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Biomedical subjects

T Nagata

Publications and source records attributed to T Nagata.

At least 55 records · Page 3Linked to original sources

Immunization with plasmid DNA encoding MHC class II binding peptide/CLIP-replaced invariant chain (Ii) induces specific helper T cells in vivo: the assessment of Ii p31 and p41 isoforms as vehicles for immunization.

A single helper T cell (Th) epitope-specific T cell subset was successfully induced in vivo by immunization with plasmid DNA encoding MHC class II binding peptide/class II-associated invariant chain peptide (CLIP)-replaced murine Ii molecules. Spleen cells from mice immunized by gene gun bombardment with plasmid DNA for Ii p31 and p41 molecules, whose CLIP regions were replaced with an I-A(d)-restricted Th epitope, ovalbumin (OVA) 323-336, showed the specific proliferation and interferon-gamma (IFN-gamma) production. A20-2J B cell lines having these plasmids were capable of stimulating spleen cells from the immunized mice and naïve DO10-transgenic mice bearing the epitope-specific T cell receptor (TCR) transgenes by examining the specific proliferative response and IFN-gamma production. Some mice immunized with the Ii p41-OVA323, but not with the Ii p31-OVA323 plasmid, produced the peptide-specific antibodies, suggesting the functional difference between Ii isoforms.

Animals↗

Identification of immunostimulatory DNA-induced genes by suppression subtractive hybridization.

Bacterial DNA and related synthetic immunostimulatory oligodeoxyribo-nucleotides (ISS-ODN) have stimulatory effects on mammalian immune cells through a Toll-like receptor, TLR9. Genes upregulated in ISS-ODN-stimulated immune cells are obviously significant to delineate the mechanism of the induced innate immunity. Employing suppression subtractive hybridization (SSH), we have generated a profile of genes induced by ISS-ODN in spleen cells. Sequencing of 87 clones isolated by the SSH showed 39 clones corresponding to known mouse genes in the public database. Eleven clones appeared to possess 80-90% homology with known mouse genes and the remaining 37 clones showed no significant homology with any known mouse genes. A series of known genes which have not previously been reported to be induced with ISS-ODN were confirmed to be induced in ISS-ODN-stimulated bone marrow-derived macrophages: NF-kappaB p105, IRF-1, PA28beta, IRG2, and MyD88. These genes were suggested to be involved in the molecular process of innate host defense mechanisms.

Adjuvants, Immunologic↗

Structure of the C-terminal RNA-binding domain of hnRNP D0 (AUF1), its interactions with RNA and DNA, and change in backbone dynamics upon complex formation with DNA.

Heterogeneous nuclear ribonucleoprotein (hnRNP) D0 has two ribonucleoprotein (RNP) -type RNA-binding domains (RBDs), each of which can specifically bind to the UUAG-sequence. hnRNP D0 also binds specifically to single-stranded d(TTAGGG)(n), the human telomeric DNA repeat. We have already reported the structure and interactions with RNA of the N-terminal RBD (RBD1). Here, the structure of the C-terminal RBD (RBD2) determined by NMR is presented. It folds into a compact alpha beta structure comprising an antiparallel beta-sheet packed against two alpha-helices, which is characteristic of RNP-type RBDs. In addition to the four beta-strands commonly found in RNP-type RBDs, an extra beta-strand, termed beta 4(-), was found just before the fourth beta-strand, yielding a five-stranded beta-sheet. Candidate residues of RBD2 involved in the interactions with RNA were identified by chemical shift perturbation analysis. Perturbation was detected on the beta-sheet side, not on the opposite alpha-helix side, as observed for RBD1. It is notable that the beta 4(-) to beta 4 region of RBD2 is involved in the interactions in contrast to the case of RBD1. The chemical shift perturbation analysis also showed that RBD2 interacts with DNA in essentially the same way as with RNA. Changes in the backbone dynamics upon complex formation with DNA were examined by means of model free analysis of relaxation data. In free RBD2, the beta 4(-) to beta 4 region exhibits slow conformational exchange on the milli- to microsecond time scale. The exchange is quenched upon complex formation. The flexibility of free RBD2 may be utilized in the recognition process by allowing different conformational states to be accessed and facilitating induced fit. Additionally, faster flexibility on the nano- to picosecond time scale was observed for loop 3 located between beta 2 and beta 3 in free RBD2, which is retained by the complex as well.

Amino Acid Sequence↗

Protective CTL response is induced in the absence of CD4+ T cells and IFN-gamma by gene gun DNA vaccination with a minigene encoding a CTL epitope of Listeria monocytogenes.

Our work was undertaken to learn the mechanism of induction of protective cytotoxic T lymphocytes (CTL) by gene gun DNA vaccination with p91m encoding an H-2Kd-restricted T cell epitope of listeriolysin O (LLO). Vaccination with p91m induced vigorous antigen-specific CD8+ CTL that produce IFN-gamma and was able to confer partial protection against listerial challenge. However, the p91m-induced protective immunity was revealed to be independent of the IFN-gamma and CD4+ T cell help. The CTL induction is also suggested to require neither adjuvant activity of the plasmid used nor IFN-gamma. The data may be feasible for the design of CTL inducing vaccines in various immunodeficiencies.

Animals↗

Functional mutagenesis of AML1/RUNX1 and PEBP2 beta/CBF beta define distinct, non-overlapping sites for DNA recognition and heterodimerization by the Runt domain.

The Runt domain family of transcription factors play key roles in transcriptional regulation of definitive hematopoiesis and osteogenesis. This transcription factor family is characterized by a DNA-binding alpha-subunit harboring the Runt domain and a secondary subunit, beta, which binds to the Runt domain and enhances its interaction with DNA. Missense mutations in the Runt domain from either the blood or bone-related gene product are associated with the onset of acute human leukemia as well as a disease of skeletal patterning known as cleidocranial dysplasia. NMR "footprinting" analysis of Runt domain/beta/DNA ternary complexes in solution previously identified the likely residues that form the heterodimerization and DNA-binding surfaces of the Runt domain. Functional mutagenesis at 37 positions in the Runt domain or beta confirms the original identification of these interaction surfaces and reveals that the heterodimerization and DNA-binding surfaces of the Runt domain occur at distinct, non-overlapping sites within the domain. The analysis of an additional 21 disease-related missense mutations identified from patients with either blood or bone disease demonstrates that the primary defect in these patients is a failure in DNA-recognition by the Runt domain. The molecular basis for the DNA-binding defect is analyzed in the context of the three-dimensional structure of the Runt domain in binary and ternary protein/DNA complexes.

Amino Acid Substitution↗

Decreased expression of c-myc family genes in thymuses from myasthenia gravis patients.

The thymus is a critical organ for the elimination of autoreactive T cells by apoptosis. We studied the expression of apoptosis-associated genes, bcl-xL, bad, caspase-3, and c-myc family genes in myasthenia gravis (MG) thymuses. We observed that the mRNA levels of myc family genes, c-myc and max, were markedly reduced in MG thymuses. These results indicate that c-myc-mediated signaling is abnormal in MG thymuses. The levels of molecules whose expressions are associated with myc, such as STAM, prothymosin-alpha, and NFkappaB, were also analyzed.

Adaptor Proteins, Signal Transducing↗

Double-blind placebo-controlled administration of fluoxetine in restricting- and restricting-purging-type anorexia nervosa.

BACKGROUND: Anorexia nervosa is an often chronic disorder with high morbidity and mortality. Many people relapse after weight restoration. This study was designed to determine whether a selective serotonin reuptake inhibitor would improve outcome and reduce relapse after weight restoration by contributing to maintenance of a healthy normal weight and a reduction of symptoms. METHODS: We administered a double-blind placebo-controlled trial of fluoxetine to 35 patients with restricting-type anorexia nervosa. Anorexics were randomly assigned to fluoxetine (n = 16) or a placebo (n = 19) after inpatient weight gain and then were observed as outpatients for 1 year. RESULTS: Ten of 16 (63%) subjects remained on fluoxetine for a year, whereas only three of 19 (16%) remained on the placebo for a year (p =.006). Those subjects remaining on fluoxetine for a year had reduced relapse as determined by a significant increase in weight and reduction in symptoms. CONCLUSIONS: This study offers preliminary evidence that fluoxetine may be useful in improving outcome and preventing relapse of patients with anorexia nervosa after weight restoration.

