Biomedical subjects

Takeshi Saito

Publications and source records attributed to Takeshi Saito.

At least 19 recordsLinked to original sources

PubMed2007

Comparison of ventilatory threshold and exercise habits between Japanese men with and without metabolic syndrome.

OBJECTIVE: We compared the levels of ventilatory threshold (VT) and exercise habits in subjects with metabolic syndrome with those in age, sex-matched subjects without metabolic syndrome. METHODS: We used data of 155 Japanese men (47.1+/-9.2 years) with metabolic syndrome; the diagnosis was given by the definition and the diagnostic standard for metabolic syndrome in Japan. The influence of metabolic syndrome on oxygen uptake, work rate and heart rate at VT, and exercise habits were evaluated. RESULTS: Oxygen uptake and work rate at VT in subjects with metabolic syndrome were significantly lower than those in subjects without metabolic syndrome even after adjusting for body mass index (BMI). The number of subjects with exercise habits was significantly lower in metabolic syndrome. The subjects with exercise habits were significantly older than that in subjects without exercise habits. Furthermore, oxygen uptake and work rate at VT were significantly higher in subjects with exercise habits than those in subjects without exercise habits. CONCLUSION: Lower level of VT was characteristic in subjects with metabolic syndrome. Promotion of exercise habits is necessary for preventing and improving metabolic syndrome in Japanese men.

Adult↗

PubMed2006

Regulation of innate antiviral defenses through a shared repressor domain in RIG-I and LGP2.

RIG-I is an RNA helicase containing caspase activation and recruitment domains (CARDs). RNA binding and signaling by RIG-I are implicated in pathogen recognition and triggering of IFN-alpha/beta immune defenses that impact cell permissiveness for hepatitis C virus (HCV). Here we evaluated the processes that control RIG-I signaling. RNA binding studies and analysis of cells lacking RIG-I, or the related MDA5 protein, demonstrated that RIG-I, but not MDA5, efficiently binds to secondary structured HCV RNA to confer induction of IFN-beta expression. We also found that LGP2, a helicase related to RIG-I and MDA5 but lacking CARDs and functioning as a negative regulator of host defense, binds HCV RNA. In resting cells, RIG-I is maintained as a monomer in an autoinhibited state, but during virus infection and RNA binding it undergoes a conformation shift that promotes self-association and CARD interactions with the IPS-1 adaptor protein to signal IFN regulatory factor 3- and NF-kappaB-responsive genes. This reaction is governed by an internal repressor domain (RD) that controls RIG-I multimerization and IPS-1 interaction. Deletion of the RIG-I RD resulted in constitutive signaling to the IFN-beta promoter, whereas RD expression alone prevented signaling and increased cellular permissiveness to HCV. We identified an analogous RD within LGP2 that interacts in trans with RIG-I to ablate self-association and signaling. Thus, RIG-I is a cytoplasmic sensor of HCV and is governed by RD interactions that are shared with LGP2 as an on/off switch controlling innate defenses. Modulation of RIG-I/LGP2 interaction dynamics may have therapeutic implications for immune regulation.

Antiviral Agents↗

PubMed2006

Palladium-catalyzed sonogashira and hiyama reactions using phosphine-free hydrazone ligands.

Palladium/copper-catalyzed Sonogashira cross-coupling reaction of aryl halides with a variety of terminal alkynes under amine-free conditions in dimethylformamide (DMF) at 80 degrees C gave internal arylated alkynes using PdCl2(MeCN)2 with phosphine-free hydrazone 2a as a ligand and CuI as the cocatalyst in good yields. We also found PdCl2/hydrazone ligand 1d in PhMe at 80 degrees C was a phosphine-free efficient catalyst system for a Hiyama cross-coupling reaction of aryl bromides with aryl(trialkoxy)silanes in good yields.

Journal Article↗

PubMed2006

Vanadate-induced activation of cytosolic phospholipase A2alpha in L929 cells: Roles of tyrosine kinase, protein kinase C, and extracellular signal-regulated kinase.

Orthovanadate (Na3VO4), which acts as an inhibitor of protein tyrosine phosphatases, has a various pharmacological effects including the release of arachidonic acid (AA) from cells. We investigated roles of alpha-type cytosolic phospholipase A2 (cPLA2alpha), Src family kinases (Src) and protein kinase C (PKC) in the release of AA induced by Na3VO4 from a murine fibroblast cell line, L929. C12 cells, a variant of L929 that lacks expression of cPLA2alpha, were used along with a clone of C12 cells that are stably expressing cPLA2alpha (C12-cPLA2alpha cells). In the presence of a Ca2+ ionophore (10 microM A23187), 5 and 10mM Na3VO4 synergistically stimulated AA release from L929 and C12-cPLA2alpha cells, and to a much lesser extent from control C12 cells. The release of AA by Na3VO4/A23187 was inhibited by a selective cPLA2alpha inhibitor (3 microM pyrrophenone). The release of AA by Na3VO4/A23187 was significantly inhibited by a PKC inhibitor (10 microM GF109203X), in PKC-depleted cells, by a Src inhibitor (2 microM PP2) and by an inhibitor of extracellular signal-regulated kinase 1/2 (ERK1/2) kinase (10 microM U0126). The phosphorylation of ERK1/2 was stimulated by Na3VO4, and the response was significantly decreased by inhibitors of Src, PKC and ERK1/2 kinase. Our data show that Na3VO4 stimulates AA release largely via cPLA2alpha activation in Ca2+-dependent manner, and the cross-talk between Src and PKC and the ERK-dependent pathways are involved in Na3VO4-induced AA release from L929 cells.

Animals↗

PubMed2006

Principles of intracellular viral recognition.

In mammalian cells, the products of microbial infection are recognized by pathogen recognition receptor (PRR) proteins. Virus recognition is mediated in part by PRRs that comprise a subset of Toll-like receptors or a family of RNA helicases, the latter of which contain caspase activation and recruitment domains, both of which induce interferons alpha and beta and antiviral immune defenses. Recent studies show that PRR engagement of specific pathogen-associated molecular patterns (PAMPs) within viral products, including viral proteins and nucleic acid, is facilitated by the discrete subcellular distribution of PRRs to sites that intersect with processes of virus entry and replication. PAMP structure and the subcellular context of PRR distribution form a basis of self versus nonself discrimination during the antiviral response. Understanding the virus/host interface of PRR function and PAMP recognition will advance therapeutic strategies for immune response regulation.

Animals↗

PubMed2006

IR-extended photoluminescence mapping of single-wall and double-wall carbon nanotubes.

A simple and efficient technique is described for measuring photoluminescence (PL) maps of carbon nanotubes (NTs) in the extended IR range (1-2.3 mum). It consists of preparing an NT/surfactant/gelatin film and measuring PL spectra using a combination of a tunable Ti-sapphire laser excitation and FTIR detection. This procedure has been applied to a wide range of single- and double-wall NTs unveiling chirality and diameter distributions that have so far been very difficult to measure. The problems associated with deducing these distributions are discussed by comparing absorption and PL mapping data for NT samples prepared under different conditions.

Journal Article↗

PubMed2006

Oxygen consumption of cell suspension in a poly(dimethylsiloxane) (PDMS) microchannel estimated by scanning electrochemical microscopy.

A quantitative analysis of the oxygen concentration profile near a poly(dimethylsiloxane) (PDMS) microfluidic device was performed using scanning electrochemical microscopy (SECM). A microchannel filled with sodium sulfite (Na(2)SO(3)) aqueous solution was imaged by SECM, showing that the oxygen diffusion layer of the PDMS microchannel was observed to be hemicylindrical. Based on a theoretical analysis of the hemicylindrical diffusion layer of the microchannel, the total oxygen mass transfer rates of oxygen to the PDMS microchannel filled with the Na(2)SO(3) solution was calculated to be (4.01 +/- 0.30) x 10(-12) mol s(-1). This is the maximum value of the oxygen transfer rate for this PDMS microchannel device. The oxygen consumption rate increased almost linearly with the logarithm of the concentration of E. coli cells (10(6) approximately 10(8) cells). The respiratory activity for a single E. coli cell was estimated to be approximately 4.31 x 10(-20) mol s(-1) cell(-1).

Cells↗

PubMed2006

Rapid simultaneous determination of ephedrines, amphetamines, cocaine, cocaine metabolites, and opiates in human urine by GC-MS.

This paper presents a simple and sensitive chromatographic procedure for the simultaneous determination and quantification of ephedrines, amphetamines, cocaine, cocaine metabolites, and opiates in human urine by gas chromatography-mass spectrometry. This method involves enzyme hydrolysis in the presence of a deuterated internal standard, liquid-liquid extraction, and derivatization with pentafluoropropionic anhydride and pentafluoropropanol. The recovery of each compound averaged at 65.8% or more. The limits of detection determined for each compound by using a 2-mL sample volume ranged from 5 to 50 ng/mL. The calibration curves were linear to 100 ng/mL for all compounds when determined using methamphetamine-d4 and MDMA-d5 as internal standards. This method was successfully applied for the analysis of urine samples suspected to contain intoxicants such as methamphetamine and heroin.

