Synthesis and identification of constituents of the cloacal gland secretion of Tuatara

Im Rahmen der vorliegenden Arbeit wurden die bereits früher durchgeführten Untersuchungen zur Zusammensetzung des Cloacaldrüsensekrets der Brückenechse (Sphenodon punctatus) ergänzt und vervollständigt. Das Sekret enthält ausschließlich Triacylglyceride. Zunächst wurden die in den Triacylglyceriden enthaltenen Fettsäuren untersucht. Mit Hilfe von Synthesen und gaschromatographisch-massenspektrometrischen Untersuchungen an achiralen und chiralen stationären Phasen konnten zwei unbekannte Säuren identifiziert und die Stereochemie aller methylverzweigten Säuren aufgeklärt werden. Die Untersuchung der Fettsäurezusammensetzung der einzelnen Sekretproben zeigte, dass diese eine charakteristische Eigenschaft einer jeden Brückenechse ist: Proben, die 2002 und 2004 von einem bestimmten Tier entnommen wurden, zeigten ein annähernd identisches Fettsäureprofil. Im zweiten Teil der Arbeit wurden die Triacylglyceride genauer betrachtet. Dafür wurde eine Methode zur Synthese von Triacylglyceriden mit definierter Fettsäurezusammensetzung entwickelt. Es wurden Untersuchungen zum chromatographischen Verhalten der Triacylglyceride durchgeführt, dabei wurden neben der Gaschromatographie die Reversed Phase Hochleistungsflüssigkeitschromatographie (RP-HPLC) sowie verschiedene Methoden der Silberionenchromatographie eingesetzt. Die massenspektrometrischen Eigenschaften der Triacylglyceride wurden unter Verwendung unterschiedlicher Ionisierungsmethoden (Elektronenstoß-Ionisation (EI-MS), Chemische Ionisation (CI-MS) und Elektrospray-Ionisation (ESI-MS)) analysiert. Des Weiteren wurden Versuche zur regio- und stereospezifischen Analyse der Triacylglyceride mit Hilfe von Spaltungs- und Derivatisierungsreaktionen durchgeführt. Die abschließende Bestimmung der Triacylglycerid-Zusammensetzung aller Cloacaldrüsensekretproben zeigte, dass auch das Triacylglycerid-Profil offensichtlich charakteristisch für jede einzelne Brückenechse ist.Within the scope of this work, previous investigations on the composition of the cloacal gland secretion of Tuatara (Sphenodon punctatus) were completed. The secretion consists only of triacylglycerols. First, the fatty acids comprised by the triacylglycerols were investigated. With the aid of syntheses and gas chromatographic-mass spectrometric investigations on achiral and chiral stationary phases, two unknown acids were identified and the stereochemistry of all methyl branched acids was elucidated. The investigation of the fatty acid composition of the secretion samples showed, that this is a characteristic of each tuatara: samples from one individual, taken in 2002 and 2004, showed nearly the same fatty acid profile. In the second part of the work, the triacylglycerols were examined. A method for the synthesis of triacylglycerols with defined fatty acid composition was developed. The chromatographic behavior of the triacylglycerols was investigated using gas chromatography, reversed phase high-performance liquid chromatography (RP-HPLC) and different methods of silver ion chromatography. The mass spectrometric properties of the triacylglycerols were analyzed with different ionization methods (electron impact ionization (EI-MS), chemical ionization (CI-MS) and electrospray ionization (ESI-MS)). In addition, attempts for the regio- and stereospecific analysis of triacylglycerols using chemical degradative and derivatization steps were made. The determination of the triacylglycerol composition of all ssecretion samples showed that the triacylglycerol profile is also a characteristic property of each tuatara

A multi-scale analysis of transforming agricultural markets in the context of globalization: implications for natural resources, food prices and rural poverty in Latin America

Vivimos una época en la que el mundo se transforma aceleradamente. La globalización está siguiendo un curso imparable, la población mundial así como la población urbana siguen creciendo, y en los países emergentes los ingresos promedios aumentan, resultando en un cambio también acelerado de las dietas y hábitos alimentarios. En conjunto esos factores están causando un aumento fundamental de la demanda de alimentos. Junto con la apertura de los mercados agrícolas, estos procesos han provocado un crecimiento del comercio internacional de alimentos durante la última década. Dado que muchos países de América Latina están dotados de abundancia de recursos naturales, estas tendencias han producido un crecimiento rápido de las exportaciones de bienes primarios desde América Latina al resto del mundo. En sólo 30 