| Part 1Audiology investigation and analysis of the radio practitioners Noise is easily encountered in social life,and noise could cause damage to the auditory system.Radio presenters will be exposed to low-intensity auditory stimuli due to long-term wearing of headphones.Therefore,this study aims to explore the audiomatic changes of radio practitioners through the audiological investigation of broadcast practitioners and put forward preventive measures.Objective:The purpose of this study is to provide a scientific basis for the prevention and intervention of hearing impairment in radio practitioners by examining the audiologic characteristics and influencing factors of radio practitioners through cross-sectional epidemiological survey of radio station practitioners.Methods:A questionnaire survey and hearing examining(pure tone audiometry,acoustic immittance,ABR)were conducted for 25 on-post staff and workers(13 workers wearing earphones and 12 headless workers)of a radio station in Jinan City.And analyse the audiological test results and influencing factors based on the severy.Results:The workers included 12 males and 13 females,which aged 24 to 54 years old.The average age of the stuff was(36.85± 8.86)years of age.Subjects who work in the test group when wearing headphones every day 1 to 5 hours.Two people on the wearing staff suffering from tinnitus(1 unilateral and 1 bilateral).Pure tone audiometry showed one people of headset wearing group were binaural high frequency of hearing loss,and one ear of another presented high threshold of flat type.All results of acoustic immittance showed type "A".Pure tone hearing threshold test found that headphone wear group and control group 4000Hz frequency threshold is statistically significant.ABR test showed wave-I appearance rate of the wearing headset group was lower than that headless group,and the ABR wave-V amplitude extended simultaneously.Conclusions:Radio station workers in the case of long-term wear headphones may cause appearance rate of ABR wave-I droped and wave-V latency extended;long-term wear headphones suffering low-intensity sound stimulation may lead to tinnitus,hidden hearing loss or other auditory system lesions.Part2 Effects of long-term low-intensity noise exposure on ribbon synapsesIn social life,noise as a kind of environmental pollution is often contacted.Hearing impairment induced by noise exposure is generally quantified by threshold shift.The noise,which only causes temporary threshold shift(TTS)without permanent threshold shift(PTS),is generally considered safe.However,animal researches in recent years found that noise could lead to extensive synaptic damage,which were located between cochlear hair cells(IHC)and type I spiral neurons(SNG).PTS was not accompanied by the synaptic damage,but time coding dysfunction expressed synchronic.The related research,however,mainly involved the high sound intensity of the short-term noise exposure,and few researches paid attention to low-intensity noise which was often encountered in the daily life[2].Therefore,the aim of this study is to investigate the effects of intermittent low-intensity noise exposure to guinea pigs,and focus on auditory electrophysiology and synapses plasticity.Objective:This study aim to investigate the effects of the noise on the guinea pig under the low noise intensity noise background(95 dB SPL),and detect the safe dose of the low intensity,which would cause no PTS.To investigate the effects of noise on the auditory function and to observe the reduction and recovery of ribbon synapsis.To explore the plasticity of the ribbon synapses and analyze the relationship between the synaptic damage with suprathreshold auditory impairment.Methods:Make the guinea pigs in the 95dB SPL white noise exposure backgrounds 4 hours a day,and continuous expose for 7 days.The animals suffered noise were divided into three groups,and respectively named group 1DPN(one day post noise),1WPN(one week post noise),1WPN(one month post noise),that each group possesses 10 guinea pigs.Auditory brainstem response(ABR)and complex action potential(CAP)were performed at the appropriate time.The synaptic membrane structure(Ctbp2)and the postsynaptic membrane structure(PSD95)were labeled by immunofluorescence,and the presynaptic elements,postsynaptic elements and double labeling structures were counted.Results:Low-intensity noise exposure was aimed to make study the effects of low intensity noise applied on the guinea pigs with a prolonged duration.It was found that long-term low-intensity noise exposure could lead to a temporary threshold shift(PTS).ABR threshold of group 1DPN is significantly increased(P<0.05)compared to group control.No apparent changes of inner hair cell shape,arrangement or number were observed,but the number of ribbon synapse was of statistical significance(P<0.05).With the extension of time after getting out of noise environment,the number of synapses recovered gradually.In the reproductive process after synaptic injury,the number of presynaptic structures gradually increased and ribbons moved from the side of the inner hair cells near OHC to the inside near the type I nerve fiber.Eventually the number of presynaptic structures in the final phase was similar to that of the postsynaptic structures,but the exact number of complete synapses which were able to express signal transfer function did not return to the pre-noise level ribbons.ABR waveform analysis suggests that ABR wave-Ⅰ latency was prolonged and CAP amplitude decreases after noise.ABR waveform analysis suggested that the latencies of wave-Ⅰ and wave-Ⅲ were prolonged after noise,and the latency of wave-Ⅲ was not restored to normal level.The amplitudes of wave-Ⅰ and wave-Ⅲ decreased and the amplitude of wave-I did not return to normal level.The compound action potential(CAP)analysis showed that the CAP amplitude reduced after noise,and the CAP amplitude stimulated by short pure tone did not return to normal level.Conclusions:In this study,the long-term low-intensity noise exposure in guinea pigs resulted in a significant decrease about ribbon synapses,but did not cause a sustained threshold shift.The repair process of synaptic injury was mainly the increase of presynaptic structures,and the distribution of presynaptic structures was present in the repair process.The functional analysis showed that the amplitude of ABR wave-I and CAP was reduced,and the time coding disorder after noise was revealed.Combined with incomplete recovery of synaptic injury,we speculated that incomplete recovery is an important factor for the loss of hearing loss caused by noise. |
PDF Full Text Request