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Biomedical subjects

D Grenier

Publications and source records attributed to D Grenier.

At least 91 records · Page 5Linked to original sources
PubMed1992

Demonstration of a bimodal coaggregation reaction between Porphyromonas gingivalis and Treponema denticola.

This study demonstrates a strong coaggregation reaction between 2 suspected periodontopathogens: Porphyromonas gingivalis and Treponema denticola. Other black-pigmented oral bacterial species tested did not coaggregate with T. denticola. This specific interbacterial aggregation was bimodal, since heating of both cell types was required to completely eliminate the reaction. The coaggregation reaction occurred between pH 4 and 9. Under some conditions, arginine and D-galactosamine were effective in preventing the coaggregation. The heat-sensitive receptor on P. gingivalis was found to be loosely bound and could be released by a light ultrasonic treatment of the cells. It is suggested that the bacterial interaction described may participate in the establishment of a potentially pathogenic subgingival plaque.

Arginine↗
PubMed1992

Nutritional interactions between two suspected periodontopathogens, Treponema denticola and Porphyromonas gingivalis.

A mutual symbiotic enhancement of growth of Porphyromonas gingivalis and Treponema denticola is described in this report. Brain heart infusion broth supplemented with vitamin K did not support the individual growth of P. gingivalis or T. denticola. However, when inoculated as a mixture, both bacterial species did grow significantly. The growth-stimulating factors produced by P. gingivalis and T. denticola were dialyzable and heat stable and were further identified as isobutyric acid and succinic acid, respectively. Since some forms of periodontal disease are associated with the presence, in affected sites, of high numbers of P. gingivalis and spirochetes, it is suggested that the bacterial interaction described in this report might be of utmost importance in the initiation and progression of the disease.

Butyrates↗
PubMed1992

Inactivation of human serum bactericidal activity by a trypsinlike protease isolated from Porphyromonas gingivalis.

A protease was isolated from an outer membrane vesicle preparation of Porphyromonas gingivalis ATCC 33277 and assessed for its ability to inactivate the bactericidal activity of normal human serum. The enzyme, which was activated by reducing agents, was found to be a trypsinlike protease with a molecular mass of approximately 80 kDa. Prior to being tested in the bactericidal assay, pooled human serum was preincubated with the partially purified enzyme. Under conditions in which the trypsinlike protease was activated, a strong reduction of the serum bactericidal activity against Capnocytophaga ochracea was noted. On the other hand, no reduction of the bactericidal action of serum was observed when the serum-protease mixture was preincubated in the presence of an inhibitor of the enzyme. As determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the protease was shown to degrade immunoglobulins G and M as well as complement factor C3. This study confirms the previous hypothesis that the proteases of P. gingivalis can interfere with the protective action of human serum.

Blood Bactericidal Activity↗
PubMed1992

Further evidence for a possible role of trypsin-like activity in the adherence of Porphyromonas gingivalis.

The present study was undertaken to evaluate a possible correlation between the level of trypsin-like activity and the adherence properties of Porphyromonas gingivalis. It was demonstrated that strains with high cell-associated trypsin-like activity attach in higher numbers to human epithelial cells than strains with low levels of trypsin-like activity. To a lesser extent, the same tendency was also noted for the agglutination of human erythrocytes. The ability of P. gingivalis to attach to erythrocytes and epithelial cells was found to be affected by the presence of arginine and thiol protease inhibitors (leupeptin, p-chloromercuriphenylsulfonic acid). The inhibition profile was partially dependent on the age of the bacterial cells used in the adherence assay. It is suggested that adherence of mid-log P. gingivalis cells involves primarily trypsin-like proteases, whereas 2-day-old cells possess additional specific attachment mechanism(s).

Arginine↗
PubMed1992

[Attitude of french speaking nurses towards AIDS].

