Biomechanics and Modeling in MechanobiologyThis is an RSS file. You can use it to subscribe to this data in your favourite RSS reader, such as GoogleReader, or to display this data on your own website or blog. Subscribe to this data using MyMedWorm.Subscribe to this data using GoogleReader.Subscribe to this data using Bloglines.Subscribe to this data using MyYahoo.

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150 records returned

Computational simulation of spontaneous bone straightening in growing children.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Periosteal surface pressures have been shown to inhibit bone formation and induce bone resorption, while tensile strains perpendicular to the periosteal surface have been shown to inhibit bone resorption and induce new bone deposition. A new computational model was developed to incorporate these experimental findings into simulations of spontaneous bone straightening in children with congenital posteromedial bowing of the tibia. Three-dimensional finite element models of the periosteum were used to determine the relationships between the defect angle and the distribution of bone surface pressures and strains due to gro...
Source: Biomechanics and Modeling in Mechanobiology - November 18, 2009 Category: Biomedical Science Authors: Carpenter RD, Carter DR Tags: Biomech Model Mechanobiol Source Type: journals

Anterior mitral leaflet curvature in the beating ovine heart: a case study using videofluoroscopic markers and subdivision surfaces.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The implantation of annuloplasty rings is a common surgical treatment targeted to re-establish mitral valve competence in patients with mitral regurgitation. It is hypothesized that annuloplasty ring implantation influences leaflet curvature, which in turn may considerably impair repair durability. This research is driven by the vision to design repair devices that optimize leaflet curvature to reduce valvular stress. In pursuit of this goal, the objective of this manuscript is to quantify leaflet curvature in ovine models with and without annuloplasty ring using in vivo animal data from videofluoroscopic marker analys...
Source: Biomechanics and Modeling in Mechanobiology - November 5, 2009 Category: Biomedical Science Authors: Göktepe S, Bothe W, Kvitting JP, Swanson JC, Ingels NB, Miller DC, Kuhl E Tags: Biomech Model Mechanobiol Source Type: journals

Influence of power-law rheology on cell injury during microbubble flows.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study we used boundary element solutions and finite element techniques to investigate how cell rheology influences the deformation and injury of cells during microbubble flows. An optimized Prony-Dirichlet series was used to model the cells' power-law rheology (PLR) and results were compared with a Maxwell fluid model. Results indicate that membrane strain and the risk for cell injury decreases with increasing channel height and bubble speed. In addition, the Maxwell and PLR models both indicate that increased viscous damping results in less cellular deformation/injury. However, only the PLR model was consistent wi...
Source: Biomechanics and Modeling in Mechanobiology - October 29, 2009 Category: Biomedical Science Authors: Dailey HL, Ghadiali SN Tags: Biomech Model Mechanobiol Source Type: journals

Modelling apical constriction in epithelia using elastic shell theory.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Apical constriction is one of the fundamental mechanisms by which embryonic tissue is deformed, giving rise to the shape and form of the fully-developed organism. The mechanism involves a contraction of fibres embedded in the apical side of epithelial tissues, leading to an invagination or folding of the cell sheet. In this article the phenomenon is modelled mechanically by describing the epithelial sheet as an elastic shell, which contains a surface representing the continuous mesh formed from the embedded fibres. Allowing this mesh to contract, an enhanced shell theory is developed in which the stiffness and bending ...
Source: Biomechanics and Modeling in Mechanobiology - October 27, 2009 Category: Biomedical Science Authors: Jones GW, Chapman SJ Tags: Biomech Model Mechanobiol Source Type: journals

A computational remodeling approach to predict the physiological architecture of the collagen fibril network in corneo-scleral shells.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Organized collagen fibrils form complex networks that introduce strong anisotropic and highly nonlinear attributes into the constitutive response of human eye tissues. Physiological adaptation of the collagen network and the mechanical condition within biological tissues are complex and mutually dependent phenomena. In this contribution, a computational model is presented to investigate the interaction between the collagen fibril architecture and mechanical loading conditions in the corneo-scleral shell. The biomechanical properties of eye tissues are derived from the single crimped fibril at the micro-scale via the co...
Source: Biomechanics and Modeling in Mechanobiology - October 3, 2009 Category: Biomedical Science Authors: Grytz R, Meschke G Tags: Biomech Model Mechanobiol Source Type: journals

Cyclic stretch downregulates arterial vascular connexin43 protein expression: an ex vivo study.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Vascular cells may communicate through gap junctions that are formed by connexin (Cx) proteins. We investigated differential regulation of arterial gap junctions by steady and cyclic stretch and the underlying mechanotransduction pathways. Ex vivo culture of rabbit thoracic aortas was used to investigate regulation of Cx43 by cyclic stretch. After culturing for 6 or 24 h, Cx43 protein levels were quantified using Western blot. Cultures under a pulsatile pressure (mean 80 mmHg, pulse 30 mmHg) decreased Cx43 protein at both 6 and 24 h as compared with cultures under a steady pressure (80 mmHg). The regulation of Cx43 pro...
Source: Biomechanics and Modeling in Mechanobiology - September 15, 2009 Category: Biomedical Science Authors: He Y, Shroff SG Tags: Biomech Model Mechanobiol Source Type: journals

