A NEW TECHNIQUE FOR ELECTRON MICROSCOPIC DRY-MOUNTING RADIOAUTOGRAPHY OF SOLUBLE-COMPOUNDS

A new technique for dry-mounting electron microscopic radioautography of water soluble-compounds has been established. Tissues containing labelled compounds are cut as small as less than 1 mm in diameter, plunged into isopentane cooled to about -160° C with liquid nitrogen, and frozen-dried at -50° C for 24-48 hours. After drying, the tissues are embedded in Epon, which is polymerized according to the conventional procedure. Ultrathin sectioning is accomplished with ethylene glycol instead of water in the knife trough so that water is not involved in the floatation and expansion of the ultrathin sections. Sections are picked up on collodion coated grid meshes from ethylene glycol. Radioautographic emulsion is diluted 1 part in 10 parts with distilled water at 40° C. Ten ml of the diluted emulsion is added with 0.2 ml of 2 per cent aqueous solution of dioctyl sodium sulfosuccinate. A thin film of the emulsion is obtained by dipping a platinum wire loop into the emulsion. The loop is set on a flat surface of a desk for air-drying. The dried film is then applied to the mesh and it is warmed at 37° C for 1 hour in order to help the film to adhere to the mesh. Thus, dry-mounting of packed monolayers of radioautographic silver crystals can be constantly achieved. The mesh is then exposed, developed and stained according to the conventional technique. © 1969 Springer-Verlag.