Discrimination method of seven species pufferfish of the genus Takifugu using DNA chromatography.

Identifying poisonous plants and animals is very important because they not only can cause food poisoning, but also can be eaten for the purpose of suicide. A pufferfish is a poisonous fish that contains tetrodotoxin. In Japan, 136 pufferfish poisoning cases occurred from 2015 to 2019, but in many cases, the specific species involved was unidentified. To address this, we focused on a rapid and simple DNA chromatography technology called Single-stranded Tag Hybridization (STH). We collected seven pufferfish species of the genus Takifugu and designed species-specific primers as target regions of cytochrome c oxidase subunit I (COI) and cytochrome b with a specific base sequence at the 3' end. STH-PCR was performed in two separate reactions. After mixing the PCR products, a developing solution was added to perform chromatograph development and the results were visually analyzed. Specific lines were detected in all seven species. The pufferfish species could be properly determined using between 0.1 ng and 50 ng of template DNA. The PCR product length was 85-149 bp, making it very resistant to degradation. The species could be properly identified even in a mixture of multiple pufferfish species DNA. Furthermore, verification was performed using the supernatants of digested samples with artificial gastric juice and processed foods. Extracted DNA was obtained in all but the highly roasted fins, enabling discrimination. Overall, we applied a novel DNA chromatography detection system capable of discriminating seven species of the genus Takifugu, which have closely related DNA sequences.

sjTREC quantification using SYBR quantitative PCR for age estimation of bloodstains in a Japanese population.

Individual age is a phenotypic trait that provides useful information in forensic investigations. Levels of signal joint T-cell receptor rearrangement excision circle (sjTREC) in human peripheral blood are known to decline with increasing age. The advantages of sjTREC quantification are the simple procedures and highly accurate age estimation results. Whereas TaqMan quantification PCR (qPCR) is widely used for sjTREC quantification, SYBR qPCR assay is not routinely used for evaluating ethnic data. Therefore, we focused on the advantages of the SYBR qPCR assay, which is cheaper and simpler to set up than the TaqMan probe assay. In this study, we developed a SYBR qPCR assay for sjTREC quantification from bloodstains from a Japanese population and evaluated the strength of correlation between sjTREC levels and actual age. The results were obtained from 194 individuals ranging from 18 to 81 years old, and showed a negative correlation between sjTREC level and individual age (r =  -0.786). The equation for age estimation was Age =  -6.27 dCt (CtTBP - CtsjTREC) - 25.841 with standard error ±8.0 years. Furthermore, this formula for the SYBR assay can be applied to not only fresh bloodstains, but also whole blood and bloodstains up to 1 month old. These results indicate that SYBR qPCR is an effective method for age estimation from bloodstains, and its practicality and affordability make it an attractive sjTREC quantification technique.

The type III secretion system-dependent repression of NF-kappaB activation to the intracellular growth of Edwardsiella tarda in human epithelial cells.

Edwardsiella tarda is a pathogen with a broad host range infecting animals and humans. We have reported recently that the type III secretion system (TTSS) is essential for intracellular replication of the bacterium in murine macrophages. The present study shows that the TTSS is also needed for intracellular growth of the bacterium in human epithelial cells (HEp-2). However, different from the previous microarray analyses on murine macrophages, upregulation of the mRNA expression level of NF-kappaB target genes was not detected in the infected HEp-2 cells. The wild-type E. tarda, but not its TTSS mutant, actually repressed the tumor necrosis factor alpha-dependent NF-kappaB activation in an NF-kappaB reporter gene assay. These results suggest TTSS-dependent repression of the NF-kappaB activation in HEp-2 cells infected with E. tarda.

Base changes in the fliC gene of Edwardsiella tarda: possible effects on flagellation and motility.

Edwardsiella tarda is a broad host-range pathogen infecting both animals and humans. E. tarda isolates from red sea bream Pagrus major are non-motile, whereas isolates from Japanese eel Anguilla japonica and Japanese flounder Paralichthys olivaceus are motile with peritrichous flagella. We compared the fliC gene coding for flagellin (FliC) in motile and non-motile E. tarda strains isolated from diseased fish. Twenty-two amino acid residues differed in the predicted FliC amino acid sequences between non-motile and motile strains. There were no significant differences either in the upstream sequences regulating transcription of the fliC gene or in the fliC transcript levels between motile and non-motile strains. The predicted secondary structure of FliC in non-motile E. tarda differed from that of motile strains, and the modeled data suggested that the secondary structure may be the important factor responsible for non-flagellation in the non-motile strains.