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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    Physiologically based kinetic modelling based prediction of oral systemic bioavailability of flavonoids, their metabolites, and their biological effects
    Boonpawa, Rungnapa - \ 2017
    Wageningen University. Promotor(en): Ivonne Rietjens, co-promotor(en): Arjen Punt. - Wageningen : Wageningen University - ISBN 9789463430371 - 180
    flavonoids - bioavailability - modeling - metabolites - quercetin - physiology - hesperidin - flavonoïden - biologische beschikbaarheid - modelleren - metabolieten - quercetine - fysiologie - hesperidine

    Flavonoids, abundantly present in fruits and vegetables, have been reported to exert various positive health effects based on in vitro bioassays. However, effects detected in in vitro models cannot be directly correlated to human health as most in vitro studies have been performed using flavonoid aglycones at high concentration ignoring extensive metabolism of flavonoids in the human body. To better understand positive health effects of flavonoids in humans, it is of importance to gain insight in at which form and concentration flavonoids are present in the systemic circulation after consumption. This insight can be obtained using physiologically based kinetic (PBK) computer modeling. The results obtained show that PBK modeling provides a useful additional research tool for studies on the fate of flavonoids in the human body and can reveal at what oral dose levels of flavonoids in vitro positive health effects can be expected to occur in vivo, presenting opportunities that are not easily provided by other methods.

    Selenium speciation and bioavailability in Dutch agricultural soils: the role of soil organic matter
    Supriatin, Supriatin - \ 2016
    Wageningen University. Promotor(en): Rob Comans, co-promotor(en): Liping Weng. - Wageningen : Wageningen University - ISBN 9789462579309 - 265
    agricultural soils - selenium - bioavailability - soil organic matter - grasslands - soil chemistry - fertilizers - fertilizer application - netherlands - landbouwgronden - selenium - biologische beschikbaarheid - organisch bodemmateriaal - graslanden - bodemchemie - kunstmeststoffen - bemesting - nederland

    Selenium (Se) is an essential micronutrient for animals and humans. In the food chain, the intake of Se by animals and humans depends largely on Se content in plants, whereas the major source of Se in plants lies in the soil. Therefore, understanding Se bioavailability in soils for plant uptake and its controlling factors and mechanisms is important. The objective of this thesis is to study the amount, speciation, bioavailability, plant uptake and fertilization of Se in agricultural soils in the Netherlands and underlying controlling factors and mechanisms, to provide guidance for soil testing and fertilization recommendation for efficient Se management in agriculture.

    The majority of agricultural soils (grassland and arable land) in the Netherlands contains low total Se (i.e. in the range of Se deficient), which is predominantly present as organic Se. Only a small fraction of total Se is present as inorganic Se (mainly as selenite) and residual Se. In this thesis, the evidences of association between Se and soil organic matter in these low Se soils have been shown. The associations include: (1) the total Se content is positively correlated to soil organic matter content; (2) the solubility and extractability of Se in soils follow the solubility and extractability of soil organic C; (3) the majority of Se present in soils is in organic form, both in the soil solution and solid phase; (4) the distributions of Se and organic C in the different fractions of solid organic matter (i.e. humic acids, hydrophobic organic neutral, hydrophilic acids) and dissolved organic matter (i.e. hydrophilic acids and fulvic acids) are comparable; and (5) the Se richness in solid and dissolved organic matter are related to properties of soil organic matter from different land uses. The relatively high soil organic matter content in these low Se soils is likely responsible for these associations.

    In general, Se content in crops (e.g. grass and wheat) grown on grassland soils and arable land soils, respectively in the Netherlands is low due to low amount of bioavailable Se in the soils. Different soil parameters determine Se plant uptake in these low Se soils with predominantly organic Se, depending on the properties of Se-containing soil organic matter. The intensity parameter of Se-rich dissolved organic matter (DOM) in soil solution (i.e. Se to DOC ratio in 0.01 M CaCl2 extraction) determines Se plant uptake in soils containing Se-rich organic matter (e.g. potato arable land soils), whereas the buffer capacity of labile organic Se to supply Se-rich DOM in soil solution limits Se plant uptake in soils containing Se-poor organic matter (e.g. grassland soils). Further research is needed to confirm the generality of the conclusion above, because the two experiments were carried out under different conditions (pot experiment and field experiment), using different plant species (wheat and grass) and covering different soil types from different land uses (potato fields and grassland). Site-specific properties in the field in addition to soil parameters included in the current study may largely (> 50%) determine Se content in grass under field conditions, which is in contrast with the results of the pot experiment in which the soil parameter explains 88% of Se content in wheat shoots. In general, the content of Se-rich DOM in soils increases with the increase of soil pH (with the decrease of soil C:N ratio), and the amount of labile organic matter in soils that can resupply Se-rich DOM is determined by the amount of clay (and Fe-(hydr)oxide). NPK fertilization, as one of the external factors, can reduce Se plant uptake, especially in organic-rich soils.

    Selenium (as selenate) fertilization on grassland with N plus cattle slurry or NPK application shows a positive effect to increase Se content in grass grown on different soil types with a large range of total Se, pH, clay content and organic matter content. Selenium content in grass grown on different soil types upon Se fertilization becomes more similar than before the fertilization. The results indicate that the effectiveness of Se fertilization is only weakly modified by soil properties, probably due to the high solubility of selenate in the soils. Nevertheless, the Se fertilization tends to be slightly more effective on sandy soils than on clay and organic rich soils.

    This thesis has shown that the content and quality of soil organic matter play an important role in determining the amount, speciation and bioavailability of Se in low Se soils with predominantly organic Se. The results in this thesis can be used as guidance to develop soil testing and fertilization recommendation for efficient Se management, especially in low Se soils with predominantly organic Se, such as in Dutch agricultural soils.

    Validation of ISO 17586 soil quality : extraction of trace elements using dilute nitric acid
    Vark, W. van; Harmsen, J. - \ 2016
    Alterra, Wageningen-UR (Alterra-rapport 2693) - 55
    soil - soil quality - trace elements - standards - bioavailability - iso - extraction - bodem - bodemkwaliteit - sporenelementen - normen - biologische beschikbaarheid - iso - extractie
    Improvement of risk assessment by integrating toxicological and epidemiological approaches: the case of isoflavones
    Islam, M.A. - \ 2015
    Wageningen University. Promotor(en): Ivonne Rietjens; Rolaf van Leeuwen; Tinka Murk. - Wageningen : Wageningen University - ISBN 9789462574649 - 174
    isoflavones - glucosides - soyabeans - toxic substances - bioavailability - biomarkers - human nutrition research - risk-benefit analysis - gene expression - isoflavonen - glucosiden - sojabonen - toxische stoffen - biologische beschikbaarheid - biomarkers - voedingsonderzoek bij de mens - risico-baten analyse - genexpressie

    Improvement of risk assessment by integrating toxicological and epidemiological approaches: the case of isoflavones

    PhD-thesis Mohammed Ariful Islam

    This thesis describes the results of a research project that aimed at the improvement of the risk/benefit assessment of soy isoflavones (SIF) by combining toxicological and epidemiological methods. The toxicological studies were carried out at the Department of Toxicology and part of the results were compared with the outcome of human intervention studies, that were carried out in parallel research project at the Division of Human Nutrition. In Chapter 1 it is explained why we considered such an integrated “tox-epi” approach to be useful for the prediction of possible effects of SIF in humans on the basis of animal data. SIF are constituents of soy based supplements, which became more and more popular in Western societies over the last decades, because of their putative beneficial health effects, that were related to the SIF present in these supplements. In spite of the long and safe history of soy consumption by the East and the South-East Asian population, the benefit and safety of soy have been challenged in recent years and concerns have been raised about possible adverse health effects. These concerns focussed primarily on the weak estrogenic and proliferative effects of SIF. Chapter 1 also provides some background information on the individual SIF, their structural similarity with the steroid hormone estradiol (E2) and their interaction with the estrogen receptors ERα and ERβ.

    Chapter 2 describes the differences between rats and humans in the conversion of the three major soy isoflavone glucosides, daidzin, genistin and glycitin, and their aglycones in a series of in vitro models. Results of studies in a Caco-2 transwell model confirmed that deconjugation of the isoflavone glucosides is essential for their transport across the intestinal barrier. It was shown that both rat and human intestinal S9 fractions were able to deconjugate the glucosides, and that intestinal enzymes plaid an important role in this deconjugation reaction. It was demonstrated that in the rat lactase phlorizin hydrolase, glucocerebrosidase, and cytosolic broad-specificity β-glucosidase contribute significantly to this deconjugation, and that in humans deconjugation mainly appeared to occur through the activity of broad-specificity β-glucosidase. Species difference in glucuronidation and sulfation were smaller than for the deconjugation reaction, and it was shown that 7-O-glucuronides were the major metabolites for all the three isoflavone aglycones. The in vitro results also indicated that glucuronidation in rats might be more efficient than in humans, again pointing towards species differences in the metabolism of isoflavone glycosides between rats and humans. It was also shown that the reconjugation reaction has a larger catalytic efficiency than the deconjugation of the glucosides, which corroborates that the detection of aglycones in the systemic circulation is unlikely.

    It has been reported in literature that following administration of SIF to humans or animals, these compounds are mainly (~98%) present in the systemic circulation in their conjugated form (i.e. as glucuronide and sulphate) of which the estrogenic potency is not yet clear. Chapter 3 provides evidence that in an intact cellular model the major SIF glucuronide metabolites in blood, genistein-7-O-glucuronide (GG) and daidzein-7-O-glucuronide (DG), only become estrogenic after deconjugation. The estrogenic potencies of genistein (Ge), daidzein (Da), GG and DG were determined using stably transfected U2OS-ERα, U2OS-ERβ reporter gene cells and proliferation was tested in T47D-ERβ and in T47D breast cancer cells. In all these assays the estrogenic potency of the aglycones was significantly higher than that of their corresponding glucuronides. UPLC analysis revealed that in the in vitro cell line assays, 0.2-1.6% of the glucuronides were deconjugated to their corresponding aglycones. It was also found that, under similar experimental conditions, rat breast tissue S9 fraction was about 30 times more potent in deconjugating these glucuronides than human breast tissue S9 fraction. The results presented in Chapter 3 confirm that SIF glucuronides are not estrogenic as such when tested in an intact cellular model system, and that the small fraction of aglycones account for the observed estrogenic effects. They also provide evidence for a significant species difference in the metabolism of SIF.

    In Chapters 4 and 5 of this thesis, two rat studies are described, that were performed to further elucidate important modes of action underlying biological effects of SIF and to facilitate an interspecies comparison of the effects observed in rats with those observed in human intervention studies. In these studies inbred ovariectomized Fischer344 rats were used, as an animal model for (post)menopausal women. In the first study described in Chapter 4, two dose levels (i.e. 2 and 20 mg/kg bw) were used to characterise plasma bioavailability, urinary and faecal concentrations of SIF and to investigate changes in gene expression in peripheral blood mononuclear cells (PBMC). The low dose was in line with the type of dosing relevant for human supplement use. Animals were dosed at 0 and 48 hr and sacrificed 4 hr after the last dose. A clear dose dependent increase of SIF concentrations in plasma, urine and faeces was observed, together with a strong correlation in changes in gene expression between the two dose groups. In the transcriptomic analysis, all estrogen responsive genes (ERG) and related biological pathways (BPs) that were found to be affected by the SIF treatment were regulated in both dose groups in the same direction, and indicate possible beneficial effects of SIF. However, most of the common genes in PBMC of rats and of (post)menopausal women, exposed to a comparable dose of the same supplement, were regulated in opposite direction. Thus based on these results no correlation was found between the changes in gene expression in rats and humans, leading to the conclusion that rats might not be a suitable model for humans.

