Biorheology - Volume 54, issue 5-6

Authors: Somogyi, Viktoria | Peto, Katalin | Deak, Adam | Tanczos, Bence | Nemeth, Norbert

Article Type: Research Article

Abstract: Background: Age- and gender-related alterations of hemorheological parameters have not been completely elucidated to date. Experiments on older animals may give valuable information on this issue. However, the majority of rheological studies have been performed in young rodents. Objective: We aimed to investigate the influence of aging and gender on hemorheological parameters in rats. Methods: Coeval male ( n = 10 …) and female ( n = 10 ) Wistar (Crl:WI) rats were followed-up over 15 months. Blood samples were obtained from the lateral tail vein at 3, 4, 5, 9, 12, 15 and 18 months of age. Hematological parameters, red blood cell deformability (elongation under shear), osmotic gradient deformability and erythrocyte aggregation were tested. Body weight and the estrus cycle (in females) were also examined. Results: Erythrocyte aggregation showed age- and gender-related variations. Red blood cell deformability was greater in females and gradually decreased over the 15-month period in both genders. Erythrocyte aggregation was greater in male rats at most ages, but did not show consistent changes with age. Conclusions: The micro-rheological parameters showed age-related alterations with gender differences. The effect of the estrous cycle cannot be excluded in female rats. The results provide reference data for studies of aging in rats and of the mechanism related to age and gender differences in hemorheology. Show more

Keywords: Hemorheology, red blood cell deformability, red blood cell aggregation, gender differences, aging, rat

DOI: 10.3233/BIR-17148

Citation: Biorheology, vol. 54, no. 5-6, pp. 127-140, 2018

Authors: Kuck, Lennart | Grau, Marijke | Simmonds, Michael J.

Article Type: Research Article

Abstract: Background: Red blood cell (RBC) deformability may increase, or decrease, following application of shear stress (“shear conditioning”), depending upon the specific magnitude and duration of exposure. However, the time course of altered RBC deformability following shear remains unresolved. Objective: We utilised shear conditioning known to increase (10 Pa) or decrease (64 Pa) RBC deformability and subsequently rested the cells; serial measurements of deformability during the rest period facilitated defining the time course of recoverability. A second experiment repeated the shear conditioning and recovery period to explore whether multiple duty-cycles augmented the response following the initial exposure. …Methods: Shear conditioning was performed for 300 s at the desired shear stress. Ektacytometry was used to quantify human RBC deformability immediately and during rest (3, 5, 60, 120, 240, 300 s) using discrete samples. RBC were shear conditioned twice in a separate experiment, with 300 s rest separating the conditioning. Results: Shear conditioning at 10 Pa induced increased cell deformability by 19.5 ± 0.3%, which reduced to 7.2 ± 0.4% after 300 s of rest. Shear conditioning at 64 Pa decreased cell deformability by 30.5 ± 13.9%, and after 300 s rest, remained decreased (19.3 ± 9.4%) compared with baseline. The second duty-cycle augmented initial responses induced by shear conditioning. Conclusion: Specific shear conditioning results in either temporarily increased cell deformability, or a less reversible decrease of RBC deformability. Show more

Keywords: Haemorheology, subhaemolytic, cellular deformability, reversibility

DOI: 10.3233/BIR-17151

Citation: Biorheology, vol. 54, no. 5-6, pp. 141-152, 2018

Authors: Sasaki, Takahiro | Seki, Junji | Itano, Tomoaki | Sugihara-Seki, Masako

Article Type: Research Article

Abstract: Background: In the microcirculation, red blood cells (RBCs) were observed to be confined to an axial stream surrounded by a marginal RBC depleted layer. This axial accumulation of RBCs is considered to arise from the RBC deformability. Objective: To quantitatively evaluate the effect of RBC deformability on their axial accumulation at a flow condition comparable to that in arterioles by developing a new observation system for accurate measurements of radial RBC positions in the cross section of capillary tubes. Methods: The cross-sectional distributions of normal and hardened RBCs as well as softened RBCs suspended in capillary …tube flows were measured with high spatial resolution. A new observation system was developed in which enface views of the cross-section of the tube were obtained at small distances upstream of the outlet at various longitudinal positions in the tube. Results: The radial positions of individual RBCs were detected within 1 μ m accuracy. It was found that normal and softened RBCs rapidly migrated away from the wall towards the tube axis, whereas glutaraldehyde-hardened RBCs were dispersed widely over the tube cross-section, depending on the concentration of glutaraldehyde solution. Conclusions: The newly devised observation system revealed quantitatively the essential role of RBC deformability in their axial accumulation. Show more

Keywords: Radial migration, axial accumulation, red cell deformability, membrane shear modulus

DOI: 10.3233/BIR-18166

Citation: Biorheology, vol. 54, no. 5-6, pp. 153-165, 2018

Authors: Schumann, Mark | Brinker, Alexander | Friedrich, Christian

Article Type: Research Article

Abstract: Background: Developments in the production of aquacultural salmonid feeds in the last 20 years have led to extruded diets with extremely low water content and a shift from mainly marine fish based ingredients towards plant content. These changes expose the industry to the vagaries of the highly dynamic plant protein market. Resulting variations in the precise composition of aqua feeds may carry unpredictable consequences for water quality, since some plant ingredients cause undesirable reductions in the mechanical stability of faeces. Dietary supplements known as binders that enhance the stability of faeces have the potential to mitigate these issues, but may …also bring negative effects. Objective and Methods: The present study employs an in vitro model to perform the first fundamental rheological characterization of salmonid chyme, and a factorial experiment designed to investigate the impacts of the presence of rheologically active substances. Results: The highest mean viscosity values were measured for a treatment containing a 2:1 ratio of tara gum:xanthan gum, resulting in chyme four times more viscous than a control formulation containing the same amount of water. Shear resistance was quantified by analyses of slopes fitting the frequency sweep measurements. Conclusions: These data open a new statistical approach to monitoring the consequences of market-driven changes in aqua feed composition and their impacts on the nutrition, health or performance of farmed fish. Show more

Keywords: Rheology, digesta properties, aquaculture, viscosity, binder

DOI: 10.3233/BIR-18167

Citation: Biorheology, vol. 54, no. 5-6, pp. 167-184, 2018