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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    Effects of repeated exposure to either vegetables or fruits on infant's vegetable and fruit acceptance at the beginning of weaning
    Barends, C. ; Vries, J. de; Mojet, J. ; Graaf, C. de - \ 2013
    Food Quality and Preference 29 (2013)2. - ISSN 0950-3293 - p. 157 - 165.
    developmental-changes - food preferences - variety - children - life - experience - formula
    This study investigated the effects of repeated exposure to either vegetables or fruits on an infant's vegetable and fruit acceptance during the first 18 days of weaning. We hypothesized that repeated exposure to a type of vegetable or fruit, would increase its intake. Furthermore, we expected that being exclusively weaned with vegetables would result in a higher acceptance of vegetables than being exclusively weaned with fruits. To investigate this, a 19-day intervention study was conducted in 101 healthy infants, aged 4-6 months. Infants were randomly assigned to one of four treatment groups. Two groups received exclusively vegetable purees as targets every other day for 18 consecutive days; green beans was the target for one group and artichoke for the other group. The other two groups received exclusively fruit purees including either apple or plums as the target fruit. On day 19, the vegetable groups consumed their first fruit pur e and the fruit groups their first vegetable pur e. At the beginning of the study on days 1 and 2 and at the end on days 17, 18 and 19, the infants were fed fruit or vegetable pur e in our laboratory. On days 3-16, the parents fed their infants the fruit or vegetable purees at home. Outcome variables were vegetable and fruit intake over time. Mean vegetable intake in the vegetable group increased significantly from 24 28 g (mean +/- SD) on days 1 and 2 to 45 +/- 44 g on days 17 and 18. Fruit intake in the fruit group increased significantly from 46 +/- 40 to 66 +/- 42 g. Fruit intake was significantly higher than vegetable intake from the start. Repeated exposure to fruit had no effect on the vegetable intake. The first intake of green beans in the fruit groups at day 19, was 24 +/- 29 g and on average as low as the green beans intake in the vegetable groups at the 1st exposure on days 1 or 2. Similarly, the first apple intake in the fruit groups on days 1 or 2 of 47 +/- 48 g did on average not differ from the first apple intake of 45 +/- 49 g in the vegetable groups on day 19. The mean intake of green beans and plums increased significantly after repeated exposure. The intake of the target food artichoke stayed low and the intake of apple only increased slightly. These findings confirm that at the first exposure fruit acceptance is higher than vegetable acceptance. Weaning with vegetables, but not with fruits, may promote vegetable acceptance in infants. (C) 2013 Elsevier Ltd. All rights reserved.
    Starch-related Enzymes during Potato Tuber Dormancy and Sprouting
    Sergeeva, L.I. ; Claassens, M.M.J. ; Jamar, D.C.L. ; Plas, L.H.W. van der; Vreugdenhil, D. - \ 2012
    Russian Journal of Plant Physiology 59 (2012)4. - ISSN 1021-4437 - p. 556 - 564.
    adp-glucose pyrophosphorylase - solanum-tuberosum - developmental-changes - hexose-phosphate - gene-expression - metabolism - sucrose - phosphorylase - biosynthesis - tuberization
    Activities of enzymes presumably involved in starch biosynthesis (ADP-glucose pyrophosphorylase, AGPase) and/or breakdown (starch phosphorylase, STP; amylases) were determined during potato (Solanum tuberosum L.) tuber dormancy and sprouting. Overall activities of all these enzymes decreased during the first stage of tuber dormancy. No clear changes were detected at the time of dormancy breaking and sprouting. However, when AGPase activity was monitored by in situ staining during the entire dormancy period, a clear decrease during the dormant period and a large increase before visible sprouting could be observed. This increase was especially evident near the vascular tissue and at the apical bud, which showed a very intensive staining. In situ staining of STP activity in sprouting tubers showed that the tissue distribution of STP was the same as for AGPase. As a possible explanation, direct starch cycling is suggested: STP produces glucose-1-phosphate during starch breakdown, which can be directly used as a substrate by AGPase for starch synthesis. Gene expression studies with the AGPaseS promoter coupled to the firefly luciferase reporter gene also clearly showed a higher activity in sprouting tubers as compared to dormant tubers, with the highest expression levels observed around the apical buds. The presence of amylase activity at dormancy initiation and AGPase activity persistent at the sprouting stage suggest that starch was cycling throughout the entire dormancy period. According to the in situ studies, the AGPase activity increased well before visible sprout growth and could therefore be one of the first physiological determinants of dormancy breakage.
    Involvement of the hypothalamic-pituitary-thyroid axis and its interaction with the hypothalamic-pituitary-adrenal axis in the ontogeny of avian thermoregulation: a review
    Debonne, M. ; Baarendse, P.J.J. ; Brand, H. van den; Kemp, B. ; Bruggeman, V. ; Decuypere, E. - \ 2008
    Worlds Poultry Science Journal 64 (2008)3. - ISSN 0043-9339 - p. 309 - 321.
    corticotropin-releasing-factor - precocial japanese-quail - altricial european starlings - chick-embryo - immunocytochemical demonstration - postnatal-development - developmental-changes - thyrotropin release - neonatal chicks - growth-hormone
    The emergence of thermoregulation in avian species is a complex matter in which neural as well as hormonal processes are involved. In a previous paper, the neural aspects of primary avian thermoregulation were discussed. In this paper the role of the hypothalamus-pituitary-thyroid axis (HPT-axis) and the hypothalamus-pituitary-adrenal axis (HPA-axis) in the ontogeny of avian thermoregulation is evaluated. The regulatory mechanisms and different important hormones of both axes, which have stimulatory or inhibitory effects, are discussed. Because the onset of functionality of the thermoregulatory system is of great interest, the ontogeny and functionality of the hormonal axes are clarified. There is a great difference between precocial and altricial birds in hormonal events as well as in neural processes which are involved in the emergence of thermoregulation. In precocial avian species the HPT-axis becomes functional during the mid- to late embryonic period while the same axis only becomes fully functional during the first week post-hatch in altricial avian species. As early as the sixties, the emergence of homeothermy in chickens was investigated. It was concluded that the thyroid gland plays an important role in the thermoregulatory mechanisms of newly hatched chicks. More recent studies however were not able to show any direct effect of the thyroid hormones on the thermoregulation of day-old chicks, although blocking the conversion of T4 to T3 caused a decrease in body temperature in young chicks. Thyrotropin releasing hormone (TRH) is known to act in thermoregulation in mammals and several authors have found an effect of TRH on the metabolism of young and older chicks. However, the exact mechanism still remains unclear. Because the HPT- and the HPA-axis show close relationships, the role of the HPA-axis in the ontogeny of thermoregulation is also taken into consideration in this review. In mammals as well as in birds, corticotropin releasing hormone (CRH) is involved in the primary thermoregulation. We conclude that the HPT-axis has an important role in the ontogeny of avian thermoregulation. The exact role of the HPA-axis remains largely unclear although at least CRH is definitely of some importance.
    Vacuolar invertase regulates elongation of Arabidopsis thaliana roots as revealed by QTL and mutant analysis.
    Sergeeva, L.I. ; Keurentjes, J.J.B. ; Bentsink, L. ; Vonk, J. ; Plas, L.H.W. van der; Koornneef, M. ; Vreugdenhil, D. - \ 2006
    Proceedings of the National Academy of Sciences of the United States of America 103 (2006)8. - ISSN 0027-8424 - p. 2994 - 2999.
    quantitative trait loci - sucrose synthase - genetic-variation - developmental-changes - plant invertases - hexose-phosphate - enzymes - potato - expression - maize
    The possible role of the sucrose-splitting enzymes sucrose synthase and invertase in elongating roots and hypocotyls of Arabidopsis was tested by using a combination of histochemical methods and quantitative trait locus (QTL) analysis. Lengths of roots and hypocotyls correlated better with invertase activities than with sucrose synthase activities. The highest correlations were observed with activities in the elongating zones of roots. The genetic basis of these correlations was studied by using QTL analysis. Several loci, affecting invertase activity, colocated with loci that had an effect on root or hypocotyl length. Further fine mapping of a major locus for root length, but not for hypocotyl length (top chromosome 1), consistently showed colocation with the locus for invertase activity containing a gene coding for a vacuolar invertase. The analysis of a functional knockout line confirmed the role of this invertase in root elongation, whereas other invertase genes might play a role in hypocotyl elongation. Thus, we show the power of QTL analysis, combined for morphological and biochemical traits, followed by fine-mapping and mutant analysis, in unraveling the function of genes and their role in growth and development
    Comparing potato tuberization and sprouting: opposite phenomena
    Vreugdenhil, D. - \ 2004
    American Journal of Potato Research 81 (2004)4. - ISSN 1099-209X - p. 275 - 280.
    solanum-tuberosum-l - gene-expression - developmental-changes - hexose-phosphate - abscisic-acid - dormancy - conversion - enzymes - sucrose - gibberellin
    The regulation of tuber formation and tuber sprouting are compared. As a starting point it is hypothesized that these two phenomena are opposite to each other. This idea is tested from three points of view: hormonal regulation, gene expression, and carbohydrate metabolism. It is concluded that there is only limited evidence to support the hypothesis. On the contrary, several examples are given indicating that similar mechanisms might be operative during tuber formation and tuber sprouting.
    Water status and carbohydrate pools in tulip bulbs during dormancy release
    Kamenetsky, R. ; Zamah, H. ; Ranwala, A.P. ; Vergeldt, F. ; Ranwala, N.K. ; Miller, W.B. ; As, H. van; Bendel, P. - \ 2003
    New Phytologist 158 (2003). - ISSN 0028-646X - p. 109 - 118.
    nuclear-magnetic-resonance - developmental-changes - stalk elongation - flower buds - apple buds - plants - visualization - endodormancy - spectroscopy - microscopy
    Changes in the physical state of cellular water and its interrelations with carbohydrate metabolism were studied during preplanting storage of tulip bulbs (Tulipa gesneriana 'Apeldoorn'). Magnetic resonance imaging, light and scanning electron microscopy and high-performance anion exchange chromatography with pulsed amperometric detection were used to follow time-dependent changes during bulb storage at 17 or 20degreesC (nonchilled) or 4degreesC (chilled). No visible differences in scale structure and central bud development were observed microscopically between chilled and nonchilled bulbs. However, the scales of the chilled bulbs exhibited higher water content, faster starch degradation and increased concentrations of sucrose and ethanol-soluble fructan. Quantitative measurements of magnetization transfer (MT) indicated a smaller fraction of a solid or a restricted-mobility proton pool in the scales of the chilled bulbs. By contrast, the MT effect was significantly higher in the central bud of the chilled than in the nonchilled bulbs. Degradation of storage polysaccharides to low-molecular-weight sugar molecules during release from dormancy could be accompanied by local release of water molecules tightly bound to the polysaccharide granules into the bulk water, or by an influx of free water molecules due to increased osmotic potential caused by the raised sugar concentration, or by a combination of both effects.
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