bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cis/trans isomerization in HIV‐1 capsid protein catalyzed by cyclophilin A: Insights from computational and theoretical studies
Authors: Agarwal Pratul K. 
Published: May 2004

AbstractA network of protein vibrations has recently been identified in the enzyme cyclophilin A (CypA) that is associated with its peptidyl‐prolyl cis/trans isomerization activity of small peptide substrates. It has been suggested that this network may have a role in promoting the catalytic step during the isomerization reaction. This work presents the results from the characterization of this network during the isomerization of the Gly89‐Pro90 peptide bond in the N‐terminal domain of the capsid protein (CAN) from human immunodeficiency virus type 1 (HIV‐1), which is a naturally occurring, biologically relevant protein substrate for CypA. A variety of computational and theoretical studies are utilized to investigate the protein dynamics of the CypA‐CAN complex, at multiple time scales, during the isomerization step. The results provide insights into the detailed mechanism of isomerization and confirm the presence of previously reported network of protein vibrations coupled to the reaction. Conserved CypA residues at the complex interface and at positions distal to the interface form parts of this network. There is HIV‐1 related medical interest in CypA; incorporation of CypA, complexed with the capsid protein, into the virion is required for the infectious activity of HIV‐1. Interaction energy and dynamical cross‐correlation calculations are used for a detailed investigation of the protein–protein interactions in the CypA‐CAN complex. The results show that CAN residues His87‐Ala‐Gly‐Pro‐Ile‐Ala92 form the majority of the interactions with CypA residues. New protein–protein interactions distal to the active site (CypA Arg148‐CAN Gln95 and CypA Arg148‐CAN Asn121) are also identified. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Markovian Backbone Negentropies: Molecular descriptors for protein research. I. Predicting protein stability in Arc repressor mutants
Authors: Ramos de Armas Ronal , González Díaz Humberto , Molina Reinaldo , Uriarte Eugenio 
Published: May 2004

AbstractAs more and more protein structures are determined and applied to drug manufacture, there is increasing interest in studying their stability. In this sense, developing novel computational methods to predict and study protein stability in relation to their amino acid sequences has become a significant goal in applied Proteomics. In the study described here, Markovian Backbone Negentropies (MBN) have been introduced in order to model the effect on protein stability of a complete set of alanine substitutions in the Arc repressor. A total of 53 proteins were studied by means of Linear Discriminant Analysis using MBN as molecular descriptors. MBN are molecular descriptors based on a Markov chain model of electron delocalization throughout the protein backbone. The model correctly classified 43 out of 53 (81.13%) proteins according to their thermal stability. More specifically, the model classified 20/28 (71.4%) proteins with near wild‐type stability and 23/25 (92%) proteins with reduced stability. Moreover, the model presented a good Mathew's regression coefficient of 0.643. Validation of the model was carried out by several Jackknife procedures. The method compares favorably with surface‐dependent and thermodynamic parameter stability scoring functions. For instance, the D‐FIRE potential classification function shows a level of good classification of 76.9%. On the other hand, surface, volume, logP, and molar refractivity show accuracies of 70.7, 62.3, 59.0, and 60.0%, respectively. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Resource‐seeking agglomeration: a study of market entry in the lodging industry
Authors: Kalnins Arturs , Chung Wilbur 
Published: May 2004

AbstractWe analyze whether firms prefer collocating with incumbent firms when choosing among markets to enter, highlighting the role of resource‐seeking as a motivation for collocation. We propose that entrants will locate near others possessing resources that can spill over, but will avoid locations where existing firms will exploit spillovers without contributing. To test these propositions, we analyze the location decisions of 570 new hotels in Texas between 1992 and 2000. We find that hotels are attracted to markets with branded upscale hotels. Further, we find that owners of upscale hotels avoid markets with hotels without similar resources. Copyright © 2004 John Wiley & Sons, Ltd.
Believing one's own press: the causes and consequences of CEO celebrity
Authors: Hayward Mathew L. A. , Rindova Violina P. , Pollock Timothy G. 
Published: May 2004

