Calcium sparks were discovered in single isolated rat cardiac myocytes by Cheng et al. (1993) while imaging fluorescence from the calcium indicator fluo-3 (Minta et al., 1989) with a confocal microscope. Cardiac muscle calcium sparks are associated with an approximate doubling of the resting fluo-3 fluorescence (⌬ F / F ϭ 1.0) and occupy a tiny region of the cell ‫ف‬ 2 ␮ m in diameter. A simple...

Bay K 8644, an L-type Ca2+ channel agonist, was shown previously to increase resting sarcoplasmic reticulum (SR) Ca2+ loss and convert post-rest potentiation to decay in dog and ferret ventricular muscle. Here, the effects of Bay K 8644 on local SR Ca2+ release events (Ca2+ sparks) were measured in isolated ferret ventricular myocytes, using laser scanning confocal microscopy and the fluorescen...

Amplitude, spatial width, and rise time of Ca(2+) sparks were compared in frog fast-twitch muscle, in three conditions that alter activation of release channels by [Ca(2+)]. A total of approximately 17,000 sparks from 30 cells were evaluated. In cells under voltage clamp, caffeine (0.5 or 1 mM) increased average spark width by 28%, rise time by 18%, and amplitude by 7%. Increases in width were ...

Ca sparks are elementary Ca-release events from intracellular Ca stores that are observed in virtually all types of muscle. Typically, Ca sparks are measured in the line-scan mode with confocal laser-scanning microscopes, yielding two-dimensional images (distance vs. time). The manual analysis of these images is time consuming and prone to errors as well as investigator bias. Therefore, we deve...

When the lightning current enters ground through grounding system, impulse dispersion performance can be observed by phenomenon of soil spark discharge, which is fundamentally determined nearby soil. At present, engineers use an empirical formula to convert discharge coefficient resistance. Therefore, there no available quantitative analysis method evaluate performance. To solve this problem, p...

the micro wire electrical discharge machining (micro wire-edm) process is a modern machining process with various applications in manufacturing micro-parts. the recast layer remaining on the machined surfaces is an inevitable complication of this process. this layer can subsequently affect the machined parts performance. to optimize the recast layer in the micro wire-edm of the molybdenum micro...

the preparation of air–fuel mixture is considerably dependent on fluid flow dynamics to achieve improved performance, efficiency, and engine combustion in the appearance of flow. in this study, the effects of mixtures of hydrogen and compressed natural gas (cng) on a spark ignition engine are numerically considered. this article presents the results of a direct-injection engine using methane–hy...

Discrete Ca2+ release events (Ca2+ "sparks") were recorded in cut segments of single frog skeletal muscle fibers using a video-rate laser-scanning confocal microscope operating in line-scan mode (63 microseconds per line). Fibers loaded with the Ca2+ indicator fluo-3 were voltage clamped at a holding potential of 0 mV, briefly reprimed at -90 mV, and then strongly depolarized with a large test ...

The properties of Ca(2+) sparks in frog intact skeletal muscle fibers depolarized with 13 mM [K(+)] Ringer's are well described by a computational model with a Ca(2+) source flux of amplitude 2.5 pA (units of current) and duration 4.6 ms (18 degrees C; Model 2 of Baylor et al., 2002). This result, in combination with the values of single-channel Ca(2+) current reported for ryanodine receptors (...