Erythrocyte Flow Research Articles

Reperfusion Microvascular Ischemia After Prolonged Coronary Occlusion: Implications And Treatment With Local Supersaturated Oxygen Delivery.

Following a prolonged coronary arterial occlusion, heterogeneously scattered, focal regions of low erythrocyte flow are commonly found throughout the reperfused myocardium. Experimental studies have also demonstrated the presence of widespread, focally patchy regions of microvascular ischemia during reperfusion (RMI). However, the potential contribution of RMI to tissue viability and function has received little attention in the absence of practical clinical methods for its detection. In this review, the anatomic/functional basis of RMI is summarized, along with the evidence for its presence in reperfused myocardium. Advances in microcirculation research related to obstructive responses of vascular endothelial cells and blood elements to the effects of hypoxia and low shear stress are discussed, and a potential cycle of intensification of RMI from such responses and progressive loss of functional capillary density is presented. In capillaries with impaired erythrocyte flow, compensatory increases in the delivery of oxygen, because of its low solubility in plasma, are effective only at high partial pressures. As discussed herein, attenuation of the cycle with oxygen at hyperbaric levels in plasma is, very likely, responsible for improved tissue level perfusion noted experimentally. Observed clinical benefits from intracoronary SuperSaturated oxygen (SSO2) delivery, including infarct size reduction, can be attributed to attenuation of RMI with improvement in microvascular blood flow.

Hemoglobin as substantial object for biomedical studies and diagnostics

Hemoglobin (Hb) is a hemoprotein consisting of the hem prosthetic group and a protein part. Its main function in human organism is oxygen binding and transportation. Different factors can violate native Hb structure. Depending on such factors, hereditary and acquired hemoglobinopathies are distinguished. Acquired ones are associated with the effect of various chemical agents, the modified Hb forms can appear in this case. It is caused by conjunction of different compounds to the molecule (hem and protein ligands). At several conditions Hb binds with the erythrocyte membrane. Changes in Hb structure can disturb its oxygen-carrying function and stability of erythrocytes; furthermore, they hamper the erythrocyte flow through microvessels. These processes take place at many pathological states as well. Because of increasing amount of information, it becomes urgent to use computer medical systems to increase the efficiency of diagnostics, including hemoglobinopathies. In the expert system elaborating by us, the results of the general haematological analysis are used, with addition of the data on modified Hb forms, among them on membrane-bound one.

Numerical simulation on the effect of surrounding fluid on the erythrocyte flow in microvessel

Numerical simulation on the effect of surrounding fluid on the erythrocyte flow in microvessel

Determination of the potentials of aqueous and ethanolic extracts of Buchholzia coriacea in preventing sodium metabisulphite-induced oxidation of some hemoglobin SS erythrocyte membrane proteins

BACKGROUND: The sustenance of the erythrocyte membrane integrity is crucial to ensuring a continuous lamina flow of erythrocytes through narrow blood vessels. So it is imperative to find a substance to attenuate the oxidation of erythrocytes that cause the membrane structure remodelling. OBJECTIVES: To investigate the hydrating strength and modulatory effect of Buchholzia coriacea seed extracts on erythrocyte membrane proteins degradation. MATERIALS AND METHODS: Aqueous and ethanolic extracts of B. coriacea were obtained following standard procedures. Blood samples (5.00 mL) from five known hemoglobin SS individuals in steady state were subjected to electrophoresis to establish the genotype of the individuals. The osmotic fragility assay was performed with 2.50, 5.00, 10.00 and 20.00 mg/mL of the extracts in the presence of different concentrations of phosphate-buffered saline. The graph of percentage hemolysis was plotted against saline concentration, and the mean corpuscular fragility (MCF) determined. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was also done using the same concentrations of extracts. RESULTS: There was no statistically significant difference (P > 0.01) between the average MCF in all the extract concentration and the control. Protein 4.1 and Ankyrin did not appear on the electrophoretic lanes of all the test samples when compared with the control. However, spectrin and ankyrin bands were visible with regular size and intensity. CONCLUSION: B. coriacea seed extracts possess antihemolytic character. However, it does not have the ability to maintain the erythrocyte membrane model despite its acclaimed antioxidant character.

