bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis, X‐ray Powder Structure, and Magnetic Properties of Layered NiII Methylphosphonate, [Ni(CH3PO3)(H2O)], and NiII Octadecylphosphonate, [Ni{CH3‐(CH2)17‐PO3}(H2O)]
Authors: Bellitto Carlo , Bauer Elvira M. , Ibrahim Said A. , Mahmoud Mohamed R. , Righini Guido 
Published: March 2003

Abstract[Ni(CH3PO3)(H2O)] (1) and [Ni{CH3‐(CH2)17‐PO3}(H2O)] (2) were synthesised by reaction of NiCl2⋅6 H2O and the relevant phosphonic acid in water in presence of urea. The compounds were characterised by elemental and thermogravimetric analyses, UV‐visible and IR spectroscopy, and their magnetic properties were studied by using a SQUID magnetometer. The crystal structure of 1 was determined “ab initio” from X‐ray powder diffraction data and refined by the Rietveld method. The crystals of 1 are orthorhombic, space group Pmn21, with a=5.587(1), b=8.698(1), c=4.731(1) Å. The compound has a hybrid, layered structure made up of alternating inorganic and organic layers along the b direction of the unit‐cell. The inorganic layers consist of NiII ions octahedrally coordinated by five phosphonate oxygen atoms and one oxygen atom from the water molecule. These layers are separated by bilayers of methyl groups and van der Waals contacts are established between them. A preliminary structure characterisation of compound 2 suggests the crystallisation in the orthorhombic system with the following unit‐cell parameters: a=5.478(7), b=42.31(4), c=4.725(3) Å. The oxidation state of the Ni ion in both compounds is +2, and the electronic configuration is d8 (S=1), as determined from static magnetic susceptibility measurements above 50 K. Compound 1 obeys the Curie–Weiss law at temperatures above 50 K; the Curie (C) and Weiss (θ) constants were found to be 1.15 cm3 K mol−1 and −32 K, respectively. The negative value of θ indicates an antiferromagnetic exchange coupling between near‐neighbouring NiII ions. No sign of 3D antiferromagnetic long‐range order is observed down to T=5 K, the lowest measured temperature. Compound 2 is paramagnetic above T=50 K, and the values of C and θ were found to be 1.25 cm3 K mol−1 and −24 K, respectively. Below 50 K the magnetic behavior of 2 is different from that of 1. Zero‐field cooled (zfc) and field‐cooled (fc) magnetisation plots do not overlap below T=21 K. The irreversible magnetisation, ΔMfc−zfc, obtained as a difference from fc and zfc plots starts to increase at T=20 K, on lowering the temperature, and it becomes steady at T=5 K. The presence of spontaneous magnetisation below T=20 K indicates a transition to a weak‐ferromagnetic state for compound 2.
Reversible Immobilization of Peptides: Surface Modification and In Situ Detection by Attenuated Total Reflection FTIR Spectroscopy
Authors: Rigler Per , Ulrich Wolf‐Peter , Hoffmann Patrik , Mayer Michael , Vogel Horst 
Published: March 2003

AbstractA generic method is described for the reversible immobilization of polyhistidine‐bearing polypeptides and proteins on attenuated total reflecting (ATR) sensor surfaces for the detection of biomolecular interactions by FTIR spectroscopy. Nitrilotriacetic acid (NTA) groups are covalently attached to self‐assembled monolayers of either thioalkanes on gold films or mercaptosilanes on silicon dioxide films deposited on germanium internal reflection elements. Complex formation between Ni2+ ions and NTA groups activates the ATR sensor surface for the selective binding of polyhistidine sequences. This approach not only allows a stable and reversible immobilization of histidine‐tagged peptides (His–peptides) but also simultaneously allows the direct in situ quantification of surface‐adsorbed molecules from their specific FTIR spectral bands. The surface concentrations of both NTA and His–peptide on silanized surfaces were determined to be 1.1 and 0.4 molecules nm−2, respectively, which means that the surface is densely covered. A comparison of experimental FTIR spectra with simulated spectra reveals a surface‐enhancement effect of one order of magnitude for the gold surfaces. With the presented sensor surfaces, new ways are opened up to investigate, in situ and with high sensitivity and reproducibility, protein–ligand, protein–protein, protein–DNA interactions, and DNA hybridization by ATR–FTIR spectroscopy.
Mossy fiber plasticity and enhanced hippocampal excitability, without hippocampal cell loss or altered neurogenesis, in an animal model of prolonged febrile seizures
Authors: Bender Roland A. , Dubé Celine , Gonzalez‐Vega Rebeca , Mina Erene W. , Baram Tallie Z. 
Published: March 2003

AbstractSeizures induced by fever (febrile seizures) are the most frequent seizures affecting infants and children; however, their impact on the developing hippocampal formation is not completely understood. Such understanding is highly important because of the potential relationship of prolonged febrile seizures to temporal lobe epilepsy. Using an immature rat model, we have previously demonstrated that prolonged experimental febrile seizures render the hippocampus hyperexcitable throughout life. Here we examined whether (1) neuronal loss, (2) altered neurogenesis, or (3) mossy fiber sprouting, all implicated in epileptogenesis in both animal models and humans, were involved in the generation of a pro‐epileptic, hyperexcitable hippocampus by these seizures. The results demonstrated that prolonged experimental febrile seizures did not result in appreciable loss of any vulnerable hippocampal cell population, though causing strikingly enhanced sensitivity to hippocampal excitants later in life. In addition, experimental febrile seizures on postnatal day 10 did not enhance proliferation of granule cells, whereas seizures generated by kainic acid during the same developmental age increased neurogenesis in the immature hippocampus. However, prolonged febrile seizures resulted in long‐term axonal reorganization in the immature hippocampal formation: Mossy fiber densities in granule cell‐ and molecular layers were significantly increased by 3 months (but not 10 days) after the seizures. Thus, the data indicate that prolonged febrile seizures influence connectivity of the immature hippocampus long‐term, and this process requires neither significant neuronal loss nor altered neurogenesis. In addition, the temporal course of the augmented mossy fiber invasion of the granule cell and molecular layers suggests that it is a consequence, rather than the cause, of the hyperexcitable hippocampal network resulting from these seizures. Hippocampus 2003;13:399–412. © 2003 Wiley‐Liss, Inc.
Differential expression of S100 proteins in the developing human hippocampus and temporal cortex
Authors: Chan Wood Yee , Xia Chun‐Lin , Dong Da‐Cui , Heizmann Claus W. , Yew David T. 
Published: March 2003

AbstractS100 calcium binding proteins have long been known to express in the adult nervous system, but their distribution in the developing brain, especially the human fetal brain, is largely unknown. We used an immunohistochemical method to determine the expression of three S100 proteins, namely S100A4, S100A5, and S100A13, in the human fetal hippocampus and temporal cortex from 12 to 33 weeks of gestation. At 12 weeks, S100A5 was strongly expressed in the cells and fibers of the polymorphic, pyramidal, and molecular layers of the hippocampus. Thereafter, its expression decreased with age. In the temporal cortex, S100A5 expression was detected from 12 weeks onwards, peaked at 20 to 24 weeks, and then decreased with age. The horizontal fibers of the marginal zone were immunoreactive at all stages examined. S100A13 immunoreactivity was also detected in both cells and fibers of the hippocampus at 12 weeks, became slightly stronger at 20 weeks, and then decreased with age. In the temporal cortex, S100A13 immunoreactivity was also strong in all cellular layers at 12 to 24 weeks before it declined with age from 28 weeks onwards. Among the three proteins examined, S100A4 showed the weakest expression, which was detected in the cells and fibers of the hippocampus and the temporal cortex at all stages examined. Our results have demonstrated for the first time, in the human fetal hippocampus and temporal cortex, specific spatio‐temporal patterns of expression of these proteins, all of which are likely to have different roles to play during development despite their pronounced sequence homology. Microsc. Res. Tech. 60:600–613, 2003. © 2003 Wiley‐Liss, Inc.
S100B in brain damage and neurodegeneration
Authors: Rothermundt Matthias , Peters Marion , Prehn Jochen H.M. , Arolt Volker 
Published: March 2003

AbstractS100B is a calcium‐binding peptide produced mainly by astrocytes that exert paracrine and autocrine effects on neurons and glia. Some knowledge has been acquired from in vitro and in vivo animal experiments to understand S100B's roles in cellular energy metabolism, cytoskeleton modification, cell proliferation, and differentiation. Also, insights have been gained regarding the interaction between S100B and the cerebral immune system, and the regulation of S100B activity through serotonergic transmission. Secreted glial S100B exerts trophic or toxic effects depending on its concentration. At nanomolar concentrations, S100B stimulates neurite outgrowth and enhances survival of neurons during development. In contrast, micromolar levels of extracellular S100B in vitro stimulate the expression of proinflammatory cytokines and induce apoptosis. In animal studies, changes in the cerebral concentration of S100B cause behavioral disturbances and cognitive deficits. In humans, increased S100B has been detected with various clinical conditions. Brain trauma and ischemia is associated with increased S100B concentrations, probably due to the destruction of astrocytes. In neurodegenerative, inflammatory and psychiatric diseases, increased S100B levels may be caused by secreted S100B or release from damaged astrocytes. This review summarizes published findings on S100B regarding human brain damage and neurodegeneration. Findings from in vitro and in vivo animal experiments relevant for human neurodegenerative diseases and brain damage are reviewed together with the results of studies on traumatic, ischemic, and inflammatory brain damage as well as neurodegenerative and psychiatric disorders. Methodological problems are discussed and perspectives for future research are outlined. Microsc. Res. Tech. 60:614–632, 2003. © 2003 Wiley‐Liss, Inc.
Electrospray ionization mass spectrometry and tandem mass spectrometry of clodronate and related bisphosphonate and phosphonate compounds
Authors: Huikko Katri , Kotiaho Tapio , Yli‐Kauhaluoma Jari , Kostiainen Risto 
Published: March 2003

AbstractThe bisphosphonate family with a P—C—P structure is a broad class of drugs, widely investigated as potential inhibitors in bone diseases and calcium metabolic disorders. In this study, the mass spectrometric (MS) behavior and fragmentation of clodronate and related bisphosphonate and phosphonate compounds was studied by using negative ion electrospray ionization (ESI) with triple quadrupole and ion trap instruments. The effect of pH on the degree of deprotonation of the polyprotic bisphosphonic and phosphonic acids in negative ion ESI‐MS was investigated, and the degree of deprotonation in the ESI mass spectra and the dissociation in the liquid phase were compared. The results provide evidence that the measured ESI mass spectra do not correlate with the chemistry in the liquid phase owing to the decrease in the pH of the solvent droplets during the ion evaporation process and the charge state neutralization in the gas phase. Ion trap MSn provided useful information on the fragmentation study of clodronate and related bisphosphonate and phosphonate compounds, in which interesting fragmentation pathways including the direct elimination of carbon monoxide from deprotonated bisphosphonates and formation of a P—P bond were observed. Reactions between the product ions with a —PO2 group and residual water in the ion trap or in the high‐pressure region of the triple quadrupole instrument formed other unexpected fragmentation paths for all the bisphosphonates studied. Copyright © 2002 John Wiley & Sons, Ltd.
Ceramide in rafts (detergent‐insoluble fraction) mediates cell death in neurotumor cell lines
Authors: Kilkus John , Goswami Rajendra , Testai Fernando D. , Dawson Glyn 
Published: March 2003

AbstractDetergent‐resistant lipid microdomains (Rafts) were isolated from human oligodendroglioma (HOG), human neuroblastoma (LA‐N‐5), and immortalized dorsal root ganglion (F‐11) cell lines by sucrose‐density gradient ultracentrifugation and shown to be enriched in cholesterol, sphingomyelin, and ceramide. [3H]palmitate labeling allowed the Raft fraction to be easily identified as a sharp peak of 3H radioactivity in the 5–30% sucrose interphase. Treatment of [3H]palmitate‐labeled cells with staurosporine (to activate caspase 8 and induce apoptosis) or exogenous sphingomyelinase specifically increased the [3H]ceramide content of the Raft fraction. Depletion of cholesterol with β‐methylcyclodextran decreased Raft formation and partially blocked staurosporine‐induced apoptosis. Similarly, treatment of cells with Fumonisin B1 to inhibit de novo sphingolipid synthesis by 50% reduced the labeling of the Raft fraction and partially blocked staurosporine‐induced apoptosis. Staurosporine treatment activated neutral sphingomyelinase but had no effect on acid sphingomyelinase activity or on other lysosomal hydrolases, such as α‐L‐fucosidase. Most of the neutral sphingomyelinase activity is in the Raft fraction, suggesting that the conversion of sphingomyelin to ceramide in Rafts is an important event in neural cell apoptosis. © 2003 Wiley‐Liss, Inc.
Electrical Response to Organic Vapor of Conductive Composites from Amorphous Polymer/Carbon Black Prepared by Polymerization Filling
Authors: Li Jun Rong , Xu Jia Rui , Zhang Ming Qiu , Rong Min Zhi 
Published: March 2003

