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T Murayama

Publications and source records attributed to T Murayama.

At least 19 recordsLinked to original sources
PubMed2001

Functional blockade of platelet-derived growth factor receptor-beta but not of receptor-alpha prevents vascular smooth muscle cell accumulation in fibrous cap lesions in apolipoprotein E-deficient mice.

BACKGROUND: The vascular smooth muscle cell (VSMC) is the central cell component involved in the fibroproliferative response in atherogenesis. As the lesion advances, VSMCs migrate from the media into the subendothelial space, thereby forming fibrous plaque lesions. Platelet-derived growth factor (PDGF) has been known to be a potent chemoattractant and mitogen for SMCs, but the pathophysiological role of the 2 PDGF receptors, receptor-alpha (PDGFR-alpha) and receptor-beta (PDGFR-beta) in atherogenesis is poorly understood. To clarify this problem, we prepared antagonistic rat monoclonal antibodies, APA5 and APB5, against murine PDGFR-alpha and PDGFR-beta, respectively. METHODS AND RESULTS: Apolipoprotein E-deficient mice were fed a high-fat diet containing 0.3% cholesterol from 6 weeks of age and subjected to injection with 1 mg/d IP of either antibody from 12 to 18 weeks every other day. In the mice injected with APB5, the aortic atherosclerotic lesion size and the number of intimal VSMCs were reduced by 67% and 80%, respectively, compared with the control mice injected with irrelevant rat IgG. In contrast, the mice that received APA5 showed only minimal reduction of lesion size, and a large number of VSMCs were observed in the intima. In the intima of advanced lesions, APB5 immunolabeled VSMCs, whereas APA5 could detect VSMCs mainly in the media. CONCLUSIONS: These results indicate that PDGFR-beta plays a significant role in formation of fibrous atherosclerotic lesions and that regulation of the signal transduction through PDGFR-beta could affect atherogenesis in mice.

Animals↗
PubMed2001

Stimulatory effects of centrally injected kappa-opioid receptor agonists on gastric acid secretion in urethane-anesthetized rats.

Gastric acid secretion has been proposed to be regulated by opioid receptors in the central nervous system (CNS). However, whether the effect of morphine is stimulatory or inhibitory, and the role of type specificity of opioid receptors have not been established. We investigated the effects of centrally injected opioid receptor agonists on gastric acid secretion in the perfused stomach of urethane-anesthetized rats. Injection of morphine (1-30 microg/rat, mu-opioid receptor agonist) into the fourth cerebroventricle inhibited the secretion stimulated by i.v. injection of 2-deoxy-D-glucose. Morphine itself did not show an inhibitory effect. In contrast, injection of kappa(1)-opioid receptor agonists such as (5alpha,7alpha,8beta)-(+)-N-methyl-N-(7-[1-pyrrolidinyl]-1-oxaspiro[4.5]dec-8-yl)benzeneacetamide (U59593, 0.3-3 microg) and (trans)-(+/-)-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl) benzeneacetamide hydrochloride (U50488H, 10 microg) and the kappa(2)-opioid receptor agonist, bremazocine (3 microg), into the lateral cerebroventricle markedly stimulated secretion. The effect of U59593 was inhibited by naloxone and norbinaltorphimine (an antagonist of kappa-opioid receptors) and in vagotomized rats. [D-Pen(2)-D-Pen(5)]enkephalin (10microg, delta-opioid receptor agonist) had no effect on secretion. The dual roles of the opioid system in the CNS in gastric acid secretion are discussed.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed2001

Enhancement of arachidonic acid release and prostaglandin F(2alpha) formation by Na3VO4 in PC12 cells and GH3 cells.

