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Improving cross-species extrapolation of chemical sensitivity
Get PDFThe aim of this thesis was to improve the development of models describing species sensitivity towards chemical stressors. This included unraveling decisions that might be of importance in the modeling process, obtaining a better mechanistic understanding of differences in species sensitivity, and providing recommendations for applying such modeling approaches within or across different taxonomic groups in freshwater ecosystems all over the globe. To accomplish this global applicability, we primarily focus on traits-based instead of taxonomy-based approaches on the development of predictive models. A trait is a phenotypic or ecological character of an organism at individual or population level, and describes the physical characteristics, ecological niche and functional role of a species within the ecosystem. We make use of traits, because they are transferable across geographies, add mechanistic and diagnostic knowledge and can be easily translated from taxonomic analyses priory preformed. We start this thesis with presenting a new predictive modelling approach for potential use in environmental risk assessment (ERA). This new approach constructs macroinvertebrate sensitivity rankings, and subsequently, predictive trait models for a set of pre-defined modes of action (MOA). Each model reveals different taxonomic patterns of species sensitivity, demonstrating that there is not one (set of) species which is most sensitive to all chemicals. The traits included in the models additionally provide information on the mechanisms underlying differences in species sensitivity. We identified, for instance, traits like life cycle duration and respiration mode as important in explaining species sensitivity, and which are hypothesized to be indicators of respectively metabolism and uptake rates. Additionally, we provide an accurate picture of which species-chemical combinations still lack sufficient data, and found that no or incomplete traits data were available for 71% of the species, making the lack of trait data the main obstacle in model construction. Although these models delivered a new understanding of species sensitivity, they also demonstrate that using traits-data alone will never results in explaining all differences in species sensitivity. Therefore, we develop the models further by adding taxonomic relatedness as an additional predictor of species sensitivity. We indeed find that model performance increases, although only marginally. Besides improving the models further, we also develop the tool further, so that it is now able to predict the sensitivity of species never tested before. We apply the developed models and tool to community assemblages at two different spatial scales (continental and national) and for two different MOAs (narcosis and acetylcholinesterase (AChE) inhibition). The community composition of European freshwater ecoregions (ERs) is used for the application of our models at the continental scale, while the reference database of the RIVPACS (River InVertebrate Prediction And Classification System) tool is used for river-type scale within the United Kingdom. We found that on a relative scale, 46% and 33% of European species were ranked as more sensitive towards narcosis and AChE inhibition, respectively. These more sensitive species were distributed with higher occurrences in the south and north-eastern regions, reflecting known continental patterns of endemic macroinvertebrate biodiversity. At the UK level, we found contradicting sensitivity patterns depending on the MOA, with more species displaying relative sensitivity to narcotic MOA in north and north-western regions, and more species with relative sensitivity to AChE inhibition MOA in south and south-western regions. Next, instead of looking for alternative predictors of species sensitivity, we look for alternative descriptors of species sensitivity. Recently, mechanistic effect models have been suggested as an alternative to the statistical summaries (e.g. LC50s) that are currently being used to assess the potential risk of chemicals to the diversity of all living species. An example of such quantitative mechanistic effect models are the toxicokinetic- toxicodynamic models of the General Unified Threshold models of Survival (GUTS) framework, which link external exposure and survival effects by describing the processes of uptake, biotransformation, elimination, damage and internal recovery. Parameterization of these models by means of traits enables prediction of standard sensitivity endpoints for a wide range of species and for multiple exposure patterns. We find that GUTS models parameterized on traits are indeed able to approximate the sensitivity of freshwater arthropods, and additionally allow us to understand the underlying processes of species sensitivity better. Since so many decisions have to be made regarding the predictors or descriptors that can be used to describe species sensitivity, we provide a review on currently existing cross-species extrapolation methodologies. We argue that risk assessment can benefit most from modelling approaches when species sensitivity is described based on effects that are ecologically relevant and robust. Additionally, specific attention should be paid to the heterogeneity of the training data, since this strongly influences the reliability of the resulting models. Regarding which predictors are useful for explaining differences in species sensitivity, we develop an integrated framework, combining the strengths of interspecies-correlation, relatedness-based, traits-based, and genomic-based extrapolation methods. Finally, we discuss that regardless of the statistical method used, statistically significant models can be found. However, the usefulness and applicability of these models varies considerably according to modelling choices made. We therefore recommend the publication of scientific code along with scientific studies to simultaneously clarify modelling choices, and enable continuation and elaboration on existing work. We conclude this thesis by explaining the three ways in which cross-species extrapolation methods can be used in the prospective risk assessment for chemicals: i) to support priority setting procedures to narrow down further assessment work, ii) to supplement the use of experimental data in weight-of-evidence approaches, and iii) to replace or completely substitute the need for experimental data. Through this development, our approach can help reduce animal testing and contribute towards a new predictive ecotoxicology framework
Considerations for application of granular activated carbon as capacitive bioanode in bioelectrochemical systems
Get PDFIn the last decades, the research in Microbial Fuel Cells (MFCs) has expanded from electricity production and wastewater treatment to remediation technologies, chemicals production and low power applications. More recently, capacitors have been implemented to boost the power output of these systems when applied as wastewater treatment technology. Specifically, the use of granular capacitive materials (e.g. activated carbon granules) as bioanodes has opened up new opportunities for reactor designs and upscaling of the technology. One of the main features of these systems is that charge and discharge processes can be separated, which offers multiple advantages over more conventional reactor types. In this manuscript, we discuss several aspects to consider for the application of capacitive granules as bioanodes in MFCs and other bioelectrochemical systems, as well as the recent advances that have been made in applying these granules in various reactor systems. Similarly, we discuss the granule properties that are key to determine system operation and performance, and show that biofilm growth is highly dependent on the efficiency of discharge.</p
Eiwittransitie in perspectief: Duurzaam en gezond eten
No full textDe Schijf van Vijf is hét advies van de overheid voor gezond en duurzaam eten in Nederland. Maar de overheid wil het voedselsysteem verder verduurzamen en stuurt daarom aan op een eiwittransitie: minder eiwit eten, waarvan een groter deel plantaardig eiwit. Dit kan gevolgen hebben voor de volksgezondheid, met name bij kwetsbare groepen
The association between dietary and skin advanced glycation end products: the Rotterdam Study
Get PDFBackgroundAdvanced glycation end products (AGEs) accumulate in tissues with age and in conditions such as diabetes mellitus and chronic kidney disease (CKD), and they may be involved in age-related diseases. Skin AGEs measured as skin autofluorescence (SAF) are a noninvasive reflection of long-term AGE accumulation in tissues. Whether AGEs present in the diet (dAGEs) contribute to tissue AGEs is unclear.ObjectivesOur aim was to investigate the association between dietary and skin AGEs in the Rotterdam Study, a population-based cohort of mainly European ancestry.MethodsIn 2515 participants, intake of 3 dAGEs [carboxymethyl-lysine (CML), N-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MGH1), and carboxyethyl-lysine (CEL)] was estimated using FFQs and the content of AGEs measured in commonly consumed foods. SAF was measured 5 y (median value) later using an AGE Reader. The association of dAGEs with SAF was analyzed in linear regression models and stratified for diabetes and chronic kidney disease (CKD, defined as estimated glomerular filtration rate ≤60 mL/min) status.ResultsMean ± SD intake was 3.40 ±0.89 mg/d for CML, 28.98 ±7.87 mg/d for MGH1, and 3.11 ±0.89 mg/d for CEL. None of them was associated with SAF in the total study population. However, in stratified analyses, CML was positively associated with SAF after excluding both individuals with diabetes and individuals with CKD: 1 SD higher daily CML intake was associated with a 0.03 (95% CI: 0.009, 0.05) arbitrary units higher SAF. MGH1 and CEL intake were not significantly associated with SAF. Nevertheless, the associations were stronger when the time difference between dAGEs and SAF measurements was shorter.ConclusionsHigher dietary CML intake was associated with higher SAF only among participants with neither diabetes nor CKD, which may be explained by high AGE formation in diabetes and decreased excretion in CKD or by dietary modifications in these disease groups. The dAGE–SAF associations were also modified by the time difference between measurements. Our results suggest that dAGEs can influence tissue AGE accumulation and possibly thereby age-related diseases. This trial was registered at the Netherlands National Trial Register as NTR6831 (http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=6831) and at the WHO International Clinical Trials Registry Platform as NTR6831 (http://www.who.int/ictrp/network/primary/en/).<br/
Nutrient solutions for Arabidopsis thaliana : A study on nutrient solution composition in hydroponics systems
Get PDFBackground: There is little information on the effect of nutrient solutions composition on Arabidopsis growth. Therefore, we compared growth performance of Arabidopsis thaliana (Col-0) grown on the most commonly used nutrient solutions in deep water culture: Hoagland and Arnon, Murashige and Skoog, Tocquin, Hermans, and Conn. In addition to these nutrient solution composition experiments, we established Arabidopsis growth response curves for nutrient solution concentration and salt stress (NaCl). Results: Arabidopsis rosette fresh and dry weight showed an approximate linear decline with NaCl dose in deep water culture, i.e. 9% reduction relative to control per unit of electrical conductivity (EC in dS m-1, for scale comprehension 1 dS m-1 equals ~ 10 mM NaCl). The Tocquin, ½Hoagland and Conn nutrient solutions had equal and optimal growth performance. Optimal nutrient solution concentration for Tocquin and Hoagland was 0.8 to 0.9 dS m-1. Close to the EC of ½Hoagland (1.1 dS m-1), which is frequently used in Arabidopsis research. Conn solution showed optimal growth at much higher EC (2 dS m-1) indicating that it is a balanced nutrient solution that matches the needs of Arabidopsis. Full Murashige and Skoog solution (5.9 dS m-1) was lethal and diluted solutions (EC of 1.6 and 1.1 dS m-1) caused stress symptoms and severe growth retardation at later developmental stages. Conclusions: Arabidopsis thaliana (Col-0) plants grown in deep water culture showed a sixfold growth difference when commonly used nutrient solutions were compared. Murashige and Skoog solution should not be used as nutrient solution in deep water culture. Conn, Tocquin and ½Hoagland are balanced nutrient solutions which result in optimal Arabidopsis growth in hydroponic systems.</p
Modeling plant production at country level as affected by availability and productivity of land and water
No full textAssessing the food availability and food security of countries is a critical exercise in which crop simulation models are essential. Application of crop models has been limited often to estimate yield per unit area of one or a few important field crops, whereas what is really required is the total national production of diverse crops including forages, vegetables and fruit trees that compete for limited resources of land and water. In this study a simple crop model (SSM-iCrop2; Simple Simulation Models) was set up for an entire country using a bottom-up approach such that it provides representative estimates of potential yield and other crop properties at provincial level as influenced by climate, soil, management and cultivar. The information is then used to calculate total plant production at province and country levels, as influenced by available land and water resources and by the efficiency of utilizing the resources using the concepts relative yield gap and irrigation efficiency. Iran was used as a case study to develop the modeling framework and illustrative outputs. Development of the framework resulted in accumulation of large bodies of valuable geospatial information and statistics across disciplines that are critical for analysis of plant production at a country level. The framework allows different scenarios of national plant production to be evaluated. This includes assessing the possibility of increasing national plant production via intensification, optimizing water allocation across plant species at province and country levels by changing the cropping pattern, and assessing and prioritizing possible ways of adapting a country's agriculture to limited land and water resources and climate change.</p
The effects of shift work and sleep duration on cancer incidence in Alberta`s Tomorrow Project cohort
No full textIntroduction: We investigated the main effects of shift work and sleep duration on cancer incidence, and effect modification of the shift work-cancer incidence association by sleep duration. Methods: Shift work and sleep duration were assessed among 21,804 participants from Alberta`s Tomorrow Project. Incident cases of breast, prostate, colorectal and lung cancers were identified through registry linkage. Results: Having worked ≥6 years of rotating shift work (HR = 1.59, 95 % CI = 1.07, 2.37; P = 0.02) and having ever worked night shifts were associated with an increased risk of lung cancer (HR=1.71, 95 % CI=1.18, 2.47; P = 0.01), whereas having ever worked night shifts was associated with a reduced risk of prostate cancer in the latency-adjusted model only (HR=0.70, 95 % CI=0.51, 0.98; P = 0.04). No associations were found between shift work or sleep duration on the risks of breast and colorectal cancers. Some evidence of effect modification by sleep duration for the rotating shift work-lung cancer incidence association was noted (P = 0.06), with stratified analyses revealing borderline increased risk of lung cancer in participants with ≥6 years of rotating shift work and 9 h of sleep/day (HR=2.99, 95 % CI=1.12, 7.97; P = 0.03). No additional evidence of effect modification by sleep duration for shift work and cancer incidence was noted. Discussion: A consistent association between shift work employment and lung cancer risk was noted in this Canadian sample. Furthermore, some evidence of effect modification of the rotating shift work-lung cancer risk association by sleep duration was noted.</p
Modeling Cost Impacts and Adaptation of Freeze-Thaw Climate Change on a Porous Asphalt Road Network
No full textChanges in weather patterns pose a threat to the serviceability and long-term performance of roads, and porous asphalt (PA) roads are particularly sensitive to the freezing-thawing (FT) phenomenon. The main objective of this research is to assess the impact of climate change, particularly freezing and thawing cycles, on PA. Climate models predict changes in air temperature, not pavement temperature. To predict the climate change impact on pavements performance, this requires first establishing a relationship between air and road temperature and a correlation between pavement performance and FT cycles. This project focuses on the Netherlands, where PA pavement use has become mandatory, and recent severe winters have increased the discussion about the cold weather performance of porous asphalt and the potential challenges of changing winter weather patterns. When considering long-term changes in climate, the cost impacts of freeze-thaw on PA pavement are predicted to vary regionally and in most areas reach a point in the middle of the century when a reactive wait-and-see approach is more advantageous than proactive adaptation. Further research is suggested to refine the relationship between observed damage and freeze-thaw impacts on PA pavement.</p
Regulation of lipid droplet homeostasis by hypoxia inducible lipid droplet associated HILPDA
Get PDFNearly all cell types have the ability to store excess energy as triglycerides in specialized organelles called lipid droplets. The formation and degradation of lipid droplets is governed by a diverse set of enzymes and lipid droplet-associated proteins. One of the lipid droplet-associated proteins is Hypoxia Inducible Lipid Droplet Associated (HILPDA). HILPDA was originally discovered in a screen to identify novel hypoxia-inducible proteins. Apart from hypoxia, levels of HILPDA are induced by fatty acids and adrenergic agonists. HILPDA is a small protein of 63 amino acids in humans and 64 amino acids in mice. Inside cells, HILPDA is located in the endoplasmic reticulum and around lipid droplets. Gain- and loss-of-function experiments have demonstrated that HILPDA promotes lipid storage in hepatocytes, macrophages and cancer cells. HILPDA increases lipid droplet accumulation at least partly by inhibiting triglyceride hydrolysis via ATGL and stimulating triglyceride synthesis via DGAT1. Overall, HILPDA is a novel regulatory signal that adjusts triglyceride storage and the intracellular availability of fatty acids to the external fatty acid supply and the capacity for oxidation.</p
Archaeal diversity in sediment slurries degrading butyrate or propionate derived from Aarhus Bay
No full textThe relationship between predominant physiological types of prokaryotes in marine sediments and propionate degradation through sulfate reduction, fermentation, and methanogenesis was studied in marine sediments. Propionate conversion was assessed in slurries containing sediment from three different biogeochemical zones of Aarhus Bay, Denmark. Sediment slurries were amended with 0, 3 or 20 mM sulfate and incubated at 25°C and 10°C for 514 - 571 days. Methanogenesis in the sulfate zone and sulfate reduction in the methane zone slurries was observed. Both processes occurred simultaneously in enrichments originating from samples along the whole sediment. Bacterial community analysis revealed dominance of Desulfobacteraceae and Desulfobulbaceae members in sulfate-amended slurries incubated at 25°C and 10°C. Cryptanaerobacter belonging to Peptococcaceae family dominated sulfate-free, methanogenic slurries at 25°C, whereas bacteria related to Desulfobacteraceae were dominant at 10°C. Archaeal community analysis revealed prevalence of different genera belonging to Methanomicrobiales in slurries incubated at different temperatures and amended with different sulfate concentrations. Methanosarcinaceae were only detected in the absence of sulfate. In summary, Aarhus Bay sediment zones contain sulfate reducers, syntrophs and methanogens interacting with each other in the conversion of propionate. Our results indicate that in Aarhus Bay sediments Cryptanaerobacter degrades propionate in syntrophic association with methanogens