Negative Effects Of High Concentrations Research Articles

Physiological Responses of Cucumber Plants to Sodium Lignosulfonate Application to Sandy Loam Soil

The use of lignosulfonates (LS) to improve soil fertility is currently under study and discussion. The effect of sodium LS application in the sandy loam soil on the accumulation of biomass, photosynthesis, respiration and their coupling in cucumber plants was studied. The LS rate of 10–25 g/kg did not have a significant effect on the studied parameters of the physiological state of plants. However, at a high LS content (50–100 g/kg), the plant growth rate and activity of the photosynthetic apparatus decreased, and the respiration rate increased, which caused the increase in the ratio of respiration to photosynthesis. The negative effect of high concentrations of LS on the physiological state of cucumber plants and their cold resistance is presumably associated with sodium salinization of the soil.

Exposure to an environmentally relevant concentration of 17α-ethinylestradiol disrupts craniofacial development of juvenile zebrafish

Endocrine disrupting chemicals (EDCs) can interact with native hormone receptors to interfere with and disrupt hormone signalling that is necessary for a broad range of developmental pathways. EDCs are pervasive in our environment, in particular in our waterways, making aquatic wildlife especially vulnerable to their effects. Many of these EDCs are able to bind to and activate oestrogen receptors, causing aberrant oestrogen signalling. Craniofacial development is an oestrogen-sensitive process, with oestrogen receptors expressed in chondrocytes during critical periods of development. Previous studies have demonstrated a negative effect of high concentrations of oestrogen on early craniofacial patterning in the aquatic model organism, the zebrafish (Danio rerio). In order to determine the impacts of exposure to an oestrogenic EDC, we exposed zebrafish larvae and juveniles to either a high concentration to replicate previous studies, or a low, environmentally relevant concentration of the oestrogenic contaminant, 17α-ethinylestradiol. The prolonged / chronic exposure regimen was used to replicate that seen by many animals in natural waterways. We observed changes to craniofacial morphology in all treatments, and most strikingly in the larvae-juveniles exposed to a low concentration of EE2. In the present study, we have demonstrated that the developmental stage at which exposure occurs can greatly impact phenotypic outcomes, and these results allow us to understand the widespread impact of oestrogenic endocrine disruptors. Given the conservation of key craniofacial development pathways across vertebrates, our model can further be applied in defining the risks of EDCs on mammalian organisms.

The stress effect of atrazine on the inducible defense traits of Daphnia pulex in response to fish predation risk: Evidences from morphology, life history traits, and expression of the defense-related genes

Herbicide pollution is persistent, which not only has a negative impact on individual organisms, but also may endanger the interspecific relationship between predators and prey. Cladocerans, i.e. zooplankton that plays an important role in the energy flow and material circulation in freshwater ecosystem, usually develop induced defense in response to predation risk. We used atrazine, one of the most used herbicides in the world, and Daphnia pulex, a representative cladocerans, to test the possible interference effect of herbicides on the induced defensive traits of cladocerans in response to predator fish (Rhodeus ocellatus) kairomone, including morphological defense, life history strategies, and the expression of defense-related genes. Atrazine reduced the body size, spine size, growth rate, total offspring, and the relative reproductive output of D. pulex, which further affected the response strength of the morphological and life history defenses, i.e., atrazine significantly reduced the spine size, relative spine size, and fecundity of D. pulex in response to R. ocellatus kairomone. Exposure to atrazine affected the expression of defense-related genes, and we speculated that atrazine affected the signaling process in the induced anti-predation defense of cladocerans. Specially, fish kairomone attenuated the negative effects of high concentrations of atrazine on the life history traits of D. pulex. Our results will help to accurately assess the potential risk of artificial compounds in freshwater ecosystems from the perspective of interspecific relationships, and help to understand the impact of environmental changes on the inducible anti-predator defense of prey in aquatic ecosystems.

A Novel Microfluidic Device for the Neutrophil Functional Phenotype Analysis: Effects of Glucose and Its Derivatives AGEs.

Neutrophil dysfunction is closely related to the pathophysiology of patients with diabetes mellitus, but existing immunoassays are difficult to implement in clinical applications, and neutrophil’s chemotaxis as a functional biomarker for diabetes mellitus prognostic remains largely unexplored. Herein, a novel microfluidic device consisted of four independent test units with four cell docking structures was developed to study the neutrophil chemotaxis, which allowed multiple cell migration observations under a single field of view (FOV) and guaranteed more reliable results. In vitro studies, the chemotaxis of healthy neutrophils to N-Formyl-Met-Leu-Phe (fMLP) gradient (0, 10, 100, and 1000 nM) was concentration-dependent. The distinct promotion or suppression in the chemotaxis of metformin or pravastatin pretreated cells were observed after exposure to 100 nM fMLP gradient, indicating the feasibility and efficiency of this novel microfluidic device for clinically relevant evaluation of neutrophil functional phenotype. Further, the chemotaxis of neutrophils pretreated with 25, 50, or 70 mM of glucose was quantitatively lower than that of the control groups (i.e., 5 mM normal serum level). Neutrophils exposed to highly concentrated advanced glycation end products (AGEs) (0.2, 0.5, or 1.0 μM; 0.13 μM normal serum AGEs level), a product of prolonged hyperglycemia, showed that the higher the AGEs concentration was, the weaker the migration speed became. Specifically, neutrophils exposed to high concentrations of glucose or AGEs also showed a stronger drifting along with the flow, further demonstrating the change of neutrophil chemotaxis. Interestingly, adding the N-benzyl-4-chloro-N-cyclohexylbenzamide (FPS-ZM1) (i.e., high-affinity RAGE inhibitor) into the migration medium with AGEs could hinder the binding between AGEs and AGE receptor (RAGE) located on the neutrophil, thereby keeping the normal chemotaxis of neutrophils than the ones incubated with AGEs alone. These results revealed the negative effects of high concentrations of glucose and AGEs on the neutrophil chemotaxis, suggesting that patients with diabetes should manage serum AGEs and also pay attention to blood glucose indexes. Overall, this novel microfluidic device could significantly characterize the chemotaxis of neutrophils and have the potential to be further improved into a tool for risk stratification of diabetes mellitus.

Performance optimization of a chitosan/anammox reactor in nitrogen removal from synthetic wastewater

Anaerobic ammonia oxidation (anammox) is an environmentally friendly, cost-effective, and biological method for nitrogen treatment from aqueous solutions. However, slow growth rate, negative effects of high concentration of nitrite, ammonia and other pollutants (such as metals) on anammox activity are the main drawbacks of using anammox. Thus, in this study, anammox was attached on chitosan to improve anammox performance. Two reactors comprising chitosan and anammox bacteria (first reactor, chitosan/anammox) and solely anammox (second reactor, control) were run for 73 d. The nitrogen loading rate (NLR) varied from 2 to 14 (gN/L/d), while the nitrogen concentration varied from 80 to 700 mg/L. The chitosan/anammox reactor showed a better performance than the sole anammox (control), with respective maximum abatement values of ammonia (NH4+), nitrite (NO2-), and total nitrogen (TN) of 90.8%, 83.5%, and 81.7% on days 20–25 under a NLR of 8–10 kgTN/(m3 d). Response surface methodology (RSM) was employed to optimize the performance of both reactors, and a reasonable R2 value showed that the RSM well optimized the performance of the reactors. After finding the optimum performance conditions for both reactors, Fe and Cu (0.5–7.0 mg/L) were added to the influent to monitor the effects of metals on the performance of both reactors. The performance of both reactors decreased to 0% following the addition of 7.0 (first reactor) and 6.5 (second reactor) mg/L Cu and Fe, respectively. This indicated that chitosan not only enhanced nitrogen removal by anammox but also improved the resistance of anammox to metals.

Adsorption studies of zinc(II) on magnetite, baobab (Adansonia digitata) and magnetite\u2013baobab composite

The negative effect of high concentration of heavy metals in the environment on living species prompted this research. A study of adsorption of zinc on synthesized magnetite (MG), baobab fruit shell (BB) and magnetite–baobab composite (MB) was carried out. The adsorption of Zn(II) ions was examined using batch equilibrium technique. The effects of initial metal ions concentrations (15–150 mg/L for zinc), adsorbent dose (0.05–0.3 g), contact time (5–150 min), pH (2–8) and temperature (303–343 K) on the sorption capacity of these adsorbents were investigated. The Zn(II) ions at a solution concentration of 150 mg/g gave maximum adsorption capacity of 38.25, 33.95 and 29.20 mg/g for MB, MG and BB, respectively. The adsorption of Zn(II) metal ions was modelled using Langmuir, Freundlich and Temkin isotherms. The highest correlation coefficient (R2) value was obtained from Freundlich model for Zn(II) adsorption on MG and MB as 0.986 and 0.973, respectively, while that of Zn(II) on BB was obtained from Langmuir model as 0.993. The kinetic and thermodynamic studies revealed that the adsorption processes followed pseudo-second-order kinetics and were endothermic in nature. Desorption experiments were conducted on the spent adsorbent using 0.1, 0.2, 0.5, 1.0 and 2.0 M HCl to determine the reusability potentials of the adsorbents. There was an decrease in the amount of Zn(II) ions adsorbed after each stage of desorption process varied between the different acid concentrations. The 0.1 M HCl gave the highest degree of adsorption for Zn(II) on BB, while 0.2 M HCl was the best for MG and MB.

Effects of mercury on the life table demography of the rotifer Brachionus calyciflorus under different algal food (Scenedesmus obliquus) densities

In aquatic ecosystems, mercuric compounds are considered to be highly toxic to a great variety of aquatic biota ranging from bacteria to fishes. In the present study, the effects of different concentrations (0, 2.0, 6.0, 10.0, 14.0 and 18.0μg·L−1) of Hg2+ on the life table demography of Brachionus calyciflorus were investigated at three densities (1.0×106, 2.0×106 and 4.0×106cells·mL−1) of Scenedesmus obliquus. The results showed that compared to the controls, Hg2+ at 14.0 and 18.0μg·L−1 significantly decreased both the average lifespan and the life expectancy at hatching, Hg2+ at 2.0–18.0μg·L−1 shortened the generation time, and Hg2+ at 18.0μg·L−1 decreased the net reproductive rate of B. calyciflorus cultured at 1.0×106cells·mL−1 of S. obliquus. Increase in algal food level reduced the negative effects of high concentrations of Hg2+ on survival, reproduction and population growth of the rotifers. Hg2+ at 6.0μg·L−1, and 6.0 and 18.0μg·L−1 increased the intrinsic rate of population increase of the rotifers cultured at 1.0×106 and 2.0×106cells·mL−1 of S. obliquus, respectively. But Hg2+ at 18.0μg·L−1 decreased the intrinsic rate of population increase of the rotifers cultured at 4.0×106cells·mL−1 of S. obliquus. Significantly nominal concentration–response relationships existed between Hg2+ concentration and each of all the five life history variables of B. calyciflorus cultured at 1.0×106cells·mL−1 of S. obliquus, the generation time of the rotifers cultured at 2.0×106cells·mL−1 of S. obliquus, as well as the intrinsic rate of population increase of the rotifers cultured at 4.0×106cells·mL−1 of S. obliquus. Among all the life history variables, generation time was the most sensitive to mercury pollution. Since algal levels chosen in the present study are much higher than those available in natural waters, except in eutrophic water bodies, the effects of mercury on survival, reproduction and population growth of the rotifers in natural waters may be more severe than those extrapolated from the present study.

Influência do excesso de nitrogênio amoniacal no tratamento de efluente têxtil em reator de bateladas sequenciais com Aspergillus niger AN 400

RESUMO Água residuária têxtil foi tratada com Aspergillus niger AN 400 em reator de bateladas sequenciais, em ciclos de 48 h para avaliar o efeito de fonte adicional de nitrogênio sobre a eficiência do sistema alimentado com efluente diluído (10% v/v) e glicose (3 g.L-1). O afluente recebeu fonte adicional de nitrogênio (etapa I), acarretando em excesso de nitrogênio amoniacal (192 mg.L-1) no meio, resultando em remoção de matéria orgânica de 85%, porém em apenas 55% de remoção de corante. Ao se diminuir a concentração média de amônia para 98 mg.L-1 (etapa II), a remoção de corante (83%) passou a ser superior à de matéria orgânica, de 69%, mostrando o efeito negativo de concentrações elevadas de amônia sobre o sistema, favorecendo ainda o crescimento de bactérias, o que provavelmente inibiu a produção de enzimas fúngicas e contribuiu para a perda de eficiência na remoção de corante e formação de subprodutos.

The hormesis effect of BDE-47 in HepG2 cells and the potential molecular mechanism

Polybrominated diphenyl ethers (PBDEs) had been used extensively in electrical and electronic products as brominated flame retardants. PBDEs are widely distributed in environment media and wildlife since they are lipophilic and persistent, resulting in bioaccumulation and bioamplification through food chains. Accumulation of PBDEs in the environment and human tissues will consequently cause potential negative effects on the ecological environment and human health. To date, some in vitro and in vivo studies have reported that PBDEs possess neurotoxicity, hepatotoxicity, immunotoxicity, reproduction toxicity, endocrine disrupting activity and carcinogenicity. BDE-47 is one of the most predominant PBDE congeners detected in human tissues. The objective of this study is to investigate whether low concentration of BDE-47 could cause hormesis effect in the human hepatoma HepG2 cells, and to explore the possible molecular mechanism. The results showed that low concentration of BDE-47 (10−10, 10−9 and 10−8M) could promote cell proliferation and cause no obvious change in DNA damage or cell apoptosis, while the high concentration significantly inhibit cell proliferation. Meanwhile, the reactive oxygen species (ROS) in low concentration BDE-47 (10−10, 10−9 and 10−8M) treated groups significantly elevated compared with the control group. After low concentration BDE-47 treatment, the expression of proliferating cell nuclear antigen (PCNA), Cyclin D1, DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and phosphorylated protein kinase B (p-Akt) in the HepG2 cells was markedly up-regulated. However, in DNA-PKcs inhibited cells, the promotion effect on cell proliferation was significantly suppressed. Cell cycle analysis showed a significant decrease in G1 phase after exposure to low concentration of BDE-47. Moreover, pre-exposure to low concentration BDE-47 seemed alleviate the negative effects of high concentration (50μM) exposure to cause DNA damage and apoptosis. These results suggested that BDE-47 has a hormesis effect in HepG2 cells and DNA-PKcs/Akt pathway may be involved in regulation of cell proliferation and apoptosis.

Effects of lactic acid and glycolic acid on human osteoblasts: A way to understand PLGA involvement in PLGA/calcium phosphate composite failure

The use of degradable composite materials in orthopedics remains a field of intense research due to their ability to support new bone formation and degrade in a controlled manner, broadening their use for orthopedic applications. Poly (lactide-co-glycolide) acid (PLGA), a degradable biopolymer, is now a popular material for different orthopedic applications and is proposed for use in tissue engineering scaffolds either alone or combined with bioactive ceramics. Interference screws composed of calcium phosphates and PLGA are readily available in the market. However, some reports highlight problems of screw migration or aseptic cyst formation following screw degradation. In order to understand these phenomena and to help to improve implant formulation, we have evaluated the effects of PLGA degradation products: lactic acid and glycolic acid on human osteoblasts in vitro. Cell proliferation, differentiation, and matrix mineralization, important for bone healing were studied. It was found that the toxicity of polymer degradation products under buffering conditions was limited to high concentrations. However, non-toxic concentrations led to a decrease in cell proliferation, rapid cell differentiation, and mineralization failure. Calcium, whilst stimulating cell proliferation was not able to overcome the negative effects of high concentrations of lactic and glycolic acids on osteoblasts. These effects help to explain recently reported clinical failures of calcium phosphate/PLGA composites, but further in vitro analyses are needed to mimic the dynamic situation which occurs in the body by, for example, culture of osteoblasts with materials that have been pre-degraded to different extents and thus be able to relate these findings to the degradation studies that have been performed previously.

Mitigation of the deleterious effect of silicon species on the conductivity of ceria electrolytes

The deleterious effect of silicon species on the conductivity of ceria electrolytes is well documented in the literature. A simple process has been developed at Praxair that alleviates the negative effect of high concentrations of silicon species on the conductivity of ceria electrolytes. The impact of this process on the conductivity of commercially available doped ceria electrolyte powders is demonstrated and a likely mechanism for the reduction of the resistivity is proposed. The influence of this process on other properties of the ceria electrolyte is discussed.

The geometry of DNA supercoils modulates topoisomerase-mediated DNA cleavage and enzyme response to anticancer drugs.

Collisions with DNA tracking systems are critical for the conversion of transient topoisomerase-DNA cleavage complexes to permanent strand breaks. Since DNA is overwound ahead of tracking systems, cleavage complexes most likely to produce permanent strand breaks should be formed between topoisomerases and positively supercoiled molecules. Therefore, the ability of human topoisomerase IIalpha and IIbeta and topoisomerase I to cleave positively supercoiled DNA was assessed in the absence or presence of anticancer drugs. Topoisomerase IIalpha and IIbeta maintained approximately 4-fold lower levels of cleavage complexes with positively rather than negatively supercoiled DNA. Topoisomerase IIalpha also displayed lower levels of cleavage with overwound substrates in the presence of nonintercalative drugs. Decreased drug efficacy was due primarily to a drop in baseline (i.e., nondrug) cleavage, rather than an altered interaction with the enzyme-DNA complex. Similar results were seen for topoisomerase IIbeta, but the effects of DNA geometry on drug-induced scission were somewhat less pronounced. With both topoisomerase IIalpha and IIbeta, intercalative drugs displayed greater relative cleavage enhancement with positively supercoiled DNA. This appeared to result from negative effects of high concentrations of intercalative agents on underwound DNA. In contrast to the type II enzymes, topoisomerase I maintained approximately 3-fold higher levels of cleavage complexes with positively supercoiled substrates and displayed an even more dramatic increase in the presence of camptothecin. These findings suggest that the geometry of DNA supercoils has a profound influence on topoisomerase-mediated DNA scission and that topoisomerase I may be an intrinsically more lethal target for anticancer drugs than either topoisomerase IIalpha or IIbeta.

Analyzing effects of pesticides on invertebrate communities in streams

The aim of this investigation was to find patterns in aquatic invertebrate community composition that are related to the effects of pesticides. Investigations were carried out in 20 central European streams. To reduce the site-specific variation of community descriptors due to environmental factors other than pesticides, species were classified and grouped according to their vulnerability to pesticides. They were classified as species at risk (SPEAR) and species not at risk (SPEnotAR). Ecological traits used to define these groups were sensitivity to toxicants, generation time, migration ability, and presence of aquatic stages during time of maximum pesticide application. Results showed that measured pesticide concentrations of 1:10 of the acute 48-h median lethal concentration (LC50) of Daphnia magna led to a short- and long-term reduction of abundance and number of SPEAR and a corresponding increase in SPEnotAR. Concentrations of 1:100 of the acute 48-h LC50 of D. magna correlated with a long-term change of community composition. However, number and abundance of SPEAR in disturbed stream sections are increased greatly when undisturbed stream sections are present in upstream reaches. This positive influence compensated for the negative effect of high concentrations of pesticides through recolonization. The results emphasize the importance of considering ecological traits and recolonization processes on the landscape level for ecotoxicological risk assessment.

Performance responses of lambs of various ages to Italian ryegrass (<i>Lolium multiflorum</i>) fertilized with various levels of nitrogen

Italian ryegrass (Lolium multiflorum cv. Midmar) is often fertilized with high levels of nitrogen (N) in order to ensure maximum dry matter (DM) yields. This practice also increases the N content of herbage. This study was conducted to determine whether differences in the nitrogen (N) content of Italian ryegrass would have an effect on the performance of South African Mutton Merino lambs. Fertilizer levels of 100, 200, 400, 600 or 800 kg N/ha were applied to the pastures in order to produce herbage containing varying concentrations of N. Nitrogen fertilization increased the total N and nitrate-N in the plant material and decreased non-structural carbohydrate concentrations. An increase in rumen ammonia-N concentration with increasing pasture N concentration was observed in twelve and four-month-old lambs. A quadratic relationship was found to exist between the N content of ryegrass and DM intake for twelve-month-old lambs, and a negative linear relationship was observed for four-month-old lambs. A quadratic relationship was observed between the N content of ryegrass and average daily gain for lambs of both age groups. The equations derived in this study illustrate the potentially negative effects of high concentrations of N and nitrate-N in Italian ryegrass on intake and growth rate of lambs. South African Journal of Animal Science, Vol 31, Issue 3, Oct – Dec (2001): pp. 142-148Key Words Average daily gain, Dry matter intake, Italian ryegrass, Lambs, Nitrogen, Nitrate-nitrogen

Resting cell studies on formation of water-soluble red pigments byMonascus sp.

A resting cell system was developed for the biosynthesis of soluble red pigments byMonascus. The medium contains glucose, glycine, ZnSO4 and MnSO4 in pH 7.0 MOPS buffer containing cycloheximide to prevent protein synthesis. The linear production observed over a period of at least four h was due to de novo polyketide synthesis and biological methylation, as shown by inhibition with cerulenin, iodoacetamide and ethionine. Production was inhibited by carbonyl reagents and stimulated by pyridoxamine suggesting that the conversion of endogenous intracellular orange pigments to extracellular red pigments involves Schiff base intermediates and vitamin B6 a cofactor. The resting cell system was used to study the mode of action of nutritional effectors previously pinpointed by experiments with growing cells. The negative effects of high concentrations of phosphate and Mg++ are due to inhibition of pigment synthase action, not to repression or inactivation of these enzymes. The positive effects of trace metals, especially Zn++, are due to stimulation of growth and enzyme action, not to induction or stabilization of the synthases.