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Biomedical subjects

N Yamamoto

Publications and source records attributed to N Yamamoto.

At least 343 records · Page 19Linked to original sources
PubMed1998

A low-molecular-weight inhibitor against the chemokine receptor CXCR4: a strong anti-HIV peptide T140.

T22 ([Tyr5,12, Lys7]-polyphemusin II) is an 18-residue peptide amide, which has strong anti-HIV activity. T22 inhibits the T cell line-tropic (T-tropic) HIV-1 infection through its specific binding to a chemokine receptor CXCR4, which serves as a coreceptor for the entry of T-tropic HIV-1 strains. Herein, we report our finding of novel 14-residue CXCR4 inhibitors, T134 and T140, on the basis of the T22 structure. In the assays we examined, T140 showed the highest inhibitory activity against HIV-1 entry and the strongest inhibitory effect on the binding of an anti-CXCR4 monoclonal antibody (12G5) to CXCR4 among all the CXCR4 inhibitors that have been reported up to now.

Amino Acid Sequence↗
PubMed1998

Liposome oligomannose-coated with neoglycolipid, a new candidate for a safe adjuvant for induction of CD8+ cytotoxic T lymphocytes.

The cytotoxic T lymphocyte (CTL) response has recently been shown to play a role in protection against human immunodeficiency virus (HIV) and it is therefore thought that a vaccine against HIV must be able to elicit a CTL response. The development of a safe, effective adjuvant is very important because alum, the only adjuvant available for use in humans at present, can barely induce a response of this type. We demonstrate here that liposomes that contain an immunodominant peptide (15 amino acids) of the envelope glycoprotein gp120 of HIV-1 and that are coated with mannopentaose-dipalmitoylphosphatidylethanolamine conjugate induce a major histocompatibility complex class I-restricted CD8+ CTL response in mice with a single subcutaneous immunization, whereas non-coated liposomes do not. Since no damage to the skin at the injection site was caused by the liposomes, and since the oligomannose-coated liposomes consist of innocuous materials ubiquitously distributed throughout the human body, they may be highly suitable for use as a safe adjuvant in vaccines inducing a CTL response against HIV.

Adjuvants, Immunologic↗
PubMed1998

Effects of human PTH(1-34) and bisphosphonate on the osteopenic rat model.

It has been demonstrated that the intermittent administration of human parathyroid hormone (hPTH) is beneficial for restoration of bone mass in osteoporotic patients. The mechanisms of anabolic effects of hPTH have been determined by ovariectomized rat models and other larger remodeling animals. However, treatment with hPTH may increase the cancellous bone mass at the expense of cortical bone mass and cessation of the treatment results in rapid bone loss. Efforts have been made to maintain newly formed bone mass after withdrawal of the hPTH treatment. These issues are not well understood. In this article, the authors would like to represent previous studies of their own and others concerning these issues.

Animals↗
PubMed1998

Heterogeneity of anterograde fast-pathway and retrograde slow-pathway conduction patterns in patients with the fast-slow form of atrioventricular nodal reentrant tachycardia: electrophysiologic and electrocardiographic considerations.

OBJECTIVES: This study sought to define the electrophysiologic and electrocardiographic characteristics of fast-slow atrioventricular nodal reentrant tachycardia (AVNRT). BACKGROUND: In fast-slow AVNRT the retrograde slow pathway (SP) is located in the posterior septum, whereas the anterograde fast pathway (FP) is located in the anterior septum; however, exceptions may occur. METHODS: Twelve patients with fast-slow AVNRT were studied. To determine the location of the retrograde SP, atrial activation during AVNRT was examined while recording the electrograms from the low septal right atrium (LSRA) on the His bundle electrogram and the orifice of the coronary sinus (CS). Further, to investigate the location of the anterograde FP, single extrastimuli were delivered during AVNRT both from the high right atrium and the CS. RESULTS: The CS activation during AVNRT preceded the LSRA in six patients (posterior type); LSRA activation preceded the CS in three patients (anterior type), and in the remaining three both sites were activated simultaneously (middle type). In the anterior type, CS stimulation preexcited the His and the ventricle without capturing the LSRA electrogram (atrial dissociation between the CS and the LSRA), suggesting that the anterograde FP was located posterior to the retrograde SP. In the posterior and middle types, high right atrial stimulation demonstrated atrial dissociation, suggesting that the anterograde FP was located anterior to the SP. In the posterior and middle types, retrograde P waves in the inferior leads were deeply negative, whereas they were shallow in the anterior type. CONCLUSIONS: Fast-slow AVNRT was able to be categorized into posterior, middle and anterior types according to the site of the retrograde SP. The anterior type AVNRT, where an anteriorly located SP is used in the retrograde direction and a posteriorly located FP in the anterograde direction, appears to represent an anatomical reversal of the posterior type which uses a posterior SP for retrograde and an anterior FP for anterograde conduction. Anterior type AVNRT should be considered in the differential diagnosis of long RP (RP > PR intervals) tachycardias with shallow negative P waves in the inferior leads.

Adult↗
PubMed1998

GABAergic neuron-to-astrocyte signaling regulates dendritic branching in coculture.

Effects of neurotransmitters on dendritic morphology were analyzed in cocultures of neurons and astrocytes from the neonatal rat olfactory bulb by means of immunocytochemical staining and morphometry. About 70% of the neurons gamma-aminobutyric acid (GABA)-immunoreactive on day 7 of the coculture. Morphometric analysis of neurons having no contact with other neurons revealed that incubation of the coculture with either a sodium channel blocker, tetrodotoxin, or GABAA receptor antagonists such as bicuculline or picrotoxin resulted in a decreased number of dendritic branch points as compared to neurons in control cultures, while the same treatment did not affect radial dendritic outgrowth or the number of primary dendrites. Application of a GABAB receptor antagonist, phaclofen, or an AMPA-type glutamate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione, had no detectable effect on dendritic morphology. Incubation of the coculture with a GABAA receptor agonist, muscimol, enhanced branching and reversed the inhibitory effect of tetrodotoxin. Branching was also enhanced by increasing extracellular K+. The inhibitory effect of tetrodotoxin or bicuculline and the stimulatory effect of muscimol or elevated K+ were abolished when neurons were grown on a monolayer of dead astrocytes, indicating that the morphoregulatory action of GABA requires living astrocytes to operate. Astrocytes pretreated with muscimol before the addition of neurons supported branching better than those without pretreatment. These results suggest that various aspects of dendritic growth are regulated by distinct mechanisms, and that neuron-to-astrocyte signaling mediated by GABA promotes dendritic branching.

Animals↗
PubMed1998

In vitro characterization of rice importin beta1: molecular interaction with nuclear transport factors and mediation of nuclear protein import.

We recently isolated two cDNAs encoding importin 3 homologues (rice importin beta1 and beta2), the first such homologues identified in plants. To address the function of rice importin beta1 in the process of nuclear import of proteins, we carried out in vitro binding and nuclear import assays. Recombinant protein of rice importin beta1 assembled a complex (PTAC) with rice importin alpha1 and NLS protein, and also bound to the nuclear envelope of tobacco BY-2 cells. Ran-GTP, but not Ran-GDP, interacted with rice importin beta1 and dissociated the heterodimer formed between rice importin alpha1 and rice importin beta1. An in vitro nuclear import assay using digitonin-permeabilized HeLa cells revealed that rice importin beta1 can mediate nuclear envelope docking of NLS proteins and their subsequent translocation into the nucleus. These data strongly suggest that rice importin beta1 functions as a component of the NLS receptor in plant cells.

Cell Nucleus↗
PubMed1998

A Gln747-->Pro substitution in the IIb subunit is responsible for a moderate IIbbeta3 deficiency in Glanzmann thrombasthenia.

To clarify a molecular defect responsible for moderate alphaIIb beta3 deficiency, we examined two unrelated patients, MT and MS, suffering from type II and type I Glanzmann thrombasthenia (GT), respectively. Sequence analysis of polymerase chain reaction (PCR) fragments derived from platelet mRNA showed a single A-->C substitution at nucleotide (nt) 2334 leading to a Gln747--> Pro in alphaIIb in both patients. Allele-specific restriction enzyme analysis (ASRA) of genomic DNA demonstrated that patient MT was homozygous for the Gln747-->Pro substitution and patient MS was compound heterozygous for this substitution and for an RNA splice mutation at the consensus sequence of the splice acceptor site of exon 18 (AG-->AA). Furthermore, ASRA showed that, among 17 unrelated Japanese GT patients, this Gln747-->Pro substitution was detected in 4 patients, including MT and MS (homozygous, 2 patients; heterozygous, 2 patients). Cotransfection of Pro747alphaIIb and beta3 constructs into 293 cells resulted in moderate reduction in the amount of alphaIIb beta3 within the transfected cells as well as on the cell surface. However, Pro747alphaIIb beta3 bound the ligand mimetic monoclonal antibody (MoAb) PAC-1 after activation of alphaIIb beta3 by the MoAb PT25-2, suggesting that the mutant alphaIIb beta3 possesses the ligand-binding function. The association between the mutant proalphaIIb and beta3 was not disturbed. Surface labeling and pulse chase study showed that the Gln747-->Pro substitution moderately impaired both intracellular transport of the alphaIIb beta3 heterodimers to the Golgi apparatus and endoproteolytic cleavage of proalphaIIb into heavy and light chains. By contrast, replacement of Gln747 with Ala by mutagenesis did not impair alphaIIbbeta3 expression on the cell surface. These results suggest that the presence of Pro, rather than the absence of Gln, at amino acid residue 747 on alphaIIb is responsible for moderate alphaIIbbeta3 deficiency.

Alleles↗
PubMed1998

Functional characterization of a plant importin alpha homologue. Nuclear localization signal (NLS)-selective binding and mediation of nuclear import of nls proteins in vitro.

Nuclear import of most nuclear proteins is initiated by recognition of the nuclear localization signal (NLS) by importin alpha. We recently isolated an importin alpha homologue from rice (rice importin alpha1) and demonstrated that transcription of the gene is down-regulated by light in rice leaves. To address the function of rice importin alpha1 in the process of nuclear import of proteins, we performed in vitro binding and nuclear import assays. The rice importin alpha1 showed specific binding to fusion proteins containing either monopartite or bipartite NLSs, but not to a fusion protein containing a Matalpha-2-type NLS, suggesting that there exists selective binding of rice importin alpha1 to different plant NLSs. The rice importin alpha1 is also capable of forming a complex with mouse importin beta and NLS protein in vitro. An in vitro nuclear import assay using permeabilized HeLa cells revealed that rice importin alpha1, in conjunction with other vertebrate transport factors, mediates the nuclear envelope docking of NLS proteins and their subsequent translocation into the nucleus. These data provide strong, direct evidence suggesting that rice importin alpha1 functions as a component of the NLS receptor in plant cells.

Animals↗
PubMed1998

Human T-cell leukemia virus type I Tax transactivates human interleukin 8 gene through acting concurrently on AP-1 and nuclear factor-kappaB-like sites.

The transactivator protein, Tax, from the human T-cell leukemia virus type I (HTLV-I) transactivates both viral and cellular genes. Previously, we had shown that interleukin 8 (IL-8) is constitutively expressed in HTLV-I-infected cells and in cells transiently expressing Tax. We show here that the IL-8 promoter is Tax responsive in Jurkat T cells. Furthermore, using several deletion and mutated plasmids of the 5'-flanking regulatory region of the IL-8 gene linked to the luciferase gene as a reporter and mutant tax gene expression vectors, we have established that both AP-1 at -126 to -120 and nuclear factor (NF)-kappaB-like cis-element at -80 to -71 are essential and sufficient for the induction of the IL-8 gene by HTLV-I Tax. In addition, overexpression of the dominant-negative mutants of NF-kappaB inhibitor molecules, IkappaBalpha and IkappaBbeta, abolished the Tax-induced activation of IL-8 gene. Gel mobility shift assays detected proteins specifically binding to the AP-1 and NF-kappaB-like sites in Tax-expressing T-cell lines infected with HTLV-I. Similarly, the nuclear translocation of proteins specifically bound to these two motifs was shown in JPX-9 cells, a subclone of Jurkat cells, carrying the Tax sequences under the control of an inducible promoter. Taken together, these results suggest that the cooperation of transcription factors NF-kappaB and AP-1 is essential for transactivation of IL-8 gene by HTLV-I Tax.

Binding Sites↗
PubMed1998

Quercetin metabolites inhibit copper ion-induced lipid peroxidation in rat plasma.

The oxidative susceptibility of plasma obtained from rats after intragastric administration of quercetin was studied to know whether or not quercetin acts as an in vivo antioxidant after metabolic conversion. Quercetin was raised in the rat blood plasma essentially as glucuronide and/or sulfate conjugates. The plasma obtained from rats after quercetin administration was more resistant against copper sulfate-induced lipid peroxidation than the control plasma on the basis of the accumulation of cholesteryl ester hydroperoxides and the consumption of alpha-tocopherol. The results strongly suggest that some conjugated metabolites of quercetin act as effective antioxidants when plasma is subject to metal ion-induced lipid peroxidation.

Animals↗
PubMed1998

Cloning of a cDNA encoding an importin-alpha and down-regulation of the gene by light in rice leaves.

The import of nuclear proteins into nuclei begins with recognition of nuclear localization signal-harboring proteins and binding to a nuclear pore targeting complex. A cDNA for an importin-alpha protein, a subunit of the complex, was isolated from rice plants. The amino acid sequence deduced from the nucleotide sequence of the cDNA exhibited a high homology to those of importin-alpha proteins from many organisms such as Arabidopsis thaliana, Saccharomyces cerevisiae, human, mouse, Xenopus laevis and Drosophila melanogaster. Down-regulation of the transcription by light was shown in the leaves of light- and dark-grown seedlings by RNA blot analysis. The down-regulation was specific to leaves, whereas no light effect was observed in root tissues or calli, in which higher levels of the transcript were detected.

Amino Acid Sequence↗
PubMed1998

A method for analyzing the qualitative and quantitative aspects of gene expression: a transcriptional profile revealed for HeLa cells.

A number of strategies have been devised by which differentially expressed genes in different cell types or tissues can be identified. We here report an efficient method to analyze the qualitative and quantitative aspects of transcripts and to construct an extensive gene expression profile in any kind of cell or tissue of interest. This method enables us to analyze the composition of mRNA species, reflecting gene activities, by measuring the frequency of appearance of concatamerized 17mer cDNA mini-fragments, which are proportional to the abundance of mRNA. As compared with a related method previously described by others, we can analyze approximately 3-4 bp longer cDNA fragments derived from amounts of total RNA as small as 1 microg. Using this technique we examined 10 100 cDNA mini-fragments from HeLa cells and constructed a gene expression profile consisting of 3665 genes. This method should thus provide an overall indication of gene activities and a rational means for monitoring gene fluctuation in different cells or tissues at different stages of development, in normal and disease states.

Gene Expression↗
PubMed1998

A novel importin alpha from rice, a component involved in the process of nuclear protein transport.

In eukaryotes, nuclear proteins that are transported into nuclei have nuclear localization signals (NLSs), which are recognized by proteins called importin alpha. We isolated a rice cDNA, #61L, and the corresponding gene that encodes a protein, which shows significant homology to the importin alpha. Although the encoded protein had only 23-27% amino acid identity to the importin alphas from various organisms including plants, the fusion protein with glutathione S-transferase showed a specific binding activity to the NLS of SV40 T-antigen. These results suggest that the rice #61L protein is a novel importin alpha in plants.

Amino Acid Sequence↗
PubMed1998

High SDF-1 expression in HIV-1 carriers does not correlate with CD8+ T-cell-mediated suppression of viral replication.

