“…Hypotheses which relate the loss of enzyme activity directly to possession of the Ph' chromosome (Alter, Dobkin, Pourfar, Rosner, and Lee, 1963) seem incompatible with the return of NAP activity in diffusion chamber cultures (Chikkappa, Boecker, Borner, Carsten, Conkling, Cook, Cronkite, and Dunwoody, 1973) and in vivo during remission of CGL while the bonemarrow cells remain Ph'-positive (Tough, Jacobs, Court Brown, Baikie, and Williamson, 1963). Normal or increased NAP activity and persisting Ph'-positivity is also seen in some cases of CGL after acute transformation (King et al, 1962;Hammouda, Quaglino, and Hayhoe, 1964).…”