Abstract
A technique for distinguishing nucleolar components by light microscopy is described. [Human lymphocytes were used as an example.] Ag staining is used for localizing nucleolar-organizing regions. A new RNA-specific fluorochrome, 4"-6-bis(2''-imidazolinyl-4''-5''H)-2-phenyl-4''-phenoxyindole, visualizes the RNA-containing granular and fibrillar structures of the nucleolus. Both staining procedures can be combined to analyze nucleolar structure and function by light microscopy.