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Biomedical subjects

J R Durocher

Publications and source records attributed to J R Durocher.

15 recordsLinked to original sources
PubMed1977

Evidence for differences in erythrocyte surface receptors for the malarial parasites, Plasmodium falciparum and Plasmodium knowlesi.

Human erythrocytes lacking various blood group determinants were susceptible to invasion by Plasmodium falciparum including Duffy-negative erythrocytes that are refractory to invasion by Plasmodium knowlesi. Erythrocytes treated with trypsin or neuraminidase had reduced susceptibility of P. falciparum and normal susceptibility to P. knowlesi. Chymotrypsin treatment (0.1 mg/ml) blocked invasion only by P. knowlesi. The differential effect of enzymatic cleavage of determinats from the erythrocyte surface on invasion by these parasites suggests that P. falciparum and P. knowlesi interact with different determinants on the erythrocyte surface.

Chymotrypsin↗
PubMed1977

Decreased fluidity of red cell membrane lipids in abetalipoproteinemia.

Acanthocytic red cells in patients with abetalipoproteinemia are morphologically similar to the red cells in spur cell anemia. Fluidity of membrane lipids is decreased in spur cells due to their excess cholesterol content. Acanthocyte membranes have an increased content of sphingomyelin and a decreased content of lecithin. To assess the effect of this abnormality of acanthocyte membrane lipid composition on membrane fluidity, we studied red cells from five patients with abetalipoproteinemia and four obligate heterozygote family members. Membrane fluidity was measured in terms of microviscosity ( eta) at 37 degrees C, assessed by means of the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. It was increased from 3.2+/-0.1 poise in normals to 4.01-4.14 poise in acanthocytes. This was associated with an increase in the sphingomyelin/lecithin ratio from 0.84+/-0.08 in normals in 1.45-1.61 in acanthocytes. The eta of acanthocyte membranes was not influenced by the degree of vitamin E deficiency. Similar changes in eta were observed in liposomes prepared from red cell lipids. Heterozygotes had normal sphingomyelin/lecithin ratios and normal values for eta. The flow activation energy for viscosity, a measure of the degree of order in the hydrophobic portion of the membrane, was decreased from 8.3 kcal/mole in normal red cells to 7.2 kcal/mole in acanthocytes, indicating that acanthocyte membrane lipids are more ordered. Variations in the sphingomyelin/lecithin mole ratio of liposomes prepared from brain sphingomyelin and egg lecithin with equimolar cholesterol caused similar changes in both eta and activation energy. The deformability of acanthocytes, assessed by means of filtration through 3-mum filters, was decreased. These studies indicate that the increased sphingomyelin/lecithin ratio of acanthocytes is responsible for their decreased membrane fluidity. As in spur cells and in red cells enriched with cholesterol in vitro, this decrease in membrane fluidity occurs coincidentally with an abnormality in cell contour and an impairment in cell deformability.

Abetalipoproteinemia↗
PubMed1975

The abnormal surface characteristics of the red blood cell membrane in congenital dyserythropoietic anaemia type II (HEMPAS).

The red blood cell membranes of patients with congenital dyserythropoietic anaemia Type II (CDA-II) were found to be abnormal. They had altered antigenic characteristics, decreased electrophoretic mobility, decreased sialic acid content, and abnormal filtration through polycarbonate filters. Proteins extracted from the CDA-II erythrocytes showed a different banding pattern on polyacrylamide gels compared to normal erythrocytes. Erythrocytes from clinically unaffected siblings and parents showed similar but less striking abnormalities of antigenic surface characteristics and banding patterns on polyacrylamide gels with nearly normal surface charge, sialic acid content, and filtration properties. These studies suggest a correlation between the degree of membrane abnormality and the clinical state of the CDA-II family member, demonstrate the erythrocyte in the heterozygote state is not normal, and support the concept of CDA-II as an autosomal recessive disease.

Agglutination Tests↗
PubMed1975

Alteration of human erythrocyte membrane properties by complement fixation.

