Excitation-contraction coupling in human heart failure examined by action potential clamp in rat cardiac myocytes.

The effect of the loss of the notch in the human action potential (AP) during heart failure was examined by voltage clamping rat ventricular myocytes with human APs and recording intracellular Ca(2+) with fluorescent dyes. Loss of the notch resulted in about a 50% reduction in the initial phase of the Ca(2+) transient due to reduced ability of the L-type Ca(2+) channel to trigger release. The failing human AP increased non-uniformity of cytosolic Ca(2+), with some cellular regions failing to elicit Ca(2+)-induced Ca(2+) release from the sarcoplasmic reticulum.

Stretch-activated channels in the heart: contributions to length-dependence and to cardiomyopathy.

The stretch-induced increase in force production of ventricular muscle is biphasic. An abrupt increase in force coincides with the stretch, which is then followed by a slower response that develops over minutes (the slow force response or SFR). The SFR is accompanied by a slow increase in the magnitude of the intracellular Ca2+ transient, but the stretch-dependent mechanisms that give rise to this remain controversial.

Soft tissue impact characterisation kit (STICK) for ex situ investigation of heart rhythm responses to acute mechanical stimulation.

Both mechanical induction and mechanical termination of arrhythmias have been reported in man. Examples include pre-cordial impacts by sports implements (baseballs, pucks) that can trigger arrhythmias, including ventricular fibrillation, or via the so-called pre-cordial thump, used as an emergency resuscitation measure to convert arrhythmias to normal sinus node rhythm. These interventions have been partially reproduced in experimental studies on whole animals.

Species- and preparation-dependence of stretch effects on sino-atrial node pacemaking.

Acute dilation of the right atrium (e.g., via increased venous return) raises spontaneous beating rate (BR) of the heart in many species.

Species-independent metabolic response to an increase of [Ca(2+)](i) in quiescent cardiac muscle.

1. The aim of the present investigation was to contrast the Ca2+ dependence of cardiac energy metabolism in two species with differential reliance on extracellular Ca2+ for excitation-contraction coupling. 2.

Effects of acute ventricular volume manipulation on in situ cardiomyocyte cell membrane configuration.

Effects of mechanical stimulation on cardiac electrical activity, gene expression, protein synthesis, and tissue remodelling have received increasing attention in recent years, as reviewed in this issue of PBMB. Little is known, though, about how changes in ventricular filling affect the cell configuration of cardiomyocytes in the ventricular wall. Here, we present first electron-microscopic insight into changes in cardiomyocyte cell structure in situ during acute ventricular volume manipulation.

Role of the 293b-sensitive, slowly activating delayed rectifier potassium current, i(Ks), in pacemaker activity of rabbit isolated sino-atrial node cells.

Objectives: (i) to characterize the electrophysiological properties of the slowly activating delayed rectifier potassium current, i(Ks), defined as the 293b-sensitive current, during the action potential (AP) of rabbit sino-atrial node (SAN) pacemaker cells; (ii) to evaluate the contribution of i(Ks) to the pacemaker AP under physiological conditions and during beta-adrenergic stimulation.

Methods: Rabbit SAN pacemaker cells were studied using the perforated patch clamp technique in voltage-, AP- and current-clamp modes.

Results: Voltage-clamp findings.