Biomedical subjects

H Vaudry

Publications and source records attributed to H Vaudry.

At least 19 recordsLinked to original sources

PubMed2006

Cardiovascular effects of native and non-native urotensin II and urotensin II-related peptide on rat and salmon hearts.

Urotensin II (UII) was first discovered in the urophyses of goby fish and later identified in mammals, while urotensin II-related peptide (URP) was recently isolated from rat brain. We studied the effects of UII on isolated heart preparations of Chinook salmon and Sprague-Dawley rats. Native rat UII caused potent and sustained, dose-dependent dilation of the coronary arteries in the rat, whereas non-native UII (human and trout UII) showed attenuated vasodilation. Rat URP dilated rat coronary arteries, with 10-fold less potency compared with rUII. In salmon, native trout UII caused sustained dilation of the coronary arteries, while rat UII and URP caused significant constriction. Nomega-nitro-(l)-arginine methyl (l-NAME) and indomethacin significantly attenuated the URP and rat UII-induced vasodilation in the rat heart. We conclude that UII is a coronary vasodilator, an action that is species form specific. We also provide the first evidence for cardiac actions of URP, possibly via mechanisms common with UII.

Animals↗

PubMed2006

Functional differences between NPFF1 and NPFF2 receptor coupling: high intrinsic activities of RFamide-related peptides on stimulation of [35S]GTPgammaS binding.

By using an optimized [(35)S]GTPgammaS binding assay, the functional activities (potency and efficacy) of peptides belonging to three members of the RFamide family; Neuropeptide FF (NPFF), prolactin-releasing peptide (PrRP) and 26RFamide, were investigated on NPFF(1) and NPFF(2) receptors stably expressed in Chinese Hamster Ovary (CHO) cells. Despite their large differences in affinity and selectivity, all analogues tested behaved as agonists toward NPFF(1) and NPFF(2) receptors. High NaCl concentration in the assay strongly increased the efficacy toward NPFF(2) receptors and augmented differences among agonists. In low sodium conditions, whereas the potencies of agonists correlated with their affinities for NPFF(1) receptors, NPFF(2) receptors exhibited an extraordinary activity since all compounds tested displayed EC(50) values of GTPgammaS binding lower than their K(I) values. Comparisons of functional values between NPFF(1) and NPFF(2) receptors revealed unexpected potent selective NPFF(2) agonists especially for the PLRFamide and the VGRFamide sequences. By using blocker peptides, we also show that Galpha(i3) and Galpha(s) are the main transducers of NPFF(1) receptors while NPFF(2) are probably coupled with Galpha(i2), Galpha(i3), Galpha(o) and Galpha(s) proteins. Our data indicate that NPPF(1) and NPFF(2) receptors are differently coupled to G proteins in CHO cells.

Animals↗

PubMed2006

Role of androgens and glucocorticoids in the regulation of diazepam-binding inhibitor mRNA levels in male mouse hypothalamus.

In peripheral organs, gonadal and adrenal steroids regulate diazepam-binding inhibitor (DBI) mRNA expression. In order to further investigate the involvement of peripheral steroid hormones in the modulation of brain DBI mRNA expression, we studied by semiquantitative in situ hybridization the effect of adrenalectomy (ADX) and castration (CX) and short-term replacement therapy on DBI mRNA levels in the male mouse hypothalamus. Cells expressing DBI mRNA were mostly observed in the arcuate nucleus, the median eminence and the ependyma bordering the third ventricle. In the median eminence and the ependyma bordering the third ventricule, the DBI gene expression was decreased in ADX rats and a single injection of corticosterone to ADX rats induced a significant increase in DBI gene expression at 3 and 12 h time intervals without completely restoring the basal DBI mRNA expression observed in intact mice. In the arcuate nucleus, ADX and corticosterone administration did not modify DBI mRNA expression. CX down-regulated DBI gene expression in the ependyma bordering the third ventricle. The administration of dihydrotestosterone (3-24 h) completely reversed the inhibitory effect of CX. In the median eminence and arcuate nucleus, neither CX or dihydrotestosterone administration modified DBI mRNA levels. These results suggest that the effects of glucocorticoids on the hypothalamo-pituitary-adrenocortical axis and androgens on the hypothalamo-pituitary-gonadal axis are mediated by DBI.

