Effects of benzo[a]pyrene as an environmental pollutant and two natural antioxidants on biomarkers of reproductive dysfunction in male rats

Benzo[a]pyrene (B[a]P) is an environmental toxicant and endocrine disruptor. Therefore, the aim of the present study was to investigate the toxicity of B[a]P in testis of rats and also to study the role of silymarin and thymoquinone (TQ) as natural antioxidants in the alleviation of such toxicity. Data of the present study showed that levels of testosterone, estrogen and progesterone were significantly decreased after treatment of rats with B[a]P. In addition, B[a]P caused downregulation of the expressions of steroidogenic enzymes including CYP17A1 and CP19A1, and decreased the activity of 17-β hydroxysteroid dehydrogenase (17β-HSD). Moreover, B[a]P decreased the activities of antioxidant enzymes including catalase (CAT), glutathione peroxidase (GP_X) and superoxide dismutase (SOD), and significantly increased free radicals levels in testis of male rats. However, pretreatment of rats with silymarin prior to administration of B[a]P was found to restore the level of free radicals, antioxidant status, and activities of steroidogenic enzymes to their normal levels in testicular tissues. Moreover, histopathological finding showed that silymarin recovered the abnormalities occurred in tubules caused by B[a] P in testis of rats. On the other hand, TQ showed pro-oxidant effects and did not ameliorate the toxic effects of B[a] P on the testicular tissue since it decreased antioxidant enzymes activities and inhibited the protein expression of CYP11A1 and CYP21A2 compared to control rats. Moreover, TQ decreased the levels of testosterone, estrogen, and progesterone either in the presence or absence of B[a]P. It is concluded that B[a]P decreased testosterone levels, inhibited antioxidant enzymes activities, caused downregulation of CYP isozymes involved in steroidogenesis, and increased free radical levels in testis. Moreover, silymarin was more effective than TQ in restoring organism health and alleviating the deleterious effects caused by B[a]P in the testis of rats. Due to its negative impact, it is highly recommended to limit the use of TQ as a dietary supplement since millions of people in the Middle East are using it to improve their health.

     

Enhanced degradation of the antibiotic tetracycline by heterogeneous electro-Fenton with pyrite catalysis

There is actually increasing concern about the accumulation of antibiotics, such as tetracycline, in soil and water bodies. There is therefore a need for efficient methods to degrade antibiotics and thus clean waters. Here we tested the degradation of tetracycline using the heterogeneous electro-Fenton-pyrite method and compared the results with the conventional electro-Fenton method. The reaction was performed with a boron-doped diamond or Pt anode and carbon-felt cathode allowing electrogeneration of H₂O₂ from O₂ reduction. Results show an increasing tetracycline mineralization using the following methods: anodic oxidation with electrogenerated H₂O₂, electro-Fenton and then electro-Fenton-pyrite using boron-doped diamond. Ion-exclusion HPLC revealed the complete removal of malic malonic, succinic, acetic, oxalic and oxamic acids. Nitrogen present in tetracycline was mainly mineralized in NH₄ ⁺. The higher efficiency of electro-Fenton-pyrite is explained by self-regulation of soluble Fe²⁺ and pH to 3.0 from pyrite catalyst favoring larger ^·OH generation from Fenton’s reaction.     

Fluoride removal from aqueous solution by direct contact membrane distillation: theoretical and experimental studies

Direct contact membrane distillation (DCMD) process using polyvinylidene fluoride (PVDF) membrane was used for fluoride removal from aqueous solution. This study has been carried out on heat and mass transfer analyses in DCMD. The dusty-gas model was used to analyze the mass transfer mechanism and to calculate the permeate flux. The heat transfer is analyzed based on energy balance, and the different layers are considered as a series of thermal resistances. Mass transfer analysis showed that the transition Knudsen-molecular diffusion is the dominant mechanism to describe the transport of water vapor through the pores of the PVDF membrane. The most significant operating parameter is the feed temperature. The permeate increases sensitively with feed temperature and velocity, and it shows insignificant change with feed salts concentration. Heat transfer analysis showed the conduction through the matrix of the membrane presents the major part of available energy. The increasing feed temperature leads to increase thermal efficiency (TE) and decrease temperature polarization coefficient (TPC). The experimental results are in good agreement with theoretical values. Therefore, it is suggested to work at high feed temperature, which will benefit both the thermal efficiency and permeate flux. The experimental results proved that DCMD process is able to produce almost fluoride-free water suitable for many beneficial uses.     

