Malaria continues to wreak havoc in tropical regions, due largely to the lack of an effective vaccine. Vaccine candidates based on whole parasites have shown promising results in malaria-naïve... Show moreMalaria continues to wreak havoc in tropical regions, due largely to the lack of an effective vaccine. Vaccine candidates based on whole parasites have shown promising results in malaria-naïve individuals, but their potency in malaria-exposed individuals is considerably lower. This dissertation described the development of a chemical strategy for boosting such parasites’ potency in pursuit of more efficacious malaria vaccines for use in endemic areas.Chapter 2 outlined the adaptation of a method for chemically modifying microbial cell surfaces.Chapter 3 showed the chemistry underlying this modification system to be stably compatible with in vivo usage.Chapter 4 demonstrated that when the chemical modification system was used to introduce immune-potentiating agents onto bacteria, better immune responses ensued.Chapter 5 tied it all together by using the chemical modification system to potentiate malaria parasites, and showed that doing so markedly improved immune responses in an in vivo immunization model.Chapter 6 summarized these findings in the context of malaria vaccine development and posited next steps forward. Show less
In this dissertation we investigate the emotional and psychiatric effects of glucocorticoids (e.g. cortisol, dexamethasone and prednisone). Glucocorticoids are widely used and their possible... Show moreIn this dissertation we investigate the emotional and psychiatric effects of glucocorticoids (e.g. cortisol, dexamethasone and prednisone). Glucocorticoids are widely used and their possible psychiatric side effects are well known. It is still unclear who is susceptible to side effects and what mechanism is behind this. In this thesis we try to better understand the underlying causes. For example, we use a relatively new static method in this research field, which can analyze changes over time better than the usual methods. In a study, we show that in depressed study participants, changes in certain affect items preceded changes in cortisol levels, while in control participants this was the other way around. Furthermore, we explore a hypothesis that may explain the mechanism of the psychiatric side effects of glucocorticoids. This mechanism is also used for a strategy to prevent the psychiatric side effects. The strategy is based on the fact that synthetic glucocorticoids are very similar to the body's own hormone cortisol, but their binding to the two cortisol receptor proteins and their effects may be different. By achieving a balanced activation of the two cortisol proteins when using glucocorticoids, the psychiatric side effects could possibly be prevented. In summary, this thesis provides further insight into the emotional and psychiatric side effects of glucocorticoids, but the search for a better understanding of the neuropsychiatric side effects remains a pressing concern, which will hopefully benefit patient care in the future. Show less
The lipids in the uppermost layer of the skin, the stratum corneum (SC), play an important role in the skin barrier function. The three main SC lipid classes are ceramides (CER), cholesterol and... Show moreThe lipids in the uppermost layer of the skin, the stratum corneum (SC), play an important role in the skin barrier function. The three main SC lipid classes are ceramides (CER), cholesterol and free fatty acids. In inflammatory skin diseases, such as atopic dermatitis and psoriasis, the SC lipid composition is altered compared to the healthy SC composition. The studies presented in this thesis focused on the effect of the CER subclass composition on the lipid organization, molecular arrangement and barrier function of the skin. First, the CER compositional changes were examined in the SC of seborrheic dermatitis patients, an inflammatory skin disease. A particular emphasis was paid to the ratio of two important CER subclasses, sphingosine CER (CER NS) and phytosphingosine CER (CER NP), and its correlation to the skin barrier. In the subsequent chapters lipid model systems with a simple CER subclass composition were used to study the influence of the CER NS: CER NP molar ratio on the barrier function and lipid organization. Show less
The dissertation investigates the role of lexical tone in spoken word recognition and production. In particular, it focuses on three groups of speakers: native speakers of Standard Chinese, bi... Show moreThe dissertation investigates the role of lexical tone in spoken word recognition and production. In particular, it focuses on three groups of speakers: native speakers of Standard Chinese, bi-dialectal speakers of Standard Chinese and Xi’an Mandarin, and bilingual speakers of Standard Chinese and English. Through a series of experiments employing the eye-tracking visual world paradigm and the picture-word interference paradigm, four key issues were explored: the role of lexical tone in Mandarin spoken word recognition; tonal interference in bi-dialectal spoken word recognition; the activation of lexical tone in bilingual spoken word production; and the influence of lexical tone on the bilingual mental lexicon. The findings of this dissertation not only showed how Mandarin listeners utilize tonal information during tone word recognition but also revealed dynamic tonal interaction between language systems. Overall, this dissertation contributes to a deeper understanding of lexical access by highlighting the significant role of lexical tone in both monolingual and bilingual contexts, shedding light on the intricate processes involved in spoken word recognition and production across languages. Show less
Manumission is the release from slavery, and therefore, a transition from the most extreme form of subjugation into another position and status in society. Some historians have defined manumission... Show moreManumission is the release from slavery, and therefore, a transition from the most extreme form of subjugation into another position and status in society. Some historians have defined manumission as a formal act, often understood as a gift that severed the bond between slave and master. More recently researchers have emphasized that it was a lengthy process that involved pre-existing dependencies and resulted in new hierarchies. This article takes a fresh look at the process and tries to gain a fuller understanding of manumission by examining it from the position of the manumitted and their social relations. Taking into consideration a wide range of documentary sources from colonial, notarial and Dutch governmental archives, we reconstruct the dependencies that were created in the process of manumission. The dependencies that evolved during manumission processes were related to family and other kinship ties, but also had an urban, communal, religious, economic and institutional logic. Manumission was not only an act at a specific moment, but also a process, and it was not a bilateral, but a multilateral one. With the instrument of manumission and within the limits set by economic reality and the colonial government, the manumittees tried to make meaningful life choices that transformed slave society profoundly. We find that they created complex dependencies across boundaries of status and racial categorization. Show less
High-grade osteosarcoma, a primary malignant bone tumour, is experiencing a global increase in reported incidence with varied prevalence. Despite advances in management, which include surgery and... Show moreHigh-grade osteosarcoma, a primary malignant bone tumour, is experiencing a global increase in reported incidence with varied prevalence. Despite advances in management, which include surgery and neoadjuvant chemotherapy often an unsatisfactory outcome is found due to poor or heterogeneous response to chemotherapy. Our study delved into chemotherapy responses in osteosarcoma patients and associated molecular expressions, focusing on CD95 receptor (CD95R), interferon (IFN)-γ, catalase, heat-shock protein (Hsp)70, and vascular endothelial growth factor (VEGF). Employing immunohistochemistry and Huvos grading of post-chemo specimens, we analysed formalin-fxed parafn-embedded (FFPE) osteosarcoma tissue of resected post-chemotherapy specimens from Dr. Soetomo General Academic Hospital in Surabaya, Indonesia (DSGAH), spanning from 2016 to 2020. Results revealed varied responses (poor 40.38%, moderate 48.08%, good 11.54%) and distinct patterns in CD95R, IFN-γ, catalase, Hsp70, and VEGF expression. Signifcant diferences among response groups were observed in CD95R and IFN-γ expression in tumour-infltrating lymphocytes. The trend of diminishing CD95R expression from poor to good responses, accompanied by an increase in IFN-γ, implied a reduction in the count of viable osteosarcoma cells with the progression of Huvos grading. Catalase expression in osteosarcoma cells was consistently elevated in the poor response group, while Hsp70 expression was highest. VEGF expression in macrophages was signifcantly higher in the good response group. In conclusion, this study enhances our understanding of immune-chemotherapy interactions in osteosarcoma and identifes potential biomarkers for targeted interventions. Show less
This thesis has studied several modalities how to increase the organ utilisation rate. The results in this thesis indicate that the acceptance of kidneys with acute kidney injury stage 1 or 2 will... Show moreThis thesis has studied several modalities how to increase the organ utilisation rate. The results in this thesis indicate that the acceptance of kidneys with acute kidney injury stage 1 or 2 will significantly contribute to the donor pool as AKI kidneys have comparable outcomes and should therefore not be discarded. Clinically relevant biomarkers such as cell-free unmethylated-INS DNA, FMN, GSN, IGFBP3 and IGF2R were identified or explored in the first part of this thesis and may, if analysed and/or validated thoroughly, contribute to a better assessment of organ viability supporting the justified decision whether to accept or decline the donor organ.The second part of this thesis describes different aspects of the organ preservation technique of abdominal normothermic regional perfusion (aNRP). This relatively new machine perfusion technique has been shown to be feasible and safe, however, consensus regarding assessment parameters during perfusion, protocols and outcome measurements is still lacking. Despite of an inspiring surgical enthusiasm and keeninterest to accept this modality as a new standard, a randomised clinical trial is still required and entirely ethically justifiable in order to scientifically demonstrate superiority of this method for each individual abdominal organ comparing it to other successful (ex-situ) preservation and perfusion strategies. If aNRP can be shown to obtain better post transplantation outcomes whilst increasing organ utilisation, it may be the least complex and most cost-effective strategy in organ preservation. On the other hand, aNRP will only be used in DCD donors. As such, uncertainty regarding the quality of higher risk organs from DBD donors will still be evaluated ex-situ during cold and/or warm machine perfusion with the potential to repair or even regenerate injured organs and making them ‘transplantable’ again. Show less
Demand for palliative care is expected to rise due to an ageing population, an increase in chronic diseases, and multimorbidity. Currently, many countries, including the Netherlands, are dealing... Show moreDemand for palliative care is expected to rise due to an ageing population, an increase in chronic diseases, and multimorbidity. Currently, many countries, including the Netherlands, are dealing with a high demand and shortages of professionals in the healthcare sector. Because of the different nature of providing palliative care compared to curative care and the expected increase in demand for palliative care, the focus of this thesis is to gain insight into the emotional impact of providing palliative care on healthcare professionals.This thesis highlights the emotional stressors healthcare professionals encounter in providing palliative care. Building personal relationships with patients bring both rewarding and emotionally experiences, especially when patients are dying. Among palliative care professionals higher burnout rates were found in general settings than in specialised palliative care settings, possibly due to insufficient training and attention to the emotional impact of providing palliative care in the former.Education and group meetings are seen as crucial for raising awareness and reducing stress. This thesis emphasizes the need for team and organisational support to adequately address the wellbeing of healthcare professionals in this growing field. It requires shared responsibility and action from organisations, teams and healthcare professionals to care about the care for healthcare professionals providing palliative care. Show less
Emotions significantly influence our perceptions and interactions with the environment, yet the impact of our emotional states on judging and responding to others remains underexplored. In this... Show moreEmotions significantly influence our perceptions and interactions with the environment, yet the impact of our emotional states on judging and responding to others remains underexplored. In this thesis, I examined how (romantic) attraction influences our attention (Part I), how we judge others’ intentions (Part II), and whether mimicking another facilitates bond formation (Part III). In two empirical chapters, I demonstrate that people have a strong attentional bias towards visual attractiveness and a tendency to indicate interest in establishing a romantic connection to attractive others. In the subsequent empirical chapter, I show that men are more likely to judge women they find attractive as more sexually aroused. Crucially, in a real-life dating study, I show that men who are attracted to another are more likely to assume mutual interest. Further, I introduce a framework suggesting that people align their actions and emotional states with others to foster romantic relationships. The final empirical chapter suggests that mimicking the attraction cues of others enhances bond formation. Overall, this dissertation sheds light on how attractiveness and attraction affect our attention, our social cognition, and the synchronization of actions and emotions, offering insights into the mechanisms underlying romantic connections. Show less
In this thesis, I focused on studying the above- and belowground interactions of J. vulgaris from a plant-soil feedback (hereafter, PSF) perspective. I investigated the temporal variation of... Show moreIn this thesis, I focused on studying the above- and belowground interactions of J. vulgaris from a plant-soil feedback (hereafter, PSF) perspective. I investigated the temporal variation of negative PSF and examined the effects of root-associated bacteria on plant performance and aboveground herbivores. Additionally, I tested the role of PSF in relation to plant population structure and the significance of soil legacy effects in natural conditions. The findings reveal that temporal dynamics in PSF are driven by changes in plant sensitivity and in the soil microbiome. Although bacteria isolated from J. vulgaris roots can negatively affect plant performance, they can also affect aboveground herbivores and other plant species. Consequently, these bacteria may not be suitable for biological control of J. vulgaris. Moreover, I discovered that soil nematodes can mediate plant-plant interactions, but often favoring J. vulgaris. In my field work, I detected soil legacy effects, but seedling recruitment spatial patterns of J. vulgaris were not soil-mediated. The insights gained from studying PSF and above- and belowground interactions have the potential to reshape traditional approaches employed in controlling invasive plants. This thesis emphasizes the importance of transitioning PSF experiments from indoor to outdoor settings considering various influencing factors simultaneously. Show less
Schakel, W.; Baumann, M.; Bolet, D.; Campbell, R.; Louwerse, T.P.; Zittel, T. 2024
Toll-like receptor 2 (TLR2) belongs to the TLR protein family that plays an important role in the immune and inflammation response system. While TLR2 is predominantly expressed in immune cells, its... Show moreToll-like receptor 2 (TLR2) belongs to the TLR protein family that plays an important role in the immune and inflammation response system. While TLR2 is predominantly expressed in immune cells, its expression has also been detected in the brain, specifically in microglia and astrocytes. Recent studies indicate that genomic deletion of TLR2 can result in impaired neurobehavioural function. It is currently not clear if the genomic deletion of TLR2 leads to any alterations in the microstructural features of the brain. In the current study, we noninvasively assess microstructural changes in the brain of TLR2-deficient (tlr2-/-) zebrafish using state-of-the art magnetic resonance imaging (MRI) methods at ultrahigh magnetic field strength (17.6 T). A significant increase in cortical thickness and an overall trend towards increased brain volumes were observed in young tlr2-/- zebrafish. An elevated T2 relaxation time and significantly reduced apparent diffusion coefficient (ADC) unveil brain-wide microstructural alterations, potentially indicative of cytotoxic oedema and astrogliosis in the tlr2-/- zebrafish. Multicomponent analysis of the ADC diffusivity signal by the phasor approach shows an increase in the slow ADC component associated with restricted diffusion. Diffusion tensor imaging and diffusion kurtosis imaging analysis revealed diminished diffusivity and enhanced kurtosis in various white matter tracks in tlr2-/- compared with control zebrafish, identifying the microstructural underpinnings associated with compromised white matter integrity and axonal degeneration. Taken together, our findings demonstrate that the genomic deletion of TLR2 results in severe alterations to the microstructural features of the zebrafish brain. This study also highlights the potential of ultrahigh field diffusion MRI techniques in discerning exceptionally fine microstructural details within the small zebrafish brain, offering potential for investigating microstructural changes in zebrafish models of various brain diseases. Show less
Cancer immunotherapies utilizing immune checkpoint blockade (ICB) therapy targeting CTLA-4 and PD-1/PD-L1 relieve tumor-induced immune suppression and induce durable tumor regression. The use of... Show moreCancer immunotherapies utilizing immune checkpoint blockade (ICB) therapy targeting CTLA-4 and PD-1/PD-L1 relieve tumor-induced immune suppression and induce durable tumor regression. The use of ICB therapy have demonstrated remarkable therapeutic efficacy in a proportion of patients with melanoma. However, still a substantial percentage of patients does not respond (durable) to ICB treatment and many questions remain. Therefore, in this thesis, the aim is to improve our understanding of ICB efficacy. We demonstrate the promise of neoadjuvant ICB therapy (approach in which ICB therapy is applied before surgery) and analyze different cohorts of melanoma patients. This results in the identification of several markers that are associated with prognosis, including IFN-y related gene signature score, Batf3 dendritic cell associated gene signature score, tumor mutational burden and systemic LRG1 expression. These markers can potentially be targeted and might facilitate rational combination therapies that can boost the efficacy of ICB therapy. For this purpose, we perform a repurposing compound screen that targets antigen cross-presentation. Togethers, this work increases our understanding of factors that determine ICB therapy efficacy and toxicity, with the goal to identify novel strategies to improve outcome of melanoma patients in a rationale and personal manner. Show less
In this thesis we examined patient readiness for shared decision making (SDM) about treatment. We first assessed associations between patient-related characteristics and the occurrence of SDM.... Show moreIn this thesis we examined patient readiness for shared decision making (SDM) about treatment. We first assessed associations between patient-related characteristics and the occurrence of SDM. Overall, we did not find consistent associations between characteristics such as age or education level, and the extent to which SDM occurred (measured from the perspective of patients, clinicians, or observers). Second, we assessed what patients need to be ready, i.e., enabled and well-equipped, to participate in SDM about treatment. We identified a wide range of skills, cognitions, and emotions. For instance, patients need to be able to understand the relevant information, be able to and dare to express themselves in consultations with clinicians, and experience an adequate amount of time to talk to clinicians and to consider the options. Finally, we developed a questionnaire, the ReadySDM. The aim of the ReadySDM is to retrospectively measure the extent to which patients felt ready for SDM during a treatment decision-making process. The questionnaire has the potential to identify novel insights into patients’ support needs and ways to enhance SDM in daily practice. Show less
Across the world, the number of citizen science projects focusing on plastic pollution is increasing. These projects often last for multiple years, which makes retaining volunteers challenging.... Show moreAcross the world, the number of citizen science projects focusing on plastic pollution is increasing. These projects often last for multiple years, which makes retaining volunteers challenging. However, our knowledge is limited regarding the effect of long-term involvement on citizen scientists’ motivation, attitude, and knowledge, especially for plastic pollution projects. Therefore, this study measured citizen scientists’ motivation, attitude, and knowledge in the Dutch Clean Rivers project before and during monitoring plastic pollution on riverbanks between 2017 and 2021.In total, 403 Clean Rivers participants completed a pre-survey, and a portion of them participated in one or multiple post-surveys throughout the years of monitoring. They were especially driven by Project Action motivations and Environmental motivations like tackling the source of pollution and doing something about the plastic soup, rather than being motivated by an Interest in Scientific Research like the desire to learn about scientific research. Project Action motivations increased significantly, especially within the first year of participation. Participants’ attitudes towards nature and science were initially high and did not increase significantly. Furthermore, while participants’ knowledge of plastic pollution was already high at the start, their knowledge of scientific research was not, and both increased significantly, especially in the first year of participation. The findings of this longitudinal study can contribute to improving the recruitment and retention of volunteers in current and future citizen science projects. Show less
