Ice crystals formed in tissue during cryosurgery. II. Electron microscopy

Tissues frozen by means of a cryosurgical probe have been examined by electron microscopy following techniques designed to preserve the ice crystal spaces.Ice crystals appeared similar whether tissues were quenched or not following cryosurgery and the various techniques of dehydration resulted in similar ice crystal architecture.Ice crystal spaces in the area deep to the freezing probe were intracellular both in epithelium and muscle although in the muscle zone some fibers contained large and others small crystal spaces. It is suggested that this might be due to variations in the local blood supply.At the periphery of the frozen area ice crystals were usually extracellular producing gross distortion of the cells which, however, retained intracellular structural integrity. These results are consistent with the belief of many workers that intracellular ice is lethal while extracellular ice is not, but no evidence of penetration of cell membrane by ice crystals was seen.