Nakaoka Yasuo, Itoh Junya, Shimizu Kikuo
Osaka University, Toyonaka, Japan.
Bioelectromagnetics. 2011 Jan;32(1):66-72. doi: 10.1002/bem.20614.
We studied the swimming orientation of the ciliated protozoan Paramecium aurelia in a static magnetic field (0.78 T). P. aurelia is a complex of species termed syngens, whose cell morphology appears similar on microscopic examination. In the magnetic field, the cells of some syngens gradually changed their swimming orientation so that they were swimming perpendicular or parallel to the magnetic field, although such sensitivity to magnetic fields differs between syngens. When the temperature of the cell suspension was raised, the magnetic sensitivity of the cells was decreased. On the other hand, when the cells were cultured beforehand at a high temperature, their magnetic sensitivity was increased. These results raise the possibility that membrane lipid fluidity, which is inversely proportional to the membrane lipid order, contributes to the magnetic orientation of syngens. In this study, measurements of membrane lipid fluidity obtained using fluorescence image analysis with the lipophilic dye, laurdan (6-lauroyl-2-dimethylaminonaphtalene), showed that the degree of membrane lipid fluidity was correlated with the differences in magnetic orientation between syngens. That is, the syngens with decreased membrane fluidity showed an increased degree of magnetic orientation. Therefore, the membrane lipid order is a key factor in the magnetic orientation of Paramecium swimming.
我们研究了纤毛原生动物双小核草履虫在静磁场（0.78 T）中的游动方向。双小核草履虫是一个被称为同宗配合的物种复合体，在显微镜检查下其细胞形态看起来相似。在磁场中，一些同宗配合的细胞逐渐改变其游动方向，以至于它们垂直或平行于磁场游动，尽管不同同宗配合对磁场的这种敏感性存在差异。当细胞悬浮液的温度升高时，细胞的磁敏感性降低。另一方面，当细胞预先在高温下培养时，它们的磁敏感性增加。这些结果增加了一种可能性，即与膜脂有序性成反比的膜脂流动性有助于同宗配合的磁定向。在本研究中，使用亲脂性染料劳丹（6 - 月桂酰 - 2 - 二甲基氨基萘）通过荧光图像分析获得的膜脂流动性测量结果表明，膜脂流动性程度与不同同宗配合之间的磁定向差异相关。也就是说，膜流动性降低的同宗配合表现出更高程度的磁定向。因此，膜脂有序性是草履虫游动磁定向的关键因素。
