Study of the activity of the nucleolus organizer segments in the chromosomes of normal, leukemic and neoplastic human cells by silver nitrate staining

The application of a modified Ag-1 method for staining nucleolar organizer regions (NOR) in chromosomes has shown that the total number of AgNO3-stained NOR varies from 6 to 8 in cells of normal individuals as well as in the phytohemagglutinin (PHA) stimulated blood cells of patients suffering from acute leukemia (AL) and chronic myelocytic leukemia (CML). No AgNO3-stained NOR were detected either in non-PHA stimulated blood cells of AL or CML patients, apart from one case of a 48 hours blood culture without PHA from blast crisis CML, where 100 per cent mitotic cells displayed 3-6 AgNO3-stained chromosomes. In a Hela cell line with the modal number equal to 50 and the average number od acrocentrics being 9.3 per cell, the AgNO3-stained NOR numbered constantly 5. In tumor cells from pleural fluid of metastatic ovary tumor patient, with the modal number of cells varying from 50 to 160, the total number of AgNO3-stained NOR increased from 13 to 26 per metaphase. A hypothesis is forward to explain the negative Nor staining property in leukemia, according to which the activities of ribosomal cistrons (rDNA) in the miotic cells of relatively mature granulocytic and erythrocytic cells are either very much reduced or totally arrested.