Diversity and species distribution of polychaetes,isopods and bivalves in the Atlantic sector of the deep Southern Ocean

We examined deep-sea benthic data on polychaetes, isopods and bivalves from the Atlantic sector of the Southern Ocean. Samples were taken during the expeditions EASIZ II (1998), ANDEEP I and II (2002) (depth: 742–6,348 m). The range between sites varies from 3 to 1,900 km. Polychaetes (175 species in total) and isopods (383 species) had a high proportion of species restricted to one or two sites (72 and 70%, respectively). Bivalves (46 species) had a higher proportion of species represented at more sites. Beta diversity (Whittaker and Jaccard) was higher for polychaetes and isopods than for bivalves. The impact of depth on species richness was not consistent among groups; polychaetes showed a negative relationship to depth, isopods displayed highest richness in the middle depth range (2,000–4,000 m), whereas bivalves showed no clear relationship to depth. Species richness was not related to latitude (58–74°S) or longitude (22–60°W) for any group.     

Interneuronal connections of the mammalian spinal cord and their examination by experimental degeneration; a review of more recent findings

Summary The structure of the interneuronal connections of the mammalian spinal cord is considered and the degeneration of the boutons or endfeet of Held and Auerbach is described. Degeneration of the boutons provides a method that has been advocated and used for tracing fiber tracts to their termination wuhin the central grey matter. The validity of this method has been questioned by some and these objections are discussed. Evidence is presented that the bouton represents a locus of especial sensitivity to forward degeneration and is protected from retrograde changes, and bouton degeneration is shown to be correlated with functional and biochemical disturbances.This paper was written as a tribute in honour of the 80^th birthday of Professor Albrecht Bethe.     

A quantum-mechanical study of the reaction mechanism of sulfite oxidase

The oxidation of sulfite to sulfate by two different models of the active site of sulfite oxidase has been studied. Both protonated and deprotonated substrates were tested. Geometries were optimized with density functional theory (TPSS/def2-SV(P)) and energies were calculated either with hybrid functionals and large basis sets (B3LYP/def2-TZVPD) including corrections for dispersion, solvation, and entropy, or with coupled-cluster theory (LCCSD(T0)) extrapolated toward a complete basis set. Three suggested reaction mechanisms have been compared and the results show that the lowest barriers are obtained for a mechanism where the substrate attacks a Mo-bound oxo ligand, directly forming a Mo-bound sulfate complex, which then dissociates into the products. Such a mechanism is more favorable than mechanisms involving a Mo–sulfite complex with the substrate coordinating either by the S or O atom. The activation energy is dominated by the Coulomb repulsion between the Mo complex and the substrate, which both have a negative charge of ?1 or ?2.