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The normal transmyocardial tissue hematocrit distribution (i.e., subepicardial greater than subendocardial) is known to be affected by red blood cell (RBC) aggregation. Prior studies employing the use of infused large macromolecules to increase erythrocyte aggregation are complicated by both increased plasma viscosity and dilution of plasma. Using a new technique to specifically alter the aggregation behavior by covalent attachment of Pluronic F-98 to the surface of the RBC, we have determined the effects of only enhanced aggregation (i.e., Pluronic F-98-coated RBCs) versus enhanced aggregation with increased plasma viscosity (i.e., an addition of 500 kDa dextran) on myocardial tissue hematocrit in rapidly frozen guinea pig hearts. Although both approaches equally increased aggregation, tissue hematocrit profiles differed markedly: 1) when Pluronic F-98-coated cells were used, the normal transmyocardial gradient was abolished, and 2) when dextran was added, the hematocrit remained at subepicardial levels for about one-half the thickness of the myocardium and then rapidly decreased to the control level in the subendocardial layer. Our results indicate that myocardial hematocrit profiles are sensitive to both RBC aggregation and to changes of plasma viscosity associated with increased RBC aggregation. Furthermore, they suggest the need for additional studies to explore the mechanisms affecting RBC distribution in three-dimensional vascular beds. myocardium; plasma viscosity; Pluronic F-98; dextran

Erythrocyte aggregation is associated with a series of physio-pathological processes in body and according to this, current study was designed to examine how the thymoquinone (TQ) and aggregation kinetics relation changes when the aggregation properties of erythrocyte suspensions are intervened using different approaches, such as changing the suspension environment or erythrocyte surface properties. Blood samples from 40 male Wistar albino rats (three months old weighing 250-300 g) were randomly divided into four groups, as 1) whole blood (control), 2) 1/2 dilution (plasma was diluted with PBS), 3) dextran 500 (1% dextran 500 was dissolved in plasma) and 4) glutaraldehyde. Blood samples were taken from abdominal aorta under anesthesia. The erythrocyte suspensions were incubated at 37°C for one hour in the absence or presence of TQ, with a final concentration of 1 mg/ml. Then, the electrical properties of erythrocyte suspensions were recorded, and the electrical capacitance was monitored using an inductance, capacitance, and resistance meter (LCR meter) at 100 kHz. It was found that TQ incubation decreased the aggregation index in control and dextran groups while increased it in 1/2 dilution and GA groups. It was also found that TQ incubation increased the time constant in whole blood and dextran while decreased it in 1/2 dilution and GA. The TQ can normalize the altered erythrocyte aggregation responses in both ways that is, it decreases the increased aggregation or increases the decreased aggregation. Therefore, it may have very critical role in rouleaux formation-induced circulatory disorders. [ABSTRACT FROM AUTHOR]

Objectives Prolidase plays a major role in collagen turnover, matrix remodeling, and cell growth. Benign prostatic hyperplasia (BPH) may be associated with an increased extracellular matrix deposition. Therefore, the present study was designed to investigate the plasma prolidase activity, oxidative status, and peripheral mononuclear leukocyte DNA damage in patients with BPH. Patients and methods Twenty-six male patients with BPH and 24 healthy male subjects were included in this study. Blood samples were collected from antecubital vein after an overnight fasting period, and the plasma was separated. Plasma prolidase activity, total antioxidant capacity (TAC), total oxidant status (TOS), and oxidative stress index (OSI) were determined. The peripheral lymphocyte oxidative DNA damage was determined using an alkaline single cell gel electrophoresis assay (comet assay). Results The plasma prolidase activity, TOS levels, OSI values, and peripheral mononuclear leukocyte DNA damage were significantly higher (P < 0.001), while the TAC levels were significantly lower (P < 0.001) in patients with BPH than controls. In BPH patients, the prolidase activity was significantly associated with TAC levels (r = −0.366, P < 0.05), TOS levels (r = 0.573, P < 0.001), and OSI (r = 0.618, P < 0.001) and peripheral mononuclear leukocyte DNA damage (r = 0.461, P < 0.001). Conclusions Our results showed that BPH might be associated with an increased oxidative stress, and also an increased plasma prolidase activity. Increased prolidase activity might play an important role in the etiopathogenesis and/or progression of BPH. [ABSTRACT FROM AUTHOR]

