Lack of Syk attenuates arterial thrombus formation ex vivo. (A) Histogram showing the critical role for Syk in mediating thrombosis on type I collagen. (B) Thrombotic deposits formed on collagen-coated capillaries exposed for 2.5 minutes to nonanticoagulated blood from Syk^+/+ (n = 9), Syk^+/− (n = 10), and radiation chimeras (Syk^−/− radiation chimera; n = 7) mice at 871 seconds⁻¹. The black arrow points to platelet-rich thrombi. Quantification was performed on semithin cross section of Epon-embedded thrombotic deposits via computer-assisted morphometry. (C) Photomicrograph of thrombotic deposits formed on tissue factor-coated capillaries at 871 seconds⁻¹ in Syk^+/+ and Syk^−/− radiation chimera mice.