PubMed Health⌕ Search

Biomedical subjects

N Muto

Publications and source records attributed to N Muto.

At least 55 records · Page 3Linked to original sources
PubMed1994

n-hexane-induced synthesis of hepatic metallothionein is mediated by IL-6 in mouse.

The mechanism of metallothionein (MT) synthesis in the liver by n-hexane (HX) was examined. The increased synthesis of MT in the liver by HX was inhibited by dexamethasone pretreatment. Serum IL-6 was increased soon after HX injection, reaching a maximum at 8-16 hr, and then decreased, but neither IL-1 nor TNF was increased. The hepatic MT concentration reached a maximum later than did the serum IL-6 concentration, at 2 days after administration. When the MT synthesis induced by HX was inhibited by dexamethasone pretreatment, the concentration of IL-6 in the serum was suppressed to a very low level. Furthermore, the increase in concentration of hepatic MT and plasma fibrinogen was significantly decreased by the anti-mouse IL-6 monoclonal antibody. The concentration of hepatic MT was higher when the concentration of HX in the olive oil of the solution for injection was higher, even when the amount of HX administered was the same. It is suggested that the cytokine(s) is produced by the macrophage and fibroblast through injury and inflammation at the site of administration. These findings suggest that MT synthesis resulting from HX is induced indirectly through cytokine(s) production, especially IL-6.

Animals↗
PubMed1994

Effect of ascorbic acid 2-O-alpha-glucoside on hydrocortisone-induced cataract formation in developing chick embryos: II. Influence on glutathione and lipid peroxide contents in the lens.

In developing chick embryos, hydrocortisone induces cataract formation following a decrease in lens glutathione content but an increase in lipid peroxide content in lens, blood and liver. The preventive effects of ascorbic acid 2-O-alpha-glucoside (AA-2G) on these parameters were compared on cataract formation with those of ascorbic acid (AsA) and ascorbic acid 2-O-phosphate (AA-2P). In these tissues, AA-2G inhibited a decrease in glutathione content and an increase in lipid peroxide content more effectively than either AsA or AA-2P. Various tissues including lens and liver have alpha-glucosidase activity, strongly suggesting that AsA is enzymatically liberated from AA-2G in these tissues. In summary, these results suggest that AA-2G exerts a potent anti-cataract activity via a reduction in oxidative damage through AsA release.

Animals↗
PubMed1994

Enhancement by ascorbic acid 2-glucoside or repeated additions of ascorbate of mitogen-induced IgM and IgG productions by human peripheral blood lymphocytes.

In this study, the effect of ascorbic acid 2-glucoside (AA-2G), a stable derivative of ascorbic acid (AsA), or repeated additions of ascorbate on antibody productions by human peripheral blood lymphocytes (PBLs) was examined, and the physiological function of AsA was evaluated. When human PBLs were stimulated with Staphylococcus aureus Cowan I or pokeweed mitogen, AA-2G remarkably increased the numbers of IgM- and IgG-secreting cells which were detected by enzyme-linked immunospot assay. Although a single addition of ascorbate was without effect, the effect of AA-2G was remarkably inhibited by the addition of castanospermine, an alpha-glucosidase inhibitor; and moreover, repeated additions of AsA to the culture medium during the culture period enhanced the response to the same level as did a single addition of AA-2G. These results indicate that AsA has the ability to stimulate the immunoglobulin productions by AA-2G. The phytohemagglutinin-induced proliferative response of PBLs was also stimulated by AA-2G. The intracellular AsA content in PBLs cultured with AA-2G was maintained at relatively high levels during the culture period, whereas the content with a single dose of AsA reached nearly zero by the end of the experiment. These in vitro findings suggest that AA-2G and AsA function as potent immunostimulators of antibody production in humans and that the intracellular AsA content is a key parameter for establishing the immune response of PBLs.

Antibody Formation↗
PubMed1993

Cytidylate cyclase activity is stimulated via activation of a guanine nucleotide-binding protein.

Cytidylate cyclase is a membrane-bound enzyme which catalyzes the biosynthesis of cytidine 3',5'-cyclic monophosphate (cCMP) from CTP. By using a sensitive and specific enzyme immunoassay method, we evaluated the participation of guanine nucleotide-binding protein (G-protein) in the regulation of cytidylate cyclase activity in rat brain and other tissues. AlF4-, an activator of G-proteins, effectively elevated the cyclase activity. The stimulation by GTP gamma S, a nonhydrolyzable GTP analogue, was also observed in time- and concentration-dependent manner during the preincubation and this effect was competitively inhibited by the addition of GDP beta S. However, islet-activating protein and cholera toxin which affected adenylate cyclase activity had no effect on cytidylate cyclase activity. These results indicate that cytidylate cyclase is associated with a certain G-protein and its activity is regulated by the mode different from that of adenylate cyclase.

