Shear-induced activation of vascular cells in vitro and in vivo. (A) Diagram of the cone-plate viscometer, where a rotating cone on a fixed plate exerts uniform shear stress on a sample of blood or platelets without exposure to a thrombogenic surface. (B) Shear stress–exposed blood passed through a stenotic coronary artery shows signs of activated platelets (increased P-selectin expression) and activated monocytes (increased CD11b) when blood samples (vertical arrows) are taken upstream or downstream of the atherosclerotic lesion from stable angina patients. The extent of stenosis and shear rates are calculated using computational angiographic imaging.