bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regeneration of the inner ear as a model of neural plasticity
Authors: Morest D. Kent , Cotanche Douglas A. 
Published: October 2004

AbstractThe publication of a paper entitled “Direct transdifferentiation gives rise to the earliest new hair cells in regenerating avian auditory epithelium” in the Journal of Neuroscience Research offers the opportunity to call attention to a well‐developed line of research on the auditory receptor of birds, which should be of interest to students of regeneration and plasticity of the mature nervous system in higher vertebrates, including mammals. Although hair cell proliferation normally stops before hatching, destruction of the auditory receptors of the chicken may be followed by complete regeneration of hair cells. Most of the new hair cells arise from a new wave of proliferation, but Roberson et al. show that about one‐third of the new hair cells are formed without undergoing cell division and thus may differentiate from so‐called supporting cells or cells with an “intermediate morphology.” This finding suggests some models for regeneration of this neuroepithelium, including the possibility that mature supporting cells could transform directly into hair cells. The present Mini‐Review discusses some of the models for neural regeneration that future studies might address in the light of our current knowledge and the new report. The possibility is raised that transitional forms of hair cell and supporting cell precursors may reside in the inner ear in a quiescent state until stimulated by damage. © 2004 Wiley‐Liss, Inc.
Astrocyte‐specific overexpression of insulin‐like growth factor‐I promotes brain overgrowth and glial fibrillary acidic protein expression
Authors: Ye Ping , Popken Greg J. , Kemper April , McCarthy Ken , Popko Brian , D'Ercole A. Joseph 
Published: October 2004

AbstractInsulin‐like growth factor‐I (IGF‐I) is widely expressed in the central nervous system (CNS). Whereas during normal development IGF‐I is expressed predominately by neurons and to a much lesser degree by glial cells, its expression in astrocytes, and often in microglia, is increased during and/or after variety of CNS injuries. Recently we have generated a new line of IGF‐I Tg mice, called IGF‐IAst/Tet‐Off Tg mice, in which IGF‐I transgene is expressed specifically in astrocytes and is tightly controlled by the tetracycline analog doxycycline. In this study we examined whether IGF‐I derived from astrocytes is capable of promoting neural cell growth during development. When the IGF‐I transgene is allowed to be expressed, IGF‐IAst/Tet‐Off Tg mice exhibit markedly increases in 1) brain weight; 2) brain DNA and protein abundance; and 3) number of neurons, oligodendrocytes, and astrocytes, as well as myelination, findings similar to those observed in our other lines of Tg mice that express IGF‐I transgene predominately in neurons. Unlike Tg mice with neuron‐specific IGF‐I expression, which manifest marked increases in the concentrations of oligodendrocyte/myelin‐specific proteins, however, IGF‐IAst/Tet‐Off Tg mice exhibit an increase in the concentration of glial fibrillary acidic protein, an astrocyte‐specific protein. Furthermore, when transgene expression is blunted, brain overgrowth in IGF‐IAst/Tet‐Off Tg mice ceases. Our data indicate that astrocyte‐derived IGF‐I is capable of promoting neural cells growth in vivo. Our data also suggest that IGF‐I's actions in CNS depend in part on the location of its expression and cellular microenvironment and that continuous presence of IGF‐I expression is necessary for brain overgrowth. © 2004 Wiley‐Liss, Inc.
Habituation to a test apparatus during associative learning is sufficient to enhance muscarinic acetylcholine receptor‐immunoreactivity in rat suprachiasmatic nucleus
Authors: Van der Zee Eddy A. , Biemans Barbara A.M. , Gerkema Menno P. , Daan Serge 
Published: October 2004

