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Biomedical subjects

R Brun

Publications and source records attributed to R Brun.

At least 55 records · Page 3Linked to original sources
PubMed1987

Human serum resistance of metacyclic forms of Trypanosoma brucei brucei, T. brucei rhodesiense and T. brucei gambiense.

Resistance against the lytic action of human serum has been tested among metacyclic and bloodstream forms of Trypanosoma brucei brucei, T.b. rhodesiense and T.b. gambiense stocks and clones. The resistance was determined by applying an in vitro human serum resistance test. Whereas the majority of T.b. gambiense metacyclic forms exhibited stable human serum resistance, T.b. rhodesiense metacyclics showed inconsistent resistance within a minority of parasites, which tended to diminish completely with prolonged passages in rodents. Infection of tsetse flies with in vivo or in vitro selected human serum resistant forms did not significantly increase the proportion of resistant parasites among extruded metacyclic forms. In a T.b. rhodesiense stock which never showed human serum resistance in the metacyclic forms, human serum resistance reappeared after a 2-day cultivation period in the presence of a mammalian serum. These results reflect important phenotypic dynamics and may lead to a better understanding of the epidemiology of African human sleeping sickness.

Animals↗
PubMed1986

[Selection of chloroquine-resistant Plasmodium falciparum strains in tourists under chemoprophylaxis].

In a prospective study 20 P. falciparum isolates imported from Africa by non-immune tourists were investigated for chloroquine sensitivity using the in vitro microtest and the results were compared with the plasma chloroquine concentration. All 6 patients taking correct chloroquine prophylaxis (chloroquine plasma levels between 0.1-0.5 nmol/ml) harboured highly resistant P. falciparum strains (schizont maturation at 3.2 and 6.4 nmol/ml blood in 3 patients each). In the 4 patients with inadequate prophylaxis (plasma levels between 0.02-0.1 nmol/ml) the degree of resistance was lower (at 1.6 and 6.4 nmol/ml blood in 2 patients each). Chloroquine-sensitive strains were found only in patients with chloroquine plasma levels below 0.02 nmol/ml and in 4 of 5 patients who did not show chloroquine in the plasma. Selection of chloroquine-resistant P. falciparum strains under short term chloroquine chemoprophylaxis appears to be highly probable.

Africa↗
PubMed1986

Microscopic and flow cytophotometric analysis of parasitemia in cultures of Plasmodium falciparum vitally stained with Hoechst 33342--application to studies of antimalarial agents.

Conditions for rapid vital staining of Plasmodium falciparum infected human erythrocytes were 1 microgram/ml of the dye Hoechst 33342 for 15 min in the standard culture medium at 37 degrees C. Fixed and stained cultures were analyzed by fluorescence microscopy and flow cytophotometry. The usefulness of this type of analysis for in vitro studies of antimalarial agents was demonstrated using three such agents--cyclosporin A, chloroquine, and pyrimethamine.

Antimalarials↗
PubMed1984

A quantitative ultrastructural study on the transformation of Trypanosoma brucei metacyclic to bloodstream forms in vitro.

The transformation of metacyclic to bloodstream forms of Trypanosoma brucei brucei was studied in vitro using light and electron microscopy. The ultrastructural composition was investigated with stereological methods and the mean cell volume determined in a Coulter Channelyzer. The mitochondrion showed the most significant changes during transformation with a reduction in volume as well as in the membrane areas. The glycosomes remained unchanged whereas the lipid inclusions increased over the 24 h incubation period. The metacyclic forms contained many vesicles in the reservoir vicinity with surface coat-like material on the inner side of the membrane. Metacyclic forms also contained a previously undescribed structure, termed "inclusion body". These large, polymorphic structures whose function and origin are unknown disappeared during transformation. The mean cell volume for metacyclic forms was 15-16 microns3. During transformation the values first dropped and then increased to about 20 microns3 after 24 h.

Animals↗
PubMed1982

Cyclical transmission of in vitro cultivated bloodstream forms and procyclic trypomastigotes of trypanosoma brucei brucei by Glossina morsitans morsitans.

In vitro cultivated bloodstream and procyclic forms of Trypanosoma b. brucei STIB 247 were cyclically transmitted by Glossina m. morsitans. The tsetse flies were infected artificially on a silicon membrane. Metacyclic trypanosomes from mature salivary gland infections were used to initiate bloodstream form cultures. They transformed into slender bloodstream forms and gave rise to established cultures that proved to be infective for the vector. The metacyclic forms retained the strain-specific basic set of variable antigen types.

Animals↗
PubMed1982

Cultivation of procyclic trypomastigotes of Trypanosoma congolense in a semi-defined medium with direct adaptation from bloodstream forms.

