bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bacterial adhesion onto azidated poly(vinyl chloride) surfaces
Authors: Lakshmi S. , Kumar S. S. Pradeep , Jayakrishnan A. 
Published: October 2004

AbstractA plasticized poly(vinyl chloride) surface was modified by azidation using sodium azide in the presence of a phase transfer catalyst in aqueous media. Subsequent to azidation, the surface was crosslinked using ultraviolet radiation. Contact angle measurements showed that the surface became hydrophilic on azidation whereas photoirradiation did not have any further effect on the hydrophilicity of the azidated surface. Control, azidated, and photocrosslinked surfaces were exposed to two strains of bacteria commonly implicated in device infection such as Staphylococcus aureus and Escherichia coli. Whereas the control and photocrosslinked surfaces showed no significant difference in bacterial adhesion, the azidated surface showed significantly reduced adhesion to both strains. Data obtained indicate that the presence of an intact azide function on the polymer surface is responsible for the reduced bacterial adherence and the surface hydrophobicity/hydrophilicity did not exert any effect in the present case. Although azides are known to be effective only against Gram‐negative species, surprising was the observation that the azidated polymer surface was equally effective against a Gram‐positive species such as S. aureus. Because sodium azide is routinely used as a preservative to prevent bacterial and fungal growth in many microbiology reagents and diagnostic kits, covalent binding of the azide onto a polymer surface or synthesizing azide containing polymers may be an interesting method to investigate in tackling the problem of bacterial adhesion and colonization of medical devices. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 26–32, 2002
Three‐dimensional macroporous calcium phosphate bioceramics with nested chitosan sponges for load‐bearing bone implants
Authors: Zhang Yong , Zhang Miqin 
Published: October 2004

AbstractThree‐dimensional macroporous calcium phosphate bioceramics embedded with porous chitosan sponges were synthesized to produce composite scaffolds with high mechanical strength and a large surface/volume ratio for load‐bearing bone repairing and substitutes. The macroporous calcium phosphate bioceramics with pore diameters of 300 μm to 600 μm were developed using a porogen burnout technique, and the chitosan sponges were formed inside the pores of the bioceramics by first introducing chiosan solution into the pores followed by a freeze‐drying process. Our scanning electron microscopy results showed that the pore size of chitosan sponges formed inside the macroporous structure of bioceramics was approximately 100 μm, a structure favorable for bone tissue in‐growth. The compressive modulus and yield stress of the composite scaffolds were both greatly improved in comparison with that of HA/β‐TCP scaffolds. The simulated body fluid (SBF) and cell culture experiments were conducted to assess the bioactivity and biocompatibility of the scaffolds. In the SBF tests, a layer of randomly oriented needle‐like apatite crystals formed on the scaffold surface after sample immersion in SBF, which suggested that the composite material has good bioactivity. The cell culture experiments showed that MG63 osteoblast cells attached to the composite scaffolds, proliferated on the scaffold surface, and migrated onto the pore walls, indicating good cell biocompatibility of the scaffold. The cell differentiation on the composite scaffolds was evaluated by alkaline phosphatase (ALP) assay. Compared with the control in tissue culture dishes, the cells had almost the same ALP activity on the composite scaffolds during the first 11 days of culture. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61:1–8, 2002
Inhibition of human squalene monooxygenase by selenium compounds
Authors: Gupta Nisha , Porter Todd D. 
Published: October 2004

