Judith Su^∗, Xingyu Jiang^†, Roy Welsch^‡, George M. Whitesides^§, Peter T. C. So^¶

Molecular & Cellular Biomechanics, Vol.4, No.2, pp. 87-104, 2007, DOI:10.3970/mcb.2007.004.087

Abstract Interactions between the cell and the extracellular matrix regulate a variety of cellular properties and functions, including cellular rheology. In the present study of cellular adhesion, area was controlled by confining NIH 3T3 fibroblast cells to circular micropatterned islands of defined size. The shear moduli of cells adhering to islands of well defined geometry, as measured by magnetic microrheometry, was found to have a significantly lower variance than those of cells allowed to spread on unpatterned surfaces. We observe that the area of cellular adhesion influences shear modulus. Rheological measurements further indicate that cellular shear modulus is a biphasic function… More >

G.V. Norton^*, J.C. Novarini^†

Molecular & Cellular Biomechanics, Vol.4, No.2, pp. 75-86, 2007, DOI:10.3970/mcb.2007.004.075

Abstract Ultrasonic imaging in medical applications involves propagation and scattering of acoustic waves within and by biological tissues that are intrinsically dispersive. Analytical approaches for modeling propagation and scattering in inhomogeneous media are difficult and often require extremely simplifying approximations in order to achieve a solution. To avoid such approximations, the direct numerical solution of the wave equation via the method of finite differences offers the most direct tool, which takes into account diffraction and refraction. It also allows for detailed modeling of the real anatomic structure and combination/layering of tissues. In all cases the correct inclusion of the dispersive properties… More >

K. Y. Volokh^*, E. Y. S. Chao^†, M. Armand^‡

Molecular & Cellular Biomechanics, Vol.4, No.2, pp. 67-74, 2007, DOI:10.3970/mcb.2007.004.067

Abstract Information about the stress distribution on contact surfaces of adjacent bones is indispensable for analysis of arthritis, bone fracture and remodeling. Numerical solution of the contact problem based on the classical approaches of solid mechanics is sophisticated and time-consuming. However, the solution can be essentially simplified on the following physical grounds. The bone contact surfaces are covered with a layer of articular cartilage, which is a soft tissue as compared to the hard bone. The latter allows ignoring the bone compliance in analysis of the contact problem, i.e. rigid bones are considered to interact through a compliant cartilage. Moreover, cartilage… More >

J. S. Ren^*

Molecular & Cellular Biomechanics, Vol.4, No.1, pp. 55-66, 2007, DOI:10.3970/mcb.2007.004.055

Abstract Formation and rupture of aneurysms due to the inflation of an artery with collagen fibers distributed in two preferred directions, subjected to internal pressure and axial stretch are examined within the framework of nonlinear elasticity. A two layer tube model with a fiber-reinforced composite based incompressible anisotropic hyperelastic constitutive material is employed to model the stress-strain behavior of the artery wall with distributed collagen fibers. The artery wall takes up a uniform inflation deformation, and there are no aneurysms in the artery under the normal condition. But an aneurysm may be formed in arteries when the stiffness of the fibers… More >

E. Shaik^∗, K.A. Hoffmann^∗, J-F. Dietiker^∗

Molecular & Cellular Biomechanics, Vol.4, No.1, pp. 41-54, 2007, DOI:10.3970/mcb.2007.004.041

Abstract A potential interaction between the local hemodynamics and the artery wall response has been suggested for vascular graft failure by intimal hyperplasia (IH). Among the various hemodynamic factors, wall shear stress has been implicated as the primary factor responsible for the development of IH. In order to explore the role of hemodynamics in the formation of IH in end-to-side anastomosis, computational fluid dynamics is employed. To validate the numerical simulations, comparisons with existing experimental data are performed for both steady and pulsatile flows. Generally, good agreement is observed with the velocity profiles whereas some discrepancies are found in wall shear… More >

Jianhua Zhou^∗, J. K. Chen^†, Yuwen Zhang^‡

Molecular & Cellular Biomechanics, Vol.4, No.1, pp. 27-40, 2007, DOI:10.3970/mcb.2007.004.027

Abstract A bioheat transfer approach is proposed to study thermal damage in biological tissues caused by laser radiation. The laser light propagation in the tissue is first solved by using a robust seven-flux model in cylindrical coordinate system. The resulting spatial distribution of the absorbed laser energy is incorporated into the bioheat transfer equation for solving temperature response. Thermal damage to the tissue is assessed by the extent of denatured protein using a rate process equation. It is found that for the tissue studied, a significant protein denaturation process would take place when temperature exceeds about 53oC. The effects of laser… More >

Jason W. Triplett^∗, Rita O’Riley^∗, Kristyn Tekulve^∗, Suzanne M. Norvell^∗, Fredrick M. Pavalko^†

Molecular & Cellular Biomechanics, Vol.4, No.1, pp. 13-26, 2007, DOI:10.3970/mcb.2007.004.013

Abstract Maintenance of optimal bone physiology requires the coordinated activity of osteoclasts that resorb old bone and osteoblasts that deposit new bone. Mechanical loading of bone and the resulting movement of interstitial fluid within the spaces surrounding bone cells is thought to play a key role is maintaining optimal bone mass. One way in which fluid movement may promote bone formation is by enhancing osteoblast survival. We have shown previously that application of fluid flow to osteoblasts in vitro confers a protective effect by inhibiting osteoblast apoptosis (Pavalko et al., 2003, J. Cell Physiol., 194: 194-205). To investigate the cellular mechanisms… More >

Hiroshi Yamada^∗,†, Hirokazu Ando^†

Molecular & Cellular Biomechanics, Vol.4, No.1, pp. 1-12, 2007, DOI:10.3970/mcb.2007.004.001

Abstract We investigated the response of apical and basal actin stress fibers (SFs) and its dependency on cell confluency for endothelial cells subjected to cyclic stretching. Porcine aortic endothelial cells from the 2^nd and 5^th passages were transferred to a fibronectin-coated silicone chamber with 5000–8000 cells/cm²(isolated condition), positioning the cells apart, or with 25,000–27,000 cells/cm²(subconfluent condition), allowing cell-to-cell contact. The substrate was stretched cyclically by 0.5 Hz for 2 h with a peak strain on the substrate that was 15% in the stretch direction and –4% in the transverse direction. The actin filaments (AFs) were stained with rhodamine phalloidin and their… More >

Wendong Shi^∗,†, Xi-Qiao Feng^*, Huajian Gao^†

Molecular & Cellular Biomechanics, Vol.3, No.3, pp. 121-126, 2006, DOI:10.3970/mcb.2006.003.121

Abstract When pulling a vesicle adhered on a substrate, both the force-displacement profile and the maximum force at pull-off are sensitively dependent upon the substrate shape. Here we consider the adhesion between a two-dimensional vesicle and a rigid substrate via long-range molecular interactions. For a given contact area, the theoretical pull-off force of the vesicle is obtained by multiplying the theoretical strength of adhesion and the contact area. It is shown that one may design an optimal substrate shape to achieve the theoretical pull-off force. More >

Baohua Ji^*, Yonggang Huang^†

Molecular & Cellular Biomechanics, Vol.3, No.3, pp. 109-120, 2006, DOI:10.3970/mcb.2006.003.109

Abstract The mechanisms governing the self-assembled structure of biomolecules (single chain and bundle of chains) are studied with an AB copolymer model via the coarse grained molecular dynamics simulations. Non-local hydrophobic interaction is found to play a critical role in the pattern formation of the assembled structure of polymer chains. We show that the polymer structure could be controlled by adjusting the balance between local (short range) and non-local (long range) hydrophobic interaction which are influenced by various factors such as the sequences, chain length, stiffness, confinement, and the topology of polymers. In addition, the competition between the intrachain hydrophobic interaction… More >