Éditeur(s) : Edinburgh, London
Siècle(s) traité(s) : 19
Provenance : Université Caen Normandie. Service commun de la documentation
Permalien : http://www.manioc.org/patrimon/CAE19033_4
CAE19033_4

Éditeur(s) : HAL CCSD Institute of Mathematics Polish Academy of Sciences
Résumé : International audience
In analogy to the classical isomorphism between L(D(Rn);D0(Rm)) and D0(Rm+n) (resp. L(S(Rn); S0(Rm)) and S0(Rm+n)), we show that a large class of moderate linear mappings acting between the space GC(Rn) of compactly supported generalized functions and G(Rn) of generalized functions (resp. the space GS(Rn) of Colombeau rapidly decreasing generalized functions and the space G (Rn) of temperate ones) admits generalized integral representations, with kernels belonging to specic regular subspaces of G(Rm+n) (resp. G (Rm+n)). The main novelty is to use accelerated -nets, which are unit elements for the convolution product in these regular subspaces, to construct the kernels. Finally, we establish a strong relationship between these results and the classical ones.
ISSN: 0137-6934

hal-01529541
https://hal.univ-antilles.fr/hal-01529541
https://hal.univ-antilles.fr/hal-01529541/document
https://hal.univ-antilles.fr/hal-01529541/file/delcroix.pdf
DOI : 10.4064/bc88-0-7

Résumé : After a period of rapid development of the sites (an increase in both reared surface area and production), tropical shrimp aquaculture is currently being faced with critical problems due to economical and ecological constraints. In many countries with favourable conditions for shrimp aquaculture such as indonesia or Vietnam, sites are often badly selected and/or over-exploited. This conducts to sorne extent to decreases or collapses in the production due to the difficulty in predicting the maximum production capacity of the sites. Furthermore, it appears that production sustainability depends on many factors among which socio-economy and ecolo gy are of prime importance. The STD3 project titled « Assessment of tropical shrimp aquaculture impact on the environment in tropical countries using hydrobiology, ecology and remote sensing as helping tools for diagnosis )) was initiated in 1994, with the aim to study the sustainability of marine shrimp aquaculture in tropical areas, main! y Indonesia and Vietnam, through the following tasks: (i) improve site selection and study the impact of aquaculture on marine environments presenting a variable sensitivity to organic sewage, (ii) analyse the socio-economical aspects and profitability of the aquaculture industry and of common resources (iii) use remote sensing and geographical data bases for diagnosis and monitoring of site degradation (iv) reinforce the capacity of Asian scientists through training. Severa! aquaculture sites have been investigated in the Lampung region (South Sumatra, Indonesia), the Mekong delta (Vietnam) and on the West coast of New-Caledonia, providing a large range of typical ecosystems encountered in Asia and in the Pacifie, from coralline sites to coastal plains with mangrove and deltaic areas. The study concerned the spatial structure and seasonal influence of these ecosystems, the temporal variation during the course of the project (3 years) and the relation between the ecological structure and farm productions. Remote sensing provides a synoptic vision over large land expanses. Severa! scenes were processed for landuse mapping using conventional classification techniques. Concerning water quality assessment, a general relation for the Java sea was found between image and field data in terms of total suspended matter. Applying this relation to a new site in Sumatra has provided an initial approach to water type and, together with land use mapping, a preliminary assessment of the suitability of the area to shrimp aquaculture development. Socio-economic research has been focused on the identification ofneeds for collective action, including public policy, in the perspective of shrimp farming sustainability. The main concern is in the regulation of shrimp farming intensification and extensification at the scale of coastal ecosystemic entities in a common property resource management perspective. The common considered here is coastal water quality. Comparing the local development profiles and the institutional grounds for the design and implementation of collective management rules shows that variables such as land tenure system, farm owner socio-economic profile, social homogeneity or heterogeneity of the farmers are key factors to analyse the potential for sustainability. The defmition of water quality and the possible means to ensure its collective management are discussed. The main conclusion is that the economie incentives to farming development are strong but there is no significant difference among traditional, semi-intensive and intensive systems in terms of economie efficiency or wealth distribution. The description of the functioning of the different kinds of ecosystems make it possible to give an advice concerning the positioning of the activity inside the ecosystem, and furthermore to have a reference state in order to determine the impact of the activity on the coastal environnement. This impact can be summarized as an increase in the concentration of total suspended matt€?r, of particulate organic matter and of sulfate reducing bacterias. This organic ma~.er is either issued from rearing activities or from telluric origine, due to mangrove eradication when building the ponds. An evaluation of the relationship existing between productivity and characteristics of each ecosystem bas been conducted by correlating ecological indicators data (concentration of total suspended matter, particulate organic matter, chlorophyll, percentage of pheopigments in total pigments and cyanobacteria and sulfatereducing bacteria in water and sediments) with the average production of the farms. This comparison lead to the compilation of a scale of observed production integrating the range of these environmental parameters with shrimp production levels, bound to facilitate the positioning of shrimp farming in relation with the confmement leve! of each ecosystem. Lastly, ali geographie data originated from the various compartments of the study have been geo-referenced and loaded into a geographical information system. This allows to display any query made on spatial variables and their related statistical data, including the ir variations over the last few years and to reveal patterns and phenomena otherwise not obvious.
Le programme mis en oeuvre par la DRV (Paris, CREMA-L'Houmeau, DELIAO Brest, COP Tahiti, GIE/RA Nouvelle Calédonie), dans le cadre d'un projet européen STD3 «(Sciences et Technique au Service du Développement», en collaboration avec l'Université de Montpellier II, l'Ecole Nationale d'Agronomie de Rennes, l'ITC (Hollande), l'Institut Océanographique de Nha Trang (Vietnam), le BADC de Jepara et le BPPT de Jakarta (Indonésie), avait pour but la mise au point de méthodes permettant d'améliorer la sélection des sites ainsi que le suivi du développement et de l'impact de l'aquaculture des crevettes Péneides en milieu tropical pour éviter la surexploitation. Quatre axes de recherche ont été défmis : a) identifier la nature et quantifier les rejets de déchets issus de ce type d'aquaculture, b) définir les caractéristiques écologiques des écosystèmes susceptibles d'accueillir l'activité aquacole et suivre leur évolution sous l'influence des rejets, c) déterminer l'influence de la gestion des fermes et des ressources (aspects économiques) sur les performances de productivité, d) déterminer la capacité de la télédétection comme outil de diagnostic d'impact à l'échelle de la région, e) mener un programme de formation d'étudiants et jeunes chercheurs Vietnamiens et Indonésiens.

Droits : 1998 Ifremer
http://archimer.ifremer.fr/doc/00132/24357/22357.pdf
http://archimer.ifremer.fr/doc/00132/24357/

Éditeur(s) :  :
Extrait de : Hanbooks prepared under the direction of the historical section of the Foreign Office
Siècle(s) traité(s) : 20
Droits : Domaine public
Provenance : Collectivité territoriale de Guyane. Bibliothèque Alexandre-Franconie
Permalien : http://www.manioc.org/patrimon/FRA12235
FRA12235

Éditeur(s) : London : Saunders and Otley
Description : History of the Caribs. Culture and way of life of Antiguans in the 18th and 19th Centuries.
Siècle(s) traité(s) : 18
Droits : Domaine public
Provenance : Ville de Pointe-à-Pitre. Réseau des bibliothèques
Permalien : http://www.manioc.org/patrimon/PAP11081
PAP11081

