Slit-flow ektacytometry: Laser diffraction in a slit rheometer

Sex-Specific Differences of Adenosine Triphosphate Levels in Red Blood Cells Isolated From ApoE/LDLR Double-Deficient Mice

In this study for the first time, we investigated the correlation between sex-specific differences in adenosine triphosphate (ATP) levels in red blood cells (RBCs) and their mechanical, biochemical, and morphological alterations during the progression of atherosclerosis in ApoE/LDLR double-deficient (ApoE/LDLR^−/−) mice. Our results indicate that both sex and age affect alterations in RBCs of both ApoE/LDLR^−/− and C57BL/6J mice. When compared with male RBCs, female RBCs were characterized by lower basal ATP and mean corpuscular hemoglobin concentration (MCHC), higher hemoglobin concentration (HGB), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), deformability, and phosphatidylserine (PS) exposure levels, regardless of age in both, ApoE/LDLR^−/− and C57BL/6J mice. ApoE/LDLR^−/− mice compared with age-matched controls showed lower basal ATP levels regardless of age and sex. Intracellular ATP level of RBCs was decreased solely in senescent female C57BL/6J mice, while it was elevated in males. Basal extracellular ATP levels were 400 times lower than corresponding intracellular level. In conclusion, basal ATP levels, RBC morphology, deformability, PS exposure levels alterations are sex-dependent in mice. Changes in basal ATP levels were correlated with PS exposure and trends of changes in MCV. Trends of changes of the most RBC parameters were similar in both sexes of ApoE/LDLR^−/− mice compared with age-matched controls; however, their kinetics and levels vary greatly between different stages of disease progression.

Different Involvement of Band 3 in Red Cell Deformability and Osmotic Fragility-A Comparative GP.Mur Erythrocyte Study

GP.Mur is a clinically important red blood cell (RBC) phenotype in Southeast Asia. The molecular entity of GP.Mur is glycophorin B-A-B hybrid protein that promotes band 3 expression and band 3–AQP1 interaction, and alters the organization of band 3 complexes with Rh/RhAG complexes. GP.Mur+ RBCs are more resistant to osmotic stress. To explore whether GP.Mur+ RBCs could be structurally more resilient, we compared deformability and osmotic fragility of fresh RBCs from 145 adults without major illness (47% GP.Mur). We also evaluated potential impacts of cellular and lipid factors on RBC deformability and osmotic resistivity. Contrary to our anticipation, these two physical properties were independent from each other based on multivariate regression analyses. GP.Mur+ RBCs were less deformable than non-GP.Mur RBCs. We also unexpectedly found 25% microcytosis in GP.Mur+ female subjects (10/40). Both microcytosis and membrane cholesterol reduced deformability, but the latter was only observed in non-GP.Mur and not GP.Mur+ normocytes. The osmotic fragility of erythrocytes was not affected by microcytosis; instead, larger mean corpuscular volume (MCV) increased the chances of hypotonic burst. From comparison with GP.Mur+ RBCs, higher band 3 expression strengthened the structure of RBC membrane and submembranous cytoskeletal networks and thereby reduced cell deformability; stronger band 3–AQP1 interaction additionally supported osmotic resistance. Thus, red cell deformability and osmotic resistivity involve distinct structural–functional roles of band 3.

Microfluidic capillary networks are more sensitive than ektacytometry to the decline of red blood cell deformability induced by storage

