  We present the evolution and the explosion of two massive stars, 15 and 25
M$_{\odot}$, spanning a wide range of initial rotation velocities (from 0 to
800 km/s) and three initial metallicities: Z=0 ([Fe/H]=$-\infty$),
$3.236\times10^{-7}$ ([Fe/H]=-5), and $3.236\times10^{-6}$ ([Fe/H]=-4). A very
large nuclear network of 524 nuclear species extending up to Bi has been
adopted. Our main findings may be summarized as follows: a) rotating models
above Z=0 are able to produce nuclei up to the neutron closure shell at N=50,
and in a few cases up to N=82; b) rotation drastically inhibits the penetration
of the He convective shell in the H rich mantle, phenomenon often found in zero
metallicity non rotating massive stars; c) vice versa rotation favors the
penetration of the O convective shell in the C rich layers with the consequence
of altering significantly the yields of the products of the C, Ne, and O
burning; d) none of the models that reach the critical velocity while in H
burning, loses more the 1 M$_{\odot}$ in this phase; e) conversely, almost all
models able to reach their Hayashi track exceed the Eddington luminosity and
lose dynamically almost all their H rich mantle.
  These models suggest that rotating massive stars may have contributed
significantly to the synthesis of the heavy nuclei in the first phase of
enrichment of the interstellar medium, i.e., at early times.

Solar and Stellar Astrophysics