Biomedical subjects

P Jacques

Publications and source records attributed to P Jacques.

At least 37 records · Page 2Linked to original sources

PubMed2000

Surfactin and iturin A effects on Bacillus subtilis surface hydrophobicity.

The synthesis of extracellular molecules such as biosurfactants should have major consequences on bacterial adhesion. These molecules may be adsorbed on surfaces and modify their hydrophobicities. Certain strains of Bacillus subtilis synthesize the lipopeptides, which exhibit antibiotic and surface active properties. In this study the high-performance liquid chromatography (HPLC) analysis of the culture supernatants of the seven B. subtilis strains, showed that the lipopeptide profile varied greatly according to the strain. Among the three lipopeptide types, only iturin A was produced by all B. subtilis strains. Bacterial hydrophobicity, evaluated by the water contact angle measurements and the hydrophobic interaction chromatography, varied according to the strain. Two strains (ATCC 15476 and ATCC 15811) showing extreme behaviors in term of hydrophobicity were selected to study surfactin and iturin A effects on bacterial hydrophobicity. The two lipopeptides modified the B. subtilis surface hydrophobicity. Their effects varied according to the bacterial surface hydrophobic character, the lipopeptide type and the concentration. Lipopeptide adsorption increased the hydrophobicity of the hydrophilic strain but decreased that of the hydrophobic. Comparison of lipopeptide effects on B. subtilis surface hydrophobicity showed that surfactin was more effective than iturin A for the two strains tested.

Journal Article↗

PubMed2000

Prevalence of hepatitis C antibodies in a large sample of Belgian healthcare workers.

OBJECTIVE: To assess the risk of hepatitis C virus (HCV) infection among Belgian (Flemish) healthcare workers. DESIGN: A seroprevalence survey of HCV IgG antibodies. SETTING AND PARTICIPANTS: A systematic sample of 5,064 employees from 22 general hospitals in Flanders and Brussels, Belgium, was tested at the annual occupational medical examination. Together with demographic and occupational data, information was collected on the frequency of blood contact, needlestick injuries, and medical and surgical history. The blood samples were tested using the third-generation Abbott Screen Kit test, with confirmation by Matrix, LIA, and an in-house polymerase chain reaction and the Quantiplex-HCV b-DNA test. RESULTS: 21 persons were found to be positive for HCV markers. The overall prevalence was 0.41% (95% confidence interval [CI95], 0.24-0.59). A statistically significant association was found with a history of blood transfusion (odds ratio [OR], 4.14; CI95, 1.67-10.31) and with history of a clinically apparent hepatitis (OR, 3.98; CI95, 1.60-9.90). Although the ORs for the frequency of blood contact were slightly elevated (between 1.17 and 2.73), this association was not significant. Moreover, a history of needlestick injuries showed a nonsignificant OR of 1.28 (CI95, 0.53-3.09), and no statistically significant difference was found with a variety of duties and tasks. The ORs for potential occupational risk factors were adjusted according to age, gender, antecedents, and other confounders using a logistic regression analysis. Based on this procedure, the ORs decreased slightly. CONCLUSIONS: Flemish healthcare workers showed a lower HCV seropositivity than is seen in the general population; a history of blood transfusion and of clinically apparent hepatitis was most strongly associated with the presence of HCV markers. We concluded that employees in Flemish regional general hospitals are not at an overall increased risk for HCV infection, although occasional transmission through percutaneous injuries is possible, and prevention therefore remains imperative.

Adult↗

PubMed2000

Plasma vitamin B-12 concentrations relate to intake source in the Framingham Offspring study.

BACKGROUND: Low vitamin B-12 status is prevalent among the elderly, but few studies have examined the association between vitamin B-12 status and intake. OBJECTIVE: We hypothesized that vitamin B-12 concentrations vary according to intake source. DESIGN: Plasma concentrations and dietary intakes were assessed cross-sectionally for 2999 subjects in the Framingham Offspring Study. The prevalence of vitamin B-12 concentrations <148, 185, and 258 pmol/L was examined by age group (26-49, 50-64, and 65-83 y), supplement use, and the following food intake sources: fortified breakfast cereal, dairy products, and meat. RESULTS: Thirty-nine percent of subjects had plasma vitamin B-12 concentrations <258 pmol/L, 17% had concentrations <185 pmol/L, and 9% had concentrations <148 pmol/L, with little difference between age groups. Supplement users were significantly less likely than non-supplement-users to have concentrations <185 pmol/L (8% compared with 20%, respectively). Among non-supplement-users, there were significant differences between those who consumed fortified cereal >4 times/wk (12%) and those who consumed no fortified cereal (23%) and between those in the highest and those in the lowest tertile of dairy intake (13% compared with 24%, respectively), but no significant differences by meat tertile. Regression of plasma vitamin B-12 on log of intake, by source, yielded significant slopes for each contributor adjusted for the others. For the total group, b = 40.6 for vitamin B-12 from vitamin supplements. Among non-supplement-users, b = 56.4 for dairy products, 35.2 for cereal, and 16.7 for meat. Only the meat slope differed significantly from the others. CONCLUSIONS: In contrast with previous reports, plasma vitamin B-12 concentrations were associated with vitamin B-12 intake. Use of supplements, fortified cereal, and milk appears to protect against lower concentrations. Further research is needed to investigate possible differences in bioavailability.

Adult↗

PubMed2000

Occupational risk of infection by varicella zoster virus in Belgian healthcare workers: a seroprevalence study.

OBJECTIVES: To assess the prevalence of varicella zoster virus (VZV) antibodies in Flemish (Belgian) healthcare workers, to investigate the association between seronegativity and selected variables, and to assess the reliability of recall about disease as a predictor of immunity. METHODS: A seroprevalence study of VZV antibodies (IgG) was conducted among a systematic sample of 4923 employees in various professional groups, employed in 22 hospitals in Flanders and Brussels (Belgium). Information about sex, age, department, job, and years of employment, the country of origin, and history of varicella was obtained. The presence of VZV antibodies was investigated with the enzyme linked immunosorbent assay (ELISA), Enzygnost anti VZV / IgG (Dade Behring, Marburg, Germany). Statistical analysis was performed by calculating prevalences and prevalence ratios (PRs) and their 95% confidence intervals (95% CIs). Sensitivity, specificity, and positive and negative predictive values (PPV and NPV) of the recalled history were determined. RESULTS: The prevalence of VZV seropositivity in Flemish healthcare workers was 98.5% (95% CI 98.1 to 98.8). Seronegativity was significantly associated with age and job, increasing with both older and younger age. The prevalence of seronegative workers was significantly less in nursing staff than non-nursing staff. There was no significant difference for sex and years of employment. The PPV and NPV of recalled history were 98.9% and 3.4%. Sensitivity and specificity were 83% and 38.9%. CONCLUSION: The prevalence of VZV seropositivity was very high in this sample of Flemish healthcare workers. Because of this low overall susceptibility, VZV infection seems not to be an important occupational risk among healthcare workers in Flanders. The increasing seronegativity above the age of 45 is possibly due to a loss of detectable antibodies. A positive history of varicella was a good predictor of immunity, but a negative history had no value as a predictor of susceptibility in adults.

Adult↗

PubMed2000

Effect of temperature on growth of psychrophilic and psychrotrophic members of Rhodotorula aurantiaca.

The thermo-dependence of growth kinetic parameters was investigated for the Antarctic psychrophilic strain Rhodotorula aurantiaca and a psychrotrophic strain of the same species isolated in Belgium (Ardennes area). Cell production, maximum growth rate (mu max), and half-saturation constant for glucose uptake (Ks) of both yeasts were temperature dependent. For the two yeasts, a maximum cell production was observed at about 0 degree C, and cell production decreased when temperature increased. The mu max values for both strains increased with temperature up to a maximum of 10 degrees C for the psychrophilic strain and 17 degrees C for the psychrotrophic strain. For both yeasts, Ks for glucose was relatively constant at low temperatures. It increased at temperatures above 10 degrees C for the psychrophilic strain and 17 degrees C for the psychrotrophic strain. Although its glucose affinity was lower, the psychrotrophic strain grew more rapidly than the psychrophilic one. The difference in growth rate and substrate affinity was related to the origin of the strain and the adaptation strategy of R. aurantiaca to environmental conditions.

