In 1997, Danen-Van Oorschot et al. described for the first time that apoptin, a protein encoded by an avian virus, induces p53-independent apoptosis in a tumor-specific way. Various pre-clinical... Show moreIn 1997, Danen-Van Oorschot et al. described for the first time that apoptin, a protein encoded by an avian virus, induces p53-independent apoptosis in a tumor-specific way. Various pre-clinical studies in animal tumor models have demonstrated apoptin as a safe and efficient anti-tumor agent. In tumor cells, apoptin is imported into the nucleus prior to the induction of apoptosis and regulated by a kinase activity specifically present in cancer cells. In this thesis, several studies have been carried out to reveal the novel aspects of the molecular pathways underlying the transformation-related apoptosis induction by the viral protein apoptin. Show less
Photosynthetic reaction centers (RCs) from plants, heliobacteria and green sulphur bacteria has been investigated with photochemically induced dynamic nuclear polarization (photo-CIDNP) MAS NMR. In... Show morePhotosynthetic reaction centers (RCs) from plants, heliobacteria and green sulphur bacteria has been investigated with photochemically induced dynamic nuclear polarization (photo-CIDNP) MAS NMR. In photosystem (PS) I of spinach, all signals appear negative which is proposed by a predominance of the three spin mixing (TSM) over the differential decay (DD) mechanism. There are contrasting magnetic-field dependence of photo-CIDNP of PSI and PSII. For PSII the optimal NMR enhancement factor of ~5000 is observed at 4.7 T, while the strongest light-induced signals of PSI are at 9.4 T. The simulations indicate that difference between bacterial RCs and plant PS I can be due to an increase of the exchange coupling between the donor and acceptor radicals. In the RCs of Chlorobium tepidum the spectra appear negative and can be tentatively assigned to two bacterio chlorophyll a molecules of the donor. The spectral pattern obtained from membrane fragments of Heliobacillus mobilis at 4.7 T, appear to be both positive and negative, which is similar to the pattern observed in the RCs of plant PSII and RCs of Rhodobacter sphaeroides R-26. However, unlike the other RCs, in this system, at 17.6 T, the positive signals undergo a sign change and appear negative. Show less
In a murine model for rheumatoid arthritis, we wished to investigated whether it was possible to skew the immune response with a cellular vaccin to protect the mice against the induction and/or... Show moreIn a murine model for rheumatoid arthritis, we wished to investigated whether it was possible to skew the immune response with a cellular vaccin to protect the mice against the induction and/or progeression of arthritis. the model that was used for this purpose was Collagen-Induced Arthritis (CIA). As dendritic cells (DCs) are the main antigen-presenting cells and key players in setting immune responses and connecting innate witth adaptive immunity, it is favorable to use these cells to manipulate the immune system to circumvent autoimmunity, in this case CIA. Because CIA is still implicated as a Th1-mediated disease, the aim was to skew the immune system towards a more Th2-like phenotype or to induce a T cell with a regulatory capacity. Therefore, several ways to stimulate DCs and subsequently the evolving T cell response were selected, to analyze whether Th2 cells or regulatory T cells were activated, resulting in the inhibition of arthritis. Show less
This thesis describes the Leiden Artificial Reproductive Techniques Follow-up Project. In this project, the potential long-term effects of intracytoplasmic sperm injection (ICSI) were assessed in 5... Show moreThis thesis describes the Leiden Artificial Reproductive Techniques Follow-up Project. In this project, the potential long-term effects of intracytoplasmic sperm injection (ICSI) were assessed in 5 __ 8-year-old singleton children. ICSI is the method of artificial reproduction in which a sperm cel is injected into an oocyte using a microinjection pipette. The technique is mainly successful in overcoming male factor infertility. Concerns about the development and health of ICSI-children have existed since the introduction of the technique in 1992, because ICSI is more invasive than the more widespread technique of in vitro fertilisation (IVF). In this project, 87 ICSI-children born as a singleton were compared with 87 singletons born after IVF and 85 singletons born after natural conception at 5-8 years of age, on various parameters: neuromotor development, cognitive development, pregnancy, perinatal outcome, congenital malformations, general health, growth, medical care utilisation, behaviour, parenting stress, and child quality of life. Although the results remain inconclusive on some outcomes, the majority of concerns regarding development and health of ICSI-children can be dispelled up to 8 years of age, in particular when ICSI is compared to IVF. Show less
