Metabolic modeling of Chlamydomonas reinhardtii: energy requirements for photoautotrophic growth and maintenance

In this study, a metabolic network describing the primary metabolism of Chlamydomonas reinhardtii was constructed. By performing chemostat experiments at different growth rates, energy parameters for maintenance and biomass formation were determined. The chemostats were run at low irradiances resulting in a high biomass yield on light of 1.25 g  mol−1. The ATP requirement for biomass formation from biopolymers (Kx) was determined to be 109 mmol g−1 (18.9 mol mol−1) and the maintenance requirement (mATP) was determined to be 2.85 mmol g−1 h−1. With these energy requirements included in the metabolic network, the network accurately describes the primary metabolism of C. reinhardtii and can be used for modeling of C. reinhardtii growth and metabolism. Simulations confirmed that cultivating microalgae at low growth rates is unfavorable because of the high maintenance requirements which result in low biomass yields. At high light supply rates, biomass yields will decrease due to light saturation effects. Thus, to optimize biomass yield on light energy in photobioreactors, an optimum between low and high light supply rates should be found. These simulations show that metabolic flux analysis can be used as a tool to gain insight into the metabolism of algae and ultimately can be used for the maximization of algal biomass and product yield

Microenvironment involved in FPR1 expression by human glioblastomas

Formyl peptide receptor 1 (FPR1) activity in U87 glioblastoma (GBM) cells contributes to tumor cell motility. The present study aimed to evaluate the FPR1 expression in human GBM, the possibility to elicit agonist induced FPR1 activation of GBM cells and inhibit this activation with chemotaxis inhibitory protein of Staphylococcus aureus (CHIPS). Immunohistochemistry was used to assess FPR1 expression in GBM patient samples, which was present in all 178 samples. Also FPR1 mRNA levels measured with quantitative PCR, could be detected in all 25 GBM patient samples tested. Activation of FPR1 in U87 cells, as measured by human mitochondrial-derived agonists, increased calcium mobilization, AKT and ERK1/2 phosphorylation, and ligand-induced migration. Inhibition of all responses could be achieved with CHIPS. Eight early passage human Groningen Glioma (GG) cell lines, isolated from primary GBM tissue were screened for the presence of FPR1. FPR1 mRNA and protein expression as well as receptor activation could not be detected in any of these early passage GG cell lines. However FPR1 was present in ex vivo tumors formed by the same GG cell lines after being implanted in mouse brains. FPR1 is highly expressed in human GBM specimens, it can be activated by human mitochondrial-derived agonists in U87 and inhibited with CHIPS. FPR1 cannot be detected in early passage GG cell lines in vitro, however when engrafted in the mouse brain these cells show FPR1 expression. These results suggest a role of the brain microenvironment in FPR1 expression in GBM.</p

Shining Light On The Laying Hen Brain: The Effect Of Light During Incubation Depends On Cognitive Task And Hybrid

The influence of early life on animal welfare later in life is increasingly recognized as important. In chickens, a promising early-life intervention is the exposure to light during incubation. Due to the position of the embryo in the egg, the two brain hemispheres receive different amounts of light stimulation via the eyes. This unequal stimulation results in increased lateralization of the brain, which is the specialization of brain hemispheres on certain functions. In current commercial practice, chickens are incubated in complete darkness. Information about the effect of light during incubation on laying hen cognition is scarce, although stronger effects are expected in hybrids coming from white eggs than brown eggs. In this experiment, we therefore incubated eggs of ISA Brown (ISAb) and Dekalb White (DW) layer hybrids (N = 1200) either in a green light-dark cycle (light), or in complete darkness (dark). At hatching, brains were collected from 80 individuals. Tyrosine hydroxylase and DoubleCortin levels were investigated, but no significant differences were found between incubation treatments or hybrids. Then, cognition tests were performed on the surviving females. In a detour test (N = 198), light-exposed chicks showed 24% more lateralized behavior (i.e., turned left from the obstacle) than chicks incubated in the dark, regardless of the hybrid. In a 5-day holeboard test (N = 78), adult hen performance results were inconsistent. Finally, during a social recognition test (N = 76), ISAb-dark showed significantly greater interest for the familiar hen, whereas DW-light showed greater interest for the unfamiliar hen. To conclude, light during incubation affected the brains and cognition of laying hens at different life stages post-hatching, although the effects were not consistent across tests or hybrids

Changes in extreme regional sea surface height due to an abrupt weakening of the Atlantic meridional overturning circulation

