Spreading and calcium flux of FcRγ^–/– mouse platelets on a collagen matrix. (A) Representative SEM images of collagen-adherent platelets from wild-type and FcRγ^–/– mice. (B) The percentage of adherent platelets (mean ± SEM) that spread on the collagen matrix was quantified as described in “Materials and methods.” (C) Calcium dye-loaded washed platelets were applied to a type 1 fibrillar collagen matrix under static conditions for 30 minutes at 37°C. Individual wild-type platelets underwent an oscillatory Ca²⁺ response following adhesion to the collagen matrix, whereas FcRγ^–/– platelets did not exhibit an oscillatory Ca²⁺ response. Calcium profiles are from representative single platelets obtained from wild-type or FcRγ^–/– mice. (D) The percentage of adherent platelets (mean ± SEM) exhibiting oscillatory calcium flux was quantitated as described in “Materials and methods.”