scholarly journals A constituent-based model of age-related changes in conduit arteries

2011 ◽  
Vol 301 (4) ◽  
pp. H1286-H1301 ◽  
Author(s):  
Alkiviadis Tsamis ◽  
Alexander Rachev ◽  
Nikos Stergiopulos
Keyword(s):  
Mechanical Properties ◽  
Time Course ◽  
Present Report ◽  
Finite Elasticity ◽  
Mixture Theory ◽  
Constrained Mixture Theory ◽  
Age Related ◽  
Constrained Mixture ◽  
Arterial Tissue ◽  
Age Related Changes

In the present report, a constituent-based theoretical model of age-related changes in geometry and mechanical properties of conduit arteries is proposed. The model was based on the premise that given the time course of the load on an artery and the accumulation of advanced glycation end-products in the arterial tissue, the initial geometric dimensions and properties of the arterial tissue can be predicted by a solution of a boundary value problem for the governing equations that follow from finite elasticity, structure-based constitutive modeling within the constrained mixture theory, continuum damage theory, and global growth approach for stress-induced structure-based remodeling. An illustrative example of the age-related changes in geometry, structure, composition, and mechanical properties of a human thoracic aorta is considered. Model predictions were in good qualitative agreement with available experimental data in the literature. Limitations and perspectives for refining the model are discussed.

scholarly journals A Two-Dimensional Model of Hypertension-Induced Arterial Remodeling With Account for Stress Interaction Between Elastin and Collagen

2019 ◽  
Vol 142 (4) ◽  
Author(s):  
Alexander Rachev ◽  
Tarek Shazly
Keyword(s):  
Mixture Theory ◽  
Natural State ◽  
Arterial Remodeling ◽  
Two Dimensional ◽  
Structural Reorganization ◽  
Constrained Mixture Theory ◽  
Novel Structure ◽  
Constrained Mixture ◽  
Arterial Tissue ◽  
The Individual

Abstract We propose a novel structure-based two-dimensional (2D) mathematical model of hypertension-induced arterial remodeling. The model is built in the framework of the constrained mixture theory and global growth approach, utilizing a recently proposed structure-based constitutive model of arterial tissue that accounts for the individual natural configurations of and stress interaction between elastin and collagen. The basic novel predictive result is that provided remodeling causes a change in the elastin/collagen mass fraction ratio, it leads to a structural reorganization of collagen that manifests as an altered fiber undulation and a change in direction of the helically oriented fibers in the tissue natural state. Results obtained from the illustrative simulations for a porcine renal artery show that when remodeling is complete the collagen reorganization might have significant effects on the initial arterial geometry and mechanical properties of the arterial tissue. The proposed model has potential to describe and advance mechanistic understanding of adaptive arterial remodeling, promote the continual refinement of mathematical models of arterial remodeling, and provide motivation for new avenues of experimental investigation.

Ageing Changes in the Tensile Properties of Tendons: Influence of Collagen Fibril Volume Fraction

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
K. L. Goh ◽  
D. F. Holmes ◽  
H.-Y. Lu ◽  
S. Richardson ◽  
K. E. Kadler ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Collagen Fibril ◽  
Volume Fraction ◽  
Area Fraction ◽  
Sectional Area ◽  
Cross Sectional ◽  
P Values ◽  
Age Related ◽  
Fibril Diameter ◽  
Age Related Changes

Connective tissues are biological composites comprising of collagen fibrils embedded in (and reinforcing) the hydrated proteoglycan-rich (PG) gel within the extracellular matrices (ECMs). Age-related changes to the mechanical properties of tissues are often associated with changes to the structure of the ECM, namely, fibril diameter. However, quantitative attempts to correlate fibril diameter to mechanical properties have yielded inconclusive evidence. Here, we described a novel approach that was based on the rule of mixtures for fiber composites to evaluate the dependence of age-related changes in tendon tensile strength (σ) and stiffness (E) on the collagen fibril cross-sectional area fraction (ρ), which is related to the fibril volume fraction. Tail tendons from C57BL6 mice from age groups 1.6–35.3months old were stretched to failure to determine σ and E. Parallel measurements of ρ as a function of age were made using transmission electron microscopy. Mathematical models (rule of mixtures) of fibrils reinforcing a PG gel in tendons were used to investigate the influence of ρ on ageing changes in σ and E. The magnitudes of σ, E, and ρ increased rapidly from 1.6monthsto4.0months (P-values <0.05) before reaching a constant (age independent) from 4.0monthsto29.0months (P-values >0.05); this trend continued for E and ρ (P-values >0.05) from 29.0monthsto35.3months, but not for σ, which decreased gradually (P-values <0.05). Linear regression analysis revealed that age-related changes in σ and E correlated positively to ρ (P-values <0.05). Collagen fibril cross-sectional area fraction ρ is a significant predictor of ageing changes in σ and E in the tail tendons of C57BL6 mice.

