Morphologic abnormalities in bone marrow MKs of ADF/n-cofilin–null mice. (A) Paraffin-embedded sections (5 μm) were stained with hematoxylin and eosin (visual field: 655 × 491 μm). White arrows indicate MKs. Numbers of MKs per visual field (328 × 246 μm) were determined. ***P < .001. (B) TEM of control and ADF/n-cofilin–deficient bone marrow MKs. Right image (higher magnification of left image) of control MKs shows the DMS (black arrow). In ADF/n-cofilin–deficient bone marrow MKs, high amounts of fibrillar material are present in the peripheral cytoplasm (see higher magnification of the boxed area). Note that this zone is clearly devoid of organelles. Scale bars represent (from left to right) 5 and 1 μm (control), and 2 and 0.5 μm (ADF/n-cofilin–null).