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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cholinergic stimulation of the lateral hypothalamic neurons with intrahypothalamic microinjections of acetylcholine or carbachol caused a marked increase in the content of the active form of glycogen (starch) synthase in the liver. Total activity of the enzyme (active plus inactive forms) was not increased significantly. The lowest effective dose of acetylcholine was 5 X 10(-10) mole, and the optimum dose was 5 X 10(-9) mole. Similar applications of other neurotransmitters, such as norepinephrine, dopamine, serotonin, and gamma-aminobutyric acid, did not affect the enzyme's activity.
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PMID:Cholinergic stimulation of the rat hypothalamus: effects of liver glycogen synthesis. 0 92

1. The influx of [3H]gamma-aminobutyric acid ([3H]GABA) into isolated rat superior cervical ganglia has been measured by radioassay, supplemented by autoradiography. Ganglia were incubated in oxygenated Krebs solution at 25 degrees C, containing 10 microM-amino-oxyacetic acid. Under these conditions more than 95% of accumulated tritium was unmetabolized [3H]GABA. 2. Ganglionic radioactivity increased linearly with incubation time, to yield an intracellular fluid/extracellular fluid concentration ratio (Ci/Co) of about 200 after 6 hr in 0.5 microM-external [3H]GABA. 3. Uptake showed saturation with an apparent transport constant (KT) of 6.8 microM and maximum influx velocity (Jmaxi) of 7 mumole 1. cell fluid-1- min-1. 4. The influx rate at Co = 0.5 microM was unaltered by raising intracellular GABA from 0.2 to 1 mM. 5. Influx velocity increased with temperature (5--35 degrees C) in a monotonic manner with an apparent activation energy of 14 kcal mole-1. 6. Concentrative uptake was depressed by reducing external [Na+] with ouabain, by raising [K+]o above 20 mM, or by removing external Cl-. Uptake was not particularly sensitive to Ca2+ or Mg2+ ions. 7. Utake of [3H]GABA (0.5 microM) was inhibited by beta-guanidinopropionic acid (apparent KI, 28 microM), beta-alanine (KI, 55 microM), gamma-amino-beta-hydroxybutyric acid (KI, 220 microM), beta-amino-n-butyric acid (KI, 708 microM), 3-aminopropanesulphonic acid (KI, 832 microM) and taurine (KI greater than 1 mM). Uptake was not depressed by 1 mM-glycine, alpha-alanine, leucine, serine, methionine or alpha-amino-iso-butyric acid. 8. Radioactively labelled methionine, leucine, glycine, serine, beta-alanine and taurine (concentrations less than or equal to 5 microM) were also taken up by ganglia. Of these, only uptake of beta-alanine and taurine were significantly depressed by 1 mM-GABA. 9. Autoradiographs confirmed that [3H]GABA and [3H] beta-alanine were taken up predominantly into extraneuronal sites (presumed to be neuroglial cells). Methionine, leucine, glycine and serine showed preferential accumulation in neurones. Neuronal uptake of leucine was not prevented by inhibiting protein synthesis. 10. Calculations of net fluxes from unidirectional tracer fluxes suggest that the sympathetic glial cells are capable of promoting net uptake of GABA at external concentrations above 1 microM.
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PMID:[3H]gamma-Aminobutyric acid uptake into neuroglial cells of rat superior cervical sympathetic ganglia. 50 28

The technique of thin-layer chromatography and 14C-dansylation has been used for simultaneous measurements of 22 individual amino acids, taurine, serotonin, and gamma-aminobutyric acid in nanolitre samples of glomerular and renal tubule fluid. Standard curves of each amino acid mixture containing all the others showed excellent linearity at amounts ranging from 5.7.10(-13) to 1.45.10(-11) mole (regression coefficients all greater than 0.95). With careful standardization of dansylation conditions, the technique permits highly reproducible measurement of less than 1 pmole of an amino acid.
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PMID:Simultaneous quantitation of twenty-two amino acids in nanolitre samples of biological fluid. 64 43

Beta-Cell-rich pancreatic islets microdissected from obese-hyperglycemic mice were used to study interactions between the metabolism of L-leucine and D-glucose. L-leucine reduced the islet content of aspartic acid whereas D-glucose, when added to L-leucine-incubated islets, increased the contents of aspartic acid and gamma-aminobutyric acid (GABA). D-glucose also increased the incorporation of L-leucine carbon into aspartic acid, GABA and glutamic acid suggesting stimulation of a malate shuttle mechanism. When expressed per mole of the individual amino acids, the incorporation of L-leucine carbon into GABA was 2.5-4 times higher than into glutamic acid indicating intracellular compartmentation of the latter amino acid. Both L-leucine and D-leucine stimulated 14CO2 production from 14C-labelled D-glucose. L-leucine did not affect 3H2O production from tritiated D-glucose. The present data do not indicate a role of other amino acids or D-glucose in L-leucine-stimulated insulin release.
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PMID:Interactions between the metabolism of L-leucine and D-glucose in the pancreatic beta-cells. 76 54

