Electron microscopy of pulmonary vasculature after application of fulvine.

, , 511-521. This is an electron microscopic study of the effect of fulvine on the pulmonary arteries and veins of the rat. Marked constriction of the arteries was evident from excessive crenation of the internal elastic membrane, resulting in squeezing of nuclei of both smooth muscle cells and endothelial cells between the folds on either side of this lamina. Four weeks after fulvine administration fibrin deposits were found in the arterial media followed by necrosis of muscle cells. In the adventitia there was a new development of smooth muscle fibres, probably derived from fibroblasts. In pulmonary veins and venules there was also constriction and hyperplasia of smooth muscle. The muscle cells showed pronounced cytoplasmic excrescences protruding into the endothelial layer. This probably reflects constriction of the muscle cells. As in the arteries, fibrin deposits and necrosis of muscle cells were observed from the fourth week onward.