O'Malley B W, Li D, Turner D S
Department of Otorhinolaryngology, Baylor College of Medicine, Houston, TX 77030, USA.
Hear Res. 1995 Aug;88(1-2):181-9. doi: 10.1016/0378-5955(95)00111-g.
The congenital hypothyroid (hyt/hyt) mouse has been described as having a homozygous recessive mutation of a single locus on chromosome 12 which results in significant endocrine hypofunction and retarded growth. Although a distinct correlation between inherited hypothyroidism and hearing loss in humans exists, there has been no previous evaluation of the auditory system in these mutant mice. We determined hearing thresholds by auditory-evoked brainstem response testing and noted a 40-45 dB elevation in the hyt/hyt mouse compared to littermate heterozygote (hyt/+) animals and normal progenitor controls BALB/cByJ (+/+). Conventional light microscopy was used to examine the general anatomy of the cochlea in these animals, and the surface structure of the organ of Corti was further evaluated with scanning electron microscopy. Heterozygote and normal control mice had no significant abnormalities of the cochlea, however the hyt/hyt mice displayed consistent morphologic abnormalities of the stereocilia on both inner and outer hair cell systems. The surrounding and supporting cells were identified in the cochleas of the hypothyroid mouse and control animals and showed no significant histologic abnormalities. The auditory, histologic, and ultrastructural characterization of this model provides a foundation for evaluating the effects of true inherited hypothyroidism on auditory pathway development.
先天性甲状腺功能减退（hyt/hyt）小鼠被描述为在12号染色体上有一个单基因座的纯合隐性突变，这导致显著的内分泌功能减退和生长迟缓。尽管人类遗传性甲状腺功能减退与听力损失之间存在明显的相关性，但此前尚未对这些突变小鼠的听觉系统进行评估。我们通过听觉脑干反应测试确定了听力阈值，发现与同窝杂合子（hyt/+）动物和正常亲代对照BALB/cByJ（+/+）相比，hyt/hyt小鼠的听力阈值升高了40 - 45分贝。我们使用传统光学显微镜检查了这些动物耳蜗的大体解剖结构，并用扫描电子显微镜进一步评估了柯蒂氏器的表面结构。杂合子和正常对照小鼠的耳蜗没有明显异常，然而hyt/hyt小鼠的内、外毛细胞系统的静纤毛均呈现出一致的形态学异常。在甲状腺功能减退小鼠和对照动物的耳蜗中识别出了周围细胞和支持细胞，它们没有明显的组织学异常。该模型的听觉、组织学和超微结构特征为评估真正的遗传性甲状腺功能减退对听觉通路发育的影响提供了基础。
