Blood Rheology and Hemodynamics.

(STH) celebrates 50 years of publishing in 2024. To celebrate this landmark event, STH is republishing some archival material. This article represents the most highly cited paper ever published in STH.

Acute and long-term effects of hyperbaric oxygen therapy on hemorheological parameters in patients with various disorders.

Inhalation of 100% oxygen in a hyperbaric chamber has been accepted as a useful treatment for patients with various pathologies who suffer from hypoxia. The oxidative effects of hyperbaric oxygen (HBO) on RBCs have been investigated in animals but there is not enough data on hemorheological parameters in patients following HBO treatment (HBOT).In this study, we investigated the effect of HBO on hemorheological and haematological parameters during treatment.

Abnormal blood rheology and chronic low grade inflammation: possible risk factors for accelerated atherosclerosis and coronary artery disease in Lewis negative subjects.

Objective: To test the hypothesis that abnormal hemorheology and chronic low-grade inflammation are more prevalent in Lewis negative individuals, possibly contributing to premature atherosclerosis.

Methods And Results: We enrolled 223 healthy subjects (154 females, mean age: 64yrs). Conventional risk factors, markers of inflammation and hemorheological profiles were measured; Lewis blood group was determined by serology.

The functional significance of the rho/rho-kinase pathway in human erythrocytes.

Objective: Erythrocyte deformability, which can be influenced by various intracellular signaling mechanisms, such as nitric oxide, cAMP, cGMP, and protein kinases, is the most important physiological factor providing the blood flow in microcirculation. However, the functional significance of the Rho/Rho-kinase pathway, which contributes cell shape changes and the reorganization of the actin cytoskeleton, has yet to be explored in erythrocytes. Therefore, we examined the influence of several activators and inhibitors of Rho/Rho-kinase signaling on human erythrocyte deformability.

Erythrocyte deformability responses to intermittent and continuous subhemolytic shear stress.

Background: Previous studies have demonstrated that red blood cells (RBC) either lyse or at least experience mechanical damage following prolonged exposure to high shear stress (≥100 Pa). Conversely, prolonged shear stress exposure within the physiological range (5-20 Pa, 300 s) was recently reported to improve RBC deformability. This study investigated the relationships between shear stress and RBC deformability to determine the breakpoint between beneficial vs.

EPO or PlacEPO? Science versus practical experience: panel discussion on efficacy of erythropoetin in improving performance.

Recombinant human erythropoietin (rHuEPO) is an agent commonly used by athletes with the aim to improve performance in endurance sports. However, the scientific community continues to debate the risks, benefits and its mechanism of action when used as a doping agent. This paper provides a brief overview on the pros and cons of rHuEPO use, as discussed by a group of scientist with diverse background, at the 17th Conference of the European Society for Clinical Hemorheology and Microcirculation in Pecs, Hungary.

Blood rheology and aging.

The flow properties of blood play significant roles in tissue perfusion by contributing to hydrodynamic resistance in blood vessels. These properties are influenced by pathophysiological processes, thereby increasing the clinical relevance of blood rheology information. There is well-established clinical evidence for impaired blood fluidity in humans of advanced age, including enhanced plasma and whole blood viscosity, impaired red blood cell (RBC) deformability and enhanced RBC aggregation.

The effect of alcohols on red blood cell mechanical properties and membrane fluidity depends on their molecular size.

The role of membrane fluidity in determining red blood cell (RBC) deformability has been suggested by a number of studies. The present investigation evaluated alterations of RBC membrane fluidity, deformability and stability in the presence of four linear alcohols (methanol, ethanol, propanol and butanol) using ektacytometry and electron paramagnetic resonance (EPR) spectroscopy. All alcohols had a biphasic effect on deformability such that it increased then decreased with increasing concentration; the critical concentration for reversal was an inverse function of molecular size.

Shear stress-induced improvement of red blood cell deformability.

Classically, it is known that red blood cell (RBC) deformability is determined by the geometric and material properties of these cells. Experimental evidence accumulated during the last decade has introduced the concept of active regulation of RBC deformability. This regulation is mainly related to altered associations between membrane skeletal proteins and integral proteins, with the latter serving to anchor the skeleton to the lipid matrix.

Red blood cell mechanical stability test.

Red blood cells (RBC) are exposed to various levels of shear stress (SS) during their flow in the circulatory system, yet no significant damage occurs if their mechanical stability is not impaired. Alternatively, normal RBC may be damaged during flow in non-physiological environments and under extreme SS (e.g.

Data reduction methods for ektacytometry in clinical hemorheology.

Laser-diffraction ektacytometry is a generally accepted technique for measuring RBC deformability induced by fluid shear stress (SS) and yields paired elongation index-SS data at several levels of stress. Unfortunately, comparison of results is hindered by the lack of simple indices that accurately characterize these data. Several mathematical models have been proposed, including those developed for analysis of enzyme kinetics (Lineweaver-Burk, Eadie-Hofstee) and curve fitting (Streekstra-Bronkhorst).

Nitric oxide generated by red blood cells following exposure to shear stress dilates isolated small mesenteric arteries under hypoxic conditions.

Red blood cells (RBC) possess a functional nitric oxide synthase (NOS) enzyme located in the cell membrane and cytoplasm. It has previously been observed that shear stress acting on RBC activates NOS and causes enhanced NO export. The aim of the present study was to investigate the physiological importance (e.

Exercise hemorheology: classical data, recent findings and unresolved issues.

