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Biomedical subjects

T Koyama

Publications and source records attributed to T Koyama.

At least 19 recordsLinked to original sources
PubMed2006

Rottlerin synergistically enhances imatinib-induced apoptosis of BCR/ABL-expressing cells through its mitochondrial uncoupling effect independent of protein kinase C-delta.

Although the BCR/ABL tyrosine kinase inhibitor imatinib is highly effective for treatment of chronic myeloid leukemia (CML) and Philadelphia-chromosome positive acute lymphoblastic leukemia (ALL), relapse with emerging imatinib-resistance mutations in the BCR/ABL kinase domain poses a significant problem. Here, we demonstrate that rottlerin, a putative protein kinase C-delta (PKCdelta)-specific inhibitor, acts synergistically with imatinib to induce apoptosis of BCR/ABL-expressing K562 and Ton.B210 cells. However, rottlerin inhibited neither PKCdelta nor BCR/ABL in these cells. On the other hand, rottlerin, previously characterized also as a mitochondrial uncoupler, transiently but significantly reduced mitochondrial membrane potential and gradually induced mitochondrial membrane permeabilization. Moreover, two other mitochondrial uncouplers, FCCP and DNP, very similarly induced apoptosis of BCR/ABL-expressing cells in a synergistic manner with imatinib. Imatinib synergistically enhanced mitochondrial membrane permeabilization induced by mitochondrial uncouplers, which led to release of cytochrome c into the cytoplasm and activation of caspases-3 and -9. Rottlerin also enhanced the cytotoxic effect of imatinib in leukemic cells from patients with CML blast crisis and Ph-positive ALL or a cell line expressing the imatinib-resistant E255K BCR/ABL mutant. The present study indicates that rottlerin synergistically enhances imatinib-induced apoptosis through its mitochondrial uncoupling effect independent of PKCdelta and may contribute to the development of new treatment strategy to overcome the imatinib resistance and to cure the BCR/ABL expressing leukemias.

Acetophenones↗
PubMed2006

Role of the simultaneous enhancement of NMDA and dopamine D1 receptor-mediated neurotransmission in the effects of clozapine on phencyclidine-induced acute increases in glutamate levels in the rat medial prefrontal cortex.

Clozapine (CLZ) can improve both the positive and negative symptoms of treatment-resistant schizophrenia (TRS), which does not respond to typical antipsychotics. This suggests that elucidation of the pharmacological mechanism for CLZ could lead to further clarification of the pathophysiology of TRS. This study examined the effects of CLZ on phencyclidine (PCP)-induced hyperlocomotion and on the acute increases in glutamate levels that occur in the medial prefrontal cortex (mPFC) in order to test the hypothesis that CLZ effect is associated with the simultaneous enhancement of N-methyl-D: -aspartate (NMDA) and dopamine D(1) receptor-mediated neurotransmission. CLZ effect on PCP-induced hyperlocomotion and increases in glutamate levels were examined by using behavioral rating scores and in vivo microdialysis, respectively. CLZ and haloperidol (HAL) dose-relatedly attenuated PCP-induced hyperlocomotion, and concentration-relatedly blocked PCP-induced acute increases in glutamate levels in the mPFC, with the decrease in saline-induced locomotor activity induced by CLZ being much weaker than that induced by HAL. CLZ also blocked, in a dose-related manner, acute increases in glutamate levels in the mPFC that were induced by local perfusion with a competitive NMDA receptor antagonist, CPP, in this region. Although an enhanced blocking effect of the sub-threshold concentration of NMDA perfusion on PCP-induced acute increases in glutamate levels in the mPFC was noted after co-perfusion with a dopamine D(1) receptor agonist, SKF-38393, perfusion with SKF-38393 did not reverse the CLZ blocking of PCP-induced increases in glutamate levels. Therefore, CLZ may block PCP-induced acute increases in glutamate levels in the mPFC by an enhancement of the NMDA receptor-mediated neurotransmission that is not accelerated by an enhanced dopaminergic transmission via dopamine D(1) receptors. This blocking effect may partially explain the CLZ-induced attenuation of PCP-induced hyperlocomotion.

Analysis of Variance↗
PubMed2006

Incidence and outcome of idiopathic pneumonia syndrome in pediatric stem cell transplant recipients.

Idiopathic pneumonia syndrome (IPS) is a rare complication following stem cell transplant (SCT) and its incidence among pediatric SCT recipients is not known. To assess the incidence of IPS, we retrospectively reviewed the incidence of IPS at our center. IPS is defined as the presence of multilobar infiltrates by chest radiograph or computed tomography scan, need for supplemental oxygenation with declining pulse oximetry and no identifiable pulmonary infection. Between July 1999 and August 2005, 11 of 93 children who received a fully ablative allogeneic SCT (11.8%) developed IPS. All 11 patients had normal pulmonary evaluation before transplant. IPS developed at a median of 17 days (range 8-42 days) after transplant. Recipients of unrelated donor transplant had increased risk of developing IPS. There was a significant association between acute or hyperacute graft-versus-host disease (GVHD) and IPS (P=0.035). All patients had significant hypoxia and five patients required assisted ventilation. IPS was the cause of death in two patients. Although there was complete resolution of respiratory symptoms in the other nine patients, overall transplant-related mortality was significantly higher among patients with IPS (64 vs 17%, P=0.002). IPS is a relatively common complication in pediatric SCT recipients and acute GVHD is an important associated factor.

Adolescent↗
PubMed2006

Relationship between development of cross-sensitization to MK-801 and delayed increases in glutamate levels in the nucleus accumbens induced by a high dose of methamphetamine.

RATIONALE: The present study hypothesized that delayed increases in extracellular glutamate (Glu) levels in the nucleus accumbens (NAC), induced by a high dose of methamphetamine (METH), can result in some functional changes of excitatory amino acid receptors, developing behavioral cross-sensitization to a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801. OBJECTIVES: The present study aims to examine whether two different doses of METH (2.5 and 1.0 mg/kg) induce different effects on the development of cross-sensitization to MK-801. To clarify the mechanisms for development and expression of cross-sensitization to MK-801, we measured extracellular Glu and dopamine (DA) levels in the NAC at METH injections in a treatment period and at MK-801 injection after a 12-day withdrawal period. MATERIALS AND METHODS: METH- or MK-801-induced changes in Glu and DA levels and in locomotion were measured using in vivo microdialysis and infrared sensor, respectively. RESULTS: METH, at only 2.5 mg/kg, produced delayed increases in Glu levels and developed behavioral cross-sensitization to MK-801 (0.2 mg/kg). MK-801 (0.2 mg/kg) induced delayed increases in Glu levels in the NAC, but this time course was not completely consistent with MK-801-induced enhanced hyperlocomotion. During this time course, MK-801 (0.2 mg/kg) did not induce any changes in DA levels. CONCLUSIONS: These results suggest that METH-induced, at 2.5 mg/kg, delayed increases in Glu levels are necessary for development of behavioral cross-sensitization to MK-801, but not METH. The enhanced locomotion-inducing effect of MK-801 might be related to some functional changes in excitatory amino acid receptors such as NMDA and DL-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid in the NAC.

Animals↗
PubMed2006

Valproate blocks high-dose methamphetamine-induced behavioral cross-sensitization to locomotion-inducing effect of dizocilpine (MK-801), but not methamphetamine.

RATIONALE: Our group has recently shown that methamphetamine (METH) (2.5 mg/kg) induced delayed increases in glutamate (Glu) levels in the rat nucleus accumbens (NAC), and that its repeated administration leads to behavioral cross-sensitization to a selective uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, dizocilpine (MK-801). OBJECTIVES: The present study aims to examine whether valproate (VPA) would inhibit the delayed increases in Glu levels and prevent METH (2.5 mg/kg)-induced behavioral cross-sensitization to MK-801 (0.2 mg/kg). MATERIALS AND METHODS: We examined the effects of post-treated VPA (50 mg/kg) on METH (2.5 mg/kg)-induced delayed increases in Glu levels. We injected VPA (50 mg/kg) at 120 min after each METH (2.5 mg/kg, once every other day, total of five times) administration and measured locomotor activity induced by challenge with MK-801 (0.2 mg/kg) or METH (0.15 mg/kg) after sufficient withdrawal period. Finally, we measured locomotion induced by MK-801 (0.2 mg/kg) after pretreatment of a competitive NMDA receptor antagonist, CPP (30 mg/kg). Effects of VPA on extracellular Glu levels were examined by using in vivo microdialysis. Locomotor activity was measured by using an infrared sensor. RESULTS: VPA administered 120 min after METH injection had no effect on METH-induced hyperlocomotion, and inhibited METH-induced delayed increases in Glu levels. Repeated VPA administration prevented METH-induced behavioral cross-sensitization to MK-801, but not sensitization to METH. MK-801-induced hyperlocomotion was enhanced when pretreated with the competitive NMDA receptor antagonist, CPP. CONCLUSIONS: These results suggest that VPA inhibits high-dose METH-induced delayed increases in Glu levels to prevent development of behavioral cross-sensitization to an NMDA antagonist, but not sensitization to METH.

Animals↗
PubMed2006

Expressional screening of interferon-stimulated genes for antiviral activity against hepatitis C virus replication.

Type-I interferons (IFNs) and the interferon-stimulated genes (ISGs) play a major role in antivirus responses against hepatitis C virus (HCV) infection. In this study, we studied expression profiles of ISGs in cells supporting subgenomic HCV replication (Huh7/Rep), and screened their activities to suppress HCV replication. Real-time PCR analyses showed that the expression levels of 23 ISGs were significantly lower in Huh7/Rep than naive Huh7 cells due to transcriptional suppression of the interferon-stimulated response element (ISRE). Furthermore, the expression level of ISGs was also decreased in the cured Huh7 cells in which replicon had been eliminated (cHuh7), indicating adaptation of the cells to support HCV replication by downregulating ISGs. On the other hand, expression of HCV replicon was significantly suppressed by overexpression of several ISGs including PKR, MxA, IRF-9, GBP-1, IFI-6-16, IFI-27, 25OAS and IRF-1. Knock down of GBP-1, IFI-6-16 and IFI-27 by short hairpin RNA resulted in increase of HCV replication. Thus, we conclude that downregulation of ISG expression is required in the host cells supporting HCV replication and that several ISGs directly suppress HCV replication. The search for ISGs that regulate HCV replication may help to elucidate the cellular antiviral defence mechanisms against HCV infection.

Cell Line↗
PubMed2006

Site-specific mutation of the interferon sensitivity-determining region (ISDR) modulates hepatitis C virus replication.

The number of amino acid substitutions in the interferon sensitivity-determining region (ISDR) in the nonstructural 5A (NS5A) gene of hepatitis C virus (HCV) is closely associated with the interferon (IFN) response and viral load. Several HCV replicon-based studies have reported that ISDR sequences had an influence on viral replication in vitro. However, it is unclear as to how different ISDR sequences affect HCV replication. Various clinically observed ISDR sequences were introduced into HCV replicons and their contribution to viral replication was investigated using a colony formation assay and/or a transient replication assay. A mapping study of the ISDR was performed to identify the amino acid positions that critically affect replication. While no colonies were formed in the colony formation assay using HCV replicons with few mutations (0, 1 and 3) in the ISDR, numerous colonies (>200) appeared when using constructs with six mutations. Introduction of various distinct ISDR sequences with multiple mutations resulted in replication enhancement in transient assays. A mapping study identified several specific sites in the ISDR that critically affected replication, including codon 2209 which, in patients, was closely associated with a strong response to IFN. ISDR sequences associated with a clinical IFN response and viral load modulated the replication of HCV replicons, suggesting the importance of the ISDR sequence in HCV infection.

Amino Acid Sequence↗
PubMed2005

A phase I-II trial of autologous peripheral blood stem cell transplantation in the treatment of refractory autoimmune disease.

