Superoxide dismutase (SOD) in <i>C</i>. <i>elegans</i> increased over generations from G1 to G4 in exposure to Cd, Cu, Pb and Zn.

<p>The average SOD of nematodes in the control was 1.2E-01 U/ng protein, and was normalized to 100% (dash line); *: significantly different from the concurrent control, p < 0.05; #: significantly from the earlier generation, p < 0.05; +: significantly different from the lower concentration, p < 0.05; Error bar: standard error.