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At least 595 records · Page 33Linked to original sources
PubMed2004

Anaplerotic input is sufficient to induce time-dependent potentiation of insulin release in rat pancreatic islets.

Nutrients that induce biphasic insulin release, such as glucose and leucine, provide acetyl-CoA and anaplerotic input in the beta-cell. The first phase of release requires increased ATP production leading to increased intracellular Ca(2+) concentration ([Ca(2+)](i)). The second phase requires increased [Ca(2+)](i) and anaplerosis. There is strong evidence to indicate that the second phase is due to augmentation of Ca(2+)-stimulated release via the K(ATP) channel-independent pathway. To test whether the phenomenon of time-dependent potentiation (TDP) has similar properties to the ATP-sensitive K(+) channel-independent pathway, we monitored the ability of different agents that provide acetyl-CoA and anaplerotic input or both of these inputs to induce TDP. The results show that anaplerotic input is sufficient to induce TDP. Interestingly, among the agents tested, the nonsecretagogue glutamine, the nonhydrolyzable analog of leucine aminobicyclo[2.2.1]heptane-2-carboxylic acid, and succinic acid methyl ester all induced TDP, and all significantly increased alpha-ketoglutarate levels in the islets. In conclusion, anaplerosis that enhances the supply and utilization of alpha-ketoglutarate in the tricarboxylic acid cycle appears to play an essential role in the generation of TDP.

Acetyl Coenzyme A↗
PubMed2003

Acid-initiated polymerization of epsilon-caprolactone under microwave irradiation and its application in the preparation of drug controlled release system.

Acid-initiated ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) was conducted under microwave irradiation (MI) at 2.45 GHz. At this frequency, metallic catalysts were no longer necessary. The effects of microwave power, irradiation time, epsilon-CL: acid molar ratio and acidity of acid on the polymerization were investigated. Both the rate of polymerization and the molar mass of polymer obtained were enhanced in comparison with conventional thermal method. Poly(epsilon-caprolactone) (PCL) with weight-average molar mass (Mw) over 12000 g/mol and Mw/Mn below 1.6 was synthesized in the presence of carboxylic acids such as maleic acid (MA), succinic acid (SA) and adipic acid (AA). The polymerization was also carried out when the monomer contained a certain amount of ibuprofen (IBU), by which, the IBU-PCL controlled release system was prepared directly. The release of IBU from the system was sustained from 12 h to 9 days with IBU content in weight increasing from 5 to 20%. It seems that this is a promising method to prepare drug controlled release systems.

Biocompatible Materials↗
PubMed2004

Characterization of sericin powder prepared from citric acid-degraded sericin polypeptides of the silkworm, Bombyx Mori.

Acid-degraded sericin powder (AC-SP) was prepared from aqueous solution containing citric acid-degraded sericin polypeptides of Bombyx mori. The morphological and biochemical properties of AC-SP were compared with those of alkali-degraded sericin powder (AL-SP) and hot-water degraded sericin powder (HW-SP). Based on an SEM analysis, AC-SP showed a thin film structure of 10-100 microm with good dispersity while AL-SP and HW-SP had a much larger thin film structure (<500 microm). The extract of AC-SP showed stronger trypsin inhibitor activity due to cocoon shell trypsin inhibitor (CSTI-IV) than that of HW-SP. The extract of AL-SP showed no CSTI-IV activity. It was found that AC-SP was a trypsin inhibitor complex powder and that the release of CSTI-IV from AC-SP depended on pH and ion strength. Similar powder materials were obtained when such organic acids as tartaric acid and succinic acid were used. These results suggest that the acid-degraded sericin polypeptides work as a protein matrix to which CSTI-IV may bind ionically.

Animals↗
PubMed2006

Medium-chain, even-numbered dicarboxylic acids as novel energy substrates: an update.

Medium-chain dicarboxylic acids are produced by higher plants and animals via fatty acid omega-oxidation or by beta-oxidation of longer-chain dicarboxylic acids. In plants, dicarboxylic acids are components of the natural protective polymers cutin and suberin; in animals, dicarboxylic acids are mainly oxidized in mitochondria, where they are transported through four different pathways. Their energy density is intermediate between glucose and fatty acids. Dicarboxylic acid administration does not require insulin or stimulate insulin secretion, and the beta-oxidation of dicarboxylic acids produces succinic acid, a gluconeogenic substrate. Therefore, dicarboxylic acids might be a suitable fuel substrate, particularly in clinical conditions in which marked insulin resistance and/or impairment of aerobic glycolysis occur.

Animals↗
PubMed1996

Microbial corrosion of aluminum alloy.

Several microbes were isolated from the contaminated fuel-oil in Taiwan and the microbial corrosion of aluminum alloy A356-T6 was tested by MIL-STD-810E test method. Penicillium sp. AM-F5 and Cladosporium resinac ATCC 22712 had significant adsorption and pitting on the surface of aluminum alloy, Pseudomonas acruginosa AM-B5 had weak adsorption and some precipitation in the bottom, and Candida sp. AM-Y1 had the less adsorption and few cavities formation on the surface. pH of the aqueous phase decreased 0.3 to 0.7 unit for 4 months of incubation. The corrosion of aluminum alloy was very significant in the cultures of Penicillium sp. AM-F2, Penicillium sp. AM-F5 and C. resinac ATCC 22712. The major metabolites in the aqueous phase with the inoculation of C. resinac were citric acid and oxalic acid, while succinic acid and fumaric acid were the minors.

Alloys↗
PubMed1999

[Studies on chemical constituents of seeds of Desmos chinensis Lour].

OBJECTIVE: To investigate the chemical constituents of Desmos chinensis. METHOD: Various column chromatographic techniques were employed for the isolation and purification of constituents from the ethanol extract. The structures were elucidated by spectral analysis. RESULT: Eleven compounds were isolated and identified as lawinal(1), desmosal(2), desmethoxymatteucinol(3), unonal(4), isounonal(5), desmosflavone(6), allantoic acid(7), succinic acid(8), daucosterol(9), beta-sitosterol(10) and stearic acid(11). The structures of compounds 1 and 2 were reconfirmed by NOEDS technique. CONCLUSION: Compound 2 is a new natural product and 7, 8 and 9 were found from this plant for the first time.

Annonaceae↗
PubMed2002

[Studies on chemical constituents of two plants from Costus].

OBJECTIVE: To study the chemical constituents of Costus speciosus and C. tonkinensis (Zingiberaceae) distributed in Yunnan province. METHOD: Chromatography and spectral analyses were used to isolate the constituents and elucidate their structure. RESULT: Six compounds were isolated from the rhizome of C. speciosus and elucidated as diosgenin(1), prosapogenin B of dioscin(2), diosgenone(3), cycloartanol(4), 25-en-cycloartenol(5) and octacosanoic acid(6). Four compounds were isolated from the rhizome of Costus tonkinensis and elucidated as tetracosanoic acid(7), succinic acid(8), beta-sitosterol(9) and daucosterin(10). CONCLUSION: Compounds of 3-6 were obtained from C. speciosus for the first time and compounds of 7-10 were obtained from C. tonkinensis for the first time too.

Costus↗
PubMed2004

[Studies on antibacterial activities of secondary metabolites from fungus Cephalosporium sp. AL031].

The antibacterial activity of fourteen identified compounds from secondary metabolites of fungus Cephalosporium sp. AL031 against eleven gram-positive or gram-negative bacteria in vitro was investigated by agar diffusion assay. The results suggested that two new compounds [S-(+)-5-hydroxymellein, S-(+)-7-hydroxymellein], together with four known compounds [S-(+)-mellein, 2,4-dihydroxy-3,6-dimethylbenzoic acid, 3,6-dihydroxy-2,4-dimethylbenzoic acid and succinic acid] had broad spectrum antibacterial activity. The minimum inhibitory concentrations (MIC) of these six compounds against Shigella sonnei, Mycobacterium tuberculosis and Streptococcus pneumoniae were determined. Their MIC were 0.03125 to approximately 0.5 mg/ml.

