779 research outputs found

    Rain, power laws, and advection

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    Localized rain events have been found to follow power-law size and duration distributions over several decades, suggesting parallels between precipitation and seismic activity [O. Peters et al., PRL 88, 018701 (2002)]. Similar power laws are generated by treating rain as a passive tracer undergoing advection in a velocity field generated by a two-dimensional system of point vortices.Comment: 7 pages, 4 figure

    Acute Loss of Iron-Sulfur Clusters Results in Metabolic Reprogramming and Generation of Lipid Droplets in Mammalian Cells

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    Iron–sulfur (Fe-S) clusters are ancient cofactors in cells and participate in diverse biochemical functions, including electron transfer and enzymatic catalysis. Although cell lines derived from individuals carrying mutations in the Fe-S cluster biogenesis pathway or siRNA-mediated knockdown of the Fe-S assembly components provide excellent models for investigating Fe-S cluster formation in mammalian cells, these experimental strategies focus on the consequences of prolonged impairment of Fe-S assembly. Here, we constructed and expressed dominant–negative variants of the primary Fe-S biogenesis scaffold protein iron–sulfur cluster assembly enzyme 2 (ISCU2) in human HEK293 cells. This approach enabled us to study the early metabolic reprogramming associated with loss of Fe-S–containing proteins in several major cellular compartments. Using multiple metabolomics platforms, we observed a ∼12-fold increase in intracellular citrate content in Fe-S–deficient cells, a surge that was due to loss of aconitase activity. The excess citrate was generated from glucose-derived acetyl-CoA, and global analysis of cellular lipids revealed that fatty acid biosynthesis increased markedly relative to cellular proliferation rates in Fe-S–deficient cells. We also observed intracellular lipid droplet accumulation in both acutely Fe-S–deficient cells and iron-starved cells. We conclude that deficient Fe-S biogenesis and acute iron deficiency rapidly increase cellular citrate concentrations, leading to fatty acid synthesis and cytosolic lipid droplet formation. Our findings uncover a potential cause of cellular steatosis in nonadipose tissues

    Pitfalls in mutational testing and reporting of common KIT and PDGFRA mutations in gastrointestinal stromal tumors

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    <p>Abstract</p> <p>Background</p> <p>Mutation analysis of <it>KIT </it>and <it>PDGFRA </it>genes in gastrointestinal stromal tumors is gaining increasing importance for prognosis of GISTs and for prediction of treatment response. Several groups have identified specific mutational subtypes in <it>KIT </it>exon 11 associated with an increased risk of metastatic disease whereas GISTs with <it>PDGFRA </it>mutations often behave less aggressive. Furthermore, in advanced GIST disease with proven <it>KIT </it>exon 9 mutation the doubled daily dose of 800 mg imatinib increases the progression free survival and is now recommended both in the European and the American Guidelines. In Germany, there are still no general rules how to perform mutational analysis.</p> <p>Methods</p> <p>When comparing results from six different molecular laboratories we recognized the need of standardisation. Six German university laboratories with experience in mutation analysis in GISTs joined together to develop recommendations for the mutation analysis of the most common and clinically relevant hot spots, i. e. <it>KIT </it>exons 9 and 11 and <it>PDGFRA </it>exon 18. We performed a three-phased interlaboratory trial to identify pitfalls in performing molecular analysis in GISTs.</p> <p>Results</p> <p>We developed a design for a continuous external laboratory trial. In 2009 this external trial was conducted by 19 laboratories via the initiative for quality assurance in pathology (QuiP) of the German Society of Pathology and the Professional Association of German Pathologists.</p> <p>Conclusions</p> <p>By performing a three-phased internal interlaboratory trial and conducting an external trial in Germany we were able to identify potential pitfalls when performing KIT and PDGFRA mutational analysis in gastrointestinal stromal tumors. We developed standard operation procedures which are provided with the manuscript to allow other laboratories to prevent these pitfalls.</p

    Agency, Values, and Well-Being: A Human Development Model

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    This paper argues that feelings of agency are linked to human well-being through a sequence of adaptive mechanisms that promote human development, once existential conditions become permissive. In the first part, we elaborate on the evolutionary logic of this model and outline why an evolutionary perspective is helpful to understand changes in values that give feelings of agency greater weight in shaping human well-being. In the second part, we test the key links in this model with data from the World Values Surveys using ecological regressions and multi-level models, covering some 80 societies worldwide. Empirically, we demonstrate evidence for the following sequence: (1) in response to widening opportunities of life, people place stronger emphasis on emancipative values, (2) in response to a stronger emphasis on emancipative values, feelings of agency gain greater weight in shaping people’s life satisfaction, (3) in response to a greater impact of agency feelings on life satisfaction, the level of life satisfaction itself rises. Further analyses show that this model is culturally universal because taking into account the strength of a society’s western tradition does not render insignificant these adaptive linkages. Precisely because of its universality, this is indeed a ‘human’ development model in a most general sense

    Late 1920s film theory and criticism as a test-case for Benjamin’s generalizations on the experiential effects of editing

