Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    '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.

    We have a manual that explains all the features 

    Current refinement(s):

    Records 1 - 10 / 10

    • help
    • print

      Print search results

    • export

      Export search results

    Check title to add to marked list
    Innate immunity of carp : fishing for receptors
    Fink, Inge - \ 2017
    Wageningen University. Promotor(en): Geert Wiegertjes; Huub Savelkoul, co-promotor(en): Maria Forlenza. - Wageningen : Wageningen University - ISBN 9789463430753 - 240
    carp - cyprinus - immunity - platelets - macrophage activation - receptors - polarization - immunostimulation - immunology - karper - cyprinus - immuniteit - bloedplaatjes - macrofaag activering - receptoren - polarisatie - immunostimulatie - immunologie

    Recent decades have seen a significant intensification of aquaculture leading to increased risk of infections with several pathogenic organisms. On economical and ethical grounds it is more appropriate to improve general welfare conditions and prevent infections rather than treating disease outbreaks once they have occurred. Immunostimulation through feed can provide more efficient and sustainable control of diseases in aquaculture through enhancing the immunocompetence of fish; however, the underlying mechanisms are poorly characterized. The overall aim of this thesis was to perform a molecular and functional characterization of how pathogen-associated molecular patterns (PAMPs), such as β-glucans, affect the innate immune response of carp and which receptors on carp leukocytes are likely candidates to play a role in sensing such PAMPs.

    In chapter 1 we provide a framework for this thesis by introducing different classes of PAMPs, including β-glucans. These molecules were the centrepiece of an intra-European training network called NEMO (Protective immune modulation in warm water fish by feeding glucans), which this PhD project was part of. The scientific aim of the NEMO network was to develop a sustainable and cost-effective use of β-glucans as immunostimulants for aquaculture, using common carp as the model fish species, since on a global scale common carp is the most cultured fish species for food consumption. Our aims within the NEMO project entailed both the characterization of carp leukocytes and the characterization of candidate pattern recognition receptors (PRRs) that could play a role in sensing PAMPs and initiating immune responses. Chapter 1 therefore introduces the thrombocytes and macrophages pertinent to this thesis, as well as important classes of PRRs.

    In our first experimental study, described in chapter 2, we investigated the relevance of thrombocytes for the immune system of carp. We found that thrombocytes from healthy carp express a large number of immune-relevant genes, among which several cytokines and Toll-like receptors (Tlrs). Furthermore, we dissected the role of thrombocytes during infections with two different, albeit related, protozoan parasites, Trypanoplasma borreli and Trypanosoma carassii, and found thrombocytes were massively depleted from blood and spleen of fish infected with T. borreli. The pathology of this infection is associated with elevated levels of tissue nitration, prompting us to investigate, ex vivo, the effect of nitric oxide on thrombocytes. Our studies revealed that nitric oxide can induce a clear and rapid apoptosis of thrombocytes from healthy carp, supporting a role for nitric oxide-mediated control of immune-relevant thrombocytes during infection with T. borreli. Thereby, this particular study provided an excellent example of interplay between pathogen and the innate immune system of carp.

    We reviewed in chapter 3 another cell type central to innate immunity: the macrophage. We focused on the heterogeneity of macrophage activation states as these cells, at least in humans and mice, have the ability to polarize in several directions during an immune response. Based on the signals that lead to activation and the effector functions and cytokine profile as a result thereof, macrophages can be broadly divided into two types: classically activated macrophages induced in a T helper 1 (TH1) cytokine environment, and alternatively activated macrophages, induced in a TH2 cytokine environment. Mirroring the TH1–TH2 dichotomy, classically activated macrophages have also been termed M1, whereas alternatively activated macrophages have been termed M2. Classically activated macrophages are typically induced by stimulation with microbial ligands such as LPS in combination with pro-inflammatory cytokines such as IFNγ, and can be viewed as an extension of innate activated macrophages which are induced by microbial ligands only, thus are independent of cytokines. Alternatively activated macrophages are generated in the presence of IL4 and/or IL13. In addition to M1 and M2, one can distinguish regulatory macrophages, which are associated with the presence of the cytokine IL10. In this chapter, we reviewed the evidence of existence of polarized macrophages in teleost fish, among other things based on observations of the fundamentally different immune responses elicited by the parasites T. borreli and T. carassii.

