Biomedical subjects

T Okamoto

Publications and source records attributed to T Okamoto.

At least 91 records · Page 5Linked to original sources

PubMed2001

Insulin-like growth factor I (IGF-I) protects cells from apoptosis by Alzheimer's V642I mutant amyloid precursor protein through IGF-I receptor in an IGF-binding protein-sensitive manner.

It has been found that insulin-like growth factor I (IGF-I) exerts cytoprotection against Abeta amyloid-induced neuronal cell death. Deposits of Abeta amyloid are one of the pathological hallmarks of Alzheimer's disease (AD). Here, we examined whether IGF-I exerts protective activity against cell death induced by a familial AD (FAD)-linked mutant of amyloid precursor protein (APP), and we found that IGF-I protected cells from toxicity of FAD-associated V642I mutant of APP in multiple cell systems. IGFBP-3 blocked this action of IGF-I, but not of des(1-3)IGF-I, which was as active as IGF-I in the presence of IGFBP-3. The data also demonstrated that the IGF-I receptor (IGF-IR) mediates the protective activity of IGF-I. The antagonizing function of the IGF-I/IGF-IR system against V642I-APP, which is further antagonized by IGFBP-3, provides a molecular clue to the understanding of AD pathophysiology and to the establishment of potential therapy for AD.

Amino Acid Substitution↗

PubMed2001

Y box-binding protein-1 binds preferentially to single-stranded nucleic acids and exhibits 3'-->5' exonuclease activity.

We have previously shown that Y box-binding protein-1 (YB-1) binds preferentially to cisplatin-modified Y box sequences. Based on structural and biochemical data, we predicted that this protein binds single-stranded nucleic acids. In the present study we confirmed the prediction and also discovered some unexpected functional features of YB-1. We found that the cold shock domain of the protein is necessary but not sufficient for double-stranded DNA binding while the C-tail domain interacts with both single-stranded DNA and RNA independently of the cold shock domain. In an in vitro translation system the C-tail domain of the protein inhibited translation but the cold shock domain did not. Both in vitro pull-down and in vivo co-immunoprecipitation assays revealed that YB-1 can form a homodimer. Deletion analysis mapped the C-tail domain of the protein as the region of homodimerization. We also characterized an intrinsic 3'-->5' DNA exonuclease activity of the protein. The region between residues 51 and 205 of its 324-amino acid extent is required for full exonuclease activity. Our findings suggest that YB-1 functions in regulating DNA/RNA transactions and that these actions involve different domains.

Binding Sites↗

PubMed2001

A multistep damage recognition mechanism for global genomic nucleotide excision repair.

A mammalian nucleotide excision repair (NER) factor, the XPC-HR23B complex, can specifically bind to certain DNA lesions and initiate the cell-free repair reaction. Here we describe a detailed analysis of its binding specificity using various DNA substrates, each containing a single defined lesion. A highly sensitive gel mobility shift assay revealed that XPC-HR23B specifically binds a small bubble structure with or without damaged bases, whereas dual incision takes place only when damage is present in the bubble. This is evidence that damage recognition for NER is accomplished through at least two steps; XPC-HR23B first binds to a site that has a DNA helix distortion, and then the presence of injured bases is verified prior to dual incision. Cyclobutane pyrimidine dimers (CPDs) were hardly recognized by XPC-HR23B, suggesting that additional factors may be required for CPD recognition. Although the presence of mismatched bases opposite a CPD potentiated XPC-HR23B binding, probably due to enhancement of the helix distortion, cell-free excision of such compound lesions was much more efficient than expected from the observed affinity for XPC-HR23B. This also suggests that additional factors and steps are required for the recognition of some types of lesions. A multistep mechanism of this sort may provide a molecular basis for ensuring the high level of damage discrimination that is required for global genomic NER.

Base Pair Mismatch↗

PubMed2001

In situ XAFS study on cathode materials for lithium-ion batteries.

Ni and Co K-edge X-ray absorption spectra of LiNi0.8Co0.2O2 have been collected using in situ coin cells. To investigate the electronic and structural changes accompanied by the capacity fading during electrochemical cycling and keeping batteries at high temperatures, the cells with different cycling states and keeping conditions (temperature, time) were prepared. Upon charging the cell, the Ni and Co K absorption edge shifted towards higher energy, and the good correlation between the range of chemical shifts upon charging and the capacity of the cell was observed. From quantitative analysis of EXAFS data, it was revealed that the capacity fading is closely related to the Jahn-Teller distortion of the NiO6 octahedron.

