Search results for "ammonium"
showing 10 items of 1070 documents
Capacitative Ca2+ entry associated with α1-adrenoceptors in rat aorta
1997
In rat aorta, depletion of internal Ca2+ stores by addition of noradrenaline (1 microM) induces a biphasic response (an initial phasic response and a tonic one) mediated by two different intracellular Ca2+ pools. This response cannot be repeated, suggesting a depletion of internal Ca2+ stores sensitive to noradrenaline. In absence of the agonist, this depletion is the signal for the entry of extracellular Ca2+, not only to refill the stores but also, under our experimental conditions, to activate the contractile proteins thus inducing an increase in the resting tone (IRT) that constitutes functional evidence of this Ca2+ entry. The ionic channels involved in the mechanism of the IRT have be…
α,β-poly(asparthylhydrazide)–glycidyltrimethylammonium chloride copolymers (PAHy–GTA): novel polymers with potential for DNA delivery
2001
Hydrophilic polycations form complexes when mixed with plasmids. Following functionalisation with glycidyltrimethylammonium chloride (GTA) alpha,beta-poly(asparthylhydrazide) (PAHy), a water-soluble synthetic macromolecule, becomes polycationic and potentially useful for systemic gene delivery. Initially the biocompatibility of PAHy and PAHy-GTA derivatives with different degrees of positive charge substitution were studied and it was shown that PAHy-GTA was neither haemolytic nor cytotoxicity up to 1 mg/ml. After intravenous injection (125)I-labelled PAHy-GTA derivative containing 46 mol% (PAHy-GTA(b)) of trimethylammonium groups did not accumulate in the liver (4.1+/-0.9% of the recovered…
Effects of menthol on circular smooth muscle of human colon: Analysis of the mechanism of action.
2014
Abstract Menthol is the major constituent of peppermint oil, an herbal preparation commonly used to treat nausea, spasms during colonoscopy and irritable bowel disease. The mechanism responsible for its spasmolytic action remains unclear. The aims of this study were to investigate the effects induced by menthol on the human distal colon mechanical activity in vitro and to analyze the mechanism of action. The spontaneous or evoked-contractions of the circular smooth muscle were recorded using vertical organ bath. Menthol (0.1 mM–30 mM) reduced, in a concentration-dependent manner, the amplitude of the spontaneous contractions without affecting the frequency and the resting basal tone. The in…
EFFECTS OF CROMAKALIM (BRL-34915) IN TRACHEA ISOLATED FROM ACTIVELY SENSITIZED GUINEA-PIGS
1993
Abstract The effects of cromakalim were examined in tracheal strips isolated from normal (unsensitized) guinea-pigs and from animals actively sensitized to bovine serum albumin. Sensitized tracheae exhibited hyper-responsiveness to KCl, acetylcholine and histamine. In normal and sensitized tracheae, cromakalim (0·01–10 μm) produced a concentration-related suppression of spontaneous tone. The ability of cromakalim to relax tracheal strips was reduced when tone was raised by KCl (25 Mm), acetylcholine (0·1 Mm) or histamine (0·1 Mm) and lost against KCl (120 Mm)-induced spasm. Procaine (5 Mm) abolished the relaxant effect of cromakalim whilst tetraethylammonium (8 Mm) was without effect. These…
A barium method for the cytochemical detection of sulfated glycosaminoglycans in mast cells and basophilic leukocytes.
