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R Schmidt-Ullrich

Publications and source records attributed to R Schmidt-Ullrich.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1979

Fractionation of Plasmodium knowlesi-induced antigens of rhesus monkey erythrocyte membranes.

In order to characterize parasite-induced host cell membrane antigens, the plasma membranes of Plasmodium knowlesi-infected rhesus erythrocytes have been compared with those of normal red cells and purified schizonts by immunochemical and biochemical techniques. Host cell membranes and schizonts were separated by differential centrifugation following nitrogen decompression. Isolated schizonts were further fractionated into several subcellular compartments. Crossed-immune electrophoresis, against monkey anti-schizont serum, of Triton X-100-solubilized material identified 7 P. knowlesi-specific antigens, of which 4 could be detected only in the host cell membranes. These membranes also contained 3 proteins, with relative molecular masses of 55 000, 65 000 and 90 000 and isoelectric points at pH 4.5, 4.5 and 5.2, respectively, which are lacking in normal membranes. Pulse-chase experiments with ((14)C)-glucosamine showed that these parasite-induced host cell membrane components are glycoproteins.

Animals↗
PubMed1978

Plasmodium knowlesi-induced antigens in membranes of parasitized rhesus monkey erythrocytes.

Highly purified Plasmodium knowlesi schizonts were used to produce a hyperimmune anti-parasite serum in a rhesus monkey. Proteins of membranes from normal and P. knowlesi-infected erythrocytes, as well as purified schizonts, were solubilized in 1% Triton X-100 and analyzed by bidimensional electrophoretic techniques. Of seven parasite-specific antigens identified in membranes of parasitized erythrocytes by crossed immune electrophoresis against monkey anti-parasite serum, only three could be detected in the purified schizonts. Bidimensional focusing-dodecyl sulfate/polyacrylamide gel electrophoresis of membranes from parasitized cells revealed three proteins, in the 55,000-90,000 molecular weight region, with isoelectric points between pH 4.5 and pH 5.2, that could not be detected in normal membranes or purified schizonts. Membranes of normal erythrocytes and uninfected erythrocytes that had been incubated with sera from monkeys with 25-50% parasitemia did not react with the monkey anti-parasite serum.

Animals↗
PubMed1977

Periodate induced cross-linking of concanavalin A-reactive membrane proteins of rabbit thymocytes.

Purified plasma membranes of rabbit thymocytes are exposed to sodium periodate and galactose oxidase at conditions similar to those used to induce mitogenic transformation of lymphocytes. The membrane proteins are then fractionated by dodecyl sulfate poly-acrylamide gel electrophoresis. At concentrations of 0.005 M, Na IO4 cross-links 55,000 D and 110,000 D glycoproteins which are known to specifically bind concanavalin A. Galactose oxidase has a similar cross-linking effect, but, at the same time causes proteolytic degradation of membrane proteins. Our data indicate that oxidizing agents, like NaIO4 and galactose oxidase, can indeed cross-link receptors of the thymocyte plasma membrane as has often been proposed as a possible mechanism of their action.

Animals↗
PubMed1977

Simian virus 40-specific proteins in the membranes of simian virus 40-transformed hamster and mouse cells.

Membranes of simian virus 40-transformed hamster lymphocytes and phagocytes, as well as of transformed mouse fibroblasts, contain two classes of antigenic virus-specific protein. The isoelectric points of these proteins, as defined by isoelectric focusing/immune electrophoresis are at pH 4.5 and 4.7. The molecular weights of the pI 4.5 and pI 4.7 components, determined by isoelectric focusing/dodecyl sulfate polyacrylamide electrophoresis, lie near 58,000 and 90,000-110,000, respectively. The pI 4.5 and pI 4.7 proteins are tentatively identified with the surface (transplantation) and U antigens, respectively.

Animals↗
PubMed1977

Antigenic distinctions of glycoproteins in plasma and mitochondrial membranes of lymphoid cells neoplastically transformed by simian virus 40.

Highly purified plasma membranes from hamster lymphocytes transformed by simian virus 40 (GD 248) were compared with the membranes of normal cells by crossed immune electrophoresis, crossed-line immune electrophoresis, and bidimensional isoelectric focusing-immune electrophoresis. Antiserum raised by inoculation of guinea pigs with GD 248 membranes was used as serologic reagent, either directly or after absorption with membranes from normal cells. Bidimensional immune electrophoresis reveals the presence in the plasma membranes of GD 248 cells of at least three antigens not detectable in the membranes from the normal cell population. At least two of these are also present in the mitochondrial membranes of GD 248 cells, but none could be detected in membranes of embryonic fibroblasts. Bidimensional isoelectric focusing-immune electrophoresis indicates that the distinctive antigens of the GD 248 membranes are glycoproteins.

