Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Perceptions of non-Western immigrant women on having breast cancer and their experiences with treatment-related changes in body weight and lifestyle : A qualitative study
    Kruif, Anja J.Th.C.M. de; Chrifou, Rabab ; Langeslag, Ghislaine L. ; Sondaal, Annemijn E.C. ; Franssen, Margret M.M. ; Kampman, Ellen ; Winkels, Renate M. ; Boer, Michiel R. de; Visser, Marjolein ; Westerman, Marjan J. - \ 2020
    PLoS ONE 15 (2020)7. - ISSN 1932-6203 - p. e0235662 - e0235662.

    BACKGROUND: The number of non-Western immigrants with breast cancer in the Netherlands has increased over the past decades and is expected to triple by 2030. Due to insufficient representation in clinical studies, it is unclear what the specific experiences and needs of these women are. Understanding how culture and religion affect these women's experience of breast cancer and how they deal with chemotherapy and treatment-related changes in body weight and lifestyle is crucial for health care professionals to be able to provide effective support. METHODS: A qualitative study was conducted using semi-structured interviews with 28 immigrant women with a history of breast cancer treated with chemotherapy. RESULTS: Women often associated breast cancer with taboo, death or bad luck. Religion offered these women guidance, strength and meaning to the disease, but also limited the women to openly talk about their disease. Women perceived lifestyle factors to have little influence on the development and treatment of cancer. After treatment, however, their thinking changed and these lifestyle factors became of paramount importance to them. They realised that they missed out on information about managing their own diet, exercise and body weight and were eager to share their experiences with other women in their culture with newly diagnosed breast cancer. CONCLUSION: Women became aware during and after breast cancer treatment that it was difficult for them to actively deal with their illness under the influence of their culture and religion. Based on their own experiences and acquired knowledge, they would like to give advice to newly diagnosed women on how to deal with breast cancer within their own culture and religion. Their recommendations could be used by mosques, churches, support groups and health care professionals, to ensure interventions during breast cancer treatment meet their religious and cultural needs and thus improve their quality of life.

    Laser Ablation Electrospray Ionization Hydrogen/Deuterium Exchange Ambient Mass Spectrometry Imaging
    Geenen, Fred A.M.G. van; Claassen, Frank W. ; Franssen, Maurice C.R. ; Zuilhof, Han ; Nielen, Michel W.F. - \ 2020
    Journal of the American Society for Mass Spectrometry 31 (2020)2. - ISSN 1044-0305 - p. 249 - 256.
    ambient mass spectrometry - hydrogen deuterium exchange - laser ablation electrospray ionization - mass spectrometry imaging - structure elucidation

    Identification and confirmation of known as well as unknown (bio)chemical entities in ambient mass spectrometry (MS) and MS imaging (MSI) mostly involve accurate mass determination, often in combination with MS/MS or MSn work flows. To further improve structural assignment, additional molecular information is required. Here we present an ambient hydrogen/deuterium exchange (HDX) laser ablation electrospray ionization (LAESI) MS method in which, apart from the accurate mass and MS/MS data, the number of exchangeable protons in (un)known molecules is obtained. While eventually presenting ambient HDX-LAESI-MSI, samples were not preincubated with deuterated solvents, but instead HDX occurred following fusion of ablated sample material with microdroplets generated by ESI of deuterated solvents. Therefore, the degree of HDX was first studied following ablation of nondeuterated sample solutions of melamine and monosaccharides. From these experiments, it was concluded that the set-up used could provide meaningful HDX data in support of molecular structure elucidation by significantly reducing the number of structure options from a measured elemental composition. This reduction was demonstrated with an unknown accurate m/z value obtained in the analysis of an orange slice, reducing the possible number of molecular structures having the same elemental composition by 87% due to the number of H/D exchanges observed. Next, deuterated and nondeuterated MS/MS experiments showed the number of exchangeable protons in the substructures from deuterated neutral losses in the product ion spectra, confirming the compound to be arginine. Finally, the potential of ambient HDX-LAESI-MSI was demonstrated by the imaging of (secondary) plant metabolites in a Phalaenopsis petal.

    Flavoenzyme-mediated regioselective aromatic hydroxylation with coenzyme biomimetics
    Guarneri, Alice ; Westphal, Adrie ; Leertouwer, J. ; Lunsonga, J. ; Franssen, M.C.R. ; Opperman, D.J. ; Hollmann, F. ; Berkel, W.J.H. van; Paul, C.E. - \ 2020
    ChemCatChem 12 (2020)5. - ISSN 1867-3880 - p. 1368 - 1375.
    Regioselective aromatic hydroxylation is desirable for the production of valuable compounds. External flavin‐containing monooxygenases activate and selectively incorporate an oxygen atom in phenolic compounds through flavin reduction by the nicotinamide adenine dinucleotide coenzyme and subsequent reaction with molecular oxygen. This study provides the proof of principle of flavoenzyme‐catalyzed selective aromatic hydroxylation with coenzyme biomimetics. The carbamoylmethyl‐substituted biomimetic in particular affords full conversion in less than two hours for the selective hydroxylation of 5 mM 3‐ and 4‐hydroxybenzoates, displaying similar rates as with NADH, achieving a 10 mM/h enzymatic conversion of the medicinal product gentisate. This biomimetic appears to generate less uncoupling of hydroxylation that typically leads to undesired hydrogen peroxide. Therefore, we show these flavoenzymes have the potential to be applied in combination with biomimetics.
    The Medicago truncatula nodule identity gene MtNOOT1 is required for coordinated apical-basal development of the root
    Shen, Defeng ; Kulikova, Olga ; Guhl, Kerstin ; Franssen, Henk ; Kohlen, Wouter ; Bisseling, Ton ; Geurts, René - \ 2019
    BMC Plant Biology 19 (2019)1. - ISSN 1471-2229
    Medicago truncatula - NBCL - NIN - NOOT-BOP-COCHLEATA-LIKE - NOOT1 - Rhizobium susceptible zone - Xylem cell differentiation

    Background: Legumes can utilize atmospheric nitrogen by hosting nitrogen-fixing bacteria in special lateral root organs, called nodules. Legume nodules have a unique ontology, despite similarities in the gene networks controlling nodule and lateral root development. It has been shown that Medicago truncatula NODULE ROOT1 (MtNOOT1) is required for the maintenance of nodule identity, preventing the conversion to lateral root development. MtNOOT1 and its orthologs in other plant species -collectively called the NOOT-BOP-COCH-LIKE (NBCL) family- specify boundary formation in various aerial organs. However, MtNOOT1 is not only expressed in nodules and aerial organs, but also in developing roots, where its function remains elusive. Results: We show that Mtnoot1 mutant seedlings display accelerated root elongation due to an enlarged root apical meristem. Also, Mtnoot1 mutant roots are thinner than wild-type and are delayed in xylem cell differentiation. We provide molecular evidence that the affected spatial development of Mtnoot1 mutant roots correlates with delayed induction of genes involved in xylem cell differentiation. This coincides with a basipetal shift of the root zone that is susceptible to rhizobium-secreted symbiotic signal molecules. Conclusions: Our data show that MtNOOT1 regulates the size of the root apical meristem and vascular differentiation. Our data demonstrate that MtNOOT1 not only functions as a homeotic gene in nodule development but also coordinates the spatial development of the root.

    Tryptophan intake and tryptophan losses in hemodialysis patients : A balance study
    Post, Adrian ; Huberts, Marleen ; Poppe, Enya ; Faassen, Martijn van; Kema, Ido P. ; Vogels, Steffie ; Geleijnse, Johanna M. ; Westerhuis, Ralf ; Ipema, Karin J.R. ; Bakker, Stephan J.L. ; Franssen, Casper F.M. - \ 2019
    Nutrients 11 (2019)12. - ISSN 2072-6643
    Dialysis - Dietary diaries - Excretion - Hydroxyindoleacetic acid - Kynurenine - Tryptophan

    Tryptophan depletion is common in hemodialysis patients. The cause of this depletion remains largely unknown, but reduced nutritional tryptophan intake, losses during dialysis or an increased catabolism due to an inflammatory state are likely contributors. Currently, little is known about tryptophan homeostasis in hemodialysis patients. We assessed dietary tryptophan intake, measured plasma tryptophan during dialysis, and measured the combined urinary and dialysate excretion of tryptophan in 40 hemodialysis patients (66 ± 15 years and 68% male). Patients had low tryptophan concentrations (27 ± 9 µmol/L) before dialysis. Mean dietary tryptophan intake was 4454 ± 1149 µmol/24 h. Mean urinary tryptophan excretion was 15.0 ± 12.3 µmol/24 h, dialysate excretion was 209 ± 67 µmol/24 h and combined excretion was 219 ± 66 µmol/24 h, indicating only 5% of dietary tryptophan intake was excreted. No associations were found between plasma tryptophan concentration and tryptophan intake, plasma kynurenine/tryptophan ratio or inflammatory markers. During dialysis, mean plasma tryptophan concentration increased 16% to 31 ± 8 µmol/L. Intradialytic increase in plasma tryptophan was associated with a lower risk of mortality, independent of age, sex and dialysis vintage (HR: 0.87 [0.76–0.99]; P = 0.04). Tryptophan intake was well above the dietary recommendations and, although tryptophan was removed during dialysis, mean plasma tryptophan increased during dialysis. The cause of this phenomenon is unknown, but it appears to be protective.

    Parasite load and site-specific parasite pressure as determinants of immune indices in two sympatric rodent species
    Hofmeester, Tim R. ; Bügel, Esther J. ; Hendrikx, Bob ; Maas, Miriam ; Franssen, Frits F.J. ; Sprong, Hein ; Matson, Kevin D. - \ 2019
    Animals 9 (2019)12. - ISSN 2076-2615
    Ecological immunology - Haptoglobin - Immune strategy - Natural antibodies - Neutrophil to lymphocyte ratio - Parasitology - Rodents - Vector-borne pathogens - Zoonosis

    Wildlife is exposed to parasites from the environment. This parasite pressure, which differs among areas, likely shapes the immunological strategies of animals. Individuals differ in the number of parasites they encounter and host, and this parasite load also influences the immune system. The relative impact of parasite pressure vs. parasite load on different host species, particularly those implicated as important reservoirs of zoonotic pathogens, is poorly understood. We captured bank voles (Myodes glareolus) and wood mice (Apodemus sylvaticus) at four sites in the Netherlands. We sampled sub-adult males to quantify their immune function, infestation load for ecto-and gastrointestinal parasites, and infection status for vector-borne microparasites. We then used regression trees to test if variation in immune indices could be explained by among-site differences (parasite pressure), among-individual differences in infestation intensity and infection status (parasite load), or other intrinsic factors. Regression trees revealed splits among sites for haptoglobin, hemagglutination, and body-mass corrected spleen size. We also found splits based on infection/infestation for haptoglobin, hemolysis, and neutrophil to lymphocyte ratio. Furthermore, we found a split between species for hemolysis and splits based on body mass for haptoglobin, hemagglutination, hematocrit, and body-mass corrected spleen size. Our results suggest that both parasite pressure and parasite load influence the immune system of wild rodents. Additional studies linking disease ecology and ecological immunology are needed to understand better the complexities of host–parasite interactions and how these interactions shape zoonotic disease risk.

    Ambient laser ablation electrospray ionization mass spectrometry imaging
    Geenen, Freddie A.M.G. van - \ 2019
    Wageningen University. Promotor(en): M.W.F. Nielen; H. Zuilhof, co-promotor(en): M.C.R. Franssen. - Wageningen : Wageningen University - ISBN 9789463439220 - 164

    Several molecular imaging techniques are available to study and understand biological objects, like positron-emission tomography, fluorescence, and magnetic resonance imaging. These techniques often require chemical probes and image in a targeted approach. As many biological questions can only be answered in a systems approach, molecular imaging methods that can simultaneously measure many molecules are desired. Mass spectrometry imaging (MSI) is capable of measuring many molecules simultaneously without the use of chemical probes. MSI experiments often require sample stage vacuum conditions and extensive sample pretreatment such as matrix application. Vacuum conditions can disrupt or damage biological samples, and sample pretreatment prevents real-time analyses and can cause analyte losses, analyte delocalization and denaturation of proteins. Ambient ionization was introduced to measure samples under ambient conditions without any sample pretreatment, and ambient MSI followed rapidly after that. A next generation of ambient MSI techniques is desired to improve its sensitivity, molecular mass range, and spatial resolution. This work aims to improve the capabilities and broaden the scope of laser ablation electrospray ionization (LAESI) MSI.

    In order to broaden the scope and increase the understanding of ambient LAESI-MS(I), polymer materials and synthetic fibers were investigated. The direct analysis of synthetic fibers under ambient conditions is highly desired to identify the polymer, the finishes applied and irregularities that may compromise its performance and value. In Chapter 2 LAESI ion mobility MS was used for the analysis of synthetic polymers and fibers. The key to this analysis was the absorption of laser light by aliphatic and aromatic nitrogen functionalities in the polymers. Analysis of polyamide (PA) 6, 46, 66, and 12 pellets and PA 6, 66, polyaramid and M5 fibers yielded characteristic fragment ions, enabling their unambiguous identification. Synthetic fibers are, in addition, commonly covered with a surface layer for improved adhesion and processing. The same setup, but operated in a transient infrared matrix-assisted laser desorption electrospray ionization mode, allowed the detailed characterization of the fiber finish layer and the underlying polymer. Differences in finish layer distribution may cause variations in local properties of synthetic fibers. In Chapter 2, also the feasibility of mass spectrometry imaging (MSI) of the distribution of a finish layer on the synthetic fiber and the successful detection of local surface defects was shown.

    Reactions in confined compartments like charged microdroplets are of increasing interest, notably because of their substantially increased reaction rates. When combined with ambient MS, reactions in charged microdroplets can be used to improve the detection of analytes or to study the molecular details of the reactions in real time. In Chapter 3, we introduce a reactive LAESI time-resolved MS method to perform and study reactions in charged microdroplets. This approach was demonstrated with so-called click chemistry reactions between substituted tetrazines and a strained alkyne or alkene. Click reactions are high-yielding reactions with a high atom efficiency. Although click reactions are typically at least moderately fast, in a reactive LAESI approach a substantial increase of reaction time is Summary 149 required for these reactions to occur. This increase was achieved using microdroplet chemistry and followed by MS using the insertion of a reaction tube between the LAESI source and the MS inlet, leading to near complete conversions due to significantly extended microdroplet lifetime. This novel approach allowed for the collection of kinetic data for a model click reaction and showed in addition excellent instrument stability, improved sensitivity, and applicability to other click reactions. In Chapter 3, reactive LAESI was also demonstrated in a mass spectrometry imaging setting to show its feasibility in future imaging experiments.

    In drug discovery it is important to identify phase I metabolic modifications as early as possible to screen for inactivation of drugs and/or activation of prodrugs. As the major class of reactions in phase I metabolism are oxidation reactions, oxidation of drugs with TiO2 photocatalysis can be used as a simple non-biological method to initially eliminate (pro)drug candidates with an undesired phase I oxidation metabolism. Analysis of reaction products is commonly achieved with mass spectrometry coupled to chromatography. However, sample throughput can be substantially increased by eliminating pretreatment steps and exploiting the potential of ambient MS. Furthermore, online monitoring of reactions in a time-resolved way would identify sequential modification steps. In Chapter 4 we introduce a novel (time-resolved) TiO2-photocatalysis LAESI-MS method for the analysis of drug candidates. This method was proven to be compatible with both TiO2-coated glass slides as well as solutions containing suspended TiO2 nanoparticles, and the results were in excellent agreement with studies on biological oxidation of several drugs. Additionally, a time-resolved LAESI-MS setup was developed and results for verapamil showed excellent analytical stability for online photocatalyzed oxidation reactions within the set-up up to at least one hour.

    Identification and confirmation of (bio)chemical entities in ambient MS mostly involves accurate mass determination, often in combination with MS/MS work flows. However, an accurate mass only provides the elemental composition of the (bio)molecule, still resulting in numerous possible structures. MS/MS procedures are often insufficient in differentiating between the hundreds possible candidate substances in database searches. Obtaining additional information and thereby improving structural assignment as well as reducing the vast number of possible candidates is thus of high importance in any ambient MS(I) study. In Chapter 5 we present an ambient hydrogen/deuterium exchange (HDX) LAESI-MS method for structure elucidation and confirmation of (bio)molecules. The concept was demonstrated with small molecules, peptides, and proteins. Moreover, the same approach could be applied to MSI as shown by the ambient MSI of arginine and oligosaccharides on an orange slice. Eventually, this approach will allow spatially resolved MSI of different protein conformers and may have a major impact in the life sciences.

    The main achievements that are described in this thesis offer insights on sample compatibility, hardware improvements to enable online time-resolved reactions and structure elucidation approaches. The outcome of the research chapters shows that LAESI-MS(I) is a highly versatile technique applicable to many research areas. Although the technique is highly 150 dependent on endogenous water in samples for analysis of intact molecules, LAESI can also be exploited for the analysis and identification of (water free) polymer materials. Unfortunately, LAESI sensitivity relative to electrospray ionization is weak, and therefore the technique can currently not live up to the status of the next generation of ambient MSI. Analytes that are present in high abundance are feasible for imaging by LAESI-MS. For low abundance analytes, however, several hardware improvements are required to substantially increase the sensitivity of the results. When the hardware improvements are developed and implemented, the road is open for many end users in, e.g., microbiology, pathology, and botany, to make significant breakthroughs in their fields.

    TiO2 Photocatalyzed Oxidation of Drugs Studied by Laser Ablation Electrospray Ionization Mass Spectrometry
    Geenen, Fred A.M.G. Van; Franssen, Maurice C.R. ; Miikkulainen, Ville ; Ritala, Mikko ; Zuilhof, Han ; Kostiainen, Risto ; Nielen, Michel W.F. - \ 2019
    Journal of the American Society for Mass Spectrometry 30 (2019)4. - ISSN 1044-0305 - p. 639 - 646.
    In drug discovery, it is important to identify phase I metabolic modifications as early as possible to screen for inactivation of drugs and/or activation of prodrugs. As the major class of reactions in phase I metabolism is oxidation reactions, oxidation of drugs with TiO2 photocatalysis can be used as a simple non-biological method to initially eliminate (pro)drug candidates with an undesired phase I oxidation metabolism. Analysis of reaction products is commonly achieved with mass spectrometry coupled to chromatography. However, sample throughput can be substantially increased by eliminating pretreatment steps and exploiting the potential of ambient ionization mass spectrometry (MS). Furthermore, online monitoring of reactions in a time-resolved way would identify sequential modification steps. Here, we introduce a novel (time-resolved) TiO2-photocatalysis laser ablation electrospray ionization (LAESI) MS method for the analysis of drug candidates. This method was proven to be compatible with both TiO2-coated glass slides as well as solutions containing suspended TiO2 nanoparticles, and the results were in excellent agreement with studies on biological oxidation of verapamil, buspirone, testosterone, andarine, and ostarine. Finally, a time-resolved LAESI MS setup was developed and initial results for verapamil showed excellent analytical stability for online photocatalyzed oxidation reactions within the set-up up to at least 1 h.
    Seasonal streamflow forecasts for Europe - Part 2 : Sources of skill
    Greuell, Wouter ; Franssen, Wietse H.P. ; Hutjes, Ronald W.A. - \ 2019
    Hydrology and Earth System Sciences 23 (2019)1. - ISSN 1027-5606 - p. 371 - 391.

    This paper uses hindcasts (1981-2010) to investigate the sources of skill in seasonal hydrological forecasts for Europe. The hindcasts were produced with WUSHP (Wageningen University Seamless Hydrological Prediction system). Skill was identified in a companion paper. In WUSHP, hydrological processes are simulated by running the Variable Infiltration Capacity (VIC) hydrological model forced with an ensemble of bias-corrected output from the seasonal forecast system 4 (S4) of the European Centre for Medium-Range Weather Forecasts (ECMWF). We first analysed the meteorological forcing. The precipitation forecasts contain considerable skill for the first lead month but hardly any significant skill at longer lead times. Seasonal forecasts of temperature have more skill. Skill in summer temperature is related to climate change and is more or less independent of lead time. Skill in February and March is unrelated to climate change. Different sources of skill in hydro-meteorological variables were isolated with a suite of specific hydrological hindcasts akin to ensemble streamflow prediction (ESP). These hindcasts show that in Europe, initial conditions of soil moisture (SM) form the dominant source of skill in run-off. From April to July, initial conditions of snow contribute significantly to the skill. Some remarkable skill features are due to indirect effects, i.e. skill due to forcing or initial conditions of snow and soil moisture at an earlier stage is stored in the hydrological state (snow and/or soil moisture) of a later stage, which then contributes to persistence of skill. Skill in evapotranspiration (ET) originates mostly in the meteorological forcing. For run-off we also compared the full hindcasts (with S4 forcing) with two types of ESP (or ESP-like) hindcasts (with identical forcing for all years). Beyond the second lead month, the full hindcasts are less skilful than the ESP (or ESP-like) hindcasts, because inter-annual variations in the S4 forcing consist mainly of noise which enhances degradation of the skill.

    Verification of Seasonal Climate Forecast Towards Hydro-Climatic Information Needs of Rice Farmers in Northern Ghana
    Nyadzi, Emmanuel ; Werners, S.E. ; Biesbroek, Robbert ; Phi Long, Hoang ; Franssen, W.H.P. ; Ludwig, F. - \ 2019
    Weather, climate and society 11 (2019)1. - ISSN 1948-8327 - p. 127 - 142.
    Farmers in sub-Saharan Africa face many difficulties when making farming decisions due to unexpected changes in weather and climate. Access to hydroclimatic information can potentially assist farmers to adapt. This study explores the extent to which seasonal climate forecasts can meet hydroclimatic information needs of rice farmers in northern Ghana. First, 62 rice farmers across 12 communities were interviewed about their information needs. Results showed that importance of hydroclimatic information depends on the frequency of use and farming type (rain-fed, irrigated, or both). Generally, farmers perceived rainfall distribution, dam water level, and temperature as very important information, followed by total rainfall amount and onset ranked as important. These findings informed our skills assessment of rainfall (Prcp), minimum temperature (Tmin), and maximum temperature (Tmax) from the European Centre for Medium-Range Weather Forecasts (ECMWF-S4) and at lead times of 0 to 2 months. Forecast bias, correlation, and skills for all variables vary with season and location but are generally unsystematic and relatively constant with forecast lead time. Making it possible to meet farmers’ needs at their most preferred lead time of 1 month before the farming season. ECMWF-S4 exhibited skill in Prcp, Tmin, and Tmax in northern Ghana except for a few grid cells in MAM for Prcp and SON for Tmin and Tmax. Tmin and Tmax forecasts were more skillful than Prcp. We conclude that the participatory coproduction approach used in this study provides better insight for understanding demand-driven climate information services and that the ECMWF-S4 seasonal forecast system has the potential to provide actionable hydroclimatic information that may support farmers’ decisions.
    Global multi-pollutant modelling of water quality: scientific challenges and future directions
    Strokal, M. ; Spanier, Emiel ; Kroeze, C. ; Koelmans, A.A. ; Florke, Martina ; Franssen, W.H.P. ; Hofstra, N. ; Langan, Simon ; Ting, Tang ; Vliet, M.T.H. van; Wada, Yoshihide ; Wang, M. ; Wijnen, Jikke van; Williams, R. - \ 2019
    Current Opinion in Environmental Sustainability 36 (2019). - ISSN 1877-3435 - p. 116 - 125.
    Assessing global water quality issues requires a multi-pollutant modelling approach. We discuss scientific challenges and future directions for such modeling. Multi-pollutant river models need to integrate information on sources of pollutants such as plastic debris, nutrients, chemicals, pathogens, their effects and possible solutions. In this paper, we first explain what we consider multi-pollutant modelling. Second, we discuss scientific challenges in multi-pollutant modelling relating to consistent model inputs, modelling approaches and model evaluation. Next, we illustrate the potential of global multi-pollutant modelling for hotspot analyses. We show hotspots of river pollution with microplastics, nutrients, triclosan and Cryptosporidium in many sub-basins of Europe, North America and South Asia. Finally, we reflect on future directions for multi-pollutant modelling, and for linking model results to policy-making.
    Renal sulfate reabsorption in healthy individuals and renal transplant recipients
    Post, Adrian ; Minović, Isidor ; Berg, Else van den; Eggersdorfer, Manfred L. ; Navis, Gerjan J. ; Geleijnse, Johanna M. ; Gans, Reinold O.B. ; Goor, Harry van; Struck, Joachim ; Franssen, Casper F.M. ; Kema, Ido P. ; Bakker, Stephan J.L. - \ 2018
    Physiological Reports 6 (2018)8. - ISSN 2051-817X
    Kidney donation - renal sulfate handling - renal transplant recipients - sulfate reabsorption

    Inorganic sulfate is essential for normal cellular function and its homeostasis is primarily regulated in the kidneys. However, little is known about renal sulfate handling in humans and particularly in populations with impaired kidney function such as renal transplant recipients (RTR). Hence, we aimed to assess sulfate reabsorption in kidney donors and RTR. Plasma and urinary sulfate were determined in 671 RTR and in 251 kidney donors. Tubular sulfate reabsorption (TSR) was defined as filtered load minus sulfate excretion and fractional sulfate reabsorption (FSR) was defined as 1-fractional excretion. Linear regression analyses were employed to explore associations of FSR with baseline parameters and to identify the determinants of FSR in RTR. Compared to kidney donors, RTR had significantly lower TSR (15.2 [11.2–19.5] vs. 20.3 [16.7–26.3] μmol/min), and lower FSR (0.56 [0.48–0.64] vs. 0.64 [0.57–0.69]) (all P < 0.001). Kidney donation reduced both TSR and FSR by circa 50% and 25% respectively (both P < 0.001). In RTR and donors, both TSR and FSR associated positively with renal function. In RTR, FSR was independently associated with urinary thiosulfate (β = −0.18; P = 0.002), growth hormone (β = 0.12; P = 0.007), the intakes of alcohol (β = −0.14; P = 0.002), methionine (β = −0.34; P < 0.001), cysteine (β = −0.41; P < 0.001), and vitamin D (β = −0.14; P = 0.009). In conclusion, TSR and FSR are lower in RTR compared to kidney donors and both associated with renal function. Additionally, FSR is determined by various dietary and metabolic factors. Future research should determine the mechanisms behind sulfate handling in humans and the prognostic value of renal sulfate reabsorption in RTR.

    One-Step Generation of Reactive Superhydrophobic Surfaces via SiHCl3-Based Silicone Nanofilaments
    Slagman, Sjoerd ; Pujari, Sidharam P. ; Franssen, Maurice C.R. ; Zuilhof, Han - \ 2018
    Langmuir 34 (2018)45. - ISSN 0743-7463 - p. 13505 - 13513.

    Superhydrophobic surfaces gain ever-growing attention because of their applicability in many (consumer) products/materials as they often display, among others, antifouling, anti-icing, and/or self-cleaning properties. A simple way to achieve superhydrophobicity is through the growth of silicone nanofilaments. These nanofilaments, however, are very often nonreactive and thus difficult to utilize in subsequent chemistries. In response, we have developed a single-step procedure to grow (SiHCl3-based) silicone nanofilaments with selective reactivity that are intrinsically superhydrophobic. The silicone nanofilaments could be further functionalized via Pt-catalyzed hydrosilylation of exposed Si-H moieties. These surfaces are easily obtained using mild conditions and are stable under hydrolytic conditions (neutral water, 24 h at 80 °C) while remaining highly transparent, which makes them well suited for optical and photochemical experiments.

    Kauniolide synthase is a P450 with unusual hydroxylation and cyclization-elimination activity
    Liu, Qing ; Beyraghdar Kashkooli, Arman ; Manzano, David ; Pateraki, Irini ; Richard, Lea ; Kolkman, Pim ; Lucas, Maria Fátima ; Guallar, Victor ; Vos, Ric C.H. de; Franssen, Maurice C.R. ; Krol, Alexander van der; Bouwmeester, Harro - \ 2018
    Nature Communications 9 (2018)1. - ISSN 2041-1723

    Guaianolides are an important class of sesquiterpene lactones with unique biological and pharmaceutical properties. They have been postulated to be derived from germacranolides, but for years no progress has been made in the elucidation of their biosynthesis that requires an unknown cyclization mechanism. Here we demonstrate the isolation and characterization of a cytochrome P450 from feverfew (Tanacetum parthenium), kauniolide synthase. Kauniolide synthase catalyses the formation of the guaianolide kauniolide from the germacranolide substrate costunolide. Unlike most cytochrome P450s, kauniolide synthase combines stereoselective hydroxylation of costunolide at the C3 position, with water elimination, cyclization and regioselective deprotonation. This unique mechanism of action is supported by in silico modelling and docking experiments. The full kauniolide biosynthesis pathway is reconstructed in the heterologous hosts Nicotiana benthamiana and yeast, paving the way for biotechnological production of guaianolide-type sesquiterpene lactones.

    Mild oxidation and functionalisation of synthetic polymer surfaces
    Slagman, Sjoerd - \ 2018
    Wageningen University. Promotor(en): J.T. Zuilhof, co-promotor(en): M.C.R. Franssen. - Wageningen : Wageningen University - ISBN 9789463435116 - 163

    How to extend the lifetime of plastics? This might sound as a somewhat odd question in the age of bio-degradable plastics, but plastics that can withstand extreme conditions can be (re)used more often and thereby thus contribute to an eco-friendly economy. In order to improve these plastics, we need to adjust them and that is not easy! Traditional plastic modification technologies often require a lot of energy or dangerous chemicals. To by-pass these traditional measures, we explored, and pushed, the boundaries of novel eco-friendly technologies. We studied how enzymes, nature’s architects, modified plastic drinking water filtration membranes, which proved to occur in in a completely unprecedented manner. Additionally, a novel eco-friendly chemical tool for modifying plastics opened up a whole new route towards water-repellent materials. We hope that, through our research, we get yet a little closer to a sustainable future.

    Chapter 1 provides the required background knowledge for any chemically oriented scholar to comprehend the interdisciplinary work presented herein. Crucial topics, such as polymer surface modification and analysis, wetting behaviour and adhesion prevention were introduced. Current methodologies for modifying polymer surfaces typically require harsh chemicals and conditions. The research described herein has therefore been focussed on acquiring a better understanding and increasing the scope of novel tools for mildly modifying polymers.

    One of these novel tools is the laccase-mediated surface functionalisation of poly(ethersulfone) membranes using 4-hydroxybenzoic acid (4-HBA). The resulting overlayer minimised membrane fouling by several biofoulants. In order to comprehend the underlying functionalisation mechanism, the solution-phase oligomerisation of 4-HBA had to be studied first, which is described in Chapter 2. Initial conversion of 4-HBA proved to occur only slowly and resulted in two main products: a C3-C3’-bound and a C3-O-bound dimer. A plurality of other products were found after 24 h of incubation, which included a C1-C3’-bound and possibly a C1-O-bound dimer. Furthermore, laccase-mediated conversion of these dimers proved to be far more rapid than conversion of 4-HBA itself, and correlated strongly with the abundance of the individual dimers. The influence of dimer reactivity on their abundance was confirmed by quantum chemical calculations. These findings provided us with handles for designing phenols with enhanced reactivity and controlled binding profiles.

    We used the gained knowledge to synthesise novel positively charged phenolic monomers that were anticipated to, upon laccase-mediated surface functionalisation, introduce anti-bacterial properties to the membrane while allowing it to be used as support membrane for layer-by-layer deposition. As is described in Chapter 3, however, in-situ laccase-mediated conversion of these phenolics did not lead to significant surface functionalisation. In order to understand why functionalisation was achieved for other monomers (i.e. 4-HBA), 4-HBA, laccase and any of several PES model compounds were incubated together and the resultant mixture was studied using LC-MS. However, no covalent bond formation between (oligomeric) 4-HBA and either of the soluble, insoluble or resin-bound PES model compounds could be observed. The use of phenols bearing negatively charged substituents did also not lead to membrane surface modification. Finally, membranes having an overlayer of oligomeric 4-HBA proved to be extensively decolourised upon washing with a detergent solution. Considering all of the above, it was concluded that laccase-mediated surface modification resulted from strong physisorption, rather than from covalent grafting of oligomeric 4-HBA.

    As it was challenging to reveal the mechanisms underlying our functionalisation strategy, we anticipated that other researchers might also have encountered similar challenges. It is therefore that in Chapter 4 recently published laccase-mediated surface modification strategies are discussed and assessed on whether grafting is likely to have occurred. This assessment was based on five factors: mechanistic rationale, pre-treatment, control experiments, washing/cleaning and the used analytical tools. Generally speaking, laccase-mediated grafting on lignocelluloses proved to be likely. Quite commonly, however, grafting coincided with physical adsorption due to insufficient washing. We concluded that a lack of proper surface analyses and studies towards the mechanisms underlying grafting on polysaccharides, proteins and synthetic polymers regularly hampered achieving covalent grafting on these materials.

    Apart from enzymatic surface modification, additional chemical strategies for achieving mild polymer functionalisation were assessed too. PMMA activation was accordingly achieved through peroxidative copper catalysis, followed by sodium borohydride reduction to result in surface hydroxylation. As was described in Chapter 5, this offered a platform for the robust growth of SiHCl3-based silicone nanofilaments, while maintaining polymer transparency. Due to their intricate nanostructure, these silicone nanofilaments granted superhydrophobicity (SWCA > 150°, sliding angles < 1°) to the material. The presence of Si-H moieties on the surface allowed for further functionalisation through hydrosilylation. As a proof of principle, we employed platinum-catalysed hydrosilylation to decorate the surface with extensively fluorinated alkenes and alkanes. This fluorinated exterior provided the material with protection towards hydrolytic degradation. We have thereby developed the first intrinsically superhydrophobic reactive silicone nanofilament-coated transparent polymer surface.

    Finally, Chapter 6 summarises the highlights of previous chapters, while offering an in-depth discussion on possible improvements and future work.

    Reactive Laser Ablation Electrospray Ionization Time-Resolved Mass Spectrometry of Click Reactions
    Geenen, Fred A.M.G. van; Franssen, Maurice C.R. ; Zuilhof, Han ; Nielen, Michel W.F. - \ 2018
    Analytical Chemistry 90 (2018)17. - ISSN 0003-2700 - p. 10409 - 10416.

    Reactions in confined compartments like charged microdroplets are of increasing interest, notably because of their substantially increased reaction rates. When combined with ambient ionization mass spectrometry (MS), reactions in charged microdroplets can be used to improve the detection of analytes or to study the molecular details of the reactions in real time. Here, we introduce a reactive laser ablation electrospray ionization (reactive LAESI) time-resolved mass spectrometry (TRMS) method to perform and study reactions in charged microdroplets. We demonstrate this approach with a class of reactions new to reactive ambient ionization MS: so-called click chemistry reactions. Click reactions are high-yielding reactions with a high atom efficiency, and are currently drawing significant attention from fields ranging from bioconjugation to polymer modification. Although click reactions are typically at least moderately fast (time scale of minutes to a few hours), in a reactive LAESI approach a substantial increase of reaction time is required for these reactions to occur. This increase was achieved using microdroplet chemistry and followed by MS using the insertion of a reaction tube - up to 1 m in length - between the LAESI source and the MS inlet, leading to near complete conversions due to significantly extended microdroplet lifetime. This novel approach allowed for the collection of kinetic data for a model (strain-promoted) click reaction between a substituted tetrazine and a strained alkyne and showed in addition excellent instrument stability, improved sensitivity, and applicability to other click reactions. Finally, the methodology was also demonstrated in a mass spectrometry imaging setting to show its feasibility in future imaging experiments.

    Elucidating the mechanism behind the laccase-mediated modification of poly(ethersulfone)
    Slagman, Sjoerd ; Jonkers, Wendy A. ; Zuilhof, Han ; Franssen, Maurice C.R. - \ 2018
    RSC Advances : An international journal to further the chemical sciences 8 (2018)48. - ISSN 2046-2069 - p. 27101 - 27110.

    Laccase-mediated oligomerisation of 4-hydroxybenzoic acid (4-HBA) derivatives and simultaneous in situ surface modification has proven to be a cost-effective, easily applicable and eco-friendly strategy for preventing biofouling of poly(ethersulfone) (PES) water filtration membranes. Modification of the membrane surface has previously been hypothesised to occur through covalent bonding of enzymatically generated phenolic radicals to the polymeric membrane. The current study shows, however, that in situ formation of soluble phenolic oligomers does not result in covalent membrane modification. We studied in situ laccase-mediated oligomerisation of custom-synthesised positively charged and commercially available negatively charged monomeric phenols, and demonstrated that their mode of binding to PES is not covalent. In addition, soluble, non-soluble and on-resin PES model compounds were synthesised and used in the laccase-mediated oligomerisation of 4-HBA. Covalent bond formation between these model compounds and (oligomeric) 4-HBA could not be observed either. Furthermore, extensive washing of PES membranes modified through laccase-mediated oligomerisation of 4-HBA resulted in substantial discolouration of the membrane surface, showing that the layer of oligomerised phenolics could easily be removed. Altogether, it was concluded that laccase-assisted modification of PES membranes resulted from strong physical adsorption of phenolic oligomers and polymers rather than from covalent bonding of those.

    Seasonal streamflow forecasts for Europe-Part I : Hindcast verification with pseudo- A nd real observations
    Greuell, Wouter ; Franssen, Wietse H.P. ; Biemans, Hester ; Hutjes, Ronald W.A. - \ 2018
    Hydrology and Earth System Sciences 22 (2018)6. - ISSN 1027-5606 - p. 3453 - 3472.

    Seasonal predictions of river flow can be exploited among others to optimise hydropower energy generation, navigability of rivers and irrigation management to decrease crop yield losses. This paper is the first of two papers dealing with a physical model-based system built to produce probabilistic seasonal hydrological forecasts, applied here to Europe. This paper presents the development of the system and the evaluation of its skill. The variable infiltration capacity (VIC) hydrological model is forced with bias-corrected output of ECMWF's seasonal forecast system 4. For the assessment of skill, we analysed hindcasts (1981-2010) against a reference run, in which VIC was forced by gridded meteorological observations. The reference run was also used to generate initial hydrological conditions for the hindcasts. The skill in run-off and discharge hindcasts is analysed with monthly temporal resolution, up to 7 months of lead time, for the entire annual cycle. Using the reference run output as pseudo-observations and taking the correlation coefficient as metric, hot spots of significant theoretical skill in discharge and run-off were identified in Fennoscandia (from January to October), the southern part of the Mediterranean (from June to August), Poland, northern Germany, Romania and Bulgaria (mainly from November to January), western France (from December to May) and the eastern side of Great Britain (January to April). Generally, the skill decreases with increasing lead time, except in spring in regions with snow-rich winters. In some areas some skill persists even at the longest lead times (7 months). Theoretical skill was compared to actual skill as determined with real discharge observations from 747 stations. Actual skill is generally substantially less than theoretical skill. This effect is stronger for small basins than for large basins. Qualitatively, the use of different skill metrics (correlation coefficient; relative operating characteristics, ROC, area; and ranked probability skill score, RPSS) leads to broadly similar spatiooral patterns of skill, but the level of skill decreases, and the area of skill shrinks, in the following order: Correlation coefficient; ROC area below-normal (BN) tercile; ROC area above-normal (AN) tercile; ranked probability skill score; and, finally, ROC near-normal (NN) tercile.

    Fast increases in river pollution from sewage: a global trend
    Strokal, M. ; Kroeze, C. ; Franssen, W.H.P. ; Hofstra, N. ; Koelmans, A.A. ; Siegfried, Max ; Vliet, M.T.H. van; Wijnen, Jikke van; Vermeulen, L.C. - \ 2018
    Geophysical Research Abstracts 20 (2018). - ISSN 1029-7006 - 1 p.
    Laccase-Mediated Grafting on Biopolymers and Synthetic Polymers : A Critical Review
    Slagman, Sjoerd ; Zuilhof, Han ; Franssen, Maurice C.R. - \ 2018
    ChemBioChem 19 (2018)4. - ISSN 1439-4227 - p. 288 - 311.
    biomass - enzyme catalysis - grafting - polymers - surface chemistry
    Laccase-mediated grafting on lignocelluloses has gained considerable attention as an environmentally benign method to covalently modify wood, paper and cork. In recent decades this technique has also been employed to modify fibres with a polysaccharide backbone, such as cellulose or chitosan, to infer colouration, antimicrobial activity or antioxidant activity to the material. The scope of this approach has been further widened by researchers, who apply mediators or high redox potential laccases and those that modify synthetic polymers and proteins. In all cases, the methodology relies on one- or two-electron oxidation of the surface functional groups or of the graftable molecule in solution. However, similar results can very often be achieved through simple deposition, even after extensive washing. This unintended adsorption of the active substance could have an adverse effect on the durability of the applied coating. Differentiating between actual covalent binding and adsorption is therefore essential, but proves to be challenging. This review not only covers excellent research on the topic of laccase-mediated grafting over the last five to ten years, but also provides a critical comparison to highlight either the lack or presence of compelling evidence for covalent grafting.
    Probabilistic maize yield prediction over East Africa using dynamic ensemble seasonal climate forecasts
    Ogutu, Geoffrey E.O. ; Franssen, Wietse H.P. ; Supit, Iwan ; Omondi, P. ; Hutjes, Ronald W.A. - \ 2018
    Agricultural and Forest Meteorology 250-251 (2018). - ISSN 0168-1923 - p. 243 - 261.
    Crop models - Dynamic crop forecasting - East Africa - Forecast lead-time - Probabilistic ensemble prediction - Rainfed agriculture
    We tested the usefulness of seasonal climate predictions for impacts prediction in eastern Africa. In regions where these seasonal predictions showed skill we tested if the skill also translated into maize yield forecasting skills. Using European Centre for Medium-Range Weather Forecasts (ECMWF) system-4 ensemble seasonal climate hindcasts for the period 1981–2010 at different initialization dates before sowing, we generated a 15-member ensemble of yield predictions using the World Food Studies (WOFOST) crop model implemented for water-limited maize production and single season simulation. Maize yield predictions are validated against reference yield simulations using the WATCH Forcing Data ERA-Interim (WFDEI), focussing on the dominant sowing dates in the northern region (July), equatorial region (March-April) and in the southern region (December). These reference yields show good anomaly correlations compared to the official FAO and national reported statistics, but the average reference yield values are lower than those reported in Kenya and Ethiopia, but slightly higher in Tanzania. We use the ensemble mean, interannual variability, mean errors, Ranked Probability Skill Score (RPSS) and Relative Operating Curve skill Score (ROCSS) to assess regions of useful probabilistic prediction. Annual yield anomalies are predictable 2-months before sowing in most of the regions. Difference in interannual variability between the reference and predicted yields range from ±40%, but higher interannual variability in predicted yield dominates. Anomaly correlations between the reference and predicted yields are largely positive and range from +0.3 to +0.6. The ROCSS illustrate good pre-season probabilistic prediction of above-normal and below-normal yields with at least 2-months lead time. From the sample sowing dates considered, we concluded that, there is potential to use dynamical seasonal climate forecasts with a process based crop simulation model WOFOST to predict anomalous water-limited maize yields.
    Enzymatic halogenation and oxidation using an alcohol oxidase-vanadium chloroperoxidase cascade
    But, Andrada ; Noord, Aster Van; Poletto, Francesca ; Sanders, Johan P.M. ; Franssen, Maurice C.R. ; Scott, Elinor L. - \ 2017
    Molecular Catalysis 443 (2017). - ISSN 2468-8231 - p. 92 - 100.
    The chemo-enzymatic cascade which combines alcohol oxidase from Hansenula polymorpha (AOXHp) with vanadium chloroperoxidase (VCPO), for the production of biobased nitriles from amino acids was investigated. In the first reaction H2O2 (and acetaldehyde) are generated from ethanol and oxygen by AOXHp. H2O2 is subsequently used in the second reaction by VCPO to produce HOBr in situ. HOBr is required for the non-enzymatic oxidative decarboxylation of glutamic acid (Glu) to 3-cyanopropanoic acid (CPA), an intermediate in the production of biobased acrylonitrile. It was found that during the one pot conversion of Glu to CPA by AOXHp-VCPO cascade, AOXHp was deactivated by HOBr. To avoid deactivation, the two enzymes were separated in two fed-batch reactors. The deactivation of AOXHp by HOBr appeared to depend on the substrate: an easily halogenated compound like monochlorodimedone (MCD) was significantly converted in one pot by the cascade reaction of AOXHp and VCPO, while conversion of Glu did not occur under those conditions. Apparently, MCD scavenges HOBr before it can inactivate AOXHp, while Glu reacts slower, leading to detrimental concentrations of HOBr. Enzymatically generated H2O2 was used in a cascade reaction involving halogenation steps to enable the co-production of biobased nitriles and acetaldehyde.
    Ambient characterization of synthetic fibers by laser ablation electrospray ionization mass spectrometry
    Geenen, F.A.M.G. van; Franssen, M.C.R. ; Schotman, A.H.M. ; Zuilhof, H. ; Nielen, M.W.F. - \ 2017
    Analytical Chemistry 89 (2017). - ISSN 0003-2700 - p. 4031 - 4037.
    Direct analysis of synthetic fibers under ambient
    conditions is highly desired to identify the polymer, the finishes
    applied and irregularities that may compromise its performance
    and value. In this paper, laser ablation electrospray ionization
    ion mobility time-of-flight mass spectrometry (LAESI-IMSTOF-
    MS) was used for the analysis of synthetic polymers and
    fibers. The key to this analysis was the absorption of laser light
    by aliphatic and aromatic nitrogen functionalities in the
    polymers. Analysis of polyamide (PA) 6, 46, 66, and 12 pellets
    and PA 6, 66, polyaramid and M5 fibers yielded characteristic
    fragment ions without any sample pretreatment, enabling their
    unambiguous identification. Synthetic fibers are, in addition,
    commonly covered with a surface layer for improved adhesion
    and processing. The same setup, but operated in a transient infrared matrix-assisted laser desorption electrospray ionization (IRMALDESI)
    mode, allowed the detailed characterization of the fiber finish layer and the underlying polymer. Differences in finish
    layer distribution may cause variations in local properties of synthetic fibers. Here we also show the feasibility of mass
    spectrometry imaging (MSI) of the distribution of a finish layer on the synthetic fiber and the successful detection of local surface
    Genome of the obligately alkaliphilic fungus Sodiomyces alkalinus reveals its adaptations to high pH.
    Grum-Grzhimaylo, A. ; Falkoski, D.L. ; Heuvel, Joost van den; Min, B. ; Choi, I.G. ; Henrissat, Bernard ; Franssen, H.G.J.M. ; Bilanenko, E.N. ; Vries, Ronald P. De; Kan, J.A.L. van; Grigoriev, I.V. ; Debets, A.J.M. - \ 2017
    In: Abstract Book 29th Fungal Genetics Conference Asilomar 17, Pacific Grove, CA, USA 14-19 March 2017. - Genetics Society of America - p. 152 - 152.
    Alkaliphilic fungi, i.e. fungi that grow optimally at high pH, are exceptional with only a handful of species described to date. Here, we sequenced the obligate alkaliphilic ascomycete S. alkalinus isolated from alkaline soda soils, and explored the features responsible for its unusual life-style. We found that PacC, the major regulator of alkaline-related genes, is up-regulated at higher pH values than PacC orthologues of neutrophilic species. To assess how this fungus can degrade carbohydrate sources under extremely alkalic conditions, we searched for the CAZymes encoded in the genome of S. alkalinus and performed enzyme assays. We revealed many cellulases, but their overall activity was low presumably because of slower induction. Although cellulolytic and hemicellulolytic activity was optimal at pH 6, there still was some activity at pH 10, at which pH it was completely absent in the neutrophilic A. oryzae. Excellent in vitro growth on xylan indicates that grasses are the preferred nutritional source for S. alkalinus in nature. We detected potent proteolytic activity at alkaline pH, compared to the neutrophilic A. oryzae, which may reflect the need for obtaining extra nitrogen, as this essential element becomes limiting at alkaline conditions. Proteins of bacterial cells, which are present in bulk at soda lakes, seem the likely source of nitrogen. In support of this hypothesis, we found several instances of horizontal transfer of prokaryotic genes into the genome of S. alkalinus, encoding enzymes that degrade bacterial cell walls. The genome of S. alkalinus will provide a valuable source to further study the biology and evolution of alkaliphilic trait in fungi with respect to neutrophilic species. In addition, it may provide alkaline-active metabolites of commercial interest.
    Identification of a drimenol synthase and drimenol oxidase from Persicaria hydropiper, involved in the biosynthesis of insect deterrent drimanes
    Henquet, M.G.L. ; Prota, N. ; Hooft, J.J.J. van der; Varbanova, M. ; Hulzink, R.J.M. ; Vos, M. de; Prins, M. ; Both, M.T.J. de; Franssen, M.C.R. ; Bouwmeester, H.J. ; Jongsma, M.A. - \ 2017
    The Plant Journal 90 (2017)6. - ISSN 0960-7412 - p. 1052 - 1063.
    The sesquiterpenoid polygodial, belonging to the drimane family, has been shown to be an antifeedant for a number of herbivorous insects. It is presumed to be synthesized from farnesyl diphosphate via drimenol, subsequent C-12 hydroxylation, and further oxidations at both C-11 and C-12 to form a dialdehyde. Here, we have identified a drimenol synthase (PhDS) and a cytochrome P450 drimenol oxidase (PhDOX1) from Persicaria hydropiper. Expression of PhDS in yeast and plants resulted in production of drimenol only. Co-expression of PhDS with PhDOX1 in yeast yielded drimendiol, the 12-hydroxylation product of drimenol, as a major product, and cinnamolide. When PhDS and PhDOX1 were transiently expressed by agro-infiltration in Nicotiana benthamiana leaves, drimenol was almost completely converted into cinnamolide and several additional drimenol derivatives were observed. In vitro assays showed that PhDOX1 only catalyzes the conversion from drimenol to drimendiol, and not the further oxidation into an aldehyde. In yeast and heterologous plant hosts, the C-12 position of drimendiol is therefore likely further oxidized by endogenous enzymes into an aldehyde and subsequently converted to cinnamolide, presumably by spontaneous hemiacetal formation with the C-11 hydroxyl group followed by oxidation. Purified cinnamolide was confirmed by NMR and shown to be deterrent with an effective deterrent dose (ED50 ) of ~200-400 μg gFW-1 against both whiteflies and aphids. The putative additional physiological and biochemical requirements for polygodial biosynthesis and stable storage in plant tissues are discussed
    The impact of dietary protein or amino acid supplementation on muscle mass and strength in elderly people : Individual participant data and meta-analysis of RCT’s
    Tieland, M. ; Franssen, R. ; Dullemeijer, C. ; Dronkelaar, C. van; Kim, H.K. ; Ispoglou, T. ; Zhu, K. ; Prince, R.L. ; Loon, L.J.C. van; Groot, Lisette C.P.G.M. de - \ 2017
    Journal of Nutrition, Health and Aging 21 (2017)9. - ISSN 1279-7707 - p. 994 - 1001.

    Objectives: Increasing protein or amino acid intake has been promoted as a promising strategy to increase muscle mass and strength in elderly people, however, long-term intervention studies show inconsistent findings. Therefore, we aim to determine the impact of protein or amino acid supplementation compared to placebo on muscle mass and strength in older adults by combining the results from published trials in a metaanalysis and pooled individual participant data analysis. Design: We searched Medline and Cochrane databases and performed a meta-analysis on eight available trials on the effect of protein or amino acid supplementation on muscle mass and strength in older adults. Furthermore, we pooled individual data of six of these randomized double-blind placebo-controlled trials. The main outcomes were change in lean body mass and change in muscle strength for both the meta-analysis and the pooled analysis. Results: The meta-analysis of eight studies (n=557) showed no significant positive effects of protein or amino acid supplementation on lean body mass (mean difference: 0.014 kg: 95% CI -0.152; 0.18), leg press strength (mean difference: 2.26 kg: 95% CI -0.56; 5.08), leg extension strength (mean difference: 0.75 kg: 95% CI: -1.96, 3.47) or handgrip strength (mean difference: -0.002 kg: 95% CI -0.182; 0.179). Likewise, the pooled analysis showed no significant difference between protein and placebo treatment on lean body mass (n=412: p=0.78), leg press strength (n=121: p=0.50), leg extension strength (n=121: p=0.16) and handgrip strength (n=318: p=0.37). Conclusions: There is currently no evidence to suggest that protein or amino acid supplementation without concomitant nutritional or exercise interventions increases muscle mass or strength in predominantly healthy elderly people.

    Cis-regulatory PLETHORA promoter elements directing root and nodule expression are conserved between Arabidopsis thaliana and Medicago truncatula
    Franssen, H.G.J.M. ; Kulikova, O. ; Willemsen, V.A. ; Heidstra, R. - \ 2017
    Plant Signaling & Behavior 12 (2017)2. - ISSN 1559-2316
    Nodules are unique organs formed on roots of legumes by soil-borne bacteria, collectively known as rhizobium. Recently, we have shown that orthologs of the AINTEGUMENTA-like (AIL) AP2 transcription factors PLETHORA (PLT) 1 to 4, that redundantly regulate Arabidopsis thaliana root development are involved in root and nodule growth in Medicago truncatula. Hence, it is conceivable that rhizobium has co-opted these genes for nodule development. Whether this co-option requires the presence of specific cis-elements in the promoters and/or specialization of PLT protein function is not clear. Here, we analyzed the qualitative expression patterns of the Arabidopsis PLT1 to 4 promoters in Medicago roots and nodules and compared these with the described expression patterns of the Medicago PLT genes. Our studies reveal that the expression patterns of the investigated promoters and their Medicago orthologs are very similar, indicating that at least all cis-elements regulating spatial PLT expression are conserved among the Arabidopsis and Medicago PLT1 to 4 promoters.
    Impacts on river systems under 2 °C warming : Bangladesh Case Study
    Zaman, A.M. ; Molla, M.K. ; Pervin, I.A. ; Mahbubur Rahman, S.M. ; Haider, A.S. ; Ludwig, F. ; Franssen, W. - \ 2017
    Climate Services 7 (2017). - ISSN 2405-8807 - p. 96 - 114.
    Bangladesh - Basin model - Climate change - Hydrodynamic model - Regional Climatic Model (RCM) - Salinity intrusion - Sea level rise

    Bangladesh is particularly vulnerable due to the combined impacts of sea level rise, rainfall and runoff variability, and changes in cyclone patterns. This paper presents the application of an integrated modelling framework used to investigate climate change impacts when global averaged surface temperature increases by 2. C from pre-industrial level. The modelling framework consists of four model types: Regional climate model (RCM), Ganges-Brahmaputra-Meghna (GBM) Basin model, Southwest Region Hydrodynamic and Salinity models. Bias corrected climate results (temperature, precipitation and evapotranspiration) from SMHI-RCA and CNRM-ARPEGE RCMs for (Representative Concentration Pathway) RCP 8.5 scenario were used. The uniqueness of this research study was that the same GCM (General Circulation Model)/RCM results were used across the whole modelling chain. In Bagerhat District, it was found that river salinity can increase by about 0.5 to 2 PPT (parts per thousand). Also, the duration of river salinity above 1 PPT can double in some locations. In Kushtia District, in the months of November and December river flows may increase but not sufficiently in other months due to lack of connectivity to the Ganges River. In the flood-prone Shariatpur District, average wet season water level increases up to 0.2 to 0.5. m. Also, duration of flood levels above the established danger level can double in some locations. Finally, this study found that dredging of the mouth of the Gorai River (in Kushtia District) is an effective adaptation measure. The dredging ensures connectivity to the Ganges River, which allows freshwater to enter the Southwest region of Bangladesh, which not only alleviates drought conditions in Kushtia Distract but also helps push back saline intrusion.

    Gram-positive anaerobe cocci are underrepresented in the microbiome of filaggrin-deficient human skin : Letter to the editor
    Zeeuwen, Patrick L.J.M. ; Ederveen, Thomas H.A. ; Krieken, Danique A. van der; Niehues, Hanna ; Boekhorst, Jos ; Kezic, Sanja ; Hanssen, Daniëlle A.T. ; Otero, Marisol E. ; Hanssen, Daniëlle A.T. ; Rodijk-Olthuis, Diana ; Falcone, Denise ; Bogaard, Ellen H.J. van den; Kamsteeg, Marijke ; Koning, Heleen D. de; Zeeuwen-Franssen, Manon E.J. ; Steensel, Maurice A.M. van; Kleerebezem, Michiel ; Timmerman, Harro M. ; Hijum, Sacha A.F.T. van; Schalkwijk, Joost - \ 2017
    Journal of Allergy and Clinical Immunology 139 (2017)4. - ISSN 0091-6749 - p. 1368 - 1371.
    Skill of ECMWF system-4 ensemble seasonal climate forecasts for East Africa
    Ogutu, Geoffrey E.O. ; Franssen, Wietse H.P. ; Supit, Iwan ; Omondi, P. ; Hutjes, Ronald W.A. - \ 2017
    International Journal of Climatology 37 (2017)5. - ISSN 0899-8418 - p. 2734 - 2756.
    Bias correction - East Africa - Ensemble prediction - Probabilistic verification - Seasonal climate forecasts

    This study evaluates the potential use of the ECMWF System-4 seasonal forecasts (S4) for impact analysis over East Africa. For use, these forecasts should have skill and small biases. We used the 15-member ensemble of 7-month forecasts initiated every month, and tested forecast skill of precipitation (tp), near-surface air temperature (tas) and surface downwelling shortwave radiation (rsds). We validated the 30-year (1981-2010) hindcast version of S4 against the WFDEI reanalysis (WATCH Forcing Data ERA-Interim) and to independent relevant observational data sets. Probabilistic skill is assessed using anomaly correlation, ranked probability skill score (RPSS) and the relative operating curve skill score (ROCSS) at both grid cell and over six distinct homogeneous rainfall regions for the three growing seasons of East Africa (i.e. MAM, JJA and OND). S4 exhibits a wet bias in OND, a dry bias in MAM and a mix of both in JJA. Temperature biases are similar in all seasons, constant with lead-time and correlate with elevation. Biases in rsds correlate with cloud/rain patterns. Bias correction clears biases but does not affect probabilistic skills. Predictability of the three variables varies with season, location and lead-time. The choice of validating dataset plays little role in the regional patterns and magnitudes of probabilistic skill scores. The OND tp forecasts show skill over a larger area up to 3 months lead-time compared to MAM and JJA. Upper- and lower-tercile tp forecasts are 20-80% better than climatology. Temperature forecasts are skillful for at least 3months lead-time and they are 40-100% better than climatology. The rsds is less skillful than tp and tas in all seasons when verified against WFDEI but higher in all lead months against the alternative datasets. The forecast system captures El-Niño Southern Oscillation (ENSO)-related anomalous years with region-dependent skill.

    Habituation to low or high protein intake does not modulate basal or postprandial muscle protein synthesis rates: a randomized trial
    Gorissen, S.H. ; Horstman, Astrid ; Franssen, Rinske ; Kouw, I.W. ; Wall, B.T. ; Burd, N.A. ; Groot, C.P.G.M. de; Loon, L.J.C. van - \ 2017
    American Journal of Clinical Nutrition 105 (2017)2. - ISSN 0002-9165 - p. 332 - 342.
    Background: Muscle mass maintenance is largely regulated by basal muscle protein synthesis rates and the ability to increase muscle protein synthesis after protein ingestion. To our knowledge, no previous studies have evaluated the impact of habituation to either low protein intake (LOW PRO) or high protein intake (HIGH PRO) on the postprandial muscle protein synthetic response. Objective: We assessed the impact of LOW PRO compared with HIGH PRO on basal and postprandial muscle protein synthesis rates after the ingestion of 25 g whey protein. Design: Twenty-four healthy, older men [age: 62 ± 1 y; body mass index (in kg/m2): 25.9 ± 0.4 (mean ± SEM)] participated in a parallel-group randomized trial in which they adapted to either a LOW PRO diet (0.7 g · kg–1 · d−1; n = 12) or a HIGH PRO diet (1.5 g · kg–1 · d–1; n = 12) for 14 d. On day 15, participants received primed continuous l-[ring-2H5]-phenylalanine and l-[1-13C]-leucine infusions and ingested 25 g intrinsically l-[1-13C]-phenylalanine– and l-[1-13C]-leucine–labeled whey protein. Muscle biopsies and blood samples were collected to assess muscle protein synthesis rates as well as dietary protein digestion and absorption kinetics. Results: Plasma leucine concentrations and exogenous phenylalanine appearance rates increased after protein ingestion (P < 0.01) with no differences between treatments (P > 0.05). Plasma exogenous phenylalanine availability over the 5-h postprandial period was greater after LOW PRO than after HIGH PRO (61% ± 1% compared with 56% ± 2%, respectively; P < 0.05). Muscle protein synthesis rates increased from 0.031% ± 0.004% compared with 0.039% ± 0.007%/h in the fasted state to 0.062% ± 0.005% compared with 0.057% ± 0.005%/h in the postprandial state after LOW PRO compared with HIGH PRO, respectively (P < 0.01), with no differences between treatments (P = 0.25). Conclusion: Habituation to LOW PRO (0.7 g · kg–1 · d–1) compared with HIGH PRO (1.5 g · kg–1 · d–1) augments the postprandial availability of dietary protein–derived amino acids in the circulation and does not lower basal muscle protein synthesis rates or increase postprandial muscle protein synthesis rates after ingestion of 25 g protein in older men. This trial was registered at as NCT01986842.
    Biosensor comprising a modified metal surface and method for the modification of a metal surface
    Alonso Carnicero, J.M. ; Franssen, M.C.R. ; Bielen, A.A.M. ; Scheres, L.M.W. ; Schütz-Trilling, A.K. ; Zeper, W.B. ; Zuilhof, J.T. ; Paassen, P.A.M. van; Olthuis, W. ; Rassaei, L. - \ 2016
    Octrooinummer: WO2016018148, gepubliceerd: 2016-02-04.
    The present invention relates to a device for the detection of an analyte in a fluid, the device comprising: (a) a working electrode comprising a modified metal surface, wherein: (1) the metal is selected from the group consisting of Ru, Rh, Pd, Ag, Ir, Pt and Au; (2) an enzyme is covalently attached to the metal surface via an alkyloxy or an alkenyloxy moiety and, optionally, a linker moiety; (3)the alkyloxy or alkenyloxy moiety is covalently bonded to said metal surface via the alkyloxy or alkenyloxy O- atom; and (4) the linker moiety, if present, is covalently bonded to theenzyme and to the alkyloxy or alkenyloxy moiety; (b) a reference electrode; and (c) means for detecting an electricalsignal, the means being operationally coupled to at least working electrode (a) and reference electrode (b). The device according to the invention is also referred to as a biosensor. The invention also relates to a process for the modification of a metal surface and to a modified metal surface obtainable by the process. Furthermore, the invention relates to an electrode comprising said modified metal surface, and to a biosensor comprising said modified metal surface.
    Characterization of the laccase-mediated oligomerization of 4-hydroxybenzoic acid
    Slagman, S. ; Escorihuela Fuentes, J. ; Zuilhof, H. ; Franssen, M.C.R. - \ 2016
    RSC Advances : An international journal to further the chemical sciences 6 (2016)101. - ISSN 2046-2069 - p. 99367 - 99375.
    Modifying inert poly(ethersulfone) membranes using laccase has proven to be an environmentally benign and easily applicable process to alter the membrane's surface properties. By this method phenolic acid monomers such as 4-hydroxybenzoic acid are grafted from the membrane surface to make it anti-fouling. In order to enhance the anti-fouling capabilities even further it is important to study the molecular details of this reaction. However, the nature of the products of laccase modification, either on a surface or in solution, has been studied only poorly. In this paper we report the formation of C3–C3′, C3–O and C1–C3′ linked dimers as the first products of the solution-phase laccase-mediated oligomerization of 4-hydroxybenzoic acid. These dimers can also act as substrate for laccase, and we show that their enzymatic oxidative coupling occurs far more rapidly than that of 4-hydroxybenzoic acid, which indicates that they are highly reactive intermediates that are efficiently polymerized onwards. The reactivity of each dimer is of large influence on its yield; dimers that are converted more rapidly are less abundant. This knowledge allows for further improvement of applications involving laccase such as the grafting of phenols on surfaces and enzymatic polymerization of lignin fragments.
    Usefulness of ECMWF system-4 ensemble seasonal climate forecasts for East Africa
    Ogutu, G.E.O. ; Franssen, W.H.P. ; Supit, I. ; Omondi, P. ; Hutjes, R.W.A. - \ 2016
    Modeling soil processes : Review, key challenges, and new perspectives
    Vereecken, H. ; Schnepf, A. ; Hopmans, J.W. ; Javaux, M. ; Or, D. ; Roose, T. ; Vanderborght, J. ; Young, M.H. ; Amelung, W. ; Aitkenhead, M. ; Allison, S.D. ; Assouline, S. ; Baveye, P. ; Berli, M. ; Brüggemann, N. ; Finke, P. ; Flury, M. ; Gaiser, T. ; Govers, G. ; Ghezzehei, T. ; Hallett, P. ; Hendricks Franssen, H.J. ; Heppell, J. ; Horn, R. ; Huisman, J.A. ; Jacques, D. ; Jonard, F. ; Kollet, S. ; Lafolie, F. ; Lamorski, K. ; Leitner, D. ; Mcbratney, A. ; Minasny, B. ; Montzka, C. ; Nowak, W. ; Pachepsky, Y. ; Padarian, J. ; Romano, N. ; Roth, K. ; Rothfuss, Y. ; Rowe, E.C. ; Schwen, A. ; Šimůnek, J. ; Tiktak, A. ; Dam, Jos van; Zee, S.E.A.T.M. van der; Vogel, H.J. ; Vrugt, J.A. ; Wöhling, T. ; Wöhling, T. ; Young, I.M. - \ 2016
    Vadose Zone Journal 15 (2016)5. - ISSN 1539-1663 - 57 p.

    The remarkable complexity of soil and its importance to a wide range of ecosystem services presents major challenges to the modeling of soil processes. Although major progress in soil models has occurred in the last decades, models of soil processes remain disjointed between disciplines or ecosystem services, with considerable uncertainty remaining in the quality of predictions and several challenges that remain yet to be addressed. First, there is a need to improve exchange of knowledge and experience among the different disciplines in soil science and to reach out to other Earth science communities. Second, the community needs to develop a new generation of soil models based on a systemic approach comprising relevant physical, chemical, and biological processes to address critical knowledge gaps in our understanding of soil processes and their interactions. Overcoming these challenges will facilitate exchanges between soil modeling and climate, plant, and social science modeling communities. It will allow us to contribute to preserve and improve our assessment of ecosystem services and advance our understanding of climate-change feedback mechanisms, among others, thereby facilitating and strengthening communication among scientific disciplines and society. We review the role of modeling soil processes in quantifying key soil processes that shape ecosystem services, with a focus on provisioning and regulating services. We then identify key challenges in modeling soil processes, including the systematic incorporation of heterogeneity and uncertainty, the integration of data and models, and strategies for effective integration of knowledge on physical, chemical, and biological soil processes. We discuss how the soil modeling community could best interface with modern modeling activities in other disciplines, such as climate, ecology, and plant research, and how to weave novel observation and measurement techniques into soil models. We propose the establishment of an international soil modeling consortium to coherently advance soil modeling activities and foster communication with other Earth science disciplines. Such a consortium should promote soil modeling platforms and data repository for model development, calibration and intercomparison essential for addressing contemporary challenges.

    Self-assembled monolayers of 1-alkenes on oxidized platinum surfaces as platforms for immobilized enzymes for biosensing
    Alonso, Jose Maria ; Bielen, Abraham A.M. ; Olthuis, Wouter ; Kengen, Servé W.M. ; Zuilhof, Han ; Franssen, Maurice C.R. - \ 2016
    Applied Surface Science 383 (2016). - ISSN 0169-4332 - p. 283 - 293.
    Enzyme immobilization - Lactate biosensor - Platinum - Self-assembled monolayers

    Alkene-based self-assembled monolayers grafted on oxidized Pt surfaces were used as a scaffold to covalently immobilize oxidase enzymes, with the aim to develop an amperometric biosensor platform. NH2-terminated organic layers were functionalized with either aldehyde (CHO) or N-hydroxysuccinimide (NHS) ester-derived groups, to provide anchoring points for enzyme immobilization. The functionalized Pt surfaces were characterized by X-ray photoelectron spectroscopy (XPS), static water contact angle (CA), infrared reflection absorption spectroscopy (IRRAS) and atomic force microscopy (AFM). Glucose oxidase (GOX) was covalently attached to the functionalized Pt electrodes, either with or without additional glutaraldehyde crosslinking. The responses of the acquired sensors to glucose concentrations ranging from 0.5 to 100 mM were monitored by chronoamperometry. Furthermore, lactate oxidase (LOX) and human hydroxyacid oxidase (HAOX) were successfully immobilized onto the PtOx surface platform. The performance of the resulting lactate sensors was investigated for lactate concentrations ranging from 0.05 to 20 mM. The successful attachment of active enzymes (GOX, LOX and HAOX) on Pt electrodes demonstrates that covalently functionalized PtOx surfaces provide a universal platform for the development of oxidase enzyme-based sensors.

    The Material practices of quantification: Measuring ‘deprivation’ in the Amsterdam Neighbourhood Policy
    Wilde, Mandy de; Franssen, Thomas - \ 2016
    Critical Social Policy 36 (2016)4. - ISSN 0261-0183 - p. 489 - 510.
    actor-network theory - evaluation - governmentality - quantification - social policy
    The use of indicators and indexes in social policy, as part of evidence-based policy, is understood by governmentality scholars as ‘techniques of governance’. However, we know very little about how the process of quantification is enacted in the material practices that constitute social policy itself. In this article we focus on a particular quantified object: the ‘Normal Amsterdam Level’ (NAP), used in an Amsterdam Neighbourhood Policy programme. We follow the NAP from its birth, to its life and its afterlife. We show that the qualification ‘deprived’ calls forth a whole set of problematic arrangements which are lost in a process of quantification. We understand the NAP as a generative device that actively assembles and arranges the world. These assemblages are rendered ‘hard’ through semiotic, statistical and visual techniques that produce facts about targeted neighbourhoods in relation to a city-wide average, thus serving as evidence and legitimisation for policy interventions.
    Seasonal forecasting of european river discharge: hindcast verification of VIC and LPJML models driven by ECMWF System4
    Greuell, J.W. - \ 2015
    In: Seasonal Hydrobiological Forecasting Workshop Book of Abstracts. - - p. 29 - 30.
    hindcast verification, river discharge, VIC model, LPJmL model
    The hydrological models VIC (Liang, Lettenmaier et al. 1994) and LPJmL (Gerten, Schaphoff et al. 2004) have been widely used for the assessment of climate change impacts on water resources and water dependent sectors, stand-alone (van Vliet, Franssen et al. 2013) and as part of multi-model ensemble studies (Haddeland, Clark et al. 2011, Prudhomme, Giuntoli et al. 2014). Here we implement the same models to assess their capabilities for seasonal forecasting purposes. We analyse whether any forecasting skill present in seasonal meteorological forecasts propagates into skill in hydrological forecasts.
    The VIC and LPJmL models are implemented for the European domain, including routing schemes on a 0.5o grid. As research models, LPJmL model parameters are not calibrated for discharge and VIC only crudely. Baseline runs and model spin up are driven by WFD-EI data (Weedon, Gomes et al. 2011). Hindcast runs are driven by the full 15 member, 30 year, monthly initiated, 7 month forecasts of the ECMWF System4 (Molteni, Stockdale et al. 2011). Each model is driven by both raw forecast data and by the same data bias-corrected against the WFD-EI data. Skill is assessed by ROCSS and RPSS scores of the three terciles (above normal, near normal and below normal), primarily for discharge against both baseline simulations and against observations (mainly obtained from GRDC) from 46 stations covering the whole of the European domain and for other water balance terms against baseline simulations only.
    Skills will be presented grouped by the major European climatic zones, as a function of lead time and season. Tentative results show considerable skill in northern Europe for positive and negative spring anomalies with up to 2 months lead time, but decreasing for summer. For central Europe the performance is similar, for western Europe we find very little skill, while for the Iberian peninsula we find some skill for negative anomalies in summer with considerable lead time. More robust results will be presented at the workshop.
    Bicarbonaat doodt schurftspore bij curatieve toepassing
    Jong, P.F. de; Anbergen, R.H.N. ; Elk, P.J.H. van; Dieren, M.C.A. van; Steeg, P. van der; Franssen-Verheijen, M.A.W. - \ 2015
    Enzymes for materials: laccase-mediated modification of poly(ethersulfone) membranes
    Franssen, M.C.R. ; Slagman, S. ; Nady, N. ; Schroen, C.G.P.H. ; Boom, R.M. ; Zuilhof, H. - \ 2015
    Chemo-enzymatic synthesis of biobased nitrogen containing bulk chemicals
    Franssen, M.C.R. - \ 2015
    - p. 20 - 20.
    Self assembled monolayers on oxidized platinum as platform for biosensors
    Alonso Carnicero, J.M. ; Bielen, A.A.M. ; Franssen, M.C.R. ; Zuilhof, H. - \ 2015
    - p. 294 - 294.
    Environmental contamination with Toxocara eggs : A quantitative approach to estimate the relative contributions of dogs, cats and foxes, and to assess the efficacy of advised interventions in dogs
    Nijsse, Rolf ; Mughini-Gras, Lapo ; Wagenaar, J.A. ; Franssen, Frits ; Ploeger, Harm W. - \ 2015
    Parasites & Vectors 8 (2015)1. - ISSN 1756-3305
    Cats - Clean-up - Contamination - Contribution - Deworming - Dogs - Eggs - Environment - Foxes - Toxocara

    Background: Environmental contamination with Toxocara eggs is considered the main source of human toxocariasis. The contribution of different groups of hosts to this contamination is largely unknown. Current deworming advices focus mainly on dogs. However, controversy exists about blind deworming regimens for >6-month-old dogs, as most of them do not actually shed Toxocara eggs. We aim to estimate the contribution of different non-juvenile hosts to the environmental Toxocara egg contamination and to assess the effects of different Toxocara-reducing interventions for dogs. Methods: A stochastic model was developed to quantify the relative contribution to the environmental contamination with Toxocara eggs of household dogs, household cats, stray cats, and foxes, all older than 6 months in areas with varying urbanization degrees. The model was built upon an existing model developed by Morgan et al. (2013). We used both original and published data on host density, prevalence and intensity of infection, coprophagic behaviour, faeces disposal by owners, and cats' outdoor access. Scenario analyses were performed to assess the expected reduction in dogs' egg output according to different deworming regimens and faeces clean-up compliances. Estimates referred to the Netherlands, a country free of stray dogs. Results: Household dogs accounted for 39 % of the overall egg output of >6-month-old hosts in the Netherlands, followed by stray cats (27 %), household cats (19 %), and foxes (15 %). In urban areas, egg output was dominated by stray cats (81 %). Intervention scenarios revealed that only with a high compliance (90 %) to the four times a year deworming advice, dogs' contribution would drop from 39 to 28 %. Alternatively, when 50 % of owners would always remove their dogs' faeces, dogs' contribution would drop to 20 %. Conclusion: Among final hosts of Toxocara older than 6 months, dogs are the main contributors to the environmental egg contamination, though cats in total (i.e. both owned and stray) transcend this contribution. A higher than expected compliance to deworming advice is necessary to reduce dogs' egg output meaningfully. Actions focusing solely on household dogs and cats are unlikely to sufficiently reduce environmental contamination with eggs, as stray cats and foxes are also important contributors.

    Rhizobium lipo-chitooligosaccharide signaling triggers accumulation of cytokinins in Medicago truncatula roots
    Zeijl, A.L. van; Camp, R.H.M. Op den; Deinum, E.E. ; Charnikhova, T. ; Franssen, H. ; Camp, H.J.M. op den; Bouwmeester, H.J. ; Kohlen, W. ; Bisseling, T. ; Geurts, R. - \ 2015
    Molecular Plant 8 (2015)8. - ISSN 1674-2052 - p. 1213 - 1226.
    Legume rhizobium symbiosis is initiated upon perception of bacterial secreted lipo-chitooligosaccharides (LCOs). Perception of these signals by the plant initiates a signaling cascade that leads to nodule formation. Several studies have implicated a function for cytokinin in this process. However, whether cytokinin accumulation and subsequent signaling are an integral part of rhizobium LCO signaling remains elusive. Here, we show that cytokinin signaling is required for the majority of transcriptional changes induced by rhizobium LCOs. In addition, we demonstrate that several cytokinins accumulate in the root susceptible zone 3 h after rhizobium LCO application, including the biologically most active cytokinins, trans-zeatin and isopentenyl adenine. These responses are dependent on calcium- and calmodulin-dependent protein kinase (CCaMK), a key protein in rhizobial LCO-induced signaling. Analysis of the ethylene-insensitive Mtein2/Mtsickle mutant showed that LCO-induced cytokinin accumulation is negatively regulated by ethylene. Together with transcriptional induction of ethylene biosynthesis genes, it suggests a feedback loop negatively regulating LCO signaling and subsequent cytokinin accumulation. We argue that cytokinin accumulation is a key step in the pathway leading to nodule organogenesis and that this is tightly controlled by feedback loops.
    Root developmental programs shape the Medicago truncatula nodule meristem
    Franssen, H. ; Xiao, T.T. ; Kulikova, O. ; Wan, X. ; Bisseling, T. ; Scheres, B. ; Heidstra, R. - \ 2015
    Development 142 (2015). - ISSN 0950-1991 - p. 2941 - 2950.
    Nodules on the roots of legume plants host nitrogen-fixing Rhizobium bacteria. Several lines of evidence indicate that nodules are evolutionarily related to roots. We determined whether developmental control of the Medicago truncatula nodule meristem bears resemblance to that in root meristems through analyses of root meristem-expressed PLETHORA genes. In nodules, MtPLETHORA 1 and 2 are preferentially expressed in cells positioned at the periphery of the meristem abutting nodule vascular bundles. Their expression overlaps with an auxin response maximum and MtWOX5, which is a marker for the root quiescent center. Strikingly, the cells in the central part of the nodule meristem have a high level of cytokinin and display MtPLETHORA 3 and 4 gene expression. Nodule-specific knockdown of MtPLETHORA genes results in a reduced number of nodules and/or in nodules in which meristem activity has ceased. Our nodule gene expression map indicates that the nodule meristem is composed of two distinct domains in which different MtPLETHORA gene subsets are expressed. Our mutant studies show that MtPLETHORA genes function redundantly in nodule meristem maintenance. This indicates that Rhizobium has recruited root developmental programs for nodule formation.
    Moet je je hond opzadelen met plofkip?
    Bosch, Guido - \ 2015
    The impact of habitual protein intake on dietary protein digestion and absorption kinetics and postprandial muscle protein synthesis rates in older males
    Gorissen, S.H. ; Horstman, A. ; Franssen, R. ; Kouw, I.W. ; Kramer, I.F. ; Wall, B.T. ; Burd, N.A. ; Groot, C.P.G.M. de; Loon, L.J.C. van - \ 2015
    In: Abstracts of the ESPEN Congress 2015. - - p. S4 - S4.
    Root and nodule : lateral organ development in N2-fixing plants
    Xiao, T.T. - \ 2015
    Wageningen University. Promotor(en): Ton Bisseling, co-promotor(en): Rene Geurts; Henk Franssen. - Wageningen : Wageningen University - ISBN 9789462572768 - 198
    medicago - wortelknolletjes - endosymbiose - symbiose - mycorrhizae - stikstoffixatie - plantenontwikkeling - moleculaire biologie - medicago - root nodules - endosymbiosis - symbiosis - mycorrhizas - nitrogen fixation - plant development - molecular biology

    Plants are sessile organisms. This characteristic severely limits their ability of approaching nutrients. To cope with this issue, plants evolved endosymbiotic relationships with soil fungi to extend their interface with surrounding environment. In case of arbuscular mycorrhizae (AM) fungi this occurred about 400 million years ago. The AM fungi can interact with most angiosperms. In this symbiotic relationship, the plant get nutrients, especially phosphate, from the fungi, and plants provide carbohydrates to the fungi in return. About 60 million years ago, a group of plants evolved N2-fixing nodule symbiosis. This includes interactions of legumes plants with rhizobium bacteria and actinorhizal plants with Frankia bacteria. Currently, all plant species that are able to establish a nodule symbiosis belong to the Rosid I clade. In the nodule symbioses the bacteria produce ammonia and the plant provides carbohydrates to the bacteria.

    In the root nodule symbiosis, the nitrogen fixing bacteria are hosted in the cell of the root nodule. Although the function and structure of the root nodule are different from the other plant organs, it does share some features with other organs, especially the lateral root. To get further insight into the similarities and differences between root nodule and lateral root, I made use of the model legume (Medicago truncatula) and the non-legume Parasponia (Parasponia andersonii) that is the only genus outside the legumes that forms nodules with rhizobium.

    In Chapter 1, I will give a general introduction on the process of root nodule formation in legume plants. I will mainly focus on nodule organogenesis and the plant hormones that are known to be important for this process. Root nodules are supposed to have a close relationship with lateral roots. Therefore a comparison between lateral root and root nodule development will be included in this introduction.

    Lateral root development has especially been studied in in Arabidopsis. To be able to compare the root and root nodule developmental process, especially at the early stages, a Medicago lateral root development fate map has been made. This will be described in Chapter 2 and showed that in addition to the pericycle, endodermis and cortex are also mitotically activated during lateral root formation. Pericycle derived cells only form part of the stem cell niche as endodermis derived cells also contribute to this.

    In Chapter 3, a Medicago root nodule fate map is presented. In this Chapter, the contribution of different root cell layers to the mature nodule will be described. A set of molecular markers for root tissue, cell cycle and rhizobial infection have been used to facilitate this analysis. The fate map showed that nodule meristem originates from the third cortical layer and many cell layers of the base of the nodule are directly derived from cells of the inner cortical layers, root endodermis and pericycle. The inner cortical cell layers form about 8 cell layers of infected cells while the root endodermis and pericycle derived cells forms the uninfected tissues that are located at the base of the mature nodule. Nodule vascular is formed from the part of the primordium derived from the cortex. The development of primordia was divided in 6 stages. To illustrate the value of this fate map, a few published mutant nodule phenotypes are re-analyzed.

    In Chapter 4, the role of auxin at early stages of Medicago nodule formation is studied. In this chapter auxin accumulation is studied during the 6 stages of primordium development. It is studied by using DR5::GUS as an auxin reporter. Auxin accumulation associates with mitotic activity within the primordium. Previously, it has been postulated by theoretical modelling that the accumulation of auxin during nodulation is induced by a local reduction of PIN (auxin efflux carriers) levels. We tested this theory, but this was hampered due to the low level of PIN proteins in the susceptible zone of the root. It is still possible that auxin accumulation is initiated by a decrease of PIN levels. However, the level of 2 PIN already increase before the first divisions are induced. In young primordia they accumulate in all cells. At later stages PINs mainly accumulate at the nodule periphery and the future nodule meristem. The subcellular position of PINs strongly indicates they play a key role in the accumulation of auxin in primordia.

    Previous studies showed that a group of root apical meristem regulators is expressed in the nodule meristem. In Chapter 5, we tested whether the Medicago nodule meristem expresses PLETHORA genes that are expressed in the root meristem. These PLETHORAs were functionally analysed, by using RNAi approach using a nodule specific promoter. Knockdown of PLETHORAs expression hampers primordium formation and meristem growth. Hence, we conclude rhizobium recruited key regulators of root development for nodule development.

    In Chapter 6, we first introduced the non-legume lateral root and nodule fate maps by using Parasponia. In Parasponia nodules the nodule central vascular bundle is completely derived from the pericycle similar as its lateral roots. The nodule infected cells were shown to be derived from cortex. Together with the data obtained in this thesis, this Chapter further discussed several developmental aspects of the different lateral root organs. Especially, it focused on the vasculature and meristem formation of legume and non-legume nodules.

    Listeria monocytogenes repellence by enzymatically modified PES surfaces
    Veen, S. van der; Nady, N. ; Franssen, M.C.R. ; Zuilhof, H. ; Boom, R.M. ; Abee, T. ; Schroën, C.G.P.H. - \ 2015
    Journal of Applied Polymer Science 132 (2015)10. - ISSN 0021-8995 - 6 p.
    stainless-steel - catalyzed modification - biofilm formation - attachment - growth - membranes - water - acid - functionalization - hydrophobicity
    : The effect of enzyme-catalyzed modification of poly(ethersulfone) (PES) on the adhesion and biofilm formation of two Listeria monocytogenes strains is evaluated under static and dynamic flow conditions. PES has been modified with gallic acid, ferulic acid and 4-hydroxybenzoic acid. The surfaces modified with any of these compounds show up to 70% reduced adhesion of L. mono-cytogenes under static conditions and up to 95% under dynamic flow conditions compared with unmodified surfaces. Also, under static conditions the formation of biofilms is reduced by 70%. These results indicate that the brush structures that are formed by the polymers on the PES surface directly influence the ability of microorganisms to interact with the surface, thereby reducing attachment and biofilm formation of L. monocytogenes. Based on these results, it is expected that enzyme-catalyzed surface modification is a promising tool to reduce microbial adhesion and biofilm formation
    Covalent Attachment of 1-Alkenes to Oxidized Platinum Surfaces
    Alonso Carnicero, J.M. ; Fabre, B. ; Trilling, A.K. ; Scheres, L.M.W. ; Franssen, M.C.R. ; Zuilhof, H. - \ 2015
    Langmuir 31 (2015)9. - ISSN 0743-7463 - p. 2714 - 2721.
    self-assembled monolayers - organic monolayers - gold - alkanethiols - functionalization - spectroscopy - activation - alkenes - layers - films
    We report the formation of covalently bound alkyl layers onto oxidized Pt (PtOx) substrates by reaction with 1-alkenes as a novel way to bind organic molecules to metal surfaces. The organic layers were characterized by static contact angle, infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The grafted alkyl layers display a hydrolytic stability that is comparable to that of alkyl thiols on Au. PtOx-alkene attachment is compatible with terminal ester moieties enabling further anchoring of functional groups, such as redox-active ferrocene, and thus has great potential to extend monolayer chemistry on noble metals.
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