Both activation of phospholipase A2 causing arachidonic acid release and tyrosine phosphorylation have been proposed to be involved in neuronal functions. Previously, we reported that orthovanadate (Na3VO4), an inhibitor of tyrosine phosphatases, stimulated tyrosine phosphorylation in proteins and enhanced Ca2+-induced noradrenaline release in rat pheochromocytoma PC12 cells. However, the role of tyrosine phosphorylation on phospholipase A2 activity and/or arachidonic acid release in neuronal cells has not been well established. The effects of Na3VO4 on arachidonic acid release and prostaglandin F(2alpha) formation were investigated in two types of neuronal cell lines. In PC12 cells, addition of Na3VO4 stimulated [3H]arachidonic acid release and prostaglandin F(2alpha) formation in a concentration-dependent manner. Co-addition of 5 mM Na3VO4 enhanced ionomycin-stimulated [3H]arachidonic acid release. Na3VO4 also enhanced ionomycin-stimulated [3H]arachidonic acid release from GH3 cells, a clonal strain from rat anterior pituitary. These findings suggest that the tyrosine phosphorylation pathway regulates arachidonic acid release by phospholipase A2 and prostaglandin F(2alpha) formation in neuronal cells.

Animals↗
PubMed2001

Involvement of noradrenaline transporters in S-nitrosocysteine-stimulated noradrenaline release from rat brain slices: existence of functional Na(+)-independent transporter activity.

Noradrenaline (NA) can be released by both exocytosis and by the membrane transporter responsible for transmitter uptake. Previously, we reported that S-nitrosocysteine (SNC), an S-nitrosothiol, stimulated [3H]NA release from the rat hippocampus. In this study, we investigated the involvement of the NA transport system in SNC-stimulated NA release from rat brain (cerebral cortex and hippocampus) slices. [3H]NA release by SNC in normal Na(+) (148 mM)-containing buffer from both slices was slightly, but significantly, inhibited by 1 microM desipramine, an NA transporter inhibitor. [3H]NA release in low Na(+) (under 14 mM)-containing buffer was inhibited by over 50% by desipramine. [3H]NA release by tyramine from both slices in normal and low Na(+) buffer was almost completely inhibited by desipramine. [3H]NA uptake into cerebral cortical slices was observed in low Na(+) buffer at 20-30% of normal Na(+) buffer levels. [3H]NA uptake in both normal and low Na(+) buffers was inhibited by desipramine and by SNC. Although [3H]NA uptake in normal Na(+) buffer was almost completely inhibited by 500 microM ouabain, the uptake in low Na(+) buffer was resistant to ouabain. These findings suggest the existence of a functional Na(+)-independent NA transport system and that SNC stimulates NA release at least partially via this system in brain slices.

Adrenergic Uptake Inhibitors↗
PubMed2001

Kinetic analysis of cytokine gene expression in patients with GVHD after donor lymphocyte infusion.

Patients who receive a donor lymphocyte infusion (DLI) for the treatment of relapsed leukemia after allogeneic BMT (alloBMT) often developed GVHD. To determine whether cytokines might have a role in GVHD, an intensive kinetic analysis of in vivo cytokine gene expression was performed on PBMC from three such patients. Expression of IL-1beta, IL-2, IFN-gamma, IL-4, IL-5, IL-8, IL-10, IL-12, TNF-alpha, and IL-2Ralpha was examined using a sensitive semi-quantitative reverse transcription (RT)-PCR assay system. Six normal controls were also analyzed for comparison. Expression of type 1 T helper (Th1) cytokines, IL-2 and IFN-gamma was greatly increased in all three patients. In particular, the changes in IL-2 gene expression correlated well with disease progression, suggesting that IL-2 has a critical role in the development of GVHD. Although the pattern of type 2 T helper (Th2) cytokine gene expression differed in each patient, the expression of IL-4 was inversely related to expression of Th1 cytokines. These results suggest that Th1 dominates in the development of human clinical GVHD.

Adult↗
PubMed2000

The immediate early gene 1 product of human cytomegalovirus is sufficient for up-regulation of interleukin-8 gene expression.

We previously observed that human cytomegalovirus (CMV) infection induced a massive production of a chemokine with potent neutrophil chemotactic activity, interleukin-8 (IL-8). Hence, we examined the effect of CMV immediate early (IE) gene products on IL-8 production by the human astrocytoma cell line, U373MG. Transient or stable transfection with a CMV IE1 gene expression vector, but not with a IE2 gene expression vector, significantly augmented IL-8 protein secretion and IL-8 mRNA expression. Luciferase activity was enhanced in U373MG cells when the cells were cotransfected with CMV IE1 and chimeric firefly luciferase reporter genes driven by the transcriptional regulatory region of the human IL-8 gene. Moreover, IE1 gene-mediated enhancement of luciferase activity was abolished by the introduction of mutations into the AP-1 or NF-kappa B factor binding elements in the regulatory region of the IL-8 promoter. Furthermore, electrophoretic mobility shift assays demonstrated that CMV IE1 gene products induced the formation of NF-kappa B or AP-1 complexes. Finally, Western blotting analysis demonstrated that the CMV IE1 gene product increased the amount of NF-kappa B complexes translocated into the nucleus. Collectively, CMV IE1 gene expression may be sufficient to activate AP-1 and NF-kappa B, resulting in IL-8 gene expression.

Base Sequence↗
PubMed2000

Changes in expressions of proinflammatory cytokines IL-1beta, TNF-alpha and IL-6 in the brain of senescence accelerated mouse (SAM) P8.

The senescence-accelerated mouse (SAM) is known to be a murine model for accelerated aging. The SAMP8 strain shows age-related deterioration of learning and memory at an earlier age than control mice (SAMR1). In the present study, we investigated the changes in expressions of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in the brain of SAMP8. In the hippocampus of 10 months old SAMP8, the expression of IL-1 mRNA was significantly elevated in comparison with that of SAMR1. In both strains of SAMs, increases in IL-1beta protein in the brain were observed at 10 months of age compared with 2 and 5 months. The only differences found between the strain in protein levels were at 10 months and were elevations in IL-1beta in the hippocampus and hypothalamus, and in TNF-alpha and IL-6 in the cerebral cortex and the hippocampus in SAMP8 as compared with SAMR1. However, lipopolysaccharide-induced increases in the expression of these cytokines in brain did not differ between SAMP8 and SAMR1. Increases in expression of proinflammatory cytokines in the brain may be involved in the age-related neural dysfunction and/or learning deficiency in SAMP8.

Aging↗
PubMed2000

Selectively suppressed Ca2+-induced Ca2+ release activity of alpha-ryanodine receptor (alpha-RyR) in frog skeletal muscle sarcoplasmic reticulum: potential distinct modes in Ca2+ release between alpha- and beta-RyR.

We reported earlier that the two ryanodine receptor (RyR) isoforms (alpha- and beta-RyR) purified from frog skeletal muscle were equipotent in the Ca(2+)-induced Ca(2+) release (CICR) activity (Murayama, T., Kurebayashi, N., and Ogawa, Y. (2000) Biophys. J. 78, 1810-1824). Whether this is also the case with the native Ca(2+) release channel in the sarcoplasmic reticulum (SR), however, remains to be determined. Taking advantage of the facts that [(3)H]ryanodine binds only to the open form of the channels and that it is practically irreversible at 4 degrees C, we devised a method to separate the total binding to contributions of alpha- and beta-RyR, using immunoprecipitation with an alpha-RyR-specific monoclonal antibody. Surprisingly, the binding of alpha-RyR was strongly suppressed to as low as approximately 4% that of beta-RyR in the SR vesicles. The two isoforms, however, showed no difference in sensitivity to Ca(2+), adenine nucleotides, or caffeine. This reduced binding of alpha-RyR was ascribed to the low affinity for [(3)H]ryanodine, with no change in the maximal binding sites. Solubilization of SR with 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonic acid partly remedied this nonequivalence, whereas 1 m NaCl was ineffective. 12-kDa FK506-binding protein (FKBP12), however, could not be responsible for it, because FK506 treatment did not eliminate the suppression, in contrast to marked removal of 12-kDa FK506-binding protein from alpha-RyR. These results suggest that alpha-RyR in the SR may serve Ca(2+) release in a mode other than CICR, being selectively suppressed in CICR.

Amino Acid Sequence↗
PubMed2000

Metal-to-insulator crossover in the low-temperature normal state of Bi(2)Sr(2-x)La(x)CuO(6+delta).

We measure the normal-state in-plane resistivity of Bi(2)Sr(2-x)La(x)CuO(6+delta) single crystals at low temperatures by suppressing superconductivity with 60 T pulsed magnetic fields. With decreasing hole doping, we observe a crossover from a metallic to an insulating behavior in the low-temperature normal state. This crossover is estimated to occur near 1/8 doping, well inside the underdoped regime, and not at optimum doping as reported for other cuprates. The insulating regime is marked by a logarithmic temperature dependence of the resistivity over two decades of temperature, suggesting that a peculiar charge localization is common to the cuprates.

Journal Article↗
PubMed2000

Apoptosis induction by a dopaminergic neurotoxin, 1-methyl-4-phenylpyridinium ion (MPP(+)), and inhibition by epidermal growth factor in GH3 cells.

A dopaminergic neurotoxin, 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine (MPTP), can induce dopaminergic denervation and Parkinsonism in humans. The active metabolite of MPTP is the 1-methyl-4-phenylpyridinium ion (MPP(+)). Previously we reported that MPP(+) is incorporated via the dopamine transport system and causes delayed cell death in GH3 cells, a clonal strain from the rat anterior pituitary. In this study, we investigated whether MPP(+) induces apoptosis. GH3 cells cultured with MPP(+) exhibited DNA laddering and fragmentation in a time- and concentration-dependent manner. The effect of MPP(+) was inhibited in GH3 cells treated with a pan-caspase inhibitor (100 microM ZVAD-fmk), an antioxidant (25 mM N-acetyl-l-cysteine), or epidermal growth factor (EGF; 50 ng/mL). Because EGF stimulated tyrosine phosphorylation of the EGF receptor and tyrphostin AG1478 [4-(3-chloroanilino)-6,7-dimethoxyquinazoline; 5 microM, a specific inhibitor of EGF receptor kinase] abolished EGF inhibition, involvement of EGF receptor kinase is assumed. Protein kinase C-dependent processes and Bcl-2 protein expression were shown not to be involved in EGF inhibition. MPP(+) increased cytochrome c immunoreactivity in cytosolic fractions in GH3 cells. The addition of 200 microM MPP(+) to isolated mitochondrial fractions from GH3 cells stimulated the release of a 13-kDa protein that cross-reacted with anti-cytochrome c antibody. The release was inhibited in EGF-treated GH3 cells. Our findings demonstrated that (i) MPP(+) induces apoptosis of GH3 cells via cytochrome c release and caspase activation, and (ii) apoptosis by MPP(+) can be blocked by N-acetyl-l-cysteine or EGF treatment.

1-Methyl-4-phenylpyridinium↗
PubMed2000

Inhibition of phospholipase A(2) activity by S-nitroso-cysteine in a cyclic GMP-independent manner in PC12 cells.

Arachidonic acid and nitric oxide (NO) act as retrograde and intercellular messengers in the nervous system. Regulation of cyclooxygenase is well established, but regulation of phospholipase A(2), the enzyme responsible for the liberation of arachidonic acid, by NO has not been thoroughly investigated. Using the PC12 cell line as a neuronal model, we studied the effects of exogenous NO compounds on arachidonic acid release. Incubation with Ca(2+) ionophores or mastoparan (wasp venom peptide) stimulated [3H]arachidonic acid release from prelabeled PC12 cells. [3H]Arachidonic acid release was inhibited by cytosolic phospholipase A(2) inhibitors, but not by dithiothreitol. A cytosolic phospholipase A(2) protein band with a molecular mass of approximately 100 kDa was detected by immunoblotting. S-Nitroso-cysteine inhibited basal and stimulated [3H]arachidonic acid release in concentration-dependent manners. Other NO compounds such as sodium nitroprusside and S-nitroso-N-acetylpenicillamine did not affect [3H]arachidonic acid release. N-Ethylmaleimide also inhibited [3H]arachidonic acid release. The inhibitory effects of S-nitroso-cysteine and N-ethylmaleimide were irreversible, because [3H]arachidonic acid release from PC12 cells preincubated with S-nitroso-cysteine or N-ethylmaleimide was much lower than that from nontreated cells. These findings suggest (a) cytosolic phospholipase A(2) is activated by Ca(2+) or mastoparan, and inhibited by S-nitroso-cysteine in a cyclic GMP-independent manner, (b) N-ethylmaleimide also inhibits cytosolic phospholipase A(2) and arachidonic acid release in PC12 cells. S-Nitroso-cysteine can regulate the production of other retrograde messenger arachidonic acid.

Animals↗
PubMed2000

Learning deficiency and alterations in acetylcholine receptors and protein kinase C in the brain of senescence-accelerated mouse (SAM)-P10.

The senescence-accelerated mouse (SAM) is known to be a murine model for accelerated aging. A novel inbred SAMP10 has shown age-related brain atrophy and learning deficiency. In the present study, we investigated the changes in learning ability and in ligand binding with muscarinic acetylcholine (mACh) receptors, alpha adrenoceptors and protein kinase C in SAMP10. In Morris's water maze task, in a control strain of SAMR1 at 9 months, the escape latency and path length decreased with increasing trial days, in contrast, escape latency and path length did not decrease in SAMP10. These results indicate that SAMP10 exhibits learning deficiency. The ligand binding activity of mACh receptors decreased in the hippocampus of SAMP10 and the protein kinase C level in the hippocampus of SAMP10 was lower than that of SAMR1. On the other hand, there was no significant difference between SAMR1 and SAMP10 regarding ligand binding activity of alpha(1) and alpha(2) adrenoceptors. Thus, a reduction of mACh receptors and protein kinase C in the brain seems to underlie dysfunction of learning and memory in SAMP10.

Aging, Premature↗
PubMed2000

Involvement of Hg2+-sensitive sulfhydryl groups in regulating noradrenaline release induced by S-nitrosocysteine in rat brain slices.

Nitric oxide has been shown to regulate neurotransmitter release. Previously, we reported that S-nitrosothiols such as S-nitrosocysteine (SNC) stimulate noradrenaline (NA) release in rat hippocampus in vivo and in vitro. To examine the role of sulfhydryl groups in SNC-induced NA release, the effects of metal ions such as Hg2+ and N-ethylmaleimide (NEM, a sulfhydryl alkylating agent) on [3H]NA release from labeled rat brain slices (hippocampus and cerebral cortex) were studied and compared with the effects of SNC. The addition of 200 microM HgCl2, but not Pb2+, Zn2+, or Cd2+, stimulated [3H]NA release from both types of slices in the presence of extracellular CaCl2. p-Chloromercuribenzoic acid (p-CMBA) also stimulated [3H]NA release. NEM stimulated [3H]NA release from both types of slices in the presence and absence of extracellular CaCl2. The effect of 200 microM NEM was enhanced, but the effect of 200 microM SNC was inhibited by co-addition of 200 microM p-CMBA in the absence of extracellular CaCl2. The concentration-response curve of SNC shifted to the right after co-addition of 200 microM p-CMBA or 100 microM HgCl2, although the effect of 200 microM NEM was additive to the effect of SNC. These findings demonstrate that SNC acts as a sulfhydryl agent on proteins that regulate NA release, and that SNC may share the same sulfhydryl groups with Hg compounds. The effect of T-588 ¿(R)-(-)-(benzo[b]thiophen-5-yl)-2-[2-(N,N-diethylamino)ethoxy]eth anol hydrochloride¿, a novel cognitive enhancer and a stimulator of NA release, was compared with the effects of sulfhydryl reagents.

Animals↗
PubMed2000

Cryptographical properties of Ising spin systems.

The relation between Ising spin systems and public-key cryptography is investigated using methods of statistical physics. The insight gained from the analysis is used for devising a matrix-based cryptosystem whereby the ciphertext comprises products of the original message bits; these are selected by employing two predetermined randomly constructed sparse matrices. The ciphertext is decrypted using methods of belief propagation. The analyzed properties of the suggested cryptosystem show robustness against various attacks and competitive performance to modern cryptographical methods.

Journal Article↗
PubMed2000

Development of an assay method for activities of serine/threonine protein phosphatase type 2B (calcineurin) in crude extracts.

Despite the physiological importance of serine/threonine protein phosphatase type 2B (PP2B/calcineurin), an accurate assay method of PP2B in crude tissue extracts has not been established. By using recombinant protein phosphatase inhibitor-1 as a substrate and ascorbic acid as an antioxidant, we developed an improved assay method for PP2B activity in crude extracts from mouse tissues and investigated tissue distribution of its activity. Under the assay conditions, the PP2B activities were stable for at least 30 min with more than 100-fold higher sensitivity than those previously reported. The specific activities of PP2B were 22.3, 0.85, 2.9, 0.36, and 1.5 mU/mg protein in mouse brain, heart, spleen, liver, and testis, respectively, and furthermore in each region of the brain they were 26.1, 13.7, 42.8, 40.5, 15.1, and 8.6 mU/mg protein in cerebrum, midbrain plus interbrain, striatum, hippocampus, cerebellum, and brain stem, respectively. This is the first paper to demonstrate a close correlation between tissue distributions and content of PP2B. These results showed that the present assay method is extremely powerful for precise measurement of a wide range of PP2B activities including not only high PP2B activity in the brain but also low PP2B activities in other tissues.

Animals↗
PubMed2000

Possible involvement of cytosolic phospholipase A(2) in cell death induced by 1-methyl-4-phenylpyridinium ion, a dopaminergic neurotoxin, in GH3 cells.

Previously we reported that 1-methyl-4-phenylpyridinium ion (MPP(+)), a dopaminergic neurotoxin, induced apoptosis of GH3 cells established from rat anterior pituitary. In the present study, the role of MPP(+) along with that of other apoptotic factors such as Ca(2+) and H(2)O(2) in cell death was examined. Ionomycin induced DNA fragmentation and lactate dehydrogenase (LDH) leakage in GH3 cells. H(2)O(2) also induced LDH leakage. Co-addition of MPP(+), in conditions where MPP(+) had no effect by itself, enhanced ionomycin- and H(2)O(2)-induced cell death. Because the stimulation of phospholipase A(2) (PLA(2)) causing arachidonic acid (AA) release has been proposed to be involved in neuronal cell death, the effect of MPP(+) on AA release in GH3 cells was investigated. MPP(+) treatment for 8 h enhanced ionomycin- and H(2)O(2)-stimulated AA release mediated by activation of cytosolic PLA(2) in a concentration-dependent manner, although MPP(+) by itself had no effect on AA release. An inhibitor of cytosolic PLA(2) inhibited MPP(+)-induced cell death. These findings suggest a synergistic effect of MPP(+) on Ca(2+)- and H(2)O(2)-induced cell death, and the involvement of cytosolic PLA(2) activation in MPP(+)-induced cell death in GH3 cells. Pretreatment with a caspase inhibitor or EGF did not modify the ionomycin- or H(2)O(2)-induced AA release, or enhancement by MPP(+), but the pretreatment inhibited the cell death in the presence and absence of MPP(+). The involvement of caspase(s) on activation of PLA(2) by MPP(+) was excluded, and EGF inhibited MPP(+)-induced cell death downstream of the AA release.

1-Methyl-4-phenylpyridinium↗
PubMed2000

Typical performance of gallager-type error-correcting codes

The performance of Gallager's error-correcting code is investigated via methods of statistical physics. In this approach, the transmitted codeword comprises products of the original message bits selected by two randomly constructed sparse matrices; the number of nonzero row/column elements in these matrices constitutes a family of codes. We show that Shannon's channel capacity is saturated for many of the codes while slightly lower performance is obtained for others which may be of higher practical relevance. Decoding aspects are considered by employing the Thouless-Anderson-Palmer approach which is identical to the commonly used belief-propagation-based decoding.

Journal Article↗