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Notes: (1) The metabolism of glucose and amino acids in vitro was compared in the rat cerebral cortex and the optic and vertical lobes of the octopus brain.(2) Specific activities and pool sizes of the five amino acids, glutamate, aspartate, glutamine, alanine and γ-aminobutyric acid (GABA), were determined in octopus and rat brain slices after 2 hr incubation with 10 mm-[U-14C]glucose, 10 mm-L-[U-14C]glutamate, and 10mm-L-[U-14C]glutamate with added 10 mM-glucose. Amino acid pool sizes were similar in rat and octopus brain, with the exception of alanine, which was higher in the octopus. Generally specific activities were from four- to 20-fold higher in rat brain. With [U-14C]glucose as substrate, specific activities of GABA and glutamate were highest in rat; those of alanine and glutamine highest in octopus brain. With L-[U-14C]glutamate the specific activities of GABA and aspartate were highest in rat, that of aspartate highest and GABA lowest in octopus. The addition of glucose to L-[U-14C]glutamate as substrate had little effect on the specific activities of any of the amino acids.(3) The uptake of some amino acids was determined by incubation with [U-14C]amino acids for 2 hr, and 14CO2 formation was also measured. The amount of label taken up by octopus was uniformly 20-25 per cent of that found for rat brain. The amount of 14CO2, however, differed according to the amino acid. Four times as much 14CO2 was generated from alanine by octopus optic lobe and twice as much by the vertical lobe than rat cortex, but from glutamate, only 24 per cent in the optic and 15 per cent in the vertical lobe. No 14CO2 was generated from [U-14C]GABA in the octopus, by contrast with the rat.(4) Activity of some of the enzymes involved in amino acid metabolism was determined in homogenates of rat cortex and octopus optic and vertical lobes, with and without activation by Triton X-100. Enzymic activities in the octopus, with the exception of alanine aminotransferase, were lower than in the rat, and glutamate decarboxylase could not be detected in octopus brain, in the absence of detergent.

Notes: (1) The in vitro metabolism of [U-14C]glucose and [U-14C]glutamate was compared in snail, octopus and locust ganglia, and in rat cerebral cortex.(2) The metabolic patterns are quantitatively similar. The major labelled metabolites formed from glucose or glutamate by rat cortex and the invertebrate systems were CO2, aspartate, glutamate, glutamine and alanine. γ-Aminobutyric acid (GABA) was formed in substantial amounts only by locust and rat.(3) A much larger proportion of labelled glucose and glutamate was converted to alanine by the invertebrates compared with rat cortex, although 14CO2 production was lower.(4) The effect of glucose in reducing aspartate formation and stimulating glutamine formation from [U-14C]glutamate in mammalian cortex was observed in the locust but not in the molluscs.(5) Labelled citric acid cycle intermediates were formed in substantial quantities from glucose and glutamate only by snail and locust.

Notes: Abstract— 〈list xml:id="l1" style="custom"〉1The metabolism of two 14C-labelled hexoses and one hexose analogue, viz. mannose, fructose and glucosamine, has been compared with that of glucose for slices of rat cerebral cortex incubated in vitro.2The metabolism of [U-14C]mannose was essentially identical to that of glucose; oxygen consumption and CO3 production were similar and maximal at a substrate concentration of 2·75 mM. Incorporation of label into lactate, aspartate, glutamate and GABA was similar for the two substrates at 5·5 mM substrate concentration.3With [U-14C]fructose, maximal oxygen consumption and CO3 production were obtained at a substrate concentration of 11 mM. At 5·5 mM, incorporation into lactate was 5 per cent, into glutamate and GABA 30 per cent, into alanine 63 per cent and into aspartate 152 per cent of that from glucose. Increasing substrate concentration to 27·5 mm was without effect on incorporation into amino acids from glucose and raised incorporation from fructose into glutamate, GABA and alanine to a level similar to that found with glucose; at the higher substrate concentration aspartate incorporation from fructose was 200 per cent and lactate 42 per cent of that with glucose. Unlabelled fructose was without effect on incorporation of radioactivity from [3-14C]pyruvate into CO2 or amino acids; it increased incorporation into lactate by 36 per cent. Unlabelled glucose diminished incorporation into CO2 from [U-14C]fructose to 35 per cent; incorporation into lactate was stimulated 178 per cent at 5·5 mM fructose; at 27·5 mM it was diminished to 75 per cent.4By comparison with [1-14C]glucose, incorporation of radioactivity from [1-14C]-glucosamine into lactate, CO2, alanine, GABA and glutamine was very low; incorporation into aspartate was similar to glucose. Thus the metabolism of glucosamine resembled that of fructose. Glucosamine-1-phosphate, glucosamine-6-phosphate, and an unidentified metabolite, all accumulated.

