Ultrastructural defects of platelets from Scl^–/Δ mice. TEM images of platelets from Scl^+/Δ (A) and Scl^–/Δ (B) mice. Primary (g) and dense (d) granules are indicated in panel A. Depleted granules (g) and dilated canalicular membrane system (c) are indicated in panel B. Scale bars represent 5 μM. Differential interference contrast (DIC) images of platelets from a Scl^+/Δ (C) and Scl^–/Δ (D) mice. Arrows in panel C show elongated forms indicative of the normal discoid shape (d), which are absent in panel D, indicating that Scl^–/Δ platelets are round. Images are at 100 × magnification.