Morris Kleinfeld

Effects of Barium Chloride on Resting and Action Potentials of Ventricular Fibers of the Frog

By means of an intracellular capillary electrode the effects of barium chloride on the resting and action potentials of ventricular fibers of the frog were recorded in hearts with circulation intact and hearts isolated and perfused. The changes were essentially similar in both preparations. The major change observed was a statistically significant (p <0.01) increase in duration of the action potential. Changes were also observed in the magnitude of the resting and action potential, in the rate of depolarization, and in rhythm, but these did not occur invariably. By a series of exclusion experiments it was demonstrated that barium has a direct effect on the ventricular fibers of the frogs heart.

THE ACTION OF IODOACETATE ON THE ELECTRICAL AND MECHANICAL ACTIVITIES OF THE ISOLATED PERFUSED FROG HEART

The use of enzyme inhibitors on cardiac tissue has permitted a better understanding of the relationship between derangements of metabolism and function. The metabolic and physiologic actions of iodoacetate (IAA) have been reported by a number of investigators (1-4). In low concentrations IAA has been show n to act as a specific inhibitor of triosephosphate dehydrogenase therebv blocking the glv coly tic process (5, 6). This is in contrast to its reported action as a general sulfhvdrvl inhibitor when relatively higher concentrations are employed (6, 7). Studies with C14 labeled pyruvate (8) have show-n that the addition of 10-3 and 10-i M IAA reduces the pyruvate utilizationi (66 per cent) in heart slices w-ithout affecting oxygen consumiption wN-hereas greater amounts depress both oxygen consuml)tion and pyruvate disappearance. Earlier studies oIn the physiological effects of IAA have demiionstrated a (lepression of contractility and spontaneous rate of isolated rabbit and frog auricles (2, 3). In a recent study on the isolated rabbit auricle Gardner. Wilson, and Farah (4) reported that IAA produced far greater effects on contractility and spontaneouis rate than on the excitability or the actioin potential. They predicate(l the differences in 1miechanical and electrical behavior on a differenice in the energy requirements of these functions. They believe the IAAsensitive functions (such as rhythmicity and contractility) require a greater amount of energy than the IAA-insensitive functions (electrical excitability and action potential) and therefore are affected earlier. In further support of this ex-

A complication of prolonged intestinal intubation: Gaseous distention of the terminal balloon

SummaryA patient with regional enteritis was treated with a Cantor tube for relief of intestinal obstruction. Gaseous distention of the terminal balloon of the tube occurred necessitating removal by laparotomy and enterostomy. This rare complication is reviewed and discussed with special reference to etiology and prevention. The relationship of this complication to prolonged intubation is emphasized.

Symptomatic Improvement in a Patient with Sick Sinus Syndrome After the Onset of Stable Atrial Flutter

A patient with sick sinus syndrome (SSS) presented with episodic lightheadedness and weakness. The electrocardiographic features were marked supraventricular bradyarrhythmias and paroxysmal atriai flutter. The symptoms lested for four years and disappeared with the onset of stable atrial flutter which has persisted for the past seven years. Over the 11‐year period of observation, there has been progressive involvement of the His‐Purkinje system manifested by the development of left anterior fascicular block, right bundle‐branch block, and prolongation of the HV conduction time. The patient has refused pacemaker implantation, In the absence of angina and in the presence of a normal heart size, the etiology of his SSS is postulated to be idiopathic fibrosis of his conduction system.

The Effect of Tetraethylpyrophosphate (TEPP) on the Transmembrane Potentials of Pacemaker and Non-pacemaker Fibers of Isolated Rabbit Atrium

When 7 × 10−7M tetraethylpyrophosphate (TEPP) was administered as constant perfusion, the results were: (1) A progressive slowing of atrial rate and subsequent block in conduction; (2) A decrease in slope of the prepotential of pacemaker fibers; (3) No significant change in membrane resting potential of sinoatrial and atrial fibers, even during block in conduction; (4) An accelerated repolarization of both types of fibers. Simultaneously with the changes in electrical activity TEPP consistently produced a progressive decrease in inotropism. Pyridine 2-aldoxime methiodide (PAM) in concentrations of 1.26–2.52 × 10−4M consistently reversed the effects of TEPP. The inotropism often exceeded the control. The data suggests that 1) the changes in transmembrane potential produced by TEPP are principally due to an acetylcholine action, 2) the decrease in contractility is more intimately related to a disturbance in metabolic energy, and 3) the reversibility of the TEPP effects by PAM is due to a reactivation of acetylcholinesterase, an action similar to that observed in vitro.