title: Observations on electron probe x-ray microanalysis compared to other methods for measuring intracellular elemental concentration.
abstract: Electron probe X-ray microanalysis provides the capability of accurately measuring the concentration of a number of elements at the subcellular level in tissues which are appropriately prepared using cryofixative procedures. This preview compares quantitative data obtained by the authors, using X-ray microanalysis, with quantitative data obtained in other laboratories using routine chemical procedures such as flame photometry, atomic absorption spectrophotometry, titrimetry, and ion-selective electrodes. Results are compared for cells in whole tissue, for cells in suspension (erythrocytes), and for subcellular analysis. Subcellular elemental data obtained after cell fractionation and isolation and after cryomicrodissection are considered. Agreements and differences between the results obtained by the different methods of analysis as compared to microprobe are discussed and the sources of the differences are explored. The biological significance of microprobe concentration data itself is limited without additional information regarding the state of the elements, such as oxidation state, ionic activity, degree of binding, etc. In this regard, the supplementation of subcellular elemental concentration with ionic activity and flux data for the large amphibian oocyte is presented as an example of how measurement of multiple parameters can be used to explain the maintenance of subcellular concentration gradients.
mesh_terms: D000818:Animals; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000032:analysis; D002713:Chlorine / Q000032:analysis; D003584:Cytological Techniques; D003593:Cytoplasm / Q000032:analysis; D004577:Electron Probe Microanalysis / Q000379:methods; D004602:Elements; D004912:Erythrocytes / Q000032:analysis; D005260:Female; D009865:Oocytes / Q000032:analysis; D010783:Photometry; D011188:Potassium / Q000032:analysis; D012015:Reference Standards; D012964:Sodium / Q000032:analysis; D013054:Spectrophotometry, Atomic; D013347:Subcellular Fractions / Q000032:analysis*
chemical_list: D004602:Elements; D002713:Chlorine; D012964:Sodium; D011188:Potassium