    We further investigated the polarization of carp macrophages in chapter 4, where we obtained gene signature profiles of carp macrophages via a transcriptome approach. Independently of cytokines, carp macrophages showed the ability to differentiate into cells with functional characteristics highly comparable to those of mammalian M1 and M2, consistent with a conserved ability of macrophages to polarize into distinct subsets. In addition to obtaining a global view of gene expression, our transcriptome approach identified gene signatures for M1 and M2 macrophages which appear conserved from fish to mammals. We selected a number of these interesting genes that were differentially regulated between M1 and M2 macrophages and discussed in detail five potential M1 markers; il1β, ptx3a, saa, nos2b, and il12a – as well as five potential M2 markers; cyr61, inhba, timp2, tgm2, and arg2. These transcriptome studies may pave the way for future studies of polarized macrophages during immune responses in fish. Furthermore, additional analyses of the datasets described in this chapter will undoubtedly lead to the characterization of more genes relevant to macrophage polarization and recognition of immunostimulants.

    As part of the characterization of candidate PRRs that could play a role in sensing PAMPs and initiating immune responses, we studied the scavenger receptor Cd36 (chapter 5), which in mammals is expressed by many different (immune) cell types and plays a role in highly diverse processes, both homeostatic and pathologic. Among other things, it is often found associated with sensing of β-glucans and also with M2 macrophage activation, sparking our interest in this molecule in fish. We studied Cd36 in common carp as well as in zebrafish, a closely related cyprinid fish species. Whereas a single cd36 gene is present in zebrafish, carp was shown to have two paralogs of cd36. Although all genes show conserved synteny compared to mammalian CD36, unexpectedly we could not detect gene expression of cyprinid cd36 in macrophages or any other immune cell type or immune organ. Yet, because gene expression of cd36 was down-regulated during Mycobacterium marinum infection of zebrafish, and knockdown of cd36 in zebrafish embryos led to higher bacterial burden upon such infection, our data imply a role for Cd36 in immune responses of fish. Future studies are needed to clarify the exact mechanisms involved.

    As characterization of candidate PRRs we also examined the Toll-like receptors Tlr1 and Tlr2 (chapter 6). We identified a full-length, expressed tlr1 gene, a tlr1 pseudogene, and a second tlr2 gene next to the tlr2 which had been described previously. Sequence, phylogenetic and synteny analyses supported the conserved nature of these genes, and three-dimensional modelling showed a good fit with the mammalian TLR1/TLR2 heterodimer including the potential to bind to the prototypical ligand Pam3CSK4. However, we were unable to demonstrate Tlr1/Tlr2-mediated ligand binding in transfected cell lines through NFκB activation, despite showing the expression and co-localization of Tlr1 and Tlr2. This prompted a discussion of methods available for studying ligand-binding properties of fish Tlrs.

    Finally, we discuss in chapter 7 the findings of this thesis in the context of the NEMO project. We present the concept of trained immunity, which could provide the conceptual framework within which the immune-stimulating ability of compounds such as β-glucans could be explained. We discuss recent advances in the field of TLR research as well as that of macrophage polarization, and highlight immunometabolism as a new area of interest which may help to illuminate the molecular events occurring in immune cells during health and disease. In conclusion, we found that carp leukocytes, along with their pattern recognition receptors, are central players of the innate immune system of carp. Our findings contribute to the understanding of mechanisms of immunostimulation, and expect this will enable the valorisation and use of immunostimulants for sustainable aquaculture and improvement of fish health.

    Fractioning electrodialysis: a current induced ion exchange process
    Galama, A.H. ; Daubaras, G. ; Burheim, O.S. ; Rijnaarts, H. ; Post, J.W. - \ 2014
    Electrochimica Acta 136 (2014). - ISSN 0013-4686 - p. 257 - 265.
    divalent ions - seawater desalination - membrane - monovalent - diffusion - transport - charge - nanofiltration - permeability - polarization
    In desalination often multi ionic compositions are encountered. A preferential removal of multivalent ions over monovalent ions can be of interest to prevent scaling in the desalination process. Recently, a novel fractionating electrodialysis stack is described by Zhang et al., 2012 (in Sep. purify. Technol. 88). In the present work a small modification to such a stack was made, to create a current induced ion exchange process, in which no longer desalination occurs. This was done by building a membrane stack in which monovalent-selective ion-exchange membranes and standard grade ion-exchange membranes, with similar charge sign (so either anion or cation exchange groups), were placed alternatingly between an anode and a cathode to form a membrane stack. A proof of principle of the fractioning electrodialysis technology is given. Ternary mixtures, with a divalent-monovalent ion ratio similar to seawater, were used as feed water. For a cation and an anion fractioning stack, maximum fractionations of divalent ions were obtained of approximately 90 and 60%. At higher applied current density, ions can be fractionated to a larger extent than at lower applied current density. For both stacks the water recovery was 50%. Coulombic efficiency of both processes decrease rapidly after the start of the experiment. This leads to relatively large volumetric energy consumptions. (C) 2014 Elsevier Ltd. All rights reserved.
    Technical notes: A detailed study for the provision of measurement uncertainty and traceability for goniospectrometers
    Peltoniemi, J.I. ; Hakala, T. ; Suomalainen, J.M. ; Honkavaara, E. ; Markelin, L. ; Gritsevich, M. ; Eskelinen, J. ; Jaanson, P. ; Ikonen, E. - \ 2014
    Journal of Quantitative Spectroscopy and Radiative Transfer 146 (2014). - ISSN 0022-4073 - p. 376 - 390.
    reflectance distribution function - laboratory goniometer system - bidirectional reflectance - diffuse-reflectance - spectro-goniometer - test field - light - polarization - snow - calibration
    The measurement uncertainty and traceability of the Finnish Geodetic Institutes¿s field gonio-spectro-polarimeter FIGIFIGO have been assessed. First, the reference standard (Spectralon sample) was measured at the National Standard Laboratory of MIKES-Aalto. This standard was transferred to FGI¿s field reference standard (larger Spectralon sample), and from that to the unmanned aerial vehicle (UAV), reference standards (1 m2 plates). The reflectance measurement uncertainty of FIGIFIGO has been estimated to be 0.01 in ideal laboratory conditions, but about 0.02–0.05 in typical field conditions, larger at larger solar or observation zenith angles. Target specific uncertainties can increase total uncertainty even to 0.1–0.2. The angular reading uncertainty is between 1° and 3°, depending on user selection, and the polarisation uncertainty is around 0.01. For UAV, the transferred reflectance uncertainty is about 0.05–0.1, depending on, how ideal the measurement conditions are. The design concept of FIGIFIGO has been proved to have a number of advantages, such as a well-adopted user-friendly interface, a high level of automation and excellent suitability for the field measurements. It is a perfect instrument for collection of reference data on a given target in natural (and well-recorded) conditions. In addition to the strong points of FIGIFIGO, the current study reveals several issues that need further attention, such as the field of view, illumination quality, polarisation calibration, Spectralon reflectance and polarisation properties in the 1000–2400 nm range.
    Improved management of winter operations to limit subsurface contamination with degradable deicing chemicals in cold regions
    French, H.K. ; Zee, S.E.A.T.M. van der - \ 2014
    Environmental Science and Pollution Research 21 (2014)15. - ISSN 0944-1344 - p. 8897 - 8913.
    penetrating radar data - solute transport - spatial variability - soil heterogeneity - dc resistivity - porous-media - water - snow - flow - polarization
    This paper gives an overview of management considerations required for better control of deicing chemicals in the unsaturated zone at sites with winter maintenance operations in cold regions. Degradable organic deicing chemicals are the main focus. The importance of the heterogeneity of both the infiltration process, due to frozen ground and snow melt including the contact between the melting snow cover and the soil, and unsaturated flow is emphasised. In this paper, the applicability of geophysical methods for characterising soil heterogeneity is considered, aimed at modelling and monitoring changes in contamination. To deal with heterogeneity, a stochastic modelling framework may be appropriate, emphasizing the more robust spatial and temporal moments. Examples of a combination of different field techniques for measuring subsoil properties and monitoring contaminants and integration through transport modelling are provided by the SoilCAM project and previous work. Commonly, the results of flow and contaminant fate modelling are quite detailed and complex and require post-processing before communication and advising stakeholders. The managers’ perspectives with respect to monitoring strategies and challenges still unresolved have been analysed with basis in experience with research collaboration with one of the case study sites, Oslo airport, Gardermoen, Norway. Both scientific challenges of monitoring subsoil contaminants in cold regions and the effective interaction between investigators and management are illustrated.
    The Impact of Balanced Risk-Benefit Information and Initial Attitudes on Post-Information Attitudes
    Dijk, H. van; Fischer, A.R.H. ; Jonge, J. de; Rowe, G. ; Frewer, L.J. - \ 2012
    Journal of Applied Social Psychology 42 (2012)8. - ISSN 0021-9029 - p. 1958 - 1983.
    genetically-modified foods - gene technology - perception - negativity - trust - polarization - pesticides - acceptance - resistance - persuasion
    In a realistic social context, people are confronted with both positive and negative information, yet research on this topic is relatively scarce. We present 2 studies examining the role of initial attitudes on the impact of one-sided vs. balanced positive and negative information on attitudes toward food production methods. The first experiment demonstrated that one-sided information influenced postinformation attitudes congruent to the direction of the message content. The second experiment showed that the effect of balanced information on post-information attitudes may depend on initial attitudes. These results demonstrate that negativity effects are dominant for people with initial positive attitudes, but change into positivity effects for people with initial negative attitudes. Implications for communicating both positive and negative information are discussed.
    Fast and simple model for atmospheric radiative transfer
    Seidel, F.C. ; Kokhanovsky, A.A. ; Schaepman, M.E. - \ 2010
    Atmospheric Measurement Techniques 3 (2010). - ISSN 1867-1381 - p. 1129 - 1141.
    aerosol retrieval - transfer code - scattering - polarization - reflectance - quantities - intensity - radiance - light - 6s
    Radiative transfer models (RTMs) are of utmost importance for quantitative remote sensing, especially for compensating atmospheric perturbation. A persistent trade-off exists between approaches that prefer accuracy at the cost of computational complexity, versus those favouring simplicity at the cost of reduced accuracy. We propose an approach in the latter category, using analytical equations, parameterizations and a correction factor to efficiently estimate the effect of molecular multiple scattering. We discuss the approximations together with an analysis of the resulting performance and accuracy. The proposed Simple Model for Atmospheric Radiative Transfer (SMART) decreases the calculation time by a factor of more than 25 in comparison to the benchmark RTM 6S on the same infrastructure. The relative difference between SMART and 6S is about 5% for spaceborne and about 10% for airborne computations of the atmospheric reflectance function. The combination of a large solar zenith angle (SZA) with high aerosol optical depth (AOD) at low wavelengths lead to relative differences of up to 15%. SMART can be used to simulate the hemispherical conical reflectance factor (HCRF) for spaceborne and airborne sensors, as well as for the retrieval of columnar AOD
    Peroxisome Proliferator-activated Receptor - Activation Promotes Infiltration of Alternatively Activated Macrophages into Adipose Tissue
    Stienstra, R. ; Duval, C.N.C. ; Keshtkar Ghiasabadi, S. ; Laak, J. van der; Kersten, A.H. ; Müller, M.R. - \ 2008
    Journal of Biological Chemistry 283 (2008)33. - ISSN 0021-9258 - p. 22620 - 22627.
    ppar-gamma - insulin-resistance - gene-expression - obesity - polarization - thiazolidinediones - differentiation - inflammation - adipocytes - muscle
    Obesity is associated with infiltration of macrophages into adipose tissue. Adipose macrophages may contribute to an elevated inflammatory status by secreting a variety of proinflammatory mediators, including tumor necrosis factor alpha and interleukin-6 (IL-6). Recent data suggest that during diet-induced obesity the phenotypeofadipose-resident macrophages changes from alternatively activated macrophages toward a more classical and pro-inflammatory phenotype. Here, we explore the effect of peroxisome proliferator-activated receptor gamma activation on obesity-induced inflammation in 129SV mice fed a high fat diet for 20 weeks. High fat feeding increased bodyweight gain, adipose tissue mass, and liver triglycerides. Rosiglitazone treatment further increased adipose mass, reduced liver triglycerides, and changed adipose tissue morphology toward smaller adipocytes. Surprisingly, rosiglitazone markedly increased the number of macrophages in adipose tissue, as shown by immunohistochemical analysis and quantification of macrophage marker genes CD68 and F4/80 +. In adipose tissue, markers for classically activated macrophages including IL-18 were down-regulated, whereas markers characteristic for alternatively activated macrophages (arginase 1, IL-10) were up-regulated by rosiglitazone. Importantly, conditioned media from rosiglitazone-treated alternatively activated macrophages neutralized the inhibitory effect of macrophages on 3T3-L1 adipocyte differentiation, suggesting that alternatively activated macrophages may be involved in mediating the effects of rosiglitazone on adipose tissue morphology and mass. Our results suggest that short term rosiglitazone treatment increases infiltration of alternatively activated macrophages in adipose tissue. The alternatively activated macrophages might play a role in peroxisome proliferator-activated receptor gamma-dependent expansion and remodeling of adipose tissue.
    Electric Birefringence Study of an Amyloid Fibril System: the Short End of the Length Distribution
    Rogers, S.S. ; Venema, P. ; Ploeg, J.P.M. van der; Sagis, L.M.C. ; Linden, E. van der - \ 2005
    European Physical Journal E. Soft Matter and Biological Physics 18 (2005). - ISSN 1292-8941 - p. 207 - 217.
    beta-lactoglobulin - polyelectrolyte solutions - charged macromolecules - human-disease - protein - polarization - mechanism - dynamics - fibrillogenesis - polarizability
    In this article, a system of amyloid fibrils, based on the protein ß-lactoglobulin, is studied by transient electric birefringence. Single pulses of an electric field were applied to the solution, and the initial rise and subsequent decay of birefringence analysed. The decay takes place on a range of relaxation times, and therefore contains information about the length distribution of fibrils in the system. The information can be extracted using theories of the electric polarisability of polyelectrolyte rods, since the fibrils are an example of these. Despite the long-standing complications of such theories, useful quantitative information about the system can still be obtained. Using the Fixman model of polyelectrolyte polarisability, we obtain a measurement of the short end of the length distribution which shows the fibril concentration as a function of length rising linearly from 0.02¿2¿m. The short end of the length distribution was unobtainable in our previous study using rheo-optics (Rogers S. S. et al., Macromolecules 38, 2948 (2005), Iss. 8), but reasonable agreement between the two techniques shows they are complementary.
    An analytical algorithm for the determination of vegetation leaf area index from TRMM/TMI data
    Wen, J. ; Su, Z. - \ 2004
    International Journal of Remote Sensing 25 (2004)6. - ISSN 0143-1161 - p. 1223 - 1234.
    soil-moisture retrieval - surface-temperature - microwave emission - tibetan plateau - polarization - field - ndvi - ghz
    In this paper, an analytical algorithm for the determination of land surface vegetation Leaf Area Index (LAI) with the passive microwave remote sensing data is developed. With the developed algorithm and the Tropical Rainfall Measuring Mission/Microwave Imager (TRMM/TMI) remote sensing data collected during the Global Energy and Water Experiment (GEWEX) Asian Monsoon Experiment in Tibet (GAME/Tibet) Intensive Observation Period (IOP'98), the regional and temporal distributions of the land surface vegetation LAI have been evaluated. To validate the developed algorithm and the retrieval results, the maximum-composite Normalized Difference Vegetation Index (NDVI) data over the same study area and period are used in this study; the cloud contaminated NDVI values have been replaced by the cloud-free values reconstructed by the Harmonic ANnalysis of Time Series (HANTS) technique. The results show that the retrieved LAI is in good agreement with the cloud-free NDVI in regional and temporal distributions and in their statistical characteristics; the vegetation characteristics can be clearly assessed from the regional distribution of the retrieved LAI. As lower frequency microwave radiation can penetrate atmosphere and thin cloud layer, with the application of the passive microwave remote sensing data, the developed algorithm can be used to monitor the land surface vegetation condition more effectively.
    Determination of land surface temperature and soil moisture from Tropical Rainfall Measuring Mission/Microwave Imager remote sensing data
    Wen, J. ; Su, Z. ; Ma, Y. - \ 2003
    Journal of Geophysical Research: Atmospheres 108 (2003)D2. - ISSN 2169-897X - p. 4038 - 4038.
    microwave emission - vegetation - polarization - field
    An analytical algorithm for the determination of land surface temperature and soil moisture from the Tropical Rainfall Measuring Mission/Microwave Imager (TRMM/TMI) remote sensing data has been developed in this study. The error analyses indicate that the uncertainties of the enrolled parameters will not cause serious errors in the proposed algorithm. By applying the proposed algorithm to TRMM/TMI remote sensing data collected during the Global Energy and Water Experiment (GEWEX) Asian Monsoon Experiment (GAME)/Tibet Intensive Observation Period field campaign in 1998 (IOP'98), the temporal and regional distributions of land surface temperature and volumetric soil moisture are evaluated over the central Tibetan plateau area. To validate the proposed method, the ground-measured surface temperature and volumetric soil moisture are compared to TRMM/TMI-derived land surface temperature and soil Fresnel reflectivity respectively. The results show that the estimated surface temperature is in good agreement with ground measurements; their difference and correlation coefficient are 0.52 ± 2.41 K and 0.80, respectively. A quasi-linear relationship exists between estimated Fresnel reflectivity and ground-measured volumetric soil moisture with a correlation coefficient 0.82. The land surface thermal status can also be clearly identified from the regional distribution of the estimated land surface temperature; the mountainous area and water bodies have a very lower surface temperature, while the river basin shows a higher surface temperature compared to the mountainous area. The southeastern part of the selected area has lower soil moisture, while the river basin exhibits high soil moisture. It is therefore concluded that the proposed algorithm is successful for the retrieval of land surface temperature and soil moisture using TRMM/TMI data over the study area.
    Check title to add to marked list

    Show 20 50 100 records per page

    Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.