Microfluidic-based laser speckle contrast imaging of erythrocyte flow and magnetic nanoparticle retention in blood

The present study aims to develop a microfluidic system in combination with laser speckle contrast imaging (LSCI) for the study of erythrocyte dynamics under various physiological flow conditions. Microfluidic device was fabricated and red blood cell suspension was introduced at various flow rate controlled by a syringe pump. Relative blood velocity profile in the microfluidic chamber was obtained by LSCI in a real-time manner and correlated well with simulated results by computational fluid dynamics. A close correlation of relative blood velocity, inlet flow rate and blood viscosity were found using this microfluidic-based LSCI system. In addition, our platform also allows the demonstration of spatiotemporal variation of blood flow in response to magnet-induced magnetic nanoparticle (MNP) retention. The flow behaviour of erythrocytes with the presence of MNPs appeared to be closely correlated with the location of the magnet placement. Our microfluidic-based LSCI measurement represents a simple yet controllable experimental model for evaluating the variations in different hemorheological conditions in vitro and has a strong potential as an easy-to-use tool for investigating local MNP retention and hemodynamic changes.

Anisotropic Properties of Blood in a Vessel with Stenosis

Preferential orientation of erythrocytes along the flow lines in the vertical plane was observed in the acceleration zone at the entry to the narrow part of the cell and inside this part when whole blood flow in a canal with stenosis was analyzed. An area where the erythrocyte orientation changed was observed in the deceleration zone; erythrocytes assumed an orientation perpendicular to the flow lines in the vertical plane after they passed through this zone. The flow of erythrocytes at a concentration of 1 vol % was studied under the same hydrodynamic conditions in order to characterize the behavior of individual erythrocytes.

Comparative methodological studies of L-asparaginase encapsulation into erythrocytes

Background. L-asparaginase is an enzyme, widely used in the therapy of acute lymphoblastic leukemia in children and adults, but its use is limited due to a wide range of side effects and anaphylactic reactions. L-asparaginase loaded into erythrocytes can solve these problems. This enzyme is protected from the immune system and plasma proteases due to erythrocyte membrane, but continues to work inside the cell because its membrane is permeable to L-asparagine. Thus, the half-life of the drug increases and anaphylactic reactions reduce. The encapsulation of L-asparaginase into erythrocytes can be performed by various osmotic methods. Each of them is characterized by the amount of encapsulated enzyme, the cell yield, as well as by the quality indices of the survived erythrocytes. An important parameter of each method is the possibility to provide sterility of this dosage form for the clinical use.The aim of the study was the comparing of three osmotic methods of L-asparaginase encapsulation into erythrocytes (hypo-osmotic lysis, dialysis and flow dialysis) to select the most promising method for clinical use.Materials and methods. A suspension of erythrocytes of healthy donors (hematocrit 60–70%) was mixed with L-asparaginase from E. сoli. The procedures of hypotonic reversible lysis, dialysis in dialysis bags, or flow dialysis using pediatric dialyzers were performed. The physiological osmolality was restored in suspensions after the procedure by the addition of a hypertonic solution, and they were incubated for 30 min at 37 °C. Then the cells were washed in isotonic phosphate-buffered saline with pH 7.4. Activity of L-asparaginase, volume, hematocrit, hematological indices and osmotic cell fragility of erythrocytes were measured in the suspensions of erythrocytes before and after the enzyme encapsulation procedure.Results. An optimal osmolality of the hypotonic buffer for each method was selected and was equal to 90–110 mOsm/kg. The yields of encapsulation were 4.2 ± 2.0, 6.0 ± 2.3 and 16.2 ± 2.2 % for hypotonic lysis, dialysis and flow dialysis, respectively. The hematological indices of the obtained erythrocyte-carriers differed from the corresponding parameters of the initial erythrocytes, but did not differ significantly for different methods.Conclusion. Comparative investigation of mentioned above parameters allowed choosing the method of flow dialysis as the most promising for clinical use.

Visualization of erythrocyte deformation induced by supraphysiological shear stress.

To elucidate development of shear-induced damage in erythrocytes, it is necessary to visualize erythrocytes under high-shear flow. Therefore, we prototyped a special shear flow chamber with a counter-rotating mechanism consisting of a transparent acrylic cone and a glass plate. The flow chamber was mounted on an inverted microscope and illuminated by a 350-W metal halide lamp. This experimental system made it possible for a digital video camera to record through the microscopes' objective lens the rheological behavior in shear flow of erythrocytes diluted in highly viscous polyvinyl pyrrolidone. We successfully visualized the blood cells' ellipsoidal deformation response to an unphysiological, high shear stress of 288 Pa, their shift into abnormal rheological behavior, and final collapse. When abnormality first appeared, the membrane surface of some ellipsoidal erythrocytes started undulating and their shape became more asymmetric. Finally, the erythrocytes appeared to fragment, although the fragments continued tumbling together suggesting that they were all still connected. One such abnormal erythrocyte became segmented through collision with other cell. The undulation of the membrane surface when erythrocytes experienced trauma suggests possible detachment of the lipid bilayer from the membrane cytoskeleton. As the damage increased, the morphological abnormality of cells became greater with less tank-treading, and then, the erythrocytes started tumbling. This unstable behavior increases the volume of flow region occupied by the erythrocytes and increases the chance that neighboring cells will hit them and break them into segmented pieces. This study clearly showed that the beginning of erythrocytes' morphological abnormality was induced by shear stress.

Noninvasive in vivo characterization of erythrocyte motion in human retinal capillaries using high-speed adaptive optics near-confocal imaging.

The flow of erythrocytes in parafoveal capillaries was imaged in the living human eye with an adaptive optics near-confocal ophthalmoscope at a frame rate of 800 Hz with a low coherence near-infrared (NIR) light source. Spatiotemporal traces of the erythrocyte movement were extracted from consecutive images. Erythrocyte velocity was measured using custom software based on the Radon transform. The impact of imaging speed on velocity measurement was estimated using images of frame rates of 200, 400, and 800 Hz. The NIR light allowed for long imaging periods without visually stimulating the retina and disturbing the natural rheological state. High speed near-confocal imaging enabled direct and accurate measurement of erythrocyte velocity, and revealed a distinctively cardiac-dependent pulsatile velocity waveform of the erythrocyte flow in retinal capillaries, disclosed the impact of the leukocytes on erythrocyte motion, and provided new metrics for precise assessment of erythrocyte movement. The approach may facilitate new investigations on the pathophysiology of retinal microcirculation with applications for ocular and systemic diseases.

Numerical simulation on the effect of non-Newtonian properties on the erythrocyte flow in microvessel

Numerical simulation on the effect of non-Newtonian properties on the erythrocyte flow in microvessel

Prospects for Human Erythrocyte Skeleton-Bilayer Dissociation during Splenic Flow

Prospects of vesiculation occurring during splenic flow of erythrocytes are addressed via model simulations of RBC flow through the venous slits of the human spleen. Our model is multiscale and contains a thermally activated rate-dependent description of the entropic elasticity of the RBC spectrin cytoskeleton, including domain unfolding/refolding. Our model also includes detail of the skeleton attachment to the fluidlike lipid bilayer membrane, including a specific accounting for the expansion/contraction of the skeleton that may occur via anchor protein diffusive motion, that is, band 3 and glycophorin, through the membrane. This ability allows us to follow the change in anchor density and thereby the strength of the skeleton/membrane attachment. We define a negative pressure between the skeleton/membrane connection that promotes separation; critical levels for this are estimated using published data on the work of adhesion of this connection. By following the maximum range of negative pressure, along with the observed slight decrease in skeletal density, we conclude that there must be biochemical influences that probably include binding of degraded hemoglobin, among other things, that significantly reduce effective attachment density. These findings are consistent with reported trends in vesiculation that are believed to occur in cases of various hereditary anemias and during blood storage. Our findings also suggest pathways for further study of erythrocyte vesiculation that point to the criticality of understanding the biochemical phenomena involved with cytoskeleton/membrane attachment.

