498 research outputs found

    Lang's Conjecture and Sharp Height Estimates for the elliptic curves y2=x3+axy^{2}=x^{3}+ax

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    For elliptic curves given by the equation Ea:y2=x3+axE_{a}: y^{2}=x^{3}+ax, we establish the best-possible version of Lang's conjecture on the lower bound of the canonical height of non-torsion points along with best-possible upper and lower bounds for the difference between the canonical and logarithmic height.Comment: published version. Lemmas 5.1 and 6.1 now precise (with resultant refinement to Theorem 1.2). Small corrections to

    The Insoluble Carbonaceous Material of CM Chondrites as Possible Source of Discrete Organics During the Asteroidal Aqueous Phase

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    The larger portion of the organic carbon in carbonaceous chondrites (CC) is present as a complex and heterogeneous macromolecular material that is insoluble in acids and most solvents (IOM). So far, it has been analyzed only as a whole by microscopy (TEM) and spectroscopy (IR, NMR, EPR), which have offered and overview of its chemical nature, bonding, and functional group composition. Chemical or pyrolytic decomposition has also been used in combination with GC-MS to identify individual compounds released by these processes. Their value in the recognition of the original IOM structure resides in the ability to properly interpret the decomposition pathways for any given process. We report here a preliminary study of IOM from the Murray meteorite that combines both the analytical approaches described above, under conditions that would realistically model the IOM hydrothermal exposure in the meteorite parent body. The aim is to document the possible release of water and solvent soluble organics, determine possible changes in NMR spectral features, and ascertain, by extension, the effect of this loss on the frame of the IOM residue. Additional information is included in the original extended abstract

    Boundedness of Pseudodifferential Operators on Banach Function Spaces

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    We show that if the Hardy-Littlewood maximal operator is bounded on a separable Banach function space X(Rn)X(\mathbb{R}^n) and on its associate space X(Rn)X'(\mathbb{R}^n), then a pseudodifferential operator Op(a)\operatorname{Op}(a) is bounded on X(Rn)X(\mathbb{R}^n) whenever the symbol aa belongs to the H\"ormander class Sρ,δn(ρ1)S_{\rho,\delta}^{n(\rho-1)} with 0<ρ10<\rho\le 1, 0δ<10\le\delta<1 or to the the Miyachi class Sρ,δn(ρ1)(ϰ,n)S_{\rho,\delta}^{n(\rho-1)}(\varkappa,n) with 0δρ10\le\delta\le\rho\le 1, 0δ00\le\delta0. This result is applied to the case of variable Lebesgue spaces Lp()(Rn)L^{p(\cdot)}(\mathbb{R}^n).Comment: To appear in a special volume of Operator Theory: Advances and Applications dedicated to Ant\'onio Ferreira dos Santo

    RASSF1A–LATS1 signalling stabilizes replication forks by restricting CDK2-mediated phosphorylation of BRCA2

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    Genomic instability is a key hallmark of cancer leading to tumour heterogeneity and therapeutic resistance. ​BRCA2 has a fundamental role in error-free DNA repair but also sustains genome integrity by promoting ​RAD51 nucleofilament formation at stalled replication forks. ​CDK2 phosphorylates ​BRCA2 (pS3291-​BRCA2) to limit stabilizing contacts with polymerized ​RAD51; however, how replication stress modulates ​CDK2 activity and whether loss of pS3291-​BRCA2 regulation results in genomic instability of tumours are not known. Here we demonstrate that the Hippo pathway kinase ​LATS1 interacts with ​CDK2 in response to genotoxic stress to constrain pS3291-​BRCA2 and support ​RAD51 nucleofilaments, thereby maintaining genomic fidelity during replication stalling. We also show that ​LATS1 forms part of an ​ATR-mediated response to replication stress that requires the tumour suppressor ​RASSF1A. Importantly, perturbation of the ​ATR–​RASSF1A–​LATS1 signalling axis leads to genomic defects associated with loss of ​BRCA2 function and contributes to genomic instability and ‘BRCA-ness’ in lung cancers

    Expression Profiling of PBMC-based Diagnostic Gene Markers Isolated from Vasculitis Patients

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    Vasculitis (angiitis) is a systemic autoimmune disease that often causes fatal symptoms. We aimed to isolate cDNA markers that would be useful for diagnosing not only vasculitis but also other autoimmune diseases. For this purpose, we used stepwise subtractive hybridization and cDNA microarray analyses to comprehensively isolate the genes whose expressions are augmented in peripheral blood mononuclear cells (PBMCs) pooled from vasculitis patients. Subsequently, we used quantitative real-time polymerase chain reaction (qRT–PCR) to examine the mRNA levels of each candidate gene in individual patients. These analyses indicated that seven genes exhibit remarkably augmented expression in many vasculitis patients. Of these genes, we analyzed G0/G1 switch gene 2 (G0S2) further because G0S2 expression is also enhanced in the PBMCs of patients with systemic lupus erythematodes (SLE). We generated G0S2 transgenic mice that ubiquitously overexpress human G0S2. Although we did not observe any obvious vasculitis-related histopathologic findings in these mice, these mice are unhealthy as they produce only few offspring and showed elevated serum levels of two autoimmunity-related antibodies, anti-nuclear antibody, and anti-double strand DNA antibody. Thus, our large-scale gene profiling study may help finding sensitive and specific DNA markers for diagnosing autoimmune diseases including vasculitis and SLE

    LeukoCatch, a quick and efficient tool for the preparation of leukocyte extracts from blood

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    <p>Abstract</p> <p>Background</p> <p>Whole-protein extracts from peripheral blood leukocytes are ideal for basic and clinical research. However, lack of a simple preparation technique has limited the use of such extracts. The aim of this study is to develop a simple and easy system that can selectively obtain leukocyte extracts without hemoglobin.</p> <p>Methods</p> <p>A filter that captures the leukocytes but not RBCs was set at the bottom of a 10-mL medical syringe by sandwiching it between plastic stoppers. The capturing efficiency of leukocytes with this tool, called LeukoCatch, was examined using human macrophage cells (MONO-MAC-6). The abilities of LeukoCatch system to capture the leukocyte proteins and to remove the hemoglobin from RBCs were tested by western blot analysis using human blood samples.</p> <p>Results</p> <p>This study presents the development of LeukoCatch, a novel tool that allows the preparation of leukocyte extracts from blood samples within 3 min without centrifugation. Tissue-cultured human macrophage cells were tested to determine the optimal filter numbers and pass-through frequencies of LeukoCatch, which was then applied to 2-mL blood samples. Samples were passed 2~5 times through a LeukoCatch equipped with 5 filters, washed twice with phosphate-buffered saline for red cell removal, and leukocyte proteins were extracted with 0.5 mL of elution buffer. Western blot analysis of the purified extract indicated that more than 90% of hemoglobin was removed by the LeukoCatch and that the protein recovery rate of leukocytes was at least 4 times better than that of the conventional centrifugation method.</p> <p>Conclusion</p> <p>We conclude that LeukoCatch is useful not only for diagnosis at the bedside but also for basic research using blood samples or tissue culture cells.</p

    Defending the genome from the enemy within:mechanisms of retrotransposon suppression in the mouse germline

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    The viability of any species requires that the genome is kept stable as it is transmitted from generation to generation by the germ cells. One of the challenges to transgenerational genome stability is the potential mutagenic activity of transposable genetic elements, particularly retrotransposons. There are many different types of retrotransposon in mammalian genomes, and these target different points in germline development to amplify and integrate into new genomic locations. Germ cells, and their pluripotent developmental precursors, have evolved a variety of genome defence mechanisms that suppress retrotransposon activity and maintain genome stability across the generations. Here, we review recent advances in understanding how retrotransposon activity is suppressed in the mammalian germline, how genes involved in germline genome defence mechanisms are regulated, and the consequences of mutating these genome defence genes for the developing germline

    External tagging does not affect the feeding behavior of a coral reef fish, Chaetodon vagabundus (Pisces: Chaetodontidae)

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    Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of for personal use, not for redistribution. The definitive version was published in Environmental Biology of Fishes 86 (2009): 447-450, doi:10.1007/s10641-009-9545-9.Increasingly, the ability to recognize individual fishes is important for studies of population dynamics, ecology, and behavior. Although a variety of methods exist, external tags remain one of the most widely applied because they are both effective and cost efficient. However, a key assumption is that neither the tagging procedure nor the presence of a tag negatively affects the individual. While this has been demonstrated for relatively coarse metrics such as growth and survival, few studies have examined the impact of tags and tagging on more subtle aspects of behavior. We tagged adult vagabond butterflyfish (Chaetodon vagabundus) occupying a 30-ha insular reef in Kimbe Bay, Papua New Guinea, using a commonly-utilized t-bar anchor tag. We quantified and compared feeding behavior (bite rate), which is sensitive to stress, of tagged and untagged individuals over four separate sampling periods spanning four months post-tagging. Bite rates did not differ between tagged and untagged individuals at each sampling period and, combined with additional anecdotal observations of normal pairing behavior and successful reproduction, suggest that tagging did not adversely affect individuals.The authors gratefully acknowledge funding from the Fulbright Program, National Science Foundation and the Australian Research Council
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