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Het bevorderen van tolerantie wordt internationaal gezien als een belangrijk onderwijsdoel. In het onderwijs worden echter verschillende opvattingen over tolerantie door elkaar heen gebruikt, waardoor het begrip haar analytische en educatieve kracht verliest. In dit artikel gaan we specifiek in op de klassieke conceptualisering van tolerantie die verwijst naar iets verdragen waar men bezwaar tegen heeft, en daarmee verschilt van een momenteel dominante herinterpretatie van het begrip (tolerantie als appreciatie). Door middel van een heranalyse van reeds verzamelde gegevens onder middelbare scholieren laten we zien dat tolerantie als verdraagzaamheid voor jongeren moeilijk is, maar niet onmogelijk. We vinden daarbij verschillen tussen leerniveaus die samenhangen met multiculturalistische overtuigingen, waarbij VWO’ers gemiddeld toleranter zijn dan VMBO’ers. Op basis van de literatuur beschrijven we vervolgens een didactiek van tolerantie als verdraagzaamheid, waarbij het leren omgaan met onoverbrugbare verschillen centraal staat.

De hygiënhypothese stelt dat de afwezigheid van infecties op de jonge kinderleeftijd gepaard gaat met een zich niet goed ontwikkelend immunoregulatienetwerk. Als gevolg hiervan zou allergische sensibilisatie toenemen en daarmee de kans op allergieën. Deze hypothese is een breed aanvaarde verklaring voor de alom geobserveerde toename van allergie in de Westerse en verwesterde samenlevingen gedurende de laatste 40 jaar. De bewijzen voor deze hypothese zijn echter zeer moeilijk te verkrijgen

In welke mate verschilt de tolerantie van homoseksualiteit in Nederland en Kroatië? Gaat dit in de toekomst veranderen? Aan de hand van voorbeelden uit de homo- en lesbische literatuur en de receptie daarvan zal ik proberen tijdens het panelgesprek antwoorden op die vragen te geven.

English summary Zinc is an important structural component and co-factor of proteins in all living organisms. The model plant species for genetic and molecular studies, Arabidopsis thaliana, expresses more than 2,000 proteins with one or more Zn binding domains. Low Zn availability in arable soils is a widespread problem around the world which results in agricultural losses and the production of grains with low Zn content. The long-term consumption of low-Zn-content food items leads to severe health problems in humans as a result of severe or mild dietary Zn deficiency. Hence the importance of studying Zn homeostasis in plants and mechanisms involved in Zn deficiency tolerance aiming to enhance Zn concentration in plants edible parts and to develop varieties with a higher tolerance to Zn deficiency. Plants are sessile organisms which trough evolution have developed specific traits in order to adapt to certain environmental conditions in their surroundings. As a result some plant genotypes are more tolerant to Zn deficiency and when exposed to low Zn conditions are able to perform better than others. To investigate the physiological mechanisms involved in Zn deficiency tolerance I examined natural variation present in a set of twenty diverse Arabidopsis thaliana accessions. In chapter 2, differences in shoot biomass production, Zn usage index (ZnUI), ionome (concentration of elements) and expression level of six key Zn deficiency responsive genes were studied. Accessions did not show large natural variation for shoot Zn concentration under Zn deficiency, while the decreases in shoot biomass and ZnUI were more variable. The conclusion from this is that accessions differ for the minimum Zn concentration required for growth which is associated with differences in Zn deficiency tolerance. We also found that the gene expression levels of three Zn transmembrane transporters (IRT3, ZIP3 and 4) in shoot were positively correlated with ZnUI and shoot biomass, but negatively correlated with shoot Zn concentration. This implies that a higher tolerance to Zn deficiency in A. thaliana is associated with an increased Zn translocation from root to shoot under low Zn. Furthermore, I used a logistic regression model to demonstrate that differences in the shoot ionome can be used as a biomarker to identify the plant Zn physiological state. Based on the changes in the concentrations of some elements in each of the Zn deficiency treatments it was possible to predict the Zn physiological state of the plants similarly to when Zn concentration is used alone. The adaptive response to Zn deficiency involves physiological changes in shoots, but also in roots which play a key role in the acquisition of nutrients. In chapter 3 I used the same twenty A. thaliana accessions as described in chapter 2 to identify root system architecture traits and changes in the root ionome involved in a higher tolerance to Zn deficiency in plants. Similar to shoots, all accessions showed a strong reduction in root Zn concentration under Zn deficiency, whereas changes in other root system architecture traits were more variable between the accessions. These analyses showed that differences between the accessions in root system architecture traits and minimum Zn concentration required for growth are important for Zn deficiency tolerance. The Zn deficiency treatment also affects the formation of lateral roots and thus root system architecture. It was therefore not surprising that the Zn deficiency treatment induced changes in the concentrations of other elements which were correlated with changes in root traits. Plants respond to different concentrations of Zn supply by changing the expression levels of genes involved in the Zn homeostasis network. This is important for the control of the Zn concentration and sequestration in plant cells, tissues and organs and involves the uptake, accumulation, transport and redistribution of Zn within the plant. Based on the work described in chapter 2, three A. thaliana accessions were selected with contrasting tolerance to Zn deficiency, and used for a whole genome transcription profiling analysis using RNA sequencing. Chapter 4 describes the identification of sets of general and core genes used by A. thaliana in its response to Zn deficiency. The purpose of using three accessions was to complement previous studies, which used only one accession, and identify new candidate genes involved in the general response to Zn deficiency in A. thaliana. General transcriptional changes were observed in the regulation of carbohydrate metabolism, glucosinolate biosynthesis and the circadian clock. As the transcriptional changes were recorded at two time points, it was also possible to distinguish early and late responses to Zn deficiency. The early response to Zn deficiency was stronger in roots with the induction of several Zn homeostasis genes and repression of Fe uptake genes. The late response to Zn deficiency comprised of the strong induction of several Zn uptake, transport and remobilization genes in both roots and shoots. These analysis confirmed several genes previously identified in Col-0 to have a general role in the Zn deficiency response, but it also led to the identification of new candidate genes, such as defensins and defensin-like genes, as very promising new actors in the A. thaliana Zn deficiency homeostasis network. Chapter 5 describes the A. thaliana accession-specific Zn deficiency responsive transcript profiles, comparing Tsu-0, Pa-2 and Col-0, with the aim to identify biological processes involved in the observed differences in Zn deficiency tolerance between these three accessions. Tsu-0 displayed a high tolerance to Zn deficiency in shoot, Col-0 (reference accession) showed a high tolerance to Zn deficiency in both root and shoot, whereas Pa-2 root and shoot were more sensitive to Zn deficiency. Some of the accession-specific Zn deficiency responsive transcripts were involved in similar biological processes, such as defence response, programmed cell death and carbohydrates and glucosinolates metabolism. The differential regulation of these processes between the three accessions may reflect their differences in Zn deficiency tolerance. Among the Col-0 specific transcripts were several genes encoding proteins kinases which may play a role in a more specific separation of the abiotic and biotic stress responses in this accession and possibly involved in its higher tolerance to Zn deficiency in both shoots and roots. Tsu-0 specifically changes the expression of a set of shoot transcripts encoding ethylene responsive transcription factors which are involved in the regulation of shoot growth and plant tolerance to abiotic and biotic stresses, corresponding well with the observed shoot Zn deficiency tolerance. Accession Pa-2 down-regulated transcripts involved in cell wall organization in roots which correlates with its high sensitivity to Zn deficiency in this organ. Finally, the accessions specific response to Zn deficiency also resulted in the differential regulation of transcripts encoding transposases which may reflect large scale chromatin reorganization or demethylation in response to the stress condition. The main findings of the research described in this thesis and their implications are described in the General Discussion (chapter 6). By investigating the response to Zn deficiency in a diverse set of A. thaliana accessions both at the physiological and transcriptional level important mechanisms involved in Zn deficiency tolerance were identified. Furthermore, several key candidate genes among the accessions general and accession-specific Zn deficiency responsive transcripts were identified. The further functional characterization of these genes is expected to reveal important new steps in the regulation of Zn homeostasis and Zn deficiency tolerance in A. thaliana.

