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Baskurt OK, Meiselman HJ. Blood Rheology and Hemodynamics. Semin Thromb Hemost 2023. [PMID: 38122808 DOI: 10.1055/s-0043-1777802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
Seminars in Thrombosis and Hemostasis (STH) celebrates 50 years of publishing in 2024. To celebrate this landmark event, STH is republishing some archival material. This manuscript represents the most highly cited paper ever published in STH. The original abstract follows.Blood is a two-phase suspension of formed elements (i.e., red blood cells [RBCs], white blood cells [WBCs], platelets) suspended in an aqueous solution of organic molecules, proteins, and salts called plasma. The apparent viscosity of blood depends on the existing shear forces (i.e., blood behaves as a non-Newtonian fluid) and is determined by hematocrit, plasma viscosity, RBC aggregation, and the mechanical properties of RBCs. RBCs are highly deformable, and this physical property significantly contributes to aiding blood flow both under bulk flow conditions and in the microcirculation. The tendency of RBCs to undergo reversible aggregation is an important determinant of apparent viscosity because the size of RBC aggregates is inversely proportional to the magnitude of shear forces; the aggregates are dispersed with increasing shear forces, then reform under low-flow or static conditions. RBC aggregation also affects the in vivo fluidity of blood, especially in the low-shear regions of the circulatory system. Blood rheology has been reported to be altered in various physiopathological processes: (1) Alterations of hematocrit significantly contribute to hemorheological variations in diseases and in certain extreme physiological conditions; (2) RBC deformability is sensitive to local and general homeostasis, with RBC deformability affected by alterations of the properties and associations of membrane skeletal proteins, the ratio of RBC membrane surface area to cell volume, cell morphology, and cytoplasmic viscosity. Such alterations may result from genetic disorders or may be induced by such factors as abnormal local tissue metabolism, oxidant stress, and activated leukocytes; and (3) RBC aggregation is mainly determined by plasma protein composition and surface properties of RBCs, with increased plasma concentrations of acute phase reactants in inflammatory disorders a common cause of increased RBC aggregation. In addition, RBC aggregation tendency can be modified by alterations of RBC surface properties because of RBC in vivo aging, oxygen-free radicals, or proteolytic enzymes. Impairment of blood fluidity may significantly affect tissue perfusion and result in functional deteriorations, especially if disease processes also disturb vascular properties.
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Affiliation(s)
- Oguz K Baskurt
- Department of Physiology, Akdeniz University Faculty of Medicine, Antalya, Türkiye
| | - Herbert J Meiselman
- Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles, California
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Ubbink R, Streng LWJM, Raat NJH, Harms FA, Te Boekhorst PAW, Stolker RJ, Mik EG. Measuring Mitochondrial Oxygen Tension during Red Blood Cell Transfusion in Chronic Anemia Patients: A Pilot Study. Biomedicines 2023; 11:1873. [PMID: 37509512 PMCID: PMC10376882 DOI: 10.3390/biomedicines11071873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 06/19/2023] [Accepted: 06/26/2023] [Indexed: 07/30/2023] Open
Abstract
In light of the associated risks, the question has been raised whether the decision to give a blood transfusion should solely be based on the hemoglobin level. As mitochondria are the final destination of oxygen transport, mitochondrial parameters are suggested to be of added value. The aims of this pilot study were to investigate the effect of a red blood cell transfusion on mitochondrial oxygenation as measured by the COMET device in chronic anemia patients and to explore the clinical usability of the COMET monitor in blood transfusion treatments, especially the feasibility of performing measurements in an outpatient setting. To correct the effect of volume load on mitochondrial oxygenation, a red blood cell transfusion and a saline infusion were given in random order. In total, 21 patients were included, and this resulted in 31 observations. If patients participated twice, the order of infusion was reversed. In both the measurements wherein a blood transfusion was given first and wherein 500 mL of 0.9% saline was given first, the median mitochondrial oxygen tension decreased after red blood cell transfusion. The results of this study have strengthened the need for further research into the effect of blood transfusion tissue oxygenation and the potential role of mitochondrial parameters herein.
