Red Blood Cell Size Research Articles

A mouse model to study thrombotic complications of thalassemia

Patients with β-thalassemia major and mainly intermedia have an increased risk for developing venous and arterial thrombosis which may be related to circulating pathological red blood cells (RBC) and continuous platelet activation. In the present study we used a modified thalassemic mice model in conjunction with a "real-time" carotid thrombus formation procedure to investigate thrombotic complications of thalassemia. Heterozygous Th3/+ mice, which lack one copy of their β-major and β-minor globin genes, exhibit anomalies in RBC size and shape, chronic anemia and splenomegaly which recapitulate the phenotype of human β-thalassemia intermedia. Flow cytometry measurements showed higher reactive oxygen species generation, indicating oxidative stress, in platelets and RBC of the thalassemic mice compared with wild type mice concomitant with an increase in reduced glutathione content which may represent a compensatory response to oxidative stress, and exposed phosphatidylserine which indicates platelet activation. To elucidate the effect of thalassemia on the development of arterial thrombosis, we studied photochemical-induced real-time thrombus formation in the carotid artery of these mice. The results indicated a significantly shorter "time to occlusion" in the thalassemic mice compared to wild type mice, which was prolonged following in vivo aspirin treatment. We suggest that this mouse model may contribute to our understanding of platelet activation and the hypercoagulable state in thalassemia and lay foundations to screening of anti-platelet drugs as well as anti-oxidants as possible therapeutics for prevention of thrombosis in thalassemia patients.

Influence of Pre-Storage Irradiation on the Oxidative Stress Markers, Membrane Integrity, Size and Shape of the Cold Stored Red Blood Cells

Background: To investigate the extent of oxidative damage and changes in morphology of manually isolated red blood cells (RBCs) from whole blood, cold stored (up to 20 days) in polystyrene tubes and subjected to pre-storage irradiation (50 Gy) and to compare the properties of SAGM-preserved RBCs stored under experimental conditions (polystyrene tubes) with RBCs from standard blood bag storage. Methods: The percentage of hemolysis as well as the extracellular activity of LDH, thiobarbituric acid-reactive substances, reduced glutathione (GSH), and total antioxidant capacity (TAC) were measured. Changes in the topology of RBC membrane, shape, and size were evaluated by flow cytometry and judged against microscopy images. Results: Irradiation caused significant LDH release as well as increased hemolysis and lipid peroxidation, GSH depletion, and reduction of TAC. Prolonged storage of irradiated RBCs resulted in phosphatidylserine exposure on the cell surface. By day 20, approximately 60% of RBCs displayed non-discoid shape. We did not notice significant differences in percentage of altered cells and cell volume between RBCs exposed to irradiation and those not exposed. Conclusion: Irradiation of RBC transfusion units with a dose of 50 Gy should be avoided. For research purposes such as studying the role of antioxidants, storage of small volumes of RBCs derived from the same donor would be more useful, cheaper, and blood-saving.

PO-0514 Assessment Of Red Cell Distrubution Width In Neonatal Sepsis As A Prognostic Factor

<h3>Background and aims</h3> Red cell distribution width (RDW) is a measure of the variability in the size of red blood cells. RDW has been shown to be associated with mortality in adult patients with severe sepsis. However, RDW changes in neonatal sepsis prognosis has not been studied. We evaluated the RDW values of neonatal sepsis from our retrospective data. <h3>Methods</h3> Complete blood count results were analysed retrospectively from 63 infants diagnosed with culture positive sepsis in Baskent University Hospital Neonatal Intensive Care Unit. The RDW difference between 1st and 3rd days and the ratio of the difference and 1st day RDW (change of percentage) were calculated. <h3>Results</h3> Gestational age, birth weight and Apgar scores at 1 and 5 min, resulting in mortality and improving infants showed no statistical difference (p &gt; 0.05). The change of RDW between 1st and 3rd days was not significant (p = 0.74). Percentage change of RDW values with mortality rates did not differ (p = 0.44-p = 0.85). <h3>Conclusions</h3> RDW could be elevated in conditions with ineffective eritropoesis or any disease with dsetruction with red blood cells. During sepsis, RDW could be found increased because of the effect of proinflammatory cytokines on red cell production. In neonatal sepsis, RDW change was not found associated with prognosis. Elevated and variable RDW levels could be explained because of different postmenstrual and gestational ages like preterm infants.

