Benzidine staining of K562 cells treated with butyrate and apicidin.

Cells were cultured in the absence (control) or presence of 0.5 μM apicidin (left panels) or 0.6 mM butyrate (right panels) for 4 days (4 d+). Thereafter, the compounds were removed from medium and cultured for another 4 days (4 d+/4 d−) or 8 days (4 d+/8 d−), respectively. After harvesting, intracellular hemoglobin was detected by benzidine staining, and cell smears were subjected to microscopy using × 400 magnification.