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Y Komori

Publications and source records attributed to Y Komori.

At least 55 records · Page 3Linked to original sources
PubMed1996

Role of nitric oxide in the development of tolerance and sensitization to behavioural effects of phencyclidine in mice.

1. To determine whether nitric oxide (NO) was involved in tolerance and sensitization to the effects of phencyclidine (PCP), we examined NO synthase activity and the number of NADPH-diaphorase (NADPH-d)-positive cells in discrete brain regions of saline-, acute PCP- and repeated PCP-treated mice. We also investigated the effects of a NO synthase inhibitor, NG-nitro-L- arginine methyl ester (L-NAME), on the behavioural changes induced by repeated PCP treatment in mice. 2. Acute PCP (1, 3, and 10 mg kg-1, s.c.) treatment induced dose-dependent hyperlocomotion, motor incoordination and stereotyped behaviours, consisting of sniffing, head movement and ataxia in mice. 3. In mice treated repeatedly with PCP (1, 3, and 10 mg kg-1 day-1), s.c., once a day for 14 days), the sniffing, head movement, ataxia and motor incoordination induced by PCP were attenuated (indicating the development of tolerance to these behaviours), whereas the hyperlocomotion induced by PCP was potentiated (indicating the development of sensitization to hyperlocomotion). The development of tolerance and sensitization to PCP-induced behaviours in the repeated PCP-treated mice was more marked at the dose of 10 mg kg-1 day-1) than at other doses. 4. NO synthase activity in the cerebral cortex and cerebellum, but not in the striatum and hippocampus, was significantly decreased by acute PCP (10 mg kg-1) treatment in comparison with saline treatment, and such changes in activity in the cerebral cortex and cerebellum were reversed by repeated PCP treatment (10 mg kg-1 day-1). 5. The number of neurones containing NADPH-d reactivity in the cerebral cortex, nucleus accumbens, and striatum of acute and repeated PCP-treated mice showed no change in comparison with saline-treated mice. 6. Tolerance to PCP (10 mg kg-1 day-1)-induced ataxia and motor incoordination was significantly attenuated by combined treatment with L-NAME (50 mg kg-1 day-1 i.p.). 7. Sensitization to PCP-induced hyperlocomotion was further enhanced by combined treatment with L-NAME (50 mg kg-1 day-1). However, NG-nitro-D-arginine methyl ester (D-NAME, 50 mg kg-1 day-1, i.p.), a less active enantiomer of L-NAME, had no effect, suggesting a stereospecific mechanism. 8. The PCP-induced behaviours in animals that had exhibited tolerance and sensitization to PCP (10 mg kg-1 day-1) were not influenced by acute L-NAME (5 and 50 mg kg-1, i.p.) or D-NAME (50 mg kg-1, i.p.) treatment. 9. These results suggest that NO may play an important role in the development, but not in the maintenance, of tolerance and sensitization to the effect of PCP in mice.

Animals↗
PubMed1996

Effects of a prescription of Chinese herbal medicine on snake venom-induced nephropathy in mice.

A prescription of Chinese herbal medicine, tentatively named P-19, was examined for its inhibitory effect and its mechanism using an experimental model of nephropathy induced by purified snake venom proteinase, Ac(1)-proteinase (Ac(1)-P). The treated mice were injected with 0.1 ml of crude extract of P-19 intraperitoneally every other day beginning 2 d before to 1 week after the injection of Ac(1)-P. The non-treated mice were injected with saline instead of the medicine P-19. The physiological condition and histopathological observation of the mice at one week after Ac(1)-P injection were better in the treated group than in the non-treated group. This indicates that P-19 inhibited the production of glomerular lesions induced in mice by Ac(1)-P. The physiological condition and histopathological changes in the mice were better with P-19 treatment than with P-3 treatment. Differences in the mechanism of action between the crude extract of P-3 and P-19 are not only in diuretic action but also in the changes in the glomerular basement membrane. On the basis of spectrophotometric studies, phenolic carboxylates were confirmed to be contained in the crude extract of P-19, having a different chemical structure of caffeic acid, which is the effective component in P-3. Immunohistochemical observation revealed a difference between the groups. In the non-treated mice, deposits of the venom were clearly observed in the glomerular tuft and Bowman's capsule, corresponding to the histopathological changes, within 2.5 min after the injection of Ac(1)-P. In the treated mice, the deposits were indistinct in the Bowman's capsule. The difference was considered to be caused by changes in the glomerular basement membrane after P-19 treatment.

Agkistrodon↗
PubMed1996

Properties of Ca++ release induced by puff adder lectin, a novel lectin from the snake Bitis arietans, in sarcoplasmic reticulum.

Puff adder lectin (PAL), a novel lectin venom purified from Bitis arietans, induced Ca++ release from the heavy fraction (HSR) but not from the light fraction of skeletal muscle sarcoplasmic reticulum with EC50 congruent to 10 microM. The potency of PAL was approximately 200-fold higher than that of caffeine. The bell-shaped profile of Ca++ dependence for PAL was almost the same as that for myotoxin a (MYTX), a peptide Ca++ releaser, but was different from that for caffeine. Typical blockers of Ca++ release channels, such as Mg+2, procaine, ruthenium red and ryanodine, markedly reduced PAL-induced Ca++ release from HSR. Interestingly, PAL inhibited 125I-MYTX binding to HSR with IC50 approximately equal to 20 microM. Scatchard analysis revealed that the mode of inhibition by PAL was noncompetitive, which suggests that PAL binds to a different site from that of MYTX. PAL did not affect 3H-ryanodine binding to HSR. These results suggest that PAL binds to a different site from that of MYTX to cause Ca++ release from HSR with novel properties.

Animals↗
PubMed1996

The role of nitric oxide in dizocilpine-induced impairment of spontaneous alternation behavior in mice.

We investigated the role played by nitric oxide in the dizocilpine-induced impairment of both spontaneous alternation behavior in a Y-maze and of performance in a multiple-trial passive avoidance task in mice. Dizocilpine (0.1 mg/kg) impaired the spontaneous alternation behavior and the retention of passive avoidance without affecting acquisition in the multiple-trial passive avoidance task. NG-nitro-L-arginine methylester (L-NAME), an inhibitor of nitric oxide (NO) synthase, dose-dependently impaired the spontaneous alternation behavior, but had no effect on either the acquisition or retention of passive avoidance. NG-nitro-D-arginine methylester had no effect on either task. The inhibitory effect of L-NAME on the spontaneous alternation behavior was completely reversed by the coadministration of L-arginine. Pretreatment with L-arginine ameliorated the dizocilpine-induced impairment of spontaneous alternation behavior, but not the impairment of the retention of passive avoidance. S-Nitroso-N-acetylpenicillamine, a generator of NO, completely inhibited the dizocilpine-induced impairment of spontaneous alternation behavior. Finally, the impairment of spontaneous alternation behavior caused by dizocilpine was significantly diminished by pretreatment with dibutyryl cyclic GMP. These results suggest that, although N-methyl-D-aspartate receptors play a critical role in both spatial working memory and long-term memory processes assessed by spontaneous alternation behavior and the passive avoidance, respectively, different neuronal mechanisms may be involved in these two processes. Further, it is suggested that the NO/cyclic GMP system may play a role in spatial working memory.

Animals↗
PubMed1996

[Etiology and hemodynamics of esophago-gastric varices].

The hemodynamics of the portal area, particularly of the left gastric vein in cases of esophago-gastric varices with portal hypertension have revealed that only one-third are featuring hepatofugal collateral flow (Type I), while hepatopetal and/or to and fro flow (Type II) forms make up about two-thirds. Furthermore, regarding the supply of blood to the varices, in all cases a contribution of arterial blood inflowing through the left gastric artery to the upper part of the stomach was found. Therefore, concerning the etiology of varices other than that due to hepatofugal collaterales, a hyperdynamic state of the upper part of the stomach area has been considered as an important factor. With regard to the micro-circulation of the gastric wall, it was proved that the hyperdynamic state was caused by an increase in submucosal arterio-venous anastomoses, and this was concluded to be directly responsible for the etiology of the varices. Therefore, the appropriate therapeutic approach to varices should as the rule be based on interruption both of hepatofugal collaterales and arterial flow, or the drainage of the hypertensive state of the local venous system.

Adult↗
PubMed1995

Primary structure of a coagulant enzyme, bilineobin, from Agkistrodon bilineatus venom.

The amino acid sequence and disulfide bridge location of the coagulant enzyme, named bilineobin, isolated from the venom of Agkistrodon bilineatus was determined by Edman sequencing of the peptides derived from digests with cyanogen bromide, clostripain, Staphylococcus aureus V8 protease, trypsin, and chymotrypsin. This enzyme has a molecular weight of 57,000 Da by sodium dodecyl sulfate-polyacrylamide gel electrophoresis; however, bilineobin consists of 235 amino acids and has a calculated molecular weight of 26,481. The enzyme contains fucose, GlcNAc, galactose, mannose and NeuAc and six N-linked glycosylation consensus sites. The carboxyterminal amino acid, proline, was determined using carboxypeptidase Y. The six disulfide bonds of bilineobin link Cys78 to Cys234, Cys120 to Cys188, Cys178 to Cys203, Cys7 to Cys141, Cys152 to Cys167, and Cys28 to Cys44. The amino acid sequence similarity to flavoxobin (T.C. Shieh et al., 1988, J. Biochem (Tokyo) 103, 596-605) and batroxobin (N. Itoh et al., 1987, J. Biol. Chem. 262, 3132-3135) was 67%. The deglycosylated enzyme more rapidly generated fibrinopeptide A than native bilineobin.

Agkistrodon↗
PubMed1995

The protective effect of tetrahydrobiopterin on the nitric oxide-mediated inhibition of purified nitric oxide synthase.

The nitric oxide synthases (NOS) are a class of enzymes responsible for the generation of NO via an oxygen and NADPH dependent oxidation of the amino acid arginine. These enzymes are ironheme proteins which contain FAD and FMN and, enigmatically, require tetrahydrobiopterin (BH4). NOS has recently been shown to be subject to inhibition by its product, NO. Preliminary data by us indicate that a possible role for BH4 is to prevent and/or reverse the NO-mediated inhibition of NOS. The objective of this study was to elucidate the mechanism by which BH4 protects NOS against NO inhibition. Protection of NOS from NO inhibition was observed by both BH4 and the BH4 regeneration system, dihydropteridine reductase (DHPR)/NADH. NO, rather than an oxidation product, appears to be the inhibitory species. Protection by BH4 is not likely due to a simple chemical reaction between BH4 and NO or its oxidation product, NO2. The results are consistent with a protective mechanism by which BH4 may act as a nonstoichiometric reducing agent for a redox active enzyme component, such as the ironheme, to prevent NO ligation.

Amino Acid Oxidoreductases↗
PubMed1995

The role of thiols in the apparent activation of rat brain nitric oxide synthase (NOS).

The role of thiols on the activation and/or stabilization of rat brain nitric oxide synthase (NOS) has been investigated. It was found that thiols are not necessary for stabilizing or protecting the protein during purification but are required during enzyme turnover for maximum activity. In the complete absence of thiols but with added tetrahydrobiopterin, the enzyme retained a low basal activity. Thiol addition to a thiol-deplete preparation of the enzyme resulted in a 4 to 7-fold increase in activity when measured after 15 min. High concentrations of dihydropteridine reductase also caused an apparent activation of NOS and was capable of replacing thiols. The data presented is consistent with a cofactor role for thiols. The possibility that they serve as reducing agents for the regeneration of tetrahydrobiopterin from dihydrobiopterins is discussed.