Ektacytometry has been the primary method for evaluating deformability of red blood cells (RBCs) in both research and clinical settings. This study was designed to test the hypothesis that the flow of RBCs through a network of microfluidic capillaries could provide a more sensitive assessment of the progressive impairment of RBC deformability during hypothermic storage than ektacytometry. RBC units (n = 9) were split in half, with one half stored under standard (normoxic) conditions and the other half stored hypoxically, for up to 6 weeks. RBC deformability was measured weekly using two microfluidic devices, an artificial microvascular network (AMVN) and a multiplexed microcapillary network (MMCN), and two commercially available ektacytometers (RheoScan-D and LORRCA). By week 6, the elongation indexes measured with RheoScan-D and LORRCA decreased by 5.8–7.1% (5.4–6.9% for hypoxic storage). Over the same storage duration, the AMVN perfusion rate declined by 27.5% (24.5% for hypoxic) and the MMCN perfusion rate declined by 49.0% (42.4% for hypoxic). Unlike ektacytometry, both AMVN and MMCN measurements showed statistically significant differences between the two conditions after 1 week of storage. RBC morphology deteriorated continuously with the fraction of irreversibly-damaged (spherical) cells increasing significantly faster for normoxic than for hypoxic storage. Consequently, the number of MMCN capillary plugging events and the time MMCN capillaries spent plugged was consistently lower for hypoxic than for normoxic storage. These data suggest that capillary networks are significantly more sensitive to both the overall storage-induced decline of RBC deformability, and to the differences between the two storage conditions, than ektacytometry.

Surface area-to-volume ratio, not cellular viscoelasticity, is the major determinant of red blood cell traversal through small channels

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.

The Effects of Different Signaling Pathways in Adenylyl Cyclase Stimulation on Red Blood Cells Deformability

Signaling pathways of red blood cells’ (RBCs) micromechanics regulation, which are responsible for maintaining microcirculation, constitute an important property of RBC physiology. Selective control over these processes may serve as an indispensable tool for correction of hemorheological disorders, which accompany a number of systemic diseases (diabetes mellitus I&II, arterial hypertension, malaria, etc.). Activation of certain pathways involving adenylyl cyclase may provide fast adaptive regulation of RBC deformability (RBC-D). However the specific molecular conditions of intracellular signal transduction in mediating RBC microrheological properties at adenylyl cyclase stimulation remain unclear. In this paper, we present the results of the in vitro study of the effects of different signaling pathways in adenylyl cyclase stimulation on RBC-D. We studied (1) the direct stimulation of adenylyl cyclase with forskolin; (2) non-selective adrenoreceptor stimulation with epinephrine; (3) β2-adrenoreceptor agonist metaproterenol; (4) membrane-permeable analog of cAMP (dibutyryl-cAMP). Using laser ektacytometry, we observed a concentration-dependent increase in RBC-D for all studied effectors. The EC50 values for each substance were estimated to be in the range of 1–100 μM depending on the shear stress applied to the RBC suspension. The results can serve as an evidence of adenylyl cyclase signaling cascade involvement in the regulation of RBC micromechanical properties presenting a complex molecular pathway for fast increase of microcirculation efficiency in case of corresponding physiologic metabolic demands of the organism, e.g., during stress or physical activity. Further studies of this molecular system will reveal new knowledge which may improve the quality of medical treatment of hemorheological disorders.

Multimodal analysis of Plasmodium knowlesi ‐infected erythrocytes reveals large invaginations, swelling of the host cell, and rheological defects

The simian parasite Plasmodium knowlesi causes severe and fatal malaria infections in humans, but the process of host cell remodelling that underpins the pathology of this zoonotic parasite is only poorly understood. We have used serial block‐face scanning electron microscopy to explore the topography of P. knowlesi‐infected red blood cells (RBCs) at different stages of asexual development. The parasite elaborates large flattened cisternae (Sinton Mulligan's clefts) and tubular vesicles in the host cell cytoplasm, as well as parasitophorous vacuole membrane bulges and blebs, and caveolar structures at the RBC membrane. Large invaginations of host RBC cytoplasm are formed early in development, both from classical cytostomal structures and from larger stabilised pores. Although degradation of haemoglobin is observed in multiple disconnected digestive vacuoles, the persistence of large invaginations during development suggests inefficient consumption of the host cell cytoplasm. The parasite eventually occupies ~40% of the host RBC volume, inducing a 20% increase in volume of the host RBC and an 11% decrease in the surface area to volume ratio, which collectively decreases the ability of the P. knowlesi‐infected RBCs to enter small capillaries of a human erythrocyte microchannel analyser. Ektacytometry reveals a markedly decreased deformability, whereas correlative light microscopy/scanning electron microscopy and python‐based skeleton analysis (Skan) reveal modifications to the surface of infected RBCs that underpin these physical changes. We show that P. knowlesi‐infected RBCs are refractory to treatment with sorbitol lysis but are hypersensitive to hypotonic lysis. The observed physical changes in the host RBCs may underpin the pathology observed in patients infected with P. knowlesi.

