Antiarrhythmic peptide has no direct cardiac actions

Summary The electrophysiologic, inotropic, and muscarinic effects of antiarrhythmic, peptide (AAP) were examined in canine cardiac Purkinje fibers, ferret papillary muscle, and canine cardiac membranes, respectively. Aside from a prolongation of time to peak force, in papillary muscle, no biologically significant effects of AAP could be determined in any, preparation, suggesting that its antiarrhythmic, effects are not mediated by direct membrane actions.     

Manganese action potentials in mammalian cardiac muscle.

The membrane potential in guinea-pig's papillary muscles from right ventricle was recorded by glass microelectrodes and stimulation was effected by current pulses applied through a sucrose-gap. Action potentials with overshoot were recorded in the solution lacking Na+ and Ca++ but containing 2-95 mM Mn++. The overshoot was increased with the increase of [Mn++]o by about 30 mV/decade. Similar Mn++ dependent action potentials were also obtained in Na-free solution containing 0.6 mM Ca++. The results indicate that Mn inward current is sufficient to generate action potentials in cardiac muscle.     

Structure and antiarrhythmic activity of three ketophosphonium salts

Summary Three alicyclic organic phosphonium salts with an oxo and a morpholino group were found to exhibit a substantial antiarrhythmic action. The different activity levels were tentatively related to the structural modifications that they could induce in the cardiac cell membrane.Acknowledgment. We thank M. Adamantidis for the pharmacological testing.     

Extracellular calcium ions modify the effects of Anemonia sulcata toxin (ATX II) in guinea-pig papillary muscles

In isolated guinea-pig papillary muscle ATX II prolonged the action potential duration to a lesser extent at high extracellular Ca++-concentrations. This is interpreted as an interference of Ca++ with ATX II-binding sites.     

小型猪骨髓间充质干细胞经心导管冠状动脉移植及其迁移和分化的研究

目的建立小型猪心导管介入冠状动脉治疗模型,为骨髓间充质于细胞（MSCs）移植治疗心血管疾病提供新的方法,观察骨髓间充质干细胞经心导管介入冠状动脉移植后在心肌内的迁移及分化。方法选用冠状动脉解剖生理特点与人类相似的小型猪,应用心导管介入技术将体外培养扩增的小型猪自体MSCs移植进入左冠状动脉前降支,用免疫荧光检测即刻移植和移植后6W移植细胞的肌钙蛋白T（cTnT）、缝隙连接蛋白43（Cx43）、anti－Ⅷfactor的表达。结果成功的完成了小型猪心导管介入冠状动脉进行自体骨髓间充质干细胞移植。移植细胞存活,向心肌组织迁移,并向心肌细胞和毛细血管方向分化。结论该方法稳定,技术先进。可进行准确的定位和动态观测,为临床应用提供了一个可靠的技术平台。MSCs移植后在心肌内发生迁移及分化。     

Supernormal responses to premature stimulation in Ca-dependent action potentials.

The responses of Ca-dependent action potentials to premature stimulation were studied in the isolated canine ventricular muscle. When very premature stimuli were applied, supernormally augmented responses with propagation occurred, while responses with long preceding intervals were small and not conducted.     

Muscle fluorometry: A determination of the depth of penetration

Summary Fluorometric recordings of NADH (nicotinamide adenine dinucleotide) were made on rabbit papillary muscles. The specimens were placed between the UV light source and a small window of the detection stage. As the muscle was moved over the window in a transverse direction, simultaneous measurement could be taken of transmitted UV light and fluorescent light for various thicknesses of tissue. It is concluded that a muscle thinckness of 0.65 mm, is optimal before absorption of the incident light decreases the fluorescence signal.     

Electrophysiological actions of chlorimipramine on guinea-pig ventricular fibres.

Chlorimipramine (CMI, 1 x 10(-5)M to 7 X 10(-5)M) decreased the amplitude, overshoot and rate of rise of ventricular action potentials and abolished the Ca-mediated action potentials elicited in guinea-pig papillary muscles. These results indicates that CMI inhibits the rise in sodium and calcium conductances during the cardiac action potential.     

Muscle fluorometry: a determination of the depth of penetration

Fluorometric recordings of NADH (nicotinamide adenine dinucleotide) were made on rabbit papillary muscles. The specimens were placed between the UV light source and a small window of the detection stage. As the muscle was moved over the window in a transverse direction, simultaneous measurements could be taken of transmitted UV light and fluorescent light for various thicknesses of tissue. It is concluded that a muscle thickness of 0.65 mm is optimal before absorption of the incident light decreases the fluorescence signal.     

Antiarrhythmic properties of 3-(2-hydroxy-3 isopropylamino-propoxy)-3 phenyl-2 isoindolinone-1, (RS, SR) in the dog]

In the Dog, 3-(2-hydroxy-3 isopropylamino-proxy)-2-phenyl-1-isoindolinone (RS, SR) possesses an anti-arrhythmic activity similar to that of quinidine but at dose levels 2 to 6 times lower than in the case of the latter compound. Furthermore, in contrast to quinidine, at the dose levels where the antiarrhythmic activity is well observed, the compound is devoid of hypotensive activity and of depressive action on cardiac contractility. The first clinical studies of this compound have shown its usefulness in the treatment of ventricular and supraventricular arrhythmias.     

Fine structural correlations between the muscle pathology of amyotrophic lateral sclerosis (ALS) patients and experimental Ca-Mg deficient rats

Nonspecific myofibrillar changes such as streaming of the Z-line, formation of rod-like structures, satellitosis, proliferation of sarcolemmal nuclei and papillary projection of the sarcolemma were recognized as a disorganization of the muscle itself. In addition, fine structural pathology in ALS specimens showed characteristically a pig-tail formation - 'Zopfformation' - which has been considered to have a neurogenic origin.     

Die Reversibilität der Wirkung von Digitoxin,Strophanthidin und Strophanthidin-3-bromazetat am Papillarmuskel und einer mikrosomalen Na+-K+-aktivierbaren ATPase des Meerschweinchens

Summary The reversibility of the inhibitory action of strophanthidin, strophanthidin-3-bromoacetate, and digitoxin on the Na⁺-K⁺-ATPase activity (microsomal fraction, guinea-pig brain) was compared with the rate of decline of their positive inotropic effects (papillary muscle, guinea-pig heart) after exposure to drug-free solution. The actions of strophanthidin and digitoxin were easily reduced on both systems. Strophanthidin-3-bromoacetate, however, was found to have an irreversible blocking effect on the transport ATPase, whereas its inotropic action could be rapidly abolished.

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Teilergebnisse der Dissertation von U.Fricke, Mainz.     

Effect of platelet activating factor on guinea-pig papillary muscle

Platelet activating factor (PAF) induces a biphasic effect on guinea-pig papillary muscle: 1. a transient positive inotropic effect preceded by an increase in action potential duration (APD); 2. a marked negative effect on inotropism and on APD. Since Ca++ slow action potentials were initially enhanced by PAF and then markedly depressed, it is suggested that PAF specifically interferes with the Ca++ slow channel.     

Electrical uncoupling by Sr action potentials in cardiac muscle

Summary Sr action potentials elicited in guinea-pig papillary muscle under Na-free conditions decreased the space constant and increased the input resistance. It suggests that Sr current induced intercellular uncoupling by increasing [Sr]_i.Supported by grant from Japanese Ministry of Education and from Japan Heart Foundation Research Grant for 1976 contributed by Tokyo Marine and Fire Insurance Co., Ltd.     

Electrophysiological actions of chlorimipramine on guinea-pig ventricular fibres

Summary Chlorimipramine (CMI, 1×10^–5M to 7×10^–5M) decreased the amplitude, overshoot and rate of rise of ventricular action potentials and abolished the Ca-mediated action potentials elicited in guinea-pig papillary muscles. These results indicates that CMI inhibits the rise in sodium and calcium conductances during the cardiac action potential.     

Effect of platelet activating factor on guinea-pig papillary muscle

Summary Platelet activating factor (PAF) induces a biphasic effect on guinea-pig papillary muscle: 1. a transient positive inotropic effect preceded by an increase in action potential duration (APD); 2. a marked negative effect on inotropism and on APD. Since Ca⁺⁺ slow action potentials were initially enhanced by PAF and then markedly depressed, it is suggested that PAF specifically interferes with the Ca⁺⁺ slow channel.     

The electrophysiological effects of ionophore X-537A on cardiac Purkinje fibres

Summary Using classical microelectrode techniques in canine cardiac Purkinje fibres, calcium ionophore X-537A was shown to shorten the action potential, hyperpolarizing the membrane and lowering the plateau, suggesting that intracellular calcium controls membrane permeability to potassium in this preparation.This work was supported by grant No. HL 05726 from the U.S. Public Health Service, National Heart Institute, Bethesda, Md.I thank Dr.N. Krasnow for his valuable advice in carrying out this work.     

The experimental induction of ultrastructural damage in cardiac muscle

Experimentally-induced rises in intracellular calcium ([Ca2+]i) promote rapid myofilament degradation in amphibian and mammalian cardiac muscle strips. The relevance of these studies to the subcellular injury produced by ischaemia, the possible involvement of lysosomal enzymes and similarities with skeletal muscle are discussed.     

Lysosomal changes related to ageing and physical exercise in mouse cardiac and skeletal muscles

Summary Physical exercise increased the activities of arylsulphatase, cathepsin D and -glucuronidase in mouse skeletal muscle but not in cardiac muscle. Exercise-induced lysosomal response was more prominent in young adult than in senescent mice. The lipofuscin content of cardiac and skeletal muscles increased markedly during ageing and was also found to increase slightly after exertion in young mice, but not in senescent ones.This study was supported by the grants from the Ministry of Education and the Academy of Finland.     

Collagen in aging muscles.

The salt, acid and insoluble collagen fractions were estimated in red, white and cardiac muscles of 10-, 15- and 20-month-old albino rats. The total collagen level with reference to total proteins is more in red than in white and cardiac muscle. Accumulation of more of insoluble collagen and decrease in salt extractable collagen is seen in all three muscles with aging.