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Monitoring of DNA breakage in embryonic stages of the African catfish Clarias gariepinus (Burchell, 1822) after exposure to lead nitrate using alkaline comet assay.
Environ Toxicol. 2008 Dec; 23(6):679-87.ET

Abstract

Increasing lead contamination in Egyptian ecosystems and high lead concentrations in food items have raised concern for human health and stimulated studies on monitoring ecotoxicological impact of lead-caused genotoxicity. In this work, the alkaline comet assay was modified for monitoring DNA strand breakage in sensitive early life stages of the African catfish Clarias gariepinus. Following exposure to 100, 300, and 500 microg/L lead nitrate, DNA strand breakage was quantified in embryos at 30, 48, 96, 144, and 168 h post-fertilization (PFS). For quantitative analysis, four commonly used parameters (tail % DNA, %TDNA; head % DNA, %HDNA; tail length, TL; tail moment, TM) were analyzed in 96 nuclei (in triplicates) at each sampling point. The parameter %TDNA revealed highest resolution and lowest variation. A strong correlation between lead concentration, time of exposure, and DNA strand breakage was observed. Here, genotoxicity detected by comet assay preceded the manifested malformations assessed with conventional histology. Qualitative evaluation was carried out using five categories are as follows: undamaged (%TDNA < or = 10%), low damaged (10% < %TDNA < or = 25%), median damaged (25 < %TDNA < or = 50%), highly damaged (50 < %TDNA < or = 75%), and extremely damaged (%TDNA > 75%) nuclei confirming a dose and time-dependent shift towards increased frequencies of highly and extremely damaged nuclei. A protective capacity provided by a hardened chorion is a an interesting finding in this study as DNA damage in the prehatching stages 30 h-PFS and 48 h-PFS was low in all treatments (qualitative and quantitative analyses). These results clearly show that the comet assay is a sensitive tool for the detection of genotoxicity in vulnerable early life stages of the African catfish and is a method more sensitive than histological parameters for monitoring genotoxic effects.

Authors+Show Affiliations

Department of Zoology, Faculty of Science, Al-Azhar University (Assiut Branch), Assiut 71524, Egypt. agosman2@yahoo.comNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

18247419

Citation

Osman, Alaa G M., et al. "Monitoring of DNA Breakage in Embryonic Stages of the African Catfish Clarias Gariepinus (Burchell, 1822) After Exposure to Lead Nitrate Using Alkaline Comet Assay." Environmental Toxicology, vol. 23, no. 6, 2008, pp. 679-87.
Osman AG, Mekkawy IA, Verreth J, et al. Monitoring of DNA breakage in embryonic stages of the African catfish Clarias gariepinus (Burchell, 1822) after exposure to lead nitrate using alkaline comet assay. Environ Toxicol. 2008;23(6):679-87.
Osman, A. G., Mekkawy, I. A., Verreth, J., Wuertz, S., Kloas, W., & Kirschbaum, F. (2008). Monitoring of DNA breakage in embryonic stages of the African catfish Clarias gariepinus (Burchell, 1822) after exposure to lead nitrate using alkaline comet assay. Environmental Toxicology, 23(6), 679-87. https://doi.org/10.1002/tox.20373
Osman AG, et al. Monitoring of DNA Breakage in Embryonic Stages of the African Catfish Clarias Gariepinus (Burchell, 1822) After Exposure to Lead Nitrate Using Alkaline Comet Assay. Environ Toxicol. 2008;23(6):679-87. PubMed PMID: 18247419.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Monitoring of DNA breakage in embryonic stages of the African catfish Clarias gariepinus (Burchell, 1822) after exposure to lead nitrate using alkaline comet assay. AU - Osman,Alaa G M, AU - Mekkawy,Imam A, AU - Verreth,Johan, AU - Wuertz,Sven, AU - Kloas,Werner, AU - Kirschbaum,Frank, PY - 2008/2/6/pubmed PY - 2009/1/29/medline PY - 2008/2/6/entrez SP - 679 EP - 87 JF - Environmental toxicology JO - Environ Toxicol VL - 23 IS - 6 N2 - Increasing lead contamination in Egyptian ecosystems and high lead concentrations in food items have raised concern for human health and stimulated studies on monitoring ecotoxicological impact of lead-caused genotoxicity. In this work, the alkaline comet assay was modified for monitoring DNA strand breakage in sensitive early life stages of the African catfish Clarias gariepinus. Following exposure to 100, 300, and 500 microg/L lead nitrate, DNA strand breakage was quantified in embryos at 30, 48, 96, 144, and 168 h post-fertilization (PFS). For quantitative analysis, four commonly used parameters (tail % DNA, %TDNA; head % DNA, %HDNA; tail length, TL; tail moment, TM) were analyzed in 96 nuclei (in triplicates) at each sampling point. The parameter %TDNA revealed highest resolution and lowest variation. A strong correlation between lead concentration, time of exposure, and DNA strand breakage was observed. Here, genotoxicity detected by comet assay preceded the manifested malformations assessed with conventional histology. Qualitative evaluation was carried out using five categories are as follows: undamaged (%TDNA < or = 10%), low damaged (10% < %TDNA < or = 25%), median damaged (25 < %TDNA < or = 50%), highly damaged (50 < %TDNA < or = 75%), and extremely damaged (%TDNA > 75%) nuclei confirming a dose and time-dependent shift towards increased frequencies of highly and extremely damaged nuclei. A protective capacity provided by a hardened chorion is a an interesting finding in this study as DNA damage in the prehatching stages 30 h-PFS and 48 h-PFS was low in all treatments (qualitative and quantitative analyses). These results clearly show that the comet assay is a sensitive tool for the detection of genotoxicity in vulnerable early life stages of the African catfish and is a method more sensitive than histological parameters for monitoring genotoxic effects. SN - 1522-7278 UR - https://www.unboundmedicine.com/medline/citation/18247419/Monitoring_of_DNA_breakage_in_embryonic_stages_of_the_African_catfish_Clarias_gariepinus__Burchell_1822__after_exposure_to_lead_nitrate_using_alkaline_comet_assay_ L2 - https://doi.org/10.1002/tox.20373 DB - PRIME DP - Unbound Medicine ER -