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Biomedical subjects

W Trager

Publications and source records attributed to W Trager.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1978

Fine structure of human malaria in vitro.

The erythrocytic cycle of the human malaria parasite, Plasmodium, falciparum, was examined by electron microscopy. Three strains of parasites maintained in continuous culture in human erythrocytes were compared with in vivo infections in Aotus monkeys. The ultrastructure of P. falciparum is not altered by continuous cultivation in vitro. Mitochondria contain DNA-like filaments and some cristae at all stages of the erythrocytic life cycle. The Golgi apparatus is prominent at the schizont stage and may be involved in the formation of rhoptries. In culture, knob-like protrusions first appear on the surface of trophozoite-infected erythrocytes. The time of appearance of knobs on cells in vitro correlates with the life cycle stage of parasites which are sequestered from the peripheral circulation in vivo. Knob material of older parasites coalesces and forms extensions from the erythrocyte surface. Some of this material is sloughed from the host cell surface. The parasitophorous vacuole membrane breaks down in erythrocytes containing mature merozoites both in vitro and in vivo. Merozoite structure is similar to that of P. knowlesi. The immature gametocytes in culture have no knobs.

Animals↗
PubMed1978

Plasmodium falciparum in culture: establishment of additional strains.

The establishment of new strains of Plasmodium falciparum in continuous culture is described. One line (FCR-2), isolated from an individual who had traveled extensively through South America, was passed initially through Aotus trivirgatus monkeys and then cultured into human erythrocytes using the flow-vial technique. A strain of P. falciparum FMG), shipped by air freight on wet ice from The Gambia, was cultured directly from a human infection into continuous culture using the Petri dish-candle jar technique, giving line FCR-3. Two other strains (6252 and FSG) were hand carried by a commercial flight on wet ice from the Gambia and were initiated into culture at the same time using the same media, sera, and erythrocytes. After 6 wk in vitro the 6252 strain became adapted as line FCR-4, whereas FSG had died out. Normal-looking gametocytes were seen in all four strains reported here. Notwithstanding their normal appearance they would not exflagellate in vitro, nor were they infective to Anopheles stephensi mosquitoes via membrane feeding. Production of new gametocytes continued for 6 mo, then gradually stopped.

Animals↗
PubMed1977

Cultivation of erythrocytic stages.

Two methods are described for the continuous cultivation of Plasmodium falciparum. One method provides for a continuous slow flow of medium over a settled layer of blood cells and does not require daily attention. With the other method, carried out in Petri dishes, the medium has to be changed manually every day. The problems and possibilities of continuous cultivation are discussed.

Animals↗
PubMed1977

Cofactors and vitamins in the metabolism of malarial parasites. Factors other than folates.

Relatively few cofactors have so far been demonstrated to be essential for the intracellular development of erythrocytic stages of malarial parasites. Besides 4-aminobenzoic acid, presumably required for the synthesis of folates, these are biotin and pantothenate. The pantothenate is not used directly by the parasites but rather as coenzyme A synthesized by the host erythrocyte. Parasites maintained extracellularly in vitro also have a requirement for exogenous adenosine triphosphate. No information is available concerning cofactor requirements of the sporogonic or pre-erythrocytic stages.

Animals↗
PubMed1976

Human malaria parasites in continuous culture.

Plasmodium falciparum can now be maintained in continuous culture in human erythrocytes incubated at 38 degrees C in RPMI 1640 medium with human serum under an atmosphere with 7 percent carbon dioxide and low oxygen (1 or 5 percent). The original parasite material, derived from an infected Aotus trivirgatus monkey, was diluted more than 100 million times by the addition of human erythrocytes at 3- or 4-day intervals. The parasites continued to reproduce in their normal asexual cycle of approximately 48 hours but were no longer highly synchronous. The have remained infective to Aotus.

Animals↗
PubMed1976

An electron microscopic study of Babesia microti invading erythrocytes.

Intracellular sporozoan parasites invade the host cell through the invagination of the plasma membrane of the host and a vacuole is formed which accommodates the entering parasite. The vacuole may disappear and the invaginated membrane of the host then becomes closely apposed to that of the parasite's own membrane. As a result the parasite is covered by two membranes. Members of the class Piroplasmea differ from other Sporozoa in that their trophozoites are covered by a single membrane. By screening numerous sections of intraerythrocytic Babesia microti belonging to the class Piroplasmea, it was found that merozoites of Babesia enter the erythrocytes of hamsters in the same way as those of the other Sporozoa. When a merozoite touches the red blood cell with its anterior end it becomes attached to the membrane of the host, which starts to invaginate and a parasitophorous vacuole is formed. The vacuolar space disappears rapidly and the membrane of the vacuole and that of the parasite become closely adjacent. At this stage the parasite is surrounded by two plasma membranes. The outer membrane derived from the invaginated host membrane disintegrates quickly and the parasite is left with a single membrane throughout its life span.

Animals↗
PubMed1975

Coezyme A requirement of malaria parasites: effects of coenzyme A precursors on extracellular development in vitro of Plasmodium lophurae.

The extracellular development in vitro of the avian malaria Plasmodium lophurae is favored by addition to the medium of coenzyme A at 0.05 mM. Coenzyme A can be replaced by dephospho-coenzyme A and to some extent by phosphopantetheine, but not by phosphopantothenoylcysteine or by phosphopantothenic acid. The activity of the two former precursors results from their conversion to coenzyme A by enzymes in the erythrocyte extract of the culture medium in the presence of ATP, also an essential ingredient of the medium. Hence, P. lophurae in its erythrocytic stage has an absolute requirement for an exogenous source of coenzyme A.

Animals↗
PubMed1975

Coenzyme A requirement of malaria parasites: enzymes of coenzyme A biosynthesis in normal duck erythrocytes and erythrocytes infected with Plasmodium lophurae.

Normal duck erythrocytes and erythrocytes infected with Plasmodium lopharae have all of the enzymes for coenzyme A biosynthesis, whereas parasites freed from their host cells have non. Since erythrocytefree cultivation of P. lophurae requires an exogenous source of coenzyme A, this parasite must obtain its coenzyme A entirely from the host cell during infection.

Adenosine Triphosphate↗
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↗
PubMed1975

On the cultivation of Trypanosoma vivax: a tale of two visits in Nigeria.

A new method is presented for obtaining in vitro development of the insect cycle of Trypanosoma vivax. Bloodstream trypanosomes from infected sheep were inoculated to tsete fly organ cultures in a modified Eagle's medium with 20% sheep serum, and incubated at 28 C. The organisms multiplied first as elongate spiral trypomastigotes. In successful cultures these transformed to epimastigotes. The epimastigotes multiplied extensively to form dense layers attached to formed structures, especially to pieces of peritrophic membrane. In older cultures transitional forms appeared, including some approaching the morphology of metacyclic trypanosomes.

Animals↗