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Biomedical subjects

E F Roth

Publications and source records attributed to E F Roth.

At least 37 records · Page 2Linked to original sources
PubMed1986

Pathways for the reduction of oxidized glutathione in the Plasmodium falciparum-infected erythrocyte: can parasite enzymes replace host red cell glucose-6-phosphate dehydrogenase?

Plasmodium falciparum-infected human red cells possess at least two pathways for the generation of reduced nicotinamide adenine dinucleotide phosphate (NADPH): (1) the glucose-6-phosphate dehydrogenase (G6PD) pathway and (2) the glutamate dehydrogenase (GD) pathway using glutamate as a substrate. Uninfected erythrocytes lack the GD pathway. The NADPH generated can be used to reduce oxidized glutathione (GSSG), which accumulates in the presence of an oxidative stress. In red cell G6PD deficiency, this pathway is reduced or absent, and the host cells as well as the parasites within them are vulnerable to oxidant stress. In view of the presence of the GD pathway in parasitized red cells and the recent description of a parasite-derived G6PD enzyme, we have asked whether the pathways for the reduction of GSSG provided by the parasite can substitute for the host G6PD in red cells deficient in G6PD activity. We have devised a functional assay in which the reduction rate of GSSG is monitored in the presence of buffered infected or control red cell lysates and substrates. Infected G6PD-deficient erythrocytes were obtained from in vitro cultures after a single prior growth cycle of the parasites in G6PD deficient cells to eliminate contaminating normal red cells. The results show that only parasitized red cells can reduce GSSG via the GD pathway. In parasitized G6PD Mediterranean red cells (completely G6PD-deficient), there is a detectable GSSG reduction via the G6PD pathway, not found in uninfected lysates from the same individual. In G6PD A- (African type, featuring partial deficiency), a small increment in the G6PD-dependent reduction of GSSG can also be detected. However, when compared to G6PD normal red cells, the activities from the parasite-derived pathways are small and could not be considered substitutes for normal host enzyme activity. It is concluded that while the plasmodium provides additional pathways for the generation of NADPH that may serve its own metabolic needs, the host red cells and hence the parasite itself remain vulnerable to oxidant stress.

Erythrocytes↗
PubMed1985

Near-normal circulatory survival of rabbit red cells exposed to high levels of Ca and ionophore in vitro.

The belief is widely held, on the basis of indirect evidence, that a substantial, even brief elevation of red cell Ca content must result in a marked shortening of circulatory survival. To test this notion directly, we exposed rabbit red cells in vitro to the ionophore A23187 and Ca so as to produce sustained uniform cell Ca levels of 40 to 360 mumol/L cells for one to 60 minutes, and compared the survival of the Ca-loaded cells in vivo with that of ionophore-treated controls, simultaneously, in the same rabbits. Despite marked reductions in cell adenosine triphosphate and dehydration of the Ca-exposed cells prior to reinfusion, the majority of cells, all of which had experienced these high cytoplasmic Ca levels, showed normal or near-normal survival in the circulation.

Animals↗
PubMed1984

The effect of pyrroline-5-carboxylic acid on nucleotide metabolism in erythrocytes from normal and glucose-6-phosphate dehydrogenase-deficient subjects.

Pyrroline-5-carboxylate, the intermediate in the interconversion of proline, ornithine, and glutamate, increases 5-phosphoribosyl 1-pyrophosphate (PP-ribose-P) and purine nucleotide formation in intact human erythrocytes. We proposed that: 1) pyrroline-5-carboxylate is converted to proline by pyrroline-5-carboxylate reductase with concomitant oxidation of NADPH, 2) NADP+ augments glucose-6-phosphate dehydrogenase activity, and 3) production of ribose-5-phosphate via the pentose shunt is increased. Since glucose-6-phosphate dehydrogenase plays a central role in this proposed mechanism, we examined the responsiveness of glucose-6-phosphate dehydrogenase-deficient erythrocytes to pyrroline-5-carboxylate. We compared erythrocytes from four Sardinian glucose-6-phosphate dehydrogenase-deficient subjects and four Sardinian normal controls. Without pyrroline-5-carboxylate treatment, the levels of pentose shunt activity, PP-ribose-P, and inosine monophosphate were comparable in the two populations. However, the response to pyrroline-5-carboxylate in erythrocytes from normal and glucose-6-phosphate dehydrogenase-deficient subjects was markedly different. In normal erythrocytes, pyrroline-5-carboxylate treatment increased pentose shunt activity 600%, PP-ribose-P formation 250%, and the incorporation of hypoxanthine into inosine monophosphate 260%. In contrast, pyrroline-5-carboxylate had no effect on glucose-6-phosphate dehydrogenase-deficient erythrocytes. These findings strongly support our proposed mechanism for the pyrroline-5-carboxylate effect on nucleotides. Furthermore, the markedly different capacities for nucleotide synthesis in the two populations with pyrroline-5-carboxylate treatment suggest a role for pyrroline-5-carboxylate-mediated modulation of nucleotide metabolism in normal cells.

Erythrocytes↗
PubMed1984

A method to correct for errors caused by generation of interfering compounds during erythrocyte lipid peroxidation.

A commonly used method for quantification of lipid peroxidation depends upon measurement of a malonaldehyde-thiobarbituric acid derivative with absorbance at 532 nm. Investigation of this assay demonstrated that erythrocyte peroxidation produces compounds that react with thiobarbituric acid to interfere with the malonaldehyde assay. Interference results from carryover absorbance at 532 nm, equivalent to 20% of the intensity of the maximum absorption peak at 453 nm. These compounds are not products of lipid peroxidation but are derived from erythrocyte hemolysate and reduced glutathione. A specific HPLC assay for malonaldehyde corroborated the improved accuracy of measuring absorbance at 453 nm and correcting for the absorbance of the interfering compounds at 532 nm when assaying erythrocyte malonaldehyde production.

Chromatography, High Pressure Liquid↗
PubMed1984

The pyrogallol assay for superoxide dismutase: absence of a glutathione artifact.

Reduced glutathione was found to affect the assay for superoxide dismutase when autooxidation of epinephrine, but not pyrogallol, was used as the indicator. Glutathione concentrations in the micromolar range, which correspond to levels in erythrocyte extracts, were capable of perturbing the epinephrine assay method and causing overestimation of enzyme content. The pyrogallol method was not significantly affected by large excesses of glutathione and appears to be a superior method for tissue extracts likely to be rich in glutathione.

Epinephrine↗
PubMed1984

The effect of chronic hypocholesterolemia in myeloproliferative disease on the distribution of plasma and erythrocyte tocopherol.

The presence of hypocholesterolemia and increased erythrocyte lipid peroxidation susceptibility in myeloproliferative disorders raised the possibility of coexistent tocopherol deficiency. Plasma and red blood cell (RBC) alpha-tocopherol, beta- + gamma-tocopherol, and free cholesterol were determined simultaneously by high performance liquid chromatography in 22 patients and 26 controls. Plasma alpha-tocopherol was correlated most highly with plasma free cholesterol and secondarily with RBC alpha-tocopherol in both groups. Plasma-free cholesterol and alpha-tocopherol were significantly reduced in myeloproliferative disease, although the ratio between the two remained normal. Erythrocyte tocopherol and free cholesterol concentrations were normal in myeloproliferative disease. High relative retention of tocopherol by erythrocytes was most pronounced in patients with the lowest plasma alpha-tocopherol and free cholesterol levels. The normal RBC tocopherol levels in these patients with chronic hypocholesterolemia indicate that the observed increase in RBC peroxidation susceptibility is not explainable by a deficiency of RBC vitamin E.

Cholesterol↗
PubMed1984

Increased erythrocyte susceptibility to lipid peroxidation in myeloproliferative disorders.

The recognition of abnormal lipoprotein metabolism that produces chronic hypocholesterolemia in myeloproliferative disorders and the known influence of altered plasma lipid levels on erythrocyte membranes prompted a study of erythrocyte susceptibility to lipid peroxidation in myeloproliferative disease. Malonyldialdehyde generation during an oxidant challenge of erythrocyte suspensions of standardized hemoglobin concentration with H2O2 was significantly greater in 32 patients with myeloproliferative disease than in 47 hematologically normal subjects. The myeloproliferative disease group had significantly lower plasma total, HDL-, and LDL-cholesterol, erythrocyte indices, and erythrocyte deformability, and higher reticulocyte counts and serum lactic dehydrogenase. In the myeloproliferative disease group, mean corpuscular hemoglobin concentration, reticulocyte count, and erythrocyte count were significant variables in accounting for the observed variation in peroxidation susceptibility. Erythrocytes of patients with myeloproliferative disease had elevated concentrations of reduced glutathione, normal glutathione stability, and normal alpha-tocopherol content. These studies demonstrate increased susceptibility to oxidative damage in myeloproliferative disease despite normal or increased concentrations of the major antioxidant compounds of the erythrocyte. The presence of reticulocytosis, elevated serum lactic dehydrogenase, and decreased erythrocyte deformability suggests that lipid peroxidation susceptibility is associated with in vivo hemolysis and may contribute to the anemia that complicates myeloproliferative disease.

Cholesterol↗
PubMed1983

Glucose-6-phosphate dehydrogenase deficiency inhibits in vitro growth of Plasmodium falciparum.

Glucose-6-phosphate dehydrogenase (G6PD; EC 1.1.1.49)-deficient red blood cells from male hemizygotes and female heterozygotes from the island of Sardinia were studied for their ability to support growth in vitro of the malaria-causing organism Plasmodium falciparum. Parasite growth was approximately one-third of normal in both hemi- and heterozygotes for G6PD deficiency. In Sardinians with the beta 0-thalassemia trait, parasite growth was normal except when G6PD deficiency occurred together with the thalassemia trait. The data support the hypothesis that G6PD deficiency may confer a selective advantage in a malarious area; the female heterozygote may be at a particular advantage because resistance to malaria equals that of male hemizygotes, but the risk of fatal hemolysis may be less. However, more female heterozygotes must be studied to confirm this hypothesis. No protective effect of beta 0-thalassemia trait could be demonstrated in vitro.

Cells, Cultured↗
PubMed1983

The effect of X chromosome inactivation on the inhibition of Plasmodium falciparum malaria growth by glucose-6-phosphate-dehydrogenase-deficient red cells.

Previous data on in vitro culture of Plasmodium falciparum malaria demonstrated that red cell glucose-6-phosphate dehydrogenase deficiency (G6PD-) inhibited parasite growth in deficient hemizygous males. This study investigated the effect of heterozygosity for G6PD- on parasite growth. Blood was obtained from 8 female Sardinian G6PD- heterozygotes with G6PD normal cells ranging from 13% to 60%. For comparison, blood from a G6PD- hemizygous male, containing 100% deficient red cells, was mixed in different proportions with compatible normal blood. In both experiments, parasite growth was inhibited by the presence of deficient cells. In both cases, it was found that the inhibition could be explained by a simple dilution of normal cells by G6PD- cells. Thus, the typical female heterozygote is also protected to a significant extent. When considering the "malaria hypothesis" as it relates to G6PD, protection of the female heterozygote as well as the male hemizygote must be taken into account.

Erythrocytes↗
PubMed1981

pH dependency of potassium efflux from sickled red cells.

Potassium efflux from deoxygenated, hemoglobin S-containing red cells is often used as an "objective" in vitro measure of aed cell sickling, particularly during tests with antisickling agents. Since varying pH is known to affect both the extent of sickling and passive K+-flux across the red cell membrane, in opposite directions, we measured the sickling-related K+-efflux in sickle cell anemia (SS) and sickle cell trait (AS) red cells as a function of extracellular and intracellular pH. The sickling-related K+-efflux was found to show the same direction of pH dependence as normal red cells, so that as the extracellular pH was reduced below 7.6, sickling and K+-efflux were increasingly dissociated. A similar dissociation was observed between sickling and K+-efflux when the intracellular pH was lowered by increasing red cell organic phosphate levels. The sickling-related K+-efflux from osmotically shrunken AS cells (whose sickling tendency resembles that of SS cells) was similar in magnitude and pH dependency to that of the SS cells. The findings suggest that measurement of K+-efflux may be an accurate estimate of the extent of intracellular polymerization in sickled red cells, provided that both the intracellular and extracellular pH levels are carefully controlled, and the experimental conditions produce no independent effects on K+ permeability.

2,3-Diphosphoglycerate↗
PubMed1981

Sickle cell crisis as evaluated from measurements of hydroxybutyrate dehydrogenase and myoglobin in plasma.

Data on plasma hydroxybutyrate dehydrogenase activity (I) and myoglobin concentration were used to evaluate painful sickle cell crises. I was increased during non-crisis steady state in patients with sickle cell disease as compared to normal values (232, SD 79.7 vs 85, SD 33 Sigma units/mL). During crisis, the mean value for I increased further to 379 (SD 139) Sigma units/mL. For 12 patients evaluated both during steady state and crisis, there was a mean increase in plasma I of 131% (SD 76%). Repeated determinations of I in sickle cell disease patients during several months while they were in steady state showed that baseline I varied by no more than 20% from the mean. Plasma myoglobin in patients with sickle cell disease was not above normal, but during crisis 21 of 39 patients tested had increased plasma myoglobin concentrations. Our data suggest that I may be a useful indicator of sickle cell crisis when the patient's own baseline value is available for comparison. Plasma myoglobin measurements give evidence of muscle damage during crisis with high specificity but low sensitivity.

Anemia, Sickle Cell↗
PubMed1980

Sickle cell disease in Sicily.

The chemical and physical properties of haemoglobin S derived from homozygotes for this haemoglobin in Sicily were examined, as well as some erythrocytic characteristics. Sicilian Hb S was identical to that found in USA black patients in electrophoretic mobility on both starch and citrate agar media, solubility, mechanical precipitation rate of oxyhaemoglobins, and minimum gelling concentration, as well as by peptide mapping and amino-acid analysis of all beta-chain peptides. Taken together with the presence in Sicily of African blood group markers and certain historical considerations, it seems clear that the source of Hb S in Sicily is Africa. While the clinical severity in nine Sicilian children did not seem remarkably different from the disease in the USA, the most severe and fatal complications were not seen. Mean Hb F Was 10.5% and 2,3-diphosphoglycerate (2,3-DPG) values were higher in Sicilian homozygotes than in black USA counterparts (21.79 mumol/g Hb vs 15.16). Red cell AT values were also slightly higher in Sicilian patients. The presence of concomitant thalassaemia was excluded by both family studies and globin chain synthetic ratios. In conclusion, haemoglobin S in Sicilian homozygotes is identical to Hb S found in USA blacks. Although the severity of the disease seems quite similar in both groups of patients, other erythrocytic properties were found to be different. Whether these factors influence severity remains to be elucidated.

Adenosine Triphosphate↗