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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Swimming Paramecium in magnetically simulated enhanced, reduced, and inverted gravity environments
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Swimming Paramecium in magnetically simulated enhanced, reduced, and inverted gravity environments

机译:在磁力模拟的增强,缩小和反向重力环境中游泳草履虫

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摘要

Earth's gravity exerts relatively weak forces in the range of 10-100 pN directly on cells in biological systems. Nevertheless, it biases the orientation of swimming unicellular organisms, alters bone cell differentiation, and modifies gene expression in renal cells. A number of methods of simulating different strength gravity environments, such as centrifugation, have been applied for researching the underlying mechanisms. Here, we demonstrate a magnetic force-based technique that is unique in its capability to enhance, reduce, and even invert the effective buoyancy of cells and thus simulate hypergravity, hypogravity, and inverted gravity environments. We apply it to Paramecium caudatum, a single-cell protozoan that varies its swimming propulsion depending on its orientation with respect to gravity, g. In these simulated gravities, denoted by f_(gm), Paramecium exhibits a linear response up to f_(gm) = 5 g, modifying its swimming as it would in the hypergravity of a centrifuge. Moreover, experiments from f_(gm) = 0 to - 5 g show that the response is symmetric, implying that the regulation of the swimming speed is primarily related to the buoyancy of the cell. The response becomes nonlinear for f_(gm) > 5 g. At f_(gm) = 10 g, many paramecia "stall" (i.e., swim in place against the force), exerting a maximum propulsion force estimated to be 0.7 nN. These findings establish a general technique for applying continuously variable forces to cells or cell populations suitable for exploring their force transduction mechanisms.
机译:地球重力直接对生物系统中的细胞施加10-100 pN范围内的相对较弱的力。但是,它会偏向游泳单细胞生物的方向,改变骨细胞的分化,并改变肾细胞中的基因表达。多种模拟不同强度重力环境的方法(例如离心法)已用于研究潜在的机理。在这里,我们演示了一种基于磁力的技术,该技术在增强,减少甚至反转细胞的有效浮力方面具有独特的能力,因此可以模拟超重力,超重力和反向重力环境。我们将其应用于尾草履虫(Paramecium caudatum),这是一种单细胞原生动物,根据其相对于重力的方向g改变其游泳推进力。在以f_(gm)表示的这些模拟重力中,草履虫表现出高达f_(gm)= 5 g的线性响应,从而像在离心机的超重力中一样改变了其游动。而且,从f_(gm)= 0到-5 g的实验表明,该响应是对称的,这意味着游泳速度的调节主要与细胞的浮力有关。当f_(gm)> 5 g时,响应变为非线性。在f_(gm)= 10 g时,许多paramecia“停转”(即逆着力游到原处),施加的最大推进力估计为0.7 nN。这些发现建立了将连续可变的力施加于适合于探索其力传导机制的细胞或细胞群的通用技术。

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