Estudio ultraestructural de la ovogénesis en Marphysa sanguinea (Annelida: Polychaeta: Eunicida) en la Laguna de Túnez

Ultrastructural features of oogenesis of the iteroparous and long lived eunicid polychaete Marphysa sanguinea (Montagu, 1815) from the Lagoon of Tunis were studied using both light and transmission electron microscopy methods. The ovaries consist of coelomic germ-cell clusters surrounded by a thin envelope of follicle cells derived from the peritoneum. They are attached to the genital blood vessels. Oogenesis is asynchronous; therefore, germ cells in premeiotic and previtellogenic phases are observed in one cluster. The oogenesis is of the extraovarian type. In each cluster the more differentiated oocytes detach and float free in the coelomic cavity where they undergo vitellogenesis as solitary cells. Inside the ovary, follicle cells are connected to young oocytes by intercellular bridges and data suggest that in the early stages of vitellogenesis, ribosomes, multivesicular bodies and dense bodies are transferred from the follicle cells to the oocytes through the intercellular bridges. Different morphological evidence supports the heterosynthetic (presence of endocytotic vesicles, abundant microvilli adorning the surface of the egg) and autosynthetic (proteosynthetic organelles well developed, formation of blebs by the external membrane of the nuclear envelope) origin of yolk in M. sanguinea. The cytoplasmic material of the mature oocytes is asymmetrically distributed; large lipid droplets (1.5 μm in size) and large yolk spheres (6 μm in size) occupy the vegetal pole of the oocyte while small yolk spheres (2-3 μm in size) and numerous membranous organelles (mitochondria, cisternae of endoplasmic reticulum) occupy the animal hemisphere. Spherical to elongated cortical granules up to 1.8 μm in size are located in the cortex of the mature oocytes. Finally, fibrogranular aggregates (“nuage”) similar to that within the nucleus are observed in the cortical ooplasm located in the animal pole of mature oocytes. These aggregates probably come from the nucleus and represent maternal cytoplasmic determinants of embryonic cell fate. Oocytes that have completed vitellogenesis measure 250–300 μm in diameter.Se estudiaron las características ultraestructurales de la ovogénesis del poliqueto de la familia Eunicidae, Marphysa sanguínea (Montagu, 1815), caracterizado por ser iteróparo y presentar una largo periodo de vida vital. Los ejemplares proceden de la Laguna de Túnez y se estudiaron tanto mediante microscopía óptica como mediante microscopía electrónica de transmisión. Esta especie presenta ovarios consistentes en agrupaciones de células germinales celómicas rodeadas por una envoltura delgada de células foliculares derivado del peritoneo y unidos a los vasos sanguíneos genitales. La ovogénesis es asincrónica, por lo que se observan células germinales en fases premeióticas y previtelogénicas en cada clúster, y es de tipo extraovárico. En cada clúster, los ovocitos más diferenciados se desprenden y flotan libres en la cavidad abdominal donde experimentan la vitelogénesis como celdas aisladas. En el interior del ovario, los ovocitos jóvenes están conectados con células foliculares mediante puentes intercelulares, los cuales según los datos obtenidos, permiten la transferencia de ribosomas, cuerpos multivesiculares y cuerpos densos desde las células foliculares a los ovocitos en las primeras etapas de vitelogénesis. Diferentes pruebas morfológicas apoyan el origen heterosintético (presencia de vesículas endocitíticas, abundantes microvellosidades adornando la superficie del huevo) y autosintético (orgánulos proteosintéticos bien desarrollados, la formación de vesículas a partir de la membrana externa de la envoltura nuclear) del vitelo en M. sanguinea. El material citoplasmático de los ovocitos maduros se distribuye asimétricamente; grandes gotas de lípidos (1,5 μm) y grandes esferas de vitelo (6 μm) ocupan el polo vegetal del ovocito, mientras que esferas pequeñas de vitelo (2-3 μm) y numerosos orgánulos membranosos (mitocondrias, cisternas del retículo endoplásmatico) ocupan el hemisferio animal. Los ovocitos maduros presentan gránulos corticales (entre esféricos y alargados y de hasta 1,8 μm) en el córtex, mientras que en el ooplasma cortical del polo animal se presentan agregados fibrogranulares (“nuage”) similares a los del núcleo. Estos agregados probablemente provienen del núcleo y representan determinantes citoplasmáticos maternos del destino de las células embrionarias. Una vez completada la vitelogénesis, los ovocitos miden entre 250-300 μm de diámetro