AbstractSelenosis in animals is characterized by a variety of neurological abnormalities, but the chemical species of selenium and the molecular targets that mediate this neurotoxicity are unknown. We have previously shown that selenite is a potent inhibitor of squalene monooxygenase, the second enzyme in the committed pathway for cholesterol biosynthesis; inhibition of this enzyme by dimethyltellurium leads to a peripheral demyelinating neuropathy similar to that seen in selenosis. To evaluate the role methylation plays in selenium toxicity, we examined the ability of three methylselenium compounds, methylselenol, dimethylselenide, and trimethylselenonium iodide, to inhibit purified recombinant human squalene monooxygenase. IC50values for methylselenol (95 μM) and dimethylselenide (680 μM) were greater than that previously obtained for selenite (37 μM), and inhibition by trimethylselenonium iodide was evident only at concentrations above 3 mM. Inhibition by methylselenol as well as by selenite was slow and irreversible, suggestive of covalent binding to the enzyme, and thiol‐containing compounds could prevent and reverse this inhibition, indicating that these compounds were reacting with sulfhydryl groups on the protein. Monothiols such as glutathione and β‐mercaptoethanol provided better protection than did dithiols, suggesting that these selenium compounds bind to only one of the two proposed vicinal cysteines on squalene monooxygenase. Unexpectedly, the inhibition by selenite was significantly enhanced by dithiols, indicating that a more toxic species, possibly selenide, was formed in the presence of these dithiol reductants. © 2002 Wiley Periodicals, Inc. J Biochem Mol Toxicol 16:18–23, 2002; DOI 10.1002/jbt.10014
Electron transfer between tryptophan and tyrosine: Theoretical calculation of electron transfer matrix element for intramolecular hole transfer
Authors: Li Xiang‐Yuan 
Published: October 2004

AbstractIn this article, the electron transfer (ET) matrix element has been estimated for the gas‐phase hole transfer between indole cation radical (InH+) and phenol (PhOH). This work consists of three parts. First, the ET reaction between the isolated indole and phenol was investigated using the AM1 method and ab initio calculation at the level of UHF/6–31++G*. Second, the intramolecular ET systems mediated by (CH2)n (n=2–5) were discussed. The linear reaction coordinate approximation has been adopted to describe the variation of the nuclear configuration. Different methods have been used to examine the crossing point of the potential energy curves. All the values of Rc from different methods show very good consistency. ET matrix elements have been evaluated for InH(CH2)nPhOH systems. Also, the AM1 method and Koopmans' theorem were used to investigate the ET process between tyrosine and tryptophan, in which the oligoproline serves as the bridge. Conformations have been optimized using the AM1 method. Based on the linear reaction coordinate approximation, ET matrix elements for the intramoleculatr hole transfer in those TrpH(Pro)nTyrOH (n=0–3) peptides have been estimated by searching for the minimum of the energy splitting factor. All the results show that if a hole transfer process exists between the indole (or indolyl side chain in tryptophan) and phenol (or phenolyl side chain in tyrosine), without deprotonation, it will be difficult for the the ET reaction to occur. All the values of Rc are found in the range of R>1, no matter if a bridge intervenes or not. Hole transfer reactions are predicted to be greatly endothermic, and to have a large activation barrier in the gas‐phase case. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 565–579, 2001
Stochastic generator of chemical structure. 4. Building polymeric systems with specified properties
Authors: Faulon Jean‐Loup 
Published: October 2004

AbstractA novel computational technique to generate close‐to‐equilibrium crosslinked polymeric systems is proposed. Compared to the current state‐of‐the‐art equilibration methods, the new technique appears to be faster by several orders of magnitude. The main advantage of the technique is that one can circumvent the bottlenecks in configuration space that inhibit relaxation in molecular dynamics or Monte Carlo simulations. The problem of polymer equilibration described by continuous equations in molecular dynamics is reduced to a discrete representation where solutions are approximated by simple algorithms. In the current study, a series of coarse‐grained, united‐atom, and fully atomistic crosslinked networks has been generated. Network statistics and topology, X‐ray scattering intensities, and elastic properties are tested vs. experimental results and similar models generated using molecular dynamics and Monte Carlo simulations. The results demonstrate the efficiency of this new method for generating large realistic polymeric systems up to 1.4 M atoms. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 580–590, 2001
Intramolecular chelation of Zn2+ by α‐ and β‐mercaptocarboxamides. A parallel ab initio and polarizable molecular mechanics investigation. Assessment of the role of multipole transferability
Authors: Tiraboschi Gilles , Fournié‐Zaluski Marie‐Claude , Roques Bernard‐Pierre , Gresh Nohad 
Published: October 2004

