Immunoperoxidase Technique in Cryoultramicrotomy for the Detection of Simian Adenovirus in Cell Nuclei

The application of immunological concepts in morphological studies is in rapid progress. While many cell components can be studied by preor postembedment immunohistology, one would like to possess an alternative method in order to overcome all problems observed in preand postembedment staining due to penetration difficulties e.g. for antibodies and cell alterations by dehydration and resin curing (4). Thus, the development of cryoultramicrotomy (1-2, 12) offered great promise for immuno-staining of cells to be done on ultrathin frozen sections without classical procedures of dehydration and plastic embedment. Several immunohistological procedures including various marker systems were tried with ultrathin frozen sections, but until now reasonable results were obtained only with ferritin as label (13). Hitherto, direct or indirect peroxidase stainings were most often disappointing inasmuch as the original 3,3'-diaminobenzidine method (3) was very capricious when applied to ultrathin frozen sections (4, 7). Recently, an approach was published for the immunoperoxidase localization of hormones in pituitary gland by use of 4-chloro-l-naphthol as substrate (9). However, the authors' tissue processing per se (glutaraldehyde fixation followed by postfixation with osmium tetroxide and uranium salt staining prior to immuno-staining) leads already to such a strong contrast of cellular organelles that the immunohistological reaction is hard to be discerned.