Figure 3.

Principal component analysis. (a) First principal component versus the second principal component of the gene-expression data. The first principal component describes variance that tracks a single outlier rat in the control day-14 group. The second principal component captures the variance between the day-4 CCl₄-treated group and the remaining animals. (b) First principal component versus the second principal component of the tissue data. The first principal component primarily captures the variability within the CCl₄-treated day-4 group discretely from the other treatment or vehicle control groups. The second principal component describes variance between individual animals in all groups. (c) First principal component versus the second principal component of the combined data. Both the first and the second principal components capture the difference between the day-4 CCl₄-treatment group and all other animals in the complete set. The treated day-7 and -14 animals completely overlap the control animals, demonstrating that the tissue appears to have returned to a nearly normal state.