Given the natural history of colorectal and breast cancer, early diagnosis appears to be the most appropriate tool to reduce disease-related mortality.[6;7] Currently, there is no early diagnostic... Show moreGiven the natural history of colorectal and breast cancer, early diagnosis appears to be the most appropriate tool to reduce disease-related mortality.[6;7] Currently, there is no early diagnostic test with high sensitivity, specificity and positive predictive value, which can be used as a routine screening tool. Therefore, there is a need for new biomarkers for both types of cancer that can improve early diagnosis, monitoring of disease progression and therapeutic response and detect disease recurrence. Proteomic expression profiles generated with mass spectrometry have been suggested as potential tools for the early diagnosis of cancer and other diseases. Because it is still in its infancy, many problems have to be overcome before clinical proteomics can be transferred form bench to bedside. Chapter 2 gives an insight in the different fields of translational research in colorectal cancer by our group. In chapter 3 reliability of human serum protein profiling using MALDI-TOF mass spectrometry is analysed. We present a pipeline for pre-processing, statistical data analysis and presentation of MALDI-TOF spectra. This novel analysis method was used to assess the effect of variable pre-analytical conditions on human serum protein profiles, and their effect on reproducibility. In line with the logistic conditions in a routine clinical setting, the effects of sample handling and storage, and also circadian rhythm factors on the serum protein profiles were analysed. In chapter 4 and 5 the feasibility of mass spectrometry based protein profiling for the discrimination of colorectal cancer patients from healthy individuals was assessed. In addition to standardizing technical factors and biological variations, we performed blinded tests and employed a randomised block design experimentation to minimize impact of potential confounding factors and to avoid bias. Especially, validation of our classifier, as a possible pitfall, was given much attention. Therefore, we performed a linear discriminant analysis with double cross-validation to separate cancer patients from healthy subjects. Chapter 6 reports on results from an identical designed protein profiling study for the detection of breast cancer. In chapter 7 a first validated study on the detection of breast cancer based on mass spectrometry generated protein profiles is described. In this study the same randomised blocked design and double cross validation is used, however the classifier was validated in an independent set of new patients and controls. Finally, the results and conclusions of all above mentioned studies and especially the current status of clinical proteomics in cancer are discussed in chapter 8. A Dutch summary of this thesis is written in chapter 9. Show less
This dissertation focuses on social dilemmas, and more specifically, on environmental uncertainty in these dilemmas. Real-life social dilemma situations are often characterized by uncertainty. For... Show moreThis dissertation focuses on social dilemmas, and more specifically, on environmental uncertainty in these dilemmas. Real-life social dilemma situations are often characterized by uncertainty. For example, fishermen mostly do not know the exact size of the fish population (i.e., resource size uncertainty). Several researchers have therefore asked themselves the question as to how such uncertainty influences people’s choice behavior. These researchers have repeatedly concluded that uncertainty is detrimental to the collective because it induces over-harvesting. The present dissertation aims to provide a more comprehensive view on uncertainty in social dilemmas. Whereas earlier research has primarily investigated how uncertainty influences harvesting decisions, this dissertation also focuses on how environmental uncertainty affects interpersonal processes. This dissertation introduces a perspective that argues that environmental uncertainty hampers the application of the equal division rule, which in turn influences how group members interact with one another. In six chapters, I elaborate on numerous implications of this notion. By focusing on three key aspects of interpersonal processes (i.e., tacit coordination, justification pressures and interpersonal emotions), and by testing my ideas in seven empirical studies, I demonstrate that the effects of uncertainty are much more differentiated than is portrayed in earlier research. Show less
Glomerulosclerosis is a general term describing the process of scarring of the glomeruli, the functional units in the kidney that filter urine from the blood. This severe, irreversible complication... Show moreGlomerulosclerosis is a general term describing the process of scarring of the glomeruli, the functional units in the kidney that filter urine from the blood. This severe, irreversible complication can occur secondary to various already established systemic or local diseases. However, not all patients with renal diseases show progression to end stage renal disease (ESRD). Thus renal patients can be subdivided into progressors and non-progressors based on clinical parameters1. Why patients with renal diseases become progressors or non-progressors is unclear, and better insight into the pathogenesis of glomerulosclerosis may improve our understanding of the process towards progression. However, the pathogenesis of glomerulosclerosis is complex and still poorly understood, although genetic factors probably play a role, given the considerable variation among individuals in both the risk of developing glomerulosclerosis and the rate of progression. Therefore, the first aim of the work described in this thesis was to identify genes involved in the progression and repair of glomerulosclerosis, using an animal model that allows a clear distinction between progression and repair after renal injury. The second aim was to gain better insight into the pathogenesis of glomerulosclerosis by investigating the expression and activity of fibrosis-related molecules in an animal model and in patients with renal diseases. Show less
The general goal of this PhD research was to study the phylogeny and systematics of selected plant genera in the subfamily Acalyphoideae s.s. of the angiosperm family Euphorbiaceae. The main focus... Show moreThe general goal of this PhD research was to study the phylogeny and systematics of selected plant genera in the subfamily Acalyphoideae s.s. of the angiosperm family Euphorbiaceae. The main focus was on two large genera, Macaranga and Mallotus, and a number of smaller genera related to them. The phylogeny of these genera was studied using sequence data from plastid (trnL-F) and nuclear (ITS, ncpGS, phyC) markers. The results show that Macaranga is a monophyletic genus, but that Mallotus is paraphyletic for two reasons: 1) Mallotus sections Hancea and Oliganthae form a separate clade together with the genera Cordemoya and Deuteromallotus, and 2) the genera Coccoceras, Neotrewia, Octospermum and Trewia are part of the main Mallotus clade. To reflect these findings in the classifications, Neotrewia, Octospermum and Trewia were merged with Mallotus (the other necessary taxonomic rearrangements have been conducted separately). A taxonomic revision for these three genera was also conducted. Further, the phylogeny of the main Mallotus clade was studied in more details using both molecular (matK, gpd) and morphological data. Additionally, a taxonomic revision of the Malesian species in the genus Cleidion was conducted, and the morphology and phylogenetic position of previously insufficiently known African genus Afrotrewia was studied. Show less
The goal of this thesis is to study charge transport phenomena in organic materials. This is done optically by means of single-moleculespectroscopy in a field-effect transistor based on a molecular... Show moreThe goal of this thesis is to study charge transport phenomena in organic materials. This is done optically by means of single-moleculespectroscopy in a field-effect transistor based on a molecular crystal.We present (in Chapter 2) a fundamental requirement for single-moleculespectroscopy concerning the energy levels of the guest molecule withrespect to the ones of the host molecule. Following this constraint, westudy (in Chapters 3 and 4) the photophysics of a new system forhigh-resolution spectroscopy at cryogenic temperatures, which consistsof dibenzoterrylene molecules inserted in a crystal of anthracene. Wethen characterise (in Chapter 5) the electrical properties of theanthracene field-effect transistor with 'conventional' methods. In Chapter 6, wefinally use the influence of an electric field on the spectroscopicproperties of fluorescent molecules to investigate locally the chargecarrier transport phenomena in a crystal of anthracene.The goal of this thesis is to study charge transport phenomena inorganic materials. This is done optically by means of single-moleculespectroscopy in a field-effect transistor based on a molecular crystal.We present (in Chapter 2) a fundamental requirement for single-moleculespectroscopy concerning the energy levels of the guest molecule withrespect to the ones of the host molecule. Following this constraint, westudy (in Chapters 3 and 4) the photophysics of a new system forhigh-resolution spectroscopy at cryogenic temperatures, which consistsof dibenzoterrylene molecules inserted in a crystal of anthracene. Wethen characterise (in Chapter 5) the electrical properties of theanthracene field-effect transistor with 'conventional' methods. In Chapter 6, wefinally use the influence of an electric field on the spectroscopicproperties of fluorescent molecules to investigate locally the chargecarrier transport phenomena in a crystal of anthracene.The goal of this thesis is to study charge transport phenomena inorganic materials. This is done optically by means of single-moleculespectroscopy in a field-effect transistor based on a molecular crystal.We present (in Chapter 2) a fundamental requirement for single-moleculespectroscopy concerning the energy levels of the guest molecule withrespect to the ones of the host molecule. Following this constraint, westudy (in Chapters 3 and 4) the photophysics of a new system forhigh-resolution spectroscopy at cryogenic temperatures, which consistsof dibenzoterrylene molecules inserted in a crystal of anthracene. Wethen characterise (in Chapter 5) the electrical properties of theanthracene field-effect transistor with 'conventional' methods. In Chapter 6, wefinally use the influence of an electric field on the spectroscopicproperties of fluorescent molecules to investigate locally the chargecarrier transport phenomena in a crystal of anthracene. Show less
An adverse early life event is considered a risk factor for stress-related psychiatric disorders in genetically predisposed individuals, probably because of its lasting effect on susceptibility to... Show moreAn adverse early life event is considered a risk factor for stress-related psychiatric disorders in genetically predisposed individuals, probably because of its lasting effect on susceptibility to stress. The objective of this thesis research was to examine in the mouse CD1 strain the immediate and permanent effects of an adverse early experience on the neuroendocrine stress system. For this purpose the hypothalamic-pituitary-adrenal (HPA) axis was examined of mouse pups that were refrained from maternal care, a laboratory model for neglect mimicking aspects of abuse. The data show that the infants__ stress response system readily adapts to daily repeated 8 hours of maternal separation, but that it continues to respond to a novelty stressor. The rapid adaptation to repeated maternal absence seems rather due to the ability to predict return of the mother than to adjust metabolism to episodic food deprivation. If maternal separation was extended to a single episode of 24 hours the immediate outcome was more profound but transient, although subtle effects on stress reactions and cognitive performance did persist. The findings demonstrate the amazing plasticity of the newborn brain and provide a basis to study the mechanistic underpinning of vulnerability or resilience to psychopathology. Show less
