Figure 4. Case study demonstrating utility of frozen cube method and high quality data obtained after prolonged storage.

Portions of liver tissue collected from female B6C3F1 mice exposed to various concentrations of a test chemical for ~90 days (n = 5/group) were minced or cut into cubes and flash frozen at the in-life laboratory and subsequently shipped to this laboratory for analysis. Minced tissue was analyzed following ~2 months of storage; due to the poor quality of the data, frozen cubed tissue was subsequently analyzed following ~22 months of storage. To ensure cells at the high end of the continuum of chemical-induced DNA damage were not excluded from the analysis, data from scorable cells that, upon visual inspection appeared to be hedgehogs, were included. (A) Group mean % tail DNA results. Compared to minced tissue, high quality results were obtained from frozen cubed tissue, even after prolonged storage. (B) Group mean % hedgehog results. Poor mincing technique is evident from the extensive non-biological DNA damage observed as hedgehog comets in the minced tissue samples. Error bars reflect standard deviation. An ANOVA with Dunnett’s test was used to evaluate for a positive response to vanadyl sulfate for each sample preparation method. There were no statistically significant (p < 0.05) dose groups detected for either method.