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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    Are we restoring functional fens? – The outcomes of restoration projects in fens re-analysed with plant functional traits
    Klimkowska, Agata ; Goldstein, Klara ; Wyszomirski, Tomasz ; Kozub, Łukasz ; Wilk, Mateusz ; Aggenbach, Camiel ; Bakker, Jan P. ; Belting, Heinrich ; Beltman, Boudewijn ; Blüml, Volker ; Vries, Yzaak De; Geiger-udod, Beate ; Grootjans, Ab P. ; Hedberg, Petter ; Jager, Henk J. ; Kerkhof, Dick ; Kollmann, Johannes ; Pawlikowski, Paweł ; Pleyl, Elisabeth ; Reinink, Warner ; Rydin, Hakan ; Schrautzer, Joachim ; Sliva, Jan ; Stańko, Robert ; Sundberg, Sebastian ; Timmermann, Tiemo ; Wołejko, Lesław ; Burg, Rob F. Van Der; Hoek, Dick Van Der; Diggelen, Jose M.H. Van; Heerden, Adrie Van; Tweel, Loekie Van; Vegelin, Kees ; Kotowski, Wiktor ; Guo, Xiao - \ 2019
    PLoS ONE 14 (2019)4. - ISSN 1932-6203
    In peatland restoration we often lack an information whether re-established ecosystems are functionally similar to non-degraded ones. We re-analysed the long-term outcomes of restoration on vegetation and plant functional traits in 38 European fens restored by rewetting (18 sites) and topsoil removal (20 sites). We used traits related to nutrient acquisition strategies, competitiveness, seed traits, and used single- and multi-trait metrics. A separate set of vegetation records from near-natural fens with diverse plant communities was used to generate reference values to aid the comparisons. We found that both restoration methods enhanced the similarity of species composition to non-degraded systems but trait analysis revealed differences between the two approaches. Traits linked to nutrient acquisition strategies indicated that topsoil removal was more effective than rewetting. After topsoil removal competitive species in plant communities had decreased, while stress-tolerant species had increased. A substantial reduction in nutrient availability ruled out the effect of initial disturbance. An ability to survive and grow in anoxic conditions was enhanced after restoration, but the reference values were not achieved. Rewetting was more effective than topsoil removal in restricting variation in traits values permitted in re-developing vegetation. We found no indication of a shift towards reference in seed traits, which suggested that dispersal constraint and colonization deficit can be a widespread phenomena. Two functional diversity indices: functional richness and functional dispersion showed response to restoration and shifted values towards reference mires and away from the degraded systems.

    We concluded that targeting only one type of environmental stressor does not lead to a recovery of fens, as it provides insufficient level of stress to restore a functional ecosystem. In general, restoration efforts do not ensure the re-establishment and long-term persistence of fens. Restoration efforts result in recovery of fen ecosystems, confirmed with our functional trait analysis, although more rigid actions are needed for restoring fully functional mires, by achieving high and constant levels of anoxia and nutrient stresses.
    An international outbreak of Salmonella enterica serotype Enteritidis linked to eggs from Poland: a microbiological and epidemiological study
    Pijnacker, Roan ; Dallman, Timothy J. ; Tijsma, Aloys S.L. ; Hawkins, Gillian ; Larkin, Lesley ; Kotila, Saara M. ; Amore, Giusi ; Amato, Ettore ; Suzuki, Pamina M. ; Denayer, Sarah ; Klamer, Sofieke ; Pászti, Judit ; McCormick, Jacquelyn ; Hartman, Hassan ; Hughes, Gareth J. ; Brandal, Lin C.T. ; Brown, Derek ; Mossong, Joël ; Jernberg, Cecilia ; Müller, Luise ; Palm, Daniel ; Severi, Ettore ; Gołębiowska, Joannna ; Hunjak, Blaženka ; Owczarek, Slawomir ; Hello, Simon Le; Garvey, Patricia ; Mooijman, Kirsten ; Friesema, Ingrid H.M. ; Weijden, Coen van der; Voort, Menno van der; Rizzi, Valentina ; Franz, Eelco ; Bertrand, Sophie ; Brennan, Martine ; Browning, Lynda ; Bruce, Ryan ; Cantaert, Vera ; Chattaway, Marie ; Coia, John ; Couper, Sarah ; Žohar Čretnik, Tjaša ; Daniel, Ondřej ; Dionisi, Anna Maria ; Fabre, Laetitia ; Fitz-James, Ife ; Florek, Karolina ; Florianová, Martina ; Fox, Eithne ; Frelih, Tatjana ; Grilc, Eva ; Katalinic Jankovic, Vera ; Jourdan, Nathalie ; Karpíšková, Renata ; Kerkhof, Hans van den; Kuiling, Sjoerd ; Kurečić Filipović, Sanja ; Laisnez, Valeska ; Lange, Heidi ; deLappes, Niall ; Leblanc, Judith ; Luzzi, Ida ; Mandilara, Georgia ; Mather, Henry ; Mattheus, Wesley ; Mellou, Kassiani ; Morgan, Deborah ; Pinna, Elizabeth de; Ragimbeau, Catherine ; Røed, Margrethe Hovda ; Salmenlinna, Saara ; Smith, Robert ; Smith-Palmer, Alison ; Špačková, Michaela ; Torpdahl, Mia ; Trkov, Marija ; Trönnberg, Linda ; Tzani, Myrsini ; Utsi, Lara ; Wasyl, Dariusz ; Weicherding, Pierre - \ 2019
    The Lancet Infectious Diseases 19 (2019)7. - ISSN 1473-3099 - p. 778 - 786.

