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T Yokoi

Publications and source records attributed to T Yokoi.

At least 145 records · Page 8Linked to original sources
PubMed1997

Diversity of epitopes recognized by cytotoxic T lymphocytes that are specific for rejection antigen peptide pRL1a presented on BALB/c leukemia RL Male 1.

Cytotoxic T lymphocytes (CTL) generated in (BALB/c x C57BL/6)F1 (CB6F1) and BALB/c spleen cells stimulated with BALB/c radiation-leukemia RL Male 1 cells or pRL1a (IPGLPLSL) peptide itself recognized pRL1a on RL Male 1 in association with Ld. We first studied pRL1a peptide residues used for binding to the Ld molecule by examining the inhibition by variant peptides with single Ala substitutions at each position (P) of recognition of P815 target cells sensitized with Ld-binding p2Ca (LSPFPFDL) peptide for BALB/c anti-p2Ca CTL. The results showed that Leu at P8 is predominantly involved in the binding and Pro at P2 is partially involved. Substitution of Gly to Ala at P3 increased binding. We then investigated the epitope residues recognized by four pRL1a-specific CTL clones by examining their cytotoxicity against the P815 target sensitized with variant pRL1a peptides. Recognition by clone Y-16 involved predominantly Leu at P4 and P6, and also Pro at P5 and Ser at P7, and partially Ile at P1. Recognition by clone U-41 involved predominantly Ile at P1 and Leu at P6, and partially Gly at P3, Leu at P4, Pro at P5 and Ser at P7. Recognition by clone P-2 involved predominantly Leu at P4 and P6, and Ser at P7, with no partial involvement of other substitutions being observed. Finally, recognition by clone B-24 predominantly involved all residues, except Gly at P3, which was partially involved. TCR V beta genes utilized by those CTL clones were different. The findings show that tumor antigen peptide pRL1a generates a wide repertoire of CTL clones that differ in TCR V beta usage and in the intrapeptide epitope residues they recognize.

Animals↗
PubMed1997

Synchronous and metachronous multicentric squamous cell carcinomas in the upper aerodigestive tract.

A rare case is presented of a 57-year-old Japanese male with synchronous and metachronous multicentric squamous cell carcinomas (SCC) in the upper aerodigestive tract. During a 9-year-period from the appearance of first primary SCC to autopsy, 14 foci of primary SCC and one severe dysplasia developed in succession in the thoracic esophagus, oral floor, soft palate, uvula, lingual radix, piriform recess, hypopharynx, cervical esophagus, trachea and lingual body. The patient died of severe bronchopneumonia due to Gram-negative bacterial infection that developed as a result of recurrent nerve paralysis. Human papilloma virus and Epstein-Barr virus, which are risk factors, were not detected by immunohistochemistry or by the polymerase chain reaction method. Genetic analysis revealed the absence of point mutations in K-ras codon 12. Heavy consumption of alcohol and excessive smoking may have been responsible for the multicentric carcinogenesis. This is the first case report in the literature of the development of so many primary SCC lesions in the upper aerodigestive tract during such a short period.

Carcinoma, Squamous Cell↗
PubMed1997

Endoscopic carpal tunnel pressure measurement: a reliable technique for complete release.

Carpal tunnel syndrome is diagnosed by clinical symptoms, Tinel's sign, Phalen's test and electromyography. Carpal tunnel pressure measurement can also aid in the precise identification of excessive pressure sites that indicate locations for release. In this study, pressure measurements made during endoscopic carpal tunnel release at 5 points were significantly higher anywhere in the carpal tunnel than outside the tunnel and decreased markedly after release. We concluded that our measurement technique can improve the reliability of endoscopic carpal tunnel release by decreasing the likelihood of missing any nerve entrapment sites.

Adult↗
PubMed1997

Cytochrome P450 responsible for the stereoselective S-oxidation of flosequinan in hepatic microsomes from rats and humans.

The forms of cytochrome P450 involved in the stereoselective S-oxidation of flosequinan [(+/-)-7-fluoro-1-methyl-3-methylsulfinyl-4-quinolone] were investigated in vitro using liver microsomes from rats and humans. Rat liver microsomes supplemented with NADPH catalyzed the four different S-oxidations, which were from flosequinan sulfide (FS; 7-fluoro-1-methyl-3-methylthio-4-quinolone) to R(+)- and S(-)-flosequinan (R-FSO and S-FSO, respectively) and from R-FSO and S-FSO to flosequinan sulfone (FSO2; 7-fluoro-1-methyl-3-methylsulfonyl-4-quinolone). The activities of all the S-oxidases in liver microsomes from male rats were higher than those from female rats. The activities of the S-oxidases measured at a high substrate concentration (1 mM) were induced by treatment of rats with phenobarbital and dexamethasone. Treatment of rats with 3-methylcholanthrene also induced the activities, but only at a low substrate concentration (50 microM), except for the S-oxidase catalyzing the reaction from FS to R-FSO. Enzymes induced by clofibrate and ethanol were not involved in the oxidations at a low substrate concentration. The activities of S-oxidases were correlated with the contents of cytochrome P450 (CYP)3A enzymes. Anti-CYP3A2 antisera inhibited the activities of the S-oxidases catalyzing the reactions from FS to R-FSO (40%) and to S-FSO (60%) at the high substrate concentration and inhibited the activities of the S-oxidases, thus catalyzing reactions from R-FSO and S-FSO to FSO2 (70%) at both high and low substrate concentrations. These results suggest that CYP3A is the major enzyme involved in all S-oxidation pathways in flosequinan metabolism in rats. On the other hand, except for the S-oxidation of FS to R-FSO, the rates of the other three S-oxidations by liver microsomes from 30 individual humans correlated highly with each other, suggesting that the same enzyme would be involved in the three S-oxidations. Anti-CYP3A2 antisera inhibited the activities of all the S-oxidases in human liver microsomes ranging from 40 to 80%, suggesting that CYP3A is also involved in all of the S-oxidations of flosequinan in humans.

Animals↗
PubMed1997

Prediction of in vivo hepatic metabolic clearance of YM796 from in vitro data by use of human liver microsomes and recombinant P-450 isozymes.

The metabolic rate of (S)-(-)-2,8-dimethyl-3-methylene-1-oxa-8-azaspiro [4,5] decane-L-tartarate monohydrate (YM796), an antidementia agent, was determined by use of 12 different human liver microsomal samples. The metabolism of YM796 was shown to consist of three components; one high-affinity (Km1 = 1.67 microM), one low-affinity (Km2 = 654 microM) and a nonsaturable component. Good correlations were observed between the individual CYP3A4 content in 12 different human liver microsomal samples and kinetic parameters such as CL(int, all), the high-affinity component clearance (Vmax1/Km1) and the low-affinity component clearance (Vmax2/Km2). Anti-human CYP3A4/5 antibodies inhibited the metabolism of YM796 at 1 microM by up to 75%. In addition, ketoconazole, an inhibitor of CYP3A4, inhibited YM796 metabolism by >90%. The metabolic clearance of YM796 in each of the 12 human liver microsomal samples was successfully predicted from the kinetic parameters obtained with the recombinant microsomes by taking into consideration the CYP3A4 content in each microsomal sample. Based on the CL(int, all) estimated from the in vitro experiments, the area under the plasma concentration-time curve after oral administration (AUC(oral)) of YM796 was also predicted by taking into account the hepatic blood flow rate (Qh), the unbound fraction of YM796 in human plasma (f(p)) and the fraction absorbed from the gut. In addition, AUC(oral) was determined in six healthy male volunteers. The predicted AUC(oral) was similar to the observed value in vivo, which suggests that the in vitro metabolism data obtained with human liver microsomes are useful for quantitatively predicting human liver metabolism in vivo and that recombinant microsomes are also available when the particular isozyme is almost completely responsible for the metabolism of the drug, the variation in P-450 content of human liver is known and the experimental conditions such as the amount of CYP reductase and cytochrome b5 are carefully optimized to mimic the activity found in native microsomes, as for YM796.

Area Under Curve↗
PubMed1997

A simple approach to single-cell microdissection and molecular analysis.

OBJECTIVE: To develop a simple approach to single-cell microdissection from Papanicolaou-stained smears and to determine its usefulness in molecular diagnosis using archival cytologic material. STUDY DESIGN: Culture cells from three cell lines (TT, A549 and Lu65) were used to prepare Papanicolaou-stained smears. Mount-Quick, a mounting medium, was used to establish the method of sorting target single cells from smear slides under direct microscopic observation. Calcitonin receptor gene and codon 12 of the K-ras oncogene were amplified to check the application of single-cell genetic analysis in cytology. RESULTS: The target single cell could be simply sorted from Papanicolaou-stained smears using the Mount-Quick microdissection technique. Boiling in water was more suitable for preparing DNA from a single cell or from fewer than five cells versus other methods. Analysis of calcitonin receptor gene and K-ras codon 12 demonstrated that molecular analysis was applicable to a single cell or a few cells from archival Papanicolaou-stained smears. CONCLUSION: This approach has significant implications for cytology: (1) it circumvents the limitations of molecular analysis in cytology and makes the combination of molecular analysis and morphologic diagnosis possible in cases with limited materials; (2) the remaining part of the smear is still preserved well for additional analysis; and (3) the approach is simple, economical and practical for cytology as well as histology.

DNA, Neoplasm↗
PubMed1996

Perinatal expression and inducibility of human CYP3A7 in C57BL/6N transgenic mice.

The expression and inducibility of CYP3A7 transgene in the fetus and suckling neonates from one of the transgenic lines (M10) were investigated by Northern and Western blot analyses. The mRNA expression could be detected as early as the 15th embryonic day and increased gradually with advancing gestation but then remarkably so after birth. The protein expression was also detectable postnatally and increased. Inducibility was achieved in neonatal mice via maternal exposure to zinc sulfate. Midazolam hydroxylase activities could be detected in liver microsomes prepared from 14-day-old neonates. These activities were significantly higher in transgenic than nontransgenic lines of mice (p < 0.001).

Aging↗
PubMed1996

Involvement of beta-glucuronidase in intestinal microflora in the intestinal toxicity of the antitumor camptothecin derivative irinotecan hydrochloride (CPT-11) in rats.

Irinotecan hydrochloride (CPT-11), an antitumor camptothecin derivative, causes severe forms of diarrhea clinically. We characterized CPT-11-induced diarrhea histologically and enzymologically and assessed the relationships between intestinal toxicity and the activity of the enzymes that play a key role in the major metabolic pathway of CPT-11 in rats. CPT-11 (60 mg/kg i.v. for 4 days) induced intestinal toxicity characterized by severe chronic diarrhea, loss of body weight, and anorexia. Histological damage was most severe in the cecum. The segmental difference in the degree of the damage showed good correlation with the beta-glucuronidase activity in the contents of the lumen in each case, but not with the intestinal tissue carboxylesterase activity, which converts CPT-11 to its active form (7-ethyl-10-hydroxycamptothecin). Inhibition of the beta-glucuronidase activity in the intestinal microflora by antibiotics (1 mg penicillin and 2 mg streptomycin per ml of drinking water) markedly ameliorated the diarrhea and reduced cecal damage. Analysis of CPT-11 and its metabolites in the feces indicated that antibiotics completely inhibited the deconjugation of the glucuronic conjugate of 7-ethyl-10-hydroxycamptothecin by beta-glucuronidase. It is suggested that CPT-11-induced diarrhea would be attributable to the damage to the cecum, and that the inhibition of the beta-glucuronidase activity in the intestinal microflora is a major protective effect of antibiotics.

Animals↗
PubMed1996

Stable expression of human CYP2E1 in Chinese hamster cells: high sensitivity to N,N-dimethylnitrosamine in cytotoxicity testing.

Involvement of human CYP2E1 expressed in genetically engineered cells in the metabolic activation of promutagens and procarcinogens was studied. An expression plasmid containing an insert of CYP2E1 cDNA and SR alpha promoter was constructed and transfected into the cultured cell line CR-119 which had previously been established by introducing a cDNA coding for NADPH-cytochrome P450 reductase. Among newly established cell lines, ER-181 showed the highest expression of CYP2E1 mRNA. Production of the CYP2E1 protein was confirmed by Western blot analysis using anti-rat CYP2E1 antibodies. Assay of 7-ethoxycoumarin O-deethylase activity demonstrated that ER-181 cells acquired the catalytic function of CYP2E1. ER-181 cells showed higher sensitivity to N,N-dimethylnitorosamine (DMN) in cytotoxicity assays as compared to parental CR-119 cells. Hypersensitivity to DMN of ER-181 cells was completely suppressed by 3-amino-1,2,4-triazole, a known inhibitor of CYP2E1. These results indicate that ER-181 cells which express human CYP2E1 are a useful tool to investigate toxicological functions of the cytochrome.

Animals↗
PubMed1996

Novel monoclonal antibody, SO-MU1, against human gastric MUC5AC apomucin.

Human gastric mucins were chemically deglycosylated with trifluoromethanesulfonic acid. A mouse monoclonal antibody (MoAb), SO-MU1, was established against the deglycosylated mucins. SO-MU1 recognized not only the deglycosylated mucins but also the native gastric mucins. Periodate treatment of the native mucins increased the SO-MU1 reactivity. Trypsin digestion abolished the antigenicity. Human gastric cDNA expression library was screened with SO-MU1 and a mucin cDNA clone was obtained. Its sequence contained the MUC5AC tandem repeat domain. We studied gastrointestinal distribution of the SO-MU1-reactive antigen immunohistochemically. Gastric surface epithelial cells and parietal cells expressed the antigen, but the glandular cells did not. The antigen was also detected in the small intestine and biliary tract but not in the colon and pancreas. In summary, (1) MoAb SO-MU1 was raised against human gastric mucins, (2) it recognized human gastric MUC5AC apomucin, and (3) the SO-MU1-reactive antigen showed characteristic distribution in the organs of endodermal origin. MoAb SO-MU1 is the first MoAb against MUC5AC.

