Phylogenetic relatedness and proboscis length contribute to structuring bumblebee communities in the extremes of abiotic and biotic gradients

Aim To improve our understanding of how biological communities assemble, we investigated changes in bumblebee communities in space along an elevation gradient. We assessed how much deterministic abiotic and biotic factors shape community assembly. We focused on proboscis length (influencing the species' dietary regime) and phylogenetic relatedness to investigate if competition and environmental filtering occur in more and less productive climates, respectively. Location Western Swiss Alps. Methods We recorded bumblebee species in 149 plots along a 1800-m wide elevation gradient. We contrasted two major clades of bumblebees, a short-tongued and a long-tongued clade. We calculated the phylogenetic and proboscis-length diversity of the bumblebee communities and compared these observed data with a random distribution to detect clustering likely to be caused by environmental filtering or overdispersion likely to be caused by competition. We compared the prevalence of clustered and overdispersed communities along the gradients of plant species richness (biotic) and temperature (abiotic). Results Under colder conditions, where plant species richness is lower and floral resources are scarcer, the clade with shorter proboscides prevails over the clade with longer proboscides, and communities are functionally and phylogenetic clustered. Under warmer conditions, we found phylogenetic but not functional overdispersion in communities. Main conclusions We show for the first time a strong correlation between phylogenetic relatedness, proboscis length and species distribution along temperature and plant richness gradients shaping bumblebee communities. The low temperatures and low levels of plant species richness limit the dispersal of the species from the long-tongued clade, which have more specialized diets, into high-elevation areas. Competition under warmer conditions may produce communities composed of less closely related species that share distinct ecological preferences. Our empirical results corroborate theoretical expectation as well as experiments on the prevalence of deterministic processes in the most severe and most productive parts of environmental gradients.

Nucleation and growth of GaN nanorods on Si (111) surfaces by plasma-assisted molecular beam epitaxy - The influence of Si- and Mg-doping

The self-assembled growth of GaN nanorods on Si (111) substrates by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions is investigated. An amorphous silicon nitride layer is formed in the initial stage of growth that prevents the formation of a GaN wetting layer. The nucleation time was found to be strongly influenced by the substrate temperature and was more than 30 min for the applied growth conditions. The observed tapering and reduced length of silicon-doped nanorods is explained by enhanced nucleation on nonpolar facets and proves Ga-adatom diffusion on nanorod sidewalls as one contribution to the axial growth. The presence of Mg leads to an increased radial growth rate with a simultaneous decrease of the nanorod length and reduces the nucleation time for high Mg concentrations.

Electroluminiscence and optical amplification in silicon nanostructures: towards the integration of electronics and photonics

This line of research of my group intends to establish a Silicon technological platform in the field of photonics allowing the development of a wide set of applications. Particularly, what is still lacking in Silicon Photonics is an efficient and integrable light source such an LED or laser. Nanocrystals in silicon oxide or nitride matrices have been recently demonstrated as competitive materials for both active components (electrically and optically driven light emitters and optical amplifiers) and passive ones (waveguides and modulators). The final goal is the achievement of a complete integration of electronic and optical functions in the same CMOS chip. The first part of this paper will introduce the structural and optical properties of LEDs fabricated from silicon nanostructures. The second will treat the interaction of such nanocrystals with rare-earth elements (Er), which lead to an efficient hybrid system emitting in the third window of optical fibers. I will present the fabrication and assessment of optical waveguide amplifiers at 1.54 ¿m for which we have been able to demonstrate recently optical gain in waveguides made from sputtered silicon suboxide materials.

Regional reproducibility of calibrated BOLD functional MRI: implications for the study of cognition and plasticity.

Calibrated BOLD fMRI is a promising alternative to the classic BOLD contrast due to its reduced venous sensitivity and greater physiological specificity. The delayed adoption of this technique for cognitive studies may stem partly from a lack of information on the reproducibility of these measures in the context of cognitive tasks. In this study we have explored the applicability and reproducibility of a state-of-the-art calibrated BOLD technique using a complex functional task at 7 tesla. Reproducibility measures of BOLD, CBF, CMRO2 flow-metabolism coupling n and the calibration parameter M were compared and interpreted for three ROIs. We found an averaged intra-subject variation of CMRO2 of 8% across runs and 33% across days. BOLD (46% across runs, 36% across days), CBF (33% across runs, 46% across days) and M (41% across days) showed significantly higher intra-subject variability. Inter-subject variability was found to be high for all quantities, though CMRO2 was the most consistent across brain regions. The results of this study provide evidence that calibrated BOLD may be a viable alternative for longitudinal and cognitive MRI studies.

The adjustment of energy expenditure and oxidation to energy intake: the role of carbohydrate and fat balance.

Evidence is accumulating that total body mass and its relative composition influence the rate of fat utilization in man. This effect can be explained by two factors operating in concert: (i) the effect of the size of the tissue mass and (ii) the nature of the fuel mix oxidized, i.e. the proportion of energy derived from fat vs. carbohydrate. In a cross-sectional study of 307 women with increasing degrees of obesity, we observed that the respiratory quotient (RQ) in post-absorptive conditions became progressively lower with increased body fatness, indicating a shift in substrate utilization. However, the RQ is known to be also influenced by the diet commonly ingested by the subjects. A short-term mixed diet overfeeding in lean and obese women has also demonstrated the high sensitivity of RQ to changes in energy balance. Following a one-day overfeeding (2500 kcal/day in excess of the previous 24 h energy expenditure), the magnitude of increase in RQ was identical in lean and obese subjects and the net efficiency of substrate utilization and storage was not influenced by the state of obesity.

