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S Nakashima

Publications and source records attributed to S Nakashima.

At least 109 records · Page 6Linked to original sources
PubMed1998

Studies on blood compatibility of terpolymers composed of methyl methacrylate, methoxypolyethyleneglycol methacrylate, and dimethylsiloxane methacrylate.

Terpolymers composed of methyl methacrylate (MMA), polydimethylsiloxane methacrylate (PDMSMA), and methoxypolyethyleneglycol methacrylate (MPEGMA), having different compositions were synthesized. Platelets were not adsorbed onto terpolymer surfaces composed of 50 wt% MMA, 25 wt% PDMSMA and 25 wt% MPEGMA, while on terpolymers with the other compositions, platelet adsorption and fibrin clot were observed. It was shown that PDMS segment was predominant on these terpolymer surfaces via XPS. Receding contact angles of terpolymers, on which no platelet was observed, showed intermediate values between PDMS- and MPEG-rich surfaces. It was suggested that these terpolymers had blood compatibility.

Adult↗
PubMed1998

Combination therapy of fasudil hydrochloride and ozagrel sodium for cerebral vasospasm following aneurysmal subarachnoid hemorrhage.

Fasudil hydrochloride is a new type of intracellular calcium antagonist, different from the calcium entry blockers that are commonly employed for clinical use. Since September 1995, the combination of fasudil hydrochloride and ozagrel sodium, an inhibitor of thromboxane A2 synthesis, has been used to treat 60 patients at risk of cerebral vasospasm after aneurysmal subarachnoid hemorrhage. The effectiveness of this combination therapy was investigated by comparison with the outcome of 57 patients previously treated with only ozagrel sodium. The combination therapy was significantly more effective (p < 0.01) in reducing the incidence of low density areas on computed tomography scans, and reduced, but not significantly, the occurrence of symptomatic vasospasm. The combination therapy of fasudil hydrochloride and ozagrel sodium has superior effectiveness over only ozagrel sodium in treating patients at risk of vasospasm after aneurysmal subarachnoid hemorrhage.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1998

[Molecular cloning of Candida albicans phospholipase D].

Phospholipase D (PLD) catalyses the hydrolysis of phosphatidylcholine, a major substrate, to phosphatidic acid and choline, and its activity is regulated by a variety of hormones, growth factors, and other extracellular signals in mammalian cells. Thus, it is now recognized as a signal transducing enzyme such as phosphatidylinositol-specific phospholipase C, adenylate cyclase, or protein tyrosine kinases. Furthermore, recent findings that regulation by members of the ADP-ribosylation factor (ARF) and Rho families of monomeric GTP-binding protein suggest roles of PLD in intracellular vesicle traffi-cking, morphological changes, and mitogenic signaling process. In Saccharomyces cerevisiae, PLD gene has been cloned and revealed to be essential for meiosis. In contrast, little is known about PLD in Candida albicans. As a first step to understand possible physiological roles of PLD in C. albicans, we cloned a PLD gene from a C. albicans genomic DNA library. Deduced amino acid sequence analysis showed the structural similarity to mammalian, yeast, and plant PLDs. It was also suggested employing RT-PCR (reverse transcriptase polymerase chain reaction) that an isozyme of C. albicans PLD was present.

Candida albicans↗
PubMed1998

Hyperintense basal ganglia on T1-weighted MR images in a patient with central nervous system lupus and chorea.

We describe a patient with central nervous system lupus and choreatic movements in whom both basal ganglia showed high signal intensity on T1-weighted MR images, while the signal on T2-weighted images remained low. Within 8 months after onset, the choreatic movements had disappeared, with a corresponding decrease in the hyperintense T1 signal. The emergence of the choreatic movement disorder in this patient might have been related to the T1 hyperintensity of the basal ganglia, which, in turn, might have resulted from a vascular insult associated with central nervous system lupus.

Adult↗
PubMed1998

[Dramatic improvement with immunoabsorption therapy in a 7-year-old girl with severe Guillain-Barré syndrome after unsuccessful gammaglobulin therapy].

We report a 7-year-old girl with severe Guillain-Barré syndrome (GBS) who showed dramatic improvement after immunoabsorption therapy. She had progressive muscle weakness with resultant respiratory failure. On the 7th day of the illness, she was nearly quadriplegic and dependent on mechanical ventilation. In addition, she had autonomic manifestations, areflexia, abolished or delayed peripheral nerve conduction, and increased CSF protein. Administration of a high dose of gammaglobulin failed to improve the symptoms. Immunoabsorption therapy using a tryptophan column was performed 9 times during 17 days. After 5 times of immunoabsorption therapy, the muscle weakness improved dramatically; she was extubated 16 days after the institution of the therapy and walked without assistance on the 41st day. She regained normal muscle power without any sequelae. The immunoabsorption therapy caused hemolysis and decrease of serum fibrinogen, but no serious complications. The clinical course of this patient suggests the efficacy of immunoabsorption therapy in GBS.

Child↗
PubMed1997

Prolonged activation of phospholipase D in Chinese hamster ovary cells expressing platelet-activating-factor receptor lacking cytoplasmic C-terminal tail.

The mechanism and role of phospholipase D (PLD) activation by platelet-activating factor (PAF) were examined with Chinese hamster ovary cells stably expressing wild-type PAF receptor (WT-H cells) and truncated PAF receptor lacking the C-terminal cytoplasmic tail (D-H cells). Treatment of D-H cells with PAF resulted in the rapid formation of Ins(1,4,5)P3, which was followed by a sustained phase for more than 10 min. In these cells, PAF-induced PLD activation lasted for more than 20 min. In contrast, PLD activation in WT-H cells was transient. PAF stimulation caused the biphasic formation of 1,2-diacylglycerol (DG) in both types of cell. The first phase was rapid and transient, coinciding with the Ins(1,4,5)P3 peak. The second sustained phase of DG formation was attenuated by butanol, which produces phosphatidylbutanol at the expense of phosphatidic acid (PA) by transphosphatidylation activity of PLD, and by propranolol, a selective inhibitor for PA phosphohydrolase catalysing the conversion of PA into DG. The DG level returned nearly to basal at 20 min after PAF stimulation in WT-H cells, whereas in D-H cells the elevated DG level was sustained for more than 20 min. The profile of translocation of protein kinase Calpha (PKCalpha) to membrane was similar to that of DG formation. In WT-H cells, PKCalpha was transiently associated with membranes and then returned to the cytosol. However, in D-H cells PKCalpha was rapidly translocated to and remained in membranes for more than 20 min. Butanol suppressed this sustained translocation of PKCalpha. Furthermore the mRNA levels of c-fos and c-jun by PAF in WT-H cells were much lower than those in D-H cells. Propranolol and butanol at concentrations that inhibited the formation of DG suppressed the PAF-induced mRNA expression of c-fos and c-jun. Taken together, the prolonged PLD activation in D-H cells confirmed a primary role for phospholipase C/PKC in PLD activation by PAF. Furthermore the results obtained here suggest that sustained PLD activation in turn leads to chronic activation and membrane translocation of PKCalpha, which might play an important role in the expression of c-fos and c-jun.

1-Butanol↗
PubMed1997

Identification of differentially expressed mRNAs during rat C6 glial cell differentiation by mRNA fingerprinting using arbitrarily primed PCR (RAP).

Differentiation of glial cells is controlled by a complex program of differential expressions of many genes. To identify differentially expressed genes that are involved in rat C6 glial cell differentiation induced by dibutyryl cyclic AMP and theophylline, mRNA fingerprinting using arbitrarily primed PCR (RAP) was used. Four cDNA fragments, that were differentially expressed during differentiation, were isolated. Sequence analysis revealed that one of them, abundantly expressed during differentiation, was homologous to a hamster calcium-dependent serine protease. Another one was highly similar to rabbit dystrobrevin and the other two clones were identical to rat triose phosphate isomerase and calnexin. The results obtained suggest that the expressions of particular genes were changed and that RAP is a useful method to identify genes which are differentially expressed during glial cell differentiation.

