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Biomedical subjects

J M Launay

Publications and source records attributed to J M Launay.

At least 163 records · Page 9Linked to original sources
PubMed1988

Melatonin biosynthesis in Drosophila: its nature and its effects.

Drosophila melanogaster homogenates incubated with tritiated 5-hydroxytryptophan, 5-hydroxytryptamine, or N-acetylserotonin have the ability of converting them into labelled indolamines, including melatonin. All these compounds were characterized by two-dimensional thin-layer chromatography by comparison with nonradiolabelled standards, and melatonin by mass spectrometry and radioimmunoassay. On the other hand, the injection of pharmacological doses of melatonin into 2-day-old female flies diminishes the mating speed and the oviposition rate.

5-Hydroxytryptophan↗
PubMed1988

Serotonin metabolism and other biochemical parameters in infantile autism. A controlled study of 22 autistic children.

The serotonin metabolism was extensively studied in 22 couples of autistic children and age- and sex-matched controls. Histamine, calcium, and uric acid were also measured in urine and whole blood or plasma. Autistics and controls did not differ in histamine, and only minor changes were noticed in calcium content. According to previous reports, serotonin levels were often, but not always, elevated in the blood of autistic children. Based on data including urinary serotonin and 5-hydroxyindoleacetic acid, platelet serotonin uptake and efflux, platelet monoamine oxidase and glutathione peroxidase activities, and uric acid and plasma tryptophan, the origin(s) of such hyperserotonemia in autism appear(s) to be of metabolic origin, i.e., a decreased catabolism and/or an increased biosynthesis of serotonin.

Adolescent↗
PubMed1988

Circulating monoamine oxidase B and phenolsulfotransferase activities in essential hypertensive patients.

Circulating monoamine oxidase (MAO) and phenolsulfotransferase M and P (PST M, PST P) activities were determined in 24 untreated essential hypertensive patients and in 35 age-matched normotensive healthy controls. These enzymes are involved in the inactivation of monoamines and their metabolites. After lysis of blood, enzymatic activities were determined by radioenzymatic techniques using as substrates [14C]-beta-phenylethylamine for MAO, 3-methoxy-4-hydroxyphenylglycol for PST M and phenol for PST P. MAO activity measured by this method is fully accounted for by platelet MAO B activity. Women presented higher MAO activity than men. Significantly lower MAO-B activities were observed in hypertensive patients, both in men and in women, when compared to normotensive controls. Circulating PST activities, of which more than 80% is platelet-derived, were similar in hypertensive and normotensive subjects. These data suggest that the intracellular serotonin inactivation processes, through MAO and PST, cannot account for the reduction of platelet 5-HT content observed in essential hypertension.

Adult↗
PubMed1987

V1a-vasopressin specific receptors on human platelets: potentiation by ADP and epinephrine and evidence for homologous down-regulation.

Using very specific vasopressin (VP) analogues, the human platelet VP receptor was characterized as a V1a rather than a V1b receptor, on the basis of the effect of the analogues on shape-change and aggregation. The platelet VP binding sites appeared to be subject to homologous down-regulation by plasma VP, in view of the inverse correlation found between the maximal capacity of binding of tritiated VP to platelets and the immunoreactive VP concentration in poor platelet plasma from the same individual. Aggregating effect of VP on human platelets was potentiated by both ADP and epinephrine. In addition, VP was able to release serotonin from human platelets, but only at high concentration.

Adenosine Diphosphate↗
PubMed1987

Hermansky-Pudlak platelets: further studies on release reaction and protein phosphorylations.

Platelets from a patient with the Hermansky-Pudlak syndrome were studied. These platelets had decreased amounts of serotonin and adenine nucleotides, and a decreased number of mepacrine-labeled dense bodies. beta-Thromboglobulin and acid hydrolases contained in alpha-granules and lysosomes respectively were present in normal amount. Platelets in platelet-rich plasma did not respond to collagen, but arachidonic acid and ionophore A 23187 induced normal aggregation and normal thromboxane (TX) synthesis. Alpha-granule release was found impaired and remained subnormal even with high doses of inducers. In response to thrombin aggregation, release and TX synthesis of isolated metrizamide gradient platelets were found at lower than normal levels. Phosphorylation of P20 and P43 proteins was normal. Only a combination of ADP plus thrombin could restore a normal aggregation, with normal alpha-granule and lysosome release and normal TX synthesis. These results indicated that in the absence of dense bodies: the release of other granules is impaired; the TX synthesis is delayed except when induced by arachidonic acid and A 23187 ionophore; the absence of dense bodies could be compensated for by the addition of ADP which restores the impaired release reaction and TX formation; and P20 and P43 polypeptides were phosphorylated as rapidly as those in normal platelets.