Work engagement, emotional exhaustion, and OCB-civic virtue among nurses: a multilevel analysis of emotional supervisor support

Introduction: This study investigates the moderating role of supervisor emotional support at the group level on the relationship between emotional exhaustion and work engagement with organizational citizenship behavior-civic virtue (OCB-civic virtue) at the individual level among nurses. Method: A cross-sectional study was carried out on 558 nurses nested in 36 working units from two hospitals in Algiers. A multilevel analysis using Hierarchical Linear Modeling was performed. Results: Results show that the positive effect of work engagement on OCB-civic virtue was moderated by supervisor emotional support at group level. The nurses emotional exhaustion and OCB-civic virtue negative relationship at the individual level is buffered by supervisor emotional support at group level. Discussion: In consequence, supervisor emotional support experienced by the team has an influence on the emotional exhaustion and work engagement OCB-civic virtue relationship

Subcellular localization of microcystin in the liver and the gonads of medaka fish acutely exposed to microcystin-LR

International audienceAmong the diverse toxic components produced by cyanobacteria, microcystins (MCs) are one of the most toxic and notorious cyanotoxin groups. Besides their potent hepatotoxicity, MCs have been revealed to induce potential reproductive toxicity in various animal studies. However, little is still known regarding the distribution of MCs in the reproductive organ, which could directly affect reproductive cells. In order to respond to this question, an acute study was conducted in adult medaka fish (model animal) gavaged with 10 μg.g −1 body weight of pure MC-LR. The histological and immunohistochemical examinations reveal an intense distribution of MC-LR within hepatocytes along with a severe liver lesion in the toxin-treated female and male fish. Besides being accumulated in the hepatocytes, MC-LR was also found in the connective tissue of the ovary and the testis, as well as in oocytes and degenerative spermatocyte-like structures but not spermatocytes. Both liver and gonad play important roles in the reproductive process of oviparous vertebrates. This observation constitutes the first observation of the presence of MC-LR in reproductive cells (female, oocytes) of a vertebrate model with in vivo study. Our results, which provide intracellular localization of MC-LR in the gonad, advance our understanding of the potential reproductive toxicity of MC-LR in fish

International Journal of Africa Nursing Sciences

Background There is growing interest in the relationships between supervisor/co-worker support and nurses’ perceived quality of care and organizational citizenship behaviours. However, few studies have investigated the effects of emotional support of supervisors and colleagues on the performance of nurses over time and the psychological mechanisms that underlie the above-mentioned relationships. Objective The aim of our study was to better understand the process promoting nurses’ perceived quality of care and organizational citizenship centred on helping others. To better understand these processes, we focused on the perceived emotional support originating from the supervisor and that from the co-workers and analysed to which extent they were, over time, related to quality of care and organizational citizenship through work engagement. Method A two-wave design was used to collect the data. Survey data was gathered from 188 nurses from two hospitals in Algeria. Mediation analyses were carried out using structural equation modelling. Results The results revealed that nurses’ work engagement mediates the relationships between quality of care, organizational citizenship behaviour and supervisor and co-workers emotional support. Conclusion Results underlined the importance of putting in place schedules to improve supervisor emotional support, co-worker emotional support and work engagement in order to improve quality of care

Highly dynamic cellular-level response of symbiotic coral to a sudden increase in environmental nitrogen

