Evaluation of five different immersion fixatives for light microscopic studies of liver tissue in Atlantic salmon Salmo salar

Abstract

ABSTRACT: Five aldehyde-containing fixatives were compared with regard to maintenance of light microscopic morphology in the liver of Atlantic salmon Salmo salar L. Parallel liver samples from adult and fish were fixed in each fixative, processed routinely, sectioned, and stained with H&E (hematoxyl~n eosin) and PAS (periodic acid-Schiff reaction). Coded H&E slides were evaluated by 3 independent observers according to defined morphological criteria, includ~ng appearance of hepatic parenchyma, vasculature, b~le ducts, and connective tissue. The data obtained were subjected to stat~stical treatment. The different fixatives' abilities to preserve cytoplasmic glycogen were assessed from PAS-stained sections. 10 % formalin with modified Millonig's phosphate buffer and Davidson's fluid were found to be most effective in maintaining liver morphology at the light microscopic level. 10 % formalin with modified Millonig's phosphate buffer also provided the best demonstration of hepato- cellular cytoplasmic glycogen deposits. The current study also illustrates the influence on fixative eval- uation of varying amounts of hepatocellular glycogen deposits, and of personal preferences by the observers.