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Biomedical subjects

C A Muller

Publications and source records attributed to C A Muller.

12 recordsLinked to original sources
PubMed1992

Bucindolol, a beta blocker, decreased ventricular fibrillation and maintained mechanical function in a pig model of acute myocardial ischemia.

Bucindolol is a new beta blocker with marked vasodilatory properties and intrinsic sympathomimetic activity. We tested its potential effect against ventricular fibrillation (VF), in a pig model of acute myocardial ischemia. Bucindolol 6 mg/kg IV was administered in two equally divided doses, the first 30 minutes prior to, and the second 10 minutes after, ligation of the anterior descending coronary artery (CAL) in anesthetized open-chest pigs. Bucindolol decreased the incidence of VF to 1/11 versus 14/16 in the control group (p less than 0.005). Bucindolol also decreased the duration of ventricular tachycardia, 15 +/- 8 seconds versus 104 +/- 32 seconds in the control group (p less than 0.01). Bucindolol maintained LVmaxdP/dt at predrug and pre-CAL values, whereas LVmaxdP/dt was decreased by CAL in the control group. Bucindolol decreased arterial pressure and heart rate. Bucindolol increased blood flow in the peripheral ischemic zone (24.6 +/- 1.8% versus 16.2 +/- 1.7% (percent of pre-CAL value) in controls, p less than 0.002), as well as in the nonischemic zones (periischemic zone: 126.4 +/- 6.1% versus 96.7 +/- 4.8% in the control group, p less than 0.0005; remote nonischemic zone: 126.6 +/- 7.1% versus 87.1 +/- 4.3% of pre-CAL value in the control group, p less than 0.0001). Bucindolol had marked antiarrhythmic effects that were associated with beneficial effects on the mechanical function of the left ventricle and on blood flow to the ischemic myocardium.

Adrenergic beta-Antagonists↗
PubMed1992

Antiarrhythmic effects of the angiotensin converting enzyme inhibitor perindoprilat in a pig model of acute regional myocardial ischemia.

Previous studies on the possible antiarrhythmic effects of angiotensin converting enzyme (ACE) inhibitors during early ischemia in pigs have been inconclusive or negative; however, proof of adequate ACE inhibition was not provided. Perindoprilat, 0.06 mg/kg, i.v., was administered 30 min prior to ligation of the anterior descending coronary artery (CAL) in anesthetised open-chest pigs. Plasma ACE activity was decreased by 95.0 +/- 1.9% when measured 5 min before CAL. Within 5 min of CAL, the ventricular fibrillation threshold (VFT) in the control group was decreased from 11.8 +/- 1.9 to 7.2 +/- 1.2 mA (p less than 0.01). Perindoprilat prevented the fall in the VFT and the increase in left ventricular end-diastolic pressure caused by CAL. Perindoprilat decreased arterial pressure. Cardiac output (thermodilution) was decreased by 23 +/- 3% after CAL in the control group and by only 10 +/- 5% (p less than 0.05) in the perindoprilat group (both versus pre-CAL values). In the control group cyclic AMP was increased from 0.97 +/- 0.04 (pre-CAL) to 1.16 +/- 0.04 nmol/g (p less than 0.05) in the central ischemic zone 20 min after CAL. Perindoprilat prevented this increase in cyclic AMP. Twenty minutes after CAL blood flow (microsphere method) in the nonischemic zone of the perindoprilat group was increased, whereas blood flow in the central ischemic zone was decreased compared to the control group. However, levels of tissue metabolites (ATP, phosphocreatine, lactate) measured in drill biopsies in the same zones of the two groups were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1990

Antiarrhythmic and metabolic effects of indoramin during acute regional ischemia and reperfusion in isolated rat heart.

