bluuebunny/crossref_metadata_2025 huggingface dataset:
SOME PROPERTIES OF GUINEA PIG BRAIN GLUTAMATE DECARBOXYLASE AND ITS INHIBITION BY THE CONVULSANT ALLYLGLYCINE (2‐AMINO‐4‐PENTENOIC ACID)1
Authors: Fisher S. K. , Davies W. E.
Published: October 2006

—Glutamate decarboxylase (l‐glutamate 1‐carboxy‐lyase EC 4.1.1.15; GAD) has been isolated from guinea pig brain and some of its properties studied. Many of its properties indicated that it was similar if not identical to the decarboxylase isolated from other species. It showed normal Michaelis‐Menten kinetics (Km= 8 mM), had a pH optimum of 6.6–7.0 and was protected by sulphydryl reagents. Its activity was stimulated by pyridoxal phosphate and inhibited by a variety of anions, cations and carbonyl trapping agents. Allylglycine strongly inhibited GAD isolated from the brains of several different species. The mechanism of this inhibition has been studied kinetically and compared to chloride induced inhibition. The kinetic data presented is consistent with the idea that allylglycine inhibits the enzyme by a partially reversible inactivation rather than by reversible competitive inhibition.
RETROGRADE AXONAL TRANSPORT OF RAPIDLY MIGRATING PROTEINS IN THE VAGUS AND HYPOGLOSSAL NERVES OF THE RABBIT
Authors: Frizell M. , Sjöstrand J.
Published: October 2006

—The redistribution of rapidly migrating [3H]leucine‐labelled proteins was studied using double ligatures applied to the vagus nerve and single ligatures, applied to the hypoglossal nerves. Rapidly migrating proteins accumulating for 16 h proximal to a distal ligature of the cervical vagus redistributed to give a retrograde accumulation distal to a second ligature. Within 6 h a substantial redistribution occurred indicating a rapid retrograde transport. After 21 h there was a further accumulation with 70 per cent of the labelled material accumulating at the distal end of the isolated nerve segment and 16 per cent accumulating at the proximal end. It was shown that about a half of the retrograde accumulation was dependent on the distal accumulation zone. Rapidly migrating proteins accumulated distal to a ligature applied to the hypoglossal nerve 16 h after labelling of the nerve cell bodies indicating that a rapid retrograde transport of labelled macromolecules occurs from the peripheral parts of the nerve in the tongue. Labelled proteins accumulated proximal to ligatures and transections of both the hypoglossal and vagus nerve when applied 16 h after labelling of the nerve cell bodies, indicating the presence of axonal proteins, migrating at a rate of transport intermediate to that of rapidly and slowly migrating proteins.
ACTIVATION, INHIBITION AND AGGREGATION OF CHOLINE ACETYLTRANSFERASE (EC 2.3.1.6)
Authors: Chao L.‐P. , Wolfgram F.
Published: October 2006

—Mercuric chloride, silver acetate and cupric sulphate (0·1 mm) completely inhibited purified choline acetyltransferase from bovine caudate nuclei. At the same concentration cadmium chloride and zinc acetate gave a 50 per cent inhibition. Potassium and sodium salts more than doubled the enzymatic activity while creatinine hydrochloride more than tripled it. Guanidine hydrochloride was less effective than creatinine hydrochloride but more effective than KCl and NaCl. Sodium chloride and creatinine hydrochloride had a synergistic effect on the enzyme.

When ammonium sulphate was used to fractionate the choline acetyltransferase that had been extracted from bovine caudate nuclei, the enzyme aggregated into different molecular sizes as determined by exclusion chromatography on Bio‐gel A‐1·5 m. The molecular weight of the largest aggregate was at least 106 daltons. The initial tissue extract contained only one molecular species of ChAc as did a partially purified preparation in which ammonium sulphate was not used in the purification.
A STUDY OF SELECTED CATECHOLAMINE METABOLIZING ENZYMES: A COMPARISON OF DEPRESSIVE SUICIDES AND ALCOHOLIC SUICIDES WITH CONTROLS1
Authors: Grote S. S. , Moses S. G. , Robins E. , Hudgens R. W. , Croninger A. B.
Published: October 2006

—The regional distributions of monamine oxidase (MAO) (EC 1.4.3.4), catechol‐O‐methyltransferase (COMT) (EC 2.1.1.6), tyrosine hydroxylase (TH) (EC 1.14.3.2), and dopamine‐β‐hydroxylase (DBH) (EC 1.14.2.1) have been examined in human brains obtained at autopsy from persons who died of natural causes (controls), and from persons who committed suicide and were further categorized as suffering from affective disorder (depression) or from alcoholism. Post mortem animal studies showed no changes in MAO or COMT activities in rabbit brain or in DBH activity in rat brain when the intact bodies were left at room temperature up to 24 h. TH activity in rabbit brains, however, began to decline immediately after death and after 24 h at room temperature it was approximately 48 per cent of the fresh brain level. There was no significant variation in activity of COMT, TH and DBH in human brain attributable to age or sex. MAO activities in the 60–70 yr decade were 34 per cent higher than in the 30–40 yr decade. MAO activities were highest in the hypothalamus and substantia nigra, TH activities were highest in substantia nigra, putamen and head of caudate, and DBH activities were greatest in tegmentum of pons and hypothalamus. Only minimal regional differences in COMT activities were observed. No significant differences were found between enzyme activities in brain areas of controls and suicides with the possible exception of TH in the substantia nigra, where the depressive suicides (but not the alcoholics) showed greater activity (P < 0·02). These findings appear not to support the catecholamine hypothesis of affective disorder.
BIOSYNTHESIS OF THYROTROPIN RELEASING FACTOR BY NEWT (TRITURUS VIRIDESCENS) BRAIN IN VITRO. ISOLATION AND CHARACTERIZATION OF THYROTROPIN RELEASING FACTOR
Authors: Grimm‐Jørgensen Yvonne , McKelvy J. F.
Published: October 2006

