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Proceedings Paper

Dimensions of calcium release domains in frog skeletal muscle fibers
Author(s): Julio L. Vergara; Marino DiFranco; David Novo
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Paper Abstract

The spatiotemporal properties of the Ca2+ release process in skeletal muscle fibers were determined using an improved confocal spot detection system. Muscle fibers were loaded with the low affinity fluorescent Ca2+ indicator OGB-5N and localized action potential-induced fluorescence signals were recorded from consecutive locations separated by 200 nm within a single sarcomere. Three-dimensional reconstructions on the Ca2+ transients illustrate the existence of domains of increased fluorescence around Ca2+ release sites in the neighborhood of the T-tubules. We estimated the dimensions of these domains by drawing isochronal curves ((delta) F/F vs. spot position) and fitting Gaussian profiles to them. It was found that the earliest detectable full-width-at-half- maximum of these profiles was 0.77 +/- 0.25 micrometers and increased rapidly with time to 1.4 +/- 0.2 micrometers at their peak (18 degree(s)C). A brief, but statistically significant delay of 0.8 +/- 0.42ms was observed between the onset of the fluorescent transients at the Z- and M-lines. Our results are compatible with the possibility that, in response to AP stimulation, Ca2+ is not released exclusively from the junctional region of the sarcoplasmic reticulum, but from a broader expanse of the triadic region.

Paper Details

Date Published: 2 July 2001
PDF: 11 pages
Proc. SPIE 4259, Biomarkers and Biological Spectral Imaging, (2 July 2001); doi: 10.1117/12.432488
Show Author Affiliations
Julio L. Vergara, Univ. of California/Los Angeles School of Medicine (United States)
Marino DiFranco, Univ. of California/Los Angeles School of Medicine (United States)
David Novo, Univ. of California/Los Angeles School of Medicine (United States)


Published in SPIE Proceedings Vol. 4259:
Biomarkers and Biological Spectral Imaging
Gregory H. Bearman; Darryl J. Bornhop; Darryl J. Bornhop; Richard M. Levenson, Editor(s)

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