bluuebunny/crossref_metadata_2025 huggingface dataset:
STRIATAL METABOLISM OF DOPAMINE IN MICE MADE AGGRESSIVE BY ISOLATION
Authors: Hutchins D. A. , Pearson J. D. M. , Sharman D. F.
Published: October 2006

Abstract— Male albino mice were made aggressive by isolation. When such mice were exposed to a second mouse or placed in a fresh environment there was an increase in the concentration of 3,4‐dihydroxyphenylacetic acid, a metabolite of dopamine, in the striatum. The possibility that this might reflect an alteration in the reuptake of dopamine into dopaminergic neurons in this tissue is considered.
RELATIVE IMPORTANCE OF CHOLINE TRANSPORT TO SPONTANEOUS AND POTASSIUM DEPOLARIZED RELEASE OF ACh
Authors: Carroll P. T. , Goldberg A. M.
Published: October 2006

—The importance of extracellular choline transport to spontaneous and K+ depolarized release of ACh was studied using mouse brain cortex minces. The results suggest that extracellular choline transport is not essential to spontaneously released ACh but is essential to K+ depolarized ACh release. Similar cumulative amounts of choline and ACh were found in the incubation media following incubation of minces in either Krebs or 35 mm‐K+ Krebs suggesting the same production of free choline during both conditions. Double reciprocal plots of choline accumulation by non‐depolarized cortex minces yield high and low affinity components. Conversely, similar analysis of choline accumulation by depolarized minces yields a single Michaelis constant (68 μm) similar to the low affinity (50 μm) Michaelis constant determined for choline accumulation by non‐depolarized minces. Kinetic analysis of ACh release as a function of extracellular choline concentration during K+ depolarization also yields a Michaelis constant of 68 μm These data suggest a link between choline transport and ACh release during K+ depolarization.
TAURINE IN THE BRAIN AND LIVER OF THE DEVELOPING HUMAN AND MONKEY
Authors: Sturman J. A. , Gaull G. E.
Published: October 2006

—The concentrations of taurine in brain and liver from human fetuses (2nd trimester) and adults and from Rhesus monkeys from mid‐gestation, through birth and neonatal life to maturity have been measured. The concentration of taurine in human and monkey fetal brain was 4‐5‐fold higher than that in adult monkey brain. In human fetal brain the concentration of taurine decreased linearly with increasing crown‐rump length (r=−0·75; P < 0·001). In fetal monkey brain, no correlation with gestational age was found. After birth, the concentration of taurine in monkey brain decreased linearly with increasing age (r=−0·96; P < 0·001) until values comparable to those found in the adult were reached 8‐9 months after birth, approximately the end of weaning.

The concentration of taurine in liver both from fetal humans and from fetal monkeys was approximately twice that in mature liver. Concentrations of taurine similar to those found in adult liver were reached within a few days of birth, compared to several months for brain.

These results suggest that taurine may be associated with brain development in addition to any functional role it may play in the mature brain.
DETERMINATION OF BRAIN‐SPECIFIC ANTIGENS IN SHORT TERM CULTIVATED RAT ASTROGLIAL CELLS AND IN RAT SYNAPTOSOMES
Authors: Bock Elisabeth , Jørgensen O. S. , Dittmann L. , Eng L. F.
Published: October 2006

—The brain‐specific antigens 14·3·2, GFA, A5, F3, D1, D2, D3 and C1 were quantitated in a short‐term astroglial cell culture taken as a model of glial cells, and in synaptosomes, synaptosomal membranes and synaptic vesicles as neuronal material. Furthermore, the antigens were quantitated in newborn rat brain, as this served as the starting material for the cell culture. The membrane antigens C1, D1, D2 and D3 were absent from the cultured astroglia, indicating a neuronal origin for these antigens. C1 was enriched 3‐fold in synaptosomes and synaptosomal membranes and more than 10‐fold in synaptic vesicles indicating that this antigen might be a marker protein for nerve endings. The name Synaptin is introduced for this antigen. Conversely, the data on the antigens D1, D2 and D3 indicated that these antigens were not restricted to the synaptosomes although they were of neuronal origin. Trace amounts of the cathodal part of the heterogeneous cytoplasmic antigen 14·3·2 were present in the cell culture, possibly originating from a few contaminating neurons. The cytoplasmic antigens A5 and F3 were found both in the astroglial culture and in the synaptosomal fraction. F3, however, was found in low concentration in the synaptosomes and 3‐fold enriched in newborn rat brain compared to rat brain from 35‐day‐old rats or to 21‐day‐old brain cell cultures. It was therefore regarded as a brain specific fetal antigen. The antigen GFA was highly enriched in the astroglial culture compared to whole brain and only trace amounts were found in the synaptosomal fraction supporting the astroglial origin of this antigen.
REGIONAL DIFFERENCES IN HIGH AFFINITY CHOLINE TRANSPORT VELOCITY IN GUINEA‐PIG BRAIN
Authors: Carroll P. T. , Buterbaugh G. G.
Published: October 2006

Abstract—

The kinetic parameters of choline accumulation by synaptosomes prepared from different regions of guinea‐pig brain (cortex, brainstem, and cerebellum) were determined. Choline was accumulated by a high affinity transport process for all regions tested and the apparent Michaelis constants were similar. However, the apparent maximal velocities of choline accumulation for the brain regions differed; the differences were related to the amount of acetylcholine formed by the respective regions. The results suggested that the maximal velocity of the high affinity transport process may reflect the density of cholinergic nerve endings within brain regions.
A COMPARATIVE STUDY OF THE METABOLISM OF DE NOVO SYNTHESIZED FATTY ACIDS FROM ACETATE AND GLUCOSE, AND EXOGENOUS FATTY ACIDS, IN SLICES OF RABBIT CEREBRAL CORTEX DURING DEVELOPMENT
Authors: Carey E. M.
Published: October 2006