Animals↗
PubMed1995

Role of nitric oxide in learning and memory and in monoamine metabolism in the rat brain.

1. We investigated the effects of NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthase, on the performance of rats in a radial arm maze and in habituation tasks, and on monoamine metabolism in the brain. 2. Daily administration of L-NAME (10-60 mg kg-1) resulted in a dose-dependent impairment of performance during the acquisition of the radial arm maze task, while it failed to affect performance in those rats that had previously acquired the task. 3. The rate of decrease in locomotor activity in the habituation task in the L-NAME-treated rats was significantly less than that in control rats. 4. NG-nitro-D-arginine methyl ester (D-NAME, a less active inhibitor of NO synthase) showed no effects in the above behavioural tasks. 5. NO synthase activity was significantly decreased in both the L-NAME and D-NAME-treated rats, with the magnitude of inhibition being greater in the L-NAME-treated animals. 6. The content of 5-hydroxyindoleacetic acid (5-HIAA) in the hippocampus and the 5-HIAA/5-hydroxytryptamine ratio in the hippocampus and cortex were significantly decreased in the L-NAME (60 mg kg-1)-treated rats compared with these values in the controls. 7. Striatal 3,4-dihydroxyphenylacetic acid (DOPAC) content was significantly increased in the L-NAME (60 mg kg-1)-treated rats compared with the values in the controls, while the DOPAC/dopamine ratio was not changed. 8. These results suggest that: (i) NO may play an important role in performance during the acquisition,but not retention, of the radial arm maze task, and (ii) that endogenous NO may be involved in the regulation of monoamine metabolism.

Animals↗
PubMed1995

[Evaluation of the residual functional reserve and the early regeneration after the hepatic resection using asialoglycoprotein receptor imaging agent].

99mTc-DTPA-galactosyl human serum albumin (99mTc-GSA) is a newly developed liver imaging ligand which specifically binds to asialoglycoprotein receptor on the hepatic cell surface. We investigated whether 99mTc-GSA scintigraphy was able to be used as indexes for the residual functional reserve and the early regeneration of the hepatocyte after the hepatic resection. Four patients with metastatic liver cancer, 3 patients with hepatocellular carcinoma, and 1 patient with cholangiocellular carcinoma were studied. Basically, each patient was examined 4 times (before, 3, 10, 20 days after the operation). Immediately after i.v. injection of 185 MBq (3 mg) of 99mTc-GSA, serial images and dynamic data were obtained. Serial changes of HH15, as an index of blood clearance of the tracer calculated from the uptake ratio of heart at 15 minutes to that at 3 minutes, and LHL15, as an index of hepatic accumulation calculated from the uptake ratio of liver to liver plus heart at 15 minutes after the injection were analyzed before and after hepatectomy. Three out of 4 lobectomy patients which showed increased HH15, and decreased LHL15 as compared with the preoperative data were considered to be decreased residual hepatic functional reserve. The remaining one lobectomy patient showed increased HH15, but increased LHL15 inversely. One patient of two partial resections of hepatocellular carcinoma with liver cirrhosis demonstrated transiently decreased HH15, and increased LHL15. Two patients with metastatic liver cancer (one partial resection, six partial resections) showed decreased HH15, and increased LHL15. Postoperatively increased hepatic accumulation was presumed to be increased functioning hepatocyte or transiently increased asialoglycoprotein receptor on the cell surface by up-regulation. 99mTc-GSA scintigraphy might be helpful for non-invasive method to detect the residual functional reserve and the early regeneration of the hepatocyte after the hepatic resection.

Aged↗
PubMed1994

Nitric oxide inhibits neuronal nitric oxide synthase by interacting with the heme prosthetic group. Role of tetrahydrobiopterin in modulating the inhibitory action of nitric oxide.