Adult↗

PubMed2006

Up-regulation of cytosolic phospholipase A2alpha expression by N,N-diethyldithiocarbamate in PC12 cells; involvement of reactive oxygen species and nitric oxide.

Disulfiram (an alcohol-aversive drug) and related compounds are known to provoke several side effects involving behavioral and neurological complications. N,N-diethyldithiocarbamate (DDC) is considered as one of the main toxic species of disulfiram and acts as an inhibitor of superoxide dismutase. Since arachidonic acid (AA) formation is regulated by reactive oxygen species (ROS) and related to toxicity in neuronal cells, we investigated the effects of DDC on AA release and expression of the alpha type of cytosolic phospholipase A(2) (cPLA(2)alpha) in PC12 cells. Treatment with 80-120 microM DDC that causes a moderate increase in ROS levels without cell toxicity stimulated cPLA(2)alpha mRNA and its protein expression. The expression was mediated by extracellular-signal-regulated kinase (ERK1/2), one of the mitogen-activated protein kinases. Treatment with N(G) nitro-L-arginine methyl ester (an inhibitor of nitric oxide synthase, 1 mM) and oxy-hemoglobin (a scavenger of nitric oxide, 2 mg/mL) abolished the DDC-induced responses (ERK1/2 phosphorylation and cPLA(2)alpha expression). We also showed DDC-induced up-regulation of the mRNA expression of lipocortin 1, an inhibitor of PLA(2). Furthermore, DDC treatment of the cells enhanced Ca(2+)-ionophore-induced AA release in 30 min, although the effect was limited. Changes in AA metabolism in DDC-treated cells may have a potential role in mediating neurotoxic actions of disulfiram. In this study, we show the first to demonstrate the up-regulation of cPLA(2)alpha expression by DDC treatment in neuronal cells.

Animals↗

PubMed2006

Viral and therapeutic control of IFN-beta promoter stimulator 1 during hepatitis C virus infection.

Viral signaling through retinoic acid-inducible gene-I (RIG-I) and its adaptor protein, IFN promoter-stimulator 1 (IPS-1), activates IFN regulatory factor-3 (IRF-3) and the host IFN-alpha/beta response that limits virus infection. The hepatitis C virus (HCV) NS3/4A protease cleaves IPS-1 to block RIG-I signaling, but how this regulation controls the host response to HCV is not known. Moreover, endogenous IPS-1 cleavage has not been demonstrated in the context of HCV infection in vitro or in vivo. Here, we show that HCV infection transiently induces RIG-I- and IPS-1-dependent IRF-3 activation. This host response limits HCV production and constrains cellular permissiveness to infection. However, HCV disrupts this response early in infection by NS3/4A cleavage of IPS-1 at C508, releasing IPS-1 from the mitochondrial membrane. Cleavage results in subcellular redistribution of IPS-1 and loss of interaction with RIG-I, thereby preventing downstream activation of IRF-3 and IFN-beta induction. Liver tissues from chronically infected patients similarly demonstrate subcellular redistribution of IPS-1 in infected hepatocytes and IPS-1 cleavage associated with a lack of ISG15 expression and conjugation of target proteins in vivo. Importantly, small-molecule inhibitors of NS3/4A prevent cleavage and restore RIG-I signaling of IFN-beta induction. Our results suggest a dynamic model in which early activation of IRF-3 and induction of antiviral genes are reversed by IPS-1 proteolysis and abrogation of RIG-I signaling as NS3/4A accumulates in newly infected cells. HCV protease inhibitors effectively prevent IPS-1 proteolysis, suggesting they may be capable of restoring this innate host response in clinical practice.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Supramolecular catalysts for the gas-phase synthesis of single-walled carbon nanotubes.

Reversed micelles containing metallic ions have been used as precursors of novel catalysts for the gas-phase synthesis of single-walled carbon nanotubes (SWNTs). This technique possesses the following advantages: (i) excellent solubility in organic solvents, which are used as reactants and (ii) facile preparation of multicomponent catalysts enabling systematic screening of catalyst compositions for the synthesis of SWNTs. In this study, we report the results of the screening study on the catalytic behavior of Fe-Mo binary catalysts during the synthesis of SWNTs. The results suggested that the catalytic ability was closely related to the strain of the crystal structure of Fe-Mo catalysts formed in the reaction and/or the phase transition caused by dissolution of the Mo atoms. The addition of lithium to the Fe-Mo binary catalysts has revealed an increase in the yield of SWNTs.

