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T Miyamoto

Publications and source records attributed to T Miyamoto.

At least 145 records · Page 8Linked to original sources
PubMed2000

Silencing mediator for retinoid and thyroid hormone receptors interacts with octamer transcription factor-1 and acts as a transcriptional repressor.

Octamer transcription factor-1 (Oct-1) is a member of the POU (Pit-1, Oct-1, unc-86) family of transcription factors and is involved in the transcriptional regulation of a variety of gene expressions related to cell cycle regulation, development, and hormonal signals. It has been shown that Oct-1 acts not only as a transcriptional activator but also as a transcriptional repressor for certain genes. The mechanism of the repressive function of Oct-1 has not been well understood. Here we demonstrate by using the glutathione S-transferase pull-down assays and coimmunoprecipitation assays that the POU domain of Oct-1 directly interacts with a silencing mediator for retinoid and thyroid hormone receptors (SMRT). The interaction surfaces are located in the C-terminal region of SMRT, which are different from previously described silencing domains I and II or receptor interacting domains I and II. In transient transfection assays in COS1 cells, overexpression of SMRT attenuated the augmentation of Oct-1 transcriptional activity by OBF-1/OCA-B, activator for Oct-1. In pull-down assays, increasing amounts of SMRT could compete the binding of OCA-B to Oct-1 POU domain. The activity of Oct-1 could be determined by a regulated balance between SMRT and OCA-B. Furthermore, cotransfected unliganded thyroid hormone receptor enhanced the transactivation by Oct-1, and addition of 3,3',5-tri-iodo-l-thyronine obliterated the stimulatory effects. Consequently, in the presence of cotransfected thyroid hormone receptor, the octamer response element acts as an element negatively regulated by 3,3',5-tri-iodo-l-thyronine. The results suggest that the transcriptional activity of Oct-1 can be modulated by interaction through its POU domain by a silencing mediator SMRT resulting in the cross-talk between Oct-1 and nuclear receptors.

Animals↗
PubMed2000

Development of CD8alpha-positive dendritic cells from a common myeloid progenitor.

Dendritic cells (DCs) are critical in both initiating adaptive immune responses and maintaining tolerance to self antigens. These apparently contradictory roles have been suggested to depend on different subsets of DCs that arise from either myeloid or lymphoid hematopoietic origins, respectively. Although DC expression of CD8alpha is attributed to a lymphoid origin, here we show that both CD8alpha+ and CD8alpha- DCs can arise from clonogenic common myeloid progenitors in both thymus and spleen. Thus, expression of CD8alpha is not indicative of a lymphoid origin, and phenotypic and functional differences among DC subsets are likely to reflect maturation status rather than ontogeny.

Animals↗
PubMed2000

An adherent condition is required for formation of multinuclear osteoclasts in the presence of macrophage colony-stimulating factor and receptor activator of nuclear factor kappa B ligand.

Identification of receptor activator of nuclear factor-kappaB (RANK) and RANK-ligand (RANKL) has provided new insights into the osteoclast differentiation pathway. Osteoclast precursor cells were isolated using monoclonal antibodies against c-Fms and RANK, and the effect of adherence on the in vitro differentiation and proliferation of these cells was examined in 2 different types of stromal-cell-free culture systems: a semisolid culture medium (a nonadherent system) and a liquid culture medium (an adherent system). Osteoclast precursor cells were not able to differentiate into mature osteoclasts efficiently in the semisolid culture system. Trimerized RANKL enhanced osteoclast differentiation in semisolid cultures, but not to the extent seen when cells were allowed to adhere to plastic. Initial precursor cells were capable of differentiating into macrophages or osteoclasts. Once these cells were transferred to adherent conditions, striking differentiation was induced. Multinuclear cells were observed even after they had displayed phagocytic activity, which suggests that cell adhesion plays an important role in the differentiation of osteoclast precursor cells. Integrins, especially the arginine-glycine-aspartic acid (RGD)-recognizing integrins alpha(v) and beta(3), were needed for osteoclast-committed precursor cells to proliferate in order to form multinuclear osteoclasts, and the increase in cell density affected the formation of multinuclear cells. A model of osteoclast differentiation with 2 stages of precursor development is proposed: (1) a first stage, in which precursor cells are bipotential and capable of anchorage-independent growth, and (2) a second stage, in which the further proliferation and differentiation of osteoclast-committed precursor cells is anchorage-dependent. (Blood. 2000;96:4335-4343)

Animals↗
PubMed2000

Serotonin inhibits voltage-gated sodium current by cyclic adenosine monophosphate-dependent mechanism in bullfrog taste receptor cells.

