Effects of Acoustic Trauma on Age-Related Hearing Loss

描述（由申请人提供）： 听力损失是一种常见的后果， 70%的美国老年人报告有一定程度的听力或平衡 disorder.许多因素导致这种与年龄相关的听力损失，包括 暴露于环境噪声、某些疾病、药物引起的耳毒性， 以及特定基因的遗传。人类和动物表现出很大的差异 在他们对噪音引起的听力损失的易感性，这表明， 另外的遗传或环境因素可能有助于这种退化性 过程此应用程序中的实验旨在研究如何 使用鸟类模型，噪声暴露导致与年龄相关的听力损失。 商业化饲养的用于肉类生产的肉鸡显示出显著的 从30周龄开始的进行性年龄相关性耳蜗变性， 在66周大时造成严重的耳蜗损伤。蛋鸡，饲养 商业上用于产蛋，在这些同时显示很少或没有耳蜗损伤， 年龄这两种鸟都生活在嘈杂的环境中，这表明肉鸡 鸟类更容易受到噪音引起的听力损失的影响。的 在肉鸡中观察到的耳蜗退化甚至更引人注目，因为所有 鸟类具有再生新的耳蜗感觉细胞（毛发）的不寻常的能力 耳蜗损伤后。我们将研究的相对贡献 噪音和遗传学对这种年龄相关的耳蜗退化的影响， 都在嘈杂和安静的环境中繁殖。在特定年龄，我们将测量 畸变产物耳声发射检测耳蜗毛细胞 功能，我们将使用扫描电子显微镜来评估耳蜗毛 细胞解剖学通过对各组之间的这些指标进行定量比较，我们将 评估噪音暴露和遗传对年龄的相对贡献- 听力损失相关在第二组实验中，我们将暴露 鸟对很大的噪音很敏感。使用相同的解剖学和生理学 我们将确定耳蜗的完整性、年龄和品种如何影响 耳蜗对短期噪声暴露的反应。除了这些措施外， 外周听觉功能，我们将检查两个解剖指数的 听觉中枢神经系统，以确定如何年龄相关的耳蜗 退化和噪音影响大脑功能。

DESCRIPTION (provided by applicant): Hearing loss is a common consequence of aging, with 70% of older Americans reporting some degree of hearing or balance disorder. Many factors contribute to this age-related hearing loss, including exposure to environmental noise, certain diseases, drug-induced ototoxicity, as well as inheritance of specific genes. Humans and animals show a wide variation in their susceptibility to noise-induced hearing loss, suggesting that additional genetic or environmental factors may contribute to this degenerative process. The experiments in this application are designed to investigate how noise exposure contributes to age-related hearing loss using an avian model. Broiler birds raised commercially for meat production show a substantial progressive age-related cochlear degeneration beginning at 30 weeks of age and producing severe cochlear damage by 66 weeks of age. Egg layer birds, raised commercially for egg production, show little or no cochlear damage at these same ages. Both breeds of birds live in a noisy environment, suggesting that broiler birds are substantially more susceptible to noise-induced hearing loss. The cochlear degeneration seen in broiler birds is even more striking because all birds have the unusual ability to regenerate new cochlear sensory cells (hair cells) following cochlear damage. We will examine the relative contributions of noise and genetics to this age-related cochlear degeneration by raising birds of both breeds in noisy and quiet environments. At specific ages we will measure distortion product otoacoustic emissions (DPOAEs) to test cochlear hair cell function, and we will use scanning electron microscopy to evaluate cochlear hair cell anatomy. By comparing these measures quantitatively between groups we will evaluate the relative contributions of noise exposure and genetics to age- related hearing loss. In a second set of experiments, we will expose groups of birds acutely to very loud noise. Using the same anatomical and physiological measures we will determine how cochlear integrity, age, and breed affect the cochlear response to short-term noise exposure. In addition to these measures of peripheral auditory function, we will examine two anatomical indices of the auditory central nervous system to determine how age-related cochlear degeneration and noise affect brain function.