FIGURE 4

Sections from a P18 rat subjected to in situ perfusion with OX26 for 15 minutes and examined for OX26 (red) and laminin (green). (A) The vascular bed is consistently labeled with OX26. (B) Simultaneous detection of OX26 and laminin using double-labeling fluorescence. The laminin-containing basal membranes sheath the OX26-containing endothelium, which explains why the green color dominates except in areas where capillaries are cut open. (C, D) Images showing the nonidentical distribution of OX26 and laminin shown at high-power magnification. (E−H) Confocal images revealing the distribution of OX26 (E) and laminin (F). (G) Merging the images shown in panels E and F does not reveal colocalization meant to be yellow, or distribution of OX26 on the nonluminal side of laminin. (H) The BCEC shown in panels E through G was reorientated at the red and green lines and shown in perpendicular planes in panels I and J, respectively. Both I and J show that OX26 fails to associate with laminin. The crossing of lines shown in panels I and J hallmarks the point of lines crossing in panel H. Scale bars =160 m (A), 80 m (B), 17 m (C, D), and 2 m (E−J)