Preliminary Design Considerations and Feasibility of a Biomimicking Tissue-Engineered Vascular Graft

2000 ◽  
Author(s):  
Joel D. Stitzel ◽  
Gary L. Bowlin
Keyword(s):  
Vascular Graft ◽  
Large Diameter ◽  
Small Diameter ◽  
Preliminary Design ◽  
Bypass Grafts ◽  
Thrombotic Occlusion ◽  
Design Considerations ◽  
Blood Flow Velocities ◽  
Vascular Replacement ◽  
Compliance Mismatch

Abstract Development of an ideal vascular replacement has been addressed with increasing urgency in recent years. To date, appropriate replacements for only large diameter bypass grafts have been realized, employing the use of Dacron and expanded polytetrafluoroethylene. A solution for small diameter (<6 mm I.D.) vessel bypass, however, has not yet been found. This is due mainly to acute thrombotic occlusion and chronic anastomotic hyperplasia that is introduced into these grafts due to the low blood flow velocities experienced by smaller caliber vessels and compliance mismatch between prosthetic and native vessel, respectively [1].

Development of a Media Equivalent as a Foundation for a Biomimicking Vascular Prosthetic

1999 ◽  
Author(s):  
Kristin J. Pawlowski ◽  
Gary L. Bowlin
Keyword(s):  
Blood Flow ◽  
Large Diameter ◽  
Small Diameter ◽  
Thrombotic Occlusion ◽  
Expanded Polytetrafluoroethylene ◽  
Blood Flow Velocities ◽  
Vascular Replacement ◽  
Compliance Mismatch ◽  
Flow Velocities

Abstract Development of an ideal vascular replacement has been addressed with increasing urgency in recent years. To date, appropriate replacements for only large diameter bypass have been realized, employing the use of Dacron and expanded polytetrafluoroethylene. A solution for small diameter vessel bypass, however, has not yet been found. This is due mainly to acute thrombotic occlusion and chronic anastomotic hyperplasia that is introduced into these grafts due to the low blood flow velocities experienced by smaller caliber vessels and compliance mismatch between prosthetic and native vessel, respectively [1].

Efficacy of the Direct Thrombin Inhibitor Ximelagatran in Maintaining Small-Diameter Vascular Graft Patency.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1871-1871
Author(s):  
Steven P. Schmidt ◽  
Michelle Evancho-Chapman ◽  
Amy Deeken ◽  
Hans Van Giezen ◽  
Stefan C. Carlsson
Keyword(s):  
Vascular Graft ◽  
Carotid Arteries ◽  
Small Diameter ◽  
Graft Patency ◽  
Direct Thrombin Inhibitor ◽  
Thrombin Inhibitor ◽  
Bypass Grafts ◽  
Vascular Bypass ◽  
Vascular Bypass Grafts ◽  
Graft Implantation

