خيارات البحث
النتائج 1571 - 1580 من 2,503
Thymol as an alternative to pesticides: persistence and effects of Apilife Var on the phototactic behavior of the honeybee Apis mellifera
2014
Carayon, Jean-Luc | Téné, Nathan | Bonnafé, Elsa | Alayrangues, Julie | Hotier, Lucie | Armengaud, Catherine | Treilhou, Michel
Thymol is a natural substance increasingly used as an alternative to pesticides in the fight against the Varroa destructor mite. Despite the effectiveness of this phenolic monoterpene against Varroa, few articles have covered the negative or side effects of thymol on bees. In a previous study, we have found an impairment of phototaxis in honeybees following application of sublethal doses of thymol—lower or equal to 100 ng/bee—under laboratory conditions. The present work shows the same behavioral effects on bees from hives treated with Apilife Var®, a veterinary drug containing 74 % thymol, with a decrease in phototactic behavior observed 1 day after treatment. Thus, thymol causes disruption of bee phototactic behavior both under laboratory conditions as well as in beehives. The bee exposure dose in treated hives was quantified using gas chromatography coupled to mass spectrometry (GC–MS), giving a median value of 4.3 μg per body 24 h after treatment, with 11 ng in the brain. The thymol level in 20 organic waxes from hives treated with Apilife Var® was also measured and showed that it persists in waxes (around 10 mg/kg) 1 year after treatment. Thus, in the light of (1) behavioral data obtained under laboratory conditions and in beehives, (2) the persistence of thymol in waxes, and (3) the high load on bees, it would appear important to study the long-term effects of thymol in beehives.
اظهر المزيد [+] اقل [-]Study on biodegradation process of lignin by FTIR and DSC
2014
Liu, Yang | Hu, Tianjue | Wu, Zhengping | Zeng, Guangming | Huang, Danlian | Shen, Ying | He, Xiaoxiao | Lai, Mingyong | He, Yibin
The biodegradation process of lignin by Penicillium simplicissimum was studied to reveal the lignin biodegradation mechanisms. The biodegradation products of lignin were detected using Fourier transform infrared spectroscopy (FTIR), UV–Vis spectrophotometer, different scanning calorimeter (DSC), and stereoscopic microscope. The analysis of FTIR spectrum showed the cleavage of various ether linkages (1,365 and 1,110 cm⁻¹), oxidation, and demethylation (2,847 cm⁻¹) by comparing the different peak values in the corresponding curve of each sample. Moreover, the differences (Tₘand ΔHₘvalues) between the DSC curves indirectly verified the FTIR analysis of biodegradation process. In addition, the effects of adding hydrogen peroxide (H₂O₂) to lignin biodegradation process were analyzed, which indicated that H₂O₂could accelerate the secretion of the MnP and LiP and improve the enzymes activity. What is more, lignin peroxidase and manganese peroxidase catalyzed the lignin degradation effectively only when H₂O₂was presented.
اظهر المزيد [+] اقل [-]Simazine degradation in bioaugmented soil: urea impact and response of ammonia-oxidizing bacteria and other soil bacterial communities
2014
Guo, Qingwei | Wan, Rui | Xie, Shuguang
The objective of this study was to investigate the impact of exogenous urea nitrogen on ammonia-oxidizing bacteria (AOB) and other soil bacterial communities in soil bioaugmented for simazine remediation. The previously isolated simazine-degrading Arthrobacter sp. strain SD1 was used to degrade the herbicide. The effect of urea on the simazine degradation capacity of the soil bioaugmented with Arthrobacter strain SD1 was assessed using quantitative PCR targeting the s-triazine-degrading trzN and atzC genes. Structures of bacterial and AOB communities were characterized using terminal restriction fragment length polymorphism. Urea fertilizer could affect simazine biodegradation and decreased the proportion of its trzN and atzC genes in soil augmented with Arthrobacter strain SD1. Bioaugmentation process could significantly alter the structures of both bacterial and AOB communities, which were strongly affected by urea amendment, depending on the dosage. This study could provide some new insights towards s-triazine bioremediation and microbial ecology in a bioaugmented system. However, further studies are necessary in order to elucidate the impact of different types and levels of nitrogen sources on s-triazine-degraders and bacterial and AOB communities in bioaugmented soil.
اظهر المزيد [+] اقل [-]Effects of sodium arsenate exposure on liver fatty acid profiles and oxidative stress in rats
2014
Kharroubi, Wafa | Dhibi, Madiha | Haouas, Zohra | Chreif, Imed | Neffati, Fadoua | Hammami, Mohamed | Sakly, Rachid
The present study aimed to evaluate the effect of arsenic on liver fatty acids (FA) composition, hepatotoxicity and oxidative status markers in rats. Male rats were randomly devised to six groups (n = 10 per group) and exposed to sodium arsenate at a dose of 1 and 10 mg/l for 45 and 90 days. Arsenate exposure is associated with significant changes in the FA composition in liver. A significant increase of saturated fatty acids (SFA) in all treated groups (p < 0.01) and trans unsaturated fatty acids (trans UFA) in rats exposed both for short term for 10 mg/l (p < 0.05) and long term for 1 and 10 mg/l (p < 0.001) was observed. However, the cis UFA were significantly decreased in these groups (p < 0.05). A markedly increase of indicator in cell membrane viscosity expressed as SFA/UFA was reported in the treated groups (p < 0.001). A significant increase in the level of malondialdehyde by 38.3 % after 90 days of exposure at 10 mg/l was observed. Compared to control rats, significant liver damage was observed at 10 mg/l of arsenate by increasing plasma marker enzymes after 90 days. It is through the histological investigations in hepatic tissues of exposed rats that these damage effects of arsenate were confirmed. The antioxidant perturbations were observed to be more important at groups treated by the high dose (p < 0.05). An increase in the level of protein carbonyls was observed in all treated groups (p < 0.05). The present study provides evidence for a direct effect of arsenite on FA composition disturbance causing an increase of SFA and TFAs isomers, liver dysfunction and oxidative stress. Therefore, arsenate can lead to hepatic damage and propensity towards liver cancer.
اظهر المزيد [+] اقل [-]Physiological and transcriptional responses of Baccharis halimifolia to the explosive “composition B” (RDX/TNT) in amended soil
2014
Ali, Asjad | Zinnert, Julie C. | Muthukumar, Balasubramaniam | Peng, Yanhui | Chung, Sang-Min | Stewart, C. Neal, Jr
Unexploded explosives that include royal demolition explosive (RDX) and trinitrotoluene (TNT) cause environmental concerns for surrounding ecosystems. Baccharis halimifolia is a plant species in the sunflower family that grows naturally near munitions sites on contaminated soils, indicating that it might have tolerance to explosives. B. halimifolia plants were grown on 100, 300, and 750 mg kg⁻¹of soil amended with composition B (Comp B) explosive, a mixture of royal demolition explosive and trinitrotoluene. These concentrations are environmentally relevant to such munitions sites. The purpose of the experiment was to mimic contaminated sites to assess the plant’s physiological response and uptake of explosives and to identify upregulated genes in response to explosives in order to better understand how this species copes with explosives. Stomatal conductance was not significantly reduced in any treatments. However, net photosynthesis, absorbed photons, and chlorophyll were significantly reduced in all treatments relative to the control plants. The dark-adapted parameter of photosynthesis was reduced only in the 750 mg kg⁻¹Comp B treatment. Thus, we observed partial physiological tolerance to Comp B in B. halimifolia plants. We identified and cloned 11 B. halimifolia gene candidates that were orthologous to explosive-responsive genes previously identified in Arabidopsis and poplar. Nine of those genes showed more than 90 % similarity to Conyza canadensis (horseweed), which is the closest relative with significant available genomics resources. The expression patterns of these genes were studied using quantitative real-time PCR. Three genes were transcriptionally upregulated in Comp B treatments, and the Cytb6f gene was found to be highly active in all the tested concentrations of Comp B. These three newly identified candidate genes of this explosives-tolerant plant species can be potentially exploited for uses in phytoremediation by overexpressing these genes in transgenic plants and, similarly, by using promoters or variants of promoters from these genes fused to reporter genes in transgenic plants for making phytosensors to report the localized presence of explosives in contaminated soils.
اظهر المزيد [+] اقل [-]Relationship of metal enrichment with adverse biological effect in the Yangtze Estuary sediments: role of metal background values
2014
Zhao, Shou | Feng, Chenghong | Wang, Dongxin | Tian, Chenhao | Shen, Zhenyao
Exclusive pristine values of As, Cd, Cr, Cu, Fe, Mn, Pb, and Zn in the Yangtze Estuary are calculated using principal components analysis (PCA) to probe the relationship between degrees of metal enrichment and their adverse biological effects. The results show that obvious differences in the degrees of metal enrichment exist when the enrichment factors are analyzed with reference background values on global, national, and local scales. Based on the low variability of aluminum, the exclusive metal background values in the estuary are obtained with PCA and are more likely to reflect the pristine contents of the abovementioned metals in the Yangtze Estuary. For the six most common metals (As, Cd, Cr, Cu, Pb, and Zn), significant correlations exist between the enrichment factors and their adverse biological effects. Arsenic shows the highest potential to cause adverse effects despite its general lack of enrichment. However, Cd is the most conservative element and is not likely to cause biological effects in the estuary.
اظهر المزيد [+] اقل [-]Influence of spontaneous vegetation in stormwater infiltration system clogging
2014
Gonzalez-Merchan, Carolina | Barraud, Sylvie | Bedell, Jean-Philippe
The paper presents the role of spontaneous vegetation on the hydraulic performance of an infiltration basin. The objective of the research was more particularly to study this role of different types of spontaneous vegetation found in situ in an infiltration basin near Lyon. The saturated hydraulic conductivity of three areas covered by Phalaris arundinacea, Polygonum mite, Rumex crispus and similar non-vegetated zones was compared. Eight field campaigns were carried out from July 2010 to May 2011 in order to compare the performance of each type of vegetation and its evolution over time. The results suggest a positive impact of vegetation on hydraulic performance in particular in summer during the growth of the plants. The hydraulic conductivity in this period was twice to four times higher than in bare areas or in vegetated zones during the plant rest periods. Some species were also found more appropriate to limit clogging (Phalaris arundinacea) likely due to its specific structure and growth process.
اظهر المزيد [+] اقل [-]Characterization of springtime airborne particulate matter-bound reactive oxygen species in Beijing
2014
Liu, Qingyang | Zhang, Yuanxun | Liu, Yanju | Zhang, Meigen
Epidemiologic studies have suggested that particulate matter (PM)-associated adverse health effects are related to particle composition. To study the toxicological characteristics of dust storm, airborne PM₁₀ was collected at two sites in Beijing from March to May 2012. The production of reactive oxygen species (ROS), quantified by dithiothreitol (DTT), was used to measure the PM-induced oxidative potential. Two dust storm (DS) samples were monitored during the sampling period: one happened on March 28th (DS1) and the other one was on April 28th (DS2). The backward trajectory results showed that both events originated from Inner Mongolia and Mongolia, respectively. The increased trends of ROS activities during the dust storm episode in PM₁₀ were observed for all the dust storms owing to a higher concentration of water-soluble components for all the PM₁₀ samples compared to nondust storm ones. Interestingly, the correlations between DTT consumption with water-soluble species yield interesting results about the spatial variability of redox activity between sites. In particular, a tracer of soil suspension, namely Fe, contributed the most fraction to ROS variability in the urban background site. Water-soluble organic carbon (WSOC) made the highest contribution to ROS variability, suggesting that vehicle emission might be important driving factors of the PM-induced oxidative stress in the urban site.
اظهر المزيد [+] اقل [-]Food sources of arsenic in pregnant Mediterranean women with high urine concentrations of this metalloid
2014
Fort, Marta | Grimalt, Joan O. | Casas, Maribel | Sunyer, Jordi
Seafood consumption provides a significant amount of arsenic, although in its organic, nontoxic forms. Mediterranean populations may incorporate high levels of this metalloid as a consequence of seafood consumption. In the present study, the significance of this input among pregnant women from a Mediterranean city (Sabadell, Catalonia, Spain) is assessed. Total urinary arsenic was analyzed in 489 pairs of urine samples, corresponding to the 12th and 32th weeks of pregnancy. Association of arsenic content with seafood and other dietary items were studied. Geometric mean concentrations were 34 and 37 μg/g creatinine during the first and third trimesters, respectively. The observed concentrations were similar to those reported in studies from other Mediterranean countries. The differences between both periods were not statistically significant. The only dietary factor significantly and positively associated with total urinary arsenic in both series of samples was seafood, particularly lean fish. Moreover, lean fish consumption during both periods was found to be the main determinant for differences in levels of arsenic between the first and third trimesters, which confirms the association between high levels of total urinary arsenic and seafood consumption.
اظهر المزيد [+] اقل [-]Using of “pseudo-second-order model” in adsorption
2014
Ho, Yuh-Shan
A research paper's contribution exists not only in its originality and creativity but also in its continuity and development for research that follows. However, the author easily ignores it. Citation error and quotation error occurred very frequently in a scientific paper. Numerous researchers use secondary references without knowing the original idea from authors. Sulaymon et al. (Environ Sci Pollut Res 20:3011–3023, 2013) and Spiridon et al. (Environ Sci Pollut Res 20:6367–6381, 2013) presented wrong pseudo-second-order models in Environmental Science and Pollution Research, vol. 20. This comment pointed the errors of the kinetic models and offered information for citing original idea of pseudo-second-order kinetic expression. In order to stop the proliferation of the mistake, it is suggested to cite the original paper for the kinetic model which provided greater accuracy and more details about the kinetic expression.
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