Pore-forming protein from Entamoeba histolytica forms voltage- and pH-controlled multi-state channels with properties similar to those of the barrel-stave aggregates.

Pore-forming protein from Entamoeba histolytica forms cation-selective channels in planar bilayers. With increasing potentials, the open-state probability of these channels decreases, and channel aggregates collapse (Young, J.D.

Pathogenic and non-pathogenic Entamoeba: pore formation and hemolytic activity.

Pore-forming activity in planar lipid bilayers and liposomes of extracts from differentially pathogenic Entamoeba and the capacity of trophozoites and subcellular fractions to lyse human red blood cells (hrbc) were investigated. In all amebas studied, the two activities paralleled each other. They were high in E.

Effects of amiloride on Na+ content and pinocytosis in Entamoeba histolytica.

Amiloride, a blocker of Na+ leak and Na+-H+ exchange in animal cells, caused cells of Entamoeba histolytica to release Na+ (up to 40% of their original Na+ content within 90 min, at an amiloride concentration of 3 mM); K+ content was not affected. By comparing the unidirectional uptake of 22Na+ with that of the fluid-phase marker 125I-labeled poly(vinylpyrrolidone) we established that the amiloride-induced Na+ loss was due to inhibition of pinocytic Na+ uptake rather than to blockage of an amiloride-sensitive transport system in the plasma membrane. Amiloride penetrated the cells, and both its intracellular concentration and its effect on pinocytosis increased with pH.

Effects of cytochalasin B on Na+ content and cell volume of Entamoeba histolytica.

Cells of Entamoeba histolytica accumulated K+ and extruded Na+ compared to the concentrations of those ions present in the growth medium. Pinocytic activity, measured by the uptake of horseradish peroxidase of 125I-polyvinylpyrrolidone, was high (up to 0.3 ml/ml cells per h).

Immunology of Entamoeba histolytica in human and animal hosts.

Although Entamoeba histolytica induces humoral and cellular immune responses in both human and animal hosts, there is no indication of postinfection immunity in humans; in contrast, several other mammals are protected by prior infection or immunization. The exacerbation of the disease by immunosuppression suggests a protective function of still-unknown defense mechanisms. Specific local and circulating antibodies are produced regularly during invasive amebiasis.

Mitogenicity of Entamoeba histolytica extracts for murine lymphocytes.

Aqueous extracts or aqueous extracts of delipidated Entamoeba histolytica (E.h.e.

Surface properties of Entamoeba: increased rates of human erythrocyte phagocytosis in pathogenic strains.

The assertion that ingestion of human erythrocytes is restricted to invasive strains of Entamoeba histolytica has not been evaluated previously by comparative studies. In this report we describe the in vitro ingestion of human erythrocytes by pathogenic and nonpathogenic Entamoeba. Microscopic evaluation of erythrophagocytosis by eight different Entamoeba grown in culture revealed that strains of E.

[Phagocytosis of human erythrocytes by Entamoeba histolytica. Quantitative study].

The degree of eythrophagocytosis of two recently isolated strains of E. histolytica was measured by microscopic examination. Amebas isolated from a patient with amebic rectocolitis (strain HM22:IMSS, monoxenic) ingested human red blood cells faster and in larger numbers than trophozoites isolated from an asymptomatic carrier (HM27:IMSS, monoxenic).

Surface charge of trypanosoma cruzi. Binding of cationized ferritin and measurement of cellular electrophoretic mobility.

The surface charge of epimastigote and trypomastigote forms of Trypanosoma cruzi was evaluated by means of binding of cationized ferritin to the cell surface as visualized by electron microscopy, and by direct measurements of the cellular microelectrophoretic mobility (EPM). Epimastigote forms had a mean EPM of -0.52 micrometer-s-1-V-1-cm and were lightly labeled with cationized ferritin.

Surface properties related to concanavalin A-induced agglutination. A comparative study of several Entamoeba strains.

Pathogenic strains of Entamoeba histolytica are more easily agglutinated with concanavalin A (Con A) than strains isolated from human asymptomatic carriers. All three pathogenic strains studied here were found to agglutinate with low concentrations of Con A in contrast to various nonpathogenic axenic strains of amebas, characterized by their ability to grow at room temperature. Our present observations suggest that the extreme susceptibility of pathogenic strains of E.

Ir-gene control of antibody class production.

The antibody response in mice to DNP-insulin is under Ir-gene control. The Ir gene defects in two strains have been analyzed. In both cases the IgG immune response was impaired whereas the IgM response was not affected.

Similar specificity of IgG1 and IgG2a antibodies in individual mice.

In this study the previous finding of similar variable regions in individual IgG1 and IgG2a antibody populations is extended by the demonstration of similar fine specificity of IgG1 and IgG2a combining sites. Antibody populations from individual mice directed against oligo-D-alanine determinants were analyzed in their cross-reactivity towards 5 heterologous dipeptides. This was done by mixing antibody and hapten followed by determination of free antibodies in a kinetic red cells sensitization assay.

Similar combining sites of IgG1 and IgG2a antibodies in individual mice as judged from affinity and rate constant measurements.

Within individual sera, mouse IgG1 and IgG2a subclass antibodies against the antigenic determinant oligo-D-alanine are likely to have similar combining sites. The antibodies are characterized by two methods, by their rate of binding to antigen equipped sheep red blood cells and by the hapten inhibition of antigen binding. The two characteristics are shown to be independent.