Biomedical subjects

Masao Fukushima

Publications and source records attributed to Masao Fukushima.

9 recordsLinked to original sources

PubMed2007

Second-order cone programming formulations for robust multiclass classification.

Multiclass classification is an important and ongoing research subject in machine learning. Current support vector methods for multiclass classification implicitly assume that the parameters in the optimization problems are known exactly. However, in practice, the parameters have perturbations since they are estimated from the training data, which are usually subject to measurement noise. In this article, we propose linear and nonlinear robust formulations for multiclass classification based on the M-SVM method. The preliminary numerical experiments confirm the robustness of the proposed method.

Artificial Intelligence↗

PubMed2006

Photodegradation of fenitrothion and parathion in tomato epicuticular waxes.

Photodegradation of (14)C-labeled fenitrothion ([O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate]) and parathion ([O,O-diethyl O-(4-nitrophenyl) phosphorothioate]) was conducted on a series of solid surfaces including isolated tomato fruit and leaf cuticle waxes. The wax-coated glass plate gave the comparative degradation of fenitrothion observed for the intact plant but both surfaces of octadecyl-capped silica gel and poly(tetrafluoroethylene) enhanced its volatilization. Photoinduced desulfuration and ester cleavage were common to both pesticides in waxes, but formation of the azo derivative was found to be a major degradation pathway characteristic of parathion. The modified electronic states of the nitro group by introduction of m-methyl group accounted for this different photoreactivity based on molecular orbital calculations.

Fenitrothion↗

PubMed2005

Tomato metabolism and porphyrin-catalyzed oxidation of pyriproxyfen.

Investigation of the metabolism of [(14)C]pyriproxyfen [4-phenoxyphenyl (R,S)-2-(2-pyridyloxy)propyl ether] in tomato fruits (Lycopersicon esculentum Mill. cv. Ponterosa) was conducted by topical application of acetonitrile solution or emulsifiable concentration formulation three times at 35, 21, and 7 days before harvest. Most of the radioactivity remained on the fruit surface or in the plant tissues as intact pyriproxyfen with minor metabolites formed via hydroxylation at the 4'-position of the phenoxy ring or cleavage of ether linkages. The biomimic chemical oxidation model using iron porphyrin as a catalyst and hydrogen peroxide was found to well reproduce the primary metabolites detected in the metabolism study. The electrophilic reaction indices obtained by AM1 molecular orbital calculations supposing involvement of cytochrome P-450 were successfully applied to evaluate the potentially higher reactive sites in pyriproxyfen.

Acetonitriles↗

PubMed2003

Detection and identification of Escherichia coli, Shigella, and Salmonella by microarrays using the gyrB gene.

Commonly, 16S ribosome RNA (16S rRNA) sequence analysis has been used for identifying enteric bacteria. However, it may not always be applicable for distinguishing closely related bacteria. Therefore, we selected gyrB genes that encode the subunit B protein of DNA gyrase (a topoisomerase type II protein) as target genes. The molecular evolution rate of gyrB genes is higher than that of 16S rRNA, and gyrB genes are distributed universally among bacterial species. Microarray technology includes the methods of arraying cDNA or oligonucleotides on substrates such as glass slides while acquiring a lot of information simultaneously. Thus, it is possible to identify the enteric bacteria easily using microarray technology. We devised a simple method of rapidly identifying bacterial species through the combined use of gyrB genes and microarrays. Closely related bacteria were not identified at the species level using 16S rRNA sequence analysis, whereas they were identified at the species level based on the reaction patterns of oligonucleotides on our microarrays using gyrB genes.

Base Sequence↗

PubMed2003

Metabolism of fenitrothion and conjugation of 3-methyl-4-nitrophenol in tomato plant (Lycopersicon esculentum).

