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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    Poverty or prosperity in northern India? New evidence on real wages, 1590s–1870s†
    Zwart, Pim de; Lucassen, Jan - \ 2020
    Economic History Review 73 (2020)3. - ISSN 0013-0117 - p. 644 - 667.

    This article introduces a new dataset on wages in northern India (from Gujarat in the west to Bengal in the east) from the 1590s to the 1870s. It follows Allen's subsistence basket methodology to compute internationally comparable real wages to shed light on developments in Indian living standards over time. It adjusts the comparative cost-of-living indices to take into account differences in climate and caloric intake due to variances in heights. The article also discusses the male/female wage gap in northern India. It demonstrates that the ‘great divergence’ started in the late seventeenth century, and widened further after the 1720s and especially after the 1800s. It was subsequently primarily England's spurt and India's stagnation in the first half of the nineteenth century that brought about most serious differences in the standard of living. If the British colonial state is to blame—as often suggested by the literature on India's persistent poverty—the fault lies in its failure to improve the situation after the British became near-undisputed masters of India in 1820.

    Dietary Intake Assessment: From Traditional Paper-Pencil Questionnaires to Technology-Based Tools
    Brouwer-brolsma, Elske M. ; Lucassen, Desiree ; Rijk, Marielle G. De; Slotegraaf, Anne ; Perenboom, Corine ; Borgonjen, Karin ; Siebelink, Els ; Feskens, Edith J.M. ; Vries, Jeanne H.M. De - \ 2020
    In: International Symposium on Environmental Software Systems (ISESS 2020) Wageningen : Springer (IFIP Advances in Information and Communication Technology ) - ISBN 9783030398149 - p. 7 - 23.
    Self-reported methods of recall and real-time recording are the most commonly used approaches to assess dietary intake, both in research as well as the health-care setting. The traditional versions of these methods are limited by various methodological factors and burdensome for interviewees and researchers. Technology-based dietary assessment tools have the potential to improve the accuracy of the data and reduce interviewee and researcher burden. Consequently, various research groups around the globe started to explore the use of technology-based tools. This paper provides an overview of the: (1) most-commonly used and generally accepted methods to assess dietary intake; (2) errors encountered using these methods; and (3) web-based and app-based tools (i.e., Compl-eatTM, Traqq, Dutch FFQ-TOOLTM, and “Eetscore”) that have been developed by researchers of the Division of Human Nutrition and Health of Wageningen University during the past years.
    Ontwikkeling broekbossen
    Runhaar, J. ; Verdonschot, R.C.M. ; Swinkels, C. ; Lucassen, E.C.H.E.T. ; Loeb, R. ; Smolders, A.J.P. - \ 2019
    Wageningen : KNNV Publishing (Rapport / Vereniging van Bos-en Natuurterreineigenare nr. 2019/OBN227-BE) - 142
    Het doel van het Kennisnetwerk Ontwikkeling en Beheer Natuurkwaliteit (OBN) is het ontwikkelen, verspreiden en benutten van kennis voor terreinbeheerders over natuurherstel, Natura 2000, PAS, leefgebiedenbenadering en ontwikkeling van nieuwe natuur. In het kader van Natura 2000 worden in Europees perspectief zeldzame soorten en vegetatietypen in Nederland beschermd. Deze studie heeft zich gericht op voor beekdalen kenmerkende broekbossen, die vallen onder het habitatsubtype H91E0_C Vochtige alluviale bossen (beekbegeleidende bossen). Het gaat daarbij met name om door Zwarte els (Alnus glutinosa) gedomineerde broekbossen. De vraag die in deze studie centraal stond is welke invloed nutriëntenbeschikbaarheid heeft op vegetatie en fauna van broekbossen en daarmee op de ontwikkelingsmogelijkheden van deze bostypen op voormalige landbouwgronden in beekdalen. De nadruk in deze studie ligt op de nutriëntenhuishouding en op de invloed die voormalig landgebruik en overstroming via de nutriëntenhuishouding hebben op de soortenrijkdom in broekbossen. Daarnaast wordt ook uitgebreid aandacht besteed aan de invloed van de vegetatiestructuur op de soortensamenstelling van de macrofauna. Dit onderzoek bevat ook een experiment met het toedienen ijzerhoudend drinkwaterslib dat vrijkomt bij productie van drinkwater. Dit experiment had tot doel om na te gaan of toediening van dit slib ook in natte organische bodems een geschikte maatregel is om fosfaat te binden. De resultaten laten zien dat het mogelijk is de mobilisatie van fosfaat succesvol tegen te gaan door de toediening van ijzer- en kalkrijk slib. Dit onderdeel is mogelijk gemaakt door financiering en medewerking van Brabant Water. De rest van de conclusies en aanbevelingen leest u in hoofdstuk 7.
    1662: Koffie, wereldhandel en de consumptie-revolutie
    Zwart, P. de - \ 2018
    In: Wereldgeschiedenis van Nederland / 't Hart, M., Davids, K., Fatah-Black, K., Heerma van Voss, L., Lucassen, L., Touwen, J., Amsterdam : - ISBN 9789026343995 - p. 275 - 280.
    In Wereldgeschiedenis van Nederland vertellen meer dan honderd aanstormende en gevestigde Nederlandse onderzoekers op het gebied van geschiedenis en cultuur het wereldwijde verhaal van onze geschiedenis, onder wie Martine Gosselink, Beatrice de Graaf, Lotte Jensen, Gert Oostindie, Lodewijk Petram en Suze Zijlstra. In dit verhelderende en prikkelende boek laten zij zien hoe Nederland de wereld door de eeuwen heen mede heeft vormgegeven, en andersom: hoe Nederland zich onder invloed van verre en nabije buren heeft ontwikkeld. Van de vondst van oermens Krijn in de Noordzee tot orkaan Irma op Sint Maarten en van Bonifatius tot Pim Fortuyn – aan de hand van talloze grote en kleine historische ontwikkelingen en gebeurtenissen laat Wereldgeschiedenis van Nederland zien hoezeer Nederland verbonden is met de wereld, en de wereld met Nederland. Wereldgeschiedenis van Nederland is een uitgave van het Huygens Instituut voor Nederlandse Geschiedenis, een knaw-onderzoeksinstituut op het gebied van geschiedenis en literatuur.

