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Biomedical subjects

W Trager

Publications and source records attributed to W Trager.

At least 19 recordsLinked to original sources
PubMed1992

Extracellular (axenic) development in vitro of the erythrocytic cycle of Plasmodium falciparum.

Merozoites of the erythrocytic stage of Plasmodium falciparum were suspended in erythrocyte sonicate medium with ATP and pyruvate and mixed with Matrigel to form a soft gel. The gel was overlaid with complete medium; this was replaced with fresh medium at 12, 24, and 36 hr. At these times and also at 45 hr rhodamine 123 was added to some cultures and gels were sampled. Viable extracellular forms showing rhodamine fluorescence were seen: rings at 12 hr, trophozoites and early schizonts with pigment at 36 hr, and late schizonts with developing merozoites at 45 hr. These merozoites were shown to be infective to erythrocytes added to the cultures at 45 hr. Electron micrographs of 36-hr trophozoites show the organisms to have only their single plasma membrane; no parasitophorous membrane is evident. We conclude that the complex process of entry, the intactness of the host erythrocyte, and the parasitophorous membrane are not essential to the development of a merozoite through its complete asexual cycle.

Adenosine Triphosphate↗
PubMed1992

Transfer of a dense granule protein of Plasmodium falciparum to the membrane of ring stages and isolation of dense granules.

A 14-kDa protein was localized to the dense granules of Plasmodium falciparum by immunoelectron microscopy with monoclonal antibody 1H1. The protein was present in dense granules in late-stage schizonts and free merozoites. After invasion, the protein was localized exclusively on the membrane of the newly invaded ring. The protein is referred to as RIMA, for ring membrane antigen. The 14-kDa protein was synthesized late in schizogony as determined by immunofluorescence microscopy and immunoblotting. At the late schizont stage it was distributed diffusely throughout the intracellular schizont. Only at the segmenter stage was the protein localized in defined spots that correspond to dense granules. Dense granules were isolated from schizont-infected erythrocytes by subcellular fractionation on a sucrose gradient. Fractions containing the 14-kDa protein were detected by immunoblotting with monoclonal antibody 1H1. The 14-kDa protein was first detected in vesicles at the late (8-nucleus) schizont stage. Mature dense granules sedimented with a peak density of 1.17 g/ml, which is similar to the density of rhoptries isolated by the same procedure.

Animals↗
PubMed1991

Initial extracellular forms of Plasmodium falciparum: their ultrastructure and their definition with monoclonal antibodies.

Merozoites of the erythrocytic stage of the human malaria parasite Plasmodium falciparum, when placed under appropriate conditions in a culture medium with erythrocyte extract, differentiate into early trophic forms. These forms have much the same ultrastructure as rings of the same age that have developed intracellularly and have then been freed from their host cells by immune lysis. However, these forms differ in two respects: the extracellular forms have only their single plasma membrane, whereas the forms freed from host cells have, in addition, a surrounding parasitophorous vacuole membrane; the forms that develop extracellularly have fewer ribosomes. Five monoclonal antibodies against the ring stage have been prepared and characterized. Their pattern of immunofluorescence localization differs in merozoites as compared with rings, but their pattern is identical in rings developed extracellularly and those developed intracellularly. These results and the observations on fine structure demonstrate biochemical and morphological differentiation in the extracellular forms.

Animals↗
PubMed1979

Tetraethylthiuram disulfide (Antabuse) inhibits the human malaria parasite Plasmodium falciparum.

Plasmodium falciparum in culture grows optimally at 3% oxygen. Oxygen levels down to 0.5% still support growth, but anaerobic conditions do not. These findings, and the absence of the Krebs cycle in Plasmodium, suggested that in this organism oxygen may not function in electron transport but rather may act through metalloprotein oxygenases. Tetraethylthiuram disulfide (Antabuse, disulfiram) and its reduction product diethyldithiocarbamate inhibit many metalloprotein oxygenases and have a lipid/H2O partition coefficient and high binding constant for metal ions, favoring selective toxicity to the malaria parasite. These compounds exhibited active antimalarial effects in vitro in concentrations down to 0.1 microgram/ml, the lowest level tested. Tetraethylthiuram disulfide at a level as low as 1 microgram/ml inhibited parasite glycolysis with no effect on glycolysis of normal erythrocytes. Erythrocytes pretreated with this drug at 10 microgram/ml did not support growth of the parasite.

Animals↗
PubMed1979

Plasmodium falciparum in culture: improved continuous flow method.

