Biomedical subjects

T Tsuchiya

Publications and source records attributed to T Tsuchiya.

At least 253 records · Page 14Linked to original sources

PubMed1997

Isolation and characterization of an Escherichia coli mutant lacking the major serine transporter, and cloning of a serine transporter gene.

L-Serine as well as L-valine inhibits the growth of Escherichia coli cells, and L-isoleucine releases this growth inhibition. We isolated an E. coli mutant (designated as WAT9) that was able to grow on lactate (or glucose) as a carbon source even in the presence of L-serine, the parent not being able to. Cells of WAT9 were not able to grow on L-serine as a carbon source even if L-isoleucine was present in the culture medium, while the parental cells grew. This mutant was shown to lack the principal L-serine transporter in E. coli, the Na+/ serine symporter. This mutant is useful for analysis of the role(s) of the Na+/serine symporter in cell physiology and as a host for the cloning of L-serine transporter gene(s). In fact, we cloned a gene encoding a serine transporter from chromosomal DNA of E. coli using WAT9 as the host. The gene enabled the mutant cells to grow on L-serine. Transport activity for L-serine was restored in the mutant cells harboring a plasmid carrying the gene. We partially sequenced the gene and found that it was the tdcC gene. We showed that TdcC is an H+/serine symporter.

Amino Acid Transport Systems↗

PubMed1997

A melibiose transporter and an operon containing its gene in Enterobacter cloacae.

We detected inducible melibiose transport activity in cells of Enterobacter cloacae IID977. H+, but not Na+, was found to be the coupling cation for this transporter. We cloned and sequenced the gene encoding the melibiose transporter. A homology search of a protein sequence database revealed that this melibiose transporter has high sequence similarity with the lactose transporter (LacY) and the raffinose transporter (RafB) and has some similarity with the melibiose transporter (MelB) of Escherichia coli.

Amino Acid Sequence↗

PubMed1997

Mutational analysis of amiloride sensitivity of the NhaA Na+/H+ antiporter from Vibrio parahaemolyticus.

The activity of the NhaA Na+/H+ antiporter of Vibrio parahaemolyticus is inhibited by amiloride. We found an amino acid sequence in the NhaA that was identical to a putative amiloride binding domain of the Na+/H+ exchanger in mammalian cells. We constructed mutant NhaAs that had amino acid substitutions in the putative amiloride binding domain by site-directed mutagenesis. These include V62L (Val62 replaced by Leu), F63Y, F64Y, and L65F. Most mutant NhaAs showed decreased sensitivity for amiloride. Among these, the F64Y mutant NhaA showed the least amiloride sensitivity, with a Ki value 7 to 10 times greater than that in the wild type. Thus, the sequence between residues V62 and L65 in NhaA, especially F64, is very important for the inhibitory effect of amiloride on the antiporter.

Amiloride↗

PubMed1997

Primary structure and properties of the Na+/glucose symporter (Sg1S) of Vibrio parahaemolyticus.

Previously, we cloned and sequenced a DNA fragment from Vibrio parahaemolyticus and found four open reading frames (ORFs). Here, we clearly demonstrate that one of the ORFs, ORF1, is the gene (sglS) encoding a Na+/glucose symporter (SglS). We characterize the Na+/glucose symporter produced in Escherichia coli mutant (JM1100) cells which lack original glucose transport activity and galactose transport activity. We also show that phlorizin, a potent inhibitor of the SGLT1 Na+/glucose symporter of animal cells, inhibited glucose transport, but not galactose transport, via the SglS system.

Bacterial Proteins↗

PubMed1997

Na+(Li+)/H+ antiporter in Pseudomonas aeruginosa and effect of Li+ on cell growth.

Everted membrane vesicles were prepared from cells of Pseudomonas aeruginosa, and cation/H+ antiport was measured. We observed activities of Na+/H+ antiport, Li+/H+ antiport and K+/H+ antiport. Judging from the competition pattern, it seems that there are at least two types of antiporter, a Na+(Li+)/H+ antiporter and a K+/H+ antiporter. Na+ was a good substrate for the Na+(Li+)/H+ system, whereas Li+ was a poor substrate. Although the K(m) value for Na+ (or Li+) was similar to those in Escherichia coli Na+/H+ antiporters, the Vmax value for Na+ (or Li+) was much smaller in the P. aeruginosa antiporter than in the E. coli antiporters. Growth of P. aeruginosa was strongly inhibited by 0.4 M LiCl, but not by NaCl or KCl.

