders G. , MacIntyre I. , Holt G. 
Published: December 2008

ABSTRACT
We have isolated from a bovine genomic library a clone which contains the calcitonin (CT) and CT gene-related peptide (CGRP) sequences, using probes representing the human CT and CGRP sequences. Sequence analysis has identified the nucleotide sequence coding for bovine CT, its C-terminal flanking peptide and bovine CGRP. The deduced amino acid sequence of bovine CGRP revealed a significant homology with other CGRPs so far reported. It differs by only one amino acid from rat CGRPα and porcine CGRP, and by three and four amino acids from human CGRPβ and α respectively. Bovine CT has, however, only 14 out of 32 residues in common with human CT. As in the human CT precursor, the C-terminal flanking peptide of bovine CT precursor is a 21 amino acid peptide. It shares only 11 residues in common with its human counterpart. This study thus provides further evidence that CGRP, in contrast to CT and its C-terminal flanking peptide, is a highly conserved molecule.
Self-inhibition of steroid secretion by amphibian adrenocortical cells is not mediated through glucocorticoid receptors
Authors: Netchitailo P. , Larcher A. , Leboulenger F. , Feuilloley M. , Philibert D. , Vaudry H. 
Published: December 2008

ABSTRACT
To investigate a possible direct action of glucocorticoids on adrenal steroidogenesis, the effect of corticosterone on the conversion of pregnenolone into various metabolites by frog adrenal tissue was examined. Frog interrenal slices were incubated with [3H]pregnenolone (1 mCi/ml) and the various labelled metabolites analysed by reverse-phase high-performance liquid chromatography. With the methanol gradient used, five identified steroids were resolved: progesterone, 11-deoxycorticosterone, corticosterone, 18-hydroxycorticosterone and aldosterone. Corticosterone (10 μg/ml) induced a 45–80% decrease in all steroids synthesized from [3H]pregnenolone. In contrast, the glucocorticoid agonist dexamethasone did not reduce the rate of conversion of pregnenolone into its metabolites. In addition, the inhibitory effect of corticosterone was not reversed by the specific glucocorticoid antagonist RU 43044. These results show that corticosterone exerts a direct inhibitory effect on adrenal steroid secretion. In addition, our data indicate that the ultra-short regulation induced by corticosterone is not mediated through glucocorticoid receptors.
Stimulation of an individual cell with peptide hormone in a prescribed region of its plasma membrane results in a compartmentalized cyclic AMP-dependent protein kinase response
Authors: Podesta E. J. , Solano A. R. , Lemos J. R. 
Published: December 2008

ABSTRACT
This work describes the stimulation by a peptide hormone of an individual cell in a prescribed region of its plasma membrane. When Leydig cells were stimulated via a section of membrane tightly sealed to an electrode containing LH, a very localized area exhibited the morphological change known as 'rounding up', which is a cyclic AMP-dependent protein kinase-mediated response. This localized stimulation did not produce a wider response through intracellular, intermembranous or extra-cellular signals. Each individual cell responded to peptide stimulation gradually, with an increase over time and with dose. In contrast, when the stimulation was accomplished using a non-hydrolysable cyclic AMP analogue in the patch electrode, a general response throughout an individual cell was produced. Locally stimulated peptide hormone receptors, adenylate cyclases and cyclic AMP-dependent protein kinases appear to be closely associated so that second messenger production and the effects it mediates are compartmentalized.
Interleukin-1β production in vivo and in vitro in rats and mice measured using specific immunoradiometric assays
Authors: Bristow A. F. , Mosley K. , Poole S. 
Published: December 2008

ABSTRACT
Activated cells of the monocyte—macrophage lineage produce two forms of the inflammatory cytokine interleukin-1 (IL-1), IL-1α and IL-1β, of which IL-1β is the predominant secreted form and has a wide range of modulatory effects on the endocrine system. Immunoassays of human IL-1β have been described, but are not suitable for measurement of rat and mouse IL-1β because of limited cross-reactivity. Polyclonal sheep anti-rat or sheep anti-mouse IL-1β antisera were used to develop sensitive and specific immunoradiometric assays for rat and mouse IL-1β. Secretion of IL-1β from endotoxin-activated monocytes or macrophages was measured in vitro or in vivo in both species. In vitro, rat monocytes and mouse macrophages produced IL-1β in response to endotoxin, with a relatively small proportion of total IL-1β being secreted. In vivo, endotoxin stimulated an increase in plasma IL-1β in both animals. The development of these assays will facilitate studies of the role of endogenous IL-1β in animal endocrine models.