Synchronization-Induced Rhythmicity of Circadian Oscillators in the Suprachiasmatic Nucleus

The suprachiasmatic nuclei (SCN) host a robust, self-sustained circadian pacemaker that coordinates physiological rhythms with the daily changes in the environment. Neuronal clocks within the SCN form a heterogeneous network that must synchronize to maintain timekeeping activity. Coherent circadian output of the SCN tissue is established by intercellular signaling factors, such as vasointestinal polypeptide. It was recently shown that besides coordinating cells, the synchronization factors play a crucial role in the sustenance of intrinsic cellular rhythmicity. Disruption of intercellular signaling abolishes sustained rhythmicity in a majority of neurons and desynchronizes the remaining rhythmic neurons. Based on these observations, the authors propose a model for the synchronization of circadian oscillators that combines intracellular and intercellular dynamics at the single-cell level. The model is a heterogeneous network of circadian neuronal oscillators where individual oscillators are damped rather than self-sustained. The authors simulated different experimental conditions and found that: (1) in normal, constant conditions, coupled circadian oscillators quickly synchronize and produce a coherent output; (2) in large populations, such oscillators either synchronize or gradually lose rhythmicity, but do not run out of phase, demonstrating that rhythmicity and synchrony are codependent; (3) the number of oscillators and connectivity are important for these synchronization properties; (4) slow oscillators have a higher impact on the period in mixed populations; and (5) coupled circadian oscillators can be efficiently entrained by light–dark cycles. Based on these results, it is predicted that: (1) a majority of SCN neurons needs periodic synchronization signal to be rhythmic; (2) a small number of neurons or a low connectivity results in desynchrony; and (3) amplitudes and phases of neurons are negatively correlated. The authors conclude that to understand the orchestration of timekeeping in the SCN, intracellular circadian clocks cannot be isolated from their intercellular communication components

O QUE PRECISAMOS SABER PARA PARA SUCESSO DE UM BOM MONITORAMENTO? DICAS BASEADAS NOS PADRÕES ABERTOS DE CONSERVAÇÃO

Monitoramento é um dos passos mais importantes em projetos de conservação e manejo. Entretanto, para um bom monitoramento necessitamos de um bom planejamento, para evitar desperdícios de tempo, esforço e dinheiro. Utilizando uma abordagem de manejo adaptativo, discutimos aqui os componentes que devem estar presentes nas etapas de planejamento e os passos para o monitoramento de um projeto de conservação. Embora aplicar a abordagem acima descrita não seja sinônimo de sucesso em um projeto de conservação, os componentes e passos descritos nesse trabalho podem aumentar suas chances de sucesso do mesmo, fornecendo e discutindo cada componente de um planejamento e monitoramento de projeto de conservação, dificilmente encontrados na maioria dos projetos hoje em dia.Para aumentar tanto a quantidade de recursos disponíveis para conservação como a eficiência com que estes recursos são gastos, discutimos neste artigo o que projetos que visam a conservação e o manejo como planejar suas estratégias, monitorar os efeitos das mesmas e avaliar as relações de custo-efetividade dessas estratégias. Usando como base a abordagem de manejo adaptativo conhecida por Padrões Abertos para a Prática de Conservação, nós sugerimos alguns componentes-chave e ferramentas de planejamento estratégico e monitoramento de projetos, em particular ferramentas de diagramação (modelos conceituais e cadeia de resultados) e a utilidade de medidas prévias e áreas de comparação (p. ex. controles) para o monitoramento da efetividade de estratégias. Para demonstrar a utilidade do manejo adaptativo, nós discutimos dois exemplos atuais de projetos publicados que tenham completado pelo menos um ciclo de manejo adaptativo (planejar, monitorar, avaliar e adaptar)

