Biological Effects of Weak Extremely Low Frequency Magnetic Fields

虽然我们正在积累极低频磁场(ELFMF)对蜗牛、老鼠和人类伤害性感受的影响的数据，但许多不同物种(昆虫、啮齿动物、爬行动物、鸟类、牛和鹿)的磁感应已经发表了大量的工作，测量的终点是指向地磁场。在这项工作中的初始转换机制的候选是a)在具有适当大小的氧化铁颗粒阵列上的扭矩以保持单一的磁区，以及b)自由基对机制(RPM)，其中地球磁场影响自由基对中的单态到三态的转变。在过去的十年里，我们已经建立了对阿片类药物相关行为的影响的初始生物物理检测机制(我们的工作)和动物定位的特征的相似性。两者都需要同时暴露在支持RPM的强度大致相同的短波长可见光下。然而，最近我们发现，在30赫兹的弱极低频磁场(WELFMF)的效应阈值是33nT或更低。此外，最近的动物定位工作显示，敏感性比最初报告的要低得多，在10nT到4uT之间的显着结果也是在极低的频率下进行的。在这些低频下的这些低强度与单区磁铁矿粒子或RPM不一致。在这里，我们建议，在小鼠和细胞的实验中测试，最初的转导是一系列超顺磁性氧化铁(SPIO)颗粒。与单域粒子不同，较小的SPIO粒子的磁矩不受其几何形状的约束。因此，在热扰动下，它们的磁矩可以改变方向，而粒子的几何形状保持不变。(SPIO表面0.1微米内的局部磁场可以超过100毫微米)考虑：1.wELFMF暴露可能通过随机共振在SPIO粒子的局部磁场上留下印记，潜在地将外加磁场的幅度增加多达1000万倍。换句话说，SPIO粒子有效地放大了所应用的纳米特斯拉磁场的变化，在毫特斯拉范围内的局部磁场中产生变化。这样的磁场肯定会高到足以改变自由基对中的单态到三态的转换。此外，这些转换将以外加磁场的频率(或可能是频率的两倍)振荡。这些ELF振荡在单重态到三重态的转换中，然后可以耦合到对这些频率敏感的生物过程。这种对外加wELFMF的“放大”将消除对RPM的所有反对意见。2.对于SPIO粒子，磁开关的持续时间小于磁铁矿中的电子自旋-晶格弛豫时间。因此，mt场的上升和下降时间可能足够短，足以诱导足够的电流来破坏分子键并直接产生自由基。3.仔细的文献回顾表明：a.目前归因于单畴粒子的许多结果可能不意味着对磁极性的敏感性，因为在实验方案中，未能解决对环境wELFMF.b.对RF辐射的广泛频率响应，显示出抵消了所谓的RPM的影响，与与存在于SPIO粒子附近的不同强度的场相关联的RPM是一致的。因此，SPIO粒子作为初始的传输点可以“解释”几乎所有与wELFMF相关的磁感应数据。

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.