A Model of the Roles of Essential Kinases in the Induction and Expression of Late Long-Term Potentiation

The induction of late long-term potentiation (L-LTP) involves complex interactions among second messenger cascades. To gain insights into these interactions, a mathematical model was developed for L-LTP induction in the CA1 region of the hippocampus. The differential equation-based model represents actions of protein kinase A (PKA), MAP kinase (MAPK), and CaM kinase II (CAMKII) in the vicinity of the synapse, and activation of transcription by CaM kinase IV (CAMKIV) and MAPK. L-LTP is represented by increases in a synaptic weight. Simulations suggest that steep, supralinear stimulus-response relationships between stimuli (elevations in [Ca2+]) and kinase activation are essential for translating brief stimuli into long-lasting gene activation and synaptic weight increases. Convergence of multiple kinase activities to induce L-LTP helps to generate a threshold whereby the amount of L-LTP varies steeply with the number of tetanic electrical stimuli. The model simulates tetanic, theta-burst, pairing-induced, and chemical L-LTP, as well as L-LTP due to synaptic tagging. The model also simulates inhibition of L-LTP by inhibition of MAPK, CAMKII, PKA, or CAMKIV. The model predicts results of experiments to delineate mechanisms underlying L-LTP induction and expression. For example, the cAMP antagonist RpcAMPs, which inhibits L-LTP induction, is predicted to inhibit ERK activation. The model also appears useful to clarify similarities and differences between hippocampal L-LTP and long-term synaptic strengthening in other systems.Comment: Accepted to Biophysical Journal. Single PDF, 7 figs include

Chaperones convert the energy from ATP into the nonequilibrium stabilization of native proteins.

During and after protein translation, molecular chaperones require ATP hydrolysis to favor the native folding of their substrates and, under stress, to avoid aggregation and revert misfolding. Why do some chaperones need ATP, and what are the consequences of the energy contributed by the ATPase cycle? Here, we used biochemical assays and physical modeling to show that the bacterial chaperones GroEL (Hsp60) and DnaK (Hsp70) both use part of the energy from ATP hydrolysis to restore the native state of their substrates, even under denaturing conditions in which the native state is thermodynamically unstable. Consistently with thermodynamics, upon exhaustion of ATP, the metastable native chaperone products spontaneously revert to their equilibrium non-native states. In the presence of ATPase chaperones, some proteins may thus behave as open ATP-driven, nonequilibrium systems whose fate is only partially determined by equilibrium thermodynamics

Estimation de la contamination du milieu aquatique par les composés organo-halogénés (AOX et EOX) : application à l'étude d'accumulation et de relargage des EOX par Anodonta cygnea L., exposé in situ aux effluents d'une usine de pâte à papier

Halogenated organic are more widespread in the environment than previously assumed, and originated either from natural and antropogenic sources. The use of the sum parameters aox (adsorbable organic halogens) and eox (extractable organic halogens), allows to palliate the analytical problems of individual identification of those compounds, among which a great majority is still unknown, and enables also their quantification in the different compartments of the aquatic environment : water, sediments and organisms. The study of four water courses has permitted to bring to the fore, and to confirm, the existence of several sources of organic halogenated compounds in the water and the sediments of North-eastern France. Among them, a chlorine bleaching pulp and paper mill is distinguished, and characterised by chronic emissions and high aox concentration in the water and the sediments of the receiving medium. In order the account the effects of such effluents on organisms, and to quantify the bioavailable fraction of micropolluants, four species of aquatic molluscs, Anodonta cygnea L. (bivalve unionidae), unio pictorum L. (bivalve unionidae), Dreissena polymorpha P. (bivalve dreissenidae) et Viviparus viviparus L. (gastropod viviparidae), were transferred and exposed up and down stream of the mill. The swan mussel, Anodonta cygnea L., has been retained as biological indicator for several reasons : its good resistance to the effluents ; its large size allowing studies on individual organisms and organs ; its high accumulation rate of halogenated organics. The accumulation and the release of these micropollutants by the mussel differ according to the considered organ, and depend on the physico-chemical characteristics of the organic halogenated compounds present in the effluentLes composés organo-halogènes sont, contrairement à ce que l'on a souvent pensé, ubiquistes dans l'environnement, et leurs origines diverses sont aussi bien naturelles qu'anthropiques. L'utilisation des paramètres de groupe aox (composés organo-halogènes adsorbables) et eox (composés organo-halogènes extractibles) permet de palier les problèmes analytiques de l'identification individuelle de ces composés, dont une grande majorité reste inconnue de nos jours, et de les quantifier dans les différents compartiments de l'écosystème aquatique : eau, sédiments et organismes. L'étude de quatre cours d'eau a permis de mettre en évidence et de confirmer l'existence de multiples sources de composés organo-halogènes dans l'eau et les sédiments du nord-est de la France. Parmi celles-ci, une usine de pâte à papier blanchissant au chlore se distingue des autres, et se caractérise par des rejets chroniques et des concentrations élevées en aox dans l'eau et les sédiments du milieu récepteur. Afin de rendre compte des effets de tels effluents sur les organismes, et de quantifier la fraction de micropolluants biodisponibles, quatre espèces de mollusques aquatiques, anodonta cygnea l. (bivalve unionidae), unio pictorum l. (bivalve unionidae), dreissena polymorpha p. (bivalve dreissenidae) et viviparus viviparus l. (gasteropode viviparidae) ont été transférés et exposés en amont et en aval des rejets de l'usine. L'anodonte, anodonta cygnea l., a été retenu comme indicateur biologique pour plusieurs raisons : sa bonne résistance aux effluents ; sa taille suffisamment grande pour permettre l'étude sur des organismes individuels et des organes ; son taux élevé d'accumulation de composés organo-halogènes. L'accumulation et le relargage de ces micropolluants par l'anodonte se font de manière différente selon les organes considérés, et dépendent des propriétés physico-chimiques des composes organo-halogènes présents dans l'effluen

Using life cycle analysis to analyse the environmental performances of organic and non-organic apple orchards

Although the conventional farming system (CV) for apple production remains the common practice worldwide, the organic farming system (OF) is becoming increasingly important. Few global assessments of the environmental impacts of organic orchard systems are currently available. In this work, we analyse the weak and strong points of the environmental performance of the growing phase of two organic and one conventional apple orchard, using a pluri-annual dataset from experimental orchard systems located in the Middle Rhone valley in France, with life cycle analysis (LCA). LCA, also referred to as cradle-to-grave analysis, allows a quantitative and global evaluation of an orchard’s environmental performance. The analysis was performed using the SALCA (Swiss Agricultural Life Cycle Assessment) method (SALCA-Crop V3.1, adapted for pome fruit) and included relevant impact categories based on characterisation models derived mainly from the EDIP97 and CML01 methods, as well as those developed by Agroscope (ART). Seven impact categories that included ecotoxicity and human toxicity, as well as energy consumption and other environmental impact categories, were calculated and are discussed here. The OF systems appeared to have less of an impact than the conventional system, considering the surface-based functional unit (ha/year). However, the basic substitution of conventional with organic inputs or mechanised activities was not sufficient to radically improve the overall environmental performance of the orchard systems. These results need several years of full production to be validated

Using life cycle analysis to analyse the environmental performances of organic and non-organic apple orchards

Although the conventional farming system (CV) for apple production remains the common practice worldwide, the organic farming system (OF) is becoming increasingly important. Few global assessments of the environmental impacts of organic orchard systems are currently available. In this work, we analyse the weak and strong points of the environmental performance of the growing phase of two organic and one conventional apple orchard, using a pluri-annual dataset from experimental orchard systems located in the Middle Rhone valley in France, with life cycle analysis (LCA). LCA, also referred to as cradle-to-grave analysis, allows a quantitative and global evaluation of an orchard’s environmental performance. The analysis was performed using the SALCA (Swiss Agricultural Life Cycle Assessment) method (SALCA-Crop V3.1, adapted for pome fruit) and included relevant impact categories based on characterisation models derived mainly from the EDIP97 and CML01 methods, as well as those developed by Agroscope (ART). Seven impact categories that included ecotoxicity and human toxicity, as well as energy consumption and other environmental impact categories, were calculated and are discussed here. The OF systems appeared to have less of an impact than the conventional system, considering the surface-based functional unit (ha/year). However, the basic substitution of conventional with organic inputs or mechanised activities was not sufficient to radically improve the overall environmental performance of the orchard systems. These results need several years of full production to be validated