How to use the erythrocyte sedimentation rate in paediatrics

The erythrocyte sedimentation rate (ESR) has become a ubiquitously used technique in medicine as a marker of systemic illness. The test involves placing anticoagulated whole blood into an upright test...

The children with microcytosis

Microcytosis is decrease of red blood cells (RBCs) size. The RBCs size is measured by the mean corpuscular volume (MCV). In the children, MCV varies by age and sex and so it must be always compared with sex and age-based norms. A MCV less than the 5th percentile defines the children microcytosis . The most frequent causes of microcytosis are iron deficiency anaemia (IDA) and haemoglobinopathies [1]. IDA is the most prevalent acquired anemia, due to iron deficiency (ID), resulting from negative iron balance. Three are the commonest causes of ID: low dietary iron intake, malabsorption and blood losses. Children are particularly vulnerable to ID because of their increased iron requirements in the periods of rapid growth. IDA causes delay in cognitive development and poor motor and sensory system functioning. Therefore, it is very important to detect ID at its earliest stage in children and replenish the iron stores by proper supplementation [1]. Hemoglobinopathies constitute a major health problem worldwide with a high carrier frequency particularly in regions where malaria has been endemic. These disorders are characterized by a clinical and hematological phenotypic heterogeneity. Differentiation between thalassemic and non thalassemic microcytosis has important clinical implications, because each has an entirely different pathogenesis, prognosis, and treatment [1-3]. Differential diagnosis requires hematological marker measurement (RBCs, MCV, RBC distribution width or RDW, which measures RBC size variance. An elevated RDW indicates RBCs of multiple sizes), quantification of HbA2 and HbF, detection of Hb variants by HPLC and valuation of iron status (measurement of ferritin, which reflects iron stores, and transferring or total iron-binding capacity, which indicates the body’s ability to transport iron for use in RBC production) [2,3]. In β thalassemia trait (βTT), the RBC count is generally higher than in IDA patients , whereas MCV value is lower. RDW is increased in anemic patients with respect to the healthy subjects, higher in IDA than βTT. The negative iron balance is a marker of ID, while the increase of HbA2 is a marker of βTT[2,3].In recent years, the identification of new proteins involved in iron trafficking and regulation have led to the discovery of new forms of hereditary microcytosis, sharing features with the classic IDA. A careful patient history and evaluation of laboratory tests may enable these rare conditions to be distinguished from the more common IDA. Molecular studies allow distinction of the different types, a prerequisite for differentiated therapy [4,5].

Global genetic architecture of an erythroid quantitative trait locus, HMIP-2.

HMIP-2 is a human quantitative trait locus affecting peripheral numbers, size and hemoglobin composition of red blood cells, with a marked effect on the persistence of the fetal form of hemoglobin, HbF, in adults. The locus consists of multiple common variants in an enhancer region for MYB (chr 6q23.3), which encodes the hematopoietic transcription factor cMYB. Studying a European population cohort and four African-descended groups of patients with sickle cell anemia, we found that all share a set of two spatially separate HbF-promoting alleles at HMIP-2, termed “A” and “B.” These typically occurred together (“A–B”) on European chromosomes, but existed on separate homologous chromosomes in Africans. Using haplotype signatures for “A” and “B,” we interrogated public population datasets. Haplotypes carrying only “A” or “B” were typical for populations in Sub-Saharan Africa. The “A–B” combination was frequent in European, Asian, and Amerindian populations. Both alleles were infrequent in tropical regions, possibly undergoing negative selection by geographical factors, as has been reported for malaria with other hematological traits. We propose that the ascertainment of worldwide distribution patterns for common, HbF-promoting alleles can aid their further genetic characterization, including the investigation of gene–environment interaction during human migration and adaptation.