años la participación en el mercado agrícola de América Latina casi se ha duplicado, desde 10% en 1980 a 18% en 2010. Este aumento del comercio agrícola ha dado lugar a un debate sobre una serie de cuestiones cruciales relacionadas con los impactos del comercio en la seguridad alimentaria mundial, en el medio ambiente o en la reducción de la pobreza rural en países en desarrollo. Esta tesis aplica un marco integrado para analizar varios impactos relacionados con la transformación de los mercados agrícolas y los mercados rurales debidos a la globalización y, en particular, al progresivo aumento del comercio internacional. En concreto, la tesis aborda los siguientes temas: En primer lugar, la producción mundial de alimentos tendrá que aumentar considerablemente para poder satisfacer la demanda de una población mundial de 9000 millones personas en 2050, lo cual plantea grandes desafíos sobre los sistemas de la producción de alimentos. Alcanzar este logro, sin comprometer la integridad del medio ambiente en regiones exportadoras, es un reto aún mayor. En este contexto, la tesis analiza los efectos de la liberalización del comercio mundial, considerando distintas tecnologías de producción agraria, sobre unos indicadores de seguridad alimentaria en diferentes regiones del mundo y sobre distintos indicadores ambientales, teniendo en cuenta escalas diferentes en América Latina y el Caribe. La tesis utiliza el modelo “International Model for Policy Analysis of Agricultural Commodities and Trade (IMPACT)” – un modelo dinámico de equilibrio parcial del sector agrícola a escala global – para modelar la apertura de los mercados agrícolas así como diferentes escenarios de la producción hasta el año 2050. Los resultados del modelo están vinculados a modelos biofísicos para poder evaluar los cambios en la huella hídrica y la calidad del agua, así como para cuantificar los impactos del cambio en el uso del suelo sobre la biodiversidad y los stocks de carbono en 2050. Los resultados indican que la apertura de los mercados agrícolas es muy importante para mejorar la seguridad alimentaria a nivel mundial, sin embargo, produce también presiones ambientales indeseables en algunas regiones de América Latina. Contrastando dos escenarios que consideran distintas modos de producción, la expansión de la tierra agrícola frente a un escenario de la producción más intensiva, se demuestra que las mejoras de productividad son generalmente superiores a la expansión de las tierras agrícolas, desde un punto de vista económico e ambiental. En cambio, los escenarios de intensificación sostenible no sólo hacen posible una mayor producción de alimentos, sino que también generan menos impactos medioambientales que los otros escenarios futuros en todas sus dimensiones: biodiversidad, carbono, emisiones de nitratos y uso del agua. El análisis muestra que hay un “trade-off” entre el objetivo de alcanzar la sostenibilidad ambiental y el objetivo de la seguridad alimentaria, independiente del manejo agrícola en el futuro. En segundo lugar, a la luz de la reciente crisis de los precios de alimentos en los años 2007/08, la tesis analiza los impactos de la apertura de los mercados agrícolas en la transmisión de precios de los alimentos en seis países de América Latina: Argentina, Brasil, Chile, Colombia, México y el Perú. Para identificar las posibles relaciones de cointegración entre los índices de precios al consumidor de alimentos y los índices de precios de agrarios internacionales, sujetos a diferentes grados de apertura de mercados agrícolas en los seis países de América Latina, se utiliza un modelo simple de corrección de error (single equation error correction). Los resultados indican que la integración global de los mercados agrícolas ha dado lugar a diferentes tasas de transmisión de precios en los países investigados. Sobre todo en el corto plazo, las tasas de transmisión dependen del grado de apertura comercial, mientras que en el largo plazo las tasas de transmisión son elevadas, pero en gran medida independientes del régimen de comercio. Por lo tanto, durante un período de shocks de precios mundiales una mayor apertura del comercio trae consigo más inestabilidad de los precios domésticos a corto plazo y la resultante persistencia en el largo plazo. Sin embargo, estos resultados no verifican necesariamente la utilidad de las políticas comerciales, aplicadas frecuentemente por los gobiernos para amortiguar los shocks de precios. Primero, porque existe un riesgo considerable de volatilidad de los precios debido a cambios bruscos de la oferta nacional si se promueve la autosuficiencia en el país; y segundo, la