Biological Effects of Static Magnetic Fields

CONTENTS 8.1 Introduction ....................................................................................................................... 204 8.2 Mechanisms of Biological Effects of Static Magnetic Fields...................................... 204 8.3 Experimental Studies on Static Magnetic Field Effects .............................................. 207

8.3.1 In Vivo Studies....................................................................................................... 207 8.3.1.1 Animal Behavior: Recognition and Analgesia .................................. 207 8.3.1.2 Reproduction and Development ......................................................... 210 8.3.1.3 Circulatory System Effects ................................................................... 212 8.3.1.4 Neuroendocrine, Visual, and Neurophysiological Systems ........... 214 8.3.1.5 Magneto-Mechanical Systems.............................................................. 215 8.3.1.6 Musculoskeletal System........................................................................ 215

8.3.2 Tissue, Molecular, and Cellular Studies............................................................ 216 8.3.2.1 DNA and Chromatin............................................................................. 216 8.3.2.2 Cell Growth, Cell Proliferation, and Cell Cycle ............................... 216 8.3.2.3 Cell Membrane and Cell Metabolic Activity..................................... 220 8.3.2.4 Gene Expression and Signal Transduction........................................ 221 8.3.2.5 Genotoxicity ............................................................................................ 222 8.3.2.6 Cell-Free System, Free Radical, Enzyme Activity ............................ 223

8.4 Miscellaneous .................................................................................................................... 225 8.4.1 Biological Sensing and Magnetite ...................................................................... 225 8.4.2 Plant Growth, Response, and Magnetotropism............................................... 227 8.4.3 Magnetotaxis.......................................................................................................... 229 8.4.4 Others...................................................................................................................... 230

8.5 Medical Applications ....................................................................................................... 230 8.5.1 Biomagnetic Phenomena ..................................................................................... 230 8.5.2 Transcranial Magnetic Stimulation.................................................................... 232 8.5.3 Magnetoencephalography ................................................................................... 234 8.5.4 Magnetic Resonance Imaging ............................................................................. 235 8.5.5 Magnetic Orientation for Tissue Engineering.................................................. 238 8.5.6 Treatments of Pain, Cancer, and Other Diseases ............................................ 240

8.6 Conclusion ......................................................................................................................... 242 Acknowledgments ..................................................................................................................... 243 References ................................................................................................................................... 244

In ancient times, magnetism, especially permanent magnets, were a symbol of mystique because of the magnetic force that remains even after numerous attractions of iron. Although William Gilbert was called the pioneer of modern magnetics, he was surprised by the magnetism associated with living organisms. Magnetism, in contrast to transient static electricity, has beenused as anexplanation for various invisible effects and is expected to possess miraculous healing powers. Although people have been using magnetism for healing purposes without any scientific evidence, there have not been significant problems concerning the side effects ofmagnetism. As permanentmagnets have improved in quality and achieved higher magnetic strength, magnetism has become more commonly used in modernmedicine. For example,magnetism is commonlyused in the correction of dentures. In the society today there are many sources of electromagnetic fields. Humans are

exposed daily to man-made and naturally originated fields. During the past decade, questions about whether the exposure to electromagnetic fields may be linked to adverse health effects have been raised. Although the interaction of electromagnetic fields with biological systems has been investigated, there are no biophysical mechanisms that can explain many of the observed biological effects of low-level of magnetic fields. Proposed mechanisms include effects on currents, direct forces on biomagnetic materials, effects on free radicals, ion cyclotron resonance, charge transfer processes, stochastic resonance, etc. Recent developments in medical instrumentation such as magnetic resonance imaging

(MRI) and transcranial magnetic stimulation (TMS) have raised questions as to whether or not strong (in the tesla range) magnetic fields influence human health. Medical applications of weak (1-200mT) magnetic fields for the purpose of pain reduction and tissue healing have also been studied for many years. Therapeutic applications of permanent magnets and other magnetic devices have recently been expanded to various areas such as treatment of pain and diseases like rheumatoid arthritis and cancer. The objective of this chapter is to describe some of the more recent information on

biological effects and medical applications of static magnetic fields. This chapter consists of four sections. Each section has a comprehensive review of a recent topic of interest. A short summary of the mechanism of static magnetic field action on biological systems is described in the second section, which includes a brief review of well-known mechanisms that are discussed before mentioning the interactions of weak static magnetic fields with biological systems. The third section reviews and summarizes more recent in vivo and in vitro experimental results of the effects of static magnetic fields, including near-zero magnetic fields, geomagnetic fields, and MRI fields. The fourth section covers special topics including magnetic sensing, magnetite, and plant response to magnetic fields. In parallel with the comprehensive review of biological effects, the development andmedical application of the static magnetic field phenomena are introduced in the fifth section and reviewed with emphasis on the applications that are currently under investigation.