Demographic responses of Daphnia magna fed transgenic Bt-maize

The food/feed quality of a variety of genetically modified (GM) maize expressing Cry1Ab Bt-toxin was tested over the life-cycle of Daphnia magna, an arthropod commonly used as model organism in ecotoxicological studies. Demographic responses were compared between animals fed GM or unmodified (UM) near isogenic maize, with and without the addition of predator smell. Age-specific data on survival and birth rates were integrated and analysed using life tables and Leslie matrices. Survival, fecundity and population growth rate (PGR) data generally disfavoured transgenic Bt-maize as feed for D. magna compared to animals fed the unmodified (UM) near isogenic line of maize. Decomposition of age-specific effects revealed that the most important contributions to a reduced PGR in the GM-fed group came from both fecundity and survival differences early in life. We conclude that juvenile and young adult stages are the most sensitive experimental units and should be prioritized in future research. These stages are often omitted in toxicological/ecotoxicological studies and in feeding trials

Role of Scrib and Dlg in anterior-posterior patterning of the follicular epithelium during Drosophila oogenesis

<p>Abstract</p> <p>Background</p> <p>Proper patterning of the follicle cell epithelium over the egg chamber is essential for the <it>Drosophila </it>egg development. Differentiation of the epithelium into several distinct cell types along the anterior-posterior axis requires coordinated activities of multiple signaling pathways. Previously, we reported that <it>lethal(2)giant larvae </it>(<it>lgl</it>), a <it>Drosophila </it>tumor suppressor gene, is required in the follicle cells for the posterior follicle cell (PFC) fate induction at mid-oogenesis. Here we explore the role of another two tumor suppressor genes, <it>scribble </it>(<it>scrib</it>) and <it>discs large </it>(<it>dlg</it>), in the epithelial patterning.</p> <p>Results</p> <p>We found that removal of <it>scrib </it>or <it>dlg </it>function from the follicle cells at posterior terminal of the egg chamber causes a complete loss of the PFC fate. Aberrant specification and differentiation of the PFCs in the mosaic clones can be ascribed to defects in coordinated activation of the EGFR, JAK and Notch signaling pathways in the multilayered cells. Meanwhile, the clonal analysis revealed that loss-of-function mutations in <it>scrib/dlg </it>at the anterior domains result in a partially penetrant phenotype of defective induction of the stretched and centripetal cell fate, whereas specification of the border cell fate can still occur in the most anterior region of the mutant clones. Further, we showed that <it>scrib </it>genetically interacts with <it>dlg </it>in regulating posterior patterning of the epithelium.</p> <p>Conclusion</p> <p>In this study we provide evidence that <it>scrib </it>and <it>dlg </it>function differentially in anterior and posterior patterning of the follicular epithelium at oogenesis. Further genetic analysis indicates that <it>scrib </it>and <it>dlg </it>act in a common pathway to regulate PFC fate induction. This study may open another window for elucidating role of <it>scrib/dlg </it>in controlling epithelial polarity and cell proliferation during development.</p

Introduction to the special issue on the work of teacher education : policy, practice and institutional conditions

This special issue of the Journal of Education for Teaching focuses on the practical activities and material conditions of higher education-based teacher educators’ work. The articles address questions of concept and practice, discourse and labour and the ways in which teacher education as an activity of higher education is related to the institutional contexts within which the activity is located. The material conditions of academic work have become the focus of much renewed interest in higher education as a series of intellectual, cultural and economic trends (Hartley 2009) have converged so as to question the roles and responsibilities of teacher educators as a category of academic workers. Generally, research suggests that partnership teacher education, in which universities and colleges work with schools to train teachers, is highly successful and there is plentiful evidence in support of this fact (e.g. Iven 1994; Christie et al 2004; Ellis et al. 2011). However, concerns about changes to initial teacher education towards more school-led approaches persist internationally. Much contemporary policy discourse has been framed around the belief that schools are best placed to train teachers and, while there may be an implied consensus of intention to support beginners in their learning during practice, the discussions do little to suggest that the notion of a research-informed teaching profession is an aim worth addressing. Troublingly, as Christie et al. (2012) recognise, the erosion of the role of higher education in teacher education may not only lead to volatility and reductions in funding and employment opportunities in education departments but is likely, by extension, to impact adversely on research capacity in teacher education institutions. Clearly, research which explores the activities and perspectives of teacher educators, their expertise and yet their increasingly difficult positioning within higher education more generally, has the potential to inform the development of the profession from within and, importantly, the strengthening of an academic culture of teacher education