摘要:

Abstract—Acetylcholine is synthesized and stored in the nerve endings from which the liberation of the nerve transmittor is regulated by the nerve activity. The aim of the present investigation was to measure thein vivoturnover of acetylcholine in this subcellular acetylcholine pool. This has been carried out by injecting labelled choline intravenously and then by measuring at different time intervals the ratio between labelled choline and acetylcholine in the fractions obtained after subcellular fractionation. It was found that the ratio radioactive choline to radioactive acetylcholine was the same (2:1) in whole brain and in the nerve ending fraction 2 to 20 min after injection. Since it was assumed that the same ratio is true also for the endogenous compounds the choline pool in the nerve terminals was considered to make up 13 nmoles/g brain. The results also indicate that plasma choline is rapidly equilibrated with the nerve terminals and transformed to acetylcholine at a rate of about 5 nmoles/g brain/mi

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb00522.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—Concentrations in whole rat brains of lipids (total lipids, phospholipids, galactolipids, cholesterol, plasmalogens) and of proteolipid protein were not altered after feeding for 2 and 6 weeks of diets containing 5 per cent excessl‐phenylalanine. After 2 weeks of diet with 7 per cent excessl‐phenylalanine there was a slight reduction (5–10 per cent) in the concentrations in whole brain of cholesterol and galactolipids. No significant effects were noted in cerebral hemispheres after 3 weeks of diets with 7 per cent excessl‐phenylalanine. In the 5 and 7 per cent supplemented groups of animals, the total amounts of the various lipids were initially reduced to levels which were within 10 per cent of those in diet‐matched controls. The results for rats indicate that after 3 weeks of age only very moderate effects on accumulation of cerebral lipids can be produced by excess dietaryl‐phenylalanine fed at the most toxic levels of supplementation, while lower levels of dietary supplementation are without effect. The results suggest further that the more mature brain is resistant to alteration of deposition of myelin lipids by high levels of

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb00523.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—Phosphorylasebkinase (ATP: phosphorylase phosphotransferase; EC 2.7.1.38), the enzyme which converts phosphorylasebto phosphorylasea(α‐1,4‐glucan: orthophosphate glucosyltransferase; EC2.4.1.1) was examined in nerve tissue. Both phosphorylase and phosphorylase kinase were present in all nerve tissues tested, with central tissues about ten times as active as peripheral nerve. Exceptions were the superior cervical and stellate ganglia, tissues rich in synapses, which displayed activity similar to brain. Phosphorylase kinase in brain had properties similar to those of the enzyme in skeletal and cardiac muscle; it was activatedin vitroby ATP and adenosine 3′,5′‐monophosphate (cyclic AMP) and by Ca2+. Subconvulsive doses of insulin or of amphetamine administered to mice produced some activation of the enzyme. It is concluded that the mechanism for activation of phosphorylase in nerve tissue is similar to th

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb00524.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—The presence of α‐galactosidase activity has been demonstrated in rat brain. This enzyme, located mainly in the crude mitochondrial fraction, actively hydrolysed the substratesp‐nitrophenyl‐α‐galactoside and melibiose, and also catalysed the hydrolysis of digalactosyl diglyceride of both animal and plant origin. The hydrolysis ofp‐nitrophenyl‐α‐galactoside, as catalysed by the α‐galactosidase, occurred optimally at pH 4·9, showed an approximateKmof 1·0 × 10−3m, and was markedly inhibited by melibiose, gala

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb00525.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—The optic ganglia, cerebral ganglia and mantle nerve of the squidDosidicus gigaswere examined for possible amines. Histamine was detected in all three tissues. The optic ganglia were also found to contain 5‐HT andN‐acetylhistamine, an infrequently found derivative of hist

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb00526.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—Myelin, synaptosomal and mitochondrial fractions obtained from homogenates of whole mouse brain contain K+which can exchange with42K+at 2º in 0·32m‐sucrose. The content and rates of exchange of K+were greater at pH 8·2 than at 6·1. In the synaptosomal preparations, the rates of exchange and content of42K+and K+declined progressively with decreasing pH.Of the total synaptosomal K+, 95 per cent could exchange with external42K+. At pH 7·5, 20 per cent of the K+and 78 per cent of the Na+appeared to reside in osmotically insensitive pools. Synaptosomal K+at 2º was slowly displaced by NaCl (0·18m) and the rate of exchange between42K+and K+was retarded. KCI (0·18m) did not readily displace endogenous Na+. Synaptosomal K+exchanged with exogenous K+more rapidly than with exogenous Na+.These observations have been discussed in terms of possible roles for ion exchange as the principal means by which K+traverses the plasma mem

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb00527.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—NAD‐kinase was purified from rat brain acetone powder according to the method of Wangand Kaplan(1954). The acetate buffer supernatant showed only very low specific activity but was largely free of the factors that interfere with the enzyme assay. The Michaelis constants for both substrates were determined, the values were 0·5 mmfor NAD and 4·0 mmfor ATP. The optimal pH was 7·4 in tris‐HCl buffer and the highest NAD‐kinase activity was observed in the hyaloplasm fraction. NADH2inhibited the enzyme whereas NADPH2did not. Finally, the reversible inhibition of SH‐binding compounds is described and the observed properties of rat brain NAD‐kinase compared with the properties of NADP synthesizing enzymes from pigeon liver

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb00528.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—TheS‐100 and 14‐3‐2 proteins, which are found only in nervous tissues, were measured in degenerating rabbit optic nerve at 0, 5 10, 20, 40, 60, 80, 100, 150 and 200 days after unilateral enucleation in order to obtain indications of the cellular localization of these proteins in the central nervous system.S‐100 increased and 14‐3‐2 decreased (both approximately 70 per cent) in cut nerves by 200 days of degeneration. Changes in amounts of the proteins were related to cellular alterations which characterize the degenerative process, as demonstrated by electron microscopy. In uncut nerves (intact eye) from these experimental animals,S‐100 increased and 14‐3‐2 decreased slightly at 5 days, after which time the levels of each returned to those approximating the content in corresponding nerves from unoperated control animals. No appreciable change in total soluble proteins was measured in degenerating or intact nerves. SinceS‐100 increased and 14‐3‐2 decreased in the degenerating optic nerve as it became relatively enriched in glial constituents but impoverished in axonal content, it is suggested thatS‐100 is primarily a glial protein and 14‐3‐2 predominantly a neuronal protei

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb00529.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—(1) Multiple samples from the piriform cortex and neocortex of the guinea pig were maintained in separate incubation vessels through which incubation solutions based on Krebs‐Ringer bicarbonate glucose media were caused to flow for chosen periods at specified rates.(2) The tissues were held in defined positions in relation to electrodes; in some experiments electrical stimuli were applied and in others incubation media were changed with respect to their oxygen, K+or glutamate content.(3) With media flowing at 3–4 ml/min, the incubated tissues were similar in contents of K salts and phosphocreatine, and in rate of glycolysis to those incubated in non‐flowing media. The tissues responded to electrical stimulation by increase in glycolysis and decrease in phosphocreatine and K content.(4) During pre‐incubation periods in non‐flowing media, samples of piriform cortex were exposed to solutions containing3H‐labelled glycine, noradrenaline or 5‐hydroxytry‐ptamine and on anlaysis were found to contain the labelled compounds at concentrations four to seven times those of the surrounding media. The labelled compounds were gradually released into the flowing incubation media, and the release of noradrenaline and 5‐hydroxytryptamine was accelerated by electrical stimulation.(5) Release of the two bases was also modified by added reagents and the course of their release is discussed in relation to other metabolic changes con

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb00530.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—Incorporation ofdl‐[1‐14C]leucine into proteins of the cerebral cortex of the rat was measured during spreading cortical depression (CSD) evoked by a single topical application of 25% (w/v) KCI. Maximal inhibition (42 per cent) of the rate of incorporation occurred 1 hr after application of KCI. Spreading depression of 2–3 hr duration was associated with 22 per cent and 13 per cent decreases, respectively, of incorporation of labelled leucine. Specific activity of the free pool leucine was not decreased during CSD but appeared to be higher than controls at 20 min after initiation of CSD. The specific activity of the total free pool amino acids was also increased at 10, 20, 60 and 120 min after application of KCI.The inhibitory effect of CSD on incorporation of leucine into proteins was uniformly distributed among the crude mitochondrial, microsomal and soluble subcellular fractions from brains of adult animals, while in fractions from 25‐day old animals there appeared to be relatively more inhibition in the crude mitochondrial

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb00531.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY