Software scaffolds to promote regulation during scientific inquiry learning

This research addresses issues in the design of online scaffolds for regulation within inquiry learning environments. The learning environment in this study included a physics simulation, data analysis tools, and a model editor for students to create runnable models. A regulative support tool called the Process Coordinator (PC) was designed to assist students in planning, monitoring, and evaluating their investigative efforts within this environment. In an empirical evaluation, 20 dyads received a “full” version of the PC with regulative assistance; dyads in the control group (n = 15) worked with an “empty” PC which contained minimal structures for regulative support. Results showed that both the frequency and duration of regulative tool use differed in favor of the PC+ dyads, who also wrote better lab reports. PC− dyads viewed the content helpfiles more often and produced better domain models. Implications of these differential effects are discussed and suggestions for future research are advanced

Fungal pathogens exposed:Novel insights into <i>Candida auris </i>and emerging relatives of the <i>Candida haemulonii</i> species complex

Fungal pathogens are on the rise. Annually more than one billion people are affected by superficial, allergic and mucosal fungal infections. However, of highest concern are the life-threatening invasive fungal infections. An increasing at-risk population together with inaccurate diagnostics and limited treatment options led to a dramatic increase in these life-threatening fungal infections and exceptionally high mortality rates, resulting in over 1.6 million deaths caused by fungi each year. Candida species are particularly prevalent in hospital settings and account for more than 750.000 invasive infections each year. This makes Candida one of the most critical groups of fungal pathogens.The last decades an epidemiological shift has been taking place from Candida albicans as the primary cause of invasive Candida infections towards other, often drug resistant, species. Especially Candida auris showed the world the ability of fungi to rapidly emerge as a significant threat to human health. More insights into the ecological mechanisms, phenotypic traits and genomic elements that contribute to the emergence of Candida pathogens, such as C. auris, are essential to both expose current and future pathogens and develop strategies to combat them.In this thesis C. auris and emerging relatives within the Candida haemulonii species complex are characterized using genomic and phenotypic approaches. Pathogenic species are compared to their closest non-pathogenic siblings, exposing specific traits that could contribute to their virulence and emergence in the nosocomial environment. In addition, ways to better understand the epidemiology and improve diagnostic tools for C. auris and the C. haemulonii complex were investigated

Fungal pathogens exposed:Novel insights into <i>Candida auris </i>and emerging relatives of the <i>Candida haemulonii</i> species complex

Fungal pathogens are on the rise. Annually more than one billion people are affected by superficial, allergic and mucosal fungal infections. However, of highest concern are the life-threatening invasive fungal infections. An increasing at-risk population together with inaccurate diagnostics and limited treatment options led to a dramatic increase in these life-threatening fungal infections and exceptionally high mortality rates, resulting in over 1.6 million deaths caused by fungi each year. Candida species are particularly prevalent in hospital settings and account for more than 750.000 invasive infections each year. This makes Candida one of the most critical groups of fungal pathogens.The last decades an epidemiological shift has been taking place from Candida albicans as the primary cause of invasive Candida infections towards other, often drug resistant, species. Especially Candida auris showed the world the ability of fungi to rapidly emerge as a significant threat to human health. More insights into the ecological mechanisms, phenotypic traits and genomic elements that contribute to the emergence of Candida pathogens, such as C. auris, are essential to both expose current and future pathogens and develop strategies to combat them.In this thesis C. auris and emerging relatives within the Candida haemulonii species complex are characterized using genomic and phenotypic approaches. Pathogenic species are compared to their closest non-pathogenic siblings, exposing specific traits that could contribute to their virulence and emergence in the nosocomial environment. In addition, ways to better understand the epidemiology and improve diagnostic tools for C. auris and the C. haemulonii complex were investigated

Validating and optimizing the effects of model progression in simulation-based inquiry learning

Model progression denotes the organization of the inquiry learning process in successive phases of increasing complexity. This study investigated the effectiveness of model progression in general, and explored the added value of either broadening or narrowing students’ possibilities to change model progression phases. Results showed that high-school students in the ‘standard’ model progression condition (n = 19), who could enter subsequent phases at will, outperformed students from a control condition (n = 30) without model progression. The unrestricted condition (n = 22) had the additional option of returning to previous phases, whereas the restricted condition (n = 20) disallowed such downward progressions as well as upward progressions in case insufficient knowledge was acquired. Both variants were found to be more effective in terms of performance than the ‘standard’ form of model progression. However, as performance in all three model progression conditions was still rather weak, additional support is needed for students to reach full understanding of the learning content

Pistil development in cleome flowers

De bloemen van Cleome -planten ontwikkelen zich aan een andromonoecische tros. Dit wil zeggen dat er afwisselend tweeslachtige en mannelijke bloemen aan de bloeiwijze gevormd worden. Dit optreden van vrouwelijk geaborteerde bloemen is onderzocht door na te gaan wat de effekten zijn van minerale voeding en toediening van regulatoren en wat de invloed is van bladeren en vruchten.Een hoog mineraal voedingsniveau begunstigt de stamperontwikkeling. De belangrijkste funktie van auxine hangt samen met de groei van de vruchten. Deze vruchten hebben een aanzienlijke "sink"-aktiviteit, waardoor voedings- en hormonale stoffen opgenomen kunnen worden. Gibberellinen aborteren de stampers en de zaadknoppen. Ethyleen stimuleert alleen maar de stamperontwikkeling in combinatie met gibberellinen. Deze gibberellinen kunnen worden verkregen uit andere plantendelen.Om na te gaan wat de effekten zijn van voedings- en hormonale stoffen was het noodzakelijk bloemknoppen van Cleome iberidella op kunstmatige media te kweken. De kroonbladontwikkeling wordt bij afnemende concentratie van organische en anorganische voedingsstoffen altijd eerst gerend, terwijl de stamperontwikkeling nog optimaal blijft. Als dezelfde voedingsafhankelijkheid ook geldt voor Cleome spinosa in vivo is het onwaarschijnlijk dat de remming van de stamperontwikkeling toegeschreven kan worden aan voedingsgebrek. Bovendien blijkt dat cytokinine, i.c. zeatine en BA, noodzakelijk is om stampergroei te verkrijgen. Exogeen zeatine, toegediend aan intakte planten, onder voor de stampergroei ongunstige condities, herstelt de stamperontwikkeling.De conclusie is dat het optreden van vrouwelijk geaborteerde bloemen het gevolg is van het tekort aan cytokininen in de bloemen boven de zich tegelijkertijd ontwikkelende vruchten, die een aanzienlijke concurrerende aktiviteit bezitten.</p

Personalities in female domesticated pigs: behavioural and physiological indications

The inconclusive evidence so far on the existence of distinct personality types in domesticated pigs, led us to perform the present experiment. A total of 128 gilts from 31 sows were systematically studied from birth to slaughter in two identical trials. Intra-test consistency in individual behavioural andror physiological reactions was studied in three different tests. We were not able to show consistencies in reactions of gilts over time to a backtest (at 2–4 days and 4 weeks of age) and to a novel environment test (at 10 and 24 weeks of age). Individual aggression, however, as measured in a group-feeding competition test in stable groups (at 10 and 24 weeks of age), proved to be highly consistent. Explanations for these discrepancies in intra-test consistencies are critically discussed. Inter-test consistencies were determined by relating the individual reactions of gilts to the backtest to various characteristics and responses to tests at a later age. The highest correlations were found when resistance in the first backtest was involved. No evidence was found for the existence of specific isolated categories of animals with respect to this resistance. For further analysis, extreme responding gilts in the first backtest (roughly the top and bottom 25% of the distribution) were classified as low resistant (LR; <3 escape attempts; n=31) or high resistant (HR; >4 escape attempts; n=45). By comparisons of mean responses of LR and HR gilts within groups, we have established a relationship between the backtest and several other variables. Behaviourally, the HR gilts showed more aggression in the group-feeding competition tests. Also, in the competition for the most productive teats at the anterior, a predominant position of HR piglets at this site was observed during the suckling period. The latter piglets also gained more weight during this period than LR ones. Compared to HR pigs, in the first novel environment test LR pigs hesitated longer to leave their home pens and to contact a human, but no difference in their locomotory behaviour was observed. Contrasts between LR and HR pigs in the second novel environment test were reduced or absent. Physiologically, when compared to HR gilts, LR ones had a higher reactivity of the hypothalamic–pituitary–adrenocortical (HPA) system. This was shown by higher cortisol responses to the first novel environment test, to routine weighing at 25 weeks of age, and to administration of a high dose of ACTH. It is discussed that these findings for LR and HR gilts, may provide support for the existence of behavioural and physiological responses in pigs, resembling those of proactive and reactive rodents.

Coexpression of Kit and the receptors for erythropoietin, interleukin 6 and GM-CSF on hemopoietic cells

The detection of functional growth factor (GF) receptors on subpopulations of hemopoietic cells may provide a further dissection of immature cell subsets. Since little information is available about coexpression of different GF receptors at the level of single hemopoietic cells, we studied the feasibility of simultaneous cell staining with a combination of biotin- and digoxigenin-labeled GFs for flow cytometric detection of functional receptors. Using this methodology, coexpression of Kit and receptors for erythropoietin (EPO), interleukin 6 (IL-6), and GM-CSF on hemopoietic cells was studied by triple-staining of rhesus monkey bone marrow (BM) cells with labeled GFs and antibodies against other cell surface markers. Most of the immature, CD34+2 cells were Kit+ but did not display detectable levels of EPO-receptors (EPO-Rs) or GM-CSF-R. Approximately 60% of these CD34+2/Kit+ cells coexpressed the IL-6-R, demonstrating that immature cells are heterogeneous with respect to IL-6-R expression. Maturation of monomyeloid progenitors, as demonstrated by decreasing CD34 and increasing CD11b expression, is accompanied by a decline of Kit and an increase in GM-CSF-R expression in such a way that Kit+/GM-CSF-R+ cells are hardly detectable. IL-6-R expression is maintained or even increased during monomyeloid differentiation. IL-6-R and GM-CSF-R were not identified on most CD71+2 cells, which indicated that these receptors are probably not expressed during erythroid differentiation. Together with previous results, our data show that both Kit and CD71 are upregulated with erythroid commitment of immature progenitors. Upon further differentiation, Kit+/EPO-R-cells lose CD34 and acquire EPO-R. Maturing erythroid cells eventually lose CD71 and Kit expression but retain the EPO-R. In conclusion, this approach enables further characterization of the specificity of GFs for different bone marrow subpopulations. Apart from insight into the differentiation stages on which individual GFs may act, information about receptor coexpression may be used to identify individual cells that can respond to multiple GFs, and allows for further characterization of the regulation of lineage-specific differentiation

Trendanalyse zware metalen in diervoeder(grondstoffen)

In dit rapport wordt er met behulp van historische waarden inzicht gegeven in het verloop van de gehalten aan kwik, cadmium en lood in diervoeders en diervoedergrondstoffen in Nederland. Het is een vervolg op het rapport 2007.001 “Trendanalyse van gehalten aan aflatoxine B1 en dioxinen/dioxine-achtige PCB’s in diervoeders” dat in 2007 is verschenen. Dit onderzoek is ook verricht op verzoek van de VWA. De resultaten van deze analyses bieden mogelijkheden voor de VWA om tot een meer risico-gestuurde bemonstering in het Nationaal Plan Diervoeders te kome

Measures of bioavailable serum testosterone and estradiol and their relationships with muscle strength, bone density, and body composition in elderly men

