ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04365.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—The binding of [14C]GABA to nerve‐ending membranes isolated from rat cerebral cortex follows a hyperbolic curve saturating at 0·4pmol/μg protein. This binding is about 60% inhibited by chloropromazine, and about 40%, inhibited by bicuculline. A hydrophobic protein fraction binding [14C]GABA was separated from the total. lipid extract of nerve‐ending membranes. The binding follows a hyperbolic curve that saturates at 10·5 pmol of [14C]GABA/μg of protein, with an apparentKd= 30 μm. The binding is competitively inhibited by bicuculline with aKi= 273 μm. These results are compared with those previously obtained on a GABA binding protein from crusta

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04366.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—(1) The effects of exposure of rats to increased atmospheric concentrations of CO2on brain metabolismin vivowere studied. (2) After 2·5 min exposure to an atmosphere of 20% CO2, the rate of glucose utilization by brain decreased from 0·61 μmol/min per g to 0·32 μmol/min per g and remained between 0·3 and 0·4 μmol/min per g for 60 min, the longest interval studied. O2utilization, calculated from the arteriovenous difference of O2across the brain and blood flow, was 3·5 μmol/min per g in controls and was 4·7 μmol/min per g after 5 min in the 20% CO2atmosphere. (3) The concentrations of glucose, glucose 6‐phosphate and aspartate were increased during the first 10 min of CO2exposure whereas the concentrations of other glycolytic intermediates, tricarboxylic acid cycle intermediates and glutamate were decreased. The amount of endogenous substrate which disappeared during the first 10 min was sufficient, if used to supplement glucose as a fuel, to maintain the O2consumption at, or slightly above, the control level. Glutamate and lactate were quantitatively the most important energy sources. (4) The mechanism whereby‘CO2decreased the rate of glucose utilization is uncertain. The initial rise in glucose 6‐phosphate and fall in fructose 1,6‐diphosphate concentrations suggested that an inhibition of phosphofructokinase was responsible. However, after 60 min in 20% CO2, the concentrations of both of these metabolites returned to normal while the rate of glucose utilizati

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04367.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—Male Wistar rats aged 24 days were divided into three groups. Two groups were given a high protein (250 g/kg casein) and a low protein (30 g/kg casein) diet respectively. The third group was given an amount of the high protein diet containing the same amount of energy as that consumed by the low protein diet rats. The plasma of the animals on low protein contained 20% of the concentration of tryptophan of animals on the other two diets. In these animals the concentration of tryptophan was reduced in the forebrain, cerebellum and brain stem, and the concentrations of 5‐HT and 5‐hydroxyindoleacetic acid were reduced in the forebrain and brain stem. The low protein diet decreased the total uptake ofl‐[G‐3H]tryptophan into the brain and its incorporation into brain protein. Plasma insulin concentrations were reduced in the low protein and ‘restricted high protein’ animals and the plasma corticosterone concentration was raised in the low protein animals. Exogenous insulin did not raise the plasma tryptophan concentration in the low protein animals but it increased the uptake ofl‐[G‐3H]tryptophan into the brain and its incorporation into protein. Rehabilitation for 7 days restored the plasma and brain tryptophan concentrations and those of brain 5‐HT and 5‐hydroxyindoleacetic a

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04368.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—The encephalitogenic basic protein has been isolated from the myelin sheath of ox brain white matter and the purity and amino acid composition have been verified. The intrinsic fluorescence characteristics of the purified basic protein have been determined and the results interpreted in terms of current ideas on the structure of the protein. Fluorescence data obtained from the basic protein in aqueous solution indicate that the tyrosine and tryptophan residues are largely exposed to the solvent and that resonance energy transfer from tyrosine to tryptophan is very inefficient. Denaturing conditions in 8m‐urea have little effect on the fluorescence properties of the protein. The ionic detergent, sodium dodecyl sulphate, interacts with the basic protein and alters the fluorescence properties in a manner which indicates that the tryptophan residue is in the hydrocarbon chain region of the detergent while the local positive charge around the tyrosine residues is neutralized by the negatively charged sulphate head‐groups. The fluorescence results suggest that the basic protein can be used as a natural, non‐perturbing probe which will report on its environment after it has reacted with other membrane com

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04369.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—The effects of amino‐oxyacetic acid, ethanolamine‐O‐sulphate and γ‐aminobutyric acid (GABA) on the contents of GABA, noradrenaline, dopamine and serotonin (5‐HT) in slices of rat hypothalamus and midbrain were studiedin vitrousing a simultaneous fluorimetric assay procedure. Following control incubations the levels of 5‐HT were raised, while the levels of the other substances remained steady. Amino‐oxyacetic acid caused a reduction in the contents of noradrenaline and 5‐HT, but had no effect on either GABA or dopamine. Ethanolamine‐O‐sulphate both raised the GABA content and lowered the noradrenaline content of slices, while the levels of dopamine and 5‐HT were not altered. The presence of GABA in the incubation medium produced complex changes in these levels, depending both on the dose of GABA used and the brain area studied. In the hypothalamus, 0·07 mm‐GABA caused an elevation in 5‐HT, a drop in noradrenaline, and no change in either GABA or dopamine. With 5 mm‐GABA, the noradrenaline level was raised slightly above control values and the endogenous GABA level doubled, while 5‐HT and dopamine levels were not different from controls. Similar changes in 5‐HT and GABA contents were observed with midbrain slices, but noradrenaline and dopamine were not affected. The possible modes of action of amino‐oxyacetic acid and ethanolamine‐O‐sulphate on the amino acid and

