PubMed Health⌕ Search

Biomedical subjects

W C Mentzer

Publications and source records attributed to W C Mentzer.

At least 37 records · Page 2Linked to original sources
PubMed1992

Low number of antibody producing cells in patients with sickle cell anemia.

B cell function is impaired in patients with sickle cell anemia. Although the number of surface IgM positive cells was similar in sickle cell patients and controls, in vitro spontaneous IgM, and PWM stimulated IgA, IgM, and IgG synthesis was significantly lower in the patients than in controls. The number of PWM induced and antigen specific immunoglobulin producing cells after immunization with Pneumovax, containing 21 serotypes of Streptococcus pneumoniae, was about 100-fold lower in the patients as compared with controls. Finally, the ability of the patients' peripheral blood mononuclear cells to proliferate in response to mitogens (PWM, SAC, PHA) was diminished. Because of the observed impairments in both nonspecific and antigen specific immunoglobulin synthesis and cell proliferation assays in the patients, we determined serum concentrations of IL-4 and IL-6, two cytokines associated with antibody production. IL-4 concentrations appeared low in sickle cell patients, and correlated with that of serum IgM. We hypothesize that B cell maturation in sickle cell patients is arrested at an IL-4 dependent stage.

Adult↗
PubMed1992

Enhancement of erythropoiesis by recombinant human erythropoietin in low birth weight infants: a pilot study.

We randomly assigned eight concurrently symptom-free premature infants (birth weight less than or equal to 1250 gm) at high risk of requiring erythrocyte transfusions for anemia of prematurity to 6 weeks of intensive treatment with either subcutaneous recombinant human erythropoietin (r-HuEPO group) or a placebo (control group). Treatment with r-HuEPO was initiated at a dose of 100 units/kg per day 5 days a week, and was increased to 200 units/kg per day after 2 or 3 weeks if target reticulocyte counts were not achieved. All patients were given supplemental oral iron therapy at a dose of 6 mg/kg per day, as tolerated. Mean reticulocyte counts in r-HuEPO-treated and control infants were 64,600 versus 67,500 cells/mm3 at entry; were 245,600 versus 78,000 cells/mm3 after 1 week; and averaged 262,600 versus 136,400 cells/mm3 during the study. Mean reticulocyte counts in r-HuEPO-treated infants were 251,200 cells/mm3 during the week when r-HuEPO, 100 units/kg per day, was given, and were 269,500 cells/mm3 after the dose was increased to 200 units/kg per day. Mean hematocrit values at entry were 33.4% in babies who received r-HuEPO versus 33.6% in the control subjects, and were 31.4% in r-HuEPO-treated and 25.2% in the control subjects at the end of treatment. One r-HuEPO-treated and three control babies received transfusions during the study; the total volume of blood given was 17 ml in the r-HuEPO group and 101 ml in the control subjects. The percentage of hemoglobin F increased in infants not given transfusions. We conclude that r-HuEPO stimulates endogenous erythropoiesis in small premature babies who are receiving supplemental oral iron therapy. A controlled multicenter trial has been undertaken to confirm these promising preliminary observations.

Anemia, Neonatal↗
PubMed1992

Potential for treatment of anaemia of prematurity with recombinant human erythropoietin: preliminary results.

There is a high level of erythropoiesis in the growing fetus. In utero relative hypoxia results in a relatively high haematocrit and predominant synthesis of haemoglobin F, with erythropoietin (EPO) produced in the liver regulating erythropoiesis. At birth after full-term pregnancy, fetal EPO concentrations are high, but decline progressively thereafter. In pre-term infants the expected postnatal decline in haemoglobin is more prolonged than in full-term infants and the premature infants may become anaemic. It has been shown in a randomized, double-blinded, placebo-controlled trial that recombinant human erythropoietin (r-HuEPO) at a dose of 100 U/kg given intravenously twice weekly for 6 weeks to infants with anaemia of prematurity produced an earlier increase in reticulocyte counts compared with placebo; however, the difference between treatments was not significant. r-HuEPO therapy did not suppress subsequent release of endogenous EPO. It is concluded that a higher dose of r-HuEPO may be required to treat anaemic premature infants.

Anemia↗
PubMed1991

Purification of band 7.2b, a 31-kDa integral phosphoprotein absent in hereditary stomatocytosis.

A 31-kDa human erythrocyte integral protein, band 7.2b, has been purified to better than 95% homogeneity. The polypeptide was found to be insoluble in most detergents and was isolated in denatured form by gel filtration in the presence of sodium dodecyl sulfate and preparative electrophoresis. In intact erythrocytes that were equilibrated with 32Pi, band 7.2b was phosphorylated in response to exogenous dibutyryl cAMP. The peptide is also palmitylated, as shown by its incorporation of radioactivity when intact erythrocytes were incubated with [9,10-3H]palmitic acid. Antisera to band 7.2b were raised in rabbits, and these antibodies cross-react with 31-kDa polypeptides in human liver and kidney. Immunoblots of red cells from a number of other species were negative, with the exception of a cross-reacting 23-kDa polypeptide in rat erythrocyte membranes. Band 7.2b was absent in erythrocyte membranes from an individual with overhydrated hereditary stomatocytes.

Amino Acids↗
PubMed1991

Recombinant human erythropoietin in the anemia of prematurity: results of a placebo-controlled pilot study.

Experimental and clinical data implicate inadequate erythropoietin production as an important reason that infants acquire this anemia and suggest that recombinant human erythropoietin (r-HuEPO) might be used to treat or prevent it. We therefore randomly assigned 20 small premature infants (birth weight less than or equal to 1250 gm) who were highly likely to require erythrocyte transfusions for anemia of prematurity to receive 6 weeks of treatment with either intravenously administered r-HuEPO (at a dose of 100 units/kg twice each week) or a placebo. Hematologic measurements, transfusion requirements, and growth were followed during therapy and for 6 months thereafter. Treated (EPO) and control babies did not differ with respect to weight, hematocrit, overall mean absolute reticulocyte count, calculated erythrocyte mass, or rate of growth. However, reticulocyte counts increased earlier in patients given r-HuEPO. Six of ten babies in the EPO group, and 8 of 10 assigned to the control group, received at least one erythrocyte transfusion during treatment. For all infants the amount of blood sampled for laboratory tests was strongly predictive of the volume of packed erythrocytes transfused (r = 0.890; p = 0.0001). Of nine infants who had less than 20 ml packed erythrocytes removed for laboratory tests, none of four given r-HuEPO received a transfusion, whereas three of five infants assigned to the placebo group received one. No toxic effects were attributable to r-HuEPO, and no significant changes in leukocyte or platelet counts occurred during treatment. Reticulocyte counts were correlated with simultaneous platelet counts and were inversely related to absolute neutrophil counts in both study groups. We conclude that r-HuEPO administration is safe and feasible at the dose studied. Additional controlled trials utilizing higher doses of r-HuEPO and larger numbers of patients are justified.

Anemia, Neonatal↗
PubMed1990

Excess of red cell membrane proteins in hereditary high-phosphatidylcholine hemolytic anemia.

Previous descriptions of hereditary high-phosphatidylcholine hemolytic anemia (HPCHA) have highlighted the association of increased erythrocyte membrane phosphatidylcholine with abnormal membrane cation permeability. We studied the function and composition of erythrocyte membranes from three individuals with HPCHA to characterize further the membrane abnormalities in this disorder. Despite significant macrocytosis, HPCHA red cells were dehydrated and showed an increased surface area to volume ratio compared to normal red cells. The passive efflux of K+ from HPCHA erythrocytes was increased fourfold at 37 degrees C. Total membrane phospholipid was increased 7-42%, largely due to excess phosphatidylcholine, which made up 35.8-37.2% of total phospholipid. Membrane cholesterol:phospholipid ratios were in the normal range. It appears that the excess phosphatidylcholine was not acquired during circulation, since plasma lipids were normal and all subpopulations of density-separated HPCHA erythrocytes were similarly abnormal. The ratio of total protein to phospholipid in white ghosts was increased, indicating that membrane protein was increased to an even greater extent than membrane lipids. No abnormal membrane proteins were identified by Coomassie or periodic acid Schiff (PAS) staining. Quantitation of the major membrane proteins indicated that the total protein excess in HPCHA membranes was due to a proportional increase in all major proteins. We conclude that HPCHA erythrocytes have excess membrane proteins and hypothesize that the changes in lipid composition and cation permeability are secondary to underlying protein abnormalities, which remain to be defined.