An efficient two-stage approach for image-based FSI analysis of atherosclerotic arteries.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Patient-specific biomechanical modeling of atherosclerotic arteries has the potential to aid clinicians in characterizing lesions and determining optimal treatment plans. To attain high levels of accuracy, recent models use medical imaging data to determine plaque component boundaries in three dimensions, and fluid-structure interaction is used to capture mechanical loading of the diseased vessel. As the plaque components and vessel wall are often highly complex in shape, constructing a suitable structured computational mesh is very challenging and can require a great deal of time. Models based on unstructured computat...
Source: Biomechanics and Modeling in Mechanobiology - September 12, 2009 Category: Biomedical Science Authors: Leach JR, Rayz VL, Mofrad MR, Saloner D Tags: Biomech Model Mechanobiol Source Type: journals

Adaptive generation of multimaterial grids from imaging data for biomedical Lagrangian fluid-structure simulations.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Spatial discretization of complex imaging- derived fluid-solid geometries, such as the cardiac environment, is a critical but often overlooked challenge in biomechanical computations. This is particularly true in problems with Lagrangian interfaces, where the fluid and solid phases share a common interface geometrically. For simplicity and better accuracy, it is also highly desirable for the two phases to have a matching surface mesh at the interface between them. We outline a method for solving this problem, and illustrate the approach with a 3D fluid-solid mesh of the mouse heart. An MRI dataset of a perfusion-fixed ...
Source: Biomechanics and Modeling in Mechanobiology - September 1, 2009 Category: Biomedical Science Authors: Carson JP, Kuprat AP, Jiao X, Dyedov V, Del Pin F, Guccione JM, Ratcliffe MB, Einstein DR Tags: Biomech Model Mechanobiol Source Type: journals

Contribution of tissue composition and structure to mechanical response of articular cartilage under different loading geometries and strain rates.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Mechanical function of articular cartilage in joints between articulating bones is dependent on the composition and structure of the tissue. The mechanical properties of articular cartilage are traditionally tested in compression using one of the three loading geometries, i.e., confined compression, unconfined compression or indentation. The aim of this study was to utilize a composition-based finite element model in combination with a fractional factorial design to determine the importance of different cartilage constituents in the mechanical response of the tissue, and to compare the importance of the tissue constitu...
Source: Biomechanics and Modeling in Mechanobiology - August 12, 2009 Category: Biomedical Science Authors: Julkunen P, Jurvelin JS, Isaksson H Tags: Biomech Model Mechanobiol Source Type: journals

Deformation-induced hydrolysis of a degradable polymeric cylindrical annulus.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
A thermodynamically consistent framework for describing the response of materials undergoing deformation-induced degradation is developed and applied to a particular biodegradable polymer system. In the current case, energy is dissipated through the mechanism of hydrolytic degradation and its effects are incorporated in the constitutive model by appropriately stipulating the forms for the rate of dissipation and for the degradation-dependent Helmholtz potential which changes with the extent of the degradation of the material. When degradation does not occur, the response of the material follows the response of a power-...
Source: Biomechanics and Modeling in Mechanobiology - August 12, 2009 Category: Biomedical Science Authors: Soares JS, Rajagopal KR, Moore JE Tags: Biomech Model Mechanobiol Source Type: journals

Proposed role of the M-band in sarcomere mechanics and mechano-sensing: a model study.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In sarcomeres of striated muscles the middle parts of adjacent thick filaments are connected to each other by the M-band proteins. To understand the role of the M-band in sarcomere mechanics a model of forces which pull a thick filament to opposite Z-disks of a sarcomere is considered. Forces of actin-myosin cross-bridges, I-band titin segments and the M-band are accounted for. A continual expression for the M-band force is obtained assuming that the M-band proteins which connect neighbor thick filaments have nonlinear elastic properties. On the ascending and descending limbs of the force-length diagram cross-bridge fo...
Source: Biomechanics and Modeling in Mechanobiology - August 7, 2009 Category: Biomedical Science Authors: Shabarchin AA, Tsaturyan AK Tags: Biomech Model Mechanobiol Source Type: journals

Biomechanics of single chondrocytes under direct shear.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Articular chondrocytes experience a variety of mechanical stimuli during daily activity. One such stimulus, direct shear, is known to affect chondrocyte homeostasis and induce catabolic or anabolic pathways. Understanding how single chondrocytes respond biomechanically and morphologically to various levels of applied shear is an important first step toward elucidating tissue level responses and disease etiology. To this end, a novel videocapture method was developed in this study to examine the effect of direct shear on single chondrocytes, applied via the controlled lateral displacement of a shearing probe. Through th...
Source: Biomechanics and Modeling in Mechanobiology - July 30, 2009 Category: Biomedical Science Authors: Ofek G, Dowling EP, Raphael RM, McGarry JP, Athanasiou KA Tags: Biomech Model Mechanobiol Source Type: journals

Modeling of drug delivery into tissues with a microneedle array using mixture theory.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper, we apply mixture theory to quantitatively predict the transient behavior of drug delivery by using a microneedle array inserted into tissue. In the framework of mixture theory, biological tissue is treated as a multi-phase fluid saturated porous medium, where the mathematical behavior of the tissue is characterized by the conservation equations of multi-phase models. Drug delivery by microneedle array imposes additional requirements on the simulation procedures, including drug absorption by the blood capillaries and tissue cells, as well as a moving interface along its flowing pathway. The contribution o...
Source: Biomechanics and Modeling in Mechanobiology - July 30, 2009 Category: Biomedical Science Authors: Zhang R, Zhang P, Dalton C, Jullien GA Tags: Biomech Model Mechanobiol Source Type: journals

Cyclic strain inhibits acute pro-inflammatory gene expression in aortic valve interstitial cells.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In conclusion, cyclic strain reduces expression of pro-inflammatory genes, which may be beneficial for the in vitro pre-conditioning of tissue engineered heart valves. PMID: 19636599 [PubMed - as supplied by publisher] (Source: Biomechanics and Modeling in Mechanobiology)
Source: Biomechanics and Modeling in Mechanobiology - July 27, 2009 Category: Biomedical Science Authors: Smith KE, Metzler SA, Warnock JN Tags: Biomech Model Mechanobiol Source Type: journals

An innovative lattice Boltzmann model for simulating Michaelis-Menten-based diffusion-advection kinetics and its application within a cartilage cell bioreactor.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study presents a LBM for simulating diffusion-advection transport of substrate in a 2-D laminar flow. The model considers the substrate influx into a set of active cells placed inside the flow field. A new innovative method was used to simulate the cells activity using the LBM by means of Michaelis-Menten kinetics. The model is validated with some numerical benchmark problems and proved highly accurate results. After validation the model was used to simulate the transport of oxygen substrates that diffuse in water to feed a set of active cartilage cells inside a new designed bioreactor. PMID: 19633990 [PubMed - as...
Source: Biomechanics and Modeling in Mechanobiology - July 25, 2009 Category: Biomedical Science Authors: Moaty Sayed AA, Hussein MA, Becker T Tags: Biomech Model Mechanobiol Source Type: journals

Growth mixture model of distraction osteogenesis: effect of pre-traction stresses.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In tensional studies of bone fragments during limb lengthening, it is usually assumed that the stress level in the gap tissue before each distraction step (pre-traction stress) is rather modest. However, during the process of distraction osteogenesis, a large interfragmentary gap is generated and these pre-traction stresses may be important. To date, to the authors' knowledge, no computational study has been developed to assess the effect of stress accumulation during limb lengthening. In this work, we present a macroscopic growth mixture formulation to investigate the influence of pre-traction stresses on the outcome ...
Source: Biomechanics and Modeling in Mechanobiology - July 6, 2009 Category: Biomedical Science Authors: Reina-Romo E, Gómez-Benito MJ, García-Aznar JM, Domínguez J, Doblaré M Tags: Biomech Model Mechanobiol Source Type: journals

Evaluating patient-specific abdominal aortic aneurysm wall stress based on flow-induced loading.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper, we develop a physiologic wall stress analysis procedure by incorporating experimentally measured, non-uniform pressure loading in a patient-based finite element simulation. First, the distribution of wall pressure is measured in a patient-based lumen cast at a series of physiologically relevant steady flow rates. Then, using published equi-biaxial stress-deformation data from aneurysmal tissue samples, a nonlinear hyperelastic constitutive equation is used to describe the mechanical behavior of the aneurysm wall. The model accounts of the characteristic exponential stiffening due to the rapid engagement ...
Source: Biomechanics and Modeling in Mechanobiology - July 3, 2009 Category: Biomedical Science Authors: Dorfmann A, Wilson C, Edgar ES, Peattie RA Tags: Biomech Model Mechanobiol Source Type: journals

Application of the multiscale FEM to the modeling of cancellous bone.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This paper considers the application of multiscale finite element method (FEM) to the modeling of cancellous bone as an alternative for Biot's model, the main intention of which is to decrease the extent of the necessary laboratory tests. At the beginning, the paper gives a brief explanation of the multiscale concept and thereafter focuses on the modeling of the representative volume element and on the calculation of the effective material parameters, including an analysis of their change with respect to increasing porosity. The latter part of the paper concentrates on the macroscopic calculations, which is illustrated...
Source: Biomechanics and Modeling in Mechanobiology - June 30, 2009 Category: Biomedical Science Authors: Ilic S, Hackl K, Gilbert R Tags: Biomech Model Mechanobiol Source Type: journals

Mathematical model of flow in the vitreous humor induced by saccadic eye rotations: effect of geometry.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Saccadic eye rotations induce a flow in the vitreous humor of the eye. Any such flow is likely to have a significant influence on the dispersion of drugs injected into the vitreous chamber. The shape of this chamber deviates from a perfect sphere by up to 10-20% of the radius, which is predominantly due to an indentation caused by the lens. In this paper we investigate theoretically the effect of the domain shape upon the flow field generated by saccades by considering an idealized model. The posterior chamber geometry is assumed to be a sphere with a small indentation, undergoing prescribed small-amplitude sinusoidal ...
Source: Biomechanics and Modeling in Mechanobiology - May 26, 2009 Category: Biomedical Science Authors: Repetto R, Siggers JH, Stocchino A Tags: Biomech Model Mechanobiol Source Type: journals

A multiscale model for red blood cell mechanics.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The objective of this article is the derivation of a continuum model for mechanics of red blood cells via multiscale analysis. On the microscopic level, we consider realistic discrete models in terms of energy functionals defined on networks/lattices. Using concepts of Gamma-convergence, convergence results as well as explicit homogenisation formulae are derived. Based on a characterisation via energy functionals, appropriate macroscopic stress-strain relationships (constitutive equations) can be determined. Further, mechanical moduli of the derived macroscopic continuum model are directly related to microscopic moduli. As...
Source: Biomechanics and Modeling in Mechanobiology - May 6, 2009 Category: Biomedical Science Authors: Hartmann D Tags: Biomech Model Mechanobiol Source Type: journals

Effects of pH on transport properties of articular cartilages.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Articular cartilages swell and shrink depending on the ionic strength of the electrolyte they are in contact with. This electro-chemo-mechanical coupling is due to the presence of fixed electrical charges on proteoglycans (PGs). In addition, at nonphysiological pH, collagen fibers become charged. Therefore, variation of the pH of the electrolyte has strong implications on the electrical charge of cartilages and, by the same token, on their transport and mechanical properties. Articular cartilages are viewed as three-phase multi-species porous media. The constitutive framework is phrased in the theory of thermodynamics ...
Source: Biomechanics and Modeling in Mechanobiology - May 5, 2009 Category: Biomedical Science Authors: Loret B, Simões FM Tags: Biomech Model Mechanobiol Source Type: journals

Experimental study and constitutive modeling of the viscoelastic mechanical properties of the human prolapsed vaginal tissue.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper, the viscoelastic mechanical properties of vaginal tissue are investigated. Using previous results of the authors on the mechanical properties of biological soft tissues and newly experimental data from uniaxial tension tests, a new model for the viscoelastic mechanical properties of the human vaginal tissue is proposed. The structural model seems to be sufficiently accurate to guarantee its application to prediction of reliable stress distributions, and is suitable for finite element computations. The obtained results may be helpful in the design of surgical procedures with autologous tissue or prosthese...
Source: Biomechanics and Modeling in Mechanobiology - May 5, 2009 Category: Biomedical Science Authors: Peña E, Calvo B, Martínez MA, Martins P, Mascarenhas T, Jorge RM, Ferreira A, Doblaré M Tags: Biomech Model Mechanobiol Source Type: journals

Young's modulus of elasticity of Schlemm's canal endothelial cells.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Schlemm's canal (SC) endothelial cells are likely important in the physiology and pathophysiology of the aqueous drainage system of the eye, particularly in glaucoma. The mechanical stiffness of these cells determines, in part, the extent to which they can support a pressure gradient and thus can be used to place limits on the flow resistance that this layer can generate in the eye. However, little is known about the biomechanical properties of SC endothelial cells. Our goal in this study was to estimate the effective Young's modulus of elasticity of normal SC cells. To do so, we combined magnetic pulling cytometry of ...
Source: Biomechanics and Modeling in Mechanobiology - April 22, 2009 Category: Biomedical Science Authors: Zeng D, Juzkiw T, Read AT, Chan DW, Glucksberg MR, Ethier CR, Johnson M Tags: Biomech Model Mechanobiol Source Type: journals

An assessment of ductus venosus tapering and wave transmission from the fetal heart.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Pressure and flow pulsations in the fetal heart propagate through the precordial vein and the ductus venosus (DV) but are normally not transmitted into the umbilical vein (UV). Pulsations in the umbilical vein do occur, however, in early pregnancy and in pathological conditions. Such transmission into the umbilical vein is not well understood. In particular, the effect of the impedance changes in the DV due to its tapered geometry is not known. This paper presents a mathematical model that we developed to study the transmission of pulsations, originating in the fetal heart, through the DV to the umbilical vein. In our ...
Source: Biomechanics and Modeling in Mechanobiology - April 21, 2009 Category: Biomedical Science Authors: Hellevik LR, Vierendeels J, Kiserud T, Stergiopulos N, Irgens F, Dick E, Riemslagh K, Verdonck P Tags: Biomech Model Mechanobiol Source Type: journals

