bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of endothelin‐1 on astrocytic protein content
Authors: Hasselblatt Martin , Bunte Marion , Dringen Ralf , Tabernero Arantxa , Medina José M. , Giaume Christian , Sirén Anna‐Leena , Ehrenreich Hannelore
Published: April 2003

The astrocytic endothelin (ET) receptors, ETA and ETB, modulate calcium signaling and the astrocytic gap junctional network. The nonselective ET receptor ligand ET‐1 inhibits gap junction permeability, an effect that can be blocked by tolbutamide. This mechanism may play a role in pathophysiological conditions such as ischemic stroke, characterized by elevated tissue ET‐1 levels and hypertrophic‐appearing reactive astrocytes. Therefore, the effect of ET‐1 on cellular protein content was investigated in confluent once‐passaged rat astrocyte cultures under serum‐free conditions, by the Lowry method. Gap junction permeability was determined by the dye transfer technique. ET‐1 prevented the decrease in astrocytic protein content observed in controls. The effect of ET‐1 on cellular protein content was most pronounced in cultures seeded at high density, but it was attenuated in ETB‐deficient (sl/sl) astrocytes. This effect could be blocked by the nonselective ET antagonist LU 302872 (10 μM), as well as by the protein synthesis inhibitor cycloheximide (10 μM). This increase in astrocytic protein content was inhibited by the ATP‐sensitive K+ channel blocker tolbutamide, which also antagonized the ET‐1‐induced reduction of gap junction permeability and reversed the morphological changes observed in astrocytes upon ET‐1 treatment. Cytosine arabinoside (10 μM), a DNA synthesis blocker, inhibited the ET‐1‐induced BrdU uptake without affecting the ET‐1‐induced increase in astrocytic protein content. To conclude, ET‐1 induces an increase in astrocytic protein content as well as changes in astrocyte morphology in vitro. This hypertrophic response involves uncoupling of the astrocytic gap junctional network and is not dependent on DNA synthesis. GLIA 42:390–397, 2003. © 2003 Wiley‐Liss, Inc.
Targeting human 8‐oxoguanine glycosylase to mitochondria of oligodendrocytes protects against menadione‐induced oxidative stress
Authors: Druzhyna Nadiya M. , Hollensworth Scott B. , Kelley Mark R. , Wilson Glenn L. , Ledoux Susan P.
Published: April 2003

Within the central nervous system (CNS), there is a differential susceptibility among cell types to certain pathological conditions believed to involve oxidative stress. Oligodendrocytes are extremely sensitive to oxidative stress, which correlates with a decreased ability to repair damage in mitochondrial DNA (mtDNA), as we have shown previously. To determine whether there is a causal relationship, studies were carried out to correct the deficit in repair of the oxidative damage in mtDNA in cultured oligodendrocytes. A vector containing a mitochondrial transport sequence (MTS) upstream of the sequence for human 8‐oxoguanine‐DNA glycosylase (OGG) was transfected into the cells. The efficiency of transfection and the localization of recombinant protein were determined by fluorescence microscopy and by Western blot analysis. Subsequent mtDNA repair studies, employing 100 μM menadione to produce reactive oxygen species, showed a significant enhancement in repair of oxidative lesions in mtDNA of MTS‐OGG transfected oligodendrocytes compared with cells transfected with vector only. Experiments were also conducted to determine the effect of changing mtDNA repair capacity on menadione‐induced apoptosis in oligodendrocytes. These experiments show that targeting the OGG repair enzyme to mitochondria reduces the release of cytochrome c from the intermitochondrial space and the activation of caspase 9 in oligodendrocytes after exposure to menadione. Therefore, targeting of DNA repair enzymes to mitochondria appears to be a viable approach for the protection of cells against some of the deleterious effects of oxidative stress. GLIA 42:370–378, 2003. © 2003 Wiley‐Liss, Inc.
Interactions of Atomic Iron Cation with Pyridine and Benzene: A Theoretical Study on an Unresolved Controversy of Bond Energies and Electronic Ground‐State Structures
Authors: Diefenbach Martin , Trage Claudia , Schwarz Helmut
Published: April 2003

The binding energies, geometries, and electronic structures of cationic ironbenzene and ironpyridine complexes have been studied by the two hybrid DFT‐HF approaches mPW1PW91 and B3LYP, as well as the AQCC and MR‐AQCC extension. The AQCC results confirm the experimental binding energies derived from threshold‐CID experiments reported by Meyer et al., and Rodgers et al. as well as the previously reported C2v‐symmetric quartet ground state of ironbenzene. The ironpyridine complex is coordinated via the N‐atom lone‐pair and has a sextet ground state. Bond energies determined by the kinetic method apparently yield a dissociation energy corresponding to the first excited quartet ironpyridine complex. Both DFT methods fail to predict the correct ground state for cationic iron pyridine.
The Structure of N1‐Hydroxylophine N3‐Oxide (=1‐Hydroxy‐2,4,5‐ triphenyl‐1H‐imidazole 3‐Oxide) in the Solid State
Authors: Sánchez‐Migallón Ana , de la Hoz Antonio , López Concepción , Claramunt Rosa M. , Infantes Lourdes , Motherwell Sam , Shankland Kenneth , Nowell Harriott , Alkorta Ibon , Elguero José
Published: April 2003

The crystal structure of 1‐hydroxy‐2,4,5‐triphenyl‐1H‐imidazole 3‐oxide (1) has been determined from laboratory X‐ray powder‐diffraction data. The two independent molecules in the asymmetric unit form chains via OH⋅⋅⋅O hydrogen bonds related by a twofold screw axis. One of the O⋅⋅⋅O distances is extremely short (2.32(1) and 2.43(1) Å). Solid‐state NMR spectroscopy (CPMAS) combined with calculation of absolute shieldings (GIAO/B3LYP/6‐31G*) allowed us to determine that the compound behaves as if the OH⋅⋅⋅O hydrogen bond has the proton in the middle (single‐well potential), resulting in the near identity of both 15N‐NMR signals.
Towards a Complete Description of a Polymorphic Crystal: The Example of Perylene
Authors: Botoshansky Mark , Herbstein Frank H. , Kapon Moshe
Published: April 2003

Crystal structures of the two polymorphs of perylene have been determined at low temperatures (150 and 200 K), and the molecular geometry was compared with earlier crystallographic and NMR measurements. Cell dimensions have been measured for both polymorphs over the ranges 150–320 K for (EI‐β) and 150–420 K for (EII‐α). Combination of thermodynamic and crystallographic measurements has permitted inference of pressuretemperature phase diagrams for perylene and pyrene that are compatible with available measurements up to ca. 50 kbar. Perylene and pyrene are both enantiotropic systems, while phenazine appears to be monotropic.
Perception of correlated attributes involving African–American and white females' faces by 10‐month‐old infants
Authors: Levy Gary D.
Published: April 2003

Thirty‐two 10‐month‐olds were habituated to stimuli containing an African–American female face or a white female face paired with a specific object. Test stimuli maintained or violated habituation stimuli pairings (i.e. categories). Results add to an emerging literature showing that 10‐month‐olds perceive categories of social information based on detection of correlated attributes. Copyright © 2003 John Wiley & Sons, Ltd.
On asymmetric coverings and covering numbers
Authors: Applegate David , Rains E. M. , Sloane N. J. A.
Published: April 2003

An asymmetric covering ${\cal D}(n,R)$ is a collection of special subsets S of an n‐set such that every subset T of the n‐set is contained in at least one special S with $|S| - |T| \le R$. In this paper we compute the smallest size of any ${\cal D}(n,1)$ for $n \le 8.$ We also investigate “continuous” and “banded” versions of the problem. The latter involves the classical covering numbers $C(n,k,k-1)$, and we determine the following new values: $C(10,5,4) = 51$, $C(11,7,6) =84 $, $C(12,8,7) = 126 $, $C(13,9,8)= 185$, and $C(14,10,9) = 259$. We also find the number of non‐isomorphic minimal covering designs in several cases. © 2003 Wiley Periodicals, Inc. J Combin Designs 11: 218–228, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jcd.10022
New families of strongly regular graphs
Authors: Ionin Yury J. , Kharaghani Hadi
Published: April 2003

We apply symmetric balanced generalized weighing matrices with zero diagonal to construct four parametrically new infinite families of strongly regular graphs. © 2003 Wiley Periodicals, Inc. J Combin Designs 11: 208–217, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jcd.10038
Surface Immobilization of Bioactive Molecules on Polyurethane for Promotion of Cytocompatibility to Human Endothelial Cells
Authors: Gao Changyou , Guan Jianjun , Zhu Yabin , Shen Jiacong
Published: April 2003

Cytocompatible polymers are of increasing importance for tissue engineering scaffolds and implanted devices. Polyurethane (PU) membranes were modified by grafting polymerization of methacrylic acid (MAA) initiated by UV light and further covalent immobilization of gelatin or arginine‐glycine‐aspartic (RGD) peptide using 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide hydrochloride as a condensing agent. The immobilization of gelatin or RGD peptide was confirmed by FTIR attenuated total reflection (ATR) spectroscopy and X‐ray photoelectron spectroscopy (XPS). The results for endothelial cells cultured in vitro proved that the PU membrane modified with gelatin or RGD peptide had better cytocompatibility than the control PU or the PMAA grafted PU membrane.

ATR‐FTIR spectra of PU‐graft‐PMAA (a), PU‐graft‐PMAA‐graft‐RGD (b), and their subtraction result (c). The PMAA grafting degree is 21.56 × 10−2 mg/cm2.

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ATR‐FTIR spectra of PU‐graft‐PMAA (a), PU‐graft‐PMAA‐graft‐RGD (b), and their subtraction result (c). The PMAA grafting degree is 21.56 × 10−2 mg/cm2.
Syntheses of polymeric cobalt dinitrogen complexes and reduction of the coordinated nitrogen
Authors: Koide Mikio , Kato Masayuki , Tsuchida Eishun , Kurimura Yoshimi
Published: April 2003

Polymeric cobalt dinitrogen complexes were synthesized by two different methods: by the ligand substitution reaction of polymers 5a – c and 6a – c, containing 4‐diphenylphosphinophenylethylene units (3) or 4‐diphenylphosphinomethylphenylethylene units (4), respectively, with hydridodinitrogentris(triphenylphosphine)cobalt(I) (CoH(N2)(PPh3)3), or by the direct reaction of tris(acetylacetonato)cobalt(III) with triphenylphosphine, the polymers 5a – c or 6a – c, and triisobutylaluminium under nitrogen. The intensity of the v band in the IR spectrum of the polymeric dinitrogen complex was found to be about four times as that of CoH(N2)(PPh3)3. Ammonia was formed after hydrolysis of the complex, which was prepared by mixing a tetrahydrofuran solution of naphthaline, lithium, and titanium tetrachloride with the polymeric dinitrogen complex. The yields of ammonia in the case of the polymeric complexes were high in comparison with that obtained with CoH(N2)(PPh3)3. The highest yields of ammonia were obtained when a mole ratio [P̄]/[Co] < 1 ([P̄] is the concentration of phosphino groups in the polymer and [Co] is that of Co in CoH(N2)(PPh3)3), a temperature of −20°C, and a reaction time of 1 h were applied.
Structure of Cu/poly(L‐glutamic acid) complex
Authors: Koide Mikio , Tsuchida Eishun , Kurimura Yoshimi
Published: April 2003

The structure of the Cu/poly(L‐glutamic acid), (Cu/1), complex was studied by magnetic susceptibility, circular dichroism, electron spin resonance, and light scattering measurements. Cu/1 (pH 5,5) formed a binuclear complex by stabilizing the helix structure using [1]/[Cu] = 10. When the amount of Cu ions became small, the structure of the Cu/1 complex changed from a binuclear complex to a mononuclear one. Furthermore, it was obvious that an intermolecular bridged complex of Cu/1 was formed at pH = 5,5, because the molecular weight of the Cu/1 complex was about 13 fold that of 1, when the mixing mole ratio [1]/[Cu] was 10.
Polymerisation via macrozwitterions, 3. Ethyl and butyl cyanoacrylates polymerised by benzyldimethyl, triethyl and tribenzylamines
Authors: Johnston David Samuel , Pepper David Charles
Published: April 2003

Anionic polymerisations of ethyl and butyl cyanoacrylates (ECA and BCA) in THF, initiated by benzyldimethylamine (BDMA), triethylamine (TEA) and tribenzylamine (TBA) were studied between 50 and −78°C. Initiator utilisation was very low, and polymer molecular weights correspondingly high, though believed to be depressed by acid impurities in the monomer samples. Conversion curves reached internal 1st order kinetics, almost instantaneously when the initiator was BDMA, more slowly with TEA, and only after a long acceleration period with TBA, which gave overall rates some two orders of magnitude lower than those induced by the other amines. With BCA initiated by BDMA or TEA, the rate constants increased as reaction temperature was lowered. A general kinetic scheme is suggested, postulating no intrinsic termination reactions, and complex initiation processes, which according to the nature of amine and monomer may involve either one or two pre‐initiation equilibria.
Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 1. Kinetik, Molekulargewichtsabhängigkeit und Frage des Bruchmechanismus
Authors: Müller Hans Georg , Klein Joachim
Published: April 2003

The mechanical shear degradation of poly(decyl methacrylate) with weight average molecular weights 1,0·106 ≤ M̄w ≤ 1,7·106, and molecular polydispersity ratio M̄w/M̄n = 5 in dilute solutions is studied in turbulent flow as a function of molecular weight using a special apparatus consisting of two vessels connected by a capillary. Shear stress and shear rate remained constant during degradation. The rate of degradation was followed up by molecular weight distribution curves using gel permeation chromatography and described by −dci/dt = ki·cn, i being a high molecular weight species of the distribution. The reaction was found to be of the first order (n = 1) independent of solvent and of capillary length. Rate constants ki in the molecular weight range from 3,2·106 to 13,5·106 proved to be proportional to the hydrodynamic volume of the polymer molecules expressed in terms of the product of intrinsic viscosity and molecular weight [η]i·Mi. This corresponds to a linear relationship between ki and Mi1,75. Additional experiments show that this type of dependence on molecular weight holds only for turbulent flow; in laminar flow the result of the literature could be confirmed that there is a linear relation between ki and Mi1. Both results are independent of capillary length. As to the mechanism of breakage in turbulent flow it seems that in one step each macromolecule is broken simultaneously into several smaller parts.
Application of electrostatic persistence length to polyelectrolyte solutions
Authors: Miyamoto Shigeaki
Published: April 2003

The effects of added simple salt and polyion charge on the chain flexibility of an alternating copolymer of isobutyl vinyl ether and maleic acid are analyzed. The persistence length of this polymer in aqueous NaCl solution is calculated from sedimentation and viscosity data on the basis of a worm‐like chain model. It is found that this polymer is in the state of a highly expanded conformation at low ionic strength, exhibiting a semi‐rigid macromolecular behaviour and that it behaves like a rather coiled polymer with small persistence length at high salt concentration. The electrostatic persistence length calculated from the theory of Fixman et al. shows a \documentclass{article}\pagestyle{empty}\begin{document}$ 1/\sqrt {C_{\rm s} } $\end{document}‐dependence on added salt concentration Cs.
Surface Functionalization of Silica with 2‐Vinylfuran by Cationic Polymerization
Authors: Höhne Susanne , Spange Stefan
Published: April 2003

Cationic surface polymerization of 2‐vinylfuran with chlorotriphenylmethane as initiator has been used for the functionalization of silica particles. The influence of monomer/initiator ratio and temperature on grafting efficiency, yield, and degree of grafting has been investigated. Grafting efficiency is a significant function of temperature and monomer/initiator ratio, because crosslinking reactions between cationically active chains increases the amount of the immobilized polyvinylfuran fraction. Thus, larger initiator concentrations on the silica cause higher polymer content on the surface. Polymer structure elucidation and surface properties are analyzed by means of solid‐state NMR spectroscopy, UV‐vis spectroscopy, BET – measurements, and scanning electron microscopy.

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The Influence of the Nature of the Catalytic System on Zirconocene‐Catalyzed Polymerization of Alkyl Methacrylates
Authors: Karanikolopoulos Giorgos , Batis Christos , Pitsikalis Marinos , Hadjichristidis Nikos
Published: April 2003

Three non‐bridged dimethylzirconocene complexes; i.e., bis(η5‐cyclopentadienyl)dimethylzirconium (1), bis(η5‐tert‐butyl‐cyclopentadienyl)dimethylzirconium (2), bis(η5‐indenyl)dimethylzirconium (3), and the chiral zirconocene rac‐ethylenebis(η5‐indenyl)dimethylzirconium (4) were synthesized and used as catalysts for the polymerization of methyl methacrylate, MMA, combined with tris(pentafluorophenyl)borate (A) or tetrakis(pentafluorophenyl)borate dimethylanilinum salt (B) in the presence of ZnEt2. The evolution of the polymerization characteristics; i.e., molecular weight, molecular‐weight distribution, and yield were examined for the above systems. The influence of the nature of the solvent was also investigated. The aggregation behavior, the steric hindrance, and the lipophilicity of the active catalytic systems are the most important parameters determining the polymerization characteristics. The tacticity of the products is reported and the influence of the catalyst structure is discussed. Finally, the polymerization of other methacrylates (alkyl = butyl, hexyl, decyl, stearyl, and sec‐butyl), was conducted and the effect of the nature of the alkyl ester group on the molecular and structural characteristics was established.

Plots of yield vs Mw for the polymerization of MMA with the catalytic systems: Cp2ZrMe2/B(C6F5)3, 1/A (▵); (ButCp)2ZrMe2/B(C6F5)3, 2/A (▿); Ind2ZrMe2/B(C6F5)3, 3/A (□); and rac‐Et(Ind)2ZrMe2/B(C6F5)3, 4/A (⋄).

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Plots of yield vs Mw for the polymerization of MMA with the catalytic systems: Cp2ZrMe2/B(C6F5)3, 1/A (▵); (ButCp)2ZrMe2/B(C6F5)3, 2/A (▿); Ind2ZrMe2/B(C6F5)3, 3/A (□); and rac‐Et(Ind)2ZrMe2/B(C6F5)3, 4/A (⋄).
Synthesis, Characterization and Ionic Conductive Properties of Phosphorylated Chitosan Membranes
Authors: Wan Ying , Creber Katherine A. M. , Peppley Brant , Bui V. Tam
Published: April 2003

Phosphorylated chitosan membranes were prepared from the reaction of orthophosphoric acid and urea on the surface of chitosan membranes in N,N‐dimethylformamide. Their ionic conductivity in the wet state was investigated. Chemical modifications contributed to improved ionic conductivities of the chitosan membranes. Compared to the unmodified chitosan membranes, it was found that hydrated phosphorylated chitosan membranes with an appropriate phosphorus content showed an increasing ionic conductivity of about one order of magnitude. The phosphorylation reaction mechanism was explained based on 13C and 31P NMR measurements. It was also observed that the crystallinity of the phosphorylated chitosan membranes and the corresponding swelling indices were changed pronouncedly, but these membranes did not lose either their tensile strength or thermal stability to a significant degree in comparison with the unmodified chitosan membranes.

Possible reaction mechanism for preparation of phosphorylated chitosan membranes.

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Possible reaction mechanism for preparation of phosphorylated chitosan membranes.
Nanostructures Developed from Semi‐Interpenetrating Polymer Network Structures
Authors: Jain Sachin H. , Murata Kazutaka , Anazawa Takanori
Published: April 2003

Morphology development from a semi‐interpenetrating polymer network structure (semi‐IPN structure), induced by first‐stage photocuring and aided by annealing, is investigated in a binary blend of a photocurable polymer (2,2‐bis(4‐(acryloxydiethoxy)phenyl)propane; BPE4), and a linear polymer (polysulfone; PSU). A blend with a miscible semi‐IPN structure is produced by photocuring below the glass transition temperature (Tg) of the homogenous mixture of BPE4 and PSU, and is then annealed and post‐cured at a higher temperature. The investigation reveals that the phase structures, which can be controlled by appropriately tuning the annealing temperature, range from BPE4‐rich domain structures, through interconnected structures, to PSU‐rich domain structures. The BPE4‐rich domains are connected linearly to form an interconnected structure. The BPE4‐rich and PSU‐rich domains are restricted to the nanometre scale, with sizes of less than 100 nm over almost the entire operating range of annealing temperatures and compositions. By adjusting the degree of the crosslinking in the semi‐IPN structures, the characteristic length scale of the phase‐separated structures can be varied. The mechanical properties (tensile strength and modulus) are at a maximum in the blend with the interconnected structure, due to the high conversion of BPE4 and the strong interfacial adhesion between the two phases, supported by the stability of the morphology resulting from the annealing.

Effect of annealing temperature on conversion of BPE4 in the blend with 50 wt.‐% PSU.

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Effect of annealing temperature on conversion of BPE4 in the blend with 50 wt.‐% PSU.
A source of screw dislocation on polyethylene single crystals
Authors: Hirai Nishio
Published: April 2003

Spiral structures on lamellar single crystals of polyethylene have been ascribed to screw dislocation. Several photographs are shown which seems to verify the possibility of origination of the screw dislocations due to the collision of two growing single crystals. This mechanism accounts for the following facts often found in these spiral structures. (1) Spiral structures often grow from the intersection of two single crystals. (2) The distances from the center of spirals to the nearest edges of the two crystals are approximately equal to each other. (3) Centers of the spirals are often located on the diagonal of the bottom single crystal on which they grew. (4) Daughter crystals formed on a contour line farther from the center of the mother crystal are smaller.
Environmental and socioeconomic multivariate analysis of the primary economic sector of Mexico
Authors: Beltrán Morales L. F. , García‐Rodríguez F. , Borges Contreras J. , Sánchez‐Mota G. , Ortega Rubio A.
Published: April 2003

Canonical correspondence analyses were made for the primary economic sector of all 32 Mexican states. Environmental, social and economic indicators were considered in the analyses. Four homogeneous units, fisheries, forestry, agriculture and anthropogenic aptitude, were identified. Coastal states showed a higher contribution to the gross national product (GNP) than noncoastal states. Jalisco had the highest contribution to the GNP. Our analysis represents a useful tool to describe and arrange homogeneous state groups inside the country. This ordering will be useful to develop national strategies, both socioeconomic and environmental. We hope this kind of analysis will be useful for the decision makers not only in Mexico, but also in other countries that use this innovative approach. Copyright © 2003 John Wiley & Sons, Ltd. and ERP Environment
NMR and circular dichroism studies of synthetic peptides derived from the third intracellular loop of the β‐adrenoceptor
Authors: Jung Hans , Windhaber Ralf , Palm Dieter , Schnackerz Klaus D.
Published: April 2003

The C‐terminal part of the third intracellular loop of the β‐adrenoceptor is capable of stimulating adenylate cyclase in the presence of phospholipid vesicles via the stimulatory guanine nucleotide binding protein (Gs) [Palm et al. (1989) FEBS Lett. 254, 89–93]. We have investigated the structure of synthetic peptides corresponding to residues 284–295 of the turkey erythrocyte adrenoceptor in micelles, trifluoroethanol and aqueous solution, by using 2D 1H NMR and CD. In the presence of phospholipid micelles the peptides display a C‐terminal α‐helical region, whereas the N‐terminal part was found to be highly flexible.
Inhibition of 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine metabolic activity of porcine FAD‐containing monooxygenase by selective monoamine oxidase‐B inhibitors
Authors: Wu Ru-Feng , Ichikawa Yoshiyuki
Published: April 2003

The MPTP metabolic activity of porcine FAD‐containing monooxygenase (FMO) (EC 1.14.13.8) was inhibited considerably by deprenyl and pargyline, selective MAO‐B inhibitors, and they showed typical competitive inhibition. Deprenyl and pargyline, amine derivatives were also examined as to whether they are substrates for the FMO. It was found that deprenyl and pargyline are excellent substrates for the FMO. The K

i
and K

m
values of deprenyl and pargyline for the FMO are 14 μM and 9 μM, and 14.3 μM and 11.6 μM, at pH 8.0 and 25°C, respectively.
ATP synthase: activating versus catalytic proton transfer
Authors: Groth Georg , Junge Wolfgang
Published: April 2003

ATP synthase (F‐ATPase) of chloroplasts, CF0CF1, is both activated and driven by transmembrane protonmotive force. We dichotomized between activating and driving proton transfer by specific inhibitors, tentoxin and venturicidin. Thylakoids membranes were submitted to voltage steps (by flashing light) superimposed to a steady pH‐difference. Transient proton intake, transfer and release by CF0CF1 was monitored by spectroscopic probes. Both activities, activation and catalysis, required all three partial reactions of the proton, however, activating proton transfer rose first (monophasically, ) followed by another phase of equal magnitude with a time lag of about 15 ms. Both types of consecutive proton transfer reactions contribute free energy for ATP synthesis.
Myogenin binds to and represses c‐fos promoter
Authors: Trouche Didier , Masutani Hiroshi , Groisman Regina , Robin Philippe , Lenormand Jean-Luc , Harel-Bellan Annick
Published: April 2003

Myogenin (a member of the myogenic basic helixloop‐helix transcription factor family) seems to be the main effector of proliferation repression, a crucial step which precedes muscle cell terminal differentiation during muscle development. Proliferation repression most likely occurs through inhibition of proliferation‐associated genes such as the proto‐oncogene, c‐fos. Here, we demonstrate that myogenin binds to an E‐box located in the main element of the c‐fos promoter, the serum response element (SRE). Results from co‐transfection experiments indicate that myogenin acts as a repressor for the SRE. Our data suggest that myogenin could play a role in c‐fos inhibition at the onset of muscle cell terminal differentiation.
Thermodynamic and functional characterization of a stable IgG conformer obtained by renaturation from a partially structured low pH‐induced state
Authors: Martsev Sergey P. , Kravchuk Zinaida I. , Vlasov Alexander P. , Lyakhnovich Georgy V.
Published: April 2003

At pH 2, rabbit IgG adopts a partially structured state that exhibits loss of thermal unfolding transition, tentatively assigned to the CH2 domain, whilst retaining a well‐defined tertiary structure for the rest of the molecule and extensive secondary structure. Renaturation of IgG from this state yields a stable conformer that differs from native IgG by a lower degree of interaction between the CH2 and CH3 domains, and stronger interaction between the CH1 and CH2 domains, as judged by differential scanning calorimetry and probing the IgG conformation with specific ligands (C1q component of complement, protein A and monospecific antibodies to the CH2 domain and hinge region).
Uptake of iron by symbiosomes and bacteroids from soybean nodules
Authors: Moreau Sophie , Meyer Jean-Marie , Puppo Alain
Published: April 2003

Symbiosomes and bacteroids isolated from soybean nodules are able to take up the iron‐citrate complex. The kinetics are characterized by initial high rates of iron internalization, and ATPase inhibitors significantly lower the uptake. This is consistent with an energy‐dependent process on both membranes, although the involvement of a simultaneous facilitated diffusion can not be completely ruled out. Citrate alone is poorly absorbed by symbiosomes; this uptake is greatly enhanced by addition of iron. Iron‐citrate was found both in the nodule cytosol and in the bacteroids. These results provide the first experimental evidence for the existence, at least in young nodules, of an important iron trafficking system from the plant host cell to the microsymbiont, through the peribacteroid membrane.
Phase separation in cytoplasm, due to macromolecular crowding, is the basis for microcompartmentation
Authors: Walter Harry , Brooks Donald E.
Published: April 2003

The macromolecular diversity and concentrations in the fluid phase of cytoplasm constitute conditions necessary and sufficient for aqueous phase separation. Consequences of phase separation in cytoplasm, including its ‘compartmentation’, are inferred from analogies with the physicochemical properties of aqueous two‐phase systems and with the partitioning behavior of biomaterials in them.
Detection and investigation of the molecular nature of low‐molecular‐mass copper ions in isolated rheumatoid knee‐joint synovial fluid
Authors: Naughton Declan P. , Knappitt Jacky , Fairburn Kevin , Gaffney Karl , Blake David R. , Grootveld Martin
Published: April 2003

Low‐molecular‐mass copper(II) species have been detected and quantified in ultrafiltrates (n = 7) of rheumatoid synovial fluid (SF) by a highly‐sensitive HPLC‐based assay system with the ability to determine Cu(II) concentrations of < 10−7 mol·dm
t‐3. High field1H NMR spectroscopy demonstrated that addition of Cu(II)(aq.) to isolated samples of RA SF ultrafiltrates resulted in complexation by histidine > alanine > formate > threonine > lactate > tyrosine > phenylalanine, their effectiveness in this context being in the given order. CD spectra of Cu(II)‐treated samples of intact SF exhibited absorption bands typical of copper(II)‐albumin complexes, in addition to a band attributable to a low‐molecular‐mass histidinate complex (λ
min 610 nm). Since both albumin and histidine are potent radical scavengers, these results indicate that any .OH radical generated from bound copper ions will be ‘site‐specifically’ scavenged. Hence, low‐molecular‐mass copper complexes with the ability to promote the generation of .OH radical which can then escape from the metal ion co‐ordination sphere (and in turn, cause damage to critical biomolecules) appear to be absent from inflammatory SF.
DNA binds neutrophil elastase and mucus proteinase inhibitor and impairs their functional activity
Authors: Belorgey Didier , Bieth Joseph G.
Published: April 2003

DNA binds neutrophil elastase and mucus proteinase inhibitor as evidenced by affinity chromatography on elastase‐Sepharose, inhibitor‐Sepharose and DNA‐cellulose. DNA is a potent hyperbolic inhibitor of elastase. The polynucleotide‐enzyme complex is partially active on synthetic substrates and on elastin. DNA strongly increases k
diss and K
i for the inhibition of elastase by mucus proteinase inhibitor. The above effects are all salt‐dependent. At physiological ionic strength, DNA is a potent inhibitor of the elastolytic activity of elastase and increases k
diss and K
i for the elastase‐mucus proteinase inhibitor interaction 160‐fold and 100‐fold, respectively.
Nitric oxide donor compounds inhibit the toxicity of oxidized low‐density lipoprotein to endothelial cells
Authors: Struck Andrew T. , Hogg Neil , Thomas James P. , Kalyanaraman B.
Published: April 2003

Photo‐oxidized low‐density lipoprotein is cytotoxic to bovine aortic endothelial cells in a concentration‐dependent manner. Total cell killing occurs at a concentration of 600 μmol/l lipid hydroperoxide (LOOH). Selenium deficiency enhances the toxicity of LOOH such that 300 μmol/l LOOH is cytotoxic. This toxicity is inhibited by desferrioxamine, a transition metal ion chelator, and by butylatedhydroxytoluene, a potent inhibitor of lipid peroxidation. Toxicity is also inhibited by the nitric oxide donors S‐nitrosoglutathione and spermine NONOate but not by reduced or oxidized glutathione and spermine. We propose that nitric oxide, released from these compounds, is inhibiting the toxicity of LOOH to selenium‐deficient endothelial cells. Furthermore we hypothesize that the mechanism for this inhibition of toxicity is the scavenging of the propagatory peroxyl and alkoxyl free radicals, by nitric oxide, that are generated during peroxidation of cell membranes.
Novel modification of ceramide: rat glioma ganglioside GM3 having 3‐O‐acetylated sphingenine
Authors: Suetake Keiji , Tsuchihashi Keiko , Inaba Kotomi , Chiba Masahiko , Ibayashi Yukihiro , Hashi Kazuo , Gasa Shinsei
Published: April 2003

A novel O‐acetylated GM3 containing 3‐O‐acetyl 4‐sphingenine was isolated with one having a non‐acetylated base from transplanted rat glioma tissue. The presence and position of the acetyl group were estimated by one‐ and two‐dimensional proton nuclear magnetic resonance, and fast atom bombardmentmass spectrometries. In addition, the O‐acetyl showed higher immunological activity toward anti‐melanoma antibody in the presence of non‐acetylated GM3 in complement‐dependent liposome lysis than did non‐acetylated or acetylated GM3 alone in the liposome, suggesting enhancement of immunological reactivity of the intact tumor cells by a small amount of O‐acetyl GM3.
Stopped‐flow kinetic studies of the reaction of barley α‐amylase/subtilisin inhibitor and the high pI barley α‐amylase
Authors: Sidenius Ulrik , Olsen Karsten , Svensson Birte , Christensen Ulla
Published: April 2003

The resulting values of the kinetic parameters were: k
2/K
1 = (1.0 ± 0.2) × 106 M−1·s−1, K
1 = 0.4 ± 0.21 mM, k
2 = 320 ± 150 s−1, k
−2 = (7.2 ± 0.6) × 10−5s−1, and the overall dissociation constant K
d = (0.7 ± 0.1) × 10−10 M. BASI thus is best characterized as a fast reacting, tight‐binding inhibitor of AMY2.
Temperature‐dependent change in the rate‐determining step in a reaction catalyzed by a hammerhead ribozyme
Authors: Takagi Yasuomi , Taira Kazunari
Published: April 2003

To characterize the reaction catalyzed by a hammerhead ribozyme, the dependence on temperature of the reaction was examined. An Arrhenius plot revealed a transition that indicated a temperature‐dependent change in the activation energy at around 25°C. Thermodynamic parameters of the reaction were estimated at 10 and 35°C. The analyses led to the following conclusions. At 25–50°C. the chemical cleavage step (k
cleav was the rate‐determining step, and the cleaved fragments dissociated from the ribozyme at a higher rate than the rate of the chemical reaction. When the temperature was below 25°C, the cleaved fragments adhered to the ribozyme more tightly and the product dissociation step became the rate‐determining step. Above 50°C, the rate of the reaction decreased because, at such high temperatures, the formation of the Michaelis‐Menten complex (duplex formation) was hampered by thermal melting. A conformational change in the ribozyme‐substrate complex was not the rate‐determining step at any of the temperatures examined.
Direct evidence of involvement of glycosylphosphatidylinositol‐anchored proteins in the heavy metal‐mediated signal delivery into T lymphocytes
Authors: Pu Meiyi , Ma Li , Ohkusu Kozo , Isobe Ken-Ichi , Taguchi Ryo , Ikezawa Hiroh , Hamaguchi Michinari , Nakashima Izumi
Published: April 2003