Éditeur(s) : HAL CCSD Paris, Masson et Cie
Résumé : National audience
Decreased frequency of pulmonary exacerbations, mainly related to immunomodulatory effects of macrolide antibiotics, has been demonstrated in bronchiectasis and chronic obstructive pulmonary diseases (COPD). Due to its tolerance, azithromycin is the antibiotic of choice for maintenance therapy at the dose of 250 mg per day or 500 mg × 3 per week (for body weight >55 kg). Maintenance therapy with macrolide could be proposed in selected patients with bronchiectasis or COPD with more than 3 acute exacerbations in the previous year or decreased lung function despite compliance with optimum treatment. The risk of sudden cardiac death with azithromycin is rare and controversial. It should be avoided in patients with a high baseline risk of cardiovascular disease, QT>450 msec, pulse rate>100 bpm and potential drug interactions, particularly those known to cause QT prolongation. It is recommended to search for hearing deficit (audiometry) and sputum culture positive for mycobacteria. Patients must also be aware that it can rapidly lead to macrolide resistance in commensal or pathogenic flora. Follow-up evaluation every 3 month can be proposed with medical history (hearing deficit) and electrocardiography. After one year, the treatment should be stopped in the absence of reduction in the frequency of exacerbations.
Points essentielsLes macrolides administrés au long cours permettent, grâce en partie à leurs propriétés anti-inflammatoires, de diminuer la fréquence des exacerbations dans la DDB et la BPCO.Du fait de sa tolérance, l’azithromycine est le macrolide de choix, pouvant être utilisé à la dose de 250 mg/j ou 500 mg 3 fois par semaine chez les patients de plus de 55 kg.Un traitement par macrolides au long cours pourrait être proposé à des patients atteints de DDB ou de BPCO ayant eu plus de 3 exacerbations l’année précédente ou ayant une dégradation de leur fonction respiratoire malgré un traitement de fond bien conduit.Du fait d’un risque rare et controversé de mort subite d’origine cardiaque, il ne doit pas être proposé en cas de pathologie cardiovasculaire évoluée, d’intervalle QT > 450 ms, de traitement pouvant allonger l’intervalle QT, de tachycardie > 100/min.Il est recommandé de s’assurer de l’absence de troubles auditifs (audiogramme) et de mycobactérie atypique dans les cultures des expectorations. Les patients doivent aussi être informés du risque d’apparition de résistance aux macrolides de la flore commensale et pathogène.Une surveillance clinique, avec en particulier la recherche de troubles auditifs et électrocardiographique, peut être proposée tous les 3 mois. L’absence de diminution de la fréquence des exacerbations, lors du bilan annuel, justifie l’arrêt du traitement.
ISSN: 0032-7867

hal-01073027
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01073027
DOI : 10.1016/j.lpm.2013.08.006
PUBMED : 24631048

Éditeur(s) : CNRS Programme Environnement : Colloque Recherche et Environnement Strasbourg, 24-25 Septembre 1990
Résumé : As the third millennium draws near, industrial societies are becoming aware of the limits of what they can do to constrain the biosphere, ending up where "primitive" societies left off. If the perverse effects of a century of technical revolution and economic expansion are above all perceptible in the area of multiple contaminations that put in danger the well-being of people, environments and in a general way the biosphere's functioning, they also concern the standardisation of products and landscapes and overinvestment in the means of exploiting resources (inputs increasing more rapidly than outputs, when they are not bringing about their decrease). The search for solutions to the growing imbalance of the relationships Man – Nature – Resources cannot reside in a partial approach or a technical resolution of the problems posed by using renewable resources.
(OCR non controlé) A l'approche du troisième millénaire, les sociétés industrielles prennent la mesure des limites de leurs possibilités de contraindre la biosphère, aboutissant là d'où partaient les sociétés "primitives". Si les effets pervers d'un siècle de révolution technique et d'expansion économique sont surtout perceptibles dans le domaine des pollutions multiples qui mettent en péril le bien-être des personnes, les milieux et d'une manière générale le fonctionnement de la biosphère, ils concernent également l'uniformisation des produits et des paysages et le surinvestissement dans les moyens d'exploitation des ressources (les intrants croissant plus vite que les rendements, quand ils n'entraînent pas leur baisse). La recherche de solutions au déséquilibre croissant des relations Hommes - Nature - Ressources ne peut résider dans une approche partielle ou une résolution technique des problèmes posés par l'utilisation des ressources renouvelables.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1990/acte-2416.pdf
http://archimer.ifremer.fr/doc/00000/2416/

