Espaces et sociétés : revue critique internationale de l'aménagement, de l'architecture et de l'urbanisation / dir. publ. Serge Jonas

1990 (N60)- (N61).

Espaces et sociétés : revue critique internationale de l'aménagement, de l'architecture et de l'urbanisation / dir. publ. Serge Jonas

1996 (N87).

Espaces et sociétés : revue critique internationale de l'aménagement, de l'architecture et de l'urbanisation / dir. publ. Serge Jonas

1981/01 (N36)-1981/06 (N37).

Espaces et sociétés : revue critique internationale de l'aménagement, de l'architecture et de l'urbanisation / dir. publ. Serge Jonas

1978/12 (N24)- (N27).

Espaces et sociétés : revue critique internationale de l'aménagement, de l'architecture et de l'urbanisation / dir. publ. Serge Jonas

1993 (N72).

Espaces et sociétés : revue critique internationale de l'aménagement, de l'architecture et de l'urbanisation / dir. publ. Serge Jonas

1998 (N94).

Espaces et sociétés : revue critique internationale de l'aménagement, de l'architecture et de l'urbanisation / dir. publ. Serge Jonas

1988 (N52)- (N53).

Espaces et sociétés : revue critique internationale de l'aménagement, de l'architecture et de l'urbanisation / dir. publ. Serge Jonas

1974/05 (N12).

Espaces et sociétés : revue critique internationale de l'aménagement, de l'architecture et de l'urbanisation / dir. publ. Serge Jonas

1987 (N48)- (N49).

Espaces et sociétés : revue critique internationale de l'aménagement, de l'architecture et de l'urbanisation / dir. publ. Serge Jonas

1987 (N50).

Espaces et sociétés : revue critique internationale de l'aménagement, de l'architecture et de l'urbanisation / dir. publ. Serge Jonas

1977/12 (N12)- (N23).

Identifying quantitative operation principles in metabolic pathways: a systematic method for searching feasible enzyme activity patterns leading to cellular adaptive responses

Background: Optimization methods allow designing changes in a system so that specific goals are attained. These techniques are fundamental for metabolic engineering. However, they are not directly applicable for investigating the evolution of metabolic adaptation to environmental changes. Although biological systems have evolved by natural selection and result in well-adapted systems, we can hardly expect that actual metabolic processes are at the theoretical optimum that could result from an optimization analysis. More likely, natural systems are to be found in a feasible region compatible with global physiological requirements. Results: We first present a new method for globally optimizing nonlinear models of metabolic pathways that are based on the Generalized Mass Action (GMA) representation. The optimization task is posed as a nonconvex nonlinear programming (NLP) problem that is solved by an outer- approximation algorithm. This method relies on solving iteratively reduced NLP slave subproblems and mixed-integer linear programming (MILP) master problems that provide valid upper and lower bounds, respectively, on the global solution to the original NLP. The capabilities of this method are illustrated through its application to the anaerobic fermentation pathway in Saccharomyces cerevisiae. We next introduce a method to identify the feasibility parametric regions that allow a system to meet a set of physiological constraints that can be represented in mathematical terms through algebraic equations. This technique is based on applying the outer-approximation based algorithm iteratively over a reduced search space in order to identify regions that contain feasible solutions to the problem and discard others in which no feasible solution exists. As an example, we characterize the feasible enzyme activity changes that are compatible with an appropriate adaptive response of yeast Saccharomyces cerevisiae to heat shock Conclusion: Our results show the utility of the suggested approach for investigating the evolution of adaptive responses to environmental changes. The proposed method can be used in other important applications such as the evaluation of parameter changes that are compatible with health and disease states.

Minimization of biosynthetic costs in adaptive gene expression responses of yeast to environmental changes

Yeast successfully adapts to an environmental stress by altering physiology and fine-tuning metabolism. This fine-tuning is achieved through regulation of both gene expression and protein activity, and it is shaped by various physiological requirements. Such requirements impose a sustained evolutionary pressure that ultimately selects a specific gene expression profile, generating a suitable adaptive response to each environmental change. Although some of the requirements are stress specific, it is likely that others are common to various situations. We hypothesize that an evolutionary pressure for minimizing biosynthetic costs might have left signatures in the physicochemical properties of proteins whose gene expression is fine-tuned during adaptive responses. To test this hypothesis we analyze existing yeast transcriptomic data for such responses and investigate how several properties of proteins correlate to changes in gene expression. Our results reveal signatures that are consistent with a selective pressure for economy in protein synthesis during adaptive response of yeast to various types of stress. These signatures differentiate two groups of adaptive responses with respect to how cells manage expenditure in protein biosynthesis. In one group, significant trends towards downregulation of large proteins and upregulation of small ones are observed. In the other group we find no such trends. These results are consistent with resource limitation being important in the evolution of the first group of stress responses.