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H Vaudry

Publications and source records attributed to H Vaudry.

At least 505 records · Page 28Linked to original sources
PubMed1986

[Alpha-melanotropin in the frog brain: regional distribution, quantification and subcellular distribution].

The distribution of alpha-MSH containing neurons was studied by immunofluorescence in the brain of the frog Rana ridibunda. Most immunoreactive cell bodies were found in the ventral hypothalamic area. A rich network of fluorescent fibers was observed in the ventral infundibular region, coursing towards the preoptic area and the ventral telencephalon. Some fibers, directed backwards, project into median eminence. By means of a specific radioimmunoassay, the concentrations of alpha-MSH immunoreactive material has been determined in 10 different regions of the brain. The highest concentrations were observed in the infundibular and the preoptic regions. Using the immunogold technique, electron microscopy showed that immunostaining was restricted to 70-100 nm dense core vesicles in positive cell bodies and fibers. These results suggest that, in addition to well known hormonal (melanotropic) activity, alpha-MSH could play the role of a neurotransmitter in the frog brain.

Animals↗
PubMed1986

[Role of calcium in TRH-induced secretion of alpha-MSH in the frog].

In amphibians, alpha-MSH secretion is stimulated by thyrotropin-releasing hormone (TRH). In the present study we show that extracellular calcium influences directly the spontaneous secretion of alpha-MSH and that it participates in the mechanism of action of TRH on frog melanotrophs.

Animals↗
PubMed1986

[Localization and identification of neuropeptide Y (NPY) in the brain of an anuran amphibian].

A neuropeptide Y (NPY)-like peptide has been localized in the frog brain by the direct immunofluorescence method. Subcellular localization of NPY has been studied by PAP immunocytochemistry and the immunogold technique. Using a specific radioimmunoassay technique, NPY-like peptide has been quantified in various brain areas and the immunoreactive material was characterized by Sephadex G-50 gel filtration and high performance liquid chromatography. The results indicate that frog NPY is closely related to the porcine molecule and largely distributed in the frog brain. This peptide may play both neurotransmitter and neuroendocrine functions in amphibia.

Animals↗
PubMed1985

Corticoliberin, somatocrinin and amine contents in normal and parkinsonian human hypothalamus.

We have compared hypothalamic contents of various neurotransmitters (dopamine (DA), norepinephrine and serotonin) and their metabolites (dihydroxyphenyl acetic acid, homovanilic acid, 5-hydroxyindoleacetic acid) in post-mortem human controls and parkinsonian hypothalami. Neurotransmitters and their metabolites were measured in 0.1 N HCl hypothalami extracts using electrochemical detection after high performance liquid chromatography. Using specific radioimmunoassays we have also measured corticoliberin and somatocrinin contents in these hypothalami. Despite a 50% decrease of DA contents in parkinsonian hypothalami, no variations of corticoliberin and somatocrinin contents were found: 16.6 +/- 1.78 pg/mg tissue in Parkinson disease vs 16.71 +/- 1.89 in controls for human corticotropin-releasing factor (hCRF 1-41) and 37.38 +/- 11 vs 45.16 for human growth-hormone-releasing factor (hGRF 1-44).

3,4-Dihydroxyphenylacetic Acid↗
PubMed1985

Pro-opiomelanocortin peptides in the human hypothalamus: comparative study between normal subjects and Parkinson patients.

The concentrations of gamma 3-melanotropin-, alpha-melanotropin-, corticotropin-, gamma-lipotropin- and beta-endorphin-immunoreactivities were determined simultaneously, before and after gel exclusion chromatography, in whole hypothalamic extracts of normal subjects and Parkinson patients. All five immunoreactivities were present and were all significantly correlated to each other. Shorter peptides (alpha-melanotropin, gamma 3-melanotropin, beta-endorphin and a lipotropin37-58-like peptide) were the dominant products. Whereas the dopamine content was significantly reduced in Parkinson patients, there was no significant difference for any peptide between normal subjects and Parkinson patients, either in tissue concentrations or in chromatographic patterns.

Adrenocorticotropic Hormone↗
PubMed1985

Relative inhibitory potency of five mineralocorticoid antagonists on aldosterone biosynthesis in vitro.