    Redactie: Karel Davids, Karwan Fatah-Black, Marjolein ’t Hart, Leo Lucassen en Jeroen Touwen. Hoofdredactie: Lex Heerma van Voss
    1607. De Beemster en het poldermodel
    Cruijningen, P.J. van - \ 2018
    In: Wereldgeschiedenis van Nederland / 't Hart, M., Davids, K., Fatah-Black, K., Heerma van Voss, L., Lucassen, L., Touwen, J., Amsterdam : - ISBN 9789026343995 - p. 207 - 212.
    Hergebruik drinkwaterslib beoogt natuurontwikkeling op fosfaatrijke gronden
    Dorland, E. ; Fujita, Y. ; Chardon, W.J. ; Lucassen, E.C.H.E.T. ; Smolders, A. ; Ketelaar, R. ; Jong, A.L. de - \ 2016
    Vakblad Natuur Bos Landschap (2016)124. - ISSN 1572-7610 - p. 3 - 5.
    natuurontwikkeling - drinkwater - slib - fosfaat - bodemverbeteraars - natuurbeheer - afvalhergebruik - veldproeven - ijzer - nature development - drinking water - sludges - phosphate - soil conditioners - nature management - waste utilization - field tests - iron
    Natuurbeheerders zitten soms in hun maag met percelen die vanwege hun landbouwkundig verleden een hoge fosfaatlast kennen, omdat dit de ontwikkeling van waardevolle natuur belemmert. Afgraven is duur, uitmijnen tijdrovend, maar wat dan? Kan hergebruik van ijzerrijk drinkwaterslib uitkomst bieden? De eerste resultaten van veldproeven met dit restproduct van drinkwaterwinning zijn hoopgevend.
    IJzerrijk drinkwaterslib en verschraling landbouwgronden: een proof of principle
    Lucassen, E.C.H.E.T. ; Chardon, W.J. ; Dorland, E. ; Sluys, M.L. van der; Poelen, M.D.M. ; Smolders, Alfons J.P. - \ 2015
    Landschap : tijdschrift voor landschapsecologie en milieukunde 32 (2015)4. - ISSN 0169-6300 - p. 160 - 169.
    fosfaat - bodemverbeteraars - ijzer - waterstand - natuurontwikkeling - bodemchemie - slib - phosphate - soil conditioners - iron - water level - nature development - soil chemistry - sludges
    Bij de inrichting van het Natuurnetwerk Nederland en van Natura 2000-gebieden worden op grote schaal landbouwgronden heringericht als soortenrijke natuur. Om op korte termijn fosfaatarme bodemcondities te krijgen wordt op locaties waar de bodem te rijk is via maaibeheer en/of uitmijnen te bereiken, vaak gekozen voor verwijdering van de fosfaatrijke bodemlaag. Een mogelijk alternatief voor ontgronden is het toedienen van ijzerslib. Dit restproduct van drinkwaterwinning verbetert de fosfaatbinding van de bodem.
    Preadvies voor herstel en ontwikkeling van vochtige bossen op de pleistocene zandgronden
    Burg, R.F. van der; Brouwer, E. ; Bijlsma, R.J. ; Burg, A. van der; Duinen, G.A. van; Hommel, P.W.F.M. ; Jansen, A.J.M. ; Lucassen, E.C.H.E.T. ; Waal, R.W. de - \ 2014
    Driebergen : Vereniging van Bos- en Natuurterreineigenaren - 260
    bossen - bodemwater - habitats - ecohydrologie - landschap - natura 2000 - forests - soil water - habitats - ecohydrology - landscape - natura 2000
    Dit preadvies geeft inzicht in de sleutelprocessen en factoren die bepalend zijn voor behoud en ontwikkeling van natuurwaarden in vochtige bossen. Ook zijn de mogelijkheden in kaart gebracht om via herstelbeheer, regulier beheer en omvormingsbeheer te komen tot herstel van natuurwaarden in het geval sleutelprocessen en factoren verminderd of niet meer werkzaam of aanwezig zijn.
    Long live the library! The Book Collections of the IISH, in Particular the KNAW Library
    Nederveen Meerkerk, E.J.V. van - \ 2014
    In: A Usable Collection: Essays in honour of Jaap Kloosterman on Collecting Social History / Blok, A., Lucassen, J., Sanders, H., Amsterdam : Amsterdam University Press - ISBN 9789089646880 - p. 264 - 273.
    Herstel broekbossen
    Runhaar, J. ; Lucassen, E.C.H.E.T. ; Smolders, A.J.P. ; Verdonschot, R.C.M. ; Hommel, P.W.F.M. - \ 2013
    Driebergen : Bosschap (Rapport / [DKI] nr. 2013/OBN169-BE) - 135
    bosecologie - ecohydrologie - fauna - aquatische ecologie - bodem-plant relaties - forest ecology - ecohydrology - fauna - aquatic ecology - soil plant relationships
    Het voorliggende rapport bevat de resultaten van het OBN-project ‘Herstel Broekbossen’. Broekbossen vormen een belangrijk onderdeel van het habiatttype H19E0, Vochtige alluviale bossen, en behoud en ontwikkeling van broekbossen vormt dan ook een belangrijk doel in het Nederlandse natuurbeleid. Als onderdeel van het project is ook een literatuuronderzoek uitgevoerd naar de fauna in broekbossen, een aspect waaraan tot nu toe nauwelijks of geen aandacht is besteed. Ten onrechte, zoals het onderzoek laat zien, want broekbossen zijn rijk aan soorten, mede dank zij de grote variatie aan habitats binnen een goed ontwikkeld broekbos. Het waterregime speelt een belangrijke rol in de overlevingsstrategieën van de verschillende organismengroepen. Daarbij vormt voor aquatische soorten droogval in de zomer een kritische factor, en voor terrestrische soorten overstroming in de winter. Het literatuuronderzoek is bij gebrek aan Nederlands onderzoek vooral gebaseerd op buitenlandse literatuur.
    Viral commercials: the consumer as marketeer
    Ketelaar, P.E. ; Lucassen, P. ; Kregting, G.H.J. - \ 2010
    Tijdschrift voor Communicatiewetenschap 38 (2010)1. - ISSN 1384-6930 - p. 22 - 48.
    word-of-mouth - internet - involvement - responses
    Research into the reasons why consumers pass along viral commercials: their motives, the content characteristics of viral commercials and the medium context in which viral commercials appear. Based on the uses and gratifications perspective this study has determined which motives of consumers, content characteristics of viral commercials and medium context explain the passing along of viral commercials. Diffusion theory has been used to determine if viral mavens and infrequent senders differ regarding their reasons to pass along viral commercials and their demographic characteristics. An online survey was held among 510 youngsters. After viewing four viral commercials, they answered questions about passing along viral commercials (motives, content characteristics and medium context) and demographic variables. The study shows that youngsters pass along surprising and entertaining viral commercials more often than viral commercials that are sexually oriented and shocking. Possibly they do not want to be associated with these controversial virals. Youngsters pass along viral commercials through e-mail and in a lesser extend by social networks. Males pass along viral commercials more often than females
    Pitrus, l 'enfant terrible van het natte natuurbeheer?
    Lamers, L.P.M. ; Smolders, A. ; Diggelen, J. van; Lucassen, E.C.H.E.T. ; Kleijn, D. ; Roelofs, J. - \ 2008
    Tussen Duin & Dijk 7 (2008)1. - ISSN 1570-7261 - p. 30 - 36.
    Lessen uit een eeuw stedelijke problematiek
    Peters, K.B.M. - \ 2007
    Vrijetijdstudies 25 (2007). - ISSN 1384-2439 - p. 51 - 52.
    woonwijken - stadsontwikkeling - stedelijke planning - sociale ontwikkeling - sociale klassen - stadsomgeving - residential areas - urban development - urban planning - social development - social classes - urban environment
    Een bespreking van een nieuw boek van Leo Lucassen en Wim Willems (red.) genaamd De krachtige stad, een eeuw omgang en ontwijking. De ontwikkeling van steden heeft de aandacht van velen. Politici, bestuurders, marktpartijen, bewoners en onderzoekers houden zich al decennia lang bezig met de stedelijke vernieuwing, de problemen die zich in steden voordoen en op welke wijze deze problemen het beste kunnen worden opgelost. Zijn de huidige problemen nieuw? In het boek wordt aan de hand van verschillende casussen gekeken of er vergelijkingen te trekken zijn tussen het verleden en de huidige tijd
    Een verkennend onderzoek aan de hand van 92 SBB-referentiepunten : selectie van ecologisch relevante bodemeigenschappen
    Hommel, P.W.F.M. ; Brouwer, E. ; Lucassen, E.C.H.E.T. ; Smolders, A.J.P. ; Waal, R.W. de - \ 2006
    Wageningen : Alterra (Alterra-rapport 1445) - 119
    bodemeigenschappen - bodemchemie - bodemwater - synecologie - vegetatietypen - botanische samenstelling - ecologie - ecohydrologie - soil properties - soil chemistry - soil water - synecology - vegetation types - botanical composition - ecology - ecohydrology
    Het belangrijkste doel van dit onderzoek was te achterhalen welke kenmerken van de bodem en het bodemvocht het meest ‘verklarend’ zijn voor de variatie in soortensamenstelling en vegetatietypen van een set van 92 referentiepunten, beschreven in diverse typen grondwaterafhankelijke, korte vegetaties in Nederland. In het algemeen komen vooral factoren die betrekking hebben op zoutgehalte, zuurgraad en trofiegraad als belangrijk naar voren. Binnen verschillende ecologisch samenhangende groepen vegetatietypen blijken echter steeds andere factoren belangrijk zijn. Een universele benadering voor de bepaling van abiotische randvoorwaarden voor alle vegetatie-eenheden is dus niet te geven. Voorts blijkt dat de meerwaarde van de chemisch analyses ten opzichte alleen de veldkenmerken groot is, de meerwaarde van aanvullende bodemvochtanalyses in het najaar is echter gering
    Stress, depression and hippocampal apoptosis
    Lucassen, P.J. ; Heine, V.M. ; Muller, M.B. ; Beek, E.M. van der; Wiegant, V.M. ; Kloet, E.R. de; Joels, M. ; Fuchs, E. ; Swaab, D.F. ; Czeh, B. - \ 2006
    CNS & Neurological Disorders 5 (2006)5. - ISSN 1871-5273 - p. 531 - 546.
