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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    Swimming-induced exercise promotes hypertrophy and vascularization of fast skeletal muscle fibres and activation of myogenic and angiogenic transcriptional programs in adult zebrafish
    Palstra, A.P. ; Rovira, M. ; Rizo-Roca, D. ; Torrella, J.R. ; Spaink, H.P. ; Planas, J.V. - \ 2014
    BMC Genomics 15 (2014). - ISSN 1471-2164 - 47 p.
    satellite cell - gene-expression - danio-rerio - muscular-dystrophies - molecular regulation - cluster-analysis - axial muscle - growth - mass - atrophy
    Background The adult skeletal muscle is a plastic tissue with a remarkable ability to adapt to different levels of activity by altering its excitability, its contractile and metabolic phenotype and its mass. We previously reported on the potential of adult zebrafish as a tractable experimental model for exercise physiology, established its optimal swimming speed and showed that swimming-induced contractile activity potentiated somatic growth. Given that the underlying exercise-induced transcriptional mechanisms regulating muscle mass in vertebrates are not fully understood, here we investigated the cellular and molecular adaptive mechanisms taking place in fast skeletal muscle of adult zebrafish in response to swimming. Results Fish were trained at low swimming speed (0.1 m/s; non-exercised) or at their optimal swimming speed (0.4 m/s; exercised). A significant increase in fibre cross-sectional area (1.290¿±¿88 vs. 1.665¿±¿106 µm2) and vascularization (298¿±¿23 vs. 458¿±¿38 capillaries/mm2) was found in exercised over non-exercised fish. Gene expression profiling by microarray analysis evidenced the activation of a series of complex transcriptional networks of extracellular and intracellular signaling molecules and pathways involved in the regulation of muscle mass (e.g. IGF-1/PI3K/mTOR, BMP, MSTN), myogenesis and satellite cell activation (e.g. PAX3, FGF, Notch, Wnt, MEF2, Hh, EphrinB2) and angiogenesis (e.g. VEGF, HIF, Notch, EphrinB2, KLF2), some of which had not been previously associated with exercise-induced contractile activity. Conclusions The results from the present study show that exercise-induced contractile activity in adult zebrafish promotes a coordinated adaptive response in fast muscle that leads to increased muscle mass by hypertrophy and increased vascularization by angiogenesis. We propose that these phenotypic adaptations are the result of extensive transcriptional changes induced by exercise. Analysis of the transcriptional networks that are activated in response to exercise in the adult zebrafish fast muscle resulted in the identification of key signaling pathways and factors for the regulation of skeletal muscle mass, myogenesis and angiogenesis that have been remarkably conserved during evolution from fish to mammals. These results further support the validity of the adult zebrafish as an exercise model to decipher the complex molecular and cellular mechanisms governing skeletal muscle mass and function in vertebrates.
    Isoflavone metabolism in domestic fcats (Felis catus): comparison of plasma metabolites detected after ingestion of two different dietary forms of genistein daidzein
    Whitehouse-Tedd, K. ; Cave, N.J. ; Ugarte, C.E. ; Waldron, L.A. ; Prasain, J.K. ; Arabshahi, A. ; Barnes, S. ; Hendriks, W.H. ; Thomas, D.G. - \ 2013
    Journal of Animal Science 91 (2013)3. - ISSN 0021-8812 - p. 1295 - 1306.
    deficient acetaminophen glucuronidation - soy isoflavones - human urine - biliary-excretion - phyto-estrogens - food-intake - adult cats - bioavailability - phytoestrogens - mass
    Some felid diets contain isoflavones but the metabolic capacity of cats towards isoflavones is relatively unknown, despite the understanding that isoflavones have divergent biological potential according to their metabolite end-products. The objective of this study was to determine the plasma metabolites detectable in domestic cats after exposure to 2 different dietary forms of isoflavones, either as a soy extract tablet (n = 6) or as part of a dietary matrix (n = 4). Serial blood samples were collected after isoflavone exposure to identify the plasma metabolites of each cat. Genistein was detected in its unconjugated form or as a monosulfate. Daidzein was detected as both a mono- and di-sulfate, as well as in its unconjugated form. Other daidzein metabolites detected included equol mono- and di-sulfate, dihydrodaidzein, and O-desmethylangolensin. No ß-glucuronide metabolites of either isoflavone were detected. Equol was produced in markedly fewer cats after ingestion of a soy extract tablet as a single oral bolus compared to cats consuming an isoflavone-containing diet. The detectable metabolites of the isoflavones, genistein, and daidzein in domestic cat plasma after dietary ingestion may have been described in the present study for the first time. The metabolic capacity for isoflavones by domestic cats appears to be efficient, with only minimal proportions of the ingested amount detected in their unconjugated forms. This has implications for the potential of isoflavones to exert physiological activity in the domestic cat when consumed at concentrations representative of dietary intake.
    Protein supplementation augments the adaptive response of skeletal muscle to resistance-type exercise training: a meta-analysis
    Cermak, N.M. ; Res, P.T. ; Groot, C.P.G.M. de; Saris, W.H.M. ; Loon, L.J.C. van - \ 2012
    American Journal of Clinical Nutrition 96 (2012)6. - ISSN 0002-9165 - p. 1454 - 1464.
    amino-acid supplementation - body-composition - dietary-protein - whey-protein - older men - dose-response - fiber adaptations - muscular strength - elderly-men - mass
    Background: Protein ingestion after a single bout of resistance-type exercise stimulates net muscle protein accretion during acute postexercise recovery. Consequently, it is generally accepted that protein supplementation is required to maximize the adaptive response of the skeletal muscle to prolonged resistance-type exercise training. However, there is much discrepancy in the literature regarding the proposed benefits of protein supplementation during prolonged resistance-type exercise training in younger and older populations. Objective: The objective of the study was to define the efficacy of protein supplementation to augment the adaptive response of the skeletal muscle to prolonged resistance-type exercise training in younger and older populations. Design: A systematic review of interventional evidence was performed through the use of a random-effects meta-analysis model. Data from the outcome variables fat-free mass (FFM), fat mass, type I and II muscle fiber cross-sectional area, and 1 repetition maximum (1-RM) leg press strength were collected from randomized controlled trials (RCTs) investigating the effect of dietary protein supplementation during prolonged (>6 wk) resistance-type exercise training. Results: Data were included from 22 RCTs that included 680 subjects. Protein supplementation showed a positive effect for FFM (weighted mean difference: 0.69 kg; 95% CI: 0.47, 0.91 kg; P <0.00001) and 1-RM leg press strength (weighted mean difference: 13.5 kg; 95% CI: 6.4, 20.7 kg; P <0.005) compared with a placebo after prolonged resistance-type exercise training in younger and older subjects. Conclusion: Protein supplementation increases muscle mass and strength gains during prolonged resistance-type exercise training in both younger and older subjects.
    II. Economic assessment for first generation green biorefinery (GBR) : scenarios for an Irish GBR blueprint
    O'Keeffe, S. ; Schulte, R.P.O. ; Sanders, J.P.M. ; Struik, P.C. - \ 2012
    Biomass and Bioenergy 41 (2012). - ISSN 0961-9534 - p. 1 - 13.
    energy crops - lactic-acid - biomass - grasslands - forages - mass
    Green biorefinery (GBR) is an alternative use of grassland biomass. GBR involves applying technology to chemically and physically fractionate (split) biomass such as grass and grass silage to produce marketable products. Three GBR system models were developed in a companion paper to determine, using scenario analysis, the most technically feasible scenario for the development of a blueprint Irish GBR system. The three GBR system models were a combination of feedstock system and biorefinery technology: Grass/silage – basic technology (GS), Silage – basic technology (S) and Silage – advanced technology (AT). The models were then assessed at different input volumes. The focus of this paper is on the development of the economic modelling component of the three GBR system models in order to identify which of the previously selected GBR scenarios is the most technically and economically viable to develop a blueprint for a first generation GBR. Six scenarios were assessed in this paper. The GS, S and AT GBR systems, at two input volume rates: medium volume and low volume. Additional scenario analyses were also carried out to investigate two possible production scenarios "No Prot" (fibre product only), and "Prot" (includes proteinaceous secondary product). Both the economic and technical scenario analyses of this paper and its companion paper suggest the most appropriate GBR systems for a first generation Irish blueprint are the combination of Silage feedstock – basic biorefinery technology (S), at the medium input volume and both "Prot" and "No Prot" systems
    A novel photocatalytic conversion of Tryptophan to Kynurenine using black light as a light source
    Hamdy Mohamed Saad, M.S. ; Scott, E.L. ; Carr, R.H. ; Sanders, J.P.M. - \ 2012
    Catalysis Letters 142 (2012)3. - ISSN 1011-372X - p. 338 - 344.
    amino-acids - human lens - photooxidation products - wool proteins - photochemistry - constituents - degradation - ozone - mass
    The photocatalytic conversion of an aqueous solution of l-tryptophan (Trp) to kynurenine (KN) was investigated under the illumination of different light sources. Results show that Trp converted to KN with a selectivity of 64% under the illumination of a medium pressure (MP) Hg lamp. KN selectivity was increased to >90% when black light (BL) was used a light source. The novel use of BL in the photocatalytic conversion of Trp to KN significantly reduces the energy consumption compared with MP light
    Effect of oxygen concentration on the growth of Nannochloropsis sp. at low light intensity
    Raso, S. ; Genugten, B. van; Vermuë, M.H. ; Wijffels, R.H. - \ 2012
    Journal of Applied Phycology 24 (2012)4. - ISSN 0921-8971 - p. 863 - 871.
    eicosapentaenoic acid - inorganic carbon - reactors - mass - photobioreactors - optimization - temperature - metabolism - microalgae - outdoors
    In large-scale microalgal production in tubular photobioreactors, the build-up of O2 along the tubes is one of the major bottlenecks to obtain high productivities. Oxygen inhibits the growth, since it competes with carbon dioxide for the Rubisco enzyme involved in the CO2 fixation to generate biomass. The effect of oxygen on growth of Nannochloropsis sp. was experimentally determined in a fully controlled flat-panel photobioreactor operated in turbidostat mode using an incident photon flux density of 100 µmol photons m-2 s-1 and with only the oxygen concentration as variable parameter. The dissolved oxygen concentration was varied from 20 to 250% air saturation. Results showed that there was no clear effect of oxygen concentration on specific growth rate (mean of 0.48¿±¿0.40 day-1) upon increasing the oxygen concentration from 20% to 75% air saturation. Upon further increasing the oxygen concentration, however, a linear decrease in specific growth rate was observed, ranging from 0.48¿±¿0.40 day-1 at a dissolved oxygen concentration of 75% air saturation to 0.18¿±¿0.01 day-1 at 250% air saturation. In vitro data on isolated Rubisco were used to predict the quantum yield at different oxygen concentrations in the medium. The predicted decrease in quantum yield matches well with the observed decrease that was measured in vivo. These results indicate that the effect of oxygen on growth of Nannochloropsis sp. at low light intensity is only due to competitive inhibition of the Rubisco enzyme. At these sub-saturating light conditions, the presence of high concentrations of oxygen in the medium induced slightly higher carotenoid content, but the increased levels of this protective antioxidant did not diminish the growth-inhibiting effects of oxygen on the Rubisco.
    Effect of differences in tendon properties on functionality of the passive stay apparatus in horses
    Gussekloo, S.W.S. ; Lankester, J. ; Kersten, W. ; Back, W. - \ 2011
    American Journal of Veterinary Research 72 (2011)4. - ISSN 0002-9645 - p. 474 - 483.
