Fig. 2

Twitch sarcomere length kinetics and Ca²⁺ transient signals from isolated, single dystrophin-intact flexor digitorum brevis (FDB) from C57BL10 (BL10; 6 mice, 93 fibers) and dystrophin-deficient FDB fibers from mdx mice (3 mice, 40 fibers). A, B Representative ensemble average of sarcomere length shortening patterns from FDB of BL10 and mdx mice. Sarcomere length on the Y-axis is inverted. Each tick on the Y-axis is 0.05 μm (blue arrow). Electric field stimulation was applied at 0.2-s point (red mark). C Peak sarcomere length shortening during twitch contraction. D Time to peak sarcomere length shortening during twitch contraction. E Time from peak to 75% of baseline of sarcomere length during twitch contraction. F, G Ensemble average of Ca²⁺ transient patterns measured by Fura-2AM fluorescence from FDB of BL10 and mdx mice. Each tick on the Y-axis is 0.1 (blue arrow). H Peak Ca²⁺ transient during twitch contraction. I Time to peak Ca²⁺ transient during twitch contraction. J Time from peak to 75% of baseline of Ca²⁺ transient during twitch contraction. ^#P < 0.05, ^##P < 0.001 by Student’s t test