Metabolic interactions with endosymbiotic photosynthetic dinoflagellate Symbiodinium spp. are fundamental to reefbuilding corals (Scleractinia) thriving in nutrient-poor tropical seas. Yet, detailed understanding at the single-cell level of nutrient assimilation, translocation, and utilization within this fundamental symbiosis is lacking. Using pulse-chase 15N labeling and quantitative ion microprobe isotopic imaging (NanoSIMS; nanoscale secondary-ion mass spectrometry), we visualized these dynamic processes in tissues of the symbiotic coral Pocillopora damicornis at the subcellular level. Assimilation of ammonium, nitrate, and aspartic acid resulted in rapid incorporation of nitrogen into uric acid crystals (after ~45 min), forming temporary N storage sites within the dinoflagellate endosymbionts. Subsequent intracellular remobilization of this metabolite was accompanied by translocation of nitrogenous compounds to the coral host, starting at ~6 h. Within the coral tissue, nitrogen is utilized in specific cellular compartments in all four epithelia, including mucus chambers, Golgi bodies, and vesicles in calicoblastic cells. Our study shows how nitrogen-limited symbiotic corals take advantage of sudden changes in nitrogen availability; this opens new perspectives for functional studies of nutrient storage and remobilization in microbial symbioses in changing reef environments. IMPORTANCE The methodology applied, combining transmission electron microscopy with nanoscale secondary-ion mass spectrometry (NanoSIMS) imaging of coral tissue labeled with stable isotope tracers, allows quantification and submicrometric localization of metabolic fluxes in an intact symbiosis. This study opens the way for investigations of physiological adaptations of symbiotic systems to nutrient availability and for increasing knowledge of global nitrogen and carbon biogeochemical cycling. © 2013 Kopp et al

Global Metabolomic Characterizations of Microcystis spp. Highlights Clonal Diversity in Natural Bloom-Forming Populations and Expands Metabolite Structural Diversity

Cyanobacteria are photosynthetic prokaryotes capable of synthesizing a large variety of secondary metabolites that exhibit significant bioactivity or toxicity. Microcystis constitutes one of the most common cyanobacterial genera, forming the intensive blooms that nowadays arise in freshwater ecosystems worldwide. Species in this genus can produce numerous cyanotoxins (i.e., toxic cyanobacterial metabolites), which can be harmful to human health and aquatic organisms. To better understand variations in cyanotoxin production between clones of Microcystis species, we investigated the diversity of 24 strains isolated from the same blooms or from different populations in various geographical areas. Strains were compared by genotyping with 16S-ITS fragment sequencing and metabolite chemotyping using LC ESI-qTOF mass spectrometry. While genotyping can help to discriminate among different species, the global metabolome analysis revealed clearly discriminating molecular profiles among strains. These profiles could be clustered primarily according to their global metabolite content, then according to their genotype, and finally according to their sampling location. A global molecular network of all metabolites produced by Microcystis species highlights the production of a wide set of chemically diverse metabolites, including a few microcystins, many aeruginosins, microginins, cyanopeptolins, and anabaenopeptins, together with a large set of unknown molecules. These components, which constitute the molecular biodiversity of Microcystis species, still need to be investigated in terms of their structure and potential bioactivites (e.g., toxicity)

A Kinetic Study of Accumulation and Elimination of Microcystin-LR in Yellow Perch (Perca Flavescens) Tissue and Implications for Human Fish Consumption

Fish consumption is a potential route of human exposure to the hepatotoxic microcystins, especially in lakes and reservoirs that routinely experience significant toxic Microcystis blooms. Understanding the rates of uptake and elimination for microcystins as well as the transfer efficiency into tissues of consumers are important for determining the potential for microcystins to be transferred up the food web and for predicting potential human health impacts. The main objective of this work was to conduct laboratory experiments to investigate the kinetics of toxin accumulation in fish tissue. An oral route of exposure was employed in this study, in which juvenile yellow perch (Perca flavescens) were given a single oral dose of 5 or 20 μg of microcystin-LR (MC-LR) via food and accumulation in the muscle, liver, and tank water were measured over 24 h. Peak concentrations of the water soluble fraction of microcystin were generally observed 8–10 h after dosing in the liver and after 12–16 h in the muscle, with a rapid decline in both tissues by 24 h. Up to 99% of the total recoverable (i.e., unbound) microcystin was measured in the tank water by 16 h after exposure. The relatively rapid uptake and elimination of the unbound fraction of microcystin in the liver and muscle of juvenile yellow perch within 24 h of exposure indicates that fish consumption may not be a major route of human exposure to microcystin, particularly in the Great Lakes