The present review focuses on the past and recent knowledge in the field of exercise hemorheology and presents some unresolved issues for opening discussion. Acute exercise is associated with a rise in hematocrit which results in an increase in blood viscosity. Whereas increased blood viscosity was previously viewed as having negative consequences for cardiovascular function and aerobic performance, recent findings suggest dynamic changes in blood viscosity might be useful for vascular function during exercise by increasing nitric oxide production.

Erythrocyte aggregation: basic aspects and clinical importance.

Red blood cell (RBC) aggregate to form two- and three-dimensional structures when suspended in aqueous solutions containing large plasma proteins or polymers; this aggregation is reversible and shear dependent (i.e., dispersed at high shear and reformed at low or stasis).

Comparative hemorheology.

Comparative data on blood composition and blood flow properties indicate different levels of interspecies variation for several parameters. Hematocrit and hemoglobin levels have relatively low variability among mammals, while mean cell volume and red blood cell (RBC) count are more variable. There is also a difference of variability between high and low shear rate blood viscosity in mammals, with low shear rate viscosity having a higher degree of interspecies variation.

Iatrogenic hyperviscosity and thrombosis.

It is well known that hemostatic-thrombotic mechanisms are influenced by hemodynamic factors, such as shear forces affecting platelets or red blood cell aggregation, in turn affecting flow in stenotic regions. Endothelial cell function is also significantly influenced by shear forces acting on the vessel wall. Further, the distribution of shear forces in the vasculature is complex and closely associated with factors determining the flow properties of blood.

Nitric oxide, erythrocytes and exercise.

Nitric oxide (NO) is accepted to be an important factor affecting the degree of vascular tone in various portions of the circulation. Until recently, research in this area has focused on endothelial cells as a NO source, and there is general agreement that: 1) the level of wall shear stress is the primary determinant of endothelial nitric oxide synthase (eNOS) expression; 2) exercise training induces changes of endothelial cell NO synthesizing activity; 3) phosphorylation patterns of eNOS are altered following exercise episodes. However, there is now a growing body of evidence for the existence of similar nitric oxide synthesizing mechanisms in human red blood cells (RBC).

Effect of lanthanides on red blood cell deformability and response to mechanical stress: role of lanthanide ionic radius.

Prior studies exploring the effects of lanthanides (Ln) on red blood cells (RBC) have primarily focused on ion transport, cell fusion, and membrane protein structure. Our previous report [Biorheology 44 (2007), 361-373] dealt only with lanthanum (La) and cell rigidity; the present study extends these observations to other lanthanides (Nd, Sm, Eu, Dy, Er) and to RBC response to mechanical shear. Deformation-shear stress behavior of normal human RBC was measured at Ln concentrations up to 200 μM.

Wavelength selection in measuring red blood cell aggregation based on light transmittance.

The reversible aggregation of red blood cells (RBC) is of current basic science and clinical interest. Using a flow channel and light transmittance (LT) through RBC suspensions, we have examined the effects of wavelength (500 to 900 nm) on the static and dynamic aspects of RBC aggregation for normal blood and suspensions with reduced or enhanced aggregation; the effects of oxygenation were also explored. Salient observations include: 1.

Measurement of red blood cell aggregation in disposable capillary tubes.

A new method is described in this paper that allows measurement of red blood cell (RBC) aggregation indexes in disposable glass tubes within minutes. Light transmission through the RBC suspension filled into a microhematocrit capillary at stasis is recorded during RBC aggregation; a novel method assures an initial dispersion of aggregates in the capillary. The resulting light transmittance-time data are analyzed to calculate various parameters.

Shear stress activation of nitric oxide synthase and increased nitric oxide levels in human red blood cells.

Red blood cells (RBC) play an important role in the balance between generation and scavenging of nitric oxide (NO) and hence its local bioavailability and influence on vasomotor control. Previous studies have reported increased NO levels in RBC suspensions subsequent to exposure to shear forces; the present study was designed to further investigate changes in intracellular NO concentration and possible mechanisms involved for RBC exposed to well-controlled shear forces. Attached human RBC were subjected to shear stresses up to 0.

A comparison of capillary and venous blood sampling methods for the use in haemorheology studies.

There is accumulating evidence that exercise may improve disturbed haemorheological parameters that are typically observed in various chronic diseases, thus there is a growing interest in exploring the influence of various exercise models for the improvement of haemorheology. Blood sampling using venipuncture, however, can be limiting during exercise and/or in field settings. The purpose of the present study was to investigate whether venous and capillary blood samples yield comparable red blood cell (RBC) deformability and aggregation indices.

Assessment of oxidant susceptibility of red blood cells in various species based on cell deformability.

The present study was designed to investigate the oxidant susceptibility of red blood cells (RBC) from four species (echidna, human, koala, Tasmanian devil) based on changes in cellular deformability. These species were specifically chosen based on differences in lifestyle and/or biology associated with varied levels of oxidative stress. The major focus was the influence of superoxide radicals generated within the cell (phenazine methosulfate, PMS, 50 μM) or in the extracellular medium (xanthine oxidase-hypoxanthine, XO-HX, 0.

Examination of aggregation of various red blood cell populations can be informative in comparison of splenectomy and spleen autotransplantation in animal experiments.

Using "Furka's spleen-chip" autotransplantation technique, in a follow-up study we investigated erythrocyte aggregation and its influencing factors regarding to asplenic-hyposplenic conditions. Healthy beagle dogs were equally divided into 4 groups: "Sham"- sham operated control, "SE"-splenectomy, "AU-5" and "AU-10"-autotransplantation with 5 or 10 spleen chips by Furka-method after splenectomy. Blood sampling for current investigation occurred on the 12th, 18th, 20th and 24th postoperative months, besides comprehensive structural and functional examinations.