bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and characterization of poly(acrylamide‐co‐acrylic acid)
Authors: Klein Joachim , Heitzmann Rudolf
Published: April 2003

A series of samples of the acrylamide/acrylic acid system with various compositions was prepared by copolymerization as well as saponification, and some new results on the kinetics of both processes are given. The products were characterized by osmometry, viscometry, GPC, DTA, and elemental analysis. The results led to the conclusion that copolymerisation and saponification lead to copolymers of identical sequential distribution of the monomeric units. It was found that the intrinsic viscosity as well as the slope factor kH · [η]2 —measured in 0,5 m NaBr solution—show a maximum at intermediate comonomer composition. This finding can be interpreted by chain stiffening due to intramolecular segmental interaction.
Enzyme‐analogue built polymers, 6. Synthesis of 5‐vinylsalicylaldehyde and a simplified synthesis of some divinyl derivatives
Authors: Wulff Günter , Akelah Ahmed
Published: April 2003

5‐Vinylsalicylaldehyde, o‐, m‐, p‐divinylbenzenes, and 1,5‐divinylnaphthalene were prepared in high yields by using the Wittig reaction of the corresponding phosphoranes with aqueous formaldehyde.
Interferenzmikroskopische charakterisierung von faserstrukturen, 3. Die änderung des radialen verlaufes der physikalischen struktur von polyethylenterephthalat‐fasern beim färben mit dispersionsfarbstoffen
Authors: Kühnle Gerhard , Schollmeyer Eckhard , Herlinger Heinz
Published: April 2003

The change of the radial structure during the diffusion of dyestuffs in fibers of poly(ethylene terephthalate), [poly(oxyethyleneoxyterephthaloyl)], is studied with regard to the relationship between the dyestuff diffusion and the structure of high polymers. The fiber structure is described by interferometric measurements, which allow statements about order and orientation as a function of the diffusion path. The experimental results show that C. I. Disperse Red 60 raises the parameters which describe the order and orientation and that C. I. Disperse Blue 139 lowers these structure parameters.
Application of spin trapping technique to radical polymerization, 17.N‐hydroxysuccinimide as a radical initiator
Authors: Sato Tsuneyuki , Metsugi Makoto , Otsu Takayuki
Published: April 2003

N‐hydroxysuccinimide (NHS) and N‐hydroxyphthalimide were found to initiate effectively vinyl polymerizations of acrylate monomers. The polymerization of methyl methacrylate (MMA) with NHS was investigated in detail. The polymerization rate (Rp) was found to depend highly on the solvents. The over‐all activation energy of the polymerization in ethyl acetate was calculated to be 76,2 kJ/mol (18,2 kcal/mol). In the low monomer concentration, Rp can be expressed as Rp = k [NHS]1/2 [MMA]3/2. The copolymerization of MMA with styrene, initiated by NHS, could be shown to proceed via radical mechanism. In order to elucidate the initiation mechanism, spin trapping technique was applied to this polymerization system. In the reaction of MMA with NHS in acetone, the 2‐carbomethoxypropyl radical was trapped by 2‐methyl‐2‐nitrosopropane, a spin trapping reagent, to give the corresponding aminyl oxide radical 2. From the results, the initiation mechanism of this polymerization is proposed and discussed.
Enthalpy of polymerisation of 2‐oxabicyclo[2.2.2]octan‐3‐one
Authors: Andruzzi Fulvio , Pilcher Geoffrey , Hacking John M. , Cavell Sue
Published: April 2003

The enthalpies of combustion of crystalline 2‐oxabicyclo[2.2.2]octan‐3‐one (1), and five different crystalline poly(oxycarbonyl‐1,4‐cyclohexylene) samples formed from 1 were measured at 298, 15 K by high‐precision bomb calorimetry. For 1, the enthalpies of combustion and of formation were, −ΔH(c) = 3717,5 ± 1,3 kJ·mol−1 and −ΔH(c) = − 466,2 ± 1,6 kJ·mol−1. After correction for the presence of n‐butyl‐ or tert‐butoxy‐end groups in the polyester samples, a consistent enthalpy of polymerisation of 1 was obtained, ΔH(c → c) = − 20,9 ± 2,3 kJ·mol−1. The enthalpy of sublimation of 1 was measured, ΔH (1) = 69,6 ± 2,1 kJ·mol−1; the value for the polyester unit was derived as 49 kJ·mol−1.
Not all polyanions induce a J‐band in the dye pseudoisocyanine
Authors: Pal M. K. , Ghosh Bijan Kumar
Published: April 2003

N,N′‐diethylpseudoisocyanine chloride (PIC) forms compounds with various vinyl poly+ and DNA, but the shapes of the spectra of the dye‐polyanion compounds depend on the nature of the polyanions. PIC forms compounds with 1:1 polyanion/dye stoichiometries with DNA (native and denatured), polymethacrylate and poly(styrenesulfonate); and the spectra of these compounds do not show any pronounced metachromasia or red‐shifted J‐band. Polyacrylate and poly(vinyl sulfate) form compounds with polyanion/dye stoichiometry of 2:1, and give spectra with extremely sharp and red‐shifted J‐band. This is the first report on the relation between the polyanion/PIC stoichiometry and the depiction of the J‐band of the resulting compound.
Mechanical behaviour of aortic tissue as a function of collagen orientation
Authors: Roveri Norberto , Ripamonti Alberto , Pulga Carla , Jeronimidis Giorgio , Purslow Peter P. , Volpin Dino , Gotte Lorenzo
Published: April 2003