Job demands and well-being among nurses : the role of emotional resources

Dans l’environnement hospitalier, les infirmiers jouent un rôle pivot dans la prestation de soin, cette population est particulièrement exposée à des niveaux élevés de demande émotionnelle ce qui peut entraîner à terme une insatisfaction, un épuisement professionnel (Dal Santo, Pohl & Battistelli, 2013), un sentiment d’impuissance et d’incapacité à accomplir un travail au niveau attendu (Davezies, 2007). Le soutien organisationnel perçu (SOP) a été supposé et démontré avoir la capacité d’atténuer les effets néfastes des tensions émotionnelles (Pohl, Battistelli & Librecht, 2013; Battistelli, Pohl & Dal Santo, 2012; George, Reed, Ballard; Halbesleben, 2006). Rhoades et Eisenberger (2002) ont ajouté que le soutien du supérieur hiérarchique (SSP) est défini par la perception qu’a le salarié de la manière dont son supérieur valorise sa contribution, et qui est considéré comme la variable qui contribue le plus significativement à la perception du soutien organisationnel. Rhoades et al (2001) ont observés un effet positif du SSP sur l’engagement organisationnel affectif ; (Wayne et al., 1997 ; Moorman et al., 1998) ont démontrés un effet direct du SSP sur le bien-être, la qualité de vie au travail et sur les comportements de citoyenneté organisationnelle. Enfin, le développement récent de la recherche confirme les effets tangibles du soutien du supérieur hiérarchique sur l’engagement affectif, l’intention de quitter et l’épuisement professionnel en témoignent Simons & Jankowski; 2008). Notre réflexion théorique s’articule en trois points. (1) Etudier les tensions psychologiques (conflit travail/famille-famille/travail) et les caractéristiques du travail (Demande psychologique, Contraintes physiques Complexité du travail…) constitue une clé d’entrée qui nécessite (2) une réflexion sur le soutien émotionnel au travail ainsi que les stratégies de régulation émotionnel comme variables modératrices, pour (3) étudier les effets de ces variables modératrices dans les modèles de recherche intégrant l’épuisement professionnel, l’engagement organisationnel, satisfaction au travail, la dissonance émotionnelle et le comportement de citoyenneté organisationnelle . Mots clé: Tensions au travail (conflit travail/famille-famille/travail) – Caractéristiques du travail (Demande psychologique, Contraintes physique, Complexité du travail) Burnout – Engagement organisationnel– Dissonance émotionnelle – comportement de citoyenneté_ Soutien émotionnel au travail –Stratégies de régulation émotionnelle.The increasing demands of work and their impact on the quality of life of employees are timely. In this perspective, the reflection on the managerial practices deserves to be thorough. This research project has three objectives: to conceptualize, measure and predict the influence of emotional support at work (ESW) on organizational commitment, job satisfaction and organizational citizenship behaviour. Our reflection is based on three points. (1) Study the psychological tensions ( conflicts Work / family -life / work) and job characteristics (psychological demand, physical constraints, Complexity of work ... ) is a key input that requires (2) a reflection on the emotional support at work and emotional regulation strategies as moderating variables for ( 3) study the effects of moderating variables in integrating research models incorporating burnout, organizational commitment , emotional dissonance, job satisfaction and organizational citizenship behaviour. The hospital raises an exemplary manner the dynamics and challenges of local management. We will consider three cases: The University Hospital of Bab El Oued (Algeria), University Hospital of Brugmann, (Belgium) and The University Hospital of Bordeaux (France). To provide some answers, we mobilize two methods: qualitative and quantitative (more about a double measure of perceived SET and a measure of emotional regulation strategies) with a comparison of the target institutions. Key words : Emotional support at work_ psychological tensions (conflict work / life and family / work) - Work Characteristics (psychological demand, physical constraints, Labor Complexity ) Burnout – organizational commitment - emotional dissonance - organizational citizenship behaviour _ Strategies work emotional regulation

