196,752 research outputs found
Scope Validity in Medicine
No full textKeuck L. Scope Validity in Medicine. In: Schermer M, Binney N, eds. A New, Pragmatic Approach to Conceptualization of Health and Disease. Dordrecht: Springer; 2024: 115-133
Mechanism of chromatin reassembly at the yeast PHO5 promoter upon repression
No full textThe goal of this study has been to elucidate the mechanisms responsible for rebuilding nucleosomes at the PHO5 promoter upon rerepression.
In this work, I could unambiguously show that histones are incorporated at the PHO5 promoter upon repression. Regarding the source of these histones, I provide evidence that a significant fraction of the deposited histones originate from a soluble histone pool, i.e. a histone source in trans. Promoter closure occurs with strikingly rapid kinetics and is independent of replication. In agreement with the finding that PHO5 repression does not require cell division, I found that histone chaperones which are associated with replication-independent nucleosome assembly are important for rapid PHO5 promoter closure. Strains deleted for histone chaperones involved in replication-dependent nucleosome assembly did not exhibit any defect in promoter closure. Other factors contributing to rapid PHO5 repression turned out to be nucleosome remodelers, whose characteristic mode of action is chromatin assembly in trans. Nucleosome remodeling mutants typically catalyzing nucleosome movements in cis are not implicated in PHO5 promoter reassembly. The phenomenon of trans-deposition of histones upon repression is not restricted to the PHO5 promoter but is also found at two other phosphate regulated promoters, PHO8 and PHO84. By its rapid mode of action, this mechanism contributes to efficiently shutting off transcription. This might also hold true for other yeast genes.
In the second part of this work I present results that indicate a role for the histone chaperone Asf1p in the activation of the PHO5 gene. Interestingly, the induction of PHO5 in an asf1 mutant is dependent on the phosphate concentration of the growth medium. Full induction occurs only when the medium is completely free of phosphate. The abundance of even trace amounts of phosphate precludes PHO5 activation altogether
Temporal probabilistic models for disease management : with applications in COPD care
No full textContains fulltext :
115726.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 04 december 2013Promotor : Lucas, P.J.F. Co-promotor : Schermer, T.R.J.129 p
Building Food Democracy: Exploring Civic Food Networks and Newly Emerging Forms of Food Citizenship
No full textIn recent years new types of consumer-producer cooperation in food networks have emerged in which consumers play an active role in the operation and thereby clearly go beyond food provisioning as such. Examples include consumer co-ops and solidarity buying groups of local and organic food, communitysupported agriculture and collective urban gardening initiatives. These initiatives raise important new questions that cannot be adequately resolved within existing theoretical perspectives based on concepts such as 'alternative food networks', 'short food supply chains' or 'local food systems'. This article explores possible new analytical frameworks for the study of contemporary dynamics in food networks and develops the concept of 'civic food networks' as an overarching concept to explore contemporary dynamics and sources of innovation within agri-food networks. Building on the empirical diversity of initiatives, this introduction to the Special Issue argues that the role of civil society as a governance mechanism for agri-food networks has increased in significance compared to market and state actors. Moreover, expressions of 'food citizenship' are reshaping the relation between food practices and the market as well as with public institutions in ways that go beyond material and economic exchange and that contribute to a 'moralization' (or even 'civilization') of food economie
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