Effect of native and introduced arbuscular mycorrhizal fungi on growth and nutrient uptake ofLygeum spartum andAnthyllis cytisoides

The interaction between native and introduced fungi and their effect on plant growth and mineral uptake were studied. The host plants wereLygeum spartum andAnthyllis cytisoides, the introduced fungus wasGlomus fasciculatum. The four soils used were selected from disturbed and contaminated by mining activities areas. Inoculated and uninoculated plants were grown in the unsterilized and sterilized soils (with and withouth native microflora, respectively). Plants inoculated withG. fasciculatum were higher and had higher tissue P concentration than uninoculated plants, especially inA. cytisoides. However, this inoculation was not effective in unsterilized substrates, suggesting a competition between introduced and native fungi. Concentration of mineral elements other than P varied depending on the host plant and soil. Decrease in Fe, Cu, Mn, Zn and Pb was observed in mycorrhizalA. cytiosides plants and a slight increase in Zn concentration was noted in mycorrhizalL. spartum plants. The study showed that the type of soil and their populations of native endophytes have a considerable effect on plant response to mycorrhizal symbiosis, especially in disturbed soils.     

Identification of root exudates from the Pb-accumulator Sedum alfredii under Pb stresses and assessment of their roles

The Pb-accumulator Sedum alfredii is a good phytoremediation material, and widely used in the phytoremediation research of soils contaminated with Pb. The root exudates from it may be playing a significant role in the process of phytoremediation. In this study, the metabonomics method which based on gas chromatography–mass spectrometry (GC–MS) and pattern recognition analysis was used to identify the remarkable root exudates from S. alfredii under different Pb stresses, including exposure concentrations (0, 10, 50, 200 and 1000?µmol/L) and times (4 and 8 days). And batch extraction experiments were used to verify the roles of these remarkable root exudates. According to the results, 11 metabolites were considered as the remarkable metabolites. Oxalic acid, galactonic acid and glyceric acid can remove Pb in soil, and the removal effect was: oxalic acid?>?galactonic acid?>?glyceric acid. Xylose, glucose and maltose have no removal effect for Pb in soil.     

Characterization of Lead in Soils of a Rifle/Pistol Shooting Range in Central Florida,USA

The distribution of lead in soil samples collected from both surface (0 to 10?cm) and profile (O 0 to 10?cm, E 11 to 30?cm, Eb 31 to 50?cm, Bw 51 to 100?cm, and C 181 to 200?cm) at a 14-year-old rifle/pistol shooting range located in central Florida were determined using EPA Method 3051a (microwave, HNO₃/HCl=3:1, v/v). In addition to total lead analysis, Toxicity Characteristic Leaching Procedure (TCLP) analysis was performed on corresponding samples to determine whether the soils would require special handling as hazardous waste if the soils were to be removed from the range. Total lead in surface soils varied from 330 to 17 850?mg Pb kg^?1, with the greatest concentration in the middle of the backstop berm. The TCLP tests indicated that lead in all surface soils exceeded the 5?mg Pb L^?1 critical level of federal regulation for solid wastes and hazardous wastes provided by the Resource Conservation and Recovery Act (RCRA) and would be characterized as hazardous waste. Sequential fractionation and X-ray diffraction (XRD) analyses revealed that lead carbonate existed predominantly (91.3%) in the berm soil. The weathering of lead bullets in the soil environments formed primarily as hydrocerussite (Pb₃(CO₃)₂(OH)₂), with small amounts of massicot (PbO) and cerussite (PbCO₃). However, the elevated soil pH, caused by the oxidization and transformation process of elemental lead in lead bullets, could be a significant factor in limiting the migration of lead in the soil.     

