  Some isospin dynamics results in heavy ion collisions from low to
relativistic energies obtained through transport approaches, largely inspired
by David M.Brink, are reviewed. At very low energies, just above the Coulomb
barrier, the stimulating implications of the prompt dipole radiation in
dissipative collisions of ions with large isospin asymmetries are discussed. We
pass then to the very rich phenomenology of isospin effects on heavy ion
reactions at intermediate energies (few AGeV range). We show that it can allow
a ``direct'' study of the covariant structure of the isovector interaction in
the hadron medium. We work within a relativistic transport frame, beyond a
cascade picture, consistently derived from effective Lagrangians, where isospin
effects are accounted for in the mean field and collision terms. Rather
sensitive observables are proposed from collective flows (``differential''
flows) and from pion/kaon production ($\pi^-/\pi^+$, $K^0/K^+$ yields). For the
latter point relevant non-equilibrium effects are stressed. The possibility of
the transition to a mixed hadron-quark phase, at high baryon and isospin
density, is finally suggested. Some signatures could come from an expected
``neutron trapping'' effect. The importance of {\it violent} collision
experiments with radioactive beams, from few AMeV to few AGeV, is stressed.
