Biomedical subjects

Rieko Matsuda

Publications and source records attributed to Rieko Matsuda.

29 records · Page 2Linked to original sources

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

Estimation of uncertainty in kinetic-colorimetric assay of bacterial endotoxins.

The relative standard deviation (R.S.D.) of measurements is estimated in the kinetic-colorimetric assay of bacterial endotoxins without recourse to the usual repeated experiments. The measurements are the slopes of kinetic curves and two major factors are considered to cause the uncertainty of the measurements: (1) the pipetting of the sample and color development reagent; and (2) noise in the detection unit. The measurement R.S.D. is formulated as a function of endotoxin concentration. Two parameters (S.D. of the pipetted volumes and S.D. of the detector noise) are also required in the uncertainty equation, but no arbitrary coefficients are included. Since the S.D. values for pipettes and detector noise can be determined independently of the endotoxin assays, the measurement R.S.D. can be estimated by the above equation without repeating the assays. However, the calibration curve is necessary. The theoretical estimation is shown to be in good agreement with the experimental R.S.D. (n = 12) over a wide concentration range.

Algorithms↗

PubMed2003

Prediction of measurement precision of apparatus using a chemometric tool in electrochemical detection of high-performance liquid chromatography.

The relative standard deviation (RSD) of measurements in high-performance liquid chromatography with electrochemical detection (HPLC-ECD) was predicted by a chemometric tool based on the 1/f fluctuation model which is made up of white noise and a Markov process, called the Function of Mutual Information (FUMI) theory. FUMI theory can provide aprecise and reliable detection limit from a single measurement of noise and signal in HPLC-ECD. To obtain RSD (n = 5) for determination of (-)-epicatechin at five concentrations required 12.5 h, while the predicted RSD by FUMI theory required only 0.5 h (one measurement). Moreover, to trace the source of instrumental noise, power spectra of chromatographic baseline were used. Selection of a suitable apparatus in HPLC-ECD system, acquisition of RSD, and detection limits for determination of catechins by HPLC-ECD were simply and easily made by this chemometric tool within a very short time. The use of the FUMI theory for the prediction of measuring precision was more efficient and the optimization was less time-consuming to be suited for determination.

Catechin↗

PubMed2003

[Precision of internal standard method in HPLC analysis].

The internal standard methods are known to compensate for the errors from sample preparation and injection into an analytical instrument. However, recent HPLC apparatuses have injectors of excellent repeatability and it is dubious whether the cancellation of injection error can lead to substantial improvement in the precision of analysis. This paper answers the above question experimentally and theoretically. The HPLC analysis of butylscopolamine bromide is taken as an example. The relative standard deviations (RSD) of measurements in the internal standard method and absolute calibration curve method are compared and the advantages of these methods are discussed. The measurement RSD is shown to be well estimated by the (function of mutual information) (FUMI) theory without repeating measurements. This report also demonstrates simple equations for calculating the measurement RSD at an arbitrary concentration of analyte and for selecting the better method between the internal standard method and absolute calibration curve method under specific experimental conditions.

Calibration↗

PubMed2003

Test of significant differences with a priori probability in microarray experiments.

A traditional method for comparing two expression levels of genes in microarray experiments is the two-sample t-test. Because of the difficulty in using a large number of microarrays, an alternative method is required which can provide a reliable judgment of the comparison from a small number of replicates, even from a single pair of control and treatment. We present a method for detecting the changes in the gene expression levels under two different conditions in microarray experiments. Our method targets a single experiment for each condition, while retaining the statistical advantages of the t-test. The new proposals are: 1) standard deviation (SD) estimates of the expression levels which are an indicator for significant differences are given a priori as a function of the expression levels; 2) the limit of detection (LOD) for the expression levels is used to eliminate the majority of genes expressed at extremely low levels. The a priori SD estimates are obtained from six replicates under a fixed condition and are shown to be the approximate, but proper description of the expression uncertainty covering diverse conditions (e.g., different samples (human and rat) and different DNA chips). The LOD is defined as three times blank SD according to the IUPAC recommendation. A cell line (HL60) which will undergo macrophage differentiation on treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA) is taken as an example. Our method is compared with the t-test for the data on duplicate TPA experiments and the former alone is evaluated with the data on a single TPA experiment. The errors from sample preparation and instrumental analysis are discussed.

Animals↗

PubMed2003

Optimization of HPLC-ECD conditions for determination of catechins with precision and efficiency based on the FUMI theory.

