Biomedical subjects

Masatake Toyoda

Publications and source records attributed to Masatake Toyoda.

At least 19 recordsLinked to original sources

PubMed2006

[Evaluation of immunochromatographic test kits for food allergens using processed food models].

It has been mandatory to label five allergenic substances (AS; egg, milk, wheat, buckwheat and peanut) in all processed foods, since April 2002 in Japan. Two kinds of ELISA kits have been provided as screening test kits for the Japanese official method. The kits have many advantages but some disadvantages, i.e., the kits are not necessarily suitable for daily monitoring in food manufacturing plants, because they require various analytical equipments and the use of complicated procedures. To overcome these drawbacks, we have developed other diagnostic kits based on immunochromatography that should enable more rapid and simple screening for food allergens. Then we examined the performance of these immunochromatographic test kits (IC kits) in terms of sensitivity, repeatability and cross-reactivity to AS proteins in 11 kinds of food models with various heating conditions and physical properties. We also examined processed food models including AS protein of constant concentration, using the IC kits and ELISA kits, and compared the results. The IC kits detected AS proteins at 5 microg/g in the extracts from processed food models, and provided highly reproducible results. Cross-reactivity among the AS proteins was not observed. The results obtained using the IC kits showed performance equivalent to that of the ELISA kits we examined in unheating processed food models including AS proteins of constant concentration. The IC kits should be more suitable for daily monitoring in food manufacturing plants.

Allergens↗

PubMed2005

Effects of cooking on concentrations of polychlorinated dibenzo-p-dioxins and related compounds in fish and meat.

We investigated the cooking-induced changes in concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (PCBs) (dioxins) using mackerel and beef. The concentrations of dioxins (29 congeners) were determined by isomer specific analyses and were compared between uncooked and cooked samples. The cooking procedures examined in this study included grilling as a fillet, boiling as a fillet, and boiling as tsumire (small, hand-rolled balls) for mackerel and boiling as a slice, broiling as a slice, and broiling as a hamburger for beef. Three trials were carried out for each cooking method. Generally, concentrations of dioxins were reduced in every cooking trial. When nondetected congener concentrations were assumed to be half the limit of detection for mackerel, the maximum percentage reductions of total concentrations given as 2,3,7,8-tetraCDD equivalents (TEQ) were 31% in grilling as a slice, 14% in boiling as a slice, and 21% in boiling as tsumire under the conditions of this study. In contrast, for beef, the reductions were 42% in boiling as a slice, 42% in broiling as a slice, and 44% in broiling as a hamburger. These results suggest that ordinary cooking processes with heating undoubtedly reduce the dioxin content in animal products, and the reductions estimated should be considered when dioxin intake is evaluated using contamination data for individual food items.

Animals↗

PubMed2005

Inhibition of human lanosterol synthase by the constituents of Colocasia esculenta (taro).

Ethanol extracts of lyophilized vegetables were tested for inhibition of human lanosterol synthase (hOSC) in order to find the compounds to suppress cholesterol biosynthesis. Of 130 samples tested, twelve samples showed significant inhibition. Among them, Colocasia esculenta (taro) showed the highest inhibition (55% inhibition at 300 microg/ml). Examination of activity variation among eight taro cultivars indicated that "Aichi-wase" and "Yatsugashira" had the most potent activity for hOSC inhibition. In order to identify the active constituent of taro, ethanol extracts of "Aichi-wase" were partitioned with hexane and aqueous methanol, and fractionated by silica gel column chromatography. Inhibitory activity was concentrated in two major active fractions. Further purification of these fractions by preparative HPLC gave three monogalactosyldiacylglycerols and five digalactosyldiacylglycerols as active compounds that showed 28 to 67% inhibitory activities at the concentration 300 microg/ml.

Colocasia↗

PubMed2005

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.

Benzofurans↗

PubMed2004

[Inter-laboratory evaluation studies for development of notified ELISA methods for allergic substances (milk)].