Éditeur(s) : HAL CCSD
Résumé : International audience
Decreased frequency of pulmonary exacerbations, mainly related to immunomodulatory effects of macrolide antibiotics, has been demonstrated in bronchiectasis and chronic obstructive pulmonary diseases (COPD). Due to its tolerance, azithromycin is the antibiotic of choice for maintenance therapy at the dose of 250 mg per day or 500 mg × 3 per week (for body weight extgreater55 kg). Maintenance therapy with macrolide could be proposed in selected patients with bronchiectasis or COPD with more than 3 acute exacerbations in the previous year or decreased lung function despite compliance with optimum treatment. The risk of sudden cardiac death with azithromycin is rare and controversial. It should be avoided in patients with a high baseline risk of cardiovascular disease, QT extgreater450 msec, pulse rate extgreater100 bpm and potential drug interactions, particularly those known to cause QT prolongation. It is recommended to search for hearing deficit (audiometry) and sputum culture positive for mycobacteria. Patients must also be aware that it can rapidly lead to macrolide resistance in commensal or pathogenic flora. Follow-up evaluation every 3 month can be proposed with medical history (hearing deficit) and electrocardiography. After one year, the treatment should be stopped in the absence of reduction in the frequency of exacerbations.
Presse Médicale (Paris, France: 1983)

hal-01063927
https://hal.archives-ouvertes.fr/hal-01063927
DOI : 10.1016/j.lpm.2013.08.006

Éditeur(s) : HAL CCSD
Résumé : 15 pages
International audience
In analogy to the classical isomorphism between $mathcal{L}left( mathcal{S}left( mathbb{R}^{n}right) ,mathcal{S}^{prime}left( mathbb{R}^{m}right) right) $ and $mathcal{S}^{prime}left( mathbb{R}^{n+m}right) $, we show that a large class of moderate linear mappings acting between the space $mathcal{G}_{mathcal{S}}left( mathbb{R}^{n}right) $ of Colombeau rapidly decreasing generalized functions and the space $mathcal{G}_{ au}left( mathbb{R}^{n}right) $ of temperate ones admits generalized integral representations, with kernels belonging to $mathcal{G}_{ au}left( mathbb{R}^{n+m}right) $. Furthermore, this result contains the classical one in the sense of the generalized distribution equality.
Math. Proc. Camb. Philos. Soc.

Droits : info:eu-repo/semantics/OpenAccess
hal-00019916
https://hal.archives-ouvertes.fr/hal-00019916
https://hal.archives-ouvertes.fr/hal-00019916/document
https://hal.archives-ouvertes.fr/hal-00019916/file/KernelSADelcroixfeb7th.pdf
ARXIV : math.FA/0603035

Éditeur(s) : London : Smith, Elder
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Ville de Pointe-à-Pitre. Réseau des bibliothèques
Permalien : http://www.manioc.org/patrimon/PAP11090
PAP11090

Date de création : 1869-01-01

Éditeur(s) : London : Bell & Daldy
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Collectivité territoriale de Guyane. Bibliothèque Alexandre-Franconie
Permalien : http://www.manioc.org/patrimon/FRA11001
FRA11001

