Prevalence of Noise-Induced Hearing Loss Related to the Mills in the Markets of the Municipality of Parakou in 2021

Introduction: Noise is the second leading cause of hearing loss in adults after presbycusis. The objective of this work was to study hearing loss induced by the noise of mills in the markets of Parakou. Methods: This was a descriptive and analytical cross-sectional study, conducted from February 3 to June 3, 2021 in the markets of Parakou. It concerned millers and sellers located within a 5 meter radius around the mills and among whom pure-tone audiometry was performed to detect a hearing loss. Subjects with no particular medical health history, under 55 years of age and having been working in these markets since more than 12 months, were included. Results: In this study, 103 subjects were selected, including 43 millers and 61 sellers. Their average age was 29 ± 13 years. The sex ratio was 0.49. The average length of service in the profession was 8 years with the extremes of 3 months and 47 years. They were exposed to noise on average 10 hours per day and 6 days a week. The average duration of weekly noise exposure was 23 h 28 min ± 13 h 32 min with the extremes of 5 h 00 min and 52 h 30 min. The average level of noise exposure was 90 dB with the extremes of 72 and 110 dB. 24 subjects reported symptoms related to noise such as headache, tinnitus, and hearing loss, with respective proportions of 22.33%, 20.39% and 06.80%. The prevalence of noise-related hearing loss was 26.21% (n = 27/103). Subjects with a notch at 4000 Hz and normal Average Hearing Loss (AHL) (20.39%) had a seven-time greater risk of developing noise-induced hearing loss (OR = 6.58;95% CI [2.54 - 18.8], p Conclusion: Hearing loss related to the noise of mills affected both millers and sellers near the mills in markets, hence the importance of regulating mills.

Evaluation of Digits-in-Noise Test and Hearing Handicap Inventory for Adults Screening in Patients with Occupational Noise-Induced Hearing Loss

Objective:To explore the clinical evaluation role of the Digits-in-Noise(DIN)test and Hearing Handicap Inventory for Adults Screening(HHIA-S)for patients with occupational noise-induced hearing loss and to observe and analyze their application values.Methods:Fifty patients with suspected occupational noise-induced hearing loss were randomly selected from the Department of Otolaryngology at the hospital as the research target.The collection period for the research cases spanned from January 2022 to November 2023,and all patients had a history of noise exposure.The DIN test and HHIA-S were used for hearing examinations,with clinical,comprehensive diagnosis serving as the gold standard to study their diagnostic performance.Results:The compliance rate of the DIN test was 88.00%,the HHIA-S’s compliance rate was 80.00%,and the combined compliance rate was 94.00%.The compliance rate of the DIN test and the combined compliance rates of the patients were statistically significant compared to the clinical gold standard data(P<0.05),while there was no difference between the compliance rate of the HHIA-S and the gold standard(P>0.05).The data shows that the sensitivity of the combined diagnosis is significantly higher than the sensitivity data of the DIN test and HHIA-S examination alone(P<0.05).Its specificity is 100.00%,and the accuracy data of the joint diagnosis in the degree were higher than those of the DIN test alone(P>0.05)and the HHIA-S alone(P<0.05).Conclusion:For patients with occupational noise-induced hearing loss,the joint evaluation of the DIN test and HHIA-S can significantly improve their diagnostic value with high sensitivity and accuracy.