This study describes the beliefs, the attitudes and the intentions to act toward persons infected with AIDS, of a group of nurses of the greater Montreal area (n = 427). A questionnaire (71 items) was mailed to 1000 randomly selected Montreal nurses and was completed by 427 of them. The majority of these nurses were female (82.5%) and did not possess a university diploma (64.8%). Most of them had at least 15 years of experience and more than half of them had already taken care of a patient with AIDS. It was found that the nurses' knowledge of AIDS was limited: they do not understand the signification of seropositivity and they had little knowledge of the epidemiological dimensions of the illness. The younger nurses tend to adopt the prejudices and beliefs already endorsed by society: isolation, obligatory testing and homophobia. A factor analysis of the beliefs, attitudes and intent to act sub-scales permits the identification of nine factors (fears, prejudices, emotional support, mistrust, avoidance, quality of care, false security, AIDS equals sex and more experience equals less fear). These factors tend to be associated with certain sociodemographic characteristics. The nurses who are less knowledgeable, who are most prejudiced, and who least intend to care for the client with AIDS are: 1) the younger nurses (21-34 years old); 2) those who see the media as their primary source of information and 3) those who have never cared for seropositive clients. This study allows us to render judgement on the values of a specific group of francophone nurses within a fixed time-place framework.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Hemin-binding property of Porphyromonas gingivalis outer membranes.

The present study indicates that the outer membranes of Porphyromonas gingivalis have a high affinity for hemin, an essential growth factor for this suspected periodontal pathogen. The hemin-binding property appears to be mediated by the lipopolysaccharides, particularly the lipid A region. It is suggested that this binding mechanism may be important for the growth and establishment of P. gingivalis in environments with a low hemin content such as periodontal pockets.

Bacteroidaceae↗
PubMed1991

Assay for protease inhibitors: qualitative measurement and detection in polyacrylamide gel electrophoretograms.

A simple and fast method for qualitative measurement of protease inhibitors has been developed. The high sensitivity of the assay is based on a casein-precipitating reaction at pH 5.5. Cellulose paper strips, moistened with protease inhibitor-containing solutions, are applied to the surface of an agar-skim milk gel previously coated with a protease solution. After incubation for 2 h at 37 degrees C, inhibitory activity is indicated by a translucent zone (absence of casein degradation) on a white background of precipitated small casein fragments. In addition to being useful for rapid screening of a large number of complex samples, the method allows the localization of protease inhibitor activity in sodium dodecyl sulfate-polyacrylamide gel electrophoretograms.

Agar↗
PubMed1991

Characteristics of hemolytic and hemagglutinating activities of Treponema denticola.

Treponema denticola, a suspected periodontal pathogen, was shown to agglutinate and lyse human red blood cells. Both activities were cell-associated, heat-labile, and produced during the exponential growth phase. Hemolytic activity was time-dependent and required incubation at 37 degrees C; further incubation at 4 degrees C increased the hemolysis. Hemagglutination was reduced in the presence of D-glucosamine, EDTA or sodium salicylate, whereas hemolytic activity was affected by calcium chloride, magnesium chloride, EDTA or sodium salicylate. These biological activities may favor a higher concentration of hemin-containing compounds in periodontal sites, and therefore represent additional potential virulence mechanisms.

Hemagglutination↗
PubMed1991

Production of trypsin and chymotrypsin inhibitors by oral bacterial isolates.

Using an agar-skim milk gel method, over 300 oral bacterial isolates were tested for their ability to produce trypsin or chymotrypsin inhibitor. Eleven bacterial strains, including seven isolates identified as Bacteroides intermedius, were found to inhibit both proteolytic activities. The inhibitory factors of the 11 bacterial strains could be divided into two categories: i) heat-stable and dialysable, and ii) heat-labile and non-dialysable. The protease inhibitor activity of B. intermedius strains, which belongs to the latter category, was found in a membrane fraction as well as in a membrane-free extract. Furthermore, three strains of B. intermedius showed this inhibitory activity in the culture supernatant. In combination with plasma-derived protease inhibitors, the production of these additional protease inhibitors by oral bacteria could protect the host from tissue degradation.

Adult↗
PubMed1991

Protective effect of Porphyromonas gingivalis outer membrane vesicles against bactericidal activity of human serum.

The present study was undertaken to evaluate the effect of Porphyromonas gingivalis outer membrane vesicles on the bactericidal activity of human serum. Human serum was pretreated with extracellular vesicles and then incubated with a cell suspension of Capnocytophaga ochracea. After 2 h at 37 degrees C, the percent viability of C. ochracea was determined by cultivation on blood agar plates. At a final concentration of 0.3 mg/ml, outer membrane vesicles completely inhibited the serum bactericidal activity against C. ochracea. Boiling the vesicles prevented this inhibition. However, partial inhibition of the serum lethal action was obtained when a higher concentration (1.5 mg/ml) of boiled vesicles was used, which indicates the involvement of both heat-labile and heat-stable components associated with vesicles. Combining vesicles at a suboptimal concentration (0.1 mg/ml) with a reducing agent brought back inhibition of the bactericidal activity, whereas combining vesicles at an optimal concentration (0.3 mg/ml) with a thiol-blocking reagent caused a restoration of the bactericidal activity. When a purified preparation of P. gingivalis lipopolysaccharides was used instead of vesicles, inhibition of the bactericidal activity was also observed. These results indicate that the lipopolysaccharides and the proteolytic enzyme(s) associated with P. gingivalis outer membrane vesicles are likely to represent the heat-stable and the heat-labile components, respectively. It is possible that outer membrane vesicles released by P. gingivalis protect other bacterial species from complement action, thus favoring the pathogenic process of periodontal disease.

Bacterial Outer Membrane Proteins↗
PubMed1990

Cellular location of a Treponema denticola chymotrypsinlike protease and importance of the protease in migration through the basement membrane.

A number of immunological methods were used to localize a cell-associated Treponema denticola chymotrypsinlike protease. Indirect immunofluorescence staining, immunogold labeling, and an enzyme-linked immunosorbent assay all indicated that the protease was attached to the outside of the cell envelope. The invasive capability of T. denticola was evaluated by following the degradation of a reconstituted basement membrane material (Matrigel) and the release of spirochetes from the gel. Under conditions where the chymotrypsinlike activity was increased, more spirochetes migrated from the gel. Protease inhibitors strongly reduced the number of cells that moved out of the gel. The purified chymotrypsinlike protease degraded the basement membrane components type IV collagen, laminin, and fibronectin. The study suggests that the T. denticola chymotrypsinlike protease may play an important role in the invasion and destruction of basement membrane.

Basement Membrane↗
PubMed1989

Bacteroides gingivalis vesicles mediate attachment of streptococci to serum-coated hydroxyapatite.

Outer membrane vesicles purified from Bacteroides gingivalis culture supernatant bound to serum coated hydroxyapatite (SeHA). The immobilized vesicles served as receptors for a number of species of oral streptococci. The binding of Streptococcus sanguis 12 to SeHA was increased 10 times by the vesicles. Vesicle-associated binding increased proportionally with an increase in the number of bound vesicles. Arginine and lactose both partially reduced binding of S. sanguis. Heating the vesicles destroyed their binding ability whereas heating S. sanguis reduced but did not eliminate vesicle-mediated binding.

Bacterial Adhesion↗
PubMed1989

Further studies on the degradation of immunoglobulins by black-pigmented Bacteroides.

