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T Kato

Publications and source records attributed to T Kato.

At least 217 records · Page 12Linked to original sources
PubMed2001

A metabotropic glutamate receptor antagonist, alpha-methyl-4-carboxyphenylglycine, attenuates immediate early gene mRNA expression following traumatic injury in cultured rat cortical glial cells.

The effects of three glutamate receptor antagonists, (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine hydrogen maleate (MK-801) for the N-methyl-D-aspartate receptor, 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f] quinoxaline-7-sulfonamide (NBQX) for the alpha-amino-3-hydroxy-5methyl-4-isoxazole propionate /kinate receptor and (S)-alpha-methyl-4-carboxyphenylglycine (MCPG) for the metabotropic receptor, on c-fos and c-jun mRNA expression were investigated in cultured cortical glial cells following traumatic scratch injury. Expression of the two genes along the edges of wounds detected by in situ hybridization was not affected by MK-801 and NBQX. However, 100 and 500 microM of MCPG remarkably reduced the hybridization signals for both c-fos and c-jun mRNAs. The present results suggest that group I metabotropic glutamate receptors might have some association with immediate early gene induction after in vitro traumatic injury in glial cells.

Animals↗
PubMed2001

Overexpression of lysosomal-type sialidase leads to suppression of metastasis associated with reversion of malignant phenotype in murine B16 melanoma cells.

Increased sialylation in cell surface glycoproteins is one characteristic feature of cancer cells, particularly related to their metastatic potential and invasiveness. Expression of lysosomal-type sialidase, which plays a major role in hydrolysis of such sialo-glycoproteins, is therefore considered to have a great influence on malignant properties of cancer cells. To investigate whether the sialidase expression level is linked to the malignant phenotype, we transfected B16-BL6 murine melanoma cells, a highly invasive and metastatic line, with an expression vector harboring a rat lysosomal sialidase cDNA; then clones were isolated and examined for changes in biological character. Sialidase-overexpressing cells showed suppression of experimental pulmonary metastasis and tumor progression. The transfectants exhibited diminished cell growth, anchorage-independent growth and increased sensitivity to apoptosis induced by suspension culture or serum depletion in vitro, but no significant alterations in invasiveness, cell motility and cell attachment to fibronectin, collagen IV and laminin. Flow cytometric analysis with either peanut agglutinin (PNA) or Ricinus communis agglutinin (RCA) lectin revealed that desialylated forms of glycoproteins on the cell surfaces were increased. In particular, a desialylated form of a cell surface glycoprotein of 83 kDa was prominent in the transfectants, as determined by galactose oxidase labeling. These observations indicate that sialidase expression is inversely associated with metastatic potential and tumor growth in cancer cells, probably through a regulation mechanism that suppresses cell growth and anchorage-independent growth and promotes apoptosis with deprivation of cell anchorage.

Animals↗
PubMed2001

Probable Langevin-like director reorientation in an interface-induced disordered SmC*-like state of liquid crystals characterized by frustration between ferro- and antiferroelectricity.

To clarify the thresholdless, hysteresis free V-shaped switching due to frustration between ferro- and antiferroelectricity, we have studied a prototype binary mixture system. The apparent orientational order parameters, and , obtained from polarized Raman scattering in thin homogeneous cells indicate that substrate interfaces induce some randomization of local in-plane directors at the tip of the V. Their correlation lengths, xi( parallel) approximately 3.5 nm and xi( perpendicular) approximately 75 nm, have been estimated by assuming the Langevin-like reorientation. Because of the much shorter xi(parallel) and xi(perpendicular) than the visible light wavelength, the switching process looks uniform.

Journal Article↗
PubMed2001

Catheter-tip fixation of a percutaneously implanted port-catheter system to prevent dislocation.

