Electron microscopic view of a cultured mature WAS MK. This MK is starting the process of platelet shedding. The nucleus (N) is excentric, the demarcation membrane system (dms) is widening, delimitating platelet territories (p) and, at the cell periphery, proplatelets (pp) start to extend. (A, -granules; gly, glycogen).M= × 7.375. Insert: Normal proplatelet (pp) extend from mature MK.M= × 2.145.