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Search Results: 1 - 10 of 31283 matches for " Jacques Robert "
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Emerging Ranaviral Infectious Diseases and Amphibian Decline
Jacques Robert
Diversity , 2010, DOI: 10.3390/d2030314
Abstract: Infectious diseases caused by ranaviruses (RV, family Iridoviridae) not only affect wild amphibian populations but also agriculture and international animal trade. Although, the prevalence of RV infections and die offs has markedly increased over the last decade, it is still unclear whether these viruses are direct causal agents of extinction or rather are the resulting (secondary) consequences of weakened health of amphibian populations leading to increased susceptibility to viral pathogens. In either case, it is important to understand the critical role of host immune defense in controlling RV infections, pathogenicity, and transmission; this is the focus of this review.
Antiviral Immunity in Amphibians
Guangchun Chen,Jacques Robert
Viruses , 2011, DOI: 10.3390/v3112065
Abstract: Although a variety of virus species can infect amphibians, diseases caused by ranaviruses ([RVs]; Iridoviridae) have become prominent, and are a major concern for biodiversity, agriculture and international trade. The relatively recent and rapid increase in prevalence of RV infections, the wide range of host species infected by RVs, the variability in host resistance among population of the same species and among different developmental stages, all suggest an important involvement of the amphibian immune system. Nevertheless, the roles of the immune system in the etiology of viral diseases in amphibians are still poorly investigated. We review here the current knowledge of antiviral immunity in amphibians, focusing on model species such as the frog Xenopus and the salamander (Ambystoma tigrinum), and on recent progress in generating tools to better understand how host immune defenses control RV infections, pathogenicity, and?transmission.
Lymphoid Tumors of Xenopus laevis with Different Capacities for Growth in Larvae and Adults
Jacques Robert,Chantal Guiet,Louis Du Pasquier
Clinical and Developmental Immunology , 1994, DOI: 10.1155/1994/37392
Recent Research Progress and Potential Uses of the Amphibian Xenopus as a Biomedical and Immunological Model System
Eva-Stina Edholm,Jacques Robert
Resources , 2013, DOI: 10.3390/resources2030167
Abstract: The amphibian Xenopus has long been a comparative model system of choice for a number of different biological research areas, including immunology. Specifically, the evolutionary distance between amphibians and mammals, including humans, allows for the study of both species-specific adaptations, as well as conserved features of the immune system. Furthermore, the Xenopus genus includes species with multiple levels of polyploidy, thereby providing a unique model to study whole genome duplication and its effects thereof on individual genes. To better exploit this amphibian model, the development and innovative applications of novel research tools have been a priority. In this regard, recent advances in adapting the transgenesis approach to Xenopus have allowed for in vivo studies of the impact of loss and gain of function of specific genes at the level of the whole organism, further enhancing the potential uses of Xenopus as an important biomedical model system. This review highlights some of the major uses and applications of the Xenopus model.
Comparison of reduced-order, sequential and variational data assimilation methods in the tropical Pacific Ocean
Céline Robert,Eric Blayo,Jacques Verron
Physics , 2007, DOI: 10.1007/s10236-006-0079-9
Abstract: This paper presents a comparison of two reduced-order, sequential and variational data assimilation methods: the SEEK filter and the R-4D-Var. A hybridization of the two, combining the variational framework and the sequential evolution of covariance matrices, is also preliminarily investigated and assessed in the same experimental conditions. The comparison is performed using the twin-experiment approach on a model of the Tropical Pacific domain. The assimilated data are simulated temperature profiles at the locations of the TAO/TRITON array moorings. It is shown that, in a quasi-linear regime, both methods produce similarly good results. However the hybrid approach provides slightly better results and thus appears as potentially fruitful. In a more non-linear regime, when Tropical Instability Waves develop, the global nature of the variational approach helps control model dynamics better than the sequential approach of the SEEK filter. This aspect is probably enhanced by the context of the experiments in that there is a limited amount of assimilated data and no model error.
Reduced-order 4D-Var: a preconditioner for the Incremental 4D-Var data assimilation method
Céline Robert,Eric Blayo,Jacques Verron
Physics , 2007,
Abstract: This study demonstrates how the incremental 4D-Var data assimilation method can be applied efficiently preconditione d in an application to an oceanographic problem. The approach consists in performing a few iterations of the reduced-order 4D-Var prior to the incremental 4D-Var in the full space in order to achieve faster convergence. An application performed in the tropical Pacific Ocean, with assimilation of TAO temperature data, shows the method to be both feasible and efficient. It allows the global cost of the assimilation to be reduced by a factor of 2 without affecting the quality of the solution.
Inter-Brain Synchronization during Social Interaction
Guillaume Dumas,Jacqueline Nadel,Robert Soussignan,Jacques Martinerie,Line Garnero
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0012166
Abstract: During social interaction, both participants are continuously active, each modifying their own actions in response to the continuously changing actions of the partner. This continuous mutual adaptation results in interactional synchrony to which both members contribute. Freely exchanging the role of imitator and model is a well-framed example of interactional synchrony resulting from a mutual behavioral negotiation. How the participants' brain activity underlies this process is currently a question that hyperscanning recordings allow us to explore. In particular, it remains largely unknown to what extent oscillatory synchronization could emerge between two brains during social interaction. To explore this issue, 18 participants paired as 9 dyads were recorded with dual-video and dual-EEG setups while they were engaged in spontaneous imitation of hand movements. We measured interactional synchrony and the turn-taking between model and imitator. We discovered by the use of nonlinear techniques that states of interactional synchrony correlate with the emergence of an interbrain synchronizing network in the alpha-mu band between the right centroparietal regions. These regions have been suggested to play a pivotal role in social interaction. Here, they acted symmetrically as key functional hubs in the interindividual brainweb. Additionally, neural synchronization became asymmetrical in the higher frequency bands possibly reflecting a top-down modulation of the roles of model and imitator in the ongoing interaction.
