The RNA content of intact cells and isolated nuclei of normal human lymphocytes and mononuclear cell populations (containing at least 50% blasts) from patients with acute lyrnphoblastic leukemia (ALL) and acute non-lymphoblastic leukemia (ANLL) was measured by flow cytometry based on metachromatic red luminescence of acridine orange-stained cells. Relative nuclear RNA (n-RNA) and cellular RNA (c-RNA) content was estimated in relation to luminescence of RNase-treated nuclei, which served as a standard. The mean values (±SE) of n-RNA were 22.6 ± 3.2, 25.8 ± 3.2, and 51.5 ± 6.1 arbitrary units for normal lymphocytes, ALL, and ANLL cell populations, respectively. The mean values for c-RNA were 51.3 ± 5.2, 71.9 ± 11.3, and 128 ± 13.4 for the same cell populations, respectively. The differences between normal lymphocytes or ALL and ANLL cell populations were statistically significant (f-test, with respect to both n- and c-RNA), while differences between normal and ALL populations were not. The proportions of n-RNA versus c-RNA were similar within all three types of cell populations. The intercellular variabilities with respect to n- and c-RNA among the G0/1 cell populations of all three types of cells were characterized by the coefficient of variation (CV) of the mean RNA and the third moment about the mean (MOM3). CV and MOM3 of c-RNA were significantly different between all three types of cell populations, whereas CV and MOM3 of n-RNA showed significant differences between control and leukemic cells. Thus, mean RNA, CV, and MOM3 of RNA on the cellular and nuclear levels of G0/1 cells discriminate normal lymphocytes, ALL lymphoblasts, and ANLL blast cells from each other fully on statistically significant levels.

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The flow cytometric measurements were performed at Memorial Sloan-Kettering Cancer Center, New York, NY, under a grant from Deutsche Forschungsgemeinschaft (DFG Wa460/1–2).

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