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H J Meiselman

Publications and source records attributed to H J Meiselman.

At least 37 records · Page 2Linked to original sources
PubMed2000

Standard aggregating media to test the "aggregability" of rat red blood cells.

Rat red blood cells (RBC) exhibit low aggregation tendency in autologous plasma and in standard aggregating media (e.g., 3% Dextran 70; MW: 70 kD). In experimental studies performed on rats, 3% Dextran 70 was found to be an unsuitable suspending medium to test the "aggregability" of RBC in a standard medium. It has been observed that solutions of higher molecular weight polymers (i.e., dextran, MW: 500 kD; polyethylene glycol , MW: 35 kD; polyvinylpyrrolidone, MW: 360 kD), at low concentrations were strong aggregators for rat RBC. Among these polymer solutions 0.5% Dextran 500 and 0.75% polyvinylpyrrolidone 360 were found to be the most suitable suspending media, to distinguish between the aggregability of RBC from septic and control rats. Therefore, these two polymer solutions are recommended as the standard aggregating media for rat RBC, to test the RBC aggregability.

Animals↗
PubMed2000

Inhibition of polymer-induced red blood cell aggregation by poloxamer 188.

Previous reports have suggested that non-ionic poloxamer surfactants of appropriate molecular mass and composition can reduce red blood cell (RBC) aggregation in whole blood and in RBC-plasma suspensions. We have thus evaluated this phenomenon for RBC aggregated by several water-soluble polymers, using poloxamer 188 (P188), a non-ionic, tri-block molecule (total molecular mass of 8.40 kDa, 80% polyoxyethylene). Human RBC were washed, then re-suspended in isotonic solutions of dextran 70 (70.3 kDa), dextran 500 (476 kDa), PVP (360 kDa) or P-L-GLU (61.2 kDa); density-separated RBC were also studied. RBC aggregation was quantitated via a computerized Myrenne Aggregometer (extent, strength) and by the Microscopic Aggregation Index (MAI) method. Over the range of 0.5 to 5 mg/ml, poloxamer 188 inhibited both the extent and strength of aggregation in a dose-dependent manner, with the magnitude of the decrease related to polymer type (e.g., at 5 mg/ml, 62% decrease for dextran 70 vs. 14% decrease for P-L-GLU); MAI results with dextran 70 also showed a dose-dependent decrease. Poloxamer 188 at 5 mg/ml was more effective with younger, less-dense cells. Based upon the depletion model for polymer-induced aggregation, these findings suggest that poloxamer 188 acts by penetrating the depletion layer near the glycocalyx, thereby reducing the osmotic gradient between the intercellular gap and the suspending medium. Regardless of the specific mechanism(s) of action, poloxamers appear to offer interesting approaches for future basic science and clinical studies, and thus the possibility for greater insight into RBC aggregation.

Cells, Cultured↗
PubMed2000

Aggregation behavior and electrophoretic mobility of red blood cells in various mammalian species.

Differences of red blood cell (RBC) aggregation among various mammalian species has been previously reported for whole blood, for RBC in autologous plasma, and for washed RBC re-suspended in polymer solutions. The latter observation implies the role of cellular factors, yet comparative studies of such factors are relatively limited. The present study thus investigated RBC aggregation and RBC electrophoretic mobility (EPM) for guinea pigs, rabbits, rats, humans and horses; RBC were re-suspended in isotonic 500 kDa dextran solutions for the EPM and aggregation measurements, with aggregation studies also done in autologous plasma. Salient results included: (1) species-specific RBC aggregation in both plasma and dextran (horse > human > rat > rabbit approximately = guinea pig) with a significant correlation between aggregation in the two media; (2) similar EPM values in PBS for rat, human and horse, a lower value for guinea pig, and a markedly reduced EPM for rabbit RBC; (3) EPM values in dextran with a rank order identical to that for cells in PBS; (4) relative EPM results indicating formation of a polymer-poor, low viscosity depletion layer at the RBC surface (greatest depletion for horse RBC). EPM-aggregation correlations were evident and generally consistent with the Depletion Model for aggregation, yet did not fully explain differences between species; additional studies at various ionic strengths and with various dextran fractions thus seem warranted.

