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Biomedical subjects

R Michel

Publications and source records attributed to R Michel.

At least 19 recordsLinked to original sources
PubMed2003

Endocytobiont KC5/2 induces transformation into sol-like cytoplasm of its host Acanthamoeba sp. as substrate for its own development.

New investigations of a novel, recently described, non-cultivable endocytobiont of Acanthamoeba sp. reveal at least three hitherto unobserved developmental stages which shed some light on the nature of this peculiar organism. The development of the endocytobiont is closely connected with conspicuous changes in the host amoeba, inducing the transformation from gel to sol-like cytoplasm which bulges like a balloon inside the host cell. Young and transitory developmental stages were found within the homogenous, sol-like cytoplasm. The infectious stages, with their voluminous cell wall and a conspicuous ostiole, could be observed within all parts of the cytoplasm with the exception of the nucleus. It is a remarkable adaptation for this parasite to be able to induce this gel-sol transformation in order to facilitate its own development. The fate of the heavily infected host amoebae is death by rupture or lysis after being overcrowded with parasites. As no structures could be observed within the endoparasites that were comparable to other bacteria, the real nature and taxonomic position of these peculiar organisms remain obscure.

Acanthamoeba↗
PubMed2003

Chemisorbed poly(propylene sulphide)-based copolymers resist biomolecular interactions.

Alkanethiolates have been widely used as chemisorbates to modify gold surfaces, in spite of their relatively poor oxidative stability. We introduce gold-chemisorbing block copolymers bearing an anchoring block of poly(propylene sulphide) (PPS), selected in the expectation of greater stability. These materials offer a more robust approach to surface modification of gold. As an example, a triblock copolymer with poly(ethylene glycol) (PEG) was selected, with the goal of minimizing biological adsorption and adhesion. The copolymer PEG17-bl-PPS25-bl-PEG9 chemisorbed to form a dense monolayer of 226 +/- 26 ng cm(-2), approximately 2.2 nm thick. The copolymeric adlayer was much more stable to oxidation than commonly used alkanethiolates. Its presence greatly reduced protein adsorption (>95%), even after exposure to whole blood serum (>55 mg x ml(-1)), as well as cell adhesion over long culture durations (>97%). PPS-containing copolymers are an attractive alternative to alkanethiolates, and PEG-bl-PPS-bl-PEG presents a powerful example for use in biodiagnostic and bioanalytical devices.

Adsorption↗
PubMed2003

Increased production of interferon-gamma by Leishmania homologue of the mammalian receptor for activated C kinase-reactive CD4+ T cells among human blood mononuclear cells: an early marker of exposure to Leishmania?

A prospective study was undertaken to define early predictive immunological marker(s) of exposure to Leishmania in naïve subjects who have never been exposed to any Leishmania and who were also free of any cutaneous leishmaniasis lesions. These naïve subjects could have been exposed to Leishmania in a rain forest where Leishmania guyanensis and their natural vectors and mammalian host are cocirculating. The production of interferon (IFN)-gamma in response to the Leishmania homologue of the mammalian receptor for activated c kinase (LACK), a candidate for vaccine against leishmaniasis was analysed. At the end of their stay in the rain forest, LACK-specific CD8+ T cells were detected in subjects whose peripheral blood mononuclear cell (PBMC) produced IFN-gamma in response to soluble Leishmania antigens (SLA) and in those whose PBMC remained unresponsive to SLA. However, LACK-specific CD4+ T cells were detected only in PBMCs from individuals who became IFN-gamma responders to SLA. In subjects whose PBMC became positive to SLA, LACK-reactive CD4+ T cells producing high level of IFN-gamma were detectable before the SLA-reactive IFN-gamma producing CD4+ T cells, suggesting that the former readout assay could be used as an early predictive immunological marker of exposure to Leishmania in subjects who remained disease free.

Animals↗
PubMed2003

Evaluation of radioactive exposure from 137Cs in contaminated areas of Northern Ukraine.

The paper gives averages of 137Cs deposition densities in soils from three areas in Northern Ukraine measured 12 to 15 y following the Chernobyl accident: in an area near Narodici (75 km west of the Chernobyl nuclear power plant in the so-called zone II) heavily contaminated by the Chernobyl fall-out and in areas around Korosten and Zhitomir showing contamination levels to be much lower. The three areas exhibited very different 137Cs deposition densities of 2.2 MBq m(-2), 400 kBq m(-2), and 5 kBq m(-2), respectively. During a 1-y observation, measurements of the 137Cs transfer in the food chain to humans and 137Cs whole body contents dependent on the 137Cs daily intake were carried out under realistic conditions of the rural inhabitants who lived in settlements within zone II. Detailed investigations of components of the daily diet showed that the high 137Cs contamination levels found in soils of zone II do not affect in any way low 137Cs concentrations of all important agricultural products harvested and consumed by villagers. With regard to consumption habits of the population of zone II, mushrooms and wild berries were found to contribute more than 95% of the 137Cs daily intake to the 137Cs whole body content of about 12 kBq (with maximum values up to 760 kBq) measured in a group of inhabitants of zone II during a period from July 1998 to July 1999. The median of the annual dose of these inhabitants from external and internal exposures was 1.2 mSv y(-1) with a geometric standard deviation of 2.6. Excluding extreme habits, the geometric mean of the total exposure was 1.0 mSv y(-1) with a geometric standard deviation of 1.3.

Adolescent↗
PubMed2003

[Correlation measures in epidemiology].

When a significant correlation has been noted between the occurrence of a disease and exposure to a risk factor, it becomes necessary to measure the strength of the correlation. This can be done using either relative risk or odds ratio techniques depending on the type of study. The purpose of article this article is to present guidelines for calculation and interpretation of these indicators using examples taken from the Médecine Tropicale journal.

Confidence Intervals↗
PubMed2002

[Statistical tests: value, principle and interpretation].

Comparison of data groups requires the use of statistical tests. This article utilizes an example taken from the Revue Médicine Tropicale to illustrate the value of statistical testing as well as an interpretation of the probability value "p" associated with test results.

Data Interpretation, Statistical↗
PubMed2002

[Everything (or almost everything) about the Kappa coefficient].

Sensitivity, specificity, and predictive value are the standard parameters used to evaluate the efficacy of diagnostic tests. However all three parameters assume the existence of a gold standard test. Thus the problem arises as to what method to use in the absence of a benchmark. The solution involves assessment of agreement between two raters. This article based on an example drawn from an African setting describes the value and computation of the most widely used tool for assessing agreement and reproducibility of measures, i.e., the kappa coefficient.

Statistics, Nonparametric↗
PubMed2001

Members of the Cytophaga-Flavobacterium-Bacteroides phylum as intracellular bacteria of acanthamoebae: proposal of 'Candidatus Amoebophilus asiaticus'.

Three Gram-negative, rod-shaped bacteria that were found intracellularly in two environmental and one clinical Acanthamoeba sp. isolates were analysed. Two endocytobionts showing a parasitic behaviour were propagated successfully outside their amoebal host cells and were identified subsequently by comparative 16S rRNA sequence analysis as being most closely affiliated with Flavobacterium succinicans (99% 16S rRNA sequence similarity) or Flavobacterium johnsoniae (98% 16S rRNA sequence similarity). One endocytobiont could neither be cultivated outside its original Acanthamoeba host (Acanthamoeba sp. TUMSJ-321) nor transferred into other amoebae. Electron microscopy revealed that the amoebal trophozoites and cysts were almost completely filled with cells of this endosymbiont which are surrounded by a host-derived membrane. According to 16S rRNA sequence analysis, this endosymbiont could also be assigned to the Cytophaga-Flavobacterium-Bacteroides (CFB) phylum, but was not closely affiliated to any recognized species within this phylogenetic group (less than 82% 16S rRNA sequence similarity). Identity and intracellular localization of this endosymbiont were confirmed by application of a specific fluorescently labelled 16S rRNA-targeted probe. Based on these findings, we propose classification of this obligate Acanthamoeba endosymbiont as 'Candidatus Amoebophilus asiaticus'. Comparative 18S rRNA sequence analysis of the host of 'Candidatus Amoebophilus asiaticus' revealed its membership with Acanthamoeba 18S rDNA sequence type T4 that comprises the majority of all Acanthamoeba isolates.

Acanthamoeba↗
PubMed2001

Development of 18S rRNA-targeted oligonucleotide probes for specific detection of Hartmannella and Naegleria in Legionella-positive environmental samples.

Aquatic protozoa are natural hosts of the human pathogen Legionella pneumophila. The fluorescence labeled 16S rRNA-targeted oligonucleotide probe LEGPNE1 has recently been shown to specifically detect extracellular legionellae as well as intracellular legionellae parasitizing protozoa. In this study we designed oligonucleotide probes which are complementary to distinct regions of the 18S rRNA of the Legionella host organisms of the genera Hartmannella and Naegleria. The specificity of the probes, HART498 and NAEG1088, was tested by in situ hybridization of various laboratory reference strains. In order to evaluate the fluorescent probes for environmental studies three selected Legionella-positive cold water habitats were examined for the presence of these protozoa. Traditional culture methods followed by morphological identification revealed an almost consistent presence of Naegleria spp. in cold water habitats. Other protozoa species including Acanthamoeba spp., Echinamoeba spp., Hartmannella spp., Platyamoeba placida, Saccamoeba spp., Thecamoeba quadrilineata, and Vexillifera spp. were found sporadically. Concomitant analysis of the pH, conductivity and temperature of the water samples revealed no preference of Legionella or the respective protozoa for certain environmental conditions. The specificity of the newly designed 18S rRNA probes demonstrates that they are valuable and rapid tools for the identification of culturable environmental protozoa.

Animals↗
PubMed2001

Distribution of free-living amoebae (FLA) during preparation and supply of drinking water.

Free-living amoebae (FLA) are widely distributed in aquatic environments with increasing importance in hygienic, medical and ecological relationship to man. Only few data are available about abundances of these protozoa in the treatment of drinking water and standards in the management of water quality are not suitable for detection of FLA. Prevalence of FLA were investigated within six selected German drinking water treatment plants in the course of the purification-process of surface water and in a subsequent drinking water supply. The data give a short survey about the prevalence and reduction of FLA in processing and supply of drinking water.

Amoeba↗
PubMed2001

Tracking occupational doses of transient workers.

A number of radioactive material licensees in the United States are unaware that they are required to track the occupational doses their radiation workers receive outside thieir facilities. As a result, these licensees may be cited for not tracking offsite occupational doses and quite possible for allowing some individuals to exceed the annual limits established by regulatory agencies. The accounting of occupational doses to "transient" workers is a difficult task. Unfortunately, written guidance to assist licensees on how to properly address this issue is not available. This paper was developed to raise awareness among radiation safety professionals of the need to establish effective measures to properly track transient worker exposures and maintain compliance with regulatory limits.

Humans↗
PubMed2001

Colonic diversion for intractable constipation in children: colonic manometry helps guide clinical decisions.

BACKGROUND: Colonic manometry helps discriminate functional and behavioral causes for childhood constipation from colonic neuromuscular disease. METHODS: Of 375 colonic manometries performed for clinical indications, 12 could not be interpreted because of chronic colonic dilation. Based on colonic manometries that showed either no contractions or an absence of the gastrocolonic response or an absence of high-amplitude propagating contractions, the authors recommended diverting colostomies or ileostomies in 12 chronically constipated children (mean age, 4 years; range, 2-14 years, 5 boys). Before study, medical treatment was ineffective in all children. These children had persistently dilated colons with pathologic diagnoses of intestinal neuronal dysplasia (n = 4), hypoganglionosis (n = 2), hollow visceral myopathy (n = 1), and normal (n = 5). RESULTS: Six to 30 months after diversion, the authors restudied all the children. Eleven of 12 diverted colons were no longer dilated. In two patients, abnormal motility involving the entire colon was unchanged from the initial study, small bowel motility was abnormal, and we recommended no further surgery. In two cases, the colon remained abnormal but small bowel motility was normal, and we recommended subtotal colectomy and ileoproctostomy. In four cases, the left colon remained abnormal, but the right colon was normal, and we recommended reanastomosis after left hemicolectomy. In four cases, motility in the diverted colons was normal, including a gastrocolonic response and high-amplitude propagating contractions, and the authors recommended reanastomosis. Defecation problems resolved in 10 of 12 when followed up 5 to 30 months after treatment. CONCLUSION: These data suggest that in some cases of intractable childhood constipation associated with colonic distention, temporary diversion improved colonic motility. Colonic manometry may be used to predict which patients will benefit from resection or reanastomosis.

