MODIFIED FORMALIN AND METHANOL FIXATION METHODS FOR MOLECULAR BIOLOGICAL AND MORPHOLOGICAL ANALYSES

Several simplified fixation methods were examined to determine their s uitability for both molecular biological analyses and morphological st udy. Fixation with 10% v/v formalin alone at 4 degrees C and containin g 5 mmol/L ethylenediamine-N, N, N', N'-tetraacetic acid (EDTA) at roo m temperature preserved significantly more high-molecular-weight DNA t han 10% v/v formalin fixation at room temperature, The morphological d ifferences between tissues fixed using these modified formalin fixatio n methods and conventional 10% v/v formalin fixation were negligible. Of the dehydration fixatives tested, 100% methanol did not cause regio nal differences due to artificial tissue shrinkage and the morphology of sections prepared by methanol fixation was preserved consistently b etter than that of acetone-or ethanol-fixed sections. All three dehydr ation fixatives preserved relatively higher-molecular-weight DNA and R NA, compared with formalin. Cold formalin, formalin containing EDTA at room temperature and 100% methanol are recommended as standard and ad ditional fixatives routine clinicopathological laboratory use.