bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local calcium changes regulate the length of growth cone filopodia
Authors: Cheng Su , Geddis Matthew S. , Rehder Vincent 
Published: August 2002

AbstractPrevious studies have demonstrated that the free intracellular calcium concentration ([Ca2+]i) in growth cones can act as an important regulator of growth cone behavior. Here we investigated whether there is a spatial and temporal correlation between [Ca2+]i and one particular aspect of growth cone behavior, namely the regulation of growth cone filopodia. Calcium was released from the caged compound NP–EGTA (o‐nitrophenyl EGTA tetrapotassium salt) to simulate a signaling event in the form of a transient increase in [Ca2+]i. In three different experimental paradigms, we released calcium either globally (within an entire growth cone), regionally (within a small area of the lamellipodium), or locally (within a single filopodium). We demonstrate that global photolysis of NP–EGTA in growth cones caused a transient increase in [Ca2+]i throughout the growth cone and elicited subsequent filopodial elongation that was restricted to the stimulated growth cone. Pharmacological blockage of either calmodulin or the Ca2+‐dependent phosphatase, calcineurin, inhibited the effect of uncaging calcium, suggesting that these enzymes are acting downstream of calcium. Regional uncaging of calcium in the lamellipodium caused a regional increase in [Ca2+]i, but induced filopodial elongation on the entire growth cone. Elevation of [Ca2+]i locally within an individual filopodium resulted in the elongation of only the stimulated filopodium. These findings suggest that the effect of an elevation of [Ca2+]i on filopodial behavior depends on the spatial distribution of the calcium signal. In particular, calcium signals within filopodia can cause filopodial length changes that are likely a first step towards directed filopodial steering events seen during pathfinding in vivo. © 2002 Wiley Periodicals, Inc. J Neurobiol 50: 263–275, 2002; DOI 10.1002/neu.10027
Heat shock‐induced thermoprotection of action potentials in the locust flight system
Authors: Wu Bernhard S. , Walker Virginia K. , Robertson R. Meldrum 
Published: August 2002

AbstractThere is increasing evidence that heat shock (HS) has long‐term effects on electrophysiological properties of neurons and synapses. Prior HS protects neural circuitry from a subsequent heat stress but little is known about the mechanisms that mediate this plasticity and induce thermotolerance. Exposure of Locusta migratoria to HS conditions of 45°C for 3 h results in thermotolerance to hitherto lethal temperatures. Locust flight motor patterns were recorded during tethered flight at room temperature, before and after HS. In addition, intracellular action potentials (APs) were recorded from control and HS motoneurons in a semi‐intact preparation during a heat stress. HS did not alter the timing of representative depressor or elevator muscle activity, nor did it affect the ability of the locust to generate a steering motor pattern in response to a stimulus. However, HS did increase the duration of APs recorded from neuropil segments of depressor motoneurons. Increases in AP duration were associated with protection of AP generation against failure at subsequent elevated temperatures. Failure of AP generation at high temperatures was preceded by a concomitant burst of APs and depolarization of the membrane. The protective effects of HS were mimicked by pharmacological blockade of I with tetraethylammonium (TEA). Taken together, these findings are consistent with a hypothesis that HS protects neuronal survival and function via K+ channel modulation. © 2001 John Wiley & Sons, Inc. J Neurobiol 49: 188–199, 2001
A comparison in terms of accuracy and efficiency between a MBS dynamic formulation with stress analysis and a non‐linear FEA code
Authors: Cuadrado J. , Gutiérrez R. , Naya M. A. , Morer P. 
Published: August 2002

