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Biomedical subjects

R Brun

Publications and source records attributed to R Brun.

At least 73 records · Page 4Linked to original sources
PubMed1989

In vitro drug sensitivity test for Trypanosoma brucei subgroup bloodstream trypomastigotes.

An in vitro test has been developed to determine drug sensitivities of bloodstream trypomastigotes of Trypanosoma (T.) brucei isolates. The incorporation of [14C]leucine, [3H]thymidine and [3H]hypoxanthine into bloodstream forms in vitro was compared and different sensitivity test procedures with trypanocidal drugs were evaluated. Bloodstream forms were added to a microtiter plate with serial dilutions of trypanocidal drugs containing a cell-free culture medium supplemented with a mammalian serum, which allows continuous cultivation of the bloodstream stages. After a preincubation period of 16 h, [3H]hypoxanthine was added, and after another 8 h, the cells were harvested with a cell harvester. The glass fiber filters on which the cells were collected were counted in a liquid scintillation counter and the percent inhibition determined as percentage of the control counts. This method gave accurate, reproducible results for T. (T.) brucei isolates tested with the trypanocidal drugs suramin, berenil, samorin, lomidine and Mel W.

Animals↗
PubMed1989

In vitro drug sensitivity of Trypanosoma gambiense isolates.

Drug sensitivities of seven Trypanosoma b. gambiense isolates from patients in the Ivory Coast were measured for Mel B, suramin and lomidine using an in vitro incorporation test. Bloodstream forms were isolated from Mastomys natalensis, incubated in serial drug dilutions in a microtiter plate, after 24 h, radiolabeled hypoxanthine was added, and the plate incubated for another 15 h. Trypanosomes were then harvested onto glass fiber filters with a cell harvester and incorporation of label was determined in a liquid scintillation counter. From the incorporation inhibition curves IC50 and IC75 values were calculated. IC50 values for Mel B ranged from 0.5 to 4.6 ng/ml, for suramin from 7.2 to 30.5 micrograms/ml, and for lomidine from 2.1 to 7.0 ng/ml. Isolate TH-1/78E(031) was the least sensitive to all three drugs while TH-1/78E(020), TH-64/78E(020) and TH-31/78E(025) were the most sensitive to the drugs used. THDAL 1030R, an isolate from a patient who relapsed after three consecutive Mel B treatments, showed an IC50 value for Mel B of 1.20 ng/ml. The in vitro drug sensitivity test gave reproducible results for the T b. gambiense isolates tested.

Animals↗
PubMed1988

Ro 15-0216: a nitroimidazole compound active in vitro against human and animal pathogenic African trypanosomes.

In vitro systems for the continuous cultivation of Trypanosoma brucei brucei, T. b. gambiense, T. b. rhodesiense, T. congolense and T. vivax were used to determine the antitrypanosomal activity of the 2-substituted nitroimidazole Ro 15-0216. For all trypanosome species, the concentration which inhibited parasite growth by 50% (IC50 value) was established: 0.0957 microgram ml-1 (T. b. brucei TC221), 0.1327 microgram ml-1 (T. b. gambiense STIB 754-A), 0.0450 microgram ml-1 (T. b. rhodesiense STIB 704-BABA), 0.0896 microgram ml-1 (T. congolense ILNat 3.1) and 0.0109 microgram ml-1 (T. vivax ILRAD 1392). The IC50 value of its major metabolite Ro 19-9638 was 0.0341 microgram ml-1 (T. b. rhodesiense STIB 704-BABA). Furthermore, minimum exposure times required to render T. b. brucei non-infective for mice as well as preventing their growth in vitro have been established to be three, four, six and ten hours at drug concentrations of 30, 10, 3 and 1 microgram ml-1, respectively.

Acetanilides↗
PubMed1988

Production of metacyclic forms by cyclical transmission of west African Trypanosoma (T.) brucei isolates from man and animals.

Fifteen West African Trypanosoma (T.) brucei isolates from man and animals were cyclically transmitted. Five stocks, belonging to the non-gambiense group, could easily be transmitted through Glossina morsitans morsitans or Glossina m. centralis infected on mice, whereas successful transmission of the 10 isolates, identified as Trypanosoma brucei gambiense, was performed using G. palpalis gambiensis as vector. Glossina p. gambiensis was infected with culture-derived procyclic trypanosomes by repeated membrane feeding. In both cases, metacyclic forms could normally be detected in saliva samples of positive flies 3 to 4 weeks after first infection. These forms of major interest were subsequently characterized relative to their resistance/sensitivity against normal human serum in vitro and their antigenic properties, using indirect immunofluorescence: Metacyclic forms of all the T. b. gambiense isolates were determined by a stable human serum resistance and a restricted metacyclic variable antigen type (mVAT) repertoire, whereas representatives of the non-gambiense group (including TH162/78E 021) were sensitive against the trypanolytic factors of normal human serum and expressed a heterogeneous metacyclic antigen profile.

Animals↗
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↗