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P Danilo

Publications and source records attributed to P Danilo.

81 records · Page 5Linked to original sources
PubMed1976

Effects of therapeutic concentrations of diphenylhydantoin on transmembrane potentials of normal and depressed Purkinje fibers.

Standard intracellular microelectrode techniques were used to study canine Purkinje fibers (PF) which had been superfused with blood or Tyrode's solution to determine the cardiac cellular electrophysiologic changes induced by antiarrhythmic concentrations of diphenylhydantoin (DPH). Some PF were normal whereas others were depressed by stretch, exposure to ouabain (125 mug/1) or superfusion with a solution in which all Na+ was replaced by tetraethylammonium. For normal fibers, therapeutic concentrations of DPH (DPH) induced slight decreases in action potential (AP) amplitude, maximum upstroke velocity of phase O (Vmax) and membrane responsiveness and somewhat greater decreases in AP duration. For fibers moderately depressed by ouabain or stretch, with reduced AP amplitude, maximum diastolic potential and Vmax, therapeutic [DPH] increased these variables. Fibers markedly depressed by Na-free solution or stretch developed slow response AP. The amplitude and Vmax of the AP were decreased by therapeutic [DPH]. Therapeutic [DPH] also suppressed automaticity and ouabain-induced delayed afterdepolarizations. Our studies suggest that the slight depression of normal PF AP characteristics induced by therapeutic [DPH] probably is of little significance with respect to antiarrhythmic effect. In contrast, both the improvement of AP characteristics of moderately depressed fibers and further depression of severely depressed fibers caused by [DPH] might modify arrhythmias. Effects of DPH on automaticity and delayed afterdepolarizations also would contribute to its antiarrhythmic effect.

Action Potentials↗
PubMed1975

The effects of dimethyl quaternary propranolol on the electrophysiologic properties of canine cardiac Purkinje fibers.

The effects of dimethyl quaternary propranolol (UM-272) on electrophysiologic properties of canine cardiac Purkinje fibers (PF) were studied using standard microelectrode techniques. In PF superfused with Tyrode's solution, the effects of UM-272, 10- minus 7 to 10- minus 5 M, were studied. In other experiments, UM-272, 3 mg/kg, was injected into donor animals whose blood was used to superfuse isolated PF. Antiarrhythmic concentrations of UM-272 decreased action potential (AP) amplitude, phase 0 upstroke velocity, membrane responsiveness, AP duration and the effective refractory period (the decrease in the effective refractory period was less than that in AP duration). Automaticity of spontaneously firing PF was suppressed. As perfusate potassium concentration was increased, the magnitude of UM-272 effect was accentuated. When the actions of equimolar concentrations of UM-272 and propranolol on PF AP were compared, propranolol attained a steady-state effect more rapidly and tended to depress the AP more markedly. UM-272 did not block epinephrine-induced increases in PF automaticity or the adenylate cyclase activation of PG homogenates induced by epinephrine. These studies indicate that UM-272 has direct effects on the PF AP similar to those of propranolol, but lacks the beta blocking properties of the latter.

Action Potentials↗
PubMedDate not supplied

Effects of terbutaline on cardiac automaticity and contractility.

The effects of terbutaline, a sympathomimetic amine with predominantly beta 2-agonist properties, on cardiac automaticity and contractility were studied. For isolated rabbit right atria, terbutaline, 1 X 10(-9) to 1 X 10(-5)M, was significantly less potent than isoproterenol. The maximum increase in heart rate induced by terbutaline was 45 +/- 17 beats/min, that by isoproterenol, 120 +/- 9 beats/min. For canine Purkinje fibers, terbutaline had less effect on spontaneous rate than isoproterenol; maximum increases above control were 9.5 +/- 2.5 and 18.6 +/- 7.0 beats/min, respectively. For isolated feline ventricular muscle, terbutaline, 1 X 10(-9) to 1 X 10(-6)M, was significantly less potent than isoproterenol in increasing peak developed tension and the rate of tension development. Superfusion with Tyrode's solution containing terbutaline, 1 X 10(-7)M, plus graded concentrations of isoproterenol, 1 X 10(-9) to 1 X 10(-6)M, resulted in response which were less than those observed when isoproterenol alone was superfused. Maximal effects of isoproterenol plus terbutaline were equivalent to those of isoproterenol in its effect on cardiac contractility and automaticity and explain the clinical observation that terbutaline is less toxic than isoproterenol in its effects on cardiac rhythm and contraction when administered for the treatment of bronchial asthma.

Animals↗
PubMedDate not supplied

Is preoperative fasting necessary?

The effects of fasting and of histamine (H2) antagonists on gastric volume and acidity were studied in 56 baboons undergoing various surgical procedures under general anesthesia and randomly allocated into 4 groups; group A--fasted for 14 hours; group B--given 100-120 ml of water 3 hours before surgery; groups C and D--also given 100-120 ml of water 3 hours before surgery; in addition, the former received cimetidine 10 mg/kg IM and the latter ranitidine 1.5 mg/kg IM 30-40 minutes before anesthesia. There were no significant differences between groups A and B with respect to the gastric volume and pH. Both ranitidine and cimetidine significantly (P < 0.02) reduced gastric volume and increased gastric pH. Thus, prolonged withholding of oral fluids does not reduce the gastric volume or increase gastric pH. H2-antagonists are effective in reducing both gastric residual volume and pH.

Animals↗
PubMedDate not supplied

[High, asymptomatic and persistent thrombocytosis in splenectomized subjects].

The Authors illustrate clinicals evaluations of tree splenectomised patients, whose platelets' counts were normal in the pre-operatory period. The patients had shown, after splenectomy, high (platelets' count upper than 10(6)/mmc), asymptomatic (without hemorrhage and thromboembolism), persistent father four months, spontaneously and progressively decreasing thrombocytosis. Clinical evaluations and blood analysis concern respectively periods of four years and six months, two years and two months, three years and six months after splenectomy. Furthermore the Authors examine the splenectomy's role into thrombocytosis, and remark, on the contrary of inherent literature, that, in some occurrences, the splenectomy produces high, persistent and asymptomatic thrombocytosis.

Adult↗