bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Benzodiazepine Receptor in Rat Brain and Its Interaction with Ethyl /3‐Carboline‐3‐Carboxylate
Authors: Martin I. L. , Doble A. 
Published: October 2006

Abstract:[3H]Ethyl β‐carboline‐3‐carboxylate ([3H]β‐CCE) binds to a homogeneous population of recognition sites in rat whole brain membranes with high affinity. The [3H]β‐CCE binding is completely displaceable by low concentrations of a number of benzodiazepines with similar potencies found when using a 3H‐benzodiazepine as the ligand. This suggests that the recognition sites for β‐CCE and the benzodiazepines are identical or that they are involved in a close interaction. The binding of [3H]β‐CCE does not obey simple mass‐action kinetics. [3H]Flunitrazepam dissociation from its receptor population is biphasic, and different methods of initiation of this dissociation indicate that cooperative interactions take place within the receptor population. We conclude that the benzodiazepine receptor is a single entity that can exist in two conformations, the equilibrium between which may be controlled by some as yet unidentified factor.
Effects of Chronic (Dietary) Choline Availability on the Transport of Choline Across the Blood‐Brain Barrier
Authors: Wecker L. , Trommer B. A. 
Published: October 2006

AbstractThe effects of dietary choline availability on the transport of choline across the blood‐brain barrier (BBB) were investigated using the intracarotid injection technique. Maintenance of rats on choline‐deficient, basal choline, or choline‐supplemented diets for 28–32 days led to respective increases in blood levels of choline and correlative increases in the velocity of transport of choline measured using a buffer injectate. When serum from these rats was included in the injectate and transport determined in control animals, there was a marked inhibition of choline transport that was related to the concentration of choline in the diets. Results suggest that the activity of the choline carrier at the BBB is antagonized by an inhibitory substance in serum whose concentration or activity may be modified by chronic alterations in circulating levels of choline and whose presence may normally regulate the velocity of choline transport.
GABA‐Mimetic Activity and Effects on Diazepam Binding of Aminosulphonic Acids Structurally Related to Piperidine‐4‐Sulphonic Acid
Authors: Falch Erik , Jacobsen Poul , Krogsgaard‐Larsen Povl , Curtis David R. 
Published: October 2006

Abstract:The relationship between structure, in vivo activity, and in vitro activity of some analogues of the γ‐aminobutyric acid (GABA) agonist piperidine‐4‐sulphonic acid (P4S) was studied. The syntheses of 1,2,3,6‐tetrahydropyridine‐4‐sulphonic acid (DH‐P4S) and (RS)‐pyrrolidin‐3‐yl‐methanesulphonamide (PMSA‐amide) are described. Like P4S, its unsaturated analogue DH‐P4S and the five‐ring isomer (RS)‐pyrrolidin‐3‐yl‐methanesulphonic acid (PMSA) were bicuculline methochloride (BMC)‐sensitive inhibitors of the firing of neurones in the cat spinal cord. Whereas isonipecotic acid was less potent than its unsaturated analogue isoguvacine as a GABA‐mimetic and as an inhibitor of GABA binding, the opposite relative potencies of P4S and DH‐P4S were observed, P4S being proportionally more potent than DH‐P4S. In contrast with P4S and DH‐P4S, PMSA, which is an analogue of the potent GABA uptake inhibitor and BMC‐sensitive GABA‐mimetic homo‐β‐proline, was a relatively weak inhibitor of GABA uptake in vitro. PMSA‐amide was more than two orders of magnitude weaker than PMSA as an inhibitor of GABA binding and did not significantly affect GABA uptake in vitro. The effects of 3‐aminopropanesulphonic acid (3‐APS), PMSA, P4S, and DH‐P4S on the binding of [3H]diazepam in vitro at 30°C, in the presence or absence of chloride ions, were studied and compared with those of the structurally related amino acids GABA, homo‐β‐proline, isonipecotic acid, and isoguvacine. Under these conditions the aminosulphonic acids were weaker than the respective amino acids in enhancing [3H]diazepam binding, the difference being more pronounced in the absence of chloride.
Purification of Phosphatidylinositol Synthetase from Rat Brain by CDP‐Diacylglycerol Affinity Chromatography and Properties of the Purified Enzyme
Authors: Ghalayini Abdallah , Eichberg Joseph 
Published: October 2006