Extracts of sausage, sauce, cookie, cereal and pasta sauce spiked with milk standard protein at a level of 5-20 ng/mL as sample solutions were analyzed in replicate in 10 laboratories. Coefficients of variation (CVs) of the three ELISA methods using a Milk Protein Casein ELISA Kit (Casein kit), a Milk Protein Beta-Lactoglobulin ELISA Kit (Beta-Lactoglobulin kit) and a FASTKIT Milk ELISA Kit (Milk ELISA kit) were mostly below 10%. Mean recoveries of the milk standard protein from the food extracts were over 40% in the three ELISA methods with a few excertions. The recoveries of milk standard protein from the sauce extract in Casein kit were improved by adjusting the extract to neutrality before the Casein kit assay. The recoveries of milk standard protein from cookie, cereal and pasta sauce were improved by the increasing the amount of antibody coated in the Milk ELISA kit. The detection limits of all the ELISA methods were 1 ng/mL in sample solutions. These results suggested that the notified ELISA methods are reliable and reproducible for the inspection of milk protein levels in extracts of sausage, sauce, cookie, cereal and pasta sauce.

Allergens↗

PubMed2004

[Inter-laboratory evaluation studies for development of notified ELISA methods for allergic substances (wheat)].

Extracts of sausage, sauce, pasta sauce, fish paste and cereal spiked with wheat standard protein at a level of 5-20 ng/mL as sample solutions were analyzed in replicate in 10 laboratories. Coefficients of variation (CVs) of both ELISA methods using a Wheat Protein ELISA Kit (Gliadin kit) and a FASTKIT Wheat ELISA Kit (Wheat ELISA kit) were mostly below 10%. Mean recoveries of the wheat standard protein from the food extracts were over 40% in the two ELISA methods except those from cereal extract determined using the Wheat ELISA kit. Repeatability relative standard deviations of wheat standard protein in the five food extracts were in the ranges of 16-26.9% and 3.7-36.2% for the Gliadin kit and the Wheat ELISA kit, respectively. Reproducibility relative standard deviations of wheat standard protein in the five food extracts were 21.6-38.5%, 29.7-53.8% for the Gliadin kit and the Wheat ELISA kit, respectively. The recoveries of wheat standard protein from the cereal extract were improved by the increasing the amount of antibody coated on the plate in the Wheat ELISA kit. The detection limits of both ELISA methods were 1 ng/mL in sample solutions. These results suggested that the notified ELISA methods are reliable and reproducible for the inspection of wheat protein levels in extracts of sausage, sauce, pasta sauce, fish paste and cereal.

Allergens↗

PubMed2004

[Inter-laboratory evaluation studies for establishment of notified ELISA methods for allergic substances (buckwheat)].

Inter-laboratory evaluation studies were conducted for the ELISA methods for allergic substances (buckwheat). Extracts of snack, bun and udon spiked with buckwheat standard protein at a level of 5-20 ng/mL as sample solutions were analyzed in replicate at 10 laboratories. Coefficients of variation (CVs) of the ELISA methods using a Buckwheat Protein ELISA Kit (Buckwheat kit) and a FASTKIT Buckwheat ELISA kit (Buckwheat ELISA kit) were mostly below 10%. Mean recoveries of the buckwheat standard protein from the food extracts were over 40% in the two ELISA methods. Repeatability relative standard deviations of buckwheat standard protein in three food extracts were in the ranges of 6.8-78.5% and 5.0-33.9% for the Buckwheat kit and the Buckwheat ELISA kit, respectively. Reproducibility relative standard deviations of buckwheat standard protein in three food extracts were 11.9-69.5% and 16.5-34.1% for the Buckwheat kit and the Buckwheat ELISA kit, respectively. The detection limits of both ELISA methods were 1 ng/mL in sample solutions. These results suggest that the notified ELISA methods are reliable and reproducible for the inspection of buckwheat protein levels in extracts of snack, bun and udon.

Allergens↗

PubMed2004

[Inter-laboratory evaluation studies for establishment of notified ELISA methods for allergic substances (peanuts)].

Inter-laboratory evaluation studies were conducted for ELISA methods for allergic substances (peanuts). Extracts of biscuit, sauce, chocolate and butter spiked with peanut standard protein at a level of 5-20 ng/mL as sample solutions were analyzed in replicate in 10 laboratories. Coefficients of variation (CVs) of the ELISA methods using a Peanut Protein ELISA Kit (Peanut kit) and a FASTKIT Peanut ELISA kit (Peanut ELISA kit) were mostly below 10%. Mean recoveries of the peanut standard protein from the food extracts were over 40% in the two ELISA methods. Repeatability relative standard deviations of peanut standard protein in four food extracts were in the ranges of 15.2-49.7% and 3.0-28.3% for the Peanut kit and the Peanut ELISA kit, respectively. Reproducibility relative standard deviations of peanut standard protein in four food extracts were 23.5-44.4%, 9.6-28.4% for the Peanut kit and the Peanut ELISA kit, respectively. The detection limits of both ELISA methods were 2-2.5 ng/mL in sample solutions. These results suggested that the notified ELISA methods are reliable and reproducible for the inspection of peanut protein levels in extracts of biscuit, sauce, chocolate and butter.

Allergens↗

PubMed2003

Evaluation of an aqueous KOH digestion followed by hexane extraction for analysis of PCDD/Fs and dioxin-like PCBs in retailed fish.

Aqueous KOH digestion followed by hexane extraction has been employed in the extraction of dioxins (polychlorinated dibenzo- p -dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls) for biological samples, but there are no reports on its evaluation. Therefore, we report here the evaluation of this extraction for the analysis of dioxins in retailed fish. The effect of the alkaline digestion on dioxins was evaluated by estimation of recoveries. The recoveries of dioxins after the alkaline digestion were good (79-106%) in various kinds of retailed fish except tuna. In tuna, loss of octachlorodibenzofuran (OCDF) was clearly observed, however, the loss was corrected by internal-standard quantification; (13)C12-labeled OCDF was added before the alkaline digestion. Comparative study showed that alkaline digestion followed by hexane extraction provides extraction efficiencies of dioxins equal to those of conventional Soxhlet extraction in fish. Additionally, in analysis of a certified reference fish sample with this extraction, the values obtained for certified isomers were almost equal to the certified values. Since the present method is very simple and inexpensive, it would be useful for analysis of dioxins in retailed fish.

Animals↗

PubMed2003

Validation of the CALUX bioassay for the screening of PCDD/Fs and dioxin-like PCBs in retail fish.

The chemical-activated luciferase expression (CALUX) assay is a reporter gene assay that detects dioxin-like compounds based on their ability to activate the aryl hydrocarbon receptor (AhR) and thus expression of the reporter gene. In this paper, the CALUX assay was examined for its application in the screening of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) in retail fish. The sample extracts were cleaned up on a sulfuric acid-silica gel column followed by an activated carbon column, and the AhR activity of the separated PCDD/F and dioxin-like PCB fractions was determined using the assay. The quantitative limit for 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) was 0.98 pg ml(-1) (0.19 pg assay(-1) in the standard curve, corresponding to 0.16 pg g(-1) of CALUX-based toxic equivalency (2,3,7,8-TCDD equivalents) in the tested sample. Recovery tests in which dioxins were added to fish samples resulted in acceptable recoveries (77-117%). The CALUX assay performed well in the analysis of dioxins in fish samples and a comparative study revealed a strong correlation between the CALUX assay and high-resolution gas chromatography-high-resolution mass spectrometry analysis for the determination of PCDD/Fs (r = 0.89) and dioxin-like PCBs (r = 0.91) in retail fish (n = 22). These data revealed that the CALUX assay would be a useful screening method for PCDD/Fs and dioxin-like PCBs in retail fish.

Animals↗

PubMed2003

Activation of the aryl hydrocarbon receptor by some vegetable constituents determined using in vitro reporter gene assay.

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates the biological action of many aromatic environmental pollutants. In this study, we investigated the activation of the AhR by some vegetable constituents using the AhR-based bioassay for dioxins, i.e., the chemical activated luciferase gene expression (CALUX) assay. Ninety-five vegetable constituents, including flavonoids, tannins, saponins, and terpenes, were tested in vitro. Among them, isoflavones such as daidzein, resveratrol having a stilbene structure, and some flavonoids such as naringenin, hesperetin, and baicalein showed AhR activation.

Animals↗

PubMed2003

Cleanup of food samples with pre-packed multi-layer silica gel column for the analysis of PCDDs, PCDFs and dioxin-like PCBs.

The cleanup procedure for the determination of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs) in food samples using a disposable pre-packed multi-layer silica gel column (multi-layer dioxin tube; D-tube) was evaluated. The blank test showed the need for conditioning of the column with n-hexane. To compare the method with the D-tube and the conventional method for the analyses of actual food samples, seven food samples (spinach, komatsuna, rice, salmon, beef, egg and butter) were extracted by shaking with acetone-n-hexane or n-hexane after alkaline treatment, and then the extracts were cleaned up by use of the D-tube or the prepared conventional column, followed by several column chromatographic steps. Both cleanup procedures gave similar values at each isomeric concentration level and showed similar efficiency with favorable recoveries. The results suggest that the D-tube is applicable to cleanup for the analysis of PCDD/Fs and dioxin-like PCBs in foods.