The biological significance of the action of glycosylphosphatidylinositol (GPI)‐anchored proteins in cell physiology and pathology when stimulated with their natural agonists is not known. Here we provide evidence that GPI‐anchored proteins play a crucial role in the recently defined heavy metal (HgCl2)‐triggered signal delivery to T lymphocytes. Thiol‐reactive HgCl2, a multi‐potent crosslinker of cell membrane proteins, induced heavy aggregation of Thy‐1, a representative GPI‐anchored protein, on murine thymocytes, and delivered a signal to induce heavy tyrosine phosphorylation of cellular proteins. This rather unusual signal delivery by HgCl2 is diminished by the pre‐treatment of cells with phosphatidylinositol‐specific phospholipase C, which partially cleaved GPI‐anchored proteins from the cell surface. Direct evidence for the involvement of GPI or GPI‐anchored proteins in the HgCl2‐mediated signaling is provided by the loss of signaling in a mutant thymoma cell line defective in the phosphatidylinositol glycan‐class A gene (PIG‐A), and its restoration in a transfectant with PIG‐A.
Presence of a novel form of phosphatidylinositol 4‐kinase in rat liver
Authors: Olsson Henric , Martínez-Arias Wilma , Drøbak Bjørn K. , Jergil Bengt
Published: April 2003

Rat liver microsomes contain two distinct forms of PtdIns 4‐kinase which were resolved by heparin‐Sepharose chromatography. One enzyme was identified as the type II PtdIns kinase previously isolated from exocytotic vesicles. The other enzyme, however, was a novel PtdIns 4‐kinase isoform with properties differing from any other PtdIns kinase so far characterized. Both kinases were recognized by a monoclonal antibody specific for type II PtdIns 4‐kinase, but the novel enzyme was considerably less sensitive to inhibition by adenosine and Ca2+ than type II enzymes, and in addition was specifically inhibited by submillimolar concentrations of dithioerythritol. The presence of a novel PtdIns 4‐kinase isoform in rat liver raises the question of whether this enzyme is unique for this organ or whether it has a more widespread distribution but so far has avoided detection.
Structure‐function studies on the biosynthesis and bioactivity of the precursor convertase PC2 and the formation of the PC2/7B2 complex
Authors: Benjannet S. , Lusson J. , Hamelin J. , Savaria D. , Chrétien M. , Seidah N.G.
Published: April 2003

Site directed mutagenesis of the prohormone convertase PC2 was used to define the effect of certain residues on the zymogen activation of proPC2 and on its binding to the neuroendocrine protein 7B2. These included the oxyanion hole Asp309 (D309N), the N‐terminal Glu25 (E25Q and E25K) of proPC2 and the Asp519 (D519E) of the RGD motif within the P‐domain of PC2. Heterologous vaccinia virus expression of the wild type and mutant PC2's in endocrine pituitary cells such as AtT20 and GH3 cells demonstrated that the most dramatic effect was observed with the D309N mutant which no longer bound pro7B2 and which exhibited a significant reduction in its capacity to produce β‐endorphin from pro‐opiomelanocortin (POMC).
Sequence specificity for removal of uracil from U·A pairs and U·G mismatches by uracil‐DNA glycosylase from Escherichia coli, and correlation with mutational hotspots
Authors: Nilsen Hilde , Yazdankhah Siamal Pour , Eftedal Ingrid , Krokan Hans E.
Published: April 2003

The rate of removal of uracil from different positions in double‐stranded DNA by uracil‐DNA glycosylase from Escherichia coli varied more than 15‐fold. Consensus sequences for good and poor removal were 5′‐(A/T)UA(A/T)‐3′ and 5′‐(G/C)U(T/G/C)‐3′, respectively. In general, the sequence context surrounding U was more important for the rate of removal than whether U was present in U·A pairs or U·G mispairs. Rates of removal of U from sites of amber mutations in the lacI gene, where mutation frequencies and deamination rates were known, indicated that the observed variation in removal is biologically significant.
Nerve growth factor stimulates tyrosine phosphorylation of paxillin in PC12h cells
Authors: Khan Muhammad Ashraf , Okumura Nobuaki , Okada Masato , Kobayashi Shin , Nakagawa Hachiro
Published: April 2003

Nerve growth factor (NGF) induces tyrosine phosphorylation of various cellular proteins to activate multiple signal transduction pathways. We show that one of these proteins is paxillin, a cytoskeletal component associated with adhesion plaques. Phospho‐amino acid analysis showed that NGF stimulated phosphorylation of its serine in addition to tyrosine residues. Tyrosine phosphorylation of paxillin by NGF was blocked by the pretreatment of the cells with cytochalasin D, an inhibitor of actin polymerization. These results suggest that phosphorylation of paxillin is involved in the signaling pathway of NGF in PC12 cells.
Stimulation of cell proliferation and autoregulation of elastin expression by elastin peptide VPGVG in cultured chick vascular smooth muscle cells
Authors: Wachi Hiroshi , Seyama Yoshiyuki , Yamashita Sabrou , Suganami Hideki , Uemura Yuko , Okamoto Kouji , Yamada Haruyoshi , Tajima Shingo
Published: April 2003

Synthetic elastin peptides, VPGVG or its polymer (VPGVG)
n
, enhanced the proliferation of smooth muscle cells 1.5‐fold during 48 h treatment at the concetrations over 10−6 M or 1.0 μg/ml, respectively. Monomeric and polymeric VPGVG sequences reduced elastin synthesis and its mRNA level to one‐third and one‐half of control respectively under the conditions in which the proliferation of cells were enhanced, but did not change collagen synthesis as measured by bacterial collagenase digestion. The elastin‐specific autoregulation by elastin fragments may reflect the feedback regulation of elastin expression which may play an essential role in elastin metabolism under the normal and diseased conditions.
In vitro dissociation and re‐assembly of peroxisomal alcohol oxidases of Hansenula polymorpha and Pichia pastoris
Authors: Evers Melchior E. , Harder Wim , Veenhuis Marten
Published: April 2003

