bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aspects of cleavage fracture initiation – relative influence of stress and strain
Authors: WALLIN K. , LAUKKANEN A. 
Published: March 2006

ABSTRACTCleavage fracture initiation has generally been assumed to be controlled mainly by matrix stress. Recently, several different cleavage fracture models have been proposed, where also strain is included in the failure criterion. However, the proposals have been rather crude and unable to provide clearly improved fracture estimates. Here, the first two steps of cleavage fracture (particle failure and grain fracture) are examined in more detail. It is shown that both stress and strain are important for cleavage fracture initiation, but that strain mainly affects particle failure, whereas grain fracture is controlled by a pure Griffith criterion. The findings are important for the development of new cleavage fracture models and to the proper way of accounting for constraint.
Glutamate receptor changes associated with transient anoxia/hypoglycaemia in hippocampal slice cultures
Authors: Quintana Patrice , Alberi Stefano , Hakkoum David , Muller Dominique 
Published: March 2006

AbstractTransient anoxia/hypoglycaemia in organotypic hippocampal slice cultures, a model of transient brain ischaemia, ultimately results in delayed cell death. Although the mechanisms underlying this delayed death remain unknown, an increase in excitatory drive has been postulated. We report here that transient anoxia/hypoglycaemia in rat hippocampal slice cultures resulted in a 70–80% enhancement of evoked, α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolpropionic acid (AMPA) receptor‐mediated, excitatory responses lasting over 60 min. This effect was prevented by blockade of N‐methyl‐d‐aspartate (NMDA) receptors, did not involve changes of paired‐pulse facilitation ratio, but was associated with a 50% increase in amplitude, but not frequency, of spontaneous miniature excitatory postsynaptic currents (mEPSCs). Consistent with this, paired recordings revealed the appearance of AMPA receptor‐mediated EPSCs at previously silent synapses and occlusion by prior induction of long‐term potentiation (LTP). Transient anoxia/hypoglycaemia further resulted in a 63% potentiation of evoked NMDA receptor‐dependent synaptic responses, accounting for the 20% increase in ratio of AMPA to NMDA responses. No change in rectification properties of AMPA receptor‐mediated currents could be detected within the first hour following anoxia/hypoglycaemia‐induced potentiation. Western blot analyses of slice cultures exposed to either control conditions or a short anoxia/hypoglycaemia revealed a marked, 50–70% increase of GluR1, GluR2/3 and NR1 subunits 1 h, but not 15 min, after the anoxic/hypoglycaemic episode. This increase was blocked by an inhibitor of protein synthesis. Together these results indicate that a transient anoxia/hypoglycaemia is associated with a marked enhancement of excitatory transmission sharing similarities with the mechanisms underlying LTP, and is correlated with an increased synthesis of excitatory receptor subunits.
Role of L‐type Ca2+ channels in neural stem/progenitor cell differentiation
Authors: D'Ascenzo Marcello , Piacentini Roberto , Casalbore Patrizia , Budoni Manuela , Pallini Roberto , Azzena Gian Battista , Grassi Claudio 
Published: March 2006

AbstractCa2+ influx through voltage‐gated Ca2+ channels, especially the L‐type (Cav1), activates downstream signaling to the nucleus that affects gene expression and, consequently, cell fate. We hypothesized that these Ca2+ signals may also influence the neuronal differentiation of neural stem/progenitor cells (NSCs) derived from the brain cortex of postnatal mice. We first studied Ca2+ transients induced by membrane depolarization in Fluo 4‐AM‐loaded NSCs using confocal microscopy. Undifferentiated cells (nestin+) exhibited no detectable Ca2+ signals whereas, during 12 days of fetal bovine serum‐induced differentiation, neurons (β‐III‐tubulin+/MAP2+) displayed time‐dependent increases in intracellular Ca2+ transients, with ΔF/F ratios ranging from 0.4 on day 3 to 3.3 on day 12. Patch‐clamp experiments revealed similar correlation between NSC differentiation and macroscopic Ba2+ current density. These currents were markedly reduced (−77%) by Cav1 channel blockade with 5 µm nifedipine. To determine the influence of Cav1‐mediated Ca2+ influx on NSC differentiation, cells were cultured in differentiative medium with either nifedipine (5 µm) or the L‐channel activator Bay K 8644 (10 µm). The latter treatment significantly increased the percentage of β‐III‐tubulin+/MAP2+ cells whereas nifedipine produced opposite effects. Pretreatment with nifedipine also inhibited the functional maturation of neurons, which responded to membrane depolarization with weak Ca2+ signals. Conversely, Bay K 8644 pretreatment significantly enhanced the percentage of responsive cells and the amplitudes of Ca2+ transients. These data suggest that NSC differentiation is strongly correlated with the expression of voltage‐gated Ca2+ channels, especially the Cav1, and that Ca2+ influx through these channels plays a key role in promoting neuronal differentiation.
The role of ARX in cortical development
Authors: Friocourt Gaëlle , Poirier Karine , Rakić Sonja , Parnavelas John G. , Chelly Jamel 
Published: March 2006

