The normalized Log ratios also were imported to Significance Analysis of Microarray (SAM) [48] software to identify differentially expressed genes. SAM assigns a score to each gene on the basis of a change in gene expression relative to the standard deviation of repeated measurements. For genes with scores greater than an adjustable threshold, SAM uses permutations of the repeated measurements to estimate the percentage of genes identified by chance-the false discovery rate (FDR). Analysis parameters (Delta) were set to result in zero FDR.