Amino Acid Sequence↗
PubMed1996

Establishment of transgenic mice carrying human fetus-specific CYP3A7.

CYP3A7 is a cytochrome P450 isozyme expressed prenatally in humans. Six lines of mice transgenic for human CYP3A7 were established by microinjecting a CYP3A7 cDNA downstream of a mouse metallothionein-1 promoter gene into the male pronucleus of fertilized mouse oocytes. The inserted CYP3A7 transgene was expressed at a mRNA level in a variety of tissues including the liver, kidney, lung, spleen, testis, small intestine, thymus, brain, skin, and heart of adult mice. The protein expression of the transgene was also detected in the liver and testis of line M10 mice. A significantly higher level of total testosterone in the serum was found in line M10 male mice. In addition, this transgenic line exhibited weight increases in the liver, kidney, and uterus but a decrease in the testis (P < 0.01). The transcript of the integrated CYP3A7 gene possessed the ability to activate aflatoxin B1 in Ames test in which the his+ revertants of Salmonella typhimurium TA100 per plate were significantly higher (P < 0.01) when liver microsomes of line M10 transgenic mice were used. This result demonstrates that the CYP3A7 gene has been integrated into the mouse genome and translated into a catalytically active enzyme. These transgenic mice are expected to give useful information for studies on fetal toxicities in humans.

Aflatoxin B1↗
PubMed1996

A new CYP2D6 allele with a nine base insertion in exon 9 in a Japanese population associated with poor metabolizer phenotype.

The CYP2D6 gene of a Japanese sparteine poor metabolizer (PM, proband) showing a urinary sparteine metabolic ratio of 31.6 was analysed, and a heterozygous CYP2D6(D), a deletional type, was found by restriction fragment length polymorphism analysis with Xba I enzyme. The PM did not have any other previously described mutations in the CYP2D6 gene causing the loss of catalytic activity of the CYP2D6 enzyme. Thus, a possible new allele(s) responsible for the PM phenotype was analysed. The results indicated that the PM possessed a new 9-base insertion in exon 9, designated CYP2D6(J9). The CYP2D6(J9) and CYP2D6(D) alleles were clarified to be inherited from the mother [2D6(W)/2D6(J9)] and the father [2D6(W)/2D6(D)], respectively. The 9-base insertion caused a large increase in the apparent K(m) value for bufuralol 1'-hydroxylation as examined by expression of the enzyme protein in yeast. Four of 300 Japanese carried a heterozygous CYP2D6(J9) allele (0.7%, 4/600 chromosomes) as determined by a polymerase chain reaction analysis.

Alleles↗
PubMed1996

CYP2D6 is the principal cytochrome P450 responsible for metabolism of the histamine H1 antagonist promethazine in human liver microsomes.

To determine which cytochrome P450 form is involved in the promethazine [10-(2-dimethylaminopropyl) phenothiazine] metabolism, in vitro analysis using human liver microsomes were performed. Promethazine was mainly biotransformed to ring-hydroxylated, S-oxidized and N-demethylated metabolites. The promethazine hydroxylase in human liver microsomes was inhibited by SKF-525A, propranolol, sparteine, quinidine and anti-CYP2D6 serum suggesting involvement of a P450 related to CYP2D6. Lineweaver-Burk plots for the hydroxylation, S-oxidation and N-demethylation indicated that the hydroxylation occurred with a low K(m) value in human liver microsomes. Microsomes from genetically-engineered human B-lymphoblastoid cells expressing CYP2D6 hydroxylated promethazine most efficiently as compared to other P450 forms, indicating that it was the principal P450 responsible for the metabolism of promethazine in human liver microsomes. The inhibition of CYP2D6-catalysed bufuralol 1'-hydroxylase by various histamine H3 antagonists including promethazine suggested that promethazine and some other histamine H1 antagonists could be inhibitors of this P450 in human liver microsomes.

Antibodies↗
PubMed1996

Clinicopathology of chondrosarcoma.

We conducted a clinicopathological analysis of chondrosarcomas in 17 patients treated in our institute. The 5- and 10-year overall survival rates of the patients were 72.3% and 61.9%, respectively. The significant prognostic factors were size and histologic grade of the tumor. Sex, age, location of the primary tumor, or the presence of a preceding exostosis did not affect the treatment results significantly. Chondrosarcomas of histologic grades I and II did not metastasize, while all grade III and dedifferentiated chondrosarcomas metastasized to the lung. The local recurrence rate depended on the surgical margin. Wide excision with an adequate surgical margin is important to achieve local control of the chondrosarcoma.

Adolescent↗