A new design of flow vessel provides a method for continuous culture of P. falciparum in a settled layer of human erythrocytes with a slow flow of culture medium over them. The parasitemia is kept fluctuating from approximately 1%, just after addition of fresh erythrocytes, to approximately 10%, 2 or 3 days later. Each vessel provides each week 3 harvests, each containing approximately 0.6--1 X 10(9) parasites.

Animals↗
PubMed1979

Isolation of stages of the human parasite Plasmodium falciparum from culture and from animal blood.

Procedures for isolation of various forms of the asexual erythrocytic stages of the human parasite Plasmodium falciparum are outlined. The procedures employ the plasma expander Physiogel, which is composed of a chemically modified, partially hydrolysed gelatin dissolved in Ringer's lactate. Based on the observation that parasitized cells which are easily separable by this technique differ appreciably at the ultrastructural level, a mechanism by which separation occurs is proposed.

Animals↗
PubMed1979

The role of hemoglobins C, S, and Nbalt in the inhibition of malaria parasite development in vitro.

The host cell competence of hemoglobin C (HbC)-containing erythrocytes for Plasmodium falciparum was studied by in vitro culture. HbC homozygous red cells did not support the growth of the intracellular parasite. Heterozygous cells, however, were competent. In addition, HbC increased the resistance of sicle cell hemoglobin (HbS) red cells when present in the double heterozygote, SC, cultured at low oxygen tension. This effect most likely resulted from the ability of HbC to enhance the sickling of HbS-containing red cells. Oxygenated SC cells were indistinguishable from normal and AS cells in host cell competence. Another double heterozygote, SNBalt, showed decreased sickling and decreased resistance to malaria parasite growth. The evolutionary significance of these results is discussed.

Animals↗
PubMed1979

Recent developments in enlarging the scale of production of Plasmodium falciparum in vitro.

Several methods are described for the cultivation of Plasmodium falciparum. They include cultivation in (a) flow vessels that contain 12 ml of RBC suspension and are harvested three times a week, (b) a "tipper" that provides a similar yield, and (c) more recently, a large flat-bottomed vessel that holds 75 ml of suspension. Attempts are being made to develop techniques for synchronizing the cultures.

Animals↗
PubMed1978

Sickling rates of human AS red cells infected in vitro with Plasmodium falciparum malaria.

The kinetics of sickling of malaria-infected red cells from humans with sickle cell trait were studied in vitro in an attempt to obtain direct experimental evidence for a selective advantage of the hemoglobin S heterozygote in a malarious region. The sickling rates of cells infected with Plasmodium falciparum and of non-infected cells were studied both in the total absence of oxygen (by dithionite addition) and at several different concentrations of oxyhemoglobin which might obtain in vivo. In all cases, red cells containing small plasmodium parasite forms (ring forms) sickled approximately eight times as readily as uninfected cells. Cells containing large parasitic forms (trophozoites and schizonts) appeared to sickle less readily than uninfected cells, by light microscopy criteria, but electron micrographs demonstrated the presence of polymerized deoxyhemoglobin S with a high frequency. It is concluded that enhanced sickling of plasmodium-infected AS cells may be one mechanism whereby the hemoglobin S polymorphism is balanced in favor of the heterozygote.

Anemia, Sickle Cell↗
PubMed1978

Chloroquine resistance produced in vitro in an African strain of human malaria.

After condinous cultivation in the presence of chloroquine, an African strain of the malaria parasite, Plasmodium falciparu, acquired resistance to the drug. The resistance was stable and comparable in vitro to that occurring naturally in a strain from Southeast Asia. This suggests that chloroquine resistance, absent until now in Africa, might arise in the future.

Animals↗
PubMed1978

Cultivation of malarial parasites.

The method for continuous cultivation of Plasmodium falciparum has now been successfully applied to several strains from different geographical areas. It has been used for tests of antimalarial drugs, for studies of parasite-host cell interactions with special reference to sickle haemoglobin, and for the production of amounts of parasite sufficient for experimental immunisation of Aotus trivirgatus monkeys.

ABO Blood-Group System↗
PubMed1978

Immunization against malaria with antigen from Plasmodium falciparum cultivated in vitro.

Aotus monkeys, which are generally killed when infected with the human malaria parasite Plasmodium falciparum, have been identified and grouped by karyotype. These animals were immunized with parasite material obtained from P. falciparum cultivated in vitro which had been maintained in culture for over a year. When sufficient amounts of this antigenic material were used with a synthetic muramyl dipeptide (MDP), protective immunity was induced without presenting the antigen in complete Freund's adjuvant.

Animals↗