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Metabolic Intermediates (metabolic + intermediate)
Selected AbstractsEvaluation of TCE and MTBE in situ Biodegradation: Integrating Stable Isotope, Metabolic Intermediate, and Microbial Lines of EvidenceGROUND WATER MONITORING & REMEDIATION, Issue 4 2007Jennifer R. McKelvie Compound specific isotope analysis (CSIA) was used to investigate biodegradation of trichloroethene (TCE) and methyl tert -butyl ether (MTBE) at contaminated field sites in Alaska and New York State, respectively. At both sites, geochemical conditions and the presence of metabolic intermediates (cis -1-2-dichloroethene and tert -butyl alcohol [TBA]) suggested the potential for biodegradation of TCE and MTBE, respectively. Given that in both cases these metabolic intermediates could also have been present as cocontaminants in the source zone, CSIA was undertaken to evaluate the possibility of in situ biodegradation. At the TCE-contaminated field site in Alaska, ,13C values of TCE in ground water determined in this study showed no evidence of biodegradation (mean ,13C of ,27.0 ± 1.0, for nine wells), and quantitative-polymerase chain reaction analyses of ground water from four wells found no evidence of dechlorinator Dehalococcoides sp. at this site. At the MTBE-contaminated field site in New York, TBA was present in the ground water but was not present in gasoline sampled from underground storage tanks (UST) on-site, suggesting that at this site, TBA was potentially a metabolite of MTBE biodegradation rather than a cocontaminant. However, at all sampling times and locations, ,13C and ,2H values of MTBE in ground water were within range of published values for undegraded MTBE in gasoline. While the occurrence of a small extent of in situ MTBE biodegradation cannot be ruled out, the findings suggest that it is more likely that multiple gasoline spills occurred through time, and while present day USTs do not contain TBA as a cocontaminant, gasoline spilled at the site in the past may have. At both contaminated field sites, CSIA, chemical, and microbiological lines of evidence suggest that biodegradation was not a significant attenuation process. The results of these two studies underscore the need for an integrated approach to site assessment that draws on measurements of metabolic intermediates, analysis of stable isotopes, and microbial evidence to give a reliable assessment of in situ biodegradation at contaminated field sites. [source] Intracerebroventricular administration of GABA-A and GABA-B receptor antagonists attenuate feeding and sleeping-like behavior induced by L -pipecolic acid in neonatal chicksJOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2003T. Takagi Abstract It has been demonstrated that L -pipecolic acid (L -PA), a major metabolic intermediate of L -lysine (L -Lys) in the mammalian and chicken brain, is involved in the functioning of the GABAergic system. A previous study has shown that intracerebroventricular (i.c.v.) injection of L -PA suppressed feeding and induced sleep-like behavior in neonatal chicks; however, the precise relationship between the GABAergic system and L -PA has not been clarified. In the present study, the role of the GABA-A or GABA-B receptors in the suppression of food intake and induction of sleeping-like behavior by L -PA was investigated. Chicks were injected i.c.v. with the GABA-A antagonist picrotoxin or GABA-B antagonist CGP54626 along with L -PA. Although suppression of food intake by L -PA was restored partially by co-injection with CGP54626, but not picrotoxin, sleep-like behavior induced by L -PA was suppressed significantly by both antagonists. These results suggested that L -PA activated both GABA-A and GABA-B receptors, and GABA-B receptors alone contributed to food intake whereas both receptors contributed to sleep-like behavior. © 2003 Wiley-Liss, Inc. [source] Tobacco Mg protoporphyrin IX methyltransferase is involved in inverse activation of Mg porphyrin and protoheme synthesisTHE PLANT JOURNAL, Issue 2 2005Ali E. Alawady Summary Protoporphyrin, a metabolic intermediate of tetrapyrrole biosynthesis, is metabolized by Mg chelatase and ferrochelatase and is directed into the Mg-branch for chlorophyll synthesis and in the Fe-branch for protoheme synthesis respectively. Regulation of the enzyme activities at the beginning of this branchpoint ensures accurate partition