Monitoring of erythrocyte aggregate morphology under flow by computerized image analysis

Chen, Siyue; Gavish, Benjamin; Zhang, S.; Mahler, Y.; Yedgar, Shaul

doi:10.1016/0006-355x(95)91988-f

Cited by 21 publications

(30 citation statements)

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“…Alonso and co-workers (1-3) found that cell-free plasma spaces resulting from red cell aggregation started to develop 5 to 10 s after sudden reduction of flow rate in straight capillary tubes (25-to 100-m ID). Chen and co-workers (12,14) observed no significant change of particle sizes in human blood in the first 10 -20 s after stopping flow in a 40-m gap flow chamber (hematocrit ϭ ϳ10%) and a sudden development of aggregation after that.…”

Section: Discussionmentioning

confidence: 99%

Aggregate formation of erythrocytes in postcapillary venules

Kim¹,

Popel²,

Intaglietta³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

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The purpose of the present study was to obtain information on erythrocyte aggregate formation in vivo. The movements of erythrocytes in postcapillary venules of the rat spinotrapezius muscle at various flow rates were recorded with a high-speed video camera before and after infusion of dextran 500. To distinguish aggregates, the following criteria were used: 1) a fixed distance (4 m) between the center points of two adjacent cells, 2) lack of visible separation between the adjacent cells, and 3) movement of the adjacent cells in the same direction. Without dextran 500 infusion, 11 and 5% of erythrocytes formed aggregates in low (33.2 Ϯ 28.3 s) and high pseudoshear (144.2 Ϯ 58.3 s) conditions, respectively, based on the above criteria. After dextran 500 infusion, 53% of erythrocytes satisfied the criteria in the low pseudoshear condition (26.5 Ϯ 17.0 s) and 13% of erythrocytes met the criteria in the high pseudoshear condition (240.0 Ϯ 85.9 s), indicating erythrocyte aggregation is strongly associated with shear rate. Approximately 90% of aggregate formation occurred in a short time period (0.15-0.30 s after entering the venule) in a region 15 to 30 m from the entrance. The time delay may reflect rheological entrance conditions in the venule.hemodynamics; in vivo blood rheology; in vivo microscopy RED BLOOD CELL AGGREGATION is a prominent feature in humans and other athletic species but not sedentary species (30). Numerous in vitro studies have shown that aggregation of blood increases as shear rate decreases. Aggregation also depends on hematocrit and the concentration of macromolecules in the plasma or suspending medium (7,10,15,16,19,25,32). However, the circumstances in which aggregation occurs in vivo and its possible importance in circulatory function are not well understood.Previous whole organ studies in the dog and cat, in which red blood cell aggregation normally occurs, have shown that venous vascular resistance in skeletal muscle increases as arterial pressure and blood flow rate decrease and provided evidence that this effect is dependent on red blood cell aggregation (11,23,24,35). From these studies, it was postulated that aggregate formation increased resistance to flow in the venular network. Recently, Bishop and co-workers (9) reported that, in rodents treated with high molecular mass dextran to induce aggregation, velocity profiles of blood flow in venules became blunted at low flow rates and red blood cells formed aggregates, which would explain, in part, the dependence of venous resistance on flow rate.

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Section: Discussionmentioning

confidence: 99%

Aggregate formation of erythrocytes in postcapillary venules

Kim¹,

Popel²,

Intaglietta³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

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“…The RBC were isolated by centrifugation (2000 rpm for 10 min), washed with PBS, pH 7.4, and resuspended to the desired hematocrit in either autologous plasma or PBS supplemented with 1% bovine serum albumin (Sigma, St Louis, MO, USA) and 0.5% dextranF500 kDa ((dextran-500), Pharmacia Biotech, Uppsala, Sweden) to induce aggregation. Dextrans have been used extensively for studying RBC aggregation, [9][10][11][12] and it was previously shown that 0.5% of dextran-500 induces the formation of RBC aggregates similar in size and shape to those formed in plasma. 16 Determination of RBC aggregation.…”

Section: Rbc Aggregationmentioning

confidence: 99%

“…The aggregability of RBC was studied using the CFA that was designed and developed in the laboratory of S Yedgar, as previously described. [9][10][11][12]16 Briefly, RBC suspension in either autologous plasma or dextran solution was prepared at 6% hematocrit. The suspension was then introduced into the flow chamber, connected to a pump exerting laminar flow, and to a pressure transducer that enables the control of shear stress during the experiment.…”

Section: Rbc Aggregationmentioning

confidence: 99%

“…9 The CFA analyzes the aggregate size distribution as a function of shear stress and can provide various measures of RBC aggregation, for example, the distribution of RBC population into aggregate sizes, the shear stress required to disperse the aggregates and the aggregation kinetics. 10 In addition, we used this method to determine the relative contribution of plasmatic factors to the observed aggregation. 11,12 We found that obese individuals present larger aggregates that are more resistant to dispersion by flow compared with nonobese individuals, and that the plasma is a significant contributor to the enhanced RBC aggregation seen in obesity.…”

Section: Introductionmentioning

confidence: 99%

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Flow-resistant red blood cell aggregation in morbid obesity

et al. 2004

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OBJECTIVE:Enhanced red blood cell (RBC) aggregation has an adverse effect on microcirculatory blood flow and tissue oxygenation. It has been previously shown that obesity is associated with increased RBC aggregation. The objectives of the present study were to further characterize obesity-related RBC aggregation and to examine whether the enhanced aggregation is a plasma-or cellular-dependent process. METHODS: Obese (body mass index (BMI) ¼ 4076.3 kg/m 2 , n ¼ 22) and nonobese (BMI ¼ 2473.4 kg/m 2 , n ¼ 18) individuals were evaluated for inflammation markers and aggregation parameters. Aggregation parameters were derived from the distribution of RBC population into aggregate sizes, and from the variation of the distribution as a function of flow-derived shear stress, using a cell flow properties analyzer. To differentiate plasmatic from cellular factors, we determined the aggregation in the presence of autologous plasma or dextran-500kDa and calculated the plasma factor (PF) in the obese group. PF ranges from 0 to 1. When the PF ¼ 1, the aggregation is all due to plasmatic factors, when PF ¼ 0, the altered aggregation depends entirely on cellular factors, whereas 0oPFo1 reflects the joint contribution of cellular and plasmatic factors. RESULTS: Obese subjects had relatively larger aggregates that were more resistant to dispersion by flow. The calculated PF in the obese group was 0.9, indicating a pronounced contribution of plasma to RBC aggregation in obesity. DISCUSSION: Our results suggest that obese individuals present pathological plasma-dependent RBC aggregation, which is probably triggered by plasma macromolecules associated with the inflammatory response. These findings impact the future attempts to develop strategies aimed at attenuation of the enhanced RBC aggregation in obese individuals.

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“…13,14 It is important to understand whether and how index matching and aggregation will affect optical clearing. We examined whether erythrocyte aggregation induced by dextrans in circulating blood with a flow rate of 5 to 100 mm/s would affect optical clearing, and also defined the optimal type and concentration of dextrans for blood optical clearing in small vessels to improve OCT penetration.…”

Section: Introductionmentioning

confidence: 99%

Optical clearing of flowing blood using dextrans with spectral domain optical coherence tomography

Chen

2008

J. Biomed. Opt.

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Spectral domain optical coherence tomography (SDOCT) images have been used to investigate the mechanism of optical clearing in flowing blood using dextrans. The depth reflectivity profiles from SDOCT indicate that dextrans become increasingly more effective in reducing scattering in flowing blood, except for 5 mgdl −1 of D×500, with increasing molecular weights (MW 70,000 and 500,000) and concentrations (0.6, 2, and 5 mgdl −1 ). Among the tested dextrans, D×500 at 2 mgdl −1 had the most significant effect on light scattering reduction with the strongest capability to induce erythrocyte aggregation. D×500 at 5 mgdl −1 contributes more refractive index matching but induces a decrease in aggregation that leads to the same level as 0.6 mgdl −1 D×500. Previous studies identified various mechanisms of light scattering reduction in stationary blood induced by optical clearing agents. Our results suggest that erythrocyte aggregation is a more important mechanism for optical clearing in flowing blood using dextrans, providing a rational design basis for effective flowing blood optical clearing, which is essential for improving OCT imaging capability through flowing blood.

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Monitoring of erythrocyte aggregate morphology under flow by computerized image analysis

Cited by 21 publications

References 0 publications

Aggregate formation of erythrocytes in postcapillary venules

Aggregate formation of erythrocytes in postcapillary venules

Flow-resistant red blood cell aggregation in morbid obesity

Optical clearing of flowing blood using dextrans with spectral domain optical coherence tomography

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