[Functioning of the nucleolus-organizer regions of the chromosomes of cultured human blood lymphocytes].

Functioning of the nucleolus-organizing regions (NORs) as studied by Ag-staining of metaphase G-banded chromosomes was compared in human blood cultures of lymphocytes of the 1st and 2nd divisions after PHA stimulation. No difference between these divisions was found in the number of Ag-stained NORs, the intensity of the staining, in the number of associated NORs, and the number of the associations per cell. However, a significant decrease in the number of metaphases containing the associations was observed in metaphases of the 2nd division. Asymmetry of the Ag-deposit observed in sister chromatids in BUdR-incorporated NORs reduced or even disappeared after additional Ag-staining of the NORs.