Structural characterization and hypoglycemic effects of arabinogalactan-protein from the tuberous cortex of the white-skinned sweet potato (Ipomoea batatas L.)

An arabinogalactan-protein (WSSP-AGP) was isolated from the tuberous cortex of the white-skinned sweet potato (WSSP; Ipomoea batatas L.). It consists of 95% (w/w) carbohydrate and 5% (w/w) protein with high contents of hydroxyproline, alanine, and serine. Its sugar composition is α-L-Rha:α-L-Ara:β-D-Gal:β-D-GlcA in a molar ratio of 1.0:4.1:7.6:1.3. Its weight-average molecular weight was estimated to be 126,800 g/mol by high-performance size exclusion chromatography coupled with multiangle laser light scattering. Structural analysis indicated that WSSP-AGP is a (1→3)-β-D-galactan highly branched at O-6 with (1→6)-β-D-galactan, in which the branched chains are substituted at the O-3 position with α-L-Araf-(1→ and α-L-Araf-(1→5)-α-L-Araf-(1→ and at the O-6 position typically with α-L-Rhap-(1→4)-β-D-GlcAp-(1→ as terminating groups. Continuous administration of WSSP-AGP to KKAy mice significantly lowered fasting plasma glucose levels. This indicates that WSSP-AGP plays an important role in the hypoglycemic effects of WSSP.     

Seasonal and Spatial Variations in the Chemical and Sulfur Isotopic Composition of Acid Deposition in Niigata Prefecture, Japan

The following measurements were carried out to clarify acid deposition in Niigata Prefecture, an area facing to the Sea of Japan. 1) Acid deposition fluxes and sulfur isotopic ratios of atmospheric deposition were measured at 9 sites in the prefecture in 1999. 2) Atmospheric deposition was collected daily at one site in 1997, to measure the sulfur isotopic variations of sulfate together with the air mass trajectory for each deposition. It became clear that: (a) The major component that acidifies atmospheric deposition is sulfuric acid. (b) Sulfate deposition increases in winter in the whole study area. (c) The sulfur isotopic ratios indicate that sulfur dioxide emitted from China affects the whole study area in winter. (d) Winter deposition of sulfate estimated to derive from coal combustion in China account for half of nss-sulfate deposition in average at 9 sites.     

Effects of revision of Japanese food composition tables on estimation of nutrient intakes, with reference to age-dependent differences

OBJECTIVE: To identify effects of revision of the Japanese food composition tables from the fourth version to the fifth version on nutrient intake estimation. DESIGN: A database on 783 samples of 24-hour food duplicate portions was re-visited. Nutrients in the duplicate portions were estimated by use of the fourth and fifth versions of the Japanese food composition tables in parallel, together with supplemental use of other databases. The two sets of estimates were subjected to comparison. SETTING: The sample collection was conducted at 31 sites all over Japan. SUBJECTS: The sample donors were 783 women aged 20-78 years. RESULTS: Compared with the estimates by use of the fourth version of the tables, the estimates by the fifth version were substantially higher for intakes of energy, carbohydrate, dietary fibre, vitamin A and niacin, and lower for iron intake. The increase in carbohydrate intake estimates was more evident in older women than in young women, whereas the decrease in the intake estimation of iron and the increase in that of dietary fibre were more marked in young women than in older women. CONCLUSION: The recent revision of food composition tables in Japan induced substantial changes in the estimation of nutrient intakes, i.e. an increase in energy, carbohydrate, dietary fibre, vitamin A and niacin, and a decrease in iron. The extent of the changes varied depending on age.     

Antioxidant activity of prune (Prunus domestica L.) constituents and a new synergist

Ethanol extract of prune was separated into hexane-soluble and H(2)O-soluble fractions, and the H(2)O-soluble fraction was further separated into a methanol (MeOH) eluate and an H(2)O eluate by Diaion HP-20 column chromatography. The MeOH eluate exhibited the strongest antioxidant activity among the separated fractions evaluated by oxygen radical absorbance capacity (ORAC). Further purification of the MeOH eluate led to isolation of a novel compound, 4-amino-4-carboxychroman-2-one, together with four known compounds (p-coumaric acid, vanillic acid beta-glucoside, protocatechuic acid, and caffeic acid), structures of which were identified by NMR and MS analyses. The ORAC values of these isolated compounds showed 0.15-1.43 units (micromol of Trolox equiv)/micromol, and the new compound showed a remarkable synergistic effect on caffeoylquinic acid isomers. The antioxidant activity of the MeOH eluate was highly dependent on the major prune components, caffeoylquinic acid isomers, with a contribution from the new synergist.     

Inhibition of post-mortem muscle softening following in situ perfusion of protease inhibitors in tilapia

ABSTRACT:     A method of introducing protease inhibitors into fish muscle through the bulbus arteriosus was developed using an in situ perfusion technique. Perfusion efficiency was initially tested using eosin and [³⁵S]-methionine. Visible fluorescence was observed in the gill, liver, intestine and dorsal muscle of the eosin-treated tilapia, and the occurrence of eosin in the blood vessels of the dorsal muscle was confirmed under a fluorescence stereoscopic microscope with ultraviolet light. The radioactivity of [³⁵S]-methionine was taken into the dorsal muscle and liver at a concentration of 7.8 Bq/g and 70.2 Bq/g, respectively, after perfusion with 1000 Bq/mL solution. Using the perfusion technique with four kinds of protease inhibitors dissolved in physiological saline, the type of proteases implicated in the post-mortem muscle softening in tilapia (867 ± 195 g, n  = 10/protease inhibitor) was investigated. After the perfusion of leupeptin (serine and cysteine protease inhibitor), benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-fmk; caspase inhibitor), chymostatin (serine protease inhibitor) and ο -phenanthroline (metalloprotease inhibitor), the breaking strength of the perfused muscle was measured as a parameter of the meat toughness and compared with that of the control fish, which were perfused with physiological saline only. The reduction of breaking strength during storage was inhibited by the perfusion of leupeptin and Z-VAD-fmk.     

The Effect of Light on the Accumulation of Lipids in Rice Seeds

To investigate the effects of light on the accumulation of assimilate in rice seeds, ears were allowed to grow in darkness 10 d after their formation. The lipid content of rice bran on the 40th day increased by cultivation of ears in darkness whereas the dry weight and starch and sucrose contents of the rice seeds decreased. In the light, the triacylglyceride (TG) content of rice seeds was lowest on the 20th day but then increased continuously for the next 20 d, while the diacylglyceride (DG) content reached a maximum value on the 20th day. In darkness, in contrast, rice seeds showed a higher TG content, with a lower DG content and lower levels of other lipids on the 20th day compared with seeds exposed to light. These results suggest that the biosynthesis of starch and lipids in rice seeds is regulated by light.     

Structure and possible function of <Emphasis Type="Italic">N</Emphasis>-glycans of an invertebrate C-type lectin from the acorn barnacle <Emphasis Type="Italic">megabalanus rosa</Emphasis>

ABSTRACT:   A C-type lectin (BRA-2) isolated from the acorn barnacle Megabalanus rosa , which was a glycoprotein having an N -linked sugar chain, was deglycosylated by N -glycopeptidase F. The structure of the released sugar chains was determined by a 2-D mapping method after derivatization with a fluorescent reagent, 2-aminopyridine, to be Manα1-6(Manα1-3)Manβ1-4GlcNAcβ1-4(Fucα1-6)GlcNAc and Manα1-6(GlcNAcβ1-2Manα1-3)Manβ1-4GlcNAcβ1-4(Fucα1-6)GlcNAc. The structures were confirmed by matrix-assisted laser desorption ionization mass spectrometry and a comparison with authentic sugar chains by high-pressure liquid chromatography. Various properties of BRA-2 were examined before and after deglycosylation. The susceptibility of BRA-2 to protease digestion was increased by deglycosylation. However, the inhibitory activity toward calcium carbonate crystallization as well as the hemagglutinating activity of deglycosylated BRA-2 was significantly decreased. These results suggest that the sugar chains of BRA-2 are important to both its structural stability and its function.