Filaments and rod-shaped tubulated bodies in the endothelia of anterior cerebral arteries in young rats.

Endothelia of the anterior cerebral arteries in rats aged 1 to 3 days were studied. Thin (about 50-90 A) and thick (about 100-110 A) filaments are present in the endothelia. Numerous spherical- or rod-shaped bodies, measuring approximately 0.07 to 0.3 micrometer in diameter and up to 0.6 micrometer in length occur in the endothelial cells. These bodies contain a tubular structure. The diameter of the individual tubules is about 200 A. The present observations suggest that spherical- or rod-shaped inclusions are first synthesized in the rough endoplasmic reticulum and thereafter these materials are transported into the Golgi complex for maturation. A small number of the inclusions, however, may originate directly from the rough endoplasmic reticulum and not pass through the Golgi apparatus.