ABSTRACT
Water pollution by pesticides and other chemical contaminants is a subject of major importance due to the risk for human health and the environment. The search for remediation processes able to withdraw chemical contaminants from water and to allows water reuse is an urgent need. Herein, a simple and cheap system for pesticides removal was constructed and evaluated using water samples contaminated with two widely used herbicides (imazapic and imazethapyr, at g L-1 level). Operation parameters and process efficiency, in terms of removal rate in the reclaimed water and degradation rate of pesticides in the dry residue, were quantitatively determined. The model was tested in real-world field experiments and was able to remove more than 99.95% of both contaminants from a 10â¯L solution containing 4.16⯱â¯0.94â¯g of imazethapyr and 1.31⯱â¯0.17â¯g of imazapic, generating reusable water with minimum volume loss (<2.5%). Liquid chromatography coupled to mass spectrometry was used to determine the herbicides content in all samples and to estimate the degree of degradation of the substances as well as the occurrence of transformation products of imazapic and imazethapyr. The system efficiency in removing contaminants of emerging concern from surface water was also evaluated. The process have generated output water with undetected levels for two fungicides present in a local river in Southern Brazil.
Subject(s)
Pesticides/isolation & purification , Water Pollutants, Chemical/isolation & purification , Water Purification/instrumentation , Brazil , Chromatography, Liquid/methods , Imidazoles/isolation & purification , Mass Spectrometry/methods , Nicotinic Acids/isolation & purification , Rivers/chemistry , Water Pollutants, Chemical/analysis , Water Purification/economics , Water Purification/methodsABSTRACT
The existing form of an ionizable organic compound can simultaneously affect its soil adsorption and plant bioactivity. In this experiment, the adsorption and bioactivity of two weak acid herbicides (WAHs), imazethapyr and 2,4-D, were studied to explore the predominant mechanism by which the soil pH and the addition of biochar can influence the phytotoxicity of WAHs in soil. Then, the WAH concentration extracted by hollow fiber-based liquid-phase microextraction (CHF-LPME), the in situ pore water concentration (CIPW) and the added concentration (CAC) were employed to estimate the phytotoxicity. The results showed that with increased pH from 5.5 to 8.5, the phytotoxicity of the WAHs to rice increased about 1-fold in the soil, but decreased in aqueous solutions, the IC50 values for imazethapyr and 2,4-D at pH 5.0 were 3- and 2-fold higher than that at pH 8.0. In addition, the soil adsorption decreased, indicating that the adsorption process was the dominant factor for the variation of the phytotoxicity of the WAHs in the tested soil instead of the decreasing bioactivity. The concentration that inhibits plant growth by 50% (IC50) calculated by the CAC in different pH and biochar soils ranged from 0.619 to 3.826â¯mg/kg for imazethapyr and 1.871-72.83â¯mg/kg for 2,4-D. The coefficient of variation (CV) of the IC50 values reached 65.61% for imazethapyr and 130.0% for 2,4-D. However, when IC50 was calculated by CIPW and CHF-LPME, the CVs of the IC50 values decreased to 23.51% and 36.23% for imazethapyr and 40.21% and 50.93% for 2,4-D, respectively. These results suggested that CIPW and CHF-LPME may be more appropriate than CAC for estimating the phytotoxicity of WAHs.
Subject(s)
2,4-Dichlorophenoxyacetic Acid/toxicity , Charcoal , Herbicides/toxicity , Nicotinic Acids/toxicity , Oryza/drug effects , Soil Pollutants/toxicity , Adsorption , Herbicides/analysis , Herbicides/isolation & purification , Hydrogen-Ion Concentration , Liquid Phase Microextraction , Nicotinic Acids/analysis , Nicotinic Acids/isolation & purification , Soil/chemistry , Soil Pollutants/analysis , Soil Pollutants/isolation & purificationABSTRACT
Earthworm metabolism is recognized as a useful tool for monitoring environmental insults and measuring ecotoxicity, yet extensive earthworm metabolic profiling using 1H nuclear magnetic resonance (NMR) spectroscopy has been limited in scope. This study aims to expand the embedded metabolic material in earthworm coelomic fluid, coelomocytes, and tissue to aid systems toxicology research. Fifty-nine metabolites within Eisenia fetida were identified, with 47 detected in coelomic fluid, 41 in coelomocytes, and 54 in whole-worm samples and tissue extracts. The newly detected but known metabolites 2-aminobutyrate, nicotinurate, Nδ,Nδ,Nδ-trimethylornithine, and trigonelline are reported along with a novel compound, malylglutamate, elucidated using 2D NMR and high-resolution MS/MS. We postulate that malylglutamate acts as a glutamate/malate store, chelator, and anionic osmolyte and helps to provide electrolyte balance.
