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Takashi Saito

Publications and source records attributed to Takashi Saito.

At least 19 recordsLinked to original sources
PubMed2006

The actin cloud induced by LFA-1-mediated outside-in signals lowers the threshold for T-cell activation.

The dynamic rearrangement of the actin cytoskeleton plays critical roles in T-cell receptor (TCR) signaling and immunological synapse (IS) formation in T cells. Following actin rearrangement in T cells upon TCR stimulation, we found a unique ring-shaped reorganization of actin called the "actin cloud," which was specifically induced by outside-in signals through lymphocyte function-associated antigen-1 (LFA-1) engagement. In T-cell-antigen-presenting cell (APC) interactions, the actin cloud is generated in the absence of antigen and localized at the center of the T-cell-APC interface, where it accumulates LFA-1 and tyrosine-phosphorylated proteins. The LFA-1-induced actin cloud formation involves ADAP (adhesion- and degranulation-promoting adaptor protein) phosphorylation, LFA-1/ADAP assembly, and c-Jun N-terminal kinase (JNK) activation, and occurs independent of TCR and its proximal signaling. The formation of the actin cloud lowers the threshold for subsequent T-cell activation. Thus, the actin cloud induced by LFA-1 engagement may serve as a possible platform for LFA-1-mediated costimulatory function for T-cell activation.

Actin Cytoskeleton↗
PubMed2006

Improved clinical outcome of patients with Candida bloodstream infections through direct consultation by infectious diseases physicians in a Japanese university hospital.

OBJECTIVE: To examine whether intervention by infectious diseases physicians (IDPs) in the treatment decisions that emphasize adequate antifungal treatment and early removal of central venous catheter for patients with Candida bloodstream infection (BSI) improves prognosis. DESIGN: Retrospective cohort study of patients with Candida BSI, comparing the prognosis of patients before and after the start of the intervention. SETTING: A 1,240-bed, tertiary care university hospital. PATIENTS: Forty patients with Candida BSI during a 2-year period, from January 2001 to December 2002, were included in the study. Twenty-three patients in the first year after the start of intervention by IDPs (intervention group) were compared with 17 patients in the first year before the start of the IDP intervention (baseline group). INTERVENTIONS: In January 2002, a total of 5 IDPs at Kyoto University Hospital gave unsolicited recommendations on antifungal treatment and advised all physicians treating inpatients who had Candida BSI to remove the central venous catheter. RESULTS: No significant difference was seen between the 2 groups in patients' clinical background, species, and fluconazole susceptibility of the causative organisms. The 30-day survival rate was significantly better in the intervention group (18 [78%] of 23 patients) than in the baseline group (7 [44%] of 16 patients; P=.04 by Fisher's exact test). More patients in the intervention group than in the baseline group received appropriate antifungal therapy (81% vs 50%) and had their central venous catheter removed at an appropriate time (95% vs 81%). CONCLUSION: The introduction of an active system of IDP consultation for every case of Candida BSI in our hospital substantially improved patient outcomes.

Adult↗
PubMed2006

Immunological synapse and microclusters: the site for recognition and activation of T cells.

An immunological synapse (IS) is formed at the interface between antigen-presenting cells and T cells, and is believed to be the structure responsible for antigen recognition and T-cell activation. However, recent imaging analyses reveal that T-cell receptor microclusters (MCs) formed prior to IS are the site for antigen recognition and T-cell activation. MCs are continuously generated at the periphery of the interface, even after IS formation, and induce sustained activation signals. MC formation is not accompanied by lipid-raft clustering. Central supramolecular activation cluster is considered functional in recycling and degradation of T-cell receptors, directional secretion of cytokines and cytolytic granules, generation of sustained signals, or maintenance of the cell-cell conjugation.

Animals↗
PubMed2006

A critical role for the innate immune signaling molecule IRAK-4 in T cell activation.

IRAK-4 is a protein kinase that is pivotal in mediating signals for innate immune responses. Here, we report that IRAK-4 signaling is also essential for eliciting adaptive immune responses. Thus, in the absence of IRAK-4, in vivo T cell responses were significantly impaired. Upon T cell receptor stimulation, IRAK-4 is recruited to T cell lipid rafts, where it induces downstream signals, including protein kinase C activation through the association with Zap70. This signaling pathway was found to be required for optimal activation of nuclear factor kappaB. Our findings suggest that T cells use this critical regulator of innate immunity for the development of acquired immunity, suggesting that IRAK-4 may be involved in direct signal cross talk between the two systems.

Animals↗
PubMed2006

A case of perinatal sepsis by Campylobacter fetus subsp. fetus infection successfully treated with carbapenem--case report and literature review.

