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Biomedical subjects

R Ramasamy

Publications and source records attributed to R Ramasamy.

At least 109 records · Page 6Linked to original sources
PubMed1990

Anti-mosquito antibodies reduce the susceptibility of Aedes aegypti to arbovirus infection.

Aedes aegypti (L.) mosquitoes showed a significant reduction in susceptibility to infection with Ross River virus and Murray Valley encephalitis virus when they were fed on a blood-virus mixture containing rabbit antibodies to mosquito midgut components. Presence of the antibodies did not demonstrably affect virus titres in infected mosquitoes, nor the transmission of virus from infected mosquitoes to vertebrates.

Aedes↗
PubMed1990

Effect of anti-mosquito antibodies on the infectivity of the rodent malaria parasite Plasmodium berghei to Anopheles farauti.

The effect of mouse anti-mosquito antibodies, present in the bloodmeal, on the infectivity of Plasmodium berghei Vincke to Anopheles farauti Laveran was investigated. Significantly fewer oocysts developed in mosquitoes feeding on mice immunized with sugar-fed mosquito midgut antigens than in mosquitoes feeding on control mice. Mosquitoes feeding on mice immunized with the midgut antigens derived from sugar-fed mosquitoes also showed reduced mortality and had lower infection rates than those fed on unimmunized mice. Blood-fed midgut antigen was less effective in producing these effects than sugar-fed midgut antigen.

Animals↗
PubMed1990

Novel cross-reactive epitopes on asexual blood stage antigens of Plasmodium falciparum.

An IgM monoclonal antibody that reacts with the merozoite membrane and internal merozoite antigens was shown to recognize several previously characterized asexual blood stage antigens of Plasmodium falciparum as well as new antigens. Among the reactive antigens identified were FIRA, GYMSSA, RESA and the S-antigen. Analysis of the cross-reactions between FIRA and GYMSSA by epitope scanning was performed. The most reactive peptides in GYMSSA had the common sequence STNS. The cross-reactive epitopes in FIRA could, in many cases, be explained by the results of a replacement net analysis performed on the STNS epitope. It is proposed that the cross-reactive epitopes, which in several cases have no obvious linear homology but possess high S, T and N content, may be present as loops or coils on the surface of the molecules.

Amino Acid Sequence↗
PubMed1989

Competition between Li+ and Mg2+ for ATP in human erythrocytes. A 31P NMR and optical spectroscopy study.

We have investigated the influence of Li+ on free intracellular Mg2+ concentration in human erythrocytes by 31P NMR and optical absorbance spectroscopies. In red cells loaded with 3 mM intracellular Li+, the chemical shift separation between the alpha- and beta-phosphate resonances of MgATP2- was approx. 0.9 ppm larger than that observed in Li+-free red cells. By analyzing the interaction of each red cell component with Mg2+ and Li+, we found that Mg2+ is displaced in part from MgATP2- upon addition of Li+ and that the released Mg2+ is bound to the red cell membrane causing an overall decrease in free intracellular Mg2+ concentration.

Adenosine Triphosphate↗
PubMed1989

Analysis of human T cell response to two Plasmodium falciparum merozoite surface antigens.

Eight novel human T cell epitopes were identified within the two major merozoite surface antigens (MSA1 and MSA2) of Plasmodium falciparum using synthetic peptides. All except one of the peptides conformed structurally to an amphipathic alpha helix and three out of the four MSA1 peptides also contained sequences containing the Rothbard motif. Peptide MSA2/2, which fitted none of these criteria, was recognized by our donors to a similar degree as the other peptides. This peptide also contains a B cell epitope. Proliferative responses were obtained in both immune and nonimmune donors, however, the number of responses in the immune donor group was significantly higher. There was no correlation between the level of proliferation and antibody titers to these antigens. No peptides were preferentially recognized in association with specific HLA class II antigens.

Animals↗
PubMed1988

Identification of T epitopes within a potential Plasmodium falciparum vaccine antigen. A study of human lymphocyte responses to repeat and nonrepeat regions of Pf155/RESA.

PBMC from Melanesians who had high antibody reactivities to fusion proteins encompassing the 3' and the 5' repeat regions of the ring infected E surface antigen (Pf155/RESA), were tested for their ability to respond to synthetic and recombinant peptides representing regions of Pf155/RESA. The aim was to identify T cell epitopes within the Ag. Most of the synthetic peptides from the nonrepeat regions of Pf155/RESA were selected for study on the basis of their tendency to form amphipathic alpha-helices. Peptides representing immunodominant B cell epitopes were also tested. Three-quarters of the Melanesian donors responded to the recombinant peptides (Ag 1505 and Ag 632-100) and to the 8 x 4 mer, a synthetic peptide representative of the 3' repeat region. Whereas all the remaining eight peptides tested elicited a response in at least one donor, three peptides (M40, M42, and BTA3) representing sequences in the nonrepeat regions showed greatest promise as potentially useful T epitopes. Responses in control donors were also observed to most of the peptides but the percentage of responders was lower. T cell bulk lines specific to Ag 1505 and Ag 632-100 were established. All donors were HLA tissue typed, but no obvious correlations between responsiveness and HLA type were observed. Our results suggest that there are T cell epitopes within and outside the repeat regions of Pf155/RESA.

