Fan Song^*

Molecular & Cellular Biomechanics, Vol.7, No.1, pp. 13-24, 2010, DOI:10.3970/mcb.2010.007.013

Abstract The electrostatic interaction effects including the interaction potential, force and torque between the neighboring chondroitin sulfate glycosaminoglycan (CS-GAG) molecular chains in the bottle brush conformation of proteoglycan aggrecan are obtained as the functions of the minimum separation distance and the mutual angle between the molecular chains based on an asymptotic solution of the Poisson-Boltzmann equation that the CS-GAGs satisfy under the normal physiological conditions of articular cartilage. The present study indicates that the electrostatic interactions are not only associated intimately with the separation distance and the mutual angle, which are shown as purely exponential in separation distance and decrease with… More >

He Gong^∗,†, Ming Zhang^‡

Molecular & Cellular Biomechanics, Vol.7, No.1, pp. 1-12, 2010, DOI:10.3970/mcb.2010.007.001

Abstract In mechanical disuse conditions associated with immobilization and microgravity in spaceflight, cortical endosteal surface moved outward with periosteal surface moving slightly or unchanged, resulting in reduction of cortical thickness. Reduced thickness of the shaft cortex of long bone can be considered as an independent predictor of fractures. Accordingly, it is important to study the remodeling process at cortical endosteal surface. This paper presents a computer simulation of cortical endosteal remodeling induced by mechanical disuse at the Basic Multicellular Units level with cortical thickness as controlling variables. The remodeling analysis was performed on a representative rectangular slice of the cross section… More >

Dilson E. Rassier^*

Molecular & Cellular Biomechanics, Vol.6, No.4, pp. 229-242, 2009, DOI:10.3970/mcb.2009.006.229

Abstract When activated skeletal muscles are stretched at slow velocities, force increases in two phases: (i) a fast increase, and (ii) a slow increase. The transition between these phases is commonly associated with the mechanical detachment of cross-bridges from actin. This phenomenon is referred to asforce enhancement during stretch. After the stretch, force decreases and reaches steady-state at levels that are higher than the force produced at the corresponding length during purely isometric contractions. This phenomenon is referred to asresidual force enhancement.The mechanisms behind the increase in force during and after stretch are still a matter of debate, and have physiological… More >

Masanori Kobayashi, Myron Spector

Molecular & Cellular Biomechanics, Vol.6, No.4, pp. 217-228, 2009, DOI:10.3970/mcb.2009.006.217

Abstract In order to achieve successful wound repair by regenerative tissue engineering using mesenchymal stem cells (MSCs), it is important to understand the response of stem cells in the scaffold matrix to mechanical stress.
To investigate the clinical effects of mechanical stress on the behavior of cells in scaffolds, bone marrow-derived mesenchymal stem cells (MSCs) were grown on a type-I collagen-glycosaminoglycan (GAG) scaffold matrix for one week under cyclic stretching loading conditions.
The porous collagen-GAG scaffold matrix for skin wound repair was prepared, the harvested canine MSCs were seeded on the scaffold, and cultured under three kinds of cyclic… More >

Kittisak Koombua^*, Ramana M. Pidaparti^∗,†,‡, P. Worth Longest^∗,‡, Kevin R. Ward^‡,§

Molecular & Cellular Biomechanics, Vol.6, No.4, pp. 203-216, 2009, DOI:10.3970/mcb.2009.006.203

Abstract Without proper knowledge of mechanical ventilation effects, physicians can aggravate an existing lung injury. A better understanding of the interaction between airflow and airway tissue during mechanical ventilation will be helpful to physicians so that they can provide appropriate ventilator parameters for intubated patients. In this study, a computational model incorporating the interactions between airflow and airway walls was developed to investigate the effects of airway tissue flexibility on airway pressure and stress. Two flow rates, 30 and 60 l/min, from mechanical ventilation were considered. The transient waveform was active inhalation with a constant flow rate and passive exhalation. Results… More >

Siva A. Vanapalli^∗,†, Yixuan Li^†, Frieder Mugele^†, Michel H. G. Duits^†

Molecular & Cellular Biomechanics, Vol.6, No.4, pp. 191-202, 2009, DOI:10.3970/mcb.2009.006.191