    Background: Salmonella spp are a major cause of food-borne outbreaks in Europe. We investigated a large multi-country outbreak of Salmonella enterica serotype Enteritidis in the EU and European Economic Area (EEA). Methods: A confirmed case was defined as a laboratory-confirmed infection with the outbreak strains of S Enteritidis based on whole-genome sequencing (WGS), occurring between May 1, 2015, and Oct 31, 2018. A probable case was defined as laboratory-confirmed infection with S Enteritidis with the multiple-locus variable-number tandem repeat analysis outbreak profile. Multi-country epidemiological, trace-back, trace-forward, and environmental investigations were done. We did a case-control study including confirmed and probable cases and controls randomly sampled from the population registry (frequency matched by age, sex, and postal code). Odds ratios (ORs) for exposure rates between cases and controls were calculated with unmatched univariable and multivariable logistic regression. Findings: 18 EU and EEA countries reported 838 confirmed and 371 probable cases. 509 (42%) cases were reported in 2016, after which the number of cases steadily increased. The case-control study results showed that cases more often ate in food establishments than did controls (OR 3·4 [95% CI 1·6–7·3]), but no specific food item was identified. Recipe-based food trace-back investigations among cases who ate in food establishments identified eggs from Poland as the vehicle of infection in October, 2016. Phylogenetic analysis identified two strains of S Enteritidis in human cases that were subsequently identified in salmonella-positive eggs and primary production premises in Poland, confirming the source of the outbreak. After control measures were implemented, the number of cases decreased, but increased again in March, 2017, and the increase continued into 2018. Interpretation: This outbreak highlights the public health value of multi-country sharing of epidemiological, trace-back, and microbiological data. The re-emergence of cases suggests that outbreak strains have continued to enter the food chain, although changes in strain population dynamics and fewer cases indicate that control measures had some effect. Routine use of WGS in salmonella surveillance and outbreak response promises to identify and stop outbreaks in the future. Funding: European Centre for Disease Prevention and Control; Directorate General for Health and Food Safety, European Commission; and National Public Health and Food Safety Institutes of the authors' countries (see Acknowledgments for full list).

    Astaxanthine 2.0 : hoogwaardige inhoudsstoffen uit algen in kassen
    Boer, Lex de; Bos, Jelle van den; Graman, Wim ; Hazewinkel, Sander ; Hemming, Silke ; Kerkhof, Gerwien ; Lans, Cees van der; Luijendijk, Teus ; Prins, Robert ; Roebroek, Eurgene ; Ruijven, Jim van; Streminska, Marta ; Ven, Joost van de; Vermeer, Chris ; Voogt, Wim ; Wisse, Wilko - \ 2018
    Bleiswijk : Wageningen Plant Research, Business unit Glastuinbouw (Wageningen Plant Research, Business unit Glastuinbouw rapport WPR 807) - 86
    Het doel van dit project was de realisatie van een proof-of-principle keten voor de productie van astaxanthine als oleoresin uit de alg Haematococcus pluvialis in fotobioreactoren in Nederlandse kassen. Astaxanthine is een sterk antioxidant dat bij kan dragen aan een gezonde voeding voor consumenten. Astaxanthine kan in Nederlandse kassen duurzaam worden geproduceerd (kassen als zonnecollector, gebruik afval CO2 uit industrie, reinigen afvalwater). Binnen dit project is onderzoek verricht naar de selectie van natuurlijke algenstammen op kasniveau, klassieke stamverbetering op labniveau (uitgangsmateriaal), procesverbetering in alle fases van de productie (voorkweek, opkweek, groene fase, rode fase) door optimalisatie teeltfactoren en hygiënisatie (teelt en productie) en het maken van een proof-of-principle eindproduct (eindformulering) volgens marktspecificatie (markt en economie). Met het project is kennis vergaard om een nieuw verdienmodel voor de productie van een hoogwaardige stof (astaxanthine) in de tuinbouw te realiseren. Er is een proof-of-principle van een economisch rendabele productieketen van uitgangsmateriaal over productie tot product eindformulering volgens specificaties van de markt aangetoond voor de productie van astaxanthine uit Haematococcus pluvialis.---The aim of this project was the realization of a proof-of-principle value chain for the production of astaxanthin as oleoresin from the algae Haematococcus pluvialis in photobioreactors in Dutch greenhouses. Astaxanthin is a strong antioxidant that can contribute to a healthy diet for consumers. Astaxanthin can be produced sustainably in Dutch greenhouses (greenhouses as solar collectors, usage of waste CO2 from industry, cleaning and recycling of waste water). Within this project, research was carried out into the selection of natural algae strains at the greenhouse level, classical strain improvement at lab level (starting material), process improvement at all stages of production, from pre-cultivation, cultivation, green phas and red phase, by the optimization of all cultivation factors and sanitation (growth and production) and designing a proof-of-principle end product (formulation) according to market specification (market and economy). With the project, knowledge has been gathered to realize a new revenue model for the production of a high-quality substance (astaxanthin) in horticulture. A proof-of-principle of an economically viable production chain of starting material from production to product final formulation according to market specifications has been demonstrated for the production of astaxanthin from Haematococcus pluvialis.
    Laser Speckle Strain Imaging reveals the origin of delayed fracture in a soft solid
    Kooij, Hanne M. van der; Dussi, Simone ; Kerkhof, Gea T. van de; Frijns, Raoul A.M. ; Gucht, Jasper van der; Sprakel, Joris - \ 2018
    Science Advances 4 (2018)5. - ISSN 2375-2548

