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1.
Partitioning of CO2 Production Between Glucose and Lactate in Excised Sympathetic Ganglia, with Implications for Brain 总被引:4,自引:1,他引:3
Martin G. Larrabee 《Journal of neurochemistry》1996,67(4):1726-1734
Abstract: Chains of lumbar sympathetic ganglia from 15-day-old chicken embryos were incubated for 4 h at 36°C in a bicarbonate-buffered salt solution equilibrated with 5% CO2 -95% O2 . Glucose (1–10 m M ), lactate (1–10 m M ), [U-14 C]glucose, [1-14 C]glucose, [6-14 C]glucose, and [U-14 C]lactate were added as needed. 14 CO2 output was measured continuously by counting the radioactivity in gas that had passed through the incubation chamber. Lactate reduced the output of CO2 from [U-14 C]glucose, and glucose reduced that from [U-14 C]lactate. When using uniformly labeled substrates in the presence of 5.5 m M glucose, the output of CO2 from lactate exceeded that from glucose when the lactate concentration was >2 m M . The combined outputs at each concentration tested were greater than those from either substrate alone. The 14 CO2 output from [1-14 C]glucose always exceeded that from [6-14 C]glucose, indicating activity of the hexose monophosphate shunt. Lactate reduced both of these outputs, with the maximum difference between them during incubation remaining constant as the lactate concentration was increased, suggesting that lactate may not affect the shunt. Modeling revealed many details of lactate metabolism as a function of its concentration. Addition of a blood-brain barrier to the model suggested that lactate can be a significant metabolite for brain during hyperlactemia, especially at the high levels reached physiologically during exercise. 相似文献
2.
ABSTRACT Earlier studies showed that Leishmania major promastigotes are sensitive to osmotic conditions. A reduction in osmolality caused the cells to shorten and to rapidly release most of their large internal pool of alanine. In this study some effects of hyper-osmotic stress were examined. an increase in osmolality of the culture medium from 308 to 625 mOsm/kg caused only a small decrease in growth rate. When cells grown in the usual culture medium (308 mOsm/kg) were washed, resuspended in iso-osmotic buffer, and subjected to acute hyper-osmotic stress by addition of mannitol, the alanine content increased even in the absence of exogenous substrate. Promastigotes, depleted of alanine by a 5-min exposure to hypo-osmotic conditions, also synthesized alanine when resuspended in iso-osmotic buffer. Washed cells resuspended in iso-osmotic buffer consume their internal pool of alanine under aerobic conditions, Rates of consumption decreased on addition of mannitol, becoming zero at about 440 mOsm/kg. At higher osmolalities, alanine synthesis occurred. to estimate whether proteolysis could account for alanine synthesis in the absence of exogenous substrate, cells that had been grown with [1-14 C]leucine were washed and resuspended under hypo-, iso-, and hyper-osmotic conditions and the amounts of 14 CO2 and 14 C-labelled peptides released in 1 h were measured. Little proteolysis occurred under these conditions, but the possibility that proteolysis was the source of the alanine increase, observed in response to hyper-osmotic stress, cannot be ruled out. 相似文献
3.
Methanolic extracts of Zea mays L. cv. Fronica root segments which had been incubated in [14 C] indole-3-acetie acid were analysed by reverse-phase high-performance liquid chromatography. Metabolism of indole-3-acetic acid was found to be rapid and extensive with at least 11 products apparent after a 2 h incubation. A comparison of metabolites of [1-14 C]– and [2-14 C] IAA, calculations of 14 CO2 evolution, and data on the polarity of products indicated that decarboxylation had not occurred. An average of 34% of the radioactivity remained associated with the indole-3-acetic acid peak. 相似文献
4.
THE EFFECT OF DIABETES, INSULIN AND WALLERIAN DEGENERATION ON LEUCINE METABOLISM OF ISOLATED RAT SCIATIC NERVES 总被引:4,自引:3,他引:1
Maria G. Buse H. Franklin Herlong Dorothy A. Weigand S. S. Spicer 《Journal of neurochemistry》1976,27(6):1339-1345
Abstract– 14 CO2 production and 14 C incorporation into proteins was studied in isolated rat sciatic nerves during incubation with 0.1 mM-[1-14 C]leucine. Rats were made diabetic with streptozotocin. Nerves from diabetic rats incubated with glucose oxidized more [14 C]leucine than controls. This difference was abolished in the presence of insulin (1 mU/ml). The effects of diabetes and insulin on leucine oxidation could not be demonstrated in the absence of glucose. Insulin stimulated the incorporation of [14 C] from leucine into proteins by nerves from controls and diabetic rats.