Abstract—

Slices of rabbit cerebral cortex, from the foetal stage to the adult have been used to compare lipid synthesis from fatty acids synthesized de novo from [U‐14C]glucose and [1‐14C]acetate, with lipid synthesis from exogenous albumin‐bound [1‐14C]palmitate. Incorporation into cellular lipid has been determined in terms of DNA, protein, wet wt. of tissue and wet weight of whole brain. On a wet wt. basis, maximum incorporation of glucose carbon into lipid occurred in the foetal brain while lipid synthesis from acetate and palmitate was maximum at 4–14 days after birth. Glucose and acetate were incorporated into a diversity of lipids (with increasing amounts of phosphatidylcholine synthesized during maturation), while palmitate was incorporated into the free fatty acid and triglyceride fractions. A greater proportion of acetate was incorporated into fatty acids of chain‐length longer than C16 compared with the incorporation of palmitate. However, on a molar basis de novo synthesized and exogenous palmitate were elongated, desaturated and incorporated into phospholipids at a similar rate, while exogenous palmitate was incorporated to a greater extent than de nova synthesized fatty acid into the triglyceride fraction. This difference in metabolism may be due to the different size of the non‐esterified fatty acid pool in the two situations. At the period of their most active formation, the very long‐chain fatty acids may be synthesized from a pool of the C18 series of fatty acids (saturated and monoenoic) not in equilibrium with the bulk of C18 acids in cerebral lipids. This could be a pool of acyl groups derived from ethanolamine phospholipids.
RAT ADRENAL DOPAMINE‐β‐HYDROXYLASE PURIFICATION AND IMMUNOLOGIC CHARACTERISTICS
Authors: Grzanna R. , Coyle J. T.
Published: October 2006

Abstract—

Dopamine‐β‐hydroxylase (DBH) was purified from rat adrenal medulla by a series of steps including sedimentation of membranes, extraction with n‐butanol, ammonium sulfate fractionation, gel chromatography and ion‐exchange chromatography. Disk gel electrophoresis revealed two protein bands, both of which were active. Antiserum was prepared against homogeneously purified bovine adrenal and rat adrenal DBH: Ouchterlony immunodiffusion, enzyme neutralization and complement fixation tests demonstrated that the respective homologous antisera were monospecific and of high titer. Antiserum to bovine DBH was only 2‐ to 3‐fold more potent than pre‐immune serum in inhibition of rat DBH activity. Complement fixation tests demonstrate that antiserum to bovine DBH has a 25,000‐fold lower immunoreactivity with rat DBH than with bovine DBH.
DISTRIBUTION AND TURNOVER RATE OF VANILLYL‐MANDELIC ACID AND 3‐METHOXY‐ 4‐ HYDROXYPHENYLGLYCOL IN RAT BRAIN
Authors: Karoum F. , Neff N. H. , Wyatt R. J.
Published: October 2006

Abstract— Vanillylmandelic acid (VMA) and 3‐methoxy‐4‐ hydroxyphenylglycol (MHPG) were measured in rat brain by a mass fragmentographic procedure. The concentration of VMA and MHPG in whole brain is 11 and 533 pmol/g, respectively. Both compounds were found in all areas of brain studied with VMA, as a percentage of both metabolites, ranging between about 1 and 8%. From the decline of the compounds after pargyline. 75 mg/kg i.p., we calculated that the rate of formation of VMA is 15 and for MHPG 202 pmol/g per h. The fractional rate of elimination of VMA and MHPG is 1.4 and 0.38 h−1, respectively. The rapid rate of loss of VMA suggests that it is transported from brain. However, we were unable to block the elimination of VMA from brain by treatment with probenecid. In contrast, the elimination of MHPG could be blocked by treatment with probenecid. Our study adds support to the notion that MHPG is a major whereas VMA is a minor product of norepinephrine metabolism in brain.
RETROGRADE AXONAL TRANSPORT OF RAPIDLY MIGRATING LABELLED PROTEINS AND GLYCOPROTEINS IN REGENERATING PERIPHERAL NERVES
Authors: Frizell M. , McLean W. G. , Sjöstrand J.
Published: October 2006

Abstract— The redistribution of rapidly migrating [3H]leucine‐labelled proteins and [3H]fucose‐labelled glycoproteins was studied in ligated regenerating hypoglossal and vagus nerves of the rabbit. When regenerating and contralateral hypoglossal nerves were ligated 16 h after labelling of the nerve cell bodies, rapidly migrating proteins and glycoproteins accumulated distal to the ligatures indicating a rapid retrograde transport from the peripheral parts of the nerves within 6 h. The retrograde accumulation of both proteins and glycoproteins was greater on the regenerating side than on the contralateral side at both 1 and 5 weeks after a nerve crush. Labelled proteins and glycoproteins also accumulated proximal to the ligatures, indicating a delayed rapid anterograde phase of axonal transport. The accumulation of this phase was also greater on the regenerating side 1 week after a nerve crush for both labelled proteins and glycoproteins. One week after a crush of the cervical vagus nerve, rapidly migrating proteins and glycoproteins redistributed between he crush zone and a proximal ligature applied 16 h after labelling of the nerve cell bodies. A retrograde accumulation occurred distal to the ligature within 6 h, indicating a rapid retrograde transport from the crush zone.
SEROTONIN BINDING PROTEIN: ENHANCEMENT OF BINDING BY Fe2+ AND INHIBITION OF BINDING BY DRUGS12
Authors: Tamir Hadassah , Klein Athalia , Rapport Maurice M.
Published: October 2006

Abstract—

The binding of serotonin to a soluble, high affinity binding protein, present in synaptosomes and associated with serotonergic tracts, has now been studied for the effects of metallic ions and various drugs. At optimal concentration (10‐4 M) of Fe2+ the enhancement of binding was close to 20‐fold. A much smaller effect was noted with Cu2+. With other ions (Fe3+, Mn2+, Co2+, Ni2+, Cr3+, Mg2+, Ca2+) little or no effect was seen. For the effect with Fe2+. preincubation was required (10 min, 25°C) and concentrations higher than 10‐4M were inhibitory. Studies based on equilibrium dialysis show that the effect of Fe2+ was on the affinity of the binding of serotonin to the protein, rather than on the binding capacity. In polydcrylamide gels at pH 8.6 the migratory properties of thc serotonin‐protein complex formed in the presence of Fe2+ differ from those of the complex formed without Fe2+. Nucleotides (ATP, GTP, ADP, AMP) inhibited thc binding. The effects of several classes of drugs (inhibitors of biogenic amine storage and uptake, psychotomimetics, MAO) inhibitors and drugs binding to contractile proteins) were also studied. The only effective inhibitors of serotonin binding were reserpine, vinblastine and CZ‐74, which caused 50% inhibition at 2 × 10‐6 M, 7.5 × 10‐6 M and 0.2 × 10‐6M respectively.
NONDIALYZABLE SULFATED SIALOGLYCOPEPTIDE FRACTIONS DERIVED FROM BOVINE HEIFER BRAIN GLYCOPROTEINS. ISOLATION, CHARACTERIZATTON AND CARBOHYDRATE‐PEPTIDE LINKAGE STUDIES1
Authors: Allen W. S. , Otterbein Elizabeth C. , Varma R. , Varma R. S. , Wardi A. H.
Published: October 2006

Abstract—

The nondialyzable sialoglycopeptides dcrived from defatted, protease digested whole boyine heifer brain tissue were isolated and characterized. The partially purified bovine heifer brain tissue were isolated and characterized. The partially purified sialoglycopeptide mixtures contained 7‐8% ester sulfate. The amount of nonsulfated material present was of the order of 15%. The total mixture was fractionated by anion exchange chromatography on AG1‐X2(CI‐) using a sodium chloride gradient to yield twelve fractions all of which contained ester sulfate to varying degrees (5.6‐21.9%).

The molecular size of the fractions ranged from molecular weights of 10,400‐12,500. The molar sulfate/galactose plus glucosamine ratios ranged from 0.3 to 1.1. Carbohydrate peptide linkage studies of the fractions by treatment with 0.2 M‐NaOH‐O.3 M‐NaBH4 led to the destruction of a portion of the threonine, serine and galactosamine and the appearance in acid hydrolysates of α‐amino‐n‐butyric acid and galactosaminitol with an increase in alanine. Partial acid hydrolysis of the most abundant sialoglycopeptide liberated detectable amounts of 2‐acetarnido‐1‐(L‐4‐aspartamido‐)‐1,2‐dideoxy‐β‐D‐ glucose. These results indicated that the GalNac at the reducing end of the alkali labile carbohydrate prosthetic groups were linked O‐glycosidically to thc hydroxyl groups of threonine and serine and the alkali‐stable region of the principal sialoglycopeptide involves N‐acetylglycosaminyl‐asparagine linkages. Mild acid hydrolysis of the alkali‐stable portion of the sulfated fractions indicated that the ester sulfate was confined to the alkali‐stable region and exists as galactose 6‐O‐sulfate and N‐acetylglucosa‐ mine 6‐O‐sulfate, structural fcatures similar to those present in rat brain glycopcptides (Markgolis & Margolis, 1970; Margoliset al.; 1972). Fucose and ester sulfate were confined to the alkali‐stable region while mannose was located in both the alkali‐labilc and alkali‐stable regions of the sialoglyco‐peptide fractions.
CENTRAL DOPAMINERGIC AND SEROTONINERGIC SYSTEMS IN THE REGULATION OF ADRENAL TYROSINE HYDROXYLASE1
Authors: Quik Maryka , Sourkes T. L.
Published: October 2006

Abstract—

Administration of the dopamine receptor agonists apomorphine, piribedil and bromocryptine caused an increase in adrenal tyrosine hydroxylase (TH; tyrosine‐3‐monooxygenase, EC 1.14.16.2) which could be partially abolished by prior injection of the dopamine blocker haloperidol. Injection of L‐dihydroxyphenylalanine, along with the decarboxylase inhibitor carbidopa, also led to a highly significant increase in adrenal TH activity. Intraventricular injection of 5,7‐dihydroxytryptamine (DHT), which destroys serotonin neurons, doubled adrenal TH activity in both normal and hypophysectomized rats. Splanchnicotomy abolished this effect of DHT. The increase in enzyme activity mediated by DHT could be partially prevented by peripheral administration of L‐5‐hydroxytryptophan together with carbidopa. Blockade of serotoninergic functions with the antagonist methiothepin also increased adrenal TH activity. The interrelationship between the dopamine and the presumed serotonin system was investigated. Intraventricular injection of 6‐hydroxydopamine partially prevented the DHT‐induced increase in adrenal TH activity. Administration of haloperidol to DHT‐treated rats had the same effect. This suggests that an intact dopaminergic system is required. When DHT and either apomorphine or piribedil were adminstered simultancously the dopamine agonist‐induced increase was potentiated. An intact serotoninergic system is therefore not required for dopamine function.

Thus, the increase in adrenal TH activity is associated with either stimulation of central dopamine receptors or destruction of serotonin neurons. It is suggested that dopaminergic and serotoninergic systems are involved in the regulation of adrenal TH and that these systems have net excitatory and inhibitory roles, respectively. Furthermore, the present evidence favors the view that the interaction between the two systems is sequential, with the serotonin system preceding the dopamine one.
HOG CEREBELLAR d‐AMINO ACID OXIDASE AND ITS HISTOCHEMICAL AND IMMUNOFLUORESCENT LOCALIZATION1
Authors: Weimar W. R. , Neims A. H.
Published: October 2006

Abstract— Hog cerebellar d‐amino acid oxidase (d‐AAO; EC 1.4.3.3) has been purified to homogeneity. The enzyme was found to be indistinguishable from crystalline hog kidney d‐AAO by a number of criteria, including electrophoresis in both cationic and anionic discontinuous buffer systems, FAD and sulfhydryl contents, and monomer molecular weights of about 40,000 as determined by SDS disc gel electrophoresis. Both preparations exhibited similar specific activities (23 μmol d‐ala oxidized min−1 mg−1 protein), substrate specificities, and susceptibilities to competitive inhibitors.

