Morphologic appearance of cultured bcl-x^-/- and bled control erythroblasts. Cytospin preparations of erythroblasts harvested at various times were stained with 3,3′-dimethoxybenzidine and hematoxylin and examined by light microscopy. (A) Bled control erythroblasts cultured with EPO for 20 hours. (B) bcl-x^-/- erythroblasts cultured with EPO for 20 hours. (C) bcl-x^-/- erythroblasts cultured without EPO for 20 hours. (D) bcl-x^-/- erythroblasts cultured with EPO for 32 hours. (E) bcl-x^-/- erythroblasts cultured with EPO for 44 hours. (F) Bled control erythroblasts cultured with EPO for 44 hours. Arrowheads indicate examples of apoptotic, benzidine-positive, mature cells that have accumulated hemoglobin; arrows indicate examples of apoptotic, benzidine-negative, immature cells that have not accumulated hemoglobin; asterisks indicate examples of extruded nuclei; and R indicates an example of a reticulocyte. Original magnification, × 560.