The aim of this study was to evaluate the incidence of catheter tip dislocation in patients with percutaneously implanted port-catheters for hepatic arterial chemotherapy with catheter tip fixation. Forty-seven patients (31 men and 16 women; mean age 66 years) with unresectable advanced liver cancers (primary liver cancer, n=19; metastatic liver cancer, n=28) underwent percutaneously implantable port-catheter system placement with the tip fixed at the gastroduodenal artery with coils and side hole opened at the common hepatic artery. In 39 patients, n-butyl cyanoacrylate (NBCA) mixed with Lipiodol was added for fixation. The position of the side hole after the indwelling port-catheter system was investigated, and the correction method in cases with catheter dislocation was determined. In 2 (25%) of the 8 patients without NBCA fixation, dislocation of the catheter was noted, in contrast to none (0%) of 37 patients with NBCA fixation. Two patients in whom NBCA was used could not undergo long-term intra-arterial chemotherapy because of hepatic arterial thrombotic occlusion which occurred after placement of the indwelling catheter, and were excluded from the evaluation. Fixation of the catheter tip with combined use of coils and NBCA--Lipiodol mixture to the gastroduodenal artery is important to prevent dislocation of the port-catheter system.

Aged↗
PubMed2001

Discontinuous elongation of nematic gels by a magnetic field.

The effects of a magnetic field on the swelling of a nematic gel immersed in a low molecular weight liquid crystal solvent are examined by using a mean field theory. The nematic-isotropic (paranematic) phase transition temperature of the gel and the solvent is controlled by the external field. As a result of an anisotropic coupling between the gel and solvent, the shape of the gel is discontinuously (or continuously) elongated with increasing the strength of the external field. We examine the condition for a first- and second-order volume phase transition of the gel under a magnetic field.

Journal Article↗
PubMed2001

Cyclic hydroxamic-acid-containing peptide 31, a potent synthetic histone deacetylase inhibitor with antitumor activity.

Cyclic hydroxamic-acid-containing peptide 1 (CHAP1), designed as a hybrid of trichostatin A and trapoxin, is a lead compound for the development of potent inhibitors of histone deacetylase (HDAC). In this study, we synthesized a series of CHAP derivatives and evaluated their biological activities by monitoring the potency of their inhibition of HDAC activity, their ability to augment the expression of MHC class-I molecules in B16/BL6 cells, and their effect on cell proliferation. A structure-activity relationship study using these three assay systems revealed several requirements of their structure for the strong inhibition of HDAC not only in the cell-free situation, but also in cells. When the structures of CHAP derivatives are represented as cyclo(-Asu(NHOH)-AA(2)-AA(3)-Pro or Pip-)(n), where Asu(NHOH) and Pip are zeta-hydroxamide-alpha-aminosuberic acid and pipecolic acid, respectively, (a) the tetrapeptide structure (n = 1) was better than the octapeptide one (n = 2); (b) AA(2) and AA(3) should be hydrophobic; and (c) the combination of amino acid chirality should be LDLD for the strongest inhibition of HDAC in cells (LDLD > LLLD, LDLL > LLDL). cyclo(-L-Asu(NHOH)-D-Tyr(Me)-L-Ile-D-Pro-) or CHAP31 was selected as one of the strongest CHAPs, and its biological activity was characterized further. CHAP31 was much more stable in the presence of cultured cells (t(1/2) > 3000 h) than trichostatin A (t(1/2) = 14.7 h) or trapoxin A (t(1/2) = 2.10 h). CHAP31 exhibited antitumor activity in C57BL x DBA/2 F(1) (BD2F(1)) mice bearing B16/BL6 tumor cells. Furthermore, CHAP31 inhibited the growth in four of five human tumor lines implanted into nude mice. These results suggest CHAP31 to be promising as a novel therapeutic agent for cancer treatment.

Animals↗
PubMed2001

Alterations in the expression of the AQP family in cultured rat astrocytes during hypoxia and reoxygenation.

Aquaporins (AQPs) are a family of water-selective transporting proteins with homology to the major intrinsic protein (MIP) of lens [Cell 39 (1984) 49], that increase plasma membrane water permeability in secretory and absorptive cells. In the central nervous system (CNS), we detected the transcripts of AQP3, 5 and 8 in addition to the previously reported transcripts of AQP4 and 9 in astrocytes, of AQP3, 5 and 8 in neurons, of AQP8 in oligodendrocytes, and none of them in microglia using RNase protection assay and the reverse transcription-polymerase chain reaction (RT-PCR). Hypoxia evoked a marked decrease in the expression levels of AQP4, 5 and 9, but not of AQP3 and 8 mRNAs, and in astrocytes in vitro subsequent reoxygenation elicited the restoration of the expression of AQP4 and 9 to their basal levels. Interestingly, AQP5 showed a transient up-regulation (about 3-fold) and subsequent down-regulation of its expression within 20 h of reoxygenation after hypoxia. The changes in the profiles of AQP expression during hypoxia and reoxygenation were also observed by Western blot analysis. These results suggest that AQP5 may be one of the candidates for inducing the intracranial edema in the CNS after ischemia injury.

Animals↗
PubMed2001

Recurrent subthreshold electrical activities of rat neocortical neurons progress during long-term culture.

The properties of neocortical neurons during long-term culture on monolayers of astrocytes were examined using whole-cell recording and immunocytochemical techniques. The soma size of neocortical neurons became larger and most neurites reached neighboring neurons within 2 weeks. Recurrent subthreshold electrical activities mediated by synaptic activation were observed at 10 days of culture and became more frequent as the neurons grew. Their frequency reached to about 1 Hz at 4 weeks. While the total number of neurons decreased during culture, the ratio of gammaaminobutyric acid (GABA) positive to total (MAP2 positive) neurons increased. These results suggest that neurons grown on astrocytes become mature during cultivation, and that recurrent subthreshold electrical activities may be related to the development of GABAergic inputs.

Animals↗
PubMed2001

Regulation of aquaporin-4 expression in astrocytes.

Aquaporin-4 (AQP4), a mercury-insensitive water channel protein, is abundant in the central nervous system and is localized in astrocytes and ependymal cells. AQP4 is speculated to maintain the homeostasis of intracellular and extracellular water in the brain, but little is known about the mechanism of induction of its expression. To investigate the expressional regulation of AQP4, we analyzed changes in its expression during chemically induced differentiation of embryonal carcinoma cells (P19) to neuronal and astrocytic cells, and during the cell cycle of glioma cells. After exposure to retinoic acid for 4 days AQP4 mRNA expression started at the initiation of astrocytic differentiation of P19 cells at 6 days, and increased markedly by 21 days. AQP4 expression was parallel to that of GFAP, a marker intermediate filament of astrocytes. In glioma cell lines, AQP4 mRNA was not detected in the growing phase, but was induced when the cell cycle was arrested at G0/G1 by transient expression of p21. Although quiescent astrocytes in the G0/G1-phase cultured under the serum-free condition exhibited a high expression of AQP4, serum supplement moved them to the S-phase and markedly decreased the AQP expression. These results suggest that AQP4 expression may be induced not only at the initiation of astrocytic differentiation of neural stem cells, but also at the G0/G1-phase during the cell cycle of astrocytes.

Animals↗
PubMed2001

BCL10 is not a major target for frequent loss of 1p in testicular germ cell tumors.

The deletion of chromosome 1p is one of the frequent genetic alterations found in testicular germ cell tumors (GCTs), suggesting the presence of a tumor suppressor gene. BCL10, which was identified as a gene altered in mucosa-associated lymphoid tissue lymphoma, has been mapped at 1p22. The gene has been reported to be mutated in a variety of human cancers. In this study, we investigated the allelic deletions on 1p and the mutation of BCL10 in 51 GCTs comprising 30 seminomas and 21 non-seminomatous germ cell tumors. Loss of heterozygosity (LOH) on 1p was tested using three microsatellite markers. The search for BCL10 mutations in each of the three exons was screened by a single-stranded conformation polymorphism (SSCP) analysis and samples with abnormal bandshifts were directly sequenced. LOH at at least one locus tested was found in 42% (21/49) of the tumors (43% of seminomas and 38% of NSGCTs). SSCP and direct sequence analyses revealed that there were single nucleotide polymorphisms at codon 5, 8, 162, and intron 1. However, there were no somatic mutations of BCL10 in the 51 tumors. In support of the previous studies, our results demonstrated that LOH on 1p is frequent in both seminomas and NSGCTs, indicating that there is an important tumor suppressor on 1p in GCT. However, the results indicate that BCL10 is not a candidate target gene of the 1p deletion.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Expression of IL-17 mRNA in ovarian cancer.

