Illustration of the step leading to the final maturation of MK from the deformation of the cytoplasm to the separation of proplatelet fragments. (a) A further example of cytoplasm and nucleus deformation of a large mature MK. (b) An extremity of a mature MK shows deformation and constriction zones (arrowheads) and the presence of projections suggesting the subsequent and early separation of the proplatelet fragments. (c) An elongated proplatelet fragment separated from the cytoplasm. As indicated by arrowheads, this particular zone is fragmenting into platelet-size fragments and is still surrounded by the organelle-free zone. Bars = 5 μm.