bluuebunny/crossref_metadata_2025_split huggingface dataset:
Membrane regulation of the Na+, K+‐ATPase during the neuroblastoma cell cycle: Correlation with protein lateral mobility
Authors: van Zoelen E. J. J. , Mummery C. L. , Boonstra J. , van der Saag P. T. , de Laat S. W. 
Published: December 2004

AbstractThe pumping activity of the plasma membrane‐bound Na+, K+‐ATPase shows considerable variation during the cell cycle of mouse neuroblastoma Neuro‐2A cells. Addition of external ATP at millimolar concentrations, which selectively enhances the plasma membrane permeability of Neuro‐2A cells for sodium ions, stimulates the Na+, K+‐ATPase pumping activity at all phases of the cell cycle from a factor of 1.05 in mitosis up to 2.2 in G1 phase. Determination of the number of Na+, K+‐ATPase copies per cell by direct 3H‐ouabain binding studies in the presence of external ATP shows a gradual increase in the number of pump sites on passing from mitosis to the late S/G2‐phase by approximately a factor of 2. From these data the pumping activity per copy of Na+, K+‐ATPase, optimally stimulated with respect to its various substrate ions, has been determined during the various phases of the cell cycle. This optimally stimulated pumping activity per enzyme copy, which is a reflection of the physicochemical state of the plasma membrane, is high in mitosis, almost twofold lower in early G1 phase, and increases gradually again during the other phases of the cell cycle. This shows that the observed regulation of Na+, K+‐ATPase activity during the cell cycle is caused by a combination of three independent factors–namely variation in intracellular substrate availability (Na+), changes in number of enzyme copies per cell, and modulation of the plasma membrane environment of the protein molecules. The modulation of the optimal pumping activity per enzyme copy shows a good correlation (ρ = 0.96) with the known modulation of protein lateral mobility during the cell cycle, such that a high protein lateral mobility correlates with a low enzyme activity. It is concluded that changes in plasma membrane properties take place during the Neuro‐2A cell cycle that result in changes in the rate of protein lateral diffusion and Na+, K+‐ATPase activity in a directly correlated way.
Purification and partial characterization of bovine pituitary fibroblast growth factor
Authors: Lemmon Sandra K. , Bradshaw Ralph A. 
Published: December 2004

AbstractA purification procedure and partial characterization of bovine pituitary fibroblast growth factor (FGF) are described. The steps of the published methods [3,4] which yield inhomogeneous material, were retained, with modifications. The final isolation, with an additional purification of ∼20‐fold, was achieved by electro‐phoresis in polyacrylamide gels at acid pH. The mitogenic peptide has a molecular weight of 14,500–15,00 as determined on SDS gels, chromatographs as a monomer in nondenaturing conditions, and is active at the picomolar level in effecting the incorporation of 3H‐thymidine in Balb/c 3T3 cells. A preliminary amino acid composition is presented.
Epidermal growth factor and gonadotropin‐releasing hormone inhibit cyclic AMP–dependent luteinizing hormone receptor formation in ovarian granulosa cells
Authors: Knecht Michael , Catt Kevin 
Published: December 2004

AbstractThe induction of luteinizing hormone (LH) receptors was studied in granulosa cells prepared from the ovaries of hypophysectomized diethylstilbestrol‐treated immature rats. Incubation of granulosa cells for 48 h with increasing concentrations of follicle‐stimulating hormone (FSH) or choleragen caused parallel rises in cAMP levels and LH receptors. These observations, with the finding that 8‐Bromo‐cAMP also induced LH receptor formation, indicate that hormonal stimulation of LH binding sites is mediated by cAMP. Peptide hormones that inhibited FSH‐stimulated cAMP production, such as epidermal growth factor (EGF) and a gonadotropin‐releasing hormone agonist (GnRHa), also prevented LH receptor formation. GnRHa and EGF had negligible effects on FSH‐stimulated cAMP production from 0 to 24 h of culture, but reduced cAMP accumulation by 80% and 90%, respectively, from 24 to 48 h when the majority of LH receptors appeared. FSH‐sensitive adenylate cyclase activity, as measured by the conversion of (3H)‐ATP to (3H)‐cAMP, was inhibited by GnRHa and EGF at 48 h of culture. EGF and GnRHa also reversed the inhibition of ectophosphodiesterase activity caused by FSH in granulosa cells between 48 and 72 h of culture. Both EGF and GnRHa inhibited induction of LH receptors by 8‐Bromo‐cAMP, suggesting that their effects are also on cAMP action. Addition of GnRHa, but not EGF, between 36 and 48 h of culture completely prevented further increases in LH receptors induced by 8‐Bromo‐cAMP, indicating that the inhibitory action of GnRHa can be initiated at later times during granulosa cell differentiation, whereas full expression of EGF action requires a longer period. These results demonstrate that EGF and GnRH inhibit FSH‐induced LH receptor formation in the granulosa cell by reducing hormone‐dependent cAMP production and also by impairing the ability of cAMP to stimulate LH receptor formation.
Autoantibodies and monoclonal antibodies in the purification and molecular characterization of neurotransmitter receptors
Authors: Fraser Claire M. , Greguski Roger , Eddy Barbara , Venter J. Craig 
Published: December 2004

AbstractThe combination of immunological advances with membrane receptor research has promoted rapid progress in the molecular characterization of neurotransmitter receptor molecules. We have to date produced monoclonal antibodies to β1‐, β2‐, and β1‐adrenergic, D2‐dopaminergic, and muscarinic receptors. In addition we have discovered that some allergic respiratory disease patients possess circulating autoantibodies to β2‐adrenergic receptors. These antireceptor antibodies in conjunction with specific receptor affinity reagents have allowed us to isolate, purify, and begin to characterize α‐ and β‐adrenergic, dopaminergic, and muscarinic receptors. For example, immunoprecipitation of turkey erythrocyte β1 receptors with monoclonal antibodies yields a single polypeptide Mr 65–70 K. In contrast, purification of β2‐adrenergic receptors using either autoantibodies or monoclonal antibodies yields a receptor species with a subunit of Mr 55–59 K. Autoantibodies to β2 receptors demonstrate a 50–100% homology among β2 receptors from humans to rats, whereas monoclonal antibody FV‐104 recognizes a determinant in the ligand binding site of all β1 and β2 receptors tested to date. These data suggest that β1‐ and β2‐adrenergic receptors may have evolved from a common ancestor, perhaps by gene duplication.
Antigens in chromatin associated with proliferating and nonproliferating cells
Authors: Briggs R.C. , Brewer G. , Goldberger A. , Wolff S.N. , Hnilica L.S. 
Published: December 2004

AbstractXenoantisera were raised to total chromatin from the leukemia cell line K562, or materials released through limited deoxyribonuclease I digestion of nuclei or during the control incubation of nuclei without enzyme. The peroxidase‐antiperoxidase method of antibody‐antigen detection was employed to visualize individual antigens resolved on one‐dimensional polyacrylamide gels following transfer to sheets of nitrocellulose (immunotransfers). Each antiserum contained multiple antigen specificities as evidenced by the diverse patterns of reactive bands displayed on the immunotransfers. The most striking difference in antigens recognized between the antisera was observed in the molecular weight region below 50,000, where two highly reactive bands were seen mainly with antiserum to nuclear materials released by deoxyribonuclease I digestion. The antigens detected with all of the antisera were present in chromatins prepared from proliferating cells, while the levels of antigens present in chromatin from non‐proliferating peripheral blood lymphocytes were greatly reduced or not detected. Antigens in chromatin from proliferating cells that migrated with apparent molecular weights of 37,000 and 100,000 were not lost once the activities to antigens in lymphocyte chromatin were absorbed out. These two activities were absorbed from antisera with the same amount of chromatins from proliferating cells. Two antigens migrating at molecular weight 52,000 and 76,000 appeared more active in the chromatin from unstimulated lymphocytes than in chromatin from proliferating cells.
Purification of a human urinary colony‐stimulating factor
Authors: Wang Fung Fang , Goldwasser Eugene 
Published: December 2004

