11 research outputs found
A rewriting of the relation between the acolinearity of annihilation photons and their energy in the context of positron emission tomography
Acolinearity of the annihilation photons observed in Positron Emission
Tomography (PET) is described as following a Gaussian distribution. However, it
is never explicitly said if it refers to the amplitude of the acolinearity
angle or its 2D distribution relative to the case without acolinearity (herein
defined as the acolinearity deviation). Since the former is obtained by
integrating the latter, a wrong interpretation would lead to very different
results. The paper of Shibuya et al. (2007), differs from the previous studies
since it is based on the precise measurement of the energy of the annihilation
photons. They also show that acolinearity follows a Gaussian distribution in
the context of PET. However, their notation, which relies on being on the plane
where the two annihilation photons travel, could mean that their observation
refers to the amplitude of the acolinearity angle. If that understanding is
correct, it would mean that acolinearity deviation follows a 2D Gaussian
distribution divided by the norm of its argument. Thus, we revisited the proof
presented in Shibuya et al. (2007) by using an explicit description of the
acolinearity in the 3D unit sphere
Molecular mechanisms of the cardiovascular protective effects of polyphenols
Epidemiological studies have reported a greater reduction in cardiovascular risk and metabolic disorders associated with diets rich in polyphenols. The antioxidant effects of polyphenols are attributed to the regulation of redox enzymes by reducing reactive oxygen species production from mitochondria, NADPH oxidases and uncoupled endothelial NO synthase in addition to also up-regulating multiple antioxidant enzymes. Although data supporting the effects of polyphenols in reducing oxidative stress are promising, several studies have suggested additional mechanisms in the health benefits of polyphenols. Polyphenols from red wine increase endothelial NO production leading to endothelium-dependent relaxation in conditions such as hypertension, stroke or the metabolic syndrome. Numerous molecules contained in fruits and vegetables can activate sirtuins to increase lifespan and silence metabolic and physiological disturbances associated with endothelial NO dysfunction. Although intracellular pathways involved in the endothelial effects of polyphenols are partially described, the molecular targets of these polyphenols are not completely elucidated. We review the novel aspects of polyphenols on several targets that could trigger the health benefits of polyphenols in conditions such as metabolic and cardiovascular disturbances
PET/CT dual-modality imaging using a common detection platform
Lâimagerie bimodale TEP/TDM (tomographie dâeÌmission par positrons/tomodensitomeÌtrie) offre la possibiliteÌ de superposer lâinformation fonctionnelle et moleÌculaire de la TEP aÌ lâinformation anatomique de la TDM. PreÌsentement, que ce soit dans le domaine clinique ou preÌclinique, les images issues des deux modaliteÌs sont acquises de manieÌre seÌquentielle aÌ lâaide dâappareils distincts juxtaposeÌs ou non dans une meÌme enceinte. Il est ici proposeÌ dâacqueÌrir les images TEP et TDM avec la meÌme plateforme de deÌtection baseÌe sur un module de deÌtection et une chaiÌne eÌlectronique capable dâenregistrer aÌ la fois les signaux geÌneÌreÌs par les rayonnements dâannihilation et X. Le fait dâemployer le meÌme anneau de deÌtection porte la promesse de reÌduire les artefacts de mouvements du sujet, en plus de laisser entrevoir une diminution de la dose administreÌe pour une qualiteÌ dâimage eÌquivalente en raison du mode dâacquisition en « comptage de photons ». Ces travaux preÌsentent, comme preuve de concept, un scanner preÌclinique inteÌgrant les deux modaliteÌs. Les progreÌs effectueÌs pour le faire passer dâun eÌtat fonctionnel dâun point de vue eÌlectronique aÌ un eÌtat dans lequel il est en mesure de produire des images seront deÌtailleÌs. Bien que lâobjectif dâune acquisition alterneÌe ou simultaneÌe des images TEP et TDM nâait pu eÌtre atteint en raison de limitations technologiques et logicielles, ces progreÌs ont permis lâacquisition dâimages bimodales sur cette plateforme unique, une premieÌre mondiale.Abstract : Bimodal PET/CT (positron emission tomography/computed tomography) imaging offers the possibility to superimpose the functional and molecular information provided by PET to the anatomical information provided by CT. Currently, whether in clinical or preclinical context, the images coming from both modalities are acquired sequentially with the help of distinct scanners juxtaposed or not in a single gantry. It is here proposed to acquire the PET and CT images with the same detection platform based on a detector and the associated electronics that are able to register both the signals generated by annihilation and X photons. The fact of using the same detector ring promises a reduction in movement artifacts of the subject, in addition to a foreseeable lowering of the administered dose for an equivalent image quality, thanks to the âphoton-countingâ acquisition mode. This work presents, as a proof of concept, a preclinical scanner integrating both modalities. The progress made to bring the scanner from an electronically functional status to a condition allowing images to be produced will be detailed. Although the objective of alternate or simultaneous acquisition of the PET and CT images could not be achieved due to technological and software limitations, this progress allowed the acquisition of bimodal images on this unique platform, a world premiere
Quantification of extra-cerebral and cerebral hemoglobin concentrations during physical exercise using time-domain near infrared spectroscopy
Fitness is known to have beneficial effects on brain anatomy and function. However, the understanding of mechanisms underlying immediate and long-term neurophysiological changes due to exercise is currently incomplete due to the lack of tools to investigate brain function during physical activity. In this study, we used time-domain near infrared spectroscopy (TD-NIRS) to quantify and discriminate extra-cerebral and cerebral hemoglobin concentrations and oxygen saturation (SO(2)) in young adults at rest and during incremental intensity exercise. In extra-cerebral tissue, an increase in deoxy-hemoglobin (HbR) and a decrease in SO(2) were observed while only cerebral HbR increased at high intensity exercise. Results in extra-cerebral tissue are consistent with thermoregulatory mechanisms to dissipate excess heat through skin blood flow, while cerebral changes are in agreement with cerebral blood flow (CBF) redistribution mechanisms to meet oxygen demand in activated regions during exercise. No significant difference was observed in oxy- (HbO(2)) and total hemoglobin (HbT). In addition HbO(2), HbR and HbT increased with subjectâs peak power output (equivalent to the maximum oxygen volume consumption; VO(2) peak) supporting previous observations of increased total mass of red blood cells in trained individuals. Our results also revealed known gender differences with higher hemoglobin in men. Our approach in quantifying both extra-cerebral and cerebral absolute hemoglobin during exercise may help to better interpret past and future continuous-wave NIRS studies that are prone to extra-cerebral contamination and allow a better understanding of acute cerebral changes due to physical exercise
La collection Ad usum Delphini. Volume I
La collection Ad usum Delphini, entreprise considĂ©rable d'Ă©dition de classiques latins et de dictionnaires de quelque soixante-dix volumes in-quarto, qui coĂ»ta si cher au TrĂ©sor royal, qui occupa tant de place dans les bibliothĂšques, qui pesa tant sur la vie de ses directeurs, l'illustre Montausier, gouverneur du Dauphin fils de Louis XIV, et le savant Huet, n'est mĂȘme plus une idĂ©e, tout juste une expression consacrĂ©e par l'usage. Ultime geste de sauvegarde de la culture latine, qui se voulait destinĂ© Ă la gĂ©nĂ©ration de 1670 comme aux suivantes : ultime et inutile, la barque ayant sombrĂ© avant le navire. Un Ă©chec, donc, mais bel Ă©chec dont il fallait retracer l'histoire, souligner l'originalitĂ© Ă©ditoriale et pĂ©dagogique, mesurer les implications et les enjeux moraux, politiques, idĂ©ologiques, pour retrouver ce qui constitue son vĂ©ritable sens : une formation intellectuelle destinĂ©e, bien au-delĂ du cadre scolaire, Ă l'honnĂȘte homme, et la certitude qu'il n'est de vĂ©ritable connaissance du monde et des hommes qu'Ă travers la littĂ©rature antique.Pour Jean Ebrar
Messages
Huxley Julian S., Russell Bertrand A. W., Auger Pierre, Coulomb Jean, Laugier Henri, Roche Jean-C., Wolff Ătienne. Messages. In: Tiers-Monde, tome 5, n°20, 1964. Science, technique et dĂ©veloppement. pp. 627-636
Messages
Huxley Julian S., Russell Bertrand A. W., Auger Pierre, Coulomb Jean, Laugier Henri, Roche Jean-C., Wolff Ătienne. Messages. In: Tiers-Monde, tome 5, n°20, 1964. Science, technique et dĂ©veloppement. pp. 627-636
Dâune AntiquitĂ© lâautre
La littĂ©rature antique classique dans les bibliothĂšques : tel est lâintĂ©rĂȘt partagĂ© qui rĂ©unit dans cet ouvrage littĂ©raires, historiens du livre et chercheurs dâhorizons divers pour confronter leurs regards et leurs mĂ©thodes. Avec lâAntiquitĂ© classique, câest une tradition qui est donnĂ©e Ă examiner une tradition fondatrice des Ă©tudes littĂ©raires, mais surtout dâun systĂšme dâĂ©ducation et de pensĂ©e, qui Ă certains moments se confond avec la culture elle-mĂȘme : lâintense renouvellement quâelle permet, et son lent et progressif affaiblissement Ă la fin de lâĂge classique mĂ©ritaient dâĂȘtre pris dans le temps long, du xve au xixe siĂšcle. Ă partir des bibliothĂšques et de leur histoire se dessine une histoire du « goĂ»t antique », celui des estampes comme celui dâune littĂ©rature dont les auteurs canoniques Ă©voluent au fil du temps. On y entend les Ă©chos dâune histoire intellectuelle, celle des mĂ©thodes de classement et de stratification des savoirs, celle qui dĂ©finit la place de lâAntiquitĂ© â et de la littĂ©rature â dans lâenseignement. On y lit Ă©galement une histoire du dialogue qui sâest nouĂ© de tout temps, et plus particuliĂšrement Ă la Renaissance, entre les anciens et les modernes. Histoire culturelle encore, qui renvoie Ă la formation de lâhonnĂȘte homme comme Ă celle de lâhomme de lâart, et illustre la force des canons bibliophiliques ou des modes et impĂ©ratifs sociaux au moins autant que les goĂ»ts individuels
La collection Ad usum Delphini. Volume II
Suite du premier volume consacrĂ© Ă la collection Ad usum Delphini dans son ensemble, Ă son Ă©laboration et Ă ses aspects bibliophiliques et pĂ©dagogiques, ce second volet aborde lâanalyse de chacun des volumes publiĂ©s concernant les auteurs anciens. Les diffĂ©rents collaborateurs se sont attachĂ©s Ă la fois Ă Ă©claircir la personnalitĂ© et la carriĂšre de ces savants du XVIIe siĂšcle, parfois jeunes ou peu connus lors de leur participation Ă lâĂ©quipe dauphine, Ă examiner leur travail philologique, mais aussi Ă le replacer dans son contexte historique et dans lâhistoire de lâĂ©dition des classiques. Il ne sâagit pas de dire ici si ces Ă©ditions sont « bonnes » au regard de notre temps, mais Ă examiner leur facture, les motifs de leurs rĂ©ussites comme de leurs silences, ce quâelles ont apportĂ© Ă lâhistoire du texte autant que ce quâelles ont figĂ© dans sa transmission. Lâensemble des deux ouvrages forme la premiĂšre Ă©tude exhaustive scientifique sur le fond de la collection Ad usum Delphini