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We present a model that provides a unified framework for studying Ca2+ sparks and Ca2+ waves in cardiac cells. The model is novel in combining 1) use of large currents (approximately 20 pA) through the Ca2+ release units (CRUs) of the sarcoplasmic reticulum (SR); 2) stochastic Ca2+ release (or firing) of CRUs; 3) discrete, asymmetric distribution of CRUs(More)
Excitation-contraction coupling was studied in mammalian cardiac cells in which the opening probability of L-type calcium (Ca2+) channels was reduced. Confocal microscopy during voltage-clamp depolarization revealed distinct local transients in the concentration of intracellular calcium ions ([Ca2+]i). When voltage was varied, the latency to occurrence and(More)
The firing pattern displayed by neuronal aggregates is thought to play a key role in cortical development and physiology. In this study, we have employed optical recording of intracellular calcium to monitor activity of multiple neurons simultaneously in primary cortical cultures. With this approach, we have observed spontaneous synchronous calcium(More)
1. We sought to distinguish two types of Ca2+ channel in guinea-pig ventricular cells (T-type and L-type) and to characterize their respective gating and permeation properties when Ca2+ (1-10 mM) is the charge carrier, as is the case physiologically. 2. Na+ was removed from both the external and internal solutions to eliminate currents through Na+ channels(More)
Previous models of cardiac Ca2+ sparks have assumed that Ca2+ currents through the Ca2+ release units (CRUs) were approximately 1-2 pA, producing sparks with peak fluorescence ratio (F/F(0)) of approximately 2.0 and a full-width at half maximum (FWHM) of approximately 1 microm. Here, we present actual Ca2+ sparks with peak F/F(0) of >6 and a FWHM of(More)
1. The mechanisms that control release of Ca2+ from the sarcoplasmic reticulum (SR) of guinea-pig ventricular cells were studied by observing intracellular calcium concentration ([Ca2+]i transients) and membrane currents in voltage-clamped guinea-pig ventricular myocytes perfused internally with Fura-2. 2. Sarcolemmal Ca2+ current was identified through the(More)
Drug-induced triggered arrhythmias in heart muscle involve oscillations of membrane potential known as delayed or early afterdepolarizations (DADs or EADs). We examined the mechanism of DADs and EADs in ferret ventricular muscle. Membrane potential, tension and aequorin luminescence were measured during exposure to elevated [Ca2+]0, strophanthidin and/or(More)
1. Membrane currents and changes in [Ca2+]i attributable to the operation of an electrogenic Na-Ca exchange mechanism were recorded in single isolated guinea-pig ventricular myocytes under voltage clamp and internal perfusion with the Ca2+ indicator Fura-2. 2. Ionic currents that interfere with the measurement of Na-Ca exchange current were blocked through(More)
1. A method has been developed for calculating the flux of Ca2+ across the sarcoplasmic reticulum (SR) during excitation-contraction coupling in mammalian heart cells. FSR will symbolize the net rate of movement of Ca2+, per litre of accessible cytoplasm, into or out of the sarcoplasmic reticulum. FSR has the units MS-1. 2. A theory of the cytoplasmic(More)