    elastic energy-storage - mechanical-properties - flexor - forelimbs - limb - locomotion - ligaments - step - mass
    Objective—To determine the effect of differences in structural and mechanical tendon properties on functionality of the passive stay apparatus in horses. Sample—5 forelimbs each from nondwarf Friesians, dwarf Friesians, and ponies. Procedures—Harvested forelimbs were loaded to test the passive stay apparatus. Tendons that stabilize the distal portion of the limb (superficial digital flexor tendon, deep digital flexor tendon, and tendo interosseus [suspensory ligament]) were isolated, and force-elongation data were obtained. Bone lengths, initial tendon lengths, and initial tendon cross-sectional areas were measured, and Young moduli were calculated. A model was used to determine whether joint angles could be explained by these 4 factors only. Results—Dwarf limbs were unable to stand passively under loading because tendons that prevent overextension of the distal limb joints were too long and compliant to prevent over-extension. Tendon properties of limbs of nondwarf Friesians appeared to be intermediate between those of ponies and dwarf Friesians. Conclusions and Clinical Relevance—Dysfunction of the passive stay apparatus in dwarf Friesians could be related to differences in structural and material properties of the tendons that result in hyperextension of the joints under loading. Nondwarf Friesians had intermediate tendon properties, which might be a breed-specific variation. Results indicated that certain tendon properties were associated with load failure of the stay apparatus and provided additional information about the functionality and requirements of the passive stay apparatus.
    Comparative proteomic profiling of 2 muscles from 5 different pure pig breeds using surface-enchanced laser desorption/ionization time-of-flight proteomics technology
    Mach Casellas, N. ; Keuning, E. ; Kruijt, L. ; Hortós, M. ; Arnau, J. ; Pas, M.F.W. te - \ 2010
    Journal of Animal Science 88 (2010)4. - ISSN 0021-8812 - p. 1522 - 1534.
    pietrain-sired pigs - seldi-tof-ms - meat quality - rearing environment - growth - duroc - mass - semimembranosus - proteins - lumborum
    The objectives of this study were to evaluate the influence of different pure pig breeds and muscle types on the expression of muscle proteins, as well as their interactions, and second, to find biomarkers for breed and muscle types. A total of 126 male pigs, including 43 Landrace, 21 Duroc, 43 Large White, 13 Pietrain, and 6 Belgian Landrace, were slaughtered at the age of 174 ± 6 d. Samples from the semimembranosus muscle (SM) and LM were collected 24 h postmortem. Proteomic spectra were generated on an anion exchanger (Q10), a cation exchanger (CM10), and on immobilized metal affinity capture (IMAC30) ProteinChip arrays and analyzed using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry ProteinChip techniques. Breed and muscle type did not affect the number of peaks per spectrum but, interestingly, affected the average intensity of the peaks. Of these peaks, a total of 4 proved to be potential protein biomarkers to differentiate LM or SM muscles, and 2 to classify specific breed types. Additionally, several peaks influenced by the interaction between muscle and breed types could correctly classify pig muscles according to their breed. Further studies need to be carried out to validate and identify these potential protein biomarkers for breed and muscle types in finishing pigs
    Soil resource supply influences faunal size–specific distributions in natural food webs
    Mulder, C. ; Hollander, H.A. Den; Vonk, J.A. ; Rossberg, A.G. ; Jagers op Akkerhuis, G.A.J.M. ; Yeates, G.W. - \ 2009
    Naturwissenschaften 96 (2009)7. - ISSN 0028-1042 - p. 813 - 826.
    body-size - numerical abundance - community structure - nematode community - population-density - nitrogen - mass - stoichiometry - ecosystems - dynamics
    The large range of body-mass values of soil organisms provides a tool to assess the ecological organization of soil communities. The goal of this paper is to identify graphical and quantitative indicators of soil community composition and ecosystem functioning, and to illustrate their application to real soil food webs. The relationships between log-transformed mass and abundance of soil organisms in 20 Dutch meadows and heathlands were investigated. Using principles of allometry, maximal use can be made of ecological theory to build and explain food webs. The aggregate contribution of small invertebrates such as nematodes to the entire community is high under low soil phosphorus content and causes shifts in the mass–abundance relationships and in the trophic structures. We show for the first time that the average of the trophic link lengths is a reliable predictor for assessing soil fertility responses. Ordered trophic link pairs suggest a self-organizing structure of food webs according to resource availability and can predict environmental shifts in ecologically meaningful ways
    Tephra stratification of volcanic ash soils in Nothern Ecuador
    Tonneijck, F.H. ; Hageman, J.A. ; Sevink, J. ; Verstraten, J.M. - \ 2008
    Geoderma 144 (2008)1-2. - ISSN 0016-7061 - p. 231 - 247.
