bluuebunny/crossref_metadata_2025 huggingface dataset:
THE EFFECT OF INTRAHIPPOCAMPAL KAINIC ACID INJECTIONS AND SURGICAL LESIONS ON NEUROTRANSMITTERS IN HIPPOCAMPUS AND SEPTUM
Authors: Fonnum F. , Walaas I.
Published: October 2006

Local injection of kainic acid (2 μg) was accompanied by destruction of intrinsic neurons in the dorsal part of hippocampus. The lesion was accompanied by a 75% reduction in glutamate decarboxylase activity, a 60% reduction in the high affinity uptake of l‐glutamate, a 40‐60% reduction in the endogeneous levels of aspartate, glutamate and GABA and no changes in the activities of choline acetyltransferase or aromatic amino acid decarboxylase in the dorsal hippocampus. Unilateral destruction of neurons in the dorsal hippocampus was followed by a 20‐40% reduction in the high affinity uptake of glutamate in lateral, but not in medial septum, on both sides. There was no reduction in choline acetyltransferase, glutamate decarboxylase or aromatic amino acid decarboxylase activities in the lateral or medial part of the septum. Transection of fimbria and superior fornix was accompanied by a severe reduction in choline acetyltransferase and aromatic amino acid decarboxylase activity in hippocampus, in the high affinity uptake of glutamate and in the endogenous level of glutamate in the lateral septum. The results are consistent with the concept that in the hippocampus kainic acid destroys intrinsic neurons and not afferent fibres. It seems therefore that all GABAergic fibres in the hippocampus belong to intrinsic neurons whereas glutamergic and aspartergic neurons belong partly to local neurons. The connection from the hippocampus to the lateral septum probably uses glutamate as a transmitter.
IRREVERSIBLE ZINC ION INHIBITION OF (Na+‐K+)‐ADENOSINETRIPHOSPHATASE, Na+‐PHOSPHORYLATION, AND K + ‐p‐NITROPHENYLPHOSPHATASE OF ELECTROPHORUS ELECTRICUS ELECTROPLAX1
Authors: Gettelfinger Dennis M. , Siegel George J.
Published: October 2006

Zinc ion in micromolar concentrations is an irreversible inhibitor of Electrophorus electricus electroplax microsomal (Na+‐K+)‐ATPase. The rate of inhibition is dependent on [ZnCl2] and the extent of inhibition varies with the ratio of ZnCl2 to microsomal protein. The same kinetics are observed for inhibition of K+ ‐p‐nitrophenylphosphatase and steady‐state levels of Na+ ‐dependent enzyme phosphorylation. The observations suggest that a Zn2+ ‐sensitive conformational restraint is important to both kinase and phosphatase activities. The fact that inhibition is irreversible has implications for models seeking to relate zinc effects in tissue to inhibition of (Na+‐K+)‐ATPase.
THE DISTRIBUTION OF CALCIUM‐DEPENDENT PHOSPHATIDYLINOSITOL‐SPECIFIC PHOSPHODIESTERASE IN RAT BRAIN
Authors: Irvine Robin F. , Dawson Rex M. C.
Published: October 2006

Abstract— The properties of Ca2+‐dependent phosphatidylinositol‐phosphodiesterase in membrane fractions and supernatants prepared from rat brain have been examined with the aim of providing firm evidence for the existence of a membrane‐bound activity distinct from the soluble enzyme found in the cytosol (EC 3.1.4.10). The soluble enzyme is either stimulated or inhibited at pH 7.0 by deoxycholate depending on the ratio of detergent to substrate. The effects of deoxycholate are pH dependent and result in a shift of the enzyme optimum to a higher pH if the enzyme is assayed in the presence of deoxycholate. The soluble enzyme cannot hydrolgse membrane‐bound phosphatidylinositol (in 32P‐labelled rat liver microsomes) unless deoxycholate is present. The pH optimum is 6.7 for this detergent‐dependent hydrolysis and this is probably dependent on the ionization of deoxycholic acid. The lactate dehydrogenase (EC 1.1.1.27) content of rat brain membrane fractions has been measured to estimate the contamination of these fractions by supernatant phosphatidylinositol‐phosphodiesterase. No evidence has been found for phosphatidylinositol‐phosphodiesterase activities that cannot be explained by such contamination. It is concluded that all the properties of calcium‐dependent phospha‐tidylinositol‐phosphodicsterase in rat brain can be explained by the existence of only the solublc cyto‐plasmic enzyme: no evidence confirming a distinct membrane‐bound activity has been obtained.
SHORT‐TERM REGULATION OF CATECHOLAMINE BIOSYNTHESIS IN A NERVE GROWTH FACTOR RESPONSIVE CLONAL LINE OF RAT PHEOCHROMOCYTOMA CELLS
Authors: Greene Lloyd A. , Rein Glen
Published: October 2006

Abstract— A clonal cell line (designated PC12) has been previously established from a transplantable rat adrenal medullary pheochromocytoma. Tissue cultures of PC12 cells synthesize, store, release and take up catecholamines. PC12 cells also respond to nerve growth factor (NGF) protein by cessation of mitosis and extension of neurites. The present studies concern the comparison of several aspects of catecholamine metabolism in PC12 cultures with that in normal noradrenergic tissues. One question was why the ratio of dopamine to norepinephrine in PC12 cultures (in contrast to that in normal noradrenergic tissue) is considerably more than one. The presence of exogenous reduced ascorbate (a cofactor for dopamine‐β‐monooxygenase) enhanced by 5–10‐fold the rate at which PC12 cultures converted [3H]tyrosine to [3H]norepinephrine. Under such conditions, the rate of synthesis of [3H]do‐pamine was unchanged. It was also found that the ratio of norepinephrine to dopamine increased by 10‐fold when the cells were grown in vivo as tumors. Since tissue culture medium is essentially free of reduced ascorbate, it is likely that the absence of this cofactor is responsible for the low norepinephrine to dopamine ratio in PC12 cultures. Experiments were also carried out on short‐term regulation of catecholamine synthesis in PC12 cultures. These studies revealed the following: (1) The rate of conversion of [3H]tyrosine to [3H]catechols was increased 2–3‐fold (as compared with controls) in the presence of depolarizing levels of K+ (51.5 mM), and by 2‐fold in the presence of 0.5–2 mM‐dibutyryl cyclic adenosine 3′, 5’monophosphoric acid (db‐cAMP). (2) Similar increases occurred in cultures which had been treated with (and had responded to) nerve growth factor. (3) The stimulatory effects of 51.5 mM‐K+ rapidly returned toward control levels when the cultures were returned to control medium and (4) required the presence of Ca2+ in the extracellular medium. (5) Stimulation of catechol synthesis by 51.5 mM‐K+ and db‐cAMP also occurred in the presence of an inhibitor of DOPA decar‐boxylase. Thus, the ultimate effects of these agents were probably at the level of conversion of tyrosine to dopa by tyrosine 3‐monooxygenase. (6) Simultaneous exposure of cultures to 51.5 mM‐K+ and mM‐db‐cAMP gave additive levels of stimulation. Such findings demonstrate that catecholamine synthesis in cultures of PC12 cells undergoes short‐term regulation which is similar to that previously demonstrated in normal monoaminergic tissues. As a homogeneous tissue culture line, the PC12 bears certain advantages for studying the primary mechanisms of such effects.
A COMPARISON BETWEEN FLUOROMETRIC AND MASS FRAGMENTOGRAPHIC DETERMINATIONS OF HOMOVANILLIC ACID AND 5‐HYDROXYINDOLEACETIC ACID IN HUMAN CEREBROSPINAL FLUID
Authors: Sjöquist Birgitta , Johansson Barbro
Published: October 2006

Abstract—

HVA and 5‐HIAA in human cerebrospinal fluid were quantitatively determined by both fluorometry and mass fragmentography. The homovanillic acid values obtained by fluorometry were significantly lower than those obtained by mass fragmentography (P < 0.05). The correlation coefficient between values for HVA obtained by the two methods was high, r= 0.90. For 5‐HIAA the concentrations obtained by the two methods were not significantly different while the correlation coefficient was lower, r= 0.55.
MULTIPLE FORMS OF CHOLINE ACETYLTRANSFERASE AND THE HIGH AFFINITY UPTAKE OF CHOLINE IN BRAIN OF DEVELOPING AND ADULT RATS
Authors: Atterwill C. K. , Prince A. K.
Published: October 2006

Abstract—

The multiple molecular forms of choline acetyltransferase (ChAT) were analysed during the postnatal development of rat brain. Changes in the sodium‐dependent, high affinity uptake of [3H]choline (HAUC) and in the efficiency of conversion of labelled choline into ACh in vitro were also examined. Both mature and 7‐day old brain contained three molecular forms of ChAT, with isoelectric points of pH 7.3, 7.9 and 8.3, but the immature brain appeared to contain smaller concentrations of the most basic form of the enzyme (pI = 8.3). Of the total choline uptake measured in slices of frontal cortex, adult samples exhibited a greater proportion of HAUC than 7‐day samples and appeared to acetylate more efficiently the [3H]choline accumulated by high affinity uptake. This evidence suggests a basic molecular form of ChAT, appearing in rat brain during postnatal development, might be responsible for the efficient coupling of the high affinity uptake and subsequent acetylation of choline in cholinergic nerve terminals.
ACCELERATION OF CHOLINE UPTAKE AFTER DEPOLARIZATION‐INDUCED ACETYLCHOLINE RELEASE IN RAT CORTICAL SYNAPTOSOMES
Authors: Roskoski Robert
Published: October 2006

Abstract— Activation of nerve elements in vivo and in vitro is associated with an increased rate of choline uptake by a Na+‐dependent high affinity transport system. Following the methodology of Barker (1976), rat cortical synaptosomes were depolarized (37°C, 10min) by 25mM‐KCl in the presence of CaCl2 (1 mM) or other divalent cations. After reisolation by centrifugation, the rate of 3H‐choline uptake (1.25μM) was measured by Millipore filtration. KCl treatment alone failed to accelerate the rate of uptake in the reisolated synaptosomes. CaCl2, BaC12 or SrCl2 (but not MgCl2 or MnCl2) were necessary (1 mM) to observe the KCl induced acceleration. Moreover, RbCl, but not LiCl or CsCl, also produced the calcium‐dependent rate enhancement in the reisolated synaptosomes. The conditions mediating the enhanced rate of choline uptake correlated strongly with those associated with neurotransmitter release. To test this possibility, synaptosomal acetylcholine content was measured in response to the various salt treatments. Treatment with KCI (25 mM) and CaCl2 (1 mM), but not KCl alone, reduced the synaptosomal acetylcholine content from 154 to 113pmol/mg protein. The respective rates of choline uptake increased about 60%. The increased rate was reversed by incubation with 50 μM‐choline followed by synaptosome reisolation. This procedure also normalized the acetylcholine content. In summary, the rate of choline uptake by the high affinity choline uptake system is inversely related to the synaptosomal acetylcholine content.
ASSOCIATIONS OF BETA NERVE GROWTH FACTOR WITH BOVINE SERUM ALBUMIN AS WELL AS WITH THE ALPHA AND GAMMA SUBUNITS OF THE 7S MACROMOLECULE1
Authors: Almon Richard R. , Varon Silvio
Published: October 2006

