  The overall hardness scale of the ultra-high energy neutrino-nucleon
interactions is usually estimated as $Q^2\sim m_W^2$. The effect of
non-conservation of weak currents pushes this scale up to the top quark mass
squared and changes dynamics of the scattering process. The Double Leading Log
Approximation provides simple and numerically accurate formula for the
top-bottom contribution to the total cross section $\sigma^{\nu N}$.
Corresponding correction to $\sigma^{\nu N}$ appears to be numerically large.
It is comparable with the leading contribution evaluated in the massless quark
approximation.
