摘要:

Abstract—The regional distributions of serine hydroxymethyltransferase (SHMT) and glycine transaminase (GT) have been determined in five areas of the CNS of the rat. The SHMT activity per mg protein varied in these areas in the following order: medulia‐pons and spinal cord>cerebellum>midbrain>telencephalon. The GT activity per mg protein was essentially the same in the four brain areas, whereas, in the spinal cord it was lower. The activity of GT did not correlate with the glycine content (r=−0.45.P>0.05). However, SHMT activity per mg protein was correlated with the glycine content in four regions (the telencephalon, midbrain, medulla‐pons and spinal cord;r= 0.997,P<0.05). When the activity of SHMT was expressed per relative number of mitochondria, the enzyme levels were correlated with the glycine content in all five areas (r= 0.952,P<0.05). The distribution of SHMT was determined in the primary subcellular fractions of the CNS. The SHMT activity in these areas of the CNS appeared to be located predominately in paniculate structures, while only 1 to 4 per cent was found in the soluble fraction. The crude nuclear (P1) and the crude mitochondrial (P2) fractions contained 90–97 per cent of the activity. Subfractionation of P2pellets obtained from the telencephalon, medulla‐pons and spinal cord indicated the SHMT activity was localized in both ‘free’ and occlud

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb04312.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—During postnatal growth the free amino acids pattern of rat retina differs at various developmental stages. The adult level for individual amino acids is reached on the 30th day of maturation. During differentiation the taurine, glutamic acid, GABA, glutamine, aspartic acid, glycine arginine, methionine and histidine levels increase while proline. alanine, ornithine and tyrosine decreas

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb04313.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The origin of the acetyl group in acetyl‐CoA which is used for the synthesis of ACh in the brain and the relationship of the cholinergic nerve endings to the biochemically defined cerebral compartments of the Krebs cycle intermediates and amino acids were studied by comparing the transfer of radioactivity from intracisternally injected labelled precursors into the acetyl moiety of ACh, glutamate, glutamine, ‘citrate’(= citrate +cis‐aconitate + isocitrate), and lipids in the brain of rats. The substrates used for injections were [1‐14C]acetate, [2‐14C]acetate, [4‐14C]acetoacetate, [1‐14C]butyrate, [1, 5‐14C]citrate, [2‐14C]glucose, [5‐14C]glutamate, 3‐hydroxy[3‐14C]butyrate, [2‐14C]lactate, [U‐14C]leucine, [2‐14C]pyruvate and [3H]acetylaspartate.The highest specific radioactivity of the acetyl group of ACh was observed 4 min after the injection of [2‐14C]pyruvate. The contribution of pyruvate, lactate and glucose to the biosynthesis of ACh is considerably higher than the contribution of acetoacetate, 3‐hydroxybutyrate and acetate; that of citrate and leucine is very low. No incorporation of label from [5‐14C]glutamate into ACh was observed. Pyruvate appears to be the most important precursor of the acetyl group of ACh.The incorporation of label from [1, 5‐14C]citrate into ACh was very low although citrate did enter the cells, was metabolized rapidly, did not interfere with the metabolism of ACh and the distribution of radioactivity from it in subcellular fractions of the brain was exactly the same as from [2‐14C]pyruvate. It appears unlikely that citrate, glutamate or acetate act as transporters of intramitochondrially generated acetyl groups for the biosynthesis of ACh. Carnitine increased the incorporation of label from [1‐14C]acetate into brain lipids and lowered its incorporation into ACh.Differences in the degree of labelling which various radioactive precursors produce in brain glutamine as compared to glutamate, previously described after intravenous, intra‐arterial, or intraperitoneal administration, were confirmed using direct administration into the cerebrospinal fluid. Specific radioactivities of brain glutamine were higher than those of glutamate after injections of [1‐14C]acetate, [2‐14C]acetate, [1‐14C]butyrate, [1,5‐14C]citrate, [3H]acetylaspartate, [U‐14C]leucine, and also after [2‐14C]pyruvate and [4‐14C]acetoacetate. The intracisternal route possibly favours the entry of substrates into the glutamine‐synthesizing (‘small’) compartment. Increasing the amount of injected [2‐14C]pyruvate lowered the glutamine/glutamate specific radioactivity ratio.The incorporation of14C from [1‐14C]acetate into brain lipids was several times higher than that from other compounds. By the extent of incorporation into brain lipids the substrates formed four groups: acetate>butyrate, acetoacetate, 3‐hydroxybutyrate, citrate>pyruvate, lactate, acetylaspartate>glucose, glutamate. The ratios of specific radioactivity of ‘citrate’ over that of ACh and of glutamine over that of ACh were significantly higher after the administration of [1‐14C]acetate than after [2‐14C]pyruvate.The results indicate that the [1‐14C]acetyl‐CoA arising from [1‐14C]acetate does not enter the same pool as the [1‐14C]acetyl‐CoA arising from [2‐14C]pyruvate, and that the cholinergic nerve endings do not form a part of the acetate‐utilizing and glutamine‐synthesizing (‘small’) metabolic compartment in the brain. The distribution of radioactivity in subcellular fractions of the brain after the injection of [1‐14C]acetate was different from that after [1, 5‐14C]citrate. This suggests tha