AbstractThe suprachiasmatic nucleus (SCN) is engaged in modulation of memory retention after (fear) conditioning, but it is unknown which pathways and neurotransmitter system(s) play a role in this action. Here we examine immunocytochemically whether muscarinic acetylcholine receptors (mAChRs), mediating cholinergic signal transduction in the SCN, are involved. For this purpose, mAChR immunoreactivity (mAChR‐ir) was studied in the SCN after various stages of passive shock avoidance (PSA) and active shock avoidance (ASA) training and, for ASA, at various posttraining time points. mAChR‐ir was significantly enhanced in SCN neurons as a result of the training procedure, and the number of mAChR‐positive glial cells in the SCN increased significantly. The increase in mAChR‐ir as a result of PSA and ASA training was not due to fear conditioning or the number of correct avoidances (in case of ASA training) but rather to behavioral arousal as a consequence of (brief) exposure to a novel environment (the test apparatus). This finding was confirmed by a cage‐change experiment in which the rats were allowed to stay in a novel cage for 15 min or 24 hr. Only the brief exposure to the fresh cage triggered alterations for SCN mAChRs 24 hr later. These results shed new light on a possible function of the cholinergic system in the SCN mediated by mAChRs in relation to modulation of memory processes and demonstrate that behavioral arousal during (the habituation stage of) a learning task is sufficient to alter the mAChR system in the SCN. © 2004 Wiley‐Liss, Inc.
Retinal glutamate transporter activity persists under simulated ischemic conditions
Authors: Bull Natalie D. , Barnett Nigel L. 
Published: October 2004

AbstractElevated extracellular concentrations of the neurotransmitter glutamate are neurotoxic and directly contribute to CNS damage as a result of ischemic pathologies. However, the main contributors to this uncontrolled rise in glutamate are still unconfirmed. It has been reported that the reversal of high‐affinity glutamate transporters is a significant contributing factor. Conversely, it has also been observed that these transporters continue to take up glutamate, albeit at a reduced saturation concentration, under ischemic conditions. We sought to determine whether glutamate transporters continue to remove glutamate from the extracellular space under ischemic conditions by pharmacologically modulating the activity of high‐affinity retinal glutamate transporters during simulated ischemia in vitro. Retinal glutamate transporter activity was significantly reduced under these ischemic conditions. The suppression of retinal glutamate transporter activity, with the protein kinase C inhibitor chelerythrine, significantly reduced ischemic glutamate uptake and enhanced retinal neurodegeneration. These findings imply a limited but protective role for retinal glutamate transporters under certain ischemic conditions, suggesting that pharmacological enhancement of high‐affinity glutamate transporter activity may reduce tissue damage and loss of function resulting from toxic extracellular glutamate concentrations. © 2004 Wiley‐Liss, Inc.
Hippocampal neurotrophin levels after injury: Relationship to the age of the hippocampus at the time of injury
Authors: Shetty Ashok K. , Rao Muddanna S. , Hattiangady Bharathi , Zaman Vandana , Shetty Geetha A. 
Published: October 2004

AbstractAging impairs the competence of the hippocampus for synaptic reorganization after injury. This potentially is due to the inability of the aging hippocampus to up‐regulate the critical neurotrophic factors for prolonged periods after injury to levels at which they can stimulate neurite outgrowth and facilitate synaptic reorganization. We hypothesize that the concentrations of neurotrophins in the hippocampus after injury depend on the age at the time of injury. We quantified the concentrations of brain‐derived neurotrophic factor (BDNF), nerve growth factor (NGF), and neurotrophin‐3 (NT‐3) in the hippocampus of young, middle‐aged, and aged Fischer 344 rats at 4 days after kainic acid (KA)‐induced injury. In comparison with the age‐matched intact hippocampus, the KA‐lesioned hippocampus exhibited increased levels of BDNF and NGF in all three age groups. In contrast, the NT‐3 concentration was unaltered after KA lesion. Notwithstanding similar percentage increases in BDNF after injury, the lesioned middle‐aged and aged hippocampus contained 45–52% less BDNF than the lesioned young hippocampus. NGF and NT‐3 levels after injury were comparable across the three age groups, however. Furthermore, lower BDNF concentration in the injured aging hippocampus was associated with normal astrocytic response but significantly diminished microglial reaction. Thus, in comparison with the injured young hippocampus, the injured aging hippocampus contains considerably less BDNF but similar levels of NGF and NT‐3. Lower BDNF levels in the injured aging hippocampus might underlie the diminished spontaneous healing response observed in the aging hippocampus after injury, particularly in terms of synaptic reorganization and dentate neurogenesis. © 2004 Wiley‐Liss, Inc.
Editorial: Math. Log. Quart. 50, No. 6
Authors: Grossmann Alexander 
Published: October 2004

