Contribution of proteases and plasmin-acquired activity in migration of Peptostreptococcus micros through a reconstituted basement membrane.

BACKGROUND/AIMS: Peptostreptococcus micros is a gram-positive bacterium that has been associated with chronic periodontitis and endodontic infections. The aims of this study were to investigate the production of proteases and the acquisition of plasmin activity by rough and smooth morphotypes of P. micros. The contribution of these properties in the migration of bacteria through a reconstituted basement membrane was also evaluated. METHODS: Protease activities were determined using chromogenic and fluorogenic substrates as well as by zymography. Plasminogen binding activity was studied using an enzyme-linked immunosorbent assay. The role of proteases and plasmin-acquired activity in tissue penetration was investigated using Matrigel. RESULTS: The rough morphotype strains of P. micros, but not the smooth morphotype strains, were found to possess chymotrypsin-like and gelatinase activities, both of which were inhibited by a serine protease inhibitor. By zymography, three gelatinase bands (165, 129, and 115 kDa) were identified. Both morphotypes of P. micros can bind human plasminogen on their cell surface. Once bound to P. micros, plasminogen activators of bacterial (streptokinase) and human (urokinase) origins were found to activate plasminogen into plasmin. Our results also showed that plasmin activity can be acquired by P. micros following co-incubation with human brain microvascular endothelial cells in culture. When non-coated cells were used, the rough morphotype strain (HG1262), which possesses chymotrypsin-like and gelatinase activities, showed a better capacity to penetrate a reconstituted basement membrane (Matrigel) than the smooth morphotype strain (HG1251). Penetration of the Matrigel by P. micros HG1262 was inhibited by the presence of a serine protease inhibitor. In addition, cells of P. micros with plasmin activity showed a significantly greater tissue penetration capacity. CONCLUSION: Our study suggests that endogenous proteolytic activities of P. micros as well as plasmin-acquired activity, may facilitate dissemination of bacterial cells to surrounding periodontal tissues and blood vessels.

Adherence of Streptococcus mutans to orthodontic brackets.

The affinity of Streptococcus mutans to orthodontic brackets made from metal, plastic, and ceramic was tested. Twelve saliva-coated brackets and 12 noncoated brackets of each type were immersed in a S. mutans solution labeled with [3H] thymidine. Each sample was then immersed in distilled water at 20 degrees C for 24, 48, and 72 hours to measure the adherence of S. mutans to these samples. During the first 24 hours, the adherence of S. mutans decreased with and without saliva coating. Between 24 and 72 hours, the adherence of S. mutans to the saliva-coated brackets remained unchanged; the adherence to uncoated brackets showed a decrease. Saliva coating caused a decreased affinity of S. mutans for all products tested. The initial affinity of S. mutans to metal brackets was statistically significantly lower than that to plastic and porcelain brackets with and without saliva coating.

Effectiveness of salt versus glass bead sterilizers.

Microorganisms can be removed from dental instruments by various methods, including treatment in salt and glass bead sterilizers. However, no rigorous, controlled, in vivo or in vitro studies have been performed to verify the respective efficiencies of these methods. The goals of this study were to determine if the positioning of instruments at the centre or edge of a salt sterilizer results in differential sterilization effectiveness, and to compare the effectiveness of salt sterilizers relative to glass bead sterilizers. Autoclaved number 60 reamers were contaminated by plunging them to the handle in a commercial Bacillus stearothermophilus spore suspension. They were then sterilized for different periods of time and at different positions in the sterilizers. Each experiment included positive and negative controls. The results showed that better sterilization is achieved at the edge of the chamber than at the centre, and that salt sterilizers are more effective than glass bead sterilizers for a given period of time (15 seconds) in the sterilizer.

The effects of smoking on periodontal structures: a literature review.

Periodontal disease seems to be more prevalent in smokers than in nonsmokers. Studies have reported both increases and decreases in gingival blood flow due to smoking. Smoking does not increase the presence of the periodontopathogens Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Bacteroides intermedius. Both the chemotaxis and the phagocytic capacity of the polymorphonuclear leukocytes (PMNs) harvested from smokers are lower than with those harvested from nonsmokers. Furthermore, smokers have lower IgA, IgG, IgM, and suppressor CD8 lymphocytes levels than nonsmokers. These differences between smokers and nonsmokers should be taken into account by clinicians during periodontal examinations, therapy, and the healing process.

[Subgingival irrigation: a heresy?]. / L'irrigation sous-gingivale, une hérésie?

Bacteria are the principal causal factor for gingivitis and adult periodontitis. This article is a review of the pertinent literature regarding subgingival irrigation with antimicrobial agents. Furthermore, the clinical significance of this technique is evaluated. In order for the antimicrobial agent to reach the base of the periodontal pocket, the canula must be placed at least 3.0 mm subgingivally. Subgingival irrigation offers no added antimicrobial effect over root scaling alone, but may extend the therapeutic effect of scaling. The effect of subgingival irrigation is none the less temporary. Subgingival irrigation must be regarded as an alternative treatment for gingivitis and adult periodontitis when root scaling alone is not sufficient.

Na+ and K+ effect on contractility of frog sartorius muscle: implication for the mechanism of fatigue.

Although a decrease in extracellular Na+ and an increase in K+ concentration are believed to contribute to the decrease in force during fatigue, the force of unfatigued muscle decreases only with quite large changes in Na+ and K+ concentration. The objective of this study was to determine whether concomitant and smaller changes in Na+ and K+ concentration have greater effects on muscle contractility than individual changes. At 3 mM K+, a large decrease in Na+ from 120 to 60 mM had no effect on the twitch force, while the tetanic force decreased by 31.2%. At 120 mM Na+, an increase in K+ from 3 to 9 mM potentiated the twitch force by 41.1%, had no effect on the tetanic force at 7 mM, and decreased the tetanic force by 40.4% at 9 mM; both the twitch force and tetanic force were completely abolished at 11 mM K+. The potentiation of the twitch force between 3 and 9 mM K+ was less at 60, 80, and 100 mM than at 120 mM Na+. A reduction in Na+ concentration also reduced the K+ concentration at which the twitch force and tetanic force decreased and were completely abolished. It is shown that the combined effects of Na+ and K+ on the twitch and tetanic contractions were greater than the sum of their individual effects. Furthermore, it is proposed that neither Na+ nor K+ alone can be considered as an important factor in the decrease in force during fatigue, whereas together they are important for the tetanic contraction, but not for the twitch contraction.