PubMed Health⌕ Search

Biomedical subjects

H Taguchi

Publications and source records attributed to H Taguchi.

At least 127 records · Page 7Linked to original sources
PubMed1995

Assignment of the 49-kDa (PRIM1) and 58-kDa (PRIM2A and PRIM2B) subunit genes of the human DNA primase to chromosome bands 1q44 and 6p11.1-p12.

DNA primase is an essential replication protein that catalyzes the synthesis of oligoribonucleotide primers. DNA primase, consisting of two subunits (p49 and p58), plays a key role in both the initiation of DNA replication and the synthesis of Okazaki fragments for lagging strand synthesis. We mapped the locations of human chromosomes of the genes coding for both subunits [p49 (PRIM1) and p58 (PRIM2)] by PCR amplification using DNAs of a panel of somatic hybrids, to chromosomes 1 and 6, respectively. The PRIM1 gene was mapped to 1q44, and two PRIM2 loci (PRIM2A and PRIM2B) were detected at 6p11.1-p12 by fluorescence in situ hybridization using several genomic DNA probes.

Animals↗
PubMed1995

Equatorial split of holo-chaperonin from Thermus thermophilus by ATP and K+.

Holo-chaperonin molecule from Thermus thermophilus is a bullet-shaped particle whose cylinder part and round top are composed of two stacked rings of the cpn60 heptamer and a single ring of the cpn10 heptamer, respectively. We found that it splits at the plane between two cpn60 rings into two halves under physiological conditions, that is, in the presence of ATP (but not AMP-PNP, ADP) + K+ (but not Na+) at 60 degrees C. This equatorial split could be functionally important although it has not been considered in any current mechanistic model of chaperonin functioning.

Adenosine Triphosphate↗
PubMed1995

Chaperonin releases the substrate protein in a form with tendency to aggregate and ability to rebind to chaperonin.

To know whether the protein released from chaperonin GroEL/ES is in a form committed to the native state or still an aggregatable non-native one, two experiments were carried out. Dilution of the [GroEL-substrate protein] binary complex prior to ATP addition significantly improved the yield of folding, suggesting that the released protein has a tendency to aggregate. When N-ethylmaleimide treated GroEL, which can form the binary complex but not release the bound protein, was added to the binary complex prior to ATP addition, productive folding was severely inhibited, indicating that the protein released from GroEL/ES can bind to N-ethylmaleimide treated chaperonin. These data favor the 'reservoir' or 'reversion' model, in which GroEL/ES acts as a buffer of folding intermediate or mediates reversion of a misfolded protein to a less folded primitive form, rather than the 'marsupium' model in which folding of the substrate protein proceeds in chaperonin.

Adenosine Triphosphate↗
PubMed1995

Isolation and characterization of the HC8 subunit gene of the human proteasome.

For study of the molecular basis of regulation of proteasome gene expression, we isolated the gene encoding the alpha-type HC8 subunit of the human proteasome. About 2.3 kb of the 5' flanking region of this gene was tested for promoter function by chloramphenicol acetyltransferase assay. This analysis revealed that CAAT and TATA boxes, but not a GC box, are essential for its promoter activity. These results differed from previous findings that the genes for the alpha-type HC3 and beta-type HC5 subunits of the human proteasome have a TATA-less promoter and that two or three GC boxes function as the promoter sequences (Tamura, T. et al. (1994) J. Mol. Biol. 244, 1117-1124). We mapped the HC8 gene at q23 on human chromosome 14, which differs from the chromosomal locations of nine other proteasomal subunit genes mapped so far.

Animals↗
PubMed1995

Assignment of the 36.5-kDa (RFC5), 37-kDa (RFC4), 38-kDa (RFC3), and 40-kDa (RFC2) subunit genes of human replication factor C to chromosome bands 12q24.2-q24.3, 3q27, 13q12.3-q13, and 7q11.23.

Replication factor C is a multimeric primer-recognition protein consisting of five subunits (p145, p40, p38, p37, and p36.5) and is essential for the processive elongation of DNA chains catalyzed by DNA polymerase delta or epsilon in human cells. We have mapped the locations on human chromosomes of the genes coding for the four smaller subunits [p36.5 (RFC5), p37 (RFC4), p38 (RFC3), and p40 (RFC2)] using both PCR amplification from DNAs of a panel of somatic hybrids and fluorescence in situ hybridization to bands 12q24.2-q24.3, 3q27, 13q12.3-q13, and 7q11.23, respectively.

Base Sequence↗
PubMed1995

Molecular cloning, expression, and characterization of chaperonin-60 and chaperonin-10 from a thermophilic bacterium, Thermus thermophilus HB8.

The gene coding a chaperonin from a thermophilic bacterium, Thermus thermophilus HB8, was cloned and sequenced. The operon structure was the same as those of other bacterial chaperonins and the deduced amino acid sequences of both subunits were highly homologous to those of other chaperonins. The cloned genes of chaperonin subunits, chaperonin-10 (T.th cpn10) and chaperonin-60 (T.th cpn60), were separately expressed in Escherichia coli cells. The expressed subunits were easily purified from other host proteins including GroE, a chaperonin of E. coli. T.th cpn60 was expressed as a tetradecameric form, like GroEL of E. coli. Since chaperonin from T. thermophilus HB8 is purified as a holochaperonin, a complex of tetradecameric T.th cpn60 and heptameric T.th cpn10, a tetradecamer of T.th cpn60 without T.th cpn10 has not been obtained before. T.th cpn60 tetradecamer tended to dissociate into monomers during storage. T.th cpn10 expressed in E. coli was purified as a stable oligomer, most likely a heptamer. The activity as holo-chaperonin was reconstituted by mixing both subunits. T.th cpn60 tetradecamer itself arrested refolding of other proteins. The monomerized T.th cpn60 was easily purified from T.th cpn60 oligomer by gel permeation chromatography. Thus-obtained T.th cpn60 monomer had an ATP-independent chaperone activity, as shown for T.th cpn60 monomer isolated from authentic holo-chaperonin.

3-Isopropylmalate Dehydrogenase↗
PubMed1995

The primary cytotoxicity in ultraviolet-a-irradiated riboflavin solution is derived from hydrogen peroxide.

The cytotoxic action of near-ultraviolet (UVA) radiation on cultured mammalian cells is dependent upon oxygen, suggesting that reactive oxygen species are involved in the cellular action of the radiation. Flavins are thought to be an important chromophore for photo-induced skin injury. Irradiation of riboflavin with UVA radiation is known to produce singlet oxygen, superoxide anions, and triplet-state riboflavin radicals, which, however, are immediately quenched by many constituents of the human skin. If the chemical produces a long-lived reactive oxygen species, hydrogen peroxide (H2O2), after UVA radiation, its deleterious effect is not limited to its generation site. Thus, we investigated whether H2O2, is produced in UVA-irradiated riboflavin solution and whether it plays an important role in the cytotoxic action of the solution. The solution showed a marked cytotoxic effect when placed on human fibroblasts, and cytotoxicity was retained in the solution for at least 40 min after radiation. Most of the toxicity appeared to be derived from H2O2 produced in the solution, because the solution lost its cytotoxicity as a result of catalase treatment, and the resultant restoration of survival was almost complete. Under our conditions, two molecules of riboflavin were calculated to produce one molecule of H2O2 after UVA radiation.

Catalase↗
PubMed1995

Flow cytometric analysis using lipophilic dye PKH-2 for adhesion of Vibrio cholerae to Intestine 407 cells.

A comparative study of indirect and direct flow cytometric analysis for adherence of Vibrio cholerae to Intestine 407 cells was performed. The direct flow cytometric analysis employed the lipophilic dye PKH-2. It was concluded that direct flow cytometry using the lipophilic dye PKH-2 is useful and convenient for analyzing bacterium-host cell interactions, since it does not require any specific antibody as the first antibody.

Bacterial Adhesion↗
PubMed1995

Chronological difference in walking impairment among Japanese group A xeroderma pigmentosum (XP-A) patients with various combinations of mutation sites.

