BIOLOGICAL EFFECTS OF MAGNETIC FIELDS

我们发展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，该脉冲磁场可以由8字形线圈产生。使用这种方法，我们能够在3-5 mm的分辨率内刺激人类皮层。我们评估了dB/dt的时变磁场对人类受试者的神经兴奋和体感感觉的阈值，使用梯形脉冲磁场序列读出回波平面成像系统的梯度脉冲。感觉阈值为80-100 T/s。我们提出了一个模型的神经兴奋引起的磁感应涡流。该模型解释了我们在磁脑刺激中的观察，即刺激电流的最佳方向存在于大脑皮层的每个功能区中。我们研究了强磁场对 ...更多信息 场高达8 T的非洲爪蟾早期胚胎发育。从卵裂前期到神经胚期，胚胎暴露于高达8 T的磁场中。从受精卵未裂期到神经胚期，在8 T的磁场下培养20 h，未观察到明显的致畸作用。我们研究了抗磁流体在8 T静磁场中的性质，观察到高梯度磁场使水的表面向后推的现象。我们还观察到溶解氧浓度在磁体中心附近的明显重新分布，并观察到磁场影响气体流动模式的现象。一个被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碍了气体流动。磁幕具有影响生命系统呼吸过程的潜力，我们还研究了磁场对纤维蛋白溶解过程的可能影响。观察纤溶酶的溶出情况，评价纤溶活性。暴露于8 T磁场的FDP（纤维蛋白降解产物）的平均水平高于未暴露于磁场的FDP。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