Emphysema severity is independently associated with a rapid annual decline in FEV1 in COPD. Sustainers and Rapid decliners warrant specific attention in clinical practice.

Streptococcus mutans is an etiological agent in human dental caries. A method for the detection of S. mutans directly from human dental plaque by polymerase chain reaction has been developed. Oligonucleotide primers specific for a portion of the dextranase gene (dexA) of S. mutans Ingbritt (serotype c) were designed to amplify a 1272-bp DNA fragment by polymerase chain reaction. The present method specifically detected S. mutans (serotypes c, e and f), but none of the other mutans streptococci: S. cricetus (serotype a), S. rattus (serotype b), S. sobrinus (serotypes d and g), and S. downei (serotype h), other gram-positive bacteria (16 strains of 12 species of cocci and 18 strains of 12 species of bacilli) nor gram-negative bacteria (1 strain of 1 species of cocci and 20 strains of 18 species of bacilli). The method was capable of detecting 1 pg of the chromosomal DNA purified from S. mutans Ingbritt and as few as 12 colony-forming units of S. mutans cells. The S. mutans cells in human dental plaque were also directly detected. Seventy clinical isolates of S. mutans isolated from the dental plaque of 8 patients were all positive by the polymerase chain reaction. These results suggest that the dexA polymerase chain reaction is suitable for the specific detection and identification of S. mutans.

A previously unidentified 120-kDa protein was detected in Streptococcus mutans strain Z1 and was involved in the cold-agglutination of the strain. We have identified the gene, designated cnm, as being involved in the agglutination of strain Z1 following random mutagenesis. The amino acid sequence of the deduced Cnm protein exhibited high similarity to those of collagen-binding adhesins from staphylococci and other organisms. To confirm whether the protein is involved in collagen-binding, we cloned a cnm gene fragment, overexpressed it in E.coli, and prepared crude extracts. The extracts containing recombinant protein exhibited binding to immobilized collagen and laminin but not to fibronectin. Compared with the parental strain Z1, the cold-agglutination-negative mutant 05A02 exhibited reduced binding to collagen and laminin but retained that to fibronectin. This gene was detected in some strains of S. mutans. Therefore, the cnm gene encoded a new strain-specific member of the collagen-binding adhesin family.

Oligonucleotide primers were designed based upon a comparison of the dextranase gene (dex) sequences from Streptococcus sobrinus and S. mutans. The primers ampli®ed a 1610-bp long DNA fragment on the dex gene by a PCR. The pair of primers was speci®c to S. sobrinus as the other members of the mutans streptococci ± S. mutans, S. downei, S. cricetus, S. rattus, S. macacae and S. ferus ± gave no PCR products. Other grampositive oral bacteria (15 strains of 10 species of cocci and 18 strains of 12 species of rods) and gram-negative oral bacteria (3 strains of 3 species of cocci and 31 strains of 22 species of rods) also gave negative results in the PCR. The PCR procedure was able to detect as little as 100 fg of puri®ed chromosomal DNA or as few as 9 cfu of S. sobrinus NIDR6715. Seven clinical isolates of S. sobrinus were also positive in the dex PCR. This laboratory developed the S. mutans-speci®c PCR (dexA PCR) method with the primers speci®c for a portion of the dextranase gene of S. mutans Ingbritt. Primers for the dex and dexA PCR methods detected two species exclusively from the mutans streptococci. Furthermore, these two species were effectively differentiated by the species-speci®c amplicons with different lengths. The application of the PCR method to human dental plaque showed that the prevalence of S. sobrinus (83%) in oral cavities was higher than currently supposed (0±50%). These results suggest that the described PCR method is suitable for the speci®c detection and identi®cation of human cariogenic bacteria, S. sobrinus and S. mutans.

We report on highly efficient polymer light-emitting devices (PLEDs) achieved using a phosphorescent polymer, which is a copolymer that has bis(2-phenylpyridine)iridium (acetylacetonate) [Ir(ppy)2(acac)], N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine (TPD) and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) as a side group. The phosphorescent polymer has an ambipolar charge-transport ability. An increase in PBD unit concentration allows an improvement in the efficiency of the PLEDs. Ba and Cs were used for electron-injection layers as well as Ca, to improve the electron injection. An external quantum efficiency of 11.8% and a power efficiency of 38.6lm∕W were obtained by using Cs. The results indicate that this can be attributed to an improvement in the charge balance of electrons and holes.

