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T Hirano

Publications and source records attributed to T Hirano.

At least 271 records · Page 15Linked to original sources
PubMed1999

Requirement for mitogen-activated protein kinase in cerebellar long term depression.

The mitogen-activated protein kinase (MAPK) cascade has been shown to play an essential role in regulation of cell proliferation and cell differentiation. Although mammalian MAPKs are most abundantly expressed in postmitotic and terminally differentiated neuronal cells, their function in the central nervous system is still largely undefined. We present evidence here for a role of the MAPK cascade in cerebellar long term depression (LTD), which is a widely studied form of synaptic plasticity in mammalian brain. In cultured Purkinje cells, LTD is known to be induced by iontophoretic application of glutamate and depolarization of Purkinje cells. We found that MAPK was activated in Purkinje cells by treatment of primary cultures of rat embryonic cerebella with glutamate and a depolarization-inducing agent, KCl. Application of PD98059, a specific inhibitor of MAPK kinase (MAPKK/MEK), inhibited both the activation of MAPK and the induction of LTD in Purkinje cells. Furthermore, the induction of LTD was completely blocked by introduction into Purkinje cells of anti-active MAPK antibody, which was found to specifically and potently inhibit the activity of MAPK. These results suggest that postsynaptic activation of the MAPK cascade is essential for the induction of cerebellar LTD.

Animals↗
PubMed1999

Co-localization of mitochondrial and double minute DNA in the nuclei of HL-60 cells but not normal cells.

In an attempt to isolate genes located on double minute (Dmin) DNA in HL-60 cells, we prepared DNA probe from purified micronuclei. Micronucleation was induced in HL-60 cells by treatment with hydroxyurea. Screening of a cDNA library unexpectedly produced a number of clones containing mitochondrial DNA (mtDNA) sequences. Here, we show that amplified mtDNA sequences were localized in nuclei and micronuclei of HL-60 and COLO 320DM cells, but not in nuclei of WI-38 normal human fibroblasts or peripheral blood T-cells. To unequivocally demonstrate the presence of mtDNA inside of nuclei and micronuclei, we obtained tomographic fluorescence in situ hybridization (FISH) images of mtDNA by confocal microscopy of consecutive sections of paraformaldehyde (PFA)-fixed material. We also located mtDNA in nuclear buds and purified micronuclei. Dmin DNA and mtDNA were always located at similar sites. The mechanisms of nuclear retention of mtDNA and Dmin DNA and the resulting influence on tumorigenesis are discussed.

Cell Cycle↗
PubMed1999

Gab-family adapter proteins act downstream of cytokine and growth factor receptors and T- and B-cell antigen receptors.

We previously found that the adapter protein Gab1 (110 kD) is tyrosine-phosphorylated and forms a complex with SHP-2 and PI-3 kinase upon stimulation through either the interleukin-3 receptor (IL-3R) or gp130, the common receptor subunit of IL-6-family cytokines. In this report, we identified another adapter molecule (100 kD) interacting with SHP-2 and PI-3 kinase in response to various stimuli. The molecule displays striking homology to Gab1 at the amino acid level; thus, we named it Gab2. It contains a PH domain, proline-rich sequences, and tyrosine residues that bind to SH2 domains when they are phosphorylated. Gab1 is phosphorylated on tyrosine upon stimulation through the thrombopoietin receptor (TPOR), stem cell factor receptor (SCFR), and T-cell and B-cell antigen receptors (TCR and BCR, respectively), in addition to IL-3R and gp130. Tyrosine phosphorylation of Gab2 was induced by stimulation through gp130, IL-2R, IL-3R, TPOR, SCFR, and TCR. Gab1 and Gab2 were shown to be substrates for SHP-2 in vitro. Overexpression of Gab2 enhanced the gp130 or Src-related kinases-mediated ERK2 activation as that of Gab1 did. These data indicate that Gab-family molecules act as adapters for transmitting various signals.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Both Stat3-activation and Stat3-independent BCL2 downregulation are important for interleukin-6-induced apoptosis of 1A9-M cells.

