THE METHYLATION-ACETYLATION METHOD - AN ULTRASTRUCTURAL CYTOCHEMISTRYFOR NUCLEIC-ACIDS COMPATIBLE WITH IMMUNOGOLD STUDIES

Methylation-acetylation (MA) is an easy and re-producible ultrastructu ral cytochemical method which gives preferential contrast to nucleic a cid containing structures. When performed en bloc before Lowicryl embe dding it does not affect the main antigenic and chemical properties of the sample and is compatible with a large variety of modern immunogol d methods permitting a better assignment of the labeling to the well-d efined nuclear structures, DNA, RNA, and nuclear proteins, with differ ent chemical nature, nuclear localization, and amount, can be immunolo calized on MA-treated samples, Ultrastructural in situ hybridization a nd other approaches for studying the functional regions of chromatin, the terminal deoxynucleotidyl transferase and the bromodeoxyuridine me thods, are also compatible with the MA procedure, It can be also perfo rmed on ultrathin cryosections and Lowicryl sections. A much better vi sualization of the nuclear structures is obtained, enhancing the disti nction between the nucleolar granular and dense fibrillar components. Moreover, the combination of the MA procedure with EDTA regressive sta ining gives preferential contrast to the RNA-rich structures, It is pr oposed as a useful approach which can be regularly used for in situ st udies of the functional organization of the nucleus in both plant and animal cells. (C) 1995 Academic Press, Inc.