Figure 4

Ultrastructural studies of the biceps femoris muscle from a Rottweiler puppy affected with XLMTM (puppy III-12). Prominent features include myofibrillar disarray, SR profiles (arrows), autophagosomes (arrowheads) and other degenerating organelles (A), centrally located nuclei (B), dilated tubular structures (arrows, C), and mitochondrial accumulation with interspersed glycogen granules (D). A cross-section of a double membrane bound (arrows) autophagic vacuole is shown with entrapment of organelles including T-tubule (arrowhead) and junctional SR (asterisk) profiles, other membranes of undetermined origin, mitochondria, and glycogen granules (E). Multiple adjacent autophagic vacuoles occupying abnormal fiber regions are shown in (F). Scale bar in lower right corner of F = 0.2 μm for A, D and E, 0.6 μm for B, 0.3 μm for C, and 0.3 μm for F.