Bleeding time in WT and S100A10^−/− mice. The last 3 mm of the tail of anaesthetized WT and S100A10^−/− mice was clipped with a scalpel blade. The clipped tails of the anaesthetized mice were placed in 37°C saline, and the time for cessation of bleeding was recorded (A). Masson trichrome staining was used to observe the morphology of tail sections from WT (B) and S100A10^−/− (C) mice. Immunohistochemistry for S100A10 was also performed on tail sections from WT (D) and S100A10^−/− (E) mice. Sections were deparaffinized and either subjected to Masson trichrome staining or anti-S100A10 antibody followed by antigoat HRP. Arrows indicate endothelial lining of vessels. Statistical analysis was performed with Student t test, the data are expressed as (±) SEM of 3 independent experiments (***P < .001). Sections were mounted with Cytoseal 60 mounting media (Richard-Allen Scientific) and viewed with a 20×/0.5 NA objective lens. Images were captured by the Nikon Eclipse E600 microscope using a Nikon DXM1200F camera. Digital acquisition of the images was performed with ACT-1 Version 2.7 software (Nikon). Figures were generated with Adobe Photoshop CS3 Version 10 (Adobe Systems Incorporated).