The objective of this study was to elucidate the mechanism by which nitric oxide (NO) inhibits NO synthase. Previous studies revealed that NO inhibits unpurified preparations of NO synthase. In the present study, the mechanism by which NO inhibits purified neuronal NO synthase from rat cerebellum was examined. The rate of L-citrulline formation from L-arginine was non-linear despite the presence of excess substrate and cofactors and was further inhibited by 30% by 200 units/ml superoxide dismutase. In contrast, 30 microM oxyhemoglobin increased NO synthase activity by 2-fold and made the reaction rate linear. These observations were consistent with the hypothesis that enzymatically generated NO inhibits NO synthase activity. Exogenous NO (0.1-10 microM) (but not NO2, nitrite, or nitrate) also inhibited NO synthase, and enzyme inhibition was not competitive with L-arginine. NO synthase inhibition by NO and other heme ligands supports the view that heme is involved in the catalytic activity of NO synthase. Oxyhemoglobin prevented but could not reverse enzyme inhibition by NO. NO synthase inhibition by NO was markedly diminished and reversed, however, by tetrahydrobiopterin (50 microM) or a tetrahydrobiopterin-regenerating system, and the latter made the reaction rate linear. In contrast, NO synthase inhibition by NO was markedly enhanced by heme oxidants (10 microM methylene blue; 3 microM ferricyanide), and these oxidants directly inhibited NO synthase activity. These observations suggest that NO interacts with enzyme-bound ferric heme to inhibit NO synthase activity. In support of this view, NO inhibited enzyme activity in the absence of turnover, when the heme iron is in the ferric state, and this inhibition was reversed by tetrahydrobiopterin. Therefore, the oxidation state of heme iron appears to be one important determinant for the inhibitory action of NO, and tetrahydrobiopterin may increase NO synthase activity by diminishing the inhibitory action of NO.

Amino Acid Oxidoreductases↗
PubMed1994

Inhibition of purified nitric oxide synthase from rat cerebellum and macrophage by L-arginine analogs.

The inhibition of nitric oxide synthase (NOS) activity by a variety of L-arginine-related compounds has been investigated. The inhibitory properties of NG-amino-, NG-methyl-, NG-hydroxy-, NG-ethyl-, NG-allyl-, NG, NG-dimethyl-, NG-methoxy-L-arginine, and several other L-arginine derivatives were compared in NOS purified from both macrophage and rat cerebellum. Also, these compounds were tested for their potential as alternate substrates by determining their ability to elicit NADPH consumption by NOS. NG-Methoxy-L-arginine appears to be an alternate substrate for NOS, whereas most other L-arginine analogs, except for the biosynthetic intermediate NG-hydroxy-L-arginine, do not elicit significant enzyme turnover.

Amino Acid Oxidoreductases↗
PubMed1994

Biochemical characterization of hemorrhagic toxin from Crotalus viridis viridis (prairie rattlesnake) venom.

Hemorrhage, necrosis and edema are some of the effects often observed following snake bites. This paper reports studies on the isolation and biological properties of hemorrhagic toxin from Crotalus viridis viridis (Prairie rattlesnake) venom. A hemorrhagic toxin was isolated from C. v. viridis venom by Sephadex G-50, DEAE-Sephacel and Q-Sepharose column chromatographies. The hemorrhagic toxin from C. v. viridis venom was shown to be homogenous as demonstrated by a single band on polyacrylamide gel electrophoresis and immunodiffusion. Its molecular weight was approximately 54,000 daltons, and it contained 471 amino acid residues. The toxin possessed hemorrhagic activity with a minimum hemorrhagic dose (MHD) of 0.11 micrograms and hydrolytic activity on dimethylcasein, casein, azocasein, azoalbumin, azocoll and hide powder azure. Hemorrhagic and casein hydrolytic activities were inhibited by EDTA, o-phenanthroline or dithiothreitol. The toxin contained 1 mole of zinc per mole of protein and zinc is essential for both hemorrhagic and proteolytic activities. Hemorrhagic toxin possessed hydrolytic activity on the B-chain of insulin, which cleaves His(5)-Leu(6), His(10)-Leu(11), Ala(14)-Leu(15), Tyr(16)-Leu(17) and Phe(24)-Phe(25) bonds. This toxin also hydrolyzed A alpha and B beta chains of fibrinogen. Intramuscular injections of hemorrhagic toxin caused an increase of creatine phosphokinase activity in mice serum from 50.3 mU/ml to 1133 mU/ml. A toxin isolated from C. v. viridis venom was shown to have strong hemorrhagic activity. Partial characterization is reported for this major hemorrhagic toxin in C. v. viridis venom.

