INTRODUCTION Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. 1.0 INTRODUCTION Our environment consists of air, water and soil. The air we breathe, water we drink and soil we use to generate food. Each compartment may be polluted by undesired or toxic substances. Since the industrial revolution, industries have been booming and, consequently, millions of anthropogenic compounds have entered our environment. Persistent organic pollutants have been found even in remote areas of the world (Ballschmiter et al., 2002). Pollution may be defined as the presence of undesired natural or anthropogenic substances in our environment or a chemical that exceeds normal background level and has the potential to cause harm. Harm is taken to include biochemical or physiological changes that adversely affect an individual, organism’s ability to breed, grow or survive (Walker et al., 1996). One of the major public health concerns in recent years has been Environmental Pollution and its effects on the living organism. Population explosion, urbanization, industrialization and human apathy have all contributed towards increasing quantities of pollutants leading to an “ecological disaster”. Pollution of water has emerged as one of the most significant environmental problem of recent times. Not only there is an increasing concern for rapidly deteriorating supply of water but the quantity of utilizable water also fast diminishing. The wide array of pollutants discharged into the aquatic environment may have physico-chemical, biological, toxic and pathogenic effects (Goel, 2000). The Industrial growth and consequent pollution let into the freshwater system are a challenge for the fragile freshwater ecosystems. The ability of water bodies to clean themselves has been affected by the sheer quantity of waste generated by ever increasing population (Ghosh, 1992). The quantity of utilizable water decreases due to over exploitation and also by pollution. This is a major environmental problem. Today Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. people must be educated to understand the need for wise and restrained use of the earth’s resources, water being the most vital one (Bhosle and Patil, 2001). Freshwater habitat occupy a relatively small portion of earth’s surface when compared to marine and terrestrial habitats, but their importance to man is far greater than their area because they are the most cheaply available water source for domestic and industrial needs. Freshwater ecosystems provide the most convenient and cheapest waste disposable systems, over exploitation and misuse of these unique systems result in environmental degradation, depletion and pollution causing health hazards. Aquatic systems are mainly polluted through domestic (sewage and nutrients), agricultural, aqua cultural and industrial wastes, endangering the existence of aquatic living resource on which millions of people depends for their existence. The protection of environment is necessary for the existence of living beings as water is the elixir of life (Kaza and Jafer, 1997). Rivers are polluted with the addition of discharged lethal waste from domestic and industrial establishments neglecting the hazards caused to the life that subsist in the water. Increasing pollution of rivers has become a matter of great concern all over the world. Moreover, these surface waters are highly sensitive to any change in the chemical balance or equilibrium due to industrial discharge. Most of the major industries in India are situated on the banks of the surface water bodies. The sensitivity or tolerance limits of inland surface waters specifically of transition zones like estuaries with regard to impact by human interference in terms of industrialization are to be considered before setting up industries at any one point. Numerous aspects of river pollution such as physio-chemical properties of different river water have been reported in India (Motwani et al., 1965; Singh et al., 1982; Anandavalli, 1986; Sheikh et al., 1997; Sharma and Pande, 1998; and David et Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. al., 2005). There are more than one thousand industries discharging their wastes directly into the river Yamuna without proper treatment, thereby increasing heavy metal concentration in surface and subsurface water bodies. Discharging of sewage and industrial effluents into the river water without any treatment causes alarming pollution. These pollutants cause changes in physiology, behavior, and histology of aquatic fauna and flora including human beings. The study of David et al., (2005) on the ecology of south Indian River Vamanapuram showed the riverine and estuarine habitats were subjected to major human imposed disturbances, which affects the fauna and flora to a greater extent. They further indicated that the practices of Coconut coir retting along the bank of the estuarine habitat and the effluent discharged into the estuary has adversely affected the health of the estuarine habitat. Due to the enormous growth of technology and industry, pollutants have been dramatically amplified in natural environments. In particular at the urban and municipal levels, seas, rivers and lakes have become a big eventual sink for man disposed pollutants. Lakes of Manzala, Borollus, Eduku and Maryut that fringe the northern side of Nile Delta are not exception. These shallow brackish water lake, that used to have high fishery production, gradually became loaded with polluted discharges from the adjacent urban and industrials settlements (El-Rayis and ElSabrouti, 1998 and Adham et al., 2002). Similar studies of the Double Lake, Porur lake, Puzhal Lake were carried out by several investigators pertaining to pollution (Mazher Sultana and Dawood Shrief, 2004). There have been numerous studies of pollution of water ways, which would not be possible to summarize (Appasamy, 1987; Sharma and Pande, 1998 and Lendhe and Yeragi, 2004), so many might be useful to illustrate the extent of pollution with Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. examples. Coovum river is comparatively uncontaminated when it enters the city; it becomes severely polluted by the time it reaches the sea since it receives a considerable amount of sewage, sullage and other urban drainage. Since the terrain is very flat, the velocity of flow is far below the self cleansing velocity and sedimentation is heavy (Mohanakrishnan, 1986). A toxicant is a agent that can produce adverse response or effect in a biological system, seriously damaging its structure or function or causing even death. Acute toxicity tests assess the biological effects of chemical toxicant and hence are used to detect and evaluate the potential toxicological effects of the chemical toxicants and pollutants on an organism (Rand and Petrocelli, 1985). The heavy metals mercury, lead, cadmium, copper, zinc and chromium are the most notorious metallic pollutants, their severity and persistence in water is generally compounded by the fact that they are generally water soluble nondegradable and strongly bonded to polypeptides and proteins. Availability and toxicity of trace metal to aquatic biota are primarily determined by the chemical nature of the aquatic environment (Sajid, 2007). Heavy metals play a vital role in the growth and development of plants. They may act as co-factors of some enzymes and help in the formation of intermediate metabolites. When excess amount of metal are absorbed by the plant toxic effects are produced resulting in impairment of growth, inhibition of respiration and abnormalities in cell division (Nakamura, 1994) and the extent of injury depends on the concentration of the metal present. Naga et al., (2002) have demonstrated that the toxic metals are capable of causing a reduction in the activities of hydrolases. Sarkar, (1999) has demonstrated Cd to be more toxic than Pb in plants. Chromium merits a special mention as it is not only an essential trace element to both plants animals but Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. also potentially toxic and tends to accumulate in organisms interfering with the integrity of the cell affecting many vital functions of the body. The quantitative study of pollutants in aquatic organisms offers an interesting challenge to the research. Heavy metals are well known environmental pollutants; they often persist, circulate and eventually accumulated throughout the food chain, thus cause a serious threat to non-target organisms (Akhtar and Mohan, 1995). Many trace metals are also important in animal nutrition, where as micronutrients, play an essential role in tissue metabolism and growth. Essential trace metals included Cd, Cu, Cr, Fe, Nn, Ni, Mo, Se, Sn and Zn severe in the imbalance in the metal micronutrients can causes mortality, where as marginal imbalance lead to poor health non - essential trace metal such as Pb, Cd and Hg also can be toxic at concentrations commonly observed in soil and natural waters (Leland and Kuwabara, 1985). Handy (1992) analyzed sediments of pollutants including heavy metals, petroleum hydrocarbons, monoaromatic hydrocarbons, organic chlorine pesticides, poly chlorinated biphenyls (PCBS) and poly cyclic aromatic hydrocarbons (PAHS). Cadmium, Chromium, Cobalt, Nickel, Selenium and Lead present in the raw materials for cement manufacture were reported to occur in coconut soils and plant tissues including coconut, collected at distances ranging from 0.1 to 5 km away from cement factories in Karnataka state, India. Presence of Fe, Cu, Mn, Zn, Cr, Pb, Ni, Co, Cd and Hg were reported in sewage sludge in an experiment based on water treatment plants with different effluent origins in Spain, where low level of organic matter in soils was a predominant problem (Clark, 1992). The increased accumulation of anthropogenic trace/toxic metals in the north Chennai harbour, Cuvum and Adyar marine environments is less desirable byproducts of industrialized society of these regions because of their extreme Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. persistence, high toxicity and tendency to bioaccumulation (De Santo, 1991). The study of Palanisamy Shanmugam et al., (2006) revealed the variations in metal concentrations before and during monsoonal storms. It is observed that copper concentrations during the monsoonal storm are found to be higher than the allowable limit (0.02 mg/l). The abrupt increase in copper concentrations is due to surface runoff and contributions of river and pipeline discharges to the coastal system. In both periods, the manganese concentrations are within the permissible limit (0.1 ppm) in all sample locations, though increased levels of magnesium at Annai Sivagami Nagar can be attributed to the concentrated municipal wastes accumulated before storms prevailed. It is evident from their results that the concentrations of nickel, cobalt, lead and cadmium appeared to be very high during September and exceeded the maximum permissible limit in most of the sample locations. As a result of monsoonal storms during October, these concentrations were considerably decreased to be within the permissible limit of the international standards. It was also observed that the river-influenced areas have high concentrations of toxic metals such as cadmium and cobalt during above periods. Such high concentrations of cadmium and cobalt could result in severe health hazards to the marine biota’s (Selvakumar et al., 1996). Based on the ecotoxicological studies, it has been suggested that slightly elevated metal levels in freshwaters, estuarine and coastal waters may cause the following sub lethal effects in aquatic organisms: (1) histological or morphological change in tissues; (2) changes in physiology, such as suppression of growth and development, poor swimming performance, changes in circulation; (3) change in biochemistry, such as enzyme activity and blood chemistry; (4) change in behavior; (5) and changes in reproduction (Connell and Miller, 1984, Mazher Sultana and Dawood Sharief, 2004 and Mazher Sultana and Bojarajan, 2007). Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. As a result, many fishing communities suffer from serious skin diseases around coastal city (Balasubramanian, 1999). Among thousands of substance of anthropogenic origin, several classes of industrial contaminants have gained interest due to their persistence, toxicity, high levels, etc. These includes PAH, PCBs, dioxins, dioxin-like compounds, phenolic compounds benzofurans, plasticisers, detergents, metabolites of all these and many others etc., (Van der Oost et al., 2003). Water pollution has become a global problem. An increasing number of organic trace pollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dibenzo-p-dioxins, and organochlorine pesticides were produced by the development of chemical industries, resulting in the environment becoming burdened with foreign organic chemicals. Many of these contaminants ultimately entered the aquatic environment, either by direct discharge, hydrologic processes or by atmospheric deposition (Van der Oost et al., 2003). Physico-chemical characteristics of water reflect the quality of water. Every human, physiologically requires 2-5 liters per day for proper functioning of vital organs. Increase in water pollutant leads to the risk of cancer, non Hodgkin‘s disease, chance of miscarriage, childhoods asthma and even juvenile diabetes. The pollutant in water damages the inner part of kidney, accordingly accumulation of certain affinity anions and cations with buffering actions, accumulates calcium oxalate, phosphate, sulphate as scales inside and adjoining parts of kidney. Such accumulations disturb the metabolic activities of digestion. Certainly the value of ingredients in the blood will deviate, e.g. increase in sugar contents, and decrease in the antibodies leading to uncontrollable diseases. This also deviates the functioning of the pancrease, lungs, heart, arteries and veins even effects the nerves. Water pollutants of certain hardness producing cations and anions damage certain organs and continuously damage soft Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. organs. It has been found that in certain specific cases digestive system’s potentiality is decreased (Byod et.al., 1992). When the pollutants enter water bodies they can have direct or indirect impacts on the biota of aquatic systems. They often interfere with the normal functioning of an organism and its ability to live in harmony with the environment (Ashraf, 2005). The changes they cause in behavior, growth, and reproduction of an organism will eventually result in undesirable effects at higher biological organization levels.The pollutants present in the water affect not only aquatic organism, but also public health as a result of bioaccumulation in food chain. The diversity of aquatic organism becomes limited with the extent of pollution. Therefore, there is a great need to assess the impacts of pollution in the aquatic environment. The prevalence of toxic heavy metals in the environment is of increasing concern to both environmental and medical communities since aquatic animals are often the first life forms to come into contacts, with these poisons. The detrimental effects, as well as the mechanism by which these animals cope with such poisons are of great interest. By such studies it may be possible to establish the biological index for heavy metal toxicity in the aquatic environment. The development of biomarkers in the late 1980’s provide enormous possibilities for using biological responses to assess environmental exposure and effects. A biomarker can be defined as a xenobiotically induced variation in cellular or biochemical components or processes, structures, or functions that is measurable in a biological system or sample (Everaarts et al., 1993). Effects of pollutants are usually expressed first at the molecular/biochemical level. Changes at these levels can induce structural and functional change at a higher level, such as hormonal regulation, Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. immune system, and metabolism in an organism. These changes may finally impair the growth, reproduction and survival ability of the organism (Adams et al., 1990). A variety of changes observable or measurable at molecular, biochemical, cellular, or physiological level in individuals have been studied as biomarkers for investigating the present or past exposure of the individual to pollutants (Kaiser, 2001). The use of biomarkers in environmental monitoring has the following advantages (McCarthy and Shugart, 1990 and Kaiser, 2001). First, measurements of biomarkers provide scientific evidence for a link between toxicant exposure and relevant biological effects on an individual, a population or a community level. Because changes in biomarkers are often indicates the exposure to a particular type of pollutant (s), biomarkers help to establish a cause-and-effect relationship between environmental exposure and their effects. Second, biomarkers can indicate the exposure of organism to toxic chemicals that do not bioaccumulate or are rapidly metabolized and eliminated. The change in biomarkers is the integrated consequences of exposure to the parent compound as well as their metabolites. Third, biomarkers reflect the integrated effect of exposure to complex mixture of contaminants and other environmental factors such as water temperature, water velocity, sediment, oxygen, and food availability. They present the cumulative effect of these factors on the target organism. Fourth, biomarkers at molecular and biochemical level respond quickly to change in the environment. The rapid response can offer early warning signals of environmental deterioration and potential effect of toxicants at sites. Because of these properties, the use of biomarkers strengthens assessment of the extent and nature of environmental degradation (Adams et al., 1990). Although there is legislation dealing with this problem in various countries, water pollution from toxic chemicals still occurs. Aquatic organisms, such as fishes Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. and mollusks, accumulate pollutants directly from contaminated water and indirectly through the ingestion of contaminated organisms. Genotoxic pollutants contaminate not only aquatic organisms but also the whole ecosystem and in the end, humans through contamination of our food (White and Rasmussen, 1998; Avishai et al., 2002; Rajaguru et al., 2002; Vigan`o et al., 2002; Ohe et al., 2003). Lipid peroxidation is a well-established mechanism of cellular injury in both plants and animals, and is used as an indicator of oxidative stress in cells and tissues. Initiation of lipid peroxidation is caused by an attack of any free radical that has sufficient reactivity to abstract a hydrogen atom from the polyunsaturated fatty acid moiety of membrane phospholipids and forms a variety of products, including lipid hydroperoxides,4-hydroxy-nonenal,conjugated-dienes,isoprostanes and alonodialdehyde. These molecules are generally reactive and some, such as isoprostanes, possess biological activity. Many have been measured as markers of oxidative stress and used as an indicator of lipid peroxidation. Plasma levels of malonodialdehyde, a marker of lipid peroxidation was measured as thiobarbituric acid reactive substances (TBARS) by fluorescence methodology (Yagi, 1976). In order to assess exposure to or effects of environmental pollutants on aquatic ecosystems, the following suite of fish biomarkers may be examined: biotransformation enzymes (phase I and II), oxidative stress parameters, biotransformation products, stress proteins, metallothioneins, MXR (multixenobiotic resistance) proteins, hematological parameters, immunological parameters, reproductive and endocrine parameters, genotoxic parameters, neuromuscular parameters, physiological, histological and morphological parameters (Van der Oost et al., 2003). Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Proteins are the most important macromolecule in the cell, as they are responsible for almost all cellular functions. They play roles that are as diverse from regulating gene expression, to playing a role in maintaining the proper cellular structure, sensing the environment, as well as acting to mediate communication between neighboring and distant cells. In multi-cellular organisms, as cells differentiate (take on specific functions), the profile of proteins that they express become different. For instance, an epithelial cell will express different proteins, than a neuron, etc. Additionally, certain cell types may contain higher protein content than others. One such cell type that contains high protein content is muscle cells. For locomotion to occur, muscles must contract and relax. The contraction and relaxation is mediated by proteins, specifically actin and myosin. Additionally, several others are important in controlling the contraction and relaxation cycle (Dong Shi Chen and King Ming Chan, 2009). Proteomics is the study of proteins, particularly their structures and functions. This term was coined to make an analogy with genomics, and while it is often viewed as the "next step", proteomics is much more complicated than genomics. Most importantly, while the genome is a rather constant entity, the proteome differs from cell to cell and is constantly changing through its biochemical interactions with the genome and the environment. One organism will have radically different protein expression in different parts of its body, in different stages of its life cycle, and in different environmental conditions. The entirety of proteins in existence in an organism throughout its life cycle, or on a smaller scale the entirety of proteins found in a particular cell type under a particular type of stimulation, are referred to as the proteome of the organism or cell type, respectively. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. Variations in an organism’s proteins may reflect physiological adaptations to an ecological niche and environment, but they originate as chance DNA mutations. Such random mutation events, if favorable, persist through the natural selection process and contribute to the evolution of new species – with new specialized functions. The discovery of the chemical structure of DNA by Watson, Crick, Wilkins, and Franklin and our understanding of how the triplet code of nitrogen bases leads to the synthesis of proteins (which is the phenotypic expression) convinced us that adaptations are the result of changes in the DNA code (mutations). However, current research in the field of proteomics is leading some scientist’s to question whether or not DNA is the final determining factor in the synthesis of proteins and thus the determining factor in evolution. Proteomics was initially defined as the effort to catalog all the proteins expressed in all cells at all stages of development. That definition has now been expanded to include the study of protein functions, protein-protein interactions, cellular locations, expression levels, and post translational modifications of all proteins within all cells and tissues at all stages of development (Dong Shi Chen and King Ming Chan, 2009; Bradley, 2002).Among the tests for genotoxicity, the micronucleus test has been widely utilized in fish to determine exposure to water pollutants, in the environment as well as under experimental laboratory conditions (Al-Sabti and Metcalfe, 1995; Minissi et al., 1996; Hayashi et al., 1998). Meanwhile, the comet assay has been proposed as a tool to monitor genotoxicity in ocean and continental waters, utilizing fish for the detection of DNA damage induced by directacting mutagens and pro-mutagens dissolved in the water as well as environmental analysis of water samples (Al-Sabti and Metcalfe, 1995; Minissi et al., 1996; Sasaki et Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. al., 1997; Hayashi et al., 1998; Mitchelmore and Chipman, 1998a, b, and Lee and Steinert, 2003). Antioxidant enzyme systems are a well developed regulatory mechanism protecting against oxidative stress. Under normal physiological states, reactive oxygen species (ROS) are rapidly eliminated by antioxidant enzymes, including superoxidate dismutase (SOD) and catalase (Yu, 1994; Abele and Puntarulo, 2004; Mohankumar and Ramasamy, 2006). The SOD catalyses the dismutation of two superoxide radicals to hydrogen peroxide (H2O2), whereas CAT degrade H2O2 (Holmblad and Soderhall, 1999; Mohankumar and Ramasamy, 2006). The studies of Farombi et al., (2007) revealed that arsenic treatment to Oreochromis mossambica increased the activity of antioxidant enzyme superoxidate dismutase (SOD) and catalase but decreased glutathione deductase activity within the day of exposure, indicating the generation of oxidative stress in fish at an early stage. They further concluded that peroxisomal H2O2 metabolizing enzymes are potential targets of arsenic toxicity in O. mossambica. Similar studies of Antonova et al., (2009) in Nile tilapia following in vivo exposure to damoic acid indicated a dose and time dependent increases in the oxidative parameters, such as SOD, CAT, GPx and GRd. These studies also recorded that the toxic effects were more pronounced in liver than in gill tissue of Nile tilapia. The critical tumor suppressor p53 plays important roles in cell-cycle arrest, apoptosis, senescence, or differentiation in response to various genotoxic and cellular stresses, including oxidative stress (Mansur, 1997). As a transcription factor, p53 consists of two N-terminal transactivation domains, a core DNA-binding domain and a C-terminal oligomerization domain (Pavletich et al, 1993). Because of its potent activity in inducing apoptosis and senescence, the p53 stability and activity are tightly Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. regulated by post translational mechanisms. Exposure to acidic environments and ROS can act synergistically to cause extensive DNA damage leading to apoptosis (programmed cell death) (Antonova et al., 2009). Oxidative stress is known to play a role in apoptosis through the products of several cell cycle genes such as p53 (Bonini et al., 2004; Ito et al., 2004). The principal function of p53 is to promote the survival or deletion of cells exposed to agents that cause DNA damage, such as hypoxia, UV radiation, ROS or mutagens (Fujita et al., 1996;Zakaria et al., 2009). Chen et al., (2005) suggest that apoptosis is a mechanism used by hepatocytes in response to microcystin-LR which has documented genotoxic potential and therefore can act as tumor initiator (e.g. Zegura et al., 2003). In most animal cells, glucose is transported across cell membranes by facilitated diffusion mediated by a family of glucose transporters (GLUTs). Several GLUT isoforms (GLUT 1-5, 8-11) have been identified in mammals, particularly in insulin-sensitive tissue such as adipose tissue, skeletal muscle and heart (Capilla et al., 2002 and Diaz et al., 2007), which is responsible for the glucose uptake by insulin. The studies of Capilla et al., (2002) on Salmonids skeletal muscle and adipose tissue revealed the expression of a structural and functional GLUT4 homolog, which can increase the glucose uptake when the transporter is expressed in Xenopus oocytes. In particular, GLUT4 is expressed predominantly in muscle and adipose tissue and is responsible for the stimulation of glucose uptake in these two tissues by insulin. In mammals, insulin rapidly increases the number of GLUT4 molecules at the plasma membrane through its stimulation of the translocation of GLUT4 from intracellular storage sites in both muscle and adipose cells (Kahn, 1996). In fish, insulin is also known to increase the in vivo uptake and utilization of glucose in skeletal muscle and to regulate the number of specific insulin receptors in muscle as Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. well as in adipose tissue. Although the direct effects of insulin on glucose uptake by fish muscle or adipose cells are not clearly established, it is possible that insulin could exert its hypoglycemic effect by stimulating glucose uptake mediated by an insulinsensitive GLUT (Capilla et.al, 2002). Teleost fish are widely known to be glucose intolerant and to produce insulin primarily in response to amino acid secretogogues (Palmer and Ryman, 1972; Ince, 1983; Mommsen and Plisetskaya, 1991; Wright, 1998). This is puzzling in the context of the observation that tilapia (Oreochromis nilotica) islets, when transplanted into streptozotocin (STZ) – diabetic athymicnude mice, will induce long-term normoglycemia and mammalian-like glucose tolerance profiles (Wright et al., 1992; Morsiani et al., 1995; Yang et al., 1997a). However, the vast majority of earlier studies which have examined aspects of glucose metabolism in fish were performed in carnivorous, cold-water species. In contrast, tilapia is omnivorous, tropical fish. The results of the transplantation studies noted above suggested that, perhaps, tilapia is not glucose intolerant or, alternatively, that tilapia are peripherally resistant to the glucose-lowering effects of insulin. Water is one of the essential factors for the maintenance of the vital functions of the living beings. With the continuous population growth and a consequent increase in water consumption, the rational use of this mineral asset has been encouraged, aiming a conservation of the quality of our waters, since this is a finite mineral resource (Frederico et al., 2009). Histology is useful technique for investigating the toxic effect of various pollutants. Such a study also offers opportunity to locate the effect of pollutants in various organs and systems of animals. This type of study in fish has been to a great extent is handicapped because of the lack of adequate histological literature Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. concerning various fish organs (Hinton et al., 1997).Considerable interest has been shown in recent years in histopathological studies while conducting sub-lethal tests in fish. Tissue changes in test organisms exposed to sub-lethal concentration of toxicant are a functional response of organisms which provides information on the nature of toxicant. Histopathological biomarkers can be indicators of the effects on organisms of various anthropogenic pollutants and are a reflection of the overall health of the entire population in the ecosystem.The alterations in cells and tissues in vertebrate fish are recurrently used biomarkers in many studies.The degree of pathological intensity is dependent on the dose and duration of exposure. These studies have been conducted to help establish causal relationships between contaminant exposure and various biological responses. Histopathological biomarkers embody tissue lesions arising as a result of a previous or current exposure of the organism to one or more toxins (Mazher Sultana and Bojarajan, 2007). There is considerable information indicating that pesticides and heavy metals are responsible for many adverse effects in fishes and other animals from the histopathological and histochemical points of view (Mazher Sultana and Dawood Sharief, 2004; Ashraf, 2005; Vinodhini and Narayanan, 2009). In this study, the water of Chrompet Lake was submitted to environmental testing using molecular and biochemical evidence for ecotoxicological impact on fresh water fish (O. mossambicus). This urban lake receives domestic waste discharge, storm water and industrial runoff. The study of monitoring the quality of the water of lake was important and necessary, since it is utilized as a domestic and recreational area. In addition, the aim was to collect data with respect to the validation of the oxidative stress related biomarkers in fish. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. A fresh water fish, O. mossambicus was selected for the investigation mainly because it serves as an important biological indicator of water quality, which is affected by the global environmental degradation. Also, because fish serve as experimental models and hypotheses deduced from investigations on them can be extrapolated to human system to a certain extent. Further fishes form a major link in the food web of the aquatic ecosystem and their ability to produce large number of off spring and survive at high population densities, make them suitable for experimentation. Overall Aim of the Study: To study the role of selected physicochemical and intracellular parameters as risk factors of pollution in a fish is evaluated by sensitive methods using biochemical and cytological, molecular biomarkers such as oxidative stress and DNA fragmentation (Comet assay), before more severe morphological alterations occur. 1.1 Specific Objectives 1. To assess the water quality (Physico-chemical parameters and metal content) of Chrompet Lake for a period of Twelve months from May 2009 to April 2010. To compare observed levels of studied parameters with the corresponding WHO guidelines values for drinking water quality. 2. To investigate the association of oxidative stress and antioxidant enzyme activity levels in control fish and pollution affected fish (O. mossambicus). 3. To investigate the molecular evidences in O. mossambicus related to senescence and resistance mechanism. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. 4. To investigate the role of eco-toxicological pollutants on biochemical and histopathological modulation in control fish and pollution affected fish O. mossambicus. 5. To create awareness among the locals of the Chrompet area with regard to the importance of the water quality and its implication. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
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