If you are seeing this message, you may be experiencing temporary network problems. Please wait a
few minutes and refresh the page. If the problem persists, you may wish to report it to your local
Network Manager.
It is also possible that your web browser is not configured or not able to display style sheets.
In this case, although the visual presentation will be degraded, the site should continue to be
functional. We recommend using the latest version of Microsoft or Mozilla web browser to help minimise
these problems.
Author's permanent address N. Shirokova: A. A. Bogomoletz Institute of Physiology, Ukranian National Academy of Sciences, Bogomoletz Street 4, Kiev 24, Ukraine.
This manuscript was accepted as a Short Paper for rapid publication.
Copyright The Physiological Society 1997
ABSTRACT
1.
Fluo-3 fluorescence associated with Ca2+ release was recorded with confocal microscopy in single muscle fibres. Clamp depolarization to −65 or −60 mV elicited Ca2+ sparks with amplitudes and spatial widths distributed approximately normally, with mean values of 0.79 of resting fluorescence and 0.8 μm (S.D., 0.17 and 0.2 μm; n= 193 ), respectively. Given these distributions, events of amplitude less than 0.45 or width less than 0.4 μm are unlikely to be sparks.
2.
Low voltage depolarization (−72 mV) elicited only one spark per triad every 6 s, but generated a relative increase in fluorescence at triads of 0.05. This increase must therefore have been due to events smaller than sparks.
3.
The variance/mean ratio of triadic fluorescence gradients averaged 0.11 at low voltages and increased severalfold at the higher voltages at which sparks appeared, indicating the existence of at least two event amplitudes.
4.
Tetracaine (200 μm) reversibly abolished sparks and the early peak of Ca2+ release at all voltages. In its presence, discrete events were smaller than the spark criterion, and triadic gradients had a variance/mean ratio of 0.11.
5.
The phenylalkylamine D600 (2 μm) reduced release at all voltages, abolishing sparks and the peak of Ca2+ release at low but not at high voltages.
6.
The parallel abolition of all sparks and the peak of Ca2+ release indicates that both phenomena are activated by Ca2+. The restoration of sparks by voltage in D600 suggests that release in small events provides the trigger Ca2+ for activation of sparks.
As the world turns its sporting gaze towards Vancouver for the 2010 Winter Olympics, Experimental Physiology marks the occasion with a special issue exploring the biological and environmental challenges elite winter athletes must overcome to win gold. Read the press release.