Rabbit antisera were prepared against each enzyme preparation. Double immunodiffusion revealed no antigenic differences between the two when antiserum against either preparation was used. Although a soluble protein, d‐AAO activity in cerebellum is particulate.

Two methods were utilized to study the histological localization of d‐AAO activity in hog cerebellum: peroxidase‐coupled histochemistry and immunofluorescence. The histochemical procedure seems specific for d‐AAO since l‐amino acids are inert and known competitive inhibitors of the purified flavoenzyme prevent staining. Rabbit antiserum prepared against purified hog cerebellar d‐AAO was visualized indirectly with fluorescein‐labeled goat antirabbit IgG antiserum. Control experiments with serum from unimmunized rabbits were negative.

The results of both techniques were identical in three respects: (1) d‐AAO was observed in many fibers emanating from cerebellar white matter; the white matter itself did not exhibit d‐AAO, despite presence of the oxidase by biochemical assay; (2) intense d‐AAO activity (or antigen) was found in mossy fiber rosettes (glomeruli) in the granular layer; (3) a peculiar and intense localization of d‐AAO was noted at the level of, but not within, the Purkinje cell soma. The molecular layer was essentially devoid of d‐AAO histochemical activity except for minimal staining near the pial surface. However, the more sensitive immunofluorescent technique revealed d‐AAO containing fibers in the molecular layer running parallel to each other and perpendicular to the pial surface; the relatively large size and small number of these fibers do not suggest identification as granule cell axons. No d‐AAO has been found in granule cell soma, Golgi Type‐II cells, or Purkinje cell soma. These results are discussed in terms of the localization of d‐AAO in mossy fibers and their terminals and in certain cell‐type(s) of cerebellar origin.
TRYPTOPHAN AND 5‐HYDROXYTRYPTAMINE METABOLISM IN THE IMMATURE RAT BRAIN DURING RECOVERY FROM ASPHYXIA
Authors: Tricklebank M. D. , Pickard F. J. , Dobbing J.
Published: October 2006

Abstract— The turnover of cerebral 5‐HT in the 5‐day‐old rat during recovery from asphyxia was assessed in the brain by determining 5‐hydroxyindoleacetic acid concentration, and by following the accumulation of 5‐HT after inhibition of MAO. Marked increases in turnover were found to persist for up to 3 h after resuscitation and this increase was accompanied by increases in brain tryptophan, plasma total tryptophan and the fraction of the plasma total tryptophan that was not bound to albumin. None of these parameters were different from those in control animals 24 h after resuscitation. Brain and plasma tyrosine levels remained unaltered by the treatment at all times investigated.
STRUCTURAL AND IMMUNOLOGICAL PROPERTIES OF NEURON SPECIFIC PROTEIN (NSP) FROM RAT, CAT AND HUMAN BRAIN: COMPARISON TO BOVINE 14‐3‐2
Authors: Marangos P. J. , Zomzely‐Neurath Claire , Goodwin F. K.
Published: October 2006

Abstract— Neuron specific protein (NSP) has been isolated from cat (NSP‐C) and human (NSP‐H) brain utilizing the purification procedure described for rat brain 14‐3‐2 (Marangoset al., 1975a,b,c), a protein which is now designated NSP‐R. The protein as isolated from cat and human brain has a molecular weight of approx 80,000 as determined by sedimentation equilibrium. Sedimentation studies done in the presence of 6mg‐HCl and 0.2%β mercaptoethanol yields a protomer M.W. of approx 40,000 for both preparations establishing the dimeric nature of each. The subunits appear identical in each case since one band is observed upon electrophoresis of either preparation in the presence of 8 M‐urea. NSP‐C and NSP‐H have identical isoelectric points of 4.7 making them slightly more acidic than NSP‐R (pi = 5.0).

Comparison of NSP‐C and NSP‐H with NSP‐R and bovine 14‐3‐2 by electrophoretic and immunological criteria revealed that the cat, human and bovine proteins were very similar. NSP‐R can be distinguished from the other three preparations electrophoretically and immunologically. The protomer unit of NSP‐R differs in amino acid composition from that of the cat, human or bovine proteins since the former can be completely resolved from any of the latter three preparations on 8 M‐urea polyacrylamide gels. The data indicate that NSP and bovine 14‐3‐2 are probably homologous proteins, and establish the general structural properties of NSP.
SUPEROXIDE DISMUTASE IN JUVENILE NEURONAL CEROID‐LIPOFUSCINOSIS (SPIELMEYER‐VOGT‐BATTEN'S DISEASE)
Authors: Marklund S. , Plum C. M.
Published: October 2006

Abstract— The ceroid‐lipofuscin pigments found in neuronal ceroid‐lipofuscinosis are believed to arise from lipid peroxidation‐damaged organelle membranes. In several in vitro systems superoxide dismutase inhibits lipid peroxidation. Erythrocytes and lymphocytes were prepared from ten patients with juvenile neuronal ceroid‐lipofuscinosis (Spielmeyer‐Vogt‐Batten's disease). Copper‐zinc and manganese superoxide dismutases were selectively assayed by a direct method on homogenates of the cells. No significant differences were found between the patients, neurological controls and healthy adults.
CARRIER MEDIATED BLOOD‐BRAIN BARRIER TRANSPORT OF CHOLINE AND CERTAIN CHOLINE ANALOGS
Authors: Cornford Eain M. , Braun Leon D. , Oldendorf William H.
Published: October 2006

Abstract—

Blood‐brain barrier (BBB) transport of choline and certain choline analogs was studied in adult and suckling rats, and additionally compared in the paleocortex and neocortex of adult rats. Saturable uptake was characterized by a single kinetic system in all cases examined, and in adult rat forebrains we determined a Km= 442 ± 60 μM and Vmax= 10.0 ± 0.6 nmol min‐1 g‐1. In 14–15‐day‐old suckling forebrains a similar Km (= 404 ± 88 μM) but higher Vmax (= 12.5 ± 1.5 nmol min‐1 g‐1) was determined. When choline uptake was compared in two regions of the forebrain, similar Michaelis‐Menten constants were determined but a higher uptake velocity was found in the neocortex (i.e. neocortex Km= 310 ± 103 μM and Vmax= 12.6 ± 2.8 nmol min‐1g‐1; paleocortex Km= 217 ± 76 μM and Vmax= 7.2 ± 1.5 nmol min‐1 g‐1).