Amiloride↗

PubMed1997

Cloning and expression of an intracellular alkaline protease gene from alkalophilic Thermoactinomyces sp. HS682.

An intracellular alkaline serine protease gene of alkalophilic Thermoactinomyces sp. HS682 was cloned and expressed in Escherichia coli. Sequence analysis showed a putative promoter region, a putative transcriptional termination signal, and an open reading frame of 963 bases, coding for a polypeptide of 321 amino acids. The protease expressed in E. coli was purified by DEAE-Toyopearl 650M and Sephadex G-75 chromatography. The N-terminal sequence (30 amino acids) of the purified protein was coincident with Asp16-Val45 of the deduced amino acid sequence of the ORF. Fifteen amino acids in the N-terminal region were removed during the purification procedures. The deduced amino acid sequence showed high similarity with microbial intracellular serine proteases. The molecular mass of this enzyme was estimated to be 38 kDa by SDS-PAGE. The enzyme was stable at pH 6.0-12.0 and below 60 degrees C in the presence of Ca2+. The temperature and pH optima of the enzyme were 65 degrees C and pH 11.0, respectively. The enzyme was inhibited by DFP and PMSF, but not by MIA and EDTA.

Amino Acid Sequence↗

PubMed1997

Activation of the erythropoietin promoter by a point mutation from GATA to TATA in the -30 region.

We show here a role of the highly conserved GATA motif in the -30 region of the erythropoietin (Epo) promoter. Epo production is reduced in normoxia and activated in hypoxia to control the oxygen supply through erythropoiesis. Although the hypoxic inducibility has been analyzed, the molecular mechanism for the low basal activity in normoxia remained unclear. The GATA motif in the -30 region upstream of the transcription initiation site is highly conserved among the species. In many genes, the consensus motif in the -30 region is TATA. The GATA motif of the Epo promoter was mutated to TATA. The transcriptional activity of the mutant was enhanced even in normoxia. Binding assays showed that TATA-binding protein (TBP) could weakly bind to the wild-type GATA motif whereas TBP bound to the mutant TATA motif with high affinity. These results indicate that the highly conserved GATA motif in the -30 region of the Epo promoter can avoid binding and activation by TBP. This evidence is considered to be the molecular basis for the low physiological expression from the Epo promoter in normoxia.

Animals↗

PubMed1997

[Structure and function of symporter and antiporter].

Structure and function of symporters and antiporters which utilize Na+ as the coupling cation are briefly reviewed. The SGLT is an Na+/glucose symporter present in animal cell membranes. So far, five isoforms of the SGLT (1 to 5) have been found in various tissues. The Me1B is an Na+/galactoside symporter present in membranes of enteric bacteria. Regions or amino acid residues of these symporters which are important for substrate recognition or cation recognition have been identified. Furthermore amino acid substitutions in the SGLT1 of glucose-galactose malabsortion families have been identified. Regions and amino acid residues which are important for the function of the Na+/H+ antiporters (or exchangers) which extrude H+ (in animal cells) or Na+ (in bacterial cells) have been also identified.

Animals↗

PubMed1997

[Cytotoxicity of chemicals used in household products: estimation of eye irritating potency of 25 chemicals tested during 1991-1996].

Cytotoxicity potential of chemicals was evaluated by determining the concentrations inducing 50% reduction of neutral red (NR) uptake into Chinese hamster fibroblast V79 cells compared with control culture (IC50). The results of cytotoxicity test for surfactants with the data produced by the in vivo Draize eye and skin irritation test were compared. There was a good correlation between cytotoxicity and eye irritation score obtained from the Draize test. In contrast, no correlation was observed between Draize skin irritation score and cytotoxic potential of chemicals. Therefore, the NR cytotoxicity test was regarded as a possible in vitro model for predicting eye irritation. Based on the IC50 values in the NR cytotoxicity test, the eye irritation classification (weak, moderate and strong) for each chemical used in household products has been established. We evaluated the cytotoxicity of 25 chemicals used for antimicrobial, rubber accelerator, rubber antioxidant, ultraviolet absorber etc. in household products, and estimated the eye irritating potency of these test chemicals according to the criterion.

