Melatonin-Induced Postconditioning Suppresses NMDA Receptor through Opening of the Mitochondrial Permeability Transition Pore via Melatonin Receptor in Mouse Neurons

Mitochondrial membrane potential regulation through the mitochondrial permeability transition pore (mPTP) is reportedly involved in the ischemic postconditioning (PostC) phenomenon. Melatonin is an endogenous hormone that regulates circadian rhythms. Its neuroprotective effects via mitochondrial melatonin receptors (MTs) have recently attracted attention. However, details of the neuroprotective mechanisms associated with PostC have not been clarified. Using hippocampal CA1 pyramidal cells from C57BL mice, we studied the involvement of MTs and the mPTP in melatonin-induced PostC mechanisms similar to those of ischemic PostC. We measured changes in spontaneous excitatory postsynaptic currents (sEPSCs), intracellular calcium concentration, mitochondrial membrane potential, and N-methyl-D-aspartate receptor (NMDAR) currents after ischemic challenge, using the whole-cell patch-clamp technique. Melatonin significantly suppressed increases in sEPSCs and intracellular calcium concentrations. The NMDAR currents were significantly suppressed by melatonin and the MT agonist, ramelteon. However, this suppressive effect was abolished by the mPTP inhibitor, cyclosporine A, and the MT antagonist, luzindole. Furthermore, both melatonin and ramelteon potentiated depolarization of mitochondrial membrane potentials, and luzindole suppressed depolarization of mitochondrial membrane potentials. This study suggests that melatonin-induced PostC via MTs suppressed the NMDAR that was induced by partial depolarization of mitochondrial membrane potential by opening the mPTP, reducing excessive release of glutamate and inducing neuroprotection against ischemia-reperfusion injury.     

Partial Oxidation of Methane to Synthesis Gas Over Ru-Loaded Y2O3 Catalyst

Ru-loaded Y₂O₃ catalyst was investigated for the partial oxidation of methane to synthesis gas. Ru(0.5 wt%)/Y₂O₃ catalyst afforded a high CH₄ conversion of 27% at a CH₄:O₂ ratio of 5 to give nearly a 1:2 ratio of CO and H₂ with a selectivity of 75% at 873 K. Ru(0.5 wt%)/Y₂O₃ catalyst maintained high catalytic activity over 10 h in the partial oxidation of methane. Carbon deposition of the catalyst surface in the reaction of CH₄ was examined by thermogravimetric analyses, and it was found that no carbon deposition occurred on the Ru(0.5 wt%)/Y₂O₃ catalyst. The synthesis-gas production proceeded basically via a two-step reaction consisting of methane combustion to give H₂O and CO₂, followed by the reforming of methane from CO₂ and steam.     

Ice crystal formation in the carbon nanotube suspension: A modelling approach

Freeze-dried porous solid foams were prepared from carbon nanotube (CNT) suspensions via either contact freezing with a heat exchanger or immersion freezing into a cryo-bath. Microstructures in the freeze-dried foam cast by ice crystals formed during the freezing step. It was found that domains of the carbon nanotubes in the freeze-dried solid foams were fairly well interconnected, and the microstructures were largely influenced by the freezing condition and freezing method. A mathematical model was proposed to simulate the observed thermal history during the freezing step; then theoretical predictions of the microstructural features were attempted. The simulated thermal history was in good agreement with experimental result. The resulting mean ice crystal sizes L* could be estimated from the calculated freezing front velocity (R) and the temperature gradient in the frozen zone (G). Interestingly, it was found that a correlation based on the power law (L*∝R^?0.2G^?0.2) was applicable to the present system for both the contact and immersion freezing methods. Though the fundamental ice crystallization phenomena were essentially the same for both freezing methods, actual temperature distribution and movement of the freezing front through the whole freezing bulk could control the morphology of ice crystal in the frozen matrix. In other words, good control of thermal flow in the freezing system would greatly contribute to rational design of microstructures of the CNT foam.     

Preparation of modified poly(vinyl chloride) containing N,N-di(β-hydroxyethyl)dithiocarbamate and its reaction with metal ions

Reaction of N,N-di(β-hydroxyethyl)dithiocarbamate ion with poly(vinyl chloride) (PVC) was undertaken, and the reaction with metal ions of the polymer obtained was investigated. The effect of γ-irradiation on the reaction with metal ion was also studied. The modified PVC (PHDC) obtained from the reaction with N,N-di(β-hydroxyethyl)dithiocarbamate ion is pale yellow even after reaction at 100°C for 5 hr in dimethylformamide (DMF); it is soluble in dipolar solvents and its chlorine content is decreased considerably. This polymer reacted well with acetate salts of copper(II), nickel(II), zinc(II), and silver(I) heterogeneously in aqueous solution because of the introduction of hydrophilic groups (two hydroxy groups). The reactivity of the metal ions toward the polymer was of the order Ag(I) ? Cu(II) > Ni(II) > Zn(II). From the result of the reaction of γ-irradiated polymer with cupric ion, the polymer was judged to have fairly good antiradiation property.     

Production of Carbon Nanotube by Ethylene Decomposition over Silica-Coated Metal Catalysts

Formation of carbon nanofibers (CNFs) and carbon nanotubes (CNTs) through the decomposition of ethylene at 973 K was achieved using various metal catalysts covered with silica layers. CNFs of various diameters were formed by ethylene decomposition over a Co metal catalyst supported on the outer surface of the silica. In contrast, silica-coated Co catalysts formed CNTs with uniform diameters by ethylene decomposition. Silica-coated Ni/SiO₂ and Pt/carbon black also formed CNTs with uniform diameters, while CNFs and CNTs with various diameters were formed over Ni/SiO₂ and Pt/carbon black without a silica coating. These results indicate that silica layers that envelop metal particles prevent sintering of the metal particles during ethylene decomposition. This results in the preferential formation of CNTs with a uniform diameter.     

Prevention of Osteoporosis by Oral Administration of Phytate-Removed and Deamidated Soybean β-Conglycinin

Phytate-removed and deamidated soybean β-conglycinin (PrDS) prepared by ion-exchange resins was supplemented to be 4% in the diet administered to ovariectomized rats to investigate its preventive effect on osteoporosis. The apparent calcium absorption rate decreased following ovariectomy and was not replenished by oral administration of phytate-removed soybean β-conglycinin (PrS) or casein. On the other hand, administration of PrDS restored the calcium absorption rate to the same level as the sham group. Markers of bone resorption, such as serum parathyroid hormone (PTH) and urinary deoxypyridinoline (DPD), increased, and the bone mineral density and breaking stress decreased following ovariectomy. However, PrDS supplementation suppressed the changes caused by the decrease in calcium absorption from the small intestine. Therefore, PrDS supplementation shows promise for the prevention of postmenopausal osteoporosis.     

Fractal characteristics of gas-solids flow in a circulating fluidized bed

A fractal approach is adopted to describe the dynamic behavior of a circulating fluidized bed. Two times series, differential pressure fluctuations along the riser height and solids momentum fluctuations along the radial direction, are measured and analyzed in terms of fractal dimensions. The influences of operating conditions and axial/radial positions on the fractal dimension are discussed. Attempts are also made to interpret the flow structure in the bed in terms of the fractal dimension. It is found that fractal analysis can provide a useful tool for understanding the characteristics of gas-solids flow in circulating fluidized beds.     

Optical resolution of racemic amino acid derivatives with chiral polyamides bearing glutamyl residue as a diacid component

Novel chiral polyamides with chiral environment in their main chains were obtained from aromatic diamine, 4,4′‐diaminodiphenylmethane (DADPM), and the D ‐isomer or the L ‐isomer of N‐α‐protected glutamic acid, such as N‐α‐benzyloxycarbonyl‐D ‐glutamic acid (Z‐D ‐Glu‐OH) or N‐α‐benzyloxycarbonyl‐L ‐glutamic acid (Z‐L ‐Glu‐OH), in the presence of triphenyl phosphite (TPP). Two types of newly prepared polyamide showed optical rotation, implying that there were asymmetric carbons in their main chains. Circular dichroism studies demonstrated that resulting chiral poly‐ amides took a helical structure. Optical resolution ability of those two types of polyamide was studied by adopting potential difference as a driving force for membrane transport. Membranes showed permselectivity toward racemic mixture of N‐α‐acetyltryptophan (Ac‐Trp). The permselectivity was dependent on the absolute configuration of diacid component. The permselectivity was expressed by diffusivity selectivity, which was determined by the presence of chiral helicity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The effect of the N-linked glycans on structural features and physicochemical functions of soybean β-conglycinin homotrimers

β-Conglycinin is a trimeric protein consisting of three subunits, α,α′,and β, which are N-glycosylated. The α and α′ subunits contain extension regions in addition to core regions common to all subunits. We purified homogeneous trimers consisting of only α, α′, or β from mutant soybean cultivars containing β-conglycinin lacking one or two subunits: α homotrimers from an α′-lacking mutant, α′ homotrimers from an α-lacking mutant, and β homotrimers from an α-and α′-lacking mutant. Structural features and physicochemical functions of the three homotrimers were examined and compared with those of recombinant homotrimers having no N-linked glycans. The native homotrimers have secondary structures very similar to those of the recombinant ones. In analogy with the recombinant homotrimers, the native ones exhibit different thermal stabilities from one another (β>α′>α), and the native α and α′ homotrimers exhibit better solubility, emulsifying ability, and heat-induced association than the native β homotrimer. Further, the N-linked glycans contribute to solubilities of the three subunits at low ionic strength (μ=0.08) and to the emulsifying ability of the native β homotrimer. N-Linked glycans also prevent heat-induced associations of the native α and α′ homotrimers but do not contribute to the secondary structure and the thermal stability of β-conglycinin.     

Ru-catalyzed anode materials for direct hydrocarbon SOFCs

A solid oxide fuel cell using a thin ceria-based electrolyte film with a Ru-catalyzed anode was directly operated on hydrocarbons, including methane, ethane, and propane, at 600 °C. The role of the Ru catalyst in the anode reaction was to promote the reforming reaction of the unreacted hydrocarbons by the produced steam and CO₂, which avoided interference from steam and CO₂ in the gas-phase diffusion of the fuels. The resulting peak power density reached 750 mW cm⁻² with dry methane, which was comparable to the peak power density of 769 mW cm⁻² with wet (2.9 vol.% H₂O) hydrogen. More important was the fact that the cell performance was maintained at a high level regardless of the change in the methane utilization from 12 to 46% but was significantly reduced by increasing the hydrogen utilization from 13 to 42%. While the anodic reaction of hydrogen was controlled by the slow gas diffusion, the anodic reaction of methane was not subject to the onset of such a gas-diffusion process.