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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Bringing eggs and bones to light : affecting leg bone development in broiler chickens through perinatal lighting schedules
Pol, Carla W. van der - \ 2017
University. Promotor(en): Bas Kemp, co-promotor(en): Henry van den Brand; Inge Van Roovert-Reijrink. - Wageningen : Wageningen University - ISBN 9789463431422 - 214
broilers - limb bones - biological development - embryonic development - eggs - light regime - incubation - hatching - circadian rhythm - animal pathology - animal health - poultry farming - vleeskuikens - beenderen van ledematen - biologische ontwikkeling - embryonale ontwikkeling - eieren - lichtregiem - broeden - uitbroeden - circadiaan ritme - dierpathologie - diergezondheid - pluimveehouderij

Leg bone pathologies are a common problem in broiler chickens, and they can lead to decreased welfare and poor production performance. It can be speculated that the ae­tiology of some leg bone pathologies lies, to some extent, in suboptimal early life bone development. One factor that can be speculated to affect bone development, and conse­quently leg health, in broiler chickens is application of light. Light has several properties, such as light intensity, color, duration, and schedule. The present thesis focuses on ligh­ting schedules. Aim was to investigate how lighting schedules applied during incubation and in the early post hatch period (the brooding period) affected leg bone development throughout a broiler’s life and leg health at slaughter age.

In 4 studies, effects of eggshell temperature (EST) and lighting schedule during incuba­tion and in the brooding period on leg bone development, leg health, and production parameters were explored. The first study found that an EST of 39.4°C led to lower bone dimensions at hatch than an EST between 37.8 and 38.6°C. It was then decided that incubation experiments on bone development would best be performed at a constant EST of 37.8°C, as this is also an EST that leads to good hatchability and chick quality. In two studies, the effects of circadian lighting schedules during incubation on leg bone development and leg health were investigated. Staining of the embryonic leg bones sho­wed that applying a circadian lighting schedule of 12 hours of light, followed by 12 hours of darkness (12L:12D) resulted in an earlier onset of embryonic ossification of the tibia than continuous light (24L). Compared to 24L, 12L:12D furthermore resulted in higher tibia weight and length, and higher tibial cortical area, cortical thickness, and second moment of area around the minor axis at hatch as revealed by MicroCT scanning. It was furthermore found that 12L:12D resulted in a lower incidence of the leg pathology tibial dyschondroplasia. Continuous darkness (24D) was mostly intermediate. On the other hand, a circadian lighting schedule of 16 hours of light, followed by 8 hours of darkness (16L:8D) did not show the same stimulatory effect on leg bone development, as no dif­ferences in gene expression markers involved in embryonic ossification were found, leg bone dimensions at hatch were not increased, and bone mineral content as determined by DXA scanning was not higher for 16L:8D. It can therefore be speculated that the dark period should exceed 8 hours per day during incubation for increased bone dimensions and ossification. However, incidence and severity of the leg bone pathologies in the form of bacterial chondronecrosis with osteomyelitis and epiphyseal plate abnormalities were lowest for broilers exposed to 16L:8D during incubation, and tibial dyschondroplasia tended to be lower for 16L:8D than for 24D. Interactions between incubation and mat­ching or mismatching post hatch lighting schedules were not found. It was speculated that the endocrine factors (pineal) melatonin, growth hormone, corticosterone, and IGF- 1 were a pathway through which light affected leg bone development, but no evidence was found to support this hypothesis. Production performance was not greatly influen­ced by incubation lighting schedule, but 24L was found to result in higher body weights at slaughter age than 16L:8D and 24D. In the final experiment, lighting schedules were applied during the brooding period from day 0 to 4 after hatching and leg bone develop­ment was measured at day 4 post hatch. 24L led to increased leg bone dimensions, but lower developmental stability of the leg bones than a lighting schedule with 1 or 6 hours of darkness after every 2 hours of light.

The overall findings of this thesis suggest that continuous light during incubation and in the brooding period had a detrimental effect on embryonic and early post hatch leg bone development and health. The involvement of endocrine factors was not clarified from the current results. Applying a light-dark rhythm during incubation may improve embryonic leg bone development and leg health at slaughter age compared to continuous light and continuous darkness, without affecting post hatch production performance, but it appears that the dark period should last longer than 8 hours per day for optimal leg bone development.

Structural basis for specific gene regulation by Auxin Response Factors
Freire Rios, Alejandra - \ 2016
University. Promotor(en): Dolf Weijers. - Wageningen : Wageningen University - ISBN 9789462579538 - 190
auxins - gene regulation - plant growth regulators - embryonic development - plant embryos - dna - auxinen - genregulatie - plantengroeiregulatoren - embryonale ontwikkeling - plantenembryo's

Auxin is a plant hormone that triggers a broad variety of responses during plant development. These responses range from correct cell division patterns during embryogenesis to formation and growth of different organs. Due to its importance for plant growth and development, many aspects of the biology of auxin have been studied. In Chapter 2, we use Arabidopsis embryogenesis as a stage to describe generalities about its biosynthesis, transport, components of its signaling pathway and transcriptional control of some know target genes.

As most of the players involved in transcriptional regulation in response to auxin have been identified, the question of how the same signal can elicit so many different responses remains open. In this thesis we approach this issue by focusing on the ultimate effectors of the auxin signaling pathway: the ARF family of transcription factors. In Chapter 3 we present the crystal structure of the DNA binding Domain (DBD) of two divergent members of the family: ARF1 and ARF5. Careful observation of the structures, followed by in vitro and in vivo experiments led to the following conclusions: 1) ARF DBDs dimerize through a conserved alpha-helix, and bind cooperatively to an inverted repeat of the canonical TGTCTC AuxRE. Dimerization of this domain is important for high-affinity DNA binding and in vivo activity. 2) Monomeric ARFs have the same binding preference for the DNA sequence TGTCGG (determined by protein binding microarray). 3) DNA-contacting residues are almost completely conserved within the ARF family members. 4) The distance between the AuxREs may play a role for binding of specific ARF dimers as for example, ARF5 can accommodate and bind to different spacing (6-9 bp) compared to ARF1 which is more rigid (7-8 bp).

In Chapter 4 we follow up on the observations made. First we again used structural biology to determine the reason of the high binding affinity to the TGTCGG sequence compared to the previously identified canonical TGTCTC element. We found that in complex with TGTCGG, His137 (ARF1) could rotate and make hydrogen bonds with either G5 or G6, as well as a hydrogen bond with the C opposing to G6. This rotation is not possible when in complex with TGTCTC and there the same histidine can make only one hydrogen bond with the G opposing to C6. We conclude then that this histidine plays a role in determining the strength of binding to TGTCNN elements and that this also reflects in its specific transcriptional activity as mutating the corresponding histidine in ARF5 renders a semi-functional protein in vivo (Chapter 3).

The next observation we followed up in Chapter 4 is the biological meaning of ARF DBDcooperative binding to DNA. We identified AuxRE inverted repeats (IR) in the promoter of the TMO5 gene and mutated them. This brought the expression of the gene to very low levels despite the presence of other multiple single AuxREs. Thus, the single inverted AuxRE repeat in the TMO5 promoter is essential for ARF5 binding and gene regulation. Importantly, mutating only a single AuxRE element within the inverted repeat led to very pronounced loss of activity, consistent with requirement of both AuxRE sites for high-affinity ARF5 binding. We then concluded that IR AuxREs have a significant effect in gene regulation by ARFs. Next we search the genome for bipartite AuxREs that correlated to auxin response and found two main elements: inverted repeat with 8 bases of spacing (IR8) and direct repeat with 5 bases of spacing (DR5). As this kind of bipartite AuxREs are rarer to find than single AuxREs, we tested their presence in promoters as predictors of auxin responsiveness by qPCR. We found that about 75% of the selected genes containing either IR8 or DR5 responded to auxin. The expression study also show that genes containing the DR5 sequence were only up-regulated when regulated. Interestingly, Surface Plasmon Resonance study showed that only class A (activator) ARFs can bind the DR5 sequence cooperatively.

As the structural differences of ARFs DBDs are subtle, we then asked if specific gene targeting is determined by this domain alone. In Chapter 5 we used a DBD swap experiment and conclude that the DBD is necessary for specific gene targeting but not sufficient and the other domains of an ARF also contribute in its specific activity.

In Chapter 5 we expand our focus from the DBD to the other ARF domains, Middle Region (MR) and C-terminal (CT). As ARFs have protein-protein interaction interfaces in all three domains, we expressed the isolated domains of ARF5 and perform immuno-precipitation followed by tandem mass-spectrometry. Although the procedure needs optimization, some interactions expected for each domain could be identified. The DBD showed to interact with the general transcription machinery and the CT could interact with another ARF and 3 Aux/IAA. These interactions seem to be specific as the Aux/IAA recovered are not the most abundant in the sampled tissue.

Finally, in Chapter 6 all the obtained results are put in a broader context and new questions derived from our results are proposed.

WET-tests with sea bass (Dicentrarchus labrax) eggs with discharge water of the MICROFADE II system : addendum to IMARES report C079/16
Kaag, N.H.B.G. - \ 2016
IJmuiden : Wageningen Marine Research (Wageningen Marine Research rapport C088/16) - 14
dicentrarchus - fish eggs - saline water - fresh water - embryonic development - visseneieren - zout water - zoet water - embryonale ontwikkeling
Incubation temperature alters thermal preference and response to heat stress of broiler chickens along the rearing phase
Morita, V.S. ; Almeida, V.R. ; Matos Junior, J.B. ; Vicentini, T.I. ; Brand, H. van den; Boleli, I.C. - \ 2016
Poultry Science 95 (2016)8. - ISSN 0032-5791 - p. 1795 - 1804.
broilers - embryonic development - preferred ambient temperature - thermal challenge - thermal manipulation

The current study aimed to investigate whether embryonic temperature manipulation may alter thermal preference throughout the rearing phase of broiler chickens and how this manipulation may affect response to thermal challenge, metabolism, growth rate and feed intake rate. Eggs were exposed to a constant incubation temperature [machine temperatures: 36°C (Low), 37.5°C (Control), and 39°C (High); eggshell temperature of 37.4 ± 0.08°C, 37.8 ± 0.15°C, and 38.8 ± 0.33°C, respectively] from d 13 till hatching. Low treatment chickens showed lower plasma T3 and GH levels at d 1 of age and lower T3 level at d 42 of age compared to the Control treatment. Preferred ambient, rectal temperature, T4 level, growth rate, food intake rate, and response to thermal challenge were not altered in these chickens. On the other hand, High-treatment chickens exhibited high preferred ambient temperature and rectal temperature during the first 2 wk post-hatch, lower plasma T3 level at d 21 and 42 and a delayed increase in respiratory movement in response to thermal challenge compared to the Control treatment. However, chickens subjected to the Control and High treatments did not differ in T4 and GH level and performance. We conclude that exposure to high temperature during late embryonic development has long-lasting effects on the thermoregulatory system of broiler chickens by affecting the heat tolerance of these chickens. Moreover, the preferred ambient temperature of the chickens from heat-treated eggs correspond to those recommended for the strain under study, whereas for the cold-treated and control-chickens it was 1°C below, indicating that incubation temperature might have consequences on the ambient temperature chickens require during the rearing phase.

Effects of temperature and CO2 during late incubation on broiler chicken development
Maatjens, C.M. - \ 2016
University. Promotor(en): Bas Kemp, co-promotor(en): Henry van den Brand; I.A.M. van Roovert-Reijrink. - Wageningen : Wageningen University - ISBN 9789462578258 - 196 p.
broilers - embryonic development - temperature - carbon dioxide - incubation - animal physiology - broiler performance - artificial hatching - hatcheries - poultry farming - vleeskuikens - embryonale ontwikkeling - temperatuur - kooldioxide - broeden - dierfysiologie - vleeskuikenresultaten - kunstmatig bebroeden - broedinstallaties - pluimveehouderij

Incubation conditions need to be adjusted to meet embryonic requirements to obtain optimal chick quality and hatchability. Eggshell temperature (EST) can be used as a non- invasive method to determine embryo temperature. A high EST of 38.9°C during the second or third week of incubation negatively affects chicken embryo development and survival compared to a constant EST of 37.8°C during that period. These negative effects of high EST might be due to a dis-balance between metabolic rate and oxygen (O2) availability. However, effects of lowering EST, which might restore the balance between metabolic rate and O2 availability, are largely unknown. Besides EST, the carbon dioxide (CO2) concentration during late incubation also seems to affect embryo development and might even interact with EST. Based on the potential effects of (lower) EST during the last week of incubation and of CO2 during only the hatching phase, the following three aims are derived: 1, to investigate effects of EST during the last phase of the incubation process, with special attention for EST below the general accepted optimal EST of 37.8°C, 2, to examine from which day of the incubation process onward EST should be changed from 37.8°C, and 3, to investigate whether CO2 concentrations are interacting with EST during the hatcher phase.

Time until hatch was longer when an EST of 35.6°C was applied during the last week of incubation, followed by 36.7, 37.8, and 38.9°C, which is probably caused by the lower metabolic rate at an EST below 37.8°C. Hatchability of fertile eggs was not affected at low EST, and EST did not affect time between internal pipping (IP) and hatch. An EST of 35.6 and 36.7°C, resulted in a higher yolk-free body mass (YFBM) at hatch compared to 37.8 and 38.9°C, and residual yolk weight was higher at hatch at 38.9°C compared to all other EST treatments. An EST of 35.6°C resulted in higher hepatic glycogen concentration and amount at IP and hatch compared to all other EST treatments. The proposed mechanism involved is that at lower EST, metabolic rate is reduced, which prevents the embryo from O2 limitation and ensures that fatty acid oxidation from the yolk can be maintained, resulting in energy production to be invested in growth and development. At an EST of 38.9°C, metabolic rate is high, resulting in a relative O2 shortage for the embryo. Consequently, lipid oxidation is reduced, which forces the embryo to switch to alternative energy sources, such as glycogen. Because glycogen storage is very limited in the egg and embryo, alternative energy sources such as amino acids obtained from muscles might be used. A clear interaction between EST and start day of treatment was found for relative heart weight. Relative heart weight was higher at an EST of 35.6°C and decreased with increase in EST. The differences among EST became larger when the EST treatment started earlier.

Effects of CO2 on embryo physiology, embryonic organ development, and chick quality were marginal. EST interacted with CO2 mainly before IP, but effects were minor at hatch. Interactions between EST and CO2 were found at an EST of 36.7 and 37.8°C, but remained absent at an EST of 38.9°C, which might indicate that physiological systems are already challenged due to the higher metabolic rate, which limits the capacity to cope with high CO2 of the embryo.

No effect of start day of treatment was indicated for embryonic organ development and chick quality found at hatch, which suggests that EST affected these parameters only in the last phase of incubation, e.g. from E19 onward. However, first week post-hatch performance was affected by start day of treatment. The beneficial effects of a lower EST of 35.6 and 36.7°C applied during the last week of incubation found at hatch, might contribute to an enhanced development during the first week post-hatch as body weight, carcass weight, and gain to feed ratio were increased.

In conclusion, results of this thesis show that an EST below 37.8°C during late incubation is beneficial for embryo development, organ growth during incubation, and growth performance during the first week post-hatch. In addition, start day of treatment did not affect chick quality and organ growth, except heart weight, at hatch, which implies that effects of EST occur during the hatching phase, e.g. from E19 onward. Although, an effect of start day of treatment was found on first week post-hatch performance, it remains to be investigated whether an EST below 37.8°C leads to improved later life quality characteristics.

Are all eggs equal? : embryonic development and nutrient metabolism in chicken eggs of different origins
Nangsuay, A. - \ 2016
University. Promotor(en): Bas Kemp, co-promotor(en): Henry van den Brand. - Wageningen : Wageningen University - ISBN 9789462577749 - 213 p.
eggs - hens - broilers - characteristics - strains - embryonic development - nutrients - metabolism - hatcheries - poultry - nutrition physiology - eieren - hennen - vleeskuikens - karakteristieken - stammen (biologisch) - embryonale ontwikkeling - voedingsstoffen - metabolisme - broedinstallaties - pluimvee - voedingsfysiologie

Hatching eggs, supplied to hatcheries are originating from different origins varying in breed, strain, and breeder age. These hatching eggs can be different in size, composition and eggshell properties, which might influence nutrient and O2 availability and consequently could affect embryonic development and nutrient metabolism. The aim of this thesis was therefore 1) to investigate effects of egg origin on nutrient and O2 availability, 2) to investigate effects of egg origins on nutrient metabolism and embryonic development and 3) to investigate consequences of different egg origins on the incubation process and hatching characteristics. In five studies, effects of different egg origins on nutrient and O2 availability, nutrient metabolism, embryo development and hatching characteristics were investigated. The first and second study focused on breeder age and egg size. The third study on breed; broilers and layers. The fourth study on broiler strain and the fifth study on breeder age, strain and eggshell temperature (EST). The overall findings in this thesis suggest that hatching eggs from different origins are not equal in availability of nutrients and O2. Nutrient availability is altered through variation in yolk size, especially by the effects of breeder age and breed. O2 availability is altered by differences in eggshell properties, which is influenced by especially breed and broiler strain. The availability of both nutrients and O2 plays a role on nutrient metabolism measured as embryonic heat production (HP) and consequently on embryonic development. Between incubation day (E) E7 and E14, both nutrient and O2 availability might affect nutrient metabolism as shown in the results of the broiler and layer comparison. Between E14 and hatching, the availability of O2 becomes the most determinant factor for nutrient metabolism and consequently for embryonic development. An increase in EST from 37.8 to 38.9°C from E7 onward resulted in an acceleration of nutrient metabolism and embryonic development until E16, but thereafter a high EST resulted in reduced yolk free body mass development. Embryos with an accelerated metabolic speed at an early stage of incubation, caused by an increased EST, might reach limited O2 availability at a higher magnitude than the embryos at a normal EST. As a result, nutrient metabolism is restricted and embryonic development is depressed. It can be concluded that not only the HP, but also the availability of O2 is crucial to be taken into account for developing incubator temperature. The principle is to obtain an optimal EST, which could maintain the balance between O2 requirement (driven by nutrient metabolism) and O2 availability for a continuing optimal nutrient metabolism to generate sufficient energy for embryonic development throughout incubation.

Microspore embryogenesis: reprogramming cell fate from pollen to embryo development
Hui Li, - \ 2014
University. Promotor(en): Gerco Angenent, co-promotor(en): Kim Boutilier. - Wageningen : Wageningen University - ISBN 9789462570702 - 224
stuifmeel - embryogenese - embryonale ontwikkeling - biologische ontwikkeling - plantenontwikkeling - in vitro kweek - plantenembryo's - brassica napus - pollen - embryogenesis - embryonic development - biological development - plant development - in vitro culture - plant embryos

Microspore embryogenesis is an expression of plant cell totipotency that leads to the production of haploid embryos. Besides being a widely exploited plant breeding tool, microspore embryogenesis is also a fascinating system that can be used to obtain a deeper mechanistic understanding of plant totipotency. This thesis aims to provide more insight into the process of microspore embryogenesis, from the formation of embryogenic cells to the outgrowth of differentiated embryos.

In Chapter 1 background information is provided on the various aspects of Brassica napus microspore culture and plant development that intersect with the topics that are studied in this thesis. Emphasis is placed on the basic requirements and limitations for successful microspore embryo culture, as well as on the roles of the plant hormone auxin and epigenetic regulation in the development of plant embryos, during both zygotic and in vitro embryo development.

Chapter 2 reviews the recent advances that have been made in understanding the developmental and molecular changes that take place during microspore embryogenesis in model systems. The commonly reported cellular changes associated with the establishment of embryo cell fate are summarized and evaluated. The subsequent differentiation of the embryo is also discussed, specifically, what is known about the establishment of polarity, with emphasis on the importance of exine rupture as a positional clue, and the processes that influence meristem maintenance during culture. Finally, the studies on the molecular changes during microspore embryo induction are put into context of male gametophytic development. Overall, the current perspective on microspore embryo initiation presents a landscape in which several routes can lead to the same final destination.

Stress treatments are widely applied to induce embryogenic growth in microspore culture. Chapter 3 explores the role of histone acetylation status in stress-induced microspore embryogenesis in Brassica napus. Inhibition of histone deactylases (HDACs) using the HDAC inhibitor trichostatin A (TSA), phenocopies the heat stress treatment that is normally used to induce embryogenic cell proliferation in B. napus microspore culture. Arabidopsis is recalcitrant for haploid embryogenesis, yet treatment with TSA also induced embryogenic cell divisions in this model species. Our observations suggest that the totipotency of the male gametophyte is kept in check by an HDAC-dependent mechanism and that the stress treatments used to induce haploid embryo development in culture impinge on this HDAC-dependent pathway. The repression of HDACs or HDAC-mediated pathways by stress and the accompanying changes in histone acetylation status could provide a single, common regulation point for the induction of haploid embryogenesis.

Chapter 4 builds on the knowledge developed in Chapter 3 on the role of HDAC proteins in plant totipotency. A wide variety of chemically distinct HDAC inhibitors was evaluated and additional inhibitors that enhance embryogenic cell induction and/or embryo yield were identified. One surprising observation was made during the course of this study: the initial donor microspore/pollen stage affects the quality of the embryo that is formed. In control cultures, embryos from progressively older stages of donor microspores/pollen became progressively compromised in their basal (axis region) region, characterized by a shift from normal embryos with apical (cotyledons) and basal (root) polarity to abnormal embryos with a reduced basal pole and ball-shaped embryos. These abnormal phenotypes could be partially complemented by treatment with HDAC inhibitors, which promoted growth of the basal region of the embryo. Progressive enhancement of embryo basal identity was accompanied by enhanced and broadened expression of the DR5 auxin response reporter. The embryo phenotypes observed in control and HDAC inhibitor treated microspore cultures are similar to the phenotypes induced by altered expression of the Arabidopsis TOPLESS (TPL)/HDAC19/BODENLOS (BDL) repressor complex, which acts to restrict expression of the AUXIN RESPONSE FACTOR ARF5/MONOPTEROS (MP) to the basal region of the embryo during zygotic embryo development.

To understand why most embryogenic callus failed to develop further, we examined the transcriptome of globular-shaped embryos that have started to histodifferentiate and compared it with embryogenic callus. The transcriptome analysis showed that the expression of many genes that regulate (auxin-related) embryo patterning were downregulated in embryogenic callus compared to globular stage embryos. This result may simply reflect the lack of patterning in these embryos or might indicate a role of auxin-signalling in embryogenic callus formation.

Chapter 5 examines how embryo identity and patterning is established in two B. napus microspore embryo pathways, a zygotic-like pathway, characterized by suspensor and then embryo proper formation, and a pathway characterized by initially unorganized structures that lack a suspensor. We specifically asked the question: how can embryo patterning be established in the absence of an initial asymmetric division and in the absence of a suspensor, two key events in zygotic embryo development. Analysis of embryo fate (GRP) and auxin (PIN1, PIN7 and DR5) markers showed that embryo fate was established prior to cell division, and independent of subsequent division pattern. The suspensorless embryo program was marked by a transient auxin maximum, followed by establishment of the apical and basal poles at the globular stage, coincident with release of the embryo from the pollen exine. Unlike zygotic embryo development, polar auxin transport (PAT) was not required for embryo initiation or polarity establishment in this system. Suspensor embryos developed in a similar fashion as zygotic embryos, PAT was required for specification of the embryo proper from the suspensor. Haploid embryogenesis therefore follows at least two programs, a PAT-dependent program that requires embryo proper specification from the suspensor, and an alternative PAT-independent program marked by an initial auxin maximum.

In the final chapter, Chapter 6, the work presented in this thesis is put in context of the broader plant development field. The epigenetic regulation of developmental transitions that respond to stress and during pollen development are highlighted. A model is provided that histone acetylation levels mediated by HAT and HDAC regulate pollen fate.

Proteomic and mechanistic analysis of Auxin Response Factors in the Arabidopsis embryo
Llavata Peris, C.I. - \ 2013
University. Promotor(en): Dolf Weijers. - S.l. : s.n. - ISBN 9789461736734 - 143
arabidopsis - auxinen - plantengroeiregulatoren - reacties - eiwitexpressieanalyse - genexpressie - embryonale ontwikkeling - embryogenese - auxins - plant growth regulators - responses - proteomics - gene expression - embryonic development - embryogenesis

Auxin is a phytohormone that is crucial for many aspects of plant development. The processes in which this hormone has been implicated span from embryo development to flower transition, defense, tropic responses, and many other processes during plant life. A key question in auxin biology is how this molecule is able to elicit such diverse responses. Auxin regulates the transcriptional activation or repression of genes through the AUXIN RESPONSE FACTOR (ARF) family of transcription factors. In my studies I focus in the ARF transcription factors as a likely source of variation in output specificity. We consider three levels at which ARFs differ. First, ARFs differ in their ability to interact with different Aux/IAA (antagonistic family of transcription factors), or to form homo- or heterodimers. Second, ARFs assemble into different protein complexes, transcription factors interact with other transcriptional regulators or other proteins to form transcription complexes. These, when different, may contribute to different functions of ARF complexes. Thirdly, ARFs bind to and regulate different target genes. My work offers a plausible explanation how specific auxin responses are generated and through which genes the developmental responses to auxin are generated.

Integrated in vitro-in silico models for predicting in vivo developmental toxicity : facilitating non-animal based safety assessment
Louisse, J. - \ 2012
University. Promotor(en): Ivonne Rietjens; Bas Blaauboer, co-promotor(en): M. Verwei. - S.l. : s.n. - ISBN 9789461732415 - 256
embryonale ontwikkeling - foetale ontwikkeling - in vitro kweek - toxiciteit - biomarkers - computational science - alternatieven voor dierproeven - risicoschatting - embryonic development - fetal development - in vitro culture - toxicity - animal testing alternatives - risk assessment

In chemical safety assessment, information on adverse effects after repeated dose and chronic exposure to low levels of hazardous compounds is essential for estimating human risks. At present, this information is almost solely obtained by performing animal experiments. Therefore, suitable methods to reduce, refine or replace (3Rs) repeated dose animal testing are urgently needed. At present, in vitro toxicity assays are able to screen compounds for toxicity, but since these tests result in in vitro concentration-response curves, whereas for the safety assessment of chemicals for human in vivo dose-response curves are needed, it is important that in vitro concentration-response curves can be translated to in vivo dose-response curves. The goal of the present project is to extrapolate in vitro concentration-response curves to in vivo dose-response curves with the help of physiologically based kinetic (PBK) models that describe the in vivo absorption, distribution, metabolism and excretion (ADME) processes. This is achieved by using the concentration-response curves, acquired in an appropriate in vitro toxicity test, as internal concentrations in the model, in order to calculate the in vivo dose levels that are needed to reach the internal (toxic) concentrations, by using the PBK-model. The predicted dose-response curves thus obtained can be used to determine safe exposure levels in chemical safety assessment.

The endpoint used in the present study is developmental toxicity. The in vitro toxicity assay used is the differentiation assay of the embryonic stem cell test (EST). With the use of a rat PBK model, predicted dose-response curves for in vivo developmental toxicity for the rat are acquired, which are compared with experimental literature data on the in vivo developmental toxicity of these compounds in the rat. To obtain the dose-response curves for in vivo developmental toxicity in human, PBK-models describing the in vivo kinetics in human are used. The combined in vitro-in silico approach described is used for compounds belonging to the chemical class of glycol ethers or the chemical class of retinoids. This enables evaluation of whether the combined in vitro - in silico approach is able to predict dose-response curves for in vivo developmental toxicity for compounds belonging to the same chemical class, but with differences in toxic potency. The results of the research reveal the feasibility of translating in vitro concentration-response curves to in vivo dose-response curves using PBK modeling. This finding shows the possibility of using in vitro toxicity data in chemical risk assessment, which will, if applied in risk assessment, highly contribute to the 3Rs.

Perinatal development and nutrient utilization in chickens : effects of incubation conditions
Molenaar, R. - \ 2010
University. Promotor(en): Bas Kemp, co-promotor(en): Henry van den Brand; R. Meijerhof. - S.l. : s.n. - ISBN 9789085858188 - 165
vleeskuikens - eieren - embryonale ontwikkeling - embryologie - broeden - voedingsfysiologie - vleeskuikenresultaten - dierfysiologie - broilers - eggs - embryonic development - embryology - incubation - nutrition physiology - broiler performance - animal physiology
Suboptimal incubation conditions can negatively affect survival and development of chicken embryos. However, physiological mechanisms that may explain these effects, and the long-lasting consequences are largely unknown. Therefore, the first aim of this thesis was to investigate effects of eggshell temperature (EST) and O2 availability during incubation on survival, development, physiology, and nutrient utilization of chicken embryos. The second aim was to investigate long-lasting effects of suboptimal EST on survival and subsequent performance of broiler chickens. The first study investigated effects of a high (38.9°C) or a normal (37.8°C) EST combined with a low (17%), normal (21%), or high (25%) O2 concentration from day 7 until 19 of incubation on the survival rate, nutrient utilization, and the developmental and physiological status of broiler embryos. The second study investigated effects of high EST on glucose metabolism in broiler embryos using [U-13C]glucose. The third study investigated effects of high EST on growth performance and the incidence of ascites in broiler chickens. Finally, effects of a high EST and a hole in the air cell on the developmental and physiological status of layer hatchlings were investigated. Results showed that a high EST or low O2 availability from the first week of incubation onward negatively affected survival and development of broiler chickens from their perinatal period until slaughter age. Body development of broiler hatchlings was reduced after high EST incubation because of a lower efficiency in protein utilization for growth. This was possibly due to the use of glucogenic amino acids as a glucogenic energy source, because high EST increased the glucose oxidation in broiler embryos during the second half of incubation and resulted in lower hepatic glycogen. Body development was proportional to the O2 availability during incubation. In addition, differences in O2 concentration during incubation seem to affect the development of adaptive mechanisms, and these mechanisms might possible influence nutrient utilization and body development. High EST in the last week of incubation in layer embryos negatively affected hatchling development, but the effect of a hole in the air cell was minimal. Effects of high EST were long-lasting in broiler chickens expressed by a lower body weight and a higher ascites incidence during the growout period. In conclusion, negative effects of suboptimal incubation conditions can be partly explained by changes in nutrient utilization and metabolite levels in the perinatal period and can have long-lasting effects on the survival and performance of broiler chickens.
Storage of Hatching Eggs : Effects of storage and early incubation conditions on egg characteristics, embryonic development, hatchability, and chicken quality
Reijrink, I.A.M. - \ 2010
University. Promotor(en): Bas Kemp, co-promotor(en): Henry van den Brand; R. Meijerhof. - [S.l. : S.n. - ISBN 9789085856658 - 164
eieren - opslag - broeden - ei-uitkomstpercentage - embryonale ontwikkeling - ei-albumen - eikwaliteit - kuikens - pluimveehouderij - dierfysiologie - eggs - storage - incubation - egg hatchability - embryonic development - egg albumen - egg quality - chicks - poultry farming - animal physiology
Key words: egg storage, embryonic development, albumen quality, hatchability, chick quality

It is well known that an increase in the storage duration increases incubation duration and decreases hatchability and chick quality. The negative effects of prolonged egg storage (> 7 days) may be caused by changes in the embryo, in the egg characteristics, or by both. The first aim of the current thesis was to investigate which physiological mechanisms are involved in the negative effects of prolonged egg storage on hatchability and chick quality. The second aim was to investigate how these negative effects of prolonged egg storage can be reduced by making changes in storage or early incubation conditions. Treatments, such as prestorage incubation, frequent warming during storage, a change in the storage air composition, different preincubation warming profiles, and hypercapnic incubation during the first 5 days of incubation were used in the current thesis to gain more insight in the cause of the negative effects of prolonged egg storage. Prestorage incubation and frequent warming during storage increased the stage of embryonic development and the number of viable embryonic cells. The effect of these treatments on hatchability was nihil, positive or negative and seems to depend on the stage of embryonic development before and after the treatment. The storage air compositions, studied in the current thesis did not affect embryonic development, hatchability, or chick quality, when eggs were stored for 14 days. This suggests that changes in albumen quality during storage do not affect hatchability and chick quality. The 24-h preincubation warming profile decreased embryonic mortality during the first 9 days of incubation in comparison with the 4-h preincubation warming profile when eggs were stored for 13 days. Hypercapnic incubation during the first 5 days of incubation decreased albumen pH during early incubation, but did not improve hatchability. In conclusion, embryo characteristics seem to have a more important role in the negative effects of prolonged egg storage than changes in the egg characteristics, such as changes in the albumen pH and albumen height.

Embryo temperature during incubation: practice and theory
Lourens, A. - \ 2008
University. Promotor(en): Bas Kemp, co-promotor(en): Henry van den Brand; R. Meijerhof. - S.l. : S.n. - ISBN 9789085852582 - 131
kuikens - embryo's - temperatuur - broeden - embryonale ontwikkeling - warmteproductie - warmteverlies - eierschaal - incubators - pluimveehouderij - chicks - embryos - temperature - incubation - embryonic development - heat production - heat loss - egg shell - poultry farming
(Key words: incubation, embryo temperature, embryonic development, heat production, heat loss)

Until recently, all incubator studies were performed using a constant machine temperature (MT). But it is embryo temperature (ET) that is of importance to the embryo, and not MT. In practice, MT is often measured at one location within the incubator, while ET can vary between eggs within an incubator. Furthermore, ET is the result of the balance between heat production (HP) and heat loss, and if HP or heat loss is affected it may have consequences for ET. Aim of this dissertation was to identify the causes of variable ET and to describe the consequences of variable ET on embryonic development, hatchability, HP and chick quality. Because the direct measurement of ET is destructive, it was chosen in this dissertation to use eggshell temperature (EST) measurements as a reflection of ET.
Long term deviations of 1.1ºC away from a constant EST of 37.8ºC decreased embryonic growth, development, hatchability, and the ability of young chicks to maintain high body temperatures after hatching, especially under cold stress. HP was considered to be positively related to embryonic development, because when more energy is used for growth, HP during incubation will increase and chicks will subsequently hatch with a larger yolk free body and with a lower amount of energy left over in the residual yolk. Within the EST zone of 1.0ºC below and above 37.8ºC it was observed that HP increased linearly with short term EST increments, and the response of the embryos to EST variations was identical in young, mid term and late term embryos. Maximizing HP based on metabolic responses to EST fluctuations will therefore increase EST above the studied EST zone, leading to decreased embryonic growth and increased embryonic mortality. High EST increases the demand for oxygen, so oxygen availability was expected to limit HP and embryonic growth more at higher EST profiles than at EST of 37.8ºC. However, despite the fact that HP at day 18 was highest for the combination of high EST with high oxygen concentration, embryonic development did not show the same relationship. At EST above 37.8ºC, the amount of energy utilized from the egg content remained the same, but the efficiency of energy transfer (EYFB) between egg and embryo decreased. Factors as egg size, breed, and oxygen availability affected HP through changes in energy utilization, and had no effect on EYFB.
In this thesis, the importance was shown to measure and control ET during incubation and not MT. Factors were identified that affect ET through changes in HP and heat loss. When ET is controlled and maintained at a constant level of 37.8ºC, embryonic development may be improved by measures that increase energy utilization through increments in gas exchange, which will increase HP.
Kennisoverdracht broederij 2006
Lourens, A. - \ 2008
Lelystad : Animal Sciences Group (Rapport / Animal Sciences Group 137) - 40
uitbroeden - broeden - broedproductie - eikwaliteit - eieren - eierproductie - embryonale ontwikkeling - kuikenembryo's - broedeieren - hatching - incubation - brood rearing - egg quality - eggs - egg production - embryonic development - chick embryos - hatching eggs
In dit rapport worden de basispresentaties weergegeven die zijn gehouden voor het project "Kennisoverdracht Broederij 2006" op 11 broederijen in Nederland, voor in totaal 115 personen door middel van een powerpointpresentatie
Lactational oestrus in sows : follicle growth, hormone profiles and early pregnancy in sows subjected to Intermittent Suckling
Gerritsen, R. - \ 2008
University. Promotor(en): Bas Kemp, co-promotor(en): P. Langendijk; Nicoline Nieuwenhuizen-Soede. - [S.l.] : S.n. - ISBN 9789085048725 - 142
zeugen - oestrus - lactatie - follikels - groei - hormonen - zwangerschap - zogen - embryonale ontwikkeling - voortplanting - sows - lactation - follicles - growth - hormones - pregnancy - suckling - embryonic development - reproduction
Keywords: sow; Intermittent Suckling; oestrus; lactation; oestradiol; LH; progesterone, embryo
survival, embryo development, cystic ovaries.

Weaning of piglets at a relatively young age (3 to 4 weeks) can compromise health and welfare. A
possible way to increase piglet welfare is to extend lactation length, but this is economically
undesirable due to lactational anoestrus of the sow. Thus, an extension of lactation would reduce the
number of litters per sow per year. Intermittent Suckling (IS), a management system in which the
lactating sow is separated from her litter for a fixed period of the day, is proposed as method to extend
lactation length without compromising sow reproductive performance. The aims of this thesis were to
study if by application of IS, lactational oestrus and ovulation could be induced in a large proportion
of the sows and to examine the quality of such a lactational oestrus by studying hormone levels and
pregnancy parameters. Within a first study, sows were separated from their piglets for either 12h
continuously or at 6h intervals from d14 of lactation onwards. In a control group, weaning occurred at
d21 of lactation. Lactational oestrus was induced in more than 80% of the sows. The pre-ovulatory LH
surge, progesterone (P4) levels and the number of ovulating sows were negatively affected by IS and
embryo development was negatively affected by the regimen of IS (6h). Low P4 levels have been
related to a low embryo survival and one factor known to affect P4 levels was feeding level. Therefore,
the aim of a second study was to examine the effect of the high lactational feeding level of IS sows on
P4 levels. Multiparous sows, subjected to IS daily for 12h continuously, were fed at a high
(±6.5kg/day) or low (±4kg/day) feeding level from ovulation to 6 days after ovulation. Results of this
study indicated that P4 levels were not affected by high lactational feeding levels and that P4 levels
were comparable to levels found in the first study. In a third study two other factors, possibly involved
in the low P4 levels, were studied: timing of start of IS and continuance of IS during early pregnancy.
Multiparous sows were subjected to IS for 12h continuously per day from d14 or d21 of lactation
onwards. Weaning occurred either at ovulation or day 20 after ovulation. An early start of IS (d14) did
not significantly affect the pre-ovulatory LH surge, but resulted in lower P4 levels at d7 after ovulation.
Continuance of IS after ovulation resulted in lower P4 levels after ovulation and also negatively
affected embryo development. Thus, lactational factors such as suckling related hormones or the
metabolic state of the sow may caused the low P4 levels in IS sows. In general, a high proportion of IS
sows developed cystic ovaries. In a final study, reproductive parameters were examined in sows
developing cysts. Sows developing cysts lacked an LH surge. A dysfunction in oestradiol feedback
seems the underlying mechanism responsible for the lack of the LH surge and may be related with
stress or the metabolic state of IS sows. In conclusion, it is possible by means of IS to induce
lactational oestrus and ovulation. The rate of success, however, is dependent on several factors such as
the breed of the sow and the timing of start of IS. The quality of lactational oestrus (hormone levels,
embryo survival) seems comparable to weaned sows when start of IS is not too early after farrowing
and IS is not continued during early pregnancy.
Nog even verder broeden
Brand, H. van den; Klein Swormink, B. - \ 2007
De Pluimveehouderij 37 (2007)32. - ISSN 0166-8250 - p. 14 - 15.
pluimveehouderij - pluimvee - eieren - embryo's - embryonale ontwikkeling - broedeieren - poultry farming - poultry - eggs - embryos - embryonic development - hatching eggs
Wageningen UR deed onderzoek naar het onder water bewaren van broedeieren. In de eerste fase van ontwikkeling verloopt de embryonale ontwikkeling erg goed, maar in de tweede fase moet die voorsprong weer worden prijs gegeven
Jonge moederdieren en korte bewaartijden: ammoniak pakt positief uit voor het embryo
Lourens, A. - \ 2006
De Pluimveehouderij 35 (2006)4. - ISSN 0166-8250 - p. 8 - 9.
kuikens - kuikenembryo's - foetale groei - embryonale ontwikkeling - pluimvee - ammoniak - chicks - chick embryos - fetal growth - embryonic development - poultry - ammonia
Voor het broedproces is een samenstelling vereist die lijkt op die van langer bewaarde broedeieren. Dit staat echter weer haaks op het streven naar een korte bewaartijd. Onderzoek heeft uitgewezen dat Ammoniak kan helpen om het ei de eigenschappen te geven van langer bewaarde eieren, maar de bewaartijd kort te houden
Detecting the effects of environmentally relevant concentrations of thyroid hormone disrupting compounds on amphibian development
Gutleb, A.C. - \ 2006
University. Promotor(en): Ivonne Rietjens, co-promotor(en): Tinka Murk. - Wageningen : s.n. - ISBN 9085043549 - 168 p.
schildklierhormonen - amphibia - embryonale ontwikkeling - foetale ontwikkeling - xenopus laevis - hormoonverstoorders - thyroid hormones - embryonic development - fetal development - endocrine disruptors
Kleine afwijkingen, grote gevolgen: proef met eischaaltemperatuur tijdens broeden
Lourens, A. ; Brand, H. van den; Kemp, B. ; Meijerhof, R. - \ 2005
De Pluimveehouderij 35 (2005)17. - ISSN 0166-8250 - p. 8 - 9.
pluimveehouderij - kuikens - kuikenproductie - eieren - temperatuur - embryonale ontwikkeling - legresultaten - kuikenembryo's - lengte-gewichtverhouding - prestatieniveau - proeven - afwijkingen - broedeieren - poultry farming - chicks - chick production - eggs - temperature - embryonic development - laying performance - chick embryos - height-weight ratio - performance - trials - abnormalities - hatching eggs
Grote afwijkingen van de eischaaltemperatuur van 37,8 C zijn slecht voor de broeduitkomsten en de kuikenkwaliteit. Dat is bekend en ook begrijpelijk. Hoe zit het eigenlijk met kleine afwijkingen? Dat is nu dankzij een proef duidelijk geworden
Molecular mechanisms governing primordial germ cell migration in zebrafish
Doitsidou, M. - \ 2005
University. Promotor(en): Ton Bisseling. - [S.l.] : S.n. - 85 p.
danio rerio - kiemcellen - embryonale ontwikkeling - embryogenese - moleculaire biologie - embryo's - germ cells - embryonic development - embryogenesis - molecular biology - embryos
Oxygen diffusion in fish embryos
Kranenbarg, S. - \ 2002
University. Promotor(en): Johan van Leeuwen; J.W.M Osse; M. Muller. - S.l. : s.n. - ISBN 9789058086808 - 183
vissen - embryo's - embryonale ontwikkeling - embryologie - zuurstof - diffusie - zuurstoftransport - zuurstofconsumptie - voedingsstoffen - beperkingen - grootte - vorm - cardiovasculair systeem - genexpressie - modellen - biofysica - fishes - embryos - embryonic development - embryology - oxygen - diffusion - oxygen transport - oxygen consumption - nutrients - constraints - size - shape - cardiovascular system - gene expression - models - biophysics - cum laude
<font size="2"><p>All vertebrate embryos pass through a developmental period of remarkably low morphological variability. This period has been called phylotypic period. During the phylotypic period, organogenesis takes place, including blood vessel development. Before the phylotypic period, the embryos rely on diffusion for the internal oxygen transport. Diffusion, however, is an efficient way of transport only over small distances. Analytical models were constructed to investigate whether physical constraints ( <em>i.e.</em> diffusional limitations) demand the development of an internal oxygen transport system as the embryos grow bigger. These models showed that teleost embryos are smaller than their theoretically maximum size during the phylotypic period, based on oxygen diffusion. Lack of oxygen does therefore not demand blood vessel development. Subsequently, numerical models of oxygen diffusion in a zebrafish embryo ( <em>Danio rerio</em> ) were developed, thereby including the realistic shape of the embryo. These models were tested and refined with oxygen micro-electrode measurements of the oxygen partial pressure profile in and around the zebrafish embryo. This numerical-experimental procedure revealed a high oxygen permeability in the yolk of the zebrafish embryo. Furthermore, lowest oxygen partial pressures were found in the head region with a gradient of posteriorly increasing oxygen partial pressures along the midline of the embryo. The three-dimensional oxygen partial pressure profile was compared with the expression pattern of the angiogenic factor ( <em>vegf</em> ), which is known to be expressed under hypoxic conditions. The apparent colocalization of low oxygen partial pressure and the expression of <em>vegf</em> suggests oxygen to play an important role in regulating blood vessel development rather than posing a direct request for its development.
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