Partial prevention of monocyte and granulocyte activation in experimental vein grafts by using a biomechanical engineering approach

1999 ◽  
Vol 32 (11) ◽  
pp. 1165-1175 ◽  
Author(s):  
S.Q. Liu ◽  
M.M. Moore ◽  
M.R. Glucksberg ◽  
L.F. Mockros ◽  
J.B. Grotberg ◽  
...  
Keyword(s):  
Vein Grafts ◽  
Engineering Approach ◽  
Biomechanical Engineering

Prevention of Mechanical Stretch-Induced Endothelial and Smooth Muscle Cell Injury in Experimental Vein Grafts

1999 ◽  
Vol 122 (1) ◽  
pp. 31-38 ◽  
Author(s):  
S. Q. Liu ◽  
M. M. Moore ◽  
C. Yap
Keyword(s):  
Smooth Muscle ◽  
Tensile Stress ◽  
Smooth Muscle Cell ◽  
Muscle Cell ◽  
Actin Filament ◽  
Vein Graft ◽  
Mechanical Stretch ◽  
Jugular Veins ◽  
Vein Grafts ◽  
Engineering Approach

Vein grafts are subject to increased tensile stress due to exposure to arterial blood pressure, which has been hypothesized to induce endothelial cell (EC) and smooth muscle cell (SMC) injury. This study was designed to verify this hypothesis and to develop a tissue engineering approach that can be used to prevent these pathological events. Two experimental models were created in rats to achieve these goals: (1) a nonengineered vein graft with increased tensile stress, which was created by grafting a jugular vein into the abdominal aorta using a conventional end-to-end anastomotic technique; and (2) an engineered vein graft with reduced tensile stress, which was created by restricting a vein graft into a cylindrical sheath constructed using a polytetrafluoroethylene membrane. The integrity of ECs in these models was examined by using a silver nitrate staining method, and the integrity of SMCs was assessed by using a fluorescein phalloidin-labeling technique. It was found that nonengineered vein grafts were associated with early EC denudation with a change in EC coverage from 100 percent in normal jugular veins to 36±10, 28±12, 18±9, 44±15, 80±13, and 97±6 percent at 1 and 6 hours and 1, 5, 10, and 30 days, respectively. Similarly, rapid SMC actin filament degradation was found during the early period with a change in SMC coverage from ∼94 percent in normal jugular veins to 80±10, 41±17, 25±9, 51±15, 79±15, 98±2 percent at 1 and 6 hours and 1, 5, 10, and 30 days, respectively, in nonengineered vein grafts. In engineered vein grafts with reduced tensile stress, EC denudation and SMC actin filament degradation were prevented significantly. These results suggested that mechanical stretch due to increased tensile stress contributed to EC and SMC injury in experimental vein grafts, and these pathological events could be partially prevented when tensile stress was reduced by using a biomechanical engineering approach. [S0148-0731(00)00701-9]

Control of Autogenous Vein Grafts Prior to Reimplantation, By Electron Microscopy

1972 ◽  
Vol 30 ◽  
pp. 106-107
Author(s):  
John H. L. Watson ◽  
John L. Swedo ◽  
M. Vrandecic
Keyword(s):  
Electron Microscopy ◽  
Light And Electron Microscopy ◽  
Physiological Saline ◽  
Experimental Conditions ◽  
Vein Grafts ◽  
Arterial Blood ◽  
Saphenous Veins ◽  
Autogenous Vein ◽  
Control Of Parameters ◽  
Post Implantation

The ambient temperature and the nature of the storage fluids may well have significant effects upon the post-implantation behavior of venus autografts. A first step in the investigation of such effects is reported here. Experimental conditions have been set which approximate actual operating room procedures. Saphenous veins from dogs have been used as models in the experiments. After removal from the dogs the veins were kept for two hours under four different experimental conditions, viz at either 4°C or 23°C in either physiological saline or whole canine arterial blood. At the end of the two hours they were prepared for light and electron microscopy. Since no obvious changes or damage could be seen in the veins by light microscopy, even with the advantage of tissue specific stains, it was essential that the control of parameters for successful grafts be set by electron microscopy.

On the nominal transverse shear strain to characterize the severity of creasing

TAPPI Journal ◽  
2018 ◽  
Vol 17 (04) ◽  
pp. 231-240
Author(s):  
Douglas Coffin ◽  
Joel Panek
Keyword(s):  
Shear Strain ◽  
Transverse Shear ◽  
Elastic Limit ◽  
Experimental Results ◽  
Transverse Shear Strain ◽  
Maximum Strain ◽  
Machine Direction ◽  
Engineering Approach ◽  
Wide Range ◽  
Analytic Expression

A transverse shear strain was utilized to characterize the severity of creasing for a wide range of tooling configurations. An analytic expression of transverse shear strain, which accounts for tooling geometry, correlated well with relative crease strength and springback as determined from 90° fold tests. The experimental results show a minimum strain (elastic limit) that needs to be exceeded for the relative crease strength to be reduced. The theory predicts a maximum achievable transverse shear strain, which is further limited if the tooling clearance is negative. The elastic limit and maximum strain thus describe the range of interest for effective creasing. In this range, cross direction (CD)-creased samples were more sensitive to creasing than machine direction (MD)-creased samples, but the differences were reduced as the shear strain approached the maximum. The presented development provides the foundation for a quantitative engineering approach to creasing and folding operations.

Real-life Bifurcation – Challenges and Potential Complications

2011 ◽  
Vol 7 (4) ◽  
pp. 283
Author(s):  
Inga Narbute ◽  
Sanda Jegere ◽  
Indulis Kumsars ◽  
Dace Juhnevica ◽  
Agnese Knipse ◽  
...  
Keyword(s):  
Stent Thrombosis ◽  
Real Life ◽  
Coronary Intervention ◽  
Side Branch ◽  
The Body ◽  
Chronic Total Occlusions ◽  
Vein Grafts ◽  
Procedural Complications ◽  
Drug Eluting ◽  
Bifurcation Lesions

Together with calcified lesions, saphenous vein grafts, chronic total occlusions and unprotected left main lesions, bifurcation lesions are complex lesions that remain among the outstanding challenges of treatment with percutaneous coronary intervention. Bifurcation lesions are associated with increased rates of procedural complications, restenosis and adverse events than lesions in the body of the vessel. The introduction of drug-eluting stents for the treatment of bifurcation lesions has dramatically decreased restenosis rates, especially in patients suffering from diabetes. However, abrupt side branch closure, side branch ostial restenosis and stent thrombosis remain areas where further improvement is needed. Although a provisional T-stent strategy is most often used when side branch stenting is required, there are true bifurcation lesions where the selected use of more complex bifurcation approaches (such as the crush technique, T-stenting or the culotte technique) seem appropriate, particularly when the main branch and side branch are larger vessels with more diffuse side branch disease. The major challenge with any technique is to ensure that the side branch is protected and there is a satisfactory final result. Many technical questions rise in trying to ensure this outcome and lower the risk of intra- and post-procedural complications such as side branch closure and restenosis, stent thrombosis, dissection and fracture of a jailed wire: how can difficult side branch access be solved? How can unfavourable side branch anatomy be re-wired after main vessel stent placement? How can fracture of a jailed wire be avoided? Is side-strut dilation beneficial?

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