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Biomedical subjects

M Pourtois

Publications and source records attributed to M Pourtois.

At least 19 recordsLinked to original sources
PubMed1995

The influence of different fluoride salts on fluoride-mediated inhibition of peroxidase activity in human saliva.

Fluoride-mediated inhibition of peroxidase potential activity in human saliva was investigated using NaF, NH4F, CaF2, Na2PO3F (MFP), SnF2 and TiF4. At pH 5.5 and for a 20 mM F concentration, the inhibition percentages increased from 2% for MFP and 5% for CaF2 to 61% for NaF and 65% for NH4F, while a 100% inhibition was observed at 10 mM for TiF4 and at 5 mM for SnF2. The inhibition was enhanced at acid pH and removed at pH 7. The inhibition could be attributed to ionized F-, except for SnF2 and TiF4, in which part of the inhibition could be imputed to the cations.

Calcium Fluoride↗
PubMed1994

Hypotheses for a re-evaluation of peroxidase activity in the oral inflammation: NAD(P)H-dependent hypohalite reduction in human neutrophils.

The balance of NADH oxidation by neutrophil lysates in the presence and in the absence of peroxidase/H2O/halide systems, pointed out a NADH oxidation excess when these hypohalite generators were actually present. This unexplained NADH consumption could not be attributed to a direct oxidation by hypohalites nor by the lysate self. Using OCI- as substrate, the NADH oxidation excess ranged from 52 to 99 mU/ml at pH 7.40 and from 446 to 1346 mU/ml at pH 6.00 (N = 6). Similar results were also found while using hypoiodous and hypothiocyanous compounds at pH 7.40 but not at pH 5.50. The authors discuss different hypotheses to explain this phenomenon and accordingly elaborate on the possible consequences of neutrophils degranulation in the oral tissues during inflammation processes.

Humans↗
PubMed1993

ATP content in 3-day-old bacterial plaques with or without a 0.2% chlorhexidine mouth rinse.

This study describes a method aimed at measuring the bacterial ATP content of dental plaques formed on a polyester support attached on tooth surfaces in the oral cavity. It reports on the variations in ATP content in 3 days old plaques of a well-defined surfaces with or without the use of 0.2% chlorhexidine mouth-wash twice daily. The results, expressed in bacterial equivalents, show a reduction of dental plaque metabolism after 3 days of chlorhexidine rinses to 19.5% of its value in the control tests without mouth-washes. Bacterial metabolism represented 6.05 bacterial equivalents per mm2 in the control group versus 1.18 equivalents in the chlorhexidine test group.

Adenosine Triphosphate↗
PubMed1992

[The antiseptic role of saliva].

The oral flora is under the control of both immunity and non specific defense factors. The immunity factors are mostly represented by polymorphonuclears immunoglobulins Non specific defense factors include lysozyme lactoferrin high molecular weight proteins, such as mucins fibronectin and beta 2 microglobulin histidine rich proteins cystatins salivary amylases salivary peroxidase system.

Antisepsis↗
PubMed1992

Fluoride inhibition of SCN- and Cl-peroxidase activities in whole saliva and of recombinant myeloperoxidase. Influence of pH and hydrogen peroxide concentration.

Fluoride (F-) inhibition of peroxidase activity in whole saliva and of recombinant human myeloperoxidase was investigated using thiocyanate (SCN-) and chloride (Cl-) as substrates. At pH 5.5, SCN(-)-linked activity in whole saliva reduced to < 40% of its initial value at F- concentration of 20 mM, while Cl- linked activity was maintained at 90% of its initial value for the same F-concentration. Based on this Cl(-)-linked activity, the contribution of natural MP to the SCN(-)-linked activity in whole saliva can be calculated. This shows a total inhibition of SCN- dependent activity of salivary peroxidase (SP) for F-concentrations > 10 mM. At a 20 mM F-concentration, recombinant MP activity reduced to 66% of its initial value with SCN-, against 88% for Cl- as substrate. This inhibition of the SCN- linked SP activity is enhanced at acid pH for a F-concentration of 20 mM: 26% residual activity at pH 5 for whole saliva + SCN-against 93% for whole saliva + Cl-; 61% for recombinant MP + SCN- and 88% for MP + Cl-. Calculated activities for SP alone showed a total inhibition at pH 5, while the inhibition was absent at pH 6.5. F-inhibition in whole saliva could also be suppressed by the addition of hydrogen peroxide.

Adult↗
PubMed1992

Susceptibility of anaerobic microorganisms to hypothiocyanite produced by lactoperoxidase.

The susceptibility of Capnocytophaga ochracea, Eikenella corrodens, Eubacterium yurii, Fusobacterium nucleatum, Peptostreptococcus micros, Prevotella intermedia, Selenomonas sputigena, Wolinella recta to hypothiocyanite (OSCN-) produced by the lactoperoxidase system was tested. Results showed a decrease of bacterial survival rate after OSCN- exposure, with an intra- and inter-species variability from 0 to 95% for C. ochracea, 34-100% for E. corrodens, 0-83% for E. yurii, 1-15% for F. nucleatum, 8-61% for P. micros, 0-100% for P. intermedia, 0-44% for S. sputigena and 0-8% for W. recta. The survival rate did not correlate with the NADH/OSCN- oxidoreductase activity present in the lysed bacteria (r = -0.3248; N = 15; NS).

Anti-Bacterial Agents↗
PubMed1992

Peroxidase activity loss after filtration and centrifugation of whole saliva. Influence of citrate.

Filtration or centrifugation are two methods frequently used to clarify human whole saliva. This study compares both the drop in peroxidase activity following filtration (49.3% +/- 16.4%; N = 12) or centrifugation (33.6% +/- 15.9%; N = 6) and the drop in total protein concentration after filtration (33.9% +/- 13.4%) and centrifugation (23.6% +/- 8.7%). After filtration, the loss was not only due to retention of the large particle-bound fraction but also to adsorption on the filter membranes. This adsorption could be inhibited by a previous dilution of saliva in a citrate buffer, which also gave rise to active subunits with a molecular weight less than or equal to 100 kDa.

Adsorption↗
PubMed1990

Inhibition of HIV infectivity by lactoperoxidase-produced hypothiocyanite.

HIV aliquots, from a supernatant of ARV-4 cell line, were mixed with an equal volume of a OSCN.generating glucose-glucose oxidase + thiocyanate-lacteroperoxidase solution, and then pre-incubated at 37 degrees C for periods of 30 secs to one hour. These mixtures were then inoculated into cultures of phytohaemagglutinin-stimulated lymphocytes. Viral growth was monitored with an ELISA quantitating the specific p24 protein either in the culture cells or in the supernatant. In control experiments, the virus produced both intra- and extra-cellular p24. In the controls, concentration of p24 per 10(6) lymphocytes grew rapidly. By contrast, HIV that was pretreated with the OSCN generating system for 30 sec., produced very little p24, and no detectable amount of this protein could be found after 2 min. pre-treatment.

Antiviral Agents↗
PubMed1990

[Antiseptic properties of saliva and metabolism of activated oxygen in neutrophils: comparison of the 2 enzymatic bactericidal systems and of their behavior in an acid environment].

Growth control of anaerobes in the oral cavity, is secured--among other means--by: 1) phagocytosis of opsonized bacteria; 2) synthesis of hypothiocyanite by the salivary peroxidase system. The former may be inhibited by bacterial acid byproducts. As for the salivary hypothiocyanite, it proved itself able of hindering in vitro the growth of bacterial strains known as customary periodontal pathogens. Its possible effectiveness in vivo remains however hypothetical in the case of deep gingival pockets according to the poor diffusion there of salivary components.

Anti-Bacterial Agents↗
PubMed1989

[Pollution and human exposure: proposal of criteria for meeting the WHO recommendations in the matter of risk reduction related to the environment].

Risk assessment methods do not refer to the dynamical processes at the back of observed values of parameters, when relating an effect to one evaluation of doses, or bio-indicator values to external contamination levels. This results in decreasing responses of the human organism as a function of increasing exposure levels. On the contrary, the ecotoxicological approach, applied to the case of lead, shows that a first order kinetics holds until blood lead of 80 micrograms/dl blood, either for the relation between tooth and blood lead, or for this between blood lead and the flux of lead absorbed daily (micrograms/day). Then, the max. admissible concentrations for various sources of Pb should be lowered strongly, for maintaining the Pb body burden below limit values. The method is proposed for application to a series of other pollutants, and for risk reevaluation.

Dose-Response Relationship, Drug↗
PubMed1989

Fluctuation of the biochemiluminescence from PMN leukocytes in a family with a high prevalence of severe periodontitis.

Rapidly progressive periodontal disease was found in three patients belonging to three different generations of the same family. Beyond the clinical inspection, blood examination allowed measurements of the luminol enhanced biochemiluminescence from the circulating PMN leukocytes. Abnormally low values were recorded in the affected individuals (75, 84 and 138 mVolts per 10(6) cells) whereas a sample of healthy individuals exhibited photonic values from 240 up to 910 mVolts per 10(6) cells. These abnormal values, however, were not constantly recorded. They gave way to higher PMN activity indices after the patients had been treated either by antibiotics, scaling, debridement or classical pocket cleaning.

Adolescent↗
PubMed1989

Anaerobes and short-chain fatty acids in crevicular fluid from adults with chronic periodontitis.

Pathogeny of adult chronic periodontitis is still unclear. Bacteriological and chemical analysis of crevicular fluid have shown, in active sites of the disease, a simultaneous presence of anaerobes and their major by-product: short-chain fatty acids. The last can decrease "in vitro" the neutrophil intracellular pH, whenever these cells are incubated in an acid medium. Clinical investigations are scarce which hold out data useful to attempt verifying this possible physiopathological mechanism. This work shows the presence of anaerobes in the active periodontal pockets, together with the presence of short-chain fatty acids likely to reach a concentration level comparable to that used for inhibiting neutrophils "in vitro". Forthcoming studies should investigate about a possible intracellular pH drop in the neutrophils and other cells of the inflamed periodontium.

Adult↗
PubMed1987

Inhibition of human polymorphonuclear leukocytes phagocytosis and protein-kinase-C activity by low pH concentrations.

PMN leukocytes from circulating blood, were investigated using the following parameters: chemiluminescence, superoxide generation, exocytic degranulation, lactoferrin, myeloperoxydase and protein-kinase-C activities. The results did not allow to point out any significative discrepancy between samples collected from either patients suffering of periodontal disease or healthy individuals. However, the phagocytic ability (as measured by light emission and superoxide production) was found to be severely inhibited in both instances, when PMN leukocytes were incubated in the presence of succinic acid. Similarly, protein-kinase-C activity in these cells, collapsed when the pH was brought down to 5.5. These data and the available literature indicate that pH decrease as well as succinic acid release in the crevicular fluid, may play a role in the pathogeny of chronic periodontitis in adults.

Acid Phosphatase↗
PubMed1984

[Odontogenesis in the human fetus: an echographic study].

During real-time ultrasound observation of swallowing movements in the human fetus, changes in the echostructure of the jaws were detected. Dense linear echoes (2-6 mm) arose symmetrically in the superior and inferior jaws from the median to the distal level with increasing gestational age. Their localisation and onset suggested they might represent tooth germs. The comparison between radiography after birth and pre- and postnatal echography confirmed that these particular echoes were indeed calcified tooth germs. The implications of this observation will be discussed in terms of fetal growth maturation and gestational age.

Deglutition↗
PubMed1981

Lead accumulation in teeth as a function of age with different exposures.

The level of lead exposure in industrial, urban, and rural populations has been evaluated by sampling permanent teeth gathered from three regions of Belgium. When tooth lead concentrations are plotted against tooth age, a linear function appears to fit the empirical results satisfactorily. On the contrary, comparing only the arithmetical means of the three samples would bring a possible bias of the results because their mean ages are different. The slope of the three best regression lines obtained respectively with data from the three regions increases significantly in the sequence rural less than urban less than industrial. A simplified mathematical model shows that this slope is directly related to the mean intake of lead under uniform exposure. It is suggested that this slope could be used as an index of the population's exposure to lead.

Adult↗