1999
Barium ions precipitate inorganic as well as organic sulfate compounds and they can be detected by a reaction with sodium rhodizonate. In this work, we describe the use of a barium method for the selective demonstration of sulfated glycosaminoglycans in cytoplasmic granules of mast cells and basophilic leukocytes. Methanol-fixed smears of mouse peritoneal mast cells and rat bone marrow basophils were treated with 5% BaCl2 for 10 min, followed by staining with either 0.2% sodium rhodizonate in 50% ethanol for 2 h at 60 degrees C, or 0.01% brilliant green in distilled water for 1 min. Light microscopic observation revealed a strong staining reaction of the cytoplasmic granules of these cell t…
Involvement of K+ channels in the relaxant effects of YC-1 in vascular smooth muscle
1999
This study addresses the question whether K(+) channels are involved in the vasorelaxant effects of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl-indazole (YC-1 ). In rat aorta, guinea pig aorta, and guinea pig a. carotis, YC-1 inhibited contractions induced by phenylephrine (3 microM) more potently than those induced by K(+)(48 mM). In rat aorta, tetraethylammonium (10 mM), charybdotoxin (0.2 microM), and iberiotoxin (0.1 microM), but not glibenclamide (10 microM), attenuated the relaxant effects of YC-1. In guinea pig a. carotis, YC-1 (30 microM) induced a hyperpolarisation which was antagonised by 1H-[1,2,4]oxadiazolo[4, 3-a]quinoxalin-1-one (ODQ; 50 microM). In rat aorta, YC-1 (30 microM) incr…
Mechanisms underlying the nitric oxide inhibitory effects in mouse ileal longitudinal muscle
2005
We investigated the mechanisms involved in the nitric oxide (NO)-induced inhibitory effects on longitudinal smooth muscle of mouse ileum, using organ bath technique. Exogenously applied NO, delivered as sodium nitroprusside (SNP; 0.1–100 µmol/L) induced a concentration-dependent reduction of the ileal spontaneous contractions. 1H-[1,2,4]oxadiazolol[4,3,a]quinoxalin-1-one (ODQ; 1 µmol/L), a guanilyl cyclase inhibitor, reduced the SNP-induced effects. Tetraethylammonium chloride (20 mmol/L), a non-selective K+ channel blocker, and charybdotoxin (0.1 µmol/L), blocker of large conductance Ca2+-dependent K+ channels, significantly reduced SNP-induced inhibitory effects. In contrast, apamin (0.1…
Subthreshold oscillation of the membrane potential in magnocellular neurones of the rat supraoptic nucleus
2000
The hypothalamic supraoptic nucleus (SON) contains two major populations of magnocellular neurosecretory neurones, producing and secreting vasopressin and oxytocin, respectively (for review see Poulain & Wakerley 1982). Neurones of a subpopulation of supraoptic neurosecretory cells share the capability of generating phasic bursts of action potentials. In these neurones, action potentials are succeeded by a depolarizing afterpotential (DAP; Andrew, 1987; Armstrong et al. 1994; Li et al. 1995). Depending on the discharge frequency, DAPs summate, eventually resulting in the generation of a plateau potential that gives rise to the discharge of a long-lasting train of action potentials. Thus, DA…
Components of after-hyperpolarization in magnocellular neurones of the rat supraoptic nucleusin vitro
1998
1. The pharmacological sensitivity of hyperpolarizing components of spike train after-potentials was examined in sixty-one magnocellular neurones of the rat supraoptic nucleus using intracellular recording techniques in a brain slice preparation. 2. In 26 % of all neurones a slow after-hyperpolarization (AHP) was observed in addition to a fast AHP. In 31 % of all neurones a depolarizing after-potential (DAP) was observed. 3. The fast AHP was blocked by apamin whereas the slow AHP was blocked by charybdotoxin (ChTX). The DAP was enhanced by ChTX or a DAP was unmasked if not present during the control period. 4. Low concentrations of TEA (0.15-1.5 mM) induced effects on the slow AHP and the D…
Different mechanisms of the inhibition of the transient outward current in rat ventricular myocytes.
1994
The mechanism of drug-induced inhibition of the transient outward current, Ito, has been investigated in rat ventricular myocytes using the whole cell patch clamp technique. Ito was activated by 300 ms depolarizing voltage clamp steps in 10 mV increments from −50 mV up to +40 mV. At +40 mV, Ito peaked after about 3 ms, and the time course of inactivation was appropriately described by two time constants, τfast = 17 ms and τslow = 203 ms. Verapamil, quinidine sulfate and nifedipine preferentially depressed Ito at the end of the 300 ms depolarizing voltage clamp step; the inactivation of Ito was accelerated by all drugs, whereas peak Ito was less affected. The time course of drug action at +4…