Silver staining of nucleolar organizers and nucleoli during mitosis and interphase of mammalian cells

Abstract

The silver staining method Ag-I was applied on metaphase spreads and monolayers of rat-kangaroo (Pt-K1), Indian muntjac, human diploid (F2000) and HeLa-derivative (Lul06) cells. This made discernible the sites of active nucleolar organizers or ribosomal DNA in chromosomes during mitosis and in nuclei during interphase. The numbers and relative sizes of Ag-stainable materials were consistent when comparing patterns observed at metaphase with those of later mitotic stages and of early interphase nuclei. The Ag-stainable material in the metaphase chromosomes is thus nucleolar in nature. Additional faintly Ag-stainable materials, probably persistent nucleoli, frequently occurred in the cytoplasm of dividing cells especially at anaphase and telophase stages. During advanced stages of interphase, the nucleoli were differentiable into beaded chain-like Ag-positive structures embedded in a brownish homogenous background. These two types of structures are most probably analogous to the nucleolonemata and pars amorpha demonstrable at the light microscopial level, and to the fibrillar and granular components at the ultrastructural level. The appearance of the beaded structures might be related to the activity of the repetitive ribosomal genes. Thus a chain-like organization would be an expression of rDNA redundancy both at the structural and functional level.

The chromosomes of two Drosophila races: D. nasuta nasuta and D. nasuta albomicans III. Localization of nucleolar organizer regions

“…The original Ag-AS silver staining method of Goodpasture & Bloom (1975) is successful in staining the NORs in a variety of organisms such as insects, amphibians and mammalians (Howell, 1977;Czaker, 1978;Varley, 1977;Heneen, 1979). However, in Drosophila nasuta nasuta and D. n. albomicans as well as in D. hydei (Beck & Srdi~, 1979) this Ag-AS method fails to label the NORs specifically.…”