Abstract— The in vitro biosynthesis of thyrotropin releasing factor (TRF) by hypothalamic and forebrain fragments from adult newts (Triturus viridescens) was studied by incubating the fragments in the presence of the radioactive amino acid precursors of thyrotropin releasing factor (TRF). The synthesized product was identified by successive chromatography and electrophoresis. A purification scheme was developed which can be applied to the processing of multiple samples labelled with l‐[3H]proline and yields a TRF peak which, when derivatized with 1‐fluoro‐2,4‐dinitrobenzene and applied to electrophoresis in acid buffer, yields a single radioactive peak corresponding to the migration of the Nim‐Dnp derivative made from standard synthetic [3H]TRF. Both forebrain and hypothalamic fragments of the adult newt are capable of synthesizing a product which migrates with standard TRF after application of this purification scheme. Hypothalamic and forebrain fragments were also assayed for biological activity of TRF and it was determined that one newt hypothalamus contains approximately 200 pg TRF and that an equal amount of TRF is present in a forebrain piece of comparable size. It is concluded that newt TRF is identical to mammalian TRF (pGlu‐His‐Pro‐NH2) and that the storage and synthesis of this substance is not confined to the hypothalamus in this species.
DEVELOPMENTAL CHARACTERISTICS OF PHENYLETHANOLAMINE AND OCTOPAMINE IN THE RAT BRAIN
Authors: Saavedra J. M. , Coyle J. T. , Axelrod J.
Published: October 2006

Abstract— Phenylethanolamine and octopamine have been detected in the developing rat brain. Maximum concentration of these amines occurs early in development (16‐17 days of gestation). At this developmental stage, the brain concentration of these amines is higher than that of norepinephrine. There is a sharp decline in the phenylethanolamine and octopamine concentrations on day 18 of gestation to approximately those of the adult. This decrease coincides with an increase in‐monoamine oxidase activity of fetal brain, with an increase in the activities of tyrosine hydroxylase and dopamine‐β‐hydroxylase, and with the appearance of a saturable active uptake mechanism for norepinephrine. The administration of iproniazid, a monoamine oxidase inhibitor, to pregnant rats produced an increase in phenylethanolamine, octopamine and norepinephrine concentrations in the fetal rat brain at 16 days of gestation. p‐Chlorophenylalanine, an inhibitor of phenylalanine hydroxylase, decreased fetal brain norepinephrine; this drug increased brain levels of phenylethanolamine and octopamine. The combined administration of iproniazid, p‐chlorophenylalanine and phenylalanine to pregnant rats resulted in increased concentrations of octopamine and in a several‐fold increase of phenylethanolamine levels; norepinephrine concentrations were sharply reduced. The possible significance of these findings in relation to pathological conditions such as phenylketonuria is discussed.
EFFECTS OF DIFFERENT LEVELS OF DIETARY PROTEIN ON BRAIN GLUTAMATE DEHYDROGENASE AND DECARBOXYLASE IN YOUNG ALBINO RATS
Authors: Rajalakshmi R. , Parameswaran M. , Ramakrishnan C. V.
Published: October 2006

Abstract— Studies were carried out to identify the minimum levels of protein (casein) needed in the diet in order to prevent or reverse the deficits in brain enzymes previously found with protein deficiency. Groups of weanling albino rats were fed diets containing variable amounts of protein (5, 8, 10, 15 or 20 per cent in experiment I, and 5, 6, 7, 8 or 20 per cent in experiment II) for 5 or 10 weeks. Deficits in brain wt and brain glutamate dehydrogenase and decarboxylase were found to be prevented by a diet containing 8 per cent or more of protein, although for optimum growth 15 per cent protein in the diet was found to be necessary. Groups of rats were fed a 5 or 20% protein diet for 10 weeks after which the 5% protein animals were either continued on the diet for another 10 weeks or changed to one containing 8, 10, 15 or 20% protein. The brain enzyme deficits found with the 5% protein diet were found to be fully reversed by feeding a 10% protein diet during rehabilitation.
TRACER KINETIC MODEL ANALYSIS OF POTASSIUM UPTAKE BY DISSOCIATED NERVE CELL CULTURES: GLIAL‐NEURONAL INTERRELATIONSHIP
Authors: Latzkovits L. , Sensenbrenner M. , Mandel P.
Published: October 2006

Abstract— Potassium transport in dissociated nerve cell cultures has been studied by analysing 86Rb and 42K uptake. For this purpose cultures prepared from cerebral hemispheres of both 8‐ and 14‐day‐old chick embryos were used in short‐term experiments. The potassium pool is in the steady‐state in all the cultures. The 86Rb is taken up more rapidly that 42K; however the ratio of amounts of 86Rb and 42K incorporated is constant with time and under different conditions. The run of kinetic curves of uptake has been studied by tracer kinetic model analysis. As a result of this analysis a glial‐neuronal interrelationship in transport has been suggested. Furthermore, it was shown that not only glial cells but neurons also take up potassium directly from the medium. Comparing the incorporated amounts in different cultures, a decreased uptake can be seen where glial cells prevail. The significance of this fact is discussed.
ENZYMATIC SULPHATION OF SOME GALACTOSE‐CONTAINING SPHINGOLIPIDS IN DEVELOPING RAT BRAIN1
Authors: Farrell D. F.
Published: October 2006

Abstract— Cerebroside sulphotransferase has been found to catalyze the transfer of sulphate from 3′‐phosphoadenosine‐5′‐phosphosulfate (PAPS) to both the α‐hydroxy fatty acid galactosylceramides and the nonhydroxy fatty acid galactosylceramides. The sulphotransferase has a higher affinity for the α‐hydroxy fatty acid galactosylceramides than for the nonhydroxy fatty acid galactosylceramides and will also use lactosylceramide as an acceptor for the transfer of sulphate from PAPS.

A second sulphotransferase, PAPS: psychosine sulphotransferase, is also present in the developing rat brain and will catalyse the transfer of sulphate from PAPS to galactosylsphingosine and lactosylsphingosine. The sulphate moiety was determined to be on the galactose and most likely on the 3′ position giving a proposed structure of: 3‐O‐SO4‐galactosylsphingosine. The possible role of this later pathway in the synthesis of sulphogaiactosylceramide remains to be elucidated.
SPINAL SUBARACHNOID PERFUSION IN THE RAT: GLYCINE TRANSPORT FROM SPINAL FLUID1
Authors: Dudzinski D. S. , Cutler R. W. P.
Published: October 2006

Abstract— A method was developed for perfusion of the spinal subarachnoid space in the rat. Bidirectional steady‐state fluxes of [14C]glycine between spinal fluid and plasma were measured. [14C]glycine clearance from spinal fluid was 5‐fold greater than its clearance from plasma. Glycine was transported out of spinal fluid by a saturable process, and the rate of transport was unaffected by the other depressant amino acids, GABA, β‐alanine, and taurine. Perfused [14C]glycine and [3H]GABA distributed in an intracellular compartment in spinal cord. The preparation should be useful for study of the release of these inhibitory amino acids from the intact spinal cord.
ACID HYDROLASES AND OTHER ENZYMES IN SECONDARY DEMYELINATION: A QUANTITATIVE HISTOCHEMICAL STUDY IN THE WOBBLER MOUSE1
Authors: Hirsch Hilde E. , Andrews J. M. , Parks Mary Ellen
Published: October 2006

Abstract— The hereditary motor neuron degeneration found in the wobbler (wr) mouse was studied as a model of secondary demyelination. Lysosomal enzymes (acid phosphatase, acid proteinase, β‐glucuronidase and β‐galactosidase) were found elevated about three‐fold in the white matter of the affected cervical spinal cord as compared with normal controls; but they were either not increased, or increased much less, in the anterior horn. Since gliosis and influx of phagocytic cells are minimal in this model, the high hydrolase levels are believed to arise primarily from (a) the accumulations of axonal dense bodies seen in involved areas, and (b) from indigenous cells engaged in breaking down the myelin fragments. Thus, secondary demyelination may, at least in this case, be initiated by enzymes of local origin.

DNA levels per unit weight of tissue in both white and gray matter of wobbler cervical cord were elevated 40‐50 per cent over controls. However, this was considered to reflect the stunted growth of wobbler mice rather than proliferation or influx of cells (an altered ratio of DNA to protein was demonstrated in the brain).

Wobbler mice had similar levels of lactic dehydrogenase as controls; glucose‐6‐phosphate dehydrogenase was moderately elevated, and glycerol‐3‐phosphate dehydrogenase was less active in the anterior horn but more active in the white matter of the spinal cord.
UBIQUINONE REDOX STATUS IN BRAIN IN VITRO
Authors: Klicpera J. A. , Hoffmann P. C.
Published: October 2006

—The redox status of ubiquinone (Q) as an index of mitochondrial respiratory chain activity in chopped telencephalon from the rat was investigated. With 12mm‐glucose under aerobic conditions Q was 73% oxidized. Three mm‐amytal and 2 μm‐rotenone, inhibitors of mitochondrial NADH oxidation, resulted in Q being further oxidized by 14 and 16%, respectively. Thus, amytal and rotenone result in shifts in Q redox status of rat telencephalon slices in accord with the known site of action of these compounds in isolated mitochondria. However, under anaerobic conditions Q redox status shifted to 25% oxidized while incubation with 1 mm‐NaCN resulted in a shift to only 58% oxidized. This discrepancy may result from concomitant inhibition in the supply of reducing equivalents to Q from substrate by NaCN or it may reflect a differential sensitivity of neuronal and glial mitochondria to NaCN. Evaluation of Q oxidation‐reduction can be used to measure the effects of drugs and physiological perturbations on the redox status of the mitochondrial compartment of intact brain preparations.
A ROLE FOR DIVALENT CATIONS IN THE UPTAKE OF NORADRENALINE BY SYNAPTOSOMES
Authors: White T. D.
Published: October 2006

–The effects of divalent cations on the initial rates of noradrenaline uptake by synaptosomes were determined using Millipore filtration to terminate the reaction. The removal of either Ca2+ or Mg2+ from the incubation medium had no effect on uptake, but when both Ca2+ and Mg2+ were removed, uptake was reduced. Uptake was also diminished when Ca2+ was absent and 1 mm‐EGTA added to the medium. It appeared that Ca2+ was required for optimal uptake but that Mg2+ could partially substitute for Ca2+ in this regard. The reduction in the rate of uptake when both Ca2+0 and Mg2+ were absent could be rapidly and completely reversed by restoring Ca2+, Mg2+, or both Ca2+ and Mg2+ to the incubation medium. Of the divalent cations tested, Ca2+ and Mg2+, but not Mn2+, supported noradrenaline uptake. When the kinetics of uptake were examined, it was found that removing both Ca2+ and Mg2+ from the medium resulted in a reduction of the Vmax for noradrenaline uptake. It is apparent from these results that, in addition to facilitating the release of noradrenaline from noradrenergic terminals, Ca2+ may also play a role in the uptake of noradrenaline by presynaptic nerve‐endings in the CNS.
CYCLIC ADENOSINE 3′,5′‐MONOPHOSPHATE IN GUINEA‐PIG CEREBRAL CORTICAL SLICES: STUDIES ON THE ROLE OF ADENOSINE
Authors: Schultz J.
Published: October 2006

