Biomedical subjects

N Tanaka

Publications and source records attributed to N Tanaka.

At least 541 records · Page 30Linked to original sources

PubMed1999

Evaluation of cyclin D1 mRNA expression in gastric and colorectal cancers.

Cyclin D1 is a G1 cyclin that controls the transition of the cell cycle from G1 phase to S phase, and its gene is located on chromosome 11q13. We evaluated the expression of cyclin D1 mRNA in surgically resected specimens of gastric and colorectal cancers using quantitative RT-PCR. In this method, cDNA derived from cyclin D1 mRNA was amplified in a tube together with an internal control. The expression of cyclin D1 mRNA was high in 8 of 36 gastric cancer tissues (22%) and 9 of 27 (33%) colorectal cancer tissues, compared to normal mucosal tissues. In gastric cancers, the rate of cyclin D1 mRNA expression (an index of the density of DNA bands) was significantly higher in patients with tumors invading beyond the submucosal layer, regional lymph nodes and lymphatic vessels (i.e., patients with stage III or IV). In colorectal cancers, the rate of cyclin D1 mRNA expression was significantly higher in patients with venous invasion. Moreover, in patients with colorectal cancer, the survival rate of high-expression group was significantly lower than in low-expression group. Our results suggested that overexpression of cyclin D1 mRNA reflected the severity of gastric cancer and poor prognosis of colorectal cancer.

Adult↗

PubMed1998

The chemopreventive role of ursodeoxycholic acid in azoxymethane-treated rats: suppressive effects on enhanced group II phospholipase A2 expression in colonic tissue.

Great interest has been focused on the chemoprevention of colonic carcinogenesis by oral administration of ursodeoxycholic acid (UDCA) because its administration reportedly reduces the incidence of colon cancer in animal experiments. To elucidate the precise role of UDCA in the chemoprevention of azoxymethane-induced colon carcinogenesis, we examined the expression levels of group II phospholipase A2 in the colonic tissue of UDCA-treated and untreated rats and correlated the levels with the findings of aberrant crypt foci, putative preneoplastic lesions. Twelve weeks after azoxymethane exposure, the total number of aberrant crypt foci in 0.4% UDCA-fed rats and 1% UDCA-fed rats was significantly decreased compared to the untreated animals. The mucosal concentrations of PGE2 and 6-keto PGF1alpha were significantly lower in the UDCA-treated rats than in untreated rats. In correlation with lowering, the enhanced activity, protein mass and mRNA levels of group II phospholipase A2 were significantly attenuated in the UDCA-treated animals. The chemopreventive role of UDCA in colon carcinogenesis may lie in its modulation of the arachidonate metabolism in colonic mucosa.

Animals↗

PubMed1998

In vitro increases in plasmid DNA supercoiling by hydrostatic pressure.

By conducting topoisomerase I-mediating supercoiling assays, effects of elevated pressure on DNA supercoiling were investigated for the first time. It was found that pressure elevations induced a progressive increase in plasmid DNA linking numbers, winding the DNA duplex by a magnitude of 1.1-1.6x10(-3) angular degree/base/MPa. Implications for the findings were discussed in terms of disturbance of the tertiary structure of DNA by elevated pressure.

DNA Topoisomerases, Type I↗

PubMed1998

Positive feedback regulation of type I IFN genes by the IFN-inducible transcription factor IRF-7.

The interferon regulatory factor (IRF) family of transcription factors regulate the interferon (IFN) system, among which IRF-3 is involved in the virus-induced IFN-beta gene expression. Here we show that another member IRF-7 is critical for the IFN-alpha gene induction. Unlike the IRF-3 gene, the IRF-7 gene is induced by IFNs through activation of the ISGF3 transcription factor, and IRF-7 undergoes virus-induced nuclear translocation. In cells lacking p48, an essential component of IFN stimulated gene factor 3 (ISGF3), ectopic expression of IRF-7 but not IRF-3 can rescue the deficiency to induce IFN-alpha genes. These results indicate that IRF-7 is a key factor in the positive feedback regulation of IFN-alpha/beta production.

