Biological Effects of Electric and Magnetic Fields (eBook)

Beneficial and Harmful Effects

Sinerik Ayrapetyan, David O. Carpenter (Herausgeber)

eBook Download: PDF | EPUB

2012 | 1. Auflage
357 Seiten
Elsevier Science (Verlag)
978-0-08-088688-6 (ISBN)

Infos

Recent concerns over the possible hazards of electrical and magnetic fields in the home and workplace are comprehensively addressed within this book. The chapters contain detailed research on the biological effects of electric and magnetic fields, and evidence for and against any interaction of electromagnetic fields (EMFs) and the biological systems. - The relative risk of exposure to EMFs - Putative behavioral and neural effects of EMFs - EMF effects on cells

Inhalt

Front Cover 1
Biological Effects of Electric and Magnetic Fields: Beneficial and Harmful Effects 4
Copyright Page 5
Table of Contents 6
Preface 24
Part I: CLINICAL APPLICATIONS AND THERAPEUTIC EFFECTS 26
Chapter 1. Effect of Electrical Fields on Neuronal Growth and Regeneration 28
I. Introduction 28
II. Neuroregenerative Effects of -Electrical Fields 29
III. Caveats and a Need for Skepticism 30
IV. Theoretical Mechanisms of Weak dc Electrical Field or Current Effects on Neurons 32
References 33
Chapter 2. Therapeutic Uses of Electric and Magnetic Fields in Orthopedics 38
I. Introduction 38
II. Surgical Perceptions 42
III. Physical Perceptions 44
IV. Clinical Considerations 49
V. Musculoskeletal Conditions Amenable to PEMF Treatment 53
VI. Educational Problems Limiting Clinical Use of PEMFs 64
VII. Summary 68
References 69
Chapter 3. Magnetic Source Imaging 74
I. Introduction 74
II. Instrumentation 77
III. Electromagnetic Concepts in MSI 83
IV. Forward Problem 85
V. Inverse Problem 88
VI. Event-Related Magnetic Fields 93
VII. Conclusions 99
References 100
Part II: CELL AND MOLECULAR BIOLOGY AND ELECTRIC AND MAGNETIC FIELDS 106
Chapter 4. Electric Field-Induced Calcium Flux and Changes in Cell Shape, Motility, and Cytoskeleton 108
I. Introduction 108
II. Galvanotaxis, Galvanotropism, and Their Biological Significance 109
III. The Mechanism of Galvanotaxis of Fibroblasts: An Example 111
IV. Implications 121
References 124
5. In Vitro Systems for the Study of Electromagnetic Effects on Bone and Connective Tissue 128
I. Introduction 128
II. Bone Cell Biology 129
III. In Vitro Systems for Study of Bone and Cartilage Metabolism 131
IV. Potential Mechanisms of ELF Effects 132
V. Recent Findings Using in Vitro Techniques 133
VI. Possible Mechanisms for EMF Effects on Bone Signal Transduction 138
References 141
Chapter 6. Electric and Magnetic Field Effects on the Immune System 146
I. Introduction 146
II. Experimental Results 151
III. Quantum Modeling 160
References 164
Chapter 7. Autoimmune Reactions as a Possible Component of StressInduced by Electromagnetic Fields 172
I. Introduction 172
II. Materials and Methods 173
III. Results 174
IV. Discussion 176
References 10
Chapter 8. Effects of Electric and Magnetic Fields on Transcription 180
I. Introduction 180
II. Experimental Approaches 182
III. Proposed Mechanisms 192
IV. Prospectives 197
References 198
Chapter 9. Electric and Magnetic Fields and Carcinogenesis 202
I. Introduction 202
II. Cell Proliferation 206
III. Cell Membranes and ELF Carcinogenesis 212
References 217
III CANCER AND OTHER HUMAN HEALTH EFFECTS 224
Chapter 10. Electric and Magnetic Fields and Cancer: The Use of Field Exposure Measurements in Epidemiological Studies 226
I. Introduction 226
II. Electric and Magnetic Field Exposure Meters 228
III. Electric and Magnetic Field Measurements in Occupational Studies 230
IV. Electric and Magnetic Field Measurements in Residential Environment 240
V. Electric and Magnetic Field Measurements in the General Environment 247
VI. Discussion 250
VII. Conclusions 252
References 253
Chapter 11. Epidemiologic Evidence on Cancer in Relation to Residential and Occupational Exposures 258
I. Introduction 258
II. Cancer in Relation to Residential Exposure to Electric and Magnetic Fields' 259
III. Cancer in Relation to Occupational Exposure to Electric and Magnetic Fields 271
IV. Conclusions 282
References 283
Chapter 12. Electric Power and Risk of Hormone-Related Cancers 288
I. Introduction 288
II. Light and Pineal Function 290
III. Summary of Light – Pineal Results 291
IV. EMF and Pineal Function 291
V. Summary of EMF – Pineal Results 294
VI. Melatonin and Cancer 295
VII. Diet, Melatonin, and Cancer 298
VIII. Epidemiological Evidence 298
IX. Direct Evidence: EMF–Mammary Cancer Experiment 299
X. Conclusion 300
References 300
Chapter 13. Thermal, Cumulative, and Life Span Effects and Cancer in Mammals Exposed to Radiofrequency Radiation 304
I. Introduction 304
II. Thermal Effects 305
III. Cumulative Effects 311
IV. Cancer and Life Span 312
V. Conclusions 316
References 317
Chapter 14. Power-Frequency Electric and Magnetic Fields: Issues of Risk Management and Risk Communication 322
I. Managing Possible Health Risks in the Face of Continuing Uncertainty 322
II. Communicating with Laypeople about Power-Frequency Fields 337
References 343
Chapter 15. The Public Health Implications of Magnetic Field Effects on Biological Systems 346
References 353
Index 356