Abstract:The complete nucleotide sequence (3,747

Sortase has been shown to be a protease that catalyzes the cell wall anchoring of surface proteins containing an LPXTG motif in gram-positive bacteria. In this study, we determined the complete nucleotide sequence of the sortase gene (srtA) of Streptococcus mutans and found a surface protein that was linked to the cell wall by the sortase. The results show that srtA gene of S. mutans consisted of 741 bp and encoded for a sortase protein of 246 amino acids with a molecular weight of 27 489. The deduced amino acid sequence of the S. mutans sortase was highly homologous (65-58%) to those of other Streptococcal species. In a S. mutans mutant lacking sortase, two surface proteins of 200 and 75 kDa were released to the culture supernatant. Western blot analysis with specific antiserum showed that the 200 kDa protein was a surface protein antigen designated PAc. These results suggest that the sortase catalyzes anchoring of the antigen PAc to the cell wall.

DNA fragments encoding the Streptococcus downei dextranase were amplified by PCR and inverse PCR based on a comparison of the dextranase gene (dex) sequences from S. sobrinus, S. mutans, and S. salivarius, and the complete nucleotide sequence of the S. downei dex was determined. An open reading frame (ORF) of dex was 3,891 bp long. It encoded a dextranase protein (Dex) consisting of 1,297 amino acids with a molecular mass of 139,743 Da and an isoelectric point of 4.49. The deduced amino acid sequence of S. downei Dex had homology to those of S. sobrinus, S. mutans and S. salivarius Dex in the conserved region (made of about 540 amino acid residues). DNA hybridization analysis showed that a dex DNA probe of S. downei hybridized to the chromosomal DNA of S. sobrinus as well as that of S. downei, but did not to other species of mutans streptococci. The C terminus of the S. downei Dex had a membrane-anchor region which has been reported as a common structure of C termini of both the S. mutans and S. sobrinus Dex, The recombinant plasmid which harbored the dex ORF of S. downei produced a recombinant Dex enzyme in Escherichia coli cells. The analysis of the recombinant enzyme on SDS-PAGE containing blue dextran showed multiple active forms as well as dextranases of S. mutans, S. sobrinus and S. salivarius. Key words: Dextranase, dex gene, Streptococcus downeiDextranase (Dex) is an enzyme which hydrolyzes o-1, 6-linkage in glucan molecule produced from sucrose by mutans streptococci (4, 10, 14,37). Although a wide range of bacterial species associated with dental plaque have been shown to produce extracellular dextranases (19), oral streptococci, in particular mutans streptococci, has been known to be a predominant producer of the dextranases (32, 37). So far, the dextranases of Streptococcus mutans and Streptococcus sobrinus were well characterized by enzyme purification and gene cloning (2,(14)(15)(16)38). Previous studies suggested important roles of Dex in plaque formation: one was that Dex supplies carbohydrate nutrients through the degradation of glucan (5, 14,24) and the other was that Dex modifies the glucan substrate to a more firm and adhesive form (5, 21, 28, 37). Consequently, Dex is thought to be one of the virulent factors in mutans streptococci.Although the Dex enzyme has abilities of both glucanhydrolysis and glucan-binding, the relationship of structure and function of the Dex molecule has not yet been clarified. To understand the relationship, comparison of the primary structure of the dextranases from different *Address correspondence to Dr. Takeshi Igarashi, Department of Oral Microbiology, Showa University School of Dentistry, 1-5-8, Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan. Fax: 03-3784-8012. E-mail: igatakes@dent.showa-u.ac.jp 341 species of mutans streptococci should be helpful. So far, the primary structure data of Dex of mutans streptococci, which is composed of 5 species: S. mutans, S. sobrinus, S. downei, S. rattus, and S. cricetus (39), has been reported only for those of S....