Distribution of double bonds in thermally degraded polyisobutylene

The distribution of double bonds in thermally degraded polyisobutylene was determined quantitatively by using pulsed Fourier transform ¹H n.m.r. spectroscopic analysis. The double bonds in the degraded polymer did not exist in the interior but at the terminal positions of the polymer chain. These olefins were of the terminal trisubstituted and terminal vinylidene types. The content of the former was much greater than that of the latter. This shows that radical chain transfer predominantly occurs at the methylene hydrogen rather than at the methyl groups of the polymer chain. The average number of double bonds per molecule, f, was greater than 1 and tended to be near 2. Thereby most of the degraded polyisobutylene was shown to have two terminal unsaturations per molecule.     

Orientation development in thermotropic liquid crystal polymers

Thermotropic liquid crystal polymers are a new class of polymeric materials that consist of rigid backbone molecules and thus, even in the quiescent condition, take extended chain conformation to form optically anisotropic melts. A systematic investigation was carried out on how this type of material responds to two basic flow fields: shear and elongation. Rheological properties of the polymer in these flow fields have also been measured. It was found that a high level of molecular orientation was readily obtained by elongational flow but not with shear flow. Specifically, extraordinarily high orientation was obtained when the melt was subjected to small elongational strains, whiel shear strain or shear rate had little effect. A possible mechanism to explain these behaviors is illustrated based on the existing observations or theories of rodlike molecules. This finding was used to interpret the orientation distribution in the extruded and injection-molded articles.     

An anaerobic bacterium isolated from Japanese spiny lobster Panulirus japonicus

Eight strains of bacteria which could not grow under aerobic conditions, were isolated from Japanese spiny lobster. All the strains were Gram-positive, non-sporeforming cocci, and grew well under anaerobic conditions. The strains required a decreased oxygen tension rather than an increased CO₂ tension. Catalase, oxidase, nitrate reductase and urease were not produced. The strains fermented glucose, cellobiose, trehalose and levulose. Indole and H₂S were not produced. Macromolecule substances including starch, esculin, casein, gelatin and chitin were not hydrolyzed. Lactic acid was the sole product from peptone-yeast extract-Fildes solution-glucose broth. Fermentable carbohydrates were not required. The strains could grow at 20 to 37°C, and required NaCl for growth. From the above results, the strains were identified as anaerobic (aerotolerant) Streptococcus sp.     

Lipid-Lowering Effect of Eriocitrin, the Main Flavonoid in Lemon Fruit, in Rats on a High-Fat and High-Cholesterol Diet

ABSTRACT:  Eriocitrin (eriodictyol 7- O -β-rutinoside) is the main flavonoid in lemon fruit. In this study, eriocitrin was investigated for its lowering effect on serum and hepatic lipids in high-fat and high-cholesterol fed rats. Rats in the control group ( N = 6) were fed a 20% lard and 1% cholesterol diet for 21 d, and rats in the 0.35% eriocitrin group ( N = 6) and 0.70% eriocitrin group ( N = 6) were fed a diet supplemented with eriocitrin 0.35% and 0.70%, respectively. The content of hepatic total cholesterol and triglyceride in the eriocitrin group was no different from that of the control group. The total cholesterol, VLDL+LDL, triglyceride, and phospholipid in the serum of the 0.35% eriocitrin group showed significantly lower concentrations than the control group ( P < 0.05), although there was no difference in the HDL concentrations among the groups. The lowering effect of eriocitrin for serum total cholesterol was thought to be caused by a decrease in VLDL+LDL. The 0.35% eriocitrin group was shown to have a significant increase in excretion of fecal bile acid ( P < 0.05) and a tendency for enhanced hepatic m-RNA levels of LDL receptor in comparison with the control group.     

Contamination levels of PCDDs, PCDFs and Co-PCBs in commercial baby foods in Japan

To examine dioxin contamination in commercial baby foods in Japan, congener analyses of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) were performed on 102 varieties of baby foods obtained from supermarkets in 2001-2002. The toxic equivalent quantity (TEQ) levels for dioxins in samples ranged from < 0.001 to 0.135 pg-TEQ/g wet weight when undetected or trace levels of congeners were taken as zero. Among 102 samples tested, 26 samples exceeded 0.010 pg-TEQ/g. The highest TEQ value was for "sardine, vegetables" (0.135 pg-TEQ/g), followed by "Japanese radish (daikon), sardine" (0.080 pg-TEQ/g). Thus, dioxins were detected at low levels in baby foods containing animal products such as fishes and/or dairy products.     

Modification of cleanup methods for dioxin analysis in green leafy vegetables and comparison of packing methods for a multi-layer silica gel column

To determine polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) in green leafy vegetables, the cleanup method was modified, and packing methods for a multi-layer silica gel column were compared in food samples. First, the additional cleanup was examined for a mono-ortho PCBs fraction obtained by alumina column chromatography from spinach extract. Small solids such as rough crystals that remained after concentration of the mono-ortho PCBs fraction were identified as long-chain hydrocarbons from leaf epicuticular wax by GC/MS. Cleanup using an activated carbon silica gel column with n-hexane as the washing solvent was effective. Next, multi-layer silica gel columns packed by wet packing and dry packing were compared using komatsuna, salmon and butter as samples. The columns prepared by both methods gave similar values at each isomeric concentration level and showed similar efficiency with favorable recoveries.     

Host-dependent activation of IS1203v excision in Shiga toxin-producing Escherichia coli

IS1203v is an insertion sequence (IS) which is identical to the most abundant IS elements in the genome of Escherichia coli O157:H7. However, there is no sequence homologous to IS1203v in the genome of E. coli K-12. We constructed a system to analyze the excision frequency of IS1203v, and demonstrated that the frequency in E. coli O157:H7 was approximately 10(5) times higher than that in E. coli K-12. We also investigated the excision frequencies of IS1203v in various E. coli isolates, and showed that the excision frequencies of IS1203v-possessing strains were approximately 10(3) times higher than those of IS1203v-nonpossessing strains. The results suggest that the IS1203v-possessing strains use a common system to enhance IS1203v excision.     

Dioxin concentrations in the edible parts of Japanese common squid and saury

We examined the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) in muscle and gut tissues from Japanese common squid and saury. These body parts are often eaten in Japan, so it is important to measure their dioxin concentrations and evaluate the risks to consumers. The toxic equivalent (TEQ) concentrations in the squid gut samples (1.0 to 14 pg-TEQ/g fresh weight, n=3) were 50-fold larger than those in the muscle tissues (0.020 to 0.22 pg-TEQ/g fresh weight, n = 3) taken from the same samples. By contrast, the TEQ concentrations in the saury gut samples (0.35 to 0.63 pg-TEQ/g fresh weight, n=3) were only 1.1- to 1.7-fold greater than those in the muscle tissues (0.33 to 0.37 pg-TEQ/g fresh weight, n= 3) from the same samples. The TEQ contents in the squid gut tissues ranged from 60 to 990 pg-TEQ/squid, accounting for about 95% of the total dioxin content of the edible parts of the samples. By contrast, the TEQ contents in the saury gut tissues ranged from 4.4 to 12 pg-TEQ/saury, accounting for less than 25% of the total dioxin content of the edible parts of the samples. These tissues showed comparable PCDD/PCDF-congener and dioxin-like PCB-isomer profiles in both species. The results indicate that squid gut tissues occasionally contain high levels of dioxins, and consumption of this foodstuff could potentially significantly increase the dietary intake of dioxins.