Glycogen phosphorylase (GP) is activated to degrade glycogen in response to different stimuli, to support both the astrocyte's own metabolic demand and the metabolic needs of neurons. The regulatory mechanism allowing such a glycogenolytic response to distinct triggers remains incompletely understood. In the present study, we used siRNA-mediated differential knockdown of the two isoforms of GP expressed in astrocytes, muscle isoform (GPMM), and brain isoform (GPBB), to analyze isoform-specific regulatory characteristics in a cellular setting. Subsequently, we tested the response of each isoform to phosphorylation, triggered by incubation with norepinephrine (NE), and to AMP, increased by glucose deprivation in cells in which expression of one GP isoform had been silenced. Successful knockdown was demonstrated on the protein level by Western blot, and on a functional level by determination of glycogen content showing an increase in glycogen levels following knockdown of either GPMM or GPBB. NE triggered glycogenolysis within 15 min in control cells and after GPBB knockdown. However, astrocytes in which expression of GPMM had been silenced showed a delay in response to NE, with glycogen levels significantly reduced only after 60 min. In contrast, allosteric activation of GP by AMP, induced by glucose deprivation, seemed to mainly affect GPBB, as only knockdown of GPBB, but not of GPMM, delayed the glycogenolytic response to glucose deprivation. Our results indicate that the two GP isoforms expressed in astrocytes respond to different physiological triggers, therefore conferring distinct metabolic functions of brain glycogen.

Maladaptive plasticity involving increased expression of AMPAtype glutamate receptors is involved in several pathologies, including neuropathic pain, but direct inhibition of AMPARs is associated with side effects. As an alternative, we developed a cell-permeable, high-affinity (~2 nM) peptide inhibitor, Tat-P 4 -(C5) 2 , of the PDZ domain protein PICK1 to interfere with increased AMPAR expression. The affinity is obtained partly from the Tat peptide and partly from the bivalency of the PDZ motif, engaging PDZ domains from two separate PICK1 dimers to form a tetrameric complex. Bivalent Tat-P 4 -(C5) 2 disrupts PICK1 interaction with membrane proteins on supported cell membrane sheets and reduce the interaction of AMPARs with PICK1 and AMPA-receptor surface expression in vivo. Moreover, Tat-P 4 -(C5) 2 administration reduces spinal cord transmission and alleviates mechanical hyperalgesia in the spared nerve injury model of neuropathic pain. Taken together, our data reveal Tat-P 4 -(C5) 2 as a novel promising lead for neuropathic pain treatment and expand the therapeutic potential of bivalent inhibitors to non-tandem protein-protein interaction domains.

The aim of this article is to discuss how mutually enriching points from both affordance theory and cultural-historical activity theory can promote theoretical ideas which may prove useful as analytical tools for the study of human life and human development. There are two issues that need to be overcome in order to explore the potentials of James Gibson’s affordance theory: it does not sufficiently theorize (a) development and (b) society. We claim that Gibson’s affordance theory still needs to be brought beyond “the axiom of immediacy.” Ambivalences in Gibson’s affordance theory will be discussed, and we will argue for certain revisions. The strong ideas of direct perceiving and of perception–action mutuality remain intact while synthesized with ideas of societal human life. We propose the concept of the affording of societal standards to be a meaningful term in order to grasp the specific societal character of affordance theory.

Employing student-driven project work in a higher education setting challenges not only the way in which we understand students’ learning and how we define the expected learning outcomes, it also challenges our ways of assessing students’ learning. This paper will address this question specifically and illustrate with a case that highlights some of the challenges that may arise in practice when assessing student-driven, problem-based projects. The case involved an assessment situation in which a discrepancy arose between the internal and external examiner in relation to what was valued. The discrepancy had consequences not only for the concrete assessment of students’ work, but also for the validity of the problem-based university pedagogy in general, and it raised the question of how to assess students’ work adequately. The research focus of this study was to explore the implications of assessing student-driven projects within a progressive approach to higher education teaching, along with the potential underlying issues. We found a need for clear assessment criteria while insisting on a space for students’ creativity and reflexivity as essential parts of a learning process. The paper thus makes a case for the notion of reflexivity as an assessment criterion to be integrated into learning objectives.

The aim of this article is to shed light on how environmental standards in the life of youths influence the development of self. We propose the concept of 'subjectified subjectivity' to grasp these person-environment dialectics in a general form. By elaborating on these conceptual understandings of youth life, the article also seeks to understand young people from their own perspectives on life and from their developing life-perspectives, rather than from general categories. Based on one of the author's data from her study of young people in their transition to (and through the first year of) high school, we carry out an analysis of a 16-year old high school student and how her approach to beer, to beer drinking as a part of Danish high school life-style, and to herself changes over time. We suggest a dialectical-ecological model to analyze the dialectical and synthetic movements over time of the girl and her environments.