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Mechanical analysis for the initial process of stimulus tarnsduction in insect mechano-sensory cell

昆虫机械感觉细胞刺激传导初始过程的力学分析

基本信息

批准号：
12440236
负责人：
SHIMOZAWA Tateo
金额：
$ 9.41万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

Mechanoreception is a fundamental element of animal-environment interaction and it is essential for the understanding of animal evolution. Mechanoreception has mainly been considered by a rather simple and macroscopic scheme of ionic channels deformed by membrane tension. Enormous high-sensitivities of mechanoreceptors have been reported in the eardrums of human and lacewing as 0.1 Angstrom i.e. one-tenth of a hydrogen atom diameter. It is obviously erroneous, however, to express the sensitivity of mechanical detector by displacement. Sensory cell is a measurement tool that converts external energy to informational entropy. The sensitivity must be discussed in terms of energy. All sensory cells receive a certain amount of energy, because any measurement without energy cost results in the thermodynamic inconsistency of Maxwell's demon. Energy threshold of the wind sensory cells in cricket is measured as very small values about 4×10^<-21> [Joule]. These mechanoreceptors would give rise a response shaken by Brownian motion of a single molecule.Pathway of conversion from mechanical energy to cellular response, particularly of its initial process is still beyond our comprehension. In order to reveal its cellular mechanisms, a direct measurement of membrane current in response to the extremely weak mechanical stimuli near Brownian motion is attempted.The receptor current was measured through a voltage clamp electrode, which also gives displacement to hair shaft. Shaft of a 1000 m long hair is clipped at 100 m to have electrical conduction through the hollow of hair shaft. Amount of energy estimated for the electrical current in response to 10-100 nm displacement at 100 m clipped shaft showed an energy amplification of about 10^6 times when compared to the mechanical energy given as the stimulus. The result suggests that the open-close of ionic channels is not a direct initial process of energy transduction in the mechanoreceptor cell.

机械感受是动物与环境相互作用的一个基本要素，对理解动物进化至关重要。机械接收主要是通过一个相当简单和宏观的方案来考虑离子通道在膜张力作用下的变形。据报道，在人类和草蛉的耳膜中，机械感受器的高度灵敏度高达0.1埃，即十分之一氢原子直径。然而，用位移来表示机械探测器的灵敏度显然是错误的。感觉细胞是一种将外部能量转化为信息熵的测量工具。灵敏度必须从能量的角度来讨论。所有的感觉细胞都接收一定量的能量，因为任何没有能量消耗的测量都会导致麦克斯韦妖的热力学不一致。蟋蟀风感觉细胞的能量阈值测量为非常小的值，约为4×10^<-21>[焦耳]。这些机械感受器会在单个分子的布朗运动下产生震动反应。机械能转化为细胞反应的途径，特别是其初始过程，我们仍然无法理解。为了揭示其细胞机制，尝试直接测量膜电流对布朗运动附近极弱机械刺激的响应。受体电流通过电压钳电极测量，这也给毛干位移。将一根1000米长的发轴剪在100米处，通过发轴的空心进行导电。与作为刺激的机械能相比，在100米夹夹轴上响应10-100纳米位移的电流能量估计值显示能量放大约10^6倍。结果表明，离子通道的开合不是机械受体细胞能量转导的直接初始过程。