The Use-Dependent Effects of Acute and Chronic Amiodarone Administration on His-Purkinje Conduction and the Interaction of β-Adrenergic Stimulation

Use-Dependent Effects of Amiodarone. Amiodarone is a highly effective antiarrhythmic agent. However, its exact mechanism of action remains uncertain. Prior studies suggest that intravenous amiodarone produces different electrophysiologic effects than chronic amiodarone administration. In addition, the effects of other antiarrhythmic agents and β-adrenergic stimulation on the electrophysiologic effects of amiodarone have not been well defined. In this study, we sought to evaluate the use-dependent effects of intravenous (acute) versus oral (chronic) amiodarone administration on His-Purkinje conduction in a closed-chest canine model. We also sought to evaluate the effects of intravenous lidocaine and isoproterenol on the use-dependent effects of chronically administered oral amiodarone. We found: (1) Acutely administered intravenous amiodarone (5 mg/kg bolus, followed by a 0.05 mg/kg/min infusion) does not produce a significant use-dependent effect on His-Purkinje conduction (serum amiodarone level 2.7 ± 1.1 mg/L), and acute beta blockade did not enhance use-dependent effects of amiodarone; (2) Chronically administered oral amiodarone (1,000 mg/day ± 2 weeks) produced significant use-dependent effects on His-Purkinje conduction at similar serum drug concentrations (mean level 2.6 ± 1.5 mg/L; (3) Intravenous lidocaine (10 mg/kg bolus, 0.2 mg/kg/min infusion) produced significant additional use-dependent effects to that of chronic oral amiodarone but only at rapid paced rates (cycle length 300-210 msec); and (4) Isoproterenol (5 μg/min infusion) significantly attenuated the use-dependent effects of chronically administered amiodarone. The mechanism of action of acutely administered intravenous amiodarone appears to be different from that of chronic oral amiodarone. In addition, the marked use-dependent effects observed after chronic amiodarone administration were reversed after catecholamine administration suggesting that attenuation of use dependence by sympathetic stimulation may negate some of salutary effects of amiodarone.     

Long-Term Neurostimulation of Skeletal Muscle: Its Potential for a Tether-Free Biologic Cardiac Assist Device

Skeletal muscle has a tremendous capacity to adapt. This adaptive phenomenon is seen perhaps to the greatest extent when skeletal muscle is subjected to chronic low frequency stimulation via the motor nerve. There is a decrease in glycolytic enzymes and an increase in oxidotive enzymes, as well as a change in the contractile proteins and an increase in the mitochondrial volume fraction of the muscle fiber. These adaptive changes result in a muscle that is considerably more fatigue-resistant. Specifically herein, we report on a pneumatic aortic counterpulsator device powered by skeletal muscle. These muscle pumps functioned continuously and pumped blood effectively in tether-free animals for several weeks.     

Peptic Ulcer in Infants: Three Case Reports and a Review of the Japanese Literature

Abstract: Three cases of peptic ulcer in children under two years of age are reported, and 33 cases of infants with peptic ulcer reported in Japan between 1955 and March, 1989 are reviewed. Case 1 was an 8-month-old male complaining of melena, and endoscopic examination showed a gastric ulcer on the lesser curvature of the antrum. Cases 2 and 3 were a 15-month-old mule and an 18-month-old male, respectively, with complaints of melena and hematemesis. Endoscopic examination revealed an active duodenal ulcer in both cases. All 3 infants were successfully treated with H₂ blocker and/or antacid. In these 3 cases, infection or drugs were speculated to be predisposing factors, and the fathers of these three infants all had histories of duodenal ulcer. Among 33 cases of infants under 2 years old with peptic ulcer in Japan, 9 had a gastric ulcer and 24 had a duodenal ulcer. Seventeen were treated with conservative therapy and 16 were operated on because of perforation or bleeding. We should always keep in mind that peptic ulcer does occur in infancy, and that endoscopic examination should be promptly performed when peptic ulcer is suspected.     

栀子化学成分的研究

由中药梔子中分离得D-甘露醇,β-谷甾醇,二十九烷和两种尚未鉴定的色素成分。