Amino Acid Sequence↗

PubMed1998

Expression of hMSH2 correlates with in vitro chemosensitivity to CDDP cytotoxicity in oral and oropharyngeal carcinoma.

We investigated the expression of hMSH2, a human mutS homologue from chromosome 2p, in oral and oropharyngeal squamous cell carcinoma (SCC) by an immunohistochemical technique and performed tumor in vitro chemosensitivity testing. In 58 oral and oropharyngeal SCC, the hMSH2 positive score was inversely associated with tumor size, but not with other clinical parameters. Among five anticancer drugs (cisplatin (CDDP), 5-FU, peplomycin, mitomycin C and doxorubicin), only for CDDP was sensitivity to cytotoxicity correlated with the hMSH2 positive score. The susceptibility of hMSH2-positive tumors to CDDP killing was significantly higher than that of hMSH2-negative tumors. Immunohistochemical results regarding hMSH2 are promising in the evaluation of the sensitivity of cancer cells to CDDP cytotoxicity and enable one to select patients for adjuvant chemotherapy for oral and oropharyngeal SCC.

Adult↗

PubMed1998

Characterization of transcription of genes involved in hairy root induction on pRi1724 core-T-DNA in two Ajuga reptans hairy root lines.

The detailed status of the transcription of genes on pRil724 T-DNA in two independent hairy root lines of the plant Ajuga reptans, Ar-4 and Ar-24, which have several different characteristics, was obtained by Northern blotting and a reverse transcription-polymerase chain reaction (RT-PCR) analysis. In the Northern blotting analysis DNA fragments corresponding to the putative open reading frames (ORFs) as probes, transcripts from putative ORFs 10 (1724rolA), 11 (1724rolB), 12 (1724rolC), 13a and 14, which are homologs to each ORF on pRiA4, were detected in both hairy root lines, whereas no transcripts derived from ORF 13 were detected. The transcription of ORF 13 was, however, detected in the RT-PCR analysis, suggesting a minor expression of ORF 13. All of the putative ORFs were transcribed with their expected directions, since DNA fragments were amplified when the antisense primers were employed in the reverse transcription. We also found that different transcripts with a reverse direction were present at the locations of 1724rolA, 1724rolC and ORF 13a, because the DNA fragments were amplified from the templates when their sense primers were used in the reverse transcription.

DNA Primers↗

PubMed1998

Effects of compositions of dimethyl-beta-cyclodextrins on enantiomer separations by cyclodextrin modified capillary zone electrophoresis.

In enantiomeric separation by capillary zone electrophoresis using dimethyl-beta-cyclodextrin (DM-beta-CD) as a chiral selector, enantioselectivities were sometimes significantly different among DM-beta-CDs from five different suppliers. The reason was due to the difference in the compositions among these commercial products, which was shown by the liquid chromatographic (LC) analysis. As for commercial DM-beta-CD from one supplier, two major components were obtained by preparative LC. NMR spectroscopic and mass spectrometric analyses of these two components were performed to estimate the structure of each component. The results implied that the commercial products consist of heptakis(2,6-di-O-dimethyl)-beta-CD and hexakis(2,6-di-O-methyl)-mono(2,3,6-tri-O-methyl)-beta-CD. Sometimes different enantioselectivities were observed between these two components including the original DM-beta-CD.

Chromatography, Liquid↗

PubMed1998

Structure of 3-isopropylmalate dehydrogenase in complex with 3-isopropylmalate at 2.0 A resolution: the role of Glu88 in the unique substrate-recognition mechanism.