    In Chapter 5 an animal experiment is described, in which rats received a dose of 2 mg SIF/kg body weight per day for a period of eight weeks. This dosing regimen was similar as that of the parallel human intervention study. Changes in gene expression in different target (i.e. breast (BT), uterus (UT) and sternum (ST)) and non-target (i.e. peripheral blood mononuclear cells (PBMC), adipose (AT) and liver (LT)) tissues were compared. Rank-rank scattered plots did not show any correlation in gene expression changes among different tissues. Out of 87 estrogen responsive genes (ERG), only 19 were found to be significantly regulated (p<0.05) in different tissues. The significantly regulated ERG were mostly found in LT, AT and UT. Surprisingly, no ERG were significantly regulated in BT and ST, although these are considered to be important estrogen sensitive target tissues. No correlation was observed with the changes in gene expression in the PBMC of two rat studies. Correlation was also not seen in the changes of gene expression in PBMC and adipose tissue between rat and humans.

    In Chapter 6 the results of the research project described in this thesis are evaluated. It was the aim of thesestudies to contribute to theimprovement ofthe risk and/or benefit assessment of SIF for humans, by using in vitro and in vivo animal and human models, and gene expression data in various animal and human tissues, as early biomarkers of effects of exposure to SIF. Although important information has been gathered on the metabolism and the estrogenic activity of SIF and their aglycones, we were not able to predict possible effects in human target tissues based on the results of changes in gene expression in target tissues obtained in the 8 weeks rat study. Possibly aged rats might be a more appropriate model than young ovariectomized rats.

    Development of an integrated in vitro model for the prediction of oral bioavailability of nanoparticles
    Walczak, A.P. - \ 2015
    Wageningen University. Promotor(en): Ivonne Rietjens, co-promotor(en): Hans Bouwmeester; Peter Hendriksen. - Wageningen : Wageningen University - ISBN 9789462572201 - 153
    nanotechnologie - deeltjes - in vitro - inname - biologische beschikbaarheid - voedingsonderzoek bij de mens - risicoschatting - nanotechnology - particles - in vitro - ingestion - bioavailability - human nutrition research - risk assessment

    Title of the PhD thesis: Development of an integrated in vitro model for the prediction of oral bioavailability of nanoparticles

    The number of food-related products containing nanoparticles (NPs) increases. To understand the safety of such products, the potential uptake of these NPs following consumption needs to be assessed. In normal safety assessment studies this is investigated using animal models. For scientific, ethical and economical reasons, there is a demand to refine, reduce and replace animal testing by developing in vitro alternatives for hazard characterization. In this thesis an in vitro model for the prediction of the uptake of NPs in the human body after consumption was developed. The model consists of two parts. The first part is a laboratory incubation model mimicking human digestion in mouth, stomach and intestine. For the second part, human intestinal wall cells are used to assess the uptake of nanoparticles. The two models were combined into the integrated in vitro model to take into consideration the potential effect of digestion on nanoparticle uptake in the gut. The main outcome of the work is that the cell-based integrated in vitro model can be used to evaluate which NPs are likely taken up by the body at the highest rate. The size of NPs and the type of chemical groups on their surface greatly influenced the uptake of NPs. The developed model can be used to prioritize the NPs for additional investigations. Using this model in the safety assessment of NPs would reduce the number of animals used in safety assessment.

    Chemical and biological rhizosphere interactions in low zinc soils
    Duffner, A. - \ 2014
    Wageningen University. Promotor(en): Ellis Hoffland; Sjoerd van der Zee, co-promotor(en): Erwin Temminghoff. - Wageningen : Wageningen University - ISBN 9789462571631 - 131
    bodem - zink - rizosfeer - voedingsstoffentekorten - bodemkunde - planten - voedingsstoffenopname (planten) - biologische beschikbaarheid - bodemkwaliteit - bodemvruchtbaarheid - soil - zinc - rhizosphere - nutrient deficiencies - soil science - plants - nutrient uptake - bioavailability - soil quality - soil fertility

    Abstract of the PhD thesis entitled “Chemical and biological rhizosphere

    interactions in low zinc soils” by Andreas Duffner

    Soil provides ecosystem services critical for life. The availability of micronutrients, such as zinc (Zn), in soils is an essential factor for normal healthy growth and reproduction of plants. Zinc deficiency is, however, a global problem in crop production due to low Zn bioavailability in soils to plants. The bioavailable Zn fraction in soils is controlled by several factors and is not directly related to the total Zn content of soils. The main objective of this thesis was the determination of factors which control Zn bioavailability in soils to plants and to assess approaches to improve the prediction of Zn plant uptake.

    Based on rhizobox experiments, in situ measurements in the rhizosphere as well as multisurface- and radial transport modeling approaches it was shown that the effect of root exuded citrate for increasing plant available Zn is soil specific and does not depend on a specific concentration of low molecular weight organic acids (e.g. citric acid) in the soil solution. Using various low Zn soils at the same time in an experimental setting improved the understanding of soil-responsiveness to root exuded citrate.

    Another insight was that multisurface models, which are widely used to assess the potential ecotoxicological risk in metal-contaminated soils, are also accurate to predict the Zn activity in soils with low Zn levels. The predictions were validated with the soil column Donnan Membrane Technique by using various soils with low Zn levels. It was predicted that soil organic matter is the dominant Zn sorbent and controlled the Zn activity also at low soil organic matter levels. Examples were shown how this modeling approach can be used to assess management options to increase bioavailable Zn to plants.

    Using soil extracted Zn fractions to directly predict the Zn plant uptake at low Zn levels was shown to be inaccurate. Using a stepwise approach where the steps of the uptake process were characterized with, respectively, Zn solid-solution distribution, adsorption of Zn to root surface, Zn uptake into root and Zn translocation to shoot made the prediction of Zn plant uptake more accurate. Root surface adsorbed Zn was shown to be a useful proxy for the bioavailable Zn.

    The framework of experimental and modeling approaches which were developed and applied in this thesis can also be used to study the plant-availability of other micronutrients at low concentration levels and how that is affected by various root exuded ligands.

    The bioavailability of four zinc oxide sources and zinc sulphate in broiler chickens
    Veldkamp, T. ; Diepen, J.T.M. van; Bikker, P. - \ 2014
    Wageningen : Wageningen UR Livestock Research (Report / Wageningen UR Livestock Research 806) - 27
    vleeskuikens - biologische beschikbaarheid - zink - belgië - voedingsstoffenbehoeften - excretie - excreten - landbouw en milieu - pluimveevoeding - pluimveehouderij - wetenschappelijk onderzoek - broilers - bioavailability - zinc - belgium - nutrient requirements - excretion - excreta - agriculture and environment - poultry feeding - poultry farming - scientific research
    Zinc is an essential trace element for all farm animal species. It is commonly included in animal diets as zinc oxide, zinc sulphate or organically bound zinc. Umicore Zinc Chemicals developed zinc oxide products with different mean particle sizes. Umicore Zinc Chemicals requested Wageningen UR Livestock Research to determine the bioavailability of four zinc oxide sources and zinc sulphate in broiler chickens. A precise estimate of the bioavailability of zinc sources is required both for fulfilling the zinc requirements of the animal and to reduce zinc excretion in excreta and the environment.
    Efficacy of iron fortified cowpea flour in improving iron status of schoolchildren in malaria endemic rural Ghana
    Abizari, A.R. - \ 2013
    Wageningen University. Promotor(en): Michael Zimmermann, co-promotor(en): Inge Brouwer; M. Armar-Klemesu. - S.l. : s.n. - ISBN 9789461735263 - 191
    vignameel - fortificatie - ijzer - ijzergebrekanemie - voedingstoestand - schoolkinderen - ghana - schoolmaaltijden - edta - biologische beschikbaarheid - voedingsprogramma - malaria - voedselsoevereiniteit - cowpea meal - fortification - iron - iron deficiency anaemia - nutritional state - school children - ghana - school meals - edta - bioavailability - nutrition programmes - malaria - food sovereignty

    Children in sub-Saharan Africa are more likely to have survived the critical first 1000 days of life carrying along unresolved micronutrient deficiencies into the school-age. Iron-deficiency is the most prevalent micronutrient problem affecting school-age children in sub-Saharan Africa and yet the most difficult to resolve. It is necessary to ensure an adequate iron intake through the diet of school-age children and school-based feeding intervention may be a way to improve iron intake of schoolchildren. Such a feeding intervention would be more sustainable if it relies on locally produced food(s) with the potential to support food sovereignty. In this context, this thesis investigated whether foods based on cowpeas, an indigenous legume crop originating from Africa, can be used in a school feeding setting to improve iron status of school-age children in Ghana.

    The investigations in this thesis comprised cross-sectional dietary and iron status assessment of schoolchildren (n=383), cowpea acceptability among schoolchildren (n=120 mother-child pairs), chemical analysis of cowpea landraces (n=14), an in vivo iron bioavailability among young women (n=16) and a randomized cowpea intervention trial (n=241) conducted mainly in Tolon-Kumbungu district of Ghana.

    The results indicated that iron-deficiency and iron-deficiency anaemia affect 8 and 7 out of every 10 schoolchildren respectively. It also showed that the probability of adequate dietary iron intake is 0.32 but much larger (~0.90) if schoolchildren benefitted from a school feeding programme. Mothers/caregivers intended to give cowpeas to their schoolchildren 2–3 times per week. The positive attitudes of mothers towards cowpea predicted their intention to give them to their schoolchildren but they were worried about the cost, long cooking time and the discomfort their children may suffer after consuming cowpeas. The chemical analysis showed that cowpeas contain appreciable amounts of iron (4.9–8.2 mg/ 100 gd.w) and zinc (2.7–4.1 mg/100 gd.w) but also high amounts of inhibitory phytate (477–1110 mg/100 gd.w) and polyphenol (327–1055 mg/100 gd.w). Polyphenol concentration in particular was higher (P<0.05) in coloured compared to white landraces. Iron bioavailability from red and white cowpeas were 1.4 and 1.7%, respectively, in NaFeEDTA-fortified meals and 0.89 and 1.2%, respectively, in FeSO4-fortified meals. Compared with FeSO4, fortification with NaFeEDTA increased the amount of iron absorbed from white and red cowpea meals by 0.05 and 0.08 mg (P < 0.05) respectively. Irrespective of the fortificant used, there was no significant difference in the amount of iron absorbed from the 2 varieties of cowpea. Finally the results from the intervention trial showed that fortification of whole cowpea flour with NaFeEDTA resulted in improvement of haemoglobin (P<0.05), serum ferritin (P<0.001) and body iron stores (P<0.001), and reduction in transferrin receptor concentration (P<0.001). Fortification also resulted in 30% and 47% reduction in the prevalence of iron-deficiency (ID) and iron-deficiency anaemia (IDA) (P<0.05), respectively.

