Biomedical subjects

Takahiko Oho

Publications and source records attributed to Takahiko Oho.

13 recordsLinked to original sources

PubMed2005

Induction of immune response to Streptococcus pneumoniae by administration of oral viridans streptococci via phosphorylcholine determinant.

Expression of the phosphorylcholine (PC) epitope was examined in 48 viridans streptococcal strains, including Streptococcus pneumoniae R36a as the positive control, and their immunogenicity to induce an S. pneumoniae-cross-reactive response was evaluated in mice. Thirteen strains were found to express the PC epitope, while no obvious association was found between the taxonomic categories and PC expression. Serum antibody responses to S. pneumoniae cells were induced in mice by intraperitoneal injection of the PC-positive, but not PC-negative, strains. The cross-reactive antibodies induced by non-pneumococcal oral streptococci were readily inhibited by free hapten PC. IgM was the sole isotype of the anti-pneumococcal and anti-PC antibodies, and the phenomenon of immunological memory was not observed. Since the anti-PC antibody is critically important for resistance against pneumococcal infection in mice, the present results indicate the possibility that PC-expressing oral commensal bacteria have a significant influence on the hosts' responsiveness to S. pneumoniae.

Animals↗

PubMed2005

Experimental abscess formation caused by human dental plaque.

Human dental plaque consists of a wide variety of microorganisms, some of which are believed to cause systemic infections, including abscesses, at various sites in the body. To confirm this hypothesis experimentally, we examined the abscess-forming ability of native dental plaque in mice, the microbial features of the infectious locus produced by the plaque, and the anti-phagocytic property of microbial isolates. Aliquots of a suspension of supragingival dental plaque containing 6 x 10(6) colony-forming unit of bacteria were injected subcutaneously into the dorsa of mice. Abscess formation was induced in 76 of 85 mice using ten different plaque samples. Thirteen microorganisms were isolated from pus samples aspirated from abscess lesions. The microbial composition of pus, examined in 17 of 76 abscesses, was very simple compared to that of the plaque sample that had induced the abscess. The majority of the isolates belonged to the Streptococcus anginosus group, normally a minor component of plaque samples. S. anginosus was the most frequently detected organism and the most prevalent in seven abscesses, and Streptococcus intermedius and Streptococcus constellatus were predominant in one and three abscess samples, respectively. Each isolate of S. anginosus group produced abscesses in mice, and heat-treated supragingival dental plaque influenced the abscess-forming ability of S. anginosus isolate. These isolates possessed a high antiphagocytic capacity against human polymorphonuclear leukocytes. Our results suggest that human supragingival dental plaque itself is a source of the infectious pathogens that cause abscess formation.

Abscess↗

PubMed2005

Experimental infective endocarditis induced by human supragingival dental plaque in rats.

Human dental plaque is thought to contribute to disease, not only in the oral cavity but also at other body sites. To investigate the pathogenicity of dental plaque in tissues remote from the mouth, we examined the ability of human supragingival dental plaque to induce infective endocarditis (IE) in rats. In total, 15 out of 27 catheterized rats survived after intravenous injections with human supragingival dental plaque suspensions containing 3 x 10(6) colony-forming units (CFU) of bacterial cells. In surviving rats, infected vegetations were formed in all except one rat. The microbial composition of the infected vegetations was different from that of the respective dental plaque inocula, with Streptococcus oralis comprising the majority of the isolates. In rats affected with endocarditis, the aortic sinus was filled with fibrinous vegetation containing bacteria. Inflammatory cells infiltrated the aortic valve, the aorta adjacent to the valve, and the cardiac muscles. The inoculation of catheterized rats with a cell suspension of S. oralis isolate (5 x 10(6) CFU) was not lethal but capable of inducing endocarditis in all animals. The results suggest that if dental plaque were introduced into the bloodstream, it could serve as a potent source of bacteria causing IE in humans.

Adult↗

PubMed2004

A peptide domain of bovine milk lactoferrin inhibits the interaction between streptococcal surface protein antigen and a salivary agglutinin peptide domain.

The peptide domain of salivary agglutinin responsible for its interaction with cell surface protein antigen (PAc) of Streptococcus mutans or bovine lactoferrin was found in the same peptide, scavenger receptor cysteine-rich domain peptide 2 (SRCRP2). Inhibition studies suggest that PAc and lactoferrin, of which residues 480 to 492 seem important, competitively bind to the SRCRP2 domain of salivary agglutinin.

Agglutinins↗

PubMed2003

Differences in the betaC-S lyase activities of viridans group streptococci.

betaC-S Lyase catalyzes the alpha,beta-elimination of L-cysteine to hydrogen sulfide, which is one of the main causes of oral malodor and is highly toxic to mammalian cells. We evaluated the capacity of six species of oral streptococci to produce hydrogen sulfide. The crude enzyme extract from Streptococcus anginosus had the greatest capacity. However, comparative analysis of amino acid sequences did not detect any meaningful differences in the S. anginosus betaC-S lyase. The capacity of S. anginosus purified betaC-S lyase to degrade L-cysteine was also extremely high, while its capacity to degrade L-cystathionine was unremarkable. These findings suggest that the extremely high capacity of S. anginosus to produce hydrogen sulfide is due to the unique characteristic of betaC-S lyase from that organism.

Base Sequence↗

PubMed2003

Development of a 5' fluorogenic nuclease-based real-time PCR assay for quantitative detection of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis.

A 5' nuclease TaqMan PCR was developed for the quantitative detection of the periodontopathic bacteria Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. The relative numbers of bacteria were measured by the comparative threshold cycle method. This simplified method is a way of obtaining the relative quantities of these organisms from specimens and of monitoring the effect of therapy.

Aggregatibacter actinomycetemcomitans↗

PubMed2003

Development of a 5' nuclease-based real-time PCR assay for quantitative detection of cariogenic dental pathogens Streptococcus mutans and Streptococcus sobrinus.

A 5' nuclease TaqMan PCR assay was developed for the quantitative detection of the major cariogenic bacteria Streptococcus mutans and Streptococcus sobrinus. The absolute and relative numbers of bacteria were measured by this method. This assay will be useful for quantifying these organisms in oral specimens and for analyzing biofilm formation.

Biofilms↗

PubMed2002

Immunization against dental caries.

Dental caries is one of the most common infectious diseases. Of the oral bacteria, mutans streptococci, such as Streptococcus mutans and S. sobrinus, are considered to be causative agents of dental caries in humans. There have been numerous studies of the immunology of mutans streptococci. To control dental caries, dental caries vaccines have been produced using various cell-surface antigens of these organisms. Progress in recombinant DNA technology and peptide synthesis has been applied to the development of recombinant and synthetic peptide vaccines to control dental caries. Significant protective effects against dental caries have been shown in experimental animals, such as mice, rats and monkeys, which have been subcutaneously, orally, or intranasally immunized with these antigens. Only a few studies, however, have examined the efficacy of dental caries vaccines in humans. Recently, local passive immunization using murine monoclonal antibodies, transgenic plant antibodies, egg-yolk antibodies, and bovine milk antibodies to antigens of mutans streptococci have been used to control the colonization of the organisms and the induction of dental caries in human. Such immunization procedures may be a safer approach for controlling human dental caries than active immunization.

Animals↗

PubMed2002

Monitoring ammonia to assess halitosis.

OBJECTIVE: This study examined the applicability of ammonia monitoring for assessing halitosis. STUDY DESIGN: The actual degree of halitosis was determined by using an organoleptic test in 61 subjects aged 28 +/- 10 years (mean +/- SD). Levels of volatile sulfur compounds and ammonia were determined by using gas chromatography and ammonia monitoring, respectively. Levels of ammonia and methyl mercaptan produced by bacteria in dental plaque and tongue-coating samples obtained from 25 subjects were quantified. In addition, changes in ammonia levels were measured before and after removing tongue coating or dental plaque. RESULTS: There was no significant correlation between the organoleptic score and the ammonia level measured with ammonia monitoring, whereas there was a significant correlation between ammonia level and the total level of volatile sulfur compounds measured with gas chromatography. Significant correlations were also observed between ammonia level and levels of methyl mercaptan produced by bacteria in dental plaque and tongue coating. Furthermore, the ammonia level decreased after the removal of tongue coating and dental plaque. CONCLUSION: These results indicate that measuring ammonia levels is useful for assessing halitosis, specifically for halitosis arising from a lack of oral hygiene.

