(A) Representative resting Wistar rat platelets fixed, adhered to poly-L-lysine–coated grids, and stained with uranyl acetate. (B through H) Wistar rat platelets allowed to adhere to Formvar-coated, carbon-stabilized grids from 30 seconds to 30 minutes, and subsequently fixed and stained with uranyl acetate. (B through H) illustrate the forms characteristic of Wistar rat platelet spreading, including rounded shapes (B), followed by the development of spindle-shaped, or tapered, forms (C) and stubby filopodia (D), the extension of elongated, multiple filopodia (E and F), expansion of lamellipodial “skirts” which fill in the filopodia ribs (G), and the final “fried-egg,” or fully spread form (H). (B through E) 30-second adherent samples, (F) 1-minute adherent sample, (G and H) 30-minute adherent samples. (A through H, original magnification ×7,000).