AbstractThe ARX protein (encoded by the aristaless‐related homeobox gene) is a member of the paired class of homeoproteins. More precisely, it is a member of the Aristaless subclass of proteins with a glutamine residue (Q) at the critical position 50 of the homeodomain (Q50). Through identification of diverse inherited or de novo mutations, genetic investigations of X‐linked mental retardation conditions have demonstrated the implication of ARXin a wide spectrum of disorders extending from phenotypes with severe neuronal migration defects, such as lissencephaly, to mild forms of X‐linked mental retardation without apparent brain abnormalities. These investigations have recently directed attention to the role of this gene in brain development. Analysis of its spatiotemporal localization profile have revealed expression mainly in telencephalic structures at all stages of development. Interestingly, in adult, ARX expression becomes restricted to a population of GABAergic neurons. Although the identification of the target genes regulated by ARX remains a crucial step to better understanding its role during brain development, studies of the role of ARX orthologs in different models have indicated that it is essential for important developmental processes such as proliferation, cell differentiation and neuronal migration.
Gene networks controlling early cerebral cortex arealization
Authors: Mallamaci Antonello , Stoykova Anastassia 
Published: March 2006

AbstractEarly thalamus‐independent steps in the process of cortical arealization take place on the basis of information intrinsic to the cortical primordium, as proposed by Rakic in his classical protomap hypothesis [Rakic, P. (1988)Science, 241, 170–176]. These steps depend on a dense network of molecular interactions, involving genes encoding for diffusible ligands which are released around the borders of the cortical field, and transcription factor genes which are expressed in graded ways throughout this field. In recent years, several labs worldwide have put considerable effort into identifying members of this network and disentangling its topology. In this respect, a considerable amount of knowledge has accumulated and a first, provisional description of the network can be delineated. The aim of this review is to provide an organic synthesis of our current knowledge of molecular genetics of early cortical arealization, i.e. to summarise the mechanisms by which secreted ligands and graded transcription factor genes elaborate positional information and trigger the activation of distinctive area‐specific morphogenetic programs.
Human disorders of cortical development: from past to present
Authors: Francis Fiona , Meyer Gundela , Fallet‐Bianco Catherine , Moreno Sarah , Kappeler Caroline , Socorro Alfredo Cabrera , Tuy Françoise Phan Dinh , Beldjord Cherif , Chelly Jamel 
Published: March 2006

AbstractEpilepsy and mental retardation, originally of unknown cause, are now known to result from many defects including cortical malformations, neuronal circuitry disorders and perturbations of neuronal communication and synapse function. Genetic approaches in combination with MRI and related imaging techniques continually allow a re‐evaluation and better classification of these disorders. Here we review our current understanding of some of the primary defects involved, with insight from recent molecular biology advances, the study of mouse models and the results of neuropathology analyses. Through these studies the molecular determinants involved in the control of neuron number, neuronal migration, generation of cortical laminations and convolutions, integrity of the basement membrane at the pial surface, and the establishment of neuronal circuitry are being elucidated. We have attempted to integrate these results with the available data concerning, in particular, human brain development, and to emphasize the limitations in some cases of extrapolating from rodent models. Taking such species differences into account is clearly critical for understanding the pathophysiological mechanisms associated with these disorders.
Some Personality Correlates of Business White‐Collar Crime
Authors: Blickle Gerhard , Schlegel Alexander , Fassbender Pantaleon , Klein Uwe 
Published: February 2006

