PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Erythrocyte Aggregation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1985

[A syllectrometric method to study erythrocyte aggregation].

The authors show a new method to study erythrocyte aggregation; the results of in vitro study, obtained by modification of several parameters (hematocrit, immunoglobulins, fibrinogen concentrations), are exposed. The authors did not find in vivo correlations between MAE and hemorheological parameters in different diseases; they found low MAE values only in myelomatous subjects. Adding erythrocytes from healthy donors to myelomatous plasma and vice versa, they found low MAE values only in samples containing erythrocytes and plasma from myeloma. These results suggest that many factors, not only erythrocyte aggregability, contribute to determine MAE (Mean Aggregation Entity).

Erythrocyte Aggregation↗
PubMed1994

Elevated erythrocyte aggregation in patients with central retinal vein occlusion and without conventional risk factors.

BACKGROUND: Retinal venous circulation is characterized by the combination of a low flow state and a high vascular resistance, which would make it particularly dependent on blood viscosity. Erythrocyte aggregation is the chief determinant of blood viscosity at low shear rates. Recent studies have demonstrated increased erythrocyte aggregation in many systemic vascular disorders and also in retinal vein occlusion. METHODS: To assess the possible role of abnormal hemorheologic findings in the pathogenesis of central retinal vein occlusion (CRVO), the authors retrospectively studied erythrocyte aggregation and hematocrit and fibrinogen levels in 33 patients with CRVO and without any known risk factors (diabetes, hypertension, smoking, hyperlipidemia, cardiovascular disease, glaucoma). Erythrocyte aggregation was assessed with a light back-scattering method. Results were compared with those of a group of 33 age- and sex-matched controls. RESULTS: Eleven (33%) of the 33 patients with CRVO had abnormal hemorheologic findings. Erythrocyte aggregation was highly significantly increased in the CRVO group when compared with the control group (P < 0.0001), as was the hematocrit level (P < 0.05). In addition, the proportion of patients with abnormal blood rheologic tests was greater (50%) in the subgroup of patients who initially had nonischemic CRVO that worsened into an ischemic CRVO during the follow-up. CONCLUSION: These data suggest that abnormal hemorheologic findings could affect the pathogenesis of CRVO, and perhaps be predictive of an aggravation. The latter hypothesis needs to be confirmed in a larger, prospective study.

Adult↗
PubMed2006

Gender differences in the expression of erythrocyte aggregation in relation to B beta-fibrinogen gene polymorphisms in apparently healthy individuals.

An increased erythrocyte aggregation (EA) is associated with capillary slow flow, tissue hypoxemia and endothelial dysfunction. Fibrinogen is a major determinant in the formation of aggregated red blood cells. It has been suggested that the B beta-fibrinogen -455 G/A polymorphism is associated with erythrocyte hyperaggregability in men with coronary artery disease. The purpose of this study was to investigate the influence of the beta-fibrinogen -455 G/A polymorphism on erythrocyte aggregation in apparently healthy individuals. Plasma fibrinogen, red blood cell count, serum lipids, erythrocyte sedimentation rate, and the genotype of the B beta-fibrinogen -455 G/A polymorphism were examined in a cohort of 545 apparently healthy individuals and those with atherothrombotic risk factors. A whole blood erythrocyte aggregation test was performed by using a simple slide test and image analysis. In men, EA levels and plasma fibrinogen levels were significantly higher in subjects carrying the -455 A allele compared to subjects with the -455 GG genotype. This association did not exist in women carrying the fibrinogen -455 A allele. The -455 GA/AA men presented significantly higher correlation between the plasma fibrinogen concentrations and EA. This observation raises the prospect of possible change in the functional properties of the -455 GA/AA fibrinogen, enhancing its ability to induce EH. This study suggests that the B beta-fibrinogen -455 A allele is related to EH in men only. Putative mechanism could be hyperfibrinogenemia and a functional change in the fibrinogen molecule that alters its ability to interact with red blood cells and supports the aggregability of these cells.

Aged↗
PubMed2005

Effect of erythrocyte aggregation at normal human levels on functional capillary density in rat spinotrapezius muscle.

Previous studies have shown that functional capillary density (FCD) is substantially reduced by erythrocyte aggregation. However, only supranormal levels of aggregability were studied. To investigate the effect of erythrocyte aggregability at the level seen in healthy humans, the FCD of selected capillary fields in rat spinotrapezius muscle was determined with high-speed video microscopy under normal (nonaggregating) conditions and after induction of erythrocyte aggregation with Dextran 500 (200 mg/kg). To examine shear rate dependence, the effect was studied both at normal and reduced arterial pressures (50 and 25 mmHg), the latter achieved by short periods of hemorrhage. In a separate study, volume flow was determined in arterioles (52.1 +/- 3.7 microm) under the same conditions. Before Dextran 500 infusion, FCD fell to 91% and 76% of control values, respectively, when arterial pressure was reduced to 50 and 25 mmHg. After Dextran 500 infusion, FCD was 96% at normal arterial pressure and fell to 79% and 37% of normal control values at 50 and 25 mmHg. All FCD values were significantly lower after dextran infusion. FCD reduction after lowering arterial pressure or dextran infusion appeared to be due to plasma skimming rather than capillary plugging. Reduction of FCD by dextran at reduced pressure was compensated by increased red blood cell flux in capillaries with red blood cell flow. We conclude that the level of aggregability seen in healthy humans is an important determinant of FCD only at reduced arterial pressure.

Animals↗
PubMed2000

The effect of low-molecular weight dextran on erythrocyte aggregation in normal and preeclamptic pregnancy.

Erythrocyte aggregation was determined by a novel method enabling the quantification of the aggregation process in whole blood. Blood samples of 47 healthy pregnant women and 39 preeclamptic patients were examined. Subjects within each group were matched for the gestational age. It was found that RBC aggregation increases with the gestational age in healthy pregnancy and further increases in preeclampsia. Addition of low-molecular weight dextran (MW = 9300) to blood samples of both healthy pregnant women and preeclamptic patients reduces RBC aggregation in a concentration-dependent manner. The obtained results indicate alterations in plasma composition as the primary factor for the increased RBC aggregation in both normal and pathological pregnancy. It is suggested that adsorption of low-molecular weight dextran on the RBC membrane reduces the surface concentration of plasma bridging molecules thereby reducing RBC aggregation toward normal.

Adsorption↗
PubMed2005

Erythrocyte aggregation is increased in preterm premature rupture of the membranes.

OBJECTIVE: To asses the degree of erythrocyte aggregation in the peripheral blood of women with preterm premature rupture of the membranes (PPROM). STUDY DESIGN: This was a prospective case control study. Twenty patients with preterm premature rupture of the membranes and matched controls were recruited at the Lis Maternity Hospital. A slide test and image analysis were used to quantitate the degree of erythrocyte aggregation. Hematological indices and markers of inflammation such as the erythrocyte sedimentation rate and C-reactive protein were also compared. RESULTS: The vacuum radius (VR) of the study group was significantly higher than in the control group at 14.8+/-1.6 microm versus 10.0+/-1.0 microm, respectively (P=0.03). Other hematological indices were not changed significantly between the groups. CONCLUSIONS: We found an increase in erythrocyte aggregation in the peripheral blood of patients with preterm premature rupture of the membranes. We used this sensitive marker of inflammation to further support the theory that PPROM is an inflammatory state.

Adult↗
PubMed2003

Typical changes of reversible erythrocyte aggregation in various pathological processes.

Examinations of patients with malignant tumors of different location (lung cancer, stomach, colorectal cancer, and head and neck tumors), patients with paranoid schizophrenia and neurotic disorders revealed enhanced reversible erythrocyte aggregation. It was found that enhancement of erythrocyte aggregation is associated with structural modification of their membrane and appearance of transformed cells (echinocytes, stomatocytes, etc.). The phenomenon of enhanced reversible erythrocyte aggregation in somatic and mental diseases can be regarded as a typical pathological process.

Adult↗
PubMed2000

Shear rate dependence of ultrasound backscattering from blood samples characterized by different levels of erythrocyte aggregation.

The objectives were (1) to determine the effect of the erythrocyte aggregation level (wide range of aggregation) and shear rate (which also affects aggregation) on the ultrasound backscattered power, and (2) to evaluate the reproducibility of the ultrasound method. Experiments were performed under steady flow (100-1250 ml/min) in a 12.7 mm diameter vertical tube. Doppler ultrasound at 10 MHz was used to measure simultaneously the velocity and the backscattered power across the tube. For each radial position, the shear rate was computed from the derivative of the velocity profile. The backscattered power decayed exponentially as a function of the shear rate, and for a given shear rate, the power increased monotonically with the level of aggregation measured by laser reflectometry. Using blood samples simulating hypo-, normal, and hyperaggregating erythrocytes, the power of the ultrasound signal varied respectively by -7.8, -13.2, and -16.1 dB as a function of the shear rate (from 0.4 to 50 s-1). The reproducibility of the backscattered power was 5.5 dB, which is less than the variations observed as a function of the shear rate. In conclusion, ultrasound backscattering is sensitive to the level of erythrocyte aggregation. At a first glance, ultrasound seems less accurate when compared to laser reflectometry but it is suggested that this is because ultrasound backscattering may be sensitive to structural aggregate changes that are not detected by the laser method.

Animals↗
PubMed1977

[Joint action of protein-chondroitin-4-keratan-sulfate and hyaluronic acid on erythrocyte aggregation and adhesion].

It was shown that the rate and the degree of erythrocytes aggregation brought about by a mixture of protein-chondroitin-4-keratan sulfate (PCKS) and hyaluronic acid (HA) was greater than the sum of the values of the corresponding indices observed during separate independent action of these proteoglycans on the aggregation of the mentioned cells concentrations as in the mixtures. It may be supposed that such phenomenon is connected with formation in the mixture of a hybrid PCKS-HA complex which is more active in respect to the erythrocyte aggregation than its components separately.

Cell Adhesion↗
PubMed2002

Effect of hydroxyethyl starch (HAES) on degree and kinetics of erythrocyte aggregation studied with dielectric spectroscopy method.

BACKGROUND: Colloidal fluids, e.g. hydroxyethyl starch (HAES), used as blood plasma substitutes during acute controlled normovolemic hemodilution may cause erythrocyte aggregation. The aim of the presented study was to assess the degree and rate of erythrocyte aggregation in the media containing different concentrations of HAES. MATERIAL/METHODS: The experiments were carried out on heparinized venous blood and on erythrocyte suspension in 0.9% NaCl. RESULTS: Under stationary conditions, an increase of blood and erythrocyte suspension relative electric permitivity (e), with an increase of HAES concentration in the sample, was observed after HAES supplementation. Sample flow through a measuring chamber resulted in decrease of the eL value (determined for 100 kHz). Stopping the flow led to non-linear increase of eL values in the function of time, where two components - characterized by rapid and slow variability, respectively, could be distinguished. The increase was characterized by t1 and t2 relaxation times, which can be related respectively to the process of erythrocyte rouleaux formation and to the formation of 3-D network aggregates. CONCLUSIONS: 1) The values of eL are differentiated by the degree of erythrocyte aggregation due to the presence of HAES, both in whole blood and in erythrocyte suspension in 0.9% NaCl solution, 2) The degree of erythrocyte disaggregation due to flow increases with the increase of flow intensity and correlates with decreasing eL value, 3) t1 and t2, which characterize the kinetics of erythrocyte aggregation, indicate a difference between aggregation processes taking place in whole blood and after hemodilution with HAES.

Electric Conductivity↗
PubMed1977

[Role of glycosaminoglycans and proteoglycans in erythrocyte aggregation and adhesion].

The action of hyaluronate potassium (HUK) and of protein chondroitin-4-sulphate potassium (PCHSK) on the aggregation and adhesion of rabbit erythrocytes suspended in physiological saline was studied. It was found that the capacity of HUK and PCHSK to produce an unspecific and reversible aggregation of erythrocytes was connected with the formation by these biopolymeres (in solutions) of complex structures of osmotic cell type and molecular sieves, displacing cells from the space occupied by them and concentrating them in a maximally limited volume. Different heparin fractions producing no such structures in solutions did not induce formation of such individual clear-cut erythrocyte-aggregations, but inhibited the aggregating action of HUK and PCHSK when the concentration of these biopolymeres were inadequate for the complete erythrocyte aggregation. Probably, the aggregating action of HUK and PCHSK necessary for adhesion served as one of the universal biological functions expressed not only towards the erythrocytes, but also towards the other cells and different tissue structural elements.

Animals↗
PubMedDate not supplied

Kinetic model for erythrocyte aggregation.

It is well known that light transmission through blood is the most widely utilized method for the study of erythrocyte aggregation. The curves obtained had been considered empirically as exponential functions. In consequence, the process becomes characterized by an only parameter that varies with all the process factors without discrimination. In the present paper a mathematical model for RBC aggregation process is deduced in accordance with von Smoluchowski's theory about the kinetics of colloidal particles agglomeration. The equation fitted the experimental pattern of the RBC suspension optical transmittance closely and contained two parameters that estimate the most important characteristics of the aggregation process separately, i.e., (1) average size of rouleaux at equilibrium and (2) aggregation rate. The evaluation of the method was assessed by some factors affecting erythrocyte aggregation, such as temperature, plasma dilutions, Dextran 500, Dextran 70 and PVP 360, at different media concentrations, cellular membrane alteration by the alkylating agent TCEA, and decrease of medium osmolarity. Results were interpreted considering the process characteristics estimated by the parameters, and there were also compared with similar studies carried out by other authors with other methods. This analysis allowed us to conclude that the equation proposed is reliable and useful to study erythrocyte aggregation.

Blood Cell Count↗
PubMed2001

Beta-estradiol effect on erythrocyte aggregation--a controlled in vitro study.

The purpose of this in vitro study was to assess the effect of 17beta-estradiol on hemorheologic parameters, namely on erythrocyte aggregation and deformability and membrane fluidity. Blood samples from 65 women (aged 57 +/- 4 years) undergoing postmenopausal hormone replacement therapy were obtained and were incubated for 5 min in absence and presence of 17beta-estradiol 10(-5) M. The measured parameters were the erythrocyte aggregation (EAI) and deformability (EI), the acetylcholinesterase activity (AChE), the plasma pH and osmolality and the erythrocyte membrane fluidity assessed by fluorescence polarization with two probes 1,6-diphenyl-1,3,5-hexatriene (DPH) and (1-(4-(trimethylamino)-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH). Data analysis was performed using t-Student and Pearson correlation analysis. A statistically significant decrease of the EAI (15.8 +/- 3.02 vs 13.45 +/- 2.3; p<0.001) and an increase of the EI (51.39 +/- 5.64 vs 52.06 +/- 5.36; p<0.01) at shear stress of 30 Pa in presence of 17beta-estradiol 10(-5) M was obtained. There was a decrease in membrane fluidity in 45 blood samples (DPH) and in the other 20 an increase, when beta-estradiol 10(-5) M was present. In vitro beta-estradiol 10(-5) M decreased erythrocyte aggregation in blood samples of postmenopausal women undergoing hormone therapy, which could prevent high blood viscosity and, consequently, cardiovascular events.

Acetylcholinesterase↗
PubMed1991

The effects of ioxaglate 320, iohexol 350, and iopamidol 370 on erythrocyte aggregation.

The authors report a randomized, double-blind prospective trial comparing the effects of nonionic with ionic low-osmolar contrast media on erythrocyte aggregation. The study group comprised 40 consecutive patients with pathology necessitating selective angiography. Patients were examined using either ioxaglate 320, iohexol 350, or iopamidol 370. Erythrocyte aggregation was assessed both macroscopically and microscopically. Erythrocyte aggregation occurred more frequently in the iopamidol group (13 of 45 samples examined) than in the iohexol (4 of 46) or ioxaglate (5 of 51) groups (P = .002).

Adolescent↗
PubMed1994

[Erythrocyte aggregation in patients treated by plasma exchange or plasma administration].

The kinetic (aggregation times) and rheological (dissociation threshold) parameters or erythrocyte aggregation were determined before and immediately after each plasma epuration, using a device based on the analysis of the back scattered light by a blood suspension. We used two techniques of plasma épuration: a) classical plasma exchange: 8 multiple myelomas, 6 Waldenström diseases, with 42 procedures tested; b) plasma treatment/cascade filtration: one Waldenström disease with 9 procedures tested and 37 procedures in one patient suffering from hypercholesterolemia. We have completed this study by checking the rheological parameters in 46 procedures applied in 6 patients with hypercholesterolemia. In these patients, we have used the Kaneka technique (dextran sulfate). The parameters studied were: primary (Ta) and final (Tf) aggregation times, total (gamma D) and partial (gamma S) dissociation parameters. In all cases, the results showed an important decrease of Ta and Tf (with good improvement) and an increase of dissociation parameters showing the efficacy of such therapies. Erythrocyte aggregation constitutes a good panel of parameters to appreciate abnormalities before and after plasma epuration.

Erythrocyte Aggregation↗
PubMed2001

Platelet activation and platelet-erythrocyte aggregates in end-stage renal disease patients on hemodialysis.

Activated platelets may engage in dynamic interplay with other blood cells. We examined the evidence for platelet activation and the formation of platelet-erythrocyte aggregates in chronic hemodialysis patients. Circulating activated platelets (P-selectin/CD63-positive platelets) were higher than normal controls (p < 0.001) and further increased during hemodialysis sessions, the increase being higher when patients were dialyzed with cellulosic than with synthetic membranes. We found direct evidence of uremic platelet-erythrocyte adherence in vitro and increased levels of circulating platelet-erythrocyte aggregates in dialysis patients, which represents a new observation in uremia. Platelet-erythrocyte aggregates were subject to further increase during hemodialysis, and again higher levels were found with cellulosic than synthetic membranes. This phenomenon was reproduced in vitro by both ADP and PAF, but not by either complement factor C3a or by heparin concentrations corresponding to those used for clinical hemodialysis. We conclude that platelet-erythrocyte aggregates occur in hemodialysis patients probably owing to a primary platelet activation mechanism.

Adenosine Diphosphate↗
PubMed2004

Increased erythrocyte aggregation in ovarian hyperstimulation syndrome: a possible contributing factor in the pathophysiology of this disease.

BACKGROUND: Many theories regarding the pathophysiology leading to ovarian hyperstimulation syndrome (OHSS) have been proposed and tested. Increased erythrocyte aggregation is associated with capillary slow flow and tissue hypoxaemia. We performed this study in order to assess the degree of erythrocyte aggregation in the peripheral blood of individuals with OHSS and undergoing controlled ovarian stimulation (COH). METHODS: Twenty women with severe OHSS, 20 women undergoing COH under IVF protocol, and 20 healthy matched controls were recruited for this prospective study. Blood samples were drawn for determination of erythrocyte aggregation as well as haematological indices. The percentage of slide covered by the cells ('erythrocyte percentage': EP) was determined using a simple slide test and image analysis. Lower EP values correspond to higher degrees of aggregation. RESULTS: The respective measures of EP were 59.2 +/- 3.0, 42.0 +/- 3.0 and 35.0 +/- 2.4% micro m for the controls, women with COH and OHSS (P < 0.01 between controls and the two stimulation groups). CONCLUSIONS: The degree of erythrocyte aggregation is enhanced in the peripheral venous blood of patients with both COH and OHSS. This finding, known to cause capillary leak, may contribute to the pathophysiology of the OHSS.

Capillaries↗