Chromatography, Gel↗

PubMed2003

[Inter-laboratory evaluation studies of notified ELISA methods for allergic substances (egg)].

Inter-laboratory evaluation studies were conducted for the notified ELISA methods for allergic substances (Egg). Standard extracts of egg spiked in extracts of sausage, sauce, cookie, bread and cereal at a level of 5-20 ng/mL as the sample solution were analyzed in replicate in 10 laboratories. Coefficients of variation (CVs) of all three ELISA methods using an Egg Protein ovalbumin ELISA Kit (ovalbumin kit), an Egg Protein ovomucoid ELISA Kit (ovomucoid kit) and a FASTKIT Egg ELISA kit (Egg ELISA kit) were mostly less than 10%. Mean recoveries of the standard extract of egg were over 40% in the three ELISA methods. Repeatability relative standard deviations of egg standard solution in five food extracts were in the ranges of 18.7-25.5%, 18.6-41.8%, 21.3-43.3% for the ovalbumin kit, the ovomucoid kit and the Egg ELISA kit, respectively. Reproducibility relative standard deviations of egg standard solution in five food extracts were 16.8-35.1%, 19.6-35.8%, 24.7-51.1% for the ovalbumin kit, the ovomucoid kit and the Egg ELISA kit, respectively. The detection limits of all the ELISA methods were 4-5 ng/mL in sample solutions. These results suggested that the notified ELISA methods are reliable and reproducible for the inspection of egg protein levels in extracts of sausage, sauce, cookie, bread and cereal.

Allergens↗

PubMed2003

Determination of enzymatic activity of 5-enolpyruvylshikimate-3-phosphate synthase by LC/MS.

A liquid chromatography-mass spectrometry (LC/MS) method for determining the enzymatic activity of 5-enolpyruvylshikimate-3-phosphate synthase (EPSP synthase), an enzyme of the shikimate pathway, was developed. EPSP synthase catalyzes the formation of 5-enolpyruvylshikimate-3-phosphate (EPSP) from shikimate-3-phosphate (S-3-P) and phosphoenolpyruvate (PEP) in microorganisms and plants. The enzymatic activity of EPSP synthase was assessed by the determination of EPSP after a 30-min incubation with S-3-P and PEP using the LC/MS system. EPSP synthase activity is given in terms of the produced EPSP (pmol/min/mg protein). Glyphosate (N-phosphonomethyl glycine)-tolerant EPSP synthase from the Agrobacterium sp. strain CP4 (CP4-EPSP synthase) in genetically modified soybeans (GM-soybeans) was found to have an enzymatic activity of 736 EPSP pmol/min/mg protein in the presence of 3 nmol of S-3-P. In contrast, the enzyme activity of non-GM-soybeans was 21 EPSP pmol/min/mg protein. The EPSP synthase activity was markedly decreased in the non-GM-soybeans by the addition of glyphosate, but the enzyme activity of the GM-soybeans was only slightly decreased with this treatment. This LC/MS system could also be applicable to the measurement of EPSP synthase activity in different plant species and the detection of herbicide-tolerant EPSP synthase in GM foods.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed2002

Detection of recombinant DNA segments introduced to genetically modified maize (Zea mays).

Polymerase Chain Reaction (PCR) techniques are increasingly used for the detection of genetically modified (GM) crops in foods. In this paper, recombinant DNAs introduced into the seven lines of GM maize, such as Event 176, Bt11, T25, MON810, GA21, DLL25, and MON802, are sequenced. On the basis of the obtained sequence, 14 primer pairs for the detection of the segments, such as promoter, terminator regions, and construct genes, were designed. To confirm the specificities of the designed primer pairs, PCR was performed on genomic DNAs extracted from GM and non-GM maize, GM and non-GM soy, and other cereal crops. Because the presence of the corresponding DNA segments was specifically detected in GM crops by the designed primer pairs, it was concluded that this method is useful for fast and easy screening of GM crops including unauthorized ones.

Amino Acid Sequence↗

PubMed2002

Characterization and structures of anthocyanin pigments generated in rosé cider during vinification.

