Journal articles: 'Viscoelastic Vessels'

1

Skalak, T. C., and G. W. Schmid-Scho¨nbein. "Viscoelastic Properties of Microvessels in Rat Spinotrapezius Muscle." Journal of Biomechanical Engineering 108, no. 3 (August 1, 1986): 193–200. http://dx.doi.org/10.1115/1.3138602.

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In order to establish a quantitative model of blood flow in skeletal muscle, the mechanical properties of the blood vessels need to be measured. We present measurements of the viscoelastic properties of arterioles, venules, and capillaries in exteriorized rat spinotrapezius muscle. Muscles were perfused with an inert silicone polymer and a uniform static pressure was established by occlusion of the venous outflow. Vessel diameters were then measured as a function of the static pressure. This study provides the first measurements of the viscoelastic properties of microvessels in skeletal muscle in situ. Over a pressure range of 20–200 mmHg, the transverse arterioles are the most distensible vessels, while the arcade venules are the stiffest. In response to a step change in pressure, all vessels show an initial elastic deformation, followed by a nonlinear creep. Based on the experimental results for different pressure histories a constitutive equation relating vessel diameter to the local transmural pressure is proposed. Diameter changes are expressed in the form of a diameter strain, analogous to a Green’s strain, and are related to the local transmural pressure using a standard linear solid model. This model has only three empirical coefficients and could be fitted to all experimental results for all vessels within error of measurement.

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Zhang, Wei, Yi Liu, and Ghassan S. Kassab. "Viscoelasticity reduces the dynamic stresses and strains in the vessel wall: implications for vessel fatigue." American Journal of Physiology-Heart and Circulatory Physiology 293, no. 4 (October 2007): H2355—H2360. http://dx.doi.org/10.1152/ajpheart.00423.2007.

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The mechanical behavior of blood vessels is known to be viscoelastic rather than elastic. The functional role of viscoelasticity, however, has remained largely unclear. The hypothesis of this study is that viscoelasticity reduces the stresses and strains in the vessel wall, which may have a significant impact on the fatigue life of the blood vessel wall. To verify the hypothesis, the pulsatile stress in rabbit thoracic artery at physiological loading condition was investigated with a quasi-linear viscoelastic model, where the normalized stress relaxation function is assumed to be isotropic, while the stress-strain relationship is anisotropic and nonlinear. The artery was subjected to the same boundary condition, and the mechanical equilibrium equation was solved for both the viscoelastic and an elastic (which has a constant relaxation function) model. Numerical results show that, compared with purely elastic response, the viscoelastic property of arteries reduces the magnitudes and temporal variations of circumferential stress and strain. The radial wall movement is also reduced due to viscoelasticity. These findings imply that viscoelasticity may be beneficial for the fatigue life of blood vessels, which undergo millions of cyclic mechanical loadings each year of life.

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Sánchez-Molina, David, Silvia García-Vilana, Jordi Llumà, Ignasi Galtés, Juan Velázquez-Ameijide, Mari Carmen Rebollo-Soria, and Carlos Arregui-Dalmases. "Mechanical Behavior of Blood Vessels: Elastic and Viscoelastic Contributions." Biology 10, no. 9 (August 26, 2021): 831. http://dx.doi.org/10.3390/biology10090831.

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The mechanical properties of the cerebral bridging veins (CBVs) were studied using advanced microtensile equipment. Detailed high-quality curves were obtained at different strain rates, showing a clearly nonlinear stress–strain response. In addition, the tissue of the CBVs exhibits stress relaxation and a preconditioning effect under cyclic loading, unequivocal indications of viscoelastic behavior. Interestingly, most previous literature that conducts uniaxial tensile tests had not found significant viscoelastic effects in CBVs, but the use of more sensitive tests allowed to observe the viscoelastic effects. For that reason, a careful mathematical analysis is presented, clarifying why in uniaxial tests with moderate strain rates, it is difficult to observe any viscoelastic effect. The analysis provides a theoretical explanation as to why many recent studies that investigated mechanical properties did not find a significant viscoelastic effect, even though in other circumstances, the CBV tissue would clearly exhibit viscoelastic behavior. Finally, this study provides reference values for the usual mechanical properties, as well as calculations of constitutive parameters for nonlinear elastic and viscoelastic models that would allow more accurate numerical simulation of CBVs in Finite Element-based computational models in future works.

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DARJANI, MORTEZA, ALI ESTEKI, and S. AHMAD HASSANTASH. "IN VITRO INVESTIGATION OF DYNAMIC VISCOELASTIC PROPERTIES OF HUMAN SAPHENOUS VEINS USING A CARDIOVASCULAR SIMULATOR." Journal of Mechanics in Medicine and Biology 16, no. 04 (June 2016): 1650044. http://dx.doi.org/10.1142/s0219519416500445.

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Coronary bypass surgery is a usual therapy for vessel-related diseases as several thousand of this kind of surgery are reported annually. In this surgery, saphenous vein, internal mammary artery or radial artery are grafted to replace coronary vessels. This research aims to evaluate viscoelastic properties of human saphenous vein vessel wall used in bypass surgery using a device designed in our laboratory. The most important feature of this device is its ability to simulate physiological conditions which exist inside humans’ bodies. During experiments, variations in both vessel diameter and exerted pressure are recorded simultaneously. After performing measurements at frequencies near to heart beat frequency and finding loss and storage modulus for each frequency, it is found that, in the scanned frequency range, Kelvin model is the best approach to assess viscoelastic behavior of vessels. Remarkably, the results found in this research are in agreement with literature.

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Eslami, M. R., and M. Shariyat. "A Technique to Distinguish the Primary and Secondary Stresses." Journal of Pressure Vessel Technology 117, no. 3 (August 1, 1995): 197–203. http://dx.doi.org/10.1115/1.2842112.

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A technique is developed which can be used to distinguish the primary and secondary stresses in pressure vessels. The general definition of the two types of stresses stated by the ASME Code is used; a simple viscoelastic model is proposed for each stress category. The proposed model can be extended to elastic as well as plastic regions of strain-hardening materials and can include the mechanical as well as thermal loads. The proposed viscoelastic models are used to judge the nature of elastic stresses and the effective stress-strain curve is used to simulate the state of stress at any stage of loading and the percentage of primary to secondary stresses at any radius of the vessel. It is found that thermal stresses cannot always be categorized as secondary stress, and in the case of thermoplastically loaded vessels they can contribute partly to the primary stress in the vessel.

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Berglund, Joseph D., Robert M. Nerem, and Athanassios Sambanis. "Viscoelastic Testing Methodologies for Tissue Engineered Blood Vessels." Journal of Biomechanical Engineering 127, no. 7 (June 6, 2005): 1176–84. http://dx.doi.org/10.1115/1.2073487.

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In order to function in vivo, tissue engineered blood vessels (TEBVs) must encumber pulsatile blood flow and withstand hemodynamic pressures for long periods of time. To date TEBV mechanical assessment has typically relied on single time point burst and/or uniaxial tensile testing to gauge the strengths of the constructs. This study extends this analysis to include creep and stepwise stress relaxation viscoelastic testing methodologies. TEBV models exhibiting diverse mechanical behaviors as a result of different architectures ranging from reconstituted collagen gels to hybrid constructs reinforced with either untreated or glutaraldhyde-crosslinked collagen supports were evaluated after 8 and 23 days of in vitro culturing. Data were modeled using three and four-parameter linear viscoelastic mathematical representations and compared to porcine carotid arteries. While glutaraldhyde-treated hybrid TEBVs exhibited the largest overall strengths and toughness, uncrosslinked hybrid samples exhibited time-dependent behaviors most similar to native arteries. These findings emphasize the importance of viscoelastic characterization when evaluating the mechanical performance of TEBVs. Limits of testing methods and modeling systems are presented and discussed.

