Effect of Hypertension on Elasticity and Geometry of Aortic Tissue From Dogs

1990 ◽  
Vol 112 (1) ◽  
pp. 70-74 ◽  
Author(s):  
Ramesh N. Vaishnav ◽  
Jafar Vossoughi ◽  
Dali J. Patel ◽  
LaVal N. Cothran ◽  
Bernell R. Coleman ◽  
...  
Keyword(s):  
Longitudinal Direction ◽  
Circumferential Direction ◽  
Tissue Response ◽  
Aortic Tissue ◽  
External Diameter ◽  
Extension Ratio ◽  
Axial Forces ◽  
Bilateral Renal Artery ◽  
Longitudinal Extension ◽  
Geometric Changes

Inflation-extension experiments were carried out on segments of the descending thoracic aortas from 4 normotensive and 4 hypertensive dogs rendered hypertensive using either unilateral or bilateral renal artery constriction. Intravascular pressures up to 200 mm Hg and axial forces up to 200 g were used. The external diameter of the segment and the distance between two longitudinally spaced gage marks were recorded photographically at each pressure-force level combination. Dimensions in the undeformed configuration were measured at the end of the inflation-extension experiment. Data were analyzed for changes in geometry and force-deformation response. Results indicate that: 1. Under sustained hypertension the wall thickness in the undeformed configuration increases with a concurrent reduction in the in-situ longitudinal extension ratio. 2. This dual tissue response accomplishes substantial reductions in the circumferential and longitudinal stresses from the levels that would be reached at equivlaent pressures in the absence of these geometric changes. 3. At comparable intravascular pressures the extensibility in the circumferential direction is slightly greater for the hypertensive aortas as compared to normals. However, the stress-extension ratio relationship in the circumferential direction is similar in the two groups. 4. The stress-extension ratio relationship in the longitudinal direction indicates that the hypertensive aorta is stiffer than its normotensive counterpart.

scholarly journals Effect of alkaline solutions on the tensile properties of glass-polyester pipes

2011 ◽  
pp. 185-195 ◽  
Author(s):  
Slavisa Putic ◽  
Marina Stamenovic ◽  
Jelena Petrovic ◽  
Marko Rakin ◽  
Bojan Medjo
Keyword(s):  
Tensile Properties ◽  
Construction Materials ◽  
Ammonium Hydroxide ◽  
Longitudinal Direction ◽  
Testing Procedure ◽  
Circumferential Direction ◽  
Process Equipment ◽  
Alkaline Solutions ◽  
Ph Values ◽  
Definite Structure

Construction materials, traditionally used in process equipment, are today successfully replaced by composite materials. Hence, many pipes are made of these materials. The subject of this study was the influence of liquids on the state of stresses and tensile strengths in the longitudinal and circumferential direction of glass-polyester pipes of a definite structure and known fabrication process. These analyses are of great importance for the use of glass-polyester pipes in the chemical industry. The tensile properties (the ultimate tensile strength and the modulus of elasticity) were tested and determined for specimens cut out of the pipes; flat specimens for the tensile properties in the longitudinal direction and ring specimens for the tensile properties in the circumferential direction. First, the tension test was performed on virgin samples (without the influence of any liquid), to obtain knowledge about the original tensile properties of the material composite studied. Subsequently, the specimens were soaked in alkaline solutions: sodium hydroxide (strong alkali) and ammonium hydroxide (weak alkali). These solutions were selected because of their considerable difference in pH values. The specimens and rings were left for 3, 10, 30 and 60 days in each liquid at room temperature. Then, the samples were tested on tension by the standard testing procedure. A comparison of the obtained results was made based on the pH values of the aggressive media in which the examined material had been soaked, as well as based on the original tensile properties and the number of days of treatment. Micromechanical analyses of sample breakage helped in the elucidation of the influence of the liquids on the structure of the composite pipe and enabled models and mechanisms that produced the change of strength to be proposed.

scholarly journals Experimental investigations of the human oesophagus: anisotropic properties of the muscular layer in large deformation

2021 ◽  
Author(s):  
Ciara Durcan ◽  
Mokarram Hossain ◽  
Gregory Chagnon ◽  
Djordje Peric ◽  
Lara Bsiesy ◽  
...  
Keyword(s):  
Strain Rate ◽  
Ex Vivo ◽  
Longitudinal Direction ◽  
Tensile Tests ◽  
Endoscopic Biopsy ◽  
Circumferential Direction ◽  
Experimental Investigations ◽  
Uniaxial Tensile ◽  
Rate Dependency ◽  
Muscular Layer

Technological advancements in the field of robotics have led to endoscopic biopsy devices able to extract diseased tissue from between the layers of the gastrointestinal tract. Despite this, the layer-dependent properties of these tissues have yet to be mechanically characterised using human tissue. In this study, the ex vivo mechanical properties of the passive muscularis propia layer of the human oesophagus were extensively investigated. For this, a series of uniaxial tensile tests were conducted. The results displayed hyperelastic behaviour, while the differences between loading the tissue in both the longitudinal and circumferential directions showcased its anisotropy. The anisotropy of the muscular layer was present at different strain rates, with the longitudinal direction being consistently stiffer than the circumferential one. The circumferential direction was found to have little strain-rate dependency, while the longitudinal direction results suggest pronounced strain-rate-dependent behaviour. The repeated trials showed larger variation in terms of stress for a given strain in the longitudinal direction compared to the circumferential direction. The possible causes of variation between trials are discussed, and the experimental findings are linked to the histological analysis which was carried out via various staining methods. Finally, the direction-dependent experimental data was simulated using an anisotropic, hyperelastic model.

Effect of Cold Storage on Mechanical Properties of Aorta

2015 ◽  
Author(s):  
Shijia Zhao ◽  
John Lof ◽  
Shelby Kutty ◽  
Linxia Gu
Keyword(s):  
Mechanical Properties ◽  
Uniaxial Tension ◽  
Cold Storage ◽  
Elastic Moduli ◽  
Heart Diseases ◽  
Axial Direction ◽  
Circumferential Direction ◽  
Control Group ◽  
Aortic Tissue ◽  
Tension Tests

Aortic allografts have been widely used in treatments of congenital heart diseases with satisfactory clinical outcomes. They were usually cryopreserved and stored for surgical use. The objective of this work was to investigate the effect of cold storage on mechanical properties of aorta, since the compliance mismatch was one important factor associated with the complication after graft surgery. The segments of porcine descending aorta were divided into two groups: the fresh samples which were tested within 24 hours after harvesting served as control group, and frozen samples which were stored in −20°C for 7 days and then thawed. The uniaxial tension tests along circumferential direction and indentation tests were conducted. The average incremental elastic moduli within each stretch range were obtained from the experimental data obtained during tension tests, and the elastic moduli were also calculated by fitting the force-indentation depth data to Hertz model when the tissue was stretched at 1.0, 1.2, 1.4 and 1.6. In addition, the average incremental elastic moduli of both fresh and frozen aortic tissue along axial direction were also obtained by using uniaxial tension tests. The comparison showed that cold storage definitely increased the average incremental elastic modulus of the aortic tissue along circumferential direction; however, the difference is not significant for the elastic moduli along axial direction.

Abstract 368: Biomechanical Properties of Scar ECM: from the Acute to Chronic Stages of Myocardial Infarction

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Bryn Brazile ◽  
J. R Butler ◽  
Sourav Patnaik ◽  
Yanyi Xu ◽  
Andrew Claude ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Heart Function ◽  
Sodium Dodecyl ◽  
Longitudinal Direction ◽  
Biomechanical Properties ◽  
Circumferential Direction ◽  
Heart Cell ◽  
Coronary Artery Ligation ◽  
Artery Ligation ◽  
Biaxial Behavior

