The evolution of the cortico-cerebellar complex in primates: anatomical connections predict patterns of correlated evolution.

Investigations into the evolution of the primate brain have tended to neglect the role of connectivity in determining which brain structures have changed in size, focusing instead on changes in the size of the whole brain or of individual brain structures, such as the neocortex, in isolation. We show that the primate cerebellum, neocortex, vestibular nuclei and relays between them exhibit correlated volumetric evolution, even after removing the effects of change in other structures. The patterns of correlated evolution among individual nuclei correspond to their known patterns of connectivity. These results support the idea that the brain evolved by mosaic size change in arrays of functionally connected structures. Furthermore, they suggest that the much discussed expansion of the primate neocortex should be re-evaluated in the light of conjoint cerebellar expansion.

Mutagenicity of the non-carcinogenic dibenzylnitrosamine and an alpha-acetoxy derivative.

The mutagenicity of a non-carcinogenic nitrosamine, N,N-dibenzylnitrosamine (I), and a chemically synthesized alpha-acetoxy derivative, N-(alpha-acetoxy-benzyl)-N-benzylnitrosamine (II), has been examined in Salmonella typhimurium TA100 and TA1535. Compound (I) was non-mutagenic when tested directly or in the presence of a metabolic activation system while (II) was highly mutagenic when tested directly. This is the first report on the conversion of a non-mutagenic N-nitrosamine to a mutagen by the formation of an alpha-acetoxy derivative.