política de proteccionismo asume el riesgo de excluir el país de participar en las cadenas de suministro de alto valor del sector agrícola, y por lo tanto esa política podría obstaculizar el desarrollo económico. Sin embargo, es indispensable establecer políticas efectivas para reducir la vulnerabilidad de los hogares a los aumentos repentinos de precios de alimentos, lo cual requiere una planificación gubernamental precisa con el presupuesto requerido disponible. En tercer lugar, la globalización afecta a la estructura de una economía y, por medios distintos, la distribución de los ingreso en un país. Perú sirve como ejemplo para investigar más profundamente las cuestiones relacionadas con los cambios en la distribución de los ingresos en zonas rurales. Perú, que es un país que está cada vez más integrado en los mercados mundiales, consiguió importantes descensos en la pobreza extrema en sus zonas rurales, pero a la vez adolece de alta incidencia de pobreza moderada y de desigualdad de los ingresos en zonas rural al menos durante el periodo comprendido entre 2004 y 2012. Esta parte de la tesis tiene como objetivo identificar las fuerzas impulsoras detrás de estas dinámicas en el Perú mediante el uso de un modelo de microsimulación basado en modelos de generación de ingresos aplicado a nivel los hogares rurales. Los resultados indican que la fuerza principal detrás de la reducción de la pobreza ha sido el crecimiento económico general de la economía, debido a las condiciones macroeconómicas favorables durante el periodo de estudio. Estos efectos de crecimiento beneficiaron a casi todos los sectores rurales, y dieron lugar a la disminución de la pobreza rural extrema, especialmente entre los agricultores de papas y de maíz. En parte, estos agricultores probablemente se beneficiaron de la apertura de los mercados agrícolas, que es lo que podría haber provocado un aumento de los precios al productor en tiempos de altos precios mundiales de los alimentos. Sin embargo, los resultados también sugieren que para una gran parte de la población más pobre existían barreras de entrada a la hora de poder participar en el empleo asalariado fuera de la agricultura o en la producción de cultivos de alto valor. Esto podría explicarse por la falta de acceso a unos activos importantes: por ejemplo, el nivel de educación de los pobres era apenas mejor en 2012 que en 2004; y también las dotaciones de tierra y de mano de obra, sobre todo de los productores pobres de maíz y patata, disminuyeron entre 2004 y 2012. Esto lleva a la conclusión de que aún hay margen para aplicar políticas para facilitar el acceso a estos activos, que podría contribuir a la erradicación de la pobreza rural. La tesis concluye que el comercio agrícola puede ser un importante medio para abastecer una población mundial creciente y más rica con una cantidad suficiente de calorías. Para evitar adversos efectos ambientales e impactos negativos para los consumidores y de los productores pobres, el enfoque debe centrarse en las mejoras de la productividad agrícola, teniendo en cuenta los límites ambientales y ser socialmente inclusivo. En este sentido, será indispensable seguir desarrollando soluciones tecnológicas que garanticen prácticas de producción agrícola minimizando el uso de recursos naturales. Además, para los pequeños pobres agricultores será fundamental eliminar las barreras de entrada a los mercados de exportación que podría tener efectos indirectos favorables a través de la adopción de nuevas tecnologías alcanzables a través de mercados internacionales. ABSTRACT The world is in a state of rapid transition. Ongoing globalization, population growth, rising living standards and increasing urbanization, accompanied by changing dietary patterns throughout the world, are increasing the demand for food. Together with more open trade regimes, this has triggered growing international agricultural trade during the last decade. For many Latin American countries, which are gifted with relative natural resource abundance, these trends have fueled rapid export growth of primary goods. In just 30 years, the Latin American agricultural market share has almost doubled from 10% in 1980 to 18% in 2010. These market developments have given rise to a debate around a number of crucial issues related to the role of agricultural trade for global food security, for the environment or for poverty reduction in developing countries. This thesis uses an integrated framework to analyze a broad array of possible impacts related to transforming agricultural and rural markets in light of globalization, and in particular of increasing trade activity. Specifically, the following issues are approached: First, global food production will have to rise substantially by the year 2050 to meet effective demand of a nine billion people world population which poses major challenges to food production systems. Doing so without compromising environmental integrity in exporting regions is an even greater challenge. In this context, the thesis explores the effects of future global trade liberalization on food security indicators in different world regions and on a variety of environmental indicators at different scales in Latin America and the Caribbean, in due consideration of different future agricultural production practices. The International Model for Policy Analysis of Agricultural Commodities and Trade (IMPACT) –a global dynamic partial equilibrium model of the agricultural sector developed by the International Food Policy Research Institute (IFPRI)– is applied to run different future production scenarios, and agricultural trade regimes out to 2050. Model results are linked to biophysical models, used to assess changes in water footprints and water quality, as well as impacts on biodiversity and carbon stocks from land use change by 2050. Results indicate that further trade liberalization is crucial for improving food security globally, but that it would also lead to more environmental pressures in some regions across Latin America. Contrasting land expansion versus more intensified agriculture shows that productivity improvements are generally superior to agricultural land expansion, from an economic and environmental point of view. Most promising for achieving food security and environmental goals, in equal measure, is the sustainable intensification scenario. However, the analysis shows that there are trade-offs between environmental and food security goals for all agricultural development paths. Second, in light of the recent food price crisis of 2007/08, the thesis looks at the impacts of increasing agricultural market integration on food price transmission from global to domestic markets in six Latin American countries, namely Argentina, Brazil, Chile, Colombia, Mexico and Peru. To identify possible cointegrating relationships between the domestic food consumer price indices and world food price levels, subject to different degrees of agricultural market integration in the six Latin American countries, a single equation error correction model is used. Results suggest that global agricultural market integration has led to different levels of price path-through in the studied countries. Especially in the short-run, transmission rates depend on the degree of trade openness, while in the long-run transmission rates are high, but largely independent of the country-specific trade regime. Hence, under world price shocks more trade openness brings with it more price instability in the short-term and the resulting persistence in the long-term. However, these findings do not necessarily verify the usefulness of trade policies, often applied by governments to buffer such price shocks. First, because there is a considerable risk of price volatility due to domestic supply shocks if self-sufficiency is promoted. Second, protectionism bears the risk of excluding a country from participating in beneficial high-value agricultural supply chains, thereby hampering economic development. Nevertheless, to reduce households’ vulnerability to sudden and large increases of food prices, effective policies to buffer food price shocks should be put in place, but must be carefully planned with the required budget readily available. Third, globalization affects the structure of an economy and, by different means, the distribution of income in a country. Peru serves as an example to dive deeper into questions related to changes in the income distribution in rural areas. Peru, a country being increasingly integrated into global food markets, experienced large drops in extreme rural poverty, but persistently high rates of moderate rural poverty and rural income inequality between 2004 and 2012. The thesis aims at disentangling the driving forces behind these dynamics by using a microsimulation model based on rural household income generation models. Results provide evidence that the main force behind poverty reduction was overall economic growth of the economy due to generally favorable macroeconomic market conditions. These growth effects benefited almost all rural sectors, and led to declines in extreme rural poverty, especially among potato and maize farmers. In part, these farmers probably benefited from policy changes towards more open trade regimes and the resulting higher producer prices in times of elevated global food price levels. However, the results also suggest that entry barriers existed for the poorer part of the population to participate in well-paid wage-employment outside of agriculture or in high-value crop production. This could be explained by a lack of sufficient access to important rural assets. For example, poor people’s educational attainment was hardly better in 2012 than in 2004. Also land and labor endowments, especially of (poor) maize and potato growers, rather decreased than increased over time. This leads to the conclusion that there is still scope for policy action to facilitate access to these assets, which could contribute to the eradication of rural poverty. The thesis concludes that agricultural trade can be one important means to provide a growing and richer world population with sufficient amounts of calories. To avoid adverse environmental effects and negative impacts for poor food consumers and producers, the focus should lie on agricultural productivity improvements, considering environmental limits and be socially inclusive. In this sense, it will be crucial to further develop technological solutions that guarantee resource-sparing agricultural production practices, and to remove entry barriers for small poor farmers to export markets which might allow for technological spill-over effects from high-value global agricultural supply chains

The role of institutional quality on the performance in the export of coconut products

The literature that addresses the role of institutions in bilateral trade is extensive. However, research that links institutional quality to specific products and their different levels of value addition is lacking. In this study, we look into institutional quality, based on three indicators from the World Bank's world governance indicators, and its indicator-specific effects on bilateral coconut trade. In particular, we study coconut products with varying degrees of value addition. We use structural gravity models to measure how institutions affect the trade performance of the top 26 coconut producing countries to the top 15 importing economies over the years 1996-2016. Our results suggest that increased government effectiveness enhances trade of high-value products, whereas better voice and accountability scores decrease trade of coconut products with both levels of value addition. No clear trade effect is observed when two countries are more similar in each of the three indicators. We conclude that each indicator has different trade effects on each of the coconut product categories. We end by giving recommendations that will help to improve the coconut export performance in their respective countries and for future research

Water and agriculture

This chapter shows the strong links between water, agriculture and the economy in Latin America and Caribbean (LAC). Both green and blue water are vital for LAC's economies and for its food security. Awareness of LAC's virtual water trade volumes and water footprints alone will not solve the local or global water problems. However, the awareness gained increases the likelihood that optimized water allocation decisions, which consider the hydrological and economical aspects of water resources, are made. • Agriculture is a significant economic sector for many LAC countries with some being major world players in the agricultural commodities world markets, such is the case for Brazil and Argentina who contribute to 13% of the global green water export. At the micro level, agriculture still plays a significant role for the food security of the population. • The consumptive water use of agricultural production was on average 1,057Gm 3 / yr for the period 1996–2005; of which, 95% corresponds to the green water footprint, whereas 5% refers to the blue component. This indicates that LAC relies heavily on green water for agricultural production, i.e. rain-fed agriculture. • Maize is a fundamental crop in Argentina, Brazil, Chile, Mexico and Peru, representing 15% of the total agricultural blue and green water footprint (773,408hm 3 /yr) and contributing to 35% of the agricultural nitrogen pollution, estimated as grey water footprint, in Argentina, Brazil, Chile, Colombia, Mexico and Peru. Only in Mexico, maize contributes 60% of the agricultural grey water footprint. • Grazing represents 24% of the total green water footprint of agriculture in these countries. The blue water consumption by the animal water supply is very significant in Argentina, Brazil, Chile, Mexico and Peru, which amounts to 13% (38,825hm 3 /yr) of the total consumption

Entwicklung eines Stammzell-basierten intraokulären Applikationssystems neurotropher Faktoren zur Verminderung des Verlustes retinaler Ganglienzellen in einem Mausmodell des Glaukoms

Loss of vison as a result of glaucomatous optic neuropathies is the second leading cause for blindness in industrialized countries. Glaucomatous optic neuropathies are characterized by a progressive degeneration of retinal ganglion cell (RGCs) bodies in the retina and their axons in the optic nerve, ultimately resulting in a disruption of signal transduction from the eye to the brain. The progressive loss of retinal ganglion cells results in localized visual field defects, and eventually in complete blindness. Clinically, the major risk factor for glaucoma is elevated intraocular pressure (IOP), and lowering IOP is currently the only proven treatment for glaucoma. However, the diseases progresses in a significant proportion of patients despite successful lowering of IOP. Furthermore, glaucoma may develop in patients despite a normal IOP. Thus, there is a need for alternative treatments of this neurodegenerative disorder of the inner retina. The aim of the present thesis was to establish a neural stem cell-based delivery system that allows a continuous and long-lasting intraocular supply of neurotrophic factors, with the ultimate aim to attenuate the loss of RGCs in a mouse model of glaucoma. In the present thesis, adherently cultivated neural stem (NS) cells from the cerebral cortex of embryonic mice were used as cellular vectors to administer neurotrophic factors to the murine retina. NS cells maintained under adherent culture conditions comprise a homeogenous population of clonogenic, symmetrically dividing tripotent stem cells. We then used polycistronic lentiviral vectors to stably co-express different neurotrophic factors together with a fluorescent reporter protein and a resistance gene in NS cells. To establish and evaluate this cell-based neuroprotective approach, we expressed three different neurotrophic factors with a known neuroprotective activity on RGCs, ciliary neurotrophic factor (CNTF), glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) in NS cells. We then took advantage from the fact that expression levels of the neurotrophic factors and the fluorescent reporter proteins from the polycistronic lentiviral vectors are proportional to each other, and selected single cells with high expression levels of the reporter gene using fluorescent activated cell sorting. Subsequent clonal expansion of these cells resulted in clonal NS cell lines with high expression levels of CNTF, GDNF or BDNF. To analyze the neuroprotective potential of the modified NS cell lines in vivo, degeneration of RGCs was induced in adult mice by an intraorbital crush of the optic nerve and cells were intravitreally grafted one day after the lesion. All three clonal cell lines attached to the posterior pole of the lenses and the vitreal surface of the retinas, preferentially differentiated into astrocytes and survived for up to four months in the host eyes. Furthermore, the donor cells stably expressed the neurotrophic factors and fluorescent reporter proteins. Adverse effects of the donor cells on the morphology of the host retinas were not observed. Importantly, all three NS cell lines significantly attenuated the lesion-induced degeneration of RGCs over a time period of at least two (for the GDNF- and BDNF-expressing cell line) or four months (for the CNTF-expressing cell line; longer post-lesion intervals were not analyzed). The CNTF-expressing NS cell line additionally stimulated long distance regeneration of the lesioned RGC axons. Of note, neuroprotection of axotomized RGCs was markedly enhanced after transplantation of a mixture of the GDNF- and CNTF-expressing cell line when compared to transplantations of each individual clonal cell lines. Quantitative analyses of these data revealed a significant synergistic neuroprotective activity of GDNF and CNTF on axotomized RGCs. Together, data of the present thesis indicate that genetically modified NS cell lines may serve as valuable tools to evaluate the therapeutic potential of a sustained cell-based intraocular administration of neurotrophic factors in animal models of glaucoma. Clonal NS cell lines with a forced expression of neurotrophic factors may also be a useful tool for combinatorial neuroprotective approaches aimed at identifying combinations of neurotrophic factors with additive or synergistic neuroprotective effects on RGCs.Das Glaukom ist die zweithäufigste Ursache für Blindheit in industrialisierten Ländern. Charakteristisch für glaukomatöse Optikusatrophie ist die progressive Degeneration der Zelkörper retinaler Ganglienzellen (RGC) in der Retina und ihrer Axone im optischen Nerven, was zu einer Unterbrechung der Signaltransduktion zwischen Auge und Gehirn führt. Der fortschreitende Verlust der RGC resultiert in lokalen Gesichtsfeld-Einschränkungen, welche schließlich zu vollständiger Blindheit führen. Der, aus klinischer Sicht, wichtigste Risikofaktor für eine Glaukomerkrankung ist ein erhöhter Augeninnendruck und eine Reduktion des Augeninnendrucks ist die zurzeit einzig bekannte Therapieoption. In einem signifikanten Teil der Patienten schreitet die Krankheit jedoch trotz einer erfolgreichen Senkung des Augeninnendrucks weiter fort, während andere Patienten auch ohne erhöhten Augeninnendruck an einem Glaukom erkranken. Es ist also notwendig für diese neurodegenerative Erkrankung der inneren Retina alternative Therapiemethoden zu entwickeln. Das Ziel der vorliegenden Arbeit war die Etablierung eines auf neuralen Stammzellen (NSC) basierenden Applikationssystems, welches eine kontinuierliche und dauerhafte Versorgung mit neurotrophen Faktoren ermöglicht, mit dem Ziel dem Verlust von RGC in einem Glaukom-Mausmodell entgegen zu wirken. In der vorliegenden Arbeit wurden adhärent kultivierte NSC aus dem zerebralen Kortex von Mausembryonen als zelluläre Vektoren genutzt um neurotrophe Faktoren der murinen Retina zuzuführen. NSC die unter adhärenten Kulturbedingungen gehalten wurden, bildeten eine homogene Population aus klonogenen, tripotenten Stammzellen, welche sich symmetrisch teilen. Diese NSC wurden dann mit einem polycistronischen lentiviralen Vektor transduziert um eine stabile Ko-Expression verschiedener neurotropher Faktoren zusammen mit fluoreszierenden Reporter-Proteinen in diesen Zellen zu erreichen. Um dieses Zell-basierte System zu etablieren und zu untersuchen wurden drei verschiedene neurotrophe Faktoren verwendet, welche bereits bekannt waren für ihre neuroprotektive Aktivität im Zusammenhang mit RGC, um diese in unseren NSC zu exprimieren. Diese drei Faktoren waren der „ciliary neurotrophic factor“ (CNTF), der „glial cell line-derived neurotrophic factor“ (GDNF) und der „brain-derived neurotrophic factor“ (BDNF). Da die Expressionsstärke der neurotrophen Faktoren und der fluoreszierenden Reporterproteine proportional zueinander stehen, konnten anschließend Zellen mit hoher Expression des Reportergens durch „fluorescent activated cell sorting“ (FACS) ausgewählt und vereinzelt werden. Diese Einzelzellen wurden dann genutzt um durch klonale Expansion klonale NSC-Linien mit hoher Expression von CNTF, GDNF und BDNF zu produzieren. Um das neuroprotektive Potential der modifizierten NSC in vivo zu analysieren, wurde die Degeneration von RGC in adulten Mäusen durch eine Quetschung des optischen Nervens induziert und die Zellen einen Tag nach der Läsion intravitreal transplantiert. Alle drei klonalen Zell-Linien adhärierten an der posterioren Seite der Linse oder an der vitrealen Seite der Retina, wo sie präferentiell in Astrozyten differenzierten und bis zu vier Monate überlebten. Weiterhin zeigten die transplantierten Zellen eine stabile Expression der neurotrophen Faktoren und der Reporterproteine über die gesamte Versuchsdauer hinweg. Negative Effekte der transplantierten Zellen auf die Morphologie der Empfängerretinas wurden nicht beobachtet. Alle drei Zell-Linien waren in der Lage die induzierte Degeneration von RGC über einen Zeitraum von zwei (im Fall der GDNF- und BDNF-Linie) oder vier Monaten (im Falle der CNTF-Linie; längere Versuchszeiträume wurde nicht untersucht) signifikant zu reduzieren. Die CNTF-exprimierende NSC-Linie stimulierte überdies eine weitreichende Regeneration der lädierten Axone. Die Neuroprotektion axotomierter RGC erhöhte sich merklich nach der Transplantation einer Mischung der GDNF- und CNTF-Linie im Vergleich zu Transplantationen der einzelnen klonalen Zell-Linien. Die quantitative Analyse dieser Daten zeigte eine signifikante synergistische neuroprotektive Aktivität von GDNF und CNTF auf axotomierte RGC. Zusammengefasst deuten die Daten der vorliegenden Arbeit darauf hin, dass genetisch modifizierte NSC-Linien als hilfreiches Werkzeug fungieren können um das therapeutische Potential einer dauerhaften Zell-basierten intraokulären Applikation von neurotrophen Faktoren in Glaukom-Tiermodellen zu untersuchen. Klonale NSC-Linien mit einer Überexpression neurotropher Faktoren könnte weiterhin nützlich sein um Kombinationen von neurotrophen Faktoren zu identifizieren, welche additive oder synergistische neuroprotektive Effecte auf RGC zeigen