The metabolism of (14)C-labeled fenitrothion (Sumithion, [O,O-dimethyl-O-(3-methyl-4-nitrophenyl)phosphorothioate]) in tomato plant (Lycopersicon esculentum Mill., cv. Ponderosa) grown in the greenhouse equipped with quartz glass was conducted to investigate the effect of sunlight on the behavior of fenitrothion and to elucidate the detailed structure of conjugated metabolites. Tomato plants (BBCH 85) were topically treated with (14)C-labeled fenitrothion twice with a 2 week interval between applications. At 15 days after the second application, more than half of the recovered (14)C was detected as unaltered fenitrothion, glucose, and cellobiose esters of 3-methyl-4-nitrophenol (NMC) in extracts from tomato fruit. The photoinduced formation of the S-methyl isomer of fenitrothion via thiono-thiolo rearrangement was detected only in the surface rinse but at trace amounts. In the whole tomato fruit, fenitrothion, the S isomer, NMC-beta-glucoside, and NMC cellobioside were detected at 34.16, 1.28, 7.47, and 15.07% of the recovered (14)C, respectively. Trace amounts of the oxon analogue of fenitrothion were detected only on tomato leaves. The chemical structure of the cellobiose conjugate of NMC, 1-O-beta-d-glucopyranosyl-(1-->4)-beta-d-glucopyranosyl-3-methyl-4-nitrophenol, was determined by spectroscopic analyses (liquid chromatography-mass spectrometry, NMR), using the metabolite obtained from leaves and stems of tomato plant hydroponically grown with (14)C-labeled NMC.

Carbon Radioisotopes↗

PubMed2003

Detection and identification of Mycobacterium species isolates by DNA microarray.

Rapid identification of Mycobacterium species isolates is necessary for the effective management of tuberculosis. Recently, analysis of DNA gyrase B subunit (gyrB) genes has been identified as a suitable means for the identification of bacterial species. We describe a microarray assay based on gyrB gene sequences that can be used for the identification of Mycobacteria species. Primers specific for a gyrB gene region common to all mycobacteria were synthesized and used for PCR amplification of DNA purified from clinical samples. A set of oligonucleotide probes for specific gyrB gene regions was developed for the identification of 14 Mycobacterium species. Each probe was spotted onto a silylated glass slide with an arrayer and used for hybridization with fluorescently labeled RNA derived from amplified sample DNA to yield a pattern of positive spots. This microarray produced unique hybridization patterns for each species of mycobacteria and could differentiate closely related bacterial species. Moreover, the results corresponded well with those obtained by the conventional culture method for the detection of mycobacteria. We conclude that a gyrB-based microarray can rapidly detect and identify closely related mycobacterial species and may be useful in the diagnosis and effective management of tuberculosis.

Base Sequence↗

PubMed2002

Improved uptake models of nonionized pesticides to foliage and seed of crops.

The residual amount of nonionized pesticides incorporated to foliage and stem (foliage) and seed (fruit) of crops via root hairs from the water phase was estimated using the uptake models newly including metabolic parameters by which the amount of intact pesticide remaining in crops was considered with its proportion in a transpiration stream. A new parameter was also introduced for the seed model that accounts for the pesticide loss by adsorption to the inner surface of xylem tissue. Validation of the model was conducted using six pesticides with soybean and spinach plants. The ratio of the predicted concentration of pesticide to the measured one was 0.44-1.49 and 0.57-2.93 with foliage and seed models, respectively, showing that these improved models would be effective as a prediction tool.

Adsorption↗

PubMed2002

Dantaxusins C and D, two novel taxoids from Taxus yunnanensis.

Two new taxane diterpenes, dantaxusin C (1) and dantaxusin D (2), were isolated from an ethanol extract of the aerial parts of Taxus yunnanensis along with 14 known taxoids. All structures were established on the basis of 1D and 2D NMR and HREIMS spectroscopic methods.

China↗

PubMed2002

Phylogenetic analysis of Salmonella, Shigella, and Escherichia coli strains on the basis of the gyrB gene sequence.

Phylogenetic analysis of about 200 strains of Salmonella, Shigella, and Escherichia coli was carried out using the nucleotide sequence of the gene for DNA gyrase B (gyrB), which was determined by directly sequencing PCR fragments. The results establish a new phylogenetic tree for the classification of Salmonella, Shigella, and Escherichia coli in which Salmonella forms a cluster separate from but closely related to Shigella and E. coli. In comparison with 16S rRNA analysis, the gyrB sequences indicated a greater evolutionary divergence for the bacteria. Thus, in screening for the presence of bacteria, the gyrB gene might be a useful tool for differentiating between closely related species of bacteria such as Shigella spp. and E. coli. At present, 16S rRNA sequence analysis is an accurate and rapid method for identifying most unknown bacteria to the genus level because the highly conserved 16S rRNA region is easy to amplify; however, analysis of the more variable gyrB sequence region can identify unknown bacteria to the species level. In summary, we have shown that gyrB sequence analysis is a useful alternative to 16S rRNA analysis for constructing the phylogenetic relationships of bacteria, in particular for the classification of closely related bacterial species.

DNA Gyrase↗