Immunogold studies localizing platelet FVIII in α-granules. Representative immunogold electron microscopy photographs of platelets from hB-FVIII/FVIII^null/VWF^+/+ mice (A) or hB-FVIII/FVIII^null/VWF^-/- mice (B-C) from a series of more than 50 photographs per study. Panels A and B were studies done with anti-human FVIII (10 nm gold beads, some indicated by arrows) and VWF (5 nm gold beads some indicated by closed arrowheads) as previously described.^10,11  (C) Studies similar to panel B but the 5 nm gold particles represent detected murine fibrinogen (5 nm gold beads, some indicated by open arrowheads). The bar in each figure represents 0.1 μm.