Viscosity Of Red Blood Cells Research Articles

Study of the mechanism of action of sand therapy on atherosclerosis based on the two-phase flow-Casson model.

Sand therapy is a non-pharmacological physiotherapy method that uses the natural environment and resources of Xinjiang to treat through the heat transfer and magnetic effects of sand. Employing the two-phase flow-Casson blood flow model, we investigate the mechanism of atherosclerosis prevention via sand therapy, offering a biomechanical theoretical rationale for the prevention of atherosclerosis through sand therapy via the prism of computational fluid dynamics (CFD). Sand therapy experiments were conducted to obtain popliteal artery blood flow velocity, and blood was considered as a two-phase flow composed of plasma and red blood cells, and CFD method was applied to analyze the hemodynamic effects of Casson's blood viscosity model before and after sand therapy. (1) The blood flow velocity increased by 0.24 m/s and 0.04 m/s at peak systolic and diastolic phases, respectively, after sand therapy; the axial velocity of blood vessels increased by 28.56% after sand therapy. (2) The average red blood cell viscosity decreased by 0.00014 Pa ⋅ s after sand therapy. (3) The low wall shear stress increased by 1.09Pa and the high wall shear stress reached 41.47Pa after sand therapy. (4) The time-averaged wall shear stress, shear oscillation index and relative retention time were reduced after sand therapy. The increase of blood flow velocity after sand therapy can reduce the excessive deposition of cholesterol and other substances, the decrease of erythrocyte viscosity is beneficial to the migration of erythrocytes to the vascular center, the increase of low wall shear stress has a positive effect on the prevention of atherosclerosis, and the decrease of time-averaged wall shear stress, shear oscillation index and relative retention time can reduce the occurrence of thrombosis.

The in vitro effect of delta-9-tetrahydrocannabinol and cannabidiol on whole blood viscosity, elasticity and membrane integrity

BackgroundThe main biological activities of cannabis are due to the presence of several compounds known as cannabinoids. Delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are two of the main cannabinoids. Studies have shown that the effects of THC can be modulated by CBD.ObjectiveThis study aims to look at the effect of different concentrations of THC and CBD separately and in combination, on blood viscosity, elasticity and membrane integrity.MethodsBlood samples were collected from twenty-four healthy adult non-smokers. Blood viscosity and elasticity were determined using the Vilastic Scientific Bioprofiler for different concentrations (0, 2.5, 25, 50 and 100 ng/ml) of CBD and THC respectively, as well as in extracts with combinations of CBD and THC in 4:1 and 1:1 ratios respectively. Repeated measures analysis of variance (ANOVA) was used to determine the difference between the means of the groups.ResultsBlood viscosity increased significantly with increasing concentrations of both THC and CBD from 25 ng/ml up to 100 ng/ml ranging from 6.45 ± 0.36 mPa·s to 11.60 ± 1.12 mPa·s for THC and ranging from 5.46 ± 0.24 mPa·s to 9.91 ± 1.10 mPa·s for CBD respectively, being more pronounced in the extracts at 21.33 ± 2.17 mPa·s for the 4THC:1CBD extract and 21.76 ± 1.88 mPa·s for the 1THC:1CBD extract. There was no significant increase in elasticity for THC and CBD separately. However, a significant increase in elasticity was observed in the extracts. THC and CBD affected red cell morphology resulting in complete disintegration at the highest concentrations.ConclusionsTHC and CBD increased red blood cell viscosity and elasticity separately and in combination. They also adversely affected membrane integrity.

Stroke mechanisms associated with coronavirus disease (COVID-19)

