Assessment criteria for rotated stereociliary bundles in the guinea pig cochlea.
OBJECTIVE
Our study examined the relationship between variant stereociliary bundles of cochlear outer hair cells (OHCs) and auditory function to analyze assessment criteria for rotated stereociliary bundles in the guinea pig cochlea.


METHODS
Auditory brainstem response and distortion product otoacoustic emission (DPOAE) were recorded on 100 guinea pigs. Variant hair cells were identified and counted by scanning electron and light microscopy.


RESULTS
The most common variation observed was rotation of stereociliary bundles in the first-row OHCs (OHC1), with most 13.3% variant OHC1 rotated 90 degrees and a few 2.5% rotated 180 degrees. Occasionally, the length and angle of the 2 arms of an OHC deviated from the norm. The auditory brainstem response threshold of affected animals increased only slightly, 20- to 30-dB sound pressure level. More importantly, amplitude of DPOAE increased significantly (40.5 dB sound pressure level).


CONCLUSIONS
Our study suggests that rotation of stereociliary bundles in the cochlear OHC was found to be prevalent in 28% of the animals. We established the assessment criteria for rotated stereociliary bundles that were more than 10% OHC1 rotated. This hair bundle seemed to be rotated by 90 degrees from the normal orientation and was accompanied with changes of auditory function. Increased amplitude of DPOAE is associated with the variation of rotated OHC that might result in hearing loss.
Li
Shengli
S
Department of Hearing Research, Center of Neuroscience and Otolaryngology of Second Hospital, Xi'an Jiaotong University of Medicine, Xi'an, China.
Zhang
Shao Qiang
SQ
Liu
Si Wei
SW
Li
Bai Ya
BY
Zhu
Hong Liang
HL
Yu
Heping
H
Zheng
Qing Yin
QY
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000633:toxicity; D002923:Cilia / Q000187:drug effects / Q000502:physiology; D003051:Cochlea / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects / Q000502:physiology; D005839:Gentamicins / Q000633:toxicity; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D017084:Otoacoustic Emissions, Spontaneous / Q000187:drug effects / Q000502:physiology
D000900:Anti-Bacterial Agents; D005839:Gentamicins