X‐ray diffraction techniques have been used to investigate the orientation under stress of collagen fibres in pig's descending aortic wall. The variation of the limit value of the incremental modulus as a function of the collagen content seems to suggest that the extra amount of collagen going from the aortic arch downwards is deposited in a preferred orientation corresponding to the circumferential direction. The results have been used to describe the uniaxial mechanical behaviour of this tissue taking into account its composite structure.
Phenolic resins for peptide synthesis, 2. Reactivities of phenolic and amino functional groups in styrene based resins
Authors: Arshady R. , Ledwith A. , Kenner G. W.
Published: April 2003

Copolymerisation of styrene, p‐acetoxystyrene, and divinylbenzene is a convenient way of obtaining resins for application in solid phase peptide synthesis. Phenolic group attachment sites are readily obtained by hydrolysis under mild conditions of the acetoxyl resin. In order to investigate possible effects of lyophilic (e.g. amino acid) units attached to the resin on subsequent reactivity in peptide synthesis, the coupling efficiencies of initially prepared phenolic resins and equivalent resins already functionalised with the tripeptide, H‐Leu‐Ala‐Gly, have been compared in reactions with Boc‐Gly‐ONSu and Boc‐Ile‐OTcp. The two resin types afford phenolic and primary amino‐functionalities respectively and exhibit marked solvent effects on reactivities, although swelling characteristics are rather similar. It is concluded that solvent effects on the particular coupling reactions are more important than solvent effects on swelling of the resins.
Caractérisation texturale de résines en milieu réactionnel
Authors: Brun Maurice , Quinson Jean‐François , Blanc Raymond , Negre Michèle , Spitz Roger , Bartholin Michel
Published: April 2003

Thermoporometry, a method based on the microcalorimetric analysis of liquid‐solid state transformation inside porous substances, gives access to porous volume versus pore size distribution. For the first time, this method is applied to the analysis of flexible products swellable in the reference medium. Conditions for applying transposition thermoporometry to this new class of porous substances are discussed. An example is given, which leads to suggest a model for the swelling process of a macroporous resin. Generalization of this method would induce a major progress in the study of swollen systems and enable better understanding of their structures.
Long‐term change in conformation of macromolecules in solution, 2. Poly(acrylamide‐co‐sodium acrylate)s
Authors: Kulicke Werner‐Michael , Kniewske Reinhard
Published: April 2003

The solution viscosity of aqueous poly(acrylamide‐co‐sodiumacrylate)s decreases with time in the scale of weeks. This unusual viscosity loss has been investigated by viscometry and by light scattering on high purity copolymer samples with different ratios of the components. — No viscosity loss can be observed in NaCl solution of high enough salt concentration. From the experiments it is concluded that a conformational change causes the viscosity decrease. No chain scission occurs. Light scattering measurements were used to directly confirm this hypothesis. — The viscosity loss may be caused by a conformational change of single molecules involving hydrogen bonds and can be interpreted as a transition from a partly stiffer, higher viscous structure to a more flexible one. As the driving force for the conformational change the entropy is discussed. The pronounced time dependence may be interpreted by a cooperative effect of loosening and combining of hydrogen bonds. — A similar behaviour has been observed earlier in aqueous poly(acrylamide) solutions. Thus, for some water soluble polymers one has to be aware of a time dependent parameter.
Syntheses of thermotropic liquid crystalline polymers, 2. polyurethanes
Authors: Iimura Kazuyoshi , Koide Naoyuki , Tanabe Hideo , Takeda Masatami
Published: April 2003

Polyurethanes were synthesized by reaction of a rigid molecule, 3,3′‐dimethyl‐4,4′‐biphenyldiyl diisocyanate (DBD), with flexible molecules, oligoethylene glycols (di‐, tri‐, and tetraethylene glycol) or α,ω‐alkanediols, and some of their thermal properties were studied. Poly(DBD‐oligoethylene glycol)s are amorphous polymers which exhibit no mesomorphic phase. Poly(DBD‐alkanediol)s are found to show a mesomorphic phase depending on the number of methylene units in the alkanediol. The polymers having methylene units from five to twelve are crystalline and show a mesomorphic phase. On the contrary, polymers having less than four methylene units do not show a mesomorphic phase since thermal decomposition of the polymers occurs before melting. The transition temperature from the mesomorphic phase to the isotropic liquid decreases with increasing length of the flexible chain of alkanediol. Ternary polymers are obtained by reaction of DBD with a mixture of hexanediol (HD) and dodecanediol (DD). The ternary polymers containing a small amount of HD and DD give a clear mesomorphic phase.
Adiabatic polymerization of ε‐caprolactam in presence of lithium chloride, 2. Properties of the resultant polymer
Authors: Alfonso Giovanni Carlo , Pedemonte Enrico , Russo Saverio , Turturro Antonio
Published: April 2003

