Fig. 1. Electron micrographs of the extensor digitorum longus fifth toe muscle from wild-type (A) or desmin-null (B) animals fixed under conditions of passive loading, displaying the method for digitizing Z-disk endpoints to yield horizontal Z-disk displacement (x_myo) and sarcomere length (SL). Note the greater stagger in adjacent Z disks in muscle from knockout versus wild-type animals. For the frames displayed (approximately one-fifteenth the area of a full micrograph), for (A), x_myo=0.09 µm and SL=3.57 µm, for (B), x_myo=0.58 µm and SL=3.60 µm. The calibration is identical for both micrographs. Scale bar, 1 µm.