Adult↗
PubMed1990

Total body irradiation and bone marrow transplantation for immunodeficiency disorders in young children.

Congenital immunodeficiency disorders such as severe combined immunodeficiency disease (SCID), Wiskott-Aldrich syndrome, and Chediak-Hegashi syndrome are almost uniformly fatal with most children dying before age one. Allogeneic bone marrow transplant (BMT) is the treatment of choice. Few of these children have matched donors. We use bone marrow processing techniques that allow us to utilize marrow from the parents. Children who lack HLA-identical donors are offered haploidentical, T-cell depleted parental BMTs. Some of these children do not have an immune deficiency severe enough to allow durable engraftment of processed mismatched bone marrow. Successful engraftment may necessitate the use of immunosuppression. Total body irradiation (TBI) is part of our intensive conditioning regimen for children with Wiskott-Aldrich and Chediak-Hegashi syndrome and most children with SCID who have undergone an unsuccessful prior mismatched, T-cell depleted BMT, or who have a high likelihood of donor marrow rejection based on pre-transplant immune function testing. TBI is considered extremely toxic therapy in infancy, with little information available on the acute and chronic effects. The 10 children presented in this report are among the youngest to have received TBI. Five patients were 2 to 6 months of age when they received TBI. The conditioning regimen for all patients was; antithymocyte globulin (25 mg/kg/day, x 3 days), cyclophosphamide (60 mg/kg/day, x 2 days), and TBI. 7.0 Gy TBI was given as a single dose AP-PA at approximately 15 cGy/min. Half value blocks shielded the brain, eyes and lungs. Six of 10 children were alive from 7 to 72 months post transplant.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Marrow Transplantation↗
PubMed1989

Hereditary stomatocytosis: consistent association with an integral membrane protein deficiency.

We studied the RBC membrane proteins of four patients, including a mother and daughter, with hereditary stomatocytosis. One- and two-dimensional gel electrophoresis revealed that a 28 kDa integral protein, present in normal RBC membranes, was absent in all four patients. This abnormality, reported once previously (Lande et al, 1982), appears to be a characteristic feature of hereditary stomatocytosis, and may be related to the underlying permeability defect in this disorder.

Adult↗
PubMed1989

Spontaneous resolution of primary erythrocytosis in two girls.

We report two girls with primary erythrocytosis in whom extensive diagnostic studies revealed no underlying cause. Normal growth of colonies derived from erythroid burst forming units (BFU-E) was observed, and serum erythropoietin concentrations were within or below the normal range. The absence of a rise in serum erythropoietin levels after isovolemic phlebotomy implicated the erythroid marrow as the site of the pathophysiologic abnormality in both patients. Spontaneous resolution of erythrocytosis occurred during the second decade of life. Our experience suggests that primary erythrocytosis may be self-limited in some children. In these cases, the proliferative abnormality may be sufficiently subtle as to not be detected by standard in vitro culture systems, which support the growth of colonies derived from erythroid progenitors.

Aging↗
PubMed1989

Human embryonic zeta-globin chains in fetal and newborn blood.

