Lesions of the islets of Langerhans in encephalomyocarditis virus-infected mice with diabetes mellitus-like disease. I. Acute lesions.

Mice infected with the M variant of the encephalomyocarditis (EMC) virus develop lesions of the islets of Langerhans associated with a diabetes mellitus-like disease. Ultrastructural alterations become evident in capillaries and beta cells at a time when large amounts of virus are present in the pancreatic tissue. Although some beta cells become necrotic, degranulation and contraction of intact cells is the prominent lesion. Changes in the capillaries appear early in the course of the infection and later are associated with interstitial fibrosis in and around the islets. During early convalescence, beta cells are degranulated and exhibit striking alterations of cytoplasmic organelles. These changes appear to be consequent to increased metabolic activity by the residual insular tissue. Interestingly enough, specific lesions of the alpha cells are not observed.