bluuebunny/crossref_metadata_2025_split huggingface dataset:
A NEW INCUBATION TECHNIQUE FOR THE STUDY OF SYNAPTOSOMAL TRANSPORT
Authors: Hwang Shing‐Mei , Roth Karl S. , Segal Stanton 
Published: October 2006

Abstract—A simple, inexpensive method is described for the incubation and study of transport in synaptosomes. This method avoids the many potential sources of error inherent in the methods currently in use. The transport of two sugars and two amino acids has been studied, using this system, and the resulting data is compared to similar studies already published by others. A steady‐state was achieved and maintained for 60 min independent of tissue concentration, except in the case of γ‐aminobutyric acid. An analysis of the entry kinetics of 2‐deoxy‐d‐glucose has been performed, the results indicating that the present method offers the advantage of substantially increasing oxygenation and hence, efficiency of the uptake. Using α‐aminoisobutyric acid, analysis of substrate flux within the system was performed, illustrating the utility of the method. The specific advantages offered by the technique over other methods in use are discussed. It is concluded that adequate oxygenation of the synaptosome during study is essential to reliable results and can easily be achieved by means of the methodology described in this report.
RAT AND MOUSE BRAIN HISTAMINE N‐METHYLTRANSFERASE: MODULATION BY METHYLATED INDOLEAMINES1
Authors: Sellinger O. Z. , Schatz R. A. , Ohlsson W. G. 
Published: October 2006

Abstract—A purification procedure for rat and mouse brain histamine N‐methyltransferase (HMT, EC 2.1.1.8) is described which achieves the preparation of 87‐fold purified rat brain and 166‐fold purified mouse brain enzyme. The purified HMT (MW 29,000) is inhibited by a number of physiologically and pharmacologically active amines, among them several methylated indoleamines, at concentrations above 5 ± 10‐6M. At concentrations below 1 ± 10‐7M, most of the methylated indoleamines stimulate HMT, provided histamine is maintained at, or close to, its optimal concentration as an HMT substrate, namely 1 ± 10‐5M. A study of the nature of the inhibitory process revealed a non‐competitive inhibition of HMT by dopamine as against a competitive inhibition of the enzyme by most methylated indoleamines. Increasing the concentration of histamine beyond the optimal value, i.e. to inhibitory levels, resulted in less stimulation. The findings support the notion that MSO elicits the formation in selected brain cells of supranormal amounts of several methylated indoleamines which are able to stimulate HMT (and possibly other methyltransferases, see Salaset al., 1977), thereby causing the depletion of the cerebral levels of S‐adenosyl‐L‐methionine, reported previously (Schatz & Sellinger, 1975b).
ACTIVATION OF GUANYLATE CYCLASE IN SYNAPTIC PLASMA MEMBRANES OF CEREBRAL CORTEX BY FREE FATTY ACIDS
Authors: Asakawa T. , Takenoshta M. , Uchida S. , Tanaica S. 
Published: October 2006

Abstract—Guanylate cyclase (EC 4.6.1.2) of synaptic plasma membranes of rat cerebral cortex was stimulated about 6‐fold by several unsaturated fatty acids (arachidonic, linolenic, linoleic, oleic, palmitoleic and myristoleic acid). Ricinoleic acid (12‐hydroxyoleic acid) was much less effective. Saturated fatty acids (C10 and C14‐C20) and the methylester of linoleic acid were ineffective. Stimulation by linoleic acid was influenced by the concentration of enzyme protein. At 480 μg/ml of protein 0.6 mm‐linoleic acid produced maximal activation of 6‐fold_ Activity stimulated by linoleic acid examined with 1.0 mm‐GTP was maximal at pH 7.8‐7.9 and with 2 mm‐MnCl2, whereas basal activity showed broad optimal pH and Mn2+‐concentration dependence. Activation of the enzyme by linoleic acid was only partially reversed by washing. Particulate guanylate cyclase of heart, small intestine, adrenal medulla, liver and lung was also activated by linoleic acid. The extents of activation (1.5‐14.7‐fold) by linoleic acid and the concentrations (0.2‐1.0 mat) required for maximal activation depended on the tissues.
HYPEROSMOLALITY‐INDUCED GABA RELEASE FROM RAT BRAIN SLICES: STUDIES OF CALCIUM DEPENDENCY AND SOURCES OF RELEASE
Authors: Chan P. H. , Wong Y. P. , Fishman R. A. 
Published: October 2006