Almost all Japanese group A xeroderma pigmentosum (XP-A) patients have nonsense and/or nonsense codon-leading mutations in the XP group A (XPA) gene, and develop neurological abnormalities. Walking ability is one of the most important neuromuscular functions of the patients, because it determines their daily activities. We studied the correlation between the various combinations of mutations found by PCR-RFLP in Japanese XP-A patients and their chronological walking impairment. We classified these patients into six groups. Group I: A patient who was homozygous for the mutation at codon 116 in exon 3 (Type 1 mutation) could never walk unaided. Group III: Typical patients who were homozygous for the mutation at intron 3 (Type 2 mutation) could walk unaided till 7-16 years of age. Group V: Patients who were compound heterozygous for Type 2 mutation and for the mutation at codon 228 in exon 6 (Type 3 mutation) began to develop some walking difficulty at 5-13 years of age and became unable to walk at 25-28 years of age. Group VI: A patient who was homozygous for Type 3 mutation could walk unaided without any difficulty till the age of 21. The walking ability of group II and IV patients is not known yet.

Adolescent↗
PubMed1995

Cloning and sequence of the gene encoding a cefotaxime-hydrolyzing class A beta-lactamase isolated from Escherichia coli.

Escherichia coli TUH12191, which is resistant to piperacillin, cefazolin, cefotiam, ceftizoxime, cefuzonam, and aztreonam but is susceptible to cefoxitin, latamoxef, flomoxef, and imipenem, was isolated from the urine of a patient treated with beta-lactam antibiotics. The beta-lactamase (Toho-1) purified from the bacteria had a pI of 7.8, had a molecular weight of about 29,000, and hydrolyzed beta-lactam antibiotics such as penicillin G, ampicillin, oxacillin, carbenicillin, piperacillin, cephalothin, cefoxitin, cefotaxime, ceftazidime, and aztreonam. Toho-1 was markedly inhibited by beta-lactamase inhibitors such as clavulanic acid and tazobactam. Resistance to beta-lactams, streptomycin, spectinomycin, sulfamethoxazole, and trimethoprim was transferred by conjugational transfer from E. coli TUH12191 to E. coli ML4903, and the transferred plasmid was about 58 kbp, belonging to incompatibility group M. The cefotaxime resistance gene for Toho-1 was subcloned from the 58-kbp plasmid by transformation of E. coli MV1184. The sequence of the gene for Toho-1 was determined, and the open reading frame of the gene consisted of 873 or 876 bases (initial sequence, ATGATG). The nucleotide sequence of the gene (DDBJ accession number D37830) was found to be about 73% homologous to the sequence of the gene encoding a class A beta-lactamase produced by Klebsiella oxytoca E23004. According to the amino acid sequence deduced from the DNA sequence, the precursor consisted of 290 or 291 amino acid residues, which contained amino acid motifs common to class A beta-lactamases (70SXXK, 130SDN, and 234KTG). Toho-1 was about 83% homologous to the beta-lactamase mediated by the chromosome of K. oxytoca D488 and the beta-lactamase mediated by the plasmid of E. coli MEN-1. Therefore, the newly isolated beta-lactamase Toho-1 produced by E. coli TUH12191 is similar to beta-lactamases produced by K. oxytoca D488, K. oxytoca E23004, and E. coli MEN-1 rather than to mutants of TEM or SHV enzymes. Toho-1 has shown the highest degree of similarity to K. oxytoca class A beta-lactamase. Detailed comparison of Toho-1 with other beta-lactamases implied that replacement of Asn-276 by Arg with the concomitant substitution of Thr for Arg-244 is an important mutation in the extension of the substrate specificity.

Amino Acid Sequence↗
PubMed1995

Relaxation of the carotid artery to hypoxia is impaired in Watanabe heritable hyperlipidemic rabbits.

