Duckert L G, Rubel E W
Department of Otolaryngology-Head and Neck Surgery, University of Washington, Seattle 98195.
Hear Res. 1990 Sep;48(1-2):161-82. doi: 10.1016/0378-5955(90)90206-5.
This experiment was designed to investigate cellular and subcellular maturational changes in regenerated immature sensory cells and support cells of the chick basilar papilla following gentamycin treatment. Scanning and transmission electron microscopy were used. The experimental animals received one subcutaneous injection of gentamycin sulfate daily (50 mg/kg) for five or 10 days. The animals receiving five days of injection were sacrificed the following day. The remaining animals were allowed to survive either seven or 28 days before sacrifice and preparation for electron microscopy. The initial lesion consisted of total degeneration of hair cells within 500 microns of the proximal tip providing the opportunity to study a 'pure' population of regenerating sensory cells. Sensory cell regeneration could be identified by one day after terminating gentamycin treatment. Early in development sensory cell precursors were morphologically very similar to supporting cells. A density gradient, based on cytoplasmic staining characteristics, was established which increased from cells displaying low density at the base of the supporting cell layer to high density cells at the luminal surface. These changes in density were equated to increase in number of and types of cytoplasmic organelles. In contrast to the empty appearing cytoplasm of the support cell, the cytoplasm of the hair cell precursor contained numerous mitochondria, clusters of ribosomes, and vesicles. As the cell approached the surface, mitochondria became more numerous as did smooth and coarse endoplasmic reticulum and Golgi apparatus. This gradient suggested that determination of the cellular phenotype occurred at the level of the basal membrane followed by migration to the surface, during which time differentiation was characterized by an increase in number and complexity of cellular organelles. Luminal surface modifications occurred as soon as the cell erupted. The development of stereocilia, rootlet, cuticular plate and cellular polarization followed the normal embryogenetic pattern. At 28 days, stereocilia organization was still incomplete as was the orientation of the bundle. To the extent that proper orientation of hair cells or bundles is necessary for normal transduction, mature function at 28 days would not be anticipated. Innervation of the presumptive hair cell precursors could be observed one day after treatment, early in the course of hair cell differentiation. Synaptogenesis followed the normal embryogenetic sequence; however, afferent and efferent nerve terminals remained immature appearing at 28 days. This observation may have physiological implications manifested by delay of hearing
本实验旨在研究庆大霉素处理后雏鸡基底乳头再生的未成熟感觉细胞和支持细胞的细胞及亚细胞成熟变化。使用了扫描电子显微镜和透射电子显微镜。实验动物每天皮下注射一次硫酸庆大霉素（50毫克/千克），持续5天或10天。接受5天注射的动物在第二天处死。其余动物在处死并准备进行电子显微镜检查前存活7天或28天。最初的损伤包括近端尖端500微米内毛细胞的完全退化，这为研究“纯”的再生感觉细胞群体提供了机会。在终止庆大霉素处理后1天即可识别感觉细胞再生。在发育早期，感觉细胞前体在形态上与支持细胞非常相似。基于细胞质染色特征建立了一个密度梯度，从支持细胞层底部显示低密度的细胞增加到腔表面的高密度细胞。这些密度变化等同于细胞质细胞器数量和类型的增加。与支持细胞看似空的细胞质相反，毛细胞前体的细胞质含有大量线粒体、核糖体簇和小泡。随着细胞接近表面，线粒体变得更多，光滑和粗糙的内质网以及高尔基体也是如此。这种梯度表明细胞表型的确定发生在基底膜水平，随后迁移到表面，在此期间分化的特征是细胞器数量和复杂性的增加。细胞一旦出现，腔表面就会发生修饰。静纤毛、小根、角质板和细胞极化的发育遵循正常的胚胎发生模式。在28天时，静纤毛的组织仍然不完整，束的方向也是如此。就毛细胞或束的正确方向对于正常转导是必要的程度而言，预计28天时不会有成熟功能。在处理后1天，即在毛细胞分化过程的早期，可以观察到假定的毛细胞前体的神经支配。突触发生遵循正常的胚胎发生序列；然而，传入和传出神经末梢在28天时仍显得不成熟。这一观察结果可能具有生理意义，表现为听力延迟