On présente dans cet article les résultats de la première étude transversale européenne portant sur les dimensions de la personnalité en relation avec les délits financiers commis par les cols blancs. Ce travail est un prolongement de la recherche de Collin & Schmidt (1992) sur les délits des cols blancs aux Etats‐Unis. Les données ont été récoltées auprès de 150 cadres en poste dans des sociétés commerciales allemandes et de 76 délinquants en col blanc anciennement cadres. Les répondants ont rempli des échelles papier crayon mesurant l’hédonisme (l’Echelle de Valeurs de Schwartz), le sens des responsabilités (NEO‐FFI), le narcissisme (DSM‐III‐R), la désirabilité sociale (Crowne & Marlowe), et le self‐control comportemental. L’analyse de régression logistique montra que 69% de la variance était commune aux deux groupes. Le délit financier commis par un col blanc dépend du sexe (les hommes sont surreprésentés), d’un faible self‐control comportemental, d’un hédonisme élevé, d’un fort narcissisme et d’un sens des responsabilités affirmé quand la désirabilité sociale est statistiquement contrôlée. Ce résultat concernant le sens des responsabilités est toutefois en contradiction avec l’interprétation que Collins et Schmidt donnent de leurs travaux (1993). On peut supposer que les délinquants en col blanc haut placés combinent malhonnêteté et sens des responsabilités élevé.In this paper the results of the first cross‐sectional study in Europe examining personality correlates of white‐collar crime in business are presented. This study is an extension of Collins and Schmidt's (1993) research on white‐collar crime in the United States. The data were obtained from 150 managers currently active in German corporations and 76 white‐collar criminals who formerly held such positions. Participants filled out paper and pencil scales measuring hedonism (Schwartz Value Scale), conscientiousness (NEO‐FFI), narcissism (DSM‐III‐R), social desirability (Crowne & Marlowe, 1960), and behavioral self‐control. The logistic regression analysis accounted for 69 per cent of the variance between the two groups. Business white‐collar crime is predicted by gender (males higher rates than females), low behavioral self‐control, high hedonism, high narcissism, and high conscientiousness after statistically controlling for social desirability. The results concerning conscientiousness, however, contradict the interpretation of findings reported by Collins and Schmidt (1993). It is argued here that high‐ranking white‐collar criminals in business combine low integrity with high conscientiousness.
Personal Goal Facilitation through Work: Implications for Employee Satisfaction and Well‐Being
Authors: Doest Laura ter , Maes Stan , Gebhardt Winifred A. , Koelewijn Hennie 
Published: February 2006

Que le travail facilite la réalisation des objectifs personnels dépend de la perception de l’impact du travail sur l’atteinte de ces objectifs personnels. En accord avec la littérature sur l’autorégulation et le modèle cybernétique du stress organisationnel proposé par Edwards (1992), la facilitation de l’accès à ses objectifs personnels par le travail fut supposée en relation positive avec les attitudes relatives à l’emploi et le bien‐être de l’employé. En outre, on a prédit un rapport plus étroit entre la facilitation de l’accès à ses objectifs personnels par le travail et les performances du salarié quand les buts personnels étaient fortement valorisés. Ces hypothèses ont été mises à l’épreuve à travers un questionnaire rempli par 1036 employés du secteur de la santé. D’après l’analyse de régression, la facilitation de l’accès à ses objectifs personnels par le travail expliquait une part importante de la variance du bien‐être et des attitudes relatives à l’emploi, même après avoir contrôlé les caractéristiques des postes en référence au modèle de Karasek concernant les relations agents stressants—tension au travail (1979; Karasek & Theorell, 1990). L’importance des objectifs n’avait qu’une influence des plus limitées. On en conclut que la facilitation de l’accès à ses objectifs personnels par le travail offre une voie prometteuse pour explorer les attitudes liées à l’emploi et le bien‐être, en complément des modèles plus traditionnels des caractéristiques de l’emploi.Personal goal facilitation through work refers to perceptions of the extent to which one's job facilitates the attainment of one's personal goals. In line with the self‐regulation literature and Edwards’ (1992) cybernetic model of organisational stress, personal goal facilitation through work was predicted to show positive associations with job attitudes and employee well‐being. Moreover, stronger relationships between personal goal facilitation through work and employee outcomes were predicted for highly valued personal goals. These predictions were investigated in a questionnaire study of 1,036 health care employees. In regression analyses, personal goal facilitation through work accounted for substantial variance in job attitudes and well‐being, even after controlling for job characteristics from Karasek's (1979; Karasek & Theorell, 1990) model of occupational stressor–strain relations. There was only very limited evidence of moderating effects of goal importance. It is concluded that personal goal facilitation through work offers a promising source of insight into job attitudes and well‐being, complementing more traditional job characteristics models.
Cultural Values as Moderators of Employee Reactions to Job Insecurity: The Role of Individualism and Collectivism
Authors: Probst Tahira M. , Lawler John 
Published: February 2006

