Le rôle écologique des bonobos (service écologique de dispersion de graine en forêt du Congo)

Les bonobos (Pan paniscus) sont menacés d extinction. Ils sont les plus grands primates et les seuls grands singes de la rive sud du bassin du Congo. Ils sont nos plus proches parents avec les chimpanzés et sont étudiés dans l urgence par les anthropologues pour comprendre nos origines Hominidé. Mais qu en est-il de leur rôle fonctionnel dans la forêt ? Leur disparition aurait-elle des conséquences graves sur l écologie forestière ? Telles sont les questions de ce projet inédit, dont les réponses sont apportées par plusieurs années d observations d un groupe en liberté habitué au site de recherche LuiKotale (RD Congo). Dans cette forêt tropicale humide, la très grande majorité des plantes a besoin des animaux pour se reproduire et disperser leurs graines. Les bonobos sont les plus grands frugivores après les éléphants. Au cours de sa vie, chaque bonobo ingèrera et dispersera 9 tonnes de graines, de plus de 91 espèces de lianes, herbes, arbres et arbustes. Ces graines voyageront 24 heures dans le tube digestif des bonobos, qui les transporteront sur plusieurs kilomètres ( 1.3km; max : 4.5 km), loin de leur plante mère, où ils seront déposées intactes dans leurs fèces. Ces graines dispersées restent viables, germent mieux et plus rapidement que les graines non passées par le tube digestif d un bonobo. La diplochorie, impliquant les bousiers (Scarabaeidae), favorise leur survie post dispersion. Certaines plantes comme les Dialium pourraient même être dépendants du bonobo pour activer la germination de leurs graines en dormance tégumentaire. Les premiers paramètres de l efficacité des bonobos comme disperseurs de graines sont présents. Leurs comportements pourraient affecter la structure des populations végétales. La majorité de ces plantes zoochores ne peuvent recruter sans dispersion et la structure spatiale homogène des arbres laisse penser à un lien direct avec leur agent de dispersion. Peu d espèces remplaceraient les bonobos en terme de leur rôle fonctionnel, tout comme les bonobos ne remplacent pas les éléphants. Il y a peu de redondance fonctionnelle entre les mammifères frugivores très différents du Congo, qui doivent faire face aux pressions de chasse des hommes et disparaissent localement. La défaunation des forêts, résultant dans le syndrome des forêts vides, est un problème grave de biologie de la conservation illustré ici. La disparition des bonobos qui dispersent les graines de 65% des arbres de leur forêt, ou encore 11.6 millions de graines au cours de la vie d un bonobo, est liée à la conservation des forêts tropicales humides du CongoBonobos (Pan paniscus) are threatened with extinction. They are the largest primates, and the only apes (except human), of the southern bank of the Congo Basin. Along with chimpanzees, they are our closest living relatives and are studied by anthropologists to include/understand our hominid origins; but what about their functional role in the forest? Would their disappearance have serious consequences for forest ecology? Answering this question is the aim of this new project, with several years of observations of a free-ranging habituated group of bonobos on the LuiKotale research station (DR Congo). In this tropical rainforest, the very great majority of plants need animals to reproduce and disperse their seeds. Bonobos are the largest frugivorous animals in this region, after elephants. During its life, each bonobo will ingest and disperse nine tons of seeds, from more than 91 species of lianas, grass, trees and shrubs. These seeds will travel 24 hours in the bonobo digestive tract, which will transfer them over several kilometers (mean 1.3 km; max: 4.5 km), far from their parents, where they will be deposited intact in their feces. These dispersed seeds remain viable, germinate better and more quickly than unpassed seeds. For those seeds, diplochory with dung-beetles (Scarabaeidae) imrpoves post-dispersal survival. Certain plants such as Dialium may even be dependent on bonobos to activate the germination of their seeds, characterized by tegumentary dormancy. The first parameters of the effectiveness of seed dispersal by bonobos are present. Behavior of the bonobo could affect the population structure of plants whose seeds they disperse. The majority of these zoochorous plants cannot recruit without dispersal and the homogeneous spatial structure of the trees suggests a direct link with their dispersal agent. Few species could replace bonobos in terms of seed dispersal services, just as bonobos could not replace elephants. There is little functional redundancy between frugivorous mammals of the Congo, which face severe human hunting pressures and local exctinction. The defaunation of the forests, leading to the empty forest syndrome, is critical in conservation biology, as will be illustrated here. The disappearance of the bonobos, which disperse seeds of 65% of the tree species in these forests, or 11.6 million individual seeds during the life of each bonobo, will have consequences for the conservation of the Congo rainforestDIJON-BU Doc.électronique (212319901) / SudocSudocFranceF