of protoporphyrin, but is still not entirely understood. Transgenic tobacco plants were generated that express antisense or sense RNA for inhibited and excessive expression of Mg protoporphyrin methyltransferase (MgPMT) respectively. This enzyme accepts Mg protoporphyrin from Mg chelatase and catalyses the transfer of a methyl group to the carboxyl group of the C13-propionate side chain. Low MgPMT activity is correlated with reduced Mg chelatase activity and a low synthesis rate of 5-aminolevulinate, but with enhanced ferrochelatase activity. In contrast, high MgPMT activity leads to inverse activity profiles: high activities of Mg chelatase and for 5-aminolevulinate synthesis, but reduced activity of ferrochelatase, indicating a direct influence of MgPMT in combination with Mg chelatase on the metabolic flux of ALA and the distribution of protoporphyrin into the branched pathway. The modified enzyme activities in tetrapyrrole biosynthesis in the transgenic plants can be explained with changes of certain corresponding mRNA contents: increased 5-aminolevulinate synthesis and Mg chelatase activity correlate with enhanced transcript levels of the HemA, Gsa, and CHLH gene encoding glutamyl-tRNA reductase, glutamate-1-semialdehyde aminotransferase and a Mg chelatase subunit respectively. It is proposed that reduced and increased MgPMT activity in chloroplasts is communicated to the cytoplasm for modulating transcriptional activities of regulatory enzymes of the pathway. [source] Homocysteine metabolism and its relation to health and diseaseBIOFACTORS, Issue 1 2010Kelly T. Williams Abstract Homocysteine is a metabolic intermediate in methyl group metabolism that is dependent on a number of nutritional B-vitamin cofactors. An emerging aspect of homocysteine metabolism is its relation to health and disease. Perturbations of homocysteine metabolism, particularly intracellular and subsequently circulating accumulation of homocysteine (i.e., hyperhomocysteinemia), are associated with vascular disease risk, as well as other pathologies. However, intervention with B-vitamin supplementation has been shown to successfully restore normal homocysteine concentrations, but without concomitant reductions in disease risk. Thus, the mechanistic relation between homocysteine balance and disease states, as well as the value of homocysteine management, remains an area of intense investigation. [source] Evaluation of TCE and MTBE in situ Biodegradation: Integrating Stable Isotope, Metabolic Intermediate, and Microbial Lines of EvidenceGROUND WATER MONITORING & REMEDIATION, Issue 4 2007Jennifer R. McKelvie Compound specific isotope analysis (CSIA) was used to investigate biodegradation of trichloroethene (TCE) and methyl tert -butyl ether (MTBE) at contaminated field sites in Alaska and New York State, respectively. At both sites, geochemical conditions and the presence of metabolic intermediates (cis -1-2-dichloroethene and tert -butyl alcohol [TBA]) suggested the potential for biodegradation of TCE and MTBE, respectively. Given that in both cases these metabolic intermediates could also have been present as cocontaminants in the source zone, CSIA was undertaken to evaluate the possibility of in situ biodegradation. At the TCE-contaminated field site in Alaska, ,13C values of TCE in ground water determined in this study showed no evidence of biodegradation (mean ,13C of ,27.0 ± 1.0, for nine wells), and quantitative-polymerase chain reaction analyses of ground water from four wells found no evidence of dechlorinator Dehalococcoides sp. at this site. At the MTBE-contaminated field site in New York, TBA was present in the ground water but was not present in gasoline sampled from underground storage tanks (UST) on-site, suggesting that at this site, TBA was potentially a metabolite of MTBE biodegradation rather than a cocontaminant. However, at all sampling times and locations, ,13C and ,2H values of MTBE in ground water were within range of published values for undegraded MTBE in gasoline. While the occurrence of a small extent of in situ MTBE biodegradation cannot be ruled out, the findings suggest that it is more likely that multiple gasoline spills occurred through time, and while present day USTs do not contain TBA as a cocontaminant, gasoline spilled at the site in the past may have. At both contaminated field sites, CSIA, chemical, and microbiological lines of evidence