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  • Open Access

    ARTICLE

    Three-Dimensional Molecular Phase Separation and Flow Patterns with Novel Multilevel Fluidics

    Jui-Ming Yang*, Philip R. LeDuc∗,†

    Molecular & Cellular Biomechanics, Vol.3, No.2, pp. 69-78, 2006, DOI:10.3970/mcb.2006.003.069

    Abstract Inorganic and organic integrated systems detect, process, and respond to signals from solid media. Advances in fluidic systems have offered an alternative to traditional signaling methods through the development of aqueous signaling systems. Here, we show an experimentally simple mechanically governed fluidic system that creates three-dimensional molecular multiphase separation in a combination of discrete and continuous gradients analogous to digital and analog signals that can be used for controlled spatiotemporal cellular stimulation. We accomplish the pattern formation by fabricating a compartmentalized multi-level fluidics device where a network of capillaries converges into a main channel. Simultaneous More >

  • Open Access

    ARTICLE

    Adhesive Force of Human Hepatoma HepG2 Cells to Endothelial Cells and Expression of E-Selectin

    Guanbin Song∗,†, Toshiro Ohashi, Naoya Sakamoto, Masaaki Sato

    Molecular & Cellular Biomechanics, Vol.3, No.2, pp. 61-68, 2006, DOI:10.3970/mcb.2006.003.061

    Abstract Expression of adhesion molecules may play an important role in the interaction of tumor cells with vascular endothelial cells during tumor invasion and metastasis. In this study, the adhesive force of human hepatoma HepG2 cells to human umbilical vein endothelial cells (HUVECs) was investigated using a micropipette aspiration technique. Expression of an adhesion molecule, E-selectin, was also observed by immunofluorescence microscopy. In particular, the adhesive force after stimulation of HUVECs with recombinant human interleukin-1β (rhIL-1β) was examined. The results demonstrated that the adhesive force of HepG2 cells to stimulated HUVECs is significantly higher than that More >

  • Open Access

    ARTICLE

    Control of Stress Propagation in the Cytoplasm by Prestress and Loading Frequency

    Shaohua Hu*, Ning Wang

    Molecular & Cellular Biomechanics, Vol.3, No.2, pp. 49-60, 2006, DOI:10.3970/mcb.2006.003.049

    Abstract One fundamental question in cell biology is how mechanical stresses are distributed inside the cytoplasm. Recently we have developed a synchronous detection approach to map cytoplasmic displacements and stresses using yellow fluorescent protein tagged mitochondria as fiducial markers of the cytoskeleton (CSK) in response to a localized load applied via an RGD-coated magnetic bead (7). We have shown that stresses are propagated to remote sites in the cytoplasm, a finding that contradicts continuum model predictions. Here we show that long distance force propagation in the cytoplasm was abolished when the contractile prestress in the CSK More >

  • Open Access

    ARTICLE

    A Mathematical Model of Cell Reorientation in Response to Substrate Stretching

    Konstantinos A. Lazopoulos1, Dimitrije Stamenović2

    Molecular & Cellular Biomechanics, Vol.3, No.1, pp. 43-48, 2006, DOI:10.3970/mcb.2006.003.043

    Abstract It is well documented that in response to substrate stretching adhering cells alter their orientation. Generally, the cells reorient away from the direction of the maximum substrate strain, depending upon the magnitude of the substrate strain and the state of cell contractility. Theoretical models from the literature can describe only some aspects of this phenomenon. In the present study, we developed a more comprehensive mathematical model of cell reorientation than the current models. Using the framework of theory of non-linear elasticity, we found that the problem of cell reorientation was a stability problem, with the More >

  • Open Access

    ARTICLE

    Compressibility of Arterial Wall in Ring-cutting Experiments

    K.Y. Volokh1

    Molecular & Cellular Biomechanics, Vol.3, No.1, pp. 35-42, 2006, DOI:10.3970/mcb.2006.003.035

    Abstract It is common practice in the arterial wall modeling to assume material incompressibility. This assumption is driven by the observation of the global volume preservation of the artery specimens in some mechanical loading experiments. The global volume preservation, however, does not necessarily imply the local volume preservation -- incompressibility. In this work, we suggest to use the arterial ring- cutting experiments for the assessment of the local incompressibility assumption. The idea is to track the local stretches of the marked segments of the arterial ring after the stress-relieving cut. In the particular case of the rabbit… More >

  • Open Access

    REVIEW

    Regulation of Vascular Smooth Muscle Cells and Mesenchymal Stem Cells by Mechanical Strain

