Search

Resume La presente etude vise a poursuivre la validation du construit d’habilitation comportementale, en examinant non seulement sa structure factorielle, mais en examinant les differences conceptuelles et empiriques entre ce type de comportements et trois autres types de comportements organisationnels, a savoir les comportements de citoyennete organisationnelle, d’innovation et d’autogestion. Des analyses factorielles confirmatoires ont ete effectuees afin d’examiner la structure du construit (N = 274) alors que des analyses correlationnelles ont permis de statuer sur le caractere distinctif des mesures (N = 104). Les resultats demontrent que les concepts sont distincts (.19 r

The sodium/ myo-inositol transporter 2 (SMIT2) is a member of the SLC5A gene family, which is believed to share the five-transmembrane segment inverted repeat of the LeuT structural family. The two-electrode voltage-clamp (TEVC) technique was used to measure the steady-state and the pre-steady-state currents mediated by human SMIT2 after expression in Xenopus laevis oocytes. Phlorizin is first shown to be a poor inhibitor of pre-steady-state currents for depolarizing voltage pulse. From an up to threefold difference between the apparent ON and OFF transferred charges during a voltage pulse, we also show that a fraction of the transient current recorded for very negative potentials is not a true pre-steady-state current coming from the cotransporter conformational changes. We suggest that this transient current comes from a time-dependent leak current that can reach large amplitudes when external Na+concentration is reduced. A kinetic model was generated through a simulated annealing algorithm. This algorithm was used to identify the optimal connectivity among 19 different kinetic models and obtain the numerical values of the associated parameters. The proposed 5-state model includes cooperative binding of Na+ions, strong apparent asymmetry of the energy barriers, a rate-limiting step that is likely associated with the translocation of the empty transporter, and a turnover rate of 21 s−1. The proposed model is a proof of concept for a novel approach to kinetic modeling of electrogenic transporters and allows insight into the transport mechanism of members of the LeuT structural family at the millisecond timescale.

Mediastinal nerve stimulation (MNS) reproducibly evokes atrial fibrillation (AF) by excessive and heterogeneous activation of intrinsic cardiac (IC) neurons. This study evaluated whether preemptive vagus nerve stimulation (VNS) impacts MNS-induced evoked changes in IC neural network activity to thereby alter susceptibility to AF. IC neuronal activity in the right atrial ganglionated plexus was directly recorded in anesthetized canines ( n = 8) using a linear microelectrode array concomitant with right atrial electrical activity in response to: 1) epicardial touch or great vessel occlusion vs. 2) stellate or vagal stimulation. From these stressors, post hoc analysis (based on the Skellam distribution) defined IC neurons so recorded as afferent, efferent, or convergent (afferent and efferent inputs) local circuit neurons (LCN). The capacity of right-sided MNS to modify IC activity in the induction of AF was determined before and after preemptive right (RCV)- vs. left (LCV)-sided VNS (15 Hz, 500 μs; 1.2× bradycardia threshold). Neuronal ( n = 89) activity at baseline (0.11 ± 0.29 Hz) increased during MNS-induced AF (0.51 ± 1.30 Hz; P < 0.001). Convergent LCNs were preferentially activated by MNS. Preemptive RCV reduced MNS-induced changes in LCN activity (by 70%) while mitigating MNS-induced AF (by 75%). Preemptive LCV reduced LCN activity by 60% while mitigating AF potential by 40%. IC neuronal synchrony increased during neurally induced AF, a local neural network response mitigated by preemptive VNS. These antiarrhythmic effects persisted post-VNS for, on average, 26 min. In conclusion, VNS preferentially targets convergent LCNs and their interactive coherence to mitigate the potential for neurally induced AF. The antiarrhythmic properties imposed by VNS exhibit memory.

La dotation dans le contexte de la diversite culturelle est devenue un veritable defi pour les organisations. Afin de venir en aide aux gestionnaires et aux specialistes des ressources humaines, cet article commence par clarifier deux phenomenes fondamentaux en matiere d’evaluation des competences : les biais culturels et l’effet defavorable. La premiere partie de l’article definit ce qu’est un outil d’evaluation non biaise sur le plan culturel et montre la difficulte a demontrer ce fait. La deuxieme partie presente quatre outils d’evaluation utilises dans la selection du personnel pour predire le rendement dans l’emploi et leur impact negatif sur les minorites culturelles. Enfin, la troisieme partie propose des recommandations de nature a aider les organisations a appliquer un processus de selection equitable.