Abstract— The effects of hyperosmolal superfusion upon the release of preloaded, radio‐labeled GABA has been studied, using both first cortical and first pontine brain slices. GABA release was stimulated with either hyperosmolal Na+ or sucrose superfusion in cortical slices. This stimulated release of radio‐labeled GABA was partially Ca2+‐dependent in cortical slices. When barium ions replaced Ca2+ in hyperosmolal medium, a similar effect was seen. High concentration of magnesium in Ca2+ ‐free hyperosmolal medium did not induce stimulation. The increased release of α‐aminoisobutyric acid (AIBA), a non‐metabolized amino acid induced by hyperosmolality, was not Ca2+‐dependent.GABA release was also stimulated with hyperosmolal sucrose superfusion in pontine slices. The effect of pre‐treatment of cortical and pontine slices with β‐alanine or L‐2,4‐diaminobutyric acid (DABA) was used to study the source of exogenous GABA release induced by hyperosmolality. In cortical slices, β‐alanine blocked the hyperosmolal release of GABA and also slightly inhibited GABA uptake. DABA did not change hyperosmolal GABA release, although it inhibited GABA uptake. In pontine slices, both DABA and β‐alanine inhibited GABA uptake, but were unable to inhibit the hyperosmolal release of GABA.The data suggest that hyperosmolality causes increased release of GABA from neurons, analogous to that seen with K+‐depolarization. AIBA, unlike GABA, is released from brain cells as a non‐Ca2+ ‐dependent response to osmotic equilibration. The observation that pre‐treatment with β‐alanine inhibits the hyperosmolal release of GABA suggests that hyperosmolality alters glial cell function.
PURIFICATION AND PROPERTIES OF CHOLINE ACETYLTRANSFERASE FROM TORPEDO CALIFORNICA
Authors: Brandon Christopher , Wu Jang‐Yen 
Published: October 2006

Abstract— Choline acetyltransferase (ChAT), the enzyme responsible for the biosynthesis of acetylcholine in nervous tissue, has been purified to apparent homogeneity from the electric organ of the electric fish Torpedo californica using ion‐exchange, gel filtration, and hydroxyapatite chromatography. The final preparation had been purified 8570‐fold to a specific activity of 30μmol ACh formed/min/mg protein. The purified protein has a pH optimum of 6.8 (phosphate buffer), is activated by low concentrations (ca. 10 mm) of ammonium or alkylammonium ions, and is strongly inhibited by a sulfhydryl blocking reagent (DTNB). ChAT has a mol. wt. of 63000 when measured by SDS‐polyacrylamide gel electrophoresis or gel filtration.A new method for the rapid assay of ChAT activity is described in which unreacted substrate ([3H]acetyl‐CoA) is removed from reaction mixtures by adsorption to charcoal: some advantages of this technique are discussed.
α‐TOXIN BINDING PROTEINS IN THE ELECTRIC ORGAN OF TORPEDO MARMORATA STUDIED BY IMMUNOCHEMICAL METHODS
Authors: Mattsson C. , Heilbronn E. , Ramlau J. , Bock E. 
Published: October 2006

Abstract——Crossed immunoelectrophoretic techniques were developed to study the efficiency of the various purification steps in the isolation of nicotinic acetylcholine receptor (nAChR) from Torpedo mormorata electric organ. A new α‐neurotoxin binding assay based on immunoelectrophoresis is also presented. In crude extracts of Torpedo electric organ membranes one type of receptor molecule (M ñ; 300, 000) was found; an earlier described higher molecular form was shown to be an artifact of affinity chromatography.Polyvalent antibodies against Torpedo electroplaque membranes, antibodies against purified membrane proteins and against Naja naja siamensisα‐neurotoxin revealed four α‐neurotoxin binding antigens (including nAChR). Two of these, nAChR and T2, were specific for electroplaque membrane and showed partial immunoidentity but different biochemical and physical properties.
POSTMORTEM AUTOLYTIC RESPONSE IN RAT BRAIN LYSOSOMES
Authors: McKeown Stephanie R. 
Published: October 2006

Abstract—Rat cerebral lysosomes were investigated during postmortem autolysis to determine the effect of the length and temperature of storage. A lysosome enriched fraction was isolated by differential ultracentrifugation and there was found to be a progressive increase in fragility as the length of storage increased. However, those lysosomes which survived the homogenisation procedure exhibited similar properties for at least 6 h after death if storage was at 21°C. Changes apparent after further storage for 18 h at 4°C were also detected in a shorter period if the temperature of storage was increased. The results suggest that, coupled with an all‐or‐none rupture of the lysosomes, there is a small increase in the permeability of the lysosomes shortly after death. In many respects the characteristics of the intact lysosomes up to 6 h after death resemble those obtained immediately.
COMPARATIVE PEPTIDE MAPPING AND ISOELECTRIC FOCUSING OF ISOLATED SUBUNITS FROM CHICK EMBRYO BRAIN TUBULIN
Authors: Nelles Lynn P. , Bamburg James R. 
Published: October 2006

Abstract—The α‐ and β‐subunits of chick embryo brain tubulin have been isolated under denaturing conditions and compared with respect to their molecular weight, amino acid composition, tryptic peptide maps, amide content and isoelectric focusing properties. An 8 M‐Urea‐containing polyacrylamide gel system with varying acrylamide concentrations was used for calculation of the retardation coefficients (KR) of the tubulin subunits. A molecular weight of 53,000 was estimated for each subunit by comparison to KR values for standard proteins. Amide contents of approx 41% of the carboxyl groups of α‐tubulin and 48% of the carboxyl groups of β‐tubulin were calculated using the average PI value, the pKintrinsic for the ionizable side chains of the amino acids and the amino acid composition of each subunit. Comparative peptide maps of trypsin digested α‐ and β‐tubulin demonstrated 16 peptides unique to each subunit and 23 peptides which comigrate. Both subunits give rise to multiple species on electrofocusing gels. The average isoelectric points for the α‐ and β‐subunits are 5.4 and 5.2, respectively.
STEADY STATE MAINTENANCE OF ELECTROLYTES IN THE SPINAL CORD OF THE FROG
Authors: Bianchi C. Paul , Erulkar S. D. 
Published: October 2006

AbstractIsolated frog spinal cords equilibrated from 3 to 24 h in Ringer's solution maintained steady state conditions with regard to electrolyte composition. Total sodium and chloride contents measured on the same spinal cords were found to be nearly equivalent (Na = 46.6 ± 1.4μmol/g wet wt vs Cl = 46.2 ± 1.2μmol/g wet wt). Calcium and magnesium contents were 3.0 ± 0.5 and 4.8 ± 0.2pμol/g wet wt respectively for fresh spinal cords and 2.1 ± 0.4 and 5.5 ± 0.9pmol/g wet wt respectively for spinal cords equilibrated for 24 h. Zinc content was 0.29 ± 0.01 μmol/g wet wt. Insulin space was found to be smaller than sucrose space (0.24 ml/g vs 0.37 ml/g). Sodium and chloride spaces were slightly higher than sucrose space. Sodium and chloride in the non‐sucrose space was 4.8 and 9.5 μmol/g wet wt. Residual radioactive sodium, or sodium content of spinal cords washed out for 180 min in non‐radioactive Ringer's solution or in choline or lithium Ringer's solution, was 4.2 ± 0.4μmol/g wet wt (n = 9). The agreement between residual sodium content and sodium in the non‐sucrose space suggests that the mean intracellular sodium content of the spinal cord neurons is low.
ACTION OF THE NEUROTOXIN KAINIC ACID ON HIGH AFFINITY UPTAKE OF l‐GLUTAMIC ACID IN RAT BRAIN SLICES
Authors: Johnston G. A. R. , Kennedy Sue M. E. , Twitchin B. 
Published: October 2006