At substrate concentrations, in medium, of 0.2 to 20 mM and at temperatures of 25 and 37 degrees C, the initial concentrative influx of the amino acids L-lysine (30 and 37 degrees C), L-valine, and gamma-aminobutyric acid into incubated mouse-cerebrum slices follows the rate equation for the initial influx of alpha-aminoisobutyric acid (Cohen, J. Physiol. 228:105, 1973), v equals Vmax/(1+Kt/S)+kuS. Kinetic constants at 37 degrees C are: Vmax equals 0.089 mumoles/g final wet wt of slices, min, Kt equals 0.69 mM, ku equals 0.037 mumoles/g final wet wt, mM-substrate, min for L-lysine; Vmax equals 0.60, Kt equals 1.30, ku equals 0.067 for L-valine; and Vmax equals 1.71, Kt equals 1.58, ku equals 0.094 for gamma-aminobutyric acid. The linear term, kuS, is due to an unsaturable process of concentrative uptake, not diffusion. Comparison of temperature coefficients reveals a "reference" pattern for typical low affinity transport of amino acids into brain slices. Its characteristics are: Activation energies associated with Vmax and ku are in range 14 to 20 kcal/mole; K, varies only slightly with temperature, L-Lysine and alpha-aminoisobutyric acid fit this pattern; L-valine and gamma-aminobutyric acid deviate in part. The Akedo-Christensen plot (J. Biol. Chem. 237:118, 1962) does not distinguish between the rateequation v equals Vmax/(1+Kt/S)+kuS for saturable uptake plus first-order unsaturable concentrative uptake, and the rate equation v equals Vmax/(1 + Kt/S)+kd(S minus Si) for saturable uptake plus first-order nonconcentrative "passive diffusion".
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PMID:A comparison of the rate equations, kinetic parameters, and activation energies for the initial uptake of L-lysine, L-valine, gamma-aminobutyric acid, and alpha-aminoisobutyric acid by mouse brain slices. 112 85

The interaction of 3H-GABA (gamma-aminobutyric acid and 14C-glutamate with lipids in an aqueous organic partition system was studied. With this partition system 3H-GABA and 14C-glutamate were able to interact with sphingomyelin, sulfatide, phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine and phosphatidic acid but not with cholesterol or ceramide. In an homogeneous aqueous medium we could not demonstrate any interaction between 3H-GABA and lipids. The apparent dissociation constants (Kd) for 3H-GABA-lipids or 14C-glutamate-lipids interactions in organic medium were in the millimolar range and maximal charge (Bmax) between 3 and 7 moles of GABA or glutamate by mole of lipid. Amino acids such as glutamic acid, beta-alanine and glycine displaced 3H-GABA with the same potency as GABA itself; thus these results show that the interaction lacks pharmacological specificity. To detect this interaction lipid concentrations higher than 2 microM were required and in the partition system 3H-GABA and lipid phosphorus were both concentrated at the interface. Therefore lipids tested with a biphasic partition system do not fulfill the classical criteria for a neurotransmitter receptor at least not for GABA and glutamate.
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PMID:GABA interaction with lipids in organic medium. 288 73

1. The release of gamma-aminobutyric acid (GABA) from the surface of the posterior lateral gyrus of the cerebral cortex was measured by a sensitive enzymic fluorimetric assay procedure. Experiments were performed with anaesthetized cats during resting conditions and during cortical inhibition produced by electrical stimulation of the brain surface or of the lateral geniculate nucleus (l.g.n.).2. The average resting release of endogenous GABA was 0.20 n-mole/ 7 min.cm(2) cortex; this was increased during stimulation of both the cortical surface (2.9 times resting release during monopolar stimulation and 7.4 times resting release during bipolar stimulation) and the l.g.n. (5.7 times resting release).3. Removal of calcium ions from the collection fluid did not affect the resting release of endogenous GABA but prevented the increase in GABA release normally evoked by stimulation of the cortical surface.4. The stimulus parameters used to increase the release of GABA also inhibited the glutamate-induced firing of single cells in the visual cortex and this inhibition was abolished in the absence of calcium ions.5. In three experiments the total amino acid content of cortical samples was examined using an amino acid analyser. With the exception of GABA, there were no significant differences between the rates of release of any other detected amino acids during periods with and without electrical stimulation of the cortex.6. It is suggested that since the release of GABA observed during inhibitory stimulation of the cortex is calcium-dependent and specific, it may originate from inhibitory nerve terminals in the cortex. The present findings support the view that GABA is a central inhibitory neurotransmitter.
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PMID:The release of gamma-aminobutyric acid during inhibition in the cat visual cortex. 432 9