Erythrocyte survival studies of complement-coated radiolabeled erythrocytes have shown rapid removal of these cells from the peripheral blood with a return of these cells into the circulation within a few hours. We studied complement-coated human erythrocytes and measured surface charge and deformability, two parameters believed to be important in erythrocyte survival. Erythrocytes were coated with complement by two in vitro techniques: the addition of (a) low ionic strength sucrose, and (b) IgM cold agglutinins. Erythrocytes obtained from three patients with cold agglutinin disease were used as a source of in vivo complement-coated cells. No difference was found in surface charge as measured by electrophoretic mobility between erythrocytes from normal subjects and complement-coated erythrocytes from any of the three sources. When deformability was measured by filtration through 3-mum polycarbonate sieves, marked decreases in deformability were found in complement-coated erythrocytes. The filtration returned toward control levels by incubating the complement-coated erythrocytes in serum for 1 h and correlated with decreases in immune adherence. Using screen filtration pressure as a measure of deformability, a positive correlation between number of C3 molecules per erythrocyte and decreased deformability was found. C3b appeared responsible for the decreased deformability of the erythrocytes, since conversion of C3b to C3d resulted in a return of deformability toward normal. The data suggested that the sequestration of complement-coated human erythrocytes in the microvasculature can be explained in part by decreased deformability and changes in immune adherence.

Agglutinins↗
PubMed1975

Interaction of leukocyte chemotactic factors with the cell surface. I. Chemotactic factor-induced changes in human granulocyte surface charge.

The negative surface charge of human granulocytes was diminished after incubation with the chemotactic factors C5a, dialyzable transfer factor, and the enzymes kallikrein and plasminogen activator. No such change was observed after incubation with human IgG, albumin, horeseradish peroxidase, or a mixture of prekallikrein and plaminogen proactivator. Hydrocortisone inhibited the effect of C5a upon granulocyte surface charge and inhibited its chemotactic activity, suggesting that steroids act at the cell surface. The chemotactic inhibitors cholchicine and cytochalsin B had no effect upon granulocyte surface charge, consistent with their presumed effect upon microtubules and microfilaments, respectively. The data suggest that the decrease in cell surface charge may be a preerequiste for normal cell movement.

Chemotaxis↗
PubMed1975

Effect of oral contraceptives and pregnancy on erythrocyte deformability and surface charge.

Erythrocyte deformability and surface charge were studied in normal premenopausal women, oral contraceptive users, and pregnant women. The increased incidence of thrombosis in women taking oral contraceptives could not be explained by decreased erythrocyte deformability or surface charge. However, the decreased erythrocyte deformability of late pregnancy may relate to thrombosis during this period and to increased hemolysis in patients with certain hemoglobinopathies.

Adenosine Triphosphate↗
PubMed1975

Role of sialic acid in erythrocyte survival.

The role of membrane sialic acid in erythrocyte survival is unclear, although there is evidence for a reduction in sialic acid and surface charge in older erythrocytes. We reduced the surface charge of human, rat, and rabbit erythrocytes by removing sialic acid with neuraminidase. Reduction in sialic acid correlated with decreases in electrophoretic mobility and loss of PAS staining of membrane glycoproteins on polyacrylamide gels. No changes in ATP levels or deformability were found. 51Cr erythrocyte survivals in rats and rabbits showed rapid clearance of desialylated erythrocytes with sequestration by the liver. These results suggest that reduction in erythrocyte sialic acid is a mechanism of erythrocyte destruction and may be important in erythrocyte senescence.

Animals↗
PubMed1973

Influence of erythrocyte membrane components on malaria merozoite invasion.

Chymotrypsin- and Pronase-treated human erythrocytes were refractory to invasion by P. knowlesi merozoites; invasion was not inhibited by trypsin or neurammidase treatment. These data implicate a surface protein other than sialoglycoprotein as the receptor site for merozoites. Invasion of rhesus erythrocytes was unaffected by pretreatment with these enzymes. Differences in membrane structure of erythrocytes from various species may explain the absence of an enzyme effect on rhesus erythrocytes.

Animals↗