Darcian permeability constant as indicator for shear stresses in regular scaffold systems for tissue engineering.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The shear stresses in printed scaffold systems for tissue engineering depend on the flow properties and void volume in the scaffold. In this work, computational fluid dynamics (CFD) is used to simulate flow fields within porous scaffolds used for cell growth. From these models the shear stresses acting on the scaffold fibres are calculated. The results led to the conclusion that the Darcian (k (1)) permeability constant is a good predictor for the shear stresses in scaffold systems for tissue engineering. This permeability constant is easy to calculate from the distance between and thickness of the fibres used in a 3D ...
Source: Biomechanics and Modeling in Mechanobiology - April 10, 2009 Category: Biomedical Science Authors: Vossenberg P, Higuera GA, van Straten G, van Blitterswijk CA, van Boxtel AJ Tags: Biomech Model Mechanobiol Source Type: journals

Viscoelastic and failure properties of spine ligament collagen fascicles.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The microstructural volume fractions, orientations, and interactions among components vary widely for different ligament types. If these variations are understood, however, it is conceivable to develop a general ligament model that is based on microstructural properties. This paper presents a part of a much larger effort needed to develop such a model. Viscoelastic and failure properties of porcine posterior longitudinal ligament (PLL) collagen fascicles were determined. A series of subfailure and failure tests were performed at fast and slow strain rates on isolated collagen fascicles from porcine lumbar spine PLLs. A...
Source: Biomechanics and Modeling in Mechanobiology - March 24, 2009 Category: Biomedical Science Authors: Lucas SR, Bass CR, Crandall JR, Kent RW, Shen FH, Salzar RS Tags: Biomech Model Mechanobiol Source Type: journals

A novel model-gel-tissue assay analysis for comparing tumor elastic properties to collagen content.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In previous work, a new assay was realized for determining soft-tissue mechanical properties. The method, named the model-gel-tissue (MGT) assay, couples material testing with a finite element model built from a micro-CT image acquisition of a gel-embedded tissue specimen to determine its mechanical properties. Given recent reports demonstrating that increased stromal collagen promotes mammary tumor initiation and proliferation, in this paper, the MGT assay is used to evaluate the modulus of murine mammary tumors and is subsequently correlated quantitatively to type I collagen content. In addition, preliminary testing ...
Source: Biomechanics and Modeling in Mechanobiology - March 24, 2009 Category: Biomedical Science Authors: Barnes SL, Young PP, Miga MI Tags: Biomech Model Mechanobiol Source Type: journals

Markers of inflammation collocate with increased wall stress in human coronary arterial plaque.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study, we hypothesized that spatial relationships exist between the local mechanical environment and inflammatory marker expression in atherosclerotic plaques, and that these relationships are plaque-progression dependent. Histologic cross-sections were collected at regular intervals along the length of diseased human coronary arteries and classified as early, intermediate, advanced, or mature based on their morphological features. For each cross-section, the spatial distribution of stress was determined using a 2D heterogeneous finite element model, and the corresponding distribution of selected inflammatory marke...
Source: Biomechanics and Modeling in Mechanobiology - March 18, 2009 Category: Biomedical Science Authors: Hallow KM, Taylor WR, Rachev A, Vito RP Tags: Biomech Model Mechanobiol Source Type: journals

On the effect of sharp rises in blood pressure in the Shah-Humphrey model for intracranial saccular aneurysms.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We present numerical simulations showing that for some forcing terms the high-frequency oscillations do not die out with time, and a much more complex behaviour may emerge as a discontinuous forcing term is approached. The key point for this situation to occur is related to the derivative of the forcing term, supporting the hypothesis that sharper rises (or falls) in blood pressure may increase the risk of aneurysm rupture. PMID: 19219622 [PubMed - as supplied by publisher] (Source: Biomechanics and Modeling in Mechanobiology)
Source: Biomechanics and Modeling in Mechanobiology - February 15, 2009 Category: Biomedical Science Authors: Freitas P Tags: Biomech Model Mechanobiol Source Type: journals

Assessment of a mechano-regulation theory of skeletal tissue differentiation in an in vivo model of mechanically induced cartilage formation.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study tested an existing theory that shear strain and interstitial fluid flow govern skeletal tissue differentiation by applying this theory to a scenario in which a bending motion applied to a healing transverse osteotomy results in cartilage, rather than bone, formation. A 3-D finite element mesh was created from micro-computed tomography images of a bending-stimulated callus and was used to estimate the mechanical conditions present in the callus during the mechanical stimulation. Predictions regarding the patterns of tissues-cartilage, fibrous tissue, and bone-that formed were made based on the distributions of fl...
Source: Biomechanics and Modeling in Mechanobiology - January 21, 2009 Category: Biomedical Science Authors: Hayward LN, Morgan EF Tags: Biomech Model Mechanobiol Source Type: journals

Origin of axial prestretch and residual stress in arteries.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The structural protein elastin endows large arteries with unique biological functionality and mechanical integrity, hence its disorganization, fragmentation, or degradation can have important consequences on the progression and treatment of vascular diseases. There is, therefore, a need in arterial mechanics to move from materially uniform, phenomenological, constitutive relations for the wall to those that account for separate contributions of the primary structural constituents: elastin, fibrillar collagens, smooth muscle, and amorphous matrix. In this paper, we employ a recently proposed constrained mixture model of...
Source: Biomechanics and Modeling in Mechanobiology - January 3, 2009 Category: Biomedical Science Authors: Cardamone L, Valentín A, Eberth JF, Humphrey JD Tags: Biomech Model Mechanobiol Source Type: journals

Cell adhesion mechanisms and stress relaxation in the mechanics of tumours.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Tumour cells usually live in an environment formed by other host cells, extra-cellular matrix and extra-cellular liquid. Cells duplicate, reorganise and deform while binding each other due to adhesion molecules exerting forces of measurable strength. In this paper, a macroscopic mechanical model of solid tumour is investigated which takes such adhesion mechanisms into account. The extracellular matrix is treated as an elastic compressible material, while, in order to define the relationship between stress and strain for the cellular constituents, the deformation gradient is decomposed in a multiplicative way distinguis...
Source: Biomechanics and Modeling in Mechanobiology - December 30, 2008 Category: Biomedical Science Authors: Ambrosi D, Preziosi L Tags: Biomech Model Mechanobiol Source Type: journals

Simultaneous determination of mechanical properties and physiologic parameters in living rat brain.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Mechanical properties were determined in living adult rat brain. Reconstructed magnetic resonance images of the rat brain before and after 2 mm compression with a 4.06 mm diameter vinyl screw showed the total volumetric strain was maximal at the site of indentation. The pressure response to stepwise brain compression showed a linear relationship to the point of respiratory compromise. Instrumented indentation was performed on live brain with intact dura using a 4-mm-diameter flat punch indenter to a maximum depth 1.2 mm at loading-unloading rates not exceeding 0.34 N/min and 1.2 mm/min. The calculated elastic modulus s...
Source: Biomechanics and Modeling in Mechanobiology - December 27, 2008 Category: Biomedical Science Authors: Shulyakov AV, Fernando F, Cenkowski SS, Del Bigio MR Tags: Biomech Model Mechanobiol Source Type: journals

A reaction-diffusion model for long bones growth.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Bone development is characterized by differentiation and growth of chondrocytes from the proliferation zone to the hypertrophying one. These two cellular processes are controlled by a complex signalling regulatory loop between different biochemical signals, whose production depends on the current cell density, constituting a coupled cell-chemical system. In this work, a mathematical model of the process of early bone growth is presented, extending and generalizing other earlier approaches on the same topic. A reaction-diffusion regulatory loop between two chemical factors: parathyroid hormone-related peptide (PTHrP) an...
Source: Biomechanics and Modeling in Mechanobiology - December 24, 2008 Category: Biomedical Science Authors: Garzón-Alvarado DA, García-Aznar JM, Doblaré M Tags: Biomech Model Mechanobiol Source Type: journals

Modeling protein-mediated morphology in biomembranes.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The equilibrium theory for lipid membranes is used to describe the structure of nuclear pores and the membrane shapes accompanying endocytosis. The commonly used variant of the theory contains a fixed parameter called the spontaneous curvature which accounts for asymmetry in the bending response of the membrane. This is replaced here by a variable distribution of spontaneous curvature representing the influence of attached proteins. The required adjustments to the standard theory are described and the resulting model is applied to the study of membrane morphology at the cites of protein-assisted nuclear pore formation ...
Source: Biomechanics and Modeling in Mechanobiology - November 13, 2008 Category: Biomedical Science Authors: Agrawal A, Steigmann DJ Tags: Biomech Model Mechanobiol Source Type: journals

The modelling of fibre reorientation in soft tissue.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this paper, a hyperelastic and thermodynamically consistent model for soft tissue is developed that is able to describe the change of the initial orientation of the collagen fibres. Full numerical implementation is considered as well. The collagen architecture is assumed to reorient driven by a specific thermodynamical force. The anisotropy is described by a strain energy function, which is decomposed into a part related to the matrix and a part related to the fibres. The initial fibre orientation is defined by a structural tensor, while the current orientation is described by a time-dependent structural tensor, whi...
Source: Biomechanics and Modeling in Mechanobiology - November 13, 2008 Category: Biomedical Science Authors: Karšaj I, Sansour C, Sorić J Tags: Biomech Model Mechanobiol Source Type: journals

Letter to the Editor commenting on "Multilevel finite element modeling for the prediction of local cellular deformation in bone," Deligianni DD and Apostolopoulos CA (2008) Biomech Model Mechanobiol 7(2):151-159.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
PMID: 18998179 [PubMed - as supplied by publisher] (Source: Biomechanics and Modeling in Mechanobiology)
Source: Biomechanics and Modeling in Mechanobiology - November 9, 2008 Category: Biomedical Science Authors: Viceconti M, Taddei F, Schileo E Tags: Biomech Model Mechanobiol Source Type: journals

