Early electrophysiologic and anatomic alterations in cat ventricular muscle after coronary artery ligation.

The effect of coronary artery ligation on electrophysiologic properties of cat ventricular muscle cells was studied. Depression of resting potential, action potential rate of rise and amplitude was observed in infarcted cells, 30 min to 5 days after ligation. Action potential duration was markedly shortened in acute stages (30-120 min) but gradually lengthened to above control by 48 h.

Role of needle aspiration in reducing the number of unnecessary breast biopsies.

The accuracy of the results obtained from 2334 open breast biopsies performed during a 9-year period at Mount Sinai Hospital in Toronto are reviewed. With meticulous follow-up and the liberal use of needle aspiration, the senior author (A.A.

Role of cytology in management of lesions of the breast.

Study of 3,724 cytologic specimens mainly obtained by fine needle aspiration biopsy of breast lesions has demonstrated several advantages in clinical management: confirmation of clinical or other impression without open biopsy; avoidance of open biopsy in inoperable instances; avoidance of operation for certain benign lesions; excision under local anaesthesia on an ambulatory basis of other benign lesions; more efficient operating room scheduling; reduction in the number of operations for benign lesions, and the institution of more effective and humane preoperative counseling. It is concluded that these benefits alone justify the use of the method, and there is no compelling need to abandon the routine use of premastectomy frozen sections. Indeed, the problems created by abandoning frozen section routinely appear to be a prime reason for the lack of wider application of the method.

Electrophysiological effects of alprenolol on depressed canine myocardium.

The electrophysiological effects of the beta-adrenergic antagonist, alprenolol, were compared in normal and depressed canine myocardium. Both (+) and (+/-)-alprenolol (5 x 10(-6) and 10(-5) mol.litre-1) decreased action potential amplitude and Vmax in Purkinje fibres superfused with Tyrode's solution in tissue bath.

[Effect of some electric signals transmitted by an induction coil on weight increase, incorporation of marker, and histological and ultrastructural appearance of the skeleton in a chick embryo].

Embryo Chicks were exposed to various types of electrical impulses transmitted by induction coils between the 6th and 13th day of incubation. Compared with controls, the Chick tibias showed a highly significant increase in weight and length as well as increased incorporation of tritiated thymidine. In addition, the total weight of the treated embryos was significantly greater than that of the controls.

Myocardial transmembrane potentials and adrenergic receptors.

The role of adrenergic amines in the genesis of cardiac arrhythmias is well known. Electrophysiological techniques of recording intracellular potentials have led to a better understanding of the cellular mechanisms by which these amines may induce arrhythmias. Stimulation of beta 1-adrenoreceptors increases automaticity, shortens action potential duration (APD), and may enhance slow action potential (AP) formation in depolarized Purkinje fibers (PF).

Depressant effects of phenoxygenzamine on potassium contracture in cat ventricular muscle.

Phenoxybenzamine has been shown to have a depressant action on K+-depolarization contracture in cat ventricular muscle. In the present study, we show that this depressant action is specific for phenoxybenzamine and occurs in the presence of beta-adrenergic receptor blockade with nadolol. K+-contracture is not depressed by phentolamine nor augmented by phenylephrine.

Sodium-dependence of sustained force in potassium contracture of cat ventricle.

Following exposure to low-Na solutuion, the initial phase of K-contracture in cat ventricle is prominent while the second (sustained) phase is markedly attenuated. Monensin, a Na-specific ionophore, enhances the second phase of K-contracture following exposure to low-Na solution.

Adrenergic innervation of the ureter.

To determine whether the ureter is innervated by the autonomic nervous system, isolated canine ureters were superfused with modified Tyrode solution, and force developed in response to 100-msec duration stimuli at a rate of 3 per min was monitored. Norepinephrine and phenylephrine significantly increased developed force; the latter more than the former. These increases in developed force were blocked by phentolamine, and propranolol enhanced the stimulatory effect of norepinephrine.

The role of canine superficial ventricular muscle fibers in endocardial impulse distribution.

