Analysis of eicosanoid production by difference spectroscopy. Neutrophils (top panel) and day 1 CD34⁺cells (bottom panel), both at 1 × 10⁷ cells/mL, were incubated, respectively, with 10 ng/mL GM-CSF or 100 ng/mL SCF, followed by 1 μmol/L A23187 or PBS diluent as indicated in the inset, and the absorption spectrum of the supernatants was measured in a dual-beam spectrometer with the cuvettes arranged as indicated.