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Biomedical subjects

Y Seto

Publications and source records attributed to Y Seto.

At least 91 records · Page 5Linked to original sources
PubMed1995

Mechanisms of cytochrome P450 1A2-mediated formation of N-hydroxy arylamines and heterocyclic amines and their reaction with guanyl residues.

Amine oxidation reactions are catalyzed by cytochrome P450 (P450) and peroxidase enzymes; both types of enzymes appear to function via aminium radical intermediates. N-Dealkylation is favored over N-oxygenation for secondary and tertiary amines with both kinds of enzymes, but in the peroxidase-like enzymes N-oxygenation is even less favorable because of apparent restriction of the Fe-O complex in the active site. Among the rat liver P450s many of the carcinogenic primary arylamines and heterocyclic amines are N-oxygenated by P450 1A2 to form the N-hydroxy arylamine derivatives. Studies with human liver P450s also indicate that P450 1A2 plays a major role in such reactions, although some arylamines such as 4,4'-methylene-bis (3-chloroaniline) and dapsone are preferentially N-oxygenated by P450 3A4. Caffeine N3-demethylation has been developed as a useful marker of P450 1A2 levels in humans; the knowledge that P450 1A2 is the major phenacetin O-deethylase also allows insight into previous human interaction studies. 2-Ethynylnaphthalene is a useful mechanism-based inactivator of rat and rabbit P450 1A2 but not human P450 1A2 enzymes; the peptides labeled in the enzymes have been identified, along with the region in rat P450 1A2 that is modified with the photoaffinity label 4-azidobiphenyl. Microcrystals of rabbit P450 1A2 have been obtained as a first course to realizing the three-dimensional structures of these enzymes. Evidence is also presented that the major C8-guanyl DNA adducts resulting from these arylamines and heterocyclic amines in DNA may be formed via rearrangement of an initial N7-guanyl-2-arylamine adduct: reaction of N-acetoxy-2-aminofluorene with C8-methylguanine derivatives led to the formation of stable N7-substituted species, and reaction of N-acetoxy-2-aminofluorene with C8-bromoguanine yielded N-(C8-guanosinyl)-2-aminofluorene in a reaction best rationalized by such a mechanism.

Amines↗
PubMed1994

Structural analysis of the functional gene and pseudogene encoding the murine granulocyte colony-stimulating-factor receptor.

Granulocyte colony-stimulating factor is a cytokine which specifically regulates the production of neutrophilic granulocytes. The granulocyte colony-stimulating-factor receptor (GCSFR) is mainly expressed in neutrophils and their precursor cells. In this study, we isolated the chromosomal gene for murine GCSFR and determined its structure. Like the human GCSFR gene homolog, it consists of 17 exons. The exon-intron organization of the murine and human GCSFR-encoding genes are very similar, except that exon 14 and exon 15 in the murine gene are interrupted by a larger intron (greater than 10 kbp) than that found in the human gene (128 bp). This GCSFR-encoding functional gene (Csfgr) was localized to the distal region of murine chromosome 4 by interspecific backcross mapping. A comparison of the 5' flanking sequence of murine and human Csfgr revealed that a sequence of approximately 300 bp upstream from the cap site is highly conserved. Within this region, an 18-nucleotide element conserved in the promoter of the genes for neutrophil-specific enzymes, was found approximately 140 bp upstream from the cap site, suggesting an involvement of this element in the specific expression of GCSFR in neutrophilic granulocytes. In addition to the functional GCSFR-encoding gene, we isolated a pseudogene for GCSFR, which is flanked by a 15-bp direct repeat at the 5' and 3' ends, and lacks all introns, exons 1-3 and exons 7-8 of the functional gene. The processed pseudogene has, in its most 5' region, a sequence of approximately 200 bp that is highly related to the DNA sequence approximately 1.2 kbp upstream of the cap site of the functional gene.

