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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Biological processes induced by ZnO, Amoxicillin, Rye and Fructooligosaccharides in cultured Intestinal Porcine Epithelial Cells : VDI-4; In-vitro tests 2013-2014
Hulst, M.M. ; Hoekman, A.J.W. ; Wijers, I. ; Schokker, D. ; Smits, M.A. - \ 2015
Wageningen : Wageningen UR Livestock Research (Livestock Research report 882) - 42
in vitro - bioassays - epithelium - livestock - feed additives - genes - immunology - biotesten - epitheel - vee - voedertoevoegingen - genen - immunologie
The objective of this study was to develop an in-vitro bioassay using cultured Intestinal Porcine Epithelial Cells (IPEC-J2) and evaluate the capability of this assay to predict enterocyte-specific physiological and immunological processes induced by nutrients/additives in the intestines of farm animals. Responses to five nutrients/feed-additives, similar to those studied in animal trials, performed in the Feed4Foodure framework, were measured by gene expression analysis of IPEC-J2 cells either under stressed (Salmonella) or non-stressed conditions. Response genes were analysed using bioinformatics web-tools in order to identify dominant biological processes induced by these nutrients/feed-additives and to predict key-genes/proteins important for regulation of these biological proc
Werken aan bodemweerbaarheid
Broek, R.C.F.M. van den; Berg, W. van den; Lamers, J.G. ; Cuijpers, W.J.M. ; Hospers-Brands, A.J.T.M. ; Smits, S. - \ 2014
Praktijkonderzoek Plant & Omgeving B.V. - 63
teeltsystemen - bodemweerbaarheid - bestrijdingsmethoden - agrarische bedrijfsvoering - phytophthora cactorum - bodemeigenschappen - gewasbescherming - proeven - biotesten - fragaria - biologische technieken - vollegrondsteelt - cropping systems - soil suppressiveness - control methods - farm management - soil properties - plant protection - trials - bioassays - biological techniques - outdoor cropping
De land- en tuinbouw ontwikkelt zich in de richting van steeds intensievere en complexere bedrijfssystemen. Vanuit de sector groeit het besef dat de chemische benadering van ziekten en plagen haar grenzen begint te bereiken. Ook de consument verlangt van de producent dat de inzet van chemische middelen gereduceerd wordt en gezocht wordt naar andere, meer duurzame oplossingen. Een van de oplossingsrichtingen is het creëren van een gezonde, veerkrachtige en weerbare bodem. Op zulke bodems groeit een gezond gewas met een goede opbrengst die minder gevoelig is voor ziekten en plagen en efficiënter omgaat met nutriënten waardoor er minder verliezen optreden. Hierdoor hoeven telers minder gewasbeschermingsmiddelen en nutriënten te gebruiken en kunnen ze, met een beter inkomen, milieuvriendelijker telen. Aardbei is een voorbeeld van een zeer intensieve teelt, die erg gevoelig is voor ziekten en plagen. In de teelt worden relatief veel gewasbeschermingsmiddelen gebruikt, en er is een sterke behoefte aan kennis die de inzet van deze middelen kan beperken. Aardbei is ook een heel geschikt toetsgewas, omdat het sterk reageert op de bodemgezondheid van een perceel. Is deze goed dan ligt de aardbeienproductie veel hoger dan op percelen waarop de bodemgezondheid matig of slecht is. Opbrengstverschillen kunnen oplopen tot meer dan 50%. De verkregen resultaten bij aardbei kunnen ook vertaald worden naar andere vollegronds gewassen.
Screening van hot spots van nieuwe verontreinigingen : een pilot studie in bodem, grondwater en oppervlaktewater
Lahr, J. ; Laak, T.L. ter; Derksen, A. - \ 2014
Wageningen : Alterra (Alterra-rapport 2538) - 87
bodemverontreiniging - waterverontreiniging - verontreinigende stoffen - toxicologie - geneesmiddelen - ecologische risicoschatting - biotesten - inventarisaties - soil pollution - water pollution - pollutants - toxicology - drugs - ecological risk assessment - bioassays - inventories
Onder nieuwe verontreinigingen verstaan we stoffen die nog niet of niet volledig zijn gereguleerd en waarvan de milieurisico’s vaak onbekend zijn. Daarbij gaat het om stoffen als natuurlijke hormonen en hormoonverstorende stoffen (weekmakers, detergenten, brandvertragers, e.d.), humane geneesmiddelen, diergeneesmiddelen, nanodeeltjes en microplastics. In de ‘waterwereld’ is altijd meer aandacht besteed aan de nieuwe verontreinigingen dan binnen andere beleidsvelden. In de bodem zijn de aanwezigheid en de mogelijke risico’s grotendeels onbekend. In 2013 heeft een consortium van diverse onderzoeksinstanties en stakeholders een pilotonderzoek uitgevoerd naar de aanwezigheid en mogelijke risico’s van hormonen en geneesmiddelen in het systeem bodem - grondwater - oppervlaktewater.
GM1-derived carbohydrates for pathogen and antibody detection : synthesis and biological evaluation
Garcia Hartjes, J. - \ 2014
Wageningen University. Promotor(en): Han Zuilhof, co-promotor(en): Tom Wennekes. - Wageningen : Wageningen University - ISBN 9789462571273 - 240
koolhydraten - moleculaire detectie - antilichamen - pathogenen - remmers - biotesten - carbohydrates - molecular detection - antibodies - pathogens - inhibitors - bioassays
Towards a realistic risk characterization of complex mixtures using in vitro bioassays
Montano Garces, M. - \ 2013
Wageningen University. Promotor(en): Tinka Murk, co-promotor(en): A.C. Gutleb. - [S.l.] : s.n. - ISBN 9789461736598
risicoschatting - persistente organische verontreinigende stoffen - verontreinigde sedimenten - mengsels - biotesten - in vitro - toxiciteit - schildklierhormonen - risk assessment - persistent organic pollutants - contaminated sediments - mixtures - bioassays - toxicity - thyroid hormones

This thesis aims to better understand and further improve the relevance and reliabilityof in vitro bioassaysfor a biobased risk characterisation of complex mixtures, with special focus on persistent organic pollutants (POPs) in sediments.

In Chapter 1 the importance of complex mixture characterization in modern society is introduced. The methods available, their current advantages and their disadvantages for complex mixture testing are described. With the shift from policy oriented chemical testing towards the inclusion of in vitro bioanalysis, important challenges have to be overcome to ensure a relevant and reliable quantification of the toxic potency of complex mixtures. These challenges are explained in the introduction, including the status of development and validation of those aspects for reliable testing. One of the main advantages that in vitro bioanalysis has to offer is the possibility to quantify the toxic potency of compounds for which chemical analytical methods have not or hardly been developed, for example because standards do not yet exist. Hydroxylated metabolites of POPs are an example of a toxicologically relevant group of compounds that can exert endocrine disrupting effects, but they cannot yet be routinely analysed. A selection of yet unsolved issues are further studied and discussed in this thesis, as outlined in the “approach and structure of the thesis”.

In Chapter 2 a meta-analysis is performed to study the occurrence and relevance of hydroxylated (OH) compounds in humans and wildlife. Reported body burdens of halogenated phenolic contaminants (HPCs), including OH-POP in different tissues from humans and wildlife species, are reviewed in relation to the concentration of their putative parent compounds to be able to reveal relevant exposure routes and sub-populations at risk. Highest OH-POP levels were found in blood plasma, and highly perfused and fetal tissues. Plasma concentrations of analysed known HPCs ranged from 0.1-100 nM in humans and up to 240, 454, 800 and 7650 nM for birds, fish, cetaceans and other mammals, respectively. Reported metabolite blood plasma levels also are compared with relevant toxicological threshold concentrations from toxicological studies, and appeared to fully fall within the in vitro (0.05–10000 nM) and in vivo (3-940 nM) effect concentrations reported for OH-POPs. Given the sensitivity of early developmental stages, and information lacking about the general population, it is advisable to determine HPC background blood levels in children and fetal tissue .

Given the toxicological relevance of the OH-POPs, Chapter 3 aims at providing solutions to the long standing problem of the in vitro production and analysis of OH-POP metabolite thyroid hormone disrupting (THD) potency via binding to plasma thyroid hormone binding proteins (THBPs). In sediments and for example seafood, the POPs occur as parent compounds that would only become THD after metabolisation (hydroxylation). Several methods have shown the competitive thyroxine (T4) T4 displacement potency of pure metabolites. However, in vitro metabolization of, among others, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers(PBDEs) followed by in vitro quantification of their potency has encountered drawbacks related to the co-extraction of compounds disturbing the T4-TTR competitive binding assay. The present study identifies and quantifies the major co-extractants, cholesterol and saturated and non-saturated fatty acids (SFA and NSFA), at levels above 20 μM (20 nmol per mg protein in the incubation mixture) following various extraction methods. A new method is presented to in vitro metabolise parent compounds into OH-metabolites followed by selective extraction of metabolites while four-fold reducing co-extraction of the disturbing compounds. In addition a microplate-format non-radioactive fluorescence displacement assay was developed to quantify the TTR binding potency of the metabolites formed. The effectiveness of the in vitro metabolism and extraction of the OH-metabolites of the model compounds CB 77 and BDE 47 was chemically quantified with a newly developed chromatographic method analyzing silylated derivatives of the OH-metabolites and co-extractants. Due to the mentioned improvements, it is now possible to make a dose-response curve up to 50% inhibition with OH-metabolites extracted from bioactivated CB 77 and BDE 47. Without taking the toxic potencies of bio-activated POPs into account with bioanalysis, the hazard and risk posed by POPs will be seriously underestimated.

The chapters 4 and 5 are committed to tackle the issues of supramaximal (SPMX) responses and sample extract concentration which are crucial to reliably quantify of the toxic potencies of complex mixtures with in vitro bioassays.

A SPMX effect is the phenomenon that compounds induce a maximum response in an assay that is significantly higher than that of the positive control. As the positive control is used to quantify the toxic potency of a sample, this could result in over-estimation of its toxic potency. As this has been most elaborately reported for in vitro estrogenicity assays, a meta-analysis was performed of such assays, compounds and conditions in which the effect is observed (Chapter 4a).For the 21 natural and industrial chemicals that could be identified as SPMX inducers, the culture and exposure conditions varied greatly among and between the assays. Relevant information on assay characteristics, however, sometimes lacked. Diethylstilbestrol (DES), genistein (GEN) and bisphenol A (BPA) were selected to build a database. The meta-analysis revealed that the occurrence of SPMX effects, could be related to a number of specific assay characteristics: 1) the type and concentration of the serum used to supplement the exposure medium; 2) the endpoint used to quantify the estrogenic potency (endogenous or transfected reporter gene), 3) the number of EREs (estrogen responsive elements) used before the reporter gene, and 4) the nature of the promoter’s. There were no indications that solvent concentration in culture, exposure period or cell model influenced the occurrence of SPMX. It is important to understand the mechanism behind this phenomenon because in vitro assays for estrogenicity are used extensively to characterize and quantify the estrogenic potency of compounds, mixtures and environmental extracts.

Several SPMX inducers also have been reported to block cellular efflux pumps in vivo and in vitro (Anselmo et al. 2012; Georgantzopoulou et al. 2013). Therefore it was hypothesized that efflux pump blockers present in environmental matrices could increase the internal concentration of bioassay agonists and thus cause the SPMX. In Chapter 4b this hypothesis was tested by adapting a 96-well plate cellular efflux pump inhibition assay (CEPIA) to the H4IIE rat hepatoma cell line used for the DR.Luc reporter gene assay for dioxin-like compounds. The influence of various environmentally relevant efflux pump inhibitors on the 2,3,7,8-tetrachlorodibenzo-p-dioxine (TCDD) response was tested. Under the DR.Luc assay conditions there was no evidence that P-gp efflux pump inhibitors modified or potentiated the activity of TCDD. Neither genistein nor quercetin, two potent SPMX inducers on ER-mediated assays, induced any signal on the DR.Luc assay, nor influenced the luciferase induction by TCDD. Future work should be focused on testing the consequences of efflux pump inhibition with an AhR-agonist which is a P-gp substrate, as this could result in intracellular accumulation of this AhR-agonist.

It is standard practice to use a high single stock concentration of extracts to further dilute test concentrations from and perform the analysis. However, a high contaminant load in an extract may oversaturate the solubility of the extracted compounds in carrier solvents and overload the clean-up columns which may reduce the efficiency of polyaromatic hydrocarbons (PAHs) elimination from the extract. These problems may cause respectively under- or over-estimation of the quantified dioxin-like toxic potency. Therefore Chapter 5 focuses on the effects of initial stock concentrations, including sonication assisted dissolution and exposure time, on the quantified dioxin-like potency of cleaned nonpolar sediment extracts. Indeed, more than 20 g sediment equivalents (SEQ)/mL DMSO) as initial stock concentrations resulted in underestimation of bio-TEQ levels in the sediments as observed for cleaned nonpolar sediment extracts from various locations in Luxembourg. An overload of extract on clean-up columns caused an over-estimation of the dioxin-like potency at 24 hours of exposure, probably due to limited removal of PAHs that can induce false positive responses in the in vitro assays. Sonication assisted dissolution of the stock before serial dilution strongly reduced the standard variation of the outcomes. Taking into account the aspects revealed in this study, in addition to already described important issues for quality control, the in vitro bioassays based bio-TEQs can be applied in a comprehensive monitoring program to determine whether sediments comply with health and safety standards for humans and the environment. For the generally applied sediment quality criteria, advices are given about maximum initial stock concentrations to achieve reliable bioassay outcomes.

The methods and concepts developed for metabolic activation of compounds in non-polar sediment extracts and in in vitro analysis of the TTR-competitive binding are applied in Chapter 6 to extracts from highly or less contaminated sediments collected in Luxembourg. Nonpolar fractions of sediment extracts were incubated with S9 rat microsomes, and the metabolites were extracted with a newly developed method that excludes most of the lipids to avoid interference in the non-radioactive 96-well plate transthyretin (TTR) competitive binding assay. Metabolic activation increased the TTR binding potency of nonpolar fractions of POP-polluted sediments up to 100 times, resulting in potencies up to 240 nmol T4 equivalents/g sediment equivalent (nmol T4-Eq/g SEQ). Without bioactivation, medium polar and polar fractions also contained potent TTR-binding compounds with potencies from 1.6 to 17 nmol T4-Eq/g SEQ. This demonstrates that a more realistic in vitro sediment THD risk characterization should also include testing ofboth polar and medium polar sediment extracts for THD, as well as bioactivated nonpolar sediment fractions. Without bioactivation THD potency is not observed in nonpolar sediment extracts, although in in vivo experiments PCBs and PBDEs, and not with dioxins or PAHs, have shown to be thyroid hormone disrupting (THD), demonstrating this bio-activation is toxicologically relevant and therefore required for sediment hazard characterisation.

Chapter 7 discusses the implications of our results to improve the relevance and reliability of in vitro bioassay applied for risk characterisation of complex mixtures from sediments and other matrices. The evidence obtained to support the relevance of POP bio-activation is considered both from the exposure perspective as well as the toxicity perspective. Various features of the newly developed methods and knowledge acquired within this PhD project are discussed in relation to in vitro bioassay risk characterization of sediments towards a realistic in vitro bioassay-based risk characterization of complex mixtures. Some important aspects for the inclusion of metabolizing systems within in vitro bioassay are discussed. In addition, alternatives to deal with the SPMX effect and the definition of suitable sample amounts to improve in vitro bioassay reliability are offered. The suitability of the developed approach application is considered for the risk characterization of sediments. Furthermore, an analysis is made to decide whether this thesis have made in vitro bioassays more reliable and relevant for risk characterization of complex mixtures. Finally, it provides some concluding remarks and aspects for further applications and research.

Rododendron spoort Phytophthora op
Evenhuis, A. - \ 2012
phytophthora - aardbeien - fruitteelt - kleinfruit - biotesten - gewasbescherming - water - pythium - strawberries - fruit growing - small fruits - bioassays - plant protection
Poster met onderzoeksinformatie. In dit onderzoek worden blaadjes van Rododendron gebruikt om Phytophthora aan te tonen in water dat gebruikt wordt voor de aardbeienteelt.
Development and validation of in vitro bioassays for thyroid hormone receptor mediated endocrine disruption
Freitas, J. de - \ 2012
Wageningen University. Promotor(en): Tinka Murk; Ivonne Rietjens, co-promotor(en): J.D. Furlow. - [S.l.] : s.n. - ISBN 9789461734372 - 192
hormoonverstoorders - biotesten - in vitro - schildklierhormonen - endocrine disruptors - bioassays - thyroid hormones

Thyroid hormones regulate crucial processes in vertebrates such as reproduction, development and energy metabolism. Endocrine disruption via the thyroid hormone system is gaining more attention both from scientists and regulators, because of the increasing incidence of hormone-related cancers and developmental defects, and the requirement that newly marketed compounds are tested for thyroid hormone disruption. To reduce the number of experimental animals used and to increase the insight into the mechanisms of toxic interference with the thyroid hormone receptor function, we developed and validated functional in vitro bioassays for thyroid hormone receptor-mediated toxicity. These assays enable quick identification and quantification of specific thyroid hormone receptor disrupting potency of compounds and contribute to the further establishment of a battery of in vitro tests for hazard identification of thyroid active compounds.

Gewasbeschermingsmiddelen, waterkwaliteit en risicobeoordeling bij toelating
Brock, T.C.M. - \ 2012
Gewasbescherming 43 (2012)4. - ISSN 0166-6495 - p. 112 - 117.
oppervlaktewater - pesticiden - waterverontreiniging - landbouw - ecotoxicologie - biotesten - kwaliteitsnormen - toelating van bestrijdingsmiddelen - besluitvorming - surface water - pesticides - water pollution - agriculture - ecotoxicology - bioassays - quality standards - authorisation of pesticides - decision making
Eén van de doelstellingen van het toelatingsbeleid van gewasbeschermingsmiddelen is te voorkomen dat, na goede landbouwkundige toepassing, deze middelen en hun omzettingsproducten een schadelijke uitwerking hebben op waterorganismen. Het kan verbazing wekken dat in watergangen de waterkwaliteitsnormen voor gewasbeschermingsmiddelen nog regelmatig overschreden worden, daar een strikt omschreven toelatingsbeleid is geïmplementeerd en diverse technische maatregelen zijn genomen om emissie van gewasbeschermingsmiddelen naar oppervlaktewater te voorkomen (o.a. drift reducerende sproeidoppen; bufferzones). Er wordt door sommigen geopperd dat het toelatingsbeleid niet geheel voldoet. Reden genoeg om nader in te gaan op recente ontwikkelingen bij de aquatische risicobeoordeling van gewasbeschermingsmiddelen in het kader van de toelating.
Nematoden als indicator voor de waterkwaliteit
Sollie, S. ; Kluck, J. ; Hooff, A. van; Helder, J. - \ 2012
H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 45 (2012)14/15. - ISSN 0166-8439 - p. 48 - 50.
waterkwaliteit - oppervlaktewater - biologische monitoring - waterbodems - nematoda - biotesten - water quality - surface water - biomonitoring - water bottoms - bioassays
Het beoordelen van de waterkwaliteit is een lastige zaak. Vaak wordt de chemische kwaliteit bepaald, maar eigenlijk willen we weten welke effecten die heeft op de biologische kwaliteit. Veld- en microscopisch onderzoek aan biologische indicatoren is bewerkelijk en bovendien zijn de resultaten niet eenduidig. Met de ontwikkeling van DNA-analysetechnieken is het mogelijk geworden nematoden in de waterbodem snel en accuraat te analyseren. Nematoden zijn kleine aaltjes (lengte 0,3 tot 1,0 mm) die in grote aantallen en met een aanzienlijke diversiteit in de waterbodem aanwezig zijn. De combinatie van hoge dichtheden en grote verscheidenheid maakt de nematodengemeenschap tot potentiële bio-indicator voor de waterkwaliteit. Een pilot liet zien dat DNA-analyse van nematoden in de waterbodem duidelijke signalen van eutrofiëring aangaf en daarmee inzicht gaf in de waterkwaliteit.
Maximale opsporingskans voor Meloidogyne chitwoodi
Beers, T.G. van; Gastel-Topper, A.W.W. van - \ 2011
actieplan aaltjesbeheersing
meloidogyne chitwoodi - biotesten - aardappelen - bodemonderzoek - bemonsteren - akkerbouw - bioassays - potatoes - soil testing - sampling - arable farming
Brochure over het opsporen van Meloidogyne chitwoodi met behulp van een biotoets.
Geringe besmetting goed zelf op te sporen
Gastel-Topper, A.W.W. van; Korthals, G.W. - \ 2011
Boerderij/Akkerbouw 97 (2011)11. - ISSN 0169-0116 - p. E14 - E15.
meloidogyne chitwoodi - biotesten - plantenparasitaire nematoden - bodempathogenen - bodemonderzoek - akkerbouw - aardappelen - pootaardappelen - bioassays - plant parasitic nematodes - soilborne pathogens - soil testing - arable farming - potatoes - seed potatoes
PPO ontwikkelde een biotoets om Meloidogyne chitwoodi op te sporen. Deze toets doer de teler zelf en geeft meer zekerheid dan een laboratoriumtoets.
Development of aquatic biomonitoring models for surface waters used for drinking water supply
Penders, E.J.M. - \ 2011
Wageningen University. Promotor(en): Ivonne Rietjens, co-promotor(en): Gerrit Alink; W. Hoogenboezem. - [S.l.] : S.n. - ISBN 9789461731012 - 176
biologische monitoring - oppervlaktewater - drinkwater - waterkwaliteit - genotoxiciteit - rijn - waterverontreiniging - biotesten - watervoorziening - biomonitoring - surface water - drinking water - water quality - genotoxicity - river rhine - water pollution - bioassays - water supply
Given the need for continued quality control of surface waters used for the production of drinking water by state-of-the-art bioassays and biological early warning systems, the objective of the present thesis was to validate and improve some of the bioassays and biological early warning systems used for quality control of surface water. Although there is a decline in the (geno)toxicity of surface waters over the years as observed for example for the water from the River Rhine over last decades, there is still a need for continued quality control. Due to the lower (geno)toxicity, bioassays with increased sensitivity are needed
Ontwikkeling biotoets voor de detectie van het quarantaineaaltje Meloidogyne chitwoodi : proefuitvoering in de nematodentuin op PPO-AGV, 2010
Gastel, A.W.W. van; Visser, J.H.M. ; Korthals, G.W. - \ 2011
Kennisakker.nl 2011 (2011)16 nov.
plantenparasitaire nematoden - meloidogyne chitwoodi - detectie - biotesten - akkerbouw - pootaardappelen - plant parasitic nematodes - detection - bioassays - arable farming - seed potatoes
Doel van dit onderzoek is het ontwikkelen van een biotoets waarmee lage besmettingen van het quarantaine aaltje M. chitwoodi voorafgaand aan de aardappelteelt betrouwbaar kunnen worden gedetecteerd. Deze toetsmethode wordt ontwikkeld voor gebruik door telers op hun bedrijf en/of in de kas.
Ontwikkeling biotoets voor de detectie van het quarantaineaaltje Meloidogyne chitwoodi : proefuitvoering in de nematodentuin op PPO AGV, 2010
Gastel-Topper, A.W.W. van; Visser, J.H.M. ; Korthals, G.W. - \ 2011
Lelystad : Praktijkonderzoek Plant & Omgeving B.V. - 20
plantenparasitaire nematoden - meloidogyne chitwoodi - biotesten - detectie - akkerbouw - aardappelen - pootaardappelen - plant parasitic nematodes - bioassays - detection - arable farming - potatoes - seed potatoes
De doelstelling van dit onderzoek is het ontwikkelen van een biotoets waarmee lage besmettingen van het quarantaine aaltje Meloidogyne chitwoodi voorafgaand aan de pootaardappelteelt of ander vermeerderingsmateriaal betrouwbaar kunnen worden gedetecteerd, in de grond of door middel van symptomen op een gevoelig gewas, zoals aardappel. Deze toets methode wordt ontwikkeld voor gebruik door telers op hun bedrijf. Voor de biotoets is aardappel als toets gewas gebruikt. Door na het groeiseizoen de aardappelen te beoordelen kan door de mogelijk ontwikkelde symptomen (op de knol) inzicht worden verkregen in de aanwezigheid van Meloidogyne chitwoodi en/of bemonstering van de grond.
Nieuwe bacterieziekte lijkt op Xanthomonas: Stenotrophomonas veroorzaker zwarte vaten in radijs
Arkesteijn, M. ; Ludeking, D.J.W. - \ 2011
Onder Glas 8 (2011)5. - p. 59 - 59.
glastuinbouw - radijsjes - bacterieziekten - biotesten - biologische technieken - stenotrophomonas - cultuurmethoden - groenten - greenhouse horticulture - radishes - bacterial diseases - bioassays - biological techniques - cultural methods - vegetables
Sinds 2007 heeft een aantal telers last van een nieuwe ziekte in radijs. Symptomen zijn misvormde knollen, uitval, extra wortelgroei en vooral zwarte vaten in het knolletje. Over de verspreiding is nog weinig bekend. Deze bacterieziekte treedt pleksgewijs op.
Bodemweerbaarheid biedt perspectieven
Os, G.J. van - \ 2010
Syscope Magazine 2010 (2010)28. - p. 24 - 24.
bodemweerbaarheid - bodembiologie - veldproeven - organische stof - biotesten - gewasbescherming - soil suppressiveness - soil biology - field tests - organic matter - bioassays - plant protection
Tien Noord-Hollandse bollentelers zijn zo geïnteresseerd geraakt door onderzoek van Gera van Os naar bodemweerbaarheid, dat ze zelf een praktijkproef hebben opgezet. Al in het eerste jaar zijn er positieve effecten.
Hormonal effects of prohormones : novel approaches towards effect based screening in veterinary growth promoter control
Rijk, J.C.W. - \ 2010
Wageningen University. Promotor(en): Michel Nielen; Ivonne Rietjens, co-promotor(en): Maria Groot; Ad Peijnenburg. - [S.l. : S.n. - ISBN 9789085858195 - 207
groeibevorderaars - hormonen - biotesten - metabolisme - metabolomica - growth promoters - hormones - bioassays - metabolism - metabolomics
Within the European Union the use of growth promoting agents in cattle fattening is prohibited according to Council Directive 96/22/EC. Interestingly, there is not a black list of substances, but 96/22/EC states that all substances having thyrostatic, estrogenic, androgenic or gestagenic activity are prohibited. Besides abuse of the “classical” synthetic steroids there is a tendency towards misuse of natural steroids and prohormones. Prohormones are compounds that exhibit limited or no hormonal activity but are direct precursors of bioactive hormones and are intended to be converted to full active hormones via enzymatic processes in the body. However, knowledge about metabolism, the mode of action and excretion profiles in cattle is often unclear, and methods to detect abuse of prohormones in livestock production are lacking. Therefore, the aim of this thesis was to get insight into the hormonal action of prohormones and to develop novel in vitro and in vivo screening methods allowing effective surveillance on the illegal use of prohormones in livestock production. Hereby the emphasis was on developing effect based approaches to better meet Council Directive 96/22/EC.
