Comparison in waterborne Cu, Ni and Pb bioaccumulation kinetics between different gammarid species and populations: Natural variability and influence of metal exposure history.

Kinetic parameters (uptake from solution and elimination rate constants) of Cu, Ni and Pb bioaccumulation were determined from two Gammarus pulex and three Gammarus fossrum wild populations collected from reference sites throughout France in order to assess the inter-species and the natural inter-population variability of metal bioaccumulation kinetics in that sentinel organism. For that, each population was independently exposed for seven days to either 2.5µgL-1 Cu (39.3nM), 40µgL-1 Ni (681nM) or 10µgL-1 Pb (48.3nM) in laboratory controlled conditions, and then placed in unexposed microcosms for a 7-day depuration period. In the same way, the possible influence of metal exposure history on subsequent metal bioaccumulation kinetics was addressed by collecting wild gammarids from three populations inhabiting stations contaminated either by Cd, Pb or both Pb and Ni (named pre-exposed thereafter). In these pre-exposed organisms, assessment of any changes in metal bioaccumulation kinetics was achieved by comparison with the natural variability of kinetic parameters defined from reference populations. Results showed that in all studied populations (reference and pre-exposed) no significant Cu bioaccumulation was observed at the exposure concentration of 2.5µgL-1. Concerning the reference populations, no significant differences in Ni and Pb bioaccumulation kinetics between the two species (G. pulex and G. fossarum) was observed allowing us to consider all the five reference populations to determine the inter-population natural variability, which was found to be relatively low (kinetic parameters determined for each population remained within a factor of 2 of the minimum and maximum values). Organisms from the population exhibiting a Pb exposure history presented reduced Ni uptake and elimination rate constants, whereas no influence on Ni kinetic parameters was observed in organisms from the population exhibiting an exposure history to both Ni and Pb. Furthermore Pb bioaccumulation kinetics were unaffected whatever the condition of pre-exposure in natural environment. Finally, these results highlight the complexity of confounding factors, such as metal exposure history, that influence metal bioaccumulation processes and showed that pre-exposure to one metal can cause changes in the bioaccumulation kinetics of other metals. These results also address the question of the underlying mechanisms developed by organisms to cope with metal contamination.

Ecotoxicoproteomic assessment of the functional alterations caused by chronic metallic exposures in gammarids.

Very few ecotoxicological studies have been performed on long-term exposure under controlled conditions, hence limiting the assessment of the impact of chronic and diffuse chemical pressures on the health of aquatic organisms. In this study, an ecotoxicoproteomic approach was used to assess the integrated response and possible acclimation mechanisms in Gammarus fossarum following chronic exposures to Cd, Cu or Pb, at environmentally realistic concentrations (i.e. 0.25, 1.5 and 5 µg/L respectively). After 10-week exposure, changes in protein expression were investigated in caeca of control and exposed males. Gel-free proteomic analyses allowed for the identification of 35 proteins involved in various biological functions, for which 23 were significantly deregulated by metal exposures. The protein deregulation profiles were specific to each metal, providing evidence for metal-specific action sites and responses of gammarids. Among the tested metals, Cu was the most toxic in terms of mortality, probably linked with persistent oxidative stress. Moulting and osmoregulation were the major biological functions affected by Cu in the long-term. In Pb-exposed gammarids, significant deregulations of proteins involved in immune response and cytoskeleton were observed. Reproduction appears to be strongly affected in gammarids chronically exposed to Cd or Pb. Besides, modified expressions of several proteins involved in energy transfer and metabolism highlighted important energetic reshuffling to cope with chronic metal exposures. These results support the fact that metallic pressures induce a functional and energetic cost for individuals of G. fossarum with potential repercussions on population dynamics. Furthermore, this ecotoxicoproteomic study offers promising lines of enquiry in the development of new biomarkers that could make evidence of long-term impacts of metals on the health of organisms.

Environmental relevance of laboratory-derived kinetic models to predict trace metal bioaccumulation in gammarids: Field experimentation at a large spatial scale (France).

Kinetic models have become established tools for describing trace metal bioaccumulation in aquatic organisms and offer a promising approach for linking water contamination to trace metal bioaccumulation in biota. Nevertheless, models are based on laboratory-derived kinetic parameters, and the question of their relevance to predict trace metal bioaccumulation in the field is poorly addressed. In the present study, we propose to assess the capacity of kinetic models to predict trace metal bioaccumulation in gammarids in the field at a wide spatial scale. The field validation consisted of measuring dissolved Cd, Cu, Ni and Pb concentrations in the water column at 141 sites in France, running the models with laboratory-derived kinetic parameters, and comparing model predictions and measurements of trace metal concentrations in gammarids caged for 7 days to the same sites. We observed that gammarids poorly accumulated Cu showing the limited relevance of that species to monitor Cu contamination. Therefore, Cu was not considered for model predictions. In contrast, gammarids significantly accumulated Pb, Cd, and Ni over a wide range of exposure concentrations. These results highlight the relevance of using gammarids for active biomonitoring to detect spatial trends of bioavailable Pb, Cd, and Ni contamination in freshwaters. The best agreements between model predictions and field measurements were observed for Cd with 71% of good estimations (i.e. field measurements were predicted within a factor of two), which highlighted the potential for kinetic models to link Cd contamination to bioaccumulation in the field. The poorest agreements were observed for Ni and Pb (39% and 48% of good estimations, respectively). However, models developed for Ni, Pb, and to a lesser extent for Cd, globally underestimated bioaccumulation in caged gammarids. These results showed that the link between trace metal concentration in water and in biota remains complex, and underlined the limits of these models, in their present form, to assess trace metal bioavailability in the field. We suggest that to improve model predictions, kinetic models need to be complemented, particularly by further assessing the influence of abiotic factors on trace metal uptake, and the relative contribution of the trophic route in the contamination of gammarids.

A biodynamic model predicting waterborne lead bioaccumulation in Gammarus pulex: Influence of water chemistry and in situ validation.

Metals bioaccumulated in aquatic organisms are considered to be a good indicator of bioavailable metal contamination levels in freshwaters. However, bioaccumulation depends on the metal, the species, and the water chemistry that influences metal bioavailability. In the laboratory, a kinetic model was used to describe waterborne Pb bioaccumulated in Gammarus pulex. Uptake and elimination rate constants were successfully determined and the effect of Ca(2+) on Pb uptake was integrated into the model. Thereafter, accumulated Pb concentrations in organisms were predicted with the model and compared with those measured in native populations from the Seine watershed (France). The predictions had a good agreement with the bioaccumulation levels observed in native gammarids and particularly when the effect of calcium was considered. To conclude, kinetic parameters experimentally derived for Pb in G. pulex are applicable in environmental conditions. Moreover, the consideration of the water's chemistry is crucial for a reliable interpretation of bioaccumulation.

Photoionization and imaging spectroscopy of rubidium atoms attached to helium nanodroplets.

Highly excited states of rubidium (Rb) atoms attached to helium (He) nanodroplets are studied by two-photon ionization spectroscopy in combination with electron and ion imaging. We find high yields of RbHe and RbHe(2) exciplexes when exciting to the 4D and 6P bands but not at the 6S band, in accord with a direct formation of exciplexes in binding RbHe pair potentials. Photoion spectra and angular distributions are in good agreement with a pseudodiatomic model for the RbHe(N) complex. Repulsive interactions in the excited states entail fast dissociation followed by ionization of free Rb atoms as well as of RbHe and RbHe(2) exciplexes.

Dopant-induced ignition of helium nanodroplets in intense few-cycle laser pulses.

We demonstrate ultrafast resonant energy absorption of rare-gas doped He nanodroplets from intense few-cycle (~10 fs) laser pulses. We find that less than 10 dopant atoms "ignite" the droplet to generate a nonspherical electronic nanoplasma resulting ultimately in complete ionization and disintegration of all atoms, although the pristine He droplet is transparent for the laser intensities applied. Our calculations at those intensities reveal that the minimal pulse length required for ignition is about 9 fs.

[Early diagnosis of liver diseases]. / Frühdiagnostik von Lebererkrankungen.

In Germany, liver diseases are the leading cause of death through illness among 30 to 45 year olds. Most are chronic diseases and timely preventative or therapeutic measures could avert their manifestation or at least the following complications. Currently, screening for liver diseases is focused on specific groups at risk such as patients with alcohol abuse, relatives of patients with a genetic disease or individuals at risk of an infection with a viral hepatitis. For some diseases, studies have been started to test the practicability of population screening, which has already been successfully implemented for Hepatitis B and C in blood donors. Screening is also recommended for advanced liver disease. It helps to detect the development of cirrhosis and its complications namely varices and hepatocellular carcinoma.

[Portal vein thrombosis in a patient with lowered protein S level]. / Pfortaderthrombose bei einem Patienten mit erniedrigtem Protein-S-Spiegel.

HISTORY AND CLINICAL FINDINGS: In a 39-year-old man with increasing spasmodic epigastric pain, nausea and vomiting, varices of the esophagus and the gastric fundus were found endoscopically. INVESTIGATIONS: A portal vein thrombosis and a consecutive thrombosis of the splenic vein were diagnosed by colour Doppler sonography and angio CT. A protein S deficiency (59 %) was found to be the underlying illness. TREATMENT AND COURSE: The thrombosis and the resulting clinical symptoms completely resolved shortly after starting therapeutic heparinization. For six months, the patient has been without complaints or clinical symptoms. CONCLUSION: Hence, an isolated protein S deficiency can be the cause for a portal vein thrombosis.

Antibiotic susceptibility of community hospital blood culture isolates of gram-negative bacilli.

The comparative in vitro activity of amikacin, cefamandole, cefoperazone, cefotaxime, cefoxitin, cephalothin, chloramphenicol, moxalactam, piperacillin, ticarcillin and tobramycin against 170 community blood culture isolates of gram-negative bacilli was investigated using the quantitative plate dilution method. Results showed that amikacin, cefoperazone, cefotaxime, moxalactam, piperacillin and tobramycin were most active on a weight basis. Tobramycin and amikacin were quite active against Pseudomonas aeruginosa but one isolate showed an MIC of 50 micrograms/ml to both. The order of activity of the remaining drugs for P. aeruginosa was cefoperazone greater than moxalactam greater than cefotaxime and piperacillin greater than ticarcillin.

Erythromycin resistance in group A beta-hemolytic streptococci.

Recent reports have indicated a high incidence of erythromycin resistance in Group A streptococci isolated from children in Japan. The present study investigated antibiotic susceptibility patterns of 280 pharyngeal isolates from ambulatory patients using the plate dilution technique. The incidences of resistance to erythromycin and tetracycline were 4.3 and 7.8%, respectively. No resistance to penicillin, ampicillin, methicillin, oxacillin, cefaclor or moxalactam was found, and there was no evidence of penicillin tolerance using the standard tube dilution technique. The erythromycin-resistant isolates were of T-pattern 12, M-type 12, and two erythromycin-resistant isolates were also resistant to tetracycline. Data on the source of the isolates suggest that a localized outbreak of erythromycin-resistant streptococcal infection occurred.