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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    Cholecalciferol or 25-hydroxycholecalciferol supplementation does not affect muscle strength and physical performance in prefrail and frail older adults
    Vaes, Anouk M.M. ; Tieland, Michael ; Toussaint, Nicole ; Nilwik, Rachel ; Verdijk, Lex B. ; Loon, Luc J.C. van; Groot, Lisette C.P.G.M. de - \ 2018
    The Journal of Nutrition 148 (2018)5. - ISSN 0022-3166 - p. 712 - 720.
    25-hydroxyvitamin D - Cholecalciferol - Lower extremity function - Muscle strength - Older adults

    Background: Vitamin D supplementation is proposed as a potential treatment strategy to counteract functional decline in older adults. However, data from randomized trials are either limited or inconsistent. Objective: This study investigated the effect of daily supplementationwith 25-hydroxycholecalciferol [25(OH)D3] or cholecalciferol (vitamin D3) on muscle strength and physical performance in older adults. Methods: This was a randomized, double-blind, placebo-controlled trial of 6 mo including 78 prefrail or frail (according to the Fried criteria), community-dwelling older adults (n = 43 men) aged ≥65 y, with a baseline 25-hydroxyvitamin D [25(OH)D] concentration between 20 and 50 nmol/L. Participants were supplemented daily with 10 μg 25(OH)D3, 20 μg vitamin D3, or a placebo capsule. Serum 25(OH)D was measured by liquid chromatography-tandem mass spectrometry. The primary outcome wasmaximal isometric knee-extension strength (Biodex System 4); secondary outcomes included knee-flexion and hand grip strength, Short-Physical Performance Battery score, Timed Up and Go score, postural sway, muscle mass (dual-energy X-ray absorptiometry), and muscle fiber type and size. Results: The mean baseline serum 25(OH)D concentration was 37.7 nmol/L (95% CI: 35.4, 39.9 nmol/L). After 6 mo of supplementation, concentrations increased to 98.7 nmol/L (95% CI: 93.1, 104.4 nmol/L) in the 25(OH)D3 group and to 72.0 nmol/L (95% CI: 66.1, 77.8 nmol/L) in the vitamin D3 group, compared with 47.5 nmol/L (95% CI: 41.8, 53.3 nmol/L) in the placebo group (P-interaction < 0.01). Knee-extension strength did not significantly change in the 25(OH)D3 group (5.9 Nm; 95% CI: -6.2, 18.0 Nm), in the vitamin D3 group (5.5 Nm; 95% CI: -6.8, 17.8 Nm), or in the placebo group (1.8 Nm; 95% CI: -10.7, 14.4 Nm) (P-interaction = 0.74). Furthermore, mean changes in physical performance tests, muscle mass, and muscle fiber type and size did not differ between the groups. Conclusion: Increasing the serum 25(OH)D concentration over a period of 6 mo did not significantly change muscle strength and physical performance in prefrail and frail older adults.

    Protein Supplementation Augments Muscle Fiber Hypertrophy but Does Not Modulate Satellite Cell Content During Prolonged Resistance-Type Exercise Training in Frail Elderly
    Dirks, Marlou L. ; Tieland, Michael ; Verdijk, Lex B. ; Losen, Mario ; Nilwik, Rachel ; Mensink, Marco ; Groot, Lisette C.P.G.M. de; Loon, Luc J.C. van - \ 2017
    Journal of the American Medical Directors Association 18 (2017)7. - ISSN 1525-8610 - p. 608 - 615.
    Amino acids - Resistance exercise - Sarcopenia - Skeletal muscle

    Objective: Protein supplementation increases gains in lean body mass following prolonged resistance-type exercise training in frail older adults. We assessed whether the greater increase in lean body mass can be attributed to muscle fiber type specific hypertrophy with concomitant changes in satellite cell (SC) content. Design: A total of 34 frail elderly individuals (77 ± 1 years, n = 12 male adults) participated in this randomized, double-blind, placebo-controlled trial with 2 arms in parallel. Intervention: Participants performed 24 weeks of progressive resistance-type exercise training (2 sessions per week) during which they were supplemented twice-daily with milk protein (2 × 15 g) or a placebo. Methods: Muscle biopsies were taken at baseline, and after 12 and 24 weeks of intervention, to determine type I and type II muscle fiber specific cross-sectional area (CSA), SC content, and myocellular characteristics. Results: In the placebo group, a trend for a 20% ± 11% increase in muscle fiber CSA was observed in type II fibers only (P = .051), with no increase in type I muscle fiber CSA. In the protein group, type I and II muscle fiber CSA increased by 23% ± 7% and 34% ± 10% following 6 months of training, respectively (P < .01). Myonuclear domain size increased over time in both groups and fiber types (P < .001), with no significant differences between groups (P > .05). No changes in myonuclear content and SC contents were observed over time in either group (both P > .05). Regression analysis showed that changes in myonuclear content and domain size are predictive of muscle fiber hypertrophy. Conclusions: Protein supplementation augments muscle fiber hypertrophy following prolonged resistance-type exercise training in frail older people, without changes in myonuclear and SC content.

    The influence of irradiance and external CO2 concentration on photosynthesis of different tomato genotypes
    Nilwik, H.J.M. ; Gosiewski, W. ; Bierhuizen, J.F. - \ 1982
    Scientia Horticulturae 16 (1982). - ISSN 0304-4238 - p. 117 - 123.
    With 4 genotypes of tomato, irradiance and CO2-response curves of net photosynthesis were analysed by means of curve fitting. Estimated values of the light compensation point Ic showed small but significant differences between the genotypes, the overall value being in the order of 8 W m−2. The photochemical efficiency (αn) and the maximum net photosynthesis per unit leaf area basis (Pnm) reached the highest values for ‘F6 IVT’ (13.3 μg CO2 J−1 resp. 0.549 mg CO2 m−2 s−1), the lowest value of αn with ‘Bonabel’ (9.9 μg CO2 J−1), and the lowest value of Pnm with ‘PI 114969’ (0.424 mg CO2 m−2 s−1). The CO2-compensation point (Cc) was relatively high (177–245 mg m−3). ‘F6 IVT’ demonstrated the highest value of Cc, the lowest carboxylation efficiency and the highest maximum rate of net photosynthesis. The results clearly demonstrate that the latter genotype requires a much higher external CO2-concentration than the other genotypes in order to exhibit the highest rate of net photosynthesis.
    The influence of temperature on photosynthesis of different tomato genotypes
    Gosiewski, W. ; Nilwik, H.J.M. ; Bierhuizen, J.F. - \ 1982
    Scientia Horticulturae 16 (1982)2. - ISSN 0304-4238 - p. 109 - 115.
    Net photosynthesis and dark respiration from whole plants of various tomato genotypes were measured in a closed system. At low irradiance (27 W m−2) and low external CO2 concentration (550 mg m−3), net photosynthesis of 10 genotypes was found to vary between 0.122 and 0.209 mg CO2 m−2 s−1. Correlation was observed between net photosynthesis, net uptake on a daily basis (8 h photoperiod at 20°C and 16 h nyctoperiod at 10°C), specific leaf weight and leaf area ratio. At high irradiance (243 W m−2), high external CO2 concentration (1480 mg m−3) and ambient temperatures of 10, 18, 20 and 26°C, four genotypes were analysed. ‘F6 I.V.T.’ had the highest rate of photosynthesis at 10°C, while ‘Sonatine’ ranked high at 26°C. Dark respiration increased with temperature, except in the case of ‘Bonabel’ where the effect of temperature was slight.
    An improved closed system for continuous measurement of photosynthesis, respiration and transpiration
    Nilwik, H.J.M. ; Boehmer, H. ten - \ 1981
    Wageningen : Veenman (Mededelingen Landbouwhogeschool no. 81-4) - 9
    ademhaling - katabolisme - fotosynthese - methodologie - biologische technieken - experimenten - uitrusting - respiration - catabolism - photosynthesis - methodology - biological techniques - experiments - equipment
    Analysis of the relationship between temperature and germination of sweet pepper
    Bierhuizen, J.F. ; Wagenvoort, W.A. ; Nilwik, H. - \ 1978
    Acta Horticulturae 83 (1978). - ISSN 0567-7572 - p. 1955 - 200.
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