  Changes in the meson-nucleon coupling constant and the vertex form factor in
nuclear matter are studied in a modified Skyrme Lagrangian including the
sigma-meson field that satisfies the scale invariance. Renormalization of the
axial-vector coupling constant, and the nucleon mass are studied in a
consistent model. The results are consistent with the empirical evidence. A
calculation of pi N commutator, sigma-term, indicates that the medium changes
its magnitude considerably.
