The ultra-structural localization of enzyme activity in unfixed sections.

A technique is described for using conventional unfixed cryostat sections for localising enzyme activities in the electron microscope. The sections are incubated on the slide in the presence of a stabiliser, and then only fixed and embedded after the reaction is complete. Thin sections can then be cut of the reacted section, for electron microscopy. The present article shows that good ultra-structural morphology is retained during the freezing and cutting stages, and although some loss of detail occurs after the incubation, sub-cellular membranes are still intact, and membrane-associated reaction product can be clearly seen.