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61.
Transfer of rare earth elements (REE) from natural soil to plant systems: implications for the environmental availability of anthropogenic REE 总被引:1,自引:0,他引:1
L. Brioschi M. Steinmann E. Lucot M. C. Pierret P. Stille J. Prunier P. M. Badot 《Plant and Soil》2013,366(1-2):143-163
Background and aims
Rare Earth Elements (REE) are widely used to trace natural geochemical processes. They are also increasingly used by man (electronics industry, medicine, agriculture) and therefore considered as emerging pollutants. The present study documents REE mobility in non-polluted natural soil-plant systems in order to characterize their environmental availability for future anthropogenic pollution.Methods
The study is based on a field approach in non-polluted natural sites with contrasting geological environments (limestone, granite, and carbonatite) and highly variable REE contents.Results
REE concentrations in soils do not directly reflect bedrock concentrations, but depend largely on pedogenetic processes and on the mineralogy of bedrock and soil. The soils of all sites are with respect to bedrock enriched in heavy REE. The REE uptake by plants is not primarily controlled by the plant itself, but depends on the concentration and the speciation in the soil and the adsorbed soil water pool.Conclusions
REE uptake by plant roots are linked with those of Fe. Roots absorb preferentially the light REE. Before translocation, REE are retained by the Casparian strip leading to much lower concentrations in the aerial parts. The transport of the REE within the xylem is associated with the general nutrient flux. 相似文献62.
Haxaire C Turpin FR Potier B Kervern M Sinet PM Barbanel G Mothet JP Dutar P Billard JM 《Aging cell》2012,11(2):336-344
Oxidative stress (OS) resulting from an imbalance between antioxidant defenses and the intracellular accumulation of reactive oxygen species (ROS) contributes to age-related memory deficits. While impaired synaptic plasticity in neuronal networks is thought to underlie cognitive deficits during aging, whether this process is targeted by OS and what the mechanisms involved are still remain open questions. In this study, we investigated the age-related effects of the reducing agent N-acetyl-L-cysteine (L-NAC) on the activation of the N-methyl-D-aspartate receptor (NMDA-R) by its co-agonist D-serine, because alterations in this mechanism contribute greatly to synaptic plasticity deficits in aged animals. Long-term dietary supplementation with L-NAC prevented oxidative damage in the hippocampus of aged rats. Electrophysiological recordings in the CA1 of hippocampal slices indicated that NMDA-R-mediated synaptic potentials and theta-burst-induced long-term potentiation (LTP) were depressed in aged animals, deficits that could be reversed by exogenous D-serine. Chronic treatment with L-NAC, but not acute application of the reducing agent, restored potent D-serine-dependent NMDA-R activation and LTP induction in aged rats. In addition, it is also revealed that the age-related decrease in D-serine levels and in the expression of the synthesizing enzyme serine racemase, which underlies the decrease in NMDA-R activation by the amino acid, was rescued by long-term dietary treatment with L-NAC. Our results indicate that protecting redox status in aged animals could prevent injury to the cellular mechanisms underlying cognitive aging, in part by maintaining potent NMDA-R activation through the D-serine-dependent pathway. 相似文献
63.
Ultraviolet A (UVA) radiation represents more than 90% of the solar UV radiation reaching Earth's surface. Exposure to solar UV radiation is a major risk in the occurrence of non-melanoma skin cancer. Whole genome sequencing data of melanoma tumors recently obtained makes it possible also to definitively associate malignant melanoma with sunlight exposure. Even though UVB has long been established as the major cause of skin cancer, the relative contribution of UVA is still unclear. In this review, we first report on the formation of DNA damage induced by UVA radiation, and on recent advances on the associated mechanism. We then discuss the controversial data on the UVA-induced mutational events obtained for various types of eukaryotic cells, including human skin cells. This may help unravel the role of UVA in the various steps of photocarcinogenesis. The connection to photocarcinogenesis is more extensively discussed by other authors in this issue. 相似文献
64.
Bastien Gérard Badr Alaoui-Sossé Pierre-Marie Badot 《Trees - Structure and Function》2009,23(2):373-380
Pedunculate (Quercus robur L.) and sessile (Q. petraea [Matt.] Liebl.) oaks are the most common oak species in Western Europe. They are known to display different ecological requirements,
particularly relative to root hypoxia induced by flooding: In a glasshouse study of seedlings, we quantified the effects of
flooding on starch mobilization from cotyledons and starch partitioning. Growth and distribution of lateral roots were also
measured. The above-ground growth of Q. robur was less affected by flooding than that of Q. petraea which failed to develop a second flush. Root growth was also severely inhibited, particularly in Q. petraea. In Q. robur, lateral root initiation as well as elongation was restricted to the soil surface layer. Flooding markedly reduced total
growth and concentrations of in all components except stems. Starch mobilization from cotyledons was delayed by flooding,
especially in Q. robur seedlings. Under flooding, the decrease of cotyledons dry mass and starch content in Q. robur was lower than in Q. petraea, whereas Q. robur displayed larger growth than Q. petraea. The features of carbohydrate management may be crucial in the observed differences in flooding tolerance of these species. 相似文献
65.
Sensing and signalling during plant flooding. 总被引:10,自引:0,他引:10
James F Dat Nicolas Capelli Hélène Folzer Pascale Bourgeade Pierre-Marie Badot 《Plant Physiology and Biochemistry》2004,42(4):273-282
Flooding is a major issue for plant survival in many regions of the world. Soil inundation induces multiple plant physiological dysfunctions, leading to a decline in plant growth and survival capacity. Some of the most important effects of flooding include a reduction in water and nutrient uptake and a decrease in metabolism. Prolonged soil flooding will also ultimately lead to anoxia conditions with profound effects on plant respiratory metabolism. However, it is still unclear which signals and which sensory mechanisms are responsible for triggering the plant response. In contrast, it is now established that flooding responses are typified by enhanced ethylene production, accompanied by a signalling cascade which includes a network of hormones and other common secondary signalling molecules. In recent years, there has been significant progress in the understanding of some of the signalling pathways involved during plant stress responses. Here, we present an overview of recent hypothesises on sensing and signalling during plant flooding. 相似文献
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69.
Fesenko SV Soukhova NV Sanzharova NI Avila R Spiridonov SI Klein D Lucot E Badot PM 《Radiation and environmental biophysics》2001,40(2):105-113
The regularities of 137Cs distribution in trees (Pinus sylvestris and Betula pendula) growing in different types of forest ecosystems were investigated. High levels of heterogeneity of 137Cs activity concentrations in different parts of the trees, resulting from their varied metabolism have been shown. The data
obtained demonstrate a non-uniform character of 137Cs distribution along the trunks, which can be explained by radio- nuclide fixation by the xylem vessel walls and by geometry
changes along the tree trunk. It has been found that the radial distribution of 137Cs in the tree trunk is dependent on the availability of 137Cs in soil, which governs the transfer of this radionuclide via xylem sap and on the properties of the xylem. The accumulation
of 137Cs by trees was influenced by the vertical distribution and availability of 137Cs in the soil as well as by the root biomass distribution in different soil horizons. A bioavailability factor, which takes
into account the vertical distribution of radiocesium in soil, bioavailability of this radionuclide and distribution of root
biomass in different soil horizons is proposed for comparative analyses of 137Cs transfer from soil to trees in different types of forest ecosystems.
Received: 8 February 2000 / Accepted: 1 December 2000 相似文献
70.
BACKGROUND: S-phase fraction (SPF) measurement by flow cytometry is a clinically useful prognostic factor in patients with breast carcinoma. Standardized SPF determination is essential. As part of a multicenter study, we evaluated the influence of the choice of software and histogram resolution (256, 512, or 1,024 channels) on SPF quantification. METHODS: One hundred thirty-three DNA histograms were analyzed in three laboratories with Modfit 5.2, Modfit LT, and Multicycle AV software. Strict rules for histogram interpretation and software management were applied. The following five options were compared: MF 5.2 1024, MF 5.2 256, MF LT 256, MC AV 256, and MC AV 512. RESULTS: In the DNA diploid and aneuploid groups, SPF distributions were not statistically different among the five options. Excellent quantitative correlations were obtained between pairs of options. When using tertiles as cutpoints for SPF classification, concordance rates ranged from 79.7% to 93.2% for DNA diploid samples and from 87.8% to 95.9% for DNA aneuploid samples, the best results being obtained with software working with a similar histogram resolution. CONCLUSIONS: Standardized use of commercially available software, including the choice of histogram resolution, provides comparable SPF results. 相似文献