scholarly journals Effect of Decellularization Protocol on the Mechanical Behavior of Porcine Descending Aorta

2010 ◽  
Vol 2010 ◽  
pp. 1-11 ◽  
Author(s):  
John C. Fitzpatrick ◽  
Peter M. Clark ◽  
Franco M. Capaldi
Keyword(s):  
Mechanical Behavior ◽  
Vascular Tissue ◽  
Statistical Significance ◽  
Sodium Deoxycholate ◽  
Rnase A ◽  
Uniaxial Tensile ◽  
Aortic Tissue ◽  
Model Parameters ◽  
Test Analysis ◽  
Tissue Samples

Enzymatic-detergent decellularization treatments may use a combination of chemical reagents to reduce vascular tissue to sterilized scaffolds, which may be seeded with endothelial cells and implanted with a low risk of rejection. However, these chemicals may alter the mechanical properties of the native tissue and contribute to graft compliance mismatch. Uniaxial tensile data obtained from native and decellularized longitudinal aortic tissue samples was analyzed in terms of engineering stress and fit to a modified form of the Yeoh rubber model. One decellularization protocol used SDS, while the other two used TritonX-100, RNase-A, and DNase-I in combination with EDTA or sodium-deoxycholate. Statistical significance of Yeoh model parameters was determined by pairedt-test analysis. The TritonX-100/EDTA and 0.075% SDS treatments resulted in relatively variable mechanical changes and did not effectively lyse VSMCs in aortic tissue. The TritonX-100/sodium-deoxycholate treatment effectively lysed VSMCs and was characterized by less variability in mechanical behavior. The data suggests a TritonX-100/sodium-deoxycholate treatment is a more effective option than TritonX-100/EDTA and SDS treatments for the preparation of aortic xenografts and allografts because it effectively lyses VSMCs and is the least likely treatment, among those considered, to promote a decrease in mechanical compliance.

Biaxial Mechanical Behavior of Aneurysmal and Nonaneurysmal Human Abdominal Aorta: Preliminary Results

2000 ◽  
Author(s):  
David A. Vorp ◽  
Michael S. Sacks ◽  
Brian J. Schiro ◽  
Michel S. Makaroun
Keyword(s):  
Stress Distribution ◽  
Mechanical Behavior ◽  
Abdominal Aorta ◽  
Large Strain ◽  
Constitutive Behavior ◽  
Accurate Estimation ◽  
Uniaxial Tensile ◽  
Aortic Tissue ◽  
Material Symmetry ◽  
Nonlinearly Elastic

Abstract Rupture of abdominal aortic aneurysm (AAA) is currently the 13th leading cause of death in the US and represents a mechanical failure of the diseased aortic wall. Therefore, accurate estimation of the wall stress distribution in AAA may be a clinically useful tool to predict their risk of rupture [1]. A necessary precursor to an accurate stress analysis is an appropriate representation of the constitutive behavior of the AAA wall. Many previous biomechanical analyses of AAA have employed a linearly elastic constitutive behavior [2,3]. However, we have shown that the AAA wall is nonlinearly elastic [4] and undergoes large strain in-vivo [5]. With this as motivation, we recently developed an isotropic, nonlinearly elastic, large strain constitutive model for AAA wall based on uniaxial tensile testing data [6]. The assumption of isotropy was not validated, however. Utilization of an isotropic material symmetry in models of anisotropic structures may lead to significant errors in stress distribution [7]. Indeed, experiments suggest that the nonaneurysmal aorta is anisotropic (orthotropic) [8,9], but the material symmetry of AAA is not presently known. Moreover, most of the previous work investigating the material symmetry of aorta has been performed on animal tissue. To evaluate the anisotropy of aortic tissue, biaxial experimentation is necessary. There has been very little published work involving the biaxial experimentation of human aortic tissue, and none for AAA tissue. We present here a preliminary evaluation of the biaxial mechanical behavior of human aneurysmal and nonaneurysmal abdominal aorta.

scholarly journals One Year Evaluation of Material Properties Changes of Polylactide Parts in Various Hydrolytic Degradation Conditions

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1496 ◽  
Author(s):  
Angela Andrzejewska
Keyword(s):  
Mechanical Behavior ◽  
Ph Value ◽  
Statistical Significance ◽  
Optimal Choice ◽  
Percentage Change ◽  
Uniaxial Tensile ◽  
Biodegradable Materials ◽  
Uniaxial Tensile Test ◽  
Degradation Medium ◽  
One Year