IL-17 is considered as a proinflammatory cytokine. We have demonstrated IL-17 is an angiogenic factor and promotes tumor growth in murine tumor models. In this report, we investigated the expression of IL-17 mRNA by RT-PCR and the relationship between IL-17 expression and microvascular density in ovarian cancer. IL-17 mRNA was expressed in 11 (64.7%) of 17 ovarian cancer. And the average number of blood vessels observed in IL-17 positive tumors (173.4 +/- 55.1/mm(2)) was significantly higher than that in negative tumors (107.7 +/- 57.8/mm(2)). These results indicated IL-17 is expressed in a considerable proportion of ovarian cancer and promotes tumor angiogenesis. There was no significant relationship between IL-17 expression and clinicopathologic parameters.

Base Sequence↗
PubMed2001

An increase in circulating mast cell colony-forming cells in asthma.

We compared a potential to generate mast cells among various sources of CD34(+) peripheral blood (PB) cells in the presence of stem cell factor (SCF) with or without thrombopoietin (TPO), using a serum-deprived liquid culture system. From the time course of relative numbers of tryptase-positive and chymase-positive cells in the cultured cells grown by CD34(+) PB cells of nonasthmatic healthy individuals treated with G-CSF, TPO appears to potentiate the SCF-dependent growth of mast cells without influencing the differentiation into mast cell lineage. CD34(+) PB cells from asthmatic patients in a stable condition generated significantly more mast cells under stimulation with SCF alone or SCF+TPO at 6 wk of culture than did steady-state CD34(+) PB cells of normal controls. Single-cell culture studies showed a substantial difference in the number of SCF-responsive or SCF+TPO-responsive mast cell progenitors in CD34(+) PB cells between the two groups. In the presence of TPO, CD34(+) PB cells from asthmatic children could respond to a suboptimal concentration of SCF to a greater extent, compared with the values obtained by those of normal controls. Six-week cultured mast cells of asthmatic subjects had maturation properties (intracellular histamine content and tryptase/chymase enzymatic activities) similar to those derived from mobilized CD34(+) PB cells of nonasthmatic subjects. An increase in a potential of circulating hemopoietic progenitors to differentiate into mast cell lineage may contribute to the recruitment of mast cells toward sites of asthmatic mucosal inflammation.

Adolescent↗
PubMed2001

Galectin-1 is a component of neurofilamentous lesions in sporadic and familial amyotrophic lateral sclerosis.

In amyotrophic lateral sclerosis (ALS), abnormal accumulation of neurofilaments induces pathological changes such as axonal spheroids, cord-like neurite swellings, and perikaryal conglomerate inclusions in degenerating motor neurons of the spinal cord, and the accumulation seems to cause motor neuron degeneration in this disease. Such ALS lesions were intensely labeled with HepSS-1, a monoclonal antibody to heparan sulfate. Since the identification of HepSS-1-immunoreactive substance seems to be an important step for understanding the molecular pathology of ALS, we purified the substance from human spinal cord tissue to homogeneity. Amino acid sequence of the protein was consistent with that of galectin-1. Immunohistochemistry using antibodies against recombinant human galectin-1 showed that galectin-1 was accumulated in these lesions in ALS. Although HepSS-1 was believed to be specific for heparan sulfate, it reacted with recombinant human galectin-1 which has no heparan sulfate moiety. The results show that galectin-1 is a component of the neurofilamentous lesions in ALS. Since galectin-1 has axonal regeneration-enhancing activity, the abnormal accumulation of galectin-1 to the lesions seems to be related to the pathological process of ALS.

Aged↗
PubMed2001

Arabidopsis NPL1: a phototropin homolog controlling the chloroplast high-light avoidance response.

