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  • 1
    Electronic Resource
    Electronic Resource
    Wall Strength and Stiffness of Aneurysmal and Nonaneurysmal Abdominal Aorta (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 800 (1996), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1996.tb33330.x
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  • 2
    Electronic Resource
    Electronic Resource
    Recurrence rate of diabetic neurotrophic foot ulcers healed using topical application of growth factors released from platelets (1996)
    Oxford, UK : Blackwell Science
    Wound repair and regeneration 4 (1996), S. 0 
    Details
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The purpose of this study was to determine the recurrence rate of diabetic neurotrophic foot ulcers that had healed in a treatment protocol using topically applied growth factors released from platelets. Thirty-six patients with diabetic neurotrophic foot ulcers were entered into a randomized prospective double-blind 20-week trial of topically applied platelet growth factors or buffered saline dressings. Ulcers had been present for 15.5 months (mean, range 2 to 60 months). Sixteen patients (44%) healed and were followed up for as many as 30 months to determine the rate of ulcer recurrence. Eleven patients (68.8%) had ulcers that recurred, including 10 treated with platelet growth factors and one treated with buffered saline solution. These ulcers had been present for 20 months (range 5 to 60 months) before healing. Average time to ulcer recurrence was 2.2 months (range 0.25 to 7 months). Five ulcers (31.2%) remained healed, including four treated with platelet growth factors and one treated with buffered saline solution. These healed, nonrecurring ulcers had been present for 5 months (range 2 to 6 months) before healing. Average follow up was 25 months (range 24 to 30 months). Ulcers were more likely to recur if they had been present longer before healing. If patients were not compliant in wearing footwear to protect the healed ulcer, the ulcers were prone to early recurrence. These data indicate that ulcers healed by using growth factors in the form of a platelet growth factors did not have more durable skin over the ulcer and were prone to early ulcer recurrence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1524-475X.1996.40210.x
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  • 3
    Electronic Resource
    Electronic Resource
    Modeling the transmural stress distribution during healing of bioresorbable vascular prostheses (1995)
    Springer
    Annals of biomedical engineering 23 (1995), S. 178-188 
    Details
    ISSN: 1573-9686
    Keywords: Bioresorbable vascular graft ; Mechanical stress ; Mathematical model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Little attention has been given to the stresses within the wall of bioresorbable vascular prostheses and how they might affect the resorption process. We modeled the graft “complex” (inner tissue capsule, residual graft, and outer tissue capsule) as a three-layered compound tube under internal pressure. Using this biomechanical model, we studied the effects of alterations in the geometry (i. e., radius and thickness) and mechanical properties of each stratum on the overall transmural stress distribution. Hypothetical simulations were performed to investigate the possible-sequence of and alterations in the radial and circumferential stresses during the resorption process. Our results suggest that early in the resorption phase, the inner tissue capsule is subjected to compressive hoop stresses and concentrated, largemagnitude compressive radial stresses. This distribution gives way to the more typical distribution for a thick-walled tube when equilibration (i.e., complete resorption) is approached. The prediction of the compressive stresses in the pseudo-intima during early resorption parallels findings of an elevated mitotic index in that region at that time. This leads to a new hypothesis, namely, that compressive stresses, both in-plane and out-of-plane with respect to the regenerated vascular cells, participate in the resorption process of bioresorbable vascular grafts by modulating elevated cellular proliferative activity and may play an important role in other aspects of vascular cell biology. Results of recent experimentation support this hypothesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02368324
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  • 4
    Electronic Resource
    Electronic Resource
    Gene Expression Is Altered in Perfused Arterial Segments Exposed to Cyclic Flexure Ex Vivo (1999)
    Springer
    Annals of biomedical engineering 27 (1999), S. 366-371 
    Details
    ISSN: 1573-9686
    Keywords: Gene expression ; Blood vessels ; Cyclic strain ; Physical stimulation ; Hemodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Certain regions of coronary and other arteries undergo cyclic flexure due to attachment to the heart or crossing of joints. Such motion gives rise to fluctuations in transmural stress and luminal shear stress. It is well known that cyclic variation of these biomechanical forces influences many aspects of vascular cell biology including gene expression. The purpose of this work was to investigate the hypothesis that cyclic flexure of arterial segments influences their gene expression. Bilateral porcine femoral arteries were obtained fresh from the abattoir. One vessel was mounted in an ex vivo perfusion system and subjected to an intraluminal pressure of 60 mm Hg and flow of 50 ml/min to serve as a control. The other vessel was mounted in a second perfusion system with similar hemodynamic conditions, but also subjected to controlled cyclic bending consistent with that found in coronary arteries in vivo. Reverse transcriptase-polymerase chain reaction analysis demonstrated that E-selectin and matrix metalloproteinase-1 (MMP-1) were consistently and significantly downregulated in the specimens subjected to 4 h of cyclic bending as compared to the control (n=8, p 〈 0.05). Our results show that cyclic flexure of arterial segments in vitro may influence their gene expression. Further investigation should follow this novel observation and focus on other known mediators to more carefully elucidate the consequence of cyclic flexure on arterial pathobiology. © 1999 Biomedical Engineering Society. PAC99: 8719Rr, 8719Uv, 8719Hh
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.158
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  • 5
    Electronic Resource
    Electronic Resource
    In Vivo Three-Dimensional Surface Geometry of Abdominal Aortic Aneurysms (1999)
    Springer
    Annals of biomedical engineering 27 (1999), S. 469-479 
    Details
    ISSN: 1573-9686
    Keywords: Abdominal aortic aneurysm ; Curvature ; Tortuosity ; Three-dimensional reconstruction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Abdominal aortic aneurysm (AAA) is a local, progressive dilation of the distal aorta that risks rupture until treated. Using the law of Laplace, in vivo assessment of AAA surface geometry could identify regions of high wall tensions as well as provide critical dimensional and shape data for customized endoluminal stent grafts. In this study, six patients with AAA underwent spiral computed tomography imaging and the inner wall of each AAA was identified, digitized, and reconstructed. A biquadric surface patch technique was used to compute the local principal curvatures, which required no assumptions regarding axisymmetry or other shape characteristics of the AAA surface. The spatial distribution of AAA principal curvatures demonstrated substantial axial asymmetry, and included adjacent elliptical and hyperbolic regions. To determine how much the curvature spatial distributions were dependent on tortuosity versus bulging, the effects of AAA tortuosity were removed from the three-dimensional (3D) reconstructions by aligning the centroids of each digitized contour to the z axis. The spatial distribution of principal curvatures of the modified 3D reconstructions were found to be largely axisymmetric, suggesting that much of the surface geometric asymmetry is due to AAA bending. On average, AAA surface area increased by 56% and abdominal aortic length increased by 27% over those for the normal aorta. Our results indicate that AAA surface geometry is highly complex and cannot be simulated by simple axisymmetric models, and suggests an equally complex wall stress distribution. © 1999 Biomedical Engineering Society. PAC99: 8719Rr, 8759Fm, 8757Gg
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.202
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