Carlson College of Veterinary Medicine

Visualization and analysis of nucleolus organizer regions (NOR) by a silverstaining is a well accepted method in cytological and histological tumor diagnostic. For specific staining of the NOR the AgNOR-method developed by HOWELL and BLACK (1980) and PLOTON et al. (1986) is performed. One major disadvantage of the AgNOR-method is the instability of the reaction products and therefore the short durability of the slide preparations. A modification of the AgNOR-method, the PEG-Th-staining, leads not only to a longer durability of the reaction products but also to a better contrast within the sections. Main characteristic of the PEG-Th-staining is a postfixation of the specific silver precipitations for 5 min in a 5% sodium thiosulfate solution. It could be proven by image analysis that there is no significant difference between the morphometric parameters evaluated on AgNOR- and PEG-Th-stained sections. Therefore results evaluated on PEG-Th-stained sections are absolutely comparable to those obtained on sections stained with the AgNOR-method thus providing the advantage of a longer durability of the reaction products and easier evaluation.