Figure 5.

Effect of 0.3 μM OM on c. Effect of 0.3 μM OM on force responses to a 2% sudden stretch at (A) short SL and (B) long SL. Force data were normalized by the isometric steady-state value before ML perturbation. c describes the rate of force decay to a minimal force point, b represents the rate constant of delayed force rise, and E_R represents the ML-mediated increase in the steady-state force (24). Parameters b, c, and E_R are estimated by fitting the nonlinear recruitment-distortion model to a family of force responses to various-amplitude ML perturbations (24). (C) Bar graph showing the effect of 0.3 μM OM on c at short and long SL. Statistical differences were analyzed by two-way ANOVA and subsequent post hoc multiple pairwise comparisons using Fisher’s least-squares difference method. Asterisks indicate a significant difference from untreated fibers (^∗p < 0.05, ^∗∗∗p < 0.001). A separate set of fibers from three hearts was used for each group. The numbers of fibers measured for untreated and 0.3 μM OM groups at short SL were 12 and 11, whereas those at long SL were 12 and 12, respectively. Data are expressed as mean ± SE.