Detection of Biomolecules Induced at Sublethal Levels of Pyrethroids

Narayanpur, Ritesh (2006) Detection of Biomolecules Induced at Sublethal Levels of Pyrethroids. PhD thesis, University of Mysore.

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Abstract

Pesticide residues are often reported in foods and known to gain entry into the human body. Pesticide body burden can induce cell mortality and thereby pose health threat. Synthetic pyrethroids like Deltamethrin, Cyhalothrin etc are the new generation pesticides used widely on crops and insect ectoparasites. According to a safety report of the WHO in 2005, pyrethroids are widely used in public health because of their relative safety for humans, high insecticidal potency at low dosages and rapid knock-down effects. Apart from their use in agriculture, pyrethroids play an important role in public health programmes. Globally, more than 520 tonnes of active ingredient of pyrethroids is annually used in vector control programmes alone. Hence, it becomes imperative to understand the safety mechanism of the pyrethroids and the reason behind their low toxicity in non-target species. In this study, we have tried to probe the possibility of programmed cell death or apoptosis being one of the possible safety mechanisms for the pyrethroids in non-target species. Cell death is due to a programmed sequence of morphological, biochemical and molecular changes which are characteristic and often unique to this mode of cell death. Specific features of apoptic cells causing these changes serve as early markers to alert the mode of cell death and can be developed as a tool to forecast the programmed cell death. The extent of apoptosis in cultures or in tissues can be measured qualitatively and quantitatively to assess cell death. Many methods have been developed to identify these changes and are based on alterations in cell morphology, plasma membrane, molecular structure, and DNA stability to denaturation and endo-nucleolytic DNA degradation. Electron microscopy, agarose gel characterization, flow cytometry, immunoassays and trypan blue exclusion are techniques generally used to identify these changes. Release of 3H thymidine by relabeled cells is another method used frequently. However, no indigenous immunoassays are available. Presence of any stress factor is required in apoptosis to trigger the cascade of biochemical events described above. This could be starvation, pollutants, physical stress etc. A few pyrethroids like deltamethrin although claimed to be “safe” have been reported to cause apoptotic changes in male rats. Deltamethrin is known to cause cell death due to apoptosis which is a genetic phenomenon involving the DNA. In general, apoptosis involves a chain of events wherein the zymogen, Caspase 3, is activated which in turn triggers Caspase 6 leading to DNA fragmentation (DNA “Ladder” formation & Nucleosome formation-mediated by endonucleases) In the present study, it was aimed to screen some pyrethroid pesticides for their apoptotic potential in CFT-Wistar rats and to study the biochemical deviations of early apoptotic biomarkers. Deltamethrin and Cyhalothrin were chosen as triggers for apoptosis. In view of this, the following objectives were chosen for the present study: 1. To study the genotoxic potential of selected pyrethroid pesticides. 2. Biochemical and morphological deviations as a result of xenobiotic exposure using in vivo (rat) and in vitro (HeLa cell culture) model systems. 3. Measurement of Caspase 3 and NOS levels to indicate initiation of apoptosis. 4. Use of the markers to develop quick detection methods.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	pyrethroids Pesticide residues biochemical studies
Subjects:	500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 26 Pesticide Chemistry
Divisions:	Food Protectants and Infestation Control
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	06 Jun 2008 07:16
Last Modified:	28 Dec 2011 09:34
URI:	http://ir.cftri.res.in/id/eprint/1745

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