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Discrete events of Ca2+ release from the sarcoplasmic reticulum (SR) have been described in cardiac, skeletal, and smooth muscle. In skeletal muscle these release events originate at individual channels. In cardiac muscle, however, it remains a question of debate whether localized Ca2+ release transients, termed Ca2+ sparks, originate from single release(More)
In mitochondria the opening of a large proteinaceous pore, the "mitochondrial permeability transition pore" (MTP), is known to occur under conditions of oxidative stress and matrix calcium overload. MTP opening and the resulting cellular energy deprivation have been implicated in processes such as hypoxic cell damage, apoptosis, and neuronal excitotoxicity.(More)
1. Confocal microscopy in combination with the calcium-sensitive fluorescent probe fluo-3 was used to study spatial aspects of intracellular Ca2+ signals during excitation-contraction coupling in isolated atrial myocytes from cat heart. 2. Imaging of [Ca2+]i transients evoked by electrical stimulation revealed that Ca2+ release started at the periphery and(More)
Confocal laser scanning microscopy and the potentiometric fluorescence probe tetramethylrhodamine ethyl ester were used to measure changes in membrane electrical potential (DeltaPsi(m)) in individual mitochondria after isolation or in the living cell. Recordings averaged over small mitochondrial populations revealed a gradual decline in DeltaPsi(m) caused(More)
1. The cellular mechanisms governing cardiac atrial pacemaker activity are not clear. In the present study we used perforated patch voltage clamp and confocal fluorescence microscopy to study the contribution of intracellular Ca2+ release to automaticity of pacemaker cells isolated from cat right atrium. 2. In spontaneously beating pacemaker cells, an(More)
Electromechanical alternans was characterized in single cat atrial and ventricular myocytes by simultaneous measurements of action potentials, membrane current, cell shortening and changes in intracellular Ca2+ concentration ([Ca2+]i). Using laser scanning confocal fluorescence microscopy, alternans of electrically evoked [Ca2+]i transients revealed marked(More)
Mitochondria have been implicated in intracellular Ca2+ signaling in many cell types. The inner mitochondrial membrane contains Ca2+-transporting proteins, which catalyze Ca2+ uptake and extrusion. Intramitochondrial (matrix) Ca2+, in turn, regulates the activity of Krebs cycle dehydrogenases and, ultimately, the rate of ATP synthesis. In the myocardium,(More)
Electrical excitation of the mammalian heart originates from specialized pacemaker cells in the right atrium. Pacemaker activity depends on multiple ion channels and transport mechanisms that reside primarily within the plasma membrane. However, recent evidence indicates that intracellular Ca2+ release from the sarcoplasmic reticulum also contributes(More)
1. Atrial myocytes obtained by enzymatic perfusion of hearts from adult guinea-pigs and cultured for 0-14 days were studied using the whole-cell voltage-clamp technique. 2. Superfusion of the myocytes with diluted sera (1:100 to 1:10,000) from different species (human, horse, guinea-pig) evoked an inward rectifying K+ current. The voltage-dependent(More)
The subcellular spatial and temporal organization of agonist-induced Ca2+ signals was investigated in single cultured vascular endothelial cells. Extracellular application of ATP initiated a rapid increase of intracellular Ca2+ concentration ([Ca2+]i) in peripheral cytoplasmic processes from where activation propagated as a [Ca2+]i wave toward the central(More)