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S Yoshida

Publications and source records attributed to S Yoshida.

At least 1,009 records · Page 56Linked to original sources
PubMed1994

Roles of endogenous nitric oxide in cerebellar cortical development in slice cultures.

Using the slice culture system for 9-day-old rat cerebellum, roles of nitric oxide (NO) in the cerebellar cortical development were examined. Granule cell migration was inhibited by N-nitro-L-arginine (L-NNA) and by haemoglobin (Hb), but not by N-nitro-D-arginine (D-NNA), added to the culture medium, showing that NO-mediated transmission is involved in some process for granule cell migration. Furthermore, immunohistochemical analysis revealed that the cessation of granule cell proliferation and the differentiation of Bergmann glia were inhibited in the presence of L-NNA and Hb. These results suggest that endogenous NO can be a signal for the differentiation of granule cells and Bergmann glia in cerebellar cortical development.

Animals↗
PubMed1994

[New development of cellulose-ferric ammonium citrate solution as a contrast-enhancement agent for magnetic resonance imaging of esophageal diseases].

For magnetic resonance imaging (MRI) of esophageal diseases, we have developed a new contrast-enhancement agent, cellulose-ferric ammonium citrate solution. Using this agent, the esophageal lumen is easily identified. This agent is expected to play a role in the MRI diagnosis of esophageal cancer and to help determine the indications for radical surgery and/or intracavitary irradiation.

Aged↗
PubMed1994

Role of phospholipase A2 in expression of the scavenger pathway in cultured aortic smooth muscle cells stimulated with phorbol 12-myristate 13-acetate.

We have demonstrated that cultured intimal smooth muscle cells (SMC) from thickened intima can metabolize acetylated low-density lipoprotein (LDL) by a scavenger pathway, but medial SMC from normal arteries cannot. In this study we investigated the expression mechanism of the scavenger pathway in medial SMC using a phorbol ester. Medial SMC were incubated with 10(-10)-10(-7) M phorbol 12-myristate 13-acetate (PMA) for 1-24 h and then their degradation of 125I-labelled acetylated LDL was assayed. Unstimulated SMC degraded little acetylated LDL, but incubation for 24 h with PMA dose-dependently stimulated its degradation by SMC, the optimal PMA concentration being 1 x 10(-8) M. Induction of expression of the scavenger pathway required more than 4 h of incubation with PMA and was completely inhibited by cycloheximide. In addition expression of the scavenger pathway was not transient but stable. Induction of expression of the scavenger pathway by PMA was not inhibited by protein kinase C inhibitors, but was inhibited about 50% by phospholipase A2 inhibitors. The study, using various phorbol esters, indicated that induction of the scavenger pathway was well correlated with their ability to stimulate phospholipase A2 in medial SMC but not with their ability to activate protein kinase C. Moreover, incubation with exogenous phospholipase A2 (0.1-10 units/ml) or its product, lysophosphatidylcholine (0.01-100 micrograms/ml) dose-dependently increased degradation of 125I-labelled acetylated LDL in medial SMC. Lysophosphatidylcholine was most effective in various lysophospholipids. These results suggest that PMA induced the scavenger pathway in part by stimulating phospholipase A2 in medial SMC, and that a product, lysophosphatidylcholine, is a mediator of expression of the scavenger pathway.

Animals↗
PubMed1994

Purification and characterization of S-adenosyl-L-methionine: norcoclaurine 6-O-methyltransferase from cultured Coptis japonica cells.

