Weaver J C, Astumian R D
Massachusetts Institute of Technology, Harvard-MIT Division of Health Sciences and Technology, Cambridge 02139.
Bioelectromagnetics. 1992;Suppl 1:119-38. doi: 10.1002/bem.2250130712.
Interactions between physical fields and biological systems present difficult conceptual problems. Complete biological systems, even isolated cells, are exceedingly complex. This argues against the pursuit of theoretical models, with the possible consequence that only experimental studies should be considered. In contrast, electromagnetic fields are well understood. Further, some subsystems of cells (viz. cell membranes) can be reasonably represented by physical models. This argues for the pursuit of theoretical models which quantitatively describe interactions of electromagnetic fields with that subsystem. Here we consider the hypothesis that electric fields, not magnetic fields, are the source of interactions, From this it follows that the cell membrane is a relevant subsystem, as the membrane is much more resistive than the intra- or extracellular regions. A general class of interactions is considered: electroconformational changes associated with the membrane. Expected results of such as approach include the dependence of the interaction on key parameters (e.g., cell size, field magnitude, frequency, and exposure time), constraints on threshold exposure conditions, and insight into how experiments might be designed. Further, because it is well established that strong and moderate electric fields interact significantly with cells, estimates of the extrapolated interaction for weaker fields can be sought. By employing signal-to-noise (S/N) ratio criteria, theoretical models can also be used to estimate threshold magnitudes. These estimates are particularly relevant to in vitro conditions, for which most biologically generated background fields are absent. Finally, we argue that if theoretical model predictions are unavailable to guide the selection of experimental conditions, an overwhelmingly large number of different conditions will be needed to find, establish, and characterize bioelectromagnetic effects in an empirical search. This is contrasted with well-established chemical dosimetry, which is much simpler. Because of the large number of possible electromagnetic field conditions, we also conclude that in vitro studies, rather than in vivo studies, should be emphasized in studies aimed at discovering and characterizing mechanisms for bioelectromagnetic effects.
物理场与生物系统之间的相互作用存在棘手的概念性问题。完整的生物系统，甚至是孤立的细胞，都极其复杂。这使得人们反对追求理论模型，可能的结果是只应考虑实验研究。相比之下，电磁场是人们所熟知的。此外，细胞的一些子系统（即细胞膜）可以用物理模型合理地表示。这支持追求能够定量描述电磁场与该子系统相互作用的理论模型。在此，我们考虑这样一种假设：电场而非磁场是相互作用的根源。由此可知，细胞膜是一个相关的子系统，因为膜比细胞内或细胞外区域的电阻大得多。我们考虑了一类普遍的相互作用：与膜相关的电构象变化。这种方法的预期结果包括相互作用对关键参数（如细胞大小、场强、频率和暴露时间）的依赖性、对阈值暴露条件的限制，以及对实验设计方式的深入了解。此外，由于已经确定强电场和中等强度电场与细胞有显著相互作用，所以可以寻求对较弱电场的外推相互作用的估计。通过采用信噪比（S/N）标准，理论模型还可用于估计阈值大小。这些估计对于体外条件尤为重要，因为在体外条件下大多数生物产生的背景场不存在。最后，我们认为，如果没有理论模型预测来指导实验条件的选择，那么在实证研究中就需要大量不同的条件来发现、确立和表征生物电磁效应。这与成熟得多且简单得多的化学剂量测定法形成对比。由于可能的电磁场条件数量众多，我们还得出结论，在旨在发现和表征生物电磁效应机制的研究中，应强调体外研究而非体内研究。