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Affiliation(s)
- Rinse Ubbink
- Laboratory of Experimental Anesthesiology, Department of Anesthesiology, Erasmus MC, University Medical Center Rotterdam, 3000 CA Rotterdam, The Netherlands
| | - Lucia W J M Streng
- Laboratory of Experimental Anesthesiology, Department of Anesthesiology, Erasmus MC, University Medical Center Rotterdam, 3000 CA Rotterdam, The Netherlands
| | - Nicolaas J H Raat
- Laboratory of Experimental Anesthesiology, Department of Anesthesiology, Erasmus MC, University Medical Center Rotterdam, 3000 CA Rotterdam, The Netherlands
| | - Floor A Harms
- Laboratory of Experimental Anesthesiology, Department of Anesthesiology, Erasmus MC, University Medical Center Rotterdam, 3000 CA Rotterdam, The Netherlands
| | - Peter A W Te Boekhorst
- Department of Hematology, Erasmus MC, University Medical Center Rotterdam, 3000 CA Rotterdam, The Netherlands
| | - Robert J Stolker
- Laboratory of Experimental Anesthesiology, Department of Anesthesiology, Erasmus MC, University Medical Center Rotterdam, 3000 CA Rotterdam, The Netherlands
| | - Egbert G Mik
- Laboratory of Experimental Anesthesiology, Department of Anesthesiology, Erasmus MC, University Medical Center Rotterdam, 3000 CA Rotterdam, The Netherlands
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Windes P, Tafti DK, Behkam B. A computational framework for investigating bacteria transport in microvasculature. Comput Methods Biomech Biomed Engin 2023; 26:438-449. [PMID: 35486738 DOI: 10.1080/10255842.2022.2066473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Blood-borne bacteria disseminate in tissue through microvasculature or capillaries. Capillary size, presence of red blood cells (RBCs), and bacteria motility affect bacteria intracapillary transport, an important yet largely unexplored phenomenon. Computational description of the system comprising interactions between plasma, RBCs, and motile bacteria in 5-10 μm diameter capillaries pose several challenges. The Immersed Boundary Method (IBM) was used to resolve the capillary, deformed RBCs, and bacteria. The challenge of disparate coupled time scales of flow and bacteria motion are reconciled by a temporal multiscale simulation method. Bacterium-wall and bacterium-RBC collisions were detected using a hierarchical contact- detection algorithm. Motile bacteria showed a net outward radial velocity of 2.8 µm/s compared to -0.5 µm/s inward for non-motile bacteria; thus, exhibiting a greater propensity to escape the bolus flow region between RBCs and marginate for potential extravasation, suggesting motility enhances extravasation of bacteria from capillaries.
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Affiliation(s)
- Peter Windes
- Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA, USA
| | - Danesh K Tafti
- Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA, USA
| | - Bahareh Behkam
- Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA, USA.,School of Biomedical Engineering and Sciences, Virginia Tech, Blacksburg, VA, USA
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Giannokostas K, Dimakopoulos Y, Tsamopoulos J. Shear stress and intravascular pressure effects on vascular dynamics: two-phase blood flow in elastic microvessels accounting for the passive stresses. Biomech Model Mechanobiol 2022; 21:1659-1684. [PMID: 35962247 DOI: 10.1007/s10237-022-01612-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 07/07/2022] [Indexed: 11/02/2022]
Abstract
We study the steady hemodynamics in physiological elastic microvessels proposing an advanced fluid-structure interaction model. The arteriolar tissue is modeled as a two-layer fiber-reinforced hyperelastic material representing its Media and Adventitia layers. The constitutive model employed (Holzapfel et al. in J Elast 61:1-48, 2000) is parametrized via available data on stress-strain experiments for arterioles. The model is completed by simulating the blood/plasma flow in the lumen, using the thixotropic elasto-viscoplastic model in its core, and the linear Phan-Thien and Tanner viscoelastic model in its annular part. The Cell-Free Layer (CFL) and the Fåhraeus and Fåhraeus-Lindqvist effects are considered via analytical expressions based on experimental data (Giannokostas et al. in Materials (Basel) 14:367, 2021b). The coupling between tissue deformation and blood flow is achieved through the experimentally verified pressure-shear hypothesis (Pries et al. Circ Res 77:1017-1023, 1995). Our calculations confirm that the increase in the reference inner radius produces larger expansion. Also, by increasing the intraluminal pressure, the thinning of the walls is more pronounced and it may reach 40% of the initial thickness. Comparing our predictions with those in rigid-wall microtubes, we conclude that apart from the vital importance of vasodilation, there is an up to 25% reduction in wall shear stress. The passive vasodilation contributes to the decrease in the tissue stress fields and affects the hemodynamic features such as the CFL thickness, reducing the plasma layer when blood flows in vessels with elastic walls, in quantitative agreement with previous experiments. Our calculations verify the correctness of the pressure-shear hypothesis but not that of the Laplace law.
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Affiliation(s)
- K Giannokostas
- Laboratory of Fluid Mechanics and Rheology, Department of Chemical Engineering, University of Patras, Patras, Greece
| | - Y Dimakopoulos
- Laboratory of Fluid Mechanics and Rheology, Department of Chemical Engineering, University of Patras, Patras, Greece.
| | - J Tsamopoulos
- Laboratory of Fluid Mechanics and Rheology, Department of Chemical Engineering, University of Patras, Patras, Greece
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5
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Hemodynamic Response During Fluid Challenge After Pediatric Cardiac Surgery. Crit Care Med 2021; 49:e541-e542. [PMID: 33854015 DOI: 10.1097/ccm.0000000000004806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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6
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Giannokostas K, Dimakopoulos Y, Anayiotos A, Tsamopoulos J. Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Steady-State Blood Flow in Microtubes. MATERIALS (BASEL, SWITZERLAND) 2021; 14:E367. [PMID: 33451107 PMCID: PMC7828603 DOI: 10.3390/ma14020367] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 01/02/2021] [Accepted: 01/09/2021] [Indexed: 12/15/2022]
Abstract
The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero.