Effect of shear-induced platelet activation on red blood cell aggregation

Mechanical shear stress is one of the important factors for platelet activation. Although shear stress has been frequently utilized in many applications of diagnostic bio-equipment, there has been little consideration as to whether shear stress induces platelet activation and consequently alters hemorheological characteristics. Therefore, we investigated the effect of shear-induced platelet activation on red blood cell (RBC) aggregation. The hypothesis of the present research is as follows: Platelets activated by high shear stress secrete substances, which can affect hemorheological characteristics to promote RBC aggregation. In our study, an increase in RBC aggregation indices (critical shear stress (CSS) and aggregation index (AI)) by shear-induced platelet activation was observed. Significantly, an increase of 19% in CSS was observed. However, deformability remained unchanged. These phenomena could be a result of the increased cellular adhesion force on RBC membranes due to secreted substances from activated platelets. Therefore, since high shear application results in the unexpected effect on RBC aggregation, conditions for shear application in diagnostic bio-equipment are to be carefully determined.

Cycling Exercise Training Alleviates Hypoxia-Impaired Erythrocyte Rheology

PURPOSE

Physical exercise or hypoxic exposure influences hemorheology and acid-base homeostasis. Band 3 protein in erythrocytes modulates cells' rheological properties and anion transport ability. This study investigated how cycling aerobic interval training (AIT) and moderate continuous training (MCT) affect the rheological function and band 3 activity of erythrocytes under hypoxic exercise (HE) stress.

METHODS

Forty-five healthy sedentary men were randomized to engage in either AIT (3-min intervals at 40% and 80% of VO2max, n = 15) or MCT (sustained 60% of VO2max, n = 15) on a bicycle ergometer for 30 min · d(-1) (5 d · wk(-1) for 5 wk) or to a control group that did not perform any exercise (n = 15). Erythrocyte rheological responses to HE (100 W under 12% O2 for 30 min) were determined before and after various regimens.

RESULTS

Acute HE increased the aggregation and osmotic fragility of erythrocytes, decreased the deformability of erythrocytes, and depressed erythrocyte band 3 activity, as indicated by lowered anion transport ability. Following 5 wk of intervention, the AIT group exhibited maximal work rate and VO2max higher than those in the MCT and control groups. Moreover, cycling AIT and MCT diminished the extent of erythrocytes' enhanced aggregation and osmotic fragility and reduced their deformability and band 3 activity caused by HE. Additionally, erythrocyte band 3 activity was directly related to erythrocyte deformability and inversely related to erythrocyte aggregation and osmotic fragility.

CONCLUSIONS

Cycling AIT is superior to cycling MCT in enhancing aerobic capacity. Moreover, either cycling AIT or MCT effectively alleviates HE-evoked impairments of erythrocyte rheological characteristics and band 3 function.

Deformability based sorting of red blood cells improves diagnostic sensitivity for malaria caused by Plasmodium falciparum

The loss of red blood cell (RBC) deformability is part of the pathology of many diseases. In malaria caused by Plasmodium falciparum infection, metabolism of hemoglobin by the parasite results in progressive reduction in RBC deformability that is directly correlated with the growth and development of the parasite. The ability to sort RBCs based on deformability therefore provides a means to isolate pathological cells and to study biochemical events associated with disease progression. Existing methods have not been able to sort RBCs based on deformability or to effectively enrich for P. falciparum infected RBCs at clinically relevant concentrations. Here, we develop a method to sort RBCs based on deformability and demonstrate the ability to enrich the concentration of ring-stage P. falciparum infected RBCs (Pf-iRBCs) by >100× from clinically relevant parasitemia (<0.01%). Deformability based sorting of RBCs is accomplished using ratchet transport through asymmetrical constrictions using oscillatory flow. This mechanism provides dramatically improved selectivity over previous biophysical methods by preventing the accumulation of cells in the filter microstructure to ensure that consistent filtration forces are applied to each cell. We show that our approach dramatically improves the sensitivity of malaria diagnosis performed using both microscopy and rapid diagnostic test by converting samples with difficult-to-detect parasitemia (<0.01%) into samples with easily detectable parasitemia (>0.1%).

