Towards light microscopic imaging of hydrated 'native' ribosomal RNA genes. A combined video microscopic and transmission electron microscopic analysis.

Investigations of the higher-order structure of 'native' genes as well as antibody localization to defined gene chromatin areas require elaborate light microscopic imaging of the chromatin structure of interest, such as visualization of unfixed and unstained gene transcription units. Since all our present structural information on the, relatively, small nucleolar rRNA genes has been obtained using transmission electron microscopy of spread genes following fixation, staining and complete dehydration, this type of EM specimen was our first specimen for LM imaging. Using Normarksi differential interference contrast video microscopy, it was found that spread EM chromatin can be sufficiently visualized by light microscopy to allow precise correlation with the conventional TEM image. In addition, it is demonstrated that video-enhanced LM can provide enough contrast enhancement for rapid visualization of spread 'native' rRNA genes in slightly fixed, fully hydrated, unstained gene chromatin.