Using an electrochemical assay to determine the biofilm elasticity change as a response to toxicant exposure

Elasticity is a trait of biofilm physiognomy which relates to cell clustering and can be measured by means of an electrochemical assay based on rotating disc electrode (RDE). This study aimed at testing the hypothesis according to which exposure of phototrophic biofilm to toxicant could reduce its elasticity. We compared biofilms developed for 21 days, in four sets of 6 replicated experimental units, in absence and presence of isoproturon at two concentrations of the inoculating suspension of biofilm, 103 and 104 diatom cell mL-1. Biofilm thickness and elasticity were measured based on RDE assay, bacterial and diatom density were measured by microscope-based numerations.Very thin biofilms (< 10 µm) were obtained as compared with a previous study. This might be linked with the way we selected the initial biofilm providing the suspension and the way we developed its growth. The biofilm elasticity mean values in the presence of isoproturon was quasi twice lower (60 ± 10 and 60 ± 41 µm rpm0.5) than the treatment without isoproturon (138 ± 93 and 115 ± 104 µm rpm0.5), for initial biofilm concentration of 103 and 104 respectively, but there was no significant difference between the mean values of each treatment. Nevertheless, the present preliminary study demonstrated the feasibility of an experiment dedicated to assessing biofilm elasticity changes as a response to toxicant exposure

In Vitro Model of Vascularized Bone: Synergizing Vascular Development and Osteogenesis

Tissue engineering provides unique opportunities for regenerating diseased or damaged tissues using cells obtained from tissue biopsies. Tissue engineered grafts can also be used as high fidelity models to probe cellular and molecular interactions underlying developmental processes. In this study, we co-cultured human umbilical vein endothelial cells (HUVECs) and human mesenchymal stem cells (MSCs) under various environmental conditions to elicit synergistic interactions leading to the colocalized development of capillary-like and bone-like tissues. Cells were encapsulated at the 1∶1 ratio in fibrin gel to screen compositions of endothelial growth medium (EGM) and osteogenic medium (OM). It was determined that, to form both tissues, co-cultures should first be supplied with EGM followed by a 1∶1 cocktail of the two media types containing bone morphogenetic protein-2. Subsequent studies of HUVECs and MSCs cultured in decellularized, trabecular bone scaffolds for 6 weeks assessed the effects on tissue construct of both temporal variations in growth-factor availability and addition of fresh cells. The resulting grafts were implanted subcutaneously into nude mice to determine the phenotype stability and functionality of engineered vessels. Two important findings resulted from these studies: (i) vascular development needs to be induced prior to osteogenesis, and (ii) the addition of additional hMSCs at the osteogenic induction stage improves both tissue outcomes, as shown by increased bone volume fraction, osteoid deposition, close proximity of bone proteins to vascular networks, and anastomosis of vascular networks with the host vasculature. Interestingly, these observations compare well with what has been described for native development. We propose that our cultivation system can mimic various aspects of endothelial cell – osteogenic precursor interactions in vivo, and could find utility as a model for studies of heterotypic cellular interactions that couple blood vessel formation with osteogenesis

The role of organisms in hyporheic processes : gaps in current knowledge, needs for future research and applications

Fifty years after the hyporheic zone was first defined (Orghidan, 1959), there are still gaps in the knowledge regarding the role of biodiversity in hyporheic processes. First, some methodological questions remained unanswered regarding the interactions between biodiversity and physical processes, both for the study of habitat characteristics and interactions at different scales. Furthermore, many questions remain to be addressed to help inform our understanding of invertebrate community dynamics, especially regarding the trophic niches of organisms, the functional groups present within sediment, and their temporal changes. Understanding microbial community dynamics would require investigations about their relationship with the physical characteristics of the sediment, their diversity, their relationship with metabolic pathways, their inter- actions with invertebrates, and their response to environmental stress. Another fundamental research question is that of the importance of the hyporheic zone in the global metabolism of the river, which must be explored in relation to organic matter recycling, the effects of disturbances, and the degradation of contaminants. Finally, the application of this knowledge requires the development of methods for the estimation of hydro- logical exchanges, especially for the management of sediment clogging, the optimization of self-purification, and the integration of climate change in environmental policies. The development of descriptors of hyporheic zone health and of new metrology is also crucial to include specific targets in water policies for the long-term management of the system and a clear evaluation of restoration strategies

