Ultrastructural electron density and heterogeneity of MKs from the spleen of GATA-1^low mice. TEM of representative MKs identified in spleen sections from GATA-1^low mice. Light and heavy electron-dense MKs are presented in panels A-B and C-D, respectively; nu indicates nuclear area; arrowhead, DMS; C, centrioles; PF, platelet field; arrows, neutrophils; asterisks, platelets. Original magnification × 3000 for all panels.