Antarctic Regions↗

PubMed1999

Irreversible site-directed labeling of the 4-aminobutyrate binding site by tritiated meta-sulfonate benzene diazonium. Contribution of a nucleophilic amino acid residue of the alpha1 subunit.

Tritiated meta-sulfonate benzene diazonium ([3H]MSBD), a molecule structurally related to 4-aminobutyrate (GABA), which presents a reactivity toward nucleophilic amino acid residues, was synthesized to investigate the GABA binding site on the GABAA receptor. Irreversible labeling reactions using [3H]MSBD were performed on purified GABAA receptors isolated from cow brain membranes and labeled receptors were analyzed by SDS/PAGE. [3H]MSBD was found to be specifically incorporated into proteins in the 45-60 kDa molecular mass range which were identified as alpha1 subunits and beta2/beta3 subunits by immunoprecipitation with subunit-specific antibodies. The specific immunoprecipitation of alpha and beta subunits confirms that binding of [3H]MSBD occurs at the boundary of these subunits. These labeling results confirm the involvement of nucleophilic residues from the beta subunit but reveal also the contribution of yet unidentified nucleophilic residues on the alpha subunit for the GABA binding site.

Animals↗

PubMed1999

Prevalence of hepatitis A antibodies in a large sample of Belgian health care workers.

Health care workers (HCW), especially women (for example, pediatric nurses and day nursery workers), have been shown to be at risk for viral hepatitis A infections. In order to obtain a more precise estimate of the risk in Belgian HCW, a seroprevalence study was undertaken. The data from this study have been compared with the age-specific seroprevalence of anti-HAV in the general population (GP) as recently estimated. During 1996-1997, a sample of 5,068 employees in 22 general hospitals, geographically distributed over the Flemish and Brussels regions of Belgium, was tested for the presence of anti-HAV. Comparison of the anti-HAV prevalences in HCW and GP shows a significantly lower prevalence in HCW for the age groups 25-34, 35-44 and 45-54 years. Within these age-groups, employees performing catering tasks have the highest prevalence. This difference could be explained by socioeconomic parameters: overrepresentation of higher social classes in better educated HCW. The number of unprotected individuals in young and older age groups (25-54 years) is greater than in the general population. In view of the changing HAV epidemiology in western Europe, the number of unprotected persons will rise in the coming years. Considering the more severe course of the disease as age increases, vaccination may become important in the occupational health strategy for HCW.

Adult↗

PubMed1999

Nanometer scale organization of mixed surfactin/phosphatidylcholine monolayers.

Mixed monolayers of the surface-active lipopeptide surfactin-C(15) and of dipalmitoyl phosphatidylcholine (DPPC) were deposited on mica and their nanometer scale organization was investigated using atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). AFM topographic images revealed phase separation for mixed monolayers prepared at 0.1, 0.25, and 0.5 surfactin molar ratios. This was in agreement with the monolayer properties at the air-water interface indicating a tendency of the two compounds to form bidimensional domains in the mixed systems. The step height measured between the surfactin and the DPPC domains was 1.2 +/- 0.1 nm, pointing to a difference in molecular orientation: while DPPC had a vertical orientation, the large peptide ring of surfactin was lying on the mica surface. The N/C atom concentration ratios obtained by XPS for pure monolayers were compatible with two distinct geometric models: a random layer for surfactin and for DPPC, a layer of vertically-oriented molecules in which the polar headgroups are in contact with mica. XPS data for mixed systems were accounted for by a combination of the two pure monolayers, considering respective surface coverages that were in excellent agreement with those measured by AFM. These results illustrate the complementarity of AFM and XPS to directly probe the molecular organization of multicomponent monolayers.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1999

Structural and functional organization of the fengycin synthetase multienzyme system from Bacillus subtilis b213 and A1/3.