AbstractKainic acid is a linear competitive inhibitor (Kis 250 μm) of the ‘high affinity’ uptake of l‐glutamic acid into rat brain slices. Kainic acid inhibits the ‘high affinity’ uptake of l‐glutamic, d‐aspartic and l‐aspartic acids to a similar extent. Kainic acid is not actively taken up into rat brain slices and is thus not a substrate for the ‘high affinity’ acidic amino acid transport system or any other transport system in rat brain slices. Kainic acid (300 μm) does not influence the steady‐state release or potassium‐stimulated release of preloaded d‐aspartic acid from rat brain slices.Kainic acid binds to rat brain membranes in the absence of sodium ions in a manner indicating binding to a population of receptor sites for l‐glutamic acid. Only quisqualic and l‐glutamic acid inhibit kainic acid binding in a potent manner. The affinity of kainic acid for these receptor sites appears to be some 4 orders of magnitude higher than for the ‘high affinity’l‐glutamic acid transport carrier.Dihydrokainic acid is approximately twice as potent as kainic acid as an inhibitor of ‘high affinity’l‐glutamic acid uptake but is some 500 times less potent as an inhibitor of kainic acid binding and at least 1000 times less potent as a convulsant of immature rats on intraperitoneal injection. Dihydrokainic acid might be useful as a ‘control uptake inhibitor’ for the effects of kainic acid on ‘high affinity’l‐glutamic acid uptake since it appears to have little action on excitatory receptors. N‐Methyl‐d‐aspartic acid is a potent convulsant of immature rats, but does not inhibit kainic acid binding or ‘high affinity’l‐glutamic acid uptake. N‐Methyl‐d‐aspartic acid might be useful as a ‘control excitant’ that activates different excitatory receptors to kainic acid and does not influence ‘high affinity’l‐glutamic acid uptake.
DISAPPEARANCE OF NEWLY SYNTHESIZED AND TOTAL DOPAMINE FROM THE STRIATUM OF THE RAT AFTER INHIBITION OF SYNTHESIS: EVIDENCE FOR A HOMOGENEOUS KINETIC COMPARTMENT
Authors: Paden Charles M. 
Published: October 2006

Abstract— The hypothesis that the biphasic disappearance of dopamine (DA) from the rat striatum following inhibition of synthesis with α‐methyl‐p‐tyrosine (AMPT) represents catabolism from separate‘functional’and 'storage’compartments (Javoy & Glowinski, 1971) was tested by administering 3H‐tyrosine i.v. 10 min before 400 mg per kg AMPT. The levels of newly synthesized 3H‐DA and total DA were then determined at 5‐min intervals. While both declined biphasically, the rate of decay of 3H‐DA was significantly less than that predicted by the two‐pool hypothesis. In fact, the patterns of change of 3H‐DA and total DA were identical and the specific activity of DA did not vary following AMPT. To determine if an increase in DA synthesis and release would result in the preferential catabolism of newly synthesized 3H‐DA, the experiment was repeated fol!owing treatment with 0.1 mg per kg haloperidol i.v. 3H‐DA and total DA still exhibited identical biphasic declines and there was no change in the specific activity of DA after AMPT even though 3H‐DA levels were increased three‐fold by haloperidol. Thus (a) no evidence for the preferential catabolism of newly synthesized 3H‐DA was obtained and (b) newly synthesized and total striatal DA behaved as if localized in a homogeneous kinetic compartment under all conditions employed.Rates of striatal DA metabolism were estimated in both experiments from changes in total DA after AMPT and by the formation of 3H‐DA in the initial 10 min after 3H‐tyrosine injection. Results of both approaches were consistent and indicated that the rates of striatal DA synthesis and catabolism may vary rapidly between approx. 20 and 90 nmol per g per h without violating single compartment kinetics. It is proposed that any labile pool contains no more than a few per cent of the DA in the striatum and the implications of this hypothesis are discussed.
THE FORMATION OF GLUTAMATE, ASPARTATE AND GABA IN THE RAT RETINA; GLUCOSE AND GLUTAMINE AS PRECURSORS
Authors: Morjaria Bharti , Voaden Mary J. 
Published: October 2006