Amino Acid Sequence↗
PubMed1994

Characterization and amino-terminal sequence of phospholipase A2-II from the venom of Agkistrodon bilineatus (common cantil).

1. Phospholipase A2 was isolated from the venom of Agkistrodon bilineatus by Sephadex G-75 and CM-Cellulose column chromatographies. 2. The purified phospholipase A2 gave a single band on disc polyacrylamide gel electrophoresis, sodium dodecyl sulfate polyacrylamide gel electrophoresis and ODS-HPLC. 3. The enzyme preparation had a mol. wt of 14,000, isoelectric point of pH 10.12 and possessed 121 amino acid residues. 4. The enzyme hydrolyzed the phospholipids phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl inositol and phosphatidyl serine. 5. The contraction of mouse diaphragm was inhibited by phospholipase A2-II. 6. Phospholipase A2 activity of this preparation was inhibited by ethylenediamine tetraacetic acid, ethyleneglycol (beta-aminoethyl) N,N,N',N'-tetraacetic acid, p-bromophenacyl bromide or N-bromosuccinimide, but not by iodoacetic acid or diisopropyl fluorophosphate. 7. The amino-terminal sequence of the PLA2-II was determined.

Amino Acid Sequence↗
PubMed1993

Kallidin-releasing enzyme from Bitis arietans (puff adder) venom.

A kallidin-releasing enzyme with arginine ester hydrolytic activity was isolated from Bitis arietans venom by Sephadex G-75, DEAE-cellulose, and Sephadex G-100 column chromatography. This enzyme was shown to be homogeneous as demonstrated by a single band on polyacrylamide gel electrophoresis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and NH2-terminal sequence analysis. The molecular weight was determined to be 58,000 Da with an isoelectric point of 4.4. Kallidin-releasing enzyme possesses proteolytic activity demonstrated by the hydrolysis of Gly(8)-Ser(9), Ala(14)-Leu(15), Tyr(16)-Leu(17), and Phe(25)-Tyr(26) bonds of oxidized insulin B chain. This enzyme did not convert fibrinogen to fibrin, yet it did hydrolyze the A alpha, B beta, and gamma chains of fibrinogen. The enzyme was shown to cleave a kininogen analog with the release of kallidin. Arginine ester hydrolytic activity of the preparation was inhibited by diisopropyl fluorophosphate and benzamidine hydrochloride, suggesting that serine and glutamic acid or aspartic acid are involved in this activity. This protein was stable to heat and over the pH range of 3-12.

Amino Acid Sequence↗
PubMed1993

The effect of nonionic detergents on the activity and/or stability of rat brain nitric oxide synthase.

The results of this study indicate that the addition of low concentrations of a nonionic detergent such as those represented by the Tween, Brij, or Triton classes causes an apparent activation of nitric oxide synthase. It is possible that this apparent activation is due to the ability of these detergents to stabilize the protein. The stabilizing influence of the detergents may be a result of inhibiting the dissociation of the dimeric protein into monomers or the dissociation of an essential cofactor or prosthetic group from the active enzyme. Regardless of the mechanism of action, the addition of low concentrations of nonionic detergents results in longer and increased nitric oxide synthase activity and may be an important tool for those involved in enzymological studies of nitric oxide synthase.

Amino Acid Oxidoreductases↗