(A) A portion of the superficial PTs was transfected with GFP-actin using an adenovirus vector. Following i.v. infusion of a small, filterable red dextran, ischemia was induced for 25 minutes, and then blood flow was returned just prior to imaging the area. A single plane from a 3D volume video shows GFP-actin–containing blebs being released from the microvillar membrane (arrows). (B) Lumen of a tubule in cross-section filled with freely filtered red dextran–containing blebs (arrows) flowing down the nephron and forming a cast. The video for B was stitched together from two successively acquired time series. Scale bar: 20 μm. (C) Rhodamine-conjugated dextran (red) is seen circulating within the peritubular microvasculature under physiologic conditions. Flow rates for rbcs, appearing as dark streaks surrounded by bright-red plasma, are high. With the addition of a nuclear dye (white), a fast-flowing wbc can be seen streaking through the vasculature (arrow). Note the absence of red dextran in the interstitial space (asterisks). (D) Rat kidney 24 hours after ischemic injury. Here, activated wbcs with distinguishable Hoechst-labeled nuclei (arrows, nuclei in blue) crawl and roll along the vasculature, slowing down rbc flow. Vessel wall integrity shows heterogeneous areas of damage as the large 150-kDa dextran leaks into the interstitial space (asterisks). The rbc flow rates are markedly reduced due to wbc and rouleaux-mediated obstruction. Scale bar: 20 μm.