PNAS：研究者发现感知地球磁场的细胞

近日刊登在<em>PNAS</em>上的一篇研究报告中，研究者指出，他们分离出了被认为是支持了某些动物通过地球磁场导航的能力的磁性细胞。

行为研究长久以来为磁场感应的存在提供了证据，但是这种组成了体内罗盘的专门化细胞的身份仍然难以捉摸。Stephan Eder及其同事从鳟鱼的鼻腔内部分离出了这种推定存在的磁场感应细胞，它含有被称为磁铁的富含铁的磁性材料的沉积物。这组作者把鳟鱼鼻腔组织的悬浮液放在了一架光学显微镜下，然后在有缓慢旋转的外部磁场存在的情况下，通过识别细胞的旋转运动，从而发现了磁性细胞。在虹吸出了这些旋转细胞从而更详细地描述它们之后，这组作者发现了每个细胞含有反光的、富含铁的磁性颗粒，它们固定在细胞膜上。

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这组作者还确定了这些细胞对磁场的灵敏度比此前估计的要多出大约100倍。这组作者说，这些发现提示这些细胞有能力探测磁北以及外部磁场的微小变化，而且可能建立了一种精确的磁场感知系统的基础。 
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<img src="http://www.bioon.com/biology/UploadFiles/201207/2012071321354478.jpg" alt="" width="113" height="149" border="0" />

<a title="" href="http://dx.doi.org/doi:10.1073/pnas.1205653109" target="_blank">doi:10.1073/pnas.1205653109</a>
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<br/><strong>Magnetic characterization of isolated candidate vertebrate magnetoreceptor cells</strong><br/>


Stephan H.K. Edera,1, Hervé Cadioub,2, Airina Muhamadb,3, Peter A. McNaughtonb, Joseph L. Kirschvinkc, and Michael Winklhofera,4

Over the past 50 y, behavioral experiments have produced a large body of evidence for the existence of a magnetic sense in a wide range of animals. However, the underlying sensory physiology remains poorly understood due to the elusiveness of the magnetosensory structures. Here we present an effective method for isolating and characterizing potential magnetite-based magnetoreceptor cells. In essence, a rotating magnetic field is employed to visually identify, within a dissociated tissue preparation, cells that contain magnetic material by their rotational behavior. As a tissue of choice, we selected trout olfactory epithelium that has been previously suggested to host candidate magnetoreceptor cells. We were able to reproducibly detect magnetic cells and to determine their magnetic dipole moment. The obtained values (4 to 100 fAm2) greatly exceed previous estimates (0.5 fAm2). The magnetism of the cells is due to a μm-sized intracellular structure of iron-rich crystals, most likely single-domain magnetite. In confocal reflectance imaging, these produce bright reflective spots close to the cell membrane. The magnetic inclusions are found to be firmly coupled to the cell membrane, enabling a direct transduction of mechanical stress produced by magnetic torque acting on the cellular dipole in situ. Our results show that the magnetically identified cells clearly meet the physical requirements for a magnetoreceptor capable of rapidly detecting small changes in the external magnetic field. This would also explain interference of ac powerline magnetic fields with magnetoreception, as reported in cattle.

<br/>来源：EurekAlert

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