Modelling Change in Ground Vegetation Response to Acid and Nitrogen Pollution, Climate Change and Forest Management at in Sweden 1500–2100 a.d.

The ForSAFE model, designed for modelling biogeochemical cycles (water, acidity, base cation, nitrogen and carbon) in terrestrial ecosystems, was modified with a vegetation response module (VEG), incorporating the effects of: nitrogen pollution, acidification, soil moisture, temperature, wind chill exposure, light and shading by trees, grazing by animals, competition between plants, above ground for light and below ground for water and nutrients. The model calculates the response of number ground vegetation plant groups. The integrated model was tested and validated at integrated level II forest monitoring sites across Sweden, four have been shown here, and used to assess the effect of acidification and nitrogen pollution in relation to factors such as climate change, forest management and changing grazing pressure. The response functions have been derived from single-factor experiments and integrated through the model structure for use on whole systems. The tests with the model suggest that the ground vegetation composition is reasonably well predicted, that much research remains before the model is fully tested and operational, and that the model may serve as a tool for assessing impacts of climate change, acid rain and forest management on plant biodiversity in forested areas.     

坦桑尼亚水质和污染研究回顾

坦桑尼亚的海岸带(图1)有多种生物栖息地,其中包括珊瑚礁、红树林、海草床、沙坝、湿地和沙滩.除了承担海岸带所有功能中的基本连接作用外,这些海岸带栖息地还提供了生物和非生物资源.     

Conservation and development

Summary This, the Second World Conservation Lecture, was presented at the Royal Institution, London, UK on 18 March 1982. The lecture organized by World Wildlife Fund, UK, concerns itself with Conservation and Development from a developing country point of view. Published with the kind permission of World Wildlife Fund UK.     

Structural characterization and visible light activated photocatalytic ability of glass–ceramics prepared from municipal solid waste

Journal of Material Cycles and Waste Management - The relationship between local structure and visible-light-activated photocatalytic ability of glass–ceramics prepared from Municipal Solid...     

Carcinogen-metabolizing enzymes and insecticides

The present study was under taken to demonstrate the effect of some commonly used insecticides on the activity of cytochrome P450 system including cytochrome b5, aryl hydrocarbon [benzo(a)pyrene] hydroxylase (AHH), N-nirosodimethylamine N-demethylase I [NDMA-dI] and NADPH-cytochrome c reductase as phase I of drug oxidation. In addition, the activity of glutathione S-transferase (GST), glutathione reductase (GR), and the level of glutathione (GSH) were determined in the liver of male mice after oral administration of sumithion, dursban, chlordane, methoxychlor, heptachlor epoxide, and lindane as single (24h) or as repeated doses for six consecutive days. Oral administration of sumithion, dursban, chlordane, methoxychlore, and heptachlor epoxide as repeated doses decreased: (i) the hepatic content of cytochrome P450 by 36, 37, 47, 37, and 67%, respectively, (ii) AHH activity by 28, 29, 70, 31, and 79%, respectively, (iii) NDMA-dI activity by 43, 44, 32, 27, and 31, respectively. On the other hand, sumithion, chlordane, and methoxychlore induced the activity of NADPH-cytochrome c reductase by 45, 62, and 43 respectively after repeated dose treatments. In addition, single and repeated-dose treatments of mice with lindane induced: (i) cytochrome P450 by 23 and 65%, respectively, (ii) cytochrome b5 by 49 and 131%, respectively, (iii) AHH activity by 64 and 50%, respectively. Repeated-dose treatments of mice with chlordane, methoxychlore, and heptachlor epoxide decreased the GSH level by 42, 38, and 68%, respectively and GST activity by 44, 44, and 55% respectively. Moreover, single- and repeated-dose treatments of mice with lindane decreased the GSH levels by 40 and 54%, respectively, and induced GST activity by 25 and 41%, respectively. Interestingly, single-dose treatments with chlordane, methoxychlore, and heptachlor epoxide decreased the activity of GR by 32, 38, and 31, respectively whereas repeated doses of these compounds induced such activity by 83, 50, and 64%, respectively. It is concluded that modifications in cytochrome P450 system by pesticides could potentiate the toxicity and carcinogenicity of environmental carcinogens such as polycyclic aromatic hydrocarbon and N-nirosodimethylamine (NDMA).