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.

Metal measurement in aquatic environments by passive sampling methods: Lessons learning from an in situ intercomparison exercise

Passive sampling devices (PS) are widely used for pollutant monitoring in water, but estimation of measurement uncertainties by PS has seldom been undertaken. The aim of this work was to identify key parameters governing PS measurements of metals and their dispersion. We report the results of an in situ intercomparison exercise on diffusive gradient in thin films (DGT) in surface waters. Interlaboratory uncertainties of time-weighted average (TWA) concentrations were satisfactory (from 28% to 112%) given the number of participating laboratories (10) and ultra-trace metal concentrations involved. Data dispersion of TWA concentrations was mainly explained by uncertainties generated during DGT handling and analytical procedure steps. We highlight that DGT handling is critical for metals such as Cd, Cr and Zn, implying that DGT assembly/dismantling should be performed in very clean conditions. Using a unique dataset, we demonstrated that DGT markedly lowered the LOQ in comparison to spot sampling and stressed the need for accurate data calculation.

Influence of effluent organic matter on copper speciation and bioavailability in rivers under strong urban pressure

This study focuses on spatiotemporal variations in the type of dissolved organic matter (DOM) and copper binding ability both upstream and downstream of Paris. It also compares the relative influence of both natural DOM upstream of Paris and effluent dissolved organic matter (EfDOM) output from a wastewater treatment plant (WWTP) on trace metal speciation and bioavailability in aquatic systems. In addition to the typical high- and low-affinity binding sites, a third family of very high-affinity binding sites has been highlighted for EfDOM. In receiving waters downstream of Paris during low-flow periods, the percentage of high- and very high-affinity sites originating from EfDOM reaches nearly 60 %. According to the speciation computation, the free copper concentration upstream of Paris exceeds the downstream Paris concentration by a factor of 2 to 4. As regards copper bioavailability, the highest EC50tot values were observed for EfDOM and downstream DOM, with a very low aromaticity and low UV absorbance. This finding suggests that specific ultraviolet absorbance (SUVA) is unlikely to be useful in assessing metal speciation and toxicity in aquatic systems subject to strong urban pressures. These results also highlight that the copper speciation computation for surface water exposed to considerable human pressures should include not only the humic and/or fulvic part of dissolved organic carbon but more hydrophilic fractions as well, originating for example from EfDOM.

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.

One-year monitoring of core biomarker and digestive enzyme responses in transplanted zebra mussels (Dreissena polymorpha)

A 12-month active biomonitoring study was performed in 2008-2009 on the Vesle river basin (Champagne-Ardenne, France) using the freshwater mussel Dreissena polymorpha as a sentinel species; allochthonous mussels originating from a reference site (Commercy) were exposed at four sites (Bouy, Sept-Saulx, Fismes, Ardre) within the Vesle river basin. Selected core biomarkers (acetylcholinesterase (AChE) activity, glutathione-S transferase (GST) activity, metallothionein concentration), along with digestive enzyme activities (amylase, endocellulase) and energy reserve concentrations (glycogen, lipids), were monitored throughout the study in exposed mussels. At the Fismes and Ardre sites (downstream basin), metallic and organic contamination levels were low but still high enough to elicit AChE and GST activity induction in exposed mussels (chemical stress); besides, chemical pollutants had no apparent deleterious effects on mussel condition. At the Bouy and Sept-Saulx sites (upstream basin), mussels obviously suffered from adverse food conditions which seriously impaired individual physiological state and survival (nutritional stress); food scarcity had however no apparent effects on core biomarker responses. Digestive enzyme activities responded to both chemical and nutritional stresses, the increase in energy outputs (general adaptation syndrome-downstream sites) or the decrease in energy inputs (food scarcity-upstream sites) leading to mid- or long-term induction of digestive carbohydrase activities in exposed mussels (energy optimizing strategy). Complex regulation patterns of these activities require nevertheless the use of a multi-marker approach to allow data interpretation. Besides, their sensitivity to natural confounding environmental factors remains to be precised.

Labile, dissolved and particulate PAHs and trace metals in wastewater: passive sampling, occurrence, partitioning in treatment plants

The occurrence and the partitioning of polycyclic aromatic hydrocarbons (PAHs) and seven metals (Al, Cd, Cr, Cu, Ni, Pb and Zn) were investigated in activated sludge wastewater treatment plants by means of passive and active sampling. Concentrations total dissolved and particulate contaminants were determined in wastewater at several points across the treatment system by means of grab sampling. Truly dissolved PAHs were sampled by means of semipermeable membrane devices. Labile (inorganic and weakly complexed) dissolved metals were also sampled using the diffusive gradient in thin film technique. This study confirms the robustness and the validity of these two passive sampling techniques in wastewater. All contaminant concentrations decreased in wastewater along the treatment, although dissolved and labile concentrations sometimes increased for substances with less affinity with organic matter. Solid-liquid and dissolved organic matter/water partitioning constants were estimated. The high variability of both partitioning constants for a simple substance and the poor relation between K(D) and K(OW) shows that the binding capacities of particles and organic matter are not uniform within the treatment and that other process than equilibrium sorption affect contaminant repartition and fate in wastewater.

Reliability of pelvic floor muscle strength measurement in elderly incontinent women

Pelvic floor muscles (PFM) play an important role in maintaining urinary continence with increasing age. Therefore, their contractile properties need to be evaluated. The aim of the study was to examine the reliability and correlation of simple techniques to measure PFM strength in elderly women with urinary incontinence. An interview was used to evaluate the ability to stop the urinary stream during micturition and to calculate the incontinence index. A pad test was applied to objectively evaluate the severity of the disease. Functional testing included a digital examination to measure the force and duration of one contraction, a perineometer measurement (Peritron) to assess maximal contraction force and contraction force of 5 s, and a cone-retention test (Femcon) while walking for 1 min and during Valsalva's manoeuvre. This procedure was performed on three separate occasions within one week. The 37 participating women with a mean age of 62+/-8 (mean+/-SD) years had a severity index of 4.4+/-2.6 and a urine loss of 9.5+/-13.6 mg during the pad test. Sixteen women were able to completely stop the urinary stream during micturition. The digital examination showed no intratester variability. The perineometer measurement showed that the absolute difference in maximal contraction force and mean contraction force within 5 s was less than 5.3 mm Hg and 4.5 mm Hg, respectively, with a probability of 0.95. While walking and during Valsalva's manoeuvre, 19 and 20 women, respectively, held the same cone in place on all three occasions. The maximal contraction force and mean force during the 5-s contraction correlated well with the ability to stop the urinary stream and the digital examination but only weakly with the cone-retention tests. The reliability of PFM strength measurement is highest in the digital examination, followed by perineometer measurements, and then by vaginal cone tests. As PFM function is easy to assess, it should be routinely done in the assessment of urinary incontinence in elderly women.

A neuromuscular test battery for osteoporotic women: a pilot study

OBJECTIVE

To examine the efficacy of a short neuromuscular test battery in elderly women suffering from osteoporosis in accordance with the World Health Organization criteria, with and without a history of fractures. Reduced bone mass and a high likelihood of falling increase the risk of osteoporotic fractures. There is a need for neuromuscular tests to identify individuals at risk for falls and fractures.

DESIGN

The women were assessed twice. Forty-two women, with a mean age of 70.0 +/- 5.1 (SD) yr, completed the first assessment. The number of postmenopausal fractures and the women's history with regard to agility and falls were assessed. The women performed neuromuscular tests (one-leg stance, tandem walk, and body sway); bone mineral density of the spine and femoral neck were measured. For the follow-up assessment, 13.2 +/- 1.3 mo later, 39 women were studied. The same outcome measurements were obtained at both evaluations.

RESULTS

During the observation period, five women fell once and one woman fell twice; there were only two vertebral fractures and no nonvertebral fracture. Neuromuscular performance did not change during this observation period. The median changes in bone mineral density between the two assessments were clinically not relevant. A comparison between patients suffering from established osteoporosis and osteoporotic patients without a history of postmenopausal fractures showed that both groups of patients did not differ with respect to age, neuromuscular performance, bone mineral density, and fear of falling.

CONCLUSION

This neuromuscular test battery is a feasible and practical tool because it is brief and economical to perform. However, its efficacy as a predictor of fractures must be tested in additional studies with a long-term follow-up and a larger group of subjects.

[Evaluating rehabilitation progress by measuring thigh circumference]

QUESTION

Thigh girth measurements have been widely used to quantify rehabilitation progress following knee surgery, but the correlation between thigh girth and other functional measures has not been investigated. This study intended to investigate whether such a correlation exists.

METHODS

15 women with bilateral osteoarthrosis of the knee participated in this study. Isokinetic knee extensor strength, thigh girth and body mass were measured immediately before, then at six weeks and six months following cementless total knee arthroplasty.

RESULTS

The involved side showed clear pre-operative isokinetic knee extensor strength deficits, and slight reductions in thigh girth. Post-operatively, mean strength deficits were reduced, whereas differences in mean thigh girth became lager. Although thigh girth changes correlated well with body mass, they did not correlate with knee extensor strength.

CONCLUSION

Changes in thigh girth are mainly due to changes in body mass. Thigh girth measurement is of no use for the quantification of the rehabilitation progress in total knee arthroplasty.

Long-term home exercise program: effect in women at high risk of fracture

OBJECTIVE

To determine whether a better outcome in terms of physical frailty could be achieved with a regular home exercise program in women at high risk of fracture.

DESIGN

Prospective long-term observational study.

SETTING

Outpatient clinic of physical medicine and rehabilitation.

PARTICIPANTS

Women with a history of postmenopausal fractures and an age-adjusted low bone mass, as determined 7 to 12 years earlier.

INTERVENTION

Home exercise program.

OUTCOME MEASURES

Thirty-three women were followed. The exercise group and control group were compared with regard to fracture rates, episodes of falling, neuromuscular performance (one-leg stance, chair rise, body sway, tandem walk, tapping test), and bone mineral density (BMD).

RESULTS

Twenty-five women with a mean age of 73.8+/-5.7 yrs appeared for the investigation. An exercise program had been prescribed in 19 women, and six served as controls. Seven women of the exercise group (36.8%) regularly performed the exercises. No differences between participants of the groups in terms of fracture rates, falling episodes, neuromuscular performance, and BMD were observed.

CONCLUSION

It appears that a home exercise program does not affect the outcome of postmenopausal women at high risk of fracture.

[Translation of the Osteoporosis Quality of Life questionnaire (OQLQ) into German]

Osteoporosis is a major health problem affecting the quality of life. The Osteoporosis Quality of Life Questionnaire (OQLQ) is a disease-specific measure intended for use in English-speaking countries. As there is a need for measures in non English-speaking countries as well, we translated the OQLQ according to a standardised protocol into the German language. Twenty-five women suffering from osteoporosis were tested in regard of quality of life. The questionnaire appears to be especially suitable for more disabled patients.