Fenestrated vessels in human hemangioblastoma

Abstract

✓ The capillaries in two cerebellar hemangioblastomas were studied by thin-section and freeze-fracture techniques. Fenestrae were found in the attenuated portions of the endothelium, and plasmalemmal vesicles in the nonfenestrated portions. In freeze-fracture preparations the fenestrae of the endothelial plasma membrane were about 450 to 550 A in diameter. They appeared as holes and “necks” in clusters of about 40 to 60 per µm 2 . When the fracture plane passed in a stepwise fashion from the luminal plasma membrane into the contraluminal plasma membrane, the fenestrae at the fracture edge involved both plasma membranes.