English summary Zinc is an important structural component and co-factor of proteins in all living organisms. The model plant species for genetic and molecular studies, Arabidopsis thaliana, expresses more than 2,000 proteins with one or more Zn binding domains. Low Zn availability in arable soils is a widespread problem around the world which results in agricultural losses and the production of grains with low Zn content. The long-term consumption of low-Zn-content food items leads to severe health problems in humans as a result of severe or mild dietary Zn deficiency. Hence the importance of studying Zn homeostasis in plants and mechanisms involved in Zn deficiency tolerance aiming to enhance Zn concentration in plants edible parts and to develop varieties with a higher tolerance to Zn deficiency. Plants are sessile organisms which trough evolution have developed specific traits in order to adapt to certain environmental conditions in their surroundings. As a result some plant genotypes are more tolerant to Zn deficiency and when exposed to low Zn conditions are able to perform better than others. To investigate the physiological mechanisms involved in Zn deficiency tolerance I examined natural variation present in a set of twenty diverse Arabidopsis thaliana accessions. In chapter 2, differences in shoot biomass production, Zn usage index (ZnUI), ionome (concentration of elements) and expression level of six key Zn deficiency responsive genes were studied. Accessions did not show large natural variation for shoot Zn concentration under Zn deficiency, while the decreases in shoot biomass and ZnUI were more variable. The conclusion from this is that accessions differ for the minimum Zn concentration required for growth which is associated with differences in Zn deficiency tolerance. We also found that the gene expression levels of three Zn transmembrane transporters (IRT3, ZIP3 and 4) in shoot were positively correlated with ZnUI and shoot biomass, but negatively correlated with shoot Zn concentration. This implies that a higher tolerance to Zn deficiency in A. thaliana is associated with an increased Zn translocation from root to shoot under low Zn. Furthermore, I used a logistic regression model to demonstrate that differences in the shoot ionome can be used as a biomarker to identify the plant Zn physiological state. Based on the changes in the concentrations of some elements in each of the Zn deficiency treatments it was possible to predict the Zn physiological state of the plants similarly to when Zn concentration is used alone. The adaptive response to Zn deficiency involves physiological changes in shoots, but also in roots which play a key role in the acquisition of nutrients. In chapter 3 I used the same twenty A. thaliana accessions as described in chapter 2 to identify root system architecture traits and changes in the root ionome involved in a higher tolerance to Zn deficiency in plants. Similar to shoots, all accessions showed a strong reduction in root Zn concentration under Zn deficiency, whereas changes in other root system architecture traits were more variable between the accessions. These analyses showed that differences between the accessions in root system architecture traits and minimum Zn concentration required for growth are important for Zn deficiency tolerance. The Zn deficiency treatment also affects the formation of lateral roots and thus root system architecture. It was therefore not surprising that the Zn deficiency treatment induced changes in the concentrations of other elements which were correlated with changes in root traits. Plants respond to different concentrations of Zn supply by changing the expression levels of genes involved in the Zn homeostasis network. This is important for the control of the Zn concentration and sequestration in plant cells, tissues and organs and involves the uptake, accumulation, transport and redistribution of Zn within the plant. Based on the work described in chapter 2, three A. thaliana accessions were selected with contrasting tolerance to Zn deficiency, and used for a whole genome transcription profiling analysis using RNA sequencing. Chapter 4 describes the identification of sets of general and core genes used by A. thaliana in its response to Zn deficiency. The purpose of using three accessions was to complement previous studies, which used only one accession, and identify new candidate genes involved in the general response to Zn deficiency in A. thaliana. General transcriptional changes were observed in the regulation of carbohydrate metabolism, glucosinolate biosynthesis and the circadian clock. As the transcriptional changes were recorded at two time points, it was also possible to distinguish early and late responses to Zn deficiency. The early response to Zn deficiency was stronger in roots with the induction of several Zn homeostasis genes and repression of Fe uptake genes. The late response to Zn deficiency comprised of the strong induction of several Zn uptake, transport and remobilization genes in both roots and shoots. These analysis confirmed several genes previously identified in Col-0 to have a general role in the Zn deficiency response, but it also led to the identification of new candidate genes, such as defensins and defensin-like genes, as very promising new actors in the A. thaliana Zn deficiency homeostasis network. Chapter 5 describes the A. thaliana accession-specific Zn deficiency responsive transcript profiles, comparing Tsu-0, Pa-2 and Col-0, with the aim to identify biological processes involved in the observed differences in Zn deficiency tolerance between these three accessions. Tsu-0 displayed a high tolerance to Zn deficiency in shoot, Col-0 (reference accession) showed a high tolerance to Zn deficiency in both root and shoot, whereas Pa-2 root and shoot were more sensitive to Zn deficiency. Some of the accession-specific Zn deficiency responsive transcripts were involved in similar biological processes, such as defence response, programmed cell death and carbohydrates and glucosinolates metabolism. The differential regulation of these processes between the three accessions may reflect their differences in Zn deficiency tolerance. Among the Col-0 specific transcripts were several genes encoding proteins kinases which may play a role in a more specific separation of the abiotic and biotic stress responses in this accession and possibly involved in its higher tolerance to Zn deficiency in both shoots and roots. Tsu-0 specifically changes the expression of a set of shoot transcripts encoding ethylene responsive transcription factors which are involved in the regulation of shoot growth and plant tolerance to abiotic and biotic stresses, corresponding well with the observed shoot Zn deficiency tolerance. Accession Pa-2 down-regulated transcripts involved in cell wall organization in roots which correlates with its high sensitivity to Zn deficiency in this organ. Finally, the accessions specific response to Zn deficiency also resulted in the differential regulation of transcripts encoding transposases which may reflect large scale chromatin reorganization or demethylation in response to the stress condition. The main findings of the research described in this thesis and their implications are described in the General Discussion (chapter 6). By investigating the response to Zn deficiency in a diverse set of A. thaliana accessions both at the physiological and transcriptional level important mechanisms involved in Zn deficiency tolerance were identified. Furthermore, several key candidate genes among the accessions general and accession-specific Zn deficiency responsive transcripts were identified. The further functional characterization of these genes is expected to reveal important new steps in the regulation of Zn homeostasis and Zn deficiency tolerance in A. thaliana.

Onderzoek werd verricht naar het voorkomen van aflatoxine M1 in 25 monsters babyvoedingsmiddel, bereid op basis van melk(produkten), 3 monsters lactose, 6 monsters caseinaat en 1 monster weipoeder, alle in poedervorm. In 91% van alle monsters kon de aanwezigheid van aflatoxine M1 worden vastgesteld (> 0,02 mug/kg). De gevonden gehalten varieerden van 0,04 - 1,39 mug/kg poedervormig produkt; gemiddeld werd 0,22 mug/kg aangetroffen. Vergeleken met de studies, uitgevoerd in 1977 en 1980 bevindt de contaminatie met M1 zich, na een veelbelovende verbetering in 1980, thans weer op het niveau van 1977. Vermoedelijk is de oorzaak hiervan gelegen in het feit dat de gehalten aan aflatoxine in melk de laatste jaren zijn toegenomen.

Onderzoek werd verricht naar het voorkomen van aflatoxine M1 in 25 monsters babyvoedingsmiddel, bereid op basis van melk(produkten), 3 monsters lactose, 6 monsters caseinaat en 1 monster weipoeder, alle in poedervorm. In 91% van alle monsters kon de aanwezigheid van aflatoxine M1 worden vastgesteld (> 0,02 mug/kg). De gevonden gehalten varieerden van 0,04 - 1,39 mug/kg poedervormig produkt; gemiddeld werd 0,22 mug/kg aangetroffen. Vergeleken met de studies, uitgevoerd in 1977 en 1980 bevindt de contaminatie met M1 zich, na een veelbelovende verbetering in 1980, thans weer op het niveau van 1977. Vermoedelijk is de oorzaak hiervan gelegen in het feit dat de gehalten aan aflatoxine in melk de laatste jaren zijn toegenomen.

Schaduwminnende potplanten kunnen veel meer licht verdragen dan ze in de praktijk krijgen, blijkt onderzoek van WUR Glastuinbouw. Daarmee is de teelt te versnellen en energie te besparen. Maar hoe ver kan een teler daarmee gaan?

Schaduwminnende potplanten kunnen veel meer licht verdragen dan ze in de praktijk krijgen, blijkt onderzoek van WUR Glastuinbouw. Daarmee is de teelt te versnellen en energie te besparen. Maar hoe ver kan een teler daarmee gaan?

Ancient Greece is often seen as the cradle of democracy, of free thought and of free speech. This article presents a number of historical cases of intellectual repression in Greece and Rome, including examples even of book-burning. It discusses the political and philosophical concept of ‘parrhèsia’ and analyses the importance of religious restrictions through well known charges of ‘asebeia’ (Anaxagoras, Protagoras and Socrates). In the second section of the article the philosophical arguments are put forward developed by Plato in favour of preventive and repressive censorship and it ends with a short discussion of the Stoic attitude towards censorship.