Regulation of red cell life-span, erythropoiesis, senescence, and clearance.

The number of red blood cells (RBCs) and their properties are optimized by nature for most efficient oxygen delivery from the lungs to hypoxic periphery. Changes in metabolic requirements or environmental oxygen availability quickly translate to modulation of the RBC number, blood rheology, oxygen affinity of hemoglobin, and even of vascular tone. Inability to match the changes in oxygen demand may be fatal and requires therapeutic intervention. The recent advances in the ongoing intensive investigations of the mechanisms in control of regulation of erythropoiesis, RBC maturation and aging, as well as the processes involved in recognition of senescent RBCs and their clearance make up the present volume. It all starts from within the mesoderm, the fetal liver and from the adult bone marrow where primitive or definitive erythropoiesis takes place (Palis, 2014). Facilitated RBC production may be induced promptly “on demand” in extended oxygen requirements upon ascent to the high altitude and quickly reversed when extra RBC mass is without benefit any more (Risso et al., 2014). Exercise and professional sport increase RBC turnover and maximize oxygen delivery to the tissues (Mairbaurl, 2013). Maturation and aging of RBCs is accompanied by multiple processes occurring at various rates driving the circulating RBCs from adolescence to senescence within approximately 120 days (Lew and Tiffert, 2013; Lutz and Bogdanova, 2013). The resulting “markers of senescence” are recognized by the macrophages and clearance of RBCs is promptly initiated (de Back et al., 2014). Premature clearance is a hallmark of various disorders associated with anemia. In each case one or multiple markers of senescence appear prematurely. Those include excessive oxidative stress (Mohanty et al., 2014), excessive cation leak with the following dehydration (Wang et al., 2014), decrease in RBC size and loss of RBC membrane through vesiculation (Alaarg et al., 2013), metabolic abnormalities (Vives-Corrons et al., 2013), or following auto-immune diseases (Lutz and Bogdanova, 2013). Blood storage damages RBCs facilitating aging. As a result clearance of transfused cells is dramatically facilitated (Bosman, 2013; Flatt et al., 2014). The present compilation does not only give an overview of the variety of opinions reflecting the current understanding of the mechanisms of erythropoiesis, aging, and clearance of RBCs. We hope that it also provides the base for future lively discussions of the up-standing problems in this rapidly developing research area.

Self-folding single cell grippers.

Given the heterogeneous nature of cultures, tumors, and tissues, the ability to capture, contain, and analyze single cells is important for genomics, proteomics, diagnostics, therapeutics, and surgery. Moreover, for surgical applications in small conduits in the body such as in the cardiovascular system, there is a need for tiny tools that approach the size of the single red blood cells that traverse the blood vessels and capillaries. We describe the fabrication of arrayed or untethered single cell grippers composed of biocompatible and bioresorbable silicon monoxide and silicon dioxide. The energy required to actuate these grippers is derived from the release of residual stress in 3–27 nm thick films, did not require any wires, tethers, or batteries, and resulted in folding angles over 100° with folding radii as small as 765 nm. We developed and applied a finite element model to predict these folding angles. Finally, we demonstrated the capture of live mouse fibroblast cells in an array of grippers and individual red blood cells in untethered grippers which could be released from the substrate to illustrate the potential utility for in vivo operations.

Conventional and novel peripheral blood iron markers compared against bone marrow in Malawian children

AimIron deficiency is an important child health problem. Its diagnosis in areas of high infection exposure remains complicated as inflammation may interfere with the accuracy of peripheral iron markers. With...

Evaluation of the new red cell parameters on Beckman Coulter DxH800 in distinguishing iron deficiency anaemia from thalassaemia trait.

