Fig. 2. Immunolocalization of gelsolin to ectoplasmic specializations in rabbit testis. (A) Fluorescence of fixed-frozen sections of rabbit testis labeled for actin and gelsolin. Apical and basal ectoplasmic specializations are indicated by the `a' and `b', respectively, in the actin panel. Bar, 10 µm. (B) Immunoelectron microscopic localization of gelsolin to the actin filament-containing region of an apical ectoplasmic specialization. The material was processed and labeled exactly as described in the legend to Fig. 1. As in the rat, the silver grains (small arrows) are associated with the actin zone of the junction plaque. Bar, 250 nm. (C) Immunoblot of rabbit testis and purified bovine gelsolin (Sigma). The antibodies from Sigma and from Transduction Laboratories reacted with a single band on immunoblots of rabbit testis, and this band migrated slightly ahead of purified bovine plasma gelsolin. A similar band was not present on control blots in which the primary antibody was replaced with a similar concentration of normal mouse IgG (not shown). The lines indicate the top and bottom of the gel. Loading densities were 0.05 µg of purified gelsolin and 100 µg of decapsulated testis homogenate.