    undisturbed paramo grasslands - colombia - geochemistry - profiles - andosols - biomass - pollen - mass
    We combined proxies traditionally used in stratigraphic research (mineral assemblages, grain size distribution, and element ratios) with soil organic carbon contents and radiocarbon dating both at a high vertical resolution, to unravel the tephra stratigraphy in volcanic ash soils. Our results show that soil profiles along an altitudinal transect intersecting the upper forest line in Northern Ecuador were formed in three distinct tephra deposits. Although the deposits contained a similar assemblage of minerals, we were able to differentiate these deposits because of their characteristic organic carbon distribution, grain size distribution and typical SrO to Na2O, CaO and crystalline Al2O3 ratios. Unravelling the tephra stratigraphy improved understanding of the vertical distribution of soil organic carbon, including paleoecological proxies, in the studied soils. We demonstrated that bioturbation likely plays an important role in current pedogenesis, resulting in overprinting (merging, mixing) of the paleosol. Surprisingly, in spite of bioturbation, a linear age depth relationship exists, leading to the hypothesis that the active zone of bioturbation shifted upwards during soil formation. Therefore, we conclude that paleoecological proxies are stratified in our soils, albeit probably somewhat more crudely than in undisturbed peat bogs or lake sediments.
    Natural occurence of Wolbachia-infected and uninfected Trichogramma species in tomato fields in Portugal
    Gonçalves, C.I. ; Huigens, M.E. ; Verbaarschot, P.G.H. ; Duarte, S. ; Mexia, A. ; Tavares, J. - \ 2006
    Biological Control 37 (2006)3. - ISSN 1049-9644 - p. 375 - 381.
    sex-ratio chromosome - biological-control - parthenogenesis - sequences - wasps - gene - mass
    Minute egg parasitoids of the genus Trichogramma (Hymenoptera; Trichogrammatidae) are promising candidates for biological control of lepidopteran pests in tomato in Portugal. This certainly applies to native Trichogramma strains that have thelytokous reproduction, i.e., produce only daughters. In Trichogramma wasps, thelytoky is mostly induced by the intracellular bacterium Wolbachia. In this study, we carried out a field survey of native Trichogramma species in four locations in Ribatejo, the main processing tomato region of Portugal, and determined the prevalence of Wolbachia in those species. Five Trichogramma species were found to emerge from lepidopteran eggs collected in the field, namely Trichogramma bourarache, Trichogramma cordubensis, Trichogramma evanescens, Trichogramma pintoi, and Trichogramma turkestanica. T. evanescens and T. pintoi were by far the dominating species representing, respectively, 64.9 and 26.4% of the trichogrammatids collected. Total natural parasitism rates of the collected lepidopteran eggs by Trichogramma wasps ranged from 28.2 to 64.6%. Three Trichogramma species were found to be infected with Wolbachia, namely T. cordubensis, T. evanescens, and T. turkestanica. All the wasp broods belonging to T. cordubensis were infected, whereas low infection rates were found in T. evanescens (0.9% of the broods) and T. turkestanica (4.5% of the broods). The latter represents the first record of a Wolbachia infection in T. turkestanica. Sequencing of the Wolbachia surface protein, wsp, revealed this Wolbachia infection to be related to other Wolbachia infections in Trichogramma wasps. As Wolbachia-infected thelytokous strains exist for T. evanescens, the most abundant Trichogramma species naturally occurring in the tomato fields of the Ribatejo region, this species offers interesting and powerful options for biological control of lepidopteran pests in processing tomato in this region.
    Fast fuelling but light flight in Broad-billed Sandpipers Limicola falcinellus: Stopover ecology at a final take-off site in spring (Sivash, Ukraine)
    Verkuil, Y. ; Have, T.M. van der; Winden, J. van der; Keijl, G.O. ; Ruiters, P.S. ; Koolhaas, A. ; Dekinga, A. ; Chernichko, I.I. - \ 2006
    Ibis 148 (2006)2. - ISSN 0019-1019 - p. 211 - 220.
    northward migrating waders - optimal fat loads - western sandpipers - wadden sea - semipalmated sandpipers - body condition - calidris - birds - mass - populations
    We studied phenology, staging time and refuelling in Broad-billed Sandpipers Limicola falcinellus stopping over during spring migration in the Sivash (Black Sea, Ukraine) in May 1991¿94. In the study area, peak staging numbers of 2000¿2500 individuals occurred in the third week of May. In May 1993, 460 birds were marked with a yellow dye and 126 of these were colour-ringed. Before 28 May no departure of birds dyed yellow could be detected; by 3 June all birds had departed. Colour-ringed adults in mid May 1993 staged for a minimum of 8.2 days. After the observed departure of large flocks (24 May and later) the staging time of colour-ringed birds decreased significantly with body mass at the time of capture. Of birds mist-netted in 1991¿94, 99.3% were in full summer plumage and 89% were adults. In second-year birds, fuel deposition rate (measured between individuals) was 0.44 g/day. In adults caught from early May to 24 May, overall fuel deposition rate was 1.04 g/day (3.4% of lean body mass). Mean adult body mass in early May was 34.8 g, increasing to 45.5 g after 24 May. Estimated body mass at departure was 51 g. Departure body mass and flight range estimates suggest that although birds refuelled quickly, fuel loads are only just sufficient for an unbroken flight to Scandinavia and the Kola Peninsula. We suggest that Broad-billed Sandpipers use the Sivash as a crucial final take-off stopover site, and that they follow a 'jumping' migration strategy, performed under narrow time constraints.
    Potential of imaging spectroscopy as tool for pasture management
    Schut, A.G.T. ; Lokhorst, C. ; Hendriks, M.M.W.B. ; Kornet, J.G. ; Kasper, G.J. - \ 2005
    Grass and Forage Science 60 (2005)1. - ISSN 0142-5242 - p. 34 - 45.
    infrared reflectance spectroscopy - grass swards - chemical-composition - nitrogen - herbage - mass - deficiency - regression - quality - nirs
    The use of imaging spectroscopy to predict the herbage mass of dry matter (DM), DM content of herbage and crude fibre, ash, total sugars and mineral (N, P, K, S, Ca, Mg, Mn, Zn and Fe) concentrations was evaluated. The experimental system used measured reflectance between 404 and 1650 nm at high spatial (0·281·45 mm2) and spectral resolution. Data from two experiments with Lolium perenne L. mini-swards were used where the degree of sward damage or N-fertilizer application varied. Regression models were calibrated and validated and the potential reduction in prediction error with multiple observations was estimated. The mean prediction errors for DM mass, DM content and N, total sugars, ash and crude fibre concentrations were 235268 kg ha1, 9·616·8 g kg1, 2·43·4 g kg DM1, 16·227·7 g kg DM1, 5·86·5 g kg DM1 and 8·410·4 g kg DM1 respectively. The predictions for concentrations of P, K, S and Mg allowed identification of deficiency levels, in contrast to the concentrations of Na, Zn, Mn and Ca which could not be predicted with adequate precision. Prediction errors of DM mass may be maximally reduced to 95142 kg ha1 with 25 replicate measurements per field. It is concluded that imaging spectroscopy can provide an accurate means for assessment of DM mass of standing grass herbage. Predictions of macronutrient content and feeding value were satisfactory. The methodology requires further evaluation under field conditions.
    Dispersal potential in plant communities depends on environmental conditions
    Ozinga, W.A. ; Bekker, R.M. ; Schaminée, J.H.J. ; Groenendael, J.M. van - \ 2004
    Journal of Ecology 92 (2004)5. - ISSN 0022-0477 - p. 767 - 777.
