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At least 19 recordsLinked to original sources

PubMed1978

The phosphoglucose isomerases of the bloodstream forms of Trypanosoma brucei and Trypanosoma vivax.

1. The phosphoglucose isomerases (PGI's) of the bloodstream forms of Trypanosoma brucei and T. vivax have been purified some 150-fold, using cellulose ion-exchange chromatography, gel filtration and isoelectric focussing. 2. The two trypanosome enzymes showed many similarities in kinetic properties, but differed from each other somewhat in thermal stability and in isoelectric point. 3. Both trypanosome enzymes differ from PGI's from other sources in having a higher Ki for the competitive inhibitor 6-phosphogluconate.

Animals↗

PubMed1979

Cyclical transmission of Trypanosoma brucei rhodesiense and Trypanosoma congolense by tsetse flies infected with culture-form procyclic trypanosomes.

Culture procyclic forms of Trypanosoma brucei rhodesiense and Trypanosoma congolense were fed to Glossina morsitans morsitans through artificial membranes. A very high percentage of the flies so fed produced established midgut infections, a proportion of which went on to develop into mature metacyclic trypanosomes capable of infecting mammalian hosts. The method offers a safe, clean way of infecting tsetse flies with African trypanosomes which reduces the need for trypanosome-infected animals in the laboratory.

Animals↗

PubMed1977

African trypanosomes: cultivation of animal-infective Trypanosoma brucei in vitro.

Trypanosoma brucei grew in the presence of bovine fibroblast-like cells in Hepes-buffered RPMI 1640 medium with 20 percent fetal bovine serum for more than 220 days at 37 degrees C. The organisms grown in this system were infective to mammalian hosts, retained the morphological and biochemical characteristics of long slender bloodstream forms, and displayed variant-antigen on their surfaces.

Animals↗

PubMed1976

Filaments of Trypanosoma brucei: some notes on differences in origin and structure in two strains of Trypanosoma (Trypanozoon) brucei rhodesiense.

Filaments attached to trypanosomes of two strains of T. (T.) brucei were studied by electron microscopy and two distinct types identified: short-thick and long-thin. The former are associated with stumpy trypanosomes and are secretions, via the flagellar pocket, which originate in the area of the Golgi complex, during the infection of the host. They are referred to as 'secretory filaments'. Their diameter is 0.09 to 0.14 mum. The long-thin filaments are associated with slender forms of trypanosome in various artificial situations; those shown by negative staining are believed to be cytoplasmic extrusions from the anatomically weak extremities of the parasite and are referred to as 'plasmanemes'. Their diameter is 0.06 mum. Both types appear to maintain their structure without the aid of the normal type of unit membrane as myelin formations.

Animals↗

PubMed1977

Cultivation of bloodstream Trypanosoma brucei.

Animal-infective forms of Trypanosoma brucei (Strain 427) were successfully propagated in HEPES-buffered RPMI 1640 medium in the presence of bovine fibroblast-like cells for over 310 days. The organisms grown in this system were morphologically identical to the long slender bloodstream forms, retained their infectivity for mammalian hosts, and displayed variant-antigen on their surface. Technical details for establishing such bloodstream form cultures are described in the present paper.

Animals↗

PubMed1977

Particle-bound enzymes in the bloodstream form of Trypanosoma brucei.

We have screened the bloodstream form of Trypanosoma brucei for the presence of enzymes that could serve as markers for the microbodies and the highly repressed mitochondrion of this organism. None of seven known microbody enzymes were detected at all, but glycerol-3-phosphate oxidase, ATPase, isocitrate dehydrogenase, acid phosphatase and part of the hyperoxide dismutase and malate dehydrogenase activities were found to be particle-bound after fractionation of homogenates by differential centrifugation. Part of the ATPase activity was sensitive to oligomycin, an inhibitor of oxidative phosphorylation. This oligomycin-sensitive activity can serve as a specific marker for the mitochondria. More than 80% of the NAD+-linked glycerol-3-phosphate dehydrogenase in T. brucei was found to be particulate and latent. The enzyme could be activated by Triton X-100, by the combined action of sonication and salt, but not by salt alone, and partially by freezing and thawing. We conclude that the NAD+-linked glycerol-3-phosphate dehydrogenase is located inside an organelle.

Acid Phosphatase↗

PubMed1979

Genital lesions in experimental chronic Trypanosoma brucei infection in rams.

Rams inoculated intravenously with Trypanosoma brucei developed scrotal oedema and a nonsuppurative granulomatous periorchitis resulting in testicular degeneration, atrophy, calcification and sclerosis. The tunica vaginalis was the seat of an intense granulomatous inflammation and focal necrosis, which extended to the epididymis and spermatic cord. Lesions in the seminal vesicles were suggestive of diminished testosterone production even though Leydig cells were discernible in the sclerotic testicular intertubular tissue. In areas where there was inflammation or focal necrosis, there was also extravascular localisation of trypanosomes. It is suggested that genital lesions in human sleeping sickness may have a similar pathogenetic mechanism involving tissue localisation of the trypanosomes and associated inflammatory and degenerative changes.

Animals↗

PubMed1977

Suppressor cells in mice infected with Trypanosoma brucei.

Within 2 to 3 days of infection with Trypanosoma brucei strain S42, the ability of spleen cells from infected CBA mice to mount a primary in vitro antibody response to sheep red blood cells (SRBC) is profoundly reduced, and suppressor cells are generated as detected by cell mixture experiments. Suppressor cell activity lies in the T and adherent cell compartments of spleens from infected mice, but not in the B cell compartment, although antibody responses to a thymus-independent antigen, DNP-Ficoll, are significantly reduced. Suppression of antibody responses of normal spleen cells depends on viable cells from infected mice. The trypanosome, itself, plays no direct role in suppression, and we have ruled out the possibility of antigenic competition as a mechanism of suppression. Our data is consistent with the model of suppressor T cells induced by concanavalin A mitogenesis. We hypothesize that trypanosome antigens may directly stimulate T cells with the concomitant release of factors with affinity for macrophage surfaces thus becoming suppressive for T and B cell responses.

Animals↗

PubMed1975

Ultracytochemistry of the surface coat/pellicle complex in Trypanosoma brucei.

Ultracytochemistry of polysaccharides and specific sugar residues reveals differences in the surface staining pattern between developmental forms of Trypanosoma brucei. The techniques used were the PA (periodic acid)-TCH (thiocarbohydrazide)-silver albumose reaction for the polysaccharides, and the Concanavalin A (Con A)-perioxdase-DAB coupling method for specific sugar residues. Blood and metacyclic forms, both possessing a surface coat, stain distinctly for carbohydrates at the level of the pellicular membrane. The external portion of the bloodform coat lacks any positive staining. Pellicles of non-coated culture and vector forms react only faintly for polysaccharides, whereas heavy staining of oxidized peroxidase/DAB reaction product, indicative of sugar bound Con A, occurs. It is suggested that the sugar moieties of the coat glycoproteins are located close to the membrane-coat junction.

Age Factors↗

PubMed1975

Identification, purification and properties of clone-specific glycoprotein antigens constituting the surface coat of Trypanosoma brucei.

Soluble glycoproteins have been purified from a series of clones of Trypanosoma brucei 427. Each clone yielded a characteristic predominant glycoprotein which induced clone-specific immunity to trypanosome infection in mice. These glycoproteins were shown by specific labelling and enzyme digestion of cells to be the major components of the trypanosome surface coat. Each glycoprotein consisted of a single polypeptide chain having an apparent molecular weight of 65 000 (as measured by SDS-polyacrylamide gel electrophoresis) and containing around 600 amino acid and 20 monosaccharide residues. Preliminary structural studies indicated large changes in amino acid sequence dispersed over a considerable length of the polypeptide chain. Proteolytic activity was demonstrated in semi-purified trypanosome extracts, providing one reason for the heterogeneity sometimes observed in surface glycoprotein antigen preparations.