Animals↗
PubMed1994

Oligonucleotide probes for Bordetella bronchiseptica based on 16S ribosomal RNA sequences.

Bordetella bronchiseptica 16S ribosomal RNA (rRNA) gene was cloned and identified. On the basis of information from computer-assisted sequence comparison of the B. bronchiseptica 16S RRNA sequences with that of other bacterial species, we constructed B. bronchiseptica-specific oligonucleotide probes complementary to variable regions in the 16S rRNA molecule. Specificity of these 32P-labeled oligo-nucleotide probes was tested in a RNA/DNA hybridization with B. bronchiseptica strains and other bacterial strains. Probe BB4 was more specific than three other oligonucleotide probes. This probe BB4 was sensitive enough to be able to detect 10(4) bacterial cells.

Base Sequence↗
PubMed1994

Characterization of a gene responsible for the Na+/H+ antiporter system of alkalophilic Bacillus species strain C-125.

An alkali-sensitive mutant, 38154, of the alkalophilic Bacillus sp. strain C-125 could not grow at an alkaline pH. The nucleotide sequence of a 3.7 kb parental DNA fragment that recovers the growth of 38154 at alkaline pH has four open reading frames (ORF1-4). By subcloning the fragment, we demonstrated that a 0.25 kb DNA region is responsible for the recovery. Direct sequencing of the mutant's corresponding region revealed a G to A substitution. The mutation resulted in an amino acid substitution from Gly-393 to Arg of the putative ORF1 product, which was deduced to be an 804-amino-acid polypeptide with a molecular weight of 89,070. The N-terminal part of the putative ORF1 product showed amino acid similarity to those of the chain-5 products of eukaryotic NADH quinone oxidoreductases. Membrane vesicles prepared from 38154 did not show membrane potential (delta psi)-driven Na+/H+ antiporter activity. Antiporter activity was resumed by introducing a parental DNA fragment which recovered the mutant's alkalophily. These results indicate that the mutation in 38154 affects, either directly or indirectly, the electrogenic Na+/H+ antiporter activity. This is the first report which shows that a gene responsible for the Na+/H+ antiporter system is important in the alkalophily of alkalophilic microorganisms.

Amino Acid Sequence↗
PubMed1994

Application of PCR to detect Norwalk virus in fecal specimens from outbreaks of gastroenteritis.

Norwalk virus (NV) and other small round-structured viruses (SRSVs) are frequent causes of gastroenteritis outbreaks. The recent cloning and sequencing of the NV genome has made it possible to detect NV and Norwalk-related viruses from fecal specimens by reverse transcription (RT)-PCR. We applied this technique to the examination of a total of 139 fecal specimens from 19 outbreaks characterized by NV serology, including 56 samples from 7 NV outbreaks, 36 from 6 Norwalk-related virus outbreaks, and 47 from 6 outbreaks with SRSVs visualized by electron microscopy that were serologically unrelated to NV. Three primer pairs were evaluated: two pairs in the polymerase region of NV and one pair near the 3' end of the genome. When one set of primers (primer pair 51-3) from the polymerase region was used, 40% of all samples were positive by RT-PCR and specimens from the NV outbreaks were more likely to be positive (64%) than those from outbreaks associated with Norwalk-related viruses (44%) or SRSVs (8%). To determine the relationship of the outbreak strains to NV, we compared the sequences of a 145-base portion of the polymerase gene from 10 specimens obtained from five different outbreaks characterized as NV by serology. No two outbreak strains had the same sequence in this 145-base portion of the polymerase gene, and the identities of the nucleotide and amino acid sequences of these products compared with the sequences of the corresponding region of NV ranged from 62 to 79% and 69 to 90%, respectively. Because of sequence diversity in the polymerase region, the successful application of RT-PCR to investigations of outbreaks of suspected NV-associated gastroenteritis will depend on the use of either multiple primer pairs or primers made against regions of the genome that are more conserved.

Amino Acid Sequence↗
PubMed1994

Sequence diversity of small, round-structured viruses in the Norwalk virus group.

We have determined the nucleotide sequences of a highly conserved region of the RNA-dependent RNA polymerase of the prototype Snow Mountain agent (SMA) and of four other small, round-structured viruses (antigenically Norwalk virus [NV]-like or SMA-like) following reverse transcription-PCR amplification of viral RNA obtained from human stools. The stool samples were either from volunteers administered SMA or from sporadic cases and outbreaks of gastroenteritis that occurred in Japan and the United Kingdom between 1984 and 1992. The GLPSG and YGDD RNA polymerase motifs were in the proper locations in the sequences of the five SRSVs, but each sequence was distinct from the 8FIIa prototype NV sequence and from each other. Analysis of the sequences and reactivities in a new NV antigen enzyme-linked immunosorbent assay showed that the five viruses could be divided into two groups (serogroups) with NV and SMA, respectively, being the prototypes. The sequences of the capsid region and a nonstructural region (2C) were determined from one strain from each group. One virus (SRSV-KY-89/89/J), isolated in Japan and antigenically similar to the prototype NV (isolated 21 years earlier in Ohio), showed a remarkable level of sequence similarity to NV. KY-89 and the 8FIIa NV showed 87.2% nucleotide similarity over 2,516 continuous nucleotides amounting to 96 to 98.9% amino acid similarity in three distinct domains in two open reading frames. Between the prototype SMA and NV, the polymerase region showed 63% nucleotide and 59% amino acid similarity, respectively. Two other antigenically SMA-like isolates (SRSV-925/92/UK and SRSV-OTH-25/89/J), from the United Kingdom and Japan, showed 80% nucleotide and 88 to 92% amino acid similarity in the polymerase region to the prototype SMA isolated 16 and 13 years earlier in the United States. The capsid region of the antigenically SMA-like OTH-25 virus showed 53% nucleotide and 65% amino acid similarity to the prototype NV capsid region. Domains of sequence diversity and conversation were identified within the capsid protein of these two distinct prototype serotypes of virus. These results indicate that NV-like and SMA-like agents are still circulating, and sequence comparisons will be useful to identify and classify distinct viruses in the NV group.

Base Sequence↗
PubMed1994

Effects of N-[(trans-4-isopropylcyclohexyl)-carbonyl]-D-phenylalanine (A-4166) on insulin and glucagon secretion in isolated perfused rat pancreas.

N-[(trans-4-isopropylcyclohexyl)-carbonyl]-D-phenylalanine (A-4166) has a structure which differs from those of other known blood glucose-lowering agents including sulfonylureas. It has been shown that oral administration of A-4166 exerts blood glucose-lowering effects in animal in vivo studies. In the present study, we investigated the effects of A-4166 on insulin and glucagon secretion at several glucose concentrations using isolated perfused rat pancreas preparations. Both 3.0 and 30 mumol/l A-4166 significantly stimulated insulin secretion as compared with basal levels at glucose concentrations of 8.0 and 11.0 mmol (p < 0.01 and p < 0.05, respectively). In contrast, glucagon secretion was not affected by administration of A-4166 up to 30 mumol/l at these glucose concentrations. At a glucose concentration of 5.6 mmol/l, neither 0.3 nor 3.0 mumol/l A-4166 produced significant changes in insulin and glucagon secretion. However, A-4166 at 30 mumol/l significantly stimulated insulin secretion and inhibited glucagon secretion as compared with basal levels (p < 0.01 and p < 0.01, respectively). We conclude that A-4166 at 3.0 and 30 mumol/l directly stimulates insulin secretion but has little effect on glucagon secretion in isolated perfused rat pancreas at glucose concentrations of 8.0 and 11.0 mmol/l. these results, taken together with previously published data, suggest that oral administration of A-4166 could be a useful strategy for stimulating endogenous insulin secretion in non-insulin-dependent diabetic patients.