A sensitive and specific radioimmunoassay (RIA) for human embryonic zeta-globin chains was used to study normal fetal blood and newborn cord blood as well as cord blood from newborns with alpha-thalassemias. From 17 weeks until 37 weeks of gestation, zeta-globin chains were present in almost all fetal and cord blood samples (0.27% +/- 0.15% in samples of weeks 17 through 30; 0.14% +/- 0.11% in samples of weeks 31 through 37). zeta-Globin chains were present in greater than 80% of cord blood hemolysates from normal, full-term newborns (0.15% +/- 0.11%) as well as from 16 near-term newborns of diabetic mothers (0.13% +/- 0.13%). zeta-Globin chains were not detected in normal infants aged 3 months to 2 years. In cord blood hemolysates from alpha-thalassemic newborns, the levels of zeta-globin chain content varied from very high to undetectable levels. Gene mapping of the zeta-alpha-globin gene cluster was performed in 12 newborns in whom cord blood zeta-globin chains had been determined. Newborns who were carriers of alpha-thalassemia-1 due to the (--SEA/) deletion had very high levels of zeta-globin chains (greater than 1.5%).

Aging↗
PubMed1988

Cellular dehydration and immunoglobulin binding in senescent neonatal erythrocytes.

The life span of neonatal erythrocytes (60-80 days) is shorter than that of adult erythrocytes (120 days). We studied neonatal red blood cells separated on stractan density gradients to further characterize the aging process and to explore the possibility that senescence antigens play a role in the destruction of neonatal erythrocytes. Quantitation of membrane proteins 4.1a and 4.1b served as a marker for cell age and confirmed an enrichment for senescent red cells in the most dense layers of the gradients. Despite the shorter life span of neonatal erythrocytes, cord blood contained a larger percentage of very dense, K+-depleted red cells than did adult blood. ATP levels in dense neonatal and adult cells were decreased to 50-80% of normal values for unseparated red cells. Levels of reduced glutathione did not fall with increasing cell density. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of red cell membrane proteins showed increased membrane-associated globin in senescent neonatal cells, but such gels run without reducing agents did not show oxidative protein cross-linking. Membrane bound immunoglobulins were detected on senescent neonatal and adult red cells by the rosetting antiglobulin test. We conclude that senescence antigens are revealed during the aging process of neonatal erythrocytes, thereby labeling them for antibody-mediated destruction in the reticuloendothelial system.

Adult↗
PubMed1988

Preservation of sickle cell blood-flow patterns during MR imaging: an in vivo study.

Magnetic fields and RF energy have been shown to affect sickle erythrocytes in vitro. Because both strong magnetic fields and RF energy are used in MR imaging, it has been suggested that capillary blood flow in patients with sickle cell disease may be altered during MR imaging. In order to examine sickle cell blood flow during MR imaging in vivo, laser-Doppler velocimetry was performed in normal control subjects and in sickle cell subjects before, during, and after MR imaging at 0.35 and 1.5 T. Mean blood flow and patterns of blood-flow variability were compared by two hematologists. No differences were found on the recordings from each subject made before, during, and after MR imaging were compared. Blood-flow patterns generally differed between control and sickle cell subjects. Periodic oscillatory blood flow, reportedly a specific finding in sickle cell subjects, was observed in one control subject and was not consistently found in sickle cell subjects. Although energies employed during MR imaging have effects on sickle erythrocytes in vitro, our data show no changes in sickle cell blood flow during MR imaging in vivo.

Anemia, Sickle Cell↗
PubMed1988

The incidence of painful crisis in homozygous sickle cell disease: correlation with red cell deformability.

To determine whether the vasoocclusive severity of homozygous sickle cell (SS) disease is influenced by cellular dehydration, we correlated the incidence of painful crisis with steady-state measurements of red cell hydration. Sixteen children with SS disease were followed for 3.3 to 8 years (mean, 6.8 years), and a single crisis rate was calculated for each patient. At the time of well visits, cellular hydration was assessed by measuring cell deformability, the percentage of red cells with a density greater than or equal to 1.1056 g/mL, and the percentage of irreversibly sickled cells (ISC). The incidence of painful crisis showed a strong positive correlation with Omax, a deformability measurement reflecting cellular hydration (r = .84, P less than .002), and with hemoglobin concentration (r = .59, P = .04). That is, higher crisis rates were observed in patients with less dehydrated, more deformable red cells and also in patients with higher hemoglobin concentrations. Furthermore, cell deformability and hemoglobin concentration were independent predictors of the incidence of painful crisis, which is consistent with separate effects of these two red cells parameters on vasoocclusive severity.

Anemia, Sickle Cell↗
PubMed1988

Hereditary poikilocytic anemia associated with the co-inheritance of two alpha spectrin abnormalities.

This report describes a black family in which two distinct structural defects of alpha spectrin were inherited singly and in combination. The propositus, who has a poikilocytic hemolytic anemia that shares many of the features of hereditary pyropoikilocytosis (HPP) or homozygous elliptocytosis, is a compound heterozygote for both the spectrin alpha 1/65 and spectrin alpha 1/50a defects as demonstrated by electrophoretic analysis of spectrin tryptic fragments. The spectrin alpha 1/65 defect alone was found in his mother and sibling, while the spectrin alpha 1/50a defect was present in the father and another sibling. The red cell spectrin content was normal in all family members. The functional consequences of inheritance of these two spectrin defects were compared with those found in an unrelated patient with classic HPP who had the alpha 1/50a spectrin defect and was spectrin deficient as well. Prolonged incubation at 37 degrees C resulted in striking budding, fragmentation, and sphering of classic HPP red cells but only minimal changes in propositus cells. The percentage of spectrin dimers was increased tenfold in classic HPP, sevenfold in the propositus, and threefold in other family members. Mechanical stability of erythrocyte ghosts, measured by ektacytometry, was reduced severely in both classic HPP and in the propositus, but only moderately in other family members. Thus, co-inheritance of two alpha spectrin defects can result in a poikilocytic hemolytic anemia milder than that usually found in HPP. The greater clinical severity of HPP may be a consequence of the presence of spectrin deficiency, a finding absent in the propositus.

Adult↗
PubMed1987

Phosphoglycerate kinase San Francisco: a new variant associated with hemolytic anemia but not with neuromuscular manifestations.

Phosphoglycerate kinase deficiency is a rare, x-linked glycolytic defect that, when severe, can be associated with hemolytic anemia, rhabdomyolysis, or neurological disorders. We report here a new phosphoglycerate kinase variant discovered in a boy with severe hemolytic anemia but no evidence of neuromuscular disease or developmental delay. The biochemical properties of the variant enzyme (greatly increased kmATP and km3-phosphoglycerate; normal pH optimum, electrophoretic mobility, and substrate specificity; resistance to heat inactivation) establish its uniqueness. Separation of light and dense red cells by centrifugation showed no greater loss of phosphoglycerate kinase activity in dense ("old") variant cells than in normal cells. We postulate that the striking stability of the variant enzyme allows cells capable of protein synthesis to accumulate sufficient enzyme to limit neuromuscular sequelae.

Anemia, Hemolytic↗
PubMed1987

Modulation of erythrocyte membrane mechanical stability by 2,3-diphosphoglycerate in the neonatal poikilocytosis/elliptocytosis syndrome.

To explain the transient anemia and poikilocytosis seen during infancy in hereditary elliptocytosis (HE), we resealed erythrocyte (RBC) ghosts from affected children or their elliptocytic parents with 2,3-diphosphoglycerate (DPG) (0-8 mM), a compound that dissociates membrane skeletons, then measured ghost mechanical stability in the ektacytometer. Without added 2,3-DPG, ghost mechanical stability was subnormal in infantile poikilocytosis (IP) and HE but was even more abnormal in hereditary pyropoikilocytosis (HPP). Addition of 2,3-DPG (2.55 mM) to IP or HE ghosts, decreased their stability to that of HPP ghosts (without 2,3-DPG). Nonphysiological 2,3-DPG levels (6-8 mM) were required to elicit a similar effect in normal ghosts. The data suggest that free 2,3-DPG, present in neonatal RBC as a consequence of diminished binding to HbF, may render HE susceptible to in vivo fragmentation. The developmental switch from fetal to adult hemoglobin, by diminishing available free 2,3-DPG, may explain the abatement of poikilocytosis and hemolytic anemia that accompanies maturation.

2,3-Diphosphoglycerate↗