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Dai Watanabe

Publications and source records attributed to Dai Watanabe.

13 recordsLinked to original sources
PubMed2006

The extracellular domain of p185(c-neu) induces density-dependent inhibition of cell growth in malignant mesothelioma cells and reduces growth of mesothelioma in vivo.

EGFR is involved in the density-dependent inhibition of cell growth, while coexpression of EGFR with erbB2 can render normal cells transformed. In this study, we have examined the effect of a species of p185 that contains the transmembrane domain and the extracellular domain of p185(c-neu), on growth properties of a human malignant mesothelioma cell line that coexpresses EGFR and erbB2. The ectodomain form of p185(c-neu) enhanced density-dependent inhibition of cell growth and we found that p21 induction appeared to be responsible for this inhibitory effect. Previously, the extracellular domain species was shown to suppress the transforming abilities of EGFR and p185(c-neu/erbB2) in a dominant-negative manner. The ability of this subdomain to affect tumor growth is significant, as it reduced in vivo tumor growth. Unexpectedly, we found that the domain did not abrogate all of EGFR functions. We noted that EGFR-induced density-dependent inhibition of cell growth was retained. Tyrosine kinase inhibitors of EGFR did not cause density-dependent inhibition of cell growth of malignant mesothelioma cells. Therefore, simultaneously inhibiting the malignant phenotype and inducing density-dependent inhibition of cell growth in malignant mesothelioma cells by the extracellular domain of p185(c-neu) may represent an important therapeutic advance.

Animals↗
PubMed2005

Requirement for CD100-CD72 interactions in fine-tuning of B-cell antigen receptor signaling and homeostatic maintenance of the B-cell compartment.

Co-receptors on the B-cell surface regulate B-cell antigen receptor (BCR) signaling; however, it remains unclear how BCR signals are coordinated to maintain immune homeostasis. CD72, a negative regulator of B-cell responses, has immunoreceptor tyrosine-based inhibitory motifs within its cytoplasmic region, and the tyrosine phosphatase SHP-1 binds these sites. The natural ligand of CD72, CD100/Sema4D, belongs to the semaphorin family and induces the dissociation of SHP-1 from CD72, thereby switching off the negative signals of CD72. In the absence of CD100, BCR signals are significantly suppressed due to the constitutive association of SHP-1 with CD72, resulting in B-cell hyporesponsiveness. Here we show that CD100 regulates the sensitivity of the BCR by preventing the association of the CD72 with BCR, and this interaction is required for proper B-cell homeostasis. Consequently, as CD100-deficient mice age, they accumulate marginal zone B cells and develop high auto-antibody levels and autoimmunity. Collectively, our findings indicate that the strength of BCR signals is strictly tuned by the interaction of CD100 with CD72, and this interaction is essential for maintaining immunological homeostasis as well as generating a proper immune response.

Animals↗
PubMed2004

Inadequate induction of suppressor of cytokine signaling-1 causes systemic autoimmune diseases.

Suppressor of cytokine signaling (SOCS)-1 is a cytokine-inducible, negative regulatory molecule of Janus kinases (JAK) and its deficiency causes hyper-response to various cytokines. SOCS-1(-/-) mice spontaneously develop a fatal disease depending on aberrantly activated lymphocytes. Here, we show that partial restoration of SOCS-1 in lymphoid cells rescues SOCS-1(-/-) mice from the early-onset fatal disease, indicating that SOCS-1 expression in vivo is especially required in lymphocytes. However, SOCS-1 expression in these SOCS-1-restored mutant mice (E( micro )-SOCS-1(-/-) mice) was insufficient for proper down-regulation of its target signaling, and these mice spontaneously exhibit hyperactivation of lymphocytes, an increase in the levels of serum Ig and anti-DNA autoantibodies, and glomerulonephritis with glomerular IgG deposition. These phenotypes resemble those of murine systemic autoimmune diseases, models for systemic lupus erythematosus (SLE). Interestingly, similar phenotypes were also observed in adult female SOCS-1(+/-) mice, indicating that the autoimmune phenotypes of these mice can be ascribed primarily to the inadequate expression of SOCS-1. In addition, autoimmune phenotypes were not observed in SOCS-1(+/-)CD4(-/-) mice, suggesting that autoimmunity is dependent on hyper-activated CD4(+) T cells. Our findings also suggest that insufficient expression of SOCS-1 results in impaired function of CD25(+)CD4(+) regulatory T cells, which may contribute to aberrant activation of CD4(+) T cells. These findings suggest that dysfunction of SOCS-1 can be a pathogenic factor of systemic autoimmune diseases such as SLE.

Animals↗
PubMed2004

Suppressor of cytokine signalling-1 gene silencing in acute myeloid leukaemia and human haematopoietic cell lines.

The aim of this study was to investigate whether the suppressor of cytokine signalling (SOCS)-1 can act as a tumour suppressor when functioning as a negative regulator of the Janus family tyrosine kinases (JAKs), which have been reported to play important roles in leukaemogenesis. For this purpose, we carried out molecular analysis of the SOCS-1 gene in human acute myeloid leukaemia (AML) and human haematopoietic cell lines. Sequencing alterations in the coding region were found in two of 90 primary AML samples and one of 17 cell lines. Hypermethylation of the SOCS-1 gene was also observed in 72% of primary cases and 52% of cell lines and aberrant methylation strongly correlated with reduced expression. Transfection of SOCS-1 into Jurkat cells harbouring the mutation and methylation suppressed cell growth at a low serum concentration. These findings indicate that SOCS-1 is frequently silenced in haematopoietic malignancies, mainly as a result of hypermethylation, and suggest that SOCS-1 may be able to function as a tumour suppressor.

Acute Disease↗
PubMed2004

Oral glucose tolerance test and determination of serum fructosamine level in beagle dogs.

The present communication deals with information regarding the practice of the oral glucose tolerance test and determination of serum fructosamine in laboratory beagles. In the oral glucose tolerance test, a 180-min level was found to be crucial following a gavage administration of 50% glucose solution at 5 mL/kg per body weight under fasting conditions. Serum fructosamine concentration as 'determined by enzymatic assay ranged between 82 and 123 micromol/L (mean of 104 micromol/L), which was about 0.285 to 0.25 times the value obtained by the chemical method described by Johnson and colleagues. Reasons for differences are ascribed to the presence of substances with reducing potential other than fructosamine in the serum.

Administration, Oral↗
PubMed2003

mGluR2 postsynaptically senses granule cell inputs at Golgi cell synapses.

In the cerebellar circuit, Golgi cells are thought to contribute to information processing and integration via feedback mechanisms. In these mechanisms, dynamic modulation of Golgi cell excitability is necessary because GABA from Golgi cells causes tonic inhibition on granule cells. We studied the role and synaptic mechanisms of postsynaptic metabotropic glutamate receptor subtype 2 (mGluR2) at granule cell-Golgi cell synapses, using whole-cell recording of green fluorescent protein-positive Golgi cells of wild-type and mGluR2-deficient mice. Postsynaptic mGluR2 was activated by glutamate from granule cells and hyperpolarized Golgi cells via G protein-coupled inwardly rectifying K+ channels (GIRKs). This hyperpolarization conferred long-lasting silencing of Golgi cells, the duration and extents of which were dependent on stimulus strengths. Postsynaptic mGluR2 thus senses inputs from granule cells and is most likely important for spatiotemporal modulation of mossy fiber-granule cell transmission before distributing inputs to Purkinje cells.

Animals↗
PubMed2003

Reversible suppression of glutamatergic neurotransmission of cerebellar granule cells in vivo by genetically manipulated expression of tetanus neurotoxin light chain.

We developed a novel technique that allowed reversible suppression of glutamatergic neurotransmission in the cerebellar network. We generated two lines of transgenic mice termed Tet and TeNT mice and crossed the two transgenic lines to produce the Tet/TeNT double transgenic mice. In the Tet mice, the tetracycline-controlled reverse activator (rtTA) was expressed selectively in cerebellar granule cells by the promoter function of the GABA(A) receptor alpha6 subunit gene. In the TeNT mice, the fusion gene of tetanus neurotoxin light chain (TeNT) and enhanced green fluorescent protein (EGFP) was designed to be induced by the interaction of doxycycline (DOX)-activated rtTA with the tetracycline-responsive promoter. The Tet/TeNT mice grew normally even after DOX treatment and exhibited a restricted DOX-dependent expression of TeNT in cerebellar granule cells. Along with this expression, TeNT proteolytically cleaved the synaptic vesicle protein VAMP2 (also termed synaptobrevin2) and reduced glutamate release from granule cells. Both cleavage of VAMP2/synaptobrevin2 and reduction of glutamate release were reversed by removal of DOX. Among the four genotypes generated by heterozygous crossing of Tet and TeNT mice, only Tet/TeNT mice showed DOX-dependent reversible motor impairments as analyzed with fixed bar and rota-rod tests. Reversible suppression of glutamatergic neurotransmission thus can be manipulated with spatiotemporal accuracy by DOX treatment and removal. These transgenic mice will serve as an animal model to study the cerebellar function in motor coordination and learning.

Animals↗
PubMed2003

Segregation and coactivation of developing neocortical layer 1 neurons.

Layer 1 in the developing cerebral cortex is populated by two basic neuronal cell types, Cajal-Retzius (CR) cells and non-CR cells. We generated transgenic mice in which green fluorescent protein (GFP) was driven by the promoter of metabotropic glutamate receptor subtype 2 and expressed specifically in CR cells during cortical development. On the basis of the precise identification of CR cells with GFP fluorescence, we pursued developmental changes and synaptic mechanisms of both CR and non-CR cells during the postnatal period. Immunostaining in combination with GFP fluorescence imaging showed that GFP and reelin, a protein involved in corticogenesis, completely overlap in CR cells at postnatal day 0. At the subsequent postnatal stage, reelin-positive neurons are segregated and categorized into GFP-positive/GABA-negative CR cells and GFP-negative/GABA-positive non-CR cells. Individual and simultaneous whole-cell recordings of CR and non-CR cells in developing cerebral slices revealed that spontaneous and electrically evoked postsynaptic currents (sPSCs and ePSCs) measured in CR and non-CR cells are differentially mediated by GABA(A) receptors versus GABA(A), AMPA, and NMDA receptors, respectively. Furthermore, CR and non-CR cells show synchronized repetitive barrages of sPSCs that reflect a network-driven activity in the developing cerebral cortex. These findings imply that the layer 1 neurons dynamically change and play a distinct and integral role in the postnatal developing neocortex.

Animals↗
PubMed2003

Impairment of reward-related learning by cholinergic cell ablation in the striatum.

The striatum in the basal ganglia-thalamocortical circuitry is a key neural substrate that is implicated in motor balance and procedural learning. The projection neurons in the striatum are dynamically modulated by nigrostriatal dopaminergic input and intrastriatal cholinergic input. The role of intrastriatal acetylcholine (ACh) in learning behaviors, however, remains to be fully clarified. In this investigation, we examine the involvement of intrastriatal ACh in different categories of learning by selectively ablating the striatal cholinergic neurons with use of immunotoxin-mediated cell targeting. We show that selective ablation of cholinergic neurons in the striatum impairs procedural learning in the tone-cued T-maze memory task. Spatial delayed alternation in the T-maze learning test is also impaired by cholinergic cell elimination. In contrast, the deficit in striatal ACh transmission has no effect on motor learning in the rota-rod test or spatial learning in the Morris water-maze test or on contextual- and tone-cued conditioning fear responses. We also report that cholinergic cell elimination adaptively up-regulates nicotinic ACh receptors not only within the striatum but also in the cerebral cortex and substantia nigra. The present investigation indicates that cholinergic modulation in the local striatal circuit plays a pivotal role in regulation of neural circuitry involving reward-related procedural learning and working memory.

Acetylcholine↗
PubMed2002

Different regulatory sequences are required for parvalbumin gene expression in skeletal muscles and neuronal cells of transgenic mice.

