Histopatholigical changes in brain of P. Ticto (HEM). Due to lead toxicity.
The studies have revealed that environment has manifold due to pollution. This has created unnatural environment not only for men but also for its basic associates. The fish which serves as high protein food for population. The pollution has entered in the environment through wreck less disposal of wastes and has entered in the organism through food chain. The fish for the purpose is the best experimental organism to assess the quality of damage which is likely to be transformed to population by its consumption as food. Pollution of the aquatic environment by heavy metals is an important problem and has attracted the attention of scientists of presently all over the globe. Common metals which have their toxic effect on aquatic bodies and aquatic organism are Pb, Cu, Cd, Zn, Hg, Mn, Ni, Li & Co etc. These metals pollute the water and disturb the whole aquatic ecosystem, hence they need exploration of different aspects of fish biology. Lead (Pb) has been an important metal in human societies over many thousands of years. The use of lead pipes for water supply was particularly significant during the period of Roman Empire. Pb has also been used over these years as a glanze on pottery, in cosmetics and as a means of sweetening wine. The use of Pb however has increased dramatically since the early days of the industrial revolution. Mining, smelting and refining of lead as well as the production and use of lead-based products gives rise to release of lead into environment. Lead concentration has been well recognized as accumulative general metabolic poison.  The toxic effects of lead and other heavy metals to fishes have been studied time to time. [17,12,11] In fishes lead is known to inhibit neural activity.  Behavior, blood chemistry and tissue glycogen show direct lethal effects in fresh water fishes C.carpio.  Heavy metal contamination may have devastating effects on the aquatic biodiversity and ecological balance. [3,9,19] The studies on heavy metal toxic effects in fishes carried out on various physiological activities and biochemical parameters both in tissue and in blood. [5,7,14,16] Mode of action of lead nitrate rendering thyroid dysfunction has been worked out by estimating hepatic type's 5'- monodeiodinase (5'-D) enzyme activity in Clarias batracus.  The order of heavy metal accumulation in the gills and liver was Cd > Pb >Ni > Cr and Pb > Cd > Ni > Cr. Similarly in case of kidney and flesh tissue the order was Pb > Cd > Cr >Ni and Pb > Cr > Cd > Ni .The bioaccumulation of lead and cadmium proportion was significantly increased in the tissue of C. carpio.  Lead nitrate causes deterious effects in tissue of brain, liver, kidney, and gills of H. fossilis with special reference to protein values. 
Material and Methods
The living specimens of P. ticto of either sex belonging to single population were obtained from local ponds. Fishes were acclimatized to tube well water condition for a period of 15 days. No mortality occurred during this period. The fishes were washed with 0.1% KMn[O.sub.4] solution to obviate any dermal infection in fishes. Fishes were fed @ 1% bodyweight per day in the evening with dry shrimp powder. After acclimatization fishes were kept in different concentrations of Pb [(N[O.sub.3]).sub.2] in different aquaria which contained 10 liters water. [LC.sub.50] value was calculated with graph method. Two fishes from each experimental concentration and control group were sacrificed and dissected and their brains fixed in aqueous Bouin's fluid. Paraffin sections of 6u thickness were prepared for histopathological observations and were stained with double stain of haematoxyline and eosin.
Results and Discussions
Fishes exposed to different concentrations of Pb (NO3)2 (1.0 ppm and 5.0 ppm) exhibited the toxic effects of lead in brain tissue in present study. Toxic effects of lead on different aspects (physiological, morphological, histopathological and on behavioral) of fish biology have been studied earlier. [6,10,17,20,23] Lead concentration was noticed in fish muscle.15 Lead nitrate and lead acetate show toxic effects on growth and some metabolic process of Scenedesmus obliquos.  Structural and functional effects of heavy metals on the nervous system including sense organs were notice in fishes.  In present study it is clear that exposure of Pb(NO3)2 to P. ticto have a direct toxic effect on histology of the brain tissue. Accumulation of heavy metals (Cd, Cr, Pb and Ni) in the tissue of C. carpio and Tilapia nilotica was observed earlier.  In control section normal structure of nerve cells was observed (Fig. 1 a), while space formation in brain tissue of fish was observed in treated group 1.0 ppm of lead nitrate which indicates the neurotoxic effects of lead nitrate on brain of P. ticto (Fig. 1 b) and it became further magnified into space in another group of lead nitrate at 5.0 ppm (Fig. 1c). There is however no deposition of metal observed in the brain.
Fishes are good source of protein and a part of food chain. These vertebrates are also main agents of biomagnification of heavy metals. These heavy metals deteriorate to aquatic life and quality of water. Therefore discharge of untreated industrial effluents and other sources of heavy metal pollution should be prohibited in these aquatic bodies which are shelter places of edible aquatic animals.
[FIGURE 1 OMITTED]
The author wish to thank to authors of all references for their support in preparation of this paper.
Symbols and Abbreviations
Inf. L.--Inferior lobe, N.C.--Nerve cell, N.S.--Necrosis of nerve cell, Opt. N.--Optic nerve. ppm--Part per million
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Seema Bharadwaj * and Lalit Choudhary
* Head of Department (Zoology), Shree Govind Guru Government. P. G. College, City-Banswara, State--Rajasthan, Country--India, Zip code -327001, E-mail: email@example.com,
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|Author:||Bharadwaj, Seema; Choudhary, Lalit|
|Publication:||International Journal of Applied Environmental Sciences|
|Date:||May 1, 2010|
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