Biomedical subjects

Rodolphe Gilbin

Publications and source records attributed to Rodolphe Gilbin.

4 recordsLinked to original sources

PubMed2006

First derivation of predicted-no-effect values for freshwater and terrestrial ecosystems exposed to radioactive substances.

The FASSET Radiation Effects Database (FRED) constitutes a unique structured resource of the biological effects of ionizing radiation on non-human species mainly from temperate ecosystems, encompassing 26,000 primary data entries. Quality-assessed data were extracted from FRED and dose-effect relationships were constructed to provide estimates of ED50 and EDR10. These estimates are Doses (or Dose Rates) related to the percent change in the average level of the endpoint for a particular effect (50% or 10% for acute or chronic exposure regimes, respectively). Acute and chronic Species Sensitivity Distributions (SSDs) were built on the basis of these data sets, and the Assessment Factor Method (AFM) was applied when data were too scarce. The Hazardous Dose corresponding to 5% of species acutely affected at the 50% effect level varied from 1 to 5.5 Gy according to the ecosystem. For chronic gamma external irradiation exposure, no-effect values varied from 10 microGy/h for freshwaters through application of the AFM to 67 microGy/h for terrestrial ecosystems, corresponding to the 5th percentile of the non-weighted SSD (vs 229 microGy/h when trophic weights are applied). These values are higher by ca. x50 to x100 than the upper bound of natural background, and lower than dose rates triggering effects at individual levels on contaminated sites.

Amphibians↗

PubMed2005

Assessment of copper bioavailability and toxicity in vineyard runoff waters by DPASV and algal bioassay.

The aim of this study was to assess the toxicity of runoff waters in an agricultural multipollution context through an in-depth assessment of copper bioavailability and toxicity. Runoff waters were screened for major ions, metals and diuron. The potential environmental impact of these runoff waters was evaluated using the conventional 72-h growth inhibition test with the green alga Pseudokirchneriella subcapitata. The results suggested that the toxicity detected in the calcareous vineyard field was due to the presence of diuron, whereas the non-calcareous runoff waters were non-toxic. Chemical speciation modelling by MINEQL revealed that most of the copper present in the non-toxic natural runoff waters was complexed by organic matter. These samples were spiked with copper, and then the toxicity and the electrochemically bioavailable copper fraction were measured. Differential pulse anodic stripping voltammetry (DPASV) was used to detect labile complexes and free copper. This combined approach highlighted the presence of some labile copper complexes in samples reaching the EC10-these could have contributed to the copper toxicity.

Agriculture↗

PubMed2004

Performance of diffusion gradient in thin films to evaluate the toxic fraction of copper to Daphnia magna.

This study investigates the relevance of the diffusion gradient in thin films technique (DGT) to measure copper's induced lethality on Daphnia magna in natural water spiked with various organic ligands. Ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and glycine were used as artificial organic ligands in controlled solutions of mineral water. With EDTA, DGT measurement makes it possible to predict the toxicity of the mixture because Cu-EDTA complexes are inert, whereas DGT is of no help in the case of NTA, because Cu-NTA complexes are fully labile. The Cu-glycine complexes appear as partly labile and toxic. Humic acids as well as fresh and aged algae extracts also were used as models for natural dissolved organic matters. All three of them form copper complexes that are not toxic to Daphnia magna and appear as partly labile with open-pored DGT. However, the use of restricted gels in DGT greatly reduces the contribution of labile complexes, at least for humic acids and aged algae copper complexes. The DGT with restrictive gels, therefore, appears to be a powerful tool for measuring bioavailable copper in natural water bodies, especially when the dissolved organic matter mostly is of humic origin. The DGTs potential ability to mimic the lability induced by the biological uptake also is discussed.

Animals↗

PubMed2003

A dynamic numerical model to characterize labile metal complexes collected with diffusion gradient in thin films devices.

The speciation of metal species extracted by diffusion gradient in thin films (DGT) devices during experimental deployments in simple metal-ligand synthetic solutions was numerically modeled, analyzed at steady state, and simulated in the dynamic regime. The modeled speciation of two well-known complexes (Cu-citrate and Cu-EDTA) are in good agreement with experimental data obtained in NaNO3 solutions. For any metal complex, the rate at which the metal accumulates on the chelating resin is proportional to the concentration of free metal in solution plus a fraction of the metal complex concentration in solution equivalent to xiD(ML)/D(M). D(M) and D(ML) are the diffusion coefficients of the free and metal complex, respectively, and xi characterizes the complex lability: it is defined as the fraction of metal complex lost when diffusing from the bulk solution to the chelating resin. Numerical simulations were used to explore the variations of xi as a function of several operational and chemical parameters. Lability increases when the dissociation rate constant or the residence time of the metal complex within the hydrogel increase (i.e., by either increasing the thickness of the hydrogel or decreasing D(ML)). Overall, the fraction of metal complex extracted by the DGT decreases when D(ML) decreases, which confirms the ability of diffusion-restrictive hydrogels to separate the free metal fraction from complex solutions. Although the DGT model does not exactly comply with the voltammetric formalism, the lability criteria deltatau(1/2) used with voltammetric macroelectrodes is similar to the lability criteria xi, except that it is valid for high metal-ligand ratio. To determine free metal concentrations in aquatic systems using DGT, it is necessary to account for the presence of numerous ligands with different complexing properties. Soon, the numerical model will be improved to include additional ligands competing for the metal, and new experiments will be designed to discriminate between different labile complexes. Experimental results obtained with different DGT devices (of different hydrogel thicknesses, for example) could be interpreted in terms of conditional kinetic characteristics of the dominant metal-ligand complex in solution.

Chelating Agents↗