AbstractIn recent years, conductive polymer composites have found applications as gas sensors because of their sudden change in electric resistance of several orders of magnitude when the materials are exposed to certain solvent vapors. However, the composites having this function reported so far are mostly based on crystalline polymeric matrices, which factually sets a limit to materials selection. The present work prepares polystyrene/carbon black composites through polymerization filling and proves that the amorphous polymer composites can also serve as gas sensing materials. The composites' percolation threshold is much lower than that of the composites produced by dispersive mixing. In addition, high responsivity to some organic vapors coupled with sufficient reproducibility is acquired. The experimental data show that molecular weight and molecular weight distribution of the matrix polymer and conducting filler content exert great influence on the electrical response behavior of the composites. As a result, composites performance can be purposely tailored accordingly. Compared with the approaches of melt‐blending and solution‐blending, the current technique is characterized by many advantages, such as simplicity, low cost, and easy to be controlled.
Effect of different organic solvent vapors on the electric resistance of PS/CB composites (CB content = 10.35 vol.‐%).magnified imageEffect of different organic solvent vapors on the electric resistance of PS/CB composites (CB content = 10.35 vol.‐%).
Spinning and Characterization of Conducting Microfibers
Authors: Okuzaki Hidenori , Ishihara Masayoshi 
Published: March 2003

AbstractConducting microfibers of poly(3,4‐ethylenedioxythiophene) doped with poly(4‐styrene sulfonate), having a diameter ranging between 4.6 and 16 μm, were fabricated by a wet‐spinning technique. The as‐spun microfiber had no notable orientation of polymer chains with poor crystallinity, and electrical conductivity was in the order of 10−1 S · cm−1 regardless of the diameter. Young's modulus, tensile strength, and elongation at break for the resulting microfiber were 1.1 ± 0.3 GPa, 17.2 ± 5.1 MPa, and 4.3 ± 2.3%, respectively.
SEM image of a PEDOT/PSS microfiber reported here.magnified imageSEM image of a PEDOT/PSS microfiber reported here.
Multiphase‐Separated Polyurethanes Studied by Micro‐Raman Spectroscopy
Authors: Janik Helena , Pałys Barbara , Petrovic Zoran S. 
Published: March 2003

AbstractMicro‐Raman spectroscopy has been used to investigate the chemical micro‐heterogeneity of multiphase‐separated poly(ether urethanes) (PETU). Analysis of PETU cross‐sections by means of micro‐Raman spectroscopy revealed the nearly complete absence of soft segments in AI aggregates (called globules). These aggregates are in the order of a few micrometers in size. The composition of the matrix and the AII aggregates (spherulites) was comparable.Example of an AFM image (sample 706, scan size 25 μm, converted to monochromatic image).magnified imageExample of an AFM image (sample 706, scan size 25 μm, converted to monochromatic image).
Influence of the annealing conditions on the polarization and electromechanical response of high‐energy‐electron‐irradiated poly(vinylidene fluoride trifluoroethylene) copolymer
Authors: Xia Feng , Wang Y. K. , Li Hengfeng , Huang Cheng , Ma Y. , Zhang Q. M. , Cheng Z.‐Y. , Bateman Fred B. 
Published: March 2003

AbstractIn this study, we investigated the influence of annealing conditions before irradiation on the ferroelectric and electromechanical properties of uniaxially stretched high‐energy‐electron‐irradiated poly(vinylidene fluoride trifluoroethylene) (HEEIP) copolymer (68/32 mol %) films. For films annealed at one fixed temperature before the irradiation (one‐step annealing), the highest crystallinity, which was highly desirable for enhancing the electromechanical response, was obtained only for films annealed between 132 and 136 °C. In addition, annealing over 10 h in this temperature window resulted in a large increase in the crystal lamellar thickness, which was required for reducing the polarization hysteresis to a minimum in the HEEIP samples. For improvements in the mechanical qualities of the uniaxially stretched films, a two‐step annealing procedure was investigated; that is, before the irradiation, the films were first annealed at a lower temperature to release the mechanical stress in the films due to the stretching and then were annealed in the high‐temperature window to raise the crystallinity and crystalline size. The experimental results indicated that this approach could produce uniaxially stretched HEEIP films with much improved mechanical qualities. Furthermore, the uniaxially stretched HEEIP films with this two‐step annealing exhibited the same electromechanical response as or an even higher one than that from the one‐step‐annealed HEEIP films. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 797–806, 2003
Alkylating reactivity and herbicidal activity of chloroacetamides
Authors: Jablonkai Istvan 
Published: March 2003

AbstractThe relationship between S‐ and N‐alkylating reactivity and herbicidal activity within a series of chloroacetamides, including several commercial herbicides and newly synthesised analogues was studied. The S‐alkylating reactivity of selected chloroacetamides, as well as those of atrazine and chlorfenprop‐methyl, was determined by in vitro GSH conjugation at a ratio of GSH to alkylating agent of 25 : 1. A spectrophotometric reaction using 4‐(4‐nitrobenzyl)pyridine was used to characterise the N‐alkylating reactivity of the chemicals. Our results indicate that a reduced level of N‐alkylating reactivity correlates with an improved herbicidal efficacy at a practical rate. However, the phytoxicity of the molecules is not simply dependent on chemical reactivities, but strictly related to the molecular structure, indicating that lipophilicity, uptake, mobility and induction of detoxifying enzymes may also be decisive factors in the mode of action.© 2002 Society of Chemical Industry
A review of physiological and biochemical aspects of resistance to atrazine and paraquat in Hungarian weeds
Authors: Szigeti Zoltán , Lehoczki Endre 
Published: March 2003

AbstractThe most important results in the field of atrazine and paraquat resistance research by Hungarian researchers are reviewed. Pleiotropic effects accompanying atrazine resistance were investigated in atrazine‐resistant (AR) and susceptible (S) biotypes of horseweed (Conyza canadensis (L) Cronq). No significant difference in carbon dioxide assimilation rate was found between the AR and S plants. The rates of the Hill reaction of the AR and S chloroplasts exhibited different temperature dependence. The thylakoid membrane lipids contained a lower amount of polar lipid and the fatty acid content exhibited a higher degree of unsaturation in the AR biotype. Photosynthetic apparatus of the AR biotype had better adaptive ability at low temperature and showed enhanced susceptibility to high‐temperature stress. AR horseweed plants had reduced activity of xanthophyll cycle, limited capacity of light‐induced non‐photochemical and photochemical quenching, higher photosensitivity and susceptibility to photo‐inhibition. In the case of paraquat resistance, horseweed found in Hungary exhibited a resistance factor of 450; the resistance is not based on an elevated level and activity of the antioxidant enzyme system. The suggested role of polyamines in the resistance mechanisms can be excluded. The higher putrescine and total polyamine content of paraquat‐treated R leaves can be regarded as a general stress response rather than as a symptom of paraquat resistance. A paraquat‐inducible, nuclear‐coded protein, which presumably functions by carrying paraquat to the vacuole, is supposed to play a role in resistance.© 2003 Society of Chemical Industry
Developmental D‐methamphetamine treatment selectively induces spatial navigation impairments in reference memory in the Morris water maze while sparing working memory
Authors: Williams Michael T. , Morford Laronda L. , Wood Sandra L. , Wallace Tanya L. , Fukumura Masao , Broening Harry W. , Vorhees Charles V. 
Published: March 2003

AbstractIn previous studies, we have shown that P11‐20 treatment with D‐methamphetamine (MA) (10 mg/kg × 4/day at 2‐h intervals) induces impairments in spatial learning and memory in the Morris water maze after the offspring reach adulthood. Using a split‐litter, multiple dose, design (0, 5, 10, and 15 mg/kg MA administered s.c. 4/day at 2‐h intervals), the spatial learning effect was further explored with a multiple shifted platform (reversal), reference memory‐based procedure and a working memory procedure. Prior to spatial learning, animals were first tested for swimming ability (in a straight swimming channel), sequential learning (in the Cincinnati multiple‐T water maze), and proximal cue learning (in the Morris water maze). Rats were then assessed in the hidden platform, reference memory‐based spatial version of the Morris maze for acquisition and on five subsequent phases in which the platform was moved to new locations. After the reference memory‐based, fixed platform position learning phases, animals were tested in the trial‐dependent, matching‐to‐sample, working memory version of the Morris maze. No group differences were found in straight channel, sequential maze, or cued Morris maze performance. By contrast, all MA groups were impaired in spatial learning during acquisition, multiple shift, and shifted with a reduced platform phases of reference memory‐based learning. In addition, MA animals were impaired on memory (probe) trials during the acquisition and shifted with a reduced platform phases of learning. No effects on trial‐dependent, matching‐to‐sample, working memory were found. The findings demonstrate that neonatal treatment with MA induces a selective impairment of reference memory‐based spatial learning while sparing sequential, cued, and working memory‐based learning. Synapse 48:138–148, 2003. © 2003 Wiley‐Liss, Inc.