Abstract— In guinea‐pig cerebral cortical slices levels of cyclic AMP increase in response to adenosine to about 200pmol/mg protein within 10 min and stay at that level up to 30 min. In the absence of calcium ions and the presence of 1mm‐EGTA in the Krebs‐Ringer‐bicarbonate medium the effect of adenosine is enhanced, cyclic AMP levels rise to about 600 pmol/mg protein within 30 min. In normal and calcium deficient media restimulation of cyclic AMP formation with adenosine is possible after a prior stimulation with adenosine. When slices are preincubated for various periods of time with histamine or adenosine before addition of the complementary agent i.e. adenosine or histamine cyclic AMP levels obtained are unaltered compared to levels seen when adenosine and histamine are added together. Slices which are rendered unresponsive to stimulation with histamine + noradrenaline by a prior incubation with these agents do not regain any response during a 100 min period of incubation in medium. The PDE inhibitors diazepam, SQ 66007 and isobutylmethylxanthine are capable of restoring the sensitivity of the slices to histamine + noradrenaline. This suggests an involvement of PDE in the unresponsive phase of the slices. Addition of adenosine to slices not affected by histamine + noradrenaline does reestablish the response of these slices to the neurohormones. A dose‐response curve of adenosine for the interaction with histamine + noradrenaline yields an ED50 of 16 μM using sensitive or desensitized slices. An adenosine concentration of only 7 μM is necessary to restore the original increase of cyclic AMP in response to histamine + noradrenaline to slices insensitive to the biogenic amines. The data are discussed in terms of a possible activation of PDE within cerebral cortical slices from guinea‐pig. Adenosine may reverse this activation. The possibility of inactivation of adenylate cyclase during stimulation of cyclic AMP formation and the role of adenosine and PDE inhibitors in this process is being considered.
RELEASE AND EXCHANGE STUDIES RELATING TO THE SYNAPTOSOMAL UPTAKE OF GABA
Authors: Raiteri M. , Federico R. , Coletti A. , Levi G.
Published: October 2006

Abstract— Synaptosomal release and exchange of [3H]GABA were studied by a superfusion technique which minimizes reuptake. The release of [3H]GABA was increased by depolarizing concentrations of KCl and showed calcium‐dependence. Superfusion with 1‐1000 μm unlabelled GABA caused a dose dependent, saturable increase in the release of radioactivity by homoexchange. The exchange process showed high substrate specificity: among the various amino acids and putative neurotransmitters tested, only γ‐amino‐β‐hydroxybutyric acid was a good stimulator of [3H]GABA release. Superfusion with sodium‐free medium (NaCl replaced by sucrose) virtually abolished homoexchange. Ouabain also increased the release of [3H]GABA, and its action was additive to that of unlabelled GABA.

The presence of exchange at concentrations that are in the range of the high affinity uptake system, the apparent similarity between calculated rates of exchange and initial uptake rates, the non‐detectability of exchange in a condition (Na+ deprivation) which inhibits high affinity uptake, and the lack of decrease of actual GABA concentration in incubation media used for uptake experiments, all suggest that homoexchange accounts for a substantial part of the synaptosomal accumulation of [3H]GABA generally interpreted as high affinity uptake.
DEVELOPMENTAL CHANGES IN THE KINETICS OF γ‐AMINOBUTYRIC ACID TRANSPORT BY CHICK RETINA
Authors: Tunnicliff G. , Firneisz G. , Ngo T. T. , Martin R. O.
Published: October 2006

—Isolated retinas from chick embryos and mature animals were incubated in [3H]GABA at 25°C for 10 min in order to investigate kinetic properties of the amino acid uptake system. Embryo retina accumulated [3H]GABA by two distinct kinetic systems with Km values of the order 10−4m and 10−5m for the low‐ and high‐affinity mechanisms respectively. However, as the retina matured, the high‐affinity process disappeared and only the low‐affinity system was detectable. No obvious explanation can be offered for this phenomenon although a similar observation has previously been made in chick brain by other workers.
DISTRIBUTION OF CHOLINE ACETYLTRANSFERASE AND GLUTAMATE DECARBOXYLASE WITHIN THE SUBSTANTIA NIGRA AND IN OTHER BRAIN REGIONS FROM CONTROL AND PARKINSONIAN PATIENTS
Authors: Lloyd K. G. , Möhler H. , Heitz Ph. , Bartholini G.
Published: October 2006

—The distribution of choline acetyltransferase (ChAc, EC 2.3.1.6) and l‐glutamate 1‐carboxylyase (glutamate decarboxylase, GAD, EC 4.1.1.15) was studied in serial frontal slices of the substantia nigra (SN) (pars compacta, PC; pars reticulata, PR; an intermediate region, IR) as well as in other brain areas from post mortem tissue of control and Parkinsonian patients.

Within the SN from control brain ChAc and GAD activities showed a distinctive distribution: ChAc activity in PC was higher than in PR and IR by 427% and 253% respectively and within PC the enzyme activity in the rostral part exceeded that in the control part by 353%. The GAD activity in PC was higher by 41% than that in PR and within PC seemed to be higher in the caudal than in the rostral part. For both enzyme activities there were no significant differences between PR and IR or within these regions.

In Parkinsonian brain both ChAc and GAD activities were reduced to 15‐25% of controls in all 3 regions of the SN. The distinctive distribution of ChAc and GAD activity found in the SN of control brain was abolished: no difference was observed between the 3 regions. However, within PC the ChAc activity was lower in the medial than in the rostral part.

Since nigral ChAc is possibly located in interneurons, the decrease in enzyme activity may be connected with the cell loss observed in the SN of Parkinsonian brain.

By contrast, nigral GAD is probably contained in terminals of strio‐nigral neurons and the decrease in enzyme activity in Parkinson's disease in the absence of striatal cell loss, may reflect a change in the functional state of these GABA neurons.

