BACKGROUND T-wave alternans, which is associated with the genesis of cardiac fibrillation, has recently been related to discordant action potential duration (APD) alternans. However, the cellular electrophysiological mechanisms responsible for discordant alternans are poorly understood. METHODS AND RESULTS We simulated a 2D sheet of cardiac tissue using phase 1 of the Luo-Rudy cardiac action ...

The restitution kinetics of action potential duration (APD) were investigated in paced canine Purkinje fibers (P; n = 9) and endocardial muscle (M; n = 9), in isolated, perfused canine left ventricles during ventricular fibrillation (VF; n = 4), and in endocardial muscle paced at VF cycle lengths (simulated VF; n = 4). Restitution was assessed with the use of two protocols: delivery of a single...

We sought to explore the distribution pattern of Na(+) channels across ventricular wall, and to determine its functional correlates, in the guinea pig heart. Voltage-dependent Na(+) channel (Na(v)) protein expression levels were measured in transmural samples of ventricular tissue by Western blotting. Isolated, perfused heart preparations were used to record monophasic action potentials and vol...

Günzel, D., P. Florian, J. F. Richter, H. Troeger, J. D. Schulzke, M. Fromm, and A. H. Gitter. Restitution of single-cell defects in the mouse colon epithelium differs from that of cultured cells. Am J Physiol Regul Integr Comp Physiol 290: R1496–R1507, 2006. First published January 5, 2006; doi:10.1152/ajpregu.00470.2005.—Integrity of colon epithelium is of crucial importance and, as small def...

BACKGROUND The combined effects of excitability and action potential duration (APD) restitution on wavefront dynamics remain unclear. METHODS AND RESULTS We used optical mapping techniques to study Langendorff-perfused rabbit hearts. In protocol IA (n=10), D600 at increasing concentrations was infused during ventricular fibrillation (VF). With concentration increased to 0.5 mg/L, fast VF (dom...

Following superficial injury, neighbouring gastric epithelial cells close the wound by rapid cell migration, a process called epithelial restitution. Na+ /H+ exchange (NHE) inhibitors interfere with restitution, but the role of the different NHE isoforms expressed in gastric pit cells has remained elusive. The role of the basolaterally expressed NHE1 (Slc9a1) and the presumably apically express...

Restoration of the colonic epithelial barrier is an important response during colitis. L-arginine (L-Arg) is a semiessential amino acid that reduces murine colitis induced by Citrobacter rodentium. Cationic amino acid transporter (CAT) proteins increase L-Arg uptake into cells. L-Arg is utilized to produce nitric oxide (NO), by inducible NO synthase (iNOS), or L-ornithine (L-Orn) by arginase (A...

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 ventricular myocardium. METHODS AND RESULTS Monophasic action potentials were recorded from the r...

OF THESIS CORRELATING THE MAGNITUDE AND SPATIAL GRADIENT OF ALTERNANS Electrical restitution has been shown to inaccurately predict the occurrence of alternans of action potential duration. A new method using the spatial gradient of alternans (SGA) is proposed to predict alternans and cardiac electrical stability. A simulated 1-D strand of tissue was used to compare indexes computed from restit...

Early epithelial restitution occurs as a consequence of intestinal epithelial cell (IEC) migration after wounding, and its defective regulation is implicated in various critical pathological conditions. Polyamines stimulate intestinal epithelial restitution, but their exact mechanism remains unclear. Canonical transient receptor potential-1 (TRPC1)-mediated Ca(2+) signaling is crucial for stimu...