AbstractThis theoretical article introduces the construct of CEO celebrity in order to explain how the tendency of journalists to attribute a firm's actions and outcomes to the volition of its CEO affects such firm. In the model developed here, journalists celebrate a CEO whose firm takes strategic actions that are distinctive and consistent by attributing such actions and performance to the firm's CEO. In so doing, journalists over‐attribute a firm's actions and outcomes to the disposition of its CEO rather than to broader situational factors. A CEO who internalizes such celebrity will also tend to believe this over‐attribution and become overconfident about the efficacy of her past actions and future abilities. Hubris arises when CEO overconfidence results in problematic firm decisions, including undue persistence with actions that produce celebrity. Copyright © 2004 John Wiley & Sons, Ltd.
Incumbent strategic behavior in financial markets and the exit of entrepreneurial start‐ups
Authors: Huyghebaert Nancy , Van de Gucht Linda M. 
Published: May 2004

AbstractThis paper empirically investigates the forces that shape the post‐entry exit probability of entrepreneurial start‐ups, with an emphasis on the impact of incumbents' strategic behavior in financial markets. We find that entrepreneurial start‐ups in highly competitive industries are more likely to exit and that leverage compounds this exit risk. However, the latter result only holds when potential adverse selection and moral hazard problems in financial markets are large at start‐up. Under these circumstances, competitors can negatively influence creditors' perceptions on entrepreneurial quality or behavior through aggressive strategic actions to impede future financing and induce the start‐up's exit. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling adoption of natural resources management technologies: the case of fallow systems
Authors: HONLONKOU ALBERT N. 
Published: May 2004

This paper presents an adoption model of a resource management technology derived from a three-step decision process (information, adoption, and intensity of adoption).From the theoretical results it is found that while the levels of technical parameters such as duration and regeneration rate of soil fertility by improved fallow are relevant for adoption, it is misleading to ignore economic and social factors as they are reflected in the discount rate, risk, information, and prices of inputs and outputs.It is also shown that models that do not take account of the problems of self-selection due to the ability of the potential adopters to acquire and process the relevant information about a technology, lead to biased estimators.Empirical estimations generally confirm the theoretical results. It is found that the acquisition of information about resources management technology is influenced by age of farmers and actions of official extension services; the adoption decision is influenced by prior utilization, the bundle of land property rights owned, and the level of financial liquidity; and the intensity of adoption is influenced by the percentage of the farm that is degraded.
Correlation between brain bradykinin receptor binding sites and cardiovascular function in young and adult spontaneously hypertensive rats
Authors: Cloutier Frank , Ongali Brice , Campos Maria M , Thibault Gaétan , Neugebauer Witold , Couture Réjean 
Published: May 2004

Intracerebroventricular (i.c.v.) effects of bradykinin (BK) B1and B2receptor agonists and antagonists were assessed on mean arterial blood pressure (MAP) and heart rate (HR) in awake unrestrained spontaneously hypertensive rats (SHR, aged of 8 and 16 weeks) and age‐matched Wistar Kyoto rats (WKY). Quantitativein vitroautoradiographic studies were also performed on the brain of both strains with specific radioligands for B2receptors [125I]HPP‐Hoe 140 and B1receptors [125I]HPP‐des‐Arg10and Hoe140.MAP increased linearly with doses of BK (81–8100 pmol) and the amplitudes were significantly greater in SHR, particularly at 16 weeks. While BK evoked a negative linear trend on HR (bradycardia) in WKY, a positive one (tachycardia) was observed in adult SHR. In both strains, BK‐induced pressor response was blocked by equimolar doses of B2receptor antagonist,D‐Arg‐[Hyp3, Thi5,D‐Tic7, Oic8]‐BK (Hoe 140), but not by B1receptor antagonist, AcLys[D‐βNal7, Ile8]des‐Arg9‐BK (R‐715).B1receptor agonists (Sar‐[D‐Phe8]‐des‐Arg9‐BK, des‐Arg9‐BK, des‐Arg10‐Kallidin) and antagonist (R‐715 alone or with Hoe 140) had no or marginal effect on MAP and HR at doses up to 8100 pmol in SHR and WKY.Higher densities of specific [125I]HPP‐Hoe 140 labelling were found in discrete brain areas of SHR, especially in regions associated with cardiovascular function. Low levels of [125I]HPP‐[des‐Arg10]‐Hoe140 binding sites were seen in WKY and SHR, yet densities were significantly greater in midbrain and cortical regions of SHR aged of 16 weeks. Contrary to SHR, ageing caused a downregulation of B2and B1receptor binding sites in specific brain nuclei in WKY.It is concluded that the hypersensitivity of the pressor response to i.c.v. BK in SHR occurs during both the early and established phases of hypertension in parallel with the enhancement of B2receptor binding sites in various cardiovascular brain centres. In contrast, brain B1receptors do not seem to participate in the central pressor effects of kinins nor in the maintenance of hypertension in SHR.British Journal of Pharmacology(2004)142, 285–296. doi:10.1038/sj.bjp.0705759
Measuring reactive species and oxidative damagein vivoand in cell culture: how should you do it and what do the results mean?
Authors: Halliwell Barry , Whiteman Matthew 
Published: May 2004

