Kirschvink J L, Kobayashi-Kirschvink A, Woodford B J
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena 91125.
Proc Natl Acad Sci U S A. 1992 Aug 15;89(16):7683-7. doi: 10.1073/pnas.89.16.7683.
Although the mineral magnetite (Fe3O4) is precipitated biochemically by bacteria, protists, and a variety of animals, it has not been documented previously in human tissue. Using an ultrasensitive superconducting magnetometer in a clean-lab environment, we have detected the presence of ferromagnetic material in a variety of tissues from the human brain. Magnetic particle extracts from solubilized brain tissues examined with high-resolution transmission electron microscopy, electron diffraction, and elemental analyses identify minerals in the magnetite-maghemite family, with many of the crystal morphologies and structures resembling strongly those precipitated by magnetotactic bacteria and fish. These magnetic and high-resolution transmission electron microscopy measurements imply the presence of a minimum of 5 million single-domain crystals per gram for most tissues in the brain and greater than 100 million crystals per gram for pia and dura. Magnetic property data indicate the crystals are in clumps of between 50 and 100 particles. Biogenic magnetite in the human brain may account for high-field saturation effects observed in the T1 and T2 values of magnetic resonance imaging and, perhaps, for a variety of biological effects of low-frequency magnetic fields.
尽管矿物磁铁矿（Fe3O4）可由细菌、原生生物及多种动物通过生化方式沉淀而成，但此前尚未在人体组织中得到证实。我们在洁净的实验室环境中使用超灵敏超导磁力计，检测到人类大脑多种组织中存在铁磁性物质。通过高分辨率透射电子显微镜、电子衍射和元素分析对溶解的脑组织进行磁性颗粒提取物检测，确定了磁铁矿-磁赤铁矿家族中的矿物质，其中许多晶体形态和结构与趋磁细菌和鱼类沉淀的物质极为相似。这些磁性测量和高分辨率透射电子显微镜测量结果表明，大脑中大多数组织每克至少存在500万个单畴晶体，而软脑膜和硬脑膜每克则超过1亿个晶体。磁性数据表明，这些晶体以50至100个颗粒的团块形式存在。人脑中的生物源磁铁矿可能是磁共振成像T1和T2值中观察到的高场饱和效应的原因，也许还与低频磁场的多种生物学效应有关。
