Gamma radiolysis of ceftriaxone sodium for water treatment: assessments of the activity.

As large quantities of antibiotics have been misused in human and veterinary medicine, many different classes of antibiotics with low concentration have been detected in the environmental water. This existence may cause severe ecosystem alterations. Ceftriaxone sodium was employed as the targeted antibiotic to evaluate gamma radiolysis of antibiotics based on the primary elimination test and activity assay. The decomposition percentage of ceftriaxone sodium (20 microg/ml) in purified water increases with increasing doses and reaches 98% under 5 kGy of gamma radiation. The residual activity after gamma radiation does not follow the corresponding decomposition percentage of ceftriaxone sodium. Liquid chromatography and mass spectrometry (LC-MS) was subsequently employed to analyze possible structures of radiolytic products relating to the activity. Different degrees of the residual activity may attribute to different cleavage pathways of ceftriaxone sodium produced by radiation with different doses. The results indicate that the radiolytic treatment is a highly-effective means for degradation of ceftriaxone sodium, and the activity status of ceftriaxone sodium after primary elimination should be taken into consideration for selecting a degrading dose. Three kGy is the appropriate dose for radiolysis of ceftriaxone sodium in purified water.

[Lysogenic infection of a Shiga toxin 2-converting bacteriophage changes host gene expression, enhances host acid resistance and motility].

Shiga toxin 2 (Stx2)-converting bacteriophages can infect and lysogenize other bacteria in vivo and in vitro, and, thus, contribute to a genotypic heterogeneity of infected host. However, the global transcription patterns accompanying the lysogenic infection of E. coli host have not been clearly resolved. In this study, gene expression profiles of Stx2 phage phi Min27(delta stx::cat) converted and native E. coli MG1655 hosts were compared using microarray assay. The phi Min27(delta stx::cat) conversion had a direct effect on the global expression of bacterial host genes as 166 genes were found to be differentially expressed (104 up-regulated and 62 downregulated). These genes were predominantly responsible for bacterial central metabolism, transport and transcription. It was shown that in addition to the down-regulation of genes involved in synthesis of thiamine and protein transporters, expression of genes associated with bacterial energy production (e.g., fadABDEHIJL, aceK, and acnA) was also suppressed. Conversely, most up-regulated genes were transport genes, flagellar synthesis genes (fliDESTZ), and acid resistance genes (e.g., gadEW, hdeABD, and adiY). Futhermore, conversion of phi Min27(delta stx::cat) was shown to change physiological properties of the host cell. In comparison with the uninfected cells the converted bacteria host had increased acid tolerance and promoted swimming motility on a semisolid agar surface.

Stimulation by epidermal growth factor of phospholipid methyltransferase in isolated rat hepatocytes.

Epidermal growth factor produces a time- and dose-dependent activation of phospholipid methyltransferase activity in hepatocytes isolated from juvenile and mature hepatectomized rats. This treatment however has no effect with hepatocytes isolated from mature or laparotomized rats. Dansylcadaverine (50 microM), an inhibitor of receptor-mediated internalization of epidermal growth factor, has no effect on basal phospholipid methyltransferase but inhibits the stimulation of this enzyme by epidermal growth factor. These results indicate a possible role of phospholipid methylation during liver proliferation.