Thin sections of canine right and left ventricular endocardium and myocardium were studied in a tissue bath to compare conduction properties of intraventricular specialized conducting tissue [Purkinje fibers (PF)], the superficial layers of subendocardial ventricular muscle (SVM), and the deeper ventricular muscle (DVM) below this level. The study was carried out because of observations that some areas of the endocardium, which are devoid of either specialized conducting tissue or of PF-VM junctions between specialized conducting tissue and ventricular muscle, conduct relatively rapidly, favoring specific orientations of propagation. Preparations containing PF, SVM, and DVM were studied electrophysiologically and histologically.

Direct and beta adrenergic blocking actions of nadolol (SQ 11725) on electrophysiologic properties of isolated canine myocardium.

Effects of nadolol, a new beta adrenergic antagonist, were determined on transmembrane potentials of canine Purkinje fibers and ventricular and atrial muscle. Significant alterations in Purkinje fiber potentials occurred only with nadolol concentrations of 10(-4) M or greater. After 1 hour exposure to 10(-4) M, resting potential and action potential amplitude were reduced; at 3 hours, action potential rate of rise, phase 2 duration and action potential duration at 75% repolarization also were decreased.

Effects of coronary bypass surgery on the electrical activity of revascularized myocardium. Immediate and early postoperativeobservations.

The effect of myocardial revascularization on bipolar epicardial electrograms was recorded with fixed wire electrodes from revascularized left ventricular sites and from control sites on the right ventricle. Studies were performed during and after surgery in 19 patients undergoing aorta-coronary bypass grafting for occlusive coronary artery disease and in 6 additional patients having aortic valve replacement for isolated aortic valve disease. In the latter 6 patients, neither left nor right ventricular electrogram voltage changed immediately following aortic valve replacement; however, left ventricular electrogram voltage gradually decreased for 5 days postoperatively.

Restorative effect of epinephrine on the electrophysiologic properties of depressed human atrial tissue.

The effects of epinephrine on the electrophysiologic properties of human right atrail tissue, obtained at cardiac surgery, were evaluated utilizing standard microelectrode techniques. In studies of electrophysiology, epinephrine had little effect on the resting membrane potential and transmembrane action potentials of normal atrial fibers. Epinephrine enhanced phase-4 depolarization and increased automaticity in normal fibers but hyperpolarized partially depolarized atrial fibers and decreased automaticity.

The effect of temperature on potassium chloride contracture in cat myocardium.

1. Contracture was induced in cat myocardium by exposure to 140 mM-KC1 In isotonic Tyrode solution. Force of contracture expressed as mg/mm2 (muscle cross-sectional area) falls with increasing cross-sectional area.

Eelctrophysiologic and ultrastructural characteristics of the canine tricuspid valve.

Collagen extending from chordae tendineae sweeps into each tricuspid leaflet in a loose fanlike arrangement merging with the annulus. Each leaflet contains variable amounts of cardiac muscle in continuity with right atrial muscle; valve fibers are sparse, and scattered myofibers and/or bundles of myofibers usually extend only 2-3 mm into the leaflet body. Valve myofibers are structurally identical to working right atrial muscle but are 2-3 mum in diameter compared to 5-7 mum in working muscle.

Caffeine and KC1 contracture in cat myocardium.

Caffeine increases the force of contracture induced in cat myocardium by exposure to 140 mM KC1 in isotonic Tyrode solution. The effect of caffeine does not require prior exposure to the drug, develops rapidly, and is partially antagonized by procaine but not by verapamil. These results suggest that caffeine acts on depolarized sarcolemma to release a sarcolemmal calcium pool.

Acetylcholine-induced reversal of canine and feline atrial myocardial depression during stretch, cardiac failure, and drug toxicity.

Microelectrode and isometric recording techniques were used to evaluate the effects of acetycholine (ACh) on depressed isolated preparations of dog and cat atrial muscle. Atrial muscles were maintained at 36-37 degrees C with warmed Tyrode's solution and were stimulated at frequencies of 30 or 60/min. Depolarization to resting potentials of approximately -50 mv was noted (1) after excessive stretch was applied, (2) in muscles obtained from cats in overt right heart failure, and (3) during exposure of the muscles to excessive concentrations of acetylstrophanthidin or lidocaine.