Pancreatic β-cell signaling: toward better understanding of diabetes and its treatment

Pancreatic β-cells play a central role in the maintenance glucose homeostasis by secreting insulin, a key hormone that regulates blood glucose levels. Dysfunction of the β-cells and/or a decrease in the β-cell mass are associated closely with the pathogenesis and pathophysiology of diabetes mellitus, a major metabolic disease that is rapidly increasing worldwide. Clarification of the mechanisms of insulin secretion and β-cell fate provides a basis for the understanding of diabetes and its better treatment. In this review, we discuss cell signaling critical for the insulin secretory function based on our recent studies.     

One-Pot Preparation of 1-Substituted Imidazole-2-thione from Isothiocyanate and Amino Acetal

Isothiocyanates were treated with amino acetal and conc. HCl (0.5 eq.) successively in one-pot to afford 1-substituted imidazole-2-thiones in good yields.     

Organic-inorganic hybrid liquid crystals: hybridization of calamitic liquid-crystalline amines with monodispersed anisotropic TiO2 nanoparticles

A novel organic-inorganic hybrid thermotropic liquid crystal (LC) is developed by the hybridization of an organic amine with a mesogenic core and an acicular anisotropic TiO2 particle through the adsorption of the amino group to the surfaces of the TiO2. The hybrid LC shows nematic phases in wide ranges of temperatures. Variable-temperature small-angle X-ray measurements reveal that the formation of the one-dimensional nematic order of the acicular particles on a submicrometer scale induces thermotropic liquid crystallinity. This technique would lead to induction of dynamic functions in inorganic particles.     

Synthesis of uniform anatase TiO2 nanoparticles by gel-sol method. 1. Solution chemistry of Ti(OH)(4-n)+(n) complexes

The mole fractions of hydroxo complexes of titanium(IV) ion in an aqueous solution with 0.10 mol dm(-3) NaClO4 at 25 degrees C have been determined as a function of pH by a newly developed analytical procedure based on UV spectrophotometry, using a metastable homogeneous solution of 1.25 x 10(-4) mol dm(-30 in total concentration of Ti(IV). Also, the total concentration of the hydroxo complexes in equilibrium with Ti(OH)4 solid, or the solubility of Ti(OH)4 solid in an inhomogeneous system, has been obtained by ICP measurement for the solution phase. A combination of these data yielded the absolute concentration of each complex species in equilibrium with Ti(OH)4 solid. Finally, Ti(OH)+3 complex has been assigned to the precursor for the formation of anatase TiO2 nanoparticles transformed from Ti(OH)4 gel from a comparison between the above equilibrium data and a kinetic study on the formation rate of the anatase TiO2 particles in the gel-sol system.     

Vacancy spectroscopy of radiation cross-linked and degraded polytetrafluoroethylenes

Polytetrafluoroethylene samples having different morphology were prepared by radiation induced cross-linking and degradation, and positron annihilation lifetimes were measured to extract information about the vacancy structure from the orth-positronium (o-Ps) component. The o-Ps intensity I₃ was inversely correlated with the crystallinity confirming that this component is associated with the amorphous part. The o-Ps lifetime τ₃ was distinctly different depending on the phase of the polymer. Below the γ relaxation temperature, the vacancies produced by degradation could be seen from an increase in the τ₃ value, but at temperatures between the γ and β relaxations such vacancies became invisible due to the activated segment motion. And above the β relaxation temperature vacancies in the interface between crystalline and amorphous parts appear to affect τ₃. The o-Ps intensity did not show stable reproducible results. Accumulation of positive charge can be responsible for it. The results, not only unveiling the not yet well understood behavior of the o-Ps component, demonstrate the uniqueness of the vacancy spectroscopy using o-Ps as a probe.     

Radiation-induced oxidation of polymers. Effect of antioxidant and antirad agent on oxygen consumption and gas evolution

The effects of antioxidants and of an antirad agent mixed in polyethylene and ethylene-propylene copolymer were investigated by means of oxygen consumption and gas evolution. The antioxidants were NBC, Irganox 1010, and DPPD, and the antirad agent was propyl fluoranthene (PFR). A small amount of the antioxidant (0.5 phr) in polymer decreased oxygen consumption by one-half or one-third compared with pure polymer, but the activity was lost with increasing irradiation. The antirad agent also decreased oxygen consumption and it was assumed to act as the energy transfer agent in the polymer matrix.     

