32 research outputs found

    Assessing the conservation value of waterbodies: the example of the Loire floodplain (France)

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    In recent decades, two of the main management tools used to stem biodiversity erosion have been biodiversity monitoring and the conservation of natural areas. However, socio-economic pressure means that it is not usually possible to preserve the entire landscape, and so the rational prioritisation of sites has become a crucial issue. In this context, and because floodplains are one of the most threatened ecosystems, we propose a statistical strategy for evaluating conservation value, and used it to prioritise 46 waterbodies in the Loire floodplain (France). We began by determining a synthetic conservation index of fish communities (Q) for each waterbody. This synthetic index includes a conservation status index, an origin index, a rarity index and a richness index. We divided the waterbodies into 6 clusters with distinct structures of the basic indices. One of these clusters, with high Q median value, indicated that 4 waterbodies are important for fish biodiversity conservation. Conversely, two clusters with low Q median values included 11 waterbodies where restoration is called for. The results picked out high connectivity levels and low abundance of aquatic vegetation as the two main environmental characteristics of waterbodies with high conservation value. In addition, assessing the biodiversity and conservation value of territories using our multi-index approach plus an a posteriori hierarchical classification methodology reveals two major interests: (i) a possible geographical extension and (ii) a multi-taxa adaptation

    Public Versus Private: Does It Matter for Water Conservation? Insights from California

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    This article asks three connected questions: First, does the public view private and public utilities differently, and if so, does this affect attitudes to conservation? Second, do public and private utilities differ in their approaches to conservation? Finally, do differences in the approaches of the utilities, if any, relate to differences in public attitudes? We survey public attitudes in California toward (hypothetical but plausible) voluntary and mandated water conservation, as well as to price increases, during a recent period of shortage. We do this by interviewing households in three pairs of adjacent public and private utilities. We also survey managers of public and private urban water utilities to see if they differ in their approaches to conservation and to their customers. On the user side we do not find pronounced differences, though a minority of customers in all private companies would be more willing to conserve or pay higher prices under a public operator. No respondent in public utility said the reverse. Negative attitudes toward private operators were most pronounced in the pair marked by a controversial recent privatization and a price hike. Nonetheless, we find that California’s history of recurrent droughts and the visible role of the state in water supply and drought management undermine the distinction between public and private. Private utilities themselves work to underplay the distinction by stressing the collective ownership of the water source and the collective value of conservation. Overall, California’s public utilities appear more proactive and target-oriented in asking their customers to conserve than their private counterparts and the state continues to be important in legitimating and guiding conservation behavior, whether the utility is in public hands or private

    How Thioredoxin Dissociates Its Mixed Disulfide

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    The dissociation mechanism of the thioredoxin (Trx) mixed disulfide complexes is unknown and has been debated for more than twenty years. Specifically, opposing arguments for the activation of the nucleophilic cysteine as a thiolate during the dissociation of the complex have been put forward. As a key model, the complex between Trx and its endogenous substrate, arsenate reductase (ArsC), was used. In this structure, a Cys29Trx-Cys89ArsC intermediate disulfide is formed by the nucleophilic attack of Cys29Trx on the exposed Cys82ArsC-Cys89ArsC in oxidized ArsC. With theoretical reactivity analysis, molecular dynamics simulations, and biochemical complex formation experiments with Cys-mutants, Trx mixed disulfide dissociation was studied. We observed that the conformational changes around the intermediate disulfide bring Cys32Trx in contact with Cys29Trx. Cys32Trx is activated for its nucleophilic attack by hydrogen bonds, and Cys32Trx is found to be more reactive than Cys82ArsC. Additionally, Cys32Trx directs its nucleophilic attack on the more susceptible Cys29Trx and not on Cys89ArsC. This multidisciplinary approach provides fresh insights into a universal thiol/disulfide exchange reaction mechanism that results in reduced substrate and oxidized Trx

    Mesenchymal stem cells: from experiment to clinic

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    There is currently much interest in adult mesenchymal stem cells (MSCs) and their ability to differentiate into other cell types, and to partake in the anatomy and physiology of remote organs. It is now clear these cells may be purified from several organs in the body besides bone marrow. MSCs take part in wound healing by contributing to myofibroblast and possibly fibroblast populations, and may be involved in epithelial tissue regeneration in certain organs, although this remains more controversial. In this review, we examine the ability of MSCs to modulate liver, kidney, heart and intestinal repair, and we update their opposing qualities of being less immunogenic and therefore tolerated in a transplant situation, yet being able to contribute to xenograft models of human tumour formation in other contexts. However, such observations have not been replicated in the clinic. Recent studies showing the clinical safety of MSC in several pathologies are discussed. The possible opposing powers of MSC need careful understanding and control if their clinical potential is to be realised with long-term safety for patients

    Does levodopa accelerate the pathologic process in Parkinson disease brain?

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    Background: Several in vitro studies have suggested levodopa (L-dopa) to be toxic to dopaminergic neurons and that it can modulate the aggregation process of Îą-synuclein. We investigated the relationship between cumulative lifetime dose of L-dopa and nigral neuronal count and Lewy body (LB) pathology in Parkinson disease (PD). Methods: Density of pigmented neurons was measured unilaterally in a single section of substantia nigra (SN) with delineation of the dorsal and ventral tiers in 96 cases of PD with well-documented clinical records relating to antiparkinsonian drug treatment. Cortical and nigral LB densities were determined using a morphometric approach. Results: Mean lifetime dose of L-dopa correlated significantly (p &lt; 0.001) with duration of PD in the entire study population (n = 96) and it was not possible to disentangle their individual effect. This was not the case in a subgroup analysis of younger onset patients with a longer duration of PD (n = 40) who showed no significant correlation between L-dopa and total SN neuronal density (p = 0.07), after adjustment for duration of illness. There was, however, a lower neuronal density in the ventral (p = 0.02) but not in the dorsal (p = 0.27) tier detected with the cumulative dose of L-dopa. We found no difference in L-dopa dose between Braak PD stages (p = 0.58). Furthermore, the subgroup analysis showed no relationship of L-dopa dose to either cortical (p = 0.47) or nigral (p = 0.48) LB density. Conclusion: Chronic use of L-dopa in PD does not enhance progression of PD pathology as far as can be determined by our observations with SN neuronal counts and LB densities.</p

    Lewy- and Alzheimer-type pathologies in Parkinson's disease dementia: which is more important?

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    The relative importance of Lewy- and Alzheimer-type pathologies to dementia in Parkinson's disease remains unclear. We have examined the combined associations of α-synuclein, tau and amyloid-β accumulation in 56 pathologically confirmed Parkinson's disease cases, 29 of whom had developed dementia. Cortical and subcortical amyloid-β scores were obtained, while tau and α-synuclein pathologies were rated according to the respective Braak stages. Additionally, cortical Lewy body and Lewy neurite scores were determined and Lewy body densities were generated using morphometry. Non-parametric statistics, together with regression models, receiver-operating characteristic curves and survival analyses were applied. Cortical and striatal amyloid-β scores, Braak tau stages, cortical Lewy body, Lewy neurite scores and Lewy body densities, but not Braak α-synuclein stages, were all significantly greater in the Parkinson's disease-dementia group (P < 0.05), with all the pathologies showing a significant positive correlation to each other (P < 0.05). A combination of pathologies [area under the receiver-operating characteristic curve = 0.95 (0.88–1.00); P < 0.0001] was a better predictor of dementia than the severity of any single pathology. Additionally, cortical amyloid-β scores (r = −0.62; P = 0.043) and Braak tau stages (r = −0.52; P = 0.028), but not Lewy body scores (r = −0.25; P = 0.41) or Braak α-synuclein stages (r = −0.44; P = 0.13), significantly correlated with mini-mental state examination scores in the subset of cases with this information available within the last year of life (n = 15). High cortical amyloid-β score (P = 0.017) along with an older age at onset (P = 0.001) were associated with a shorter time-to-dementia period. A combination of Lewy- and Alzheimer-type pathologies is a robust pathological correlate of dementia in Parkinson's disease, with quantitative and semi-quantitative assessment of Lewy pathology being more informative than Braak α-synuclein stages. Cortical amyloid-β and age at disease onset seem to determine the rate to dementia
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