Ag‐Nor staining in human chromosomes: Differential staining in normal and leukemic bone‐marrow samples

A silver staining technique developed by Goodpasture and Bloom (1975) stains a specific protein associated with the activity of ribosomal cistrons during the preceding interphase. By counting the number of chromosomes with darkly stained nucleolus organizer regions (NORs), the number of active NORs per metaphase can be determined. A comparison of NOR activity in bone-marrow cells from leukemic patients in different stages of disease with that of bone marrow from normal, healthy individuals was conducted and differential NOR activity was detected. The control group showed significantly lower NOR activity when compared with a group of patients with acute lymphocytic leukemia (ALL). These preliminary data indicate that this simple cytochemical technique can be effectively used to differentiate between normal and ALL bone-marrow samples.