Nerves undergoing Wallerian degeneration showed a marked increase in DNA content and stimulated incorporation of [14 C]leucine into proteins. 14 CO2 production from leucine proceeded at 75% of the rate observed in intact nerves. Neither insulin nor diabetes affected leucine metabolism in degenerating nerves.
Neither the extracellular space nor the concentration of free amino acids were significantly different in nerves obtained from control and diabetic rats, except for lower glutamine content in the latter.
In vitro leucine metabolism of nerves is affected by diabetes, insulin and the integrity of the axon. The Schwann cell is suggested as a possible site of the observed changes in leucine metabolism. 相似文献
Nerves undergoing Wallerian degeneration showed a marked increase in DNA content and stimulated incorporation of [
Neither the extracellular space nor the concentration of free amino acids were significantly different in nerves obtained from control and diabetic rats, except for lower glutamine content in the latter.
In vitro leucine metabolism of nerves is affected by diabetes, insulin and the integrity of the axon. The Schwann cell is suggested as a possible site of the observed changes in leucine metabolism. 相似文献
5.
TIME-DEPENDENT PARTITIONING OF GLUCOSE CARBONS METABOLIZED BY THE SUPERIOR CERVICAL GANGLION FROM CALVES 总被引:1,自引:0,他引:1
Abstract— Glucose metabolism in the superior cervical ganglion for calves has been studied by incubating slices with [1-14 C]-, [6-14 C]- and [U-14 C]-labelled glucose at 37°C and pH 7.4. Glucose utilization and the metabolic partitioning of glucose carbon in products during different incubation periods ranging from 5 to 60 min were determined by isotopic methods.
Separation and identification of labelled compounds have been achieved by anion and cation exchange chromatography as well as by TLC and enzymatic analyses.
From the data obtained a carbon balance could be constructed showing lactate to be the major product of glucose metabolism followed by CO2 and amino acids. Measuring the release of 14 CO2 from differently 4 C-labelled glucose, the existence of an active pentose phosphate pathway in the ganglion could be demonstrated although this pathway seems to contribute only to a small extent to glucose metabolism. The marked decrease of the C-U: C-6 and the C-U:C-1 ratios in 14 CO2 observed in the course of incubation is discussed in terms of a time-dependent change in the rate of synthesis of amino acids which are directly connected with intermediates of the citric acid cycle. 相似文献
Separation and identification of labelled compounds have been achieved by anion and cation exchange chromatography as well as by TLC and enzymatic analyses.
From the data obtained a carbon balance could be constructed showing lactate to be the major product of glucose metabolism followed by CO
6.
David Pleasure Mattie Hardy Gary Johnson Robert Lisak Donald Silberberg 《Journal of neurochemistry》1981,37(2):452-460
Abstract: Oligodendroglia prepared from minced calf cerebral white matter by trypsinization at pH 7.4, screening, and isosmotic Percoll (polyvinylpyr-rolidone-coated silica gel) density gradient centrifugation survived in culture on polylysine-coated glass, extending processes and maintaining phenotypic characteristics of oligodendroglia. In the present study, ethanolamine glycerophospholipid (EGP) metabolism of the freshly isolated cells was examined during short-term suspension culture by dual label time course and substrate concentration dependence experiments with [2-3 H]glycerol and either [1,2-14 C]ethanolamine or L-[U-14 C]serine. Rates of incorporation of 3 H from the glycerol and of 14 C from the ethanolamine into EGP were constant for 14 h. In medium containing 3 mM-[1,2-14 C]ethanolamine and 4.8 mM-[2-3 H]glycerol, rates of incorporation of 14 C and 3 H into diacyl glycerophosphoethanolamine (diacyl GPE) were similar. Under the same conditions, 3 H specific activities of alkylacyl GPE and alkenylacyl GPE were much lower than 14 C specific activities, likely as a result of the loss of tritium during synthesis of these forms of EGP via dihydroxyacetone phosphate. L-[U-14 C]serine was incorporated into serine glycerophospholipid (SGP) by base exchange rather than de novo synthesis. 14 C from L-[U-14 C]serine also appeared in EGP after an initial lag period of several hours. Methylation of oligodendroglial EGP to choline glycerophospholipid (CGP) was not detected. 相似文献
7.
Abstract— The effect of 15 h continuous exposure to CS2 on the metaboliam of glucose and free amino acids in the brain of rats was studied. CS2 caused a moderate hypoglycaemia. There were also changes in the amounts of some amino acids in the brain. Glutamate and γ-aminobutyrate were lower whereas glutamine was markedly increased. Comparative studies in vivo of the metabolism of [2-14 C]glucose and [1-14 C]butyrate indicated that CS2 did not affect glycolysis or the incorporation of 14 C from glucose into amino acids except into γ-aminobutyrate which was reduced. Contrary to the findings with [14 C]glucose, CS2 provoked distinct changes in the labelling of amino acids when [14 C]butyrate was the precursor. The most notable change was a markedly increased incorporation of 14 C into glutamine. Based on the two-compartment model of brain glutamate the experimental findings indicated that CS2 affected metabolism associated with the 'small' pool of glutamate but had a minimal effect on metabolism associated with the 'large' glutamate pool. The possibility is suggested that the changes observed involved an increased rate of ammonia removal. The low incorporation of 14 C into γ-aminobutyrate from either precursor is consistent with other evidence showing that CS2 interferes with pyridoxal phosphate-dependent enzymes. 相似文献
8.
Abstract: We studied the effects of denervation and reinnervation of the rat extensor digitorum longus muscle (EDL) on the oxidation of [6-14 C]glucose to 14 CO2 . The rate of 14 CO2 production decreased dramatically following denervation, and the decrease became significant 20 days after nerve section. Prior to day 20, changes apparently reflected the decline of muscle mass. Decreased 14 CO2 production was due to reduced capacity of the enzymatic system (apparent Vmax ); there was no change in apparent affinity for glucose (apparent K m ). Mixing experiments revealed that the loss of oxidative capacity following denervation is not caused by production of soluble inhibitors by degenerating muscle. Oxidative metabolism, as measured by 14 CO2 evolution, recovered during reinnervation. Surprisingly, the specific activity in reinnervated muscles displayed an "overshoot" of approximately 50%, which returned to control by day 60, possibly reflecting increased energy demand by the growing muscle. The time-course of the denervation-mediated change indicates that altered oxidative capacity is secondary to events that initiate denervation changes in muscle. Nevertheless, diminished oxidative capacity may be of considerable metabolic significance in denervated muscle. 相似文献
9.
Abstract: Acute administration of vitamin B6 to rats (10 mg/kg body weight) led to reduced urinary excretion of N 1 -methyl nicotinamide and methyl pyridone carboxamide, indicating inhibition of the oxidative metabolism of tryptophan. There was a considerable reduction in the production of 14 CO2 from [ ring -2-14 C]tryptophan, and a significant inhibition of hepatic tryptophan oxygenase when measured in liver homogenates, together with an increase in the concentration of tryptophan in plasma. There was an increase in both the concentration of tryptophan in the brain and the uptake into the brain of peripherally administered [3 H]tryptophan, accompanied by a small increase in the rate of synthesis of 5-hydroxy-tryptamine in the brain. It is suggested that this increase in the uptake of tryptophan into the brain following a relatively large dose of vitamin B6 may explain the beneficial action of the vitamin in some cases of depressive illness. 相似文献
10.
Abstract— Ninhydrin decarboxylation experiments were carried out on the labelled amino acids produced following intraventricular injection of either γ-hydroxy-[1-14 C]butyric acid (GHB) or [1-14 C] succinate. The loss of isotope (as 14 CO2 ) was similar for both substances. The [1-14 C]GHB metabolites lost 75% of the label and the [1-14 C] succinate metabolites lost 68%. This observation gives support to the hypothesis that the rat brain has the enzymatic capacity to metabolize [1-14 C]GHB to succinate and to amino acids that have the isotope in the carboxylic acid group adjacent to the a-amino group. These results also indicate that the label from [1-14 C]GHB does not enter the Krebs cycle as acetate. The specific activity ratio of radiolabelled glutamine to glutamic acid was determined in order to evaluate which of the two major metabolic compartments preferentially metabolize GHB. It was found that for [1-14 C]GHB this ratio was 4.20 ± 0.18 (S.E. for n = 7) and for [l-14 C]succinate this ratio was 7.71 (average of two trials, 7.74 and 7.69). These results suggest that the compartment thought to be associated with glial cells and synaptosomal structures is largely responsible for the metabolism of GHB. Metabolism as it might relate to the neuropharmacological action of GHB is discussed. 相似文献
11.
Uridine and cytidine are major nucleosides and are produced as catabolites of pyrimidine nucleotides. To study the metabolic fates and role of these nucleosides in plants, we have performed pulse (2 h) and chase (12 h) experiments with [2-14 C]uridine and [2-14 C]cytidine and determined the activities of some related enzymes using tubers and fully expanded leaves from 10-week-old potato plants ( Solanum tuberosum L.). In tubers, more than 94% of exogenously supplied [2-14 C]uridine and [2-14 C]cytidine was converted to pyrimidine nucleotides and RNA during 2-h pulse, and radioactivity in these salvage products still remained at 12 h after the chase. Little degradation of pyrimidine was found. A similar pyrimidine salvage was operative in leaves, although more than 20% of the radioactivity from [2-14 C]uridine and [2-14 C]cytidine was released as 14 CO2 during the chase. Enzyme profile data show that uridine/cytidine kinase (EC 2.7.1.48) activity is higher in tubers than in leaves, but uridine nucleosidase (EC 3.2.2.3) activity was higher in leaves. In leaves, radioactivity from [U-14 C]uracil was incorporated into β-ureidopropionic acid, CO2 , β-alanine, pantothenic acid and several common amino acids. Our results suggest two functions of uridine and cytidine metabolism in leaves; these nucleosides are not only substrates for the classical pyrimidine salvage pathways but also starting materials for the biosynthesis of β-alanine. Subsequently, some β-alanine units are utilized for the synthesis of pantothenic acid in potato leaves. 相似文献
12.
Confirmation of operative acetate, H2 /CO2 and methanol methanogenic pathways in the solid-state refuse fermentation 总被引:2,自引:2,他引:0
By use of the radiolabelled substrates sodium [1–14 C] acetate, sodium [2–14 C] acetate, NaH14 CO3 and 14 CH3 OH, three of the possible methanogenic pathways in fermenting refuse were confirmed. Due to the absence of a methanol pool, however, the relative contribution of each could not be determined. Circumstantial evidence for an operative trimethylamine pathway was gained but not confirmed whilst preliminary attempts to stimulate methanogenesis in refuse by supplementation with mono-and dimethylamine proved unsuccessful. 相似文献
13.
Metabolic Precursors and Compartmentation of Cerebral GABA in Vigabatrin-Treated Rats 总被引:1,自引:0,他引:1
Abstract: The metabolic precursors and cerebral compartmentation of the augmented GABA pool induced by vigabatrin, an irreversible inhibitor of GABA transaminase, have been investigated by 13 C NMR. Adult rats receiving rat chow ad libitum were given either drinking water only or drinking water containing 2.5 g/L vigabatrin for 7 days. Both groups of animals were infused either with [1,2-13 C2 ]acetate (15 µmol/min/100 g body weight), an exclusive precursor of GABA formation through the glial glutamine pathway, or with [1,2-13 C2 ]glucose (15 µmol/min/100 g body weight), a substrate that can produce GABA through the glial glutamine pathway or by direct metabolism in the neurons. The brains were frozen in situ, extracted with perchloric acid, and analyzed by 13 C NMR. In vigabatrin-treated animals [13 C]glutamine, a common intermediate for [13 C]GABA synthesis from glucose or acetate, was accumulated to similar amounts during infusions with [1,2-13 C2 ]glucose or [1,2-13 C2 ]acetate. However, [13 C]GABA accumulation was sevenfold higher during [1,2-13 C2 ]glucose infusions or twofold higher during [1,2-13 C2 ]acetate infusions. These results show that the direct pathway of GABA formation by neuronal metabolism of glucose predominates over the alternative pathway through glial glutamine. Near-equilibrium relationships of the aminotransferases of GABA and aspartate imply that the observed [13 C]GABA accumulation occurs initially in the neuronal compartment. 相似文献
14.