The application of optical coherence tomography angiography in retinal diseases

Optical coherence tomography angiography (OCTA) is a new, noninvasive imaging technique that generates real-time volumetric data on chorioretinal vasculature and its flow pattern. With the advent of high-speed optical coherence tomography, established enface chorioretinal segmentation, and efficient algorithms, OCTA generates images that resemble an angiogram. The principle of OCTA involves determining the change in backscattering between consecutive B-scans and then attributing the differences to the flow of erythrocytes through retinal blood vessels. OCTA has shown promise in the evaluation of common ophthalmologic diseases such as diabetic retinopathy, age-related macular degeneration, and retinal vascular occlusions. It quantifies vascular compromise reflecting the severity of diabetic retinopathy. OCTA detects the presence of choroidal neovascularization in exudative age-related macular degeneration and maps loss of choriocapillaris in nonexudative age-related macular degeneration. We describe principles of OCTA and findings in common and some uncommon retinal pathologies. Finally, we summarize its potential future applications. Its current limitations include a relatively small field of view, inability to show leakage, and a tendency for image artifacts. Further larger studies will define OCTAs utility in clinical settings and establish if the technology may offer its utility in decreasing morbidity through early detection and guide therapeutic interventions in retinal diseases.

Particle tracking for the assessment of microcirculatory perfusion

In recent years the development of portable microscopes, which enable the noninvasive bedside evaluation of the sublingual microcirculation in critically ill patients, has expanded the clinical research on this level of the cardiovascular system. Several semi-quantitative scores have been defined in order to provide researchers with a standardized framework for the offline assessment of the microcirculation status. Among those, space-time diagrams (STDs) constitute an established method for obtaining an estimate of the red blood cells (RBCs) flow velocity in capillaries. However, STDs have the drawback of being time-consuming, inherently subjective, and difficult to manage when the flow is not regular. Objective. In this work we propose an automated method for calculating erythrocyte flow speed, aiming to provide a fast and objective tool for the evaluation of peripheral blood perfusion. Approach. The proposed method exploits an image segmentation module for estimating the positions of candidate flowing cells. A multi-object tracking algorithm based on Kalman filters analyzes and matches the positions corresponding to specific erythrocytes within consecutive frames. Thus, the output of the filter enables to estimate the displacement of each cell, yielding their instantaneous speed. Main results. The method has been validated against the results obtained by the manual analysis of STDs, proving a good agreement for speeds up to 300 μm s−1. At higher speeds, RBC tracking becomes unstable due to the currently limited video acquisition rate (25 Hz) of state-of-the-art devices, that makes the matching between objects appearing in consecutive frames very challenging.

非ニュートンが微小血管内の赤血球流れに与える影響に関する数値解析

非ニュートンが微小血管内の赤血球流れに与える影響に関する数値解析

Peripheral circulation indicators in veteran trail runners.

[Purpose] Competitive sport places strict demands on the cardiovascular systems of veteran trail runners. Our research objective was to evaluate the dynamics of microcirculation parameters of veteran runners in hypoxic and mid-altitude conditions. [Subjects and Methods] Seven male runners from Russia and Italy between the ages of 50 and 60 years were examined whilst competing at mid-altitude (1,500–2,000 m above sea level). The same runners were examined in a simulated mid-altitude hypoxic environment, which was a hypoxic chamber with 16% oxygen concentration, for 720 minutes. Under both conditions, peripheral circulation was studied using a laser Doppler flowmeter attached to the distal phalange of the second finger of the subject’s right hand. All subjects had a microcirculation parameter assessed, which was the standard deviation of the erythrocytes flow vibration in peripheral circulation, under both conditions. In order to assess the intensity of vasomotor reactions of the microcirculatory vessels, the coefficient of variation was used. [Results] In the hypoxic environment, a decrease in the microcirculation parameter was noted in the short-term (360 minutes), with a subsequent compensatory increase in the long-term (720 minutes). However, the coefficient of variation showed a reverse trend with an increase in the vasomotor activity of microvessels from 12.4% to 18.2% at the stage of maximum training load within one month in the mid-altitude in the hypoxic environment, with a consequent reduction in preparation for the start. [Conclusion] In the hypoxic environment, the subjects demonstrated a two-stage change in the dynamics of the microcirculation parameter: an initial fall and a subsequent increase reaching the initial values. Similar changes were found when subjects were competing at mid-altitude. Our results show that the assessment of the peripheral circulation in a simulated mid-altitude hypoxic environment can be used to determine the readiness of veteran sportsmen for long-term trail running in mid-altitude conditions.