Adolescent↗

Differential involvement of p38 MAP kinase pathway and Bax translocation in the mitochondria-mediated cell death in TCR- and dexamethasone-stimulated thymocytes.

Mitochondria play a central role in many apoptotic reactions. Although mitochondrial apoptotic changes and caspase activation have been demonstrated in the apoptotic thymocytes, cell death signal through mitochondria in TCR-stimulated thymocytes has not been fully understood. In this study, we show that TCR stimulation induced disruption of mitochondrial transmembrane potential (Delta Psi(m)), the cytochrome c release from mitochondira, capase-3 activation, and the cell death of thymocytes. Bongkrekic acid, an inhibitor of Delta Psi(m) disruption, blocked the cytochrome c release from mitochondria and the following caspase-3-mediated cell death. Furthermore, a pro-apoptotic Bcl-2 family protein, Bax, but not Bad or Bid, was translocated from cytosol to mitochondria in TCR-stimulated thymocytes. This translocation and the following apoptotic changes were inhibited by SB203580, a p38 kinase inhibitor, in a specific manner. These results suggest that activated p38 kinase pathway by TCR stimulation induces translocation of Bax to mitochondria, causing Delta Psi(m) disruption, and the release of cytochrome c, which finally induces caspase-3-mediated apoptosis in thymocytes.

Animals↗

Toxic shock syndrome toxin-1 accelerated collagen-induced arthritis in mice.

The aim of this study was to explore the roles of toxic shock syndrome toxin-1 (TSST-1) in collagen-induced arthritis (CIA). DBA/1 mice were immunized with type II collagen (CII) and treated with TSST-1. Intraperitoneal and intravenous injections of TSST-1 aggravated CIA, enhancing its incidence and severity. CIA was accompanied by an increase in anti-CII IgG Ab levels. Intraperitoneal administration with TSST-1 enhanced IFN-gamma, TNF-alpha, and IL-4 production in DBA/1 mice. We discovered the mRNA expressions of IFN-gamma, IL-2, TNF-alpha, IL-1beta, and iNOS in spleen cells stimulated with TSST-1 in vitro. However, IL-12 and IL-4 mRNA expression were seen constitutively without stimulation. Only a little increase of IL-12 and IL-4 mRNA expression was seen at 2-3 h after treatment with TSST-1. Our experiments demonstrated that CIA was aggravated by the treatment with TSST-1, which may have induced various proinflammatory cytokines and the production of both Th1 and Th2 cytokines.

Animals↗

Evaluation of liver regeneration using the L-[1-13C]methionine breath test.

BACKGROUND: We examined the relationship between changes in the liver weight/body weight percentage, amount of hepatic tissue total DNA, and the results of the [1-(13)C]methionine ((13)Cmet) breath test during hepatic regeneration in a rat model of 70% hepatectomy, to assess their usefulness for evaluating hepatic regeneration. MATERIALS AND METHODS: Male Wistar rats (230-290 g) were subjected to 70% hepatectomy under anesthesia with Nembutal. One, 2, 3, 7, and 14 days postoperatively, 40 mg/kg (13)Cmet was intravenously injected into the femoral vein, and the increase in exhaled (13)CO(2) (Delta(13)CO(2)) was measured for 15 min. Simple laparotomy was performed in control rats. Following the breath test, the regenerated liver was removed and weighed. The amount of DNA was determined. RESULTS: The correlation coefficients (r) between liver weight/body weight (LW/BW) and results of the (13)Cmet breath test, and between DNA and results of the (13)Cmet breath test were 0.892 and 0.800, respectively. CONCLUSIONS: The (13)Cmet breath test is considered to be very useful for assessing liver regeneration, and total (13)CO(2) output over 15 min in the (13)Cmet breath test graph seems to be an effective indicator for evaluating liver regeneration.

Animals↗

Induction of E-selectin after partial hepatectomy promotes metastases to liver in mice.