Les exigences du travail et le bien-être dans la profession infirmière : le rôle des ressources émotionnelles

The increasing demands of work and their impact on the quality of life of employees are timely. In this perspective, the reflection on the managerial practices deserves to be thorough. This research project has three objectives: to conceptualize, measure and predict the influence of emotional support at work (ESW) on organizational commitment, job satisfaction and organizational citizenship behaviour. Our reflection is based on three points. (1) Study the psychological tensions ( conflicts Work / family -life / work) and job characteristics (psychological demand, physical constraints, Complexity of work ... ) is a key input that requires (2) a reflection on the emotional support at work and emotional regulation strategies as moderating variables for ( 3) study the effects of moderating variables in integrating research models incorporating burnout, organizational commitment , emotional dissonance, job satisfaction and organizational citizenship behaviour. The hospital raises an exemplary manner the dynamics and challenges of local management. We will consider three cases: The University Hospital of Bab El Oued (Algeria), University Hospital of Brugmann, (Belgium) and The University Hospital of Bordeaux (France). To provide some answers, we mobilize two methods: qualitative and quantitative (more about a double measure of perceived SET and a measure of emotional regulation strategies) with a comparison of the target institutions. Key words : Emotional support at work_ psychological tensions (conflict work / life and family / work) - Work Characteristics (psychological demand, physical constraints, Labor Complexity ) Burnout – organizational commitment - emotional dissonance - organizational citizenship behaviour _ Strategies work emotional regulation .Dans l’environnement hospitalier, les infirmiers jouent un rôle pivot dans la prestation de soin, cette population est particulièrement exposée à des niveaux élevés de demande émotionnelle ce qui peut entraîner à terme une insatisfaction, un épuisement professionnel (Dal Santo, Pohl & Battistelli, 2013), un sentiment d’impuissance et d’incapacité à accomplir un travail au niveau attendu (Davezies, 2007). Le soutien organisationnel perçu (SOP) a été supposé et démontré avoir la capacité d’atténuer les effets néfastes des tensions émotionnelles (Pohl, Battistelli & Librecht, 2013; Battistelli, Pohl & Dal Santo, 2012; George, Reed, Ballard; Halbesleben, 2006). Rhoades et Eisenberger (2002) ont ajouté que le soutien du supérieur hiérarchique (SSP) est défini par la perception qu’a le salarié de la manière dont son supérieur valorise sa contribution, et qui est considéré comme la variable qui contribue le plus significativement à la perception du soutien organisationnel. Rhoades et al (2001) ont observés un effet positif du SSP sur l’engagement organisationnel affectif ; (Wayne et al., 1997 ; Moorman et al., 1998) ont démontrés un effet direct du SSP sur le bien-être, la qualité de vie au travail et sur les comportements de citoyenneté organisationnelle. Enfin, le développement récent de la recherche confirme les effets tangibles du soutien du supérieur hiérarchique sur l’engagement affectif, l’intention de quitter et l’épuisement professionnel en témoignent Simons & Jankowski; 2008). Notre réflexion théorique s’articule en trois points. (1) Etudier les tensions psychologiques (conflit travail/famille-famille/travail) et les caractéristiques du travail (Demande psychologique, Contraintes physiques Complexité du travail…) constitue une clé d’entrée qui nécessite (2) une réflexion sur le soutien émotionnel au travail ainsi que les stratégies de régulation émotionnel comme variables modératrices, pour (3) étudier les effets de ces variables modératrices dans les modèles de recherche intégrant l’épuisement professionnel, l’engagement organisationnel, satisfaction au travail, la dissonance émotionnelle et le comportement de citoyenneté organisationnelle . Mots clé: Tensions au travail (conflit travail/famille-famille/travail) – Caractéristiques du travail (Demande psychologique, Contraintes physique, Complexité du travail) Burnout – Engagement organisationnel– Dissonance émotionnelle – comportement de citoyenneté_ Soutien émotionnel au travail –Stratégies de régulation émotionnelle

Dissonance émotionnelle et bien-être au travail :le rôle médiateur du soutien émotionnel du supérieur perçu.

info:eu-repo/semantics/nonPublishe