Biorheology - Volume 51, issue 1

Article Type: Other

DOI: 10.3233/BIR-140663

Citation: Biorheology, vol. 51, no. 1, pp. 1-1, 2014

Authors: Wang, Weiwei | Lindsey, John P. | Chen, Jianchun | Diacovo, Thomas G. | King, Michael R.

Article Type: Research Article

Abstract: Platelet aggregation and thrombus formation at the site of injury is a dynamic process that involves the continuous addition of new platelets as well as thrombus rupture. In the early stages of hemostasis (within minutes after vessel injury) this process can be visualized by transfusing fluorescently labeled human platelets and observing their deposition and detachment. These two counterbalancing events help the developing thrombus reach a steady-state morphology, where it is large enough to cover the injured vessel surface but not too large to form a severe thrombotic occlusion. In this study, the spatial and temporal aspects of early stage thrombus …dynamics which result from laser-induced injury on arterioles of cremaster muscle in the humanized mouse were visualized using fluorescent microscopy. It was found that rolling platelets show preference for the upstream region while tethering/detaching platelets were primarily found downstream. It was also determined that the platelet deposition rate is relatively steady, whereas the effective thrombus coverage area does not increase at a constant rate. By introducing a new method to graphically represent the real time in vivo physiological shear stress environment, we conclude that the thrombus continuously changes shape by regional growth and decay, and neither dominates in the high shear stress region. Show more

Keywords: Hemostasis, shear stress, platelet deposition, thrombus growth/decay

DOI: 10.3233/BIR-130648

Citation: Biorheology, vol. 51, no. 1, pp. 3-14, 2014

Authors: Laesecke, Arno | Burger, Jessica L.

Article Type: Research Article

Abstract: Aqueous solutions calf thymus DNA at three concentrations were studied by viscosity measurements at ambient pressure. A gravitational capillary viscometer and a rotating cylinder viscometer were employed. Three polycations were tested as viscosity-reducing agents with measurements from 25°C to 50°C. The most significant viscosity reduction was achieved with spermine in a solution of DNA at 2 mg/ml concentration. Measurements of DNA solutions without agents from 10°C to 90°C revealed concentration-dependent viscosity maxima in the range from 50°C to 65°C. The associated increases in viscosity were as high as 400%. A two-liquids model for solutions of double- and single-stranded DNA was …developed that closely represented the experimental data. Show more

Keywords: Calf thymus DNA, capillary viscometer, cystic fibrosis, rotating concentric cylinder viscometer, sputum, viscosity

DOI: 10.3233/BIR-140649

Citation: Biorheology, vol. 51, no. 1, pp. 15-28, 2014

Authors: Burger, Jessica | Yamamoto, Hideki | Suzuki, Takamasa | Laesecke, Arno

Article Type: Research Article

Abstract: High-concentration DNA solutions are common both in vitro and in vivo, and understanding the rheological properties is a critical area of bioscience. Our previous measurements on high-concentration DNA solutions (2–6 mg/ml) interestingly provided evidence for a viscosity maximum with temperature. Under the influence of temperature, the measured viscosities indicated distinct differences in the interactions of highly polymerized DNA in unbuffered and buffered aqueous solutions. Under the same conditions, the buffered solutions were always less viscous, and in addition the viscosity maximum was not observed. In this research we have utilized a falling-needle rheometer in order to gain more insight into …the nature of the previously observed viscosity maxima. The shape of the flow curves for all the DNA solutions indicated that the solutions are shear-thinning and has allowed us to confirm the existence of the viscosity maximum in unbuffered DNA solutions. Also we have been able to measure flow curves at very low shear rates, <10 s−1 . These results showed that the flow curves intersect and that the lower the concentration of DNA in solution, the lower is the temperature where the flow curves will intersect. Thus, the viscosity–temperature dependence is also a function of the shear rates experienced by the solution. Finally, as expected, the flow behavior of the DNA solutions becomes more Newtonian with increasing temperature, and there appears to be a small yield stress that decreases with increasing temperature. Show more

