Herbert J. Meiselman

Antibody against poly(ethylene glycol) adversely affects PEG‐asparaginase therapy in acute lymphoblastic leukemia patients

Rapid clearance of poly(ethylene glycol)‐asparaginase (PEG‐ASNase) has been reported for up to one‐third of patients treated for acute lymphoblastic leukemia (ALL), potentially rendering their treatment ineffective. A 25% occurrence of an antibody against PEG (anti‐PEG) was previously reported in healthy blood donors. The objective of the study was to determine whether anti‐PEG was associated with rapid clearance PEG‐ASNase.

New guidelines for hemorheological laboratory techniques

This document, supported by both the International Society for Clinical Hemorheology and the European Society for Clinical Hemorheology and Microcirculation, proposes new guidelines for hemorheolog ...

Depletion-Mediated Red Blood Cell Aggregation in Polymer Solutions

Polymer-induced red blood cell (RBC) aggregation is of current basic science and clinical interest, and a depletion-mediated model for this phenomenon has been suggested; to date, however, analytical approaches to this model are lacking. An approach is thus described for calculating the interaction energy between RBC in polymer solutions. The model combines electrostatic repulsion due to RBC surface charge with osmotic attractive forces due to polymer depletion near the RBC surface. The effects of polymer concentration and polymer physicochemical properties on depletion layer thickness and on polymer penetration into the RBC glycocalyx are considered for 40 to 500 kDa dextran and for 18 to 35 kDa poly (ethylene glycol). The calculated results are in excellent agreement with literature data for cell-cell affinities and with RBC aggregation-polymer concentration relations. These findings thus lend strong support to depletion interactions as the basis for polymer-induced RBC aggregation and suggest the usefulness of this approach for exploring interactions between macromolecules and the RBC glycocalyx.

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.

GLUT1 reductions exacerbate Alzheimer's disease vasculo-neuronal dysfunction and degeneration

The glucose transporter GLUT1 at the blood-brain barrier (BBB) mediates glucose transport into the brain. Alzheimers disease is characterized by early reductions in glucose transport associated with diminished GLUT1 expression at the BBB. Whether GLUT1 reduction influences disease pathogenesis remains, however, elusive. Here we show that GLUT1 deficiency in mice overexpressing amyloid β-peptide (Aβ) precursor protein leads to early cerebral microvascular degeneration, blood flow reductions and dysregulation and BBB breakdown, and to accelerated amyloid β-peptide (Aβ) pathology, reduced Aβ clearance, diminished neuronal activity, behavioral deficits, and progressive neuronal loss and neurodegeneration that develop after initial cerebrovascular degenerative changes. We also show that GLUT1 deficiency in endothelium, but not in astrocytes, initiates the vascular phenotype as shown by BBB breakdown. Thus, reduced BBB GLUT1 expression worsens Alzheimers disease cerebrovascular degeneration, neuropathology and cognitive function, suggesting that GLUT1 may represent a therapeutic target for Alzheimers disease vasculo-neuronal dysfunction and degeneration.

Ineffective erythropoiesis in β-thalassemia major is due to apoptosis at the polychromatophilic normoblast stage

Beta-thalassemia major is characterized by ineffective erythropoiesis, although it is difficult to define the dynamics of this process from the static information revealed by analysis of bone marrow (BM) aspirates. We aimed to study the kinetics of sequential erythroid differentiation in beta-thalassemia major. We isolated the progenitor cells (CD34(+) and CD34(+)CD38(-) cells) from BM of thalassemia major patients and studied in vitro erythropoiesis. This is the first report of an in vitro study in human beta-thalassemia major from purified BM CD34(+) progenitor cells, using erythroid culture conditions, which allow unilineage differentiation to mature enucleated red blood cells. In contrast to normal donors, a high proportion of BM CD34(+) and CD34(+)CD38(-) progenitors from beta-thalassemia major coexpressed the late erythroid lineage-specific protein glycophorin A and generated a higher proportion of erythroid colonies. However, despite the marked increase in erythroid clonogenicity of the progenitor population, erythroid cultures initiated from beta-thalassemia major BM CD34(+) cells expanded 10- to 20-fold less than from normal BM. There were less viable cells during differentiation, specifically after the polychromatophilic normoblast stage. There was a progressive increase in the apoptotic erythroid progeny with differentiation, and apoptosis occurred predominantly at the polychromatophilic normoblast stage. In thalassemia major, BM progenitor cells show increased erythroid clonogenicity, increased expression of late erythroid lineage-specific proteins, and accelerated erythroid differentiation. However, despite the apparent increased erythroid commitment, ineffective erythropoiesis occurs due to apoptosis at the polychromatophil stage. Identification of the differentiation stage at which apoptosis occurs will permit further studies of the underlying mechanisms and target therapeutic strategies to improve red cell production.

Red blood cell aggregation in experimental sepsis

Red blood cell (RBC) aggregation was investigated in a rat model of sepsis with special emphasis on RBC-related factors. Sepsis was produced by cecal ligation/puncture, whereas another group had only laparotomy (sham operation); blood samples also were obtained from control, unoperated-on animals. RBC aggregation was measured in autologous plasma and in 3% dextran 70, 18 hours after the operations, by using a Myrenne Aggregometer system and the zeta sedimentation ratio (ZSR) method. RBC aggregation in autologous plasma was found to be enhanced in both sham-operated and septic animals and was consistent with their increased plasma fibrinogen levels. However, RBC aggregation in dextran was significantly higher than control only in the sepsis group. RBCs from septic animals also aggregated more in septic plasma compared with RBCs from control animals. In the sepsis group, RBC deformability was significantly decreased, whereas RBC lipid peroxidation was significantly increased. Our results thus confirm the known increase of RBC aggregation in septicemia and, in addition, demonstrate marked alterations of intrinsic RBC properties that further enhance red cell aggregation.

Red blood cell aggregation, aggregate strength and oxygen transport potential of blood are abnormal in both homozygous sickle cell anemia and sickle-hemoglobin C disease

Recent evidence suggests that red cell aggregation and the ratio of hematocrit to blood viscosity, an index of the oxygen transport potential of blood, might considerably modulate blood flow dynamics in the microcirculation. The findings of this study indicate that patients with sickle cell disease and those with sickle cell hemoglobin C disease have low ratios of hematocrit to blood viscosity as compared to normal controls. This may play a role in tissue hypoxia and clinical status of these patients. Background Recent evidence suggests that red blood cell aggregation and the ratio of hematocrit to blood viscosity (HVR), an index of the oxygen transport potential of blood, might considerably modulate blood flow dynamics in the microcirculation. It thus seems likely that these factors could play a role in sickle cell disease. Design and Methods We compared red blood cell aggregation characteristics, blood viscosity and HVR at different shear rates between sickle cell anemia and sickle cell hemoglobin C disease (SCC) patients, sickle cell trait carriers (AS) and control individuals (AA). Results Blood viscosity determined at high shear rate was lower in sickle cell anemia (n=21) than in AA (n=52), AS (n=33) or SCC (n=21), and was markedly increased in both SCC and AS. Despite differences in blood viscosity, both sickle cell anemia and SCC had similar low HVR values compared to both AA and AS. Sickle cell anemia (n=21) and SCC (n=19) subjects had a lower red blood cell aggregation index and longer time for red blood cell aggregates formation than AA (n=16) and AS (n=15), and a 2 to 3 fold greater shear rate required to disperse red blood cell aggregates. Conclusions The low HVR levels found in sickle cell anemia and SCC indicates a comparable low oxygen transport potential of blood in both genotypes. Red blood cell aggregation properties are likely to be involved in the pathophysiology of sickle cell disease: the increased shear forces needed to disperse red blood cell aggregates may disturb blood flow, especially at the microcirculatory level, since red blood cell are only able to pass through narrow capillaries as single cells rather than as aggregates.

Hemorheological factors in cerebral ischemia

We investigated 100 consecutive cerebral ischemia patients for hemorheological alterations. We measured whole and adjusted blood viscosity at 75 and 1,500 sec-1, plasma viscosity, red blood cell aggregation by the zeta sedimentation ratio, and red blood cell deformability using the centrifugal deformability technique. Patients were studied within 72 hours of the acute ischemic event, and 66 were available for follow-up evaluation approximately 2 months later. Two age- and sex-matched control groups were evaluated: 20 nonvascular neurological inpatients (patient controls) and 45 normal volunteers (normal controls). Compared with normal controls, we found significant acute increases in whole blood viscosity (1,500 sec-1), plasma viscosity, fibrinogen concentration, and zeta sedimentation ratio; the latter two variables were also increased at follow-up. Fibrinogen concentration was significantly associated with zeta sedimentation ratio and plasma viscosity and was increased for patient controls. There was a trend toward normalization of acute abnormalities over the 2-month follow-up period, and patients with more severe strokes tended to have more extensive hemorheological abnormalities. Among patients with severe stroke, fibrinogen concentration was significantly associated with the platelet activation peptide beta-thromboglobulin acutely (r = 0.63, p less than 0.005). We conclude that hemorheological abnormalities in cerebral ischemia are largely nonspecific findings, with the likely exception of patients with severe stroke.

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 vaso‐occlusion or impaired blood flow, e.g., myocardial infarction, sickle cell disease. Am. J. Hematol. 56:26–28, 1997.