Abstract— The distribution of the neuroactive amino acids taurine, GABA, glycine, glutamate and aspartate, together with glutamine, have been studied in the rat retina. Peak levels of taurine were found in photoreceptor cells and of GABA and glycine in a retinal fraction enriched in amacrine cells and, synaptic terminals. In vitro, GABA formation from [3H]glutamine and [14C]glucose was also most prominent in this fraction; at 500 μm [3H]glutamine was the better precursor.Observations on metabolism in the photoreceptor cell layer of the tissue suggest an active turnover of glutamate, aspartate and GABA, and show that glutamine may serve as an alternative substrate to glucose here, perhaps via the GABA bypath.
GABA FLUXES IN PRESYNAPTIC NERVE ENDINGS FROM IMMATURE RATS
Authors: Levi Giulio , Gallo Vittorio , Ciotti Teresa , Raiteri Maurizio 
Published: October 2006

Abstract— Several parameters of GABA Auxes across the synaptosomal membrane were studied using synaptosomes prepared from the brain of immature (8‐day‐old) rats. The following aspects of GABA carrier‐mediated transport were similar in immature and mature synaptosomes: (1) magnitude of [3H]GABA accumulation; (2) GABA homoexchange in normal ionic conditions; (3) GABA homoexchange in the presence of cationic fluxes (Na+ and Ca2+ influx, K+ efflux) characteristic of physiological depolarization. As in adult synaptosomes (Levi & Raiteri, 1978), in these conditions the stoichiometry of GABA homoexchange was in the direction of net outward transport (efflux > influx).The essential differences between the behaviour of 8‐day‐old and adult synaptosomes were the following: (1) β‐alanine (a glial uptake inhibitor) inhibited GABA uptake in immature synaptosomes (the inhibition being greater in crude than in purified preparations) and was without a significant effect in adult synaptosomes. DABA and ACHC (two neuronal uptake inhibitors) depressed GABA uptake more efficiently in purified than in crude immature synaptosomes, but were as effective in crude and purified nerve endings from adult animals. The data suggest a greater uptake of GABA in the‘gliosomes’contaminating the synaptosomal preparations from immature animals. (2) In immature synaptosomes prelabelled with [3H]GABA the specific radioactivity of the GABA released spontaneously or by heteroexchange (with 300 μm‐OH‐GABA) was the same as that present in synaptosomes, while in adult synaptosomes OH‐GABA released GABA with increased specific radioactivity. The data suggest a homogeneous distribution of the [3H]GABA taken up within the endogenous GABA pool in immature, but not in mature synaptosomes. (3) In immature synaptosomes the release of GABA (radioactive and endogenous) induced by depolarization with high KC was not potentiated by Ca2+, unless the synaptosomes had been previously depleted of Na+ These data suggest that, although a Ca2+ sensitive pool of GABA may be present, this pool is not susceptible to being released in normal conditions, probably because the high intrasynaptosomal Na+ level prevents a sufficient depolarization. The possible significance of these findings in terms of functional activity of GABAergic neurotransmission in the immature brain is discussed.
AXOTOMY INDUCED CHANGES IN CHOLINERGIC ENZYMES IN RAT NERVE AND MUSCLES1
Authors: Ranish Norman A. , Kiauta Tomaz , Dettbarn Wolf‐D. 
Published: October 2006