AbstractMathematical logic and foundations of mathematics experienced a large boom in the 1950s and 60s due to their close connections to the theoretical fundamentals of computer science. The theory of algorithms and automata developed in line with computer technology; cybernetics was the buzzword of the times. It was during this exciting period that G�nter Asser founded the Zeitschrift für Mathematische Logik und Grundlagen der Mathematik while doing his doctorate at the Humboldt‐Universität in Berlin, together with his supervisor, Karl Schröter.The first issue appeared in 1955 and, alongside work by R. Péter and K. Schröter, contained a paper by Günter Asser entitled “Eine semantische Charakterisierung der deduktiv abgeschlossenen Mengen des Prädikatenkalküls der ersten Stufe”. Numerous further works would cement his status as a central figure in logic in East Germany as well as his international reputation.In 1960 Günter Asser was called to Greifswald University. He gave his students not merely a holistic view of the mathematical disciplines, but also of their history and philosophical background. As time went on, he became Dean of his faculty and Deputy Vice Chancellor (Prorektor) of the University. He went on to become a board member of the GDR Mathematical Society and, in 1977, was elected a member of the Academy of Science.His companion and mentor of many years, Karl Schröter, died that same year and Günter Asser assumed sole responsibility of the Zeitschrift für Mathematische Logik und Grundlagen der Mathematik. From a scientific viewpoint, the 70s were characterized by a tendency towards complexity theory. Günter Asser's influence was now mainly reflected in many publications from his field as well as in his opening up the journal to contributions on complexity theory.It is due to Günter Asser that the ZML, which in the meantime is called Mathematical Logic Quarterly, continues to enjoy such an eminent standing among the community, despite scientific and political paradigm shifts. As its editor, he ensured not only the high quality of the papers, but was also actively involved in the technical side of the journal's production.Günter Asser has accompanied the journal with his untiring, personal commitment for 50 years. We now wish to express our heartfelt thanks to the co‐founder and retiring editor for his efforts on behalf of the journal, and wish him all the best for the future. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Free Radical Polymerization of Acrylonitrile in Green Ionic Liquids
Authors: Cheng Liang , Zhang Yumei , Zhao Tingting , Wang Huaping 
Published: October 2004

AbstractFree radical polymerization of acrylonitrile (AN) in ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim][BF4]), 2,2;m1‐azobisisobutyronitrile (AIBN) as initiator was investigated. Early investigations on polymerizations using ionic liquids indicate that they serve as especially good solvents to achieve high molecular weight polymers. Free radical polymerizations result in higher molecular weight polymers, for ionic liquids have low chain transfer constants and act to stabilize the active radical during the process of polymerization. The thermal stability of polymers synthesized in ionic liquids have be improved obviously than that in traditional solvents.
Chitosan‐Pectin Composite Gel Spheres: Effect of Some Formulation Variables on Drug Release
Authors: Sriamornsak Pornsak , Puttipipatkhachorn Satit 
Published: October 2004

AbstractChitosan‐pectin composite gel spheres were prepared by ionotropic gelation method. Pectin solution containing indomethacin, a model drug, was extruded into a mixture of chitosan and calcium chloride. The release behavior of indomethacin from composite gel spheres was investigated in‐vitro. The influence of factors affecting release behavior, such as type of pectin, molecular weight of chitosan, cross‐linking time and release medium, were discussed in this study. Adding chitosan into gelation medium could retard the release of indomethacin from gel spheres. The different type of pectin used demonstrated slightly different drug release profiles. The higher molecular weight of chitosan showed less indomethacin release than the lower one. The increased cross‐linking time slowed the drug release from composite gel spheres. The release of indomethacin from composite gel spheres was also dependent on the release medium. The drug release was slower in tris buffer where no phosphate ions which can induce the precipitation of calcium phosphate. The results suggested that the composite gel spheres of pectin and chitosan could be used as a controlled release drug delivery carrier.
Polymer Architectures via Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization
Authors: Takolpuckdee Pittaya , Westwood James , Lewis David M. , Perrier Sébastien 
Published: October 2004

AbstractVarious versatile chain transfer agents (CTAs) have been synthesized for reversible addition fragmentation chain transfer (RAFT) polymerzation. Such CTAs have been used to modify hydroxyl containing materials and produce well‐controlled molecular architectures such as amphiphilic copolymer from poly (ethylene glycol), AB block copolymer consisting of a biodegradable segment, poly (l‐lactic acid) (PLLA) and grafted copolymers of poly (styrene), poly (methyl methacrylate) and poly (methyl acrylate) from cellulose.
Non‐Isocyanate‐Based Polyurethanes Derived upon the Reaction of Amines with Cyclocarbonate Resins
Authors: Diakoumakos Constantinos D. , Kotzev Dimiter L. 
Published: October 2004

AbstractLaprolate‐803 (L‐803) was used as the model cyclocarbonate resin for reactivity and kinetic studies of non‐isocyanate‐based solventless polyurethanes derived upon the reaction of amines with the 1,3‐dioxolan‐2‐one (dioxolanone) rings of L‐803. It was shown that the reaction could undergo either acid‐, base‐ or metal‐type catalysis yielding polyurethanes with 100% conversion of the dioxolanone rings at approximately half the time needed for their uncatalyzed counterparts. The activation energy of the reaction of L‐803 with diethylene triamine in the presence or absence of a catalyst was determined via Arhenious studies. The reactivity of amines towards the aforementioned model resin was correlated to their chemical structure. A model non‐isocyanate‐based polyurethane displayed Tg of −1°C (DMA), fast gel time (390 min) at room temperature and good elongation (∼70%).
Styrene/(Styrene Derivative) and Styrene/(1‐Alkene) Copolymerization using Ph2Zn‐Additive Initiator Systems
Authors: Rabagliati Franco M. , Cancino Rodrigo A. , Pérez Mónica A. , Rodríguez Francisco J. 
Published: October 2004

AbstractDiphenylzinc‐metallocene‐MAO initiator systems have proven to be effective initiator systems for styrene and for substituted styrenes as well as for their styrene/(styrene‐derivative) copolymerization. Titanocene produced almost pure syndiotactic polymers while zirconocenes gave atactic polystyrene together with a low content, less than 20%, of syndiotactic polystyrene. Systems including a zirconocene, particularly ethenyl(bisindenyl)zirconium dichloride were effective initiators of 1‐alkene polymerization and of styrene/1‐alkene copolymerization. Conversion to polymer increases with the molecular size of 1‐alkene. Styrene derivative and styrene/(styrene derivative) polymerization was greatly influenced by the inductive effect of substituent and by steric hindrance due to the monomer.
Approaches to Conjugated Polymers via New Solid State Polymerizations
Authors: Sandman Daniel J. , Njus Jeffrey M. , Tran Bao 
Published: October 2004

AbstractSolid state polymerization is the most convenient approach for the synthesis of macroscopic polymer single crystals. Motivations for seeking fully crystalline specimens of conjugated polymers other than polydiacetylenes (PDA) are presented. The thermal reactivity of p‐ethynylbenzoiic acid (EBA) is found to be a topochemically initiated solid state polymerization. The studies of EBA led to a new paradigm for solid state reactivity in such systems. Systems related to the paradigm, namely p‐cyanobenzoic acid (CNBA) and p‐cyanocinnamic acid (CNCA) have been studied. Sublimation competed with thermal processes in CNBA and CNCA, and a detailed product description has proved difficult to date. Thermochromism and charge‐transfer transitions in PDA are discussed.
Surface Modification of Chitosan Films‐Grafting Ethylene Glycol Oligomer and Its Effect on Protein Adsorption
Authors: Amornchai Wimonsiri , Hoven Vipavee P. , Tangpasuthadol Varawut 
Published: October 2004

AbstractThis work is a part of a series on surface modification of materials made of chitosan. This report focused on grafting monomethoxy ethylene glycol oligomers (mPEG) on the surface of chitosan films. The chemical reactions were performed by immersing the films in organic solvent containing aldehyde derivative of mPEG. The presence of ethylene glycol moieties was determined by attenuated total reflectance‐infrared spectroscopy (ATR‐IR) and nuclear magnetic resonance (NMR). The hydrophobicity of the modified surface, determined by air‐water contact angle, decreased when the ethylene glycol derivatives were grafted on the film. The modified films were also subjected to protein adsorption study in order to assess their uses in biomedical applications. It was found that the presence of ethylene glycol units reduced the adsorption of proteins (albumin and lysozyme) on the films. We therefore have shown that manipulation of the interaction between chitosan and bio‐macromolecules is possible by chemically modifying the surface of chitosan.
Synthesis and Characterization of a Novel Poly(aryl ether) Containing 4‐Chloro‐2,5‐diphenyloxazole
Authors: Pimpha Nuttaporn , Tantayanon Supawan , Harris Frank 
Published: October 2004

Abstract4‐Chloro‐2,5‐bis(4‐fluorophenyl)oxazole monomer has successfully been synthesized using cyclization reaction of 4‐fluorobenzoyl cyanide with 4‐fluorobenzaldehyde. This monomer was converted to poly(aryl ether)s by nucleophilic substitution of the fluorine atoms on the benzene rings of oxazole monomer with bisphenol A. The influence of the reaction time on the molecular weight had been investigated. The polymers were identified by FT‐IR,1H‐NMR and TGA. The products exhibited weight‐average molar masses up to 2.81 x 104g mol−1 in GPC. These poly(aryl ether)s showed very high thermal stability up to 363 °C for 5 % weight loss in TGA under N2.
Enthalpic Partition‐Assisted Size Exclusion Chromatography: 1. Principle of Method
Authors: Berek Dusan 
Published: October 2004

AbstractA novel high performance liquid chromatographic (HPLC) method viz. “enthalpic partition assisted size exclusion chromatography” deliberately combines entropic and enthalpic partition mechanisms. It enables separation of homopolymers according to their molar mass with increased selectivity, as well as discrimination of polymer species differing in their nature/composition. Enthalpic partition of macromolecules takes place between the mobile phase and the stationary “liquid” of a different chemical nature, which is immobilized within pores of an appropriate carrier (a bonded phase). The extent of enthalpic partition depends on the accessibility of bonded phase for macromolecules and on the difference of polymer solubility in the mobile phase and in the solvated bonded phase. The enthalpic partition in favor of column packing arises from better solubility of polymer solutes in the solvated stationary phase compared to the mobile phase. Macromolecules are “pushed” into the solvated stationary phase and their retention volumes (VR) increase. In the area of high molar masses, the extent of enthalpic partition as rule raises with the increasing size of macromolecules. However, under properly chosen experimental conditions the enthalpic partition may rapidly diminish with the sample molar mass (M), likely due to the solubility changes and/or due to partial exclusion of macromolecules from the pores. As result, the corresponding retention volumes sharply drop within a narrow range of M with the increasing size of macromolecules. This results in the log M vs. VR dependences, which resemble in their form that for size exclusion chromatography but are much more flat indicating highly selective separations of homopolymers according to their molar masses. In this way, enthalpic partition “assists” entropic partition (size exclusion). Polymer species, which do not undergo enthalpic partition, elute from the HPLC column in the conventional size exclusion mode and can be discriminated from the partitioning species. Enthalpic partition assisted size exclusion chromatography can be utilized in separation and characterization of various homopolymers, and polymer blends.
Effect of Ground Rubber Powder on Properties of Natural Rubber
Authors: Li Shuyan , Lamminmäki Johanna , Hanhi Kalle 
Published: October 2004

AbstractGround rubber powder (GRP) with three different sizes was incorporated into nature rubber matrix with different loading. Cure characteristics, swelling behaviour, crosslink density, tensile fractured surface, and mechanical properties have been studied. Based on the cure characteristics, it is evident that the processability of the rubber compounds has not changed obviously with the different GRP loading. The introduction of GRP in virgin rubber leads to the increase in swelling degree and the decrease in crosslink density. Tensile strength, hardness and abrasion resistant deteriorate with the increase of GRP loading, but the tear resistance gets better. If the ground rubber particles are smaller, the properties are more similar to the virgin rubber. Because of the phase separation of the GRP and matrix, the properties get worse with the bigger ground rubber powder.