Introduction: Myocardial infarction (MI) affects more than 8 million Americans, causing massive heart cell death and heart function decrease. To better understand the scar biomechanics, we characterized the mechanical properties of pure scar ECM, obtained by decellularizing the MI tissues. Materials and Methods: Infarcted rat hearts were generated by a permanent left coronary artery ligation (PLCAL) and harvested at 15 min, 1, 2, and 4 weeks (per acute to chronic stages of MI)(N = 6 each). Scar ECM were obtained by decellularizing the infarcted hearts in 0.1% sodium dodecyl sulfate (SDS) solution for 3 weeks. Scar ECM specimens were trimmed into square shape, and then subjected to biaxial testing with one edge aligned with the circumferential direction and the other edge aligned with the longitudinal direction of the rat heart. After 10 cycle preconditioning, an equibiaxial tension protocol of T circ : T rad = 30:30 N/m was performed to capture the tissue biaxial behavior. Results and Discussion: Scar ECM 15 minutes through 4 weeks post infarction showed a stiffening biaxial behavior along with the time (Fig.1). The decrease of extensibility along longitudinal direction was more noticeable than circumferential direction, which led to a decrease in degree of anisotropy. Conclusions: Scar ECM biomechanics showed a stiffening behavior with a marked reduction in extensibility (longitudinal) with time. This change in biomechanical properties can be correlated to the collagen structure changes with progression of MI. Knowledge of the structural-mechanical relationship of scar ECM will help us understand MI progression and help formulate regenerative therapies.

High rate failure properties of human aortic tissue under longitudinal extension

2018 ◽  
Vol 4 (2/3) ◽  
pp. 125 ◽  
Author(s):  
Piyush Gaur ◽  
Khyati Verma ◽  
Anoop Chawla ◽  
Sudipto Mukherjee ◽  
Sanjeev Lalwani ◽  
...  
Keyword(s):  
High Rate ◽  
Aortic Tissue ◽  
Failure Properties ◽  
Longitudinal Extension

scholarly journals Biomechanical Properties of Human Dilated Ascending Aorta

2019 ◽  
Vol 73 (2) ◽  
pp. 107-111
Author(s):  
Ivars Brečs ◽  
Pēteris Stradiņš ◽  
Mārtiņš Kalējs ◽  
Uldis Strazdiņš ◽  
Iveta Ozolanta ◽  
...  
Keyword(s):  
Modulus Of Elasticity ◽  
Linear Part ◽  
Longitudinal Direction ◽  
Biomechanical Properties ◽  
Ascending Aorta ◽  
Circumferential Direction ◽  
Human Aorta ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Tangential Modulus

Abstract Aneurysms of ascending aorta are dilatation of the first part of the human aorta. They commonly show no clinical symptoms. This condition increases the risk of aorta dissection, which is a life-threatening condition. In this study we attempted to elucidate the changes in the biomechanical properties that occur in the dilated human ascending aorta. Fourteen specimens of ascending aorta wall were mechanically tested under a uniaxial tensile test. Two specimens from each ascending aorta anterior region were cut in longitudinal and circumferential directions. The samples were stretched until rupture of the sample occurred. The obtained experimental data were processed to determine maximal stress, maximal strain and the tangential modulus of elasticity in the linear part of the stress-strain curve. The obtained results showed a remarkable anisotropy of the ascending aorta tissue. We found higher strength of the tissue in the circumferential direction than in the longitudinal direction. There were no statistically significant differences between the strains of the samples. Tangential modulus of elasticity of the aortic samples in the longitudinal direction was significantly lower than the elastic modulus of the samples in the circumferential direction. The tissue in the circumferential direction is stronger and stiffer than in the longitudinal direction.

Characterization of the Gel-Spun Tubular Scaffold for Cardiovascular Tissue Engineering

2007 ◽  
Vol 342-343 ◽  
pp. 321-324
Author(s):  
Eun Na Chung ◽  
Sang Heon Kim ◽  
Young Gun Ko ◽  
Jae Hyun Kwon ◽  
Jeong Woo Han ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Degradation Rate ◽  
Longitudinal Direction ◽  
Circumferential Direction ◽  
Gel Spinning ◽  
Sem Images ◽  
Fibrous Scaffold ◽  
Cardiovascular Tissue ◽  
Degradation Rates ◽  
Cardiovascular Tissue Engineering

A tubular and fibrous scaffold was fabricated from an elastic polymer, poly (L-lactideco- ε-caprolactone) (PLCL; Mn 193,813, Mw 538,623) 50:50 by using a novel gel spinning apparatus. To characterize the gel-spun scaffold, we investigated morphology, tensile property, tissue in-growth rate and degradation rate. From SEM images, fibrous structure in the scaffold wasn’t fabricated well in the condition of 4% gel concentration. In general, the thickness level of microfibers increased as the gel concentration increased. In addition, the gel-spun scaffolds showed stronger tensile properties in the circumferential direction than the longitudinal direction. 5%, 7.5%, 10% and 12.5% scaffolds were analyzed in both directions: circumferential direction and longitudinal direction. On the other hand, the gel-spun scaffolds have been implanted in mouse to examine the degradation rate in vivo and tissue in-growth aspects, compared to extruded scaffolds. Both shows very similar degradation rates, but the aspect in tissue in-growth was different. In conclusion, gel-spun PLCL scaffolds have good characteristics as a plausible scaffold for cardiovascular tissue engineering.

High rate failure properties of human aortic tissue under longitudinal extension

2018 ◽  
Vol 4 (2/3) ◽  
pp. 125
Author(s):  
Ravi Kiran Chitteti ◽  
Pronoy Ghosh ◽  
Christian Mayer ◽  
Sudipto Mukherjee ◽  
Sanjeev Lalwani ◽  
...  
Keyword(s):  
High Rate ◽  
Aortic Tissue ◽  
Failure Properties ◽  
Longitudinal Extension

MECHANICAL CHARACTERIZATION OF SPINAL DURA USING A PD-CONTROLLED BIAXIAL TENSILE TESTER

2020 ◽  
Vol 20 (05) ◽  
pp. 2050023
Author(s):  
ATSUTAKA TAMURA ◽  
WATARU YANO ◽  
DAICHI YOSHIMURA ◽  
SOICHIRO NISHIKAWA
Keyword(s):  
Dura Mater ◽  
Mechanical Response ◽  
Longitudinal Direction ◽  
Mechanical Tests ◽  
Circumferential Direction ◽  
Lumbar Region ◽  
Biaxial Tensile ◽  
Tensile Tester ◽  
Significant Difference ◽  
Upper Thoracic

In this study, we developed an equi-load biaxial tensile tester and applied it to a series of mechanical tests using specimens obtained from the porcine spinal dura mater. The dural sample exhibited a nonlinear and anisotropic behavior as it was more deformable in the longitudinal direction rather than in the circumferential direction at lower strains; i.e., mechanical response of the longitudinal direction was significantly compliant in the Toe region compared to that of the circumferential direction under 1:1 biaxial stretching. However, we have not observed a significant difference with respect to the resultant strain and Young’s modulus between the longitudinal and circumferential directions at higher strains or in the Linear region. Our results also indicated that the upper thoracic region (T1) was relatively compliant compared to the lumbar region (L), where the failure load was almost equal between them because the dural thickness of T1 was five-fold greater than that of L; i.e., spinal dura mater became stiffer and stronger at further distances from the brain. This shows structural effectiveness and may be preferable to mechanically protect the vulnerable spinal cord from externally applied impact loads.

Right and left ventricular wall deformation patterns in normal and left heart hypoplasia chick embryos

2000 ◽  
Vol 279 (3) ◽  
pp. H959-H969 ◽  
Author(s):  
Kimimasa Tobita ◽  
Bradley B. Keller
Keyword(s):  
Circumferential Strain ◽  
Normal Development ◽  
Mechanical Load ◽  
Longitudinal Direction ◽  
Left Ventricular ◽  
Circumferential Direction ◽  
Chick Embryos ◽  
Left Heart ◽  
Wall Deformation ◽  
Deformation Patterns

The vertebrate embryonic ventricle transforms from a smooth-walled single tube to trabeculated right ventricular (RV) and left ventricular (LV) chambers during cardiovascular morphogenesis. We hypothesized that ventricular contraction patterns change from globally isotropic to chamber-specific anisotropic patterns during normal morphogenesis and that these deformation patterns are influenced by experimentally altered mechanical load produced by chronic left atrial ligation (LAL). We measured epicardial RV and LV wall strains during normal development and left heart hypoplasia produced by LAL in Hamburger-Hamilton stage 21, 24, 27, and 31 chick embryos. Normal RV contracted isotropically until stage 24 and then contracted preferentially in the circumferential direction. Normal LV contracted isotropically at stage 21, preferentially in the longitudinal direction at stages 24 and 27, and then in the circumferential direction at stage 31. LAL altered both RV and LV strain patterns, accelerated the onset of preferential RV circumferential strain patterns, and abolished preferential LV longitudinal strain ( P < 0.05 vs. normal). Mature patterns of anisotropic RV and LV deformation develop coincidentally with morphogenesis, and changes in these deformation patterns reflect altered cardiovascular function and/or morphogenesis.

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