Search PubMed⌕ Search

Biomedical subjects

K Isono

Publications and source records attributed to K Isono.

At least 91 records · Page 5Linked to original sources
PubMed1998

[Relaxation of canine pulmonary arteries caused by stimulation of atypical beta-adrenergic receptors].

To examine possible contributions of beta(3)-adrenoceptors to catecholamine-induced pulmonary vasodilation, we studied isolated canine pulmonary arterial segments under isometric conditions. Addition of beta-adrenoceptor agonists produced a concentration-dependent relaxation of tissues precontracted with 50 mM KCl; the rank order of potency was isoproterenol (ISO, 1) > salbutamol (SAL, 0.97) > selective beta(3)-adrenoceptor agonists CL 316243 (CL, 0.87) and BRL 37344 (BRL, 0.86). Relaxant responses to SAL were competitively antagonized by the beta(2)-adrenoceptor antagonist ICI 118551 and the pA2 value was 6.67 +/- 0.21 (mean +/- SE), whereas the response to CL was weekly antagonized only by a high concentration of ICI 118551 (10(-5) M) and the apparent pA2 value was 5.24 when alpha-and beta(1)-adrenergic receptors were blocked. By contrast, the atypical beta-adrenoceptor antagonist cyanopindolol antagonized CL-induced relaxation in a competitive manner; the pA2 value was 6.71 +/- 0.12, which was lower than that with salbutamol (p < 0.05). Intracellular cyclic AMP levels were increased in a contraction-dependent manner by CL. These results suggest that beta(3)-adrenoceptors may exist in canine pulmonary arterial smooth muscle and that stimulation of this atypical receptor causes vasodilation through a cyclic AMP-dependent pathway.

Adrenergic beta-Agonists↗
PubMed1997

Leaf-specifically expressed genes for polypeptides destined for chloroplasts with domains of sigma70 factors of bacterial RNA polymerases in Arabidopsis thaliana.

Genes for sigma-like factors of bacterial-type RNA polymerase have not been characterized from any multicellular eukaryotes, although they probably play a crucial role in the expression of plastid photosynthesis genes. We have cloned three distinct cDNAs, designated SIG1, SIG2, and SIG3, for polypeptides possessing amino acid sequences for domains conserved in sigma70 factors of bacterial RNA polymerases from the higher plant Arabidopsis thaliana. Each gene is present as one copy per haploid genome without any additional sequences hybridized in the genome. Transient expression assays using green fluorescent protein demonstrated that N-terminal regions of the SIG2 and SIG3 ORFs could function as transit peptides for import into chloroplasts. Transcripts for all three SIG genes were detected in leaves but not in roots, and were induced in leaves of dark-adapted plants in rapid response to light illumination. Together with results of our previous analysis of tissue-specific regulation of transcription of plastid photosynthesis genes, these results indicate that expressed levels of the genes may influence transcription by regulating RNA polymerase activity in a green tissue-specific manner.

Amino Acid Sequence↗
PubMed1997

Identification and characterization of a novel human phosphatidylinositol 4-kinase.

The extensive sequence homology that exists among the catalytic domains of phosphatidylinositol 3- and 4-kinases allowed us to clone a novel human gene encoding a putative phosphatidylinositol kinase, NPIK. Among other known phosphatidylinositol 3- and 4-kinases, NPIK was most closely related to yeast PIK1 phosphatidylinositol 4-kinase. Several forms of NPIK cDNAs were isolated, and expression of NPIK message was detected in a wide variety of tissues. Fluorescence in situ hybridization and radiation hybrid analyses assigned the NPIK gene to human chromosome 1. Recombinant NPIK protein catalyzed a conversion from phosphatidylinositol to phosphatidylinositol 4-phosphate. The catalytic activity of NPIK was augmented by Triton X-100, and was reduced in the presence of adenosine. Using green fluorescent protein system we determined that NPIK is localized in the cytoplasm. Taken together, the data suggest that NPIK may play a pivotal role in regulating the synthesis of phosphatidylinositol 4-phosphate at the site(s) accessible from cytoplasm.

1-Phosphatidylinositol 4-Kinase↗
PubMed1997

Identification of likely genes on chromosome VI of Saccharomyces cerevisiae by correlating transcripts and nucleotide sequence data.

