We used preparative freeze-fracture to crush glutaraldehyde fixed tissues after impregnation in cryoprotective solution. The fragments were thawed and labeled with wheat germ agglutinin permeated with concanavalin A. They were also fracture- permeated with native ferritin and with cationized ferritin. In autonomic ganglia, primary sensory ganglia and peripheral nerves, fracture-label provides access to all plasma and intracellular membranes as well as extracellular matrices. Con A, WGA and cationized ferritin intensely labels the basal membrane. Furthermore, con A and WGA appears to be localized to synaptic vesicles and the synaptic complex. We worked also with rat glomeruli where freeze-fracture was used as a means to get generalized access to the cell surfaces. This new approach by-passes successive permeability barriers (endothelial cells, basement membranes) that had to be passed in previous cytochemical studies of the glomerulus. In human lymphocytes we used monoclonal anti-T3 and anti-T4 antibodies to study the partition of the transmembrane proteins which contain these antigens. During freeze-fracture, the T4 antigen partitions completely with the protoplasmic half of the membrane, gave an indication of its association with components of the membrane skeleton or of the cytoskeleton.
