INTRACELLULAR CALCIUM IN HAIR CELLS

我们的长期目标是了解细胞机制。 听觉毛细胞的转导和频率选择性。这项工作 将侧重于细胞内钙离子的作用，特别是那些与 来调节调节感受器的电共振机制 许多低等脊椎动物毛细胞的潜能。电气设备 共振源于电压依赖的钙电流和 钙激活的钾电流。然而，这种细胞机制 根据毛细胞的调谐特性决定毛细胞的调谐特性 基底膜上的位置尚不清楚。这些实验将会 观察海龟和短吻鳄单个毛细胞的属性 应用膜片钳记录和成像来自钙离子的信号的耳蜗 敏感染料。这一时期的具体目标是：(1)绘制 耳蜗毛细胞中的离子电流，测试细胞是否调谐 更高的频率有更多的电压依赖性钙离子通道和更快的 激活K+通道；(2)表征单个细胞的大小和动力学 膜片上的K+通道及其受因素调控的研究 如体内钙离子和蛋白质磷酸化；(3)利用钙离子敏感 染料，用于测量细胞内钙的代谢，其休眠状态 浓缩及其进入和挤出机制。休息的时候 浓度随毛细胞的调谐频率而变化？(4)通过 控制其细胞内浓度，以检测钙的 参与机械-电转导通道的适应 以及它与发束主动运动的联系；机械方面的差异 属性将在高短毛细胞之间寻找 短吻鳄耳蜗虫。所有这样的实验都将涉及测量 通过用弹性纤维取代发束来改变发束的力学 已知的合规性。 来自这些研究的信息可能会导致对机制的深入了解 控制膜通道的表达和定位，可能 在疾病中成为故障的目标。它还可能揭示出一种严格的 对细胞内钙离子水平的需求以进行通道调节和 毛细胞的功能。细胞内钙离子的调节机制 可能是所有毛细胞共有的，包括哺乳动物的毛细胞。 耳蜗，它们可能是发生不可逆转损伤的部位 在听觉过度刺激或氨基糖苷类药物中毒期间 抗生素。

The long-term objectives are to understand the cellular mechanisms of transduction and frequency selectivity in auditory hair cells. The work will focus on the roles of intracellular Ca2+, especially those pertinent to regulation of the electrical resonance mechanism that tunes the receptor potentials of hair cells in many lower vertebrates. The electrical resonance stems from the interplay of a voltage-dependent Ca2+ current and a Ca2+-activated K+ current. However, the cellular mechanism which dictates a hair cell's tuning characteristics according to the cell's location on the basilar membrane is not known. The experiments will examine the attributes of single hair cells of the turtle's and alligator's cochleas employing patch-clamp recording and imaging of signals from Ca2+- sensitive dyes. The specific aims during this period are: (1) to map the ionic currents in hair cells along the cochlea, testing whether cells tuned to higher frequencies have more voltage-dependent Ca2+ channels and faster activating K+ channels; (2) to characterize the size and kinetics of single K+ channels in membrane patches and explore their modulation by factors such as internal Ca2+ and protein phosphorylation; (3) using Ca2+-sensitive dyes, to measure the metabolism of intracellular Ca2+, its resting concentration and its entry and extrusion mechanisms. Does the resting concentration vary with the frequency of tuning of the hair cell? (4) by manipulating its intracellular concentration, to examine calcium's involvement in adaptation of the mechano-electrical transduction channels and its link to active motion of the hair bundle; differences in mechanical properties will be sought between tall and short hair cells of the alligator's cochlea. All such experiments will involve measuring the mechanics of the hair bundles by displacing them with a flexible fibre of known compliance. Information from these studies may lead to insights into the mechanisms controlling the expression and localization of membrane channels which may be a target for malfunction in disease. It may also reveal a stringent demand on the intracellular Ca2+ level for channel regulation and functioning of the hair cells. The mechanisms mediated by internal Ca2+ are probably common to all hair cells, including those in the mammalian cochlea, and they may be the sites at which irreversible damage occurs during acoustic over-stimulation or poisoning with aminoglycoside antibiotics.