Abstract Objective: A clinically successful small-diameter prosthetic vascular graft has yet to be developed. Improved performance outcomes are also needed with larger-diameter prosthetic vascular grafts for arterial bypass. Ximelagatran (ExantaTM), a fixed-dose, oral direct thrombin inhibitor, is under investigation for thromboprophylaxis in various clinical settings. We hypothesized that ximelagatran could be successful in promoting patencies of small-diameter prosthetic vascular bypass grafts. We hypothesized that ximelagatran could be successful in promoting patencies of small-diameter prosthetic vascular bypass grafts. This 6-month study compared the performances of grafts implanted in carotid arteries in dogs treated with ximelagatran, aspirin, or ximelagatran + aspirin vs non-treated controls. Methods: Dogs (n=6 per group) received bilateral 6-cm long surgical implants of 4 mm internal diameter standard-walled ePTFE vascular grafts. Grafts were interpolated with end-to-end anastomoses as interposition grafts into the common carotid arteries. Ximelagatran administration (200 mg BID p.o.) began 4 hours post graft-implantation. Aspirin (325 mg QD p.o.) was initiated 3 days pre surgery. Medications were continued until study end point. Vascular graft patencies were assessed by non-invasive ultrasound studies 2 weeks post graft-implantation, then monthly. Study end points were bilateral graft failure or 6 months of implantation, whichever was first. A pathologist performed blinded evaluations of the retrieved grafts through calculations of thrombus-free surface areas (TFSA) and histological analyses of healing. Results: One ximelagatran- and one aspirin-treated dog were excluded from the study owing to surgical complications. Ximelagatran was well tolerated. There were no deviations from canine blood norms other than expected elevated PTs and APTTs in ximelagatran-treated animals. Graft Patency: At 6 months, mean graft patencies were similar for the ximelegatran and the ximelagatran + aspirin groups, but both groups were significantly different compared to the aspirin alone and control groups.1TFSA: Mean TFSA of grafts from both the ximelagatran and ximelagatran + aspirin groups were similar but were significantly different from the aspirin alone group.2Intimal Hyperplasia: Statistical differences between groups were not evident between specific locations. However, grafts from the control and aspirin alone groups had more intimal hyperplasia overall than the ximelagatran and ximelagatran + aspirin groups. Conclusions: Ximelagatran-treated dogs had small-diameter vascular graft implants with higher patencies, greater TFSAs and a trend toward less intimal hyperplasia compared with dogs medicated with aspirin alone or controls. We believe that further investigation is warranted in defining the potential use of ximelagatran in maintaining small-diameter vascular graft patencies. Study Group Drug Dose(s) Patency* TFSA % 1 Month 3 Months 6 Months *ratio of number of grafts open to the flow of blood to the total number of evaluable grafts at each time period Ximelagatran 200 mg BID 100% (10/10) 100% (10/10) 88%1 (7/8) 63.4%2 Aspirin 325 mg QD 70% (7/10) 40% (4/10) 30% (3/10) 22.4 Ximelagatran + Aspirin 200 mg BID + 325 mg QD 83% (10/12) 66% (8/12) 66%1 (8/12) 55.0%2 Control - 17% (2/12) 0 (0/12) 0 (0/12) 0

Differences in the brain stem terminations of large- and small-diameter vestibular primary afferents

1995 ◽  
Vol 74 (3) ◽  
pp. 1362-1366 ◽  
Author(s):  
J. A. Huwe ◽  
E. H. Peterson
Keyword(s):  
Brain Stem ◽  
Large Diameter ◽  
Small Diameter ◽  
Movement Control ◽  
Three Dimensions ◽  
Significant Shift ◽  
Axon Diameter ◽  
Vestibular Complex ◽  
The Brain ◽  
Adjacent Brain

1. We visualized the central axons of 32 vestibular afferents from the posterior canal by extracellular application of horseradish peroxidase, reconstructed them in three dimensions, and quantified their morphology. Here we compare the descending limbs of central axons that differ in parent axon diameter. 2. The brain stem distribution of descending limb terminals (collaterals and associated varicosities) varies systematically with parent axon diameter. Large-diameter afferents concentrate their terminals in rostral regions of the medial/descending nuclei. As axon diameter decreases, there is a significant shift of terminal concentration toward the caudal vestibular complex and adjacent brain stem. 3. Rostral and caudal regions of the medial/descending nuclei have different labyrinthine, cerebellar, intrinsic, commissural, and spinal connections; they are believed to play different roles in head movement control. Our data help clarify the functions of large- and small-diameter afferents by showing that they contribute differentially to rostral and caudal vestibular complex.

scholarly journals Elastic Modulus and Elasticity Ratio of Malignant Breast Lesions with Shear Wave Ultrasound Elastography: Variations with Different Region of Interest and Lesion Size

Diagnostics ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1015
Author(s):  
Antonio Bulum ◽  
Gordana Ivanac ◽  
Eugen Divjak ◽  
Iva Biondić Špoljar ◽  
Martina Džoić Dominković ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Shear Wave ◽  
Large Diameter ◽  
Small Diameter ◽  
Shear Wave Elastography ◽  
Lesion Size ◽  
Ultrasound Elastography ◽  
Breast Lesions ◽  
Malignant Breast ◽  
The Impact

Shear wave elastography (SWE) is a type of ultrasound elastography with which the elastic properties of breast tissues can be quantitatively assessed. The purpose of this study was to determine the impact of different regions of interest (ROI) and lesion size on the performance of SWE in differentiating malignant breast lesions. The study included 150 female patients with histopathologically confirmed malignant breast lesions. Minimal (Emin), mean (Emean), maximal (Emax) elastic modulus and elasticity ratio (e-ratio) values were measured using a circular ROI size of 2, 4 and 6 mm diameters and the lesions were divided into large (diameter ≥ 15 mm) and small (diameter < 15 mm). Highest Emin, Emean and e-ratio values and lowest variability were observed when using the 2 mm ROI. Emax values did not differ between different ROI sizes. Larger lesions had significantly higher Emean and Emax values, but there was no difference in e-ratio values between lesions of different sizes. In conclusion, when measuring the Emin, Emean and e-ratio of malignant breast lesions using SWE the smallest possible ROI size should be used regardless of lesion size. ROI size has no impact on Emax values while lesion size has no impact on e-ratio values.

Analysis Influence of Pile Embedded Depth and Diameter on Pile Tip Resistance

2013 ◽  
Vol 353-356 ◽  
pp. 459-462
Author(s):  
Ying Jie Zheng ◽  
Bin Fang ◽  
Lian Xiang Li
Keyword(s):  
Large Diameter ◽  
Small Diameter ◽  
Stiffness Ratio ◽  
Initial Stiffness ◽  
Tip Resistance

Pile tip absolute settlement curves and relative settlement curves of several working cases were analyzed. It is found that load-settlement curve characteristic related to the selection standard. The tip resistance initial stiffness of each case was analyzed. Results show that the small diameter pile has higher initial stiffness than large diameter pile, embedded depth has little influence on initial stiffness ratio, but increment of initial stiffness is linear with embedded depth growth.

scholarly journals Decellularised Human Umbilical Artery as a Vascular Graft Elicits Minimal Pro-Inflammatory Host Response Ex Vivo and In Vivo

2021 ◽  
Vol 22 (15) ◽  
pp. 7981
Author(s):  
Alexander Høgsted Ahlmann ◽  
Shu Fang ◽  
Sussi Bagge Mortensen ◽  
Line Weis Andersen ◽  
Pernille Gejl Pedersen ◽  
...  
Keyword(s):  
Vascular Graft ◽  
Umbilical Artery ◽  
Ex Vivo ◽  
White Blood Cells ◽  
Small Diameter ◽  
M1 Macrophages ◽  
Host Immune Responses ◽  
Cytokine Levels ◽  
Anti Inflammatory Cytokine

Small diameter (<6 mm) vessel grafts still pose a challenge for scientists worldwide. Decellularised umbilical artery (dUA) remains promising as small diameter tissue engineered vascular graft (TEVG), yet their immunogenicity remains unknown. Herein, we evaluated the host immune responses, with a focus on the innate part, towards human dUA implantation in mice, and confirmed our findings in an ex vivo allogeneic human setup. Overall, we did not observe any differences in the number of circulating white blood cells nor the number of monocytes among three groups of mice (1) dUA patch; (2) Sham; and (3) Mock throughout the study (day −7 to 28). Likewise, we found no difference in systemic inflammatory and anti-inflammatory cytokine levels between groups. However, a massive local remodelling response with M2 macrophages were observed in the dUA at day 28, whereas M1 macrophages were less frequent. Moreover, human monocytes from allogeneic individuals were differentiated into macrophages and exposed to lyophilised dUA to maximize an eventual M1 response. Yet, dUA did not elicit any immediate M1 response as determined by the absence of CCR7 and CXCL10. Together this suggests that human dUA elicits a minimal pro-inflammatory response further supporting its use as a TEVG in an allogeneic setup.

New method of poultry selection

2021 ◽  
pp. 61-66
Author(s):  
E. Rehleckaya ◽  
A. Dymkov ◽  
L. Lazarets ◽  
A. Maltsev
Keyword(s):  
Egg Production ◽  
Initial Period ◽  
Large Diameter ◽  
Small Diameter ◽  
Live Weight ◽  
Individual Variability ◽  
Egg Laying ◽  
New Method ◽  
Egg Diameter ◽  
Correlation Rate

