Fig. 9. Electron micrographs reveal structural defects in basement membrane. (A) Electron micrographs of longitudinal sections of EDL muscles isolated from phenotypic SSPN-Tg and non-Tg mice. Two neighboring muscle fibers are shown in each field. The sarcolemma is denoted by arrows. Bar, 1 µm. (B) Electron micrographs were taken at higher magnifications to visualize the basement membrane. The distance between adjacent sarcolemmas is greater in the SSPN-Tg muscle than in the non-Tg muscle (white arrows). The extracellular matrix is visualized as a tight linear structure between two neighboring sarcolemmas in the non-Tg tissue. However, the extracellular matrix is randomly placed in dense, disorganized clumps in the phenotypic SSPN-Tg muscle (black arrows). Bar, 200 nm.