  Full evolutionary models have been built to follow the phases of asymptotic
giant branch evolution with mass loss for metal mass fractions from Z=0.0002 to
Z=0.004. For the first time, we find that temperatures close to or even larger
than 10^8 K are achieved at low Z; the full CNO cycle operates at the base of
the envelope, the Oxygen abundance for the most metal-poor models of 4 and 5
solar masses is drastically reduced, and sodium and aluminum production by by
proton capture on neon and magnesium can occur. These results may be relevant
for the evolution of primordial massive globular clusters: we suggest that the
low-mass stars may have been polluted at the surface by accretion from the gas
that was lost from the evolving intermediate-mass stars at early ages.