Physical and mechanical properties of poly(ε‐caprolactam) synthesized in presence of various amounts of lithium chloride are measured on compression moulded films and correlated to the molecular organization, both in the amorphous and in the crystalline regions. By increasing the amount of LiCl present in the system it can be observed a heigtening of Tg and density of the amorphous phase as well as an increase of tensile modulus and yield strength. A transition from ductile to brittle failure occurs for both semicrystalline and amorphous samples in dry conditions, when the salt content in the amorphous phase is about 6 wt.‐%. These phenomena and the capability of the salt to reduce the crystallinity of the polymer are interpreted in the frame of the already accepted model of ion‐dipole interactions between lithium ion and the carbonyl groups of the polyamide. Effects due to moisture uptake are also discussed.
The rôle of water in the metachromatic reaction
Authors: Lawton John B. , Phillips Glyn O.
Published: April 2003

The effect of water on the metachromatic complexes of methylene blue and cellulosic polyanions has been studied by diffuse reflectance spectroscopy. Complete dehydration causes the complexes to become orthochromatic and rehumidification reverses the change. These effects are explained in terms of site‐binding. It is postulated that the dye cations are bound more tightly in the anhydrous state and this modifies the dye‐dye interactions that are the cause of the metachromatic colour change. Anionic celluloses produced hypsochromic shifts in the absorption spectrum of the dye in the order: sulfate > phosphate > carboxyl > carboxymethyl. This is the reverse of the order of electrostatic attractions between the sites and the dye cations. Such attractions are shown to modify dye‐dye interactions, with the result that for a given spacing of negative sites, the polycarboxylates initiate least metachromatic colour change.
Liquid crystalline polymers, 8. Structurally ordered thermotropic polyesters of glycol ethers
Authors: Galli Giancarlo , Chiellini Emo , Ober Christopher K. , Lenz Robert W.
Published: April 2003

A series of polysters based on a triad aromatic ester mesogenic unit but containing different poly(alkylene oxide) flexible spacers in the main chain was prepared and its properties examined. The flexible spacers consisted of poly(alkylene oxide)s of varying lengths based on either oligomers of ethylene oxide or propylene oxide. The spacer types, lengths and distributions were found to strongly affect the mesophase and melting behaviors of the polymers. Polymers with spacers having more than 10 units were not liquid crystalline, whereas those of shorter length exhibited mesophase properties. The polymers containing spacers with two, three, or four oxyethylene units showed two mesophases, and the textures of their mesophases suggested that both smectic and nematic phases were formed.
A kinetic study of the thermal degradation of cellulose and its derivatives
Authors: Jain Rajesh K. , Lal Krishan , Bhatnagar Hari L.
Published: April 2003

The kinetics of the pyrolysis of cellulose and its derivatives (2,2‐dichloropropionate and acetate) in nitrogen and air were studied by dynamic thermogravimetry and differential thermal analysis from ambient temperature to 600°C. From the resulting data various thermodynamic parameters could be obtained following the methods of Freeman and Carroll, Broido, and Dave and Chopra. The values of ΔE* for cellulose and its derivatives were found to be in the range 120 to 260 kJ · mol−1. However, the values of the free energy of activation for the degradation of cellulose and its derivatives are almost the same, i. e. 187 to 199 kJ · mol−1, indicating that the basic steps for the thermal degradation of cellulose and its derivatives are the same. Based on Scotney's work on the thermal degradation of cellulose triacetate, a mechanism for the thermal degradation of cellulose 2,2‐dichloropropionate is proposed. The IR spectra of the pyrolysis residues of cellulose dichloropropionate indicate that dehydration takes place and a compound containing carbonyl groups is formed.
Polymerization of lactams, 53. Anionic polymerization of 2‐pyrrolidone accelerated with CO2, part 2
Authors: Brožek Jiří , Roda Jan , Králíček Jaroslav , Šanda Karel
Published: April 2003

The anionic polymerization of 2‐pyrrolidone (3) initiated with its potassium salt (1) (2‐oxo‐1‐pyrrolidinylpotassium) and carbon dioxide was studied under optimal conditions. On the basis of a detailed experimental analysis, it is suggested to consider the investigated polymerization in the presence of gaseous CO2 as an accelerated non‐activated polymerization. Alkali 2‐oxo‐1‐pyrrolidine carboxylate, which is formed in the system by reaction of CO2 with 1, probably does not take part directly in the polymerization process and excerts only a controlling role.
Chelation ion‐exchange properties of salicylic acid/thiourea/trioxane terpolymers
Authors: Manavalan Rajagopal , Patel Mohan M.
Published: April 2003

Terpolymers prepared by condensation of salicylic acid and thiourea with trioxane in presence of acid catalysts, proved to be selective chelating ion‐exchange resins for certain metals. Chelation ion‐exchange properties of these terpolymers were studied for Cu2+, Ni2+, Fe3+, Mn2+, Co2+, Zn2+, and UO22+ ions. A batch equilibration method was employed in the study of the selectivity of metal ion uptake involving the measurement of distribution of a given metal ion between the polymer sample and a solution containing the metal ion. The study was carried out over a wide pH range and in media of various ionic strengths. The terpolymers showed a higher selectivity for Cu2+, Fe3+, and UO22+ ions than for Mn2+, Co2+, and Zn2+ ions.
DSC analyses of bound water in the microdomains of interpolymer complexes
Authors: Ohno Hiroyuki , Shibayama Masashi , Tsuchida Eishun
Published: April 2003

Bound water in polymers and polymer complexes was analyzed quantitatively by means of differential scanning calorimetry in a temperature range from −50 to + 20°C. The water molecules were bound to the polymer chains with different strength, as reflected in a shift of the melting temperature. The existence of non‐freezing water was also confirmed from the relation between the incorporated water content and the heat of fusion. About 0,3 to 0,6 g of water was revealed to exist as non‐freezing water in 1,0 g of the polyelectrolyte complexes. This amount varied with the structure of the polymers investigated. The melting temperature of bound water increases with increasing water content of the component polymers or polymer complexes. The number of bound water molecules per monomeric unit of the polymer is about 3 to 7, and decreases by complex formation. It is speculated from the obtained results that desolvation is accompanied with complex formation, but the solvated state is maintained largely in spite of a drastic decrease in segmental motion of the polymer chains in the polymer complexes.
Polymers containing enzymatically degradable bonds, 8. Degradation of oligopeptide sequences in N‐(2‐hydroxypropyl)methacrylamide copolymers by bovine spleen cathepsin B
Authors: Rejmanová Pavla , Kopeček Jindřich , Pohl Jan , Baudyš Miroslav , Kostka Vladimír
Published: April 2003

Three types of copolymers of N‐(2‐hydroxypropyl)methacrylamide(HPMA) were prepared which contain oligopeptide sequences: (a) HPMA copolymers containing oligopeptide side‐chains terminated with p‐nitroaniline; (b) soluble HPMA copolymers containing oligopeptide sequences in crosslinks connecting two poly(HPMA) chains; (c) a hydrophilic gel, i.e. a three dimensional copolymer of HPMA containing an oligopeptide sequence in the crosslinks. These polymeric substrates (suitable as drug carriers) containing potentially degradable oligopeptide sequences were incubated with an intracellular proteolytic enzyme, bovine spleen cathespin B. The degradation process of the substrates made it possible to reveal the relationship between the structure of oligopeptide sequences and their degradability. The results suggest an important role played by cathepsin B in the degradation of polymeric substrates investigated in this study under physiological conditions.
Determining the scope and impact of market orientation profiles on strategy implementation and performance
Authors: Dobni C. Brooke , Luffman George
Published: April 2003

Strategy implementation and performance in organizations are influenced by its market orientation. Market orientation is the collective of employee behaviors that affects strategy implementation, how an organization interacts with its environment and adjusts to changes within that context. The relationship between market orientation, strategy implementation, and performance is robust across environmental contexts. This study identifies ideal behavioral profiles for organizations seeking to maximize performance by considering the scope and impact of market orientation on strategy implementation. This is accomplished by considering market orientation and strategy profiles in relation to performance in a holistic coalignment perspective, corresponding to competitive contexts characterized by varying degrees of market turbulence and competitive intensity. Important strategic and performance implications of this dynamic are revealed that should be considered by academics and practitioners alike. Copyright © 2003 John Wiley & Sons, Ltd.
Prenatal ultrasound diagnosis of fetal craniosynostosis
Authors: Delahaye S. , Bernard J. P. , Rénier D. , Ville Y.
Published: April 2003

Objective

Craniosynostosis is defined as the premature closure of the calvarial sutures. The prevalence of this heterogeneous condition is 1 in 2000 and approximately 100 different forms have been described with an established genetic transmission in half of them. Prenatal diagnosis of craniosynostosis relies mainly on identification of associated anomalies and molecular analysis of fetal DNA, which is only feasible in some syndromic forms and in well‐documented families. The objective of this study was to investigate the value of prenatal ultrasound examination of cranial sutures in fetuses at risk for craniosynostosis.

Methods

Forty fetuses at risk for craniosynostosis on the basis of either a family history (Group 1, n = 16) or skull deformity suspected on a first‐level fetal ultrasound examination (Group 2, n = 24) were retrospectively investigated. Craniosynostosis was suspected on the basis of skull deformities when present, however the diagnosis was only made in cases where there was a loss of hypoechogenicity of the normal sutures. All infants had both clinical and radiological investigations performed postnatally.

Results

In Group 1, serial ultrasound examination from 12 weeks' gestation onwards led to accurate prenatal diagnosis in all 16 cases. Dysmorphism and skull deformity preceded closure of the sutures by 4 to 16 weeks. In Group 2, prenatal diagnosis was correct in 23/24 cases. There were no false‐negative results in either group.

Conclusions

This series questions further the uncertain genetic determinism of craniosynostosis and seems to rule out the hypothesis of a deformation sequence following primary closure of the cranial sutures. It also suggests that ultrasound examination is useful to demonstrate closure of the sutures in the third trimester of pregnancy in most affected cases. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Is Working Memory Still Working? 1Copyright © 2001 by the American Psychological Association. Reprinted with permission from the original publication: . “Is Working Memory Still Working?” American Psychologist, 56, 849-864. This re-print publication is arranged in recognition of the conferral on Dr. Baddeley of the Aristotle Prize at the VIIth European Congress of Psychology, London, in July 2001, for his outstanding research on human working memory. The original publication in the American Psychologist related to Prof. Baddeley's receipt of the Distinguished Scientific Contribution Award of the American Psychological Association in 2001.
Authors: Baddeley Alan D.
Published: April 2003

The current state of A.D. Baddeley and G.J. Hitch's (1974) multicomponent working memory model is reviewed. The phonological and visuospatial subsystems have been extensively investigated, leading both to challenges over interpretation of individual phenomena and to more detailed attempts to model the processes underlying the subsystems. Analysis of the controlling central executive has proved more challenging, leading to a proposed clarification in which the executive is assumed to be a limited capacity attentional system, aided by a newly postulated fourth system, the episodic buffer. Current interest focuses most strongly on the link between working memory and long-term memory and on the processes allowing the integration of information from the component subsystems. The model has proved valuable in accounting for data from a wide range of participant groups under a rich array of task conditions. Working memory does still appear to be working.
Expression profiling reveals altered satellite cell numbers and glycolytic enzyme transcription in nemaline myopathy muscle
Authors: Sanoudou Despina , Haslett Judith N. , Kho Alvin T. , Guo Shaoqiang , Gazda Hanna T. , Greenberg Steven A. , Lidov Hart G. W. , Kohane Isaac S. , Kunkel Louis M. , Beggs Alan H.
Published: April 2003

The nemaline myopathies (NMs) are a clinically and genetically heterogeneous group of disorders characterized by nemaline rods and skeletal muscle weakness. Mutations in five sarcomeric thin filament genes have been identified. However, the molecular consequences of these mutations are unknown. Using Affymetrix oligonucleotide microarrays, we have analyzed the expression patterns of >21,000 genes and expressed sequence tags in skeletal muscles of 12 NM patients and 21 controls. Multiple complementary approaches were used for data analysis, including geometric fold analysis, two-tailed unequal variance
t
test, hierarchical clustering, relevance network, and nearest-neighbor analysis. We report the identification of high satellite cell populations in NM and the significant down-regulation of transcripts for key enzymes of glucose and glycogen metabolism as well as a possible regulator of fatty acid metabolism, UCP3. Interestingly, transcript level changes of multiple genes suggest possible changes in Ca
2+
homeostasis. The increased expression of multiple structural proteins was consistent with increased fibrosis. This comprehensive study of downstream molecular consequences of NM gene mutations provides insights in the cellular events leading to the NM phenotype.
Predicting the practice effects on the blood oxygenation level-dependent (BOLD) function of fMRI in a symbolic manipulation task
Authors: Qin Yulin , Sohn Myeong-Ho , Anderson John R. , Stenger V. Andrew , Fissell Kate , Goode Adam , Carter Cameron S.
Published: April 2003

Based on adaptive control of thought-rational (ACT-R), a cognitive architecture for cognitive modeling, researchers have developed an information-processing model to predict the blood oxygenation level-dependent (BOLD) response of functional MRI in symbol manipulation tasks. As an extension of this research, the current event-related functional MRI study investigates the effect of relatively extensive practice on the activation patterns of related brain regions. The task involved performing transformations on equations in an artificial algebra system. This paper shows that the base-level activation learning in the ACT-R theory can predict the change of the BOLD response in practice in a left prefrontal region reflecting retrieval of information. In contrast, practice has relatively little effect on the form of BOLD response in the parietal region reflecting imagined transformations to the equation or the motor region reflecting manual programming.
Structure and assembly of an augmented Sm-like archaeal protein 14-mer
Authors: Mura Cameron , Phillips Martin , Kozhukhovsky Anna , Eisenberg David
Published: April 2003

To better understand the roles of Sm proteins in forming the cores of many RNA-processing ribonucleoproteins, we determined the crystal structure of an atypical Sm-like archaeal protein (SmAP3) in which the conserved Sm domain is augmented by a previously uncharacterized, mixed α/β C-terminal domain. The structure reveals an unexpected SmAP3 14-mer that is perforated by a cylindrical pore and is bound to 14 cadmium (Cd
2+
) ions. Individual heptamers adopt either “apical” or “equatorial” conformations that chelate Cd
2+
differently. SmAP3 forms supraheptameric oligomers (SmAP3)

n

= 7,14,28
in solution, and assembly of the asymmetric 14-mer is modulated by differential divalent cation-binding in apical and equatorial subunits. Phylogenetic and sequence analyses substantiate SmAP3s as a unique subset of SmAPs. These results distinguish SmAP3s from other Sm proteins and provide a model for the structure and properties of Sm proteins >100 residues in length, e.g., several human Sm proteins.
Recombinant human erythropoietin protects the myocardium from ischemia-reperfusion injury and promotes beneficial remodeling
Authors: Calvillo Laura , Latini Roberto , Kajstura Jan , Leri Annarosa , Anversa Piero , Ghezzi Pietro , Salio Monica , Cerami Anthony , Brines Michael
Published: April 2003

Erythropoietin (EPO), originally identified for its critical hormonal role in promoting erythrocyte survival and differentiation, is a member of the large and diverse cytokine superfamily. Recent studies have identified multiple paracrine/autocrine functions of EPO that coordinate local responses to injury by maintaining vascular autoregulation and attenuating both primary (apoptotic) and secondary (inflammatory) causes of cell death. Experimental evidence also supports a role for EPO in repair and regeneration after brain and spinal cord injury, including the recruitment of stem cells into the region of damage. Tissue expression of the EPO receptor is widespread, especially during development, and includes the heart. However, it is currently unknown as to whether EPO plays a physiological function in adult myocardial tissue. We have assessed the potential protective role of EPO
in vitro
with adult rat cardiomyocytes, and
in vivo
in a rat model of myocardial infarction with reperfusion. The results show that EPO markedly prevents the apoptosis of cultured adult rat myocardiocytes subjected to 28 h of hypoxia (≈3% normal oxygen). Additional studies employing a rat model of coronary ischemia–reperfusion showed that the administration of recombinant human EPO (5,000 units/kg of body weight; i.p. daily for 7 days) reduces cardiomyocyte loss by ≈50%, an extent sufficient to normalize hemodynamic function within 1 week after reperfusion. These observations not only suggest a potential therapeutic role for recombinant human EPO in the treatment of myocardial ischemia and infarction by preventing apoptosis and attenuating postinfarct deterioration in hemodynamic function, but also predict that EPO is likely a tissue-protective cytokine in other organs as well.
Essential
Bacillus
subtilis
genes
Authors: Kobayashi K. , Ehrlich S. D. , Albertini A. , Amati G. , Andersen K. K. , Arnaud M. , Asai K. , Ashikaga S. , Aymerich S. , Bessieres P. , Boland F. , Brignell S. C. , Bron S. , Bunai K. , Chapuis J. , Christiansen L. C. , Danchin A. , Débarbouillé M. , Dervyn E. , Deuerling E. , Devine K. , Devine S. K. , Dreesen O. , Errington J. , Fillinger S. , Foster S. J. , Fujita Y. , Galizzi A. , Gardan R. , Eschevins C. , Fukushima T. , Haga K. , Harwood C. R. , Hecker M. , Hosoya D. , Hullo M. F. , Kakeshita H. , Karamata D. , Kasahara Y. , Kawamura F. , Koga K. , Koski P. , Kuwana R. , Imamura D. , Ishimaru M. , Ishikawa S. , Ishio I. , Le Coq D. , Masson A. , Mauël C. , Meima R. , Mellado R. P. , Moir A. , Moriya S. , Nagakawa E. , Nanamiya H. , Nakai S. , Nygaard P. , Ogura M. , Ohanan T. , O'Reilly M. , O'Rourke M. , Pragai Z. , Pooley H. M. , Rapoport G. , Rawlins J. P. , Rivas L. A. , Rivolta C. , Sadaie A. , Sadaie Y. , Sarvas M. , Sato T. , Saxild H. H. , Scanlan E. , Schumann W. , Seegers J. F. M. L. , Sekiguchi J. , Sekowska A. , Séror S. J. , Simon M. , Stragier P. , Studer R. , Takamatsu H. , Tanaka T. , Takeuchi M. , Thomaides H. B. , Vagner V. , van Dijl J. M. , Watabe K. , Wipat A. , Yamamoto H. , Yamamoto M. , Yamamoto Y. , Yamane K. , Yata K. , Yoshida K. , Yoshikawa H. , Zuber U. , Ogasawara N.
Published: April 2003

To estimate the minimal gene set required to sustain bacterial life in nutritious conditions, we carried out a systematic inactivation of
Bacillus subtilis
genes. Among ≈4,100 genes of the organism, only 192 were shown to be indispensable by this or previous work. Another 79 genes were predicted to be essential. The vast majority of essential genes were categorized in relatively few domains of cell metabolism, with about half involved in information processing, one-fifth involved in the synthesis of cell envelope and the determination of cell shape and division, and one-tenth related to cell energetics. Only 4% of essential genes encode unknown functions. Most essential genes are present throughout a wide range of Bacteria, and almost 70% can also be found in Archaea and Eucarya. However, essential genes related to cell envelope, shape, division, and respiration tend to be lost from bacteria with small genomes. Unexpectedly, most genes involved in the Embden–Meyerhof–Parnas pathway are essential. Identification of unknown and unexpected essential genes opens research avenues to better understanding of processes that sustain bacterial life.
A complex microbiota from snowball Earth times: Microfossils from the Neoproterozoic Kingston Peak Formation, Death Valley, USA
Authors: Corsetti Frank A. , Awramik Stanley M. , Pierce David
Published: April 2003

A thin carbonate unit associated with a Sturtian-age (≈750–700 million years ago) glaciogenic diamictite of the Neoproterozoic Kingston Peak Formation, eastern California, contains microfossil evidence of a once-thriving prokaryotic and eukaryotic microbial community (preserved in chert and carbonate). Stratiform stromatolites, oncoids, and rare columnar stromatolites also occur. The microbial fossils, which include putative autotrophic and heterotrophic eukaryotes, are similar to those found in chert in the underlying preglacial units. They indicate that microbial life adapted to shallow-water carbonate environments did not suffer the significant extinction postulated for this phase of low-latitude glaciation and that trophic complexity survived through snowball Earth times.
Plasma membrane localization and function of the estrogen receptor α variant (ER46) in human endothelial cells
Authors: Li Lei , Haynes M. Page , Bender Jeffrey R.
Published: April 2003

Estrogen receptor (ER) α variants have been identified in an array of nonendothelial cells. We previously demonstrated that estrogen rapidly induces nitric oxide release via a phosphatidylinositol 3-kinase/Akt/endothelial nitric-oxide synthase (eNOS) pathway in EA.hy926 cells (immortalized human endothelial cells), which express a 46-kDa ER. We now confirm that, due to alternative splicing, the 46-kDa endothelial cell protein (ER46) is an amino-terminal truncated product of full-length ERα (ER66). ER46 is expressed in the plasma membrane, cytosol, and nucleus of resting, estrogen-deprived cells. Flow cytometric and immunofluorescence microscopic analyses demonstrated that the ER46 C but not N terminus is Ab-accessible in the plasma membrane. Inhibition of palmitoylation with tunicamycin and [3H]palmitic acid labeling demonstrated an estrogen-induced, palmitoylation-dependent plasma membrane ER46 recruitment, with reorganization into caveolae. In reconstituted, estrogen-stimulated COS-7 (ER-null) cells, membrane ER46 more efficiently triggered membrane eNOS phosphorylation than ER66. Conversely, ER66 more efficiently mediated estrogen response element reporter-gene transactivation than ER46. These results demonstrate that ER46 is localized and further dynamically targeted to the plasma membrane in a palmitoylation-dependent manner. ER46 more efficiently modulates membrane-initiated estrogen actions, including eNOS activation, than full-length ER66. These findings may have important implications in vascular-specific targeting of estrogen receptor agonists.
L-SIGN (CD 209L) is a liver-specific capture receptor for hepatitis C virus
Authors: Gardner Jason P. , Durso Robert J. , Arrigale Robert R. , Donovan Gerald P. , Maddon Paul J. , Dragic Tatjana , Olson William C.
Published: April 2003

Hepatitis C virus (HCV) infects nearly 3% of the population of the world and is a major cause of liver disease. However, the mechanism whereby the virus targets the liver for infection remains unknown, because none of the putative cellular receptors for HCV are both expressed specifically in the liver and capable of binding HCV envelope glycoproteins. Liver/lymph node-specific intercellular adhesion molecule-3-grabbing integrin (L-SIGN) is a calcium-dependent lectin expressed on endothelial cells of liver and lymph nodes. Dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN), a homologous molecule expressed on dendritic cells, binds HIV and promotes infection. By using a virus-binding assay, we demonstrate that L-SIGN and DC-SIGN specifically bind naturally occurring HCV present in the sera of infected individuals. Further studies demonstrate that binding is mediated by the HCV envelope glycoprotein E2 and is blocked by specific inhibitors, including mannan, calcium chelators, and Abs to the lectin domain of the SIGN molecules. Thus, L-SIGN represents a liver-specific receptor for HCV, and L-SIGN and DC-SIGN may play important roles in HCV infection and immunity.
Measuring the effect of environmental uncertainty on process activities, project team characteristics, and new product success
Authors: Bstieler Ludwig , Gross Charles W.
Published: April 2003

This empirical study examines the influence of environmental uncertainty on industrial product innovation. Addresses a perceived shortcoming in the new product development literature and explores direct and moderating effects of environmental uncertainty on the development process, project organization, and on new product success. Finds that several external market and technology factors do impact new product success directly. Further, finds that several market and technological uncertainties moderate the relationship between development process, project organization, and new product success. Consequently, innovating companies benefit by adapting their development approaches to different environmental conditions and to varying degrees of uncertainty. The results of 82 product development projects indicate, among others, that under conditions of high market and technology unpredictability process compression may increase time efficiency and product profitability.
Extracellular Vestibule Determinants of Ca2+ Influx in Ca2+‐Permeable AMPA Receptor Channels
Authors: Jatzke Claudia , Hernandez Matthew , Wollmuth Lonnie P.
Published: April 2003

At certain synapses in the brain, Ca2+‐permeable AMPA receptor (AMPAR) channels represent an important pathway for synaptically controlled Ca2+ entry. However, the molecular determinants of this Ca2+ influx are poorly defined. In NMDA receptor (NMDAR) channels, where the influx is much greater, the extracellular vestibule, specifically the M3 segment and regions C‐terminal to it in the NR1 subunit, contains elements critical to their high Ca2+ influx under physiological conditions. We therefore investigated the contribution of homologous positions in AMPAR as well as kainate receptor (KAR) subunits to the process of Ca2+ influx. Substitutions of a conserved asparagine (N) in M3 of AMPAR GluR‐B(Q) channels strongly attenuated Ca2+ permeability measured using reversal potentials under biionic conditions and fractional Ca2+ currents recorded under physiological conditions. Hence, as in NMDAR channels, the conserved N makes a significant contribution to Ca2+ influx in AMPAR channels. In addition, C‐terminal to M3, substitutions of negatively (glutamate, E) or positively (arginine, R) charged residues also altered Ca2+ influx. However, in contrast to charged residues occupying homologous positions in NMDAR channels, these effects were about equal and opposite suggesting that this ER in AMPARs does not contribute significantly to the mechanism of Ca2+ influx. Opposite charge substitutions of two negative residues C‐terminal to M3 in KAR GluR‐6(Q) subunits had no effect on Ca2+ permeability. We conclude that the different contribution of residues C‐terminal to M3 to Ca2+ permeation in NMDAR and non‐NMDAR channels reflects a different positioning of these residues relative to the tip of the M2 loop.
Introduction to health economics for the medical practitioner
Authors: Kernick D P
Published: April 2003