The purpose is to identify the pathophysiological mechanisms of stroke development in patients with COVID-19.MethodsA total of 92 patients (46.72+1.72 years) with impairments of cerebral circulation due to COVID-19 (confirmed by positive PCR test results) had been examined. Among them, 67 patients had an ischemic stroke, 14–a transient ischaemic attack, 11–an intracerebral hemorrhage, 3– a subarachnoid hemorrhage.The parameters of hemostasis were measured by standard methods, electrical and viscoelastic parameters of red blood cells (RBC) by the dielectrophoresis method was carried out.ResultsMost of the surveyed persons (60 patients) showed signs of an intravascular coagulation and thrombosis: accelerated platelet-leukocyte aggregation, increased levels of coagulation products, reduced fibrinolysis activity (p=0.002–0.04). The levels of D-dimer, fibrinogen, ESR, platelet count were significantly higher in this group compared to patients in the second one (p<0.01). A moderate increase in summarized rigidity, viscosity of RBC was noted. The level of RBC hemolysis was associated with platelet count (r=0.727, p<0.05), D-dimer level (r=0.422, p=0.04), and fibrinogen level (r=0.318, p<0.05).In the second group of patients (32 persons with a predominance of men - 25 male subjects), the markers of thrombosis had moderate deviations. A sharply reduced RBC deformability with increased summarized rigidity and viscosity was dominant coupled with the background of high electrical conductivity of cell membranes compared to the indicators in the first group (p<0.01). There was a decrease in membrane capacity, surface charge, electrical dipole moment of the cells and polarizability at all frequencies of the electric field than those in the first group (p=0.0001–0.05). A sharp decrease in RBC deformability creates obstacles to overcoming small-diameter capillaries, leading to violations of microcirculatory blood flow.The RBC deformability was associated with levels of ferritin (r=0.407, p=0.024), HbA1c (r=0.419, p=0.033), uric acid (r=−0.303, p<0.05), and LDL cholesterol (r=0.426, p=0.029).Incubation of blood samples in vitro for 10 min with riboflavin, nicotinamide, inosine, which ensures RBC energy metabolism (anaerobic glycolysis and pentose phosphate pathway) restored the reduced the RBC deformability (p<0.01), and decreased the RBC aggregation (p<0.001). Similar changes were obtained when coenzymes were administered to patients in vivo.ConclusionTwo independent mechanisms of cerebral circulatory disturbances have been identified in COVID-19 stroke patients: both thrombotic and hemorheologic. The thrombotic variant is associated with a procoagulant state and with an activity of inflammation. The hemorheologic variant is caused by a decrease in the activity of the RBC energy metabolism enzymes; it is associated with the presence of metabolic disorders and is to be eliminated by an administration of coenzymes and metabolites.FUNDunding AcknowledgementType of funding sources: Other. Main funding source(s): This research was done within the framework of the topic “Epidemiological monitoring of the population state of health and studies on molecular genetic and molecular biological mechanisms of the development of common internal diseases in Siberia for improvement of the relevant diagnostic, preventive, and therapeutic methods” in State Assignment No. 0324-2018-0001, registration No. AAAA-A17-117112850280-2

Deformability of different red blood cell populations and viscosity of differently trained young men in response to intensive and moderate running.

Red blood cell (RBC) deformability and blood viscosity are essential to ensure optimal microcirculation and may contribute to athletic performance. To investigate the acute responses of density fractionated young, middle old and old RBC, RBC viscosity (RBCV), plasma viscosity (PV) and hematological changes to two running modes (intensive and moderate). 27 young and healthy men of different training status participated in this study and were grouped into three groups in accordance to their VO2peak and conducted an intensive and moderate running test, respectively (crossover design). Pre and Post exercise, RBC were fractionated via percoll density gradient centrifugation. RBC deformability of the entire RBC population and the fractionated RBC was determined. Viscosity, hematocrit and mean cellular volume were determined. Baseline results reveal that high trained subjects possess more young RBC and show increased deformability of un-fractioned RBC and middle aged RBC. Baseline PV, RBCV, hematocrit and mean cellular volume did not differ between groups. Applied running modes did not change RBC deformability of any sub-fractions. Viscosity only increased after intensive running. Hematological changes were observed after both exercises. Acute effects of exercise on RBC are marginal, but chronic differences can be observed in RBC function.

Cryopreservation of red blood cells: Effect on rheologic properties and associated metabolic and nitric oxide related parameters

