No abstract

Our findings indicated that ascorbic acid increases the ALP activity of PDL cells via type I collagen production and also enhances the expression of alpha2beta1 integrin, which is a major receptor of type I collagen. These results suggest that ascorbic acid promotes the osteoblastic differentiation of PDL cells by modulating type I collagen-alpha2beta1 integrin interaction.

To investigate the exact isolation frequency of 16S rRNA methylase-producing, gram-negative pathogenic bacteria, we tested 87,626 clinical isolates from 169 hospitals. Twenty-six strains from 16 hospitals harbored 16S rRNA methylase genes, which suggests sparse but diffuse spread of pan-aminoglycoside-resistant microbes in Japan.

Shiga toxin 1 (Stx1) of enterohemorrhagic Escherichia coli O157:H7 was cloned, and four mutant Stx1s were constructed by site-directed mutagenesis with PCR. The wild-type and mutant Stx1s with amino acid replacements at positions 167 and 170 of the A subunit were purified by one-step affinity chromatography with commercially available Globotriose Fractogel, and the mutant Stxs were used for the immunization of mice. The mutant toxins were nontoxic to Vero cells in vitro and to mice in vivo and induced the immunoglobulin G antibody against the wild-type Stx1, which neutralized the cytotoxicity of Stx1. The induced antibody titers depended on the mutation at position 170 of the A subunit. The mice immunized with the mutant Stx1s were protected against a challenge of approximately 100 times the 50% lethal dose of the wild-type Stx1, suggesting that the mutant toxins are good candidates for toxoid vaccines for infection by Stx1-producing E. coli.

In Salmonella typhimurium, the transcription of several virulence genes including spvB is regulated by the PhoP/PhoQ regulatory system. To further examine the relationship between the PhoP/PhoQ and Spy systems for virulence in mice, we examined a non-polar phoP mutation combined with different virulence plasmid genotypes for effects on virulence of S. typhimurium in the mouse model. PhoP-/Spv+ and PhoP-/ Spv-mutants were not detectably recovered from the spleens of subcutaneously or orally inoculated mice. The phoP gene constitutively expressed from the lacZ promoter of a low copy number vector (phor) only partially complemented the non-polar phoP mutation for mouse-virulence in both the Spy and Spy-backgrounds; both PhoPc strains exhibited virulence equal only to a PhoP)+/Spy-strain. Interestingly, in a PhoP+ background, the phoPc gene reduced splenic infection of the Spy but not Spv-salmonellae after subcutaneous or oral inoculation compared with the PhoP+ parents. Additionally, the phoPc gene in an Spy+ background reduced the net growth of salmonellae in macrophages in vitro; phoPc in an Spy-background was without effect. These data suggest that the constitutive expression of the phoP gene attenuates the virulence of S. typhimurium in mice in an Spy-dependent manner.