Characterizing Poroelasticity of Biological Tissues by Spherical Indentation: An Improved Theory for Large Relaxation

Flow of fluids within biological tissues often meets with resistance that causes a rate-and size-dependent material behavior known as poroelasticity.Characterizing poroelasticity can provide insight into a broad range of physiological functions,and is done qualitatively in the clinic by palpation.Indentation has been widely used for characterizing poroelasticity of soft materials,where quantitative interpretation of indentation requires a model of the underlying physics,and such existingmodels are well established for cases of small strain and modest force relaxationWe showed here that existing models are inadequate for large relaxation,where the force on the indenter at a prescribed depth at long-time scale drops to below half of the initially peak force.We developed an indentation theory for such cases of large relaxation,based upon Biot theory and a generalized Hertz contact model.We demonstrated that proposed theory is suitable for biological tissues(e.g.,spleen,kidney,skin and human cirrhosis liver)with both small and large relaxations.The proposed method would be a powerful tool to characterize poroelastic properties of biological materials for various applications such as pathological study and disease diagnosis.

烟碱对线粒体调节作用的研究进展

烟碱是烟草中的主要致瘾性成分,也是一种毒性物质。线粒体作为一种半自主细胞器,在细胞的生长、分化、凋亡、能量供应与信息传递等过程中发挥重要的功能,线粒体相关机制的失调会对细胞乃至机体产生不可逆的损害。已有研究表明,线粒体是烟碱作用的潜在靶点,烟碱可通过依赖或不依赖烟碱型乙酰胆碱受体的方式对线粒体进行调节,且烟碱浓度、烟碱作用时间和作用靶细胞不同时,对线粒体的调节作用也不同。该文聚焦烟碱对线粒体基因表达、动力学、呼吸链、氧化应激及钙稳态和单胺氧化酶活性等的影响,从正向和负向调节作用两方面,综述了烟碱对线粒体的调节作用及其机制,以期为后续研究烟碱对线粒体产生的多重生物学效应的相关机制及防控策略提供思路。