Administration of radiolabelled choline at low (5 μM) and high (100 μM) concentrations, followed by microwave fixation 60 s later and chloroform‐methanol‐water separations of the homogenized brain did not suggest a relationship between concentration and the appearance of label in lipid or aqueous fractions as observed in another in‐vitro study elaborating two‐component kinetics of choline uptake. It was observed that 60s after carotid injection 12–14% of the radiolabel in the ipsilateral cortex was found in the chloroform‐soluble fraction.

Hemicholinium‐3 (Ki= 111 μM), dimethylaminoethanol (Ki= 42 μM), tetraethyl ammonium chloride, tetramethyl ammonium chloride, 2‐hydroxyethyl triethylammonium iodide, carnitine, normal rat serum, and to a lesser extent lithium and spermidine all inhibited choline uptake in the BBB. Unsubstituted ammonium chloride and imipramine did not inhibit choline uptake.

No difference was observed in blood‐brain barrier choline uptake of unanesthetised, carotid artery‐catheterized animals, and comparable sodium pentobarbital‐anesthetized controls.
BLOCKADE OF FAST AXONAL TRANSPORT BY DIPHTHERITIC DEMYELINATION IN THE CHICKEN SCIATIC NERVE
Authors: Kidman Antony D. , Dolan Louise , Sippe H. Jane
Published: October 2006

Abstract—

Chicken sciatic nerves undergo demyelination following intraneural injection of diphtheria toxin due to a lesion at the site of injection. Paresis occurs after 1 week and lasts for approx 3 weeks; at the height of the lesion we injected [14C]Ieucine into the ventral horn cells of the spinal cord and followed the axonal transport of fast flowing labelled proteins down the sciatic nerve fibres making measurements of flow rates at two different times. The results showed the fast flowing labelled proteins were blocked at the demyelination site. We measured total protein in the nerves and examined them histologically to confirm the lesion. Further studies are in progress on the post synaptic muscle cells and the impaired nerves.
SOME PROBLEMS INHERENT IN TRANSPORT STUDIES IN SYNAPTOSOMES
Authors: Wheeler D. D.
Published: October 2006

Abstract—

A technique utilizing a 30‐place manifold has been developed to study synaptosomal transport; some problems associated with such studies have been identified and clarified. The time course of L‐glutamic acid uptake has been used to test variations in experimental protocol.

Synaptosomes apparently become increasingly labile with increased time of incubation. This is indicated by a drop in the curve of uptake vs time after 8–12 min. Ninety seven to 98% of the glutamate taken up from a 10−6m solution is released by osmotic shock.

Synaptosomes can be stored in 0.32 m ice‐cold sucrose suspension for periods up to 50 min without decline in measured uptake. Storage for 3 h or more results in a very substantial decline in measured uptake. Neither the decline in measured uptake with time, nor the decline with storage, is prevented by increasing the osmolarity of the solutions used or by use of synaptosomes from the initial 1085 g supemate rather than after sedimentation and resuspension. Although prewarming synaptosomes at 30°C for 20 min prior to their use lessened or eliminated the decline following peak uptake, the difference between stored and non‐stored synaptosomes was not improved. Uptake was also much less when synaptosomes were used from the first supernate or when warmed prior to their use. Storage of tissue prior to homogenization resulted in synaptosomes that gave minimal reductions in measured uptake.

Washing synaptosomes after separation from incubation medium resulted in a variable loss of substrate radioactivity, depending on such variables as brand of filter, pore size, composition of wash solution, and temperature of wash solution. The results support the hypothesis that washing causes lysis of a portion of the synaptosomes. However, with Millipore filters (0.45 μm) and a 30°C Krebs‐Henseleit wash solution, the loss caused by washing is minimized (about 15%).

Measured uptake is found to depend on the type of filter used. Uptake is much greater with Millipore 0.45 pm filters than with Gelman 0.45 μm filters. Use of Nuclepore (0.4 μm) filters results in measured uptakes only about 5% of that when Millipore 0.45 μm filters are used. With Millipore filters, 0.30 μm pore size filters gave uptakes only 68% of that using 0.45 pm pore size filters.
EFFECTS OF AMMONIUM IONS ON SPONTANEOUS ACTION POTENTIALS AND ON CONTENTS OF SODIUM, POTASSIUM, AMMONIUM AND CHLORIDE IONS IN BRAIN IN VITRO
Authors: Benjamin A. M. , Okamoto K. , Quastel J. H.
Published: October 2006

Abstract—

The effects of ammonium ions on the frequency of spontaneous action potentials in guinea‐pig cerebellar slices, recorded with an extracellular microelectrode, and on the contents of sodium, potassium and chloride ions in incubated guinea‐pig cerebellar, and rat brain cortex, slices have been investigated. The frequencies of the spontaneous action potentials are partially suppressed by concentrations of NH4Cl less than 2 mm and completely abolished by concentrations exceeding 2 mm. The amplitudes of the spike discharges are unaffected. A lag period of at least 15 s precedes the inhibition. The suppressing action of NH on the spike frequency is reversible, as shown by complete recovery on removal of NH after short time intervals. Deficiency of Cl− in the superfusion medium causes conversion of inhibition by NH to excitation. Reduction of [K+], or of [Na+], causes increase of inhibition by NH in a normal [Cl1], and reduction of excitation in a low [Cl1], medium. The inhibitory effects of NH on spike frequency are unaffected by picrotoxin or strychnine. NH4Cl, even at 1 or 2 mm, causes a significant increase of aerobic glycolysis. It is suggested that the lag period preceding the suppression of the frequency of spike discharges by NH is partly due to a metabolic change induced by NH, perhaps a transient lowering of pH in the responsible neurons, causing changed permeability to Cl− and possibly to K+ and Na+, NH promotes, in guinea‐pig cerebellar slices, an inward flow of Na+ and an outward flow of K+, the latter being greater than that due to exchange of K+ for NH. NH4Cl at 1 or 2 mm causes an outward flow of K+ and an inward flow of Cl− in rat brain cortex slices. The movement of Cl− is biphasic, the first phase, seen with low [NH], consisting of an increase of tissue content of Cl− with little or no fluid uptake and a second phase, seen with high (> 5 mm) concentrations of NH, in which the uptake of Cl− is directly proportional to the fluid uptake. It is suggested that the first phase is largely neuronal in location whilst the second is largely glial. In infant rat brain cortex slices, there seems to be predominantly an equal exchange of NH for K+. There is little evidence of energy assisted concentrative uptake of NH by brain slices and this is thought to be due largely to the rapid diffusion of undissociated NH3 across cell membranes. It is suggested that some NH (amounting to about 2 mequiv/1) may be bound in the brain. It is concluded that changes in ionic permeabilities, particularly that of Cl−, partly due to a metabolic action, may be responsible for some of the acute cerebral effects of NH administration.
NEURONAL PIGMENTS: SPECTROSCOPIC CHARACTERIZATION OF HUMAN BRAIN MELANIN
Authors: Das K. C. , Abramson M. B. , Katzman R.
Published: October 2006

Abstract— A method has been established for the characterization of synthetic melanins obtained from dopamine, norepinephrine, and structurally related compounds which permits the identification of the precursor substrate of the melanin. This is done by interpreting the absorption spectra and the first derivative curves of these melanins solubilized in sodium borohydride. Using this method, the melanin pigment obtained from the substantia nigra of human brain has been shown to be very similar to dopamine‐melanin and not DOPA‐ or norepinephrine‐melanins.
NEURONAL AND NEUROPIL FRACTIONS FROM DEVELOPING RAT BRAIN
Authors: Sinha A. K. , Rose S. P. R. , Sinha L. , Spears D.
Published: October 2006

Abstract— A method is described for the preparation of enriched fractions containing isolated neuronal and glial cells from brains derived from 1 to 20‐day‐old rats. The method is based on mechanical disaggregation in a medium containing Ficoll‐PVP followed by centrifugation on a single‐stage two‐step gradient at 13,000g for 30min. The neuronal and neuropil (glial) fractions are approx 70–80% pure in cellular terms.

The cells showed well‐preserved cytoplasmic and nuclear morphology at the light and electron microscope level and between 70 and 80% excluded trypan blue. Despite changes in the total cell population with age due to glial proliferation, the proportionate recovery of cells in the separated fractions was fairly constant: based on DNA determination, 23 and 29% of all neurons and 15 and 17% of glia were recovered in the purified fractions from Day 1 and Day 20 animals respectively.

Changes in neuronal cell size with age were reflected in a 2.5‐fold increase in protein recovered in the neuronal fraction per mg DNA. Protein and RNA levels/mg DNA in the neuropil fraction reached a maximum at Day 10. It is concluded that the method produces a defined and reliable purification of cells in the separated fractions throughout the studied age range and therefore provides a sound basis for studies on the distribution of biochemical systems between cell types during post‐natal development.
CORRELATION OF PLASMA AND BRAIN AMINO ACID AND PUTATIVE NEUROTRANSMITTER ALTERATIONS DURING ACUTE HEPATIC COMA IN THE RAT
Authors: Mans A. M. , Saunders S. J. , Kirsch R. E. , Biebuyck J. F.
Published: October 2006

Abstract—

During acute hepatic coma following two‐stage hepatic devascularization in the rat, profound changes occurred in plasma and whole‐brain amino acids and putative neurotransmitters. Brain ammonia, glutamine and GABA were increased, aspartate was decreased, while glutamate was unchanged. An increase in brain tryptophan was accompanied by a similar increase in plasma unbound tryptophan but decreased plasma total tryptophan. These changes occurred in the presence of high plasma levels of the other neutral amino acids, including the branched chain amino acids. Plasma insulin was unchanged while glucagon levels rose, resulting in a decreased insulin to glucagon ratio. These results suggest that while plasma unbound tryptophan may influence brain tryptophan levels, altered plasma concentrations of neutral amino acids which compete with tryptophan for transport into the brain do not contribute to the increase in brain tryptophan observed during acute hepatic coma.
GABA CONTENT OF DISCRETE BRATN NUCLEI AND SPINAL CORD OF THE RAT
Authors: Van der Heyden J. A. M. , de Kloet E. R. , Korf J. , Versteeg D. H. G.
Published: October 2006

Abstract– The GABA content of the spinal cord and of approx 70 discrete rat brain nuclei is measured with a simple rapid semi‐automated fluorimetric assay, after prevention of post‐mortem effects with 3‐mercaptopropionic acid. We found that microwave irradiation produced decreases in the GABA contents of the microdissected zona reticulata of the substantia nigra, indicating that microwave fixation is not suitable to measure GABA levels in microdissected brain nuclei. In approx 70% of the nuclei in the anterior half of the brain the GABA concentration was found to be between 41 and 90nmol GABA/mg protein. The GABA content varied from 11 to 40 nmol GABA/mg protein in the posterior half of the brain. High GABA levels were found in some hypothalamic nuclei, the globus pallidus and eminentia mediana. An extremely high GABA level was found in the zona reticulata of the substantia nigra. GABA is unevenly distributed in the striatum. The highest concentration was found in the caudal part and in the ventral region at any level of the striatum. In the spinal cord the highest concentration of GABA was in the sacral region.
EFFECTS OF DIETARY PROTEINS ON FETAL BRAIN PROTEIN AND GLUTAMIC ACID METABOLISM IN RAT
Authors: Prasad Chandrika , Devi Ram , Agarwal K. N.
Published: October 2006

