A short note on micronucleoli in the course of terminal maturation of human erythroblasts

The incidence of micronucleoli in the course of terminal differentiation of human erythroblasts was studied by the cytochemical procedures for demonstration of RNA and characteristic proteins of interphase AgNORs. The last dividing stages of the erythroid lineage--polychromatophylic erythroblasts--characterized by the presence of micronucleoli exhibited significantly larger values of the nucleolar coefficient in specimens stained for AgNOR proteins than in those stained for RNA. In addition, both these and terminal non-dividing nucleated stages of the erythroid lineage--orthochromatic erythroblasts--possessed micronucleoli after staining for RNA in a much smaller percentage of cells than after staining for AgNOR proteins. Thus, both these observations indicate that micronucleoli in the course of terminal maturation of erythroblasts apparently lose the nucleolar RNA detectable by the light microscopic cytochemistry. In addition, silver-stained micronucleoli--nucleolar remnants--were also noted in erythroblasts expelling the nucleus.