Citrulline increases arginine pools and restores nitrogen balance after massive intestinal resection

Objective: Arginine supplementation seems logical in situations where this amino acid becomes essential, for example after massive intestinal resection. Arginine is taken up and metabolised by the liver to a large extent and its supplementation is potentially unsafe. Citrulline is not captured by the liver and passes freely to the kidneys where it is metabolised to arginine, and so is a good candidate to generate arginine and thereby improve nutritional status. Methods: Twenty four rats were assigned to four groups: citrulline, arginine, control, and sham. The sham group underwent transection and the three other groups resection of 80% of the small intestine. All rats were fed by enteral nutrition and its composition was as follows: supplementation with citrulline in the citrulline group, supplementation with arginine in the arginine group, and standard polymeric enteral nutrition in the control and sham groups. All groups received isonitrogenous nutrition and citrulline and arginine intakes were equimolar in their respective groups. After 10 days, the rats were sacrificed. Results: Arginine concentration was higher (p<0.05) in plasma and muscle in the citrulline group than in the three other groups. Plasma levels of arginine were 110 (12), 79 (7), 167 (22), and 228 (13) μmol/l in the sham, control, arginine, and citrulline groups respectively. Arginine concentrations in the gastrocnemius were: 0.15 (0.02), 0.16 (0.02), 0.40 (0.05), and 0.94 (0.20) μmol/g, respectively. Citrulline preserved nitrogen balance in resected rats but not in arginine supplemented rats (mean J10: 2.27 (0.29), 1.67 (0.15), 1.98 (0.29), and 2.43 (0.41) g/24 hours in the sham, control, arginine, and citrulline groups, respectively). Conclusion: Supplementing the diet with citrulline is a very efficient means of increasing arginine levels and improving nitrogen balance after massive intestinal resection. The results of this study form a strong rationale for citrulline supplementation in these patients

Mechanical Characterization of the Soft Tissues of a Native Human Knee: A Pilot Study

Abstract: The importance of ligaments in providing joint stability and the incidence of injuries, dictates a need to increase their structural and mechanical properties understanding. Additionally, one of the challenges in the orthopedic industry is to design TKA (total knee arthroplasty) aiming to be soft-tissues friendly. This requires a priori knowledge of physiological knee function, in which the passive stability is achieved and guaranteed by the complex envelope of soft tissues around the joint. Therefore, the knowledge of the mechanical behavior of knee ligaments is fundamental. For this reason, our study aims to define and apply in a pilot study, an ad-hoc methodology to mechanically characterize ligaments of native human knees. The cruciate and collateral ligaments from a fresh frozen cadaver leg were accurately harvested. Each ligament was independently tested during a tensile test at different strain rates, simulating different deformation speeds during gait. Moreover, additional tensile tests until failure were also performed. Axial force and deformation were continuously recorded during each test. Results show that each ligament exhibited own typical non-linear, speed-related behavior. High repeatability in the results is observed among the different repeated tests confirming the robustness of the used methodology. This information will be helpful for clinicians, engineers and researchers to improve the biomechanical knowledge about knee, to develop better implants and to be able to improve the currently available numerical models of the human knee

Development of interferometric techniques for nuclei size measurement in cavitation tunnel

International audienceThe knowledge of the nuclei content is essential in naval hydrodynamics for cavitation inception prediction on propellers and hydrofoils. As a matter of fact, tip vortex cavitation which is, generally, the first cavitation to occur on foils or propellers, is very sensitive to the nuclei content. Typically, the nuclei we are looking at, are tiny bubbles which sizes range from 1µm up to 100µm.Two different types of techniques are generally used: optical techniques that measure the nuclei size and Venturi techniques which measure the critical pressure of the nuclei.We present here developments of two new optical techniques: the digital in-line holography technique and the Interferometric Laser Imaging Technique based on the PIV optical arrangement. Both techniques have been implemented in the French Large Cavitation Tunnel so called GTH and comparative measurements have been done with CSM technique