Biorheology - Volume 53, issue 1

Authors: Kokkinos, Dimitrios | Dakhil, Haider | Wierschem, Andreas | Briesen, Heiko | Braun, André

Article Type: Research Article

Abstract: Background: High-density cultures require operating below the critical threshold of shear stress, in order to avoid reducing the specific growth rate of the cells. When determining this threshold, direct inspection of the cells in flow provides insight into the conditions of shearing. Objective: Aim of this study was using a novel rheo-optical setup for the observation of cells in laminar shear flow and the determination of the critical shear stress required to damage them in their natural environment. Methods: Dunaliella salina cells were sheared and observed in flow for shear stresses of up to 90 Pa, …at ambient temperature, without adding thickeners. The critical shear stress was determined by fitting a hydrodynamics-based criterion to the experimental data on the percentage of deformed cells after shearing. Results: Single cells, clusters and strings of cells were visible in shear flow. The strings formed at maximum shear stresses of 10 Pa or higher. Cells lost motility for maximum shear stresses higher than 15 Pa, and more than 80% of the cells were deformed at maximum shear stresses higher than 60 Pa. The estimated critical shear stress was 18 Pa. Conclusions: Shear stresses higher than 18 Pa should be avoided when cultivating D. salina . Show more

Keywords: Microalgae, high shear stress, rheo-optics, narrow-gap geometry, parallel-plate configuration

DOI: 10.3233/BIR-15057

Citation: Biorheology, vol. 53, no. 1, pp. 1-11, 2016

Authors: Wang, Yali | Hu, Feng | Mu, Xiaoyan | Wu, Feng | Yang, Dechun | Zheng, Guixiang | Sun, Xiaoning | Gong, Kaizheng | Zhang, Zhengang

Article Type: Research Article

Abstract: Objectives: Drag-reducing polymers (DRPs) are blood-soluble macromolecules which may increase blood flow and reduce vascular resistance. The purpose of the present study was to observe the effect of DRPs on monocrotaline-induced pulmonary hypertension (PH) in the rat model. Methods: A total of 64 male Wistar rats were randomly divided into four groups: Group I (pulmonary hypertension model + DRP treatment); Group II (pulmonary hypertension model + saline treatment); Group III (control + DRP treatment); Group IV (control + saline treatment). After five weeks, comparisons were made of the following indices: survival rate, body weight, blood pressure, right ventricular systolic pressure, right ventricular hypertrophy, …wall thickness of pulmonary arteries, the internal diameter of small pulmonary arteries, plasma IL-1β and IL-6. Results: The survival rate after 5 weeks varied significantly across all groups (P = 0.013 ), but the survival rates of Groups I and II were not statistically significantly different. Administration of DRP (intravenous injection twice weekly) attenuated the PH-induced increase in right ventricular systolic pressure and suppressed the increases in right ventricular (RV) weight and the ratio of right ventricular weight to left ventricle plus septum weight (RV/LV + S). DRP treatment also significantly decreased the wall thickness of pulmonary arteries, augmented the internal diameter of small pulmonary arteries, and suppressed increases in the plasma levels of IL-1β and IL-6. Conclusions: DRP treatment with intravenous injection effectively inhibited the development of monocrotaline-induced pulmonary hypertension in the rat model. DRPs may have potential application for the treatment of pulmonary hypertension. Show more

Keywords: Drag-reducing polymers, monocrotaline, pulmonary hypertension

DOI: 10.3233/BIR-15062

Citation: Biorheology, vol. 53, no. 1, pp. 13-22, 2016

Authors: Maslov, Mikhail Y. | Plotnikova, Tatiana M. | Anishchenko, Anna M. | Aliev, Oleg I. | Nifantiev, Nikolay E. | Plotnikov, Mark B.

Article Type: Research Article

Abstract: Background: Postmenopausal women often develop hemorheological disorders which may affect the systemic blood circulation and present a cardiovascular risk factor. Objective: We evaluated effects of secoisolariciresinol (SECO), a phytoestrogen, on hemorheological parameters and lipid peroxidation in a model of the age-related and/or surgical menopause induced by ovariectomy in rats. Methods: Arterial blood was sampled from sham-operated female rats, ovariectomized rats (OVX), and OVX treated with SECO (OVXSECO ) (20 mg/kg/day intragastrically for two weeks). Plasma estrogen concentration and the following hemorheological parameters were measured: RBC aggregation (half-time of aggregation, T1/2 ; amplitude of aggregation, AMP; aggregation …index, AI), RBC deformability (elongation index, EI), whole blood viscosity at the shear rate of 3–300 s−1 , plasma viscosity, hematocrit, plasma fibrinogen. Lipid peroxidation was evaluated by measuring conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS) in plasma. Results: Ovariectomy in rats caused a 60% decrease in plasma estrogen level and triggered the development of macro- and microhemorheological abnormalities. Blood viscosity increased by 12–31%, RBC elongation index reduced by 16–28%, and T1/2 and AI increased by 35% and 29% respectively. The increase in blood viscosity correlated predominantly with reduced RBC deformability. Plasma CD and TBARS were elevated by 47% and 104% respectively. SECO therapy for OVX rats reduced blood viscosity by 9–18% and T1/2 by 32%, and increased EI by 4–17%. SECO therapy disrupted the correlation between blood viscosity and RBC deformability. Lipid peroxidation was significantly inhibited, as shown by the reduction in CD and TBARS plasma concentrations by 89% and 70% respectively. SECO did not affect plasma viscosity, estrogen or fibrinogen levels. Conclusions: SECO treatment for OVX rats improves blood macro- and microrheological parameters, possibly through antioxidant protection of RBC. Show more

Keywords: Ovariectomized rats, secoisolariciresinol, whole blood viscosity, plasma viscosity, RBC aggregation, RBC deformability

DOI: 10.3233/BIR-15066

Citation: Biorheology, vol. 53, no. 1, pp. 23-31, 2016

Authors: Rajendran, Saranya | Sundaresan, Lakshmikirupa | Rajendran, Krithika | Selvaraj, Monica | Gupta, Ravi | Chatterjee, Suvro

Article Type: Research Article

Abstract: Background: Fluid flow plays an important role in vascular development. However, the detailed mechanisms, particularly the link between flow and modulation of gene expression during vascular development, remain unexplored. In chick embryo, the key events of vascular development from initiation of heart beat to establishment of effective blood flow occur between the stages HH10 and HH13. Therefore, we propose a novel in vivo model to study the flow experienced by developing endothelium. Objective: Using this model, we aimed to capture the transcriptome dynamics of the pre- and post-flow conditions. Methods: RNA was isolated from extra …embryonic area vasculosa (EE-AV) pooled from three chick embryos between HH10–HH13 and RNA sequencing was performed. Results: The whole transcriptome sequencing of chick identified up-regulation of some of the previously well-known mechanosensitive genes including NFR2 , HAND1 , CTGF and KDR . GO analyses of the up-regulated genes revealed enrichment of several biological processes including heart development, extracellular matrix organization, cell-matrix adhesion, cell migration, blood vessel development, patterning of blood vessels, collagen fibril organization. Genes encoding for gap junctions proteins which are involved in vascular remodeling and arterial–venous differentiation, and genes involved in cell–cell adhesion, and ECM interactions were significantly up-regulated. Validation of selected genes through semi quantitative PCR was performed. Conclusion: The study indicates that shear stress plays a major role in development. Through appropriate validation, this platform can serve as an in vivo model to study conditions of disturbed flow in pathology as well as normal flow during development. Show more

Keywords: Vascular development, shear forces, mechanotransducer genes, transcriptome

DOI: 10.3233/BIR-15075

Citation: Biorheology, vol. 53, no. 1, pp. 33-47, 2016