Animals↗

PubMed1979

Detection of multiple variable antigen types in metacyclic populations of Trypanosoma brucei.

The identification of antigen types in tsetse salivary gland metacyclic populations of Trypanosoma brucei requires the production of monospecific antisera to the corresponding bloodstream variable antigen types. Monospecific antisera against clones from cyclically transmitted populations are difficult to prepare, however, owing to the antigenic lability of such clones. This problem has been overcome by isolating an antigenically stable clone from a syringe-infected rabbit at a time when its serum showed incipient activity towards metacyclic trypanosomes. Monospecific antisera raised against this clone reacted with up to 20% metacyclics in trypanolysis and immunofluorescence tests, confirming that a clone-derived metacyclic population of T. brucei is heterogeneous with respect to variable antigen type.

Animals↗

PubMed1979

The blood volumes and erythrokinetics of Ndama and Zebu cattle experimentally infected with Trypanosoma brucei.

The responses of susceptible Ndama and Zebu cattle to experimental infection with Trypanosoma brucei were compared using haematological, parasitological and radioisotopic methods. Animals of both breeds became anaemic, but this was more severe in the Zebu cattle, one of which died. Although the prepatent period was the same in animals of both breeds, the levels of the first and subsequent peaks of parasitaemia were higher in the Zebu. The anaemia was due to an accelerated rate of red cell break-down which was more marked in the Zebu cattle. Haemodilution was not a feature. There was no evidence of dyshaemopoiesis but iron reutilisation from degraded erythrocytes was impaired. The greater resistance of the Ndama to T brucei infection could not be attributed to the capacity of this breed to mount a more effective erythropoietic response than the Zebu.

Animals↗

PubMed2026

Disruption of GxxxG motifs in pATOM36 impairs biogenesis of the mitochondrial protein translocase of the outer membrane in Trypanosoma brucei.

Mitochondrial biogenesis requires efficient import of cytosolically produced proteins and correct segregation of the mitochondrial genome during cytokinesis. In Trypanosoma brucei, a parasitic protozoan with a single mitochondrion harboring a single-unit mitochondrial genome, protein import across the outer membrane is mediated by the ATOM complex. An important, yet poorly understood role is played by the integral membrane protein pATOM36 of the outer mitochondrial membrane, which is essential for both ATOM complex assembly and mitochondrial DNA segregation. Here, we combined in vivo functional mutational analysis and structural modeling to investigate the function of pATOM36. AlphaFold3-based models predict five highly tilted helices forming a funnel-shaped cavity open toward the cytoplasm, reminiscent of membrane protein insertases. In the model, the protein is sealed towards the mitochondrial intermembrane space by tight helix packing, with conserved GxxxG motifs potentially facilitating these helix-helix interactions. Progressive replacement of these glycines by isoleucines does not affect protein production or correct localization but leads to defective ATOM complex biogenesis and arrest of growth, while mitochondrial DNA segregation is largely unaffected. Based on the predicted structure, these effects can be rationalized by hydrophobic bulking that interferes with associated electrostatic interactions. This hypothesis is supported by experimental mutational analysis of the respective electrostatic interactions in the presence of native GxxxG motifs. Together, our data support the hypothesis that pATOM36 functions as an outer mitochondrial insertase and arose by convergent evolution. The GxxxG motifs, also found in unrelated yeast and human outer membrane insertases, are crucial for protein activity.

Trypanosoma brucei brucei↗

PubMed1979

Detection and characterization of DNA polymerase from Trypanosoma brucei.

The predominant DNA polymerase activity has been isolated from the parasitic flagellated protozoan, Trypanosoma brucei. Like mammalian DNA polymerase-alpha the trypanosome DNA polymerase is of large molecular weight (S, 6--8), is resistant to thermal denaturation, is sensitive to N-ethylmaleimide, and is inhibited by high ionic strength. However, specific antisera that cross-react with mammalian DNA polymerase-alpha from different species fail to cross-react with the trypanosome polymerase.

