Search results for "Sénescence"
showing 4 items of 4 documents
Grain legume seed filling in relation to nitrogen acquisition: A review and prospects with particular reference to pea
2001
International audience; Seed filling depends not only on the instantaneous supply of C and N, but also on their remobilisation from vegetative organs. C supply during seed filling depends mostly on current photosynthesis, but N assimilation and N$_2$ fixation decline during seed filling, with newly acquired N generally insufficient for the high seed demand. As seeds are strong sinks for mobilised nutrients, seed growth becomes metabolically closely associated with N remobilisation. N remobilisation from vegetative tissues to filling seeds interacts with photosynthesis since it induces senescence, which reduces the seed filling period. Hence improved grain legume seed filling requires either…
Senescence and longevity : from physiological mechanisms to evolutionary processes : studies in birds and mammals
2012
There is an incredible diversity of lifespan in the animal kingdom ranging from a few days for small gastrotrichs worms to several hundred of years for some bivalves or tortoises. This amazing diversity has long questioned biology researchers. The growing interest in the phenomenon of aging, mainly due to the increase in life expectancy in humans, has questioned researchers on processes that determine patterns of longevity and ageing. On the one hand, biomedical and biogerontological studies helped describe numerous cellular and physiological mechanisms related to aging. Among these mechanisms, oxidative stress has been identified as playing a major role, through life-time accumulation of d…
insecte senescence : interactions between survival, reproduction and immunity
2020
Senescence is an almost universal process in multi-cellular organisms corresponding to an age-dependent decline of reproductive, immune and survival performance. Among the theories explaining such a phenomenon, the disposable soma theory of ageing proposes that senescence is caused by a resource allocation trade-off between reproduction and somatic maintenance. Hence, high early-life allocation to reproduction should be achieved at the expense somatic defences, including immunity, which would increase reproductive and actuarial senescence.This thesis studied the relationships between reproduction, immunity and senescence in the mealworm beetle, Tenebrio molitor (Coleoptera, Tenebrionidae) b…
Etude des mécanismes d'action d'une immunothérapie par un lipide A, seul ou associé à l'oxaliplatine, dans des modèles de cancers coliques
2013
Colorectal cancer is a major public health concern in France. Resistance to standard chemotherapy requires development of novel therapeutic approaches. In the past decades, our team showed the immunotherapeutic properties of lipid A in a model of colon cancer in rats. 95% of rats bearing small carcinomas were cured following treatment by lipid A. The study of mechanisms underlying this immunotherapy allowed us to show that the antitumor effect of lipid A was dependent on cytotoxicity induced by granzyme B produced by intratumoral neutrophils. Indeed, we have shown that, in the tumor microenvironment, neutrophils produced granzyme B and had a pro-tumorigenic N2 phenotype. When rats were trea…