Contractile activity of C2C12 myotubes.

<p>(A) The average of contractile activity is shown. The contractile activity of the cells was evaluated as the distance shortened between specified points on a myotube using a motion analyzer. Change in the distance was tracked during contraction. Contraction of the myotubes is synchronized with the intermittent electrical stimulation (see Movie S1). The myotubes were stimulated with electrical pulses of 50 V at 1 Hz for 3 ms at 997-ms intervals. The onset of the electric pulses is shown by solid arrows and their cessation is shown by dashed arrows. Data are mean ± S.E.M., n = 5. (B) Integrated values for 5-s change in the distance at 0, 1, 2, and 3 h after the onset of electrical stimulation. The video is shown in Movies S2, S3, S4 and S5 (0–3 h). The change in the distance at 0, 1, 2, and 3 h after the onset of stimulation are shown as the integral values of the areas above the curves for 5 s (the values are converted to positive number). The integrated values 1, 2, and 3 h after stimulation onset are comparable with that at the onset (0 h). Data are shown as mean ± S.E.M., n = 3.