ABSTRACT
CONTENTS 9.1 Introduction ....................................................................................................................... 261
9.1.1 General Remarks................................................................................................... 261 9.1.2 Background History ............................................................................................. 264
9.2 Experimental Evidence .................................................................................................... 266 9.2.1 Rat Behavior .......................................................................................................... 269 9.2.2 Plants....................................................................................................................... 270 9.2.3 Bone......................................................................................................................... 274 9.2.4 Harmonics .............................................................................................................. 276 9.2.5 Physiological Reversals........................................................................................ 278 9.2.6 Water....................................................................................................................... 278
9.3 Theoretical Approaches ................................................................................................... 280 9.3.1 Physical Constraints ............................................................................................. 280 9.3.2 Ion Channels.......................................................................................................... 281 9.3.3 Dependence on AC Magnetic Field................................................................... 283 9.3.4 Precessional Effects............................................................................................... 285 9.3.5 Coherence Domains.............................................................................................. 285
9.4 Discussion .......................................................................................................................... 286 References ................................................................................................................................... 287
9.1.1 General Remarks
Ion cyclotron resonance (ICR) is one among a number of possible mechanisms that have been advanced to explain observed interactions between weak low-frequency electromagnetic fields and biological systems. Despite the failure to find a reasonable physical explanation, there remains an impressive body of experimental evidence that can be taken as an empirical basis for this hypothesis. The ICR suggestion has proven fruitful in framing both experimental and theoretical work, despite the biophysical situation being far from the literal cyclotron resonance model of an isolated classical charged particle moving in a vacuum under the influence of a magnetic field. The properties of the applied fields that are used in ICR experiments include linear or
circular polarization, the presence of a finite magnetostatic field, frequencies ranging from a few to several hundred hertz, magnetic intensities ranging from about 1mT to 1mT, and,
the orientation of the time-varying electromagnetic field to the magnetostatic (DC) field. This orientation requires that timevarying magnetic fields be parallel to the DC field or, equivalently, that time-varying electric fields are perpendicular to the DC field. The ICR hypothesis holds that the physiological activity of those ions implicated in cell
signaling processes, including, among others, Ca2þ, Mg2þ, and Kþ, can be altered when the ratio of applied signal frequency to the static magnetic field is equal to the ionic charge-to-mass ratio. This is expressed as
v=B ¼ q=m (9:1)
where the radial frequency v ¼ 2pf, as measured in radians per second, is used instead of f, the frequency measured in hertz. In SI units, B is the DC field intensity measured in tesla, and q/m is the ratio of the ionic charge to mass, in coulombs per kilogram. For any given ionic species, the specific frequency that equals the product of B and q/m is called the cyclotronic frequency, vc. The resonance concept is attractive for a number of reasons. There is a potential
connection to interactions involving the Earth’s magnetic field (geomagnetic field [GMF]). Further, the ICR mechanism may help provide the basis for at least some of the reports of low-frequency electromagnetic interactions that otherwise lack explanation. Finally, given the wide variety of biological systems in which ICR effects are observed, it is reasonable to ask if there are fundamental scientific questions connected to this phenomenon. The ICR hypothesis has especial significance attached to magnetostatic fields whose
intensity is of the order of the GMF (20-60mT). This becomes apparent when the chargeto-mass ratios of key biological ions are substituted into Equation 9.1. These ratios range from about 2 to 8 106C/kg, implying that a static magnetic field of 50mT corresponds to resonance frequencies of the order of 10-100Hz (Figure 9.1). Such frequencies could
conceivably have physiological significance since they correspond approximately to the frequency range generated in the central nervous system [1]. This, coupled to the focus on the potential hazards attached to 50/60-Hz electromagnetic power delivery sources [2], has sparked study of the ICR hypothesis, in terms of both experiments specifically designed to test this hypothesis as well as theoretical models seeking an explanatory basis at the molecular level. Some specific ions that have been implicated are listed in Table 9.1. Note that four polar
amino acids and the hydronium ion are included. The ratios of frequency to DC magnetic field, as calculated from Equation 9.1, are shown in the right-hand column. This ratio can be regarded as an invariant characteristic for any given ion. Although experimental evidence provides support for the ICR hypothesis [3], there is
no widely accepted theoretical explanation. Indeed, because of constraints mainly arising from unfavorable damping conditions, there are strong arguments [4] against the occurrence in living tissue of any classical ICR mechanism [5], as occurs, say, for energetic charged particles moving in a vacuum under the influence of parallel static and AC magnetic fields. The circular and helical paths associated with such undamped motion are invariably the result of the Lorentz force, which imparts an acceleration a to a charged particle of mass m moving at velocity v in a magnetic field B:
a ¼ (q=m)(v B) (9:2)
Nevertheless, arguments have been raised [6-11] that although the biological response may not correspond to the effects resulting from ICR-specific helical pathways of charged particles [4], the coupling is nevertheless a function of the ICR frequency as predicted by Equation 9.1. Although there has been no consistent experimental verification for any of these models, there is little question concerning the observed dependence on the cyclotron resonance frequency. Because the cyclotronic frequency is the common denominator in all these models, it is preferable to subsume all of them under the umbrella term ICR hypothesis. The great variety of biosystems in which ICR effects have been observed implies a
ubiquitous response that may have fundamental physiological significance. One can generalize this response R in terms of its functional dependence. From Equation 9.1, we can write
R ¼ R(v, B, q=m) (9:3)
the of the AC magnetic field, BAC. Thus, the expanded expression for the response R ¼ R(v, B, BAC, q/m), or, in terms of the two key variables,
R ¼ R(vc, BAC) (9:4)
There is no question as to the relevance of BAC in studying the interactions between ICR field combinations and biological systems. However, it is not clear if the experimentally observed dependences on BAC are a direct result of the underlying resonance mechanism, as has been suggested [7,9], or if there are other separate physiological factors that limit the levels of the AC field under which an ICR mechanism may be operative.
