Genotoxic potential of porphyrin type photosensitizers with particular emphasis on 5-aminolevulinic acid: implications for clinical photodynamic therapy

Photodynamic therapy (PDT) uses exogenously administered photosensitizers activated by light to induce cell death or modulation of immunological cascades, presumably via formation of reactive oxygen species (ROS). 5-Aminolevulinic acid (ALA) mediated photosensitization is increasingly used for the treatment of nonmelanoma skin cancer and other indications including benign skin disorders. Long-term side effects of this investigational modality are presently unknown. Just as tumor treatments such as ionizing radiation and chemotherapy can cause secondary tumor induction, PDT may potentially have a carcinogenic risk. Evaluation of the biological effects of ALA in absence of activating light and analysis of the mechanism of ALA-PDT and porphyrin-type photosensitizers mediated photosensitization indicate that this therapy has a pro-oxidant and genotoxic potential. However, porphyrin type molecules also possess antioxidant and antimutagenic properties. ALA-PDT delays photocarcinogenesis in mice, and topical ALA alone does not increase skin cancer incidence in these animals. Patients with increased tissue levels of ALA have an increased incidence of internal carcinoma, however, it is not clear whether this relationship is casual or causal. There is no evidence indicating higher rates of skin cancer in patients with photosensitivity diseases due to presence of high protoporphyrin IX (PP) levels in skin. Overall, the presently available data indicate that the risk for secondary skin carcinoma after topical ALA-PDT seems to be low, but further studies must be carried out to evaluate the carcinogenic risk of ALA-PDT in conditions predisposed to skin cancer.     

The Thermosensitive Potassium Channel TREK-1 Contributes to Coolness-Evoked Responses of Grueneberg Ganglion Neurons

Neurons of the Grueneberg ganglion (GG) residing in the vestibule of the murine nose are activated by cool ambient temperatures. Activation of thermosensory neurons is usually mediated by thermosensitive ion channels of the transient receptor potential (TRP) family. However, there is no evidence for the expression of thermo-TRPs in the GG, suggesting that GG neurons utilize distinct mechanisms for their responsiveness to cool temperatures. In search for proteins that render GG neurons responsive to coolness, we have investigated whether TREK/TRAAK channels may play a role; in heterologous expression systems, these potassium channels have been previously found to close upon exposure to coolness, leading to a membrane depolarization. The results of the present study indicate that the thermosensitive potassium channel TREK-1 is expressed in those GG neurons that are responsive to cool temperatures. Studies analyzing TREK-deficient mice revealed that coolness-evoked responses of GG neurons were clearly attenuated in these animals compared with wild-type conspecifics. These data suggest that TREK-1 channels significantly contribute to the responsiveness of GG neurons to cool temperatures, further supporting the concept that TREK channels serve as thermoreceptors in sensory cells. Moreover, the present findings provide the first evidence of how thermosensory GG neurons are activated by given temperature stimuli in the absence of thermo-TRPs.     

Transgenic Melon and Squash Expressing Coat Protein Genes of Aphid-borne Viruses do not Assist the Spread of an Aphid Non- transmissible Strain of Cucumber Mosaic Virus in the Field

Transgenic melon and squash containing the coat protein (CP) gene of the aphid transmissible strain WL of cucumber mosaic cucumovirus (CMV) were grown under field conditions to determine if they would assist the spread of the aphid non-transmissible strain C of CMV, possibly through heterologous encapsidation and recombination. Transgenic melon were susceptible to CMV strain C whereas transgenic squash were resistant although the latter occasionally developed chlorotic blotches on lower leaves. Transgenic squash line ZW-20, one of the parents of commercialized cultivar Freedom II, which expresses the CP genes of the aphid transmissible strains FL of zucchini yellow mosaic (ZYMV) and watermelon mosaic virus 2 (WMV 2) potyviruses was also tested. Line ZW-20 is resistant to ZYMV and WMV 2 but is susceptible to CMV. Field experiments conducted over two consecutive years showed that aphid-vectored spread of CMV strain C did not occur from any of the CMV strain C-challenge inoculated transgenic plants to any of the uninoculated CMV-susceptible non- transgenic plants. Although CMV was detected in 3% (22/764) of the uninoculated plants, several assays including ELISA, RT- PCR-RFLP, identification of CP amino acid at position 168, and aphid transmission tests demonstrated that these CMV isolates were distinct from strain C. Instead, they were non-targeted CMV isolates that came from outside the field plots. This is the first report on field experiments designed to determine the potential of transgenic plants expressing CP genes for triggering changes in virus-vector specificity. Our results indicate that transgenic plants expressing CP genes of aphid transmissible strains of CMV, ZYMV, and WMV 2 are unlikely to mediate the spread of aphid non-transmissible strains of CMV. This finding is of practical relevance because transgenic crops expressing the three CP genes are targeted for commercial release, and because CMV is economically important, has a wide host range, and is widespread worldwide.     

New services of the EMBL Data Library.

The existing services of the EMBL Data Library for external users have been improved and extended in several ways. The EMBL File Server has been reorganised, and many new databases and other information relevant to biologists are now accessible via global computer networks. A broad range of software for molecular biology is freely available for different popular computer systems, including the EMBL enhancements to the Wisconsin (GCG) Package. The new Mail-Quicksearch and Mail-FastA services give access to the latest sequence data for database searches by ordinary electronic mail.     

Directed evolution of Aspergillus niger glucoamylase to increase thermostability

Using directed evolution and site‐directed mutagenesis, we have isolated a highly thermostable variant of Aspergillus niger glucoamylase (GA), designated CR2‐1 . CR2‐1 includes the previously described mutations Asn20Cys and Ala27Cys (forming a new disulfide bond), Ser30Pro, Thr62Ala, Ser119Pro, Gly137Ala, Thr290Ala, His391Tyr and Ser436Pro. In addition, CR2‐1 includes several new putative thermostable mutations, Val59Ala, Val88Ile, Ser211Pro, Asp293Ala, Thr390Ser, Tyr402Phe and Glu408Lys, identified by directed evolution. CR2‐1 GA has a catalytic efficiency (k_cat/K_m) at 35°C and a specific activity at 50°C similar to that of wild‐type GA. Irreversible inactivation tests indicated that CR2‐1 increases the free energy of thermoinactivation at 80°C by 10 kJ mol^?1 compared with that of wild‐type GA. Thus, CR2‐1 is more thermostable (by 5 kJ mol^?1 at 80°C) than the most thermostable A. niger GA variant previously described, THS8 . In addition, Val59Ala and Glu408Lys were shown to individually increase the thermostability in GA variants by 1 and 2 kJ mol^?1, respectively, at 80°C.     

Deposition of Sodium Metal at the Copper-NaSICON Interface for Reservoir-Free Solid-State Sodium Batteries

“Anode-free” solid-state battery concepts are explored extensively as they promise a higher energy density with less material consumption and simple anode processing. Here, the homogeneous and uniform electrochemical deposition of alkali metal at the interface between current collector and solid electrolyte plays the central role to form a metal anode within the first cycle. While the cathodic deposition of lithium has been studied intensively, knowledge on sodium deposition is scarce. In this work, dense and uniform sodium layers of several microns thickness are deposited at the Cu|Na_3.4Zr₂Si_2.4P_0.6O₁₂ interface with high reproducibility. At current densities of ≈1 mA∙cm⁻², relatively uniform coverage is achieved underneath the current collector, as shown by electrochemical impedance spectroscopy and 3D confocal microscopy. In contrast, only slight variations of the coverage are observed at different stack pressures. Early stages of the sodium metal growth are analyzed by in situ transmission electron microscopy revealing oriented growth of sodium. The results demonstrate that reservoir-free (“anode-free”) sodium-based batteries are feasible and may stimulate further research efforts in sodium-based solid-state batteries.     

Weiteres zur Keimungsphysiologie von Puccinia graminis tritici (Pers.) Erickss. u. Henn.

Ohne Zusammenfassung     

Zur Methodik der Züchtung auswuchsfesten Getreides

Ohne Zusammenfassung