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    This article investigates Walter Benjamin’s influential generalization that the effects of cinema are akin to the hyper-stimulating experience of modernity. More specifically, I focus on his oft-cited 1935/36 claim that all editing elicits shock-like disruption. First, I propose a more detailed articulation of the experience of modernity understood as hyper-stimulation and call for distinguishing between at least two of its subsets: the experience of speed and dynamism, on the one hand, and the experience of shock/disruption, on the other. Then I turn to classical film theory of the late 1920s to demonstrate the existence of contemporary views on editing alternative to Benjamin’s. For instance, whereas classical Soviet and Weimar theorists relate the experience of speed and dynamism to both Soviet and classical Hollywood style editing, they reserve the experience of shock/disruption for Soviet montage. In order to resolve the conceptual disagreement between these theorists, on the one hand, and Benjamin, on the other, I turn to late 1920s Weimar film criticism. I demonstrate that, contrary to Benjamin’s generalizations about the disruptive and shock-like nature of all editing, and in line with other theorists’ accounts, different editing practices were regularly distinguished by comparison to at least two distinct hyper-stimulation subsets: speed and dynamism, and shock-like disruption. In other words, contemporaries regularly distinguished between Soviet montage and classical Hollywood editing patterns on the basis of experiential effects alone. On the basis of contemporary reviews of city symphonies, I conclude with a proposal for distinguishing a third subset – confusion. This is an original manuscript / preprint of an article published by Taylor & Francis in Early Popular Visual Culture on 02 Aug 2016 available online: https://doi.org/10.1080/17460654.2016.1199322

    IMI - Myopia Genetics Report

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    The knowledge on the genetic background of refractive error and myopia has expanded dramatically in the past few years. This white paper aims to provide a concise summary of current genetic findings and defines the direction where development is needed. We performed an extensive literature search and conducted informal discussions with key stakeholders. Specific topics reviewed included common refractive error, any and high myopia, and myopia related to syndromes. To date, almost 200 genetic loci have been identified for refractive error and myopia, and risk variants mostly carry low risk but are highly prevalent in the general population. Several genes for secondary syndromic myopia overlap with those for common myopia. Polygenic risk scores show overrepresentation of high myopia in the higher deciles of risk. Annotated genes have a wide variety of functions, and all retinal layers appear to be sites of expression. The current genetic findings offer a world of new molecules involved in myopiagenesis. As the missing heritability is still large, further genetic advances are needed. This Committee recommends expanding large-scale, in-depth genetic studies using complementary big data analytics, consideration of gene-environment effects by thorough measurement of environmental exposures, and focus on subgroups with extreme phenotypes and high familial occurrence. Functional characterization of associated variants is simultaneously needed to bridge the knowledge gap between sequence variance and consequence for eye growth

    OxPhos Defects Cause Hypermetabolism and Reduce Lifespan in Cells and in Patients With Mitochondrial Diseases

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    Patients with primary mitochondrial oxidative phosphorylation (OxPhos) defects present with fatigue and multi-system disorders, are often lean, and die prematurely, but the mechanistic basis for this clinical picture remains unclear. By integrating data from 17 cohorts of patients with mitochondrial diseases (n = 690) we find evidence that these disorders increase resting energy expenditure, a state termed hypermetabolism. We examine this phenomenon longitudinally in patient-derived fibroblasts from multiple donors. Genetically or pharmacologically disrupting OxPhos approximately doubles cellular energy expenditure. This cell-autonomous state of hypermetabolism occurs despite near-normal OxPhos coupling efficiency, excluding uncoupling as a general mechanism. Instead, hypermetabolism is associated with mitochondrial DNA instability, activation of the integrated stress response (ISR), and increased extracellular secretion of age-related cytokines and metabokines including GDF15. In parallel, OxPhos defects accelerate telomere erosion and epigenetic aging per cell division, consistent with evidence that excess energy expenditure accelerates biological aging. To explore potential mechanisms for these effects, we generate a longitudinal RNASeq and DNA methylation resource dataset, which reveals conserved, energetically demanding, genome-wide recalibrations. Taken together, these findings highlight the need to understand how OxPhos defects influence the energetic cost of living, and the link between hypermetabolism and aging in cells and patients with mitochondrial diseases

    Childhood gene-environment interactions and age-dependent effects of genetic variants associated with refractive error and myopia : The CREAM Consortium

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    Myopia, currently at epidemic levels in East Asia, is a leading cause of untreatable visual impairment. Genome-wide association studies (GWAS) in adults have identified 39 loci associated with refractive error and myopia. Here, the age-of-onset of association between genetic variants at these 39 loci and refractive error was investigated in 5200 children assessed longitudinally across ages 7-15 years, along with gene-environment interactions involving the major environmental risk-factors, nearwork and time outdoors. Specific variants could be categorized as showing evidence of: (a) early-onset effects remaining stable through childhood, (b) early-onset effects that progressed further with increasing age, or (c) onset later in childhood (N = 10, 5 and 11 variants, respectively). A genetic risk score (GRS) for all 39 variants explained 0.6% (P = 6.6E-08) and 2.3% (P = 6.9E-21) of the variance in refractive error at ages 7 and 15, respectively, supporting increased effects from these genetic variants at older ages. Replication in multi-ancestry samples (combined N = 5599) yielded evidence of childhood onset for 6 of 12 variants present in both Asians and Europeans. There was no indication that variant or GRS effects altered depending on time outdoors, however 5 variants showed nominal evidence of interactions with nearwork (top variant, rs7829127 in ZMAT4; P = 6.3E-04).Peer reviewe
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