AMINO ACID TRANSPORT IN BRAIN CORTEX SLICES: I. THE RELATION BETWEEN ENERGY PRODUCTION AND THE GLUCOSE-DEPENDENT TRANSPORT OF GLYCINE

1962 ◽  
Vol 40 (11) ◽  
pp. 1575-1590 ◽  
Author(s):  
P. N. Abadom ◽  
P. G. Scholefield
Keyword(s):  
Incubation Medium ◽  
Energy Production ◽  
Brain Cortex ◽  
Ionic Composition ◽  
Metabolic Inhibitors ◽  
Experimental Conditions ◽  
X Irradiation ◽  
Brain Cortex Slices ◽  
Cortex Slices ◽  
Dependent Transport

Incubation of rat brain cortex slices with glycine in the presence of glucose leads to an accumulation of glycine in the slice. The extent of the accumulation is proportional to the level of adenosine triphosphate in the slice under a wide variety of experimental conditions which lead to changes in this level. Such conditions include change in the glucose concentration in the incubation medium, the presence of metabolic inhibitors, addition of uncoupling agents, alteration of the ionic composition of the medium, incubation under anaerobic conditions, addition of glutamate, X-irradiation, the use of rats of various ages, and the presence of adenosine in the incubation medium. The proportionality is apparent from the constancy of a factor, termed the transport quotient, which is obtained by dividing the extent of uptake of glycine by the observed level of nucleotide pyrophosphate present in the slices.

AMINO ACID TRANSPORT IN BRAIN CORTEX SLICES: I. THE RELATION BETWEEN ENERGY PRODUCTION AND THE GLUCOSE-DEPENDENT TRANSPORT OF GLYCINE

1962 ◽  
Vol 40 (1) ◽  
pp. 1575-1590 ◽  
Author(s):  
P. N. Abadom ◽  
P. G. Scholefield
Keyword(s):  
Incubation Medium ◽  
Energy Production ◽  
Brain Cortex ◽  
Ionic Composition ◽  
Metabolic Inhibitors ◽  
Experimental Conditions ◽  
X Irradiation ◽  
Brain Cortex Slices ◽  
Cortex Slices ◽  
Dependent Transport

Incubation of rat brain cortex slices with glycine in the presence of glucose leads to an accumulation of glycine in the slice. The extent of the accumulation is proportional to the level of adenosine triphosphate in the slice under a wide variety of experimental conditions which lead to changes in this level. Such conditions include change in the glucose concentration in the incubation medium, the presence of metabolic inhibitors, addition of uncoupling agents, alteration of the ionic composition of the medium, incubation under anaerobic conditions, addition of glutamate, X-irradiation, the use of rats of various ages, and the presence of adenosine in the incubation medium. The proportionality is apparent from the constancy of a factor, termed the transport quotient, which is obtained by dividing the extent of uptake of glycine by the observed level of nucleotide pyrophosphate present in the slices.

BIOCHEMICAL STUDIES ON CHLORPROMAZINE: 2. EFFECTS OF CHLORPROMAZINE ON INCORPORATION INTO PROTEINS, AND BREAKDOWN OF GLYCINE-1-C14BY ISOLATED RAT BRAIN CORTEX

1957 ◽  
Vol 35 (1) ◽  
pp. 1145-1150 ◽  
Author(s):  
O. Lindan ◽  
J. H. Quastel ◽  
S. Sved
Keyword(s):  
Rat Brain ◽  
Brain Cortex ◽  
Experimental Conditions ◽  
Rat Brain Cortex ◽  
Brain Cortex Slices ◽  
High Concentrations ◽  
Cortex Slices ◽  
The Given ◽  
The Brain ◽  
Stimulation Of

