Dimitrije Stamenovic´ ¹

Molecular & Cellular Biomechanics, Vol.2, No.2, pp. 69-76, 2005, DOI:10.3970/mcb.2005.002.069

Abstract It is well established that adherent cells change their orientation in response to non-uniform substrate stretching. Most observations indicate that cells orient away from the direction of the maximal substrate strain, whereas in some cases cells also align with the direction of the maximal strain. Previous studies suggest that orientation and steering of the cell may be closely tied to cytoskeletal contractile stress but they could not explain the mechanisms that direct cell reorientation. This led us to develop a simple, mechanistic theoretical model that could predict a direction of cell orientation in response to mechanical nonuniformities of the substrate.… More >

X. Neil Dong^1,2, Xiaohui Zhang¹, X. Edward Guo¹

Molecular & Cellular Biomechanics, Vol.2, No.2, pp. 63-68, 2005, DOI:10.3970/mcb.2005.002.063

Abstract In human cortical bone, cement lines (or reversal lines) separate osteons from the interstitial bone tissue, which consists of remnants of primary lamellar bone or fragments of remodeled osteons. There have been experimental evidences of the cement line involvement in the failure process of bone such as fatigue and damage. However, there are almost no experimental data on interfacial properties of cement lines in human cortical bone. The objective of this study is to design and assemble a precision and computer controlled osteon pushout microtesting system, and to experimentally determine the interfacial strength of cement lines in human cortical bone… More >

Quang Dang^1,1, Hans Gregersen^2,2, Birgitte Duch^2,2, Ghassan S. Kassab^1,1

Molecular & Cellular Biomechanics, Vol.2, No.2, pp. 53-62, 2005, DOI:10.3970/mcb.2005.002.053

Abstract Biliary duct obstruction is an important clinical condition that affects millions of people worldwide. We have previously shown that the common bile duct (CBD) undergoes significant growth and remodelling post obstruction. The mechanical stress-strain relation is expected to change due to growth and remodeling in response to obstruction and hence pressure-overload. The objective of the present study was to characterize the material properties of the CBD of the sham group and at 3 hours, 12 hours, 2 days, 8 days and 32 days (n=5 in each group) after obstruction. The Fung's exponential strain energy function was used to relate stress… More >

Wei Zhang^1,2, Carly Herrera¹, Satya N. Atluri¹, Ghassan S. Kassab^2,3

Molecular & Cellular Biomechanics, Vol.2, No.1, pp. 41-52, 2005, DOI:10.3970/mcb.2005.002.041

Abstract It is well known that blood vessels shorten axially when excised. This is due to the perivascular tethering constraint by side branches and the existence of pre-stretch of blood vessels at the \textit {in situ} state. Furthermore, vessels are radially constrained to various extents by the surrounding tissues at physiological loading. Our hypothesis is that the axial pre-stretch and radial constraint by the surrounding tissue homogenizes the stress and strain distributions in the vessel wall. A finite element analysis of porcine coronary artery and rabbit thoracic aorta based on measured material properties, geometry, residual strain and physiological loading is used… More >

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 >