Structure and function of the extracellular matrix of anuran eggs

The extracellular matrix (ECM) surrounding the anuran egg is composed of jelly coat layers, an envelope, and the perivitelline space, which separates the envelope from the egg plasma membrane. Both the jelly coat layers and egg envelopes are required for fertilization in anurans. This paper reviews the current understanding of the structure-function relations of the ECM, with emphasis on the egg envelope. The fibrous egg envelope exists in four related forms. The envelope forms differ in their ultrastructures, macromolecular compositions, and cellular functions. After the oocyte is released from the ovary, conversion of one envelope form to another is brought about by factors secreted by the oviduct prior to fertilization and by factors released from the egg in the sperm-triggered cortical reaction. An additional extracellular matrix structure, located in the perivitelline space, has recently been identified in Xenopus laevis, as well as a previously undescribed reorganization of envelope fibers occurring at fertilization. The molecular changes in the ECM glycoproteins (limited proteolysis, lectin-ligand binding, and conformational changes) and the oviductal and egg macromolecules responsible for the conversion of envelope forms are discussed. New experimental evidence that supports the lectin-ligand hypothesis for the formation of the fertilization layer is presented. It is proposed that the molecular changes in the ECM are responsible for the ultrastructural alterations of the ECM and for modifications of the fertilization and developmental functions of the anuran egg ECM.     

Synthesis and photophysical properties of a charm-bracelet type C60-grafted PPV derivative

Synthesis and photophysical properties of a new soluble C₆₀-grafted PPV polymer have been described. Fluorescence quenching of the PPV moiety in C₆₀-grafted PPV polymer was observed, suggesting the energy- and/or electron transfer within the polymer. The fluorescence decay profiles at around 500 nm of this polymer both in chloroform and benzonitrile display a single exponential decay giving the fluorescence lifetimes of 1.10-1.27 ns, which are slightly shorter than that of PPV (about 1.50 ns). The nanosecond transient absorption band of C₆₀-grafted PPV polymer was observed at 740 nm corresponded to the excited triplet state of C₆₀, which decreased in benzonitrile, indicating the existence of the extra decay path of the singlet excited state of the C₆₀ other than intersystem crossing. Upon heating this polymer exhibits typical semilunar liquid crystalline texture, being closely associated with its polymeric structure with long solubilizing alkoxy side chains.     

Temperature‐Induced Hydrogels Through Self‐Assembly of Cholesterol‐Substituted Star PEG‐b‐PLLA Copolymers: An Injectable Scaffold for Tissue Engineering

Partially cholesterol‐substituted 8‐arm poly(ethylene glycol)‐block‐poly(L ‐lactide) (8‐arm PEG‐b‐PLLA‐cholesterol) has been prepared as a novel star‐shaped, biodegradable copolymer derivative. The amphiphilic 8‐arm PEG‐b‐PLLA‐cholesterol aqueous solution (polymer concentration, above 3 wt%) exhibits instantaneous temperature‐induced gelation at 34 °C, but the virgin 8‐arm PEG‐b‐PLLA does not, irrespective of concentration. Moreover, an extracellular matrix (ECM)‐like micrometer‐scale network structure has been created with favorable porosity for three‐dimensional proliferation of cells inside the hydrogel. This network structure is mainly attributed to specific self‐assembly between cholesterol groups. The 10 and 20 wt% hydrogels are eroded gradually in phosphate buffered saline at 37 °C over the course of a month, and after that the gel becomes completely dissociated. Moreover, L929 cells encapsulated into the hydrogel are viable and proliferate three‐dimensionally inside the hydrogels. Thus, in‐vitro cell culture studies demonstrate that 8‐arm PEG‐b‐PLLA‐cholesterol is a promising candidate as a novel injectable cellular scaffold.     

Development of insulation technology in compact SF6 gas‐filled bushings: Development of compact 800‐kV SF6 gas‐filled bushings

Efforts of designers of gas‐insulated switchgear (GIS) are currently focused on such features as smaller installation area and economical efficiency. Circuit breakers (CB), disconnecting switches (DS), and earthing switches (ES) have been redesigned in more compact configurations. Compactness and light‐weight requirements are applied also to bushings used in GIS. GIS bushings can be divided in three general types: capacitor, gas‐filled, and molded bushings. Requirements of the light weight and the economical efficiency of gas‐filled bushings can be satisfied by improvements in insulation technology. Size reduction can be effectively achieved by moderation of the electric field strength on the outside surface of the hollow insulator in the area of the inner grounded electrode tip. We devised a new inner grounded electrode structure consisting of a cylindrical electrode and a ring electrode supported by column electrodes. This paper describes the effect of reduction of the maximum value of electric field strength on the outside surface of the hollow insulator by a new type of grounded electrode. Then, improvement of insulation performance for electrodes with insulation coating in SF₆ gas is described as the composite insulation technology. Finally, the efficiency of these insulation technologies is described by the basic insulation test results of a prototype compact 800‐kV SF₆ gas‐filled bushing. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(1): 19–27, 2010; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20898     

Properties and microstructures of epoxy resin/TiO2 and SiO2 hybrids

Epoxy resin/TiO₂ and epoxy resin/SiO₂ hybrids were prepared by different procedures, and their mechanical properties were correlated to their microstructures, as indicated by small‐angle X‐ray scattering (SAXS) measurements. Epoxy resin/TiO₂ hybrids were prepared by mixing the epoxy resin (EP828) with N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilane (S320) in acetone, and then titanium‐n‐butoxide (TnBU) was added. In addition, epoxy/SiO₂ hybrids were prepared by mixing EP828 with a curing agent, a diamino heterocyclic compound (B002) in acetone, and an organo silica sol (silica nanoparticles dispersed in methylethylketone) was added. In the EP828/S320/TiO₂ hybrid systems, the TiO₂ component was attached to both of the chain ends of the epoxy matrix, hence leading to the formation of inorganic domains via the covalent bonds. SAXS profiles of these hybrids showed peaks at q = 2.3 nm^?1, caused by interference between the domains. The storage modulus increased with increasing TiO₂ content above the T_g, owing to the strong interactions between TiO₂ and the epoxy matrix. The tanδ peak position did not change, although the intensity decreased with increasing TiO₂ content. The SAXS profiles of the EP828/B002/SiO₂ hybrids were very different to those of the corresponding EP828/S320/TiO₂ hybrids, and indicated that SiO₂ particles with rough surfaces were randomly dispersed in the epoxy matrix. The storage moduli of the EP828/B002/SiO₂ hybrid systems increased only slightly with SiO₂ content, because of the weak interactions. These mechanical properties are well explained by the microstructures derived from the SAXS profiles. Copyright © 2004 Society of Chemical Industry     

Influence of free‐air CO2 enrichment (FACE) on the eating quality of rice

Rice plants (Oryza sativa L cv Akitakomachi) were grown under free‐air CO₂ enrichment (FACE) in farmers' fields in Shizukuishi, Iwate, Japan during 1999 and 2000. The grains were harvested and subsequently analyzed for protein and amylose contents as well as the traits related to cooked‐rice viscosity. The cooked rice was also subjected to sensory evaluation. The protein content of rice grains grown under elevated CO₂ was significantly lower than that of rice grown under ambient conditions. In addition, CO₂ enrichment increased the whiteness of the grains in both brown and milled rice and reduced their surface hardness. Although the amylose content of rice grains was unaffected, starch pasting properties demonstrated that rice grains in elevated CO₂ had higher maximum viscosity and breakdown than those grown in ambient conditions. Sensory evaluation of cooked rice with respect to umami (deliciousness), appearance, aroma, hardness, stickiness and overall palatability index indicated that the sensory properties were not significantly altered by the CO₂ enrichment treatment. Therefore, we conclude that the growth of the rice cultivar Akitakomachi under elevated CO₂ concentration decreased the protein content, but did not change the palatability to a level that may be detected by sensory taste panel evaluation. Copyright © 2005 Society of Chemical Industry     

Xanthohumol,a prenylated chalcone from Humulus lupulus L., inhibits cholesteryl ester transfer protein

High density lipoprotein (HDL)-cholesterol levels are correlated with a low risk of atherosclerosis. The inhibition of cholesteryl ester transfer protein (CETP), which catalyses cholesterol transfer between lipoproteins, leads to an increase in HDL-cholesterol and is expected to be the next anti-atherogenic target. This study revealed that xanthohumol, a prenylated chalcone, showed the highest inhibition against CETP from screening of natural products in various plants. We investigated the inhibitory activity of some chalcones and flavanones. Naringenin chalcone showed weak CETP inhibition compared with xanthohumol. In addition, isoxanthohumol and naringenin drastically decreased the inhibitory activity. These results suggest that the prenyl group and chalcone structure of xanthohumol were responsible for the CETP inhibitory activity.