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Affiliation(s)
- Konstantinos Giannokostas
- Laboratory of Fluid Mechanics and Rheology, Department of Chemical Engineering, University of Patras, 26504 Patras, Greece; (K.G.); (J.T.)
| | - Yannis Dimakopoulos
- Laboratory of Fluid Mechanics and Rheology, Department of Chemical Engineering, University of Patras, 26504 Patras, Greece; (K.G.); (J.T.)
| | - Andreas Anayiotos
- Department of Mechanical and Materials Engineering, Cyprus University of Technology, Limassol 3036, Cyprus;
| | - John Tsamopoulos
- Laboratory of Fluid Mechanics and Rheology, Department of Chemical Engineering, University of Patras, 26504 Patras, Greece; (K.G.); (J.T.)
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7
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Namvar A, Blanch AJ, Dixon MW, Carmo OMS, Liu B, Tiash S, Looker O, Andrew D, Chan LJ, Tham WH, Lee PVS, Rajagopal V, Tilley L. Surface area-to-volume ratio, not cellular viscoelasticity, is the major determinant of red blood cell traversal through small channels. Cell Microbiol 2020; 23:e13270. [PMID: 32981231 PMCID: PMC7757199 DOI: 10.1111/cmi.13270] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 08/14/2020] [Accepted: 09/18/2020] [Indexed: 12/12/2022]
Abstract
The remarkable deformability of red blood cells (RBCs) depends on the viscoelasticity of the plasma membrane and cell contents and the surface area to volume (SA:V) ratio; however, it remains unclear which of these factors is the key determinant for passage through small capillaries. We used a microfluidic device to examine the traversal of normal, stiffened, swollen, parasitised and immature RBCs. We show that dramatic stiffening of RBCs had no measurable effect on their ability to traverse small channels. By contrast, a moderate decrease in the SA:V ratio had a marked effect on the equivalent cylinder diameter that is traversable by RBCs of similar cellular viscoelasticity. We developed a finite element model that provides a coherent rationale for the experimental observations, based on the nonlinear mechanical behaviour of the RBC membrane skeleton. We conclude that the SA:V ratio should be given more prominence in studies of RBC pathologies.
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Affiliation(s)
- Arman Namvar
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia.,Department of Biomedical Engineering, University of Melbourne, Parkville, Victoria, Australia
| | - Adam J Blanch
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Matthew W Dixon
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Olivia M S Carmo
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Boyin Liu
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Snigdha Tiash
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Oliver Looker
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Dean Andrew
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Li-Jin Chan
- Division of Infection & Immunity, Walter & Eliza Hall Institute, Parkville, Victoria, Australia.,Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Wai-Hong Tham
- Division of Infection & Immunity, Walter & Eliza Hall Institute, Parkville, Victoria, Australia.,Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Peter V S Lee
- Department of Biomedical Engineering, University of Melbourne, Parkville, Victoria, Australia
| | - Vijay Rajagopal
- Department of Biomedical Engineering, University of Melbourne, Parkville, Victoria, Australia
| | - Leann Tilley
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
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Reinhart WH, Piety NZ, Shevkoplyas SS. Influence of red blood cell aggregation on perfusion of an artificial microvascular network. Microcirculation 2018; 24. [PMID: 27647727 DOI: 10.1111/micc.12317] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 09/12/2016] [Indexed: 02/06/2023]
Abstract
OBJECTIVE RBCs suspended in plasma form multicellular aggregates under low-flow conditions, increasing apparent blood viscosity at low shear rates. It has previously been unclear, however, if RBC aggregation affects microvascular perfusion. Here, we analyzed the impact of RBC aggregation on perfusion and 'capillary' hematocrit in an AMVN at driving pressures ranging from 5 to 60 cm H2 O to determine if aggregation could improve tissue oxygenation. METHODS RBCs were suspended at 30% hematocrit in either 46.5 g/L dextran 40 (D40, non-aggregating medium) or 35 g/L dextran 70 (D70, aggregating medium) solutions with equal viscosity. RESULTS Aggregation was readily observed in the AMVN for RBCs suspended in D70 at driving pressures ≤40 cm H2 O. The AMVN perfusion rate was the same for RBCs suspended in aggregating and non-aggregating medium, at both 'venular' and 'capillary' level. Estimated 'capillary' hematocrit was higher for D70 suspensions than for D40 suspensions at intermediate driving pressures (5-40 cm H2 O). CONCLUSIONS We conclude that although RBC aggregation did not affect the AMVN perfusion rate independently of the driving pressure, a higher hematocrit in the 'capillaries' of the network for D70 suspensions suggested a better oxygen transport capacity in the presence of RBC aggregation.