Subject(s)
Glutamic Acid/metabolism , Malates/metabolism , Metabolome , Metabolomics/methods , Oligochaeta/metabolism , Alkaloids/isolation & purification , Alkaloids/metabolism , Aminobutyrates/isolation & purification , Aminobutyrates/metabolism , Animals , Ecotoxicology/methods , Glutamic Acid/analogs & derivatives , Glutamic Acid/isolation & purification , Magnetic Resonance Spectroscopy , Malates/isolation & purification , Nicotinic Acids/isolation & purification , Nicotinic Acids/metabolism , Oligochaeta/chemistry , Ornithine/analogs & derivatives , Ornithine/isolation & purification , Ornithine/metabolism , Tandem Mass SpectrometryABSTRACT
Areca nut (seed of Areca catechu) is consumed by people from different parts of Asia, including India. The four major alkaloids present in areca nut are arecoline, arecaidine, guvacoline and guvacine. Upon cutting, the nut reveals two kinds of regions; white and brown. In our present study, we have monitored the formation of these two regions within the nut during maturation, using the non-invasive techniques of magnetic resonance imaging (MRI) and volume localized magnetic resonance spectroscopy (MRS). Electrospray ionization mass spectrometry (ESI MS) and desorption electrospray ionization mass spectrometry (DESI MS) imaging have been used to study the associated change in the alkaloid contents of these two regions during the growth of the nut. Our study reveals that white and brown regions start forming within the nut when the liquid within starts solidifying. At the final stage of maturity, arecoline, arecaidine and guvacoline get segregated in the brown region whereas guvacine gets to the white region of the nut. The transport of molecules with maturity and corresponding pattern formation are expected to be associated with a multitude of physiochemical changes.
Subject(s)
Alkaloids/chemistry , Areca/chemistry , Nuts/chemistry , Arecoline/chemistry , Arecoline/isolation & purification , Humans , India , Magnetic Resonance Imaging , Molecular Structure , Nicotinic Acids/chemistry , Nicotinic Acids/isolation & purification , Nuclear Magnetic Resonance, BiomolecularABSTRACT
Secoiridoid glucosides, including two conjugates with a phenolic and two conjugates with a nicotinic acid derivative (3 and 4), together with seven known secoiridoid derivatives, were isolated from flower buds of Lonicera japonica. The structures were elucidated by spectroscopic analyses. Anti-influenza activities of six isolated compounds were also evaluated by plaque assay and neuraminidase inhibitory assay.
Subject(s)
Iridoid Glucosides/isolation & purification , Lonicera/chemistry , Nicotinic Acids/isolation & purification , Phenols/isolation & purification , Antiviral Agents/pharmacology , Flowers/chemistry , Influenza A virus/drug effects , Iridoid Glucosides/chemistry , Iridoid Glucosides/pharmacology , Molecular Structure , Neuraminidase/antagonists & inhibitors , Nicotinic Acids/chemistry , Phenols/chemistry , Phenols/pharmacologyABSTRACT
A sensitive and reliable method based on MEKC has been developed and validated for trace determination of neonicotinoid insecticides (thiamethoxam, acetamiprid, and imidacloprid) and the metabolite 6-chloronicotinic acid in water and soil matrices. Optimum separation of the neonicotinoid insecticides was obtained on a 58 cm long capillary (75 µm id) using as the running electrolyte 40 mM SDS, 5 mM borate (pH 10.4), and 5% (v/v) methanol at a temperature of 25°C, a voltage of 25 kV and with hydrodynamic injection (10 s). The analysis time was less than 7 min. Prior to MEKC determination, the samples were purified and enriched by carrying out extraction-preconcentration steps. For aqueous samples, off-line SPE with a sorptive material such as Strata-X (polymeric hydrophobic sorbent) and octadecylsilane (C18) was carried out to clean up and preconcentrate the insecticides. However, for soil samples, matrix solid-phase dispersion (MSPD) was applied with C18 used as the dispersant. Good linearity, accuracy, and precision were obtained and the detection limits were in the range between 0.01 and 0.07 µg mL⻹ for river water and 0.17 and 0.37 µg g⻹ for soil samples. Recovery levels reached greater than 92% for all of the assayed neonicotinoids in river water samples with Strata-X. In soil matrices, the best recoveries (63-99%) were obtained with MSPD.
Subject(s)
Chromatography, Micellar Electrokinetic Capillary/methods , Insecticides/analysis , Soil Pollutants/analysis , Solid Phase Extraction/methods , Water Pollutants, Chemical/analysis , Imidazoles/analysis , Imidazoles/chemistry , Imidazoles/isolation & purification , Insecticides/chemistry , Insecticides/isolation & purification , Limit of Detection , Linear Models , Neonicotinoids , Nicotinic Acids/analysis , Nicotinic Acids/chemistry , Nicotinic Acids/isolation & purification , Nitro Compounds/analysis , Nitro Compounds/chemistry , Nitro Compounds/isolation & purification , Oxazines/analysis , Oxazines/chemistry , Oxazines/isolation & purification , Pyridines/analysis , Pyridines/chemistry , Pyridines/isolation & purification , Reproducibility of Results , Soil Pollutants/chemistry , Soil Pollutants/isolation & purification , Thiamethoxam , Thiazoles/analysis , Thiazoles/chemistry , Thiazoles/isolation & purification , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/isolation & purificationABSTRACT
In search for an effective oral treatment for diabetes, we examined the capacity of glucose tolerance factor (GTF) extracted from yeast and administered orally to reduce hyperglycaemia in rat models exhibiting insulin deficiency. The cellular effect of GTF on the insulin signalling pathway was investigated in vitro. GTF (oral bolus), insulin (intraperitoneal) or their combination was administered to streptozotocin-diabetic (STZ) or hyperglycaemic Cohen diabetic-sensitive (hyp-CDs) rats. Blood glucose (BG) and insulin levels were measured in the postprandial (PP) state and during an oral glucose tolerance test. Deoxy-glucose transport and insulin signal transduction were assessed in 3T3-L1 adipocytes and myoblasts incubated with the GTF. Low dose of insulin produced a 34 and 12·5 % reduction in the PP-BG levels of hyp-CDs and STZ rats, respectively. GTF induced a 33 and 17 % reduction in the PP-BG levels of hyp-CDs and STZ rats, respectively. When combined with insulin, a respective decrease (58 and 42 %) in BG levels was observed, suggesting a partially additive (hyp-CDs) or synergistic (STZ rats) effect of the GTF and insulin. GTF did not induce insulin secretion in hyp-CDs rats, yet it lowered their BG levels, proposing an effect on glucose clearance by peripheral tissues. GTF induced a dose-dependent increase in deoxy-glucose transport into myoblasts and fat cells similar to insulin, while the combined treatment resulted in augmented transport rate. GTF induced a dose- and time-dependent phosphorylation of insulin receptor substrate 1, Akt and mitogen-activated protein kinase independent of insulin receptor phosphorylation. GTF exerts remarkable insulin-mimetic and insulin-potentiating effects, both in vivo and in vitro. It produces an insulin-like effect by acting on cellular signals downstream of the insulin receptor. These results demonstrate a potential source for a novel oral medication for diabetes.
Subject(s)
Amino Acids/pharmacology , Chromium/pharmacology , Insulin/administration & dosage , Molecular Mimicry , Nicotinic Acids/pharmacology , Yeasts/chemistry , Administration, Oral , Amino Acids/administration & dosage , Amino Acids/isolation & purification , Animals , Blood Glucose/analysis , Cell Line , Chromium/administration & dosage , Chromium/isolation & purification , Diabetes Mellitus, Experimental/blood , Diabetes Mellitus, Experimental/drug therapy , Glucose Tolerance Test , In Vitro Techniques , Insulin/blood , Male , Nicotinic Acids/administration & dosage , Nicotinic Acids/isolation & purification , Phosphorylation , RatsABSTRACT
A selection of actinomyces that could degrade imazethapyr was conducted to provide actinomyces source for bioremediation of soil contaminated by imazethapyr. A strain of actinomyces was isolated from the samples of soil where imazethapyr had been applied for a long-term by use of bottle enriched culture and named S181. The strain had strong ability to degrade imazethapyr and could grow using mazethapyr as the sole nitrogen. The strain was related and shared characteristics to genus Streptomyces omiyaensis according to the physiological and biochemical properties as well as 16S rRNA sequence analysis. The influencing factors (temperature, pH, concentration and inoculum) were studied with fungus growth mass and degradation ratio as indexes. The results showed that the optimal degradation ratio occurred at the condition of inoculation ratio of 3%, 200 mg x L(-1) imazethapyr, at 30 degrees C and pH 7.0. Under these conditions, 84% imazethapyr had been degraded by S181 in medium Gao 1 without nitrogen after 5 days.
