EVALUATION OF 5 DIFFERENT IMMERSION FIXATIVES FOR LIGHT-MICROSCOPIC STUDIES OF LIVER-TISSUE IN ATLANTIC SALMON SALMO-SALAR

Five aldehyde-containing fixatives were compared with regard to mainte nance of light microscopic morphology in the liver of Atlantic salmon Salmo salar L. Parallel liver samples from adult fish were fixed in ea ch fixative, processed routinely, sectioned, and stained with H&E (hem atoxylin and eosin) and PAS (periodic acid-Schiff reaction). Coded H&E slides were evaluated by 3 independent observers according to defined morphological criteria, including appearance of hepatic parenchyma, v asculature, bile ducts, and connective tissue. The data obtained were subjected to statistical treatment. The different fixatives' abilities to preserve cytoplasmic glycogen were assessed from PAS-stained secti ons. 10 % formalin with modified Millonig's phosphate buffer and David son's fluid were found to be most effective in maintaining liver morph ology at the light microscopic level. 10 % formalin with modified Mill onig's phosphate buffer also provided the best demonstration of hepato cellular cytoplasmic glycogen deposits. The current study also illustr ates the influence on fixative evaluation of varying amounts of hepato cellular glycogen deposits, and of personal preferences by the observe rs.