Free radicals and other reactive species (RS) are thought to play an important role in many human diseases. Establishing their precise role requires the ability to measure them and the oxidative damage that they cause.This article first reviews what is meant by the terms free radical, RS, antioxidant, oxidative damage and oxidative stress.It then critically examines methods used to trap RS, including spin trapping and aromatic hydroxylation, with a particular emphasis on those methods applicable to human studies.Methods used to measure oxidative damage to DNA, lipids and proteins and methods used to detect RS in cell culture, especially the various fluorescent ‘probes’ of RS, are also critically reviewed.The emphasis throughout is on the caution that is needed in applying these methods in view of possible errors and artifacts in interpreting the results.British Journal of Pharmacology(2004)142, 231–255. doi:10.1038/sj.bjp.0705776
Lack of intraspecific biological variation between two geographical populations of Oomyzus sokolowskii (Hymenoptera: Eulophidae), a gregarious larval–pupal parasitioid of Plutella xylostella (Lepidoptera: Plutellidae)
Authors: Mahmood A.R. , Liu S.S. , Shi Z.H. , Song X.H. , Zalucki M.P. 
Published: May 2004

AbstractThe chalcid, Oomyzus sokolowskii Kurdjumov has been recorded in many parts of the world as a major larval–pupal, gregarious endoparasitoid of the diamondback moth, Plutella xylostella (Linnaeus), a serious pest of brassica vegetable crops worldwide. This study investigated intraspecific variation between two populations of O. sokiolowskii, one from Cape Verde Islands, West Africa and the other from Hangzhou, China. In all crosses and backcrosses between the two geographical populations, the numbers of progeny and sex ratio of progeny were similar to those obtained within each of the populations, demonstrating complete reproductive compatibility between the two populations. The two populations showed similar responses to temperature with respect to development time and survival of immature stages. Observations on the interactions between the two O. sokolowskii populations and Cotesia plutellae (Kurdjumov), another major parasitoid of P. xylostella, showed that neither population could achieve successful parasitism of P. xylostella larvae already parasitized by C. plutellae. However, both O. sokolowskii populations could achieve hyperparasitism by ovipositing into a mid-late stage larva of C. plutellae developing inside the primary host. Contrary to earlier reports, no evidence of intraspecific variations in ability to hyperparasitize between these two populations of O. sokolowskii was found.
Recent advances in transgenic arthropod technology
Authors: Kramer M.G. 
Published: May 2004

AbstractThe ability to insert foreign genes into arthropod genomes has led to a diverse set of potential applications for transgenic arthropods, many of which are designed to advance public health or improve agricultural production. New techniques for expressing foreign genes in arthropods have now been successfully used in at least 18 different genera. However, advances in field biology are lagging far behind those in the laboratory, and considerable work is needed before deployment in nature can be a reality. A mechanism to drive the gene of interest though a natural population must be developed and thoroughly evaluated before any field release, but progress in this area has been limited. Likewise, serious consideration of potential risks associated with deployment in nature has been lacking. This review gives an overview of the most promising techniques for expressing foreign genes in arthropods, considers the potential risks associated with their deployment, and highlights the areas of research that are most urgently needed for the field to advance out of the laboratory and into practice.
An aerial netting study of insects migrating at high altitude over England
Authors: Chapman J.W. , Reynolds D.R. , Smith A.D. , Smith E.T. , Woiwod I.P. 
Published: May 2004

