Decrease in saliva causes serious problems in clinical dentistry. There have been previous reports on tissue injuries of parotid glands inducing a dedifferentiation signal that causes the loss of function of acinar cells. Since both inhibitors for Src family kinase(SFK)and p38 MAP kinase(p38 MAPK)suppressed the dedifferentiation, SFK-p38 MAPK pathway was considered essential for the signaling. Even though Src and Yes were expressed in the parotid glands, the increase in phosphorylation level was not detected for conserved tyrosine residue in the kinase domain of Src or Yes that promotes kinase activity, following tissue injuries. In this study, the kinase activities were assayed by using the specific substrate for SFK to examine whether the enhancement of kinase activity of SFK was eventuated by tissue injuries. As a result, the activity of the total SFK was elevated after the cellular damage and was sustained for 2 h. To determine the activated SFK member, the SFK activity was examined by immunoprecipitation method with specific antibodies against each SFK member. Elevation of kinase activities of both Src and Yes was detected after cell damages. The elevation ratio of Src activity was higher than Yes, suggesting that the contribution of Src in the dedifferentiation signaling is higher. Diphenyleneiodonium, an NADPH oxidase inhibitor, suppressed the activation of SFK and p38 MAPK, and the expression of claudin-4, a dedifferentiation marker. These results suggest that the activation of SFK is induced by oxidative stresses and is essential for p38 MAPK-mediated dedifferentiation signaling.

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　Green fluorescent protein(GFP)is one of the most useful biological markers for monitoring gene expression and the localization of particular cells. We constructed a GFP-expressing Aggregatibacter actinomycetemcomitans transformant by transposon insertion. This anaerobic, oral, gram-negative bacterium is thought to be the major causative agent in localized aggressive periodontitis and possesses the gene coding for leukotoxin(ltx). As this gene is stably expressed, the region extending from the ltx promoter to the initiation codon was amplified using PCR and temporarily cloned into a small Escherichia coli plasmid, pResKm. The DNA fragment containing the GFP gene(gfp)ORF was excised from the commercially available plasmid pAcGFP1-C1, purified by gel electrophoresis, and inserted downstream of the ltx initiation codon in the correct reading frame. This gene fusion was further cloned into the Not I site of the commercially available shuttle plasmid, pUTmini-Tn5, which contains the gene coding for the transposase, and then introduced into the chromosome of A. actinomycetemcomitans strain HK1651 by electroporation. Transformants were isolated by screening for the appropriate antibiotic resistance. FACS analysis revealed that the final A. actinomycetemcomitans-GFP integrant exhibited slightly more intense fluorescence than wild-type A. actinomycetemcomitans. These data demonstrate that transposon-mediated chromosomal integration is a useful approach for constructing mutant A. actinomycetemcomitans strains.

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　Cefpodoxime proxetil, an ester prodrug of cefpodoxime, is an oral third-generation cephalosporin antibiotic that is used for the treatment of odontogenic infections such as periodontitis, pericoronitis, and osteitis of jaw. However, there are only a few studies on cephalosporin concentrations in human oral tissues. The present study therefore was undertaken to determine cefpodoxime concentrations in human oral tissues following oral administration of cefpodoxime proxetil. Cefpodoxime concentrations in human serum, gingiva, mandibular bone, and dental follicle following a single oral administration of 200- mg cefpodoxime proxetil were measured by a paper disk method. The mean peak concentrations in serum, gingiva, mandibular bone, and dental follicle occurred at the same time point, 3 hours post-dose, and were 3.07 ± 0.96 μg/mL, 1.16 ± 0.35 μg/g, 0.60 ± 0.27 μg/g, and 1.13 ± 0.34 μg/g, respectively. Mean cefpodoxime concentration ratios of gingiva / serum, mandibular bone / serum, and dental follicle / serum at the peak time were 0.40 ± 0.15, 0.20 ± 0.05, and 0.37 ± 0.03, respectively. Mean concentrations in gingiva, mandibular bone, and dental follicle at the peak time exceeded the minimum inhibitory concentration for 80% of clinically isolated strains of oral streptococci. Therefore, cefpodoxime proxetil may be a valuable antimicrobial agent for the treatment of odontogenic infection.

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　Live attenuated Salmonella strains are thought to be potential vaccines or vaccine vectors for delivery of recombinantly expressed vaccine antigens(Ags). A non-replicative recombinant mutant strain of Salmonella(rSalmonella)that expresses fragment C of tetanus toxin(Tox C)has been shown to be strongly immunogenic, causing induction of significant systemic and mucosal antibody(Ab)responses against the Tox C Ag. However, since previous studies reported that administration of live attenuated strains of Salmonella resulted in side effects, it is preferable to use inactivated bacterial vaccines. Thus, in this study, we assessed the immunogenicity of a heat-killed attenuated strain of rSalmonella. The results showed that oral immunization with heat-killed rSalmonella-Tox C induced tetanus toxoid(TT)-specific systemic IgM Ab responses at levels indistinguishable from those of mice administered live bacteria. However, rSalmonella-Tox C had to be administered at a 10-fold higher oral dose than live bacteria to produce similar levels of TT-specific IgM-forming cells. Even at this higher dose, heat-killed rSalmonella-Tox C induced TT-specific systemic IgG Ab responses that were significantly lower than those obtained in mice dosed with live bacteria. Furthermore, no anti-TT IgA response was detected in the intestinal secretions of mice that were orally dosed with heat-killed rSalmonella-Tox C. Markedly decreased numbers of TT-specific IgG- and IgA-producing cells were detected in the lymph nodes of mice immunized with rSalmonella-Tox C. These results suggest that heat-killed rSalmonella-Tox C may not be appropriate for use as an oral vaccine or vaccine vector.

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　The salivary glands help to keep the mouth and other parts of the digestive system moist. There have been only a few reports on the salivary glands of the marsupial gray short-tailed opossum(Monodelphis domestica). The aim of this study was to reveal the ultrastructure of the parotid and submandibular glands in the gray short-tailed opossum using transmission electron microscopy(TEM). Using TEM, the parotid glands were found to consist only of serous acinar cells. Secretory granules were highly electron dense. The submandibular glands were composed of both serous and mucous acinar cells, showing a mixture of glands. Also, the submandibular glands possessed special serous cells. Secretory granules were divided into homogeneous density type, two biphasic types and annual ring types. The properties of the granules were different in each cell type. However, some cells contained a mixture of every type of granule. It appeared that the variety of granules in the special serous cells represented stages in the cell cycle and was not a property of the cell. Striated ducts of submandibular glands consisted both of columnar epithelium with or without basal infoldings, although typical striated ducts were found in parotid glands.

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