Response of normal and PV SCFR tyrosine phosphorylation intensity to treatment with vanadate. Cell lysates from 8 normal donors and 5 PV patients were treated as described in the legend for Fig 7. Scanning densitometry was performed using the LKB 2222-010 UltroScan XL Laser Densitometer. The intensity measured in the controls not treated with vanadate was taken as 100%. The purity of the PV ECFC from 5 patients, including repeat cultures, ranged from 39% ± 8% to 79% ± 6% and from 8 normal donors ranged from 34% ± 4% to 79% ± 2%.