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Results for “Erythrocyte Aggregation”

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At least 145 records · Page 8Linked to original sources
PubMed2004

Application of validated ultrasound indices to investigate erythrocyte aggregation in pigs. Preliminary in vivo results.

Although some studies concerning the ultrasound (US) characterization of erythrocyte aggregation reported in the literature have been conducted in vivo, none of them has led to quantitative indices. To achieve this objective, we first finalized a method on a hydrodynamic bench. Particularly, we define a kinetic protocol consisting of applying a 200 s(-1) shear rate followed up by a rapid decrease to reach a residual shear rate between 0 to 32 s(-1). From the backscattered intensity curve recorded all along the kinetic procedure, US dynamic parameters were defined and validated by correlation with reference laser indices obtained with the same model suspensions of erythrocytes (different concentrations of dextran 70 kD). A particular interesting behavior has been demonstrated when studying aggregation vs. the residual shear rate applied. The aim of the present study was to test the applicability of this aggregation kinetics protocol during in vivo investigations in pigs and possibly to recover the same aggregating behavior. The backscattered intensity was recorded all along the kinetic procedure as defined in vitro. Taking the derivative of the velocity profile recorded on 56 electronic windows, the shear rate was finely computed in the same measurement window where the backscattered intensity was calculated. Each US parameter could, therefore, be correlated with the residual shear rate corresponding to the same depth of measurement. We found that the blood aggregation behavior was identical to that observed in vitro. Apparently, a specific range of residual shear rates accelerates the activation of the aggregation process and the final aggregation level attained.

Acoustics↗
PubMed1989

Influence of the red blood cell Ca2+-ion concentration on the erythrocyte aggregation in stasis.

Ca2+ ions were transported into the cell by incubation of the erythrocyte suspension with ionophore A23187, a lipophil electric neutral ion complexing substance. Erythrocyte aggregation could be increased twice, when doubling the intracellular Ca2+-ion concentration. Our measurements lead to the suggestion that an increase of the cytoplasmatic Ca2+ ion changes the physical and/or biochemical properties of the aggregation receptors on the membrane surface, i.e., cell-protein interactions are regulated by alteration of the intracellular Ca2+-ion concentration.

Adolescent↗
PubMed1997

Platelet activation and platelet-erythrocyte aggregates in patients with sickle cell anemia.

Vascular occlusion and vasculopathy underlie much of the morbidity in patients with sickle cell anemia. Platelets may play a role in this vasculopathy. Samples from 12 adults patients with sickle cell anemia were examined for evidence of platelet activation and formation of platelet-erythrocyte aggregates (PEA) using fluorescent-labeled monoclonal antibodies and flow cytometry. We noted an increased expression of activation-dependent antigens on the platelets from patients with sickle cell anemia compared with those from both white and black control subjects. In addition, patients with sickle cell anemia had increased levels of platelet microparticles and PEA. Platelets are activated in patients with sickle cell anemia and they adhere to sickle erythrocytes. The significance of this activation and adherence are the subject of further investigation.

Adolescent↗
PubMedDate not supplied

[Erythrocyte aggregation in vivo and diabetic microangiopathy. Physiopathologic determinants and clinical correlations].

Conjunctival angioscopy is a non invasive way for visualization and quantitative evaluation of the microcirculation. Grading red blood cell aggregation is possible in vivo using Ditzel's four grades score. The two-dimensional organization of conjunctival microvessels allows morphometric quantification of microvascular density. The aim of our study was to evaluate the determinant factors of erythrocyte aggregation and the place of conjunctival angioscopy in the early detection of diabetic microangiopathy. Conjunctival parameters were red blood cell aggregation (Ditzel's score) and morphometric evaluation of capillary, venular and arteriolar density. Criteria of diabetic microangiopathy were microalbuminuria and retinal fluorescein angiogram. Both conjunctival angioscopy and retinal angiogram were scored independently. Results obtained in 30 type 1 diabetic patients, with multifactorial statistical analysis, show that red blood cell aggregation in vivo is an essential discriminant factor for diabetic retinopathy and nephropathy. This rheological phenomenon depends more on duration of diabetes (analysis of variance p = .0005, r = .65) and metabolic control than on albuminemia or fibrinogenemia such as in non-diabetic patients. Manual morphometric data confirmed vascular rarefaction associated with excessive red blood cell aggregation (beta = .50). These results suggest that grading red blood cell aggregation in vivo is an interesting tool for physiopathological and clinical studies of diabetic microangiopathy.

Analysis of Variance↗
PubMedDate not supplied

Influence of hematocrit on erythrocyte aggregation kinetics for suspensions of red blood cells in autologous plasma.

The influence of hematocrit on red blood cell aggregation was investigated using a modified automated Myrenne Aggregometer System. Hematocrit values ranged from 20-70% at 10% increments, and were produced by resuspending washed red cells in autologous plasma. The Myrenne System produced seven kinetic parameters of red cell aggregation. The results indicate that hematocrit (Hct) had a strong and nonlinear effect on erythrocyte aggregability. At both low and high hematocrit, the aggregation intensity (AI) tends to decrease, reaching a plateau at 40% hematocrit. The disaggregation shear rate demonstrates an exponential relationship as In gamma TMIN = 3.29-0.0837 Hct. Time constants of the aggregation process such as T1/2, TSLOW and TFAST were rather inconsistent. The increase of hematocrit increased the rate of the fast phase aggregation and slightly slowed the secondary aggregation.

Biomechanical Phenomena↗
PubMed1985

The erythrocyte aggregation value as a measure of the risk of myocardial infarction and arteriosclerosis of peripheral arteries.

The erythrocyte aggregation value (AW) has been determined in groups of patients with and without coronary heart disease (CHD) and in a group of apparently normal subjects, using the Metricell apparatus as described by Kachel et al. The following results were obtained: There was a close correlation between the AW and the existence of CHD or arteriosclerosis of peripheral arteries. The precision of the retrospective prediction of CHD by this noninvasive test in male subjects aged over 45 years (total CHD prevalence = 0.494) was: sensitivity = 0.571, specificity = 0.767. The predictive value of positive tests (PVpos) was 0.706, of negative test (PVneg) 0.647. The discriminatory ability of the AW test was superior to that of serum cholesterol determinations or measurement of other CHD risk factors made in the same population. The AW rises exponentially with the total score for risk factors for CHD hazard for the subject. It appears, however, from the insignificant correlations observed that there is no direct connection between the AW and any single risk factor.

Cholesterol↗
PubMed1990

[Effect of contrast media products on the erythrocyte aggregation and deformability in vitro].

It has been suggested that contrast media could interfere with red blood cell aggregation, hyperosmolar media leading to an inhibition of red blood cell aggregation whereas non ionic products might induce a sludge phenomenon. We present an in vitro study accompanying two contrast media: 1) Ioxitalamate of sodium and meglumin (ionic, hyperosmolar). 2) Iopaminol (non ionic). In their effect on hemorheological parameters of red blood cell aggregation. Blood samples have been obtained from 7 healthy donors. Contrast media have been tested at increased contrast media (O.1, 1, 2, 10, 100 mg/ml of Iodine in final concentration). The following parameters have been studied: hematocrit, fibrinogen level, erythrocyte aggregation using the Erythro-aggregometer*, whole blood viscosity at 3 different shear rates (0.87, 18.74, 118 sec.-1) using Low Shear 30*. Deformability of red blood cell was assessed by ektacytometry. Osmolarity was controlled in each sample. Results show an inhibition effect of both contrasts media on red blood cell aggregation. There is a concomitant decrease of blood viscosity at low shear rates. On the contrary, apparent viscosity increases at high shear rates in parallel with the contrast media concentration. This effect is more pronounced with ioxitalamate above a concentration of 10 mg/ml. Ektacytometric parameters are not modified by contrast media and this could indicate a complete reversibility of the media-induced alteration on red blood cell. In order to precise the prothrombotic effect on contrast media, hemorheological studies have to be completed by the assessment of their effect on hemostatic parameters.

Adult↗
PubMedDate not supplied

Technique for direct and quantitative evaluation of erythrocyte aggregability in blood samples.

An improved technique for the assessment of red blood cell aggregability in human (or animal) blood is proposed, which can provide medical workers and researchers with direct microscopic quantitative data on this essential index of blood rheological properties in the microcirculation. The procedure of treating the blood samples is optimized: the red cells remain in their natural environment (their own blood plasma), while the manipulations and effects that might distort their natural aggregability index is accomplished in glass chambers using an image analyzer. Examples of the erythrocyte aggregability changes in hypertensive patients as compared with those in the healthy control group testify to the significance of the obtainable data.

Erythrocyte Aggregation↗
PubMed1998

Clinical application of the measurement of spontaneous erythrocyte aggregation and disaggregation. A pilot study.

Aggregation and disaggregation kinetics of erythrocytes in samples of whole blood were studied using a backscattering nephelometry technique. Blood was drawn from normal subjects and from patients suffering from different diseases: chronic glomerulonephritis, systemic lupus erythematosus, hereditary hypercholesterolemia, pulmonary hypertension, intestinal tumors preoperatively (age > 60 years), psoriasis, psoriatic arthritis, ischemia and ischemia with diabetes. Blood samples of healthy donors were used as controls. The backscattering signal in the erythroaggregometer was processed according to algorithms yielding quantitative data on the full amplitude of aggregation, characteristic times of spontaneous aggregation, average hydrodynamic strength of all aggregates and, whenever possible, additionally, strength of the largest aggregates. The obtained results confirm that the complexity of erythrocyte aggregation kinetics requires multiparametric description which, when applied to clinical material, enables the differentiation of aggregation characteristics between diseases.

Biomarkers↗
PubMed1989

[Venous insufficiency and hemorheology. Influence of venous stasis on erythrocyte aggregation and disaggregation].

UNLABELLED: The aim of this study was to assess the rheological properties of blood in patients with superficial venous insufficiency, in the very exact place of the hemodynamic disturbance i.e. in the veins of the lower limbs. MATERIAL AND METHODS: Several hemorheological parameters were studied in 20 patients (12 females and 8 males, 20 to 44 years old) with varicose veins of the lower limbs (insufficiency of the superficial venous system and no history of thrombosis). The results were compared to those obtained in 20 healthy controls matched for sex, age, weight and schedule for blood withdrawal. Two blood samples were obtained from the veins of the lower limbs of each subject: the first one at rest and the second after 10 minutes of "venous stasis" (standing position and 100 mm Hg tourniquet), in a temperature controlled room (22 degrees C). Every blood test was performed within one hour after blood withdrawal: --hematocrit (microcentrifugation) and fibrinogen (nephelometry); --plasma viscosity in a 37 degrees C temperature controlled capillary viscometer (Myrenne KSPV4); --erythrocyte filterability using the Hemorheometer (8% hematocrit and polycarbonate nuclepore membrane with a pore diameter of 5 microns); --erythrocyte aggregation and disaggregation (Myrenne AMM1 aggregometer and Erythroaggregometer SEFAM). RESULTS: 1. Hematocrit was not significantly different between both groups of subjects at rest. However, it increased significantly after venous stasis in patients with varicose veins (44.2% vs 41.8%, p. less than 0.05) and that was not found in controls. 2. At rest, the fibrinogen level was higher in patients than in controls (3.54 milligrams vs 2.41 milligrams, p less than 0.01). After statis, a significant increased was found only in the patients group (3.93 milligrams, p less than 0.05). 3. In a similar way, plasma viscosity at rest was significantly higher in patients (1.23 mPa.s) than in controls (1.11 mPa.s, p less than 0.01), and after stasis a further increase was found in the patients group (1.32 mPa.s, p less than 0.01). 4. Also the erythrocyte filterability index was altered at rest in patients (20.9) when compared to controls (15.1, p less than 0.01). A significant increase of this index was only found in the patients group (23, p less than 0.01). 5. Every aggregation parameters were significantly different at rest when comparing subjects groups, the most significant difference concerning the threshold of disaggregation (171.2 s-1 vs 106.8 S-1, p less than 0.001. Erythrocyte aggregation index was increased after stasis in patients but not in controls, with both 600 S-1 and 3 S-1 shear rates. 6. Positive correlations were found between low shear rate aggregation index on one hand and fibrinogen (r = 0.61), plasma viscosity (r = 0.51) and erythrocyte filterability index (r = 0.47) on the other hand...

Adult↗