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Approximately 60-70% of the total fiber calcium was localized in the terminal cisternae (TC) in resting frog muscle as determined by electron-probe analysis of ultrathin cryosections. During a 1.2 s tetanus, 59% (69 mmol/kg dry TC) of the calcium content of the TC was released, enough to raise total cytoplasmic calcium concentration by approximately 1 mM.(More)
Homogeneous populations of single myocytes showing good preservation of ultrastructure were obtained by enzymatic digestion of rabbit and rat hearts, and maintained in a relaxed state in the presence of free Ca2+ concentrations less than 10(-7) M. Ultrastructural details such as a cytoskeleton of 100-A filaments connected to the sarcolemma at the Z lines(More)
Two novel methods used to study smooth muscles-electron probe X-ray microanalysis and Ca2+-sensitive indicators (which are used for resolving, respectively, the spatial distribution and temporal distribution of calcium)-are briefly reviewed and the major findings obtained are summarized. In smooth muscle the sarcoplasmic reticulum is the major intracellular(More)
The composition of dark-adapted and illuminated retinal rod outer and inner segments and mitochondria was determined with electron probe X-ray micro-analysis of cryosections. The concentration of Ca in the outer segment was 0.4 mmol/kg dry wt. (0.1 Ca/rhodopsin) and did not measurably change upon illumination with saturating light for 5 min. The(More)
Inositol 1,4,5-trisphosphate (InsP3) can stimulate skinned smooth and skeletal muscle to contract by initiating Ca2+ release from the sarcoplasmic reticulum. Whether this process is an integral component of the in vivo muscle activation mechanism was tested by releasing InsP3 rapidly within skinned muscle fibers of rabbit main pulmonary artery and frog(More)
The distribution of filaments was studied in hypertrophied rabbit vascular smooth muscle. Hypertrophy was induced by partial ligation of the portal-anterior mesenteric vein. 14 d after ligation, there was an approximately threefold increase in the number of intermediate filaments per cross-sectional area, as compared to control values. The(More)
The recognition that the endoplasmic reticulum (ER), rather than the mitochondria, is the main organelle regulating the cytoplasmic Ca2+ concentration in non-muscle cells supports the notion that an alternative physiological role of mitochondrial Ca transport is the modulation of Ca-sensitive mitochondrial enzymes through small (micromolar) fluctuations in(More)
The amplitude of interrupted contractions evoked by noradrenaline or caffeine in Ca2+-free, high-K+ solutions containing EGTA or La3+ was determined in small (40-60 micron thick) bundles of guinea-pig portal anterior mesenteric vein. Interrupted contractions were produced by removing the stimulating agent as soon as the amplitude of the tension record(More)