The temperature dependence of the interaction of three benzodiazepines with their receptors in rat brain membranes containing about 2 microM (endogenous) gamma-aminobutyric acid was investigated. van't Hoff plots of the equilibrium dissociation constants were linear for [3H]diazepam and its N-desmethyl derivative (N-desmethyldiazepam, NDz), whereas for [3H]flunitrazepam a break between two linear portions occurred at about 10 degrees. Binding of diazepam, NDz, and flunitrazepam (for the latter, at temperature greater than 10 degrees) is enthalpy-driven (delta H approximately -40 to -50 kJ/mole with a negligible contribution from delta S. The latter result indicates that the interaction is not a simple hydrophobic association, but that it may be more complex in nature, possibly involving a conformational transition of the receptor-ligand complex. The activation energy for dissociation of the [3H]flunitrazepam- and [3H]diazepam-receptor complexes is about 100 kJ/mole. Consequently, the complexes dissociate about 100 times faster on changing temperature from 0 degrees to 37 degrees.
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PMID:Temperature dependence of the benzodiazepine-receptor interaction. 628 71

The composition of the amino acid and amine derivatives obtained with the o-phthaldialdehyde (OPA)/3-mercaptopropionic acid (MPA) and with the OPA/N-acetyl-L-cysteine (NAC) reagents was investigated by on-line HPLC-electrospray ionization MS. The initially formed derivatives proved to be, as expected, the corresponding isoindoles while their transformed species contained one additional OPA molecule. Based on the MS spectra of all transformed OPA derivatives a reaction pathway is suggested. This reaction mechanism was supported both by the molecular ions of the endproducts and by the presence of several selective fragment ions that served as an explanation to the structure of the believed to be less stable OPA derivatives. It has been shown that more than one OPA derivative forms in all those cases when the compound to be derivatized does contain the NH2-CH2-R moiety. Thus, amino acids like e.g. glycine, histidine, beta-alanine, gamma-aminobutyric acid, epsilon-aminocaproic acid, ornithine, and also several aliphatic mono- and diamines provide more than one OPA derivative. Analytical consequences of this experience were utilized by altering the reagent's composition. Reagents containing mole ratios of [OPA]/[MPA] or [OPA]/[NAC]=1/50 resulted in two benefits, simultaneously: (i) in a decrease of the transformation rate of the initially formed derivative, and, (ii) in an increase of the overall stability of the total of derivatives.
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PMID:Advances in the evaluation of the stability and characteristics of the amino acid and amine derivatives obtained with the o-phthaldialdehyde/3-mercaptopropionic acid and o-phthaldialdehyde/N-acetyl-L-cysteine reagents. High-performance liquid chromatography-mass spectrometry study. 1199 63

The amino acid composition of endosperm cavity sap and of sieve tube saps from the flag leaf, peduncle, rachis, grain pedicel, and grain were determined for wheat plants just past the mid-half of grain filling. On a mole percent basis, glutamine accounted for almost half of the amino acids in sieve tube sap from the peduncle and ear. Other protein amino acids, plug gamma-aminobutyrate, were present in varying, but mostly low (a few mole percent) proportions. The amino acid composition of phloem exudate resembled that of the mature wheat grain. The proportions of amino acids in the endosperm cavity were generally similar to those of the sieve tube sap supplying the grain. Cysteine, however, while virtually absent from sieve tube sap, comprised 1 to 2 mole percent of amino acids in the endosperm cavity, suggesting it is transported in a different form. Also, alanine and, to a lesser extent, glutamate were relatively more prominent in endosperm cavity sap than in the sieve tube sap. Thus, while most amino acids were more concentrated in the sieve tube sap than in the endosperm cavity sap, alanine and glutamate appeared to be moving from the sieve tube to the endosperm cavity in the absence of, or perhaps even against, their concentration gradients.
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PMID:Amino Acid Composition Along the Transport Pathway during Grain Filling in Wheat. 1666 28


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