Journal Article↗

PubMed2006

Assessment of diffusion coefficients of general solvents by PFG-NMR: investigation of the sources error.

Accurate measurements of the diffusion coefficients, including an estimate of uncertainty, of various solvent molecules using the PFG-NMR method were performed in this study. Accurate diffusion coefficients were obtained using the Shigemi NMR tube. The relative combined standard uncertainties of the diffusion coefficients were found to be within approximately 0.4%. The three uncertainty sources (signal decay of the standard and the solvent, and diffusion coefficient of standard) equally affect the combined standard uncertainties. Unreliable data were obtained using a normal NMR tube, indicating that convection and background gradient effects significantly affected the accurate measurement of the diffusion coefficients.

Journal Article↗

PubMed2006

Sennidin stimulates glucose incorporation in rat adipocytes.

A novel small molecule compound which exerts insulin mimetic is desirable. Dozens of natural products that have quinone, naphthoquinone, or anthraquinone structure, were tested by a glucose incorporation assay. We found that sennidin A, anthraquinone derivative, stimulated glucose incorporation to near level of maximal insulin-stimulated and sennidin B, a stereoisomer of sennidin A, also stimulated, but the activity of sennidin B was lower than sennidin A. Sennidin A-stimulated glucose incorporation was completely inhibited by wortmannin. Sennidin A did not induce tyrosine phosphorylation of insulin receptor (IR) and insulin receptor substrate-1 (IRS-1), but induced phosphorylation of Akt and glucose transporter 4 (GLUT4) translocation. Our results suggest that in rat adipocytes, sennidin A stimulates glucose incorporation in the phosphatidylinositol 3-kinase (PI3K)- and Akt-dependent, but in the IR/IRS1-independent manner.

Adipocytes↗

PubMed2006

Repeatable focal seizure suppression: a rat preparation to study consequences of seizure activity based on urethane anesthesia and reversible carotid artery occlusion.

Seizures can be associated with serious systemic complications (even death) due to autonomic nervous system or respiratory dysfunction. Clinical and laboratory studies examining the relationship between seizures and autonomic dysfunction have not resolved important questions, such as whether autonomic changes result primarily from muscle activation or from limbic cortical seizure activity, because correlational studies are limited by opportunities to observe seizures and study seizure spread. We describe a rat preparation that will greatly facilitate such studies. First, we show that systemic kainic acid in urethane anesthetized animals causes a period of status epilepticus as it does in ketamine/xylazine anesthetized or awake animals, but with a critical distinction: limbic cortical seizures occur without neocortical involvement. No paralytic agents are necessary to keep animals "safely" in a stereotaxic frame because there are not motor convulsions, yet animals continue to breathe on their own. Second, we describe the construction of a simple device to permit remote reversible unilateral or bilateral common carotid artery occlusion, and show that seizure activity in dorsal hippocampal regions can be unilaterally or bilaterally suppressed during periods of occlusion. Using this preparation, we found an increase in vagus nerve activity and a decrease in mean arterial pressure during suppression of right dorsal hippocampal seizures. By contrast, suppression of left dorsal hippocampal seizures caused no changes in vagus nerve activity and a small increase in mean arterial pressure. This preparation will be invaluable for defining the dynamic interactions of limbic brain regions and the interactions of limbic brain regions with autonomic brain regions.

Anesthetics, Intravenous↗

PubMed2006

Hemoperfusion with an immobilized polymyxin B column reduces the blood level of neutrophil elastase.

BACKGROUND: We investigated whether direct hemoperfusion with an immobilized polymyxin B column (DHP with PMX) could reduce the blood level of neutrophil elastase. METHODS: 20 sepsis patients were enrolled in the study. DHP with PMX was performed twice within a 24-hour period. Neutrophil elastase was measured 7 times. RESULTS: Neutrophil elastase was 468 +/- 75.1 microg/l, while it was 1,531 +/- 201.7 microg/l immediately after the first session, declined to 351 +/- 73.9 microg/l before the second session of DHP with PMX, and increased again to 599.3 +/- 112.7 microg/l immediately after the second session, 328 +/- 73.7 microg/l at 24 h, 264 +/- 39.3 microg/l at 48 h, and 230 +/- 36.1 microg/l at 72 h after DHP with PMX. The levels from 48 h onwards were significantly lower compared with that before treatment. CONCLUSION: DHP with PMX has an overall effect that reduces circulating neutrophil elastase levels.

Adsorption↗

PubMed2006

Peripheral neuropathy caused by high-dose cytosine arabinoside treatment in a patient with acute myeloid leukemia.

The central nervous system toxicity of high-dose cytosine arabinoside is well recognized, but the toxicity of cytosine arabinoside in the peripheral nervous system has been infrequently reported. A 49-year-old Japanese man was diagnosed with acute myeloid leukemia. After he achieved complete remission, he received high-dose cytosine arabinoside treatment (2 g/m2 twice a day for 5 days; total, 20 g/m2) as consolidation therapy. The first course of high-dose cytosine arabinoside resulted in no unusual symptoms, but on day 21 of the second course of treatment, the patient complained of numbness in his right foot. Electromyogram and nerve-conduction studies showed peripheral neuropathy in both peroneal nerves. This neuropathy was gradually resolving; however, after the patient received allogeneic bone marrow transplantation, the symptoms worsened, with the development of graft-versus-host disease, and the symptoms subsequently responded to methylprednisolone. Although the mechanisms of peripheral neuropathy are still unclear, high-dose cytosine arabinoside is a therapy that is potentially toxic to the peripheral nervous system, and auto/alloimmunity may play an important role in these mechanisms.

Acute Disease↗

PubMed2006

The perinatal transition of the hepatobiliary cyst size provides information about the condition of bile flow in biliary cystic malformation cases.

PURPOSE: The aim of this study was to understand the level of bile flow by perinatal transitions of the hepatobiliary cyst size in biliary cystic malformation (BCM) cases and to examine the association between the transitions of the cyst size, cholangiographic images of the intrahepatic bile ducts (IHBDs), and histological features of the liver specimens in BCM. METHODS: We measured perinatal size of the hepatobiliary cyst in 7 BCM cases, composed of 1 case with choledochal cyst and 6 cases with biliary atresia (BA). Bile excretion was inferred from the transition of cyst size and the postoperative course. The IHBD cholangiographic images were also examined. In addition, histology of liver specimens obtained at the time of initial surgery was evaluated for IHBD maturity and fibrosis. RESULTS: The size of the small cyst in 2 BA cases remained almost unchanged throughout gestation. These cases required longer postoperative period for the clearance of jaundice. Their IHBD images were indistinct, and histology showed severe fibrosis. The ratio of bile ducts to portal tracts was 0.5 in 1 of the cases. However, in other BCM cases where the cysts grew large perinatally, bile excretion was good postoperatively, and their jaundice cleared in shorter period. Their cholangiographic images demonstrated clearer periphery of the IHBDs, and their histology showed mild or moderate fibrosis, if any. CONCLUSIONS: The perinatal transition of the cyst size in BCM cases can be helpful in assessing the level of bile flow. BCM with a small cyst during gestation can include some BAs with poorer bile flow, vaguer IHBD images, and prominent liver fibrosis. For the treatment of BCM cases, especially patients with a small biliary cyst, prompt response may be required after birth.

Bile↗

PubMed2006

Pediatric gastroesophageal varices: treatment strategy and long-term results.

BACKGROUND/PURPOSE: There are various treatment strategies for gastroesophageal varices in children. We studied the therapeutic value of endoscopic variceal clipping (EVC) and ligation (EVL). METHODS: Four hundred ninety-nine endoscopic examinations performed between 1991 and 2005 were retrospectively analyzed. F2 and F3 varices with red color signs on follow-up endoscopy were treated with prophylactic EVC. In variceal rupture cases, EVC and EVL were used in combination. RESULTS: Eighty-two prophylactic EVCs were done, and variceal progression was prevented in 89.9%. However, some patients had persistent red color signs and required frequent EVC. Ten emergent procedures were done for variceal rupture, and, in 4 cases, EVL was used to arrest massive variceal bleeding. Five patients developed bleeding during follow-up cause by rupture of gastric fundal varices, which probably had been aggravated by prior treatment for esophageal varices. CONCLUSIONS: The control of gastroesophageal varices by routine EVC was satisfactory. However, ruptures during follow-up suggested the importance of controlling gastric fundal varices. Endoscopic variceal ligation is a simple, effective, and safe treatment tool, particularly for ruptured varices. However, it is difficult to treat gastric fundal varices with EVL; this disadvantage of EVL can be overcome by the concomitant use of EVC.

Adolescent↗