Relationship between Functional and Structural Changes in Diabetic Vessels in Optical Coherence Tomography Angiography.

The decorrelation signals in optical coherence tomography angiography (OCTA) are derived from the flow of erythrocytes and concomitantly delineate the retinal vasculature. We compared the structural and functional characteristics of vascular lesions visualized in fluorescein angiography (FA), OCTA, and en-face OCT images in 53 eyes (28 patients) with diabetic retinopathy (DR). The foveal avascular zone (FAZ) areas in OCTA images in the superficial layer almost corresponded to those in FA images. The FAZ areas in the en-face OCT images in the superficial layer were smaller than those in the FA images and correlated with each other, which agreed with the finding that en-face OCT images often delineated the vascular structure in the nonperfused areas in FA images. Microaneurysms appeared as fusiform, saccular, or coiled capillaries in OCTA images and ringed, round, or oval hyperreflective lesions in en-face OCT images. OCTA and en-face OCT images detected 41.0 ± 16.1% and 40.1 ± 18.6%, respectively, of microaneurysms in FA images, although both depicted only 13.9 ± 16.4%. The number of microaneurysms in FA images was correlated with that in OCTA and en-face OCT images. Comparisons of these modalities showed the associations and dissociations between blood flow and vascular structures, which improves the understanding of the pathogenesis of DR.

Investigation of High-Speed Erythrocyte Flow and Erythrocyte-Wall Impact in a Lab-on-a-Chip.

To better understand erythrocyte high-speed motion, collision characteristics, and collision-induced hemolysis probability in rotary blood pumps, a visual experimental investigation of high-speed erythrocyte flow and erythrocyte-wall collision in a lab-on-a-chip was performed. The erythrocyte suspension was driven by a microsyringe pump connected to the microchip, and the erythrocyte flow and erythrocyte-wall impact process were observed and imaged by an optical microscope and a high-speed camera. Two types of microchips with different impact surfaces (flat and curved) were employed. The motion and deformation features before and after collision were studied in detail. The results show that erythrocytes not only move along the flow direction in the flow plane but also rotate and roll in three-dimensional space. Erythrocytes keep discoid shape during the movement in the straight channel, but their deformations during collision are mainly classified into two types: erythrocyte structure is still stable and the erythrocyte performance can be ensured to a certain extent in the TypeA deformation, while the TypeB deformation makes the membrane more likely to fracture on the stretched side, increasing the probability of hemolysis. Furthermore, the movements and deformations of the erythrocytes after collision are analyzed and classified into two types: bouncing and slipping. Moreover, a simulation method for the flow in microchip was performed and validated through a comparison of the streamlines and experimental erythrocytes tracks, which can be further employed to predict the high-speed blood flow, associated with collision process in mechanical blood pump.

Erythrocyte Flux vs. Flow in Microchannels as a Function of Bifurcation Architecture and Re

In microvascular systems with arteriolar diameters approximately 5 to 10 times larger than the average red blood cells (RBC) the distribution of RBC at bifurcations is not only influenced by flow properties such as Reynolds number (Re), but also by the geometry of the bifurcation region (bifurcation angle, radius of curvature). Red blood cells, while they do not follow the traditional Poiseuille flow streamlines, they do follow the path with lower resistance, which is a function of both the flow properties and complex regional geometry. Yet, the flux vs. flow relationship remains poorly understood. We study these coupled effects using a fabricated PDMS microchannel system (square, 25μm), and observe RBC distribution at bifurcations with varying angles (45°, 90° and 135°) and radius of curvature (0.5, 1 and 2 tube diameters). The flow rate in the feed, Qf, feed continuation, Qfc, and branch, Qb, were confirmed by the velocities of 0.5μm fluorescently labeled microspheres (particle: tube ratio = 1:50) The main observation, also seen in vivo, is that regardless of the Re number, the relative flux of RBC into the branch is always less than the relative flow rate into the branch. This trend is more significant at higher Re (Re: 0.001 to 0.1). Moreover, 90‐degree bifurcation angles draw fewer RBCs (lower flux) than the other two angles; one cause could be the decreased cross‐sectional area of the branch opening associated with 90° vs. 45° or 135° angles. Although viscous effects are dominant in our system and we cannot use the ‘potential flow theories’ fully, the existing flow paths suggest a stagnation point in each microchannel that affects the particle flow direction, and thus the RBC flux distribution to the branch vs. continuing along the feed. Therefore we can predict the RBC distribution at a bifurcation knowing the flow properties (Re), the geometry that creates this stagnation point (angle, radius of curvature) and radial position of the RBC 2–3 tube diameters upstream of the junction.

