Functions of Phytochrome Interacting Factors (PIFs) in Adapting Plants to Biotic and Abiotic Stresses.

Plants possess the remarkable ability to sense detrimental environmental stimuli and launch sophisticated signal cascades that culminate in tailored responses to facilitate their survival, and transcription factors (TFs) are closely involved in these processes. Phytochrome interacting factors (PIFs) are among these TFs and belong to the basic helix-loop-helix family. PIFs are initially identified and have now been well established as core regulators of phytochrome-associated pathways in response to the light signal in plants. However, a growing body of evidence has unraveled that PIFs also play a crucial role in adapting plants to various biological and environmental pressures. In this review, we summarize and highlight that PIFs function as a signal hub that integrates multiple environmental cues, including abiotic (i.e., drought, temperature, and salinity) and biotic stresses to optimize plant growth and development. PIFs not only function as transcription factors to reprogram the expression of related genes, but also interact with various factors to adapt plants to harsh environments. This review will contribute to understanding the multifaceted functions of PIFs in response to different stress conditions, which will shed light on efforts to further dissect the novel functions of PIFs, especially in adaption to detrimental environments for a better survival of plants.

Sequential washing and eluent regeneration with agricultural waste extracts and residues for facile remediation of meta-contaminated agricultural soils.

Washing with organic acids and dissolved organic carbon (DOC) is a promising technique for effective removal of potentially toxic metals from agricultural soils and the two key factors are the screening of inexpensive, high-efficiency, and environmentally friendly washing agents and the safe treatment of waste eluent. We used extracts from agro-forestry wastes (pineapple peel, lemon peel, grapefruit peel and gardening crabapple fruit) to develop a facile two-stage sequential washing method (extracts and/or citric acid (CA) and coupled with extracts) and regenerated waste eluent. The washing efficiencies of Cd and Cu were significantly increased by pineapple peel (PP) using two-stage sequential washing with the sequence of PP + CA-PP > CA-PP > PP-PP. The potential pollution risk from soil Cd was lowered by 33.0% from moderate to low risk, and soil nutrient contents increased. 80.9% of Cd and 81.3% of Cu in waste eluent were efficiently removed by the PP residues. The removal mechanisms of metals in soils and eluents by PP washing agents and residues can be attributed to acid activation, cation exchange and complexation between metal ions and carboxyl groups. Therefore, the PP extracts and residues are potentially suitable for the removal of Cd and Cu from polluted agricultural soils and washing waste eluents.

As, Cd, and Pb relative bioavailability in contaminated soils: Coupling mouse bioassay with UBM assay.

The robustness of in vitro bioaccessibility assays to predict oral relative bioavailability (RBA) of multiple metals in contaminated soils requires validation using additional soil samples. In this study, 11 contaminated soils from mining/smelting areas were analyzed for As-, Cd-, and Pb-RBA using a mouse bioassay and metal bioaccessibility via the UBM gastric phase assay. Metal-RBA varied considerably among soils, with As-RBA (2.5-23%, mean 12%) being generally lower than Cd-and Pb-RBA (3.4-88 and 3.3-59%, mean 42 and 28%), due to higher proportions of As in the residual fractions. Metal-RBA generally decreased with increasing metal concentrations probably due to reduced labile metal fractions. In addition, strong negative correlations were observed between total Fe with As-, Cd-, and Pb-RBA (R2 = 0.46-0.77), suggesting the role of Fe in controlling metal-RBA in soils. Like RBA, metal bioaccessibility by the UBM assay also varied among samples. However, strong in vivo-in vitro correlations (IVIVCs) were observed between metal-RBA and bioaccessibility (R2 = 0.52-0.81). Further, there were little differences when As-, Cd-, and Pb-IVIVCs established using soils from this study and soils pooled from literature were compared, suggesting the robustness of the UBM assay to predict metal-RBA in contaminated soils.

Pathways of root uptake and membrane transport of Cd2+ in the zinc/cadmium hyperaccumulating plant Sedum plumbizincicola.

Uptake and membrane transport of cadmium (Cd) in roots of the hyperaccumulator Sedum plumbizincicola X.H. Guo et S.B. Zhou ex L.H. Wu was characterized by assessing the impact of various inhibitors and ion channel blockers on Cd accumulation as well as the real-time net Cd2+ flux at the roots with application of the scanning ion-selective electrode technique. The uncouplers 2,4-dinitrophenol and P-type adenosine triphosphatase inhibitor Na3 VO4 significantly limited Cd2+ uptake and transport kinetics in the root of S. plumbizincicola. These findings indicate that Cd is actively taken up into the roots. The Cd content in plant was significantly decreased with pretreatments of the Ca2+ channel blocker La3+ or Gd3+ and the K+ channel blocker tetraethylammonium, as well as in the presence of higher concentration of Ca2+ and K+ . These findings indicated that uptake of Cd2+ into the root of S. plumbizincicola proceeds through ion channels that are permeable to both Ca2+ and K+ as confirmed by the direct evidence of real-time net Cd2+ fluxes at the root surface in the treatments with ion channel inhibitors, as well as in the presence of elevated concentrations of Ca2+ and K+ . In addition, the results suggested a role for phytochelatin and protein synthesis in mediating Cd2+ uptake by S. plumbizincicola. These findings increase the understanding of Cd2+ uptake and membrane transport pathways in roots of the Zn/Cd hyperaccumulator S. plumbizincicola. Environ Toxicol Chem 2017;36:1038-1046. © 2016 SETAC.

Characteristics of cadmium uptake and membrane transport in roots of intact wheat (Triticum aestivum L.) seedlings.

Wheat is one of several cereals that is capable of accumulating higher amounts of Cd in plant tissues. It is important to understand the Cd2+ transport processes in roots that result in excess Cd accumulation. Traditional destructive technologies have limited capabilities in analyzing root samples due to methodological limitations, and sometimes may result in false conclusions. The mechanisms of Cd2+ uptake into the roots of wheat seedlings (Triticum aestivum L.) were investigated by assessing the impact of various inhibitors and channel blockers on Cd accumulation as well as the real-time net Cd2+ flux at roots with the non-destructive scanning ion-selective electrode technique. The P-type ATPase inhibitor Na3VO4 (500 µM) had little effect on Cd uptake (p < 0.05) and the kinetics of transport in the root of wheat, suggesting that Cd2+ uptake into wheat root cells is not directly dependent on H+ gradients. While, the uncoupler 2,4-dinitrophenol significantly limited Cd2+ uptake (p < 0.05) and transport kinetics in the root of wheat, suggesting the existence of metabolic mediation in the Cd2+ uptake process by wheat. The Cd content at the whole-plant level in wheat was significantly (p < 0.05) decreased upon pretreatment with the Ca2+ channel blockers La3+ or Gd3+ and Verapamil, but not in case of pretreatment with the K+ channel blocker tetraethylammonium (TEA). In addition, the inhibitors of the Ca2+ channel, as well as high concentrations of Ca2+, reduced the real-time net Cd2+ fluxes at the root surface in SIET experiments. These results indicate that Cd2+ moves across the plasma lemma of the wheat root via Ca2+ channels. In addition, our results suggested a role for protein synthesis in mediating Cd2+ uptake and transport by wheat.

Caffeic acid phenethyl ester attenuates pro-inflammatory and fibrogenic phenotypes of LPS-stimulated hepatic stellate cells through the inhibition of NF-κB signaling.

Hepatic stellate cells (HSCs) are the major cell type involved in liver fibrosis. Lipopolysaccharide (LPS)-mediated signaling through Τoll-like receptor 4 (TLR4) in HSCs has been identified as a key event in liver fibrosis, and as the molecular link between inflammation and liver fibrosis. In this study, we investigated the effects of caffeic acid phenethyl ester (CAPE), one of the main medicinal components of propolis, on the pro-inflammatory and fibrogenic phenotypes of LPS-stimulated HSCs. HSCs from rats were isolated and cultured in Dulbecco's modified Eagle's medium (DMEM). Following treatment with LPS, HSCs showed a strong pro-inflammatory phenotype with an upregulation of pro-inflammatory mediators, and a fibrogenic phenotype with enhanced collagen synthesis, mediated by transforming growth factor-ß1 (TGF-ß1). CAPE significantly and dose-dependently reduced LPS-induced nitrite production, as well as the transcription and protein synthesis of monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6) and inducible nitric oxide synthase (iNOS), as determined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), western blotting and enzyme-linked immunosorbent assays (ELISA). CAPE further reduced the TGF-ß1-induced transcription and translation (protein synthesis) of the gene coding for collagen type I α1 (col1A1), in LPS-stimulated HSCs. Following LPS stimulation, the phosphorylation of the nuclear factor-κB (NF-κB) inhibitor IκBα and consequently, the nuclear translocation of NF-κB, were markedly increased in the HSCs, and these changes were reversed by pre-treatment with CAPE. In conclusion, CAPE attenuates the pro-inflammatory phenotype of LPS-stimulated HSCs, as well as the LPS-induced sensitization of HSCs to fibrogenic cytokines by inhibiting NF-κB signaling. Our results provide new insight into the treatment of hepatic fibrosis through regulation of the TLR4 signaling pathway.

[A theoretical and experimental study on the Fuzzy evaluation model of biological performance of Chinese materia medica with an either cold or hot herbal property].

OBJECTIVE: The concepts of cold and hot herbal properties in traditional Chinese medicine (TCM), reflecting the efficacy trends of medicinal herbs, have the Fuzzy characteristics. It is suited for the application of Fuzzy mathematics in research of herbal properties. For a comprehensive evaluation of herbal properties, this work constructed and made a practice of the Fuzzy discrimination model regarding the biological performance of Chinese materia medica. METHODS: Firstly, TCM formulas of cold or hot property were employed for setting the reference values and calculating the membership functions of cold and hot Fuzzy sets with Fisher discriminant. Then the model parameters of cold performance function (CPF) and hot performance function (HPF) were acquired. Second, the experimental data from studies on changes in multisystem indicators of animals given the classical cold formula (Sanhuang Fang) and hot formula (Jiangfugui Fang) were collected to calculate CPF and HPF. Then an experiment of administration of hot property herbs, Rougui (Cortex Cinnamomi) and Xianmao (Rhizoma Curculiginis), and cold property herbs, Huangbai (Cortex Phellodendri) and Zhizi (Fructus Gardeniae) to normal animals and animals with glucocorticoid-induced yang-deficiency or yin-deficiency state was designed. The relative changes in animal states were analyzed by the evaluation model to find the way in which herbal properties are represented. RESULTS: The HPF values of biological performance were higher than the CPF values in administration of Rougui to animals of normal (0.528>0.221), yang-deficiency (0.203>-0.490) and yin-deficiency (1.750>-0.479) states, and in administration of Xianmao to animals of normal (0.474>-1.601) and yang-deficiency (0.288>-1.923) states, which represented the hot property. The HPF values of biological performance were lower than the CPF values in administration of Huangbai to animals of normal (-0.870<0.798) and yang-deficiency (-0.339<0.194) states, and in administration of Zhizi to animals of yin-deficiency (-1.802<0.354) state, which represented the cold property. CONCLUSION: The herbal properties and the biological performance characteristics of herbal formulas are ascertained by using the Fuzzy evaluation model. The personalities, as well as commonalities of herbal properties are key areas for focus because of the multi-approach biological performance of cold and hot property.

[Ridit analysis of experimental data from animal models of yang deficiency induced by different doses of hydrocortisone].

OBJECTIVE: Hydrocortisone-induced yang-deficiency animal model has now become the generally accepted model of yang deficiency. However, assessing the most appropriate dose of hydrocortisone is a long-term challenge. For analyzing the modeling dose, the authors have built several kinds of yang-deficiency models induced by hydrocortisone at different doses, and analyzed the experimental data with various mathematical statistical methods. In order to discuss the effects of the modeling dose on the basis of previous research, the authors introduced Ridit analysis. METHODS: After categorizing 27 batches of experiments with four different doses (including 2.5, 3.75, 10 and 20 mg/kg), the data were standardized and the data type was changed to meet the needs of subsequent calculations. Then, by using Ridit analysis, the authors compared the variation of 19 biochemistry indexes involving nervous-endocrine system, immune system, metabolic system and the function of the liver and kidney, so as to analyze the similarities and differences of those yang-deficiency models mentioned above. The effects of modeling dose were then discussed. RESULTS: With regard to the overall state of the animal model, the difference between the models induced by different doses of hydrocortisone (2.5, 3.75, 10 and 20 mg/kg) showed no statistical significance, indicating that differences in hydrocortisone dose barely lead to significant changes in yang-deficiency models. For the trends of changing in different indexes, indexes had different performances when the doses differs: gonad indexes (estradiol and testosterone) showed better performance in 2.5 mg/kg group, immunological indexes (immunoglobulin M and immunoglobulin G) showed better performance in 3.75 mg/kg group and metabolic indexes (triglyceride and total cholesterol) showed better performance in 10 mg/kg group, etc. This indicates that the dose of hydrocortisone should be determined according to the research purposes. CONCLUSION: Ridit analysis can be used as an integration analysis method for animal models of yang deficiency induced by hydrocortisone at different doses.

[Pharmacological effects of Oleum Cinnamomi and water extract of Cortex Cinnamomi in rats with yang-deficiency cold syndrome and the mathematical analysis].

OBJECTIVE: To compare the effects of Oleum Cinnamomi and water extract of Cortex Cinnamomi in rats with yang-deficiency cold syndrome based on mathematical analysis. METHODS: A total of 48 male Sprague-Dawley rats were randomly divided into 4 groups (normal, model, Oleum Cinnamomi and water extract of Cortex Cinnamomi). Yang-deficiency cold syndrome was induced by hydrocortisone sodium succinate. Oleum Cinnamomi and water extract of Cortex Cinnamomi were given by gastrogavage daily for one week to respective groups. Material metabolism indexes such as glucose (GLU), uric acid (UA), total cholesterol (TC), triacylylyceral (TAG), total protein (TP) and albumin (ALB); energy metabolism indexes such as lactic acid (LAC), lactate dehydrogenase (LDH), succinate dehydrogenase (SDH) and adenosine triphosphatase (ATPase); endocrine system indexes such as corticosteroid (CS), triiodothyronine (T3), tetraiodothyronine (T4), thyroid stimulating hormone (TSH), estradiol (E(2)), vitamin C (VC) and 17-hydroxycorticosteriod (17-OHCS); and immune system indexes such as immunoglobulin M (IgM), immunoglobulin G (IgG), complement 3 (C3) and complement 4 (C4) were measured. And then the data were analyzed by mathematical analysis method. RESULTS: Oleum Cinnamomi and water extract of Cortex Cinnamomi had similar influence on some indexes of material metabolism, energy metabolism and endocrine and immune systems in rats with yang-deficiency cold syndrome. Positive effects were showed in GLU, TC, TAG, TP, ALB, IgM, E(2), CS, VC and 17-OHCS. Water extract of Cortex Cinnamomi had no significant effects on TSH, LAC and SDH, but Oleum Cinnamomi had, while water extract of Cortex Cinnamomi had significant effects on ATPase, LDH and IgG. CONCLUSION: There is a complex relationship between Oleum Cinnamomi and water extract of Cortex Cinnamomi in their effects on rats with yang-deficiency cold syndrome. They have similar property, however, disparities exist between them to some extent. The exact mechanism needs further research.

[Study of biological performance of Chinese materia medica with either a cold or hot property based on the three-element mathematical analysis model].

OBJECTIVE: The properties of Chinese materia medica are believed to be the summarization of the effects of biological performance on the various body states. Systemic discussion of chemical-factor elements, body-condition elements, biological-performance elements and their interrelationships is needed for research into the properties of Chinese materia medica. Following the practical characteristics of Chinese medicine, the three-element mathematical model was formed by introducing some mathematical concepts and methods and was used to study the cold or hot property of Chinese medicine, and to investigate the difference in biological performances of the two properties. METHODS: By using the concept of different functionality of Chinese medicine on abnormal states and the idea of interaction in mathematics, the effects of chemical-factor elements and body-condition elements were normalized to the amount of biological performance which was represented by some important indicators. The three-element mathematical model was formed with scatter plots through four steps, including effect separation, intensity calculation, frequency statistics and relevance analysis. A comparison pharmacology experiment of administration of hot property medicines, Fuzi (Radix Aconiti Lateralis Preparata) and Rougui (Cortex Cinnamomi), and cold property medicines, Huangbai (Cortex Phellodendri) and Zhizi (Fructus Gardeniae) on normal and glucocorticoid-induced yang-deficiency and yin-deficiency states was designed. The results were analyzed by the mathematical model. The scatter plots were the main output of model analysis. The expression of cold property and hot property was able to be quantified by frequency distribution of biological indexes of administrations on yang-deficiency and yin-deficiency states in the "efficacy zone" and "toxicity zone" of the plots and by the relevance analysis. RESULTS: The ratios of biological indicator frequency in the "efficacy zone" of administrations on yang-deficiency state and yin-deficiency state were 7:3 for Fuzi, 3:3 for Rougui, 4:4 for Huangbai and 1:5 for Zhizi. The sums of the biological indicator frequency in the "toxicity zone" of administration on the two states were 4 for Fuzi, 0 for Rougui, 2 for Huangbai and 4 for Zhizi. The relevance analysis showed that the order from Fuzi, Rougui, Huangbai to Zhizi was proportional to the change from "be true of yang-deficiency state" to "be true of yin-deficiency state". The extent of the hot property decreased while that of the cold property increased in the order of Fuzi, Rougui, Huangbai and Zhizi. The stronger the efficacy of above medicines is, the more obvious the toxicity displayed. CONCLUSION: The three-element mathematical model employed in this study is effectively capable of explaining the different biological expressions between hot property medicines and cold property medicines. This suggests that it may provide a mathematical tool and theoretical basis for the modern interpretation of cold property and hot property of Chinese medicine, and provide new ideas for further studing into the essence of Chinese medicine property theory.

A QICAR approach for quantifying binding constants for metal-ligand complexes.

Relative metal-ligand complex stability is predicted by evaluating the relationships between physicochemical properties of metal ions and their experimental biotic and abiotic binding constants, K. Linear regression analysis showed that the softness index (σ(p)) and the covalent index (χ(2)(m) r) were especially useful in model construction for rainbow trout (Oncorhynchus mykiss), fathead minnows (Pimephales promelas) and crustaceansaquatic (Daphnia magna) based on RMSE and F-ratio criterion (F(observed)/F(critical) of ≥4). The absolute value of the log of the first hydrolysis constant |logK(OH)| correlated best with logK values for barley (R(2)=0.74, p=0.02) and earthworm (R(2)=0.82, p=0.01). In contrast, the ionic index Z(2)/r explained most of the variability of logK values for the two clays kaolinite and montmorillonite, while |logK(OH)| was a better predictor of the generic NICA-Donnan parameters for HA and FA (0.67

Toxicity of zinc oxide nanoparticles in the earthworm, Eisenia fetida and subcellular fractionation of Zn.

The extensive use of nanoparticles (NPs) in a variety of applications has raised great concerns about their environmental fate and biological effects. This study examined the impact of dissolved organic matter (DOM) and salts on ZnO NP dispersion/solubility and toxicity to the earthworm Eisenia fetida. To be able to better evaluate the toxicity of NPs, exposure in agar and on filter paper was proposed for enabling a comparison of the importance of different uptake routes. A dose-related increase in mortality was observed in earthworms exposed in agar with almost 100% mortality after 96 h exposure to the highest concentration (1000 mg ZnO/kg agar). Scanning electron microscopy (SEM) showed that the addition of salts enhanced the aggregation of ZnO NPs in agar and consequently affected the dissolution behavior and biological availability of the particles. On filter paper, mortality was the highest at the lowest exposure concentration (50 mg ZnO/L) and seemed to decrease with increasing exposure levels. TEM images of ZnO showed that the solubility and morphology of NPs were changed dramatically upon the addition of humic acids (HA). The subcellular distribution pattern of Zn in earthworms after 96 h exposure in agar and on filter paper showed that the Zn taken up via dietary ZnO particles (from agar) was mainly found in organelles and the cytosol while the Zn accumulated as soluble Zn from filter paper was mainly distributed in cell membranes and tissues. Antioxidant enzymatic activities (SOD, CAT, and GSH-px) were investigated in the worms surviving the toxicity tests. A slight increase of SOD activities was observed at the lowest exposure dose of ZnO (50mg/kg), followed by a decrease at 100mg/kg in the agar cubes. Activities of both CAT and GSH-Px enzymes were not significantly influenced in the worms exposed to agar, although a slight decrease at 500 and 1000 mg ZnO/kg agar was observed. A similar change trend of SOD activities was observed for the earthworms on filter paper, but a significant decrease began at a higher ZnO NP concentration of 500 mg ZnO/L. The use of soil extracts instead of deionized water (DW) to simulate a realistic exposure system significantly reduced the toxicity of the ZnO NPs on filter paper, which increases the predictive power of filter paper toxicity tests for the environmental risk assessment of NPs.

[Mathematical analysis of characteristics of glucocorticoid-induced yang deficiency or yin deficiency syndrome in animal models based on information entropy theory].

OBJECTIVE: Based on information entropy theory, this study analyzes the experimental indicators of glucocorticoid-induced traditional Chinese medicine yang deficiency or yin deficiency syndrome in animal models, thus laying the foundation of defining and interpreting the model state. METHODS: Data of biochemical indicators from 24 groups of animal models with different modeling conditions (type of modeling agent, dosage of modeling agent and modeling time) were collected. Information gain values for three study objects (type of modeling agent, dosage of modeling agent and modeling time) were calculated respectively after standardization, and then characteristics of yang deficiency or yin deficiency syndrome models were interpreted with these values and ranking map. RESULTS: Greatest information gain values of most indicators were got when the study object was the type of modeling agent, which is the most important factor in the differentiation of model state. With this study object, triglyceride (TG), total cholesterol (TC), total protein (TP), albumin (ALB), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and corticosteroid (CS) got larger information gain values than testosterone (T), lactic dehydrogenase (LDH), and cyclic adenosine monophosphate (cAMP). This indicated that the former seven indicators may be significantly different between the two animal models induced by hydrocortisone and dexamethasone, respectively. In the study of the modeling time, AST may be affected more than others. In the study of the dosage of modeling agent, TC and ALB may be affected more in the model of hydrocortisone and no indicators were significantly affected by the dosage of modeling agent in the dexamethasone model. CONCLUSION: Mathematical method based on information entropy theory allows researchers to analyze experimental data in several experiments at the same time and to interpret the trend and stability of indicators. Based on this study and by analyzing the impacts of different modeling conditions on the indicators, elucidations of the characteristics of glucocorticoid-induced yang deficiency or yin deficiency syndrome in animal models and some biochemical indicators for model comparison are in need.

Evaluating the biotic ligand model for toxicity and the alleviation of toxicity in terms of cell membrane surface potential.

The electrostatic nature of plant cell membrane (CM) plays significant roles in ionic interactions at the CM surface and hence in the biotic effects of metal ions. Increases in major cations (commonly Ca2+, Mg2+, H+, Na+, K+, etc.) in bulk-phase medium reduce the negativity of CM surface electrical potential (psi0), but these slightly increase the driving force of a metal ion crossing CMs (surface-to-surface transmembrane potential difference, Em,surf). Toxicologists commonly attributes the interactions between heavy metals and common cations (e.g., H+, Ca2+, and Mg2+) to competitions for binding sites at a hypothetical CM surface ligand. The psi0 effects are likely to be more important to metal toxicity and the alleviation of toxicity than site-specific competition. Models that do not consider psi0, such as the biotic ligand model (BLM) and the free ion activity model (FIAM), as usually employed are likely to lead to false conclusions about competition for binding at CM surface ligands. In the present study a model incorporating psi0 effects and site-specific competition effects was developed to evaluate metal (Cu2+, Co2+, and Ni2+) toxicities threshold (EA50, causing 50% inhibition) for higher plants. In addition, the mechanisms for the effects of common cations on toxicity of metals were also explored in terms of CM surface electrical potential.

What role does cell membrane surface potential play in ion-plant interactions.

Almost all cell membrane surfaces (CMS) are intrinsically negatively charged. These negative charges create a surface electrical potential (Psi(0)) which affects ion concentrations at the CMS and consequently affects the phytotoxicity of metallic cations and metalloid anions in different ways. The Psi(0) is also controlled by the ionic composition of the bulk-phase medium (BM). Common cations, especially H(+), Ca(2+) and Mg(2+), can reduce the negativity of Psi(0) by ionic screening and binding. Treatments that reduce the negativity of Psi(0) would reduce the surface activity of Cu(2+) ({Cu(2+)}(0)) and increase the surface activity of arsenate ({As(V)}(0)) at the CMS, and consequently alleviation of Cu(2+) toxicity but aggravation As toxicity would be expected. It is the Psi(0), rather than site-specific competition, that plays the principal role in ionic interactions and biotic effects.

Solid/solution Cu fractionations/speciation of a Cu contaminated soil after pilot-scale electrokinetic remediation and their relationships with soil microbial and enzyme activities.

The aim of this study was to investigate the detailed metal speciation/fractionations of a Cu contaminated soil before and after electrokinetic remediation as well as their relationships with the soil microbial and enzyme activities. Significant changes in the exchangeable and adsorbed-Cu fractionations occurred after electrokinetic treatment, while labile soil Cu in the solution had a tendency to decrease from the anode to the cathode, and the soil free Cu(2+) ions were mainly accumulated in the sections close to the cathode. The results of regression analyses revealed that both the soil Cu speciation in solution phase and the Cu fractionations in solid phase could play important roles in the changes of the soil microbial and enzyme activities. Our findings suggest that the bioavailability of soil heavy metals and their ecotoxicological effects on the soil biota before and after electroremediation can be better understood in terms of their chemical speciation and fractionations.

Effect of cation competition on cadmium uptake from solution by the earthworm Eisenia fetida.

Metal speciation alone is insufficient to predict metal accumulation in aquatic and terrestrial organisms, because competition between cations can play an important role. In the present study, the effects of competing cations (Ca2+, Mg2+, and H+) on Cd uptake by the earthworm Eisenia fetida were quantified through short-term experiments over a large Cd concentration range in aqueous exposure solutions. Free Cd2+ activity was a better predictor for Cd accumulation in the earthworms than was total Cd concentration in solution, thus supporting the free ion activity model. The presence of the other cations at environmentally pertinent concentrations inhibited Cd uptake to different degrees. A competitive equilibrium model based on the biotic ligand model was developed to quantify the effect of the cations. The model parameters are the conditional constants for binding of H+ (log K = 4.97), Ca2+ (log K = 3.00), and Mg2+ (log K = 2.64) to the biological uptake sites of E. fetida. Autovalidation of the model with experimental results showed that 48-h Cd accumulation in the earthworm could be successfully predicted with activities of free Cd2+ and the major cations (Ca2+, Mg2+, and H+) as input.

Effect of cations on copper toxicity to wheat root: implications for the biotic ligand model.

The extent to which calcium, magnesium, sodium, potassium and hydrogen ions independently mitigate Cu rhizotoxicity to wheat (Triticumaestivum) in nutrient solutions was examined. Increasing activities of Ca2+ and Mg2+ but not Na+, K+ and H+ linearly increased the 2 d EC50 (as Cu2+ activity), supporting the concept that some cations can compete with Cu2+ for binding the active sites at the terrestrial organism-solution interface (i.e., the biotic ligand, BL). According to the biotic ligand model (BLM) concept, the conditional stability constants for the binding of Cu2+, Ca2+ and Mg2+ to the BL were derived from the toxicity data. They were 6.28, 2.43 and 3.34 for logK(CuBL), logK(CaBL) and logK(MgBL), respectively. It was calculated that on average 43.6% of BL sites need to be occupied by Cu2+ to induce 50% root growth inhibition. Using the estimated parameters, a BLM was successfully developed to predict Cu toxicity for wheat as a function of solution characteristics.

Subcellular distribution of Cd and Pb in earthworm Eisenia fetida as affected by Ca2+ ions and Cd-Pb interaction.

A semi-static solution culture method was used to study the effects of Ca(2+) supply and interaction of Cd-Pb on the subcellular distribution of Cd and Pb in earthworm Eisenia fetida. The subcellular distribution of Cd and Pb was shown to be metal specific. About 80% of the Cd was distributed in the cytosol (fraction G), and only about 20% of total Cd was found in the tissue and cell membrane (fraction E) and the microsomes (fraction F). Nearly 50% of the Pb was rich in the tissue and cell membrane (fraction E). The supply of Ca(2+) ions significantly decreased Cd concentration in the cytosol (fraction G) and the whole tissue of the E. fetida. At the subcellular level, the addition of Pb(2+) ions significantly decreased the Cd percentage associated with fraction G from 83.7% to 58.4% and increased fraction E from 10.7% to 34.0%, respectively.

Effect of major cations and pH on the acute toxicity of cadmium to the earthworm Eisenia fetida: implications for the biotic ligand model approach.

The purpose of this study was to characterize the individual effect of different cations (Ca(2+), Mg(2+), Na(+), K(+), and H(+)) on the acute toxicity of Cd to the earthworm Eisenia fetida. Higher activities of the considered cations increased the 48-h LC(50) (expressed as Cd(2+) activities) linearly to different extents in simulated soil solution. The conditional constants for the binding of H(+ )(log K = 5.41), Cd(2+ )(log K = 4.0), Ca(2+ )(log K = 3.35), Mg(2+ )(log K = 2.82), Na(+ )(log K = 1.57), and K(+ )(log K = 2.31) to the biotic ligand (BL) of E. fetida were derived from the toxicity data based on the biotic ligand model (BLM). Furthermore, it was calculated that on average 72% of the BL sites needed to be occupied by Cd(2+) to induce 50% lethal effect. Autovalidation of the model with the results of the test sets showed that 48-h LC(50 )could be predicted within a factor of two.