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Biomedical subjects

Kazuo Yamamoto

Publications and source records attributed to Kazuo Yamamoto.

At least 19 recordsLinked to original sources
PubMed2006

Detection of weak sugar binding activity of VIP36 using VIP36-streptavidin complex and membrane-based sugar chains.

High mannose-type glycan-lectin interactions play important roles especially in quality control of glycoproteins. VIP36 is a receptor with homology to plant leguminous lectins in its luminal region. The luminal region of VIP36 with a C-terminal biotinylation-tag (sVIP36) was expressed in Escherichia coli and oligomerized with R-phycoerythrin (PE)-labelled streptavidin. Flow cytometric analysis revealed that PE-labelled sVIP36-SA complex (sVIP36-SA) bound to deoxymannojirimycin (DMJ)- and kifunensine (KIF)-treated HeLaS3 cells. The binding of sVIP36-SA to HeLaS3 cells treated with DMJ or KIF was abolished by endo-beta-N-acetylglucosaminidase H treatment of the cells. Furthermore, the binding of sVIP36-SA to the cells was inhibited by high mannose-type glycans especially Man(7-9) GlcNAc(2), indicating that the binding of sVIP36-SA to cell surfaces was mediated by high mannose-type glycans. Although VIP36 has the lower affinity for ligands than typical homologous plant lectins, we were able to monitor the sugar-binding activity of VIP36 using less than 100 ng of the sVIP36-SA. This method is highly sensitive and suitable for detecting interactions between lectins and sugar chains of low affinity.

1-Deoxynojirimycin↗
PubMed2006

Effects of potassium alkalis and sodium alkalis on the dechlorination of o-chlorophenol in supercritical water.

Effects of potassium alkalis and sodium alkalis on the dechlorination of o-chlorophenol (o-CP) in supercritical water (SCW) were studied in this paper under the conditions of 450 degrees C and 25 MPa. Experimental results indicated that the dechlorination of o-CP can be accelerated significantly by all alkalis investigated. The dechlorination of o-CP proceeded mainly via two pathways: hydrodechlorination and hydrolysis. Both of the two pathways can be promoted by alkalis, and the dechlorination of o-CP can be accelerated by both the cations and hydroxide ion dissociated from alkalis. The overall dechlorination of o-CP can be accelerated by cations via promoting the hydrodechlorination pathway, while, hydroxide ion via promoting the hydrolysis pathway. In addition, the hydrodechlorination can be accelerated faster by sodium alkalis than that by potassium ones, while, the hydrolysis can be promoted faster by potassium alkalis. This difference may be caused by the different charge density between potassium ion and sodium ion, and the different solubility and dissociation constant between potassium alkalis and sodium alkalis in SCW. Dechlorination of o-CP with addition of alkalis prior to supercritical water oxidation (SCWO) process not only can avoid the reactor corrosion caused by the generated hydrochloric acid in direct SCWO of o-CP, but also can reduce the formation of toxic chlorinated byproducts compared with direct SCWO process or SCWO of o-CP with addition of alkali.

Alkalies↗
PubMed2006

MHC class I-like MILL molecules are beta2-microglobulin-associated, GPI-anchored glycoproteins that do not require TAP for cell surface expression.

MILL (MHC class I-like located near the leukocyte receptor complex) is a family of MHC class I-like molecules encoded outside the MHC, which displays the highest sequence similarity to human MICA/B molecules among known class I molecules. In the present study, we show that the two members of the mouse MILL family, MILL1 and MILL2, are GPI-anchored glycoproteins associated with beta2-microglobulin (beta2m) and that cell surface expression of MILL1 or MILL2 does not require functional TAP molecules. MILL1 and MILL2 molecules expressed in bacteria could be refolded in the presence of beta2m, without adding any peptides. Hence, neither MILL1 nor MILL2 is likely to be involved in the presentation of peptides. Immunohistochemical analysis revealed that MILL1 is expressed in a subpopulation of thymic medullary epithelial cells and a restricted region of inner root sheaths in hair follicles. The present study provides additional evidence that MILL is a class I family distinct from MICA/B.

Animals↗
PubMed2006

FOXO3a-dependent regulation of Puma in response to cytokine/growth factor withdrawal.

Puma is an essential mediator of p53-dependent and -independent apoptosis in vivo. In response to genotoxic stress, Puma is induced in a p53-dependent manner. However, the transcription factor driving Puma up-regulation in response to p53-independent apoptotic stimuli has yet to be identified. Here, we show that FOXO3a up-regulates Puma expression in response to cytokine or growth factor deprivation. Importantly, dysregulated Akt signaling in lymphoid cells attenuated Puma induction upon cytokine withdrawal. Our results suggest that Puma, together with another BH3 only member, Bim, function as FOXO3a downstream targets to mediate a stress response when PI3K/Akt signaling is down-regulated.

Animals↗
PubMed2006

Regulation of transactivation-independent proapoptotic activity of p53 by FOXO3a.

The tumor suppressor p53 can trigger cell death independently of its transcriptional activity through subcellular translocation and activation of proapoptotic Bcl-2 family members. The regulation of such activity of endogenous p53 in response to stress remains largely unknown. Here we show that nuclear, activated FOXO3a could impair p53 transcriptional activity. However, activation of FOXO3a either on serum starvation or by expressing a constitutively active form of FOXO3a could induce p53-dependent apoptosis, even in cells bearing a transcriptionally inactive form of p53. Furthermore, FOXO3a could promote p53 cytoplasmic accumulation by increasing its association with nuclear exporting machinery. Our data also suggest that PUMA and Bax are required for p53-dependent apoptosis in manner that is independent of p53 transcriptional activity.

Animals↗
PubMed2006

Loss of heterozygosity in yeast can occur by ultraviolet irradiation during the S phase of the cell cycle.

A CAN1/can1Delta heterozygous allele that determines loss of heterozygosity (LOH) was used to study recombination in Saccharomyces cerevisiae cells exposed to ultraviolet (UV) light at different points in the cell cycle. With this allele, recombination events can be detected as canavanine-resistant mutations after exposure of cells to UV radiation, since a significant fraction of LOH events appear to arise from recombination between homologous chromosomes. The radiation caused a higher level of LOH in cells that were in the S phase of the cell cycle relative to either cells at other points in the cell cycle or unsynchronized cells. In contrast, the inactivation of nucleotide excision repair abolished the cell cycle-specific induction by UV of LOH. We hypothesize that DNA lesions, if not repaired, were converted into double-strand breaks during stalled replication and these breaks could be repaired through recombination using a non-sister chromatid and probably also the sister chromatid. We argue that LOH may be an outcome used by yeast cells to recover from stalled replication at a lesion.

Cell Cycle↗
PubMed2006

Optimization of wastewater feeding for single-cell protein production in an anaerobic wastewater treatment process utilizing purple non-sulfur bacteria in mixed culture condition.

Impacts of operation timing of feeding and withdrawal on anaerobic wastewater treatment utilizing purple non-sulfur bacteria have been investigated in mixed culture condition with acidogenic bacteria. Simulated wastewater containing glucose was treated in a laboratory-scale chemostat reactor, changing the timing of wastewater feeding and withdrawal. Rhodopseudomonas palustris, which does not utilize glucose as a substrate, was inoculated in the reactor. Rps. palustris was detected by a fluorescent in situ hybridization (FISH) technique using the specific Rpal686 probe. As a result, population ratios of Rps. palustris were over 20% through the operation. Rps. palustris could grow by utilizing metabolites of acidogenic bacteria that coexisted in the reactor. A morning feed was effective for a good growth of purple non-sulfur bacteria. A protein content of cultured bacteria was the highest when wastewater was fed in the morning. Dissolved organic carbon (DOC) removal was 94% independent of the timing control. Consequently, feeding in the morning is the optimum feed-timing control from the aspects of growth of purple non-sulfur bacteria and single-cell protein production.

Bioreactors↗
PubMed2006

Reconstruction technique for off-axis electron holography using coarse fringes.

A reconstruction technique for off-axis electron holography not requiring Fourier transformation is presented. Background intensity and amplitude modulation recorded in a hologram are normalized using an envelope function, and a cosine-function image corresponding to interference fringes is retrieved from the hologram. A reconstructed phase image is then calculated from the retrieved cosine image. After phase unwrapping, the phases due to carrier frequency and Fresnel diffraction from the biprism are removed using a reference hologram, and the corrected phase image is obtained. One advantage of this method is that the spatial resolution does not rely on the interference fringe spacing. Another advantage is that the phase image has no artifacts due to windowing of the sideband, which occurs in the usual Fourier-transformation method. Details of the calculation process and demonstrations of the method using a latex sphere particle and self-assembled Co nanoparticles are described.

Journal Article↗
PubMed2006

Specificity of replicative and SOS-inducible DNA polymerases in frameshift mutagenesis: mutability of Salmonella typhimurium strains overexpressing SOS-inducible DNA polymerases to 30 chemical mutagens.

DNA replication is frequently hindered because of the presence of DNA lesions induced by endogenous and exogenous genotoxic agents. To circumvent the replication block, cells are endowed with multiple specialized DNA polymerases that can bypass a variety of DNA damage. To better understand the specificity of specialized DNA polymerases to bypass lesions, we have constructed a set of derivatives of Salmonella typhimurium TA1538 harboring plasmids carrying the polB, dinB or mucAB genes encoding Escherichia coli DNA polymerase II, DNA polymerase IV or DNA polymerase RI, respectively, and examined the mutability to 30 chemicals. The parent strain TA1538 possesses CGCGCGCG hotspot sequence for -2 frameshift. Interestingly, the chemicals could be classified into four groups based on the mutagenicity to the derivatives: group I whose mutagenicity was highest in strain YG5161 harboring plasmid carrying dinB; group II whose mutagenicity was almost equally high in strain YG5161 and strain TA98 harboring plasmid carrying mucAB; group III whose mutagenicity was highest in strain TA98; group IV whose mutagenicity was not affected by the introduction of any of the plasmids. Introduction of plasmid carrying polB did not enhance the mutagenicity except for benz[a]anthracene. We also introduced a plasmid carrying polA encoding E. coli DNA polymerase I to strain TA1538. Strikingly, the introduction of the plasmid reduced the mutagenicity of chemicals belonging to groups I, II and III, but not the chemicals of group IV, to the levels observed in the derivative whose SOS-inducible DNA polymerases were all deleted. These results suggest that (i) DNA polymerase IV and DNA polymerase RI possess distinct but partly overlapping specificity to bypass lesions leading to -2 frameshift, (ii) the replicative DNA polymerase, i.e., DNA polymerase III, participates in the mutagenesis and (iii) the enhanced expression of E. coli polA may suppress the access of Y-family DNA polymerases to the replication complex.

Benzo(a)pyrene↗
PubMed2006

Killer cell lectin-like receptor G1 binds three members of the classical cadherin family to inhibit NK cell cytotoxicity.

Killer cell lectin-like receptor G1 (KLRG1) is an inhibitory receptor expressed on subsets of natural killer (NK) cells and T cells, for which no endogenous ligands are known. Here, we show that KLRG1 binds three of the classical cadherins (E-, N-, and R-), which are ubiquitously expressed in vertebrates and mediate cell-cell adhesion by homotypic or heterotypic interactions. By expression cloning using the mouse KLRG1 tetramer as a probe, we identified human E-cadherin as a xenogeneic ligand. We also identified a syngeneic interaction between mouse KLRG1 and mouse E-cadherin. Furthermore, we show that KLRG1 binds N- and R-cadherins. Finally, we demonstrate that E-cadherin binding of KLRG1 prevents the lysis of E-cadherin-expressing targets by KLRG1+ NK cells. These results suggest that KLRG1 ligation by E-, N-, or R-cadherins may regulate the cytotoxicity of killer cells to prevent damage to tissues expressing the cadherins.

Animals↗
PubMed2006

Studies of DNA recognition mechanism of transcription factor IRF-4.

Transcription factor IFN regulatory factor-4 (IRF-4) prefers a DNA sequence including CCGAAA, though the consensus DNA-binding sequence of the IRF family proteins is NNGAAA, and the crystal structure of PU.1/IRF-4/DNA (GTGAAA) ternary complex indicates the NN region of DNA does not interact with IRF-4 directly. This suggests that there is an indirect DNA recognition mechanism in IRF-4. In order to account for the sequence preference of IRF-4, we focused on structural properties of DNA duplexes recognized by IRF-4. Here, we performed solution NMR studies on DNA duplexes containing GGGAAA and CCGAAA sequences, and assigned most of proton resonances of DNA 17 mer with GGGAAA. (1)H-(1)H NOESY spectra indicated B-form like structure for GGGAAA. We also assigned imino proton resonances of DNA 17 mer with CCGAAA. For the imino proton region, the (1)H-(1)H NOESY spectra of these two DNA duplexes were similar.