Most of the 97 transcripts of the genes on chromosome VI of Saccharomyces cerevisiae that were identified by a series of Northern hybridization experiments (Yoshikawa and Isono, Nucl. Acids Res., 19, 1189-1195, 1991) have been correlated with the open reading frames (ORFs) deduced from the nucleotide sequence data of this chromosome (Murakami et al., Nature Genet., 10, 261-268, 1995). This was performed by comparing the experimentally constructed physical map and the one produced from the nucleotide sequence data, as well as the sizes and positions of observed transcripts and those of sequenced ORFs. Thus, 75 ORFs of chromosome VI were correlated uniquely with the corresponding transcripts and 3 ORFs with two transcripts of different sizes. Comparing the relative abundance levels of individual transcripts with that of the RPO41 transcript, highly expressed genes of chromosome VI were found to be located almost exclusively on the Crick strand. Based on the correlation between the abundance level of the experimentally identified transcripts and the codon adaptation indices of the corresponding gene, the genes on chromosome VI of S. cerevisiae were classified into three groups. The data thus provides information concerning their chromosomal locations as well as their likely levels of expression in vegetatively growing cells.

Chromosome Mapping↗
PubMed1997

Construction of a contiguous 874-kb sequence of the Escherichia coli -K12 genome corresponding to 50.0-68.8 min on the linkage map and analysis of its sequence features.

The contiguous 874.423 base pair sequence corresponding to the 50.0-68.8 min region on the genetic map of the Escherichia coli K-12 (W3110) was constructed by the determination of DNA sequences in the 50.0-57.9 min region (360 kb) and two large (100 kb in all) and five short gaps in the 57.9-68.8 min region whose sequences had been registered in the DNA databases. We analyzed its sequence features and found that this region contained at least 894 potential open reading frames (ORFs), of which 346 (38.7%) were previously reported, 158 (17.7%) were homologous to other known genes, 232 (26.0%) were identical or similar to hypothetical genes registered in databases, and the remaining 158 (17.7%) showed no significant similarity to any other genes. A homology search of the ORFs also identified several new gene clusters. Those include two clusters of fimbrial genes, a gene cluster of three genes encoding homologues of the human long chain fatty acid degradation enzyme complex in the mitochondrial membrane, a cluster of at least nine genes involved in the utilization of ethanolamine, a cluster of the secondary set of 11 hyc genes participating in the formate hydrogenlyase reaction and a cluster of five genes coding for the homologues of degradation enzymes for aromatic hydrocarbons in Pseudomonas putida. We also noted a variety of novel genes, including two ORFs, which were homologous to the putative genes encoding xanthine dehydrogenase in the fly and a protein responsible for axonal guidance and outgrowth of the rat, mouse and nematode. An isoleucine tRNA gene, designated ileY, was also newly identified at 60.0 min.

Base Sequence↗
PubMed1997

Identification and characterization of the genes for mitochondrial ribosomal proteins of Saccharomyces cerevisiae.

We have purified 13 large subunit proteins of the mitochondrial ribosome of the yeast Saccharomyces cerevisiae and determined their partial amino acid sequences. To elucidate the structure and function of these proteins, we searched for their genes by comparing our sequence data with those deduced from the genomic nucleotide sequence data of S. cerevisiae and analyzed them. In addition, we searched for the genes encoding proteins whose N-terminal amino acid sequences we have reported previously [Grohmann, L., Graack, H.-R., Kruft, V., Choli, T., Goldschmidt-Reisin, S. & Kitakawa, M. (1991) FEBS Lett. 284, 51-56]. Thus, we were able to identify and characterize 12 new genes for large subunit proteins of the yeast mitochondrial ribosome. Furthermore, we determined the N-terminal amino acid sequences of seven small subunit proteins and subsequently identified the genes for five of them, three of which were found to be new.

Amino Acid Sequence↗
PubMed1997

Detection of hepatitis B virus x transcripts in human hepatocellular carcinoma tissues.

BACKGROUND: The hepatitis B virus (HBV) or hepatitis C virus (HCV) sequences were frequently detected in hepatocellular carcinoma (HCC) tissues by the method of polymerase chain reaction (PCR). However, the expression levels of HBV and HCV in HCC tissues remain to be documented. This study evaluates the mRNA expression levels of those virus sequences in the human HCC tissues through Northern blot hybridization. METHODS: We performed Northern blot hybridization to identify the HBV x mRNA and HCV RNA in HCC tissues of 14 cases excised at Chiba University Hospital. RESULTS: The HBV x transcripts could be identified in the tumor tissues from all three serum HBsAg-positive cases and two cases among 11 HBsAg-negative patients. One HBsAg-negative case showed the most intensive signal in those five cases. However, HCV RNA could not be identified by this method. The HBV x gene transcript is predicted to have a size of about 0.7 kb; however, the molecular weight of HBV x specific mRNA is not consistent and is distributed between approximately 2.0 and 9.0 kb. The hybridization signal intensity is also variable according to the cases. CONCLUSION: These observations suggest that HBV x gene may be transcribed with flanking cellular sequences and the carcinogenic activity may be different according to the expressed levels. The identification of HBV x transcripts in HCC tissues on the Northern blot level also suggests that HBV x mRNA expression might be significant and concerned with the development of human HCC even in HBsAg-negative cases.

Adult↗
PubMed1997

The characterization of reconstituted passenger leukocytes on the induction of tolerance in rat liver transplantation.

The tolerance induced by orthotopic liver transplantation [DA (RT1a) rats to PVG (RT1c) rats] can be prevented by total body irradiation of the donor rat. Reconstitution of the irradiated donor with DA splenic leukocytes reintroduces this tolerance. To investigate the major histocompatibility complex (MHC) specificity of passenger leukocytes, irradiated DA donors were reconstituted by third-party BN (RT1n) splenic leukocytes. The reconstitution with BN splenocytes re-established DA-specific tolerance in PVG recipients, as confirmed by subsequent DA cardiac allografting, while BN hearts were rejected with second-set tempo. To determine which cell components play an important role in re-establishing liver graft tolerance, DA splenic leukocytes were further purified into three types: T, B, and adherent cells. Only "T-cell-enriched" preparations restored liver graft tolerance in three out of five PVG recipients. These results suggest that passenger leukocytes of differing MHC types can help to induce liver-specific tolerance and that T cells in the liver graft may be essential to regulate tolerance induction.

Animals↗
PubMed1997

A randomized trial of surgery with and without chemotherapy for localized squamous carcinoma of the thoracic esophagus: the Japan Clinical Oncology Group Study.

OBJECTIVE: To determine whether postoperative adjuvant chemotherapy confers a survival benefit on patients with esophageal squamous cell carcinoma undergoing radical surgery, we undertook a cooperative, prospective randomized controlled trial. METHODS: A total of 205 patients underwent transthoracic esophagectomy with lymphadenectomy at eleven institutions between December 1988 and July 1991. These patients were prospectively randomized into two groups (100 patients underwent surgery alone and 105 patients had additional two courses of combination chemotherapy with cisplatin (70 mg/m2) and vindesine (3 mg/m2). The two groups did not differ with respect to sex, age, location of tumor, and distributions of pT, pN, pM, or p stage. RESULTS: The 5-year survival was 44.9% in the surgery alone group and 48.1% in the surgery plus chemotherapy group. The relative risk was estimated to be 0.89 (95% confidence interval, 0.61 to 1.31) in the surgery plus chemotherapy group compared with the surgery alone group. No significant differences in survival were detected between the two groups, even with lymph node stratification. CONCLUSION: Postoperative adjuvant chemotherapy with cisplatin and vindesine has no additive effect on survival in patients with esophageal cancer compared with surgery alone.

Adult↗
PubMed1997

Identification of hepatitis B virus integration in hepatitis C virus-infected hepatocellular carcinoma tissues.