Parvalbumin (PV) is expressed in fast-twitch fibers in skeletal muscles and a subpopulation of inhibitory neurons in the CNS. We generated transgenic mice that expressed the human interleukin-2 receptor alpha-subunit-green fluorescent fusion protein (hIL-2R-GFP) using two types of PV transgene. One contained the hIL-2R-GFP gene downstream of a 16.5-kb 5'-upstream PV genomic sequence (PV line). The other comprised the hIL-2R-GFP gene in bacterial artificial chromosome (BAC) with either a 180-kb (PA line) or 155-kb (PB line) insert encompassing the PV gene. Independent lines of all transgenic mice showed a faithful hIL-2R-GFP expression in fast-twitch muscle fibers. However, appreciable hIL-2R-GFP expression in the CNS occurred only in the PA transgenic lines. In one line of PA transgenic mice, hIL-2R-GFP was properly expressed in PV-containing neurons in the cerebellum, thalamic reticular nucleus, globus pallidus and cerebral cortex, though ectopic expression was observed in a particular subset of cerebellar astrocytes. Another line of PA transgenic mice showed a selective and mosaic expression of hIL-2R-GFP in PV-containing Purkinje, basket and stellate cells in the cerebellum. These results indicate that the 16.5-kb PV genomic sequence is sufficient for fiber-type-selective transcription but additional regulatory sequences comprised in BAC DNA are required for proper expression in PV-containing neurons.

Animals↗
PubMed2002

Roles of inhibitory interneurons in the cerebellar cortex.

The roles of inhibitory interneurons in the cerebellar cortex were investigated. First, Golgi cells were specifically eliminated in transgenic mice in which Golgi cells expressed human interleukin-2 receptor alpha subunit (IL2Ralpha). Injection of exotoxin coupled to anti-IL2Ralpha antibody in the cerebellum of the transgenic mouse eliminated Golgi cells and abolished GABA and synaptic inhibition in the granular layer. After elimination of Golgi cells, acute severe ataxia and subsequent mild motor discoordination were observed. In the latter chronic phase, NMDA receptor-mediated synaptic response was reduced in granule cells. Our findings indicate that elimination of GABAergic inhibition in the granular layer caused overexcitation of granule cells resulting in severe ataxia, and then NMDA receptors in granule cells were downregulated, compensating for the reduction of GABAergic inhibition and improving motor control. In the second part, we report on the regulation mechanism of synaptic plasticity at inhibitory synapses on Purkinje cells (PCs). Inhibitory synaptic transmission on a PC is potentiated after repetitive PC depolarization. This synaptic plasticity (rebound potentiation, RP) was suppressed when a presynaptic neuron was activated during the PC depolarization. This synaptic regulation is unique in the sense that the homosynaptic activity suppresses the induction of synaptic plasticity. The mechanism of how presynaptic activity suppresses RP was examined. GABA released from the presynaptic terminal activated not only GABA(A) receptor but also GABA(B) receptor. The latter was coupled to Gi/o proteins, which downregulated adenylyl cyclase reducing cAMP and inactivated cAMP-dependent protein kinase (PKA). Downregulation of PKA suppressed RP induction.

Animals↗
PubMed2002

[Chemotherapy for small-cell lung cancer (SCLC) patients with renal failure].

We administered chemotherapy in three cases of small-cell lung cancer (SCLC) with renal failure under different situations. Hemodialysis (HD) was used in 2 out of the 3 cases. Case 1 was complicated by acute renal failure from extensive bilateral tumor invasion. After chemotherapy (CBDCA + ETP) under HD, renal metastases regressed and renal function improved, although the final response was PD. In case 2, HD had been introduced for diabetic nephropathy. After 2 cycles of chemotherapy (CBDCA + ETP) under HD, the patient attained a PR. Case 3 is an example of paraneoplastic nephrotic syndrome with renal failure. Chemotherapy including CBDCA or CDDP was performed and the QOL of the patient improved. Pro-GRP and serum creatinine changed in parallel during the clinical course of 6 admissions. In conclusion, individualized therapy is necessary to increase survival time of SCLC patients with renal failure. Although chemotherapy is useful, further study is needed for the selection of suitable chemotherapeutic regimens, optimal dosage of each drug and the timing of HD.

Adult↗