bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties and Partial Purification of Choline Acetyltransferase from the Nematode Caenorhabditis elegans
Authors: Rand James B. , Russell Richard L. 
Published: October 2006

Abstract:We have stabilized and studied choline acetyltransferase from the nematode Caenorhabditis elegans. The enzyme is soluble, and two discrete forms were resolved by gel filtration. The larger of these two forms (MW ∼ 154,000) was somewhat unstable and in the presence of 0.5 M NaI was converted to a form indistinguishable from the “native”small form (MW ˜ 71,000). We have purified the small form of the enzyme >3,300‐fold by a combination of gel filtration, ion‐exchange chromatography, and nucleotide affinity chromatography. The purified preparation has a measured specific activity of 3.74 μmol/min/mg protein, and is free of acetylcholinesterase and acetyl‐CoA hydrolase activities. The Vmax of the purified enzyme is stimulated by NaCl, with half‐maximal stimulation at 80 mM NaCl. The Km for each substrate is also affected by salt, but in different manners from each other and the Vmax; the kinetic parameter Vmax/Km thus changes significantly as a function of the salt concentration.
Neurotoxicity of L‐Glutamate and DL‐Threo‐3‐Hydroxyaspartate in the Rat Striatum
Authors: McBean Gethin J. , Roberts Peter J. 
Published: October 2006

Abstract:Destruction of the glutamatergic corticostriatal pathway potentiates the neurotoxic action of 1 μmol L‐glutamate injected into the rat striatum, whereas the toxic effects of 10 nmol kainate are markedly attenuated. Injection of 170 nmol of the glutamate uptake inhibitor, DL‐threo‐3‐hydroxyaspartate, into the intact striatum also causes neuronal degeneration, which is accompanied by a reduction in markers for cholinergic and GABAergic neurones. Prior removal of the corticostriatal pathway destroys the ability of DL‐threo‐3‐hydroxyaspartate to cause lesions in the striatum. These results indicate that removal, or blockade, of uptake sites for glutamate increase the vulnerability of striatal neurones to the toxic effects of synaptically released glutamate.
Short Communication Occupation of Dopamine Receptors by N‐n‐Propylnorapomorphine or Spiperone and Acetylcholine Levels in the Rat Striatum
Authors: Korf Jakob , Sebens Jantiena B. , Flentge Frans , van der Werf Jan F. 
Published: October 2006

Abstract:In an attempt to quantify the interactions between dopaminergic and cholinergic processes, the consequences of complete or partial activation (with N‐n‐propylnorapomorphine) or blockade (with spiperone) of dopamine receptors for the acetylcholine levels in the rat striatum were studied. The number of specific striatal binding sites (receptors) of spiperone was nearly three times that of N‐n‐propylnorapomorphine (76 and 26 pmol g−1 wet weight, respectively). The agonist produced a significant increase in the striatal levels of acetylcholine, but there was no simple relationship between receptor binding and these levels. A linear negative correlation was found between the striatal levels of acetylcholine and specific spiperone binding, showing that further receptor blockade induces a decrease in acetylcholine levels, which is independent of the receptors already occupied by the antagonist. The results of this study are evidence that one striatal dopamine receptor regulates the metabolism of at least 400 molecules of acetylcholine.
Characterization of “High‐Affinity”[3H]Ouabain Binding in the Rat Central Nervous System
Authors: Hauger R. , Luu H. M. D. , Meyer D. K. , Goodwin F. K. , Paul S. M. 
Published: October 2006

Abstract:The characteristics of [3H]ouabain binding were examined in various areas of rat brain. In the striatum, Scatchard analysis revealed a single class of “high‐affinity” binding sites with an apparent binding affinity (KD) of 10.4 ± 0.9 nM and an estimated binding capacity (Bmax) of 7.6 ± 1.9 pmol/mg protein. Similar monophasic Scatchard plots were found in the brainstem, cerebellum, hypothalamus, and frontal cerebral cortex. [3H]Ouabain binding to rat brain was sodium‐ and ATP‐dependent and strongly inhibited by potassium. Proscillariden A was the most potent cardiac glycoside tested in inhibiting specific [3H]ouabain binding to brain membranes, and the rank order of inhibitory potencies for a series of cardiac glycosides was similar to that previously reported for inhibition of heart Na,K‐ATPase. To assess whether the high‐affinity binding sites for [3H]ouabain were localized to neuronal or nonneuronal membranes, the effect of discrete kainic acid lesions on striatal [3H]ouabain binding was examined. Kainic acid lesions of the striatum reduced [3H]ouabain binding to striatal homogenates by 79.6 ± 1.6%. This suggests that the “high‐affinity”[3H]ouabain binding sites measured in our experiments are localized to neuronal elements. Thus, the high‐affinity binding of [3H]ouabain to brain membranes may selectively label a neuronal form or conformation of Na,K‐ATPase.
Agonist‐Induced Regulation of Adrenoceptor Subtypes in Cerebral Cortical Slices
Authors: Nukina Itaru , LaBella Frank S. 
Published: October 2006

AbstractCerebral cortical slices from rat brain were incubated at 37°C for 2 h in the presence of isoproterenol, noradrenaline, or adrenaline, and binding affinities and densities of adrenoceptor subtypes were subsequently examined in homogenized tissue. The density of α2‐and total β‐adre‐noceptors was estimated using the radioligands [3H]rauwolscine and [3H]dihydroalprenolol (DHA), respectively. The percentages of β1‐and β2‐adrenoceptors were denned by inhibiting the binding of [3H]DHA with the β1‐selective antagonist metoprolol. Exposure of slices to noradrenaline and adrenaline significantly decreased the maximal number of binding sites (Bmax) of α2‐adrenoceptors (48 and 37% respectively) without significantly affecting affinity; isoproterenol had no effect. Exposure to isoproterenol, noradrena line, and adrenaline significantly decreased the Bmax of β‐adrenoceptors (by 60, 34, and 24%, respectively) but did not affect the affinity. Isoproterenol and adrenaline significantly decreased the density of β1‐adrenoceptors by 75 and 24% and β2‐radrenoceptors by 23 and 28%, respectively. Noradrenaline significantly decreased the density of β1‐adreno‐ceptors by 42% without affecting the number of β2‐adreno‐ceptors. These findings indicate that subtypes of adrenoceptors in rat cerebral cortex are differentially regulated by adrenergic agonists.
Angiotensin III: A Potent Inhibitor of Enkephalin‐Degrading Enzymes and an Analgesic Agent
Authors: Shimamura Mariko , Kawamuki Kosei , Hazato Tadahiko 
Published: October 2006

AbstractVarious angiotensins, bradykinins, and related peptides were examined for their inhibitory activity against several enkephalin‐degrading enzymes, including an aminopeptidase and a dipeptidyl aminopeptidase, purified from a membrane‐bound fraction of monkey brain, and an endopeptidase, purified from the rabbit kidney membrane fraction. Angiotensin derivatives having a basic or neutral amino acid at the N‐terminus showed strong inhibition of the aminopeptidase. Dipeptidyl aminopeptidase was inhibited by angiotensins II and III and their derivatives, whereas the endopeptidase was inhibited by angiotensin I and its derivatives. The most potent inhibitor of aminopeptidase and dipeptidyl aminopeptidase was angiotensin III, which completely inhibited the degradation of enkephalin by enzymes in monkey brain or human CSF. The Ki values for angiotensin III against aminopeptidase, dipeptidyl aminopeptidase, endopeptidase, and angiotensin‐converting enzyme, which degraded enkephalin, were 0.66 × 10‐6, 1.03 × 10‐6, 2.3 × 10‐4, and 1.65 × 10‐6M, respectively. Angiotensin III potentiated the analgesic activity of Met‐enkephalin after intracerebroventricular coadministration to mice in the hot plate test. Angiotensin III itself also displayed analgesic activity in that test. These actions were blocked by the specific opiate antagonist naloxone.
Cetiedil, a Drug That Inhibits Acetylcholine Release in Torpedo Electric Organ
Authors: Gaudry‐Talarmain Y. Morot , Israël M. , Lesbats B. , Morel N. 
Published: October 2006

AbstractThe effects of cetiedil, a vasodilatator substance with reported anticholinergic properties, were examined on cholinergic presynaptic functions at the nerve electroplaque junction of Torpedo marmorata using either synaptosomes or slices of intact tissue. Cetiedil abolished the calcium‐dependent release of acetylcholine (ACh) triggered by depolarization or by addition of A23187 ionophore, a finding localizing the site of action downstream from the calcium entry step. In addition, a direct effect on the release process itself was indicated by the observation that cetiedil blocks the release of ACh mediated by a recently isolated presynaptic membrane protein, the mediatophore, reconstituted into ACh‐containing proteoliposomes. In all three preparations, ACh release was inhibited by cetiedil with a Ki of 5–8 μM. Under the conditions used in these release experiments, the synthesis of ACh and its compartmentation within the nerve terminals were not modified. However, the drug was able to reduce high‐affinity choline uptake and vesicular ACh incorporation when it was given together with the radioactive precursor, a result showing that cetiedil has a broad inhibitory action on cholinergic uptake processes.
Potentiation by Kainate of Excitatory Amino Acid Release in Striatum: Complementary In Vivo and In Vitro Experiments
Authors: Young A. M. J. , Crowder J. M. , Bradford H. F. 
Published: October 2006

AbstractThe effect of kainate on extracellular levels of amino acids in corpus striatum was investigated in vitro and in vivo, to elucidate the mechanism underlying its neurotoxicity. Kainate increased extracellular glutamate and aspartate in both striatal slices in vitro and intact striatum in vivo, as previously reported. Both in vitro and in vivo, DL‐threo‐3‐hydroxyaspartate increased extracellular glutamate and aspartate levels (to between 150 and 200% of basal), and also enhanced their kainate‐evoked release. The action of kainate in vivo was reduced by prior frontal decortication, whereas in vitro the kainate‐evoked responses were only slightly reduced by tetrodotoxin. and remained above control values. These results confirm that kainate increases extracellular glutamate and aspartate. and provide evidence that this is due to synaptic release evoked by an action on receptors on glutamatergic neurone terminals. These findings may be relevant to the understanding of epilepsy.
Effects of ATP on Phosphatidylinositol‐Phospholipase C and Inositol 1‐Phosphate Accumulation in Rat Brain Synaptosomes
Authors: Huang H.‐M. , Sun G. Y. 
Published: October 2006

AbstractIncubation of rat brain synaptosomes prelabeled with [2‐3H]inositol resulted in a time‐dependent release of labeled inositol 1 ‐phosphate. This process was Ca2+ dependent, and ATP (1 mM) enhanced the inositol 1‐phosphate formation three‐ to fivefold. Using [l‐14C]arachidonoyl‐phosphatidylinositol which was introduced into saponin‐permeabilized synaptosomes, ATP (1 mM) and free Ca2+ (˜20 μM) enhanced the phospholipase C hydrolysis of this substrate to form labeled diacylglycerol. When the same permeabilized synaptosomal preparation was incubated with [2‐3H]inositol‐phosphatidylinositol, ATP not only enhanced the formation of labeled inositol 1‐phosphate, but also inhibited the conversion of inositol 1‐phosphate to inositol. Furthermore, ATP appeared to reduce the Ca2+ requirement of the phosphatidylinositol‐phospholipase C. Inhibition of the conversion of inositol 1‐phosphate to inositol could not be overcome by increasing the Mg2+ concentration in the incubation medium. Although the ATP effect is not viewed as a receptor‐mediated event, it is possible that such an event may occur in synaptosomes under conditions in which intrasynaptic Ca2+ concentration becomes elevated.
Localization of Glycogen Synthase in Brain
Authors: Inoue Nobuhiro , Matsukado Yasuhiko , Goto Satoshi , Miyamoto Eishichi 
Published: October 2006

AbstractAntisera against glycogen synthase from canine brain were prepared and used for investigation of the localization of the enzyme in the brain. Antisera cross‐reacted only with the 88‐kilodalton protein that is the subunit of brain glycogen synthase. Immunoreactivity of glycogen synthase was universally distributed in all regions of the brain, although hippocampus, cerebral cortex, caudatoputamen, and cerebellar cortex had relatively high immunoreactivity. Light microscopic examination revealed that the immunoreactivity was found in all cell types, such as neurons in several regions, astrocytes, ependymal cells surrounding the ventricle, oligodendrocytes, and epithelial cells of the choroid plexus in the ventricle. Immunoreactive intensity was more prominent in neurons than glial cells. Immunostaining may be a useful tool for investigation of the state of glycogen metabolism under normal and pathological conditions.
Fatty Acid Transport Through the Blood‐Brain Barrier
Authors: Spector Reynold 
Published: October 2006

AbstractAcross the cerebral capillaries, the anatomical locus of the blood‐brain barrier, the unidirectional influxes of the saturated fatty acids, octanoic and myristic acids, and the unsaturated essential fatty acid, linoleic acid, were measured. Employing an in situ rat brain perfusion technique that allows control of perfusate composition and accurate measurement of perfusate‐to‐brain fatty acid transport, we found that both [14C]octanoic and [14C]myristic acids were transported through the blood‐brain barrier in vivo, in large part, by a specific, probenecid‐sensitive transport system. However, the transport of [14C]linoleic acid was not probenecid sensitive. With 0.5 μM fatty acid but no plasma proteins in the perfusate, the permeability‐surface area constant was higher for myristic acid (4.8 × 10‐‐2× s‐1) than for octanoic and linoleic acids (1.5 and 1.2 × 10‐‐2× s‐1, respectively). Approximately 70, 30, and 25% of the [14C]myristic, [14C]octanoic, or [14C]linoleic acids, respectively, were extracted from the perfusate.
Biochemical and Autoradiographic Study of Cerebral Protein Synthesis with [18F]‐ and [14C]Fluorophenylalanine
Authors: Bodsch W. , Coenen H. H. , Stocklin G. , Takahashi †K. , Hossmann K.‐A. 
Published: October 2006

AbstractFluorine‐18‐labeled ortho or para isomers of l‐fluorophenylalanine were used in double‐label experiments together with l‐[3H]phenylalanine for amino acid incorporation into cerebral proteins of Mongolian gerbil brain. It was demonstrated by qualitative regional comparison of the 18F and 3H autoradiographic images that l‐p‐[18F]fluo‐rophenylalanine is incorporated into proteins and exhibits a regional cerebral protein synthesis pattern. To a minor extent, l‐p‐fluorophenyl[3–14C]alanine and l‐o‐[18F]fluo‐rophenylalanine are hydroxylated in vivo to form labeled tyrosine or tyrosine analogues that are incorporated into cerebral proteins as well. The advantage and validity of the application of l‐p‐[18F]fluorophenylalanine with positron emission tomography for noninvasive studies of cerebral protein synthesis in humans are evaluated on the basis of an experimental animal approach.
Alteration in Fatty Acid Composition of Adult Rat Brain Capillaries and Choroid Plexus Induced by a Diet Deficient in n‐3 Fatty Acids: Slow Recovery After Substitution with a Nondeficient Diet
Authors: Homayoun P. , Durand G. , Pascal G. , Bourre J. M. 
Published: October 2006

AbstractWistar rats were fed for three generations with a semisynthetic diet containing either 1.5% sunflower oil (940 mg% of C18:2n‐6, 6 mg% of C18:3n‐3) or 1.9% soya oil (940 mg% of C18:2n‐6, 130 mg% of C18:3n‐3). At 60 days of age, the male offspring of the third generation were killed. The fatty acyl composition of isolated capillaries and choroid plexus was determined. The major changes noted in the fatty acid profile of isolated capillaries were a reduction (threefold) in the level of docosahexaenoic acid and, consequently, a fourfold increase in docosapentaenoic acid in sunflower oil‐fed animals. The total percentage of poly‐unsaturated fatty acids was close to that in the soya oil‐fed rats, but the ratio of n‐3/n‐6 fatty acids was reduced by threefold. In the choroid plexus, the C22:6n‐3 content was also reduced, but by 2.6‐fold, whereas the C22:5n‐6 content was increased by 2.3‐fold and the ratio of n‐3/n‐6 fatty acids was reduced by 2.4‐fold. When the diet of sunflower oil‐fed rats was replaced with a diet containing soya oil at 60 days of age, the recovery in content of n‐6 and n‐3 fatty acids started immediately after diet substitution; it progressed slowly to reach normal values after 2 months for C22:6n‐5 and 2.5 months for C22:6n‐3. The recovery in altered fatty acids of choroid plexus was also immediate and very fast. Recovery in content of C22:5n‐6 and C22:6n‐3 was complete by 46 days after diet substitution.
Dose‐Dependent, K+‐Stimulated Efflux of Endogenous Taurine from Primary Astrocyte Cultures Is Ca2+‐Dependent
Authors: Philibert Robert A. , Rogers Keith L. , Allen Albert J. , Dutton Gary R. 
Published: October 2006

AbstractThe K+‐stimulated efflux of endogenous taurine from primary rat cerebellar astrocyte cultures prepared from 7–9‐day‐old rats was studied at 16–18 days in vitro using HPLC analysis. Taurine efflux was dose‐dependent at K+ concentrations between 10 mM and 80 mM, with an EC50 of approximately 50 mM. Maximum stimulation of efflux above basal levels ranged from 56% at 10 mM K+ (204 pmol/min/mg protein) to 470% at 80 mM K+ (960 pmol/min/mg protein). Removal of Ca2+ from the buffer and the addition of either 1 mM EGTA or 10 mM Mg2+ abolished K.+‐stimulated efflux. Taurine efflux peaked and fell in parallel with the K+ concentration, but with an approximate lag of 3–5 min. The time course and amount of preloaded [3H]taurine released did not differ significantly from that seen for endogenous efflux. Basal taurine efflux varied inversely with the extracellular concentration of Ca2+ over the concentration range 0–5.0 mM. The observed Ca2+ dependence is consistent with a role for Ca2+ in the regulation of taurine release. Furthermore, taurine release from astrocytes in response to elevated K+ may reflect a neuromodulatory role for this amino acid in the CNS.
Possible Involvement of Pertussis Toxin Substrates (Gi, Go) in Desipramine‐Induced Refractoriness of Adenylate Cyclase in Cerebral Cortices of Rats
Authors: Okada Fumihiko , Tokumitsu Yukiko , Ui Michio 
Published: October 2006

AbstractTo evaluate the efficiency of coupling between β‐receptor and adenylate cyclase catalyst via a GTP‐binding protein, Gs, in the brain membrane two parameters were employed: a β‐agonist‐induced increase in the membrane GTP‐dependent adenylate cyclase activity and a β‐agonist‐induced shortening of the lag time preceding the onset of the steady‐state activation by guanyl‐5′‐yl‐β‐γ‐imidodiphosphate [Gpp(NH)p] of the membrane cyclase. Both parameters showed lower values in membranes from desipramine‐treated rats compared with untreated rats. Thus, coupling of β‐adrenergic receptors to adenylate cyclase in the brain membrane was impaired by the desipramine treatment. Rats once injected intraventricularly with isletactivating protein (IAP), pertussis toxin, were subjected to desipramine treatment, for the purpose of studying effects of another kind of the GTP‐binding protein (Gi), which loses its function as a signal transducer on being ADP‐ribosylated selectively by the toxin. IAP treatment did not impair the β‐receptor coupling by itself, since neither of the above two parameters for the coupling were reduced by IAP treatment. Moreover, the first parameter was normalized. though the second one was not, by superimposition of the IAP treatment upon the desipramine‐treated rats. It seems likely, therefore, that Gi interacts with a Gs‐adenylate cyclase coupling in an inhibitory fashion in brain membranes. The desensitization might be overcome when the inhibitory interaction of Gi on the subsequent process is attenuated by IAP treatment.
Characteristics of Sorbitol Uptake in Rat Glial Primary Cultures
Authors: Stahl Bernd , Wiesinger Heinrich , Hamprecht Bernd 
Published: October 2006