Animals↗
PubMed1997

Effect of wortmannin and 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) on N-formyl-methionyl-leucyl-phenylalanine-induced phospholipase D activation in differentiated HL60 cells: possible involvement of phosphatidylinositol 3-kinase in phospholipase D activation.

Phospholipase D (PLD) plays an important role in neutrophil activation. However, despite various proposed mechanisms, its detailed regulatory mechanism is not fully understood. The functional coupling between phosphatidylinositol 3-kinase (PI 3-kinase) and PLD was investigated in N-formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated human promyelocytic leukemia HL60 cells, using wortmannin, a fungal metabolite that is known as a selective inhibitor for phosphatidylinositol 3-kinase. Treatment of cells with this drug inhibited the formation of both phosphatidylinositol 3,4,5-trisphosphate (PIP3), a product of PI 3-kinase, and phosphatidylbutanol (PBut), the specific product of transphosphatidylation due to PLD in the presence of butanol, with similar concentration dependence (IC50 = 30-70 nM). Another PI 3-kinase inhibitor, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) also inhibited PBut formation in a concentration-dependent manner. However, wortmannin failed to inhibit phorbol 12-myristate 13-acetate-induced PLD activation in whole cells and membrane PLD activity in an in vitro assay system, indicating that inhibition of fMLP-induced PLD activation by wortmannin was not due to its direct effect on PLD activity. These results suggest that a major part of inhibition of PLD activation by wortmannin might be mediated through its effect on PI 3-kinase.

Androstadienes↗
PubMed1997

Characterization of two alternately spliced forms of phospholipase D1. Activation of the purified enzymes by phosphatidylinositol 4,5-bisphosphate, ADP-ribosylation factor, and Rho family monomeric GTP-binding proteins and protein kinase C-alpha.

We previously reported the cloning of a cDNA encoding human phosphatidylcholine-specific phospholipase D1 (PLD1), an ADP-ribosylation factor (ARF)-activated phosphatidylcholine-specific phospholipase D (Hammond, S. M., Tsung, S., Autschuller, Y., Rudge, S. A., Rose, K., Engebrecht, J., Morris, A. J., and Frohman, M. A. (1995) J. Biol. Chem. 270, 29640-29643). We have now identified an evolutionarily conserved shorter splice variant of PLD1 lacking 38 amino acids (residues 585-624) that arises from regulated splicing of an alternate exon. Both forms of PLD1 (PLD1a and 1b) have been expressed in Sf9 cells using baculovirus vectors and purified to homogeneity by detergent extraction and immunoaffinity chromatography. PLD1a and 1b have very similar properties. PLD1a and 1b activity is Mg2+dependent but insensitive to changes in free Ca2+ concentration. Phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate activate PLD1a and 1b but a range of other acidic phospholipids are ineffective. PLD1a and 1b are highly responsive to activation by GTP-gammaS-liganded ADP-ribosylation factor-1 (ARF-1) and can also be activated to a lesser extent by three purified RHO family monomeric GTP-binding proteins, RHO A, RAC-1, and CDC42. Activation of PLD1a and 1b by the RHO family monomeric GTP-binding proteins is GTP-dependent and synergistic with ARF-1. Purified protein kinase C-alpha activates PLD1a and 1b in a manner that is stimulated by phorbol esters and does not require ATP. Activation of PLD1a and 1b by protein kinase C-alpha is synergistic with ARF and with the RHO family monomeric GTP-binding proteins, suggesting that these three classes of regulators interact with different sites on the enzyme.

Adenosine Diphosphate Ribose↗
PubMed1997

Increased activity of small GTP-binding protein-dependent phospholipase D during differentiation in human promyelocytic leukemic HL60 cells.