In this thesis I considered the dynamics of self-propelling particles (SPP). Flocking of living organisms like birds, fishes, ants, bacteria etc. is an area where the theory of the collective... Show moreIn this thesis I considered the dynamics of self-propelling particles (SPP). Flocking of living organisms like birds, fishes, ants, bacteria etc. is an area where the theory of the collective behaviour of SPP can be applied. One can often see how these animals develop coherent motion, amazing the observer by the diversity of its forms and shapes. In this thesis a hydrodynamic model with so-called kinematic constraints, which are imposed on the orientations of the velocities of the particles, is proposed. The tendency of the particles to adjust their velocities to the ones of the neighbours leads to the emergence of a coherent motion. In our model two types of stationary flows are obtained: linear and vortical hydrodynamic flows. A remarkable property of the vortical flow is that it has finite flocking behaviour, where the density and the velocity fields are coupled. From the physical point of view these flows are of interest because of their realization in nature. The stability properties of the stationary flows are determined. Further a hydrodynamic model is derived from the discrete description using the averaging procedure. The connection between the discrete and continuous approaches is analysed. Show less
From its origin at the center of a star to the edge, through the surrounding gas and dust in the distant galaxy, through the intergalactic medium, traveling billions of light years only to be... Show moreFrom its origin at the center of a star to the edge, through the surrounding gas and dust in the distant galaxy, through the intergalactic medium, traveling billions of light years only to be reflected by a mirror and captured by a detector; the little amount of light observed from galaxies in the early universe contains a wealth of historic information. This thesis concentrates on translating the luminosities and colors of distant galaxies to physical properties such as distance, mass, age of the stellar population, and dust content. Analyzing deep optical and infrared observations of distant (redshift z~2.5) galaxies, we learn that massive galaxies have on average redder colors than less massive galaxies, although simulations show that mass underestimates of star-forming galaxies are possible. Roughly half of the red galaxies at high redshift owe their color to an old, quiescent stellar population. The other half is still actively star-forming, but obscured by large columns of dust. The abundance of star-forming and quiescent galaxies is consistent with a model that assigns a key role to collisions between gas-rich disk galaxies involving quasar activity, and leaving red spheroids as remnants. However, this model does not reproduce the colors of dusty red galaxies. Show less
The studies in this thesis describe the clinical impact of several matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in H. pylori-induced gastritis and gastric... Show moreThe studies in this thesis describe the clinical impact of several matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in H. pylori-induced gastritis and gastric cancer. In patients with H. pylori-induced gastritis, significantly increased mucosal MMP-9 levels were found. By successful H. pylori eradication, active and chronic inflammation decreased, accompanied by a significant decrease of mucosal MMP-9. MMP-2, MMP-7, MMP-8 and MMP-9, lipocalin-2, MMP-9/lipocalin-2 and TIMP-1 were significantly increased in tumour tissue of gastric cancer patients compared to normal gastric mucosa whereas only enhanced levels of MMP-2 and MMP-9/lipocalin-2 complexes were independently related to worse prognosis. Subsequently the genotype distribution of single-nucleotide polymorphisms (SNPs) of MMPs and TIMPs in gastric cancer was studied. The genotype distribution of MMP-7-181A>G was associated with H. pylori status and tumour-related survival of the patients. Single-nucleotide polymorphism TIMP-2-303C>T correlated significantly with tumour-related survival. First-order dendrogram cluster analysis combined with Cox analysis identified the MMP-7-181A>G and TIMP-2-303C>T polymorphism combination to have a major impact on patients survival outcome. Show less
