bluuebunny/crossref_metadata_2025 huggingface dataset:
MANIFESTATION OF METABOLIC COMPARTMENTATION DURING THE MATURATION OF THE RAT BRAIN
Authors: Patel A. J. , Balázs R.
Published: October 2006

—(1) The fate of [U‐14C]leucine was studied in rat brain in vivo from birth to five weeks of age. The major route of leucine metabolism at all ages was conversion into protein. The rate of protein synthesis was low in the newborn; it reached a peak at about 15 days and slowed down moderately later. Incorporation into brain lipids was relatively low under the experimental conditions (less than 2 per cent of the total tissue 14C).

(2) The conversion of leucine‐carbon into amino acids associated with the tricarboxylic acid cycle was low in the first 9 days after birth (less than 4 per cent of the acid‐soluble 14C at 10 min after injection) and increased rapidly until 15 days when the level characteristic of the adult was approached (about 20 per cent of the acid‐soluble 14C). The results indicated that the oxidation of acetyl‐CoA derived from leucine reached the adult level at an earlier age than that derived from glucose.

(3) The glutamine/glutamate specific radioactivity ratio was 0·3 in the brain of newborn animals and increased progressively; it was 1·3 and 2·4 at 15 and 35 days of age respectively. The specific radioactivity of aspartate and of GABA relative to that of glutamate was less than 1 throughout the experimental period.

(4) The factors involved in the development of metabolic compartmentation in brain were analysed. It is proposed that although the experimental results show that a 'small’compartment becomes functionally manifested with maturation the primary cause is the development of the‘large’metabolic compartment.

(5) Morphological correlates of the metabolic compartments in brain tissue are suggested and it is concluded that the manifestation of metabolic compartmentation is related to maturational changes in glia‐neuronal relations rather than to developmental processes affecting the individual components only.
COMPARTMENTATION OF CITRIC ACID CYCLE METABOLISM IN BRAIN: LABELLING OF GLUTAMATE, GLUTAMINE, ASPARTATE AND GABA BY SEVERAL RADIOACTIVE TRACER METABOLITES1
Authors: Berl S. , Nicklas W. J. , Clarke D. D.
Published: October 2006

—(1) Compartmentation of the metabolism of amino acids in brain has been studied in slices of cerebral cortex incubated with sodium [1‐14C]acetate, sodium [1‐14C]‐bicarbonate, [1‐14C]GABA or l‐[1‐14C]glutamate and in samples of brain after injection in vivo of [1‐14C]‐ or [3H]acetate.

(2) The method of treatment of the slices (a) maintained in ice‐cold medium prior to incubation; (b) preincubation at 37°C and transfer to fresh medium affected the metabolism of the added, labelled substrate, particularly its labelling of glutamine.

(3) The specific activity of glutamine labelled from the above metabolites was greater than that of glutamic acid in experiments of 10–30 minutes duration, whether or not subjected to pretreatment in the cold.

(4) Incubation in medium containing 27 mm‐K+ was associated with a decrease in the relative specific activity (RSA) of glutamine, except for the increase when l‐[1‐14C]glutamate was the precursor.

(5) The data have been discussed in terms of metabolic compartmentation and their consistency with the concept of the presence in brain of more than one citric acid cycle, one containing the relatively smaller pools of intermediates and associated with synthetic processes; the other containing the relatively larger pools of intermediates and functioning as a homeostatic buffer for energy metabolism.
dl‐[2‐14C]p‐CHLOROPHENYLALANINE AS AN INHIBITOR OF TRYPTOPHAN 5‐HYDROXYLASE
Authors: Gál E. M. , Roggeveen A. E. , Millard S. A.
Published: October 2006

Abstract—

The distribution in vivo of dl‐[2‐14C]p‐chlorophenylalanine (p‐CP) in regions and subcellular fractions of the rat brain was determined. The half‐lives of p‐CP and its metabolite p‐chlorophenylpyruvic acid (p‐CPPA) in plasma and brain were correlated with the development of inhibition of cerebral tryptophan 5‐hydroxylase (EC 1.99.1.4). There was active transamination in vivo of p‐CP and p‐CPPA in the brain. Transport of indolealkylamino acids into brain was impaired by p‐CP. Inhibition of tryptophan 5‐hydroxylase could not be reversed by administration of large doses of l‐tryptophan, l‐tyrosine, or l‐phenylalanine. After administration of [2‐14C]p‐CP in vivo, appreciable radioactivity was bound to cerebral proteins, including those with tryptophan 5‐hydroxylase activity, as well as to phenylalanine 4‐hydroxylase (EC 1.99.1.2) purified from liver. Amino acid analysis of the acid hydrolysate of purified, radioactive hepatic phenylalanine 4‐hydroxylase showed over 80 per cent of the radioactivity to be present as p‐CP.

Neither the inhibition in vivo nor in vitro of tryptophan 5‐hydroxylase could be reversed by dialysis; in controls, dialysis resulted in marked loss of enzyme activity. After incubation for 5 min with p‐CP in vitro, enzymic activity was inhibited 60 per cent. In vitro, p‐CPPA labelled protein much more extensively than p‐CP, yet inhibited the enzyme less. Some of the label from p‐CPPA was removable by dialysis.
EFFECT OF THYROID HORMONE ON THE BIOCHEMICAL MATURATION OF RAT BRAIN: CONVERSION OF GLUCOSE‐CARBON INTO AMINO ACIDS
Authors: Cocks J. A. , Balázs R. , Johnson A. L. , Eayrs J. T.
Published: October 2006

Abstract—

The rapid and extensive conversion of glucose‐carbon into amino acids is an index of the final coordination of the mechanisms underlying energy metabolism in the adult brain. This phenomenon develops in the rat during a short period extending from 10 to about 19 days after birth. The underlying factors have been analysed.

The development of the pattern of distribution of glucose‐carbon characteristic of the adult brain was markedly influenced by the thyroid state of the animals. The age‐curve for the conversion of glucose‐carbon into brain amino acids was displaced to the left after treatment with thyroid hormone (T3) in infancy thus indicating an accelerated maturation. Conversely, neonatal thyroidectomy resulted in a significant retardation in the conversion of glucose‐carbon into amino acids.

The specific radioactivity of glutamate increased five‐fold in the brain of normal rats from the 10th to the 19th day of age. The values (as a percentage of those for littermate controls) were 220 in the case of the 10 day‐old thyroid treated rats and about 30 for the 19 day‐old thyroid deficient animals. At the age of 10 days neither treatment affected the concentration of glutamate which was also only slightly less than the control values in the brain of 19 day‐old thyroid deficient animals (–17 per cent).

Specific pool(s) of glutamate associated with the formation of GABA can be demonstrated in the brain of 19 day‐old rats after administration of [U‐14C]glucose as a result of anoxia post mortem. These pools did not develop in the brain of 10 day‐old animals. Neonatal thyroidectomy retarded the development of these glutamate pools.

Evidence is summarized which indicates that the development of the rapid conversion of glucose‐carbon into amino acids reflects the enlargement, during maturation, of the metabolic compartments which are associated with neuronal processes.
THE DIFFERENTIATION OF PHOSPHOLIPASE A1 AND A2 IN RAT AND HUMAN NERVOUS TISSUES
Authors: Cooper Mary F. , Webster G. R.
Published: October 2006

—Lipid‐free extracts of rat and human brain have been prepared and shown to contain phospholipase A1 and A2 activities and a lysophospholipase. The phospholipase Aj activity has pH optima of 4·2 and 4·6 in rat and human brain, respectively; it can be partially purified and isolated in high yields by dialysing the extracts at low pH. The purified preparations hydrolyse the ester bond at the 1‐position in lecithin, phosphatidyl‐ethanolamine and phosphatidylserine, but have little or no action on triglyceride or cholesterol ester. An assay system for the enzyme is described.

Phospholipase A2 activity is optimal at pH 5·5 in rat brain extracts and at pH 5·0 in extracts of human brain. The phospholipase A2 activity of human cerebral cortex is largely unaffected by heating extracts at 70°C for 5 min, whereas this treatment substantially inactivates phospholipase A1 and completely destroys lysophospholipase.

Phospholipase A1 is widely distributed in both grey and white matter of human brain and is also present in peripheral nerve. Phospholipase A2 activity is lower than A1 in all regions of the CNS examined so far, and is absent from peripheral nerve. Neither enzyme appears to require Ca2+ but both are inhibited by di‐isopropylfluorophosphate (DFP, 2 × 10−6 m) and thus differ from phospholipase A of pancreas.

These studies confirm that the phospholipase A1 and A2 activities in brain are due to separate enzymes.
NORADRENALINE METABOLIZING ENZYMES IN NORMAL AND SYMPATHETICALLY DENERVATED VAS DEFERENS
Authors: Jarrott B. , Iversen L. L.
Published: October 2006

—A surgical technique for sympathetically denervating the vas deferens has been evaluated biochemically. A slight fall in soluble muscle protein content and no significant change in DNA content of the operated vas deferens were found. This indicates that the surgical procedure causes only a slight degree of tissue damage and may be useful for investigating the cellular localization and properties of noradrenaline metabolizing enzymes. In three species examined (rat, guinea pig and rabbit), monoamine oxidase activity of the vas deferens fell by approximately 50 per cent after denervation. The time course of the fall in monoamine oxidase activity of rat vas deferens was parallel to that of the disappearance of noradrenaline suggesting that this proportion of the total enzyme activity had a neuronal localization. The remaining enzyme activity is presumably located extraneuronally.

Significant falls in catechol‐O‐methyl transferase activity were found in rat and rabbit vas deferens after denervation but not in guinea pig. The rabbit and rat vas deferens had respectively approximately 60 and 30 per cent of the catechol‐O‐methyl transferase activity associated with the sympathetic nerves. A complete loss of DOPA decarboxylase and tyrosine hydroxylase activities occurred in rat vas deferens after denervation, suggesting that these noradrenaline synthesizing enzymes have an entirely neuronal localization.
THE EFFECT OF VOLATILE ANAESTHETICS ON LEVELS OF METABOLITES AND ON METABOLIC RATE IN BRAIN1
Authors: Brunner E. A. , Passonneau Janet V. , Molstad C.
Published: October 2006

Abstract—

Anaesthesia with ether, halothane, methoxyflurane (Penthrane) and Ohio 347 (Ethrane) increased the energy stores in mouse brain as much as 1·7‐fold above the control values. The greatest increases were observed in glucose and glycogen. Glucose‐6‐P was increased in some cases and UDP glucose was consistently lower in the anaesthetized animals. Hypothermia in conjunction with anaesthesia modified some of the observed changes. Hypothermia alone was associated with an increase in P‐creatine and glucose and a decrease in UDPglucose in the brain.

The cerebral metabolic rate was depressed by all the anaesthetic agents to about 50 per cent of the control value. When the body temperature was lowered to 25°, the cerebral metabolic rate fell to 73 per cent of the control rate. A temperature coefficient of 1·035 was calculated as the fractional change/degree between 25° and 34°.
THE EFFECT OF ELECTROSHOCK ON REGIONAL CNS ENERGY RESERVES IN MICE1
Authors: Ferrendelli J. A. , McDougal D. B.
Published: October 2006

ATP, phosphocreatine, glycogen, glucose and lactate levels were measured in the cerebral cortex, thalamus, cerebellum, brain stem and spinal cord of mice following supramaximal electroshock. During the initial 17 s after the onset of a 2 s electrical stimulus high energy phosphate expenditure exceeded formation in all regions but was slower in spinal cord than in the other regions. In cerebral cortex high energy phosphate utilization continued to exceed formation for 32 s which was twice as long as in any other region studied. Altered levels of metabolites recovered most rapidly in spinal cord and least rapidly in cerebral cortex. Pretreatment with a non‐anaesthetic dose of phenobarbitone influenced the effect of electroshock. Most of the clinical seizure was prevented, and increased high energy phosphate utilization was sustained for a much shorter period. Only in cerebral cortex did high energy phosphate expenditure exceed formation for as long as 15 s after the electrical stimulus; but even in this region the excess of expenditure over formation was much less than in untreated animals.
BIOCHEMICAL STUDIES IN CAT AND HUMAN GANGLIOSIDOSIS1, 2
Authors: Handa S. , Yamakawa T.
Published: October 2006

The biochemical analysis of the hereditary neurological disease found in a family of Siamese cat is reported. The accumulation of GM1ganglioside in the brain was noted. Several glycosidase activities of these cat brains were compared with that of human gangliosidoses (Tay‐Sachs disease and GM1‐gangliosidosis). Glycosidase activities were estimated using ρ‐nitrophenyl‐glycosides, glucosyl‐, galactosyl‐ceramide and GM1‐ganglioside as substrates. The results indicated the defect of the β‐galactosidase activities for the ρ‐nitrophenyl‐β‐galactoside and GM1‐ganglioside in both cat and human GM1‐gangliosidoses. Glycosidase activities for glucosyl‐ and galactosyl‐ceramide were not changed in either gangliosidoses.
THE EFFECTS OF PYRIDOXINE DEFICIENCY AND OF CALORIC RESTRICTION ON LIPIDS IN THE DEVELOPING RAT BRAIN1
Authors: Williamson Barbara , Coniglio J. G
Published: October 2006

Abstract— The effects of dietary deficiency of pyridoxine upon the contents of lipids in the brain were determined at several times after birth for three groups of rats. The mothers of the nursing pups were fed one of the following dietary regimes: pyridoxine‐deficient diet ad lib., pyridoxine‐supplemented diet ad lib., or pyridoxine‐supplemented diet in restricted amounts. At 7 and 14 days of postnatal age there were no significant differences between supplemented and deficient animals for any of the cerebral lipids studied. At 21 days the content of sphingomyelin in the brains of deficient animals was significantly lower than that in brains from the supplemented or calorically restricted animals in terms of percentage of total lipid and phospholipid phosphorus or tissue weight. On a per brain basis the content of sphingomyelin in the brains of calorically‐restricted rats was significantly lower than in the brains of rats fed the supplemented diet ad lib. The contents of cerebrosides but not of sulphatides or ceramides were also significantly lower in brains of the deficient group than in brains from the other two groups.

The contents of pyridoxine in brains and in livers of the deficient animals were considerably lower than the contents found in the same organs of the other dietary groups. The results suggest that one reason for the abnormal development of the brains of rats on a pyridoxine‐deficient diet during the early postnatal period may be due to decreased quantities of sphingolipids.
ACTIVITY OF STEROL‐SULPHATE SULPHOHYDROLASE IN RAT BRAIN: CHARACTERIZATION, LOCALIZATION AND CHANGE WITH AGE1
Authors: Kishimoto Y. , Sostek R.
Published: October 2006

Abstract— Homogenates of rat brain hydrolysed the sulphate esters of dehydroepiandrosterone, oestrone and pregnenolone to free steroids. The pH optimum was 6.6 for all three steroid sulphates. Under similar conditions, cholesterol sulphate was not hydrolysed to a significant extent. Unlike sterol sulphatases (EC 3.1.6.2) from extraneural tissues, most of the activity in brain was found in the crude nuclear fraction. The remainder of the activity was found in the crude mitochondrial fraction and almost none was detected in microsomal or cytosol fractions. Sterol sulphatase activity was present in the foetal brain and increased rapidly with increasing postnatal age to a plateau at approx. 25 days of postnatal age. The enzymic activity did not differ significantly with the sex of the animal. The sulphatase activity was found throughout the brain, with cerebellum and brain stem exhibiting a slightly higher activity per wet wt. of tissue than other regions. Inhibition of enzymic activity occurred in the presence of sodium deoxycholate, Triton X‐100, sodium dodecyl sulphate and inorganic phosphate or sulphate.
STUDIES ON GANGLIOSIDES OF GOLDFISH BRAIN1
Authors: MCCluer R. H. , Agranoff B. W.
Published: October 2006

Abstract— Purified gangliosides from goldfish brain have been separated on thin layer chromatography. Incorporation of radioactivity into gangliosides from intracranially‐ injected [3H]galactose was not affected by concentrations of puromycin (170 μg intra‐ cranially) known to exert behavioural effects. Puromycin (500 μg intracranially) inhibited the incorporation of radiolabelled galactose into infant rat brain gangliosides, a result which confirms a previous report in the literature.
N‐ACETYL‐l‐ASPARTIC ACID CONTENT OF HUMAN NEURAL TUMOURS AND BOVINE PERIPHERAL NERVOUS TISSUES
Authors: Nadler J. V. , Cooper J. R.
Published: October 2006

Abstract— Abstract‐Tumors of the human nervous system were utilized to investigate the cellular distribution of N‐acetyl‐L‐aspartic acid (NAA). Astroglial tumours contained about 0.144 μmol/g. Oligodendrogliomas and medulloblastomas contained somewhat larger amounts. However, the level of NAA in all gliomas studied was less than that of normal human white matter. NAA was undetectable in meningiomas and acoustic neurinomas. If these results may be taken as representative of normal tissue, they imply a predominantly neuronal localization for NAA.