suggest that biodegradation was not a significant attenuation process. The results of these two studies underscore the need for an integrated approach to site assessment that draws on measurements of metabolic intermediates, analysis of stable isotopes, and microbial evidence to give a reliable assessment of in situ biodegradation at contaminated field sites. [source] Degradation of isooctane by Mycobacterium austroafricanum IFP 2173: growth and catabolic pathwayJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2004F. Solano-Serena Abstract Aims:, Isooctane (2,2,4-trimethylpentane), a major component of gasoline formulations, is recalcitrant to biodegradation probably because of the quaternary carbon group it contains. Information on the biodegradability of this hydrocarbon is essential to evaluate its fate in the environment. For these reasons, the degradation kinetics and the catabolic pathway of isooctane were investigated in Mycobacterium austroafricanum IFP 2173, the only strain characterized to use it as sole carbon and energy source. Methods and Results:, The selected strain exhibited a rather moderate maximum growth rate (,max = 0·053 h,1) but degraded isooctane up to 99% with a mineralization yield of 45%, indicating attack of the quaternary carbon group. The GC/MS identification of metabolites, 2,4,4-trimethylpentanoic and dimethylpropanoic (pivalic) acids, which transiently accumulated in the cultures indicated that degradation started from the isopropyl extremity of the molecule and subsequently proceeded by catabolism of the tert -butyl moiety. The degradation of putative metabolic intermediates was investigated. The initial isooctane oxidation system was tentatively characterized. Conclusions:, The isooctane-degrading strain harboured two candidate systems for initial alkane oxidation. Although a cytochrome P450 was induced by isooctane degradation, the functional oxidation system was probably a nonheme alkane monooxygenase as indicated by PCR amplification and RT-PCR expression of an alkB gene. Significance and Impact of the Study:, Isooctane is a recalcitrant branched alkane. A plausible pathway of its degradation by Myco. austroafricanum was put forward. [source] Biological treatment of textile dye Acid violet-17 by bacterial consortium in an up-flow immobilized cell bioreactorLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2004D.K. Sharma Abstract Aims:, To develop a cost effective and efficient biological treatment process for small scale textile processing industries (TPI) releasing untreated effluents containing intense coloured Acid violet-17 (AV-17), a triphenyl methane (TPM) group textile dye. Methods and Results:, The samples collected from effluent disposal sites of TPI were used for selective enrichment of microbial populations capable of degrading/decolourizing AV-17. A consortium of five bacterial isolates was used to develop an up-flow immobilized cell bioreactor for treatment of feed containing AV-17. The bioreactor, operating at a flow rate of 6 ml h,1, resulted in 91% decolourization of 30 mg AV-17/l with 94·3 and 95·7% removal of biochemical oxygen demand and chemical oxygen demand of the feed. Comparison of the input and output of the bioreactor by UV-visible, thin layer chromatography and 1H-nuclear magnetic resonance spectroscopy indicates conversion of the parent dye into unrelated metabolic intermediates. Significance:, These results will form a basis for developing ,on-site' treatment system for TPI effluents to achieve decolourization and degradation of residual dyes. [source] Reflections on the application of 13C-MRS to research on brain metabolismNMR IN BIOMEDICINE, Issue 6-7 2003Peter Morris Abstract The power of 13C-MRS lies in its unique chemical specificity, enabling detection and quantification of metabolic intermediates which would not be so readily monitored using conventional radiochemical techniques. Examples from animal studies, by examination of tissue extracts from the whole brain, brain slices and cultured cells, include observation of intermediates such as citrate and triose phosphates which have yielded novel information on neuronal/glial relationships. The use of 13C-labelled acetate as a specific precursor for glial metabolism provided evidence in support of the view that some of the GABA produced in the brain is derived from glial glutamine. Such studies have also provided direct