Journal Article↗

PubMed2001

Local structure analyses of Ce0.5Zr0.5O2 mixed oxides by XAFS.

Three types of CeO2-ZrO2 with the same composition (Ce/Zr = 1) were prepared by different methods, exhibited the different oxygen storage/release capacity (OSC). To investigate the relationship between the OSC and the local structure, the Ce and Zr K-edges XAFS spectra for these samples were measured. The features of Fourier transforms of these samples were different from each other. This suggested that the OSC was remarkably exerted by the local structure around Ce and Zr. The quantitative curve-fitting analysis of EXAFS was applied, and it was concluded that homogeneous Ce(0.5)Zr(0.5)O2 solid solution at atomic level exhibited the highest OSC among these CeO2-ZrO2 with the same composition (Ce/Zr = 1).

Journal Article↗

PubMed2001

Occurrence of D-Amino Acids and a pyridoxal 5'-phosphate-dependent aspartate racemase in the acidothermophilic archaeon, Thermoplasma acidophilum.

Free D-amino acid content in some archaea was investigated and D-forms of several amino acids were found in them. In the acidothermophilic archaeon, Thermoplasma acidophilum, the proportion of D-aspartate (D-Asp) to total Asp was as high as 39.7%. Crude extracts of Thermoplasma acidophilum had Asp-specific racemase activity that was pyridoxal 5'-phosphate (PLP)-dependent. The relative insensitivity to a SH-modifying reagent distinguished this activity from those of the PLP-independent Asp racemases found in other hyperthermophilic archaea (Matsumoto, M., et al., J. Bacteriol. 181, 6560-6563 1999). Thus, high levels of d-Asp should be produced by a new type(s) of Asp-specific racemase in Thermoplasma acidophilum, although the function of d-Asp in this archaeon remains unknown.

Alanine↗

PubMed2001

Involvement of the pro-oncoprotein TLS (translocated in liposarcoma) in nuclear factor-kappa B p65-mediated transcription as a coactivator.

In this study, we have demonstrated that translocated in liposarcoma (TLS), also termed FUS, is an interacting molecule of the p65 (RelA) subunit of the transcription factor nuclear factor kappaB (NF-kappaB) using a yeast two-hybrid screen. We confirmed the interaction between TLS and p65 by the pull-down assay in vitro and by a coimmunoprecipitation experiment followed by Western blot of the cultured cell in vivo. TLS was originally identified as part of a fusion protein with CHOP arising from chromosomal translocation in human myxoid liposarcomas. TLS has been shown to be involved in TFIID complex formation and associated with RNA polymerase II. However, the role of TLS in transcriptional regulation has not yet been clearly elucidated. We found that TLS enhanced the NF-kappaB-mediated transactivation induced by physiological stimuli such as tumor necrosis factor alpha, interleukin-1beta, and overexpression of NF-kappaB-inducing kinase. TLS augmented NF-kappaB-dependent promoter activity of the intercellular adhesion molecule-1 gene and interferon-beta gene. These results suggest that TLS acts as a coactivator of NF-kappaB and plays a pivotal role in the NF-kappaB-mediated transactivation.

Cell Line↗

PubMed2001

Human chorionic gonadotropin beta-core fragment is directly produced by cancer cells.

The present study was undertaken to investigate whether hCG beta-core fragment (hCGbeta cf) was directly produced by cancer cells. Fifteen cell lines, including four choriocarcinoma and five ovarian cancer cell lines, were tested, and immunoreactivity of hCGbeta cf was present in the culture media of five of the cell lines. It was also present in the culture media of Chinese hamster ovary (CHO) cells transfected with hCGbeta gene. In addition to hCGbeta cf, gel chromatography and Western blot analysis of the culture media showed the presence of an hCGbeta cf immunoreactive material with a molecular weight of approximately 40 kDa. In an in vivo study, hCGbeta cf immunoreactivity was detected in the sera of the mice transplanted with NaUCC-3 choriocarcinoma cells, although the ratios of hCGbeta cf/hCG and hCGbeta cf/free hCGbeta were lower than those in the culture medium. Incubation experiments of purified hCGbeta cf in the serum showed no substantial decrease in its values, ruling out the possibility that formation of a macromolecule with serum components may mask hCGbeta cf immunoreactivity in the serum. Taken together, these results indicate that hCGbeta cf immunoreactive materials are directly produced by cancer cells and hCGbeta cf is not a urinary metabolite of hCG or hCGbeta alone. Also, reduced levels of hCGbeta cf in the serum compared with that of intact hCG or free hCGbeta are likely due to its short half-life.

