Figure 1.

Electron micrographs of vessels in the normal brain (A), VEGF:CHO (B), and M1S (C) tumors growing in the brain. An extensive electron-dense endothelial junction is common to normal brain vessels (A, j). This junction is drastically compromised in tumor vessels, in which the intercellular gaps can be as large as 260 nm (B and C, asterisks). VEGF:CHO tumors had numerous gaps (B, asterisks), which may be remnants of fenestrations (arrowheads). B: Boxed areas are shown as insets. Bars (A, B, insets, and C), 500 nm.