  The results of kinetic simulations of magnetic reconnection in Harris current
sheets are analyzed. A range of guide fields is considered to study
reconnection in plasmas characterized by different $\beta$ values, $\beta >
m_e/m_i$. Both an implicit Particle-in-Cell (PIC) simulation method and a
parallel explicit PIC code are used. Simulations with mass ratios up to the
physical value are performed. The simulations show that the reconnection rate
decreases with the guide field and depends weakly on the mass ratio. The
off-diagonal components of the electron pressure tensor break the frozen-in
condition, even in low $\beta$ plasmas. In high $\beta$ plasmas, evidence is
presented that whistler waves play a key role in the enhanced reconnection,
while in low $\beta$ plasmas the kinetic Alfv\'en waves are important. The
in-plane and the out-of-plane ion and electron motion are also considered,
showing that they are influenced by the mass ratio and the plasma $\beta$.
