bluuebunny/crossref_metadata_2025 huggingface dataset:
ACTH1–24 Releases a Protein from Synaptosomal Plasma Membranes
Authors: Aloyo V. J. , Zwiers H. , Gispen W. H.
Published: October 2006

Abstract: Brain membranes contain several protein kinases, all of which appear to play a role in the regulation of neuronal functioning. These membranes also contain numerous (phospho) proteins. It has been proposed that the degree of phosphorylation of some of these proteins may affect neuronal membrane properties. In a series of previous reports we showed that ACTH1‐24 inhibits the endogenous phosphorylation of several synaptosomal plasmamembrane (SPM) proteins including the B‐50 protein. Although we have speculated that the degree of phosphorylation of B‐50 may be important in regulating the turnover of membrane (poly)‐phosphoinositides, the exact nature of the interaction between ACTH1‐24 and B‐50/B‐50 protein kinase is unknown. The purpose of the present study was to determine whether treatment of SPM with ACTH1‐24 will lead to a specific release of proteins from SPM. We found that ACTH1‐24 specifically releases a 41,000 Mr protein from rat brain SPM. Although we are not certain about the biological significance of the release of this polypeptide, it is of sufficient interest for further research in view of the lack of success of finding binding of labeled ACTH to brain membranes.
The Differential Effect of Ischemia on the Active Uptake of Dopamine, γ‐Aminobutyric Acid, and Glutamate by Brain Synap to somes
Authors: Weinberger Jesse , Cohen Gerald
Published: October 2006

Abstract: Ischemic stroke was induced in the Mongolian gerbil by left common carotid ligation. No change in uptake of [3H]dopamine, [3H]γ‐aminobutyric acid ([3H]GABA), or [14C]glutamate in synaptosomes obtained from the ischemic hemisphere was observed for up to 8 h. At 16 h after ligation, marked decrements in uptake were observed in animals showing hemiparesis: Uptake values expressed as a percent of the corresponding control hemisphere were 15.2% for dopamine, 28.0% for GABA, and 47.5% for glutamate. The differential sensitivity of dopamine terminals compared with glutamate terminals was highly significant. Separate experiments performed with synaptosomes isolated from the corpus striatum showed that the greater sensitivity to damage was intrinsic to the dopamine nerve terminal and not the result of regional variations in ischemic damage in brain. No bilateral effect of ischemia on dopamine uptake was evident. In animals exhibiting milder behavioral deficits (circling), a smaller and comparable decrement in uptake of dopamine, GABA, and glutamate was evident at 16 h, whereas animals not affected behaviorally showed no decrement at 16 h. Following uptake, the subsequent fractional release of neurotransmitter stimulated by 60 mM‐potassium ions was not affected at any time point studied. Therefore, the loss in uptake at 16 h probably represents overt destruction of nerve terminals. Experiments with urethane used in place of pentobarbital for anesthesia during carotid occlusion showed that “protection” by pentobarbital was not a factor in the delayed response to ischemia. These results show that damage or destruction of nerve terminals is a delayed event following ischemia and that dopamine terminals are intrinsically more sensitive than glutamate terminals.
Transport of GABA at the Blood‐CSF Interface
Authors: Löscher W. , Frey H.‐H.
Published: October 2006

Abstract: The entry of GABA into cerebrospinal fluid (CSF) was studied in dogs anesthetized with pentobarbital and relaxed with suxamethonium. GABA was administered intravenously as a priming dose and subsequent maintenance infusion to compensate for the rapid elimination of the amino acid. Steady state concentrations of GABA in CSF were reached between 10 and 60 min after injection, the rate of entry tending to decrease with increasing plasma levels. During steady state conditions CSF concentrations showed great interin‐dividual differences and varied between 0.03 and 5.1% of those in plasma. Probenecid and sodium valproate considerably enhanced the CSF/plasma concentration ratio of GABA. When GABA was directly injected into the liquor space, probenecid slowed down the elimination of GABA from CSF. The results suggest a transport of GABA into and out of CSF, the outward transport being inhibited by probenecid and sodium valproate.
ADP‐Ribosylation of Membrane Proteins in Cholinergic Nerve Terminals
Authors: Lester Henry A. , Steer Michael L. , Michaelson Daniel M.
Published: October 2006

Abstract: Lysed Torpedo synaptosomes or washed synaptosomal membranes were incubated with [32P]NAD+ and subjected to electrophoresis on SDS‐polyacrylamide gels. More than eight membrane proteins were ADP‐ribosylated. The most intensely labeled proteins were those of Mr= 62,000 and 82,000. Radiolabeling was more intense in synaptosomes than in other subcel‐lular fractions. Cholera toxin caused ribosylation of additional synaptosomal proteins with Mr= 42,000 and (in some preparations) 49,000. Neither endogenous nor cholera toxin‐catalyzed ADP‐ribosylation required added guanyl nu‐cleotides. Cholera toxin increased the adenylate cyclase activity of synaptosomal membranes, suggesting that the cholera toxin substrates are regulatory components of adenylate cyclase in these synaptosomes.
Unstimulated and Amphetamine‐Stimulated Release of Endogenous Noradrenaline and Dopamine from Rat Brain In Vivo
Authors: Philips S. R. , Robson A. M. , Boulton A. A.
Published: October 2006

Abstract: The in vivo release rates of endogenous noradrenaline from the hypothalamus and dopamine from the caudate nucleus of the rat have been determined. Artificial CSF perfusates collected from a push‐pull cannula inserted into specific areas of the brain were assayed for the amines by a sensitive radioenzymatic procedure. The release rates of noradrenaline and dopamine into artificial CSF perfusates were 38 ± 6 and 46 ± 6 pg/h (225 ± 36 and 301 ± 39 fmol/h), respectively; when 0.5 mM amphetamine was added to the CSF, the release rates of noradrenaline and dopamine increased to 176 ± 50 and 1183 ± 453 pg/h (1041 ± 296 and 7732 ± 2961 fmol/h), respectively.
Identification and Distribution of Phenylacetic Acid in the Brain of the Rat
Authors: Durden David A. , Boulton Alan A.
Published: October 2006

Abstract: Phenylacetic acid, the major metabolite of phenylethylamine, has been identified and quantitated in rat brain regions by capillary column high‐resolution gas chromatography mass spectrometry. Its distribution is heterogeneous and correlates with that of phenylethylamine. The values obtained were (ng/g ± SEM): whole brain, 31.2 ± 2.7; caudate nucleus, 64.6 ± 6.5; hypothalamus, 60.1 ± 7.4; cerebellum, 31.3 ± 2.9; brainstem, 33.1 ± 3.3, and the “rest,” 27.6 ± 3.0.
Calcium‐Dependent Proteases in Neuroblastoma Cells
Authors: DeMartino George N. , Croall Dorothy E.
Published: October 2006

Abstract: Extracts of neuroblastoma cells contained calcium‐dependent proteolytic activity. This activity was accounted for by two distinct proteases. These proteases were separated by ion‐exchange chromatography. Although each was totally dependent on calcium, the calcium requirements of the enzymes were different; one enzyme required approximately 40 μM Ca2+ for half‐maximal activity and the other enzyme required approximately 150 μM Ca2+ for half‐maximal activity.
Differential Labeling of Depot and Active Acetylcholine Pools in Nondepolarized and Potassium‐Depolarized Rat Brain Synaptosomes
Authors: Suszkiw J. B. , O'Leary M. E.
Published: October 2006

Abstract: To test the hypothesis that a pool of newly synthesized acetylcholine (ACh) turns over independently of preformed ACh, compartmentation and K+ ‐evoked release of ACh were examined in perfused synaptosomal beds intermittently stimulated by 50 mM K+. In resting synaptosomes, endogenous and labeled ACh was distributed between synaptic vesicles and the cytoplasm in a dynamic equilibrium ratio of 4:6. In the absence of new ACh synthesis, five sequential K+ ‐depolarizations caused a decremental release of preformed labeled ACh totaling 30% of the initial transmitter store. Further depolarization evoked little additional release, despite the fact that 60% of the labeled ACh remained in these preparations. Release of the preformed [14C]ACh was unaltered while new ACh was being synthesized from exogenous [3H]choline. Since the evoked release of [3H]ACh was maintained while that of [14C]ACh was decreasing, the [3H]ACh/[14C]ACh ratio in perfusate increased with each successive depolarization. This ratio was six to ten times higher than the corresponding ratio in vesicles or cytoplasm. These results indicate that the newly synthesized ACh did not equilibrate with either the depot vesicular or cytoplasmic ACh pools prior to release.
Regional Distribution of Neurotensin in Human Brain
Authors: Manberg Paul J. , Youngblood William W. , Nemeroff Charles B. , Rossor Martin N. , Iversen Leslie L. , Prange Arthur J. , Kizer John S.
Published: October 2006

Abstract: Neurotensin (NT) is an endogenous neuropeptide that is active in many preclinical screening tests for neuroleptic drugs. Using a radioimmunoassay, we have studied the regional distribution of NT in postmortem human brain and in cerebrospinal fluid. Highest levels were present in the hypothalamus, substantia nigra, and limbic areas, whereas much lower amounts were found in the cortex and striatum. The chromatographic properties of hypothalamic immunoreactivity on ion‐exchange and high pressure liquid chromatography were similar to those of the synthetic tridecapeptide. We conclude that NT is present in human brain with a distribution resembling that seen in other species, such as rat and monkey.
Adenylate Cyclase of Torpedo Synaptosomes Is Inhibited by Calcium and Not Affected by Muscarinic Ligands
Authors: Pinchasi Irit , Michaelson Daniel M.
Published: October 2006

Abstract: Cholinergic synaptosomes isolated from the electric organ of Torpedo contain membrane‐bound adenylate cyclase activity (∼6 pmol/mg proteidmin), which is dependent on the presence of guanine nucleotides. The activity is strongly dependent on temperature and only slightly affected by NaCl. The Torpedo adenylate cyclase is completely inhibited by low levels of free Ca2+ (K0∼ 0.5 μM). This effect is not altered by either trifluoperazine or addition of exogenous calmodulin. Ca3+ has no effect on the activation step of the adenylate cyclase by guanyl‐5′‐yl imidodiphosphate (GppNHp), and Mn2+ abolishes the Ca2+‐dependent inhibition of cyclic AMP synthesis. These findings suggest that Ca2+ exerts its effect by direct interaction with a site located on the catalytic subunit. Torpedo synaptosomes contain presynaptic inhibitory muscarinic receptors. The binding of muscarinic agonists to the receptors is modulated (to lower affinity) by GTP. However, muscarinic ligands, examined under a variety of assay conditions, have no effect on adenylate cyclase activity. These results suggest that although both the muscarinic receptor and the adenylate cyclase are coupled to G proteins, they either interact with different G proteins or are situated in different regions of the presynaptic membrane.
Effects of Free Fatty Acids on Synaptosomal Amino Acid Uptake Systems
Authors: Rhoads D. E. , Kaplan M. A. , Peterson N. A. , Raghupathy E.
Published: October 2006

Abstract: The Na+‐dependent synaptosomal uptakes of proline, aspartic acid, glutamic acid, and γ‐aminobutyric acid were strongly inhibited by monounsaturated fatty acids. With oleic acid, half‐maximal inhibition was observed at about 15 μM. The Na+‐independent uptakes of leucine, phenylalanine, histidine, and valine were less sensitive to inhibition by the unsaturated fatty acids. In contrast, the uptakes of all of these amino acids were unaffected by saturated fatty acids. The inhibition of proline uptake (and that of the other Na+‐dependent amino acids) by oleic acid was overcome by the addition of serum albumin and the data presented further indicate that the previously reported stimulation of proline uptake by albumin could be related to its fatty acid binding properties.
Enzyme‐Linked Immunosorbent Assay of Substance P: A Study in the Eye
Authors: Stjernschantz Johan , Gregerson Dale , Bausher Larry , Sears Marvin
Published: October 2006