Adrenalectomy↗

PubMed2006

Pituitary adenylate cyclase-activating polypeptide directly modulates the activity of proopiomelanocortin neurons in the rat arcuate nucleus.

Pituitary adenylate cyclase-activating polypeptide (PACAP) and the proopiomelanocortin (POMC)-derived peptide alpha-melanocyte-stimulating hormone (alpha-MSH) both regulate multiple neuroendocrine functions and feeding behavior. Two subtypes of PACAP receptor mRNAs, pituitary adenylate cyclase-activating polypeptide-specific receptor (PAC1-R) and pituitary adenylate cyclase-activating polypeptide/vasoactive intestinal polypeptide mutual receptor (VPAC2-R), are actively expressed in the arcuate nucleus of the hypothalamus, where POMC cell bodies are located. This observation led us to investigate the possible regulatory action of PACAP on rat POMC neurons. Double-labeling in situ hybridization histochemistry revealed that approximately 50% of POMC-producing neurons express PAC1-R and/or VPAC2-R mRNAs. The proportion of POMC neurons that also contain PAC1-R mRNA was homogeneous along the rostro-caudal axis of the arcuate nucleus while POMC-positive cell bodies expressing the VPAC2-R subtype were more abundant in the rostral region. Incubation of mediobasal hypothalamic explants with PACAP (10(-7) M; 30 min) increased POMC mRNA expression, and this effect was blocked by PACAP6-38 (10(-6) M). In contrast, incubation with vasoactive intestinal polypeptide (10(-7) M) did not affect POMC mRNA level. Incubation of hypothalamic fragments with PACAP (10(-7) M) caused a significant increase in alpha-MSH content in the tissue and in the incubation medium. Altogether, the present results reveal that exogenous PACAP, acting probably through PAC1-R, regulates the activity of POMC neurons in the rat hypothalamus. These data suggest that the effects of PACAP on the gonadotropin-releasing hormone neuroendocrine axis and the regulation of feeding behavior may be mediated, at least in part, through modulation of POMC neurons.

Animals↗

PubMed2006

In vitro effects of crude extracts of Parkia biglobosa (Mimosaceae), Stereospermum kunthianum (Bignoniaceae) and Biophytum petersianum (Oxalidaceae) on corticosteroid secretion in rat.

Previous studies conducted in guinea pig, rat and rabbit have revealed that crude extracts from Parkia biglobosa, Stereospermum kunthianum and Biophytum petersianum exert hypotensive and/or hypoglycemic activities. Since corticosteroids are involved in the control of arterial blood pressure and glycemia, we have investigated the possible effects of these plant extracts on rat adrenal tissue in vitro. Short-term administration of crude semi-ethanolic extracts of P. biglobosa and S. kunthianum to perifused rat adrenal tissue did not induce any significant changes in corticosteroid output. Conversely, the B. petersianum extract caused a dose-dependent increase in corticosterone and aldosterone secretion. Repeated infusions or prolonged administration of B. petersianum extract did not produce any apparent attenuation of the steroid response. Altogether, these data indicate that a semi-ethanolic extract of B. petersianum dose-dependently stimulates corticosterone and aldosterone secretion in rat without any desensitization phenomenon.

Acacia↗

PubMed2006

Novel role of 26RFa, a hypothalamic RFamide orexigenic peptide, as putative regulator of the gonadotropic axis.

