Techniques and application of microscopic radioautography.

The techniques for light and electron microscopic radioautography developed in our laboratory are described. The outlines of the applications to various tissues and organs are also briefly summarized. First, the techniques are explained in detail. These techniques 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 is limited in application to only insoluble compounds, while the latter is universally applicable to any kind of compounds including soluble compounds. Both procedures, the chemical fixation wet-mounting procedure and the cryo-fixation dry-mounting procedure at light and electron microscopic levels are described. Next, the applications of both the procedures to various compounds are 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, cyrofixation followed by dry-mounting radioautography demonstrates soluble small molecular compounds such as macromolecular precursors, hormones, neurotransmitters, vitamins, inorganic compounds and drugs or toxins. These procedures are expected to be applied for various inorganic and organic compounds in living organisms to elucidate the sites of their incorporation, synthesis and discharge.