Keywords: Calf thymus DNA, falling-needle rheometer, yield stress, melting temperature, viscosity

DOI: 10.3233/BIR-140650

Citation: Biorheology, vol. 51, no. 1, pp. 29-45, 2014

Authors: Ayyildiz, Mehmet | Aktas, Ranan Gulhan | Basdogan, Cagatay

Article Type: Research Article

Abstract: BACKGROUND: In liver transplantation, the donor and recipient are in different locations most of the time, and longer preservation periods are inevitable. Hence, the choice of the preservation solution and the duration of the preservation period are critical for the success of the transplant surgery. OBJECTIVE: In this study, we examine the mechanical and histological properties of the bovine liver tissue stored in Lactated Ringer's (control), HTK and UW solutions as a function of preservation period. METHODS: The mechanical experiments are conducted with a shear rheometer on cylindrical tissue samples extracted from 3 bovine livers and the change …in viscoelastic material properties of the bovine liver is characterized using the fractional derivative Kelvin–Voigt Model. Also, the histological examinations are performed on the same liver samples under a light microscope. RESULTS: The results show that the preservation solution and period have a significant effect on the mechanical and histological properties of the liver tissue. The storage and loss shear moduli, the number of the apoptotic cells, the collagen accumulation, and the sinusoidal dilatation increase, and the glycogen deposition decreases as the preservation period is longer. CONCLUSIONS: Based on the statistical analyses, we observe that the liver tissue is preserved well in all three solutions for up to 11 h. After then, UW solution provides a better preservation up to 29 h. However, for preservation periods longer than 29 h, HTK is a more effective preservation solution based on the least amount of change in mechanical properties. On the other hand, the highest correlation between the mechanical and histological properties is observed for the liver samples preserved in UW solution. Show more

Keywords: Liver, rheology, histology, mechanical characterization, preservation, transplantation

DOI: 10.3233/BIR-14007

Citation: Biorheology, vol. 51, no. 1, pp. 47-70, 2014

Authors: Nawrocka-Bogusz, Honorata | Marcinkowska-Gapińska, Anna

Article Type: Short Communication

Abstract: In this study we attempted to assess the effect of light of 855 nm wavelength (IR-light) on the rheological parameters of blood in vitro. As an anticoagulant, heparin was used. The source of IR-light was an applicator connected to the special generator – Viofor JPS® . The blood samples were irradiated for 30 min. During the irradiation the energy density was growing at twelve-second intervals starting from 1.06 J/cm2 to 8.46 J/cm2 , then the energy density dropped to the initial value; the process was repeated cyclically. The study of blood viscosity was carried out with a Contraves LS40 …oscillatory-rotational rheometer, with a decreasing shearing rate from 100 to 0.01 s−1 over 5 min (flow curve) and applying constant frequency oscillations f=0.5 Hz with decreasing shear amplitude ˙γ0 (viscoelasticity measurements). The analysis of the results of rotational measurements was based on the assessment of hematocrit, plasma viscosity, whole blood viscosity at four selected shear rates and on the basis of the numerical values of parameters from Quemada's rheological model: k0 (indicating red cell aggregability), k∞ (indicating red cell rigidity) and ˙γc (the value of the shear rate for which the rouleaux formation begins). In oscillatory experiments we estimated viscous and elastic components of the complex blood viscosity in the same groups of patients. We observed a decrease of the viscous component of complex viscosity (η′) at ˙γ0 =0.2 s−1 , while other rheological parameters, k0 , k∞ , and relative blood viscosity at selected shear rates showed only a weak tendency towards smaller values after irradiation. The IR-light effect on the rheological properties of blood in vitro turned out to be rather neutral in the studied group of patients. Show more

Keywords: IR-light, hemorheology, blood viscosity, erythrocytes aggregation, erythrocytes deformation

DOI: 10.3233/BIR-140662

Citation: Biorheology, vol. 51, no. 1, pp. 71-79, 2014