摘要:

Abstract—In any assay for the determination of acetylcholine based on the conversion of choline to a product, the immediate problem is the removal of endogenous choline. Other published enzymatic assays have taken advantage of electrophoresis to accomplish this goal. In the assay to be described, this is accomplished by the enzymatic phosphorylation of endogenous choline by choline kinase. Once this reaction is complete, endogenous acetylcholine is simultaneously hydrolysed and then phosphorylated with [32P]ATP. The labelled product [32P]phosphorylcholine is separated from the labelled substrate by precipitation of the ATP and further separation is accomplished on microcolumns of ion exchange resin. Using this methodology, picomole amounts of acetylcholine, derived from tissue, can be measure

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12097.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—The formation of active suphate has been assayed in developing rat brain, the activity of the enzyme system being maximal at birth and thereafter decreasing gradually. The activity of phenolsuphotransferase, present in rat brain, is minimal at birth and increases gradually to the adult valu

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12098.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—The mechanism of histamine methyltransferase (HMT) inhibition byS‐adenosylhomocysteine (SAH) has been investigated on a partially purified enzyme from guinea‐pig brain. The kinetic data indicated that this inhibition was competitive with respect toS‐adenosylmethionine (SAMe) and noncompetitive with respect to histamine. TheKt, values (about 5 ± 10−6M in both cases) indicated that SAH had a higher affinity than SAHe or histamine for the enzyme.In rats, after administration of a small dose of SAH, methylation of intracisternally injected [3H]histamine was not modified.However, treatment withl‐DOPA or pyrogallol induced a decrease in [3H]histamine methylation, presumably due to a modification in the SAMe/SAH ratio in the brain. Hence, histamine methylation in brain could be regulated according to the value of this ratio and thus related to methylation of other bio

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12099.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Effects of the acute and chronic administration of ethanol have been investigated in mouse brain on the redox‐state, citric acid cycle function, levels of adenine nucleotides and other metabolites. Cerebral oxidation of ethanol, activity of alcohol dehydrogenase and the permeability of brain and liver mitochondrial preparations after chronic ethanol administration have been also investigated. Acute or chronic administration of ethanol resulted in a small but significant increase in the reduced components of certain dehydrogenase‐linked substrate pairs in brain. Pyrazole, an inhibitor of alcohol dehydrogenase, prevented the ethanol‐induced changes in brain.14CO2production from several substrates was inhibited in brains from chronically ethanol‐fed animals. Addition of pyrazole, however, prevented the ethanol‐mediated inhibition of14CO2production. Chronic administration of ethanol resulted in decreased levels of ATP and creatine phosphate in the brain, and increased contents of ADP and AMP. The cerebral activities of alcohol dehydrogenase and succinic dehydrogenase, oxidation of ethanol, mitochondrial oxidation of a‐glycerophosphate, and levels of NADH remained unaffected by the chronic administration of ethanol. In contrast to liver, where chronic administration of ethanol increased the contribution of 'substrate shuttles’resulting in increased oxidation of ethanol; in brain, the contribution of these 'shuttles’re

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12100.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—–A method is described by which inorganic phosphate may be extracted from brain when bone fragments are present. Inorganic phosphate is extracted into 80% methanol and this does not hydrolyse phosphate esters of brain or dissolve bone. The inorganic phosphate content of brain was 217 μmol/g in both fed and 24 h starved

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12101.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—β‐N‐Acetyl D‐galactosaminidase was studied in isolated neuronal and neuropil fractions from cerebral cortex and subcellular fractions derived from them. Although the enzyme activity evinced some latency properties, its subcellular distribution pattern was broader than that observed with other acid hydrolases. By contrast with nine other acid hydrolases, it was more active in neuropil than neuronal fractions (neuronal/neuropil activity ratio 0.63). This ratio was preserved in lysosomal subfractions derived from the isolated cell fractions. The data is taken as further evidence for the microheterogeneity of lysosomal particles from t

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12102.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Choline acetyltransferase (ChAc; EC 2.3.1.6) was assayed in the membranous cochlea and in the eighth cranial nerve (both the vestibular and cochlear components) from the point where it leaves the brain stem to the internal auditory meatus of the cat. To determine the contribution of the efferent innervation of the cochlea to this enzymatic activity both eighth nerves and both membranous cochleae were assayed at 17–29 days following section of the right, crossed and uncrossed olivo‐cochlear bundles (OCB) in the cat. The lesion was produced along the right sulcus limitans on the floor of the fourth ventricle. The left eighth nerves and cochleae served as controls in the ChAc assay. There was a significant decrease in ChAc activity in the right cochlea and eighth nerve after OCB section and degeneration. The mean activity of ChAc in the right cochleae of the 6 operated cats was 15 ± 7 μg of ACh formed. h−1(g wet wt. of tissue)−1in comparison to the rate of all the intact cochleae of 156 ± 38 μg of ACh formed. h−1. (g of tissue)−1, a statistically significant difference (P<0005). The mean activity of ChAc in the right eighth nerves of the cats with OCB lesions was 30 ± 8 n‐g of ACh formed. h−1. (g of tissue)−1in comparison to 91 ± 19 fig of ACh formed . h−1. (g of tissue)−1found for intact eighth nerves. This difference was also significant (P<0005). Thus, section and degeneration of the crossed and uncrossed OCB reduce the activity of ChAc in the eighth nerve and membranous cochlea. This finding provides support for the hypothesis suggesting the cholinergic nature o