AbstractDay and night sampling of windborne arthropods at a height of 200 m above ground was undertaken at Cardington, Bedfordshire, UK, during July 1999, 2000 and 2002, using a net supported by a tethered balloon. The results from this study are compared with those from the classic aerial sampling programmes carried out by Hardy, Freeman and colleagues over the UK and North Sea in the 1930s. In the present study, aerial netting was undertaken at night as well as daytime, and so the diel periodicity of migration could be investigated, and comparisons made with the results from Lewis and Taylor’s extensive survey of flight periodicity near ground level. In some taxa with day-time emigration, quite large populations could continue in high-altitude flight after dark, perhaps to a previously underrated extent, and this would greatly increase their potential migratory range. Any trend towards increases in night temperatures, associated with global warming, would facilitate movements of this type in the UK. Observations on the windborne migration of a variety of species, particularly those of economic significance or of radar-detectable size, are briefly discussed.
Arthropod community structure in pastures of an island archipelago (Azores): looking for local–regional species richness patterns at fine-scales
Authors: Borges P.A.V. , Brown V.K. 
Published: May 2004

AbstractThe arthropod species richness of pastures in three Azorean islands was used to examine the relationship between local and regional species richness over two years. Two groups of arthropods, spiders and sucking insects, representing two functionally different but common groups of pasture invertebrates were investigated. The local–regional species richness relationship was assessed over relatively fine scales: quadrats (= local scale) and within pastures (= regional scale). Mean plot species richness was used as a measure of local species richness (= α diversity) and regional species richness was estimated at the pasture level (= γ diversity) with the ‘first-order-Jackknife’ estimator. Three related issues were addressed: (i) the role of estimated regional species richness and variables operating at the local scale (vegetation structure and diversity) in determining local species richness; (ii) quantification of the relative contributions of α and β diversity to regional diversity using additive partitioning; and (iii) the occurrence of consistent patterns in different years by analysing independently between-year data. Species assemblages of spiders were saturated at the local scale (similar local species richness and increasing β-diversity in richer regions) and were more dependent on vegetational structure than regional species richness. Sucking insect herbivores, by contrast, exhibited a linear relationship between local and regional species richness, consistent with the proportional sampling model. The patterns were consistent between years. These results imply that for spiders local processes are important, with assemblages in a particular patch being constrained by habitat structure. In contrast, for sucking insects, local processes may be insignificant in structuring communities.
An interspersed refuge for Sitodiplosis mosellana (Diptera: Cecidomyiidae) and a biocontrol agent Macroglenes penetrans (Hymenoptera: Pteromalidae) to manage crop resistance in wheat
Authors: Smith M.A.H. , Lamb R.J. , Wise I.L. , Olfert O.O. 
Published: May 2004

AbstractAn interspersed refuge of susceptible plants in a resistant, spring-sown wheat crop was tested as a strategy to protect crop resistance against evolution of virulence by the wheat midge Sitodiplosis mosellana (Géhin), and also to conserve a biocontrol agent Macroglenes penetrans(Kirby). Eight replicated field experiments were conducted using seed mixtures of 0, 5, 10, 15 and 100% or 0, 5 and 100% susceptible wheat with an agronomically similar wheat expressing the antibiotic resistance gene Sm1. The frequencies of eggs, mature larvae and parasitized larvae in susceptible and resistant wheat spikes, and midge-affected seeds in the harvest, were recorded for each plot. In susceptible wheat, insect densities and seed damage were typical of those in commercial wheat. In resistant wheat, few larvae completed development, 2% or less compared with about 80% in susceptible wheat, when larvae were sampled at maturity. This resistant wheat also deterred midge oviposition, reducing egg densities by 65% compared with susceptible wheat. The wheat midge and its parasitoid oviposited throughout the plots, and parasitism was density independent. The densities of mature midge larvae and parasitoids were in proportion to the size of the refuge. A 5% susceptible refuge produced about 41 mature larvae for each mature larva from the resistant wheat, and provided effective control of damage. An interspersed refuge of susceptible plants in resistant wheat is a promising strategy for sustaining resistance conferred by Sm1 and biocontrol of the wheat midge.
Effects of age and food source on secondary chemistry of larvae of Lymantria species (Lepidoptera: Lymantriidae)
Authors: Deml R. 
Published: May 2004

