Biological Effects of Weak Extremely Low Frequency Magnetic Fields

弱极低频磁场的生物效应

• 批准号: RGPIN-2014-05589
• 负责人: Prato, Frank
• 金额: $ 3.06万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=611722
• 关键词: Biological; Effects; Weak; Extremely; Low

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.

当我们积累极低频磁场（ELFMF）对蜗牛，小鼠和人类伤害感受的影响的数据时，已经发表了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）的磁感受的工作，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者是a）氧化铁颗粒阵列上的扭矩，所述氧化铁颗粒具有保持单个磁场域的正确尺寸，以及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线态跃迁。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）和动物定向的影响的初始生物物理检测机制特征的相似性。两者都需要同时暴露于支持RPM的强度大致相同的短波长可见光。然而，最近我们已经表明，在30 Hz的弱极低频磁场（wELFMF）的影响的阈值是或低于33 nT。此外，最近的动物定向工作显示灵敏度远低于最初报告的灵敏度，在极低频率下，在10 nT和4µT之间也有显著结果。在这些低频率下的这些低强度与单畴磁铁矿颗粒或RPM不一致。 在这里，我们建议，在小鼠和细胞实验中进行测试，初始转导是一个阵列的超顺磁性氧化铁（SPIO）颗粒。与单畴粒子不同，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 µm范围内的局部场可超过100 mT。） 请考虑： 1. wELFMF暴露可以通过随机共振“印记”到SPIO粒子的局部磁场上，潜在地增加所施加的场的幅度多达一千万倍。换句话说，SPIO粒子有效地放大了所施加的纳特斯拉场的变化，在毫特斯拉范围内产生局部场的变化。这样的电场肯定足够高，足以改变自由基对中单线态到三线态的转换。而且，这些转换将以所施加的场的频率（或可能的两倍频率）振荡。这些单重态到三重态转换中的ELF振荡可以耦合到对这些频率敏感的生物过程。对所应用的wELFMF的这种“放大”将消除对RPM的所有异议。 2.对于SPIO粒子的磁开关的持续时间是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，以诱导足够的电流来破坏分子键并直接产生自由基。 3.对文献的仔细审查表明： a.目前可归因于单畴粒子的许多结果可能并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的敏感性。 B.对RF辐射的宽频率响应显示为否定所声称的RPM的效果，这与与存在于SPIO粒子附近的不同强度的场相关联的RPM一致。 因此，SPIO粒子作为初始转导网站可以“解释”几乎所有的磁接收数据与wELFMF。