Search results for "Methylhistamines"
showing 10 items of 10 documents
External Influences on Invertebrate Brain Histamine and Related Compounds via an Automated Derivatization Method for Capillary Electrophoresis.
2017
8 pages; International audience; Histamine has been shown to modulate visual system and photic behavior in arthropods. However, few methods are available for the direct quantification of histamine and its precursor and metabolites in arthropod brain. In this work, a method for the separation of histamine, its precursor histidine, and its metabolite N-methyl-histamine from brain extracts of a freshwater crustacean has been developed using capillary electrophoresis with laser-induced fluorescence detection. Molecules were tagged on their primary amine function with naphthalene-2,3-dicarboxaldehyde, but derivatized histamine and N-methyl-histamine exhibited poor stability in contrast to deriva…
Effect of histamine and histamine analogues on human isolated myometrial strips.
1992
1. The effect of histamine and histamine H1- and H2-receptor agonists on isolated myometrium strips of premenopausal women has been examined. The effect of acetylcholine was also determined. 2. Histamine, 2-pyridylethylamine, 4-methylhistamine and acetylcholine, but not dimaprit, produced a concentration-related contractile response in human isolated myometrial strips. Histamine also produced a further contraction in human isolated myometrial strips precontracted with KCl (55 mM). 3. The contractile response to histamine was antagonized by the histamine H1-receptor antagonist, clemizole (0.1 microM) but was potentiated by the histamine H2-receptor antagonist, ranitidine (10 microM). Clemizo…
Urinary metabolites of histamine and leukotrienes before and after placebo-controlled challenge with ASA and food additives in chronic urticaria pati…
2002
Background: The recovery of mediator metabolites from urine has the potential to provide a rapid, safe, and easily available index of release of mediators. We aimed to determine urinary metabolites of both histamine and leukotrienes (LTs) in patients affected by chronic urticaria (CU). Methods: Twenty patients with CU were studied. They were selected on the basis of double-blind placebo-controlled challenge (DBPC) with acetyl salicylic acid (ASA) and food additives. Ten patients (group B) were negative to both challenges. Ten patients (group C) presented urticaria and/or the appearance of angioedema during or 24 h after challenge, with reactions to ASA (five patients) or food additives (fiv…
Histaprodifens: synthesis, pharmacological in vitro evaluation, and molecular modeling of a new class of highly active and selective histamine H(1)-r…
2000
A new class of histamine analogues characterized by a 3, 3-diphenylpropyl substituent at the 2-position of the imidazole nucleus has been prepared outgoing from 4,4-diphenylbutyronitrile (4b) via cyclization of the corresponding methyl imidate 5b with 2-oxo-4-phthalimido-1-butyl acetate or 2-oxo-1,4-butandiol in liquid ammonia, followed by standard reactions. The title compounds displayed partial agonism on contractile H(1) receptors of the guinea-pig ileum and endothelium-denuded aorta, respectively, except 10 (histaprodifen; 2-[2-(3, 3-diphenylpropyl)-1H-imidazol-4-yl]ethanamine) which was a full agonist in the ileum assay. While 10 was equipotent with histamine (1), methylhistaprodifen (…
Influence of hormonal treatment on the response of the rat isolated uterus to histamine and histamine receptor agonists.
1992
The response of the isolated uterus to histamine and histamine agonists was investigated in progesterone- and oestrogen-treated rats. The uterine inhibitory responses to histamine and 4-methylhistamine (a histamine H2 receptor agonist) were similar in KCl-contracted uteri from progesterone- and oestrogen-treated rats. The histamine H1 receptor agonist, 2-pyridyl-ethylamine, produced a relaxant response only in progesterone dominant uterus. This was inhibited by the histamine H1 receptor antagonist. In the rat isolated uterus which was not preconstricted by KCl, neither histamine, 4-methylhistamine, nor 2-pyridyl-ethylamine produced any effect in the presence or absence of ranitidine. Raniti…
Histamine inhibits 5-hydroxytryptamine release from the porcine small intestine: Involvement of H3 receptors
1992
Abstract Strips of the porcine small intestine were incubated in vitro, and the release of 5-hydroxytryptamine (5-HT) was determined by high-pressure liquid chromatography with electrochemical detection. Removal of the mucosa resulted in a large reduction (95%) of tissue 5-HT, suggesting that enterochromaffin cells are the main source of 5-HT. The release of 5-HT was reduced by 70% after omission of calcium. Tetrodotoxin and hexamethonium reduced the release of 5-HT by 30%–40% in a nonadditive manner, indicating a spontaneous neuronal (nicotinic) excitatory input to the enterochromaffin cells. Histamine inhibited the release of 5-HT by about 50%. This effect was not affected by mepyramine o…
Responses to histamine and selective H2-receptor agonists in lung parenchymal strips from normal and sensitized guinea-pigs.
1989
Histamine produces concentration-dependent contractions of lung parenchyma strips obtained from normal and sensitized guinea-pigs. The responsiveness of the sensitized lung strips to histamine was significantly increased compared to normal tissues. Clemizole (0.1 microM) was equally effective as an H1-antagonist in normal (dose-ratio 9.12) and sensitized (dose-ratio 9.77) tissues. The concentration-response curves to histamine were displaced to the left by cimetidine (0.1 microM to 0.1 mM) with similar dose-ratios in normal and sensitized tissues. Cimetidine enhanced maximal responses to histamine only in normal lung strips. The effects of submaximal equieffective concentrations of histamin…
Gastric histamine methyltransferase: Different methylation rates for enantiomers of side-chain methylated histamine analogues using a highly purified…
1984
The inhibitor/activator and substrate properties of enantiomers of two methylated histamines (MH) were investigated using a histamine methyltransferase preparation which was purified 1207-fold from pig fundic mucosa by ultracentrifugation, ion-exchange chromatography on DEAE-cellulose and preparative electrofocusing. In 1-100 microM concentrations, S-alpha-MH and R-alpha-MH were acceptor substrates as good as histamine itself. When substrate concentrations were increased to 1 mM these substances were methylated to an even greater extent than histamine, since they did not exert substrate inhibition on HMT. Introduction of a further methyl-group into the N alpha-position reduced acceptor subs…
Pharmacological investigation into the effects of histamine and histamine analogues on guinea-pig and rat colon in vitro.
1986
The effects of histamine and specific histamine agonists has been examined on isolated longitudinal colon strips of guinea-pig and rat. Histamine and 2-pyridyl-ethylamine but not 4 methylhistamine produced a concentration-related contractile response in the guinea-pig colon. The H1-antagonist clemizole antagonized competitively the effect of histamine but the H2-antagonist ranitidine did not modify the dose-response curve to histamine in the guinea-pig colon. Atropine, hexamethonium, prazosin and propranolol failed to modify the contractile response to histamine. Tone induced with KCl in guinea-pig isolated colon was not modified by histamine agonists even in tissues pretreated with clemizo…
Histamine-sensitive adenylate cyclase of human gastric mucosa: a model for H2-receptor excitation.
1978
Recent studies revealed that human gastric mucosa contains a histamine-sensitive adenylate cyclase which is almost completely localized within the acid-secreting area of the stomach. In an attempt to further characterize the effector system of histamine’s action, we compared the effects of H 1 — and H 2-receptor agonists upon the adenylate cyclase in human fundic gastric mucosa.