[Normal structure of stereocilia and recovery from ciliary damage in the organ of Corti after acoustic overstimulation].
The normal structure of outer hair cell (OHC) stereocilia in the organ of Corti, as well as damage and the recovery of OHC stereocilia after acoustic overstimulation, were demonstrated using scanning electron microscopy and tannic acid-osmium staining techniques. The highest row of OHC stereocilia is known to show an orderly gradation in height along the length of the cochlea. The present study demonstrated that the middle and lower rows of stereocilia possess a similar height gradation pattern. These findings suggest that the orderly gradation of stereocilia may play an important role in the tuning capability of the organ of Corti sensory cell. To investigate the mechanisms of recovery from ciliary acoustic damage, guinea pigs were exposed to a 4.00 kHz pure tone at an intensity of 120 dB for 120 minutes. All animals showed temporarily elevated hearing thresholds, which had returned to normal one week later. The first detectable change after acoustic overstimulation was a derangement of the cilia with a loss of ciliary interconnections. The tip links connecting the tips of the stereocilia to their taller neighbours were also affected showing elongation or disappearance. In comparing ciliary damage immediately after and one week after acoustic overstimulation, no signs of recovery in hair cell cilia which had been already lost, could be detected, while stereocilia with slight damage seemed to recover in the early post-sound exposure stage. Some lost tip links also seem to reappear in surviving cilia. In addition side links have the possibility of recovery.
Nikaido
M
M
Department of Otolaryngology, Hiroshima University School of Medicine.
D000161:Acoustic Stimulation / Q000009:adverse effects*; D000818:Animals; D002923:Cilia / Q000648:ultrastructure; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000648:ultrastructure*; D006317:Hearing Loss, Noise-Induced / Q000473:pathology*; D008855:Microscopy, Electron, Scanning; D009925:Organ of Corti / Q000648:ultrastructure