BACKGROUND/AIMS: The integration of HBV DNA is thought to be involved in the initial stage of hepatocarcinogenesis, and it has been reported that transactivating factors encoded by the X and preS2/S genes stimulate transcription of multiple viral and cellular genes. We assessed the possible contributions of hepatitis B virus integration to the occurrence of hepatocellular carcinoma in hepatitis C virus-infected as well as in hepatitis B virus-infected patients by identifying the integrated HBV DNA sequence, and the X and preS2/S regions were further investigated in HBV DNA-integrated cases. METHODS: Southern blot hybridization for detecting HBV DNA in tumor tissues from 28 hepatocellular carcinoma patients was carried out with full-length HBV DNA, and then with X and preS2/S regions as probes. We also carried out reverse transcription-polymerase chain reaction for detecting HCV RNA to confirm hepatitis C virus-infection in liver tissues. RESULTS: Clonally integrated HBV DNA sequences were demonstrated in 16 of 28 patients (57.1%), including five HBsAg seropositive and 11 HBsAg seronegative patients. Of these 11 HBsAg seronegative patients, 10 were also positive for anti-HCV in their sera, and all nine examined cases had HCV RNA in liver. Furthermore, the X region was identified in 14 of 16 HBV DNA integrated cases (87.5%), and the preS2/S region in 6/16 (37.5%). CONCLUSIONS: The present Southern blot analysis demonstrates that clonally integrated HBV DNA sequences were identified even in hepatitis C virus-infected hepatocellular carcinoma patients at a high rate (10/18, 55.6%), and suggests that integrated hepatitis B virus, whose major component is the X gene, may play an important role in hepatocarcinogenesis in hepatitis B virus-integrated cases with and without hepatitis C virus infection.

Adult↗
PubMed1997

Hepatic protein synthesis rate of liver specimens as a predictor of viability in rat cold ischemia liver transplantation model.

BACKGROUND/AIMS: We have previously reported that the hepatic protein synthesis rate, calculated as the uptake rate of L-[4.5 3H] leucine by the protein fraction during a 10-min incubation of a 16-G needle biopsy specimen of liver tissue, represents a high level of liver function and is therefore useful for evaluating liver function. We investigated the hepatic protein synthesis rate level in a pre-transplant liver to learn if it might predict the outcome in a rat orthotopic liver transplantation model. METHODS: Grafts were stored, liver specimens were obtained using a 21-G Chiba type II skinny needle, and the hepatic protein synthesis rate was calculated. Subsequently, liver transplantation was performed, and the hepatic protein synthesis rate level of revascularized liver, tissue blood flow rate, serum alanine aminotransferase, lactate dehydrogenase, hyaluronic acid, ketone body rate, and 2-week survival were examined. RESULTS: The hepatic protein synthesis rate of pretransplant liver was correlated with parameters of post-transplant liver function: hepatic protein synthesis rate of the revascularized liver (r=0.92, p<0.0001), tissue blood flow rate (r=0.77, p<0.004), serum alanine aminotransferase (r=-0.69, p<0.003), lactate dehydrogenase (r=-0.54, p<0.03), hyaluronic acid (r=-0.86, p<0.0002), and ketone body rate (r=0.57, p<0.02). Pretransplant hepatic protein synthesis rate in survivors was 263.6+/-54.2 nmol/mg protein/10 min, while that in nonsurvivors was significantly lower at 162.0+/-39.0 (p<0.0001). When evaluation was made using a logistic regression model, the accuracy predicted using the value of hepatic protein synthesis rate was 95% (19/20). CONCLUSIONS: These results suggest that measuring the hepatic protein synthesis rate of the grafts with a 21-G Chiba type II skinny needle may be a predictive criterion in the assessment of graft viability.

Alanine Transaminase↗
PubMed1997

Tyrosine phosphorylation controls internalization of CTLA-4 by regulating its interaction with clathrin-associated adaptor complex AP-2.

CTLA-4 is a costimulation receptor that binds to the same ligands, CD80 and CD86, as CD28 with high affinity and is transiently expressed on the cell surface of activated T cells. CTLA-4 delivers an inhibitory signal through association of a phosphotyrosine-containing motif in the cytoplasmic domain with Syp tyrosine phosphatase. We now demonstrate that CTLA-4 interacts with the mu2 subunit of the plasma membrane-associated adaptor complex, AP-2, through the same motif involved in the interaction with Syp, except that the interaction with mu2 requires unphosphorylated tyrosine. The interaction with mu2 likely induces rapid internalization of CTLA-4 from the cell surface. Our results suggest that the phosphorylation state of a single tyrosine residue determines whether CTLA-4 delivers a negative signal or is internalized.

Abatacept↗
PubMed1997

Role of Ca(2+)-activated K+ channel in epithelium-dependent relaxation of human bronchial smooth muscle.

