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P Bastien

Publications and source records attributed to P Bastien.

At least 55 records · Page 3Linked to original sources
PubMed1991

Long-range restriction maps of size-variable homologous chromosomes in Leishmania infantum.

In order to clarify the interpretation of molecular karyotype polymorphisms in Leishmania, the three smallest chromosomes from five cloned strains of Leishmania infantum were identified by chromosome-specific anonymous DNA probes. The presence in the same clone of homologous chromosomes of a different size was demonstrated. The chromosome size polymorphism appeared even more dramatic, with size variations affecting up to 20% of the chromosome, and the two smallest bands in one strain being equivalent to six bands in another strain. Long-range restriction maps of five different-sized homologues of chromosome I showed the size-variation to be located to a terminal fragment in 4 out of 5 cases, and to a central fragment in one. The size-variable sequence was present on at least three other chromosomes as determined by hybridisation analysis. This suggests an instability of the subtelomeric regions such as that in Plasmodium falciparum. Lastly, the finding of several pairs of distinct-sized homologous chromosomes, together with other studies, strongly suggest that Leishmania is diploid in at least part of its chromosomal complement.

Animals↗
PubMed1990

Public-health epidemiology in Vanuatu.

Vanuatu, which formerly was known as the New Hebrides, is an archipelago in the southwest Pacific Ocean with a tropical humid climate. The national health system and the state of health of the population generally are satisfactory. The main diseases of public-health importance are malaria and tuberculosis. Their epidemiology and control are discussed. An epidemic of Plasmodium falciparum malaria, which commenced in 1980, is described; this possibly can be explained by an increase in chloroquine-resistant P. falciparum over the same period. Other diseases also are reviewed. Many tropical diseases of great significance elsewhere are not of much significance in Vanuatu. Medical advice for visiting travellers is provided.

Adolescent↗
PubMed1990

Interclonal variations in molecular karyotype in Leishmania infantum imply a 'mosaic' strain structure.

The molecular karyotypes of 36 clones derived from 8 strains of Leishmania infantum were examined by pulsed-field gel electrophoresis. Although there appeared to be a high degree of genetic relatedness between the clones and the parent strain, a limited degree of polymorphism was noted in 50% of the clones, expressed mainly as the presence of an additional chromosome or as a chromosome size modification. Repeated subcloning in one strain showed that chromosomal rearrangements could occur during the cloning process. Chromosome homologies were examined by Southern analysis with chromosome-specific DNA probes. The results suggest a disomy for some chromosomes, but cannot exclude aneuploidy. The mechanisms possibly leading to such heterogeneity are discussed: they could involve frequent DNA amplification/deletion, and imply a 'mosaic' structure of the cultured strains or clones, with different individuals possessing differently sized versions of the same chromosomes.

Animals↗
PubMed1990

Taxonomy of Leishmania. Use of isoenzymes. Suggestions for a new classification.

The authors propose a new classification for the genus Leishmania Ross, 1903 based both on the use of intrinsic and extrinsic characters and on Linnean and Adansonian methods. The type of vertebrate host makes it possible to recognize the genus group: Leishmania designates Kinetoplastida parasites of mammals. Neighbouring forms which parasite reptiles are now grouped in the genus Sauroleishmania Ranque, 1973. Characteristics of the intravectorial cycle (supra- and peri-pyloric) are used to define the subgenus group (Leishmania, Viannia Lainson and Shaw, 1987). The classification uses biochemical, particularly enzymatic, characters. Elementary taxonomic units are made up of all the strains having the same isoenzyme profile, i.e. the zymodeme. The grouping of the zymodemes is usually performed through automatic techniques which lead to bush-like trees (dendrograms) showing either simple affinities between units (phenograms) or their phyletic relationships (cladograms). The branches recognized as being stable are individualized as "zymodeme complexes". They bear the name of either the previously defined species taxa or that of a specially created one. Two examples of taxonomic constructions, phenetic and cladistic, are presented. Finally, a general classification of the genus is proposed.

Animals↗
PubMed1989

Chromosome size and number polymorphisms in Leishmania infantum suggest amplification/deletion and possible genetic exchange.

We have studied the molecular karyotypes of 21 strains and 14 clones of Leishmania infantum using pulsed field gel electrophoresis (PFGE). We detected a high degree of polymorphism within this species, with 'strain-specific' patterns for most isolates, even within a restricted endemic area. Variations relate to both the size of chromosomes (270-2600 kb) and their number, which can vary from 24 to 31 between closely related isolates. This polymorphism does not correlate with isoenzyme analysis. Small size variations between homologous chromosomes of different strains are suggestive of DNA amplification/deletion events. Strains are also shown to be multiclonal, with slight differences between most clones, but with a predominant clone concealing the others in PFGE analysis. The analysis of these data leads to the hypothesis of occasional genetic exchange by nuclear fusion in Leishmania, as recently shown in the related protozoan Trypanosoma brucei.