AimHigh glycerol cryopreservation of red blood cells (RBCs) reduces metabolic processes at ultralow temperatures but less is known regarding the effect of cryopreservation on RBC nitric oxide (NO) metabolism, haemorheological properties, structural behaviour and membrane fragility. MethodsBlood from ten healthy participants was sampled, glycerolized and stored at −80 °C (SB). Aliquots were thawed and further processed after 4, 8 and 12 weeks, respectively. At these time points, fresh blood (FB) was additionally sampled from each participant. FB/SB mixtures were prepared corresponding to transfusion of 1–3 blood bags. Additionally, mixtures were exposed to shear stress similar to that found in the circulation and deformability was measured to estimate possible behaviour of cryopreserved RBC in vivo. ResultsAgeing of RBC was reduced during cryopreservation. Markers for RBC metabolism (ATP, 2,3-DPG) were not altered but RBC sodium levels increased and potassium and calcium decreased, respectively. Mean cellular volume was higher and accordingly, mean cellular haemoglobin concentration was lower in SB. Deformability was altered during storage with less shear stress necessary to deform RBCs. Changes were also detectable in blood mixtures. Deformability remained unaltered in shear stress settings in FB and SB. RBC viscosity was reduced in SB. RBC-NOS content and phosphorylation sites as well as nitrite and RxNO levels seem not to be affected by the intervention. ConclusionCryopreservation maintains RBC metabolic function in vitro, but structure and function of cryopreserved RBC seems to be altered. Impact of these alterations in vivo seems to be less but needs further investigation.

Comparison between a generalized Newtonian model and a network-type multiscale model for hemodynamic behavior in the aortic arch: Validation with 4D MRI data for a case study

Blood is a complex fluid in which the presence of the various constituents leads to significant changes in its rheological properties. Thus, an appropriate non-Newtonian model is advisable; and we choose a Modified version of the rheological model of Phan-Thien and Tanner (MPTT). The different parameters of this model, derived from the rheology of polymers, allow characterization of the non-Newtonian nature of blood, taking into account the behavior of red blood cells in plasma. Using the MPTT model that we implemented in the open access software OpenFOAM, numerical simulations have been performed on blood flow in the thoracic aorta for a healthy patient. We started from a patient-specific model which was constructed from medical images. Exiting flow boundary conditions have been developped, based on a 3-element Windkessel model to approximate physiological conditions. The parameters of the Windkessel model were calibrated with in vivo measurements of flow rate and pressure. The influence of the selected viscosity of red blood cells on the flow and wall shear stress (WSS) was investigated. Results obtained from this model were compared to those of the Newtonian model, and to those of a generalized Newtonian model, as well as to in vivo dynamic data from 4D MRI during a cardiac cycle. Upon evaluating the results, the MPTT model shows better agreement with the MRI data during the systolic and diastolic phases than the Newtonian or generalized Newtonian model, which confirms our interest in using a complex viscoelastic model.

Viscoelastic Transient of Confined Red Blood Cells

The unique ability of a red blood cell to flow through extremely small microcapillaries depends on the viscoelastic properties of its membrane. Here, we study in vitro the response time upon flow startup exhibited by red blood cells confined into microchannels. We show that the characteristic transient time depends on the imposed flow strength, and that such a dependence gives access to both the effective viscosity and the elastic modulus controlling the temporal response of red cells. A simple theoretical analysis of our experimental data, validated by numerical simulations, further allows us to compute an estimate for the two-dimensional membrane viscosity of red blood cells, ηmem2D ∼ 10−7 N⋅s⋅m−1. By comparing our results with those from previous studies, we discuss and clarify the origin of the discrepancies found in the literature regarding the determination of ηmem2D, and reconcile seemingly conflicting conclusions from previous works.

Effect of N‐ethylmaleimide, chymotrypsin, and H2O2 on the viscoelasticity of human erythrocytes: Experimental measurement and theoretical analysis

The physiological functions of erythrocytes depend critically on their morphology, deformability, and aggregation capability in response to external physical and chemical stimuli. The dynamic deformability can be described in terms of their viscoelasticity. We applied jumping optical tweezers to trap and stretch individual red blood cells (RBCs) to characterize its viscoelasticity in terms of the Young's modulus and viscosity by analyzing the experimental data of dynamic deformation using a 2-parameter Kelvin solid model. The effects of three chemical agents (N -ethylmaleimide, Chymotrypsin, and Hydrogen peroxide) on RBC's mechanical properties were studied by comparing the Young's modulus and viscosity of RBCs with and without these chemical treatments. Although the effects of each of these chemicals on the molecular structures of RBC may not be exclusive, based on the dominant effect of each chemical, we attempted to dissect the main contributions of different constituents of the RBC membrane to its viscosity and elasticity.