Animals↗
PubMed2000

Dielectric approach to investigation of erythrocyte aggregation. II. Kinetics of erythrocyte aggregation-disaggregation in quiescent and flowing blood.

A method based on dielectric properties of dispersed systems was applied to investigate the kinetics of RBC aggregation and the break-up of the aggregates. Experimentally, this method consists of measuring the capacitance at a frequency in the beginning of the beta-dispersion. Two experimental protocols were used to investigate the aggregation process. In the first case, blood samples were fully dispersed and then the flow was decreased or stopped to promote RBC aggregation. It was found that the initial phases of RBC aggregation are not affected by the shear rate. This finding indicates that RBC aggregation is a slow coagulation process. In the second case, RBCs aggregated under flow conditions at different shear rates and after the capacitance reached plateau levels, the flow was ceased. The steady-state capacitance of the quiescent blood and the kinetics of RBC aggregation after stoppage of shearing depend on the prior shear rate. To clarify the reasons for this effect, the kinetics of the disaggregation process was studied. In these experiments, time courses of the capacitance were recorded under different flow conditions and then a higher shear stress was applied to break up RBC aggregates. It was found that the kinetics of the disaggregation process depend on both the prior and current shear stresses. Results obtained in this study and their analysis show that the kinetics of RBC aggregation in stasis consists of two consecutive phases: At the onset, red blood cells interact face-to-face to form linear aggregates and then, after an accumulation of an appropriate concentration of these aggregates, branched rouleaux are formed via reactions of ends of the linear rouleaux with sides of other rouleaux (face-to-side interactions). Branching points are broken by low shear stresses whereas dispersion of the linear rouleaux requires significantly higher energy.

Adult↗
PubMed1999

Ifosfamide-induced stomatocytosis and mesna-induced echinocytosis: influence on biorheological properties of blood.

Ifosfamide is an alkylating agent which has poorly understood toxic side effects such as encephalopathy. We hypothesized that ifosfamide and concomitantly applied mesna could have an influence on the flow properties of blood, and thus carried out an in vitro study. Whole blood was incubated in vitro with increasing concentrations of ifosfamide (0-50 mg/ml), mesna (0-20 mg/ml) and combinations thereof. Chloroacetaldehyde, a major metabolite of ifosfamide, was also studied (0-5 mmol/l). Ifosfamide led to a dose-dependent stomatocytic shape transformation and mesna to an echinocytic shape transformation of erythrocytes. These shape changes were reversible upon removal of the causing agent. Both shape changes increased whole blood viscosity. Erythrocyte aggregation was decreased by both drugs at high concentration. Erythrocyte deformability, as measured with the transit time through 5-microm pores, was decreased by mesna and remained unaffected by ifosfamide. These effects were seen at concentrations which may be reached in vivo at the infusion site of the drugs into a vein and in the urinary tract. We conclude that ifosfamide and mesna interact with the lipid bilayer of the cell membrane, which may contribute to the toxicity of the compounds.

Adult↗
PubMed1999

Increased rigidity and priming of polymorphonuclear leukocytes in sepsis.

It has been proposed that abnormal mechanical properties may contribute to capillary retention of polymorphonuclear leukocytes (PMN) in sepsis, leading to the development of organ dysfunction. The present study was designed to determine whether PMN rigidity is increased in severe sepsis, and whether changes in the rheologic behavior of PMN correlate with the clinical course in sepsis. Eighteen adults with severe sepsis were studied over a period of 14 d; 11 survived and seven died. PMN deformation behavior was investigated via micropore filtration, using the cell transit analyzer. On Day 0, PMN rigidity was 2.5-fold greater for sepsis patients than for five normal controls (p < 0.001). PMN rigidity progressively improved over the 14 d study period for patients who recovered, but not for those who died; clinical indicators correlated with PMN rigidity. Patient PMN also exhibited a 5-fold greater increase in rigidity in response to formyl-methionylleucylphenylalanine (fMLP) than did control PMN. Both the increased rigidity and enhanced response to fMLP could be simulated in vitro by incubation of normal PMN with tumor necrosis factor-alpha (TNF-alpha). We conclude that circulating PMN are more rigid in severe sepsis, and are "primed" for an augmented response to chemotactic stimuli. These findings support the hypothesis that cytokine-mediated increases of PMN rigidity may lead to sequestration of these cells in capillaries and to the consequent impairment of microvascular perfusion in sepsis.

