Ecotourism in the Himalayas : the Nepalese experience

French version available in IDRC Digital Library: Écotouristes au Népal : rendez-vous à Namche Baza

Development of a lectin-affinity chromatography step for the downstream processing of influenza virus vaccines

Influenza remains due to its annual death rate and potential to cause pandemics a major public health concern. Efforts to control the annual spread of influenza have centered on prophylactic vaccinations. Human influenza vaccines are traditionally produced in embryonated hen s eggs. However, major constraints with this method, e.g. allergic reactions induced by egg proteins and lack of scalability have lead to the development of cell culture based production processes. In recent years, several continuous cell lines such as the Madin Darby canine kidney (MDCK) or the African green monkey kidney Vero cells have been successfully established for the production of influenza vaccines in cell culture. These processes require the modification of existing but also the development of new downstream strategies to account for the changed upstream technology. Downstream processing of biological products is conventionally subdivided into three steps: capture or concentration, separation or fractionation and polishing. The capture step is commonly the most expensive unit operation. Hence, the efficiency of this step has a large impact on the total process economics. The presented study focuses on the development of a proficient capture step based on lectin-affinity chromatography. Lectins are a class of carbohydrate specific proteins of non-immune origin that have a selective affinity for a carbohydrate or a group of carbohydrates. Immobilized lectins have been used successfully for many years to separate and isolate glycoconjugates, polysaccharides, soluble cell components, and cells containing glycoproteins with specific carbohydrate structures on its surface. The influenza A virus contains two spike glycoproteins on its surface: hemagglutinin (HA) and neuraminidase (NA). HA is the most abundant surface protein. It is a trimeric glycoprotein containing per subunit 3 to 9 N-linked glycosylation sites depending on the viral strain. Here the influenza A/PR/8/34 virus has been selected as a model. The HA molecule of this particular virus contains according to the NetNGlyc 1.0 Server prediction six glycosylation sites. Detailed analysis of these sites and their individual glycan structures are presently performed. Based on preliminary structural glycan analysis studies and literature data several HA-binding lectins are selected for a pre-screening via lectin-blots. The most promising lectinblot results are obtained from lectins specific for terminal galactose e.g. Erythrina cristagalli (ECL), Arachis hypogaea (PNA). Lectins, by which lectin-blot analysis suggests an interaction with viral membrane proteins, are currently screened for their suitability as an affinity matrix ligand. Therefore, centrifuged cultivation broths of influenza A/PR/8/34 virus infected MDCK cells are applied to various agaroseimmobilized lectins. Components interfering with the immobilized lectins are selectively adsorbed. Non or weak binding components are washed from the column. Subsequently, bound components are dissociated from the lectin by competitive elution with suitable hapten carbohydrates. This fraction contains the influenza virus particles and virally encoded membrane proteins, which have to be further processed for vaccine manufacturing. The extend of the subsequent purification depends on the specificity of the lectin binding to virally encoded surface proteins. Lectins with weak or no interaction with host cell proteins or medium components and strong interaction with viral membrane glycoproteins represent a powerful tool to concentrate and purify viral surface proteins from contaminating nucleic acids, medium components, and non-virally encoded host cell proteins

Alternative splicing of exon 10 in the tau gene as a target for treatment of tauopathies

Tau aggregation is one of the major features in Alzheimer's disease and in several other tauopathies, including frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17), and progressive supranuclear palsy (PSP). More than 35 mutations in the tau gene have been identified from FTDP-17 patients. A group of these mutations alters splicing of exon 10, resulting in an increase in exon 10 inclusion into tau mRNA. Abnormal splicing with inclusion of exon 10 into tau mRNA has also been observed in PSP and AD patients. These results indicate that abnormal splicing of exon 10, leading to the production of tau with exon 10, is probably one of the mechanisms by which tau accumulates and aggregates in tauopathic brains. Therefore, modulation of exon 10 splicing in the tau gene could potentially be targeted to prevent tauopathies. To identify small molecules or compounds that could potentially be developed into drugs to treat tauopathies, we established a cell-based high-throughput screening assay. In this review, we will discuss how realistic, specific biological molecules can be found to regulate exon 10 splicing in the tau gene for potential treatment of tauopathies

Reaching out for paradise : welcome to Annapurna Lodge

Version anglaise disponible dans la Bibliothèque numérique du CRDI: Ecotourism in the Himalayas : the Nepalese experienc

Essays on Networks and Industrial Organization

Chapter I: Cohesive Anarchy --- In a conflict, a small force may overcome a larger one if the latter fails to coordinate. To understand how incentives drive such failures, I study Tullock contests between a cohesive faction and a group embedded in a network. The group’s strength equals the sum of its members' efforts, where links measure their pairwise complementarity or interference. I characterize equilibria for general networks, and find only few members are likely to contribute. Furthermore, the prize and a network measure of interconnectedness jointly improve the internalization of spillovers by the group, so its performance varies with the stakes -- escalation induces cohesion. Chapter II: Spectral Oligopolies --- We study how demand interactions incentivize multiproduct oligopolists to reduce their variable production costs. Our starting point is an equivalence between multimarket competition over dependent products and single-market competition over independent bundles from which we derive three insights. First, heterogeneous innovativeness begets a core-fringe separation. While strong innovators dominate clusters of complementary markets through demand-side economies of scope, others retreat towards niches whose isolation attenuates the impact of investments. Second, the translation from innovative advantage into profits is strongest in `contractor' graphs, the antipodes of expanders. These graphs comprise clusters which are densely linked within but scarcely without, yet synergize well both by themselves as well as collectively. Consequently, the parts and the whole make for attractive and relatively independent investment targets. Third, as demand interactions scale up, both the market concentration and consumers' share of the surplus rise under broad conditions, so market-share based indices of concentration tend to suggest losses for consumers when the opposite is the case. We construct a generalized Herfindahl index which overcomes this limitation. Chapter III: Dominant Firms --- Many consumer industries evolve into partial oligopolies where firms with and without market power coexist. I develop a framework of dynamic competition which explains this pattern. Starting from a market with a continuum of firms, companies stochastically adjust their product offerings through the accumulation of thin-tailed innovations. In conjunction with discrete-choice founded demand, disruption becomes possible: if the spread of tastes relative to innovations' volatility falls below a threshold, occasionally a firm separates from the continuum with an outstanding product. As a result, this dominant firm accrues a positive market share and profit margin until a future innovator supplants it. During these cycles of disruptive turnover, the fringe provides a `seedbed': since incumbents emerge as frontrunners of the ongoing race of innovations, their products' qualities increase in the number of candidate firms from which they are drawn. Through this mechanism, the fringe’s measure is a first-order generator of surplus over time even if its output is not

Dataset for Extensive programmed centriole elimination unveiled in C. elegans embryos

<p>Spreadsheets, confocal and wide field microscopy images and related scripts. Related to the publication "Extensive programmed centriole elimination unveiled in C. elegans embryos." For the complete dataset, please refer to https://doi.org/10.5075/epfl-upgon-305930 </p&gt

Towards understanding centriole elimination

Centrioles are microtubule-based structures crucial for forming flagella, cilia and centrosomes. Through these roles, centrioles are critical notably for proper cell motility, signalling and division. Recent years have advanced significantly our understanding of the mechanisms governing centriole assembly and architecture. Although centrioles are typically very stable organelles, persisting over many cell cycles, they can also be eliminated in some cases. Here, we review instances of centriole elimination in a range of species and cell types. Moreover, we discuss potential mechanisms that enable the switch from a stable organelle to a vanishing one. Further work is expected to provide novel insights into centriole elimination mechanisms in health and disease, thereby also enabling scientists to readily manipulate organelle fate

Preparative Size-Exclusion Chromatography

Size-exclusion chromatography in group separation mode is an efficient unit operation for the separation of influenza virions from host cell protein [1]. In order to avoid this operation becoming a bottleneck in vaccine production processes, however, the column load has to be optimised balancing productivity with purity. Design principles and the results of a loading study on Sepharose 4 FF are resented in this article

Entwicklung eines kooperativen Managements wandelbarer Produktionsnetze. Teilprojekt 1: Organisatorische Gestaltung und betriebswirtschaftliche Instrumente des Managements wandelbarer Produktionsnetze Schlussbericht

SIGLEAvailable from TIB Hannover: DtF QN1(90,36) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman