Read by QxMD icon Read

David vorp

James R Thunes, Siladitya Pal, Ronald N Fortunato, Julie A Phillippi, Thomas G Gleason, David A Vorp, Spandan Maiti
Incorporation of collagen structural information into the study of biomechanical behavior of ascending thoracic aortic (ATA) wall tissue should provide better insight into the pathophysiology of ATA. Structurally motivated constitutive models that include fiber dispersion and recruitment can successfully capture overall mechanical response of the arterial wall tissue. However, these models cannot examine local microarchitectural features of the collagen network, such as the effect of fiber disruptions and interaction between fibrous and non-fibrous components, which may influence emergent biomechanical properties of the tissue...
June 14, 2016: Journal of Biomechanics
Jeffrey T Krawiec, Justin S Weinbaum, Han-Tsung Liao, Aneesh K Ramaswamy, Dominic J Pezzone, Alexander D Josowitz, Antonio D'Amore, J Peter Rubin, William R Wagner, David A Vorp
Many preclinical evaluations of autologous small-diameter tissue-engineered vascular grafts (TEVGs) utilize cells from healthy humans or animals. However, these models hold minimal relevance for clinical translation, as the main targeted demographic is patients at high cardiovascular risk such as individuals with diabetes mellitus or the elderly. Stem cells such as adipose-derived mesenchymal stem cells (AD-MSCs) represent a clinically ideal cell type for TEVGs, as these can be easily and plentifully harvested and offer regenerative potential...
May 2016: Tissue Engineering. Part A
Ly Phan, Katherine Courchaine, Amir Azarbal, David Vorp, Cindy Grimm, Sandra Rugonyi
Abdominal aortic aneurysm (AAA) intervention and surveillance is currently based on maximum transverse diameter, even though it is recognized that this might not be the best strategy. About 10% of patients with small AAA transverse diameters, for whom intervention is not considered, still rupture; while patients with large AAA transverse diameters, for whom intervention would have been recommended, have stable aneurysms that do not rupture. While maximum transverse diameter is easy to measure and track in clinical practice, one of its main drawbacks is that it does not represent the whole AAA and rupture seldom occurs in the region of maximum transverse diameter...
May 2016: Journal of Biomechanical Engineering
Alkiviadis Tsamis, Julie A Phillippi, Ryan G Koch, Patrick G Chan, Jeffrey T Krawiec, Antonio D'Amore, Simon C Watkins, William R Wagner, David A Vorp, Thomas G Gleason
OBJECTIVE: Ascending thoracic aortic aneurysm (ATAA) in patients with bicuspid aortic valve (BAV) commonly dilate asymmetrically compared with patients with tricuspid aortic valve (TAV). This discrepancy in aneurysm geometry led us to hypothesize that microarchitectural differences underlie the observed asymmetric dilatation pattern. The purpose of this study was to characterize the microarchitectural distinctions of the extracellular matrix of the 2 phenotypes with a focus on the proportion of radially oriented elastin and collagen fibers in different circumferential aortic regions...
June 2016: Journal of Thoracic and Cardiovascular Surgery
Jayashree Rao, Bryan N Brown, Justin S Weinbaum, Emily L Ofstun, Michel S Makaroun, Jay D Humphrey, David A Vorp
OBJECTIVE: Little is known about the etiologic factors that lead to the occurrence of intraluminal thrombus (ILT) during abdominal aortic aneurysm (AAA) development. Recent work has suggested that macrophages may play an important role in progression of a number of other vascular diseases, including atherosclerosis; however, whether these cells are present within the ILT of a progressing AAA is unknown. The purpose of this work was to define the presence, phenotype, and spatial distribution of macrophages within the ILT excised from six patients...
September 2015: Journal of Vascular Surgery
Ali Hemmasizadeh, Alkiviadis Tsamis, Rabee Cheheltani, Soroush Assari, Antonio D'Amore, Michael Autieri, Mohammad F Kiani, Nancy Pleshko, William R Wagner, Simon C Watkins, David Vorp, Kurosh Darvish
Determination of correlations between transmural mechanical and morphological properties of aorta would provide a quantitative baseline for assessment of preventive and therapeutic strategies for aortic injuries and diseases. A multimodal and multidisciplinary approach was adopted to characterize the transmural morphological properties of descending porcine aorta. Histology and multi-photon microscopy were used for describing the media layer micro-architecture in the circumferential-radial plane, and Fourier Transform infrared imaging spectroscopy was utilized for determining structural protein, and total protein content...
July 2015: Journal of the Mechanical Behavior of Biomedical Materials
Giampaolo Martufi, Alessandro Satriano, Randy D Moore, David A Vorp, Elena S Di Martino
Wall stress is a powerful tool to assist clinical decisions in rupture risk assessment of abdominal aortic aneurysms. Key modeling assumptions that influence wall stress magnitude and distribution are the inclusion or exclusion of the intraluminal thrombus in the model and the assumption of a uniform wall thickness. We employed a combined numerical-experimental approach to test the hypothesis that abdominal aortic aneurysm (AAA) wall tissues with different thickness as well as wall tissues covered by different thrombus thickness, exhibit differences in the mechanical behavior...