Textauszug

1

Effect of Electrical Fields on Neuronal Growth and Regeneration

Wise Young

I INTRODUCTION

Cells utilize electrical signals to communicate with each other. Neurons, in particular, not only respond to electrical fields but also generate electrical fields. These characteristics of neurons have naturally led many scientists to believe that exogenously imposed electrical fields influence neuronal activity, growth, and function. Since central neurons do not regenerate effectively, the possibility of applying electrical fields to stimulate and maintain neuronal regeneration has long been an area of intense speculation and exploration. Despite many years of concerted research, the subject has remained controversial. I review below some of the data that support electrical field effects on neuronal growth and regeneration, discuss why such bioelectrical manipulation of regeneration has not achieved widespread acceptance, and briefly discuss ionic mechanisms that may underlie observed effects of weak electromagnetic fields on neuronal growth and regeneration.

II NEUROREGENERATIVE EFFECTS OF ELECTRICAL FIELDS

Some evidence indicates that electromagnetic fields, particularly those arising from dc electrical currents, influence neuronal growth. The evidence falls into several categories. First, explanted dorsal root sensory ganglia have shown remarkable tendencies to migrate toward anodal poles of applied dc fields. Second, neuroblasts and other cultured cells also grow toward the negative (anodic) pole of applied dc electrical fields. Third, dc electrical currents and pulsed radiofrequency electromagnetic fields have been reported to increase the rate and extent of peripheral nerve regeneration. Finally, dc electrical currents were observed to reduce axonal dieback and facilitate axonal regrowth after transection of the spinal cords. These are described in sequence below.

A Chick Dorsal Root Sensory Ganglion Explants

Early studies (D. Ingvar, 1947; S. Ingvar, 1920) of electrical field effects on explanted sensory ganglia were flawed by inattention to the direction and intensity of currents delivered. In 1946, Marsh and Beam provided one of the first convincing reports that 100 mV/mm fields suppressed chick neurite growth at the anode (negative) but accelerated and deflected neurite outgrowth at the cathode (positive) side of the explant. Other workers have claimed positive effects (Sisken and Smith, 1975) but did not rule out the possibility of electrode products contaminating the cultures. Using wick electrodes, Jaffe and Poo (1979) showed that dorsal root ganglion explants were exquisitely responsive to 30–100 mV/mm fields. The ganglionic neurons migrated toward the anode, exhibiting a well-known tendency of cells called galvanotaxis (Ambrose, 1965; Erickson and Nucitelli, 1984). Higher fields of 70 mV/mm enhanced neurite outgrowth in the direction of the cathode. Reversal of the field inhibited growth but did not deflect neurite growth toward the cathode.

B Cultured Neuroblasts

Hinkle et al. (1981) studied the effects of imposed electrical fields on neurite outgrowth of neuroblasts from frog (Xenopus) eggs. They found that electrical fields markedly enhanced neurite outgrowth and direction of growth toward the cathode, while neurites on the anodal side showed retarded growth. Patel and Poo (1982, 1984) found that neurites would change directions of growth toward the cathode. McCaig (1986a,b) observed two- to threefold increases in neurite growth toward the cathode and decreased growth rate and neurite absorption on the anodal side (McCaig, 1987). Other investigators (DeBoni and Anderchek, 1986), however, did not find these results under similar experimental conditions.

C Peripheral Nerves

Weak dc currents (100–200 nA) have been reported to enhance peripheral nerve regeneration in frogs (Borgens et al., 1977, 1979). Axon sprouting increased in mammalian nerves exposed to such currents (Pomeranz et al., 1984; Pomeranz, 1986). Similarly weak currents (10 μA/cm2 at 100 mV/cm) increased reinnervation of hindpaw muscles after cut and suture did not crush lesions of the sciatic nerve (McDevitt et al., 1987). Other investigators have reported positive results (Politis et al., 1988; Zanakis, 1988). Raji (1984; Raji and Bowden, 1983) reported that pulsed radiofrequency electromagnetic fields increased the rate of peripheral nerve regeneration but did not rule out the possibility that these fields heated the nerves. More recently, McGinnis and Murphy (1992) were unable to show a quantitative increase in the number or rate of regenerating axons in mammalian sciatic nerves subjected to crush injury.

