Laser-induced thrombosis in the cremaster muscle microcirculation. Mice were injected with Alexa488-labeled Fab fragments of MWReg30. (A,D) Changes in fluorescence intensity over time measured after laser injury in cremaster muscle arterioles (A) or venules (D) of the following mouse groups: WT (black line), CalDAG-GEFI^−/− (KO, red), WT/clopidogrel (WT + clop., blue), CalDAG-GEFI^−/− / clopidogrel (KO + clop., green). Results represent the mean fluorescence intensity ± SEM measured in 3 independent experiments (n = 9-27 vessels for each group). Only significant differences (*P < .05; **P < .01; ***P < .001) are shown. (B,E) Representative images taken at t = 150” after laser injury in arterioles (B) and venules (E). See supplemental Videos 5-8 for a better visualization of the differences in thrombus growth and stability observed in the respective study groups. Images were obtained on a Olympus BX61WI microscope (Olympus) with a ×40/0.8 numeric aperture water-immersion objective lens, using Slidebook software (Intelligent-Imaging-Systems). Dotted lines mark the vessel wall. White bar = 100 μm. (C,F) Number of emboli with a diameter of more than 10 μm forming after laser injury in arterioles (C) or venules (F) of WT, WT/clopidogrel, and CalDAG-GEFI^−/− mice. n = 7-9. Mean venule diameter: WT: 63.4 ± 8.5 μm; WT + clopidogrel: 69.1 ± 8.8 μm; CalDAG-GEFI^−/−: 55.9 ± 6.1 μm; CalDAG-GEFI^−/− + clopidogrel: 60.2 ± 4.2 μm; P = nonsignificant (NS) for all comparisons. Mean arteriole diameter: WT: 37.3 ± 3.0 μm; WT + clopidogrel: 33.7 ± 1.7 μm; CalDAG-GEFI^−/−: 38.1 ± 2.5 μm; CalDAG-GEFI^−/− + clopidogrel: 37.1 ± 1.9 μm; P = NS for all comparisons.