Diet and the risk of head and neck cancer: a pooled analysis in the INHANCE consortium.

We investigated the association between diet and head and neck cancer (HNC) risk using data from the International Head and Neck Cancer Epidemiology (INHANCE) consortium. The INHANCE pooled data included 22 case-control studies with 14,520 cases and 22,737 controls. Center-specific quartiles among the controls were used for food groups, and frequencies per week were used for single food items. A dietary pattern score combining high fruit and vegetable intake and low red meat intake was created. Odds ratios (OR) and 95% confidence intervals (CI) for the dietary items on the risk of HNC were estimated with a two-stage random-effects logistic regression model. An inverse association was observed for higher-frequency intake of fruit (4th vs. 1st quartile OR = 0.52, 95% CI = 0.43-0.62, p (trend) < 0.01) and vegetables (OR = 0.66, 95% CI = 0.49-0.90, p (trend) = 0.01). Intake of red meat (OR = 1.40, 95% CI = 1.13-1.74, p p (trend) < 0.01) was positively associated with HNC risk. Higher dietary pattern scores, reflecting high fruit/vegetable and low red meat intake, were associated with reduced HNC risk (per score increment OR = 0.90, 95% CI = 0.84-0.97).

What can animal memory study bring to the assessment of memory and cognitive skills for intellectual Disability?

Three case studies are presented to investigate the possibility of evaluating memory and cognitive capacities of severe intellectual disability with attention given to the ecological environment. Two 22-year-old male patients and a 27-year-old male patient, all three with severe intellectual disability with no verbal communication skills, were evaluated with a new and original paradigm adapted to study cognition in humans from experimental paradigms. We developed a test based on animal models to complement the "home" scale of the Adolescent and Adult Psychoeducational Profile (AAPEP), an assessment instrument designed for adolescents and adults with severe developmental disabilities. Results show that the new instrument is helpful, not only to staff members who can better understand the poor performances of their patients in daily life activities but also in the elaboration of individual acquisition plans. These preliminary results demonstrate the interest in developing a larger controlled study and in publishing our procedure.

The role of WNT and mTOR in human memory T cell formation

Cancer is one of the world's leading causes of death with a rising trend in incidence. These epidemiologic observations underline the need for novel treatment strategies. In this regard, a promising approach takes advantage of the adaptive effector mechanisms of the immune system, using T lymphocytes to specifically target and destroy tumour cells. However, whereas current approaches mainly depend on short-lived, terminally differentiated effector T cells, increasing evidence suggests that long lasting and maximum efficient immune responses are mediated by low differentiated memory T cells. These memory T cells should display characteristics of stem cells, such as longevity, self-renewal capacity and the ability to continuously give rise to further differentiated effectors. These stem celllike memory T (TSCM) cells are thought to be of key therapeutic value as they might not only attack differentiated tumour cells, but also eradicate the root cause of cancer, the cancer stem cells themselves. Thus, efforts are made to characterize TSCM cells and to identify the signalling pathways which mediate their induction. Recently, a human TSCM cell subset was described and the activation of the Wnt-ß-catenin signalling pathway by the drug TWS119 during naive CD8+ T (TN) cell priming was suggested to mediate their induction. However, a precise deciphering of the signalling pathways leading to TSCM cell induction and an in-depth characterization of in vitro induced and in vivo occurring TSCM cells remain to be performed. Here, evidence is presented that the induction of human and mouse CD8+ and CD4+ TSCM cells may be triggered by inhibition of mechanistic/mammalian target of rapamycin (mTOR) complex 1 with simultaneously active mTOR complex 2. This molecular mechanism arrests a fraction of activated TN cells in a stem cell-like differentiation state independently of the Wnt-ß-catenin signalling pathway. Of note, TWS119 was found to also inhibit mTORCl, thereby mediating the induction of TSCM cells. Suggesting an immunostimulatory effect, the acquired data broaden the therapeutic range of mTORCl inhibitors like rapamycin, which are, at present, exclusively used due to their immunosuppressive function. Furthermore, by performing broad metabolic analyses, a well-orchestrated interplay between intracellular signalling pathways and the T cells' metabolic programmes could be identified as important regulator of the T cells' differentiation fate. Moreover, in vitro induced CD4+ TSCM cells possess superior functional capacities and share fate-determining key factors with their naturally occurring counterparts, assessed by a first-time full transcriptome analysis of in vivo occurring CD4+ TN cell, TSCM cells and central memory (TCM) cells and in vitro induced CD4+ TSCM cells. Of interest, a group of 56 genes, with a unique expression profile in TSCM cells could be identified. Thus, a pharmacological mechanism allowing to confer sternness to activated TN cells has been found which might be highly relevant for the design of novel T cell-based cancer immunotherapies.