Biorheology - Volume 53, issue 5-6

Authors: Schmid-Schönbein, Geert W.

Article Type: Research Article

Abstract: Transformation of circulating leukocytes from a dormant into an activated state with changing rheological properties leads to a major shift of their behavior in the microcirculation. Low levels of pseudopod formation or expression of adhesion molecules facilitate relatively free passage through microvessels while activated leukocytes with pseudopods and enhanced levels of adhesion membrane proteins become trapped in microvessels, attach to the endothelium and migrate into the tissue. The transformation of leukocytes into an activated state is seen in many diseases. While mechanisms for activation due to infections, tissue trauma, as well as non-physiological biochemical or biophysical exposures are well recognized, …the mechanisms for activation in many diseases have not been conclusively liked to these traditional mechanisms and remain unknown. We summarize our recent evidence suggesting a major and surprising role of digestive enzymes in the small intestine as root causes for leukocyte activation and microvascular disturbances. During normal digestion of food digestive enzymes are compartmentalized in the lumen of the intestine by the mucosal epithelial barrier. When permeability of this barrier increases, these powerful degrading enzymes leak into the wall of the intestine and into the systemic circulation. Leakage of digestive enzymes occurs for example in physiological shock and multi-organ failure. Entry of digestive enzymes into the wall of the small intestine leads to degradation of the intestinal tissue in an autodigestion process. The digestive enzymes and tissue/food fragments generate not only activate leukocytes but also cause numerous cell dysfunctions. For example, proteolytic destruction of membrane receptors, plasma proteins and other biomolecules occurs. We conclude that escape of digestive enzymes from the intestinal track serves as a major source of cell dysfunction, morbidity and even mortality, including abnormal leukocyte activation seen in rheological studies. Show more

Keywords: Intestine, pancreas, digestive enzyme, intestinal mucosa, permeability, trypsin, chymotrypsin, elastase, lipase, matrix metalloproteinases, diabetes, hypertension, metabolic disease

DOI: 10.3233/BIR-17131

Citation: Biorheology, vol. 53, no. 5-6, pp. 179-191, 2016

Authors: Lin, Haoming | Shen, Yuanyuan | Chen, Xin | Zhu, Ying | Zheng, Yi | Zhang, Xinyu | Guo, Yanrong | Wang, Tianfu | Chen, Siping

Article Type: Research Article

Abstract: Background: Ultrasound elastography has been widely used to measure liver stiffness. However, the accuracy of liver viscoelasticity obtained by ultrasound elastography has not been well established. Objective: To assess the accuracy of ultrasound elastography for measuring liver viscoelasticity and compare to conventional rheometry methods. In addition, to determine if combining these two methods could delineate the rheological behavior of liver over a wide range of frequencies. Methods: The phase velocities of shear waves were measured in livers over a frequency range from 100 to 400 Hz using the ultrasound elastography method of shearwave dispersion ultrasound vibrometry …(SDUV), while the complex shear moduli were obtained by rheometry over a frequency range of 1 to 30 Hz. Three rheological models, Maxwell, Voigt, and Zener, were fit to the measured data obtained from the two separate methods and from the combination of the two methods. Results: The elasticity measured by SDUV was in good agreement with that of rheometry. However, the viscosity measured by SDUV was significantly different from that of rheometry. Conclusions: The results indicate that the high frequency components of the dispersive data play a much more important role in determining the dispersive pattern or the viscous value than the low frequency components. It was found that the Maxwell model is not as appropriate as the Voigt and Zener models for describing the rheological behavior of liver. Show more

Keywords: Viscoelasticity, liver, elastography, rheometry, dispersion, shearwave dispersion ultrasound vibrometry

DOI: 10.3233/BIR-16091

Citation: Biorheology, vol. 53, no. 5-6, pp. 193-207, 2016

Authors: Uchimura, Isao | Kaibara, Makoto | Nagasawa, Masayuki | Hayashi, Yoshihito

Article Type: Research Article

Abstract: Background: Hypercoagulability in type 2 diabetes mellitus (T2DM) patients increases their risk of cardiovascular diseases. Objective: The aim of this work was to investigate the hypercoagulation mechanism in T2DM patients in terms of circulating tissue factor (TF). Methods: Whole blood coagulation tests by damped oscillation rheometry and dielectric blood coagulometry (DBCM) were performed. Results: The average coagulation time was significantly shorter for T2DM patients than for healthy controls. In vitro addition of either anti-TF or anti-activated factor VII (FVIIa) antibody to hypercoagulable blood samples prolonged coagulation times for one group of patients, while …coagulation times remained short for another group. The levels of circulating TF were estimated in the former group by measuring the coagulation times for blood samples from healthy subjects with addition of various concentrations of TF and comparing them with the coagulation times for the group. The results indicated that the levels of circulating TF were on the order of subpicomolar at most. Conclusions: Circulating TF is at least partially responsible for a hypercoagulable group of T2DM patients, while an abnormality in the intrinsic coagulation pathway probably occurs in the other group. Show more

Keywords: Dielectric spectroscopy, extrinsic/intrinsic coagulation pathway, coagulation time, hypercoagulable state

DOI: 10.3233/BIR-16107

Citation: Biorheology, vol. 53, no. 5-6, pp. 209-219, 2016

Authors: Connelly, Kelly | Sharif-Kashani, Pooria | Farajzadeh, Matt | Hubschman, Jean-Pierre | Kavehpour, H. Pirouz

Article Type: Research Article

Abstract: Background: Rheology experiments have been performed on the vitreous humor, a soft gel that rests inside of the eye, to study its viscoelastic behavior and underlying macromolecular structure. A significant challenge for experimentalists is preserving the macromolecular structure when removing vitreous from in vivo conditions. Objective: We have developed a novel probe-like rheometer geometry that allows us to perform shear rheology experiments on the vitreous humor in situ . The aim of this study is to assess the feasibility of the probe geometry. Methods: Creep compliance responses of silicone oils, Xanthan gum solutions, and bovine …and porcine vitreous humor were measured using the probe geometry and compared to measurements performed with standard geometries. Results: Viscosities calculated from the creep responses of silicone oils closely match between the probe and standard geometry. Viscosities and creep compliance values of Xanthan gum measurements achieve order of magnitude agreement between the probe and standard geometry. Significant differences are detected with the probe between bovine and porcine vitreous (p < 0.001 ). Conclusions: These results suggest the probe may feasibly measure viscosities of Newtonian fluids, and correctly detect differences in the creep response of complex fluids with varying viscoelastic behaviors. Show more

Keywords: Eye, vitreous gel, biorheology, viscoelasticity

DOI: 10.3233/BIR-16112

Citation: Biorheology, vol. 53, no. 5-6, pp. 221-236, 2016

Authors: Simmonds, Michael J. | Meiselman, Herbert J.

Article Type: Research Article

Abstract: Background: Current generation mechanical circulatory assist devices are designed to minimize high shears to blood for prolonged durations to avoid hemolysis. However, red blood cells (RBC) demonstrate impaired capacity to deform when exposed to shear stress (SS) well below the “hemolytic threshold”. Objective: We endeavored to identify how changes in the magnitude and duration of SS exposure alter RBC deformability and subsequently develop a model to predict erythrocyte subhemolytic damage. Methods: RBC suspensions were exposed to discrete magnitudes of SS (1–64 Pa) for specific durations (1–64 s), immediately prior to RBC deformability being measured. Analyses included exploring the …maximal RBC deformation (EI max ) and SS required for half EI max (SS 1 / 2 ). A surface-mesh was interpolated onto the raw data to predict impaired RBC deformability. Results: When SS was applied at < 16 Pa , limited changes were observed. When RBC were exposed to 32 Pa, mild impairments in EI max and SS 1 / 2 occurred, although 64 Pa caused a dramatic impairment of RBC deformability. A clear relation between SS duration and magnitude was determined, which could predict impaired RBC deformability. Conclusion: The present results provide a model that may be used to predict whether RBC deformability is decreased following exposure to a given level and duration of SS, and may guide design of future generations of mechanical circulatory assist devices. Show more

Keywords: Blood damage, haemocompatibility, haemorheology, mechanical damage, sublethal

DOI: 10.3233/BIR-16120

Citation: Biorheology, vol. 53, no. 5-6, pp. 237-249, 2016

Article Type: Other

Citation: Biorheology, vol. 53, no. 5-6, pp. 251-253, 2016