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Biomedical subjects

M Tibayrenc

Publications and source records attributed to M Tibayrenc.

At least 127 records · Page 7Linked to original sources
PubMed1987

Exotic stock of Trypanosoma cruzi (Schizotrypanum) capable of development in and transmission by Triatoma protracta protracta from California: public health implications.

A stock of Trypanosoma cruzi was recovered from a Triatoma dimidiata from Tegucigalpa, Honduras. This stock was shown to be capable of development and transmission by native California Triatoma protracta protracta. Isozyme analysis indicated that this T. cruzi is closely related to the Tehuantepec strain and to a lesser extent the Miles' zymodeme 1 strain. The potential public health significance of development and transmission of exotic stocks of T. cruzi by native reduviids is discussed.

Animals↗
PubMed1987

[High correlation between isoenzyme classification and kinetoplast DNA variability in Trypanosoma cruzi].

By means of 14 restriction enzymes, we have studied the kinetoplast DNA polymorphism in 21 Trypanosoma cruzi isolates previously classified into 19 different genotypes based on the analysis of 15 isozyme loci. We have found a high correlation (p less than 0.001) between the proportion of restriction bands (fragments) common to any two given isolates and the corresponding genetic identities calculated from the isozyme data. This shows that the two classifications (kDNA and isozymes) corrobate one another and strongly suggests that the two types of variability are correlated with time (molecular clocks). The phylogenic classifications so obtained can be used as rational bases for medical and epidemiological studies. Although they are correlated, the two types of analysis are complementary as they do not yield identical results. Like the isozyme genetic distances and genetic identities, the values obtained for the proportion of common restriction bands (fragments) exhibit a continuum. This seems to confirm that natural T. cruzi populations exhibit a wide range of genotypes rather than a few well-differentiated clusters of strains.

Animals↗
PubMed1986

Additional data on Trypanosoma cruzi isozymic strains encountered in Bolivian domestic transmission cycles.

We have collected in Bolivia 212 stocks of Trypanosoma cruzi from domestic transmission cycles and have assayed for nine enzyme systems (11 gene loci). Only a few different isozyme profiles exist, without recombination between them, a situation also encountered in previous Bolivian samples. The 212 stocks, combined with 207 stocks previously studied, have been analysed to uncover any spatial patterns. The frequency of heterozygous strains (2 and 2a) decreases westwards and with increasing altitude. Given that longitude and altitude are correlated with each other, it is not possible to decide which of these two geographic variables is the relevant one, or if both are. These associations might be due to climatic factors. Studies by other authors have shown, however, that heterozygous strains are rare or absent in the Amazon Basin, which is at low altitude.

Altitude↗
PubMed1986

Natural populations of Trypanosoma cruzi, the agent of Chagas disease, have a complex multiclonal structure.

We have studied 15 gene loci coding for enzymes in 121 Trypanosoma cruzi stocks from a wide geographic range--from the United States and Mexico to Chile and southern Brazil. T. cruzi is diploid but reproduction is basically clonal, with very little if any sexuality remaining at present. We have identified 43 different clones by their genetic composition; the same genetic clone is often found in very distant places and in diverse hosts. There is much genetic heterogeneity among the different clones, and they cannot be readily classified into a few discrete groups that might represent natural taxa. These findings imply that the biological and medical characteristics need to be ascertained separately for each natural clone. The evidence indicates that clonal evolution is very ancient in T. cruzi. We propose two alternative hypotheses concerning the relationship between the biochemical diversity and the heterogeneity in other biological and medical characteristics of T. cruzi. One hypothesis is that the degree of diversity between strains simply reflects the time elapsed since their last common ancestor. The second hypothesis is that biological and medical heterogeneity is recent and reflects adaptation to different transmission cycles. A decision between the two hypotheses can be reached with appropriate studies, with important medical consequences.

Alleles↗
PubMed1985

Agent of Chagas' disease from Honduran vector capable of developing in California insects: implications for cardiologists.

An exotic strain of Trypanosoma cruzi recovered from Triatoma dimidiata from Tegucigalpa, Honduras, was shown by isoenzyme studies to be closely related to the Miles' zymodeme 1 and laboratory reference strain Tehuantepec. It was injected into Swiss random-bred ICR mice. Clean Triatoma protracta nymphs and adults, which had been captured in Winters, California, fed on inoculated mice and were then examined over a 15-month period. Their feces contained multiplying epimastigote and infective trypomastigote forms of T. cruzi. This shows that exotic strains of T. cruzi can develop and survive for long periods in local California vectors. The increasing number of immigrants from Central America who enter California and other states may have public health implications in regard to the introduction of pathogenic strains that are capable of producing cardiomyopathy. Cardiologists who examine patients with cardiomyopathy from Central and South America should rule out Chagas' disease as a cause, since pathogenic T. cruzi strains are present in most Central and South American countries.

Animals↗
PubMed1985

[Natural hosts of Trypanosoma cruzi in French Guiana. High endemicity of zymodeme 1 in wild marsupials].