Nef-mediated Clathrin-coated Pit Formation

The sequence of events leading to clathrin-coated pit (CCP) nucleation on the cell surface and to the incorporation of receptors into these endocytic structures is still imperfectly understood. In particular, the question remains as to whether receptor tails initiate the assembly of the coat proteins or whether receptors migrate into preformed CCP. This question was approached through a dissection of the mechanisms implemented by Nef, an early protein of human and simian immunodeficiency virus (HIV and SIV, respectively), to accelerate the endocytosis of cluster of differentiation antigen type 4 (CD4), the major receptor for these viruses. Results collected showed that: (a) Nef promotes CD4 internalization via an increased association of CD4 with CCP; (b) the Nef-mediated increase of CD4 association with CCP is related to a doubling of the plasma membrane area occupied by clathrin-coated structures; (c) this increased CCP number at the plasma membrane has functional consequences preferentially on CD4 uptake and does not significantly affect transferrin receptor internalization or fluid-phase endocytosis; (d) the presence of a CD4 cytoplasmic tail including a critical dileucine motif is required to induce CCP formation via Nef; and (e) when directly anchored to the cytoplasmic side of the plasma membrane, Nef itself can promote CCP formation. Taken together, these observations lead us to propose that CD4 can promote CCP generation via the connector molecule Nef. In this model, Nef interacts on one side with CD4 through a dileucine-based motif present on CD4 cytoplasmic tail and on the other side with components of clathrin-coated surface domain (i.e., adaptins). These Nef-generated complexes would then initiate the nucleation of CCP

Modélisation numérique de l'assise médicale spécifique à la formation d'escarres de pression (S13)

Cet article, propose un modèle éléments finis 3D d'un fessier humain en contact avec un coussin en nid d'abeille à base de thermoplastique polyuréthane (TPU). L'objectif est d'étudier la pression à l'interface fessier/coussin, afin d'améliorer le confort du patient se déplaçant en fauteuil roulant, en particulier dans le cadre de la prévention d'escarres. Pour différents cas de figures de coussins disponibles sur le marché, les résultats numériques démontrent que le coussin à base de TPU est un des coussins les plus approprié et adapté pour réduire la formation d'escarres

Etude échographique du diamètre de l’enveloppe du nerf optique chez l’enfant noir africain sain

Introduction: l'objectif de cette étude était de déterminer le diamètre échographique de l'enveloppe du nerf optique (DENO) dans une population d'enfants sains noirs Africains au Bénin. Méthodes: une étude transversale descriptive a été menée sur une période de 6mois. Le DENO a été mesuré chez 304 enfants sains. Deux mesures échographiques du DENO (coupe transversale et sagittale) ont été réalisées 3mm en arrière de la papille sur chaque œil. Le DENO d'un patient est égal à la moyenne des quatre mesures. Résultats: l'âge moyen était de 35, 72 ± 35,38 mois et la sex-ratio H/F de 0,96. La mesure moyenne du DENO était de 3, 31±0,54mm avec des extrêmes de 2,02 et de 4,44mm. Le DENO croît avec l'âge avec une moyenne corrélation significative (r=0,58 et p<0,0001). Cette croissance est plus marquée pendant les 48 premiers mois de vie. Il n'y avait pas de différence entre les garçons et les filles (p=0, 45). Conclusion: les valeurs retrouvées dans cette étude ne diffèrent pas de ce qui est classiquement décrit dans les autres populations. Un DENO supérieur à 4,40 (IC 95%) doit être considéré comme anormal

‘Race’, sexualities and the French public intellectual: an interview with Eric Fassin

French academic Eric Fassin is interviewed about his work in the field of public sociology, particularly around race and sexuality, over the last two decades. He explains the background and context of intellectuals in France before moving on to the specifics of addressing firstly ‘race’, and secondly sexuality. He argues that 1989 and 2005 are the key turning points in public discourse on ‘race’. Prior to 1989, which saw the first of the ‘Headscarf crises’, ‘race’ was not dealt with explicitly, either in French colonial history or its postcolonial present. The headscarf crisis clarified the tensions within the republican tradition (in which people are formally divided only into French citizens and foreigners, rather than recognised as classes or ethnic groups). The discourse surrounding the riots of 2005 made this the other key year. The framing of debate was along the lines of discrimination (between French citizens) rather than integration (of foreigners into Frenchness), marking a shift towards an acceptance that racism was a social issue. Fassin coins the term ‘sexual democracy’ to encapsulate the distinction between characteristics that are immanent rather than transcendent, and argues that discourse about sexuality and families represents a conflict between those who see them as governed by the social, and those who see them as outside these norms, beyond the social