Adult↗

PubMed2002

lcd from Streptococcus anginosus encodes a C-S lyase with alpha,beta-elimination activity that degrades L-cysteine.

Hydrogen sulfide is highly toxic to mammalian cells. It has also been postulated that hydrogen sulfide modifies haemoglobin resulting in haemolysis. The enzyme that produces hydrogen sulfide from L-cysteine was purified from Streptococcus anginosus. Using the N-terminal amino acid sequence of the purified enzyme, the lcd gene encoding L-cysteine desulfhydrase was cloned; the recombinant protein was then purified to examine its enzymic and biological characteristics. This L-cysteine desulfhydrase had the Michaelis-Menten kinetics K(m)=0.62 mM and V(max)=163 micro mol min(-1) mg(-1). DL-Cystathionine, L-cystine, S-(2-aminoethyl)-L-cysteine, 3-chloro-DL-alanine and S-methyl-L-cysteine were substrates for the enzyme, whereas D-cysteine, DL-homocysteine, L-methionine, DL-serine, DL-alanine, L-cysteine methyl ester, L-tryptophan, L-tyrosine and L-phenylalanine were not. These findings suggest that this L-cysteine desulfhydrase is a C-S lyase that catalyses the alpha,beta-elimination (alphaC-N and betaC-S) reaction. In addition, it is demonstrated that the hydrogen sulfide produced by this enzyme caused the modification and release of haemoglobin in sheep erythrocytes.

Amino Acid Sequence↗

PubMed2002

Passive immunization with bovine milk containing antibodies to a cell surface protein antigen-glucosyltransferase fusion protein protects rats against dental caries.

Cell surface protein antigen (PAc) and glucosyltransferases (GTF) of Streptococcus mutans are major colonization factors of the organism. We prepared bovine milk containing antibodies against a fusion of the saliva-binding alanine-rich region of PAc with the glucan-binding domain of GTF-I. This study examined the effect of the immune milk on the cariogenicity of S. mutans in a rat model. Concentrated immune milk was fed to rats once a day for 55 days. The group that received immune milk had significantly less caries development than controls.

Animals↗

PubMed2002

Functional domain of bovine milk lactoferrin which inhibits the adherence of Streptococcus mutans cells to a salivary film.

The bovine lactoferrin molecule and relatively long lactoferrin fragments containing residues 473 to 538 strongly inhibited adherence of Streptococcus mutans to saliva-coated hydroxyapatite beads. Each cysteine residue in Lf411 (residues 473 to 538) was replaced by a serine residue, and the mutants Lf411-C481S and Lf411-C532S strongly inhibited S. mutans adherence. These results suggest that the functional domain of lactoferrin that binds to a salivary film lies in residues 473 to 538 and that the region might be concealed by disulfide bond formation between Cys481 and Cys532 in the Lf411 fragment.

Animals↗

PubMed1998

Biological functions of UDP-glucose synthesis in Streptococcus mutans.

A gene encoding glucose-1-phosphate uridylyltransferase (EC 2.7.7.9) was isolated from Streptococcus mutans. A cell extract of Escherichia coli expressing the cloned gene exhibited glucose-1-phosphate uridylyltransferase activity. The enzyme catalyses the conversion of D-glucose 1-phosphate and UTP into UDP-D-glucose. Rabbit antiserum against the serotype-c-specific antigen did not react with autoclaved extracts from mutant cells in which the cloned gene was insertionally inactivated. The glucose content of the cell-wall preparation purified from the mutant was very much lowered, whereas there was no observable decrease in the content of rhamnose. When the mutant strain was grown in an acidic environment, its cell viability was much lower than that of the wild-type. These results suggest that UDP-D-glucose functions not only as an immediate precursor of the serotype-c-specific antigen of S. mutans (as a glucose donor for side-chain formation), but is also important for the organism's viability in environmental conditions of low pH.

Base Sequence↗