Cryofixation methods for ion localization in cells by electron probe microanalysis: a review

Electron probe microanalysis data on the intracellular content and distribution of electrolyte ions depends critically on the functional state of the cells at the moment of cryofixation. Whereas tissue specimens often require special in-situ freezing techniques, isolated and cultured cells can be frozen within their environmental medium under physiologically controlled conditions. Thus, they represent a feasible system to study functional ion-related intracellular parameters such as the K/Na ratio. Specifically modified freezing devices allow the study of ion shifts related to dynamic processes in cells, for example, locomotion and exocytosis. The time resolution achieved by time-controlled cryofixation is approximately 1 ms.