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb04314.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Effects of acute or chronic administration of ethanol and its withdrawl on the steady‐state levels and turnover rates of certain neurotransmitters have been investigated in mice. The influence of long‐term administration of ethanol on the activities of enzymes involved in the metabolism of these transmitters has also been studied. Acute administration of ethanol or acetaldehyde or chronic administration of ethanol resulted in a decrease in the cerebral contents of acetylcholine, acetylCoA and CoA. Brain levels of 5‐hydroxytryptamine, norepinephrine and choline remained unchanged after acute administration of ethanol. However, chronic administration of ethanol resulted in a decrease in the norepinephrine content without significantly affecting 5‐hydroxytryptamine or choline contents. Cerebral levels of γ‐aminobutyric acid increased with both acute or chronic administration of ethanol. The total incorporation of [3H]choline into acetylcholine in brain was depressed upon acute administration of ethanol. After withdrawal of ethanol for one day cerebral levels of norepinephrine returned to normal; however, γ‐aminobutyric acid and acetylcholine returned to normal levels at 2 and 4 days after ethanol withdrawal, respectively. Pretreatment of mice with pyrazole, an inhibitor of alcohol dehydrogenase, prevented the ethanol‐induced decrease in cerebral acetylcholine levels. The activities of cerebral choline acetyltransferase and glutamic decarboxylase were decreased after 2 weeks of chronic ethanol administration. However, the activities of acetyl cholinesterase and GABA‐transaminase remained unaffected after 2 weeks

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb04315.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Three days after superior cervical ganglionectomy of adult Sprague‐Dawley rats, the levels of endogenous norepinephrine, the uptake process for [3H]norepinephrine and the activity of tyrosine hydroxylase decreased 99 per cent in the ipsilateral salivary gland. In contrast, the activity of dopamine‐β‐hydroxylase and DOPA decarboxylase fell to 30 per cent of the activity of the contralateral innervated gland. Examination of the cofactor requirements, the characteristics of activation by cupric ion and the immunologic identity of this residual hydroxylase activity indicated that it was authentic dopamine‐β‐hydroxylase. The residual dopamine‐β‐hydroxylase in the denervated gland had the same subcellular distribution as the enzyme in the innervated salivary gland. Procedures that caused atrophy or hypertrophy of the acinar cells did not affect the total content of dopamine‐β‐hydroxylase in the denervated salivary gland. Chemical sympathectomy with 6‐hydroxy‐dopamine caused a 40 per cent decrement in the serum levels of dopamine‐β‐hydroxylase but a 30 per cent increase in its activity in the denervated salivary gland. Although denervation caused a complete loss of endogenous norepinephrine in the salivary gland, it resulted in only a 15 per cent decrement in the levels of endogenous octopamine and β‐phenylethanolamine, two other

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb04316.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Dorsal and ventral roots, dissected from rats anaesthetized with sodium pentobarbitone, accumulated three to four times more GABA thanl‐glutamate, 1‐aspartate or glycine during 30 min incubation at 37°C. GABA was taken up into spinal roots by a structurally specific, sodium‐dependent process with an apparentKmof approx. 3 × 10−5m. This uptake process appears to be very similar to that described in rat brain, spinal cord and dorsal r

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb04317.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—GABA levels determined after the brain was removed, then frozen, were found to be generally compatible to levels after the brain was frozenin situprovided removal and freezing were effected in less than 60 s. Optimal GABA values were realized when the brain was removed and frozen in liquid nitrogen within 30 s of death. Beginning at 60 s post‐mortem, GABA levels increased until the 4th min with the greatest rate occurring between 60 and 120 s at 30 μg/g/min. When frozen brains were dissected into regions by a partial thawing technique, post‐mortem increases were not found to occur. Microwave irradiation, investigated as a potential sampling technique for GABA assay, showed considerable variability between samples and was rejected as a practical alternative at thi

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb04318.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The rate of degradation of acetylcholinesterase [EC 3.1.1.7] in mature rat cerebral cortex was determined from the time course of the label introduced into the protein by one intraventricular injection ofl‐leucine‐l‐14C. The half life of the enzyme was 2.84 ±

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb04319.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Acetylcholinesterase (EC 3.1.1.7) from cerebral cortex of mature rats was purified by means of affinity chromatography, to a specific activity of 4.5 mmol acetylthiocholine hydrolysed × min−1× mg−1protein. The enzyme is a glycoprotein and contains a single subunit with a mol. wt of about 80,000. Electrofocusing either a pure or a crude preparation of the enzyme produces six enzymatically active bands with a range of isoelectric points from 5.04 to 5.54. Gel filtration yields oligomers with molecular weights of about 150,000, 320,000, 500,000 and 650,000, with 60 per cent of the activity in the 150,000 fraction. The gel fractions with molecular weights 150,000 and 320,000 produce the same isoelectric patterns. Different subcellular fractions of the cortex show different characteristic isoenzyme p

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb04320.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Alterations in whole‐brain and hypothalamic levels of serotonin (5‐HT), 5‐hydroxyindoleacetic acid (5‐HIAA), norepinephrine (NE), dopamine (DA) as well as the turnover rates of NE and DA of adult male rats were analysed fluorometrically at either 3 weeks or 6 weeks following castration. Significant increases were observed in whole‐brain (minus hypothalamus) 5‐HIAA levels and hypothalamic DA levels, fractional rate constants and utilization rates at the 3 but not the 6 week intervals. Elevated levels of 5‐HT were observed at both time intervals while an increase in whole‐brain DA was seen only at the 6 week interval. Whole brain NE turnover rates of castrated animals did not differ significantly from those of sham‐castrate control animals at either test interval. However, a tendency toward increased hypothalamic NE turnover rates was seen in the castrated animals. These biochemical changes resulted in decreased NE/5‐HT and DA/5‐HT ratios for the castrate rats as compared to controls.The results are discussed in relation to emotional and aggressive behavior and are interpreted as being consistent with the hypothesis purporting an inhibitory role for 5‐HT and excitatory role for NE and DA in sex‐specific behavior pa

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb04321.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY