Morphologic changes in extraocular muscles of the dystrophic hamster.

Cardiomyopathic hamsters (UM-X7.1 strain) have demonstrable myopathy involving both skeletal and cardiac muscle. In addition, they have multiple ocular abnormalities. In this study, extraocular muscles were examined by light and electron microscopy. Changes observed within affected muscle fibers were variable and included coagulation necrosis, lysis of myofibrils, mitochondrial changes, and infiltration by phagocytic cells. Regenerative changes included duplication of myoblast nuclei, proliferation of sarcoplasmic reticulum, and myofibrillogenesis. The lesions are presumably myogenic in origin. The cardiomyopathic hamster may be useful as an animal model for certain types of ocular myopathy in man.