Ultrastructural aspect of megakaryocytes.

(Top) A large mononucleated megakaryocyte with large membrane complex (MBC). Only few demarcation membranes are free (arrows). Magnification × 4750. (Bottom) Lytic mature megakaryocyte. The nucleus has the typical aspect of apoptotic cells with clumps of chromatin. The cytoplasm contains numerous granules (arrows). The cell membrane and intracytoplasmic membrane are lysed. A granulocytic peroxidase is present at the periphery. Note the presence of a fibroblast (F) closely associated to the lytic megakaryocyte. Magnification × 5320.