Biodegradable biocompatible materials are widely used in medical applications. Determining the possibility of using biodegradable materials depends on determining the changes in their parameters over time due to degradation. The current scientific research on biodegradable materials has presented results based on research methods characterized by the different geometry and cross-section size of the specimen, type of degradation medium, or different pH value of the medium or maximum degradation time. This paper presents the results of a one-year study on the influence of the type of degradation medium on the changes in mechanical behavior and the uptake of the degradation medium by biodegradable specimens with large cross-sections. In addition, a prototype of a test stand was created, which allowed for the specimens to be stored vertically to ensure regular medium exposure and eliminate the interaction of the surface of the tested specimens with the sides of the container. The obtained results allowed the statistical significance of differences in the mechanical parameters determined in the uniaxial tensile test after 2, 4, 6, 12, 26, 39, and 52 weeks of degradation to be indicated depending on the type of degradation medium. It was proven that the changes in mechanical behavior depend on the percentage change in the mass of the specimens during degradation. The percentage change in mass depends on the type of degradation medium. Based on the results of this research, it was noted that in long-term degradation above 12 weeks, buffered sodium chloride solution is the optimal choice for the degradation medium. However, distilled water or physiological saline solution can be used as an alternative during the degradation period for up to 12 weeks.

Tanshinone IIA attenuates elastase-induced AAA in rats via inhibition of MyD88-dependent TLR-4 signaling

VASA ◽  
2014 ◽  
Vol 43 (1) ◽  
pp. 39-46 ◽  
Author(s):  
Tao Shang ◽  
Feng Ran ◽  
Qian Qiao ◽  
Zhao Liu ◽  
Chang-Jian Liu
Keyword(s):  
Nuclear Factor Κb ◽  
Tanshinone Iia ◽  
Myeloid Differentiation ◽  
Aortic Tissue ◽  
Toll Like Receptor ◽  
Sprague Dawley ◽  
Toll Like Receptor 4 ◽  
Tissue Samples ◽  
Myeloid Differentiation Factor ◽  
And Control

Background: The purpose of this study was to determine whether myeloid differentiation factor88-dependent Toll-Like Receptor-4 (TLR-4) signaling contributed to the inhibition of abdominal aortic aneurysm (AAA) by Tanshinone IIA (Tan IIA). Materials and methods: Male Sprague-Dawley rats (n = 12 / group) were randomly distributed into three groups: Tan IIA, control, and sham. The rats from Tan IIA and control groups under-went intra-aortic elastase perfusion to induce AAAs, and those in the sham group were perfused with saline. Only the Tan IIA group received Tan IIA (2 mg / rat / d). Aortic tissue samples were harvested at 24 d after perfusion and evaluated using reverse transcriptase-polymerase chain reaction, Western blot, immunohistochemistry and immunofluorescence. Results: The over-expression of Toll-Like Receptor-4 (TLR-4), Myeloid Differentiation factor 88 (MyD88), Phosphorylated Nuclear Factor κB (pNF-κB) and Phosphorylated IκBα (pIκBα) induced by elastase perfusion were significantly decreased by Tan IIA treatment. Conclusions: Tan IIA attenuates elastase-induced AAA in rats possibly via the inhibition of MyD88-dependent TLR-4 signaling, which may be one potential explanation of why Tan IIA inhibits AAA development through multiple effects.

Influence of post-welding tempering on mechanical behavior of friction welded joints from medium-carbon steels during tensile test

2020 ◽  
pp. 40-49
Author(s):  
A. S. Atamashkin ◽  
E. Yu. Priymak ◽  
N. V. Firsova
Keyword(s):  
Mechanical Behavior ◽  
Welded Joints ◽  
Welded Joint ◽  
Crack Nucleation ◽  
Carbon Steels ◽  
Uniaxial Tensile ◽  
Medium Carbon ◽  
Uniaxial Tensile Testing ◽  
Rotary Friction Welding ◽  
Medium Carbon Steels

The paper presents an analysis of the mechanical behavior of friction samples of welded joints from steels 30G2 (36 Mn 5) and 40 KhN (40Ni Cr 6), made by rotary friction welding (RFW). The influence of various temperature conditions of postweld tempering on the mechanical properties and deformation behavior during uniaxial tensile testing is analyzed. Vulnerabilities where crack nucleation and propagation occurred in specimens with a welded joint were identified. It was found that with this combination of steels, postweld tempering of the welded joint contributes to a decrease in the integral strength characteristics under conditions of static tension along with a significant decrease in the relative longitudinal deformation of the tested samples.

scholarly journals Experimental and Numerical Evaluation of Mechanical Properties of 3D-Printed Stainless Steel 316L Lattice Structures