    Stresses well below the critical fracture stress can lead to highly unpredictable delayed fracture after a long period of seemingly quiescent stability. Delayed fracture is a major threat to the lifetime of materials, and its unpredictability makes it difficult to prevent. This is exacerbated by the lack of consensus on the microscopic mechanisms at its origin because unambiguous experimental proof of these mechanisms remains absent. We present an experimental approach to measure, with high spatial and temporal resolution, the local deformations that precipitate crack nucleation. We apply this method to study delayed fracture in an elastomer and find that a delocalized zone of very small strains emerges as a consequence of strongly localized damage processes. This prefracture deformation zone grows exponentially in space and time, ultimately culminating in the nucleation of a crack and failure of the material as a whole. Our results paint a microscopic picture of the elusive origins of delayed fracture and open the way to detect damage well before it manifests macroscopically.

    A Diurnal Rhythm in Brown Adipose Tissue Causes Rapid Clearance and Combustion of Plasma Lipids at Wakening
    Berg, Rosa van den; Kooijman, Sander ; Noordam, Raymond ; Ramkisoensing, Ashna ; Abreu-Vieira, Gustavo ; Tambyrajah, Lauren L. ; Dijk, Wieneke ; Ruppert, Philip ; Mol, Isabel M. ; Kramar, Barbara ; Caputo, Rosanna ; Puig, Laura Sardón ; Ruiter, Evelien M. de; Kroon, Jan ; Hoekstra, Menno ; Sluis, Ronald J. van der; Meijer, Onno C. ; Willems van Dijk, Ko ; Kerkhof, Linda W.M. van; Christodoulides, Constantinos ; Karpe, Fredrik ; Gerhart-Hines, Zachary ; Kersten, Sander ; Meijer, Johanna H. ; Coomans, Claudia P. ; Heemst, Diana van; Biermasz, Nienke R. ; Rensen, Patrick C.N. - \ 2018
    Cell Reports 22 (2018)13. - ISSN 2211-1247 - p. 3521 - 3533.
    angiopoietin-like 4 - APOE3-Leiden.CETP mice - brown adipose tissue - circadian rhythm - diurnal rhythm - fatty acids - lipoprotein lipase - postprandial lipid response - triglycerides
    Many favorable metabolic effects have been attributed to thermogenic activity of brown adipose tissue (BAT). Yet, time of day has rarely been considered in this field of research. Here, we show that a diurnal rhythm in BAT activity regulates plasma lipid metabolism. We observed a high-amplitude rhythm in fatty acid uptake by BAT that synchronized with the light/dark cycle. Highest uptake was found at the onset of the active period, which coincided with high lipoprotein lipase expression and low angiopoietin-like 4 expression by BAT. Diurnal rhythmicity in BAT activity determined the rate at which lipids were cleared from the circulation, thereby imposing the daily rhythm in plasma lipid concentrations. In mice as well as humans, postprandial lipid excursions were nearly absent at waking. We anticipate that diurnal BAT activity is an important factor to consider when studying the therapeutic potential of promoting BAT activity. van den Berg et al. show a strong circadian rhythm in fatty acid uptake by brown adipose tissue that peaks at wakening regardless of the light exposure period. Consequently, postprandial lipid handling by brown adipose tissue is highest at wakening, resulting in the lowest postprandial plasma lipid excursions.
    PowerPoint Slides as Speaking Notes: The Influence of Speaking Anxiety on the Use of Text on Slides
    Woerkum, C.M.J. van; Hertz, B. ; Kerkhof, P. - \ 2016
    Business and Professional Communication Quarterly 79 (2016)3. - ISSN 2329-4906 - p. 348 - 359.
    PowerPoint presentations are often criticized for the excessive use of text on the
    slides. In a study of 97 academic scholars, we found that presenters indeed used
    substantially more text than is advised. Speaking anxiety was found to be related to
    the time spent on preparing and rehearsing, and time spent on rehearsing is related
    to the number of words on the slides. Anxious presenters appear to use PowerPoint
    slides as speaking notes. Presenters should be trained to overcome their speaking
    anxiety by means other than the abundant use of words on their slides.
    A mechanistic view of drying suspension droplets
    Kooij, Hanne M. Van Der; De Kerkhof, Gea T. Van; Sprakel, Joris - \ 2016
    Soft Matter 12 (2016)11. - ISSN 1744-683X - p. 2858 - 2867.