BACKGROUND: The liver is the most frequent site of tumor metastasis. It has been suggested that partial hepatectomy promotes liver metastasis of malignant disease and that expression of E-selectin, a cell adhesion molecule, plays roles in tumor metastasis. However, no reports are available concerning the expression of E-selectin after hepatectomy. METHODS: In the present study, we used BALB/c mice subjected to 30% partial hepatectomy after injection of 1 x 10(4) colon 26 cells to determine the effects of partial hepatectomy on tumor metastasis to liver. E-Selectin expression within the liver after partial hepatectomy was evaluated using reverse transcription polymerase chain reaction and Western blotting. In addition, we injected polyclonal antibody to E-selectin into mice in which partial hepatectomy had augmented liver metastasis. RESULTS: Mice subjected to partial hepatectomy had significantly increased numbers of liver metastases (sham operation, 1.5 +/- 2.0, vs partial hepatectomy, 35.5 +/- 19.3; P < 0.001). Expression of E-selectin mRNA within the liver was markedly increased 4 h after partial hepatectomy, but subsequently decreased at 24 h. E-Selectin protein was detected 8 h after hepatectomy, but subsequently decreased at 24 h as measured by Western blotting. Mice subjected to intraperitoneal injection of neutralizing antibody after operation had significantly decreased numbers of liver metastases (phosphate-buffered saline, 20.6 +/- 9.2, P < 0.05, and normal IgG, 18.0 +/- 8.0, P < 0.05, compared with polyclonal antibody to E-selectin, 5.6 +/- 4.8). CONCLUSION: Induction of E-selectin by partial hepatectomy promotes hematogenous liver metastasis. Our findings can be applied to surgical treatment of liver tumor to reduce the recurrence of liver metastasis after hepatectomy by inhibiting E-selectin-mediated adhesion using reagents to E-selectin.

Animals↗

Melatonin's gastroprotective and antistress roles involve both central and peripheral effects.

Systemic administration of melatonin (5 to 20 mg/kg) has been reported to inhibit the induction of acute gastric mucosal lesions by stress or ischemia-reperfusion in rats. We recently demonstrated that intracisternal (i.c.) melatonin at low doses (1 to 100 ng) dose-dependently decreased acid and pepsin outputs in rats. The aim of the present study was to further investigate the peripheral and central roles of melatonin in gastric mucosal defense. Using a radioimmunoassay, we measured melatonin concentrations in the plasma and cerebrospinal fluid (CSF) of the cisterna magna in rats subjected to water immersion restraint stress and given intraperitoneal (i.p.) or i.c. injection of melatonin. Water immersion restraint stress was followed by a significant duration-related increase in peripheral plasma melatonin levels; the stress similarly produced a time-dependent increase in the extent of gastric mucosal lesions. Administration of melatonin (1 or 10 mg/kg, i.p., or 100 ng/10 microl, i.c.) significantly reduced the extent of stress-induced gastric damage, by 46%, 67%, and 54%, respectively. The effective i.c. dose of melatonin was at least 10,000-fold smaller than the effective i.p. dose. Melatonin levels in plasma and CSF after the i.p. injection of melatonin at 10 mg/kg were dramatically higher than those after the i.c. injection of vehicle or 100 ng of melatonin. Our results suggest that the peripheral gastroprotective action of melatonin should be investigated with due regard to these central effects.

Animals↗

Sequence diversity of NS(M) movement protein of tospoviruses.

In order to determine the diversity of the movement protein (NS(M)) among tospoviruses, the NSM genes of five distinct tospovirus species occurring in Brazil (Tomato chlorotic spot virus, Groundnut ring spot virus, Chrysanthemum stem necrosis virus, Zucchini lethal chlorosis virus and Iris yellow spot virus) were cloned, sequenced and compared with NS(M) sequences of other available tospoviruses. The 'D-motif', a conserved region present in the majority of '30K superfamily' virus movement proteins, is present in all NSM amino acid sequences available. In addition to the 'D-motif', a conserved phospholipase A2 motif was found. The NSM amino acid sequence comparisons among tospovirus species revealed several conserved regions located in the internal part of the protein and diverse domains mainly located in the amino-terminus. Prediction of secondary structure showed similar patterns among all NS(M) proteins analyzed. Considering the geographical prevalence and phylogenetic analysis of N and NS(M) proteins, tospoviruses were tentatively clustered in 'American' and 'Eurasian' groups. Both phylogenetic trees may reflect the natural evolution of tospovirus species within distinct ecological niches. The sequence information obtained in this work would facilitate functional analysis of NS(M) during the tospovirus infection process.

