bluuebunny/crossref_metadata_2025_split huggingface dataset:
Covalent labeling of the cocaine‐sensitive catecholamine transporter
Authors: Howard B. D. , Cho A. K. , Zhang M.‐b. , Koide M. , Lin S. 
Published: February 2006

AbstractXylamine is an alkylating agent that is a substrate for and specific irreversible inhibitor of the cocaine‐sensitive catecholamine transporter that functions in catecholamine reuptake into neurons and PC12 cells. [3H]xylamine prominently labels nine PC12 proteins; the relative xylamine‐alkylation of a Mr 54,000 protein was decreased by cocaine and increased in the case of a PC12 variant, B9, which is deficient in catecholamine transport. [3H]xylamine labels no such protein in another transport variant, MPT1. We propose that this Mr 54,000 protein (1) is a component of the catecholamine transporter, (2) is present in B9 cells but in a conformation that reduces transporter activity and makes alkylation by xylamine more likely, and (3) is absent in MPT1 cells. Nerve growth factor treatment restores transporter activity in B9 cells but not in other transporter‐deficient variants.
Mechanisms of [3H] γ‐aminobutyric acid release by chromaffin cells in primary culture
Authors: Oset‐Gasque M. J. , Castro E. , González M. P. 
Published: February 2006

AbstractThe basal and evoked [3H] γ‐aminobutyric acid (GABA) release from chromaffin cells in primary cultures was studied and compared with that of [3H]NA. [3H]GABA was found to be released, in a dose‐dependent fashion, by different secretagogues known to induce noradrenaline (NA) release, that is, the cholinergic agonist nicotine, high‐potassium chloride, veratridine, and calcium ionophores. In general, there was a parallelism between percentages of release of both [3H]GABA and [3H]NA, although in all circumstances the former were lower. The nicotine‐and high‐potassium‐evoked [3H]GABA release was absolutely calcium dependent, thus indicating the existence of a exocytotic‐like mechanism, whereas in the veratridine‐induced release, a calcium‐independent component was also detected. This latter component was sodium dependent, as it showed an absolute requirement for extracellular sodium and was enhanced by ouabain. Moreover, it was inhibited by known GABA uptake inhibitors, which indicate that this component of [3H]GABA release induced by veratridine could be due to GABA outflow through the membrane carrier. The above results, together with that obtained from studies about subcellular localization of [3H]GABA taken up by chromaffin cells, seem to support the existence of two mechanisms for [3H]GABA release by chromaffin cells: one calcium‐dependent, exocytotic‐like, and another calcium‐independent and sodium‐dependent, possibly mediated by the GABA carrier. Both processes could have a functional role on the regulation of extracellular GABA levels and so in the control of catecholamine release by chromaffin cells.
Quantitative brain autoradiography of [9, 10‐3H]palmitic acid incorporation into brain lipids
Authors: Noronha J. G. , Bell J. M. , Rapoport S. I. 
Published: February 2006

AbstractThe distribution of radioactivity within brain metabolic compartments was examined following the intravenous injection of [9,10‐3H]palmitate into awake rats. Brain radioactivity reached a maximum value by 15 min after [9,10‐3H]palmitate injection and remained unchanged for at least 4 hr. Regional differences in radioactivity could be determined with high resolution by quantitative autoradiography, at the level of cell layers within the hippocampus and cerebral cortex, and between striosomes of the caudate nucleus. Regional brain radioactivities were converted to normalized regional radioactivities (k) by dividing them by the integrated plasma fatty acid radioactivity (integrated over the time course of the experiment). These values reflected incorporation mainly into brain phospholipids; radioactivity due to nonlipid components was minimal. Indeed, about 85% of brain radioactivity was within lipids between 5 min and 4 hr postinjection, the remainder being equally divided between protein‐associated pellet and aqueous‐soluble metabolites. The major lipids labeled were phospholipids, particularly phosphatidylcholine, which contained about 75% of phospholipid radioactivity. The results show that [9,10‐3H]palmitate can be used to examine incorporation of plasma palmitate into individual brain regions via quantitative autoradiography. Furthermore, the tracer is a rather selective marker for phosphatidylcholine and can be used to examine turnover and synthesis of this phospholipid. [9,10‐3H]palmitate has advantages over [U‐14C]palmitate for autoradiographic studies of incorporation; following the 14C‐tracer, significant label even at 4 hr after injection is in nonlipid compartments (glutamate and aspartate), and the long path length of 14C limits resolution at the cell layer level.
Changes with aging in the levels of amino acids in rat CNS structural elements: IV. Methionine and basic amino acids
Authors: Banay‐Schwartz M. , Lajtha A. , Palkovits M. 
Published: February 2006

AbstractThis paper reports the distribution of methionine, histidine, lysine, arginine, and ornithine in 53 discrete brain areas of 3‐and 29‐month‐old male Fischer 344 rats microdissected by the punch technique. Like that of the other amino acids we reported in previous papers of this series, the distribution of methionine and the basic amino acids was regionally highly heterogeneous. The ratios of levels in the areas of highest concentrations to levels in the areas of lowest concentration varied from 10 to 15 for these amino acids, except that it was 23 for arginine. This heterogeneity is also illustrated by the finding that in some areas arginine was more than 5% of the total amino acid content and in others was less than 0.5%.The distribution of methionine differed from that of the basic amino acids, which were high in hypothalamic areas and low in the limbic system.With aging, methionine and basic amino acids, like the other amino acids studied in this series, mainly decreased in level, although in a few cases increases could be seen. Significant decreases were noted more than five times as often as increases.
Iron‐dependent peroxidation of rat brain: A regional study
Authors: Subbarao K. V. , Richardson J. S. 
Published: February 2006

AbstractIron has been shown to initiate a variety of free radical reactions in biological systems. The present study examined the in vitro susceptibility of homogenates prepared from different regions of rat brain to iron‐induced peroxidation. Among the regions studied, basal thiobarbituric acid‐reactive product (TBAR) formation is highest in the cerebellum and amygdala, intermediate in the cortex, hippocampus, and neo‐stratium, and lowest in the hypothalamus, midbrain, and brainstem. In the presence of 200 μM FeCl3, there is a 20–25‐fold increase in the net TBAR formation in all regions, with TBAR formation in the cerebellum and amygdala being significantly higher than in the midbrain and brainstem. Time‐course and dose‐response studies of iron‐induced peroxidation showed that the cerebellum and amygdala are the most susceptible regions with respect to concentration of iron and duration of the incubation time, whereas the midbrain and brainstem are the least affected areas. Following low‐speed (1,000g) centrifugation of brain part homogenates, TBAR formation in the supernatant fractions is quite uniform across regions, while the pellet fractions give the same regional variations as the whole homogenates. TBAR formation in both fractions is increased 20–30‐fold in the presence of 200 μM iron. Brain tissue TBAR formation induced by 200 μM iron is inhibited by the iron chelator desferrioxamine (IC50 = 600μM), by Tris buffer pH = 8.0 (2.5 mM Tris gives 50% inhibition by trapping hydroxyl radicals), and by high concentrations of the cyclooxygenase inhibitor indomethacin (IC50 = 1.2 mM).
Effect of lithium on tachykinins, calcitonin gene‐related peptide, and neuropeptide Y in rat brain
Authors: Mathé A. A. , Jousisto‐Hanson J. , Stenfors C. , Theodorsson E. 
Published: February 2006

AbstractThe effects of lithium on brain regional concentrations of substance P (SP)‐, neurokinin A (NKA)‐, calcitonin gene‐related peptide (CGRP)‐ and neuropeptide Y (NPY)‐like immunoreactivities (‐LI) were studied in rat. In the pilot study, rats were divided into three groups that were administered vehicle, or 1 or 4 mEq/kg lithium sulphate, respectively, intraperitoneally once/day for 9 days. In the second experiment, rats were divided into three groups receiving vehicle, or 1 or 2 mEq/kg lithium sulphate, respectively, intraperitoneally twice/day for 9 days. After sacrifice by focused microwave irradiation, brains were dissected, weighed, and frozen. Peptides were extracted and measured in extract aliquots by specific radioimmunoassays. Marked regional differences (P<.001) were found for each of the peptides measured. In the pilot study the higher lithium dose, 4 mEq/kg, significantly raised neuropeptide levels. However, animals receiving this dose also showed signs of toxicity. In the second experiment, lithium increased SP‐LI concentrations in striatum and hypothalamus (72 and 29%, P's<.001 and .05). NKA‐LI was also elevated in striatum (44%, P<.01). CGRP‐LI, in parallel to SP‐LI, was increased in striatum and hypothalamus (58 and 78%, P's <.05 and .01). In contrast, lithium decreased CGRP‐LI in the pituitary gland (56%, P < .01). NPY‐LI was increased in striatum, and frontal and occipital cortex (30, 66, and 60%, respectively; P's < .01, .01, and .05). In conclusion, lithium, in doses equivalent to those used clinically, has a significant effect on SP‐, NKA‐, CGRP‐, and NPY‐LI concentrations in several brain structures, most prominently in the striatum. These findings raise the possibility that lithium's effects on neuropeptides are specific and may represent one of its mechanisms of action on mood and motor behavior.
Calcitonin gene‐related peptide identifies spinal motoneurons in vitro
Authors: Juurlink B. H. J. , Munoz D. G. , Devon R. M. 
Published: February 2006

AbstractCell dissociation of E6 chick spinal cord followed by isolation of larger low‐density cells by using a discontinuous density metrizamide gradient resulted in the obtention of a motoneuron‐enriched fraction of cells. These cells were cultured in the presence of horse serum and muscle extract for a period of 8 days and examined for the presence of calcitonin gene‐related peptide. More than 90% of such cells were positive for calcitonin gene‐related peptide. When E14 spinal cord was examined, calcitonin gene‐related peptide was present only in the axons of primary sensory neurons and in the somas of motoneurons in the ventral horns. It is concluded that more than 90% of the neurons in our cultures are motoneurons.
Glial fibrillary acidic protein messenger RNA and glutamine synthetase activity after nervous system injury
Authors: Condorelli D. F. , Dell'Albani P. , Kaczmarek L. , Messina L. , Spampinato G. , Avola R. , Messina A. , Stella A. M. Giuffrida 
Published: February 2006

AbstractThe level of the mRNA for glial fibrillary acidic protein (GFAP), the major protein of the intermediate filaments of astroglial cells, and the activity of glutamine synthetase (GS), an enzyme selectively localized in astrocytes, were measured at different times after a unilateral mechanical lesion in the rat cerebral cortex. A rapid and early increase (6 hours post‐lesion) in GFAP mRNA was observed; GFAP mRNA level reached a peak at 1–3 days and then decreased. Moreover, an astrocytic activation in cortical zones far from the injury site and in the contralateral hemisphere was detected. No change of GS activity was observed in the same model of brain injury, showing that this astroglial marker is not modified during the reactive gliosis obtained with this experimental model. GFAP mRNA has also been detected in the rat sciatic nerve; however, its level was not modified after nerve transection, suggesting a different regulation of GFAP expression in the peripheral nervous system.
Réaction de Fries appliquée aux poly(vinyl‐4 benzoates de phényl)
Authors: Pinazzi Christian , Fernandez Alain 
Published: February 2006

AbstractLes vinyl‐4 benzoates de phényle (3a) et de méthoxy‐3 phényle (3b) ont été synthétisés et polymérisés par voie radicalaire. Leur copolymérisation avec le styrène montre une aptitude plus grande à la polymérisation que ce dernier. Les polymères de 3a et 3b ont été traités dans les conditions de la réaction de Fries chimique. Les caractéristiques spectrales des structures attendues dans la réaction de réarrangement ont été déterminées à l'aide d'homopolymères modèles. L'étude de la réaction dans les deux cas a été réalisée en couplant les données des spectres d'absorption UV avec une méthode programmée de calcul. Les résultats traduisent un mécanisme intermoléculaire avec une formation d'acide plus importante que dans le cas de molécules organiques. La réaction du poly(vinyl‐4 benzoate de méthoxy‐3 phényle) (4b) conduit à un polymère contenant une forte proportion de groupes hydroxy‐2 benzoyl phenyle.
Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 5. Polymérisation du méthacrylate de méthyle sous rayonnement ultraviolet
Authors: Pinazzi Christian , Lenain Jean‐Claude , Brosse Jean‐Claude , Legeay Gilbert 
Published: February 2006