Adenine Nucleotides↗
PubMed1987

Up- and down-regulation of membrane receptors as possible mechanisms related to the antiulcer actions of milk in rat gastric mucosa.

The effects of a cow's milk diet on receptor activity and histamine metabolism in gastric glands and mucosa isolated from adult rats were examined. The milk diet was associated with (1) a decreased mobilization of H2 receptors by histamine and (2) an increased mobilization of PGE2 (prostaglandin E2) receptors in mucous cells (cytoprotective effect) and parietal cells (antiacid effect). These changes are not observed for the receptors reducing pentagastrin- and histamine-induced gastric acid secretion (pancreatic/enteroglucagons, somatostatin) and stimulating mucus, bicarbonate and pepsin secretions in the rat (secretin). Cimetidine produced a parallel displacement of the histamine dose-response curve, suggesting competitive inhibition between this classical H2 receptor antagonist and histamine in the two experimental groups. Prostaglandins and other components in milk such as EGF (epidermal growth factor) and somatostatin might therefore protect gastric mucosa by a differential control of PGE2 and histamine H2 receptor activity either directly (PGE2 in milk) or indirectly (inhibition of endogenous histamine synthesis/release and stimulation of PGE-I synthesis/release).

Animals↗
PubMed1987

Catecholamines metabolism in infantile autism: a controlled study of 22 autistic children.

In a group of 22 autistic children aged 5 to 16 years and a group of normal controls matched for age and sex, catecholamines metabolism was investigated in plasma, platelets, and urine. This investigation was part of a research project in which several biological parameters (including serotonin) were explored simultaneously in the same children. In the autistic group, epinephrine and norepinephrine were significantly elevated in plasma, while epinephrin, norepinephrine, and dopamine were significantly lower in isolated platelets. No significant difference was found between the two groups for the urinary excretion of epinephrine, norepinephrine, dopamine, DOPAC, and MHPG. Other differences between the two groups in the statistical correlations of several biochemical parameters also suggest abnormalities of bioamine metabolism in the platelets of autistic children.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1987

Whole blood and plasma histamine in common migraine.

Whole blood and plasma histamine levels were measured in 27 non-medicated patients with common migraine. In nine cases blood was drawn 1-2 h after the onset of a migraine attack. The whole blood histamine levels of migraineurs and controls did not differ significantly. In contrast, histamine levels were significantly increased in plasma from patients both during and between migraine attacks, as compared with controls (p less than 0.001). Finally, plasma taken from migraine patients induced a significantly greater release of histamine from control whole blood than did plasma taken from control subjects (p less than 0.01).

Adolescent↗
PubMed1987

[Blood phenolsulfotransferase and monoamine oxidase-B activity in essential arterial hypertension].

Circulating phenolsulfotransferase M and P and monoamine oxidase activities were determined in 18 untreated essential hypertensive patients and in 35 normotensive healthy controls. Phenolsulfotransferase M is involved in the sulfoconjugation of catecholamines and their metabolites while PST P preferentially sulfates phenolic substrates. After lysis of whole blood, enzymatic activities were determined by radioenzymatic techniques using as substrates 3-methoxy-4-phenoxyphenylglycol for PST M, phenol for PST P and [14C] beta-phenylethylamine for MAO. Blood MAO activity measured by this method is fully accounted for by platelet MAO-B activity. Concerning blood PST activities, no significant difference was found in hypertensive patients compared to normotensive controls (PST M: 1.69 +/- 0.17 versus 1.66 +/- 0.08 nmoles of MHPG-sulfate/ml of blood/hour; PST P: 0.36 +/- 0.05 versus 0.27 +/- 0.04 nmoles of phenol-sulfate/ml of blood/hour). MAO activity was higher in women than in men. Significantly lower MAO B activities were observed in hypertensive patients both in men (19.25 +/- 2.20, n = 8 versus 24.35 +/- 2.22, n = 14, desaminated beta-phenyl-ethylamine/10(9) platelets/hour, x +/- SEM, p less than 0.05) and in women (23.92 +/- 2.74, n = 10 versus 35.76 +/- 2.35, n = 21, p less than 0.01) when compared to normotensive controls of the same sex. Recent in vitro studies have suggested that a reduction in platelet MAO B activity may be induced by an alteration in the phospholipidic and/or calcium environment of the enzyme. Low MAO activity in other tissues such as liver or vascular endothelium could contribute to the high sympathetic tone observed in these patients.

Arylsulfotransferase↗
PubMed1986

Nature and properties of human platelet vasopressin receptors.

