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D Le Ray

Publications and source records attributed to D Le Ray.

At least 73 records · Page 4Linked to original sources
PubMed1985

Influence of the salmon mutant of Glossina morsitans morsitans on the susceptibility to infection with Trypanosoma congolense.

Four phenotypes of a sex-linked, maternally influenced semi-lethal eye color mutant of Glossina morsitans morsitans Westwood were fed on Trypanosoma congolense Broden infected guinea pigs. Infection rates were evaluated 25 days later by means of dissection. Procyclic as well as mature infections were significantly more common among females with salmon-colored eyes (sal/sal) than among heterozygous (+/sal, phenotypically wild-type) females. A tendency was found for more mature infections among sal/Y males than among wild-type males. Similarly, females tended to be more infected than males with both procyclic and mature infections. These results indicate that the genotype of the fly, exemplified by the allele salmon, might influence the development of T. congolense in G.m. morsitans. A possible explanation for this phenomenon is discussed.

Animals↗
PubMed1984

Enzyme variation in Trypanosoma brucei spp. I. Evidence for the sub-speciation of Trypanosoma brucei gambiense.

Three groups of stocks of Trypanosoma brucei ssp, defined by the criteria of host, human serum resistance and place of isolation as T. b. gambiense, T. b. brucei (Nigeria) and T. b. brucei/rhodesiense (non-gambiense, Uganda) were screened for electrophoretic variation at 20 enzyme loci. One enzyme (Peptidase C) was found to differentiate all T. b. gambiense stocks from the other T. brucei stocks and, taken together with specific variants of 5 other enzymes, could be used to unambiguously define T. b. gambiense stocks. Using a population genetics approach, the frequencies of the different variants in the three groups of stocks were estimated and from them the average similarity and difference between groups were measured using the statistics of genetic identity (I) and genetic distance (D). These results show firstly, that T. b. gambiense is more different from the other two groups than they are from each other and, secondly, that the values of I and D obtained are consistent with T. b. gambiense constituting a sub- or sibling species of T. brucei. Three domestic animal isolates from Zaire and Cameroun were also screened for enzyme variation and two of these identified as T. b. gambiense, thereby establishing the existence of an animal reservoir host. In parallel, these stocks were tested for human serum resistance resulting in the same identification. Studies of the antigen repertoires and antigen gene structure were carried out by other workers on all the T. b. gambiense stocks reported here and the same conclusions reached as to the identification and ability to discriminate this subspecies from other groups of T. brucei stocks. The results presented here are discussed in relation to other published data on enzyme variation in T. brucei.

Alleles↗
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

At least two transposed sequences are associated in the expression site of a surface antigen gene in different trypanosome clones.

The expression of several trypanosome surface antigen genes proceeds by duplication of a basic copy (BC) of the gene and transposition of the expression-linked copy (ELC) into an expression site. This site, which seems to be the same for different genes of the same repertoire, is located near a chromosome end. In the AnTat 1.1 antigen gene expression site, the ELC is found associated with another sequence that we have called the "companion." We found that this companion is the transposed copy of another sequence also located in an unstable DNA terminus, and that it is conserved in the expression site of AnTat 1.10 and AnTat 1.1B, two clones successively derived from AnTat 1.1. The companion sequence is not part of the surface antigen gene, but we may infer from extensive homologies with another ELC sequence (IoTat 1.3, J. E. Donelson, personal communication) that it represents a 5' residual fragment of a former ELC. In three other AnTat 1.1-like clones, the companion sequence was not found associated with the ELC. It is concluded that the expression-linked duplicative transposition of variable antigen genes is a flexible mechanism, which can apply to variably sized stretches of the same BC.

Animals↗
PubMed1981

Gene duplication and transposition linked to antigenic variation in Trypanosoma brucei.

DNA sequence complementary to Trypanosoma brucei mRNAs coding for the synthesis of the variant-specific antigens AnTat 1.1 and AnTat 1.8 have been cloned and characterized. These sequences have been used as probes to analyze the corresponding genes in the nuclear DNA. The two genes seem to be represented in several (three to six) copies, some of which are incomplete. Transcription of one or the other of these two genes is linked to a genetic rearrangement implying duplication and transposition of the "basic" coding sequence. There is probably one additional copy of each gene, and it seems to be complete. The 3' end of each cloned sequence contains, within a 300-base-pair fragment, a genetic element that seems to be repeated and widely distributed in the genome. This repetitive sequence is variant specific. The expression-linked copy of the gene is lost in the culture (procyclic) form of the trypanosome, where the synthesis of variant-specific antigens is shut down. Comparison of two different cloned populations expressing the same serotype (AnTat 1) showed that the recurrence of a given antigenic type may be accompanied by the production of the same additional copy.

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↗