AbstractHaemolymph and osmeterial secretions of caterpillars of Lymantria monacha (Linnaeus) and L. concolor Walker were analysed by gas chromatography/mass spectrometry for low molecular weight secondary metabolites. The similarities of their chemical compositions were determined by means of cluster analysis techniques in order to characterize possible chemical variations related to developmental stage or food of the larvae. For this purpose, two dissimilarity coefficients (Euclidean distances, Canberra metrics) and four clustering methods (UPGMA, WPGMA, WPGMC, single linkage) were combined. The patterns of secondary compounds obtained from the haemolymph and osmeterial secretions studied did not differ statistically significantly between two groups of L. monacha larvae fed with either larch, Larix decidua Mil., or Norway spruce, Picea abies (L.), indicating no relevant influence of plant chemistry. However, haemolymph of penultimate instar larvae of L. concolor fed on Rhododendroncontained a mixture of compounds differing statistically significantly from that of last instar caterpillars. The total compositions of the corresponding gland secretions were statistically identical though the presence/amounts of individual compounds varied. This suggested that the haemolymph composition reflected changing physiological requirements of the successive instars, whereas the composition of the defensive mixtures remained comparatively constant, possibly due to a constant spectrum of potential enemies. A more pronounced age-dependence of larval chemistry was shown by a similar analysis of data from various developmental stages of L. dispar (Linnaeus) and one of its food plants. This analysis suggested plant composition affected the secondary chemistry of early larval instars of L. dispar. The results are discussed in terms of the roles of secondary metabolites in defence against natural enemies.
Fasciola hepatica and Paramphistomum daubneyi: field observations on the transport and outcome of floating metacercariae in running water
Authors: Rondelaud D. , Vignoles P. , Vareille-Morel C. , Abrous M. , Mage C. , Mouzet R. , Dreyfuss G. 
Published: May 2004

AbstractExperimental investigations in eight open drainage ditches and furrows from central France were carried out to analyse the dispersal of floating metacercariae of two digenean species by running water and to determine the outcome of larvae which settled on Nasturtium officinale (watercress). The frequencies of larvae found after their transport by water ranged from 33% to 49.7%, thus indicating that more than half of the metacercariae used in this experiment had fallen to the bottom of the water during this transport. The nature of the site (furrow, or ditch supplied by a spring) had a significant effect on the distribution of floating larvae, while the digenean species had no effect. Low percentages of metacercariae on watercress were noted in furrows (3.5–4.3% of larvae) and ditches (0.8–1.3%). When the watercress grew, most larvae that had settled on leaves and stems died but there were always several living metacercariae on this plant (0.7–1.5% of larvae for Fasciola hepatica and 0.2–0.5% for Paramphistomum daubneyi). The weak buoyancy of these floating cysts on running water limited their dispersal and, consequently, led to a real diminution of risks incurred by definitive hosts towards these metacercariae.
Epidemiology of Ancylostoma spp. in the endangered Iberian lynx (Lynx pardinus) in the Doñana National Park, south-west Spain
Authors: Vicente J. , Palomares F. , Ruiz de Ibañez A. , Ortiz J. 
Published: May 2004

AbstractThe epidemiology of Ancylostoma spp. was studied in the endangered Iberian lynx (Lynx pardinus) in the Doñana National Park, south-west Spain. Faecal samples were collected throughout a complete annual cycle (August 1997 to September 1998). The overall egg prevalence of Ancylostoma spp. was 57.8%. The pattern of abundance of Ancylostoma spp. eggs in faeces was overdispersed. Juvenile lynx demonstrated a statistically higher prevalence and abundance of Ancylostoma spp. than in adults. These levels of egg output (maximum 21195 epg), as previously reported in free ranging large felid cubs, could be close to disease involvement. The potential pathogenicity of hookworms and the influence of individual and ecological factors on hookworm transmission in the Iberian lynx from the Doñana National Park population are discussed.