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Seyssiecq, I., A. Tolofoudyé, H. Desplanches, and Y. Gaston-Bonhomme. "Viscoelastic Liquids in Stirred Vessels– Part I: Power Consumption in Unaerated Vessels." Chemical Engineering & Technology 26, no. 11 (November 10, 2003): 1155–65. http://dx.doi.org/10.1002/ceat.200301689.

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8

Lee, J., E. P. Salathe, and G. W. Schmid-Schonbein. "Fluid exchange in skeletal muscle with viscoelastic blood vessels." American Journal of Physiology-Heart and Circulatory Physiology 253, no. 6 (December 1, 1987): H1548—H1556. http://dx.doi.org/10.1152/ajpheart.1987.253.6.h1548.

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A mathematical model of capillary-tissue fluid exchange in a viscoelastic blood vessel is presented, and the Landis occlusion experiment is simulated. The model assumes that the fluid exchange is governed by Starling's law and that the protein and red blood cells are conserved in the capillary. Before occlusion, in the steady flow state, the pressure in the capillary decreases from the arterial to venous end due to viscous dissipation. After occlusion a constant pressure is established along the capillary. We assume the capillary to be distensible with viscoelastic wall properties. Immediately following occlusion an instantaneous distension of the capillary occurs. The vessel continues to expand viscoelastically while fluid is filtered for a period of several minutes, until it reaches an equilibrium state. A full numerical solution of the governing equations has been obtained. We use this model to compute the distance variation between two labeled erythrocytes as obtained in the Landis occlusion experiment and compare the results with experimental data obtained recently for the spinotrapezius muscle in our laboratory. The new model can fit the experimental data better than previous models that neglect the distensibility of the capillaries.

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9

Hackett, Robert M., and Jan D. Dozier. "Viscoelastic/Damage Modeling of Filament-Wound Spherical Pressure Vessels." Journal of Reinforced Plastics and Composites 6, no. 2 (April 1987): 126–37. http://dx.doi.org/10.1177/073168448700600202.

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10

Schmid-Scho¨nbein, G. W. "A Theory of Blood Flow in Skeletal Muscle." Journal of Biomechanical Engineering 110, no. 1 (February 1, 1988): 20–26. http://dx.doi.org/10.1115/1.3108401.

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A theoretical analysis of blood flow in the microcirculation of skeletal muscle is provided. The flow in the microvessels of this organ is quasi steady and has a very low Reynolds number. The blood is non-Newtonian and the blood vessels are distensible with viscoelastic properties. A formulation of the problem is provided using a viscoelastic model for the vessel wall which was recently derived from measurements in the rat spinotrapezius muscle (Skalak and Schmid-Scho¨nbein, 1986b). Closed form solutions are derived for several physiologically important cases, such as perfusion at steady state, transient and oscillatory flows. The results show that resting skeletal muscle has, over a wide range of perfusion pressures an almost linear pressure-flow curve. At low flow it exhibits nonlinearities. Vessel distensibility and the non-Newtonian properties of blood both have a strong influence on the shape of the pressure-flow curve. During oscillatory flow the muscle exhibits hysteresis. The theoretical results are in qualitative agreement with experimental observations.

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11

Townsend, Patrick, Juan Carlos Suárez, and Alvaro Rodríguez-Ortìz. "The Use of Hybrid Viscoelastic Sheets in the Shipbuilding of GFRP Planing Hull Vessels Externally Adhered to the Laminate." Engineering Innovations 3 (September 1, 2022): 35–40. http://dx.doi.org/10.4028/p-o984an.

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The use of viscoelastic sheets in the hull of vessels built from GFRP has been raised in previous works as an option to protect the vessel from the destructive damage of slamming. The present work proposes its use in boats previously built by adhering to the outside of the hulls of the ships. Its installation process is shown, and this new type of installation is compared. Through impact tests with GFRP panels, it is shown that the viscoelastic material maintains its property of absorbing slamming energy and protecting the interior of the laminate. Fatigue tests on the order of 5x104 cycles are carried out to evaluate the impact force, the accelerations that deform the laminate and the virtual energy work imposed on the panel. This option shows that designers have a new option to protect the hull of already built boats.

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Mitsotakis, Dimitrios, Denys Dutykh, Qian Li, and Elijah Peach. "On some model equations for pulsatile flow in viscoelastic vessels." Wave Motion 90 (August 2019): 139–51. http://dx.doi.org/10.1016/j.wavemoti.2019.05.004.

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Townsend, Patrick, Juan Carlos Suárez, Paz Pinilla, and Nadia Muñoz. "Insertion of a Viscoelastic Layer to Reduce the Propagation of Energy by Vertical Impacts of Slamming in Planing Hull Vessels." Key Engineering Materials 889 (June 16, 2021): 65–70. http://dx.doi.org/10.4028/www.scientific.net/kem.889.65.

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For the design of vessels built by GFRP laminates, an insert with a viscoelastic layer is proposed to reduce the spread of damage produced by the vertical impact of the ship's bottom with the sea or slamming phenomenon. Using vertical drops-weight impact machine that reproduce the energy inferred to the panel during navigation, the propagation of the damage of OoA cured prepreg panels is studied comparing it with modified panels with insertion of viscoelastic layer. The use of acceleration data reading allows the benefits of viscoelastic modification during impact to be quantified through the developed formulation. The force, displacement and energy returned by the panel after impact have also been quantified, which does not become intralaminar and interlaminar damage. It is shown that under 40 joules of impact, the viscoelastic sheet has its best ability to return energy and above 130 joules it loses its capacity.

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García-Vilana, Silvia, David Sánchez-Molina, Jordi Llumà, Ignasi Galtés, Juan Velázquez-Ameijide, M. Carmen Rebollo-Soria, and Carlos Arregui-Dalmases. "Viscoelastic Characterization of Parasagittal Bridging Veins and Implications for Traumatic Brain Injury: A Pilot Study." Bioengineering 8, no. 10 (October 18, 2021): 145. http://dx.doi.org/10.3390/bioengineering8100145.

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Many previous studies on the mechanical properties of Parasagittal Bridging Veins (PSBVs) found that strain rate had a significant effect on some mechanical properties, but did not extensively study the viscoelastic effects, which are difficult to detect with uniaxial simple tensile tests. In this study, relaxation tests and tests under cyclic loading were performed, and it was found that PSBVs do indeed exhibit clear viscoelastic effects. In addition, a complete viscoelastic model for the PSBVs is proposed and data from relaxation, cyclic load and load-unload tests for triangular loads are used to find reference values that characterize the viscoelastic behavior of the PSBVs. Although such models have been proposed for other types of blood vessels, this is the first study that clearly demonstrates the existence of viscoelastic effects from an experimental point of view and also proposes a specific model to explain the data obtained. Finally, this study provides reference values for the usual viscoelastic properties, which would allow more accurate numerical simulation of PSBVs by means of computational models.

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Jimenez Rios, Jorge L., Paul S. Steif, and Yoed Rabin. "Stress-Strain Measurements and Viscoelastic Response of Blood Vessels Cryopreserved by Vitrification." Annals of Biomedical Engineering 35, no. 12 (September 9, 2007): 2077–86. http://dx.doi.org/10.1007/s10439-007-9372-0.

