bluuebunny/crossref_metadata_2025_split huggingface dataset:
METABOLISM OF PUTATIVE TRANSMITTERS IN INDIVIDUAL NEURONS OF APLYSIA CALIFORNICA
Authors: MCaman R. E. , Dewhurst Susan A. 
Published: October 2006

AbstractThe activities of acetylcholinesterase (acetylcholine acetyl‐hydrolase; EC 3.1.1.7) and catechol‐O‐methyl transferase (S‐adenosylmethionine: catechol‐O‐methyl transferase; EC 2.1.1 .a) were measured in the various ganglia of the nervous system of Aplysia californica and in some of the individually identifiable neurons in these ganglia. All of the neurons studied had measurable levels of activity for both enzymes. Since different individual neurons exhibited approximately the same level of activity we concluded that neither of these enzymes could be used to classify neurons as ‘cholinergic’ vs. ‘aminergic’ or ‘cholinoceptive’ vs. ‘aminoceptive'. The ubiquitous distribution of either or both of these enzymes in different single neurons may be related to glial contamination.
FAST AXONAL TRANSPORT IN VITRO IN THE SCIATIC SYSTEM OF THE FROG
Authors: Edström A. , Mattsson H. 
Published: October 2006

Abstract— An in vitro system from the frog has been used to study fast axonal protein transport. The preparation, which was incubated in a specially made chamber, consisted of the gastrocnemius muscle, the sciatic nerve, the dorsal ganglia and part of the spinal cord. The parts were separated from each other by silicone grease barriers, which made it possible to follow the migration of labelled proteins from the spinal cord and ganglia, along the sciatic nerve, towards the muscle. About 80 per cent of transported proteins in the sciatic nerve originated from the dorsal spinal ganglia and moved antidromically at a rate of 60–90 mm per day at 18°C. The rapidly transported proteins were 90 per cent particulate and mainly associated with structures sedimenting in the microsomal fraction.The effects of cyclohexirnide showed that the synthesis of rapidly moving proteins and their transport were separate processes. A low concentration of colchicine inhibited the transport when it was present in the medium surrounding the ganglia, but had no effect even at a higher concentration, when it was added to the nerve compartment. The presence of vinblastine at a low concentration in either of the two compartments completely arrested the protein transport. Likewise N‐ethylmaleimide or p‐chloromercuribenzene sulphonic acid in the nerve medium effectively blocked the fast transport. Results from experiments performed to test the possibility of disto‐proximal flow and of transfer of proteins from the muscle to the nerve are discussed.
VARIATIONS IN AROMATIC AMINO ACID DECARBOXYLASE ACTIVITY TOWARDS DOPA AND 5‐HYDROXYTRYPTOPHAN CAUSED BY pH CHANGES AND DENATURATION
Authors: Bender D. A. , Coulson W. F. 
Published: October 2006

Abstract—DOPA and 5‐hydroxytryptophan (5‐HTP) are generally supposed to be decarboxylated in mammalian tissues by a single enzyme, the two activities being present in constant ratio through a variety of purification procedures. It has now been shown that the ratio of activity of the liver enzyme towards the two substrates can be altered by mild treatments, such as might be used in solubilization of brain preparations. DOPA decarboxylase activity was preferentially inactivated by sodium dodecyl sulphate treatment, and 5‐HTP decarboxylation by urea.Previous reports that the two substrates show different pH optima but are mutually competitive, have been confirmed. The Km of the enzyme towards 5‐HTP was lowest at pH 7.8 (the optimum pH for decarboxylation of this amino acid), but the variation with pH of the Km towards DOPA was unrelated to the pH optimum for decarboxylation. There appeared to be no relation between the probable ionization state of the substrates and the pH dependence of the enzyme. Studies on the binding characteristics of the enzyme for the two products, dopamine and serotonin, did not show any specific saturable binding.It is proposed that the enzyme has a complex active site, with separate affinity sites for the two substrates, adjacent to a single catalytic site.
DIFFERENTIAL DETERMINATION OF HEXOSAMINIDASES A AND B AND OF TWO FORMS OF β‐GALACTOSIDASE, IN THE LAYERS OF THE HUMAN CEREBELLUM1
Authors: Hirsch Hilde E. 
Published: October 2006