The ability of several species of black-pigmented Bacteroides to degrade immunoglobulins A and G was confirmed in this study. The cleavage products from IgG strongly stimulated the growth of bacteria degrading IgG. Growth of Bacteroides gingivalis on limiting media supplemented with IgG paralleled growth on complete medium. The degradation of IgG and IgA by black-pigmented Bacteroides appeared to occur in 2 stages. The molecules were broken into large fragments which were subsequently degraded into small peptides not visible on SDS-PAGE. B. gingivalis degraded IgG to peptides with Mrs of 33,000 and 11,000 whereas Bacteroides asaccharolyticus, Bacteroides intermedius and Bacteroides loescheii formed only the 33,000 Mr peptide. Electrophoresis in polyacrylamide gels containing covalently linked IgG, IgA and bovine serum albumin revealed that B. gingivalis elaborated 8 electrophoretically distinct proteolytic activities. The proteases protected the cell from reaction with anti-B. gingivalis antibody and were capable of hydrolyzing antibody bound to the bacterial cell surface.

Bacteroides↗
PubMed1989

Characterization of sodium dodecyl sulfate-stable Bacteroides gingivalis proteases by polyacrylamide gel electrophoresis.

Profiles of the proteolytic activities found in Bacteroides gingivalis culture supernatants, outer membranes, vesicles, and cell extracts were analyzed in sodium dodecyl sulfate-polyacrylamide gels containing covalently bound bovine serum albumin. A total of eight distinct bands of proteolytic activity could be detected. Four of these were found in the culture supernatant (P1, P2, P3, and P4). The outer membranes, vesicles, and the cell extract each contained seven major proteolytic bands (P1, P3, P4, P5, P6, P7, and P8). No activity was found in the membrane-free extract, suggesting that the proteases were associated with the cell envelope. With the exception of P7 and P8, all the proteolytic bands were dependent on reducing agents for activity. The eight proteolytic bands were distributed in an identical manner in all four strains of B. gingivalis studied. The effects of protease inhibitors, pH, and heat were determined. Sulfhydryl group reagents and N-alpha-p-tosyl-L-lysine chloromethyl ketone reduced proteolytic activity. The optimum pH was found to be between 7 and 8. A 30-min preincubation at 50 degrees C inactivated the P6, P7, and P8 proteolytic bands. All proteolytic activity was lost after the samples were heated at 75 degrees C for 30 min.

Bacteroides↗
PubMed1989

Surface location of a Bacteroides gingivalis glycylprolyl protease.

Various immunological methods were used to localize a glycylprolyl protease previously isolated from Bacteroides gingivalis ATCC 33277. The results obtained by enzyme-linked immunosorbent assay, indirect immunofluorescence staining, and indirect immunogold labeling suggest that the glycylprolyl protease is present on the surface of the cell outer membrane and is specific to B. gingivalis strains. The enzyme was removed from the cell envelope by treatment of the whole cells with sodium dodecyl sulfate, Triton X-100, sodium deoxycholate, and proteinase K.

Bacterial Outer Membrane Proteins↗
PubMed1988

Isolation of a chymotrypsinlike enzyme from Treponema denticola.

A chymotrypsinlike protease with an Mr of 95,000 was extracted from Treponema denticola ATCC 35405 and was partially purified by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The proteolytic activity was detected in an electrophoretogram containing polyacrylamide that was conjugated to bovine serum albumin. A single band of activity was detected when the T. denticola extract was solubilized and electrophoresed in the presence of sodium dodecyl sulfate. No activity was found in extracts of Treponema vincentii. The enzyme hydrolyzed transferrin, fibrinogen, alpha 1-antitrypsin, immunoglobulin A, immunoglobulin G, gelatin, bovine serum albumin, and a synthetic peptide containing phenylalanine. It did not degrade collagen or synthetic substrates containing arginine or proline. For the hydrolysis of azocoll, the pH optimum of the enzyme was 7.5. Heating at temperatures above 50 degrees C destroyed the activity. Reducing agents and the chelators EDTA and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid increased the enzyme activity, while phenylmethylsulfonyl fluoride, L-1-tosylamide-2-phenylethyl chloromethyl ketone, sulfhydryl reagents, and human serum reduced activity. The ability of the enzyme to hydrolyze a number of humoral proteins suggests that it may be involved in spirochete invasiveness and tissue destruction.

Chymotrypsin↗