Bloodstream forms of Trypanosoma congolense added to the semi-defined medium 109-c (Minimum Essential Medium with Earle's salts, 60 mM HEPES, haemin, and heat-inactivated FBS) and incubated at 28 degrees C transformed into procyclic trypomastigotes. Established cultures of the procyclic forms yielded up to 4.5 X 10(7) parasites/ml. The cultivated populations consisted only of trypomastigotes and were not infective for mice. The amino acids consumed to the greatest extent were glutamine, proline, and threonine. Changes in glucose, pyruvate, and lactate concentrations during growth were determined. The procyclic organisms possessed a well-developed mitochondrion.

Adenosine↗
PubMed1982

Comparative morphometric analysis of bloodstream and lymph forms of Trypanosoma (T.) brucei brucei grown in vitro and in vivo.

The fine structure of bloodstream forms of Trypanosoma brucei cultivated in vitro, and of trypanosomes from lymph and blood of mammalian hosts, was compared morphometrically. The cell volume, quantitative parameters of the mitochondrion and of glycosomes were mainly investigated. A Coulter Channelyzer was used for the first time to measure the mean cell volume of living parasites. In vitro, the monomorphic trypanosomes between the feeder layer cells showed lower values for mitochondrial parameters than the slightly pleomorphic forms from the supernatant medium. Trypanosomes in culture were very similar morphologically to forms from lymph nodes of rats. Despite some morphometric differences between cultivated blood stream forms and those grown in vivo, the similarity of both populations was clear. Both populations, however, differed significantly from stages found in the vector or from procyclic culture forms.

Animals↗
PubMed1982

In vitro cultivation of animal-infective forms of a West African Trypanosoma vivax stock.

Animal-infective forms of a West African Trypanosoma vivax stock were grown in culture for three months using Minimum Essential Medium (MEM) with Earle's salts, supplemented with 20% inactivated goat serum over fibroblast-like cell lines isolated from the embryo of Microtus montanus or of an East African Galla crossbred goat at 36.5 degrees C and in 4% CO2 - 96% air. The bloodstream trypanosomes used to initiate the culture had been isolated from an infected goat. The cultured organisms grown in this system could be subcultured, were infective for mammalian hosts, retained their morphological characteristics and virulence, and could be readily established in Glossina morsitans centralis from goats injected with the cultured T. vivax.

Animals↗
PubMed1982

[Evolution of contact dermatitis factors in a population. Epidemiology 1975-1981 ].

Comparative results between positive patch tests found during the periods 1968-1974 and 1975-1981 are presented. The number of sensitised patients to nickel, chromate and Peru balsam has significantly increased. On the other hand, the number of turpentine-oil-positive patch tests has strongly decreased. This mirrors the drop in the imported quantities of this product. A schema concerning factors influencing the apparent allergenicity is given.

Allergens↗
PubMed1981

In vitro cultivation of bloodstream forms of Trypanosoma brucei, T. rhodesiense, and T. gambiense.

A series of new in vitro systems for the cultivation of bloodstream forms of Trypanosoma (Trypanozoon) brucei brucei, T. (T.) b. rhodesiense, and T. (T.) b. gambiense was developed. The standard system consists of a feeder layer of fibroblast-like cells derived from embryos of New Zealand White rabbits (REF( or a mountain vole, Microtus montanus (MEF), with HEPES-buffered Minimum Essential Medium (MEM), with Earle's salts, supplemented with 15% inactivated rabbit serum. These two and other feeder layers were cross-checked with different sera to test for growth support of bloodstream forms of the three trypanosome subspecies studied. Cultures could be initiated with bloodstream forms from mammalian hosts or from cryopreserved stabilates. Metacyclic forms from infected Glossina m. morsitans could also be sued as inoculum; they transformed within 6 h to bloodstream forms. Maintenance of cultures and growth properties are described in detail. Experiments were undertaken to confirm that the cultivated bloodstream forms still possess some fo the characteristic features of pleomorphic bloodstream populations. Cultivated bloodstream forms were always infective for mice, and a surface coat could be demonstrated by electron microscopy. They could also be cyclically transmitted through tsetse flies, and the metacyclic forms from these flies could be brought back into culture. In vitro cloning with single bloodstream forms and metacyclic forms could be achieve with high cloning efficiency. The consumption of glucose and the production of pyruvate and lactate were determined.

Animals↗
PubMed1980

Pyrazolopyrimidine metabolism in African trypanosomes: metabolic similarities to Trypanosoma cruzi and Leishmania spp.

Growth inhibition and radioisotope incorporation studies with allopurinol (4-hydroxypyrazolo(3,4-d)pyrimidine) have shown that the African trypanosomes are biologically and biochemically similar to Leishmania spp. and Trypanosoma cruzi with respect to their response to this compound. These organisms, as a group, share the unique ability to convert allopurinol sequentially to its ribonucleoside monophosphate and 4-aminopyrazolo(3,4-d)pyrimidine ribonucleoside mono-, di- and triphosphates.

Allopurinol↗