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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    The role of strigolactones and the fungal microbiome in rice during drought adaptation
    Andreo Jimenez, Beatriz - \ 2017
    Wageningen University. Promotor(en): H.J. Bouwmeester, co-promotor(en): C. Ruyter-Spira. - Wageningen : Wageningen University - ISBN 9789463437028 - 205
    drought resistance - drought - abiotic injuries - rice - oryza sativa - plant-microbe interactions - nutrient uptake - defence mechanisms - hormones - fungi - genes - droogteresistentie - droogte - abiotische beschadigingen - rijst - oryza sativa - plant-microbe interacties - voedingsstoffenopname (planten) - verdedigingsmechanismen - hormonen - schimmels - genen

    Rice is the most important food crop in the world, feeding over half the world’s population. However, rice water use efficiency, defined by units of yield produced per unit of water used, is the lowest of all crops. The aim of this thesis was to study the effect of plant hormones and the root microbiome on drought tolerance in rice. The new plant hormone, strigolactone, was shown to be upregulated under drought and to regulate drought tolerance in interaction with the drought-hormone abscisic acid. Using a large collection of rice genotypes grown in the field, we showed that the composition of the root associated fungal microbiome is determined by the rice genotype and can contribute to drought tolerance.

    Food reward from a behavioural and (neuro)physiological perspective
    Bruijn, Suzanne E.M. - \ 2017
    Wageningen University. Promotor(en): C. de Graaf; R.F. Witkamp, co-promotor(en): G. Jager. - Wageningen : Wageningen University - ISBN 9789463436748 - 154
    food - physiological functions - feeding behaviour - food preferences - perception - hormones - responses - neurohormonal control - stomach bypass - gastric bypass - satiety - voedsel - fysiologische functies - voedingsgedrag - voedselvoorkeuren - perceptie - hormonen - reacties - neurohormonale controle - maag bypass - buik bypass - verzadigdheid

    Food reward is an important driver of food intake and triggers consumption of foods for pleasure, so-called hedonic eating, even in the absence of any energy deficits. Hedonic eating can trigger overeating and may therefore lead to obesity. Given the rise in obesity rates and the health risks associated with being obese, hedonic eating and food reward are important phenomena to study. This thesis aimed to add on to the existing knowledge on food reward. The phenomenon was approached from a behavioural, sensory and (neuro)physiological perspective in healthy, lean and in obese gastric bypass populations.

    For the behavioural perspective, the main outcome measure used in this thesis was food preferences. To be able to study food preferences for four macronutrient and two taste categories, a new food preference task was developed. In chapter 2, the development and validation of the Macronutrient and Taste Preference Ranking Task (MTPRT) were described. The MTPRT uses a ranking method to determine preferences for four macronutrient (high-carbohydrate, high-fat, high-protein, low-energy) and two taste (sweet and savoury) categories.

    For the sensory and physiological perspective, focus was put on the endocannabinoid system (ECS): a neuromodulatory system that plays a role in food reward. To gain more insight into this role, the effect of ECS modulation with pharmacological challenges on sensory perception of sweet taste and on food preferences were studied, as well as endocannabinoid responses to food intake. In chapter 3 it was shown that inhaling Cannabis with low doses of Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) does not alter sweet taste intensity perception and liking in humans, nor does it affect food preferences. Vice versa, in chapter 4 it was found that liking of a food taste does not affect endocannabinoid responses to food intake, after controlling for expectations. When palatability of the food is unknown until the first bite, response of endocannabinoids, ghrelin and pancreatic polypeptide did not differ between a palatable and a neutral food across anticipatory, consummatory and post-ingestive phases of food intake. Endocannabinoid and ghrelin plasma concentrations decreased after food intake, which suggests an orexigenic function for endocannabinoids.

    In chapters 5, 6 and 7, studies with patients who underwent Roux-en-Y gastric bypass surgery were described. These studies were intended to gain more insight into alterations in food reward in relation to (morbid) obesity and in response to surgical treatment by RYGB surgery.

    First, in chapter 5 food preferences were assessed before, and at two months and one year after RYGB. It was shown that patients have decreased preference for high-carbohydrate and high-fat foods, and increased preference for low-energy foods after compared with before surgery. In addition, liking ratings for the high-carbohydrate and high-fat foods were decreased after RYGB surgery, whereas liking of low-energy products changed minimally. Potential mechanisms behind these alterations in food preferences include changes in neural processing of food cues and changes in appetite-related gut hormones.

    In chapter 6, it was shown that alterations in food preferences after RYGB surgery are indeed related to changes in neural activation in response to food cues. With regards to the appetite-related hormones it was shown that plasma concentrations of the endocannabinoid anandamide were increased after compared with before surgery. Plasma concentrations of other endocannabinoids and ghrelin did not change. Moreover, changes in endocannabinoid or ghrelin concentrations did not correlate with changes in food preferences or neural response to food cues. Together, these results suggest that changes in neural processing of food cues contribute to changes in food preferences towards low-energy foods, and provide a first indication that the endocannabinoid system does not seem to play a role in this process.

    To gain more insight into behavioural responses to food cues, a response-inhibition paradigm was used in chapter 7, in which response-inhibition to high-energy and low-energy food cues was assessed during brain imaging. The behavioural data did not show differences in performance when comparing before and two months after RYGB surgery. The brain imaging data showed that activation in reward-related brain areas was decreased in response to both high- and low-energy food pictures after RYGB surgery. Also, prefrontal brain areas were more activated in response to the high-energy pictures, which suggests improved response inhibition.

    In conclusion, the findings in this thesis show that modulating the ECS with low doses of THC and CBD does not influence sweet taste perception and liking and food preferences, and vice versa, food taste liking in the absence of expectations does not affect endocannabinoid responses to food intake. With regards to RYGB surgery it was uncovered that changes in food preferences after RYGB surgery are related to altered brain reward processing, but no relation with changes in endocannabinoid tone was found. The success of RYGB surgery and the changes in food choice might in part be caused by an improved inhibitory response to high-energy foods.

    Intestinal nutrient sensing : a gut feeling for food
    Wielen, N. van der - \ 2016
    Wageningen University. Promotor(en): Renger Witkamp, co-promotor(en): Jocelijn Meijerink; Henk F.J. Hendriks. - Wageningen : Wageningen University - ISBN 9789462576995 - 200
    obesity - hormones - intestines - gastrointestinal hormones - pancreozymin - vasoactive intestinal peptide - sensing - in vivo experimentation - animal models - in vitro - gastric bypass - food - weight reduction - stevia rebaudiana - release - obesitas - hormonen - darmen - maagdarmhormonen - pancreozymine - vasoactief intestinaal peptide - aftasten - in vivo experimenten - diermodellen - in vitro - buik bypass - voedsel - gewichtsvermindering - stevia rebaudiana - vrijgeven

    The alarming increase in obesity rates creates an urgent need for effective prevention and treatment strategies. The most effective treatment for obesity today is bariatric surgery. Bariatric surgery comprises a number of different procedures having in common that they induce weight loss and alter gut hormone release. Gut hormones are well known for their effects on food intake behavior and their role in weight loss after bariatric surgery is undeniable. In addition, the therapeutic use of GLP-1 (Glucagon-Like Peptide-1) analogues including liraglutide in type II diabetes and obesity is on the rise. This underlines why gut hormones are considered promising targets for the development of new treatment strategies against obesity and its comorbidities.

    The secretion of gut hormones, among which GLP-1, is influenced by nutrient ingestion. The interactions of dietary components or their breakdown products with receptors and transporters located on the enteroendocrine cells of the intestinal tract can induce their release, a process called intestinal nutrient sensing. In this thesis, we aimed to further elucidate intestinal nutrient sensing mechanisms on a cellular level. First, the regional expression of several gut nutrient sensing related genes along the intestinal tract was assessed in three commonly studied species, namely mouse, pig and man. Gene expression of receptors, transporters and peptides involved in nutrient sensing shows a distinctive distribution pattern along the small intestine, which is in the distal small intestine highly similar between the species. Subsequently, we sought to investigate if this expression was changed after a weight loss inducing bariatric procedure. By whole transcriptome analysis, we showed that upper gastrointestinal tissue expression of genes associated with nutrient sensing was hardly changed. In contrast, a considerable reduction in inflammatory pathways was observed.

