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At least 109 records · Page 6Linked to original sources
PubMed2006

Comparison of erythrocyte aggregability changes during ischemic and hemorrhagic stroke.

The aim of this work was to perform a comparative investigation of erythrocyte aggregability changes in the peripheral and cerebral circulation during ischemic and hemorrhagic stroke. Subjects of the present study were patients with ischemic brain infarcts (14 patients) and with hemorrhagic stroke (21 patients) from the Intensive Care Unit of the Institute of Neurology and Neurosurgery. The blood samples were obtained from the following blood vessels: the common carotid artery carrying blood to the primarily damaged brain hemisphere, both jugular veins carrying blood from the primarily damaged and the contralateral hemispheres, as well as from the cubital vein to obtain specimens of the systemically circulating blood. Erythrocyte aggregation was evaluated by using the "Georgian technique". We found that the RBC aggregation indices increased in both the regional as well as the systemic circulation of the hemorrhagic stroke patients as compared to ischemic stroke patients. The results of the present study demonstrate different changes of erythrocyte aggregation in ischemic and hemorrhagic stroke patients. Therefore, the role of blood rheological properties in their pathogenesis seems also to be different.

Brain Ischemia↗
PubMed2003

Comparison of new ultrasound index with laser reference and viscosity indexes for erythrocyte aggregation quantification.

We have previously established new ultrasonic indexes for erythrocyte aggregation using a Couette device, and validated them toward the Rayleigh's theory and reproducibility. Two hydrodynamic protocols were applied on various suspensions and their aggregation degrees were characterized by: 1. for the decreasing shear rates protocol: the power P(US) at the nominal frequency of the transducer used; 2. for the kinetic protocol: aggregation times (latency and half-rise times), variation between initial disaggregated state (Vo) and final aggregated state (V(inf)) and AI(US), which is the integral of the kinetic curve over time. The objective of the present study was to demonstrate the ability of these indexes to characterize the aggregation dynamics of suspensions with various levels of aggregation induced by concentrations of dextran 70 kD (Dx) of 10, 20 and 40 g/L added to washed red cells resuspended in saline solution. The results showed a maximum of backscattered power (P(US)) for Dx = 40 g/L with the decreasing shear rates protocol. We measured a final aggregation level (V(inf)), a minimal aggregation time (T(m)) and a maximal value of AI(US) for Dx = 40 g/L with the aggregation kinetics protocol. On the other hand, viscosity is increased with dextran concentration. These evolutions of the ultrasound (US) indexes and viscosity with dextran concentrations are consistent with literature reports. In addition, a particularly interesting phenomenon of US backscattering enhancement was observed for kinetics with no null final shear rate, which has never before been reported in such a precise manner. By another way, each of the dextran suspensions was tested on the laser erythroaggregometer that is presently considered as the "gold standard" method for erythrocyte characterization. The laser indexes (aggregation time T(a), aggregation indexes AI(10s) and AI(60s)), deduced from a kinetic protocol, have similar significance to the US ones. Statistical comparisons have been done between laser and ultrasonic indexes and significant correlations (0.001 < p < 0.01) were obtained. The set of results allowed us to conclude that ultrasonic indexes are suitable markers for the erythrocyte aggregation.

Acoustics↗
PubMedDate not supplied

Direct evaluation of erythrocyte aggregability in human, sheep and cow blood samples with a computerized image analysis.

The non-Newtonian properties of blood are caused by the unique properties of red blood cells to aggregate and to deform. Aggregation mechanism of erythrocytes contributes significantly to blood viscosity. Techniques for the assessment of red cell aggregability have major implications for medical practice. A number of techniques based on various principles have been proposed by many researches. However, as yet, none of these techniques have been applied on a wide basis. The aim of the present paper is to determine red cell aggregability in sheep, cow and human blood samples. The red cells remain in the their natural environment (their own blood plasma). First, we had to transform an IBM-PC computer into an Image Acquisition System, so we designed a frame-grabber and the soft driver necessary to assure the image acquisition taken by the TV camera by means of the microscope. These images are digitized, transformed in a standard format BMP and can be compressed and stored or processed. The entire system software is written in C++ assembly language. To evaluate the aggregability index in the blood sample was determined the total area occupied by all automatically detected erythrocytes (Stot) and the overall area occupied by the aggregated erythrocytes (Saggreg). . EAI = (Saggreg/Stot) x 100%; EAI shows the tendency of red blood cell to form aggregates.

Algorithms↗
PubMed1997

Differences in the erythrocyte aggregation level between veins and arteries of normolipidemic and hyperlipidemic individuals.

The objectives of this study were to detect differences in the Doppler power backscattered by blood in vivo, and to identify factors affecting the backscattered power. The main hypothesis was that variations in the erythrocyte aggregation level between veins and arteries of normolipidemic and hyperlipidemic individuals can be detected with power Doppler ultrasound. Doppler measurements were performed at 5 MHz, with an Acuson 128 XP/10 system, over the carotid artery and jugular vein, external iliac artery and vein, common femoral artery and vein and popliteal artery and vein. Doppler signals were recorded at the center of each vessel to optimize the detection of erythrocyte aggregation, and processed off-line to obtain the backscattered power. The power of each recording was compensated for Doppler gain differences, tissue attenuation with depth and transmitted power variations occurring with pulse-repetition interval modifications. Results showed statistically stronger backscattered power in veins compared to arteries for the iliac, femoral and popliteal sites. In comparison with healthy subjects, stronger powers were observed in hyperlipidemic patients for the femoral and popliteal sites. Power differences were also found between peripheral measurements. On the other hand, no difference was observed between the power measured in the carotid artery and jugular vein for both groups of individuals. Multiple linear regression analyses were performed to identify factors affecting the backscattered power. Results showed a correlation (r) of 71.2% between the Doppler power in the femoral vein and the linear combination of two parameters: an erythrocyte aggregation index S10 measured with a laser scattering method, and the diameter of the vessel measured on B-mode images. Statistically significant linear correlation levels were also found between S10 and the Doppler power in various vessels. In conclusion, this study showed that power Doppler differences exist in vivo in large vessels between veins and arteries of normolipidemic and hyperlipidemic individuals. The Doppler power variations were also shown to be related to erythrocyte aggregation.

Adult↗
PubMed2001

Influence of plasma proteins on erythrocyte aggregation in three mammalian species.

The aggregation capacity of human erythrocytes lies between that of the non-aggregating bovine erythrocytes and the remarkably aggregating equine ones. As the ability to aggregate is attributed to cell factors and the composition of the plasma proteins, the role that plasma proteins play in the aggregation process in these three species was studied. Washed erythrocytes were suspended in phosphate-buffered saline (PBS; pH 7.4, 300 mOsm/L) plus polyvinylpyrrolidone (PVP) in a suitable concentration to obtain an average intensity of aggregation (control media). The superimposed effect of replacing 80% of the medium by either autologous plasma, serum or albumin solution was studied. The plasma proteins appeared to enhance aggregation by human and equine erythrocytes, but impaired this process in bovine erythrocytes. Some evidence was obtained supporting the existence of serum factors capable of reducing aggregation of erythrocytes in cattle and it was concluded that the non-aggregating behaviour of bovine erythrocytes may be due to the cells interacting particularly with the macromolecules in the serum.

Animals↗
PubMed1988

Erythrocyte aggregation in iohexol and other nonionic media.

Erythrocytes aggregate when blood comes into contact with solutions of nonionic substances such as glucose or the contrast medium iohexol, especially at a reduced pH (eg, 6.8). The aggregates are not clots because they form rapidly even in heparinized blood, do not contain fibrin, and disappear at once when they are added to plasma or other ionic media. Formation of these aggregates in solutions of glucose or iohexol can be decreased by including a low concentration of an ionic solute such as NaCl or by maintaining the pH close to 7.4.

Buffers↗
PubMed1988

Mechanism of erythrocyte aggregate formation in presence of magnetic field and dextrans as analyzed by laser light scattering.

The mechanism of erythrocyte aggregation has been studied in normal plasma, dextran 40 and dextran 70 suspensions in presence and absence of magnetic field at a concentration of 5 percent by laser light scattering. The inhomogeneous magnetic field enhances the aggregating tendency of normal erythrocytes. The growth of aggregates due to dextran 70 is enhanced in presence of magnetic field. On the other hand the disaggregating effect of dextran 40 is reduced due to this field. The induced changes due to magnetic field during the development of erythrocyte aggregates in these media are determined.

Dextrans↗
PubMed1991

[Roles of plasma proteins and surface negative charge of erythrocytes in erythrocyte aggregation].