In response to dibutyryl cyclic AMP (dbcAMP) and all-trans retinoic acid, human promyelocytic leukemic HL60 cells differentiate into granulocyte-like cells. In cell lysate and in vitro reconstitution system, phospholipase D (PLD) activity in response to guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) was up-regulated by dbcAMP or all-trans retinoic acid treatment. In the present study, the mechanism(s) for increased PLD activity during differentiation was examined. Western blot analysis revealed that the contents of ADP-ribosylation factor, Rac2, and Cdc42Hs but not RhoA and Rac1 in the cytosolic fraction were elevated during differentiation. However, the cytosolic fraction from undifferentiated cells was almost equally potent as the cytosolic fraction from differentiated cells in the ability to stimulate membrane PLD activity. It was shown that the GTPgammaS-dependent PLD activity in membranes from differentiated cells was much higher than that in membranes from undifferentiated cells, suggesting that the increased PLD activity during differentiation was due to alterations in some membrane component(s). Clostridium botulinum ADP-ribosyltransferase C3 and C. difficile toxin B, which are known as inhibitors of RhoA and Rho family proteins, respectively, effectively suppressed PLD activity in membranes from differentiated cells. In fact, the amount of membrane-associated RhoA was increased during differentiation. Furthermore, the extent of GTPgammaS-dependent PLD activity partially purified from membranes from differentiated cells was greater than that from membranes from undifferentiated cells in the presence of recombinant ADP-ribosylation factor 1. The PLD (hPLD1) mRNA level was observed to be up-regulated during differentiation, as inferred by reverse transcription-polymerase chain reaction. Our results suggest the possibility that the increased Rho proteins in membranes and the changed level of PLD itself may be, at least in part, responsible for the increase in GTPgammaS-dependent PLD activity during granulocytic differentiation of HL60 cells.

ADP-Ribosylation Factors↗
PubMed1997

Phospholipase D activity in the Tetrahymena pyriformis GL.

Phospholipase D (PLD) is an enzyme which participates in the signaling mechanism cleaving phosphatidylcholine (PC) to choline and phosphatidic acid (PA). In Tetrahymena pyriformis GL this enzyme activity is enhanced by different kinds of agonists (sodium orthovanadate, sodium fluoride and phorbol 12-myristate 13-acetate), and its activity can be inhibited by inhibitors such as pertussis toxin, calphostin C, genistein, trifluoperazine. These results suggest that the PLD signalling pathway is connected with the tyrosine kinase, phospholipase C, phosphatidylinositol and G-protein coupled signalling pathways. By demonstrating the PLD activity in Tetrahymena our knowledge on the signaling mechanisms at a unicellular level has been extended. The results support our view that most transducing mechanisms that are characteristic of mammalian cells are also in the protozoan Tetrahymena.

Animals↗
PubMed1997

Possible involvement of pertussis toxin-sensitive G protein in hepatocyte growth factor-induced signal transduction in cultured rat hepatocytes: pertussis toxin treatment inhibits activation of phospholipid signaling, calcium oscillation, and mitogen-activated protein kinase.

Treatment of primary cultured rat hepatocytes with hepatocyte growth factor (HGF) gives rise to inositol phosphate formation, cytosolic calcium oscillation, activation of mitogen-activated protein (MAP) kinase and phospholipase D (PLD), and arachidonic acid release, leading to DNA synthesis. Pretreatment of cultured hepatocytes with pertussis toxin (PT), which is known to adenosine diphosphate-ribosylate Gi and Go guanine nucleotide -binding proteins and to inhibit their functions, partially inhibited HGF-induced [3H]thymidine incorporation in a concentration-dependent manner. These results suggest that HGF-mediated DNA synthesis of hepatocytes is partly regulated via PT-sensitive guanine nucleotide-binding protein. Therefore, the effects of PT treatment on HGF-induced signal-transduction pathways were investigated. HGF-induced MAP kinase activation and arachidonic acid release were decreased by PT treatment, whereas PLD activation was diminished by PT to the level of unstimulated control. PT also interfered with HGF-induced inositol phosphate formation and cytosolic calcium oscillation. These results suggest that both PT-sensitive and PT-insensitive pathways are involved in HGF-induced signaling.