    Next, we sought to investigate the effects of the non-caloric sweetener rebaudioside A. This Stevia rebaudiana-derived compound was approved on the European market in 2011. As there is still some controversy about the effects of sweeteners in general on GLP-1 release, we investigated the effects of this specific sweetener. Because of the short half-life of GLP-1, the effect of nutrient stimulation was mainly studied in ex vivo and in vitro models in which local intestinal hormone release could be determined. A two dimensional gut model using intestinal organoids derived from murine intestinal crypts was developed to study location-specific hormone secretion. Rebaudioside A was found to induce GLP-1 and PYY release ex vivo from porcine intestinal tissue and in two dimensional organoids. This induction of the release was specific for the intestinal location, with the ileum being most potently stimulated by rebaudioside A. Moreover, prolonged exposure to rebaudioside A increased enteroendocrine cell numbers in two dimensional organoids. When studying the underlying mechanism in enteroendocrine STC-1 cells, we concluded that rebaudioside A-induced GLP-1 release was independent of the sweet taste receptor.

    The studies presented in this thesis add to our understanding the role of receptors and other molecular structures that are likely to be involved in nutrient sensing and the modulation of gut hormone release. What we know now is that several factors play a role in gut hormone release. This includes not only the nature and dose of the active compound(s), but also the location and timing of its (their) interactions with receptors and other targets along the gastrointestinal tract. We have shown that rebaudioside A may be a potential compound to induce gut hormone release in vivo, especially when applied to the distal small intestine. Therefore, rebaudioside A may be a promising compound to influence food intake, possibly most potent when delivered in the ileum.

    Smartphone controleert koeien op doping
    Versluis, K. ; Ludwig, S.K.J. ; Sterk, S.S. - \ 2015
    WageningenWorld (2015)4. - ISSN 2210-7908 - p. 32 - 33.
    melkveehouderij - rundveehouderij - hormonen - informatietechnologie - innovatie adoptie - monitoring - dairy farming - cattle husbandry - hormones - information technology - innovation adoption - monitoring
    RIKILT Wageningen UR heeft een methode ontwikkeld voor het opsporen van verboden hormonen bij koeien. Een klein meetapparaatje kan samen met een smartphone op de boerderij bepalen of een boer zijn dieren het verboden hormoon rbST geeft.
    Offspring sex ratio bias and sex related characteristics of eggs in chicken
    Aslam, M.A. - \ 2014
    Wageningen University. Promotor(en): Mari Smits; T.G.G. Groothuis, co-promotor(en): Henri Woelders. - Wageningen : Wageningen University - ISBN 9789462570757 - 192
    kippen - eieren - geslachtsverhouding - karakteristieken - nageslacht - toewijzing - polymerase-kettingreactie - hormonen - voedselbeperking - dierveredeling - fowls - eggs - sex ratio - characteristics - progeny - allocation - polymerase chain reaction - hormones - food restriction - animal breeding

    Understanding the factors influencing sex of egg and sex ratio in laying chicken may lead to finding potential solutions for the problem of killing of day old male chicks, which is the current practice in breeding of laying hens. In studies described in this thesis, it was investigated if the sex of the chicken egg can be predicted by measurable differences in male and female eggs at unincubated stage and if the female primary sex ratio can be induced in laying chicken using different experimental conditions such as feed restriction and corticosterone feeding. The method of sex determination in unincubated chicken eggs using PCR targeted to CHD1 gene was first developed. This method was subsequently used to study the primary sex ratio bias as well as relationship between egg sex and yolk hormones. No significant relationship of the sex of egg with concentrations of several hormones (testosterone, estradiol, androstenedione, progesterone, dihydrotestosterone) and glucose in yolk as well as of egg parameters (mass, width and length) was found. Effect of feed availability on sex ratio was tested in two separate studies. In one study, the rate of change of hen body mass between day of laying and day of laying minus 2 days (encompass time of meiosis completion) was a significant predictor for the sex of that egg, suggesting meiotic drive as mechanism of sex ratio bias. This relationship was not found in the later study. The difference in results could be due to the reason that hens decreased in body mass much less in the later study as compared to earlier study. Blood corticosterone concentrations were associated with sex ratio per hen in the earlier study. Effect of egg mass on egg sex was studied during the later experiment of feed restriction. The egg sex ratio per hen was negatively associated with the average egg mass per hen in the feed restriction group. Two groups of hens were selected from the feed restriction group i.e. male biased hens with low egg mass and female biased hens with high egg mass for microarray analysis of gene expression in the germinal disc of collected F1 follicle. The results did not show differential expression of genes between the groups. However, gene set enrichment analysis showed that a number of processes related to cell cycle progression, mitotic/meiotic apparatus and chromosomal movement were differently enriched between the groups, supporting meiotic drive as potential mechanisms underlying sex ratio determination. In another experiment, blood circulating levels of corticosterone in hens were increased by feeding corticosterone mixed feed under ad libitum. The blood levels of corticosterone were significantly higher in treated hens but these levels were not associated with sex ratio. Treatment did not affect the overall sex ratio, but affected the sex ratio in interaction with hen body mass. In the corticosterone group, sex ratio, laying rate, and fertility rate per hen were decreased in heavy hens. These results suggest that three parameters (sex ratio, laying rate and fertility rate) are connected at the level of ovarian physiology. Interference with meiosis have been shown to affect these three parameters, suggesting the involvement of meiotic drive as mechanism of sex ratio bias.

    Hormonen vaak betrokken bij versterking eigen afweer van planten : veel ontwikkelingen bij plantenhormonen
    Heuvelink, E. ; Kierkels, T. - \ 2013
    Onder Glas 10 (2013)1. - p. 13 - 15.
    glastuinbouw - potplanten - groeifactoren - hormonen - verdedigingsmechanismen - plantengroeiregulatoren - weerstand - landbouwkundig onderzoek - gewasbescherming - greenhouse horticulture - pot plants - growth factors - hormones - defence mechanisms - plant growth regulators - resistance - agricultural research - plant protection
    Vroeger was het simpel: er zijn vijf groepen plantenhormonen en dat is het. Maar het ligt veel ingewikkelder. Naarmate het inzicht groeit, wordt de lijst van hormonen langer. Opvallend veel daarvan zijn betrokken bij weerstand tegen stress, ziekten en plagen. Daar kan de tuinbouw in de toekomst wellicht voordeel bij hebben.
    Abscisinezuur speelt rol bij resistentie tegen stress-omstandigheden : je kunt de plant ook te veel 'pamperen'
    Heuvelink, E. ; Kierkels, T. - \ 2012
    Onder Glas 9 (2012)11. - p. 26 - 27.
    glastuinbouw - plantenziekten - abscisinezuur - hormonen - resistentiemechanismen - cultuurmethoden - plaagresistentie - weerstand - greenhouse horticulture - plant diseases - abscisic acid - hormones - resistance mechanisms - cultural methods - pest resistance - resistance
    Abscisinezuur zorgt ervoor dat planten ongunstige omstandigheden kunnen overleven. In de kas proberen we zulke situaties juist te vermijden. Maar je kunt de plant ook te veel ‘pamperen’. Dat kan leiden tot een ongevoeligheid voor dit ‘stress-hormoon’ die zich later wreekt.
    Hormoongehaltes in bloembollen voor teeltsturing en maat voor kwaliteit
    Gude, H. ; Bouwmeester, H.J. ; Charnikova, T. ; Verstappen, F.W.A. - \ 2012
    BloembollenVisie 2012 (2012)259. - ISSN 1571-5558 - p. 22 - 23.
    bloembollen - hormonen - groeifactoren - groeiregulatoren - cultuurmethoden - landbouwkundig onderzoek - ornamental bulbs - hormones - growth factors - growth regulators - cultural methods - agricultural research
    Meer dan altijd zichtbaar en merkbaar is, spelen hormonen een cruciale rol in de teelt van bloembollen. Het Laboratorium voor Plantenfysiologie in Wageningen en PPO Bloembollen in Lisse onderzochten welke hormonen er zoal in bloembollen voorkomen en hoe hun gehaltes door de tijd heen al dan niet veranderen. Inmiddels kunnen er 48 stoffen in één keer worden gemeten.
    Cytokinine is meer dan hormoon dat celdeling stimuleert : sturen hormoonhuishouding gecompliceerd
    Heuvelink, E. ; Kierkels, T. - \ 2012
    Onder Glas 9 (2012)8. - p. 28 - 29.
    potplanten - sierplanten - cytokinen - plantenontwikkeling - cultuurmethoden - hormonen - groeifactoren - glastuinbouw - pot plants - ornamental plants - cytokines - plant development - cultural methods - hormones - growth factors - greenhouse horticulture
    Cytokinine staat bekend als het hormoon dat celdeling stimuleert. Daar ontleent het zelfs zijn naam aan. Maar zoals alle hormonen heeft ook dit meerdere effecten, die ook nog eens worden bepaald door verhouding met andere hormonen. Vooral de balans met auxine is van belang.
    Plantenhormoon auxine heeft vele functies in de cel : teeltmaatregelen hebben effect op evenwicht tussen hormonen
    Heuvelink, E. ; Kierkels, T. - \ 2012
    Onder Glas 9 (2012)4. - p. 26 - 27.
    landbouwplantenteelt - glastuinbouw - teelt - cultuurmethoden - hormonen - groeifactoren - groeiregulatoren - plantenontwikkeling - effecten - crop husbandry - greenhouse horticulture - cultivation - cultural methods - hormones - growth factors - growth regulators - plant development - effects
    Zonder dat hij er zich van bewust is, stuurt de teler met klimaatregeling en teeltmaatregelen vaak het evenwicht tussen de hormonen in de plant. Het zijn de signaalstoffen die veel processen in werking stellen. De komende maanden behandelen we in de serie plantkunde in Onder glas verschillende hormonen. Deze keer auxine. Dit plantenhormoon is onder andere verantwoordelijk voor de wortelvorming bij stek, celstrekking, apicale dominantie en de zetting en uitgroei van vruchten.
    Hormoongehaltes van bloembollen als maat voor inwendige kwaliteit
    Gude, H. ; Charnikhova, T. ; Verstappen, F.W.A. ; Bouwmeester, H.J. - \ 2012
    bloembollen - hormonen - groeifactoren - groeiregulatoren - monitoring - methodologie - landbouwkundig onderzoek - bereikt resultaat - ornamental bulbs - hormones - growth factors - growth regulators - monitoring - methodology - agricultural research - achievement
    Bevindingen met nieuwe bepalingsmethode van Wageningen UR naar hormoongehaltes van bloembollen
    Mitofood conference : bioactive food components, energy metabolism and human health, 13-15 April 2011, Wageningen, The Netherlands : celebrating 90 years of human and animal physiology at Wageningen University : final conference of COST Action FA0602: bioactive food components, mitochondrial function and health
    Keijer, J. - \ 2011
    [Wageningen] : Wageningen UR - 87
    voedselsamenstelling - bioactieve verbindingen - voedingsstoffen - energiemetabolisme - gezondheid - polyfenolen - lipiden - vitaminen - hormonen - verouderen - bio-energetica - mitochondria - voeding - food composition - bioactive compounds - nutrients - energy metabolism - health - polyphenols - lipids - vitamins - hormones - aging - bioenergetics - nutrition
    Hormoongehaltes in bloembollen als instrument voor teeltsturing en kwaliteit, Thema: Innovatieve tuinbouw BO-12.03-006-004
    Gude, H. - \ 2011
    bloembollen - hormonen - kwaliteitszorg - gewaskwaliteit - monitoring - monsters - cultuurmethoden - ornamental bulbs - hormones - quality management - crop quality - monitoring - samples - cultural methods
    Onderzoek om met de modernste bepalingsmethoden de gehaltes van zoveel mogelijk plantenhormonen in één bollenmonster te bepalen.
    Moderate alcohol consumption, adiponectin, inflammation and type 2 diabetes risk : prospective cohort studies and randomized crossover trials
    Joosten, M.M. - \ 2011
    Wageningen University. Promotor(en): Renger Witkamp, co-promotor(en): H.F.J. Hendriks. - [S.l. : S.n. - ISBN 9789085858256 - 192
    alcoholinname - diabetes mellitus - risico - genexpressie - vetweefsel - hormonen - alcohol intake - diabetes mellitus - risk - gene expression - adipose tissue - hormones
    Background: Moderate alcohol consumption has been associated with a lower risk of type 2 diabetes in various populations. However, the underlying mechanisms are not entirely clear. The aims of this thesis were 1) to substantiate the evidence of the association between alcohol consumption and type 2 diabetes in observational research and 2) to examine physiological mechanisms in randomized trials with specific attention to adiponectin, inflammation and insulin sensitivity which may mediate the association between alcohol consumption and type 2 diabetes.

    Methods: Two prospective cohort studies, one among 38,031 U.S. men (age: 45-75 y) of the Health Professionals Follow up Study (HPFS) and one among 35,625 Dutch men and women (age: 20-70 y) of the European Prospective Investigation into Cancer and Nutrition (EPIC)-NL cohort. Four randomized, crossover trials of eight to twelve weeks with consumption of 25-30 g alcohol/day in the form of vodka with orange juice, beer, or white wine (twice) compared to orange juice, alcohol free beer, white grape juice or water among 24 young men, 24 premenopausal and 36 and 22 postmenopausal women, respectively.

    Results: A 7.5 g/day increase in alcohol consumption over four years was associated with lower diabetes risk among initial non-drinkers (hazard ratio [HR]: 0.78; 95% confidence interval (CI): 0.60, 1.00) and drinkers initially consuming <15 g/d (HR: 0.89; 95% CI: 0.83, 0.96) but not among men initially drinking ≥15 g/d (HR: 0.99; 95% CI: 0.95, 1.02) (Pinteraction < 0.01) in U.S. men. Among Dutch subjects with ≥3 out of 4 low-risk lifestyle behaviors, moderate alcohol consumption was associated with a lower risk of type 2 diabetes compared with abstention (HR: 0.56; 95% CI: 0.32, 1.00).
    In the randomized crossover trials, alcohol consumption consistently increased circulating adiponectin levels by about 10% compared to abstention (P < 0.05) regardless of beverage type, gender or age. These increases were evident after a minimum of three weeks of alcohol consumption. Moderate alcohol consumption also increased expression of the gene encoding adiponectin in adipose tissue and lowered serum fasting insulin and triglyceride levels (all P < 0.05). An integrated approach of large-scale profiling of proteins and genes revealed that moderate alcohol consumption for four weeks altered gene expression profiles of white blood cells and circulating markers related to inflammation in men (all P < 0.05). However, we did not observe an attenuated inflammatory response after a low-dose in vivo endotoxin bolus, despite increased high-density lipoprotein cholesterol and apolipoprotein levels after four weeks of alcohol consumption compared to abstention. Six minutes of oral white wine exposure without swallowing substantially (-20%; P < 0.05) and temporarily (~20 min) decreased circulating free fatty acid concentrations compared with oral water exposure.

    Conclusions: Moderate alcohol consumption was associated with a lower risk of type 2 diabetes compared with abstention. The association persisted among subjects already at low risk based on combined favorable lifestyle behaviors. Also, increases in alcohol consumption among initially rare and light drinking men were associated with higher adiponectin levels and lower risk of type 2 diabetes. Increased adiponectin levels, anti-inflammatory effects and decreased insulin and triglyceride levels, may partially explain the inverse association between moderate alcohol consumption and type 2 diabetes.

    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.

    Hormoonverstoring in oppervlaktewater; waargenomen en veronderstelde effecten in de natuur
    Lahr, J. ; Lange, H.J. de - \ 2009
    Utrecht : Stowa (Rapport / STOWA 2009 38) - ISBN 9789057734588 - 27
    hormonen - waterverontreiniging - oppervlaktewater - aquatisch milieu - waterorganismen - effecten - nadelige gevolgen - oestrogenen - fauna - toxicologie - hormoonverstoorders - aquatische ecosystemen - ecotoxicologie - hormones - water pollution - surface water - aquatic environment - aquatic organisms - effects - adverse effects - oestrogens - fauna - toxicology - endocrine disruptors - aquatic ecosystems - ecotoxicology
    In laboratoria wordt het nodige onderzoek verricht naar de hormonale, of hormoonverstorende werking van een groot aantal stoffen. Van een aantal van deze stoffen is inmiddels aangetoond dat ze in risicovolle concentraties voorkomen in het watermilieu. Maar het is vaak niet bekend wat de daadwerkelijke, waarneembare effecten van deze hormoonverstorende stoffen zijn op (aquatische) organismen. Bij een aantal diersoorten is aangetoond dat de verhouding tussen het aantal mannetjes en vrouwtjes niet meer gelijk is en tevens dat er soms geslachtsverandering optreedt. Dit rapport vat samen wat er op dit ogenblik bekend is over de hormoonverstorende effecten van stoffen op aquatische organismen. Onderzoekers onderscheidden: schelpen en slakken, Kreeftachtigen en insecten, Vissen; Amfibieën; Vogels en zoogdieren (otters)
    Nieuw ontdekt plantenhormoon remt vertakking : strigolactonen al lang bekend, maar niet als hormoon
    Bouwmeester, H.J. ; Heuvelink, E. ; Kierkels, T. - \ 2009
    Onder Glas 6 (2009)6. - p. 32 - 33.
    tuinbouwbedrijven - kassen - hormonen - planten - vertakking - plantenveredeling - fosfaat - glastuinbouw - market gardens - greenhouses - hormones - plants - branching - plant breeding - phosphate - greenhouse horticulture
    Wageningse onderzoekers hebben een nieuwe groep plantenhormonen ontdekt : de strigolactonen. Ze reguleren de vertakking van de plant. Ook spelen ze een rol bij aantrekken van mycorrhiza's (nuttige schimmels). Veredelaars en kwekers kunnen op termijn met de nieuwe inzichten wellicht de vertakking beter sturen
    Moderne biotechnologie : een nieuwe doos van Pandora?
    Tramper, J. ; Yang Zhu, Yang - \ 2009
    Wageningen : Wageningen Academic - ISBN 9789086861378 - 281
    biotechnologie - voedselbiotechnologie - kazen - brood - wijnen - vlees - gezondheid - gentherapie - antibiotica - hormonen - biotechnology - food biotechnology - cheeses - bread - wines - meat - health - gene therapy - antibiotics - hormones
    Is moderne biotechnologie zo'n doos van Pandora, zoals de antibiotechnologie bewegingen doen geloven? Dit is de centrale vraag in het boek. Moderne biotechnologie maakt gebruik van de recombinant-DNA technologie om micro-organismen, planten en dieren genetisch te modificeren en zo meer geschikt te maken voor allerlei toepassingen zoals verbouwen van voedselgewassen, het bakken van brood, maken van wijn, antibiotica en hormonen, xenotransplantatie, en gen- en stamceltherapie. In het boek komen vooral de controversiële aspecten van deze toepassingen aan bod.
    Xeno-estrogenic compounds in precipitation
    Peters, R.J.B. ; Beeltje, H. ; Delft, R.J. - \ 2008
    Journal of Environmental Monitoring 10 (2008). - ISSN 1464-0325 - p. 760 - 769.
    neerslag - regen - oestrogenen - hormonen - verontreiniging - geurstoffen - hormoonverstoorders - precipitation - rain - oestrogens - hormones - pollution - odours - endocrine disruptors - polychlorinated-biphenyls - musk fragrances - german bight - great-lakes - air - urban - atmosphere - exposure - samples - norway
    The exposure to some chemicals can lead to hormone disrupting effects. Presently, much attention is focused on so-called xeno-estrogens, synthetic compounds that interact with hormone receptors causing a number of reactions that eventually lead to effects related to reproduction and development. The current study was initiated to investigate the presence of a number of such compounds in precipitation as a follow-up on a previous study in which pesticide concentrations in air and precipitation were determined. Rainwater samples were collected at about 50 locations in The Netherlands in a four week period. The samples were analysed for bisphenol-A, alkylphenols and alkylphenol ethoxylates, phthalates, flame retardants and synthetic musk compounds. The results clearly indicated the presence of these compounds in precipitation. The concentrations ranged from the low ng l-1 range for flame retardants to several thousands of ng l-1 for the phthalates. Bisphenol-A was found in 30% of the samples in concentrations up to 130 ng l-1, while alkylphenols and alkylphenol ethoxylates were found in virtually all locations in concentrations up to 920 ng l-1 for the individual compounds. Phthalates were by far the most abundant xeno-estrogens in the precipitation samples and were found in every sample. Di-isodecyl phthalate was found in a surprisingly high concentration of almost 100000 ng l-1. Polybrominated flame retardants were found in the low ng l-1 range and generally in less than 20% of the samples. Noticeable was the finding of hexabromocyclododecane, a replacement for the polybrominted diphenyl ethers at one location in a concentration of almost 2000 ng l-1. Finally, as expected, synthetic musk compounds were detected in almost all samples. This is especially true for the polycyclic musks HHCB and AHTN. Nitro musks were found, but only on a few locations. Kriging techniques were used to calculate precipitation concentrations in between actual sampling locations to produce contour plots for a number of compounds. These plots clearly show located emission sources for a number of compounds such as bisphenol-A, nonylphenol ethoxylate, phthalates and AHTN. On the contrary, the results for HHCB and some phthalates indicated diffuse emission patterns, probably as the result of the use of consumer products containing these compounds
    Lactational oestrus in sows : follicle growth, hormone profiles and early pregnancy in sows subjected to Intermittent Suckling
    Gerritsen, R. - \ 2008
    Wageningen University. Promotor(en): Bas Kemp, co-promotor(en): P. Langendijk; Nicoline Nieuwenhuizen-Soede. - [S.l.] : S.n. - ISBN 9789085048725 - 142
    zeugen - oestrus - lactatie - follikels - groei - hormonen - zwangerschap - zogen - embryonale ontwikkeling - voortplanting - sows - oestrus - lactation - follicles - growth - hormones - pregnancy - suckling - embryonic development - reproduction
    Keywords: sow; Intermittent Suckling; oestrus; lactation; oestradiol; LH; progesterone, embryo
    survival, embryo development, cystic ovaries.

