181 research outputs found

    Salt marsh ecosystem biogeochemical responses to nutrient enrichment: a paired N-15 tracer study

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    We compared processing and fate of dissolved NO3- in two New England salt marsh ecosystems, one receiving natural flood tide concentrations of similar to 1-4 mu mol NO3-/L and the other receiving experimentally fertilized flood tides containing similar to 70-100 mu mol NO3-/L. We conducted simultaneous (NO3-)-N-15 (isotope) tracer additions from 23 to 28 July 2005 in the reference (8.4 ha) and fertilized (12.4 ha) systems to compare N dynamics and fate. Two full tidal cycles were intensively studied during the paired tracer additions. Resulting mass balances showed that essentially 100% (0.48-0.61 mol NO3-N.ha(-1).h(-1)) of incoming NO3- was assimilated, dissimilated, sorbed, or sedimented (processed) within a few hours in the reference system when NO3- concentrations were 1.3-1.8 mu mol/L. In contrast, only 50-60% of incoming NO3- was processed in the fertilized system when NO3- concentrations were 84-96 mu mol/ L; the remainder was exported in ebb tidewater. Gross NO3- processing was similar to 40 times higher in the fertilized system at 19.34- 24.67 mol NO3-N.ha(-1).h(-1). Dissimilatory nitrate reduction to ammonium was evident in both systems during the first 48 h of the tracer additions but \u3c1% of incoming (NO3-)-N-15 was exported as (NH4+)-N-15. Nitrification rates calculated by (NO3-)-N-15 dilution were 6.05 and 4.46 mol.ha(-1).h(-1) in the fertilized system but could not be accurately calculated in the reference system due to rapid (\u3c4 h) NO3- turnover. Over the five-day paired tracer addition, sediments sequestered a small fraction of incoming NO3-, although the efficiency of sequestration was 3.8% in the reference system and 0.7% in the fertilized system. Gross sediment N sequestration rates were similar at 13.5 and 12.6 mol.ha(-1).d(-1), respectively. Macrophyte NO3- uptake efficiency, based on tracer incorporation in aboveground tissues, was considerably higher in the reference system (16.8%) than the fertilized system (2.6%), although bulk uptake of NO3- by plants was lower in the reference system (1.75 mol NO3-.ha(-1).d(-1)) than the fertilized system (similar to 10 mol NO3-.ha(-1).d(-1)). Nitrogen processing efficiency decreased with NO3- load in all pools, suggesting that the nutrient processing capacity of the marsh ecosystem was exceeded in the fertilized marsh

    The Influence of Spatial Registration on Detection of Cerebral Asymmetries Using Voxel-Based Statistics of Fractional Anisotropy Images and TBSS

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    The sensitivity of diffusion tensor imaging (DTI) for detecting microstructural white matter alterations has motivated the application of voxel-based statistics (VBS) to fractional anisotropy (FA) images (FA-VBS). However, detected group differences may depend on the spatial registration method used. The objective of this study was to investigate the influence of spatial registration on detecting cerebral asymmetries in FA-VBS analyses with reference to data obtained using Tract-Based Spatial Statistics (TBSS). In the first part of this study we performed FA-VBS analyses using three single-contrast and one multi-contrast registration: (i) whole-brain registration based on T2 contrast, (ii) whole-brain registration based on FA contrast, (iii) individual-hemisphere registration based on FA contrast, and (iv) a combination of (i) and (iii). We then compared the FA-VBS results with those obtained from TBSS. We found that the FA-VBS results depended strongly on the employed registration approach, with the best correspondence between FA-VBS and TBSS results when approach (iv), the “multi-contrast individual-hemisphere” method was employed. In the second part of the study, we investigated the spatial distribution of residual misregistration for each registration approach and the effect on FA-VBS results. For the FA-VBS analyses using the three single-contrast registration methods, we identified FA asymmetries that were (a) located in regions prone to misregistrations, (b) not detected by TBSS, and (c) specific to the applied registration approach. These asymmetries were considered candidates for apparent FA asymmetries due to systematic misregistrations associated with the FA-VBS approach. Finally, we demonstrated that the “multi-contrast individual-hemisphere” approach showed the least residual spatial misregistrations and thus might be most appropriate for cerebral FA-VBS analyses

    Generation of tumour-specific cytotoxic T-cell clones from histocompatibility leucocyte antigen-identical siblings of patients with melanoma

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    Lymphodepletion and infusion of autologous expanded tumour-infiltrating lymphocytes is effective therapy for patients with malignant melanoma. Antitumour responses are likely to be mediated by HLA class I- and II-restricted immune responses directed at tumour antigens. We assessed whether the peripheral blood of normal HLA-matched siblings of patients with melanoma could be used to generate lymphocytes with antimelanoma activity for adoptive immunotherapy after allogeneic blood or marrow transplantation. Melanoma cell lines were derived from two donors and were used to stimulate the mononuclear cells of three HLA-identical siblings. CD4+ clones dominated cultures. Of these, approximately half were directly cytotoxic towards recipient melanoma cells and secreted interferon-γ in response to tumour stimulation. More than half of the noncytotoxic clones also secreted interferon-γ after melanoma stimulation. No CD4+ clones responded to stimulation with recipient haemopoietic cells. The majority of CD8+ clones directly lysed recipient melanoma, but did not persist in long-term culture in vitro. No crossreactivity with recipient haemopoietic cells was observed. The antigenic target of one CD4+ clone was determined to be an HLA-DR11-restricted MAGE-3 epitope. Antigenic targets of the remaining clones were not elucidated, but appeared to be restricted through a non-HLA-DR class II molecule. We conclude that the blood of allogeneic HLA-matched sibling donors contains melanoma-reactive lymphocyte precursors directed at tumour-associated antigens. Adoptive immunotherapy with unselected or ex vivo-stimulated donor lymphocytes after allogeneic stem cell transplantation has a rational basis for the treatment of malignant melanoma

    Scholarly publishing depends on peer reviewers

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    The peer-review crisis is posing a risk to the scholarly peer-reviewed journal system. Journals have to ask many potential peer reviewers to obtain a minimum acceptable number of peers accepting reviewing a manuscript. Several solutions have been suggested to overcome this shortage. From reimbursing for the job, to eliminating pre- publication reviews, one cannot predict which is more dangerous for the future of scholarly publishing. And, why not acknowledging their contribution to the final version of the article published? PubMed created two categories of contributors: authors [AU] and collaborators [IR]. Why not a third category for the peer-reviewer

    A Politico-Communal Reading of the Rose

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    Lettura del Fiore in rapporto alle fonti retoriche e politiche di ambiente comunal

    The horror of orthodoxy: Christina Mirabilis, thirteenth-century ‘zombie’ saint

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    In 1232, Thomas of Cantimpré wrote his Life of Christina Mirabilis (c. 1150–1224), an account of the miraculous life and three deaths of an unenclosed holy woman from the Low Countries. The text opens with an explicit vindication of Christina’s return(s) as divinely mandated. Yet, the narrative shows that her community struggles to deal with the revenant in their midst. Through her example, they must confront the terrifying mechanics of purgatory, resurrection, and the co-incidence of body and soul. A similar unease is found in modern scholarship, in which Christina is typically referred to dismissively in terms more commonly applied to cinematic monsters. I work with such dismissive language – specifically the term ‘zombie’ – to move beyond this heuristic roadblock. The terms of filmic zombie-ism provide new insight into the merging of orthodoxy and terror in Christina’s vita

    CPF-Associated Phosphatase Activity Opposes Condensin-Mediated Chromosome Condensation

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    International audienceFunctional links connecting gene transcription and condensin-mediated chromosome condensation have been established in species ranging from prokaryotes to vertebrates. However, the exact nature of these links remains misunderstood. Here we show in fission yeast that the 3′ end RNA processing factor Swd2.2, a component of the Cleavage and Polyadenylation Factor (CPF), is a negative regulator of condensin-mediated chromosome condensation. Lack of Swd2.2 does not affect the assembly of the CPF but reduces its association with chromatin. This causes only limited, context-dependent effects on gene expression and transcription termination. However, CPF-associated Swd2.2 is required for the association of Protein Phosphatase 1 PP1Dis2 with chromatin, through an interaction with Ppn1, a protein that we identify as the fission yeast homologue of vertebrate PNUTS. We demonstrate that Swd2.2, Ppn1 and PP1Dis2 form an independent module within the CPF, which provides an essential function in the absence of the CPF-associated Ssu72 phosphatase. We show that Ppn1 and Ssu72, like Swd2.2, are also negative regulators of condensin-mediated chromosome condensation. We conclude that Swd2.2 opposes condensin-mediated chromosome condensation by facilitating the function of the two CPF-associated phosphatases PP1 and Ssu72
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