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Affiliation(s)
- Walter H Reinhart
- Department of Internal Medicine, Kantonsspital Graubünden, Chur, Switzerland
| | - Nathaniel Z Piety
- Department of Biomedical Engineering, Cullen College of Engineering, University of Houston, Houston, Texas, USA
| | - Sergey S Shevkoplyas
- Department of Biomedical Engineering, Cullen College of Engineering, University of Houston, Houston, Texas, USA
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Ueyama H, Kiyonaka S. Predicting the Need for Fluid Therapy-Does Fluid Responsiveness Work? J Intensive Care 2017; 5:34. [PMID: 28603624 PMCID: PMC5461727 DOI: 10.1186/s40560-017-0210-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 01/26/2017] [Indexed: 12/31/2022] Open
Abstract
Fluid overdose can be harmful in critically ill patients. Since central venous pressure (CVP) is currently considered to be an inappropriate indicator of preload, much attention is being given to predicting fluid responsiveness, i.e., the response of stroke volume (SV) or cardiac output (CO) to fluid challenge. However, when fluid responsiveness was evaluated in critically ill patients, including sepsis, only 40–50% of the patients responded. Moreover, most fluid responders do not show significant hemodynamic improvement after fluid administration. In this review, we discuss why fluid responsiveness based on the Starling mechanism did not work well in the clinical setting. According to the Starling mechanism, a patient whose SV/CO significantly increases after a fluid challenge is considered to be a fluid responder and judged to need fluid therapy. However, the currently recommended fluid challenge dose of crystalloid 250–500 mL has little effect on increasing blood volume and is not sufficient to increase the preload of the Starling curve. Especially in septic patients, due to their vascular hyperpermeability, increase in blood volume is even smaller. Furthermore, Infusion induced hemodilution is known to reduce blood viscosity and hematocrit, as a result, decreasing afterload. This indicates that the increased SV/CO after fluid challenge is caused not only by increased preload but also by decreased afterload. For these reasons, fluid responsiveness with small crystalloid challenge is questionable as a clinical indicator of fluid therapy.
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Affiliation(s)
- Hiroshi Ueyama
- Department of Anesthesiology, Kansai Rosai Hospital, 3-1-69, Inabaso, Amagasaki, 660-8511 Hyogo Japan
| | - Sawami Kiyonaka
- Department of Anesthesiology, Kansai Rosai Hospital, 3-1-69, Inabaso, Amagasaki, 660-8511 Hyogo Japan
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10
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Microvasculature on a chip: study of the Endothelial Surface Layer and the flow structure of Red Blood Cells. Sci Rep 2017; 7:45036. [PMID: 28338083 PMCID: PMC5364477 DOI: 10.1038/srep45036] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 02/17/2017] [Indexed: 12/20/2022] Open
Abstract
Microvasculatures-on-a-chip, i.e. in vitro models that mimic important features of microvessel networks, have gained increasing interest in recent years. Such devices have allowed investigating pathophysiological situations involving abnormal biophysical interactions between blood cells and vessel walls. Still, a central question remains regarding the presence, in such biomimetic systems, of the endothelial glycocalyx. The latter is a glycosaminoglycans-rich surface layer exposed to blood flow, which plays a crucial role in regulating the interactions between circulating cells and the endothelium. Here, we use confocal microscopy to characterize the layer expressed by endothelial cells cultured in microfluidic channels. We show that, under our culture conditions, endothelial cells form a confluent layer on all the walls of the circuit and display a glycocalyx that fully lines the lumen of the microchannels. Moreover, the thickness of this surface layer is found to be on the order of 600 nm, which compares well with measurements performed ex or in vivo on microcapillaries. Furthermore, we investigate how the presence of endothelial cells in the microchannels affects their hydrodynamic resistance and the near-wall motion of red blood cells. Our study thus provides an important insight into the physiological relevance of in vitro microvasculatures.
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Agrawal R, Smart T, Nobre-Cardoso J, Richards C, Bhatnagar R, Tufail A, Shima D, H Jones P, Pavesio C. Assessment of red blood cell deformability in type 2 diabetes mellitus and diabetic retinopathy by dual optical tweezers stretching technique. Sci Rep 2016; 6:15873. [PMID: 26976672 PMCID: PMC4792142 DOI: 10.1038/srep15873] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 09/21/2015] [Indexed: 12/11/2022] Open
Abstract
A pilot cross sectional study was conducted to investigate the role of red blood cells (RBC) deformability in type 2 diabetes mellitus (T2DM) without and with diabetic retinopathy (DR) using a dual optical tweezers stretching technique. A dual optical tweezers was made by splitting and recombining a single Nd:YAG laser beam. RBCs were trapped directly (i.e., without microbead handles) in the dual optical tweezers where they were observed to adopt a "side-on" orientation. RBC initial and final lengths after stretching were measured by digital video microscopy, and a Deformability index (DI) calculated. Blood from 8 healthy controls, 5 T2DM and 7 DR patients with respective mean age of 52.4 yrs, 51.6 yrs and 52 yrs was analysed. Initial average length of RBCs for control group was 8.45 ± 0.25 μm, 8.68 ± 0.49 μm for DM RBCs and 8.82 ± 0.32 μm for DR RBCs (p < 0.001). The DI for control group was 0.0698 ± 0.0224, and that for DM RBCs was 0.0645 ± 0.03 and 0.0635 ± 0.028 (p < 0.001) for DR group. DI was inversely related to basal length of RBCs (p = .02). DI of RBC from DM and DR patients was significantly lower in comparison with normal healthy controls. A dual optical tweezers method can hence be reliably used to assess RBC deformability.
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Affiliation(s)
- Rupesh Agrawal
- Moorfields Eye Hospital NHS Foundation Trust, London, UK.,Department of Mechanical Engineering, University College London, London, UK.,Institute of Ophthalmology, University College London, London, UK.,National Healthcare Group Eye Institute, Tan Tock Seng Hospital, Singapore
| | - Thomas Smart
- Department of Physics and Astronomy, University College London, London, UK
| | | | | | - Rhythm Bhatnagar
- Department of Mechanical Engineering, University College London, London, UK
| | - Adnan Tufail
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - David Shima
- Institute of Ophthalmology, University College London, London, UK
| | - Phil H Jones
- Department of Physics and Astronomy, University College London, London, UK
| | - Carlos Pavesio
- Moorfields Eye Hospital NHS Foundation Trust, London, UK.,Institute of Ophthalmology, University College London, London, UK
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12
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Fitzgibbon S, Spann AP, Qi QM, Shaqfeh ESG. In vitro measurement of particle margination in the microchannel flow: effect of varying hematocrit. Biophys J 2016; 108:2601-2608. [PMID: 25992738 DOI: 10.1016/j.bpj.2015.04.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 01/07/2015] [Accepted: 04/09/2015] [Indexed: 10/23/2022] Open
Abstract
It has long been known that platelets undergo margination when flowing in blood vessels, such that there is an excess concentration near the vessel wall. We conduct experiments and three-dimensional boundary integral simulations of platelet-sized spherical particles in a microchannel 30 μm in height to measure the particle-concentration distribution profile and observe its margination at 10%, 20%, and 30% red blood cell hematocrit. The experiments involved adding 2.15-μm-diameter spheres into a solution of red blood cells, plasma, and water and flowing this mixture down a microfluidic channel at a wall shear rate of 1000 s(-1). Fluorescence imaging was used to determine the height and velocity of particles in the channel. Experimental results indicate that margination has largely occurred before particles travel 1 cm downstream and that hematocrit plays a role in the degree of margination. With simulations, we can track the trajectories of the particles with higher resolution. These simulations also confirm that margination from an initially uniform distribution of spheres and red blood cells occurs over the length scale of O(1 cm), with higher hematocrit showing faster margination. The results presented here, from both experiments and 3D simulations, may help explain the relationship between bleeding time in vessel trauma and red blood cell hematocrit as platelets move to a vessel wall.
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Affiliation(s)
- Sean Fitzgibbon
- Chemical Engineering, Stanford University, Stanford, California
| | - Andrew P Spann
- Institute for Computational and Mathematical Engineering, Stanford University, Stanford, California
| | - Qin M Qi
- Chemical Engineering, Stanford University, Stanford, California.
| | - Eric S G Shaqfeh
- Chemical Engineering, Stanford University, Stanford, California; Mechanical Engineering, Stanford University, Stanford, California; Institute for Computational and Mathematical Engineering, Stanford University, Stanford, California
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13
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Sriram K, Intaglietta M, Tartakovsky DM. Non-Newtonian flow of blood in arterioles: consequences for wall shear stress measurements. Microcirculation 2015; 21:628-39. [PMID: 24703006 DOI: 10.1111/micc.12141] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 04/02/2014] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Our primary goal is to investigate the effects of non-Newtonian blood properties on wall shear stress in microvessels. The secondary goal is to derive a correction factor for the Poiseuille-law-based indirect measurements of wall shear stress. METHODS The flow is assumed to exhibit two distinct, immiscible and homogeneous fluid layers: an inner region densely packed with RBCs, and an outer cell-free layer whose thickness depends on discharge hematocrit. The cell-free layer is assumed to be Newtonian, while rheology of the RBC-rich core is modeled using the Quemada constitutive law. RESULTS Our model provides a realistic description of experimentally observed blood velocity profiles, tube hematocrit, core hematocrit, and apparent viscosity over a wide range of vessel radii and discharge hematocrits. CONCLUSIONS Our analysis reveals the importance of incorporating this complex blood rheology into estimates of WSS in microvessels. The latter is accomplished by specifying a correction factor, which accounts for the deviation of blood flow from the Poiseuille law.
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Affiliation(s)
- Krishna Sriram
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, California, USA
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14
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Erythrocyte: A systems model of the control of aggregation and deformability. Biosystems 2015; 131:1-8. [DOI: 10.1016/j.biosystems.2015.03.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 03/18/2015] [Accepted: 03/19/2015] [Indexed: 02/08/2023]
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15
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Ong PK, Jain S, Kim S. Temporal variations of the cell-free layer width may enhance NO bioavailability in small arterioles: Effects of erythrocyte aggregation. Microvasc Res 2011; 81:303-12. [PMID: 21345341 DOI: 10.1016/j.mvr.2011.02.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 02/11/2011] [Accepted: 02/12/2011] [Indexed: 11/29/2022]
Abstract
Recently, we have shown that temporal variations in the cell-free layer width can potentially enhance nitric oxide (NO) bioavailability in small arterioles. Since the layer width variations can be augmented by red blood cell aggregation, we tested the hypothesis that an increase in the layer width variations due to red blood cell aggregation could provide an underlying mechanism to improve NO bioavailability in the endothelium and promote vasodilatory effects. Utilizing cell-free layer width data acquired from arterioles of the rat cremaster muscle before and after dextran infusion in reduced flow conditions (wall shear stress=0.13-0.24Pa), our computational model predicted exponential enhancements of NO bioavailability in the endothelium and soluble guanylyl cyclase (sGC) activation in the smooth muscle layer with increasing temporal variability of the layer width. These effects were mediated primarily by the transient responses of wall shear stress and NO production rate to the layer width variations. The temporal variations in the layer width were significantly enhanced (P<0.05) by aggregation, leading to significant improvements (P<0.05) in NO bioavailability and sGC activation. As a result, the significant reduction (P<0.05) of sGC activation due to the increased width of the layer after aggregation induction was diminished by the opposing effect of the layer variations. These findings highlighted the possible enhancement of NO bioavailability and vascular tone in the arteriole by the augmented layer width variations due to the aggregation.
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Affiliation(s)
- Peng Kai Ong
- Division of Bioengineering & Department of Surgery, National University of Singapore, Singapore
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16
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Ong PK, Jain S, Namgung B, Woo YI, Sakai H, Lim D, Chun KJ, Kim S. An automated method for cell-free layer width determination in small arterioles. Physiol Meas 2011; 32:N1-12. [PMID: 21252418 DOI: 10.1088/0967-3334/32/3/n01] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Histogram-based thresholding techniques utilized for cell-free layer width measurement in arteriolar flow may produce an overestimation of the layer width since they do not consider faint shaded regions near the vessel wall as part of the erythrocyte column. To address this problem, we developed a new method for detecting the boundary of the erythrocyte column based on an edge detection algorithm. This automated method (grayscale method) provides local detections of the inner vessel wall as well as the boundary between the cell-free layer and the erythrocyte column without binarization of grayscale images. The cell-free layer width measurements using the grayscale method and existing techniques (minimum method and Otsu's method) were compared with those determined manually in arteriolar flows of the rat cremaster muscle. In the absence of the shaded regions, values obtained by the grayscale method and minimum method were statistically in good agreement with the manual method but not in the case of Otsu's method. When the faint shaded regions were present, the grayscale method appeared to produce more accurate results than the minimum method and Otsu's method.
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Affiliation(s)
- P K Ong
- Division of Bioengineering and Department of Surgery, National University of Singapore, Singapore
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17
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Ong PK, Namgung B, Johnson PC, Kim S. Effect of erythrocyte aggregation and flow rate on cell-free layer formation in arterioles. Am J Physiol Heart Circ Physiol 2010; 298:H1870-8. [PMID: 20348228 DOI: 10.1152/ajpheart.01182.2009] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Formation of a cell-free layer is an important dynamic feature of microcirculatory blood flow, which can be influenced by rheological parameters, such as red blood cell aggregation and flow rate. In this study, we investigate the effect of these two rheological parameters on cell-free layer characteristics in the arterioles (20-60 mum inner diameter). For the first time, we provide here the detailed temporal information of the arteriolar cell-free layer in various rheological conditions to better describe the characteristics of the layer variation. The rat cremaster muscle was used to visualize arteriolar flows, and the extent of aggregation was raised by dextran 500 infusion to levels seen in normal human blood. Our results show that cell-free layer formation in the arterioles is enhanced by a combination of flow reduction and red blood cell aggregation. A positive relation (P < 0.005) was found between mean cell-free layer widths and their corresponding SDs for all conditions. An analysis of the frequency and magnitudes of cell-free layer variation from their mean value revealed that the layer deviated with significantly larger magnitudes into the red blood cell core after flow reduction and dextran infusion (P < 0.05). In accordance, the disparity of cell-free layer width distribution found in opposite radial directions from its mean became greater with aggregation in reduced flow conditions. This study shows that the cell-free layer width in arterioles is dependent on both flow rate and red blood cell aggregability, and that the temporal variations in width are asymmetric with a greater excursion into the red blood cell core than toward the vessel wall.