    Weaning of piglets at a relatively young age (3 to 4 weeks) can compromise health and welfare. A
    possible way to increase piglet welfare is to extend lactation length, but this is economically
    undesirable due to lactational anoestrus of the sow. Thus, an extension of lactation would reduce the
    number of litters per sow per year. Intermittent Suckling (IS), a management system in which the
    lactating sow is separated from her litter for a fixed period of the day, is proposed as method to extend
    lactation length without compromising sow reproductive performance. The aims of this thesis were to
    study if by application of IS, lactational oestrus and ovulation could be induced in a large proportion
    of the sows and to examine the quality of such a lactational oestrus by studying hormone levels and
    pregnancy parameters. Within a first study, sows were separated from their piglets for either 12h
    continuously or at 6h intervals from d14 of lactation onwards. In a control group, weaning occurred at
    d21 of lactation. Lactational oestrus was induced in more than 80% of the sows. The pre-ovulatory LH
    surge, progesterone (P4) levels and the number of ovulating sows were negatively affected by IS and
    embryo development was negatively affected by the regimen of IS (6h). Low P4 levels have been
    related to a low embryo survival and one factor known to affect P4 levels was feeding level. Therefore,
    the aim of a second study was to examine the effect of the high lactational feeding level of IS sows on
    P4 levels. Multiparous sows, subjected to IS daily for 12h continuously, were fed at a high
    (±6.5kg/day) or low (±4kg/day) feeding level from ovulation to 6 days after ovulation. Results of this
    study indicated that P4 levels were not affected by high lactational feeding levels and that P4 levels
    were comparable to levels found in the first study. In a third study two other factors, possibly involved
    in the low P4 levels, were studied: timing of start of IS and continuance of IS during early pregnancy.
    Multiparous sows were subjected to IS for 12h continuously per day from d14 or d21 of lactation
    onwards. Weaning occurred either at ovulation or day 20 after ovulation. An early start of IS (d14) did
    not significantly affect the pre-ovulatory LH surge, but resulted in lower P4 levels at d7 after ovulation.
    Continuance of IS after ovulation resulted in lower P4 levels after ovulation and also negatively
    affected embryo development. Thus, lactational factors such as suckling related hormones or the
    metabolic state of the sow may caused the low P4 levels in IS sows. In general, a high proportion of IS
    sows developed cystic ovaries. In a final study, reproductive parameters were examined in sows
    developing cysts. Sows developing cysts lacked an LH surge. A dysfunction in oestradiol feedback
    seems the underlying mechanism responsible for the lack of the LH surge and may be related with
    stress or the metabolic state of IS sows. In conclusion, it is possible by means of IS to induce
    lactational oestrus and ovulation. The rate of success, however, is dependent on several factors such as
    the breed of the sow and the timing of start of IS. The quality of lactational oestrus (hormone levels,
    embryo survival) seems comparable to weaned sows when start of IS is not too early after farrowing
    and IS is not continued during early pregnancy.
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