G K Moe

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The dynamic behavior of the cardiac pacemaker in response to single or to periodically repeated perturbations was studied using kitten sinoatrial (SA) nodal strips mounted in a sucrose gap. Sustained stepwise applications of current across the gap produce lasting variations in pacemaker cycle length that depend on current magnitude and polarity, but not on(More)
Isolated false tendons excised form dog hearts were mounted in a three-chamber tissue bath. Isotonic sucrose solution was perfused in the central chamber to provide a region of depressed conductivity between the fiber segments in chambers 1 and 3, which were perfused with Tyrode's solution. The electrotonic influence of spontaneous or driven responses(More)
When an impulse arrives at an area of impaired conductivity, a slowly rising electrotonic potential may bring the distal tissue to threshold after a delay imposed by the passive electrical properties of the system and by the time-dependent changes of these properties during diastole. This phenomenon can be demonstrated in Purkinje strands in which an area(More)
A narrow zone of block in isolated false tendon preparations was created by perfusion of the central compartment (gap) of a three-compartment tissue bath with either an isotonic sucrose solution or a solution designed to mimic the extracellular milieu in ischemic tissue. Driven responses on the proximal side of the gap were transmitted to the distal side(More)
Models of electrotonically mediated transmission were created by superfusion of the central fiber segment of a three-compartment Purkinje fiber preparation with either an "ion-free" or "ischemic" solution or by localized application of pressure. The frequency-dependent impairment of impulse conduction across such inexcitable gaps was found to be the result(More)
The hyperpolarizing effects of long periods of vagal stimulation were studied in kitten sinoatrial node-vagus nerve preparations. Verapamil (2.2 x 10(-6) M) was used to arrest spontaneous pacemaker activity, thus permitting uninterrupted observation of the time course of cholinergically mediated hyperpolarizations. With progressively longer vagal trains the(More)
Functional determinants of postrepolarization refractoriness were studied with microelectrodes in isolated cat and dog ventricular muscle preparations mounted in a three-chambered bath. Frequency-dependent conduction delay and block were readily manifested when the central segment (1 mm) was superfused with high potassium (20-30 mM) Tyrode's solution.(More)
When the heart rate is accelerated, rate-dependent intraventricular block may occur. This block has been attributed to abnormal action potential prolongation in a diseased conducting pathway. Less often, intraventricular block develops during slowing of the heart rate and has been explained in terms of phase 4 depolarization in potentially automatic cells(More)
The relationship between interelectrode conduction time and "take-off" potential (TOP) was studied with microelectrode techniques in isolated canine false tendons. Conduction of regular or test beats initiated during phase 4 dopolarization or late phase 3 repolarization speeded as TOP decreased. Similarly, beats initiated during digitalis-induced(More)