...Niels Westergaard; Ursula Sonnewald; Arne Schousboe Use of 13 C-labeled precursors for the neuroactive amino acids glutamate and GABA as well as [U- 13 C]glutamate and glutamine combined with NMR spectroscopy has allowed detailed studies to be performed on cultured neurons and astrocytes yielding...

... the rates of 14 CO 2 production from 1 mM D-[6- 14 C]glucose, L-[U- 14 C]glutamine, D-3-hydroxy[3- 14 C]butyrate, L-[U- 14 C]lactate and L-[U- 14 C]malate by synaptic terminals isolated from 17- to 18-day-old and 7- to 8-week-old rat brain. The rates of 14 CO 2 production from glucose, glutamine, 3...

... and glutamine, both of which may be nitrogen sinks in the brain. Elevation of large neutral amino acids in the interstitial space suggests a decreased concentration in neurons which might have an effect on the synthesis of serotonin and catecholamines and suggests a mechanism by which elevated leucine may...

...Mary C. McKenna; J. Tyson Tildon; Joseph H. Stevenson; Xueli Huang Studies from several groups have provided evidence that glutamate and glutamine are metabolized in different compartments in astrocytes. In the present study we measured the rates of 14 C0 2 production from U-[ 14 C]glutamate and U...

..., pyruvate dehydrogenase and pyruvate recycling was used to determine the relative anaplerotic flux and glutamine oxidation of astrocytes in culture under different substrate conditions. Combinatory analysis of mass isotopomers formed from the condensation of labeled oxaloacetate with labeled acetyl-CoA...

.... Glutamine and citrate resonances represent glial metabolism if a combination of [1- 13 C]glucose + [2- 13 C]acetate is used, but only for short time periods. A combination of [2- 13 C]glucose + [2- 13 C]acetate will label –COO – groups from glucose and – CH 2 groups from acetate, respectively, which...

...Michel Merle; Magali Martin; Annick Villégier; Paul Canioni We analyzed the glutamine isotopomers released into the extracellular medium by cerebellar astrocytes incubated with. [1- 13 C]glucose. We developed a mathematical model of the tricarboxylic acid (TCA) cycle to determine the relative flux...

... chromatography of the dansylated amino acids. No indication was found of classical metabolic compartmentation, i.e., the specific radioactivity of glutamine ( 14 C/ 3 Hratio) never exceeded that of its precursor, glutamate. In accordance with a relatively late maturation of glutamine synthetase activity the rate...

...Claudia Zwingmann; Ulrich Flögel; Josef Pfeuffer; Dieter Leibfritz NH 4 Cl (10 m M ) caused a sustained increase in the cell volume in immobilized, perfused F98 glioma cells to approx. 125% of control after 3 h, as measured by diffusion-weighted 1 H NMR spectroscopy. Concomitantly, the glutamine...

...Y. Tsukada; T. Kanamatsu; H. Watanabe; K. Okamoto To investigate the metabolism of glutamate and glutamine in living monkey brain, a system of in vivo 13 C magnetic resonance spectroscopy (MRS) using 1 H-decoupled 13 C spectroscopy combined with monitoring temperature changes in the brain by MR...

... the cells in media containing 0.5 m M [U- 13 C]glucose in the absence or presence of glutamine (0.5 m M ). Lyophilized cell extracts were analyzed by 13 C nuclear magnetic resonance (NMR) spectroscopy and HPLC. The present findings were compared to results previously obtained using 1.0 m M [U- 13 C]lactate...

..., C3 and C4 positions of both glutamate and the well-resolved C2, C3 and C4 resonances of glutamine and at the C2 and C3 positions of aspartate. GABA was clearly observed for the first time in vivo, suggesting a substantial GABA turnover in the normal human visual cortex. Likewise, lactate C3 labeled...

...Claudia Zwingmann; Annette Brand; Christiane Richter-Landsberg; Dieter Leibfritz Glutamine synthesis, the major pathway of ammonia detoxification, and the intracellular concentration of organic osmolytes in primary astrocytes and F98 glioma cells were investigated with multinuclear magnetic...

... and perfused with artificial CSF containing either 14 C-glutamate, 14 C-glutamine or 14 C-glucose. Dialysate fractions were collected during 20 min intervals for determination of 14 CO 2 . The amount of labelled 14 CO 2 increased for 40 to 60 min and then plateaued and remained relatively constant for at least...

...Arne Schousboe; Niels Westergaard; Ursula Sonnewald; Steffen B. Petersen; Rong Huang; Liang Peng; Leif Hertz Metabolism of glutamate and glutamine in cultured mouse cerebral cortical astrocytes has been investigated using either radioactively labelled ( 14 C) amino acids or 13 C-labelled amino...

...U. Sonnewald; N. Westergaard; B. Hassel; T.B. Müller; G. Unsgård; F. Fonnum; L. Hertz; A. Schousboe; S.B. Petersen Neocortical astrocytes were incubated with 13 C-labeled substrates to determine metabolic pathways. 13 C NMR spectroscopy was used to analyze 13 C incorporation into glutamine...

... into the medium by the astrocyte cultures and the mixed astroglial/neuronal cultures, measurable amounts of label were present in lactate C-3 and C-2, glutamine C-2, C-3 and C-4, acetate C-2, citrate C-2 or C-4 and C-3, glycerol C-1 or C-3, succinate C-2 or C-3 and several unidentified metabolites. Of the labeled...

.... Here we report the kinetics of [U- 14 C]2-OG uptake by crude synaptosomal preparations from bovine and rat retina and brain, and the modulatory effects of glutamate and glutamine. In all four tissues, 2-OG uptake was mediated by a high-affinity system (K t ≈ 1 µ M) that was subject to negative feedback...

...Liang Peng; Leif Hertz; Rong Huang; Ursula Sonnewald; Steffen B. Petersen; Niels Westergaard; Orla Larsson; Arne Schousboe In the present review evidence is presented that (1) glutamine synthesis in astrocytes is essential for synthesis of GABA in neurons; (2) α-ketoglutarate in the presence...

..., the nerve endings require a supply of glutamate precursors that will not cause depolarization. The major precursor to neuronal glutamate is glutamine, which is synthesized in astrocytes and converted to glutamate in neurons. However, glutamine is not the sole source. Alanine also might serve as a precursor...