The effect of plasma proteins (and IgG fragments) and sialic acid content of erythrocytes on the aggregation of human erythrocytes was quantitatively examined by using a rheoscope combined with a television image analyser and a computer. (1) The velocity of erythrocyte aggregation by plasma proteins was increased with increasing in their molecular weight, i.e., IgG less than IgA less than fibrinogen less than IgM. F(ab')2. Fab and Fc could not induce the aggregation. (2) The aggregation induced by fibrinogen was accelerated by IgG and its peptic fragment, F(ab')2, but was unaffected by the plasmic fragments, Fab and Fc. The accelerating effect by IgG and F(ab')2 was inhibited by Fab and Fc. (3) The aggregation of erythrocytes was accelerated by decreasing the sialic acid content (due to the reduction of the electrostatic repulsive force among erythrocytes), and the effect of desialylation on the IgG-induced aggregation was greater than that of desialylation on the fibrinogen-induced aggregation. (4) The roles of plasma proteins and of sialic acid content of erythrocytes on the aggregation of erythrocytes were discussed.

Electricity↗
PubMed1986

Effects of fibrinogen, globulin, albumin and hematocrit on the kinetics of erythrocyte aggregation in man.

The effects of fibrinogen, globulin, albumin, and packed blood cell volume (hematocrit) on the kinetics of erythrocyte aggregation (RBC-A) after stasis were quantitatively evaluated by recording the changes of light transmission through the blood in transparent tubing with an apparatus consisting of a light-emitting diode and a silicon photodiode. The measurements were done on samples of heparinized whole blood, suspensions of erythrocytes containing various concentrations of fibrinogen (0.5 to 25 g/L) or gamma globulin (25 to 150 g/L), and blood of various hematocrit values prepared from three samples of whole blood having different concentrations of fibrinogen. The half-time of the increase of light transmission after the flow-stop was used as an index of the kinetics of RBC-A (T1/2). This simple and rapid method for estimating erythrocyte aggregation had excellent reproducibility (N = 51, r = 0.99). The values of T1/2 showed significant negative correlations with the concentrations of fibrinogen and globulin but a positive correlation with that of albumin. The T1/2 value decreased markedly and then remained almost constant with increase in the value of hematocrit, but the influence of hematocrit on T1/2 was markedly dependent on the concentration of fibrinogen.

Blood Proteins↗
PubMedDate not supplied

The appearance of aggregated erythrocytes in the peripheral blood of individuals with insulin resistance.

BACKGROUND: Insulin resistance is associated with low-grade inflammatory response. The probability that the acute-phase response is associated with enhanced erythrocyte adhesiveness/aggregation was not explored. METHODS: The degree of erythrocyte adhesiveness/aggregation was evaluated by using a simple slide test. The insulin resistance was evaluated by insulin and glucose concentrations after a night of fasting. The inflammatory response was evaluated by variables of acute-phase response. RESULTS: A significant correlation (r = -0.2, p = 0.02) was noted between insulin resistance expressed as the HOMA index and the degree of erythrocyte adhesiveness/aggregation. This was probably due to the concomitant acute-phase response and the presence of increased amounts of inflammation-sensitive proteins that were found to correlate significantly with the degree of erythrocyte adhesiveness/aggregation. In the multiple linear regression analysis, erythrocyte sedimentation rate and fibrinogen concentration but not HOMA index were found to correlate significantly (p < 0.0001 and p = 0.0007 respectively) with the degree of red blood cell adhesiveness/aggregation. CONCLUSIONS: Insulin resistance is associated with an enhanced degree of erythrocyte adhesiveness/aggregation and this is related to the presence of enhanced inflammation-sensitive plasma proteins that are part of the acute-phase response. These findings might have hemorheological consequences and might contribute to the pathophysiology of the insulin-resistance syndrome.

Erythrocyte Aggregation↗
PubMed1984

Increased erythrocyte aggregation in diabetes mellitus and its relationship to glycosylated haemoglobin and retinopathy.

The velocity of erythrocyte aggregation in vitro was determined in 15 non-diabetic and 28 Type 1 (insulin-dependent) diabetic subjects, in autologous plasma under uniform shear flow using a rheoscope combined with a television image analyzer and a computer. In the diabetic subjects, the velocity of aggregation showed a significant correlation with the haemoglobin A1 level, and was significantly increased in the proliferative retinopathy group. An alteration of plasma protein composition in the diabetic subjects (increase of phi- and alpha 2-fractions) also influenced erythrocyte aggregation, being related to the haemoglobin A1 level. The percentage of the phi-fraction and a parameter, (alpha 2 + phi)/albumin, defined by plasma electrophoresis, showed a strong correlation with the velocity of aggregation.

Aged↗
PubMedDate not supplied

Enhanced erythrocyte aggregability in neurosurgical interventions carried out with mannitol administration.

Blood rheological properties were examined in patients before, during and after neurosurgical operations of arterial aneurisms, as well as in patients where no operation was carried out, and in healthy volunteers. Erythrocyte aggregability was quantified by using the "Georgian technique" and compared with other indices of blood rheological disorders. Prior to the operations the erythrocyte aggregability did not differ significantly in both healthy probands and neurosurgical patients. In the course of surgery the index increased gradually and became almost two times higher than before operation in the same patients. Evidence was obtained that this effect was accounted for the mannitol administration, since in the control cases, without operations, its infusion into the circulation produced a comparable increase of the aggregability. Other indices of hemorheological disorders did manifest no regular and significant changes in the same patients. The enhanced erythrocyte aggregability might be a factor disturbing to a degree the blood rheological properties in cerebral microvessels of neurosurgical patients operated with mannitol.

Aneurysm↗
PubMed2004

Effect of nitric oxide initial blood levels on erythrocyte aggregability during 12 hours from ischemic stroke onset.

The aim of study was the investigation of blood nitric oxide (NO) and nitrates (NO2) levels in 12 hours of ischemic stroke onset and establishment of correlation of these data with erythrocyte aggregability and initial ischemic lesion size. 48 patients, aged 45 to 70 years, 26 female, 22 male were investigated. Glasgow Coma Scale (GCS) and National Institute Health Stroke Scale (NIHSS) assessed initial neurological impairment. Patients were divided in mild and severe stroke groups. Control comprised 20 healthy individuals. Ischemic lesions were evaluated on conventional MRI scans. NO levels were measured by electron paramagnet resonance (EPR) method. NO2 levels were defined by spectrophotometer method. Erythrocyte aggregability index (EAI) was measured by sound method [Biorheology 30(2) (1993), 153-161]. Pearson correlation and multivariate model of logistic regression was applied. Significant negative correlation was established between NO initial blood levels and the EAI (r=-0.75; p<0.001), as well as between blood NO2 and NO initial levels and ischemic lesion size (r=-0.79, p<0.01; r=-0.61, p<0.02, respectively). Endothelialy derived NO correlates with erythrocyte aggregability and probably has a positive impact on restoration of cerebral blood flow in the initial stage of acute brain ischemia.

Brain Ischemia↗
PubMed2001

Improvement of hemorheology by DALI apheresis: acute effects on plasma viscosity and erythrocyte aggregation in hypercholesterolemic patients.

Plasma viscosity (PV) and erythrocyte aggregation (EA) are determinants of microcirculation, especially under the compromised hemodynamic conditions resulting from atherosclerosis. Direct adsorption of lipoproteins (DALI) apheresis is the first method for direct adsorption of lipoproteins; it drastically reduces low-density lipoprotein (LDL)-cholesterol and lipoprotein (a) (Lp[a]), and may therefore improve PV and EA. The current study was performed to test the effect of DALI on hemorheology. Six hypercholesterolemic patients who had been on regular LDL apheresis for at least several months were treated on a weekly or biweekly basis, on average 5 times each by DALI. Before and after each session, PV was measured by a capillary tube plasma viscosimeter and EA by rotational aggregometry. Single DALI sessions (n = 31) acutely decreased PV from 1.18 +/- 0.04 to 1.06 +/- 0.3 mPa (-10%) while EA improved from 22.8 +/- 4.4 to 13.3 +/- 4.5 (arbitrary units) (-42%). LDL-cholesterol, Lp(a), and very-low-density lipoprotein (VLDL)-cholesterol were effectively reduced while the decrease of triglycerides and fibrinogen was only moderate. DALI apheresis exerted an acute positive effect on blood hemorheology which may have beneficial effects on microcirculation. This hypothesis is in accordance with the clinical observation that in some patients, improvement of angina and/or exercise tolerance can be observed after only a few DALI sessions where changes of coronary stenoses cannot be expected yet.

Adsorption↗
PubMed1986

[Erythrocyte aggregation and its repercussions on conjunctival microcirculation in man. Morphometric study and biological correlates].

This study, involving the application of morphometric techniques to the conjunctival capillary bed in man, revealed a rarefaction of functional capillary density in patients with arteriolar sludge. Overall, in the population sample studied, capillary density and the degree of erythrocyte aggregation were correlated to erythrocyte sedimentation rate, despite the existence of discordant cases. These discordances were partially reduced by taking the hematocrit into account. Furthermore, multifactorial analysis of these parameters showed that hematocrit had an inhibitory action on erythrocyte aggregation which was more marked in vitro than in the microcirculation in vivo. By contrast, in vivo aggregation was more influenced by serum albumin levels. In both cases fibrinogen appeared to be the most significant pro-aggregant factor.

Blood Sedimentation↗