Animals↗
PubMed1988

[The chloroquine resistance of Plasmodium falciparum in Vanuatu (1980-1984): appearance, evolution, distribution].

Chloroquine resistance of P. falciparum was studied in Vanuatu from March 1981 to July 1984, with limited means, and a non-systematic procedure; it was first evidenced in 1980. In vivo chloroquine resistance criteria were those established by W. H. O. In vitro testing methods were the standard W. H. O. macro-test and micro-test. 124 in vivo chloroquine resistant cases were seen: 111 cases in hospital (63 R III, 28 R II and 20 R I) and 13 cases in field studies (1 R III, 4 R II and 8 R I). 87 in vitro chloroquine sensitivity tests were carried out. A high failure rate was apparently due to a defective batch of lyophilised culture medium. Out of the 25 isolates successfully tested, 22 showed in vitro chloroquine resistance (88%). Correlation between in vivo and in vitro resistance was good in 13 cases studied by both methods. Moreover, 13 in vitro mefloquine sensitivity tests evidenced a high sensitivity to this drug. Chloroquine resistant malaria thus appears to be extended to the whole country. Its prevalence remains unknown but was estimated at 60% at least in 1984. Moreover, a geographical spread of chloroquine resistance from north to south of the group was evidenced between 1980 and 1984, identical to that of the dramatic increase of P. falciparum incidence at the same period of time. Possible mechanisms of the advent of chloroquine resistance in Vanuatu are discussed.

Adolescent↗
PubMed1987

[Inhibition of the infectivity of Plasmodium gametocytes by the serum of the parasite host. Perfecting an experimental model].

In the course of experimental malarial infections the infectivity of the gametocytes falls abruptly and at an early stage of the infection. This phenomenon is independent of the production of circulating antibodies. With Plasmodium yoelii nigeriensis infecting the white mouse, the maximum infectivity of gametocytes for Anopheles stephensi occurs on day 2, and on day 5 no more oocysts develop in the mosquito. The behaviour of the plasmodial strain in the mouse and particularly the "crisis" phenomenon were studied in detail in standardized experimental conditions. The decrease of the infectivity for the Anopheles begins just before the peak of parasitaemia, and a concomitant increase in the number of circulating gametocytes is observed. These events are very shortly followed by the crisis. The more severe is the crisis and virulent the infection, the earlier and more abrupt is the loss of infectivity. Previous studies having shown that this inhibition of the gametocytes infectivity was linked to a serum factor, our research aimed at setting up an experimental model allowing the identification of this factor. The intravenous injection of 5th day serum to mice harbouring infective gametocytes did not determine any loss of the gametocytes infectivity in the receiving mice. In order to study in vitro the effect of the 5th day serum, this one was added to blood from mice with highly infective gametocytes, and mosquitoes were fed on this through a membrane. As a result, a significant decrease of the infectivity of gametocytes was observed. This inhibition is immediate and does not appear to be "dose-dependent". Inversely, serum from mice still infective to the mosquito did not reduce the infectivity of the gametocytes. The experimental model set up thus comprises: a) mouse blood containing P. y. nigeriensis infective gametocytes to which is added the serum to be tested; b) Anopheles stephensi fed through a membrane; this allows quantifying the infectivity of the gametocytes in the presence of normal serum (control) or inhibitory serum. This model proved to be reliable; it should promote the study of any factor likely to modify the infectivity of Plasmodium gametocytes to the mosquito.

Animals↗
PubMed1986

[Malaria in Vanuatu. Recent epidemiological data].

The Republic of Vanuatu, ex-Condominium of New-Hebrides, is an archipelago in the South Pacific, between Solomon Islands and New-Caledonia. Although the health system is quite satisfactory, malaria has become the major health problem in the whole country. Its epidemiological characteristics are reviewed, and particularly the biology of the only known vector, the Anopheles farauti complex. A sudden and severe aggravation of the malaria morbidity since 1980 is then evidenced. This increase of the yearly incidence (from 21% to 183% between 1980 and 1984) has privileged the rising of Plasmodium falciparum which reached 75% of the national paraside index. Moreover, it has clearly followed a geographical progression from north to south within the group during the four years. Various possible causes to this alarming situation are examined, among which the emergence of chloroquin-resistant strains of P. falciparum, and the possibility of modifications in the vector's population, particularly hold the attention.

Adult↗