Stromal cell-derived factor 1 (SDF-1) inhibits T-cell tropic (T-tropic) HIV-1 infection in vitro. In this study, we examined the regulatory role of SDF-1 on HIV-1 replication in peripheral blood mononuclear cells (PBMC) of HIV-infected individuals. We found that the amount of SDF-1 mRNA in freshly isolated PBMC of HIV-1 carriers was higher than in healthy donors. Moreover, PBMC from some asymptomatic carriers (ACs) exhibited high levels of SDF-1 mRNA expression. The level of SDF-1 expression in PBMC did not correlate with the magnitude of CD8+ T-cell-mediated suppression of HIV-1 among ACs SDF-1 inhibited HIV-1 replication at the viral entry step, whereas a single-cycle HIV-1 infection system showed that the major part of the CD8+ T-cell-mediated suppression occurs after intracellular penetration of the virus. Our results suggest that SDF-1 acts as a suppressor of virus replication in a CD8+ T-cell-independent mechanism in HIV-infected individuals.

Base Sequence↗
PubMed1998

Cellular basis of skin allograft rejection in mice: specific lysis of allogeneic skin components by non-T cells.

BACKGROUND: It has been generally assumed that CD8+ T cells mediate direct lysis of allografts and that their growth, differentiation, and activation are dependent upon cytokine production by CD4+ T cells. However, both the generation of CD4- or CD8-deficient mice and adoptive transfer experiments with CD4+ T cells from CD8-deficient mice demonstrate that noncytotoxic CD4+ T cells alone are sufficient to induce skin or organ allograft rejection. Furthermore, we have reported that the major effector cells responsible for allografted-tumor (e.g., Meth A) rejection are allograft-induced macrophages (AIM) with MHC haplotype specificity. METHODS: We characterized the macrophages migrating into the rejection site of allografted skin by immunohistochemical and in situ hybridization analyses using an antibody (K16.5) specific for AIM and a cDNA (pK30) encoding the antigen. To determine the in situ effector cells responsible for the rejection, we prepared both effector cells and target cells from the graft-graft bed border. RESULTS: The macrophages seemed to be morphologically (monocytic), phenotypically (K16.5+/pK30+), and functionally (cytotoxic against Meth A cells) AIM. The AIM population in bulk infiltrates taken from the rejection site was cytotoxic against allografted, but not self, skin components (e.g., fibroblasts, myocytes, endothelial cells, and epithelial cells). In contrast, other types of infiltrating cells including lymphocytes and granulocytes were virtually inactive toward these targets, and NK-1.1+ cells hardly infiltrated into the rejection site. CONCLUSIONS: These data suggest that the major effector cells mediating allografted skin rejection are AIM and not T cells.

Animals↗
PubMed1998

Effects of intranasal administration of recombinant murine interferon-gamma on murine acute myocarditis caused by encephalomyocarditis virus.

BACKGROUND: Viral myocarditis has been strongly implicated in the pathogenesis of dilated cardiomyopathy as well as acute myocarditis. Among the antiviral therapies, interferons (IFNs) have been widely studied and become very important in clinical practice. METHODS AND RESULTS: To investigate the possibilities of IFN therapy in viral myocarditis, we analyzed the effects of recombinant murine interferon (mIFN)-gamma and natural mIFN-alpha/beta by the intranasal and intramuscular routes on the development of acute murine myocarditis caused by encephalomyocarditis virus. Both mIFN-gamma and mIFN-alpha/beta treatment by either route significantly increased the survival rate; none of the mIFN-gamma-treated mice died. The effect of mIFN-gamma was significantly greater than that of mIFN-alpha/beta. Furthermore, intranasal administration of mIFN-gamma significantly suppressed virus replication and inflammation in the heart. CONCLUSIONS: Our data demonstrate that IFN therapy, especially intranasal administration of IFN-gamma, dramatically improved the prognosis of acute murine viral myocarditis by suppressing virus replication and raises the possibility of antiviral therapy with IFN-gamma in patients with acute myocarditis.

Administration, Intranasal↗