    In this review, we summarize and discuss recent studies on structural plasticity changes, particularly apoptosis, in the mammalian hippocampus in relation to stress and depression. Apoptosis continues to occur, yet with very low numbers, in the adult hippocampal dentate gyrus (DG) of various species. Stress and steroid exposure modulate the rate of apoptosis in the DG. Contrary to earlier studies, the impact of chronic stress on structural parameters of the hippocampus like cell number and volume, is rather modest, and requires prolonged and severe stress exposure before only small reductions (<10 %) become detectable. This does not exclude other structural parameters, like synaptic terminal structure, or dendritic arborization from being significantly altered in critical hippocampal subregions like the DG and/or CA3. Neither does it imply that the functional implications of the changes after stress are also modest. Of interest, most of the structural plasticity changes appear trasient and are generally reversible after appropiate recovery periods, or following cessation or blockade of the stress or corticosteroid exposure. The temporary slowing down of both apoptosis and adult proliferation, i.e. the DG turnover, after chronic stress will affect the overall composition, average age and identity of DG cells, and will have considerable consequences for the connectivity, input and properties of the hippcampal circuit and thus for memory function. Modulation of apoptosis and neurogenesis, by drugs interfering with stress components like MR and/or GR, and/or mediators of the cell death cascade, may thererfore provide drug targets for the modulation of mood and memory
    Compression/expansion rheology of oil/water interfaces with adsorbed proteins. Comparison with the air/water surface
    Benjamins, J. ; Lyklema, J. ; Lucassen-Reynders, E.H. - \ 2006
    Langmuir 22 (2006)14. - ISSN 0743-7463 - p. 6181 - 6188.
    liquid-liquid interface - beta-casein adsorption - air-water-interface - fluid interfaces - hexadecane/water interface - flexible proteins - drop tensiometer - layers - monolayers - macromolecules
    Dynamic interfacial tensions and surface dilational moduli were measured for four proteins at three fluid interfaces, as a function of time and concentration. The proteins-ß-casein, ß-lactoglobulin, bovine serum albumin, and ovalbumin - were adsorbed from aqueous solution against air, n-tetradecane, and a triacylglycerol oil. The sinusoidal interfacial compression/expansion, at frequencies ranging from 0.005 to 0.5 Hz, was effected in a dynamic drop tensiometer suited to viscous oil phases. Generally, at interfacial pressures up to 15 mN/m, dilational moduli were purely elastic at frequencies from 0.1 Hz. In this elastic range, in-surface relaxation either was essentially completed or had not yet started within a time on the order of 10 s. Within this time span, protein exchange with the bulk solution was negligible. In cases where in-surface relaxation was completed in the imposed time, the moduli depended only on the equilibrium ¿(¿) relationship. We interpret these results in terms of a simple two-dimensional solution model, based on a Gibbs dividing surface, accounting for nonideal mixing to the first order with respect to both entropy and enthalpy. Interfacial mixing enthalpy is shown to have a major effect on the elasticity, with both quantities increasing in the sequence triacylglycerol ¿ tetradecane ¿ air. We also suggest a strong correlation between enthalpy and clean-interface tension that increases in the same order. At each interface, the enthalpy increases with increasing molecular rigidity: ß-casein ¿ ß-lactoglobulin ¿ bovine serum albumin ¿ ovalbumin. Best agreement with the experimental data was obtained with a recently extended version of the model accounting for proteins adopting smaller molecular areas with increasing surface pressure. For interfacial pressures above 15 mN/m, the moduli were generally no longer purely elastic, with viscous loss angles ranging up to 36 degrees. In this range of high pressures, the moduli depended on relaxation mechanisms for which specific kinetic models must be developed
    Wie heeft er baat bij bodeminformatie? Inventarisatie van gebruikers, toepassingen en gewenste typen van bodeminformatie
    Nieuwenhuis, R.H. ; Appelman, J. ; Rietra, R.P.J.J. ; Busink, E.R.V. ; Lucassen, M.A. - \ 2006
    Bodem 16 (2006)3. - ISSN 0925-1650 - p. 91 - 93.
    landgebruik - bodem - bodemfysica - informatiesystemen - bodemkwaliteit - land use - soil - soil physics - information systems - soil quality
    Inventarisatie van gebruikers, toepassingen en gewenste typen van bodeminformatie. Dit in het kader van Landsdekkend Beeld Bodemkwaliteit, sinds januari 2005 BIELLS genaamd: BodemInformatie Essentieel voor Locale en Landelijke Sturing. Het project valt onder het uitvoeringsprogramma van de Beleidsbrief Bodem. De partijen, die onderscheiden zijn (als belanghebbenden) zijn: VROM, LNV, V&W, provincies, gemeenten, natuurorganisaties, landbouworganisaties en waterwinners
    Fat intake in patients newly diagnosed with type 2 diabetes: a 4-year follow-up study in general practice
    Laar, F.A. van de; Lisdonk, E.H. van de; Lucassen, P.L.B.J. ; Tigchelaar, J.M.H. ; Meyboom, S. - \ 2004
    British Journal of General Practice 54 (2004)500. - ISSN 0960-1643 - p. 177 - 182.
    mellitus - risk - diet