scholarly journals Decorin expression is important for age-related changes in tendon structure and mechanical properties

2013 ◽  
Vol 32 (1) ◽  
pp. 3-13 ◽  
Author(s):  
Andrew A. Dunkman ◽  
Mark R. Buckley ◽  
Michael J. Mienaltowski ◽  
Sheila M. Adams ◽  
Stephen J. Thomas ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Age Related ◽  
Age Related Changes

scholarly journals Age-related changes in the mechanical properties of the epimysium in skeletal muscles of rats

2008 ◽  
Vol 41 (2) ◽  
pp. 465-469 ◽  
Author(s):  
Yingxin Gao ◽  
Tatiana Y. Kostrominova ◽  
John A. Faulkner ◽  
Alan S. Wineman
Keyword(s):  
Mechanical Properties ◽  
Skeletal Muscles ◽  
Age Related ◽  
Age Related Changes

Influence of Badminton Practice on Age-Related Changes in Patellar and Achilles Tendons

2020 ◽  
pp. 1-9
Author(s):  
Alfredo Bravo-Sánchez ◽  
Pablo Abián ◽  
Filipa Sousa ◽  
Fernando Jimenez ◽  
Javier Abián-Vicén
Keyword(s):  
Mechanical Properties ◽  
Achilles Tendon ◽  
Age Groups ◽  
Control Group ◽  
Physically Active ◽  
Tendon Stiffness ◽  
Sport Practice ◽  
Age Related ◽  
Age Related Changes

Regular sport practice could prevent age-related changes in tendinous tissues. The purpose of the study was to investigate the effect of regular badminton practice on patellar and Achilles tendon mechanical properties in senior competitive badminton players (>35 years old) and to compare the results with physically active people matched by age. One hundred ninety-two badminton players and 193 physically active people were divided by age into four groups, between 35 and 44 (U45), between 45 and 54 (U55), between 55 and 64 (U65), and over 65 (O65) years old. A LogiqS8 transducer in elastography mode and a MyotonPRO myotonometer were used to assess patellar and Achilles mechanical properties. Achilles tendon stiffness was higher in the control group than the badminton players for the U45, U55, and O65 age groups (p < .01). Also, the elastography index was higher in the control group than the badminton players for the U45, U55, U65, and O65 age groups (p < .05). In conclusion, regular badminton practice could prevent the decline in mechanical properties of the patellar and Achilles tendons.

scholarly journals Age-related changes in deformability of human erythrocytes

Blood ◽  
1985 ◽  
Vol 65 (2) ◽  
pp. 275-282 ◽  
Author(s):  
SP Sutera ◽  
RA Gardner ◽  
CW Boylan ◽  
GL Carroll ◽  
KC Chang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Time Course ◽  
Dynamic Equilibrium ◽  
Chemical Properties ◽  
Significant Loss ◽  
Human Erythrocytes ◽  
Mean Corpuscular Hemoglobin ◽  
Mean Cell Volume ◽  
Age Related ◽  
Age Related Changes

Abstract The present study was designed to further the characterization of age- related changes in the deformability of human erythrocytes. The top (approximately young) and bottom (approximately old) 10% fractions of density-separated red cells from ten normal donors were subjected to graded levels of shear stress in a rheoscope. Measurements were made of steady-state elongation (cells tank treading in a state of dynamic equilibrium) and the time course of shape recovery following abrupt cessation of shear. In parallel with the rheologic experiments, several physical and chemical properties were assayed to determine correlates of mechanical properties. These included mean cell volume, mean corpuscular hemoglobin concentration, type A1 hemoglobin, glucosylation of membrane proteins, and membrane phospholipid and protein concentration. The microrheologic observations revealed that only about 90% of the old cells retained their capacity to tank tread. However, the tank-treading cells elongated less than their younger counterparts at corresponding levels of shear stress, thus demonstrating a reduced level of deformability. Further analysis of the data indicates that increases in membrane viscosity and elastic modulus along with a significant loss in excess surface area contribute to the limitation of the ability of the older cells to change shape.

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