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Affiliation(s)
- Peng Kai Ong
- Division of Bioengineering and Department of Surgery, National University of Singapore, Singapore
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18
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Kim S, Kong RL, Popel AS, Intaglietta M, Johnson PC. Temporal and spatial variations of cell-free layer width in arterioles. Am J Physiol Heart Circ Physiol 2007; 293:H1526-35. [PMID: 17526647 DOI: 10.1152/ajpheart.01090.2006] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Separation of red blood cells and plasma in microcirculatory vessels produces a cell-free layer at the wall. This layer may be an important determinant of blood viscosity and wall shear stress in arterioles, where most of the hydraulic pressure loss in the circulatory system occurs and flow regulatory mechanisms are prominent. With the use of a newly developed method, the width of the cell-free layer was rapidly and repeatedly determined in arterioles (10- to 50-μm inner diameter) in the rat cremaster muscle at normal arterial pressure. The temporal variation of the cell-free layer width was non-Gaussian, but calculated mean and median values differed by <0.2 μm. The correlation length of the temporal variations downstream (an indication of mixing) was ∼30 μm and was independent of pseudoshear rate (ratio of mean velocity to vessel diameter) and of vessel diameter. The cell-free layer width was significantly different on opposite sides of the vessel and inversely related. Increasing red blood cell aggregability reduced this inverse relation but had no effect on correlation length. In the diameter range studied, the mean width of the cell-free layer increased from 0.8 to 3.1 μm and temporal variations increased from 30% to 70% of the mean width. Increased aggregability did not alter either relationship. In summary, the cell-free layer width in arterioles is diameter dependent and shows substantial non-Gaussian temporal variations. The temporal variations increase as diameter increases and are inversely related on opposite sides of the vessel.
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Affiliation(s)
- Sangho Kim
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093-0412, USA
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19
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20
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Abstract
With one or two exceptions, biological materials are "soft", meaning that they combine viscous and elastic elements. This mechanical behavior results from self-assembled supramolecular structures that are stabilized by noncovalent interactions. It is an ongoing and profound challenge to understand the self-organization of biological materials. In many cases, concepts can be imported from soft-matter physics and chemistry, which have traditionally focused on materials such as colloids, polymers, surfactants, and liquid crystals. Using these ideas, it is possible to gain a new perspective on phenomena as diverse as DNA condensation, protein and peptide fibrillization, lipid partitioning in rafts, vesicle fusion and budding, and others, as discussed in this selective review of recent highlights from the literature.
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Affiliation(s)
- Ian W Hamley
- Department of Chemistry, University of Reading, Reading, Berkshire RG6 6AD, UK.
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21
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Yalcin O, Uyuklu M, Armstrong JK, Meiselman HJ, Baskurt OK. Graded alterations of RBC aggregation influence in vivo blood flow resistance. Am J Physiol Heart Circ Physiol 2004; 287:H2644-50. [PMID: 15284061 DOI: 10.1152/ajpheart.00534.2004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although the effects of red blood cell (RBC) aggregation on low-shear rate blood viscosity are well known, the effects on in vivo flow resistance are still not fully resolved. The present study was designed to explore the in vivo effects of RBC aggregation on flow resistance using a novel technique to enhance aggregation: cells are covalently coated with a block copolymer (Pluronic F-98) and then suspended in unaltered plasma. RBC aggregation was increased in graded steps by varying the Pluronic concentration during cell coating and was verified by microscopy and erythrocyte sedimentation rate (ESR), which increased by 200% at the highest Pluronic level. RBC suspensions were perfused through an isolated in situ guinea pig hindlimb preparation while the arterial perfusion pressure was held constant at 100 mmHg via a pressure servo-controlled pump. No significant effects of enhanced RBC aggregation were observed when studies were conducted in preparations with intact vascular control mechanisms. However, after inhibition of smooth muscle tone (using 10−4M papaverin), a significant change in flow resistance was observed in a RBC suspension with a 97% increase of ESR. Additional enhancements of RBC aggregation (i.e., 136 and 162% increases of ESR) decreased flow resistance almost to control values. This was followed by another significant increase in flow resistance during perfusion with RBC suspensions with a 200% increase of ESR. This triphasic effect of graded increases of RBC aggregation is most likely explained by an interplay of several hemodynamic mechanisms that are triggered by enhanced RBC aggregation.