Substantial amounts of NAA were found in peripheral nervous tissues and retina. Neurons seem to vary widely in NAA content.
ADENOSINE KINASE OF MAMMALIAN BRAIN: PARTIAL PURIFICATION AND ITS ROLE FOR THE UPTAKE OF ADENOSINE
Authors: Shimizu H. , Tanaka S. , Kodama T.
Published: October 2006

Abstract— Adenosine metabolism in the homogenate of brain mainly undergoes deamination to inosine and hypoxanthine, while uniformly labelled [14C]adenosine injected into the carotid artery or [8‐14C]adenosine incubated with brain slices was mostly phosphorylated to [14C]adenine nucleotides in brain cells. Adenosine kinase has now been partially purified from homogenates of guinea pig brain. The kinase preparation was free of adenosine deaminase, almost free of adenosine triphosphatase and had a Km of the order of 2 × 10‐5M for adenosine.

Kinetic studies with brain slices showed that adenosine reached the cells by diffusion and that the diffusion was facilitated by subsequent phosphorylation to adenine nucleotides. From the following experimental results, it is concluded that the phosphorylation is catalysed by adenosine kinase quantitatively. (1) During the uptake and phosphorylation of adenosine by brain slices, the nucleoside did not split to adenine and ribose moieties. (2) The rate of formation of adenine nucleotides in the slices was a hyperbolic function of the concentration of adenosine in the medium, showing an apparent Km foradenosine of the order of 2 × 10‐5 M. (3) Some analogues of adenosine inhibited both the facilitated diffusion of adenosine and the kinase activity, but ouabain (0.005 mM) did not inhibit either.
HISTAMINE FORMATION IN RAT BRAIN IN VIVO: EFFECTS OF HISTIDINE LOADS12
Authors: Schwartz J. C. , Lampart C. , Rose C.
Published: October 2006

Abstract— Administration of l‐histidine at the rate of 500 mg/kg induced an increase of nearly 50 per cent in the level of histamine in rat brain which lasted several hours. The augmentation of histamine level was not significant 3 h after lower doses or after d‐histidine α‐methyl DOPA and Ro 4‐4602 neither affected the cerebral level of histamine nor its elevation induced by l‐histidine. Brocresine, a known histidine decarboxylase inhibitor not only prevented the effect of histidine load but also induced a prompt fall in the amine level. These results confirm those from earlier experiments in vitro indicating that histamine synthesis in rat brain depends on a specific decarboxylase (EC 4, 1.1.22) which is not normally saturated by the endogenous level of its substrate.

When histamine levels were enhanced by histidine treatment, histidine decarboxylase activity, as evaluated on hypothalamus homogenates, was significantly reduced; intracisternal administration of cycloheximide, an inhibitor of protein synthesis, had similar effects. On the other hand, enzyme activity was not altered by the addition of histamine to hypothalamus homogenates. These results are compatible with the existence of a regulation mechanism of histidine decarboxylase involving repression by its end‐product.
24‐Hydroxycholesterol levels in human brain1
Authors: SMITH Leland L. , Ray D. R. , Moody J. A. , Wells J. D. , Van Lier J. E.
Published: October 2006

24‐Hydroxycholesterol (cerebrosterol, cholest‐5‐ene‐3β;, 24ξ‐diol) occurs at low levels in human (Di Frisco, De Ruggieri and Ercoli, 1953; Ercoli and De Ruggieri, 1953a, 19536; Schubert, Rose and Burger, 1961; Van Lier and Smith, 1969, 1970), equine (Ercoli, Di Frisco and De Ruggieri, 1953a; Ercoli and De Ruggieri, 1953a, 1953b; Fieser, Huang and Bhattacharyya, 1957) and bovine (Richter and Dannenberg, 1969) brain tissue. Only one of two possible C‐24 epimeric alcohols appears to occur in human brain (Van Lier and Smith, 1970) and the sterol may be regarded as a true endogenous trace‐level sterol and not as an artifact of autoxidation derived during isolation and analysis. As a phase of our continuing interests in the presence of trace‐level polar sterols in human tissues (Van Lier and Smith, 1967, 1969, 1970, 1971a; Smith and Van Lier, 1970), we sought to measure levels of 24‐hydroxycholesterol in different parts of human brain by gas chromatographic means. The present report deals with our measurements of 24‐hydroxycholesterol in human cortex, subcortical white matter, midbrain, pons, and cerebellum.
METABOLIC CONTROL MECHANISMS IN MAMMALIAN SYSTEMS
Authors: Schwark W. S. , Singhal R. L. , Ling G. M.
Published: October 2006

Abstract— The regulation by thyroid hormone of the activities of hexokinase (ATP: D‐hexose 6‐phosphotransferase; EC 2.7.1.1), phosphofructokinase (ATP: D‐fructose‐6‐ phosphate 1‐phosphotransferase; EC 2.7.1.11) and pyruvate kinase (ATP: pyruvate phosphotransferase; EC 2.7.1.40) has been investigated in the soluble fractions of the cerebral cortex and cerebellum of the rat. Ontogenetic studies on these key glycolytic enzymes demonstrated marked increases in the normal cerebral cortex between 1 day and 1 yr of age; less pronounced increases in enzyme activities were noted in the normal cerebellum. Neonatal thyroidectomy, induced by treatment of 1‐day‐old rats with 100 μCi of 131I, ied to an impairment of body and brain growth and inhibited the developmental increases in hexokinase, phosphofructokinase and pyruvate kinase in both the cerebral cortex and cerebellum. Whereas 50 μCi of 131I had little or no effect on these brain enzymes, 200 μCi of the radioisotope markedly inhibited (35–65 per cent) the developmental increases of the various enzyme activities investigated. When administration of the radioisotope was delayed for 20 days after birth, little or no inhibition of the development of brain glycolytic enzymes was observed. Whereas treatment of normal neonatal animals with L‐tri‐iodothyronine had no significant effect on the activities of cerebro‐cortical and cerebellar glycolytic enzymes, the hormone increased their activities in young cretinous rats. However, when the initiation of tri‐iodothyronine treatment was delayed until neonatally thyroidectomized rats had reached adulthood, this hormone failed to produce any appreciable change in enzyme activity. Our results indicate that thyroid hormone exerts an important regulatory influence on the activities of hexokinase, phosphofructokinase and pyruvate kinase in the developing cerebral cortex and cerebellum.
AXONAL TRANSPORT OF S‐100 PROTEIN IN MAMMALIAN NERVE FIBRES
Authors: Miani N. , De Renzis G. , Michetti F. , Correr S. , Sangiacomo C. Olivieri , Caniglia A.
Published: October 2006

Abstract— The brain‐specific S‐100 protein is a neuronal as well as a glial protein. Neuronal S‐100 is a migratory protein from soma to terminal of the hypoglossal, vagus and glossopharyngeal nerves of the rabbit (axonal transport of S‐100 protein). There is a distinctive rate of flow for S‐100 in the somatic and parasympathetic efferent fibres of such cranial nerves.
UPTAKE OF [3H‐METHYL]CHOLINE BY MICROSOMAL, SYNAPTOSOMAL, MITOCHONDRIAL AND SYNAPTIC VESICLE FRACTIONS OF RAT BRAIN
Authors: Diamond I. , Milfay D.
Published: October 2006

Abstract— Microsomal, mitochondrial, synaptosomal and synaptic vesicle fractions of rat brain took up [3H‐methyl]choline by a similar carrier‐mediated transport system. The apparent Km for the uptake of [3H‐methyl]choline in these subcellular fractions was about 5 × 10−5 M. Choline uptake was also observed in microsomal fractions prepared from liver and skeletal muscle. Virtually identical kinetic properties for [3H‐methyl]choline transport were found in the synaptosomal fractions prepared from the whole brain, cerebellum or basal ganglia. Countertransport of [3H‐methyl]choline from the synaptosomal fraction was demonstrated against a concentration gradient. HC‐3 was a competitive inhibitor of the uptake of [3H‐methyl]choline in brain microsomal, synaptosomal and mitochondria] fractions with respective values for Ki of 4.0, 2.1 and 2.3 × 10−5 M. HC‐15 was a competitive inhibitor of the transport of [3H‐methyl]choline in the synaptosomal fraction, with a Ki of 1.7 × 10−4 M. Upon entry into the microsomal fraction, 74 per cent of the radioactivity could be recovered as unaltered choline, 10 per cent as phosphorylcholine, 1.5 per cent as acetylcholine and 2.5 per cent as phospholipid.

Choline acetyltransferase (EC 2.3.1.6) was assayed with [14C]acetylCoA in synaptosomal fractions prepared from basal ganglia and cerebellum, and in the 31,000 g supernatant fraction of a rat brain homogenate. Enzyme activity was 11‐fold greater in the synaptosomal fraction from the basal ganglia than in that from the cerebellum. HC‐3 did not inhibit choline acetyltransferase and there was no evidence for acetylation of HC‐3.

Our findings suggest that choline uptake is a ubiquitous property of membranes in the CNS and cannot serve to distinguish cholinergic nerve endings and their synaptic vesicles.
TRYPTOPHAN 5‐HYDROXYLASE: APPROXIMATION OF HALF‐LIFE AND RATE OF AXONAL TRANSPORT
Authors: Meek J. L. , Neff N. H.
Published: October 2006

—The half‐life of tryptophan 5‐hydroxylase (EC 1.14.3) in rats was estimated from the return of enzyme activity after administration of p‐chlorophenylalanine and from the decline of enzyme activity in spinal cord after transection or an intraspinal injection of colchicine. The half‐life was 2–3 days. Axonal transport of enzyme, estimated from the reappearance of activity in consecutive portions of spinal cord after treatment with p‐chlorophenylalanine, was of the order of 5–7 mm/day. This rate is characteristic of 'slow’axonal flow. Our results suggest that changes in the synthesis of new enzyme are probably not responsible for acute changes in the turnover of serotonin.
TRANSPORT AND TURNOVER OF DOPAMINE‐β‐HYDROXYLASE (EC 1.14.2.1) IN SYMPATHETIC NERVES OF THE RAT
Authors: Brimijoin S.
Published: October 2006

Axoplasmic transport of dopamine‐β‐hydroxylase (DBH), a marker enzyme for catecholamine storage vesicles, was studied in sympathetic nerves of the rat. At 24 h after ligation of the sciatic nerve, there was a marked accumulation of DBH activity in the first 3 mm proximal to the ligature. Immediately distal to the ligature, a slight accumulation took place. Accumulation proximal to the ligature was a linear function of time for at least 6 h; the velocity of transport was calculated as 4.6 mm/h. Local application of 1 ·l of 0.1 M colchicine, caused a rapid increase in DBH activity in superior cervical ganglia. This increase remained linear for 22 h and its rate indicated a turnover time of 12 h for DBH in these ganglia. After application of colchicine to the ganglia, there was a decrease in DBH activity in the submaxillary salivary glands. The initial rate of this decrease was less than the rate of increase in the ganglia and probably reflected the normal turnover of the enzyme. Our results indicated that the turnover time for DBH in salivary glands ranged between 3.6 and 6.3 days.
KINETICS OF THE SODIUM‐DEPENDENT TRANSPORT OF GAMMA‐AMINOBUTYRIC ACID BY SYNAPTOSOMES
Authors: Martin D. L.
Published: October 2006