The binding of 3H-labelled [8-arginine]vasopressin to human platelets or crude platelet membranes was examined. Both preparations specifically bound [8-arginine]vasopressin. The binding increased linearly with protein concentration, it was temperature- and time-dependent, saturable and could be reversed to a large extent by EDTA (10 mM). In this latter case, addition of an excess of MgCl2 (20 mM) restored the initial level of binding. Intact platelets and membranes derived from these platelets presented a single population of binding sites with a dissociation constant (Kd) of 1.3 +/- 0.2 and 1.8 +/- 0.3 nM and a maximal binding capacity of 142 +/- 48 and 270 +/- 17 fmol/mg of protein, respectively. The Kd values of various analogues correlated well with those determined on rat liver membrane V1 vasopressin receptors but not with those determined on rat kidney membrane V2 receptors.

Arginine Vasopressin↗
PubMed1986

Biochemical and pharmacological characterization of histamine-mediated up-regulation of human platelet serotonin uptake. Evidence for a subclass of histamine H2 receptors (H2h) highly sensitive to H2 receptor antagonists.

The stimulatory effect of histamine: H (1.2 to 3-fold increase) on serotonin (5-HT) uptake by human platelets was observed after a 5 min incubation period in the presence of 2.5 X 10(-7) M histamine, followed by subsequent 5 min incubation of the platelets with 10(-7) M [3H] 5-HT. Methyl, ethyl and acetyl substituents in the side chain of H mimicked the stimulatory effect of H. In contrast, H analogs methylated at the position N-1 of the imidazole ring of H, as well as imidazole and histidine inhibited platelet 5-HT uptake. The cAMP-inducing agents forskolin and theophylline have no effect on 5-HT uptake when they are tested alone or in combinations with H. In contrast, the cGMP-inducing agent sodium nitroprusside (10(-7) M-10(-6) M) stimulated and potentiated H-mediated up-regulation of 5-HT uptake. Histamine H2 receptor agonists and antagonists are more potent than drugs acting on H1 receptors (H2 greater than H1). However, the inhibition constants Ki are not consistent with those determined for typical H1, H2, H3 receptors characterized in other tissues. This findings provide further evidence for the existence of multiple forms of H receptors and suggest the involvement of a subpopulation of H2 receptors, highly sensitive to H2 receptor antagonists (H2h), mediating 5-HT uptake in human platelets.

Blood Platelets↗
PubMed1986

Histamine H2 receptor activity and histamine metabolism in human U-937 monocyte-like cells and human peripheral monocytes.

Functional and specific histamine H2 receptors were characterized in human peripheral monocytes and in U-937 cells, before and after retinoic acid--induced differentiation into monocyte/macrophage-like cells. The relative potencies of histamine and the H1, H2 receptor agonists and antagonists studied are remarkably similar in U-937 cells and U-937 monocytes. There is no change in histamine concentration and activity of the enzymes forming and degrading histamine during monocytic-like differentiation. The results raise the possibility that histamine H2 receptors might be involved in pathophysiological regulations (proliferation/differentiation and biological function) of normal and leukemic monocytes.

Adult↗
PubMed1985

[Common migraine. Changes in conjugated and unconjugated catecholamines].

Plasma levels of conjugated and unconjugated catecholamines were measured in 27 migraineurs between attacks, in 9 migraineurs 1 to 2 hours after the onset of an attack, and in 30 controls. There were no significant changes in conjugated catecholamines; in contrast, a significant rise (p less than 0.01; KS test) in unconjugated dopamine, noradrenaline and adrenaline levels was observed during attacks. These results confirm that migrainous attacks are associated with platelet activation and with overactivity of the sympathetic system.

Adolescent↗
PubMed1985

Simultaneous determination of histamine and N alpha-methylhistamine in biological samples by an improved enzymatic single isotope assay.

A modified highly sensitive and specific radioenzymatic assay for the simultaneous determination of histamine (HA) and N alpha-methylhistamine (N alpha-MH) in tissues and body fluids is described. In the presence of the enzyme histamine-N-methyltransferase and of the methyl donor [3H]-S-adenosylmethionine, the transmethylation process was about seven times more effective for HA than for N alpha-MH. In the same conditions only very low amounts of N alpha, N alpha-dimethylhistamine (N alpha, N alpha-DMH) were converted into its 1-methylated derivative. The high degree of specificity attained by this method is due to the rapid quantitative extraction of the biological fluids, to the partially purified enzyme preparation and to the thin-layer chromatography system used which allows an excellent separation of the 3H-1-methyl products of HA, N alpha-MH and N alpha, N alpha-DMH. This method is highly sensitive for the assay of HA and N alpha-MH (detection limit 10 and 50 picograms, respectively), but due to lack in sensitivity, it cannot be extended to the measurement of N alpha, N alpha-DMH. The HA content of 20-30 samples can be determined in duplicate by one person in a working day. The concentrations of HA measured by this method in different biological samples (human whole blood, plasma, urine, gastric juice and skin biopsies) were in good agreement with the values reported in the literature. The presence of minute amounts of N alpha-MH in the human gastric juice was established by rigorous checking.

Body Fluids↗