The close link between reproductive function and body energy stores relies on a complex neuroendocrine network of common regulatory signals, the nature of which is yet to be fully elucidated. Recently, 26RFa was identified in amphibians and mammals as a conserved hypothalamic neuropeptide of the RFamide family, with a potent orexigenic activity. Yet, despite its proposed role as hypophysiotropic factor, the function of 26RFa in the control of pituitary gonadotropins and, hence, of the reproductive axis remains unexplored. In the present study, the effects of 26RFa on gonadotropin secretion were evaluated in the rat by a combination of in vitro and in vivo approaches. At the pituitary, 26RFa dose-dependently enhanced basal and gonadotropin-releasing hormone (GnRH)-stimulated luteinizing hormone (LH) secretion from male and cyclic female rats. This effect was mimicked by the active fragment 26RFa(20-26), as well as by the related 43RFa peptide. Moreover, expression of the genes encoding 26RFa and its putative receptor, GPR103, was demonstrated in rat pituitary throughout postnatal development. In vivo, intracerebral injection of 26RFa evoked a significant increase in serum LH levels in cyclic and ovariectomized females; this response which was also observed after central injection of 26RFa(20-26) and 43RFa peptides, as well as after systemic administration of 26RFa. Conversely, central and systemic injection of 26RFa failed to significantly modify gonadotropin secretion in adult male rats, even after repeated administration of the peptide. In summary, we present herein novel evidence for the potential role of the orexigenic peptide 26RFa in the control of the gonadotropic axis, thus suggesting its potential involvement in the joint control of energy balance and reproduction, especially in the female.

Amino Acid Sequence↗

PubMed2006

RT-PCR analysis of the expression of POMC and its processing enzyme PC1 in amphibian melanotropes.

The frog intermediate lobe comprises two functionally distinct cell subtypes, referred to as secretory and storage melanotropes, which differ in their ultrastructure, secretory, and synthetic rates, and display dissimilar responses to hypothalamic regulatory factors. All these differences make melanotrope subtypes an excellent model to analyze the expression and regulation of genes involved in the control and maintenance of the secretory state of endocrine cells. However, quantification of the expression levels of genes involved in the secretory process requires the characterization of a gene whose expression remains constant irrespective of the secretory state of the cells. In this study, we have cloned the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene from frog pituitary and have evaluated its suitability as internal standard in gene expression studies in melanotropes. A semiquantitative RT-PCR system developed to this end revealed that secretory melanotropes and storage melanotropes possess similar expression levels of GAPDH, whereas, as expected, secretory melanotropes showed higher levels of POMC transcripts than storage cells. Furthermore, we found that the expression of the convertase PC1, an intracellular protease involved in POMC processing, parallels that of POMC, thus suggesting that the higher secretory rate of the POMC-derived peptide alpha-MSH exhibited by secretory melanotropes is supported by their higher PC1 expression levels. In addition, we have shown that both POMC and PC1 mRNAs are up-regulated by the hypothalamic factor TRH in melanotrope cell cultures. In contrast, the inhibitory factor NPY reduced the expression level of the convertase but did not modify that of POMC. Taken together, these results demonstrate that PC1 expression is regulated in melanotropes by both stimulatory (TRH) and inhibitory (NPY) hypothalamic signals, in a manner which essentially parallels that observed for the precursor POMC.

Amino Acid Sequence↗

PubMed2005

Differential expression and processing of chromogranin A and secretogranin II in relation to the secretory status of endocrine cells.

Chromogranin A (CgA) and secretogranin II (SgII) are neuroendocrine secretory proteins that participate in regulation of the secretory pathway and also serve as precursors of biologically active peptides. To investigate whether there is a relationship between the expression, distribution, and processing of CgA and SgII and the degree of secretory activity, we employed two melanotrope subpopulations of the pituitary intermediate lobe that exhibit opposite secretory phenotypes. Thus, although one of the melanotrope subtypes shows high secretory activity, the other exhibits characteristics of a hormone storage phenotype. Our data show that SgII expression levels were higher in secretory melanotropes, whereas CgA expression showed similar rates in both cell subsets. The use of various antibodies revealed the presence of the unprocessed proteins as well as three CgA-derived peptides (67, 45, and 30 kDa) and six SgII-derived peptides (81, 66, 55, 37, 32, and 30 kDa) in both subpopulations. However, the smallest molecular forms of both granins predominated in secretory melanotropes, whereas the largest SgII- and CgA-immunoreactive peptides were more abundant in storage melanotropes, which is suggestive of a more extensive processing of granins in the secretory subset. Confocal microscopy studies showed that CgA immunoreactivity was higher in storage cells, but SgII immunoreactivity was higher in secretory melanotropes. Taken together, our results indicate that SgII and CgA are differentially regulated in melanotrope subpopulations. Thus, SgII expression is strongly related to the secretory activity of melanotrope cells, whereas CgA expression may not be related to secretory rate, but, rather, to hormone storage in this endocrine cell type.

Animals↗

PubMed2005

In vivo action of a new octadecaneuropeptide antagonist on neuropeptide Y and corticotropin-releasing hormone mRNA levels in rat.

It has been reported that several of the effects induced by an octadecaneuropeptide (ODN), derived from an 86-amino-acid polypeptide termed diazepam-binding inhibitor, could be mediated by activation of a metabotropic receptor. In order to investigate the role and mechanism of action of ODN in the regulation of corticotropin-releasing factor (CRH) and neuropeptide Y (NPY) expression in the paraventricular nucleus and arcuate nucleus, respectively, we studied the effects of the acute intracerebroventricular administration of ODN (2 microg/rat) and the ODN antagonist to metabotropic receptor, cyclo(1-8)[Dleu5]OP (20 microg/rat), on the gene expression of the two neuropeptides in castrated male rat. ODN administration resulted in a 45% increase in CRH mRNA expression, an effect which was reversed by cyclo(1-8)[Dleu5]OP. When cyclo(1-8)[Dleu5]OP was administered alone, it induced a 19% decrease in CRH mRNA levels. ODN administration induced a 17% decrease in NPY mRNA expression while cyclo(1-8)[Dleu5]OP increased by 21% the hybridization signal. The administration of both ODN and ODN antagonist completely abolished the depressing effect of ODN on NPY mRNA. These data suggest that the effects of ODN on CRH and NPY mRNA might be mediated by interaction with metabotropic receptors. Moreover, since cyclo(1-8)[Dleu5]OP can by itself influence the expression of two peptide mRNAs, it might be suggested that ODN is exerting a tonic influence on NPY and CRH neurons.

Animals↗

PubMed2005

Melanotrope cells as a model to understand the (patho)physiological regulation of hormone secretion.

Regulation of hormone secretion is a complex process that comprises the sequential participation of numerous subcellular mechanisms. Hormone secretion is dictated by extracellular stimuli that are transduced intracellularly into activation/deactivation of different mechanisms, such as hormone expression, processing and exocytosis, which will ultimately determine the precise availability of hormone to be secreted. Malfunction in any of these steps may result in deficient or excessive hormone release and the subsequent appearance of endocrine disorders. Given the complexity of this system, it is difficult to find appropriate cellular models wherein to investigate the multiple components of the secretory process in a physiologically relevant, experimentally manipulable setting. In this review, we present recent evidence on the use of the intermediate lobe (IL) of the pituitary as a powerful tool to understand different aspects of the regulated secretory pathway. IL is composed of a single endocrine cell type, alpha-melanocyte stimulating hormone (alpha-MSH)-producing melanotropes, a fact that greatly facilitates its study. Furthermore, melanotropes can be separated using classic cell separation techniques into two cell subtypes showing opposite morphophysiological phenotypes of hypo- and hypersecretory cells. Comparison of their gene expression fingerprints has unveiled the existence of certain genes preferentially expressed in each melanotrope subtype. Because of their direct participation in the secretory pathway, we postulate that characterization of these gene products in an endocrine cell type may represent novel and useful markers for reliably determining the general secretory status in an endocrine gland, as well as a valuable new tool to further investigate this complex process.

Amphibians↗

PubMed2005

Androgenic down-regulation of urotensin II precursor, urotensin II-related peptide precursor and androgen receptor mRNA in the mouse spinal cord.