Abstract—In order to determine whether or not various histological elements of the nervous system may differ in their relative content of hexosaminidase A and B (O'Brien, Okada, Chen and Fillerup, 1970) and in the‘acid’and‘neutral’forms of β‐galactosidase (Ho and O'Brien, 1971), these isoenzymes were determined separately in the layers of human cerebellum. The proportion of the heat‐stable hexosaminidase B was greater in the granular layer than in the molecular layer or underlying white matter. The activity of the‘neutral’form of β‐galactosidase was very low compared to the‘acid’type, but its distribution was similar.
BRAIN PROTEINS: QUALITATIVE AND QUANTITATIVE CHANGES, SYNTHESIS AND DEGRADATION DURING FETAL DEVELOPMENT OF THE RABBIT
Authors: Cain D. F. , Ball E. D. , Dekaban A. S. 
Published: October 2006

AbstractThe composition and metabolism of the proteins of the cerebral pallium of the rabbit during the final one‐third of the gestational period were measured. During this period, the brain increased in size almost 10‐fold and the migration of neuroblasts to form the cerebral cortex became complete. Concurrent with the marked structural changes, the solubility characteristics and electrophoretic distribution of various brain proteins showed little change. However, at the time of birth and in the adult, significant differences in gel electrophoresis patterns were apparent. The rate of synthesis of protein in brain slices from the fetus of 20 days gestation was 3‐fold higher per mg of tissue than in the neonate and about 30‐fold higher than in the adult. Activities of acidic and neutral proteases per unit weight were virtually the same and nearly constant throughout the late fetal period. However, during this stage, while rapid growth persists, the total protein synthetic activity of the pallium predominated over the total proteolytic activity, whereas sometime after birth the ratios of these activities reversed consequent to a shutdown of the synthetic process.
HISTOCHEMISTRY OF MYELIN–XV. CHANGES IN THE MYELIN PROTEINS OF THE PERIPHERAL NERVE UNDERGOING WALLERIAN DEGENERATION–ELECTROPHORETIC AND MICRODENSITOMETRIC OBSERVATIONS
Authors: Adams C. W. M. , Csejtey J. , Hallpike J. F. , Bayliss O. B. 
Published: October 2006

AbstractThe chronological order of changes in rat peripheral nerve proteins during Wallerian degeneration has been investigated by microdensitometric and electrophoretic techniques. Both methods revealed an early loss of myelin proteins. The histochemical microdensitometric study showed a very substantial early loss of stainable protein basic groups and a somewhat slower progressive loss of the major protein component of peripheral nerve myelin (the J band). The electrophoretic study showed an early loss of both the J band protein and the slower‐moving basic protein band. The histochemical study also suggested that some cerebroside may be lost in the early stage of Wallerian degeneration. It is concluded that degradation of myelin proteins is an initial event in the process of myelin breakdown.
INCORPORATION OF PHENYLALANINE, TYROSINE AND TRYPTOPHAN INTO PROTEIN OF HOMOGENATES FROM DEVELOPING RAT BRAIN: KINETICS OF INCORPORATION AND RECIPROCAL INHIBITION
Authors: Oja S. S. 
Published: October 2006

AbstractThe kinetics of the incorporation into protein of [3H]phenylalanine, [3H]tyrosine and [3H]tryptophan were studied with homogenates prepared from whole brain of 1‐, 7‐, 21‐ and 60‐day‐old rats. The maximal velocities (Vmax)of incorporation of phenylalanine and tyrosine decreased and the apparent Michaelis‐constants (Km) for all three amino acids increased with increasing age of the rats. Tyrosine had the smallest and tryptophan the largest Km values in all age groups. Phenylalanine competitively inhibited the incorporation of tyrosine, but tyrosine inhibited non‐competitively the incorporation of phenylalanine. Tryptophan inhibited competitively the incorporation of phenylalanine, but at least partially non‐competitively the incorporation of tyrosine. Phenylalanine and tyrosine did not significantly affect the incorporation of tryptophan in homogenates from 60‐day‐old rats. In 1‐day‐old rats only a very large excess of phenylalanine or tyrosine inhibited detectably. The Ki for phenylalanine in the incorporation of tyrosine was significantly smaller in 1‐ than in 60‐day‐old rats. In every case the inhibition presumably occurred at a single rate‐limiting step in the complicated process of incorporation of amino acids into protein.
HYPOXANTHINE‐GUANINE‐PHOSPHORIBOSYL‐TRANSFERASE FROM RAT BRAIN (PURIFICATION, KINETIC PROPERTIES, DEVELOPMENT AND DISTRIBUTION)
Authors: Gutensohn W. , Guroff G. 
Published: October 2006

AbstractHypoxanthine‐guanine‐phosphoribosyltransferase (HGPR Tase; ECC 2.4.2.8) has been purified from rat brain 650‐fold to about 50 per cent purity by conventional methods. An isoenzyme pattern of at least three components is observed on DEAE‐cellulose chromatography. On polyacrylamide disc electrophoresis only one sharp band of enzyme activity can be detected. The apparent Km‐value determined for phosphoribosylpyrophosphate (PRPP) is about 0.2 mM. The product, GMP, and also GDP, GTP, UMP, CMP, AMP and ATP are competitive inhibitors with respect to PRPP. Inhibition by a number of other nucleotides has also been investigated. Studies on the development of enzyme activity in the brain of the young rat show that a rapid increase occurs during the first 15‐20 days of life and reaches a plateau thereafter. The regional distribution of HGPRTase activity in adult rat brain is more homogenous than that reported for human brain. The enzyme is predominantly a constituent of the soluble supernatant fraction, but can also be found in carefully washed synaptosomes. An antiserum against rat brain HGPRTase obtained from rabbits inhibits this enzyme to about 30 per cent of control activity, but does not crossreact with HGPRTases from rabbit or human erythrocytes.
RAPID AXONAL TRANSPORT IN VITRO IN THE SCIATIC SYSTEM OF THE FROG OF FUCOSE‐, GLUCOSAMINE‐ AND SULPHATE‐CONTAINING MATERIAL
Authors: Edstroum A. , Mattsson H. 
Published: October 2006

Abstract—An in vitro system from the frog has been used to study fast axonal transport of glycoproteins. The migration of [3H]fucose‐, [3H]glucosamine‐ and [35S]sulphate‐labelled material was followed from the dorsal ganglia, along the sciatic nerve towards the gastrocnemius muscle.The distribution in different subcellular fractions, effect of cycloheximide and transport kinetics did not differ very much between fucose‐ and glucosamine‐incorporation into the nerve. Cycloheximide blocked the synthesis of TCA‐insoluble radioactivity, which was transported at a rate of 60–90 mm per day at 18°C, more effectively than the synthesis of stationary proteins in the ganglia. About 10 per cent of the TCA‐insoluble and transported radioactivity was extracted by chloroform‐methanol (2:1, v/v) and might be glycolipids and the rest glycoproteins. Results suggest that TCA‐soluble activity, which was recovered in the nerve, originated in part from labelled macromolecules consumed along the axons. The rapidly transported TCA‐insoluble radioactivity was 85 per cent particulate and mainly associated with structures sedimenting in the microsomal fraction.[35S]Sulphate‐labelled TCA‐insoluble material was resistant towards chloroform‐methanol (2:1, v/v) extraction and rapidly transported from the ganglia into the nerve. The synthesis was inhibited by cycloheximide. The material, probably proteoglycans, represented a quantitatively minor part of transported glycoproteins.
CONTROL OF AEROBIC GLYCOLYSIS IN GUINEA‐PIG CEREBRAL CORTEX SLICES
Authors: Takagaki G. 
Published: October 2006

Abstract—The effect of glutamate on aerobic glycolysis in guinea‐pig cerebral cortex slices was analysed in comparison with that of high‐potassium. In contrast to the increased glycolysis in 50 mm‐potassium medium which was accompanied by increases of fructose diphosphate and triose phosphates in the slices, the addition of 5 mm‐d‐glutamate to the medium increased the rate of glycolysis without increasing these intermediates. When increasing the concentration of potassium in the medium up to 20 mm, the rate of aerobic glycolysis was not increased although fructose diphosphate and triose phosphates in the slices were increased. At this potassium concentration in the medium ATP in the slices was highest. At 30 mm‐potassium the rate of glycolysis was increased significantly, but fructose diphosphate and triose phosphates were decreased. ATP was lower at 30 mm‐ than at 20 mm‐potassium. By increasing potassium to 40 mm and above, the rate of glycolysis was further increased, and fructose diphosphate and triose phosphates were again increased. Between 5 and 20 mm‐potassium in the medium the increasing effect of glutamate on glycolysis was very pronounced. d‐Glutamate decreased the amounts of ATP, fructose diphosphate and triose phosphates at any concentration of potassium in the medium. When adding cyclic AMP and 5′AMP to the slices, fructose diphosphate and triose phosphates were increased, but the rate of glycolysis was not increased. On the basis of these observations mechanisms of the control over glycolysis in guinea‐pig cerebral cortex slices are discussed. It is suggested that the glycolysis is controlled by the changes in ATP concentration through their action on the glyceraldehyde 3‐phosphate dehydrogenase and phosphoglycerate kinase system. The changed patterns of the glycolytic intermediate profile in the slices when adding ATP to the medium are consistent with this suggestion. The addition of l‐phenylalanine to guinea‐pig cerebral cortex slices did not inhibit the rate of glycolysis, although it inhibited the activity of pyruvate kinase.
THE MITOCHONDRIAL REDOX STATE OF RAT BRAIN
Authors: Miller A. L. , Hawkins R. A. , Veech R. L. 
Published: October 2006

AbstractThe use of the glutamate dehydrogenase (EC 1.4.1.3) and β‐hydroxybutyrate dehydrogenase (EC 1.1.1.30) reactions for the calculation of the mitochondrial redox state of brain has been examined. To prevent post‐mortem anoxic metabolism, brains were frozen in less than a second by using a new technique. Levels of ketone bodies in brain were so low relative to the contamination by blood and extracellular fluid that calculation of the mitochondrial redox state using the β‐hydroxybutyrate dehydrogenase reaction was not practical. The concentrations of the non‐nucleotide substrates of the glutamate dehydrogenase reaction could be accurately measured in brain and themitochondrial [NAD+]/[NADH] ratio calculated from the ratio [α‐oxoglutarate] [NH4+]/[glutamate]. The calculation is valid if the ratio [α‐oxoglutarate] [NH4+]/[glutamate] in mitochondria is the same as that measured in whole tissue. The evidence supporting this conclusion is the near‐equilibrium of the aspartate aminotransferase (EC 2.6.1.l) reaction in brain and the observation by others that the distribution of label between α‐oxoglutarate and glutamate in brain, after administration of labelled precursors, conforms to expectation. The alanine aminotransferase (EC 2.6.1.2) reaction was not near equilibrium in brain, probably because of the low in vivo activity of the enzyme.
LYSOLECITHIN AND SPHINGOSINEPHOSPHORYL‐CHOLINE IN THE METABOLISM OF BRAIN PHOSPHOLIPIDS OF THE RHESUS MONKEY (MACAC A MULATTA): EFFECTS OF DEVELOPMENT
Authors: Portman O. W. , Illingworth D. R. , Alexander M. 
Published: October 2006

AbstractThe rates of incorporation of palmitate from palmitoyl CoA into lecithin or sphingomyelin by homogenates of neural tissue of rhesus monkeys were greatly increased by the addition of lysolecithin or sphingosinephosphorylcholine (SPC). Labelled lysolecithin and SPC were also incorporated into lecithin and sphingomyelin. There was a low level of nonenzymic sphingomyelin formation from SPC and palmitoyl CoA. Choline from CDP‐choline was rapidly incorporated into lecithin and slowly into SPC and sphingomyelin by homogenates of pons. The activity of lysolecithin acyl hydrolase (EC 3.1.1.5) was high throughout life in homogenates of pons and cerebral cortex. The rate of utilization of palmitoyl CoA and lysolecithin for phospholipid synthesis was higher in neural tissue from fetal and neonatal monkeys than from adults. Lysolecithin was acylated most rapidly with palmitoleic, linoleic and arachidonic acids. All phospholipid metabolic activities were higher in the cerebral cortex than in the pons.
FEEDBACK REGULATION OF 5‐HT SYNTHESIS IN RAT STRIATAL SLICES
Authors: Hamon M. , Bourgoin S. , Glowinski J. 
Published: October 2006

AbstractThe effects of changes in intraneuronal levels of 5‐HT induced by monoamine oxidase inhibitors (MAOI) given in vivo or exogenous 5‐HT added in vitro on 5‐HT synthesis in striatal slices of the rat have been examined. The synthesis of 5‐HT was estimated by the measurement of the total formation of [3H]5‐HT and [3H]5‐hydroxyindole acetic acid from [3H]tryptophan and by calculation of the conversion index (CI) of tryptophan into 5‐HT. The small formation of [3H]tryptamine and [3H]indole acetic acid from [3H]tryptophan was taken into account in the estimation of 5‐HT synthesis. Both MAOI pretreament (180 min) and 5‐HT (2·8 μM) inhibited synthesis. The latter effect persisted in catecholamine depleted tissues and was related to intraneuronal changes in 5‐HT levels, since it could be prevented by chlorimipramine. The inhibition of 5‐HT synthesis was related to the decreased conversion of tryptophan into 5‐hydroxytryptophan and could not be prevented by p‐chloro‐phenylalanine pretreatment which depleted 5‐HT levels or by dibutyryl cyclic AMP which normally stimulated 5‐HT synthesis. Tryptophan uptake in slices was not affected by exogenous 5‐HT. The various mechanisms possibly involved in the end product regulation process of 5‐HT synthesis are discussed.
MONOAMINE OXIDASE (EC 1.4.3.4): ISOLATION AND CHARACTERIZATION OF MULTIPLE FORMS OF THE BRAIN ENZYME
Authors: Shih Jean Chen , Eiduson S. 
Published: October 2006

AbstractMonoamine oxidase (MAO) in crude mitochondrial preparations from rat brain was solubilized, and different MAO‐active fractions were separated by agarose columns and by Sephadex electrophoresis. Any combination of these techniques yielded at least three fractions possessing MAO activity as measured by assays using radioactive serotonin and benzylamine as substrates. The molecular weight of one of the MAO forms was found to be approximately 400,000 daltons while another was at least 1.5 × 106 daltons. The crude mitochondria1 MAO was inhibited by [14C]‐labelled pargyline and then solubilized and the radioactivity of the soluble and particulate MAO was compared to the enzyme activity found in the soluble and particulate fractions. Our studies suggest that appreciable MAO activity is lost upon solubilization and that the conformation of MAO may be altered.
PHYSICO‐CHEMICAL CHARACTERISTICS AND REGIONAL DISTRIBUTION STUDIES OF GP‐350, A SOLUBLE SIALOGLYCOPROTEIN FROM BRAIN
Authors: Van Nieuw Amerongen A. , Roukema P. A. 
Published: October 2006

AbstractThe apparent molecular weight of GP‐350, a sialoglycoprotein from calf and rat brain, has been determined by SDS‐polyacrylamide gel electrophoresis. The electrophoretic mobility corresponds to the mobility of a polypeptide with a molecular weight of 11,600 ± 200. On this basis it can be calculated that only one sialic acid residue is present/GP‐350 molecule.From isoelectric focusing experiments it appeared that the isoelectric point of GP‐350 is about 2. The determination of the amide content of the polypeptide chain showed that out of 22.0 acidic amino acid residues of glutamic acid and aspartic acid, only 4.9 residues are amidated. The total amount of the basic amino acid residues lysine and arginine, is 6.5. So, per molecule GP‐350 10.6 acidic amino acid residues are not counteracted by basic amino acid residues. The surplus of the acidic amino acid residues as well as sialic acid result in the pronounced acidic character of GP‐350. This fact is supported by the electrophoretic experiments.The carbohydrate‐polypeptide linkage type has been studied by alkaline sodium borohydride treatment. Two thirds of all the galactosamine was destroyed, whereas the amount of glucosamine remained the same. Amino acid analysis indicated a decrease in serine and threonine with a concomitant small increase in alanine. These data point to the occurrence of linkages between the carbohydrate chain and the polypeptide core of the galactosamineserine or –threonine type. Per molecule GP‐350 about two residues of galactosamine are destroyed, indicating that two carbohydrate chains of this binding type are present. Only one of these chains can be terminated by a sialic acid residue. The other carbohydrate chain may be terminated by fucose.Regional distribution studies showed the presence of GP‐350 in all brain areas studied; in relatively large amounts in the regions rich in ganglia such as caudate nucleus, cerebellar grey matter, pons and medulla oblongata, and in relatively small amounts in the regions poor in ganglia such as corpus callosum, cerebral white, cerebral grey and cerebellar white matter.GP‐350 is also present in the pituitary gland. In the cerebrospinal fluid a glycoprotein is present with the same electrophoretic mobility as GP‐350. However, this glycoprotein gave no precipitin reaction with GP‐350 specific antiserum. Moreover, the amino acid composition was quite different from that of GP‐350.Subcellular distribution study revealed that GP‐350 is present in the soluble cell fraction and in the synaptosomal membrane fraction, whereas it is absent from the purified nuclei, mitochondria, myelin, and also from the microsomal fraction.
SUBCELLULAR LOCALIZATION OF [14C]ADENINE DERIVATIVES NEWLY‐FORMED IN CEREBRAL TISSUES AND THE EFFECTS OF ELECTRICAL EXCITATION
Authors: Kuroda Y. , McIlwain H. 
Published: October 2006

Abstract— Guinea pig neocortical tissues were incubated with [14C]adenine, dispersed in cold isotonic sucrose and subcellular fractions prepared by centrifugation. Some 98 per cent of the assimilated 14C was found as acid‐soluble nucleotides in the incubated tissues. In primary fractions obtained by differential centrifugation, about 60 per cent of the [14C]‐nucleotides were in supernatant fractions, in distinction to ATP of which the greatest molar quantity (61 per cent of that in the dispersion) was in the crude mitochondrial fraction. When the crude mitochondrial fraction was separated by density gradient centrifugation, most 14C was found in synaptosomal fractions and about 85 per cent of this 14C was adenine nucleotides.Electrical stimulation of incubating tissues immediately prior to their dispersion and centrifugation greatly diminished the proportion of 14C subsequently found in nucleotides (collectively) in the supernatant fraction, and increased their inosine and hypoxanthine. Stimulation increased the tissue's cyclic AMP but a preferential localization for this was not established. Results are tentatively interpreted in terms of liberation of an adenine derivative on excitation, and its action or reuptake at a tissue component different from that from which it was liberated. Fractionation of tissues which had been incubated with both [14C]‐adenine and [3H]adenosine suggested that of the two compounds, more adenosine was taken up by synaptic regions in preference to other cellular regions of the tissue.