A chemometric tool based on the Function of Mutual Information (FUMI) theory can provide a relative standard deviation (RSD) without repetitive measurements in high-performance liquid chromatography with electrochemical detection (HPLC-ECD). Two parameters: precision (= information content) phi and efficiency (= information content/time) theta, which were calculated from predicted RSD based on the FUMI theory, were used to optimize HPLC-ECD conditions, such as applied potential, flow rate, column length, and size of ODS porous packing. We selected catechins as analytes, and found that the most optimum applied potential and flow rate were +600 mV vs. SCE and 0.9 mL/min, respectively, because they gave the largest phi and theta values. Buffer concentration in mobile phase is less effective for giving large phi and theta values. Since the FUMI theory makes it possible to predict RSD without repetitive measurements, the present method saves considerable amounts of chemicals and experimental time, and was found to be useful for the optimization of experimental conditions for determination by HPLC-ECD.

Journal Article↗

PubMed2003

[Estimation of daily oral exposure to phthalates derived from soft polyvinyl chloride baby toys].

Daily oral exposure of babies to phthalate was estimated on the basis of the mouthing time of infants and the oral concentration of diisononyl phthalate (DINP) released from polyvinyl chloride (PVC) toy specimens. Total mouthing time, including the use of pacifiers, ranged widely from 11.4 min to 351.8 min with the mean of 105.3 +/- 72.1 min. The mean of the total mouthing time without pacifiers was 73.9 +/- 32.9 min. The average amount of DINP in saliva was 92.4 +/- 56.8 micrograms/10 cm2/hr, ranging from 13.2 micrograms/10 cm2/hr to 240.4 micrograms/10 cm2/hr. The exposure of phthalate in two different trials was estimated by the method of Monte Carlo simulation, one with the total mouthing time with pacifiers and the other with the total mouthing time without pacifiers. The average exposure in the former trial was 21.4 micrograms/kg/day and the 95th percentile was 65.8 micrograms/kg/day, while in the latter it was 14.8 micrograms/kg/day and the 95th percentile was 35.7 micrograms/kg/day.

Humans↗

PubMed2002

Validation of HPLC and GC-MS systems for bisphenol-A leached from hemodialyzers on the basis of FUMI theory.

This paper proposes a method for the validation of chromatography systems in which many experiments to estimate SD or RSD are difficult or impossible to carry out because of time, cost, etc. HPLC systems with UV-Vis and fluorescence detectors and GC-MS system for bisphenol-A leached from hemodialyzers are taken as an example. Examined as validation characteristics are not only the ordinary quantities (precision, accuracy, range, limit of detection (LOD), limit of quantitation (LOQ), specificity and linearity) but also precision plots (measurement RSD vs. concentration), 95% confidence intervals of calibration lines and LOD signals over baselines. The precision plots, calibration confidence intervals and LOD signals are shown to be advantageous to validate and compare the analytical performance of the systems. The LOD, LOQ, precision plots and 95% confidence intervals of calibration lines are all derived from the SD of measurements and the reliability of these quantities and plots depends totally on the reliability of the SD estimates. This paper uses a probability theory, called the FUMI theory, to estimate as exact a measurement SD as possible without the replication. The precision of the HPLC and GC-MS systems is shown to coincide with the repeatability obtained by the repetition of measurements.

Benzhydryl Compounds↗

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↗

PubMed2002

[Estimation of precision in system suitability tests].

In system suitability tests, the daily conditions of an analytical instrument are checked with the standard deviation (SD) of measurements as a criterion. This paper examines how exactly the SD values obtained from the measurements can indicate instrumental conditions. The HPLC measurement for acetaminophen is repeated six times daily to obtain an SD estimate, and these procedures are repeated for seven days. The degree of scattering of the seven SD values corresponds well to the 95% confidence intervals calculated from the chi-square distribution (n = 6). Therefore it is concluded that the variability of the daily conditions of the HPLC system used in this study is too small to detect by referring to the SD estimates (n = 6) and the daily change in the SD estimates only represents the error of the SD estimation itself. However, if the repetition number is 40 (n = 40), the SD estimates will be a good indicator. Forty measurements are practically impossible for a slow analysis like HPLC, and this paper recommends the function of mutual information theory as a substitute for repetitive measurement.

Acetaminophen↗

PubMedDate not supplied

Interlaboratory evaluation of two enzyme-linked immunosorbent assay kits for the detection of egg, milk, wheat, buckwheat, and peanut in foods.

The labeling of 5 major allergenic ingredients (egg, milk, wheat, buckwheat, and peanut) is mandatory in Japan, and 2 series of enzyme-linked immunosorbent assay (ELISA) kits have been established as official screening methods. However, these official methods have not provided the necessary sensitivity, due in part to poor extraction efficiency. To address this need, 2 novel ELISA kits have been developed: the FASTKIT ELISA Ver. II Series and the FASPEK Allergenic Substances Detection Kit. The new kit systems use an improved extraction buffer that can extract insoluble proteins produced by processing and feature new antibodies that bind to the denatured proteins extracted with the new extraction buffer. The analytical performances of the 2 new ELISA kit series were evaluated in an interlaboratory study. Ten laboratories participated in the study and determined the major allergenic ingredients contained in 5 types of model processed food. The 2 ELISAs displayed fairly good reproducibility and sufficient recovery.

Allergens↗