Adenylyl Cyclases↗
PubMed1993

Enhancement of in vitro antibody production of murine splenocytes by ascorbic acid 2-O-alpha-glucoside.

Using an antigen-specific plaque forming cell (PFC) assay, we have studied the effect of ascorbic acid 2-O-alpha-glucoside (AA-2G), a new stable derivative of ascorbic acid (AsA), on antibody production in cultured murine splenocytes in comparison with that of AsA. A single addition of AA-2G (0.0625-1.0 mM) remarkably stimulated both anti-SRBC (sheep red blood cell, TD antigen) and anti-TNP (trinitrophenyl, TI antigen) PFC responses in a dose-dependent manner, although AsA failed to stimulate their responses. However, repeated additions of AsA at 12-h intervals during the cultivation resulted in enhancement of the anti-SRBC PFC response, and the magnitude of stimulation was comparable to that obtained by a single addition of AA-2G. AA-2G's effect was abrogated in the presence of castanospermine (alpha-glucosidase inhibitor) in the medium, indicating that the immunostimulation brought about by AA-2G is attributed to AsA released from the glucoside by alpha-glucosidase of cultured cells. In fact, the cells maintained a certain amount of AsA for a relatively long time after exposure to AA-2G. In contrast, AsA levels in the cells treated with AsA quickly decreased. AA-2G markedly enhanced lipopolysaccharide(LPS)-induced proliferative response, and could affect the concanavalin A (Con A) response weakly. These results suggest that AsA effectively potentiates B-cell functions in the humoral immune system. Thus, we conclude that AA-2G is capable of enhancing antibody production in the cultured splenocytes via a continuous supplementation of AsA and that AA-2G is available for long-term cell cultures as a useful tool for analyzing biological function of AsA.

Animals↗
PubMed1992

Comparison of ascorbic acid and ascorbic acid 2-O-alpha-glucoside on the cytotoxicity and bioavailability to low density cultures of fibroblasts.

Ascorbic acid 2-O-alpha-glucoside (AA-2G) is a stable ascorbate derivative which has vitamin C activity in vivo and in vitro. We studied whether AA-2G exerts a prooxidant action in cultured fibroblasts from chick embryo and human skin, as does ascorbic acid. At concentrations of 0.1-1.0 mM, ascorbic acid markedly reduced the viable cell number of low density cultures within 24 hr, whereas AA-2G had no such effect. The ascorbate cytotoxicity was dependent on the cell density at the time of its addition and it was characteristic of low density cultures. This cytotoxicity was completely prevented by catalase and partially by an Fe3+ ion chelator, desferrioxamine. In the early culture stage at which a morphological change in the fibroblasts began to occur, intracellular ascorbate concentrations in low density cultures after addition of ascorbic acid were much higher than in high density cultures. However, at the same concentrations, AA-2G did not cause an elevation even in low density cultures and it was also effective on collagen synthesis at high and medium densities. These results suggest that the abnormally accumulated ascorbic acid in the cells cultured at low density possibly amplifies the generation of oxygen radicals through the reduction of Fe3+ ions and subsequent oxidative reactions, leading to cell death. Therefore, it is concluded that AA-2G which supplies an adequate amount of ascorbic acid during culture period is a bioavailable ascorbate source without cytotoxicity.

Animals↗
PubMed1992

The crystal structure and physicochemical properties of L-ascorbic acid 2-glucoside.

The stable L-ascorbic acid glucoside produced by the action of the cyclomaltodextrin glucanotransferase (CGTase, EC 2.4.1.19) from Bacillus stearothermophilus was crystallized from an aqueous solution. Determination of the molecular structure by single crystal X-ray analysis showed the compound to be 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G). The crystals are orthorhombic, space group P2(1)2(1)2(1), with unit-cell dimensions a = 11.929 A, b = 24.351 A, and c = 4.864 A. The D-glucopyranose residue has the 4C1 conformation. These conclusions are in good agreement with those based on the 13C-NMR spectrum. The general physicochemical properties of crystalline AA-2G are reported.

Ascorbic Acid↗
PubMed1992

Collagen synthesis in human skin fibroblasts is stimulated by a stable form of ascorbate, 2-O-alpha-D-glucopyranosyl-L-ascorbic acid.

We evaluated the effect of 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) on collagen synthesis in cultured human skin fibroblasts and on proliferation of fibroblasts. At concentrations of 0.1-0.5 mmol/L, AA-2G effectively stimulated collagen synthesis with an effectiveness comparable to that of L-ascorbic acid. On the other hand, 6-O-alpha-D-glucopyranosyl-L-ascorbic acid showed a weak effect. The stimulation of collagen synthesis by AA-2G was attenuated by the addition of a collagen synthesis inhibitor, L-azetidine 2-carboxylic acid, in a dose-dependent manner. In addition, AA-2G-induced stimulation of collagen synthesis could be completely inhibited by the addition of castanospermine, an inhibitor of neutral alpha-glucosidase. Relatively high alpha-glucosidase activity, which would contribute to release of ascorbic acid from AA-2G, could be detected in the lysate of cultured fibroblasts. The stimulatory activity of AA-2G on collagen synthesis was observed after 5 d in culture, whereas L-ascorbic acid tended to lose its stimulatory activity. Continuous supplementation of AA-2G (0.25 mmol/L) to culture medium for 24 d enhanced the cell growth four times that of the control. These results indicate that AA-2G is gradually cleaved by the cellular alpha-glucosidase to release L-ascorbic acid, which adequately stimulates collagen synthesis and proliferation of human skin fibroblasts.

Alkaline Phosphatase↗
PubMed1992

Bioavailability and biological activity of L-ascorbic acid 2-O-alpha-glucoside.

AA-2G is a new stable derivative of AsA which is efficiently synthesized by regioselective transglucosylation with alpha-glucosidase and CGTase. AA-2G serves as a vitamin C supplement in experimental animals. AA-2G is easily hydrolyzed in vivo by alpha-glucosidase and also synthesized as a metabolite under some specified conditions. AA-2G stimulates collagen synthesis in cultured fibroblasts and enhances antibody production in cultured splenocytes. AA-2G which has no cytotoxicity is a promising AsA derivative for medical and nutritional uses.

Animals↗
PubMed1992

Evaluation of ascorbic acid 2-O-alpha-glucoside as vitamin C source: mode of intestinal hydrolysis and absorption following oral administration.

Ascorbic acid 2-O-alpha-glucoside (AA-2G) has been reported to have antiscorbutic activity in guinea pigs. The present experiments examined the metabolic fate of AA-2G following ingestion. Oral administration of AA-2G (96 mg) to guinea pigs resulted in a remarkable increase of ascorbic acid in various tissues as well as plasma, but intact AA-2G was detected only in plasma, but intact AA-2G was detected only in plasma and urine in small amounts. The absorption efficiency of AA-2G and ascorbic acid was further determined by using everted gut sacs of rats. Ascorbic acid released from AA-2G on the mucosal side was effectively taken up across intestinal membranes into the serosal side, whereas AA-2G poorly permeated via a passive transport system. The hydrolysis of AA-2G on the mucosal surface of everted gut was completely inhibited by an alpha-glucosidase inhibitor and the hydrolytic activity of a crude membrane extract diminished to one-forth after immunoprecipitation with the antibody specific to maltase. From these results, it is concluded that ingested AA-2G serves as a vitamin C source through the hydrolysis by intestinal membrane-bound alpha-glucosidase, mainly maltase, and the subsequent absorption of released ascorbic acid.

Administration, Oral↗
PubMed1991

Evidence for the in vivo formation of ascorbic acid 2-O-alpha-glucoside in guinea pigs and rats.

In vivo formation of ascorbic acid 2-O-alpha-glucoside (AA-2G) in guinea pigs and rats given ascorbic acid (AA) orally in combination with maltose was examined. A metabolite of AA which has the same HPLC retention characteristics as authentic AA-2G was detected in the blood, urine and liver of guinea pigs 1-2 hr after their administration. The metabolite was isolated from the urine by chromatographic procedures and identified as AA-2G by its UV spectrum, non-reducibility, susceptibility to alpha-glucosidase hydrolysis, HPLC profile and elementary analysis. The same glucoside was also synthesized by rats and found in the urine, although it could not be determined qualitatively in the blood. AA-2G-forming activities of tissue homogenates from both animals were apparently correlated with their alpha-glucosidase activities and, moreover, both activities were completely inhibited by a specific neutral alpha-glucosidase inhibitor. Thus, we conclude that AA-2G is a possible metabolite produced by enzymatic alpha-glucosidation after a combined administration of AA and maltose to guinea pigs and rats.

Animals↗
PubMed1991

Characterization of Bacillus stearothermophilus cyclodextrin glucanotransferase in ascorbic acid 2-O-alpha-glucoside formation.

In this study, we characterized cyclodextrin glucanotransferase (CGTase) from Bacillus stearothermophilus in L-ascorbic acid-2-O-alpha-D-glucoside (AA-2G) formation and compared its enzymological properties with those of rat intestinal and rice seed alpha-glucosidases which had the ability to form AA-2G. CGTase formed AA-2G efficiently using alpha-cyclodextrin (alpha-CD) as a substrate and ascorbic acid (AA) as an acceptor. Several AA-2-oligoglucosides were also formed in this reaction mixture, and they could be converted to AA-2G by the additional treatment of glucoamylase. The optimum temperature for AA-2G formation was 70 degrees C and its optimum pH was around 5.0. CGTase also utilized beta- and gamma-CDs, maltooligosaccharides, dextrin, amylose, glycogen and starch as substrates, but not any disaccharides except maltose. CGTase showed the same acceptor specificity as two alpha-glucosidases, whereas its hydrolyzing activity towards AA-2G was very low compared with those of alpha-glucosidases. Cleavage profiles of AA-2-oligoglucosides by CGTase present a possible mechanism for AA-2G formation that CGTase transfers a glucose-hexamer to an acceptor at the first step and then a glucose is stepwisely removed from the non-reducing end of the product through glucoamylase-like action of this enzyme. These results indicate that CGTase is able to synthesize AA-2G more efficiently than rat and rice alpha-glucosidases and utilization of this enzyme makes the mass production of AA-2G possible.

Animals↗
PubMed1991

Successful transcatheter embolization of pseudoaneurysm associated with pancreatic pseudocyst.

Hemorrhage into a pancreatic pseudocyst is a rare event, but is the most rapidly lethal complication of chronic pancreatitis. Visceral-vessel aneurysms are an unexpectedly common finding in arteriography of patients with chronic pancreatitis. This case report describes bleeding from an anterior superior pancreaticoduodenal artery aneurysm, caused by chronic pancreatitis. The aneurysm was successfully treated by embolization with a steel coil.

Aneurysm↗
PubMed1990

[Augmentation in mitogen-induced proliferation of rat splenocytes by low dose whole body X-irradiation].

The hypothesis of radiation hormesis has been proposed. To elucidate the hormetic effect on the immune system, we studied the effect of low dose whole body irradiation on the in vitro mitogen-induced proliferation of rat thymocytes and splenocytes. The rats were irradiated with low doses (0.01-2 Gy) of X-ray and the cells were cultivated in the presence of various mitogens. The cell proliferation was evaluated by the incorporation of 3H-thymidine into the cells. Concanavalin A (Con A)-induced proliferation of splenocytes prepared at 4 hr after irradiation was augmented with 0.05 Gy, whereas that of thymocytes was not affected. Irradiation of rats with 0.05 Gy also induced the enhanced proliferation of splenocytes stimulated by phytohemagglutinin or lipopolysaccharide, though their responses were lower than that by Con A. This augmentation in mitogen-induced proliferation of splenocytes was observed within a few hours after irradiation, being a temporary effect. These results suggest that very low dose whole body irradiation possibly induce a hormesis-like effect on the immune splenocytes.

Animals↗
PubMed1990

Formation of a stable L-ascorbic acid alpha-glucoside by mammalian alpha-glucosidase-catalyzed transglucosylation.

Enzymatic transglucosylation from maltose to L-ascorbic acid (AA) with mammalian tissue homogenates was determined by a high-performance liquid chromatography method and compared with the reaction catalyzed by alpha-glucosidase from Aspergillus niger. The homogenates of small intestine and kidney had a high transglucosylase activity to form a new type of glucosylated AA, which was associated with alpha-glucosidase activity. The new compound was demonstrated to be an equimolar conjugate of AA and glucose by the spectral and quantitative analyses. In particular, it showed a high stability in a neutral solution and no reducing activity toward cytochrome c and a dye. These properties were very different from those of AA and L-ascorbic acid alpha-glucoside formed with alpha-glucosidase from A. niger, but they were consistent with those of L-ascorbic acid 2-O-phosphate and L-ascorbic acid 2-O-sulfate. Moreover, it exhibited a reducing power associated with AA after mild acid hydrolysis or treatment with rat intestinal alpha-glucosidase. These results indicate that it should be assigned the 2-O-alpha-glucoside structure. Consequently, it is concluded that mammalian alpha-glucosidase is able to form a very stable and nonreducing form of glucosylated AA through a specific transglucosylation reaction distinct from that of microbial alpha-glucosidase.

Animals↗
PubMed1990

Development of a sensitive enzyme immunoassay for OPC-7251, a novel antimicrobial agent for percutaneous application.

A sensitive enzyme immunoassay for OPC-7251, a novel pyridone carboxylic acid antimicrobial agent, was developed and applied for the determination of human plasma levels. OPC-7251 was coupled to bovine serum albumin through a formation of N-hydroxysuccinimide ester. By immunization of rabbits, highly specific antiserum was raised. Using the antiserum and beta-D-galactosidase-labeled hapten, the homologous assay system allowed the detection of 2 pg of this compound. Plasma samples were precisely analyzed down to the minimum value of 200 pg/ml after heat treatment. The system was further validated by the recovery test and correlation with the HPLC analyses. Percutaneous application of 10 g of 1% OPC-7251 cream to healthy volunteers resulted in the peak plasma value of 1.6 ng/ml about 8 hours after dosing, indicating extremely low absorption efficiency through a transdermal system.

Administration, Cutaneous↗