The new red blood cell (RBC) parameters such as reticulocyte haemoglobin content and percentage of hypochromic red cells or equivalent, although useful in the laboratory assessment of iron deficiency anaemia (IDA), are confounded by thalassaemia trait (TT). We aim to evaluate the new red cell parameters on the Beckman Coulter DxH800 in distinguishing between IDA and TT. A total of 246 normal subjects, 102 patients with IDA and 115 subjects with TT were accrued for the study. The parameters studied were red blood cell size factor (RSF), low haemoglobin density (LHD%), microcytic anaemia factor (MAF), standard deviation of conductivity of the nonreticulocyte population (SD-C-NRET) and unghosted cell (UGC). Comparison between groups was performed by Student's t-test, and the diagnostic performance was determined by receiver operating characteristic (ROC) curve analysis. Both the LHD% and RSF were significantly higher in IDA than TT, whereas MAF and SD-C-NRET were significantly lower. The SD-C-NRET showed the best diagnostic performance as a single parameter. A formula, [(RBC + Hb) × (HCT + SD-C-NRET)]/RDW-SD, was devised to distinguish between IDA and TT. With a cut-off value of 23, the area under the curve (AUC) was 0.995 (95% CI of 0.99-1.00), the sensitivity was 97%, and the specificity was 99.1%. The new RBC parameters on Beckman Coulter DxH800 provide useful information in distinguishing between IDA and TT, which is important for clinical decision-making and for streamlining laboratory testing. A new formula is devised that performs better than other discriminant functions in the literature.

Elevated red cell distribution width level is associated with oxidative stress and inflammation in a canine model of rapid atrial pacing

Atrial fibrillation (AF) is the most common clinically significant cardiac arrhythmia. The prevalence of AF has been increasing for the past few decades with the aging population [1]. The pathogenesis underlying AF is multi-factorial. Accumulating evidences suggest that oxidative stress and inflammation may play an important role in the pathogenesis and perpetuation of AF [2–6]. The red blood cell distributionwidth (RDW) reflects variability in the size of circulating red blood cells (RBCs) and is mostly used in the differential diagnosis of anemia. Recently, several studies showed the potential association of increased RDW levels with adverse cardiovascular events. Elevated RDW levels may also have been correlated with nonvalvular AF [7]. However, the potential mechanisms between elevated RDW and the development of AF are still unclear. In the present study, we aimed to assess whether elevated levels of RDW are associated with oxidative stress and inflammation markers in a canine model of rapid atrial pacing (RAP). In the present study, all animals were cared for and used in compliance with the Experimental Animal Administration Committee of Tianjin Medical University and the Tianjin Municipal Commission for ‘Experimental Animal Control’. For this study, 20 mongrel dogs of either gender were randomly divided into two groups: sham group and paced group, 10 dogs in each group. We used a previously described approach to induce and maintain sustained AF in our experimental animals [8]. The dogs were anesthetized with intravenous 3% sodium pentobarbital (30 mg · kg−1). After mechanical ventilation, under aseptic condition, a modified unipolar J pacing lead (St. Jude Medical, USA) was inserted via the right jugular vein and the distal end of the lead was positioned in the right atrium or right auricular appendage under fluoroscopy. The proximal end of the pacing lead was connected to a programmable pacemaker (Fudan University, China), which was implanted into a subcutaneous pocket in the neck. The dogs in the paced group were paced at 500 bpm (120-ms cycle length) with the 0.2-ms square-wave pulses at twice the threshold current for 2 weeks. The dogs in the sham group were also instrumented but without pacing. Electrocardiogram (ECG) was verified after 24 h in awake dogs to ensure continuous 1:1 atrial capture. Hemodynamics parameters were monitored by a multi-channel electrophysiological recorder (Hongtong TOP2001, China) at baseline and after 2 weeks of rapid atrial pacing (RAP). After the above treatment for 2 weeks, venous blood samples were obtained from the two groups of dogs, and RDW levels were analyzed using an automated hematology analyzer (Mindray BC6800, China). The serum levels of superoxide dismutase (SOD), malondialdehyde (MDA), Toll-like receptor 4 (TRL4) and interleukin-18 (IL-18) were measured by ELISA kit (Nanjing Jiancheng Bioengineering Institute, China). All animals were survived to the end of the experiment. There was no difference in gender, body weight, ventricular rate and blood pressure between the two groups whether at baseline and after 2 weeks of RAP (P N 0.05) (Table 1). Our study showed that the RDW level was increased apparently by RAP from 12.37% ± 1.48% to 14.83% ± 2.24% (P b 0.05). We investigated the circulating serum levels of SOD, MDA, TLR4 and IL-18 in the two groups and found that the levels of SOD, MDA, TLR4 and IL-18 were higher in the paced group compared to the sham group (P b 0.01) (Table 1). The serum levels of SOD, MDA, TLR4 and IL-18 had no correlation to RDW in the sham group (r = 0.014, P = 0.976; r = 0.479, P =0.276; r = 0.101, P = 0.830; r = 0.032, P = 0.946, respectively), whereas they were correlated to RDW levels (P b 0.05 or P b 0.01) in the paced group (Fig. 1). Several studies have shown that RDW, a laboratory measure of the variability of red blood cell sizes, is a strong independent predictor of increased morbidity and mortality in patients with cardiovascular disease [9–14]. Our recent study [15] indicated that RDWmay serve as a promising and useful marker for paroxysmal AF. Adamsson et al. [16] also showed that RDW was associated with incidence of AF independently of several cardiovascular, nutritional and hematological factors in a recent study of middle-aged subjects from the general population. However, there are limited data regarding the potential mechanisms between RDW and AF in animal models. The potential mechanism behind their relationship may result from a direct effect of changes in erythrocyte volume and function on the heart, or may reflect other pathophysiological processes acting