During an epidemiological survey in French Guiana, three species of Marsupiala were found infected by Trypanosoma cruzi with high infection rates (30,8% for Didelphis marsupialis). Six Triatomine bug species were recorded, five of them being well known vectors of Chagas' disease. Iso-enzyme characterization of 22 stocks isolated (16 from D. marsupialis, 3 from Philander opossum and 3 from Rhodnius prolixus) revealed that they were all related to zymodeme 1 of Miles. The silvatic cycle is endemic in the various ecotopes studied. The high prevalence rates of infection in D. marsupialis in the human settlement of Cacao and the finding in this locality of domestic breeding of Rhodnius pictipes lead to suspect the occurrence of a peridomestic cycle in this village. The evidence of R. prolixus colonizing houses in the vicinity of Cayenne emphasizes the risk of Chagas' disease in French Guiana.

Animals↗
PubMed1985

[Preliminary results suggesting a tenuous or nonexistent relation between clinical forms of Chagas disease and isoenzyme strains of Trypanosoma cruzi].

Trypanosoma cruzi strains obtained by xenodiagnosis carried out on 23 Bolivian patients whose pathology was known, were analysed by enzymic typing. 3 patients were infected with mixed strains of both isozymic groups 1 and 2; Isozymic strains of groups 1 and 2 were both associated with cardiac pathology as well as digestive one. Any of the strains present a special relation with a cardiac pathology.

Chagas Cardiomyopathy↗
PubMed1984

The microdistribution of isoenzymic strains of Trypanosoma cruzi in southern Bolivia; new isoenzyme profiles and further arguments against Mendelian sexuality.

132 Trypanosoma cruzi stocks were collected in southern Bolivia (99 stocks in Tupiza, 33 in Tarija), and were characterized using five enzymes (six loci). From these 132 stocks, a sample of 21 was studied using 10 enzymes (12 loci) to establish the genetic distances between them. Only five different isoenzymic strains were registered among the 132 stocks: the taxonomic status of these strains is discussed. The distribution of the strains indicated that a Founder effect was not a constant fact at the level of the house and of the suburb, but that a Founder effect was more apparent for greater geographical distances. All strains were transmitted sympatrically by the same vector Triatoma infestans. Genotype frequencies demonstrated the lack of Mendelian sexuality among stocks of T. cruzi from southern Bolivia, confirming our previous results.

Alcohol Oxidoreductases↗
PubMed1984

[Isoenzymatic strains of Trypanosoma cruzi: recent or ancient, homogeneous or heterogeneous origin?].

Genetic variability studied among 13 Trypanosoma cruzi laboratory reference stocks confirms the existence of three principal isozymic categories. As the main part of enzymic variability is now recognized, it seems possible to attribute any stock to the taxon T. cruzi with safety. Genetic parameters allow to infer two main hypotheses relative to the evolutionary origin of these categories: ancient origin (either by mitotic evolution or by speciation), or recent origin (by clone sampling among a sexual ancestral population). The possibility of a heterogeneous origin of the strains is discussed.

Animals↗
PubMed1983

The presence in Bolivia of two distinct zymodemes of Trypanosoma cruzi, circulating sympatrically in a domestic transmission cycle.

The enzyme profiles of 109 Bolivian stocks of Trypanosoma cruzi were determined by cellulose acetate electrophoresis using the four enzymes: malate dehydrogenase (oxaloacetate decarboxylating) (NADP+) (E.C.1.1.1.40, ME), phosphogluconate dehydrogenase (E.C.1.1.1.44, 6PGDH), phosphoglucomutase (E.C.2.7.5.1, PGM) and glucosephosphate isomerase (E.C.5.3.1.9, GPI). As previously, two principal zymodemes were found sympatrically. Both were isolated from man, one appeared to be more frequent at high altitude, the other appeared to be more frequent at low altitude. These results agree with our previous hypothesis on the genetics of T. cruzi (diploidy, lack of actual sexuality).

Altitude↗
PubMed1983

A genetic comparison between Brazilian and Bolivian zymodemes of Trypanosoma cruzi.

The enzyme profiles of three major Brazilian Trypanosoma cruzi zymodemes (Brazilian Z1, Brazilian Z2, Brazilian Z3) and of two principal Bolivian zymodemes were compared. Relationships were assessed both intuitively and by calculating genetic distances. One of the Bolivian zymodemes, Bolivian Z1, was closely related to the Brazilian Z1. The second Bolivian zymodeme, Bolivian Z2, was related to brazilian Z2 but differed from all the Brazilian zymodemes in the occurrence of typical heterozygous isozyme patterns in five out of 12 enzyme loci. Parental stocks and clones of Bolivian Z2 had the same putative heterozygous patterns. The evidence from enzyme profiles on the ploidy of T. cruzi and the possibility of recombination was considered. The presence of putative heterozygous patterns in Bolivian Z2 supported the hypothesis that T. cruzi is diploid. The definition of T. cruzi as a single polytypic species or as a species complex was considered to be dependent on the presence or absence of genetic recombination between or within the zymodemes, which has not been demonstrated in the ecotopes so far examined.

Animals↗