S-adenosyl-L-methionine:norcoclaurine 6-O-methyltransferase (norcoclaurine 6-O-methyltransferase), which catalyzes the transfer of the S-methyl group of S-adenosyl-L-methionine to the 6-hydroxyl group of 1,2,3,4-tetrahydro-1-[(4-hydroxyphenyl)methyl]-6,7- isoquinolinediol (norcoclaurine), was purified from cultured Coptis japonica cells and its enzymic properties were characterized. Purified norcoclaurine 6-O-methyltransferase had apparent pI 4.7, a native molecular mass of 95 kDa (determined by gel filtration) and subunit molecular mass of 40 kDa (SDS/PAGE). The enzyme did not require a divalent cation for activity, and the addition of Fe2+, Cu2+, Co2+, Zn2+, Mn2+, or Ni2+ at 5 mM severely inhibited enzyme activity. Neither p-chloromercuribenzoate, N-methylmaleimide nor iodoacetamide inhibited enzyme activity at 1 mM. 5,6-Dihydro-9,10-dimethoxybenzo[g]-1,3-benzodioxolo[5,6-a]qu inolizinium (berberine, the end-product of the biosynthetic pathway in which norcoclurine 6-O-methyltransferase catalyzes an intermediate step) also inhibited the activity by 50% at 10 mM. Norcoclaurine 6-O-methyltransferase methylated both (S)-norcoclaurine and (R)-norcoclaurine and (R,S)-norlaudanosoline. Further characterization of substrate-saturation kinetics and product inhibition of the purified enzyme indicated that norcoclaurine 6-O-methyltransferase follows a bi-bi ping-pong mechanism with Km values of 2.23 mM and 3.95 mM for (R,S)-norlaudanosoline and S-adenosyl-L-methionine, respectively, while Ki values for S-adenosylhomocysteine versus S-adenosyl-L-methionine and (R,S)-norlaudanosoline were 2.1 mM and 0.18 mM, respectively.

Amino Acid Sequence↗
PubMed1994

Differential inhibition of eukaryotic DNA polymerases by halenaquinol sulfate, a p-hydroquinone sulfate obtained from a marine sponge.

Halenaquinol sulfate, a p-hydroquinone sulfate obtained from a marine sponge, inhibited the activity of eukaryotic DNA polymerases in varying degrees; the Ki values for DNA polymerases, alpha, beta, delta and epsilon were 1.3, 80, 17.5 and 2.0 microM, respectively, whereas it was less effective against E. coli DNA polymerase I. The inhibition occurred competitively with each of dATP and dTTP, but non-competitively with dCTP, dGTP and the template DNA. Thus, halenaquinol sulfate is demonstrated to be a potential inhibitor of DNA polymerases alpha and epsilon, and be a useful tool for analyzing the dNTP binding sites of DNA polymerases.

Animals↗
PubMed1994

Sphingosine inhibits the synthesis of RNA primers by primase in vitro.

We have previously shown the presence of sphingomyelin and sphingomyelinase in cell nuclei, suggesting that they may play a role in the intranuclear production of sphingosine, a potent bioactive molecule modulating diverse cellular functions. In the present study, the direct effects of sphingosine (C18:1) on the activity of DNA replication/repair polymerases were studied in vitro. Sphingosine had no effect on DNA polymerases alpha and beta and slightly inhibited DNA polymerases gamma, delta, and epsilon. In contrast, sphingosine strongly inhibited the activity of primase in a dose-dependent manner. On the other hand, dihydrosphingosine (C18:0), glycolipids, sphingomyelin, and ceramide had no effect on primase activity. Sphingosine equally inhibited the activity of primase complexed with DNA polymerase alpha, as well as its free form, with a Ki value of 4 microM. A gel-retardation analysis showed that the binding of primase with 32P-labeled template DNA was suppressed by sphingosine. Inhibition by sphingosine was competitive with the DNA template, but not with the substrate NTPs. After product analysis, a dose-dependent decrease in the amount of RNA primer products, consisting mainly of 10- and 11-mers, was observed in the presence of sphingosine, indicating that it inhibits the synthesis of RNA primers by primase. Sphingosine, however, had no effect on T7 RNA polymerase.

Animals↗
PubMed1994

IFN-alpha inhibits antigen-induced eosinophil and CD4+ T cell recruitment into tissue.

In a murine model of airway late phase reaction, we have previously shown that Ag-induced eosinophil recruitment into the tissue of sensitized mice is mediated by CD4+ T cells and IL-5. To determine whether IFN-alpha regulates Ag-induced eosinophil recruitment into tissue, we studied the effects of rIFN-alpha, endogenous IFN-alpha production induced by poly I.C, and anti-IFN-alpha mAb on the eosinophil infiltration of the trachea induced by Ag inhalation in mice. The i.p. administration of rIFN-alpha prevented Ag-induced eosinophil infiltration in the trachea of sensitized mice. In addition, the inhibitory effect of rIFN-alpha on Ag-induced eosinophil infiltration was not recovered by pretreatment with anti-IFN-gamma mAb. The administration of rIFN-alpha also inhibited Ag-induced CD4+ T cell infiltration in the trachea. However, the administration of rIFN-alpha did not significantly affect blood eosinophil counts nor the number of blood and splenic CD4+ T cells. On the other hand, pretreatment with anti-murine IFN-alpha mAb enhanced Ag-induced eosinophil and CD4+ T cell infiltration in the trachea. Finally, endogenous IFN-alpha/beta production induced by poly I.C also inhibited Ag-induced eosinophil infiltration in the trachea and this inhibition of the eosinophil infiltration was abrogated by pretreatment with anti-IFN-alpha/beta mAb. These results indicate that IFN-alpha suppresses Ag-induced eosinophil and CD4+ T cell recruitment into tissue.

Aerosols↗
PubMed1994

The glycoprotein B genes of Marek's disease virus serotypes 2 and 3: identification and expression by recombinant fowlpox viruses.

The nucleotide sequences of the glycoprotein B (gB) genes of Marek's disease virus (MDV) serotypes 2 and 3 were determined (gB-2 and gB-3, respectively). The genomic locations of these genes coincide with that of the gB gene of serotype 1 MDV (gB-1). Alignment with gB-1 (Ross et al., 1989, J. Gen. Virol. 70, 1789-1804) revealed predicted amino acid identities of 83 and 82% for gB-2 and gB-3, respectively. Excluding the predicted N-terminal signal sequences, 8 of 9 potential N-linked glycosylation sites and all 10 cysteine residues in gB-1 are conserved in both gB-2 and gB-3. In addition, the putative proteolytic cleavage sites for processing of precursors (gp100s) to gp60s and gp49s are conserved among the three gB homologs. Fowlpox virus (FPV) recombinants expressing either the gB-2 or the gB-3 gene were constructed. We detected expression of authentic gB-2 and gB-3 complexes in cells infected with these FPV recombinants. Digestion of immunoprecipitated gB-1 and gB-3 with endoglycosidases revealed that both gp60s are modified by the additions of O-glycans and complex carbohydrates after cleavage of gp100s, while gp100s and gp49s contain only high-mannose carbohydrates. We confirm that the size differences between gB-1 and gB-3 complexes are due to different carbohydrate modifications.

Amino Acid Sequence↗
PubMed1994

Purification and characterization of nuclear phospholipase C specific for phosphoinositides.

A phosphoinositide-specific phospholipase C (PLC) was solubilized from the isolated nuclei of rat ascites hepatoma AH7974 cells by ultrasonication in 2 M KCl. The extract was then subjected to five steps of column chromatographies in the order of Sephacryl S-300, phosphocellulose, Mono Q, Mono S, and Superose 6. Four forms of PLC (tentatively designated as N1, N2, N3, and N4) were purified 440-1400-fold. N1, N2, N3, and N4 showed apparent molecular masses of 85, 83, 80, and 88 kDa, respectively, on SDS-polyacrylamide gel electrophoresis. N1 cross-reacted with the antibody against the delta 1 isoform, while the other three forms did not cross-react with any of the antibodies against PLC-delta 1, -gamma 1, -gamma 2, and -beta 1. They hydrolyzed phosphatidylinositol (PI), phosphatidylinositol 4-monophosphate (PIP), and phosphatidylinositol 4,5-bisphosphate (PIP2) but did not show any activities against phosphatidylcholine and phosphatidylethanolamine. They showed the same optimal pH:pH 6.5 for PI hydrolysis and pH 7.0 for both PIP and PIP2 hydrolyses. They absolutely required Ca2+ for activity, with optimal concentrations of 10(-3)-10(-5) M for PIP and 10(-4)-10(-5) M for PIP2. For PI hydrolysis, N1, N2, and N3 required a Ca2+ concentration higher than 10(-2) M whereas N4 revealed significant activity even at 10(-5) M Ca2+ concentrations. Two forms of plasma membrane PLC and three forms of cytosolic PLC were purified from AH7974 cells by the same procedure as for nuclear PLC. Comparative study with these three groups revealed that all of the purified PLC isoforms shared similar enzymological properties except N4, which showed an exceptionally high affinity to Mono S column and was active at low concentrations of Ca2+ for PI as substrate. Furthermore, when PLC isoforms of nuclei from adult resting rat liver were compared with those from regenerating rat liver after partial hepatectomy, a PLC isoform corresponding to N4 of AH7974 cells was found only in regenerating liver nuclei. From these results, it was suggested that the nuclei of growing liver cells possessed a unique form of PLC (N4).

Animals↗
PubMed1994

Platelet-derived growth factor is a potent stimulator of expression of intercellular adhesion molecule-1 in human arterial smooth muscle cells.

The effects of platelet-derived growth factor (PDGF) on the expression of intercellular adhesion molecule-1 (ICAM-1) as an indicator of cell activation were investigated in cultured human arterial smooth muscle cells (SMC). PDGF-BB and -AB but not -AA at 2-10 ng/ml stimulated ICAM-1 expression at a subconfluent but not a confluent state in a dose-dependent manner. ICAM-1 expression was induced at 2h, reached a plateau at 4h, and continued for at least 24h after stimulation with PDGF. The maximal stimulatory effect of PDGF-BB at 10 ng/ml was comparable to that by optimal concentrations of other cytokines and inflammatory agents. These data suggested that PDGF was a potent stimulator of ICAM-1.

Antigens, CD↗
PubMed1994

DNA polymerase alpha overcomes an error-prone pause site in the presence of replication protein-A.

Eukaryotic DNA polymerase alpha pauses at some sites on the natural DNA template of M13mp2. Terminal misincorporations of dA or dG, in place of dT, by DNA polymerase alpha have been reported to be within one of the pause sites, pause site II (positions 6269 and 6270 (Fry, M., and Loeb, L.A. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 763-767)). The DNA products arrested within pause site II (position 6270) were separated, annealed with synthetic templates, and further elongated by DNA polymerase alpha. It was confirmed that a considerable amount of terminal misincorporation of dG in place of dT occurred at this position. When M13mp2 DNA was coated with various amounts of replication protein-A (RP-A), however, DNA polymerase alpha was able to overcome the pause site II, whereas pause bands at other sites barely decreased. In contrast, Escherichia coli single-stranded DNA-binding protein did not specifically abolish the arrested band at pause site II, though it generally suppressed the reaction. Since RP-A hardly increased the elongation frequency from the primer carrying a 3'-mismatched terminal deoxynucleotide, the reduction of arrested products by RP-A may be attributed to the change in the incorporation mode from noncomplementary to complementary deoxynucleotides within pause site II and may not be due to the reinitiation from the mismatched 3'-terminal deoxynucleotide. To confirm this, we amplified the reaction products at pause site III by means of a polymerase chain reaction method and showed that the complementary strand to pause site II, which was elongated in the presence of RP-A, did not carry any detectable misinsertion. Therefore, the errorprone step of the DNA synthesis catalyzed by DNA polymerase alpha may be readily avoided by RP-A.

Animals↗
PubMed1994

Observation of the highly organized development of granule cells in rat cerebellar organotypic cultures.

Cerebellar slices of 9-day-old rats were cultured for a week at the interface between air and a culture medium containing horse serum and hormone cocktail, and the development of granule cells was characterized morphologically. The typical layered structure of the cerebellar cortex was well preserved during the cultivation. Many granule cells in the external granular layer (EGL) proliferated actively within the early culture period. They were migrating downward at 3 days in vitro (DIV) and almost completed the migration to the internal granular layer (IGL) after 6 DIV. In the middle and upper molecular layer (ML), parallel fibers were elongated horizontally, which is the orientation 90 degrees rotated compared to that in vivo. They formed synapses with Purkinje cell dendrites. Regional differences in synapse density and maturity existed which might reflect a gradient in progressive synapse formation comparable to that in vivo. Thus, a serial process of highly organized development of granule cells was realized for the first time in vitro, although some spatial or temporal modifications existed. Such a culture system could be a useful experimental model for the study of cellular and molecular mechanisms of spatiotemporally organized neuronal development.

Animals↗