    When a dispersion droplet dries, a rich variety of spatial and temporal heterogeneities emerge. Controlling these phenomena is essential for many applications yet requires a thorough understanding of the underlying mechanisms. Although the process of film formation from initially dispersed polymer particles is well documented and is known to involve three main stages - evaporation, particle deformation and coalescence - it is impossible to fully disentangle the effects of particle deformation and coalescence, as these stages are closely linked. We circumvent this problem by studying suspensions of colloidal rubber particles that are incapable of coalescing. Varying the crosslink density allows us to tune the particle deformability in a controlled manner. We develop a theoretical framework of the main regimes and stresses in drying droplets of these suspensions, and validate this framework experimentally. Specifically, we show that changing the particle modulus by less than an order of magnitude can completely alter the stress development and resulting instabilities. Scanning electron microscopy reveals that particle deformability is a key factor in stress mitigation. Our model is the suspension equivalent of the widely used Routh-Russel model for film formation in drying dispersions, with additional focus on lateral nonuniformities such as cracking and wrinkling inherent to the droplet geometry, thus adding a new dimension to the conventional view of particle deformation.

    Why do scholars use PowerPoint the way they do?
    Hertz, Brigitte ; Woerkum, Cees van; Kerkhof, Peter - \ 2015
    Business Communication Quarterly 78 (2015)3. - ISSN 1080-5699 - p. 273 - 291.
    PowerPoint - Presentations - Scholars - Teaching communication

    PowerPoint has received much criticism regarding excessive use of text and the lack of contact with the audience. Why presenters use PowerPoint in this way has not been studied so far. Our study using interviews with beginning and advanced presenters shows that some use the program as a speaking note and as a means to draw the attention away from themselves. Some even think that PowerPoint can replace rhetorical skills. Slides are mainly designed on the basis of commonsense, instead of guidelines based on human information processing. Implications for the teaching of PowerPoint use in business communication are discussed.

    Spotlight on the presenter : a study into presentations of conference papers with PowerPoint
    Hertz, B. - \ 2015
    Wageningen University. Promotor(en): Cees van Woerkum, co-promotor(en): P. Kerkhof. - Wageningen : Wageningen University - ISBN 9789462573192 - 193
    publiceren - informatieverspreiding - communicatievaardigheden - verbale communicatie - toepassingen - wetenschappers - openbare redes - publishing - diffusion of information - communication skills - verbal communication - applications - scientists - public speeches

    Abstract

    1. Introduction

    PowerPoint is the most widely used presentation software tool. As of 2012, PowerPoint had more than 200 million presenters worldwide. Presenters all over the world use the program. Some use it for university teaching, others for business meetings and some even use PowerPoint to deliver a sermon. But the program doesn’t always seem to be used to the satisfaction of the audience. In many critical articles, presenters are accused of using too many words on their slides and too often looking at the projection instead of keeping eye contact with the audience. Some authors also criticize the program itself for what they see as a negative influence on presentations.

    If these critical observations are valid, then PowerPoint presentations don’t conform to the advice given in instruction books nor to the outcome of research into human information processing. This advice usually proposes the use of minimal text on slides, and instead using pictures or other graphics. This would help the audience process the information. In addition, the instruction book stress the importance of maintaining eye contact with the audience. It is remarkable that the program is so frequently used, while it is so often criticized for what seem to be valid reasons.

    There has been some research into PowerPoint use in the classroom, investigating the effects on student appreciation and grades. Much of this research does not describe how nor why the program is used in these situations. The critical articles on PowerPoint are mainly based on personal experiences and not on research. So there has not been much empirical evidence that presenters actually do use too many words or that they look too often at the projection, nor has the influence of PowerPoint on the presentation been established. In addition it is not clear why so many presenters don’t seem to follow the advice in instruction books, which say to use a minimum amount of text on a slide and which stress the importance of maintaining eye contact with the audience.

    This dissertation focuses on the role of the presenter. It investigates how presenters use PowerPoint and if they are guilty of the negative behavior mentioned above. If they are guilty, what are the reasons they use PowerPoint in this way? Some authors have suggested that presenters use PowerPoint not only for the benefit of the audience, but that they also use the words on the slides as speaking notes. In particular, presenters suffering from speaking anxiety might be afraid of being “lost for words” or forgetting the structure of their presentation. They would then be able to turn to the text on the slides as support. This dissertation will investigate the possible role of speaking anxiety and how it affects PowerPoint usage.

    The research looks at the use of PowerPoint by scholars presenting conference papers. Conferences play a central role in the network of scientific communication and are important for a researcher’s profile. The majority of scholars present their work at conferences several times a year and these presentations can be demanding and challenging. In contrast with writing and publishing a paper, conferences allow scholars to interact with an audience of their peers who will evaluate their work by posing critical questions. Challenging exposure of this kind might well engender or increase speaking anxiety in the presenter.

    Clearly there is a need for empirical research on PowerPoint use, research focused on the program’s use in delivering scholarly presentations. Questions to be answered by the research include:

    • How do scholars use PowerPoint?

    • Why do scholars use PowerPoint in the way that they do?
    • Does speaking anxiety influence the way that scholars use PowerPoint?

    • Does PowerPoint influence the quality of presentations?

    This thesis studies the use of PowerPoint in a real life setting and looks at presentations as being complex interactions among slides, presenter behavior and audience. An overview of the different elements regarding the presenter, his/her background, the presentation, the presenter’s behavior and the PowerPoint program itself can be found in Figure I.

    2. Method

    There is a literature review and three empirical studies. The literature review compares the program with its predecessors and describes the software, slide design and the user’s presentation behavior, focusing on the interaction of these elements. Instruction books and articles on PowerPoint, criticism and empirical research on the topics of slide design, presentation behavior and its effects on audiences are discussed.

    In the first empirical study, fifteen scientific presentations of language scientists are analyzed on the use of text and pictures on the slides. The physical and verbal behavior of the presenter has also been studied, specifically investigating how often presenters look at the projection and if they verbally introduce a slide. Furthermore the relation between the slides and the presenter’s behavior has been analyzed.

    The second empirical study employs interviews with scholars about their reasons for PowerPoint use. It distinguishes between first-year PhD students (beginners) and advanced, prize winning scholars from different disciplines of science (humanities, physical science, social science and medical science). Special attention is given to the acquisition of PowerPoint skills.

    The third study consists of a survey using social scientists and focuses on the influence of speaking anxiety on the use of PowerPoint. It tests if speaking anxiety causes presenters to spend more time on preparing and rehearsing the presentation, and analyzes the possible relationships among speaking anxiety, time spent on preparing and rehearsing a presentation, and the use of words on a slide.

    3. Results

    Certain characteristics of PowerPoint such as its default-settings and the ability to use slides on the Internet and as handouts may tempt the presenter to increase the amount of text on slides. These choices, however, are not necessary, and are decisions made by the presenter. The scholars in our study used a relatively large number of words when compared to what instruction books advise (a maximum of 20 to 36 words per slide, depending on the author). An average number of 35 (language scientists) and 50 (social scientists) per slide was found. Many of the scholars used a small number of pictures (depending on the scientific discipline).

    Presenters look on average 73 times at the projection during their presentation of 20 minutes (more than three times a minute). Looking at the projection to indicate a new slide or ‘new’ elements on a slide seems to be characteristic for the use of PowerPoint. Presenters turn away from the audience and break eye-contact, something which is considered negative in making presentations. The critics of PowerPoint clearly have a point when they complain about the high number of words on the slides and about presenters looking towards the projection.

    There are differences, however, between beginning and advanced presenters. Beginners use more than twice as many words per minute than advanced presenters and only half as many pictures. In maintaining contact with the audience there is also a difference between beginning and advanced scholars. Advanced presenters often like to present without the use of PowerPoint because this allows more contact with their audience.

    Some scholars say that they use the text on the slides as speaking notes. Many have also said that they use pictures almost exclusively for the benefit of the audience. Beginners probably use more text and fewer pictures because they suffer more from speaking anxiety than advanced presenters. They might be more concerned with their own performance. Advanced scholars on the other hand have indicated that they have their audience in mind when preparing and delivering a presentation. Speaking anxiety, in an indirect way, also plays a role in the number of words used on the slides. Anxious presenters spend more time rehearsing the presentation; this is related to the number of words used on the slides.

    Scholars often seem to lack knowledge about how to use PowerPoint in an appropriate manner. Instead of receiving training in using PowerPoint, they learn to present with the program by experimenting and by observing colleagues and designing slides on the basis of common sense, which is often against the advice in instruction books. Moreover some scholars erroneously think that PowerPoint makes rhetorical skills redundant.

    4. Conclusions

    The concept of “performance” seems to be appropriate in describing all the elements that matter in the presentation itself: speech, animated slides, working with projections, physical motion and maintaining eye contact with the audience. Presenters need an understanding of how audiences process different sources of information, and they must then be able to orchestrate their presentation skills in appropriate ways. If we look at PowerPoint presentations as performances, we can see that presenters must be designers, actors and directors at the same time.

    It is clear that PowerPoint elicits behavior that is not always consistent with what is considered to be good presentation form. This, however, is not the fault of the program. The apparent user friendliness of PowerPoint might disguise the fact that presentations with the program are in fact complex. It is not PowerPoint itself which causes some bad presentations, but the choices and behavior of the presenters who must deal with all the new possibilities and requirements inherent in this program.

    Presenters should be educated in appropriate slide design. They also should be taught how to direct the attention of the audience. It is not sufficient to teach presenters how they should design and present their slides, however, if they aren’t helped to learn how to reduce their speaking anxiety in ways other than using the PowerPoint slides as support. This thesis suggests ways of teaching these skills

    Dietary Linoleic and a-Linolenic Acid Affect Anxiety-Related Responses and Exploratory Activity in Growing Pigs
    Clouard, C.M. ; Gerrits, W.J.J. ; Kerkhof, I. van; Smink, W. ; Bolhuis, J.E. - \ 2015
    The Journal of Nutrition 145 (2015)2. - ISSN 0022-3166 - p. 358 - 364.
    polyunsaturated fatty-acids - docosahexaenoic acid - inflammatory processes - open-field - behavior - brain - rats - mice - deficiency - piglets
    Background: Growing evidence suggests that the dietary ratio of linoleic acid (LA) to a-linolenic acid (ALA), the precursors of arachidonic acid (AA) and docosahexaenoic acid (DHA), respectively, may affect behavior in mammals. Objective: This study aimed at evaluating the impact of dietary LA and ALA intake on behaviors of growing pigs, a pertinent model for human nutrition. Methods: At 7 wk of age, 32 pigs were allocated to 4 dietary treatments varying in daily intake of LA (1.3 and 2.6 g · kg body weight-0.75 · d-1 for low- and high-LA groups, respectively) and ALA (0.15 and 1.5 g · kg body weight-0.75 · d-1 for low- and high-ALA groups, respectively) for 4 wk. Between days 12 and 18, general behavior in the home pen was observed and pigs were subjected to an open field and novel object test. At 11 wk of age, brain fatty acid composition was analyzed. Results: Compared with high LA intake, low LA intake increased the time spent on exploration, particularly nosing in the home pen (P <0.05) and the open field (P <0.05), and tended to reduce the time spent lying with eyes open in the home pen (P = 0.09). Time spent lying with eyes open also tended to be affected by LA × ALA interaction (P = 0.08). A high-LA/high-ALA intake (ratio of 2; P <0.05) and a low-LA/high-ALA intake (ratio of 1; P = 0.06) decreased the latency to approach the novel object compared with a low-LA/low-ALA intake (ratio of 9). DHA in the frontal cortex was positively correlated with exploratory behaviors in the home pen (rs = 0.56, P <0.01), whereas AA was negatively correlated with time spent lying with eyes closed (rs = –0.48, P <0.01). Conclusions: Low LA intake and a low dietary LA:ALA ratio increased exploration and decreased anxiety-related behaviors in pigs. It is suggested that changes in brain DHA and AA induced by dietary LA and ALA intake mediate these behavioral changes.
    Screen time, adiposity and cardiometabolic markers: mediation by physical activity, not snacking, among 11-year-old children
    Berendtzen, N.E. ; Smit, H.A. ; Rossem, L. van; Gehring, U. ; Kerkhof, M. van de; Postma, D.S. ; Boshuizen, H.C. - \ 2014
    International Journal of Obesity 38 (2014). - ISSN 0307-0565 - p. 1317 - 1323.
    body-mass index - sedentary behavior - risk-factors - computer use - television - obesity - health - youth - association - adolescents
    Background:There is evidence for a relation of TV viewing with adiposity and increased cardiometabolic risk factors in children and adolescents. It is unclear to what extent this relation is mediated by snacking and lack of physical activity. We determined whether associations of screen time with adiposity and cardiometabolic markers were mediated by these behaviours.Methods:Children from a population-representative Dutch birth cohort (n=1447) reported screen time and other lifestyle factors by a questionnaire around the age of 11 years (range 10-14) and had anthropometry and cardiometabolic markers measured around the age of 12 years (range 12-14). Adjusted associations of screen time with snacking, physical activity, adiposity and cardiometabolic markers (total-to-high-density lipoprotein cholesterol (TC/HDLC) ratio, blood pressure, glycated haemoglobin) were assessed by using formal mediation analysis. We tested the hypothesized paths by structural equation modeling, which allows quantification of the indirect effects associated with potential mediators.Results:Children with ¿20¿h screen time per week consumed more snacks (1.9 vs 1.3 portions per day) and were less physically active (4.3 vs 4.8 days per week) than children with maximum 6¿h screen time. Screen time was directly associated with higher adiposity (standardized ß=0.10-0.12 depending on the outcome, P
    Dialogues in the COOL Project
    Stalpers, S.I.P. ; Kroeze, C. - \ 2013
    In: Participation and Interaction in Foresight: Dialogue, Dissemination and Visions / Borch, K., Dingli, S., Sorgaard Jorgensen, M., UK : Edward Elgar Publishing Limited - ISBN 9781781956137 - p. 187 - 200.
    The Climate Options for the Long-term (COOL) Project is a participatory integrated assessment (PIA) comprising extensive dialogues at three levels: national, European and global. The objective of the COOL Project was to ‘develop strategic notions on how to achieve drastic reductions of greenhouse gas emissions in the Netherlands in the long term, in a European and global context, by using a participatory approach’ (Van de Kerkhof, 2004: 93). A secondary objective of the project was to further develop PIA methodology. This chapter focuses on the COOL National and European Dialogues as an illustration of the participatory backcasting analysis in a broad socio-economic foresight project that incorporates not only technical and economic aspects of policy options but also social implications. The global dialogue is not covered because of a lack of documentation on the process, and because the results of the global dialogue had little impact on the National and European Dialogues.
    Wetenschappelijke presentaties met Power-Point. Schadelijke software?
    Hertz, B. ; Woerkum, C. van; Kerkhof, P. - \ 2013
    In: Studies in taalbeheersing / Boogaart, R., Janssen, H., Assen : Van Gorcum - ISBN 9789023249917 - p. 125 - 134.
    Longitudinal analyses of indoor temperature and BMI in children in the PIAMA birth cohort study
    Scheffers, F.R. ; Bekkers, M.B.M. ; Kerkhof, M.F. ; Gehring, U. ; Koppelman, G.H. ; Schipper, M. ; Haveman-Nies, A. ; Wijga, A.H. - \ 2012
    Microbiome dynamics of human epidermis following skin barrier disruption
    Zeeuwen, P.L. ; Boekhorst, J. te; Bogaard, E.H. van den; Koning, H.D. de; Kerkhof, P.M. van de; Saulnier, D.M. ; Swam, I.I. van; Hijum, S.A.F.T. van; Kleerebezem, M. ; Schalkwijk, J. ; Timmerman, H.M. - \ 2012
    Genome Biology 13 (2012). - ISSN 1474-7596
    atopic-dermatitis patients - molecular analysis - wound microbiota - bacterial biota - gut microbiota - diversity - psoriasis - disease - expression - defense
    Background - Recent advances in sequencing technologies have enabled metagenomic analyses of many human body sites. Several studies have catalogued the composition of bacterial communities of the surface of human skin, mostly under static conditions in healthy volunteers. Skin injury will disturb the cutaneous homeostasis of the host tissue and its commensal microbiota, but the dynamics of this process have not been studied before. Here we analyzed the microbiota of the surface layer and the deeper layers of the stratum corneum of normal skin, and we investigated the dynamics of recolonization of skin microbiota following skin barrier disruption by tape stripping as a model of superficial injury. Results - We observed gender differences in microbiota composition and showed that bacteria are not uniformly distributed in the stratum corneum. Phylogenetic distance analysis was employed to follow microbiota development during recolonization of injured skin. Surprisingly, the developing neo-microbiome at day 14 was more similar to that of the deeper stratum corneum layers than to the initial surface microbiome. In addition, we also observed variation in the host response towards superficial injury as assessed by the induction of antimicrobial protein expression in epidermal keratinocytes. Conclusions - We suggest that the microbiome of the deeper layers, rather than that of the superficial skin layer, may be regarded as the host indigenous microbiome. Characterization of the skin microbiome under dynamic conditions, and the ensuing response of the microbial community and host tissue, will shed further light on the complex interaction between resident bacteria and epidermis
    Lack of evidence for zoonotic transmission of Schmallenberg virus
    Reusken, C. ; Wijngaard, C. van den; Beek, P. van; Beer, M. ; Bouwstra, R.J. ; Godeke, G.J. ; Isken, L. ; Kerkhof, H. van den; Pelt, W. van; Poel, W.H.M. van der; Reimerink, J. ; Schielen, P. ; Schmidt-Chanasit, J. ; Vellema, P. ; Vries, A. de; Wouters, I. ; Koopmans, M.P.G. - \ 2012
    Emerging Infectious Diseases 18 (2012)11. - ISSN 1080-6040 - p. 1746 - 1754.
    genus orthobunyavirus - hemorrhagic-fever - simbu serogroup - northern brazil - oropouche virus - reassortant - infection - disease - arboviruses - bunyavirus
    The emergence of Schmallenberg virus (SBV), a novel orthobunyavirus, in ruminants in Europe triggered a joint veterinary and public health response to address the possible consequences to human health. Use of a risk profiling algorithm enabled the conclusion that the risk for zoonotic transmission of SBV could not be excluded completely. Self-reported health problems were monitored, and a serologic study was initiated among persons living and/or working on SBV-affected farms. In the study set-up, we addressed the vector and direct transmission routes for putative zoonotic transfer. In total, 69 sheep farms, 4 goat farms, and 50 cattle farms were included. No evidence for SBV-neutralizing antibodies was found in serum of 301 participants. The lack of evidence for zoonotic transmission from either syndromic illness monitoring or serologic testing of presumably highly exposed persons suggests that the public health risk for SBV, given the current situation, is absent or extremely low.
    Serum micronutrient concentrations and childhood asthma: the PIAMA birth cohort study
    Oeffelen, A.A.M. van; Bekkers, M.B.M. ; Smit, H.A. ; Kerkhof, M. van de; Koppelman, G.H. ; Haveman-Nies, A. ; A, D.L. van der; Jansen, E.H.J.M. ; Wijga, A.H. - \ 2011
    Pediatric Allergy and Immunology 22 (2011)8. - ISSN 0905-6157 - p. 784 - 793.
    nutrition examination survey - vitamin-d levels - zinc status - trace-elements - t-lymphocytes - smooth-muscle - children - magnesium - selenium - cells
    Background: Research suggests an influence of micronutrients on childhood asthma. So far, evidence mainly originates from cross-sectional studies using nutrient intake data, which is not an accurate measure of nutrient status. This study aimed to investigate the cross-sectional and prospective associations between serum concentrations of magnesium, vitamin D, selenium, and zinc and prevalence of (severe) asthma, atopy, and bronchial hyperresponsiveness (BHR) in childhood. Methods: In the Prevention and Incidence of Asthma and Mite Allergy birth cohort study, serum nutrient concentrations were available for a 4-yr-old subgroup (n = 372) and for a different 8-yr-old subgroup (n = 328). Yearly questionnaires inquired about asthma prevalence until 8 yr of age. Allergic sensitization was measured at 4 and 8 yr of age; BHR was measured at 8 yr of age. Data were analyzed with logistic regression and generalized estimating equations models. Results: There was a consistent (non-significant) inverse association between serum magnesium concentrations and asthma prevalence. Serum vitamin D concentrations measured at age 4 were inversely associated with asthma at ages 4–8 [e.g., cross-sectional association between vitamin D tertile 3 vs. 1 and severe asthma: odds ratio (OR): 0.49, 95% confidence interval (CI): 0.25–0.95], whereas vitamin D measured at age 8 was positively associated with asthma at age 8 (e.g., cross-sectional association between vitamin D tertile 3 vs. 1 and severe asthma: OR: 2.14, 95% CI: 0.67–6.82). Conclusions: Our study contributes to the evidence that children with higher serum magnesium concentrations are less likely to have asthma. The associations between serum vitamin D concentrations and asthma were age-dependent
