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.

Noise Induced Hearing Loss in Children:Preventing the Silent Epidemic

Noise-induced hearing loss and related tinnitus are often unrecognized problems, especially in non-occupational settings. Research indicates that increasing numbers of children and adolescents have or are acquiring noise induced hearing losses. Noise induced hearing loss can almost completely be prevented with simple precautionary measures. Educational programs rarely exist outside of those mandated in occupational settings. Health Communication theory can be applied to hearing health for developing effective loss prevention programs. Dangerous Decibels is one example of an effective multi-disciplinary effort to develop and disseminated prevention strategies.

Deep Brain Stimulation──A new treatment for tinnitus

Intractable tinnitus can lead to serious consequences. Study evidence indicates that the central nervous system is involved in generation and maintenance of chronic tinnitus and that tinnitus and other neurologic symptoms such as chronic pain may share similar mechanisms. Brain ablation and stimulation are used to treat chronic pain with success. Recent studies showed that ablation and stimulation in non-auditory areas resulted in tinnitus improvement. Deep brain stimulation (DBS) may be an alternative treatment for intractable tinnitus and deserves further study.

声波在耳蜗内的逆行传导机制

耳蜗是内耳的听觉转换器官,其主要功能是把声波引起的机械振动转变为生物电信号并经听神经传输到听觉中枢。正常耳蜗也可以产生声信号,通常把在外耳道记录到的耳蜗产生的声信号称为耳声发射。虽然耳声发射已经被应用于临床听觉功能测试和研究耳蜗工作的原理,耳声发射从耳蜗逆向传出的机理仍不清楚。近年的生理实验研究结果显示声波在耳蜗的逆向延迟明显小于其从耳蜗底回向顶回传导的延迟,这些结果提示耳声发射是经耳蜗内的液体纵波,而不是普遍认为的逆向行波传导至外耳道的。这一新的发现不仅能够促进耳声发射的临床应用,而且对于研究耳蜗的基本工作原理具有重要意义。

Critical role of SDF-1/CXCR4 signaling pathway in stem cell homing in the deafened rat cochlea after acoustic trauma

Previous animal studies have shown that stromal cell-derived factor-1 （SDF-1）/CXC chemokine receptor-4 （CXCR4） signaling pathway plays an important role in the targeted migration of bone marrow-derived mesenchymal stem cells （BMSCs） to the injured area. In the present study, we aimed to investigate the potential role of chemotactic SDF-1/CXCR4 signaling pathway in the homing of transplanted BMSCs to the injured cochlea after noise-induced hearing loss （NIHL） in a rat model. White noise exposure （110 dB） paradigm was used for hearing loss induction in male rats for 6 hours in 5 days. Distortion-product otoacoustic emission （DPOAE） responses were recorded before the experiment and post noise exposure.Hoechst 33342-labeled BMSCs and CXCR4 antagonist （AMD3100）-treated BMSCs were injected into the rat cochlea through the round window. SDF-1 protein expression in the cochlear tissue was assayed using western blot assay. The number of labeled BMSCs reaching the endolymph was determined after 24 hours.SDF-1 was significantly increased in the cochlear tissue of rats in the noise exposure group than in the control group. The number of Hoechst 33342-labeled BMSCs reaching the endolymph of the cochlea was significantly smaller in the AMD3100-treated BMSCs group than in the normal BMSCs group. Our present findings suggest that the SDF-1/CXCR4 signaling pathway has a critical role in BMSCs migration to the injured cochlea in a rat model of noise-induced hearing loss.

特定抗生素致聋的药物途径和意义

1氨基甙类药物及其耳毒性以庆大霉素为主的氨基甙类药物为广谱抗生素，于临床应用已有六十余年。这类抗生素可用于多种细菌感染性疾病，包括术前术后用药和肺结核的治疗”，在国内多用于治疗由革兰氏阴性杆菌引起的脑膜炎以及中或重度肠道感染，而在欧美国家则用于防止早产新生儿败血症。

Mammalin cochlear supporting cells transdifferentiation into outer hair cells

Objective To study the recovery of the outer hair cells in the bat cochlea after gentamicin exposure. Methods Bats were injected with a daily dose of gentamicin for 15 consecutive days and bromodeoxyuridine (BrdU) was given from day 16 to day 40 of this recovery phase. Hearing was assessed by overt acoustic behavior and auditory brainstem responses analysis, which was performed one day prior to the first injection and a day after the last injection (day 16). On day 40 animals were sacrificed for detection of cells that could take up BrdU. Results After 15 days of gentamicin treatment, all of the animals were proved to be deafened with significant increases of ABR thresholds, compared with control group. The findings in immunocytochemical stained samples and scanning electron microscopy revealed that BrdU labeled nuclei were observed in the cochlea in all of the deafened animals most commonly in the regions of the first-row and second-row Deiter’s cells (DCs) and occasionally in the regions of the third-row DCs. Conclusion We suggest that, under sufficient drug and enough time, the bat cochlear supporting cells can directly transdifferentiate into the outer hair cells after aminoglycoside exposure. This transdifferentation process is essential for repair of outer hair cells and recovery of normal function after gentamicin exposure.

Electrically evoked auditory nerve responses in the cochlea with normal outer hair cells

As hybrid cochlear implant devices are increasingly used for restoring hearing in patients with residual hearing, it is important to understand electrically evoked responses in cochleae having functional hair cells. To test the hypothesis that extracochlear electrical stimulation (EES) from sinusoidal current can provoke an auditory nerve response with normal frequency selectivity, the EES-evoked compound action potential(ECAP) was investigated in this study. Brief sinusoidal electrical currents, delivered via a round window electrode, were used to evoke ECAP. The ECAP waveform was observed to be the same as the acoustically evoked CAP(ACAP), except for a shorter latency. The input/output and intensity/latency functions of ACAPs and ECAPs were also similar. The maximum acoustic masking for both ACAP and ECAP occurred near probe frequencies. Since the masked tuning curve of a CAP reflects the frequency selectivity of neural excitation, these data demonstrate a highly specific activation of the auditory nerve, which would result in high degree of frequency selectivity. This frequency selectivity likely results from the cochlear traveling wave caused by electrically stimulated outer hair cells.

Noise exposure induced cochlear hair cell death pathways in guinea pig

Objective To understand the mechanism of noise exposure induced outer hair cells(OHCs) death pathways. Methods Thirty two guinea pigs were used in this study. The animals were either exposed for 4 h/day to broadband noise at 122 dB SPL (A-weighted) for 2 consecutive days or perfused with MNNG. After auditory test, the cochleae of animals were dissected. Propidium iodide (PI), a DNA intercalating fluorescent probe, was used to trace morphological changes in OHC nuclei. F-actin staining was used to determine missing OHCs. Caspase-3 was detected in living organ of Corti whole mounts using the fluorescent probe. The single strand DNA (ssDNA) in apoptotic OHCs in guinea pigs and apoptosis inducing factor (AIF) in hair cells in guinea pigs were examined by immunohistology method. Whole mounts of organ of Corti were prepared. Morphological and fluorescent changes were examined under a confocal microscope. Results (1) Both apoptotic and necrotic hair cells appeared following noise exposure. (2) Noise exposure induced single strand DNA in apoptotic OHCs but not in the normal OHCs. (3) Either after noise exposure or after MNNG perfusion, apoptotic OHCs were featured by nuclear condensation or fragmentation with caspase-3 activation, whereas necrotic OHCs were characterized by nuclear swelling without caspase-3 activation. (4) In normal organ of Corti, AIF was located in the mitochondria areas. After noise exposure, AIF was translocated from mitochondria in apoptotic and necrotic OHCs. Conclusion These findings indicate that noise exposure damages DNA in the OHC, which triggers action of Caspase-3. Subsequently, AIF is translocated to the nucleus, leading to DNA damage and OHCs death.

Role of the hippocampus in contextual modulation of fear extinction

Fear extinction is an important form of emotional learning, and affects neural plasticity. Cue fear extinction is a classical form of inhibitory learning that can be used as an exposure-based treatment for phobia, because the long-term extinction memory produced during cue fear extinction can limit the over-expression of fear. The expression of this inhibitory memory partly depends on the context in which the extinction learning occurs. Studies such as transient inhibition, electrophysiology and brain imaging have proved that the hippocampus - an important structure in the limbic system - facilitates memory retrieval by contextual cues. Mediation of the hippocampus-medial prefrontal lobe circuit may be the neurobiological basis of this process. This article has reviewed the role of the hippocampus in the learning and retrieval of fear extinction. Contextual modulation of fear extinction may rely on a neural network consisting of the hippocampus, the medial prefrontal cortex and the amygdala.

MEASUREMENT OF AMPLITUDE AND DELAY OF STIMULUS FREQUENCY OTOACOUSTIC EMISSIONS

Although stimulus frequency otoacoustic emissions (SFOAEs) have been used as a non-invasive measure of cochlear mechanics, clinical and experimental application of SFOAEs has been limited by difficulties in accurately deriving quantitative information from sound pressure measured in the ear canal. In this study, a novel signal processing method for multicomponent analysis (MCA) was used to measure the amplitude and delay of the SFOAE. This report shows the delay-frequency distribution of the SFOAE measured from the human ear. A low level acoustical suppressor near the probe tone significantly suppressed the SFOAE, strongly indicating that the SFOAE was generated at characteristic frequency locations. Information derived from this method may reveal more details of cochlear mechanics in the human ear.

The distance between stapedial footplate and incus in otosclerosis surgery

Background: The measurement of the piston length during stapedotomy is important and it may have significant effects on the surgical outcome.Objective: To determine the piston length in a group of otosclerosis patients who underwent primary stapedotomy.Material and methods: Between Sep 2013 and Sep 2014, 85 patients with diagnosed otosclerosis underwent primary stapedotomy. Teflon prosthesis of 0.6 mm of diameter was used in all patients. The distance between medial surface of the long process of incus and center point of the stapedial footplate measured. The piston length calculated by adding 0.25 mm for the thickness of footplate and 0.50 mm for placement of the prosthesis into the vestibule.Results: The distance between stapedial foot plate and incus ranged from 3.50 to 4.50 mm. The mean distance was 3.95 ± 0.16 mm. In majority of cases(74.1%) piston length was 4.75 mm followed by 4.50 mm in 15.3% and 5.00 mm in 5.9%. Piston length was 4.25 mm in 3.5% and5.25 mm in only 1.2% of patients. There was no significant post-operative complication and air bone gap closure obtained in all patients.Conclusion: The most common distance between foot plate and incus is 4.00 mm. No case needed a piston longer than 5.25 mm or shorter than4.25 mm.

Phosphatidylserine-positive particles in the apical domain of sensory hair cells

Apical membrane recycling has been proposed to be important for normal hair cell function. The current study reports an in vitro work that demonstrates the presence of phosphatidylserine (PS) and PS-positive vesicles labeled by Annexin V in the apical portion of hair cells. The following characteristics of the PS-positive vesicles were noticed using scanning confocal fluorescence microscopy:(1) variable sizes around 200 nm; (2) variable distribution patterns (either uniformly along individual stereocilia in the hair bundle or irregular) in the stereocilia from cell to cell; (3) variable sizes and numbers at locations along the border of the cuticular plate (CP), with a large number of them located at the vestigal kinocilial location; (4) motility with some of the vesicles during the observation period; (5) increase in PS labeling and the number of PS-positive vesicles after loud sound stimulation; and (6) decreased PS labeling and PS-positive vesicle numbers following treatment with LY-294002, a PI3 -kinase inhibitor. These results suggest that the presence of PS-positive vesicles at the apical area of hair cells may be indicative of vesicle shedding or transportation of a protein or rafts.

An Overview of Electrically Evoked Otoacoustic Emissions in the Mammalian Cochlea

Alternating currents injected into the cochlea are able to evoke outer hair cell-mediated basilar membrane motion, thus give rise to production of otoacoustic emissions. This electrically evoked otoacoustic emission(EEOAE) provides a useful tool for the research of out hair cell electromotility in vivo. This article reviews the research work on EEOAEs in mammals. Features of the EEOAEs and theories of their generation are introduced. Methods of EEOAE measurement are also described.

Sino-nasal outcome Test-22 and Lund–Mackay CT score to select endoscopic sinus surgery in chronic rhinosinusitis

Objectives:Chronic rhinosinusitis is one of the common diseases that cause morbidity and affects a person's quality of life.We tried to provide a more appropriate and effective approach to selecting patients for endoscopic sinus surgery.Methods:The study population is chronic rhinosinusitis children referred to the ear,nose,and throat clinic of two general hospitals in Tehran,Iran,who have previously undergone sufficient drug treatment and have not recovered.The Lund–Mackay score is calculated by examining the computed tomography(CT)scan.The Sino-nasal Outcome Test-22(SNOT-22)questionnaire was provided to the patients before the operation,after the operation,and 3 and 6 months later in the clinic.Results:Before the operation,the most SNOT-22 score people were in the range of 40–59 points.The SNOT-22 score before the operation is significantly different from 3 and 6 months after the operation.The highest frequency of Lund–Mackay CT(LMCT)scan score was in the range of 18–23 points.The LMCT scan score did not show any significant relationship with the SNOT-22 score before surgery,3 months,and 6 months after surgery.Sensitivity to aspirin had a significant relationship with SNOT-22 scores and the history of asthma and nasal polyps had a significant relationship with the preoperative LMCT scan score.Conclusions:The LMCT scan scoring system cannot be a good measure of chronic rhinosinusitis severity or the prognosis of patients after surgery.The SNOT-22 questionnaire can be used as a predictive tool to help the doctor and the patient in deciding to operate and the possibility of obtaining a relative recovery.