Animals↗
PubMed1994

[Pharmacological study of ebastine, a novel histamine H1-receptor antagonist].

The anti-allergic activity of ebastine, a novel antihistamine, was assessed in comparison with several antihistamines. 1) Orally administered ebastine dose-dependently inhibited 7-day homologous passive cutaneous anaphylaxis (PCA), experimental allergic rhinitis and experimental asthma in guinea pigs or rats (ED50-values were 2.17, 0.29 and 0.35 mg/kg, respectively); and its anti-allergic activity was more potent than those of terfenadine and mequitazine. Moreover, its PCA-inhibitory activity was still observed 24 hr after the administration. 2) Orally administered ebastine also inhibited histamine-induced skin reaction in rats (ED50: 1.10 mg/kg). 3) In isolated guinea pig trachea, ebastine had no effect on histamine-induced contraction, but carebastine, a main metabolite of ebastine, inhibited this contraction (IC50: 0.12 microM). 4) Carebastine (30-100 microM) suppressed the histamine release from rat peritoneal mast cells and human basophils. 5) Ebastine at a high oral dose showed slight inhibition of the specific binding of 3H-mepyramine to the histamine H1-receptor in rat brain. This binding-inhibitory activity of ebastine was little more potent than that of terfenadine, but much less potent than those of mequitazine and ketotifen. These results indicated that ebastine has potent and long acting anti-allergic activity with few side effects based on the antihistaminic activity in the central nervous system. Furthermore, it was suggested that these effects of ebastine are due to the action of a main metabolite, carebastine.

Administration, Oral↗
PubMed1994

Arthroscopy in 19 children with Perthes' disease. Pathologic changes of the synovium and the joint surface.

Arthroscopy of the hip joint was performed in 19 children with Legg-Calvé-Perthes' disease. Proliferation of the synovium was pronounced both in the acetabular fossa and over the inner wall of the capsule. Hypervascularity was seen on the acetabular labrum in every stage of the disease. Microscopically, hyperplasia of the synovial lining cells was observed, but inflammatory changes in the synovial tissue were inconspicuous in the early stage of the disease. Although hypertrophy of the endothelial cells of the vessels was seen in the late stage of the disease, it was not distinct in the initial or fragmentation stages. Joint pain improved after irrigation during arthroscopy.

Adolescent↗
PubMed1994

[Differences in influenza epidemics in Osaka City--epidemiological surveillance of infectious disease].

Influenza viruses in outpatients with influenza symptoms in Osaka City were analyzed in an epidemiological surveillance of infectious disease between 1989 and 1993. During influenza epidemics a mixed prevalence of several types of influenza viruses existed. Three types of influenza viruses, AH1, AH3 and B, were isolated during the 1990/1991 season. Remarkably the three types of viruses were discovered in samplings collected on the same day and within a narrow area inside a radius of 800-1,000m from the surveyed hospitals. Different types of viruses were detected between brothers and among school children from same housing complexes. Influenza AH3 viruses detected in 1992/1993 season differed in antigenicity from those detected in the 1990/1991 and 1991/1992 seasons. Therefore it appears that mutation of the AH3 virus contributed to the large-scale influenza epidemic which occurred in the 1992/1993 season.

Adolescent↗
PubMed1993

Liquid chromatographic determination of para-substituted N,N-dialkylaniline N-oxides.

A high-performance liquid chromatographic method for the determination of p-substituted N,N-dialkylaniline N-oxides [N,N-dimethylaniline N-oxide (DMANO), N,N-dimethyl-p-toluidine N-oxide, N,N-diethylaniline N-oxide, N-ethyl-N-methylaniline N-oxide (EMANO), p-cyano-N,N-dimethylaniline N-oxide (pCNDMANO), and N-phenylpyrrolidine N-oxide (PPNO)] has been developed. It uses an octadecylsilica column, a mobile phase of methanol-phosphate buffer (pH 7.0, adjusted by triethylamine) and ultraviolet detection. N-Oxides were eluted in the order of hydrophilicity except for PPNO, which eluted between DMANO and EMANO. The number of theoretical plates and the detection limit under optimized conditions were between 2400 (DMANO) and 5400 (pCNDMANO) and between 2.3 microM (pCNDMANO) and 30 microM (PPNO), respectively. The concentration of N-oxides recovered from enzyme reaction mixtures by solid-phase extraction using Sep-Pak C18 (prior to chromatography) was also optimized with regard to the sensitivity and interference.

Aniline Compounds↗
PubMed1993

Partitioning between N-dealkylation and N-oxygenation in the oxidation of N,N-dialkylarylamines catalyzed by cytochrome P450 2B1.

Aminium radicals have been proposed as intermediates in amine N-dealkylations and N-oxygenations catalyzed by cytochrome P450 (P450) and some other enzymes. P450s can form some N-oxides and hydroxylamines but these are not favored whenever N-dealkylation is possible. However, if a paradigm involving 1-electron oxidation is valid, then some finite level of partitioning of aminium radicals between N-oxygenation and N-dealkylation might be expected in all cases. Methods were developed for the selective and sensitive measurement of N,N-dialkylaniline N-oxides using high performance liquid chromatography, radiochromatography, and TiCl3 reduction. These N-oxides were relatively stable in the presence of P450 2B1. In the presence of NADPH and NADPH-P450 reductase some reduction to N,N-dialkylamines occurred, along with N-dealkylation (to monoalkylanilines); there was also slow N-dealkylation in the absence of NADPH, which is interpreted in terms of homolytic scission of the N-O bond; N,N-dialkylanilines were not formed nor did the N-oxides support other oxygenation reactions. P450 2B1 (with its reductase and NADPH) formed N-oxides at low rates from several N,N-dialkylaniline derivatives, including N,N-dimethylaniline, N,N-diethylaniline, N-ethyl-N-methylaniline, 4-methyl-N,N-dimethylaniline, 4-cyano-N,N-dimethylaniline, N-phenylpyrrolidine, and N,N-dimethyl-2-aminofluorene. The ratio of N-dealkylation:N-oxygenation varied from 1020 to 6 in this series. These results are consistent with the view that aminium radicals are a branch point in N-oxygenation and N-dealkylation reactions catalyzed by metalloproteins, although some alternate explanations cannot be ruled out. While N-dealkylation is the dominant process in all of the P450-catalyzed amine oxidations, there should be a finite partition ratio between these reactions depending upon the particular enzyme and substrate. The N-oxygenation reaction is probably more complex than a direct radical recombination event and is postulated to involve one or more intermediates.

Alkylation↗
PubMed1993

Role of reflux oesophagitis and acid in the development of columnar epithelium in the rat oesophagus.

The role of reflux oesophagitis and acid in the development of oesophageal columnar epithelium was investigated in the rat. Twenty-four animals underwent total gastrectomy and oesophagojejunostomy, inducing reflux of duodenal contents into the oesophagus, and were divided into two groups: an 'acid' group, which drank syrup water with hydrochloric acid (pH 1.8), and a 'non-acid' group, which drank only syrup water (pH 6.5). Four rats were killed at 4, 8 and 12 weeks after surgery. Reflux oesophagitis was found in the lower portion of the oesophagus in all cases. Columnar epithelium was observed in the oesophagus of one rat in the non-acid group at week 8 and of three in the acid group at week 12. These results indicate that the development of columnar epithelium of the oesophagus is preceded by reflux oesophagitis and that acidic conditions may promote this change. Columnar epithelialization may result from metaplasia of squamous epithelium as well as from upward extension of columnar epithelium.

Animals↗
PubMed1993

Measurement of acetabular angle using ultrasound.