Abstract Endogenous granules (EGs) that consist of lipid droplets and mitochondria have been commonly used to assess intracellular mechanical properties via multiple particle tracking microrheology (MPTM). Despite their widespread use, the nature of interaction of EGs with the cytoskeletal network and the type of forces driving their dynamics - both of which are crucial for the interpretation of the results from MPTM technique - are yet to be resolved. In this report, we study the dynamics of endogenous granules in mammalian cells using particle tracking methods. We find that the ensemble dynamics of EGs is diffusive in three types of mammalian… More >

R. M. Ardito Marretta^*, G. Barbaraci^†

Molecular & Cellular Biomechanics, Vol.6, No.3, pp. 175-190, 2009, DOI:10.3970/mcb.2009.006.175

Abstract This study, through a typical aerospace systems architecture, suggests an engineering design of a human cancer cell circuitry in which a digital optimal control matrix is assigned to repair the DNA damage level and/or to trigger its apoptosis.
Here, the conceived machinery is proposed taking into account the state of the art in cancer investigation. However, it could be further generalized. The most recent studies on cancer pathologies give a predominant role to the oncosuppressor protein p53 and its antagonist, the oncogene Mdm2.
Experimental and theoretical approaches are in agreement in deducing a “digital” response of the p53 when genomic… More >

Yoshitaka Shimada^∗,†, Taiji Adachi^∗,†,‡, Yasuhiro Inoue^∗,†, Masaki Hojo^∗

Molecular & Cellular Biomechanics, Vol.6, No.3, pp. 161-174, 2009, DOI:10.3970/mcb.2009.006.161

Abstract The actin filament, which is the most abundant component of the cytoskeleton, plays important roles in fundamental cellular activities such as shape determination, cell motility, and mechanosensing. In each activity, the actin filament dynamically changes its structure by polymerization, depolymerization, and severing. These phenomena occur on the scales ranging from the dynamics of actin molecules to filament structural changes with its deformation due to the various forces, for example, by the membrane and solvent. To better understand the actin filament dynamics, it is important to focus on these scales and develop its mathematical model. Thus, the objectives of this study… More >

Anna M. Raskin^∗,†, Masahiko Hoshijima^†, Eric Swanson^†, Andrew D. McCulloch^*, Jeffrey H. Omens^∗,†,‡

Molecular & Cellular Biomechanics, Vol.6, No.3, pp. 145-160, 2009, DOI:10.3970/mcb.2009.006.145

Abstract Altered mechanical stress and strain in cardiac myocytes induce modifications in gene expression that affects cardiac remodeling and myocyte contractile function. To study the mechanisms of mechanotransduction in cardiomyocytes, probing alterations in mechanics and gene expression has been an effective strategy. However, previous studies are self-limited due to the general use of isolated neonatal rodent myocytes or intact animals. The main goal of this study was to develop a novel tissue culture chamber system for mouse myocardium that facilitates loading of cardiac tissue, while measuring tissue stress and deformation within a physiological environment. Intact mouse right ventricular papillary muscles were… More >

Dominik R. Haudenschild^∗,†, Jianfen Chen^∗,†, Nikolai Steklov^†, Martin K. Lotz^*, Darryl D. D’Lima^∗,‡

Molecular & Cellular Biomechanics, Vol.6, No.3, pp. 135-144, 2009, DOI:10.3970/mcb.2009.006.135

Abstract The actin cytoskeleton is a dynamic network required for intracellular transport, signal transduction, movement, attachment to the extracellular matrix, cellular stiffness and cell shape. Cell shape and the actin cytoskeletal configuration are linked to chondrocyte phenotype with regard to gene expression and matrix synthesis. Historically, the chondrocyte actin cytoskeleton has been studied after formaldehyde fixation - precluding real-time measurements of actin dynamics, or in monolayer cultured cells. Here we characterize the actin cytoskeleton of living low-passage human chondrocytes grown in three-dimensional culture using a stably expressed actin-GFP construct. GFP-actin expression does not substantially alter the production of endogenous actin at… More >