VITAMINS

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It is well known that elevated plasma levels of low density lipoproteins (LDLs) are atherogenic. Recent advances in investigations on metabolism of lipoproteins by the artery wall with regard to uptake of LDL by macrophages resulting in fatty streak formation have yielded new insights into the factors involved in the arterial responses. A large amount of studies, in vitro and in vivo, supports the hypothesis that LDLs undergoing oxidative modifications are metabolized through a specific receptor, the acetyl LDL or scavenger receptor, on macrophages in arterial walls. In addition, it has been reported that some species of modified LDLs such as glycated LDL and malondialdehyde (MDA) -rich LDL probably exist in circulation. Then, the present study was undertaken to characterize MDA-LDL and their heterogeneity as a model of modified LDL, as compared with native LDL occurring in healthy and disease blood samples. MDA-LDL was produced by MDA and CuCl_2 reacted with normal LDL (n-LDL) (MDA-LDL_M and MDA-LDL_<Cu>, repectiveiy) in vitro. The LDL from uremics was enrolled in the study as a native modified LDL (MDA-LDL_<HD>). By elution through a gradient ion-exchange chromatography, the peak of MDA rich fraction (MRF) was separated at higher ionic strength, as compared with MDA poor fraction (MPF). The MPF was largest in MDA-LDL, especially MDA-LDL_<Cu>. The MDA-LDL_<Cu> showed fractions with most cathodal mobility on the agarose electrophoretic patterns, while MDA-LDL_M and MDA-LDL_<HD> had fractions with slightly cathodal mobility, as compared with n-LDL. Apolipoprotein (apo) B-100 in the MRF of n-LDL and MDA-LDL_<HD> showed electrophoretically an appearance of high molecular weight fractions, which also increased in MDA-LDL_M with additionally increasing amounts of MDA. Whereas, electrophoretic patterns in apo B-100 in MDA-LDL_<Cu> showed a number of the bands with low molecular weight fractions. From the findings, MDA-LDL_M is thought to be a model of modified LDL existing in native samples, since chemical characteristics are found to be similar between MDA-LDL_M and LDL_<HD>.

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Serum total PL and PLP concentrations were investigated in 97 adult patients with NIDDM by the HPLC method. The mean total PL and PLP concentrations in NIDDM were significantly lower than those of healthy controls. Forty-nine percent of the diabetic patients had concentrations of total PL below the mean value of the controls minus 1 SD. The insulin-treated patients had on average a lower serum total PL than those with either drug therapy or diet therapy. There were a statistical correlation between serum CPR and total PL. The mean total PL concentrations below 10% of HbA_1. With the reduction of HbA_1 after therapy, the total PL concentrations tended to increase. These results suggest that B_6 relates to discase statis of diabetics.

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A rapid and reproducible procedure using triplicate extraction system with ethyl acetate/n-hexane (1 : 9) after saponification, is described for the determination of tocopherols (Tocs) in foods by the high performance liquid chromatography. The results obtained by the proposed procedure were comparable to those by the procedure using the ethyl ether extraction system. Recoveries of Tocs from pork separable fat were 97.5% for α-Toc, 97.9% for β-Toc, 97.7% for γ-Toc, 97.7% for δ-Toc. The coefficients of variation for α-, β-, γ- and δ-Tocs were 2.8%, 4.4%, 2.6% and 1.4% in 10 replicated analyses of mayonnaise, respectively.

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Prototype of lactic acid sensor system, which was constructed with oxygen electrode, lactate oxidase immobilized membrane and personal computer, was improved. As the results lactic acid can be determined within 1 min as low as 5 ppm without lowering accuracy. The greatest advantage of this method is that the determination can be carried out directly even with turbid or muddy samples. Lactic acid and niacin contents in 24 kinds of fermented milk and lactic acid bacteria beverages on the market were determined with this improved method. Then favorable results were obtained and practical use of this method was suggested.

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