Correlation of Zn and Fe levels in DRG of 13 normal controls and 7 cases of FA. Zn levels increase with Fe levels in controls (closed back squares) and FA patients (open red circles). Each symbol represents the mean Zn and Fe level in a single subject, with horizontal and vertical lines representing the S.D. of Zn and Fe determinations, respectively, within that subject. Mean and S.D. are calculated from non-overlapping 0.25 mm2 areas in controls and FA, covering the entire neural tissue region of DRG (see methods). Regression result for all subjects is shown by the dashed line: Zn = 0.81 + 0.285 × Fe; slope p<0.001; R2=0.45. Multiple linear regression showed no significant difference between controls and FA subjects in either slope (p=0.16) or intercept (p=0.41).