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Affiliation(s)
- Ozlem Yalcin
- Dept. of Physiology, Akdeniz Univ. Faculty of Medicine, Kampus, 07058 Antalya, Turkey
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22
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Tateishi N, Suzuki Y, Shirai M, Cicha I, Maeda N. Reduced oxygen release from erythrocytes by the acceleration-induced flow shift, observed in an oxygen-permeable narrow tube. J Biomech 2002; 35:1241-51. [PMID: 12163313 DOI: 10.1016/s0021-9290(02)00068-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The oxygen release from flowing erythrocytes under accelerational force (0-4 g) was examined using an oxygen-permeable, fluorinated ethylenepropylene copolymer tube (25 microm in inner diameter). The narrow tube was fixed vertically on the rotating disk of a new centrifuge apparatus, and erythrocyte suspension was perfused in the direction of Earth gravity. The accelerational force was applied perpendicularly to the flow direction of cells by centrifugation. The microscopic images of the flowing cells obtained at five different wavelengths were analyzed, and marginal cell-free layer and oxygen saturation of the cells were measured. By lowering oxygen tension around the narrow tube, erythrocytes were deoxygenated in proportion to their traveling distance, and the deoxygenation was enhanced with decreasing flow velocity and hematocrit. With increase of the g-value, the shift of flowing erythrocyte column to the centrifugal side was increased, the column was compressed, and the oxygen release from the cells was suppressed. Qualitatively, similar results were obtained by inducing erythrocyte aggregation with Dextran T-70 (MW = 70,400), without accelerational force. These results conclude that both the accumulation of erythrocytes under accelerational force and the enhancement of erythrocyte aggregation by macromolecules lead to the reduction of oxygen release from the flowing cells.
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Affiliation(s)
- Norihiko Tateishi
- Department of Physiology, School of Medicine, Ehime University, Shigenobu, Onsen-gun, Ehime 791-0295, Japan
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23
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Tateishi N, Suzuki Y, Cicha I, Maeda N. O(2) release from erythrocytes flowing in a narrow O(2)-permeable tube: effects of erythrocyte aggregation. Am J Physiol Heart Circ Physiol 2001; 281:H448-56. [PMID: 11406514 DOI: 10.1152/ajpheart.2001.281.1.h448] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of erythrocyte aggregation on O(2) release were examined using O(2)-permeable fluorinated ethylenepropylene copolymer tubes (inner diameter, 25 microm; outer diameter, 100 microm). Measurements were performed using an apparatus built on an inverted microscope that contained a scanning-grating spectrophotometer with a photon count detector connected to two photomultipliers and an image processor through a video camera. The rate of O(2) release from the cells flowing in the narrow tube was determined based on the visible absorption spectrum and the flow velocity of the cells as well as the tube size. When the tube was exposed to nitrogen-saturated deoxygenated saline containing 10 mM sodium dithionite, the flowing erythrocytes were deoxygenated in proportion to the traveling distance, and the deoxygenation at a given distance increased with decreasing flow velocity and cell concentration (hematocrit). Adding Dextran T-70 to the cell suspension increased erythrocyte aggregation in the tube, which resulted in suppressed cell deoxygenation and increased marginal cell-free-layer thickness. The deoxygenation was inversely proportional to the cell-free-layer thickness. The relation was not essentially altered even when the medium viscosity was adjusted with Dextran T-40 to remain constant. The rate of O(2) release from erythrocytes in the tube was discussed in relation to the O(2) diffusion process. We conclude that the diffusion of O(2) from erythrocytes flowing in narrow tubes is inhibited primarily by erythrocyte aggregation itself and partly by thickening of the cell-free layer.
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Affiliation(s)
- N Tateishi
- Department of Physiology, School of Medicine, Ehime University, Shigenobu, Onsen-gun, Ehime 791-0295, Japan
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24
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Abstract
Blood flow in microvessels differs significantly from that of red blood cells (RBC) flowing through long, straight glass tubes in vitro. The in vivo situation is characterized by the presence of plasma favoring aggregation, by the irregular geometry of vessel segments, and by frequent branching points. Here, a method is presented to characterize flow patterns in microvascular blood flow during intravital microscopy based on Fourier analysis of recorded light intensity patterns. The interpretation of the resulting power spectra in terms of pattern size distribution was validated by model experiments employing artificial textures and by reverse transformation of idealized spectra. The determined size of RBC flow patterns in microvessels ranged from approximately 8 microm in capillaries to approximately 14 microm in vessels of >30 microm. With increasing shear rate above approximately 100 s(-1) pattern size increased, possibly reflecting formation of short-lived flow clusters. Below approximately 100 s(-1) an increase of pattern size with decreasing shear rate was found in experiments using local occlusion and treatment with high-molecular-weight dextran, suggesting the formation of aggregates. The dynamic process of generation and destruction of RBC flow patterns could well contribute to flow resistance in vivo in peripheral vascular beds.
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Affiliation(s)
- K Osterloh
- Department of Physiology, Freie Universität Berlin, D-14195 Berlin, Germany
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25
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Cicha I, Suzuki Y, Tateishi N, Maeda N. Rheological changes in human red blood cells under oxidative stress. PATHOPHYSIOLOGY 1999. [DOI: 10.1016/s0928-4680(99)00005-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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