Ultrastructural cytopathology of mouse myocardium associated with EMC viral infection

Lesions in the mouse myocardium are described which are fairly characteristic of cytopathology caused by direct infection with EMC virus. The lesions consisted of formation of numerous cytoplasmic membrane-bound vesicles and vacuoles. Viral crystals were frequently associated with these lesions in the newborn mouse. Accompanying the lesion was a breakdown of the myofibrils, mitochondria, sarcoplasmic reticulum and transverse tubular system. The absence of these organelles clearly indicates a reduced contractability of the damaged myocytes. Possible factors resulting in membrane proliferation and mechanisms for cell lysis are discussed.