Cette recherche part de l’hypothèse que les valeurs culturelles sont l’un des déterminants des réactions des salariés face à l’insécurité professionnelle. Dans la première investigation, les valeurs culturelles ont été appréhendées au niveau de l’individu à partir des réponses de 141 salariés de diverses origines ethniques appartenant à une grande entreprise agro‐alimentaire américaine qui réduisait ses effectifs. Les répondants ont rempli des questionnaires évaluant leurs valeurs culturelles, leur perception de la sécurité au travail, leurs attitudes professionnelles, leurs réactions affectives vis‐à‐vis de la réduction des effectifs et leur niveau de stress lié au travail. Les résultats ont montré que le sentiment d’insécurité professionnelle avait un impact généralement négatif sur les employés. Toutefois, les salariés présentant des valeurs culturelles communautaires ressentaient plus négativement que leurs homologues individualistes le sentiment d’insécurité professionnelle. Dans le second volet de la recherche, la culture a été définie au niveau national. On a proposé aux salariés de sept organisations, quatre chinoises et trois américaines, de remplir des questionnaires appréciant leurs réactions à leur perception de l’insécurité professionnelle. Il apparut que les Chinois (mentalité communautaire) réagissaient plus négativement que les Américains individualistes face à la menace constituée par l’insécurité professionnelle. Les résultats sont analysés à la lumière du développement de pratiques organisationnelles qui comprennent la réduction des effectifs et autres procédures qui impliquent une moindre stabilité des emplois.This research explored the hypothesis that cultural values moderate employee reactions to job insecurity. In the first study, cultural values were measured at an individual level of analysis based on responses from one hundred and forty‐one ethnically diverse employees of a large US‐based food‐processing company undergoing a downsizing. Participants completed surveys assessing their cultural values, perceptions of job security, job attitudes, affective reactions to the downsizing, and job‐related stress levels. Results indicated that the perception of job insecurity had a generally negative impact on employees. However, employees with collectivist cultural values were more negatively affected by the perception of job insecurity than their individualist counterparts. In the second study, culture was operationalised at the national level of analysis. Employees from seven organisations (four based in China; three based in the US) completed surveys assessing their reactions to perceived job insecurity. Results suggest that Chinese (i.e. collectivist) employees reacted more negatively to the threat of job insecurity than their US counterparts (i.e. individualist employees). These results are discussed in light of growing organisational trends that include the use of downsizing and other techniques that herald a decrease in job stability.
Local vs. regional control on species richness: a new approach to test for competitive exclusion at the community level
Authors: Herzog Sebastian K. , Kessler Michael 
Published: February 2006

ABSTRACTAim The degree to which ecosystem properties (niche availability) and interspecific competition limit local species richness continues to be debated. We present a new method that takes advantage of special biogeographical conditions where habitat islands are embedded in a moderately dissimilar matrix. Small, isolated islands lack habitat specialists to varying degrees, allowing matrix species to occupy island habitat. We examined the relative influence of local vs. biogeographical factors on bird richness of habitat islands by evaluating three predictions each for three hypotheses (competitive exclusion, mass effect, species‐area effects).Location Five naturally isolated dry forest islands and eight extensive dry forest sites in Bolivia.Methods Linear and multiple regressions were calculated between standardized species richness, the number of typical dry forest, humid forest and habitat generalist species vs. canopy height, elevation, precipitation, habitat area and distance from evergreen forest. The same analyses were performed at the guild level.Results Our data are consistent with one prediction under each hypothesis, thus partly supporting and partly rejecting all three hypotheses. Bird richness of dry forest islands was primarily determined by local ecosystem properties (vegetation complexity, productivity), with a minor effect of habitat area (inverse) and distance to evergreen forest. The number of dry forest specialists was influenced by habitat area and isolation from source habitats, with elevation and precipitation adding moderate explanatory power. The number of humid forest specialists was determined by precipitation, habitat area (inversely) and canopy height. These patterns were also evident at the guild level, demonstrating that the loss of dry forest species in a given guild was correlated with a gain of humid forest species in the same guild, rather than random species turnover.Main conclusionsTotal local species richness of semi‐isolated habitat islands is determined primarily by local (niche availability) but also by regional (biogeographical) factors, exemplifying MacArthur's paradox. Small dry forest islands historically lost part of their habitat specialists. Vacant niches were filled by species from adjacent humid forest that are competitively excluded by habitat specialists from large dry forest areas, ideally until the community is saturated, although this pattern is to some degree modified by biogeographical factors. This ‘semipermeable island’ approach can be applied to other taxa and regions and is a promising, widely applicable tool for gaining new insights into the regulation of diversity.
On defining and quantifying biotic homogenization
Authors: Olden Julian D. , Rooney Thomas P. 
Published: February 2006

ABSTRACTOngoing species invasions and extinctions are changing biological diversity in different ways at different spatial scales. Biotic homogenization (or BH) refers to the process by which the genetic, taxonomic or functional similarities of regional biotas increase over time. It is a multifaceted process that encompasses species invasions, extinctions and environmental alterations, focusing on how the identities of species (or their genetic or functional attributes) change over space and time. Despite the increasing use of the term BH in conservation biology, it is often used erroneously as a synonym for patterns of species invasions, loss of native species or changes in species richness through time. This reflects the absence of an agreed‐upon, cogent definition of BH. Here, we offer an operational definition for BH and review the various methodologies used to study this process. We identify the strengths and weaknesses of these approaches, and make explicit recommendations for future studies. We conclude by citing the need for researchers to: (1) consider carefully the definition of BH by recognizing the genetic, taxonomic and functional realms of this process; (2) recognize that documenting taxonomic homogenization requires tracking the identity of species (not species richness) comprising biotas through space and time; and (3) employ more rigorous methods for quantifying BH.