Combining Cryo and Conventional Specimen Preparation Methods to Improve the Preservation of Cell Ultrastructure

Extract

Poor specimen preparation techniques affect all subsequent EM imaging operations, whether simple descriptions or sophisticated computer reconstruction and analysis. Therefore, EM researchers continue to put effort into developing methods that will preserve the fine structure of the cell as close to the native state as possible. Much attention has been paid to the primary or initial fixation because this is probably the singlemost important step in EM processing. Evidence from a variety of sources. shows that cryofixation is more likely to give good preservation than conventional chemical fixation for most cell types. Among the choices for cryofixation, high pressure freezing is probably the best for most samples, even those that are small enough to be frozen by other means.

Dehydration is another key point in processing where high resolution structure can be lost or distorted, though it has received relatively little attention compared to primary fixation.