bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Distortion in Reactive Chemical Intermediates
Authors: Miller Terry A.
Published: December 2003

The benzene radical cation is not a regular hexagon. This statement, previously only substantiated with photoelectronic spectra of benzene, ESR spectra of C6H in a freon matrix, or the laser‐induced fluoresence halogen‐substituted benzenes, was strongly supported by the results of ZEKE‐PE experiments by Müller‐Dethlefs et al. These results should lead soon to a quantification of the Jahn – Teller geometric distortion in C6H and the energy stabilization derived therefrom.
Heterodimetallic Complexes with an Unbridged, Polar Metal–Metal Bond
Authors: Herberhold Max , Jin Guo‐Xin
Published: December 2003

The metal–metal bonds are stable without bridging ligands in the heterodinuclear complexes 1 and 2. The combination of one metal center in a high oxidation state and one in a low oxidation state causes these bonds to be strongly polarized. The reactivity of such systems promises to be interesting–recently the direct insertion of CO2 into the ZrFe and ZrRu bond of related complexes has been achieved. R = p‐tolyl.
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Reactions of [(C5Me5)ZrF3] with AlMe3–Synthesis and Structure of a Zirconium–Aluminum–Carbon Cluster
Authors: Herzog Axel , Roesky Herbert W. , Zak Zdirad , Noltemeyer Mathias
Published: December 2003

Transfer of methyl groups from 2 to 1 leads to the first Zr3Al6C7 cluster 3 [Eq. (a)], in which six metal atoms form an open cube shielded by Al and C atoms. The ZrAl distances in the cube are remarkably short. Zr/Al/C compounds are of interest with regard to Ziegler–Natta catalysts.
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Synthesis, Crystal and Molecular Structure of Boc‐Pro‐ ΔPhe‐Ala‐ ΔPhe‐ Ala‐OMe; A Pentapeptide with a Novel β‐Bend Ribbon Structure
Authors: Rajashankar Kanagalaghatta Ramabhatta , Ramakumar Suryanarayanarao , Mal Tapas Kumar , Chauhan Virander Singh
Published: December 2003

Neither a helical structure nor a spiral β‐bend ribbon structure, but a flat β‐bend ribbon is formed by the title compound. Peptides with 2,3‐didehydroamino acid esters (α,β‐didehydroamino acid esters) such as dehydrophenylalanine (ΔPhe) are of great interest as model compounds for the study of structure–function relationships, since the dehydroamino acids strongly influence the conformation and the enzymatic degradation of peptides. The comparison of the structure of the title compound with that of corresponding Aib‐containing peptides is informative.
Prostacyclin and Thromboxane Synthase: New Aspects of Hemethiolate Catalysis
Authors: Ullrich Volker , Brugger Roland
Published: December 2003

The arachidonic acid metabolites thromboxane A2 and prostacyclin are highly potent regulators of cell physiology. They are both formed by enzymatic rearrangement of the 9,11‐epidioxy prostaglandin H2 catalyzed, however, by thromboxane and prostacyclin synthase, respectively. The two enzymes have been isolated, sequenced, and characterized as hemethiolate (“P450”) enzymes. The different isomerization products can be explained on the same catalytic principle by a different ligation of the heme centers with the two epidioxy oxygens atoms. This requires different conformations for substrate binding at the active site, which is substantiated by the different inhibitors and amino acid sequences of the enzymes. In a hypothesis which has mechanistic principles in common with the P450‐monooxygenases and the allene oxide synthases, oxy radicals are formed first and rearrange to carbon radicals. These could then rapidly be converted into carbocations by the ferrylthiolate or iron(III)thiyl structures formed as intermediates.
Bolaamphiphiles: From Golf Balls to Fibers
Authors: Escamilla Gregory H. , Newkome George R.
Published: December 2003

Molecular structures can perform diverse functions. Tailored bolaamphiphiles were used to prepare vesicles containing redox‐active centers or (chiral) binding sites for guests, as well as aggregates. In addition, monomeric and polymeric bolaamphiphiles can disrupt membranes. RNA‐based bolaamphiphiles of this type may also find application in biochemistry as antisense agents.
Ring Closures on Polymeric Supports—Formation of Extremely Large Macrocycles by Intrapolymeric Cyclooligomerizations
Authors: Rothe Manfred , Lohmüller Manfred , Breuksch Ulrich , Schmidtberg Günter
Published: December 2003

Extremely large rings with up to several hundred ring atoms are obtained by cyclooligomerization of polymer‐bound linear molecules, for example cyclic oligoamides of ϵ‐aminohexanoic acid with up to 280 ring atoms. Thus weakly crosslinked polymeric supports do not enforce steric isolation of covalently bound bifunctional molecules, as previously reported. Instead intrapolymer reactions with subsequent ring closure dominate.
Thermal and Optical Switching of Iron(II) Complexes
Authors: Gütlich Philipp , Hauser Andreas , Spiering Hartmut
Published: December 2003

Transition metal chemistry contains a class of complex compounds for which the spin state of the central atom changes from high spin to low spin when the temperature is lowered. This is accompanied by changes of the magnetic and optical properties that make the thermally induced spin transition (also called spin crossover) easy to follow. The phenomenon is found in the solid state as well as in solution. Amongst this class, iron(II) spin crossover compounds are distinguished for their great variety of spin transition behavior; it can be anything from gradual to abrupt, stepwise, or with hysteresis effects. Many examples have been thoroughly studied by Mössbauer and optical spectroscopy, measurements of the magnetic susceptibilities and the heat capacities, as well as crystal structure analysis. Cooperative interactions between the complex molecules can be satisfactorily explained from changes in the elastic properties during the spin transition, that is, from changes in molecular structure and volume. Our investigations of iron(II) spin crossover compounds have shown that green light will switch the low spin state to the high spin state, which then can have a virtually unlimited lifetime at low temperatures (this phenomenom is termed light‐induced excited spin state trapping—acronym: LIESST). Red light will switch the metastable high spin state back to the low spin state. We have elucidated the mechanism of the LIESST effect and studied the deactivation kinetics in detail. It is now well understood within the theoretical context of radiationless transitions. Applications of the LIESST effect in optical information technology can be envisaged.
Novel Copper Nitrosyl Complexes: Contributions to the Understanding of Dissimilatory, Copper‐Containing Nitrite Reductases
Authors: Averill Bruce A.
Published: December 2003

The first functional models for copper nitrite reductases, enzymes that play a central role in the nitrogen cycle, were recently prepared by Tolman et al. Thus, complex 1 in which one nitrite ligand is coordinated through the N atom to the Cu1 center reacts smoothly with two equivalents of acid to give NO, and Cu1 complexes of the type 2 react with NO in a novel disproportionation reaction to give N2O and CuIINO2 complexes—in both cases the complexes can mimic certain aspects of the reactivity of copper nitrite reductases. L1 = N,N′,N″‐triisopropyl‐1,4,7‐triazacyclononane, L2 = substituted hydridotris(pyrazolyl)borate.
Localization of Electrons in Intermetallic Phases Containing Aluminum
Authors: Häussermann Ulrich , Wengert Steffen , Hofmann Patrick , Savin Andreas , Jepsen Ove , Nesper Reinhard
Published: December 2003

Many forms of chemical bondingare exhibited by Al in intermetallic and Zintl phases. This is revealed by the calculation of the electron localization function for the series Al, CaAl2, SrAl2, BA14, CaAl2Si2, and Si. With this procedure it is possible to distinguish clearly between metallic, covalent multicenter, and homo‐ and hetero‐nuclear single bonding.
NiO/CaO‐Catalyzed Formation of Syngas by Coupled Exothermic Oxidative Conversion and Endothermic CO2 and Steam Reforming of Methane
Authors: Choudhary Vasant R. , Rajput Amarjeet M. , Prabhakar Bathula
Published: December 2003

An energy efficient and safe conversion of methane to syngas is possible by carrying out the exothermic oxidation of methane and the endothermic reaction of methane with steam and CO2 simultaneously with the same NiO/CaO catalyst. By coupling the two reactions and manipulating the relative concentrations of CH4, O2, CO2, and steam in the feed, the overall methane‐to‐syngas conversion can be made mildly exothermic, thermoneutral, or mildly endothermic. The H2/CO ratio of the product can be varied from roughly 1.5 to 2.5.
Practical and Rapid Vicinal Hydroxylation of Alkenes by Catalytic Ruthenium Tetraoxide
Authors: Shing Tony K. M. , Tai Vincent W.‐F. , Tam Eric K. W.
Published: December 2003

Within minutes simple olefins, α,β‐unsaturated ketones and esters, allyl acetates, and allyl benzyl ethers can be cis‐dihydroxylated. The oxidation, an extension of Sharpless's method, is conducted with 0.07 equivalents of RuCl3·3H2O and 1.5 equivalents of NaIO4 in a two‐phase solvent system consisting of ethyl acetate, acetonitrile, and water at 0 °C! The low extent of diol cleavage and ketol formation is surprising.
A Novel Type of Stereoisomerism in Calix[4]arene‐Based Carceplexes
Authors: Timmerman Peter , Verboom Willem , van Veggel Frank C. J. M. , van Duynhoven John P. M. , Reinhoudt David N.
Published: December 2003

Different orientations of the guest in the cavity of a carcerand lead to a new type of stereoisomerism, “carceroisomerism”. The structure of the host–guest compound (which is shown on the cover of this issue) and its dynamic behavior was studied in detail by NMR methods. Such compounds could perhaps find application as molecular switches for electronic devices.
The Consequences of an Electrostatic “Forced Marriage” between Two Electron‐Rich Particles: Strained Ion Pairs
Authors: Weiss Robert , Brenner Thomas , Hampel Frank , Wolski Alexander
Published: December 2003

Because of the extraordinary electronic situation in tris(dimethylamino)cyclopropenylium chloride 1, a salt with an electron‐rich cation and anion, the “naked” CI− ions in 1 show a very high readiness to coordinate to acceptors. Thus, stable adducts with hydrogen bonds are formed from 1 and carboxylic acids or phenol derivatives.
Computational Evidence for the Existence of CuIII Intermediates in Addition and Substitution Reactions with Dialkylcuprates
Authors: Dorigo Andrea E. , Wanner Jutta , von Ragué Schleyer Paul
Published: December 2003

When the copper center is stabilized by donor ligands such as H2O and NH3, trialkylcopper compounds correspond to energy minima at all levels of theory used in the calculations (MP2, SCRF, BLYP). These results support proposals that such species are intermediates in cuprate addition and substitution reactions and at the same time suggest that descriptions of trialkylcopper systems as CuII rather than CuIII complexes may be more appropriate.
Phosphinidine‐Bridged Silver Clusters
Authors: Fenske Dieter , Simon Falk
Published: December 2003

