Superoxide-generated ethidium fluorescence in human Schwann cells cultured in 5.5 mmol/l glucose (1), 5.5 mmol/l glucose + 5 mmol/l ABA (2), 5.5 mmol/l glucose + 50 μmol/l Mn(III) TBAP (3), 30 mmol/l glucose (4), 30 mmol/l glucose + 5 mmol/l ABA (5), and 5.5 mmol/l glucose + 50 μmol/l Mn(III) TBAP (6). Mean ± SE, n = 5 per group. **P < 0.01 vs. cells cultured in 5.5 mmol/l glucose; ##P < 0.01 vs. cells cultured in 30 mmol/l glucose without additions of ABA or Mn(III) TBAP. UF, units of fluorescence.