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Biomedical subjects

T Yanagimoto

Publications and source records attributed to T Yanagimoto.

11 recordsLinked to original sources
PubMed1997

Mouse cytochrome P450 (Cyp3a11): predominant expression in liver and capacity to activate aflatoxin B1.

S1 mapping analysis for the expression of Cyp3a11 and Cyp3a13 indicated that Cyp3a11 mRNA is predominantly expressed in mouse liver, compared with that of Cyp3a13. In addition, all of six inducers, such as dexamethasone, 3-methylcholanthrene, phenobarbital, polychlorinated biphenyl, pregnenolone 16 alpha-carbonitrile, and rifampicin, increased the expression of the Cyp3a11 mRNA more extensively than that of Cyp3a13. The level of mRNAs corresponding to Cyp3a11 and Cyp3a13 reached the maximum level between 4 and 8 weeks after birth. Cyp3a11 enzyme was expressed into CR119 cells which had been established as a cell line stably expressing NADPH-cytochrome P450 reductase cDNA of guinea pigs. These transformants showed aflatoxin B1-dependent cytotoxicity in proportion to the amounts of Cyp3a11 mRNA. This cytotoxicity was enhanced by 7,8-benzoflavone, a known activator of CYP3A protein. Based on these results, we confirm that CYP3A in the mouse, which is an animal species known to be relatively insensitive to aflatoxin B1 genotoxicity, can activate this mycotoxin efficiently.

Aflatoxin B1↗
PubMed1997

Gene structure of mouse Cyp3a11: evidence for an enhancer element within its 5' flanking sequences.

A mouse Cyp3a11 gene was isolated from a mouse sperm DNA library with mouse Cyp3a11 cDNA as a probe. The nucleotide sequences determined for the gene and the 5' flanking region revealed that the mouse Cyp3a11 gene was composed of 13 exons and 12 introns. The exons spun about 23 kb. The nucleotide sequence of the exons was completely identical to Cyp3a11 cDNA. Within the 5' flanking sequence, putative binding sites of several transcriptional factors were found. Transient transfection assays were carried out with HepG2 cells, a human hepatoma cell line, using constructs containing different lengths of 5' flanking sequence fused to a reporter, chloramphenicol acetyltransferase gene. The results showed that a cis-acting element(s) was located from -1609 to -907.

Animals↗
PubMed1994

Molecular cloning and functional expression of a mouse cytochrome P-450 (Cyp3a-13): examination of Cyp3a-13 enzyme to activate aflatoxin B1 (AFB1).

A cDNA encoding a novel member of the cytochrome P-450 superfamily, Cyp3a-13, has been isolated from mouse liver cDNA library by hybridization screening. The Cyp3a-13 encoded 503 amino acid residues and shared 71% amino acid identity with Cyp3a-11. When Cyp3a-13 cDNA was expressed in CR119 cells which had been established as a cell line stably expressing NADPH-cytochrome P-450 reductase cDNA of guinea pigs, aflatoxin B1-dependent cytotoxicity was observed. This cytotoxicity was enhanced by alpha-naphthoflavone (7,8-benzoflavone), which is known to augment the CYP3A enzymatic activity. The results indicate that CYP3A in mice, which are relatively insensitive to aflatoxin B1, can activate aflatoxin B1 to a genotoxic product.

Aflatoxin B1↗
PubMed1994

A novel form of mouse cytochrome P450 3A (Cyp3a-16). Its cDNA cloning and expression in fetal liver.

A complementary DNA clone coding for a novel form of cytochrome P450, Cyp3a-16, in mouse fetal livers was isolated and completely sequenced. This clone encoded a polypeptide of 504 deduced amino acids and showed 87.3% and 66.6% amino acid identities with mouse Cyp3a-11 and Cyp3a-13, respectively. Cyp3a-16 transcript was detectable before birth and remarkably diminished five weeks after birth in mice. We conclude that Cyp3a-16 is a fetal- and puberty-specific cytochrome P450 in mice.

Amino Acid Sequence↗
PubMed1994

Statistical methods for the beta-binomial model in teratology.