Adaptive hearing in the vocal plainfin midshipman fish:getting in tune for the breeding season and implications for acoustic communication

The plainfin midshipman fish(Porichthys notatus Girard,1854)is a vocal species of batrachoidid fish that gen-erates acoustic signals for intraspecific communication during social and reproductive activity and has become a good model for investigating the neural and endocrine mechanisms of vocal-acoustic communication.Reproduc-tively active female plainfin midshipman fish use their auditory sense to detect and locate“singing”males,which produce a multiharmonic advertisement call to attract females for spawning.The seasonal onset of male adver-tisement calling in the midshipman fish coincides with an increase in the range of frequency sensitivity of the female’s inner ear saccule,the main organ of hearing,thus leading to enhanced encoding of the dominant frequency components of male advertisement calls.Non-reproductive females treated with either testosterone or 17β-estradiol exhibit a dramatic increase in the inner ear’s frequency sensitivity that mimics the reproductive fe-male’s auditory phenotype and leads to an increased detection of the male’s advertisement call.This novel form of auditory plasticity provides an adaptable mechanism that enhances coupling between sender and receiver in vocal communication.This review focuses on recent evidence for seasonal reproductive-state and steroid-dependent plasticity of auditory frequency sensitivity in the peripheral auditory system of the midshipman fish.The potential steroid-dependent mechanism(s)that lead to this novel form of auditory and behavioral plasticity are also dis-cussed.

周细胞在血脑屏障中的作用

周细胞是血脑屏障的一种重要细胞成分,在脑微血管生成、内皮细胞紧密连接形成、血脑屏障分化、微血管动态运动和结构稳定性方面起调节作用.周细胞在一些疾病,如脑血管病、神经退行性疾病、神经免疫性疾病和外伤性脑损伤中,呈现很独特的功能特性.文章对周细胞在血脑屏障中的作用做了综述.

噪声刺激致豚鼠外毛细胞凋亡时半胱氨酸天冬氨酸蛋白酶3激活和凋亡诱导因子转移

目的探讨噪声损伤后豚鼠外毛细胞发生凋亡的通路及其机制。方法分离解剖对照组(12只)和噪声暴露组(12只)豚鼠耳蜗,利用免疫荧光抗体和免疫荧光染料,分别染色细胞核、线粒体、凋亡诱导因子(apoptosis inducing factor,AIF)和半胱氨酸天冬氨酸蛋白酶3(Caspase 3),按表面制备法行耳蜗铺片,观察凋亡和坏死毛细胞内的荧光信号。结果对照组正常耳蜗毛细胞内没有激活的 Caspase 3,AIF 分布在毛细胞的线粒体内。实验组动物暴露于声压级120 dB 的白噪声环境中每天4 h,连续2 d 后,耳蜗外毛细胞出现死亡,表现为坏死和凋亡两种方式,但以凋亡为主。在凋亡的外毛细胞中,Caspase 3被激活,AIF 从线粒体转移到细胞核中;而在坏死的外毛细胞中,没有 Caspase3的激活,只有 AIF 自线粒体向细胞核的转移。结论噪声损伤后耳蜗外毛细胞的凋亡以 Caspase 依赖型的通路为主;线粒体释放的 AIF 在外毛细胞死亡通路中起重要作用。

血管生成中周细胞相关信号通路的研究进展

周细胞（pericytes）作为一种血管外周细胞包绕在微血管壁外侧，支持血管结构的稳定。周细胞向新生血管周围募集成为新生血管成熟的标志性事件。周细胞由于参与肿瘤血管新生、糖尿病性血管病变、缺氧／缺血性血管增生等诸多病理过程而成为研究的重点。研究生理性及病理性状态下血管生成过程中周细胞相关信号转导通路，对深入理解周细胞的生物学功能及其在相关疾病中的作用有重要意义。