    Predicting the risk of newborn children to become overweight later in childhood: the PIAMA birth cohort study
    Steur, M. ; Smit, H.A. ; Schipper, C.M.A. ; Scholtens, S. ; Kerkhof, M. van de; Jongste, J.C. de; Haveman-Nies, A. ; Brunekreef, B. ; Wijga, A.H. - \ 2011
    International Journal of Pediatric Obesity 6 (2011)2-2. - ISSN 1747-7166 - p. e170 - e178.
    self-reported height - regression-analysis - obesity - weight - prevention - validity - smoking - pregnancy - allergy - models
    Objective. To develop a decision rule by which children with a high risk to develop overweight can be distinguished at birth from children at low risk. Design, setting and participants. Data of 1 687 Dutch children born in 1996/1997 who participated in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) longitudinal birth cohort study were analysed. Perinatal candidate predictors of overweight at 8 years of age were selected and a prediction model was developed using stepwise model selection based on the Akaike Information Criterion (AIC). The prediction model was internally validated using resampling techniques. Outcome measure. Overweight at the age of 8 years. Results. A total of 13.9% (n = 253) of the children were overweight at 8 years of age. Independent positive predictors of overweight were paternal and maternal body mass index, female gender, smoking in the parental house, birth weight and hospital delivery. From the model, a decision rule was derived by which an overweight score could be calculated. Of the children with an overweight score below 89.45, only 2.7% were overweight at the age of 8, whereas in children with an overweight score above 105.02 the prevalence of overweight was 35.4%. Conclusion. The risk of overweight at the age of 8 years can be predicted with six characteristics that are available at birth. The decision rule developed in this study may help to target early preventive measures against overweight in high-risk children
    Predicting the risk of newborn children to become overweight later in childhood
    Steur, M. ; Smit, H.A. ; Schipper, C.M.A. ; Scholtens, S. ; Kerkhof, M. van de; Jongste, J.C. de; Haveman-Nies, A. ; Brunekreef, B. ; Wijga, A.H. - \ 2010
    In: 3rd European Public Health Conference, Amsterdam, The Netherlands, 10 - 13 November, 2010. - - p. 66 - 66.
    To develop a decision rule by which children with a high risk to develop overweight can be distinguished at birth from children at low risk. Design, setting and participants. Data of 1 687 Dutch children born in 1996/1997 who participated in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) longitudinal birth cohort study were analysed. Perinatal candidate predictors of overweight at 8 years of age were selected and a prediction model was developed using stepwise model selection based on the Akaike Information Criterion (AIC). The prediction model was internally validated using resampling techniques. Outcome measure. Overweight at the age of 8 years. Results. A total of 13.9% (n = 253) of the children were overweight at 8 years of age. Independent positive predictors of overweight were paternal and maternal body mass index, female gender, smoking in the parental house, birth weight and hospital delivery. From the model, a decision rule was derived by which an overweight score could be calculated. Of the children with an overweight score below 89.45, only 2.7% were overweight at the age of 8, whereas in children with an overweight score above 105.02 the prevalence of overweight was 35.4%. Conclusion. The risk of overweight at the age of 8 years can be predicted with six characteristics that are available at birth. The decision rule developed in this study may help to target early preventive measures against overweight in high-risk children.
    Clinical effectiveness of attentional bias modification training in abstinent alcoholic patients
    Schoenmakers, T.M. ; Bruin, M. de; Lux, I.F.M. ; Goertz, A.G. ; Kerkhof, D.H.A.T. van; Wiers, R.W. - \ 2010
    Drug and Alcohol Dependence 109 (2010)1-3. - ISSN 0376-8716 - p. 30 - 36.
    experimental manipulation - heavy drinkers - incentive-sensitization - anxiety disorders - dependence - cues - addiction - smokers - vulnerability - association
    A new training to decrease attentional bias (attentional bias modification training, ABM) was tested in a randomized controlled experimental study with alcohol-dependent patients as an addition to cognitive behavioral therapy. In alcohol dependence, attentional bias has been associated with severity of alcoholism, craving, treatment outcome, and relapse. Forty-three patients with DSM-IV diagnosis of alcohol dependence were randomly assigned to an ABM intervention or control training. The procedure consisted of five sessions in which patients were trained to disengage attention from alcohol-related stimuli (ABM condition) or in which they were trained on an irrelevant reaction-time test (control condition). We measured the effects of ABM on the visual-probe task, with stimuli that were presented in the ABM and with new stimuli. Craving was measured with the Desires for Alcohol Questionnaire. Follow-up data were gathered for overall treatment success, and relapse up to 3 months after the intervention. ABM was effective in increasing the ability to disengage from alcohol-related cues. This effect generalized to untrained, new stimuli. There were no significant effects on subjective craving. For other outcome measures there were indications of clinically relevant effects. Results indicate that ABM among alcohol-dependent patients was effective and that it may affect treatment progression. Large-scale trials are warranted to further investigate this new field
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