Deformability measurement of red blood cells using a microfluidic channel array and an air cavity in a driving syringe with high throughput and precise detection of subpopulations

Red blood cell (RBC) deformability has been considered a potential biomarker for monitoring pathological disorders. High throughput and detection of subpopulations in RBCs are essential in the measurement of RBC deformability. In this paper, we propose a new method to measure RBC deformability by evaluating temporal variations in the average velocity of blood flow and image intensity of successively clogged RBCs in the microfluidic channel array for specific time durations. In addition, to effectively detect differences in subpopulations of RBCs, an air compliance effect is employed by adding an air cavity into a disposable syringe. The syringe was equally filled with a blood sample (V(blood) = 0.3 mL, hematocrit = 50%) and air (V(air) = 0.3 mL). Owing to the air compliance effect, blood flow in the microfluidic device behaved transiently depending on the fluidic resistance in the microfluidic device. Based on the transient behaviors of blood flows, the deformability of RBCs is quantified by evaluating three representative parameters, namely, minimum value of the average velocity of blood flow, clogging index, and delivered blood volume. The proposed method was applied to measure the deformability of blood samples consisting of homogeneous RBCs fixed with four different concentrations of glutaraldehyde solution (0%-0.23%). The proposed method was also employed to evaluate the deformability of blood samples partially mixed with normal RBCs and hardened RBCs. Thereafter, the deformability of RBCs infected by human malaria parasite Plasmodium falciparum was measured. As a result, the three parameters significantly varied, depending on the degree of deformability. In addition, the deformability measurement of blood samples was successfully completed in a short time (∼10 min). Therefore, the proposed method has significant potential in deformability measurement of blood samples containing hematological diseases with high throughput and precise detection of subpopulations in RBCs.

Sub-population analysis of deformability distribution in heterogeneous red blood cell population

We present a method for sub-population analysis of deformability distribution using single-cell microchamber array (SiCMA) technology. It is a unique method allowing the correlation of overall cellular characteristics with surface and cytosolic characteristics to define the distribution of individual cellular characteristics in heterogeneous cell populations. As a proof of principle, reticulocytes, the immature sub-population of red blood cells (RBC), were recognized from RBC population by a surface marker and different characteristics on deformability between these populations were characterized. The proposed technology can be used in a variety of applications that would benefit from the ability to measure the distribution of cellular characteristics in complex populations, especially important to define hematologic disorders.

Inability to maintain GSH pool in G6PD-deficient red cells causes futile AMPK activation and irreversible metabolic disturbance

AIMS

Glucose 6-phosphate dehydrogenase (G6PD) is essential for maintenance of nicotinamide dinucleotide hydrogen phosphate (NADPH) levels and redox homeostasis. A number of drugs, such as antimalarial drugs, act to induce reactive oxygen species and hemolytic crisis in G6PD-deficient patients. We used diamide (DIA) to mimic drug-induced oxidative stress and studied how these drugs affect cellular metabolism using a metabolomic approach.

RESULTS

There are a few differences in metabolome between red blood cells (RBCs) from normal and G6PD-deficient individuals. DIA causes modest changes in normal RBC metabolism. In contrast, there are significant changes in various biochemical pathways, namely glutathione (GSH) metabolism, purine metabolism, and glycolysis, in G6PD-deficient cells. GSH depletion is concomitant with a shift in energy metabolism. Adenosine monophosphate (AMP) and adenosine diphosphate (ADP) accumulation activates AMP protein kinase (AMPK) and increases entry of glucose into glycolysis. However, inhibition of pyruvate kinase (PK) reduces the efficacy of energy production. Metabolic changes and protein oxidation occurs to a greater extent in G6PD-deficient RBCs than in normal cells, leading to severe irreversible loss of deformability of the former.

