K. Y. Volokh ^{1, 2} , Y. Lev³

Molecular & Cellular Biomechanics, Vol.2, No.1, pp. 27-40, 2005, DOI:10.3970/mcb.2005.002.027

Abstract A simple phenomenological theory of tissue growth is used in order to demonstrate that volumetric growth combined with material anisotropy can lead to accumulation of residual stresses in arteries. The theory is applied to growth of a cylindrical blood vessel with the anisotropy moduli derived from experiments. It is shown that bending resultants are developed in the ring cross-section of the artery. These resultants may cause the ring opening or closing after cutting the artery \textit {in vitro} as it is observed in experiments. It is emphasized that the mode of the arterial ring opening is affected by the parameters… More >

Nan Shen^1,2, Dabajyoti Datta¹, Chris B. Schaffer^1,3,4,5, Eric Mazur^1,6

Molecular & Cellular Biomechanics, Vol.2, No.1, pp. 17-26, 2005, DOI:10.3970/mcb.2005.002.017

Abstract Analysis of cell regulation requires methods for perturbing molecular processes within living cells with spatial discrimination on the nanometer-scale. We present a technique for ablating molecular structures in living cells using low-repetition rate, low-energy femtosecond laser pulses. By tightly focusing these pulses beneath the cell membrane, we ablate cellular material inside the cell through nonlinear processes. We selectively removed sub-micrometer regions of the cytoskeleton and individual mitochondria without altering neighboring structures or compromising cell viability. This nanoscissor technique enables non-invasive manipulation of the structural machinery of living cells with several-hundred-nanometer resolution. Using this approach, we unequivocally demonstrate that mitochondria are… More >

Christopher A. Lemmon^1,2, Nathan J. Sniadecki³, Sami Alom Ruiz^1,3, John L. Tan, Lewis H. Romer^2,4,5, Christopher S. Chen^3,4

Molecular & Cellular Biomechanics, Vol.2, No.1, pp. 1-16, 2005, DOI:10.3970/mcb.2005.002.001

Abstract The interplay of mechanical forces between the extracellular environment and the cytoskeleton drives development, repair, and senescence in many tissues. Quantitative definition of these forces is a vital step in understanding cellular mechanosensing. Microfabricated post array detectors (mPADs) provide direct measurements of cell-generated forces during cell adhesion to extracellular matrix. A new approach to mPAD post labeling, volumetric imaging, and an analysis of post bending mechanics determined that cells apply shear forces and not point moments at the matrix interface. In addition, these forces could be accurately resolved from post deflections by using images of post tops and bases. Image… More >

Muhammad H. Zaman¹, Mohammad R. Kaazempur-Mofrad²

Molecular & Cellular Biomechanics, Vol.1, No.4, pp. 291-302, 2004, DOI:10.3970/mcb.2004.001.291

Abstract α-actinin, an actin binding protein, plays a key role in cell migration, cross-links actin filaments in the Z-disk, and is a major component of contractile muscle apparatus. The flexibility of the molecule is critical to its function. The flexibility of various regions of the molecule, including the linker connecting central subunits is studied using constant force steered molecular dynamics simulations. The linker, whose structure has been a subject of debate, is predicted to be semi-flexible. The flexibility of the linker is compared to all possible segments of equal length throughout the molecule. The stretching profile of the molecule at different… More >

A. Shukla^1,1, A.R. Dunn^2,2, M.A. Moses^3,3, K.J. Van Vliet^4,4

Molecular & Cellular Biomechanics, Vol.1, No.4, pp. 279-290, 2004, DOI:10.3970/mcb.2004.001.279

Abstract Although it is established that endothelial cells can respond to external mechanical cues (e.g., alignment in the direction of fluid shear stress), the extent to which mechanical stress and strain applied via the endothelial cell substrate impact biomolecular and cellular processes is not well-understood. This issue is particularly important in the context of inflammation, vascular remodeling, and cancer progression, as each of these processes occurs concurrently with localized increases in strain and marked changes in molecules secreted by adjacent cells. Here, we systematically vary the level and duration of cyclic tensile strain applied to human dermal microvascular and bovine capillary… More >

Hong Qian¹

Molecular & Cellular Biomechanics, Vol.1, No.4, pp. 267-278, 2004, DOI:10.3970/mcb.2004.001.267

Abstract In recent single-particle tracking (SPT) measurements on Listeria monocytogenes motility in cells [Kuo and McGrath (2000)], the actin-based stochastic dynamics of the bacterium movement has been analyzed statistically in terms of the mean-square displacement (MSD) of the trajectory. We present a stochastic analysis of a simplified polymerization Brownian ratchet (BR) model in which motions are limited by the bacterium movement. Analytical results are obtained and statistical data analyses are investigated. It is shown that the MSD of the stochastic bacterium movement is a monotonic quadratic function while the MSD for detrended trajectories is linear. Both the short-time relaxation and the… More >

M.R. Kaazempur Mofrad^1,2, J. Golji², N.A. Abdul Rahim², R.D. Kamm³

Molecular & Cellular Biomechanics, Vol.1, No.4, pp. 253-266, 2004, DOI:10.3970/mcb.2004.001.253

Abstract Membrane-bound integrin receptors are linked to intracellular signaling pathways through focal adhesion kinase (FAK). FAK tends to colocalize with integrin receptors at focal adhesions through its C-terminal focal adhesion targeting (FAT) domain. Through recruitment and binding of intracellular proteins, FAs transduce signals between the intracellular and extracellular regions that regulate a variety of cellular processes including cell migration, proliferation, apoptosis and detachment from the ECM. The mechanism of signaling through the cell is of interest, especially the transmission of mechanical forces and subsequent transduction into biological signals. One hypothesis relates mechanotransduction to conformational changes in intracellular proteins in the force… More >

Warren D. Marcus^1,2, Rodger P. McEver³, Cheng Zhu¹

Molecular & Cellular Biomechanics, Vol.1, No.4, pp. 245-252, 2004, DOI:10.3970/mcb.2004.001.245

Abstract When a cell adhered to another cell or substratum via surface proteins is forced to detach, lipid membrane tethers are often extruded from the cell surface before the protein bond dissociates. For example, during the inflammatory reaction leukocytes roll on the surface of activated endothelial cells. The rolling adhesion is mediated by interactions of selectins with their ligands, e.g., P-selectin glycoprotein ligand (PSGL)-1, which extrudes membrane tethers from the surfaces of both leukocytes and endothelial cells. Membrane tether extrusion has been suggested to regulate leukocyte rolling. Here we examine several factors that may affect forces required to initiate membrane tethers,… More >

Bryan Pfister¹, George Oyler², Michael Betenbaugh³, Gang Bao⁴

Molecular & Cellular Biomechanics, Vol.1, No.4, pp. 233-244, 2004, DOI:10.3970/mcb.2004.001.233

Abstract The Bcl-2 family of proteins has recently been implicated as a possible player in the complex cascade of neural cell death due to traumatic brain injuries. However, it is unclear if the Bcl-2 pathways are activated in mechanically injured neurons. Here we report the effects of BclX_L and Bax over-expression on stretch-induced neural cell death using an in vitro uniaxial stretch model of traumatic axonal injury. Specifically, YFP, YFP-tagged Bax and YFP-tagged BclX_L proteins were expressed in differentiated NG108-15 cells and stretch-injury assays were carried out at different strain and strain rate combinations. As a control, insults known to act… More >

Alvaro Valencia¹

Molecular & Cellular Biomechanics, Vol.1, No.3, pp. 221-232, 2004, DOI:10.3970/mcb.2004.001.221

Abstract Flow dynamics play an important role in the pathogenesis and treatment of intracranial aneurysms. The evaluation of the velocity field in the aneurysm dome and neck is important for the correct placement of endovascular coils, and the temporal and spatial variations of wall shear stress in the aneurysm are correlated with its growth and rupture. This numerical investigation describes the hemodynamic in two models of terminal aneurysm of the basilar artery. Aneurysm models with a aspect ratio of 1.0 and 1.67 were studied. Each model was subject to physiological representative waveform of inflow for a mean Reynolds number of 560.… More >