Adult↗
PubMed1988

Isolation and partial characterisation of a 26 kilodalton antigen from Plasmodium falciparum recognised by an inhibitory monoclonal antibody.

A 26 kDa protein, present in trophozoites and schizonts of Plasmodium falciparum, has been identified as the target of a monoclonal antibody that weakly inhibits parasite growth in vitro. The antigen has been purified to homogeneity by immuno-affinity chromatography and electrophoresis. The sequence of 19 amino acids at the N-terminus of the protein has been determined.

Amino Acid Sequence↗
PubMed1988

An epitope recognised by inhibitory monoclonal antibodies that react with a 51 kilodalton merozoite surface antigen in Plasmodium falciparum.

Monoclonal antibodies designated 8G10/48 and 9E3/48 raised against mature asexual blood stages of Plasmodium falciparum inhibit parasite growth in vitro. Both antibodies bind to an epitope which includes the linear sequence Ser Thr Asn Ser and which is present in a cDNA clone from a P. falciparum expression library. These antibodies recognise a glycosylated antigen of approximately 51 kDa which is located on the merozoite surface membrane.

Amino Acid Sequence↗
PubMed1988

Identification of two integral membrane proteins of Plasmodium falciparum.

We describe the isolation and cloning of two integral membrane protein antigens of Plasmodium falciparum. The antigens were isolated by Triton X-114 temperature-dependent phase separation, electrophoretically transferred to nitrocellulose, and used to affinity-purify monospecific human antibodies. These antibodies were used to isolate the corresponding cDNA clones from a phage lambda gt11-Amp3 cDNA expression library. Clone Ag512 corresponds to a Mr 55,000 merozoite rhoptry antigen, and clone Ag513 corresponds to a Mr 45,000 merozoite surface antigen. Both proteins can be biosynthetically labeled with [3H]glucosamine and [3H]myristic acid, suggesting that they may be anchored in membranes via a glycosylphosphatidylinositol moiety. Similarities in the C-terminal sequences of the Mr 45,000 merozoite surface antigen and the Trypanosoma brucei variant surface glycoproteins provides further evidence that this antigen has a glycosylphosphatidylinositol anchor.

Amino Acid Sequence↗
PubMed1988

Anti-mosquito antibodies decrease the reproductive capacity of Aedes aegypti.

Aedes aegypti (L.) fed on rabbits immunized with mosquito antigens showed a reduction in fecundity in the first oviposition and decreased viability of the progeny. Feeding behaviour of mosquitoes was not affected and no significant mortality was observed due to the presence of anti-mosquito antibodies in the bloodmeal. Antibodies were detected in the oocytes of mosquitoes 48 h after the bloodmeal. The role of specific antibodies in influencing fecundity is discussed.

Aedes↗
PubMed1987

Studies on glycoproteins in the human malaria parasite Plasmodium falciparum--lectin binding properties and the possible carbohydrate-protein linkage.

Several glycoproteins of the human malarial parasite Plasmodium falciparum are shown to bind to the lectins concanavalin A, wheat germ agglutinin, Ricinus communis 120 lectin and Bandeirea simplicifolia lectin. There was reduced binding of [125I]-concanavalin A to several red blood cell glycoproteins, including the anion transport protein, in parasitised cells. The carbohydrates of parasite glycoproteins are not typical N-linked oligosaccharides since the enzyme peptide: N-glyconase F fails to cleave them. In contrast, many of the parasite glycoproteins are labelled with [3H]-myristic acid consistent with a possible linkage of carbohydrate to a membrane anchoring phospholipid.

Amidohydrolases↗
PubMed1986

Electrophoretic variants of alpha 2u-globulin in the livers of adult male rats: a possible polymorphism.

Two-dimensional polyacrylamide gel electrophoresis has been used to examine the microsomal fractions from the livers of 32 adult male Alpk/AP (Wistar-derived) rats for the presence of alpha 2u-globulin variants of differing isoelectric point. Three major such isoelectric variants are described. Different combinations of these three forms were found in the population examined, with one-half of the animals expressing all three variants in approximately equal proportions and with one variant being present in all the animals examined. An understanding of the relevance of such different alpha 2u-globulin profiles to the individual animal must now await the assignment of a biological role for alpha 2u-globulin.

Alpha-Globulins↗
PubMed1986

Terminal galactose residues and the antigenicity of Plasmodium falciparum glycoproteins.

The presence of terminal alpha-D-galactosyl residues in the carbohydrate chains of glycoprotein antigens from the asexual blood stages of Plasmodium falciparum is demonstrated by the alpha-D-galactosidase sensitivity of particular parasite antigens, the use of specific glycosidases to cleave sugars from parasite glycoproteins radiolabeled with [3H]glucosamine, and the ability of Bandeirea simplicifolia lectin, which has a specificity for terminal alpha-galactosyl residues, to bind to the parasite. The carbohydrate side chains, and in particular the terminal alpha-galactosyl residues, are shown to have an important role in determining the binding of antibodies to parasite glycoproteins.

Animals↗