Abstract: A solid phase enzyme‐linked immunosorbent assay for quantitation of substance P is presented. The assay measures the capacity of soluble substance P to compete with the solid phase antigen for a limited quantity of specific substance P antibody. The solid‐phase antigen consists of a synthetic substance P. poly‐D‐glutamic acid conjugate coated to polystyrene micro‐ELISA plate wells. Soluble substance P and antibodies to substance P are first preincubated together and then added to the wells containing solid‐phase antigen. Subsequently the wells are incubated with anti‐antibodies conjugated to alkaline phosphatase. The wells are finally incubated with p‐nitrophenyl phosphate and the absorbance is read in a spectrophotometer 16‐24 h after the start of the assay. The threshold for detection of substance P was 5‐10 pg per well (0.25 ml). Substance P was extracted from rabbit eyes and the values obtained with the present method are compared with previously reported values based on radioimmunoassay.
Identification and Characterization of Sulfhydryl‐Containing Proteolytic Fragments Involved in the Ca2+‐Induced Conformational Change of Beef Brain S‐100
Authors: Nika H. , Haglid K. G. , Wrońki A. , Hansson H.‐A.
Published: October 2006

Abstract: The Ca2+‐dependent conformational alteration of the brain‐specific S‐100 protein was studied by reacting the protein with N‐ethyl[2,3‐14C]maleimide in the absence and presence of Ca2+ and under denaturing conditions. Peptic hydrolysates of the 14C‐labeled protein were analyzed and fractionated by high‐performance liquid chromatography. Labeled peptide fractions were characterized by high‐voltage electrophoresis and TLC. A clear distinction could be made between two classes of sulfhydryl‐containing fragments: (a) neutral, hydrophobic, and (b) acidic. Ca2+ markedly favored 14C incorporation into the former components, whereas the latter were readily available only under denaturing conditions.
Subclasses of Adenosine Receptors in Brain Membranes from Adult Tissue and from Primary Cultures of Chick Embryo
Authors: Barnes Eugene M. , Thampy K. George
Published: October 2006

Abstract: Membranes from adult chicken brain have high‐affinity binding sites for N6‐cyclohexyl[3H]adenosine (CHA) (KD= 4 nM, Bmax= 0.6 pmol/mg protein). This CHA binding could be attributed to adenosine receptors of the A1 type, since substituted adenosine analogs, e.g. N6‐(l‐2‐phenylisopropyl)adeno sine (IC50= 60 nM), were very potent displacers. Binding sites for 1,3‐diethyl‐ 8‐[3H]phenylxanthine (DPX) in adult brain membranes have a moderate affinity (KD= 50 nM, Bmax= 1.5 pmol/mg). The association of DPX with these sites could be completely displaced by 8‐phenyltheophylline (IC50= 300 nM) and other xanthines, but only 45% of specific DPX binding could be displaced by phenylisopropyladenosine. This suggests that about half of DPX sites are putative A1 receptors and the other half are of the A2 type. Primary cultures of pure glial and neuronal cells from chick embryo brain were also examined for adenosine receptors. Specific binding of CHA could not be detected in these preparations, but both glial and neuronal membranes have specific sites for DPX. At a [3H]DPX concentration of 20 nM, specific binding was 50% higher (per mg protein) in glial than in neuronal membranes. The maximum binding of DPX to glial membranes (Bmax= 1.6 pmol/mg) was comparable to values for adult brain, but the glial affinity (KD= 90 nM) was somewhat less. Phenylisopropyladenosine was able to displace less than 20% of the total glial sites for DPX. This finding was in accord with the lack of CHA sites and demonstrates that A1 receptors make little contribution to DPX binding in glial membranes. In decreasing order of potency, 8‐phenyltheophylline, CHA, theophylline, caffeine, and 3‐isobutyl‐I‐methylxanthine completely displace DPX association with glia. DPX binding to glial membranes thus appears due to a single class of receptors, which may prove to be of the A2 type.
Concanavalin A Receptors Associated with Rat Brain Synaptic Junctions Are High Mannose‐Type Oligosaccharides
Authors: Gurd James W. , Fu Sheung Chun
Published: October 2006

Abstract: Glycoproteins were isolated from a rat brain synaptic junction fraction by affinity chromatography on Concanavalin A‐agarose. The isolated glycoproteins were digested with pronase and radiolabeled with 125I‐Bolton Hunter reagent, and 125I‐Concanavalin A‐binding glycopeptides were isolated by chromatography on Concanavalin A‐agarose. Treatment of the 125I‐Concanavalin A‐binding glycopeptides with either α‐mannosidase or endo‐β‐N‐acetylglucosaminidase‐C11 abolished their interaction with Concanavalin A. The pronase digest was reacted with endo‐β‐N‐acetylglucosaminidase‐C11 and released oligosaccharides were reduced with NaB3H4. Following affinity chromatography on Concanavalin A‐agarose, Concanavalin A‐binding [3H]oligosaccharides were chromatographed on Biogel P4. Two major oligosaccharides corresponding to standard carbohydrates containing eight and five mannose residues were identified. Treatment of these oligosaccharides with α‐mannosidase converted them to smaller saccharides having a mobility on Biogel P4 columns equal to the standard disaccharide mannose‐β‐1‐4‐N′‐acetylglucosamine. These results demonstrate that the Concanavalin A receptor activity associated with CNS synaptic junctions resides in asparaginelinked oligosaccharides of the high‐mannose type.
Demonstration of Conjugated Dopamine in Monkey CSF by Gas Chromatography‐Mass Spectrometry
Authors: Elchisak M. A. , Powers K. H. , Ebert M. H.
Published: October 2006

Abstract: A method for measuring unconjugated and conjugated dopamine in body tissues and fluids is described. Conjugated dopamine was hydrolyzed in acid to unconjugated dopamine, separated from the sample matrix by alumina chromatography, and assayed by gas chromatography‐mass spectrometry. Conjugated dopamine was detected in greater concentrations than unconjugated dopamine in CSF taken from lateral ventricle or thecal sac of the Rhesus monkey. Haloperidol administration did not increase the levels of conjugated dopamine in lumbar CSF.
Postnatal Development of Noradrenaline and 3‐Methoxy‐4‐Hydroxyphenylethyleneglycol Sulphate Levels in Rat Brain Regions
Authors: Kohno Yasuko , Tanaka Masatoshi , Nakagawa Ryoichi , Ida Yoshishige , Iimori Kenichiro , Nagasaki Nobuyuki
Published: October 2006

Abstract: Developmental changes in brain levels of noradrenaline (NA) and 3‐methoxy‐4‐hydroxyphenylethyleneglycolsulphate (MHPG‐SO4) were studied in rats. In most brain regions, MHPG‐SO4 level rapidly increased to approach or exceed adult levels at the time of weaning, while NA levels increased more gradually and reached adult levels following weaning, Pharmacological studies showed that the MHPG‐SO4 level in the neonatal brain reflects the degradation of released NA. The developmental characteristics of noradrenergic neurons in eight discrete brain regions are discussed.
[3H]Spiperone Labels Non‐Cyclase‐Linked Dopamine Receptors in the Ventral Tegmental Area of Rat Brain
Authors: Gundlach A. L. , McDonald D. , Beart P. M.
Published: October 2006

Abstract: The binding of [3H]spiperone, a neuroleptic/dopamine receptor ligand, to membranes of the ventral tegmental area of the rat was studied in vitro and found to be rapid, saturable, reversible, and of high affinity. Specific binding was displaced by the dopaminergic agonists dopamine, apomorphine, and 2‐amino‐6,7‐dihydroxytetralin, and stereospecifically by the neuroleptic drugs butaclamol and flupenthixol. Bromocryptine and other ergots displaced the binding, as did the D‐2 antagonists domperidone, molindone, metoclopramide, and sulpiride. Noradrenergic, histaminergic, and serotonergic components of the binding were not detected in displacement studies with various agonists and antagonists. These data are consistent with the hypothesis that [3H]spiperone labels dopamine receptors in the ventral tegmental area that are not linked to adenylate cyclase and are therefore likely to be of the D‐2 type.
Activation of Retinal Tyrosine Hydroxylase In Vitro by Cyclic AMP‐Dependent Protein Kinase: Characterization and Comparison to Activation In Vivo by Photic Stimulation
Authors: Iuvone P. M. , Rauch A. L. , Marshburn P. B. , Glass D. B. , Neff N. H.
Published: October 2006

Abstract: Tyrosine hydroxylase in rat retina is activated in vivo as a consequence of photic stimulation. Tyrosine hydroxylase in crude extracts of dark‐adapted retinas is activated in vitro by incubation under conditions that stimulate protein phosphorylation by cyclic AMP‐dependent protein kinase. Comparison of the activations of the enzyme by photic stimulation in vivo and protein phosphorylation in vitro demonstrated several similarities. Both treatments decreased the apparent Km of the enzyme for the synthetic pterin cofactor 6MPH4. Both treatments also produced the same change in the relationships of tyrosine hydroxylase activity to assay pH. When retinal extracts containing tyrosine hydroxylase activated either in vivo by photic stimulation or in vitro by protein phosphorylation were incubated at 25°C, the enzyme was inactivated in a time‐dependent manner. The inactivation of the enzyme following both activation in vivo and activation in vitro was partially inhibited by sodium pyrophosphate, an inhibitor of phosphoprotein phosphatase. In addition to these similarities, the activation of tyrosine hydroxylase in vivo by photic stimulation was not additive to the activation in vitro by protein phosphorylation. These data indicate that the mechanism for the activation of tyrosine hydroxylase that occurs as a consequence of light‐induced increases of neuronal activity is similar to the mechanism for activation of the enzyme in vitro by protein phosphorylation. This observation suggests that the activation of retinal tyrosine hydroxylase in vivo may be mediated by phosphorylation of tyrosine hydroxylase or some effector molecule associated with the enzyme.
Myelin Lipids in the Developing Cerebrum, Cerebellum, and Brain Stem of Normal and Undernourished Children
Authors: Martínez Manuela
Published: October 2006

Abstract: The developmental lipid profiles in the human cerebrum, cerebellum and brain stem are presented, with special reference to galactolipids as myelin markers to trace myelination in the three main parts of the human CNS. A group of undernourished children were also studied to test the vulnerability of myelinogenesis in the different regions of the human brain. Myelination was well advanced in the brain stem with regard to the other brain regions, a fact reflected in the much higher concentration of myelin lipids in the brain stem of the human foetus of 26 weeks of gestational age. The cerebrum, on the other hand, had the lowest galactolipid concentration during the prenatal period, galactolipid levels in the cerebellum being four times higher. From just before the end of gestation the accretion of galactolipids accelerated enormously in the cerebrum, whereas it slowed down considerably in the cerebellum. Consequently, in relation to prenatal levels galactolipids increased most rapidly in the cerebrum, followed by the cerebellum and finally by the brain stem. These regional differences were in clear contrast to data from the rat, as was the finding that only the cerebrum of undernourished children had a galactolipid concentration significantly decreased with respect to normal values. A relationship between the different myelination patterns in the human and the rat and the distinct vulnerability of myelinogenesis in the two species is suggested.
Degranulation of Rat Cerebellum Induces Selective Variations in Gene Expression
Authors: Eliyahu Daniel , Soreq Hermona
Published: October 2006

Abstract: Selective variations in the composition of poly(A)‐containing mRNA were found to be induced in the rat cerebellum by X‐irradiation. mRNA populations prepared from normal and X‐irradiated rat cerebella at different stages of their development displayed equal efficiencies when translated in vitro in reticulocyte lysates. Specific differences were revealed, however, when the labeled translation products of both mRNA preparations were subjected to two‐dimensional gel electrophoresis followed by fluorography of the dried gels. Of more than 100 polypeptide products, several showed marked intensity differences, indicating changes in the abundance of their directing mRNA species. These differences appear both in developing and in mature cerebellar mRNA, and the extent of modification in mRNA is much higher than the consequent changes in the composition of proteins in the irradiated cerebellum. The degranulation‐induced modifications in levels of specific cerebellar mRNA species can be used to identify proteins whose biosynthesis depends on the presence of interneurons.
Neuroblastoma Cell Membranes: Specificity for Cell Fusion Mediated by a Temperature‐Sensitive Mutant of Vesicular Stomatitis Virus
Authors: Dille Bruce J. , McGee James E. , Johnson Terry C.
Published: October 2006

Abstract: Temperature‐sensitive mutant G3 1 of vesicular stomatitis virus induces mouse neuroblastoma N‐18 cells to fuse during infections that are nonpermissive for virus replication, but BHK‐21 cells do not undergo the viral glycoprotein‐mediated cell fusion. The viral glycoprotein was expressed at the cell surface of both N‐18 and BHK‐21 cells; therefore, the host cell specificity did not stem from an absence of the viral glycoprotein at the surface of BHK‐21 cells. Cell fusion readily occurred between infected and uninfected N‐18 cells in mixed cultures, demonstrating that the viral glycoprotein was interacting with an uninfected cell for the initial cell‐cell interaction of the cell fusion. Mixing infected BHK‐21 cells with uninfected N‐18 cells resulted in cell fusion initiated by BHK‐21 cell‐synthesized viral glycoprotein, but 88% of the nucleiin polykaryocytes were N‐18 nuclei. The N‐18 cell fusion specificity was readily apparent when infected N‐18 cells were mixed with uninfected BHK‐21 cells; 98% of the nuclei in polykaryocytes were N‐18 nuclei. Similar results also were obtained with mixed cultures of N‐18 cells and primary astroglial cells. Thus, the viral glycoprotein synthesized in any of the cell types could initiate cell fusion, but the properties of plasma membranes of neuroblastoma cells appeared to be much more suitable for cell‐cell fusion.
Fluorometrical Analysis of Guanidino Compounds in Human Cerebrospinal Fluid
Authors: Mori Akitane , Watanabe Yoko , Fujimoto Noboru
Published: October 2006

Abstract: Guanidino compounds in CSF of 57 human subjects were determined fluorometrically after reaction with phenanthrenequinone in alkali solution, using HPLC. Creatinine (65.2 ± 13.4 nmol/ml), arginine (24.7 ± 6.4 nmol/ml), and homoarginine (0.7 ± 0.3 nmol/ml) were found in all subjects. Trace amounts of guanidinosuccinic acid and guanidinoacetic acid were detected in some of the subjects. Brain guanidino compounds, taurocyamine, N‐acetylarginine, and methylguanidine were not detected in CSF.
Adenosine‐Elicited Accumulation of Adenosine 3′, 5′‐Cyclic Monophosphate in the Chick Embryo Retina
Authors: de Carvalho R. Paes , de Mello F. G.
Published: October 2006

Abstract: The cyclic AMP level of 17‐day‐old chick embryo retina increased from 20 to 331 pmol/mg protein when the tissue was incubated for 20 min in the presence of 4‐(3‐butoxy‐4‐methoxybenzyl‐2‐imidozolinone) (RO 20‐1724). The addition of 0.5 mm‐3‐isobutyl‐1‐methylxanthine (IBMX) or 0.5 units/ml of adenosine deaminase (EC 3.5.4.4) to the medium reduced the increase of cyclic AMP content from 20 to 100 pmol/mg protein. Dipyridamole did not interfere with the rise of the retina cyclic AMP level observed with RO 20‐1724. The EC50 of 6‐amino‐2‐chloropurine riboside (2‐chloroadenosine)‐elicited accumulation of cylic AMP of retinas incubated in the presence of RO 20‐1724 plus adenosine deaminase was approximately 1 μm. When retina incubation was carried out in the presence of 0.5 mm‐IBMX, the 2‐chloroadenosine dose–response curve was shifted to the right two orders of magnitude. Maximal stimulation of the cyclic AMP level of 17‐day‐old chick embryo retina incubated in the presence of 0.5 mm‐IBMX was observed at 1 mm‐adenosine concentration. This effect was not blocked by dopamine antagonists. Guanosine and adenine did not affect the retinal cyclic AMP level. AMP and ATP had a slight stimulatory effect. Adenosine response of embryonic retina increased sharply from the 14th to the 17th embryonic day. A similar, but not identical, adenosine effect was observed in cultured retina cells.
Alterations in Neurotransmitter Receptor Binding in Discrete Areas of the Copper‐Deficient Rat Brain
Authors: Feller D. J. , O'Dell B. L. , Bylund D. B.
Published: October 2006

Abstract: Neonatal copper deficiency produced alterations in central neurotransmitter receptors that were selective with respect both to brain region and to neurotransmitter receptor type. Both high‐ and low‐affinity dopamine receptor densities in the corpus striatum were significantly lowered, 55% and 29%, respectively, when expressed on a wet weight basis. There was a significant decrease in the level of muscarinic receptors in the striatum whether expressed on the basis of wet weight (50%) or protein (27%). A smaller reduction in muscarinic receptor density was observed in the cortex, whereas there was no effect of copper deficiency in the cerebellum. The treatment did not change β‐adrenergic receptor binding in either the cortex or cerebellum. The affinities of the receptors for the ligands was not affected by the low‐copper diet. It was previously reported that copper deficiency produces regionally specific decreases in the concentrations of dopamine and norepinephrine. The greatest reduction occurred in the concentration of dopamine in the corpus striatum. The results from both studies suggest that copper deficiency in post‐weanling rats may induce a selective morphological lesion.
Effects of Enucleation on High‐Affinity Binding Sites in Chick Optic Tecta
Authors: Por Suzanne B. , Bondy Stephen C.
Published: October 2006

Abstract: The effect of unilateral eye extirpation on the development of the chick optic tectum has been studied in both the embryo and the newly hatched chick. Although the prevention of normal afferentation of the embryonic tectum retarded its growth, there appeared to be a significant increase of muscarinic acetylcholine binding site in the noninnervated tectum. This phenomenon was repeated also in the posthatch denervated system wherein the functioning optic nerve is severed. A significant increase in the number of binding sites as well as reduced dissociation constant of the interactions of this receptor with [3H]quinuclindinyl benzilate was found in the deafferented optic tectum. This may suggest the presence of a denervation‐supersensitivity‐like modulation. Similar increases were not detected with other binding sites studied in either the noninnervated embryonic or deafferented posthatch optic lobes. The possibility that acetylcholine is a primary neurotransmitter of the optic system is discussed.
The Effects of Chronic Manganese Chloride Treatment Expressed as Age‐Dependent, Transient Changes in Rat Brain Synaptosomal Uptake of Amines
Authors: Lai James C. K. , Leung Thomas K. C. , Guest Julian F. , Davison Alan N. , Lim Louis
Published: October 2006

Abstract: As a result of chronic manganese treatment of rats from conception onwards, a decrease was observed in the uptake of dopamine, but not of noradrenaline or serotonin, by synaptosomes isolated from hypothalamus, striatum, and midbrain and in choline uptake by hypothalamic synaptosomes obtained from 70–90‐day‐old animals. In 100–120‐day‐old manganese‐treated rats the only difference observed was increased choline uptake by striatal synaptosomes. All comparisons were with age‐matched controls. These results, which are consistent with views of a dopaminergic and cholinergic involvement in manganese encephalopathy, point out that changes in these systems are observable only at specific times during manganese intoxication.
Monoamine Oxidase‐Catalyzed Metabolism of 3,4‐Dihydroxyphenylethylamine in the Dopaminergic Synaptosomes from Rat Corpus Striatum
Authors: Katz Ira R.
Published: October 2006

Abstract: This communication describes conditions under which the monoamine oxidase‐catalyzed metabolism of 3,4‐dihydroxyphenylethylamine can be assayed in dopaminergic synaptosomes from the rat striatum. In contrast to the activity of the isolated enzyme or that of free mitochondria, the synaptosomal reaction exhibits sigmoidal kinetics with respect to substrate concentration. This is consistent with a kinetic mechanism in which intrasynaptosomal substrate partitions between reaction and saturable storage in synaptic vesicles. The reaction is inhibited at moderately decreased oxygen tension, where catecholamine uptake is unaffected. The specificity of this effect suggests that it reflects limited availability of oxygen as an enzyme substrate.
In Vivo Methylation of an Arginine in Chicken Myelin Basic Protein
Authors: Small D. H. , Carnegie P. R.
Published: October 2006

Abstract: The amino acid sequence around the sole methylarginine residue in chicken myelin basic protein was determined and was found to be similar to that previously reported for mammalian myelin basic protein. The ratio NG, N′G‐dimethylarginine: NG‐monomethylarginine:arginine was approximately 1.3:0.9:1.0. No NG, NG‐dimethylarginine was detected in the protein. The in vivo incorporation of methyl groups from [methyl‐3H]methionine into methylarginines in myelin was found to occur readily in 2‐day‐old chickens. Radioactively labelled NG,N′G‐dimeth‐ylarginine and NG‐monomethylarginine in myelin were derived solely from myelin basic protein. Radioactivity was also incorporated into NG,NG‐dimeth‐ylarginine, although this was not derived from myelin basic protein. As NG‐monomethylarginine was easily separated from the dimethylarginines, and as it was derived from myelin basic protein, it may be a good marker for myelin basic protein turnover in vivo. A time course study of the incorporation showed that radioactivity was incorporated into NG‐monomethylarginine up to 6 h after injection, and decayed slowly, with an apparent half‐life of about 40 days.
An In Vitro Characterization of γ‐Glutamylhistamine Synthetase: A Novel Enzyme Catalyzing Histamine Metabolism in the Central Nervous System of the Marine Mollusk, Aplysia californica
Authors: Stein Cathy , Weinreich Daniel
Published: October 2006

Abstract: The properties of the histamine metabolizing enzyme, γ‐glutamylhistamine synthetase (γ‐GHA synthetase) were studied in Aplysia ganglia in vitro. This enzyme catalyzes the incorporation of histamine into peptide linkage with l‐glutamate to form a peptidoamine, γ‐glutamylhistamine (γ‐GHA). γ‐GHA synthetase is a soluble enzyme with an apparent Km of 653 μm for histamine and 10.6 mm for l‐glutamate. Synthesis of‐γ‐GHA is energy ‐dependent, having an absolute requirement for ATP. Magnesium ions and di‐thiothreitol are also essential for activity. Of a variety of γ‐glutamyl compounds and glutamate analogs tested, only l‐glutamate was effectively incorporated into peptide linkage with histamine. Similarly, the enzyme has a higher affinity for histamine than for numerous imidazole analogs. In addition, 3,4‐dihydroxyphenylethylamine (dopamine), 5‐hydroxytryptamine, octopamine, and several other amines tested are effective inhibitors of‐γ‐GHA synthesis. Ganglia, nerve trunks, and the capsule surrounding the ganglion had the highest synthetase activity. The specific activity of the enzyme in muscle, heart, and hemolymph was <10% of that in ganglia. Differences in substrate specificity and effect of inhibitors distinguish ‐γ‐GHA synthetase from ‐γ‐glutamyl transpeptidase, glutamine synthetase, and carnosine synthetase.
The Immunological Identification of Brain Proteins on Cellulose Nitrate in Human Demyelinating Disease
Authors: Newcombe J. , Glynn P. , Cuzner M. L.
Published: October 2006

Abstract: An immunological technique has been employed to identify proteins, separated in polyacrylamide gels, which show changes in brain samples from cases of multiple sclerosis and subacute sclerosing panencephalitis. Sodium dodecylsulphate‐treated proteins in particulate and soluble fractions were separated in polyacrylamide slab gels, transferred electrophoretically onto cellulose nitrate sheets, incubated with specific antisera and visualized by an immunoperoxidase method. Protein bands showing changes were identified using antisera raised against the myelin basic and Wolfgram proteins, the neurofilament triplet proteins, tubulin and glial fibrillary acidic protein. In addition to the loss of myelin proteins, decreases in the neurofilament proteins and in tubulin were seen in both multiple sclerosis and subacute sclerosing panencephalitis samples. The distribution of glial fibrillary acidic protein polypeptides in the particulate and soluble fractions of plaque samples appeared to vary according to the degree of fibrosis. Changes in the levels of the myelin‐associated glycoprotein, the lower molecular weight component of the Wolfgram protein, albumin and immunoglobulin G, none of which were visualized by protein staining, were also seen. This immunological technique has allowed a closer examination of changes occurring in brain protein spectra in multiple sclerosis and subacute sclerosing panencephalitis.
Effect of Kainic Acid, Glutamate, and Aspartate on CO2 Production by Goldfish Tectal Slices
Authors: Migani Paolo , Poli Alessandro , Contestabile Antonio , Bissoli Rosanna , Cristini Giuliana , Barnabei Ottavio
Published: October 2006

Abstract: For a study of the excitatory effect of kainate, glutamate, and aspartate in the goldfish optic tectum, these substances were tested on the production of CO2 from radioactive glucose in tectal slices incubated in Krebs‐Ringer medium for fish. Kainate increased the rate of CO2 production for up to 30 min in a dose‐related manner, the effect being maximum at 0.1 mM concentration and decreasing at higher doses. The effect was blocked by ouabain (1 mM) as well as by the substitution of cholinc for Na+ in the incubation medium. Glutamate and aspartate exerted a less pronounced excitatory effect on CO2 production at higher concentration than kainate. This effect was also abolished by ouabain. Glutamate, added to the medium at a concentration at least 100‐ fold higher than kainate, partially reversed the increase in CO2 production induced by kainic acid. No similar effect was noticed for aspartate. The supposed glutamate antagonists glutamic acid diethylester (1 mM) and proline (5mM) did not affect the excitatory action of kainic acid or exert an antagonistic effect towards glutamate. At higher concentration (10 mM) glutamic acid diethylester increased CO2 production, an effect that was, however, ouabain insensitive. Methyltetrahydrofolic acid (1 mM), a substance reported to compete for the kainate receptor, did not inhibit the effect of kainic acid or increase CO, production.
Effect of Nucleotides and Other Inhibitors on the Inactivation of Glutamate Decarboxylase
Authors: Martin David L. , Martin Sandra B.
Published: October 2006

Abstract: The effects of 17 nucleotides and nucleotide analogs and 11 other compounds on the glutamate‐promoted inactivation of brain glutamate decarboxylase were examined. Among the nucleotides, the major determinant of potency was the polyphosphate chain, Glutamate‐promoted inactivation was strongly enhanced by low concentrations (<100 μM) of adenosine tetraphosphate and all eight nucleoside triphosphates tested. Nucleoside diphosphates enhanced inactivation, but were much less effective than the nucleoside triphosphates; nucleoside monophosphates were not effective. Modification of the polyphosphate chain of the nucleoside triphosphates also affected potency; adenylylimidodiphosphate and α,β‐methylene ATP were about as effective as nucleoside diphosphates, but α,β‐methylene ATP was nearly as effective as ATP. The nucleoside base had only a small effect on potency; purine nucleotides were more potent than pyrimidine nucleotides, and one nucleotide with a tricyclic base, 1, N6‐etheno ATP, was as effective as the purine nucleoside triphosphates. The 2′‐hydroxyl group of ribose was unimportant, since deoxy ATP was as effective as ATP. Three nonnucleotide polyanions were strong promoters of inactivation; inositol hexasulfate and 5‐phosphorylribose 1‐pyrophosphate were at least as effective as ATP; inositol hexaphosphate (phytate) was as effective as the nucleoside diphosphates. These results suggest that a major determinant of potency was a strong negative charge on the molecule. Negative charge was not sufficient, however, since fructose 1,6‐bisphosphate did not promote inactivation. Inactivation by all of these compounds was slow, requiring more than 20 min for full effect. Two competitive inhibitors, chloride and glutarate, acted immediately and also reduced rather than enhanced glutamate‐promoted inactivation.
Selective Stimulation of Neurotransmitter Release from Chick Retina by Kainic and Glutamic Acids
Authors: Tapia Ricardo , Arias Clorinda
Published: October 2006

Abstract: The excitatory action of kainic and glutamic acids in chick whole retina was demonstrated as an immediate stimulation of the release of labeled γ‐aminobutyric acid (GABA) and glycine in a superfusion system. This stimulatory effect was 3–10 times greater than that produced by a depolarizing K+ concentration; in addition, it was independent of Caz+ in the medium, but notably inhibited when Na+ was omitted from the medium. Under identical experimental conditions, neither kainic nor glutamic acid had any effect on the release of labeled dopamine or α‐aminoisobutyric acid, thus indicating that their effect is not unspecific or due to cell damage. Similar although less marked stimulation of labeled GABA and glycine release by kainic acid was obtained in subcellular retinal fractions, particularly in fraction PI, which contained photoreceptor terminals and outer segments. This stimulation was also Ca2+ independent and greatly reduced when Na+ was omitted from the medium. It is suggested that the stimulation of GABA release by kainic and glutamic acids is probably due to a Na+‐dependent, carrier‐mediated mechanism that responds to the entry of Na+ produced by the interaction of glutamic and kainic acids with retinal membranes. In cortical or striatal slices from mouse brain, these acids had a negligible stimulatory effect on GABA and dopamine release.
Cyclocreatine Phosphate, an Analogue of Creatine Phosphate, Does not Improve Hypoxic Tolerance in Mice
Authors: Artru Alan A. , Michenfelder John D.
Published: October 2006