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Inorganic arsenic is a toxic environmental contaminant to which humans are mainly exposed through drinking water. This metalloid impairs functions of several key immune cells. Particularly, it reduces IL-2 secretion and proliferation of blood peripheral mononuclear cells stimulated by lectins that, however, do not mimic physiological T cell activation. The present study used isolated human T cells activated, in a more physiological manner, through stimulation with CD3/CD28 antibodies, to carefully analyze the impact of arsenic on T cell proliferation and cytokine expression. We demonstrate that non cytotoxic concentrations of sodium arsenite (As(III), 0.25-2μM) significantly reduce T cell proliferation by increasing the percentage of non dividing cells blocked in G1 phase and by preventing cyclin D3 and CDC25A expression. They also markedly, although not totally, reduces IL-2 expression at both mRNA and protein levels; however, metalloid-dependent inhibition of T cells could not be reversed by addition of recombinant IL-2. In addition, As(III) markedly reduces secretion of interferon-γ without impairing that of IL-4 and IL-13; it also decreases interferon-γ mRNA levels but increases those of IL-13. Finally, simultaneously to its immune effects, As(III) rapidly and potently increases expression of the redox-sensitive genes HMOX1, NQO1 and GCLM in activated T cells without altering the levels of reactive oxygen species. In conclusion, our results demonstrate that As(III) inhibits T cell proliferation, independently of IL-2, and alters the Th balance of cytokines secreted by co-stimulated T cells which thus constitute direct targets of this major environmental contaminant.
ISSN: 0300-483X

inserm-00872848
http://www.hal.inserm.fr/inserm-00872848
DOI : 10.1016/j.tox.2012.05.025
PUBMED : 22683347

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : The Oman ophiolite consists of several massifs cropping out along a 500 km long band trending NW-SE along the coast of Oman; it is one of the best exposed sections of oceanic crust and mantle in the world. There is a gradient in igneous processes and composition in the ophiolite, with the northern massifs recording a polygenetic igneous history involving an increasingly important subduction component, whereas the southern massifs were formed primarily via a mid-ocean ridge basalt (MORB)-like, single-stage process at a submarine spreading ridge. In this study we use geochemical data from Wadi Tayin, which is one of the southern massifs of the Oman ophiolite, to constrain the composition and genesis of oceanic crust and upper mantle. The Wadi Tayin harzburgites are residues of partial melting that are as depleted as the most depleted mid-ocean ridge peridotites. They have low middle- to heavy rare earth element ratios, most probably reflecting melting close to and beyond the exhaustion of clinopyroxene. Like many abyssal peridotites, the Wadi Tayin samples show enrichment in highly incompatible elements, giving rise to U-shaped MORB-normalized trace element patterns. We favor the idea that this is caused by enrichment of highly incompatible elements along grain boundaries in peridotite, which may be the result of near-equilibrium partitioning between grain boundaries and grain interiors, rather than disequilibrium processes. Equilibrium partitioning between crystals and grain boundaries during melting and melt extraction is also our preferred explanation for ubiquitous high Pb contents relative to Ce and La in our samples as well as in most abyssal peridotites. The Wadi Tayin samples record substantial variability in terms of osmium isotopic composition and platinum group element (PGE) concentrations. The more radiogenic nature of the dunites and impregnated peridotites compared with the residual harzburgites may be due to relatively high Os-187/Os-188 in melt transported through the dunites. The presence of residual peridotites with whole-rock osmium isotopic compositions less radiogenic than MORB may be explained by melting of a veined (upwelling) mantle forming mixed melts in which much of the Os derives from veins with high Re/Os in a matrix of previously depleted peridotite. An important result of this study is that the shallowest samples are refertilized (i.e. anomalously enriched in incompatible elements), and record relatively high metamorphic closure temperatures. These observations suggest that migrating melt underwent crystallization during rapid cooling in the uppermost mantle during and immediately after ridge magmatism. A variety of geothermometers all yield the result that the stratigraphically highest harzburgites equilibrated at higher temperature than the deeper ones. The systematic decrease in closure temperature with increasing depth below the Moho transition zone probably reflects systematic variation in cooling rate as a function of depth in the mantle section. We hypothesize that the refertilization and higher closure temperatures recorded by the uppermost mantle samples are linked. More rapid cooling led to higher closure temperatures, and to partial crystallization of migrating melts in the shallowest part of the mantle section, yielding slightly elevated abundances of elements such as Ca and Na, and incompatible trace elements.
ISSN: 0022-3530

hal-00456056
https://hal.archives-ouvertes.fr/hal-00456056
DOI : 10.1093/petrology/egp077

