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Biomedical subjects

T Akaike

Publications and source records attributed to T Akaike.

At least 181 records · Page 10Linked to original sources
PubMed1995

High cell-density culture system of hepatocytes entrapped in a three-dimensional hollow fiber module with collagen gel.

A compact three-dimensional (3D) module is needed for hepatocyte culture in order to develop an effective hybrid artificial liver system that can retain hepatocellular structure and differentiated functions. We treated the 3D module with collagen gel to entrap rat hepatocytes. This method yielded a high hepatocellular density (2 x 10(7) cells/ml) over a period of 14 days and maintained the secretion of albumin and ureogenesis at the same level as the control monolayer method. The ammonia removal remained at 43% of the Day 0 value over 8 days of perfusion. Our data show that this approach may be useful for liver support therapy in an extracorporeal circuit.

Albumins↗
PubMed1995

Antiviral effect of oryzacystatin, a proteinase inhibitor in rice, against herpes simplex virus type 1 in vitro and in vivo.

Oryzacystatin (OC) is the first-described cystatin originating from rice seed; it consists of two molecular species, OC-I and OC-II, which have antiviral action against poliovirus in vitro (H. Kondo, S. Ijiri, K. Abe, H. Maeda, and S. Arai, FEBS Lett. 299:48-50, 1992). In the experiments reported here, we investigated the effects of OC-I and OC-II on the replication of herpes simplex virus type 1 (HSV-1) in vitro and in vivo. HSV-1 was inoculated onto monolayers of monkey kidney epithelial cells (CV-1 cells) at a multiplicity of infection of 0.1 PFU per cell. After adsorption of the virus onto cells, the cultures were incubated in the presence of either OC-I or OC-II in the concentration range of 1.0 to 300 microM, and the supernatant virus yield was quantitated at 24 h. The effective concentration for 90% inhibition of HSV-1 was 14.8 microM, while a cytotoxic effect on CV-1 cells without infection of HSV-1 was not observed below 500 microM OC-I. Therefore, the apparent in vitro chemotherapeutic index was estimated to be more than 33. In the mouse model of HSV-1-induced keratitis and encephalopathy, topical administration of OC-I to the mouse cornea produced a significant decrease in virus production in the cornea (mean virus yields: 3.11 log10 PFU in the treated group and 4.37 log10 PFU in the control group) and significant improvement in survival rates (P = 0.01). The in vivo antiherpetic effect of OC-I was comparable to that of acyclovir, indicating that topical treatment of HSV-1 infection in humans with OC-I might be possible. Our data also suggest the importance of some thiol proteinases, which may be derived from either the host's cells or HSV-1, during the replication process of HSV-1.

Animals↗
PubMed1995

Effect of neurotropic virus infection on neuronal and inducible nitric oxide synthase activity in rat brain.

To elucidate the potential role of inducible nitric oxide synthase (iNOS) and neuronal constitutive nitric oxide synthase (cNOS) in the pathogenesis of virus-induced encephalopathy, the activities of both NOS isoforms were determined in the brains of rats infected with Borna disease virus (BDV) or rabies virus. iNOS activity strongly increased, whereas neuronal cNOS activity significantly decreased in a time-dependent manner after either BDV or rabies virus infection. Choline acetyltransferase activity in the brain remained unchanged during both virus infections, suggesting that the decrease in cNOS activity does not reflect a generalized neuronal loss. Immunohistochemistry and Northern blot analyses indicate that the decrease in neuronal cNOS activity is due to a decrease in cNOS protein and mRNA synthesis. These results suggest that both an excessive generation of NO by activated macrophages or microglia, as well as a decrease of NO production in neurons may contribute to the neuropathogenesis of neurotropic virus infections.

Animals↗
PubMed1995

Primary cultured murine hepatocytes but not hepatoma cells regulate the cell number through density-dependent cell death.

The mechanisms by which hepatocytes regulate their cell numbers in culture have been examined. We found that when murine hepatocytes were cultured at an overconfluent stage, the number of viable cells were reduced to that of the confluent stage 48 h later by cell death. Cell death was accompanied by LDH release, and it was observed only in primary cultured hepatocytes but not in hepatoma cells. Genomic DNA analysis using electrophoresis showed that DNA fragmentation, a biochemical hallmark of apoptosis, was induced in superconfluent cultures of hepatocytes in a cell-density-dependent fashion, but not in pre-confluent cells. DNA fragmentation was rapidly induced 2 h after the beginning of the in vitro culture and continued up to 24 h later. Flow cytometry analysis demonstrated that the nuclei from the hepatocytes in a high density culture were condensed and that the DNA content was reduced. These data suggest that the mechanism of cell death is apoptosis. The DNA fragmentation seen in the high density hepatocyte culture was not observed in hepatoma cell lines. Moreover, apoptosis was induced in hepatocytes of MRL/lpr mice, suggesting that the Fas antigen was not involved in the apoptotic process. Apoptosis was inhibited by a protein synthesis inhibitor, cycloheximide, and by a calmodulin antagonist, W-7. Taken together, the results indicate that high density culture of murine hepatocytes though not hepatoma cells regulate their cell numbers by an apoptotic mechanism. The apoptosis is dependent on de novo protein synthesis and intracellular calcium metabolism.

Journal Article↗
PubMed1995

Protective effect of hepatocyte growth factor on interferon-gamma-induced cytotoxicity in mouse hepatocytes.

We examined the interactive effect of several cytokines (interleukin-1 beta [IL-1 beta], tumor necrosis factor alpha [TNF-alpha], interferon gamma [IFN-gamma], IL-6, IFN-alpha/beta, and hepatocyte growth factor [HGF]) presumably involved in hepatitis, on primary cultured murine hepatocytes. Among these cytokines, only IFN-gamma induced LDH release from hepatocytes in both time- and dose-dependent fashions. The cytotoxic effect was inhibited by antiserum-containing anti-mouse IFN-gamma monoclonal antibodies (R4-6A2). Moreover, intriguingly, IFN-gamma induced DNA fragmentation in the hepatocytes in a time- and dose-dependent fashion according to the gel electrophoresis of genomic DNA and flow cytometry analysis. These results suggest that the cytotoxic effect of IFN-gamma on hepatocytes was caused by inductive apoptosis. The LDH release and DNA fragmentation induced by IFN-gamma were inhibited by HGF in a dose-dependent manner, whereas they seemed to be accelerated by TNF-alpha. Flow cytometry analysis of the nuclei of treated hepatocytes confirmed the interactions in DNA degradation. The DNA synthesis of cultured hepatocytes was also reduced by IFN-gamma but recovered by hepatocyte growth factor. Taken together, IFN-gamma is presumed to be a critical cytokine in hepatic damage, and the network composed of IFN-gamma, TNF-alpha, and HGF may play an important role in the regulation of liver injury.

Animals↗
PubMed1995

Superoxide radical generation from heterocyclic amines.

Highly purified cytochrome P-450 reductase (also called cytochrome C reductase; EC 1.6.2.4.) and NADPH were found to generate superoxide radical (O2.-) from 11 different heterocyclic amines (HCAs) as identified by electron spin resonance spectroscopy (ESR) using the spin trapping method with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The signal intensity of DMPO-OOH(-O2.-) (i.e., the DMPO spin adduct of O2.-) was strongest for 2-amino-3,4-dimethylimidazo[4,5-f]-quinoline (MeIQ). O2.- generation with HCAs was decreased in the following order: 2-amino-3,8-dimethylimidazo[4,5-f]-quinoxaline (MeIQx) = 2-amino-3-methylimidazo[4,5-fl-quinoline (IQ) > 2-amino-3,4,8-trimethylimidazo[4,5-f]-quinoxaline (diMeIQx) > or = other HCAs; O2.- generation was lowest with 2-amino-3-methyl-9H-pyrido[2,3-b]indole-CH3COOH (MeA alpha C). By using Lineweaver-Burk plots, Km values of cytochrome P-450 reductase for mitomycin C, IQ, and MeIQ were determined to be 1.60 x 10(-6)M, 1.97 x 10(-5)M, and 2.83 x 10(-6) M, respectively. The N-hydroxyl derivative of 3-amino-1-methyl-5H-pyrido[4,3-b]-indole-HCI-CH3COOH (Trp-P-2), which is considered to be a key intermediate in the reaction of Trp-P-2 with cytochrome P-450 systems, yielded very little generation of O2.-. Because of the known presence of cytochrome P-450 reductase in the cell at significant amount, the present findings are an important implication for carcinogenesis and tumor promotion due to the known effect of oxygen radicals on promotion/progression, cell kill and proliferation.