BACKGROUND: Bacillus subtilis strains produce a broad spectrum of lipopeptides that are potent biosurfactants and have specific antimicrobial and antiviral activities. The cyclic lipodecapeptide fengycin is one such compound. Although the fengycin biosynthetic genes in B. subtilis 168 (pps genes) and F29-3 (fen genes) have been well characterized, only limited information is available about the biochemical features of the fengycin synthetase multienzyme system. RESULTS: Five multifunctional peptide synthetases (Fen1-5) that catalyze biosynthesis of the peptide portion of fengycin have been purified from crude extracts of the B. subtilis b213 and A1/3 strains. These enzymes activate all fengycin amino-acid components as aminoacyl adenylates or aminoacyl thioesters. Fen1, Fen2 and Fen3 are each approximately 286 kDa, Fen4 is approximately 400 kDa and Fen 5 is approximately 140kDa; each enzyme activates a different set of L-amino acids. A five-gene cluster (fen1-5) was detected in the B. subtilis A1/3 genome that shows high homology to the pps and fen genes in B. subtilis strains 168 and F29-3. Disruption of fen4 resulted in a loss of fengycin production. The fengycin synthetase enzymes isolated from B. subtilis b213 were assigned to the corresponding A1/3 fen genes by their amino-terminal sequences. CONCLUSIONS: The structural and functional organization of the fengycin synthetase system from B. subtilis b213 has been characterized in detail and correlated with the corresponding pps and fen genes in B. subtilis strains 168, A1/3 and F29-3. Biosynthesis of the peptide part of fengycin involves five multifunctional modular proteins that assemble the lipopeptide chain using a nonribosomal, multiple carrier thiotemplate mechanism.

Amino Acid Sequence↗

PubMed1999

The startle disease mutation Q266H, in the second transmembrane domain of the human glycine receptor, impairs channel gating.

Hyperekplexia (startle disease) results from mutations in the glycine receptor chloride channel that disrupt inhibitory synaptic transmission. The Q266H missense mutation is the only hyperekplexia mutation located in the transmembrane domains of the receptor. Using recombinant expression and patch-clamping techniques, we have investigated the functional properties of this mutation. The ability of glycine and taurine to open the channel was reduced in the mutated channel, as shown by a 6-fold shift in the concentration-response curve for both agonists. This was not accompanied by similar changes in agonist displacement of strychnine binding, suggesting that the mutation affects functions subsequent to ligand binding. Taurine was also converted to a weak partial agonist and antagonized the actions of glycine, consistent with changes in its channel gating efficacy. Because the Q266H mutation is within the pore-forming second transmembrane domain, we tested for a direct interaction with permeating ions. No change in either the cation/anion selectivity ratio or in single channel conductance levels was observed. No differential effects of Zn++, pH, and diethylpyrocarbonate were observed, implying that the histidine side chain is not exposed to the channel lumen. Single-channel recordings revealed a significant reduction in open times in the mutant receptors, at both high and low agonist concentrations, consistent with the open state of the channel being less stable. This study demonstrates that residues within the second transmembrane domain of ligand-gated ion channel receptors, even those whose side chains do not directly interact with permeating ions, can affect the kinetics of channel gating.

Anions↗

PubMed1999

The structure of two fengycins from Bacillus subtilis S499.

The structures of the two fengycins, lipopeptides from Bacillus subtilis, were elucidated by spectroscopic methods and chemical degradation. They show a close structural relationship to the plipastatins from Bacillus cereus differing only in the stereochemistry of the Tyr residues.

Amino Acid Sequence↗

PubMed1999

Identification of a new ligand binding domain in the alpha1 subunit of the inhibitory glycine receptor.

Four discontinuous extracellular sequence domains have been proposed to form the ligand binding sites of the ligand-gated ion channel receptor superfamily. In this study, we investigated the role of 12 contiguous residues of the inhibitory glycine receptor that define the proposed "loop A" ligand binding domain. Using the techniques of site-directed mutagenesis and patch-clamp electrophysiology, four of the 12 residues were shown to have impaired ligand binding. Three mutants, 193A, A101H, and N102A, resulted in significant (17-44-fold) increases in the agonist EC50 values as compared with the wild-type glycine receptor, whereas Hill coefficients, ImaX values, and antagonist affinity remained largely unaffected. Consideration of receptor efficacy values indicates that these residues are involved in ligand binding rather than channel activation. A fourth mutant, W94A, failed to give rise to any glycine-activated currents, although cell-surface expression was observed, suggesting that this residue may also be involved in agonist binding. These data provide the most extensive characterization of the loop A ligand binding domain available to date and define two new residue locations, Ile93 and Asn102, as contributing to the four-loop model of ligand binding.

