Induction of TNF-alpha production from human peripheral blood monocytes with beta-1,3-glucan oligomer prepared from laminarin with beta-1,3-glucanase from Bacillus clausii NM-1

We prepared a beta-1,3-glucan oligomer (DP> or = 4) from laminarin (DP: 25-30) derived from Laminaria digitata with beta-1,3-glucanase, and examined its effect on human peripheral blood monocytes. Conditioned medium prepared by incubating monocytes (MC-CM) with the beta-1,3-glucan oligomer showed strong inhibitory activity against the proliferation of human leukemic U937 cells. Since the beta-1,3-glucan oligomer had no direct cytotoxic effect on U937 cells up to 1000 microg/ml, the cytotoxicity of the MC-CM may be due to cytotoxic cytokines produced from monocytes stimulated by the beta-1,3-glucan oligomer. On the other hand, the MC-CM prepared with original laminarin had little effect on the growth of U937 cells. The cytotoxicity of the MC-CM prepared with the beta-1,3-glucan oligomer was significantly reduced by an anti-TNF-alpha antibody, but the anti-TNF-beta antibody had no effect. Our results suggest that the enzymatically depolymerized beta-1,3-glucan oligomer induces TNF-alpha production from human monocytes.     

Statistical thermodynamics of carbon solutions in metals

Fundamental formulae for statistical thermodynamic analysis of carbon solutions in metals are presented and some examples of applications of these equations are given. The importance is pointed out of the vapour pressure measurements of M over the single phase MC_x as a function of x as the data source for the statistical thermodynamic analysis of MC_x.     

Sequence requirements for cytochromes P450IIA1 and P450IIA2 catalytic activity: evidence for both specific and non-specific substrate binding interactions through use of chimeric cDNAs and cDNA expression

Cytochrome P450s IIA1 and IIA2, encoded by the CYP2A1 and CYP2A2genes, display 88% amino acid sequence similarities. The dissimilaritiesof sequence between these two enzymes are primarily localizedwithin four discrete regions of the polypeptides that are separatedby regions of absolute sequence identity. IIA1 specificallyhydroxylates the prototype substrate testosterone at the 7 and6 position with a predominance of 7 metabolite. IIA2, on theother hand, hydroxylates this steroid at eight positions onthe molecule, with one of the most abundant metabolites being15hydroxytestosterone. To determine those amino acids responsiblefor the difference in testosterone hydroxylation specificities,chimeras were constructed between IIA1 and IIA2 cDNAs and expressedin cell culture using vaccinia-virus-mediated cDNA expression.Chimeras, in which the first 355 amino acids correspond to asingle enzyme, maintain the specificity associated with thatenzyme. Of six chimeras which have substitutions between aminoacids 161 and 276, two are inactive and the remaining four givesimilar metabolite profiles, in which both 7 and 15 hydroxylationspecificities have been lost. Two of these four chimeras arediametric apposites, suggesting that modification of eitherthe N-terminal or central regions of the enzymes results inconformational changes that prevent the specific binding interactionsresponsible for the narrow regioselectivity associated withIIA1 and 15-hydroxytestosterone formation associated with IIA2.     

Synthesizing higher nitride of molybdenum (Mo) and iron (Fe) in ammonia (NH3) gas stream under irradiation of concentrated solar beam in a solar furnace

Flowing gaseous ammonia NH₃ with suppressed extent of dissociation (un‐cracked NH₃) is acknowledged to function as a powerful nitriding medium to realize formation of metal nitride MN_x with considerably high N/M ratio x that cannot be achieved through reaction of M with N₂ gas. For example, mono‐nitride δ‐MoN of Mo and ε‐FeN_x phase of Fe with x = 0.33 ? 0.50 (i. e. hypo‐stoichiometric sub‐nitride ε‐Fe₂N) were reported to be difficult to prepare in N₂ gas environment even at elevated pressure but might be synthesized in flowing NH₃ gas at normal pressure when reaction temperature and NH₃ gas flow rate were set adequately. In the present work, nitriding experiments for Mo and Fe were carried out in flowing NH₃ gas under irradiation with concentrated solar beam. The acquired experimental evidences demonstrated that temperature range for formation of δ‐MoN was somewhat extended in flowing NH₃ gas under heating with concentrated solar beam compared with that under heating in conventional laboratory or industrial electric furnace. On the other hand, no such merit of extending temperature range for formation of ε‐Fe₂N in flowing NH₃ gas was detected in the present work under heating with concentrated solar beam.     

Further studies on copper nanocomposite with dispersed single-digit-nanodiamond particles

This paper describes the microstructures and mechanical properties of Cu nanocomposites containing 0–30 at.% diamond nanoparticles. The Cu nanocomposite powders are fabricated by mechanical milling method and are consolidated by spark plasma sintering and hot extrusion. Microstructural observation shows that the homogeneous distribution of diamond nanoparticles in the Cu nanocomposite can be achieved by extrusion with large plastic deformation, in spite of 20 at.% diamond content, and that the nanocomposite with homogeneous distribution of diamond nanoparticles has ultra-fine grain structure, approximately 50 nm. Vickers hardness and compression tests on the SPS-consolidated and hot-extruded samples show that the detonation nanodiamond dispersed homogeneously in the Cu matrix enhances the mechanical properties.     

Comparative study of solubilities of hydrogen,nitrogen and carbon in α-iron

Solubility data of hydrogen, nitrogen and carbon in -iron are analysed on the basis of statistical thermodynamics. Present analysis appears to yield realistic values for the enthalpy term of the solutions of these interstitial elements into -Fe, while the entropy terms remain ambiguous. During the course of this analysis a parameter _x, which refers to the solubility limit of the specific interstitial element X (X=hydrogen, nitrogen or carbon), is also estimated; _H< _N< _C. This order of _X values appears to be in accord with the observation that, under normal conditions, the solubility of carbon is the highest and that of hydrogen the lowest in -Fe, while the atomic size increases with the order hydrogen相似文献   

Corrosion of Pb–Ca–Sn alloy during potential step cycles

Potential step was applied to Pb–Ca–Sn alloy electrode at various potential and time regimes. No severe corrosion was observed during potential step cycle with cathodic potential under −140 mV or over −40 mV versus Pb/PbSO₄ (3.39 M H₂SO₄), or at constant potential without stepping. On the other hand, the Pb–Ca–Sn alloy was severely corroded during potential step with cathodic potential from −120 mV to −60 mV and with anodic potential of +40 mV or more positive. The corrosion could not be decreased with periodical rest at 0 mV, while it could be decreased with periodical reduction at high polarization of, e.g. −160 mV. It was found out that the severe corrosion occurs when the oxidation of Pb to PbSO₄ and partial reduction of passive film of PbSO₄ take turns many times.     

The action modes of an extracellular beta-1,3-glucanase isolated from Bacillus clausii NM-1 on beta-1,3-glucooligosaccharides

The mode of action of an extracellular -1,3-glucanase from Bacillus clausii NM-1 on beta-1,3-3glucooligosaccharides and their alditols was studied. The enzyme could not hydrolyze laminaribiose or laminaritriose. beta-1,3-Glucooligosaccharides higher than laminarihexaose were rapidly hydrolyzed, while laminaritetraose was slowly hydrolyzed. The k(cat)/K(m) ratios for a series of beta-1,3-glucooligosaccharides from laminaritetraose to laminariheptaose showed that the substrate binding site of the enzyme covered a wide range of beta-1,3-glucooligosaccharides having six glucose residues. The action pattern of the enzyme on the alditols corresponding to each laminarioligosaccharide suggested that the catalytic site of the enzyme existed between the third and fourth glucose residue from the non-reducing terminal. The value of k(cat)/K(m) also suggested that the sixth binding position contributed to the catalytic efficiency and stability.