Promotive Effects of Yokukansan, a Traditional Japanese Medicine, on Proliferation and Differentiation of Cultured Mouse Cortical Oligodendrocytes

Effects of yokukansan, a traditional Japanese medicine, on proliferation and differentiation of oligodendrocytes were examined using purified mouse cortical oligodendrocyte precursor cells (OPCs). OPCs were cultured for four days, and proliferation was evaluated by counting A2B5 (a specific antibody to OPC)-reactive cells on the second day of cell culture. Differentiation from OPC to oligodendrocyte was evaluated by counting O4 (a specific antibody to detect differentiated cells in various stages)-reactive cells on the fourth day of culture. The effects of yokukansan (final concentration: 100 or 200 μg/ml) on proliferation and differentiation were examined by adding it to the medium for four days. Yokukansan increased not only the number of A2B5-positive cells on the second day but also the number of O4-positive cells on the fourth day compared to those in the corresponding controls. A WST-8 assay was used to identify active components from seven components of Uncaria Hook (UH), one of the constituent galenicals of yokukansan. Geissoschizine methyl ether (GM: 0.1 - 3.0 μM) was identified by this screening assay and increased the number of A2B5-positive cells on the second day and O4-positive cells on the fourth day as yokukansan did. These results suggest that yokukansan promotes the proliferation and differentiation of oligodendrocytes, and also that GM contained in UH is one of active components responsible for this effect of yokukansan.

Electrically conductive nanowires controlled one pivotal route in energy harvest and microbial corrosion via direct metal-microbe electron transfer

Extracellular electron transfer(EET)plays a critical role in bioelectrochemical processes,allowing cou-pling between microorganisms and extracellular solid-state electrodes,metals,or other cells in energy metabolism.Previous studies have suggested a role for outer-surface c-type cytochromes in direct metal-to-microbe electron transfer by Geobacter sulfurreducens,a model electroactive bacterium.Here,we ex-amined the possibility of other microbially produced electrical contacts by deleting the gene for PilA,the protein monomer that G.sulfurreducens assembles into electrically conductive protein nanowires(e-pili).Deleting pilA gene inhibited electron extraction from pure iron and 316L stainless steel up to 31%and 81%,respectively more than deleting the gene for the outer-surface cytochrome OmcS.This PilA-deficient phenotype,and the observation that relatively thick biofilms(21.7μm)grew on the metal surfaces at multi-cell distances from the metal surfaces suggest that e-pili contributed significantly to microbial cor-rosion via direct metal-to-microbe electron transfer.These results have implications for the fundamental understanding of electron harvest via e-pili by electroactive microbes,their uses in bioenergy production,as well as in monitoring and mitigation of metal biocorrosion.

Elucidating microbial iron corrosion mechanisms with a hydrogenase-deficient strain of Desulfovibrio vulgaris

Sulfate-reducing microorganisms extensively contribute to the corrosion of ferrous metal infrastructure.There is substantial debate over their corrosion mechanisms.We investigated Fe^(0) corrosion with Desulfovibrio vulgaris,the sulfate reducer most often employed in corrosion studies.Cultures were grown with both lactate and Fe^(0) as potential electron donors to replicate the common environmental condition in which organic substrates help fuel the growth of corrosive microbes.Fe^(0) was corroded in cultures of a D.vulgaris hydrogenase-deficient mutant with the 1:1 correspondence between Fe^(0) loss and H_(2) accumulation expected for Fe^(0) oxidation coupled to H+reduction to H_(2).This result and the extent of sulfate reduction indicated that D.vulgaris was not capable of direct Fe^(0)-to-microbe electron transfer even though it was provided with a supplementary energy source in the presence of abundant ferrous sulfide.Corrosion in the hydrogenase-deficient mutant cultures was greater than in sterile controls,demonstrating that H_(2) removal was not necessary for the enhanced corrosion observed in the presence of microbes.The parental H_(2)-consuming strain corroded more Fe^(0) than the mutant strain,which could be attributed to H_(2) oxidation coupled to sulfate reduction,producing sulfide that further stimulated Fe^(0) oxidation.The results suggest that H_(2) consumption is not necessary for microbially enhanced corrosion,but H_(2) oxidation can indirectly promote corrosion by increasing sulfide generation from sulfate reduction.The finding that D.vulgaris was incapable of direct electron uptake from Fe^(0) reaffirms that direct metal-to-microbe electron transfer has yet to be rigorously described in sulfate-reducing microbes.

Desulfovibrio vulgaris as a model microbe for the study of corrosion under sulfate-reducing conditions

Corrosion of iron-containing metals under sulfate-reducing conditions is an economically important problem.Microbial strains now known as Desulfovibrio vulgaris served as the model microbes in many of the foundational studies that developed existing models for the corrosion of iron-containing metals under sulfate-reducing conditions.Proposed mechanisms for corrosion by D.vulgaris include:(1)H2 consumption to accelerate the oxidation of Fe0 coupled to the reduction of protons to H2;(2)production of sulfide that combines with ferrous iron to form iron sulfide coatings that promote H2 production;(3)moribund cells release hydrogenases that catalyze Fe0 oxidation with the production of H2;(4)direct electron transfer from Fe0 to cells;and(5)flavins serving as an electron shuttle for electron transfer between Fe0 and cells.The demonstrated possibility of conducting transcriptomic and proteomic analysis of cells growing on metal surfaces suggests that similar studies on D.vulgaris corrosion biofilms can aid in identifying proteins that play an important role in corrosion.Tools for making targeted gene deletions in D.vulgaris are available for functional genetic studies.These approaches,coupled with instrumentation for the detection of low concentrations of H2,and proven techniques for evaluating putative electron shuttle function,are expected to make it possible to determine which of the proposed mechanisms for D.vulgaris corrosion are most important.