Acremonium↗
PubMed2005

[A new flavonoid glycoside from the roots and stems of Sphaerophysa salsula].

AIM: To study the chemical constituents of Sphaerophysa salsula (Pall.) DC. METHODS: Compounds were isolated by repeated chromatography, on silica gel and Sephadex LH-20 columns and identified by spectroscopic data (ESI-MS, 1H and 13C NMR, HSQC, HMBC). RESULTS: Eight compounds have been isolated and identified as: isorhamnetin-3-O-[6"-(3-hydroxy-3-methylglutaroyl)-beta-D-glucopyranoside] (I), quercitrin (II), n-butyl-O-beta-D-fructopyranoside (III), nicotinic acid (IV), succinic acid (V), erythrol (VI), D-mannitol (VII), uridine (VIII). CONCLUSION: Compound I is a new compound. Compounds I -VI were isolated from this genus for the first time.

Fabaceae↗
PubMed2006

[Studies on chemical constituents in roots of Rumex dentatus].

OBJECTIVE: To investigate the active constituents from Rumex dentatus. METHOD: Compounds were isolated by silica gel, Sephadex LH -20 and ODS column chromatography and identified by chemical and spectroscopic methods. RESULT: Ten compounds were obtained and identified as helonioside A (1), gallic acid (2), isovanillic acid (3), p-hydroxycinnamic acid (4), succinic acid (5), n-butyl-beta-D-fructopyranoside (6), quercetin (7), hexadecanoic acid 2, 3-dihydroxy propyl ester (8), beta-sitosterol (9) and daucosterol (10). CONCLUSION: Compounds 1, 3-6 and 8 were isolated from the genus of Rumex for the first time.

Fructose↗
PubMed1976

Inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in hepatoma tissue culture cells by pure cholesterol and several cholesterol derivatives. Evidence supporting two distinct mechanisms.20l.

Pure cholesterol associated in complexes with lipoproteins (whole serum and human low density lipoproteins) or esterified with succinic acid (cholesteryl succinate) and bound to albumin effectively suppresses 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity in hepatoma tissue culture (HTC) cells grown in lipoprotein-poor serum medium during short 4-hour) incubation periods. Simultaneous measurments of the kinetics of uptake of radioactive unesterified cholesterol of whole serum and cholesteryl succinate, their conversion to lipid products, and the decay in enzyme activity, suggest that the cholesterol-induced suppression is mediated by the sterol itself rather than by inhibitory lipid products derived from its metabolism. Several cholesterol derivatives such as cholestenone, 7-ketocholesterol, and 7alpha-and 25-hydroxycholesterol also suppress reductase activiy in HTC cells and are significantly more inhibitory than the pure cholesterol preparations. The decrease in enzyme activity produced by cholesterol and its derivatives is concentration-dependent and specific. [1-14C]Oleate incorporation experiments indicate that cholesterol ester formation in HTC cells is not increased at inhibitory concentrations of the steroids. These data suggest that sterol ester formation is not an obligatory process in the feedback control of HMG-CoA reductase activity. The half-life of the reductase (3 to 4 hours) is not significantly changed by cycloheximide, plus or minus whole serum, and cholesteryl succinate. In contrast, the half-life is strongly reduced when HTC cells are incubated with cycloheximide plus maximal concentrations of 25-hydroxycholesterol, 7-ketocholesterol, or cholestenone, resulting in t1/2 values of 24, 36, and 60 min, respectively. Increasing concentrations of whole serum and cholesteryl succinate have no significant effect on the apparent rate constant of inactivation of the enzyme, whereas its apparent rate of synthesis is decreased 3- and 10-fold, respectively. These results are reversed with oxygenated steroid inhibitors. The rate of synthesis of reductase is essentially unchanged as the concentrations of 25-hydroxycholesterol, 7-ketocholesterol, and cholestenone are increased in the culture medium, whereas the apparent rate constant for degradation is increased 9-, 7-, and 3-fold, respectively. HMG-CoA reductase activity in HTC cells thus appears to be modulated by two different mechanisms in which steroid structure is important. Whole serum and cholesteryl succinate specifically decrease the rate of enzyme synthesis, while 25-hydroxycholesterol, 7-ketocholesterol, and cholestenone increase the rate of inactivation of the reductase.

Alcohol Oxidoreductases↗
PubMed1990

[Experimental development of a chitosan-bonded hydroxyapatite bone filling paste].

Chitosan, a naturally occurring high molecule or weight polymer which is stable in vivo like collagen, has proved a useful biomaterial in applications such as suture thread and artificial skin. A hydroxyapatite bone-filling material was developed with chitosan sol as a binder. Measurements were made of the solubility of chitosan, and of the setting time, compressive strength, and pH value of the material. X-ray microanalysis and diffraction analysis of the material were also conducted. Chitosan is freely soluble in malic acid and succinic acid, but insoluble in citric acid and oxalic acid. The setting time of the bone-filling material tended to decrease with increase in the amounts of its CaO and ZnO components. The setting time increased with increasing ratio of sol to other (powdered) ingredients. The pH value decreased with increasing ratios of chitosan sol to the powdered ingredients. High pH values resulted from increases in both CaO and ZnO. The time between the preparation of the chitosan sol and the onset of kneading significantly affected the compressive strength of the material when set. The strength measured roughly 50% more for times between 90 and 150 minutes than for times shorter or longer than that range. Greater compressive strength was generally observed for increases in both CaO and ZnO. The results of the X-ray microanalysis of the hardened paste showed calcium crystals other than hydroxyapatite.

Bone and Bones↗
PubMed1983

Special bacterial polysaccharides and polysaccharases.

Alcaligenes faecalis var. myxogenes 10C3, which we isolated from soil, produces a water-soluble and an insoluble extracellular polysaccharide. The former (succinoglycan) is composed of glucose, galactose, pyruvic acid and succinic acid (molar proportions 7:1:1:1) with (beta 1-3)-, (beta 1-4)- and (beta 1-6)-glucosidic linkages. The latter (curdlan) is composed entirely of (beta 1-3)-linked D-glucose and forms a resilient firm gel when heated in suspension. The organism also produces extracellularly a repeating-unit octasaccharide of succinoglycan and cyclic (beta 1-2)-D-glucan. These polymers or oligomers are also produced by many strains of Agrobacterium and Rhizobium. Spontaneous mutation in ability to produce these polysaccharides or oligosaccharides occurs in these strains. The structures of succinoglycan, and similar polymers containing riburonic acid or galactose as the end residue of the side chain, were elucidated by successive fragmentation with two special enzymes obtained from Cytophaga arvensicola followed by methylation analysis. It is interesting that the unit compound in the biosynthesis of succinoglycan is identical with the unit compound in the enzymic decomposition of the polymer. Studies on curdlan gel by X-ray, 13C n.m.r. and electron-microscopic analysis and other physicochemical methods showed that the molecular structure of curdlan changes from a single helix to a triple stranded helix on heat treatment at high temperature. Curdlan seems to be useful for making new types of jelly products and may also be useful in new procedures for food production. Interestingly, curdlan possesses marked antitumour activity. Extracellular isoamylase (EC 3.2.1.68; glycogen 6-glucanohydrolase) of Pseudomonas amyloderamosa SB 15, which we isolated from soil, is very useful for elucidation of the structure of amylopectin and glycogen, and also for the commercial production of amylose or maltose alone or in combination with beta-amylase. Maltose is useful as a sugar for injection, being better than glucose. Maltitol is easily produced from maltose by chemical reduction and is used as a low-calorie sweetener. The isoamylase is also effective for enhancing the production of glucose from starch by the action of glucoamylase.

Alcaligenes↗
PubMed1982

[Analysis and stability of suxamethonium chloride. 1. Detection and quantitative determination of the intact active agent with its degradation products].

The authors developed methods permitting to follow the course of degradation in injectable solutions of suxamethonium chloride. The qualitative detection of the active agent in the presence of degradation products is achieved by thin-layer chromatography and spraying with Dragendorff's reagent and bromocresol green indicator solution. The same separation technique may be used for determining with sufficient accuracy the intact agent in the eluate, using the method of Okken and Haas. Furthermore, a modified Draganic procedure (which is based on the spectrophotometric determination of the hydrolysis products succinic acid monocholine chloride and succinic acid as a Cu-benzidine complex) is suited for estimating the degree of degradation. No previous separation is required because the molar extinction efficients of the monoester and of the acid are in agreement, so that the degree of degradation can be calculated from the sum of the molar concentrations. The value of these methods is demonstrated by analyzing experimental mixtures of the intact agent and degradation products.

Drug Stability↗
PubMed1995

Standardized method for high-resolution 1H-NMR of cerebrospinal fluid.

This study describes a standardized method for recording single-pulse 1H-nuclear magnetic resonance (1H-NMR) spectra from cerebrospinal fluid (CSF). Quantitative data for alanine, valine, threonine, and lactic acid correlated well with data obtained with conventional techniques. The pH of the samples is important for the reproducibility of the chemical shift of resonances, and should be standardized to improve recognition and assignment of resonances. A database of resonances from various metabolites is presented. Fifty compounds could be identified in CSF, 15 of which had not been observed earlier in NMR studies of CSF. We describe for the first time in the literature, to our knowledge, 3-hydroxyisovaleric acid as a regular component of many CSF samples. As examples of the diagnostic power of the technique, spectra are shown of CSF from patients with three different inborn errors of metabolism. We found high concentrations of N-acetylaspartic acid, citric acid, and succinic acid in CSF from a patient with Canavan disease. This is indirect evidence for the existence of a carrier mechanism that is shared by these di- and tricarboxylic acids.

Adult↗
PubMed2005

The effect of crystal morphology and mill type on milling induced crystal disorder.

Milling is a key process in the preparation of many solid dosage forms. One possible milling induced change is the production of small levels of disorder or amorphous material found predominantly at the surface of a powder, which could lead to significant chemical and physical instability. The influence of crystal habit on this change was investigated using beta-succinic acid, in plate like and needle like morphologies. beta-Succinic acid crystals with these habits were processed in a ball mill and a jet mill. SEM images indicated jet milled material was finer than the ball milled product. Powder X-ray diffraction of the milled powders revealed an amorphous halo at lower angles and peak broadening suggesting disorder though this could not be quantified accurately. In addition, a partial conversion during milling to the alpha form was noted. Quantitation of the alpha form in the milled powders indicated it was present at <2% (w/w). Plate and needle shaped particles had similar heats of solution pre-milling, however, all milled powders had lower heats of solution compared to the unmilled powers. The contribution of the alpha polymorph to the lower heats of solution was calculated to be insignificant. Therefore, the reduced heat of solution is attributed to a loss in crystallinity. The largest decreases were seen in the plate like morphology. These findings suggest that beta-succinic acid crystals with plate like morphology are more prone to crystallinity loss on milling compared to the needle like morphology. The mill type has also been shown to influence the final crystallinity.

Calorimetry, Differential Scanning↗
PubMed1992

Study of activated oxygen production by some thiols using chemiluminescence.

2-3-dimercapto-1-propane sulfonic acid, D-penicillamine and meso-dimercapto succinic acid, drugs widely applied as antidota against metal poisoning, and cysteine and glutathione were studied with respect to their ability to generate and to scavenge superoxide anion radical. Superoxide production and scavenging were tested by means of luminol-dependent chemiluminescence. In presence of 1 mumol/l ADP-Fe3+ only cysteine and meso-dimercapto succinic acid induced chemiluminescence which could be inhibited by superoxide dismutase. 2,3-dimercapto-1-propane sulfonic acid, D-penicillamine and glutathione acted as O2- scavengers. These thiols inhibited O2(-)-dependent lipid peroxidation thus acting as antioxidants, whereas cysteine and meso-dimercapto succinic acid accelerated peroxidation. It is suggested that the toxic side effects of thiols may be due to their ability to generate or to scavenge free radicals.

Cysteine↗