As an extreme scenario of dynamical sea level changes, regional sea surface height (SSH) changes that occur in the North Atlantic due to an abrupt weakening of the Atlantic meridional overturning circulation (AMOC) are simulated. Two versions of the same ocean-only model are used to study the effect of ocean model resolution on these SSH changes: a high-resolution (HR) strongly eddying version and a low-resolution (LR) version in which the effect of eddies is parameterised. The weakening of the AMOC is induced in both model versions by applying strong freshwater perturbations around Greenland. A rapid decrease of the AMOC in the HR version induces much shorter return times of several specific regional and coastal extremes in North Atlantic SSH than in the LR version. This effect is caused by a change in main eddy pathways associated with a change in separation latitude of the Gulf Stream

Early-life interventions to prevent feather pecking and reduce fearfulness in laying hens

Severe feather pecking, the pulling out of feathers of conspecifics, is a major welfare issue in laying hens. Possible underlying causes are fearfulness and lack of foraging opportunities. Because early life is a crucial stage in behavioral development, adapting the incubation and rearing environment to the birds' needs may reduce fearfulness and prevent the development of feather pecking. In a 2 × 2 factorial design study, we investigated whether a green light-dark cycle throughout incubation, which resembles natural incubation circumstances more than the standard dark incubation, and foraging enrichment with live larvae during rearing reduce fearfulness and feather pecking and increase foraging behavior of laying hen pullets from an early age onwards. In this 2-batch experiment, 1,100 ISA Brown eggs were incubated under either 0 h of light/24 h of darkness or 12 h of green LED light/12 h of darkness. After hatching, 400 female chicks (200 per batch) were housed in 44 pens (8–10 chicks per pen). During the entire rearing phase (0–17 wk of age), half of the pens received black soldier fly larvae in a food puzzle as foraging enrichment. We assessed fear of novel objects and humans, feather pecking, plumage condition, foraging behavior, and recovery time after a 3-fold vaccination (acute stressor). A slight increase in the number of foraging bouts was only seen with larvae provisioning (rate ratio 1.19, 95% CI 1.02–1.29, P = 0.008). Neither lighted incubation nor larvae provisioning affected fearfulness, feather pecking, plumage condition or recovery time after vaccination. In conclusion, the present study showed no effects of light during incubation and minor effects of foraging enrichment during rearing on the behavior of laying hen pullets. Further research is recommended on other welfare aspects

On the complexities of utilizing large-scale lightpath-connected distributed cyberinfrastructure

In Autumn 2013, we—an international team of climate scientists, computer scientists, eScience researchers, and e-Infrastructure specialists—participated in the enlighten your research global competition, organized to showcase advanced lightpath technologies in support of state-of-the-art research questions. As one of the winning entries, our enlighten your research global team embarked on a very ambitious project to run an extremely high resolution climate model on a collection of supercomputers distributed over two continents and connected using an advanced 10 G lightpath networking infrastructure. Although good progress was made, we were not able to perform all desired experiments due to a varying combination of technical problems, configuration issues, policy limitations and lack of (budget for) human resources to solve these issues. In this paper, we describe our goals, the technical and non-technical barriers, we encountered and provide recommendations on how these barriers can be removed so future project of this kind may succeed

Adjusted Light and Dark Cycles Can Optimize Photosynthetic Efficiency in Algae Growing in Photobioreactors

Biofuels from algae are highly interesting as renewable energy sources to replace, at least partially, fossil fuels, but great research efforts are still needed to optimize growth parameters to develop competitive large-scale cultivation systems. One factor with a seminal influence on productivity is light availability. Light energy fully supports algal growth, but it leads to oxidative stress if illumination is in excess. In this work, the influence of light intensity on the growth and lipid productivity of Nannochloropsis salina was investigated in a flat-bed photobioreactor designed to minimize cells self-shading. The influence of various light intensities was studied with both continuous illumination and alternation of light and dark cycles at various frequencies, which mimic illumination variations in a photobioreactor due to mixing. Results show that Nannochloropsis can efficiently exploit even very intense light, provided that dark cycles occur to allow for re-oxidation of the electron transporters of the photosynthetic apparatus. If alternation of light and dark is not optimal, algae undergo radiation damage and photosynthetic productivity is greatly reduced. Our results demonstrate that, in a photobioreactor for the cultivation of algae, optimizing mixing is essential in order to ensure that the algae exploit light energy efficiently