    Overall, this thesis has shown that in a malarious region with high iron-deficiency like (northern) Ghana, iron status of schoolchildren can be improved through the consumption of cowpeas within a school feeding programme. The improvement in iron status is however unlikely to result from the usual/conventional consumption of cowpeas but through fortification of whole cowpea flour with a highly bioavailable iron compound. This thesis has also shown that the most suitable iron compound for such whole cowpea flour fortification is NaFeEDTA irrespective of whether the cowpea has high or low concentration of polyphenols.

    Biobeschikbaarheid: sturende factor bij besluitvorming rond bodemsanering en duurzaam bodemgebruik?
    Harmsen, J. ; Brand, E. - \ 2012
    Bodem 3 (2012). - ISSN 0925-1650 - p. 26 - 28.
    biologische beschikbaarheid - bodemverontreiniging - bodemkwaliteit - beleid - bioavailability - soil pollution - soil quality - policy
    Bij de beoordeling van de bodemkwaliteit komt de term biobeschikbaarheid regelmatig aan de orde. De term wordt vooral gebruikt om effecten van bodemverontreinigingen op receptoren te verklaren. Internationaal wordt er gediscussieerd over de invloed van biobeschikbaarheid op risico's van verontreinigingen. Ook in Nederland is dit een punt van aandacht. Kan Nederland iets leren van de internationale kennis?
    The impact of metal transport processes on bioavailability of free and complex metal ions in methanogenic granular sludge
    Bartacek, J. ; Fermoso, F.G. ; Vergeldt, F. ; Gerkema, E. ; Maca, J. ; As, H. van; Lens, P.N.L. - \ 2012
    Water Science and Technology 65 (2012)10. - ISSN 0273-1223 - p. 1875 - 1881.
    afvalwaterbehandeling - bioreactoren - anaërobe omstandigheden - korrelslib - biologische beschikbaarheid - metalen - toxiciteit - kernspintomografie - waste water treatment - bioreactors - anaerobic conditions - granular sludge - bioavailability - metals - toxicity - magnetic resonance imaging - magnetic-resonance - dynamics - immobilization - biofilm - nickel
    Bioavailability of metals in anaerobic granular sludge has been extensively studied, because it can have a major effect on metal limitation and metal toxicity to microorganisms present in the sludge. Bioavailability of metals can be manipulated by bonding to complexing molecules such as ethylenediaminetetraacetate (EDTA) or diethylenetriaminepentaacetate (DTPA). It has been shown that although the stimulating effect of the complexed metal species (e.g. [CoEDTA]2-) is very fast, it is not sustainable when applied to metal-limited continuously operated reactors. The present paper describes transport phenomena taking place inside single methanogenic granules when the granules are exposed to various metal species. This was done using magnetic resonance imaging (MRI). The MRI results were subsequently related to technological observations such as changes in methanogenic activity upon cobalt injection into cobalt-limited up-flow anaerobic sludge blanket (UASB) reactors. It was shown that transport of complexed metal species is fast (minutes to tens of minutes) and complexed metal can therefore quickly reach the entire volume of the granule. Free metal species tend to interact with the granular matrix resulting in slower transport (tens of minutes to hours) but higher final metal concentrations.
    Development and hazard assessment of nanoparticles
    Bhattacharjee, S. - \ 2012
    Wageningen University. Promotor(en): Ivonne Rietjens; Han Zuilhof, co-promotor(en): Gerrit Alink; Ton Marcelis. - S.l. : s.n. - ISBN 9789461733481 - 240
    nanotechnologie - deeltjes - gezondheidsgevaren - risicoschatting - cytotoxiciteit - ratten - biologische beschikbaarheid - werkwijze - nanotechnology - particles - health hazards - risk assessment - cytotoxicity - rats - bioavailability - mode of action

    A series of highly monodisperse silicon nanoparticles (Si NP) with either
    positively (amine), neutral (azide) or negatively (carboxylic acid) charged
    covalently attached organic monolayers were synthesized and investigated for
    their cytotoxicity. Infrared data confirmed the presence of these covalently
    attached surface groups. The Si NP were characterized by absorption and
    fluorescence spectroscopy. The cytotoxicity was investigated in Caco -2 cells by
    determining the cell viability and proliferation. The EC50 values for the Si NP
    ranged from 20 μg/l for the amine-terminated Si NP, via 550–850 μg/l for the
    azide-terminated Si NP to non-toxic (no measureable EC50) for the carboxylic acid -
    terminated Si NP. These results indicated a trend in cytotoxicity, depending on
    surface charge, i.e. that positively charged Si NP we re more cytotoxic than
    negatively charged Si NP. Interestingly, it appeared that the cytotoxicity of the
    amine terminated Si NP (Si NP-NH2) depended strongly on the presence of fetal calf
    serum (FCS) in the medium.

    Advice on implementing bioavailability in the Dutch soil policy framework : user protocols for organic contaminants
    Brand, E. ; Smedes, F. ; Jonker, M.T.O. ; Harmsen, J. ; Peijnenburg, W.J.G.M. ; Lijzen, J.P.A. - \ 2012
    Bilthoven : RIVM (RIVM report 711701102/2012) - 73
    bodemchemie - bodemverontreiniging - ecotoxicologie - biologische beschikbaarheid - bodemkwaliteit - soil chemistry - soil pollution - ecotoxicology - bioavailability - soil quality
    In ecological risk evaluations of contaminated sites, soil quality is determined on the basis of total contaminant concentration. These measured total concentrations are compared with Soil Quality Standards of the relevant contaminants. If the soil concentration exceeds the Soil Quality Standards, a supplementary risk evaluation can be performed to determine whether a site needs remediation.
    Onderzoek naar biomiddelen voor weerbaar telen: Wat werkt en wat niet? (interview met o.a. André van der Wurff)
    Sleegers, J. ; Wurff, A.W.G. van der - \ 2011
    Vakblad voor de Bloemisterij 66 (2011)35. - ISSN 0042-2223 - p. 30 - 31.
    sierteelt - cultuurmethoden - plantengroeiregulatoren - plantenontwikkeling - biologische beschikbaarheid - bodemweerbaarheid - ornamental horticulture - cultural methods - plant growth regulators - plant development - bioavailability - soil suppressiveness
    Vanuit de gangbare teelten is er veel belangstelling voor middelen die de weerbaarheid van de bodem en het gewas verhogen. Daarvan zijn er tientallen op de markt, al dan niet toegelaten. Wat werkt en wat niet? Een consortium van onderzoeksinstellingen gaat het kaf van het koren scheiden.
    Impacts of manipulated regime shifts in shallow lake model ecosystems on the fate of hydrophobic organic compounds
    Roessink, I. ; Moermond, C.T.A. ; Gillissen, F. ; Koelmans, A.A. - \ 2010
    Water Research 44 (2010). - ISSN 0043-1354 - p. 6153 - 6163.
    organische verbindingen - meren - biologische beschikbaarheid - polychloorbifenylen - zoetwaterecologie - ecologisch evenwicht - sediment - polycyclische aromatische koolwaterstoffen - aquatische ecosystemen - bioaccumulatie - organic compounds - lakes - bioavailability - polychlorinated biphenyls - freshwater ecology - ecological balance - sediment - polycyclic aromatic hydrocarbons - aquatic ecosystems - bioaccumulation - polycyclic aromatic-hydrocarbons - fresh-water microcosms - food webs - community structure - suspended-solids - fish - responses - polychlorobiphenyls
    Regime shifts in shallow lakes may significantly affect partitioning of sediment-bound hydrophobic organic chemicals (HOCs) such as polychlorobiphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH). In replicated experimental model ecosystems mimicking the alternative stable states ‘macrophyte-dominated’ and ‘suspended solid – phytoplankton dominated’, we tested the effects of macrophytes and benthivorous fish presence on mass distribution and bioaccumulation of hexachlorobenzene, PCBs and PAHs. HOC mass distributions and lipid-normalized concentrations in sediment (Soxhlet- and 6-h Tenax-extractable), suspended solids, macrophytes, periphyton, algae, zooplankton, invertebrates and carp revealed that mobile, i.e. less hydrophobic or less aged HOCs were more susceptible to ecological changes than their sequestered native counterparts. Macrophytes were capable of depleting considerable percentages of the bioavailable, fast desorbing HOC fractions in the sediment upper (bioactive) layer, but did not have a significant diluting effect on lipid-normalized HOC concentrations in carp. Carp structured invertebrate communities through predation and stimulated partitioning of HOCs to other system compartments by resuspending the sediment. These results show that shifts in ecosystem structure have clear effects on fate, risks and natural attenuation of sediment-bound organic contaminants.
    Bioavailability of lysine in heat-treated foods and feedstuffs
    McArtney Rutherfurd, S. - \ 2010
    Wageningen University. Promotor(en): Wouter Hendriks; Martin Verstegen, co-promotor(en): P.J. Moughan. - [S.l. : S.n. - ISBN 9789085856825 - 139
    lysine - biologische beschikbaarheid - voer - voedingsmiddelen - melkproducten - huisdierenvoer - ontbijtgranen - warmtebehandeling - maillard-reactie - maillard-reactieproducten - verteerbaarheid - lysine - bioavailability - feeds - foods - milk products - pet foods - breakfast cereals - heat treatment - maillard reaction - maillard reaction products - digestibility
    During the processing of foodstuffs, lysine can react with other compounds present to form nutritionally unavailable derivatives, the most common example of which are Maillard products. Maillard products can cause serious problems when determining the available lysine content of processed foods or feedstuffs as they can revert to lysine during amino acid analysis. Several methods have been developed to determine the dietary lysine available for the metabolic processes of animals including animal growth-based assays, reactive lysine chemical methods and digestibility assays. However, growth-based assays are laborious, highly variable and tend to determine utilization rather than availability. Chemically reactive lysine assays do accurately determine the unmodified lysine in a food or feedstuff, but do not determine available lysine as they incorrectly assume that reactive lysine digestion and absorption is 100%. Ileal digestibility assays measure digestible total lysine rather than digestible reactive lysine (available lysine) and so are inaccurate, especially when applied to processed protein sources. This thesis describes the development of a true ileal digestible reactive lysine assay for determining dietary (bio)available lysine. This assay couples the guanidination reaction, for determining reactive lysine, with a true ileal digestibility assay. The resulting apparent digestibility estimate is corrected to a true digestibility value by accounting for the endogenous ileal lysine flow.

    Selected reaction conditions for the guanidination of lysine in a heated lactose/casein mixture and digesta of rats fed unheated casein and heated lactose/casein was examined. Overall, suitable reaction conditions were 0.6 M O-methylisourea for 7 d in a shaking waterbath at 21 ± 2 °C with an O-methylisourea to lysine ratio of 1000 and a reaction mixture pH of 10.6 for casein and heated lactose/casein and 11.0 for digesta. The accuracy of the guanidination method for determining reactive lysine in a range of “ready-to-eat ” cereal-based breakfast foods and selected feedstuffs was tested by comparison with the reactive lysine content of the same protein sources when determined using the fluorodinitrobenzene method. Overall, there was excellent agreement between the two methods. The accuracy of the newly developed bioassay for determining digestible reactive (available) lysine for predicting lysine deposition was also tested using a heated skim milk powder. The true ileal total and reactive lysine digestibilities were determined for the heated skim milk powder which was then fed to pigs, along with two control diets which were formulated based on either total lysine digestibility or reactive lysine digestibility. All diets were limiting in lysine. The pigs fed the heated skim milk powder deposited the same (P > 0.05) amount of lysine (9.1 g d-1) as the pigs fed the control diet that was formulated based on reactive lysine digestibility (9.1 g d-1) but deposited significantly (P < 0.05) more than the pigs fed the control diet that was formulated based on total lysine digestibility (5.4 g d-1). Consequently for the heated skim milk powder at least, the true ileal digestible reactive lysine assay accurately determined the available lysine content.