The bioactivity of a wide variety of supplements which contained prohormones were tested using a yeast androgen bioassay. For supplements containing solely prohormones the value of this bioactivity based screening appeared to be limited as they require metabolism to become active. Therefore, screening methods for animal feed, supplements and preparations were set-up by using the same yeast androgen bioassay in combination with bovine liver models as well as enzymatic and chemical deconjugation procedures to mimic in vivo metabolic bioactivation. The use of either bovine liver S9, liver slices, pure enzymes or alkaline hydrolysis showed that prohormones could be activated, resulting in a significant increase in bioactivity as determined by the androgen yeast bioassay.
For the detection of prohormone abuse at the farm and/or slaughterhouse the usefulness of ‘omics’ based profiling techniques was investigated. Within this scope a comprehensive metabolomics based screening strategy for steroid urine profiling was developed. Comparison of urinary profiles revealed large differences between the profiles of controls and dehydroepiandrosterone (DHEA) as well as pregnenolone treated animals. Moreover this steroid urine profiling approach allowed identification of biomarkers for treatment by specific prohormones. This resulted in respectively 7 and 12 specific mass peak loadings which could potentially be used as biomarkers for pregnenolone and DHEA treatment.
In addition, the feasibility of a liver gene expression profiling approach was investigated to monitor the effects of DHEA treatment at the transciptome level. It was shown that identification and application of genomic biomarkers for screening of DHEA abuse in cattle is substantially hampered by biological variation. On the other hand, it was demonstrated that comparison of pre-defined gene sets versus the whole genome expression profile of an animal allows to distinguish DHEA treatment effects from variations in gene expression due to inherent biological variation.
Altogether the results of this thesis increase the knowledge about the metabolism and bioactivation of prohormones in vitro as well as in vivo. Based on this knowledge, a panel of new effect based concepts and screening methods was developed that complement and improve the current testing programs. These new concepts will facilitate better implementation of the European ban on growth promoters in livestock production as described in Council Directive 96/22/EC.


Soil suppressiveness of Meloidogyne, Verticillium and Pythium in diverse agricultural soils: possible mechanisms, and options for sustainable management
Wurff, A.W.G. van der; Stooten, M. van; Hamelink, R. ; Bohne, S. ; Wensveen, W. van; Os, G.J. van; Postma, J. ; Bloem, J. - \ 2010
Gewasbescherming 41 (2010)3. - ISSN 0166-6495 - p. 141 - 141.
meloidogyne incognita - pythium aphanidermatum - verticillium dahliae - biotesten - bodemweerbaarheid - glastuinbouw - bioassays - soil suppressiveness - greenhouse horticulture
Grond uit veertien verschillende glastuinbedrijven is door middel van biotoetsen getest op ziektewerend vermogen tegen drie belangrijke pathogenen, namelijk Meloidogyne incognita, Pythium aphanidermatum and Verticillium dahliae.
Eerste resultaten onderzoek zwarte vaatbundels in radijs
Hofland-Zijlstra, J.D. ; Janse, J. ; Wensveen, W. van; Pham, K.T.K. - \ 2010
radijsjes - plantenziekteverwekkers - biotesten - xanthomonas - moleculaire detectie - radishes - plant pathogens - bioassays - molecular detection
Poster met onderzoeksinformatie naar de oorzaak van zwarte vaatbundels in radijs.
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 - bioavailability - bioassays - toxicology - netherlands - ecotoxicology
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.
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