De hygiënhypothese stelt dat de afwezigheid van infecties op de jonge kinderleeftijd gepaard gaat met een zich niet goed ontwikkelend immunoregulatienetwerk. Als gevolg hiervan zou allergische sensibilisatie toenemen en daarmee de kans op allergieën. Deze hypothese is een breed aanvaarde verklaring voor de alom geobserveerde toename van allergie in de Westerse en verwesterde samenlevingen gedurende de laatste 40 jaar. De bewijzen voor deze hypothese zijn echter zeer moeilijk te verkrijgen

De hygiënhypothese stelt dat de afwezigheid van infecties op de jonge kinderleeftijd gepaard gaat met een zich niet goed ontwikkelend immunoregulatienetwerk. Als gevolg hiervan zou allergische sensibilisatie toenemen en daarmee de kans op allergieën. Deze hypothese is een breed aanvaarde verklaring voor de alom geobserveerde toename van allergie in de Westerse en verwesterde samenlevingen gedurende de laatste 40 jaar. De bewijzen voor deze hypothese zijn echter zeer moeilijk te verkrijgen

Praktijkonderzoek Plant & Omgeving heeft een tweetal proeven uitgevoerd in twee jaren (2002 en 2003): een veldproef met rassen met verschillende tolerantieniveaus en een biotoets met daarin de bepaling van de bodembesmetting vóór en na de veldproef en "uitzieking" van de grond door de jaren heen bij verschillende telers. De uitzieking wordt afgeleid door de besmettingsgraad van diverse percelen van één teler onderling te vergelijken. Er zijn percelen bij waar onlangs vatbare uien hebben gestaan en percelen waar 6 tot 8 jaar geleden vatbare uien hebben gestaan

Praktijkonderzoek Plant & Omgeving heeft een tweetal proeven uitgevoerd in twee jaren (2002 en 2003): een veldproef met rassen met verschillende tolerantieniveaus en een biotoets met daarin de bepaling van de bodembesmetting vóór en na de veldproef en "uitzieking" van de grond door de jaren heen bij verschillende telers. De uitzieking wordt afgeleid door de besmettingsgraad van diverse percelen van één teler onderling te vergelijken. Er zijn percelen bij waar onlangs vatbare uien hebben gestaan en percelen waar 6 tot 8 jaar geleden vatbare uien hebben gestaan

Dit micro-organisme is in staat tot verhoogde druktolerantie en derhalve tot overleving na conservering van voedingsmiddelen

Dit micro-organisme is in staat tot verhoogde druktolerantie en derhalve tot overleving na conservering van voedingsmiddelen

Overzicht van voorhanden bestrijdingsmethoden tegen Varroa destructor op de korte termijn en vooruitzichten voor de bestrijding op langere termijn. In de nabije toekomst gaat het om bestrijding met diergeneesmiddelen van natuurlijke oorsprong (mierenzuur, oxaalzuur, thymol) in het kader van een jaarbestrijdingsconcept. De verdere toekomst zal gericht zijn op het gebruik maken van natuurlijke vijanden (ziekteverwekkende virussen of schimmels) of natuurlijke signaalstoffen (feromonen), en het ontwikkelen van een varroaresistente bij door selectie op varroatolerantie

Overzicht van voorhanden bestrijdingsmethoden tegen Varroa destructor op de korte termijn en vooruitzichten voor de bestrijding op langere termijn. In de nabije toekomst gaat het om bestrijding met diergeneesmiddelen van natuurlijke oorsprong (mierenzuur, oxaalzuur, thymol) in het kader van een jaarbestrijdingsconcept. De verdere toekomst zal gericht zijn op het gebruik maken van natuurlijke vijanden (ziekteverwekkende virussen of schimmels) of natuurlijke signaalstoffen (feromonen), en het ontwikkelen van een varroaresistente bij door selectie op varroatolerantie

Schaduwminnende potplanten kunnen veel meer licht verdragen dan ze in de praktijk krijgen, blijkt onderzoek van WUR Glastuinbouw. Daarmee is de teelt te versnellen en energie te besparen. Maar hoe ver kan een teler daarmee gaan?

Overzicht van voorhanden bestrijdingsmethoden tegen Varroa destructor op de korte termijn en vooruitzichten voor de bestrijding op langere termijn. In de nabije toekomst gaat het om bestrijding met diergeneesmiddelen van natuurlijke oorsprong (mierenzuur, oxaalzuur, thymol) in het kader van een jaarbestrijdingsconcept. De verdere toekomst zal gericht zijn op het gebruik maken van natuurlijke vijanden (ziekteverwekkende virussen of schimmels) of natuurlijke signaalstoffen (feromonen), en het ontwikkelen van een varroaresistente bij door selectie op varroatolerantie

Dit micro-organisme is in staat tot verhoogde druktolerantie en derhalve tot overleving na conservering van voedingsmiddelen