Electron microscopic study on the proximal portions of the anterior cerebral arteries in rats with long-term hypertension.

Proximal portions of the anterior cerebral arteries in rats with long-term hypertension were electron microscopically studied. The abnormal substances such as granules, vesicles, vacuoles and other membranous structures, relatively homogeneous masses, and basement membrane-like substances were observed around the medial smooth muscle cells. Basement membrane-like substances were increased with advancing age and the majority of these substances are thought to be turned from the granulo-vesicles. Abnormal substances deposited in the media are thought to be "hyalino-fibrous materials". The majority of our materials had a clear-cut border between the media and the adventitia. The subendothelial spaces were slightly distended with fibrillar and/or finely granular substances with age, but neither cellular element nor fibrinoid substance was found in them.