Reply to the Letter to the Editor commenting on "Multilevel finite element modeling for the prediction of local cellular deformation in bone by Deligianni DD and Apostolopoulos CA (2008) Biomech Model Mechanobiol 7(2):151-159"Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
PMID: 18998180 [PubMed - as supplied by publisher] (Source: Biomechanics and Modeling in Mechanobiology)
Source: Biomechanics and Modeling in Mechanobiology - November 9, 2008 Category: Biomedical Science Authors: Deligianni DD, Apostolopoulos CA Tags: Biomech Model Mechanobiol Source Type: journals

Spherical indentation of soft matter beyond the Hertzian regime: numerical and experimental validation of hyperelastic models.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The lack of practicable nonlinear elastic contact models frequently compels the inappropriate use of Hertzian models in analyzing indentation data and likely contributes to inconsistencies associated with the results of biological atomic force microscopy measurements. We derived and validated with the aid of the finite element method force-indentation relations based on a number of hyperelastic strain energy functions. The models were applied to existing data from indentation, using microspheres as indenters, of synthetic rubber-like gels, native mouse cartilage tissue, and engineered cartilage. For the biological tiss...
Source: Biomechanics and Modeling in Mechanobiology - November 2, 2008 Category: Biomedical Science Authors: Lin DC, Shreiber DI, Dimitriadis EK, Horkay F Tags: Biomech Model Mechanobiol Source Type: journals

Kidney damage in extracorporeal shock wave lithotripsy: a numerical approach for different shock profiles.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In shock-wave lithotripsy-a medical procedure to fragment kidney stones-the patient is subjected to hypersonic waves focused at the kidney stone. Although this procedure is widely applied, the physics behind this medical treatment, in particular the question of how the injuries to the surrounding kidney tissue arise, is still under investigation. To contribute to the solution of this problem, two- and three-dimensional numerical simulations of a human kidney under shock-wave loading are presented. For this purpose a constitutive model of the bio-mechanical system kidney is introduced, which is able to map large visco-e...
Source: Biomechanics and Modeling in Mechanobiology - September 18, 2008 Category: Biomedical Science Authors: Weinberg K, Ortiz M Tags: Biomech Model Mechanobiol Source Type: journals

Modeling distraction osteogenesis: analysis of the distraction rate.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Distraction osteogenesis is a useful technique aimed at inducing bone formation in widespread clinical applications. One of the most important factors that conditions the success of bone regeneration is the distraction rate. Since the mechanical environment around the osteotomy site is one of the main factors that affects both quantity and quality of the regenerated bone, we have focused on analyzing how the distraction rate influences on the mechanical conditions and tissue regeneration. Therefore, the aim of the present work is to explore the potential of a mathematical algorithm to simulate clinically observed distr...
Source: Biomechanics and Modeling in Mechanobiology - September 16, 2008 Category: Biomedical Science Authors: Reina-Romo E, Gómez-Benito MJ, García-Aznar JM, Domínguez J, Doblaré M Tags: Biomech Model Mechanobiol Source Type: journals

Computational modeling of volumetric soft tissue growth: application to the cardiac left ventricle.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
As an initial step to investigate stimulus-response relations in growth and remodeling (G&R) of cardiac tissue, this study aims to develop a method to simulate 3D-inhomogeneous volumetric growth. Growth is regarded as a deformation that is decomposed into a plastic component which describes unconstrained growth and an elastic component to satisfy continuity of the tissue after growth. In current growth models, a single reference configuration is used that remains fixed throughout the entire growth process. However, considering continuous turnover to occur together with growth, such a fixed reference is unlikely to ...
Source: Biomechanics and Modeling in Mechanobiology - August 30, 2008 Category: Biomedical Science Authors: Kroon W, Delhaas T, Arts T, Bovendeerd P Tags: Biomech Model Mechanobiol Source Type: journals

Probing the influence of myelin and glia on the tensile properties of the spinal cord.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Although glia have been historically classified as the structurally supporting cells of the central nervous system, their role in tissue mechanics is still largely unstudied. The influence of myelin and glia on the mechanical properties of spinal cord tissue was examined by testing embryonic day 18 chick embryo spinal cords in uniaxial tension following disruption of the glial matrix using either ethidium bromide (EB) or an antibody against galactocerebroside (alphaGalC) in the presence of complement. Demyelination was confirmed by myelin basic protein immunoreactivity and quantified using osmium tetroxide staining. A ...
Source: Biomechanics and Modeling in Mechanobiology - August 23, 2008 Category: Biomedical Science Authors: Shreiber DI, Hao H, Elias RA Tags: Biomech Model Mechanobiol Source Type: journals

Multi-axial mechanical properties of human trabecular bone.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In the context of osteoporosis, evaluation of bone fracture risk and improved design of epiphyseal bone implants rely on accurate knowledge of the mechanical properties of trabecular bone. A multi-axial loading chamber was designed, built and applied to explore the compressive multi-axial yield and strength properties of human trabecular bone from different anatomical locations. A thorough experimental protocol was elaborated for extraction of cylindrical bone samples, assessment of their morphology by micro-computed tomography and application of different mechanical tests: torsion, uni-axial traction, uni-axial compre...
Source: Biomechanics and Modeling in Mechanobiology - August 9, 2008 Category: Biomedical Science Authors: Rincón-Kohli L, Zysset PK Tags: Biomech Model Mechanobiol Source Type: journals