Abstract— The effects of feeding dietary wheat and Bengal gram proteins to pregnant rats on brain protein and glutamic acid metabolism in 15‐, 17‐ and 19‐day fetuses were investigated. Wheat and Bengal gram diets resulted in loss of brain weight with decreased DNA, RNA, protein, free x amino N and deficits in the activities of brain glutamine synthetase, glutaminase I. glutaminase II and glutamate decarboxylase at all the gestational ages studied without any change in glutamine transferase activity. The concentrations of the amino acids alanine, glutamic acid, glutamine and GABA were found to be significantly lower on wheat and Bengal gram diets than the control on a 10% casein diet. The wheat with lysine and Bengal gram with methionine, cystine and tryptophan resulted in similar mean values of all the characteristics studied to the mean values observed in rats on the control diet. However, glutaminase I activity remained significantly low on lysine fortified wheat diet, and aspartic acid content was found to increase on both fortified and unfortified wheat and Bengal gram diets. A 20% casein diet showed increased brain weight, DNA. RNA. protein and free x amino N concentrations as compared with the 10% casein diet, while the other parameters remained unchanged.
RELATIONSHIP BETWEEN Ca2+‐DEPENDENT AND INDEPENDENT RELEASE OF [3H]GABA EVOKED BY HIGH K+, VERATRIDINE OR ELECTRICAL STIMULATION FROM RAT CORTICAL SLICES
Authors: Szerb John C.
Published: October 2006

Abstract— It has been reported that the release of GABA by high K+ is Ca2+‐dependent while release induced by veratridine or electrical stimulation has been frequently found to be independent of Ca2+. To see the source of Ca2+‐dependent and independent release of GABA, cortical slices which had accumulated [3H]GABA were exposed to 50 mm‐K+ or 50 μm‐veratridine for 48min. In the presence of Ca2+ the 2 agents released approx the same amount of [3H]GABA but tetrodotoxin (TTX) abolished release induced only by veratridine, while omission of Ca2+ reduced release induced only by 50mm‐K+. Pre‐exposure of the slices for 48min to 50mm‐K+ in the presence of Ca2+ reduced the second release by 50mm‐K+ by 77% and that by veratridine by 74%, suggesting that in the presence of Ca2+ the 2 depolarizing agents release [3H]GABA from the same pool. Pre‐exposure to 50mm‐K+ in the absence of Ca2+ reduced the second release by 50mm‐K+ or by veratridine only by 37 and 27% respectively, indicating that most of the reduction in release was the result of a depletion of releasable [3H]GABA stores. The second exposure to 50mm‐K+ in the absence of Ca2+ reduced the evoked release further, while exposure to veratridine in the absence of Ca2+, after depletion of the stores, enhanced release 2.7 times. Electrical stimulation (64 Hz, 2 ms, 40 mA, alternating polarity) during 24min in the presence of Ca” caused an initial 5‐fold increase in efflux, which declined subsequently. In the absence of Ca2+, instead of a rapid increase, a slow but smaller increase in the efflux of [3H]GABA was found. TTX almost completely abolished the electrically evoked increase in release. Pre‐treatment with 50mm‐K+ reduced the electrically evoked release by 94% but electrical stimulation in the absence of Ca2+ after depletion of releasable stores doubled this release. Results suggest that in the presence of Ca2+, high K+, veratridine and electrical stimulation release [3H]GABA from the same Ca2+‐dependent store, but in the absence of Ca2+ veratridine and electrical stimulation enhance the release from a Ca2+‐independent store, probably as a result of an increased influx of Na+.
Newborn Rabbit Blood–Brain Barrier Is Selectively Permeable and Differs Substantially from the Adult
Authors: Braun Leon D. , Cornford Eain M. , Oldendorf William H.
Published: October 2006

Abstract: Examination of blood‐brain barrier (BBB) function by the intracarotid injection technique has been utilized in studies of newborn (6–30 h) and adult rabbits. The exclusion of mannitol (mol. wt. 182), dextran (mol. wt. 60,000–90,000) and indium‐bound EDTA indicate that the newborn BBB has restrictive properties similar to the adult. At birth, saturable, carrier‐mediated transport mechanisms are present, regulating the entry of glucose, amino acids, organic acids, purines, nucleosides and choline. No difference in brain uptake of glucose was observed between adult and newborn, but considerably higher uptake rates for arginine, choline and adenine were seen in the newborn. In contrast to suggestions of an immature barrier in young animals, these studies indicate that a sophisticated, selective BBB is operative at birth. Furthermore, the specific selectivity and dramatic increases seen for certain metabolites imply a vital function in the newborn for these carrier systems.
Temperature Coefficients for the Oxidative Metabolic Responses to Electrical Stimulation in Cerebral Cortex
Authors: LaManna Joseph C. , Rosenthal Myron , Novack Roger , Moffett David F. , Jöbsis Frans F.
Published: October 2006

Abstract: Temperature coefficients of both cat and toad brain have been calculated for the active metabolic state induced by electrical stimulation. Values are higher than most of the values previously reported for “rest” metabolism, whether calculated from Arrhenius plots or from linear graphs. Relative rates of oxidative metabolism were obtained by measuring the time course of the transient changes in NADH fluorescence and cytochrome aa3 absorption by reflectance techniques directly from the surface of the exposed cat cerebral cortex in vivo and from the isolated intact toad brain mounted in a cuvet. These findings demonstrate that such optical methods accurately record metabolic processes.
Aminophospholipid Asymmetry in Murine Synaptosomal Plasma Membrane
Authors: Fontaine Robert N. , Harris R. Adron , Schroeder Friedhelm
Published: October 2006

