[Fine structure of the guinea pig organ of Corti revealed by a quick-freeze, freeze-substitution method]

Abstract

A quick-freeze, freeze-substitution method was applied to the guinea pig organ of Corti. Many similarities were apparent between the conventionally fixed samples and the freeze-substituted samples, including the lateral membrane system of the cochlear outer hair cells consisting of the lateral plasma membrane, pillars, cytoskeletal lattice and subsurface cysternae. However, some ultrastructural differences were found in the cells prepared by the freeze-substitution method. Electron-dense mosaic structures were found in the lumen of the tubules of the subsurface cysternae. Tangential sections of the tubules of the subsurface cysternae showed spirally wound parallel rows of electron-dense materials. In a rectangularly cut membrane with a trilaminar structure, the electron-dense materials appeared to be triangular protrusions from the outer leaflet of the unit membrane. These structures suggest that the subsurface cysternae may play an important role in the contraction of cochlear outer hair cells.