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D F Wallach

Publications and source records attributed to D F Wallach.

At least 37 records · Page 2Linked to original sources
PubMed1982

Membrane potential of Plasmodium-infected erythrocytes.

The membrane potential (Em) of normal and Plasmodium chabaudi-infected rat erythrocytes was determined from the transmembrane distributions of the lipophilic anion, thiocyanate (SCN), and cation, triphenylmethylphosphonium (TPMP). The SCN- and TPMP-measured Em of normal erythrocytes are -6.5 +/- 3 mV and -10 +/- 4 mV, respectively. The TPMP-measured Em of infected cells depended on parasite developmental stage; "late" stages (schizonts and gametocytes) were characterized by a Em = -35 mV "early stages (ring and copurifying noninfected) by a low Em (-16 mV). The SCN-determined Em of infected cells was -7 mV regardless of parasite stage. Studies with different metabolic inhibitors including antimycin A, a proton ionophore (carbonylcyanide m-chlorophenylhydrazone [CCCP] ), and a H+ -ATPase inhibitor (N,N'-dicyclohexylcarbodiimide, [DCCD] ) indicate that SCN monitors the Em across the erythrocyte membrane of infected and normal cells whereas TPMP accumulation reflects the Em across the plasma membranes of both erythrocyte and parasite. These inhibitor studies also implicated proton fluxes in Em-generation of parasitized cells. Experiments with weak acids and bases to measure intracellular pH further support this proposal. Methylamine distribution and direct pH measurement after saponin lysis of erythrocyte membranes demonstrated an acidic pH for the erythrocyte matrix of infected cells. The transmembrane distributions of weak acids (acetate and 5,5-dimethyloxazolidine-2,4-dione) indicated a DCCD-sensitive alkaline compartment. The combined results suggest that the intraerythrocyte parasite Em and delta pH are in part the consequence of an electrogenic proton pump localized to the parasite plasma membrane.

Animals↗
PubMed1982

Simian virus 40 (SV40)-specific isoelectric point-4.7--94,000-Mr membrane glycoprotein: major peptide homology exhibited with the nuclear and membrane-associated 94,000-Mr SV40 T-antigen in hamsters.

Tryptic peptide maps of electrophoretically purified 94,000-molecular weight (relative) (Mr) nuclear and membrane-associated simian virus 40 (SV40) T-antigens, TN and TM, respectively, were compared to those of the SV40-specific isoelectric point (pI)- 4.7--94,000-Mr plasma membrane component reactive with anti-T-sera from Syrian golden hamsters. Bidimensional thin-layer electrophoresis and chromatography of TN labeled with 125I revealed about 27 tryptic peptides. A similar number of peptides was identified for TM and the pI-4.7--94,000-Mr component. A peptide homology between TN and TM or TN and the pI-4.7-94,000-Mr protein exists and indicates that the previously described pI-4.7--94,000-Mr membrane component represents TM. Only 4 of 27 peptides were labeled when TM was subjected to lactoperoxidase-catalyzed radioiodination from the outer surface of the plasma membrane. One of these TM peptides was metabolically labeled with [14C]glucosamine. The data indicate that TM is partially exposed on the cell surface and represents a glycosylated form of TN. Closely associated with TM is a pI-4.5--55,000-Mr membrane component. This component does not exhibit significant peptide homology with the 94,000-Mr SV40 protein and, therefore, appears to be coded for by the host cell genome.

Animals↗
PubMed1982

Immunogenic antigens common to Plasmodium knowlesi and Plasmodium falciparum are expressed on the surface of infected erythrocytes.

Sera of Gambian individuals and rhesus monkeys immune against infections with Plasmodium falciparum and plasmodium knowlesi, respectively, were reacted with triton X-100-solubilized membranes of infected erythrocytes. Indirect immune precipitation with Staphylococcus aureus, Cowan strain A, followed by dodecylsulfate-polyacrylamide gel electrophoresis, were used to identify interspecies plasmodial antigens that were immunogenic in vivo. Both types of sera specifically precipitated Plasmodium-specific antigens with Mrs of 125,000, 90,000, and 65,000 to 50,000 from membranes of P. knowlesi-infected erythrocytes that had been labeled with 125I using the lactoperoxidase-catalyzed radioiodination or metabolically with 14C-amino acids. In addition, P. falciparum inhibited the precipitation of P. knowlesi antigens by the Gambian immune sera. Our results indicate, that during erythrocytic schizogony, interspecies Plasmodium antigens are exposed on the surfaces of infected erythrocytes.

Animals↗
PubMed1981

Plasmodial modifications of erythrocyte surfaces.

The maturation of malarial parasites in red blood cells produces major alterations in the composition and properties of the host cell surfaces. Existing surface-exposed proteins are modified and new antigenic glycoproteins are synthesized by the parasite and inserted into the membrane. Some of the neoproteins are associated with surface excrescences on the host cells and in some cases these foster adhesion of those cells to capillary endothelium. The erythrocyte endoskeleton is degraded and in association the infected cells become deformed and lose pliability. An increase in intracellular Ca2+ may contribute to the changes in host cells surfaces.

Adhesiveness↗
PubMed1981

Rhesus monkeys protected against Plasmodium knowlesi malaria produce antibodies against a 65,000-MrP. knowlesi glycoprotein at the surface of infected erythrocytes.

Sera from 27 rhesus monkeys immunized in various ways against the H strain of Plasmodium knowlesi were analyzed by quantitative crossed immunoelectrophoresis. The reaction of the sera was compared with a reference immune serum only reactive with P. knowlesi-specific 65,000-Mr glycoprotein-immune component 13 (gp65/ic13) in membranes of infected rhesus monkey erythrocytes. Triton X-100-solubilized, 125I-labeled membranes of schizont-infected erythrocytes were used as an antigen. Sera from 9 or 10 monkeys immunized by repeated infections with P. knowlesi reacted with gp65/ic13. In 6 of 10 sera, anti-gp65/ic13 was the only antibody reacting with host cell membrane proteins. In contrast, vaccination of 15 monkeys with predominantly sexual stages or trophozoites of P. knowlesi in Freund complete adjuvant resulted in protection against blood challenges in 7 monkeys, only 2 of which contained precipitating antibody against gp65/ic13. None of the sera from monkeys not protected by infections or vaccinations contained detectable levels of precipitating antibodies against gp65/ic13. Our data indicate that gp65/ic13 acts as a prominent immunogen in vivo during natural p. knowlesi infections of rhesus monkeys. There is a positive correlation suggested between anti-gp65/ic13 antibody and protection in the monkeys analyzed. This correlation does not apply to monkeys protected against P. knowlesi malaria by vaccination, pointing to other effective immune defense mechanisms.

Animals↗
PubMed1980

Determinants on surface proteins of Plasmodium knowlesi merozoites common to Plasmodium falciparum schizonts.

In this report and (R. Schmidt-Ullrich, L. H. Miller, and D. F. H. Wallach. Manuscript in preparation.), we have demonstrated that malaria proteins on the surface of merozoites and infected erythrocytes cross-react between at least two primate malarias, Plasmodium knowlesi and P. falciparum. Sera from five Gambian adults who were highly immune to P. falciparum were used as a reagent to study the cross-reactivity between P. falciparum schizonts and surface proteins on P. knowlesi merozoites. Although the sera bound to the surface of viable, intact P. knowlesi merozoites, the sera did not block invasion of rhesus erythrocytes. 125I-lactoperoxidase-labeled surface proteins on merozoites formed complexes with the antibody. All major protein bands seen in the electrophoresis of the original Triton extract were bound by the immune sera. Because Gambians have never been exposed to P. knowlesi malaria, the antibodies that reacted with P. knowlesi merozoites must be directed against antigens of another parasite such as P. falciparum. We tested this hypothesis by competition for antibody in a Gambian serum between Triton-extracted antigens from P. falciparum schizont-infected erythrocytes and from surface-labeled P. knowlesi merozoites. P. falciparum inhibited the reaction, thus indicating cross-reaction between antigens in P. falciparum schizonts and P. knowlesi merozoites.

Animals↗
PubMed1980

Concanavalin A induces an intraluminal alkalinization of thymocyte membrane vesicles.

Weak acid distribution methods demonstrate that mitogenic levels of concanavalin A induce an intravesicular alkalinization of isolated thymocyte membrane vesicles. Experiments with chemical reagents that crosslink the high affinity concanavalin A receptor and extensive correlation with known cellular events suggest that a "membrane Bohr effect" may participate in the initiation of mitogenesis.

Animals↗
PubMed1980

Metabolic labelling of P. knowlesi-specific glycoproteins in membranes of parasitized rhesus monkey erythrocytes.

Rhesus monkey erythrocytes infected with P. knowlesi at high degrees of synchrony were metabolically labeled in vitro during the early schizont stage, using 14C-amino acids and 14C-glucosamine as precursors. Parasite-specific proteins in purified schizonts and host-cell membranes were characterized by their isoelectric points and molecular masses, using isoelectric focusing in polyacrylamide and dodecyl sulfate polyacrylamide gel electrophoresis, respectively. Both 14C-amino acids and 14C-glucosamine caused labelling of 60,000-90,000D proteins/glycoproteins, focusing between pH 4.5 and pH 5.2. The plasmodial parasites synthesized gangliosides and/or other glycolipids, leading to their appearance in the host cell membrane.