INNOVATION AND CONCLUSION

Normal and G6PD-deficient RBCs differ in their responses to oxidants. Normal cells have adequate NADPH regeneration for maintenance of GSH pool. In contrast, G6PD-deficient cells are unable to regenerate enough NADPH under a stressful situation, and switch to biosynthetic pathway for GSH supply. Rapid GSH exhaustion causes energy crisis and futile AMPK activation. Our findings suggest that drug-induced oxidative stress differentially affects metabolism and metabolite signaling in normal and G6PD-deficient cells. It also provides an insight into the pathophysiology of acute hemolytic anemia in G6PD-deficient patients.

Biomechanical properties of red blood cells in health and disease towards microfluidics

Red blood cells (RBCs) possess a unique capacity for undergoing cellular deformation to navigate across various human microcirculation vessels, enabling them to pass through capillaries that are smaller than their diameter and to carry out their role as gas carriers between blood and tissues. Since there is growing evidence that red blood cell deformability is impaired in some pathological conditions, measurement of RBC deformability has been the focus of numerous studies over the past decades. Nevertheless, reports on healthy and pathological RBCs are currently limited and, in many cases, are not expressed in terms of well-defined cell membrane parameters such as elasticity and viscosity. Hence, it is often difficult to integrate these results into the basic understanding of RBC behaviour, as well as into clinical applications. The aim of this review is to summarize currently available reports on RBC deformability and to highlight its association with various human diseases such as hereditary disorders (e.g., spherocytosis, elliptocytosis, ovalocytosis, and stomatocytosis), metabolic disorders (e.g., diabetes, hypercholesterolemia, obesity), adenosine triphosphate-induced membrane changes, oxidative stress, and paroxysmal nocturnal hemoglobinuria. Microfluidic techniques have been identified as the key to develop state-of-the-art dynamic experimental models for elucidating the significance of RBC membrane alterations in pathological conditions and the role that such alterations play in the microvasculature flow dynamics.

Impaired red blood cell deformability after transfusion of stored allogeneic blood but not autologous salvaged blood in cardiac surgery patients

BACKGROUND

Both cardiopulmonary bypass (CPB) and red blood cell (RBC) storage are associated with detrimental changes in RBC structure and function that may adversely affect tissue oxygen delivery. We tested the hypothesis that in cardiac surgery patients, RBC deformability and aggregation are minimally affected by CPB with autologous salvaged blood alone but are negatively affected by the addition of stored allogeneic blood.

METHODS

In this prospective cohort study, 32 patients undergoing cardiac surgery with CPB were divided into 3 groups by transfusion status: autologous salvaged RBCs alone (Auto; n = 12), autologous salvaged RBCs + minimal (<5 units) stored allogeneic RBCs (Auto+Allo min; n = 10), and autologous salvaged RBCs + moderate (≥5 units) stored allogeneic RBCs (Auto+Allo mod; n = 10). Ektacytometry was used to measure RBC elongation index (deformability) and critical shear stress (aggregation) before, during, and for 3 days after surgery.

RESULTS

In the Auto group, RBC elongation index did not change significantly from the preoperative baseline. In the Auto+Allo min group, mean elongation index decreased from 32.31 ± 0.02 (baseline) to 30.47 ± 0.02 (nadir on postoperative day 1) (P = 0.003, representing a 6% change). In the Auto+Allo mod group, mean elongation index decreased from 32.7 ± 0.02 (baseline) to 28.14 ± 0.01 (nadir on postoperative day 1) (P = 0.0001, representing a 14% change). Deformability then dose-dependently recovered toward baseline over the first 3 postoperative days. Changes in aggregation were unrelated to transfusion (no difference among groups). For the 3 groups combined, mean critical shear stress decreased from 359 ± 174 mPa to 170 ± 141 mPa (P = 0.01, representing a 54% change), with the nadir at the end of surgery and returned to baseline by postoperative day 1.

