UHRA compounds inhibit thrombus formation in mouse cremaster arterioles. (A-E) Binarized images from 1 representative injury each showing the accumulation of platelets (red) and fibrin (green) 120 seconds after laser-induced injury to the vessel wall in mice administered either (A) saline or the following UHRA compounds at 40 mg/kg: (B) UHRA-8, (C) UHRA-9, (D) UHRA-10, or (E) UHRA-14. Scale bars: 10 μm. (F-I) Statistical analyses of the effect of administering UHRA compound on thrombus formation; data are from 27 to 30 injuries to 5 mice for each condition. Median integrated fluorescence intensities (nonbinarized) were plotted vs time for accumulation of (F) platelets and (H) fibrin. In addition, the area under the curve (total fluorescence intensity) was plotted for accumulation of (G) platelets and (I) fibrin (each point represents 1 injury, plotted as log value). When median values were evaluated by the Mann-Whitney U test, both UHRA-9 and -10 significantly reduced total accumulation of platelets and fibrin compared with control. *P < .05; ***P < .0005. Brightfield and fluorescent images of arterioles were acquired with a Zeiss Axioplan microscope equipped with a Lumencore 4-LED light engine, an ×20 water immersion lens (Zeiss W-Plan APOCHROMAT ×20/1.0 NA), and a Rolera EM-C² EMCCD Camera (Q-Imaging). Endothelial injury to the vascular wall of 50- to 70-µm diameter arterioles that resulted in thrombus formation was effected by using a 532-nm pulsed-laser system integrated with the image capture and analysis software (VIVO Imaging System with Ablate! Photomanipulation Module; Intelligent Imaging Innovations). Fluorescence images were acquired continuously, platelet fluorescence was imaged with a Cy-5 filter and 15 ms exposure, and fibrin was imaged with a fluorescein filter set and 10 ms exposure. Brightfield images were captured with a 10 ms exposure periodically (1 image every 100 captures).