Spirolactones are mineralocorticoid antagonists which bind to aldosterone receptors in the distal nephron. During the last decade, several antimineralocorticoids, which are more potent than spironolactone in competing for mineralocorticoid receptors have been developed. In the present study, we have compared the direct activity of spironolactone and four related compounds: prorénone (SC 23133), SC 19886, SC 26304 and its carboxylic analog SC 27169, on aldosterone biosynthesis. Two of them (SC 26304 and its carboxylic analog SC 27169) had no effect on adrenal steroidogenesis, even at concentrations up to 10(-3)M. Spironolactone and prorenone (SC 23133) induced a marked but reversible inhibition of aldosterone biosynthesis. SC 19886 totally inhibited aldosterone production and the activity of this compound lasted for more than 7 hours. In addition, SC 19886 and prorenone (SC 23133) totally suppressed ACTH and angiotensin II-induced stimulation of aldosterone biosynthesis whereas SC 27169 was unable to block adrenal response to these corticotropic hormones. Our results suggest that compounds such as prorenone (SC 23133), SC 19886 and spironolactone, which are potent inhibitors of aldosterone biosynthesis could be more active in the treatment of primary aldosteronism than those antimineralocorticoids which are devoid of action on aldosterone biosynthesis.

Adrenocorticotropic Hormone↗
PubMed1985

Immunocytochemical evidence for intragranular processing of pro-opiomelanocortin in the melanotropic cells of the rabbit.

The immunogold technique, employing antisera with clear-cut specificities, was used to localise different processing stages of pro-opiomelanocortin (POMC) in rabbit melanotropic cells. While the antiserum against gamma 3-MSH labelled all the secretory granules including intrasaccular condensations in the Golgi apparatus, antisera against alpha-MSH only labelled extra-Golgi secretory vesicles (SV). All extra-Golgi SV were likewise labelled with the three antisera against alpha-MSH used, despite their different specificities for the deacetylated, N-acetylated or C-amidated forms of the peptide. The antibody against beta-endorphin also labelled the extra-Golgi SV, while only some SV were labelled with the antibody against gamma-endorphin. These results correlate with biochemical data in favour of mainly--if not exclusively--intragranular processing of POMC. Except for gamma 3-MSH, the cleavage of which could coincide with Golgi packaging of secretory material, other post-translational modifications of the precursor seem to occur when SV are discharged outside the Golgi area. The cleavage of gamma-endorphin appears to be a later step in POMC processing, occurring in some mature SV.

Animals↗
PubMed1985

Effect of calcium on corticosteroid secretion by isolated frog interrenal gland.

The direct effect of extracellular calcium concentrations on corticosteroidogenesis has been examined in the frog, using a perifusion system technique. The release of corticosterone and aldosterone in the effluent medium was monitored by specific radioimmunoassays. Increasing concentrations of Ca2+ (from 2 to 15 mM) gave rise to a dose-related stimulation of corticosteroid release, whereas the increment of either Na+ or K+ concentrations did not modify steroid production. Iterative administration of a moderate concentration of calcium (6 mM) led to a reproducible stimulation of steroid secretion whereas the same dose infused during 6 h induced a transient rise in corticosteroid secretion followed by a plateau. The direct effect of Ca2+ on steroidogenesis was confirmed by the dose-dependent stimulation of steroid secretion induced by the calcium ionophore A 23187. Perifusion with a calcium-free medium or blockade of Ca2+ channels by 4 mM Co2+ both resulted in a significant decrease in steroid production. Conversely, the administration of verapamil (up to 10(-4) M) did not affect steroidogenesis. These results provide evidence that extracellular calcium ions are required for basal production of corticosteroids in amphibians and that Ca2+ influx does not occur through voltage-dependent channels. Since, in the frog, blood Ca2+ concentrations vary in a rather large range, these results suggest that circulating Ca2+ levels may regulate corticosteroid production in these animals.

Adrenal Glands↗
PubMed1985

In vitro effect of cytochalasin B on adrenal steroidogenesis in frog.

In order to examine the role of microfilaments in adrenal steroidogenesis, we have studied the effect of cytochalasin B on corticosteroid secretion by frog interrenal tissue in vitro. Perifusion of interrenal fragments with increasing concentrations of cytochalasin B (ranging from 10(-8) to 10(-4) M) led to a dose-related inhibition of corticosterone and aldosterone secretion. Immunohistochemical examination of adrenocortical fragments, using specific anti-actin antibodies, showed that cytochalasin B (5 X 10(-5) M) was responsible for the disappearance of the microfilament network. Administration of 2 consecutive doses of cytochalasin B (5 X 10(-5) M) was responsible for a reproducible and reversible inhibition of corticosteroid secretion. In addition, cytochalasin B (5 X 10(-5) M) totally inhibited the stimulatory effect of angiotensin II, prostaglandin E1 and VIP. It also induced a marked decrease in both ACTH- and dbcAMP-induced stimulation of corticosteroidogenesis. These data indicate that cytochalasin B, which blocked the effect of all adrenal stimulating factors tested, interferes with a late step in the common pathway involved in the response of frog adrenocortical cells to all corticotropic stimuli.

Actin Cytoskeleton↗
PubMed1985

Immunohistochemical localization and radioimmunoassay of corticotropin-releasing factor in the forebrain and hypophysis of the frog Rana ridibunda.

The distribution of immunoreactive corticotropin-releasing hormone (CRF) in the forebrain and pituitary of the frog Rana ridibunda was studied by means of specific radioimmunoassay and immunohistochemistry using the indirect immunofluorescence and the peroxidase-antiperoxidase techniques. Relatively high concentrations of CRF-like material were found in both chiasmatic and infundibular regions of the hypothalamus (352 +/- 11 and 422 +/- 36 pg, respectively). Large amounts of CRF were also found in neurointermediate lobe extracts. Standard curves of synthetic CRF and the dilution curves for hypothalamic or neurointermediate lobe extracts were parallel. After Sephadex G-75 gel filtration, CRF-like immunoreactivity eluted in a single peak, in the same position as synthetic ovine CRF. Reversed-phase high-performance liquid chromatography of the material purified on Sephadex G-75 revealed 5 components with CRF-like immunoreactivity. The major peak had a retention time of 22 min as compared to 25.4 min for ovine CRF and 36 min for rat CRF. The detection of CRF-like immunoreactivity in neurons was facilitated by colchicine pretreatment of the frogs. The great majority of the CRF-positive perikarya were seen in the ventral region of the preoptic nucleus. A few scattered perikarya were also observed in the dorsal preoptic nucleus and in the retrochiasmatic region. Immunoreactive fibers were found in the infundibular nucleus and in various extrahypothalamic zones. CRF-containing neurons were apparently distinct from mesotocinergic and vasotocinergic neurons. A large number of immunoreactive nerve fibers were observed in the median eminence in close contact with the capillaries of the pituitary portal plexus and in the neural lobe. A few CRF-positive fibers were detected in the intermediate lobe, whereas the distal lobe was totally negative. These results show that the diencephalon and pars intermedia-nervosa of the frog contain a peptide immunologically related to mammalian CRF.

Animals↗
PubMed1985

Variations of plasma growth hormone (GH)-releasing factor levels during GH stimulation tests in children.

GH-releasing factor (GHRH) was measured by RIA in the plasma of 22 constitutionally short children given an ornithine infusion or an oral dose of L-dopa. After an overnight fast and 1 h of rest, plasma GHRH levels were 49.7 +/- 7.3 pg/ml (+/- SEM). In 5 children, L-dopa induced an increase in mean GH levels from 1.8 to 12 ng/ml at 60 min. Mean plasma GHRH levels increased from 47 pg/ml to a peak of 96 pg/ml at 15 min (P less than 0.02). In 4 other children, no increase in either GH or GHRH occurred after L-dopa treatment. In these 9 children, a significant correlation was found between the peak GH and GHRH concentrations (r = 0.841; P less than 0.001). On the contrary, ornithine-induced GH release was not preceded by a GHRH rise, but was followed by a GHRH decrease, from 51 to 27 pg/ml (P less than 0.02). We conclude that the 2 tests stimulate GH release in different ways, and that GH levels may be involved in the feedback control of GHRH secretion.

Adolescent↗
PubMed1985

[Role of alpha-MSH and related peptides in the central nervous system].