Éditeur(s) : New York : Francis P. Harper London : Gibbings
Siècle(s) traité(s) : 17
Droits : Domaine public
Provenance : Communauté d'agglomération de La Rochelle. Médiathèque Michel-Crépeau
Permalien : http://www.manioc.org/patrimon/MMC16037
MMC16037

Éditeur(s) : HAL CCSD Elsevier
Résumé : We have studied the phase transformation of forsterite to wadsleyite under shear stress at the Earth's transition zone pressure and temperature conditions. Two-step experiments were performed using a multi-anvil press. First, we hot pressed iron-free forsterite at 6 or 11 GPa and 1100 degrees C. Then we deformed a slab of this starting material using a direct simple shear assembly at 16 GPa and 1400 degrees C for 1, 15, 35, 40, or 60 min. Both the starting material and the deformed samples were characterized using optical and scanning electron microscopy including measurements of crystal preferred orientations (CPO) by electron back scattered diffraction (EBSD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The phase transformation occurs very rapidly, in less than 1 min, and metastable forsterite relics are not observed after deformation. The grain size of wadsleyite is slightly smaller than the forsterite starting material. The water contents obtained from FTIR analyses in forsterite and wadsleyite are 65-124 wt ppm H2O and 114-736 wt ppm H2O, respectively, which are well below water solubility at similar conditions in the presence of free water. Wadsleyite aggregates display weak CPO patterns with [1 0 0] axes concentrated at low angle to the shear direction, [0 1 0] axes perpendicular to the shear plane and nearly random [0 0 1] axes. Only a few dislocations were observed in wadsleyite with TEM. This observation is consistent with the assumption that most dislocations formed during the initial high-stress stages of these stress-relaxation experiments, were consumed in the phase transformation, probably enhancing the transformation rate. CPO patterns vary as a function of the water content: with increasing water content the density of [1 0 0] axes parallel to the shear direction decreases, and the density of [0 0 1] axes increases. Viscoplastic self-consistent modeling of CPO evolution using previously reported glide systems for wadsleyite, i.e., [1 0 0]{0 k 1} and 1/2 (1 1 1){1 0 1}, cannot reproduce the measured CPO, unless the [0 0 1](0 1 0) system, for which dislocations have not been observed by TEM, is also activated. In addition, wadsleyite grain growth suggests the participation of diffusion-assisted processes in deformation. Calculated anisotropies for P and S-waves using measured CPO are always below 1%. This very low anisotropy is due to both the low finite strain achieved in the experiments, which leads to weak wadsleyite CPO, and to the diluting effect of added majorite. The present experiments emphasize the importance of stress, grain size evolution and water content in the forsterite to wadsleyite phase transformation and subsequent deformation in the transition zone.
ISSN: 0031-9201

hal-00617430
https://hal.archives-ouvertes.fr/hal-00617430
DOI : 10.1016/j.pepi.2010.11.001

Éditeur(s) : HAL CCSD Académie Serbe des Sciences et des Arts
Résumé : International audience
ISSN: 0561-7332

hal-01530760
https://hal.univ-antilles.fr/hal-01530760

Éditeur(s) : London : Saunders and Otley
Description : Découverte en 1493 par Christophe Colomb, l'île d'Antigua située dans les Petites Antilles sera baptisée ainsi en l'honneur de l'église de Santa Maria la Antigua de Séville. Elle sera plus tard colonisée par les Britanniques en 1632...
Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Ville de Pointe-à-Pitre. Réseau des bibliothèques
Permalien : http://www.manioc.org/patrimon/PAP11082
PAP11082