CONCLUSIONS

In cardiac surgery patients, transfusion with stored allogeneic RBCs, but not autologous salvaged RBCs, is associated with a decrease in RBC cell membrane deformability that is dose-dependent and may persist beyond 3 postoperative days. These findings suggest that autologous salvaged RBCs may be of higher quality than stored RBCs, since the latter are subject to the so-called storage lesions.

Decreased erythrocyte deformability after transfusion and the effects of erythrocyte storage duration

BACKGROUND

Erythrocyte cell membranes undergo morphologic changes during storage, but it is unclear whether these changes are reversible. We assessed erythrocyte cell membrane deformability in patients before and after transfusion to determine the effects of storage duration and whether changes in deformability are reversible after transfusion.

METHODS

Sixteen patients undergoing posterior spinal fusion surgery were studied. Erythrocyte deformability was compared between those who required moderate transfusion (≥ 5 units erythrocytes) and those who received minimal transfusion (0-4 units erythrocytes). Deformability was measured in samples drawn directly from the blood storage bags before transfusion and in samples drawn from patients before and after transfusion (over 3 postoperative days). In samples taken from the blood storage bags, we compared deformability of erythrocytes stored for a long duration (≥ 21 days), those stored for a shorter duration (<21 days), and cell-salvaged erythrocytes. Deformability was assessed quantitatively using the elongation index (EI) measured by ektacytometry, a method that determines the ability for the cell to elongate when exposed to shear stress.

RESULTS

Erythrocyte deformability was significantly decreased from the preoperative baseline in patients after moderate transfusion (EI decreased by 12% ± 4% to 20% ± 6%; P = 0.03) but not after minimal transfusion (EI decreased by 3% ± 1% to 4% ± 1%; P = 0.68). These changes did not reverse over 3 postoperative days. Deformability was significantly less in erythrocytes stored for ≥ 21 days (EI = 0.28 ± 0.02) than in those stored for <21 days (EI = 0.33 ± 0.02; P = 0.001) or those drawn from patients preoperatively (EI = 0.33 ± 0.02; P = 0.001). Cell-salvaged erythrocytes had intermediate deformability (EI = 0.30 ± 0.03) that was greater than that of erythrocytes stored ≥ 21 days (P = 0.047), but less than that of erythrocytes stored <21 days (P = 0.03).

CONCLUSIONS

The findings demonstrate that increased duration of erythrocyte storage is associated with decreased cell membrane deformability and that these changes are not readily reversible after transfusion.

Effects of Hyul-Bu-Chuke-Tang on Erythrocyte Deformability and Cerebrovascular CO(2) Reactivity in Normal Subjects

Aim. Hyul-bu-chuke-tang (HCEt) is a well-known traditional herbal medicine that is used for the treatment of ischemic cerebrovascular disorders. We investigated the acute effects of HCEt on erythrocyte deformability and cerebrovascular CO₂ reactivity (CVR) in healthy male subjects. Materials and Methods. We examined erythrocyte deformability in an HCEt group (n = 14) and a control group (n = 10). CVR was measured using hyperventilation-induced CO₂ reactivity of the middle cerebral artery and transcranial Doppler (TCD) in the HCEt group (n = 11). A historical control group (n = 10) of CVR measurements was also created from our previous study. All measurements were performed prior to and 1, 2, and 3 hours after HCEt administration. Results. HCEt significantly improved erythrocyte deformability 1 hour after administration compared to the control group (2.9 ± 1.1% versus −0.6 ± 1.0%, P = 0.034). HCEt significantly improved the CVR 2 hours after administration compared to the historical control group (9.1 ± 4.0% versus −8.1 ± 4.1%, P = 0.007). The mean blood pressure and pulse rate did not vary from baseline values in either group. Conclusions. We demonstrated that HCEt improved erythrocyte deformability and CVR. Our findings suggest that an improvement in erythrocyte deformability contributes to HCEt's effect on cerebral microcirculation.