Effect of Microcytic Hypochromic Anemia and Parasitic Infestations on Stature in Adolescents

Bakground: Microcytic hypochromic anemia is the commonest form of iron deficiency anemia in adolescents. The occurrence of this type of anemia among adolescents is around 27% in developing countries. Clinical management should be based on a full knowledge of the prevalence of this disease in the age group mentioned. Subjects and Methods: The present study reported the distribution of this type of anemia across age, anthropometric guides, and parasitic infestations in a sample of 300 adolescents attending various schools in Giza region, Egypt. Red blood cell size and iron concentration were assessed by mean corpuscular volume, hemoglobin levels, serum ferritin and total iron binding capacity from a venous blood sample. The adolescent was considered to have the microcytic form of anemia when their mean corpuscular volume was below 80 femtoliters (fL). An adolescent with hypochromic anemia was defined as any subject with hemoglobin (Hb) below the WHO cutoff for age and sex: 12.0 g/dl for girls and for boys aged 12.5–14.99 years and 13.0 g/dl for boys aged ≥ 15 years. Also, hypochromic anemia included every subject having either serum iron 400 µg/dL. Results: The incidence of microcytic hypochromic anemia in this study was 53%. There were highly statistically significant differences between anemic and non-anemic groups as regards age and height (P 0.05). Signs of pallor were more common in adolescents suffering from microcytic hypochromic anemia. Subjects with a history of chronic conditions such as cardiac diseases, renal failure or cancer had a significantly higher incidence of anemia than adolescents who did not. Conclusion: It was concluded that the anemic group of adolescents enrolled in the study were susceptible to growth retardation. This type of anemia is more common in adolescents who do not have lunch, have a chronic disease or a parasitic infestation.

High Control, Fast Growth OEG-Based Dendron Synthesis via a Sequential Two-Step Process of Copper-Free Diazo Transfer and Click Chemistry

Dendrons up to generation 3 were quickly synthesized using two sequential steps of diazo transfer and click chemistry reactions. The building blocks for dendron synthesis were made by incorporating monodisperse oligoethylene glycol (OEG) chains of exact length onto diethyelenetriaminepentaacetic acid (DTPA)-derived moieties to obtain first-generation dendrons. Afterward, the amine groups of the first-generation core dendron were converted to azides by means of the diazo transfer reaction. The second- and third-generation dendrons were constructed using the copper-catalyzed azide–alkyne cycloaddition (CuAAC). Hemocompatibility studies including hemolysis, red blood cell morphology, cell count and size distribution, hemostasis, and complement system activation were performed to evaluate their safety in blood.

Clinical usefulness of measuring red blood cell distribution width in patients with systemic sclerosis

Red blood cell distribution width (RDW) is a biomarker quantifying the variability of red blood cell size in peripheral blood. Elevated RDW has been found to be an independent prognostic factor for cardiovascular events. SSc is characterized by generalized micro- and macroangiopathy. Our aim was to investigate RDW as a potential biomarker for the assessment of the severity of vascular involvement. One hundred and sixty-eight consecutive SSc patients--62 with dcSSc and 106 with lcSSc--were investigated at baseline and after 1-year of follow-up. Measurements in 93 patients with primary RP and 40 healthy subjects served as controls. The median RDW value of patients with SSc was higher [14.2% (25th-75th percentiles 13.5-14.8%) compared with the group of primary RP patients [13.9% (13.4-14.4%); P < 0.05) and healthy volunteers [13.6% (13.2-13.8%; P < 0.01]. dcSSc and anti-topoisomerase antibody-positive cases showed elevated RDW values compared with lcSSc and anti-topoisomerase antibody-negative cases (P < 0.05). RDW showed a positive correlation with inflammatory markers, including ESR (P < 0.05) and CRP (P < 0.05), and a negative correlation with forced vital capacity (P < 0.05) and diffusing capacity of the lung for carbon monoxide (DLCO) (P < 0.05) during the follow-up. An increase in RDW of >5% during follow-up was associated with an average 8.9% decrease in left ventricular ejection fraction (LVEF) and 7% in DLCO and these associations were independent of each other. RDW in SSc may represent an integrative measure of multiple pathological processes including extensive vasculopathy, fibrosis or ongoing inflammation. An increase in RDW may indicate an impairment of cardiorespiratory function.

Red blood cell in vitro quality and function is maintained after S‐303 pathogen inactivation treatment

Over the past decade there has been a growth in the development of pathogen reduction technologies to protect the blood supply from emerging pathogens. This development has proven to be difficult for red blood cells (RBCs). However the S-303 system has been shown to effectively inactivate a broad spectrum of pathogens, while maintaining RBC quality. A paired three-arm study was performed to compare the in vitro quality of S-303-treated RBCs with RBCs stored at room temperature (RT) for the duration of the treatment (18-20 hr) and control RBCs stored at 2 to 6°C. Products were sampled weekly over 42 days of storage (n = 10) and tested using an array of in vitro assays to measure quality, metabolism, and functional variables. During S-303 treatment there was a slight loss of RBCs and hemoglobin (Hb < 5 g). Hemolysis, glucose consumption, and potassium release were similar in all groups during the 42 days of storage. S-303-treated RBCs had a significantly lower lactate concentration and pH compared to the paired controls. The S-303-treated RBCs had significantly higher adenosine triphosphate than the RT and control RBCs. There was a significant loss of 2,3-diphosphoglycerate in the S-303-treated products, which was also observed in the RT RBCs. Flow cytometry analysis demonstrated similar RBC size, morphology, expression of CD47, and glycophorin A in all groups. RBCs treated with S-303 for pathogen reduction had similar in vitro properties to the paired controls and were within transfusion guidelines.

Global analysis of induced transcription factors and cofactors identifies Tfdp2 as an essential coregulator during terminal erythropoiesis

Key transcriptional regulators of terminal erythropoiesis, such as GATA-binding factor 1 (GATA1) and T-cell acute lymphocytic leukemia protein 1 (TAL1), have been well characterized, but transcription factors and cofactors and their expression modulations have not yet been explored on a global scale. Here, we use global gene expression analysis to identify 28 transcription factors and 19 transcriptional cofactors induced during terminal erythroid differentiation whose promoters are enriched for binding by GATA1 and TAL1. Utilizing protein-protein interaction databases to identify cofactors for each transcription factor, we pinpoint several co-induced pairs, of which E2f2 and its cofactor transcription factor Dp-2 (Tfdp2) were the most highly induced. TFDP2 is a critical cofactor required for proper cell cycle control and gene expression. GATA1 and TAL1 are bound to the regulatory regions of Tfdp2 and upregulate its expression and knockdown of Tfdp2 results in significantly reduced rates of proliferation as well as reduced upregulation of many erythroid-important genes. Loss of Tfdp2 also globally inhibits the normal downregulation of many E2F2 target genes, including those that regulate the cell cycle, causing cells to accumulate in S phase and resulting in increased erythrocyte size. Our findings highlight the importance of TFDP2 in coupling the erythroid cell cycle with terminal differentiation and validate this study as a resource for future work on elucidating the role of diverse transcription factors and coregulators in erythropoiesis.

