Comparison of vestibular and cochlear ototoxicity from transtympanic streptomycin administration.

Hypothesis: The relative dose-related cochlear and vestibular ototoxicity produced by transtympanically injected streptomycin (SM) compared to that of gentamicin (GM) was assessed.

Background: Although SM, the first aminoglycoside used transtympanically, is thought to be selectively vestibulotoxic, it has been replaced by GM in current clinical use. Little experimental data exist that directly demonstrate the relative cochlear and vestibular ototoxicity resulting from transtympanic administration of SM compared to GM.

Relationships between the variability of magnitude matching and the slope of magnitude level functions.

Binaural loudness matching and intermodal magnitude matching experiments were performed to test systematically the origins of the phenomenon observed earlier that the variability of binaural loudness matches was larger when sound intensity was varied in the normal ear than when it was varied in the contralateral ear with raised threshold and loudness recruitment. In the experiments, the raised threshold and loudness recruitment were produced by masking a 1-kHz tone with narrow-band random noise. In intermodal experiments, magnitude matches were performed between the masked tone and the length of lines projected on a translucent window pan.

Intensity just-noticeable differences at equal-loudness levels in normal and pathological ears.

The relationship between loudness level and intensity discrimination was investigated in the frequency range 0.5-6.5 kHz by comparing the intensity just-noticeable differences (jnd's) at a number of equal-loudness levels in the better and poorer ears of eight individuals with essentially unilateral hearing loss of cochlear origin.

Electron-microscopic localization of type II, IX, and V collagen in the organ of Corti of the gerbil.

The presence of types II, IX and V collagen was probed in the organ of Corti of the adult gerbil cochlea by use of immunocytochemistry at the light- and electron-microscopic levels. Type II collagen is found in the connective tissues of the osseous spiral lamina and spiral limbus. In the region of the sensory hair cells it is present in the tectorial membrane and antibodies bind to the thick unbranched radial fibers.

Type II and type IX collagen form heterotypic fibers in the tectorial membrane of the inner ear.

The presence of type II and IX collagen in the adult gerbil inner ear was probed by use of preembedding and post-embedding immunocytochemistry. Monoclonal antibodies to type II and IX collagen both label the tectorial membrane, an acellular structure which lies over the cochlear sensory hair cells and plays an essential role in the transduction process. At the light microscopic level, the antibodies are localized throughout the tectorial membrane.