August 2015: Annals of Biomedical Engineering
Andrés I Rodríguez, Gábor Csányi, Daniel J Ranayhossaini, Douglas M Feck, Kory J Blose, Lillian Assatourian, David A Vorp, Patrick J Pagano
OBJECTIVE: Blood vessel hemodynamics have profound influences on function and structure of vascular cells. One of the main mechanical forces influencing vascular smooth muscle cells (VSMC) is cyclic stretch (CS). Increased CS stimulates reactive oxygen species (ROS) production in VSMC, leading to their dedifferentiation, yet the mechanisms involved are poorly understood. This study was designed to test the hypothesis that pathological CS stimulates NADPH oxidase isoform 1 (Nox1)-derived ROS via MEF2B, leading to VSMC dysfunction via a switch from a contractile to a synthetic phenotype...
February 2015: Arteriosclerosis, Thrombosis, and Vascular Biology
Alkiviadis Tsamis, Siladitya Pal, Julie A Phillippi, Thomas G Gleason, Spandan Maiti, David A Vorp
We recently reported a mechanistic model to link micro-architectural information to the delamination strength (Sd) of human ascending thoracic aorta (ATA). That analysis demonstrated that the number density (N) and failure energy (Uf) of the radially-oriented collagen fibers contribute to the Sd of both aneurysmal (ATAA) and non-aneurysmal (CTRL-ATA) aortic tissue. Among the set of ATAA samples, we studied specimens from patients displaying bicuspid (BAV) and tricuspid aortic valve (TAV) morphologic phenotypes...
December 18, 2014: Journal of Biomechanics
Kory J Blose, Terri L Ennis, Batool Arif, Justin S Weinbaum, John A Curci, David A Vorp
AIM: Demonstrate that periadventitial delivery of adipose-derived mesenchymal stem cells (ADMSCs) slows aneurysm progression in an established murine elastase-perfusion model of abdominal aortic aneurysm (AAA). MATERIALS & METHODS: AAAs were induced in C57BL/6 mice using porcine elastase. During elastase perfusion, a delivery device consisting of a subcutaneous port, tubing and porous scaffold was implanted. Five days after elastase perfusion, 100,000 ADMSCs were delivered through the port to the aorta...
2014: Regenerative Medicine
Yaniv Shilo, Joseph E Pichamuthu, Timothy D Averch, David A Vorp
Introduction: Ureteral injuries such as avulsion are directly related to mechanical damage of the ureter. Understanding the tensile strength of this tissue may assist in prevention of iatrogenic injuries. Few published studies have looked at the mechanical properties of the animal ureter, and of those none have determined the tensile strength of the human ureter. Therefore, the purpose of this work was to determine the tensile strength of the human ureter. Materials and Methods: We harvested 11 human proximal ureters from patients who were undergoing nephrectomy for either kidney tumors or non-functioning kidney...
September 15, 2014: Journal of Endourology
Jeffrey T Krawiec, Justin S Weinbaum, Claudette M St Croix, Julie A Phillippi, Simon C Watkins, J Peter Rubin, David A Vorp
Autologous tissue-engineered blood vessels (TEBVs) generated using adult stem cells have shown promising results, but many preclinical evaluations do not test the efficacy of stem cells from patient populations likely to need therapy (i.e., elderly and diabetic humans). Two critical functions of these cells will be (i) secreting factors that induce the migration of host cells into the graft and (ii) differentiating into functional vascular cells themselves. The purpose of this study was to analyze whether adipose-derived mesenchymal stem cells (AD-MSCs) sourced from diabetic and elderly patients have a reduced ability to promote human smooth muscle cell (SMC) migration and differentiation potential toward SMCs, two important processes in stem cell-based tissue engineering of vascular grafts...
February 2015: Tissue Engineering. Part A
Rabee Cheheltani, Cushla M McGoverin, Jayashree Rao, David A Vorp, Mohammad F Kiani, Nancy Pleshko
Extracellular matrix (ECM) is a key component and regulator of many biological tissues including aorta. Several aortic pathologies are associated with significant changes in the composition of the matrix, especially in the content, quality and type of aortic structural proteins, collagen and elastin. The purpose of this study was to develop an infrared spectroscopic methodology that is comparable to biochemical assays to quantify collagen and elastin in aorta. Enzymatically degraded porcine aorta samples were used as a model of ECM degradation in abdominal aortic aneurysm (AAA)...
June 21, 2014: Analyst
Alkiviadis Tsamis, Luka Pocivavsek, David A Vorp
Crohn's disease is a challenging inflammatory process with a propensity for focal gastro-intestinal tract inflammation and stricture. Surgically, Crohn's is often treated with resection. However, a subtype of diffuse disease with multiple strictures is treated by strictureplasty procedures in hope of avoiding short-gut syndrome. Prior work by Pocivavsek et al. defined the geometry of a Heineke-Mikulicz strictureplasty. Here, we bring this analysis one step closer to clinical and biological relevance by calculating the mechanical stresses and strains that the strictureplasty deformation generates on a model intestinal wall...
