Methods for the freeze-fracturing of nerve tissue cultures and cell monolayers

Two methods for freeze-cleaving of thin tissue layers are presented. Whereas a simple technique can be employed to fracture continuous, relatively firm tissue layers, a more sophisticated technique employing special carriers is needed to fracture very thin and incomplete layers, e.g., the fiber outgrowth of cultured nerve tissue or sparsely seeded isolated cells. Both methods basically consist of freezing the specimens sandwiched between two small metal carriers which are then fractured apart so that the cleavage plane runs through the tissue. In the resulting replicas of such thin specimens, large membrane areas are exposed, and new information is provided on the topography of membrane properties in entire cells or cell processes. The technique should also be useful for studies on the interactions of cells grown in culture.