2021 ◽  
Author(s):  
M. Carraturo ◽  
G. Alaimo ◽  
S. Marconi ◽  
E. Negrello ◽  
E. Sgambitterra ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Mechanical Behavior ◽  
Numerical Simulations ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Lattice Structures ◽  
Stainless Steel 316L ◽  
Research Attention ◽  
Octet Truss

AbstractAdditive manufacturing (AM), and in particular selective laser melting (SLM) technology, allows to produce structural components made of lattice structures. These kinds of structures have received a lot of research attention over recent years due to their capacity to generate easy-to-manufacture and lightweight components with enhanced mechanical properties. Despite a large amount of work available in the literature, the prediction of the mechanical behavior of lattice structures is still an open issue for researchers. Numerical simulations can help to better understand the mechanical behavior of such a kind of structure without undergoing long and expensive experimental campaigns. In this work, we compare numerical and experimental results of a uniaxial tensile test for stainless steel 316L octet-truss lattice specimen. Numerical simulations are based on both the nominal as-designed geometry and the as-build geometry obtained through the analysis of µ-CT images. We find that the use of the as-build geometry is fundamental for an accurate prediction of the mechanical behavior of lattice structures.

scholarly journals Assessment of Immunological Features in Muscle-Invasive Bladder Cancer Prognosis Using Ensemble Learning

Cancers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1624
Author(s):  
Christos G. Gavriel ◽  
Neofytos Dimitriou ◽  
Nicolas Brieu ◽  
Ines P. Nearchou ◽  
Ognjen Arandjelović ◽  
...  
Keyword(s):  
Bladder Cancer ◽  
Statistical Significance ◽  
Tnm Staging ◽  
Cancer Prognosis ◽  
Clinical Staging ◽  
Invasive Bladder Cancer ◽  
P Value ◽  
Muscle Invasive Bladder Cancer ◽  
Tissue Samples ◽  
Muscle Invasive

The clinical staging and prognosis of muscle-invasive bladder cancer (MIBC) routinely includes the assessment of patient tissue samples by a pathologist. Recent studies corroborate the importance of image analysis in identifying and quantifying immunological markers from tissue samples that can provide further insight into patient prognosis. In this paper, we apply multiplex immunofluorescence to MIBC tissue sections to capture whole-slide images and quantify potential prognostic markers related to lymphocytes, macrophages, tumour buds, and PD-L1. We propose a machine-learning-based approach for the prediction of 5 year prognosis with different combinations of image, clinical, and spatial features. An ensemble model comprising several functionally different models successfully stratifies MIBC patients into two risk groups with high statistical significance (p value < 1×10−5). Critical to improving MIBC survival rates, our method correctly classifies 71.4% of the patients who succumb to MIBC, which is significantly more than the 28.6% of the current clinical gold standard, the TNM staging system.

scholarly journals A Flow Stress Model of 300M Steel for Isothermal Tension

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 252
Author(s):  
Rongchuang Chen ◽  
Shiyang Zhang ◽  
Xianlong Liu ◽  
Fei Feng
Keyword(s):  
Flow Stress ◽  
Constitutive Model ◽  
Tensile Deformation ◽  
Flow Behavior ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Model Parameters ◽  
Average Deviation ◽  
Cross Sectional ◽  
300M Steel

To investigate the effect of hot working parameters on the flow behavior of 300M steel under tension, hot uniaxial tensile tests were implemented under different temperatures (950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C) and strain rates (0.01 s−1, 0.1 s−1, 1 s−1, 10 s−1). Compared with uniaxial compression, the tensile flow stress was 29.1% higher because dynamic recrystallization softening was less sufficient in the tensile stress state. The ultimate elongation of 300M steel increased with the decrease of temperature and the increase of strain rate. To eliminate the influence of sample necking on stress-strain relationship, both the stress and the strain were calibrated using the cross-sectional area of the neck zone. A constitutive model for tensile deformation was established based on the modified Arrhenius model, in which the model parameters (n, α, Q, ln(A)) were described as a function of strain. The average deviation was 6.81 MPa (6.23%), showing good accuracy of the constitutive model.

