[Application of nucleolar organizer region staining technique to air-dried blood smears]

Silver staining of nucleolar organizer regions (NOR) was applied to air-dried peripheral and bone marrow smears of normal subjects and leukemic patients. Specimens were fixed in buffered acetone formalin. Even in smears kept for 2 years at room temperature, the stainability of Ag-NOR was well preserved. By dipping Giemsa-stained smears in 5% trichloracetic acid and then placing them in methanol for 5 minutes, the stain was leached out. After the dye had been removed, the smears were clearly stained by a Ag-NOR staining technique. The mean number of Ag-NOR per nucleus of mature granulocytes and mononuclear cells in normal peripheral bloods was 0.59 and 1.43 respectively. The mean number of Ag-NOR per nucleus of peripheral and bone marrow leukemic cells from patients with acute leukemia and chronic myelocytic leukemia in blastic crisis was 2.32 and 2.66 respectively. On the other hand, the mean number of Ag-NOR per nucleus of peripheral leukemic cells from patients with chronic lymphocytic leukemia was 1.48. These results suggest that acute leukemia cells possess a more active proliferating potential. The Ag-NOR staining technique is very simple and might be useful for investigation of hematologic cells.