AgNOR Counts in S-phase Human Cells

Kim, Seung Il; Lee, Eun Jung

Abstract

The nucleolus of human cell is a morphologically well recognizable nuclear organelle and the argyrophilic NORs (AgNORs) are nucleic acid-argyrophilic nonhistone protein complex in the nucleoli and the silver staining allows their identification and enumeration at the light microscopic level. The AgNOR counts are in parallel with mitotic activity and vary in different phase of cell cycle. It has been reported that human cells have one AgNOR during interphase and S-phase. However, the correlation between the number of AgNORs and S-phase markers is still controversial and they have never been studied simultaneously. In this study, AgNOR and PCNA were stained simultaneously to find out the relationship of AgNOR counts with cell cycle (S-phase) in human palatine tonsil, gastric carcinoma, liver and brain tissues. S-phase cells (PCNA-positive) were found predominantly in lymphoid follicles in palatine tonsil but gastric carcinoma showed diffuse immunoreactivity for PCNA. The AgNOR counts varied according to the type and locus of tissue. More than one AgNOR were identified in S-phase cells and some of hepatocytes and neurons in the brain which were not in S-phase contained two or more AgNORs. The above results suggest that the number of AgNOR is a characteristic feature of each type of cells and can be more than one even in S-phase.