Some remarks on derivations in algebras of measurable operators

This paper is concerned with derivations in algebras of (unbounded) operators affiliated with a von Neumann algebra $\mathcal{M}$. Let \mathcal{% A} be one of the algebras of measurable operators, locally measurable operators or, $\tau$-measurable operators. We present a complete description of von Neumann algebras $\mathcal{M}$ of type $I$ in terms of their central projections such that every derivation in $\mathcal{A}$ is inner. It is also shown that every derivation in the algebra $LS(\mathcal{M})$ of all locally measurable operators with respect to a properly infinite von Neumann algebra $\mathcal{M}$ vanishes on the center of $LS(\mathcal{M})$.