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Biomedical subjects

K Kikuchi

Publications and source records attributed to K Kikuchi.

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

Up-regulation of I-2(PP2A)/SET gene expression in rat primary hepatomas and regenerating livers.

I-2(PP2A)/SET, an inhibitor of protein phosphatase 2A, is supposed to be one of the oncoproteins associated with human myeloid leukemia. The I-2(PP2A)/SET gene expression was observed ubiquitously among all the rat tissues examined, but low in liver. Of interest is that the expression in the rat primary hepatomas and hyperplastic nodules was significantly elevated. The experiments using regenerating livers after partial hepatectomy showed that the expression of I-2(PP2A)/SET mRNA was low at the quiescent hepatocytes, but up-regulated at 12-24 h after partial hepatectomy, which corresponds to the mid G1 to S transition in the cell cycle. These results suggested the importance of I-2(PP2A)/SET in the hepatocarcinogenesis and hepatic cell proliferation.

Amino Acid Sequence↗
PubMed2000

Identification and characterization of 5' extension of mammalian agrin cDNA, the exons and the promoter sequences.

Agrin, which is secreted from motor neurons, is essential for the formation and maintenance of the vertebrate neuromuscular junctions. Here we show the complete N-terminal sequence of the mammalian cDNA required for the expression and secretion as well as the intron/exon structure and the 5'-flanking sequence required for basal promoter activity. The 5'-flanking region and the first exon are extremely GC rich and contain a CpG island. These features may account for hindrance in identification of the 5' end of the cDNA and the promoter region of the mammalian agrin gene.

Agrin↗
PubMed2000

Identification and characterization of a novel protein inhibitor of type 1 protein phosphatase.

We have isolated human cDNA for a novel type 1 protein phosphatase (PP1) inhibitory protein, named inhibitor-4 (I-4), from a cDNA library of germ cell tumors. I-4, composed of 202 amino acids, is 44% identical to a PP1 inhibitor, inhibitor-2 (I-2). I-4 conserves functionally important structure of I-2 and exhibited similar biochemical properties. I-4 inhibited activity of the catalytic subunit of PP1 (PP1C), specifically with an IC(50) of 0.2 nM, more potently than I-2 with an IC(50) of 2 nM. I-4 weakly inhibited the activity of myosin-associated phosphates (PP1M). However, the level of inhibition of PP1M was increased during preincubation of PP1M with I-4, suggesting that the inhibition is caused by interaction of I-4 with PP1C in such a manner that it competes with the M subunit of PP1M. Gel overlay experiments showed that I-4 binds PP1C directly. Three I-4 peptides containing the N-terminal residues 1-123, 1-131, and 1-142 all showed strong binding ability to PP1C but did not show PP1 inhibitory activity, whereas an I-2 peptide (residues 1-134), lacking the corresponding C-terminal residues, potently inhibited PP1C activity as previously reported. Removal of the 18 N-terminal amino acid residues from I-4 dramatically reduced the PP1 binding activity with a correlated loss of inhibitory activity, whereas removal of the 10 N-terminal residues had only a little effect. The two peptides GST-I-4(19-131) and GST-I-4(132-202) showed ability to bind to PP1C, albeit very weakly. These results strongly suggest a multiple-point interaction between I-4 and PP1C, which is thought to cause the inhibition of I-4 which is stronger than the inhibition of I-2.

Amino Acid Sequence↗
PubMed2000

Development of a time-resolved fluorometric detection system using diffusion-enhanced energy transfer

A novel detection system using both emission energy transfer and time-resolved fluorometry (TRF) was developed, with a europium chelate as the energy donor and a novel fluorophore SNR1, excitable with long-wavelength light corresponding to europium emission, as the energy acceptor. When the donor and acceptor molecules were mixed in solution, energy transfer was observed without direct attachment of the donor and the acceptor, via a diffusion-enhanced energy-transfer mechanism. Thus, the acceptor emission can be detected as a long-lifetime fluorescence in TRF. When the fluorescence properties of the acceptor molecule are changed by interaction with an enzyme or other bioactive molecule, the change can be detected as a long-lived sensitized emission. If we develop or select suitable acceptor molecules, this simple and convenient system should be applicable to a wide variety of bioactive molecules. Since it is based on TRF, it can be used for high-resolution assay.

Journal Article↗
PubMed2000

Protein-tyrosine phosphatase PTPepsilon C inhibits Jak-STAT signaling and differentiation induced by interleukin-6 and leukemia inhibitory factor in M1 leukemia cells.