Abstract— The association of 125 I‐diiodo‐Beta nerve growth factor with bovine serum albumin (BSA), as well as with the Gamma and Alpha subunits of the 7S nerve‐growth factor (NGF) macromolecule are described. In the absence of added protein, the stable thermodynamic state for Beta (pH 7.4) at concentrations below 10−7 M is absorbed to the walls of the reaction vessel. Above 10−7 M the sites on the wall of the reaction vessel begin to saturate, and Beta is found free in solution. Addition of other soluble proteins to the system (i.e. BSA, Alpha and Gamma) causes a displacement of the Beta from the walls of the reaction vessel. This displacement is the result of the binding of the Beta to the added soluble protein. The binding of Beta to BSA is a complex function of BSA concentration, suggesting multiple sets of sites and/or cooperative interactions. In contrast, the characteristics of the association of Beta with Gamma and Alpha indicate an interaction between discrete sets of sites on the respective polypeptide chains. The Beta‐Gama association is a bimolecular association with an apparent first thermodynamic association constant of 6.25 × 105M−1. The association between Beta and Alpha is also bimolecular and has an apparent first thermodynamic association constant of 2.0 × 105M−1. In addition, dissociation studies suggest that the Gamma‐Beta complex binds Alpha with a substantially higher affinity than does Beta or Gamma alone. These data strongly support the conclusion that there is a unique biologically determined relationship among these polypeptides. The data are discussed with respect to the experimental use of Beta NGF. A new operational paradigm for the controlled use of the Beta NGF is presented. This approach is based on the use of a thermodynamically stabilized 7S complex and the analysis of relative apparent affinities.
ADRENERGIC α‐ AND β‐RECEPTORS EXPRESSED BY THE SAME CELL TYPE IN PRIMARY CULTURE OF PERINATAL MOUSE BRAIN
Authors: Van Calker D. , Müller M. , Hamprecht B.
Published: October 2006

Abstract— The β‐adrenergic agonist, isoproterenol and the α‐ and β‐adrenergic agonist. NA. raise the intracellular concentration of cyclic AMP in cultures of dissociated perinatal mouse brain. This rise is prevented by a β‐ but not by an α‐adrenergic antagonist. The maximal level of cyclic AMP reached in the presence of isoproterenol is markedly higher than that found after exposure to NA. However, if NA is used along with an α‐adrenergic antagonist, cyclic AMP levels as high as those after isoproterenol are measured. Agonists with α‐adrenergic activity including NA decrease the response to isoproterenol. The decrease is blocked by α‐adrenergic antagonists. From this and additional evidence it is concluded: (1) The increase in the level of cyclic AMP caused by β‐adrenergic agonists is due to β‐receptor‐mediated stimulation of adenylate cyclase; (2) the inhibition of this effect by α‐adrenergic agonists is mediated by adrenergic α‐receptors; (3) the α‐ and β‐adrenergic receptors are likely to be located on the same cells, probably the most abundant putative glial precursor cells. The simultaneous stimulation of α‐ and β‐adrenergic receptors on the same cell may be of significance in the regulation of the response to NA.
VITAMIN B6 TRANSPORT IN THE CENTRAL NERVOUS SYSTEM: IN VITRO STUDIES
Authors: Spector Reynold
Published: October 2006

Abstract— The transport into and release of tritium labeled vitamin B6 ([3H]B6) from rabbit brain slices and isolated choroid plexuses were studied. In vitro, both brain slices and choroid plexus concentrated [3H]B6 by an energy dependent uptake system when [3H]pyridoxine (PIN) was added to the incubation medium. Most of the [3H] within the tissues was phosphorylated [3H]B6. In each tissue, the nonphosphorylated vitamers inhibited the uptake of [3H]PIN from the medium significantly more than the phosphorylated vitamers. The concentrations of the nonphosphorylated B6 vitamers necessary to inhibit brain and choroid plexus uptake of [3H]PIN from the medium by 50% were approx 0.4 μm and 5–10μm respectively after a 30 min incubation. Both brain slices and choroid plexus readily released (46 and 56% respectively in 30 min) previously accumulated [3H]B6 into artificial CSF. However, brain slices released only nonphosphorylated [3H]B6, whereas the choroid plexus released predominantly phosphorylated [3H]B6. Addition of unlabeled PIN to the release media significantly increased the percentage of [3H]B6 released by both brain slices and choroid plexus. The results of these in vitro studies provide evidence that: (1) both brain slices and chloroid plexus possess specific uptake and release mechanisms for B6, and (2) these mechanisms tend to regulate intracellular B6 levels. These studies also suggest that the choroid plexus serves as a locus for the transfer of B6 from blood to CSF and is the source of most of the phosphorylated B6 in CSF.
REGIONAL BRAIN LEVELS OF γ‐HYDROXYBUTYRATE IN HUNTINGTON'S DISEASE
Authors: Ando N. , Gold B. I. , Bird E. D. , ROTH R. H.
Published: October 2006

Abstract—

A highly sensitive electron capture gas chromatographic method was developed for quantitation of γ‐hydroxybutyrate (GHB) in tissue. This method involves an improved, extraction and purification procedure and a one‐step derivatization of GHB to the methyl ester‐O‐heptafluorobutyrate. As low as 5 ng of GHB in tissue was accurately quantitated by this method.

By means of this improved method, endogenous levels of GHB in several regions of brains obtained post‐mortem from patients with Huntington's disease were determined, and compared with brain samples obtained post‐mortem from non‐neurological controls. The levels of GHB found in the caudate and substantia nigra obtained from Huntington's patients were significantly higher than the GHB levels found in similar regions of brain obtained from a non‐neurological control group. The content of GABA in the same choreic and control brain samples was also determined. No significant correlation between changes in GHB and GABA levels was observed although there was a trend towards an inverse relationship. The high level of GHR in Huntington's disease may be related to the decrease in succinate:oxidoreductase (EC 1.3.99.1) activity reported by Stahl & Swanson (1974).

In two subjects (one control and one Huntington patient) the zonal distribution of GHB in substantia nigra was also determined. The zona reticulata from choreic brain contained a substantially higher level of GHB, whereas the zona compacta contained an amount similar to the level found in control brain.
PROTEOLIPID PROTEIN: SYNTHESIS AND ASSEMBLY INTO QUAKING MOUSE MYELIN
Authors: Greenfield S. , Williams N. I. , White M. , Brostoff S. W. , Hogan E. L.
Published: October 2006

The incorporation of radioactive glycine into the major myelin proteolipid protein isolated from whole brain and from purified myelin of Quaking mice and normal littermates was compared. In a typical experiment, four Quaking mice and four littermate controls were injected intracranially with 250 μCi [2‐3H]glycine and 25 μCi [U‐14C]glycine respectively. Three hours later, the eight mice were killed and their brains combined. Equivalent portions were taken for (1) chloroform‐methanol (2:1) extraction followed by ether precipitation of proteolipid from the brain and (2) myelin preparation. The 3H/14C ratios for the microsomes:, the major myelin proteolipid as well as the other non‐myelin proteolipids extracted from whole brain was approx 3.0. while the 3H/14C ratio for proteolipid protein in myelin was near 0.4. These findings were consistent for ages studied between 18 and 90 days. The results indicate that the synthesis of the major myelin proteolipid protein in the whole brain of Quaking mouse, as seen previously in our studies on basic protein, proceeds at a normal rate relative to microsomes but its incorporation into myelin is depressed. A working hypothesis of myelin membrane assembly is presented to account for the defect in the incorporation of these proteins into Quaking myelin.
HETEROGENEITY OF HISTAMINE Hi‐RECEPTORS: SPECIES VARIATIONS IN [3H]MEPYRAMINE BINDING OF BRAIN MEMBRANES
Authors: Chang Raymond S. L. , Tran Vinh Tan , Snyder Solomon H.
Published: October 2006

[3H]Mepyramine binds with high affinity to membranes from brain of human, rat, guinea‐pig, rabbit and mouse with drug specificity indicating an association with histamine H1receptors. Considerable species differences occur in the affinity of [3H]mepyramine, with guinea‐pig and human having 34 times greater affinity than rat, mouse or rabbit. The greater affinity of [3H]mepyramine in guinea‐pig than in rat is attributable both to faster association and slower dissociation rates in guinea‐pig. Species differences in affinity for H1 receptor sites occur for some antihistamines but not for others. Some tricyclic antidepressant and neuroleptic drugs are extremely potent inhibitors of [3H]mepyramine binding, exceeding in potency any H1 antihistamines examined. The tricyclic antidepressant doxepin and the neuroleptic clozapine are the most potent of all drugs examined in competing for [3H]mepyramine binding. The regional distribution of specific [3H]mepyramine binding differs considerably in the various species examined.
THE EFFECTS OF CHRONIC REGIMENS OF CLORGYLINE AND PARGYLINE ON MONOAMINE METABOLISM IN THE RAT BRAIN
Authors: Campbell I. C. , Robinson D. S. , Lovenberg W. , Murphy D. L.
Published: October 2006

The effects of chronic administration of clorgyline and pargyline on rat brain monoamine metabolism have been examined. The inhibitory selectivity of these drugs towards serotonin deamina‐tion (MAO type A) and phenylethylamine deamination (MAO type B) can be maintained over a 21‐day period by proper selection of low doses of these drugs (0.5‐1.0 mg/kg/24h). The results are consistent with MAO type A catalyzing the deamination of serotonin and norepinephrine and with MAO type B having little effect on these monoamines. Dopamine appears to be dcaminated in vivo principally by MAO type A. Clorgyline administration during a 3‐week period was accompanied by persistent elevations in brain norepinephrine concentrations; serotonin levels were also increased during the first 2 weeks, but returned towards control levels by the third week of treatment. Low doses of pargyline did not increase brain monoamine concentrations, but treatment with higher doses for 3 weeks led to elevations in brain norepinephrine and 5‐hydroxytryptamine; at this time significant MAO‐A inhibition had developed. The changes in monoamine metabolism seen at the end of the chronic clorgyline regimen are not due to alterations in tryptophan hydroxylase activity. At this time tyrosine hydroxylase activity was also unaffected.
EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS: SEQUESTERED ENCEPHALITOGENIC DETERMINANT IN THE BOVINE MYELIN BASIC PROTEIN12
Authors: Hashim G. A. , Sharpe R. D. , Carvalho E. F.
Published: October 2006

The presence of a sequestered encephalitogenic determinant for Lewis rats in the bovine myelin BP was demonstrated with synthetic peptide sequences prepared in our laboratory by the Merrifield solidphase method. The sequence of the encephalitogenic determinant (residues 75‐84) from bovine BP (peptide S6), H‐Ala‐Gln‐Gly‐His‐Arg‐Pro‐Gln‐Asp‐Glu‐Asn‐OH, is similar but not identical to the sequence reported for the guinea pig BP (peptide S53), H‐Ser‐Gln‐(–)‐(–)‐Arg‐Ser‐Gln‐Asp‐Glu‐Asn‐OH. The presence or the absence of Gly‐His from the sequence of either the bovine or the guinea‐pig determinants did not alter their encephalitogenic potencies; however, the presence of Gly‐His at positions 77 and 78 together with H‐Gly‐Ser‐Leu‐Pro‐Gln‐Lys‐ (residues 69‐74) at the N‐terminal end of the bovine determinant destroyed its encephalitogenic potency.

In contrast to the absence of Gly‐His from the potent encephalitogenic guinea‐pig BP, guinea‐pig fragment 44‐89, and synthetic peptide S49, its presence in the bovine sequence prevents recognition of this determinant and renders the parent bovine BP, bovine fragment 44‐89, and synthetic peptide S8 (residues 69‐84) relatively non‐encephalitogenic. The results of this study suggest that intramolecular interactions occur between adjacent amino acids, conferring secondary or tertiary structures upon this region of the bovine BP which renders the encephalitogenic determinant inaccessible for recognition by the host animal. The presence of sequestered disease‐inducing determinants needs to be considered in choosing a particular BP for therapeutic use.
AMINO ACID AND SUBSTANCE P CONTENTS IN SPINAL CORD OF CATS WITH EXPERIMENTAL HIND‐LIMB RIGIDITY PRODUCED BY OCCLUSION OF SPINAL CORD BLOOD SUPPLY
Authors: Homma Shinji , Suzuki Toshio , Murayama Satoshi , Otsuka Masanori
Published: October 2006

Abstract— Experimental hind‐limb rigidity of spinal origin was produced in cats by temporary occlusion of thoracic aorta and internal mammary arteries. In the lumbar segments (L6‐ S1) of these rigid cats, the monosynaptic reflex recorded from ventral roots was enhanced whereas the polysynaptic reflexes as well as the dorsal root reflexes were almost abolished. On morphological examination of the lumbar spinal cord, the number of interneurons was greatly reduced, whereas the small sized cells, presumably glial cells, were increased by about two times. Ventral horn motoneurons were also reduced. The lumbar spinal cords of the rigid cats were analysed for amino acid and substance P contents. Four major amino acids, aspartate, glutamate, glycine and GABA, were definitely reduced in both grey and white matter except that the glutamate level in the dorsal white was within the normal range. Content and distribution pattern of substance P were not altered in the lumbar cord of the rigid cats. These results are consistent with the notions that GABA occurs in the dorsal horn interneurons subserving primary afferent depolarisation, and that substance P is concentrated in primary afferent fibre terminals. The implications of the decrease of aspartate, glutamate and glycine in the spinal cord of rigid cats are discussed.
METABOLITE LEVELS IN BRAIN FOLLOWING EXPERIMENTAL SEIZURES: THE EFFECTS OF ISONIAZID AND SODIUM VALPROATE IN CEREBELLAR AND CEREBRAL CORTICAL LAYERS
Authors: McCandless D. W. , Feussner G. K. , Lust W. D. , Passonneau J. V.
Published: October 2006

Abstract— Levels of glucose, lactate, GABA and cyclic nucleotides were examined in discrete layers of the cerebellum and cerebral cortex of mice following treatment with the anticonvulsant, sodium valproate, and/or the convulsant, isoniazid. The concentrations of the metabolites were essentially uniform among the layers of each region, whether from control or from drug‐treated mice. Metabolite concentrations in the isoniazid‐treated mice were determined either 30 min after administration (preconvulsive state), or immediatley after the onset of seizures. Glucose and lactate, two markers of energy status in the brain, were only minimally affected by drug treatment. However, the levels of GABA and cyclic nucleotides were markedly different from control values in the drug‐treated animals. In the preconvulsive state, GABA levels in cerebellar layers were depressed and the cyclic nucleotides were elevated in most layers of both regions. At the onset of seizures, the reduction of GABA and the elevation of cyclic AMP in both regions was more pronounced than during the preconvulsive state. While the concentration of cyclic GMP remained elevated in the cerebellar layers at the onset of seizures, the level in the cerebral cortex returned to control values. Valproate elevated GABA in all the layers of both regions and decreased the cyclic GMP in the cerebellar layers. Generally, when valproate was administered in combination with isoniazid, it dampened the isoniazid induced changes in the metabolites. The events leading up to a seizure as well as those that sustain it may be reflected by the disparate responses of the metabolites in the cerebellum and cerebral cortex.
PHOSPHATE ACTIVATED GLUTAMINASE ACTIVITY AND GLUTAMINE UPTAKE IN PRIMARY CULTURES OF ASTROCYTES
Authors: Schousboe A. , Hertz L. , Svenneby G. , Kvamme E.
Published: October 2006

Abstract— Uptake and release of glutamine were measured in primary cultures of astrocytes together with the activity of the phosphate activated glutaminase (EC 3.5.1.2). In contrast to previous findings of an effective, high affinity uptake of other amino acids (e.g. glutamate, GABA) no such uptake of glutamine was observed, though a saturable, concentrative uptake mechanism did exist (Km= 3.3 ± 0.5 mm; Vmax= 50.2 ± 12.6 nmol ± min−1± mg−1). The phosphate activated glutaminase activity in the astrocytes (6.9 ± 0.9 nmol ± min−1± mg−1) was similar to the activity found in whole brain (5.4 ± 0.7 nmol ± min −l± mg−1), which may contrast with previous findings of a higher activity of the glutamine synthetase (EC 6.3.1.2) in astrocytes than in whole brain. The observations are compatible with the hypothesis of an in vivo flow of glutamate (and GABA) from neurons to astrocytes where it is taken up and metabolized, and a compensatory flow of glutamine towards neurons and away from astrocytes although the latter cell type may be more deeply involved in glutamine metabolism than envisaged in the hypothesis.
EFFECTS OF LITHIUM TREATMENT IN VITRO AND IN VIVO ON ACETYLCHOLINE METABOLISM IN RAT BRAIN
Authors: Jope Richard S.
Published: October 2006

Abstract— The effects of LiCl on cholinergic function in rat brain in vitro and in vivo have been investigated. The high affinity transport of choline and the synthesis of acetylcholine in synaptosomes were reduced when part (25‐75%) of the NaCl in the buffer was replaced with LiCl or sucrose. This appeared to be due to lack of Na+ rather than to Li+, as addition of LiCl to normal buffer had little effect.

Following an injection of LiCl (10mmol/kg, i.p.) into rats the concentration of a pulsed dose of [2H4]choline (20 μmol/kg, i.v., 1 min) and its conversion to [2H4]acetylcholine, and the concentrations of [2H2]acetylcholine and [2H0]choline were measured in the striatum, cortex, hippocampus and cerebellum. The [2H4]choline and [2H4]acetylcholine were initially (15 min after LiCl) reduced (to −30% in the cortex) and later (24 h after LiCl) increased (to + 50% in the striatum). There was a corresponding initial increase (to +50% in the cerebellum) and later decrease (to −30% in the hippocampus) of the endogenous acetylcholine and choline. These results indicate an initial decrease and later increase in the utilization of acetylcholine after acute treatment with LiCl.

Following 10 days of treatment with LiCl there was an increased rate of synthesis of [2H4]acetylcholine from pulsed [2H4]choline in the striatum, hippocampus and cortex (P < 0.05). The high affinity transport of [2H4]choline and its conversion to [2H4]acetylcholine was activated (131% of control; P < 0.01) in synaptosomes isolated from brains of 10‐day treated rats. Investigation of synaptosomes isolated from striatum, hippocampus and cortex revealed that only striatal [2H4]acetylcholine synthesis was significantly stimulated. Kinetic analysis demonstrated that the apparent KT for choline was decreased by 30% in striatal synaptosomes isolated from rats treated for 10 days with LiCl. Striatal synaptosomes from 10‐day treated rats compared to striatal synaptosomes from untreated rats also released acetylcholine at a stimulated rate in a medium containing 35 mM‐KCl. These results indicate that LiCl treatment stimulates cholinergic activity in certain brain regions and this may play a significant role in the therapeutic effect of LiCl in neuropsychiatric disorders.
A MODEL OF HIGH AFFINITY GLUTAMIC ACID TRANSPORT BY RAT CORTICAL SYNAPTOSOMES–A REFINEMENT OF THE ORIGINALLY PROPOSED MODEL
Authors: Wheeler D. D.
Published: October 2006

Abstract– In a previous publication (Wheeler & Hollingsworth, 1978), a model was presented which accounted for the role of sodium in the high affinity transport of glutamic acid in rat brain synaptosomes. Subsequent studies confirmed a lack of fit of the model to the data at the higher sodium and glutamate concentrations. The model has therefore been reexamined and refined. By removing some of the restrictions placed on the original model, a model emerges which fits the data at all sodium and glutamate concentrations with an average per cent error of only 2.14% per experimental data point. The kinetic constants describing uptake have been redefined and recalculated in accordance with this revised model.
ACETOACETATE AND d‐(‐)‐BETA‐HYDROXYBUTYRATE AS PRECURSORS FOR STEROL SYNTHESIS BY CALF OLIGODENDROCYTES IN SUSPENSION CULTURE: EXTRAMITOCHONDRIAL PATHWAY FOR ACETOACETATE METABOLISM
Authors: Pleasure David , Lichtman Craig , Eastman Sarah , Lieb Marge , Abramsky Oded , Silberberg Donald
Published: October 2006

Abstract— Oligodendroglia prepared from calf cerebral white matter were incubated with [3‐14C]aceto‐acetate (AcAc), d‐[3‐14C](‐)‐beta‐hydroxybutyrate (OHbut) or 3H2O. Addition to the medium of the ATP‐rate oxaloacetate lyase inhibitor (‐)‐hydroxycitrate diminished sterol labelling from OHbut and 3H2O, but caused 4‐fold stimulation of sterol labelling from AcAc. The discrepancy between results with the two ketone bodies indicates the existence in oligodendroglia of an extrarnitochondrial pathway for conversion of AcAc but not OHbut to acetyl CoA. Acetoacetyl CoA synthetase, the first enzyme in this pathway, was more than 20‐fold enriched in oligodendroglia over whole brain.
[1251]2α‐BUNGAROTOXIN AND [3H]QUINUCLIDINYLBENZILATE BINDING IN CENTRAL NERVOUS SYSTEMS OF DIFFERENT SPECIES
Authors: Salvaterra Paul M. , Foders Renée M.
Published: October 2006

Abstract— [125I]Diiodo α‐bungarotoxin ([125I]2BuTx) and [3H]quinuclidinylbenzilate ([3H]QNB) binding sites were measured in post‐nuclear membrane fractions prepared from whole brains or brain regions of several species. Species studied included Drosophila melanogaster (fruit fly), Torpedo californiea (electric ray), Carassius auratus (goldfish), Ram pipiens (grass frog), Kana cutesheiana (bullfrog), Rattus norvegicus (rat, Sprague‐Dawley), Mus muscalus (mouse, Swiss random, C58/J, LG/J), Oryctolagus cuniculus (rabbit, New Zealand Whitc), and Bos (cow). Acetyl‐CoA: choline O‐acetyltransferase (EC 2.3.1.6) levels were also determined in the post nuclear supernatants and correlated with the number of binding sites.

All species and regions except Drosophila had 16–150 fold more [3H]QNB binding sites than [125I]2BuTx binding sites. Brain regions with the highest levels of [125I]2BuTx binding were Drosophila heads (300 fmol/mg), goldfish optic tectum (80fmol/mg), and rat and mouse hippocampus (3040 fmol/mg). The highest levels of [3H]QNB binding were seen in rat and mouse caudate (1.3–1.6 pmol/mg). Lowest levels of [3H]QNB and [125I]2BuTx binding were seen in cerebellum. The utility of [125I]2BuTx and [3H]QNB binding as quantitative measures of nicotinic and muscarinic acetylcholine receptors in CNS is discussed.
IDENTIFICATION OF SEROTONIN WITHIN VITAL‐STAINED NEURONS FROM LEECH GANGLIA
Authors: Lent Charles M. , Ono Joyce , Keyser Kent T. , Karten Harvey J.
Published: October 2006

Abstract— We have measured serotonin (5‐HT) within large and small neurosomata which are vitally stained by Neutral Red dye. A micro‐radioenzymatic technique which is sensitive to 50fmol of 5‐HT was employed on intact ganglia, 75 μm Retzius Cells (RZ) and a 10 μm ventro‐lateral cell (VL) taken from the leech Macrobdella decora. The stain does not affect the levels of 5‐HT in either ganglia or RZ. The VL cell body contains 5‐HT at concentrations of at least 100 mm. Microspectrofluorometry of all the ganglionic neurosomata which fluoresce following the Falck‐Hillarp formaldehyde condensation reaction detected rapidly‐fading emission peaks of 509–523 nanometers. We conclude that all seven fluorescent neurons in the leech ganglion very probably contain serotonin.
MASS FRAGMENTOGRAPHY OF PHENYLETHYLAMINE, m‐ AND p‐TYRAMINE AND RELATED AMINES IN PLASMA, CEREBROSPINAL FLUID, URINE, AND BRAIN
Authors: Karoum F. , Nasrallah H. , Potkin S. , Chuang L. , Moyer‐Schwing J. , Phillips I. , Wyatt R. J.
Published: October 2006

—A mass fragmentographic method for the assay of phenylethylamine (PEA) and a number of related amines in several biological materials is described. The gas chromatographic column employed for this analysis is a 12ft 1/8 in. o.d. steel column packed with 0.5% OV22+ 2% SE54 + 1% OV210 coated on 80/100 mesh chromosorb W (HP). The mass spectral characteristics of these amines are illustrated, compared, and discussed.

Of the various monoamines which could be measured, only PEA, m‐ and p‐tyramine were detected in measurable quantities. Phenylethanolamine and p‐octopamine were found in trace amounts in urine, plasma, cerebrosponal fluid, and rat brain. No diurnal variation in the urinary excretion of PEA, m‐ and p‐tyramine was observed. Plasma concentration of PEA or p‐tyramine did not significantly change 1 h after eating a breakfast. Furthermore, consuming 200 g of Cadbury milk chocolate containing about 1 mg of PEA, 0.1 mg of phenylethanolamine and 10 mg of p‐tyramine did not significantly alter urine excretions of these three amines.

In the brain, as has been reported by others, we found that PEA and p‐tyramine are not evenly distributed and that the highest concentrations are found in the hypothalamus and caudate.

From the results obtained we concluded that PEA, m‐ and p‐tyramine are probably produced from endogenous sources and that the direct contribution of diet to their urine excretion is small.
Dissociation of Myelin from its‘Enzyme Markers’During Ontogeny
Authors: Waehneldt T. V. , Lane J. D.
Published: October 2006

: To avoid any loss of membranes, total particulate material prepared from the forebrain and spinal cord of rats of different ages was fractionated on linear sucrose gradients. Particle distribution, proteins and enzyme activities were measured. Beginning at early ages, optical density increases were observed around 0.60 m‐sucrose, which corresponded to myelin deposition, and were expressed by the appearance of typical myelin proteins, which paralleled the peak activity of myelin‐associated enzymes. During later development myelin proteins were found over a broad density range together with optical density shifts to higher (forebrain) and lower (spinal cord) values. In both regions myelin‐associated enzymes shifted to heavier densities and were dissociated from the density region commonly considered to be compacted myelin.
Stability of Bovine Adrenal Medulla Cells in Culture
Authors: Kilpatrick Daniel L. , Ledbetter Freeman H. , Carson Keith A. , Kirshner Annette G. , Slepetis Ruta , Kirshner Norman
Published: October 2006

: The functional stability of primary cultures of adrenal medulla cells was investigated. Isolated cells were prepared by treatment of bovine adrenal glands with collagenase followed by purification on Percoll density gradients and were maintained in Dulbecco's medium containing 10% fetal calf serum. Within 12 h after plating on plastic culture dishes, the cells became firmly attached and exhibited good survival for periods of time up to 3 weeks, as indicated by their morphology using light and electron microscopy, by maintenance of their content of catecholamines, tyrosine hydroxylase, dopamine‐β‐hydroxylase, and phenylethanolamine N‐methyltransferase, and their ability to respond to secretagogues. During the first 10 days to 2 weeks in culture there was little or no change in any of these parameters. During the 3rd week there were progressive losses of catecholamine and enzyme activities and increased vacuolization of medullary cells. The cells synthesized protein and RNA with no apparent loss in activities over the period studied, but did not incorporate [3H]thymidine into PCA‐precipitable material. The cells responded to secretagogues and secretory antagonists similarly to isolated perfused adrenal glands. The studies described here demonstrate that primary cultures of adrenal medulla cells provide an excellent experimental system for obtaining more detailed information on stimulus‐secretion coupling and other functional aspects of the adrenal medulla.
Phylogenetic Distribution of Neuron‐Specific Enolase
Authors: Clark‐Rosenberg R. L. , Marangos P. J.
Published: October 2006

: Neurons and neuroendocrine cells contain a unique isoenzyme of the glycolytic enzyme enolase which is not found in other cells. This acidic enolase isoenzyme has been designated neuron specific enolase or NSE and is easily identified by its elution on DEAE sephadex. The present study shows that brain tissue from species such as yeast, fish and frog do not contain appreciable amounts of acidic “NSE‐like” enolase suggesting that lower species do not have this neuronal isoenzyme.
Effects of Albumin, Amino Acids and Clofibrate on the Uptake of Tryptophan by the Rat Brain
Authors: Bloxam D. L. , Tricklebank M. D. , Patel A. J. , Curzon G.
Published: October 2006