The ion-trap technique is an experimental approach allowing measurement of changes in ionic concentrations within a restricted space (the trap) comprised of a large-diameter ion-selective electrode apposed to a voltage-clamped Xenopus laevis oocyte. The technique is demonstrated with oocytes expressing the Na+/glucose cotransporter (SGLT1) using Na+- and H+-selective electrodes and with the electroneutral H+/monocarboxylate transporter (MCT1). In SGLT1-expressing oocytes, bath substrate diffused into the trap within 20 s, stimulating Na+/glucose influx, which generated a measurable decrease in the trap Na+concentration ([Na+]T) by 0.080 ± 0.009 mM. Membrane hyperpolarization produced a further decrease in [Na+]T, which was proportional to the increased cotransport current. In a Na+-free, weakly buffered solution (pH 5.5), H+drives glucose transport through SGLT1, and this was monitored with a H+-selective electrode. Proton movements can also be clearly detected on adding lactate to an oocyte expressing MCT1 (pH 6.5). For SGLT1, time-dependent changes in [Na+]Tor [H+]Twere also detected during a membrane potential pulse (150 ms) in the presence of substrate. In the absence of substrate, hyperpolarization triggered rapid reorientation of SGLT1 cation binding sites, accompanied by cation capture from the trap. The resulting change in [Na+]Tor [H+]Tis proportional to the pre-steady-state charge movement. The ion-trap technique can thus be used to measure steady-state and pre-steady-state transport activities and provides new opportunities for studying electrogenic and electroneutral ion transport mechanisms.

Background: Burst electrical stimuli delivered to intra-pericardial mediastinal nerves (MNS) during the atrial refractory period reproducibly evoke atrial fibrillation (AF), an effect dependent upon heterogeneous activation of intrinsic cardiac (IC) neurons. The objective of this study was to determine whether pre-emptive vagus nerve stimulation (VNS) alters MNS-induced neuronal imbalance within the IC neurons thereby impacting susceptibility to AF. Methods: Activities of right atrial ganglionated plexus neurons were identified in anesthetized canines (n=11) using a linear microelectrode array. IC neuron activity was characterized in response to: 1) touch and great vessel occlusion versus (2) stellate ganglion or vagal stimulation. Right MNS was evaluated in relation to evoked IC activity and the potential to induce atrial tachyarrhythmias. Responses were assessed prior to and after pre-emptive left (LCV) or right (RCV) cervical VNS (15 Hz, 500 μs; 1.2x chronotropic threshold; 3 min). Results: In control, 100% MNS sites induced AF. Pre-emptive RCV VNS prevented MNS-induced AF induction from 37% of sites; it shortened AF duration in 56% of sites. Pre-emptive LCV VNS potentiated AF in 46% of right-sided MNS sites, prevented AF in 27% of sites, shortened AF in 7% of sites; it was without effect in 20% of sites. Pre-emptive VNS induced a memory effect of ~40 minutes before the MNS-induced AF returned. VNS effects on IC neuronal responses were related primarily to neurons that responded to both touch/vessel occlusion and efferent activation, as such being defined as local circuit neurons (LCNs). A RCV VNS related decrease in IC LCNs activity (0.61±1.83 to 0.16±0.57 Hz) was correlated with reduction in AF inducibility (p Conclusions: VNS decreases the activity of the IC LCNs while maintaining their stochastic behavior, thereby mitigating AF excitability secondary to local neural imbalances. These anti-arrhythmic effects of VNS exhibit memory. Ipsilateral VNS projections more effectively stabilize discrete IC neuronal networks, likely owing to preferential nerve distributions.

Recent multielectrode array recordings in ganglionated plexi of canine atria have opened the way to the study of population dynamics of intrinsic cardiac neurons. These data provide critical insights into the role of local processing that these ganglia play in the regulation of cardiac function. Low firing rates, marked non-stationarity, interplay with the cardiovascular and pulmonary systems and artifacts generated by myocardial activity create new constraints not present in brain recordings for which almost all neuronal analysis techniques have been developed. We adapted and extended the jitter-based synchrony index (SI) to (1) provide a robust and computationally-efficient tool for assessing the level and statistical significance of SI between cardiac neurons, (2) estimate the bias on SI resulting from neuronal activity possibly hidden in myocardial artifacts, (3) quantify the synchrony or anti-synchrony between neuronal activity and the phase in the cardiac and respiratory cycles. The method was validated on firing time series from a total of 98 individual neurons identified in 8 dog experiments. SI ranged from −0.14 to 0.66, with 23 pairs of neurons with SI>0.1. The estimated bias due to artifacts was typically < 1%. Strongly cardiovascular- and pulmonary-related neurons (SI>0.5) were found. Results support the use of jitter-based synchrony index in the context of intrinsic cardiac neurons.

