Spatial mapping of juxtacrine axo-glial interactions identifies novel molecules in peripheral myelination

Cell-cell interactions promote juxtacrine signals in specific subcellular domains, which are difficult to capture in the complexity of the nervous system. For example, contact between axons and Schwann cells triggers signals required for radial sorting and myelination. Failure in this interaction causes dysmyelination and axonal degeneration. Despite its importance, few molecules at the axo-glial surface are known. To identify novel molecules in axo-glial interactions, we modified the 'pseudopodia' sub-fractionation system and isolated the projections that glia extend when they receive juxtacrine signals from axons. By proteomics we identified the signalling networks present at the glial-leading edge, and novel proteins, including members of the Prohibitin family. Glial-specific deletion of Prohibitin-2 in mice impairs axo-glial interactions and myelination. We thus validate a novel method to model morphogenesis and juxtacrine signalling, provide insights into the molecular organization of the axo-glial contact, and identify a novel class of molecules in myelination

Functionally distinct PI 3-kinase pathways regulate myelination in the peripheral nervous system

The PI 3-kinase (PI 3-K) signaling pathway is essential for Schwann cell myelination. Here we have characterized PI 3-K effectors activated during myelination by probing myelinating cultures and developing nerves with an antibody that recognizes phosphorylated substrates for this pathway. We identified a discrete number of phospho-proteins including the S6 ribosomal protein (S6rp), which is down-regulated at the onset of myelination, and N-myc downstream-regulated gene-1 (NDRG1), which is up-regulated strikingly with myelination. We show that type III Neuregulin1 on the axon is the primary activator of S6rp, an effector of mTORC1. In contrast, laminin-2 in the extracellular matrix (ECM), signaling through the alpha 6 beta 4 integrin and Sgk1 (serum and glucocorticoid-induced kinase 1), drives phosphorylation of NDRG1 in the Cajal bands of the abaxonal compartment. Unexpectedly, mice deficient in. 6. 4 integrin signaling or Sgk1 exhibit hypermyelination during development. These results identify functionally and spatially distinct PI 3-K pathways: an early, pro-myelinating pathway driven by axonal Neuregulin1 and a lateracting, laminin-integrin-dependent pathway that negatively regulates myelination

Experiences from two ways of integrating Pre- and Post-course Multiple-choice assessment questions in educational events for surgeons

To examine how to optimise the integration of multiple-choice questions (MCQs) for learning in continuing professional development (CPD) events in surgery, we implemented and evaluated two methods in two subspecialities over multiple years. The same 12 MCQs were administered pre- and post-event in 66 facial trauma courses. Two different sets of 10 MCQs were administered pre- and post-event in 21 small animal fracture courses. We performed standard psychometric tests on responses from participants who completed both the pre- and post-event assessment. The average difficulty index pre-course was 57% with a discrimination index of 0.20 for small animal fractures and 53% with a discrimination index of 0.15 for facial trauma. For the majority of the individual MCQs, the scores were between 30%-70% and the discrimination index was >0.10. The difficulty index post-course increased in both groups (to 75% and 62%). The pre-course MCQs resulted in an average score in the expected range for both formats suggesting they were appropriate for the intended level of difficulty and an appropriate pre-course learning activity. Post-course completion resulted in increased scores with both formats. Both delivery methods worked well in all regions and overall quality depends on applying a solid item development and validation process

Hepatitis C virus and alcohol: Same mitotic targets but different signaling pathways

Background & Aims: Chromosomal aberrations are frequently observed in hepatitis C virus (HCV)- and alcohol-related hepatocellular carcinomas (HCCs). The mechanisms by which chromosomal aberrations occur during hepatocarcinogenesis are still unknown. However, these aberrations are considered to be the result of deregulation of some mitotic proteins, including the alteration of Cyclin B1 and Aurora kinase A expression, and the phosphorylation of gamma-tubulin. Our study aims at investigating changes in expression of the above mentioned proteins and related intracellular pathways, in in vitro and in vivo models of both HCV- and alcohol- dependent HCCs.Methods: In this study, the molecular defects and the mechanisms involved in deregulation of the mitotic machinery were analyzed in human hepatoma cells, expressing HCV proteins treated or not with ethanol, and in liver tissues from control subjects (n = 10) and patients with HCV- (n = 10) or alcohol-related (n = 10) HCCs.Results: Expression of Cyclin B1, Aurora kinase A, and tyrosine-phosphorylated gamma-tubulin was analyzed in models reproducing HCV infection and ethanol treatment in HCC cells. Interestingly, HCV and alcohol increased the expression of Cyclin B, Aurora kinase A, and tyrosine-phosphorylated gamma-tubulin also in tissues from patients with HCV- or alcohol-related HCCs. In vitro models suggest that HCV requires the expression of PKR (RNA-activated protein kinase), as well as JNK (c-Jun N-terminal kinase) and p38MAPK (p38 mitogen-activated protein kinase) proteins; while, ethanol bypasses all these pathways.Conclusions: Our results support the idea that HCV and alcohol may promote oncogenesis by acting through the same mitotic proteins, but via different signaling pathways. (C) 2011 Published by Elsevier B.V. on behalf of the European Association for the Study of the Liver

MCD and Induced CD of a Tetraphenoxyperylene-Based Dye in Chiral Solvents: An Experimental and Computational Study

The magnetic circular dichroism (MCD) spectrum of N,N '-bis(2,6-diisopropylphenyl)-1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetracarboxydiimide, also known as Lumogen Red 300 or ROT-300, has been recorded both in achiral and chiral solvents. The induced CD spectra in chiral solvents have, similarly, been recorded. A discussion of the spectroscopic response, both in CD and in MCD experiments, is presented in this paper. Both types of spectra have been predicted most satisfactorily by DFT calculations; the CD spectra were obtained by assuming the prevalence of one "enantiomeric" conformer and the same set of conformers could also be used for MCD, since "enantiomeric" structures present identically in MCD spectra