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1.
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
2.
J. JOSEPH BLUM 《The Journal of eukaryotic microbiology》1991,38(3):229-233
Leishmania major promastigotes were washed and resuspended in an iso-osmotic buffer. The rate of oxidation of 14 C-labeled substrates was then measured as a function of osmolality. An acute decrease in osmolality (achieved by adding H2 O to the cell suspension) caused an increase in the rates of 14 CO2 production from [6-14 C]glucose and, to a lesser extent, from [1, (3)-14 C]glycerol. An acute increase in osmolality (achieved by adding NaCl, KCl, or mannitol) strongly inhibited the rates of 14 CO2 production from [1-: 14 C]alanine, [1-14 C]glutamate, and [1, (3)-14 C]glycerol. The rates of 14 CO2 formation from [1-14 C]laurate, [1-14 C]acetate, and [2-14 C]glucose (all of which form [1-14 C]acetyl CoA prior to oxidation) were also inhibited, but less strongly, by increasing osmolality. These data suggest that with increasing osmolality there is an inhibition of mitochondrial oxidative capacity, which could facilitate the increase in alanine pool size that occurs in response to hyper-osmotic stress. Similarly, an increase in oxidative capacity would help prevent a rebuild up of the alanine pool after its rapid loss to the medium in response to hypo-osmotic stress. 相似文献
3.
ACTIVATION OF HEXOSE MONOPHOSPHATE PATHWAY IN BRAIN BY ELECTRICAL STIMULATION IN VITRO 总被引:2,自引:1,他引:1
Abstract— The incubation of cerebral cortical slices for 15 min in Krebs-Ringer-tris (pH 7.6) solution at 37°C with [1-14 C]glucose or [6-14 C]glucose as substrates yielded a C-1:C-6 14 CO2 ratio of 1.21, whereas this ratio increased to 3.01 after the application of electrical stimulation (ES). Tissue levels of 6-phosphoglu-conate (6PG) and glucose 6-phosphate (G6P), intermediary metabolites of hexose monophosphate (HMP) pathway, were 7 and 180 nmol/g tissue following 15 min incubation, and increased by 33 and 45 per cent respectively following the application of ES. Activities of 6-phosphogluconate dehydrogenase (6PGDH, 6-phospho- d -gluconate: NADP+ 2-oxidoreductase, EC 1.1.1.44) and glucose-6-phosphate dehydrogenase (G6PDH, d -glucose-6-phosphate: NADP+ 1-oxidoreductase, EC 1.1.1.49), important enzymes in regulating the activity of HMP pathway, in cerebral cortical slices were 689 and 907 pmol/mg protein/min and were increased by 66 and 25 per cent respectively by the application of ES. Synaptosomal G6PDH and 6PGDH activities were maximally activated by the addition of 40 m m -Na+ to the reaction mixture, whereas no activation by Na+ was observed in microsomal G6PDH and 6PGDH. Amobarbital inhibited more strongly the Embden–Meyerhof (EM) pathway than the HMP pathway, while imipramine had a stronger inhibitory effect on HMP pathway than on EM pathway in the electrically stimulated cerebral tissues.
The present results indicate that the HMP shunt pathway in the cerebral cortex is activated by the application of ES in vitro , possibly at synaptic regions and may play an important metabolic and functional role in the brain. 相似文献
The present results indicate that the HMP shunt pathway in the cerebral cortex is activated by the application of ES in vitro , possibly at synaptic regions and may play an important metabolic and functional role in the brain. 相似文献
4.
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
5.
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
6.
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
7.
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
8.
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
9.
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
10.
When D-[14 C-U]-glucose was administered intraperitoneally into goldfish Carassius amatus at 20° C and 12L: 12D (dark period 1800–0600 hours) at 0600, 1200, 1800, 2400 and 0600 hours on the following day, glucose was metabolized to release 14 CO2 and then it was incorporated into otoliths as carbonate. The rate of metabolic activity, judging from the ratio of inorganic to organic radiocarbon in plasma, was low during the dark period. Carbon incorporation into otoliths was also minimized during 1800–2400 h. When fish were exposed to ambient water containing NaH14 CO3 , plasma radioactivity was lowest during 1800–2400 hours, during which time carbon incorporation into otoliths was lowest. Plasma total CO2 levels markedly increased during the dark period. These results clearly indicate that carbonate formation in otoliths has a diel variation with a nadir lasting 6 h from 1800 to 2400 hours under the photoperiod used. 相似文献
11.
