Biomedical subjects

P Jacques

Publications and source records attributed to P Jacques.

At least 19 recordsLinked to original sources

PubMed2005

Direct measurements of Ab and Ac using vertex and kaon charge tags at the SLAC detector.

Exploiting the manipulation of the SLAC Linear Collider electron-beam polarization, we present precise direct measurements of the parity-violation parameters A(c) and A(b) in the Z-boson-c-quark and Z-boson-b-quark coupling. Quark-antiquark discrimination is accomplished via a unique algorithm that takes advantage of the precise SLAC Large Detector charge coupled device vertex detector, employing the net charge of displaced vertices as well as the charge of kaons that emanate from those vertices. From the 1996-1998 sample of 400 000 Z decays, produced with an average beam polarization of 73.4%, we find A(c)=0.673+/-0.029(stat)+/-0.023(syst) and A(b)=0.919+/-0.018(stat)+/-0.017(syst).

Journal Article↗

PubMed2004

Hepatitis B vaccination coverage in Belgian health care workers.

BACKGROUND: The hepatitis B virus (HBV) vaccination policy for health care workers (HCW) started in Belgium in 1983. An update of vaccination coverage and rates of seroconversion and seroprotection among HCW can give an insight into the actual status and encourage further development of vaccination programs. PATIENTS AND METHODS: 5,064 HCW were tested for anti-HBs. We considered those who had a positive anti-HBs test as seroconverted (SC) and those who had an anti-HBs titer > 10 IU/l as seroprotected (SP). RESULTS: 4,771 HCW were eligible for vaccination; 84.9% of them were effectively vaccinated. Among high-risk professions (nurses, care and laboratory workers), 94.79% were vaccinated; for other professions the vaccination coverage was 69.26%. Of the 1,015 non-vaccinated persons, 293 were anti-HBs positive. Among these 54.95% declared they had had a previous hepatitis infection that was serologicaLly proven to be HBV (anti-HBc positive). Of the remaining 132 positives, 70.45% had previously undergone surgery and/or transfusion. Among these 1,015 non-vaccinated HCW, 59.03% were anti-HBs positive. Of these, 373 were nurses, care or laboratory workers. This contrasts with the results for HCW in other sectors, where 11.49% were anti-HBs positive. CONCLUSION: In our sample, high vaccination, seroconversion and seroprotection rates were achieved, at least for higher risk HCW. The same conclusion can be drawn if we consider hospital departments which carry a higher risk of blood-borne infections.

Adult↗

PubMed2004

Role of lipopeptides produced by Bacillus subtilis GA1 in the reduction of grey mould disease caused by Botrytis cinerea on apple.

AIM: Test of Bacillus subtilis strain GA1 for its potential to control grey mould disease of apple caused by Botrytis cinerea. METHODS AND RESULTS: GA1 was first tested for its ability to antagonize in vitro the growth of a wide variety of plant pathogenic fungi responsible for diseases of economical importance. The potential of strain GA1 to reduce post-harvest infection caused by B. cinerea was tested on apples by treating artificially wounded fruits with endospore suspensions. Strain GA1 was very effective at reducing disease incidence during the first 5 days following pathogen inoculation and a 80% protection level was maintained over the next 10 days. Treatment of fruits with an extract of GA1 culture supernatant also exerted a strong preventive effect on the development of grey mould. Further analysis of this extract revealed that strain GA1 produces a wide variety of antifungal lipopeptide isomers from the iturin, fengycin and surfactin families. A strong evidence for the involvement of such compounds in disease reduction arose from the recovery of fengycins from protected fruit sites colonized by bacterial cells. CONCLUSIONS: The results presented here demonstrate that, despite unfavourable pH, B. subtilis endospores inoculated on apple pulp can readily germinate allowing significant cell populations to establish and efficient in vivo synthesis of lipopeptides which could be related to grey mould reduction. SIGNIFICANCE AND IMPACT OF THE STUDY: This work enables for the first time to correlate the strong protective effect of a particular B. subtilis strain against grey mould with in situ production of fengycins in infected sites of apple fruits.

Antifungal Agents↗

PubMed2003

Improved direct measurement of the parity-violation parameter Ab using a mass tag and momentum-weighted track charge.

We present an improved direct measurement of the parity-violation parameter A(b) in the Z boson-b-quark coupling using a self-calibrating track-charge technique applied to a sample enriched in Z-->bb events via the topological reconstruction of the B hadron mass. Manipulation of the Stanford Linear Collider electron-beam polarization permits the measurement of A(b) to be made independently of other Z-pole coupling parameters. From the 1996-1998 sample of 400,000 hadronic Z decays, produced with an average beam polarization of 73.4%, we find A(b)=0.906+/-0.022(stat)+/-0.023(syst).

Journal Article↗

PubMed2003

Fluorescent Pseudomonas mainly produce the dihydro form of pyoverdine at low specific growth rate.

AIMS: To analyse the influence of cell growth rate and iron concentration on the production of pyoverdines (PVDs) and of their reduced dihydro forms by three fluorescent Pseudomonas strains (P. putida BTP16, P. fluorescens BTP7 and P. aeruginosa 7NSK2). METHODS: PVD and dihydropyoverdine (DHPVD) productions were determined by LC ESI-MS and spectrophotometry during batch and chemostat culture at different dilution rates. SIGNIFICANCE: The relatively high PVD-to-DHPVD ratio (0.57) observed in pH-controlled batch cultures suggested that a base-catalysed chemical oxidation of the dihydroform is not the prime mechanism involved in generating PVDs. Interestingly, in chemostat cultures the PVD-to-DHPVD ratio was significantly reduced at low specific growth rate. Our results suggest that the oxidation of DHPVD to PVD is catalysed by an iron-dependent enzymatic reaction rather than a chemical oxidation.

Biomass↗

PubMed2002

The immunogenicity and reactogenicity profile of a candidate hepatitis B vaccine in an adult vaccine non-responder population.

Approximately 5% of vaccinees display an inadequate response after the administration of the standard three dose hepatitis B vaccine. A new hepatitis B vaccine (HBsAg/AS04) formulated with the adjuvant AS04 which contains 3'-deacylated monophosphoryl lipid A (3D-MPL) and alum has been developed. AS04 enhances the immune response which may be beneficial to non-responders. In a single-blind, randomised study, we tested the immunogenicity and reactogenicity of the new vaccine with that of commercially established hepatitis B vaccine, both on a 0, 1, 6 months schedule in 20-60 years old non-responders (titre <10 m IU/ml after four doses of hepatitis B vaccine). One month after the first dose the seroprotection rate was 44% for group 1 (58 subjects) receiving the established vaccine versus 66% for group 2 receiving HBsAg/AS04 (57 subjects) (P=0.03). One month after the second dose this was 58 and 81%, respectively (P<0.005) and 1 month after the third dose this was 68 and 98%, respectively (P<0.001). One month after each dose, GMTs were 34, 56 and 111 mIU/ml for group 1 versus 123222 and 1937 mIU/ml for the HBsAg/AS04 group (P<0.05, <0.01 and 0.0001, respectively). Pain at the injection site was the most commonly reported local symptom and very few symptoms were scored as severe. In this group of adult non-responders to previous hepatitis vaccination, the HBsAg/AS04 vaccine was well tolerated and induced, at all time-points, a superior immune response compared to the licensed hepatitis B vaccine.

Adjuvants, Immunologic↗

PubMed2002

Improved direct measurement of A(b) and A(c) at the Z(0) pole using a lepton tag.

The parity violation parameters A(b) and A(c) of the Zb(b) and Zc(c) couplings have been measured directly, using the polar angle dependence of the polarized cross sections at the Z(0) pole. Bottom and charmed hadrons were tagged via their semileptonic decays. Both the electron and muon analyses take advantage of new multivariate techniques to increase the analyzing power. Based on the 1993-1998 SLD sample of 550,000 Z(0) decays produced with highly polarized electron beams, we measure A(b) = 0.919+/-0.030(stat)+/-0.024(syst), and A(c) = 0.583+/-0.055(stat)+/-0.055(syst).

Journal Article↗

PubMed2001

The homolytic and heterolytic fatty acid hydroperoxide lyase-like activities of hematin.

Pentenols and pentene dimers are biosynthetized in plants by homolytic fatty acid hydroperoxide lyase (HPL) or HPL-like enzymes. It has been found that these compounds can modify the flavor of olive oil. Reactions between hematin and 13-hydroperoxyoctadecatrienoic acid resulted in the formation of the same compounds via a free radical reaction in which an alkoxyl radical derived from linolenic acid hydroperoxide undergoes a beta-scission. (Z)-3-Hexenal has also been detected as a minor product of the reaction. It is bioconversed from the same substrate in plants by heterolytic HPL. Thanks to the redox cycle of its central iron, hematin has both homolytic and heterolytic HPL-like activities.

Aldehyde-Lyases↗

PubMed2001

Imaging mixed lipid monolayers by dynamic atomic force microscopy.

Phase imaging with tapping mode atomic force microscopy (AFM) and force modulation microscopy were used to probe the mechanical properties of phase-separated lipid monolayers made of a mixture (0.25:0.75) of the surface-active lipopeptide surfactin and of dipalmitoylphosphatidylcholine (DPPC). The pi-A isotherms and the result of a molecular modeling study revealed a loose, 2-D liquid-like organization for the surfactin molecules and a closely packed, 2-D solid-like organization for DPPC molecules. This difference in molecular organization was responsible for a significant contrast in height, tapping mode phase and force modulation amplitude images. Phase imaging at light tapping, i.e., with a ratio of the set-point tapping amplitude with respect to the free amplitude A(sp)/A(0) approximately 0.9, showed larger phase shifts on the solid-like DPPC domains attributed to larger Young's modulus. However, contrast inversion was observed for A(sp)/A(0)<0.7, suggesting that at moderate and hard tapping the image contrast was dominated by the probe-sample contact area. Surprisingly, force modulation amplitude images showed larger stiffness for the liquid-like surfactin domains, suggesting that the contrast was dominated by contact area effects rather than by Young's modulus. These data emphasize the complex nature of the contrast mechanisms of dynamic AFM images recorded on mixed lipid monolayers.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2001

Improved direct measurement of leptonic coupling asymmetries with polarized Z bosons.

We present final measurements of the Z boson-lepton coupling asymmetry parameters A(e), A(mu), and A(tau) with the complete sample of polarized Z bosons collected by the SLD detector at the SLAC Linear Collider. From the left-right production and decay polar angle asymmetries in leptonic Z decays we measure A(e) = 0.1544+/-0.0060, A(mu) = 0.142+/-0.015, and A(tau) = 0.136+/-0.015. Combined with our left-right asymmetry measured from hadronic decays, we find A(e) = 0.1516+/-0.0021. Assuming lepton universality, we obtain a combined effective weak mixing angle of sin (2)theta(eff)(W) = 0.230 98+/-0.000 26.

Journal Article↗

PubMed2001

First symmetry tests in polarized Z0 decays to bbg.

We have made the first direct symmetry tests in the decays of polarized Z0 bosons into fully identified bbg states, collected in the SLD experiment at SLAC. We searched for evidence of parity violation at the bbg vertex by studying the asymmetries in the b-quark polar- and azimuthal-angle distributions, and for evidence of T-odd, CP-even or CP-odd, final-state interactions by measuring angular correlations between the three-jet plane and the Z0 polarization. We found results consistent with standard model expectations and set 95% C. limits on anomalous contributions.

Journal Article↗

PubMed2001

Influence of moderate temperatures on myristoyl-CoA metabolism and acyl-CoA thioesterase activity in the psychrophilic antarctic yeast Rhodotorula aurantiaca.

The inability of psychrophilic microorganisms to grow at moderate temperatures (>20 degrees C) presently represents an unresolved thermodynamic paradox. Here we report for the psychrophilic yeast Rhodotorula aurantiaca A19, isolated from Antarctic ice, that the inability to grow at temperatures close to 20 degrees C is associated with profound alterations in cell morphology and integrity. High performance liquid chromatography analysis of the intracellular acyl-CoA esters revealed an abnormal accumulation of myristoyl-CoA (C14-CoA) in cells cultivated close to the nonpermissive temperature. Its concentration (500 microm) was found to be 28-fold higher than in cells cultivated at 0 degrees C. If one considers its ability to disrupt membrane bilayers and to inhibit many cellular enzymes and functions, intracellular myristoyl-CoA accumulation in the psychrophile R. aurantiaca represents one of the principal causes of growth arrest at moderate temperatures. Intracellular acyl-CoA concentrations are believed to be regulated by thioesterase activity. Thus in an attempt to explore the mechanism by which temperature disrupts myristoyl-CoA metabolism, we isolated and characterized a long chain acyl-CoA thioesterase. The monomeric 80-kDa thioesterase from the psychrophilic yeast shows a very strong specificity for myristoyl-CoA. The affinity for substrate and the catalytic efficiency of the thioesterase are optimal below 5 degrees C (temperatures habitually experienced by the strain) and dramatically decrease with increasing temperature. The loss of affinity for substrate is related to the intracellular increase of myristoyl-CoA concentration. Our observations reveal one of the probable mechanisms by which temperature fixes the limit of growth for this psychrophilic yeast.

Acyl Coenzyme A↗

PubMed2001

Photooxidation of the phenylazonaphthol AO20 on TIO2: kinetic and mechanistic investigations.

The results of the photocatalytic and photosensitized degradations of the monoazo dye AO20 in aqueous solution using suspended titanium dioxide are presented. Kinetic and mechanistic details have been elucidated using UV/Vis, FTIR and TCO techniques. It was proven that adsorption of dye molecules onto the support material is essential for the processes to be effective. Moreover, even if their mechanisms differ during the early stages, photocatalysis and photosensitization lead to very similar ultimate breakdown products. Indeed, the original dye anchored to the oxide surface systematically undergoes fast decomposition until it is transformed into CO2 or aliphatic acids (formic, acetic, oxalic acids), which react rather slowly with hydroxyl radicals or trapped holes.

Adsorption↗

PubMed2001

Influence of electrical properties on the evaluation of the surface hydrophobicity of Bacillus subtilis.

The surface hydrophobicity of nine Bacillus subtilis strains in different states (spores, vegetative cells, and dead cells) was assessed by water contact angle measurements, hydrophobic interaction chromatography (HIC) and bacterial adhesion to hydrocarbon (BATH). Electrokinetic properties of B. subtilis strains were characterized by zeta potential measurements and found to differ appreciably according to the strain. Correlations between HIC data, BATH data and zeta potential showed that HIC and BATH are influenced by electrostatic interactions. Water contact angle measurements thus provide a better estimate of cell surface hydrophobicity. The water contact angle of B. subtilis varied according to the strain and the state, the spores tending to be more hydrophobic than vegetative cells.

Bacillus subtilis↗

PubMed2001

Whole grain intake and risk of ischemic stroke in women.

In a recent prospective study, whole grain intake was associated with a reduced risk of ischemic stroke. Refined grain, however, did not elicit such protection. Given the potential health benefits associated with whole grain diets, further exploration on the effects of whole grains on health and risk of chronic disease is warranted.

Brain Ischemia↗

PubMed2001

Underestimation of the importance of homocysteine as a risk factor for cardiovascular disease in epidemiological studies.

BACKGROUND: In epidemiological studies, within-person variability in plasma total homocysteine (tHcy) measurements may dilute the association of 'usual' levels of tHcy with risk of cardiovascular disease, referred to as 'regression dilution'. The aim of this report was to estimate the magnitude of regression dilution after varying intervals of follow-up. METHODS: Regression dilution ratios (RDR) for tHcy were calculated using replicate tHcy measurements obtained after 3, 6 and 8 years from the Rotterdam, Hordaland and Framingham studies, respectively, and after 3, 6, 9 and 12 years from the United Kingdom Prospective Study of type 2 Diabetes Mellitus (UKPDS). RESULTS: The RDR for tHcy decreased with increasing interval in the three population-based studies and in the UKPDS. Moreover, the rate of decline of the RDR in the population-based studies was similar to that obtained in the UKPDS. Using linear regression analysis for the population-based studies, these results suggest an RDR of 0.83 at 2 years, 0.71 at 6 years and 0.53 at 12 years. CONCLUSIONS: These results have important implications for the interpretation of prospective studies of tHcy and cardiovascular disease. Failure to correct for increasing regression dilution using lower RDRs for longer follow-up may underestimate the relative risks of cardiovascular disease associated with tHcy by about one-fifth after 2 years and one-half after 10 years.

Aged↗

PubMed2001

Dissemination of catabolic plasmids among desiccation-tolerant bacteria in soil microcosms.

The dissemination of catabolic plasmids was compared to bioaugmentation by strain inoculation in microcosm experiments. When Rhodococcus erythropolis strain T902, bearing a plasmid with trichloroethene and isopropylbenzene degradation pathways, was used as the inoculum, no transconjugant was isolated but the strain remained in the soil. This plasmid had a narrow host range. Pseudomonas putida strain C8S3 was used as the inoculum in a second approach. It bore a broad host range conjugative plasmid harboring a natural transposon, RP4::Tn4371, responsible for biphenyl and 4-chlorobiphenyl degradation pathways. The inoculating population slowly decreased from its original level (10(6) colony-forming units [CFU]/g of dry soil) to approx 3 x 10(2) CFU/g of dry soil after 3 wk. Transconjugant populations degrading biphenyl appeared in constant humidity soil (up to 2 x 10(3) CFU/g) and desiccating soil (up to 10(4) CFU/g). The feasibility of plasmid dissemination as a bioaugmentation technique was demonstrated in desiccating soils. The ecologic significance of desiccation in bioaugmentation was demonstrated: it upset the microbial ecology and the development of transconjugants.

Bacteria↗

PubMed2001

Influence of culture conditions on lipopeptide production by Bacillus subtilis.

Bacillus subtilis produces various families of lipopeptides with different homologous compounds. To produce "new molecules" with improved activities and to select strains that produced a reduced number of homologs or isomers, we studied the effects of different media on the nature of the synthesis of fatty acid chains for each lipopeptide family. This study focused on two B. subtilis strains cultivated in flasks. Optimized medium for lipopeptide production and Landy medium modified by replacing glutamic acid with other alpha-amino acids were used. We found that the intensity of production of homologous compounds depends on the strain and the culture medium. Analysis of these lipopeptides by high-performance liquid chromatography showed that the strain B. subtilis NT02 yielded various homologous compounds when cultivated in Landy medium (L-Glu), but primarily one homologous product in high relative amounts when cultivated in the optimized medium. Mass spectrometric analysis and determination of the amino acid composition of this molecule enabled us to identify it as Bacillomycine L c15.

Amino Acids↗