Infection due to Campylobacter fetus subsp. fetus during pregnancy is uncommon in humans. We report a case of a pregnant woman who experienced premature labor. The infant was diagnosed with neonatal sepsis due to C. fetus subsp. fetus, and was successfully treated with carbapenem. Maternal clinical symptoms and severe villitis suggested that the route of fetal infection was hematogenous spread. We also review previous reports in the literature that describe this infection during pregnancy.

Adult↗
PubMed2006

Rapid diagnosis of glycine encephalopathy by 13C-glycine breath test.

OBJECTIVE: It is currently problematic to confirm the clinical diagnosis of glycine encephalopathy, requiring either invasive liver biopsy for enzymatic analysis of the glycine cleavage system or exhaustive mutation analysis. Because the glycine cleavage system breaks down glycine generating carbon dioxide, we suppose that the glycine cleavage system activity could be evaluated in vivo by measuring exhaled (13)CO(2) after administration of [1-(13)C]glycine. METHODS: The [1-(13)C]glycine breath test was performed in 10 control subjects and 5 glycine encephalopathy patients with GLDC mutation, including 1 patient with mild glycine encephalopathy. RESULTS: All the patients showed lower (13)CO(2) excretion than any control subject. INTERPRETATION: Not only typical GE but also atypical GE can be reliably diagnosed by the (13)C-glycine breath test. Because it is rapid, non-invasive, and requires little expertise, the breath test could be useful as a standard test for diagnosing GE.

Adolescent↗
PubMed2006

Inhibition of SMAD2 expression prevents murine palatal fusion.

Transforming growth factor (TGF)-beta 3 is known to regulate the disappearance of murine medial edge epithelium (MEE) during palatal fusion. Our previous studies showed that SMAD2, a TGF-beta signaling mediator, was expressed and phosphorylated primarily in the MEE and that SMAD2 phosphorylation in the MEE was temporospatially regulated by TGF-beta 3. The goal of this study was to examine the requirement for SMAD2 to complete the developmental events necessary for palatal fusion. SMAD2 expression was inhibited with Smad2 siRNA transfection into palatal tissues in vitro. The results showed that Smad2 siRNA transfection resulted in the maintenance of MEE cells in the palatal midline. Western blot and immunofluorescence analyses confirmed that the endogenous SMAD2 and phospho-SMAD2 levels were reduced following siRNA transfection. The SMAD3 level was not altered by the Smad2 siRNA transfection. The persistence of the MEE and the decreased SMAD2/phospho-SMAD2 levels were coincident with increased MEE cell proliferation. Addition of exogenous TGF-beta 3 increased p-SMAD2 level but not the total SMAD2 level. Therefore, exogenous TGF-beta 3 was not able to induce p-SMAD2 enough to rescue the palatal phenotype in the Smad2 siRNA group. The results indicated that the endogenous SMAD2 level is crucial in the regulation of disappearance of MEE during palatal fusion.

Animals↗
PubMed2006

Enzymatic preparation of hollow magnetite microspheres for hyperthermic treatment of cancer.

Ferrimagnetic materials can be expected to be useful as thermal seeds for hyperthermic treatment of cancer, especially where the cancer is located in deep parts of body, as they can generate heat by magnetic hysteretic loss when they are placed in an alternating magnetic field. In this study, hollow magnetite (Fe(3)O(4)) particles were prepared using an enzymatic reaction of urease. A hollow particle was obtained by using a Pasteur pipette. The particle was 500 microm in size and was composed of Fe(3)O(4). Its saturation magnetization and coercive force were 57 emuxg(-1) and 183 Oe, respectively. Its heat generation under an alternating magnetic field of 300 Oe at 100 kHz was estimated to be 45 Wxg(-1). Microspheres 30 microm in diameter were also successfully obtained by using a spray gun.

Biocompatible Materials↗
PubMed2006

T cell receptor-proximal signals are sustained in peripheral microclusters and terminated in the central supramolecular activation cluster.

T cell receptor (TCR) signaling is initiated and sustained in microclusters; however, it's not known whether signaling also occurs in the TCR-rich central supramolecular activation cluster (cSMAC). We showed that the cSMAC formed by fusion of microclusters contained more CD45 than microclusters and is a site enriched in lysobisphosphatidic acid, a lipid involved in sorting ubiquitinated membrane proteins for degradation. Calcium signaling via TCR was blocked within 2 min by anti-MHCp treatment and 1 min by latrunculin-A treatment. TCR-MHCp interactions in the cSMAC survived these perturbations for 10 min and hence were not sufficient to sustain signaling. TCR microclusters were also resistant to disruption by anti-MHCp and latrunculin-A treatments. We propose that TCR signaling is sustained by stabilized microclusters and is terminated in the cSMAC, a structure from which TCR are sorted for degradation. Our studies reveal a role for F-actin in TCR signaling beyond microcluster formation.