AbstractSous l'action du rayonnement ultra‐violet (253,7 nm), le peroxyde d'hydrogène est scindé en radicaux hydroxyle pouvant agir comme agents d'amorcage d'un processus de polymérisation. On peut ainsi obtenir des polymères hydroxytéléchéliques. L'adjonction d'un alcool au milieu réactionnel modifie les conditions de la polymérisation et permet de moduler les taux de conversion et les masses molécularies moyennes en nombre. Les résultats sont différents selon que le polymère est soluble ou non dans l'alcool. La polymérisation du méthacrylate de méthyle selon ce procédé, dans le méthanol non‐solvant du polymère, fait l'object du présent travail. La nature des polymères obtenus est déterminée: mode de distribution des masses moléculaires, microstructure, taux de groupements hydroxyle par macromolécule; l'influence de divers paramètres est également étudiée: durée, proportions d'eau oxygénée, nature du milieu réactionnel.
Mechanism of interfacial polycondensation and the direct synthesis of stable polyamide membranes
Authors: Enkelmann Volker , Wegner Gerhard 
Published: February 2006

AbstractThe mechanism of membrane formation by interfacial polycondensation was studied. For the time‐conversion curves the equation

was derived (x′ = reduced membrane thickness). The membrane morphology was investigated by x‐ray scattering and electron microscopy. It was found that the polymer chains are mainly oriented perpendicularly to the interface in the direction of membrane growth. The order of chain packing decreases with increasing thickness. Stable polyamide membranes consisting of two layers can be obtained by formation of a supporting layer of crosslinked copolyamide on a thin layer of Nylon‐6,10. The swelling properties of these membranes were studied.
Polymere Imidazolcarbonsäuren, 1. Darstellung und Eigenschaften einiger vernetzter Polyvinylimidazolcarbonsäuren
Authors: Manecke Georg , Schlegel Rainer 
Published: February 2006

AbstractDurch radikalische Lösungsmittelpolymerisation einiger vinylsubstituierter Imidazolcarbonsäureester wurden Homopolymere erhalten und deren Eigenschaften untersucht. Der 1‐Vinylimidazol‐4‐carbonsäure‐methylester (1b), der 1‐Vinylimidazol‐4,5‐dicarbonsäure‐dimethylester (1d), sowie der 2‐(p‐Vinylphenyl)imidazol‐4,5‐dicarbonsäure‐dimethylester (3a) wurden mit Divinylbenzol (DVB) copolymerisiert. Durch alkalische Verseifung der Copolymeren wurden die neuen Chelatharze 5–7 erhalten. Zur Charakterisierung wurden die scheinbaren Dissoziationskonstanten pK′ der Harze bestimmt. Das Quellverhalten bei verschiedenen pH‐Werten, das Bindungsvermögen der Harze für Cu2+‐Ionen bei pH 5,0 und die Zeitabhängigkeit der Cu2+‐Ionenaufnahme wurden untersucht.
The synthesis of monomers that expand on polymerization. Synthesis and polymerization of 8,10,19,20‐tetraoxatrispiro[5.2.2.5.2.2]heneicosane
Authors: Endo Takeshi , Katsuki Hirokazu , Bailey William J. 
Published: February 2006

AbstractA spiro orthocarbonate containing two cyclohexyl groups, 8,10,19,20‐tetraoxatrispiro[5.2.2.5.2.2]heneicosane (1), was prepared. The monomer was polymerized with Lewis acids such as boron trifluoride etherate or stannic chloride as catalysts. The IR and NMR spectra indicated that the polymer was an alternating copolymer with ether and carbonate linkages. This monomer underwent expansion on polymerization.
Stereochemistry of copolymerization of optically active cyclohexylepoxyethane with carbon dioxide
Authors: Hirano Takashi , Inoue Shohei , Tsuruta Teiji 
Published: February 2006

AbstractThe stereochemistry of alternating copolymerization of carbon dioxide with S‐(+)‐cyclohexylepoxyethane (1) using a diethylzinc/water system as catalyst was investigated. The optically active copolymer, poly[(oxycarbonyloxy)‐1‐cyclohexylethylene], was hydrolyzed and the epoxide was transformed into the form 1,2‐bis(trimethylsilyloxy)‐1‐cyclohexylethane (2). From the determination of optical activity of this ether, it is concluded that the ring opening of 1 in the copolymerization takes place predominantly at the methylene‐oxygen linkage.
Synthesis of new monomers by addition reactions of diethylamine to 1,4‐divinylbenzene catalyzed by lithium diethylamide
Authors: Tsuruta Teiji , Narita Tadashi , Nitadori Yoshiaki , Irie Tadashi 
Published: February 2006

AbstractAddition reactions of diethylamine onto 1,4‐divinylbenzene (DVB) catalyzed by lithium diethylamide were examined to find a synthetic route to a group of new monomers possessing dialkylamino substituents, which is expected to be a starting material for biomedical polymers such as ionic polymer complexes, polycations, and others. It was found that 1‐(2‐diethylaminoethyl)‐4‐vinylbenzene (1) and 1,4‐bis(2‐diethylaminoethyl)‐benzene (2) can be prepared selectively, because the rate of the first step of the addition reaction was twenty times as large as that of the second step. Results of kinetic studies on the addition reactions towards DVB are discussed with the aid of 13C NMR data and compared with other p‐vinylbenzene derivatives.
Self‐crosslinkable polymers, 2. High pressure copolymerization of 2,3‐epoxy‐1‐propyl methacrylate with 2‐vinyl‐5‐ethylpyridine
Authors: Tanaka Yoshio , Atsukawa Morishige , Shimura Yukio , Okada Akira , Sakuraba Hideki , Sakata Tokuji 
Published: February 2006

Abstract2,2′‐Azoisobutyronitrile‐initiated copolymerization of 2,3‐epoxy‐1‐propyl methacrylate (1) (M1) with 5‐ethyl‐2‐vinyl‐pyridine (2) (M2) was studied in tetrahydrofuran at 60°C under high pressure up to 15 kbar. Under pressure, soluble linear polymers with pendant epoxy and pyridyl groups were obtained and can be used as self‐curable resins. The monomer reactivity ratios, r1 and r2, became larger with increasing pressure (r1, r2, and pressure given): 0,60, 0,64 at 2 kbar; 0,64, 0,66 at 4 kbar; 0,72, 0,69 at 7 kbar; 0,78, 0,72 at 10 kbar; 0,87, 0,76 at 13 kbar; 0,91, 0,80 at 15 kbar. Therefore, the change of activation volume of the chain propagation, ΔV, may vary from one type of propagation step to another. The intrinsic viscosities of the copolymers were found in tetrahydrofuran at 30°C to be 0,26 to 1,35 and to be dependent upon the copolymer composition and the pressure. These copolymers were amorphous, had no clear melting points and became insoluble crosslinked polymers under heating without further addition of any curing agents.
1H NMR‐spektroskopische Untersuchungen zur Strukturaufklärung von Oligo(hydroxy‐5‐nitro‐1,3‐phenylen)methylen Verbindungen
Authors: Deveaux Jürgen , Böhmer Volker 
Published: February 2006

AbstractDie 1H NMR‐Spektren von 51 Oligo(hydroxy‐5‐nitro‐1,3‐phenylen)methylen Verbindungen (17 Zwei‐, 18 Drei‐, 14 Vier‐ und 2 Fünfkernverbindungen) wurden in Pyridin als Lösungsmittel aufgenommen. Bei Verbindungen mit ortho‐Nitrophenolbausteinen zeigten die Signale für die Protonen der Methyl‐ bzw. Methylengruppen in allen Fällen charakteristische chemische Verschiebungen δ, so daß eine eindeutige Unterscheidung zwischen Methylgruppen in para‐ (δ=2,09−2,15 p.p.m.) und ortho‐Stellung (δ=2,22−2,28 p.p.m.) zur phenolischen Hydroxyl‐Gruppe, sowie zwischen para‐para‐ (δ=3,77−3,97 p.p.m.), ortho‐para‐ (δ=4,02−4,12 p.p.m.) und ortho‐ortho‐Methylenbrücken (δ=4,21−4,32 p.p.m.) möglich war. Bei Verbindungen mit para‐Nitrophenolbausteinen lagen die chemischen Verschiebungen entsprechender Methyl‐ oder Methylengruppen dagegen in einem weiteren Bereich. Am Beispiel von zwei Zweikernverbindungen wurde die Abhängigkeit der chemischen Verschiebung von der Pyridinkonzentration in Benzol untersucht.
Incréments d'indice de réfraction de polymères en solution: Étude des lois de mélange. Influence de la masse moléculaire et de la structure
Authors: Candau Françoise , Dufour Claude , François Jeanne 
Published: February 2006

AbstractNous étudions la variation de l'incrément d'indice de réfraction (dn/dc) avec la masse moléculaire et la structure pour des séries de polystyrènes linéaires et ramifiés parfaitement définis en solution dans le benzène.Une étude réalisée dans le cadre des théories de mélange de Lorenz‐Lorentz et d'Onsager‐Böttcher nous a permis de montrer que:

Au‐dessous d'une masse moléculaire critique de l'ordre de 2.104, la variation linéaire dn/dc=f(1/Mn)s'explique entièrement par l'influence des hétérogénéités chimiques contenues dans la chaǐne (groupements terminaux, noeuds de ramification, etc.).
Les lois de mélange ne tiennent pas compte des interactions spécifiques polymère‐solvant et ne sont pas parfaitement rigoureuses.
Les variations de (dn/dc) et du volume spécifique partiel du polymère, v̄p, déjà observées pour des masses moléculaires supérieures à 2·104 s'accompagnent d'une variation de la réfractivité spécifique partielle. Nous relions ces effets à l'influence de la densité en segments à l'intérieur de la pelote linéaire ou ramifiée.
Une série homologue de polyoxyéthylène‐glycols (α‐hydro‐ω‐hydroxypoly(oxyéthylène)s) dans le benzène présente le měme comportement.
Cationic polymerization of cyclic sulfides, 6. Polymerization of propylene sulfide with different initiators
Authors: van Ooteghem Daniël , Goethals Eric J. 
Published: February 2006

AbstractThe kinetics of the cationic ring‐opening polymerization of propylene sulfide initiated with different initiators has been investigated and the results were compared with those obtained with triethyloxonium tetrafluoroborate as described in a previous paper. With triethyloxonium hexafluorophosphate, the polymerization showed the same characteristics, that is: an initial very fast non‐stationary stage A is followed by a much slower stage B which leads to quantitative conversion. With triethyloxonium hexachloroantimonate, the B‐stage stopped at limited conversions which was attributed to a sulfonium ion‐destroying termination reaction between the growing species and the SbCl anion to give an alkylchloride and SbCl5. Perchloric acid gives a polymerization which is analogous to the oxonium tetrafluoroborate initiated polymerizations which indicates that perchloric acid also gives a rapid and quantitative initiation reaction. Methyl fluorosulfonate on the contrary is a slow initiator. In the polymerization with boron trifluoride etherate, water acts as a co‐initiator and the maximum activity is reached at a ratio H2O/BF3OEt2 equal to 0,5. All polymerizations, with the exception of that initiated with triethyloxonium hexachloroantimonate, are of the dormant type and the polymers slowly degrade to form a mixture of low molecular weight polymer and cyclic oligomers, mainly tetramer.