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Biomedical subjects

M Wery

Publications and source records attributed to M Wery.

At least 19 recordsLinked to original sources
PubMed2004

Quantitative determination of hydrogen in solids by gas chromatography.

Processes such as electroplating or acid cleaning are notorious causes of post-processing failure through hydrogen embrittlement. So, the determination of amounts of hydrogen in metals is of great importance. An analysis method for investigation of H content in solids has been established based on hot extraction and gas chromatography system. Hot extraction in inert gas enables complete and/or partial removal of the hydrogen from the samples. A gas chromatography system is used to determine quantitatively the amount of thermally desorbed hydrogen. An investigation of the baking operating conditions is made of the hydrogen desorption rate of zinc-plated steel parts. Then, an analysis of the polarisation conditions upon chromium electroplating is given.

Calibration↗
PubMed2001

HU-GFP and DAPI co-localize on the Escherichia coli nucleoid.

The heterodimeric HU protein, one of the most abundant DNA binding proteins, plays a pleiotropic role in bacteria. Among others, HU was shown to contribute to the maintenance of DNA superhelical density in Escherichia coli. By its properties HU shares some traits with histones and HMG proteins. More recently, its specific binding to DNA recombination and repair intermediates suggests that HU should be considered as a DNA damage sensor. For all these reasons, it will be of interest to follow the localization of HU within the living bacterial cells. To this end, we constructed HU-GFP fusion proteins and compared by microscopy the GFP green fluorescence with images of the nucleoid after DAPI staining. We show that DAPI and HU-GFP colocalize on the E. coli nucleoid. HU, therefore, can be considered as a natural tracer of DNA in the living bacterial cell.

Bacterial Proteins↗
PubMed2000

Overproduction and improved strategies to purify the threenative forms of nuclease-free HU protein.

The heterodimeric HU protein was isolated from Escherichia coli as one of the most abundant DNA binding proteins associated with the bacterial nucleoid. HUalphabeta is composed of two very homologous subunits, but HU can also be present in E. coli under its two homodimeric forms, HUalpha(2) and HUbeta(2). This protein is conserved either in its heterodimeric form or in one of its homodimeric forms in all bacteria, in plant chloroplasts and in some viruses. HU can participate, like the histones, in the maintenance of DNA supercoiling and in DNA condensation. This protein which does not recognize any specific sequence on double-stranded DNA, has been shown to bind specifically to cruciform DNA as does the eukaryotic HMG1 protein and to a series of structures which are found as intermediates of DNA repair, e.g., nick, gap, 3'overhang, etc. The strong binding of HU to these diverse DNA structures could explain, in part at least, its pleiotropic role in the bacterial cell. To understand all the facets of its interactions with nucleic acids, it was necessary to develop a procedure which allowed the purification of the three forms of HU under their native form and without the nuclease activity strongly associated with the protein. We describe here such a procedure as well as demonstrating that the three histidine-tagged HUs we have produced, have conserved the binding characteristics of native HUs. Interestingly, by two complementation tests, we show that the histidine-tagged HUs are fully active in vivo.

Bacterial Proteins↗
PubMed1999

Irradiated sporozoites prime mice to produce high antibody titres upon viable Plasmodium berghei sporozoite challenge, which act upon liver-stage development.

C57BL6 mice were protected against Plasmodium berghei sporozoite challenge by immunization with live 12 krad dose-irradiated sporozoites, but not by 20 krad dose-irradiated sporozoites. Immunization with 12 krad irradiated sporozoites generated low levels of antibody reactive to liver-stage parasites (titres of 1/100). Inoculation of as few as 100 live P. berghei sporozoites induced complete host protection accompanied by a very quick and high boost of antibody titres up to 1/4000. This sporozoite challenge-drive antibody boost was absent in mice immunized by 20 krad sporozoites and in non-protected, and non-immunized mice. Antibody was mainly liver-stage (LS) specific and due to an increase of IgG2a and IgG2b. The in vitro effect of pre- and post-challenge sera upon either sporozoite invasion or LS development was assessed in Hep-G2 cultures. Both were found to have a strong effect upon LS development even at 1/2500 dilution, and conversely a low effect upon invasion. These results suggest that sporozoites irradiated at doses that induce protection are able to prime T-cells which, upon challenge by non-irradiated sporozoites, provide help to B-lymphocytes to trigger the production of high titres of anti-LS antibodies that can inhibit LS development in vitro.

Animals↗
PubMed1999

Plasmodium berghei development in irradiated sporozoite-immunized C57BL6 mice.

The C57BL6 strain of mice is highly susceptible to Plasmodium berghei sporozoite infections and consequently requires repeated immunizations with irradiated sporozoites to obtain protective immunity. After a live sporozoite challenge in the immunized hosts, hepatic-stage parasites found in the liver after 48 h are of different sizes--small schizonts corresponding to blocked forms (derived from irradiated sporozoites), and schizonts of intermediate size (derived from live sporozoites). Large schizonts corresponding to mature hepatic forms are found only in unimmunized but challenged C57BL6 mice. Using monoclonal and polyclonal antibodies directed to liver-stage parasites, different patterns of binding reactivity to the above forms are observed. More than 20% of the irradiated sporozoites transform into blocked forms after immunization and persist in the liver. Upon sporozoite challenge in such immunized animals the rate of transformation of sporozoites into hepatic parasites is less than 2%. These observations shed light on the fate of live sporozoite development in irradiated sporozoite-immunized C57BL6 mice.

Animals↗
PubMed1998

Blocked hepatic-stage parasites and decreased susceptibility to Plasmodium berghei infections in BALB/c mice.

The BALB/c strain of mice is comparatively more resistant to sporozoite infections of Plasmodium berghei than the C57BL6 strain. Infection with live sporozoites results in the formation of small hepatic forms in the BALB/c liver that persist for as long as 6 days. Upon infection with small numbers of sporozoites, some of the parasites are destroyed in the liver whereas the rest persist as blocked forms. When larger numbers of sporozoites are injected the same process occurs but, in addition, a fraction of the liver-stage parasites complete full development and give rise to blood forms. Although blocked liver forms persist until day 6 post-infection they actually develop to only 24 h of maturity. The nature of these persistent forms is similar to those obtained from irradiated sporozoite immunization. There is a stronger cell proliferation to liver-stage antigens by spleen lymphocytes of irradiated sporozoite-immunized BALB/c mice in comparison to that of immunized C57BL6 mice suggesting that a stronger priming to liver-stage antigens, probably due to the presence of blocked hepatic forms in the liver for a longer period of time (as compared to C57BL6), occurs in the BALB/c mice. This could be a reason for the long-lasting protective memory observed in BALB/c mice.

Animals↗
PubMed1995

A conserved peptide sequence of the Plasmodium falciparum circumsporozoite protein and antipeptide antibodies inhibit Plasmodium berghei sporozoite invasion of Hep-G2 cells and protect immunized mice against P. berghei sporozoite challenge.

Minutes after injection into the circulation, malaria sporozoites enter hepatocytes. The speed and specificity of the invasion process suggest that it is receptor mediated. The region II sequence of Plasmodium falciparum circumsporozoite (CS) protein includes a nonapeptide (WSPCSVTCG) which is highly conserved in all of the CS proteins sequenced to data, including the one from Plasmodium berghei. We have found that two peptides based on the P. falciparum region II sequence, P18 (EWSPCSVTCGNGIQVRIK) and P32 (IEQYLKKIKNS ISTEWSPCSVTCGNGIQVRIK), significantly inhibited P. berghei sporozoite invasion into Hep-G2 cells in vitro. This inhibition was enhanced if either peptide was preincubated with Hep-G2 cells prior to sporozoite invasion. We confirm that region II is a sporozoite ligand for the hepatocyte receptor; moreover, despite the few differences between P. falciparum and P. berghei region II sequences around the nonapeptide sequence (66% homology), the functional characteristics of the motif sequences are not affected. Since the conserved motifs represent a crucial sequence involved in Plasmodium sporozoite invasion of hepatocytes, antibodies to region II should inhibit sporozite invasion into hepatocytes. Indeed, we found that polyclonal antibodies generated to the P. falciparum-based peptide P32 inhibited P. berghei sporozoite invasion of Hep-G2 cells. Furthermore, inbred mice (C57BL/6) immunized with P32 were protected against a lethal challenge of P. berghei sporozoites. Our results suggest that the conserved region II of the CS protein contains crucial B- and T-cell epitopes, that such peptide sequences from the human malaria parasite P. falciparum can be screened in the P. berghei rodent model, and, finally, that region II can be considered useful as one of the components of a malaria vaccine.