Animals↗

PubMed1996

Mutation of potential N-linked glycosylation sites in the Alzheimer's disease amyloid precursor protein (APP).

In order to study the mechanism of intracellular sorting and processing of the Alzheimer's disease amyloid precursor protein (APP), we deleted two potential N-linked glycosylation sites of APP by site-directed mutagenesis. Substitution of alanines for the critical asparagine residues Asn467 and Asn496 was performed. Wild-type and mutant APPs were expressed in COS-1 cells by cDNA transfection and the expressed of the protein and secretion of N-terminal large fragment was observed. The initial secretion of the mutant APP appeared to be slow compared with wild-type. In addition, we found that a distinct APP fragment, the cytosolic form, is transiently increased in the cytosol fraction of COS-1 cells. These results suggest that aberrant processing occurs following the expression of a mutant APP with Ala substituted for Asn, and that glycosylation may modulate the intracellular sorting of APP.

Alzheimer Disease↗

PubMed1996

BDNF gene can Be activated by Ca2+ signals without involvement of de novo AP-1 synthesis.

Although stimulation of N-methyl-D-aspartate receptors or voltage-dependent calcium channels induces both the activation of c-fos and brain-derived neurotrophic factor (BDNF) genes, it is not certain how the activation of these genes is related. Using primary cultures of rat hippocampal neurons, we found that exposing the cells to cycloheximide allowed subsequent activation of BDNF mRNA expression, although activation of AP-1 DNA-binding activity resulting from the c-fos induction was abolished. Super-induction of BDNF gene was also caused by cycloheximide. The estimated half-life of BDNF mRNA was approximately 2.5 hrs, which was almost identical to that of c-fos mRNA. These results indicate that nascent AP-1 is not required for the activation of BDNF gene, leading to the notion that the BDNF gene can be activated by Ca2+ signals as an immediate early gene.

Animals↗

PubMed1996

The upper turnover site in the reentry circuit of common atrial flutter.

The upper turnover site of the reentry circuit of common atrial flutter was examined with the uses of atrial activation mapping and extrastimulus techniques during atrial flutter. The findings suggest that it is anterior to the orifice of the superior vena cava, i.e., between the superior vena cava and tricuspid annulus.

Adult↗

PubMed1996

Modulation of degranulation and superoxide generation in human neutrophils by unsaturated fatty acids of odd carbon numbers.

Unsaturated fatty acids of odd carbons, 13:1(12), 17:1(10trans), 19:1(7) and 19:1(10) inhibited release of myeloperoxidase (MPO) from fMet-Leu-Phe-cytochalasin B-treated neutrophils. The inhibitory effect was smaller than that of aseanostatins which have been isolated as microbial-derived free fatty acids with a methyl blanch (i-14:0 and ai-15:0) (Journal of Antibiotics (1991) 44, 524-532). These unsaturated fatty acids also inhibited lactoferrin release by the same treatment. On the other hand, 13:1(12), 15:1(10) and 19:1(10) inhibited fMet-Leu-Phe-stimulated superoxide generation of neutrophils, and the fatty acids 15:1(10), 17:(10) and 19:2(10,13) induced superoxide generation in both unstimulated cells and the cell-free system. However, none of unsaturated fatty acids of odd carbons tested inhibited beta-glucuronidase release, whereas 15:1(10), 17:1(10), 19:1(10) and 19:2(10,13) rather enhanced an increase in beta-glucuronidase activity liberated from cells at high concentrations over 35 microM, indicating cellular damages by these fatty acids. These observations suggest that unsaturated free fatty acids having odd carbons such as 13, 15, 17 and 19 may act as modulators of neutrophil functions including degranulation and superoxide generation.

Adult↗

PubMed1996

Rapid attenuation of AP-1 transcriptional factors associated with nitric oxide (NO)-mediated neuronal cell death.