Inhibition of the synthesis of acetylcholine in rat brain slices by (-)-hydroxycitrate and citrate 总被引:6,自引:6,他引:0
Abstract: Slices of rat caudate nucleus were incubated in a solution of 123 mM-NaCl, 5 mM-KCl, 1.2 mM-MgCl2 , 1.2 mM-NaH2 PO4 , 25 mM-NaHCO3 , 0.2 mM-choline chloride, 0.058 mM-paraoxon, 1 mM-EGTA, and oxidizable substrates. (−)-Hydroxycitrate, a specific inhibitor of ATP-citrate lyase (EC 4.1.3.8), used at a concentration of 2.5 mM, inhibited the synthesis of acetylcholine (ACh) from [1,5-14 C]citrate by 82–86%, but that from [U-14 C]glucose by only 33%, from [2-14 C]pyruvate by 24% and from [1-14 C-acetyl]carnitine by 8%; the production of 14 CO2 from these substrates was not substantially changed. The synthesis of ACh from glucose and pyruvate was in hibited also by citrate; 2.5 mM- and 5 mM-citrate diminished it by 43% and 66%, respectively; the production of from [U-14 C]glucose and from [1-14 C]pyruvate was not affected. The mechanism of the inhibitory effect of citrate on the synthesis of ACh is not clear; the possibility is discussed that citrate alters the intracellular milieu in cholinergic neurons by chelating the intracellular Ca2+ and decreases the supply of mitochondrial acetyl-CoA to the cytosol. The results with (−)-hydroxycitrate indicate that the cleavage of citrate by ATP-citrate lyase is not responsible for the supply of more than about one-third of the acetyl-CoA which is used for the synthesis of ACh when glucose or pyruvate are the main oxidizable substrates. This proportion may be even smaller, since (−)-hydroxycitrate possibly affects the synthesis of ACh from glucose and pyruvate by a mechanism (unknown) similar to that of citrate, rather than by the inhibition of ATP-citrate lyase. 相似文献
15.
Polyamine content and the activity of arginine decarboxylase (EC 4.1.1.19) and ornithine decarboxylase (EC 4.1.1.17) were studied with respect to meristematic activity in primary roots and in developing lateral roots of Zea mays L. (cv. Neve Ya'ar 170) seedlings. Comparative localization of active ornithine decarboxylase and of meristematic activity were determined by labelling roots either with α-[5-14 C]-difluoromethyl ornithine or with [3 H]-thymidine, respectively.
Lateral roots were formed during the 72 h post-decapitation period, accompanied by an initial decline in putrescine content and by a significant increase in spennidine con-tent at 48–72 h. High levels of spermidine and lower levels of putrescine were found in the primary root apex as well. A marked increase in ornithine and arginine decarboxylase activity, as measured by14 CO2 release, was found during the 72 h post-decapitation period of lateral root development. This increase in ornithine decarboxylase activity was confirmed also by a parallel rise in the incorporation of α-[5-14 C]-difluoromethyl ornithine into trichloroacetic acid-insoluble fractions. Microautoradiographs of longitudinal and cross sections of roots, labelled with α-[5-14 C]-difluoromethyl ornithine, showed that ornithine decarboxylase is localized mainly in the meristematic zones, as evidenced by [3 H]-thymidine incorporation. A close correlation between meristematic activity and polyamines was demonstrated in situ , suggesting that polyamine content and biosynthesis may have a role in meristematic activity in corn roots. 相似文献
Lateral roots were formed during the 72 h post-decapitation period, accompanied by an initial decline in putrescine content and by a significant increase in spennidine con-tent at 48–72 h. High levels of spermidine and lower levels of putrescine were found in the primary root apex as well. A marked increase in ornithine and arginine decarboxylase activity, as measured by
16.
Abstract: Production of [14 C]acetylcholine and 14 CO2 was examined by using tissue prisms from neocortex, hippocampus, and striatum from rats aged approximately 5 months, 13 months, and 27 months. [14 C]Acetylcholine synthesis in the striatum showed highly significant decreases with age for measurements in the presence of both 5 m m - and 31 m m -K+ , contrasting with the lack of significant change in 14 CO2 production in this region. The neocortex and hippocampus showed only small changes, especially when comparison was made between 13-month and senescent animals. Measurements of the release of [14 C]acetylcholine and influence of atropine on this release confirmed the relative stability with age of the cholinergic system in the neocortex. 相似文献
17.