BACKGROUND: 3-Isopropylmalate dehydrogenase (IPMDH) and isocitrate dehydrogenase (ICDH) belong to a unique family of bifunctional decarboxylating dehydrogenases. Although the ICDH dimer catalyzes its reaction under a closed conformation, known structures of the IPMDH dimer (without substrate) adopt a fully open or a partially closed form. Considering the similarity in the catalytic mechanism, the IPMDH dimer must be in a fully closed conformation during the reaction. A large conformational change should therefore occur upon substrate binding. RESULTS: We have determined the crystal structure of IPMDH from Thiobacillus ferrooxidans (Tf) complexed with 3-isopropylmalate (IPM) at 2.0 A resolution by the molecular replacement method. The structure shows a fully closed conformation and the substrate-binding site is quite similar to that of ICDH except for a region around the gamma-isopropyl group. The gamma group is recognized by a unique hydrophobic pocket, which includes Glu88, Leu91 and Leu92 from subunit 1 and Val193' from subunit 2. CONCLUSIONS: A large movement of domain 1 is induced by substrate binding, which results in the formation of the hydrophobic pocket for the gamma-isopropyl moiety of IPM. A glutamic acid in domain 1, Glu88, participates in the formation of the hydrophobic pocket. The C beta and C gamma atoms of Glu88 interact with the gamma-isopropyl moiety of IPM and are central to the recognition of substrate. The acidic tip of Glu88 is likely to interact with the nicotinamide mononucleotide (NMN) ribose of NAD+ in the ternary complex. This structure clearly explains the substrate specificity of IPMDH.

3-Isopropylmalate Dehydrogenase↗

PubMed1998

Functionally inactivating point mutation in the tumor-suppressor IRF-1 gene identified in human gastric cancer.

Loss of heterozygosity (LOH) observed in human tumors strongly suggests the existence of (a) tumor-suppressor gene(s) at the concerned locus. A series of studies has revealed that LOH on the long arm of chromosome 5 (5q) frequently occurs in differentiated gastric adenocarcinomas. Furthermore, it has been shown that the interferon regulatory factor-1 (IRF-1) locus on chromosome 5q31.1 is one of the common minimal regions of LOH in these cancers. IRF-1 is a transcriptional activator that shows tumor-suppressor activity in the mouse. In the present study, we examined the sequence of the IRF-1 gene in 9 cases of histologically differentiated gastric adenocarcinomas, all of which exhibited LOH at the IRF-1 locus. We identified a mis-sense mutation in the residual allele in one case. This mutated form of IRF-1 showed markedly reduced transcriptional activity. In addition, overexpression of wild-type IRF-1 induced cell-cycle arrest, whereas such activity was attenuated in the mutant IRF-1. These results suggest that the loss of functional IRF-1 is critical for the development of human gastric cancers.

3T3 Cells↗

PubMed1998

The hereditary renal cell carcinoma 3;8 translocation fuses FHIT to a patched-related gene, TRC8.

The 3;8 chromosomal translocation, t(3;8)(p14.2;q24.1), was described in a family with classical features of hereditary renal cell carcinoma. Previous studies demonstrated that the 3p14.2 breakpoint interrupts the fragile histidine triad gene (FHIT) in its 5' noncoding region. However, evidence that FHIT is causally related to renal or other malignancies is controversial. We now show that the 8q24.1 breakpoint region encodes a 664-aa multiple membrane spanning protein, TRC8, with similarity to the hereditary basal cell carcinoma/segment polarity gene, patched. This similarity involves two regions of patched, the putative sterol-sensing domain and the second extracellular loop that participates in the binding of sonic hedgehog. In the 3;8 translocation, TRC8 is fused to FHIT and is disrupted within the sterol-sensing domain. In contrast, the FHIT coding region is maintained and expressed. In a series of sporadic renal carcinomas, an acquired TRC8 mutation was identified. By analogy to patched, TRC8 might function as a signaling receptor and other pathway members, to be defined, are mutation candidates in malignant diseases involving the kidney and thyroid.

Acid Anhydride Hydrolases↗

PubMed1998

Enhanced expression of full-length TrkB receptors in young rat brain with hypoxic/ischemic injury.

