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Different mechanisms are responsible for the contractile effects of histaminergic compounds on isolated intestinal smooth muscle cells
No full textThe effects of histamine and dimaprit on intestinal smooth muscle contractility were investigated on isolated cells from longitudinal muscle of the guinea pig ileum. Both histamine (10(-14)-10(-10) M) and dimaprit (10(-13)-10(-10) M) exerted a concentration-dependent contraction of intestinal cells, causing a maximum decrease in cell length of about 20%. This effect was not significantly different from that induced by cholecystokinin-octapeptide (CCK-8) 10(-9) M. The concentration-response curves to histamine and dimaprit were shifted to the left in the presence of the histamine H-2-receptor antagonist famotidine (10(-7) M) indicating the occurrence in the smooth muscle of H-2 receptors mediating relaxation. Whereas the contraction produced by histamine was competitively antagonized by the HI receptor antagonist mepyramine (10(-8) M), neither mepyramine (10(-7) M) nor temelastine (10(-7) M) did modify the contractile effect of dimaprit. In contrast, atropine (10(-8) M) significantly depressed the maximum response to dimaprit without affecting that exerted by histamine. These data indicate that histamine and dimaprit can modify intestinal contractility, by acting via different mechanisms; while the contractile action of histamine is related to H-1 receptor activation, that produced by dimaprit involves cholinergic pathways
Comparison of the protective effect of (R)-alpha-methylhistamine and its prodrugs on gastric mucosal damage induced by ethanol in the rat
No full text1. The gastroprotective activity of two azomethine prodrugs of (R)-alpha-methylhistamine was examined in lesions induced by absolute ethanol (1 ml/rat intragastrically for 1 h).
2. Pretreatment with (R)-alpha-methylhistamine as well as with the prodrugs (30 and 100 mg/kg intragastrically [IG]) significantly reduced macroscopically visible lesions caused by ethanol, with protection being almost complete at 100 mg/kg.
3. Histologically, in rats pretreated with the three compounds ata dose of 100 mg/kg, the evidence of ; damage was rare, with the appearance of gastric mucosa being similar in the different treatment groups.
4. Present results are suggestive of a local component in the protective activity of (R)-alpha-methylhistamin
The effects of stimulants and inhibitors of histamine receptors on acid secretion from guinea pig gastric fundus
No full textTwo selective H2 receptor stimulants (5-methyl-N-methylhistamine and dimaprit) so far never tested in isolated gastric preparations, were found to be strong stimulants of acid secretion from the guinea pig isolated gastric fundus. Although some differences were observed in the cumulative dose-response curves for these two agonists, the peak responses obtained were not significantly different from the maximum response to histamine. Cimetidine produced parallel displacement of the dose-response curves to the right with the maximum response unchanged, suggesting competitive antagonism on H2 receptors. The dose-response curve for histamine was not affected by the simultaneous administration of an H1 receptor agonist, 2(2-aminoethyl)thiazole, or of an H1 receptor antagonist, pyrilamine. This indicates that the action of histamine on the isolated guinea pig gastric fundus is associated exclusively with H2 receptor stimulation
Contractile and relaxant effects of dimaprit on guinea pig isolated intestinal cells
No full textThe effect of the histamine H-2 receptor agonist dimaprit on intestinal contractility was characterized on smooth muscle cells isolated from the longitudinal muscle of the guinea pig ileum. Dimaprit exerted two opposite effects on the contractility of isolated muscle cells. relaxation of cholecystokinin octapeptide (CCK-8)-induced contractions in the range of concentrations 10(-17)-10(-13) M and contraction at concentrations higher than 10(-13) M. The relaxant effect of dimaprit was totally prevented by the H-2 blocker famotidine (10(-7) M), which, at the same time, enhanced the contractile effect of dimaprit, shifting to the left the concentration-response curve to the agonist. This contraction was not modified by the histamine H-1 receptor antagonists pyrilamine and temelastine, tested both at 10(-7) M. By contrast, atropine 10(-8) M abolished the contractile effect of dimaprit, while leaving unchanged the response to CCK-8. Our results clearly indicate that longitudinal muscle cells of the guinea pig ileum possess inhibitory H-2 receptors, which can be activated by very low concentrations of dimaprit; moreover, they revealed that dimaprit can have non-histaminergic effects, probably due to muscarinic receptor activation; however, concentrations about 10000 times higher than those necessary to activate Hz receptors,are require
Stimulation of gastric acid secretion by (R)-alpha-methylhistamine in the rat: influence of the increased gastric juice volume on ethanol-induced lesions.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Gastroprotective activity of the novel proton pump inhibitor lansoprazole in the rat
No full text1. The protective activity of lansoprazole was evaluated on gastric mucosal lesions induced by intragastric 25% NaCl (1 ml/rat for 1 hr) and by indomethacin (20 mg/kg for 6 hr) in the rat and compared with that of omeprazole.
2. Lansoprazole (3, 10 and 30 mu mol/kg i.g.) dose-dependently prevented the formation of indomethacin-induced lesions, the inhibition being 99% at the highest dose. Omeprazole, 10 mu mol/kg i.g., enhanced the damage by indomethacin while higher doses caused a reduction, lesion index being reduced by 98% at 100 mu mol/kg.
3. Histologically in lansoprazole- as well as in omeprazole-pretreated rats, indomethacin-induced necrosis of the mucosa was absent, luminal epithelium being intact.
4. Lansoprazole (30, 100 and 300 mu mol/kg) and omeprazole (30, 100 and 300 mu mol/kg) dose dependently reduced the formation of lesions by hypertonic saline.
5. Present results indicate that lansoprazole and omeprazole protect the gastric mucosa in different experimental models of gastric ulceration
Are histamine receptors involved in the gastroprotection evoked by (R)-alpha-Methylhistamine?
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