Effect of the endectocide ivermectin on filamentous fungi

We investigated the effect of ivermectin, at environmental concentrations and above, on several strains of filamentous fungi. Ivermectin did not show significant short-term effect on biomass production and germination rate of the spores. By contrast, the spore production was stimulated twofold in Phanerochaete chrysosporium and Mucor racemosus cultures, whereas that endpoint was reduced in Fusarium cultures. A long-term exposure of F. oxysporum to ivermectin reduced both production and germination of fungal spores. Ivermectin was not an inducer of exocellular oxidases.     

Optimal foraging in bumblebees: Why is nectar left behind in flowers?

Summary Queen bumblebees (Bombus appositus) leave nectar behind in Delphinium nelsoni flowers with high-standing crops of nectar. Bumblebees deplete flowers in areas with lower-standing crops. Residual volumes predicted by an optimal feeding hypothesis agree with field measurements.     

Estimating the objectives of a public firm in a natural resource industry

The purpose of this paper is to understand the behavior of policymakers in a public firm. To accomplish this goal, the objectives of a government-owned firm operating in the Saskatchewan uranium industry are econometrically estimated. The estimates are used to determine the importance policymakers attach to the outcomes resulting from their behavior and to examine how the firm might respond to changes in its economic environment. Empirical results indicate that the public firm is willing to reduce profits in order to increase employment and reserves.     

Serum concentrations of perfluorooctanesulfonate and other fluorochemicals in an elderly population from Seattle, Washington

Perfluorooctanesulfonyl fluoride (POSF, C₈F₁₇SO₂F) related-materials have been used as surfactants, paper and packaging treatments, and surface (e.g., carpet, textile, upholstery) protectants. A metabolite, perfluorooctanesulfonate (PFOS, C₈F₁₇SO₃⁻), has been identified in the serum and liver of non-occupationally exposed humans and wildlife. Because of its persistence, an important question was whether elderly humans might have higher PFOS concentrations. From a prospective study designed to examine cognitive function in the Seattle (WA) metropolitan area, blood samples were collected from 238 dementia-free subjects (ages 65–96). High-pressure liquid chromatography-electrospray tandem mass spectrometry determined seven fluorochemicals: PFOS; N-ethyl perfluorooctanesulfonamidoacetate; N-methyl perfluorooctanesulfonamidoacetate; perfluorooctanesulfonamidoacetate; perfluorooctanesulfonamide; perfluorooctanoate; and perfluorohexanesulfonate. Serum PFOS concentrations ranged from less than the lower limit of quantitation (3.4 ppb) to 175.0 ppb (geometric mean 31.0 ppb; 95% CI 28.8–33.4). An estimate of the 95% tolerance limit was 84.1 ppb (upper 95% confidence limit 104.0 ppb). Serum PFOS concentrations were slightly lower among the most elderly. There were no significant differences by sex or years residence in Seattle. The distributions of the other fluorochemicals were approximately an order of magnitude lower. Similar to other reported findings of younger adults, the geometric mean serum PFOS concentration in non-occupational adult populations likely approximates 30–40 ppb with 95% of the population’s serum PFOS concentrations below 100 ppb.     

Microbial degradation of metal complexed cyanides and thiocyanate from mining wastewaters

A microbiological examination of the soil from a cyanide wastewater storage basin was carried out. The storage basin contained water from the cyanidation process of gold extraction, and it was composed principally of simple cyanide, metal complexed cyanide, mainly cuprocyanide, ferro-ferricyanides and thiocyanate. Pseudomonas species were the principal bacteria identified in the soil. Using the storage basin soil as a seed sludge, its potential for the biodegradation of all the cyanide complexes in the mining wastewater was studied in the laboratory, using batch, fed-batch and continuous processes. The ammonia and sulphate produced were quantified. The presence of intermediate products was suspected. In the continuous process, total degradation of all cyanide was observed at a dilution rate of 0.066 day(-1).     

Xenobiotics: Substrates and inhibitors of the plant cytochrome P450

The ability of a plant cytochrome P450 to bind and metabolise plant endogenous molecules and xenobiotics was investigated. The work was performed on the yeast-expressed CYP73A1, a cinnamate 4-hydroxylase isolated fromHelianthus tuberosus. CYP73 controls the general phenylpropanoid pathway and is likely to be one of the most abundant sources of P450 in the biosphere. The enzyme shows a high selectivity toward plant secondary metabolites. Nevertheless, it oxygenates several small and planar xenobiotics with low efficiency, including an herbicide (chlorotoluron). One xenobiotic molecule, 2naphthoic acid, is hydroxylated with an efficiency comparable to that of the physiological substrate. This reaction was used to devise a fluorimetric test for the rapid measurement of enzyme activity. A series of herbicidal molecules (hydroxybenzonitriles) are shown to bind the active site without being metabolised. These molecules behave as strong competitive inhibitors of CYP73 with a K_i in the same micromolar range as the K_m for the physiological substrate. It is proposed that their inhibition of the phenylpropanoid pathway reinforces their other phytotoxic effects at the level of the chloroplasts. All our results indicate a strong reciprocal interaction between plant P450s and xenobiotics.     

Effect of metallic cations on the sorption of pesticides on soil

We studied the adsorption and desorption of two pesticides, namely isoproturon and dimetomorph, onto a model soil sample. We first show that the adsorption of isoproturon depends on pH, from 1 mg g⁻¹ at pH 4 to 2 mg g⁻¹ at pH 10, contrary to the adsorption of dimetomorph (5.8 mg g⁻¹). We also studied the influence of metallic cations, copper(II), iron(III), manganese(II), and chromium(III), on the sorption of isoproturon and dimetomorph. We found that in the case of isoproturon, the presence of metallic cations does influence the retention capacity of the soil sample. The sorption becomes very weak in the presence of copper and chromium, whereas in the case of iron and manganese the sorption properties are slightly modified.     

Immune response of earthworms (Lumbricus terrestris, Eisenia andrei and Aporrectodea tuberculata) following in situ soil exposure to atmospheric deposition from a cement factory

In order to reduce their energy costs, many cement plants use fuel product substitutes (old tyres and used oil). The combustion of these products generates a metal increase (e.g. Cu, Cd, Pb and Zn) in the atmospheric emissions. After their release, these elements are deposited into the environment and could eventually accumulate up to concentrations of concern. At the Saint-Laurent cement factory (Joliette, QC, Canada), maximum deposition of these elements occurs in the direction of prevailing winds (North-East). We evaluated the potential impact of these depositions upon the immune system of three earthworm species (Lumbricus terrestris, Eisenia andrei and Aporrectodea tuberculata) exposed in a natural environment. The exposure sites were 0.5, 1.0, and 2.0 km downwind from the cement factory, along with an upwind reference site. The immune parameters studied were the cell viability and phagocytic potential of the immune cells (coelomocytes). For both L. terrestris and E. andrei, after 7 d exposure, none of the measured parameters showed significant differences among the sites. On the other hand, for the indigenous worm A. tuberculata, in the most exposed zone (at 0.5 km), we observed an increase in cell viability and phagocytic potential. This increase could possibly be attributed to physicochemical effects such as the alkaline pH of the soil, or alternatively, it could result from beneficial effects induced by an increased calcium supply.     

Analyzing censored environmental data using survival analysis: Single sample techniques

The occurrence of censored data due to less than detectable measurements is a common problem with environmental data. The methods of survival analysis, although designed primarily for right censored data and time measured variables, can be adapted to apply censored environmental data. These methods have several theoretical and practical advantages over many existing techniques for dealing with less than detectable measurements.Work performed under the auspices of the U.S. Department of Energy, DOE Contract No. DE-AC07-76ID01570.