Bullfrog heart muscle trabecula are shock-frozen in liquid propane cooled by liquid nitrogen and then processed for X-ray microanalysis in two different ways: 1. Freeze-drying followed by vacuum embedding. 2. Cryoultramicrotomy and freeze-drying.
Stained sections of freeze-dried, embedded tissue exhibit detailed ultrastructure, but are useless for X-ray microanalysis. Unstained, dry cut plastic-sections are suitable for X-ray microanalysis, but the ultrastructure appears faint. Higher electron optical contrast and peak-to-background ratio of X-ray spectra are generally obtained in freeze-dried cryosections. Both preparation methods show that the X-ray spectra are influenced by the quality of cryofixation. The phosphorus/potassium ratio in nuclei increases with increasing ice crystal size.
Meyer, R.; Schmitz, M.; and Zierold, K.
"The Influence of Different Cryopreparations on the Distribution of Ions in Bullfrog Myocard Cells,"
Scanning Electron Microscopy: Vol. 1985
, Article 38.
Available at: https://digitalcommons.usu.edu/electron/vol1985/iss1/38