Techniques and application of electron microscopic radioautography

The techniques for electron microscopic radioautography can be divided into two categories, i.e., chemical fixation followed by wet-mounting radioautography and cryo-fixation followed by dry-mounting radioautography, The former procedure is limited in application to only insoluble compounds, while the latter is universally applicable to any kind of compound including soluble compounds, The both procedures, the chemical fixation wet-mounting procedure and the cryo-fixation dry-mounting procedure at the electron microscopic level, which were developed in our laboratory, are described in detail in this article, The applications of both the procedures are also briefly mentioned, Chemical fixation with glutaraldehyde and osmium tetroxide followed by wet-mounting radioautography demonstrates insoluble macromolecular synthesis such as nucleic acids (both DNA and RNA), proteins, glucides and lipids, On the other hand, cryo-fixation followed by dry-mounting radioautography demonstrates soluble small molecular compounds such as macromolecular precursors, or hormones, vitamins, drugs and inorganic compounds, These procedures are expected to be applied for various organic and inorganic substances in living organisms to clarify the sites of their incorporation, synthesis and discharge.