title: Evaluation of single-cell gel electrophoresis data: combination of variance analysis with sum of ranking differences.
abstract: Specimens of the mussel Mytilus galloprovincialis were collected from five sites in the Boka Kotorska Bay (Adriatic Sea, Montenegro) during the period summer 2011-autumn 2012. Three types of tissue, haemolymph, digestive gland were used for assessment of DNA damage. Images of randomly selected cells were analyzed with a fluorescence microscope and image analysis by the Comet Assay IV Image-analysis system. Three parameters, viz. tail length, tail intensity and Olive tail moment were analyzed on 4200 nuclei per cell type. We observed variations in the level of DNA damage in mussels collected at different sites, as well as seasonal variations in response. Sum of ranking differences (SRD) was implemented to compare use of different types of cell and different measure of comet tail per nucleus. Numerical scales were transferred into ranks, range scaling between 0 and 1; standardization and normalization were carried out. SRD selected the best (and worst) combinations: tail moment is the best for all data treatment and for all organs; second best is tail length, and intensity ranks third (except for digestive gland). The differences were significant at the 5% level. Whereas gills and haemolymph cells do not differ significantly, cells of the digestive gland are much more suitable to estimate genotoxicity. Variance analysis decomposed the effect of different factors on the SRD values. This unique combination has provided not only the relative importance of factors, but also an overall evaluation: the best evaluation method, the best data pre-treatment, etc., were chosen even for partially contradictory data. The rank transformation is superior to any other way of scaling, which is proven by ordering the SRD values by SRD again, and by cross validation.
authors.affiliation: Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudósok Krt. 2 H-1117 Budapest, Hungary. Electronic address: heberger.karoly@ttk.mta.hu.
authors.forename: Károly
authors.initials: K
authors.lastname: Héberger
authors.affiliation: Center for Genotoxicology and Ecogenotoxicology, Chair of Microbiology, Faculty of Biology, University of Belgrade, Studentski trg 16, Belgrade, Serbia.
authors.forename: Stoimir
authors.initials: S
authors.lastname: Kolarević
authors.affiliation: Institute for Biological Research "Siniša Stanković", University of Belgrade, Despota Stefana 142, Belgrade, Serbia.
authors.forename: Margareta
authors.initials: M
authors.lastname: Kračun-Kolarević
authors.affiliation: Department of Natural Resources and Environmental Sciences, Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, Belgrade, Serbia.
authors.forename: Karolina
authors.initials: K
authors.lastname: Sunjog
authors.affiliation: Department of Natural Resources and Environmental Sciences, Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, Belgrade, Serbia.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Gačić
authors.affiliation: Institute of Marine Biology - Kotor, University of Montenegro, Dobrota bb, 85330 Kotor, Montenegro.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Kljajić
authors.affiliation: Institute of Marine Biology - Kotor, University of Montenegro, Dobrota bb, 85330 Kotor, Montenegro.
authors.forename: Milena
authors.initials: M
authors.lastname: Mitrić
authors.affiliation: Center for Genotoxicology and Ecogenotoxicology, Chair of Microbiology, Faculty of Biology, University of Belgrade, Studentski trg 16, Belgrade, Serbia.
authors.forename: Branka
authors.initials: B
authors.lastname: Vuković-Gačić
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D020552:Comet Assay / Q000706:statistics & numerical data*; D004249:DNA Damage; D003627:Data Interpretation, Statistical; D004781:Environmental Exposure / Q000032:analysis / Q000706:statistics & numerical data; D004784:Environmental Monitoring / Q000379:methods* / Q000706:statistics & numerical data*; D054548:Montenegro; D049878:Mytilus / Q000187:drug effects / Q000235:genetics; D012621:Seasons; D018709:Statistics, Nonparametric; D014873:Water Pollutants / Q000633:toxicity
chemical_list: D014873:Water Pollutants
keywords: Analysis of variance; Comet assay; Ecogenotoxicity; Fluorescence; Mussels; Ranking