We have studied the in vitro inactivation/dissociation and subsequent reactivation/re‐assembly of peroxisomal alcohol oxidases (AO) from the yeasts Hansenula polymorpha and Pichia pastoris. Both proteins are homo‐oligomers consisting of eight identical subunits, each containing one FAD as the prosthetic group. They were both rapidly inactivated upon incubation in 80% glycerol, due to their dissociation into the constituting subunits, which however still contained FAD. Dilution of dissociated AO in neutral buffer lead to reactivation of the protein due to AO re‐assembly, as was demonstrated by non‐denaturing PAGE. After use of mixtures of purified AO from H. polymorpha and P. pastoris active hybrid AO oligomers were formed. When prior to dissociation FAD was chemically removed from AO, reactivation or re‐assembly did not occur independent of externally added FAD.
The γ subunit in the Escherichia coli ATP synthase complex (ECF1F0) extends through the stalk and contacts the c subunits of the F0 part
Authors: Watts Spencer D. , Zhang Ying , Fillingame Robert H. , Capaldi Roderick A.
Published: April 2003

A mutant, in which a cysteine has been site‐directed into the polar loop region of the c subunit at residue 44, has been studied. Cross‐linking of the c subunit to both the γ and ϵ subunits was observed with cupric 1,10‐phenanthrolinate treatment. The linkage between the c and γ subunits was localized to that part of the γ subunit between residues 202–286, based on peptide analysis. Reference to the high resolution structure of F1 [Abrahams et al. (1994) Nature 370, 621–628] appears to limit this contact site to the region including residues 202–230. This segment contains 4 tyrosines and 1 tryptophan as possible reactive residues for cross‐linking with the c subunit cysteine.
Adenophostin‐medicated quantal Ca2+ release in the purified and reconstituted inositol 1,4,5‐trisphosphate receptor type 1
Authors: Hirota Junji , Michikawa Takayuki , Miyawaki Atsushi , Takahashi Masaaki , Tanzawa Kazuhiko , Okura Ichiro , Furuichi Teiichi , Mikoshiba Katsuhiko
Published: April 2003

Kinetics of Ca2+ release by adenophostin, a novel agonist of inositol 1,4,5‐trisphosphate (IP3) receptor, in the purified and reconstituted IP3 receptor type 1 (IP3R1) was investigated using the fluorescent Ca2+ indicator fluo‐3. Submaximal concentrations of adenophostin caused quantal Ca2+ release from the purified IP3R1 as IP3 did. Adenophostin‐induced Ca2+ release by the purified IP3R1 exhibited a high positive cooperativity (nH = 3.9 ± 0.2, EC50 = 11 nM), whereas the IP3‐induced Ca2+ release exhibited a moderate one (nH = 1.8 ± 0.1, EC50 = 100 nM). Inhibition of [3H]IP3 binding to the purified IP3R1 by adenophostin exhibited a positive cooperativity (nH = 1.9, K
i = 10 nM), whereas IP3 did not (nH = 1.1, K
i = 41 nM).
Effects of delta‐sleep inducing peptide (DSIP) and some analogues on the activity of monoamine oxidase type A in rat brain under hypoxia stress
Authors: Khvatova Elena M. , Rubanova Natalia A. , Prudchenko Igor A. , Mikhaleva Inessa I.
Published: April 2003

Metabolic effects of delta‐sleep inducing peptide (DSIP) under hypoxia stress were investigated in rats subjected to short‐term hypoxic conditions (about 0.26 Bar). It was found that DSIP partially restricted stress‐induced changes in activity of mitochondrial monoamine oxidase type A (MAO‐A) and serotonin level in rat brain. A number of DSIP analogues was tested and among them there were some compounds with enhanced ability to counteract hypoxia induced changes in MAO‐A activity and serotonin content in comparison with native neuropeptide.
The principal neutralizing determinant of HIV‐1 located in V3 of gp120 forms a 12‐residue loop by internal hydrophobic interactions
Authors: Zvi Anat , Kustanovich Irina , Hayek Yehezkiel , Matsushita Shuzo , Anglister Jacob
Published: April 2003

The interactions of the peptide RP135a (RKSIRIQRGPGRAFVT), corresponding to residues 311–326 of gp120 of HIV‐1IIIB, with the anti‐gp120 HIV‐1IIIB neutralizing antibody 0.5β were studied by NMR. The NOESY difference spectra measured using specifically deuterated derivatives of the peptide show exclusively the interactions of the deuterated residues both within the bound peptide and with the Fab fragment of the antibody. These measurements reveal hydrophobic interactions within the bound peptide between Ile‐4, Ile‐6 and Val‐15 that create a 12‐residue loop with these residues at the base and the conserved GPGR sequence at its top.
Diffuse vesicular distribution of Rab3D in the polarized neuroendocrine cell line AtT‐20
Authors: Martelli Alberto M. , Bareggi Renato , Baldimi Giovanna , Scherer Philipp E. , Lodish Harvey F. , Baldini Giulia
Published: April 2003

The neuroendocrine cell line AtT‐20 has two types of storage vesicles: dense core granules and synaptic vesicles, both sequestered at the tip of the processes. Here we show that Rab3D protein, which is abundant in fat cells, is also expressed in AtT‐20 cells. Differently from Rab3A, which is localized in secretory vesicles accumulated at the tips, Rab3D has a diffuse vesicular distribution in the cytoplasm of the cell body, the processes and the tips. In AtT‐20 cells, Rab3D may define a regulated secretory pathway which functions independently from cell polarity.
Promoter‐specific regulation of gene expression by an exogenously added homeodomain that promotes neurite growth
Authors: Le Roux Isabelle , Duharcourt Sandra , Volovitch Michel , Prochiantz Alain , Ronchi Elettra
Published: April 2003

pAntp, a 60 amino acid long peptide corresponding to the homeodomain of the Drosophila Antennapedia protein, translocates through neuronal membranes when added exogenously to neurons in culture, where it accumulates in the nucleus and promotes neurite outgrowth. We proposed that the peptide, once internalized, may compete for homeoprotein DNA binding sites. To investigate this point, we have produced a permanent fibroblast cell line which carries a luciferase reporter gene under the control of a 93 bp genomic region of the HOXD9 promoter with binding sites for homeoproteins. Externally added pAntp specifically down‐regulates the expression of the reporter gene, suggesting that the neurotrophic effects observed previously are mediated by direct binding of pAntp to homeoprotein target sites.