Abstract: The influences of total tryptophan concentration, albumin binding and amino acid competition on the rate of tryptophan influx into rat brain were compared using a single‐pass injection technique with tritiated water as a freely diffusible reference. Omission of 3% bovine albumin from a bolus containing tryptophan in Krebs–Ringer bicarbonate buffer injected into the carotid artery increased non‐albumin bound (free) tryptophan concentration threefold but tryptophan uptake by only 35% and 30% into forebrain and hypothalamus, respectively. However, tryptophan uptake from injected rat plasma was more markedly elevated when free tryptophan concentration was raised. Thus, when free tryptophan was doubled, but total tryptophan unchanged, by in vitro addition of clofibrate to a plasma bolus, uptake was increased by 53% and 28% into forebrain and hypothalamus respectively. When clofibrate was injected in vivo so that plasma total tryptophan concentration was decreased by 45% but neither free tryptophan nor competing amino acid concentrations were altered, then uptake from a bolus of the rat's own plasma was unchanged. Addition of competing amino acids at physiological concentrations to tryptophan in Krebs‐Ringer buffer significantly reduced tryptophan influx into both brain regions, but did not increase the effect of albumin binding. The results indicate that tryptophan uptake into rat forebrain is substantially influenced by albumin binding and competition from other amino acids, but that hypothalamic uptake is less influenced by these factors.
Studies on the Linkage of Energy Metabolism and Neuronal Activity in the Isolated Perfused Rat Brain
Authors: Dirks B. , Hanke J. , Krieglstein J. , Stock R. , Wickop G.
Published: October 2006

An isolated rat brain preparation was perfused using glucose‐free (=aglycemic) media. The high‐energy phosphates, substrates of the glycolytic pathway, free atnino acids, acetylcholine as well as the intracellular distribution of hexokinase activity were determined in brain tissues. The EEG was evaluated visually. The levels of glycolytic substrates, glutamate, and glutamine in cortical tissue decreased after aglycemic perfusion, whereas the aspartate level increased and the GABA level remained unchanged. The high‐energy phosphate content seemed to be unaffected for about 15 min of aglycemic perfusion and fell significantly after 20 min. The EEG of the isolated brain changed rapidly after starting aglycemic perfusion and became isoelectric after 12–15 min. Hyperglycemic perfusion (35 mmol glucose per liter perfusion medium) did not alter the energy metabolism of the isolated brain. The breakdown of cerebral energy metabolism and of EEG activity was postponed when thiopental was added to the perfusion medium. The soluble hexokinase activity measured in cortical tissue was reduced after aglycemic perfusion and was enhanced after thiopental. Hyperglycemic perfusion did not influence the intracellular hexokinase distribution. The acetylcholine level in the striatum of the isolated rat brain was significantly decreased by aglycemia and was increased in hypothalamus by thiopental. It was suggested that hexokinase bound to the mitochondrial membrane may play an important role in the relationship of energy metabolism and neuronal activity.
Increase in Striatal [3H]Muscimol Binding Following Intrastriatal Injection of Kainic Acid: A Denervation Supersensitivity Phenomenon
Authors: Kuriyama Kinya , Kurihara Etsuo , Ito Yoshihisa , Yoneda Yukio
Published: October 2006

The effect of intrastriatal microinjection of kainic acid (KA) on specific binding of [3H]muscimol to the particulate fractions obtained from corpus striatum (CS), globus pallidus (GP), substantia nigra (SN), and cerebral cortex (CC) was examined. Seven days after the unilateral intrastriatal microinjection of KA, the amount of specifically bound [3H]muscimol was significantly increased at the injected site, whereas no significant alteration of [3H]muscimol binding was found in GP, SN, or CC. Scatchard analysis of striatal binding revealed that microinjection of KA significantly increased the affinity (KD) of GABA receptors on the injected (lesioned) side of the CS without affecting the total number of binding sites (Bmax) therein. This significant increase in [3H]muscimol binding, however, was eliminated by pretreating particulate fractions from the CS with Triton X‐100, a non‐ionic detergent. No statistically significant difference in amounts of [3H]muscimol binding was detected when the preparations from the KA‐treated and non‐treated CS were preincubated with 0.05% Triton X‐100, respectively. Scatchard analysis using CS preparations treated with 0.05% Triton X‐100 revealed that the affinity of the GABA receptor was increased by treatment with Triton X‐100, while the total number of binding sites (Bmax) was unchanged by this treatment. These results suggest that neuronal degeneration produced by KA in vivo and pretreatment of particulate preparations with Triton X‐100 in vitro may increase the amount of specifically bound [3H]muscimol to CS preparations by a similar molecular mechanism.
Degradation of Melanotropin Inhibiting Factor by Brain
Authors: Hui Koon‐Sea , Cheng Kwok‐Ping , Wong Ka‐Ho , Salschutz Michael , Lajtha Abel
Published: October 2006

Degradation of melanotropin inhibiting factor (MIF) was measured by fluorometry, using pareptide as an internal standard, following the separation of the dansyl derivatives of MIF and its metabolites by HPLC. MIF was not split by carboxypeptidases A and B, prolidase, or pyroglutamate aminopeptidase. It was hydrolyzed by leucine aminopeptidase, aminopeptidase M, and carboxypeptidase Y. Rat brain hydrolyzed 159 nmol of MIF per mg of protein per h; the activity was linear with enzyme concentration. Hydrolysis starts from the N‐terminal end, as shown by the appearance of proline as the first metabolite of the MIF degradation, followed by leucine, glycinamide, leucylglycine, and glycine. Activity in the rat brain regions was in the order striatum, medulla oblongata > cortex, hippocampus, midbrain > hypothalamus, cerebellum, and pituitary. The enzyme was mostly in the supernatant, with significant amounts in the myelin and synaptosomal fractions. MIF aminopeptidase could be separated from carboxypeptidase by centrifugation at 30,000 ×g for 20 min and precipitation with 45‐75% (NH4)2SO4. It showed pH optima in the alkaline range (8.25 and 8.75) and was inhibited by EDTA, EGTA, SQ 14,225, puromycin, bacitracin, and bestatin.