We engineered and expressed both a wild-type and mutant cytosolic isoform of PTPepsilon (PTPepsilonC) in murine M1 leukemic cells, which can be induced to growth arrest and monocytic differentiation by interleukin (IL)-6 and leukemia inhibitory factor (LIF). Forced expression of PTPepsilonC inhibited IL-6- and LIF-induced monocytic differentiation and apoptosis in M1 cells, whereas expression of PTPepsilonM, a transmembrane isoform of PTPepsilon, did not. PTPepsilonC expression resulted in lower levels of IL-6-induced tyrosine phosphorylation of Jak1, Tyk2, gp130, and Stat3 compared with parent cells. In M1 transfectants expressing an inactive mutant of PTPepsilonC, both tyrosine phosphorylation and apoptosis induced by IL-6 and LIF were potentiated rather than inhibited. These results suggest an important role for PTPepsilonC in negative regulation of IL-6- and LIF-induced Jak-STAT signaling.

Animals↗
PubMed2000

Discovery of novel and potent retinoic acid receptor alpha agonists: syntheses and evaluation of benzofuranyl-pyrrole and benzothiophenyl-pyrrole derivatives.

In the course of our studies on retinoic acid receptor (RAR) agonists, we have designed and synthesized a series of benzofuran and benzothiophene derivatives. Some of these compounds (1a,b,e,f,j) markedly inhibited LPS-induced B-lymphocyte proliferation and exerted RARalpha selectivity. One of them, 4-[5-(4,7-dimethylbenzofuran-2-yl)pyrrol-2-yl]benzoic acid (1b), when orally administered significantly inhibited mouse antibody production and delayed type hypersensitivity (DTH) responses from a dose of 0.1 mg/kg.

Administration, Oral↗
PubMed2000

High glucose attenuates insulin-induced mitogen-activated protein kinase phosphatase-1 (MKP-1) expression in vascular smooth muscle cells.

The mechanisms for the effect of hyperglycemia on insulin-induced mitogenesis were investigated using rat vascular smooth muscle cells (VSMC). VSMC were preincubated in serum-free medium with low (5 mM) glucose (LG condition) or high (25 mM) glucose (HG condition), and examined for DNA synthesis using bromodeoxyuridine (BrdUrd) incorporation. Mitogen-activated protein kinase (MAPK) activity and MAPK phosphatase (MKP-1) protein expression were detected by Western blot analysis. Phosphatidylinositol 3-kinase (PI-3K) activity was detected by thin layer chromatography. Insulin induced a dose-dependent increase in BrdUrd incorporation (123.3+/-2.6% over basal level with 1 microM insulin) in the LG group and this effect was significantly enhanced (161.6+/-10.4% over basal level) in the HG group. In the LG group, MAPK activity was transient with a peak activation (137.4+/-11.2% over basal level) after 10 min exposure to 100 nM insulin. In the HG group, the MAPK activity was significantly potentiated (two-fold compared to the LG group) and was sustained even after 60 min. Insulin also induced PI-3K activity and MKP-1 expression, both of which were blocked by the PI-3K inhibitor wortmannin. In the HG group, insulin-induced PI-3K and MKP-1 expression was almost abolished. In conclusion, high glucose enhances insulin-induced mitogenesis associated with the potentiation of insulin-stimulated MAPK activity in VSMC. These effects of glucose might in part be due to the attenuation of MKP-1 expression through the blockage of the insulin-PI-3K signal pathway.

Animals↗
PubMed2000

STAM2, a new member of the STAM family, binding to the Janus kinases.

We here cloned a cDNA encoding STAM2, a new member of the STAM family, which contains an SH3 domain and ITAM. STAM2 like STAM1 is associated with Jak2 and Jak3, and involved in the signaling for DNA synthesis and c-myc induction mediated by IL-2 and GM-CSF. Co-expression of the SH3 deletion mutants of STAM1 and STAM2 induces an additive effect on suppressing DNA synthesis upon stimulation with IL-2 and GM-CSF, suggesting that STAM1 and STAM2 exhibit compensatory effects on the signaling pathways downstream of Jak2 and Jak3 upon stimulation with GM-SCF and IL-2, respectively.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Basophilic cytoplasmic inclusions in a case of sporadic juvenile amyotrophic lateral sclerosis.

A 24-year-old woman presented with progressive muscle atrophy and weakness of the right upper extremity. Subsequently her weakness rapidly extended to the left upper extremity, neck and lower extremities. Neurological examination disclosed involvement of the lower motor neuron system. She died 7 months after the onset. There was neuronal loss and reactive gliosis in the anterior horns of the spinal cord and much less frequently in the motor cortex. Basophilic cytoplasmic inclusions were observed in the thalamus and brain stem as well as the upper and lower motor neurons. Ultrastructurally, the inclusions lacked a limiting membrane and consisted of a meshwork of filamentous structures associated with granules. The inclusions failed to react with antibodies against phosphorylated neurofilament or cystatin C. Most of the inclusions show no reaction with anti-ubiquitin antibody, however, a few inclusions show granular reaction product deposits with this antibody. The inclusions were not immunostained with antibodies against TGN46 and MG-160, markers of the trans-Golgi network and the medial cisternae of the Golgi apparatus, respectively, suggesting that they were not derived from the Golgi apparatus which was fragmented.

