BACKGROUND:Magnesium alloy is a material that is easily degradable and has good mechanical properties.OBJECTIVE:To study the effects of the two kinds of magnesium aloy materials (AM50 and WE43) on proliferation and morphology of human umbilical vein endothelial cells.METHODS: Human umbilical vein endothelial cells at logarithmic phase were cultured in 100%, 50%, 10% extracts of AM50 and WE43 or directly seeded on the surface of AM50 and WE43 for 24 hours to study the morphological effect of magnesium alloys on the cells. Human umbilical vein endothelial cells cultured routinely served as negative controls. Relative growth rate of the cells was detected at 12, 24, 48 hours after culture. Cell morphology was observed using immunofluorescence staining at 24 hours after culture, and pH and element levels in the cell supernatant were measured.RESULTS AND CONCLUSION: (1) AM50 and WE43 extracts showed no effects on the proliferation of human umbilical vein endothelial cells in comparison with the negative control group. (2) Compared with the negative control group, reduced area of human umbilical vein endothelial cells was found on the surface of AM50 or WE43 alloy by the immunofluorescent staining, and the cytoskeleton of the cytoplasm was blurred. However, after 24 hours of culture, morphological changes of the cells cultured in 10%, 50% and 100% AM50 or WE43 extracts were consistent with those cultured routinely. The cytoskeleton of the cytoplasm was clearly visible. (3) Compared with the negative control group, the pH values of 100% AM50 and WE43 extract groups were significantly upregulated, and the level of magnesium element was also increased remarkably. In summary, AM50 and WE43 alloys possess good cytocompatibility with human umbilical vein endothelial cells, and have no influence on the cell proliferation and growth.

OBJECTIVETo analyze horizontal transmission patterns of Streptococcus mutans among caries-active preschool children for early interventions of dental caries.

METHODSPlaque samples obtained from 20 caries-active preschool children between 4 and 5 years of age were cultured under anaerobic conditions for isolating S. mutans, which were identified by morphological and biochemical analyses and PCR using primers homologous to the surface protein glucosyltransferase B (gtfB). The genotypes of the isolated S. mutans strains were determined by arbitrarily primed PCR (AP-PCR).

RESULTSOf the 200 S. mutans isolates obtained, 19 were excluded by biochemical analysis, and the remaining 181 isolates were identified as S. mutans by PCR with primers of gtfB, showing 37 different genotypes as identified by AP-PCR. Six children were found to carry S. mutans of a single genotype, 11 carried 2 genotypes, 2 had 3 genotypes, and 1 had 4 genotypes; 2 children from different classes were found to carry S. mutans of the same single genotype.

CONCLUSIONWe identified 37 genotypes of S. mutans in these caries-active preschool children, among whom horizontal transmissions of the strains were not found.

Child, Preschool ; Dental Caries ; microbiology ; Dental Plaque ; Genotype ; Glucosyltransferases ; Humans ; Polymerase Chain Reaction ; Streptococcal Infections ; transmission ; Streptococcus mutans ; classification

OBJECTIVETo select and identify ssDNA aptamers specific to Streptococcus mutans strains with different cariogenicity isolated from clinical specimens.

METHODSSubtractive SELEX technology targeting the whole intact cells was used to screen for ssDNA aptamers specific to the clinical isolates Streptococcus mutans strains with different cariogenicity. Radioactive isotope, flow cytometry, gene cloning and sequencing, MEME online software and RNA structure analysis software were employed to analyze the first and secondary structures of the aptamers and identify the screened aptamers.

RESULTSDetection by radioactive isotope showed sufficient pool enrichment after 9 rounds of subtractive SELEX. Flow cytometry showed that the selected aptamers H1, H16, H4, L1, L10 and H19 were capable of binding specifically with highly cariogenic Streptococcus mutans strains but not with strains with a low cariogenicity. The aptamer H19 had the strongest binding capacity to highly cariogenic Streptococcus mutans strains, with a dissociation constant of 69.45∓38.53 nmol/L.

CONCLUSIONWe have obtained the ssDNA aptamers specific to the clinical isolates of highly cariogenic Streptococcus mutans strains.

Aptamers, Nucleotide ; genetics ; Cloning, Molecular ; DNA Primers ; Dental Caries ; microbiology ; Gene Library ; Humans ; Nucleic Acid Conformation ; SELEX Aptamer Technique ; Species Specificity ; Streptococcus mutans ; classification ; genetics ; isolation & purification

OBJECTIVETo screen of high cariogenicity Streptococcus mutans (S. mutans) strains isolated from clinical specimens preliminary.

METHODSAcidogenicity, aciduricity, extracellular polysaccharide production and adhesion of 41 strains of S. mutans isolated from clinical specimens were investigated to screen high cariogenicity S. mutans strains.

RESULTSThere were different cariogenicity among 41 strains of S. mutans, in which 3 strains of S. mutans had all high ability to produce extracellular polysaccharide, adhere to the saliva-coated hydroxyapatite, produce acid and tolerate acid, indicated there were 3 strains with high cariogenicity S. mutans strains isolated from clinical specimens. Another 3 strains of S. mutans with all low ability to produce extracellular polysaccharide, adhere to the saliva-coated hydroxyapatite, produce acid and tolerate acid indicated they were low cariogenicity S. mutans strains isolated from clinical specimens.

CONCLUSIONWe may have obtained high cariogenicity S. mutans strains isolated from clinical specimens.

Dental Caries ; Durapatite ; Humans ; Saliva ; Streptococcus mutans

OBJECTIVETo identify Streptococcus mutans (S. mutans) strains from clinical samples.

METHODSPlaque samples from caries-active and caries-free sites on enamel surfaces were obtained and cultivated for S. mutans isolation. Morphology, biochemistry, automatic microorganism analysis system and polymerase chain reaction using primers homologous to surface protein antigen I/II (spaP), glucosyltransferase B (gtfB) and dextranase (dexA) were used to identify S. mutans. Genotype of isolated S. mutans was determined by arbitrarily primed polymerase chain reaction.

RESULTSForty-six strains of S. mutans were obtained from the 32 subjects and were identified as S. mutans by biochemistry, automatic microorganism analysis system and polymerase chain reaction. Five identical genotypes were found by arbitrarily primed polymerase chain reaction.

CONCLUSIONForty-one strains of S. mutans with different genotype were obtained from clinical samples.

Dental Caries ; Dental Plaque ; Genotype ; Glucosyltransferases ; Humans ; Polymerase Chain Reaction ; Streptococcus mutans