The kinetics of transport of gamma‐aminobutyric acid [2,3‐3H] by synaptosomes from rat brain was studied by means of a rapid filtration technique. The rate of uptake was proportional to the protein concentration over the range 0.05—0.2 mg of synaptosomal protein per ml. Although apparent allosteric kinetics were observed with sodium, transport followed simple saturation kinetics with respect to GABA and no heterotropic, cooperative effects of GABA on sodium on kinetics were observed. A minimum of three interacting sodium sites is suggested the basis of Hill plots of the sodium data. Both the apparent Km and Vmax for GABA were functions of the sodium ion concentration but the effect of sodium was considerably greater on Vmax than on the apparent Km The Vmax for GABA was 1.1 ± 0.5 nmol.min−1 mg−1 of protein at 95 mm sodium and decreased to 12 per Cent of this value at 19 mm sodium. The apparent Km for GABA increased from 4.0 ± 1.0 μm at 95 mm sodium to 8.4 ± 2.0 μm at 19 mm sodium. Potassium was a noncompetitive inhibitor with respect to GABA and did not affect the apparent cooperativity observed with sodium. These findings are discussed in terms of models of GABA transport.
DIFFERENTIAL INCORPORATION OF LYSINE INTO RETINAL PROTEIN FRACTIONS FOLLOWING FIRST EXPOSURE TO LIGHT
Authors: Richardson K. , Rose S. P. R.
Published: October 2006

—Soluble and insoluble proteins from the retina of dark‐reared rats and from similar rats exposed to light for the first time, were subjected to electrophoresis on polyacrylamide gels. After injection of [3H] or [14C]lysine, using a double‐labelling technique, striking differences were observed in the pattern of incorporation into the forty‐one fractions investigated. After exposure for 1 h significant differences emerged in 13 of these fractions (High Differential Activity fractions) when compared with incorporation in control animals, a finding which persisted, irrespective of the order of labelling. Histochemical examination for acetylcholinesterase and glycoprotein material, showed the presence of these substances in some of the high differential activity fractions, and molecular weight determination was carried out on the insoluble fractions separated on SDS‐gels. It is concluded that the consistent enhancement of incorporation of precursor into retinal proteins which accompanies first exposure to light is a complex response involving a number of particular protein species, rather than a general elevation.
IN VIVO EFFECTS OF AMPHETAMINE ON METABOLITES AND METABOLIC RATE IN BRAIN
Authors: Nahorski S. R. , Rogers K. J.
Published: October 2006

—The concentrations of several metabolites, including glucose, glycogen, glucose‐6‐phosphate, lactate, ATP and phosphocreatine have been measured in the brains of mice rapidly frozen at various intervals after the intraperitoneal injection of d‐amphetamine sulphate (5 mg/kg). During the initial 30 min following injection, amphetamine induced a fall in cerebral glycogen and phosphocreatine and an elevation of lactate. Changes in glucose and brain/blood glucose ratios were less marked over this period. The metabolite levels returned to control values at 60 min. The cerebral metabolic rate calculated by the ‘closed system’ technique also showed a biphasic change. An initial depression of energy flux over the first 15 min following amphetamine injection was followed by an increase that appeared to be closely associated with the increase in locomotor activity over this period. The results have been discussed in relation to the known catecholamine‐releasing action of amphetamine, and differential effects on glial cells and neurons have been proposed.
SOME PROPERTIES OF A HOMOCARNOSINE‐CARNOSINE SYNTHETASE ISOLATED FROM RAT BRAIN1
Authors: Skaper S. D. , Das S. , Marshall F. D.
Published: October 2006

—An enzyme from rat brain catalysing the synthesis of the histidine‐containing dipeptides carnosine and homocarnosine (l.‐histidine: β‐alanine ligase (AMP) [EC 6.3.2.11]) was purified about 30‐40‐fold from a 100,000 g supernatant. Assays were conducted by measuring the incorporation of L‐[14C]histidine into carnosine and homocarnosine isolated by paper electrophoresis from the incubation mixture. The ratios of specific activities for the formation of carnosine and homocarnosine were not significantly different for the various purification steps. This was taken as evidence of one enzyme synthesizing both dipeptides. In studying the properties of this enzyme, a pH optimum of 7.4 was shown for carnosine synthesis. The concentrations of amino acid substrates giving maximal synthesis of both dipeptides were in the physiological range found for rat brain. An apparent requirement for ATP, Mg2+, and DPN was seen for dipeptide synthesis. A substrate dependent, enzymecatalysed 32PPi‐ATP exchange reaction was observed, suggesting the formation of an aminoacyl‐AMP intermediate. Certain other nucleoside triphosphates could substitute for the ATP; this effect showed a specificity toward the dipeptide being synthesized. The apparent requirement for DPN was quite specific, with a number of related compounds having no effect. The stoichiometry of enzyme‐catalysed carnosine synthesis was studied. A one to one relationship between carnosine formed and ATP hydrolysed was demonstrated. However, the ratio between carnosine synthesized and DPN hydrolysed was about 6 to 1, indicating a catalytic role for the DPN. The breakdown of DPN did not occur with enzyme alone but was dependent on the presence of substrate.
MYELINATION IN RAT BRAIN: METHOD OF MYELIN ISOLATION1
Authors: Norton W. T. , Poduslo Shirley E.
Published: October 2006