The effects of lead,nickel, and strontium nitrates on cell division and elongation in maize roots

The effects of Pb, Sr, and Ni nitrates on the root growth, its cell division and elongation were studied. Two-day-old maize seedlings were incubated on the 35 μM Ni(NO₃)₂, 10 μM Pb(NO₃)₂, or 3 mM Sr(NO₃)₂ in the presence or absence of 3 mM Ca(NO₃)₂. Metal toxicity was evaluated after the inhibition of root growth for the first and second days of incubation in comparison with the roots kept on water or Ca(NO₃)₂ solution. The contents of metals were determined in the apical (the first centimeter from the tip) and basal (the third centimeter from the kernel) root parts by voltamperometry and atomic-absorption spectrophotometry. We measured the length of the meristem, the length of the fully elongated cells, counted the mitotic index (MI) in the meristem and the number of meristematic cells in the cortex row; we also calculated duration the cell cycle. In the absence of Ca(NO₃)₂, the metal content in the apical root region was higher than in basal one. In the presence of Ca(NO₃)₂, we observed reverse ratio most pronounced in the case of Pb and Sr. All metals tested markedly reduced MI in the cortex, which was determined by the increase in the cell cycle duration and accompanied by the meristem shortening. These metals affected differently cell division and elongation: Ni inhibited mainly cell division and to a lesser degree their elongation, whereas Sr and Pb affected both cell division and elongation; only Sr treatment resulted in the increased length of the fully elongated cells. In the presence of Ca, all studied growth indices changed less than in the absence of Ca, which was manifested in the less severe suppression of the root growth and was in agreement with the lower accumulation of the metals in the root tips. Possible causes for the heavy metal action on growth are discussed in connection with the specificity of their transport and accumulation.     

Removal of Lead from a Calcareous Soil by Chloride Complexation

Remediation of a lead-contaminated calcareous soil using NaCl solutions was examined. The removal of Pb from a coarser fraction of the soil was found to be 83% after three successive extractions at a NaCl concentration of 8?M, whereas an average of 9% of the calcium was removed. Multibatch extractions of Pb from finer soil containing a higher level of Pb were also performed. The removal of Pb from this soil after six successive extractions with 8?M NaCl was found to be 93%. The removal of Pb increased with time in a batch test and approached 80% after 90?h. It was found that the data were adequately described by a first-order rate, and hence it is believed that a single reaction mechanism controlled the release of Pb (i.e., from carbonate bound or exchangeable Pb fractions in the soil). Increasing removal of Pb was found as the volume of water added was increased as the mass of NaCl in solution remained constant. The removal of Pb from the leachate was found to be 90%, 99.7%, and 35% with lime (25.20?g/L), sodium carbonate (4.48?g/L), and calcium carbonate (82.0?g/L) addition, respectively. In the case of sodium carbonate, the removal of Pb was further improved when the pH was adjusted to 8.2. The recycling of free chloride that was generated from leachate resulted in 91% removal of Pb from the soil (particle size < 4.75?mm) after six recycles.     

Pyruvate Metabolism in the Brain of Young Rats Intoxicated with Organic and Inorganic Lead

Abstract: The activities of lipoyl dehydrogenase, aspartate transaminase, and alanine transaminase, and levels of lactate were estimated in cerebral cortex, cerebellum, and brainstem of rats intoxicated acutely with tetraethyl lead and chronically with lead acetate. A significant inhibition of lipoyl dehydrogenase was observed in both groups of animals, whereas transaminase activities were increased in inorganic lead toxicity. Oxidative decarboxylation and anaplerosis of pyruvate was assessed in brain slices using [l-¹⁴C]pyruvate. Pyruvate dehydrogenase activity was decreased in both organic and inorganic lead toxicity, whereas labelling of aspartate and alanine was increased in inorganic lead toxicity. In studies in vitro , lead acetate showed a more significant effect than tetraethyl lead. The higher anaerobic metabolism in inorganic lead toxicity, as evidenced by increased anaerobic lactate production by brain slices, could either be an adaptive mechanism or be due to the delayed maturation of brain in the developing rat. Such a mechanism does not occur in acute organic lead toxicity, as the compound brings about massive and rapid degenerative changes in brain, resulting in convulsive seizures and death of the animals.     

Evaluation of protein–ligand affinity prediction using steered molecular dynamics simulations

In computational drug design, ranking a series of compound analogs in a manner that is consistent with experimental affinities remains a challenge. In this study, we evaluated the prediction of protein–ligand binding affinities using steered molecular dynamics simulations. First, we investigated the appropriate conditions for accurate predictions in these simulations. A conic harmonic restraint was applied to the system for efficient sampling of work values on the ligand unbinding pathway. We found that pulling velocity significantly influenced affinity predictions, but that the number of collectable trajectories was less influential. We identified the appropriate pulling velocity and collectable trajectories for binding affinity predictions as 1.25 Å/ns and 100, respectively, and these parameters were used to evaluate three target proteins (FK506 binding protein, trypsin, and cyclin-dependent kinase 2). For these proteins using our parameters, the accuracy of affinity prediction was higher and more stable when Jarzynski’s equality was employed compared with the second-order cumulant expansion equation of Jarzynski’s equality. Our results showed that steered molecular dynamics simulations are effective for predicting the rank order of ligands; thus, they are a potential tool for compound selection in hit-to-lead and lead optimization processes.     

An ultrasound study of the effect of chronic lead exposure on endometrial cycle changes in the female cynomolgus monkey.

The effect of up to 10 years of lead (Pb) exposure (1500 micrograms/kg BW/day) on endometrial cycle changes in adult cynomolgus monkeys (n = 30) were examined by real-time ultrasound. Pb exposure had no effect on peak serum estradiol (E2) or progesterone (P4) concentrations, menstrual cycle length, and endometrial response to gonadal steroids as determined by ultrasound.     

The Ethics of Research on Less Expensive,Less Effective Interventions: A Case for Analysis

The Kennedy Krieger lead paint study is a landmark case in human experimentation and a classic case in research ethics. In this paper I use the lead paint study to assist in the analysis of the ethics of research on less expensive, less effective interventions. I critically evaluate an argument by Buchanan and Miller who defend both the Kennedy Krieger lead paint study and public health research on less expensive, less effective interventions. I conclude that Buchanan and Miller’s argument is flawed but that does not mean that research designed to find less effective interventions cannot be justified in some situations. Based on my analysis, I suggest questions to ask when considering such research and I offer some principles to guide us. In the process, light is shed on the various debates and issues raised by the lead paint study; e.g. standards of care, researchers’ responsibilities to research subjects, the distinction between treatment and research and the question of what it is that legitimizes public health research. Merle Spriggs is supported by a grant from the Alfred Felton Bequest which is managed by ANZ Trustees.     

Biological responses of the sea urchin, Arbacia punctulata, to lead contamination for an estuarine ecological risk assessment

An estuarine ecological risk assessment for thePortsmouth Naval Shipyard (PNS) Kittery, ME, wasconducted utilizing the U.S. EPA's Framework forEcological Risk Assessment (ERA). As part of theanalysis phase of the ERA, laboratory studies wereconducted to develop quantitative exposure-responserelationships for lead (Pb), a key contaminant ofconcern for PNS, in order to evaluate the role of Pbin the ecological stress observed near PNS, and toestimate the probability of ecological risk associatedwith Pb contamination at the site. Biological effectsof exposure to Pb via sediment or diet were evaluatedusing several life stages of the sea urchin, Arbacia punctulata. This strategy was employedbecause echinoderm species, including A.punctulata, are amenable to laboratory testing andhave been used frequently to assess the toxicity ofestuarine waters and sediments. In addition, lifestage-specific biological effects could be comparedand integrated into projections of population-levelresponses to Pb. Results indicated that adult seaurchins accumulated Pb in direct proportion toexposure medium Pb concentration, whether exposureoccurred via sediment or diet. High Pb concentrationsreduced survival and gamete production in females, buthad no effect on the viability of produced gametes. Aqueous Pb exposure concentrations that producedadverse effects on adult sea urchin survival andreproduction were also directly toxic to early lifestages. In addition to their utility for this ERA,these results have applicability for the prediction ofbiological effects or the retrospective analysis ofcausal relationships at other estuarine sites.