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PubMed2002

A new ultrasound principle for characterizing erythrocyte aggregation: in vitro reproducibility and validation.

RATIONALE AND OBJECTIVES: There is no method currently available to quantify erythrocyte aggregation in vivo. In this work, using a Couette system, we defined new ultrasound indexes potentially applicable for non-invasive investigations. METHODS: Two ultrasound protocols were developed: (1) a protocol in which decreasing shear rates ranging from 200 to 1 s-1 were applied to solutions; and (2) a protocol in which a 200 s-1 shear rate was initially applied followed by stoppage of flow (a kinetics protocol). New ultrasound indexes were defined as: the power PUS at the nominal frequency of each transducer, Rayleigh's slope (tangent of the curve PUS = f(log(F)) through the 3.5 to 15 MHz frequency bandwidth) and kinetic indexes characterizing the aggregation/aggregability of the suspension. RESULTS: Using washed erythrocytes resuspended in saline, it was shown that the ultrasound intensity is dependent at 3.54 +/- 5.9% (NS) to the power of the frequency (theoretical value = 4). Using 10 total blood samples extracted from a single pig, good reproducibility for all indexes (5%) was demonstrated. CONCLUSIONS: A suitable and reproducible methodology was developed and validated for studying erythrocyte aggregation in calibrated in vitro conditions.

Calibration↗
PubMed2003

Erythrocyte aggregation determined with the Myrenne aggregometer at two modes (M0, M1) and at two times (5 and 10 sec).

Erythrocyte aggregation index determined with the Myrenne aggregometer gives a wide range of values both in healthy and disease, as observed in the literature, making results less comparable. This is due to the fact that it gives two aggregation indexes depending on the rotation speed of the cone, M0 (at stasis) and M1 (at 3 s(-1)) and time elapsed (5 or 10 sec), after the cone is stopped abruptly. We determined in 112 healthy volunteers both indexes at two modes and at two times, along with fibrinogen, plasmatic lipids and hematimetric indexes. The correlations between both the 5 and 10 sec mode, and the different variables were analysed and although a statistically significant correlation was observed in both modes, M1 at 5 sec gave the highest correlation values: 0.445, 0.485, 0.364, 0.460 for T-Chol, LDL-Chol, Apo B/A1 and fibrinogen, respectively; p<0.01. Therefore, we suggest that all the erythrocyte aggregation measurements should be performed at a hematocrit adjusted to 45%, with autologous plasma, and that an aggregation time of 5 sec (as opposed to 10 sec) should be used in order to avoid confusion and misunderstanding and to allow for comparability of results with the de Myrenne aggregometer between laboratories.

Adult↗
PubMed2003

Effects of contrast media on erythrocyte aggregation during sedimentation.

To evaluate the effects of contrast media (CMs) on erythrocyte aggregation, we measured the erythrocyte sedimentation with Westergren method at 25 degrees C. CMs were diatrizoate (Urografin 76%) for ionic CM and iopamidol (Iopamiron 370) for nonionic CM. Swine red blood cells (RBCs) were suspended in autologous plasma containing diatrizoate (URO), iopamidol (IOP), and saline (SAL) at 6.7% w/w, as well as in plasma alone (PLA), at 40% of the hematocrit. Sigmoid sedimentation curves were fitted to the Puccini et al. (1977) equation, and the average number of RBCs per aggregate m was calculated by Stokes' law against the time t. According to the Murata-Secomb (1988) theory we estimated the collision rate K between two aggregates from dm/dt in the stationary phase during sedimentation. Corresponding to the maximal ESR, the dm/dt (in cells/s) was 0.52 in PLA, 0.09 in SAL, 0.06 in URO and 0.03 in IOP, so that K also decreased in proportion to dm/dt from 145 fL/s in PLA to 8 fL/s in IOP. Both the ionic and nonionic CMs tend to inhibit the RBC aggregation more than that in SAL; the latter iopamidol appears to be inhibitory more than the former diatrizoate in autologous plasma.

Animals↗
PubMedDate not supplied

Erythrocyte aggregation: experimental approaches and clinical implications.

From a clinical point of view, quantitative studies of erythrocyte aggregation or rouleau formation is of great interest. However, in order to approach the phenomenon, structural parameters (rouleau shape), kinetic parameters (rouleau formation and dissociation velocity) and rheological parameters (dissociation thresholds) must be determined. At present, optical dynamic methods are available for use in clinical hemorheology. They involve optical measurements in a viscometer. The first method consists of a study of the light intensity transmitted through the measuring chamber of a cone plan viscometer. A device calculates and index I, which provides a whole approach to the aggregation kinetics. On the other hand, a systemic which also involves a cone-plain viscometer and an inverted microscope (Rheoscope) allows to collect data by means of microphotographs, microcinematography or numerical image processing. In that case, an adimensional K index typical of the morphology of the aggregates can be determined. The second method involves the analysis of the light intensity backscattered by the red blood cells sheared in a Couette flow. An automatic system has been developed and aggregation times, orientation and structure index, total and partial disaggregation thresholds can be determined on the basis of the curves of variations of backscattered light.

Blood Viscosity↗
PubMed1999

Comparison of three optical methods to study erythrocyte aggregation.

The aim of this work was to evaluate three optical methods designed to determine erythrocyte aggregation: Erythroaggregometer (EA; Regulest, France), Laser-assisted Optical Rotational Cell Analyzer (LORCA; Mechatronics, Netherlands) and Fully Automatic Erythrocyte Aggregometer (FAEA; Myrenne, GmbH, Germany). Blood samples were taken from fifty donors (26 males and 24 females). The aggregation of normal red blood cell (RBC) and RBCs suspended in three normo- and hyperaggregating suspending media was studied. The results revealed some significant correlations between parameters measured by these instruments, in particular, between the indexes of aggregation of EA and LORCA. Further, RBC aggregation of multiple myeloma patients was also studied and a hyper erythrocyte aggregation state was found by EA and LORCA.

Adult↗
PubMed1992

Influence of erythrocyte aggregability and plasma fibrinogen concentration on CBF with aging.

The influence of the rheological properties of the blood on cerebral perfusion is still unresolved. Data on normal subjects are lacking and difficulties arise regarding the effect of blood viscosity owing to its close relationship with hematocrit. For these reasons we have studied the relationship between two rheological hematocrit-independent parameters and CBF in normal subjects of various ages. 36 normal volunteers, aged 20-74, free from risk factors, have been studied. CBF was measured by the Xenon inhalation method. Erythrocyte aggregability was expressed as Mean Erythrocyte Aggregation Index (MEA). Plasma fibrinogen concentration was evaluated by the coagulative method in 26 subjects. No correlation was found between CBF and MEA or fibrinogen in the subjects under the age of 45. A significant negative correlation was found between CBF and MEA (p = 0.015) and between CBF and fibrinogen (p = 0.011) in the subjects over 45. These data show that cerebral perfusion is influenced by the rheological properties of the microcirulation only with aging. We suggest that a "rheological autoregulation" exists and that it works properly in youth, only to be lost with physiological aging. This finding can be of significance in the pathogenesis of cerebrovascular disease processes in humans.

Adult↗
PubMed2000

Comparative values of erythrocyte aggregability versus other indices of hemorheological disorders in patients with ischemic brain infarcts.

The aim of the present study is comparison of changes of principal hemorheological factors responsible for blood flow disorders in the microcirculation in patients with ischemic brain infarcts. It was found that in venous blood samples the erythrocyte aggregability (examined with a direct, highly sensitive, quantitative technique) was considerably more increased (by mean of 120%) than the blood plasma fibrinogen contents, blood plasma viscosity, and hematocrit which increased only by 23.7%, 7.4% and 3.6%, respectively, as compared to the same hemorheological factors in the healthy controls. These results led us to the following conclusion: among the other tests the enhanced erythrocyte aggregability, when measured with an appropriate technique, is the best diagnostic indicator of hemorheological derangements during development of the ischemic brain infarct.

Adult↗
PubMed1996

Influence of sialic acid on erythrocyte aggregation in hypercholesterolemia.

The respective role of adhesive forces induced by fibrinogen and repulsive forces induced by erythrocyte sialic acid content on erythrocyte aggregation, was investigated in hypercholesterolemic and control subjects. Aggregation index (AI) and disaggregation shear rate threshold (gamma t) were determined in the presence of either autologous plasma or dextran. Compared with controls, fibrinogen (p < 0.001) and aggregation parameters (AI p < 0.01; gamma t p < 0.01) were higher in hypercholesterolemics while erythrocyte sialic acid content (p < 0.001) was lower; in addition total serum sialic acid was increased (p < 0.01). The aggregation properties of erythrocytes, independent of plasma environment using dextran as a bridging macromolecule, showed an enhanced disaggregation shear rate threshold and an inverse relationship with erythrocyte sialic acid content. We conclude that decreased erythrocyte sialic acid content may intensify the effect of fibrinogen on aggregation and disaggregation of erythrocytes and participate in the development of atherothrombotic complications.

Erythrocyte Aggregation↗
PubMed1998

Alterations in erythrocyte aggregability in diabetics: the influence of plasmatic fibrinogen and phospholipids of the red blood cell membrane.

In order to ascertain whether the increased aggregability observed in the red blood cells of diabetic patients is induced exclusively by plasma factors or is also influenced by membrane lipids, we examined the phospholipids of the erythrocyte membrane, the plasma fibrinogen concentration and erythrocyte aggregation in 86 insulin and non insulin-dependent diabetic patients. The data obtained show that the erythrocyte aggregability of the diabetic patients is higher than that of the control group (10.0+/-2.4 vs. 7.8+/-1.6%). This increased aggregability correlates not only with a higher fibrinogen concentration but also with changes observed in the membrane phospholipids. The percentage of sphingomyelin (SP) in the patients is higher than in the controls (22.6+/-6.8 vs. 18.4+/-5.4%) and that of phosphatidylserine (PS) is lower (9.5+/-6.1 vs. 12.1+/-5.1%). No differences in the percentages of the other two phospholipids identified (phosphatidylcholine, PC, and phosphatidylethanolamine, PE) were observed. The increase in the saturated nature of the phospholipids of the erythrocyte membrane, which can be measured by the (SP + PC)/(PE + PS) ratio, is statistically related (r = 0.39; p < 0.05) to the increased red blood cell aggregability observed in these patients.

Adult↗
PubMed1994

Simultaneous influence of erythrocyte deformability and macromolecules in the medium on erythrocyte aggregation: a kinetic study by a laser scattering technique.

The aggregation and sedimentation kinetics of human erythrocytes was studied by modifying the cellular properties and medium compositions simultaneously. Dextrans of average molecular weight 70400 and 494000 were used to provide suspending medium modifications, while diamide (diazene dicarboxylic acid bis(N,N-dimethylamide)) was used to alter the membrane structural properties. Laser scattering method was employed for this study, and it was compared with a kinetic method combined with a low-shear rheoscope and an image analyzer. From scattered light intensity profiles continuously obtained during aggregation of erythrocytes and sedimentation of the aggregates, characteristic kinetic parameters were computed. Kinetic parameters obtained from a phase of the one-dimensional aggregate formation and sedimentation corresponded well to the velocity of rouleaux formation obtained by the low-shear rheoscope technique. Dextrans accelerated the erythrocyte aggregation and the sedimentation, and diamide treatment suppressed the process by decreasing the erythrocyte deformability. The aggregating force by dextrans overcame the disaggregating force by the decreased deformability. However, the arrangement of erythrocytes as expressed in specific units for aggregates (i.e., rouleaux) became irregular by decreasing the erythrocyte deformability. In conclusion, the progression of erythrocyte aggregation and the structure of the aggregates were dependent on both erythrocyte properties and macromolecules in the medium.

Blood Sedimentation↗
PubMed2005

Long-term prognostic value of protein C activity, erythrocyte aggregation and membrane fluidity in transmural myocardial infarction.

The objective of this study was to evaluate the long-term predictive value of the haemostatic, inflammatory and haemorheologic disturbances in transmural myocardial infarction (MI). Sixty-four (59 male) consecutive survivors of a MI, with a mean age of 58.3 +/- 12.0 years, were followed over a period of 36 months. Eighteen patients had a cardiovascular event defined as the composite of death, non-fatal MI, unstable angina and stroke. The haemostatic (protein C activity-PtC, antithrombin III, plasminogen activator inhibitor-1), haemorheologic (blood fluidity and components, erythrocyte membrane fluidity) and inflammatory (polymorphonuclear elastase, leukocyte count) profiles were determined at hospital discharge, using standard methodology. Our results can be summarized as follow: (i) at hospital discharge, the subgroup of patients with events had higher leukoactivity, leukocyte count, membrane fluidity, prognosis cyte count (7833.0 +/- 1696.0 vs. 10294.0 +/- 3129.0; p = 0.011), lower PtC (100.65 +/- 19.08 vs.81.25 +/- 19.95; p = 0.002), and lower erythrocyte aggregation (14.26 +/- 5.94 vs. 11.47 +/- 3.45; p = 0.031) in relation to the ones without events; (ii) By Cox regression the protein C activity lower tertile (OR 0.169; 0.045-0.628; p = 0.008); erythrocyte membrane outer layer fluidity upper tertile (OR 0.067; 95% CI 0.011 - 0.393; p = 0.003); and erythrocyte aggregation lower tertile (OR 0.182; 0.038 - 0.876; p = 0.034) were independent predictors of the composite endpoint. We can conclude that some haemostatic, haemorheologic and inflammatory disturbances, at hospital discharge, are long-term independent predictors of recurrent cardiovascular events in transmural myocardial infarction survivors.

Adult↗
PubMed1994

Influence of HDL subfractions on erythrocyte aggregation in hypercholesterolemic men. PCVMETRA Group.

Recent studies have suggested that rheological mechanisms may be involved in the pathogenesis of ischemic syndromes in hyperlipidemias. We investigated the association between erythrocyte aggregation and components of lipoproteins in the blood of 60 normotensive, hypercholesterolemic men aged 45 +/- 8 years. The rheological parameters assessed were aggregation index (AI) and disaggregation shear rate threshold (gamma t) as determined by laser reflectometry, plasma fibrinogen, total serum protein, and hematocrit. The lipoprotein variables included total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol and its subfractions HDL2 cholesterol and HDL3 cholesterol, apolipoprotein (apo) B, apoA-I, HDL particles containing apoA-I without apoA-II (LpA-I), and HDL particles containing both apoA-I and apoA-II (LpA-I/A-II). Covariables considered for possible confounding effects were age, body mass index, and smoking behavior. Fibrinogen, total serum protein, and both aggregation parameters (AI and gamma t) were elevated in this hypercholesterolemic population. Univariate analysis showed that both AI and gamma t correlated positively with fibrinogen (P < .001) and total serum protein (P < .01) and negatively with HDL2 cholesterol (P < .01) and LpA-I (P < .01); gamma t also provided a positive correlation with LpA-I/A-II (P < .05). A multivariate model analysis demonstrated that HDL2 cholesterol, LpA-I, and LpA-I/A-II also emerged as significant factors influencing erythrocyte aggregation; 60% to 68% of the variance of AI and 47% to 64% of the variance of gamma t could be explained by these factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Increase of erythrocyte aggregation in hypertensive men with dyslipidemia].

We have already reported that erythrocyte aggregation (EA) is increased in hypertensive subjects. To study the influence of other risk factors in EA, we have measured aggregation index IA and disaggregation shear rate threshold (gamma c) by a laser technique and the biochemical parameters in 16 normotensive normocholesterolemic subjects (NT/NCT) and 45 hypertensive subjects where 17 were normocholesterolemic (HT/NCT), 18 were pure hypercholesterolemic (HT/HCTIIa) and 10 were hypercholesterolemic hypertriglyceridemic (HT/HCTIIb). The results show that IA and gamma c are more important in HT/NCT than NT/NCT patients and much more in patients with hypercholesterolemia and hypertriglyceridemia. The cumulative effects of hypertension and hyperlipidemia merit take into consideration in pathophysiology of cardiovascular complications and could help to new strategy therapeutic developments for treatment of these complications.

Adult↗
PubMed1999

Enhanced erythrocyte aggregation in type 2 diabetes with late complications.

