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1.
Xinyuan Xu Jiazhen Jiang Xinru Wang Zhigang Shen Ranhong Li Zhiqiang Zhou 《Chirality》2011,23(10):860-866
We investigated the stereoselective degradation kinetics and toxicity of fluroxypyr methylheptyl ester (FPMH) in rat hepatocytes using a chiral high‐performance liquid chromatographic method. The T1/2 of (−)‐FPMH was about two times longer than that of (+)‐FPMH after the rat hepatocytes were incubated with 10, 20, and 50 μM of rac‐FPMH. There was no chiral conversion or transformation during their incubation with the hepatocytes. Toxicity differences were observed among the two enantiomers of FPMH and fluroxypyr (FP) in their EC50 values in rat hepatocytes. Of all the tested compounds, FP was most toxic to the rat hepatocytes. The (−)‐FPMH enantiomer showed higher toxicity than the (+)‐FPMH, whereas the racemic mixture displayed intermediate toxicity. The data presented here are important for a more thorough understanding of this pesticide and should be useful for its full environmental assessment. Chirality, 2011. © 2011 Wiley‐Liss, Inc. 相似文献
2.
Malaisse WJ Ladrière L Kadiata MM Verbruggen I Willem R 《Archives of biochemistry and biophysics》2000,381(1):61-66
Hepatocytes from fed rats were incubated for 120 min in the presence of alpha-D-[1,2-13C]glucose pentaacetate (1.7 mM), both D-[1,2-13C]glucose (1.7 mM) and acetate (8.5 mM), alpha-D-glucose penta[2-13C]acetate (1.7 mM), or D-[1,2-13C]glucose (8.3 mM). The amounts of 13C-enriched L-lactate and D-glucose and those of acetate and beta-hydroxybutyrate recovered in the incubation medium were comparable under the first two experimental conditions. The vast majority of D-glucose isotopomers consisted of alpha- and beta-D[1,2-13C]glucose. The less abundant single-labeled isotopomers of D-glucose were equally labeled on each C atom. The output of 13C-labeled L-lactate, mainly L-[2-13C]lactate and L-[3-13C]lactate, was 1 order of magnitude lower than that found in hepatocytes exposed to 8.3 mM D-[1,2-13C]glucose, in which case the total production of the single-labeled species of D-glucose was also increased and that of the C3- or C4-labeled hexose was lower than that of the other 13C-labeled isotopomers. In cells exposed to alpha-D-glucose penta[2-13C]acetate, the large majority of 13C atoms was recovered as [2-13C]acetate and, to a much lesser extent, beta-hydroxybutyrate labeled in position 2 and/or 4. Nevertheless, L-[2-13C]lactate, L-[3-13C]lactate, and single-labeled D-glucose isotopomers were also produced in amounts higher or comparable to those found in cells exposed to alpha-D-[1,2-13C]glucose pentaacetate. However, a modest preferential labelling of the C6-C5-C4 moiety of D-glucose, relative to its C1-C2-C3 moiety, and a lesser isotopic enrichment of the C3 (or C4), relative to that of C1 (or C6) and C2 (or C5), were now observed. These findings indicate that, despite extensive hydrolysis of alpha-D-glucose pentaacetate (1.7 mM) in the hepatocytes, the catabolism of its D-glucose moiety is not more efficient than that of unesterified D-glucose, tested at the same molar concentration (1.7 mM) in the presence of the same molar concentration of unesterified acetate (8.5 mM), and much lower than that found at a physiological concentration of the hexose (8.3 mM). The present results also argue against any significant back-and-forth interconversion of D-glucose 6-phosphate and triose phosphates, under conditions in which sizeable amounts of D-glucose are formed de novo from 13C-enriched Krebs cycle intermediates generated from either D-[1,2-13C]glucose or [2-13C]acetate. 相似文献
3.