Amino Acids↗
PubMed1980

State modifications of thymocyte plasma membrane proteins and lipids by mitogenic doses of concanavalin A: a Raman study on isolated membrane vesicles.

Sealed plasma membrane vesicles from rabbit thymocytes were reacted with 0.4-10 micrograms concanavalin A/ml, that is at concentrations that produce cooperative lectin-binding in vivo and in vitro and induce mitogenesis of intact cells. The effects of concanavalin A were monitored by laser Raman spectroscopy of the vesicles in the CH-stretching region. This technique revealed moderately cooperative lipid state transitions in untreated membranes centered at about -6 degrees and 25 degrees, as well as a protein state change at about 43 degrees C. Concanavalin A treatment of the membranes lowered the transition temperatures of the integral of 25 degrees an integral of 43 degrees state changes indicating a direct effect of lectin binding on membrane protein/lipid organization. It is proposed that the primary protein involved is the 55,000D transmembrane protein (Schmidt-Ullrich, R., Mikkelsen, R. B. and Wallach, D. F. H. (1978), J. Biol. Chem. 253, 6973-6978), known to be the high-affinity receptor for concanavalin A, and that the concanavalin A-sensitive integral of 25 degrees transition arises from lipids associated with this protein.

Animals↗
PubMed1980

Host cell-modified T-antigen in membranes of simian virus 40-transformed hamster cells.

Highly purified plasma membranes of simian virus 40 (SV40)-transformed hamster and mouse cells were subjected to indirect immunoprecipitation and bidimensional isoelectric focusing-immunoelectrophoresis with high-titer (greater than or equal to 512) sera against SV40 T-antigen. An SV40-specific protein of approximately 100,000 daltons and pH-4.7 isoelectric point cross-reacted immunologically with T-antigen, which indicated the presence of a T-antigen species. However, this protein appeared to be host cell modified because of its low isoelectric point and its reactivity with heterologous antisera containing antibodies specific for neuraminidase- and trypsin-sensitive carbohydrate and/or peptide moieties lacking nuclear T-antigen. Another protein specific for the membranes of SV40-transformed cells had a molecular mass near 60,000 daltons and an isoelectric point at pH 4.5 and appeared closely associated with membrane T-antigen. It coprecipitated with membrane T-antigen upon direct immunoprecipitation with anti-T serum. However, when this protein was dissociated from membrane T-antigen by isoelectric focusing in the presence of Triton X-100 and urea, its reactivity with anti-T serum was lost. This suggested that the protein was not encoded in the SV40 genome.

Animals↗
PubMed1979

Two Plasmodium knowlesi-specific antigens on the surface of schizont-infected Rhesus monkey erythrocytes induce antibody production in immune hosts.

Purified schizonts (6--10 nuclei) and membranes of schizont-infected erythrocytes from the Malaysian and Philippine strain of Plasmodium knowlesi are analyzed immunochemically using immunoglobulin of rhesus monkey hyperimmune sera against schizonts and of sera from naturally immune monkeys. The anti-schizont Ig identifies less than 20 immune components in Triton X-100-solubilized schizonts and membranes of infected cells. Of these antigens, 9 (component 1, 3, 4, 5, 6, 10, 11, 18, and 20) are common to parasites and membranes of infected erythrocytes, and 12 (2A,B, 6, 8, 9, 12, 13p, 14, 16A,B, 19 A,Bp, 21, 22p, and 23) are predominantly found in the parasite; 4 components (13i, 19A,Bi, 22A, B, and 24) are unique to the membrane of infected erythrocytes. Only three parasite-specific components (1, 13, and 19) are exposed on the surface of parasitized erythrocytes as revealed by both lactoperoxidase-catalyzed radioiodination and extensive absorption of anti-schizont Ig using intact infected erythrocytes. Two plasmodium-specific antigens (1 and 13) on the surface of infected erythrocytes are recognized by sera of rhesus monkeys rendered naturally immune against P. knowlesi infections and, therefore, represent antigens in vivo. Analyses of schizonts and membranes of parasitized erythrocytes of the two different strains of P. knowlesi yields only some minor quantitative, but no qualitative differences when analyzed with both types of antisera. Importantly, components 1 and 13 appear identical in both strains.

Animals↗