    Although treatment targets for the consumption of dietary fat in patients with type 2 diabetes mellitus are well accepted, little is known about the actual fat consumption by newly diagnosed patients or the dietary adjustments that they make in the following years. AIMS: To measure fat intake in patients with type 2 diabetes in general practice at diagnosis, shortly after dietary consultation, and after 4 years. DESIGN OF STUDY: A prospective cohort study. SETTING: Thirty-three general practices in The Netherlands. METHOD: One hundred and forty-four patients with newly diagnosed type 2 diabetes were referred to a dietician, and fat consumption (the main outcome measure) was assessed with a 104-item food frequency questionnaire at diagnosis, 8 weeks following diagnosis, and after 4 years. Reference values for fat consumption were obtained from an age-matched sample of a population-based survey. RESULTS: At diagnosis, total energy intake was 10.6 MJ/day and cholesterol intake was 300 mg/day. Total fat consumption was 40.9% of energy intake, with saturated fatty acids 15.0%, monounsaturated fatty acids 14.3%, and polyunsaturated fatty acids 9.2% of energy intake. All levels, except for polyunsaturated fatty acids, were significantly unfavourable compared with those for the general population. After 8 weeks, consumption of saturated fatty acids had decreased to a lower level than in the general population and all other levels measured were similar to those for the general population. After 4 years there was a slight increase in the consumption of total fat and monounsaturated fatty acids, but cholesterol and saturated fatty acid consumption had decreased further. CONCLUSIONS: Patients with newly diagnosed type 2 diabetes have an unfavourable fat consumption at diagnosis. They adapt to a more desirable consumption shortly after diagnosis, and this improved dietary behaviour is sustained for 4 years. Recommendations regarding consumption of total and saturated fat are, in contrast to those for cholesterol, not met by patients in general practice.
    Neuronal Number, Volume, and Apoptosis of the Left Dentate Gyrus of Chronically Stressed Pigs Correlate Negatively With Basal Saliva Cortisol Levels
    Beek, E.M. van der; Wiegant, V.M. ; Schouten, W.G.P. ; Eerdenburg, F.J.C.M. van; Loijens, L.W.S. ; Plas, C. ; Benning, M.A. ; Vries, H. de; Kloet, E.R. de; Lucassen, P.J. - \ 2004
    Hippocampus 14 (2004)6. - ISSN 1050-9631 - p. 688 - 700.
    pituitary-adrenal axis - chronic psychosocial stress - unipolar major depression - granule cell layer - hippocampal volume - glucocorticoid-receptors - postnatal-development - stereotyped behavior - alzheimers-disease - hypoxia-ischemia
    Although the consequences of stress and hypercortisolemia for the rodent hippocampal dentate gyrus (DG) are well known, little is known about other species. For pigs, tethered housing represents a well-established chronic stressor that shares many similarities with restraint paradigms, as evidenced by profound changes in behavior and autonomic and endocrine dysfunction, including flattened cortisol rhythms and hypercortisolemia all conditions that may threaten hippocampal viability in rat. Here, we studied structural parameters of the porcine DG after 5 months of tethered housing in relation to basal saliva cortisol measured antemortem. We further investigated whether any neuropathology or alterations in apoptosis had occurred in the left hippocampal hemisphere. Stereological analysis revealed high correlations between DG volume and neuron number in individual animals in both hemispheres. Within individual animals, neuron numbers of the left and right lobes were not correlated. Notably, basal cortisol was negatively correlated with volume and neuron number of the left, but not the right DG. Although obvious neuropathology was absent, apoptosis was present in DG and alveus and less so in CA areas. Despite the short window of time during which apoptosis is detectable, their stereologically estimated numbers in the DG, but not in other regions, were negatively correlated with cortisol. In conclusion, our data indicate for the first time a profound lateralization in the relationship between DG structure, apoptosis, and basal cortisol after stress in pigs. Five months of chronic stress failed to induce lasting neuropathology. Although accumulating changes in apoptosis could have contributed to the structural DG alterations, further studies should reveal whether stress has been instrumental, or whether the differences between animals were present from birth onward. The present lateralization after stress is, however, consistent with lateralized hippocampal volume changes in stress-related human disorders and suggests that these effects are not limited to this species alone.
    Static and dynamic properties of proteins adsorbed at liquid interfaces
    Benjamins, J. - \ 2000
    Agricultural University. Promotor(en): J. Lyklema; E.H. Lucassen-Reynders. - S.l. : S.n. - ISBN 9789058083173 - 212
    colloïdale eigenschappen - eiwitten - adsorptie - schuim - emulsies - colloidal properties - proteins - adsorption - foams - emulsions