Preliminary study of the influence of red blood cells size on the determinism of the breed in cattle.

This study was carried out on five cattle groups, local, cross, Prim'Holstein, Montbeliard, and Brown of the Alps, in order to study the influence of breed on erythrocytes diameter. For each breed, blood samples were taken from 15 adult females by jugular venipuncture; blood smears were made on slides immediately after the blood collection and stained according to the method of May-Gründwald Giemsa. Morphometric study was realized using the OPTIKA Pro Vision software. The statistical analysis was assessed by using the descriptive boxplots test and ANOVA. The size of red blood cells is greater in the imported Brown of the Alps breed (5,32 ± 0,19) and also in our local breed (5,23 ± 0,10), whereas they were smaller in the Montbeliard breed (4,79 ± 0,21). This investigation allowed us to show that from a drop of blood we can have an idea of the bovine breeds, taking into account the size of the erythrocytes.

Investigation of Blood Flow Analysis and Red Blood Cell Aggregation

This work aims to develop a method for quantitatively analyzing red blood cell (RBC) aggregates under controlled flow conditions. Images of experiments are captured and processed in order to quantify aggregation. The experimental setup consists of RBC suspensions in blood plasma entrained by a phosphate-buffered saline solution in a 110 × 60μm polydimethylsiloxane microchannel. The experiments are performed by varying the hematocrit (5, 10, and 15%) and the flow rate (Q=5 and 10μl/hr) in order to observe the effect of shear rate on RBC aggregation. Microchannel dimensions as well as fluid flow rates are determined using numerical simulations. The flow is visualized using a highspeed camera coupled to a micro particle image velocimetry system. Videos obtained with the high-speed camera are processed using a MATLAB program, with each frame analyzed separately. RBC aggregates are detected based on the image intensities and the connectivity between RBCs, using image processing techniques. The average aggregate size and distribution of RBCs for various aggregate sizes are determined for each of the shear rates and hematocrits. These aggregates are shown to be larger at low flow rates where the shear rate is small. Results from tests performed at high hematocrits also show larger RBC aggregates.

Prevention and Treatment of Thrombosis in Pediatric and Congenital Heart Disease

Thrombosis has long been recognized as a potentially life-threatening complication in children with congenital heart disease (CHD), children with acquired heart disease, and in adults with CHD. High-risk groups include patients with shunt- dependent single ventricles (shunt thrombosis, 8%–12%; 4%

The significant blood resistance to lung nitric oxide transfer lies within the red cell

The lung nitric oxide (NO) diffusing capacity (DlNO) mainly reflects alveolar-capillary membrane conductance (Dm). However, blood resistance has been shown in vitro and in vivo. To explore whether this resistance lies in the plasma, the red blood cell (RBC) membrane, or in the RBC interior, we measured the NO diffusing capacity (Dno) in a membrane oxygenator circuit containing ∼1 liter of horse or human blood exposed to 14 parts per million NO under physiological conditions on 7 separate days. We compared results across a 1,000-fold change in extracellular diffusivity using dextrans, plasma, and physiological salt solution. We halved RBC surface area by comparing horse and human RBCs. We altered the diffusive resistance of the RBC interior by adding sodium nitrite converting oxyhemoglobin to methemoglobin. Neither increased viscosity nor reduced RBC size reduced Dno. Adding sodium nitrite increased methemoglobin and was associated with a steady fall in Dno (P < 0.001). Similar results were obtained at NO concentrations found in vivo. The RBC interior appears to be the site of the blood resistance.