The antiarrhythmic effect of alpha 1-adrenoceptor antagonists during myocardial ischemia and reperfusion remains controversial. The potential antiarrhythmic properties of indoramin, an alpha 1-antagonist, were assessed in the isolated perfused rat heart during regional ischemia and during sustained reperfusion. Coronary artery ligation (CAL) decreased the ventricular fibrillation threshold (VFT) of control hearts from 9.1 +/- 1.3 (pre-CAL, mean +/- SEM) to 2.1 +/- 0.5 mA 15 min post-CAL (p less than 0.0001). Perfusion with indoramin 10(-8) M (alpha 1-receptor antagonistic concentration) started 5 min prior to CAL did not prevent the fall in VFT after CAL. Indoramin 10(-6) M prevented the fall in VFT after CAL relative to the control group. Indoramin 10(-5) M markedly increased the VFT before CAL from 9.9 +/- 1.0 to 28.6 +/- 2.9 mA (p less than 0.0001) and prevented the fall in VFT after CAL. During reperfusion, indoramin 10(-5) M decreased the incidence of spontaneous ventricular fibrillation (VF) to 1 of 6 vs. 6 of 6 in the control group (p less than 0.02). Indoramin 10(-5) M preserved adenosine triphosphate in the reperfused myocardium: 2.82 +/- 0.06 vs. 2.16 +/- 0.21 mumol/g in the control group (p less than 0.05). Specific alpha 1-antagonist properties of indoramin did not appear to be involved in the antiarrhythmic effects.

Animals↗
PubMed1990

Studies in search of a suitable experimental insect model for xenodiagnosis of hosts with Chagas' disease. 4--The reflection of parasite stock in the responsiveness of different vector species to chronic infection with different Trypanosoma cruzi stocks.

Previous studies (1982, 1987) have emphasized the superiority of sylvatic vector species over domestic species as xenodiagnostic agents in testing hosts with acute or chronic infections by T. cruzi "Y" stock. The present study, which is unique in that it contains data on both infectivity rates produced by the same stock in 11 different vector species and also the reaction of the same vector species to seven different parasite stocks, establishes the general validity of linking efficiency of xenodiagnosis to the biotope of its agent. For example, infectivity rates produced by "São Felipe" stock varied from 82.5% to 98.3% in sylvatic vectors but decreased to 42.5% to 71.3% in domestic species. "Colombiana"stock produced in the same sylvatic vectors infectivity rates ranging from 12.5% to 45%. These shrank to 5%-22.5% in domestic bugs. The functional role of the biotope in the vector-parasite interaction has not been elucidated. But since this phenomenon has been observed to be stable and easy to reproduce, it leads us to believe that the results obtained are valid. Data presented also provide increasing evidence that the infectivity rates exhibited by bugs from xenodiagnosis in chronic hosts, are parasite stock specific. For example, infectivity rates produced by "Berenice", "Y", "FL" and "CL" varied in R. neglectus from 26.3% to 75%; in P. megistus from 56.3% to 83.8%; in T. sordida from 28.8% to 58.8% in T. pseudomaculata from 41.3% to 66.3% and in T. rubrovaria from 48.8% to 85%. Data from xenodiagnosis in the same hosts, carrying acute infections by the same parasite stocks, gave the five sylvatic vectors a positive rating of approximately 100%, thus suggesting that the heavy loads of parasites circulating in the acute hosts obscured the characteristic interspecific differences for the parasite stock. Nonetheless these latter were revealed in the same hosts with chronic infections stimulated by very low numbers of the same parasite stocks. Certain observations here described lead us to speculate as to the possibility of further results from other parasite stocks, allowing the association of the infectivity rates produced in bugs by different parasite stocks with the isoenzymic patterns revealed by these stocks.

Animals↗
PubMed1989

Critical role of dose in protection by propranolol against ventricular fibrillation in a pig model of acute myocardial ischemia.

We hypothesized that the antiarrhythmic efficacy of propranolol during acute myocardial ischemia could be dose related. Propranolol was administered in two equally divided doses 30 min before and 10 min after ligation of the anterior descending coronary artery (CAL) in anesthetized open-chest pigs. Only the lowest dose of propranolol, i.e., 0.1 mg/kg intravenously (i.v.) (plasma level 22 +/- 2 ng/ml) decreased the incidence of ventricular fibrillation (VF), i.e. 3 of 12 versus 16 of 20 in control group (p less than 0.01). VF incidence with propranolol 0.5 or 3 mg/kg was 4 of 6 and 8 of 9, respectively (both NS vs. control group). Propranolol 0.1 mg/kg did not change left ventricular (LV) blood flow. Propranolol 3 mg/kg reduced blood flow in the peripheral ischemic myocardium to 13.2 +/- 1.2 versus 19.2 +/- 1.4 ml/100 g/min in control group (p less than 0.01), and in the midischemic zone to 4.4 +/- 0.5 versus 7.0 +/- 0.9 ml/100 g/min in control group (p less than 0.001). Propranolol 0.1 mg/kg prevented a disparity of levels of cyclic AMP from arising between ischemic and non-ischemic myocardium, whereas propranolol 3.0 mg/kg did not. Furthermore, LV mechanical function was suppressed by propranolol 3 mg/kg. Only the lowest dose of propranolol (i.e., 0.1 mg/kg) decreased the incidence of VF in this model.