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Lee, Usik, and Injoon Jang. "Spectral element modeling and analysis of the blood flows in viscoelastic vessels." Applied Mathematics and Computation 218, no. 13 (March 2012): 7295–307. http://dx.doi.org/10.1016/j.amc.2012.01.008.

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Kopachevsky, N. D. "Problems on Small Motions of Systems of Two Viscoelastic Fluids in Fixed Vessels." Journal of Mathematical Sciences 263, no. 6 (June 2022): 860–86. http://dx.doi.org/10.1007/s10958-022-05970-1.

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Baloch, A., P. W. Grant, and M. F. Webster. "Parallel computation of two‐dimensional rotational flows of viscoelastic fluids in cylindrical vessels." Engineering Computations 19, no. 7 (November 2002): 820–53. http://dx.doi.org/10.1108/02644400210444339.

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Bertaglia, Giulia, Valerio Caleffi, and Alessandro Valiani. "Modeling blood flow in viscoelastic vessels: the 1D augmented fluid–structure interaction system." Computer Methods in Applied Mechanics and Engineering 360 (March 2020): 112772. http://dx.doi.org/10.1016/j.cma.2019.112772.

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Rehal, Devinder, Xiaomei Guo, Xiao Lu, and Ghassan S. Kassab. "Duration of no-load state affects opening angle of porcine coronary arteries." American Journal of Physiology-Heart and Circulatory Physiology 290, no. 5 (May 2006): H1871—H1878. http://dx.doi.org/10.1152/ajpheart.00910.2005.

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The zero-stress state of a blood vessel has been extensively studied because it is the reference state for which all calculations of intramural stress and strain must be based. It has also been found to reflect nonuniformity in growth and remodeling in response to chemical or physical changes. The zero-stress state can be characterized by an opening angle, defined as the angle subtended by two radii connecting the midpoint of the inner wall. All prior studies documented the zero-stress state or opening angle with no regard to duration of the no-load state. Our hypotheses were that, given the viscoelastic properties of blood vessels, the zero-stress state may have “memory” of prior circumferential and axial loading, i.e., duration of the no-load state influences opening angle. To test these hypotheses, we considered ring pairs of porcine coronary arteries to examine the effect of duration in the no-load state after circumferential distension. Our results show a significant reduction in opening angle as duration of the no-load state increases, i.e., vessels that are reduced to the zero-stress state directly from the loaded state attain much larger opening angles at 30 min after the radial cut than rings that are in the no-load state for various durations. To examine the effect of axial loading, we found similar reductions in opening angle with duration in the no-load from the in situ state, albeit the effect was significantly smaller than that of circumferential loading. Hence, we found that the zero-stress state has memory of both circumferential and axial loading. These results are important for understanding viscoelastic properties of coronary arteries, interpretation of the enormous data on the opening angle and strain in the literature, and standardization of future measurements on the zero-stress state.

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Faturechi, Rahim, Ata Hashemi, Nabiollah Abolfathi, Atefeh Solouk, and Alexander Seifalian. "Fabrications of small diameter compliance bypass conduit using electrospinning of clinical grade polyurethane." Vascular 27, no. 6 (May 22, 2019): 636–47. http://dx.doi.org/10.1177/1708538119850994.

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Objective Compliance and viscoelastic mismatches of small diameter vascular conduits and host arteries have been the cause of conduit’s failure. Methods To reduce these mismatches, the aim of this study was to develop and characterize a polyurethane conduit, which mimics the viscoelastic behaviors of human arteries. Electrospinning technique was used to fabricate tubular polyurethane conduits with similar properties of the human common carotid artery. This was achieved by manipulating the fiber diameter by altering the syringe flow rate of the solution. The mechanical and viscoelastic properties of the fabricated electrospun polyurethane conduits were, then, compared with commercially available vascular conduits, expanded polytetrafluoroethylene, polyethylene terephthalate (Dacron®) and the healthy human common carotid arteries. In addition, a comprehensive constitutive model was proposed to capture the visco-hyperelastic behavior of the synthetic electrospun polyurethanes, commercial conduits and human common carotid arteries. Results Results showed that increasing the fiber diameter of electrospun polyurethanes from 114 to 190 nm reduced Young’s modulus from 8 to 2 MPa. Also, thicker fiber diameter yielded in higher conduits’ viscosity. Furthermore, the results revealed that proposed visco-hyperelastic model is strongly able to fit the experimental data with great precision which proofs the reliability of the proposed model to address both nonlinear elasticity and viscoelasticity of the electrospun polyurethanes, commercial conduits and human common carotid arteries. Conclusions In conclusion, statistical analysis revealed that the elastic and viscous properties of 190 nm fiber diameter conduit are very similar to that of human common carotid artery in comparison to the commercial expanded polytetrafluoroethylene and Dacron® that are up to nine and seven times stiffer than natural vessels. Therefore, based on our findings, from the mechanical point of view, by considering the amount of Young’s modulus, compliance, distensibility and viscoelastic behavior, the fabricated electrospun polyurethane with fiber diameter of 189.6 ± 52.89 nm is an optimum conduit with promising potential for substituting natural human vessels.

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Drozdov, A. D., and A. L. Kalamkarov. "Optimal Design Problems in Mechanics of Growing Composite Solids, Part I: Preload Optimization." Journal of Applied Mechanics 62, no. 4 (December 1, 1995): 975–82. http://dx.doi.org/10.1115/1.2896032.

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Optimal design problems arising in mechanics of growing composite viscoelastic and elastic solids subjected to aging are considered. The growth means a continuous mass influx to the body surface. Due to this process, the size of the body increases in time. The mass influx with pretensioning causes the rise of stresses in the growing body. The purpose of the current study is to propose a new class of the optimal design problems for the growing viscoelastic composite solids subjected to aging, and to solve the mechanical design problems of this new type. In the current paper, we analyze the optimal preload distribution in the winding process for cylindrical solids. The proposed approach and the obtained new solutions are of a special interest and importance for the optimization of winding of composite pressure vessels.

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Bouriquet, N., and D. Casellas. "Chronic L-NAME hypertension in rats and autoregulation of juxtamedullary preglomerular vessels." American Journal of Physiology-Renal Physiology 269, no. 2 (August 1, 1995): F190—F197. http://dx.doi.org/10.1152/ajprenal.1995.269.2.f190.

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The impact of chronic NG-nitro-L-arginine methyl ester (L-NAME)-induced hypertension (20 mg.kg-1.day-1 po, for 25 days) on pressure responsiveness was assessed in vessels ranging from arcuate arteries (ArcA) to juxtaglomerular afferent arterioles (JAA), using videomicroscopy and blood-perfused juxtamedullary nephron (JMN) preparations. Respective tail-cuff pressures of control and L-NAME rats were 127 +/- 2 (n = 8) and 173 +/- 4 mmHg (n = 5). Corresponding vessels of both groups had similar calibers at 60 mmHg. Increasing blood perfusion pressure to 200 mmHg constricted control ArcA and JAA by 26 +/- 4% (n = 20) and 43 +/- 5% (n = 15), respectively. Instead, a respective 3 +/- 4% (n = 15) and 21 +/- 9% (n = 6) pressure-induced dilation occurred in L-NAME vessels, and 86 +/- 2% of glomeruli expressed alpha-smooth muscle actin. Responses to acetylcholine (1 microM) but not to nitroprusside (1 mM) were impaired by L-NAME. Maximal relaxation induced by Mn2+ (10 mM) revealed equal basal tone and similar passive viscoelastic properties in control and L-NAME vessels. No vascular hypertrophy was found in L-NAME vessels. Chronic L-NAME hypertension is therefore associated with a selective loss of vascular autoregulation in JMNs, which may contribute to glomerular injury.

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BATTISTA, CHRISTINA, DANIEL BIA, YANINA ZÓCALO GERMÁN, RICARDO L. ARMENTANO, MANSOOR A. HAIDER, and METTE S. OLUFSEN. "WAVE PROPAGATION IN A 1D FLUID DYNAMICS MODEL USING PRESSURE-AREA MEASUREMENTS FROM OVINE ARTERIES." Journal of Mechanics in Medicine and Biology 16, no. 02 (March 2016): 1650007. http://dx.doi.org/10.1142/s021951941650007x.

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This study considers a 1D fluid dynamics arterial network model with 14 vessels developed to assimilate ex vivo 0D temporal data for pressure-area dynamics in individual vessel segments from 11 male Merino sheep. A 0D model was used to estimate vessel wall parameters in a two-parameter elastic model and a four-parameter Kelvin viscoelastic model. This was done using nonlinear optimization minimizing the least squares error between model predictions and measured cross-sectional areas. Subsequently, estimated values for elastic stiffness and unstressed area were related to construct a nonlinear relationship. This relation was used in the network model. A 1D single vessel model of the aorta was then developed and used to estimate the inflow profile and parameters for total resistance and compliance for the downstream network and to demonstrate effects of incorporating viscoelasticity in the arterial wall. Lastly, the extent to which vessel wall parameters estimated from ex vivo data can be used to realistically simulate pressure and area in a vessel network was evaluated. Elastic wall parameters in the network simulations were found to yield pressure-area relationships across all vessel locations and sheep that were in ranges comparable to those in the ex vivo data.

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Arribas, Silvia M., Ana M. Briones, Catherine Bellingham, M. Carmen González, Mercedes Salaices, Kela Liu, Yanting Wang, and Aleksander Hinek. "Heightened aberrant deposition of hard-wearing elastin in conduit arteries of prehypertensive SHR is associated with increased stiffness and inward remodeling." American Journal of Physiology-Heart and Circulatory Physiology 295, no. 6 (December 2008): H2299—H2307. http://dx.doi.org/10.1152/ajpheart.00155.2008.

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Elastin is a major component of conduit arteries and a key determinant of vascular viscoelastic properties. Aberrant organization of elastic lamellae has been reported in resistance vessels from spontaneously hypertensive rats (SHR) before the development of hypertension. Hence, we have characterized the content and organization of elastic lamellae in conduit vessels of neonatal SHR in detail, comparing the carotid arteries from 1-wk-old SHR with those from Wistar-Kyoto (WKY) and Sprague Dawley (SD) rats. The general structure and mechanics were studied by pressure myography, and the internal elastic lamina organization was determined by confocal microscopy. Cyanide bromide-insoluble elastin scaffolds were also prepared from 1-mo-old SHR and WKY aortas to assess their weight, amino acid composition, three-dimensional lamellar organization, and mechanical characteristics. Carotid arteries from 1-wk-old SHR exhibited narrower lumen and greater intrinsic stiffness than those from their WKY and SD counterparts. These aberrations were associated with heightened elastin content and with a striking reduction in the size of the fenestrae present in the elastic lamellae. The elastin scaffolds isolated from SHR aortas also exhibited increased relative weight and stiffness, as well as the presence of peculiar trabeculae inside the fenestra that reduced their size. We suggest that the excessive and aberrant elastin deposited in SHR vessels during perinatal development alters their mechanical properties. Such abnormalities are likely to compromise vessel expansion during a critical period of growth and, at later stages, they could compromise hemodynamic function and participate in the development of systemic hypertension.

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Abels, Helmut, and Yadong Liu. "On a fluid–structure interaction problem for plaque growth." Nonlinearity 36, no. 1 (December 9, 2022): 537–83. http://dx.doi.org/10.1088/1361-6544/aca5e1.

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Abstract We study a free-boundary fluid–structure interaction problem with growth, which arises from the plaque formation in blood vessels. The fluid is described by the incompressible Navier–Stokes equations, while the structure is considered as a viscoelastic incompressible neo-Hookean material. Moreover, the growth due to the biochemical process is taken into account. Applying the maximal regularity theory to a linearization of the equations, along with a deformation mapping, we prove the well-posedness of the full nonlinear problem via the contraction mapping principle.

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SELEZOV, IGOR, GIOVANNI PALLOTTI, GIUSEPPE FRATAMICO, and PAOLO PETTAZZONI. "VISCOELASTICITY WITH PERMANENT DEFORMATION IN INVESTIGATION OF PULSE PROPAGATION IN BLOOD VESSELS." Journal of Mechanics in Medicine and Biology 01, no. 02 (October 2001): 139–52. http://dx.doi.org/10.1142/s0219519401000210.

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The models of viscoelasticity are considered from the point of view of their applicability to describe the behavior of blood vessel wall material. First, some convenient and popular models are considered briefly. These models are widely used, particularly in engineering applications, because of their simplicity and clear physical treatment. At the same time, these models are not representative of many real (and particularly anatomical) materials. As a result, new nonlinear models have been developed by Fung and other researchers for biomaterials. However before them, one of the generalized model of viscoelasticity has been developed by Knopoff and MacDonald. Here this model is considered and applied for evaluation of blood vessel wall characteristics. Unlike the convenient models, this model is based on fundamental thermodynamic concepts, and takes into account some more realistic features of viscoelastic solids. Application of this model to determine the characteristics of blood vessel material is presented.

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Batyuk, L. V., and Natalya Kizilova. "Modeling of blood cell surface oscillations as fluid-filled multilayer viscoelastic shells." Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics, no. 1 (2022): 40–43. http://dx.doi.org/10.17721/1812-5409.2022/1.4.

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Rheological properties of the red blood cells (RBC) determine their movement in the larger and smaller blood vessels, oxygen and carbon dioxide delivery to/from the cells. Those properties vary significantly with age and health state of an organism. In this paper a new rheological model of RBC as a thin multilayer shell, which includes the cytoskeleton, lipid bilayer, glycocalyx, and hydrate shell as Maxwell's viscoelastic bodies is proposed. Mechanical properties of the rheological model in isotonic, isometric and dynamic experiments are studied. The oscillations of the surfaces of erythrocytes or other cells in the approximation of multilayer viscoelastic shell filled with a viscous fluid are investigated. The expressions for the dynamic Young’s modules and viscosity/fluidity coefficients as functions of the viscoelastic and geometric parameters of the layers are obtained. The problem of propagation of small perturbations along the cell surface is considered. The solutions of the problem in the form of Young and Lamé waves are obtained. The method of identification of the erythrocyte parameters from the experimental measurements of the wave propagation on the basis of the developed mathematical model for the purposes of clinical diagnostics of diseases with use of a microdrop of blood of the patient is proposed.

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Urban, Matthew, Daniel Rosario, Miguel Bernal, Wilkins Aquino, and James Greenleaf. "Viscoelastic response of cylindrical vessels surrounded by gelatin and excited using impulsive ultrasound radiation force." Journal of the Acoustical Society of America 124, no. 4 (October 2008): 2445. http://dx.doi.org/10.1121/1.4782581.

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Giezeman, M. J., E. VanBavel, C. A. Grimbergen, and J. A. Spaan. "Compliance of isolated porcine coronary small arteries and coronary pressure-flow relations." American Journal of Physiology-Heart and Circulatory Physiology 267, no. 3 (September 1, 1994): H1190—H1198. http://dx.doi.org/10.1152/ajpheart.1994.267.3.h1190.

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Compliance of small arteries is important for the interpretation of arterial pressure-flow relations. Six coronary small arteries (mean diameter 189 +/- 46 microns) were cannulated. Pressure-cross-sectional area (CSA) relations were obtained from isolated vessels by slowly varying pressure between 10 and 120 mmHg. Subsequently, small pressure variations were superimposed on constant mean pressures of 10, 30, and 50 mmHg with frequencies of 0.1-10 Hz. Normalized compliance (C0) was calculated as the compliance divided by the CSA at 50 mmHg. In vessels without tone, static C0 was 27.5 +/- 8.9, 6.4 +/- 1.1, and 3.8 +/- 1.0 x 10(-3) mmHg-1 at 10, 30, and 50 mmHg, respectively. At a frequency of 0.1 Hz, C0 decreased to one-third of static C0 at any pressure. Under these conditions, the phase shift between pressure and CSA was rather constant and ranged from -21 to -5 degrees. In four small arteries, smooth muscle tone was induced by the administration of acetylcholine. Activation decreased dynamic C0 by 60%. Two models of coronary input impedance were evaluated: the first model includes viscoelastic properties of the arterial wall and the second takes into account the blood inertia effect. The second model predicts much better the wall mechanics of single small arteries. The viscoelastic model overestimates the frequency dependence of compliance by a factor of 2 and the phase lag by a factor of 4. Moreover this model predicts a strong frequency dependence of induction of tone on compliance and phase lag, whereas this dependence is absent in the experimental results.

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Ramesh, Katta, Dharmendra Tripathi, Muhammad Mubashir Bhatti, Kaouther Ghachem, Sami Ullah Khan, and Lioua Kolsi. "Mathematical modeling and simulation of electromagnetohydrodynamic bio-nanomaterial flow through physiological vessels." Journal of Applied Biomaterials & Functional Materials 20 (January 2022): 228080002211147. http://dx.doi.org/10.1177/22808000221114708.

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Gold-based metal nanoparticles serve a key role in diagnosing and treating important illnesses such as cancer and infectious diseases. In consideration of this, the current work develops a mathematical model for viscoelastic nanofluid flow in the peristaltic microchannel. Nanofluid is considered as blood-based fluid suspended with gold nanoparticles. In the investigated geometry, various parametric effects such as Joule heating, magnetohydrodynamics, electroosmosis, and thermal radiation have been imposed. The governing equations of the model are analytically solved by using the lubrication theory where the wavelength of the channel is considered large and viscous force is considered more dominant as compared to the inertia force relating the applications in biological transport phenomena. The graphical findings for relevant parameters of interest are given. In the current analysis, the ranges of the parameters have been considered as: [Formula: see text]The current results reveal that, A stronger magnetic field leads the enhancement in nanoparticle temperature and shear stress, and it reduces the velocity and trapping bolus. The nanoparticle temperature rises with the increasing parameters such as Brinkman number and Joule heating parameter.

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Kim, Yongsam, Yunyoung Park, and Sookkyung Lim. "3D Simulations of Blood Flow Dynamics in Compliant Vessels: Normal, Aneurysmal, and Stenotic Arteries." Communications in Computational Physics 19, no. 5 (May 2016): 1167–90. http://dx.doi.org/10.4208/cicp.scpde14.20s.

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AbstractArterial diseases such as aneurysm and stenosis may result from the mechanical and/or morphological change of an arterial wall structure and correspondingly altered hemodynamics. The development of a 3D computational model of blood flow can be useful to study the hemodynamics in major blood vessels and may provide an insight into the noninvasive technique to detect arterial diseases in early stage. In this paper, we present a three-dimensional model of blood flow in the aorta, which is based on the immersed boundary method to describe the interaction of blood flow with the aortic wall. Our simulation results show that the hysteresis loop is evident in the pressure-diameter relationship of the normal aorta when the arterial wall is considered to be viscoelastic. In addition, it is shown that flow patterns and pressure distributions are altered in response to the change of aortic morphology.

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Bessems, D., M. C. M. Rutten, and F. N. van de Vosse. "Experimental validation of a wave propagation model of blood flow in vessels with viscoelastic wall properties." Journal of Biomechanics 39 (January 2006): S310. http://dx.doi.org/10.1016/s0021-9290(06)84212-0.

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Bessems, David, Christina G. Giannopapa, Marcel C. M. Rutten, and Frans N. van de Vosse. "Experimental validation of a time-domain-based wave propagation model of blood flow in viscoelastic vessels." Journal of Biomechanics 41, no. 2 (January 2008): 284–91. http://dx.doi.org/10.1016/j.jbiomech.2007.09.014.

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Glushkova, T. V., V. V. Sevostyanova, L. V. Antonova, K. Yu Klyshnikov, E. A. Ovcharenko, E. A. Sergeeva, G. Yu Vasyukov, A. M. Seifalian, and L. S. Barbarash. "BIOMECHANICAL REMODELING OF BIODEGRADABLE SMALL-DIAMETER VASCULAR GRAFTS IN SITU." Russian Journal of Transplantology and Artificial Organs 18, no. 2 (June 25, 2016): 99–109. http://dx.doi.org/10.15825/1995-1191-2016-2-99-109.

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Aim: to evaluate the biomechanical remodeling of polymer grafts modified with vascular endothelial growth factor (VEGF) after implantation into rat abdominal aorta.Materials and methods. Vascular grafts of2 mmdiameter were fabricated by electrospinning from polycaprolactone (PCL) and a mixture of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) and PCL. The grafts were modified with VEGF by biphasic electrospinning. Morphology of the grafts was assessed by scanning electron microscopy. Physico-mechanical properties of PCL and PHBV/PCL grafts were estimated using uniaxial tensile test and physiological circulating system equipped with state-of-theart ultrasound vascular wall tracking system. Physico-mechanical testing of PCL/VEGF and PHBV/PCL/VEGF was performed before and after implantation into rat abdominal aorta for 6 months. The modeling of coronary artery bypass grafting (CABG) was performed by finite element analysis for modified grafts.Results. Durability of PCL and PHBV/PCL grafts did not differ from that of human internal mammary artery; however, elasticity and stiffness of these grafts were higher compared to internal mammary artery. Viscoelastic properties of the grafts were comparable to those of native blood vessels. Modification of the grafts with VEGF reduced material stiffness. Six months postimplantation, PCL/VEGF and PHBV/PCL/VEGF were integrated with aortic tissue that induced changes in the physico-mechanical properties of the grafts similar to the native vessel. Biomechanical modeling confirmed the functioning of modified grafts in bypass position for CABG.Conclusion. PCL/VEGF and PHBV/PCL/VEGF grafts have satisfactory physico-mechanical properties and can be potentially used in the reconstruction of blood vessels.

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Sasikumar, J., and R. Senthamarai. "Chemical reaction and viscous dissipation effect on MHD oscillatory blood flow in tapered asymmetric channel." Mathematical Modeling and Computing 9, no. 4 (2022): 999–1010. http://dx.doi.org/10.23939/mmc2022.04.999.

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MHD viscous oscillating type blood flow through lumen in arteries and varicose veins motivating to the study of blood flow in disordered blood vessels and veins. The blood flow in disordered nervous system, like varicose veins and other micro arteries in respiratory system is modeled geometrically in the shape of tapered curvy walls of varying cross section which is the new approach in this problem and the same has advantage compared to the other geometrical channel shapes. Blood taken as viscoelastic and optically thick fluid flowing through porous structure. Magnetic force considered in normal direction to the nervous system. Viscous dissipation and chemical reaction effects on blood flow are analyzed.

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Yoshinari, Hiromi, A. Toshimitsu Yokobori, Jr., and Tsuneo Ohkuma. "Theoretical Foundation on a Noninvasive Estimation for Viscoelastic Mechanical Property of Blood Vessels by Ultrasonic Doppler Effect." Bio-Medical Materials and Engineering 4, no. 2 (1994): 77–86. http://dx.doi.org/10.3233/bme-1994-4203.

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Meghezi, Sébastien, Frédéric Couet, Pascale Chevallier, and Diego Mantovani. "Effects of a Pseudophysiological Environment on the Elastic and Viscoelastic Properties of Collagen Gels." International Journal of Biomaterials 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/319290.

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Vascular tissue engineering focuses on the replacement of diseased small-diameter blood vessels with a diameter less than 6 mm for which adequate substitutes still do not exist. One approach to vascular tissue engineering is to culture vascular cells on a scaffold in a bioreactor. The bioreactor establishes pseudophysiological conditions for culture (medium culture, 37°C, mechanical stimulation). Collagen gels are widely used as scaffolds for tissue regeneration due to their biological properties; however, they exhibit low mechanical properties. Mechanical characterization of these scaffolds requires establishing the conditions of testing in regard to the conditions set in the bioreactor. The effects of different parameters used during mechanical testing on the collagen gels were evaluated in terms of mechanical and viscoelastic properties. Thus, a factorial experiment was adopted, and three relevant factors were considered: temperature (23°C or 37°C), hydration (aqueous saline solution or air), and mechanical preconditioning (with or without). Statistical analyses showed significant effects of these factors on the mechanical properties which were assessed by tensile tests as well as stress relaxation tests. The last tests provide a more consistent understanding of the gels' viscoelastic properties. Therefore, performing mechanical analyses on hydrogels requires setting an adequate environment in terms of temperature and aqueous saline solution as well as choosing the adequate test.

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Hochmuth, Robert M. "Measuring the Mechanical Properties of Individual Human Blood Cells." Journal of Biomechanical Engineering 115, no. 4B (November 1, 1993): 515–19. http://dx.doi.org/10.1115/1.2895533.

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The largest human blood cells—the red cells (erythrocytes) and white cells (leukocytes)—must undergo a significant amount of deformation as they squeeze through the smallest vessels of the circulation and the small openings between bone, vessel and tissue. This ability to deform in response to external forces shows that cells exhibit material behavior and behave as either elastic solids or viscous liquids. The question then is “how can we measure the deformation and flow of something as small as a blood cell and what kinds of constitutive equations describe cellular deformation”? In this paper the use of the micropipet to measure red cell and white cell, especially neutrophil, deformation will be described and the viscoelastic models used to describe the deformation behavior of red cell membrane and neutrophil cytoplasm will be discussed. Values for the elasticities of a red cell membrane subjected to shear, area expansion and bending will be given. The viscosity of red cell membrane in shear will also be discussed. Finally, the cortical tension of the neutrophil and the Newtonian and Maxwell models used to characterize its apparent viscosity will be discussed even though neither is wholly successful in describing the viscous behavior of the neutrophil. Thus, alternate models will be suggested.

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Lins Barros, Paloma, Farhad Ein-Mozaffari, and Ali Lohi. "Gas Dispersion in Non-Newtonian Fluids with Mechanically Agitated Systems: A Review." Processes 10, no. 2 (January 30, 2022): 275. http://dx.doi.org/10.3390/pr10020275.

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Gas dispersion in non-Newtonian fluids is encountered in a broad range of chemical, biochemical, and food industries. Mechanically agitated vessels are commonly employed in these processes because they promote high degree of contact between the phases. However, mixing non-Newtonian fluids is a challenging task that requires comprehensive knowledge of the mixing flow to accurately design stirred vessels. Therefore, this review presents the developments accomplished by researchers in this field. The present work describes mixing and mass transfer variables, namely volumetric mass transfer coefficient, power consumption, gas holdup, bubble diameter, and cavern size. It presents empirical correlations for the mixing variables and discusses the effects of operating and design parameters on the mixing and mass transfer process. Furthermore, this paper demonstrates the advantages of employing computational fluid dynamics tools to shed light on the hydrodynamics of this complex flow. The literature review shows that knowledge gaps remain for gas dispersion in yield stress fluids and non-Newtonian fluids with viscoelastic effects. In addition, comprehensive studies accounting for the scale-up of these mixing processes still need to be accomplished. Hence, further investigation of the flow patterns under different process and design conditions are valuable to have an appropriate insight into this complex system.

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Cugno, Andrea, Alex Marki, and Klaus Ley. "Biomechanics of Neutrophil Tethers." Life 11, no. 6 (May 31, 2021): 515. http://dx.doi.org/10.3390/life11060515.

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Leukocytes, including neutrophils, propelled by blood flow, can roll on inflamed endothelium using transient bonds between selectins and their ligands, and integrins and their ligands. When such receptor–ligand bonds last long enough, the leukocyte microvilli become extended and eventually form thin, 20 µm long tethers. Tether formation can be observed in blood vessels in vivo and in microfluidic flow chambers. Tethers can also be extracted using micropipette aspiration, biomembrane force probe, optical trap, or atomic force microscopy approaches. Here, we review the biomechanical properties of leukocyte tethers as gleaned from such measurements and discuss the advantages and disadvantages of each approach. We also review and discuss viscoelastic models that describe the dependence of tether formation on time, force, rate of loading, and cell activation. We close by emphasizing the need to combine experimental observations with quantitative models and computer simulations to understand how tether formation is affected by membrane tension, membrane reservoir, and interactions of the membrane with the cytoskeleton.

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Xinhui, Si, Zheng Liancun, Zhang Xinxin, Si Xinyi, and Li Min. "Asymmetric viscoelastic flow through a porous channel with expanding or contracting walls: a model for transport of biological fluids through vessels." Computer Methods in Biomechanics and Biomedical Engineering 17, no. 6 (August 14, 2012): 623–31. http://dx.doi.org/10.1080/10255842.2012.708341.

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Zhao, Fan, Laijun Liu, Yang Yang, Fujun Wang, and Lu Wang. "The Crimping and Expanding Performance of Self-Expanding Polymeric Bioresorbable Stents: Experimental and Computational Investigation." Materials 11, no. 11 (November 4, 2018): 2184. http://dx.doi.org/10.3390/ma11112184.

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Abstract: Polymeric bioresorbable stents (PBRSs) are considered the most promising devices to treat cardiovascular diseases. However, the mechanical weakness still hampers their application. In general, PBRSs are crimped into small sheathes and re-expanded to support narrowed vessels during angioplasty. Accordingly, one of the most significant requirements of PBRSs is to maintain mechanical efficacy after implantation. Although a little research has focused on commercial balloon-expanding PBRSs, a near-total lack has appeared on self-expanding PBRSs and their deformation mechanisms. In this work, self-expanding, composite polymeric bioresorbable stents (cPBRSs) incorporating poly(p-dioxanone) (PPDO) and polycaprolactone (PCL) yarns were produced and evaluated for their in vitro crimping and expanding potential. Furthermore, the polymer time-reliable viscoelastic effects of the structural and mechanical behavior of the cPBRSs were analyzed using computational simulations. Our results showed that the crimping process inevitably decreased the mechanical resistance of the cPBRSs, but that this could be offset by balloon dilatation. Moreover, deformation mechanisms at the yarn level were discussed, and yarns bonded in the crossings showed more viscous behavior; this property might help cPBRSs to maintain their structural integrity during implantation.

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Linder, Houston R., Austin A. Glass, Delbert E. Day, and Scott A. Sell. "Manipulating Air-Gap Electrospinning to Create Aligned Polymer Nanofiber-Wrapped Glass Microfibers for Cortical Bone Tissue Engineering." Bioengineering 7, no. 4 (December 20, 2020): 165. http://dx.doi.org/10.3390/bioengineering7040165.

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Osteons are the repeating unit throughout cortical bone, consisting of canals filled with blood and nerve vessels surrounded by concentric lamella of hydroxyapatite-containing collagen fibers, providing mechanical strength. Creating a biodegradable scaffold that mimics the osteon structure is crucial for optimizing cellular infiltration and ultimately the replacement of the scaffold with native cortical bone. In this study, a modified air-gap electrospinning setup was exploited to continuously wrap highly aligned polycaprolactone polymer nanofibers around individual 1393 bioactive glass microfibers, resulting in a synthetic structure similar to osteons. By varying the parameters of the device, scaffolds with polymer fibers wrapped at angles between 5–20° to the glass fiber were chosen. The scaffold indicated increased cell migration by demonstrating unidirectional cell orientation along the fibers, similar to recent work regarding aligned nerve and muscle regeneration. The wrapping decreased the porosity from 90% to 80%, which was sufficient for glass conversion through ion exchange validated by inductively coupled plasma. Scaffold degradation was not cytotoxic. Encapsulating the glass with polymer nanofibers caused viscoelastic deformation during three-point bending, preventing typical brittle glass fracture, while maintaining cell migration. This scaffold design structurally mimics the osteon, with the intent to replace its material compositions for better regeneration.

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Arani, A. Tabatabaie, Ali Ghorbanpour Arani, and Reza Kolahchi. "Non-Newtonian pulsating blood flow-induced dynamic instability of visco-carotid artery within soft surrounding visco-tissue using differential cubature method." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 16 (January 7, 2015): 3002–12. http://dx.doi.org/10.1177/0954406214566038.

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The high blood rate that often occurs in carotid arteries may play a role in artery failure and tortuosity which leads to blackouts, transitory ischemic attacks, and other diseases. However, dynamic analysis of carotid arteries conveying blood is lacking. The objective of this study was to present a biomechanical model for dynamic instability analysis of the embedded carotid arteries conveying pulsating blood flow. In order to present a realistic model, the carotid arteries and tissues are assumed viscoelastic using Kelvin–Voigt model. Carotid arteries are modeled as elastic cylindrical vessels based on Mindlin cylindrical shell theory (MCST). One of the main advantages of this study is considering the pulsating non-Newtonian nature of the blood flow using Carreau, Casson, and power law models. Applying energy method, Hamilton’s principle and differential cubature method (DCM), the dynamic instability region (DIR) of the visco-carotid arteries is obtained. The detailed parametric study is conducted, focusing on the combined effects of the elastic medium and non-Newtonian models on the dynamic instability of the visco-carotid arteries. It can be seen that with increasing the tissue stiffness, the natural frequency of visco-carotid arteries decreases. The current model provides a powerful tool for further experimental investigation about arterial tortuosity.

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Van Liedekerke, Paul, Johannes Neitsch, Tim Johann, Enrico Warmt, Ismael Gonzàlez-Valverde, Stefan Hoehme, Steffen Grosser, Josef Kaes, and Dirk Drasdo. "A quantitative high-resolution computational mechanics cell model for growing and regenerating tissues." Biomechanics and Modeling in Mechanobiology 19, no. 1 (November 20, 2019): 189–220. http://dx.doi.org/10.1007/s10237-019-01204-7.

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AbstractMathematical models are increasingly designed to guide experiments in biology, biotechnology, as well as to assist in medical decision making. They are in particular important to understand emergent collective cell behavior. For this purpose, the models, despite still abstractions of reality, need to be quantitative in all aspects relevant for the question of interest. This paper considers as showcase example the regeneration of liver after drug-induced depletion of hepatocytes, in which the surviving and dividing hepatocytes must squeeze in between the blood vessels of a network to refill the emerged lesions. Here, the cells’ response to mechanical stress might significantly impact the regeneration process. We present a 3D high-resolution cell-based model integrating information from measurements in order to obtain a refined and quantitative understanding of the impact of cell-biomechanical effects on the closure of drug-induced lesions in liver. Our model represents each cell individually and is constructed by a discrete, physically scalable network of viscoelastic elements, capable of mimicking realistic cell deformation and supplying information at subcellular scales. The cells have the capability to migrate, grow, and divide, and the nature and parameters of their mechanical elements can be inferred from comparisons with optical stretcher experiments. Due to triangulation of the cell surface, interactions of cells with arbitrarily shaped (triangulated) structures such as blood vessels can be captured naturally. Comparing our simulations with those of so-called center-based models, in which cells have a largely rigid shape and forces are exerted between cell centers, we find that the migration forces a cell needs to exert on its environment to close a tissue lesion, is much smaller than predicted by center-based models. To stress generality of the approach, the liver simulations were complemented by monolayer and multicellular spheroid growth simulations. In summary, our model can give quantitative insight in many tissue organization processes, permits hypothesis testing in silico, and guide experiments in situations in which cell mechanics is considered important.

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Wattanutchariya, Wassanai, Timothy Quek, and Suthipas Pongmanee. "The Biocompatibility and Occlusion Ability of a Zein-Based Biomaterial for Bone Surgery." Solid State Phenomena 266 (October 2017): 221–25. http://dx.doi.org/10.4028/www.scientific.net/ssp.266.221.

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During surgical procedures on bone, a common method of producing haemostasis at bleeding cancellous bone is the occlusion of blood vessels. This is often achieved with bone wax, which is not bioresorbable, unlike the zein-based biomaterial investigated in the present research. Zein is a prolamin derived from corn, and has been gaining importance as a bio-medical material. Taking advantage of its solubility in ethanol-water solvents but insolubility in water, a zein-based viscoelastic solid can be produced which effectively occludes the flow of fluids through a porous surface modelling cancellous bone. Zein powder was dissolved into a 70% ethanol-in-water solution, and the ethanol was later leached out through exposure to an alcohol-free media. The insoluble zein ‘resin’ produced could occlude water flow through a porous surface. Experiments were conducted to determine the optimum composition of the precursor zein solution, varying the proportion of zein dissolved in the ethanol-water solvent. A 0.7 w/v composition was selected as the preferred ratio. A cell viability test using the resazurin assay showed that unleached ethanol in the zein-based biomaterial does not pose a threat, as the metabolic activity of osteoblasts on zein resin outperformed that on bone wax after 24 hours of incubation. Subsequent characterisation of the zein resin was performed with a rheometer: results showed that the 0.7 w/v composition had a higher storage modulus and loss modulus for the range of frequencies tested.

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Reymond, Philippe, Fabrice Merenda, Fabienne Perren, Daniel Rüfenacht, and Nikos Stergiopulos. "Validation of a one-dimensional model of the systemic arterial tree." American Journal of Physiology-Heart and Circulatory Physiology 297, no. 1 (July 2009): H208—H222. http://dx.doi.org/10.1152/ajpheart.00037.2009.

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A distributed model of the human arterial tree including all main systemic arteries coupled to a heart model is developed. The one-dimensional (1-D) form of the momentum and continuity equations is solved numerically to obtain pressures and flows throughout the systemic arterial tree. Intimal shear is modeled using the Witzig-Womersley theory. A nonlinear viscoelastic constitutive law for the arterial wall is considered. The left ventricle is modeled using the varying elastance model. Distal vessels are terminated with three-element windkessels. Coronaries are modeled assuming a systolic flow impediment proportional to ventricular varying elastance. Arterial dimensions were taken from previous 1-D models and were extended to include a detailed description of cerebral vasculature. Elastic properties were taken from the literature. To validate model predictions, noninvasive measurements of pressure and flow were performed in young volunteers. Flow in large arteries was measured with MRI, cerebral flow with ultrasound Doppler, and pressure with tonometry. The resulting 1-D model is the most complete, because it encompasses all major segments of the arterial tree, accounts for ventricular-vascular interaction, and includes an improved description of shear stress and wall viscoelasticity. Model predictions at different arterial locations compared well with measured flow and pressure waves at the same anatomical points, reflecting the agreement in the general characteristics of the “generic 1-D model” and the “average subject” of our volunteer population. The study constitutes a first validation of the complete 1-D model using human pressure and flow data and supports the applicability of the 1-D model in the human circulation.

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Bogunovic, Natalija, Jorn P. Meekel, Jisca Majolée, Marije Hekhuis, Jakob Pyszkowski, Stefan Jockenhövel, Magnus Kruse, et al. "Patient-Specific 3-Dimensional Model of Smooth Muscle Cell and Extracellular Matrix Dysfunction for the Study of Aortic Aneurysms." Journal of Endovascular Therapy 28, no. 4 (April 26, 2021): 604–13. http://dx.doi.org/10.1177/15266028211009272.

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Introduction: Abdominal aortic aneurysms (AAAs) are associated with overall high mortality in case of rupture. Since the pathophysiology is unclear, no adequate pharmacological therapy exists. Smooth muscle cells (SMCs) dysfunction and extracellular matrix (ECM) degradation have been proposed as underlying causes. We investigated SMC spatial organization and SMC-ECM interactions in our novel 3-dimensional (3D) vascular model. We validated our model for future use by comparing it to existing 2-dimensional (2D) cell culture. Our model can be used for translational studies of SMC and their role in AAA pathophysiology. Materials and Methods: SMC isolated from the medial layer of were the aortic wall of controls and AAA patients seeded on electrospun poly-lactide- co-glycolide scaffolds and cultured for 5 weeks, after which endothelial cells (EC) are added. Cell morphology, orientation, mechanical properties and ECM production were quantified for validation and comparison between controls and patients. Results: We show that cultured SMC proliferate into multiple layers after 5 weeks in culture and produce ECM proteins, mimicking their behavior in the medial aortic layer. EC attach to multilayered SMC, mimicking layer interactions. The novel SMC model exhibits viscoelastic properties comparable to biological vessels; cytoskeletal organization increases during the 5 weeks in culture; increased cytoskeletal alignment and decreased ECM production indicate different organization of AAA patients’ cells compared with control. Conclusion: We present a valuable preclinical model of AAA constructed with patient specific cells with applications in both translational research and therapeutic developments. We observed SMC spatial reorganization in a time course of 5 weeks in our robust, patient-specific model of SMC–EC organization and ECM production.

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Arellano-Rodrigo, Eduardo, Irene Lopez-Vilchez, Patricia Molina, Marcos Pino, Maribel Diaz-Ricart, Joanne van Ryn, and Gines Escolar. "Idarucizumab Fully Restores Dabigatran-Induced Alterations on Platelet and Fibrin Deposition on Damaged Vessels: Studies in Vitro with Circulating Human Blood." Blood 124, no. 21 (December 6, 2014): 2878. http://dx.doi.org/10.1182/blood.v124.21.2878.2878.

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Abstract BACKGROUND: Despite the proven efficacy and safety profile of dabigatran as compared to warfarin, bleeding remains a concern as with all anticoagulants and the reversal of dabigatran’s anticoagulant effect for emergency procedures remains controversial. Recently, idarucizumab, a specific antidote for dabigatran, has been functionally characterized and its efficacy demonstrated in animal models and healthy volunteer studies. AIMS: We explored the effects of dabigatran on hemostasis in human blood focusing on possible interference with platelet and coagulation responses to vessel injury under flow conditions. We also compared the potential efficacy of idarucizumab with procoagulant strategies such as prothrombin complex concentrates (PCC), activated PCC (aPCC) or rFVIIa at reversing the antithrombotic action of dabigatran to better understand local processes in response to injury. METHODS: Concentrations of dabigatran equivalent to the Cmax reported at steady state after therapy with 150 mg twice daily (184 ng/mL) were added in vitro to blood aliquots from 11 healthy donors. Whole blood samples were used to evaluate modifications in different coagulation biomarkers: 1) fibrin and platelet deposition on damaged vascular segments with whole blood under flow conditions at a shear rate of 600 s-1, 2) dynamics of thrombin generation (TG) in plasma using a fluorogenic assay (Technothrombin TGA) and 3) viscoelastic parameters of clot formation in whole blood using by thromboelastometry (ROTEM) The efficacy of specific reversal with idarucizumab 0.3, 1 and 3 mg/mL was compared with that of non specific procoagulant concentrates such as aPCC 25 and 75 IU/kg, PCC 70 IU/kg, or rFVIIa 120 µg/kg. RESULTS: Dabigatran (184 ng/mL) caused a pronounced 85% reduction of fibrin coverage on the damaged vessel from 67.2±9.8 to 9.5±1.3 % (p<0.01) and a moderate 35% reduction of platelet deposition from 25.9±2.7 to 16.9±2.9 % (p<0.01). Dabigatran also altered dynamics of TG with a prolongation of the lag-phase and a reductions in the maximal thrombin peak and potential of thrombin generation (p<0.01). In ROTEM, dabigatran significantly prolonged clotting time to 352±60 sec (p<0.01) and clot formation time to 312±76 sec (p<0.05). Idarucizumab completely reversed the alterations in all different biomarkers induced by dabigatran. Additionally, fibrin coverage and platelet deposition were restored to baseline values in flow studies. TG and ROTEM parameters also returned to normal values after idarucizumab. Reversal strategies with aPCC or PCC normalized and even over-compensated alterations in TG kinetics and partially improved alterations in ROTEM parameters caused by dabigatran. Interestingly, aPCC and PCC moderately improved the alteration in fibrin deposition caused by dabigatran in flow studies (15.7±8.2, 29.3±14.5, and 15.2±3.7 %, respectively for aPCCs 25, 75 or PCCs 70 IU/kg). However, levels of fibrin formation did not return to baseline values before dabigatran (67.2±32.5 %). rFVIIa showed only moderate effects on some of the biomarkers evaluated, though values were never restored to the baseline. CONCLUSIONS: Dabigatran (184 ng/mL) added to blood from healthy volunteers caused evident alterations in hemostasis parameters related to its recognized anticoagulant action. Procoagulant concentrates significantly compensated for the overall anti-hemostastic action of dabigatran. Overall, 75 U/kg aPCC seemed the more efficient nonspecific reversal therapy. In clear contrast with non specific procoagulant strategies, idarucizumab, the specific antidote to dabigatran completely reversed all alterations in coagulation parameters evaluated in circulating human blood and in assay systems. (Supported by SAF 2011-2814 and PI13/00517, Spanish Gov & FEDER) Disclosures van Ryn: Boehringer Ingelheim Pharma: Employment. Escolar:Boehringer Ingelheim Pharma: Investigator Sponsored Research Funding Other.

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Journal articles on the topic 'Viscoelastic Vessels'

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