Expression of TrkB receptors were studied in the cerebral cortex of normal rats and young rats with hypoxic/ischemic injury. TrkB expressing cells were present in the piriform cortex at birth and increased in number with age, and were finally present in the entire cerebral cortex. Density of TrkB cells reached adult levels at P30. They were morphologically regarded as pyramidal neurons and interneurons. Hypoxic/ischemic injury induced a tentative increase of full-length TrkB receptors. A novel appearance of TrkB expressing neurons and enhanced immunostaining on both cell soma and dendrites were observed in the peri-infarct areas and increased number of TrkB expressing neurons were detected in the contralateral cortex after carotid artery ligation. This increase was no longer evident after 48 h of hypoxia. Double immunostaining using antiserum against GFA or OX-42 revealed no co-localization of TrkB receptors and these molecules, while there were only slight co-localization of TrkB and calbindin-D28k molecules. The altered levels in responses to injury indicate that TrkB may play a crucial role in the early protective mechanism of the neurons with hypoxic/ischemic injury through ligands BDNF and/or NT-4/5.

Age Factors↗

PubMed1998

Crystallization and preliminary X-ray studies on the hyperstable 3-isopropylmalate dehydrogenase from the thermoacidophilic archaeon Sulfolobus sp. strain 7.

3-Isopropylmalate dehydrogenase from the thermoacidophilic archaeon, Sulfolobus sp. strain 7, has been crystallized by the vapor-diffusion method. The crystals were grown from a solution containing ammonium sulfate, 2-methyl-2,4-pentanediol and magnesium chloride. The crystallization requires 2-methyl-2,4-pentanediol to avoid twinning of the crystals. The crystal belongs to the orthorhombic system with the space group P2221 and unit-cell dimensions a = 67.9, b = 93.3 and c = 134.1 A.

3-Isopropylmalate Dehydrogenase↗

PubMed1998

Application of a fine thread beam to the structure analysis of a hemihedrally twinned crystal of hydroxylamine oxidoreductase.

Accurate diffraction intensity data have been collected from a twinned P6(3) crystal of the 24-haem protein hydroxylamine oxidoreductase, from a nitrifying chemoautotrophic bacterium Nitrosomonas europaea, using synchrotron radiation at station BL6A of the Photon Factory. Estimation of the twinning fraction and deconvoluted intensity data, including native and heavy-atom derivative data, gave an improved Patterson function. Four diffraction data sets were collected from one crystal and an estimation of the twinning fraction to confirm the phenomena was undertaken. The successfully detwinned data sets were utilized in the structure analysis of the present enzyme. The mechanism of twinned-crystal formation is also discussed.

Journal Article↗

PubMed1998

Structure and function of 6,7-dicarboxyheme-substituted myoglobin.

Myoglobin was reconstituted with 6,7-dicarboxy-1,2,3,4,5, 8-hexamethylheme, a compact synthetic heme with the shortest acid side chains, to pursue the structural and functional consequences after intensive disruption of the heme propionate-apoglobin linkages in the native protein. The electron-withdrawing carboxylate groups directly attached to the porphyrin ring lowered the oxygen affinity by 3-fold as compared with native myoglobin. Autoxidation of the oxy derivative to the ferric protein proceeded with 1.6 x 10(-)2 min-1 at pH 7.0 and 30 degrees C. The crystallographic structure of the cyanomet myoglobin with 1.9 A resolution shows that the heme adopts a unique orientation in the protein pocket to extend the two carboxylates toward solvent sphere. The native globin fold is conserved, and the conformations of globin side chains are almost intact except for those located nearby the heme 6,7-carboxylates. The 7-carboxylate only weakly interacts with Ser92 and His97 through two mediating water molecules. The 6-carboxylate, on the other hand, forms a novel salt bridge with Arg45 owing to conformational flexibility of the guanidinium side chain. The proton NMR shows that the small heme does not fluctuate about the iron-histidine bond even at 55 degreesC, suggesting that the salt bridge between Arg45 and heme 6-carboxylate is of critical importance to recognize and fix the heme in myoglobin.

Animals↗

PubMed1998

Expression of multidrug resistance-associated protein (MRP) in head and neck squamous cell carcinoma.