Stimulation of glutamate receptors causes several intracellular reactions including activation of activator protein-1 (AP-1) production and nitric oxide (NO) generation. Exposing mouse cerebellar granule cells to N-methyl-D-aspartate or kainate (KA) in culture induced an increase of AP-1 DNA binding activity that was blocked by further addition of sodium nitroprusside (SNP), a typical NO donor. Immunoblotting using anti-c-Fos antiserum revealed the specific attenuation of AP-1, although total protein synthesis was not affected. Since the level of c-fos mRNA expression stimulated by KA remained constant even after exposure to SNP, the AP-1 attenuation can be post-transcriptionally induced. SNP did not affect the Ca2+ influx into the cells stimulated by KA. The involvement of NO in the AP-1 attenuation was supported by the fact that potassium ferrocyanide (K4Fe(CN)6), an analogue of SNP but devoid of NO, failed to inhibit the AP-1 DNA binding activity stimulated by KA. SNP alone induced neuronal cell death, which was blocked by the simultaneous addition of antioxidants, superoxide dismutase and catalase, and an NO scavenger, suggesting a direct role of peroxynitrite in the cell death. In good agreement with these effects, the AP-1 attenuation by SNP was also blocked by antioxidants. These results indicated that post-transcriptional attenuation of AP-1 is involved in the early processes of NO-mediated neuronal cell death.

Animals↗

PubMed1996

Synthesis of dibekacin analogs containing 3-oxa- and 3-aza-2,3,4-trideoxy-D-glycero-hexopyranose.

6-O-(3-Oxa-2,3,4-trideoxy-alpha-D-glycero-hexopyranosyl) derivatives (10 and 17) of both 3',4'-dideoxyneamine and 5-epifluoro-5,3',4'-trideoxyneamine have been prepared by coupling ethyl 6-O-benzyl-3-oxa-2,3,4-trideoxy-1-thio-D-glycero-hexopyranoside (5) with suitable aglycons. The corresponding 3"-aza derivative (19) of dibekacin (6) was prepared by oxidation of 1,3,2',6'-tetra-N-tosyldibekacin (7) with Pb(OAc)4 followed by treatment with NH4OAc and reduction with NaBH3CN. Related ring-opening compounds (11 and 25) were also prepared.

Anti-Bacterial Agents↗

PubMed1996

Mutational analysis of the CitA citrate transporter from Salmonella typhimurium: altered substrate specificity.

The CitA citrate transporter in Salmonella typhimurium is encoded by the citA gene and consists of 434 amino acid residues that probably include 12 membrane-spanning segments [Shimamoto. T., et al. (1991) J. Biochem. 110, 22-28]. CitA mutants with altered substrate specificities were isolated by in vitro mutagenesis using nitrous acid. The mutants could grow on isocitrate as a sole carbon source which normally cannot be transported well by the CitA transporter of S. typhimurium. The mutation sites in the citA gene of the nine mutants were determined to involve single residues at seven sites (one mutation per mutant). The original amino acid residues at these sites (Arg-19, Ala-38, Glu-51, Gly-132, Ala-169, Pro-262 and Leu-271) were identified to be responsible for the altered substrate specificity. All these amino acid residues were conserved in four other homologous citrate transporters from Escherichia coli, Citrobacter amalonaticus and Klebsiella pneumoniae and are suggested to be involved in substrate recognition by the CitA transporter.

Amino Acid Sequence↗

PubMed1996

Novel harmful effects of [60]fullerene on mouse embryos in vitro and in vivo.

[60]Fullerene (C60) was solubilized with poly(vinylpyrrolidone) (PVP) in water, and the aqueous solution was applied to a mouse midbrain cell differentiation system. On incubation of C60 with various concentrations of PVP, cell differentiation and proliferation were potently inhibited, although weaker than the vehicle controls. C60 was clearly distributed into the yolk sac and embryos by intraperitoneal administration to pregnant mice at 50 mg/kg and had a harmful effect on both conceptuses by microscopical evaluation. This in vivo and in vitro action on embryogenesis is a novel and seriously harmful activity of C60.

Animals↗

PubMed1996

Synthesis of kanamycin A analogs containing 6-amino-3-oxa-2,3,4,6-tetradeoxy-D- and -L-glycero-hexopyranose.

6-Azido-3-oxa-2,3,4,6-tetradeoxy-D- and -L-glycero-hexopyranoses were synthesized in five steps from (2S)-and (2R)-1,2-O-isopropylideneglycerols, respectively. After conversion into the corresponding ethyl 1-thioglycosides, each was condensed with a protected derivative of 6-O-(3-amino-3-deoxy-alpha-D-glucopyranosyl)-2-deoxystreptamine (16). Deprotection and reduction of the azido group of the condensation products gave the title compounds.

Anti-Bacterial Agents↗