Amino Acid Sequence↗
PubMed1995

An etiologic study of hemoglobinuria and blackwater fever in the Kivu Mountains, Zaire.

Between January 1985 and March 1986, in the high altitude area of Kivu, Eastern Zaïre, 38 patients presenting with hemoglobinuria as main manifestation were investigated. Profound glucose-6-phosphate dehydrogenase deficiency was detected in 4 patients, leptospirosis in 2 and Hantaan virus infection in 2. Hemolysis was doubtful (haptoglobin > 40 mg/dl, Hemoglobin > 12 g/dl) in 2 patients. Other potential causes of hemoglobinuria such as hemoglobinopathy, toxic agents, infectious diseases or blood transfusion incompatibility were carefully screened and excluded. The syndrome observed in the remaining 28 cases was strongly suggestive of blackwater fever (BWF) as described in malaria patients by several authors under the french name "fièvre bilieuse hémoglobinurique". Quinine was used as curative treatment of malaria before admission in a significant greater proportion (p < 0.01) of patients with BWF compared to patients with uncomplicated malaria, suggesting that this drug might have played a triggering role in the genesis of BWF. However, quinine was usually administered at inadequate doses to malaria patients non responding to chloroquine and belonging to a population of whom 50% are non immune. It may thus also be hypothesized that BWF in our patients could result from a hyperparasitemic state that remained undetected because of an unusual synchronous lysis of infected erythrocytes. In the latter case BWF would correspond to a major complication of falciparum malaria only coincidentally related to the use of quinine.

Adolescent↗
PubMed1994

Rodent malaria parasites: molecular karyotypes characterize species, subspecies and lines.

The molecular karyotypes of the African murine malaria parasites P. berghei (3 strains, 2 lines) P. yoeli (2 strains) P. chabaudi (3 strains, 1 line) and P. vinckei (4 strains) have been studied using orthogonal field alternation gel electrophoresis (OFAGE). The genome of each species was resolved into 9 to 11 distinct chromosomal DNA banas molecules of varying intensities which seem to represent 14 chromosomes ranging in size from 600 kb to 3500 kb. The position of certain chromosomes allowed the identification of a unique karyotype for each of the strains and lines under study. P. yoelii appears by criteria of chromosome size, chromosome numbers and localisation of DNA probes to differ considerably from the other three rodent malaria species. The chromosomal location of 5 DNA probes allowed the identification of corresponding chromosomes in rodent malaria parasites and the differentiation between species and strains. Assignment of the "PMMSA" gene of P. c. chabaudi IP-PC 1 enables the distinction of the four rodent malaria species. The molecular karyotype combined to chromosomal assignment of DNA probes provides a useful tool for a more precise characterization by a genetic definition of malaria parasites.

Animals↗
PubMed1994

A highly efficient in vitro cloning procedure for asexual erythrocytic forms of the human malaria parasite Plasmodium falciparum.

A very reliable and productive technique for cloning of Plasmodium falciparum in vitro is proposed, as demonstrated by successive limiting dilution of suspensions of asexual erythrocytic forms of the NF 54 strain. The introduction and the study of reliable clones is of extreme importance for a better understanding of the behaviour of the parasite, also in field conditions. The method is rapid, simple and efficient. The growth of the clones was individually monitored and the culture conditions were constantly adjusted during their stay in recipients of increasing size. A yield of 18/96 (18.75%) of provisional clones was obtained, while the supercloning phase resulted in 16/80 (20%) positive cultures. The probability that the latter were derived from a single progenitor is very high (99%). It was shown that three randomly selected clones (A1A9, A1B11, and A1C10) have excellent growth characteristics before and after cryopreservation, and after a longer period of culture in standard conditions.

Animals↗
PubMed1994

Population dynamics of anophelines in a malathion treated village in the intermediate zone of Sri Lanka.

As part of research programme on malaria transmission in Sri Lanka, a study was made of man-biting anophelines at Nikawehera, a village on the border of the intermediate and dry rainfall zones. Weekly mosquito collections by night human bait (NHB) were performed inside and outside four fixed stations from October 1992 till March 1993. Houses in the village were treated with malathion by the Anti-Malaria Campaign in October and at the end of January 1993. An. culicifacies and An. tesselatus were the most abundant species. An. culicifacies was probably the only species responsible for malaria transmission. An. culicifacies densities varied between stations and reflected differences in availability of breeding places. An. culicifacies aggressivity is closely related to the rainfall pattern, increasing after the first monsoon rains in November and reaching a peak in late December--early January. Vectorial capacity, however, decreased during the first weeks of the rainy season. The maximum vectorial capacity was found in January. The night biting cycle of An. culicifacies showed a peak between 20.00 and 23.00 h. Since the introduction of electricity in the village, people go to bed later. This might reduce the impact of impregnated bednets on malaria transmission. The results show that malathion spraying as performed now is not very effective. The timing of the spray rounds should be improved. In order to limit malaria transmission, we suggest to advance the malathion spraying campaign of January with one month.

Animals↗
PubMed1992

Transmission factors in malaria epidemiology and control in Africa.

Genetic and environmental components of factors contributing in malaria transmission are reviewed. Particular attention is given to density dependent regulation of vector populations in relation to the survival rate of anophelines. The expectation of vector control activities are different according to the epidemiological characteristics of malaria, mainly its stability. In areas with perennial and high transmission (stable malaria) vector control could reduce malaria related morbidity and mortality, without any effect on the endemicity. However this need further investigations. In areas where the transmission period is very short (unstable malaria), vector control will have an important impact on the disease and on the endemicity. Control projects using indoor spraying with insecticide and impregnated bed nets are discussed.

Africa↗
PubMed1989

[Complete inhibition of cyclic transmission by immunization against Plasmodium berghei Anka ookinetes].

An antiserum raised against P. berghei Anka ookinetes binds specifically to ookinetes and zygotes surface as assessed by indirect immunofluorescence. The transmission blocking activity of this serum was assessed by feeding mosquitoes on immunized mice. A serum showing an antibody titer of 1/320 reached after 6 immunizations completely blocks ookinetes development. This immune serum might be used to screen P. berghei genomic or cDNA library in order to identify or clone sequences involved in the process of gametocyte infectivity.

Animals↗
PubMed1989

[Study of general mortality and of mortality related to malaria in the mountains of Kivu, Zaire].

A longitudinal study in the "health region" of Katana (Kivu, Zaïre) has permitted to determine age and disease specific mortality rates. The infant mortality rate is 172 per 1000/year, the child mortality rate 45 p.1000/year and the crude rate 24 p.1000/year. Two thirds of this mortality are related to infectious and parasitic diseases: measles, diarrhoea, respiratory diseases and malaria. In the mountainous Katana region (4500 feet), malaria is responsible for 12%, of the decrease and the specific mortality rates are 3 p.1000/year in the general population and 18 and 6 p.1000/year in, respectively, the 0 to 11 month and 1 to 4 year age groups. We discuss the potential of PHC to improve, in the framework of an integrated development approach, this unfavorable health situation.

Adolescent↗