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BACKGROUND Cardiac memory (CM) refers to T-wave changes induced by ventricular pacing or arrhythmia that accumulate in magnitude and duration with repeated episodes of abnormal activation. We report herein the kinetics of long-term CM and its association with the ventricular action potential. METHODS AND RESULTS Dogs were paced from the ventricles at(More)
The purpose of this study was to determine whether oligonucleotides the size of siRNA are permeable to gap junctions and whether a specific siRNA for DNA polymerase beta (pol beta) can move from one cell to another via gap junctions, thus allowing one cell to inhibit gene expression in another cell directly. To test this hypothesis, fluorescently labelled(More)
INTRODUCTION Cultured neonatal rat ventricular myocytes (NRVM) reestablish gap junctions as they form synchronously and spontaneously beating monolayers, thus providing a useful model for studying activation and repolarization. METHODS AND RESULTS We used the multielectrode array data acquisition system with 60 unipolar electrodes to investigate the(More)
Human mesenchymal stem cells (hMSCs) are a multipotent cell population with the potential to be a cellular repair or delivery system provided that they communicate with target cells such as cardiac myocytes via gap junctions. Immunostaining revealed typical punctate staining for Cx43 and Cx40 along regions of intimate cell-to-cell contact between hMSCs. The(More)
Alpha-adrenergic amines exert concentration-dependent actions on the automaticity of cardiac Purkinje fibers (Posner, P., E. L. Farrar, and C. R. Lambert. 1976. Am. J. Physiol. 231:1415-1420; Rosen, M. R., A. J. Hordof, J. P. Ilvento, and P. Danilo, Jr. 1977. Circ. Res. 40:390-400; Rosen, M. R., R. M. Weiss, and P. Danilo, Jr. 1984. J. Pharmacol. Exp. Ther.(More)
BACKGROUND Ca2+ leak from the sarcoplasmic reticulum (SR) may play an important role in triggering and/or maintaining atrial arrhythmias, including atrial fibrillation (AF). Protein kinase A (PKA) hyperphosphorylation of the cardiac ryanodine receptor (RyR2) resulting in dissociation of the channel-stabilizing subunit calstabin2 (FK506-binding protein or(More)
During development, there are changes in the response of automatic cardiac fibers to alpha-adrenergic agonists. In neonatal rat ventricle, in vitro phenylephrine (1 X 10(-8) M) induces an increase in automatic rate from 115 +/- 12 (mean +/- SEM) to 168 +/- 10 beats/min, P less than 0.05. In contrast, in adult rat ventricle, the rate decreases from 36 +/- 8(More)
OBJECTIVE Although the incidence of atrial fibrillation (AF) increases with age, the cellular electrophysiological changes that render the atria of aged individuals more susceptible to AF remain poorly understood. We hypothesized that dispersion of atrial repolarization increases with aging, creating a substrate for initiation of AF. METHODS Four groups(More)
OBJECTIVE Our goal was to study rate adaptation of atrial action potentials in non-steady and steady states to further our understanding of mechanisms determining inducibility and stability of atrial fibrillation. METHODS We used standard microelectrode techniques to examine the characteristics of steady-state action potentials paced at regular cycle(More)