We had previously shown that in rat spinal cord motoneurons urotensin II (UII) precursor mRNA was down-regulated by androgens. Very recently, a gene encoding the precursor of a UII analog, termed UII-related peptide (URP), has been identified. Using in situ hybridization, we studied the localization of UII and URP precursor as well as androgen receptor (AR) mRNA in the male mouse thoracic spinal cord. We also evaluated the androgenic regulation of the two peptide precursor and AR mRNA expression in the ventral horn of the mouse thoracic spinal cord. The results revealed that URP precursor mRNA was localized in motoneurons and that the vast majority of the motoneurons expressed both peptide precursor as well as AR mRNA. Seven-day castration induced an increase in UII and URP precursor and AR mRNA levels. Short term (3-24 h) administration of dihydrotestosterone to castrated animals restored the three protein mRNA levels to the levels observed in intact animals. These results suggest that in the ventral horn of the mouse spinal cord both UII and URP precursor and AR mRNA are expressed by the same neurons and that circulating androgens are exerting a down-regulation of the three protein mRNA expression, possibly by a direct action on motoneurons.

Animals↗

PubMed2005

Effect of prolyl endopeptidase inhibition on arginine-vasopressin and thyrotrophin-releasing hormone catabolism in the rat brain.

Compound S 17092 is a potent and selective inhibitor of prolyl endopeptidase (EC 3.4.21.26, PEP) that may be of therapeutic value for the treatment of memory impairment associated with neurodegenerative diseases. In the present study, we investigated the effects of S 17092 on the catabolism of the promnesic neuropeptides thyrotrophin-releasing hormone (TRH) and arginine-vasopressin (AVP) in the rat brain. In vitro, bacterial PEP hydrolysed both TRH and AVP, and the breakdown of the two peptides was almost completely prevented by 10(-5) M S 17092. In vivo, a single oral administration of S 17092 provoked a significant increase in TRH-like immunoreactivity (TRH-LI) in the cerebral cortex (+63% for a 10 mg/kg dose and +72% for a 30 mg/kg dose), as well as AVP-LI in the hippocampus (+54% for a 30 mg/kg dose), but did not affect TRH-LI in the amygdala nor AVP-LI in the cerebral cortex. Chronic administration of S 17092 (10 or 30 mg/kg daily) lead to a significant increase in THR-LI in the cerebral cortex (+55% and +56%, respectively), but did not modify AVP-LI in the hippocampus, nor in the cerebral cortex. These results show that the selective PEP inhibitor S 17092 increases TRH and AVP content in discrete regions of the rat brain. The present data suggest that the promnesic and antiamnesic effects of S 17092 can be accounted for, at least in part, by blockage of AVP and TRH degradation by PEP.

Amygdala↗

PubMed2005

Biochemical characterisation and immunohistochemical localisation of the secretogranin II-derived peptide EM66 in the hypothalamus of the jerboa (Jaculus orientalis): modulation by food deprivation.

The neuroendocrine protein secretogranin II is the precursor of several neuropeptides, including secretoneurin and a novel 66-amino acid peptide, EM66, the sequence of which has been highly conserved across the vertebrae phylum. The presence of EM66 has been detected in the adult and fetal human adrenal gland, as well as the rat pituitary and adrenal glands. The present study aimed to explore a possible neuroendocrine role of EM66 by analysing its occurrence and distribution within the jerboa hypothalamus, and its potential implication in the control of feeding behaviour. High-performance liquid chromatography analysis of jerboa hypothalamic extracts combined with a radioimmunoassay of EM66 revealed a single peak of immunoreactive material exhibiting the same retention time as recombinant EM66. Immunocytochemical labelling showed that EM66-producing neurones are widely distributed in several hypothalamic regions, including the preoptic area, the suprachiasmatic, supraoptic, parvocellular paraventricular and arcuate nuclei, and the lateral hypothalamus. Food deprivation for 5 days induced a significant increase in the number of EM66-containing neurones within the arcuate nucleus (105% increase) and the parvocellular aspect of the paraventricular nucleus (115% increase), suggesting that EM66 could be involved in the control of feeding behaviour and/or the response to stress associated with fasting. Altogether, these data reveal the physiological plasticity of the EM66 system in the hypothalamus and implicate this novel peptide in the regulation of neuroendocrine functions.

