FREEZE-ETCHING AND DIRECT OBSERVATION OF FREEZING DAMAGE

Freeze-etching, as a method of preparing specimens for electron microscopy, is perhaps the best method for visualizing the fine structure of freezing damage to cells. New equipment permits the preparation of multiple specimens and double replicas, and rapid temperature changes. These make possible direct comparisons of different suspending media, different freezing rates, and apposed fracture surfaces. Also, recrystallization and condensation studies can be made. Freeze-etching is particularly useful for studies of membranes because the fracture plane often follows membrane surfaces and, even when large ice crystals destroy much of the detail within a cell, many membranes remain intact. © 1969.