1994 Fiscal Year Final Research Report Summary
BIOLOGICAL EFFECTS OF MAGNETIC FIELDS
| Project/Area Number |
04452210
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
計測・制御工学
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| Research Institution | UNIVERSITY OF TOKYO (1994)
Kyushu University (1992-1993) |
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Principal Investigator |
UENO Shoogo UNIVERSITY OF TOKYO,FACULTY OF MEDICINE,PROFESSOR, 医学部(医), 教授 (00037988)
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| Co-Investigator(Kenkyū-buntansha) |
SHIOKAWA Koichiro UNIVERSITY OF TOKYO,FACULTY OF SCIENCE,PROFESSOR, 理学部, 教授 (20037295)
IWASAKA Masakazu UNIVERSITY OF TOKYO,FACULTY OF MEDICINE,RESEARCH ASSOCIATE, 医学部(医), 助手 (90243922)
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| Project Period (FY) |
1992 – 1994
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| Keywords | Biomagnetic effects / Magnetic stimulation / Embryonic development / Magnetic curtain / Parting of water / Dissolved oxygen / Fibrinolysis / Eight-figure-coil |
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| Research Abstract |
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
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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
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