Dermal xenobiotic metabolism: a comparison between native human skin, four in vitro skin test systems and a liver system.

The xenobiotic metabolism of 4 in vitro human skin test systems (2D and 3D) was compared with that of the native human skin samples from which the skin test systems had been produced. In total 3 skin samples were investigated, each from a different donor to exclude variability due to gender, donor or tissue supplier. In addition, the skin cultures were compared with a surrogate of the liver. Basal and induced phase I and phase II enzymes were analyzed regarding gene/protein expression as well as enzyme activity. The distinctions between the different test systems and the two dermal compartments (epidermis and dermis) were more noticeable than any donor variability. The 3D models of skin and liver mirrored the in vivo situation more realistically than did the monolayer cultures. Phase I metabolism was more pronounced in the hepatic model, whereas phase II metabolism was more prominent in the reconstructed skin. These results show that reconstructed skin models are a valuable tool for organ-specific safety assessment with regard to xenobiotic metabolism.

THz triangulation and stand-off measurement of the refractive index.

We have constructed a pulsed THz imaging system based on the triangulation method. The system is capable of stand-off measurements, especially of retrieving the refractive index in a non-tactile manner even if the thickness of the object is unknown. The distance between emitter and imaged object for the presented measurements was 1.3m. We have measured a variety of samples in order to determine the capabilities and to optimize the optical properties of the instrument.

A pulsed THz imaging system with a line focus and a balanced 1-D detection scheme with two industrial CCD line-scan cameras.

We present a pulsed THz Imaging System with a line focus intended to speed up measurements. A balanced 1-D detection scheme working with two industrial line-scan cameras is used. The instrument is implemented without the need for an amplified laser system, increasing the industrial applicability. The instrumental characteristics are determined.

Phylogenomics of the reproductive parasite Wolbachia pipientis wMel: a streamlined genome overrun by mobile genetic elements.

The complete sequence of the 1,267,782 bp genome of Wolbachia pipientis wMel, an obligate intracellular bacteria of Drosophila melanogaster, has been determined. Wolbachia, which are found in a variety of invertebrate species, are of great interest due to their diverse interactions with different hosts, which range from many forms of reproductive parasitism to mutualistic symbioses. Analysis of the wMel genome, in particular phylogenomic comparisons with other intracellular bacteria, has revealed many insights into the biology and evolution of wMel and Wolbachia in general. For example, the wMel genome is unique among sequenced obligate intracellular species in both being highly streamlined and containing very high levels of repetitive DNA and mobile DNA elements. This observation, coupled with multiple evolutionary reconstructions, suggests that natural selection is somewhat inefficient in wMel, most likely owing to the occurrence of repeated population bottlenecks. Genome analysis predicts many metabolic differences with the closely related Rickettsia species, including the presence of intact glycolysis and purine synthesis, which may compensate for an inability to obtain ATP directly from its host, as Rickettsia can. Other discoveries include the apparent inability of wMel to synthesize lipopolysaccharide and the presence of the most genes encoding proteins with ankyrin repeat domains of any prokaryotic genome yet sequenced. Despite the ability of wMel to infect the germline of its host, we find no evidence for either recent lateral gene transfer between wMel and D. melanogaster or older transfers between Wolbachia and any host. Evolutionary analysis further supports the hypothesis that mitochondria share a common ancestor with the alpha-Proteobacteria, but shows little support for the grouping of mitochondria with species in the order Rickettsiales. With the availability of the complete genomes of both species and excellent genetic tools for the host, the wMel-D. melanogaster symbiosis is now an ideal system for studying the biology and evolution of Wolbachia infections.

Enantioselective, intermolecular [2+2] photocycloaddition reactions of 3-acetoxyquinolone: total synthesis of (-)-pinolinone.

The natural product (-)-pinolinone was synthesised via a concise route (six steps, 17% overall yield) from 3-acetoxyquinolone, employing an enantioselective intermolecular [2+2] photocycloaddition as the key step.

Enantioselectivity in visible light-induced, singlet oxygen [2+4] cycloaddition reactions (type II photooxygenations) of 2-pyridones.

3-Substituted 2-pyridones were enantioselectively (68-90% ee) converted into the respective 3-hydroxypyridine-2,6-diones by a sequence consisting of a template-mediated type II photooxygenation and an acid-catalysed rearrangement.

Increased expression of catalase in human hepatoma cells by the soy isoflavone, daidzein.

The reduced incidence of cancer that has been observed in Asian population traditionally consuming soy-based food has been linked to the antioxidant potential of soy isoflavones, in particular daidzein and genistein. The present study was undertaken in order to test the antioxidative potential of daidzein and to examine the effect of daidzein treatment on the expression of the antioxidant enzyme catalase in the human hepatoma cell lines Huh-7 and HepG2. Daidzein itself did not display radical scavenging activity but it significantly increased the activity of the antioxidant enzyme catalase. Huh-7 cells were much more susceptible to daidzein cytotoxicity than HepG2 cells and showed much lower basal activity in luciferase reporter gene assays with the 3.2 kb fragment of the human catalase promoter. However, treatment with daidzein at a non-toxic concentration resulted in a similar induction of promoter activity in both cell lines. Reporter gene studies with different promoter constructs in HepG2 cells restrict the potential localization of the main regulatory elements for basal and inducible activity of the catalase promoter to a region approximately 120 bp to 300 bp upstream of the start codon of the catalase gene. From our results, we conclude that in human hepatoma cells daidzein at a non-toxic concentration increases the activity of human catalase and induces the transcription of the catalase gene via interaction with the proximal part of the promoter.

A genome phylogeny for mitochondria among alpha-proteobacteria and a predominantly eubacterial ancestry of yeast nuclear genes.

Analyses of 55 individual and 31 concatenated protein data sets encoded in Reclinomonas americana and Marchantia polymorpha mitochondrial genomes revealed that current methods for constructing phylogenetic trees are insufficiently sensitive (or artifact-insensitive) to ascertain the sister of mitochondria among the current sample of eight alpha-proteobacterial genomes using mitochondrially-encoded proteins. However, Rhodospirillum rubrum came as close to mitochondria as any alpha-proteobacterium investigated. This prompted a search for methods to directly compare eukaryotic genomes to their prokaryotic counterparts to investigate the origin of the mitochondrion and its host from the standpoint of nuclear genes. We examined pairwise amino acid sequence identity in comparisons of 6,214 nuclear protein-coding genes from Saccharomyces cerevisiae to 177,117 proteins encoded in sequenced genomes from 45 eubacteria and 15 archaebacteria. The results reveal that approximately 75% of yeast genes having homologues among the present prokaryotic sample share greater amino acid sequence identity to eubacterial than to archaebacterial homologues. At high stringency comparisons, only the eubacterial component of the yeast genome is detectable. Our findings indicate that at the levels of overall amino acid sequence identity and gene content, yeast shares a sister-group relationship with eubacteria, not with archaebacteria, in contrast to the current phylogenetic paradigm based on ribosomal RNA. Among eubacteria and archaebacteria, proteobacterial and methanogen genomes, respectively, shared more similarity with the yeast genome than other prokaryotic genomes surveyed.