Animals↗
PubMed1997

Messenger RNA fingerprinting analysis using arbitrarily primed PCR (RAP) of genes expressed during rat C6 glioma cell differentiation.

To identify differentially expressed genes involved in rat C6 glioma cell differentiation induced by cyclic AMP, we adopted mRNA fingerprinting using arbitrarily primed polymerase chain reaction (PCR) (RAP). Four complementary DNA (cDNA) fragments differentially expressed during differentiation were isolated, and they appeared to contain coding regions of corresponding mRNAs. RAP can be used to efficiently identify cDNA fragments by comparing nucleotide and deduced amino acid sequences with those in databases, and is thus a useful method to search for and identify important genes involved in complex cellular processes such as glioma cell differentiation.

Animals↗
PubMed1997

Differential expression of Rho family GTP-binding proteins and protein kinase C isozymes during C6 glial cell differentiation.

The differential expression of Rho family of low molecular weight GTP-binding proteins and protein kinase C (PKC) isozymes were examined during differentiation of rat C6 glial cells to astrocytic phenotypes induced by dibutyryl cAMP (dbcAMP)/theophylline. The cells showed rapid and distinct morphological changes, resembling stellate astrocytes at 12 h after the treatment. The treated cells had a round cell body that extended several long processes each with a beaded appearance. In addition to morphological changes, Western blot analysis revealed that S-100 protein, known as a glial cell differentiation marker, increased and reached the maximal level (approximately 6-fold increase) at 24 h following the addition of dbcAMP. In the control experiments with cells cultured in the absence of serum but also without dbcAMP/theophylline, morphological changes were marginal and apparent increases of S-100 protein were not observed by Western blotting. In response to dbcAMP/theophylline treatment, RhoA showed increases in the mRNA level followed by the protein level, as inferred by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting, respectively. Rac1 and Cdc42 proteins were undetectable by Western blot analyses. In PKC isozymes, increases were observed in PKC beta 1, epsilon, and zeta by RT-PCR, and in beta 1 and epsilon by Western blotting. Among them, PKC epsilon showed the most distinct changes. Its mRNA level transiently increased from 3 to 6 h and then decreased even below the basal level at 18 h after the treatment. In contrast, Western blot analysis revealed that PKC epsilon gradually increased time-dependently to 24 h (approximately 6-fold increase), and remained elevated until 48 h. These results suggested that RhoA and PKC epsilon, and probably also PKC beta 1 and PKC zeta, were closely implicated in C6 cell differentiation.

Animals↗
PubMed1997

Implication of Ca(2+)-dependent protein tyrosine phosphorylation in carbachol-induced phospholipase D activation in rat pheochromocytoma PC12 cells.

The mechanism for carbachol (CCh)-induced phospholipase D (PLD) activation was investigated in [3H]palmitic acid-labeled pheochromocytoma PC12 cells with respect to the involvement of protein tyrosine phosphorylation and Ca2+. PLD activity was assessed by measuring the formation of [3H]phosphatidylbutanol in the presence of 0.3% butanol. Pretreatment of cells with the tyrosine kinase inhibitors herbimycin A, genistein, and tyrphostin inhibited PLD activation by CCh. Western blot analysis revealed several apparent tyrosine-phosphorylated protein bands (111, 91, 84, 74, 65-70, 44, and 42 kDa) in PC12 cells treated with CCh. Phosphorylation of the 111-, 91-, 84-, and 65-70-kDa proteins peaked within 1 min, and their time-dependent changes seemingly correlated with that of PLD activation. Others (74, 44MAPK, and 42MAPK kDa) were phosphorylated rather slowly, and maximal tyrosine phosphorylation was observed at 2 min. Herbimycin A inhibited PLD activity and tyrosine phosphorylation of four proteins (111, 91, 84, and 65-70 kDa) in a preincubation time- and concentration-dependent fashion. In Ca(2+)-free buffer, CCh-induced [3H]phosphatidylbutanol formation and protein tyrosine phosphorylation were abolished. A Ca2+ ionophore, A23187, caused PLD activation and tyrosine phosphorylation of four proteins of 111, 91, 84, and 65-70 kDa only in the presence of extracellular Ca2+. Extracellular Ca2+ dependency for CCh-induced PLD activation was well correlated with that for tyrosine phosphorylation of the four proteins listed above, especially the 111-kDa protein. These results suggest that Ca(2+)-dependent protein tyrosine phosphorylation is closely implicated in CCh-induced PLD activation in PC12 cells.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Changes in the activity and mRNA levels of phospholipase D during ceramide-induced apoptosis in rat C6 glial cells.