Deformation measurement of individual cells in large populations using a single-cell microchamber array chip

We analyze the deformability of individual red blood cells (RBCs) using SiCMA technology. Our approach is adequate to quickly measure large numbers of individual cells in heterogeneous populations. Individual cells are trapped in a large-scale array of micro-wells, and dielectrophoretic (DEP) force is applied to deform the cells. The simple structures of micro-wells and DEP electrodes facilitate the analysis of thousands of RBCs in parallel. This unique method allows the correlation of red cell deformation with cell surface and cytosolic characteristics to define the distribution of individual cellular characteristics in heterogeneous populations.

Exertional periodic breathing potentiates erythrocyte rheological dysfunction by elevating pro-inflammatory status in patients with anemic heart failure

BACKGROUND

Exertional periodic breathing (EPB) or anemia is associated with an adverse prognosis in advanced heart failure (HF). The disturbed rheological properties of erythrocytes may contribute to circulatory disorders. This study investigated whether EPB with/without anemia influences rheological/hemodynamic functions in patients with HF.

METHODS

According to the WHO criteria for anemia, 168 HF patients were divided into six groups: non (N)-anemic with (n=27)/without (n=56) EPB, light (L)-anemic with (n=17)/without (n=21) EPB, and moderate/several (M/S)-anemic with (n=21)/without (n=26) EPB groups. These HF patients and 30 healthy counterparts performed an incremental exercise test using a bicycle ergometer. Rheological and hemodynamic characteristics were determined by slit-flow ektacytometer and bioreactance-based device/near infrared spectrometer, respectively.

RESULTS

In the HF patients with EPB, both L- and M/S-anemic groups exhibited 1) higher plasma myeloperoxidase/interleukin-6 concentrations, 2) more blood senescent/spherical erythrocyte counts, 3) larger aggregability and smaller deformability of erythrocytes under shear flows, 4) higher systemic vascular resistance, which was accompanied by smaller amounts of blood distributed to cerebral/muscular tissues during exercise, 5) less VO(2peak) and ventilatory efficiency, and 6) lower Short Form-36 physical/mental component scores and higher Minnesota Living with HF questionnaire score than N-anemic group. Additionally, plasma myeloperoxidase/interleukin-6 levels were directly related to erythrocyte aggregability and inversely related to erythrocyte deformability. However, there were no significant differences in pro-inflammatory factors, rheological/hemodynamic properties, and aerobic capacity between L- and N-anemic groups in the HF patients without EPB.

CONCLUSION

EPB potentiates anemia-related rheological/hemodynamic dysfunctions by elevating pro-inflammatory status, reducing physical fitness in patients with HF.

Diffraction pattern study for cell type identification

This paper presents our study regarding diffracted intensity distribution in Fresnel and Fraunhofer approximation from different cell types. Starting from experimental information obtained through digital holographic microscopy, we modeled the cell shapes as oblate spheroids and built their phase-only transmission functions. In Fresnel approximation, the experimental and numerical diffraction patterns from mature and immature red blood cells have complementary central intensity values at different distances. The Fraunhofer diffraction patterns of deformed red blood cells were processed in the reciprocal space where, the isoamplitude curves were formed independently for each degree of cell deformation present within every sample; the values on each separate isoamplitude curve are proportional with the percentage of the respective cell type within the sample.

Analysis of light scattering by red blood cells in ektacytometry using global pattern fitting

Ektacytometry measures the shape of red blood cells under shear stress by analyzing the diffraction pattern of laser light passing through a thin layer of suspended cells. Here we model the diffraction pattern using a combination of Bessel and anomalous scattering functions, and employ a global pattern-fitting technique over nine different shear stresses to determine the separate mechanical properties of normal and non-deformable cells. This technique is capable of yielding the correct elongation index of the normal cells over a range of shear stresses even when they are mixed with as much as 50% non-deformable cells. Additionally, the relative concentrations of normal and non-deformable cells can be determined.