We tested the hypothesis that relaxation of the carotid artery during hypoxia is mediated by activation of glibenclamide-sensitive potassium channels and that this response is impaired in hyperlipidemic rabbits. In New Zealand White rabbits (plasma cholesterol, 69 +/- 12 mg/dL, mean +/- SEM) and Watanabe heritable hyperlipidemic (WHHL) rabbits (plasma cholesterol, 677 +/- 99 mg/dL), tension of the carotid artery was measured in an organ bath under control conditions and during two levels of hypoxia. In normal rabbits, mild hypoxia produced 21 +/- 2% relaxation in arteries precontracted with phenylephrine. Removal of endothelium or the nitric oxide synthase inhibitor NG-nitro-L-arginine (10(-4) mol/L) almost abolished relaxation in response to mild hypoxia in normal rabbits. Glibenclamide (10(-6) mol/L), an inhibitor of ATP-sensitive potassium channels, attenuated relaxation during mild hypoxia by almost 60%. In WHHL rabbits mild hypoxia relaxed the carotid artery by only 9 +/- 4% (P < .05 versus normal rabbits). Severe hypoxia produced greater relaxation of the carotid artery in normal than in WHHL rabbits (85 +/- 5% versus 52 +/- 8%, respectively, P < .05). Glibenclamide but not endothelial denudation or NG-nitro-L-arginine attenuated relaxation during severe hypoxia in normal and WHHL rabbits. Relaxation of the carotid artery to sodium nitroprusside was similar in normal and WHHL rabbits. These findings suggest that relaxation of the carotid artery in response to mild and severe hypoxia is impaired in WHHL rabbits and is mediated, in large part, by activation of glibenclamide-sensitive potassium channels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1995

Relaxation of the aorta during hypoxia is impaired in chronically hypertensive rats.

We investigated mechanisms by which hypoxia produces relaxation of the aorta and tested the hypothesis that these mechanisms are altered during chronic hypertension. Tension of thoracic aortae from normotensive Wistar-Kyoto (WKY) rats and stroke-prone spontaneously hypertensive rats (SHRSP) was measured in an organ bath under control conditions and at two levels of hypoxia. In WKY rats, mild and severe hypoxia produced relaxation of the aortae (precontracted with phenylephrine) by 33 +/- 4% and 82 +/- 3%, respectively (mean +/- SEM). Removal of endothelium or administration of NG-nitro-L-arginine (10(-4) mol/L), an inhibitor of nitric oxide synthase, abolished relaxation of the aortae in response to mild hypoxia but did not affect relaxation during severe hypoxia. Glibenclamide (10(-6) mol/L), an inhibitor of potassium channels, attenuated relaxation of the aortae during mild and severe hypoxia by 49 +/- 16% and 74 +/- 4%, respectively. In SHRSP, mild hypoxia produced little relaxation of the aortae (3 +/- 4%, P < .05 compared with WKY). Indomethacin did not increase relaxation to mild hypoxia in SHRSP, which suggests that a cyclooxygenase-derived contracting factor does not contribute to impaired relaxation. Severe hypoxia relaxed the aortae by 86 +/- 4% in SHRSP, and glibenclamide inhibited this response by 60 +/- 9%. These findings suggest that relaxation of the aorta in response to mild hypoxia in WKY rats is mediated primarily by endothelium-derived relaxing factor, and the response to mild hypoxia is markedly impaired in SHRSP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Dilatation of cerebral arterioles in response to activation of adenylate cyclase is dependent on activation of Ca(2+)-dependent K+ channels.

The role of Ca(2+)-dependent potassium channels in mediating vascular responses to activation of adenylate cyclase in vivo is not known. The goal of this study was to examine the hypothesis that dilatation of cerebral arterioles in response to activation of adenylate cyclase is mediated by activation of Ca(2+)-dependent potassium channels. Diameters of cerebral arterioles were measured in vivo in anesthetized rabbits. Topical application of forskolin (1 and 10 mumol/L), a direct activator of adenylate cyclase, dilated cerebral arterioles by 40 +/- 8% (mean +/- SEM) and 71 +/- 9%, respectively, from a control diameter of 85 +/- 4 microns. Iberiotoxin (50 and 100 nmol/L), a selective inhibitor of Ca(2+)-dependent potassium channels, inhibited dilatation in response to both concentrations of forskolin by 45% to 60%. We obtained similar results by using charybdotoxin (50 nmol/L), another inhibitor of Ca(2+)-dependent potassium channels. Vasodilatation in response to dibutyryl cAMP (a cell-permeable cAMP analogue) was also inhibited by iberiotoxin. In contrast, dilatation of cerebral arterioles in response to sodium nitroprusside and acetylcholine (activators of guanylate cyclase) and aprikalim (activator of ATP-sensitive potassium channels) was not inhibited by iberiotoxin. These findings suggest that dilatation of cerebral arterioles in response to forskolin and increases in intracellular concentrations of cAMP are mediated by activation of Ca(2+)-dependent potassium channels. Thus, activation of Ca(2+)-dependent potassium channels may be a major mechanism of cerebral vasodilatation in response to activation of adenylate cyclase in vivo.