    Kyle Kurpinski1,2,3, Jennifer Park1,2,3, Rahul G. Thakar1,2,3, Song Li1,2

    Molecular & Cellular Biomechanics, Vol.3, No.1, pp. 21-34, 2006, DOI:10.3970/mcb.2006.003.021

    Abstract Vascular smooth muscle cells (SMCs) populate in the media of the blood vessel, and play an important role in the control of vasoactivity and the remodeling of the vessel wall. Blood vessels are constantly subjected to hemodynamic stresses, and the pulsatile nature of the blood flow results in a cyclic mechanical strain in the vessel walls. Accumulating evidence in the past two decades indicates that mechanical strain regulates vascular SMC phenotype, function and matrix remodeling. Bone marrow mesenchymal stem cell (MSC) is a potential cell source for vascular regeneration therapy, and may be used to More >

  • Open Access

    ARTICLE

    Stretching Short DNAs in Electrolytes

    Jizeng Wang1,2, Xiaojun Fan2, Huajian Gao2

    Molecular & Cellular Biomechanics, Vol.3, No.1, pp. 13-20, 2006, DOI:10.3970/mcb.2006.003.013

    Abstract This paper is aimed at a combined theoretical and numerical study of the force-extension relation of a short DNA molecule stretched in an electrolyte. A theoretical formula based on a recent discrete wormlike chain (WLC) model of Kierfeld et al. (Eur. Phys. J. E, Vol. 14, pp.17-34, 2004) and the classical OSF mean-field theory on electrostatic stiffening of a charged polymer is numerically verified by a set of Brownian dynamics simulations based on a generalized bead-rod (GBR) model incorporating long-ranged electrostatic interactions via the Debye-Hueckel potential (DH). The analysis indicates that the stretching of a short More >

  • Open Access

    ARTICLE

    Substrate Modulation of Osteoblast Adhesion Strength, Focal Adhesion Kinase Activation, and Responsiveness to Mechanical Stimuli

    E. Takai1, R. Landesberg2, R.W. Katz2, C.T. Hung3, X.E Guo1,4

    Molecular & Cellular Biomechanics, Vol.3, No.1, pp. 1-12, 2006, DOI:10.3970/mcb.2006.003.001

    Abstract Osteoblast interactions with extracellular matrix (ECM) proteins are known to influence many cell functions, which may ultimately affect osseointegration of implants with the host bone tissue. Some adhesion-mediated events include activation of focal adhesion kinase, and subsequent changes in the cytoskeleton and cell morphology, which may lead to changes in adhesion strength and cell responsiveness to mechanical stimuli. In this study we examined focal adhesion kinase activation (FAK), F-actin cytoskeleton reorganization, adhesion strength, and osteoblast responsiveness to fluid shear when adhered to type I collagen (ColI), glass, poly-L-lysine (PLL), fibronectin (FN), vitronectin (VN), and serum… More >

  • Open Access

    ARTICLE

    Wave Propogation Characteristics of Rotating Uniform Euler-Bernoulli Beams

    K.G. Vinod1, S. Gopalakrishnan1, R. Ganguli1

    CMES-Computer Modeling in Engineering & Sciences, Vol.16, No.3, pp. 197-208, 2006, DOI:10.3970/cmes.2006.016.197

    Abstract A spectral finite element formulation for a rotating beam subjected to small duration impact is presented in this paper. The spatial variation in centrifugal force is modeled in an average sense. Spectrum and dispersion plots are obtained as a function of rotating speed. It is shown that the flexural wave tends to behave non-dispersively at very high rotation speeds. The numerical results are simulated for two rotating waveguides of different dimensions. The results show that there is a steep increase in responses with the response peaks and the reflected signals almost vanishing at higher rotating More >

  • Open Access

    ARTICLE

    Sedimentation of a Solid Particle Immersed in a Fluid Film

    A. Sellier1, L. Pasol2

    CMES-Computer Modeling in Engineering & Sciences, Vol.16, No.3, pp. 187-196, 2006, DOI:10.3970/cmes.2006.016.187

    Abstract This paper examines the slow viscous settling migration of a solid particle immersed in a viscous fluid film confined by {two plane and parallel solid wall and free surface}. The approach rests on the use of suitable boundary-integral equations on the surface of the particle and the analytical calculation of a new Green tensor that complies with all the boundary conditions satisfied by the liquid flow on the plane boundaries. The numerical implementation resorts to standard boundary elements on the particle's surface and provides at a reasonable cpu time cost the motion of the particle More >

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