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T Imamura

Publications and source records attributed to T Imamura.

At least 235 records · Page 13Linked to original sources
PubMed1997

TGF-beta receptor-mediated signalling through Smad2, Smad3 and Smad4.

Smad family members are newly identified essential intracellular signalling components of the transforming growth factor-beta (TGF-beta) superfamily. Smad2 and Smad3 are structurally highly similar and mediate TGF-beta signals. Smad4 is distantly related to Smads 2 and 3, and forms a heteromeric complex with Smad2 after TGF-beta or activin stimulation. Here we show that Smad2 and Smad3 interacted with the kinase-deficient TGF-beta type I receptor (TbetaR)-I after it was phosphorylated by TbetaR-II kinase. TGF-beta1 induced phosphorylation of Smad2 and Smad3 in Mv1Lu mink lung epithelial cells. Smad4 was found to be constitutively phosphorylated in Mv1Lu cells, the phosphorylation level remaining unchanged upon TGF-beta1 stimulation. Similar results were obtained using HSC4 cells, which are also growth-inhibited by TGF-beta. Smads 2 and 3 interacted with Smad4 after TbetaR activation in transfected COS cells. In addition, we observed TbetaR-activation-dependent interaction between Smad2 and Smad3. Smads 2, 3 and 4 accumulated in the nucleus upon TGF-beta1 treatment in Mv1Lu cells, and showed a synergistic effect in a transcriptional reporter assay using the TGF-beta-inducible plasminogen activator inhibitor-1 promoter. Dominant-negative Smad3 inhibited the transcriptional synergistic response by Smad2 and Smad4. These data suggest that TGF-beta induces heteromeric complexes of Smads 2, 3 and 4, and their concomitant translocation to the nucleus, which is required for efficient TGF-beta signal transduction.

Activin Receptors, Type I↗
PubMed1997

Functional importance of heat shock protein 90 associated with insulin receptor on insulin-stimulated mitogenesis.

The role of stress proteins on the function of insulin receptor is not well understood. In the rat-1 fibroblasts overexpressing human insulin receptors, heat shock protein (Hsp) 90 was co-immunoprecipitated with insulin receptors and the association was not affected by insulin stimulation. A GST-fusion protein containing the intracellular insulin receptor beta subunit was associated with Hsp 90 in vitro, suggesting the direct interaction of this protein with insulin receptor beta-subunit. Furthermore, microinjection of anti-Hsp 90 antibody into these cells completely inhibited insulin-stimulated mitogenesis. However, neither epidermal growth factor-stimulated nor serum-stimulated mitogenic signal in the cells was affected by the antibody microinjection. These results suggest that Hsp 90 constitutively binds to insulin receptor beta-subunit, which may be necessary for insulin signaling in mitogenesis.

Animals↗
PubMed1997

Activation of blood coagulation factor X by arginine-specific cysteine proteinases (gingipain-Rs) from Porphyromonas gingivalis.

The effect of two arginine-specific cysteine proteinases (gingipain Rs) from Porphyromonas gingivalis, a causative bacterium of adult periodontitis, on human blood coagulation was investigated. Activated partial thromboplastin time and prothrombin time were shortened by these proteinases, with a 95-kDa gingipain R containing adhesin domains being 5-fold more efficient in comparison to a 50-kDa gingipain R containing the catalytic domain alone. The 50-kDa enzyme reduced each coagulation time in several plasmas deficient in various coagulation factors, while it was ineffective in factor X-deficient plasma unless reconstituted with this protein. Each proteinase activated factor X in a dose- and time-dependent manner, with Michaelis constants (Km) being found to be lower than the normal plasma factor X concentration, strongly suggesting that factor X activation by gingipain Rs, especially the 95-kDa form which is strongly activated by phospholipids, could occur in plasma. This is the first report of factor X activation by bacterial proteinases and indicates that the gingipain Rs could be responsible for the production of thrombin and, indirectly, with the generation of prostaglandins, interleukin-1, etc., which have been found to be associated with the development of periodontitis induced by P. gingivalis infections. Furthermore, the data support the hypothesis that induction of blood coagulation by bacterial proteinases may be a causative agent in the pathogenesis of disseminated intravascular coagulation in sepsis.

Adhesins, Bacterial↗
PubMed1997

Overexpression of resistance-related proteins (metallothioneins, glutathione-S-transferase pi, heat shock protein 27, and lung resistance-related protein) in osteosarcoma. Relationship with poor prognosis.

BACKGROUND: The prognosis for patients with osteosarcoma has improved over the past 20 years, mainly due to developments in chemotherapy. Some proteins have been reported to show drug resistance. Theoretically, overexpression of some of these proteins makes treatment difficult, leading to poorer outcome. METHODS: Specimens taken from conventional osteosarcomas of the extremity bones from 60 patients younger than 30 years were used. In all cases, preoperative oncostatic chemotherapy was undertaken after biopsy. If available, biopsy specimens were also used for sequential comparison. Among resistance-related proteins, expression of metallothioneins (MTs), glutathione-S-transferase pi (GST pi), heat shock protein 27 (Hsp27), and lung resistance-related protein (LRP) was evaluated immunohistochemically in paraffin sections. The log rank test was used for univariate analysis and the Cox regression model for multivariate analysis. RESULTS: At biopsy, only overexpression of Hsp27 was associated with poor prognosis. At surgery, a relationship was observed between poor prognosis and overexpression of GST pi, Hsp27, and LRP. Groups overexpressing one protein tended to overexpress another. Overexpression of these proteins in surgical specimens also correlated with histologic response to preoperative chemotherapy and clinical stage. In multivariate analysis, Hsp27 overexpression at biopsy was an independent prognostic factor. CONCLUSIONS: Inherent overexpression of Hsp27 is independently related to poor outcome in osteosarcoma patients. Overexpression of GST pi, Hsp27, and LRP at surgery might be associated with failure of preoperative chemotherapy. Control of the expression of these proteins may improve the outcome for patients with osteosarcoma.

Adolescent↗
PubMed1997

Death attributed to the toxic interaction of triazolam, amitriptyline and other psychotropic drugs.

A 71-year-old man was found dead in a car into which exhaust fumes had been introduced. His wife who was in the same car recovered consciousness following hospitalization. She claimed that they had both attempted suicide by taking a large number of sleeping pills. Autopsy revealed no significant external injuries or medical disorders that would have led to the husband's death. The concentrations of alcohol and carbon-monoxide hemoglobin in his whole blood were 0.26 mg/ml and < 10%, respectively. Therefore, poisoning by carbon monoxide from the exhaust fumes was ruled out, and further toxicological examinations were undertaken. Triazolam, pentobarbital, amitriptyline and bromazepam were all detected in the tissues of the victim; whole blood concentrations were 45.60, 386.4, 521.2 and 166.7 ng/g, respectively. Triazolam (7.350 ng/g) and pentobarbital (288.2 ng/g) were also detected in the whole blood of the wife, collected 17 h after admission to hospital. When evaluating these results in the light of existing literature, we concluded that the victim and his wife had indeed attempted suicide by taking triazolam and pentobarbital. However, only the man had died of triazolam poisoning due to its apparently lethal combination with amitriptyline and other psychotropic drugs which had been prescribed to treat his depression.

Aged↗
PubMed1997

Rat liver 4S-benzo[a]pyrene-binding protein is distinct from glycine N-methyltransferase.

Rat liver 4S-benzo[a]pyrene-binding protein (BAP) was reported to be identical to the subunit (Mr 32,500) of the tetrameric glycine N-methyltransferase (GNMT). We have reevaluated this study. When a liver cytosol was subjected to Sephacryl S-200 gel permeation chromatography, enzyme activity as well as cross-reactivity with anti-GNMT antibody were found only at the elution position of the purified GNMT. Chromatograph of the cytosol pretreated with [3H]benzo[a]pyrene showed two peaks in the void volume and at the position of an approximate Mr of 40,000. The latter, corresponding to the 4 S BAP, did not cross-react with the anti-GNMT antibody. An extract of nuclei in which GNMT was proposed to act as a mediator of cytochrome P4501A1 gene expression contained the tetrameric GNMT but no binding activity. The lung, in which no GNMT mRNA occurred, had the 4 S BAP. Extracts of Escherichia coli and COS-7 cells expressing large amounts of GNMT showed no 4 S BAP. These findings suggest that the 4 S BAP is distinct from the subunit of GNMT.

Aldehyde Dehydrogenase↗
PubMed1997

Functional importance of Shc tyrosine 317 on insulin signaling in Rat1 fibroblasts expressing insulin receptors.

Shc is phosphorylated on Tyr-317, which serves as a docking site for Grb2. To investigate the specific role of Shc phosphorylation and Shc.Grb2 coupling on insulin signaling, we generated expression vectors for wild-type (WT-Shc) and a mutant Shc with a Tyr-317 --> Phe substitution (317Y/F-Shc) and stably transfected them into Rat1 fibroblasts expressing insulin receptors (HIRc). From different clonal cell lines, cells expressing 10 times greater amounts of WT-Shc or 317Y/F-Shc compared with endogenous Shc were chosen for analysis of insulin signaling. Insulin-induced Shc phosphorylation and subsequent association with Grb2 was enhanced in WT-Shc cells. Because of competition between Shc and IRS-1 for interaction with the insulin receptor, insulin-stimulated tyrosine phosphorylation of IRS-1 was decreased in WT-Shc cells compared with that in HIRc cells. Likewise, reduction of endogenous Shc expression by antisense Shc mRNA resulted in increased insulin stimulation of IRS-1 phosphorylation. Although 317Y/F-Shc was also able to interact with insulin receptor, decreased amounts of Shc phosphorylation and Shc association with Grb2 were observed in 317Y/F-Shc cells, indicating that 317Y/F-Shc functions as a dominant-negative mutant. The kinetics of mitogen-activated protein (MAP) kinase activation closely paralleled the kinetics of Shc phosphorylation. Thus, insulin stimulation of MAP kinase activation occurred more rapidly and was prolonged in WT-Shc cells, while the activation was delayed and transient in 317Y/F-Shc cells compared with that in HIRc cells. Importantly, WT-Shc cells displayed enhanced sensitivity to insulin stimulation of thymidine and bromodeoxyuridine incorporation, whereas the sensitivity was decreased in 317Y/F-Shc cells. These results indicate that Shc Tyr-317 phosphorylation plays an important role, via coupling with Grb2 and competition with IRS-1, in signal transduction to MAP kinase by insulin, ultimately leading to mitogenesis in Rat1 fibroblasts.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Sensitive determination of sulpiride in human plasma by high-performance liquid chromatography.

We developed a simple, sensitive and reliable method for the determination of sulpiride, a specific antipsychotic drug, in human plasma using high-performance liquid chromatography. A structurally related benzamide, tiapride, was used as the internal standard. A Sep-Pak C18 cartridge was used to extract a sample from 1 ml of plasma. The extract was dissolved in methylene chloride, and then back-extracted with 0.01 M hydrochloric acid. The aqueous layer was put on a octadecylsilica column with a mobile phase of 50% acetonitrile in 0.01 M phosphate buffer (pH 3.0). A fluorescence detector with excitation at 300 nm and emission at 365 nm was used for detection. The calibration curve was linear in the concentration range of 10-1500 ng/ml, and the lower limit of detection was 1 ng/ml. We used this method to examine plasma levels of sulpiride in 14 inpatients being treated with sulpiride for 6 months. The determined plasma levels were 70.1-1121.2 ng/ml, and the correlation between daily dose and plasma concentration was positive. This simple, reliable method is expected to be put to good use in forensic and hospital laboratories.

Adult↗
PubMed1997

Selective determination of sultopride in human plasma using high-performance liquid chromatography with ultraviolet detection and particle beam mass spectrometry.

We developed a sensitive and selective method for determining levels of sultopride, a neuroleptic drug of the substituted benzamide, in human plasma using high-performance liquid chromatography (HPLC) combined with UV detection and particle beam mass spectrometry (PBMS). Sultopride was extracted with tert.-butylmethyl ether using a salting-out technique. Tiapride served as an internal standard (I.S.). Sultopride and I.S. were separated by HPLC on a silica column with a mobile phase of acetonitrile-0.1 M ammonium acetate (94:6, v/v). The calibration curves were linear over the concentration range from 5 to 1000 ng/ml by HPLC with UV detection and from 10 to 1000 ng/ml with PBMS detection. The limit of quantitation was 5 ng/ml with UV detection and 10 ng/ml with PBMS detection. The absolute recovery was 92% and the within-day coefficients of variation were 2.9-7.1% at plasma concentrations from 50 to 500 ng/ml, determined by HPLC with UV detection. Using this method, we measured the plasma concentrations of sultopride with replicate analyses in four hospitalized patients and steady-state plasma levels were determined to be 161.6 +/- 30.8, 321.1 +/- 93.7, 726.5 +/- 143.1 and 1273.6 +/- 211.2 ng/ml, respectively.

Adult↗
PubMed1997

Identification of Smad2, a human Mad-related protein in the transforming growth factor beta signaling pathway.

Transforming growth factor-beta (TGF-beta) superfamily members are multifunctional cytokines that exert their effects via heteromeric complexes of two distinct serine and threonine kinase receptors. Drosophila mothers against decapentaplegic and related genes in Caenorhabditis elegans, Xenopus, and mammals were shown to function downstream in the intracellular signaling pathways of TGF-beta superfamily members. Here we report the cloning of a Mad-related protein, termed Sma- and Mad-related protein 2 (Smad2). TGF-beta stimulated the phosphorylation and nuclear translocation of Smad2 in nontransfected Mv1Lu cells. In addition, we demonstrated that TGF-beta and activin mediated phosphorylation of Smad2 after its overexpression with appropriate type I and II receptors in COS cells. Smad2 and Smad1 were found to be broadly expressed in human tissues. Smad2 is closely linked to DPC4 on chromosome 18q21.1, a region often deleted in human cancers. Cells that lack Smad2 may escape from TGF-beta-mediated growth inhibition and promote cancer progression.

Animals↗
PubMed1997

Orthotopic ossification of the spinal ligaments of Zucker fatty rats: a possible animal model for ossification of the human posterior longitudinal ligament.

Ossification of the posterior longitudinal ligament is a human genetic disease in which pathological ectopic ossification of the spinal ligaments develops. This leads to myelopathy or radiculopathy due to compression of the spinal cord. In this study, we investigated the histological features of orthotopic ossification of the spinal ligaments of senile Zucker fatty rats. A remarkably high incidence of orthotopic ossification was observed mainly in the thoracic spinal ligaments as compared with controls. The histopathological findings were similar to those for ossification of the human posterior longitudinal ligament. Bone morphogenetic proteins and activins, which exert their effects by way of specific type-I and type-II serine/threonine kinase receptors, play important roles in the formation of bone and cartilage. In the spinal ligaments of Zucker fatty rats, bone morphogenetic protein receptors and activin receptors were immunohistochemically detected around the ossified foci in a manner similar to that previously shown for the ossified tissue from patients who had ossification of the posterior longitudinal ligament. Thus, bone morphogenetic proteins and activin receptors might play important roles in orthotopic ossification of the spinal ligaments of Zucker fatty rats as well as in ossification of the posterior longitudinal ligament of humans. In addition, bone morphogenetic protein-receptor-IA was expressed in the nonossified ligament, suggesting that the spinal ligaments, of the rats may have a predisposition to orthotopic ossification. In the controls, no expression of bone morphogenetic protein receptors or of activin receptors was observed. In conclusion, there is a great degree of similarity between orthotopic ossification of the spinal ligaments of Zucker fatty rats and ossification of the posterior longitudinal ligament of humans. Thus, the rats provide a useful animal model for the study of ossification of the human posterior longitudinal ligament.

Activin Receptors↗
PubMed1997

Immunohistochemical expression of nm23 gene product, nucleotide diphosphate kinase, in pancreatic neoplasms.

CONCLUSION: Our findings suggest that contrary to the proposed role for the nm23 protein as a tumor metastasis suppressor, in pancreatic tumors, the nm23 protein does not play an important role as a suppressor against tumor metastasis. BACKGROUND: The nm23 gene product, nucleotide diphosphate kinase, is believed to suppress tumor metastasis. Although a number of studies on many kinds of tumors have examined the relationship between nm23 expression and metastatic potential, the antimetastatic activity of nm23 remains controversial. The expression of the nm23 protein has not been examined in pancreatic tumors, except for a few reports on pancreatic duct cell carcinomas. METHODS: We have investigated nm23 expression in pancreatic duct cell carcinomas, islet cell tumors, and ampullary carcinomas by immunohistochemical methods. RESULTS: In 73 cases of pancreatic duct cell carcinomas, the nm23 expression was increased when compared with the adjacent normal pancreatic ducts; diffuse immunostaining was detected in 21 (29%) cases, focally positive immunostaining in 47 (64%) cases, and negative immunostaining in 5 cases (7%). All five negative samples were obtained from distant metastatic regions. However, there was no significant difference in the nm23 expression between primary tumors and regional lymph node metastases. Furthermore, there was no significant correlation between nm23 expression and the prognosis of the 55 resected cases. In the 15 cases of ampullary carcinomas, all 15 tumors were positive for nm23 protein (6 diffuse and 9 focal), and the staining intensity was stronger than in normal pancreatic ducts. There was no significant difference in the nm23 expression in the primary regions between patients with and without lymph node metastasis (2 diffuse and 5 focal out of 7 patients with lymph node metastasis, and 4 diffuse and 4 focal out of 8 patients without lymph node metastasis). All 12 islet cell tumors showed strong and diffuse staining for the nm23 protein.

Adenoma, Islet Cell↗
PubMed1997

Cytokeratin 19 fragment in serum and tissues of patients with pancreatic diseases.

CONCLUSION: The present study has shown that increased serum levels of cytokeratin 19 fragment reflect increases in the size of the pancreatic carcinomas, although the sensitivity for detecting small pancreatic carcinomas was low. BACKGROUND: Cytokeratin is a member of the intermediate family of filaments in epithelial cells. The cytokeratin 19 fragment is an acidic cytokeratin, which is found in various epithelial tissues. Recently, the serum fragment of cytokeratin 19 has been measured and found to be a good marker for squamous cell carcinoma. Cytokeratin 19 is known to be expressed in normal pancreatic tissues and pancreatic carcinomas. However, serum cytokeratin 19 levels in pancreatic diseases have not been precisely detailed. METHODS: In this study, we evaluated serum cytokeratin 19 levels and the immunohistochemical expression of cytokeratin 19 in various pancreatic diseases. RESULTS: Serum cytokeratin 19 levels were high (> 2 ng/mL) in 51 of 99 (52%) cases of pancreatic duct cell carcinoma, but were low in all 24 cases of chronic pancreatitis and in 7 cases of islet cell tumors. The sensitivity of the cytokeratin 19 assay increased with increased size of the pancreatic carcinomas, but was not influenced by the presence of obstructive jaundice. Immunohistochemical studies using a monoclonal anticytokeratin 19 antibody showed that staining for cytokeratin was positive in all 38 of the pancreatic carcinomas examined and in 2 of 6 islet tumors.

Biomarkers, Tumor↗
PubMed1997

Regional cerebral blood flow and oxygen metabolism in a patient with Korsakoff syndrome.

We report a functional neuroimaging study of a patient clinically diagnosed with Korsakoff syndrome. Positron emission tomography (PET) with the 15O inhalation method showed decreased regional cerebral blood flow (rCBF) and decreased regional cerebral metabolic ratio for oxygen (rCMRO2) in the bilateral fronto-temporal areas and in the left thalamus. These results suggest that dysfunction of the frontal-thalamic neural network plays a role in the disturbance of Korsakoff syndrome.

Alcohol Amnestic Disorder↗
PubMed1997

Fatty acid induced insulin resistance in rat-1 fibroblasts overexpressing human insulin receptors: impaired insulin-stimulated mitogen-activated protein kinase activity.

Saturated fatty acids cause insulin resistance but the underlying molecular mechanism is still unknown. We examined the effect of saturated nonesterified fatty acids on insulin binding and action in transfected Rat-1 fibroblasts, which over-expressed human insulin receptors. Incubation with 1.0 mmol/l palmitate for 1-4 h did not affect insulin binding, insulin receptor autophosphorylation, insulin-stimulated tyrosine kinase activity toward poly(Glu4:Tyr1), pp185 and Shc phosphorylation and PI3-kinase activity in these cells. However, the dose response curve of insulin-stimulated glucose transport was right-shifted. Palmitate inhibited the maximally insulin-stimulated mitogen activated protein (MAP) kinase activity toward synthetic peptide to 7% that of control. The palmitate treatment influenced neither cytosolic protein kinase A activity nor cAMP levels. These results suggested that 1) palmitate did not inhibit the early steps of insulin action from insulin binding to pp185 or Shc phosphorylation but inhibited insulin-stimulated MAP kinase, and that 2) palmitate decreased insulin sensitivity as manifested by inhibited insulin-stimulated glucose uptake. In conclusion, the mechanism of saturated non-esterified fatty acid induced insulin resistance in glucose uptake may reside at post PI3-kinase or Shc steps, including the level of MAP kinase activation.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Association of apolipoprotein allele epsilon 2 with psoriasis vulgaris in Japanese population.

We studied phenotypic variations of apolipoprotein E (apoE) and the corresponding allele frequencies in 100 Japanese patients with psoriasis vulgaris (PV). The phenotypes of apoE were examined using analytical isoelectric focusing followed by immunoblotting with goat anti-apoE antibody and alkaline phosphatase-conjugated rabbit antigoat IgG. The phenotypic frequency of apoE3/2 in PV was significantly higher than in healthy controls, and this elevation was associated with an increased frequency of the epsilon 2 allele. Therefore, it is suggested that the apoE molecule plays an important role in the development of PV.

Adolescent↗
PubMed1997

The usefulness of thiosulfate as an indicator of hydrogen sulfide poisoning: three cases.

We examined the usefulness of thiosulfate as an indicator of hydrogen sulfide poisoning by analysing sulfide and thiosulfate in three cases. In the first (non-fatal) case sulfide and thiosulfate were not detected in the blood samples from any of the four workers involved in the accident. In the urine samples, only thiosulfate was detected in three out of the four workers at a concentration of 0.12-0.43 micromol/ml, which was 4-14 times higher than the level in a healthy person. In the second (fatal) case sulfide and thiosulfate were detected in the blood sample at concentrations of 0.007 micromol/ml for sulfide, and 0.025 micromol/ml for thiosulfate. The thiosulfate concentration was at least 8 times higher than the level in a healthy person. In the third (fatal) case sulfide and thiosulfate were detected in the blood sample at concentrations of 0.95 micromol/ml for sulfide, and 0.12 micromol/ml for thiosulfate. Based on the above results, we concluded that thiosulfate in urine is the only indicator to prove hydrogen sulfide poisoning in non-fatal cases, while the analysis of sulfide in fatal cases should be accompanied by the measurement of thiosulfate in blood.

Adult↗