Adenylyl Cyclases↗
PubMed1995

Role of potassium channels in cerebral blood vessels.

BACKGROUND: Hyperpolarization of vascular muscle in response to activation of potassium channels is a major mechanism of vasodilatation. In cerebral blood vessels, four different potassium channels have been described: ATP-sensitive potassium channels, calcium-activated potassium channels, delayed rectifier potassium channels, and inward rectifier potassium channels. SUMMARY OF REVIEW: Activation of ATP-sensitive and calcium activated potassium channels appears to play a major role in relaxation of cerebral arteries and arterioles in response to diverse stimuli, including receptor-mediated agonists, intracellular second messengers, and hypoxia. Both calcium-activated and delayed rectifier potassium channels may contribute to a negative feedback system that regulates tone in large cerebral arteries. The influence of ATP-sensitive and calcium-activated potassium channels is altered in disease states such as hypertension, diabetes, and atherosclerosis. CONCLUSIONS: Activation of potassium channels is a major mechanism of cerebral vasodilatation. Alteration of activity of potassium channels and impairment of vasodilatation may contribute to the development or maintenance of cerebral ischemia or vasospasm.

Adenosine Triphosphate↗
PubMed1995

Dairy farmers have increased methacholine bronchial responsiveness independent of sensitization to mold antigens.

Patients with farmer's lung disease (FLD) and dairy farmers have nonspecific bronchial hyperresponsiveness. To examine the factors determining bronchial hyperresponsiveness among dairy farmers, we studied airway functions, airway responses to inhaled methacholine, serum total IgE levels, and antigen-specific IgE levels in 37 dairy farmers and 11 local control subjects. The 37 dairy farmers consisted of three groups; 12 farmers with episodes of FLD (FLD group), 13 farmers with serum antibody to Micropolyspora faeni (MF) and/or Thermoactinomyces vulgaris (TV) but without episodes of FLD (Ab(+) group), and 12 farmers without serum antibodies to MF and TV and without episodes of FLD (Ab(-) group). Pulmonary function tests showed small airways disorders among farmers (each of the three groups versus control subjects; p < 0.05). Methacholine provocation test, utilizing PD35Grs (a cumulative dose of methacholine that induces 35% reduction in respiratory conductance [Grs]), showed bronchial hyperresponsiveness in each group of dairy farmers compared with that in control subjects (Log PD35Grs, mean +/- SEM: 1.22 +/- 0.18, 1.00 +/- 0.17, and 1.20 +/- 0.20, respectively, versus 2.10 +/- 0.09; p < 0.001). However, there was no statistically significant difference in bronchial responsiveness among the three groups of dairy farmers. In addition, there was no significant difference in serum total IgE levels and specific IgE antibodies among the four groups. These results suggest that the bronchial hyperresponsiveness to methacholine among dairy farmers is not due to past episodes of FLD or sensitization to MF and/or TV, but is possibly due to the occupational environment of dairy farming.

Antibodies, Bacterial↗
PubMed1995

Amino acids and peptides. XL. Synthesis of Ac-Tyr-Val-Ala-Asp-MCA using newly developed acetylating reagent.

2-Acetoxy-3-benzyl-5-methyl-6-isobutylpyrazine was prepared by cyclization of H-Phe-Leu-CH2Cl, followed by acetylation with acetic anhydride. This pyrazine derivative can react with amino groups of amino acids or peptides to produce acetyl amino acids or acetyl peptides without acetylation of hydroxy group of Tyr, Ser and Thr. Using this acetylating reagent, Ac-Tyr-Val-Ala-Asp-MCA, which is a specific substrate of the interleukin-I (IL-I) processing enzyme, was prepared.

Alkylating Agents↗