| Objective: Low frequency strong sound is common in people's living environment.Its slow attenuation,long wave length and easy crossing obstacles make the effect of low frequency strong sound on human body longer than that of high frequency and strong voice.Small pig is very similar to human in ear anatomy,inner ear morphology,electrophysiology and so on.This experiment from the auditory brainstem response(Auditory Brainstem,Response,ABR),distortion product otoacoustic emission(Distortion Product Otoacoustic Emission,DPOAE),pathological morphology,cochlear basilar membrane preparation and fluorescence staining were observed.Results compared with the control group,to investigate the damage of pig auditory system Bama different frequency and sound pressure the strong low-frequency sound continued after exposure of 30min;to investigate the long time low-frequency noise exposure after hair cell injury.It provides the basic and theoretical support for the further study of the influence of low frequency strong sound on human auditory system.Methods:(1)The control group was only 13 Bama miniature pigs were randomly divided(3 rats)and experimental group(10 rats),were in the experiment on auditory brainstem response and DPOAE test,the experimental group were randomly divided into experimental group 50 Hz and experimental group 70 Hz.(2)The 50 Hz and 70 Hz group were placed in the 50Hz(167d B),70Hz(164d B)strong sound field(around the same sound pressure level),continuous exposure to 30 min,the control group was not given other noise exposure,keeping the same conditions with the experimental group.(3)The noise exposure immediately after auditory brainstem response(ABR)and distortion product otoacoustic emission(DPOAE)detected by HE staining,changing each animal inner ear structure were observed;immunohistochemical staining was used to detect expression of Caspase-3 and the corresponding animal inner ear structure of Tunel by immunofluorescence;4',6--two-2-phenyl amidine two indole hydrochloride(DAPI)method of labelled nuclei further observe hair cell loss,and calculate the loss rate of hair cell.Results:(1)Every group of Bama miniature pigs before and after noise exposure,auditory brainstem response(ABR),distortion product otoacoustic emission(DPOAE)comparison: before the experiment pigs ABR threshold is 20-50 d B,the control group was 33.1 + 8.6 d B,50 Hz in experimental group was 33.5 + 9.4d B,70 Hz in experimental group was 33.2 + 9.2d B.After exposure to noise,the experimental group ABR was not elicited;in the control group and the experimental group,before exposure,more than2000 Hz DPOAE could be elicited,and the DPOAE above the exposure of2000 Hz was not elicited.In Bama miniature pig auditory function have severe damage of noise exposure.(2)HE staining showed that the Corti cells were arrayed in the experimental group,and the spiral ligament was stripped from the volute.There was also a phenomenon of striped veins from the spiral ligament in the 70 Hz experimental group.The control group and the experimental group of Bama miniature pigs in different parts of the cochlea by immunohistochemical staining of Caspase-3 and Tunel showed no positive expression.The cochlear hair cell immunofluorescence results(nuclear PI staining,gray scale imaging)showed normal hair cells arranged orderly,low-frequency noise exposure,arranged in disorder,irregular 50 Hz experimental group of outer hair cells,hair cell loss,disorder,irregular 70 Hz experimental group of outer hair cells,a large number of hair cell loss,compared with 50 Hz group of outer hair cell missing serious.Conclusion:(1)The strong low-frequency sound exposed 30 min on Bama miniature pig auditory system caused serious irreversible damage,outer hair cell injury visible 70 Hz experimental group compared with the 50 Hz experimental group was seriously damaged.(2)After prolonged exposure to low frequency and strong sound(30min),the death mode of hair cells may be necrosis. |
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