Notes: Abstract— 1. Histochemical evidence was presented illustrative of the composition of neuronal and neuropil (‘glial’) fractions isolated according to a previously published procedure. The neuropil refers to all cortical tissue other than neuronal perikarya.2. On the basis of cell counts and of DNA content, an average cell mass of 100-110 pg was calculated for cells in the neuronal fraction. Eight per cent of the total DNA was recovered in the neuronal fraction.3. Both fractions synthesized ATP in vitro. Concentrations after 60 min incubation with glucose were: neuropil, 7–36 μmoles/mg protein; neuronal, 12–31 μmoles/mg protein.4. Osmotic shock or homogenization resulted in changes in turbidity of the cell fractions which were interpreted as indicative of loss of cell structure. The free pool amino acids glutamate, glutamine, GABA, aspartate and alanine were retained in the precipitable material through several washes with isotonic solutions. Homogenization released 72 per cent of the neuronal and 68 per cent of the neuropil amino acids into the supernatant, but only 37 per cent and 19 per cent respectively of the protein.5. By contrast with earlier reports, K+ accumulation has now been demonstrated in both neuronal and neuropil fractions. After incubation with glucose, K+ level were calculated as being 80 per cent of slice in the neuronal, and 65 per cent in the neuropil fraction. These results, and those of the osmotic shock experiments, were taken as indicative of the retention of some cell structure.6. By comparison, cell fractions prepared by other procedures, using acetone-glycerol-water or tetraphenylboron for tissue disaggregation, produced preparations with limited metabolic capabilities; oxygen uptake, CO2 and lactate production were all lowered substantially.

Notes: Abstract— 〈list xml:id="l1" style="custom"〉1The metabolism of three substrates, [U-14C]glucose, [U-14C]pyruvate and [U-14C]glutamate has been studied in vitro in neuronal and glial cell fractions obtained from rat cerebral cortex by a density gradient technique.2The mixed cell suspension, after washing, metabolized glucose and glutamate in a manner essentially similar to the tissue slice. Exceptions were a reduced ability to generate lactate from glucose and alanine from glutamate, and a lowered effect of added glucose in suppressing the production of aspartate from glutamate.3After 2 hr incubation with [U-14C]glucose, the concentration of the amino acids glutamate, glutamine, GABA, aspartate and alanine were raised in the neuronal, compared to the glial fraction to 234 per cent, 176 per cent, 202 per cent, 167 per cent and 230 per cent respectively although both were lower than in the tissue slice. Incorporation of radio-activity was absolutely lower in the neuronal fraction, however, and the specific activities of the amino acids were: glutamate 12 per cent, GABA 18 per cent, aspartate 34 per cent, and alanine 33 per cent of those in the glial fraction.4After the incubation with [U-14C]pyruvate, the pool size of the amino acids were higher than after incubation with glucose, except for GABA, which was reduced to one-third. The concentrations of the amino acids glutamate, glutamine, GABA, aspartate, and alanine in the neuronal fraction were respectively 46 per cent, 143 per cent, 105 per cent, 97 per cent, and 57 per cent of those in the glial. Thus, with the exception of alanine, the specific activity of the neuronal amino acids compared to the glial was little increased when pyruvate replaced glucose as substrate.5After 2 hr incubation with [U-14C]glutamate in the presence of non-radioactive glucose, the pool sizes of all the amino acids were increased in both neuronal and glial fractions, with the exception of neuronal alanine and glial glutamine. The concentrations of the amino acids glutamine, GABA, aspartate and alanine were raised in the neuronal fraction, compared to the glial, to 425 per cent, 187 per cent, 222 per cent, and 133 per cent respectively. The specific activities of all the amino acids were higher than with glucose alone with the exception of alanine, and neuronal GABA. Neuronal glutamine and aspartate had specific activities respectively 102 per cent and 84 per cent of glial.6An unidentified amino acid, with RF comparable to that of alanine and specific activity close to that of glutamate, was also present after incubation. It was relatively concentrated in the neuronal fraction.7The distribution of the enzymes glutamate dehydrogenase, aspartate aminotransferase, glutamate decarboxylase and glutamine synthetase between the cell fractions was studied. With the exception of glutamine synthetase, none of the enzymes was lost from the cell fractions during their preparation. Only 14 per cent of the glutamine synthetase, compared with 75 per cent of total protein, was recovered in the fractions. Of the enzymes, glutamate dehydrogenase activity was 406 per cent, and glutamate synthetase activity 177 per cent in the neuronal fraction compared to the glial in the absence of detergent. In the presence of detergent, glutamate dehydrogenase control was 261 per cent, aspartate aminotransferase activity 237 per cent is the neuronal as compared to the glial fraction.8Incorporation of radioactivity into acid-insoluble material from either glutamate or pyruvate was twice as high into the neuronal as the glial fraction.9The extent to which these differences may be extrapolated back to the intact tissue is considered, and certain correction factors calculated. The significance of the observations for an understanding of the compartmentation of amino acid pools and metabolism in the brain, and the possible identification of such compartments, is discussed.

Notes: [Auszug] Six batches of Chunky chicks were hatched and kept in a dark incubator until the start of the experiment. Because the readiness with which birds can be imprinted is dependent on maturational age4'6, half the chicks were drawn from the early part of the hatch and half from the late part. The early ...