I/R-induced platelet-endothelial cell interactions in vivo. Rhodamine-6G-labeled platelets are visualized within postcapillary venules using intravital fluorescence microscopy. Whereas few platelets adhere to the venular endothelium in sham-operated animals (group B, left panel), platelet attachment to the endothelium is significantly enhanced in response to I/R already 5 minutes after the onset of reoxygenation (group A, right panel, arrow). Original monitor magnification × 450.