Biorheological Action of Ascaris lumbricoides Larvae on Human Erythrocytes

Previous studies have shown that A. lumbricoides extracts capture sialic acid (SA) from human red blood cells (RBC). The aim of this work was to study hemorheological alterations in vitro caused by parasite larvae. The biorheological action of three larva concentrates of first and second larval stage on group O erythrocytes was analyzed by incubating the erythrocyte packed together with an equal volume of larvae (treated RBC) and PBS (control RBC). Distribution and parameters of aggregation (digital image analysis), aggregation kinetics (erythroaggregameter), and viscoelasticity (erythrodeformeter) were measured. The digital image analysis showed that all the larvae diminished the isolated cells percentage and increased the size of the formed aggregates. The aggregate formation velocity was lower in the treated than in the control. The deformability index (ID) values of treated RBC did not present variations with respect to those of the control, but a decrease in the erythrocyte elastic modulus (μ(m)) and membrane surface viscosity (η(m)) values was observed, indicating that the larvae not only induced a diminution in the membrane surface viscosity of RBC but also altered the dynamic viscoelasticity of the membrane. Experiments carried out in vitro support the conclusion that the contact between larvae and RBC produces hemorheological alterations.

Application of refutas model to estimate erythrocyte viscosity in a dextran solution

Whole blood viscosity has been considered as a significant clinical parameter in diagnosis and prevention of various cardiovascular diseases and a useful reference to monitor certain diseases. The blood viscosity can be influenced by several factors, such as red blood cell aggregation, hematocrit, and plasma viscosity. In many cardiovascular disease conditions, the concentration of plasma proteins (particularly fibrinogen) increases and this effect may elevate the aggregation level of red blood cells as well as plasma viscosity. This kind of phenomenon can also be observed in many in vitro studies that utilize high molecular weight dextrans (Dextran 70 and Dextran 500) to induce red blood cell aggregation. The red blood cells in such a dextran medium in general show a tendency of aggregation. Furthermore, with increasing dextran concentration, not only the aggregation level but also medium viscosity rises. In such case, it becomes difficult to determine individual quantitative effects of aggregation and plasma viscosity on blood viscosity, in particular on red blood cell viscosity. Information on the red blood cell viscosity is important in the microcirculation since a phase-separation phenomenon becomes apparent in microvessels, which leads to formation of a plasma layer near the vessel wall and a red blood cell rich region near the centerline. Thus, the viscosity in the core region (red blood cell viscosity) becomes much higher than the effective viscosity of blood. The Refutas model was first introduced to estimate the viscosity of oil mixture. This model can be used to predict the viscosity of a fluid mixture by measuring viscosities of individual fluid components. Alternatively, this model can be used to estimate the viscosity of an unknown component from the viscosity of its mixture. In this study, we attempted to use the Refutas model in estimating the viscosity of packed red blood cells by measuring blood and medium viscosities. Thus, the main purpose of the present study was to examine possibility of applying Refutas model to quantify the sole effect of red blood cell aggregation on red blood cell viscosity.

Transfusion massive : analyse des pratiques en fonction des dispositifs médicaux disponibles

IntroductionAn assessment of practices and available medical devices during the treatment of a massive haemorrhage has been realised in the shock unit of our hospital. Material and methodsParameters influencing transfusion flow rate have been identified. Medical devices and equipment to accelerate the flow rate were analyzed on the basis of manufacturers’ data and users opinion in relation with their practices. ResultsThe system, from blood bags to venous access, influences flow rate: red blood cell viscosity, catheter and pressure gradient. Three types of acceleration systems are available: accelerated transfusion set, pressure cuff with a gravity blood IV set and fast-flow fluid warmers. Their benefits and disadvantages are presented and discussed. DiscussionMaximum flow rates noted by manufacturers are not the real values because some parameters such as venous catheter diameter (limitative factor) and the red blood cell viscosity (diluted or not) are not considered. The choice of an infusion system is mainly based on the technical capacities (flow rate fluctuations, pressure gradient on blood bags, warming, air purging), practical modalities of use (medical devices and assembly) and cost. The pressure cuff with transfusion gravity set should be limited to non-critical situations or during the assembly of the fast flow fluid warmers (but no warming fluids, no air embolism prevention). The accelerated transfusion set is not the best option for a shock unit because it needs an operator permanently. The fast-flow fluid warmers are recommended for all types of massive haemorrhages, they are more secure but they require a long time to be assembled.