We have developed a method of measuring the acetabular angle by using ultrasound. Normal acetabular roofs are delineated as curvilinial hyperechoic lines on the screen, whereas in displastic hips the outlines of the acetabular roofs are shallower and more vertical. The values of 150 acetabular angles of 75 babies measured by ultrasound were in reasonably good agreement with those derived from roentgenography. This is a safe, handy, and effective for measuring the acetabular angle.

Acetabulum↗
PubMed1993

In vitro antiviral activity of polyoxomolybdates. Mechanism of inhibitory effect of PM-104 (NH4)12H2(Eu4(MoO4)(H2O)16(Mo7O24)4).13H2O on human immunodeficiency virus type 1.

A screening for inhibitors of human immunodeficiency virus type 1 (HIV-1) among various types of isopolyoxomolybdates and heteropolyoxomolybdates was carried out by using an in vitro assay system measuring the cytopathogenicity of HIV-1 in CD4+ human MT-4 cells. A novel heteropolyoxomolybdate named PM-104 with the chemical formula (NH4)12H2(Eu4(MoO4)(H2O)16(Mo7O24)4).13H2O was found to be associated with potent anti-HIV-1 activity. PM-104 interferes with virus infection at a very early step such as adsorption and/or penetration into the cells. In addition to the cytopathic effect of HIV-1 on MT-4 cells, syncytium formation between mock-infected MOLT-4 cells and MOLT-4 cells chronically infected with either HIV-1 or HIV-2 is suppressed by PM-104. PM-104 also blocks the replication of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2). The antiviral properties of PM-104 could be attributed to the combined effect of europium atoms and its peculiar three-dimensional anion structure.

Antiviral Agents↗
PubMed1993

Effects of bile acids and taurine on the lipid fluidity of hepatic microsomes in normal and bile duct-ligated rats--a spin label study.

In cholestasis and obstructive jaundice, hepatic bile acids and taurine content increase significantly and bile acids change in compositions. For example, increases in cholic acid, beta-muricholic acid and taurine-conjugated bile acids occur in rats. In this study, to clarify the significance of changes in bile acid composition in obstructive jaundice, the effects of various bile acids and taurine on the fluidity of the hepatic microsomal membrane were studied by the electron spin resonance spin-label method in normal and bile duct-ligated (for 10 days) rats. The flow properties (order parameter) of the shallow and deep layers of the membrane were determined with 5- and 12-doxyl stearic acid, respectively. Bile acids mainly affected the fluidity of the shallow membrane layer. The fluidity of the hepatic microsomal membrane was decreased in bile duct-ligated rats. Conjugated cholic acid (taurine-conjugated cholic acid, glycine-conjugated cholic acid and non-conjugated beta-muricholic acid exerted effects that increased fluidity in comparison with non-conjugated cholic acid and chenodeoxycholic acid, a precursor of beta-muricholic acid. Taurine had no clear effect on fluidity. In conclusion, cholic acid conjugation and beta-muricholic acid formation may be mechanisms which protect against the decrease in lipid fluidity of hepatic biomembranes in cholestasis or obstructive jaundice. Taurine may also affect fluidity through the formation of taurine-conjugated bile acids.

Animals↗
PubMed1993

Three-dimensional spinal deformity in scoliosis associated with cerebral palsy and with progressive muscular dystrophy.

The authors analyzed lateral deviation, anteroposterior deformity, and rotation of the spinal column of 11 patients with scoliosis associated with cerebral palsy (CP) and 11 patients with progressive muscular dystrophy (PMD). There was a correlation between the magnitude of Cobb angle and that of the vertebral rotation in scoliosis associated with both CP and PMD, but the ratio of spinal rotation to Cobb angle in the former was lower than that in the latter. The magnitudes of thoracic kyphosis and of lumbar lordosis were not correlated with Cobb angle in either group, but the sagittal plane deformity in the CP patients was less severe than that in the PMD patients, and the latter demonstrated kyphosis of the lumbar spine and lordosis of the thoracic spine.

Adolescent↗