Glycine is decomposed in rat brain cortex to yield carbon dioxide. This process, in which C14O2is formed from glycine-1-C14, is markedly stimulated by the presence of 10 mM glucose, the rate of production of C14O2being increased at least threefold. The presence of succinate exercises a much smaller stimulation of C14O2formation. The addition of KCl (0.1 M) or of 2,4-dmitrophenol (0.025 mM), whilst stimulating the rate of oxygen uptake, does not increase the rate of C14O2formation from glycine-1-C14. The addition of K+tends to diminish the rate. The process of glycine-1-C14breakdown to C14O2is almost insensitive to chlorpromazine, under the given experimental conditions, until relatively high concentrations (e.g. 0.6 mM) are used. The presence of chlorpromazine, however, brings about an inhibition of the rate of glycine-1-C14incorporation into rat brain cortex proteins, an inhibition of 20% being recorded at a concentration of the drug (0.2 mM) that has little or no effect on the respiration of the brain or on the rate of breakdown of glycine-1-C14into C14O2. Glycine incorporation into brain cortex proteins is a process relatively sensitive to chlorpromazine, the magnitude of inhibition being of the same order as that brought about by amytal at similar concentrations. It is suggested that chlorpromazine brings about its effects by an uncoupling of phosphorylation from oxidation in brain cortex slices.

Effects of Cerebral Stimuli on Adenine Incorporation into Nucleotides and RNA in Brain Slices from the Rat

1972 ◽  
Vol 50 (6) ◽  
pp. 672-683 ◽  
Author(s):  
N. B. Glick ◽  
J. H. Quastel
Keyword(s):  
Brain Tissue ◽  
Incubation Medium ◽  
Rna Synthesis ◽  
Brain Cortex ◽  
Specific Activity ◽  
Brain Slices ◽  
Brain Cortex Slices ◽  
Specific Activities ◽  
Cortex Slices ◽  
The Brain

Comparisons have been made of the rates of incorporation of [8-14C]adenine into RNA and of the specific activities of labelled ATP, in rat brain cortex slices incubated under conditions affecting nucleotide and RNA synthesis.The presence of 50 mM KCl in the incubation medium causes a considerable reduction of the rate of [8-14C]-adenine incorporation into RNA, with no diminution of the specific activity of the cerebral ATP or of the rate of nucleotide formation from adenine. It is inferred that cerebral RNA synthesis is suppressed by 50 mM KCl in the incubation medium.When K+ is omitted from the incubation medium or in the presence of 198 mM NaCl or 5 mM sodium L-glutamate, both the rate of [8-14C]adenine incorporation into RNA and the specific activity of cerebral ATP are diminished to approximately the same extent. This suggests that the process of RNA synthesis in the brain tissue is but little affected either by the increased ceil concentration of Na+ or by the diminished ATP concentration that obtain under these incubation conditions. The process, however, of [8-14C]adenine incorporation into cell nucleotides is markedly suppressed.The presence of protoveratrine (10 μM) causes at least 40% reduction in the rates of [8-14C]adenine incorporation into both RNA and nucleotides with little reduction in the specific activity of the cerebral ATP. The effects of protoveratrine are abolished by tetrodotoxin, indicating that the effects of protoveratrine are confined to the neurons.It is concluded that reductions of the specific activity of cerebral ATP derived from labelled adenine are due to the diminished rates of nucleotide formation from adenine that occur under specific incubation conditions. Such reductions may give rise to the observed diminutions in the rates of incorporation of labelled adenine into RNA. The relatively small fail in the specific activity of isolated ATP after incubation of brain tissue in the presence of protoveratrine is attributed to the localization of the effects of this drug to the neurons, in which the content and specific activity of ATP are suppressed, while those in the glia are undiminished.

BIOCHEMICAL STUDIES ON CHLORPROMAZINE: 2. EFFECTS OF CHLORPROMAZINE ON INCORPORATION INTO PROTEINS, AND BREAKDOWN OF GLYCINE-1-C14BY ISOLATED RAT BRAIN CORTEX

1957 ◽  
Vol 35 (12) ◽  
pp. 1145-1150 ◽  
Author(s):  
O. Lindan ◽  
J. H. Quastel ◽  
S. Sved
Keyword(s):  
Rat Brain ◽  
Brain Cortex ◽  
Experimental Conditions ◽  
Rat Brain Cortex ◽  
Brain Cortex Slices ◽  
High Concentrations ◽  
Cortex Slices ◽  
The Given ◽  
The Brain ◽  
Stimulation Of