AbstractUptake of [U‐14C]sorbitol was studied in astroglia‐rich rat primary cultures. Initial rate of sorbitol uptake is proportional to sorbitol concentration between 20 μM and 400 mM. Sorbitol transport is not inhibited by glucose, fructose, and a variety of structurally related polyols, or by cy‐tochalasin B, an inhibitor of glucose transport. Phloretin, phlorizin, filipin, and n‐hexanol, all compound that alter the properties of biological membranes, and the sulfhydryl reagent p‐chloromercuribenzoate inhibit sorbitol uptake to various degrees. Variation in the concentrations of extracellular Na+ and K+ does not affect transfer of sorbitol across the cell membrane. It is concluded that sorbitol is taken up into glial cells by a diffusion process, not involving a carrier and probably not through the lipid bilayer, but through a proteinaceous channel‐like structure.
Dual Effects of K+ Depoiarisation on Inositol Polyphosphate Production in Rat Cerebral Cortex
Authors: Baird John G. , Nahorski Stefan R. 
Published: October 2006

AbstractDepoiarisation of [3H]inosito]‐prelabejled slices of rat cerebral cortex with elevated extracellular Kr induced a rapid and marked increase in inositol polyphosphate accumulation. Addition of the muscarinic antagonist atropine (10 μM) markedly inhibited the K+‐induced accumulation of inositol tetrakisphosphate (InsP4), with only a slight reduction in stimulated inositol bis‐ and trisphosphate levels. Inhibitory effects on InsP4 were noted at the earliest time period measured (30 s) and suggested the involvement of released endogenous acetylcholine in part of the response. The atropine‐insensitive component of depoiarisation did not! appear to be secondary to release of noradrenaline, histamine, or 5‐hydroxytryptamine, because addition of prazosip, mepyr‐amine, or ketanserin was without effect on the K+ response. Furthermore, secretion of a neuropeptide that could stimulate phosphoinositide hydrolysis was unlikely, because the peptidase inhibitor bacitracin was also without effect. The results suggest that endogenous acetylcholine can stimulate phosphoinositide metabolism by interacting with muscarinic receptors and that this is particularly evident on InsP4 accumulation. Atropine‐insensitive responses may be secondary to Ca2+ entry via voltage‐sensitive channels.
Ganglioside Composition in Human Meningiomas
Authors: Davidsson Pia , Fredman Pam , Collins V. Peter , von Hoist Hans , Mansson Jan‐Eric , Svennerholm Lars 
Published: October 2006

AbstractThe ganglioside composition in meningioma specimens from 20 patients was analyzed to find potential me‐ningioma‐associated structures. The characterization was performed by immunological staining with specific monoclonal antibodies to gangJioside antigens and fast atom bombardment‐mass spectrometry. The major gangliosides were GM3 and GD3, and most of the meningioma specimens could be divided into a “GM3‐rich” or a “GD3‐rich” group. Gangliosides of the gangliotetraose series were represented by GM1, GD1 a, GDlb, and GT1b, which were found in minor amounts in all the specimens. The ratios of GM1/ GD1a and GD1a/GDlb differed from that in normal brain, and therefore existence of this series could not be explained by contamination with brain material. Ganglioside 3′‐isoLM1, found in human malignant glioma, could not be detected in any meningioma specimen.