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12103.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Mitochondria isolated from rat brain contained ribosomes, with an apparent sedimentation constant (j) of 60, which were dissociable into 45sand 32ssubunits. The RNA associated with the 45ssubunit had ansvalue of 16; the RNA of the 32ssubunit had ansvalue of 13. These values were essentially like those found for the mitochondria of rat liver. Nascent protein associated with the 60smonosome was reduced by chloramphenicol but not by cycloheximide. All cycloheximide‐sensitive activity found in brain mitochondria prepared from sucrose or Ficoll‐sucrose gradients and most of that associated with nerve‐ending preparations that were similarly prepared could be attributed to a contaminant that was probably a membrane‐enclosed, cytoplasmic‐like system which contained, in addition to 18sand 28sRNA, one or more mitochondria. Nerve‐ending preparations from which most or all of this contamination had been removed exhibited very little cycloheximide‐sensitive protein syn

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12104.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—–Changes in glycogen, glucose, lactate and monoamine levels in various brain structures were studied after unilateral diencephalic lesions in the rat. These lesions were placed to transect the fibres of the medial forebrain bundle within the lateral hypothalamus as well as to encroach upon the medial aspect of the internal capsule. Such lesions are known to produce unilateral reduction of telencephalic monoamines rostral to the lesion. In paraformaldehyde‐perfused brain, the level of glycogen increased by 30 per cent (+0 82 μmol/g) in the caudate nucleus ipsilateral to the lesion in comparison to that in the caudate of the non‐lesioned side. Other telencephalic areas, as well as cerebellum and brainstem, showed no significant change in glycogen levels. In brains from unanaesthetized rats, frozen 15–30 s after decapitation (to simulate anoxia, with consequent glycogen mobilization), a caudate‐containing sample from the lesion side had 31 per cent (+0 51 μmol/g) more glycogen than a comparable sample from the control side. Glucose levels were also elevated by 72 per cent (+0 05 μmol/g, whereas lactate levels were not significantly changed. Similar samples obtained from animals 3anaesthetized with phenobarbital for 2 h prior to killing showed a 76 per cent increase in glycogen in both lesion and control caudate nuclei when compared to those obtained from the unanaesthetized group. Glycogen levels were increased by 15 per cent (+0 41 μmol/g) and glucose by 72 per cent (+0 31 μmol/g) on the lesion side in comparison to the values obtained from the control side in the anaesthetized group. Lactate levels were not significantly affected. The dopamine levels in these caudate samples from the lesion side were reduced by 97 and 88 per cent in the unanaesthetized and anaesthetized animals, respectively. In samples of caudate allowed to glycolyse under anoxic conditions for 10 min, the amount of lactate found on the lesion side was increased 29 per cent over that found in identical samples from the non‐lesioned side. Dopamine was reduced by 78 per cent in these samples. The remaining telencephalic areas exhibited no significant side to side difference in lactate levels despite a 71 per cent decrease in their levels of norepinephrine. These findings demonstrate that glycogen metabolism in the neostriatum is affected by diencephalic lesions which result in a loss of striatal monoamines, observations suggesting that brain biogenic amines may play a role in the regulation of neuronal metabolism

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12105.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Abstract—Diphtheria toxin (DT) did not produce measurable degradation of myelin proteins or sulphatide in sciatic nerves of chick embryos after incubationin vitrofor 4 h. In contrast, DT inhibited thein vitroincorporation of L‐[U‐14C]leucine into myelin proteins by the nerves after a delay of 1 h. Separation of the myelin proteins by SDS‐polyacrylamide gel electrophoresis indicated that the synthesis of Wolfgram proteins and proteins not entering the gel was inhibited by 21–22 per cent, whereas synthesis of myelin proteolipid and basic proteins was inhibited by 79–88 per cent. Incorporation of35SO4into myelin [35S]sulphatide was also inhibited by DT after a delay of 2 h. The inhibition of [35S]sulpha‐tide incorporation into myelin caused by DT differed from that observed with puromycin in that it did not depend on depletion of an intracellular transport lipoprotein. Instead, the inhibition seemed to be secondary to the decreased synthesis of myelin proteolipid and b

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1973.tb12106.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY