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H Vaudry

Publications and source records attributed to H Vaudry.

At least 541 records · Page 30Linked to original sources
PubMed1983

Catecholaminergic control of alpha-melanocyte-stimulating hormone (alpha MSH) release by frog neurointermediate lobe in vitro: evidence for direct stimulation of alpha MSH release by thyrotropin-releasing hormone.

The role of dopaminergic and adrenergic innervation of the intermediate lobe of amphibian pituitary in the release of alpha MSH has been studied in vitro. Neurointermediate lobes of frog (Rana ridibunda Pallas) have been perifused in amphibian culture medium (ACM) for 5-7 h. alpha MSH released in the effluent perifusate was measured by means of a sensitive and specific RIA. No significant morphological alteration of neurointermediate lobe cells was observed during the perifusion experiment, even at the electron microscopic level. The existence of dopaminergic receptors, responsible for an inhibition of frog melanotrophs, was shown using the dopaminergic agonists apomorphine (10(-6) M) and bromo-2-ergocryptine (10(-8) and 10(-7) M), which initiated a marked reduction of alpha MSH secretion. The effect of apomorphine was obliterated by the dopaminergic antagonist haloperidol. Haloperidol itself induced a dose-related stimulation, and the monoamine oxidase inhibitor nialamide (4 x 10(-3) M) inhibited alpha MSH secretion. In addition, haloperidol led to a complete reversal of the inhibitory effect of nialamide on alpha MSH secretion. These results demonstrate the existence, in the parenchyme of the intermediate lobe, of dopaminergic nerve fibers that are functionally active. The beta-adrenergic agonist isoproterenol was responsible for a dose-related stimulation of alpha MSH secretion; the stimulatory effect was reversed by the beta-adrenergic antagonist propranolol. TRH is a potent stimulator of alpha MSH secretion in amphibians. Since haloperidol and propranolol did not abolish the stimulation of alpha MSH release induced by TRH, it appeared that TRH action was not mediated via an inhibition of dopamine release or via a stimulation of adrenergic nerve fibers.

Animals↗
PubMed1983

Characterization of immunoreactive proopiomelanocortin-related peptides in rat testes.

alpha-Endorphin, beta-endorphin, gamma-endorphin, and N-terminal ACTH immunoreactivity were detectable in acid extracts of rat testes with concentrations of 0.07 +/- 0.01, 0.18 +/- 0.03, 0.06 +/- 0.01, and 0.33 +/- 0.08 (+/- SD) pmol/g wet wt, respectively. The forms of these immunoreactive peptides were characterized by reverse phase high performance liquid chromatography. Immunoreactive beta-endorphin was also analyzed by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The results indicated that the major form of immunoreactive beta-endorphin present appears to be beta-endorphin-(1-31). No alpha-N-acetylated forms of beta-endorphin or beta-lipotropin-sized material were detected. Immunoreactive alpha- and gamma-endorphin appear to be present as alpha-endorphin and des-Tyr1-gamma-endorphin, respectively. Immunoreactive alpha MSH was present as its desacetylated form. No immunoreactive ACTH fractionating with ACTH-(1-39) or its glycosylated forms was detected. This peptide profile is most similar to that seen for proopiomelanocortin-derived peptides in the brain. The low concentrations of these peptides in rat testes suggest a paracrine function.

Adrenocorticotropic Hormone↗
PubMed1983

[Direct action of mineralocorticoid antagonists on biosynthesis of aldosterone: comparative activities of several new compounds].

Spironolactone is a diuretic steroid which is capable of blocking the binding of aldosterone to its cytosol receptor at the distal convoluted tubule. In addition, it has been shown that spironolactone is a strong inhibitor of steroidogenesis. More recently, new aldosterone antagonists have been discovered. Some of these compounds are more active than spironolactone in competing with aldosterone and have higher specificity for mineralocorticoid receptors. In this study we compare the direct activity of new antimineralocorticoids (SC 23133, SC 19886, SC 26304, and SC 27169) on aldosterone biosynthesis. Marked differences were found in the activity of these compounds upon steroidogenesis. SC 23133 gave rise to a strong inhibiting activity (90%). This activity was reversible (recovery of spontaneous production occurs 150 min after the end of the administration of SC 23133). SC 19886 totally inhibited aldosterone biosynthesis (95%) in a lasting mean. Conversely, SC 27169 and SC 26304 presented no or weak inhibiting effect. Further experiments showed that SC 27169 was unable to block the stimulation of aldosterone biosynthesis induced by corticotropic peptides, whereas the administration of SC 23133 and SC 19886 totally suppressed the stimulatory effect of ACTH and angiotensin II. Owing to the important stimulation of the renin-angiotensin system induced by antimineralocorticoid treatment, these results suggest that SC 23133 and SC 19886 will exert a higher antinatriuretic activity than SC 27169.

Adrenocorticotropic Hormone↗
PubMed1982

Further studies on the identification of neurons containing immunoreactive alpha-melanocyte-stimulating hormone (alpha-MSH) in the rat brain.

In order to identify more accurately the organelles containing immunoreactive alpha-melanocyte-stimulating hormone (alpha-MSH) in the rat brain, attempts were made to improve the ultrastructural preservation of the neural tissue used for immunostaining of the peptide. With the post-embedding staining technique, the quality of the preservation was not adequate since only low concentrations (0.2-0.5%) of OsO4 could be used for postfixation. Higher concentrations of OsO4 completely destroyed the antigenicity of alpha-MSH. With the pre-embedding technique in which the immunostaining is performed prior to postfixation with OsO4, a good preservation could be obtained making possible the identification of organelles and classification of endings containing immunoreactive alpha-MSH. In the dendrites, the staining was rather diffuse without any clear association with organelles. In the endings, the staining was mostly restricted to dense core vesicles with some degree of diffusion in the cytoplasm. None of the positive endings were seen making synaptic contact. These results support the hypothesis that alpha-MSH could be released in sites other than the classical synaptic junction and act as a local hormone.

Animals↗
PubMed1982

Effect of aldosterone antagonists on mineralocorticoid synthesis in vitro. Inhibition of aldosterone production by prorenoate-K.

A perifusion technique using frog adrenal glands has been applied to investigate the effects of long-term administration of a new aldosterone antagonist (potassium prorenoate; SC 23992) on mineralocorticoid production. Whatever the duration of administration of potassium prorenoate, at a constant concentration of 5 X 10(-4) M, a significant inhibition of aldosterone output occurred during the passage of the compound. The inhibition was immediate (lag period less than 10 min); the amplitude of the inhibition was constant during the whole experiment and ranged from 77 to 89%; the aldosterone output returned to a regular basal value 80-100 min after the end of infusion of potassium prorenoate. We have also investigated the effect of a concentration gradient of potassium prorenoate (similar to the concentration gradient of aldosterone antagonist observed in plasma after a single oral administration of the molecule) upon aldosterone production over 12 h. From this study, we have established the existence of a highly significant correlation between the extent of the inhibition of aldosterone production and the concentration of the aldosterone antagonist. Finally we have observed that potassium prorenoate blocked the stimulation of aldosterone secretion induced by synthetic ACTH and significantly reduced the angiotensin-induced aldosterone stimulation. The present results indicate that, besides the well-known competitive inhibition of aldosterone binding exerted by potassium prorenoate at the renal receptor site, a direct inhibition of aldosterone biosynthesis also accounts for the pharmacological activity of this aldosterone antagonist.

Adrenocorticotropic Hormone↗
PubMed1982

Interrelations between binding affinity and metabolic clearance rate for the main corticosteroids in the rabbit.

In the rabbit, the metabolic clearance rate (MCR) was found to be higher for corticosterone than for cortisol. At the same time corticosterone, aldosterone and 11-dehydrocorticosterone showed similar MCR while cortisone ranged at intermediate levels between cortisol and corticosterone. The relative binding affinity of transcortin to the corticosteroids, as calculated by an in vitro technique, decreased progressively from cortisol, to cortisone, then to corticosterone, then 11-dehydrocorticosterone and, finally to aldosterone. The occurrence of antibodies in plasma, induced against aldosterone, corticosterone or even cortisone resulted in a marked decrease in the MCR of the corresponding steroid, to the level measured in controls for cortisol. We deduced that, in rabbits: (1) the MCR of a corticosteroid is clearly connected with its binding to a specific protein; (2) in spite of the relatively high binding affinity of transcortin for corticosterone as compared to other species it nevertheless appears unable to significantly protect the steroid against peripheral metabolism; (3) a very effective protection is however, induced, by raising a specific antibody with a high binding affinity for corticosterone.

Adrenal Cortex Hormones↗
PubMed1981

Effect of hypophysectomy and pituitary stalk transection on alpha-melanocyte-stimulating hormone-like immunoreactivity in the brain of the frog, Rana ridibunda Pallas.

The existence of an alpha-MSH-like molecule in the frog brain led us to investigate the role of the pituitary gland in the maintenance of the alpha-MSH content in 3 different regions of the brain. Acetic acid extracts of hypothalamus, rhombencephalon and telencephalon were analyzed by means of a highly specific radioimmunoassay for alpha-MSH in normal, sham-operated, pituitary disconnected and hypophysectomized frogs. Transection of the pituitary stalk gave rise to a significant decrease in alpha-MSH content in the intermediate lobe of the pituitary gland (-71% after 3 days), but did not affect alpha-MSH content in the distal lobe or in the brain. Eight days after total hypophysectomy, an alpha-MSH immunoreactive compound, co-eluting with synthetic alpha-MSH on Sephadex G-25, was found in the 3 brain regions studied. Removal of the whole pituitary gland did not significantly modify alpha-MSH content in the hypothalamus and the telencephalon. A slight increase in alpha-MSH was even observed in the rhombencephalon of hypophysectomized animals. Furthermore, no modification in alpha-MSH immunoreactivity occurred in any region of hypophysectomized animals. These results demonstrate the existence of alpha-MSH-like material in the brain of Rana ridibunda and establish that brain alpha-MSH in the frog is not of pituitary origin.

Animals↗
PubMed1981

Differential projections of two immunoreactive alpha-melanocyte stimulating hormone (alpha-MSH) neuronal systems in the rat brain.

Immunocytochemical localization of alpha-MSH was performed in the brain of rats of which the arcuate nucleus has been destroyed by treatment with monosodium glutamate in the neonatal period. In these animals, alpha-MSH cell bodies normally found in the arcuate nucleus were almost completely absent. The reactive fibers found in the ACTH-beta-LPH pathway were also markedly decreased. On the other hand, alpha-MSH cell bodies located in the dorsolateral hypothalamus as well as fibers located outside the ACTH-beta-LPH pathway were not decreased. These results strongly suggest that alpha-MSH cell bodies in dorsolateral hypothalamus have projections completely different from those located in the arcuate nucleus.

Animals↗
PubMed1981

Stimulatory effect of prostaglandin E1 on thyroliberin-induced alpha-melanotropin release from perifused neuro-intermediate lobes of frog pituitary gland.

A possible direct effect of prostaglandins on alpha-melanotropin (alpha-MSH) release at the level of the intermediate lobe of the frog pituitary was investigated in vitro using a perifusion system technique. The effect of prostaglandins was studied on both spontaneous and TRH-stimulated alpha-MSH secretion. No significant effect of PGE1, PGE2, PGF1 alpha or PGF2 alpha on basal release of alpha-MSH could be detected. Indomethacin did not alter the alpha-MSH release induced by TRH. Conversely a significant increase in TRH-induced alpha-MSH secretion was observed in the presence of 1 x 10(-6) M PGE1. This magnifying effect was directly related to the concentration of TRH for doses ranging from 1 x 10(-8) M to 1 x 10(-6) M.

Animals↗
PubMed1981

The Mr 80,000 common forms of neurophysin and vasopressin from bovine neurohypophysis have corticotropin- and beta-endorphin-like sequences and liberate by proteolysis biologically active corticotropin.

We have tested the hypothesis that the high M(r) forms common to both neurophysin and vasopressin detected in bovine neurohypophysis extracts (Nicolas, P., Camier, M., Lauber, M., Masse, M.-J. O., Möhring, J. & Cohen, P. (1980) Proc. Natl. Acad. Sci. USA 77, 2587-2591) might also contain the sequences of other known neuropeptides. The following evidence indicates that corticotropin- and beta-endorphin-like sequences are associated with similar high M(r) forms and are included in these M(r) 80,000 molecules. During the fractionation steps of high M(r) material, both corticotropin and beta-endorphin immunoreactive species were found to coelute with the neurophysin and vasopressin ones, either under M(r) 140,000 (in 0.1 M formic acid) or M(r) 70,000-80,000 (in 6 M guanidine) elution volumes. Corticotropin immunoreactivity was found to cofocus at pIs 6.05 and 5.8 with the M(r) 80,000 neurophysin-containing species. This material was submitted to affinity chromatography on purified anti-neurophysin antibodies covalently attached to Sepharose 4B. Both the corticotropin and beta-endorphin immunoreactivities, together with the neurophysin and vasopressin immunoreactivities, were retained on the immunoadsorbent and codesorbed by either a drastic pH change or by selective displacement with an excess of neurophysin. Comparison of the tryptic-digest maps of either the M(r) 68,000 fragment immunoprecipitated by anti-corticotropin antibodies or the M(r) 68,000 fragment released after precipitation of the M(r) 80,000 species by anti-neurophysin antibodies indicated large sequence homologies. Exposure of either the M(r) 80,000 or 68,000 components to mild proteolytic activities resulted in the formation of lower-size fragments. The resulting corticotropin-like immunoreactive material, recovered under the elution volume of standard (125)I-labeled corticotropin-(1-24), was tested for its ability to activate glucocorticoid biogenesis by the amphibian interrenal tissue (adrenal) in perifusion. It was found to exhibit a noticeable activity qualitatively undistinguishable from the one of the reference human corticotropin-(1-39). The name neurohypophyseal "coenophorin" (from the Greek word for common) is proposed for this class of M(r) 80,000 polypeptides that might represent the common precursor store-house for a set of neuropeptides produced in the hypothalamo-neurohypophyseal tract.

Adrenal Glands↗