Uropod elongation during leukocyte extravasation of CD18-mCFP mice. (A) CD18-mCFP mice were used to visualize leukocytes in cremaster venules using MP-IVM. The rolling leukocytes were visualized in the unstimulated cremaster muscle venules (left). The venules were stimulated with chemokine (1 nM CXCL2), and the adhered/extravasating leukocytes are shown (right). Texas red dextran was i.v. injected to stain the blood vessel (red). A representative still image is shown from at least 10 stimulated venule images from the cremasters of five mice. See corresponding Video 1. (B) Representative time-lapse images of cell elongation during leukocyte extravasation were taken from the videos of CXCL2-stimulated venules in CD18-mCFP mice. The arrows indicate the elongation direction. Bars, 30 µm. (C–E) Cell lengths in each step of transmigration, rolling, crawling, and extravascular (Ext.) retention. The extravascular retention times were also measured in CXCL2 (C)-, fMLP (D)-, and TNF (E)-stimulated cremaster venules of CD18-mCFP mice. The cell lengths were determined from the longest distance across cells (from head to tail) at each stage. The extravascular retention times represent the time period between the end of TEM and the completion of tail detachment from the endothelium. The cell length and the extravascular retention time were measured from images of at least three venules stimulated for >30 min. Horizontal lines indicate the mean. *, P < 0.005. (F) Correlation between the elongation and the extravascular retention time during leukocyte extravasation. The cell length and the extravascular retention time were measured from images of at least three venules stimulated for >30 min with CXCL2. P = 0.003.