Against a background of increasing demands on limited resources, health economics is exerting an influence on decision making at all levels of health care. Health economics seeks to facilitate decision making by offering an explicit decision making framework based on the principle of efficiency. It is not the only consideration but it is an important one and practitioners will need to have an understanding of its basic principles and how it can impact on clinical decision making. This article reviews some of the basic principles of health economics and in particular economic evaluation.
Challenges in Enzyme Mechanism and Energetics
Authors: Kraut Daniel A. , Carroll Kate S. , Herschlag Daniel
Published: April 2003

▪ Abstract  Since the discovery of enzymes as biological catalysts, study of their enormous catalytic power and exquisite specificity has been central to biochemistry. Nevertheless, there is no universally accepted comprehensive description. Rather, numerous proposals have been presented over the past half century. The difficulty in developing a comprehensive description for the catalytic power of enzymes derives from the highly cooperative nature of their energetics, which renders impossible a simple division of mechanistic features and an absolute partitioning of catalytic contributions into independent and energetically additive components. Site-directed mutagenesis has emerged as an enormously powerful approach to probe enzymatic catalysis, illuminating many basic features of enzyme function and behavior. The emphasis of site-directed mutagenesis on the role of individual residues has also, inadvertently, limited experimental and conceptual attention to the fundamentally cooperative nature of enzyme function and energetics. The first part of this review highlights the structural and functional interconnectivity central to enzymatic catalysis. In the second part we ask: What are the features of enzymes that distinguish them from simple chemical catalysts? The answers are presented in conceptual models that, while simplified, help illustrate the vast amount known about how enzymes achieve catalysis. In the last section, we highlight the molecular and energetic questions that remain for future investigation and describe experimental approaches that will be necessary to answer these questions. The promise of advancing and integrating cutting edge conceptual, experimental, and computational tools brings mechanistic enzymology to a new era, one poised for novel fundamental insights into biological catalysis.
IRONSTATUS ANDNEURALFUNCTIONING
Authors: Beard John L. , Connor James R.
Published: April 2003

▪ Abstract  Iron deficiency in early life is associated with delayed development as assessed by a number of clinical trials using similar global scales of development; this poor development during infancy persists in most cases after iron therapy has corrected iron status. If iron deficiency occurs in preschool and older children, the consequences appear reversible with treatment. The biologic understanding of this relationship between development, brain iron status, and functioning is sparse though animal studies repeatedly demonstrate alterations in dopamine metabolism and in the myelination process. Dietary iron deficiency can rapidly deplete brain iron concentrations and repletion is able to normalize them. Residual alterations in striatal dopamine metabolism and myelin production persist if neonatal animals are used. Future studies with more specific measures of neurodevelopment in iron-deficient human infants, and animal models, will allow investigators to more clearly define causal roles of brain iron in neural development and functioning.
Central Monoamines in Free-Ranging Lizards: Differences Associated with Social Roles and Territoriality
Authors: M. Matter John , J. Ronan Patrick , Summers Cliff H.
Published: April 2003

During the breeding season different social classes of field-active lizards, Sceloporus jarrovi, exhibit regionally specific changes in central monoaminergic activation. Changes in serotonergic content and turnover between lizards from different social classes are seen in forebrain structures (telencephalon and diencephalon) and reflect events associated with reproductive behaviors, stress and aggression. Males without territories (satellite males) exhibit higher forebrain serotonin (5-HT) system activation compared to territorial males and adult females. This serotonergic activation includes increased 5-hydroxyindoleacetic acid (5-HIAA) and 5-HIAA/5-HT ratio, suggesting increased release and catabolism. Satellite males also exhibit higher 5-HIAA/5-HT ratios (serotonergic turnover) compared to territorial males following agonistic interactions. Territorial males, immediately following aggressive defense of territories against intruder males, exhibit increased 5-hydroxytryptophan (5-HTP) levels, higher 5-HIAA levels and 5-HIAA/5-HT ratio, higher epinephrine levels, greater MHPG/NE, more DOPAC and larger DOPAC/DA ratio compared to territorial males that did not have an aggressive encounter. These differences suggest activation of 5-HT, norepinephrine (NE), and dopamine (DA) systems by the synthesis and release of more 5-HT and the release of more NE and DA during aggressive defense of territory. The highest activity of serotonergic systems is exhibited by satellite males compared to territorial males, perhaps reflecting stress in subordinate animals from social and ecological sources.
Head Orientation and Trajectory of Locomotion during Jumping and Walking in Domestic Chicks
Authors: R. Green Patrick
Published: April 2003

The relationships between the head orientation of domestic chicks and their trajectory of locomotion were examined in three tasks: jumping over gaps of different depths and widths; walking on surfaces of different slopes; and walking on a level transparent surface above a slope. Head orientation was measured as the angle between the horizontal and a line joining the centre of the eye to the beak tip. At the initiation of a jump, head angle increased with increasing depth of the gap but was not affected by gap width. During walking, head angle increased with increasing downwards slope of the walking surface and decreased with increasing upwards slope. The same effect of a downwards slope was observed when chicks walked on a level transparent surface above a slope, indicating that the effect does not depend on kinaesthetic information. The findings are discussed together with measurements of pigeon head orientation during landing flight. Explanations in terms of specialised retinal areas, binocular visual fields and lower visual field myopia are considered and rejected. It is proposed that the results instead reflect a general role of head orientation as a component in the visual control of locomotion in birds.