Anthocyanin pigments, which are not found in apple juice, were detected in rosé cider. We confirmed by HPLC/DAD and LC/ESI-MS analyses that some of these anthocyanin pigments generated in rosé cider during vinification corresponded to those formed in model cider containing anthocyanin and flavan-3-ol in the presence of acetaldehyde. To confirm their structures, two anthocyanin pigments formed in a model cider containing cyanidin-3-galactoside and (-)-epicatechin in the presence of acetaldehyde were isolated and purified, and their structures were elucidated by high resolution FAB-MS and (1)H and (13)C NMR analyses. These two pigments were found to consist of cyanidin-3-galactoside and (-)-epicatechin linked by a CH(3)-CH bridge at the 8-position. They were diastereomers that differed in the configuration of the asymmetric methine carbon.

Anthocyanins↗

PubMed2002

Acylated anthocyanins from red radish (Raphanus sativus L.).

Twelve acylated anthocyanins were isolated from the red radish (Raphanus sativus L.) and their structures were determined by spectroscopic analyses. Six of these were identified as pelargonidin 3-O-[6-O-(E)-feruloyl-2-O-beta-D-glucopyranosyl]-(1-->2)-beta-D-glucopyranoside]-5-O-(beta-D-glucopyranoside), pelargonidin 3-O-[6-O-(E)-caffeoyl-2-O-(6-(E)-feruloyl-beta-D-glucopyranosyl)-(1-->2)-beta-D-glucopyranoside]-5-O-(beta-D-glucopyranoside), pelargonidin 3-O-[6-O-(E)-p-coumaroyl-2-O-(6-(E)-caffeoyl-beta-D-glucopyranosyl)-(1-->2)-beta-D-glucopyranoside]-5-O-(beta-D-glucopyranoside), pelargonidin 3-O-[6-O-(E)-feruloyl-2-O-(6-(E)-caffeoyl-beta-D-glucopyranosyl)-(1-->2)-beta-D-glucopyranoside]-5-O-(beta-D-glucopyranoside), pelargonidin 3-O-[6-O-(E)-p-coumaroyl-2-O-(6-(E)-feruloyl-beta-D-glucopyranosyl)-(1-->2)-beta-D-glucopyranoside]-5-O-(beta-D-glucopyranoside), and pelargonidin 3-O-[6-O-(E)-feruloyl-2-O-(2-(E)-feruloyl-beta-D-glucopyranosyl)-(1-->2)-beta-D-glucopyranoside]-5-O-(beta-D-glucopyranoside).

Acylation↗

PubMed2002

Recent survey and effects of cooking processes on levels of PCDDs, PCDFs and Co-PCBs in leafy vegetables in Japan.

We report here the latest levels of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) and coplanar polychlorinated biphenyls (Co-PCBs) in leafy vegetables in Japan as well as the effect of cooking processes on the reduction of these contaminants. Three kinds of leafy vegetables ("komatsuna", lettuce and spinach) from seven districts in Japan in 1998 were analyzed for the 2,3,7,8-chlorine substituted PCDD/Fs and three non-ortho-PCBs (#77, 126 and 169). The mean total TEQ levels (using the WHO-TEFs) in the komatsuna, lettuce and spinach were 0.094, 0.025 and 0.196 pg/g fresh weight, respectively. The TEQ levels are dominated by 2.3,7,8-TCDD, 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF and 3,3',4,4',5-PeCB in many of the samples. For one of these isomers, the 2,4,7,8-PeCDF TEQ levels showed good correlation with the total TEQ levels in the samples (r = 0.957). This suggests that 2,3,4,7,8-PeCDF may be an indicator for dioxin contamination in the analysis of the leafy vegetables. Also, the effects of two cooking processes (washing and washing followed by boiling) on the dioxin levels in two types of spinach samples were investigated. On average, in both samples, the total concentrations of the PCDDs, PCDFs and Co-PCB were reduced to about 38%, 73% and 88% of the initial concentrations by washing. and to 21%, 35%, and 61% of the initial concentrations by washing followed by boiling. The total TEQ levels were reduced to about 30% of the initial TEQ levels by washing followed by boiling. Significant reductions in the TEQ levels were observed in the cooked samples. Thus, the cooking processes may reduce the risk of dioxin intake from the leafy vegetables.

Benzofurans↗