Alpha-melanocyte stimulating hormone (alpha-MSH) is a tridecapeptide secreted by intermediate lobe cells and synthesized in the brain as well. As a hormonal peptide, the physiological function of alpha-MSH consists mainly in the control of pigment movements within dermal melanophores. At the pituitary level, alpha-MSH secretion is under multifactorial control: it is inhibited by dopamine and GABA and stimulated by corticoliberin (CRF), thyroliberin (TRH), beta-adrenergic agonists and (or) serotonin. Identification of alpha-MSH containing neurons in the hypothalamus and other brain regions (septum, thalamus, mid-brain, striatum, hippocampus, cerebral cortex and spinal cord) has been carried out by means of immunological and biochemical techniques combined with bioassays. In the central nervous system (CNS) as in the hypophysis, alpha-MSH is synthesized from a high molecular weight precursor, pro-opiomelanocortin (POMC). Maturation of this protein yield similar end products in the hypothalamus and the intermediate lobe. Several peptides chemically related to alpha-MSH are generated including the desacetyl and monoacetyl (authentic alpha-MSH) forms; the latter has the greatest behavioral activity. The demonstration that alpha-MSH has numerous central nervous system effects has raised the possibility that this neuropeptide acts as a neuromodulator or a neurotransmitter. In the rat, intra-cerebroventricular administration of ACTH/MSH peptides induces the stretching-yawning syndrome (SYS) which is frequently preceded by excessive grooming. This excessive grooming is blocked by neuroleptics indicating that the central dopaminergic neurons are implicated in this behavioral effect of the peptide. alpha-MSH is involved in memory, arousal and attention; in hypophysectomized animals, the learning ability is restored after administration of MSH or related peptides. Injection of alpha-MSH delays also extinction of passive avoidance behavior and affects performances motivated by hunger as well as aggressive behavior. Recent studies concerning the role of alpha-MSH have been undertaken in human beings. The effects of MSH-related peptides favour a role of these peptides in arousal: they maintain a high level of vigilance and improve visual discrimination. These behavioral changes were accompanied by marked changes in CNS electrophysiology. Current studies, which aim at establishing a neurotransmitter function for alpha-MSH, concern the distribution and characterization of alpha-MSH receptors in the central nervous system and the mechanism controlling the release of neuronal alpha-MSH.

Aggression↗
PubMed1985

[Immunofluorescence localization of corticoliberin neurons in the brain of pigeons].

With immunofluorescence techniques using one anti-rat or two different anti-ovine CRF, the localization of corticotropin-releasing factor (CRF) producing neurons was characterized in frozen sections of pigeon brain. Colchicine was administered intraventricularly at various day hours. The CRF neurons were localized in the telencephalon: lobus parolfactorius, nucleus (n.) accumbens, anterior commissure; in the diencephalon: n. dorso-medialis and lateralis thalami and in different structures of the hypothalamus: n. praeopticus periventricularis and medialis, paraventricularis, supraopticus medialis, lateralis, ectomamillaris and in the stratum cellulare externum. Concerning the hypothalamic localizations, results are discussed in the light of physiological studies on corticotropic regulations in pigeons. Additional populations of CRF neurons were also located in various brainstem areas substantia grisea centralis, locus caeruleus, n. tegmenti dorsalis, sensorius principalis nervi trigemini, vestibularis latetalis, solitarius, nervi hypoglossi, in the dorsal area of the n. pontis lateralis and in the n. paramedianus paragiganto--cellularis, raphes, nervi facialis, subcaeruleus and the area ventralis. These particular localizations may lead to the assumption that CRF might be involved in nervous regulations other than those related to the corticotropic function.

Animals↗
PubMed1985

[Intermediate lobe of the amphibian pituitary gland: an endocrine gland with multiple secretions and under multi-hormonal control].