A unique subclone of a bone marrow-derived stromal cell line, BMS2.4, produces soluble factors that inhibit proliferation of several types of hematopoietic cell lines. An understanding of these molecules may be informative about negative regulatory circuits that can potentially limit blood cell formation. We used expression cloning to identify interleukin-6 (IL-6) as one factor that suppressed growth of a pre-B-cell variant line, 1A9-M. Moreover, IL-6 induced macrophage-differentiation and apoptosis of 1A9-M cells. During this process, IL-6 downregulated expression of BCL2 in 1A9-M cells and stimulated BCL-XL expression, but had no effect on p53, Bax, or Bak gene expression. Mechanisms for transduction of IL-6-induced signals were then evaluated in IL-6-stimulated 1A9-M cells. Whereas the signal transducer and activator of transcription 3 (Stat3) was phosphorylated and activated, there was no effect on either Stat1 or Stat5. The importance of BCL2 and Stat3 on IL-6-induced macrophage-differentiation and apoptosis was studied with 1A9-M cells expressing human BCL2 or a dominant-negative form of Stat3, respectively. IL-6-induced apoptosis, but not macrophage-differentiation, was blocked by continuously expressed BCL2. A dominant-negative form of Stat3 inhibited both macrophage-differentiation and apoptosis induced by IL-6. However, diminished Stat3 activity did not prevent IL-6-induced downregulation of the BCL2 gene. Therefore, activation of Stat3 is essential for IL-6-induced macrophage-differentiation and programmed cell death in this model. Whereas overexpression of BCL2 abrogates the apoptotic response, Stat3-independent signals appear to downregulate expression of the BCL2 gene.

Apoptosis↗
PubMed1999

Molecular cloning of CLC chloride channels in Oreochromis mossambicus and their functional complementation of yeast CLC gene mutant.

We have cloned two members of the CLC chloride channel family (OmCLC-3 and OmCLC-5) from gill cDNA libraries of the euryhaline tilapia Oreochromis mosammbicus. At the amino acid level, OmCLC-3 is 90.5% identical to rat CLC-3 and OmCLC-5 is 79.2% identical to rat CLC-5. Ribonuclease protection assay revealed that OmCLC-5 was mainly expressed in the gill, kidney, and intestine in both freshwater- (FW) and seawater- (SW) adapted tilapia. Although the mRNA of OmCLC-3 was broadly expressed in tissues of FW- and SW-adapted tilapia, the most intense signals were observed in the gill, kidney, intestine, and brain. Injection of OmCLC-3 and OmCLC-5 cRNAs into Xenopus oocytes did not elicit chloride currents, but these clones did functionally complement the gef1 phenotype of YPH250(gef), a yeast strain in which a single CLC channel (GEF1) has been disrupted by homologous recombination. These results clearly indicated that CLC channels closely related to the mammalian CLC-3, -4, and -5 subfamily exist also in tilapia and that OmCLC-3 and OmCLC-5 function as intracellular chloride channels.

Amino Acid Sequence↗
PubMed1999

Novel peptide inhibitor of ecto-ADP-ribosyl cyclase of bone marrow stromal cell antigen-1 (BST-1/CD157).

cADP-ribose, which is produced by ecto-ADP-ribosyl cyclase of CD38 or bone marrow stromal cell antigen-1 (BST-1), is a key regulator of Ca2+-induced calcium release in an Ins(1,4,5)P3-independent manner. In the present study, we have identified a specific peptide inhibitor for ADP-ribosyl cyclase of BST-1. A 15-mer random peptide phage library was screened with a soluble form of BST-1 expressed in baculovirus-infected insect cells. After biopanning, two potent sequences reactive towards BST-1 were isolated. The two synthetic peptides corresponding to the identified sequences were shown to antagonize each other's ability to inhibit the binding of the two isolated phage to BST-1, suggesting that they bind at a common binding site on BST-1. One of the peptides (SNP-1) was shown to inhibit ADP-ribosyl cyclase activity of BST-1 in an uncompetitive manner with a Ki value of 180+/-40 nM (n=3). SNP-1 also inhibited cyclic ADP-ribose hydrolase activity of BST-1 dose-dependently. Selected phage did not cross-react with a soluble form of CD38. SNP-1 did not show any inhibitory effect on ADP-ribosyl cyclase activity of CD38, and therefore this peptide inhibitor will be useful to serve as a starting tool for understanding the roles of these intriguing ecto-enzymes. This is the first report of a specific ADP-ribosyl cyclase inhibitor.

ADP-ribosyl Cyclase↗
PubMed1999

STAT3 is required for the gp130-mediated full activation of the c-myc gene.

