Comparing the sensitivity of geographically distinct Lemna minor populations to atrazine

The objectives of this study were to compare the sensitivities of field populations and a laboratory culture of a duckweed species (Lemna minor) to the herbicide atrazine using three different endpoints and to determine whether sensitivity to atrazine was affected by past exposure to the herbicide. L. minor cultures were purchased commercially or collected from field sites within an agricultural watershed and exposed to atrazine for 7 days under greenhouse conditions. Populations differed significantly in their sensitivity to atrazine. Biomass was more sensitive than frond number, while chlorophyll fluorescence was not a sensitive endpoint. Overall, the sensitivity of the various populations to atrazine was not strongly related to measures of past exposure to agriculture stressors. Positive correlations between biomass twenty-five percent inhibition concentrations (IC25s), biomass estimated marginal means and in-stream atrazine concentrations were observed, providing evidence that atrazine exposure is linked to a decrease in sensitivity to atrazine. However, IC25s generated for each population were similar, ranging from 19 to 40 and 57 to 92 μg/L atrazine for biomass and frond data respectively, and likely do not represent biologically significant differences in atrazine sensitivity. Given the small range in sensitivity observed between populations, commercial laboratory cultures appear to provide a good estimate of the sensitivity of field populations of L. minor to atrazine and should continue to be used in regulatory phytotoxicity testing.

Effects of chlorimuron ethyl on terrestrial and wetland plants: Levels of, and time to recovery following sublethal exposure

Current pesticide registration guidelines call for short-term testing of plants; long-term effects on vegetative parts and reproduction remain untested. The aims of our study were to determine level of recovery and recovery times for plants exposed to the sulfonylurea herbicide chlorimuron ethyl using data collected from single species, dose-response greenhouse experiments. The nine terrestrial and eight wetland species tested showed variable levels of recovery and recovery timeframes. Many species (six terrestrial and five wetland) were vegetatively stunted at sublethal doses and were reproductively impaired. Full recovery did not occur at all doses and maximum recovery times varied from 3 to 15 weeks in this controlled environment. In a complex community, affected species may be displaced by tolerant species, through interspecific competition, before they fully recover. It is plausible that individual populations could be diminished or eliminated through reduced seedbank inputs (annuals and perennials) and asexual reproduction (perennials).

Vanadium pentoxide phytotoxicity: effects of species selection and nutrient concentration

Vanadium concentrations in soil can be increased through anthropogenic inputs and can be harmful to plants. A Petri dish experiment was conducted to assess the effect of vanadium toxicity on the germination and survival of the garden lettuce, Lactuca sativa. A second study was conducted in a greenhouse to investigate the influence of species selection and nutrient concentration on the toxicity of vanadium pentoxide to plants. L. sativa and four non-crop native plant species, two grasses (Elymus virginicus and Panicum virgatum) and two broad-leaved species (Lycopus americanus and Prunella vulgaris) were selected. Artificial soil was used in both experiments, and a geometric progression of five vanadium concentrations plus controls was selected for the soil treatments. Results of the Petri dish experiment showed that seedling survival is a less sensitive end point than above-ground dry weight (DW) as measured in the greenhouse experiment. Nutrient level (100, 10, and 1 kg/ha) was found to strongly influence vanadium toxicity in the greenhouse study. At 100 kg/ha, plant tolerance to vanadium was greatest, as indicated by higher no-observed, lowest-observed, and percentage effect concentration values. Results showed that forbs (L. americanus and P. vulgaris) tended to be more sensitive than both the crop (L. sativa) and grasses (E. virginicus and P. virgatum) at high concentrations of vanadium. Soil concentrations resulting in a 25 % decrease in shoot DW were generally less than the Canadian soil quality guideline for vanadium, suggesting that 130 mg/kg may not be protective of the Canadian native plant species used in this study.

Natural-killer cell-mediated cytotoxicity of blood-lymphocytes from patients with malignant mesothelioma treated by intrapleural interleukin-2

The most impressive biological effect of recombinant Interleukin-2 (rIL-2) is the generation of nonspecific killer cells that have lytic activity for a variety of tumor cells. Numerous studies have shown that these non specific killer cells might be of NK cell lineage even though they are different from resident NK-cell. We have examined the kinetics of the NK cell-mediated cytotoxicity of blood lymphocytes in patients after intrapleural rIL-2 administered for the treatment of pleural cancer. Escalating doses of rIL-2 were administered by intrapleural route to treat 11 patients with malignant pleural effusions due to malignant pleural mesothelioma (4 stage I, 4 stage II, 2 stage III, 1 stage IV). Two patients received respectively 3 cycles and 2 cycles of treatment. Peripheral blood lymphocyte cytotoxicity was assessed by an in vitro, chromium release microcytotoxicity assay against K562 cell line. Preliminary results indicate: (i) an important and prolonged increase in the cytotoxic response of blood lymphocytes in all patients but one having a clinical response and (ii) a lack of cytotoxicity or a baseline cytotoxic response of blood lymphocytes in all patients but one with no clinical response. These results likely point out the significance of NK-activity in the IL-2-induced antitumoral response and the interest of this in vitro assay for screening patients for further cycles of treatment.

Small-area analysis of social inequalities in residential exposure to road traffic noise in Marseilles, France

BACKGROUND

Few studies have focused on the social inequalities associated with environmental noise despite its significant potential health effects. This study analysed the associations between area socio-economic status (SES) and potential residential exposure to road traffic noise at a small-area level in Marseilles, second largest city in France.

METHODS

We calculated two potential road noise exposure indicators (PNEI) at the census block level (for 24-h and night periods), with the noise propagation prediction model CadnaA. We built a deprivation index from census data to estimate SES at the census block level. Locally estimated scatterplot smoothing diagrams described the associations between this index and PNEIs. Since the extent to which coefficient values vary between standard regression models and spatial methods are sensitive to the specific spatial model, we analysed these associations further with various regression models controlling for spatial autocorrelation and conducted sensitivity analyses with different spatial weight matrices.

RESULTS

We observed a non-linear relation between the PNEIs and the deprivation index: exposure levels were highest in the intermediate categories. All the spatial models led to a better fit and more or less pronounced reductions of the regression coefficients; the shape of the relations nonetheless remained the same.

CONCLUSION

Finding the highest noise exposure in midlevel deprivation areas was unexpected, given the general literature on environmental inequalities. It highlights the need to study the diversity of the patterns of environmental inequalities across various economic, social and cultural contexts. Comparative studies of environmental inequalities are needed, between regions and countries, for noise and other pollutants.

Phytotoxicity testing for herbicide regulation: shortcomings in relation to biodiversity and ecosystem services in agrarian systems

The purpose of this paper is to present current knowledge on methods employed to perform phytotoxicity tests and risk assessments and to highlight shortcomings in relation to biodiversity and ecosystem services. Ecosystem services are benefits provided to humankind by a multitude of organisms present in natural ecosystems. Several studies were conducted between 2001 and 2010 aimed at investigating some of the deficiencies in phytotoxicity testing (new and existing data are presented). Herbicide toxicity responses were similar when comparing a suite of crop versus wild species. However, the validity of the evaluation was limited because of the narrow types of species tested. The number of species tested, currently set between six and ten, appears insufficient. The trait-based approach (i.e. the use of plant attributes to predict species sensitivity to toxicants) can be used to improve species selection. This approach puts more emphasis on the shared biological characteristics that affect plant function within ecological communities rather than on plant phylogeny. Results presented showed that further studies are needed. In test guidelines, protocols require that crop species be sprayed as young vegetative plants, which is assumed to be the most sensitive growth stage to herbicides. In contrast, during herbicide spray, herbicides may reach non-target plants that are at various phenological stages. Several studies demonstrated that plants may be at greater risk when contamination occurs at the reproductive stage. No data on long-term effects, plant recovery or on effects on reproductive stages are requested in current guidelines. Preliminary evidence suggests that this may be an important aspect to consider in risk assessment. In addition, herbicide impacts on plant community diversity as well as biodiversity at other trophic levels have been demonstrated in only a limited number of studies and therefore should warrant more attention in risk assessment.