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
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.
Mesophyll cells isolated from Phaseolus vulgaris and Lycopersicon esculentum show decreasing photosynthetic rates when suspended in media containing increasing concentrations of osmoticum. The photosynthetic activity was sensitive to small changes in osmotic potential over a range of sorbitol concentrations from 0.44 M (−1.08 MPa) to 0.77 M (−1.88 MPa). Photorespiration assayed by 14 CO2 release in CO2 -free air and by 14 CO2 release from the oxidation of [1–14 C] glycolate also decreased as the osmotic potential of the incubation medium was reduced. The CO2 compensation points of the cells increased with increasing concentration of osmoticum from approximately 60 μ I−1 1 at −1.08 MPa to 130 μl 1−1 for cells stressed at −1.88 MPa. Changes in photosynthetic and photorespiratory activities occurred at moderate osmotic potentials in these cells suggesting that in whole leaves during a reduction in water potential, non- stomatal inhibition of CO2 assimilation and glycolate pathway metabolism occurs simultaneously with stomatal closure. 相似文献
14.
TAKASHI KAGEYAMA SUSUMU Y. TAKAHASHI TADAKAZU OHOKA EIJI OHNISHI 《Development, growth & differentiation》1980,22(6):859-865
The mechanism of polyol accumulation in diapausing Bombyx eggs, conversion of [6-14 C] glucose-6-phosphate into polyols and other neutral sugars was investigated in in vitro reaction systems. When a crude homogenate or a press juice of the eggs was incubated with [6-14 C]glucose-6-P, the labelled trehalose, sorbitol and glycerol accumulated in the reaction mixture. In the press juice incubation system of developing eggs at day 1, 14 C-sorbitol was detected in appreciable amounts, but it decreased rapidly with the development of the embryos. When the press juice was prepared from eggs in diapause, the formation of 14 C-sorbitol was 3–5 times greater in eggs at early stages (day 2 to day 4) than in developing eggs. 相似文献
15.
16.
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
17.
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
18.
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
19.
Masahisa Nakamura Masayuki Komukai Ryoichi Matsuda Shoichi Okinaga Kiyoshi Arai 《Development, growth & differentiation》1989,31(2):179-188
The effect of lactate on synthesis of new proteins in isolated spermatids and spermatocytes of rats was examined. Lactate stimulated[35 S]methionine ([35 S]met) incorporation into both spermatids and spermatocytes. The rate of protein synthesis was positively correlated with the intracellular level of ATP. The [35 S]met-labeled proteins in the two types of cells were compared by one and two dimensional polyacrylamide gel electrophoresis (1D and 2D-PAGE) and autoradiography. The syntheses of several stagespecific and non-specific proteins were observed. When spermatids and spermatocytes were cultured in medium without lactate, two major proteins of molecular weight (Mr) 43 kD and 55 kD were detected in the water-soluble fraction (105,000 g supernatant), and one major protein of Mr 24 kD was observed in the membrane-rich fraction. Addition of lactate to the incubation medium dramatically increased the synthesis of six proteins (Mr 14 kD, 16 kD, 43 kD, 55 kD, 84 kD and 135 kD) in the water-soluble fractions of spermatids and spermatocytes, but did not stimulate the synthesis of the Mr 24 kD protein in the membrane-rich fraction. In addition, after 1D and 2D-PAGE and electrophoretic transfer to nitrocellulose, two proteins of Mr 43 kD and 55 kD were identified as actin and tubulin, respectively, on the basis of their reactivities with specific antisera. Tubulin was also produced by in vitro translation using a spermatid lysate. These results suggest that lactate may play an important role in changing the cell structure and shape during spermatogenesis by regulating the syntheses of actin and tubulin. 相似文献
20.
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