Amino Acid Sequence↗

Acylated anthocyanidin 3-sophoroside-5-glucosides from Ajuga reptans flowers and the corresponding cell cultures.

Four anthocyanins from Ajuga reptans flowers and its cell cultures were isolated, and a fifth was also characterized by HPLC-mass spectrometry. By means of chemical and spectroscopic analyses, their structures were identified as delphinidin 3-(p-coumaroyl-feruloyl)sophoroside-5-malonylglucoside, delphinidin 3-(diferuloyl)sophoroside-5-malonylglucoside, and cyanidin 3-(di-p-coumaroyl)sophoroside-5-glucoside, respectively. The other two were tentatively identified as delphinidin 3-(diferuloyl)sophoroside-5-glucoside and cyanidin 3-(feruloyl-p-coumaroyl)sophoroside-5-malonylglucoside. In neutral aqueous solution, the crude extract from A. reptans flower cell cultures and the major anthocyanin cyanidin 3-(di-p-coumaroyl)sophoroside-5-malonylglucoside were more stable than cyanidin 3-glucoside, and also prevented more efficiently peroxidation than did the latter. A. reptans flower cell culture anthocyanins may have a potential as natural colorants for food utilities or other purposes.

Acylation↗

Special cytochemistry in cell biology.

Cytochemistry is a science of localizing chemical components of cells and organelles on histological sections by using various techniques. We first aimed at studying cytochemistry by developing new techniques using various principles such as enzyme cytochemistry, microincineration, microspectrophotometry, radioautography, cryo-techniques, X-ray microanalysis and immunocytochemistry. We first concentrated on developing methodologies in the 1960s to 1970s. We then applied these special techniques to various kinds of cells in men and animals. Earlier, I proposed to classify these methods into three categories, i.e., chemical, physical, and biological techniques. The methodology has been well developed to form a new science which should be designated as "general cytochemistry" similarly to the general histology. On the other hand, these techniques should be applied to various cells in various organ systems, such as the skeletal, muscular, digestive, respiratory, urinary, reproductive, endocrine, circulatory, nervous and sensory systems similarly to the special histology or the histology of organs. I summarize the results of cytochemical studies on cells of various organs carried out in our laboratory during these 44 years since 1955. The results obtained from cytochemical studies applied to various cells in respective organ systems should be designated as "special cytochemistry."

Aging↗

Uniform 13C/15N-labeling of DNA by tandem repeat amplification.

An optimized procedure has been described for the large-scale production of stable isotopeenriched duplex oligonucleotides of designed sequence. Large-scale production of labeled nucleotide triphosphates can be produced in this procedure simultaneously with labeled proteins, thereby providing synthetic dNMP precursors at no additional cost. The procedure is robust, with a minimum product:template yield of 800:1 overall, and produces > 99% single-length product. Tandem repeat PCR amplification is a general approach to large scale synthesis of duplex oligonucleotides and may have applications to both NMR and X-ray methods, particularly for product lengths in excess of 25 base pairs where failed sequences from solid-phase synthesis can be difficult to remove chromatographically. A drawback of the present approach is that the product is a duplex of two equal-length strands, making single-stranded products more difficult to prepare. For this reason, it could be preferable to produce single-stranded products by the [figure: see text] method of Zimmer and Crothers. Although a single base type can be selectively enriched in this approach, chemical synthesis will provide greater flexibility for labeled DNAs requiring site-specific labels at only one or a small number of nucleotide positions in the sequence. Therefore, maximum flexibility in labeling patterns can be realized by judicious choice of labeling method appropriate to the type of DNA product and extent of isotopic enrichment desired.

Base Sequence↗