Abstract
Summary
The femoral arteries of newborn mice which were experimentally infected with encephalomyocarditis (EMC) virus were studied electron microscopically. Viral crystalline aggregates were observed within the cytoplasm of adventitial fibroblasts in 4 of 5 animals studied and within a macrophage of one animal. The nuclear chromatin of medial smooth muscle cells was frequently marginated, and margination or pyknosis of nuclear material was observed in fibroblasts of the tunica adventitia.
Cytonecrosis typical of infection with picornavirus was observed in adventitial fibroblasts. The most prominent feature of this cytonecrosis was the abundance of membrane-vesicle complexes. The rough endoplasmic reticulum was occasionally dilated and fragmented. Mac-rophages were present in the adventitial and loose connective tissue surrounding the artery. There was an increase of collagen fibers around the internal elastic lamina, which may suggest an irritation or inflammation of the arterial wall. Such early inflammation, which may indicate a toxic reaction, may be the result of viral injury.
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