The beta-binomial model is widely used for analyzing teratological data involving littermates. Recent developments in statistical analyses of teratological data are briefly reviewed with emphasis on the model. For statistical inference of the parameters in the beta-binomial distribution, separation of the likelihood introduces an likelihood inference. This leads to reducing biases of estimators and also to improving accuracy of empirical significance levels of tests. Separate inference of the parameters can be conducted in a unified way.

Animals↗
PubMed1992

Mouse liver cytochrome P-450 (P-450IIIAM1): its cDNA cloning and inducibility by dexamethasone.

A full-length cDNA complementary to mouse liver mRNA coding for one of the cytochromes P-450 (P-450) in the P-450IIIA family, namely P-450IIIM1, was isolated and completely sequenced. The sequence of this cDNA clone, pMDex13, revealed that it encoded a polypeptide of 504 deduced amino acid residues (Mr = 57,853). The deduced amino acid sequence showed 87.3 and 84.9% identity with rat P-450IIIA1 and P-450IIIA2, respectively. The NH2-terminal 24 amino acid sequences of P-450IIIAM1 were completely identical with purified mouse P-450UT protein. RNA blot analysis showed that mRNA content of hepatic P-450IIIAM1 was remarkably increased by treatment of mice with dexamethasone.

Amino Acid Sequence↗
PubMed1992

Genomic organization of human fetal specific P-450IIIA7 (cytochrome P-450HFLa)-related gene(s) and interaction of transcriptional regulatory factor with its DNA element in the 5' flanking region.

P-450IIIA7 is a form of cytochrome P-450 which was isolated from human fetal livers and termed P-450HFLa. This form has been clarified to be expressed during fetal life specifically (Komori, M., Nishio, K., Kitada, M., Shiramatsu, K., Muroya, K., Soma, M., Nagashima, K. and Kamataki, T. (1990) Biochemistry 29, 4430-4433). In the present study, we isolated five independent clones which probably corresponded to the human P-450IIIA7 gene. These clones were completely sequenced, all exons, exon-intron junctions and the 5' flanking region from the cap site to-869. Although the sequences in the coding region were completely identical to P-450IIIA7, it is possible that genomic fragments sequenced in this study encode portions of other P-450IIIA7-related genes since we could not obtain a complete overlapping set of genomic clones. Within its 5' flanking sequence, the putative binding sites of several transcriptional regulatory factors existed. Among them, it was shown that a basic transcription element binding factor (BTEB) actually interacted with the 5' flanking region of this gene.

Adult↗
PubMed1990

Empirical Bayes methods for smoothing data and for simultaneous estimation of many parameters.

A recent successful development is found in a series of innovative, new statistical methods for smoothing data that are based on the empirical Bayes method. This paper emphasizes their practical usefulness in medical sciences and their theoretically close relationship with the problem of simultaneous estimation of parameters, depending on strata. The paper also presents two examples of analyzing epidemiological data obtained in Japan using the smoothing methods to illustrate their favorable performance.

Bayes Theorem↗
PubMed1985

Point process models in asthma attacks for assessing environmental risk factors.

Point process models are reviewed and discussed for assessing the effects of environmental risk factors on asthma attacks. It is pointed out that the logit model and proportional intensity model are useful for analyzing the data based on the diaries recorded consecutively during several months or during a few years. Some covariates that seems to influence upon asthmatics are explored using these models. Further work on estimating the smoothed base-line intensity function is briefly discussed in terms of the Bayes model.

Asthma↗
PubMed1979

Estimation of safe doses: critical review of the hockey stick regression method.

The hockey stick regression method is a convenient method to estimate safe doses, which is a kind of regression method using segmented lines. The method seems intuitively to be useful, but needs the assumption of the existence of the positive threshold value. The validity of the assumption is considered to be difficult to be shown. The alternative methods which are not based on the assumption, are given under suitable dose-response curves by introducing a risk level. Here the method using the probit model is compared with the hockey stick regression method. Computational results suggest that the alternative method is preferable. Furthermore similar problems in the case that response is measured as a continuous value are also extended. Data exemplified are concerned with relations of SO2 to simple chronic bronchitis, relations of photochemical oxidants to eye discomfort and residual antibiotics in the lever of the chicks. These data was analyzed by the original authors under the assumption of the existence of the positive threshold values.

Animals↗