Subject(s)
Actinomyces/isolation & purification , Actinomyces/metabolism , Nicotinic Acids/isolation & purification , Nicotinic Acids/metabolism , Actinomyces/classification , Biodegradation, Environmental , Herbicides/isolation & purification , Herbicides/metabolism , Soil Pollutants/isolation & purification , Soil Pollutants/metabolism , Streptomyces/classification , Streptomyces/isolation & purification , Streptomyces/metabolismABSTRACT
A vitamin B(6) degradative pathway has recently been identified and characterized in Mesorhizobium loti MAFF303099. One of the enzymes on this pathway, 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase (MHPCO), is a flavin-dependent enzyme and catalyzes the oxidative ring-opening of 2-methyl-3-hydroxypyridine-5-carboxylic acid to form E-2-(acetamino-methylene)succinate. The gene for this enzyme has been cloned, and the corresponding protein has been overexpressed in Escherichia coli and purified. The crystal structure of MHPCO has been solved to 2.1 A using SAD phasing with and without the substrate MHPC bound. These crystal structures provide insight into the reaction mechanism and suggest roles for active site residues in the catalysis of a novel oxidative ring-opening reaction.
Subject(s)
Alphaproteobacteria/enzymology , Mixed Function Oxygenases/chemistry , Mixed Function Oxygenases/metabolism , Nicotinic Acids/chemistry , Nicotinic Acids/metabolism , Binding Sites/genetics , Catalysis , Cloning, Molecular , Crystallography, X-Ray , Dimerization , Escherichia coli/genetics , Flavin-Adenine Dinucleotide/chemistry , Flavin-Adenine Dinucleotide/metabolism , Histidine/chemistry , Hydrogen Bonding , Ligands , Mixed Function Oxygenases/genetics , Models, Molecular , Nicotinic Acids/genetics , Nicotinic Acids/isolation & purification , Oxidation-Reduction , Protein Binding/genetics , Protein Structure, Secondary , Recombinant Proteins/analysis , Recombinant Proteins/chemistry , Recombinant Proteins/isolation & purification , Recombinant Proteins/metabolism , Substrate Specificity/genetics , UltracentrifugationABSTRACT
Worldwide, tuberculosis (TB) kills nearly 2 million people annually, yet rapid diagnosis still relies on a 100-year-old method of sputum staining for acid-fast bacilli. The advent of solid phase micro-extraction and gas chromatography/mass spectrometry makes it possible to systematically investigate whether volatile metabolites from organisms belonging to the genus Mycobacterium can be used as a rapid and highly selective alternative to the traditional diagnostic methods. We have identified four specific compounds (methyl phenylacetate, methyl p-anisate, methyl nicotinate and o-phenylanisole) from Mycobacterium tuberculosis and Mycobacterium bovis cultures grown in vitro that are distinctive volatile markers. These compounds are detectable before the visual appearance of colonies, potentially useful as the basis of a non-invasive diagnostic test for TB and have characteristic odors.
Subject(s)
Mycobacterium avium/chemistry , Mycobacterium bovis/metabolism , Mycobacterium tuberculosis/chemistry , Odorants/analysis , Sputum/microbiology , Tuberculosis, Pulmonary/diagnosis , Animals , Anisoles/isolation & purification , Bacteriological Techniques , Benzoates/isolation & purification , Biomarkers/analysis , Biphenyl Compounds/isolation & purification , Humans , Nicotinic Acids/isolation & purification , Phenylacetates/isolation & purification , Rats , Tuberculosis, Pulmonary/microbiologyABSTRACT
Chiral high-performance liquid chromatography (HPLC) is one of the most powerful tools to prepare enantiopure standards of chiral compounds. In this study, the enantiomeric separation of imidazolinone herbicides, i.e., imazethapyr, imazapyr, and imazaquin, was investigated using chiral HPLC. The enantioselectivity of Chiralpak AS, Chiralpak AD, Chiralcel OD, and Chiralcel OJ columns for the three analytes was compared under similar chromatographic conditions. Chiralcel OJ column showed the best chiral resolving capacity among the test columns. The resolved enantiomers were distinguished by their signs of circular dichroism detected at 275 nm and their structures confirmed with LC-mass spectrometric analysis. Factors affecting the chiral separation of imidazolinones on Chiralcel OJ column were characterized. Ethanol acted as a better polar modifier than the other alcohols including 2-propanol, 1-butanol, and 1-pentanol. Although the acidic modifier in the mobile phase did not influence chiral recognition, it was necessary for reducing the retention time of enantiomers and suppressing their peak tailing. Thermodynamic evaluation suggests that enantiomeric separation of imidazolinones on Chiralcel OJ column is an enthalpy-driven process from 10 to 40 degrees C. This study also shows that small amounts of pure enantiomers of imidazolinones may be obtained by using the analytical chiral HPLC approach.
Subject(s)
Herbicides/isolation & purification , Imidazoles/isolation & purification , Niacin/analogs & derivatives , Nicotinic Acids/isolation & purification , Quinolines/isolation & purification , Chromatography, High Pressure Liquid , Niacin/isolation & purification , StereoisomerismABSTRACT
From the whole plant of Euphorbia peplus L., five new diterpenes based on a jatrophane skeleton (pepluanins A-E, 1-5) were isolated, together with two known analogues (6 and 7), which served to divulge in detail the structure-activity relationships within this class of P-glycoprotein inhibitors. The results revealed the importance of substitutions on the medium-sized ring (carbons 8, 9, 14, and 15). In particular, the activity is collapsed by the presence of a free hydroxyl at C-8, while it increases with a carbonyl at C-14, an acetoxyl at C-9, and a free hydroxyl at C-15. The most potent compound of the series, pepluanin A, showed a very high activity for a jatrophane diterpene, outperforming cyclosporin A by a factor of at least 2 in the inhibition of Pgp-mediated daunomycin transport.
Subject(s)
Diterpenes/isolation & purification , Drug Resistance, Multiple/drug effects , Nicotinic Acids/isolation & purification , ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , Antibiotics, Antineoplastic/metabolism , Biological Transport , Cell Line, Tumor , Cyclosporine/pharmacology , Daunorubicin/metabolism , Diterpenes/chemistry , Diterpenes/pharmacology , Drug Resistance, Neoplasm/drug effects , Humans , Magnetic Resonance Spectroscopy , Nicotinic Acids/chemistry , Nicotinic Acids/pharmacology , Structure-Activity RelationshipABSTRACT
In a survey of plant secondary metabolites regulating the behavior of phytopathogenic Aphanomyces cochlioides zoospores, we found that leaf extracts of Amaranthus gangeticus and cotyledon extracts of pea (Pisum sativum) remarkably halted the motility of zoospores. Bioassay-directed fractionation of A. gangeticus and pea constituents revealed that the halting activity was dependent on a single chemical factor (halting factor). The active principle was identified as nicotinamide (1) by comparing its biological activity and spectroscopic properties with those of the authentic compound. Nicotinamide (1) showed potent halting activity toward the zoospores of A. cochlioides and A. euteiches, but it exhibited very less activity against other Oomycetes, Pythium aphanidermatum and Phytophthora infestans zoospores. Interestingly, the zoospores halted by nicotinamide (1) encysted within 10-15 min and then the resulting cystospores regenerated zoospores instead of germination. Nicotinamide (1) and related compounds were subjected to the halting activity bioassay to elucidate the structure-activity relationships. These bioassays revealed that part structures of (A) the aromatic ring containing at least one nitrogen atom, (B) carbonyl-like group adjacent to the aromatic ring and (C) hydrogen atoms on the amide group are responsible for the strong activity. So far, this is the first report of halting activity of nicotinamide (1) against fungal zoospores.
Subject(s)
Amaranthus/chemistry , Niacinamide/pharmacology , Nicotinic Acids/pharmacology , Oomycetes/physiology , Nicotinic Acids/chemistry , Nicotinic Acids/isolation & purification , Oomycetes/drug effects , Phytophthora/drug effects , Phytophthora/physiology , Plant Extracts/pharmacology , Plant Leaves/chemistry , Plants, Medicinal/chemistry , Spores, Fungal/drug effects , Spores, Fungal/physiology , Structure-Activity RelationshipABSTRACT
Fermentations with yeast Saccharomyces cerevisiae in semiaerobic and in static conditions with the addition of chromic chloride into the used molasses medium were analysed. It was proved that the addition of optimal amounts of CrCl3 into the basal medium enhanced the kinetics of alcohol fermentations. The addition of 200 mg/l CrCl3 into the medium stimulated both the yeast growth and the ethanol production in all experimental conditions. On the other hand, the results showed that Cr3+ ions were incorporated into yeast cells during fermentation. Under these conditions the accumulation of Cr3+ ions was performed by yeast cells during the exponential growth phase, and with enriched amounts of 30-45 microg/g(d.m) of cells. Yeast biomass enriched with chromium ions was extracted with 0.1 mol/l NH4OH assuming that the extracts had the glucose tolerance factor (GTF). Then the extracts were passed through a gel-filtration column in order to isolate and purify the GTF. The presence of GTF in the purified fractions was determined by measuring the absorbance at 260 nm. It is evident from the obtained results that the added purified fractions enhanced the rates of CO2 production as well as the glucose utilization during alcoholic fermentation. As expected, the enhancement of both rates depended on the amounts of extracts added to the fermentation substrate. Thus, it is evident that purified extracts contained the GTF compound, and that Cr3+ ions were bonded to the protein molecule.
Subject(s)
Amino Acids/isolation & purification , Biomass , Chromium/isolation & purification , Chromium/metabolism , Nicotinic Acids/isolation & purification , Saccharomyces cerevisiae/metabolism , Amino Acids/metabolism , Carbon Dioxide/metabolism , Ethanol/metabolism , Fermentation , Nicotinic Acids/metabolism , Saccharomyces cerevisiae/growth & developmentABSTRACT
Adsorption of the imidazolinone herbicides imazapyr, imazethapyr, and imazaquin on synthetic ferrihydrites, either freeze-dried or not-freeze-dried, has been studied. The synthetic ferrihydrites were characterized by X-ray diffraction, scanning electron micrographs, and specific area determination. On each ferrihydrite, adsorption was found to be strongly dependent on pH. The highest extent of adsorption took place at pH values close to the pK(a) of the carboxylic group of the herbicides. No adsorption was observed at pH > 8. The freeze-drying process reduced the adsorptive capacity of the ferrihydrite by formation of larger aggregates provoking a decrease of the surface area. The chemical differences between the herbicides did not strongly affect the adsorption process of the herbicides. However, imazaquin was more adsorbed than the other two herbicides, in particular at pH close to its pK(a).
Subject(s)
Ferritins , Herbicides/isolation & purification , Imidazoles/isolation & purification , Niacin/analogs & derivatives , Niacin/isolation & purification , Nicotinic Acids/isolation & purification , Quinolines/isolation & purification , Adsorption , Ferric Compounds , Ferritins/chemistry , Freeze Drying , Herbicides/chemistry , Hydrogen-Ion Concentration , Imidazoles/chemistry , Kinetics , Microscopy, Electron, Scanning , Niacin/chemistry , Nicotinic Acids/chemistry , Quinolines/chemistry , X-Ray DiffractionABSTRACT
Chromium is essential for proper carbohydrate and lipid metabolism in mammals, although the mechanism of this action has previously proved elusive. Low-molecular-weight chromium-binding protein (LMWCr), a biologically active form of chromium in mammals, potentiates the effect of insulin on the conversion of glucose into lipid and into carbon dioxide in isolated adipocytes. Kinetics studies indicate that LMWCr isolated from bovine liver activates phosphotyrosine phosphatase (PTP) activity in adipocyte membranes while having no intrinsic phosphatase activity. This activation is directly proportional to the amount of added LMWCr. The pattern of inhibition of this activity in the presence of a number of known phosphatase inhibitors suggests the involvement of a membrane phosphotyrosine phosphatase similar to PTP1A' or PTP1B. We propose that chromium plays a biological role in the activation of a membrane phosphotyrosine phosphatase.