Animals↗

PubMed2001

Identification of a membrane-associated cysteine protease with possible dual roles in the endoplasmic reticulum and protein storage vacuole.

SH-EP is a vacuolar cysteine proteinase from germinated seeds of Vigna mungo. The enzyme has a C-terminal propeptide of 1 kDa that contains an endoplasmic reticulum (ER) retention signal, KDEL. The KDEL-tail has been suggested to function to store SH-EP as a transient zymogen in the lumen of the ER, and the C-terminal propeptide was thought to be removed within the ER or immediately after exit from the ER. In the present study, a protease that may be involved in the post-translational processing of the C-terminal propeptide of SH-EP was isolated from the microsomes of cotyledons of V. muno seedlings. cDNA sequence for the protease indicated that the enzyme is a member of the papain superfamily. Immunocytochemistry and subcellular fractionation of cotyledon cells suggested that the protease was localized in both the ER and protein storage vacuoles as enzymatically active mature form. In addition, protein fractionations of the cotyledonary microsome and Sf9 cells expressing the recombinant protease indicated that the enzyme associates with the microsomal membrane on the luminal side. The protease was named membrane-associated cysteine protease, MCP. The possibility that a papain-type enzyme, MCP, exists as mature enzyme in both ER and protein storage vacuoles will be discussed.

Amino Acid Sequence↗

PubMed2001

Treatment of murine collagen-induced arthritis by ex vivo extracellular superoxide dismutase gene transfer.

UNLABELLED: OBJECTIVE; Superoxide dismutase (SOD) is a potent antiinflammatory enzyme that has received growing attention for its therapeutic potential. This study was undertaken to examine the efficacy of extracellular SOD (EC-SOD) gene therapy in murine collagen-induced arthritis. METHODS: Embryonic DBA/1 mouse fibroblasts were infected with a recombinant retrovirus expressing human EC-SOD. DBA/1 mice that had been treated with type II collagen were administered subcutaneous injections of 2 x 10(7) EC-SOD-expressing fibroblasts on day 29, when symptoms of arthritis were already present. The severity of arthritis in individual mice was evaluated in a double-blind manner; each paw was assigned a separate clinical score, and hind paw thickness was measured with a caliper. Mice were killed on day 50 for histologic examination of the joints. RESULTS: High serum concentrations of EC-SOD were maintained for at least 7 days. Mice treated with the transgene exhibited significant suppression of clinical symptoms such as disabling joint swelling, deformity, and hind paw thickness, compared with the untreated group (mean +/- SD maximum clinical score in the untreated and the transgene-treated groups 2.71 +/- 1.08 and 1.35 +/- 1.22, respectively; P < 0.01, and hind paw thickness 3.04 +/- 0.18 mm and 2.56 +/- 0.12 mm, respectively; P < 0.05). Histologic abnormalities, including destruction of cartilage and bone, infiltration of mononuclear cells, and proliferation of synovial cells, were also markedly improved in the EC-SOD-treated mice compared with the control group (histopathologic score 7.50 +/- 1.13 and 4.13 +/- 1.88 in the untreated and transgene-treated groups, respectively; P < 0.05). CONCLUSION: These results indicate that EC-SOD gene transfer may be an effective form of therapy for rheumatoid arthritis.

Animals↗

PubMed2001

Matrix metalloproteinases induction by pseudomonal virulence factors and inflammatory cytokines in vitro.

The pathogenesis of pseudomonal keratitis was investigated by focusing on induction and activation of matrix metalloproteinases (MMPs) by pseudomonal virulence factors and proinflammatory cytokines. Corneal lesions and MMP induction in vivo were evaluated in rabbit corneas infected with a clinical isolate of Pseudomonas aeruginosa. Effects of pseudomonal virulence factors [elastase, alkaline protease, exotoxin A and lipopolysaccharide (LPS)], tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta on MMP induction and activation were further examined in vitro in rabbit corneal fibroblasts (RCF) and human fibrosarcoma (HT1080) cells using reverse transcriptase-polymerase chain reaction (RT-PCR), zymography and immunoblotting. Corneal ulcers with typical ring abscesses were observed 12-24 h after infection, and MMPs, particularly MMP-9, were upregulated in infected corneas. Pseudomonal elastase caused the most extensive damage to both cell types. RCF treated with pseudomonal exoproteases or LPS expressed and secreted MMP-9. Exotoxin A had no effect on MMP expression. Both IL-1beta and TNF-alpha augmented MMP-9 expression in HT1080 cells. Pseudomonal elastase proteolytically activated MMP-2 and MMP-9 released from the cells. In conclusion, corneal destruction seen with P. aeruginosa infections may result from enhanced expression of MMPs by corneal stromal cells stimulated with pseudomonal exoproteases and proinflammatory cytokines and the proteolytic activation of MMPs by pseudomonal elastase.