Hyperpolarized 129Xe NMR signature of living biological cells

We show that the differentiation between internal and external compartments of various biological cells in suspension can be made via simple NMR spectra of hyperpolarized (129) Xe. The spectral separation between the signals of (129) Xe in these two compartments is already known for red blood cells, because of the strong interaction of the noble gas with hemoglobin. The observation of two separate peaks in the 200-ppm region can be seen with both eukaryotic and prokaryotic cells, some of which are not known to contain paramagnetic proteins in large quantities. Using different experiments in which the cells are lysed, swell or are blocked in G2 phase, we demonstrate that the low-field-shifted peak observed corresponds to xenon in the aqueous pool inside the cells and not in the membranes. The presence of this additional peak is a clear indication of cell integrity, and its integration allows the quantification of the total cell volume. The relaxation time of intracellular xenon is sufficiently long to open up promising perspectives for cell characterization. The exchange time between the inner and outer cell compartments (on the order of 30 ms) renders possible the targeting of intracellular receptors, whereas the observation of chemical shift variations represents a method of revealing the presence of toxic species in the cells.

The value of woody hedgerows for moth diversity on organic and conventional farms

Habitat destruction and degradation are important drivers of biodiversity loss within agro-ecosystems. However, little is known about the effect of farming practices and the value of woody hedgerows on Lepidoptera in North America. The purpose of this work was to study moth diversity in woody hedgerows and croplands of organic and conventional farms. In addition, the influence of vegetation composition and abiotic variables on species richness, abundance, and composition was examined. Moths were sampled with light traps during six weeks in the summer of 2001. Vegetation data and abiotic variables were obtained for all sites. In total, 26,020 individuals from 12 families and 408 species were captured. Most species were uncommon. Only 35 species included >100 individuals while for 71% of species <10 individuals were found. The Noctuidae represented 221 species and 85% of all individuals captured. Woody hedgerows harbored more species and in greater number than croplands. There was no significant difference in moth diversity between organic and conventional farms, except that the Notodontidae were significantly more species rich in organic than in conventional sites. Results show that species richness, abundance, and composition were greatly influenced by habitat types (hedgerow versus crop field) and abiotic variables (minimum temperature which was correlated to moon illumination, rainfall, and cloud cover). Moth species composition was significantly correlated to vegetation composition. This study broadens our understanding of the factors driving moth diversity and expands our knowledge of their geographic range. The maintenance of noncrop habitats such as woody hedgerows within agro-ecosystems seems paramount to preserving the biodiversity and abundance of many organisms, including moths.

Cell uptake of a biosensor detected by hyperpolarized 129Xe NMR: the transferrin case

For detection of biological events in vitro, sensors using hyperpolarized (129)Xe NMR can become a powerful tool, provided the approach can bridge the gap in sensitivity. Here we propose constructs based on the non-selective grafting of cryptophane precursors on holo-transferrin. This biological system was chosen because there are many receptors on the cell surface, and endocytosis further increases this density. The study of these biosensors with K562 cell suspensions via fluorescence microscopy and (129)Xe NMR indicates a strong interaction, as well as interesting features such as the capacity of xenon to enter the cryptophane even when the biosensor is endocytosed, while keeping a high level of polarization. Despite a lack of specificity for transferrin receptors, undoubtedly due to the hydrophobic character of the cryptophane moiety that attracts the biosensor into the cell membrane, these biosensors allow the first in-cell probing of biological events using hyperpolarized xenon.

A water-soluble Xe@cryptophane-111 complex exhibits very high thermodynamic stability and a peculiar (129)Xe NMR chemical shift

The known xenon-binding (±)-cryptophane-111 (1) has been functionalized with six [(η(5)-C(5)Me(5))Ru(II)](+) ([Cp*Ru](+)) moieties to give, in 89% yield, the first water-soluble cryptophane-111 derivative, namely [(Cp*Ru)(6)1]Cl(6) ([2]Cl(6)). [2]Cl(6) exhibits a very high affinity for xenon in water, with a binding constant of 2.9(2) × 10(4) M(-1) as measured by hyperpolarized (129)Xe NMR spectroscopy. The (129)Xe NMR chemical shift of the aqueous Xe@[2](6+) species (308 ppm) resonates over 275 ppm downfield of the parent Xe@1 species in (CDCl(2))(2) and greatly broadens the practical (129)Xe NMR chemical shift range made available by xenon-binding molecular hosts. Single crystal structures of [2][CF(3)SO(3)](6)·xsolvent and 0.75H(2)O@1·2CHCl(3) reveal the ability of the cryptophane-111 core to adapt its conformation to guests.

Sublethal effects of the herbicide glufosinate ammonium on crops and wild plants: short-term effects compared to vegetative recovery and plant reproduction

Current guidelines for phytotoxicity testing rely heavily on short-term testing of primarily crop species to predict the sensitivity of non-target, wild plants to herbicides. However, little is known on how plants recover following initial growth inhibitions in standard 14-28 day greenhouse tests conducted for pesticide assessment and registration. The objectives of this study were to assess the ability of plant species to recover (biomass and reproduction) when tested at the juvenile stage (routine regulatory testing), comparing crop and wild species and using the herbicide glufosinate ammonium. Ten crops and 10 wild species were tested with a one-time exposure to glufosinate ammonium in a greenhouse. Half the plants of each species (9 doses × 6 replicates) were harvested 3 weeks after being sprayed (short-term). The remaining plants were harvested several weeks later, coinciding with seed set or natural senescence (long-term). Total aboveground biomass and several endpoints related to crop production and plant reproduction were measured. Calculated IC50 values (dosage that results in a 50% decrease in the biomass of a plant as compared to the untreated controls) based solely on aboveground biomass, for species harvested in the long-term were generally higher than those obtained in the short-term (with two exceptions), indicating recovery over time. Crop species did not differ from wild species in terms of sensitivity. However, in seven out of 12 cases where reproduction was measurable, reproductive endpoints were more sensitive than either short or long-term biomass endpoints, indicating the importance of examining these parameters in phytotoxicity testing. Glufosinate ammonium was found to be phytotoxic at low doses (2.64-7.74% g ai/ha of the label rate).

Comparison of the effects of glyphosate and atrazine herbicides on nontarget plants grown singly and in microcosms

Intensification of agriculture and the corresponding increase in herbicide use has led to concern regarding the effects these chemicals may have on nontarget plants of agroecosystems. Current pesticide registration guidelines are focused on testing crop species grown singly in pots under greenhouse conditions and may not provide adequate measures of protection to noncrop species. The objective of the present study was to compare the response of terrestrial and wetland plants to the herbicides glyphosate and atrazine when grown singly in pots versus under different microcosm conditions. Greenhouse microcosms were generally more sensitive than single-species tests. Plants grown for an extended test period or in seminatural field conditions were generally less sensitive to herbicides. Sensitivity was found to be dependent on interactions between species and test conditions. Changes in community structure were observed in herbicide-treated microcosms that would not be predicted from single-species testing. Single-species tests are useful because they are inexpensive, can demonstrate clear dose-response patterns uncomplicated by other factors influencing growth, and are able to provide a measure of the sensitivity of a given species to glyphosate and atrazine. However, they are unable to predict subtle changes in community structure that may have important long-term consequences.

Measuring variability in phytotoxicity testing using crop and wild plant species

A series of experiments was conducted to assess the level of variability in phytotoxicity testing and to investigate factors that may explain some of the observed uncertainties and inconsistencies. The work was conducted in greenhouse or growth chamber environments with plants growing individually in pots and harvested 28 d after spraying with two herbicides, glyphosate and atrazine, as formulated products. Between six and 10 doses were used on five or six replicates, necessitating over 4,500 individually growing plants. In the first set of experiments, several ecotypes (originating from different areas of the world) of eight wild plant species were tested. Significant differences in sensitivity to atrazine and glyphosate were found among ecotypes of most species tested. In the second suite of experiments, the reproducibility of results during different seasons (when growing conditions vary) was investigated using three crops and four wild plant species. Results showed that seasonal variability elicited a pronounced discrepancy in response between plants tested at different times of the year. It was found that no consistent effects could be attributed to the biotic or abiotic factors investigated. Several ecotypes of the same species differed in their seed size, percentage germination, or germination requirements, as well as in growth patterns, but these differences could not explain differences in herbicide sensitivity. Likewise, differences in phytotoxicity could not be attributed to factors such as temperature, light intensity, and sunlight duration. The present study supports the inclusion of an uncertainty factor in risk assessments to account for the intrinsic variability in plant sensitivity to herbicides.

High heterogeneity of plasma membrane microfluidity in multidrug-resistant cancer cells

Diffusion-time distribution analysis (DDA) has been used to explore the plasma membrane fluidity of multidrug-resistant cancer cells (LR73 carcinoma cells) and also to characterize the influence of various membrane agents present in the extracellular medium. DDA is a recent single-molecule technique, based on fluorescence correlation spectroscopy (FCS), well suited to retrieve local organization of cell membrane. The method was conducted on a large number of living cells, which enabled us to get a detailed overview of plasma membrane microviscosity, and plasma membrane micro-organization, between the cells of the same line. Thus, we clearly reveal the higher heterogeneity of plasma membrane in multidrug-resistant cancer cells in comparison with the nonresistant ones (denoted sensitive cells). We also display distinct modifications related to a membrane fluidity modulator, benzyl alcohol, and two revertants of multidrug resistance, verapamil and cyclosporin-A. A relation between the distribution of the diffusion-time values and the modification of membrane lateral heterogeneities is proposed.

Germination requirements for 29 terrestrial and wetland wild plant species appropriate for phytotoxicity testing

BACKGROUND

Species selected for phytotoxicity testing have been limited to a few standard crop species owing to restrictive recommendations at the regulatory level. However, guidelines by the Organisation for Economic Development and Cooperation (OECD) were recently amended in 2006 to include a list of herbaceous non-crop plant species suitable for testing. The objective of this study was to outline the optimum germination requirements for a selection of wild species for which seeds were readily available from commercial suppliers.

RESULTS

Of the 29 herbaceous terrestrial and wetland species included in this study, all achieved 50% germination and 23 reached > 70% germination to meet the criterion outlined in the OECD guidelines. Most species attained their maximum germination within 14 days or less. Cold stratification of imbibed seeds improved germination for 14 species. Increasing sowing soil depth did not improve seed germination. The variance attained in this experiment between replicates was low, especially for species with > 70% germination (standard error approximately 5%).

CONCLUSION

The present study showed that 23 of the 29 species tested required minimal pretreatments and produced consistent, reliable and uniform germination reaching at least 70%. The inclusion of wild plant species in regulatory testing should be given real consideration.

Herbicidal effects on nontarget vegetation: investigating the limitations of current pesticide registration guidelines

The impact of herbicide exposure on nontarget vegetation within agroecosystems has sparked extensive research that revealed that current pesticide registration guidelines may be inadequate at predicting the effects of herbicides on wild plants and habitats. This study extends the current interest by presenting three experiments highlighting some of the limitations to current phytotoxicity testing guidelines. Several crops and wild plant species were grown under greenhouse conditions following standard protocol for phytotoxicity testing. Plants were sprayed with five different herbicides at the four- to six-leaf stage, and biomass was recorded at 28 d after spray. Results showed that current regulatory protocol will likely underestimate herbicide phytotoxicity if testing does not include data for the complete tank-mix formulation. The present study also showed that the range in herbicide sensitivity among cultivars of the same crop can be quite extensive and that, depending on the cultivar included in a risk assessment, conclusions regarding the phytotoxicity of any given herbicide may differ. Although no significant differences in sensitivity were found between crops and related wild species, results revealed that current guidelines are too rigid in terms of species selection. Considering the variability among crop cultivars, coupled with the ecological importance and the ease of germination of many noncrop plant species, pesticide regulatory guidelines would be improved if wild species were included in testing. Findings of the present study indicate that current pesticide regulatory guidelines require modifications to ensure a more accurate assessment of herbicide effects on nontarget plant species.