Allotment of aircraft spare parts using genetic alorithms
Batchoun, Pascale;Ferland, Jacques A.;Cléroux, Robert;
Pesquisa Operacional , 2003, DOI: 10.1590/S0101-74382003000100011
Abstract: in this paper we attempt to determine the optimal allocation of aircraft parts used as spares for replacement of defective parts on-board of a departing flight. in order to minimize the cost of delay caused by unexpected failure, genetic algorithms (gas) are used to allocate the initial quantity of parts among the airports. gas are a class of adaptive search procedures, that distinguish themselves from other optimization techniques by the use of concepts from population genetics to guide the search. problem-specific knowledge is incorporated into the problem and efficient parameters are identified and tested for the task of optimizing the allocation of parts. the approach is illustrated by numerical results.
Silva, Simone Helena da;Vieira, Enio Cardillo;Nicoli, Jacques Robert;
Revista de Microbiologia , 1998, DOI: 10.1590/S0001-37141998000300016
Abstract: in an ex vivo agar plate assay, we monitored the appearance of an inhibitory halo against vibrio cholerae from the feces of wistar and fischer rats aged 10 to 42 days. the frequency of wistar rats showing halo increased from 0% (10 days) to a maximum of 80.0% (29 days) and then decreased to 53.3% (42 days). a similar pattern was obtained with fischer rats but with a lower intensity (maximum frequency of 50.0% by day 36). in a separate experiment, when wistar rats were fed a low-protein diet for 7 days, the inhibitory halo decreased drastically. three apparently different colony morphologies were isolated from the dominant fecal microbiota: a facultative anaerobe (fan) and two strict anaerobes (san). the ex vivo inhibitory test showed a halo around the feces of germfree mice monoassociated with the fan bacterium or one of the san bacterium but not of the germfree ones. after oral challenge of all groups with v. cholerae, a permissive and a drastic barrier effects were observed in mice with fan and san associated bacteria, respectively. the fan and one san bacteria used in the in vivo challenges were identified as escherichia coli and streptococcus intermedius, respectively. the potent antagonism developed by the rat intestinal microbiota against v. cholerae seems to be due, in part, to diffusible compounds and this phenomenon depends apparently on age, strain and nutrition of the animals. these preliminary results also suggest that this effect was due to more than one bacterial component at any given moment.
Lipid Replacement Therapy Functional Food Formulation with NT Factor for Reducing Weight, Girth, Body Mass, Appetite and Fatigue While Improving Blood Lipid Profiles
Rita R. Ellithorpe,Robert Settineri,Brett Jacques,Cyndee A. Mitchell
Functional Foods in Health and Disease , 2012,
Abstract: Background: Lipid Replacement Therapy using NT Factor plus kidney bean alpha-amylase inhibitor (Healthy Curb ) was used in a two month weight loss clinical trial to reduce weight and improve fatigue without changing easting or exercise patterns and without use of drugs, stimulants or herbs. Objectives: To determine the effects of an all-natural functional food, NT Factor plus alpha-amylase inhibitor (Healthy Curb ), on weight loss, body girth, body mass and index, basal metabolic rate, appetite, carvings for sweets and fatigue as well as blood lipid profiles during a 2-month open label clinical trial without food restrictions or increases in physical activity.Methods: Thirty subjects (Mean Age = 56.8 ± 1.8; 24 females and 6 males) used the functional food containing NT Factor (500 mg) and alpha-amylase inhibitor (500 mg) 30 min before each meal in tablet form. Participants were told to eat and exercise normally. Weight, waist and hip measurements were taken weekly. Appetite and sweet cravings were assessed weekly by standard methods. Fatigue was determined using the Piper Fatigue Scale. Blood samples were taken prior to and at the end of the trial for lipid and chemical analyses. Results: Sixty-three percent of the participants lost an average of 6.11 ± 0.28 pounds (2.77 ± 0.12 Kg) (p<0.001) along with average reductions of 2.51 ± 0.05 inches (6.4 ± 0.13 cm) (p<0.0001) and 1.5 ± 0.04 inches (3.8 ± 0.10 cm) (p<0.0001) from waist and hip circumferences, respectively. The entire Functional Foods in Health and Disease 2012, 2(1):11-24 group lost an average of 3.63 ± 0.13 pounds (1.65 ± 0.11 Kg) (p<0.001) with average reductions of 1.59 ± 0.03 inches (4.04 ± 0.06 cm) (p<0.0001) and 1.13 ± 0.02 inch (2.87 ± 0.05 cm) (p<0.0001) from waist and hip circumferences, respectively. Weight loss and body measurement decreases were gradual, consistent and significant, along with reductions in body mass index (BMI) and basal metabolic rate (BMR) measurements. Overall hunger was reduced 44.5% (p<0.001), with reduced cravings for sweets and fats, and there was a 23.9% reduction in fatigue (p<0.009). Along with fatigue reduction there was a 26.8% perceived improvement (p<0.004) in cognition and ability to concentrate, remember and think clearly. Blood lipid profiles at the end of the trial suggested improved cardiovascular lipid profiles, and there were no adverse events from the product.Conclusions: The participants lost weight, showed significant decreases in waist and hip measurements and had reduced average overall body mass. Their fatigue was significantly reduced,
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