Mechanical behavior of chemically treated ostrich pericardium subjected to uniaxial tensile testing: influence of the suture

2002 ◽  
Vol 62 (1) ◽  
pp. 73-81 ◽  
Author(s):  
J. M. García Páez ◽  
A. Carrera ◽  
E. Jorge Herrero ◽  
I. Millán ◽  
A. Rocha ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Tensile Testing ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Testing ◽  
Chemically Treated

Design and Mechanical Evaluation of Sutureless Implants for the Surgery Treatment of Rotator Cuff Tears

2021 ◽  
Author(s):  
Marcília Valéria Guimarães ◽  
Elton Bonifácio ◽  
Thiago Carmo ◽  
Cleudmar Araújo
Keyword(s):  
Rotator Cuff ◽  
Mechanical Behavior ◽  
Functional Disability ◽  
Statistical Significance ◽  
Testing Machine ◽  
Rotator Cuff Tears ◽  
Suture Anchors ◽  
Pullout Strength ◽  
Rigid Foam ◽  
Pullout Tests

Abstract Rotator cuff (RC) tears cause pain and functional disability of the shoulder. Despite advances in suture anchors, there are still reports about the incidence of surgical-related injuries to RC mainly associated with sutures. The purpose of this study was to design and evaluate the mechanical behavior of sutureless implants to repair RC tears. We hypothesized that the implants present mechanical characteristics suitable for the surgical treatment of RC tears as suture anchors. Three different implants (T1,T2,T3) were designed and fabricated with titanium: T1 has two rods and rectangular head; T2 has two rods with a small opening and enlarged rectangular head and T3 has three rods and a circular head. The implants were fixed in rigid polyurethane foam blocks by a series of blows, and the applied mechanical loads along with the number of blows were quantified. Pullout tests using tapes fixed between the implant head and testing machine grip were conducted until implant failure. The maximum pullout strength and displacement of the implant relative to the rigid foam block were computed. Statistical significance was set at p &lt; 0.05. Owing to its geometric configuration, implant T2 presented the best characteristics related to stability, strength, and ease of insertion. Implant T2 confirms our hypothesis that its mechanical behavior is compatible with that of suture anchors which could lead to the reduction of RC repair failures and simplify the arthroscopic procedure.

Abstract P211: Single High Na + Ingestion Leads To An Increase In Oxidative Stress And Triggers Inflammation.

Hypertension ◽  
2021 ◽  
Vol 78 (Suppl_1) ◽  
Author(s):  
Ginette Bordcoch ◽  
Ivan Tavera Busso ◽  
Juan Masjoan Juncos ◽  
Luis I Juncos
Keyword(s):  
Oxidative Stress ◽  
The United States ◽  
Male Rats ◽  
Control Group ◽  
Aortic Tissue ◽  
Tissue Samples ◽  
Extracellular Signal ◽  
High Prevalence ◽  
Markers Of Oxidative Stress ◽  
The Difference

Hypertension has been linked to a progressive increased in oxidative stress and inflammation. The high prevalence of hypertension poses a great risk to public health as 108 million adults in the United States have the condition. For that reason, a better understanding of the link between a high Na+ intake and the development of hypertension is of crucial importance. We hypothesize that a single ingestion of a high Na+ solution leads to increased oxidative stress and triggers an inflammatory response. Wistar 200-250 g male rats had gastric infusions through the esophagus. Groups were infused with 8 mL liquid Vaseline (Control), 8 mL of NaCl 0.684 M (4% m/v), and 8 mL of NaCl 1.368 M (8% m/v). After infusion, blood was collected at different time points during the first hour. Tissue samples were obtained from the aorta, heart, and kidney. Electron Microscopy (EM) was performed on all tissues, which were also analyzed for molecular markers of oxidative stress: Superoxide Dismutase (SOD) and Malondialdehyde (MDA), and an inflammation marker: Extracellular Signal-Regulated Kinase (ERK). At 2 and a half minutes, serum Na+ concentration was unchanged in the control group compared to an increase observed in animals receiving 4% and 8% Na+ with concentrations of 135±1.4 mEq/L, 141±2.0 mEq/L, and 140±1.2 mEq/L respectively. At the 1-hour time point after infusion, the difference was further increased in the 8% group with serum concentrations of 135±1.8 mEq/L, 140±1.5 mEq/L, and 152±1mEq/L respectively (p<0.05). There was an increase in oxidative stress in the aorta from values of 36.22±4.64 mU/mg SOD and 0.131±0.013 pg/mL MDA in the control group, to 47.11±4.89 mU/mg SOD and 0.291±0.022 pg/mL MDA in the 8% group (p<0.05 in both cases). The same was observed in the heart, where values were: 174.6125.26 mU/mg SOD, 0.026±0.007 pg/mL MDA in controls, and 259.22±21.98 mU/mg SOD, 0.215±0.073 pg/mL MDA in 8% group (p<0.05 both cases). Increased ERK in aortic tissue, values of 0.29±0.03 pg/mL in controls, 2.68±0.18 pg/mL in 4% group and 3.97±0.68pg/mL in 8% group (p<0.05) suggest increased inflammation. We conclude that the elevation in serum Na+ concentration that follows Na+ ingestion leads to increased oxidative stress and inflammation.

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