    The new assay demonstrated that for a range of milk protein-based foods, there was little difference between digestible total lysine and digestible reactive lysine for most of the milk products tested. In contrast, for a range of “ready-to-eat” cereal-based breakfast foods, available lysine was 5 – 50% lower than that determined using the traditional assay, which is of concern given that breakfast cereals are perceived to be “healthy” foods. Similarly, the available lysine content of a range of moist and dry commercial cat foods was significantly (P < 0.05) lower (15-55% lower) than previously estimated using the traditional true ileal digestible total lysine assay. The assay was also used to examine the effect of storage for extended periods at elevated temperatures on a hydrolysed-lactose skim milk powder and overall, there was a significant decrease in the available lysine content over time, as much as 60% over 6 mth when the powder was stored at 40 °C. In addition, the decrease in available lysine content of the hydrolysed-lactose skim milk powder was 2 – 5.5 times greater than observed for a normal skim milk powder depending on the storage time and temperature. Overall, foods and feedstuffs that have undergone processing often contain lower amounts of available lysine than thought previously. This new assay not only highlights the inaccuracy of the traditional true ileal digestible total lysine assay as a method for determining available lysine in processed protein sources, but permits the accurate assessment of the available lysine content of processed foods and feedstuffs.

    Increasing hesperetin bioavailability by modulating intestinal metabolism and transport
    Brand, W. - \ 2010
    Wageningen University. Promotor(en): Ivonne Rietjens; G. Williamson; Peter van Bladeren. - [S.l. : S.n. - ISBN 9789085856443 - 168
    flavanoïden - biologische beschikbaarheid - metabolisme - darmen - flavanoids - bioavailability - metabolism - intestines
    Vervolgonderzoek ecologische risico's Noorderbos : chemische en biologische beschikbaarheid van chroom : rapportage fase 2
    Groenenberg, J.E. ; Bloem, J. ; Faber, J.H. ; Dijcker, R. - \ 2009
    Wageningen : Alterra (Alterra-rapport 1998) - 47
    bossen - bodemverontreiniging - ecologie - risico - zware metalen - chroom - monitoring - biologische beschikbaarheid - biotesten - toxicologie - nederland - ecotoxicologie - noord-brabant - forests - soil pollution - ecology - risk - heavy metals - chromium - monitoring - bioavailability - bioassays - toxicology - netherlands - ecotoxicology - noord-brabant
    Dit rapport beschrijft de resultaten van het vervolgonderzoek van de chemische en biologische monitoring van de ernstig met chroom vervuilde bodem van het Noorderbos in Tilburg. Er is specifiek aandacht besteed aan de chemische en biologische beschikbaarheid van metalen met name van chroom waarvan de speciatie in oplossing gemeten is. De belangrijkste conclusie van het onderzoek is dat zowel de chemische als de biologische beschikbaarheid van chroom laag zijn. Met de gebruikte bio-sassays werden geen toxische effecten vastgesteld.
    Heavy metals in paddy fields in Taiwan: chemical behavior in soil and uptake by brown rice
    Chu, C.L. ; Romkens, P.F.A.M. ; Guo, H.Y. - \ 2009
    Wageningen : Alterra (Alterra-rapport 1823) - 112
    bodemchemie - bodemverontreiniging - padigronden - zware metalen - rijst - biologische beschikbaarheid - cadmium - voedingsstoffenopname (planten) - voedselveiligheid - risicoschatting - taiwan - soil chemistry - soil pollution - paddy soils - heavy metals - rice - bioavailability - cadmium - nutrient uptake - food safety - risk assessment - taiwan
    Levels of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) were measured in 19 individual paddy fields in Taiwan. Total, reactive, and available metal levels were measured using Aqua Regia, 0.43 N HNO3, 0.1 M HCl, 0.05 M EDTA and 0.01 M CaCl2. Total metal levels ranged from below background levels to polluted and were highly heterogeneous across most fields. In general levels of metals in the soil decreased with an increase in distance from the water inlet which suggests that most metals originate from the irrigation water. Availability as measured by 0.01 M CaCl2 could be predicted well (Cd, Ni, Zn) by a Freundlich model similar to the one used in non-tropical soils. The fit of models for Cu and Pb was poor due to the lack of data on dissolved organic carbon (DOC). For Cr no fit was obtained at all. Uptake of Cd by rice was highly correlated to the availability as measured by CaCl2. Uptake models based on either the CaCl2 extractable Cd and Zn in soil solution, or a combination of the reactive Cd content in combination with pH and CEC proved equally suitable to predict Cd in rice. The impact of pH and, to a lesser extent, CEC urges the need to considere both properties when deriving soil quality standards (SQS). Uptake by rice by Indica species was markedly higher than that of Japonica although uptake by roots proved to be similar between both species. This suggests that differences between Japonica and Indica are more related to internal redistribution rather than differences in root uptake processes. Using the models, user friendly tools are designed allowing farmers and policy makers alike to evaluate the quality of the soil for a specific cultivar. This allows for a more accurate assessment of the suitability of the soil to be used for rice cropping compared to present soil standards based on Aqua Regia or HCl. As such the approach can be transferred easily to other countries as well based on a limited number of field tests.
    Dietary A- and B-type procyanidins : characterization and biofunctional potential of an abundant and diverse group of phenolics
    Appeldoorn, M.M. - \ 2009
    Wageningen University. Promotor(en): Harry Gruppen, co-promotor(en): Jean-Paul Vincken; Peter Hollman. - [S.l. : S.n. - ISBN 9789085853671 - 168
    fenolverbindingen - flavonoïden - biologische beschikbaarheid - darmabsorptie - bioconversie - phenolic compounds - flavonoids - bioavailability - intestinal absorption - bioconversion
    Procyanidins (PCs) are phenolic compounds that belong to the class of flavonoids and are oligomers of monomeric (epi)catechin units. These monomeric units can be linked to each other by a single C4-C8 or C4-C6 linkage, which is referred to as B-type. Besides these single linkages an additional ether bond can be present, C2-O-C7 or C2-O-C5, which is referred to as A-type. PCs are highly abundant in our diet. Well known PC food sources are cocoa, apple, grape seeds, wine and nuts. After the intake of PC-rich sources health beneficial effects have been detected, which are mainly related to the prevention of cardiovascular diseases such as lowering of blood pressure.
    The aims of this thesis were to study the bioavailability, bioconversion and bioactivity of purified PCs. Therefore, we first developed techniques for the efficient purification of both A- and B-type PCs from peanut skins and grape seeds, respectively. Furthermore, tools were set-up to analyze and characterize individual PCs in complex mixtures.
    We showed that A-type PC dimers were absorbed from the small intestine of rats and that they were better absorbed than B-type PC dimers. The PC dimers were not conjugated or methylated upon absorption in contrast to their monomeric units (epi)catechin. Furthermore, the presence of A-type PC tetramers enhanced the absorption of B-type PC dimers.
    The microbial conversion of B-type PC dimers was studied by exposing them to human microbiota. The main microbial metabolites were 2-(3,4-dihydroxyphenylacetic acid and 5-(3,4-dihydroxyphenyl)-γ-valerolactone. Based on these and other metabolites that were detected, a tentative microbial degradation route was proposed for B-type PC dimers, in which the interflavanic bond does not need to be cleaved upon degradation.
    Subsequently, the vasorelaxing potential of purified PCs and their microbial metabolites was analyzed by measuring their effect on the NO production of endothelial cells. Both A- and B-type PCs showed a tendency (insignificant) to increase NO production with increasing degree of polymerization and several of their human microbial metabolites that were tested were inactive. Besides enhancing NO production, several other mechanisms could be targets of PCs and were also discussed.
    This thesis increased our knowledge on the absorption, biotransformation and bioactivity of A- and B-type PCs. A possible interaction between oligomers with a high and low degree of polymerization, influencing absorption processes has been discussed, which suggests that until now the biofunctional potential of PAs has been underestimated.