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. In another series of experiments, RBC were exposed to mechanical stress (190 Pa, 300 s) at 50 μM Ln and deformation-stress data obtained prior to and after this stress. Data were fitted to a Lineweaver-Burke model to obtain the shear stress at one-half maximum deformation (SS1/2). Our results include: (1) lanthanides cause decreased cell deformability with the magnitude of the decrease dependent on concentration and shear stress; (2) this decrease of deformability is affected by Ln ionic radius such that La>Nd>Sm>Eu>Dy>Er and is reversible for cells in Ln-free media; (3) mechanical stress decreases deformability (i.e., increases SS1/2) such that compared to control, La and Sm reduce and Dy and Er enhance the mechanical stress effect; (4) the decrease of deformability consequent to mechanical stress scales inversely with Ln ionic radius. These results indicate a reciprocal relation between cell rigidity and sensitivity to mechanical stress that is mediated by Ln ionic radius. Additional studies are clearly warranted, particularly those that explore membrane-glycocalyx and intracellular mechanisms. [ABSTRACT FROM AUTHOR]

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. Measurement of erythrocyte sedimentation rate (ESR) and RBC aggregation using well established methods and the newly developed capillary tube aggregometer in blood samples with a wide range of RBC aggregation indicated significant correlations between these parameters. Additionally, light transmittance during complete disaggregation allows estimating hematocrit, thereby enabling hematocrit correction of the measured and calculated parameters. The newly developed capillary tube RBC aggregometer is suitable for use as a method to rapidly monitor disease activity and the acute phase response, especially at the point-of-care (e.g., health care facilities, physician's office) and for field studies. [ABSTRACT FROM AUTHOR]

Red blood cells (RBC) in normal human blood undergo reversible aggregation at low flow or stasis. The extent and kinetics of this phenomenon have been studied using various optical and electrical methods, yet results using such methods are not always in concordance. This study employed a horizontal glass tube in which blood flow could be established, then abruptly stopped. Normal blood and RBC suspensions with enhanced or decreased aggregation were studied. Light transmittance (LT) and electrical impedance at 100 kHz were recorded during high-shear flow and for 120 s after flow was abruptly stopped during which RBC aggregation occurs. Capacitance values were also obtained based on the imaginary part of impedance data and recorded. Various aggregation parameters were calculated, using the time course of LT, impedance, and capacitance, then compared with each other and with results from laboratory aggregometers. RBC aggregation parameters were calculated, using the time course of impedance data often failed to correlate with known changes of aggregation, even reporting aggregation for cells in nonaggregating media (i.e., RBC in buffered saline). Alternatively, RBC aggregation parameters based upon the time course of capacitance data are in general agreement with those derived from LT data and with RBC aggregation indexes, measured using commercial instruments. [ABSTRACT FROM AUTHOR]

The International Society for Clinical Hemorheology organized a workshop to compare three instruments for measuring RBC aggregation: LORCA, Myrenne Aggregometer and RheoScan-A. The Myrenne Aggregometer provides indices at stasis (M) and at low shear (M1), with four indices obtained with the LORCA and RheoScan-A: amplitude (AMP), half-time (T1/2), surface area (SA) above (LORCA) or below (RheoScan-A) the syllectogram, and the ratio (AI) of the area above (LORCA) or below (RheoScan-A) the syllectogram to total area (AI). Intra-assay reproducibility and biological variability were determined; also studied were RBC in diluted plasma and in 1% 500 kDa dextran, and 0.003% glutaradehyde (GA)-treated cells in plasma. All measurements were performed at 37°C. Standardized difference values were used as a measure of power to detect differences. Salient results were: (1) intra-assay variations below 5% except for RheoScan-A AMP and SA; (2) biological variability greatest for T1/2 with other indices similar for the three devices; (3) all instruments detected progressive changes with plasma dilution; (4) the Myrenne and LORCA, but not the RheoScan-A, detected differences for cells in dextran; (5) GA-treatment significantly affected the LORCA (AMP, T1/2, SA, AI), the RheoScan-A (AMP, SA, AI) and the Myrenne M parameter. It is concluded that: (a) the LORCA, Myrenne and the RheoScan-A have acceptable precision and suitable power for detecting reduced aggregation due to plasma dilution; (b) greatly enhanced RBC aggregation may not be sensed by the RheoScan-A while the Myrenne M1 index may be insensitive to minor increases of cell rigidity; (c) future studies should define each instrument's useful range for detecting RBC aggregation. [ABSTRACT FROM AUTHOR]

Measurement of red blood cell (RBC) deformability by ektacytometry yields a set of elongation indexes (EI) measured at various shear stresses (SS) presented as SS-EI curves, or tabulated data. These are useful for detailed analysis, but may not be appropriate when a simple comparison of a global parameter between groups is required. Based on the characteristic shape of SS-EI curves, two approaches have been proposed to calculate the maximal RBC elongation index (EImax) and the shear stress required for one-half of this maximal deformation (SS1/2): (i) linear Lineweaver-Burke (LB) model; (ii) Streekstra-Bronkhorst (SB) model. Both approaches have specific assumptions and thus may be subject to the measurement conditions. Using RBC treated with various concentrations of glutaraldehyde (GA) and data obtained by ektacytometry, the two approaches have been compared for nine different ranges of SS between 0.6–75 Pa. Our results indicate that: (i) the sensitivity of both models can be affected by the SS range and limits employed; (ii) over the entire range of SS-data, a non-linear curve fitting approach to the LB model gave more consistent results than a linear approach; (iii) the LB method is better for detecting SS1/2 differences between RBC treated with 0.001–0.005% glutaraldehyde (GA) and for a 40% mixture of rigid cells but is equally sensitive to SB for 10% rigid cells; and (iv) the LB and SB methods for EImax are equivalent for 0.001% and 0.003% GA and 40% rigid, with the SB better for 0.005% GA and the LB better for 10% rigid. [ABSTRACT FROM AUTHOR]

Blood samples used in hemorheological studies may be stored for a period of time, the effects of storage have yet to be fully explored. This study evaluated the effects of storage temperature (i.e., 4°C or 25°C) and duration on RBC deformability and aggregation for blood from healthy controls and from septic patients. Our results indicate that for normal blood, RBC deformability over 0.3–50 Pa is stable up to six hours regardless of storage temperature; at eight hours there were no significant differences in EI but SS1/2 calculated via a Lineweaver–Burk method indicated impaired deformability. Storage temperature affected the stable period for RBC aggregation: the safe time was shorter at 25°C whereas at 4°C aggregation was stable up to 12 hours. Interestingly, blood samples from septic patients were less affected by storage. Blood can thus be stored at 25°C for up to six hours for deformability studies, but should be limited to four hours for RBC aggregation; storage at 4°C may prolong the storage period up to 12 hours for aggregation but not deformability measurements. Therefore, the time period between sampling and measurement should be as short as possible and reported together with results. [ABSTRACT FROM AUTHOR]

In December 2008, the International Society for Clinical Hemorheology organized a workshop to evaluate and compare three ektacytometer instruments for measuring deformability of red blood cells (RBC): LORCA (Laser-assisted Optical Rotational Cell Analyzer, RR Mechatronics, Hoorn, The Netherlands), Rheodyn SSD (Myrenne GmbH, Roetgen, Germany) and RheoScan-D (RheoMeditech, Seoul, Korea). Intra-assay reproducibility and biological variation were determined using normal RBC, and cells with reduced deformability (i.e., 0.001–0.02% glutaradehyde (GA), 48°C heat treatment) were employed as either the only RBC present or as a sub-population. Standardized difference values were used as measure of the power to detect differences between normal and treated cells. Salient results include: (1) All instruments had intra-assay variations below 5% for shear stress (SS)>1 Pa but a sharp increase was found for Rheodyn SSD and RheoScan-D at lower SS; (2) Biological variation was similar and markedly increased for SS<3–5 Pa; (3) All instruments detected GA-treated RBC with maximal power at 1–3 Pa, the presence of 10% or 40% GA-modified cells, and the effects of heat treatment. It is concluded that the LORCA, Rheodyn SSD and RheoScan-D all have acceptable precision and power for detecting reduced RBC deformability due to GA treatment or heat treatment, and that the SS range selected for the measurement of deformability is an important determinant of an instrument's power. [ABSTRACT FROM AUTHOR]

Measurements of red blood cell (RBC) deformability and aggregation can be subject to influence by pre-analytical handling procedures, with the degree of hemoglobin oxygenation having the potential to affect the results. To examine such effects, RBC deformability and aggregation were studied before and after oxygenation or deoxygenation of human blood samples. RBC deformability was assessed using a laser-diffraction ektacytometer having Couette geometry. RBC aggregation was assessed using the same system by monitoring light backscattering after a sudden cessation of high shear; aggregation was also measured by monitoring light transmittance through RBC suspensions. RBC deformability was found to be significantly increased after equilibrating RBC with ambient air (pO2: 142.0±3.1 mmHg) compared to the non-oxygenated sample (pO2: 42.4±1.8 mmHg). In contrast, equilibration with 100% nitrogen resulted in significant impairment in RBC deformability. RBC aggregation parameters were also affected by oxygenation if measured based on light backscattering, but not if measured using light transmittance. It is thus recommended that blood samples be oxygenated by repeated exposure to ambient air prior to the measurement of hemorheological parameters. [ABSTRACT FROM AUTHOR]

Venipuncture procedures are widely thought to influence biochemical, hematological or hemorheological measurements. In line with the preparation of the new Guidelines for the standardization of hemorheological measurement, we compared various blood rheological parameters (i.e., red blood cell deformability and aggregation indices) assessed in blood samples obtained after 5, 30, 60 and 90 s following the tourniquet removal and a blood sample obtained without applying a tourniquet (control sample). A slight but significant improvement in red blood cell (RBC) deformability after the removal of tourniquet compared to the control sample was observed. RBC deformability was maximal in the samples obtained 30 s after tourniquet removal and remained slightly higher than the control in the following samples (at 60 and 90 s after tourniquet removal). The aggregation index (AI) decreased with time after tourniquet removal reaching significantly lower values than the control at 90 s after tourniquet removal. This finding was supported by a greater half time for RBC aggregation in the samples obtained 60 and 90 s after tourniquet removal. In conclusion, this study revealed that RBC deformability and aggregation might be significantly altered in the samples obtained after the application and removal of a tourniquet, as a part of the blood sampling procedure. Recommendation “remove the tourniquet at least 5 s prior to the start of blood sampling” may need to be revised. [ABSTRACT FROM AUTHOR]

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are the most commonly used cholesterol-lowering drugs, with recent clinical trends usually aimed at achieving the lowest possible plasma cholesterol levels. Although the effects of increased plasma cholesterol have been previously reported, it is not obvious how very low plasma cholesterol levels would affect membrane composition and the deformability of red blood cells (RBC). The present study investigated the effects of hypocholesterolemia achieved by atorvastatin therapy on RBC membrane and mechanical properties in guinea pigs fed a normal diet. Two groups of animals were used (atorvastatin-treated, n=12; control n=12), and atorvastatin given orally in isotonic phosphate-buffered saline (PBS) at a dose of 20 mg/kg/day for a 21-day period. Our results indicate that the atorvastatin-treated group had significantly lower plasma total cholesterol (17.42±1.70 mg/dl), low-density lipoprotein cholesterol (5.25±2.22 mg/dl) and triglycerides (42.60±3.78 mg/dl) than the control group (34.08±1.72, 21.17±1.41 and 60.64±2.43 mg/dl, respectively). In addition, membrane cholesterol content was lower (p<0.0001) and phospholipid content higher (p<0.0001) in the atorvastatin-treated group, thus decreasing the cholesterol to phospholipid ratio; a significant enhancement in sodium-potassium-ATPase activity also occurred. However, in spite the marked changes of plasma and RBC membrane composition, there was no change of RBC deformability. Note that although our results indicate no adverse rheological alterations, extension of our findings to humans requires caution. [ABSTRACT FROM AUTHOR]

The normal transmyocar-dial tissue hematocrit distribution (i.e., subepicardial greater than subendocardial) is known to be affected by red blood cell (RBC) aggregation. Prior studies employing the use of infused large macro- molecules to increase erythrocyte aggregation are complicated by both increased plasma viscosity and dilution of plasma. Using a new technique to specifically alter the aggregation behavior by covalent attachment of Pluronic F-98 to the surface of the RBC, we have determined the effects of only enhanced aggregation (i.e., Pluronic F-98-coated RBC5) versus enhanced aggregation with increased plasma viscosity (i.e., an addition of 500 kDa dextran) on myocardial tissue hematocrit in rapidly frozen guinea pig hearts. Although both approaches equally increased aggregation, tissue hematocrit profiles differed markedly: 1) when Pluronic F-98-coated cells were used, the normal transmyocardial gradient was abolished, and 2) when dextran was added, the hematocrit remained at subepicardial levels for about one-half the thickness of the myocardium and then rapidly decreased to the control level in the subendocardial layer. Our results indicate that myocardial hematocrit profiles are sensitive to both RBC aggregation and to changes of plasma viscosity associated with increased RBC aggregation. Furthermore, they suggest the need for additional studies to explore the mechanisms affecting RBC distribution in three-dimensional vascular beds. [ABSTRACT FROM AUTHOR]

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. significant effects of wavelength on aggregation parameters reflecting the extent of aggregation (i.e., number of RBC per aggregate); 2. no significant effects of wavelength on parameters reflecting the time course of RBC aggregation; 3. a prominent influence of hemoglobin oxygen saturation on both extent and time-course related aggregation parameters measured at wavelengths less than 700 nm, but only on the time-course at 800 nm; and 4. the power of parameters in detecting a given alteration of RBC aggregation is affected by wavelength, in general being greater at higher wavelengths. It is recommended that light sources with wavelengths around 800 nm be used in instruments for measuring RBC aggregation via LT.

Red blood cell (RBC) aggregation is the reversible and regular clumping in the presence of certain macromolecules. This is a clinically important phenomenon, being significantly enhanced in the presence of acute phase reactants (e.g., fibrinogen). Both light reflection (LR) and light transmission (LT) from or through thin layers of RBC suspensions during the process of aggregation are accepted to reflect the time course of aggregation. It has been recognized that the time courses of LR and LT might be different from each other. We aim to compare the RBC aggregation measurements based on simultaneous recordings of LR and LT. The results indicate that LR during RBC aggregation is characterized by a faster time course compared to simultaneously recorded LT. This difference in time course of LR and LT is reflected in the calculated parameters reflecting the overall extent and kinetics of RBC aggregation. Additionally, the power of parameters calculated using LR and LT time courses in detecting a given difference in aggregation are significantly different from each other. These differences should be taken into account in selecting the appropriate calculated parameters for analyzing LR or LT time courses for the assessment of RBC aggregation.