Retrotransposable elements in the Dictyostelium discoideum genome

Repetitive DNA is a major component of any living cell. In eukaryotes retrotransposable elements make up several percent of the genome size, and consequently, retroelements are often identified in experiments aimed at establishing physical maps and whole genome sequences. In this review, recent progress in the characterization of retrotransposable elements in the genome of the eukaryotic mi croorganism Dictyostelium discoideum is summarized with a focus on retroelements which integrate near transfer RNA genes with intriguing position specificity. Received 21 November 1997; received after revision 6 January 1998; accepted 6 January 1998     

Preface:Recent Developments in Semantic Web

<正>The World Wide Web (WWW) has revolutionized many aspects of society in the past two decades.Emerging applications of the World Wide Web have not only fostered industrial     

Predicting weather and climate: Uncertainty,ensembles and probability

Simulation-based weather and climate prediction now involves the use of methods that reflect a deep concern with uncertainty. These methods, known as ensemble prediction methods, produce multiple simulations for predictive periods of interest, using different initial conditions, parameter values and/or model structures. This paper provides a non-technical overview of current ensemble methods and considers how the results of studies employing these methods should be interpreted, paying special attention to probabilistic interpretations. A key conclusion is that, while complicated inductive arguments might be given for the trustworthiness of probabilistic weather forecasts obtained from ensemble studies, analogous arguments are out of reach in the case of long-term climate prediction. In light of this, the paper considers how predictive uncertainty should be conveyed to decision makers.     

High-pressure storage of hydrogen fuel: ammonia borane and its related compounds

As a promising candidate material for hydrogen storage, ammonia borane（NH3BH3） has attracted significant interest in recent years due to its remarkably high hydrogen content. Subjecting this material to high pressure not only enables the formation of novel phases and compounds with exotic properties, but also improves our basic understanding of material’s behavior at different levels of atomic and molecular interactions. This review focuses on the perspective of high-pressure chemical hydrogen storage related to NH3BH3-based materials. Four main aspects are discussed： the structures and bonding of NH3BH3 over a wide pressure–temperature space, thermolysis of NH3BH3 at high pressure, the formation of a novel high-pressure H-rich compound as a result of storage of additional molecular H2 in NH3BH3, and the potential rehydrogenation of the thermally decomposed NH3BH3 under the extreme of pressure.     

Peritoneal dialysis in small laboratory animals

Summary Healthy rats and guinea-pigs were treated with a simple method of continuous peritoneal dialysis for 12, 24 and 48 h. Increasing with time, both animal species developed severe hypoproteinemia and hemoconcentration due to protein loss into the dialyzate fluid. These changes were associated with a high mortality rate, when Sterofundin^® was used for dialysis. Therefore, protein loss should be substituted and the type of dialyzate must be considered in experimental long-term dialysis using these small laboratory animals.Supported by Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg, La 369/1.Acknowledgment. Our thanks are due to Jutta Otto and Ulrich Oberdieck for expert technical assistance.     

Imprinting on distal chromosome 7 in the placenta involves repressive histone methylation independent of DNA methylation

Imprinted genes are expressed from only one of the parental chromosomes and are marked epigenetically by DNA methylation and histone modifications. The imprinting center 2 (IC2) on mouse distal chromosome 7 is flanked by several paternally repressed genes, with the more distant ones imprinted exclusively in the placenta. We found that most of these genes lack parent-specific DNA methylation, and genetic ablation of methylation does not lead to loss of their imprinting in the trophoblast (placenta). The silent paternal alleles of the genes are marked in the trophoblast by repressive histone modifications (dimethylation at Lys9 of histone H3 and trimethylation at Lys27 of histone H3), which are disrupted when IC2 is deleted, leading to reactivation of the paternal alleles. Thus, repressive histone methylation is recruited by IC2 (potentially through a noncoding antisense RNA) to the paternal chromosome in a region of at least 700 kb and maintains imprinting in this cluster in the placenta, independently of DNA methylation. We propose that an evolutionarily older imprinting mechanism limited to extraembryonic tissues was based on histone modifications, and that this mechanism was subsequently made more stable for use in embryonic lineages by the recruitment of DNA methylation.     

A common genetic variant in the NOS1 regulator NOS1AP modulates cardiac repolarization

Extremes of the electrocardiographic QT interval, a measure of cardiac repolarization, are associated with increased cardiovascular mortality. We identified a common genetic variant influencing this quantitative trait through a genome-wide association study on 200 subjects at the extremes of a population-based QT interval distribution of 3,966 subjects from the KORA cohort in Germany, with follow-up screening of selected markers in the remainder of the cohort. We validated statistically significant findings in two independent samples of 2,646 subjects from Germany and 1,805 subjects from the US Framingham Heart Study. This genome-wide study identified NOS1AP (CAPON), a regulator of neuronal nitric oxide synthase, as a new target that modulates cardiac repolarization. Approximately 60% of subjects of European ancestry carry at least one minor allele of the NOS1AP genetic variant, which explains up to 1.5% of QT interval variation.