The Ag-NOR proteins present a crescent-shaped distribution at the secondary constrictions of metaphase PtK1 chromosomes

• Published in: Cytogenetics and cell genetics Vol. 75; no. 2-3; p. 155
• Main Authors: Suja, J A, Hernandez-Verdun, D
• Format: Journal Article
• Language: English
• Published: Switzerland 01-01-1996
• Subjects: Animals; Azure Stains; Cell Line; Chromatids - chemistry; Chromatids - ultrastructure; Chromosome Banding; Chromosomes - chemistry; Chromosomes - ultrastructure; Macropodidae; Metaphase; Microscopy, Electron; Nuclear Proteins - analysis; Nucleolus Organizer Region - chemistry; Nucleolus Organizer Region - ultrastructure; Silver Staining; X Chromosome - chemistry; X Chromosome - ultrastructure
• ISSN: 0301-0171
• DOI: 10.1159/000134468

The ultrastructural distribution of the proteins responsible for the silver staining of NORs was analyzed on serial thin sections of preembedded silver-stained rat kangaroo PtK1 metaphase chromosomes. Our results show that the Ag-NOR proteins present a crescent-shaped distribution at the secondary constriction of each chromatid. Moreover, in some cases the crescent-shaped structures of both chromatids are not symmetrically arranged but show different orientations. These observations, together with our own and previously reported light microscopy results obtained on silver-stained mammalian chromosomes, lead us to suggest a mechanism for the formation of apparent secondary constrictions at NORs.