1. To elucidate whether K+ channels play a role in the action of epithelium-dependent bronchodilatation, we studied responses in human bronchial strips in the presence of indomethacin and NG-nitro-L-arginine methylester under isometric conditions, in vitro. 2. Mechanical removal of the epithelium increased the contractile responses to acetylcholine; the pD2 values increased from 5.0 +/- 0.2 to 5.9 +/- 0.3 (P < 0.001). This potentiation was abolished by iberiotoxin but not by apamin or glibenclamide. 3. In cascade bioassay, application of the bathing medium from dispersed, bronchial epithelial cells to epithelium-denuded bronchial strips decreased acetylcholine-induced contraction by 44 +/- 6%. This effect was reduced to 10 +/- 3% (P < 0.01) when the epithelial cells were pretreated with iberiotoxin, and to 4 +/- 1% (P < 0.001) when the epithelial cells were incubated with Ca(2+)-free medium containing [1,2-bis(2) aminophenoxy] ethane N,N,N',N'-tetraacetic acid-acetomethoxy ester. 4. In contrast, the bronchodilator effect of the medium bathing epithelial cells was not altered by the direct addition of iberiotoxin to epithelium-denuded tissues. 5. These results suggest that the Ca(2+)-activated K+ channel may play a role in the synthesis and/or release of smooth muscle relaxing factor, which is neither nitric oxide nor a cyclo-oxygenase product, from airway epithelial cells.

Acetylcholine↗
PubMed1997

Role of Na(+)-K+ ATPase in cyclic GMP-mediated relaxation of canine pulmonary artery smooth muscle cells.

1. Sodium-potassium adenosine triphosphate (Na(+)-K+ ATPase) plays a role in the regulation of vascular tone, but contribution of this enzyme to intravasodilator-induced pulmonary vasodilation remains uncertain. We thus studied the interaction between guanosine 3':5'-cyclic monophosphate (cyclic GMP) and Na(+)-K+ ATPase in smooth muscle cells isolated from canine pulmonary artery. 2. To assess the contractile properties, changes in smooth muscle cell length were determined microscopically. Application of potassium chloride (KCl) shortened the cell length, an effect which was reduced by sodium nitroprusside and 8-bromo-cyclic GMP in a concentration-dependent manner. Pretreatment of cells with the cyclic GMP-dependent kinase inhibitor KT 5823 (2 microM) abolished the effects of sodium nitroprusside and 8-bromo-cyclic GMP. 3. Ouabain (0.3 microM) did not alter the KCl-induced muscle shortening, but inhibited the relevant responses to sodium nitroprusside and 8-bromo-cyclic GMP. 4. Incubation of smooth muscle cells with sodium nitroprusside concentration-dependently increased intracellular cyclic GMP levels and ouabain-sensitive 86Rb uptake, and these values were significantly correlated. In the presence of KT 5823, sodium nitroprusside increased cyclic GMP levels but did not alter ouabain-sensitive 86Rb uptake. 5. These results suggest that there is a link between accumulation of intracellular cyclic AMP and activation of sarcolemmal Na(+)-K+ ATPase in pulmonary artery smooth muscle cells and that this link may be involved in the sodium nitroprusside-induced pulmonary vasodilatation.

Animals↗
PubMed1997

Inhibition of growth and invasive activity of human pancreatic cancer cells by a farnesyltransferase inhibitor, manumycin.

The effects of manumycin, a competitive farnesyltransferase (FTase) inhibitor, on pancreatic cancer cell lines with or without K-ras mutation were studied. Manumycin inhibited the growth of human pancreatic cancer cells (SUIT-2, MIA PaCa-2, AsPC-1, BxPC-3) in a dose-dependent manner. The 50% inhibitory concentration (IC50) in cell lines with a mutant K-ras gene (SUIT-2, MIA PaCa-2, AsPC-1) was lower than that in BxPC-3 with a wild-type ras. Both mitogen-activated protein kinase activity after growth stimuli and the ability for chemotactic invasion were markedly more inhibited by manumycin in SUIT-2 than in BxPC-3. These results suggest that mutated Ras is more sensitive to manumycin than the wild type. Furthermore, tumor growth and liver metastasis in nude mice inoculated with manumycin-treated SUIT-2 cells were inhibited dose dependently. Inhibition of Ras activity might be a new anticancer strategy in pancreatic cancer in which Ras plays a role.

Alkyl and Aryl Transferases↗