Figure 6.
Immunogold localization of MERG. Cochlear sites of MERG expression were examined with immunogold electron microscopy with the postembedding technique. Thin mid-modiolar sections (70 nm) of cochlea used previously for routine ultrastructural examination were etched with sodium metaperiodate before incubation in primary and secondary antibodies conjugated to either 16 nm (A, F, G) or 10 nm (B–E) colloidal gold particles (arrows). A, C, In the stria vascularis, particles were localized in the cytoplasm and processes of the intermediate cells. Occasional particles were noted on the plasmalemma of marginal cells. The number of particles on intermediate cell interdigitations or cytosol around the nucleus exceeds the label on the marginal cell processes by ∼40–45%. Label was seen only in the processes that extend into the interstrial space; no label was seen on the cell body of the marginal cells. Of the marginal or intermediate cells (A, C), 90–95% of the specific label is adjacent to or near the plasmalemma, and, in a few instances, several gold particles are clumped together and it is impossible to determine which cell type they localize. B, In the spiral ligament, labeling was found on the type II fibrocytes in the region in which their amplified processes were interspersed with the upper root cells. D, The area immediately above the nucleus of the outer hair cell showed some gold particles. E, In the inner hair cell, however, gold label was observed at the base of the hair cell and in the cytosol of afferent fibers. A, Afferent nerve; E, efferent nerve. G, Gold particles were also found in nerve fibers in Rosenthal's canal. F, However, no particles were observed in the cytosol or plasmalemma of the basal cells of the stria vascularis. The nuclear location of gold particles may be nonspecific binding associated with the colloidal gold technique (Smith and Jarett, 1993). RC, Root cell; II, type II fibrocytes.