ABSTRACT
Objective To investigate the effect of impulse noise expose on the expression of growth associated protein 43(Gap-43) in inferior colliculus in rat.Methods SPF grade Male SD rats were randomly divided into 5 groups.The normal control group received noise exposure.The model groups received an averange impulse noise exposure of 156 dB SPL with a pulse duration of 0.23 ms, once for 6 s, for 50 times.Auditory brainstem responses (ABRs) were measured before and 3,7,14, and 28 d after noise exposure with tone pips of 2,4,8,16, and 32 kHz, from 20 to 110 dB SPL.Bilateral inferior colliculus of rats in the model groups was collected and treated by immunohistochemical staining.Gap-43 expression of rats in different groups was measured by determining the gray value of inferior immunohistochemical images.Results After noise exposure, ABRs threshold in the model groups were significantly higher than those of in the normal group (P<0.05 or P<0.01).ABRs threshold at 14 and 28 days after noise exposure were significantly lower than 3 days after impulse exposure (P<0.05).Expression of Gap-43 in inferior colliculus was significantly up-regulated in the noise exposed groups compared with the normal group (P<0.05 or P<0.01).Expression of Gap-43 was significantly down-regulated 28 days after noise expose compared with 3 days after noise expose(P<0.05).Conclusion Impulse noise exposure leads to significant elevation of ABR thresholds and up-regulation of Gap-43 expression in inferior colliculus.Impulse noise exposure may induce auditory cortex prominent remodeling.
ABSTRACT
Guinea pigs were exposed to 10 impulses of either 157-or 163dB peak SPL.The threshold shift recovery was monitored for 30 d, and tympanometric changes and co-chlear hislochemistry were investigated.The results showed that the 157dB level produced a recovey pattern linear to post-exposure log time and no PTS was found.The 163dB level produced a recovery-stop-recovery pattern, showing 13dB threshold shift on the 30th day after exposure.There are no TM perforation in both groups but most of the cochleas showed loss of outer hair cells or reduced activity of succinic dehydrogenase (SDH).
ABSTRACT
The present paper deals with the effect of impulse noise, which is produced by launching of miniature tactical missiles, on hearing of guinea pigs situated in the control room of the missile launching vehicle. 20 normal hearing guinea pigs are placed in the control room in which impulse noise level is 160-170dB (sound pressure level) and duration is longer than Is. 48h after sound exposure, the mean threshold shift is 2 dB, and threshold shift of 2/40 ears is greater than 10dB. Histological observation reveals that cochlear hair cells are undamaged in 15 ears. Howeves, staining on bloc shows hydrops of cochlear partition in 5 ears.
ABSTRACT
Ultrastructural changes in the spiral organ of cochlea at various intervals after exposure to impulse noise were investigated. Guinea pigs were exposed to 10 impulses noise of 166 dB SPL peak level which had duration of 0.1 ms. Thirteen of the exposed animals were used to systematically measure threshold shift at regular intervals from 30 min to 30d post-exposure. The other fourteen animals who had been exposed to the same impulse noise were killed for transmission electron microscopy (TEM) examination at the same intervals, respectively. The recovery pattern of threshold shift showed a nonmonotonic type. There was a progressive deterioration of changes in the hair cells between 30 min and 8h after exposure. Intracellular degeneration reached a peak at 8h and marked edema and swelling leading to deformation of the outer hair cells (OHCs), fused stereocilia, large vesicles in cytoplasm and swollen submembraneous cisterns were found. After that time the extent of degeneration in the hair cells reduced. The time sequence of changes in the spiral organ of cochlea in the present study was associated with the recovery pattern of threshold shift.