Amino Acid Sequence↗

PubMed2005

In situ hybridization localization of TRH precursor and TRH receptor mRNAs in the brain and pituitary of Xenopus laevis.

We examined the distribution of the mRNAs encoding proTRH and the three TRH receptor subtypes (xTRHR1, xTRHR2, and xTRHR3) in the Xenopus laevis CNS and pituitary. A positive correlation was generally observed between the expression patterns of proTRH and xTRHR mRNAs. xTRHRs were widely expressed in the telencephalon and diencephalon, where two or even three xTRHR mRNAs were often simultaneously observed within the same brain structures. In the pituitary, xTRHR2 was selectively expressed in the distal lobe, and xTRHR3 was found exclusively in the intermediate lobe of white background-adapted animals, indicating that, in amphibians, the effect of TRH on alpha-melanotropin (alpha-MSH) secretion from melanotrope cells is mediated through the novel receptor subtype xTRHR3.

Animals↗

PubMed2005

Analysis of Rab18 and a new golgin in the secretory pathway.

Two new amphibian genes have been isolated and characterized from frog melanotropes, and the level of expression of these genes is related to the secretory status of the cells. Both genes, Rab18 and a novel member of the golgin family of proteins, are ubiquitously expressed in endocrine and nonendocrine tissues, and their corresponding proteins appear to show intracellular distributions associated with discrete vesicular and tubular structures, respectively, suggesting that they may play relevant roles in the regulation of the secretory pathway.

Animals↗

PubMed2005

Neuroendocrine regulation of frog adrenocortical cells by neurotensin.

We previously characterized the primary structure of neurotensin (NT) from an extract of the intestine of the frog Rana esculenta. In this study, we provide evidence for the involvement of NT in the neurocrine regulation of the secretory activity of frog adrenocortical cells. Immunohistochemical studies revealed that the adrenal gland of R. esculenta is innervated by a dense network of NT-immunoreactive fibers. Graded concentrations of frog NT induced a dose-dependent stimulation of corticosterone and aldosterone secretion by frog adrenocortical explants through activation of two receptors with pEC(50) of 9.8 and 6.9. These data support the view that NT, released by nerve fibers within the frog adrenal gland, acts locally to control corticosteroid secretion.

Adrenal Cortex↗

PubMed2005

Expression of proopiomelanocortin and its cleavage enzyme genes in Rana esculenta and Xenopus laevis gonads.

Proopiomelanocortin (POMC) is the precursor protein of different hormones and neuropeptides, and the POMC-derived peptides are produced through proteolytic cleavage. Prohormone convertase PC1 and PC2 are enzymes responsible for the cleavage of the POMC prohormone. The coexpression of POMC, PC1, and PC2 genes was previously described in the brain and the pituitary gland of Rana esculenta and Xenopus laevis, but no data are available for the gonad. The present work demonstrates a gonadal POMC convertase gene expression in Rana esculenta and Xenopus laevis.

Animals↗

PubMed2005

Time-course effects of centrally administered native urotensin-II on motor and cardioventilatory activity in trout.

Although in most vertebrate species urotensin-II (UII) is synthesized in neurons of the central nervous system, little is known regarding the physiological actions of UII in the brain. We have investigated the effects of intracerebroventricular (ICV) administration of synthetic trout UII (1, 5, and 50 pmol) on total motor activity (ACT), ventilatory frequency (VF), ventilatory amplitude (VA), and heart rate (HR) in the unanesthetized trout. ICV injection of UII increased ACT in a dose-dependent manner, and the maximal effect was observed at a dose of 5 pmol. At doses of 1 and 5 pmol, UII did not affect VF, VA, or HR. At the highest dose tested (50 pmol), UII not only increased ACT, but also significantly activated VF, VA, and HR. In contrast, ICV injection of synthetic trout angiotensin-II (5 pmol) did not produce any effect on ACT, VF, or VA, but sharply increased HR. These data provide the first evidence that UII can act centrally to induce motor activity in a nonmammalian vertebrate species.

Animals↗