Biorheology - Volume 46, issue 3

Authors: Salazar Vázquez, B.Y. | Martini, J. | Chávez Negrete, A. | Cabrales, P. | Tsai, A.G. | Intaglietta, M.

Article Type: Review Article

Abstract: The circulation is adapted to specific levels of blood viscosity resulting in a balance that simultaneously sets peripheral vascular resistance, blood pressure and cardiac output, factors in part mediated by the production of nitric oxide by the endothelium. Although it is generally perceived that decreasing blood viscosity is beneficial for cardiovascular function, small increases of blood viscosity in normal healthy experimental subjects significantly improve cardiovascular function. These changes are within the normal variations of viscosity due to the variations of hematocrit in the healthy population. Hemodilution reduces blood viscosity, which is proposed to be physiologically beneficial. However, in extreme hemodilution, …increased plasma viscosity via the use of viscogenic plasma expanders sustains microvascular and tissue function at significantly reduced levels of oxygen delivery. Studies in hemorrhagic shock resuscitation using oxygen carrying and non-carrying red blood cells show that restoration of blood viscosity is as important as restoration of oxygen carrying capacity. It is concluded that although hemodilution is indicated for reducing abnormally high blood viscosities, it is beneficial to increase plasma viscosity when hematocrit is reduced. Furthermore small increases in hematocrit may be beneficial due to the related increase in blood viscosity, independently of the increase of oxygen delivery capacity. Show more

Keywords: Microcirculation, blood pressure, vascular resistance, nitric oxide, plasma expander, hemodilution, hemoconcentration

DOI: 10.3233/BIR-2009-0539

Citation: Biorheology, vol. 46, no. 3, pp. 167-179, 2009

Authors: Kim, Sangho | Ong, Peng Kai | Yalcin, Ozlem | Intaglietta, Marcos | Johnson, Paul C.

Article Type: Review Article

Abstract: This review discusses the cell-free layer at the wall of the microcirculatory vessels with emphasis on the influence of blood rheological parameters on its formation as well as its possible effects on microvascular functions. Understanding cell-free layer characteristics in the microcirculation has been of increased interest for its possible influence on physiological function. The availability of better imaging and measurement techniques in recent years has created an excellent opportunity for researchers to examine the cell-free layer in much greater detail than possible previously. The most recent approach enables capturing spatial and temporal information of cell-free layer characteristics which can provide …new insights to how cell-free layer width and its variations can impact physiological function. Cell-free layer formation is dependent on diameter of the vessel, flow rate, and rheological properties of blood including hematocrit, red blood cell aggregation, and deformability. Specifically in microvessels, its formation can also be affected by the presence of the glycocalyx layer that lines the luminal surface of the vessel wall. As the cell-free layer is omnipresent in microcirculatory vessels, its formation at the vessel wall could affect function throughout the microvascular network by altering wall shear stress, local hematocrit, flow distribution, effective viscosity and nitric oxide production as well as its scavenging by red blood cells. Show more

Keywords: Blood rheology, glycocalyx, microcirculatory blood flow, NO scavenging, endothelium, shear stress

DOI: 10.3233/BIR-2009-0530

Citation: Biorheology, vol. 46, no. 3, pp. 181-189, 2009

Authors: Boudou, Thomas | Ohayon, Jacques | Picart, Catherine | Pettigrew, Roderic I. | Tracqui, Philippe

Article Type: Review Article

Abstract: Because of their tunable mechanical properties, polyacrylamide gels (PAG) are frequently used for studying cell adhesion and migratory responses to extracellular substrate stiffness. Since these responses are known to heavily depend on the tensional balance between cell contractility and substrate mechanical resistance, a precise knowledge of PAG's mechanical properties becomes quite crucial. Using the micropipette aspiration technique, we first exhibited the nonlinear elastic behavior of PAG and then successfully modeled it by an original strain-energy function. This function depends on the Poisson's ratio and on two material parameters, which have been explicitly related to acrylamide and bis-acrylamide concentrations. Implications of …these results have been highlighted with regard to traction force microscopy experiments where cellular force quantification is derived from displacements of beads embedded in PAG. We found that considering PAG as a linear elastic medium tends to significantly underestimate traction forces for substrate displacements larger than 2 μm. Interestingly, we also showed that in the range of cellular force amplitude and PAG stiffness currently used in cell traction force experiments, finite size effects become critical for PAG substrate thickness below 60 μm. Thus, our improved characterization of PAG nonlinear mechanical properties through a new constitutive law could have significant impact onto biological experimentations where such extracellular substrates experience large strains. Show more

Keywords: Elastic substrate, finite layer thickness, finite element analysis, micropipette aspiration, cell traction forces

DOI: 10.3233/BIR-2009-0540

Citation: Biorheology, vol. 46, no. 3, pp. 191-205, 2009

Authors: Thomas, Susan N. | Tong, Ziqiu | Stebe, Kathleen J. | Konstantopoulos, Konstantinos

Article Type: Review Article

Abstract: The efficiency of secondary tumor establishment is controlled by the ability of tumor cells to withstand a barrage of mechanical and immunological stresses during their passage through the circulatory system. Accumulating evidence suggests that the selectin-dependent interactions of circulating tumor cells with host cells promote their survival and extravasation from the vasculature, therefore representing a critical checkpoint for colonization of distant organs. These observations have motivated the identification and biochemical characterization of functional selectin ligands such as CD44 variant isoforms, carcinoembryonic antigen and podocalyxin-like protein, present on the surface of metastatic colon carcinoma cells. Understanding the molecular underpinnings of selectin-ligand …interactions involved in heterotypic tumor cell–host cell adhesion events may provide guidelines for developing novel cancer diagnostics. Recent advancements in diagnostic device fabrication and design integrated with novel biomarkers exploiting the tissue specific biochemistry of malignant versus normal tissue-expressed selectin ligands may hold promise in providing effective alternatives to current cancer diagnostic technologies. Show more

Keywords: Adhesion, selectins, CD44v, carcinoembryonic antigen, podocalyxin-like protein, soft lithography, microcontact printing, microfluidics

DOI: 10.3233/BIR-2009-0534

Citation: Biorheology, vol. 46, no. 3, pp. 207-225, 2009

Authors: Bursac, P. | Arnoczky, S. | York, A.