    long-distance dispersal - seed dispersal - wind dispersal - indicator values - population-size - life-history - grassland - ecology - mass - coexistence
    Local plant communities can only function within a metacommunity context if they are connected by appropriate dispersal vectors, accommodating the transport of propagules between sites. The capacity for long-distance dispersal may be a key factor in the survival of local populations, especially in fragmented landscapes, and hence may have a large impact on local species composition. Dispersal vectors with a large efficiency for long-distance dispersal included in this study are: water, wind, large mammals and birds. We tested the hypothesis that variation in dispersal traits across plant communities is related to the position of the communities along major environmental gradients. This hypothesis was tested for (i) separate long-distance dispersal vectors and (ii) multiple dispersal vectors (the number of potential long-distance dispersal vectors per species). To quantify linkages between dispersal traits and environmental gradients, we coupled a data base containing dispersal attributes with another data base, containing 40 000 local vegetation descriptions aggregated into 123 plant communities. For each dispersal vector, the proportions of species that have access to this vector per community (weighted trait scores) were projected along three major environmental gradients: soil moisture, nutrient availability and light availability. The potential importance of individual dispersal vectors showed clear differences along the three environmental gradients, with the greatest differences along the light availability gradient. The differences in dispersal traits probably reflect environmental constraints on the availability or efficiency of individual dispersal vectors. The ability to be dispersed by multiple dispersal vectors is a common phenomenon in most plant communities (an average of 2.15 vectors per species). The mean number of potential long-distance dispersal vectors per species increases with light availability. This probably implies that plant communities differ in their response to both habitat fragmentation and habitat restoration. Despite differences in trait spectra among communities, all dispersal syndromes are represented in nearly all communities. An important consequence of this complementarity in dispersal traits is that species within the same community may experience different connectivity. The results emphasize the need for dispersal models based upon multiple dispersal vectors that explicitly include parameters for habitat characteristics.
    Vitamin B12 status is associated to bone mineral content and bone mineral density in frail elderly women, but not in men
    Dhonukshe-Rutten, R.A.M. ; Lips, M. ; Jong, N. ; Chin A Paw, M.J.M. ; Hiddink, G.J. ; Dusseldorp, M. van; Groot, C.P.G.M. de; Staveren, W.A. van - \ 2003
    The Journal of Nutrition 133 (2003)3. - ISSN 0022-3166 - p. 801 - 807.
    physical-activity scale - methylmalonic acid - osteoporosis - determinants - nutrition - exercise - mass - absorptiometry - homocysteine - vegetarian
    Subclinical vitamin B-12 deficiency is common in the elderly. Encouraged by early indications, we investigated the plasma vitamin B-12 status in association with bone mineral content (BMC) and bone mineral density (BMD) in frail elderly people. Data of 194 free-living Dutch frail elderly (143 women and 51 men) were available. BMC and BMD were measured by dual energy X-ray analysis. Biochemical analyses were performed on plasma or serum including vitamin B-12, methylmalonic acid, homocysteine, 25-hydroxy vitamin D and parathyroid hormone. Women had higher plasma vitamin B-12 (288 and 238 pmol/L, respectively) and lower plasma homocysteine levels (15.8 and 21.3 mumol/L, respectively) than men. Of the total explained variance of BMC and BMD in women (46 and 22%, respectively), 1.3-3.1% was explained by plasma vitamin B-12, in addition to weight and height or energy intake. In men, the variance of BMC and BMD was explained by weight, smoking and/or height (total R-2 was 53 and 25%, respectively), but not by plasma vitamin B-12. Osteoporosis occurred more often among women whose vitamin B-12 status was considered marginal or deficient than in women with a normal status, i.e., the prevalence odds ratios (after adjustment for weight, age and calcium intake) (95% confidence intervals) were 4.5 (0.8;24.8) and 6.9 (1.2;39.4), respectively. These results suggest that vitamin B-12 status is associated with bone health in elderly women. Future studies on bone health should take into account a possible role of vitamin B-12 status in different populations.
    Nauwelijks compostering vaste mest op het lagekostenbedrijf
    Blanken, K. ; Dooren, H.J. van - \ 2001
    Rundvee praktijkonderzoek 14 (2001)3. - ISSN 1569-805X - p. 5 - 7.
    stalmest - rundveemest - mest - opslag - compostering - samenstelling - chemische samenstelling - volume - massa - gewicht - mestverwerking - farmyard manure - cattle manure - manures - storage - composting - composition - chemical composition - volume - mass - weight - manure treatment
    Gedurende een half jaar werd daarom de opslag van de vaste mest in een proefopstelling gevolgd. Hieruit bleek dat er vrijwel geen compostering op gang kwam en dat de massareductie daardoor minder is dan verwacht.
    Body weights in grey and red squirrels: do seasonal weight increases occur in conifer woodland?