Amines↗
PubMed1994

Generation of free radicals from neocarzinostatin mediated by NADPH/cytochrome P-450 reductase via activation of enediyne chromophore.

Neocarzinostatin (NCS) is one of the most potent antitumor agents. It contains a chromophore of a unique enediyne structure as its prosthetic group. Here, we report the generation of free radicals from NCS by the NADPH/cytochrome (cyt) P-450 reductase system. Free radical species, which were generated in the reaction mixture of NCS/NADPH/cyt P-450 reductase, were identified by using electron spin resonance spin trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The spin adducts of superoxide and hydroxyl radical (DMPO-OOH and DMPO-OH, respectively) were generated in the reaction of NCS with the NADPH/cyt P-450 reductase system. From kinetic analyses of DMPO-OOH generation as a function of the concentration of NCS, the Vmax/Km value of the reaction was 0.4 x 10(6) M-1min-1. In addition, we identified thiyl radical generation in this system in the presence of glutathione. These results indicate that NCS is a potent generator of free radicals in cells where cyt P-450 reductase is available. Moreover, it seems that free radicals, generated by enzymatic activation of NCS, are involved in cytotoxicity of NCS as well as in DNA damage.

Animals↗
PubMed1994

Vasodilator effect of carboxy-2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl in the coronary circulation: in vivo and in vitro studies.

2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) derivatives, new radical forms of nitric oxide (NO) antagonists, are reported to react with NO and generate NO2 and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl (PTI) derivatives. We found that carboxy-PTI, a water-soluble derivative of PTI, showed a potent vasodilator effect in the canine coronary artery system. In anesthetized dogs, intracoronary infusion of carboxy-PTI significantly increased the coronary flow in a dose-dependent manner without altering systemic hemodynamic variables. This coronary flow increasing effect of carboxy-PTI was not influenced by pretreatment with either NG-nitro-L-arginine methyl ester or 8-phenyltheophylline or autonomic blockade. However, the flow increasing effect of carboxy-PTI was abolished by reducing carboxy-PTI with ascorbic acid to a non-radical form of carboxy-PTI, indicating that carboxy-PTI shows its effect only in a radical form. In isolated canine coronary arterial rings, carboxy-PTI caused endothelium-independent relaxation. This relaxation response was significantly attenuated by pretreatment with methylene blue, an inhibitor of soluble guanylate cyclase. Thus, carboxy-PTI has an endothelium-independent coronary vasodilator effect in both large conduit arteries and small resistance vessels. The results of the in vitro experiment suggested that the activation of soluble guanylate cyclase of the vascular smooth muscle cell may be involved, at least in part, in the vasodilator mechanism of carboxy-PTI in large conduit arteries.

Animals↗
PubMed1994

Therapeutic effects of imidazolineoxyl N-oxide against endotoxin shock through its direct nitric oxide-scavenging activity.