Pulsatile flow in a coronary artery using multiphase kinetic theory

Pulsatile flow in a model of a right coronary artery (RCA) was previously modeled as a single-phase fluid and as a two-phase fluid using experimental rheological data for blood as a function of hematocrit and shear rate. Here we present a multiphase kinetic theory model which has been shown to compute correctly the viscosity of red blood cells (RBCs) and their migration away from vessel walls: the Fahraeus–Lindqvist effect. The computed RBC viscosity decreases with shear rate and vessel size, consistent with measurements. The pulsatile computations were performed using a typical cardiac waveform until a limit cycle was well established. The RBC volume fractions, shear stresses, shear stress gradients, granular temperatures, viscosities, and phase velocities varied with time and position during each cardiac cycle. Steady-state computations were also performed and were found to compare well with time-averaged transient results. The wall shear stress and wall shear stress gradients (both spatial and temporal) were found to be highest on the inside area of maximum curvature. Potential atherosclerosis sites are identified using these computational results.

Multiphase non‐Newtonian effects on pulsatile hemodynamics in a coronary artery

AbstractHemodynamic stresses are involved in the development and progression of vascular diseases. This study investigates the influence of mechanical factors on the hemodynamics of the curved coronary artery in an attempt to identify critical factors of non‐Newtonian models. Multiphase non‐Newtonian fluid simulations of pulsatile flow were performed and compared with the standard Newtonian fluid models. Different inlet hematocrit levels were used with the simulations to analyze the relationship that hematocrit levels have with red blood cell (RBC) viscosity, shear stress, velocity, and secondary flow. Our results demonstrated that high hematocrit levels induce secondary flow on the inside curvature of the vessel. In addition, RBC viscosity and wall shear stress (WSS) vary as a function of hematocrit level. Low WSS was found to be associated with areas of high hematocrit. These results describe how RBCs interact with the curvature of artery walls. It is concluded that although all models have a good approximation in blood behavior, the multiphase non‐Newtonian viscosity model is optimal to demonstrate effects of changes in hematocrit. They provide a better stimulation of realistic blood flow analysis. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Vitamin E–bonded hemodialyzer improves atherosclerosis associated with a rheological improvement of circulating red blood cells

Vitamin E-bonded hemodialyzer is known to improve oxidative stress in patients with hemodialysis. However, there is little information available as to whether or not this membrane clinically improves atherosclerosis. Furthermore, it remains unknown whether there is any effect of the membrane on rheology of circulating red blood cells. We conducted a randomized, open-labeled, prospective control study (N = 34) for 1 year to investigate the effect of vitamin E-bonded cellulose membrane dialyzer (EE) (N = 17) on carotid atherosclerotic changes [intima-media thickness (IMT) of carotid arteries] and the viscosity, percentage of dysmorphism (%DMR) of red blood cells (RBCs) and their distribution width-standard deviation (RDW-SD), in comparison with cellulose membrane (SU) (N = 17) identical to EE without vitamin E-bonded membrane. Erythropoietin (EPO) dose used for the treatment of uremic anemia was also calculated. The IMT significantly decreased in the EE group, while in the SU group the IMT significantly increased. The viscosity of RBCs in hemodialysis patients (4.70 +/- 0.45 cP) was greater than that in healthy individuals (3.73 +/- 0.15 cP). EE significantly improved the viscosity (from 4.84 +/- 0.41 cP to 4.51 +/- 0.54 cP, P < 0.01), %DMR (from 2.29 +/- 2.17% to 1.90 +/- 1.49%, P < 0.01), and RDW-SD (from 54.4 +/- 7.6 fL to 49.3 +/- 5.9 fL, P < 0.01). On the contrary, these parameters all worsened in the SU group. EPO dose needed for the treatment of anemia was significantly (P < 0.05) reduced from 5383 +/- 2655 U/week to 4235 +/- 3103 U/week in the EE group. During these period, mean blood pressure, Kt/V urea, and serum beta2-microglobulin were not changed between the two groups. These findings suggest that vitamin E-bonded hemodialyzer is very useful for improving atherosclerosis from a clinical point of view. As one of the underlying mechanisms, as well as antioxidant effects, we want to address an important role of the improvement of rheology of circulating RBCs, which may also help to reduce the requirement of EPO dose in the treatment of anemia of ESRD patients.

