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BIOLOGICAL EFFECTS OF MAGNETIC FIELDS

磁场的生物效应

基本信息

批准号：
04452210
负责人：
UENO Shoogo
金额：
$ 4.29万
依托单位：
UNIVERSITY OF TOKYO (1994)Kyushu University (1992-1993)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1994
项目状态：
已结题

项目摘要

We have developed a method of localized magnetic stimulation of brain. The basic idea is to concentrate induced eddy currents on a target by a pair of opposing pulsed magnetic fields, which can be produced by a figure-of-eight coil. Using this method, we were able to stimulate the human cortex within a 3-5 mm resolution. We evaluated the threshold of time-changing magnetic fields of dB/dt for nerve excitation and somatosensory sensation of human subjects, using a train of trapezoidal pulsed magnetic fields for read-out gradient pulses of echo-planar imaging systems. The threshold for the sensation was 80-100 T/s. We have proposed a model of nerve excitation elicited by magnetically induced eddy currents. The model explains our observation in magnetic brain stimulation that an optimal direction of stimulating currents exists in each functional area in the cortex.Biological effects of static magnetic fields have been poorly understood. We studied a possible influence of intense magnetic … More fields up to 8T on the early embryonic development of Xenopus laevis. Embryos were exposed to magnetic fields up to 8T for the period from the pre-cleavage stage to neurula stage. No apparent teratogenic effects were observed when embryos were cultured under magnetic fields up to 8 T for 20 h from the stage of uncleaved fertilized egg to the neurula stage.We studied the properties of diamagnetic fluid in static magnetic fields up to 8 T.We observed the phenomenon that the surface of the water was pushed back by magnetic fields of higher gradients. We also observed a clear redistribution of dissolved oxygen concentration around the center of the magnet.We have observed the phenomenon that flow patterns of gases are influenced by magnetic fields. A model called a magnetic curtain has been introduced to explain these phenomena. The computer simulation shows magnetic fields blocking gas flow. The magnetic curtain has the potential to influence respiratory processes in living systems.We also studied the possible effects of magnetic fields on the fibrinolytic process. Fibrin dissolution was observed and the fibrinolytic activities were evaluated. Mean levels of FDPs(fibrin degradation products)exposed to 8 T magnetic fields were higher than those not exposed to fields. Less

我们开发了一种局部磁刺激大脑的方法。基本思想是通过一对相反的脉冲磁场将感应涡流集中在目标上，这可以由8字线圈产生。使用这种方法，我们能够在3-5毫米的分辨率内刺激人类皮层。我们利用一列梯形脉冲磁场作为回波平面成像系统读出梯度脉冲，评估了人体神经兴奋和体感感觉的dB/dt随时间变化的磁场阈值。这种感觉的阈值为80-100 T/s。我们提出了一个由磁致涡流引起的神经兴奋模型。这个模型解释了我们在脑磁刺激中观察到的，在皮层的每个功能区都存在一个最佳的刺激电流方向。人们对静磁场的生物效应了解甚少。研究了高达8T的强磁场对非洲爪蟾早期胚胎发育的可能影响。胚胎从前卵裂期到神经节期暴露在高达8T的磁场中。从未裂受精卵期到神经胚期，在8 T以上磁场下培养20 h，未见明显的致畸作用。我们研究了抗磁性流体在高达8 t的静磁场中的性质。我们观察到水的表面被更高梯度的磁场向后推的现象。我们还观察到磁体中心周围溶解氧浓度的明显重新分布。我们已经观察到气体的流动形态受磁场影响的现象。一种叫做磁幕的模型被引入来解释这些现象。计算机模拟显示磁场阻碍气体流动。磁幕有可能影响生命系统的呼吸过程。我们还研究了磁场对纤溶过程的可能影响。观察纤维蛋白溶出度，评价纤维蛋白溶解活性。暴露于8 T磁场下的fdp（纤维蛋白降解产物）的平均水平高于未暴露于磁场的人。少