Abstract:A purification procedure for rat brain phosphatidylinositol synthetase (PI synthetase; CDP‐1,2‐diacylsn‐glycerol:myo‐inositol 3‐phosphatidyltransferase; EC 2.7.8.11) is described. The enzyme was purified 200–250‐fold from the homogenate by solubilization with Triton X‐100 from microsomal membranes and affinity chromatography on CDP‐diacylglycerol‐Sepharose. Elution of enzyme activity required the presence of Triton X‐100, CDP‐diacylglycerol, and either phosphatidylcholine or asolectin. The product that was obtained in 5–10% yield from whole brain and in 70% yield from the microsomal fraction contained three protein bands as determined by sodium dodecylsulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE). The final preparation contained levels of CDP‐diacylglycerol hydrolase and CDP‐diacylglycerol: sn‐glycero‐3‐phosphate 3‐phosphatidyltransferase activities that were less than 1% of PI synthetase activity. The purified enzyme displayed a pH optimum of 8.5–9.0, required either Mg2+ or Mn2+ and exhibited a Km of 4.6 mM for myo‐inositol.
Arachidonic Acid Release and Catecholamine Secretion from Digitonin‐Treated Chromaffin Cells: Effects of Micromolar Calcium, Phorbol Ester, and Protein Alkylating Agents
Authors: Frye Roy A. , Holz Ronald W. 
Published: October 2006

Abstract:The relationship between catecholamine secretion and arachidonic acid release from digitonin‐treated chromaffin cells was investigated. Digitonin renders permeable the plasma membranes of bovine adrenal chromaffin cells to Ca2+, ATP, and proteins. Digitonin‐treated cells undergo exocytosis of catecholamine in response to micromolar Ca2+ in the medium. The addition of micromolar Ca2+ to digitonin‐treated chromaffin cells that had been prelabeled with [3H]arachidonic acid caused a marked increase in the release of [3H]arachidonic acid. The time course of [3H]arachidonic acid release paralleled catecholamine secretion. Although [3H]arachidonic acid release and exocytosis were both activated by free Ca2+ in the micromolar range, the activation of [3H]arachidonic acid release occurred at Ca2+ concentrations slightly lower than those required to activate exocytosis. Pretreatment of the chromaffin cells with N‐ethylmaleimide (NEM) or p‐bromophenacyl bromide (BPB) resulted in dose‐dependent inhibition of 10 μM Ca2+‐stimulated [3H]arachidonic acid release and exocytosis. The IC50 of NEM for both [3H]arachidonic acid release and exocytosis was 40 μM. The IC50 of BPB for both events was 25 μM. High concentrations (5–20 mM) of Mg2+ caused inhibition of catecholamine secretion without altering [3H]arachidonic acid release. A phorbol ester that activates protein kinase C, 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), caused enhancement of both [3H]arachidonic acid release and exocytosis. The findings demonstrate that [3H]arachidonic acid release is stimulated during catecholamine secretion from digitonin‐treated chromaffin cells and they are consistent with a role for phospholipase A2 in exocytosis from chromaffin cells. Furthermore the data suggest that protein kinase C can modulate both arachidonic acid release and exocytosis.
Effects of 1‐Methyl‐4‐Phenyl‐1,2,5,6‐Tetrahydropyridine and Related Compounds on the Uptake of [3H]3,4‐Dihydroxyphenylethylamine and [3H]5‐Hydroxytryptamine in Neostriatal Synaptosomal Preparations
Authors: Heikkila Richard E. , Youngster Stephen K. , Manzino Lawrence , Cabbat Felicitas S. , Duvoisin Roger C. 
Published: October 2006

Abstract:1‐Methyl‐4‐phenyl‐1,2,5,6‐tetrahydropyridine (MPTP) is known to cause a destruction of the dopaminergic nigrostriatal pathway in certain animal species including mice. MPTP and some structurally related analogs were tested in vitro for their capacity to inhibit the uptake of [3H]3,4‐dihydroxyphenylethylamine‐([3H]DA), [3H]5‐hydroxytryptamine ([3H]5‐HT), and [3H]γ‐aminobutyric acid ([3H]GABA) in mouse neostriatal synaptosomal preparations. MPTP was a very potent inhibitor of [3H]5‐HT uptake (IC50 value 0.14 μM), a moderate inhibitor of [3H]DA uptake (IC50 value 2.6 μM), and a very weak inhibitor of [3H]GABA uptake (no significant inhibition observed at 10 μM MPTP). In other experiments, MPTP caused some release of previously accumulated [3H]DA and [3H]5‐HT, but in each case MPTP was considerably better as an uptake inhibitor than as a releasing agent. The 4‐electron oxidation product of MPTP, i.e., 1‐methyl‐4‐phenyl‐pyridinium iodide (MPP+), was a very potent inhibitor of [3H]DA uptake (IC50 value 0.45 μM) and of [3H]5‐HT uptake (IC50 value 0.78 μM) but MPP+ was a very weak inhibitor of [3H]GABA uptake. These data may have relevance to the neurotoxic actions of MPTP.
Developmental and Functional Studies of Parvalbumin and Calbindin D28K in Hypothalamic Neurons Grown in Serum‐Free Medium
Authors: Pfyffer Gaby E. , Faivre‐Bauman Annie , Tixier‐Vidal Andrée , Norman Anthony W. , Heizmann Claus W. 
Published: October 2006

