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Biomedical subjects

S Sakaguchi

Publications and source records attributed to S Sakaguchi.

At least 55 records · Page 3Linked to original sources
PubMed2001

Abnormal activation of glial cells in the brains of prion protein-deficient mice ectopically expressing prion protein-like protein, PrPLP/Dpl.

BACKGROUND: Some lines of mice homozygous for a disrupted prion protein gene (Prnp), including Ngsk Prnp(0/0) mice, exhibit Purkinje cell degeneration as a consequence of the ectopic overexpression of the downstream gene for prion protein-like protein (PrPLP/Dpl) in the brain, but others, such as Zrch I Prnp(0/0) mice, show neither the neurodegeneration nor the expression of PrPLP/Dpl. In the present study, we found that Ngsk Prnp(0/0), but not Zrch I Prnp(0/0) mice, developed gliosis involving both astrocytes and microglia in the brain. MATERIALS AND METHODS: The brains from wild-type (Prnp(+/+)), Ngsk Prnp(0/0), Zrch I Prnp(0/0), and reconstituted Ngsk Prnp(0/0) mice carrying a mouse PrP transgene, designated Tg(P) Ngsk Prnp(0/0) mice, were subjected into Northern blotting and in situ hybridization using probes of glial fibrillary acidic protein (GFAP) and lysozyme M (LM) specific for astrocytes and microglia, respectively. Immunohistochemistry was also performed on the brain sections using anti-GFAP and anti-F4/80 antibodies. RESULTS: Northern blotting demonstrated upregulated expression of the genes for GFAP and LM in the brains of Ngsk Prnp(0/0), but not in Zrch I Prnp(0/0) mice. A transgene for normal mouse PrP(C) successfully rescued Ngsk Prnp(0/0) mice from the glial activation. In situ hybridization and immunohistochemistry revealed activated astrocytes and microglia mainly in the white matter of both the forebrains and cerebella. In contrast, there was no evidence of neuronal injury except for the Purkinje cell degeneration. Moreover, the glial cell activation was notable well before the onset of the Purkinje cell degeneration. CONCLUSIONS: These findings strongly suggest that ectopic PrPLP/Dpl in the absence of PrP(C) is actively involved in the glial-cell activation in the brain.

Aging↗
PubMed2000

Rearrangement of allyl homoallyl ethers to gamma,delta-unsaturated carbonyl compounds catalyzed by iridium complexes

Iridium complexes were found to promote the conversion of allyl homoallyl ethers to gamma,delta-unsaturated carbonyl compounds. For example, treatment of 1-allyl-1-allyloxycyclohexane in the presence of catalytic amounts of [Ir(cod)Cl](2), PCy(3), and Cs(2)CO(3) in toluene at 100 degrees C afforded 4-cyclohexyliden-2, 3-dimethylbutanal in 74% yield. The reaction presumably proceeds through double bond migration to allyl vinyl ethers, which then undergo the Claisen rearrangement.

Journal Article↗
PubMed2000

Roles of selenium in endotoxin-induced lipid peroxidation in the rats liver and in nitric oxide production in J774A.1 cells.

