Articles de revues sur le sujet « Fluorescence induite par LED »

L’article présente les résultats d’une pédagogie collaborative sur 2 forums ainsi que les différents outils utiles pour partager des résultats techniques et scientifiques. Depuis 5 ans, ce type de pédagogie est utilisé au département GEII en IUT sur différents projets techniques. L’article dévoile comment faire un choix de forums pour atteindre un auditoire suffisamment intéressé sur le sujet pour le faire avancer. Les avantages et les inconvénients pédagogiques de l’écriture collaborative sont exposés ainsi que la différence induite par une rédaction en langue française ou en langue anglaise. En fin de module, un questionnaire aux étudiants a été effectué pour permettre de faire un bilan de ce qu’ils pensent du partage collaboratif ainsi que leur bilan personnel. Les résultats du questionnaire est unanimement positif. Des statistiques données par les forums sur les « vues » permettent de savoir si le partage du travail est dynamique. Cependant, l’article montre aussi que les statistiques données par les forums sont parfois peu pertinentes. Enfin, la question du mode de partage sera repondu Est qu’il vaut mieux partager dans un forum ou dans un wiki ?

Objectifs : Évaluer la faisabilité, la fiabilité, le rôle actuel et l’intérêtde la cystoscopie de fluorescence en lumière bleue induite par l’hexaminolévulinate (Hexvix, Photocure ASA) pour la détection des tumeurs urothéliales. Préciser le profil des tumeurs plus particulièrement concernées par cette technique.Patients et méthodes : De janvier 2009 à janvier 2010, une lésion vésicale papillaire typique ou une lésion suspecte a été décelée en cystoscopie chez un total de 30 patients (64 prélèvements). Une résection endoscopique a été réalisée après la détection des lésions vésicales en lumière blanche et en lumière bleue (Hexvix). Une limite de l’étude est l’utilisation répétée d’Hexvix aux fins du suivi de patients porteurs d’un cancer de la vessie n’a pas été étudiée.Résultats : L’âge moyen des patients était de 70 ans (56-84 ans ; 27 hommes et 3 femmes). La cytologie préopératoire s’est révélée positive chez 17 patients, et négative chez 13 patients. Notre étude de 30 patients a permis d’analyser 64 prélèvements. Trente cinq tumeurs papillaires et 10 lésions non papillaires, mais suspectes, ont été repérées en lumière blanche. Cinquante-six prélèvements présentaient une fluorescence positive en lumière bleue, dont 19 lésions étaient seulement décelables sous cette sourcede lumière.Conclusion : Notre étude nous a permis de conclure que la cystoscopiede fluorescence à l’hexaminolé vulinate améliore sensiblement la détection des tumeurs superficielles de la vessie, particulièrement des carcinomes in situ (CIS). De plus, elle permet une résection plus complète qu’en cystoscopie standard à la lumière blanche et diminue le taux de tumeurs résiduelles après résection transurétrale de la vessie (RTUV).

The paper deals with the differences in sensitivity of Antarctic lichen to photoinhibition. Thalli of Usnea antarctica were collected at the James Ross Island, Antarctica (57°52´57´´W, 63°48´02´´S) and transferred in dry state to the Czech Republic. After rewetting in a laboratory, they were exposed to 2 high light treatments: short-term (30 min), and long-term (6 h). In short-term treatment, the sample were exposed to 1000 and 2000 µmol m-2 s-1 of photosynthetically active radiation (PAR). In long-term experiment, PAR of 300, 600, and 1000 µmol m-2 s-1 were used. Photosynthetic efficiency of U. antarctica thalli was monitored by chlorophyll fluorescence parameters, potential (FV/FM) and actual (FPSII) quantum yield of photochemical processes in photosystem II in particular. In short-term treatments, the F0, FV and FM signals, as well as the values of FV/FM, and FPSII showed light-induced decrease, however substantial recovery after consequent 30 min. in dark. Longer exposition (60 min) to high light led to more pronounced decrease in chlorophyll fluorescence than after 30 min treatment, however dark recovery was faster in the thalli treated before for longer time (60 min). Long-term treatment by high light caused gradual decrease in FV/FM and FPSII with the time of exposition. The extent of the decrease was found light dose-dependent. The time course was biphasic for FV/FM but not for FPSII. The study showed that wet thalli of Usnea antarctica had high capacity of photoprotective mechanisms to cope well either with short- or long-term high light stress. This might be of particular importance in the field at the James Ross Island, particularly at the begining of growing season when melting water is available and, simultaneously, high light stress may happen on fully sunny days.

The increase in the demand for almonds, the development of novel self-fertile and late-flowering varieties, and the establishment of plantations in new irrigated areas have led to significant progress in the productive techniques of almond tree cultivation. One of the most important has been the increase in planting density, due to the development of dwarfing rootstocks. This paper presents a comparison between two training systems with ‘Soleta’ almond cultivar: a super high density (SHD) system using Rootpac-20 dwarfing rootstock versus an open-center training system using GF-677 rootstock. To this end, several parameters related to chlorophyll content (fluorescence and SPAD) and light interception (from photosynthetically active radiation (PAR) measurements) were monitored throughout two vegetative cycles, and other productive conditions (flowering, fruit set and production) were tracked at specific times of the cycle. The open-center system resulted in higher PAR interception than the SHD system, but also in the presence of poorly illuminated fractions of the canopy. Differences were observed between both systems in terms of average fruit weight and yield per canopy volume. Lower yields were obtained in SHD system than in open-center, which may be significantly increased by adapting the inter-row spacing. However, the degree of efficiency in the use of resources or productive inputs, such as irrigation, was favorable to the new SHD training system, so its potential to become a reference system in modern plantations (using over-the-row harvesters similar to those used for vine and olive trees) seems promising.

Rising tropospheric ozone (O3) in the atmosphere is detrimental to crop’s productivity and is one of the reasons for a warmer climate. The present study describes diurnal changes in gaseous exchange, chlorophyll fluorescence, ascorbic acid, and photoassimilate parameters in flag leaves of four Indian wheat (Triticum aestivum L.) cultivars (two early sown and two late sown cultivars) under ambient and elevated O3 treatments, using the open-top chambers (OTCs). Results showed that the diurnal pattern of photosynthetic rate (Ps), sucrose, and ascorbic acid content varied according to changes in photosynthetically active radiation (PAR) and O3 concentrations during the daytime and were maximum between 10:00 to 12:00. The present study suggested that elevated O3 caused more negative effects on photosystem II in early sown compared to late sown cultivars. The greater loss of photosynthesis led to lower production of photoassimilates in early sown cultivars, which utilized more assimilates in ascorbic acid formation for detoxification of ROS formed due to elevated O3. This work will also help to identify the robustness of physiological machinery in different wheat cultivars under elevated levels of O3, and may be used for selection of suitable cultivars during future breeding programs.

Abstract Although anucleate, platelets are recognized to undergo apoptotic-like events, with some characteristics of activated platelets resembling those of apoptotic nucleated cells, e.g. membrane blebbing (microparticle (MP) formation), exposure of phosphatidylserine (PS). There are reports in the older literature that platelets from BSS patients expose more PS and have enhanced senescence. In the present study, using flow cytometry, we investigated apoptotic-like events, specifically PS exposure, MP formation, cell shrinkage and loss of mitochondrial inner membrane potential (ΔΨm) in platelets from 2 BSS patients (BSS-Ps), compared with platelets from a patient with another inherited macrothrombocytopenia - an MYH9-related disorder (MYH9-RD-P) - and from normal controls. Investigations were done using whole blood to avoid platelet manipulation, especially of the large platelets. Citrated blood was mixed with GPRP and Ca2+, and the agonists collagen (C; 20 μg/mL), thrombin (T; 1 U/mL), SFLLRN (PAR1 activating peptide (AP); 50 μM), AYPGKF (PAR4 AP; 250 μM), or combinations of C with T or the PAR APs. Platelets and MPs were identified as CD41-positive events; platelet size was expressed as median forward scatter (mFSC); MPs were defined as events <0.8 μm; PS exposure was measured as the % platelets with bound fluorescently-labeled annexin A5 and the mean fluorescence intensity (MFI) of bound annexin A5; and loss of ΔΨm was determined by decreased fluorescence of the potential-sensitive probe TMRM concurrently with PS exposure. Resting BSS and MYH9-RD platelets were larger than controls (mFSC of BSS-Ps: 136, 163; MYH9-RD-P: 126; controls: 50±2). Slightly more resting BSS platelets exposed PS than controls, as did MYH9-RD platelets (Table). Activation with C significantly increased the % platelets exposing PS, which was synergistically increased by T or the PAR1 and/or PAR4 APs; more BSS and MYH9-RD platelets exposed PS than did corresponding activated controls (Table). % PS Exposure Agonist(s) BSS-P1 BSS-P2 MYH9-RD-P controls none (resting platelets) 3.0 3.5 3.0 1.3±0.4 C 27.0 29.9 37.9 7.0±1.5 C+T 11.3 35.3 64.5 13.5±1.7 C+PAR1 AP 20.1 43.6 49.5 16.4±3.1 C+PAR4 AP 31.6 47.8 49.7 18.4±3.7 C+PAR1 AP+PAR4 AP 33.4 49.5 54.8 20.6±3.4 Interestingly, the platelets in the PS-exposing subpopulation were small (mFSC of BSS-Ps: 27, 30; MYH9-RD: 32; controls 18±1) and the annexin A5 MFI of this subpopulation of BSS and MYH9-RD platelets was .5-fold higher than that of controls irrespective of the platelet agonist(s). Unstimulated blood samples from patients and controls had 1–2% MPs; adding combinations of agonists led to the highest MP production, with control platelets producing 5–6% MPs, and BSS and MYH9-RD platelets, a 1.5–2.5-fold greater amount. Another apoptosis hallmark, cell shrinkage, was observed upon platelet activation in the non-PS-exposing population; in response to the various agonists, the size of this platelet population in patients and controls correlated inversely with the amount of PSexposing platelets formed (P<0.0.001) and the amount of MPs formed (P<0.0.001). In nucleated cells, dissipation of ΔΨm precedes PS exposure. However, activated BSS, MYH9-RD and control platelets exposed PS with or without a dissipated ΔΨm; ~50% of activated PS-exposing platelets did not exhibit loss of ΔΨm. While only 5–10% of activated non-PS-exposing control or MYH9-RD platelets exhibited ΔΨm loss, a substantial proportion, ~50%, of activated non-PS-exposing BSS platelets had a dissipated ΔΨm; in a rabbit model, we have previously found non-PS-exposing platelets with a collapsed ΔΨm to be associated with platelet senescence. In summary, we show that: PAR1 and PAR4 mediate the synergistic effect of T on C-stimulated PS expression on BSS, MYH9-RD and control platelets; the apoptotic-like event of cell shrinkage occurs in BSS platelets as well as MYH9-RD and control platelets; other such events, PS exposure and MP formation, are enhanced in BSS platelets compared with controls likely due to the large size of BSS platelets since they are also observed in MYH9-RD platelets; activation to expose PS can occur independently of ΔΨm dissipation in BSS, MYH9-RD and control platelets; and the loss of ΔΨm in non-PS-exposing platelets, an apoptotic-like event that is associated with platelet senescence and one that occurs only to a limited extent in MYH9-RD and control platelets, is a previously unrecognized characteristic of BSS platelets.