MASAHISA NAKAMURA IKUO YASUMASU SHOICHI OKINAGA KIYOSHI ARAI 《Development, growth & differentiation》1982,24(3):265-272
Rotenone-sensitive 14 CO2 formation from [14 C]lactate and oxygen consumption by round spermatids were found to be greater at elevated temperatures than at 34°C. More than 96% of the total radioactivity of the metabolized [14 C]lactate was recovered in the released CO2 and the acid soluble fraction of the cells. There was practically no incorporation of [14 C]latctate into the lipid, nucleic acid, and protein fractions. Intracellular level of ATP in spermatids was enhanced in the presence of lactate (20 mM) at 34°C (scrotal temperature), whereas it was decrease at 37°C (body temperature). However, this was reversible when the cells were transferred from the elevated temperature to 34°C. It was also found that oxygen consumption and CO2 production were increased at 34°C by 2, 4-dinitrophenol (DNP), but decreased by oligomycin. On the other hand, oligomycin and DNP had no effect on oxygen consumption and 14 CO2 formation at the elevated temperature.
These findings provide evidence that lactate utilization by spermatids is coupled with oxidative phosphorylation at scrotal temperature, but becomes uncoupled at elevated temperature, although more lactate is consumed. 相似文献
These findings provide evidence that lactate utilization by spermatids is coupled with oxidative phosphorylation at scrotal temperature, but becomes uncoupled at elevated temperature, although more lactate is consumed. 相似文献
18.
L-GLUTAMIC ACID DECARBOXYLASE IN NON-NEURAL TISSUES OF THE MOUSE 总被引:7,自引:5,他引:2
Abstract— Low levels of γ-aminobutyric acid (GABA) and of glutamic acid decarboxylase (GAD) activity have been detected in mouse kidney, liver, spleen and pancreas. Quantitation of both 14 CO2 and [14 C]GABA produced in radiometric assays from [U-14 CJglutamic acid has shown that measurement of 14 CO2 evolution alone is not, in all cases, a valid estimate of true GAD activity. As evidenced by increased ,14 CO2 production upon addition of NAD and CoA to assay mixtures, radiometric assay of GAD activity in crude homogenates may yield 14 CO2 via the coupled reactions of glutamic acid dehydrogenase and a-ketoglutarate dehydrogenase. The addition of 1 mM aminooxyacetic acid (AOAA) to assays of kidney homogenates inhibited [,14 C]GABA production 92 per cent while 14 CO2 production was inhibited only 53 per cent. No evidence was found to confirm the reported existence of a second form of the enzyme, GAD II. previously described by Haber el al. (H aber B., K uriyama K. & R oberts E. (1970) Biochem. Pharmac. 19, 1119-1136). Based on sensitivity-to AOAA and chloride inhibition, the GAD activity in mouse kidney is. apparently, indistinguishable from that of neural origin. 相似文献
19.
Abstract: Synaptosomes from normoxic and hypoxic rats were incubated aerobically in the presence and absence of veratridine. In the absence of veratridine, no significant difference was observed between the two types of preparation regarding either ATP/ADP ratio or 14 CO2 or [14 C]acetylcholine synthesis from D-[U-14 C]glucose. However, in the presence of veratridine, significant reductions in the output of 14 CO2 and [14 C]acetylcholine by synaptosomes from hypoxic rats were apparent. It was concluded that irreversible metabolic lesions occur at the synapse as a result of hypoxia, which are apparent only when the metabolism of the preparation is accelerated to a level comparable with the maximal rate occurring in vivo. The presence of such lesions is further evidenced by the significant reductions in ATP/ADP ratio, 14 CO2 output, and [14 C]acetylcholine synthesis that occur in synaptosomes from hypoxic rats made anoxic in vitro and permitted to recover. Such decreases are not seen when synaptosomes from normoxic rats are similarly treated. 相似文献
20.
S ummary : Growth in soils of Mycobacterium paraffinicum with 0, 5, 15, 45 and 270 p/m of ethane was assayed by adding ethane-1,2-14 C and measuring the 14 CO2 produced. With < 45 p/m of ethane the lag period lasted several months. Differences in growth associated with different soils suggest that the microbial method of oil prospecting is unlikely to be commercially successful. 相似文献