The application of the nucleolar organizer region silver staining (AgNOR) to backscattered electron imaging (BEI)

Abstract
Until recently scanning electron microscopes were mainly used to observe surfaces. A backscattered electron detector can give an image (BEI) of the specimen''s internal structure after heavy metal staining. Ag staining was applied for NOR-associated proteins to scanning electron microscopy, studying C3H10T1/2 cells in culture. This techique allows to localize, inside the nucleus, the nucleolar arrangement of AgNOR-associated proteins. In BEI imaging, the Ag staining shows several intranucleolar Ag spot-like deposits sometimes associated in doublets as on metaphasic chromosomes. These Ag grains probably represent the fibrillar center location, thought to be the interphasic counterpart of the NOR. These Ag spot granules are more numerous during interphase.