evidence on the contribution of anaplerotic pathways to intermediary metabolism. Analogous studies are now being performed on the human brain, where 13C-acetate is used to quantitate the overall contribution of glial cells to intermediary metabolism, and use of 13C-glucose enables direct calculation of rates of flux through the TCA (FTCA) and of the glutamate,glutamine cycle (FCYC), leading to the conclusion that the rate of glial recycling of glutamate accounts for some 50% of FTCA. The rate of 0.74,,mol,min,1,g,1 for FTCA is compatible with PET rates of CMRglc of 0.3,0.4,,mol,min,1,g,1 (since each glucose molecule yields two molecules of pyruvate entering the TCA). Our brain activation studies showed a 60% increase in FTCA, which is very similar to the increases in CBF and in CMRglc observed in PET activation studies. Copyright © 2003 John Wiley & Sons, Ltd. [source] Kinetic characterization of vero cell metabolism in a serum-free batch culture processBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010Emma Petiot Abstract A global kinetic study of the central metabolism of Vero cells cultivated in a serum-free medium is proposed in the present work. Central metabolism including glycolysis, glutaminolysis, and tricarboxylic acid cycle (TCA) was demonstrated to be saturated by high flow rates of consumption of the two major substrates, glucose, and glutamine. Saturation was reavealed by an accumulation of metabolic intermediates and amino acids, by a high production of lactate needed to balance the redox pathway, and by a low participation of the carbon flow to the TCA cycle supply. Different culture conditions were set up to reduce the central metabolism saturation and to better balance the metabolic flow rates between lactate production and energetic pathways. From these culture conditions, substitutions of glutamine by other carbon sources, which have lower transport rates such as asparagine, or pyruvate in order to shunt the glycolysis pathway, were successful to better balance the central metabolism. As a result, an increase of the cell growth with a concomitant decrease of cell death and a better distribution of the carbon flow between TCA cycle and lactate production occurred. We also demonstrated that glutamine was a major carbon source to supply the TCA cycle in Vero cells and that a reduction of lactate production did not necessary improve the efficiency of the Vero cell metabolism. Thus, to adapt the formulation of the medium to the Vero cell needs, it is important to provide carbon substrates inducing a regulated supply of carbon in the TCA cycle either through the glycolysis or through other pathways such as glutaminolysis. Finally, this study allowed to better understand the Vero cell behavior in serum-free medium which is a valuable help for the implementation of this cell line in serum-free industrial production processes. Biotechnol. Bioeng. 2010;107: 143,153. © 2010 Wiley Periodicals, Inc. [source] A study of D-lactate and extracellular methylglyoxal production in lactate Re-Utilizing CHO culturesBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010Tomas Paoli Abstract In large-scale mammalian cell culture, the key toxic by-products assessed and monitored are lactate and ammonia. Often no distinction between the two isoforms of lactate is made. Here, we present profiles of both D - and L -lactate. D -Lactate is the end molecule of the methylglyoxal pathway. D -Lactate unlike L -lactate is not re-utilized, and although during normal culture time frames it represents one-tenth of total lactate, during lactate re-use it represents nearly 35%. This indicates significant carbon flow through pathways not associated with primary metabolites. We have observed that the behavior of D -lactate is radically different from that of L -lactate with the level of one isoform changing, whilst the concentration of the other remains constant. This is an example of an alternate carbon flow pathway containing metabolic intermediates that may potentially have a detrimental effect on cells. The activity of the methylglyoxal pathway when measured as a proportion of glucose consumption in this study far exceeds any previously reported. This highlights the potential importance of "non-primary" metabolisms to long lifespan mammalian fermentation practices. Biotechnol. Bioeng. 2010;107: 182,189. © 2010 Wiley Periodicals, Inc. [source] | ||||||||||