We investigated the expression of multidrug resistance-associated protein (MRP) in 115 cases of head and neck squamous cell carcinoma (H&NSCC) by immunohistochemistry and examined the relationship between MRP expression and clinical factors. Thirty-four (30%) of 115 cases of H&NSCC had expression of MRP. The clinical stage was inversely associated with the expression of MRP (P = 0.0090), but not with age, sex, tumor size, metastasis, recurrence, death from disease or overall survival rate for 5 years. In vitro chemosensitivity to five chemotherapeutic agents (cis-diamminedichloroplatinum, 5-fluorouracil, peplomycin, mitomycin C and Adriamycin) was tested by ATP assay and no correlation between the sensitivity of tumor cells to the cytotoxicity of any drug and MRP expression was found. These results suggest that the resistance to anticancer drugs is not dependent only on the expression of MRP in H&NSCC.

ATP-Binding Cassette Transporters↗

PubMed1998

Isolation and characterization of an invertase and its repressor genes from Schizosaccharomyces pombe.

PCR was used to isolate an invertase homolog gene from the fission yeast Schizosaccharomyces pombe. The cloned inv1(+) gene encodes a protein of 581 amino acids with 16 potential asparagine-linked glycosylation sites, and has 39% and 38% identity to the Schwanniomyces occidentalis and Saccharomyces cerevisiae SUC2 invertases. When the inv1(+) gene was disrupted, S. pombe strains lacked detectable invertase activity. This result showed that the inv1(+) gene encodes only one active invertase in S. pombe cells. The transcription of inv1(+) is repressed in the presence of glucose. The transcription of inv1(+) was not affected in cyr1Delta strain which lacks adenylate cyclase activity, unlike transcription of S. pombe fbp1(+) gene. We have identified an S. pombe gene (scr1(+)) that encodes a homolog of the Aspergillus nidulans CREA which is required for glucose repression of the glyconeogenic pathway. Although the deletion of scr1(+) did not influence the transcription of fbp1(+) gene, glucose repression of the inv1(+) gene was severely affected. These results showed that glucose repression of inv1(+) gene is dependent on scr1(+) gene, and S. pombe cAMP signalling pathway may not be essential for glucose repression of inv1(+) gene.

Amino Acid Sequence↗

PubMed1998

Involvement of the IRF family transcription factor IRF-3 in virus-induced activation of the IFN-beta gene.

The virus-induced activation of interferon alpha/beta (IFN-alpha/beta) gene transcription is essential for host defense. The IFN-beta promoter is controlled primarily by the virus-inducible enhancer elements, the IRF-Es. Here we show that IRF-3, an IRF family transcription factor, translocates to the nucleus from the cytoplasm upon virus infection in NIH/3T3 cells. The nuclear IRF-3 is phosphorylated, interacts with the co-activators CBP/p300, and binds specifically to the IFN-beta IRF-E. Furthermore, overexpression of IRF-3 causes a marked increase in virus-induced IFN-beta mRNA expression. Thus, IRF-3 is a candidate transcription factor mediating the activation of the IFN-beta gene.

3T3 Cells↗

PubMed1998

Development of genotoxicity assay systems that use aquatic organisms.

Our aim is to develop and evaluate monitoring systems that use aquatic organisms to assess the genotoxicity of water in the field and in the laboratory. In a field study, we have shown that the micronucleus assay is applicable to freshwater and marine fishes and that gill cells are more sensitive than hematopoietic cells to micronucleus-inducing agents. Gill cells from Carassius sp. (Funa) and Zacco platypus (Oikawa) collected upstream on the Tomio River (Nara, Japan), tended to have lower micronucleus frequencies than gill cells from fish collected at the midstream of the river. Leiognathus nuchalis (Hiiragi) and Ditrema temmincki (Umitanago), small marine fishes collected periodically at Mochimune Harbor (Shizuoka, Japan), showed seasonal differences in the frequencies of micronucleated gill cells and erythrocytes; they were highest in summer. For laboratory studies, we developed a method for analyzing chromosomal aberrations and micronuclei using Rhodeus ocellatus ocellatus (rose bitterling) embryos. One day after artificial insemination (gastrula stage), we observed structural chromosomal aberrations and micronuclei in the cells of embryos grown in water containing trichloroethylene. Although more work is needed to fully assess their sensitivity, these assays show promise as a means of detecting environmental genotoxins.

Animals↗