Early detection of noise-induced hearing loss

BACKGROUND Noise-induced hearing loss(NIHL)is the second most common acquired hearing loss following presbycusis.Exposure to recreational noise and minimal use of hearing protection increase the prevalence of NIHL in young females.NIHL is irreversible.Identifying minor hearing pathologies before they progress to hearing problems that affect daily life is crucial.AIM To compare the advantages and disadvantages of extended high frequency(EHF)and otoacoustic emission and determine an indicator of hearing pathologies at the early sub-clinical stage.METHODS This cross-sectional study was implemented in West China Hospital of Sichuan University from May to September 2019.A total of 86 participants,aged 18-22 years,were recruited to establish normative thresholds for EHF.Another 159 adults,aged 18-25 years with normal hearing(0.25-8 kHz≤25 dBHL),were allocated to low noise and noise exposure groups.Distortion otoacoustic emission(DPOAE),transient evoked otoacoustic emissions(TEOAE),and EHF were assessed in the two groups to determine the superior technique for detecting early-stage noise-induced pathologies.The chi-square test was used to assess the noise and low noise exposure groups with respect to extended high-frequency audiometry(EHFA),DPOAE,and TEOAE.P≤0.05 was considered statistically significant.RESULTS A total of 86 participants(66 females and 20 males)aged between 18 and 22(average:20.58±1.13)years were recruited to establish normative thresholds for EHF.The normative thresholds for 9,10,11.2,12.5,14,16,18,and 20 kHz were 15,10,20,15,15,20,28,and 0 dBHL,respectively.A total of 201 participants were recruited and examined for eligibility.Among them,159 adults aged between 18 and 25 years were eligible in this study.No statistical difference was detected between the noise exposure and the low noise exposure groups using EHFA,DPOAE,and TEOAE(P>0.05)except in the right ear at 4 kHz using TEOAE(abnormal rate 20.4%vs 5.2%,respectively;P=0.05).CONCLUSION These results showed TEOAE as the earliest indicator of minor pathology compared to DPOAE and EHFA.However,a multicenter controlled study or prospective study is essential to verify these results.

Involvement of NLRP3-inflammasome pathway in noise-induced hearing loss

The inflammasome is a multiprotein oligomer in the cell cytoplasm and is part of the innate immune system.It plays a crucial role in the pathological process of noise-induced hearing loss(NIHL).However,the mechanisms of NLR family pyrin domain containing 3(NLRP3)inflammasome activation in NIHL have not been clearly demonstrated.In this study,miniature pigs were exposed to white noise at 120 dB(A)and auditory brainstem response measurements were used to measure their hearing function.Immunofluorescence staining,confocal laser scanning microscopy,western blot assay,and quantitative reverse transcription-polymerase chain reaction were used to analyze inflammasome-related protein distribution and expression.NLRP3,interleukin-1β,interleukin-18,and cleaved-caspase-1 were highly expressed in the cochlea after 120 dB(A)white noise exposure.Our findings suggest that NLRP3-inflammasomes in the cochlea may be activated after acoustic trauma,which may be an important mechanism of noise-induced hearing loss.

Saturated hydrogen saline protects against noise-induced hearing loss

Objective To study effects of saturated hydrogen saline in preventing noise-induced hearing loss. Methods Fifteen guinea pigs were randomly divided into 3 groups （5 each）, group one was for control, group two was treated with normal saline and group three was treated with saturated hydrogen saline, which was given intraperitoneally at 1 hour before noise exposure at 1 ml/100 g. One hundred rounds of impulse noise （ 157 dB SPL peak） were delivered as noise exposure. Immediately after exposure to impulse noise and on Days 1, 2, 4 and 8 following exposure, auditory brainstem response （ABR） thresholds were measured. Outer hair cell morphological changes and sueeinate dehydrogenase （SDH） activity were examined on Day 8 post-exposure. Results Immediately after noise exposure, ABR thresholds in saturated hydrogen saline treated animals were lower than the non-treated animals （P 〈 0.05 ）. Microscopy showed little SDH staining, cell swelling and irregular cell arrangement in the non-treated or normal saline treated animals. Whereas in the saturated hydrogen saline treated animals, there was deep SDH staining with significantly reduced cell loss and more regular cellular arrangement compared to the other two groups. The surviving cells counts was 45.17 ±12.15 for non-treated animals, 44.50 ±10.02 for normal saline treated animals and,116.50±2.38 for animals treated with saturated hydrogen saline. While the count was similar between non-treated and normal saline treated animals, it was significantly higher in saturated sions Intraperitoneal injection of saturated hydrogen saline damage. hydrogen saline treated animals （P 〈 0.05）. Concluappears to protect the cochlea against noise-induced damage.

NRN1 and CAT Gene Polymorphisms, Complex Noise, and Lifestyles interactively Affect the Risk of Noise-induced Hearing Loss

Objective The effects of interactions between genetic and environmental factors on the noise-induced hearing loss(NIHL)are still unclear.This study aimed to assess interactions among gene polymorphisms,noise metrics,and lifestyles on the risk of NIHL.Methods A case-control study was conducted using 307 patients with NIHL and 307 matched healthy individuals from five manufacturing industries.General demographic data,lifestyle details,and noise exposure levels were recorded.The Kompetitive allele-specific polymerase chain reaction(KASP)was used to analyze the genotypes of 18 SNPs.Results GMDR model demonstrated a relevant interaction between NRN1 rs3805789 and CAT rs7943316(P=0.0107).Subjects with T allele of rs3805789 or T allele of rs7943316 had higher risks of NIHL than those with the SNP pair of rs3805789-CC and rs7943316-AA(P<0.05).There was an interaction among rs3805789,rs7943316,and kurtosis(P=0.0010).Subjects exposed to complex noise and carrying both rs3805789-CT and rs7943316-TT or rs3805789-CT/TT and rs7943316-AA had higher risks of NIHL than those exposed to steady noise and carrying both rs3805789-CC and rs7943316-AA(P<0.05).The best six-locus model involving NRN1 rs3805789,CAT rs7943316,smoking,video volume,physical exercise,and working pressure for the risk of NIHL was found to be the interaction(P=0.0010).An interaction was also found among smoking,video volume,physical exercise,working pressure,and kurtosis(P=0.0107).Conclusion Concurrence of NRN1 and CAT constitutes a genetic risk factor for NIHL.Complex noise exposure significantly increases the risk of NIHL in subjects with a high genetic risk score.Interactions between genes and lifestyles as well as noise metrics and lifestyles affect the risk of NIHL.

The impact of hearing impairment and noise-induced hearing injury on quality of life in the active-duty military population:challenges to the study of this issue

The objectives of this review were to 1)summarize the available evidence on the impact of hearing loss on quality of life(QOL)among U.S.active-duty service members,2)describe the QOL instruments that have been used to quantify the impact of hearing loss on quality of life,3)examine national population-level secondary databases and report on their utility for studying the impact of hearing loss on QOL among active-duty service members,and 4)provide recommendations for future studies that seek to quantify the impact of hearing loss in this population.There is a lack of literature that addresses the intersection of hearing impairment,the military population,and quality of life measures.For audiological research,U.S.military personnel offer a unique research population,as they are exposed to noise levels and blast environments that are highly unusual in civilian work settings and can serve as a model population for studying the impact on QOL associated with these conditions.This review recommends conducting a study on the active-duty service member population using a measurement instrument suitable for determining decreases in QOL specifically due to hearing loss.

The Effect of a High-Frequency-Hearing-Threshold Weighted Value on the Diagnosis of Occupational-Noise-Induced Deafness

Objective: In order to provide a theoretical basis for the revision of the current diagnostic criteria for occupational noise-induced deafness (ONID), we evaluated the degree of ONID by analyzing different high-frequency-hearing- threshold-weighted values (HFTWVs). Methods: A retrospective study was conducted to evaluate the diagnosis of patients with ONID from January 2016 to January 2017 in Guangdong province, China. Based on 3 hearing tests (each interval between the tests was greater than 3 days), the minimum threshold value of each frequency was obtained using the 2007 edition’s diagnostic criteria for ONID. The speech frequency and the HFTWVs were analyzed based on age, noise exposure, and diagnostic classi-fication using SPSS21.0. Results: 168 patients in total were involved in this study, 154 males and 14 females, and the average age was 41.18 ± 6.07. The diagnosis rate was increased by the weighted value of the high frequencies and was more than the mean value of the pure speech frequency (MVPSF). The diagnosis rate for the weighted 4 kHz frequency level increased by 13.69% (χ2 = 9.880, P = 0.002), the weighted 6 kHz level increased by 15.47% (χ2 = 9.985, P = 0.002), and the weighted 4 kHz + 6 kHz level increased by 15.47% (χ2 = 9.985, P = 0.002). The differences were all statistically significant. The diagnostic rate of the different thresholds showed no obvious difference between the genders. The age groups were divided into less than or equal to 40 years old (group A) and 40 - 50 years old (group B). There were several groups with a high frequency: high frequency weighted 4 kHz ( group A χ2 = 3.380, P = 0.050;group B χ2 = 4.054, P = 0.032), high frequency weighted 6 kHz (group A χ2 = 6.362, P = 0.012;group B χ2 = 4.054, P = 0.032), weighted 4 kHz + 6 kHz (group A χ2 = 6.362 P = 0.012;B χ2 = 4.054, P = 0.032) than those of MVPSF in the same group on ONID diagnosis rate. The differences between the groups were statistically significant. There was no significant difference between the age groups (χ2 = 2.265, P = 0.944). The better ear’s (the smaller hearing threshold weighted value) MVPSF and the weighted values for the different high frequencies were examined in light of the number of working years;the group that was exposed to noise for more than 10 years had significantly higher values than those of the average thresholds of each frequency band in the groups with 3 - 5 years of exposure (F = 2.271, P = 0.001) and 6 - 10 years of exposure (F = 1.563, P = 0.046). The differences were statistically significant. The different HFTWVs were higher than those of the MVPSF values, and the high frequency weighted 4 kHz + 6 kHz level showed the greatest difference, with an average increase of 2.83 dB. The diagnostic rate that included the weighted high frequency values was higher for the mild, moderate, and severe cases than those patients who were only screened with the pure frequency tests. The results of the comparisons of the diagnosis rates for mild ONID were as follows: the weighted 3 kHz high frequency level (χ2 = 3.117, P = 0.077) had no significant difference, but the weighted 4 kHz level (χ2 = 10.835, P = 0.001), 6 kHz level (χ2 = 9.985, P = 0.002), 3 kHz + 4 kHz level (χ2 = 6.315, P = 0.012), 3 kHz + 6 kHz level (χ2 = 6.315, P = 0.012), 4 kHz + 6 kHz level (χ2 = 9.985, P = 0.002), and 3 kHz + 4 kHz + 6 kHz level (χ2 = 7.667, P = 0.002) were significantly higher than the diagnosis rate of the mean value of the PSF. There was no significant difference between the 2 groups for the moderate and severe grades (P > 0.05). Conclusion: Different HFTWVs increase the diagnostic rate of ONID. The weighted 4 kHz, 6 kHz, and 4 kHz + 6 kHz high frequency values greatly affected the diagnostic results, and the weighted 4 kHz + 6 kHz high frequency hearing threshold value has the maximum the effect on the ONID diagnosis results.

Genetic Effects on Sensorineural Hearing Loss and Evidence-based Treatment for Sensorineural Hearing Loss

In this article,the mechanism of inheritance behind inherited hearing loss and genetic susceptibilityin noise-induced hearing loss are reviewed.Conventional treatments for sensorineural hearing loss(SNHL),i.e.hearing aid and cochlear implant,are effective for some cases,but not without limitations.For example,they provide little benefit for patients of profound SNHL or neural hearing loss,especially when the hearing loss is in poor dynamic range and with low frequency resolution.We emphasize the most recent evidence-based treatment in this field,which includes gene therapy and allotransplantation of stem cells.Their promising results have shown that they might be options of treatment for profound SNHL and neural hearing loss.Although some treatments are still at the experimental stage,it is helpful to be aware of the novel therapies and endeavour to explore the feasibility of their clinical application.

NOISE INDUCED HEARING LOSS IN CHINA:A POTENTIALLY COSTLY PUBLIC HEALTH LSSUE

Hearing loss and tinnitus are among the most common consequences of long term noise exposure and re-main an under-addressed heath issue in most developing nations including China. The rapid industrializa-tion and life style changes in China increase the concern over noise exposure and noise induced hearing loss (NIHL). Research on NIHL in China is limited. The current paper reviews studies published in English and Chinese language literatures regarding noise exposure and NIHL in China. Their implication on the Chi-nese population is discussed. The possible utility of a research model such as the Dangerous Decibels? as a means to increase understanding of the scope of NIHL among the Chinese population, to educate the gener-al public in China (especially the young) about NIHL and its prevention, and to study effects of language and cultural factors on international information dissemination and behavioral interventions is proposed.

EFFECTS OF MODERATE NOISE EXPOSURE ON HEARING FUNCTION IN C57BL/6J MICE

Objective To study characteristics of hearing loss after exposure to moderate noise exposure in C57BL/6J mice. Methods Male C57BL/6J mice with normal hearing at age of 5-6 weeks were chosen for this study. The mice were randomly sclccted to be studied immediately after exposure （Group P0）, or 1 day （Group P1）, 3 days （Group P3）, 7 day （Group P7） or 14 days （P14） after exposure. Their before exposure condition served as the normal control. All mice were exposed to a broad-band white noise at 100 dB SPL for 2 hours, ABR thresholds were used to estimate hearing status at each time point. Results ABR threshold elevation was seen at every tested frequency at P0 （P〈0.01）. Elevation at high-frequencies （16 kHz and 32 kHz） was greater than at lower frequencies （4 kHz and 8 kHz, P〈0.05）. From P1 to P14, ABR thresholds continuously improved, and there was no significant difference between P14 and before exposure （P〉0.05）. Conclusion There is a frequency specific re- sponse to 100 dB SPL broad-band white noise in C57BL/6J mice, with the high-frequency being more susceptible. Hearing loss induced by moderate noise exposure appears reversible in C57BL/6J mice.

Impact of noise on hearing in the military

Hearing plays a vital role in the performance of a soldier and is important for speech processing. Noise-induced hearing loss is a significant impairment in the military and can affect combat performance. Military personnel are constantly exposed to high levels of noise and it is not surprising that noise induced hearing loss and tinnitus remain the second most prevalent service-connected disabilities. Unfortunately, unlike civilian personnel, military personnel have little option but to remain in noisy environments in order to complete specific tasks and missions. Use of hearing protection devices and follow-up audiological tests have become the mainstay of prevention of noise-induced hearing loss. This review focuses on sources of noise within the military, pathophysiology and management of patients with noise induced hearing loss.

Investigation on gunner's hearing organ damage:ear drum inspection and acoustic impedance measurement

The ear drums of 279 long-range gunners and 156 short-range gunners who hadparticipated in a battle for 4 months were inspected and 442 ears were subjected to acousticimpedance measurement.The results showed that retraction was the main change of the ear drums,then,opacity and atrophy.The average static compliance was 1.06,tympanograms were 75.6% oftype A and 21.1% of AD.No obvious difference in acoustic reflex threshold at different frequencieswas found between the 2 sorts of gunners.But the short-range cannon gunners suffered a more seri-ous high frequency hearing loss.

Prophylactic effect of Ca^(2+)-deficient artificial perilymph perfusion on noise-induced hearing loss

Objective To investigate the prophylactic effect of low calcium concentration perilymph on noise-induced hearing loss. Methods Forty guinea pigs with normal hearing weighing 250-350 g were assigned to five groups (8 in each group): (1) Ca2+-deficient perilymph perfusion (CDP) for 2 h; (2) white noise (120 dB SPL) exposure (WNE) only for 1 h, (3) combination of calcium-deficient perilymph perfusion and white noise (120 dB SPL) exposure (WNE+CDP); (4) normal artificial perilymph (NAP) perfusion for 2 h; and (5) white noise exposure + normal artificial perilymph perfusion (WNE+NAP) for 2 h. Compound action potentials (CAP) evoked by click was recorded from round window every 15 min. The cochleae from 5 animals in each group were examined with scanning electron microscope. Results The CAP for group 1 experienced a threshold shift (TS) of 15-26 dB, while group 2 yielded a 46-59 dB TS and group 3 a 37-45 dB TS; no threshold shift occurred in group 4. The CAP TS in group 5 was 33-64 dB. The CAP TS of group 3 was less than that of group 2. After one hour of noise exposure, the CAP TS of group 3 were 45.92±2.90 dB and 59.30±3.95dB in group 2. There were significant differences (P<0.05) between groups 3 and 2. The CAP TS of group 3 was less than that of group 5 at the points of 1, 1.5 and 2 h after noise exposure. There was a significant difference between groups 3 and 5 (P<0.01). Stereocilia of 89 OHC3 were in disarray in five cochleae after noise exposure in group 2. The cuticular plates of 8 OHC2,3 sank and the stereocilia became fused in only one animal cochlea after noise exposure in group 3 combined with low calcium perilymph perfusion. Conclusions Low calcium concentration appears to participate in preventing noise-induced hearing loss and the rising of calcium concentrations in inner hair cells after noise exposure, which may have been due to the opening of calcium channels in inner hair cells during noise exposure. The mechanism of the prophylactic effect might be caused by a lower calcium concentration in inner hair cells in the cochlea attenuating the influence of noise exposure on hearing loss; calcium deficient perilymph perfusion prevented calcium accumulation in inner hair cells of the cochlea. The motility of the OHCs might be partially inhibited by low calcium concentration that reduced noise-induced hearing loss in turn.

宽频带白噪声适度暴露对小鼠听力损害的实验研究

目的：通过100dB SPL宽频带白噪声对成年C57小鼠进行单次2小时的暴露，观察该种噪声对小鼠听功能损害的特点。方法选取5-6周龄ABR听阈正常的C57小鼠（每组5-7只），随机分为5个实验组分别为：噪声暴露后即刻（P0）、1天（P1）、3天（P3）、7天（P7）、14天（P14）。实验组小鼠于100dB SPL宽频带白噪声环境下暴露2h，本实验采用噪声暴露前的小鼠作为对照组。每只实验小鼠分别于噪声暴露前及暴露后各时间点进行ABR阈值检测以评估听力受损情况，实验采用统计噪声暴露前、后各时间点小鼠ABR差值（阈移）的方法分析实验结果。结果噪声暴露后即刻，小鼠各频率的ABR阈移均为最大值（P〈0.01）：Click（11.92±7.51dB）、4kHz（11.92±5.60dB）、8kHz（12.31±5.99dB）、16kHz （21.54±8.75dB）、32kHz（20.00±8.90dB），且在各个频率的阈移中，以16kHz及32kHz处的高频听力损失最严重，明显高于Click、4kHz及8kHz处的阈移（P〈0.05）。脱离噪声环境24小时后各频率的ABR阈移开始下降，2周以后，小鼠各频率ABR阈值均完全恢复至暴露前水平（P〉0.05）：Click（1.11±6.01dB）、4kHz（1.11±3.33dB）、8kHz（1.11±4.17dB）、16kHz （1.67±4.33）、32kHz（2.78±4.41）。结论100dB SPL宽频带白噪声单次有限暴露可以造成小鼠出现一定程度的听力损害。在频率分布上，高频区域的听力损害更为明显。同时，本研究表明，这种噪声下小鼠听力损害可以表现自我主动恢复的特征。

隐性听力下降小鼠耳蜗内毛细胞突触的病理改变

目的探讨噪声暴露后出现暂时性阈移的小鼠在听觉反应阈值完全恢复正常后耳蜗内毛细胞突触的病理改变。方法将小鼠分为正常对照组和实验组,实验组小鼠进行强度98 dB SPL、时长2 h的噪声暴露,建立暂时性阈移模型。将对照组和暂时性阈移模型小鼠进行全基底膜铺片并行免疫荧光染色,共聚焦显微镜拍照成像并观察细胞形态。利用耳蜗长度计算耳蜗所处的频率位置,最后用图形处理软件对突触结构进行三维重建,观察对照组小鼠和实验组小鼠的耳蜗内毛细胞突触前、后结构的空间分布规律及其病理改变特点。结果对照组小鼠耳蜗内毛细胞的突触复合体有明显的分布特点,每个内毛细胞通过5~30个突触与耳蜗神经纤维形成突触连接,靠近蜗轴侧的突触前结构体积较大,与之相匹配的突触后结构体积较小。靠近柱细胞侧的突触前结构体积偏小,与之相匹配的突触后结构体积偏大。实验组小鼠在高强度噪声暴露后第2天听觉测试结果显示,听性脑干反应(auditory brain-stem response,ABR)和畸变产物耳声发射(distortion product otoacoustic emission,DPOAE)阈值升高30~40 dB,2周后再次测试显示阈值恢复正常,但是ABR的Ⅰ波波幅下降46.1%,且耳蜗内毛细胞的突触复合体结构数量也减少了41.3%。而内毛细胞和螺旋神经节细胞没有明显丢失。结论听觉阈值功能测试对判断小鼠耳蜗内毛细胞突触的损害和丢失不敏感;而听觉阈上功能测试对评价小鼠耳蜗内毛细胞突触的损害和丢失相对敏感。

噪声环境作业工人血清中3种微量元素检测结果分析

目前,噪声污染越来越受到关注,高强度的噪声刺激会导致耳蜗血管产生病理变化,随着暴露噪声的时间增加,耳蜗受损范围逐渐扩大,累及言语频率范围,出现明显的听觉障碍。这个过程是缓慢发展的,通常暴露噪声10年以下的作业人员,他们的言语频率基本不会受到影响[1]。而人体的各种疾病又与体内微量元素平衡失调有着密切的关系,尤其是人体必需微量元素是维持人体正常新陈代谢的保证,各种酶的活性、脂肪、蛋白质、碳水化合物的合成分解和代谢,也是体内过氧化物和毒素的排除、免疫功能的调节所必需的条件。

噪声所致听力损失现象的物种差异及可能生理机制研究进展

噪声广泛存在于人和动物的生活环境中,从无脊椎动物到哺乳动物乃至人类,都会受到噪声的负面影响.强烈的噪声会损伤听觉系统的结构和功能,引起噪声性听力损失(noise-induced hearing loss,NIHL).本文对噪声性听力损失的类型、影响因素、噪声所致不同程度听力损失形成的可能机制进行了总结,发现NIHL主要与突触结构肿胀、谷氨酸引起的可逆兴奋性中毒以及活性氧引起的氧化应激、细胞凋亡、带状体损伤、α激动型鸟嘌呤核苷酸结合蛋白(guanine nucleotide binding protein alpha stimulating,GNAS)基因的mRNA及其上游lncRNA Sept7的表达量上调等因素有关.比较噪声暴露后不同物种听力损失情况的差异,发现鱼类和鸟类由于具有毛细胞再生能力而能够较快从听力损伤中恢复,啮齿类较容易受到噪声影响,而回声定位鲸类噪声暴露后的暂时性听觉阈移较小,非常有趣的是回声定位蝙蝠在噪声高强度暴露后未表现出暂时性听觉阈移的现象.上述结论提示,对不同物种的比较生理研究可深入揭示NIHL机制,并为听力保护以及噪声所致的听力损伤后修复等提供理论参考.

100dB SPL白噪声暴露对小鼠耳蜗听神经髓鞘的影响

目的观察中等强度噪声暴露是否对成年C57BL/6J小鼠耳蜗听神经造成损害。方法选取24只听阈正常的6周龄雄性C57BL/6J小鼠随机分为4组(6只/每组),实验组按照暴露后时间分别为暴露后即刻(P0)、暴露后7天(P7)和暴露后14天(P14)组,另外一组未经噪声暴露,设为对照组;实验组小鼠用100dB SPL宽频带白噪声暴露2小时,在噪声暴露后即刻、7天和14天分别检测小鼠ABR阈值,之后取小鼠耳蜗行基底膜免疫荧光观察,并进一步采用透射电镜观察小鼠听神经髓鞘结构的变化。结果 1)听力学表现:P0组C57BL/6J小鼠各个频率的ABR阈值均明显高于对照组(P<0.05),以8kHz、16kHz及32kHz最为显著(P<0.01);P7时各频率阈值基本恢复,仅在32kHz显著高于对照组(P<0.05);P14时小鼠ABR阈值与对照组相比已无显著差异(P>0.05)。2)形态学表现:经共聚焦显微镜观察发现P0时听神经髓鞘信号偶有轻微减弱,而各组标本中髓鞘信号的数量和密度无明显差异。冰冻切片显示各实验组与对照组相比,髓鞘信号均有效表达,信号强度均匀、致密连贯,条索样结构清晰,数量亦无明显缺失。透射电镜下各时间点听神经髓鞘成像清晰,排列整齐,且板层样结构致密,边缘光滑,与对照组相比髓鞘形态上并无明显差异(P>0.05)。结论 100dB SPL宽频带白噪声暴露后可造成小鼠出现暂时性阈移(TTS);此种噪声暴露下耳蜗听神经髓鞘并未观察到明显的形态学改变。

中-低强度噪声暴露对耳蜗带状突触的影响

哺乳动物耳蜗是编码声音信号的器官,其中外毛细胞(Outer Hair Cells, OHCs)、内毛细胞(Inner Hair Cells, IHCs)与螺旋神经节神经元(Spiral Ganglion Neurons,SGNs)是将声波振动转化成神经信号的三个关键结构,其对声音暴露、耳毒性物质、衰老以及遗传缺陷等因素都很敏感。高强度的噪声暴露可以损伤耳蜗毛细胞等结构进而导致耳聋,最新研究表明,中-低强度噪声暴露可导致暂时性听阈升高,然而这种暴露常常并未引起耳蜗毛细胞的缺失或损伤;进一步的研究则发现内毛细胞和螺旋神经纤维之间的带状突触很容易受到噪声损伤,从而产生不可逆转病变,进而导致各种形式听功能的异常表现。内毛细胞带状突触(Ribbon Synapses)是听觉通路中第一个兴奋性传入突触,该结构对于声音的编码具有决定性作用。不同强度和频率的声刺激会引起带状突触在数量、结构、形态及功能方面发生相应的改变。本文通过对中-低等强度噪声暴露对小鼠耳蜗带状突触的影响以及它所引起的听觉障碍做一简要综述,希望对感音神经性耳聋患者的疾病预防有一定的指导。