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The Xmrk oncogene involved in melanoma formation in the fish Xiphophorus was formed relatively recently by duplication of the epidermal growth factor co-orthologue egfrb. In the platyfish X. maculatus, Xmrk is located close to the major sex-determining locus in a subtelomeric region of the X and Y sex chromosomes that frequently undergoes duplications and other rearrangements. This region accumulates repetitive sequences: more than 80% of the 33-kb region 3' of Xmrk is constituted by retrotransposable elements. The high degree of nucleotide identity between X- and Y-linked sequences and the rarity of gonosome-specific rearrangements indicated that the instability observed was not a manifestation of gonosome-specific degeneration. Seven other duplicated genes were found, all corresponding, in contrast to Xmrk, to pseudogenes (nonfunctionalization). Functional persistence of Xmrk in a highly unstable region in divergent Xiphophorus species suggests a beneficial function under certain conditions for this dispensable and potentially injurious gene.  相似文献   
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Riboflavin (vitamin B2), essential in tiny amounts as a precursor for oxidoreductase coenzymes, is a yellow pigment. Although it causes cytotoxicity via photoinduced damage of macromolecules, several microorganisms are striking overproducers. A question, unanswered for decades, is whether riboflavin overproducers can benefit from this property. Here, we report an ultraviolet (UV) protective effect of riboflavin. The spores of Ashbya gossypii , a riboflavin-overproducing fungus, are more sensitive to UV than those of Aspergillus nidulans . The addition of riboflavin to suspensions improves the UV resistance of both spore types. Interestingly, we show that regulation of sporulation and riboflavin overproduction in A. gossypii are linked. In batch culture, both were elevated when growth ceased. At constant growth rates, obtained in a chemostat culture, neither was elevated. Supplementation of cultures by cAMP, a known stress signal, negatively affected sporulation as well as riboflavin overproduction, establishing a second, independent argument for the linkage.  相似文献   
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In this study, we have demonstrated that the critical hydrogen bonding motif of the established 3-aminopyrazinone thrombin inhibitors can be effectively mimicked by a 2-aminopyridine N-oxide. As this peptidomimetic core is more resistant toward oxidative metabolism, it also overcomes the metabolic liability associated with the pyrazinones. An optimization study of the P(1) benzylamide delivered the potent thrombin inhibitor 21 (K(i) = 3.2 nM, 2xaPTT = 360 nM), which exhibited good plasma levels and half-life after oral dosing in the dog (C(max) = 2.6 microM, t(1/2) = 4.5 h).  相似文献   
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There is a lack of studies that analyze the association between micronutrient-related biomarker status and physical fitness in adolescents. In the present study, biochemical parameters for iron and vitamin status were studied, along with objective measures of physical fitness in healthy male and female European adolescents. One thousand eighty-nine adolescents (580 girls, 12.5-17.5 yr) from the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) cross-sectional study were included. Hierarchical linear models were performed to determine the associations between micronutrient biomarkers and physical fitness. Age, seasonality, latitude, body mass index, menarche (in girls), and physical activity were used as covariates. For cardiorespiratory fitness, concentrations of hemoglobin, retinol, and vitamin C in male adolescents and β-carotene and 25(OH)D in female adolescents were associated with maximal oxygen consumption. For muscular fitness, concentrations of hemoglobin, β-carotene, retinol, and α-tocopherol in male adolescents and β-carotene and 25(OH)D in female adolescents were associated with better performance of the standing long jump test. In summary, concentrations of hemoglobin and most antioxidant vitamins in male adolescents and β-carotene and 25(OH)D in female adolescents were positively associated with cardiorespiratory and muscular fitness, after controlling for relevant confounders. The associations between physical fitness and iron or vitamin status observed in this cross-sectional study in adolescents should be followed up by a study specifically designed to evaluate causal relationships.  相似文献   
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Difficulty in accessing high quality reference materials has been a limiting factor in the advancement of archaeobotanical research. However, new developments in online open source content management technology and faster downloading capabilities make high quality and low cost dynamic online curation of archaeobotanical reference images increasingly feasible. We describe the establishment of Paleobot.org, an open access online reference collection database for macrobotanical, microbotanical and isotopic data to help standardize and improve the identification of archaeobotanical remains.  相似文献   
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Sb‐doped SnO2 (ATO) is used as an alternative support material to replace carbon in the highly corrosive environment of a fuel cell cathode. Two ATO powders with different morphologies are decorated with Pt nanoparticles and afterwards used as the cathode catalyst. The commercial ATO powder exhibits crystallites in the nanometer range, while the home‐made ATO powder, which was synthesized by ultrasonic spray pyrolysis, consists of polycrystalline hollow spheres. The spheres have diameters in the micrometer range and are composed of individual nanocrystallites. The unusual morphology of the home‐made ATO offers nano‐ and microporosity at the same time and opens up new possibilities for the controlled design of electrode structures in low‐temperature polymer electrolyte fuel cells. Both materials are characterized by XRD, SEM, and TEM and tested in a single cell set‐up. While almost no current is gained from the membrane electrode assembly with the commercial ATO support, the cell with the home‐made ATO achieves a mediocre performance. This higher activity, however, is obtained with approximately half the Pt content compared to the catalyst with the commercial support. The different behaviours of both ATO powders can therefore mainly be attributed to differences in the specific support morphology.  相似文献   
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The anti-murine CD40L monoclonal antibody MR1 has been widely used in immunology research to block the CD40-CD40L interaction for induction of transplantation tolerance and to abrogate autoimmune diseases. The availability of recombinant CD40L with high binding capacity for MR1 would provide a valuable immunologic research tool. In this study, we constructed the single chain murine soluble CD40L monomer, dimer, trimer and successfully expressed them in yeast Pichia pastoris under the control of the alcohol oxidase promoter. The secreted single chain murine soluble CD40L monomers, dimers, and trimers were initially enriched through histidine tag capture by Ni-Sepharose 6 fast flow resin and further purified on a cation exchange resin. Purity reached more than 95% for the monomer and dimer forms and more than 90% for the trimer. Protein yield following purification was 16 mg/L for the monomer and dimer, and 8 mg/L for the trimer. ELISA analysis demonstrated that the CD40L dimers and trimers correctly folded in conformations exposing the MR1 antigenic determinant.  相似文献   
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