Biorheology - Volume 47, issue 2

Authors: Brun, Jean-Frédéric | Varlet-Marie, Emmanuelle | Connes, Philippe | Aloulou, Ikram

Article Type: Review Article

Abstract: Alterations of blood rheology related to muscular activity have been extensively studied over the last 20 years. It has been shown that exercise exerts a “triphasic” action on the rheological properties of blood. In the short term, exercise induces a transient hyperviscosity, mostly due to a rise in hematocrit and plasma viscosity, but also to alterations in erythrocyte rheology. Reversal of this hyperviscosity pattern over the following 24 h can be described as an “autohemodilution”. Later, training results in several profiles of “hemorheologic fitness” with a low hematocrit reflecting an expansion in plasma volume, and improvements in red cell rheology …(increased deformability, decreased aggregation, reduced disaggregation shear rate). Some specific aspects of these long-term adaptations have been described, such as the intriguing occurrence of a paradoxical improvement in RBC deformability during exercise in some athletes, and overtraining, which is associated with higher plasma viscosity. Given the variety of modes of exercise and the wide heterogeneity of their effects on blood rheology in the short and long term, many investigations remain to be performed in this area of clinical hemorheology. Show more

Keywords: Exercise, blood viscosity, erythrocyte deformability, erythrocyte aggregation, training, overtraining

DOI: 10.3233/BIR-2010-0563

Citation: Biorheology, vol. 47, no. 2, pp. 95-115, 2010

Authors: Murphy, Jonathan B. | Boyle, Fergal J.

Article Type: Research Article

Abstract: The benefit of coronary stent implantation is reduced by excessive intimal hyperplasia which re-narrows the artery and the prevention of which is still a primary concern for clinicians. Abnormal hemodynamics create non-physiological viscous stress on the artery wall, one of the root causes of intimal hyperplasia following stent implantation. A methodology to comprehensively evaluate the viscous stress on the artery wall following stent implantation would be useful to evaluate a stent's hemodynamic performance. The proposed methodology employs 3D computational fluid dynamics, the variables wall shear stress (WSS), WSS gradient (WSSG), WSS angle gradient (WSSAG) and a statistical analysis to …evaluate the viscous stress. The methodology is demonstrated and compared to a commonly used “threshold technique” for evaluating a stent's hemodynamic performance. It is demonstrated that the threshold technique is not adequate to fully analyse the viscous stress on the artery wall and can even be misleading. Furthermore, all three of the aforementioned variables should be considered as each provides a different perspective on the abnormalities that can arise in the arterial viscous stress. The hemodynamic performance of a stent can be assessed more comprehensively than with previously used methods by examining the arterial viscous stresses using the proposed methodology. Show more

Keywords: Stent, intimal hyperplasia, viscous stress, statistical analysis

DOI: 10.3233/BIR-2010-0568

Citation: Biorheology, vol. 47, no. 2, pp. 117-132, 2010

Authors: Klatt, Dieter | Friedrich, Christian | Korth, Yasmin | Vogt, Robert | Braun, Jürgen | Sack, Ingolf

Article Type: Research Article

Abstract: The mechanical properties of liver can sensitively indicate the progression of hepatic fibrosis. Mechanical tissue characterization involves the analysis of the complex shear modulus measured either by oscillatory rheometry or by in vivo elastography. In this study, bovine liver specimens were investigated by oscillatory rheometry and multifrequency magnetic resonance elastography (MRE) in a common frequency range between 25.0 and 62.5 Hz. The results were compared with in vivo MRE of human liver. Storage and loss moduli were quantified, and the data were also analyzed employing a springpot model, yielding a stiffness-related parameter of 2.96±0.53 kPa in bovine liver by rheometry …and of 2.20±0.45 kPa in human liver by in vivo MRE. Furthermore, MRE of excised bovine liver showed that stiffness tended to increase with decreasing sample temperature. In conclusion, mechanical tissue characterization by multifrequency MRE agrees well with oscillatory rheometry, which validates MRE as a method for investigating the rheology of liver tissue. Show more

Keywords: Magnetic resonance elastography, rheometry, liver viscoelasticity, springpot

DOI: 10.3233/BIR-2010-0565

Citation: Biorheology, vol. 47, no. 2, pp. 133-141, 2010

Authors: Agosti, C.D. | Bell, K.M. | Plazek, D.J. | Larson, J. | Kang, J.D. | Gilbertson, L.G. | Smolinski, P.

Article Type: Short Communication

Abstract: Tissue engineering approaches are now being investigated for altering the course of intervertebral disc degeneration (IDD). Because the disease changes the mechanical properties of the load bearing tissues of the disc, viscoelastic tissue behavior is a key measure for comparing the efficacy of treatments. To investigate the basic viscoelastic behavior of nucleus pulposus tissue, tissue from the rabbit disc was tested in torsional creep. Both the Andrade and Nutting creep models had a good fit to the data, however, the Andrade creep model gave a much better prediction of the longer term creep. This is the first application of Andrade …creep to biological tissue and results indicate that this model may be particularly well suited for characterizing the viscoelastic behavior of very soft biological tissues. Show more

Keywords: Viscoelasticity, intervertebral disc, torsion, Nutting model

DOI: 10.3233/BIR-2010-0564

Citation: Biorheology, vol. 47, no. 2, pp. 143-151, 2010

Authors: Kamada, Haruhiko | Okamoto, Takayuki | Hayashi, Tatsuya | Suzuki, Koji

Article Type: Other

Abstract: New in vitro methods are desirable for the analysis of platelet aggregation and screening novel anti-platelet agents using whole blood. To this end, we examined platelet aggregation and thrombus formation in whole human blood from healthy volunteers using a microchannel array flow analyzer (MC-FAN). Platelet aggregation in whole blood, treated with the activating agents ADP, collagen or ristocetin was detected in the MC-FAN by measuring the decrease in flow rate as a function of agent concentration. The results were compared with aggregation in platelet rich plasma (PRP) in a conventional aggregometer, as measured by the increase in optical density. The …MC-FAN detected platelet aggregation in whole blood at two- to four-fold lower concentrations of agonist compared to those in PRP in the aggregometer. Anti-platelet agents attenuated the decrease in blood flow rate in the MC-FAN by inhibiting fibrin formation and platelet aggregation, but anticoagulants only inhibited fibrin formation and did not affect blood flow rates. These findings suggest that the MC-FAN system may be a useful method for the evaluation of platelet activation and facilitate the development of novel anti-platelet agents. Show more

Keywords: Platelet aggregation, blood coagulation, anti-platelet agents, drug discovery, MC-FAN

DOI: 10.3233/BIR-2010-0566

Citation: Biorheology, vol. 47, no. 2, pp. 153-161, 2010

Authors: Amos, Jennifer R. | Li, Shigeng | Yost, Michael | Phloen, Harry | Potts, Jay D.

Article Type: Correction

Abstract: Related article: http://iospress.metapress.com/content/92grn7704701p673/

DOI: 10.3233/BIR-2010-0571

Citation: Biorheology, vol. 47, no. 2, pp. 163-163, 2010