D Spinal Cord

Stronger dc currents (7–10 μA) increased both the rate and extent of giant axon regeneration in lamprey (Borgens, 1982; Borgens et al., 1981) and inhibited dieback of these axons (Roederer et al., 1983). These observations were extended to guinea pigs after dorsal hemisections (Borgens et al., 1986a) in studies showing that dorsal column axons not only grow back to the lesion site but course around the lesion in remarkable hairpin turns (Borgens et al., 1986b). The regeneration was associated with significant neurophysiological and behavioral evidence of recovered function (Borgens et al., 1987, 1990). Other investigators have reported similar cathode-oriented dorsal column axonal regeneration in contused rat spinal cord (Politis and Zanakis, 1988) and that dc currents (Wallace et al., 1987b) but not ac currents (Wallace et al., 1987a) enhanced behavioral recovery in rats after clip compression injuries of the spinal cord.

III CAVEATS AND A NEED FOR SKEPTICISM

Despite the numerous reports of electrically enhanced regeneration, many scientists have remained skeptical of electromagnetic effects on neuronal systems for one principle reason. The mechanisms of weak electromagnetic bioelectric effects are poorly understood. In contrast, the effects of strong electromagnetic fields on nervous tissues are well known and accepted. For example, electrical stimulation forms the basis of much of neurophysiology. Electrical stimulation of neurons requires currents or fields on the order of 1–10 mA/cm2 or 1–10 V/mm (Chan et al., 1988). Very intense magnetic fields are required to activate neurons (Cohen et al., 1991). Sensory detection of high-frequency electromagnetic fields usually occurs only when fields heat the tissue (Schwan, 1957). The electrical currents and fields reported to have biological effects are several orders of magnitude smaller, in the range of microamperes per square centimeter and millivolts per milliliter or smaller.

Exogenously applied currents and fields claimed to have bioelectric effects are in fact frequently smaller than endogenous currents and fields generated by the cells. While some investigators (Borgens and McCaig, 1989) have regarded this as an argument in favor of “natural” electrical currents being a cause of growth and healing, it is nevertheless difficult to attribute cause to fields that are “vanishingly small in comparison with potentials needed to yield significant membrane responses” (Schwan, 1982). For instance, most living cells normally have a transmembrane dc potential of about − 60 mV. An imposed electrical field of 100 mV/mm will induce less than 0.1 mV shifts of membrane potentials in intact cells, at the level of noise fluctuations. Likewise, exogenously applied dc electrical currents of 1–100 μA tend to pass around cells in the extracellular space and minimally penetrate cells (Schwan, 1984). Bioelectric effects from weak electromagnetic fields cannot be attributed to classical membrane ionic channels, transport, and receptor mechanisms.

Unfortunately, difficult-to-test hypotheses (e.g., Jacobson, 1991) and expansive claims have long demonated bioelectromagnetic studies. For centuries, many physicians and charlatans have attributed miraculous health effects to electrotherapy. Even well-established and institutionally approved medical applications of electrical stimulation, such as healing of nonunion bony fractures (Brighton, 1981), have seldom been put to rigorous clinical testing. In fact, the only double-blind randomized trial of pulsed electromagnetic field effects for bone healing was negative (Barker et al., 1984). Failures to replicate experimental findings, even in well-controlled in vitro situations, are common. The application of even dc electrical currents is fraught with pitfalls (Robinson, 1989), and the problems attending high-frequency electromagnetic field application are legend. Finally, regeneration is a difficult phenomenon to demonstrate and quantify. Combined, these problems have led to continued skepticism and a failure of bioelectromagnetic field studies to join mainstream neurobiology.

The ability of electromagnetic fields to promote neuronal regeneration nevertheless deserves careful and critical consideration for several reasons. First, the phenomenon of...

Produkt-Details

• Erscheint lt. Verlag: 2.12.2012
• Sprache: englisch
• Themenwelt: Sachbuch/Ratgeber ► Natur / Technik ► Natur / Ökologie
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► Arbeits- / Sozial- / Umweltmedizin
• Themenwelt: Studium ► 2. Studienabschnitt (Klinik) ► Pharmakologie / Toxikologie
• Themenwelt: Naturwissenschaften ► Biologie ► Biochemie
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Angewandte Physik
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Elektrodynamik
• Themenwelt: Technik
• ISBN-10: 0-08-088688-4 / 0080886884
• ISBN-13: 978-0-08-088688-6 / 9780080886886