AbstractColony‐stimulating factor (CSF), a protein required for the in vitro formation of colonies composed of granulocytes and/or macrophages, was isolated from the urine of anemic patients by using a seven‐step procedure. The purified, homogeneous CSF had a specific activity of 1.9 × 108 U/absorbance unit at 280 nm (AU). This represents an overall purification of 25,330‐fold and a total recovery of 3.8%. Upon iodination of the protein, the radioactivity migrated on sodium dodecyl sulfate (SDS) gel electrophoresis as a single peak with an apparent molecular weight of 46,000; reduction with mercaptoethanol caused dissociation to a single component of molecular weight 23,000. Only the dimer is active in stimulating colony formation. Urinary CSF stimulates formation of colonies comprising only macrophages in the mouse bone' marrow cell culture assay. A neutralizing antibody raised against mouse L‐cell CSF did not neutralize the activity of the urinary CSF but did bind it. This may indicate that the relative positions of antibody binding sites and the active sites are different in these two glycoproteins.
Cell‐surface associated proteins of corneal fibroblasts: Dissection with monoclonal antibodies
Authors: SundarRaj Nirmala , Martin Judith , Sundar‐Raj C.V. 
Published: December 2004

AbstractIt is now generally accepted that the cell surface is involved in the interaction of the cells with the extracellular matrix. To identify and characterize cell‐surface‐associated components of corneal fibroblasts, several monoclonal antibodies were developed. Hybridomas were developed by fusing mouse myeloma cells SP2/OAg14 with spleen cells from mice immunized with membrane fractions of corneal fibroblasts grown in culture. Twenty‐five hybridomas secreting monoclonal antibodies to cell‐surface components were selected by an enzyme‐linked immunosorbent assay using corneal fibroblasts grown in microtiter plates as the substrate. Immunohistochemical staining demonstrated that the antigenic determinants recognized by these antibodies were not present on corneal epithelial cells, but were present on skin fibroblasts. The antigenic deteminants recognized by two of these antibodies, designated 10D2 and 716, were matrix components of the corneal stroma. Immunochemical characterization of the antigens was carried out by indirect precipitation of the radioactively labeled cellular proteins with the monoclonal antibodies and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) analysis of the precipitates. Four antibodies were able to precipitate antigens from cell extract in detectable amounts. Antibodies designated 5E2, 9G2, and 10D2 recognized antigens consisting of polypeptides of approximate molecular weights 105K and 110K, while antibody 716 recognized an antigen of 100K molecular weight. However, based on the tissue distribution and cell‐surface distribution, these antibodies reacted with different antigenic determinants. The antigen recognized by 716 was also secreted by cells in culture but consisted of 220K and 200K polypeptide chains. It was tentatively identified as cellular fibronectin, based on the reaction of this antigen with polyclonal antibodies to plasma fibronectin.
Influence of protein kinase C on transcription of the tight junction elements ZO‐1 and occludin
Authors: Weiler Frank , Marbe Theresa , Scheppach Wolfgang , Schauber Jürgen 
Published: December 2004

AbstractTight junctions as an epithelial barrier against paracellular diffusion have mainly been investigated on the protein level with particular respect to subcellular localization. In this study, real‐time PCR has been established to investigate the influence of protein kinase C (PKC) modulation on the transcription of tight junction elements occludin and ZO‐1 in the cell line T84. Activation of PKC by the phorbol ester TPA induced ZO‐1 and occludin transcription, whereas PKC inhibition lead to decreased expression levels. Activation of PKC exerted its effect on transcript level directly. PKC signal was partially transduced via MEK1/MEK2 but depended strongly on MAPK independent pathways probably involving nuclear localized PKC, whereas p38 signaling was not implicated. TPA induced loss of function concomitant with a dislocation of ZO‐1 and occludin could be prevented by inhibition of MEK1 by PD98059. Overall ZO‐1 and occludin seem to be identically regulated in colonic epithelium on the transcript level. © 2004 Wiley‐Liss, Inc.
Binding sites of [Ru(bpy)2(H2O)2](BF4)2 with sulfur‐ and histidine‐containing peptides studied by electrospray ionization mass spectrometry and tandem mass spectrometry
Authors: Hong Jin , Miao Yi , Miao Ren , Yang Gaosheng , Tang Huiwei , Guo Zijian , Zhu Longgen 
Published: December 2004

AbstractThe composition and binding sites of cis‐[Ru(II)(bpy)2]2+‐bound sulfur‐containing peptides of Met‐Arg‐Phe‐Ala, glutathione and oxidized glutathione, and also histidine‐containing peptide of oxidized insulin B chain, were investigated by electrospray ionization mass spectrometry (ESI‐MS) and tandem mass spectrometry (MS/MS). The composition of Ru(II)‐containing peptides was precisely determined by ESI‐MS, zoom scan and simulation of isotope distribution patterns. MS/MS analysis shows that, in sulfur‐containing peptides, the Ru(II) complex prefers to anchor to a carboxyl group, although some other potential binding sites of thiol, thioether and N‐terminal amino groups present in these peptides, and in oxidized insulin B chain, Ru(II) first anchors to His10, then either to the hydroxyl group of Thr27 or to the carboxyl group of Ala30. Its secondary structure and microenvironment surrounding the potential binding sites may affect the binding ability of cis‐[Ru(II)(bpy)2]2+ to oxidized insulin B chain. Copyright © 2004 John Wiley & Sons, Ltd.
In Vitro Mineralization of Collagen in Demineralized Fish Bone
Authors: Chen Jinglu , Burger Christian , Krishnan Chirakkal V. , Chu Benjamin , Hsiao Benjamin S. , Glimcher Melvin J. 
Published: December 2004

AbstractSummary: Simultaneous small‐ and wide‐angle X‐ray diffraction of in vitro calcified highly ordered decalcified shad fish bone collagen have identified the calcium phosphate (Ca‐P) crystals, formed as poorly crystalline apatite, and their highly ordered spatial, axial distribution with respect to the supramolecular packing of collagen fibrils. The extent of in vitro calcification was significantly diminished when the supramolecular collagen packing was disrupted. These findings are similar to both electron microscopic and small angle X‐ray scattering (SAXS) studies of native shad and other species of fish bone and other animal species and of in vitro experiments of the calcification of purified and reconstituted native type collagen fibrils. The results emphasize the important role of the supramolecular packing of collagen fibrils in the heterogeneous nucleation of apatite crystals initiating calcification. The exquisite spatial relationships of the inorganic crystal and the supramolecular packing of native collagen fibrils also form a two‐phase composite substance, providing distinct mechanical properties and other physiological functions to bone substance and tissue.The integrated 1D WAXD profiles of shad bone samples demineralized in 0.1 M EDTA for different times.magnified imageThe integrated 1D WAXD profiles of shad bone samples demineralized in 0.1 M EDTA for different times.
Surface Functionalized ZnO Particles Designed for the Use in Transparent Nanocomposites
Authors: Khrenov Victor , Klapper Markus , Koch Mathias , Müllen Klaus 
Published: December 2004

AbstractSummary: We present a new method for preparing a nanocomposite containing highly dispersed ZnO nanoparticles. The essence of this approach is the formation of surface modified inorganic particles and their homogeneous incorporation into a polymeric matrix. Therefore, an inverse emulsion of an inorganic salt, for example, zinc acetate stabilized by amphiphilic statistical copolymers, is prepared. By hydrolysis under basic conditions ZnO particles of a size below 100 nm are formed within the micelles. As the surfactant remains adsorbed on the surface of the particles, a surface functionalization with hydrophobic chains is performed. These chains can be considered as compatibilizers for blending of the ZnO nanoparticles in PMMA affording transparent nanocomposite films avoiding particle aggregated. The present approach is in principle applicable to all nanoparticles prepared in a sol‐gel process.TEM image of redispersed ZnO particles.magnified imageTEM image of redispersed ZnO particles.
Computer Simulations of the “Hairy Rod” Model
Authors: Limbach Hans Jörg , Holm Christian , Kremer Kurt 
Published: December 2004

AbstractSummary: Using extensive Molecular Dynamics simulations we study the behavior of very rigid polyelectrolytes with hydrophobic side chains that are known to form cylindrical micelles in aqueous solution. We investigate the stability of such micelles with respect to hydrophobicity, Coulomb interaction, and micellar size. We show that for the parameter range relevant for poly(p‐phenylene sulfonate)s (PPP) one finds a stable finite micellar size close to the experimental parameter region. We also point out that our model has some similarities to DNA solutions with added condensing agents, hinting to the possibility that the size of DNA aggregates is under certain circumstances thermodynamically limited.DNA‐like morphologies of the polyelectrolytes.magnified imageDNA‐like morphologies of the polyelectrolytes.
Effects of Ionic Liquid [Me3NC2H4OH]+[ZnCl3]− on γ‐Radiation Polymerization of Methyl Methacrylate in Ethanol and N,N‐Dimethylformamide
Authors: Wu Guozhong , Liu Yaodong , Long Dewu 
Published: December 2004

AbstractSummary: Radiation‐induced polymerization of methyl methacrylate (MMA) in ethanol (EtOH) and N,N‐dimethylformamide (DMF) in the presence of ionic liquid [Me3NC2H4OH]+[ZnCl3]− is reported. A substantial increase in monomer conversion and molecular weight is observed at room‐temperature ionic liquid (RTIL) >60 vol.‐%, and the resulting PMMA has a broad multimodal MWD. A clear difference in the MWD pattern is noted between EtOH/RTIL and DMF/RTIL systems, probably due to the complicated interactions between the solvent and ionic liquid.Gel permeation chromatography traces of poly(methyl methacrylate) obtained by radiation polymerization in EtOH/RTIL and DMF/RTIL mixed solvent. Organic/RTIL (v/v): 1) 100:0; 2) 80:20; 3) 60:40; 4); 40:60; 5) 0:100.imageGel permeation chromatography traces of poly(methyl methacrylate) obtained by radiation polymerization in EtOH/RTIL and DMF/RTIL mixed solvent. Organic/RTIL (v/v): 1) 100:0; 2) 80:20; 3) 60:40; 4); 40:60; 5) 0:100.
Synthesis of Poly(arylene ether amine)s from a Monomer Containing an Electron‐Donating Amine Group in a Nucleophilic Aromatic Substitution Reaction
Authors: Lee Mong Sup , Kim Sang Youl 
Published: December 2004

AbstractSummary: Poly(arylene ether amine)s were synthesized by a nucleophilic aromatic substitution polycondensation of bis[4‐fluoro‐3‐(trifluoromethyl)phenyl]amine with several bisphenols. Even though the monomer has an electron‐donating diphenylamine moiety, which normally deactivates a nucleophilic aromatic substitution (SNAr) reaction, the polymerization proceeded by a SNAr reaction to give high‐molecular‐weight polymers. The polymers show good solubility in common organic solvents and have Tgs in the range of 123 °C to 177 °C.High‐molecular‐weight poly(arylene ether amine)s synthesized by a SNAr reaction with the monomer containing an electron‐donating diphenylamine moiety.imageHigh‐molecular‐weight poly(arylene ether amine)s synthesized by a SNAr reaction with the monomer containing an electron‐donating diphenylamine moiety.
Novel Azaferrocenyliminonickel Catalysts for Olefin Polymerization
Authors: Watanabe Makoto 
Published: December 2004

AbstractSummary: The azaferrocenyliminonickel dibromide complexes 1 bearing a pentaphenylcyclopentadienyl group and a wide range of N‐aryl groups were synthesized and examined as catalysts for ethylene polymerization. Both the ortho‐ (R1) and para‐substituents (R2) of the N‐aryl groups in 1 were found to strongly influence both the polymerization activity and the properties of the obtained polyethylenes. The effect of changing the polymerization conditions, such as temperature, ethylene pressure, and cocatalyst, was also examined.Azaferrocenyliminonickel(II) complexes.imageAzaferrocenyliminonickel(II) complexes.
Preparation of Well‐Defined Diblock Copolymers with Short Polypeptide Segments by Polymerization of N‐Carboxy Anhydrides
Authors: Lutz Jean‐François , Schütt Dagmar , Kubowicz Stephan 
Published: December 2004

AbstractSummary: The ring‐opening polymerization of N‐carboxy anhydrides (NCA) of γ‐benzyl‐L‐glutamate and β‐benzyl‐L‐aspartate was studied in the presence of an ammonium chloride‐functionalized poly(ethylene oxide) macroinitiator, which possibly prevents side reactions such as NCA deprotonation. Although polymerization initiated by such macroinitiators was found to be quite slow, well‐defined conjugates of poly(ethylene oxide)‐block‐poly(γ‐benzyl‐L‐glutamate) and poly(ethylene oxide)‐block‐poly(β‐benzyl‐L‐aspartate) with polydispersity indexes as low as 1.05 were prepared. Moreover, the presence of ammonium chloride chain ends significantly prevented end‐group cyclization of poly(γ‐benzyl‐L‐glutamate) after polymerization.Gel permeation chromatograms recorded for the diblock copolymers of poly(ethylene oxide)‐block‐poly(γ‐benzyl‐L‐glutamate) prepared by N‐carboxy anhydride polymerization initiated either by PEO‐NH2 macroinitiator or PEO‐NHCl− macroinitiator.imageGel permeation chromatograms recorded for the diblock copolymers of poly(ethylene oxide)‐block‐poly(γ‐benzyl‐L‐glutamate) prepared by N‐carboxy anhydride polymerization initiated either by PEO‐NH2 macroinitiator or PEO‐NHCl− macroinitiator.
Elastomere. Physikalische Untersuchungen im Hinblick auf ihre Abgrenzung zu anderen Polymerwerkstoffen
Authors: Timm Thies 
Published: December 2004

AbstractDie in der ASTM D 1418–67 und in der ASTM D 1566–68a sowie der entsprechenden vorläufigen ISO‐Empfehlung (DIR 1382) enthaltenen Definitionen der Begriffe „Elastomer”︁ und „Rubber”︁ sind unter sich widersprüchlich und reichen auch im einzelnen nicht aus, um eine präzise Abgrenzung gegenüber anderen Polymerwerkstoffen zu ermöglichen. Der DIN‐Entwurf 7724 (Febr. 1969) bedeutet diesbezüglich einen wesentlichen Fortschritt, weil er Komplikationen vermeidet, die durch die Einbeziehung von Ausgangsstoffen und Vorprodukten entstehen, und weil er unter Außerachtlassen ihrer spezifischen Konstitution die Polymerwerkstoffe allein anhand der Temperaturfunktion von Schubmodul und mechanischem Verlustfaktor klassifiziert. Aus dem Kurvenhabitus, der Glasumwandlungstemperatur und den Schubmoduli im gummielastischen Zustandsbereich ergibt sich die Gruppierung der Polymeren in Thermoplaste (Plastomere) — Elastomere — Thermoelaste — Duromere (Duroplaste). — Möglichkeiten und Grenzen dieser Methode wurden an 29 Polymeren (unvernetzt bzw. vernetzt) untersucht und führten zu einer im ganzen positiven Beurteilung des Klassifizierungssystems.