Fig. 6. Reduced PC recruitment to brain capillaries in endothelium-specific Pdgfb knockouts. Whole-mount ß-gal staining of PCs in the midbrain. (A-D) Ventricular view of entire midbrain hemispheres; (E-H) Distribution of PCs (nuclear staining) in the subventricular zone (SVZ) plexus of the hemisphere. Black arrowheads indicate extensively dilated vessels; red arrowheads indicate focal hemorrhages. Note the dramatic PC deficiency in Pdgfb^–/– tissue (B,F,J) and the intermediate PC densities in lox/– tissue (C,D,G,H,K,L). (I-L) Sections (100 µm thick) of midbrain hemispheres, with the meningeal surface to the left and the ventricular surface to the right. The distribution of ß-gal-positive PCs along the radial vessels (rad) is seen. In the lox/– embryos (K,L) many radial branches completely lack ß-gal-positive PC coverage (green arrowheads), as in the –/– embryos (J), whereas other branches show normal coverage (white arrowheads).