BIOLOGICAL EFFECTS OF MAGNETIC FIELDS

我们开发了一种脑局部磁刺激的方法。其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，脉冲磁场可以由一个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的大脑皮层。我们使用一系列梯形脉冲磁场序列作为回波平面成像系统的读出梯度脉冲，评估了人体神经兴奋和体感时变磁场的分贝/dt阈值。感觉阈值为80-100T/S。我们提出了磁感应涡流诱发的神经兴奋模型。该模型解释了我们在大脑磁刺激中观察到的最优刺激电流方向存在于大脑皮层的每个功能区。对静态磁场的生物效应了解甚少。我们研究了强磁…的可能影响更多的领域高达8T的非洲爪哇早期胚胎发育。将胚胎暴露在8T的磁场中，从卵裂前期到神经胚期。从受精卵未卵裂期到神经胚期，在高达8T的磁场下培养20h，未观察到明显的致畸作用。我们研究了抗磁流体在高达8T的静磁场中的性质，观察到高梯度磁场将水面向后推的现象。我们还观察到了磁场中心附近溶解氧浓度的明显重新分布。我们观察到了气体流型受磁场影响的现象。一种称为磁幕的模型被引入来解释这些现象。计算机模拟显示，磁场阻止了气体流动。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。观察纤维蛋白溶解情况，并评价其纤溶活性。暴露在8T磁场中的FDP(纤维蛋白降解产物)的平均水平高于未暴露在磁场中的那些人。较少

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