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Rennes, France

Pierre J.-S.,French National Center for Scientific Research | Masson J.-P.,Agrocampus Rennes | Wajnberg E.,French National Institute for Agricultural Research
Journal of Theoretical Biology | Year: 2012

A famous motivational model proposed for insect parasitoids by Waage (1979) provides a candidate mechanism for patch-leaving decision rules in foragers. In this model, the animal is supposed to enter a patch of resources with an initial tendency to stay in it, which then regularly decreases. Every encounter with a resource item increases or decreases this tendency, and the forager is supposed to leave the patch when this tendency or motivation falls below a given threshold. Evidence of such increases and drops in this tendency to stay were often obtained by analyzing experimental data with a Cox (1972) proportional hazards model. The Waage (1979) model is purely deterministic and predicts a fixed departure time for a fixed set of encounters with foraging items. On the other hand, empirical data show a large variability of departure times under fixed conditions. We present a fully stochastic version which overcomes this problem and gives a quasi close form expression for the distribution of patch residence times as well as a statistical procedure to estimate its parameters. Two examples of the model fitting on experimental data sets are provided. This novel model, although more complicated than Waage (1979) model, improves its realism and provides a stochastic interpretation of motivation as a proximal mechanism leading foragers to optimality. © 2012 Elsevier Ltd. Source


Kostov B.,Transverse Group for Research in Primary Care | Kostov B.,Polytechnic University of Catalonia | Becue-Bertaut M.,Polytechnic University of Catalonia | Husson F.,Agrocampus Rennes
Food Quality and Preference | Year: 2014

In sensory analysis, results from word-count based methods are customary analyzed through correspondence analysis applied to the global table products. ×. words summing the citations of a same word given by all the panelists. This approach assumes that a same word mentioned by different panelists corresponds to a similar perception, which is not always verified. To solve this problem, we propose a new methodology based on multiple factor analysis for contingency tables. This methodology offers a mean configuration of the products taking into account all the individual words but spots these that are consensual to ease the interpretation. The consensual words have the same meaning for most of the consumers as far as they describe the same products. A test, based on resampling techniques, allows for assessing the significance of the consensus. A real example shows how this methodology eases the interpretation of the word-count based methods by solving problems arising from the large diversity of vocabulary and the different meanings possibly associated to a same word. © 2013 Elsevier Ltd. Source


Hibert F.,CIRAD - Agricultural Research for Development | Calenge C.,Office National de la Chasse et de la Faune Sauvage | Calenge C.,CNRS Biometry and Evolutionary Biology Laboratory | Fritz H.,CNRS Biometry and Evolutionary Biology Laboratory | And 6 more authors.
Biodiversity and Conservation | Year: 2010

Traditional rangelands in many developing countries are currently being encroached by cultivation, driving some herders to illegally use protected areas for grazing their cattle. Since cattle are an exotic species in these ecosystems, they might have an impact on the local wild herbivore communities, notably through competition. We used point pattern statistics to characterise the spatial relationships between wild ungulate species and cattle herds within a protected area in west Africa undergoing seasonal intrusions by cattle. We predicted that the wild ungulate species that are ecologically and morphologically similar to cattle, in terms of body mass and diet, would be more sensitive to grass depletion by cattle and would be separated from cattle to a larger extent. The spatial distribution of browsing and mixed-feeding antelopes did not seem to be affected much by cattle presence, whereas most grazing species showed spatial separation from cattle. Interestingly, elephants also showed significant separation from cattle herds. We discuss the likely processes that may have contributed to the observed spatial patterns. The spatial displacement of certain wild species, including megaherbivores, affects the whole community structure and, thus, other components of the ecosystem. © 2010 Springer Science+Business Media B.V. Source


Patras A.,Teagasc | Brunton N.P.,Teagasc | Downey G.,Teagasc | Rawson A.,Teagasc | And 2 more authors.
Journal of Food Composition and Analysis | Year: 2011

The purpose of this study was to gain insights into the variations in antioxidant profiles between fruits and vegetables using pattern recognition tools; classification was achieved based on global antioxidant activity, levels of antioxidant groups (total phenolics, total anthocyanins, ascorbic acid) and quality parameters (instrumental colour, moisture). Six vegetables (broccoli, carrot [organic and intensively grown], butterhead lettuce, red onion, yellow onion) and eight fruits (blueberries, cherry tomato, cranberries, red grapes, green pepper, raspberry, red pepper and strawberry) commonly consumed in Ireland were analysed. Antioxidant activity (ARP) and concentrations of bioactive compound groups differed according to sample type. Berry fruits had the highest antioxidant activity (1.51-2.97(g/L) -1). By contrast, vegetables were quite low in antioxidant activity (0.14-0.39(g/L) -1). Interrelationships between the parameters analysed and the different fruits and vegetables were investigated by principal component analysis (PCA) and hierarchical cluster analysis (HCA). PCA revealed that the first two components represented 62% of the total variability in antioxidant activity and different antioxidant groups. HCA classified samples into four main groups on the basis of the measured parameters. © 2010 Elsevier Inc. Source


Sirotkin A.V.,Animal Production Research Center | Sirotkin A.V.,Constantine the Philosopher University | Laukova M.,Slovak Academy of Sciences | Ovcharenko D.,Altogen Biosystems | And 2 more authors.
Journal of Cellular Physiology | Year: 2010

Previous studies have shown that microRNAs (miRNAs) can control steroidogenesis in cultured granulosa cells. In this study we wanted to determine if miRNAs can also affect proliferation and apoptosis in human ovarian cells. The effect of transfection of cultured primary ovarian granulosa cells with 80 different constructs encoding human pre-miRNAs on the expression of the proliferation marker, PCNA, and the apoptosis marker, Bax was evaluated by immunocytochemistry. Eleven out of 80 tested miRNA constructs resulted in stimulation, and 53 miRNAs inhibited expression of PCNA. Furthermore, 11 of the 80 miRNAs tested promoted accumulation of Bax, while 46 miRNAs caused a reduction in Bax in human ovarian cells. In addition, two selected antisense constructs that block the corresponding miRNAs mir-15a and mir-188 were evaluated for their effects on expression of PCNA. An antisense construct inhibiting mir-15a (which precursor suppressed PCNA) increased PCNA, whereas an antisense construct for mir-188 (which precursor did not change PCNA) did not affect PCNA expression. Verification of effects of selected pre-mir-10a, mir-105, and mir-182 by using other markers of proliferation (cyclin B1) and apoptosis (TdT and caspase 3) confirmed specificity of miRNAs effects on these processes. This is the first direct demonstration of the involvement of miRNAs in controlling both proliferation and apoptosis by ovarian granulose cells, as well as the identification of miRNAs promoting and suppressing these processes utilizing a genome-wide miRNA screen. © 2009 Wiley-Liss, Inc. Source

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