Abstract— A procedure is described for the preparation from rat brain of myelin having the same degree of purity at all ages. Such a procedure is essential for the study of myelin composition during development. Microsomal contamination was successfully eliminated by adjusting the method to maintain a constant amount of brain per unit volume in the initial density gradient step, and by including two osmotic shocks and two low‐speed centrifugation steps. Myelin prepared in this way from animals ranging from 15 days to 14months of age had a total ATPase activity of 0.3‐2.0 μmol of Pi.h−1.mg−1 dry wt of myelin, representing 0.1‐1.2 per cent recovery of the total homogenate activity; a Na+, K+‐ ATPase activity of 0.1‐1.6 μfnol of Pi.h−1.mg−1 dry wt, representing 0.04‐1.5 per cent recovery; a nucleic acid content of 0.2‐0.7 per cent of myelin dry wt, representing 0.2‐2.0 per cent recovery; and a ganglioside NANA content of 0.04‐0.07 per cent of myelin dry wt. representing 0.2‐4.6 per cent recovery. The myelin prepared from 20‐day animals had the highest content of the first three constituents; otherwise the values of the four constituents were relatively constant per unit weight of myelin. The amounts of nucleic acid and ganglioside recovered in the myelin fractions increased with increasing age and myelin yield.
MYELINATION IN RAT BRAIN: CHANGES IN MYELIN COMPOSITION DURING BRAIN MATURATION1
Authors: Norton W. T. , Poduslo Shirley E.
Published: October 2006

Abstract— Myelin was isolated from rat brains during development by a procedure giving fractions of constant purity at all ages. The lipid composition of these fractions and of whole brains of littermates was determined. The amount of myelin recovered per brain was a nearly linear function of the logarithm of age from the youngest (15 days) to the oldest (425 days) animals studied. With the exception of the earliest age point, the isolated myelin accounted for approximately 40 per cent of total brain galactolipid, evidence that a constant fraction (calculated to be 60 per cent) of myelin was recovered at all ages. Although the lipid‐protein ratio of the myelin was constant with age, marked changes were seen in the amounts of cerebroside, sulphatide, phosphatidylcholine and desmosterol. The total galactolipid increased from 21 per cent of the total lipid at age 15 days to about 31 per cent at maturity. Phosphatidylcholine decreased from 17 to 11 per cent during the same period. Desmosterol decreased from 2.5 per cent of the total sterol to 0.2‐0.3 per cent. All of these changes were complete between 2 and 5 months of age; no other ‘lower phase’ lipids showed significant changes with age. Although qualitatively similar to those reported by others, the changes differed in magnitude, with more stability in the levels of cholesterol and phosphatidalethanolamine with development. A sensitive indicator of the maturation of myelin was the mole ratio galactolipid/phosphatidylcholine, which varied from 1.2 at age 15 days to 2.8 at maturity. The maximum rate of myelination occurred at 20 days of postnatal age when myelin was deposited at the rate of 3.5 mg day−1 brain−1. However, at this age the rat brain had only 15 per cent of its eventual complement of myelin. The rate of accumulation of cerebroside in the whole brain paralleled that of myelin, and was the only lipid to show this relationship. Myelin deposition appeared to be almost solely responsible for the continued increase in brain weight after about 100 days of age.
PROTEINS IN THE DEGENERATIVE RETINA OF C3H MICE: DEFICIENCY OF A CYCLIC‐NUCLEOTIDE PHOSPHODIESTERASE AND OPSIN1
Authors: Farber D. B. , Lolley R. N.
Published: October 2006

Abstract— The protein patterns from retinae of mice with inherited blindness (C3H/HeJ) were compared with those from normal (DBA/1J) retinae during postnatal maturation. The number of protein bands, as determined by polyacrylamide gel electrophoresis in sodium dodecyl sulphate, increased in the normal retina with development and, by adulthood, 30 bands of protein were observed, with molecular weights ranging from 13,500 to 105,000 daltons. Four bands of retinal protein were suggested to be histones, and one was identified as tubulin. The patterns of protein bands from the immature C3H retinae were similar to those from the DBA retinae but, by adulthood, the pattern from the C3H retina was deficient in three bands of protein, two of which were identified as opsin and a cyclic‐nucleotide phosphodiesterase.
γ‐AMINOBUTYRIC ACID (GABA) IN THE RAT BRAIN: RE‐EVALUATION OF SAMPLING PROCEDURES AND THE POST‐MORTEM INCREASE1
Authors: Alderman J. L. , Shellenberger M. K.
Published: October 2006

—GABA levels determined after the brain was removed, then frozen, were found to be generally compatible to levels after the brain was frozen in situ provided 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 this time.
CTP SYNTHETASE ACTIVITY IN NEONATAL AND ADULT RAT BRAIN
Authors: Genchev D. D. , Mandel P.
Published: October 2006

—The activity of CTP synthetase (UTP:ammonia ligase (ADP‐forming), EC 6.3.4.2) in adult and new‐born rat brain was determined by an enzyme assay using [14C]UTP as a substrate. The activity was age‐dependent and showed a distinctive distribution pattern between the cerebral hemispheres and cerebellum. The possible correlations between the activity of CTP synthetase and the rate of RNA or lipid biosynthesis, as well as the regulatory importance of the enzyme in the formation of cytidine nucleotides are discussed.
CHOLINE ACETYLTRANSFERASE, ACETYLCHOLINESTERASE AND AROMATIC l‐AMINO ACID DECARBOXYLASE IN SINGLE IDENTIFIED NERVE CELL BODIES FROM SNAIL HELIX ASPERSA
Authors: Emson P. C. , Fonnum F.
Published: October 2006

—The distribution of choline acetyltransferase, aromatic l‐amino acid decarboxylase and acetylcholinesterase in the nervous system of Helix aspersa has been studied using homogenates of whole ganglia, microdissection from freeze‐dried sections and dissection of single neurons from fresh tissue. Choline acetyltransferase was found in both the cell body and neuropil layers of all the Helix ganglia. The enzyme was not specifically localized to any ganglion or region of ganglion. Between 10 and 30 per cent of the isolated single cell bodies contained the enzyme. The enzymic activity corresponded to 50–200 mmol ACh/1 cell bodies/h. Choline acetyltransferase is probably a specific marker for cholinergic cells in this species.

