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.

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    Derde Wereld : Speciaal nummer: Reünie van de redactie
    Arts, B.J.M. ; Boekrand, Edith ; Hees, Ted van; Hebinck, Paul ; Hoebink, Paul ; Kesteren, Johan van; Lindert, Paul van; Maasen van den Brink, Monica ; Meeuws, René ; Naerssen, Ton van; Nijpels, Maarten ; Ploeg, Jan Douwe van der; Scheffer, Rudolf ; Toor, Toon van; Velden, Fons van der; Vossen, Jan ; Wesemael-Smit, Lillian van - \ 2019
    Derde Wereld, Een eenmalige uitgave 2019 (2019). - 138 p.
    Temperature responsive polyelectrolyte complexes : Bio-inspired wet-adhesives
    Hees, Ilse Adriënne van - \ 2019
    Wageningen University. Promotor(en): J. van der Gucht; M. Kamperman. - Wageningen : Wageningen University - ISBN 9789463950633 - 182

    For wound closure, adhesives provide many advantages over the use of sutures. However, adhesives are not yet common practice in internal medicine, due to limited adhesive properties in wet conditions, Chapter 1. In this thesis, we developed bio-inspired temperature responsive polyelectrolytes that can be applied as underwater adhesive, and may serve as biomedical adhesive as well.

    A thorough understanding of natural underwater adhesives is needed for bio-mimicry and, therefore, we reviewed the adhesion mechanisms by sandcastle worms and mussels, Chapter 2. Sandcastle worms are marine organisms that build protective shells from minerals found in their surroundings, which are stuck together by adhesive proteins. Before secretion, these proteins are stored in granules in which anionic and cationic macromolecules are combined. Upon combining oppositely charged macromolecules, complex coacervation occurs, which explains the fluidic, yet concentrated, character of the packaged proteins. Mussels adhere through byssal threads and the two proteins closest to the surface are rich in the amino acid L-3,4-dihydroxyphenylalanine (DOPA). Therefore, DOPA is believed to be an adhesion promotor through a versatility of chemical interactions. Moreover, oxidation of DOPA can lead to covalent bonding, which can be used to solidify adhesives. Accordingly, DOPA is often used in the development of underwater adhesives.

    In literature, several examples can be found of adhesives based on electrostatic interactions, which are composed of either recombinant proteins or synthetic polymers. From those articles, we extracted common features important for optimizing adhesive properties, Chapter 2. First, complexation between oppositely charged molecules improves adhesion, because significantly weaker adhesion is obtained when only one of the charged molecules is used. Moreover, multiple charged groups per molecule seem to result in materials with more powerful adhesive properties, than molecules that carry just one unit of charge. Furthermore, the adhesive strength of charged materials is improved upon the addition of catechol groups, such as DOPA, and even further enhanced by oxidation of DOPA after application to the surface. Finally, the inclusion of metal ions for metal coordination, or a second covalent network were also shown to increase the adhesive strength of complex coacervate based materials.

    The adhesive proteins of sandcastle worms contain large amounts of oppositely charged and hydrophobic amino acids, and only limited amounts of DOPA. Therefore, we investigated adhesives based on electrostatic and hydrophobic interactions. The electrostatic interactions originate from oppositely charged polyelectrolytes (polyions) that form fluidic complex coacervates which enable easy application and a large adhesive interface. Solidification of the adhesive is achieved by introducing a thermo-responsive polymer with a lower critical solution temperature (LCST). In aqueous solution, this polymer is soluble at low temperatures, but becomes insoluble upon exceeding the LCST, because hydrophobic interactions become more dominant. As a result, temperature responsive polyelectrolyte complexes gel upon temperature increase.

    The temperature responsive polyelectrolytes were prepared by reversible addition fragmentation chain-transfer (RAFT) polymerization, Chapter 3. Poly(N-isopropylacrylamide)-b-poly(acrylic acid)-b-poly(N-isopropylacrylamide) (PNIPAM-b-PAA-b-PNIPAM) was prepared by deprotection of PNIPAM-b-poly(tert-butyl acrylate)-b-PNIPAM, through a novel deprotection method to obtain complete removal of the tert-butyl groups, yielding anionic AA only. Two polymers with either 20 or 80 mole% NIPAM and a Mw/Mn of ~1.6 were prepared successfully. Moreover, we investigated the synthesis of the cationic PNIPAM-b-poly(dimethylaminoethyl methacrylate)- b-PNIPAM (PNIPAM-b-PDMAEMA-b-PNIPAM). The chain transfer agent and cationic PDMAEMA precursor were successfully synthesized and purified. However, it remained unclear whether extension with temperature responsive NIPAM succeeded. As a result, further investigations are required and we proceeded with commercially available polyactions.

    Micelles are formed by mixing PNIPAM-b-PAA-b-PNIPAM and PNIPAM-b-PDMAEMA, with low PNIPAM contents, in aqueous solutions with various NaCl concentrations, Chapter 4. At low salt, the anionic PAA and cationic PDMAEMA form a complex and become insoluble, while PNIPAM has a temperature dependent solubility. Consequently, complex coacervate core micelles (C3M) with a PNIPAM corona were formed at low temperatures, while the polymers aggregate above the LCST. At high NaCl concentrations, however, the polyelectrolytes are soluble at room temperature because complexation is prevented by salt. Moreover, PNIPAM is salted out and therefore insoluble at any investigated temperature. Accordingly, a PNIPAM core micelle with a polyelectrolyte corona is formed at low temperatures. Upon heating, complex coacervation reoccurs and the polymers aggregate.

    Temperature responsive polyelectrolyte complexes (TERPOC) are prepared in Chapter 5, by mixing PNIPAM-b-PAA-b-PNIPAM and PDMAEMA at various polymer and NaCl concentrations. At low temperatures, concentrated solutions with C3Ms were obtained, whereas heating caused gelation. The resulting TERPOCs are strong, turbid, but somewhat brittle gels because of the high PNIPAM content. Upon gelation, the sample volume is preserved, which is likely caused by the polyelectrolytes, e.g. by forming water pockets. Moreover, charge neutralization by PDMAEMA is required to retrieve strong gels. Furthermore, the strength of the TERPOC and the gelation temperature, Tgel, can be adjusted by altering the salt or polymer concentration. Consequently, the toughest TERPOC was obtained at high salt and polymer concentrations. However, a maximum work of adhesion, Wadh, was achieved for a submerged TERPOC with a lower salt concentration because of a higher Tgel. The Wadh was comparable to many other underwater adhesives, and therefore TERPOCs are a promising element for underwater adhesives.

    It is expected that guanidinium thiocyanate, GndSCN, improves the polymer solubility compared to NaCl, as GndSCN is more weakly hydrated. Therefore, we compared TERPOCs with GndSCN and NaCl, in Chapter 6. Indeed, a higher Tgel and lower cs,cr were observed for GndSCN containing samples which resulted in clear ordered phase symmetries. The TERPOCs adapted a lamellar morphology below cs,cr, while cylinders seemed present above cs,cr. Moreover, considerably lower moduli and peak strains were found, which may be caused by the weaker electrostatic and hydrophobic interactions. Accordingly, varying the salt type is an easy tool to adjust the properties of TERPOCs which is important for adhesive development.

    It was shown that materials with solely electrostatic and hydrophobic interactions can be used as underwater adhesive. To further improve the adhesive properties, it is important to lower the water content, while maintaining the deformability upon application, Chapter 7. This can be achieved by extrusion, by introducing more hydrophobic electrolytes, or by adding hydrophobic moieties into the polymer. Moreover, it can be interesting to introduce more molecular interactions, such as π- π, cation-π, or metal coordination, which can be realized by incorporating aromatic or catechol groups, such as DOPA. In addition, solidification by lowering the salt concentration after application can be explored. Over all, we believe that TERPOCs are a good candidate for the development of underwater adhesives.

    Dietary fibre enrichment of supplemental feed modulates the development of the intestinal tract in suckling piglets
    Hees, H.M.J. Van; Davids, M. ; Maes, D. ; Millet, S. ; Possemiers, S. ; Hartog, L.A. Den; Kempen, T.A.T.G. Van; Janssens, G.P.J. - \ 2019
    Journal of Animal Science and Biotechnology 10 (2019)1. - ISSN 1674-9782
    Dietary fibre - Gut maturation - Gut microbiota - Suckling piglets

    Background: Commercial pre-weaning diets are formulated to be highly digestible and nutrient-dense and contain low levels of dietary fibre. In contrast, pigs in a natural setting are manipulating fibre-rich plant material from a young age. Moreover, dietary fibre affects gastrointestinal tract (GIT) development and health in older pigs. We hypothesised that supplemental diets that contain vegetal fibres are accelerating GIT development in suckling piglets in terms of size and functionality. From d 2 of life, sow-suckled piglets had access to a low fibre diet (CON), a diet with a fermentable long-chain arabinoxylan (lc-AXOS), a diet with a largely non-fermentable purified cellulose (CELL), or a diet containing both fibres. During the initial 2 weeks, the control diet was a high-density milk replacer, followed by a dry and highly digestible creep meal. Upon weaning at 25 d, 15 piglets from each treatment group, identified as eaters and originating from six or seven litters, were sacrificed for post-mortem examination of GIT morphology, small intestinal permeability and metabolic profile of the digesta. The microbiota composition of the mid-colon was evaluated in a sub-set of ten piglets. Results: No major statistical interactions between the fibre sources were observed. Piglets consumed the fibre-containing milk supplements and creep diets well. Stomach size and small intestinal permeability was not affected. Large intestinal fill was increased with lc-AXOS only, while relative large intestinal weight was increased with both fibre sources (P < 0.050). Also, CELL decreased ileal pH and tended to increase ileal DM content compared to CON (P < 0.050). Moreover, the concentration of volatile fatty acids was increased in the caecum (P < 0.100) and mid-colon (P < 0.050) by addition of CELL. lc-AXOS only stimulated caecal propionate (P < 0.050). The microbiota composition showed a high individual variation and limited dietary impact. Nonetheless, CELL induced minor shifts in specific genera, with notable reductions of Escherichia-Shigella. Conclusions: Adding dietary fibres to the supplemental diet of suckling piglets altered large intestinal morphology but not small intestinal permeability. Moreover, dietary fibre showed effects on fermentation and modest changes of microbial populations in the hindgut, with more prominent effects from the low-fermentable cellulose.

    Self-assembly of oppositely charged polyelectrolyte block copolymers containing short thermoresponsive blocks
    Hees, I.A. Van; Swinkels, P.J.M. ; Fokkink, R.G. ; Velders, A.H. ; Voets, I.K. ; Gucht, J. Van Der; Kamperman, M. - \ 2019
    Polymer Chemistry 10 (2019)23. - ISSN 1759-9954 - p. 3127 - 3134.

    The assembly of oppositely charged block copolymers, containing small thermoresponsive moieties, was investigated as a function of salt concentration and temperature. Aqueous solutions of poly-[N-isopropylacrylamide]-b-poly[dimethylaminoethyl methacrylate] (NIPAM44-b-DMAEMA216) and PNIPAM-b-poly[acrylic acid]-b-PNIPAM (NIPAM35-b-AA200-b-NIPAM35) were mixed in equal charge stoichiometry, and analysed by light scattering (LS), NMR spectroscopy and small angle X-ray scattering (SAXS). At room temperature, two different micelle morphologies were found at different salt concentrations. At NaCl concentrations below 0.75 M, complex coacervate core micelles (C3M) with a PNIPAM corona were formed as a result of interpolyelectrolyte complexation. At NaCl concentrations exceeding 0.75 M, the C3M micelles inverted into PNIPAM cored micelles (PCM), containing a water soluble polyelectrolyte corona. This behavior is ascribed to the salt concentration dependence of both the lower critical solution temperature (LCST) of PNIPAM, and the complex coacervation. Above 0.75 M NaCl, the PNIPAM blocks are insoluble in water at room temperature, while complexation between the polyelectrolytes is prevented because of charge screening by the salt. Upon increasing the temperature, both types of micelles display a cloud point temperature (Tcp), despite the small thermoresponsive blocks, and aggregate into hydrogels. These hydrogels consist of a complexed polyelectrolyte matrix with microphase separated PNIPAM domains. Controlling the morphology and aggregation of temperature sensitive polyelectrolytes can be an important tool for drug delivery systems, or the application and hardening of underwater glues.

    Reduced Feed Intake, Rather than Increased Energy Losses, Explains Variation in Growth Rates of Normal-Birth-Weight Piglets
    Erp, Rik J.J. van; Hees, Hubert M.J. van; Zijlstra, Ruurd T. ; Kempen, Theo A.T.G. van; Klinken, Jan Bert van; Gerrits, Walter J.J. - \ 2018
    The Journal of Nutrition 148 (2018)11. - ISSN 0022-3166 - p. 1794 - 1803.
    Background: Substantial variation in growth rates exists in normal-birth-weight piglets, possibly due to differences in energy efficiency. Within this population, slow growth rates are associated with reduced insulin sensitivity. Slowly digestible starch (SDS) may improve growth efficiency in slowly growing pigs, because it reduces postprandial blood glucose.Objective: The aim of this study was to investigate maintenance energy requirements and efficiency of energy used for growth (incremental energy efficiency) of slow-growing or fast-growing piglets (SG-pigs and FG-pigs, respectively) with equal birth weight that were fed either an SDS or a rapidly digestible-starch (RDS) diet.Methods: Sixteen groups of either five 10-wk-old SG-pigs (mean ± SD: 11.3 ± 1.4 kg) or FG-pigs (15.1 ± 1.7 kg) were housed in climate respiration chambers and fed diets containing 40% RDS or SDS for 2 wk. In week 1, feed was available ad libitum. In week 2, feed supply was restricted to 65% of the observed weekly averaged feed intake [kJ · kg body weight (BW)-0.6 · d-1] in week 1. After week 2, pigs were feed deprived for 24 h, after which heat production was determined. Energy balances, apparent total tract digestibility (ATTD), and incremental energy efficiencies were calculated and analyzed using a general linear model.Results: Gross energy intake (kJ · kg BW-0.6 · d-1) was 4% greater (P = 0.047) for FG-pigs than for SG-pigs. ATTD of fat was 6%-units greater (P = 0.003) for RDS-fed than for SDS-fed pigs. Fasting heat production and incremental energy efficiencies did not differ between pig types or diets. Incremental use of metabolizable energy for fat retention was 2% units (P = 0.054) greater for RDS-fed than SDS-fed pigs.Conclusions: A lower energy intake rather than greater maintenance requirements or lower energy efficiency explains the slow growth of SG-pigs. Incremental RDS intake increased fat deposition more than SDS, whereas energy efficiency was not affected. Thus, feeding SDS instead of RDS does not improve growth efficiency but may result in slightly leaner pigs.
    Rapid and Quantitative De- tert-butylation for Poly(acrylic acid) Block Copolymers and Influence on Relaxation of Thermoassociated Transient Networks
    Filippov, Alexei D. ; Hees, Ilse A. van; Fokkink, Remco ; Voets, Ilja K. ; Kamperman, Marleen - \ 2018
    Macromolecules 51 (2018)20. - ISSN 0024-9297 - p. 8316 - 8323.

    The synthesis of charged polymers often requires the polymerization of protected monomers, followed by a polymer-analogous reaction to the polyelectrolyte product. We present a mild, facile method to cleave tert-butyl groups from poly(tert-butyl acrylate) blocks that yields poly(acrylic acid) (pAA) blocks free of traces of the ester. The reaction utilizes a slight excess of HCl in hexafluoroisopropanol (HFIP) at room temperature and runs to completion within 4 h. We compare deprotection in HFIP with the common TFA/DCM method and show that the latter does not yield clean pAA. We show the effect of complete tert-butyl cleavage on a ABA triblock copolymer, where poly(N-isopropylacrylamide) (pNIPAM) is A and pAA is B, by means of viscosimetry, DLS, and SAXS on solutions above overlap. The pNIPAM blocks dehydrate, and their increased self-affinity above the lower critical solution temperature (LCST) results in network formation by the triblocks. This manifests itself as an increase in viscosity and a slowing down of the first-order correlation function in light scattering. However, this stickering effect manifests itself exclusively when the pAA block is tert-butyl-free. Additionally, SAXS shows that the conformational properties of tert-butyl-free pAA copolymers are markedly different from those with residual esters. Thus, we illustrate a surprising effect of hydrophobic impurities that act across blocks and assert the usefulness of HCl/HFIP in pAA synthesis.

    Functional Polymeric Materials Inspired by Geckos, Mussels, and Spider Silk
    Yang, Juan ; Włodarczyk-Biegun, Małgorzata K. ; Filippov, Alexei ; Akerboom, Sabine ; Dompé, Marco ; Hees, Ilse A. van; Mocan, Merve ; Kamperman, Marleen - \ 2018
    Macromolecular Chemistry and Physics 219 (2018)16. - ISSN 1022-1352
    Adhesives - Bioinspiration - Biomaterials - Coatings - Polymer science

    Nature has developed elegant and economical strategies to produce materials that are well-adapted to their purposes. As biology evolved to remarkable and complex designs, synthetic mimics are evolving toward new levels of complexity achieving larger combinations of properties within one material. The field of bioinspiration encompasses a wide range of advanced materials ranging from biooptics to energy materials, to biomaterials. In this paper an overview is given of selected recent developments in the field of bioinspired material design focusing on gecko-inspired adhesives, mussel-inspired coatings, and spider silk-inspired biomaterials.

    Effects of reduced intramammary antimicrobial use during the dry period on udder health in Dutch dairy herds
    Vanhoudt, A. ; Hees-Huijps, K. van; Knegsel, A.T.M. van; Sampimon, O.C. ; Vernooij, J.C.M. ; Nielen, M. ; Werven, T. van - \ 2018
    Journal of Dairy Science 101 (2018)4. - ISSN 0022-0302 - p. 3248 - 3260.
    antimicrobial - dairy cow - dry period - selective dry cow therapy - udder health
    Dry cow therapy (DCT) in the Netherlands changedfrom mainly blanket to selective antimicrobial DCT.This transition was supported by a national guideline,with the individual somatic cell count (SCC) at thelast milk recording before dry-off as the main selectioncriterion for antimicrobial DCT. The aim of this retrospectiveobservational study is to evaluate the SCCdynamics during the dry period at the herd and individualdry period level following the national transitionfrom mainly blanket to selective antimicrobial DCT.At the herd level, we used 2 data sets to evaluate theSCC dynamics during the dry period: (1) a nationaldata set containing 3,493 herds with data availablefrom 2011 through 2015 and (2) a veterinary practicedata set containing 280 herds with data available from2013 through 2015. The herd level analysis was carriedout using key performance indicators provided via milkrecording (CRV, Arnhem, the Netherlands): the percentageof cows that developed a new intramammaryinfection (IMI) during the dry period and the percentageof cows cured of an IMI during the dry period.The effect of DCT at individual dry period level wasanalyzed with a mixed-effects logistic regression modelbased on 4,404 dry periods from 2,638 cows in 20 herdswithin the veterinary practice data set. For these 20herds, individual SCC data from milk recordings andindividual cow DCT were available from 2013 through2015. No significant changes were observed to the SCCdynamics during the dry period at the herd level. Thepercentage of cows that developed a new IMI duringthe dry period ranged between 16 and 18%, and thepercentage of cows cured from an IMI during the dryperiod ranged between 74 and 76%. At the individual dry period level, a low SCC at the first milk recordingfollowing a dry period was associated with the use ofintramammary antimicrobial DCT with or without theconcurrent use of an intramammary teat sealer [oddsratio (OR) = 2.16 and OR = 2.07, respectively], the useof DCT with an intramammary teat sealer only (OR =1.35), and a low SCC at the last milk recording beforedry-off (OR = 1.78). This study demonstrates that theselection of cows for DCT without antimicrobials basedon SCC thresholds at the last milk recording is possiblewithout significant changes to udder health andreduced the use of antimicrobials.
    Bioinspired Underwater Adhesives by Using the Supramolecular Toolbox
    Hofman, Anton H. ; Hees, Ilse A. van; Yang, Juan ; Kamperman, Marleen - \ 2018
    Advanced Materials 30 (2018)19. - ISSN 0935-9648 - 38 p.
    Adhesion - Bioinspired materials - Mussels - Sandcastle worms - Supramolecular chemistry
    Nature has developed protein-based adhesives whose underwater performance has attracted much research attention over the last few decades. The adhesive proteins are rich in catechols combined with amphiphilic and ionic features. This combination of features constitutes a supramolecular toolbox, to provide stimuli-responsive processing of the adhesive, to secure strong adhesion to a variety of surfaces, and to control the cohesive properties of the material. Here, the versatile interactions used in adhesives secreted by sandcastle worms and mussels are explored. These biological principles are then put in a broader perspective, and synthetic adhesive systems that are based on different types of supramolecular interactions are summarized. The variety and combinations of interactions that can be used in the design of new adhesive systems are highlighted.
    Short communication : insoluble fibres in supplemental pre-weaning diets affect behaviour of suckling piglets
    Clouard, C. ; Stokvis, L. ; Bolhuis, J.E. ; Hees, H.M.J. van - \ 2018
    Animal 12 (2018)2. - ISSN 1751-7311 - p. 329 - 333.
    cellulose - dietary fibre - manipulative behaviours - mastication - pigs
    We investigated the effect of offering supplementary dietary fibres to suckling piglets on their behaviour and performance before weaning. From 5 to 22 days of age, suckling piglets were offered a high-fibre diet (HF; 5% cellulose; n=5 litters), or a control low-fibre diet (n=5 litters). Piglets were housed with the sows in individual farrowing pens, and had access to maternal milk until weaning, at 23 days of age. Behaviours of six focal piglets per pen were scored at 6, 16 and 21 days of age. All piglets were individually weighed at 5, 15 and 20 days of age and feed intake was measured daily at the pen level. Piglets on the HF diet were more active than controls (P=0.05), and spent more time suckling or massaging the udder (P=0.01) and interacting with pen mates (P=0.008). Time spent manipulating pen mates, which may reflect re-directed foraging activity in the absence of substrate, accounted for most of the time spent interacting with pen mates (⩾73% of total time spent interacting). Dietary fibres had no effect on BW and feed intake. In conclusion, inclusion of cellulose in the supplemental diet of suckling piglets affects behaviour, with no deleterious effects on performance before weaning.
    Nutritional strategies to establish a responsible use of antibiotics in swine
    Hartog, L.A. den; Hees, H. van; Ferguson, N. ; Smits, C. - \ 2017
    In: Proceedings Banff Pork Seminar. - University of Alberta (Advances in Pork Production ) - p. 177 - 188.
    Fruitteeltkundige evaluatie onderstammen Xenia : 2de productiejaar (2017)
    Ravesloot, M.B.M. ; Steeg, Pieter van der; Sluis, B.J. van der; Anbergen, R.H.N. ; Hees, D. van; Peeters, Jan - \ 2017
    Effect of the rate of starch digestion on energy metabolism in low and high performing pigs
    Erp, Rik van; Hees, H. van; Zijlstra, Ruurd ; Gerrits, W.J.J. - \ 2016
    The effect of the rate of starch digestion on energy efficiency in low and high performing piglets
    Erp, Rik van; Hees, H. van; Zijlstra, Ruurd ; Gerrits, W.J.J. - \ 2016
    In: Energy and protein metabolism and nutrition. - Wageningen Academic Publishers (EAAP publication 137) - ISBN 9789086862863 - p. 167 - 168.
    Differences in growth performance of piglets during lactation might be related to differences in insulin sensitivity. Therefore glucose metabolism may be affected differently in low performing (LP) and high performing pigs (HP) at weaning when feeding either a slowly digestible starch (SDS) or rapidly digestible starch (RDS). In a 2×2 factorial block design 30 LP pigs and 30 HP pigs equal
    in birth weight were housed in one of four respiration chambers and fed diets containing either RDS or SDS. In the first week feed was available ad libitum. In the second week feed supply was restricted to 65% of the observed feed intake in the first week. Energy and nitrogen balances were calculated for both weeks. Results were used to calculate incremental efficiencies of gross energy
    (GE) and metabolised energy (ME) for growth. Incremental efficiency of GE for growth was higher when feeding RDS compared with SDS, particularly so in LP pigs (diet×pig type; P=0.05). The incremental efficiency of ME for growth tended to be lower with SDS compared with RDS (74.1 vs 75.6; P=0.05) but was not affected by growth retardation during lactation.
    The effect of the rate of starch digestion on diurnal heat production and RQ in low and high performing piglets
    Erp, Rik van; Hees, H. van; Zijlstra, Ruurd ; Gerrits, W.J.J. - \ 2016
    In: Energy and protein metabolism and nutrition. - Wageningen Academic Publishers (EAAP publication 137) - ISBN 9789086862863 - p. 217 - 218.
    Fruitteeltkundige evaluatie onderstammen Xenia® : 1ste productiejaar (2016)
    Ravesloot, M.B.M. ; Peeters, Jan ; Anbergen, R.H.N. ; Hees, Dirk van; Steeg, Pieter van der; Sluis, B.J. van der - \ 2016
    Supplementation of piglets with nutrient-dense complex milk replacer improves intestinal development and microbial fermentation
    Greeff, A. de; Resink, J.W. ; Hees, H.M.J. van; Ruuls, L. ; Klaassen, G.J. ; Rouwers, S.M.G. ; Stockhofe-Zurwieden, N. - \ 2016
    Journal of Animal Science 94 (2016)3. - ISSN 0021-8812 - p. 1012 - 1019.
    Circular intestinal growth - Gene expression - Gut health - Nutrient-dense complex milk replacer - Pig

    Weaning of piglets causes stress due to environmental, behavioral, and nutritional stressors and can lead to postweaning diarrhea and impaired gut development. The diet changes experienced during weaning require extensive adaptation of the digestive system. A well-developed piglet that had creep-feed experience before weaning performs better after weaning. In the current study, the effect of providing sow-fed piglets with a supplemental nutrient-dense complex milk replacer (NDM) on gut development and growth performance was studied. Litters of sows with similar parities (3.6 ± 0.8) and similar numbers of live born piglets (13.5 ± 0.3) were assigned to 1 of 2 groups: 1 group of piglets had ad libitum access to NDM from Day 2 through 21 after birth, whereas the other group was used as controls. Nutrient-dense complex milk replacer–fed piglets were shown to be significantly heavier after 21 d of supplementation compared with the control piglets. At Day 21, 3 piglets from each litter were euthanized for morphological and functional analyses of the intestinal tract. The small intestines of NDM-fed piglets had significantly higher weights (g) as well as significantly higher relative weight:length ratios (g//cm) compared with the small intestines of control piglets (P <0.05). Morphometric analysis demonstrated that villi length and numbers of goblet cells did not differ between groups. However, NDM-fed piglets had deeper crypts (P <0.001) and an increased expression of the cell-proliferation marker proliferating cell nuclear antigen in crypts (P <0.05), suggesting higher cell-proliferation rates. The gene encoding IGF- 1 showed a tendency to higher gene expression in the jejunum from NDM-fed piglets (P = 0.07) compared with the jejunum from control piglets, suggesting that IGF-1 might be involved in the regulation of cell proliferation and intestinal growth. Finally, as a result of dietary fiber in NDM, piglets showed significantly increased concentrations of metabolic fermentation products. This suggests differences in metabolic activity in the colon between treatment groups. In conclusion, providing sow-fed piglets with NDM before weaning stimulates intestinal proliferation, leading to increased circular growth. Nutrient-dense complex milk replacer supplementation might, therefore, help piglets through the transition period at weaning by increased BW and increased capacity for uptake of nutrients.

    Heparin as a Bundler in a Self-Assembled Fibrous Network of Functionalized Protein-Based Polymers
    Wlodarczyk-Biegun, Gosia ; Slingerland, Cornelis J. ; Werten, Marc W.T. ; Hees, Ilse A. van; Wolf, Frits A. de; Vries, Renko de; Cohen Stuart, Martien ; Kamperman, Marleen - \ 2016
    Biomacromolecules 17 (2016)6. - ISSN 1525-7797 - p. 2063 - 2072.

    Nature shows excellent control over the mechanics of fibrous hydrogels by assembling protein fibers into bundles of well-defined dimensions. Yet, obtaining artificial materials displaying controlled bundling remains a challenge. Here, we developed genetically engineered protein-based polymers functionalized with heparin-binding KRSR domains and show controlled bundling using heparin as a binder. The protein polymer forms fibers upon increasing the pH to physiological values and at higher concentrations fibrous gels. We show that addition of heparin to the protein polymer with incorporated KRSR domains, induces bundling, which results in faster gel formation and stiffer gels. The interactions are expected to be primarily electrostatic and fiber bundling has an optimum when the positive charges of KRSR are approximately in balance with the negative charges of the heparin. Our study suggests that, generally, a straightforward method to control the properties of fibrous gels is to prepare a fiber former with specific binding domains and then simply adding an appropriate amount of binder.

    Sense and Non-Sense of Local–Global Food Chain Comparison, Empirical Evidence from Dutch and Italian Pork Case Studies
    Oostindie, Henk ; Broekhuizen, Rudolf Van; Roest, Kees De; Belletti, Giovanni ; Arfini, Filippo ; Menozzi, Davide ; Hees, Eric - \ 2016
    Sustainability 8 (2016)4. - ISSN 2071-1050
    Priority setting between local versus global food chains continues to be subject of debate among food, rural and agricultural scholars with an interest in how to support more sustainable food provision and consumption patterns. Recently the FP7 European GLAMUR project targeted to assess and compare the performances of local versus global food chains in a systematic way covering multiple performance dimensions. Especially drawing on empirical research on the performances of three Italian and three Dutch pork chains, it will be argued that meaningful performance comparison needs to acknowledge the complex, multi-facetted and time and place specific interaction patterns between (more) global and (more) local pork chains. Therefore, as regards these pork chains, local–global performance comparison is thought to have hardly significance in isolation from complementary “horizontal” (place-based) and “circular” (waste or by-product valorization oriented) assessments. As will be concluded, this methodological complexity of food chain performance comparison doesn’t allow for simple statements regarding the pros and cons of (more) global versus (more) local pork chains. Hence, it is recommended to avoid such less fruitful local–global dichotomy and to concentrate on more policy relevant questions as: how to facilitate fundamentally different resource-use-efficiency strategies and how to optimize the place-specific interaction between more “local” versus more “global” food systems?
    Essential amino acids in the gluten-free diet and serum in relation to depression in patients with celiac disease
    Hees, Nathalie J.M. van; Giltay, E.J. ; Tielemans, S.M.A.J. ; Geleijnse, J.M. ; Puvill, Thomas ; Janssen, Nadine ; Does, Willem van der - \ 2015
    Coeliac disease - gluten intolerance - psychopathology - depression - diet adherence - gluten-free diet - amino acids - tryptophan - tyrosine - Trp/LNAA ratio
    Introduction: Celiac disease (CD) is associated with an increased risk of major depressive disorder, possibly due to deficiencies in micronutrients in the gluten-free diet. We aimed to investigate whether essential amino acids (i.e., the precursors of serotonin, dopamine and other neurotransmitters) are depleted in the diet and serum of CD patients with major depressive disorder. Methods: In a cross-sectional study we assessed dietary intake of amino acids and serum levels of amino acids, including in 77 CD patients on a gluten-free diet and in 33 healthy controls. , major depressive disorder was assessed with structured interviews (using the Mini International Neuropsychiatric Interview Plus). Dietary intake of amino acids was assessed (using a 203-item food frequency questionnaire), and serum levels of amino acids were assessed. Results: Participants had a mean age of 55 years and 74% were women. The intake of vegetable protein was significantly lower in CD patients than in healthy controls (mean difference of 7.8 g/d; 95% CI: 4.7 - 10.8), as were serum concentrations of tyrosine, phenylalanine and tryptophan (all p < 0.005). However, within the CD patient groups, the presence of major depressive disorder (n = 42) was not associated with intake or serum levels of essential amino acids. Conclusions: We found that patients with CD on a long-term successful gluten-free diet, with good adherence, consume significantly less vegetable protein than controls, and their serum levels of several essential amino acids were also lower in CD versus controls. Despite its potential adverse effect, intake and serum levels of essential amino acids were not related to major depression.
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