The major goal of this project is to elucidate the mechanisms by which excessive exposure to noise (or other noxious agents) causes cellular degeneration in the inner ear. Another goal is to determine how the magnitude and pattern of hearing loss and structural damage are altered as the physical parameters of the stimulus (e.g. frequency, intensity, duration and scheduling of noise) are systematically varied. These studies are designed to identify the general principles of injury in the inner ear rather than to specify damage-risk criteria for human exposures. In addition to the experiments involving noise exposure, studies are planned in the areas of morphometric analysis of cochlear structures, cochlear perfusion and ischemia. Work in these additional areas is essential in order to attain our long-term goals. More objective methods for evaluating cellular alterations are needed in order to detect early or mild cochlear damage. To this end, morphometric analysis of various cellular and subcellular parameters in normal cochleas will provide a baseline to which data from damaged ears can be compared. The studies involving cochlear perfusions and ischemia will permit the testing of some of the current hypotheses concerning mechanisms of damage in the inner ear. Some of the experimental animals will be trained by food-reward, operant-conditioning techniques so that measures of auditory function (e.g. pure-tone thresholds, temporal integration functions, frequency DL's) can be obtained before, during and after their exposure to noise. Histological evaluation of the specimens will include detailed phase-contrast study of plastic-embedded flat preparations. Counts of missing sensory and supporting cells will be made and cytocochleograms prepared for all specimens. Multiple areas in the normal and pathological cochleas will then be sectioned for light and/or transmission electron microscopic study in order to conduct the morphometric analyses.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS001791-29
Application #
3393229
Study Section
(SSS)
Project Start
1978-12-01
Project End
1990-11-30
Budget Start
1986-12-01
Budget End
1987-11-30
Support Year
29
Fiscal Year
1987
Total Cost
Indirect Cost
Name
Washington University
Department
Type
Schools of Medicine
DUNS #
062761671
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
Clark, W W; Bohne, B A (1987) Attenuation and protection provided by ossicular removal. J Acoust Soc Am 81:1093-9
Bohne, B A; Yohman, L; Gruner, M M (1987) Cochlear damage following interrupted exposure to high-frequency noise. Hear Res 29:251-64
Clark, W W; Bohne, B A; Boettcher, F A (1987) Effect of periodic rest on hearing loss and cochlear damage following exposure to noise. J Acoust Soc Am 82:1253-64
Sinex, D G; Clark, W W; Bohne, B A (1987) Effects of periodic rest on physiological measures of auditory sensitivity following exposure to noise. J Acoust Soc Am 82:1265-73
Baggot, P J; Bohne, B A; Bozzay, D G et al. (1987) Use of phase contrast microscopy to determine the height of the organ of Corti in whole-mount preparations. J Acoust Soc Am 81:1499-506
Bohne, B A; Bozzay, D G; Harding, G W (1986) Interaural correlations in normal and traumatized cochleas: length and sensory cell loss. J Acoust Soc Am 80:1729-36
Bohne, B A; Carr, C D (1985) Morphometric analysis of hair cells in the chinchilla cochlea. J Acoust Soc Am 77:153-8
Bohne, B A; Marks, J E; Glasgow, G P (1985) Delayed effects of ionizing radiation on the ear. Laryngoscope 95:818-28
Harding, G W; Towe, A L (1985) Fiber analysis of the pyramidal tract of the laboratory rat. Exp Neurol 87:503-18
Bohne, B A; Zahn, S J; Bozzay, D G (1985) Damage to the cochlea following interrupted exposure to low frequency noise. Ann Otol Rhinol Laryngol 94:122-8