We examined the role of selenium (Se) in the mechanism of oxidative stress caused by endotoxin by feeding rats deficient a diet in this element. In rats fed the Se-deficient diet (concentration of Se, less than 0.027 microg g(-1)) for 10 weeks, Se level and glutathione peroxidase (GSH-Px) activity in the liver were about 47 and 43% lower, respectively, than those in rats fed a Se-adequate diet (Se, 0.2 microg g(-1)). Rat fed the Se-deficient diet and given endotoxin (6 mg kg(-1), i.p.) showed a mortality rates of about 43% at 18 h. Nevertheless, no lethality was observed with endotoxin (4 mg kg(-1), i.p.) challenge. Levels of serum lactate dehydrogenase and acid phosphatase leakage were significantly higher in Se-deficient rats than those in Se-adequate diet 18 h after endotoxin (4 mg kg(-1), i. p.) challenge. Superoxide anion generation and lipid peroxide formation in the liver of Se-deficient rat were markedly increased 18 h after endotoxin (4 mg kg(-1), i.p.) injection compared with those in the endotoxin/Se-adequate diet group, whereas non-protein sulfhydryl level in the liver after administration of endotoxin to Se-deficient rats was lower than that in Se-adequate rats treated with endotoxin. We investigated whether Se can suppress nitric oxide (NO) generation and cytotoxicity in endotoxin-treated J774A.1 cells. Treatment with Se (10(-6) M) markedly inhibited endotoxin (0.1 microg ml(-1))-induced NO production in J774A.1 cells. Se induced an increased activity of GSH-Px in cells after 24 h of incubation, suggesting that the preventive effect of Se on NO production in endotoxemia is due to the induction of Se-GSH-Px activity. However, Se did not affect endotoxin-induced cytotoxicity in J774A.1 cells. These findings suggested that the oxidative stress caused by endotoxin may be due, at least in part, to changes in Se regulation during endotoxemia.

Animals↗
PubMed2000

PrP fragment 106-126 is toxic to cerebral endothelial cells expressing PrP(C).

A hydrophobic, fibrillogenic peptide fragment of human prion protein (PrP106-126) had in vitro toxicity to neurons expressing cellular prion protein (PrP(C)). In this study, we proved that primary cultures of mouse cerebral endothelial cells (MCEC) express PrP(C). Incubation of MCEC with PrP106-126 (25-200 microM) caused a dose-dependent toxicity assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, lactate dehydrogenase release, bis-benzimide staining for nuclear morphology, and trypan blue exclusion test. Pentosan polysulphate (50-100 microg/ml), a drug effective in scrapie prophylaxis, dose-dependently attenuated the injury. MCEC cultures from mice homogenous for the disrupted PrP gene were resistant to the toxicity of PrP106-126. In conclusion, cerebral endothelium expressing PrP(C) may be directly damaged during spongiform encephalopathies.

Amino Acid Sequence↗
PubMed2000

Efficient oxidation of alcohols to carbonyl compounds with molecular oxygen catalyzed by N-hydroxyphthalimide combined with a Co species

Highly efficient catalytic oxidation of alcohols with molecular oxygen by N-hydroxyphthalimide (NHPI) combined with a Co species was developed. The oxidation of 2-octanol in the presence of catalytic amounts of NHPI and Co(OAc)2 under atmospheric dioxygen in AcOEt at 70 degrees C gave 2-octanone in 93% yield. The oxidation was significantly enhanced by adding a small amount of benzoic acid to proceed smoothly even at room temperature. Primary alcohols were oxidized by NHPI in the absence of any metal catalyst to form the corresponding carboxylic acids in good yields. In the oxidation of terminal vic-diols such as 1,2-butanediol, carbon-carbon bond cleavage was induced to give one carbon less carboxylic acids such as propionic acid, while internal vic-diols were selectively oxidized to 1,2-diketones.

Journal Article↗
PubMed2000

An efficient synthesis of dinitrile derivatives by the reaction of oxime esters or acid anhydrides with cyanotrimethylsilane catalyzed by La(O(i)()Pr)(3)

The reaction of oxime esters with cyanotrimethylsilane (Me(3)SiCN) under the influence of a catalytic amount of lanthanide compounds produced alpha-trimethylsilyloxydinitrile derivatives in excellent yields accompanied with the formation of trimethylsilyl oxime ethers. Among the lanthanoid catalysts examined, La(O(i)()Pr)(3) was found to be the best catalyst. The reaction seems to proceed through the formation of acyl cyanides as intermediates, followed by the addition of Me(3)SiCN to them. Additionally, the reaction of acetic anhydride with Me(3)SiCN catalyzed by La(O(i)()Pr)(3) gave 1-trimethylsilyloxyethane dinitrile. Thus, various alpha-trimethylsilyloxydinitriles were synthesized in good yields by allowing oxime esters or acid anhydrides to react with Me(3)SiCN in the presence of a catalytic amount of La(O(i)()Pr)(3).

Journal Article↗
PubMed2000

Immunologic self-tolerance maintained by CD25(+)CD4(+) regulatory T cells constitutively expressing cytotoxic T lymphocyte-associated antigen 4.

This report shows that cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) plays a key role in T cell-mediated dominant immunologic self-tolerance. In vivo blockade of CTLA-4 for a limited period in normal mice leads to spontaneous development of chronic organ-specific autoimmune diseases, which are immunopathologically similar to human counterparts. In normal naive mice, CTLA-4 is constitutively expressed on CD25(+)CD4(+) T cells, which constitute 5-10% of peripheral CD4(+) T cells. When the CD25(+)CD4(+) T cells are stimulated via the T cell receptor in vitro, they potently suppress antigen-specific and polyclonal activation and proliferation of other T cells, including CTLA-4-deficient T cells, and blockade of CTLA-4 abrogates the suppression. CD28-deficient CD25(+)CD4(+) T cells can also suppress normal T cells, indicating that CD28 is dispensable for activation of the regulatory T cells. Thus, the CD25(+)CD4(+) regulatory T cell population engaged in dominant self-tolerance may require CTLA-4 but not CD28 as a costimulatory molecule for its functional activation. Furthermore, interference with this role of CTLA-4 suffices to elicit autoimmune disease in otherwise normal animals, presumably through affecting CD25(+)CD4(+) T cell-mediated control of self-reactive T cells. This unique function of CTLA-4 could be exploited to potentiate T cell-mediated immunoregulation, and thereby to induce immunologic tolerance or to control autoimmunity.

Abatacept↗
PubMed2000

Inhibition of rho-associated kinase results in suppression of neointimal formation of balloon-injured arteries.

BACKGROUND: Rho-associated kinase (ROCK), an effector of small GTPase Rho, regulates vascular tone via a calcium sensitization mechanism and plays a key role in the pathogenesis of hypertension. However, its role in vascular growth remains unclear. METHODS AND RESULTS: Y-27632, a specific ROCK inhibitor, and the overexpression of dominant-negative ROCK suppressed the mitogen-induced DNA synthesis of cultured vascular smooth muscle cells (VSMCs), which indicates the essential role of ROCK in the control of VSMC proliferation in vitro. Y-27632 also suppressed the chemotaxis of VSMCs. Male Wistar rats were systemically given Y-27632 (35 to 70 mg. kg(-1). day(-1)) through an intraperitoneal infusion. The neointimal formation of balloon-injured carotid arteries was significantly suppressed in Y-27632-treated rats (intima/media ratio, 0.22+/-0.02) compared with vehicle-treated rats (intima/media ratio, 0.92+/-0.21) or hydralazine-treated rats with a similar blood pressure decrease (intima/media ratio, 1.03+/-0.15). The phosphorylation of myosin phosphatase and myosin light chain was elevated in injured arteries in a Y-27632-sensitive manner, indicating the augmentation of ROCK activity in neointimal formation. The downregulation of the cyclin-dependent kinase inhibitor p27(kip1) in injured vessels was reversed by Y-27632 treatment, reflecting the antiproliferative effect of ROCK inhibition in vivo. CONCLUSIONS: We conclude that ROCK plays a key role in the process of neointimal formation after balloon injury. Thus, the inhibition of ROCK may be a potential therapeutic strategy for treating vascular proliferative disorders and hypertension.

Amides↗
PubMed2000

Acetalization of alkenes catalyzed by Pd(OAc)2/NPMoV supported on activated carbon under a dioxygen atmosphere

[reaction: see text] The acetalization of terminal alkenes such as ethyl acrylate and acrylonitrile with alcohols under O2 was efficiently achieved by Pd(OAc)2 supported on activated carbon combined with molybdovanadophosphate (NPMoV). For example, ethyl acrylate was subjected to acetalization with EtOH acidified by CH3SO3H under O2 (1 atm) in the presence of [8 wt%Pd(OAc)2/C] and NPMoV to form ethyl 3,3-diethoxypropionate in quantitative yield.

Journal Article↗
PubMed2000

Physiological expression of the gene for PrP-like protein, PrPLP/Dpl, by brain endothelial cells and its ectopic expression in neurons of PrP-deficient mice ataxic due to Purkinje cell degeneration.

Recently, a novel gene encoding a prion protein (PrP)-like glycoprotein, PrPLP/Dpl, was identified as being expressed ectopically by neurons of the ataxic PrP-deficient (PRNP(-/-)) mouse lines exhibiting Purkinje cell degeneration. In adult wild-type mice, PrPLP/Dpl mRNA was physiologically expressed at a high level by testis and heart, but was barely detectable in brain. However, transient expression of PrPLP/Dpl mRNA was detectable by Northern blotting in the brain of neonatal wild-type mice, showing maximal expression around 1 week after birth. In situ hybridization paired with immunohistochemistry using anti-factor VIII serum identified brain endothelial cells as expressing the transcripts. Moreover, in the neonatal wild-type mice, the PrPLP/Dpl mRNA colocalized with factor VIII immunoreactivities in spleen and was detectable on capillaries in lamina propria mucosa of gut. These findings suggested a role of PrPLP/Dpl in angiogenesis, in particular blood-brain barrier maturation in the central nervous system. Even in the ataxic Ngsk PRNP(-/-) mice, the physiological regulation of PrPLP/Dpl mRNA expression in brain endothelial cells was still preserved. This strongly supports the argument that the ectopic expression of PrPLP/Dpl in neurons, but not deregulation of its physiological expression in endothelial cells, is involved in the neuronal degeneration in ataxic PRNP(-/-) mice.

Adenosine Triphosphatases↗
PubMed2000

Modification of tumor necrosis factor-induced acute toxicity D-galactosamine challenge by polymyxin B, an anti-endotoxin.

Polymyxin B (PMB), an antibiotic with anti-endotoxin activity, was used to examine the participation of endogenously produced endotoxin in the enhancement of recombinant human tumor necrosis factor (rhTNF)-induced toxicity in D-galactosamine (GalN)-sensitized mice. GalN-sensitized mice (700 mg/kg, intraperitoneally (i.p.)) injected together with rhTNF (1x10(4) U/mouse, intravenously (i.v.)) exhibited severe symptoms, with 100% mortality at 18 h. However, mice pretreated with PMB (20 mg/kg, i.p.) showed protection against the rhTNF-induced lethality following GalN sensitization. Little or no effects were observed on alanine aminotransferase (ALT) activity or lactate dehydrogenase (LDH) isozyme leakage in serum in mice 7 h after administration of rhTNF alone. Administration of rhTNF to GalN-sensitized mice resulted in marked increases in ALT activity and LDH isozyme leakage relative to those in mice treated with rhTNF alone. In mice pretreated with PMB, the levels of ALT and LDH isozyme leakage 7 h after rhTNF/GalN injection were significant decreased as compared with those in mice treated with rhTNF/GalN. Similarly, injection of PMB markedly decreased lipid peroxide formation in the liver of the GalN-sensitized mice treated with rhTNF. The injection of a low endotoxin dose (0.1 mg/kg, i.p.) markedly increased the lethality in mice treated with rhTNF (5x10(3) U/mouse, i.v.) and GalN, and these animals showed 100% mortality at 8 h. These findings suggested that the extent of TNF-induced toxicity caused by GalN administration may be a result of synergism between TNF and gut-derived endotoxin. It is likely that endogenously produced endotoxin play a significant role in rhTNF/GalN-hypersensitized mice.

Alanine Transaminase↗
PubMed2000

Animal models of autoimmunity and their relevance to human diseases.

T cells mediate various autoimmune diseases. Pathologic autoimmunity can be induced by manipulating thymic or peripheral control of self-reactive T cells. There is, for example, accumulating evidence that elimination or dysfunction of regulatory T cells can elicit T cell mediated, destructive autoimmune disease in otherwise normal animals and enhance autoimmunity in spontaneous models.

Animals↗
PubMed2000

Early appearance but lagged accumulation of detergent-insoluble prion protein in the brains of mice inoculated with a mouse-adapted Creutzfeldt-Jakob disease agent.

1. To elucidate mechanisms for the generation of the detergent-insoluble, proteinase K-resistant prion protein (PrP(Sc)) from the detergent-soluble, proteinase K-sensitive PrP (PrP(C)) and the replication of the infectious agent in prion diseases, we followed the kinetics of detergent-insoluble PrP and PrP(Sc) levels, infectious titers, and associated pathological changes in the brains of mice inoculated with a mouse-adapted Creutzfeldt Jakob disease agent. 2. PrP(Sc) in brain homogenate and detergent-insoluble PrP enriched by two-cycle ultracentrifugation were detected by immunoblotting and their relative amounts were estimated according to a standard curve plotted between the amount of PrP and signal intensity on immunoblotting. The titer of infectivity was determined by the incubation periods of mice inoculated with the unfractionated homogenate on the basis of a standard curve plotted between the titer and incubation period. 3. Detergent-insoluble PrP became detectable 4 weeks postinoculation (p.i.) well before the detection of PrP(Sc). The low level of detergent-insoluble PrP continued until dramatic accumulation occurred at 14 weeks p.i., correlating well with the accumulation of PrP(Sc) and development of pathological changes. The infectious titer was undetectable at 4 weeks p.i. and its logarithmic increase occurred 10 weeks p.i. preceding the logarithmic accumulation of PrPs. 4. The lag time of detergent-insoluble PrP accumulation and the discrepancy between infectious titers and PrPs observed during the early period after inoculation suggest a slow and rate-limiting step for the detergent-insoluble PrP to become the infectious agent-associated PrP(Sc).

Animals↗
PubMed2000

Identification of a novel gene encoding a PrP-like protein expressed as chimeric transcripts fused to PrP exon 1/2 in ataxic mouse line with a disrupted PrP gene.

1. Mouse lines lacking prion protein (PrP(C)) have a puzzling phenotypic discrepancy. Some, but not all, developed late-onset ataxia due to Purkinje cell degeneration. 2. Here, we identified aberrant mRNA species in the brain of Ngsk Prnp0/0 ataxic, but not in nonataxic Zrch Prnp0/0 mouse line. These mRNAs were chimeric between the noncoding exons 1 and 2 of the PrP gene (Prnp) and the novel sequence encoding PrP-like protein (PrPLP), a putative membrane glycoprotein with 23% identity to PrP(C) in the primary amino acid structure. The chimeric mRNAs were generated from the disrupted Prnp locus of Ngsk Prnp0/0 mice lacking a part of the Prnp intron 2 and its splice acceptor signal. 3. In the brain of wild-type and Zrch Prnp0/0 mice, PrPLP mRNA was barely detectable. In contrast, in the brain of Ngsk Prnp0/0 mice, PrP/PrPLP chimeric mRNAs were expressed in neurons, at a particularly high level in hippocampus pyramidal cells and Purkinje cells under the control of the Prnp promoter. 4. In addition to the functional loss of PrP(C), ectopic PrPLP expression from the chimeric mRNAs could also be involved in the Purkinje cell degeneration in Ngsk Prnp0/0 mice.

Amino Acid Sequence↗
PubMed2000

Atrial fibrillation: defining potential curative ablation targets.

The concept that atrial fibrillation (or at least certain forms of the arrhythmia) may be amenable to reversal or amelioration by transcatheter ablation techniques has become increasingly accepted in recent years. As yet, however, the techniques being studied for ablation of atrial fibrillation address neither known critical anatomic elements nor well defined electrophysiologic markers. The approaches, although essentially empirical, are conceptually based on the 'multiple wavelet' or 'focal origin' hypotheses. To date, addressing 'focal origin' atrial fibrillation by transcatheter ablation has been the more encouraging. However, as technology evolves, both in terms of catheter design and possibly endocardial mapping techniques, approaches to wavelet or rotor mechanisms may become similarly effective. This communication examines concepts regarding the manner in which atrial fibrillation is initiated and maintained. The goals are to better understand the encouraging success of empirical ablation methods, and possibly derive insights which may help refine ablation targeting in the future.

Atrial Fibrillation↗
PubMed2000

Effect of nitric oxide synthase inhibitors on lipid peroxide formation in liver caused by endotoxin challenge.

This study investigated the effect of nitric oxide on lipid peroxide formation during endotoxaemia. Nitric oxide synthase inhibitors N(G)-monomethyl-L-arginine acetate (L-NMMA, 20 mg/kg, intravenously), N(G)-nitro-L-arginine-methyl ester (L-NAME, 10 mg/kg, intravenously), and N(G)-nitro-L-arginine (L-NA, 10 mg/kg, intravenously), and a relatively selective inducible nitric oxide synthase inhibitor aminoguanidine (10 mg/kg, intravenously), did not protect against endotoxin-induced death of mice. Superoxide dismutase activity in liver 18 hr after administration of endotoxin (6 mg/kg, intraperitoneally) to L-arginine analogues (L-NMMA, L-NAME, L-NA)-treated mice was lower than in mice treated with endotoxin alone, whereas the administration of L-arginine analogues increased xanthine oxidase activity in the livers of endotoxin-injected mice compared with mice treated with endotoxin alone. In mice treated with L-arginine analogues and aminoguanidine, the levels of non-protein sulfhydryl and lipid peroxide in liver 18 hr after endotoxin injection did not show significant differences from mice treated with endotoxin alone. L-Arginine analogues and aminoguanidine had little effect on lipid peroxide formation in liver caused by endotoxin. Treatment with aminoguanidine (300 microM) significantly inhibited endotoxin-induced intracellular peroxide in J774A.1 cells, however, aminoguanidine did not affect endotoxin-induced cytotoxicity in J774A.1 cells. Our results clearly demonstrate that treatment with catalase (10 microg/ml), D-mannitol (10 mM), or superoxide dismutase (100 U/ml), has little or no effect on nitric oxide production by endotoxin (1 microg/ml)-activated J774A.1 cells. These findings suggest that nitric oxide is not crucial for lipid peroxide formation during endotoxaemia. Therefore, it is unlikely that nitric oxide plays a significant role in liver injury caused by free radical generation in endotoxaemia.

Animals↗
PubMed2000

Naturally anergic and suppressive CD25(+)CD4(+) T cells as a functionally and phenotypically distinct immunoregulatory T cell subpopulation.

A CD4(+) T cell subpopulation defined by the expression levels of a particular cell surface molecule (e.g. CD5, CD45RB, CD25, CD62L or CD38) bears an autoimmune-preventive activity in various animal models. Here we show that the expression of CD25 is highly specific, when compared with other molecules, in delineating the autoimmune-preventive immunoregulatory CD4(+) T cell population. Furthermore, although CD25 is an activation marker for T cells, the following findings indicate that immunoregulatory CD25(+)CD4(+) T cells are functionally distinct from activated or anergy-induced T cells derived from CD25(-)CD4(+) T cells. First, the former are autoimmune-preventive in vivo, naturally unresponsive (anergic) to TCR stimulation in vitro and, upon TCR stimulation, able to suppress the activation/proliferation of other T cells, whereas the latter scarcely exhibit the in vivo autoimmune-preventive activity or the in vitro suppressive activity. Second, such activated or anergy-induced CD25(-) spleen cells produce various autoimmune diseases when transferred to syngeneic athymic nude mice, whereas similarly treated normal spleen cells, which include CD25(+)CD4(+) T cells, do not. Third, upon polyclonal T cell stimulation, CD25(+)CD4(+) T cells express CD25 at higher levels and more persistently than CD25(-)CD4(+) T cell-derived activated T cells; moreover, when the stimulation is ceased, the former revert to the original levels of CD25 expression, whereas the latter lose the expression. These results collectively indicate that naturally anergic and suppressive CD25(+)CD4(+) T cells present in normal naive mice are functionally and phenotypically stable, distinct from other T cells, and play a key role in maintaining immunologic self-tolerance.

Animals↗