Fig. 7. Abnormal endothelial cell morphology in class B integrin ß8-deficient brains. (A-D) Electron micrographs of capillary structure in E12.5 wild-type (A) and integrin ß8-deficient mutant (B-D) brains. In contrast to the wild type (A), the endothelial cells in the mutant display abundant active membrane protrusions (B, arrows) and large empty spaces surrounding the capillaries (B,C, *). In addition, fenestrations (D, arrows) are often seen in the mutant endothelium. P, pericyte; EC, endothelial cell. Scale bars: 5 µm in A-C; 1 µm in D.