Abstract: Dietary cyclocreatine has been reported to increase brain highenergy stores in mice and to prolong the generation and utilization of these stores following decapitation. A possible cerebral protective action after 50 days of dietary cyclocreatine 0.5% and 1.0% was therefore examined in mice. Cyclocreatine 0.5% did not increase survival time during hypoxia (5% 02). Cyclocreatine 1.O% in the absence of hypoxia caused significant mortality and decreased weight in survivors despite prophylactic antibiotic treatment. Dietary cyclocreatine offers no cerebral protection against hypoxia in mice.
Effects of Corticotropin‐(1–24)‐Tetracosapeptide on Polyphosphoinositide Metabolism and Protein Phosphorylation in Rabbit Iris Subcellular Fractions
Authors: Akhtar Rashid A. , Taft William C. , Abdel‐Latif Ata A.
Published: October 2006

Abstract: Effects of the neuropeptide corticotropin‐(1–24) ‐tetracosapeptide (ACTH) on the endogenous and exogenous phosphorylation of lipids and endogenous phosphorylation of proteins were investigated in microsomes and a 110,000 ×g supernatant fraction [30–50% (NH4)2SO4 precipitate; ASP30–50] obtained from rabbit iris smooth muscle. Subcellular distribution studies revealed that both of these fractions are enriched in diphosphoinositide (DPI) kinase. The 32P labeling of lipids and proteins was measured by incubation of the subcellular fractions with [γ‐32P]ATP. The labeled lipids, which consisted of triphosphoinositide (TPI), DPI, and phosphatidic acid (PA) were isolated by TLC. The microsomal and ASP30–50 fractions were resolved into six and nine labeled phosphoprotein bands, respectively, by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The basal labeling of both lipids and proteins was rapid (30–60 s), and it was dependent on the presence of Mg2+ in the incubation medium; in general it was inhibited by high concentrations (>0.2 mM) of Ca2+. ACTH stimulated the labeling of TPI and inhibited that of PA in a dose‐dependent manner, with maximal effect observed at 50–100 μ of the peptide. ACTH appears to increase TPI labeling by stimulating the DPI kinase. Under the same experimental conditions ACTH (100 μM) inhibited significantly the endogenous phosphorylation of six microsomal phosphoproteins (100K, 84K, 65K, 53K, 48K, and 17K). In the ASP30–50 fraction, ACTH inhibited the phosphorylation of three phosphoproteins (53K, 48K, and 17K) and stimulated the labeling of six phosphoprotein bands (117K, 100K, 84K, 65K, 42K, and 35K). The effects of ACTH on lipid and protein phosphorylation are probably Ca2+‐independent; thus the neuropeptide effects were not influenced by either 1 μM EGTA or low concentrations of Ca2+ (50 μ.M). We conclude that a relationship may exist between polyphosphoinositide metabolism and protein phosphorylation in the rabbit iris smooth muscle.
On the Similarity of Triacylglycerol and Acylcholesterol Lipases in Rat Brain
Authors: Arnaud J. , Nobili O. , Boyer J.
Published: October 2006

Abstract: Previously, we described a similar stimulating effect of adrenocorticotrophic hormone (ACTH) and ACTH‐related synthetic peptides on triacylglycerol (TAGL) and acylcholesterol (ACL) lipase activities of rat brain. In present study, TAGL and ACL activities from rat brain were further investigated and compared through the use of tri‐[3H]oleoylglycerol and [14C]oleoylcholesterol, respectively, as the substrates. A number of specific properties proved to be similar for both activities: (a) comparable rates of activity decay were observed upon heat treatment, (b) similar reaction kinetics as determined at different substrate concentrations with and without ACTH (10−4M), (c) both activities showed a common susceptibility to the presence of sodium taurocholate (5 mM) or trace amounts (5 μ/ml) of organic solvent in the assay medium, (d) the distributions of the two activities in various brain regions were comparable. Taken together, these data, along with the similar activability by ACTH, suggest a common structural basis for TAGL and ACL activities in rat brain.
Characterization of Brain Synaptic Vesicle Phospholipase A2 Activity and Its Modulation by Calmodulin, Prostaglandin E2, Prostaglandin F2α, Cyclic AMP, and ATP
Authors: Moskowitz Nathan , Puszkin Saul , Schook William
Published: October 2006

Abstract: Brain synaptic vesicle phospholipase A2 (PLA2) activity was characterized. It is Ca2+‐dependent and has a pH optimum of 9.0. The enzyme has a Km of 60 μM and a Vmax of 2.0 nmol/mg/h. Calmodulin, prostaglandin F2α, and cAMP, and ATP all increased the Vmax of the enzyme. Prostaglandin E2 inhibited the Vmax in the presence or absence of calmodulin. Light‐scattering techniques in conjunction with phase‐contrast and electron microscopy demonstrated that an increase in Vmax of PLA2 was correlated with synaptic vesicle aggregation, lysis, and possible fusion. In vitro synaptic vesicle‐vesicle association that was stimulated by conditions that in creased PLA2 activity could be diminished when synaptic vesicles were preincubated with PLA2 inhibitors. It is suggested that endogenous synaptic vesicle PLA2 activity may be an important mechanism underlying Ca2+ ‐mediated neurotransmitter release.