Article Type: Research Article

Abstract: The menisci of the knee play a significant role in the complex biomechanics of the joint and are critically important in maintaining articular cartilage health. While a general form–function relationship has been identified for the structural orientation of the extra-cellular matrix of the meniscus, the role of individual biochemical components has yet to be fully explored. To determine if correlations exist between the dynamic and static compressive modulus of human menisci and their major extra-cellular matrix constituents (collagen, glycosoaminoglycan and water content), 12 lateral and 11 medial menisci from 13 adult donors were examined. The results showed that in dynamic …compression at high loading frequencies (0.1–1 Hz) the menisci behave as a rubber-like elastic material while at lower frequencies (0.01–0.03 Hz) significant viscous dissipation occurs. While regional variations in compressive moduli and extra-cellular matrix composition were observed, the magnitude of both dynamic and static compressive moduli were found to be insensitive to collagen content (p>0.4). However, this magnitude was found to significantly increase with increasing glycosaminoglycan content (p<0.001) and significantly decrease with increasing water content (p<0.001). The results of this study identify significant relationships between the viscoelastic behavior of the meniscus and its extra-cellular matrix composition. Show more

Keywords: Viscoelasticity, GAG, collagen, lateral, medial, mechanics

DOI: 10.3233/BIR-2009-0537

Citation: Biorheology, vol. 46, no. 3, pp. 227-237, 2009

Authors: Baskurt, O.K. | Uyuklu, M. | Meiselman, H.J.

Article Type: Research Article

Abstract: The electrical properties of red blood cell (RBC) suspensions are influenced by flow conditions, and prior studies indicate that electrical properties may reflect the kinetics of RBC aggregation. Changes of conductance and capacitance were monitored and had a time course resembling a “syllectogram” (i.e., temporal change of light reflectance from an RBC suspension after sudden cessation of flow). In the present study, both AC electrical conductance (EC) across and light transmission (LT) through a 1 mm ID glass tube were recorded simultaneously after a sudden stoppage of flow for RBC at various hematocrits in plasma or in isotonic saline (PBS). …Preliminary results indicate that EC and LT signals for RBC in plasma have similar time courses, both increasing after an initial decrement of a few seconds duration. Aggregation indexes and aggregation half times calculated using LT and EC showed a similar dependence on hematocrits between 30–50%. Interestingly, RBC in PBS also exhibited a syllectogram time course for conductance, whereas LT continued to decrease after an initial decline reflecting RBC shape recovery. These results suggest that electrical conductance in aggregating and non-aggregating suspensions may be sensitive to phenomena other than RBC aggregation. Show more

Keywords: Red blood cell aggregation, electrical conductance, light transmission, syllectrogram

DOI: 10.3233/BIR-2009-0541

Citation: Biorheology, vol. 46, no. 3, pp. 239-249, 2009

Authors: Baskurt, Oguz K. | Hardeman, M.R. | Uyuklu, Mehmet | Ulker, Pinar | Cengiz, Melike | Nemeth, Norbert | Shin, Sehyun | Alexy, Tamas | Meiselman, Herbert J.

Article Type: Research Article

Abstract: In December 2008, the International Society for Clinical Hemorheology organized a workshop to evaluate and compare three ektacytometer instruments for measuring deformability of red blood cells (RBC): LORCA (Laser-assisted Optical Rotational Cell Analyzer, RR Mechatronics, Hoorn, The Netherlands), Rheodyn SSD (Myrenne GmbH, Roetgen, Germany) and RheoScan-D (RheoMeditech, Seoul, Korea). Intra-assay reproducibility and biological variation were determined using normal RBC, and cells with reduced deformability (i.e., 0.001–0.02% glutaradehyde (GA), 48°C heat treatment) were employed as either the only RBC present or as a sub-population. Standardized difference values were used as measure of the power to detect differences between normal and treated …cells. Salient results include: (1) All instruments had intra-assay variations below 5% for shear stress (SS)>1 Pa but a sharp increase was found for Rheodyn SSD and RheoScan-D at lower SS; (2) Biological variation was similar and markedly increased for SS<3–5 Pa; (3) All instruments detected GA-treated RBC with maximal power at 1–3 Pa, the presence of 10% or 40% GA-modified cells, and the effects of heat treatment. It is concluded that the LORCA, Rheodyn SSD and RheoScan-D all have acceptable precision and power for detecting reduced RBC deformability due to GA treatment or heat treatment, and that the SS range selected for the measurement of deformability is an important determinant of an instrument's power. Show more

Keywords: Erythrocyte deformability, ektacytometry

DOI: 10.3233/BIR-2009-0536

Citation: Biorheology, vol. 46, no. 3, pp. 251-264, 2009