We have investigated the effect of 5-hydroxytryptamine (serotonin) (5-HT) on the membrane properties of bullfrog taste receptor cells (TRCs) using patch-clamp technique. External application of 5-HT reversibly suppressed the voltage-gated Na(+) current (I(Na)) in about half of the TRCs sampled. The magnitude of suppression of peak I(Na) was dependent on the holding potential of the cell. Forskolin and cyclic adenosine monophosphate (cAMP) mimicked the suppressive effect of 5-HT on I(Na), but an internal protein kinase A-inhibitor potentiated I(Na). These results suggest that 5-HT suppresses I(Na) of bullfrog TRCs via protein kinase A-dependent phosphorylation, resulting in suppression of the excitability of bullfrog TRCs.

Animals↗
PubMed2000

Cell-fate conversion of lymphoid-committed progenitors by instructive actions of cytokines.

The primary role of cytokines in haemato-lymphopoiesis is thought to be the regulation of cell growth and survival. But the instructive action of cytokines in haematopoiesis has not been well addressed. Here we show that a clonogenic common lymphoid progenitor, a bone marrow-resident cell that gives rise exclusively to lymphocytes (T, B and natural killer cells), can be redirected to the myeloid lineage by stimulation through exogenously expressed interleukin (IL)-2 and GM-CSF (granulocyte/macrophage colony-stimulating factor) receptors. Analysis of mutants of the beta-chain of the IL-2 receptor revealed that the granulocyte- and monocyte-differentiation signals are triggered by different cytoplasmic domains, showing that the signalling pathway(s) responsible for these unique developmental outcomes are separable. Finally, we show that the endogenous myelomonocytic cytokine receptors for GM-CSF and macrophage colony-stimulating factor (M-CSF) are expressed at low to moderate levels on the more primitive haematopoietic stem cells, are absent on common lymphoid progenitors, and are upregulated after myeloid lineage induction by IL-2. We conclude that cytokine signalling can regulate cell-fate decisions and propose that a critical step in lymphoid commitment is downregulation of cytokine receptors that drive myeloid cell development.

Animals↗
PubMed2000

AML1/ETO-expressing nonleukemic stem cells in acute myelogenous leukemia with 8;21 chromosomal translocation.

Leukemia-specific AML1/ETO transcripts are detectable in most patients with t(8;21) acute myelogenous leukemia (AML) in long-term remission. To understand the inconsistency between the clinical cure and the presence of "residual disease" at a molecular level, we separated and identified the cells expressing AML1/ETO by phenotype and function. Here we demonstrate that AML1/ETO transcripts are present in a fraction of stem cells, monocytes, and B cells in remission marrow, and in a fraction of B cells in leukemic marrow, but not in T cells. AML1/ETO transcripts also were demonstrated in a fraction of colony-forming cells of erythroid, granulocyte-macrophage, and/or megakaryocyte lineages in both leukemic and remission marrow. These data strongly suggest that the acquisition of the t(8;21) occurs at the level of stem cells capable of differentiating into B cells as well as all myeloid lineages, and that a fraction of the AML1/ETO-expressing stem cells undergo additional oncogenic event(s) that ultimately leads to transformation into AML.

Adult↗
PubMed2000

Dynamics of lymphocyte subpopulation changes in the cecal tonsils of chickens infected with Salmonella enteritidis.

Salmonella enteritidis (SE)-induced changes in various T and B lymphocyte subpopulations in the cecal tonsils of chickens were analyzed using flow cytometry. At 1 day post-SE inoculation, the percentages of CD3(+) and CD8(+) T lymphocytes were significantly decreased in the group inoculated with 1x10(9) SE colony-forming units (CFU) (SE high) and in the group inoculated with 1x10(6) SE CFU (SE low) compared with the uninfected control group. The percentage of CD4(+) T lymphocytes was significantly increased in the SE high group compared to the uninfected and the SE low groups at 4 days after SE inoculation. The percentage of IgG(+) B lymphocytes was also significantly increased in both SE high and low groups compared to the uninfected control at 6 days post-SE inoculation. In contrast, the SE low group showed significantly fewer IgM(+) B lymphocytes compared to the uninfected and SE high groups. These results show that SE infection induces significant changes in the cecal tonsil lymphocytes subpopulations shortly following SE inoculation.

Animals↗
PubMed2000

B lymphopoiesis in the thymus.

The thymus has been regarded as the major site of T cell differentiation. We find that in addition to alphabeta and gammadelta T cells, a significant number (approximately 3 x 104 per day) of B220+IgM+ mature B cells are exported from the thymus of C57BL/6 mice. Of these emigrating B cells, we estimate that at least approximately 2 x 104 per day are cells which developed intrathymically, whereas a maximum of approximately 0.8 x 104 per day are cells which circulated through the thymus from the periphery. The thymus possesses a significant number of pro-B and pre-B cells that express CD19, VpreB, lambda5, and pax-5. These B cell progenitors were found in the thymic cortex, whereas increasingly mature B cells were found in the corticomedullar and medullary regions. Other lymphoid cells, including NK cells and lymphoid dendritic cells, are not exported from the thymus at detectable levels. Thus, the thymus contributes to the formation of peripheral pools of B cells as well as of alphabeta and gammadelta T cells.

Animals↗
PubMed2000

A clonogenic common myeloid progenitor that gives rise to all myeloid lineages.

Haematopoietic stem cells give rise to progeny that progressively lose self-renewal capacity and become restricted to one lineage. The points at which haematopoietic stem cell-derived progenitors commit to each of the various lineages remain mostly unknown. We have identified a clonogenic common lymphoid progenitor that can differentiate into T, B and natural killer cells but not myeloid cells. Here we report the prospective identification, purification and characterization, using cell-surface markers and flow cytometry, of a complementary clonogenic common myeloid progenitor that gives rise to all myeloid lineages. Common myeloid progenitors give rise to either megakaryocyte/erythrocyte or granulocyte/macrophage progenitors. Purified progenitors were used to provide a first-pass expression profile of various haematopoiesis-related genes. We propose that the common lymphoid progenitor and common myeloid progenitor populations reflect the earliest branch points between the lymphoid and myeloid lineages, and that the commitment of common myeloid progenitors to either the megakaryocyte/erythrocyte or the granulocyte/macrophage lineages are mutually exclusive events.

Animals↗
PubMed2000

Autocrine signaling through Ras prevents apoptosis in vascular smooth muscle cells in vitro.

Vascular smooth muscle cell (SMC) apoptosis contributes to physiological and pathological vascular remodeling. Autocrine fibroblast growth factor (FGF) signaling promotes survival in SMC in vitro. Interruption of autocrine FGF signaling results in apoptosis that can be rescued by other growth factors such as PDGF (platelet-derived growth factor) or EGF (epidermal growth factor). Such heterologous growth factor rescue is prevented by pharmacological inhibition of MAPK, implicating signaling through Ras in mediating survival. This study was designed to test the hypothesis that signaling through Ras is both necessary and sufficient to mediate SMC survival in vitro. Recombinant adenoviruses encoding dominant-negative (Ras(N17)) and constitutively active (Ras(L61)) mutants of Ras were used. Ras(N17) blocks growth factor-mediated MAPK activation and can itself induce SMC apoptosis. Ras(N17) is synergistic with inhibition of autocrine FGF signaling in triggering apoptosis and prevents heterologous growth factor rescue. Conversely, Ras(L61) prevents apoptosis resulting from inhibition of autocrine FGF signaling. Rescue by Ras(L61) can be partially prevented by pharmacological inhibition of MEK or phosphatidylinositol 3-kinase, two downstream effectors of Ras. These results suggest that Ras signaling is both necessary and sufficient to mediate survival in SMC in vitro. Further work is required to determine how these signaling events are regulated in the context of vascular remodeling in vivo.

Animals↗
PubMed2000

Genetic linkage analysis of X-ray hypersensitivity in the LEC mutant rat.

The LEC rat has been reported to exhibit X-ray hypersensitivity and deficiency in DNA double-strand break (DSB) repair. The present study was performed to map the locus responsible for this phenotype, the xhs (X-ray hypersensitivity), as the first step in identifying the responsible gene. Analysis of the progeny of (BN x LEC)F(1) x LEC backcrosses indicated that the X-ray hypersensitive phenotype was controlled by multiple genetic loci in contrast to the results reported previously. Quantitative trait loci (QTL) linkage analysis revealed two responsible loci located on Chromosomes (Chr) 4 and 1. QTL on Chr 4 exhibited very strong linkage to the X-ray hypersensitive phenotype, while QTL on Chr 1 showed weak linkage. The Rad52 locus, mutation of which results in hypersensitivity to ionizing radiation and impairment of DNA DSB repair in yeast, was reported to be located on the synteneic regions of mouse Chr 6 and human Chr 12. However, mapping of the rat Rad52 locus indicated that it was located 23 cM distal to the QTL on Chr 4. Furthermore, none of the radio-sensitivity-related loci mapped previously in the rat chromosome were identical to the QTL on Chrs 4 and 1 in the LEC rat. Thus, it seems that X-ray hypersensitivity in the LEC rat is caused by mutation(s) in as-yet-undefined genes.

Animals↗
PubMed2000

Immunolocalization of TGF-beta1, -beta2, and -beta3, and TGF-beta receptors in human lens capsules with lens implants.

PURPOSE: To establish the alteration in expression pattern of transforming growth factor (TGF)-betas and their receptors during repair of lens capsules after cataract surgery, we immunohistochemically located TGF-beta isoforms and their receptors in human lens capsules before and after cataract surgery. METHODS: Ten post-cataract surgery capsular specimens were obtained during vitrectomy. Three sections of the anterior capsules were obtained during cataract surgery. A whole lens capsular bag immediately after lens extraction was obtained during vitrectomy. Cryosections of these specimens were processed for immunohistochemical analysis for TGF-beta1, TGF-beta2, TGF-beta3, TGF-beta receptor type I (TbetaR-I), type II (TbetaR-II) and type III (TbetaR-III), and were observed under light micros-copy. RESULTS: Lens epithelial cells (LECs) lining the inner surface of the anterior capsules exhibited immunoreactivity for TGF-beta2 and TbetaR-II. Immunoreactivity for TGF-beta1, -beta3, TbetaR-I and TbetaR-III was negative. In the whole capsular bag specimen, equatorial LECs were positive for TGF-beta1 and -beta2, but not for -beta3. In post-cataract surgery specimens, antibodies for each TGF-beta isoform labelled either the LECs or ECM accumulated on the capsules. Post-surgical LECs expressed TbetaR-I and TbetaR-II, and had also TbetaR-III in seven of the nine specimens examined. CONCLUSION: Expression pattern of TGF-beta s in quiescent LECs showed regional heterogeneity. Anterior LECs exhibited TGF-beta2 immunoreactivity, while equatorial LECs were positive for TGF-beta1 and -beta2. Quiescent LECs expressed TbetaR-II. LECs proliferating around IOLs expressed proteins of each TGF-beta isoform and each TbetaR. TGF-beta s were also localized in the ECM on capsules undergoing repair. TGF-beta3, TbetaR-I and TbetaR-III are up-regulated in LECs after cataract surgery.

Adult↗
PubMed2000

Microvilli and desmosomes of squamous cell carcinoma cells in tongue carcinoma related to regional lymph node metastasis: ultrastructural and immunohistochemical studies with transferrin receptor.

Squamous cell carcinomas of the tongue (n = 49), consisting of 21 cases with cervical lymph node metastasis and 28 nonmetastatic cases, were examined by electron microscopy with special emphasis on tumor cell attachment. No difference of tumor size (T classification) or pathological findings between the metastatic group and the nonmetastatic group was found. The metastatic cases had numerous microvilli and a small number of desmosomes regardless of the width of the intercellular spaces. The nonmetastatic cases had few microvilli in relatively wide intercellular spaces, or, in the cases in which numerous microvilli were present in the narrow intercellular spaces, the tumor cells were connected by a large number of desmosomes. Transferrin receptor, which is a marker of cell proliferation, was localized in the cell membrane by immunohistochemistry and especially in microvilli by immunoelectron microscopy. It is suggested that microvilli might be related to the proliferation and the metastasis of squamous cell carcinoma cells.

Adult↗
PubMed2000

Tracking the apparent location of targets in interpolated motion.