Alanine↗

PubMed1998

Isolation of highly performant sulfate reducers from sulfate-rich environments.

Eleven pure strains of sulfate-reducing bacteria have been isolated from lab-scale bioreactors or gypsum disposal sites, all featuring relatively high concentrations of sulfate, and from natural environments in order to produce sulfide from gypsum using hydrogen as energy source. The properties of the eleven strains have been investigated and compared to these of three collection strains i.e. Desulfovibrio desulfuricans and Dv. vulgaris and Desulfotomaculum orientis. Particular attention was paid to the volumetric and specific sulfide production rate and to the hydrogen sulfide inhibition level. By comparison to the three collection strains, a 75% higher production rate and a hydrogen sulfide inhibition level about twice as high i.e. 25.1 mM have been achieved with strains isolated from sulfate-rich environments. The strain selection, particularly from sulfate-rich environments, should be considered as an optimization factor for the sulfate reduction processes.

Biodegradation, Environmental↗

PubMed1998

Zinc potentiation of the glycine receptor chloride channel is mediated by allosteric pathways.

Molecular mechanisms of zinc potentiation were investigated in recombinant human alpha1 glycine receptors (GlyRs) by whole-cell patch-clamp recording and [3H]strychnine binding assays. In the wild-type (WT) GlyR, 1 microM zinc enhanced the apparent binding affinity of the agonists glycine and taurine and reduced their concentrations required for half-maximal activation. Thus, in the WT GlyR, zinc potentiation apparently occurs by enhancing agonist binding. However, analysis of GlyRs incorporating mutations in the membrane-spanning domain M1-M2 and M2-M3 loops, which are both components of the agonist gating mechanism, indicates that most mutations uncoupled zinc potentiation from glycine-gated currents but preserved zinc potentiation of taurine-gated currents. One such mutation in the M2-M3 loop, L274A, abolished the ability of zinc to potentiate taurine binding but did not inhibit zinc potentiation of taurine-gated currents. In this same mutant where taurine acts as a partial agonist, zinc potentiated taurine-gated currents but did not potentiate taurine antagonism of glycine-gated currents, suggesting that zinc interacts selectively with the agonist transduction pathway. The intracellular M246A mutation, which is unlikely to bind zinc, also disrupted zinc potentiation of glycine currents. Thus, zinc potentiation of the GlyR is mediated via allosteric mechanisms that are independent of its effects on agonist binding.

Cell Line↗

PubMed1997

The prevalence of infections in psychiatric institutes in Belgium.

To assess the prevalence of infections in psychiatric institutes in Belgium, a cross-sectional study was performed within a cluster sample of psychiatric patients from 29 psychiatric institutes (about 40% of all Belgian psychiatric institutes). During May 1992, 8679 patients were analysed. Of the study population 59% were men. The mean age +/- SD was 54.5 +/- 18.3 years, with a median of 55 years. The mean hospitalization period was 9.6 +/- 14.5 years with a median of 2 years. A total of 1334 infections were reported, and 13.1% of the patients had a least one infection (95% CI: 12.4-13.8%) at the time of the study. The most common infections were dermatological infections (31.6%), lower respiratory tract infections (25.8%), urinary tract infections (12.4%) and conjunctivitis (11.6%). Statistically significant associations with infection prevalence were found with age, psychiatric diagnosis, activity of daily living score, the duration of hospitalization, and the qualification of the person answering the survey form. The relevance and the limitations of this study are discussed.

Adolescent↗

PubMed1997

Frequent short rest breaks from computer work: effects on productivity and well-being at two field sites.

Computer operators at two work sites (n = 73, n = 19) were prompted to take three 30-s and one 3-min break from computer work each hour in addition to conventional rest breaks. Some operators were asked to perform stretching exercises during the short breaks. Mood state and musculoskeletal discomfort were assessed at each work site over a 2- or 3-week baseline period and a 4- or 6-week treatment period, respectively. Operator productivity measures were obtained from company records. Operators complied with about half of the added breaks but favoured 3-min breaks over 30-s breaks. No improvement in productivity or well-being was found at the larger work site. At the smaller work site, productivity, eye, leg and foot comfort all improved when the short breaks included stretching exercises. These results provide evidence that frequent short breaks from continuous computer-mediated work can benefit worker productivity and well-being when the breaks integrate with task demands.

Adult↗

PubMed1997

Cyclosporin C is the main antifungal compound produced by Acremonium luzulae.

A strain of Acremonium luzulae (Fuckel) W. Gams was selected in screening new microorganisms for biological control of fruit postharvest diseases, especially gray and blue mold diseases on apples and strawberries. This strain manifests a very strong activity against a large number of phytopathogenic fungi. In this work, the product responsible for this antifungal activity was isolated from modified Sabouraud dextrose broth cultures of A. luzulae. It was purified to homogeneity by reverse-phase column chromatography. On the basis of UV, infrared, and 1H and 13C nuclear magnetic resonance spectra, mass spectral analysis, and the amino acid composition of the acid hydrolysates, the antibiotic was determined to be cyclosporin C. Cyclosporin C showed a broad-spectrum activity against filamentous phytopathogenic fungi but no activity against bacteria or yeasts. Its antifungal activity is only fungistatic. In contrast to Tolypocladium inflatum, another cyclosporin-producing strain, A. luzulae, did not produce additional cyclosporins. This was confirmed by in vivo-directed biosynthesis.

Acremonium↗

PubMed1996

Folic acid fortification of the food supply. Potential benefits and risks for the elderly population.

OBJECTIVE: To estimate the potential benefits and risks of food folic acid fortification for an elderly population. Benefits are expected through the improvement of folate and homocysteine status, but there is also a risk of masking or precipitating clinical manifestations related to vitamin B12 deficiency with increasing exposure to folic acid. DESIGN: Cross-sectional analysis, with projected change at various levels of folic acid fortification. SETTING: Participants in the Framingham Heart Study original cohort. PARTICIPANTS: A total of 747 subjects aged 67 to 96 years who both completed usable food frequency questionnaires and had blood concentrations of B vitamins and homocysteine measured. MAIN OUTCOME MEASURES: Projected blood folate and homocysteine concentrations and combined high folate intake and low plasma vitamin B12 concentration. RESULTS: Percentages of this elderly population with folate intake below 400 microg/d are projected to drop from 66% at baseline to 49% with 140 microg of folate per 100 g of cereal-grain product, to 32% with 280 microg, to 26% with 350 microg, and to 11% with 700 microg. Percentages with elevated homocysteine concentrations (>14 micromol/L) are projected to drop from 26% at baseline to 21% with 140 microg of folate per 100 g, to 17% with 280 microg, to 16% with 350 microg, and to 12% with 700 microg. Without fortification, the prevalence of combined high folate intake (>1000 microg/d) and low plasma vitamin B12 concentration (<185 pmol/L [<250 pg/mL]) was 0.1%. This is projected to increase to 0.4% with folate fortification levels of 140 to 350 microg/100 g and to 3.4% with 700 microg. CONCLUSION: The evidence suggests that, at the level of 140 microg/100 g of cereal-grain product mandated by the Food and Drug Administration, the benefits of folate fortification, through projected decreases in homocysteine level and heart disease risk, greatly outweigh the expected risks. However, quantification of the actual risks associated with vitamin B12 deficiency remains elusive. Before higher levels of folic acid fortification are implemented, further research is needed to better understand the clinical course of various forms of vitamin B12 deficiency, to measure the potential effect of high folate intake on this course, and to identify cost-effective approaches to the identification and treatment of all forms of vitamin B12 deficiency.

Aged↗