Effects of lipoic acid on glucose utilization, protein glycosylation and viscosity of high glucose-treated red blood cells

UTILIZATION, PROTEIN GLYCOSYLATION AND VISCOSITY OF HIGH GLUCOSE-TREATED RED BLOOD CELLS Sushi1 K. Jain, Melissa Palmer, Yanyun Chen Department of Pediatrics, Louisiana State University Medical Center, Shreveport, LA 71130 USA Glycosylation of proteins can cause inactivation of enzymes and alterations in the structure and function of collagen and membranes. which may play a role in the long-term complications of diabetes and aging. Lipoic acid has been shown beneficial in reducing diabetic complications. such as. neuropathy. The present study was undertaken to test the hypothesis that lipoic acid increases glucose utilization and thereby reduces protein glycosylation and viscosity of red blood cells (RBC). RBC (15% hematocrit in PBS) were treated with high glucose levels (6-45 mM) with and without lipoic acid (5-200 LM) for 24 hrs in a shakine water bath at 3?‘C. Glucose was ‘determined using gl&ose oxidasel Glycosylated hemoglobin (HbAI) was determined using affinity chromatography to assess protein glycosylation. an: viscositv of washed RBC at tixed hematocrit was determined using computerized Brookfield viscometer. Lipoic acid treatment increased glucose utilization in high glucose (45 mM) exposed RBC by 75-120%. Over untreated fresh RBC, the increase in HbA, level in high glucose treated RBC was reduced by 22-40% in the presence of lipoic acid compared with high glucose alone. Treatment of RBC with high glucose increased viscosity of RBC. However. presence of lipoic acid in the medium significantly blocked increase in viscosity of high glucose-treated RBC. The level of glycated hemoglobin in blood has been considered to reflect the degree of glycation of other proteins that are freely exposed to circulating glucose. Using REX as a model. this study demonstrates that lipoic acid can reduce glycosylation of proteins and viscosity of cells exposed to high glucose. LIPID PEROXIDATION AND ANTIOXIDANT ENZYMES IN IMMUNE COMPLEX DISEASE G. Wbjcicka, A. Marciniak, D. G6my, R. CzabakGarbacz’, A. Korolczuk’, J. Beltowski Dept of Pathophysiologv, ‘Dept of Physiology, 2Dept of Pathomorphology, University of Medicine, Lublin, Poland The purpose of this study was to investigate lipid peroxidation and antioxidant mechanisms during early stage of immunisation and developed type III hypersensitivity. The male New Zeland rabbits (2.5 3 kg) were immunised by i.v. BSA. Four days after BSA administration malonyldialdehyde (MDA) level increased in plasma, renal cortex and renal medulla by 63%, 246% and 140% respectively, conjugated diens (CDs) increased in plasma, renal cortex and renal medulla by 76%, 122% and 63% respectively, lipid hydroperoxides (HPE) increased in plasma by 14%, in renal cortex by 11% and in renal medulla by 85%. Superoxide dismutase (SOD) activity in erythrocytes increased by 17%, blood glutathione peroxidase (Gpx) increased by 63% and total antioxidant status (TAS) decreased by 19%. Proteinuria was maximal 8 days after BSA administration. This day we observed 110% increase in MDA level in renal cortex and 271% increase in renal medulla. CDs increased by 60% in plasma, by 23% in renal cortex and by 40% in renal medulla. HPE in plasma was increased by 20% and in renal cortex by 100%. SOD and Gpx increased by 61% and 57% respectively whereas TAS decreased by 45%.

Covalent binding of poly(ethylene glycol) (PEG) to the surface of red blood cells inhibits aggregation and reduces low shear blood viscosity.

A simple method to coat human red blood cells (RBC) with PEG is described. Using a reactive derivative, monomethoxy-PEG (mPEG) was covalently attached to the surface of RBC in aqueous media under mild conditions. The PEG coating dramatically reduced aggregation and low shear viscosity of RBC resuspended in autologous plasma, and inhibited RBC agglutination by blood group-specific antibodies. Morphology and deformability of the PEG-treated cells were unaltered. The PEG coating of the RBC surface may be of significant benefit in the treatment of a variety of diseases characterized by vasoocclusion or impaired blood flow, e.g., myocardial infarction, sickle cell disease.