Hypoxic exercise training causes erythrocyte senescence and rheological dysfunction by depressed Gardos channel activity

Despite enhancing cardiopulmonary and muscular fitness, the effect of hypoxic exercise training (HE) on hemorheological regulation remains unclear. This study investigates how HE modulates erythrocyte rheological properties and further explores the underlying mechanisms in the hemorheological alterations. Twenty-four sedentary males were randomly divided into hypoxic (HE; n = 12) and normoxic (NE; n = 12) exercise training groups. The subjects were trained on 60% of maximum work rate under 15% (HE) or 21% (NE) O2condition for 30 min daily, 5 days weekly for 5 wk. The results demonstrated that HE 1) downregulated CD47 and CD147 expressions on erythrocytes, 2) decreased actin and spectrin contents in erythrocytes, 3) reduced erythrocyte deformability under shear flow, and 4) diminished erythrocyte volume changed by hypotonic stress. Treatment of erythrocytes with H2O2that mimicked in vivo prooxidative status resulted in the cell shrinkage, rigidity, and phosphatidylserine exposure, whereas HE enhanced the eryptotic responses to H2O2. However, HE decreased the degrees of clotrimazole to blunt ionomycin-induced shrinkage, rigidity, and cytoskeleton breakdown of erythrocytes, referred to as Gardos effects. Reduced erythrocyte deformability by H2O2was inversely related to the erythrocyte Gardos effect on the rheological function. Conversely, NE intervention did not significantly change resting and exercise erythrocyte rheological properties. Therefore, we conclude that HE rather than NE reduces erythrocyte deformability and volume regulation, accompanied by an increase in the eryptotic response to oxidative stress. Simultaneously, this intervention depresses Gardos channel-modulated erythrocyte rheological functions. Results of this study provide further insight into erythrocyte senescence induced by HE.

Assessment of the hemorheological profile of koala and echidna

Koala, a marsupial, and echidna, a monotreme, are mammals native to Australia. Blood viscosity (62.5-1250s(-1)), red blood cell (RBC) deformability, RBC aggregation, aggregability and surface charge, and hematological parameters were measured in blood samples from six koalas and six echidnas and compared to adult human blood. Koala had the largest RBC mean cell volume (107.7+/-2.6fl) compared to echidna (81.3+/-2.6fl) and humans (88.4+/-1.2fl). Echidna blood exhibited the highest viscosity over the entire range of shear rates. Echidna RBC were significantly less deformable than koala RBC but more deformable than human RBC. Echidna RBC had significantly lower aggregability (i.e., aggregation in standardized dextran medium) than koala or human RBC, while aggregation in autologous plasma was similar for the three species. Erythrocyte surface charge as indexed by RBC electrophoretic mobility was similar for human and echidna cells but was 40% lower for koala RBC. Data obtained during this preliminary study indicate that koala and echidna have distinct hemorheological characteristics; investigation of these properties may reveal patterns relevant to specific behavioral and physiological features of these animals.

Immune and hemorheological changes in chronic fatigue syndrome

Background

Chronic Fatigue Syndrome (CFS) is a multifactorial disorder that affects various physiological systems including immune and neurological systems. The immune system has been substantially examined in CFS with equivocal results, however, little is known about the role of neutrophils and natural killer (NK) phenotypes in the pathomechanism of this disorder. Additionally the role of erythrocyte rheological characteristics in CFS has not been fully expounded. The objective of this present study was to determine deficiencies in lymphocyte function and erythrocyte rheology in CFS patients.

Methods

Flow cytometric measurements were performed for neutrophil function, lymphocyte numbers, NK phenotypes (CD56^dimCD16⁺ and CD56^brightCD16^-) and NK cytotoxic activity. Erythrocyte aggregation, deformability and fibrinogen levels were also assessed.

Results

CFS patients (n = 10) had significant decreases in neutrophil respiratory burst, NK cytotoxic activity and CD56^brightCD16^- NK phenotypes in comparison to healthy controls (n = 10). However, hemorheological characteristic, aggregation, deformability, fibrinogen, lymphocyte numbers and CD56^dimCD16⁺ NK cells were similar between the two groups.

Conclusion

These results indicate immune dysfunction as potential contributors to the mechanism of CFS, as indicated by decreases in neutrophil respiratory burst, NK cell activity and NK phenotypes. Thus, immune cell function and phenotypes may be important diagnostic markers for CFS. The absence of rheological changes may indicate no abnormalities in erythrocytes of CFS patients.