Inhibition of differentiation and growth of erythroid cells cocultivated with HZ or treated with HNE. The May-Grünwald/Giemsa stains of cytospins of cells cultivated for 21 days show numerous fully mature RBCs (arrows) in the untreated control (CTRL) cultures, and negligible numbers of fully mature RBCs in presence of HZ (25μM HZ-heme) or HNE (7μM). Differences in staining and cell size between controls and HZ/HNE-treated cells indicate the delayed differentiation caused by treatments. Optical microscope photographs (Leica DM LB, 40×; acquisition software: Leica DFC Twain, version 6.5.0; camera: Leica DFC 320).