Microscopic photometric quantification of stiffness and relaxation time of red blood cells in a flow chamber

The Microscopic Photometric Monolayer Technique provides a tool to measure red blood cell (RBC) stiffness (resistance to elongation) and relaxation time. It combines many of the advantages of flow channel studies of point-attached RBCs with the simplicity, sensitivity and accuracy of photometric light transmission measurement This technique allows the study of the effects of physicochemical factors on the elongation and relaxation time of the same cells within an average of four to five thousand cells adhered as a monolayer to glass. Further, the time course of physicochemical effects on cell membrane and wash-in/wash-out kinetics of interactions can be followed. An automated version of this technique was developed. A dense monolayer of point-attached RBCs was prepared at the bottom of a flow-chamber. A steady-state flow, with stepwise increases of flow rate, induced the RBC elongation. The light transmission perpendicular through the monolayer plane was measured photometrically. Photomicrographs compared with photometric results showed that the flow-induced bending and curvature change of RBC membrane was associated with the increase of light transmission. There was a linear correlation between the photometric index of elongation and the elongation taken from photomicrographs for shear stresses up to 0.75 Pa. A stiffness parameter, S (in Pa), was defined as the ratio of shear stress and elongation at a shear stress of 0.25 Pa. Following a sudden flow stoppage, the RBCs returned to their resting shape and the RBC relaxation time was measured. The stiffness-relaxation time product, V (in mPas), was calculated to provide an estimate of viscosity. Diamide treatment, known to stiffen RBCs, did result in dose-dependent decreases of elongation and relaxation time. With increasing temperature, the relaxation time decreased at a rate of −2.96 ms/K; the stiffness increased significantly at a rate of 0.0038 Pa/K, and the stiffness-relaxation time product decreased with −2.95 mPas/K, reflecting an inverse relationship between RBC viscosity and temperature. Using the automated version of this technique (Elias-c-) to test RBCs of 36 healthy subjects, we found the inter-individual coefficients of variation to be 8.6% for stiffness, 7.9% for relaxation time and 12.4% for stiffness-relaxation time product.

Structural changes of proteins in fish red blood cells after copper and mercury treatment.

Exposure of fish red blood cells to increased concentrations (0.05–0.3 mmol/L) of copper and mercury ions may initiate structural changes in cells as detected by spin labeling method. Both heavy metals decreased membrane fluidity as indicated by methyl 5-doxylpalmitate and methyl 12-doxylstearate spectra. Furthermore, copper and mercury have been found to induce conformational alterations of internal peptides and proteins as determined by using 4-maleimido-2,2,6,6-tetramethylpiperidine-1-oxyl. Both heavy metal ions changed the internal viscosity of red blood cells. These results suggest that the possible cause of the damage of cells may be metal-protein interactions in the cells, but may exclude the oxidative mechanism of such damage.

Ionizing radiation-induced structural modification of human red blood cells

The effect of gamma radiation on red blood cells have been examined using a spin labeling method. For this purpose two spin labels were used to monitor membrane fluidity: methyl 5-doxylpalmitate (Met 5-DP) and methyl 12-doxylstearate (Met 12-DS). The irradiation of red cells with the doses of 200 and 500 Gy caused decrease of microviscosity in certain regions of lipid bilayer (as indicated by Met 5-DP and Met 12-DS spectra) but did not affect lipid order parameter. The behavior of two other spin labels, maleimide(4-maleimido-2,2,6,6-tetramethylpiperidine-1-oxyl) and TEMPONE (4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl) indicated: 1) conformational changes of membrane proteins, 2) modification of cell internal peptides and proteins, 3) decreased internal viscosity of red blood cells.

Radiation-induced structural alterations in fish red blood cells

The structural properties of gamma-irradiated fish red blood cells were studied using a spin labelling method. The gradient increase of lipid fluidity with the increasing gamma radiation doses was indicated by methyl 5-doxylpalmitate and methyl 12-doxylstearate spin labels spectra. In turns, the spectra of maleimide spin label (4-maleimido-2,2,6,6-tetramethylpiperidine-1-oxyl) and TEMPONE (4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl) indicated a modification of the internal proteins and the increased internal viscosity of red blood cells. The results encourage the conclusion that the increase in membrane fluidity may result from theernations in lipid-protein interactions rather than lipid peroxidation.