《Biocatalysis and Biotransformation》2013,31(6):299-310
AbstractThe lipase-catalyzed synthesis of cyclic ester oligomers from non-activated succinic acid (A) and 1,4-butanediol (B) in the presence of immobilized Candida antarctica lipase B was investigated. Batch and pulse fed-batch systems were implemented to increase the formation of cyclic ester products. The substrate conversions after 24 h were 86% and 95% under batch and fed-batch operation, respectively and the product of the reaction was, for both systems, a mixture of cyclic (CEOs) and linear (LEOs) ester oligomers. Fed-batch operation afforded a product containing 71% cyclic ester oligomers (CEOs) as compared with only 52% CEOs in batch operation. Cyclic ester oligomers accumulated as the reaction progressed, with the dimer CEO1 the most predominant product (i.e. 50% of the total products formed in fed-batch operation). The pulse fed-batch operation system was superior to the batch operation not only because higher substrate conversion and more CEOs were obtained, but also because it resulted in products with a higher degree of polymerization (DP up to 7). Cyclic ester oligomers are produced from the early stage of the reaction simultaneously with the linear ester oligomers by a ring-closure reaction on the active site of the enzyme, and not as a result of ring-chain equilibria. 相似文献
4.
Hormonal modulation of hepatic plasma membrane lactate transport was studied in primary cultures of isolated hepatocytes from fed rats to examine the mechanism for the known enhancement of lactate transport in starvation and diabetes. Total cellular lactate entry was increased by 14% in the presence of dexamethasone; this was accounted for by an approximately 40% increase in the carrier-mediated component of entry with no effect on diffusion. A trend of similar magnitude was evident with glucagon. The effects of dexamethasone and glucagon on lactate transport constitute an additional potential mechanism for enhancement of gluconeogenesis by these hormones. 相似文献
5.
To clarify the unique characteristics of amino acid metabolism derived from glucose in the central nervous system (CNS), we injected [1-13C]glucose intraperitoneally to the rat, and extracted the free amino acids from several kinds of tissues and measured the amount of incorporation of13C derived from [1-13C]glucose into each amino acid using13C-magnetic resonance spectroscopy (NMR). In the adult rat brain, the intensities of resonances from13C-amino acids were observed in the following order: glutamate, glutamine, aspartate, -aminobutyrate (GABA) and alanine. There seemed no regional difference on this labeling pattern in the brain. However, only in the striatum and thalamus, the intensities of resonances from [2-13C]GABA were larger than that from [2,3-13C]aspartate. In the other tissues, such as heart, kidney, liver, spleen, muscle, lung and small intestine, the resonances from GABA were not detected and every intensity of resonances from13C-amino acids, except13C-alanine, was much smaller than those in the brain and spinal cord. In the serum,13C-amino acid was not detected at all. When the rats were decapitated, in the brain, the resonances from [1-13C]glucose greatly reduced and the intensities of resonances from [3-13C]lactate, [3-13C]alanine, [2, 3, 4-13C]GABA and [2-13C]glutamine became larger as compared with those in the case that the rats were sacrificed with microwave. In other tissues, the resonances from [1-13C]glucose were clearly detected even after the decapitation. In the glioma induced by nitrosoethylurea in the spinal cord, the large resonances from glutamine and alanine were observed; however, the intensities of resonances from glutamate were considerably reduced and the resonances from GABA and aspartate were not detected. These results show that the pattern of13C label incorporation into amino acids is unique in the central nervous tissues and also suggest that the metabolic compartmentalization could exist in the CNS through the metabolic trafficking between neurons and astroglia.Abbreviations NMR
nuclear magnetic resonance
- GABA
-aminobutyrate
- GFAP
glial fibrillary acidic protein
Special issue dedicated to Dr. Bernard W. Agranoff. 相似文献
6.
M P Viola-Magni P B Gahan E Albi R Iapoce P F Gentilucci 《Cell biochemistry and function》1986,4(4):283-288
Nuclear, chromatin and microsomal fractions were isolated from hepatocytes prepared from rats injected with [32P]O4(2-) and killed subsequently at times between 1 and 48 h. Specific activities of the total phospholipids (PL) were determined for each subcellular fraction. The major points noted were the initial specific activity of the chromatin PL was half that of both nuclear and microsomal PL at 1 h; the first peak of labelling occurred at 6 h in both nuclear and microsomal PL, but was 3 h later (9h) in the chromatin PL; and a second peak of labelling occurred in the chromatin and microsomal PL, but not in those of the nuclei. On fractionation of the PL, the major and most metabolically active components were phosphatidylcholine + phosphatidylethanolamine, whilst sphingomyelin accounted for only about 8 per cent of the total PL. The chromatin and microsomal fractions were somewhat similar in their labelling patterns though with a delayed peaking of activity in the chromatin. This is indicative of a synthesis and transport of PL from the microsomes to the chromatin. 相似文献
7.