November 2014: Biomechanics and Modeling in Mechanobiology
Ryan G Koch, Alkiviadis Tsamis, Antonio D'Amore, William R Wagner, Simon C Watkins, Thomas G Gleason, David A Vorp
The aorta possesses a micro-architecture that imparts and supports a high degree of compliance and mechanical strength. Alteration of the quantity and/or arrangement of the main load-bearing components of this micro-architecture--the elastin and collagen fibers--leads to mechanical, and hence functional, changes associated with aortic disease and aging. Therefore, in the future, the ability to rigorously characterize the wall fiber micro-architecture could provide insight into the complicated mechanisms of aortic wall remodeling in aging and disease...
March 21, 2014: Journal of Biomechanics
Siladitya Pal, Alkiviadis Tsamis, Salvatore Pasta, Antonio D'Amore, Thomas G Gleason, David A Vorp, Spandan Maiti
Aortic dissection (AoD) is a common condition that often leads to life-threatening cardiovascular emergency. From a biomechanics viewpoint, AoD involves failure of load-bearing microstructural components of the aortic wall, mainly elastin and collagen fibers. Delamination strength of the aortic wall depends on the load-bearing capacity and local micro-architecture of these fibers, which may vary with age, disease and aortic location. Therefore, quantifying the role of fiber micro-architecture on the delamination strength of the aortic wall may lead to improved understanding of AoD...
March 21, 2014: Journal of Biomechanics
Alkiviadis Tsamis, Julie A Phillippi, Ryan G Koch, Salvatore Pasta, Antonio D'Amore, Simon C Watkins, William R Wagner, Thomas G Gleason, David A Vorp
It was recently demonstrated by our group that the delamination strength of ascending thoracic aortic aneurysms (ATAA) was lower than that of control (CTRL, non-aneurysmal) ascending thoracic aorta (ATA), and the reduced strength was more pronounced among bicuspid (BAV) vs. tricuspid aortic valve (TAV) patients, suggesting a different risk of aortic dissection for BAV patients. We hypothesized that aortic valve morphologic phenotype predicts fiber micro-architectural anomalies in ATA. To test the hypothesis, we characterized the micro-architecture in the longitudinal-radial (Z-RAD) and circumferential-radial (Θ-RAD) planes of human ATA tissue that was artificially dissected medially...
November 15, 2013: Journal of Biomechanics
Joseph E Pichamuthu, Julie A Phillippi, Deborah A Cleary, Douglas W Chew, John Hempel, David A Vorp, Thomas G Gleason
BACKGROUND: Ascending thoracic aortic aneurysm (ATAA) predisposes patients to aortic dissection and has been associated with diminished tensile strength and disruption of collagen. Ascending thoracic aortic aneurysms arising in patients with bicuspid aortic valve (BAV) develop earlier than in those with tricuspid aortic valves (TAV) and have a different risk of dissection. The purpose of this study was to compare aortic wall tensile strength between BAV and TAV ATAAs and determine whether the collagen content of the ATAA wall is associated with tensile strength and valve phenotype...
December 2013: Annals of Thoracic Surgery
Julie A Phillippi, Benjamin R Green, Michael A Eskay, Mary P Kotlarczyk, Michael R Hill, Anne M Robertson, Simon C Watkins, David A Vorp, Thomas G Gleason
OBJECTIVES: Patients with bicuspid aortic valves (BAV) are predisposed to developing ascending thoracic aortic aneurysms (TAA) at an earlier age than patients who develop degenerative TAAs and have a tricuspid aortic valve (TAV). The hypothesis tested is that BAV-associated aortopathy is mediated by a mechanism of matrix remodeling that is distinct from that seen in TAAs of patients with tricuspid aortic valves. METHODS: Aortic specimens were collected during ascending aortic replacement, aortic valve replacement, and heart transplants from nonaneurysmal (NA) donors and recipients...
March 2014: Journal of Thoracic and Cardiovascular Surgery
Salvatore Pasta, Antonino Rinaudo, Angelo Luca, Michele Pilato, Cesare Scardulla, Thomas G Gleason, David A Vorp
The aortic dissection (AoD) of an ascending thoracic aortic aneurysm (ATAA) initiates when the hemodynamic loads exerted on the aneurysmal wall overcome the adhesive forces holding the elastic layers together. Parallel coupled, two-way fluid-structure interaction (FSI) analyses were performed on patient-specific ATAAs obtained from patients with either bicuspid aortic valve (BAV) or tricuspid aortic valve (TAV) to evaluate hemodynamic predictors and wall stresses imparting aneurysm enlargement and AoD. Results showed a left-handed circumferential flow with slower-moving helical pattern in the aneurysm's center for BAV ATAAs whereas a slight deviation of the blood flow toward the anterolateral region of the ascending aorta was observed for TAV ATAAs...
June 21, 2013: Journal of Biomechanics
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"