Among various areas of control brains ChAc activity was highest in caudate nucleus and putamen while GAD was highest in SN. caudate nucleus, putamen and cerebral cortex. In Parkinsonian brain the most severe reduction in ChAc and GAD activities was found in the SN.
EFFECTS OF INGESTION OF A CARBOHYDRATE‐FAT MEAL ON THE LEVELS AND SYNTHESIS OF 5‐HYDROXYINDOLES IN VARIOUS REGIONS OF THE RAT CENTRAL NERVOUS SYSTEM
Authors: Colmenares J. L. , Wurtman R. J. , Fernstrom J. D.
Published: October 2006

—The concentrations of tryptophan, serotonin (5‐HT), and 5‐hydroxyindoleacetic acid (5‐HIAA) in spinal cord and most brain regions increase 2 h after fasted rats begin to consume a carbohydrate‐fat meal: indole levels rise in all portions of the brain studied, but the increase is not statistically significant in the hypothalamus and corpus striatum. The rate at which the brain synthesizes 5‐hydroxy‐indoles (as estimated in vivo by measuring 5‐hydroxytryptophan accumulation following an injection of the decarboxylase inhibitor RO4‐4602) is also accelerated in all of the regions in which the experimental diet elevates tryptophan, 5‐HT and 5‐HIAA levels. These observations indicate that the previously reported increase in brain 5‐hydroxyindole levels following consumption of a protein‐free meal reflects accelerated serotonin synthesis, and occurs within both the cell bodies and the terminals of serotonin‐containing neurons. It is possible that diet‐induced changes in neuronal serotonin levels influence the quantities of the neurotransmitter released into synapses, either spontaneously or in response to drugs.
BIOSYNTHESIS OF LONG CHAIN FATTY ACIDS BY OLIGODENDROGLIA ISOLATED FROM BOVINE WHITE MATTER1
Authors: Fewster Mona E. , Ihrig T. , Mead J. F.
Published: October 2006

Abstract— Radioactively labelled fatty acids were incubated with interfascicular oligodendroglial preparations isolated from 9 month fetal and adult bovine CNS white matter to study their metabolism by these cells. Of the various acids studied, the uptake was greatest for palmitic acid and decreased with decreasing chain length. Laurie acid was converted to the greatest extent to other fatty acids. The incorporation of oleic and linoleic acids in the oligodendroglia from both the fetal and adult brains was higher than that of linolenic acid. Fatty acids underwent chain elongation, desaturation and oxidation. Oleic acid was elongated to nervonic acid. Fatty acids were incorporated into both cerebrosides and phospholipids, with preferential incorporation into ethanolamine phosphoglyceride.
GANGLIOSIDES IN DEVELOPING MOUSE BRAIN MYELIN
Authors: Yu R. K. , Yen S. I.
Published: October 2006

Abstract— Gangliosides were isolated from myelin prepared from mouse brains of different ages (23 to 490 days). Quantitative estimation of lipid‐bound sialic acid levels indicated a gradual increase from 560 μg/g of myelin at 23 days to about 1200 μg/g of myelin at older ages. The major ganglioside in all myelin preparations was the monosialoganglioside G4 (GM1). However, considerable amounts of di‐ and trisialo species also were found in myelin from young animals. In contrast to human myelin in which the monosialoganglioside, sialosylgalactosylceramide (G7) was highly enriched (Ledeenet al., 1973), a much smaller enrichment of this ganglioside was noticed in mouse brain myelin. Ganglioside G7 was not detectable in myelin until the animals were 35 days old, and showed a slight increase with increasing age after that. The results strongly indicated that the concentration of G7 in myelin is species specific and age dependent. The study also demonstrated that the ganglioside accretion in developing mouse brain myelin was attributable to the enrichment of monosialogangliosides G4 (GM1), G5 (GM2) and G7 at the expense of polysialogangliosides.
QUANTITATIVE HISTOCHEMISTRY OF γ‐AMINOBUTYRIC ACID IN CAT SPINAL CORD WITH SPECIAL REFERENCE TO PRESYNAPTIC INHIBITION
Authors: Miyata Y. , Otsuka M.
Published: October 2006

Abstract— A method is described for quantifying the GABA distribution in cat spinal cord at 200–500 μn resolution. Isolated spinal cord (L5–S1) was frozen and sectioned at about 150 μm thickness. The frozen tissue section was cut into 200 or 500 μm square blocks. The GABA content of each square tissue block was determined by enzymic micromethods and GABA distribution was mapped quantitatively. Average GABA concentrations were: 0·4 mmol/l. in white matter, 1·2 mmol/l. in ventral horn and 1·7 mmol/l. in dorsal horn. The highest concentrations of GABA (2–3 mmol/l.) were found in the dorsolateral part of dorsal horn. In order to destroy the interneurons of dorsal horn, the blood vessels supplying the dorsal horn of the lumbar enlargement were unilaterally cauterized. Seven to 30 days after operation, both the size of dorsal root potential and the GABA level in the dorsal horn were markedly reduced on the cauterized side. These results suggest that GABA is highly concentrated in the interneurons of dorsal horn and functions as a transmitter of presynaptic inhibition.
BRAIN UPTAKE AND PROTEIN INCORPORATION OF AMINO ACIDS STUDIED IN RATS SUBJECTED TO PROLONGED HYPERPHENYLALANINAEMIA
Authors: Antonas K. N. , Coulson W. F.
Published: October 2006

Abstract— The uptake into brain and the incorporation into brain protein of intraperitoncally administered, labelled amino acids has been studied in myelinating rats during prolonged hyperphenylalaninaemia maintained by administration of p‐chlorophenylalanine. Compared with controls, there was a 50% reduction in both uptake and incorporation into protein of leucine and a parallel reduction in the acid‐soluble leucine pool. With glycine and lysine no such changes were observed. On the other hand, when each of the three amino acids was injected directly into the brain, the only significant differences observed between controls and hyperphenylalaninaemic animals were again with leucine, which showed an increased incorporation into protein and an increased specific activity in the otherwise reduced acid‐soluble pool.