Under appropriate conditions, a target moving in discrete steps can appear to move smoothly and continuously even within the portions of the path where no physical stimulus is present. We investigated the nature of this interpolated motion in attentive tracking displays as well as apparent motion. The results showed that the apparent location of the target moved smoothly through space between the two discrete locations and the judgements of interpolated motion for attentive tracking and apparent motion were comparable to those for continuous motion in both the perceived path and the precision of the judgements. There were few, if any, differences between judgements for real and interpolated motion. An alignment procedure showed that the smooth change in location judgements was real and not a consequence of averaging across discrete locations actually seen on each trial. We also found that the slowest alternation rate which supported accurate location judgements corresponded to a critical SOA of about 500 ms, similar to the longest SOA which supported a subjective impression of motion in the display. Deviations from a constant velocity which were shorter than 200 ms did not register in the judged motion path, suggesting a fairly long time constant for the integration of velocity information into the perceived motion. These results suggest a specialized motion analysis which provides an accurate, explicit model of the interpolated motion path.

Attention↗
PubMed2000

Human leukocyte antigen DRB1 1302 protects against bile duct damage and portal lymphocyte infiltration in patients with chronic hepatitis C.

BACKGROUND/AIMS: To confirm the immune reaction of hosts in chronic hepatitis C, we examined the association of human leukocyte antigen (HLA) DR with the histopathological outcome including bile duct damage and steatosis, which are characteristic of hepatitis C virus (HCV) infection. METHODS: One hundred and fifty-five patients with chronic HCV infection were examined. The pathological appearance of liver biopsy specimens was evaluated by both Knodell's histological activity index and examination of bile duct damage and steatosis. HLA DRB1 was determined by the polymerase chain reaction sequence-specific oligonucleotide probe method. RESULTS: HLA DRB1 1302 was found with significantly higher frequency in patients without than with bile duct damage (34.8% vs. 4.7%, p=0.0001, p corrected by Bonferroni's inequality method=0.002). It was also found more frequently in patients without marked portal lymphocyte infiltration (28.6% vs. 7.7%, p=0.0015, p corrected by Bonferroni's method=0.03). HLA DRB1 1101 was found more frequently in patients without than with piecemeal necrosis (p=0.004). In contrast, the frequency of HLA DRB1 1502 tended to be higher in patients with than without piecemeal necrosis and marked portal lymphocyte infiltration (p=0.015 and p=0.03, respectively). HLA DRB1 1201 and 0802 were seen more frequently in bile duct damage-negative (p=0.02) and piecemeal necrosis-negative patients (p=0.03), respectively. Interestingly, serum HCV levels of HLA DRB1 1302-positive patients were significantly higher than those of 1302-negative patients (mean: 7.7 Meq/ml vs. 3.1 Meq/ml, p=0.0007). CONCLUSION: These findings suggest that some histopathological changes in chronically HCV-infected livers could be caused by the host's immune reaction regulated by HLA DR.

Adolescent↗
PubMed2000

Acid and salt responses in mouse taste cells.

Acid and salt responses of taste cells induced by natural stimulation have not been investigated with exception of early studies with conventional microelectrode method, due to the toxicity of high concentration of salt or low pH of acid stimuli applied to isolated taste cells. This indicates that the application of rapid and localized stimulation to the apical membrane of taste cells is necessary for recording of natural responses to salt or acid stimuli using patch clamp technique. Recently we have developed a procedure to accomplish the quasi-natural condition including rapid, localized stimuli to the apical receptive membrane and the maintenance of taste bud polarity. In this review, we present our recent results obtained under quasi-natural condition using patch clamp techniques, comparing with the previously proposed hypothesis. One of our major finding is the fact that the acid-induced responses of taste cells in the mouse fungiform papillae are never suppressed by amiloride but an apical proton-gated conductance and a basolateral Cl(-) conductance possibly contribute to sour transduction. On the other hand, salt-induced responses are suppressed by amiloride, although the salt-induced responses recorded from a single cell involve both amiloride-sensitive and -insensitive components. Furthermore, the amiloride-insensitive component of salt responses possibly consists of multiple subcomponents including an apical sodium-gated nonselective cation conductance and a basolateral Cl(-) conductance. Recent reports also support the hypothesis that both acid and salt responses require specific receptor mechanisms of inorganic cations such as H(+) and Na(+) at the apical receptive membrane.

Acids↗