Chloroplasts relocate their positions in a cell in response to the intensity of incident light, moving to the side wall of the cell to avoid strong light, but gathering at the front face under weak light to maximize light interception. Here, Arabidopsis thaliana mutants defective in the avoidance response were isolated, and the mutated gene was identified as NPL1 (NPH-like 1), a homolog of NPH1 (nonphototropic hypocotyl 1), a blue light receptor used in phototropism. Hence, NPL1 is likely a blue light receptor regulating the avoidance response under strong light.

Alleles↗
PubMed2001

Human neuroblastomas with unfavorable biologies express high levels of brain-derived neurotrophic factor mRNA and a variety of its variants.

The expression of human brain-derived neurotrophic factor (BDNF) was investigated in 16 primary human neuroblastomas with favorable biologies, 15 with unfavorable biologies, and in human neuroblastoma cell lines. We demonstrated higher expressions of human BDNF mRNA in neuroblastomas with unfavorable biologies and with N-myc amplification than in those with favorable biologies. For the first time we revealed the composition of splice variants of human BDNF mRNA and analyzed their expression in neuroblastomas by reverse transcription polymerase chain reaction (RT-PCR). Interestingly, human BDNF mRNA consisted of at least six isoforms, four isoforms resembling those of rat BDNF mRNA, a human-specific isoform and a new isoform. The expression of four isoforms were more prominent in tumors with unfavorable biologies than in those with favorable biologies (P<0.05). As previously we had reported, over 80% of the primary tumors expressed either the full-length form of BDNF receptor, TRKB, or a truncated form of TRKB lacking the tyrosine kinase domain. The full-length TRKB was predominantly detected in tumors with unfavorable biologies, and the truncated one in those with favorable biologies. These results suggest that an autocrine and/or paracrine mechanism involving BDNF may stimulate signal transduction via TRKB receptors rich in neuroblastomas with unfavorable biologies, resulting in an aberrant survival of tumor cells.

Age Factors↗
PubMed2001

Genome-wide analysis of gene expression in human hepatocellular carcinomas using cDNA microarray: identification of genes involved in viral carcinogenesis and tumor progression.

To disclose detailed genetic mechanisms in hepatocellular carcinoma (HCC) with a view toward development of novel therapeutic targets, we analyzed expression profiles of 20 primary HCCs and their corresponding noncancerous tissues by means of cDNA microarrays consisting of 23,040 genes. Up-regulation of mitosis-promoting genes was observed in the majority of the tumors examined. Some genes showed expression patterns in hepatitis B virus-positive HCCs that were different from those in hepatitis C virus-positive HCCs; most of them encoded enzymes that metabolize carcinogens and/or anticancer agents. Furthermore, we identified a number of genes associated with malignant histological type or invasive phenotype. Accumulation of such data will make it possible to define the nature of individual tumors, to provide clues for identifying new therapeutic targets, and ultimately to optimize treatment of each patient.

Carcinoma, Hepatocellular↗
PubMed2001

Identification of CRE1 as a cytokinin receptor from Arabidopsis.

Cytokinins are a class of plant hormones that are central to the regulation of cell division and differentiation in plants. It has been proposed that they are detected by a two-component system, because overexpression of the histidine kinase gene CKI1 induces typical cytokinin responses and genes for a set of response regulators of two-component systems can be induced by cytokinins. Two-component systems use a histidine kinase as an environmental sensor and rely on a phosphorelay for signal transduction. They are common in microorganisms, and are also emerging as important signal detection routes in plants. Here we report the identification of a cytokinin receptor. We identified Arabidopsis cre1 (cytokinin response 1) mutants, which exhibited reduced responses to cytokinins. The mutated gene CRE1 encodes a histidine kinase. CRE1 expression conferred a cytokinin-dependent growth phenotype on a yeast mutant that lacked the endogenous histidine kinase SLN1 (ref. 10), providing direct evidence that CRE1 is a cytokinin receptor. We also provide evidence that cytokinins can activate CRE1 to initiate phosphorelay signalling.

Arabidopsis↗