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Toxins produced in cyanobacterial water blooms - toxicity and risks
Luděk Bláha, Pavel Babica, Blahoslav Mar álek
Interdisciplinary Toxicology , 2009, DOI: 10.2478/v10102-009-0006-2
Abstract: Cyanobacterial blooms in freshwaters represent a major ecological and human health problem worldwide. This paper briefly summarizes information on major cyanobacterial toxins (hepatotoxins, neurotoxins etc.) with special attention to microcystins - cyclic heptapeptides with high acute and chronic toxicities. Besides discussion of human health risks, microcystin ecotoxicology and consequent ecological risks are also highlighted. Although significant research attention has been paid to microcystins, cyanobacteria produce a wide range of currently unknown toxins, which will require research attention. Further research should also address possible additive, synergistic or antagonistic effects among different classes of cyanobacterial metabolites, as well as interactions with other toxic stressors such as metals or persistent organic pollutants.
Health Risk Assessment for Cyanobacterial Toxins in Seafood  [PDF]
Vanora Mulvenna,Katie Dale,Brian Priestly,Utz Mueller,Andrew Humpage,Glen Shaw,Graeme Allinson,Ian Falconer
International Journal of Environmental Research and Public Health , 2012, DOI: 10.3390/ijerph9030807
Abstract: Cyanobacteria (blue-green algae) are abundant in fresh, brackish and marine waters worldwide. When toxins produced by cyanobacteria are present in the aquatic environment, seafood harvested from these waters may present a health hazard to consumers. Toxicity hazards from seafood have been internationally recognised when the source is from marine algae (dinoflagellates and diatoms), but to date few risk assessments for cyanobacterial toxins in seafood have been presented. This paper estimates risk from seafood contaminated by cyanobacterial toxins, and provides guidelines for safe human consumption.
Gastroenteritis and liver carcinogenesis induced by cyanobacterial toxins
Piotr Rzymski, Barbara Poniedzia?ek, Jacek Karczewski
Polish Gastroenterology , 2011,
Abstract: Cyanobacteria (Cyanophycae, blue-green algae) are prokaryotic autotrophic microorganisms related in general to aquatic (marine and freshwater) environments. Several dozens of the species produce secondary metabolites highly toxic to mammals, including humans. Bioaccumulation of these toxic compounds in aquatic animals has been shown. Depending on the mechanism of action they can be classified as dermato-, cyto-, neuro- and hepatotoxins. Within the last group, microcystins, nodularins and cylindrospermopsins can be distinguished. Swallowing water or consuming food contaminated with cyanobacterial hepatotoxins can lead to acute gastroenteritis or even death. Promotion of carcinogenesis in hepatocytes by cyanotoxins has also been shown. Water reservoirs used for recreational purposes or as a source of food should be monitored regularly. Gastroenterologists should be aware of a potential impact of cyanotoxins on the gastrointestinal tract.
Influences of Cyanobacterial Toxins Microcystins on the Seedling of Plants  [PDF]
Thanh-Son Dao, Thai-Hang Le, Thanh-Luu Pham, Lan-Chi Do-Hong, Phuoc-Dan Nguyen
Journal of Environmental Protection (JEP) , 2014, DOI: 10.4236/jep.2014.51005
Abstract:

Cyanobacterial blooms associated by their toxins have been increasing in frequency in fresh water bodies throughout the world. Among the cyanobacterial toxins, microcystins (MC) are the most common and cause severe adverse impacts on plants, aquatic organisms and human beings. In this study, the effects of MC (at the concentrations of 20 and 200 μg·L-1) from field water and crude extract of cyanobacterial scum (mainly Microcystis spp.) from the Dau Tieng Reservoir, Vietnam, on the seedlings of three plants, Brassica rapa-chinensis, B. narinosa and Nasturtium officinale, were investigated for over a period of 7 days. The results showed that MC reduced the fresh weight, root and shoot length of the exposed seedlings. In addition, abnormalities of leaf shape and color of B. rapa-chinensis under exposure to MC were observed. The results implied that MC were taken up and might be accumulated in the seedlings possessing potential risk to consumers as seedlings of these plants are a common food source for Vietnamese. To the best of our knowledge, this is the first report on the effects of MC on B. rapa-chinensis, B. narinosa and N. officinale.

Physiological Studies on Tilapia Fish (Oreochromis niloticus) as Influenced by the Cyanobacterial Toxins Microcystin  [PDF]
M. A. Al-Kahtani,A. A. Fathi
Journal of Biological Sciences , 2008,
Abstract: The effects of microcystin produced by the toxic cyanobacterial strain Microcystis aeruginosa on bioaccumulation and antioxidant enzymes (superoxide dismutase and catalase) of tilapia fish (collected from Al-Khadoud spring, Al-Hasa, Saudi Arabia) were investigated. The results showed that microcystin contained in cyanobacterial blooms induce CAT and SOD activity in a time-dependent manner. The data also shows that microcystin concentration in muscle was much lower than in liver, as the liver is the target organ of these toxins. In addition, microcystin concentration in faeces increased gradually until the end of the treatment period.
Temporal and spatial variability of cyanobacterial toxins microcystins in three interconnected freshwater reservoirs  [PDF]
LUDěK BLáHA,LUCIE BLáHOVá,JI?í KOHOUTEK,OND?EJ ADAMOVSKY
Journal of the Serbian Chemical Society , 2010,
Abstract: In spite of substantial research on health and the ecological risks associated with cyanobacterial toxins in the past decades, the understanding of the natural dynamics and variability of toxic cyanobacterial blooms is still limited. Herein, the results of long term monitoring 1998–1999/2001–2008 of three reservoirs (Vír, Brno and Nové Mlyny, Chech Republic), where toxic blooms develop annually, are reported. These three reservoirs provide a unique model because they are interconnected by the Svratka River, which allows possible transfer of phytoplankton as well as toxins from one reservoir to another. The frequency of the occurrence and dominance of the major cyanobacterial taxa Microcystis aeruginosa did not change during the investigated period but substantial variability was observed in the composition of other phytoplankton. Although absolute concentrations of the studied toxins (microcystins) differed among the reservoirs, there were apparent parallel trends. For example, during certain years, the microcystin concentrations were systematically elevated in all three studied reservoirs. Furthermore, the concentration profiles in the three sites were also correlated (parallel trends) within individual seasons based on monthly sampling. Microcystin-LR, a variant for which the World Health Organization has recommended a guideline value, formed only about 30–50 % of the total microcystins. This is of importance, especially in the Vír reservoir that serves as a drinking water supply. The maxima in the cell-bound microcystins (intracellular; expressed per dry weight biomass) generally preceded the maxima of total microcystins (expressed per volume of water sample). Overall, the maximum concentration in the biomass (all three reservoirs, period 1993–2005) was 6.1 mg g-1 dry weight and the median values were in the range 0.065–2.3 mg g-1 dry weight. These are generally high concentrations in comparison with both Czech Republic and worldwide reported data. The present data revealed substantial variability of both toxic cyanobacteria and their peptide toxins that should be reflected by detailed monitoring programs.
Cyanobacterial toxins: A short review on phytotoxic effect in an aquatic environment
S Saqrane, B Oudra
African Journal of Environmental Science and Technology , 2011,
Abstract: Cyanobacteria are photosynthetic prokaryotes which frequently form blooms in eutrophic water bodies. Some species of cyanobacteria are able to produce toxins (cyanotoxins) that can cause aquatic environment and diverse organisms living there to be at a serious risk. One of the more serious impacts of eutrophication on aquatic ecosystems is the disappearance of submerged macrophytes and the shift to a phytoplankton-dominated state. Hence, cyanobacterial blooms may be of significant negative ecological impact. This may represent a sanitary risk due to toxin bioaccumulation and biotransfer through the food chain. So, with the increasing number of new researches made on this subject, we propose this paper to review clearly many recent and original reports that have demonstrated the effects of cyanotoxins on some biological and physiological pathways in different aquatic plants.
Occupational and environmental hazard assessments for the isolation, purification and toxicity testing of cyanobacterial toxins
Ian Stewart, Wayne W Carmichael, Ross Sadler, Glenn B McGregor, Karen Reardon, Geoffrey K Eaglesham, Wasantha A Wickramasinghe, Alan A Seawright, Glen R Shaw
Environmental Health , 2009, DOI: 10.1186/1476-069x-8-52
Abstract: Over 40 species in some 20 cyanobacterial genera can produce a range of structurally and functionally diverse toxins, known as cyanotoxins. Freshwater and marine cyanobacteria, encompassing both planktonic and benthic forms, can produce potent toxins, some of which have been well characterised in terms of their toxic effects and some of which are less well-understood [1]. The known cyanotoxins can exert their toxic effects through a variety of mechanisms (depending on the particular toxin): some are potent neurotoxins that can cause respiratory dysfunction and death through paralysis of respiratory muscles, e.g. saxitoxins, anatoxin-a, anatoxin-a(S). Some affect the liver and other organs, e.g. microcystins, nodularin, cylindrospermopsin, and some exert acute irritant effects on the skin and mucous membranes, e.g. debromoaplysiatoxin, lyngbyatoxin A. Some cyanotoxins are potent tumour promoters, e.g. debromoaplysiatoxin, lyngbyatoxin A, microcystins, nodularin. Long-term, low-dose exposures to microcystins and/or cylindrospermopsin in drinking water are suspected (but so far unproven) risk factors for the development of some types of cancer. Cyanobacteria are rich sources of novel bioactive compounds, many of which are poorly researched with respect to toxicity [2].Several cyanotoxins have been chemically synthesised, e.g. anatoxin-a [3-5], cylindrospermopsins [6,7], saxitoxins [8,9], lyngbyatoxin A [10,11], aplysiatoxins [12], and one of the microcystins and some microcystin structural components [13,14]. However, the processes involved in synthesis of cyanotoxins like cylindrospermopsin and microcystins are complex and multiple steps are required, so those particular molecules are unlikely to be synthesised on a commercial scale in the near future. Therefore the most efficient methods for obtaining research-enabling quantities of many cyanotoxins in the short to medium turn will be to bulk-harvest cyanobacteria from natural waterbodies or to grow laboratory isolat
Health Risk Assessment of Cyanobacterial (Blue-green Algal) Toxins in Drinking Water  [PDF]
Ian R. Falconer,Andrew R. Humpage
International Journal of Environmental Research and Public Health , 2005, DOI: 10.3390/ijerph2005010043
Abstract: Cyanobacterial toxins have caused human poisoning in the Americas, Europe and Australia. There is accumulating evidence that they are present in treated drinking water supplies when cyanobacterial blooms occur in source waters. With increased population pressure and depleted groundwater reserves, surface water is becoming more used as a raw water source, both from rivers and lakes/reservoirs. Additional nutrients in water which arise from sewage discharge, agricultural run-off or storm water result in overabundance of cyanobacteria, described as a ‘water bloom’. The majority of cyanobacterial water-blooms are of toxic species, producing a diversity of toxins. The most important toxins presenting a risk to the human population are the neurotoxic alkaloids (anatoxins and paralytic shellfish poisons), the cyclic peptide hepatotoxins (microcystins) and the cytotoxic alkaloids (cylindrospermopsins). At the present time the only cyanobacteral toxin family that have been internationally assessed for health risk by the WHO are the microcystins, which cause acute liver injury and are active tumour promoters. Based on sub-chronic studies in rodents and pigs, a provisional Guideline Level for drinking water of 1μg/L of microcystin-LR has been determined. This has been adopted in legislation in countries in Europe, South America and Australasia. This may be revised in the light of future teratogenicity, reproductive toxicity and carcinogenicity studies. The other cyanobacterial toxin which has been proposed for detailed health risk assessment is cylindrospermopsin, a cytotoxic compound which has marked genotoxicity, probable mutagenicity, and is a potential carcinogen. This toxin has caused human poisoning from drinking water, and occurs in water supplies in the USA, Europe, Asia, Australia and South America. An initial health risk assessment is presented with a proposed drinking water Guideline Level of 1μg/L. There is a need for both increased monitoring data for toxins in drinking water and epidemiological studies on adverse health effects in exposed populations to clarify the extent of the health risk.
Green Liver Systems? for Water Purification: Using the Phytoremediation Potential of Aquatic Macrophytes for the Removal of Different Cyanobacterial Toxins from Water  [PDF]
Stephan Pflugmacher, Sandra Kühn, Sang-Hyup Lee, Jae-Woo Choi, Seungyun Baik, Kyu-Sang Kwon, Valeska Contardo-Jara
American Journal of Plant Sciences (AJPS) , 2015, DOI: 10.4236/ajps.2015.69161
Abstract: The protection and reasonable use of freshwater is one of the main goals for our future, as water is most important for all organisms on earth including humans. Due to pollution, not only with xenobiotics, but also with nutrients, the status of our water bodies has changed drastically. Excess nutrient load induces eutrophication processes and, as a result, massive cyanobacterial blooms during the summer times. As cyanobacteria are known to produce several toxic secondary metabolites, the so-called cyanotoxins, exhibiting hepato-, neuro- and cell-toxicity, a potential risk is given, when using this water. There is an urgent need to have a water purification system, which is able to cope with these natural toxins. Using aquatic plants as a Green Liver, the Green Liver System?, was developed, able to remove these natural pollutants. To test the ability of the Green Liver System?, several cyanobacterial toxins including artificial and natural mixtures were tested in a small-scale laboratory system. The results showed that within 7 - 14 days a combination of different aquatic macrophytes was able to remove a given toxin amount (10 μg·L-1) by 100%. The phytoremediation technology behind the Green Liver Systems? uses the simple ability of submerged aquatic plants to uptake, detoxify and store the toxins, without formation and release of further metabolites to the surrounding water.
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