Spontaneous mitochondrial release of cytochrome

c in MDS progenitors: inhibition by G-CSF. (A) Mitochondria were stained with MitoTracker (red fluorescence), and cytochrome c localization was revealed by indirect immunofluorescence (green fluorescence). The punctate yellow pattern denotes mitochondrial localization of cytochrome c, and the diffuse green pattern indicates cytochrome c that has been released into the cytosol. Data are derived from normal bone marrow (NBM; left panel), RARS progenitors (middle panel), and RARS progenitors incubated in the presence of G-CSF (100 ng/mL; right panel), at day 7 of culture. Original magnification × 40; insets,  × 100. (B) Release of cytochrome c from mitochondria of erythroid progenitors at day 4 and day 7, as determined by digital confocal microscopy. For each position, 500 nucleated cells were counted and each bar represents a single patient. Samples were obtained from patients with RA and patients with RARS, respectively, as well as from NBM. Each group could be further subdivided according to the new World Health Organization (WHO) classification. Hence, there were 2 patients with RA, one of whom carried the 5q− aberration, 4 patients with RCMD, 3 of whom had the 5q− aberration, 4 patients with RARS, and 2 with RCMD-RS. (C) Cytochrome c release in CD34⁺ (day 4) erythroid precursors incubated in the presence or absence of G-CSF (100 ng/mL). (D) Experimental procedure same as in panel C, for CD36⁺ (day 7) erythroid progenitors.