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Theoretical studies have indicated that alternans (period-doubling instability) of action potential duration is associated with a restitution relation with a slope >or=1. However, recent experimental findings suggest that the slope of the restitution relation is not necessarily predictive of alte...
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Defining the cellular electrophysiological mechanisms for ventricular tachyarrhythmias is difficult, given the wide array of potential mechanisms, ranging from abnormal automaticity to various types of reentry and kk activity. The degree of difficulty is increased further by the fact that any partic...
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We have previously demonstrated that cardiac myocytes isolated from the hearts of adult dogs develop rapid repetitive cytosolic Ca2+ transients, membrane depolarization, and cell contraction by mobilization of sarcoplasmic reticulum Ca2+ stores when exposed to a soluble factor from the trypomastigot...
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Non-viral gene vectors have attracted much attention recently due to setbacks with viral delivery systems. Here a new non-viral delivery system based on nanobiohybrids synthesized by the intercalation of a full gene and promoter encoding Green Fluorescent Protein (GFP) between the layers of an inorg...
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BACKGROUND: Restitution kinetics and alternans of ventricular action potential duration (APD) have been shown to be important determinants of cardiac electrical stability. In this study, we tested the hypothesis that APD restitution and alternans properties differ between normal and diseased human v...
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Heterogeneity of cardiac electrical properties can lead to heart rhythm disorders. Numerical studies have shown that stimuli chosen to maximize dynamic heterogeneity terminate wave propagation. However, experimental investigations suggest that similar sequences induce fragmentation of the wave front...
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In dogs and in humans, potassium channels formed by ether-a-go-go-related gene 1 protein ERG1 (KCNH2) and KCNQ1 alpha-subunits, in association with KCNE beta-subunits, play a role in normal repolarization and may contribute to abnormal repolarization associated with long QT syndrome (LQTS). The mole...
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We present details of a novel bioelectric interface formed by placing microfabricated probes into insect during metamorphic growth cycles. The inserted microprobes emerge with the insect where the development of tissue around the electronics during the pupal development allows mechanically stable an...
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To test whether hyperkalemia suppresses ventricular fibrillation (VF) by reducing the slope of the action potential duration (APD) restitution relation, we determined the effects of the extracellular K(+) concentration (K(+)](o)) (KCl] = 2.7-12 mM) on the restitution of APD and maximum upstroke velo...
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A perspective on systems containing many action potential waves that, individually, are prone to spiral wave breakup is proposed. The perspective is based on two quantities, 'predator' and 'prey,' which we define as the fraction of the system in the excited state and in the excitable but unexcited s...
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Sudden cardiac death, secondary to ventricular fibrillation (VF), remains the leading cause of death in many developed countries. Substantial experimental and theoretical support exists for the idea that VF is caused by spiral wave re-entry. The initiation and subsequent break-up of spiral waves hav...
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Alternation in the duration of consecutive cardiac action potentials (electrical alternans) may precipitate conduction block and the onset of arrhythmias. Consequently, suppression of alternans using properly timed premature stimuli may be antiarrhythmic. To determine the extent to which alternans c...
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Cardiac electrical alternans, characterized by a beat-to-beat alternation in action potential waveform, is a naturally occurring phenomenon, which can occur at sufficiently fast pacing rates. Its presence has been putatively linked to the onset of cardiac reentry, which is a precursor to ventricular...
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The pattern of action potential propagation during various tachyarrhythmias is strongly suspected to be composed of multiple re-entrant waves, but has never been imaged in detail deep within myocardial tissue. An understanding of the nature and dynamics of these waves is important in the development...
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Objectives: Background: Methods: Results: Conclusion: The age-dependence of the development of ventricular arrhythmias was studied in German shepherd dogs with inherited ventricular arrhythmias and sudden death.A colony of German shepherd dogs has been established that exhibit inherited ventricular ...
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Heart rate-dependent alterations in the duration of the electrically active state of cardiac cells, the action potential, are an important determinant of lethal heart rhythm disorders. The relationship between action potential duration and heart rate can be modelled as a nonlinear one-dimensional ma...
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Interruption of periodic wave propagation by the nucleation and subsequent disintegration of spiral waves is thought to mediate the transition from normal sinus rhythm to ventricular fibrillation. This sequence of events may be precipitated by a period doubling bifurcation, manifest as a beat-to-bea...
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The effectiveness of chaos control in large systems increases with the number of control sites. We find that electric field induced wave emission from heterogeneities (WEH) in the heart gives a unique opportunity to have as many control sites as needed. The number of pacing sites grows with the ampl...
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Non-steroidal anti-inflammatory drugs (NSAIDs) contribute to gastrointestinal ulcer formation by inhibiting epithelial cell migration and mucosal restitution; however, the drug-affected signaling pathways are poorly defined. We investigated whether NSAID inhibition of intestinal epithelial migration...
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Cardiac arrhythmias are a leading cause of morbidity and mortality in many developed countries. Despite intensive investigation, the cellular mechanisms for most cardiac arrhythmias have not been clearly established. As a consequence, drug therapy for most forms of atrial and ventricular arrhythmias...
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The mechanism for the reduction of the transient outward K+ current (Ito) in diseased myocardium is unknown. To identify potential mechanisms, the reduction of Ito and its subsequent restoration by norepinephrine (NE) were studied in cultured canine epicardial myocytes. After myocytes were cultured ...
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BACKGROUND: Electrically based therapies for terminating atrial fibrillation (AF) currently fall into 2 categories: antitachycardia pacing and cardioversion. Antitachycardia pacing uses low-intensity pacing stimuli delivered via a single electrode and is effective for terminating slower tachycardias...