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H Ikeda

Publications and source records attributed to H Ikeda.

At least 541 records · Page 30Linked to original sources
PubMed1996

Pioglitazone improves insulin signaling defects in skeletal muscle from Wistar fatty (fa/fa) rats.

The effects of pioglitazone, a novel antidiabetic insulin-sensitizing agent, on insulin signaling in skeletal muscles from genetically obese Wistar fatty rats and their lean littermates were studied. Increased tyrosine phosphorylation levels of insulin receptors (IRs) and insulin receptor substrate 1 (IRS-1) in response to insulin were not observed in fatty rats. Insulin-stimulated phosphatidylinositol (PI) 3-kinase activity was reduced in fatty rats. Administration of pioglitazone (3 mg/kg/day) to fatty rats for 10 or 18 days reversed the decline in the insulin-stimulated tyrosine phosphorylated IR and IRS-1 levels and the reduced insulin-stimulated PI 3-kinase activities. In contrast, insulin-stimulated tyrosine phosphorylation of IR and IRS-1 and PI 3-kinase activity in lean rats was not changed by pioglitazone. IR expression in fatty rats was down-regulated, which was not affected by pioglitazone. There was no difference between the PI 3-kinase expression levels in fatty and lean rats and pioglitazone did not change these expression levels. These results indicate that pioglitazone can correct the insulin signaling defects of Wistar fatty rats, thereby ameliorating insulin resistance.

Animals↗
PubMed1996

Hdf1, a yeast Ku-protein homologue, is involved in illegitimate recombination, but not in homologous recombination.

Hdf1 is the yeast homologue of the mammalian 70 kDa subunit of Ku-protein, which has DNA end-binding activity and is involved in DNA double-strand break repair and V(D)J recombination. To examine whether Hdf1 is involved in illegitimate recombination, we have measured the rate of deletion mutation caused by illegitimate recombination on a plasmid in an hdf1 disruptant. The hdf1 mutation reduced the rate of deletion formation by 20-fold, while it did not affect mitotic and meiotic homologous recombinations between two heteroalleles or homologous recombination between direct repeats. Hence Hdf1 participates in illegitimate recombination, but not in homologous recombination, in contrast to Rad52, Rad50, Mre11 and Xrs2, which are involved in both homologous and illegitimate recombination. The illegitimate recombination in the hdf1 disruptant took place between recombination sites that shared short regions of homology (1-4 bp), as was observed in the wild-type. Based on the DNA end-binding activity of Hdf1, we discuss models in which Hdf1 plays an important role in the late step of illegitimate recombination.

Base Sequence↗
PubMed1996

A novel homozygous mutation of the myelin Po gene producing Dejerine-Sottas disease (hereditary motor and sensory neuropathy type III).

We have previously reported that heterozygosity for myelin Po gene mutations were associated with Charcot-Marie-Tooth disease type 1B (CMT1B) or Dejerine-Sottas disease. We investigated the Po gene in a family with clinical Dejerine-Sottas disease and found two children were homozygous for a deletion of Phe 64. The parents were heterozygous first cousins with subclinical CMT1B and slow nerve conduction velocities. These results suggest that the effect of homozygous Phe 64 deletion on impairment of myelination is dosage-dependent. Clinical phenotype and/or myelin impairment may be determined both by the type of mutation and by the dosage of mutated gene.

Base Sequence↗
PubMed1996

Construction of beta-lactamase-encoding ApR gene cassettes for rapid identification of cloned genes.

We have constructed two Escherichia coli plasmids, pYK18 and pYK19, from which the BamHI, SmaI or EcoRI DNA fragments containing the ApR gene, conferring resistance to ampicillin, can be excised. The ApR cassettes have an annealing site for the sequencing primer of pUC plasmids at each end. Therefore, when the cassette is inserted into a gene, we can determine the nucleotide sequence of the gene from the insertion site using the sequencing primers of the pUC plasmids. This method is useful for identifying a cloned gene.

Ampicillin Resistance↗
PubMed1996

Tumor bed implant brachytherapy for residual carcinoma after palliative esophagectomy.