AbstractThe Ca2+‐binding proteins parvalbumin (Mr= 12K) and calbindin D28K [previously designated vitamin D‐dependent Ca2+‐binding protein (Mr= 28K)] are neuronal markers, but their functional roles in mammalian brain are unknown. The expression of these two proteins was studied by immunocytochemical methods in serum‐free cultures of hypothalamic cells from 16‐day‐old fetal mice. Parvalbumin is first detected in all immature neurons, but during differentiation, the number of parvalbumin‐immunoreactive neurons greatly declines to a level reminiscent of that observed in vivo, where only a subpopulation of neurons stains for parvalbumin. In contrast, calbindin D28K was expressed throughout the period investigated only in a distinct subpopulation of neurons. Depolarization of fully differentiated hypothalamic neurons in culture resulted in a dramatic decrease of parvalbumin immunoreactivity but not of calbindin D28K immunoreactivity. The parvalbumin staining was restored on repolarization. Because the anti‐parvalbumin serum seems to recognize only the metal‐bound form of parvalbumin, the loss of immunoreactivity may signal a release of Ca2+ from intracellular parvalbumin during depolarization of the cells. We suggest that parvalbumin might be involved in Ca2+‐dependent processes associated with neurotransmitter release.
Two‐Site Immunoassay for Acetylcholinesterase in Brain, Nerve, and Muscle
Authors: Brimijoin S. , Hammond P. , Rakonczay Z. 
Published: October 2006

AbstractTwo‐site methods were developed for immunoassay of acetylcholinesterase (AChE; EC 3.1.1.7) in crude extracts of rat and human tissues. A radiometric assay for human AChE utilized a specific monoclonal AChE antibody adsorbed to polystyrene microtiter wells at alkaline pH. AChE bound strongly to this antibody after 24 h at 4°C. Bound enzyme was detected with an 125I‐labeled antibody against a different AChE epitope. The assay signal was quasilinearly related to AChE concentration in purified and crude samples, with a detection threshold near 100 pg. Tetrameric and dimeric AChE behaved equivalently in the assay. Two‐site methods with a different pair of species‐selective antibodies worked equally well for immunoassay of rat AChE. Assays of the rat enzyme showed that immunoreactivity was lost as rapidly as enzyme activity during heating to 54°C. On the other hand, immunoreactivity was preserved despite loss of enzyme activity after exposure to anti cholinesterases or trypsin. A biotinylated second antibody detected by alkaline‐phosphatase‐conjugated avidin was used to develop an AChE enzyme‐linked immunosorbent assay (ELISA) with a sensitivity similar to that of the radio‐metric assay. Either the ELISA or the radiometric immunoassay may be useful whenever proteolysis or other mechanisms are suspected of dissociating enzyme activity and immunoreactivity. In denervated muscle and ligated peripheral nerve, application of the two‐site method showed closely parallel variations in immunoreactivity and enzyme activity.
Synthetic Sialyl Compounds as Well as Natural Gangliosides Induce Neuritogenesis in a Mouse Neuroblastoma Cell Line (Neuro2a)
Authors: Tsuji Shuichi , Yamashita Tatsuro , Tanaka Makoto , Nagai Yoshitaka 
Published: October 2006

AbstractAmphipathic compounds containing N‐acetylneuraminic acid (sialic acid) [for example, D‐N‐acetylneuraminyl‐(α2‐1)‐2S, 3R,4E‐2‐N‐tetracosanoyl sphingenine, sialyl alkyl glycerol ethers, and sialyl cholesterols] induced neuritogenesis in a neuroblastoma cell line (Neuro2a). The sialic acid in the hydrophilic moiety of the compounds is specifically required for neuritogenesis. The requirement for molecular specificity of the hydrophobic moiety, however, is rather low. Regarding the hydrophobic moiety, no preference for cholesterol, alkyl glycerol ether, or ceramide residues was observed as to their neuritogenic activity. Sialyl compounds with α‐ketosidic sialyl linkages were more active than the corresponding β‐anomers. These sialyl compounds induced the growth of only one neurite, but a long one, from the cell body. This type of neuritogenesis is completely different from that induced by compounds capable of elevating the concentration of intracellular cyclic AMP, which induced the appearance of many neurites from a single cell body. Besides this morphological change, the active sialyl compounds also caused a change in the carbohydrate composition of the cell surface. Sialyl compound treatment drastically increased the concentration of peanut agglutinin binding sites.
K+‐Dependent Stimulation of Dopamine Synthesis in Striatal Synaptosomes Is Mediated by Protein Kinase C
Authors: Chowdhury Muhammad , Fillenz Marianne 
Published: October 2006

AbstractDopamine synthesis rate was measured in striatal synaptosomes. Removal of Na+ increased synthesis rate; this was blocked in Ca2+‐free medium and by addition of the Ca2+/calmodulin inhibitor N‐6‐aminohexyl‐5‐chloro‐1‐naphthalenesulfonamide (W7). The increase in dopamine synthesis rate caused by the addition of the phorbol ester 12‐O‐tetradecanoylphorboI‐13‐acetate (TPA) was blocked by the protein kinase C inhibitor polymyxin B. K+‐stimulated synthesis was unchanged in Ca2+‐free medium or by addition of W7; it was blocked by polymyxin B. The effect of 50 mM K+ was additive with that of 8‐Br cyclic AMP and of Na+ removal; the combined effect of 50 mM K+ and TPA was no greater than that of either alone. These results suggest that stimulation of dopamine synthesis in striatal synaptosomes by 50 mM K+ is mediated by protein kinase C.
Biosynthesis of Neutral Glucocerebroside Homologues in the Absence of Myelin Assembly After Nerve Transection
Authors: Yao Jeffrey K. , Poduslo Joseph F. 
Published: October 2006

AbstractThe biosynthesis of myelin‐associated glycolipids during various stages of myelination was studied by in vitro incorporation of [3H]Gal, [3H]Glc, or [35S]sulfate into the endoneurium of rat sciatic nerve. In the normal adult nerve, where the level of myelin assembly is substantially reduced and Schwann cells are principally involved in maintaining the existing myelin membrane, [3H]Gal was primarily incorporated into monogalactosyl diacylglycerol (MGDG) and the galactocerebrosides (GalCe) with lower levels of incorporation into the sulfatides. Such incorporation was enhanced 35 days after crush injury of the adult rat sciatic nerve, which is characterized by active myelin assembly. In contrast, at 35 days after permanent nerve transection where there is no axonal regeneration or myelin assembly, the incorporation of [3H]Gal or [3H]Glc into GalCe was nearly undetected whereas the incorporation of [3H]Gal into MGDG was completely inhibited. Instead, the 3H‐labeled glycolipids in transected nerve were identified as the glucocerebrosides (GlcCe) and oligohexosylceramide derivatives with tetrahexosylceramide being a major product. In contrast, [35S]sulfate was incorporated into endo‐neurial sulfatides in the transected nerve, which suggests that endogenous GalCe rather than newly synthesized GalCe served as the substrate for the sulfotransferase reaction. The GlcCe homologues are not considered as constituents of the myelin membrane but are likely plasma membrane components synthesized in the absence of myelin assembly. It is likely that the cells responsible for GlcCe biosynthesis are Schwann cells, since they comprise 90% of the total endoneurial cell area in the distal nerve segment at 35 days after transection. The biosynthesis of these GlcCe homologues, therefore, may represent the phenotypic expression of Schwann cells in the absence of myelin assembly and axonal contact.
Release of Proteins from the Surface of Bovine Central Nervous System Myelin by Salts and Phospholipases
Authors: Smith Ross , Braun Peter E. 
Published: October 2006

AbstractIncubation of bovine CNS myelin with phospho‐lipase C from Bacillus cereus under conditions that lead to extensive phospholipid degradation caused 10% of the myelin protein to be released from the membrane. The myelin basic protein (MBP) was a major component of the dissolved protein. Comparable incubations with phospholi‐pase C from Clostridium perfringens, phosphatidylinositol‐specific phospholipase C from Staphylococcus aureus, or cabbage phospholipase D removed little MBP. However, concentrations of sodium chloride near 1 M and concentrations of divalent metal ions between 50 and 600 mM released typically 9‐12% of the total myelin protein, with MBP again as the predominant component. Repetitive washing with calcium chloride solutions resulted in dissolution of over 90% of the MBP. When myelin was incubated in 1.0 M sodium chloride or 25 mM calcium chloride, the MBP was cleaved largely into two major peptides with apparent molecular weights near 14,000 and 12,000, but with 200 mM or higher concentrations of calcium chloride most of this protein remained intact. With appropriate manipulation of the ionic milieu, it is thus possible to remove most of this extrinsic protein from the myelin surface under relatively mild conditions. The conditions that release the protein suggest that it is held at the membrane surface by ionic interactions.
Neuronal Localization of Specific Angiotensin II Binding Sites in the Rat Inferior Olivary Nucleus
Authors: Walters D. E. , Speth R. C. 
Published: October 2006

AbstractAdult male Sprague‐Dawley rats were treated with 3‐acetylpyridine, a neurotoxin selective for the inferior olivary nucleus. Following treatment, the rats exhibited deficits in locomotor behavior indicative of destruction in the inferior olivary nucleus. The rats were sacrificed 3 weeks later, and the binding of125I‐sarcosine1, isoleucine8angiotensin II to brain homogenates and slide‐mounted sections of brainstem was determined. Treatment with 3‐acetylpyridine significantly decreased specific125I‐sarco‐sine', isoleucine8angiotensin II binding in homogenates of posteroventral brainstem (containing the inferior olivary nucleus) by approximately 50%. Homogenates of dorsal brainstem and hypothalamus‐thalamus‐midbrain showed no significant changes in specific binding. Treatment with 3‐acetylpyridine did not significantly alter the radioligand binding affinity which was determined in the hypothalamus‐thalamus‐midbrain. Autoradiographic analysis of125I‐sarcosine1, isoleucine8angiotensin II binding in the brainstem sections indicated that specific angiotensin II binding sites in the inferior olivary nucleus were virtually eliminated by the 3‐acetylpyridine treatment. In addition, a comparatively small, but significant, decrease in specific125I‐sarcosine1, isoleucine8angiotensin II binding occurred in the solitary tract nucleus/dorsal vagal motor nucleus complex. These results indicate that specific angiotensin II binding sites in the inferior olivary nucleus occur exclusively on neuronal perikarya and/or dendrites.
Distribution of [3H]Dihydrotetrabenazine Binding in Bovine Striatal Subsynaptic Fractions: Enrichment of Higher Affinity Binding in a Synaptic Vesicle Fraction
Authors: Meshgin‐Azarian Sassan , Chang Warren , Cugier Debbie L. , Vincent Michael S. , Near Joseph A. 
Published: October 2006

Abstract[3H]Dihydrotetrabenazine bound to a single class of binding sites in bovine striatal synaptic vesicles with an apparent dissociation constant of 3‐9 nM. This is comparable to the inhibitory potency of dihydrotetrabenazine in catecholamine transport assays. In contrast to these results, [3H]dihydrotetrabenazine bound to at least two classes of sites in all other subsynaptic fractions investigated. The higher affinity class of sites was comparable in affinity to that of synaptic vesicles, whereas the lower affinity sites exhibited an apparent dissociation constant of 95‐400 nM. Higher affinity sites were most abundant in the synaptic vesicle fraction, and little higher affinity binding was observed in mitochondrial and myelin fractions, or in highly purified synaptic plasma membranes. Lower affinity binding was not enriched in any subsynaptic fraction and was the only class of binding sites detected in homogenates of liver and diaphragm. The distribution of the presynaptic vesicle marker synaptophysin corresponded with that of higher affinity but not lower affinity binding. These results are consistent with the expectation that the higher affinity sites are associated primarily with synaptic vesicles and other neuronal entities that are in communication with these organelles.
Chronic Exposure to Pertussis Toxin Alters Muscarinic Receptor‐Mediated Regulation of Cyclic AMP Metabolism in Neuroblastoma × Glioma NG108–15 Hybrid Cells
Authors: Westlind‐Danielsson Anita , Gillenius Pekka , Askelof Per , Bartfai Tamas 
Published: October 2006

AbstractChronic pertussis toxin treatment (5 days) of NG108–15 neuroblastoma × glioma hybrid cells had no significant effect on basal cyclic AMP levels whereas it effectively blocked the inhibitory action of acute (10 min) exposure of carbachol (10−‐4M) on intracellular cyclic AMP accumulation, stimulated by prostaglandin E1. This action of pertussis toxin was found to be long lasting: exposure of the cells to pertussis toxin (100 ng/ml) for only 24 h followed by a 5‐day withdrawal period still was shown effective on day 7 in abolishing the inhibitory action of carbachol on prostaglandin E1‐stimulated cyclic AMP production. Chronic exposure (5 days) of NG108–15 cells to carbachol (10−‐5M) causes an increase in basal cyclic AMP levels by 98%, and a desensitization of the muscarinic inhibition of cyclic AMP accumulation, assessed after a 24‐h withdrawal period. When carbachol treatment is carried out in the presence of pertussis toxin (100 ng/ml) both of these effects of carbachol are abolished.