Éditeur(s) : HAL CCSD
Résumé : The ovary is not solely the unique source of oocytes necessary for fertilization but also a crucial conductor of endocrine regulations of the reproductive system. In the fetal ovary, oocytes grouped in clusters are surrounded by somatic pre-granulosa cells, altogether delineated by a basement membrane and constituting ovarian cords. The formation of the definitive ovarian functional units requires their fragmentation into follicles formed by a single oocyte surrounded by granulosa cells and delineated by a basement membrane. This partitioning occurs within a tiny period and is dependent on the correct timing of the meiotic process, on an apoptotic wave that specifically targets oocytes and the remodelling of the basement membrane. Follicle formation is a crucial event of ovarian development because the follicle stock formed at the end of this process is non-renewable. Therefore, any disturbance of this process can lead to reproductive abnormalities in adulthood. Recent data on endocrine disruptors displaying estrogenic activity have involved the fragile estrogenic homeostasis in the process. We aimed at better understanding how the endogen estrogen 17b-estradiol (E2) contributes to follicle formation. To assess it, Sprague-Dawley rats were treated with E2 at different doses during follicle formation, /i.e./ in the 3 days following birth. We show that although this treatment impairs the development of the hepatic and ovarian detoxification systems, the female neonate is able to increase its estrogen clearance capabilities. Nevertheless, E2 treatment within this critical period triggers a dose-dependent decrease of oocyte number per ovary. Regardless of the E2 dose, puberty is advanced. All treated females are at least transiently fertile, yet these reproductive capabilities rapidly decline. A high (10 µg/day) dose of E2 leads to a secondary infertility characterized by anovulation that probably result from a dysfunction of the whole reproductive tract. By contrast, a lower (0.1 µg/day) dose of E2, that does not significantly modify neonatal oocyte survival, leads to a progressive reproductive senescence likely due to ovarian failure. Long-term troubles may originate from precocious E2 impact on the ovary since it disturbs ovarian transcriptome and produces many lesions on ovarian cell DNA.
L'ovaire est au cœur de la physiologie de la reproduction féminine. Il est à la fois à l'origine des ovocytes nécessaires à la fécondation et acteur des régulations endocrines du système reproducteur. Les ovocytes de l'ovaire fœtal sont groupés en amas bordés de cellules somatiques et d'une membrane basale, formant les cordons ovariens. Ces cordons ovariens se fragmentent pour former les follicules ovariens: un ovocyte bordé de cellules somatiques et d'une membrane basale. Cette fragmentation se déroule sur une courte période (/in utero/ chez la femme et juste après la naissance chez les rongeurs) et fait intervenir une vague de mort cellulaire programmée touchant les ovocytes pendant leur méiose et un remodelage de la membrane basale. La formation des follicules est une période cruciale du développement ovarien puisque le stock de follicules formés à l'issue de ce processus est non renouvelable. Son altération peut donc être à l'origine de troubles de la fonction de reproduction chez le futur adulte. Il existe une fragile homéostasie œstrogénique en place au moment de la formation folliculaire: chez la femme, l'ovaire se développe /in utero/, sous l'influence des œstrogènes circulants maternels et la production ovarienne fœtale. Chez les rongeurs, les follicules se forment lors de la levée de l'imprégnation hormonale maternelle au moment de la naissance. Nous avons souhaité comprendre comment le 17b-œstradiol (E2), œstrogène endogène, pouvait contribuer à la mise en place des follicules. Pour cela, des rattes Sprague-Dawley ont été traitées pendant la période de formation des follicules avec de l'E2 à différentes doses entre 0.01 et 10 µg/jour. Nos travaux démontrent que le traitement de rattes par des œstrogènes entre leur naissance et 3 jours induit une réduction dose-dépendante de leur nombre d'ovocytes. Bien que le traitement entrave le développement normal du système de détoxication hépatique et ovarien, l'animal est capable d'accroître ses capacités d'élimination des œstrogènes. Ces capacités sont toutefois insuffisantes pour bloquer les effets du traitement. Quelle que soit la dose d'E2 utilisée (0.1 ou 10 µg/jour), la puberté est plus précoce chez les femelles exposées mais toutes sont fertiles, au moins transitoirement. Cependant le traitement induit une dégradation rapide des capacités reproductives. L'E2 modifie la dynamique folliculaire chez l'adulte, longtemps après l'arrêt du traitement. Si une forte dose d'E2 réduit la survie des ovocytes lors de la formation des follicules et conduit à une infertilité secondaire due à un dysfonctionnement général du tractus reproducteur, une dose faible n'affecte pas la survie des ovocytes à court terme mais conduit à une sénescence reproductive précoce vraisemblablement d'origine ovarienne. L'origine de ces troubles pourrait résider dans les effets précoces de l'exposition à E2 : cette molécule altère le transcriptome ovarien et induit de nombreuses lésions de l'ADN des cellules ovariennes.
https://tel.archives-ouvertes.fr/tel-00953657