OBJECTIVES: To carry out a phase I-II trial to elucidate the feasibility and efficacy of high dose cyclophosphamide (CY) supported by autologous peripheral blood stem cell transplantation (PBSCT) in the treatment of severe and refractory autoimmune disease (AD). METHODS: Peripheral blood stem cells (PBSCs) were mobilised during haematological recovery after relatively high dose CY (2 g/m2) for 2 days, followed by administration of granulocyte colony stimulating factor. After collecting PBSCs--more than 2x10(6) CD34+ cells/kg--by apheresis, CD34+ cells were immunologically selected and cryopreserved. Eight patients were enrolled--five had systemic sclerosis (SSc) alone, one had SSc with systemic lupus erythematosus, one amyopathic dermatomyositis (ADM), and one Wegener's granulomatosis (WG). All of the patients were treated with high dose CY (50 mg/kg) for 4 days and autologous PBSCT. RESULTS: Haematopoietic reconstitution was rapid and sustained. Toxicity due to the regimen included various infections such as pneumonia, sepsis, cystitis, herpes zoster, and acute heart failure. However, there was no treatment related mortality. Encouraging results were obtained after autologous PBSCT. Sclerosis of the skin was markedly improved in all of the patients with SSc. Interstitial pneumonia (IP), evaluated by PaO2, serum KL-6 levels, and pulmonary high resolution computed tomography, improved significantly. In a patient with ADM, severe and progressive IP also improved markedly. In a patient with WG, the size of the left orbital granuloma decreased substantially, resulting in reduction of the exophthalmos. CONCLUSIONS: These observations suggest that high dose CY with autologous PBSCT is feasible and may be effective in the treatment of severe and refractory AD.

Adult↗
PubMed2005

Structure of a quantized vortex near the BCS-BEC crossover in an atomic Fermi gas.

In order to clarify the structure of a singly quantized vortex in a superfluid fermion gas near the Feshbach resonance, we numerically solve the generalized Bogoliubov-de Gennes equation in the boson-fermion model. The superfluid gap, which contains contributions from both condensed fermion pairs and condensed bosons, is self-consistently determined, and the quasiparticle excitation levels bound in the vortex core are explicitly shown. We find that the boson condensate contributes to enhance the matter density depletion and the discreteness of localized quasiparticle spectrum inside the core. It is predicted that the matter density depletion and the discrete core levels are detectable in the vicinity of the BCS-Bose-Einstein condensation crossover point.

Journal Article↗
PubMed2005

Effect of the protein kinase C inhibitor, staurosporine, on the high dose of methamphetamine-induced behavioral sensitization to dizocilpine (MK-801).

RATIONALE: In our preliminary study, methamphetamine (METH) at 2.5 mg/kg, but not at 1.0 mg/kg, induced a delayed increase in glutamate levels in the nucleus accumbens (NAc). We hypothesize that repeated increases in glutamate levels produces behavioral sensitization to a selective uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, dizocilpine (MK-801), and that an activation of protein kinase C (PKC) plays an important role for this sensitization. OBJECTIVES: This study was conducted to confirm delayed increases in glutamate levels induced by a higher dose of METH (2.5 mg/kg), and to examine the effect of straurosporine, a PKC inhibitor, on the higher dose of METH-induced sensitization to dizocilpine. METHODS: The effects of METH on extracellular glutamate levels in the NAc were studied using in vivo microdialysis. Locomotor activity was measured by using an infrared sensor. RESULTS: METH at 2.5 mg/kg, but not at 1.0 mg/kg, induced delayed increases in glutamate levels. The acute administration of staurosporine did not affect the locomotor activity by a single injection of METH (2.5 mg/kg). Repeated METH administrations (2.5 mg/kg, once in every other day, for five times) developed behavioral sensitization to the locomotion-inducing effect of dizocilpine (0.2 mg/kg), a selective uncompetitive NMDA receptor antagonist. Staurosporine (0.1 mg/kg), given 120 min later for every METH treatment, inhibited the development of behavioral sensitization to dizocilpine. CONCLUSIONS: These results suggest the involvement of increased glutamate levels and an activation of PKC in delayed-induced synaptic and cellular plasticity underlying the higher dose of METH-induced behavioral sensitization to dizocilpine.

Animals↗
PubMed2005

Development of the needle insertion robot for percutaneous vertebroplasty.

Percutaneous Vertebroplasty (PVP) is an effective and less invasive medical treatment for vertebral osteoporotic compression fractures. However, this operative procedure is quite difficult because an arcus vertebra, which is narrow, is needled with accuracy, and an operator's hand is exposed to X-ray continuously. We have developed a needle insertion robot for Percutaneous Vertebroplasty. Its experimental evaluation on the basic performance of the system and needle insertion accuracy are presented. A needle insertion robot is developed for PVP. This robot can puncture with accuracy and an operator does not need to be exposed to X-ray. The mechanism of the robot is compact in size (350 mm x D 400 mm x H270 mm, weight: 15 kg) so that the robot system can be inserted in the space between C-arm and the patient on the operating table. The robot system is controlled by the surgical navigation system where the appropriate needle trajectory is planned based on pre-operative three-dimensional CT images. The needle holding part of the robot is X-ray lucent so that the needle insertion process can be monitored by fluoroscopy. The position of the needle during insertion process can be continuously monitored. In vitro evaluation of the system showed that average position and orientation errors were less than 1.0 mm and 1.0 degree respectively. Experimental results showed that the safety mechanism called mechanical fuse released the needle holding disk properly when excessive force was applied to the needle. These experimental results demonstrated that the developed system has the satisfactory basic performance as needle insertion robot for PVP.

Bone Cements↗
PubMed2005

p38 MAP kinase plays a role in G2 checkpoint activation and inhibits apoptosis of human B cell lymphoma cells treated with etoposide.

p38 MAPK is mainly activated by stress stimuli and mediates signals that regulate various cellular responses, including cell-cycle progression and apoptosis, depending on cell types and stimuli. Here we examine the role of p38 in regulation of apoptosis and cell cycle checkpoint in Daudi B-cell lymphoma cells treated with the topoisomerase II inhibitor etoposide. Etoposide activated p38, inhibited the G2/M transition with the persistent inhibitory phosphorylation of Cdc2 on Tyr15, and caused apoptosis of Daudi cells. Inducible expression of a dominant negative p38alpha mutant in Daudi cells reduced the inhibition of Cdc2 as well as G2/M arrest and augmented apoptosis induced by etoposide. SB203580, a specific inhibitor of p38alpha and p38beta, similarly reduced the inhibitory phosphorylation of Cdc2 as well as G2/M arrest and augmented apoptosis of Daudi cells treated with etoposide. These results suggest that p38 plays a role in G2/M checkpoint activation through induction of the persistent inhibitory phosphorylation of Cdc2 and, thereby, inhibits apoptosis of Daudi cells treated with etoposide. The present study, thus, raises the possibility that p38 may represent a new target for sensitization of lymphoma cells to DNA-damaging chemotherapeutic agents.

CDC2 Protein Kinase↗
PubMed2005

Distinction between some saccharides in scattered optical sum frequency intensity images.

Using an optical sum frequency (SF) microscope with visible and infrared light pulses for excitation, we have attempted to distinguish among four saccharide species. The saccharides we studied were d-glucose, amylopectin, beta-cyclodextrin, and amylose. The wavelength of the infrared light was resonant to CH vibration. Amylose showed very weak sum frequency scattering for CH vibration among the four saccharides. As for the other three saccharides, we found a big difference in the sum frequency spectra of their CH stretching vibration near 2900 cm-1, when the incident visible and infrared light pulses were p- and s-polarized, respectively. Based on these facts, we have demonstrated a distinction between these three saccharides in the scattered SF intensity images.

Amylopectin↗
PubMed2005

Pericardial effusion and cardiac tamponade in pediatric stem cell transplant recipients.

Pericardial effusion and cardiac tamponade is a rarely reported complication following stem cell transplant (SCT). The incidence among pediatric SCT recipients is not well defined. To assess the frequency of clinically significant pericardial effusions, we retrospectively examined clinically significant cardiac effusions at our center. Between January of 1993 and August 2004, clinically significant pericardial effusions were identified in nine of 205 patients (4.4%). The median age at the time of transplant was 9 years (range 0.6-18 years) and seven received an allogeneic transplant. All nine had normal cardiac function prior to transplant. The effusion developed at a median of 30 days (range 18-210 days). All allogeneic recipients had acute or clinically extensive graft-versus-host disease (GVHD) at the time the effusion was diagnosed. Seven patients (78%) required pericardiocentesis or surgical creation of a pericardial window. No patient died as a complication of the effusion or the therapeutic procedures. Clinically significant pericardial effusions are more common than previously reported in pediatric SCT recipients. Acute and chronic GVHD is an associated factor.

Adolescent↗
PubMed2005

Association of MBL gene polymorphisms with major bacterial infection in patients treated with high-dose chemotherapy and autologous PBSCT.

A growing body of evidence indicates that genetic factors are involved in an increased risk of infection. We investigated whether mannose-binding lectin (MBL) gene polymorphisms that cause low levels of MBL are associated with the occurrence of major infections in patients, mainly bearing hematological malignancies, after high-dose chemotherapy (HDT) rescued by autologous peripheral blood stem cell transplantation (auto-PBSCT). A retrospective evaluation of 113 patients treated with HDT and auto-PBSCT revealed that the low-producing genotypes, B/B and B/LXA, were associated with major bacterial infection (P=0.0016, OR 7.9). We next performed a nation-wide large-scale study to assess the allele frequency of the MBL coding mutation in a total of 2623 healthy individuals in Japan. The frequency of allele B was estimated to be approximately 0.2, almost the same in seven different areas of Japan. This common occurrence suggests that MBL deficiency may play an important role in the clinical settings of immunosuppression.

Alleles↗
PubMed2005

Prevention of the rehaemorrhage of bleeding peptic ulcers: effects of Helicobacter pylori eradication and acid suppression.

AIM: This study aimed to investigate the consequences of Helicobacter pylori eradication and acid suppression on rehaemorrhage caused by bleeding peptic ulcers. METHODS: A total of 320 patients who had been diagnosed with bleeding peptic ulcers between January 1994 and December 2001 were included in the study. Cases between 1994 and 1997, prior to the introduction of eradication therapy, were assigned to group A, whereas those between 1998 and 2001, after the eradication therapy, were assigned to group B. RESULTS: Of the 320 cases, 162 were designated as group A (113 gastric ulcers and 49 duodenal ulcers) and 158 as group B (116 and 42, respectively). Rehaemorrhage occurred in 24 cases (15%) and five cases (3%) in groups A and B, respectively, presenting a significantly decreased rate of rehaemorrhage in group B. Among those without eradication, rehaemorrhage was observed in 15 of 128 cases (12%) that received treatment with histamine(2)-receptor antagonist (famotidine), and 14 of 142 cases (10%) treated with proton-pump inhibitors, with no significant difference between the two. CONCLUSIONS: Helicobacter pylori eradication lowered the rates of rehaemorrhage. Treatment with histamine(2)-receptor antagonist or proton-pump inhibitors did not produce a difference in the rate of rehaemorrhage.

Adult↗
PubMed2005

Relationship between temporary inhibition and structure of disulfide-linkage analogs of marinostatin, a natural ester-linked protein protease inhibitor.

A 12-residue marinostatin [MST(1-12): (1)FATMRYPSDSDE(12)] which contains two ester linkages of Thr(3)-Asp(9) and Ser(8)-Asp(11) strongly inhibits subtilisin. In order to study the relationship between the inhibitory activity, structure, and stability of MST, MST analogs were prepared by changing ester linkages to a disulfide linkages. The analogs without the disulfide linkage between 3 and 9 positions lost their inhibitory activity. The K(i) value of 1SS(C(3)-C(9)) ((1)FACMRYPSCSDE(12)), which has a single disulfide linkage of Cys(3)-Cys(9) was comparable with those of MST(1-12) and MST-2SS ((1)FACMRYPCCSCE(12)), a doubly linked analog of Cys(3)-Cys(9) and Cys(8)-Cys(11). However, 1SS(C(3)-C(9)) and MST-2SS showed temporary inhibition, but not MST(1-12): These analogs were inactivated after incubation with subtilisin for 30 min, and were specifically hydrolyzed at the reactive site. (1)H NMR study showed that 1SS(C(3)-C(9)) has two conformations, which contain a cis- (70%) or trans- (30%) Pro residue, while MST-2SS as well as MST(1-12) takes a single conformation containing only a cis-Pro residue. Hydrogen-deuterium exchange rate of the Arg(5) (P1') NH proton of the MST analogs was about 100 times faster than that of MST(1-12). These results indicate that the linkage between the positions 8 and 11 plays a role for fixing the cis-conformation of the Pro(7) residue, and that the linkage between 3 and 9 is indispensable for the inhibition, but not enough for stable protease-inhibitor complex.

ATP-Binding Cassette Transporters↗