Adult↗
PubMed1999

Hemorheologic alterations in hypertension: chicken or egg?

The serious pathophysiologic consequences of systemic hypertension have prompted numerous basic science and clinical studies related to cardiac or vascular abnormalities. More recently, hemorheologic alterations in hypertension have been explored in an attempt to determine the import of rheologic factors vis-à-vis the elevated total peripheral resistance observed in hypertensive patients. To date, various studies have documented several abnormalities (e.g., increased blood and plasma viscosity, elevated hematocrit), with some suggesting altered RBC or WBC rigidity. However, there is much less information relevant to the "chicken or egg" problems: (1) are reported hemorheological abnormalities the cause or the result of hypertension; (2) does normalization of blood pressure also normalize hemorheological parameters? In overview, the current literature indicates that hemorheology and hypertension may be linked, but that the details of this association and its cause-effect relations remain unclear.

Animals↗
PubMed1999

Susceptibility of equine erythrocytes to oxidant-induced rheologic alterations.

OBJECTIVE: To evaluate the rheologic responses of equine versus human RBC to oxidant stress induced by superoxide anions. SAMPLE POPULATION: Equine blood samples were obtained from 8 healthy, 3- to 6-year-old various breed horses of either sex; human blood samples were obtained from 8 healthy adults. PROCEDURE: Washed RBC were exposed to superoxide anions generated by the xanthine oxidase (XO)-hypoxanthine system (XO activity of 0 to 0.1 U/ml). Deformability of RBC was assessed by ektacytometry, and RBC aggregation was measured in autologous plasma or 3% solution of dextran 70 via a defined-shear photometric technique. RESULTS: Equine RBC had XO dose-dependent increases in methemoglobin concentration that were greater by 60 to 110% than in human RBC and an enhanced tendency for echinocyte formation (ie, 40% echinocyte formation at highest activity of XO). Oxidant stress reduced deformability (ie, increased rigidity) for equine and human RBC with the effect more prominent for equine RBC. Equine RBC aggregation had a biphasic response with a significant increase in plasma and dextran 70 at low XO activities and inhibition at high activities; echinocytes were incorporated into equine, but not human, RBC aggregates. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with human RBC, equine RBC are more sensitive to oxidant damage as judged by the extent of methemoglobin formation, alteration of aggregation, and reduction of cellular deformability. The high susceptibility of equine RBC to oxidant damage, and the resulting hemorheologic alterations, may have important consequences for tissue perfusion and cardiovascular adequacy in horses; they may be of particular relevance in physiologic or pathophysiologic changes associated with increased oxidant stress.

Animals↗
PubMed1999

Dielectric approach to the investigation of erythrocyte aggregation: I. Experimental basis of the method.

A method based on dielectric properties of dispersed systems was developed to investigate red blood cell (RBC) aggregation in blood and RBC suspensions. Measurements of capacitance and resistance were made in a rectangular channel at low (0.2 MHz) and high (14 MHz) frequencies relative to the mid-point of the beta-dispersion range. Compared to capacitance, minimal post-shearing changes of resistance were observed; capacitance changes at 0.2 MHz were two orders of magnitude larger than those at 14 MHz and hence subsequent measurements were carried out at the lower frequency. It is shown that post-shearing changes in the capacitance are affected by the recovery of RBC shape and relaxation processes at the electrode-suspension interface. However, the dominant factor contributing to time-dependent changes in the capacitance is the dynamic process of RBC aggregation. It is experimentally shown that the time record of the capacitance at 0.2 MHz quantitatively reflects the aggregation process in RBC-plasma suspensions with hematocrit up to 0.56 (v/v) and in suspensions of RBCs in artificial aggregating media. It is concluded that a dielectric approach to the study of RBC aggregation in whole blood offers great potential for basic studies and for diagnostic use.

