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The effects of four class I antiarrhythmic chemicals on the Ca current were compared to those of single isolated frog ventricular cells in single isolated frog ventricular cells. With a 50% effective dose at ten and 20 microM, respectively, there was no obvious use-dependent inhibition; there was no apparent use-dependent inhibition. Both tonic and use-dependent inhibition were present in Ethmozine and ethacizine derivatives, two phenothiazine derivatives. These compounds were only 3- to 10-fold less effective on the ICa than on the Na current results in parallel experiments, with flecainide showing the highest potency. Consequently, the absence of use-dependence inhibition with quinidine and flecainide may have been the result of a relatively fast association of the two compounds with the open channels that would be fully operational during the 200-meter depolarizing pulse.
Source link: https://doi.org/10.1152/ajpcell.1989.256.3.c549
Using the patch-clamp method, the effects of the enantiomers quinine and quinidine on the transient outward current and the L-type Ca 2+ current were investigated in rat ventricular cardiomyocytes. A change in extracellular pH from 7. 3 to 8. 3 did not have a significant effect on the medications' effects on I to or I Ca.
Source link: https://doi.org/10.1159/000064342
In organotypic brain slices of Meynert's nucleus basalis, we hypothesize that quinidine can modulate the protective effects of NGF and memantine on cholinergic neurons. Methods: Organotypic brain slices of nBM were incubated with 100 ng/mL NGF, 10 u00b5M memantine, 10 u00b5M quinidine, and 10 mg/mL quinidine, and combinations of these drugs for 2 weeks. Cell death of cholinergic nBM neurons is shown by our results: NGF, as well as memantine counteracted cell death of cholinergic nBM neurons. Quinidine alone had no adverse effect on cholinergic neurons, but when used simultaneously, it stifled the protective action of NGF and memantine.
Source link: https://doi.org/10.1159/000515907
PURPOSE: To investigate the effects of quinidine, a putative regulator of P-glycoprotein-mediated drug resistance, on epilepsy and toxic profile in patients with advanced breast cancer. PATIENTS AND MEHODS Between 1989 and 1992, 223 eligible patients were randomized in double-blind fashion for epidnisolone 100 mg/m2 by intravenous bolus and prednisolone 25 mg orally twice daily, as well as placebo or quinidine capsules, taken for 4 days before and 2 days after chemotherapy. In vitro, a median quinidine level was 5. 5 mumol/L; at this concentration, the drug partially reverses anthracycline resistance in multidrug-resistant breast carcinoma cells. The response rate in the placebo arm was 44%, while in the quinidine arm was 43 percent. After epiduicin chemotherapy in patients with advanced breast cancer, Quinidine at this dose does not appear to change the toxicity profile, response rate, or survival.
Source link: https://doi.org/10.1200/jco.19188.8.131.521
Several attempts at plantation production were unsuccessful after the discovery of natural stands of Cinchona in the Andes. The governments of the United States and Guatemala, a major pharmaceutical company, and four Guatemalan coffee planters began working together to develop techniques for successful cultivation of Cinchona in the western hemisphere just before World War II.
Source link: https://doi.org/10.21273/horttech.1.1.17
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