N-Acetylsphingosine (C2-ceramide), a membrane-permeable analogue, induced apoptosis in C6 glial cells. Phase-contrast micrographs showed that the round cells appeared 3 h after exposure to 25 microM C2-ceramide and the number of floating cells increased time-dependently. Staining with Hoechst 33258 dye showed condensed or fragmented nuclei in round cells at 12 h. DNA fragmentation was also observed by agarose gel electrophoresis at 12 h. To understand the mechanism underlying glial cell death induced by C2-ceramide treatment, changes in phospholipase D (PLD) activity in response to guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) and expression of mRNA levels of PLD isozymes were examined. In cell lysate, GTPgammaS-dependent PLD activity was down-regulated after ceramide treatment in a time-dependent manner. In the in vitro PLD assay, membrane-associated PLD activation in response to recombinant ADP-ribosylation factor 1 was greatly suppressed. Furthermore, levels of rPLD1a and rPLD1b mRNAs were found to be down-regulated, whereas the level of rPLD2 mRNA increased gradually, peaking at 3 h, followed by a slow decrease, as inferred by reverse transcription-polymerase chain reaction. Decreases in GTPgammaS-dependent PLD activity were well correlated with those in rPLD1a and rPLD1b mRNAs levels. Taken together, these data suggest that levels of PLD enzymes might be decreased by ceramide treatment.

ADP-Ribosylation Factors↗
PubMed1997

Hydrogen peroxide-induced phospholipase D activation in rat pheochromocytoma PC12 cells: possible involvement of Ca2+-dependent protein tyrosine kinase.

The mechanism for hydrogen peroxide (H2O2)-induced phospholipase D (PLD) activation was investigated in [3H]palmitic acid-labeled PC12 cells. In the presence of butanol, H2O2 caused a great accumulation of [3H]phosphatidylbutanol in a concentration- or time-dependent manner. However, treatment with H2O2 of cell lysates exerted no effect on PLD activity. Treatment with H2O2 had only a marginal effect on phospholipase C (PLC) activation. A protein kinase C (PKC) inhibitor, Ro 31-8220, did not inhibit but rather slightly enhanced H2O2-induced PLD activity. Thus, H2O2-induced PLD activation is considered to be independent of the PLC-PKC pathway in PC12 cells. In contrast, pretreatment with tyrosine kinase inhibitor herbimycin A, genistein, or ST638 resulted in a concentration-dependent inhibition of H2O2-induced PLD activation. Western blot analysis revealed several apparent tyrosine-phosphorylated protein bands after the H2O2 treatment and tyrosine phosphorylation of these proteins was inhibited by these tyrosine kinase inhibitors. Moreover, depletion of extracellular Ca2+ abolished H2O2-induced PLD activation and protein tyrosine phosphorylation. Extracellular Ca2+ potentiated H2O2-induced PLD activation in a concentration-dependent manner. Taken together, these results suggest that a certain Ca2+-dependent protein tyrosine kinase(s) somehow participates in H2O2-induced PLD activation in PC12 cells.

Animals↗