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04370.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—Aromatic: 2‐oxoglutarate aminotransferase has been purified about 950‐fold from rat brain mitochondria. The purified enzyme was homogeneous in polyacrylamide gel electrophoresis and had a molecular weight of approx 63,000. On the basis of substrate specificity, substrate inhibition, purification ratio, yield, polyacrylamide gel electrophoresis and some other properties of the enzyme it has been suggested that brain mitochondrial tyrosine:2‐oxoglutarate aminotransferase (l‐tyrosine: 2‐oxoglutarate aminotransferase, EC 2.6.1.5) is identical with brain mitochondrial phenylalanine and kynurenine: 2‐oxoglutarate aminotransferases (l‐kynurenine: 2‐oxoglutarate aminotransferase, EC 2.6.1.7), and also with aspartate: 2‐oxoglutarate aminotransferase (l‐aspartate: 2‐oxoglutarate aminot

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04371.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—We studied the axoplasmic transport of choline acetyltransferase (CAT) activity in sciatic nerves of normal mice of various ages. For at least 3 days after unilateral ligation of sciatic nerves of 6 and 30‐week‐old mice, the CAT activity in the ligated nerve increased as a linear function of time and the increase was confined to the 3 mm length of nerve immediately proximal to the ligature. The rate of increase of CAT activity in the ligated nerves of the 30‐week‐old mice was only 45 ± 6% that of the 6‐week‐old mice, whereas the CAT activity of non‐ligated sciatic nerves of the older mice was 87 ± 6% more than that of the younger mice (n = 18,P<0·001). The average velocity of axoplasmic transport of CAT activity was five times greater in the younger mice (1·5 ± 0·2 mm/day vs 0·3 ± 0·1 mm/day, n = 6,P<0·01). Even greater differences were observed between still younger and older animals: the av velocity of axoplasmic transport of 2‐week‐old mice (3·5 ± 0·2 mm/day) was 17·5 times greater than that of 36‐week‐old mice (0·2 ± 0·1 mm/day). We also studied the axoplasmic transport of CAT activity in 6‐week‐old mice after unilateral section of the sciatic nerve. For at least 3 months after the operation, there were no differences between the sectioned nerves and the intact contralateral nerves with respect to the increase in CAT activity immediately proximal to a ligature placed at various times after neurotomy and one day before sacrifice. On the other hand, there was a reduction in the CAT activity of more proximal segments of the sectioned nerves. The reduction of CAT activity was maximal (52 ± 3%) 3 weeks after the operation when the maximum increase (2·5‐fold) in the av velocity of axoplasmic transport of CAT activity was recorded (n = 6,P<0·001). The inclusion of purified (100‐fold) mouse brain CAT activity in the assays for the CAT activity of nerve segments demonstrated that the differences in content and rate of transport were not due to the presence of activators or inhibitors of CAT activity. These differences probably reflect physiologic changes in the axoplasmic transport of chol

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04372.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—Proteolipids were previously considered to be resistant to proteolytic digestion. In the present study, crude bovine white matter proteolipid, proteolipid apoprotein, and chemically modified proteolipids were subjected to the action of the following proteolytic enzymes in the absence and presence of detergents: trypsin, α‐chymotrypsin, elastase, thermolysin and collagenase. The course of digestion was followed by the release of Fluorescamine‐reactive groups. Tryptic digestion of the crude proteolipid and the apoprotein in the absence of detergent amounted to 10 and 40% respectively of the digestion in the presence of detergent. Peptide mapping and protein analyses of both the soluble digests and the insoluble residues confirmed digestion. In the presence of either sodium deoxycholate or Triton X‐100, essentially all of the crude proteolipid and 60% of the proteolipid apoprotein were solubilized by trypsin. Digestion of the apoprotein was observed only in preparations which had not been dried. In the absence of detergent, (1) the oxidized crude proteolipid was more susceptible to tryptic digestion than were either the unoxidized or carboxymethylated preparations, (2) both the apoprotein and the oxidized proteolipid were digested by thermolysin or α‐chymotrypsin, and (3) all preparations were attacked

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04373.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Abstract—The inhibition of γ‐glutamylcysteine synthetase and its influence on the concentration of intermediates associated with the metabolism of glutathione was studied in mice receiving methionine sulfoximine, a convulsant agent. The activity of the enzyme decreased significantly in the liver and kidney 1‐4 h after administration of methionine sulfoximine; the activity of the enzyme in the brain was unchanged after 1 and 2 h but decreased significantly after 4 h. There was a rapid and sharp decrease in the concentration of glutathione in the kidney and a slower decrease in the liver. Brain glutathione concentrations were unaffected. Methionine sulfoximinein vivo, inhibited the synthesis ofl‐γ‐glutamyl‐l‐α‐aminobutyrate after administration ofl‐α‐aminobutyrate, a reaction catalyzed by γ‐glutamylcysteine synthetase. The inhibitor also lowered the concentration of pyrrolidone carboxylate in mouse tissues and prevented the accumulation of this intermediate after administration ofl‐α‐aminobutyrate. The results show that methionine sulfoximinein vivoaffects the metabolism of glutathione and that this action may contribu

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1975.tb04374.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY