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Biomedical subjects

J Tenovuo

Publications and source records attributed to J Tenovuo.

At least 127 records · Page 7Linked to original sources
PubMed1983

Effect of growth phase and cell envelope structure on susceptibility of Salmonella typhimurium to the lactoperoxidase-thiocyanate-hydrogen peroxide system.

The lactoperoxidase-thiocyanate-hydrogen peroxide system was found to have both bacteriostatic and bactericidal activities against strains of Salmonella typhimurium. The bactericidal activity was clearly dependent on the permeability of the bacterial cell envelope. The deep rough mutant TA1535, with the most permeable cell envelope, was killed both at neutral and acid pH, whereas very little or no killing was observed with the intact cells of the parent strain hisG46. The delta gal mutant, TA1530, representing an intermediate in cell envelope permeability, was inhibited to a much lesser extent than TA1535. Bacteria in log phase of growth were more sensitive to the bactericidal effects than were those in stationary phase. Growth phase had little influence on the bacteriostatic effects. The hisG46 strain produced significant quantities of acid in the presence of glucose. This acid production was inhibited by the lactoperoxidase-thiocyanate-hydrogen peroxide system, and, in contrast to results obtained with several strains of streptococci, this inhibition was not reversed by addition of a reducing agent (2-mercaptoethanol).

Cell Membrane Permeability↗
PubMed1983

A mouthrinse which optimizes in vivo generation of hypothiocyanite.

We report here the properties of a mouthrinse which enhances one of the natural defense factors in human saliva, the salivary peroxidase system. Concentrations of the antimicrobial agent, the hypothiocyanite (OSCN-) ion, can be increased in vivo to bacteriostatic levels by use of a mouthrinse which is 4 mM (0.014%) in hydrogen peroxide and 1 mM (0.0097%) in potassium thiocyanate at pH 5.5. The volume of the rinse, the H2O2 concentrations, and the pH were shown to be determinants of the concentration of OSCN- generated by the rinse.

Anti-Infective Agents↗
PubMed1983

Effect of xylitol and sucrose plaque on release of lysosomal enzymes from bones and macrophages in vitro.

Plaque formed during a 5-day xylitol or sucrose chewing gum diet was used as an irritating agent in bone and macrophage culture. The release of hydrolytic enzymes was monitored. The contents of protein, DNA, and ATP were analyzed, to characterize plaque formed during different dietary periods. The release of glycosidases and phosphatases was lower in the presence of xylitol plaque when compared with sucrose plaque as an immediate reaction in macrophage cultures at 3 h and also in bone cultures at 3 days. The results indicate that xylitol plaque had a less irritating effect on macrophages and bones in vitro than sucrose plaque according to the parameters used in this study.

Adult↗
PubMed1982

Human milk peroxidase is derived from milk leukocytes.

Peroxidase enzymes present in human colostrum, saliva, polymorphonuclear leukocytes, and bovine milk were compared with respect to their molecular exclusion chromatographic behavior and immunological cross-reactivity. Human milk peroxidase gave an elution profile similar to myeloperoxidase derived from blood polymorphonuclear leukocytes. Human salivary peroxidase reacted with an antibody directed against bovine lactoperoxidase, but with the same antibody preparation no reaction was detected either with human milk peroxidase or leukocyte myeloperoxidase. We conclude that the peroxidase enzyme in human milk is different from the human salivary and the bovine enzymes and is probably derived from milk leukocytes.

Colostrum↗
PubMed1982

Kinetics of hypothiocyanite production during peroxidase-catalyzed oxidation of thiocyanate.

We report here a kinetic study of the generation of hypothiocyanite (OSCN-), a product of lactoperoxidase-catalyzed oxidation of thiocyanate ion. Previous studies have measured OSCN- by reactions involving the oxidation of sulfhydryl compounds. Our results show that a more suitable kinetic analysis of OSCN- can be based on absorbance changes measured at 235 nm. About 90% of the oxidation products of SCN- observed at 235 nm were reactive with sulfhydryls and could be reduced with 2-mercaptoethanol. Both thiocyanate and peroxide were rate-limiting and the formation of OSCN- was proportional to the initial concentration of H2O2 until an equimolar concentration of H2O2 and SCN- was reached. This equimolar concentration gave the maximum generation of OSCN-. High concentrations (greater than 100 micrograms/ml) of lactoperoxidase decreased OSCN- generation, but only if the SCN- was added to the enzyme prior to addition of H2O2. With lactoperoxidase concentrations exceeding 1 microgram/ml, the reaction velocity was rapid, but the decay of OSCN- was slow. Free H2O2 in the reaction mixture always resulted in rapid decay of OSCN-. Addition of varying concentrations of peroxide to solutions containing 1 microgram/ml of enzyme and [SCN-] = 5 mM gave a family of hyperbolic A235 vs. time curves. Both the initial slopes and the plateaus of these curves increased linearly with increasing initial peroxide concentrations up to [H2O2] = 0.4 mM, remained relatively constant in the range [H2O2] = 0.4 to 0.8 mM, and decreased rapidly above [H2O2] = 0.8 mM. These results are consistent with the following kinetic model: Hydrogen peroxide reacts rapidly with lactoperoxidase to produce compound I. This compound I oxidizes SCN- to OSCN- and also oxidizes OSCN- to O2SCN-. The OSCN- also reacts with SCN-. The formation of OSCN- is associated with the appearance of an absorbance peak at 225-235 nm. The oxidation of OSCN- by excess peroxide or its decomposition at high concentrations is associated with a decrease in A235 and the appearance of a peak at 245-255 nm. The extinction coefficient for OSCN- was determined to be 1.29 x 10(3) M-1 . cm-1. The second-order rate constant for the oxidation of thiocyanate by compound I was estimated to be 2 x 10(5) M-1 . s-1.

Kinetics↗
PubMed1982

Lactoperoxidase-catalyzed oxidation of thiocyanate: polarographic study of the oxidation products.

The lactoperoxidase-catalyzed oxidation of thiocyanate (SCN-) was studied by two different polarographic techniques: direct current polarography and linear sweep voltammetry. The main oxidation product at pH 6.5, with a half-wave potential (E1/2) of -0.39 to -0.44 V, was identified as hypothiocyanite (OSCN-) ion. The E1/2 for OSCN- was not available in the literature. The identification of OSCN- was based on a close correlation between the current of the OSCN- peak and the concentration of chemically assayed OSCN-. Also the specific rates of decay of the current and that of chemically detectable OSCN- were similar, and both curves followed apparent first-order kinetics. Subsequently, the addition of a reducing agent (2-mercaptoethanol) resulted in immediate disappearance of both chemically detectable OSCN- and the OSCN- wave in the polarograms. All three components of the lactoperoxidase (LPO) system (SCN-, H2O2, and LPO) were needed to produce the OSCN- peak. Addition of excess H2O2 or H2O2-LPO to an OSCN--SCN- mixture resulted in a formation of a new peak with a characteristic peak potential (Ep) of -0.20 to -0.25 V. The generation of this new peak was associated with a simultaneous, markedly enhanced decrease of OSCN- concentration, indicating a possible reaction between H2O2 (or H2O2-LPO) and OSCN-. No equivalent reaction was obtained by the addition of buffer alone. This new peak may represent higher oxy acids of SCN- (O2SCN-, O3SCN-), formed in the oxidation of OSCN- by H2O2 or by H2O2-LPO. This type of reaction can explain why, in solutions which already contain OSCN- (e.g., in saliva), the addition of H2O2 results in the formation of highly reactive, short-lived antimicrobial products in addition to OSCN-.

Animals↗
PubMed1982

The effect of human dental plaque on bone resorption and hyaluronic acid synthesis in in-vitro cultures of fetal rat calvaria.

Dental bacterial plaque affects bone demineralization both in vivo and in vitro. Since hyaluronic acid may play a role in demineralization, calcium release into the media as a measure of bone resorption was correlated with the synthesis of [3H]-glucosamine-labelled macromolecules in bone culture. The synthesis of glycosaminoglycans was determined by both a Millipore method and by DEAE-cellulose chromatography. Addition of plaque extract to the culture media stimulated both the synthesis and release of hyaluronic acid to the culture media, while stimulating calcium release. Thus, the bone-demineralizing effect of dental plaque seems to be associated to the induced synthesis of hyaluronic acid.

Animals↗
PubMed1982

Peroxidase antimicrobial system of human saliva: hypothiocyanite levels in resting and stimulated saliva.