ADP Ribose Transferases↗

PubMed2001

Degradation of ribulose-bisphosphate carboxylase by vacuolar enzymes of senescing French bean leaves: immunocytochemical and ultrastructural observations.

The possible involvement of vacuolar cysteine proteinases in degradation of ribulose-bisphosphate carboxylase (Rubisco) in senescing French bean leaves was studied by ultrastructural and immunocytochemical analyses with antibodies raised against the large subunit (LSU) of Rubisco and SH-EP, a cysteine proteinase from Vigna mungo that is immunologically identical to one of the major proteinases of French bean plants. Primary leaves of 10-day-old plants were detached and placed at 25 degrees C in darkness for 0, 4, and 8 days to allow their senescence to proceed. The leaves at each senescence stage were subjected to the conventional electron microscopic and immunocytochemical studies. The results indicated that the chloroplasts of senescing French bean leaves were separated from the cytoplasm of the cell periphery and taken into the central vacuole and that the Rubisco LSU in the chloroplasts was degraded by vacuolar enzymes such as an SH-EP-related cysteine proteinase that developed in senescing leaves. The present results together with the results of previous biochemical studies using vacuolar lysates support the view that Rubisco is degraded through the association of chloroplasts with the central vacuole during the senescence of leaves that were detached and placed in darkness.

Aging↗

PubMed2001

The effects of stimulating protease-activated receptor-1 and -2 in A172 human glioblastoma.

Human glioblastoma cell line A172 expressed protease-activated receptor-1 and -2 (PAR-1 and PAR-2). We investigated the effects of the stimulation of these receptors by receptor-activating agonist peptides on the Ca2+ signaling, protein kinase C translocation, cell morphology and cell proliferation in A172. Both PAR-1 agonist SFLLRN and PAR-2 agonist SLIGKV induced an increase in [Ca2+]i. The prior treatment of A172 with PAR-2 agonist SLIGKV did not influence the [Ca2+]i response to PAR-1 agonist SFLLRN or thrombin, however, the prior treatment with PAR-1 agonist SFLLRN or thrombin completely abolished the second response to PAR-2 agonist SLIGKV. Treatment with each agonist peptide produced thinner and fewer processes in A172. The PAR-2 agonist inhibited the proliferation of A172 significantly while PAR-1 agonist did not. PKC-alpha and gamma were translocated from cytosol to membrane with either PAR-1 or PAR-2 stimulation, however, L was specifically translocated with SFLLRN, and lambda with SLIGKV, respectively. These results indicated that PAR-1 and PAR-2 stimulation produced a similar [Ca2+]i response and morphological changes in A172 glioblastoma while the effects on the cell proliferation and activation of PKC isozymes were distinct, suggesting that different signal transduction pathways were activated by these receptors. The uni-directional cross desensitization implies a functional linkage between PAR-1 and PAR-2 receptors.

Blotting, Western↗

PubMed2001

Identification of GFAT1-L, a novel splice variant of human glutamine: fructose-6-phosphate amidotransferase (GFAT1) that is expressed abundantly in skeletal muscle.

Glutamine:fructose-6-phosphate amidotransferase (GFAT1) is the rate-limiting enzyme in the hexosamine biosynthetic pathway, which plays an important role in hyperglycemia-induced insulin resistance. To evaluate the role of GFAT1 expression, we analyzed the expression profiles of GFAT1 mRNA in various human tissues using reverse transcriptase-polymerase chain reaction. We report here the identification and cDNA cloning of a novel GFAT1 splice variant expressed abundantly in skeletal muscle and heart. This subtype, designated GFAT1-L, contains a 54-bp insertion within the GFAT1 coding sequence. Recombinant GFAT1-L protein possessed functional GFAT activities and biochemical characteristics similar to GFAT1. Previously, GFAT1 was considered a simplex enzyme. The identification of a novel GFAT1 subtype possessing functional enzymatic activity and tissue-specific expression should provide additional insight into the mechanism of skeletal muscle insulin resistance and diabetes complications.

Alternative Splicing↗

PubMed2001

Excision of an invasive thymoma: a cure for ulcerative colitis?

Thymoma is often associated with other diseases, including autoimmune diseases and endocrine disorders. Ulcerative colitis is a nonspecific inflammatory disease and is thought to be an immune-mediated disorder; however, coincidence of thymoma and ulcerative colitis is rare. We treated a 51-year-old woman with invasive thymoma and ulcerative colitis. After excision of the invasive thymoma with partial resections of pericardium, left lung, brachiocephalic vein, and left phrenic nerve, the ulcerative colitis was cured.

Colitis, Ulcerative↗

PubMed2001

Urinary trypsin inhibitor concentration can predict the immunological insult of chemotherapy and complications after bone marrow transplantation.

Urinary trypsin inhibitor has attracted attention as an index of the systemic inflammatory response syndrome. In this study, the urine concentration of trypsin inhibitor was measured to compare the immunological insult of conventional chemotherapy and conditioning chemotherapy for bone marrow transplantation. We also investigated whether urinary trypsin inhibitor was a useful index of the complications and outcome of bone marrow transplantation. Urinary trypsin inhibitor concentration was determined before chemotherapy, on the day after finishing chemotherapy (day 0 of transplantation), and during recovery of the white cell count, in 17 patients (seven receiving conventional chemotherapy and 10 receiving conditioning for bone marrow transplantation). Urinary trypsin inhibitor concentrations were significantly higher after conditioning for bone marrow transplantation than after conventional chemotherapy (P < 0.001), indicating that conditioning was more invasive. After bone marrow transplantation, the incidence of severe complications and the mortality rate were higher in patients whose urinary trypsin inhibitor concentrations rose during recovery of the white cell count. Comparison of urinary trypsin inhibitor concentrations suggested that conditioning for bone marrow transplantation was more invasive than conventional chemotherapy. This study also suggested that the urine concentration of trypsin inhibitor could be useful for predicting the risk of complications and outcome of bone marrow transplantation.

Adolescent↗

PubMed2001

Increased hepatocyte growth factor in serum in acute graft-versus-host disease.

Hepatocyte growth factor (HGF) was reported to be effective in preventing acute graft-versus-host disease (GVHD) in a murine model. We examined serum HGF concentrations in 38 patients receiving allogeneic bone marrow transplants, and investigated the relationship of serum HGF concentrations to severity of acute GVHD. More HGF was present in sera from patients with than without acute GVHD. Serum HGF correlated significantly with grade of acute GVHD. Furthermore, serum HGF correlated with serum concentrations of C-reactive protein, gamma-glutamyltranspeptidase (GTP), and aspartate aminotransferase (AST). Serum concentrations of HGF in transplanted patients without GVHD were consistently low, while those in patients with acute GVHD increased with exacerbation. We conclude that HGF was produced during induction of the GVH reaction, and probably increased as a physiological response.

Acute Disease↗

PubMed2001

Oral eicosapentaenoic acid for complications of bone marrow transplantation.

The 'systemic inflammatory response syndrome' (SIRS) may represent the underlying cause of complications after bone marrow transplantation (BMT). This study was conducted to determine whether blocking the etiologic factors of SIRS could improve the complications of BMT. Sixteen consecutive patients with unrelated donors were allocated alternately to two groups. Seven patients received 1.8 g/day of eicosapentaenoic acid (EPA) orally from 3 weeks before to about 180 days after transplantation, while nine patients did not. These two groups were compared with respect to complications, survival, and various cytokines and factors causing vascular endothelial damage. All seven patients receiving EPA survived and only two had grade III graft-versus-host disease (GVHD). Among the nine patients not receiving EPA, three had grade III or IV GVHD. In addition, thrombotic microangiopathy developed in four patients and cytomegalovirus disease occurred in four. Five patients died in this group. The levels of leukotriene B(4), thromboxane A(2), and prostaglandin I(2) were significantly lower in patients receiving EPA than in those not receiving it (all P < 0.01). Cytokines such as tumor necrosis factor-alpha, interferon-gamma, and interleukin-10 were also significantly decreased by EPA (P < 0.05), as were factors causing vascular endothelial damage such as thrombomodulin and plasminogen activator inhibitor-1 (P < 0.05). The survival rate was significantly higher in the group given EPA (P < 0.01). EPA significantly reduced the complications of BMT, indicating that these complications may be manifestations of the systemic inflammatory response syndrome.

6-Ketoprostaglandin F1 alpha↗