Dynamic compression inhibits fibronectin fragment induced iNOS and COX-2 expression in chondrocyte/agarose constructs.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study examined the combined effects of dynamic compression and the NH(2)-hep I or COOH-hep II FN-fs on the expression levels of iNOS and COX-2 and production of (.)NO and PGE(2) release. Both types of fragments induced iNOS and COX-2 expression and stimulated the production of (.)NO release. This response was inhibited by dynamic compression. Inhibitor experiments indicated that both dynamic compression and the iNOS inhibitor were important in restoring cell proliferation and proteoglycan synthesis in the presence of the FN-fs. This is the first study which demonstrates a downregulation of the FN-f-induced iNOS and CO...
Source: Biomechanics and Modeling in Mechanobiology - August 3, 2008 Category: Biomedical Science Authors: Raveenthiran SP, Chowdhury TT Tags: Biomech Model Mechanobiol Source Type: journals

An extended biphasic model for charged hydrated tissues with application to the intervertebral disc.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Finite element models for hydrated soft biological tissue are numerous but often exhibit certain essential deficiencies concerning the reproduction of relevant mechanical and electro-chemical responses. As a matter of fact, singlephasic models can never predict the interstitial fluid flow or related effects like osmosis. Quite a few models have more than one constituent, but are often restricted to the small-strain domain, are not capable of capturing the intrinsic viscoelasticity of the solid skeleton, or do not account for a collagen fibre reinforcement. It is the goal of this contribution to overcome these drawbacks...
Source: Biomechanics and Modeling in Mechanobiology - July 27, 2008 Category: Biomedical Science Authors: Ehlers W, Karajan N, Markert B Tags: Biomech Model Mechanobiol Source Type: journals

Residual stress in the adult mouse brain.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This work provides direct evidence that sustained tensile stress exists in white matter of the mature mouse brain. This finding has important implications for the mechanisms of brain development, as tension in neural axons has been hypothesized to drive cortical folding in the human brain. In addition, knowledge of residual stress is required to fully understand the mechanisms behind traumatic brain injury and changes in mechanical properties due to aging and disease. To estimate residual stress in the brain, we performed serial dissection experiments on 500-mum thick coronal slices from fresh adult mouse brains and de...
Source: Biomechanics and Modeling in Mechanobiology - July 24, 2008 Category: Biomedical Science Authors: Xu G, Bayly PV, Taber LA Tags: Biomech Model Mechanobiol Source Type: journals

Collagen-related gene and protein expression changes in the lung in response to chronic hypoxia.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Collagen accumulation likely contributes to increased vascular and airway impedance in hypoxia-induced pulmonary hypertension (HPH). Collagen exists in multiple subtypes and can accumulate via increased synthesis or decreased degradation. To better understand the individual contributions of fibrillar (FB) and basement membrane (BM) collagen, matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) to pulmonary vascular and airway remodeling in HPH, we investigated the temporal changes in gene and protein expression in the lungs of mice exposed to hypoxia for 0, 3, 6, 10 and 15 days. The earliest and large...
Source: Biomechanics and Modeling in Mechanobiology - July 20, 2008 Category: Biomedical Science Authors: Estrada KD, Chesler NC Tags: Biomech Model Mechanobiol Source Type: journals

Combined computational study of mechanical behaviour and drug delivery from a porous, hydroxyapatite-based bone graft.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This paper presents a numerical model of a porous, hydroxyapatite-based bone graft also suitable as a drug delivery device. The graft was positioned in different sites and with different porosities inside a human femur model. The structural analyses were carried out to verify the graft mechanical strength, using the Tsai-Wu criterion, and the maximum porosity at which static failure does not occur. A local stress shielding risk was also calculated as the ratio between the bone stress in the intact condition and the stress after implantation of the graft. Drug release kinetics was calculated by means of the finite eleme...
Source: Biomechanics and Modeling in Mechanobiology - July 17, 2008 Category: Biomedical Science Authors: Galbusera F, Bertolazzi L, Balossino R, Dubini G Tags: Biomech Model Mechanobiol Source Type: journals

A structural constitutive model for the human lens capsule.Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Published data on the mechanical performance of the human lens capsule when tested under uniaxial and biaxial conditions are reviewed. It is concluded that two simple phenomenological constitutive models (namely a linear elastic model and a Fung-type hyperelastic model) are unable to provide satisfactory representations of the mechanical behaviour of the capsule for both of these loading conditions. The possibility of resolving these difficulties using a structural constitutive model for the capsule, of a form that is inspired by the network of collagen IV filaments that exist within the lens capsule, is explored. The ...
Source: Biomechanics and Modeling in Mechanobiology - July 13, 2008 Category: Biomedical Science Authors: Burd HJ Tags: Biomech Model Mechanobiol Source Type: journals