1991 Fiscal Year Final Research Report Summary
Experimental study on ototoxicity through the round window memberane
| Project/Area Number |
02670758
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Otorhinolaryngology
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| Research Institution | University of Tokyo |
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Principal Investigator |
HARADA Takehiko University of Tokyo Medical School, Dept. of Otolaryngology, Assistant Professor, 医学部(病), 講師 (30010440)
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| Co-Investigator(Kenkyū-buntansha) |
YAGI Masato University of Tokyo Medical School, Dept. of Otolaryngology, Senior Resident, 医学部附属病院, 医員 (20230188)
YAMASOBA Tatsuya University of Tokyo Medical School, Dept. of Otolaryngology, Assistant, 医学部(病), 助手 (30220362)
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| Project Period (FY) |
1990 – 1991
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| Keywords | otitis media with effusion / sensorineural hearing loss / ototoxicity / round window membrane / endotoxin / lipopolysaccharide / lipoteichoic acid / cochlear damage |
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| Research Abstract |
The pathogenesis of sensorineural hearing loss which accompanies various forms of otitis media is attracting increasing interest. Endotoxin frequently found in middle ear effusion is considered to be one of the substances which might penetrate the round window membrane from the middle ear and exhibit ototoxicity in the inner ear. In this paper, the possible pathogenesis of the sensorineural hearing loss by a similar process was investigated by using endotoxin-like substance(lipoteichoic acid from Staphylococcus aureus).
In Group A, the middle ear bulla of 31 guinea pigs was opened and 5 mg of lipoteichoic acid was placed on the round window membrane. In 12 guinea pigs of Group B, a very small amount of lipoteichoic acid solution(10 mg/ml)was injected into the scala tympani through the round window membrane. After various time intervals, the animals were sacrificed, , the temporal bones removed, and histologic sections prepared. The cochlea was examined under a light microscope for possible pathology.
No definite pathology was observed either in Group A or in the control group. In 5 out of 12 guinea pigs of Group B, severe cochlear pathology was observed. The pathology consisted of various combinations of fibrosis in the scala tympani and the scala vestibuli, atrophy and cystic degeneration of the stria vascularism cyst-like formation of Reissner's membrane, degeneration of the organ of Corit with loss of hair cells, disappearance of the tectorial membrane, and inflammatory cell infiltration of the endolymphatic space.
The results of the study did not prove that an endotoxin-like substance in the middle ear could cause cochlear damage, but they suggest the possibility that, once introduced into the inner ear, it could potentially cause cochlear pathology.
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