Artifacts caused by dehydration and epoxy embedding in transmission electron microscopy

Epoxy resins are the principal embedding media for the preservation of tissues to be sectioned and examined by transmission electron microscopy. Their primary advantages are good ultrastructural preservation, little or no shrinkage, ease of sectioning, and reasonable stability in the electron beam. However, epoxy resins also have disadvantages; namely, some are toxic, they may mask antigenic sites to a greater extent than do some other embedding resins, and they do not penetrate tissues as well as less viscous embedding formulations. Some unusual characteristics may also be revealed, for example, as shrinkage of organelles, as problems in poststaining sections, and as movement of tissue elements within the block and section. Some of the properties of epoxy resins are discussed in this report.