AbstractTo perform the mechanical design of a machine through computer‐aided techniques, at least three main different products should be used: a CAD software, to model the parts of the machine; a MBS program, to analyse the kinematics and dynamics of the whole system; and a FEA code, to determine the level of stress and strain suffered by each component. If it is true that CAD software is usually well connected with the two other tools, the same does not happen in what respects to FEA–MBS interfaces. Moreover, since both the large‐amplitude motion and the elastic deformation are coupled, they cannot be solved separately, and the usual practice consisting of first analysing the machine motion assuming rigid bodies, and then calculating stresses under the loads previously generated, is just an approximation. In order to provide mechanical designers with a tool which makes easier and shorter the design‐cycle, this paper presents a comparison between the two options that are currently available to address the mentioned problem: a dynamic MBS formulation which simultaneously solves motion and performs stress analysis by considering flexible bodies; and a non‐linear module of a FEA code, which takes into account large displacements and finite rotations. The comparison is carried out in terms of accuracy and efficiency through four examples. The results lead to the conclusion that, for similar accuracy, the first method is largely more efficient. Therefore, the interest of developing MBS commercial codes which integrate motion calculation and stress analysis through the mentioned approach is envisioned, as long as they would provide faster solutions. Copyright © 2001 John Wiley & Sons, Ltd.
Prenatal diagnosis of multiple acyl‐CoA dehydrogenase deficiency: association with elevated α‐fetoprotein and cystic renal changes
Authors: Chisholm Christian A. , Vavelidis Fotini , Lovell Mark A. , Sweetman Lawrence , Roe Charles R. , Roe Diane S. , Frerman Frank E. , Wilson William G. 
Published: August 2002

AbstractWe report the occurrence of multiple acyl‐CoA dehydrogenase deficiency (MADD) in two consecutive pregnancies in a young, Caucasian, non‐consanguineous couple. In the first pregnancy, the maternal serum α‐fetoprotein was elevated. A sonogram showed growth delay, cystic renal disease, and oligohydramnios; the parents decided to terminate the pregnancy. Postmortem examination confirmed the cystic renal disease and showed hepatic steatosis, raising the suspicion of a metabolic disorder. The diagnosis of MADD was made by immunoblot studies on cultured fibroblasts. In the subsequent pregnancy, a sonogram at 15 weeks' gestation showed an early growth delay but normal kidneys. The maternal serum and amniotic fluid concentrations of α‐fetoprotein were elevated, and the amniotic fluid acylcarnitine profile was consistent with MADD. In vitro metabolic studies on cultured amniocytes confirmed the diagnosis. A follow‐up sonogram showed cystic renal changes. These cases provide additional information regarding the evolution of renal changes in affected fetuses and show a relationship with elevated α‐fetoprotein, which may be useful in counseling the couple at risk. MADD should be considered in the differential diagnosis of elevated α‐fetoprotein and cystic renal disease. Early growth delay may be an additional feature. Copyright © 2001 John Wiley & Sons, Ltd.
Obstetric outcome after fetal reduction to singleton pregnancies
Authors: De Catte L. , Foulon W. 
Published: August 2002

AbstractObjectiveTo study the outcome after fetal reduction or selective termination to singleton pregnancies for various indications.MethodsFetal reduction or selective feticide to singleton pregnancies was performed in 80 multiple gestations (congenital malformations, 17 cases; high‐risk obstetric conditions, 25 cases; or social/psychological indications, 38 cases).ResultsThe overall pregnancy loss rate was 10%; however, pregnancy failure was significantly higher in selective reductions performed for preterm prelabor rupture of membranes (PPROM) (4/8) compared with monochorionic twin and bad obstetric history. Fetal reduction to singletons for psychological reasons resulted in a pregnancy wastage of 5.3% (2/38). Procedures performed at ≤14 weeks showed a significantly lower fetal loss rate (2/61; 3.3%), a higher mean gestational age at delivery (38.3±2.2 weeks), and a decreased prematurity rate (p≤0.001). The number of reduced fetuses, prenatal diagnosis by chorionic villus sampling before the reduction and maternal age did not interfere with pregnancy outcome.ConclusionFetal reduction to singleton pregnancies has a favorable outcome, especially when performed before 14 weeks of gestation. Copyright © 2002 John Wiley & Sons, Ltd.
Kinetics of the reaction of β‐alkoxyvinyl methyl ketones with amines
Authors: Vdovenko Sergei I. , Gerus Igor I. , Wójcik Jacek 
Published: August 2002

AbstractThe kinetics of the reaction of β‐alkoxyvinyl methyl ketones R1O—CR2CH— COCX3 (1a–e)(a, R1CH3, R2H, XH; b, R1C2H5, R2H, XF; c, R1C2H5, R2H, XCl; d, R1R2CH3, XCl;e, R1R2CH3, XF) with aliphatic amines was studied in various solvents. The details of appropriate enaminoketone (2a–d) formation are discussed in terms of an addition–elimination reaction. It is shown that the limiting step of the reaction is the decomposition of a zwitterionic intermediate, and that the observed second‐order reaction rate constants are a function of the solvent's relative permittivity ϵr. At high amine concentrations in non‐polar solvents, the third‐order rate coefficient appears in the reaction rate equation as a consequence of a catalyzed route of the intermediate decomposition. The reaction has low ΔH≠ and high negative ΔS≠ values owing to the formation of a highly polar zwitterionic intermediate. Its lifetimes are determined mainly by the electron‐withdrawing ability of COCX3. Copyright © 2001 John Wiley & Sons, Ltd.
Reduction of the 2‐azetidinone moiety in the polymer main chain: A novel synthetic route to polyamine with hydroxymethyl pendant
Authors: Sudo Atsushi , Sato Masato , Endo Takeshi 
Published: August 2002

