Impact of kinetic isotope effects in isotopic studies of metabolic systems

Background: Isotope labeling experiments (ILEs) are increasingly used to investigate the functioning of metabolic systems. Some enzymes are subject to kinetic isotope effects (KIEs) which modulate reaction rates depending on the isotopic composition of their substrate(s). KIEs may therefore affect both the propagation of isotopes through metabolic networks and their operation, and ultimately jeopardize the biological value of ILEs. However, the actual impact of KIEs on metabolism has never been investigated at the system level. Results: First, we developed a framework which integrates KIEs into kinetic and isotopic models of metabolism, thereby accounting for their system-wide effects on metabolite concentrations, metabolic fluxes, and isotopic patterns. Then, we applied this framework to assess the impact of KIEs on the central carbon metabolism of Escherichia coli in the context of C-13-ILEs, under different situations commonly encountered in laboratories. Results showed that the impact of KIEs strongly depends on the label input and on the variable considered but is significantly lower than expected intuitively from measurements on isolated enzymes. The global robustness of both the metabolic operation and isotopic patterns largely emerge from intrinsic properties of metabolic networks, such as the distribution of control across the network and bidirectional isotope exchange. Conclusions: These results demonstrate the necessity of investigating the impact of KIEs at the level of the entire system, contradict previous hypotheses that KIEs would have a strong effect on isotopic distributions and on flux determination, and strengthen the biological value of C-13-ILEs. The proposed modeling framework is generic and can be used to investigate the impact of all the isotopic tracers (H-2, C-13, N-15, O-18, etc.) on different isotopic datasets and metabolic systems. By allowing the integration of isotopic and metabolomics data collected under stationary and/or non-stationary conditions, it may also assist interpretations of ILEs and facilitate the development of more accurate kinetic models with improved explicative and predictive capabilities

Cloning, expression pattern and heterologous expression of recombinant glycoprotein hormone subunits-related molecules GPA2 and GPB5 from rat, bovine and amphioxus

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In-cell NMR: from metabolites to macromolecules

In-cell NMR of macromolecules has gained momentum over the last ten years as an approach that might bridge the branches of cell biology and structural biology. In this review, we put it in the context of earlier efforts that aimed to characterize by NMR the cellular environment of live cells and their intracellular metabolites. Although technical aspects distinguish these earlier in vivo NMR studies and the more recent in cell NMR efforts to characterize macromolecules in a cellular environment, we believe that both share major concerns ranging from sensitivity and line broadening to cell viability. Approaches to overcome the limitations in one subfield thereby can serve the other one and vice versa. The relevance in biomedical sciences might stretch from the direct following of drug metabolism in the cell to the observation of target binding, and thereby encompasses in-cell NMR both of metabolites and macromolecules. We underline the efforts of the field to move to novel biological insights by some selected examples

Portage des médicaments rétrocédés au domicile du patient : intérêts, limites et perspectives?

National audienceIntroduction. Le portage des médicaments au domicile du patient est une pratique dérogatoire que l'on voit se développer dans le contexte de la rétrocession hospitalière. Il est actuellement mis en œuvre à l'initiative soit de prestataires de santé à domicile (PSAD), soit de laboratoires commercialisant des spécialités pharmaceutiques particulièrement onéreuses. Dans le premier cas, la société effectuant la prestation définie dans le cadre de la liste des produits et prestations remboursables (LPPR) assure à sa charge le transport du médicament au domicile du patient. Dans le deuxième cas, le laboratoire pharmaceutique finance cette prestation par le biais d'un tiers effectuant le transport. Ces offres de service proposées au médecin et au patient sont mises en œuvre sous réserve de l'accord du pharmacien hospitalier qui engage sa responsabilité. Objectif. Nous présentons ici la réflexion menée, d'une part, sur les conditions de mise en œuvre du portage, d'autre part, sur ses alternatives envisageables pour l'amélioration de l'accessibilité au médicament rétrocédé. Discussion. Après l'exposé du contexte réglementaire et l'illustration du propos par quelques exemples observés dans le cadre de la rétrocession hospitalière, les auteurs discuteront de l'intérêt de cette offre de service pour les différents acteurs, de ses limites et conséquences éventuelles sur l'organisation des soins, et enfin des perspectives d'évolution. Conclusion. Une réflexion doit être menée, d'une part, sur les conditions de mise en oeuvre du portage, d'autre part, sur ses alternatives envisageables pour l'amélioration de l'accessibilité au médicament rétrocédé

The role of testicular fluid on blood plasma levels of FSH and LH in the ram (1)

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AGATA: mechanics and infrastructures

The successful operation of AGATA requires a complex mechanical support structure for the safe and reliable operation of the detectors. Three mechanical structures were designed for the scientific campaigns at LNL, GSI and GANIL, each accommodating an increasing number of detectors. The present phase of the project, to increase the number of detectors from 60 to 180 (the $$4\pi$$ spectrometer), required a new concept in mechanical support. The detectors also require a suite of associated instrumentation, infrastructures and good system design for their optimum performance. This includes the automatic liquid nitrogen filling system, high and low voltage power supplies, and a series of signal cables and distribution systems. A well-designed electromagnetic compatibility across all the sub-systems is essential. An additional requirement is an easily accessible database that records the status of the wide range of components utilised on the project. This article describes all aspects of the mechanics and infrastructures