    Lurz, P.W.W. ; Lloyd, A.J. - \ 2000
    Journal of Zoology 252 (2000)4. - ISSN 0952-8369 - p. 539 - 543.
    sciurus-vulgaris - carolinensis - replacement - energetics - mass - fat
    Seasonal body weight changes were investigated in red and grey squirrels in spruce-dominated conifer plantations in the north of England. Annual seed food availability, particularly in the spruce plantations, varies markedly and is characterized by years with large cone crops (‘mast crops’) followed by several years of intermediate or low crops. The last mast crop in Kielder Forest District occurred in 1991 and we studied the two squirrel species when food availability was intermediate and low between 1992 and 1999. Neither red nor grey squirrels in the conifer plantations significantly increased their body weight for the autumn or winter. The responses of red and grey squirrels to the different foraging conditions in deciduous and conifer woodlands and the accumulation of seasonal fat stores may have to be seen in the context of habitat type and the pattern and predictability of seed availability. Our findings suggest that fat accumulation is likely to be less pronounced in conifer habitats where autumn and winter food supplies are more predictable, and manoeuvrability to feed on cones in the canopy is important
    Milde snavelbehandeling op tien dagen leeftijd: geen stagnatie in gewichtsverloop bij batterijhennen
    Reuvekamp, B.F.J. ; Niekerk, Th.G.C.M. van - \ 2000
    Praktijkonderzoek voor de Pluimveehouderij 11 (2000)1. - ISSN 0924-9087 - p. 14 - 15.
    batterijhuisvesting - hennen - snavelkappen - jonge dieren - gewicht - massa - diervoedering - lichtregiem - dierverzorging - battery husbandry - hens - debeaking - young animals - weight - mass - animal feeding - light regime - care of animals
    Het Praktijkonderzoek Pluimveehouderij (PP) Het Spelderholt voert momenteel de zesde proef voor het onderzoek met verrijkte kooien. Niet snavelbehandelen gaf in de voorgaande proeven nog teveel problemen met verenpikkerij en kannibalisme. Om deze reden worden op de verrijkte kooien ongekapte hennen vergeleken met op 10 dagen leeftijd behandelde dieren. In dit artikel gaan we in op de resultaten van de opfok.
    Ontwikkeling lichaamsgewichten zesde koppel voor de batterijstal leghennen
    Emous, R.A. van; Reuvekamp, B.F.J. ; Niekerk, Th.G.C.M. van - \ 1999
    Praktijkonderzoek voor de Pluimveehouderij 10 (1999)2. - ISSN 0924-9087 - p. 7 - 12.
    hennen - kippen - pluimveehokken - batterijkooien - belichting - lichtregiem - verlichting - licht - groei - massa - gewicht - ontwikkeling - productiviteit - rentabiliteit - diervoedering - voer - dierfysiologie - ovipositie - agrarische bedrijfsvoering - snavelkappen - fysische factoren - dierverzorging - hens - fowls - poultry housing - battery cages - illumination - light regime - lighting - light - growth - mass - weight - development - productivity - profitability - animal feeding - feeds - animal physiology - oviposition - farm management - debeaking - physical factors - care of animals
    In de batterijstal van het Praktijkonderzoek Pluimveehouderij Het Spelderholt (PP) is in december 1998 een nieuw koppel leghennen opgezet. Gedurende de opfok waren al verschillen aangebracht op het gebied van verlichtingsschema's en snavelbehandeling.In dit artikel gaan we in op het verloop en de resultaten van de opfokperiode.
    Milde snavelbehandelingen: geen stagnatie in gewichtsverloop
    Reuvekamp, B.F.J. ; Niekerk, Th.G.C.M. van - \ 1999
    Praktijkonderzoek voor de Pluimveehouderij 10 (1999)1. - ISSN 0924-9087 - p. 3 - 9.
    hennen - diervoedering - jonge dieren - snavelkappen - gewicht - massa - groei - ontwikkeling - dierverzorging - hens - animal feeding - young animals - debeaking - weight - mass - growth - development - care of animals
    In dit artikel gaan we in op deze resultaten tijdens de opfok bij de niet gekapte hennen en op drie toegepaste milde snavelbehandelingen.
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