Labelling experiments with [2-13C]- and [1,2-13C]acetate showed that both photopigments of Anacystis nidulans, chlorophyll a and phycocyanobilin, share a common biosynthetic pathway from glutamate. The fate of deuterium during these biosynthetic events was studied using [2-13C, 2-2H3]acetate as a precursor and determining the labelling pattern by 13C NMR spectroscopy with simultaneous [1H, 2H]-broadband decoupling. The loss of 2H (ca 20%) from the precursor occurred at an early stage during the tricarboxylic acid cycle. After formation of glutamate there was no further loss of 2H in the assembly of the cyclic tetrapyrrole intermediates or during decarboxylation and modification of the side-chains. Thus the labelling data support a divergence in the pathway to cyclic and linear tetrapyrroles after protoporphyrin IX. 相似文献
8.
Ladrière L. Grue-Sørensen G. Björkling F. Malaisse W.J. 《Molecular and cellular biochemistry》1999,198(1-2):135-139
The metabolism of glycerol-1,2,3-trimethylsuccinate ester was investigated in rat hepatocytes. The ester displayed a greater nutritional value than D-glucose, as a precursor of either CO2 or glycogen. In terms of 14CO2 production, the value calculated from experiments conducted in the presence of 1.9 mM [U-14C] glycerol-1,2,3-trimethylsuccinate, glycerol-1,2,3-trimethyl[1,4-14C] succinate and glycerol- 1,2,3-trimethyl[2,3-14C] succinate represented about 50 times that found in cells incubated with 1.0 mM D-[U-14C] glucose. For glycogen synthesis, the results found with the ester were approximately 7-8 times higher than those found with the hexose. A further advantage of the ester over D-glucose consisted in the fact that, at increasing concentrations of these nutrients, a maximal metabolic response may be reached at lower levels of glycerol-1,2,3-trimethylsuccinate than D-glucose. By comparison with previous data obtained in the same experimental model, glycerol-1,2,3-trimethylsuccinate was also found to display a higher nutritional value than the dimethyl ester of succinic acid. It is proposed, therefore, that glycerol-1,2,3-trimethylsuccinate could be used to support ATP generation in cells endangered by an imbalance between the rate of synthesis and hydrolysis of this adenine nucleotide. 相似文献
9.
10.
The effects of hypoxia on the metabolism of the central nervous system were investigated in rats submitted to a low oxygen atmosphere (8% O(2); 92% N(2)). [1-(13)C]glucose and [2-(13)C]acetate were used as substrates, this latter being preferentially metabolized by glial cells. After 1-h substrate infusion, the incorporation of 13C in brain metabolites was determined by NMR spectroscopy. Under hypoxia, an important hyperglycemia was noted. As a consequence, when using labeled glucose, the specific enrichment of brain glucose C1 was lower (48.2+/-5.1%) than under normoxia (66.9+/-2.5%). However, relative to this specific enrichment, the (13)C incorporation in amino acids was increased under hypoxia. This suggested primarily a decreased exchange between blood and brain lactate. The glutamate C2/C4 enrichment ratio was higher under hypoxia (0.62+/-0.01) than normoxia (0.51+/-0.06), indicating a lower glutamate turnover relative to the neuronal TCA cycle activity. The glutamine C2/C4 enrichment ratio was also higher under hypoxia (0.87+/-0.07 instead of 0.65+/-0.11), indicating a new balance in the contributions of different carbon sources at the acetyl-CoA level. When using [2-(13)C]acetate as substrate, no difference in glutamine enrichment appeared under hypoxia, whereas a significant decrease in glutamate, aspartate, alanine and lactate enrichments was noted. This indicated a lower trafficking between astrocytes and neurons and a reduced tricarboxylic acid cycle intermediate recycling of pyruvate. 相似文献
11.
S. Leoni S. Spagnuolo M. Massimi F. Terenzi L. Conti Devirgiliis 《Bioscience reports》1992,12(2):135-141
Amino acid uptake mediated by system A was studied in cultured fetal and adult hepatocytes, subjected to growth stimulation
by EGF and insulin, or to growth inhibition by high cell density.
The mitogenic stimulation induced a strong transport increase only in fetal cells, while the cell density-dependent growth
inhibition, probably mediated by molecules present on adult hepatocyte membranes, provoked the decrease of amino acid uptake
only in the adult cells.
The results indicate that the different modulation of amino acid transport by cell growth is dependent on the age and the
differentiation stage of hepatocytes. 相似文献
12.
Ognen A. C. Petroff Alessandro P. Burlina Joel Black James W. Prichard 《Neurochemical research》1991,16(11):1245-1251
This study explored the utility of1H and13C magnetic resonance spectroscopy to study a standard synaptosomally enriched fraction (P2 pellet) made from rat cerebrum. The preparations contained high concentrations of N-acetylaspartate and -aminobutyric acid and low concentrations of glutamine, indicating that they were in fact rich in neuronal cytosol. The metabolic competence of the preparation was assessed by quantitative measurements of its ability to convert [1-13C]glucose into lactate, glutamate, aspartate, and other metabolites under well oxygenated conditions in 30 minutes. The minimum mean glycolytic rate was 0.8 mM glucose/min and the flow through the tricarboxylic acid cycle was equivalent to 0.2 mM glucose/min.Abbreviations ppm
parts per million (chemical shift scale)
- NMR
nuclear magnetic resonance
- GABA
-aminobutyric acid
- PBS
phosphate-buffered normal saline solution
- TSP
3-trimethylsilylpropionate
During the performance of these studies Dr. A.P. Burlina was on leave from Instituto di Clinica delle Malattie Nervose e Mentali, University of Padua, Padua, Italy. 相似文献
13.
[2-13C]Succinate has been used to examine the metabolic carbon flux from the Krebs cycle in rat renal proximal convoluted tubular (PCT) cells under physiological and pathophysiological conditions. Therefore, we developed a mathematical model that enabled us to determine the metabolic fluxes of the Krebs cycle. A mathematical model for the calculation of flux from [2-13C]succinate was used to determine fluxes in rat PCT cells during chronic acidosis in the presence and absence of 0.1 mM angiotensin II. The relative carbon efflux via glutamate dehydrogenase in rat renal PCT cells increases during chronic acidosis from 0.27 to 0.39, whereas this carbon flux is not affected by the presence of peptide hormone angiotensin II in the incubation medium. The fraction of intermediate 13C-labelled oxaloacetate transformed into the phosphoenolpyruvate and aspartate pools increases significantly from 0.41 to 0.57 in the case of chronic acidosis. The carbon efflux is not affected by angiotensin II. The 13C-NMR data also show that the carbon efflux through phosphoenolpyruvate carboxykinase increases from 0.35 to 0.56 in rat renal PCT cells derived from chronic acidotic animals, as well as in the presence of angiotensin II. The present results indicate that angiotensin II affects only the flux through phosphoenolcarboxykinase, whereas chronic acidosis increases the flux through phosphoenolpyruvate carboxykinase as well as the gluconeogenic flux. 相似文献
14.
Iraz M Ozerol E Gulec M Tasdemir S Idiz N Fadillioglu E Naziroglu M Akyol O 《Cell biochemistry and function》2006,24(4):357-361
Cisplatin is one of the most active cytotoxic agents in the treatment of cancer. High doses of cisplatin have also been known to produce hepatotoxicity. Several studies suggest that supplementation with an antioxidant can influence cisplatin-induced hepatotoxicity. The present study was designed to determine the effects of cisplatin on the liver oxidant/antioxidant system, and the possible protective effects of caffeic acid phenethyl ester (CAPE) on liver toxicity induced by cisplatin. Twenty-four adult female Wistar albino rats were divided into four groups of six rats each: control, cisplatin, CAPE, and cisplatin+CAPE. Cisplatin and CAPE were injected intraperitoneally. Liver tissue was removed to study the activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), myeloperoxidase (MPO), xanthine oxidase (XO), adenosine deaminase (ADA), and the levels of malondialdehyde and nitric oxide (NO). The activities of SOD and GSH-Px increased in the cisplatin+CAPE and CAPE groups compared with the cisplatin group. CAT activity was higher in the cisplatin +CAPE group than the other three groups. XO activity was lower in the cisplatin group than the control group. MPO activity was also increased in the cisplatin group compared to the control and CAPE groups. It can be concluded that CAPE may prevent cisplatin-induced oxidative changes in liver by strengthening the antioxidant defence system by reducing reactive oxygen species and increasing antioxidant enzyme activities. 相似文献
15.
R H Dunstan F R Whatley W Greenaway 《Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain)》1988,233(1270):1-15
The biosynthesis in vivo of a number of amino acids, sugars, and purines in Paracoccus denitrificans grown on either [2,3-13C]succinate or [1,4-13C]succinate was investigated by using gas chromatography-mass spectrometry. The distribution of label in the TCA-cycle-related amino acids indicated that carbon intermediates of energy metabolism were utilized as precursors for the biosynthesis of these amino acids in vivo. The biosynthesis of glycine, serine, phenylalanine and glycerol from labelled succinate in vivo were consistent with phosphoenol pyruvate as an intermediate. A mechanism for the formation of C4, C5 and C6 sugars without the use of fructose-1,6-bisphosphate aldolase (which has not been detected in P. denitrificans) is proposed. The 13C-enrichments of ribose in the bacterium indicate that there are at least three routes of ribose biosynthesis operating during growth on labelled succinate. The probability distribution of labelled purine molecules was successfully predicted for adenine, guanine and adenosine, thus confirming their generally accepted route of biosynthesis in vivo. 相似文献
16.
Gluconeogenesis in hepatocytes determined with [2-13C] acetate and quantitative 13C NMR spectroscopy
《The International journal of biochemistry》1993,25(1):1-5
- 1.1. In the present study the major metabolic pathways of glucose metabolism were determined in isolated liver cells using [2-13C]acetate and 13C magnetic resonance spectroscopy.
- 2.2. The relative reaction rates of glucose synthesis to the TCA cycle were determined from the 13C distribution in glucose where the overall 13C enrichment of glucose was 6.41 ± 1.94% (mean ± SD; n = 6) and the mean 13C enrichment of C1, C2, C5, C6 to C3, C4 was 2.63 ± 0.30.
- 3.3. Since the distribution of tracer in glucose is a function of the relative entry rates of pyruvate to acetyl-CoA into the oxaloacetate pool this was calculated to be 0.32 ± 0.15 and the factor for carbon exchange (1/P) between the gluconeogenic pathway and the TCA cycle was calculated to be 1.03 ± 0.20.
- 4.4. With this carbon exchange factor and the approximated 13C enrichment of acetyl-CoA the intramitochondrial 13C enrichment of phosphoenolpyruvate was calculated and the “true” rate of hepatic gluconeogenesis from phosphoenolpyruvate estimated.
- 5.5. Since acetate was metabolized solely in liver cells the 13C enrichment of acetyl-CoA could be approximated from that of 3-hydroxybutyrate.
- 6.6. The carbon 13 enrichment of 3-hydroxybutyrate and phosphoenolpyruvate was 5.89 ± 0.90% and 5.96 ± 1.67%, respectively.
- 7.7. The per cent gluconeogenesis from phosphoenolpyruvate calculated as the ratio of the 13C enrichment of glucose to that of 3-hydroxybutyrate times 1/P was 107 ± 8%.
- 8.8. In this study the validity of assessing isotopic exchange at oxaloacetate as suggested by Katz [Katz J. (1985) Am. J. Physiol.248, R391–R399] when interpretation of the data are not obscured by pseudoketogenesis.
- 9.9. Magnetic resonance spectroscopy provides direct information about intramolecular tracer distribution by which flux rates in major metabolic pathways are derived.
17.