It is concluded that hyperphenylalaninaemia reduces the rate of transport of leucine into the brain and hence reduces the brain pool of leucine, but that any effects on protein synthesis are small. The validity of the model, and the implications of the findings, in relation to phenylketonuria, are discussed.
AN EXAMINATION OF THE CATALYTIC PROPERTIES OF SEVERAL AMINOTRANSFERASES IN BRAIN AND LIVER BY MEANS OF AN IMPROVED RADIOMETRIC ASSAY WITH DINITROPHENYLHYDRAZINE
Authors: Lees G. J. , Weiner N.
Published: October 2006

Abstract— The assay of aminotransferases, performed by solvent extraction of keto acids formed from labelled amino acids, has been modified to enhance the recovery of both aliphatic and aromatic keto acid products. The keto acids are first converted to their respective dinitrophenylhydrazones which are more completely extracted into less polar organic solvents. By this manoeuvre, both keto acid extraction is increased and the extraction of the precursor amino acid is reduced. Employing this technique, the kinetics of brain‐stem γ‐aminobutyric acid (GABA), tryptophan, 3,4‐dihydroxyphenylalanine (DOPA) aminotransferases and brain‐stem and liver tyrosine aminotransferases were examined. Brain‐stem aminotransferases, particularly the aromatic amino acid transferases, have a higher affinity for both the amino acid and the keto acid when the aromatic keto acid, phenylpyruvate (0·8 mM), is employed as amino group acceptor, whereas maximal velocities for aminotransferase reactions are much greater when α‐ketoglutarate (0·8 mm) is the amino group acceptor. Brain‐stem tyrosine aminotransferase exhibits a much lower affinity for tyrosine in the presence of either 0·8mm‐α‐ketoglutarate or 0·8 mm‐phenylpyruvate than does liver tyrosine aminotransferase. p‐Chlorophenylpyruvate and phenylpyruvate exhibit similar properties as amino group acceptors for brain‐stem tryptophan aminotransferase. Cysteine inhibits tryptophan aminotransferase when phenylpyruvate is the amino group acceptor, in a manner which is competitive with the amino acid. Benzoylformate inhibits both tryptophan and DOPA aminotransferases when phenylpyruvate is the amino group acceptor, but this inhibition does not appear to be competitive with phenylpyruvate.
THE UPTAKE OF SPERMIDINE AND SPERMINE BY SLICES OF MOUSE CEREBRAL HEMISPHERES
Authors: Pateman A. J. , Shaw G. G.
Published: October 2006

Abstract— Spermidine and spermine are taken up into mouse cerebral hemisphere slices by active transport and can be accumulated well above the medium concentration. The uptake process shows saturation kinetics and resembles that for amino acid uptake in that it is sensitive to temperature and inhibited by cyanide, 2,4‐dinitrophenol or by the absence of glucose from the medium. However, at low initial medium concentrations spermine is taken up by a process which is insensitive to metabolic inhibitors or to temperature. It is suggested that either physical binding to a cellular constituent or exchange transport may account for this uptake. Ouabain does not inhibit polyamine uptake. Spermidine or spermine uptake is inhibited by cadaverine and putrescine. Spermine is the most potent inhibitor of spermidine uptake and vice‐versa. Polyamine uptake differs from that of amino acids in that it is increased by a reduction in medium sodium or calcium content and decreased by an increase in medium potassium content. Recently taken up spermine undergoes heteroexchange with spermidine and homoexchange with recently entered spermine. Spermidine undergoes neither heteroexchange with spermine nor homoexchange.
REGIONAL AND SUBCELLULAR DISTRIBUTION AND KINETIC PROPERTIES OF RAT BRAIN CHOLINE ACETYLTRANSFERASE–SOME FUNCTIONAL CONSIDERATIONS
Authors: Kuczenski R. , Segal D. S. , Mandell A. J.
Published: October 2006

Abstract—

The kinetic properties of soluble and membrane‐bound choline acetyltransferase (ChAc) were determined as a function of homogenization media and solubilization procedure in various regions of rat brain. Treatment of homogenate and/or subcellular fractions with KCl, Triton X‐100, or ether dramatically altered the apparent Vmax and the degree of solubilization of the enzyme, but no fraction exhibited Km values substantially different from 12 μM for acetyl‐CoA and 200 μM for choline. On the other hand, increasing the ionic strength of the assay medium for a given fraction from 0‐02 M to 0‐5 M increased both Vmax and Km values for both substrates. The absolute levels and subcellular distribution of ChAc were determined in 11 brain regions to localize cholinergic cell bodies and nerve endings. Levels of ChAc varied from 139 m‐units/g tissue in caudate‐putamen to 5‐7 m‐units/g tissue in cerebellum. The fraction of ChAc activity associated with synaptosomes varied from near 75 per cent in caudate‐putamen, hippocampus and cortical regions to near 20 per cent in septum, locus coeruleus area and substantia nigra area. The apparent parallel distribution of cholinergic and catecholaminergic nerve endings is discussed in terms of a hypothetical model for the pathophysiology and treatment of Parkinson's syndrome.
MOBILIZATION OF SYNAPTIC MEMBRANE‐BOUND CALCIUM BY ACIDIC AMINO ACIDS1
Authors: Tan A. T.
Published: October 2006