Actins↗
PubMed2006

IRAK-4--a shared NF-kappaB activator in innate and acquired immunity.

The human body is protected against external pathogens by two immune systems: innate and acquired immunities. Whereas innate immunity exhibits immediate responses to external pathogens by recognizing pathogen-associated molecular patterns (PAMPs), adaptive immunity uses T cells to recognize and defend against pathogens by developing effector cells, antibodies and memory cells. Although each system seems to possess distinct activation mechanisms, interleukin-1 receptor-associated kinase (IRAK)-4 is essential for NF-kappaB activation in Toll-like receptor (TLR) and T-cell receptor (TCR) signaling pathways. This implies possible crosstalk between innate and acquired immunities, and evolutionary development that resulted in the use of innate signaling molecules by the acquired immune system. Here, we discuss the impact of these evolutionarily conserved molecules on innate and acquired immunity, and their potential as drug targets for the simultaneous modulation of both immunities.

Adolescent↗
PubMed2006

RNA polymerase I-specific subunit CAST/hPAF49 has a role in the activation of transcription by upstream binding factor.

Eukaryotic RNA polymerases are large complexes, 12 subunits of which are structurally or functionally homologous across the three polymerase classes. Each class has a set of specific subunits, likely targets of their cognate transcription factors. We have identified and characterized a human RNA polymerase I (Pol I)-specific subunit, previously identified as ASE-1 (antisense of ERCC1) and as CD3epsilon-associated signal transducer (CAST), and here termed CAST or human Pol I-associated factor of 49 kDa (hPAF49), after mouse orthologue PAF49. We provide evidence for growth-regulated Tyr phosphorylation of CAST/hPAF49, specifically in initiation-competent Pol Ibeta complexes in HeLa cells, at a conserved residue also known to be important for signaling during T-cell activation. CAST/hPAF49 can interact with activator upstream binding factor (UBF) and, weakly, with selectivity factor 1 (SL1) at the rDNA (ribosomal DNA repeat sequence encoding the 18S, 5.8S, and 28S rRNA genes) promoter. CAST/hPAF49-specific antibodies and excess CAST/hPAF49 protein, which have no effect on basal Pol I transcription, inhibit UBF-activated transcription following functional SL1-Pol I-rDNA complex assembly and disrupt the interaction of UBF with CAST/hPAF49, suggesting that interaction of this Pol I-specific subunit with UBF is crucial for activation. Drawing on parallels between mammalian and Saccharomyces cerevisiae Pol I transcription machineries, we advance one model for CAST/hPAF49 function in which the network of interactions of Pol I-specific subunits with UBF facilitates conformational changes of the polymerase, leading to stabilization of the Pol I-template complex and, thereby, activation of transcription.

HeLa Cells↗
PubMed2006

Use of a Peltier chip with a newly devised local brain-cooling system for neocortical seizures in the rat. Technical note.

Local cortical cooling for termination of epileptic discharges (EDs) has recently become a focus of research. The authors report on a newly devised cooling system that uses a thermoelectric (Peltier) chip and examine the system's performance in experimental neocortical seizures. Experiments were performed in adult male Sprague-Dawley rats after induction of halothane anesthesia. The Peltier chip was attached to a heat sink with a water channel. Two silicon tubes were connected to the heat sink, and water at 37 degrees C was circulated in the channel. The newly designed device was placed on the surface of the cortex. Kainic acid (KA) was injected into the cortex to provoke EDs. In the nonepileptic cortex, the temperature of the cortical surface decreased to 14.8 +/- 1.5 degrees C and that 2 mm below the surface to 27.1 +/- 3.1 degrees C within 30 seconds after the start of cooling. The temperature of the heated side of the chip was maintained at approximately 36.9 degrees C. Without water circulation, the temperature of the cortical surface decreased to 20 degrees C but soon began to increase, peaking at 30 degrees C. The temperature of the heated side of the chip rose to more than 60 degrees C. The EDs, which appeared within 20 minutes after KA injection, began to decrease in amplitude immediately after cooling began and continued to decrease as the temperature of the cortex was lowered. Sufficient miniaturization and good performance of the cooling device was demonstrated. Further efforts to develop implantable cooling systems and improve existing ones should be continued.

Animals↗
PubMed2005

Mechanistic basis of pre-T cell receptor-mediated autonomous signaling critical for thymocyte development.

The pre-T cell receptor (TCR) is crucial for early T cell development and is proposed to function in a ligand-independent way. However, the molecular mechanism underlying the autonomous signals remains elusive. Here we show that the pre-TCR complex spontaneously formed oligomers. Specific charged residues in the extracellular domain of the pre-TCR alpha-chain mediated formation of the oligomers in vitro. Alteration of these residues eliminated the ability of the pre-TCR alpha-chain to support pre-TCR signaling in vivo. Dimerization but not raft localization of CD3epsilon was sufficient to simulate pre-TCR function and promote beta-selection. These results suggest that the pre-TCR complex can deliver its signal autonomously through oligomerization of the pre-TCR alpha-chain mediated by charged residues.

Amino Acid Sequence↗
PubMed2005

Newly generated T cell receptor microclusters initiate and sustain T cell activation by recruitment of Zap70 and SLP-76.

T cell receptor (TCR) activation and signaling precede immunological synapse formation and are sustained for hours after initiation. However, the precise physical sites of the initial and sustained TCR signaling are not definitively known. We report here that T cell activation was initiated and sustained in TCR-containing microclusters generated at the initial contact sites and the periphery of the mature immunological synapse. Microclusters containing TCRs, the tyrosine kinase Zap70 and the adaptor molecule SLP-76 were continuously generated at the periphery. TCR microclusters migrated toward the central supramolecular cluster, whereas Zap70 and SLP-76 dissociated from these microclusters before the microclusters coalesced with the TCR-rich central supramolecular cluster. Tyrosine phosphorylation and calcium influx were induced as microclusters formed at the initial contact sites. Inhibition of signaling prevented recruitment of Zap70 into the microclusters. These results indicated that TCR-rich microclusters initiate and sustain TCR signaling.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Highly stable gold(III) complex with a hydantoin ligand in alkaline media.

A novel gold(III) complex with a monodentate 5,5-dimethylhydantoin ligand, [Au(dmh)4]-, is square planar in geometry, inert and highly stable in alkaline solutions because of soft acid-base interactions, and electrochemically reduced near -0.3 V vs Ag/AgCl to give a gold(0) film with a high current efficiency.

Journal Article↗
PubMed2005

Down-regulation of basophil function by human CD200 and human herpesvirus-8 CD200.

Human and rodent CD200 are recognized by the inhibitory CD200R, and these molecules play an important role in the regulation of the immune system. Several viruses, such as human herpesvirus-6 (HHV-6), HHV-7, and HHV-8, possess a CD200 homologue, suggesting that these viruses regulate the immune response via CD200R. In this study, we analyzed the effect of human CD200 and the viral CD200 homologues on human CD200R-expressing cells. We found that human CD200R is predominantly expressed on basophils in amounts higher than on other human peripheral blood leukocytes. Furthermore, the viral CD200 homologues as well as human CD200 were recognized by human CD200R, and the activation of basophils was down-regulated by these CD200 proteins. These results suggested that CD200R is an important regulatory molecule of basophil activation. In addition, the presence of CD200 homologues on several viruses suggests a potentially unique relationship between basophil function and viral infection.

Animals↗
PubMed2005

DNA polymerase theta contributes to the generation of C/G mutations during somatic hypermutation of Ig genes.

Somatic hypermutation of Ig variable region genes is initiated by activation-induced cytidine deaminase; however, the activity of multiple DNA polymerases is required to ultimately introduce mutations. DNA polymerase eta (Poleta) has been implicated in mutations at A/T, but polymerases involved in C/G mutations have not been identified. We have generated mutant mice expressing DNA polymerase (Pol) specifically devoid of polymerase activity. Compared with WT mice, Polq-inactive (Polq, the gene encoding Pol) mice exhibited a reduced level of serum IgM and IgG1. The mutant mice mounted relatively normal primary and secondary immune responses to a T-dependent antigen, but the production of high-affinity specific antibodies was partially impaired. Analysis of the J(H)4 intronic sequences revealed a slight reduction in the overall mutation frequency in Polq-inactive mice. Remarkably, although mutations at A/T were unaffected, mutations at C/G were significantly decreased, indicating an important, albeit not exclusive, role for Pol activity. The reduction of C/G mutations was particularly focused on the intrinsic somatic hypermutation hotspots and both transitions and transversions were similarly reduced. These findings, together with the recent observation that Pol efficiently catalyzes the bypass of abasic sites, lead us to propose that Pol introduces mutations at C/G by replicating over abasic sites generated via uracil-DNA glycosylase.

Animals↗