A Further Study on the Incidence of Nucleoli in Myeloblasts of Patients Suffering from Acute Myeloid Leukemia.

Nucleoli in bone marrow myeloblasts of patients suffering from acute myeloid leukemias (FAB M1-M4) untreated with cytostatics were investigated in smear preparations stained for RNA to provide the missing information on the incidence of main nucleolar types in these cells. Most myeloblasts possessed large nucleoli with a relatively uniform distribution of RNA which are known to be active with respect to the transcription of the nucleolar-ribosomal RNA. A small proportion of myeloblasts contained functionally dominant "resting" ring shaped nucleoli or "inactive" micronucleoli. The nucleolar asynchrony, i.e., the presence of "active large nucleoli" and "resting" ring shaped nucleoli in one and the same nucleus present in some myeloblasts of all investigated patients apparently represents a regular phenomenon in these cells. No significant differences were noted in the incidence of functionally dominant nucleoli between bone marrow and peripheral blood myeloblasts. On the other hand, the larger percentage of "active large nucleoli" in bone marrow myeloblasts and the increased percentage of "resting" ring shaped nucleoli in peripheral blood myeloblasts of the same patients may indicate a decreased transcription activity of nucleoli in the latter. No significant differences in the values of the nucleolar coefficient were found between bone marrow and peripheral blood myeloblasts. The presence of main nucleolar types in leukemic myeloblasts visualized by a simple but sensitive cytochemical procedure for the demonstration of RNA seems to be an useful tool for the evaluation of individual leukemic cells and provides an additional information on their biology.