Susceptibility of spores of different ploidy levels from Antarctic Gigartina skottsbergii (Gigartinales, Rhodophyta) to ultraviolet radiation

Cet article a pour objet un bref tour d'horizon de la production scientifique de Jeffrey Scot Banks décédé le 21 Décembre 2000 à l'âge de 42 ans. Il a contribué à de nombreux domaines de la théorie économique et politique et compte aussi à son actif des articles d'économie expérimentale. Cette présenta- tion aborde de nombreux aspects de son travail avec une attention toute particulière à un ensemble qui porte aujourd'hui son nom et occupe une place de premier choix dans l'analyse des méthodes de décision à la majorité.This article is dedicated to a brief overview of the scientific work of Jeffrey Scot Banks who died on december 21 2000 at the age of 42. He has contributed to many fields in economic and political theory and also wrote several papers in experimental economics. Our presentation spans several dimensions of his work with a special focus on a set (known as the Banks set) which plays an important role in the analysis of majoritarian collective decision making

Effects of increased temperature and decreased salinity on Antarctic benthic marine diatoms

The most dramatic effects of Antarctic climate change are predicted around the Antarctic Peninsula. The temperature increase and glacier retreat are already affecting the marine environment. Here, the planktonic primary productivity is not sufficient to cover the carbon demand by benthic fauna. Hence, benthic microalgal productivity is of uttermost importance for the ecosystem functioning. In an outdoor set-up we tested the effects of increased temperature on benthic microalgal communities (primarily pennate diatoms) sampled from 5-7 m water depth. During 12 days, the diatoms were exposed to a temperature gradient in steps of ca 2°C, from ambient (2°C) up to ca 10°C. No effects on total cell numbers (growth) were observed (diatom composition remains to be analysed). Treatment effects in ΔF/Fm’ were found with highest yield at the highest temperature. In parallell to the outdoor experiment, a laboratory experiment was set-up to test the effect of decreased salinity from ambient salinity 33 to 21 units. Over 11 days, no treatment effects on cell number (growth) or photosynthetic activity (Fv/Fm) were observed. Therefore, an additional treatment with salinity 14 was set-up. Only Fv/Fm was tested but over 7 days, again no treatment effects were observed compared to the control. However, significantly lower NPQ values were found for salinity 33. Samples for analyses of bacterial biomass, photosynthetic pigments (HPLC), lipid peroxidation (thiobarbituric acid reactive substances (TBARs) assay) and biomass of heterotrophic bacteria are currently transported to Sweden. In conclusion, our preliminary results show that the benthic diatoms studied have a wide tolerance to rapid changes in both temperature and salinity, and as a community these diatoms do not seem affected by effects of the ongoing climate change around King George Island

Synergistic growth inhibition mediated by dual PI3K/mTOR pathway targeting and genetic or direct pharmacological AKT inhibition in human glioblastoma models

Molecular genetic aberrations in the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway are common in human cancers including glioblastoma, yet, novel therapeutic approaches targeting this pathway in glioblastoma have not been successful. We hypothesized that molecular profiling in combination with in vitro drug sensitivity testing allows to identify signatures associated with sensitivity or resistance to PI3K/mTOR pathway inhibition. We analyzed the molecular mechanisms determining sensitivity to PI3K/mTOR inhibition using gene silencing or pharmacological target inhibition and proliferation, clonogenicity or spherogenicity as readouts, in human long-term glioma cell (LTC) lines and glioma-initiating cells (GIC). Cultured glioma cells were universally sensitive to growth inhibition induced by PQR309, a novel, dual pan-PI3K/mTOR antagonist. Cells exhibited profound growth arrest, but little apoptotic or necrotic cell death as confirmed by electron microscopy; yet, there was evidence of senescence. Cell lines with high basal levels of phosphorylated (active) AKT, low levels of phosphorylated (inactive) protein translation repressor eukaryotic initiation factor (eIF) 4E-binding protein 1 (p4E-BP1), and high levels of Ser9-phosphorylated (inactive) glycogen synthase kinase 3 beta (pGSK3β) were more sensitive to PQR309. Accordingly, the activity of PQR309 was synergistically enhanced by AKT gene silencing or direct pharmacological AKT inhibition. In vivo studies confirmed the anti-glioma activity of PQR309 alone or in combination with AKT inhibition in the orthotopic LN-229 glioma xenograft model in nude mice. These data justify to explore combined targeted therapy approaches in glioblastoma that aim at down-regulating AKT function to enhance the therapeutic potential of dual PI3K/mTOR inhibitors

Total oxygen fluxes, and diatom density, diatom biomass and diversity of the diatom community in spring 2016 and environmental photosynthetically active radiation from 2015 and 2016 from three stations in Potter Cove, Antarctica

The Antarctic Peninsula experiences a fast retreat of glaciers, which correlates with an increased release of particles and related increased sedimentation and thus, a decrease in the available light for benthic primary production. We investigated how changes in the general sedimentation and shading patterns affect the primary production by benthic microalgae, the microphytobenthos. In order to determine potential net primary production and respiration of the microphytobenthic community, sediment cores from locations exposed to different sedimentation rates and shading were exposed to photosynthetic active radiation (PAR, 400–700 nm) of 0–70 µmol photons m-2 s-1. Total oxygen fluxes and microphytobenthic diatom community structure, density, and biomass were determined. Our study revealed that the net primary production of the microphytobenthos decreased with increasing sedimentation and shading, while the microphytobenthic diatom density and composition remained similar. By comparing our experimental results with in situ measured PAR intensities, we furthermore assessed the microphytobenthic primary production as an important carbon source within Potter Cove's benthic ecosystem. We propose that the microphytobenthic contribution to the total primary production may drop drastically due to Antarctic glacial retreat and correlated sedimentation and shading, with yet unknown consequences for the benthic heterotrophic community, its structure, and diversity