We recently found a new class of nitric oxide (NO) antidote, i.e., 2-phenyl-4,4,5,5,-tetramethylimidazoline-1-oxyl-3-oxide derivatives (PTIOs). It has a potent inhibitory action against endothelium-derived relaxing factor. Here, we report the effect of a water-soluble carboxy derivative of PTIO (carboxy-PTIO) on endotoxin shock. Endotoxin [lipopolysaccharide (LPS)] (10 mg/kg) was injected into Wistar rats, and the mean arterial blood pressure (MABP), heart rate and urinary parameters were continuously measured. The MABP and urine volume gradually decreased during 1 hr after LPS injection, and within 4 hr, both values decreased to 50-70%. When carboxy-PTIO at 0.056-1.70 mg/kg/min was infused for 1 hr beginning 90 min after the LPS injection, the hypotension, renal dysfunction and survival rate were much improved and the state of shock was avoided. Carboxy-PTIO administered to normal rats did not affect each parameter. Measurement of urinary output of carboxy-PTIO and carboxy-2-phenyl-4,4,5,5-tetramethylimidazole-1-oxyl (carboxy-PTI), which is a reaction product of carboxy-PTIO and NO, showed that conversion of carboxy-PTIO to carboxy-PTI was augmented by LPS treatment due to the increased production of NO, and that the enhanced conversion (PTIO-->PTI) was significantly inhibited by administration of N omega-monomethyl-L-arginine. This indicates that carboxy-PTIO exhibits a potent therapeutic value in endotoxin shock through the direct scavenging action against NO.

Animals↗
PubMed1994

Multiple functions of nitric oxide in pathophysiology and microbiology: analysis by a new nitric oxide scavenger.

A wide range of biological functions of nitric oxide (NO) was analyzed using a newly discovered nitric oxide scavenger, 2-phenyl-4,4,5,5-tetramethylimidazolineoxyl-1-oxyl-3-oxide (PTIO) or its water-soluble derivative carboxy-PTIO. The chemistry is very simple in that NO was oxidized by PTIO, yielding one mole each of NO2 and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl. Based on the potent NO-scavenging activity of PTIO derivatives, the diverse functions of NO under physiological states as well as various pathological conditions such as endotoxin shock and viral diseases are now explicated. It was found that PTIO and carboxy-PTIO showed significant inhibitory activity against a series of biological actions of NO: (1) endothelium-dependent vascular relaxation in an ex vivo system, (2) pathogenicity of NO produced excessively in endotoxin shock in rats and in influenza virus pneumonitis in mice, and (3) enhanced vascular permeability in solid tumors mediated by NO. PTIO directly extinguishes NO generated by NO synthase (NOS) without affecting NOS activity, which is a clear contrast to NOS inhibitors. Therefore, characterization of this unique mode of action of PTIO appears to be helpful not only in understanding of the pathophysiological role of NO but also in the treatment of various diseases caused by excessive production of NO.

Animals↗
PubMed1994

Preparation of nanoparticles bearing high density carbohydrate chains using carbohydrate-carrying polymers as emulsifier.

A novel method of preparing nanoparticles bearing high density carbohydrate chains on their surface is described. Carbohydrate-bearing nanoparticles of poly(lactic acid) or polystyrene were prepared by the solvent evaporation method using a carbohydrate-carrying polystyrene derivative which served as both an emulsifier and a surface coating. The diameter of the obtained nanoparticles ranged from 80 to 300 nm depending on the concentration of the polystyrene derivative. As the concentration of the polystyrene derivatives increased the nanoparticle diameter decreased, indicating that the polystyrene derivatives worked as an emulsifier. The obtained particles were specifically aggregated by carbohydrate-specific lectin, showing that the polystyrene derivative was retained on the particle surfaces and expressed carbohydrate residues. The density of carbohydrates on the particle surfaces was determined to be 3-5 molecules per square nanometre. The particles prepared by the present method were stably dispersed and hardly aggregated in aqueous media during storage and centrifugal treatment compared with the post-coated particles that were prepared by adsorbing polystyrene particles with the polystyrene derivative. In vitro study with isolated rat hepatocytes revealed that surface carbohydrate chains were recognized by hepatocytes.

Animals↗
PubMed1994

Potentiation of infectivity and pathogenesis of influenza A virus by a house dust mite protease.

Common house dust mites (e.g., Dermatophagoides farinae) excrete a serine-type (Df) protease. Df protease obtained from cultured mites enhanced viral replication in vitro via proteolytic cleavage of viral hemagglutinin (HA) into HA1 and HA2, which confers potent viral infectivity. Its potency is 2- to 5-fold higher than bovine trypsin or human plasmin. Df protease also markedly accelerated virus propagation in vivo: A minute quantity of protease (estimated delivered amount, 0.8-3.2 micrograms) produced approximately 4- to 100-fold increases in infectious virus in the mouse lung. Similar augmentation of viral replication by Df protease was observed in ferret models of nasopharyngeal infections of influenza virus. All extracts from ordinary house dust contained a serine-type protease that cleaved HA into HA1 and HA2. Thus, mite protease in house dust may enhance the pathogenesis of influenza virus.