    Isothiocyanates from cruciferous vegetables: kinetics, biomarkers and effects
    Vermeulen, M. - \ 2009
    Wageningen University. Promotor(en): Peter van Bladeren; Ivonne Rietjens, co-promotor(en): W.H.J. Vaes. - [S.l. : S.n. - ISBN 9789085853121 - 144
    bladgroenten - glucosinolaten - isothiocyanaten - biologische beschikbaarheid - metabolisme - biomarkers - leafy vegetables - glucosinolates - isothiocyanates - bioavailability - metabolism - biomarkers
    Cruciferous vegetables like cabbages, broccoli, mustard and cress, have been reported to be beneficial for human health. They contain glucosinolates, which are hydrolysed into isothiocyanates that have shown anticarcinogenic properties in animal experiments. To study the bioavailability, kinetics and effects of isothiocyanates from cruciferous vegetables, biomarkers of exposure and for selected beneficial effects were developed and validated.
    As a biomarker for intake and bioavailability, isothiocyanate mercapturic acids were chemically synthesised as reference compounds and a method for their quantification in urine was developed. The validity of this biomarker was proven in a study in which three volunteers consumed 19 different raw and cooked vegetables and condiments. Urinary excretion levels of isothiocyanate mercapturic acids were higher after the consumption of raw vegetables and condiments (bioavailability 60%, range 8.2-113%) compared to cooked vegetables (10%, range 1.8-43%). In a second study, in which eight smoking men consumed cooked and raw broccoli, higher levels of sulforaphane were found when broccoli was eaten raw (bioavailability 37%) versus cooked (3.4%).
    Also as a biomarker for kinetics, sulforaphane conjugates were determined in blood samples also collected in the second study. The area under the blood-concentration curve was higher when broccoli was eaten raw (0.50 µM•h, dose of 9.9 µmol sulforaphane) versus cooked (0.29 µM•h, dose of 61 µmol glucoraphanin). It is concluded that the bioavailability of isothiocyanates from glucosinolates is higher from raw than from cooked vegetables.
    The induction of phase 2 metabolism enzymes via an electrophile responsive element (EpRE), that is present in the promotor region of the genes coding for these enzymes, was used as a biomarker for a beneficial health effect. Isothiocyanates containing a methyl-sulfur side chain (like sulforaphane, EC50 value 1.2 µM) are more potent inducers, in this in vitro assay, than aliphatic and aromatic isothiocyanates (e.g. allyl isothiocyanate, EC50 value 6.5 µM). The estimated concentrations of individual isothiocyanates in the body after consumption of cruciferous vegetables may amount to 0.04-4 µM. Since cruciferous vegetables contain several isothiocyanates which act synergistically, concentrations might thus reach these EC50 values for EpRE induction, and represent biologically active concentrations.
    In conclusion, the biomarkers developed and validated in the present thesis show that higher and physiologically relevant amounts of isothiocyanates are absorbed after the consumption of raw cruciferous vegetables, compared to cooked vegetables. Broccoli (cress) is favorite since it contains high amounts of sulforaphane, which is, based on the results of the present studies, the most promising isothiocyanate because it shows the lowest EC50 for EpRE induction.
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