AbstractA polymer with a 2‐azetidinone moiety in its main chain was efficiently synthesized by [2 + 2] cycloaddition of bisimine with bisketene. The bisketene was easily prepared by dehydrochlorination of the corresponding dicarboxylic acid chloride and was used without purification. The treatment of the obtained polymer with lithium aluminum hydride resulted in a reductive ring‐opening reaction of the 2‐azetidinone moiety in the main chain that gave the corresponding linear polyamine with hydroxymethyl side chains. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3789–3796, 2001
Copolycondensations of bisphenols with aggregates of isophthalic acid and terephthalic acid activated by tosyl chloride/dimethylformamide/pyridine in different manners
Authors: Higashi Fukuji , Shirai Takayo , Mitani Kiyoshi , Sugishita Kanako 
Published: August 2002

AbstractA mixture of isophthalic acid (IPA) and terephthalic acid (TPA) was activated by a tosyl chloride/dimethylformamide/pyridine (Py) condensing agent in two steps via the treatment of a mixture of the initially activated IPA/TPA with additional TPA followed by the activation of TPA with the agent. The resulting mixture showed a solubility in Py different from that obtained by the activation of them all at once; the difference might be due to different structures of the aggregates of the activated IPA and TPA at the same composition of the diacids. The structures of the aggregates were evaluated on the basis of melting points and the IR spectra of a mixture of dimethyl esters of IPA and TPA produced by the quenching of the reaction mixtures with methanol. The mixture obtained by two‐step activation showed lower melting points and spectral changes due to enhanced associations of the esters with respect to the mixture prepared by the activation of them all at once. The aggregates were also examined in terms of the distributions of IPA and TPA in thermotropic copolyesters prepared from methylhydroquinone and chlorohydroquinone by their transition temperatures and 13C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3884–3892, 2001
2,2,6,6‐Tetramethyl‐1‐piperidinyl‐oxyl/[bis(acetoxy)‐iodo]benzene‐mediated oxidation: A versatile and convenient route to poly(ethylene glycol) aldehyde or carboxylic acid derivatives
Authors: Masson Christophe , Scherman Daniel , Bessodes Michel 
Published: August 2002

AbstractA new and very convenient route to oxidized poly(ethylene glycol), with a catalytic nitroxyl radical oxidant (2,2,6,6‐tetramethyl‐1‐piperidinyl‐oxyl) regenerated in situ by stoichiometric amounts of [bis(acetoxy)‐iodo]benzene, is described. Under these conditions, the reaction is quantitative and leads to the pure product by a simple process such as precipitation and washing with diethyl ether. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4022–4024, 2001
Glycoconjugated polymer. I. Synthesis and characterization of amphiphilic polystyrenes with glucose, maltose, and maltohexaose as hydrophilic segments
Authors: Narumi Atsushi , Kaga Harumi , Kawasaki Kosei , Taniguchi Yasuo , Satoh Toshifumi , Kakuchi Toyoji 
Published: August 2002

AbstractGlucosyl styrene (1a), maltosyl styrene (1b), and maltohexaosyl styrene (1c) were prepared by the glycosylation of 4‐vinylbenzyl alcohol with the corresponding glycosyl trichloroacetimidates with boron trifluoride diethyl ether complex. The copolymerizations of 1a–1c with styrene were carried out with 2,2′‐azobis(2‐methylpropionitrile) as an initiator in dry N,N‐dimethylformamide at 60 °C, and this was followed by deacetylation to produce amphiphilic polystyrenes with glucose (3a), maltose (3b), and maltohexaose (3c) as hydrophilic segments. 3 showed various solubility characteristics that were dependent on the content of glucose residues, especially within a range of 20–50 wt %. The solubility characteristics of 3, related to the copolymer composition, indicated that the hydrophilic property was remarkably improved with an increased number of glucose units, that is, in the order 3a < 3b ≪ 3c. The results described in this article provide useful information for the design of glycoconjugated architectures with desired amphiphilic properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4061–4067, 2001
Polythiophene formation within hyperbranched grafts on polyethylene films
Authors: Bergbreiter David E. , Liu Martha L. 
Published: August 2002

AbstractInterphase oligomerization of thiophene within a supported thin film is described. Polyethylene (PE) surfaces containing an irregularly hyperbranched poly(acrylic acid) (PAA) graft were first prepared by multistep grafting of poly(tert‐butylacrylate) onto oxidized PE. The product ultrathin PAA grafts were then further modified by amidation or esterification with thiophenes containing amino or hydroxyl groups to form new interfaces containing thiophene monomers. These thiophene‐modified grafts were characterized by attenuated total reflectance infrared spectroscopy and were shown to be suitable as substrates in an oxidative polymerization method with FeCl3 as an oxidant. The product 2,5‐coupled thiophene oligomers (3‐PAA/PE–oligomerized thiophene ester, OTE) emitted a yellow‐green light under UV irradiation, indicating that a conjugated fluorescence oligothiophene had been prepared within these hyperbranched films. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4119–4128, 2001
Metallocene derivatives as active supports of zirconium‐based catalysts for ethene polymerization
Authors: Mortara Stefano , Fregonese Daniele , Bresadola Silvano , Boaretto Rita , Sostero Silvana 
Published: August 2002

AbstractCyclopentadienyl magnesium chloride (MgClCp) and its functionalized derivatives represent original and interesting supporting materials to heterogenize metallocene catalysts for olefin polymerizations. The synthesis of MgClCp, its functionalization, and the preparation of a catalytic system in which the ZrCl2(Flu)+ moiety is joined on the support through a cyclopentadienyl ligand are reported. This catalyst was tested in ethene polymerization, and both the catalytic activity and properties of the produced polymer were measured. Its performance was compared with that shown by the catalyst ZrCl2CpFlu employed under the same conditions for both unsupported and conventional supports, such as MgCl2. The results showed a remarkable improvement in terms of the activity and polymer properties with these heterogenized catalysts. Moreover, this system showed stability toward leaching processes and was characterized by good morphological control of the growing polymer. Finally, catalysts in which [HB(3,5‐Me2pyrazolyl)3]ZrCl and [HB(3,5‐Me2pyrazolyl)3]ZrClOtBu+ moieties were bonded to a functionalized MgClCp− support were also synthesized and tested. The results showed that the proposed supports could be usefully used to heterogenize tailored metallocene homogeneous catalysts. In fact, new catalysts were prepared that combined the peculiar advantages of both heterogeneous and homogeneous catalysts and overcame the disadvantages of the latter, such as a lack of morphology and reactor fouling. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4243–4248, 2001
High‐temperature elastomers from silarylene‐siloxane‐diacetylene linear polymers
Authors: Homrighausen Craig L. , Keller Teddy M. 
Published: August 2002

AbstractThe syntheses and characterization of linear silarylene‐siloxane‐diacetylene polymers 3a–c and their thermal conversion to crosslinked elastomeric materials 4a–c are discussed. Inclusion of the diacetylene unit required synthesis of an appropriate monomeric species. 1,4‐Bis(dimethylaminodimethylsilyl)butadiyne [(CH3)2N Si(CH3)2CCCC(CH3)2SiN(CH3)2] 2 was prepared from 1,4‐dilithio‐1,3‐butadiyne and 2 equiv of dimethylaminodimethylchlorosilane. The linear polymers were prepared via polycondensation of 2 with a series of disilanol prepolymers. The low molecular weight silarylene‐siloxane prepolymers 1a–c (terminated by hydroxyl groups) were synthesized via solution condensation of an excess amount of 1,4‐bis(hydroxydimethylsilyl)benzene with bis(dimethylamino)dimethylsilane. The linear polymers were characterized by 1H and 13C NMR, Fourier transform infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis (TGA), and DSC. The elastomers exhibited long‐term oxidative stability up to 330 °C in air as determined by TGA. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 88–94, 2002
Synthesis of end‐functionalized poly(methyl methacrylate) by ruthenium‐catalyzed living radical polymerization with functionalized initiators
Authors: Baek Kyung‐Youl , Kamigaito Masami , Sawamoto Mitsuo 
Published: August 2002

AbstractA series of functionalized 2‐bromoisobutyrates and 2‐chloro‐2‐phenylacetates led to α‐end‐functionalized poly(methyl methacrylate)s in Ru(II)‐catalyzed living radical polymerization; the terminal functions included amine, hydroxyl, and amide. These initiators were effective in the presence of additives such as Al(Oi‐Pr)3 and n‐Bu3N. The chlorophenylacetate initiators especially coupled with the amine additive gave polymers with well‐controlled molecular weights (Mw/Mn = 1.2–1.3) and high end functionality (Fn ∼ 1.0). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1937–1944, 2002
Synthesis and electrooptic properties of side‐chain methacrylate polymers containing a new azophenylbenzoxazole chromophore
Authors: Beltrani T. , Bösch M. , Centore R. , Concilio S. , Günter P. , Sirigu A. 
Published: August 2002

AbstractThe synthesis and characterization of four methacrylate copolymers obtained by radical addition polymerization of methyl methacrylate as well as a new methacrylate azophenylbenzoxazole chromophore in percentages of 10, 30, 50, and 70% were explored. The copolymers were amorphous and showed glass‐transition temperatures ranging from 132 to 146 °C. High‐quality polymer films were easily obtained by spin coating from N‐methylpyrrolidone solutions. Polymer films spun cast on iridium tin oxide (ITO) substrates were used in the electro‐optic (EO) experiments to evaluate the EO coefficients r33 using the reflection technique. The measured values fell in the range of 1.7–3.7 pm/V (laser incident wavelength of 1.552 μm) depending on the percentage of chromophore in the polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1162–1168, 2001
Cationic ring‐opening polymerization of six‐membered cyclic carbonates with ester groups
Authors: Nemoto Nobukatsu , Sanda Fumio , Endo Takeshi 
Published: August 2002

AbstractThis work deals with the cationic ring‐opening polymerization of the ester‐substituted cyclic carbonates 5‐methyl‐5‐benzoyloxymethyl‐1,3‐dioxan‐2‐one (CC1) and 4‐benzoyloxymethyl‐1,3‐dioxan‐2‐one (CC4). The polymerization was carried out with trifluoromethanesulfonic acid, methyl trifluoromethanesulfonate, boron trifluoride etherate, or methyl iodide as the initiator. The reactivity of CC1 and CC4 was higher than that of 5,5‐dimethyl‐1,3‐dioxan‐2‐one, which had no ester moiety. These results suggest that this ring‐opening polymerization was accelerated by the intramolecular ester group. CC1 showed a higher polymerizability than CC4, affording a polymer with a higher molecular weight. Additionally, using methyl iodide as the initiator was effective for increasing the molecular weight of the obtained polycarbonate and decreasing decarboxylation. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1305–1317, 2001
Synthesis and characterization of liquid–crystalline polyesters with chiral and achiral twin spacers
Authors: Srinivasan Rukmani , Radhakrishnan Ganga 
Published: August 2002

AbstractA series of novel thermotropic main‐chain chiral liquid–crystalline random copolyesters consisting of spacers of two different types—chiral and achiral—was synthesized. Polyesters (BmTa) with tartaric acid as the chiral spacer (Ta), aliphatic diols (with ‘m’ = 2–10 methylene groups) as the achiral spacers, and 4,4′‐dihydroxy biphenyl (B) as the mesogen were synthesized via condensation polymerization in solution after duly protecting the 2,3‐dihydroxy groups of tartaric acid by acetylation. The copolymers were characterized by Fourier transform infrared spectroscopy, 1H and 13C NMR spectra, gel permeation chromatography, and thermogravimetric analysis. Transition temperatures for phase changes recorded by DSC were corroborated with the textures observed by a hot‐stage optical polarizing microscope. The wide‐angle X‐ray diffraction (WAXD) profiles indicated a SmE phase at room temperature. The lower angle region at 2θ = 0.5–2.45 covered by WAXD indicated a layer of thickness of 161 Å, less than the molecular length for B0Ta. The [αD] values were recorded on a digital polarimeter. The birefringence was lost at higher mesophase temperatures in lower members with m < 5, a behavior found in certain chiral systems, and the higher members with m > 5 showed a lesser number of phase transitions. On cooling, the polyesters produced a texture with the formation of transition bars. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1743–1752, 2001