近日刊登在PNAS上的一篇研究報告中,，研究者指出，他們分離出了被認為是支持了某些動物通過地球磁場導(dǎo)航的能力的磁性細胞,。
行為研究長久以來為磁場感應(yīng)的存在提供了證據(jù),，但是這種組成了體內(nèi)羅盤的專門化細胞的身份仍然難以捉摸,。Stephan Eder及其同事從鱒魚的鼻腔內(nèi)部分離出了這種推定存在的磁場感應(yīng)細胞，它含有被稱為磁鐵的富含鐵的磁性材料的沉積物,。這組作者把鱒魚鼻腔組織的懸浮液放在了一架光學(xué)顯微鏡下,，然后在有緩慢旋轉(zhuǎn)的外部磁場存在的情況下，通過識別細胞的旋轉(zhuǎn)運動,，從而發(fā)現(xiàn)了磁性細胞,。在虹吸出了這些旋轉(zhuǎn)細胞從而更詳細地描述它們之后，這組作者發(fā)現(xiàn)了每個細胞含有反光的,、富含鐵的磁性顆粒,，它們固定在細胞膜上。
這組作者還確定了這些細胞對磁場的靈敏度比此前估計的要多出大約100倍,。這組作者說,，這些發(fā)現(xiàn)提示這些細胞有能力探測磁北以及外部磁場的微小變化，而且可能建立了一種精確的磁場感知系統(tǒng)的基礎(chǔ),。（生物谷Bioon.com）
doi:10.1073/pnas.1205653109
PMC:
PMID:
Magnetic characterization of isolated candidate vertebrate magnetoreceptor cells
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.