Atherosclerosis is a progressive disease of the large arteries characterized by lipid deposition, inflammation, cell death and fibrosis and it is the major cause of death in the Western world. In... Show moreAtherosclerosis is a progressive disease of the large arteries characterized by lipid deposition, inflammation, cell death and fibrosis and it is the major cause of death in the Western world. In this thesis new and experimental therapies against atherosclerosis are designed and tested. New targets for these therapies were identified by using a mouse model for atherosclerosis, the LDL receptor deficient mouse. We used micro-arrays to compare gene expression from mice with atherosclerosis to control mice and the following targets, all related to leukocyte migration and activation, were identified; CCR5, CXCR3, CD99, IL-16, OX-40 and CD127. Vaccines against CD99, IL-16 and CD127 were designed and tested. Specific antagonists of CCR5 and CXCR3 were used to block these molecules and a specific antibody against OX40 ligand was tested in LDL receptor deficient mice. The effects of these treatment strategies are described in the chapters of this thesis. In conclusion, modulation of leukocyte activation and migration provides an attractive possibility for future drug design in the field of atherosclerosis. Show less
The major targets in Systemic lupus erythematosus (SLE, a systemic autoimmune disease) are nuclear components (DNA, histones, ribonucleoproteins), which are mainly derived from dying cells ... Show moreThe major targets in Systemic lupus erythematosus (SLE, a systemic autoimmune disease) are nuclear components (DNA, histones, ribonucleoproteins), which are mainly derived from dying cells (apoptotic and necrotic cells). Defective clearance of dying cells by phagocytes may lead to the breakdown of peripheral tolerance and initiation of autoimmune SLE. I have investigated the role of the innate immune system in the processing of dying cells and its immunological consequences. I found that a subset of macrophages driven by M-CSF have intrinsic anti-inflammatory properties and are potent phagocytes that have the unique capacity to preferentially bind and ingest early apoptotic cells in a silent manner. I also identified that human peritoneal macrophages freshly isolated from patients on peritoneal dialysis resemble functionally the in vitro-generated M-CSF-driven macrophages. I further showed that the anti-inflammatory and pro-inflammatory macrophages co-exist but can re-differentiate towards opposing phenotype depending on the local cytokine environment. Next to the phagocyte system, I investigated the role of components of the innate immune system in the processing of dying cells. I found that one of the complement regulators called properdin, binds predominantly to late apoptotic and necrotic cells independently of C3b, resulting alternative pathway complement activation. Show less
A key issue in astronomy today is understanding the star-formation and assembly history of massive galaxies. Stellar population studies show that the bulk of the stars in low-redshift massive... Show moreA key issue in astronomy today is understanding the star-formation and assembly history of massive galaxies. Stellar population studies show that the bulk of the stars in low-redshift massive galaxies is formed at z~2 or even higher. Furthermore, there are strong indications that about 50% of the massive, quiescent galaxies in the local universe was already in a quiescent phase when the universe was only half its current age. This raises the question of whether quiescent galaxies can be found at even earlier epochs, and when massive galaxies formed and assembled their stellar mass. In order to address these questions we have pushed current studies to higher redshift and conducted a near-infrared spectroscopic survey of massive galaxies at z~2.5. In total we obtained deep spectra with a wavelength coverage of 1-2.5 micron for a sample of 36 galaxies. A surprising result of our survey is that a significant fraction of the massive galaxies at z~2.5 is already in a quiescent phase. Furthermore, several massive galaxies host active galactic nuclei, which may be responsible for the quenching of star formation. This thesis introduces the survey, presents these main results, and discusses the resulting constraints on the formation history of massive galaxies. Show less
The perfect anticancer drug would kill cancer cells without causing any harm to the surrounding healthy tissues. That ideal medicine is searched for in this thesis, in the form of a ruthenium... Show moreThe perfect anticancer drug would kill cancer cells without causing any harm to the surrounding healthy tissues. That ideal medicine is searched for in this thesis, in the form of a ruthenium coordination complex.Metal complexes are known to interact with DNA in several different modes, amongst which are coordination, intercalation of the aromatic part of the molecule between the DNA base-pairs and binding of the complex to one of the DNA grooves.Is there a correlation between the ruthenium–DNA interactions and the cytotoxicity of these complexes? Three ruthenium polypyridyl complexes (1a-c) were synthesized and characterized, which can coordinate to guanine. The structure-related 1e and 1f, as well as the dinuclear complex 1g, were also chosen for these studies. The interactions between each ruthenium complex and DNA were studied; the activities of the compounds in different cancer cells were tested.The results of these tests suggest that 1a-c and 1e coordinate to DNA, while 1g probably fits in the DNA groove. These complexes display moderate activity in some cancer cell lines. The inactive complex 1f can coordinate to guanine and bind to DNA via intercalation or groove-binding. 1f is the only one of the studied compounds that lacks an azo group, which suggests that this group is essential for cytotoxicity.The interactions between metal complexes and other biological molecules are also mentioned. Show less