Aromatic l‐amino acid decarboxylase was more selectivity localized and its distribution corresponded well with that of monoamine containing cells as visualized by the fluorescence histochemical technique. A large proportion of cell bodies were localized in the boundary between the visceral and right parietal ganglia and in the pedal ganglion. The other ganglia contained few such cells. The activity of aromatic l‐amino acid decarboxylase corresponded 10–50 mmol dopamine/1 cell bodies/h. A method was developed to measure the enzyme activity towards 5‐hydroxytryptophan and DOPA in single cells simultaneously. The ratio between the activity towards both substrates did not vary significantly for the different cells. The enzyme is probably a specific marker for monoamine cells, but cannot be used to differentiate between the different monoamine cells.

Acetylcholinesterase was uniformly distributed in the ganglia and was probably present in all nerve cells.
MYELIN PROTEINS FROM DIFFERENT REGIONS OF THE CENTRAL NERVOUS SYSTEM
Authors: Lees Marjorie B. , Paxman Sally A.
Published: October 2006

—The protein composition of myelin prepared from specific anatomical regions of the bovine brain and spinal cord was studied by a modification of the method of Gonzalez‐Sastre (1970). Spinal cord myelin contained lesser amounts of chloroform‐methanol soluble protein and proteolipid protein and had a lower activity of the enzyme 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase than did myelin from subcortical white matter. There was no difference, however, in the protein composition of myelin from the various levels of the spinal cord. The amino acid composition of both proteolipid and basic protein showed no significant regional differences. Myelin preparations from both brain and spinal cord contained DM‐20 protein.
GP‐350, A SIALOGLYCOPROTEIN FROM CALF BRAIN: ITS SUBCELLULAR LOCALIZATION AND OCCURRENCE IN VARIOUS BRAIN AREAS
Authors: van Nieuw Amerongen A. , Roukema P. A.
Published: October 2006

Abstract— A membrane‐bound form of GP‐350, a sialoglycoprotein from calf brain has been shown to occur in the crude mitochondrial fraction (P2). After subfractionation on a discontinuous sucrose gradient, consisting of 0.8 and 1.2 m‐sucrose, GP‐350 was immunologically only detectable in the synaptosomal fraction. After further separation of the lysed synaptosomal fraction on a discontinuous sucrose gradient (0.4, 0.8 and 1.2m) GP‐350 could be detected only in the 0.8–1.2 m‐sucrose interface.

The membrane‐bound GP‐350 from the cerebellar grey matter was purified and analysed. The amino acid composition and the data obtained for galactose, galactosamine, glucosamine and sialic acid were quite similar to those of the soluble GP‐350, indicating their identity, which was sustained by immunodif‐fusion, immunoelectrophoresis and polyacrylamide gel electrophoresis.

The membrane‐bound GP‐350 was isolated from 15 different brain areas. Per g wet wt at least 60 μg (corpora quadrigemina inferior) and at most 470 μg (thalamus) of GP‐350 protein were obtained. Compared to the soluble GP‐350 protein 10–52 per cent could be isolated from the crude mitochondrial fraction. Our results on GP‐350 indicate an association with membranes of nerve endings.
CHANGES IN BRAIN ALCOHOL DEHYDROGENASE ACTIVITY DURING CHRONIC ETHANOL INGESTION AND WITHDRAWAL
Authors: Raskin N. H. , Sokoloff L.
Published: October 2006

Abstract— Chronic ethanol ingestion in rats leads to a slow rise in brain alcohol dehydrogenase activity which levels off after 2 weeks at approximately twice the initial activity. The half‐time of the rise is approximately 8 days. Abrupt withdrawal of the ethanol is followed by a rapid decline of the brain alcohol dehydrogenase activity to the normal level with a half‐time of approximately 15 h. The difference in time constants between the rise in enzyme activity during ethanol‐feeding and its decline following withdrawal suggests that the increased enzyme activity is at least in part the result of a reduced rate constant of enzyme degradation in the presence of ethanol. The effect of ethanol on brain alcohol dehydrogenase activity is not altered by supplementation of the diet with carbohydrate or vitamins. The effect is seen only in the cerebral hemispheres and not in the brain‐stem. Acquisition of tolerance to ethanol during chronic ethanol ingestion and its extinction following withdrawal follow almost the same time courses as the changes in brain alcohol dehydrogenase activity.
MEASUREMENT OF THE RATE OF GLUCOSE UTILIZATION BY RAT BRAIN IN VIVO
Authors: Hawkins R. A. , Miller A. L. , Cremer Jill E. , Veech R. L.
Published: October 2006

Abstract— A method is described by which the rate of glucose utilization by whole brain of conscious rats may be measured. The basis is the uptake of 14C derived front [2‐14C] glucose into the acid‐soluble metabolite pool of brain. Catheters are placed in the femoral artery and vein under light ether anesthesia. After full recovery of consciousness a single intravenous injection of [2‐14C] glucose is given and arterial blood samples taken at intervals. Simultaneous with the last sample the brain is removed and frozen within 1 s. The accumulation of 14C into the acid‐soluble metabilite pool is measured and the rate of glucose utilization is calculated according to the equation:

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The integral is calculated from the plasma glucose specific activity curve and evidence is presented to justify this procedure. The rate of glucose utilization measured by this method was 0·62 μmol/min per g in conscious rats and 0·28 μmol/min per g in sodium pentobarbital anesthetized rats.