    The aim of the investigation described in this thesis was to increase the level of understanding of the role that proteins play in the preparation and subsequent stabilisation of foams and emulsions. One aspect of this role is facilitation of break-up, due to surface tension lowering. A second aspect is the formation of a viscoelastic interfacial layer, which affects both the short-term and long-term stability of the dispersion. Therefore, a systematic study of the changes in static and dynamic interfacial properties induced by proteins was carried out.

    For part of this study, dealing with the interfacial rheology, several experimental techniques were used. These techniques were either properly modified existing techniques (Chapter 3, modified longitudinal wave set-up) or newly developed (Chapter 4, Dynamic Drop Tensiometer; Chapter 5, Concentric Ring Surface Shear Rheometer) to meet the requirements for measuring the rheology of adsorbed protein layers at liquid/liquid interfaces. These requirements are (i) isotropic deformation, without leakage of the interfacial layer, for the dilational modulus measurements at air/water and oil/water interfaces and (ii) shear modulus measurements at small oscillatory deformation.

    The proteins chosen for this study wereβ-casein,β-lactoglobulin (BLG), bovine serum albumin (BSA), ovalbumin and lysozyme. This set of proteins was chosen, because they differ considerably in relevant aspects, such as molecular weight, molecular structure and iso-electric point.

    In Chapter 1 the scope and context of this study are given including a brief introduction into (i) the molecular properties of these proteins, that are relevant to the adsorption, (ii) protein adsorption and interfacial rheology, and (iii) the relation between interfacial properties and the properties of emulsions and foams.

    Chapter 2 deals with the adsorption of proteins at the air/water interface. The adsorption was determined by ellipsometry, a method by which not only the adsorbed amount but also the layer thickness and protein concentration in the adsorbed layer could be determined. The ellipsometric studies were combined with surface tension measurements at the same surface.

    All proteins examined show high affinity adsorption, i.e. strong adsorption at low concentration in solution. The initial rate of adsorption of all proteins is well described by a simple diffusion equation. For all proteins examined, the value of the surface pressure (Π) are protein-specific, but otherwise unique, time-independent functions of the adsorption (Γ). Time independence of theΠ(Γ) curve was concluded from the finding thatΠandΓpairs measured at different bulk concentrations and at different stages of adsorption, all collapse into one single curve. In other words, each protein has a unique surface equation of state indicated by its measuredΠ(Γ) curve. This curve reflects the relative rigidity of the protein molecule. For flexible molecules likeβ-casein and PVA ,Γ min (=ΓwhereΠstarts to deviate measurably from zero) is low and from this point onward the surface pressure increases gradually with increasingΓ. For rigid globular proteins (BSA, ovalbumin and lysozyme)Γ min is higher and with further increase of the surface concentration the surface pressure increases steeply. At high protein concentration and long adsorption times, for most proteins multilayer adsorption takes place.

    For ovalbumin, in the pH range 4-8 the effect of pH on theΠ-Γcurve is small, which indicates that electrostatic intermolecular forces do not contribute much to the surface pressure.

    In Chapter 3 a longitudinal wave technique, modified to ensure isotropic surface deformation, was used to determine the dilational modulus,ε, of adsorbed protein layers, at the air/water interface. This modification fully eliminated the complicating shear effects that became apparent in dilational modulus measurements with adsorbed layers of proteins in a conventional set-up.

    For all proteins examined at frequencies in the range from 0.01 to 1 rad/s, the initial part of theε(Π) plot is a straight line through the origin. The slope of this initial part ranges between +4 and +12 . No clear relationship between the slope and the rigidity of the protein molecule was found. However, the extent of this linear range is smaller for the flexible molecules (β-casein and PVA). From the fact that this slope significantly exceeds the ideal value of +1, it must be concluded that the behaviour of the adsorbed layer is far from ideal. In the linear range, the measured moduli coincide with the limiting moduli,ε 0 , calculated from theΠ(Γ) curve. This indicates that the surface pressure adjusts "instantaneously" to the changing adsorption during a compression-expansion cycle in time-scales ranging from 1 to 100 s. This also means that the modulus is purely elastic, i.e. the effect of relaxation processes is negligible. In this elastic range, differences between individual proteins are related to different degrees of non-ideality, reflected in the surface equation of state.

    At higher surface concentrations a relaxation mechanism becomes operative, which is most probably not caused by diffusional exchange between surface and solution. This conclusion is based on calculations of the diffusional transport rate and the theoretical frequency spectrum of the modulus. Relaxation due to conformational changes is plausible. In the visco-elastic regionε≥ε 0 for all proteins examined. This is an extra argument against diffusional exchange.

    The modulus increases in the order: PVA <β-casein

    Chapter 4 describes a new method, the Dynamic Drop Tensiometer, especially suitable for determining the dynamic properties of proteins adsorbed at oil/water interfaces. According to this method, a small drop is subjected to sinusoidal oscillations of its volume. The corresponding area changes produce interfacial tension changes, which are evaluated from measurements of the fluctuating shape of the drop, using the Young-Laplace equation. Compared to the conventional Langmuir trough set-up, this method is particularly suited for liquid/liquid interfaces, because (i) interfacial leakage is fully eliminated and (ii) uniform deformation is ensured even if one of the liquids is a viscous oil. An additional advantage of the method is its short response time. The dynamic properties of adsorbed protein layers at three interfaces (TAG (triacylglycerol)-oil/water, tetradecane/water and air/water) were compared. At the three interfaces, at low protein concentration, the conformation change upon adsorption is fairly fast, occurring within 1 min.. However, at high protein concentration (> 1g/l), during the first minutes after adsorption a situation exists that differs from the equilibriumΠ(Γ) curve. At low interfacial pressures, during a modulus measurement, the adaptation of the conformation is faster (< 1 s.). Non-ideality of the adsorbed layer increases in the sequence TAG-oil < tetradecane < air, which is probably related to a decrease of solution quality for the more hydrophobic amino acids, which decreases in the same sequence. At each of the different interfaces non-ideality increases with increasing rigidity of the protein molecule (β-casein<β-lactoglobulin

    The surface shear properties of adsorbed protein layers are described in Chapter 5. These properties were determined with a newly developed concentric ring surface shear rheometer. The technique allows measurements over a wide range of frequencies and deformations. As the magnitude of the shear deformation markedly affects the shear modulus,μ s , an extrapolation to zero deformation is required to asses the shear properties of the undisturbed surface. Because the surface dilational modulus and the surface shear modulus both increase in the sequence PVA< Na-caseinate s ≥3 indicates that the adsorbed protein layer can be modelled as a thin homogeneous gel layer. Such a model points to a significant ideal monolayer contribution toεat low to medium surface concentrations.

    In Chapter 6 models describing the surface equation of state of adsorbed macromolecules were applied to the experimentalΠ(Γ) curves. These models were also applied to understand the dynamic behaviour of these layers. Statistical models, in which it is assumed that the macromolecules adsorb with all segments in direct contact with the surface, e.g. Singer equation, only explain the very low pressure part of the experimental curves of PVA andβ-casein. To explain the higher pressure part, progressive loop formation and molecular interaction must be accounted for. For rigid globular proteins, simple statistical models are unable to fit any part of the experimental curves, because such molecules only slightly change their conformation upon adsorption and consequently, will adsorb with only a small fraction of the segments at the surface, even at very low pressures.

    A 2-D solution model, which accounts to first order for both entropy and enthalpy, is used to describe the non-ideal behaviour of adsorbed protein layers. This non-ideality was deduced from the highΓneeded to produce a measurableΠand the steep initial slopes of theε(Π) curves.

    All above models need modification to describe the S-shaped part of theΠ(Γ) curves at high surface concentrations. This part of the curve can be described by the Soft Particle concept, which is a modification of the surface equation of state of a 2-D hard sphere fluid. The S-shape is attributed to a decrease of the molecular cross-sectional area with increasing surface concentration. This effect appears to be more pronounced for flexible molecules like PVA andβ-casein than for globular rigid molecules like BSA, ovalbumin and lysozyme. Experimentalε(Π) curves are within the limits that are predicted by this concept. A promising option is combining a molecular compressibility as used in the Soft Particle concept with the 2-D solution model.

    In Chapter 7 it is shown that interfacial properties typical for proteins predict a larger drop size and a lower stability against recoalescence during production compared to low molecular weight (LMW) surfactants.

    In the presence of both types of surfactant, concentrations and conditions can be chosen such that the LMW surfactant determines the dispersion efficiency, while the protein determines the long-term stability. A comparison between the different proteins reveals that, in the production stage, a higher dilational modulus at short times correlates with a faster build-up of stability against recoalescence. For a good long term stability a high dilational modulus of adsorbed protein layers at longer times is more important. In foams, retardation of Ostwald ripening, i.e. the growth of large bubbles at the expense of small ones, is probably the major factor. This mechanism depends on the ratio of the modulus to the surface tension, which ratio is considerably higher for proteins than for LMW surfactants in relevant cases.

    For a measurable shear modulus a high surface concentration is required. Therefore, shear properties may only affect long term stability of emulsions and foams, but not break-up and stability against recoalescence during production.

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