Purpose: Install the influence of the «small diameter of the egg» on the living mass and the reproductive qualities of chickens of meat crosses and the quail of meat breeds.Materials and methods. The selection was carried out along egg production and mass of eggs and additionally on the average small diameter of 5 eggs by value of ≥0.5σ from the average for the herd, while the evaluation on the basis of the «small diameter of the egg» was carried out in chickens aged 238 days of life, quails — 70 days of life. Calculated the average for each female and the average for the herd. For further reproduction, chickens carrying eggs with a small egg diameter ≥0.5σ from the average for the herd. Studies were held in SibNIP on quail and on the courses.Results. In the initial period of the egg laying, the individual variability of the small diameter of the egg — more than 10% (in the future, the figure decreased). The close correlation rate of the small egg diameter in the first half of the egg laying with such at the end of the bird's operation period was revealed. It has been established that the large diameter of the egg has a positive reliable connection with a lively mass, but negative with egg production. The reliable correlation rate of the small diameter of the egg with a live weight at a 42-day age, as well as with the derivation of eggs. The inheritance coefficients of the small diameter of the egg are comparable to the inheritance coefficients of the mass of eggs and significantly exceed those for a large diameter of the egg. The selection according to the small diameter of the eggs by ≥0.5σ from the average for the herd led to the fact that the chickens of the experimental groups reliably exceeded the live weight in the SB level of 1.57%, in the line G8 — by 1.35%. The superiority of a lively mass of quail of experienced groups was more pronounced than that of the chickens: the Pharaoh breed — by 4.15%, the Texas white breed is 4.22%. In relation to the derivation of eggs, a similar trend was traced. The derivation of eggs in quails of experienced groups was more than 4.59–4.98%; Country, respectively, 4.57–5.22%. Egg production of females of comparable groups of both chickens and quail was almost on the same level, and the difference was unreliable.Conclusion. It was established that a new method of breeding the poultry of the meat direction of productivity allows without decreasing egg production to increase the living mass of chickens of meat crosses by 1.5%, rewinds of meat breeds — by 4%, the derivation of eggs, respectively, by 4–5%. The method is intended for early prediction of females productivity during breeding selection.

Design, Preparation, and Performance of a Novel Bilayer Tissue‐Engineered Small‐Diameter Vascular Graft

2018 ◽  
Vol 19 (3) ◽  
pp. 1800189 ◽  
Author(s):  
Xiaolin Ran ◽  
Zhiyi Ye ◽  
Meiling Fu ◽  
Qilong Wang ◽  
Haide Wu ◽  
...  
Keyword(s):  
Vascular Graft ◽  
Small Diameter ◽  
And Performance

Copolymer-Nanoparticles Mixture in a Cylindrical Pore

NANO ◽  
2017 ◽  
Vol 12 (04) ◽  
pp. 1750045
Author(s):  
Jun-Xing Pan ◽  
Yu-Qi Guo ◽  
Yu-Fang Han ◽  
Min-Na Sun ◽  
Jin-Jun Zhang
Keyword(s):  
Phase Transition ◽  
Electrical Conductivity ◽  
Polymer Nanocomposites ◽  
Diblock Copolymer ◽  
Large Diameter ◽  
Small Diameter ◽  
Confinement Effect ◽  
Cylindrical Pore ◽  
Disorder Phase Transition ◽  
Novel Structures

Computer simulation is carried out for investigating the effect of nanoparticles on diblock copolymer morphology under cylindrical confinement. The phase diagrams of polymer nanocomposites with nanoparticle-block wetting strength and concentration of nanoparticles are obtained in different nanopores. In small diameter nanopore, there is almost no influence of nanoparticles on the diblock copolymer morphology because of the stronger confinement effect; in middle diameter nanopore, the system can self-assemble into various novel structures due to the interaction between confinement effect and nanoparticles effect; in large diameter nanopore, due to the stronger effect of nanoparticles, a disorder-order-disorder phase transition occurs with the wetting strength and concentration of nanoparticles increasing. This result can be useful in designing new nanocomposites with advanced electrical conductivity and/or mechanical strength.

Characterization of silk sponge in the wet state using13C solid state NMR for development of a porous silk vascular graft with small diameter

RSC Advances ◽  
2014 ◽  
Vol 4 (9) ◽  
pp. 4427-4434 ◽  
Author(s):  
Tetsuo Asakura ◽  
Toshiki Saotome ◽  
Derya Aytemiz ◽  
Haruka Shimokawatoko ◽  
Takahito Yagi ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Vascular Graft ◽  
Small Diameter
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