Pseudo-color fluorescence video images of fura-2–loaded platelets adhering to fibrinogen or collagen matrices in the presence of 2 mmol/L CaCl₂ and FITC-labeled annexin V. (A) Fura-2 ratio image of platelets adhering to fibrinogen during 20 minutes. (B) FITC-annexin V intensity image of platelets adhering to fibrinogen during 20 minutes and subsequent stimulation with 10 μmol/L ionomycin. (C and D) Corresponding fura-2 ratio image (C) and FITC-annexin V intensity image (D) from one microscopic field of platelets adhering to fibrinogen during 20 minutes in the presence of 2 nmol/L α-thrombin. (E and F ) Corresponding fura-2 ratio image (E) and FITC-annexin V intensity image (F ) from one microscopic field with platelets adhering to collagen during 20 minutes. The false-color rainbow of fura-2 fluorescence ratio was set such that dark blue indicates basal levels of [Ca²⁺]_i and that color changes from light blue, green, yellow to red point to increasing levels of [Ca²⁺]_i . Color changes from blue to red also indicate increasing intensities of FITC fluorescence.