LOW-VOLTAGE FIELD-EMISSION SCANNING ELECTRON-MICROSCOPY OF NON-COATEDGUINEA-PIG HAIR CELL STEREOCILIA

The stereociliar structures of the guinea-pig cochlear organ of Corti were studied at low-voltage (1-5 kV) with field-emission scanning elec tron microscope (SEM) using various pre- and post-fixation methods, su ch as OTOTO 4/thiocarbohydrazide/OsO4/thiocarbohydrazide/OsO4) and TAO (tannic acid/arginine/OsO4), and different dissection procedures of t he cochlea. A perfusion and immersion pre-fixation with glutaraldehyde , in combination with removal of the bony wall and stria vascularis fr om the cochlea, followed by the TAO non-coating treatment, gave the be st result at 2 kV acceleration voltage. Due to these new techniques, s everal interesting delicate structures of the stereocilia, in particul ar fine surface structures, were detected for the first time using SEM . These findings include the different types of cross-links and tip li nks, i.e., the fine surface morphology of the stereocilia and their at tachments and imprints in the tectorial membrane (TM). One of the most interesting findings in this study is a network of long filamentous s tructures, which has been identified mainly at the top of the longest stereocilia and the undersurface of the TM and which may represent the glycocalyx. These findings and their possible implications in the pro cess of mechanoelectrical transduction will be discussed.