Clusters containing 18, 45, and 50 silver atoms can be synthesized from the reaction of AgCl with PhP(SiMe3)2 in the presence of PnPr3. The structures of the phosphinidine‐bridged silver clusters formed depends upon the temperature and the stoichiometric ratio of the reactants. [ Ag50(PPh)20Cl7P(PnPr3)13] is the biggest known silver cluster and one of the largest structurally characterized cluster complexes to date.
Novel High‐Performance Ceramics—Amorphous Inorganic Networks from Molecular Precursors
Authors: Baldus Hans‐Peter , Jansen Martin
Published: December 2003

Materials research is an interdisciplinary field in which engineers and physical scientists work together. Since the major binary oxides, nitrides, and carbides, which are currently used as high‐performance ceramics, were discovered in the last century, the role of chemistry in the development of materials has become barely noticeable. This has changed only in the recent past as, for example, purity and defined morphology of starting powders were recognized as crucial parameters for enhancing the reliability of ceramic workpieces. While the application of chemical methods led to gradual–though significant–improvements, the true potential of chemistry lies rather in the exploitation of new chemical systems and the development of new preparative routes to already known materials. Such an approach is the preparation of ceramics from molecular or polymeric precursors. Herein we survey the most important contributions to those preparative routes starting from the pioneering work in the 1960s and the 1970s; a certain emphasis is placed on the concepts that we have applied to the preparation of multinary, nonoxide materials and amorphous inorganic networks. The name “amorphous high‐performance ceramics” is in fact a contradiction in terms. Such materials are thermodynamically unstable with respect to the transformation or decomposition to crystalline phases, thus excluding their application in sensitive areas at high temperatures. However, the selection of element combinations for which the binding energies are derived from strong, local covalent bonds and which are therefore less dependent on a long‐range crystalline order, can yield amorphous materials of remarkable thermal and mechanical durability. This is exemplified by novel quaternary ceramics in the Si/B/N/C system, for which an efficient synthesis, starting from raw materials suitable for industrial production, has been developed. For instance, a material of the composition SiBN3C remains amorphous up to 1900°C, which is unique, and, with respect to oxidation, is the most stable nonoxide ceramic known to date. Another advantage of this in several respects unsurpassed material is the simple way, in which the viscosity of the polymeric precursors can be adjusted to various methods of shaping. So far infiltrations and coatings have been realized. Most developed is the preparation of fibers, which in terms of their performance characteristics are significantly better than those currently available.
Adsorption of Gases on Complex Solid Surfaces
Authors: Freund Hans‐Joachim
Published: December 2003

During the last thirty years the research field of surface science with its various disciplines has progressively played a more and more important role in the field of catalysis. The main focus of attention for a long time was research on metal surfaces, on which, in time, the whole spectrum of developed surface analytical methods was applied. This led to a better understanding of the mechanisms of catalytic reaction, such as the synthesis of ammonia and the oxidation of CO, especially through the work of Gerhard Ertl.[1, 2] In contrast to clean metal surfaces, surfaces of real catalysts are complex entities, the structures of which can have a strong influence on the processes occurring on the surface. Thus, it seems logical to employ the typical structural characteristics and the morphology of the catalytic surface as guidelines in the investigation of complex model systems. In this review the preparation, and structural and electronic characterization of such model systems will be dicussed. Clean surfaces of catalytically active oxides, as well as model systems for dispered transition metal/support catalysts will be characterized in terms of their morphology and electronic structure as well as their adsorption and reaction capabilities.
In Vitro Selected Receptors Rationalized: The First 3D Structures of RNA Aptamer/Substrate Complexes
Authors: Egli Martin
Published: December 2003

Mystery solved! The structural principles behind RNA′s receptor properties have been probed by solution NMR studies of substrate/RNA aptamer complexes. Differences with the interactions in protein–DNA complexes are apparent. Small organic molecules recognize not merely nucleotide sequences but also certain three‐dimensional structural motifs of the receptor.
Unprecedented Layered Structure of a Fulleride: Synthesis, Structure, and Magnetic Properties of a Potassium‐Containing Salt with a C Counterion
Authors: Fässler Thomas F. , Spiekermann Annette , Spahr Michael E. , Nesper Reinhard
Published: December 2003

For corrigendum see DOI:10.1002/anie.199709511

For corrigendum see DOI:10.1002/anie.199713711
Organometallic Homogeneous Catalysis—Quo vadis?
Authors: Herrmann Wolfgang A. , Cornils Boy
Published: December 2003

Homogeneous catalysis is the success story of organometallic chemistry. Otto Roelen's initial discovery of hydroformylation in 1938 not only entailed large‐capacity production plants but was later followed by systematic research into the catalytic chemistry of the ever‐growing class of organometallic compounds. Further developments in industrial chemistry towards clean, low‐temperature, low‐pressure, and economic processes—in feedstock or in the fine chemicals and polymer area—clearly depend on improved catalysts. Molecularly defined, tailor‐made structures are the safest prerequisites for chemical selectivity; hence, organometallic compounds with their overwhelming variety of compositions and structures offer the most promising approach. Wilkinson's catalysts [HRh(CO){P(C6H5)3] and [ClRh{P(C6H5)}3}3] are outstanding examples. On the other hand, process technology has to be considered also (for example catalyst‐product separation and hear‐exchange problems). The following review attempts to critically assess the future trends and present demands in the applied area of orgnometallic catalysis–a “gentle art” that is far from being a mature field.
Electronic Structure of Manganese(III) Compounds from High‐Frequency EPR Spectra
Authors: Barra Anne‐Laure , Gatteschi Dante , Sessoli Roberta , Abbati Gian Luca , Cornia Andrea , Fabretti Antonio C. , Uytterhoeven Myriam G.
Published: December 2003

The use of high magnetic field and high frequency in an unconventional spectrometer has provided very informative EPR spectra of a manganese(III) octahedral complex for the first time. The parameters of the spin Hamiltonian operator are in fair agreement with those calculated with ligand‐field theory. High‐frequency EPR is thus a powerful tool for the structural investigation of complexes that contain metal ions with integer spins.
New Insights into the Mechanism of the McMurry Reaction
Authors: Villiers Claude , Ephritikhine Michel
Published: December 2003

Not only pinacolate intermediates appear in McMurry reactions of aliphatic ketones R2CO (R = Me, Et, iPr) with MCl4Li(Hg) (M = Ti, U) [Eq. (1)]. Rather, carbenoid species must also be considered. This conclusion was drawn from an exact analysis of the reaction products as well as control experiments with pinacol derivatives.
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Valence Tautomeric Interconversion in Transition Metal 1,2‐Benzoquinone Complexes
Authors: Gütlich Philipp , Dei Andrea
Published: December 2003

For the development of molecule‐based switching devices, cobalt and manganese complexes of 1,2‐benzoquinone ligands are of great interest. These compounds have electronically labile ground states, which leads to phenomena such as mixed valency, spin crossover, and valence tautomerism. Recently, the electronic behavior of these complexes was investigated carefully, and there are indications that complexes that show such characteristics can also be obtained with other metals.
Structural Evolution from the Solid State to the Molecule for BaI2: Synthesis and Crystal Structures of [BaI2(μ2‐OH2)2]3/∞, [BaI2(μ2‐OH2)(OC3H6)]2/∞, [BaI2(thf)3]1/∞, and [BaI2(thf)5] · THF
Authors: Fromm Katharina M.
Published: December 2003

The use of different donor ligands as chemical scissors allows fragments to be “cut out” from the solid‐state structure of BaI2, which results in the barium compounds given in the title. According to X‐ray structural analyses these compounds exhibit different dimensionalities.
Stepwise Reaction of Bis(iodozincio)methane with Two Different Electrophiles
Authors: Utimoto Kiitiro , Toda Narihiro , Mizuno Takeshi , Kobata Masami , Matsubara Seijiro
Published: December 2003

[Pd2(dba)3] in the presence of trifurylphosphane catalyzes the stepwise reaction of CH2(ZnI)2 with different electrophiles [Eq. (a)]. The homologous Zn2 compound CH3CH(ZnI)2 reacts in the first step analogously with cinnamyl chloride; however, stoichiometric amounts of CuCN/LiCN are required for the coupling with allyl bromide in the second step
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Play deprivation without social isolation: Housing controls
Authors: Holloway Kevin S. , Suter Robert B.
Published: December 2003

Three experiments were conducted to control for the effects of housing conditions during play deprivation on subsequent play rebound in periadolescent rats. To address play deprivation without the confound of social isolation, in Experiment 1 pairs of subjects were housed either in cages divided by wire mesh that allowed for olfactory, visual, auditory, and tactile interactions with a same‐sex agemate but prevented rough and tumble play or in standard cages. Running wheels were provided to similarly housed subjects in Experiment 2 to control for the ability to engage in physical activity. In Experiment 3, standard and brooder cages were used to control for the effects of housing area. Play‐deprived subjects in all conditions showed a greatly increased number of play responses immediately following deprivation. The results from these experiments more clearly indicate that the absence of play is the crucial feature that brings about play rebound following deprivation. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 44: 58–67, 2004.
Working memory and inhibitory control in early childhood: Contributions from physiology, temperament, and language
Authors: Wolfe Christy D. , Bell Martha Ann
Published: December 2003

This study examined the cognitive skills of working memory and inhibitory control (WMIC) in relation to physiological functioning, temperament, and language in early childhood. WMIC skills were assessed in twenty‐five 4½‐year‐old children using the day–night Stroop‐like task and the yes–no task; each task required the child to remember two rules and to inhibit a dominant response. Electroencephalogram (EEG) and heart period (HP) were recorded during baseline and WMIC tasks. An increase in 6‐ to 9‐Hz EEG power from baseline to task was found for the medial frontal region. In addition, a decrease in HP (i.e., an increase in heart rate) was found from baseline to task. Associations were found between performance on the WMIC tasks and scales of the Children's Behavioral Questionnaire (CBQ) related to the effortful control of behavior. The Peabody Picture Vocabulary Test‐III (PPVT‐III) distinguished between high and low WMIC performance. Results of a discriminant function analysis indicated that physiology, temperament, and language were able to correctly predict 90% of WMIC performance. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 44: 68–83, 2004.
Expression and functional properties of group I metabotropic glutamate receptors in bovine chromaffin cells
Authors: Arce C. , del Campo A.B. , Figueroa S. , López E. , Aránguez I. , Oset‐Gasque M.J. , González M.P.
Published: December 2003

We demonstrate the presence and functional properties of Group I metabotropic glutamate receptors (mGluRs) expressed in chromaffin cells. Immunocytochemical techniques revealed that two mGluR subtypes (mGluR1α and mGluR5) are expressed in chromaffin cells, located in both the cytoplasmic membrane and the cytosol surrounding the nucleus. These mGluRs are functionally active on catecholamine (CA) secretion in chromaffin cells because both (1S, 3R)‐1‐aminocyclopentane‐1,3‐dicarboxylic acid (t‐ACPD) and the specific agonist of Group I mGluRs, (S)‐3,5‐dihydroxyphenylglycine (DHPG), were able to stimulate the release of CAs (adrenaline and noradrenaline) in a dose‐response manner. These effects were specifically reversed by L‐(+)‐2‐amino‐3‐phosphonopropionic acid (L‐AP3), a selective antagonist of the Group I metabotropic glutamate receptors. t‐ACPD induced an increase in CA secretion in both the presence and absence of extracellular calcium, the former effect being accompanied by cell membrane depolarization. Noradrenaline (NA) release was higher in the presence of extracellular calcium than in its absence, whereas adrenaline release was of the same order under both conditions. These results indicate that different subtypes of Group I mGluRs are present in noradrenergic and adrenergic cells. Fluorescence imaging techniques in single cells showed different t‐ACPD‐induced increases in intracellular calcium in different chromaffin cells: in chromaffin cells, 67% expressed functional metabotropic glutamate receptors and with nicotinic receptors, whereas the remaining 33% expressed only nicotinic receptors. In the absence of external calcium, only about 25% of cells responded to t‐ACPD‐increased intracellular calcium by increasing inositol 1,4,5‐trisphosphate (IP3) concentration and subsequent calcium mobilization from intracellular stores, whereas the remaining 75% increased intracellular calcium by promoting Ca2+ influx from the extracellular medium through L‐ and N‐ but not P/Q voltage‐dependent calcium channels. © 2003 Wiley‐Liss, Inc.
Retinoic acid‐induced neuritogenesis of human neuroblastoma SH‐SY5Y cells is ERK independent and PKC dependent
Authors: Miloso Mariarosaria , Villa Daniela , Crimi Marco , Galbiati Stefania , Donzelli Elisabetta , Nicolini Gabriella , Tredici Giovanni
Published: December 2003

Retinoic acid (RA), an active metabolite of vitamin A, is a natural morphogen involved in development and differentiation of the nervous system. To elucidate signaling mechanisms involved in RA‐induced neuritogenesis, we used human neuroblastoma SH‐SY5Y cells, an established in vitro model for studying RA action, to examine the role of extracellular signal‐regulated kinase (ERK) 1 and 2 in RA‐induced neuritogenesis and cell survival. From immunoblotting experiments, we observed that RA induced delayed but persistent ERK1 and ERK2 phosphorylation (until 96 hr) that was reduced significantly by the specific mitogen‐activated protein kinase (MAPK)/ERK kinase (MEK) inhibitor U0126. For the subsequent studies we chose 24 hr as the reference time. Inhibition of ERK activation did not affect RA‐induced neuritogenesis (percentage of neurite‐bearing cells and neurite length) but significantly reduced cell survival. In addition, we analyzed the signaling pathway that mediates ERK activation. Our results suggest that RA‐induced ERK phosphorylation does not follow the classic Raf kinase‐dependent pathway. Protein kinase C (PKC) and phosphatidylinositol 3‐kinase (PI 3‐K) are possible alternative kinases involved in the ERK signaling pathway. In fact, in the presence of the specific PKC inhibitor GF 109203X, or the specific PI 3‐K inhibitor wortmannin, we observed a significant dose‐dependent reduction in ERK phosphorylation. RA‐induced neuritogenesis and cell survival were reduced by GF 109203X in a concentration‐dependent manner. These results suggest that rather than ERK1 and ERK2, it is PKC that plays an important role during early phases of RA‐induced neuritogenesis. © 2003 Wiley‐Liss, Inc.
Repetitive transcranial magnetic stimulation improves open field locomotor recovery after low but not high thoracic spinal cord compression‐injury in adult rats
Authors: Poirrier Anne‐Lise , Nyssen Yves , Scholtes Felix , Multon Sylvie , Rinkin Charline , Weber Géraldine , Bouhy Delphine , Brook Gary , Franzen Rachelle , Schoenen Jean
Published: December 2003

Electromagnetic fields are able to promote axonal regeneration in vitro and in vivo. Repetitive transcranial magnetic stimulation (rTMS) is used routinely in neuropsychiatric conditions and as an atraumatic method to activate descending motor pathways. After spinal cord injury, these pathways are disconnected from the spinal locomotor generator, resulting in most of the functional deficit. We have applied daily 10 Hz rTMS for 8 weeks immediately after an incomplete high (T4–5;n= 5) or low (T10–11;n= 6) thoracic closed spinal cord compression‐injury in adult rats, using 6 high‐ and 6 low‐lesioned non‐stimulated animals as controls. Functional recovery of hindlimbs was assessed using the BBB locomotor rating scale. In the control group, the BBB score was significantly better from the 7th week post‐injury in animals lesioned at T4–5 compared to those lesioned at T10–11. rTMS significantly improved locomotor recovery in T10–11‐injured rats, but not in rats with a high thoracic injury. In rTMS‐treated rats, there was significant positive correlation between final BBB score and grey matter density of serotonergic fibres in the spinal segment just caudal to the lesion. We propose that low thoracic lesions produce a greater functional deficit because they interfere with the locomotor centre and that rTMS is beneficial in such lesions because it activates this central pattern generator, presumably via descending serotonin pathways. The benefits of rTMS shown here suggest strongly that this non‐invasive intervention strategy merits consideration for clinical trials in human paraplegics with low spinal cord lesions. © 2003 Wiley‐Liss, Inc.
Subpopulations of rat dorsal root ganglion neurons express active vesicular acetylcholine transporter
Authors: Tata Ada Maria , De Stefano M. Egle , Srubek Tomassy Giulio , Vilaró M. Teresa , Levey Allan I. , Biagioni Stefano
Published: December 2003

The vesicular acetylcholine transporter (VAChT) is a transmembrane protein required, in cholinergic neurons, for selective storage of acetylcholine into synaptic vesicles. Although dorsal root ganglion (DRG) neurons utilize neuropeptides and amino acids for neurotransmission, we have previously demonstrated the presence of a cholinergic system. To investigate whether, in sensory neurons, the vesicular accumulation of acetylcholine relies on the same mechanisms active in classical cholinergic neurons, we investigated VAChT presence, subcellular distribution, and activity. RT‐PCR and Western blot analysis demonstrated the presence of VAChT mRNA and protein product in DRG neurons and in the striatum and cortex, used as positive controls. Moreover, in situ hybridization and immunocytochemistry showed VAChT staining located mainly in the medium/large‐sized subpopulation of the sensory neurons. A few small neurons were also faintly labeled by immunocytochemistry. In the electron microscope, immunolabeling was associated with vesicle‐like elements distributed in the neuronal cytoplasm and in both myelinated and unmyelinated intraganglionic nerve fibers. Finally, [3H]acetylcholine active transport, evaluated either in the presence or in the absence of ATP, also demonstrated that, as previously reported, the uptake of acetylcholine by VAChT is ATP dependent. This study suggests that DRG neurons not only are able to synthesize and degrade ACh and to convey cholinergic stimuli but also are capable of accumulating and, possibly, releasing acetylcholine by the same mechanism used by the better known cholinergic neurons. © 2003 Wiley‐Liss, Inc.
Water maze learning and forebrain mRNA expression of the neural cell adhesion molecule L1
Authors: Venero César , Tilling Thomas , Hermans‐Borgmeyer Irm , Herrero Ana I. , Schachner Melitta , Sandi Carmen
Published: December 2003

L1 and NCAM, two cell adhesion molecules of the immunoglobulin superfamily, have been implicated in the formation of neural circuits, synaptic plasticity, and cognitive function. In this study, we sought to investigate whether differences in the steady‐state levels of L1 and NCAM expression in specific brain regions could account for individual differences in learning abilities. Using adult male Wistar rats, we evaluated mRNA levels of L1, NCAM, and the NCAM180 isoform in different brain regions (hippocampus, thalamus, striatum, prefrontal and frontal cortices) immediately after submitting rats to a massed training protocol in the water maze. The results showed that untrained and trained rats exhibited similar levels of mRNA for these molecules, which supports the view that training did not influence their immediate level of expression. However, in most of the brain regions we investigated (with the exception of prefrontal and frontal cortices), L1 mRNA levels were positively correlated with the latency to find the hidden platform in the water maze task and with posttraining plasma corticosterone levels. However, no correlations were observed for total NCAM or NCAM180 mRNA in the brain regions examined in this study. Given that animals with a slower spatial acquisition curve exhibited more anxiety‐like responses, including thigmotactic behavior in the water maze and increased corticosterone levels, and that recent genetic studies indicate a role for L1 in anxiety, the current findings suggest a relationship among L1, anxiety, and cognitive processes. © 2003 Wiley‐Liss, Inc.
Axonal transport and neuronal transcytosis of trophic factors, tracers, and pathogens
Authors: von Bartheld Christopher S.
Published: December 2003

Neurons can specifically internalize macromolecules, such as trophic factors, lectins, toxins, and other pathogens. Upon internalization in terminals, proteins can move retrogradely along axons, or, upon internalization at somatodendritic domains, they can move into an anterograde axonal transport pathway. Release of internalized proteins from neurons after either retrograde or anterograde axonal transport results in transcytosis and trafficking of proteins across multiple synapses. Recent studies of binding properties of several such proteins suggest that pathogens and lectins may utilize existing transport machineries designed for trafficking of trophic factors. Specific pathways may protect trophic factors, pathogens, and toxins from degradation after internalization and may target the trophic or pathogenic cargo for transcytosis after either retrograde or anterograde transport along axons. Elucidating the molecular mechanisms of sorting steps and transport pathways will further our understanding of trophic signaling and could be relevant for an understanding and possible treatment of neurological diseases such as rabies, Alzheimer's disease, and prion encephalopathies. At present, our knowledge is remarkably sparse about the types of receptors used by pathogens for trafficking, the signals that sort trophins or pathogens into recycling or degradation pathways, and the mechanisms that regulate their release from somatodendritic domains or axon terminals. This review intends to draw attention to potential convergences and parallels in trafficking of trophic and pathogenic proteins. It discusses axonal transport/trafficking mechanisms that may help to understand and eventually treat neurological diseases by targeted drug delivery. © 2003 Wiley Periodicals, Inc. J Neurobiol 58: 295–314, 2004
From snails to sciatic nerve: Retrograde injury signaling from axon to soma in lesioned neurons
Authors: Perlson Eran , Hanz Shlomit , Medzihradszky Katalin F. , Burlingame Alma L. , Fainzilber Mike
Published: December 2003

The cell body of a lesioned neuron must receive accurate and timely information on the site and extent of axonal damage, in order to mount an appropriate response. Specific mechanisms must therefore exist to transmit such information along the length of the axon from the lesion site to the cell body. Three distinct types of signals have been postulated to underlie this process, starting with injury‐induced discharge of axon potentials, and continuing with two distinct types of retrogradely transported macromolecular signals. The latter include, on the one hand, an interruption of the normal supply of retrogradely transported trophic factors from the target; and on the other hand activated proteins emanating from the injury site. These activated proteins are termed “positive injury signals”, and are thought to be endogenous axoplasmic proteins that undergo post‐translational modifications at the lesion site upon axotomy, which then target them to the retrograde transport system for trafficking to the cell body. Here, we summarize the work to date supporting the positive retrograde injury signal hypothesis, and provide some new and emerging proteomic data on the system. We propose that the retrograde positive injury signals form part of a complex that is assembled by a combination of different processes, including post‐translational modifications such as phosphorylation, regulated and transient proteolysis, and local axonal protein synthesis. © 2003 Wiley Periodicals, Inc. J Neurobiol 58: 287–294, 2004
Cargo‐carrying motor vehicles on the neuronal highway: Transport pathways and neurodegenerative disease
Authors: Gunawardena Shermali , Goldstein Lawrence S. B.
Published: December 2003

Within axons vital cargoes must be transported over great distances along microtubule tracks to maintain neuronal viability. Essential to this system are the molecular motors, kinesin and dynein, which transport a variety of neuronal cargoes. Elucidating the transport pathways, the identity of the cargoes transported, and the regulation of motor‐cargo complexes are areas of intense investigation. Evidence suggests that essential components, including signaling proteins, neuroprotective and repair molecules, and vesicular and cytoskeletal components are all transported. In addition newly emerging data indicate that defects in axonal transport pathways may contribute to the initiation or progression of chronic neuronal dysfunction. In this review we concentrate on microtubule‐based motor proteins, their linkers, and cargoes and discuss how factors in the axonal transport pathway contribute to disease states. As additional cargo complexes and transport pathways are identified, an understanding of the role these pathways play in the development of human disease will hopefully lead to new diagnostic and treatment strategies. © 2003 Wiley Periodicals, Inc. J Neurobiol 58: 258–271, 2004
Retrograde transport of neurotrophins: Fact and function
Authors: Campenot Robert B. , MacInnis Bronwyn L.
Published: December 2003

Retrograde signals generated by nerve growth factor (NGF) and other neurotrophins promote the survival of appropriately connected neurons during development, and failure to obtain sufficient retrograde signals may contribute to neuronal death occurring in many neurodegenerative diseases. The discovery over 25 years ago that NGF supplied to the axon terminals is retrogradely transported to the cell bodies suggested that NGF must reach the cell body to promote neuronal survival. Research during the intervening decades has produced a refinement of this hypothesis. The current hypothesis is that NGF bound to TrkA at the axon terminal is internalized into signaling endosomes, with NGF in their lumens bound to phosphorylated TrkA in their membranes, which are retrogradely transported to the cell bodies, where TrkA activates downstream signaling molecules that promote neuronal survival and regulate many aspects of neuronal gene expression. This model has been extrapolated to retrograde signaling by all neurotrophins. We consider the evidence for this model, focusing on results of experiments with neurons in compartmented cultures. Results to date indicate that while the transport of signaling endosomes containing NGF bound to TrkA may carry retrograde signals, retrograde survival signals can be carried by another mechanism that is activated by NGF at the axon terminal surface and travels to the cell body unaccompanied by the NGF that initiated it. It is hypothesized that multiple mechanisms of retrograde signaling exist and function under different circumstances. The newly discovered potential for redundancy in retrograde signaling mechanisms can complicate the interpretation of experimental results. © 2003 Wiley Periodicals, Inc. J Neurobiol 58: 217–229, 2004
Physical test data for the appraisal of design procedures for bolted joints in pultruded FRP structural shapes and systems
Authors: Mottram J T , Turvey G J
Published: December 2003

A review is presented of the tests undertaken to characterize bolted joints (no adhesive bonding) for pultruded fibre‐reinforced plastic (PFRP) structural shapes and systems. The review is written with regard to the appraisal of existing connection design procedures for plate‐to‐plate bolted joints. It is shown that 15 uncoordinated series of tests on single‐bolt and multi‐bolt double lap joints provide 800 ultimate strength results. Each of the series of tests had different objectives and so different joint variables were studied. This reflects the current state of guidance on joint design and installation in pultruders' design manuals and elsewhere, which is shown to be limited and inconsistent.

By rationalizing the number of variables the authors have tested a further 900 joints in order to generate a larger database of strengths and modes of failure, which may be used to appraise connection design procedures, such as the Hart‐Smith and EUROCOMP Design Code and Handbook simplified and rigorous methods. Observations are made on the findings from 16 series of tests with respect to the current state of design of PFRP plate‐to‐plate bolted joints.
Complex seismic site effects in sediment‐filled valleys and implications on design spectra
Authors: Faccioli Ezio , Vanini Manuela
Published: December 2003

Evidence of complex site effects in two‐dimensional geological configurations is illustrated first, and the related difficulties in interpreting ground motion observations are discussed, using weak motion data recorded in three alpine valleys in Northern Italy. While, on one hand, such valleys are mostly located in regions of low or moderate seismic hazard, where ground motion data are scarce, on the other hand investment in buildings and infrastructure has been substantial and may not always have been protected by adequate earthquake‐resistant provisions and zoning criteria. Moreover, experience and data obtained in regions hit by destructive earthquakes cannot be easily transferred to such a different context. The combined influence of one‐dimensional propagation effects on the dominant frequencies of motion, and of two‐dimensional effects on the amplification level and significant frequency band, are highlighted.

Concerning design elastic spectra, estimates of response spectra on hard and soft soil are performed, using observed weak motion data and the empirical Green's functions method. Comparison of results with Eurocode 8 spectra shows that the latter may not be conservative at periods larger than 1 s. The relatively large response at such is related to the geological configuration of the valleys, which appear to require a reasonably accurate definition of their two‐dimensional geometry.
Students' perceptions of academic dishonesty in the chemistry classroom laboratory
Authors: Del Carlo Dawn I. , Bodner George M.
Published: December 2003

Although the literature on both academic dishonesty and scientific misconduct is extensive, research on academic dishonesty has focused on quizzes, exams, and papers, with the virtual exclusion of the classroom laboratory. This study examined the distinctions undergraduate chemistry majors made between academic dishonesty in the classroom laboratory and scientific misconduct in the research laboratory. Across the spectrum of undergraduate chemistry courses, from the introductory course for first‐semester chemistry majors to the capstone course in instrumental analysis, we noted that students believe the classroom lab is fundamentally different from a research or industrial lab. This difference is so significant that it carries over into students' perceptions of dishonesty in these two environments. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 41: 47–64, 2004
Teacher change in beliefs and practices in science and literacy instruction with English language learners
Authors: Lee Okhee
Published: December 2003

This study examined patterns of change in beliefs and practices as elementary teachers learned to establish instructional congruence, a process of mediating academic disciplines with linguistic and cultural experiences of diverse student groups. The study focused on six bilingual Hispanic teachers working with fourth‐grade, mostly Hispanic students. The results indicated that teacher learning and change occurred in different ways in the areas of science instruction, students' language and culture, English language and literacy instruction, and integration of these areas in establishing instructional congruence. The results also indicated that establishing instructional congruence was a gradual and demanding process requiring teacher reflection and insight, formal training, and extensive support and sharing. Implications for further research in promoting achievement for all students are discussed. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 41: 65–93, 2004
Online computer gaming: a comparison of adolescent and adult gamers
Authors: Griffiths M.D , Davies Mark N.O , Chappell Darren
Published: December 2003

Despite the growing popularity of online game playing, there have been no surveys comparing adolescent and adult players. Therefore, an online questionnaire survey was used to examine various factors of online computer game players (n=540) who played the most popular online game Everquest. The survey examined basic demographic information, playing frequency (i.e. amount of time spent playing the game a week), playing history (i.e. how long they had been playing the game, who they played the game with, whether they had ever gender swapped their game character, the favourite and least favourite aspects of playing the game, and what they sacrifice (if anything) to play the game. Results showed that adolescent gamers were significantly more likely to be male, significantly less likely to gender swap their characters, and significantly more likely to sacrifice their education or work. In relation to favourite aspects of game play, the biggest difference between the groups was that significantly more adolescents than adults claimed their favourite aspect of playing was violence. Results also showed that in general, the younger the player, the longer they spent each week playing.
Secondary motions of the knee during weight bearing and non‐weight bearing activities
Authors: Dyrby Chris O. , Andriacchi Thomas P.
Published: December 2003

The objective of this study was to test the hypothesis that during a weight bearing activity such as walking, a dynamic range (envelope of motion) exists in the relationship between the secondary knee motions (anterior‐posterior (AP) translation, internalexternal (IE) rotation, and abduction‐adduction (Ab‐Adduction)) and knee flexion angle. In addition differences in the envelope of motion between a weight bearing and non‐weight bearing activity were tested. The hypothesis was evaluated by testing for differences (offsets) in secondary displacements at specific knee flexion angles during the walking cycle and seated leg extension (nonweight bearing). Kinematic measurements were obtained using a previously developed point cluster technique to analyze the sixdegrees of freedom movement of the knee. During walking, phase plots of the IE rotation and AP translation versus knee flexion demonstrated significant offsets from one phase of the gait cycle to another at the same flexion angle. During the non‐weight bearing activity, no significant offset in the secondary movement was found; the knee followed the same pathway of motion during the flexion and extension phase of this activity. The characteristics of the secondary motions during walking indicated that secondary knee movements are caused by the external forces (muscle, inertial and gravitational) that act on the knee during the various phases of the walking cycle. The boundaries of the envelope appear to reflect the characteristics of the passive restraints. The weight bearing secondary motion AP and IE rotation seen during a walking activity demonstrated an envelope of dynamic laxity that could potentially be used to evaluate functional instabilities at the knee. © 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.