Glycine is decomposed in rat brain cortex to yield carbon dioxide. This process, in which C14O2is formed from glycine-1-C14, is markedly stimulated by the presence of 10 mM glucose, the rate of production of C14O2being increased at least threefold. The presence of succinate exercises a much smaller stimulation of C14O2formation. The addition of KCl (0.1 M) or of 2,4-dmitrophenol (0.025 mM), whilst stimulating the rate of oxygen uptake, does not increase the rate of C14O2formation from glycine-1-C14. The addition of K+tends to diminish the rate. The process of glycine-1-C14breakdown to C14O2is almost insensitive to chlorpromazine, under the given experimental conditions, until relatively high concentrations (e.g. 0.6 mM) are used. The presence of chlorpromazine, however, brings about an inhibition of the rate of glycine-1-C14incorporation into rat brain cortex proteins, an inhibition of 20% being recorded at a concentration of the drug (0.2 mM) that has little or no effect on the respiration of the brain or on the rate of breakdown of glycine-1-C14into C14O2. Glycine incorporation into brain cortex proteins is a process relatively sensitive to chlorpromazine, the magnitude of inhibition being of the same order as that brought about by amytal at similar concentrations. It is suggested that chlorpromazine brings about its effects by an uncoupling of phosphorylation from oxidation in brain cortex slices.

BIOCHEMICAL STUDIES ON TOFRANIL

1961 ◽  
Vol 39 (3) ◽  
pp. 551-558 ◽  
Author(s):  
P. N. Abadom ◽  
K. Ahmed ◽  
P. G. Scholefield
Keyword(s):  
Rat Brain ◽  
Rat Liver ◽  
Brain Cortex ◽  
Respiratory Activity ◽  
Liver Mitochondria ◽  
Brain Mitochondria ◽  
Inhibitory Effect ◽  
Rat Liver Mitochondria ◽  
Brain Cortex Slices ◽  
Cortex Slices

Tofranil inhibits the respiratory activity of rat brain cortex slices incubated in a glucose-containing medium. It also inhibits the uptake and incorporation of glycine-1-C14at concentrations which have only a slight inhibitory effect on the respiration of slices. Tofranil also inhibits oxidative phosphorylation in both rat liver and rat brain mitochondria but at higher concentrations respiration is greatly affected. Tofranil differs quantitatively from chlorpromazine in its greater inhibitory effect on the ATP–Pi32exchange reaction and its lesser effect on the cytochrome c oxidase activity of rat liver mitochondria.

EFFECTS OF ACETYLSALICYLATE AND 2,4-DINITROPHENOL ON METABOLISM AND TRANSPORT IN RAT BRAIN CORTEX IN VITRO

1963 ◽  
Vol 41 (2) ◽  
pp. 435-454 ◽  
Author(s):  
O. Gonda ◽  
J. H. Quastel
Keyword(s):  
Amino Acids ◽  
Rat Brain ◽  
Brain Cortex ◽  
Transport Processes ◽  
Rat Brain Cortex ◽  
High K ◽  
Increased Sensitivity ◽  
Brain Cortex Slices ◽  
Cortex Slices

The effects of acetylsalicylate and of 2,4-dinitrophenol on the metabolism and transport processes of rat brain cortex slices incubated at 37° in glucose–Ringer media under various conditions have been investigated. The following processes are suppressed by acetylsalicylate (5 mM) or dinitrophenol (0.05 mM) to a much greater extent in media containing 105 mM KCl or 10 mM NH4Cl (which stimulate brain respiration) than in normal media:(a) respiration;(b) incorporation of phosphate into ATP and ADP;(c) conversion of creatine to phosphocreatine;(d) uptake of glutamate or of creatine from the medium to the tissue.The two drugs increase the leakage of amino acids from rat brain cortex slices into the medium, the effects being greatest in the presence of 105 mM KCl or 5 mM glutamate or in the absence of glucose. They change the yields of labelled amino acids from labelled glucose or labelled glutamate.Labelled glutamate is converted to labelled aspartate, γ-aminobutyrate and glutamine in rat brain cortex slices, the addition of glucose bringing about increased yields of glutamine and γ-aminobutyrate and a decreased yield of aspartate. The formation of labelled glutamine from either labelled glutamate or from labelled glucose is suppressed by acetylsalicylate or dinitrophenol, the effects being greater in the presence of 105 mM KCl or 10 mM NH4Cl.The increased sensitivity of the stimulated tissue metabolism to the drugs, in the presence of high K+, or of NH4+or of glutamate, is probably explained by the fact that there is a fall, under these conditions, in the tissue phosphocreatine level. There is, therefore, less reserve phosphocreatine to maintain the level of ATP when neuronal oxidative phosphorylation is suppressed by the addition of acetylsalicylate or of dinitrophenol.

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