Adenosine Triphosphate↗
PubMed1979

Protective action of amiodarone against ventricular fibrillation in the isolated perfused rat heart.

The pretreatment of rats with amiodarone for 2 minutes to 3 weeks before the excision of their hearts caused a dose-related decrease in heart rate and an increase in the ventricular fibrillation threshold both before and after coronary arterial ligation. Similarly, amiodarone decreased the incidence of ventricular premature extrasystoles, ventricular tachycardia and fibrillation during the period of regional ischemia after coronary arterial ligation and also after reperfusion of the ischemic myocardium. There was no evidence of a metabolic protective effect on ischemic myocardium because tissue high energy phosphate content decreased to a similar extent in ischemic myocardium from control and amiodarone-treated rats. Instead, the protective effect of amiodarone against fibrillation was accompanied by attenuation of the increase in tissue cyclic adenosine monophosphate in ischemic myocardium after coronary arterial ligation. It is proposed that amiodarone exerts a potent antifibrillatory effect by decreasing tissue cyclic adenosine monophosphate in ischemic myocardium.

Amiodarone↗
PubMed1979

[Prevention of paralytic ileus after colonic surgery by continuous peridural sympathetic block. Preliminary report].

Gastrointestinal atony must be considered as a reflex response to surgical intervention, due to activation of sympathetic nerves. Following colonic surgery, the duration of this response may be notably extended and the ensuing intestinal distension becomes the paramount factor of a persisting ileus. Blocking the sympathetic fibers prevents intestinal distension. Introducing appropriate catheter into the peridural space up to the level of the 10th--11th thoracic vertebra makes it possible to realize a segmental continuous block between T6--L2, where gastrointestinal sympathetic innervation actually originates. Using bupivacaine at low concentration (0.125% with epinephrine 1/400,000) reduces untoward effect on circulation and may even prove beneficial if volaemia is effective. In addition, it produces a selective block on the visceromotor fibers which allows a differential diagnosis of the ileus, without risking to pass over a perforation of the gut whenever a coexisting mechanical factor is suspected.

Autonomic Nerve Block↗
PubMed1978

Cyclic A.M.P. and arrhythmias revisited.

Further evidence is presented for a hypothesis linking cyclic adenosine 3', 5' monophosphate (cyclic A.M.P.) and arrhythmias: in the isolated rat heart, changes in tissue cyclic A.M.P. are accompanied by changes in the ventricular-fibrillation threshold; and in the pig, large infarcts are associated with raised tissue cyclic A.M.P. and ventricular fibrillation, whereas small infarcts are not. Data showing that changes in the metabolism of potassium, glucose, fatty acids, and lactate can influence the action-potential duration are incorporated into a revised hypothesis which allows for multifactorial arrhythmogenic mechanisms in the early stages of acute myocardial infarction.

Action Potentials↗
PubMed1978

[Closed hemorrhoidectomy using Ferguson's technic].

The author describes the "closed" method of hemorrhoidectomy, as advised by J.A. Ferguson, about forty years ago. In retrospect, reviewing 237 cases operated with this method between 1963 and 1976, it appears that the closed hemorrhoidectomy induces less postoperative pain and is fraught with less postoperative complications. Hospitalization averages 5 days. The complete duration of treatment is 4 weeks with an average loss of work of 19.5 days. If our fellow-surgeons are really prepared to relinquish sectarism and to seek for "modern" techniques, they should consider closed hemorrhoidectomy as the treatment of choice for this untoward condition.

Hemorrhoids↗