Twenty-six patients with esophageal carcinoma at stage pT4 underwent esophagectomy with lymph node dissection leaving part of the tumor in adjacent organs. Several plastic catheters were fixed to the tumor bed and led to the outside of the thorax for postoperative brachytherapy. Using these catheters, the patients underwent brachytherapy followed by external beam irradiation. The operative mortality rate was 11.5%. No serious complications resulting directly from the brachytherapy occurred. Recurrent disease was found in 17 patients, among whom only six had local recurrence. The median survival of the patients was 314 days, and the 5-year survival rate was 16.2%. Of the 10 patients at stage pT4N0, three survived more than three years after surgery. Tumor bed implant brachytherapy for residual tumor after esophagectomy is a safe and useful treatment strategy for patients with pT4 tumor, especially those without lymph node metastasis.

Aged↗
PubMed1996

A new transgenic mouse mutagenesis test system using Spi- and 6-thioguanine selections.

A new transgenic mouse mutagenesis test system has been developed for the efficient detection of point mutations and deletion mutations in vivo. The mice carry lambda EG10 DNA as a transgene. When the rescued phages are infected into Escherichia coli YG6020-expressing Cre recombinase, the phage DNA is converted into plasmid pYG142 carrying the chloramphenicol-resistance gene and the gpt gene of E. coli. The gpt mutants can be positively detected as colonies arising on plates containing chloramphenicol and 6-thioguanine. The EG10 DNA carries a chi site along with the red and gam genes so that the wild-type phages display Spi- (sensitive to P2 interference) phenotype. Mutant phages lacking both red and gam genes can be positively detected as plaques that grow in P2 lysogens of E. coli. These mutant phages are called lambda Spi-. The spontaneous gpt mutation frequencies of five independent transgenic lines were 1.7 to 3.3 x 10(-5) in bone marrow. When the mice were treated with ethylnitrosourea (single i.p. treatments with 150 mg/kg body weight; killed 7 days after the treatments), mutation frequencies were increased four- to sevenfold over the background in bone marrow. The average rescue efficiencies were more than 200,000 chloramphenicol-resistant colonies per 7.5 micrograms bone marrow DNA per packaging reaction. In contrast to gpt mutation frequencies, spontaneous Spi- mutation frequencies were 1.4 x 10(-6) and 1.1 x 10(-6) in bone marrow and sperm, respectively. No spontaneous Spi- mutants have been detected so far in spleen, although 930,000 phages rescued from untreated mice were screened. In gamma-ray-treated animals, however, induction of Spi- mutations was clearly observed in spleen, at frequencies of 1.4 x 10(-5) (5 Gy), 1.2 x 10(-5) (10 Gy), and 2.0 x 10(-5) (5O Gy). These results suggest that the new transgenic mouse "gpt delta" could be useful for the efficient detection of point mutations and deletion mutations in vivo.

Animals↗
PubMed1996

Role of superoxide anions in airway hyperresponsiveness induced by cigarette smoke in conscious guinea pigs.

To investigate the involvement of superoxide in airway hyperresponsiveness and bronchoconstriction induced by cigarette smoke (CS), we evaluated the effects of superoxide dismutase (SOD), a scavenger of superoxide anion, and apocynin, an inhibitor of superoxide anion-generating NADPH oxidase in phagocytes, on the airway responses induced by CS in conscious guinea pigs. Airway responsiveness was assessed by PC200Mch, the concentration required to produce a doubling in the baseline specific airway resistance (sRaw) to an inhaled methacholine aerosol, in nonanesthetized spontaneously breathing animals. Before being exposed to ten puffs of CS, animals inhaled either SOD (5,000 units/ml or 25,000 units/ml) or vehicle. Although SOD did not affect PC200Mch in the air control group, this agent significantly reduced the CS-induced airway hyperresponsiveness. Repeated administration of apocynin (12 mg/kg for 4 days) did not affect PC200Mch after exposure to CS. These data suggest that the superoxide from CS was involved in the airway hyperresponsiveness induced by CS, whereas phagocytic reactive oxygen species were not. The data also suggest a potential therapeutic role for antioxidants in airway hyperresponsiveness.

Acetophenones↗
PubMed1996

Cyclophosphamide-induced apoptosis induces phocomelia in the mouse.

Phocomelia (absence of upper fore and/or hind limbs) was induced in mouse fetuses using cyclophosphamide. On day 11 of gestation, pregnant mice were injected intraperitoneally with 10 ml/kg of saline containing cyclophosphamide (CP) at a dosage of 20 mg/kg body weight. On day 18, the fetuses were removed by Caesarean section from dams given CP on day 11 and were examined for external anomalies. Of 22 fetuses from CP-treated dams, 13 were dead or absorbed, but the surviving 9 fetuses were found to have phocomelia with various other external anomalies. In order to examine the direct cytotoxic effect of CP on fetal limb buds, fetuses were removed at 8, 16, 24, and 48 h after CP administration on day 11, revealing the presence of frequent pyknotic nuclei and apoptotic bodies in hematoxylin and eosin (H & E) preparations. Cell-nuclei and apoptotic bodies were frequently observed by nick end-labeling in limb buds. Transmission electron microscopy demonstrated the typical changes of apoptosis. DNA extracted from the fetal limb buds submitted to CP was analysed by agarose gel electrophoresis, showing the ladder pattern characteristic of internucleosomal cleavage. These findings suggest that cyclophosphamide causes apoptosis in mouse fetal limb buds and that this process induces the external anomalies of phocomelia.

Animals↗
PubMed1996

A retrospective analysis of different modalities for treatment of primary orbital non-Hodgkin's lymphomas.

We have reviewed 37 patients with primary orbital lymphoma, using the Ann Arbor criteria and the Working Formulation and its modification. Thirty-one patients had stage I disease, four stage II, one stage III and one stage IV. The male to female ratio was 2.7:1. There were 34 low-grade tumours (including 24 mantle zone) and three intermediate-grade. Patients were divided into three groups according to their primary treatment. Group 1: radiotherapy (17 cases); Group 2: surgery alone (13 cases); Group 3: chemotherapy (seven cases). Patients were followed up from 5 months to 24.3 years, with a mean and median of 7.6 and 6.2 years, respectively. The BMDP software package was used for survival estimation (Kaplan-Meier) and determination of prognostic variable (univariate Cox regression). Local relapse-free survival at 10 years was 100% in Group 1, 0% in Group 2 and 42% in Group 3 with a statistically significant difference (p < 0.01) in favour of radiotherapy. Statistically significant good prognostic features were: complete remission (CR) in response to initial treatment, primary radiotherapy and older age. For stage I cases, there was no difference in distant relapse-free survival in the three groups. The overall cause-specific survival for stage I patients at 10 years was 100% for each group and at 20 years was 100, 67 and 0% for Groups 1, 2 and 3. The difference between the primary radiotherapy and chemotherapy-treated groups was significant at the p = 0.08 level. Statistically significant prognostic factors were early stage, low-grade histology and primary radiotherapy. In one patient, ptosis and diplopia appeared after surgery. One case of glaucoma required enucleation, one patient suffered severe dry eye syndrome. All patients (11/11) in whom the lens received direct radiation developed cataracts of different degrees if follow-up was long enough. Cataract formation was prevented by adequate lens shielding. One patient in CR from a stage I low-grade tumour died from chemotherapy-induced marrow aplasia. Primary orbital lymphoma is an indolent, usually stage I disease, showing low to intermediate-grade histology. After biopsy the best treatment is 30 (low-grade) to 40 Gy (intermediate-grade) carefully planned, lens-sparing megavoltage radiation without adjuvant chemotherapy.

Adult↗
PubMed1996

Expression of ICAM-1 on glomeruli is associated with progression of diabetic nephropathy in a genetically obese diabetic rat, Wistar fatty.

We developed an animal model for non-insulin-dependent diabetes mellitus, a genetically obese rat strain, Wistar fatty. These rats show obesity-related features such as hyperinsulinemia and hyperlipemia, and only males develop diabetic features including hyperglycemia, glucoseuria and polyuria as they age. Histopathological study demonstrated a deposition of PAS-positive granules in the epithelial cells and a diffuse thickening of the mesangial area and moderate changes of the renal tubules. We found that ICAM-1 is expressed on the glomeruli of male Wistar fatty rats and the expression is associated with the development of nephropathy; it is weak at 5 weeks, becomes markedly strong at 15 weeks and progresses further at 29 weeks of age. We tried in vivo administration of monoclonal antibody, anti-ICAM-1 alone or together with anti-LFA-1 into male Wistar fatty rats during the period from 5 weeks to 17 weeks of age. The treatment, however, could not prevent the development of nephropathy. ICAM-1 expressed on the glomeruli of Wistar fatty rats seems not to play a key role in development of the nephropathy by mediating leukocyte infiltration. It will be a useful marker of the development of the disease.

Aging↗
PubMed1996

Aminophylline reduces cardiac ischemic pain during percutaneous transluminal coronary angioplasty.

OBJECTIVES: We investigated the effect of aminophylline, an antagonist of the adenosine P1 receptor, on cardiac pain experienced during percutaneous transluminal coronary angioplasty (PTCA). BACKGROUND: Adenosine may mediate cardiac pain because the administration of adenosine provokes cardiac pain like angina. However, it is not known whether endogenous adenosine released during myocardial ischemia is responsible for cardiac pain. METHODS: This was a single-blind, placebo-controlled randomized study. Of 21 men with stable effort angina with one-vessel coronary artery disease who underwent balloon inflation four times during PTCA, 11 received intravenously administered aminophylline before the fourth balloon inflation and the other 10 were given saline solution. The severity of cardiac pain based on the pain score and ST segment elevation on standard surface and intracoronary electrocardiograms were assessed. RESULTS: All patients experienced cardiac pain during balloon inflation. Aminophylline significantly prolonged the duration of both the symptom-free interval (from 42 +/- 13 to 64 +/- 27 s, mean +/- SD, p < 0.05) and inflation time (from 79 +/- 23 to 103 +/- 20 s, p < 0.05), and it significantly reduced the pain score from 7.6 +/- 1.4 to 4.6 +/- 2.3 (p < 0.01). However, aminophylline did not affect ST segment elevation. Saline solution did not affect any of these variables. Balloon diameter and pressure were not different between the third and the fourth inflation in either group. CONCLUSIONS: Aminophylline significantly reduced the severity of cardiac pain during PTCA without affecting ST segment elevation. These findings suggest that the activation of P1 receptors by endogenous adenosine may be partially responsible for cardiac pain during ischemia.

Aminophylline↗
PubMed1996

Expanded polyglutamine in the Machado-Joseph disease protein induces cell death in vitro and in vivo.

Recently, we identified a novel gene, MJD1, which contains an expanded CAG triplet repeat in Machado-Joseph disease. Here we report the induction of apoptosis in cultured cells expressing a portion of the MJD1 gene that includes the expanded CAG repeats. Cell death occurs only when the CAG repeat is translated into polyglutamine residues, which apparently precipitate in large covalently modified forms. We also created ataxic transgenic mice by expressing the expanded polyglutamine stretch in Purkinje cells. Our results demonstrate the potential involvement of the expanded polyglutamine as the common aetiological agent for inherited neurodegenerative diseases with CAG expansions.

Animals↗
PubMed1996

DNA nicking by Escherichia coli topoisomerase IV with a substitution mutation from tyrosine to histidine at the active site.

BACKGROUND: Escherichia coli topoisomerase IV is a type II topoisomerase composed of ParC and ParE subunits and plays a major role in the decatenation of replicated molecules. The reaction with type II topoisomerases involves the cutting through transesterification between an active-site tyrosine and a DNA phosphodiester bond and a rejoining of cleaved DNA. RESULTS: To genetically analyse the mechanism of this reaction, we isolated dominant-negative topoisomerase IV mutants. In one of them, the parC10 mutant, there was a substitution by histidine of the active-site tyrosine. Purified mutant topoisomerase IV did not show normal DNA cutting activity but retained DNA nicking activity, even in the absence of ATP. The DNA ends of the product were not covalently bound to the ParC subunits, suggesting that the DNA is not cut via transesterification but by hydrolysis. CONCLUSIONS: We have shown genetically that the 120th tyrosine residue is important for the DNA cutting step in the topoisomerase reaction. The 120th amino acid residue, tyrosine or histidine, appears to be activated and the histidine residue forces the hydrogen-bonded water to attack the phosphoryl group of the DNA in hydrolysis, while the tyrosine residue directly attacks the phosphoryl group during transesterification.

Base Sequence↗