An effective synthesis of α-glycosides of -acetylneuraminic acid derivatives by use of 2-deoxy-2β-halo-3β-hydroxy-4,7,8,9-tetra- -acetyl- -acetylneuraminic acid methyl ester

Condensation of a new glycosyl donor, methyl 5-acetamido-4, 7,8,9-tetra- -acetyl-2,3-dibromo-2,3,5-trideoxy-β- -2-nonulopyranosonate with various acceptors such as methyl 2,3,4-tri- -benzyl-α- -glucopyranoside, cholesterol, methyl 2,4,6-tri- -bonzyl-α- -galactopyranoside, and nethyl 5-acetamido-4,7,9-tri- -acetyl-2,6-anhydro-3,5-dideoxy- -non-2-enopyranosonate gave only the corresponding β-glycosides. The 3α-bromo group of the glycoaides obtained above was reduced with tributylstannane to the corresponding glycosids, which were deprotected to give the free glycoaides in high yields.     

Formation of ternary ion associates using diprotic acid dyes and its application to determination of cationic surfactants

A sensitive and selective method is described for the determination of cationic surfactants, such as benzethonium, benzalkonium, cetylpyridinium and trimethylstearylammonium, based on the formation and extraction of ternary ion associates with an acid dye (bromophenol blue or bromochlorophenol blue) and quinidine. Quinidine reacts with divalent anionic dyestuffs to form a bulky 11 complex anion, which is extractable into 1,2-dichloroethane as ternary ion associates with cationic surfactants in nearly neutral media. The ternary ion associate gives a blue product. Linearity of the calibration curve is improved and the extractability of the cationic surfactants is enhanced in the presence of quinidine. In addition, many other amines do not interfere with the determination. The blue ion associates can be used for the selective and sensitive spectrophotometric determination of cationic surfactants.     

Preparation and examination of calcium ion-selective electrodes for flow analysis

The preparation of calcium ion-selective electrodes based on known alkylphenylphosphate exchangers or on the ETH 1001 ionophore, and their use in a flow-through cell in a flow-injection system for the determination of calcium are described. The response and lifetime of the electrodes and the effects of magnesium and sodium ions on the determination of 10^?3?10^?5 M calcium are examined in detail. The ionophore electrode is shown to be most satisfactory.     

Systematic control of size,shape, structure,and magnetic properties of uniform magnetite and maghemite particles

As an application of the gel-sol method especially developed for the synthesis of general monodisperse particles in large quantities, uniform hematite (alpha-Fe2O3), magnetite (Fe3O4), and maghemite (gamma-Fe2O3) particles, precisely controlled in size, aspect ratio, and internal structure, have been prepared. For the synthesis of uniform ellipsoidal single-crystal particles of alpha-Fe2O3, a highly condensed suspension of fine beta-FeOOH particles doped with a prescribed amount of PO4(3-) ion in their interiors was aged at 140 degrees C for 24 h with seed particles of alpha-Fe2O3 in an acidic medium containing optimum concentrations of HCl and NaNO3. Systematic control of the aspect ratio and mean size was achieved by regulating the concentration of PO4(3-) ion incorporated into the beta-FeOOH particles and the number of seeds added. The resulting hematite particles were converted into magnetite by reduction in a H2 stream at 330 degrees C for 6 h; the magnetite was then oxidized to maghemite in an air stream at 240 degrees C for 2 h. Magnetite and maghemite thus prepared retained the original shape of the hematite. On the other hand, polycrystalline hematite particles of different sizes and aspect ratios were also prepared by aging a condensed Fe(OH)3 gel in the presence of different concentrations of SO4(2-) ion and seeds. The polycrystalline hematite particles were similarly converted into magnetite and then maghemite. The magnetic properties of these magnetite and maghemite particles were analyzed as a function of their mean particle volume, aspect ratio, and internal structure.