Electrochemical detection of the toxic dinoflagellate Alexandrium ostenfeldii with a DNA-biosensor

The steady rise of observations of harmful or toxic algal blooms throughout the world in the past decades constitute a menace for coastal ecosystems and human interests. As a consequence, a number of programs have been launched to monitor the occurrence of harmful and toxic algae. However, the identification is currently done by microscopic examination, which requires a broad taxonomic knowledge, expensive equipment and is very time consuming. In order to facilitate the identification of toxic algae, an inexpensive and easy-to-handle DNA-biosensor has been adapted for the electrochemical detection of the toxic dinoflagellate Alexandrium ostenfeldii. The detection of the toxic algae is based on a sandwich hybridisation, which is carried out on a disposable sensor chip. A set of two probes for the species specific identification of A. ostenfeldii was developed. The specificity of the probes could be shown in dot-blot hybridisation and with the DNA-biosensor. The sensitivity of the DNA-biosensor was optimised with respect to hybridisation temperature and NaCl-concentration and a significant increase of the sensitivity of the DNA-biosensor could be obtained by a fragmentation of the rRNA prior to the hybridisation and by adding a helper oligonucleotide, which binds in close proximity to the probes to the hybridisation

Toxic effects and mechanisms of action of renal cancerogenic substances in vitro

The natural compounds Aristolochic Acid (AA), Ochratoxin A (OTA) and Cycasin are nephrotoxic and carcinogenic in rodents. AA and OTA exposure in humans are known and human exposure to Cycasin is suspected. Despite exposure, toxic effects in humans are only proven for AA. However, the observed effects of the genotoxic substance AA in humans were different to those seen in rodents, suggesting a species-specific mechanism of action. In vitro-models could serve as a powerful tool to evaluate species-specific toxicity. Especially the use of human primary cells could enable characterisation and evaluation of possible human-specific effects.It was postulated, that in vitro-systems, in addition to in vivo-Studies, are a valuable tool to investigate species-specific toxicity of AA, OTA and Cycasin. The aim of the study was to examine the susceptibility of different kidney cortex cell models (continuous cell lines, primary cells) to the toxin in question and therefore their value for studying species-specific effects.In this study, the cytotoxicity of AA, OTA and MAMAc was evaluated and used for a pre-selection of cells (cell line, primary cells) sufficiently susceptible to the toxin in question. Furthermore, effects of the genotoxic compounds AA and MAMAc on the cell cycle and the induction of DNA-strand breaks and DNA-repair were examined. Finally, the effects of AA and OTA on gene-expression were studied.Cytotoxic response was generally higher in primary cells as in the corresponding cells lines, possibly reflecting the higher status of differentiation in primary cells. The observed reduction of cell proliferation and the observed induction of cdkn1a-gene-expression indicate a genotoxic effect of AA in vitro, which seems to reflect sufficient susceptibility of the used cell model. In contrast to this, AA and OTA had only a small effect on gene-expression. However, the low degree of deregulation as well as the small number of deregulated genes could be a result of the low toxin concentrations used. Nevertheless, deregulation of toxin-relevant genes was observed. In this study, species-specific differences in cytotoxicity of AA and MAMAc were shown, with toxicity being highest in kidney cortex cells of porcine origin. These results are in accordance with prior results, showing metabolic activation of AA to be species-dependent, with minipigs having the most effective activation system followed by human and rat. Although cytotoxicity assays can not allow discrimination of distinctive mechanistic responses, it is suspected that the description of constitutive differences in the susceptibility of cells originating of different species can be achieved.From this study, primary kidney cortex cells appear to be a valuable tool to investigate the toxicity of AA, OTA and Cycasin. Furthermore, human primary cells seem to be useful for the evaluation of possible human-specific effects. However, the availability and quality of biopsy material from primary care facilities for the establishment of primary human cell culture is highly variable and commercially available cells are expensive. Given the genetic proximity of human and pigs and the anatomical and physiological similarity of the kidneys, future direction should therefore consider the use of primary porcine cell models as an alternative system