NNT : 2013REN1S107
tel-00953657
https://tel.archives-ouvertes.fr/tel-00953657
https://tel.archives-ouvertes.fr/tel-00953657/document
https://tel.archives-ouvertes.fr/tel-00953657/file/CHALMEY_Clementine.pdf

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
A temporary network of 10 broad-band seismic stations has been installed in French Polynesia for the Polynesian Lithosphere and Upper Mantle Experiment (PLUME). All the seismic stations were installed either on volcanic islands or on atolls of the various archipelagos of French Polynesia in a manner which complements the geographic coverage provided by the regional permanent stations. The primary aim of PLUME is to image the upper mantle structures related to plate motion and hotspot activity. However, because of its proximity to all sites, the ocean is responsible for a high level of noise in the seismic data and we show that these data can also be used to analyse ocean wave activity. The power spectral density (PSD) analyses of the seismic data recorded in French Polynesia show clear peaks in the 0.05– 0.10 Hz band (periods between 10 and 20 s), which corresponds to swell frequencies. Clear peaks in this frequency band are also observed in infrasonic data recorded on Tahiti. Ground motion analysis shows that the swell-related seismic noise (SRSN) is linearly polarized in the horizontal plane and its amplitude decreases rapidly with the distance from the shore. The microseismic and the infrasonic 'noise' amplitudes show very similar variations from station to station and both are strongly correlated with the swell amplitudes predicted by the National Oceanic and Atmospheric Administration (NOAA), wind-forced, 'WaveWatch' models. The swell direction can be estimated from SRSN polarization analysis but this has to be done with care since, for some cases, the ground motions are strongly controlled by the islands' anisometric shapes and by swell refraction processes. We find cases, however, such as Tahiti or roughly circular Tuamotu atolls, where the azimuth of the swell is in good agreement with the seismic estimates. We, therefore, demonstrate that the SRSN and the infrasonic signal observed in French Polynesia can be used in such cases as a proxy for swell amplitude and azimuth. From the continuous analysis of the data recorded in 2003 at the permanent seismic station PPTL in Tahiti, transfer functions have been obtained. This could provide a way to quantify the swell activity during the last two decades and, therefore, assist in the investigation of climate changes.
ISSN: 0956-540X

hal-01388809
http://hal.univ-reunion.fr/hal-01388809
http://hal.univ-reunion.fr/hal-01388809/document
http://hal.univ-reunion.fr/hal-01388809/file/Barruol_swell_GJI2006.pdf
DOI : 10.1111/j.1365-246X.2006.02871.x

Siècle(s) traité(s) : 19
Droits : Domaine public
Provenance : Université des Antilles. Service commun de la documentation
Permalien : http://www.manioc.org/patrimon/HASH015cec1d83692f3063aead21
HASH015cec1d83692f3063aead21