Biological and radiological exploration and management of non-functioning pituitary adenoma

AbstractNon-functioning pituitary adenoma may be totally asymptomatic and discovered “incidentally” during radiological examination for some other indication, or else induce tumoral signs with compression of the optic chiasm and pituitary dysfunction. Non-functioning adenomas are mainly gonadotroph, but may also be “silent”. Treatment strategy depends on initial clinical, biological, ophthalmological and radiological findings. The present French Society of Endocrinology Consensus work-group sought to update the pitfalls associated with hormone assay and outline a hormonal exploration strategy for diagnosis and follow-up, without overlooking the particularities of silent adenoma. We also drew up basic rules for initial exploration and radiological follow-up of both operated and non-operated pituitary adenomas

A systems-wide understanding of photosynthetic acclimation in algae and higher plants

The ability of phototrophs to colonise different environments relied on the robust protection against oxidative stress in phototrophs, a critical requirement for the successful evolutionary transition from water to land. Photosynthetic organisms have developed numerous strategies to adapt their photosynthetic apparatus to changing light conditions in order to optimise their photosynthetic yield, crucial for life to exist on Earth. Photosynthetic acclimation is an excellent example of the complexity of biological systems, in which highly diverse processes, ranging from electron excitation over protein protonation to enzymatic processes coupling ion gradients with biosynthetic activity interact on drastically different timescales, ranging from picoseconds to hours. An efficient functioning of the photosynthetic apparatus and its protection is paramount for efficient downstream processes including metabolism and growth. Modern experimental techniques can be successfully integrated with theoretical and mathematical models to promote our understanding of underlying mechanisms and principles. This Review aims to provide a retrospective analysis of multidisciplinary photosynthetic acclimation research carried out by members of the Marie Curie Initial Training Project “AccliPhot”, placing the results in a wider context. The Review also highlights the applicability of photosynthetic organisms for industry, particularly with regards to the cultivation of microalgae. It aims to demonstrate how theoretical concepts can successfully complement experimental studies broadening our knowledge of common principles in acclimation processes in photosynthetic organisms, as well as in the field of applied microalgal biotechnology

Conception, mise en oeuvre et modélisation d'un photobioréacteur à membrane pour l'étude du comportement de la cyanobactérie Arthospira platensis en microgravité

CLERMONT FD-BCIU Sci.et Tech. (630142101) / SudocSudocFranceF

Analyse systémique du métabolisme carboné et énergétique de Chlamydomonas reinhardtii

La thèse porte sur le calcul des flux métaboliques de Chlamydomonas reinhardtii, la microalgue modèle, en conditions photoautotrophes dans le but de comprendre la conversion et le stockage de l'énergie. Ce travail a nécessité le développement d'outils méthodologiques incluant (i) la reconstruction d'un réseau métabolique à l'échelle du génome, nommé iAM557, comprenant 557 gènes pour 532 métabolites liés de manière stoechiométrique par 599 réactions métaboliques et (ii) la conception d'un photobioréacteur spécifique à la réalisation d'expériences de marquage au carbone 13 en régime isotopique non stationnaire. Deux approches de calcul des flux métaboliques développées, fondées soit sur une stratégie sous contraintes soit sur l'exploitation de profils d'enrichissements isotopiques collectés au cours des expériences de marquage isotopique, ont permis de modéliser le comportement du système vivant en conditions de croissance pour différentes densités de flux de photons incidentes (200 et 400 mol/m-2s-1) et taux de dilution. Le métabolisme en croissance a pu être décomposé en trois processus responsables de la croissance de la biomasse, de la maintenance cellulaire et d'un mécanisme futile . Plusieurs scénarios métaboliques probables sont avancés pour expliquer cette dissipation d'énergie sans synthèse de biomasse en présence d'une zone sombre dans le volume réactionnel. L'étude de l'effet d'une restriction azotée (carence et limitation) a mis en évidence une remobilisation des réserves macromoléculaires de la microalgue vers la synthèse de composés glucidiques et notamment d'amidon, une molécule d'intérêt bioénergétique.The presented thesis deals with metabolic flux computation of the model microalgae Chlamydomonas reinhardtii under photoautotrophic conditions, in order to understand energy storage and conversion. This work needed the development of methodological tools, such as (i) a genome-scale metabolic network reconstruction, named iAM557, including 557 genes for 532 metabolites connected stoichiometrically by 599 metabolic reactions, and (ii) the design of a specific photobioreactor devoted to isotopic non stationary carbon 13 labeling experiment. Both metabolic flux computation methods, based either on constraints or on isotopic enrichment profiles collected during isotopic labeling experiments, allowed to model living system behavior during growth for different incident photon flux densities (200 and 400 mol/m-2s-1) and dilution rates. Growth metabolism was split up into three processes responsible for biomass growth, cell maintenance and a futile mechanism. Several proposed metabolic scenarios might explain this energy dissipation without biomass synthesis when a dark zone within the reaction volume occured. The study of nitrogen restriction (deprivation and limitation) featured microalgae macromolecular stock restructuration to synthesize carbohydrates compounds and especially starch, a molecule potientially used as bionergy.NANTES-BU Sciences (441092104) / SudocSudocFranceF