Subject(s)
Amino Acids/pharmacology , Chromium/pharmacology , Nicotinic Acids/pharmacology , Protein Tyrosine Phosphatases/metabolism , Adipocytes/enzymology , Amino Acids/chemistry , Amino Acids/isolation & purification , Animals , Cattle , Cell Membrane/enzymology , Chromium/chemistry , Chromium/isolation & purification , Enzyme Activation , Enzyme Inhibitors/pharmacology , Glucose/metabolism , Insulin/metabolism , Kinetics , Lipid Metabolism , Liver/chemistry , Male , Metals/pharmacology , Nicotinic Acids/chemistry , Nicotinic Acids/isolation & purification , Nitrophenols/metabolism , Organophosphorus Compounds/metabolism , Phosphorylation , Protein Binding , Protein Tyrosine Phosphatases/antagonists & inhibitors , Rats , Rats, Sprague-DawleyABSTRACT
The effect of the addition of cetyltrimethylammonium bromide (CTAB) to the buffer system in capillary electrophoresis on electroosmotic flow (EOF) is examined. At a CTAB concentration of 2.5 x 10(-4) M, EOF is anodal (flow towards the positive detector column end). With bare silica columns, anodal EOF first increases with increasing pH, up to a maximum in the pH range 4-6 depending on CTAB concentration, then decreases as pH is further increased. Optimum resolution of pyridinecarboxylic acid isomers is obtained at pH 2.7 with a 10 mM phosphate buffer and 30 mM CTAB. Using the same buffer system, optimum resolution for hydroxy-substituted pyridinecarboxylic acid isomers is obtained at pH 7.5. The use of CTAB results in a dramatic improvement in peak shape. Preliminary results, using an excimer laser operated at 248 nm, show that the fluorescence intensity of isonicotinic acid is substantially enhanced with the addition of 0.3% hydrogen peroxide to the phosphate buffer system.
Subject(s)
Cetrimonium Compounds/chemistry , Electrophoresis/methods , Nicotinic Acids/isolation & purification , Cetrimonium , Detergents , Electrochemistry , Hydrogen-Ion Concentration , IsomerismABSTRACT
A high performance liquid chromatographic method for the simultaneous quantitative determination of nicotinic acid, nicotinamide and nicotinuric acid in human plasma is described. The method is based on solid phase extraction in combination with ion-paired reversed phase high performance liquid chromatography. Recoveries of nicotinic acid, nicotinamide and nicotinuric acid are 92.9, 95.8 and 87.8%, respectively. The procedure shown was applied to the determination of the plasma time-concentration profile of nicotinic acid, nicotinamide and nictotinuric acid after nicotinic acid ingestion in humans.
Subject(s)
Niacin/blood , Niacinamide/blood , Nicotinic Acids/blood , Adult , Chromatography, High Pressure Liquid , Humans , Male , Niacin/isolation & purification , Niacinamide/isolation & purification , Nicotinic Acids/isolation & purification , Reproducibility of Results , Sensitivity and Specificity , Time FactorsABSTRACT
Low-molecular-weight, cationic samples, that were previously reported to contain a glucose tolerance factor, were obtained by partial purification from yeast extract. These samples increased the rate of glucose transport in isolated cardiomyocytes 2.0- to 2.5-fold. A further purification by gel filtration led to the separation of two active components that were identified as (i) L-alanine and (ii) an elevated osmolarity. Moreover, the effect of partially purified fractions (before gel filtration) (i) was decreased upon alanine depletion with alanine dehydrogenase and (ii) was mimicked by the additive action of alanine and of a hyperosmolar medium. These findings indicate that the effect of this partially purified material is not accounted for by a putative glucose tolerance factor. Interestingly, alanine elicited its effect at concentrations that correspond to physiological plasma values, which suggests that this amino acid might be involved in the regulation of glucose transport in cardiomyocytes. Furthermore, the effect of alanine was prevented by DL-cycloserine (1 mM) or aminooxyacetate (1 mM), but not by cycloheximide (35 microM), indicating that (a) transamination reaction(s), but not protein synthesis, is required.