par Thomas, René 
;Thieffry, Denis
Référence MS. Médecine sciences, 11, 2, page (189-197)
Publication Publié, 1995
;Thieffry, Denis Référence MS. Médecine sciences, 11, 2, page (189-197)
Publication Publié, 1995
Article révisé par les pairs
| Résumé : | Organized systems such as living organisms or cells require that the level of crucial elements somehow be evaluated and taken into account to determine their future rate of production. This regulation is effected by feedback loops, which are oriented circuits of interactions. There are two types of feedback loops, negative and positive, depending on the parity of the number of negative interactions. Their role are radically different: negative loops promote homeostasis while positive loops permit multistationarity, with its biological modality, differentiation. Appropriate combinations of positive and negative feedback loops may generate extremely complex behaviour. Real regulatory systems usually comprise several feedback loops which may be intertwined in complex ways. A major aspect of our work has been the development of methods which permit to derive the dynamics of such complex networks from their structure. Recent progress has shown that a networks can be treated (without loss of rigor) as the set of its interacting loops rather than as the set of all its interacting elements. This is somewhat like considering the wheels of a clock rather than the individual teeth which compose the wheels. This approach is illustrated by various concrete biological examples. |