Abstract— The effect of axotomy on acetylcholinesterase (AChE. EC 3.1.1.7). butyrylcholinesterase (BuChE. EC 3.1.1.8) and choline acetyltransferase (CAT, EC 2.3.1.6) activities in sciatic nerve stumps above (proximal) and below (distal) the site of transection. as well as in soleus (SOL) and extensor digitorum longus (EDL) muscles, has been studied in rat. Within 2 weeks. AChE activity decreased on a per mm basis, in proximal nerve by 65%, in distal nerve by 80% and on a per whole muscle basis, in denervated muscle by 85%.BuChE activity increased in proximal nerve and distal nerve to 150% of control and decreased in muscle to 51% of control. CAT activity in the proximal nerve stump was reduced to 70% of control and in the distal stump to less than 1% within 1 week. CAT activity in muscle decreased to 20 and 30% of control for soleus and EDL respectively during a 14 day period.The reduction in AChE and CAT activity observed in the proximal nerve segment may reflect changes in the synthesis, as well as the transport and local degradation of these enzymes. Previous studies on axotomy induced changes have not examined the simultaneous changes in proximal and distal nerve as well as denervated muscle in a single animal species.
Nucleoside Uptake by Slices of Mouse Brain
Authors: Banay‐Schwartz M. , Guzman T. De , Lajtha A. 
Published: October 2006

Abstract: The properties of the uptake of nucleosides and nucleotides by brain cells were examined in slices of mouse brain. Of the compounds tested, adenine and adenosine had the most rapid uptake and reached the highest levels. Uptake was mediated, as shown by saturability and strong inhibition, by low temperature, or by cyanide, and was only partially sodium‐ or calcium‐dependent. The inhibition pattern by analogues indicated the presence of several uptake systems (possibly four), as shown by differences between adenine and guanine uptake, between adenine and adenosine uptake, and between adenosine and cytidine uptake. The properties of uptake systems for nucleotides and nucleosides were somewhat different from those for amino acids.
Intraneuronal Site of Action for Imipramine in Rat Striatal Slices
Authors: Daniels A. J. , Gysling K. , Arqueros L. 
Published: October 2006

Abstract: The uptake of 3H‐labeled imipramine ([3H]IMI) in rat corpus striatum slices was found to be strongly temperature‐dependent. The accumulation was shown to be saturable and two apparent Km's were found: 2.2 × 10−8 and 3.5 × 10−7m. Once incorporated, the labeled drug was released from superfused slices by K+ (55 mm) depolarization in the presence of calcium ions. Imipramine was also studied for its ability to induce the release of [3H]dopamine ([3H]DA) which had been previously accumulated by striatal slices. It was found that striatal slices superfused during 1 or 6 min with imipramine (10−6‐10−4m) release substantial amounts of radioactive dopamine, independently of the presence of Ca2+ in the medium. This release is completely abolished after reserpine pretreatment. It is proposed that imipramine enters the dopaminergic storage vesicles and displaces dopamine. An intraneuronal mechanism of action for imipramine is discussed.
Glycine in the Central Nervous System in Experimental Allergic Encephalomyelitis
Authors: Turecký L. , Líška B. , Pecháň I. 
Published: October 2006

Abstract: The content of glycine, a possibly inhibitory neurotransmitter was studied in central nervous system of guinea pigs with experimental allergic encephalomyelitis (EAE). The glycine level was increased in spinal cord, but not in the brain of animals with EAE. The greatest increase in glycine concentration was in lumbosacral cord, and at the time of appearance of clinical signs of disease. The results are discussed in terms of possible connection between the changes of glycine concentration and clinical signs of EAE.
Modification of the Rate of Ouabain Binding to (Na++ K+)ATPase by Lithium Ions
Authors: Krishnan Nagaswamy , Albers R. Wayne 
Published: October 2006

Abstract: We report on the interactions of Li+, a congener of K+ with the (Na++ K+)‐ATPase from E Electricus as measured by their effects on the rate of [3H]‐ouabain binding to this enzyme. Like K+, Li+ slows ouabain binding under both Type I (Na++ ATP) and Type II (Pi) conditions, but with lower affinity. In contrast to K+, the Li+ inhibition curve is hyperbolic, suggesting interaction at an uncoupled site. Also differing from the complete inhibition by high K+, a residual ouabain‐binding rate persists at high Li+. The interactions of Li+ and K+ are synergistic: the apparent K+ affinity increases 3 to 4‐fold in presence of Li+. These results are consistent with the conclusion that Li+ interacts with only one of the two K+ sites and may be of interest in interpreting lithium pharmacology.