L’intégration de la dimension transversale du maxillaire dans le plan de traitement

L’intégration de la dimension transversale du maxillaire est un point fondamental dans l’élaboration d’un plan de traitement orthodontico-chirurgical. Capitales d’un point de vue fonctionnel, les anomalies du sens transversal maxillaire n’ont que peu de retentissements esthétiques, ce qui expose au risque de les sous-estimer. Le diagnostic d’une anomalie transversale maxillaire doit être réalisé pendant l’enfance en précisant la part alvéolaire (endo- ou exoalvéolie) et la part basale (endo- ou exognathie maxillaire) de la dysmorphose. Les auteurs, orthodontiste et chirurgien maxillofacial, apportent leurs regards respectifs sur ces anomalies du sens transversal maxillaire et présentent les moyens thérapeutiques qui peuvent être utilisés, le plus souvent dans le cadre d’une collaboration orthodontico-chirurgicale. L’intégration de la dimension transversale dans le plan de traitement orthodontico-chirurgical est indispensable du point de vue de la stabilité occlusale à long terme

Incorporating the maxillary transverse dimension in the treatment plan

Transverse dimension of the maxilla is a key point to consider when elaborating a surgical-orthodontic approach. Though the esthetic impact of transverse maxillary disharmonies is mild, their functional impact is major, with a tendency to underestimate it. The diagnosis of a transverse maxillary disharmony should be made during childhood, pointing out the alveolar part (endo or exoalveoly) and the skeletal part (endo or exognathy) of the dysmorphosis. The authors, an orthodontist and a maxillofacial surgeon, bring their respective look upon transverse maxillary disharmonies and present the various therapeutic means that can be utilized, most of the time through a surgical-orthodontic collaboration. Long-term occlusal stability definitely requires the integration of the maxillary transverse dimension when elaborating a surgical-orthodontic therapeutic approach

Physiological and genetic factors as sources of variation in locomotion and activity rhythm in a parasitoid wasp (Trichogramma brassicae)

International audienceThe circadian rhythm of locomotor activity in the parasitoid Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae) varies according to genetic and non-genetic factors. The physiological state of the adult influences the circadian rhythm of locomotor activity. Mating is responsible for a long-term decrease in the activity of males, while an increase in female activity is observed. In females, a previous oviposition reduces the spontaneous activity for 2 days. Food deprivation causes a 2-day increase in daily activity, followed by a strong decrease for both sexes. The daily amount of activity is much more affected by physiological variations of the parasitoid than the temporal distribution of the activity (i.e. phase and pattern of activity). In all experiments, variation in locomotor activity was related to path variations. Furthermore, comparison of inbred lines proved the genetic variability of these behavioural traits and of infestation capacity within a strain. Correlations between successive generations demonstrated their transmissibility. The genetic variability constitutes an evolutionary potential allowing the population to display an adaptive response to predictable (i.e. periodic) environmental variations. The behavioural plasticity resulting from physiological changes allows an individual response to unpredictable variations of the environment. Both mechanisms optimize resource exploitation by insect parasitoids

Concevoir, traduire et valider un questionnaire. A propos d'un exemple, EUROQUEST.

Les questionnaires sont des outils de recueil d'information souvent irremplacables en recherche. Les échelles multidimensionnelles sont les mieux adaptées à l'exploration des maladies ou dysfonctionnements intégrant plusieurs composantes. Les auteurs ont établi une synthèse entre les méthodes psychosociales et biomédicales pour l'élaboration et l'évaluation des questionnaires. Cette synthèse a permis de définir des principes de rédaction d'un questionnaire ainsi que des méthodologies de traduction et de comparaison des méthodes d'évaluation qualitatives et quantitatives. La mise à l'épreuve de ces méthodes sur EUROQUEST (questionnaire de symptômes neurotoxiques pour des salariés exposés à des produits chimiques ayant des effets sur le système nerveux) a mis en lumière l'inadéquation, pour cet exemple, de certaines méthodes classiquement décrites. Le calcul des odds ratios entre deux items ou la classification hiérarchique ascendante sont, par contre, des méthodes plus efficaces