Amino Acid Sequence↗
PubMed1994

Highly efficient transfection into primary cultured mouse hepatocytes by use of cation-liposomes: an application for immunization.

Transfection methods for primary cultured mouse hepatocytes were examined. Of four conventional transfection methods examined, involving use of DEAE-dextran, calcium phosphate, cation-liposomes (lipofection), and cation-multilamellar liposomes, only cation-liposomes induced highly efficient transfection into primary cultured mouse hepatocytes. The highest transfection rate reached more than 60% of the total cells. Three other commonly used cell types (CHO-K1, COS-1, 3T3-L1) were also tested as target cells, but highly efficient transfection was observed specifically in primary cultured mouse hepatocytes. The transfection remained at a high level from 6 to 48 h after the start of incubation with the cation-liposome-DNA complex in the absence of serum, and the transfection rate decreased in inverse relation to the increase in cell density. The transfection was inhibited by free low density lipoprotein (LDL), EDTA, and an endocytosis inhibitor, cytochalasin B. These data suggest that the transfection is mediated not only by membrane fusion, as is generally accepted, but also by endocytosis. This information should be useful for research in hepatocyte biology and the development of gene therapy. As one of the applications, simple and successful immunization was achieved by administration of hepatocytes transfected with murine adhesion molecule, integrin VLA beta 1 subunit, genes into a Syrian hamster.

3T3 Cells↗
PubMed1994

Enhanced vascular permeability in solid tumor is mediated by nitric oxide and inhibited by both new nitric oxide scavenger and nitric oxide synthase inhibitor.

A newly discovered nitric oxide radical scavenger, an imidazolineoxyl N-oxide derivative, was used to investigate the role of nitric oxide radical (.NO) in the vascular permeability enhancement of solid tumor. Sarcoma-180 solid tumor in ddY mice was used for this experiment. Electron spin resonance spectroscopy was used to quantitate the reacted and unreacted scavenger. The results showed that extensive extravasation, assessed by intravenous injection of Evans blue, could be greatly suppressed by both .NO scavenger administered orally and .NO synthase inhibitor administrated intraperitoneally. This indicates that .NO is responsible for the vascular permeability in solid tumors.

Amino Acid Oxidoreductases↗
PubMed1994

Activation signal induces the expression of B cell-specific CD45R epitope (6B2) on murine T cells.

T lymphocytes express multiple forms of the leukocyte-common antigen CD45, transcribed by alternative usage of leukocyte-common antigen exon 4-6. The various isoforms of CD45R expressed differentially on T cells are involved in different stages of development and activation. The monoclonal antibody (MoAb) RA3-6B2 is established as a B cell-type isoform (B220)-specific marker. However, it reacts with certain activated T cells although the relationship between 6B2 expression and T-cell activation is unclear. We have examined the 6B2 expression on activated T cells and found that concanavalin A, anti-CD3 antibody and staphylococcal enterotoxin B (SEB) induced 6B2 expression on T cells. The expression was found on both CD4+ and CD8+ T cells and also was induced by SEB in vivo predominantly on CD8+ T cells. The 6B2+ T cells are IL-2R+ and blasted cells according to flow cytometry analysis. Therefore, the 6B2+ T cells are supposed to be in an activated stage. Enzymatic analysis demonstrated that trypsin treatment decreased the 6B2 expression, whereas neuraminidase increased the intensity on activated T cells. Neither endo-D or endo-H have any effect on the expression and there are no differences, in the results of immunoprecipitation and RT-PCR analysis, between control T cells and activated T cells. Taken together, the 6B2 epitope is presumed to be the product of CD45R modification and is expressed on activated T cells. These results illustrate a novel classification of a T-cell subpopulation bearing a 6B2 epitope.

Animals↗