Animals↗
PubMed1977

Transformation by simian virus 40 induces virus-specific, related antigens in the surface membrane and nuclear envelope.

Nucleus- and mitochondrion-free membranes from hamster lymphocytes transformed by simian virus 40 (SV40), GD248 cells, cause guinea pigs to produce immune sera that reveal the presence in GD248 plasma membranes and mitochondria of two types of glycoprotein that are not detected in membranes of normal lymphocytes [Schmidt-Ullrich, R., Thompson, W. S. & Wallach, D. F. H. (1977) Proc. Natl. Acad. Sci. USA 74, 643-647]. Indirect immune fluorescence of living, SV40-transformed T19 hamster reticulum cells, Balb/c 3T3 mouse fibroblasts, and W18 VA2 human fibroblasts, using the antisera against GD248 membrane, at 4 degrees produced a distinct cell surface fluorescence; however, above 20 degrees , staining at the nuclear perimeter, the SV40 U-antigen reaction, becomes equally prominent. In SV40-transformed cells that had been fixed in cold acetone, as well as in purified GD248 nuclei, thermostable U-antigen staining is dramatic, but there is no reaction for nuclear T-antigen. Rabbit antisera against T19 cells gave immunofluorescence reactions equivalent to those obtained with the antisera against GD248 cells. Normal guinea pig or rabbit sera and cells that had not been transformed by SV40 gave no reaction. Our sera from tumor-bearing hamsters gave only nuclear T-antigen fluorescence. The results indicate the presence of related, SV40-specific antigens in the surface membranes, nuclear envelope, and possibly other intracellular organelles of SV40-transformed cells.

Antigens, Viral↗
PubMed1977

Differences between the structural dynamics of plasma membranes of normal hamster lymphocytes and lymphoid cells neoplastically transformed by simian virus 40 as revealed by laser Raman spectroscopy.

The Raman spectra of highly purified plasma membranes from SV40-transformed GD248 lymphocytes have been compared with the spectra of the membranes of normal cells over the spectral region 100 cm-1 to 3010 cm-1. Striking differences between the two membrane categories were observed in the thermal response of the CH-stretching and acoustical regions. Analysis of CH-stretching shows that the membranes of normal cells exhibit a thermal transition centered at 7 degrees and approximately 5 degrees wide. The membranes of GD248 cells, in contrast, show a lipid transition centered at -5 degrees and 12-18 degrees wide. Analysis of the acoustical region yields equivalent results. The membrane proteins of normal membranes undergo a large thermotropic transition, starting at 39 degrees (sample temperatures), whereas this transition begins at 23 degrees with GD248 plasma membranes. The results suggest the possibility that SV40-specific membrane proteins may modify the collective thermotropic behavior of both normal membrane proteins and membrane lipids.

Animals↗
PubMed1976

Interaction of concanavalin A with rabbit thymocyte plasma membranes. Distinction between low affinity assoication and positively cooperative binding mediated by a specific glycoprotein.

1. We have analyzed the interaction of the mitogenic lectin, concanavalin A, with purified plasma membranes isolated from rabbit thymocytes. 2. Scatchard analyses show that in native membranes binding is positively cooperative at low concanavalin A concentrations and non-interacting at high lectin levels. 3. In contrast, membranes treated with 0.0064 M glutaraldehyde exhibit diphasic Scatchard plots, indicating the presence of high- and low-affinity binding sites. The high-affinity zone corresponds to the region of positive cooperativity in native membranes. 4. The number of high-affinity binding sites per cell-equivalent corresponds approximately to the number of glycoprotein (mol. wt. 55000) molecules (1-10(6)/cell), but account for less than 25% of the total lectin binding. 5. Treatment of membranes with 0.0064 M glutaraldehyde selectively crosslinks the glycoprotein (mol. wt. 55000) and its multimers, correlating directly with the modifications of concanavalin A-binding. 6. We conclude that high-affinity binding of concanavalin A to thymocyte membranes is a cooperative process mediated by the glycoprotein (mol. wt. 55000). We further conclude that the bulk of concanavalin A binding is through low-affinity associations, not involving specific membrane macromolecules.

Animals↗