In the present cross-sectional study of 403 independently living elderly men, we tested the hypothesis that the decreases in bone mass, body composition, and muscle strength with age are related to the fall in circulating endogenous testosterone (T) and estrogen concentrations. We compared various measures of the level of bioactive androgen and estrogen to which tissues are exposed. After exclusion of subjects with severe mobility problems and signs of dementia, 403 healthy men (age, 73-94 yr) were randomly selected from a population-based sample. Total T (TT), free T (FT), estrone (E1), estradiol (E2), and sex hormone-binding globulin (SHBG) were determined by RIA. Levels of non-SHBG-bound T (non-SHBG-T), FT (calc-FT), the TT/SHBG ratio, non-SHBG-bound E2, and free E2 were calculated. Physical characteristics of aging included muscle strength measured using dynamometry, total body bone mineral density (BMD), hip BMD, and body composition, including lean mass and fat mass, measured by dual-energy x-ray absorptiometry. In this population of healthy elderly men, calc-FT, non-SHBG-T, E1, and E2 (total, free, and non-SHBG bound) decreased significantly with age. T (total and non-SHBG-T) was positively related with muscle strength and total body BMD (for non-SHBG-T, respectively, beta = 1.93 +/- 0.52, P < 0.001 and beta = 0.011 +/- 0.002, P < 0.001). An inverse association existed between T and fat mass (beta = -0.53 +/- 0.15, P < 0.001). Non-SHBG-T and calc-FT were more strongly related to muscle strength, BMD, and fat mass than TT and were also significantly related to hip BMD. E1 and E2 were both positively, independently associated with BMD (for E2, beta = 0.21 +/- 0.08, P < 0.01). Non-SHBG-bound E2 was slightly strongly related to BMD than total E2. The positive relation between T and BMD was independent of E2. E1 and E2 were not related with muscle strength or body composition. In summary, bioavailable T, E1, total E2, and bioavailable E2 all decrease with age in healthy old men. In this cross-sectional study in healthy elderly men, non-SHBG-bound T seems to be the best parameter for serum levels of bioactive T, which seems to play a direct role in the various physiological changes that occur during aging. A positive relation with muscle strength and BMD and a negative relation with fat mass was found. In addition, both serum E1 and E2 seem to play a role in the age-related bone loss in elderly men, although the cross-sectional nature of the study precludes a definitive conclusion. Non-SHBG-bound E2 seems to be the best parameter of serum bioactive E2 in describing its positive relation with BMD

Occupational allergy in Strawberry Greenhouse workers

Background: Employees in strawberry greenhouses are highly exposed to several (potential) allergenic agents. However, no occupational allergy in this branch has been described before. First, the presence of work-related allergic symptoms in strawberry workers was explored. Second, we aimed to prove the concept that an IgE-mediated allergy could be responsible for work-related symptoms. To test the possibility of an IgE response secondary to cross-reactivity to birch or grass pollen, inhibition experiments were performed. Methods: First, a questionnaire survey concerning work-related allergic symptoms among strawberry workers in the Netherlands was carried out. Second, 3 workers with work-related symptoms were investigated in detail. Skin tests, serum-specific IgE tests with home-made extracts of strawberry pollen and other possible allergenic agents of the strawberry greenhouse environment were executed. Furthermore, immunoblots and nasal provocations with strawberry pollen extract were performed. In addition, inhibition experiments were performed. Results: 29 of 75 questionnaire respondents (38.7%) reported work-related symptoms. Sensitization to strawberry pollen was found in skin tests in all 3 employees with work-related symptoms. ELISA and immunoblotting with strawberry pollen showed positive results in 2 employees. Birch and grass pollen failed to inhibit IgE binding to strawberry pollen in 1 of 2 employees. Partial inhibition was seen in the second employee. Nasal provocation validated clinically relevant allergy to these pollens in 2 of 3 subjects. Conclusions: Allergic symptoms attributable to the workplace are present among a proportion of strawberry greenhouse employees. An IgE-mediated occupational allergy to strawberry pollen may contribute to these symptoms