IMAGE-ANALYSIS-BASED ASSESSMENT OF THE EFFECTS OF THE CA2-JUMP TECHNIQUE ON SARCOMERE UNIFORMITY()

A new image analysis-based technique was used to quantitatively examin e the effects of the ''Ca2+-jump'' activation protocol on the maintena nce of fiber quality in skinned rabbit psoas muscle fiber segments. Sp ecifically, contractions in pCa 4.6 were preceded by short-duration '' preactivation'' soaks in a solution in which EGTA was replaced with th e low-Ca2+ buffering capacity analog hexamethylenediamine-N, N, N', N' -tetraacetate, which facilitated rapid Ca2+ equilibration within the f iber segments. Fiber quality was assessed by examining the Fourier spe ctra of the muscle fiber images before, during, and after activation. Segment lengths were typically below 500 mu m, thus allowing the major ity of the sarcomeres to be visualized in the held of view (x200 and x 400 magnification). The preactivation protocol resulted in less deteri oration of fiber quality with repetitive activation. In addition, ther e was also a significant reduction in the time required to reach the 5 0% level of maximum tension, with no significant change in the maximum tension level.