Animals↗

PubMed1977

The synthesis of a variant-specific antigen by Trypanosoma brucei in vitro.

A variant-specific surface antigen from a cloned population of Trypanosoma brucei S42 has been isolated and partially characterized. [35S]L-methionine was found to be incorporated into this material by cells incubated in vitro in a chemically defined medium. Incorporation of [35S]L-methionine was inhibited by cycloheximide and puromycin at concentrations which are known to specifically inhibit protein synthesis in other systems. The rate of synthesis of the variant-specific antigen in vitro has been estimated to be about 8% of the rate in vivo. Newly synthesized [35S]L-methionine-labelled variant-specific antigen was incorporated into the surface coat.

Animals↗

PubMed1979

The isolation and partial characterization of the plasma membrane from Trypanosoma brucei.

Whole sheets of plasma membrane, each with their attached flagellum, were purified from Trypanosoma brucei. The method devised for their isolation included a new technique of cell breakage that used a combination of osmotic stress followed by mechanical sheer and avoided the problem of extreme vesiculation as well as the trapping of organelles in cell 'ghosts'. The purified membranes all contained the pellicular microtubular array. The antigenic surface coat was completely released from the plasma membrane during the isolation procedure. The membranes had a very high cholesterol/phospholipid ratio (1.54). A large proportion (42%) of the cellular DNA was recovered in the plasma-membrane fraction unless a step involving deoxyribonuclease treatment, which decreased the DNA content to less than 13%, was included before secrose-density gradient centrifugation. This step also aided the separation of plasma membranes from other cellular components. The ouabain-sensitive Na+ + K+-stimulated adenosine triphosphatase and adenylate cyclase co-purified with the plasma membranes. Although 5'-nucleotidase was thought to be a plasma-membrane component, it was easily detached from the membrane. The purified membranes were essentially free of L-alanine-alpha-oxoglutarate aminotransferase, L-asparte-alpha-oxoglutarate aminotransferase, malate dehydrogenase, oligomycin-sensitive adenosine triphosphatase, glucose 6-phosphatase, Mg2+-stimulated p-nitrophenyl phosphatase and catalase.

Cell Fractionation↗

PubMed1979

Identification by the blood incubation infectivity test of Trypanosoma brucei subspecies isolated from game animals in the Luangwa Valley, Zambia.

A total of 7 stocks of Trypanosoma brucei subspecies, isolated from naturally infected game animals in the Luangwa Valley, Eastern Province, Zambia were examined using a modified version of the Blood Incubation Infectivity Test (BIIT). One stock giving consistent BIIT responses typical of T.b. rhodesiense, was obtained from warthog (Phacochoerus aethiopicus). Four other stocks, 2 from hyaena (Crocuta crocuta), 1 from a waterbuck (Kobus ellipsiprymnus) and 1 from a lion (Panthera leo) responded like T.b. brucei. One stock from a waterbuck and 1 from a giraffe (Giraffa camelopardalis) failed to infect mice after incubation in human serum for 30 min at 37 degrees C when first tested, but after 5 or 6 further serial passages in mice and even with serum incubation time increased to 5 h, they retained infectivity.

Animal Population Groups↗

PubMed1979

Evidence for reappearance of Trypanosoma brucei variable antigen types in relapse populations.

Seven out of 11 bovines infected with different clones of Trypanosoma brucei showed 2 peaks of antibody activity against the infecting clone within 7 weeks, as measured by immunofluorescence, radioimmunoassay, and neutralization of infectivity tests. Using other clones from an unrelated Stock, antibodies to these clones were not detectable, indicating that the antibodies produced were specific to the infecting organisms. These results suggest that there was a reappearance or increase in numbers of the infecting organisms or of organisms with variable surface antigens similar to those of the infecting clones. The reappearance of variable antigen types in the presence of specific antibodies would imply that antibody plays a selective rather than an inductive role in the process of antigenic variation in African trypanosomes.

Animals↗