We investigated whether erythrocyte aggregation (EA) is enhanced in type 2 diabetic patients who have developed microvascular or macrovascular complications. EA rates at high and low shear rates were analysed in 141 patients with type 2 diabetes who were further divided into 4 subgroups according to the status of diabetic complications and degree of metabolic control. Groups 1 (n = 43) and 2 (n = 23) consisted of well-controlled patients without and with clinically evident late complications, while groups 3 (n = 33) and 4 (n = 42) represented poorly controlled patients without and with these complications, respectively. 124 healthy subjects served as the control group. Mean EA rate was comparable between control subjects and group 1 both at high (2.05 +/- 0.03 vs. 2.14 +/- 0.07, respectively) and low (6.96 +/- 0.02 vs. 7.04 +/- 0.06, respectively) shear rates. Mean EA rate was also comparable between groups 2 and 4 at high (2.76 +/- 0.09 vs. 2.94 +/- 0.07, respectively) and low (8.18 +/- 0.13 vs. 8.41 +/- 0.1, respectively) shear rates. However, EA at both shear rates in groups 2 and 4 were significantly higher than control subjects, group 1 (p < 0.0001) and group 3 (high shear rate EA: 2.76 +/- 0.09 and low shear rate EA: 7.48 +/- 0.07 (p < 0.01). In group 3, EA rates were significantly higher than control subjects and group 1 (p < 0.05) at both shear rates. No significant correlation was found between EA at high and low shear rates and fibrinogen levels in diabetic subgroups and control subjects. The data suggest that patients with type 2 diabetes who had developed clinically evident late complications have enhanced EA regardless of the degree of metabolic control. Whether enhanced EA is a primary phenomenon contributing to the development of these complications or it occurs secondary to their development remains to be clarified.

Adult↗
PubMed1995

Increasing erythrocyte aggregability with the progressive grades of chronic venous insufficiency: importance and mechanisms.

Erythrocyte aggregation (EA) has appeared as the most interesting parameter among rheological measurements in chronic venous insufficiency (CVI). We therefore conducted two different kinds of studies to provide further information about the distribution and mechanisms of EA in CVI. We first analysed EA values in 67 patients, classified according to 3 evolutive groups: 27 patients suffering only from subjective symptoms of venous disease (grade 1), 19 patients with varicosis and sapheno-femoral incompetence (grade 2), 21 patients with varicosis and trophic skin changes (grade 3). EA values were also measured in 22 healthy controls. Analysis of EA was performed for equal concentrations of fibrinogen and adjusted for age. EA was significantly higher in CVI. The aggregation index, related to the kinetics of aggregates formation, rose significantly even from grade 1 while compared to controls and rose further with the evolutive grades. The same trend was found with the partial dissociation threshold (i.e. red cells aggregates cohesion). As the measurements were performed at standardized hematocrit and the results expressed after fibrinogen levels adjustment, this suggests the involvement of other factors. We subsequently investigated whether red cells from CVI patients aggregate more than those of controls when suspended in the same medium. The results showed that a cellular factor is unlikely to be involved, and that an interaction between red cells and plasma proteins other than fibrinogen could also explain the increased EA in CVI.

Adult↗
PubMed1987

Highly significant negative correlations between erythrocyte aggregation value and serum concentration of high density lipoprotein cholesterol in a sample from a normal population and in patients with coronary heart disease.

In a previous clinical study it was found that patients with coronary heart disease and diabetics with peripheral artery disease often have an elevated erythrocyte aggregation value (AW) and that there is a positive correlation between AW and the number of risk factors found in a subject. In the present investigation we studied the relationship between AW and the serum concentration of high density lipoprotein cholesterol (HDL-C), which is known to be inversely associated with coronary heart disease (CHD) incidence. We found highly significant negative correlations between AW and HDL-C both in a subsample of the study population of a cross-sectional epidemiologic study on CHD risk factors (First Survey of the MONICA Project Augsburg) and in male patients with angiographically confirmed CHD. Correlation coefficients were -0.233 for normal men (P less than 0.01, n = 136), -0.261 for normal women (P less than 0.01, n = 117), and -0.745 for CHD patients (P less than 0.01, n = 14). The results support the concept that the erythrocyte aggregation value as an indicator of cardiovascular risk is consistent with established risk factor associations.

Adult↗
PubMedDate not supplied

A new laser photometric technique for the measurement of erythrocyte aggregation and sedimentation kinetics.

The aggregation kinetics of erythrocytes is studied by using laser light scattering. Laser light is passed through a well mixed sample of blood and the forward-scattered light intensity is recorded continuously. During the process of aggregation and sedimentation under a gravitational field, erythrocytes are subjected to different orientations. The events of a single cell's movement, formation of aggregates and their sedimentation produce a variation in scattered-light intensity. The mean intensity variation that bears this information is effectively employed to arrive at the kinetics of single cells, one-dimensional aggregates and three-dimensional aggregates during sedimentation. In addition to this, the time intervals of different phases of aggregation and sedimentation are also measured. All these parameters are obtained for erythrocytes suspended in native plasma. Then, the results are compared with erythrocytes suspended in dextran (Dx) 70 and Dx 500.

Blood Sedimentation↗