摘要:

Abstract—The rate of spontaneous efflux of several isotopically‐labelled amino acids was measured in superfused slices of rat brain. The group specificity of amino acid efflux was studied by examining the pattern of accelerated efflux in the presence of extracellular unlabeled amino acid. The mediated efflux of γ‐aminobutyric acid andl‐glutamic acid was highly specific. Less specificity was found for amino acids in the small neutral, large neutral and basic groups. The efflux of γ‐aminobutyric acid andl‐glutamic acid was accelerated by structurally similar amino acids which are known to depress or excite motor neurons. This finding raises the possibility that the physiological effects of non‐specific amino acids during local iontophoresis may be secondary to an accelerated release of more specific transmitter amino acids from nei

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12117.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—–Enzymic transformation of [4‐14C]dehydroepiandrosterone or [4‐14C]dehydro‐epiandrosterone sulphate to androstenediol or its sulphate occurred when incubated with a microsomal preparation of rat brain or a whole rat blood homogenate. The brain enzyme which appeared to cause this transformation had a pH optimum at 60, was NADPH2‐dependent, and had an apparentKmof 4·6 × 10−6m. When the subcellular fractions of rat brain were compared for transformation, microsomes had the highest specific activity, followed by the cytosol. The crude nuclear and mitochondrial fractions had no significant activity. The level of enzymic activity in the brain microsomes increased from that for rats sacrificed at 7 days of postnatal age to a maximum for rats sacrificed at 1 month of age; then the activity appeared to level off in rats older than 1 month. Microsomes obtained from the cerebellum had the highest specific activity in comparison to that obtained from the cerebral cortex, the diencephalon, and the brain stem. The incubated preparations of rat brain also converted dehydroepiandrosterone sulphate to androstenediol sulphate without hydrolysis.The enzyme in rat blood which was similar to that in the brain was also partially characterized. The blood enzyme had a pH optimum at 6–5, was nearly exclusively present in erythrocytes, was also NADPH2‐dependent, and had an apparentKmof 2·7 × 10−4m. The developmental pattern of the blood enzyme specific activity was similar to that of the rat brain enzyme. Upon haemolysis, most activity was recov

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12118.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—The effects of inorganic salts, gallamine triethiodide and (+)‐tubocurarine chloride on mammalian acetylcholinesterase (AChE) were examined. The results were obtained mainly from soluble erythrocyte AChE; particle‐bound and detergent‐solubilized rat brain enzymes were also used. Three aspects of AChE were examined, namely direct effects on activity, the recovery of activity of the diethylphosphorylated enzyme and thirdly the aggregation of the enzyme at low ionic strength as shown by chromatography on columns of Sepharose 6B. The action of gallamine on AChE was controlled by the substrate concentration and the ionic strength of the medium. Both inhibition and activation by gallamine could be observed, depending on the particular conditions used. All effects of gallamine disappeared when the ionic strength was raised to 015. The action of gallamine closely resembled the result of increasing ionic strength by adding NaCl, for in both cases the apparent affinity of AChE for substrate decreased and concomitantly the maximum velocity of hydrolysis increased. The phosphorylated enzyme recovered activity more rapidly when gallamine or tubocurarine were present, or when the ionic strength was increased. Aggregation of all enzyme forms was observed at low ionic strength; an increase toI= 015 dissociated AChE to the single molecular form. It was concluded that the mammalian enzymes closely resembled electric eel AChE. The possible methods by which regulation of AChE activity could occur are discussed in relation to these

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12119.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12120.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12121.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12122.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12123.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12124.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12096.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY