Search results for "Grammar"
showing 10 items of 662 documents
Effects of Ca2+ channel antagonists in guinea-pig normal and skinned gall bladder.
1993
CaCl2 (0.01-50 mM, in K(+)-depolarized tissues), KCl (0.1-100 mM) and acetylcholine (1 nM-10 mM) produced concentration-dependent contractions of guinea-pig isolated gall bladder. Nifedipine (1-100 microM), verapamil (1-100 microM), diltiazem (1-100 microM), cinnarizine (1-100 microM), and flunarizine (1-100 microM) each produced a concentration-related inhibition of the log concentration-effect curve for CaCl2. The rank order of potencies of these antagonists, measured as the IC50 against Ca2+ (50 mM)-induced contraction of depolarized gall bladder, was diltiazem (0.25 microM)or = verapamil (0.8 microM) approximately nifedipine (1.2 microM)cinnarizine (25 microM) approximately flunarizine …
Influence of nitric oxide on neurogenic contraction and relaxation of the human gastroepiploic artery.
2003
Abstract Background The objective of this study was to characterize the neurogenic contraction and relaxation of the human gastroepiploic artery and to determine whether the responses are mediated by nitric oxide (NO) from neural or endothelial origin. Methods Rings of human gastroepiploic artery were obtained from 18 patients (12 men, 6 women) undergoing gastrectomy. The rings were suspended in organ baths for isometric recording of tension. We studied the contractile and relaxant responses to electrical field stimulation. Results In arteries under resting conditions, electrical field stimulation (2 to 8 Hz) caused frequency-dependent contractions that were of greater magnitude in arteries…
Role of endothelium in the responses to noradrenaline in normal and sensitized guinea-pig aorta
1993
1. The pharmacological reactivity of sensitized blood vessels has been less studied than that of the airways. Aorta rings were obtained from normal (non-sensitized) and actively sensitized guinea-pigs, and prepared for isometric recording of tension changes. 2. Noradrenaline (10 nM-0.1 mM), histamine (0.1 microM-0.1 mM) and KCl (10-100 mM) produced concentration-related contractions of normal tissues. Removal of endothelium resulted in a marked leftward and upward shift of the concentration-response curve for noradrenaline but it did not alter histamine- or KCl-induced responses. Pretreatment with L-NG-nitroarginine (L-NOARG, 30 microM), haemoglobin (5 microM) or ibuprofen (10 microM) enhan…
Modulatory role of magnesium on the contractile response of rat aorta to several agonists in normal and calcium-free medium.
1993
Abstract Acute withdrawal of external Mg2+ increased basal tone of rat isolated aorta incubated in the presence of Ca2+. Above normal levels of Mg2+ (1–4 Mm) inhibited basal tone while much higher levels of the divalent cation (64–256 Mm) evoked contractile responses regardless of the presence of Ca2+. Contractile responses to noradrenaline (1μm) and KCl (80 Mm) were inhibited by addition of cumulative concentrations of Mg2+. Acetylcholine-induced contractions in the presence of physiological concentrations of Mg2+ (1 Mm) decreased gradually to the basal tone, but a sustained contraction was observed in the absence of this ion. In Ca2+-free medium, acetylcholine-induced phasic responses ind…
Calcium dependence of the contraction produced by endothelin (ET-1) in isolated guinea-pig trachea.
1990
Endothelin (ET-1, 1 pM to 0.1 microM) produced a concentration-dependent contraction of isolated guinea-pig trachea. BAY K 8644 (1 microM) did not significantly alter the concentration-response curve for ET-1. Incubation with nicardipine (10 microM) partly inhibited responses to low concentrations (10 pM to 1 nM) of ET-1 while verapamil (10 microM) and diltiazem (10 microM) were ineffective. La3+ (10 microM) and Cd2+ (10 microM) preferentially depressed the responses evoked by high concentrations (30 nM-0.1 microM) of ET-1 without affecting the responses evoked by low concentrations of the peptide. Incubation in Ca2(+)-free (with EDTA, 1 mM) medium resulted in suppression of the responses e…
Neurotensin: dual effect on the motor activity of rat duodenum
1992
The effects of neurotensin on mechanical activity of rat duodenum were investigated using an isometric-isovolumic preparation. Neurotensin (1 pM to 10 nM) induced a concentration-dependent, tetrodotoxin (TTX)-insensitive fall in both endoluminal pressure and isometric tension. At higher concentrations of neurotensin (1 nM to 1 microM) the relaxation was followed by a concentration-dependent TTX-insensitive contraction, detected only by an increase in endoluminal pressure. Different concentrations of neurotensin were required to desensitize the relaxant and the contractile actions of the neuropeptide. The relaxation was antagonized by apamin, while the contractile response was blocked by nif…
Transmural distribution of biochemical markers of total protein and collagen synthesis, myocardial contraction speed and capillary density in the rat…
1988
The effect of angiotensin II-induced hypertension on selected biochemical parameters was studied in Sprague-Dawley rats. Angiotensin II infusion at rates of 41.7 micrograms h-1 kg-1 and 12.5 micrograms h-1 kg-1 for 2, 5, 10 and 15 days elevated the systolic blood pressure from 143 +/- 7 mmHg to 215-230 mmHg (P less than 0.001) and 185-195 mmHg (P less than 0.001), respectively. The left ventricular weight/body weight ratio increased 10-14% (P less than 0.05) and 23-32% (P less than 0.001) after 2-15 days in rats treated at the lower and higher infusion rates, respectively. Prolyl 4-hydroxylase (PH) activity, a marker of collagen synthesis, was evenly distributed in the left ventricle. PH ac…
Characterization of two different Ca2+ entry pathways dependent on depletion of internal Ca2+ pools in rat aorta
1998
Ryanodine (10 microM), thapsigargin (1 microM) and cyclopiazonic acid (10 microM) produced a slow, sustained contractile response in rat aorta that only can be observed in Ca2+-containing solution. In Ca2+-free medium, no response to the drugs was obtained, which suggests that the contraction elicited in presence of Ca2+ is mainly due to the contribution of extracellular influx. This Ca2+ entry does not depend on the opening of dihydropyridine-dependent Ca2+-channels for nimodipine does not affect this. Noradrenaline (1 microM) induced a biphasic response in Ca2+-free medium that was mediated by two different Ca2+ compartments, one of which is common to caffeine (10 mM), and is also deplete…
Pharmacological analysis of the responsiveness of guinea-pig lung parenchymal strip to dopamine
1984
Abstract Responses to dopamine were examined in the guinea-pig isolated lung parenchymal strip. Complete cumulative concentration-response curves to dopamine exhibited a biphasic pattern with a small initial contraction at concentrations below 10(-5) M followed by a dose-dependent relaxation at higher concentrations. Phentolamine (10(-5) M) completely abolished the contractile component and enhanced sensitivity and maximal relaxation to dopamine. In the presence of phentolamine, propranolol antagonized the dopamine-induced relaxation (pA2 = 8.54 +/- 0.07). In the presence of propranolol (10(-6) M), dopamine produced a dose-related contraction displaced to the right by phentolamine. Incubati…
Experimental diabetes induces hyperreactivity of rabbit renal artery to 5-hydroxytryptamine.
2002
Abstract The influence of diabetes on the response of isolated rabbit renal arteries to 5-hydroxytryptamine (5-HT) was examined. 5-HT induced a concentration-related contraction that was higher in arteries from diabetic rabbits than in arteries from control rabbits. Endothelium removal did not significantly modify 5-HT contractions in arteries from control rabbits but enhanced the response to 5-HT in arteries from diabetic rabbits. Incubation with N G -nitro- l -arginine ( l -NA) enhanced contractions to 5-HT in arteries from control and diabetic rabbits. In arteries with endothelium, this l -NA enhancement was lower in diabetic rabbits than in control rabbits. In arteries without endotheli…