Expression of the Na(+)/glucose cotransporter SGLT1 in Xenopus oocytes is characterized by a phlorizin-sensitive leak current (in the absence of glucose) that was originally called a "Na(+) leak" and represents some 5-10% of the maximal Na(+)/glucose cotransport current. We analyzed the ionic nature of the leak current using a human SGLT1 mutant (C292A) displaying a threefold larger leak current while keeping a reversal potential (V(R)) of approximately -15 mV as observed for wt SGLT1. V(R) showed only a modest negative shift when extracellular Na(+) concentration ([Na(+)](o)) was lowered and it was completely insensitive to changes in extracellular Cl(-). When extracellular pH (pH(o)) was decreased from 7.5 to 6.5 and 5.5, V(R) shifted by +15 and +40 mV, respectively, indicating that protons may be the main charge carrier at low pH(o) but other ions must be involved at pH(o) 7.5. In the presence of 15 mM [Na(+)](o) (pH(o) = 7.5), addition of 75 mM of either Na(+), Li(+), Cs(+), or K(+) generated similar increases in the leak current amplitude. This observation, which was confirmed with wt SGLT1, indicates a separate pathway for the leak current with respect to the cotransport current. This means that, contrary to previous beliefs, the leak current cannot be accounted for by the translocation of the Na-loaded and glucose-free cotransporter. Using chemical modification and different SGLT1 mutants, a relationship was found between the cationic leak current and the passive water permeability suggesting that water and cations may share a common pathway through the cotransporter.

The Na(+)/glucose cotransporter (SGLT1) is a membrane protein that couples the transport of two Na(+) ions and one glucose molecule using the so-called alternating access mechanism. According to this principle, each cotransporter molecule can adopt either of two main conformations: one with the binding sites accessible to the extracellular solution and one with the binding sites facing the intracellular solution. The turnover rate (TOR) is the number of complete cycles that each protein performs per second. Determination of the TOR has important consequences for investigation of the cotransport mechanism, as none of the rate constants involved in mediating transport in a given direction (conformational changes and binding and unbinding reactions) can be slower than the TOR measured under the same conditions. In addition, the TOR can be used to estimate the number of cotransporter molecules involved in generating a given ensemble activity. In this study, we obtain an independent estimation of the TOR for human SGLT1 expressed in Xenopus laevis oocytes applying the ion-trap technique. This approach detects the quantity of ions released in or taken up from the restricted space existing between the oocyte plasma membrane and the tip of a large ion-selective electrode. Taking advantage of the fact that hSGLT1 in the absence of Na(+) can cotransport glucose with protons, we used a pH electrode to determine a TOR of 8.00 ± 1.3 s⁻¹ in the presence of 35 mM α-methyl-glucose at -150 mV (pH 5.5). For the same group of oocytes, a TOR of 13.3 ± 2.4 s⁻¹ was estimated under near-V(max) conditions, i.e., in the presence of 90 mM Na(+) and 5 mM α-methyl-glucose. Under these circumstances, the average cotransport current was -1.08 ± 0.61 μA (n = 14), and this activity was generated by an average of 3.6 ± 0.7 × 10¹¹ cotransporter molecules/oocyte.

reply: The history of science shows that discoveries are generally the result of a chain of studies that build on one another over long time periods. In their letter to the editor, M. D. Parker, R. Musa-Aziz, and W. F. Boron ([4][1]) argue that the technical approach that we named “the ion-trap

Bien que le phénomène soit documenté dans les domaines musicaux, scolaires et sportifs, peu d’études se sont intéressées à l’anxiété de performance en milieu de travail. Cet article décrit une étude exploratoire conduite auprès de dix participants ayant fait l’expérience d’anxiété de performance au travail. Il fait état des déterminants, des manifestations cognitives, émotionnelles, physiologiques et comportementales des participants, des stratégies d’adaptation privilégiées et des conséquences de l’anxiété de performance au travail rapportés par les participants. Il contribue à la compréhension du phénomène en milieu du travail ainsi qu’à l’identification de pistes de recherches futures et de recommandations., Although performance anxiety is well documented in music, school, and sports, very few studies have looked at the phenomenon in the workplace. This article describes an exploratory study conducted with ten participants who experienced performance anxiety at work. It describes participants’ anxiety performance determinants, cognitive, emotional, physiological and behavioural manifestations, preferred coping strategies and consequences. This study contributes to the understanding of the phenomenon in the workplace as well as to the identification of avenues for future research and recommendations.