Adolescent↗
PubMed2001

[Antimalarial chemoprophylaxis in the French army: development from 1986 to 2001].

In 1999, almost 25,000 French soldiers were deployed in malaria transmission areas. With an incidence of 4.5 p. 100 men.year, malaria infection remains a serious problem requiring priority status for control in military personnel. Epidemiological surveillance provides data necessary to assess morbidity due to malaria, monitor changing patterns of Plasmodium falciparum drug-sensitivity, and evaluate the efficacy of malaria control measures. In 1990, the French army replaced chemoprophylaxis using chloroquine alone with combination treatment using a single capsule containing 100 mg of chloroquine base and 200 mg of proguanil chlorhydrate. This measure in association with the use deltamethrine impregnated bed-nets led to a significant decrease in incidence. However a comeback was observed from 1993 to 1997. Since 1995, the effectiveness of the chloroquine-proguanil combination has diminished mainly in the stable malaria areas. In response to increasing Plasmodium falciparum resistance to chloroquine-proguanil chemoprophylaxis, it was necessary to find an alternative. Two studies carried out among French soldiers in Sub-Saharian Africa between 1996 and 1998 demonstrated that a daily dose 100 mg doxycycline was more effective than the chloroquine-proguanil combination. In addition the 1998 study showed that doxycycline monohydrate in the form of a multiparticle tablet was better tolerated. In 2001 four drugs are used for malaria chemoprophylaxis in the army personnel, i.e., chloroquine and proguanil in combination, mefloquine, and doxycycline, depending on location and duration of mission. The chloroquine-proguanil combination is used in countries with chloroquine-resistant strains, e.g., Chad and Senegal. Mefloquine and doxycycline are used in countries with chloroquine-resistant strains. Due to increasing resistance, it will be necessary to evaluate other drugs or antipaludian combinations.

Animals↗
PubMed2001

[Disease vector control strategy in the French army].

Disease vector control is a major priority for the Medical Health Corps of the French Armed Forces which maintains around 23,000 troops in tropical areas and is involved in numerous military and humanitarian missions throughout the world. Control strategy includes both general and personal control measures. Personal control measures include wearing permetherin-impregnated combat uniforms, application of repellents to the skin, and use of deltamethrin-impregnated bednets. General measures are implemented in facilities and in the environment. Measures in facilities include not only physical deterrents such as screens on openings and air-conditioning but also application of chemical insecticides to walls, curtains, and screening. Environmental measures include control of larval deposits and elimination of potential breeding areas. Low-volume wide-area spraying of imagocides is a supplemental option used in case of disease outbreak. For units stationed in tropical areas, command and surveillance of vector control operations is under the responsibility of the mosquito control committee which includes personnel from the affected field unit. Strategies are chosen in function of local climate and operational conditions. The efficacy of vector control programs is assessed annually by reviewing the incidence in armed forces personnel of the main vector-transmitted diseases: malaria, dengue fever, and leishmaniasis. Documentation and training are dispensed to all units stationed in tropical areas. To ensure that knowledge of military physicians remains current, three courses on malaria control are offered each year at the Tropical Medicine Institute of the Armed Forces Health Corps (Le Pharo) in Marseille. Field research conducted in collaboration with military or civilian organizations independent of the Armed Services Health Corps makes it possible to keep chiefs of staff informed of state-of-the art vector control measures adapted to use by personnel on assignment or mission in tropical areas.

Animals↗
PubMed2001

[Epidemiologic surveillance of dengue fever in the French army from 1996 to 1999].

Dengue fever is a widespread disease that can occur outside tropical areas. Several thousand French military personnel are exposed to this infectious risk each year and exposure is expected to rise with the creation of a professional army and the increasing number of foreign missions. As a result, dengue fever has become a major priority for the Armed Services Health Corps (ASHC). A system of epidemiological surveillance based on the active participation of all military physicians has been designed by the ASHC to collect and analyze all data relevant to cases of dengue fever involving French military personnel stationed overseas or at home. The purpose of this study is to present data compiled for the period from 1996 to 1999. Analysis of these data demonstrated that the incidence of dengue fever peaked in 1997 due to epidemic outbreaks occurring in French Polynesia and Martinique. In response to these outbreaks control measures were adapted especially in regard to vector control. This study shows that the system of surveillance implemented by the ASHC is an effective but still perfectible tool.

Adult↗