Verfahren zum strukturierten Aufbringen einer thermoplastischen Paste auf ein Substrat und dessen Verwendung

DE1004056492 B UPAB: 20060825 NOVELTY - The method involves exhibiting a temperature by a printing block, at which the paste is fluid so that the paste flows into a recess and releases from the recess during transfer of a transfer medium (3). The medium exhibits another temperature, at which the paste takes up a dimensionally stable state. The substrate exhibits third temperature, at which the paste is transferred from the medium to the substrate and the paste remains stable. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for an application for the method for structured application of a metal contained thermoplastic paste on a substrate. USE - Used for structured application of a metal contained thermoplastic paste on a substrate (claimed). Can also be used for superimposing metallic contacts, electrical conducting, dielectric or electrical isolating structures on an uneven substrate surfaces in the thick film technologies, and for super imposing electrical conducting contacts and structures on solar cells. ADVANTAGE - The method enables to provide improved transmission of the metal contained thermoplastic paste on the substrate, in the context of the pad printing or indirect applied on the thickfilm technology and gravure printing. The method enables to superimpose fine contact structure on the substrate. The method enables to achieve the contact structure breadth of below 50 micrometer and thickness of more than two micrometer

Screen-printed epitaxial silicon thin-film solar cells with 13.8% efficiency

Amidst the different silicon thin-film systems, the epitaxial thin-film solar cell represents an approach with interesting potential. Consisting of a thin active c-Si layer grown epitaxially on top of a low-quality c-Si substrate, it can be implemented into solar cell production lines without major changes in the current industrial process sequences. Within this work, 30-m-thick epitaxial layers on non-textured and highly doped monocrystalline Czochralski (Cz) and multicrys talline (mc) Si substrates have been prepared by CVD. Confirmed efficiencies of 138% on Cz and 123% on mc-Si substrates have been achieved by applying an industrial process scheme based on tube and in-line phosphorus diffusion, as well as screen-printed front and back contacts fired through a SiNx anti-reflection coating. An extensive solar cell characterisation, including infrared lock-in therm ography and spectral response measurements is presented

Microstructural analysis of Ag thick-film contacts on n-type silicon emitters

The microstructural properties of Ag thick-film contacts on P diffused [100] Si wafers are investigated. By transmission electron microscopy, the contact interface is ound to be composed of mostly 100-500 nm sized Ag crystallites penetrating into the si on average up to 100 nm. The crystallites are mostly in epitaxial relation with Si, indicating their growth from the glass frit melt. A quasi continuous glassy layer is present between the crystallites and the Ag grains forming the contact bulk. Conductive atomic force microscopy on cross sections shows that the interface crystallites form a low contact resistivity with the Si emitter below 2x10 7 Gcm2. The measurements indicate selective current paths across the interface via few isolated Ag crystallites. In-plane atomic force microscopy on Si after contact removal confirms the statistical nature of the interface and an improved contact uniformity in case of firing through processes

Species-specific Toxicity of Aristolochic Acid (AA) in vitro

Differences in toxicity and carcinogenicity of the nephrotoxic compound aristolochic acid between rodents and humans suggest a species-dependent mechanism of action. The goal of this study was to investigate constitutive differences in the susceptibility of renal cortex cells originating from human, rat and porcine origin in vitro. Effects of 24 and 48 h AA exposure on cell number and MTT reduction were studied. Furthermore, using the effective concentrations causing 20 and 50 % reduction (cell number), cell cycle, 3H-thymidine incorporation and DNA damage analyses were conducted. AA cytotoxicity was observed in all cell types in a time- and concentration dependent manner with species-specific differences, with porcine cells being the most sensitive. AA had a comparable effect on the cell cycle in primary human and porcine cells and the rat NRK-52E cell line following 48 h exposure, also corroborated by the reduced 3H-thymidine incorporation in NRK-52E cells. In addition, DNA unwinding, suggestive of enhanced DNA damage, was observed in primary porcine cells. These results provide an initial insight into the sensitivity and suitability of different in vitro-systems and suggest that primary porcine renal cortex cells could be a valuable in vitro-system to study AA toxicit