[Nucleolar asynchrony in human acute myeloid leukemia blast cells]

Nucleolar asynchrony (the presence of "active" and "sleeping" nucleoli with respect to the RNA synthesis in one and the same nucleus) was noted and studied in blastic cells of the peripheral blood in patients of acute myeloid leukemias (M1 - M4 according to FAB classification) by means of light microscopy of smears after visualization of RNA containing structures. Nucleolar asynchrony seems to be a regular phenomenon in a certain number of blastic cells in the peripheral blood and has been also verified by electron microscopy. No significant difference has been noted in the incidence of blasts with nucleolar asynchrony between the peripheral blood of patients treated and untreated by cytostatic therapy at the time of taking samples for the present study: The presence of the nucleolar asynchrony/might contribute to the resistance of a certain population of leukemic blasts to the cytostatic therapy. This supposition is supported by the present experiments "in vitro" on mouse leukemic myeloblasts sensitive and resistant to Doxorubicin. The Doxorubicin resistant myeloblasts were characterized by a significantly larger incidence of the nucleolar asynchrony as compared with myeloblasts of the Doxorubicin sensitive cell line.