Real time monitoring of photoautotrophic microalgae growth in photobioreactor, based on gas analysis

International audienceMicroalgae growth in a photobioreactor (PBR) is a complex process influenced by multiple parameters, such as photosynthetic light capture and attenuation, nutrient uptake, PBR hydrodynamics and gas – liquid (G – L) mass transfer. Like for any bioprocess, culture monitoring is a key aspect, as it allows controlling and optimizing operating parameters for improved production. In practice, real-time monitoring is mainly limited to pH and temperature. Online measurement of biomass concentration using optical density sensors needs improvements for providing accurate measurements. One alternative is to use on-line measurements such as pH, CO2 and O2 concentrations in- and off- gas stream. Software sensors based of first principle in combination with items as CO2 and O2 concentrations have been successfully implemented in fermentation since many years and in most recently in recombinant processes [1]. Despite their interest, the development of such tool in the context of microalgae application is underrepresented in the literature. Indeed, in phototrophs, CO2 and O2 are quantitatively the most important substrate and product, respectively. They allow quantifying on-line growth related parameters as net O2 production rate, CO2 uptake rate. Based on these quantities, biomass and nutrients concentrations could be estimated on-line. This study focusses on the development of such an estimation tool in the context of photoautotrophic growth cultivation of microalgae in closed PBR, in non-limiting mineral conditions. The proposed method uses a minimalistic model relying on macroscopic mass balances in liquid and gas phases and G - L mass transfer laws, without any assumption about the kinetic rate. Biomass concentration and growth rate have been estimated from net O2 production, assuming constant conversion yield. Combining in-situ O2 and CO2 measurements, the estimation of key parameters as dissolved CO2 and / or transfer coefficients is discussed. Although the methodology proposed here is rather general, online computation of net O2 and CO2 rates could be more or less complex, depending on gas vector through the PBR, G - L mass properties, and hydrodynamic conditions. A simulation study, based on a previous validated model [2] has been used to discuss limitations depending on the made assumptions. To demonstrate the methodology, the proposed tool has been experimentally implemented in a laboratory PBR throughout the photoautotrophic growth of a C. reinhardtii culture, its efficiency being proved under several operating conditions. Online estimation of biomass concentration has been in agreement with dry weight off-line measurements, even in batch operation, on a wide range of incident illumination conditions and gas flow rate through the PBR. In continuous conditions, online estimates have been successfully coupled with a feedback linearizing controller for biomass concentration. Since key process variables are available online, the proposed tool enables further control strategies. This is part of our ongoing research

Chracterization of the central carbon metabolism of Arthrospira platensis cultivated in contrasted conditions in photobioreactor

National audienc

Influence of culture conditions on EPS biosynthesis in Arthrospira platensis.

National audienc

Chracterization of the central carbon metabolism of Arthrospira platensis cultivated in contrasted conditions in photobioreactor

International audienc

The GCMS characterization of the central carbon metabolism of Arthrospira platensis brings insights to its original polysaccharide composition when submitted to various culture conditions

National audienc