Improvement of nonradioactive DNA in situ hybridization.

With the introduction of microwave pretreatment, the quality of nonradioactive in situ hybridization (NISH) using DNA probes on formalin fixed tissue has significantly improved. Even after microwave treatment, however, there are cases where NISH results remain unsatisfactory. Therefore, we tried to improve NISH by testing other buffer systems as alternatives to the citrate buffer that is routinely applied during microwave pretreatment. By using buffer systems originally designed for immunohistochemistry, we significantly improved our NISH results. Difficult tissue samples were more accessible to NISH using these alternative buffer systems and made the quantitative evaluation easier. These results may also be of interest for combined applications of NISH and immunohistochemistry.