Vol. 85, Issue 3, 955-961, September 1998
Image-analysis-based assessment of the effects of
the "Ca2+-jump" technique on
sarcomere uniformity
M. P.
Slawnych,
L.
Morishita, and
B. H.
Bressler
Department of Anatomy, University of British Columbia,
Vancouver, British Columbia, Canada V6T 1Z3
A new image
analysis-based technique was used to quantitatively examine the effects
of the "Ca2+-jump"
activation protocol on the maintenance of fiber quality in skinned
rabbit psoas muscle fiber segments. Specifically, contractions in pCa
4.6 were preceded by short-duration "preactivation" soaks in a
solution in which EGTA was replaced with the
low-Ca2+ buffering capacity analog
hexamethylenediamine-N, N, N', N'-tetraacetate, which facilitated rapid Ca2+
equilibration within the fiber segments. Fiber quality was assessed by
examining the Fourier spectra of the muscle fiber images before, during, and after activation. Segment lengths were typically below 500 µm, thus allowing the majority of the sarcomeres to be visualized in
the field of view (×200 and ×400 magnification). The
preactivation protocol resulted in less deterioration of fiber quality
with repetitive activation. In addition, there was also a significant reduction in the time required to reach the 50% level of maximum tension, with no significant change in the maximum tension level.
muscle fiber quality image analysis; uniform fiber activation