Application of Controlled Shear Stresses on the Erythrocyte Membrane as a New Approach to Promote Molecule Encapsulation

Human red blood cells (RBCs) have a remarkable capacity to undergo reversible membrane swelling. Resealed erythrocytes have been proposed as carriers and bioreactors to be used in the treatment of various diseases. This work is aimed at developing a setup allowing the encapsulation of test molecules into erythrocytes by inducing reversible pore formation on the RBC membrane through the application of controlled mechanical shear stresses. The designed setup consists of two reservoirs connected by a glass capillary. Each reservoir is connected to a compressor; during the tests, the reservoirs were in turn pressurized to promote erythrocyte flow through the capillary. The setup was filled with a suspension of erythrocytes, phosphate buffer, and FITC-dextran. Dextran was chosen as the diffusive molecule to check membrane pore dimensions. Samples of the suspension were withdrawn at scheduled times while the setup was operating. Flow cytometry and stereo-optical microscopy analyses were used to evaluate the erythrocyte dextran uptake. The setup was shown to be safe, well controlled, and adjustable. The outcomes of the experimental tests showed significant dextran uptake by RBCs up to 8%. Microscopy observations highlighted the formation of echinocytes in the analyzed samples. Erythrocytes from different donors showed different reactions to mechanical stresses. The experimental outcomes proved the possibility to encapsulate test molecules into erythrocytes by applying controlled mechanical shear stresses on the RBC membrane, encouraging further studies.

ZEISS Angioplex™ Spectral Domain Optical Coherence Tomography Angiography: Technical Aspects.

ZEISS Angioplex™ optical coherence tomography (OCT) angiography generates high-resolution three-dimensional maps of the retinal and choroidal microvasculature while retaining all of the capabilities of the existing CIRRUS™ HD-OCT Model 5000 instrument. Angioplex™ OCT angiographic imaging on the CIRRUS™ HD-OCT platform was made possible by increasing the scanning rate to 68,000 A-scans per second and introducing improved tracking software known as FastTrac™ retinal-tracking technology. The generation of en face microvascular flow images with Angioplex™ OCT uses an algorithm known as OCT microangiography-complex, which incorporates differences in both the phase and intensity information contained within sequential B-scans performed at the same position. Current scanning patterns for en face angiographic visualization include a 3 × 3 and a 6 × 6 mm scan pattern on the retina. A volumetric dataset showing erythrocyte flow information can then be displayed as a color-coded retinal depth map in which the microvasculature of the superficial, deep, and avascular layers of the retina are displayed together with the colors red, representing the superficial microvasculature; green, representing the deep retinal vasculature; and blue, representing any vessels present in the normally avascular outer retina. Each retinal layer can be viewed separately, and the microvascular layers representing the choriocapillaris and the remaining choroid can be viewed separately as well. In addition, readjusting the contours of the slabs to target different layers of interest can generate custom en face flow images. Moreover, each en face flow image is accompanied by an en face intensity image to help with the interpretation of the flow results. Current clinical experience with this technology would suggest that OCT angiography should replace fluorescein angiography for retinovascular diseases involving any area of the retina that can be currently scanned with the CIRRUS™ HD-OCT instrument and may replace fluorescein angiography and indocyanine green angiography for some choroidal vascular diseases.