using Komet 5.0 Computer Software.28 Among the parameters available for analysis of the comets, Olive tail moment (OTM) was chosen as the most relevant measure of genotoxicity. Tail length and the percentage of DNA in comet tails and heads were collected. These values were used to calculate OTM, using the relationship: OTM = (tail mean – head mean) X tail % DNA / 100 in arbitrary units.29 Analysis was restricted to OTM as this parameter takes into consideration the intensity profile of the DNA signal and percentage of DNA in the comet heads and tails.
Images of 50 comets were collected from each of two replicate slides per sample, OTMs were calculated, and the significance of treatment-related differences tested using SAS/STAT statistical software version 8e.30 Descriptive statistics was performed by the MEANS procedure. OTM records were tested for normal distribution with the UNIVARIATE procedure. The chi- square distribution, which is a special case of the gamma distribution, fitted well to our data. As a consequence, data were then analysed by the GENMOD procedure (Generalised Linear Models). Statistically significant differences between groups were evaluated by the linear contrast method.