Abstractα‐ and β‐mercaptocarboxamides constitute the Zn2+‐ligating entity of several highly potent metalloenzyme inhibitors. We have studied their interaction energies with Zn2+ using the polarizable molecular mechanics procedure SIBFA, and compared them to the corresponding ab initio supermolecule ones. Such validations are necessary to subsequently undertake simulations on complexes of Zn2+–metalloenzymes with inhibitors. If the distributed multipoles and polarizabilities are those derived for each ligand in its appropriate Zn2+‐binding conformation, a close reproduction of the ab initio binding energies is afforded. However, this representation is not tractable upon increasing the size of the ligands and/or to explore a continuum of binding conformations. This makes it necessary to construct the ligands by resorting to a library of constitutive fragments, namely in this case methanethiolate, formamide, and methane covalently connected together. A close reproduction of the ab initio interaction energies is enabled, but only if the ligand–ligand interactions are computed simultaneously with those occurring with Zn2+. This representation accounts for the nonadditivity occurring in the Zn2+–methanethiolate–formamide complex, and justifies the use of the distributed multipoles on the fragments for the construction of larger and flexible molecules. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1038–1047, 2001
Validation of nitroxyl spin‐label force‐field parameters through molecular dynamics simulations
Authors: Van Zele Christopher J. , Cunningham Mark A. , Makinen Marvin W. 
Published: October 2004

AbstractA molecular mechanics parameter set for the nitroxyl spin‐label 3‐formyl‐2,2,5,5‐tetramethyl‐1‐oxypyrroline was developed by application of Gaussian94 at the HF/6‐31G(d) level suitable for use in molecular dynamics simulations. The parameter set was validated through molecular dynamics calculations for the methyl ester of N‐(2,2,5,5‐tetramethyl‐1‐oxypyrrolinyl‐3‐carboxyl)‐L‐tryptophan to simulate its conformation and structure in methanol and in chloroform at 300 K with use of the program package CHARMM. Excellent agreement of structural parameters derived by molecular dynamics simulations of the solute in both solvent systems was observed with the structure and conformation of the solute defined through electron nuclear double resonance studies [Wells, G. B. et al., J Am Chem Soc 1990, 112, 2566]. Although rotation about the C(2)C(15) bond connecting the oxypyrrolinyl ring system to the carbonyl group in the pseudopeptide linkage of the tryptophanyl moiety was governed by a potential energy function having two symmetrically placed minima separated by ±42° and a barrier height equivalent to only 2.5 kJ/mol, the spin label exhibited preferred occupancy of the −42° conformer, in direct agreement with spectroscopic studies. The excellent agreement observed between molecular dynamics and spectroscopically derived results provides a firm base for further applications of the force‐field parameter set of this spin label for investigation of macromolecular structure and conformational flexibility through electron magnetic resonance methods. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1113–1123, 2001
Theoretical prediction of vertical transition energies of diaminosilylenes and aminosubstituted disilenes
Authors: Takahashi Masae , Kira Mitsuo , Sakamoto Kenkichi , Müller Thomas , Apeloig Yitzhak 
Published: October 2004

AbstractVertical electronic transition energies of diaminosilylenes and their dimers (disilenes and nitrogen‐bridged) were investigated by ab initio and density functional calculations. A good linear correlation was found between the observed UV transition energies of various silylenes and disilenes and those of model compounds calculated using the CIS and TD–DFT methods. On the basis of these computations the experimental UV absorption maximum observed for the dimer of (i‐Pr2N)2Si: (λmax 439 nm at 77 K), could be assigned to an SiSi bonded dimer with an unusually long SiSi distance of 2.472 Å, and the isomeric amino‐bridged cyclic dimer could be discarded. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1536–1541, 2001
Political violence, social integration, and youth functioning: Palestinian youth from the Intifada
Authors: Barber Brian K. 
Published: October 2004

AbstractInformed by social ecological, social capital, and social disorganization theories, this study tested an ecological model of youth experience in the Palestinian Intifada. The sample included 6,000 Palestinian 14 year olds, assessed in 1994 and 1995 after the end of the conflict. Data from retrospective self‐reports of youth exposure to and involvement in political violence, and self‐reports of current individual functioning (depression and antisocial behavior) and integration in several social contexts (family, peer relations, religion, education, and community), revealed: direct associations between Intifada experience and antisocial behavior and depression (females only); Intifada experience was positively associated with religiosity and unrelated to social integration in family, school, and peer relations; in some cases, social integration in family, education, religion, and peer relations significantly moderated the associations between Intifada experience and youth problems; integration in the several social contexts was directly related in predictable ways to youth problem behaviors, with neighborhood disorganization the most consistent and powerful predictor. The discussion centers around youth resilience to the effects of political violence, the role of psychological meaning children and adolescents can attach to political violence, and the overall salience of social integration in youth development. © 2001 John Wiley & Sons, Inc.
A micro‐level analysis of developmental, parenting, and family milieu variables that differentiate stress‐resilient and stress‐affected children
Authors: Kilmer Ryan P. , Cowen Emory L. , Wyman Peter A. 
Published: October 2004

AbstractMicroanalyzed global parent interview variables that had previously differentiated stress‐resilient (SR) and stress‐affected (SA) outcomes in independent samples (4th–6th and 2nd–3rd grade) of multiethnic, highly stressed, urban children. The in‐depth interview assessed caregiving environment and early child development. On item‐level t tests for the pooled sample, 36 of 144 items differentiated the groups. Discriminant function analysis identified a cluster of nine sensitive items that correctly classified 81.7% of children as SR or SA. Factor analysis of the 36 items identified a 4‐factor solution: Child Adjustment, Early Temperament, Parent‐Child Relationship, and Developmental Milestones; SR parents exceeded SAs on each. Structurally comparable analyses using only Sample 2 and including the second interview's new measures, replicated and extended findings from the pooled sample. Overall, study findings enhance understanding of resilience and testify to the merit of using a microanalytic approach in this research area. Implications for streamlining existing measures and for future research directions are considered. © 2001 John Wiley & Sons, Inc.
Dyadic attachments and community connectedness: Links with youths' loneliness experiences
Authors: Chipuer Heather M. 
Published: October 2004

AbstractIn this article, we explored the belongingness hypothesis by examining the influence of youths' dyadic attachments and community connectedness on their experiences of loneliness. Fifth and sixth graders (N = 187) reported on their attachments to their mothers, fathers, best friends, and their connectedness to their schools and neighborhoods. Self‐reports of global loneliness, loneliness in the school and neighborhood contexts, and emotional and social loneliness were obtained. Youths' dyadic attachment to their best friends was more significant in accounting for their loneliness experiences than their attachments to either parent. Youths' connectedness to their school and neighborhood communities was significantly associated with their experiences of global, social, and neighborhood loneliness. The data suggest that youths' sense of community within their different environmental contexts (i.e., neighborhood, school) differentially influence their psychological well‐being, as demonstrated by their associations to loneliness. The importance of creating communities that meet youths' needs is discussed. © 2001 John Wiley & Sons, Inc.
Doppler velocimetry of maternal renal circulation in pregnancy‐induced hypertension
Authors: Miyake Hidehiko , Nakai Akihito , Koshino Tatsuo , Araki Tsutomu 
Published: October 2004

AbstractPurposeThe purpose of this study was to evaluate whether the Doppler waveforms of the maternal main renal, segmental, and interlobar arteries are altered in women with pregnancy‐induced hypertension (PIH) compared with healthy pregnant women.MethodsFlow waveforms of the maternal main renal, segmental, and interlobar arteries were obtained from 42 healthy pregnant women between 24 and 41 weeks of gestation and 21 women with PIH between 28 and 40 weeks of gestation using pulsed Doppler sonography. We used spectral analysis to measure the peak systolic and end‐diastolic velocities and the acceleration time. The presence or absence of the normal early systolic compliance peak‐reflective‐wave complex (ESP) was assessed in only the main renal artery.ResultsThe acceleration times of the segmental and interlobar arteries were significantly prolonged in the PIH group compared with those in the healthy pregnant women. Of the 21 women with PIH, 3 showed loss of the ESP in the renal artery, but these changes were not significant.ConclusionsDecreased systolic acceleration and the absence of ESP, the hemodynamic indicators for significant proximal stenosis, suggest that severe stenosis or continuous vasospasm in the proximal arteries, such as the main renal or segmental artery, may be implicated in the pathogenesis of PIH. © 2001 John Wiley & Sons, Inc. J Clin Ultrasound 29:449–455, 2001.
Sonographic evaluation of the normal hypothenar compartment musculature
Authors: Grechenig Wolfgang , Peicha Gerolf , Tesch Norbert Peter , Seibert Franz Josef 
Published: October 2004

AbstractPurposeWe propose a standardized sonographic examination technique to evaluate the muscles of the hypothenar region and describe their normal sonographic appearance.MethodsThe hypothenar region was studied with sonography in 20 healthy volunteers using 5–12‐MHz linear‐array transducers. The assessment included dynamic testing.ResultsAll hypothenar muscles could be identified in all subjects and their courses followed entirely. In addition, their function could be assessed by scanning during active and passive movements.ConclusionsKnowledge of the normal sonographic anatomy of the hypothenar region is essential for evaluation of pathologic conditions. © 2001 John Wiley & Sons, Inc. J Clin Ultrasound 29:441–448, 2001.
Signal processing in a simple visual system: The locust ocellar system and its synapses
Authors: Simmons Peter J. 
Published: October 2004

AbstractThe neurons with the widest axons that carry information into a locust brain belong to L‐neurons, the large, second‐order neurons of the ocelli. L‐neurons play roles in flight control and boosting visual sensitivity. Their morphology is simple, and their axons convey graded potentials from the ocellus with little decrement to the brain, which makes them good subjects in which to study transmission of graded potentials. L‐neurons are very sensitive to changes in light, due to an abnormally high gain in the sign inverting synapses they receive from photoreceptors. Adaptation ensures that L‐neurons signal contrast in a light signal when average light intensity changes, and that their responses depend on the speed of change in light. Neurons L1‐3 make excitatory output synapses with third‐order neurons and with L4‐5. These synapses transmit tonically, but are unable to convey hyperpolarising signals about large increases in light. Graded rebound spikes enhance depolarising responses. L1‐3 also make reciprocal inhibitory synapses with each other and transmission at these decrements so rapidly that it normally requires a presynaptic spike. The resolution with which graded potentials can be transferred has been studied at the inhibitory synapses, and is limited by intrinsic variability in the mechanism that determines neurotransmitter release. Electron microscopy has shown that each excitatory connection made from an L‐neuron to a postsynaptic partner consists of thousands of discrete synaptic contacts, in which individual dense‐staining bars in the presynaptic neuron are associated with clouds of vesicles. Acetylcholine is likely to be a neurotransmitter released by L‐neurons. Microsc. Res. Tech. 56:270–280, 2002. © 2002 Wiley‐Liss, Inc.
Developmental changes in the structure and function of the central olfactory system in gregarious and solitary desert locusts
Authors: Anton Sylvia , Ignell Rickard , Hansson Bill S. 
Published: October 2004

AbstractDesert locusts are guided by olfactory cues in different behavioural contexts. In order to understand the basis for the variable olfactory guided behaviour displayed by different developmental stages and by solitary and gregarious locusts, we investigated their central olfactory system with neuroanatomical and neurophysiological methods. The primary olfactory centre of the brain, the antennal lobe (AL), increases in size during development due to an increased number and size of glomeruli. These glomeruli are innervated by a constant number of projection neurons that display increased dendritic arborizations during the development of the locust. The anatomical parameters do not differ between gregarious and solitary locusts. In parallel with the observed neuroanatomical changes, neurophysiological changes in response spectra and response specificity of AL neurons were found. During development, the percentage of neurons responding specifically to aggregation pheromone components decreases, whereas an increase in both pheromone‐generalists and plant‐pheromone generalist neurons is observed. The percentage of neurons responding to green leaf volatiles, however, remains constant. A decrease in the number of nymph blend‐specific neurons was also observed. Our data show that anatomical and physiological properties of the AL and its neurons to a large extent reflect the changes in olfactory guided behaviour during development and between phases. The majority of our results are also in accordance with findings that the number of olfactory receptor neurons increases during development, resulting in increasing convergence on AL neurons. Microsc. Res. Tech. 56:281–291, 2002. © 2002 Wiley‐Liss, Inc.