听觉器官线粒体DNA缺失在老年聋发病中的意义

目的 探讨听觉器官中线粒体DNA缺失在老年聋发病中的意义。方法:饲养不同年龄组的大鼠,测试ABR阈值,PCR检测其耳蜗、蜗核、大脑、颞肌和外周血中是否存在mtDNA~(4834)缺失,对存在的缺失进行定量分析;PCR产物进行克隆、测序。结果:老年组大鼠的ABR平均阈值为92.22±10.60dBSPL(n=20),中年组为42.75±5.73dBSPL(n=24),青年组为30.50±1.54dBSPL(n:24),老年组大鼠的ABR阈值明显高于中年组和青年组,其差别具有非常显著性的意义(方差分析,P<0.01);(2)所有老年大鼠的听觉器官和颞肌中均存在mtD-NA~(4834)缺失,其缺失发生率高于中年组,青年组mtDNA~(4834)缺失发生率最低;(3)定量分析显示不同年龄大鼠听觉器官中mtDNA~(4834)缺失占总mtDNA的百分比不同,老年组mtDNA~(4834)缺失占总mtDNA的百分比高于中年组。结论:老年大鼠的ABR阈值明显升高,其包括耳蜗、蜗核在内的多种组织中普遍存在的mtDNA~(4834)缺失,提示mtDNA缺失在老化和老年聋的发生中具有重要意义。     

Current status of auditory aging and anti‐aging research

The development of presbycusis, or age‐related hearing loss, is determined by a combination of genetic and environmental factors. The auditory periphery exhibits a progressive bilateral, symmetrical reduction of auditory sensitivity to sound from high to low frequencies. The central auditory nervous system shows symptoms of decline in age‐related cognitive abilities, including difficulties in speech discrimination and reduced central auditory processing, ultimately resulting in auditory perceptual abnormalities. The pathophysiological mechanisms of presbycusis include excitotoxicity, oxidative stress, inflammation, aging and oxidative stress‐induced DNA damage that results in apoptosis in the auditory pathway. However, the originating signals that trigger these mechanisms remain unclear. For instance, it is still unknown whether insulin is involved in auditory aging. Auditory aging has preclinical lesions, which manifest as asymptomatic loss of periphery auditory nerves and changes in the plasticity of the central auditory nervous system. Currently, the diagnosis of preclinical, reversible lesions depends on the detection of auditory impairment by functional imaging, and the identification of physiological and molecular biological markers. However, despite recent improvements in the application of these markers, they remain under‐utilized in clinical practice. The application of antisenescent approaches to the prevention of auditory aging has produced inconsistent results. Future research will focus on the identification of markers for the diagnosis of preclinical auditory aging and the development of effective interventions. Geriatr Gerontol Int 2014; 14: 40–53.     

Clinical observation on hearing conditions of centenarians in northern district of China

Conclusion: The hearing conditions of the centenarians were quite poor as regards hearing thresholds and speech detection ability. Objective: To investigate hearing conditions of centenarians. Methods: A total of 54 centenarians in Rizhao and Linyi Districts in Shandong Province were investigated to assess hearing conditions of centenerians comprehensively by questionnaire investigation, pure-tone audiometry, acoustic immitance, intelligence evaluation, and speech detection scores. Also, 135 individuals were recruited as controls and divided into four groups according to their age: 45–59 years, 60–69 years, 70–79 years, and 80–89 years. Results: The hearing thresholds of the centenarians were dramatically higher than those of the control group (p < 0.05) and all centenarians suffered moderate to profound hearing loss according to the World Health Organization (WHO) criteria. Few centenarians had normal level of speech detection scores. All centenarians showed descending hearing curve, and the hearing threshold of the male centenarians at 8000 Hz was higher than that of the females (p = 0.047). There was a significant air–bone conduction gap in the centenarians (p < 0.05).     

