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Biomedical subjects

A Kilejian

Publications and source records attributed to A Kilejian.

At least 37 records · Page 2Linked to original sources
PubMed1980

Stage-specific proteins and glycoproteins of plasmodium falciparum: identification of antigens unique to schizonts and merozoites.

Establishment of highly synchronized cultures of Plasmodium falciparum enabled identification of stage-specific proteins, glycoproteins, and antigens. Comparison of metabolically labeled constituents of rings, trophozoites, mature schizonts, and merozoites indicated the absence of major proteins or glycorproteins unique to rings or trophozoites. A burst of new synthetic activity occurred during schizogony when several schizont- and merozoite-specific proteins and glycoproteins became apparent. In addition to the knob protein, which was previously shown to be associated with protrusions on the host erythrocyte membrane, a major glycoprotein of parasite origin was identified on the surface membrane of schizonts. Analysis of antigens solubilized from different developmental stages indicated that immune sera, which inhibit growth of parasites in vitro, react mainly with merozoite- and schizont-associated antigens.

Animals↗
PubMed1980

Prospects and problems in the use of recombinant DNA for the production of a malaria vaccine.

Recent advances in malaria immunology and the discovery of an in vitro culture method for Plasmodium falciparum have opened the way for the feasibility of formulating a vaccine as a control measure for this most virulent species of human malaria. The successful use of recombinant DNA technology for the production of scarce cellular constituents has made available a great option for mass synthesis of malaria antigens, which otherwise could be prohibitive if it were to depend on the use of human serum and cells. The translation of feasibility to reality of production of a practical human malaria vaccine will depend on the definition of a safe and effective antigen.

Animals↗
PubMed1979

Characterization of a protein correlated with the production of knob-like protrusions on membranes of erythrocytes infected with Plasmodium falciparum.

Membranes of erythrocytes infected with Plasmodium falciparum develop protrusions called "knobs." These protrusions are not apparent on erythrocytes infected with young parasites (rings) but develop with the growth of parasites to the trophozoite and schizont stages. The nature and origin of knobs were characterized by comparing the stage-specific proteins of two culture lines of P. falciparum, K+ and K-. K+ parasites produce knobs; K- parasites do not. Erythrocytes infected with both types of parasites were labeled metabolically and samples were analyzed by electrophoresis in sodium dodecyl sulfate/polyacrylamide gels. There were no apparent differences in Coomassie blue-stained or radioactive components of rings of K+ and K- parasites. However, erythrocytes infected with K+ trophozoites or schizonts showed a major labeled protein, with an apparent molecular weight of approximately 80,000, that was not present in any developmental stage of K- parasites or in K+ rings. A fraction enriched in membranes from erythrocytes infected with K+ trophozoites showed enrichment of this protein. The results indicate that this protein, synthesized by the parasites, is correlated with the formation of knobs on the host cell membrane. Two additional labeled components were identified. These appeared with the development of schizonts in both K+ and K- parasites and are therefore stage-dependent and not correlated with knobs.

Antigens, Surface↗
PubMed1979

Purification of Plasmodium lophurae exoerythrocytic merozoites by an ion exchange column.

Exoerythrocytic merozoites of Plasmodium lophurae grown in embryonic turkey brain cells were successfully separated from host cell material by elution from a DEAE-cellulose column at ionic strength 0.22. Purity of parasite samples was assessed by sodium dodecyl sulphate acrylamide gel electrophoresis and electron microscopy. Increasing the ionic strength gave greater recoveries of merozoites, but host cell contamination increased.

Animals↗
PubMed1979

Proteins and glycoproteins from human erythrocytes infected with Plasmodium falciparum.

The purpose of this study was to determine whether metabolites of parasite origin are incorporated into the "knob-like" protrusions of membranes of erythrocytes infected with Plasmodium falciparum. Intraerythrocytic parasites were grown in culture and labelled metabolically with ((35)S)-methionine. Fractions enriched in membranes with knobs and fractions poor in knobs were prepared and analysed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Labelled components were visualized by autoradiography. Fractions enriched in membranes with knobs showed a consistent relative increase in a labelled band with an apparent relative molecular mass around 70-80 thousand. Membrane-enriched fractions were also tested for glycoprotein components using lectin-binding. No differences were observed between wheat germ agglutinin-binding components in membranes from normal and parasitized erythrocytes. On the other hand, membranes from parasitized erythrocytes showed distinct concanavalin A-binding components around 70-80 thousand relative molecular mass range. Further experiments are required to conclude whether the metabolically labelled protein component observed within the same relative molecular mass range is a membrane-associated glycoprotein identical to the concanavalin A-binding component.

Animals↗
PubMed1978

Histidine-rich protein as a model malaria vaccine.

Ducklings were successfully immunized against Plasmodium lophurae with a purified and characterized histidine-rich protein as antigen. The use of adjuvant is not required for this protective effect, and immunity can be passively transferred with serum.

Animals↗
PubMed1977

A histidine-rich protein from Plasmodium falciparum and its interaction with membranes.

In previous studies, an unusual protein with 70% of histidine was isolated from Plasmodium lophurae. It was shown to have a possible function in the penetration of merozoites into erythrocytes. The results of the present study indicate the presence of a similar histidine-rich protein in Plasmodium falciparum. Like that of P. lophurae, the histidine-rich protein of P. falciparum is acid-soluble, but it has a slightly higher molecular weight.

Animals↗
PubMed1976

Does a histidine-rich protein from Plasmodium lophurae have a function in merozoite penetration?

Autoradiography was used to localize the distribution of L-[3H]histidine incorporated in vitro by developing segmenters of Plasmodium lophurae. Under conditions used for the visualization of high specific activity loci, radioactivity appeared associated mainly with the histidine-rich protein of cytoplasmic granules as well as with rhoptries and micronemes of merozoites. The isolated histidine-rich protein caused agglutination of erythrocytes and increased their osmotic fragility. Based on the observed evidence suggesting the presence of this histidine-rich protein in the polar organelles of merozoites and its reactivity with erythrocyte membranes, the hypothesis that such a protein may have a function in the penetration of merozoites is proposed.

Agglutination↗
PubMed1975

Circular mitochondrial DNA from the avian malarial parasite Plasmodium lophurae.

The avian malarial parasite, Plasmodium lophurae, was liberated from duck erythrocytes with antiduck erythrocyte serum and freed from host cell nuclei by differential centrifugation followed by treatment with trypsin and DNAase. Total as well as mitochondrial DNA isolated from such a preparation of free parasites showed overlapping densities of 1.679 g/ml in CsCl density gradients. To retain the structural integrity of mitochondrial DNA, the treatment of liberated parasites with trypsin and DNAase was eliminated and all steps of isolation of the mitochondrial fraction was performed at ice bath temperature. Under these conditions, mtDNA liberated by osmotic lysis appeared as super coiled molecules. After isolation of DNA from mitochondrial pellets prepared under the above conditions, only a single DNA band was apparent in ethidium bromide/CsCl gradients and open circular molecules with a mean contour length of 10.3 mum were observed.

Animals↗
PubMed1975

On primary structure and biosynthesis of histidine-rich polypeptide from malarial parasite Plasmodium lophurae.

Experiments on the primary structure of a histidine-rich polypeptide isolated from the malarial parasite Plasmodium lophurae indicate that the smaller quantities of amino acids other than histidine form an integral part of the polypeptide and do not arise from a protein contaminating a histidine homopolymer. In culture, the parasites incorporate over 50% of exogenously supplied histidine into the histidine-rich polypeptide and this incorporation is inhibited by puromycin.

Amino Acid Sequence↗