Adult↗
PubMed2000

Novel retinoic acid receptor alpha agonists: syntheses and evaluation of pyrazole derivatives.

We have designed and synthesized a series of pyrazole derivatives as candidate retinoic acid receptor (RAR) agonists. One of them, 4-[5-(1, 5-diisopropyl-1H-3-pyrazolyl)-1H-2-pyrrolyl]benzoic acid (11b), which possesses a 2,5-disubstituted pyrrole moiety, showed selective transactivation activity for the RAR alpha receptor, and had highly potent cell-differentiating activity on HL-60 cells.

Binding, Competitive↗
PubMed2000

Increasing CNS norepinephrine levels by the precursor L-DOPS facilitates beam-walking recovery after sensorimotor cortex ablation in rats.

The present investigation was conducted to document a role of L-threo-3,4-dihydroxyphenylserine (L-DOPS), precursor of L-norepinephrine (NE), in the functional recovery from beam-walking performance deficits in rats after unilateral sensorimotor cortex ablation. L-DOPS was administered simultaneously with benserazide (BSZ; a peripheral aromatic amino acid decarboxylase inhibitor), and the regional contents of NE in the cerebral cortex, hippocampus, and cerebellum were assayed. Behavioral recovery was demonstrated by the rats treated with L-DOPS and BSZ, and the rate of recovery was significantly different from that of either BSZ-treated or vehicle-treated control rats. The NE tissue levels in the three discrete regions of the rat brain were significantly elevated in the experimental rats receiving both L-DOPS and BSZ. The present studies indicate that increasing NE levels by the precursor L-DOPS may be responsible for facilitating behavioral recovery from beam-walking performance deficits in rats, and further suggest that L-DOPS may become one of the candidate compounds for further clinical human trials promoting functional recovery after injuries to the cerebral cortex.

Animals↗
PubMed2000

A new predictive factor for hepatocellular carcinoma based on two-dimensional electrophoresis of genomic DNA.

Molecular genetic analyses have clarified that accumulation of genomic changes provides important steps in carcinogenesis and have identified a number of valuable genetic markers for certain cancers. To date, however, no prognostic markers have been identified for hepatocellular carcinoma (HCC). In this study, we used restriction landmark genomic scanning (RLGS), a new high-speed screening method for multiple genomic changes, to detect unknown genetic alterations in HCC. Thirty-one HCC samples and their normal counterparts were examined by RLGS. Eight spot changes were common in several cases, and all were seen only on the HCC profile. Five of these spots were detected in more than 12 of 31 cases (38.7%). Viral infection had no influence on changes in the RLGS spots. The disease-free survival rate for patients with > or =16 changed RLGS spots was significantly lower than that for patients with fewer changed RLGS spots (< or =15 spots) (P<0.001). In multivariate analysis, the number of changed spots was proven to retain an independent prognostic value (relative risk 1.095: P = 0.0031). These results suggest that the number of changed RLGS spots may be a useful biological marker for recurrence of HCC.

Adult↗
PubMed2000

NKT cells in the rat: organ-specific distribution of NK T cells expressing distinct V alpha 14 chains.

Rat invariant TCR alpha-chains and NKT cells were investigated to clarify whether CD1d-mediated recognition by NKT cells is conserved further in evolution. Rats had multiple-copies of TRAV14 genes, which can be categorized into two types according to the diversity accumulated in the CDR2 region. Rats retained invariant TCR alpha forms with the homogeneous junctional region similar to mouse invariant TRAV14-J281. The proportion of invariant TCR among V alpha 14+ clones was 12.9% in the thymus and increased in the periphery, 31% in the spleen and 95% in hepatic sinusoidal cells. The invariant TRAV14-J281 was expressed by liver sinusoidal and splenic NKT cells with CD8, CD44high, and TCR V beta 8. Type 1 invariant TCR alpha was expressed more frequently in hepatic lymphocytes, while type 2 invariant TCR alpha was expressed predominantly in the spleen. Both types of cells cytolyzed to and were stimulated to proliferate by CD1d-expressing cells in a CD1d-restricted manner. These results suggested that rat NKT cells bearing distinct V alpha 14 chains are distributed in a tissue-specific pattern. NKT cell populations in rats were more variable than those in mice, indicating that they play novel roles in nature. The implication of the molecular interaction between the structurally diverse invariant TCR alpha and CD1d/ligand complex in different organs is discussed.

Amino Acid Sequence↗