The cells of the frog pars intermedia synthesize a 36 000 (36K) protein called proopiomelanocortin (POMC). After [3H]glucosamine incorporation, separation of newly synthesized products by SDS-polyacrylamide gel electrophoresis showed that this 36K protein was glycosylated. Tryptic mapping revealed only one site of glycosylation and showed that the carbohydrate side-chain was located in the N-terminal region of POMC. The 36K protein was not released by the melanotrophs, but it generated, through specific intracellular proteolytic cleavage, a number of smaller peptides which were subsequently released. These peptides were identified by various methods including selective amino-acid incorporation, HPLC purification, acid-urea gel electrophoresis, tryptic and chymotryptic mapping, assay of melanotropic activity, radioimmunoassays and immunoprecipitations. Some of the newly synthesized N-terminal (18K) fragment of the POMC was secreted intact while a portion of it was further processed, via an intermediate peptide, to give mature gamma-MSH. All three of these peptides were glycosylated. In addition, the mature peptide (gamma-MSH) exhibited a low but significant melanotropic activity. The C-terminal portion of the prohormone was very rapidly processed to give des N alpha-acetyl alpha-MSH, corticotropin-like-intermediate lobe peptide (CLIP) and beta-endorphin. Authentic alpha-MSH was always absent in cellular extracts: acetylation to give rise to alpha-MSH was a late enzymatic process strictly linked to hormonal release. Since acetylation of alpha-MSH is required for full biological activity of this peptide, it is possible to conceive that this later step could be under neuroendocrine control. Using the perifusion technique we have been able to show the complexity of the control mechanisms regulating amphibian melanotrophs. It is generally accepted that the aminergic innervation of the intermediate lobe of the pituitary is involved in the hypothalamic control of melanotropin release. We have demonstrated that, in amphibians, dopamine inhibits alpha-MSH secretion through D2-type dopaminergic receptors whereas norepinephrine and (or) epinephrine stimulate alpha-MSH secretion via beta-adrenergic receptors. The existence of peptidergic fibers within parenchymal cells of the pars intermedia has been demonstrated. Evidence for TRH-containing fibers has been obtained by immunohistochemistry. Using a specific radioimmunoassay for TRH, we have confirmed the presence of TRH in the neurointermediate lobe of the frog. We have shown that TRH is a powerful MSH-releasing factor in these animals.(ABSTRACT TRUNCATED AT 400 WORDS)

Amphibians↗
PubMed1984

Immunological detection of pro-corticotropin releasing factor (CRF) in rat hypothalamus and pancreatic extracts. Evidence for in vitro conversion into CRF.

Extracts of both rat hypothalamus and pancreas were analyzed for their corticotropin releasing factor (CRF)-like immunoreactivity by radioimmunoassay (RIA). In the case of the hypothalamus, besides the rat CRF, further identified by high-pressure liquid chromatography (HPLC), two peptide components, a 20-kDa and a 10-kDa species were detected. The 20-kDa component was stable under acidic pH conditions and was further purified by reverse-phase HPLC. When exposed to proteolytic activities coeluting with 'high-molecular-mass CRF' at pH 6, processing was observed and the CRF generated was identified both by RIA, molecular sieve filtration and HPLC under different experimental conditions. It is concluded that this 20-kDa CRF may represent the CRF precursor and that hypothalamic extracts may contain processing enzymes involved in its selective post-translational cleavage. In the pancreatic extract two immunoreactive forms of CRF were detected, the smaller coeluting with the rat CRF and the other corresponding to the intermediate 10-kDa component detected in the hypothalamus. Pancreatic rat CRF, analyzed using RIA both by molecular sieve filtration and HPLC, was indistinguishable from the hypothalamic rat CRF.

Animals↗
PubMed1984

In vitro study of frog (Rana ridibunda Pallas) interrenal function by use of a simplified perifusion system. VII. Lack of effect of somatostatin on angiotensin-induced corticosteroid production.

Somatostatin (SRIF), the somatotropin release inhibiting factor of the hypothalamus, has been reported to inhibit the production of angiotensin II (AII)-stimulated aldosterone in the rat adrenal glomerulosa cells. Since the interrenal of the frog is the homolog of mammalian adrenal zona glomerulosa, the effect of synthetic SRIF on perifused dice of Rana ridibunda was tested. Graded doses of SRIF did not modify the spontaneous production of corticosterone and aldosterone. The highest concentration of SRIF (10(-5) M) did not alter the stimulatory effect of the AII agonist [Sar1-Val5] AII upon corticosteroidogenesis. Thus, in apparent contradiction to recent findings in mammals, SRIF did not alter the effect of AII in the frog interrenal cell.

Adrenal Glands↗