, Diagnosis an-&& of Shrimp Diseases - Central Institute of ...

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which may also be toxic. LPO products are measured by their reaction with thiobarbituricacid, and have been generally used as an index of oxidant and free radical damage.Reaction with proteinsFree radicals and oxidants react with proteins mainly in two ways. By abstractinghydrogen from thiol groups, proteins are oxidised, leading to disulphide linkages and theresultant conformational and functional changes. Such reactions occur in the cells due to thesimultaneous presence of molecular oxygen, transition metal ions of iron and copper and freeradicals or free radical inducers. These are named 'Mixed Function Oxidation' and have beenrenamed 'Metal Catalysed Oxidation' by Stadtman and his group (Levine et al., 1990).Oxidative stress can result from exogenous sources i.e., redzox active xenobiotics or freeradical generators. The possible fate of oxidised cellular proteins can be depicted as,Proteins -+ DenaturedIHydrophobic proteinsThis leads to cross-linking and formation of insoluble aggregates, fragmentation andincreased susceptibility to proteolysis. Denaturation occurs due to variety of possibilities suchas(a) The interconversion of aminoacids, exemplified by the oxidation of cysteine (SH) tocystine(-S-S-).(b) Other alterations in the aminoacid side chain reported include Carbonyl oxidation ofthe lysine residue forming y glutamyl semialdehyde and(c) hydroxylation of phenylalanine to tyrosine.These alterations change the primary structure of the proteins, the isoelectric point,folding and hydrophobicity. Hydrophobic patches on proteins contribute to proteinaggregation. These authors have also observed good corr~lation between increases inhydrophobicity and proteolysis.Reaction with DNAExposure to free radicals and oxidants and increased cellular generation of superoxide andhydroxide radicals and H202 lead to DNA strand breakage. The strand break may occur dueto activation of some specific DNA-cleaving mechanism. Both purine and pyrimidine basesare modified by free radicals, especially the hydroxy radicals.Exposure of E.coli cells exposed to H202 at concentrations in the range of 1-3mM isfound to be mediated through superoxide and hydroxyl radicals, which leads to DNA damage.This can be blocked by iron chelating agents which prevent the Fenton-reaction within the
cells. It has been shown that possibly some cancers may originate as a result of faulty repairof DNA damage produced by free radicals.Lipid peroxidation, (LPO) in biological membranes causes alterations in fluidity, fallin membrane potential, increased permeability to H+ and other ions and eventual ruptureleading to release of cell and organelle contents such as lysosomal hydrolytic enzymes.Earlier it was shown that the disrupted or damaged tissues undergo lipid peroxidation at afaster rate than their healthy counterparts. Hence the sequence of events may be conjured upas:Disease or Toxin + cell damage or death + increased LPO which will well expIainthe elevated lipid peroxidation products in disease and toxicology.Cellular Defense by Antioxidant Enzymes and free Radical ScavengersAvoidance of free radical formationPotentially injurious effects of oxidants and free radicals on the living organism areprevented by a well-organised defense system and they function at four levels. The first andbest effort is avoidance. This is achieved by cytochrome oxidase and other metalloenzymes. They help the cells in carrying out the tetravalent reduction of oxygen to waterwithout releasing the toxic intermediates in a free state. Further, metal ions, which couldparticipate in the oxidant producing reactions, are generally carried or sequestered by proteinslike transferrin and ferritin, so as to minimise the amount of free iron in the cells. Similarlycopper is bound to ceruloplasmin and the ionic form is not generally available in the freestate. Albumin binds copper tightly and iron weakly. Haptoglobin/hemopexin binds freehemoglobinlheme. Hemoglobin and methemoglobin are powerful peroxides and canaccelerate lipid peroxidation while haptoglobin inhibits the reaction by binding tohaemoglobin. The antioxidanf role of urate is due to its ability to tightly bind iron and copperions.Prevention of free radicals (FRs) acting on the cellThe second line of defense is prevention, by providing a continuous supply of GSH.The oxidised and reduced glutathiones are interconvertible and the cell maintains the bulk inthe active (reduced) form. This reaction-is catalysed by the enzyme glutathione reductase.GlutathioneGSSG + NADPH2GSH + NADPreductase
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OVERVIEW OF STRATEGIES FOR PREVENTI
Page 7 and 8:
in harmonizing aquatic animal healt
Page 9 and 10:
SI-IRXMP DISEASES: GENEIL4L ASPECTS
Page 11 and 12:
quantitative level of pathogen is i
Page 13 and 14:
presence of prominent eosinophiiic
Page 15 and 16:
Disease affected the shrimps of all
Page 19 and 20: BACTERIAL AND FUNGAL DISEASES OF SH
Page 21 and 22: Cause: The epibiotic bacteria stich
Page 23 and 24: PARASiTIC AND NON-INFECTIOUS IIISEA
Page 25 and 26: XOS-INFECTIOUS DISEASESNon-infectio
Page 27 and 28: INVESTIGATING SHRIMP DISEASES: OBSE
Page 29 and 30: lnay be a predisposing factor for b
Page 31 and 32: BACTERIOLOGICAL METHODSS.V. Alavand
Page 34 and 35: In place of ZMA, nutrient agar prep
Page 36 and 37: Interpretation: Positive reaction i
Page 38 and 39: Incubate at 37°C for 1-2 h.Examine
Page 40 and 41: Alkaligens: etc. are resistant. The
Page 42 and 43: Culture Media, Reagents and StainsC
Page 45 and 46: Differential characteristics of Vib
Page 47 and 48: Davidson's Alcohol Formatin Acetic
Page 49 and 50: Paraffin cold impregnationXylene an
Page 51 and 52: ProcedureDe-paraffinise the slid'c
Page 53 and 54: Biochemistry of Nucleic Acids with
Page 55 and 56: DNA e.rl1i6it.v base equivuleizcc!E
Page 57 and 58: hydrolyzed by dilute alkali. The su
Page 59 and 60: Polymerase Chain Reaction (PCR) is
Page 61 and 62: a number of viral, bacterial and pa
Page 63 and 64: from 15-30 bases. Negative controls
Page 65 and 66: PCR Primers for Indian WSVTwo sets
Page 67 and 68: ANTIOXIDANTS IN MANAGEMENT OF OXIDA
Page 69: Many potent chemical carcinogens ar
Page 73 and 74: AFB, induced ~nutagenesis in Salmon
Page 75 and 76: FIGURE 2. An overview of oxygen rad
Page 77 and 78: were responsible for production los
Page 79 and 80: for Asiatic region. The participati
Page 81 and 82: charge of the DNA fragment. The neg
Page 83 and 84: European countries have in place th
Page 85: irth to a new concept to treatment
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