R H Dunstan F R Whatley W Greenaway 《Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain)》1987,231(1264):349-358
Paracoccus denitrificans was grown on either [2,3-13C]succinate or [1,4-13C]succinate, and extracts were analysed by using gas chromatography-mass spectrometry. The distribution of label in isoleucine indicated that the 2-ketobutyrate required for isoleucine biosynthesis was mainly produced from pyruvate by 2-keto-acid chain elongation (i.e. the 'pyruvate elongation pathway'). Approximately 10% of isoleucine was produced by a second pathway involving propionyl CoA. Threonine and glutamate were not utilized by P. denitrificans as a source of 2-ketobutyrate production for isoleucine biosynthesis under the growth conditions used. 相似文献
18.
Elsie M. B. Sorensen Nancy K. R. Smith Cindy S. Boecker Daniel Acosta 《In vitro cellular & developmental biology. Plant》1984,20(10):771-779
Summary Parenchymal hepatocytes from neonatal rats were isolated, cultured about 24 h, exposed to cadmium with or without calcium,
and processed for scanning electron microscopy. To assess the severity of cadmium-induced changes, exposed hepatocytes were
categorized based upon the extent of morphological damage. Differences in surface blebbing, alterations in microvilli, variations
in the degree of swelling, and changes in cell shape were used to categorize the severity of cell damage. A double-blind morphometric
analysis (a geometricostatistical processing of two-dimensional data for the collection of three-dimensional information)
of cellular changes was conducted for each exposure time and for each concentration of cadmium in the presence or absence
of calcium. Significant decreases occurred in the percent relative volume of normal, flattened cells present in cultures exposed
for 30 min to 50 or 100 μM cadmium in the absence of calcium. In contrast, the percent relative volume of severely damaged spherical cells was significantly
increased after exposure to solutions containing 50 or 100 μM cadmium and lacking calcium. Percent relative volume of intermediate cells (which were slightly swollen and showed changes
in microvillar number) was significantly increased following a 30 min exposure to all cadmium concentrations in the absence
of calcium. The examination of hepatocytes exposed for 60 min showed that the degree of cadmium-induced cytotoxicity was more
severe in the absence of calcium than was the case for the hepatocyte cultures exposed for 30 min: approximately 30% more
spherical cells and 30% fewer flattened cells were present if cultures were exposed in the absence of calcium for 60 min compared
to those exposed for 30 min. The degree of blebbing was significantly greater at all cadmium concentrations in the absence
of calcium. The presence of calcium, therefore, reduced cadmium-induced cytotoxicity in primary cultures of rat hepatocytes
subjected to morphometric analysis after scanning electron microscopy. 相似文献
19.
Bolus injection of [13N]ammonia into the femoral vein of pentobarbital-anesthetized rats was followed by rapid clearance from the blood and first-pass extraction of nearly 30% by the lungs. Of the label present in the lungs at 6 s after injection (about 27% of the dose), more than 20% was in metabolized form. Of the label present in the lungs at 2 min after injection (about 10% of the dose), 18-25% was in ammonia, about 75% was in glutamine (amide) and less than 1% was in glutamate and aspartate. Thus, despite the presence of significant amounts of glutamate dehydrogenase, the overwhelming route for metabolism of ammonia entering the rat lung in vivo was the glutamine synthetase reaction. Lung tissue that was removed 6 s after intravenous injection of [13N]ammonia and incubated in Krebs-Ringer glucose medium at 37 degrees C for 20 min, showed a significant increase (more than one-third), compared to unincubated lung tissue in the quantity of label in glutamine. Between 6s and 2 min after injection, during which time the total 13N content of the lungs decreased by more than 60%, the maintenance of a quasi-steady state in the concentration of labeled glutamine suggested a short-term balance between formation from extracted ammonia and loss of glutamine into the circulation. Our data support the concept that the lungs are a source of circulating glutamine in the rat. Despite the large fractional extraction of blood-borne [13N]ammonia by the lungs, only minute amounts of tracer (0.2-0.6 ppm of the injected dose) were detected in the expired air within the first 5 min after administration of [13N]ammonia to anesthetized rats, so that pulmonary excretion was not a significant pathway of ammonia elimination. The present findings emphasize the importance of the lungs in the maintenance of whole-body nitrogen homeostasis and suggest the use of [13N]ammonia and 13N-labeled amino acids as non-invasive probes in the study of normal and diseased lung metabolism. 相似文献