Megakaryocyte visibility following MK-801 treatment. (A) Detection of viable, early apoptotic, late apoptotic, and necrotic cells in the presence and absence of MK-801, using propidium iodide (PI)/annexin V–FITC detection by flow cytometry. Area 1 is representative of viable cells (PI-negative, annexin V–negative), area 2 of early apoptotic cells (PI-negative, annexin V–positive), area 3 of late apoptotic cells (PI-positive, annexin V–positive), and area 4 of necrotic cells (PI-positive, annexin V–negative). The results demonstrated that MK-801 treatment did not significantly affect apoptosis or necrosis when compared with untreated controls, with approximately 90% of cells in both groups remaining viable after 14 days in culture (B). Results represent mean of 3 independent experiments, ± SEM.