FREEZE-FRACTURE, DEEP-ETCH, AND FREEZE-SUBSTITUTION STUDIES OF OLFACTORY EPITHELIA, WITH SPECIAL EMPHASIS ON IMMUNOCYTOCHEMICAL VARIABLES

Freeze-fracturing and deep-etching are a well-suited set of methods to study membrane and cytoplasmic features. Various approaches are avail able. Possible variables include tissue preparation, fracturing only o r fracturing followed by etching, modes and materials of replication, and various ways of combining freeze-fracturing and/or deep-etching wi th (immuno)cytochemistry. Freeze-substitution, in particular combined with embedding in methacrylate resins such as the Lowicryls, is becomi ng rather widely accepted for purposes of ultrastructural (immuno)cyto chemistry. Most investigators active in this field agree that this com bination yields superior results compared to (immuno)cytochemistry com bined with more conventional means of thin section transmission electr on microscopy. Yet relatively little information is available on the v ariations that can occur with different approaches of freeze-substitut ion immunocytochemistry. This review deals with some of the variations in freeze-fracturing, freeze-etching, and freeze-substitution as appl ied to olfactory epithelial structures and with the effectiveness of o bservations obtained by application of the above sets of methods in re lating the special morphology of olfactory epithelial cellular structu res with those obtained by other approaches. Indeed, the data obtained continue to provide an integral image in which that morphology can be related to the special biochemistry, cell and molecular biology, and electrophysiology of olfactory epithelial structures. (C) 1995 Wiley-L iss, Inc.