The signal transducers and activators of transcription (STAT) family members have been implicated in regulating the growth, differentiation, and death of normal and transformed cells in response to either extracellular stimuli, including cytokines and growth factors, or intracellular tyrosine kinases. c-myc expression is coordinately regulated by multiple signals in these diverse cellular responses. We show that STAT3 mostly mediates the rapid activation of the c-myc gene upon stimulation of the interleukin (IL)-6 receptor or gp130, a signal transducing subunit of the receptor complexes for the IL-6 cytokine family. STAT3 does so most likely by binding to cis-regulatory region(s) of the c-myc gene. We show that STAT3 binds to a region overlapping with the E2F site in the c-myc promoter and this site is critical for the c-myc gene promoter- driven transcriptional activation by IL-6 or gp130 signals. This is the first identification of the linkage between a member of the STAT family and the c-myc gene activation, and also explains how the IL-6 family of cytokines is capable of inducing the expression of the c-myc gene.

Animals↗
PubMed1999

Isolation and cDNA cloning of somatolactin in rabbitfish (Siganus guttatus).

We report the isolation and cDNA cloning of somatolactin (SL) from rabbitfish, Siganus guttatus. Rabbitfish SL was isolated from an alkaline extract of the pituitary glands by gel filtration chromatography on Sephadex G-100 and reversed-phase high-performance liquid chromatography. SL was monitored by immunoblotting with flounder SL antiserum. The preparation (yield: 0.86 mg/g wet tissues) contained two immunoreactive bands of 24 and 28 kDa on SDS-PAGE. Overlapping partial cDNA clones corresponding to teleost SLs were amplified by PCR from single-strand cDNA from pituitary glands. Excluding the poly(A) tail, rabbitfish SL cDNA is 1605 bp long. It contains a 693-bp open reading frame encoding a signal peptide of 24 amino acids (aa) and a mature protein of 207 aa. Rabbitfish SL has two possible N-glycosylation sites at positions 11 and 121 and seven half Cys residues. The deduced amino acid sequence shows over 80% identity with those of advanced teleosts like sea bream, red drum, and flounder, 76% with the salmonids, 57% with the eel, and 46% with the goldfish SL.

Amino Acid Sequence↗
PubMed1999

Cytokine suppressive agent improves survival rate in rats with acute pancreatitis of closed duodenal loop.

This study was designed to evaluate the possible role of cytokines (IL-1 and TNF-alpha) in the pathogenesis of acute pancreatitis in the early stage of the disease and to evaluate the protective effect of the cytokine suppressive agent, FR167653, against pancreatic injuries. Acute pancreatitis was induced in rats by closed duodenal loop. However, the free passage for the gastrointestinal contents was maintained by inserting the tube into the duodenum. In this model, the survival rate was significantly decreased as compared with the control sham-operated rats at 48 h after induction of pancreatitis. Marked hyperamylasemia and a significant increase in pancreatic water and trypsin contents were observed at 24 h after induction of pancreatitis. Pancreatic subcellular redistribution of lysosomal enzyme cathepsin B from the lysosomal fraction to the zymogen fraction was also observed. However, treatment with FR167653 at a dose of 1.5 mg/kg (four times, every 6 h after induction of pancreatitis) significantly prevented all these pancreatic injuries, improving the survival rate. These results indicate that cytokines such as IL-1 and TNF-alpha may be involved in the pathogenesis of acute pancreatitis in the early stage of the disease, and that a cytokine-suppressive agent might be of therapeutic value for the treatment of acute pancreatitis.

Acute Disease↗
PubMed1999

Prevention of hepatic ischemia-reperfusion injury by SOD-DIVEMA conjugate.