Electric Conductivity↗
PubMed1998

An in vitro model of human red blood cell production from hematopoietic progenitor cells.

Hemoglobinopathies, such as beta-thalassemias and sickle cell anemia (SCA), are among the most common inherited gene defects. Novel models of human erythropoiesis that result in terminally differentiated red blood cells (RBCs) would be able to address the pathophysiological abnormalities in erythrocytes in congenital RBC disorders and to test the potential of reversing these problems by gene therapy. We have developed an in vitro model of production of human RBCs from normal CD34(+) hematopoietic progenitor cells, using recombinant growth factors to promote terminal RBC differentiation. Enucleated RBCs were then isolated to a pure population by flow cytometry in sufficient numbers for physiological studies. Morphologically, the RBCs derived in vitro ranged from early polylobulated forms, resembling normal reticulocytes to smooth biconcave discocytes. The hemoglobin pattern in the in vitro-derived RBCs mimicked the in vivo adult or postnatal pattern of beta-globin production, with negligible gamma-globin synthesis. To test the gene therapy potential using this model, CD34(+) cells were genetically marked with a retroviral vector carrying a cell-surface reporter. Gene transfer into CD34(+) cells followed by erythroid differentiation resulted in expression of the marker gene on the surface of the enucleated RBC progeny. This model of human erythropoiesis will allow studies on pathophysiology of congenital RBC disorders and test effective therapeutic strategies.

Adult↗
PubMed1998

Effect of superoxide anions on red blood cell rheologic properties.

The human red blood cell (RBC) is known to be susceptible to oxidant damage, with both structural and functional properties altered consequent to oxidant attack. Such oxidant-related alterations may lead to changes of RBC rheologic behavior (i.e., deformability, aggregability). Two different models of oxidant stress were used in this study to generate superoxide anions either internal or external to the RBC. Our results indicate that generation of superoxide within the RBC by phenazine methosulfate decreases RBC deformability without effects on cell aggregation. Conversely, superoxide generated externally by the xanthine oxidase-hypoxanthine system primarily affects RBC aggregability: the shear rate necessary to disaggregate RBC was markedly increased while the extent of aggregation decreased slightly. Increased disaggregation shear rate (i.e., greater aggregate strength) as a result of superoxide radical damage may adversely affect the dynamics of blood flow in low-shear portions of the circulation, and may also play a role in the no-reflow phenomena encountered after ischemia-reperfusion.

Erythrocyte Aggregation↗
PubMed1998

Activated polymorphonuclear leukocytes affect red blood cell aggregability.

Activated leukocytes can affect adjacent cells by generating oxygen free radicals and secreting proteolytic enzymes, and red blood cells (RBC) exposed to such agents should be susceptible to their effects. This study was thus designed to investigate the effects of activated polymorphonuclear leukocytes (PMN) on RBC aggregability (i.e., on intrinsic RBC aggregation characteristics). PMN were isolated from human blood by density separation and suspended in glucose-enriched buffer with RBC isolated from the same blood sample (RBC/PMN ratio of 150:1). PMN were then activated in this suspension by adding 1 ng/mL tumor necrosis factor alpha (TNF-alpha) and 10(-7) M N-formyl-methionyl-leucyl-phenylalanine (fMLP) or fMLP alone. After incubation for 2 h at 37 degrees C, RBC aggregation behavior in autologous plasma was assessed; RBC deformability and partition coefficients were also measured. RBC aggregation was significantly increased after incubation and deformability and partitioning were decreased; these effects were prevented by phenylmethylsulfonyl fluoride (1 mM) or superoxide dismutase (20 microg/mL) plus catalase (40 microg/mL). TNF-alpha and fMLP alone had no effect on RBC aggregation if PMN were not present. Activated PMN can thus markedly affect RBC aggregability, apparently via both proteolytic enzymes and oxygen free radicals; enhanced aggregation seen in clinical states associated with PMN activation or observed during in vivo RBC aging may also involve such PMN-RBC interactions.

Adult↗
PubMed1998

Red blood cell deformability in sepsis.

The microcirculatory disturbances in sepsis have prompted micropore bulk-filtration studies of red blood cell (RBC) mechanical behavior (i.e., deformability). However, these prior reports may not solely reflect RBC behavior because of possible white blood cell (WBC) occlusion of the filter pores. The present study was designed to examine RBC mechanical alterations in human and experimental sepsis using techniques that are not affected by WBC artifacts. RBC were obtained from adult patients with sepsis and from healthy control donors. RBC were also obtained from Swiss-albino rats in which experimental sepsis was induced via cecal ligation-puncture. Red cell mechanical behavior was tested using a computerized micropore filtration system (CTA) and a laser-diffraction shearing device (LORCA); the latter provides the extent of RBC deformation at various stresses and the time constant for RBC shape recovery. Salient findings include: (1) for human RBC, significantly decreased deformability at fluid shear stresses < 5 Pa (LORCA) yet no differences from control with the CTA; (2) for rat RBC in experimental sepsis, significant decreases of deformability and shape-recovery time constant (LORCA) but no differences with the CTA. We conclude that RBC deformability is reduced in sepsis but that micropore bulk-filtration methods may not be appropriate for detecting these changes.

Adult↗
PubMed1998

Measurement of red blood cell aggregation in a "plate-plate" shearing system by analysis of light transmission.

The analysis of light reflection from or transmission through a blood sample under defined shearing conditions is widely used to assess red blood cell (RBC) aggregation. Different shearing geometries have been used to generate a constant shear rate within the blood sample, including "cone on plate" and Couette systems. In this study, a rotating glass plate, together with a parallel stationary plate, was used to generate a given shear rate at the point of light transmission measurement. The system gave reproducible results and proved to be sensitive to alterations in RBC aggregation. A comparison between different RBC aggregation parameters that can be calculated using the same light transmission curves (syllectograms) was also made. The index calculated by integrating the area under the syllectogram (M index) was found to be the most appropriate aggregation parameter to be used for comparisons between two groups of blood samples with different aggregation characteristics.

Adult↗
PubMed1997

Combined use of micropipette aspiration and perifusion for studying red blood cell volume regulation.

We combined micropipette aspiration with a new technique of perifusion to study volume behavior of single red blood cells (RBCs) during anisotonic conditions. Other techniques have suggested that RBC volume changes are complete within 1 s, but our pipette data indicate a slower volume response of 5-10 s. This difference appears to be due to the partial aspiration of the cell into the pipette, which in part prevents exposure of the membrane area to the anisotonic medium. However, we found that medium will pass the aspirated RBC (-20 mm H2O aspiration pressure) and enter the pipette at a volume rate of 0.3 micron3/s; this rate was measured by introducing a flow marker, a separate RBC or a cell fragment, into the pipette. The osmotic balance across the RBC also affected the flow: if the outside fluid was made hypertonic, the pipette flow decreased, but a hypotonic conditions, the flow increased and contributed to the exposure of the aspirated portions of the RBC. However, after the initial 10 s, the RBC geometry can be precisely monitored; at 200 mOsm, the RBC swelled by 41.0 +/- 0.9% and then demonstrated a small but significant (P < 0.001) regulatory volume decrease. We suggest that this technique is very precise in measuring the dynamics of geometric regulation, although acute changes are affected by the partial cell aspiration and pipette flow.

Adult↗
PubMed1997

Covalent binding of poly(ethylene glycol) (PEG) to the surface of red blood cells inhibits aggregation and reduces low shear blood viscosity.

A simple method to coat human red blood cells (RBC) with PEG is described. Using a reactive derivative, monomethoxy-PEG (mPEG) was covalently attached to the surface of RBC in aqueous media under mild conditions. The PEG coating dramatically reduced aggregation and low shear viscosity of RBC resuspended in autologous plasma, and inhibited RBC agglutination by blood group-specific antibodies. Morphology and deformability of the PEG-treated cells were unaltered. The PEG coating of the RBC surface may be of significant benefit in the treatment of a variety of diseases characterized by vasoocclusion or impaired blood flow, e.g., myocardial infarction, sickle cell disease.

Blood Viscosity↗