The asymmetric distribution of aminophospholipids in isolated murine synaptosomal plasma membranes was determined by a chemical labeling procedure. Under nonpenetrating conditions, mouse brain synaptosomes were reacted with trinitrobenzenesulfonic acid (TNBS) to label outermonolayer aminophospholipids covalently. About 10‐15% of the phosphatidylethanolamine and 20% of the phosphatidylserine were found to be in the outer monolayer of the synaptosomal plasma membrane. Furthermore, the fatty acyl group composition of the labeled phosphatidylethanolamine (outer monolayer) consisted of more saturated fatty acid than did the unlabeled phosphatidylethanolamine (inner monolayer). These results demonstrated an aminophospholipid asymmetry in synaptosomal plasma membranes which was independent of serum‐lipoprotein exchange processes and also of phosphatidylethanolamine‐methylatingenzymes.
Influx of γ‐Aminobutyric Acid and α‐Aminoisobutyric Acid into Mouse Cerebrum Slices Incubated in a Pyruvate Medium with or without Added Glucose or Glucose Analogues Compared with Influx from a Glucose Medium
Authors: Cohen Stephen R.
Published: October 2006

Concentrative influx of γ‐aminobutyric acid (GABA) and α‐aminoisobutyric acid (AIB) into incubated mouse cerebrum slices is decreased when pyruvate is substituted for glucose. Influx of GABA from pyruvate medium is not increased by presence of glucose, 2‐deoxy‐d‐glucose (2‐DOG), or 3‐O‐methyl‐d‐glucose (3‐O‐MeG). Influx of AIB is restored to the rate from glucose medium if 2‐DOG is present initially, but is not restored if 2‐DOG is added with AIB. Influx is not restored if 3‐O‐MeG is present initially, but is restored if 3‐O‐MeG is added with AIB. Influx is restored if glucose is present initially or is added with AIB.
Elevated Monoamine Levels in the Cerebral Hemispheres of Microencephlic Rats Treated Prenatally with Methylazoxymethanol or Cytosine Arabinoside
Authors: Matsutani T. , Nagayoshi M. , Tamaru M. , Tsukada Y.
Published: October 2006

Abstract: Methylazoxymethanol (MAM) injection to rats on day 15 of gestation caused a significant rise in monoamine concentrations (1.6, 2.0, and 2.8 times the control value for serotonin, norepinephrine, and dopamine, respectively) accompanying a decrease in the brain weight and DNA content in the cerebral hemispheres of the offspring at 3 months of age; in the brain stem, these changes were much smaller. Similar change of monoamine concentrations was observed in cytosine arabinoside‐induced microencephaly. The decrease of DNA content and the elevation of monoamine levels were lower with MAM injection on day 15, 13, or 17 of gestation (in that order). Serotonin content of the MAM‐treated cerebral hemispheres was already 50% higher than the control immediately after birth. The activity of tryptophan hydroxylase in the MAM‐treated cerebrum was 1.6 times the control value, with no change in the brain stem, while the concentration of tryptophan in the brain and plasma was equal to the control value, suggesting an important role played by this enzyme in the elevation of serotonin content. Although the marked decrease of DNA content in the cerebral hemispheres of MAM‐treated rats indicates a loss of cerebral cells due to prenatal MAM poisoning, the kind of cells destroyed remain to be studied. That the remaining neurons, axons, and oligodendroglia were intact was suggested by the normal activity of CNPase.
The In Vitro Synthesis of RNA within the Rat Nodose Ganglion Following Vagotomy
Authors: Langford C. J. , Scheffer J. W. , Jeffrey P. L. , Austin L.
Published: October 2006

Abstract: This report describes the application of an in vitro labelling procedure for the evaluation of changes in the uptake and incorporation of tritiated nucleotides into RNA of the rat nodose ganglion following crush injury of the cervical vagus nerve. Significant changes in the incorporation into 28S, 18S and 4S RNA were observed at 3 and 9 days after injury which confirms and extends our previous in vivo observations where [32P]orthophosphate was used as the precursor. An early stimulation in the uptake of nucleotides, which was maximal at 2 days after injury, was also observed. Evidence is presented which indicates that this data reflects a real increase in RNA synthesis within the injured tissue concomitant with an increase in the uptake of nucleotide precursors which may reflect an increase in the nucleotide pool size. The transient nature of the rRNA synthetic responses and their occurrence prior to the peak of the chromatolytic changes suggest that there may be a shift in the distribution of ribosome types resulting in qualitative changes in protein production rather than an overall increase in protein synthesis resulting from an increased ribosome population.
Dopaminergic Mechanisms in the Teleost Retina
Authors: Watling Keith J. , Dowling John E.
Published: October 2006

Abstract: A specific dopamine‐sensitive adenylate cyclase has been identified in homogenates of the teleost (carp) retina. Maximal stimulation by 100 μM‐dopamine resulted in a 5‐10‐fold increase in adenylate cyclase activity with half‐maximal stimulation occurring at a concentration of 1 μM. l‐Noradrenaline and l‐adrenaline were some 10 times less potent than dopamine whilst the α‐and β‐adrenoreceptor agonists, l‐phenylephrine and dl‐isoprenaline were inactive. Apomorphine elicited a partial stimulation of adenylate cyclase activity whilst various ergot alkaloids produced mixed agonist/antagonist responses. Dopamine‐stimulated adenylate cyclase activity was potently antagonised by various neuroleptic drugs including fluphenazine, α‐flupenthixol and α‐piflutixol, and to a lesser extent by the butyrophenone derivatives haloperidol and spiperone. The benzamide derivatives, metoclopramide and sulpiride. together with the α‐ and β‐adrenoreceptor blocking agents, phentolamine and propranolol respectively, were essentially inactive at blocking dopamine‐stimulated adenylate cyclase activity. These data suggest the presence of a highly specific dopamine‐sensitive adenylate cyclase in homogenates of teleost retina possessing similar pharmacological properties to the dopamine‐sensitive adenylate cyclase observed in the mammalian central nervous system.