The antimicrobial oxidizing agent hypothiocyanite ion (OSCN-) was measured in resting (drooling) and stimulated (expectorated) whole saliva. Stimulation of the saliva flow rate resulted in a rapid decrease in OSCN- concentration, whereas the thiocyanate ion (SCN-) concentration and peroxidase activity were increased. The decrease in OSCN- levels was greater than could be accounted for by dilution of the whole saliva volume. Assuming that the antimicrobial activity of the salivary peroxidase system is proportional to OSCN- concentration, this system may be more effective in resting saliva than in stimulated saliva.

Adult↗
PubMed1982

Interaction of specific and innate factors of immunity: IgA enhances the antimicrobial effect of the lactoperoxidase system against Streptococcus mutans.

The antimicrobial effect of the lactoperoxidase (LPO) system (enzyme with the thiocyanate ion and hydrogen peroxide) on Streptococcus mutans NCTC 10449 (serotype c) was significantly enhanced when the system was combined with secretory IgA. Similar enhancement was observed with LPO-myeloma IgA1 or IgA2 combinations. This enhancement of the antimicrobial efficiency was not dependent on the presence of specific antibodies to S. mutans in the IgA preparation, but seemed to require binding between LPO and immunoglobulin. However, neither human polyclonal nor myeloma IgG or IgM nor rabbit IgG enhanced the antibacterial activity of the LPO system. None of the immunoglobulins, when added alone, produced antimicrobial effects. LPO was shown to bind to colostral secretory IgA, myeloma IgA1, IgA2, and to a lesser degree to monoclonal and polyclonal IgG and monoclonal IgM. This binding had a stabilizing effect on the enzyme activity. Our results suggest that IgA significantly enhances the antibacterial efficiency of one of the innate immune factors--the LPO system.

Animals↗
PubMed1981

Different molecular forms of human salivary lactoperoxidase.

The two different molecular forms shown to exist probably represent a monomer and an aggregate. The pI of lactoperoxidase (8.1) did not change during aggregation. The presence of substrate (SCN-) could cause some disaggregation suggesting that the mechanism of the dissociation is influenced by the substrate. Purified milk lactoperoxidase had a similar chromatographic pattern to salivary lactoperoxidase. Another peroxidase with pI 4.3 occurs in whole saliva but not in parotid secretions, and is possibly of leukocytic origin. However, its characteristics differ from those of neutrophil myeloperoxidase but resemble those of peroxidase of inflammatory exudate and gingival fluid.

Chemical Phenomena↗
PubMed1981

Inhibition of dental plaque acid production by the salivary lactoperoxidase antimicrobial system.

Resting human whole saliva inhibited acid production by glucose-stimulated, homologous plaque. The degree of inhibition of plaque acid production correlated positively with the concentration of hypothiocyanite (OSCN-) ions in saliva. Supplementation of saliva with an appropriate combination of thiocyanate and hydrogen peroxide resulted in a significant increase in the concentration of OSCN- ions and in more effective inhibition of plaque acid production. In most cases, the inhibition was complete when the supplements were added directly to saliva-plaque mixtures. Acid production resumed when the inhibitory effect of OSCN- was reversed by addition of thiols. Among the oral defense factors, the salivary lactoperoxidase system seems to play an important role by producing highly reactive antibacterial products (including OSCN-) which can regulate bacterial metabolism in the human mouth. The concentration of OSCN- in normal human whole saliva seems to be just below the threshold level required for plaque inhibition. Therefore, enhancement of this system in vivo may be effective in the regulation of plaque acid production.

Animals↗
PubMed1981

The effect of dental plaque grown in the presence of xylitol or sucrose on bone resorption in vitro.

Bone culture was used as an experimental model in studying the ability of dental plaque grown in the presence of xylitol or sucrose to induce bone resorption. Plaque samples were collected in young adults after six or ten days with no oral hygiene and with frequent use of xylitol- or sucrose-sweetened chewing gum. The rate of resorption was assayed by measuring the release of both acid phosphatase and 45Ca from bones into culture media during a three-day incubation period. Sucrose-induced plaque collected after ten days increased both of these indicators of bone resorption, while xylitol plaque decreased or had no effect under identical conditions. Xylitol consumption induced a marked increase in acid phosphatase activity of dental plaque - a phenomenon which would appear to be unrelated to bone resorption. The results suggest that the inflammatory potential of dental plaque may be reduced during xylitol consumption as compared to sucrose consumption.

Acid Phosphatase↗