Abstract—

A fluorescent chelate probe (chlorotetracycline) and radioactive 45Ca were used to study the effects of amino acids on the calcium bound to external synaptosomal membranes isolated from guineapig brain. Acidic amino acids released some of the membrane‐bound calcium. On the basis of 45Ca studies, the order of mobilization potency‐DL‐homocysteic acid and l‐cysteic acid > l‐aspartic acid, l‐glutamic acid, d‐glutamic acid > N‐methyl‐dl‐glutamic acid and dl‐cyteic acid‐is in general agreement with that found by fluorescent chelate method with the exception of N‐methyl‐dl‐aspartic acid and N‐methyl‐dl‐glutamic acid, which are at least as potent as dl‐homocysteic acid. This order of potency is observed only with a fraction enriched in external synaptosomal membranes, but not with microsomes, myelin and mitochondria. Neutral and basic amino acids, including glutamine. glycine and γ‐aminobutyric acid are ineffective. These results suggest that acidic amino acids have a specific ability to mobilize membranebound calcium; this is consistent with the proposed role of some of these compounds as excitatory transmitters in the central nervous system.
ALTERATIONS IN BRAIN RNA METABOLISM FOLLOWING CHRONIC ETHANOL INGESTION
Authors: Tewari S. , Fleming E. W. , Noble E. P.
Published: October 2006

Abstract—

The in vivo labelling of various brain RNA fractions was found to be altered due to chronic ethanol ingestion by C57BL/6J mice. Ingestion of ethanol resulted in a marked decrease in the incorporation of intraventricularly injected [5‐3H] orotic acid into tRNA, rRNA and polyribosomal RNA. The inhibition was more pronounced in the polyribosomal fraction than the ribosomal fraction. In the nucleus, a biphasic effect of ethanol was demonstrated in the nRNA fraction where increased incorporation of precursor label at early time points was followed by marked depression. Absence of a similar increase in the cytoplasmic RNA fractions is suggestive of a possible defect in the transport of RNA from nucleus to cytoplasm resulting in the accumulation of RNA in the nucleus. Ethanol ingestion had no effect on the synthesis of acid soluble nucleotides following the in vivo administration of [5‐3H]orotic acid or [5‐3H]uridine into the brain. Over 90 per cent of the radioactivity in either ‘control’ or ‘ethanol’ brain could be recovered in the UMP fraction with negligible conversion to GMP, AMP or CMP. The results suggest that the observed changes in RNA metabolism following chronic ethanol ingestion are due to an alteration in the transcription and/or the processing of RNA in the nucleus rather than a function of reduced availability of nucleotides.
A METHOD FOR THE ISOLATION AND ESTIMATION OF GABA, GLUTAMATE AND GLUTAMINE FROM COMPLEX MIXTURES BY A COMBINATION OF ENZYMIC INTERCONVERSION AND FORMATION OF 1‐DIMETHYLAMINONAPHTHALENE‐5‐SULPHONYLBUTYROLACTAM
Authors: Strang R. H. C.
Published: October 2006

Abstract— A method is presented which allows the isolation and estimation of GABA, glutamate and glutamine in extracts of nervous tissue. It depends on the enzymic conversion of the last two compounds to GABA, before isolating the GABA as DNS‐γ‐butyrolactam. The low polarity of this compound makes this possible without the use of chromatography. Furthermore, the specific radioactivities of these 3 compounds in a complex mixture may be found without elaborate separation procedures. Details are given of optimum reaction conditions, and comparisons made with other methods of estimation of these amino acids.
THE EFFECTS OF HYPERKETONEMIA ON GLUTAMATE AND GLUTAMINE METABOLISM IN DEVELOPING RAT BRAIN
Authors: Ozand P. T. , Stevenson J. H. , Tildon J. T. , Cornblath M.
Published: October 2006

Abstract— The effect of increased exposure to ketone bodies in the developing rat brain suggest that intrauterine and postnatal hyperketonemia lead to an altered metabolism of glutamine and glutamate. It is postulated that this effect is related to the delayed development of glutaminase (l‐glutamine amido‐hydrolase EC 3.5.1.2) and glutamate dehydrogenase (l‐glutamate: NAD oxidoreductase EC 1.4.1.2).

The specific activities of glutamate dehydrogenase (GDH), glutaminase and glutamine synthetase (l‐glutamate: ammonia ligase EC 6.3.1.2) in the brains of newborn rats increased during early development. A positive correlation was observed between the specific activity of glutaminase and the concentration of glutamate in the brain as well as between the concentrations of blood and brain glutamine and glutamate in both control and hyperketonemic pups. This indicates a different degree of permeability and metabolism for glutamine and glutamate in the brain during the neonatal period, as compared to adulthood.

In hyperketonemic pups, glutamine and glutamate metabolism were found to differ from that in control animals. The concentrations of glutamate were higher, and glutamine lower, in both the blood and brain as compared to that in controls. The concentrations of α‐ketoglutarate were also lower in their brain. In the brains of hyperketonemic and control pups, the concentration of malate was the same. During the first 3 weeks of life the increase of spec. act. of GDH and glutaminase was found to be suppressed in the brains of hyperketonemic pups. However, the spec. act. of glutamine synthetase was similar to that of the control pups.
METABOLISM OF BIOGENIC AMINES IN NEUROBLASTOMA AND GLIOMA CELLS IN CULTURE1
Authors: Skaper S. D. , Adelson G. L. , Seegmiller J. E.
Published: October 2006

Abstract—

The kinetic parameters of monoamine oxidase (MAO; E.C 1.4.3.4) and catechol‐O‐methyl‐transferase (COMT; EC 2.1.1.6) were evaluated in extracts of adrenergic and non‐adrenergic mouse neuroblastoma cells and in rat glioma cells. Using the naturally‐occurring substrates tyramine, tryptamine, serotonin and norepinephrine, the affinity of MAO for a given substrate was independent of the presence of the catecholaminergic pathway or cell type used, with apparent Km values ranging from 8–14 μM for tryptamine to 510–580 μM for norepinephrine. The MAO activity in glioma cells was substantially greater than in either neuroblastoma clone, but Vmax values varied little with substrate among cell lines. Both the neuronal and glial COMT had a similar Km for I‐norepinephrine (200μM); the corresponding Vmax values were also similar among the different cell lines, but represented only 2–10% of the maximal MAO activity. Neuroblastoma and glioma cells, when grown from early logarithmic to stationary phase, showed no significant changes in specific activity of either MAO or COMT. Growth of cells for 3 days with 1 mM‐N6,O2′ ‐dibutyryl adenosine‐3′,5′‐cyclic monophosphate resulted in no marked change in either MAO or COMT activity.

These results suggest that in neurons neither MAO nor COMT plays a major role in the type of transmitter inactivation that is analogous to that of acetylcholinesterase in cholinergic synapses. The occurrence of considerable MAO and acetylcholinesterase activities in glioma cells may indicate a role for these cells in neurotransmitter inactivation.
MOUSE BRAIN PROTEIN COMPOSITION DURING POSTNATAL DEVELOPMENT: AN ELECTROPHORETIC ANALYSIS
Authors: Kelly P. T. , Luttges M. W.
Published: October 2006

Abstract—

Changes in the concentrations of mouse brain proteins during postnatal maturation were characterized by a combination of subcellular fractionation and electrophoresis. Sodium dodecyl sulfate gel electrophoresis revealed changing protein concentrations in fractions enriched in nuclei, mitochondria plus synaptic endings, microsomes and cytosol. Postnatal maturational changes in protein concentrations were most pronounced in fractions of purified myelin membranes. The use of exponential gradient gels resulted in increased resolution of low molecular weight myelin proteins. Nuclei treated with Triton X‐100 exhibited no change in relative histone concentrations during brain maturation. Nonnuclear contamination of untreated nuclear fractions was shown to be a potential source of erroneous interpretations. These findings are discussed in terms of genetic products and sodium dodecyl sulfate polyacrylamide gel electrophoresis resolution.
INHIBITION OF GLUCOSE UTILIZATION FOR ACETYLCHOLINE SYNTHESIS BY CEREBROSPINAL FLUID1
Authors: Thomas L. L. , Radulovački M. , Schulman M. P.
Published: October 2006

Abstract— Replacement of bicarbonate‐Locke incubation medium with feline CSF reduced [14C]ACh formation from [U‐14C]glucose by rat brain mince approx 30%. CSF was obtained from a cannula leading to the cisterna magna of freely moving cats. The component of CSF responsible for inhibition was characterized as a dialyzable heat‐stable organic anion. Choline acetyltransferase activity was not altered by CSF. [14C]ACh synthesis and 14CO2 production from [U‐14C]glucose but not from [2‐14C]‐pyruvate were inhibited by CSF, suggesting inhibition in the metabolism of glucose to pyruvate. The anionic fraction of human CSF was as potent as that from feline CSF in inhibiting 14CO2 production from [U‐14C]glucose. Brain hexokinase was inhibited by the anionic fraction of feline CSF. The inhibition was non‐competitive with respect to glucose and uncompetitive with respect to ATP. It is suggested that inhibition of hexokinase by CSF was responsible at least in part for the inhibition of glucose metabolism which resulted in decreased [14C]ACh synthesis and 14CO2 production.
A STUDY OF THE METABOLISM AND RELEASE OF DOPAMINE AND AMINO ACIDS FROM NERVE ENDINGS ISOLATED FROM SHEEP CORPUS STRIATUM
Authors: De Belleroche J. S. , Bradford H. F. , Jones D. G.
Published: October 2006

Abstract— Synaptosomes prepared from sheep corpus striatum showed a linear rate of respiration over a 90 min period of incubation in Krebs‐bicarbonate medium containing glucose (10 mm) and the rate of respiration was stimulated by electrical pulses. Dopamine was released from synaptosome beds to the medium by either electrical pulses or 56mm‐K+ (10min), increasing 108% and 76% respectively above control levels of release. The presence of d‐ or 1‐amphetamine (0.12mm) in the incubation medium (40 min) increased the accumulation of dopamine in the medium by 310 and 275% respectively and 56mm‐K+ also caused a significant increase in the release of glutamate, GABA and aspartate. Radioactively labelled dopamine was synthesized by the synaptosomes from l‐[14C]tyrosine, l‐DOPA or dl‐DOPA, and electrical pulses caused a 35% increase in the rate of dopamine production from [U‐14C] tyrosine. No increased release of [14C]dopamine in response to depolarizing stimuli was found to occur when synaptosome beds were transferred from medium containing radioactive precursors to fresh medium for further incubation (20 min). In the presence of 1‐ and d‐amphetamine, accumulation of 14C‐labelled doparnine in the incubation media was increased 129% and 380% respectively, the latter was partially depressed by absence of calcium from the medium. Three radioactively labelled metabolites formed by synaptosomes during incubation in dl‐[2‐14C]DOPA were detected; the major ones were dihydroxyphenylacetic acid and homovanillic acid and the third was unidentified. When the synaptosome beds were transferred to medium containing no radioactive precursors, it was found that labelled dihydroxyphenylacetic acid was 7 times more abundant than labelled dopamine in the incubation medium (20 min) and one‐third as abundant in the synaptosomes. The dihydroxyphenylacetic acid n Ci/dopamine n Ci ratio was greatly affected by K+ stimulation, decreasing 52% and 34% in the incubation medium and synaptosomes respectively. A pathway of dihydroxyphenylacetic acid degradation was shown to occur through decarboxylation. These results are discussed in terms of the compartmentation of dopamine and its metabolism. It is proposed that one pool of dopamine is released by depolarizing agents and during the period of incubation it is replaced by synthesis from the endogenous tyrosine (19.5 nmol/100 mg protein) and not by the labelled dopamine in the synaptosome. The synaptosomal pool of dopamine which is radioactively labelled after pulse labelling with dl‐[2‐14C]DOPA appears to be prone to oxidation to DOPAC and homovanillic acid which are preferentially released from the synaptosomes.