Biological Effects of Weak Extremely Low Frequency Magnetic Fields

在我们积累极低频磁场（ELFMF）对蜗牛、老鼠和人类伤害感受影响的数据的同时，大量关于许多不同物种（昆虫、啮齿动物、爬行动物、鸟类、牛和鹿）磁感受的工作已经发表，测量的终点是地磁场的方向。在这项工作中，初始转导机制的候选对象是a)大小合适的氧化铁颗粒阵列上的扭矩，以维持单个磁场域；b)自由基对机制（RPM），其中地磁场影响自由基对中的单线态到三重态的转变。在过去的十年中，我们已经建立了对阿片类药物相关行为（我们的工作）和动物取向影响的初始生物物理检测机制的特征的相似性。两者都需要同时暴露在支持RPM的大约相同强度的短波可见光下。然而，最近我们已经表明，弱极低频磁场（wELFMF）在30 Hz下的影响阈值等于或低于33 nT。此外，最近的动物定向工作显示，灵敏度远低于最初报道，在极低频下，10 nT至4µT之间的显著结果。这些低频率的低强度与单畴磁铁矿颗粒或RPM不一致。

While we were accumulating data on the effects of extremely low frequency magnetic fields (ELFMF) on nociception in snails, mice and humans, a considerable amount of work has been published on magnetoreception in many different species (insects, rodents, reptiles, birds, cattle and deer) with the measured end point being orientation to the geomagnetic field. Candidates for the initial transduction mechanism in this work have been a) torque on an array of iron oxide particles which are of the correct size to maintain a single magnetic field domain and b) a radical pair mechanism (RPM) where the geomagnetic field affects singlet to triplet transitions in free radical pairs. Over the last ten years we have established a similarity in the characteristics of the initial biophysical detection mechanism for effect on opioid related behaviours (our work) and animal orientation. Both require simultaneous exposure to short wave length visible light of approximately the same intensity which supports the RPM. However very recently we have shown that the threshold for effects of a weak Extremely Low Frequency Magnetic Field (wELFMF) at 30 Hz is at or below 33 nT. Also recent animal orientation work shows sensitivities much lower than initially reported with significant results between 10 nT and 4µT also at extremely low frequencies. These low intensities at these low frequencies are inconsistent with either a single domain magnetite particle or the RPM. Here we propose, to test in experiments in mice and cells, that the initial transduction is an array of Super Paramagnetic Iron Oxide (SPIO) particles. Unlike single domain particles the smaller SPIO particles have their magnetic moments unbound by their geometry. Hence, under thermal perturbations, their magnetic moment can change orientation while the particle’s geometry remains fixed. (Local fields within 0.1 µm of the SPIO surface can exceed 100 mT.) Consider: 1.wELFMF exposure could “imprint”, via stochastic resonance, onto the local magnetic field of SPIO particles potentially increasing the amplitude of the applied field as much as ten million times. In other words, SPIO particles effectively amplify variations in applied nano-tesla fields, producing changes in local fields in the milli-tesla range. Such fields would certainly be high enough to alter singlet to triplet conversions in radical pairs. Also these conversions would oscillate at the frequencies (or possible double the frequency) of the applied field. These ELF oscillations in singlet to triplet conversions, could then couple to biological process susceptible to these frequencies. This “amplification” of the applied wELFMF would eliminate all objections to the RPM. 2.For SPIO particles the duration of the magnetic switching is less that the electron spin-lattice relaxation time in magnetite. Hence the rise and fall times of the mT fields might be short enough to induce sufficient currents to break molecular bonds and create free radicals directly. 3.A careful review of the literature suggests: a.that many of the results currently attributable to single domain particles may not imply sensitivity to magnetic polarity as there was failure to address, in the experimental protocols, sensitivity to ambient wELFMF. b.the broad frequency response to RF irradiation shown to negate the effects of a purported RPM is consistent with a RPM associated with fields of different strengths which exist in close proximity to the SPIO particles. Hence SPIO particles as the initial transduction site could “explain” almost all magnetoreception data associated with wELFMF.