A protective effect of the SOD (superoxide dismutase)-DIVEMA (divinyl ether and maleic anhydride) conjugate on I-R (ischemia-reperfusion) liver injury was demonstrated. Twenty minutes of normothermic hepatic ischemia was induced by clamping the portal triad of Sprague-Dawley rats. Five minutes before the end of ischemia, SOD, SOD-DIVEMA, or NaCl (0.9%) was given intravenously. Using intravital fluorescence microscopy, hepatic microvascular perfusion was analyzed before ischemia and repeatedly during the 120-min reperfusion period. SOD-DIVEMA significantly restored the sinusoidal perfusion rate (control, 98.0 +/- 0.5; NaCl, 65.5 +/- 7. 7; SOD, 81.5 +/- 8.2; SOD-DIVEMA, 95.8 +/- 0.7%) and reduced the number of leukocytes stagnant in acini (control, 4.4 +/- 0.9; NaCl, 36.6 +/- 6.3; SOD, 27.7 +/- 6.8; SOD-DIVEMA, 12.3 +/- 3.3 cells/lobule) and adherent in postsinusoidal venules (control, 55.0 +/- 24; NaCl, 417 +/- 63; SOD, 253 +/- 58; SOD-DIVEMA, 40.0 +/- 14 cells/mm2). In addition, SOD-DIVEMA maintained postischemic hepatocellular integrity. The SOD-DIVEMA-treated group revealed higher serum SOD enzyme activity compared to the SOD group after 120 min of reperfusion (SOD-DIVEMA, 33.0 +/- 5.9; SOD, 8.6 +/- 3.1 U/ml). The beneficial effect of SOD-DIVEMA was most prominent after 120 min of reperfusion, indicating a longer intravascular half-life of SOD-DIVEMA.

Animals↗
PubMed1999

A group I intron in the 18S ribosomal DNA from the parasitic fungus Isaria japonica.

The nucleotide sequence of the 18S rDNA coding gene in the ascomycetes parasitic fungus Isaria japonica contains a group I intron with a length of 379 nucleotides. The identification of the DNA sequence as a group I intron is based on its sequence homology to other fungal group I introns. Its group I intron contained the highly conserved sequence elements P, Q, R, and S found in other group I introns. Surprisingly, the intron sequence of I. japonica is more similar to that of Ustilago maydis than to the one found in Sclerotinia sclerotiorum. This is in contrast to the sequence identity found on the neighboring rDNA. This is an interesting finding and suggests a horizontal transfer of group I intron sequences.

Ascomycota↗
PubMed1999

Dietary restriction reduces the prevalence of osteonecrosis of the caput femoris in spontaneously hypertensive rats.

We investigated the effects of dietary restriction (DR), an experimental intervention known to suppress several strain-specific diseases, on the prevalence of osteonecrosis of the caput femoris in spontaneously hypertensive rats (SHR). At 6 weeks of age, the food intake of DR rats was restricted to 65% of the mean intake of control rats fed ad libitum (AL). Acute osteonecrosis of the caput femoris without reparative tissue response (RTR) was observed at 10 and 15 weeks in both DR and AL groups; no such acute lesion was seen at 20 and 30 weeks. The prevalence of osteonecrosis, osteonecrosis with/without reparative tissue response was significantly reduced in DR rats at 15 and 20 weeks, but not at 10 weeks. DR reduced the body weight by 30% and the length of the femur by 10%. Ossification of the caput femoris, known to be delayed in AL rats compared with Wistar Kyoto rats, was also restored by DR. Our results showed that dietary restriction reduced the prevalence of osteonecrosis and modulated the mechanical factors involved in the lesion. They also indicate that utilization of dietary restriction is a useful research tool for investigating the underlying mechanisms of osteonecrosis of the caput femoris in SHR.

Acute Disease↗
PubMed1999

Wear of alumina ceramics prosthesis.

To investigate the process of wear in the total knee prosthesis consisting of alumina ceramics (Al-ceramics) and ultra-high molecular weight polyethylene (UHMWP) in vivo, we observed the fine structures of the articular surface of the prostheses used for four patients with osteosarcoma of the distal femur. We also examined the wear debris in the surrounding soft tissues. The prostheses were extracted at autopsy between 13 and 48 months after surgery. An increase of pores, indicating where Al-ceramics grains fell off, and many streaks on the UHMWP running parallel to the gliding direction of the joint were observed on the articular surface. The streaks had similar widths to the Al-ceramics grains. Al-ceramics debris was detected in the soft tissues around the joint mixed with UHMWP debris. We concluded that the wear of UHMWP in Al-ceramics prosthesis was promoted by interposition of Al-ceramics debris.

Adolescent↗
PubMed1999

Large-dose ascorbic acid administration suppresses the development of arthritis in adjuvant-infected rats.

We performed animal experiments to test the hypothesis that active oxygen species (AOS) play a major role in adjuvant-induced arthritis in rats and to determine whether large-dose ascorbic acid administration would suppress the development of arthritis, reducing the level of damaging AOS in the same animal model. Arthritis was induced in male Lewis rats by adjuvant injection into the base of the tail. Ascorbic acid at doses of 0.5, 1.0, and 2.0 g/kg body weight (BW) was injected intraperitoneally twice each week for 3 weeks (9 rats per group). The BW, hind paw edema, and arthritis score of the extremities were monitored during the period. On day 21, synovial tissues obtained from the ankle joints were examined histologically and for the activity of superoxide dismutase (SOD). The SOD activity in the red blood cells (RBC) was also measured. The arthritic control rats showed significant increases in paw volume and arthritis score from day 11. These changes were dose-dependently reduced by ascorbic acid administration. The infiltration of inflammatory cells into the synovial tissues was markedly decreased by ascorbic acid. The increases in SOD activities produced by the adjuvant injection were significantly reduced in both the synovium and the RBC at ascorbic acid doses of 1.0 and 2.0 g/kg BW. In conclusion, large-dose ascorbic acid administration reduced the increases in hind paw inflammatory edema, arthritis in the extremities, and infiltration of the inflammatory cells into the synovial tissue in the adjuvant-induced arthritis rats. Since these anti-arthritic effects were associated with a decrease in SOD activities in both the synovium and RBC, the decrease in SOD activity could be one of the mechanisms underlying the suppressive effects of large-dose ascorbic acid on the development of arthritis in this animal model, inhibiting the damaging AOS.

Animals↗
PubMed1999

Adenoma arising from the cystic duct and extending to the confluence of the extrahepatic biliary tract.

We describe a rare case of adenoma with a few foci of severe atypia arising from the cystic duct in a 68-year-old woman, initially diagnosed by the presence of intracholecystic tumefactive sludge on abdominal ultrasonography. Endoscopic retrograde cholangiography (ERC) disclosed a tuberous filling defect at the orifice of the cystic duct. Pathology examination of the biopsied specimen obtained from ERC disclosed not a cancerous but an adenomatous lesion. Macroscopically, the resected specimen showed a superficially spreading and shallowly elevated lesion extending from the cystic duct to the common bile duct. Although a few sporadic foci of severe atypia were observed, microscopy did not reveal any cancer findings, but confirmed the tumorous lesion as benign adenoma, showing mild-to-moderate atypia. Postoperative immunohistochemistry revealed no expression of p53 protein. We briefly refer to the rarity of adenoma in the biliary tract and discuss the difficulty of differential diagnosis of neoplastic lesions in the extrahepatic biliary tract.

Aged↗
PubMed1999

Targeting of superoxide dismutase to the liver results in anti-inflammatory effects in rats with fibrotic livers.

BACKGROUND/AIMS: The rapid clearance from plasma and the limited uptake of superoxide dismutase (SOD) in the liver hampers the effectiveness of this enzyme in liver diseases. We therefore compared the pharmacokinetics and in vivo efficacy of SOD with two modified forms of this protein: SOD coupled to the copolymer DIVEMA and mannosylated-SOD. METHODS: Reactive oxygen scavenging activity of SOD conjugates was tested in livers of bile duct ligated rats. Intrahepatic production of reactive oxygen species (ROS) and neutrophil infiltration were studied immunohistochemically and related to the organ and cellular distribution of radiolabeled SOD conjugates. RESULTS: Native SOD was rapidly cleared from the circulation and accumulated in renal tubuli. The enzyme had no effect on the intrahepatic ROS production. Covalent attachment of SOD to DIVEMA yielded a polyanionic conjugate with a prolonged elimination half-life compared to native SOD. In contrast to native SOD, DIVEMA-SOD was taken up by the liver via scavenger receptors. Mannosylation of SOD (Man-SOD) resulted in a conjugate that was rapidly cleared from the blood. This Man-SOD was taken up by non-parenchymal liver cells. The pharmacokinetics of SOD and its derivatives were similar in normal and bile duct ligated rats. Efficacy studies with Man-SOD revealed only a slight decrease in intrahepatic ROS production. However, DIVEMA-SOD exhibited a potent inhibitory effect on ROS production in the liver. Nearly complete ROS-scavenging activity was observed in the portal areas. CONCLUSIONS: Considering the prolonged half-life, the increased delivery of SOD to the target cells, and the concomitant increased effectiveness, application of DIVEMA-SOD seems a promising new approach to attenuate intrahepatic inflammatory processes.

Animals↗