Base Sequence↗
PubMed2006

Transactivation of CCL20 gene by Epstein-Barr virus latent membrane protein 1.

CCL20 is expected to play a crucial role in the initiation of immune responses and tumour growth. However, expression of CCL20 in Epstein-Barr virus (EBV)-associated diseases has not been studied. We examined the contribution of EBV infection and EBV-encoded latent membrane protein (LMP)-1 to CCL20 expression. EBV infection and LMP-1 induced CCL20 mRNA expression in the EBV-negative Burkitt lymphoma (BL) cell lines and the embryonic kidney cell line. Histone deacetylase inhibitor-stimulated endogenous LMP-1 also induced CCL20 expression in an EBV-positive BL cell line. Analysis of the CCL20 promoter showed that it was activated by LMP-1 C-terminal activation region (CTAR)-1 and CTAR-2. Co-expression of IkappaB alpha, IkappaB beta, IkappaB kinase (IKK)alpha, IKKbeta, IKKgamma, nuclear factor (NF)-kappaB-inducing kinase and tumour necrosis factor receptor-associated factor 2 dominant-negative constructs with LMP-1 inhibited the activation of the CCL20 promoter by LMP-1, suggesting that LMP-1 induces CCL20 via NF-kappaB signalling. The requirement for the NF-kappaB-binding site in the CCL20 promoter in LMP-1 responsiveness was established. Our results indicate that activation of the NF-kappaB pathway by LMP-1 is required for the activation of CCL20 expression.

Burkitt Lymphoma↗
PubMed2006

The treatment of refractory pneumothorax in diffuse panbronchiolitis by intravenous administration of coagulation factor XIII concentrate.

This case report presents a patient with advanced diffuse panbronchiolitis accompanied by chronic respiratory failure, marked cachexia, and refractory spontaneous pneumothorax. Because instillation of a pleurodesis agent and thoracoscopy were considered highly risky and invasive, we instead treated the patient with intravenous administration of a coagulation factor XIII concentrate, and the pneumothorax resolved. This case suggests refractory pneumothorax in a restrictive ventilatory disorder can be effectively treated with noninvasive intravenous administration of coagulation factor XIII concentrate.

Bronchiolitis↗
PubMed2006

Detection of lymph node micrometastasis in pN0 early gastric cancer: efficacy of duplex RT-PCR with MUC2 and TFF1 in mucosal cancer.

We previously reported that MUC2 is a useful marker in the detection of lymph node micrometastasis (LMM) in gastric cancer. To improve the detection rate, we focused on a TFF1 gene. We used the duplex reverse transcriptase-polymerase chain reaction (RT-PCR) method with MUC2 and TFF1 genes to detect LMM in histologically node negative (pN0) early gastric cancer (EGC) and evaluated their effectiveness. A total of 310 lymph nodes from 33 patients with pN0 EGC were analyzed. All carcinoma specimens were positive for MUC2 and/or TFF1. The positive rate of TFF1 was significantly higher than MUC2 in the undifferentiated carcinoma specimens (p=0.002). The detection rate of duplex RT-PCR with MUC2 and TFF1 was higher than that of MUC2 or TFF1 alone. In mucosal cancer, 7 cases were positive for duplex RT-PCR. Of these 7 cases, 3 were MUC2-positive/TFF1-negative while 4 were MUC2-negative/TFF1-positive. LMMs were not detected in elevated-type primary mucosal cancers with a 20-30-mm diameter. The duplex RT-PCR assay with both MUC2 and TFF1 provides a higher LMM detection rate than either MUC2 or TFF1 alone, especially in mucosal gastric cancer. LMM detected in this manner may prove useful in broadening the indications for endoscopic mucosal resection in elevated-type cancer.

Adult↗
PubMed2006

Current situation of web-based chemical registration system in the University of Tokyo.

The web-based University of Tokyo Chemical Registration Information System with computational support has been introduced in all areas using chemicals owing to the unified management of the university and the management of chemicals in conformity with legal controls. This system enables chemical users to manage chemicals easily and reduces the burden inflicted by such management. In this report, we introduce the style of chemical management in the University of Tokyo, the functions of the web-based chemical registration system, the current situation of the system and future plans.

Chemical Phenomena↗