Presbycusis: a human temporal bone study of individuals with flat audiometric patterns of hearing loss using a new method to quantify stria vascularis volume

OBJECTIVE: The purpose of this study was to determine the prevalence of stria vascularis atrophy in individuals with presbycusis and flat audiometric patterns of hearing loss. Individuals with presbycusis have historically been categorized by the shape of their audiograms, and flat audiometric thresholds have been reported to be associated with atrophy of the stria vascularis. Stria vascularis volume was not measured in these studies. STUDY DESIGN: Retrospective case review. METHODS: Archival human temporal bones from individuals with presbycusis were selected on the basis of strict audiometric criteria for flat audiometric thresholds. Six temporal bones that met these criteria were identified and compared with 10 temporal bones in individuals with normal hearing. A unique quantitative method was developed to measure the stria vascularis volume in these temporal bones. The hair cell and spiral ganglion cell populations also were quantitatively evaluated. RESULTS: Only one of the six individuals with presbycusis and flat audiometric thresholds had significant atrophy of the stria vascularis. This individual with stria vascularis atrophy also had reduced inner hair cell, outer hair cell, and ganglion cell populations. Three of the individuals with presbycusis had spiral ganglion cell loss, three individuals had inner hair cell loss, and all six individuals had outer hair cell loss. CONCLUSIONS: The results of this investigation suggest that individuals with presbycusis and flat audiometric patterns of hearing loss infrequently have stria vascularis atrophy. Outer hair cell loss alone or in combination with inner hair cell or ganglion cell loss may be the cause of flat audiometric thresholds in individuals with presbycusis.     

The Aging of the Middle Ear in 129S6/SvEvTac and CBA/CaJ Mice: Measurements of Umbo Velocity,Hearing Function,and the Incidence of Pathology

Measurements of umbo velocity and auditory brainstem response (ABR) were made on two different strains of mice, 129S6/SvEvTac (129S6) and CBA/CaJ (CB), within three different age ranges. The velocity measurements were made with a laser Doppler vibrometer using a semiclosed sound delivery system; the frequency range of accurate velocity measurements is from 1 to 21 kHz. The visual detection threshold of the ABR was determined at selected frequencies between 2 and 32 kHz. The velocity results suggest a small but significant change in umbo velocity with age in both strains, between the youngest (1.5–3 months) and mid-aged (12–14 months) groups. There is also a clear difference in the umbo velocity in the youngest animals of the two strains, with the 129S6 having more sensitive middle-ear function than the CB. These results support the existence of a small age-related loss in middle-ear sensitivity in the mouse that was first described in the BALB/6J strain. The age-related changes in middle-ear function observed in both CB and 129S6 are much smaller than the age-related decreases in ABR. Our results also describe a statistically significant increase in the incidence of middle-ear pathology with age in the 129S6.     

Patterns of hearing loss and psychiatric morbidity in elderly patients attending a hearing clinic

This study examines the relationship between hearing loss and psychiatric diagnosis in a geriatric population attending a hearing clinic. Major depression was the most frequent psychiatric disorder and was diagnosed in 30% of subjects. A sensorineural type hearing loss was diagnosed in 85% of the depressed subjects. More hearing loss was seen in subjects with onset of depression after age 55 years, in comparison to geriatric patients with depression onset before age 55 years, subjects with other psychiatric disorders and subjects without a psychiatric diagnosis (p <0.001). The audiogram and speech audiometry suggest involvement of auditory nerve and central auditory pathways in late onset depression.     

Fibronectin-like immunoreactivity of the basilar membrane of young and aged rats

Dysfunction of cochlear mechanics has been hypothesized to be a source of age-related hearing loss and the basilar membrane mass and stiffness contribute to normal cochlear mechanics. Fibronectin, a large, extracellular matrix protein and a major component of the basilar membrane, may contribute to both the mass and stiffness of the membrane. Mesothelial cells underlying the basilar membrane may produce the fibronectin and also contribute to the mass of the membrane. Changes in either the fibronectin or the mesothelial cells might, therefore, have an effect on cochlear mechanics. In order to assess basilar membrane changes in aged animals, young adult (2–4 months) and aged (24–26 months) Sprague-Dawley rats were evaluated for the presence of fibronectin-like protein and mesothelial cells. The basilar membrane in the young animals had strong fibronectin-like immunoreactivity throughout its length. The old animals, on the other hand, showed normal fibronectin immunoreactivity in the basilar membrane of the basal turn, but little or no reactivity in the apical cochlear turn. The number of mesothelial cells was reduced throughout the length of the membrane in aged animals, with the greatest loss in the basal turn (60% fewer cells). These two degenerative changes, which appear to be independent of each other, may contribute to the observed threshold shifts in aged cochleas. © 1993 Wiley-Liss, Inc.