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Management-Audit
(2001)
The filtration rate of Daphnia galeata was determined in in situ experiments in Bautzen Reservoir and in laboratory experiments, where daphnids were exposed to filtrates that previously contained either natural phytoplankton or cultured eukaryotic algae (Scenedesmus obliquus or Asterionella formosa), respectively. Individual filtration rate (FR) was measured using fluorescent beads, taking into account ingested beads in the gut only. Compared to heated control treatments (100°C), dissolved compounds released by the nutritious cultured algae during the preconditioning phase or by the natural phytoplankton assemblages from Bautzen Reservoir strongly reduced the filtration rate of D. galeata (down to 60 %). Heating deactivated these dissolved compounds. A significant correlation was found between primary production measured in situ and the reduction of FR in the filtrate of reservoir water, indicating that extra- cellular products released during photosynthesis triggered the reduction of the filtration rate. The ratio of ingested to collected beads was used to quantify the proportion of food, which was not only collected but passed the mouth of D. galeata. The ratio of ingestion to collection was compared between filtered and unfiltered reservoir water both media identical with respect to the concentration of dissolved compounds, whereas other factors (e. g. food concentration, temperature, filtration rate) were different. The changes in this ratio between filtered and unfiltered reservoir water suggest that D. galeata is capable of a chemosensory control of the ingestion behaviour by detecting external metabolites.
The factors that determine the efficiency of energy transfer in aquatic food webs have been investigated for many decades. The plant-animal interface is the most variable and least predictable of all levels in the food web. In order to study determinants of food quality in a large lake and to test the recently proposed central importance of the long-chained eicosapentaenoic acid (EPA) at the pelagic producer-grazer interface, we tested the importance of polyunsaturated fatty acids (PUFAs) at the pelagic producerconsumer interface by correlating sestonic food parameters with somatic growth rates of a clone of Daphnia galeata. Daphnia growth rates were obtained from standardized laboratory experiments spanning one season with Daphnia feeding on natural seston from Lake Constance, a large pre-alpine lake. Somatic growth rates were fitted to sestonic parameters by using a saturation function. A moderate amount of variation was explained when the model included the elemental parameters carbon (r2 = 0.6) and nitrogen (r2 = 0.71). A tighter fit was obtained when sestonic phosphorus was incorporated (r2 = 0.86). The nonlinear regression with EPA was relatively weak (r2 = 0.77), whereas the highest degree of variance was explained by three C18-PUFAs. The best (r2 = 0.95), and only significant, correlation of Daphnia's growth was found with the C18-PUFA α-linolenic acid (α-LA; C18:3n-3). This correlation was weakest in late August when C:P values increased to 300, suggesting that mineral and PUFA-limitation of Daphnia's growth changed seasonally. Sestonic phosphorus and some PUFAs showed not only tight correlations with growth, but also with sestonic α-LA content. We computed Monte Carlo simulations to test whether the observed effects of α-LA on growth could be accounted for by EPA, phosphorus, or one of the two C18-PUFAs, stearidonic acid (C18:4n-3) and linoleic acid (C18:2n-6). With >99 % probability, the correlation of growth with α-LA could not be explained by any of these parameters. In order to test for EPA limitation of Daphnia's growth, in parallel with experiments on pure seston, growth was determined on seston supplemented with chemostat-grown, P-limited Stephanodiscus hantzschii, which is rich in EPA. Although supplementation increased the EPA content 80-800x, no significant changes in the nonlinear regression of the growth rates with α-LA were found, indicating that growth of Daphnia on pure seston was not EPA limited. This indicates that the two fatty acids, EPA and α-LA, were not mutually substitutable biochemical resources and points to different physiological functions of these two PUFAs. These results support the PUFA-limitation hypothesis for sestonic C:P < 300 but are contrary to the hypothesis of a general importance of EPA, since no evidence for EPA limitation was found. It is suggested that the resource ratios of EPA and α-LA rather than the absolute concentrations determine which of the two resources is limiting growth.
The factors that determine the efficiency of energy transfer in aquatic food webs have been investigated for many decades. The plant-animal interface is the most variable and least predictable of all levels in the food web. In order to study determinants of food quality in a large lake and to test the recently proposed central importance of the long-chained eicosapentaenoic acid (EPA) at the pelagic producer-grazer interface, we tested the importance of polyunsaturated fatty acids (PUFAs) at the pelagic producer-consumer interface by correlating sestonic food parameters with somatic growth rates of a clone of Daphnia galeata. Daphnia growth rates were obtained from standardized laboratory experiments spanning one season with Daphnia feeding on natural seston from Lake Constance, a large pre-alpine lake. Somatic growth rates were fitted to sestonic parameters by using a saturation function. A moderate amount of variation was explained when the model included the elemental parameters carbon (r2 = 0.6) and nitrogen (r2 = 0.71). A tighter fit was obtained when sestonic phosphorus was incorporated (r2 = 0.86). The nonlinear regression with EPA was relatively weak (r2 = 0.77), whereas the highest degree of variance was explained by three C18-PUFAs. The best (r2 = 0.95), and only significant, correlation of Daphnia's growth was found with the C18-PUFA a-linolenic acid (a-LA; C18:3n-3). This correlation was weakest in late August when C:P values increased to 300, suggesting that mineral and PUFA- limitation of Daphnia's growth changed seasonally. Sestonic phosphorus and some PUFAs showed not only tight correlations with growth, but also with sestonic alpha-LA content. We computed Monte Carlo simulations to test whether the observed effects of alpha-LA on growth could be accounted for by EPA, phosphorus, or one of the two C18-PUFAs, stearidonic acid (C18:4n-3) and linoleic acid (C18:2n-6). With >99% probability, the correlation of growth with alpha-LA could not be explained by any of these parameters. In order to test for EPA limitation of Daphnia's growth, in parallel with experiments on pure seston, growth was determined on seston supplemented with chemostat-grown, Plimited Stephanodiscus hantzschii, which is rich in EPA. Although supplementation increased the EPA content 80-800x, no significant changes in the nonlinear regression of the growth rates with alpha-LA were found, indicating that growth of Daphnia on pure seston was not EPA limited. This indicates that the two fatty acids, EPA and alpha-LA, were not mutually substitutable biochemical resources and points to different physiological functions of these two PUFAs. These results support the PUFA-limitation hypothesis for sestonic C:P < 300 but are contrary to the hypothesis of a general importance of EPA, since no evidence for EPA limitation was found. It is suggested that the resource ratios of EPA and alpha-LA rather than the absolute concentrations determine which of the two resources is limiting growth.
Einfache Decarbonylierungen und stereoselektive Oxidationen von Cyclohexadienen und Cyclohexenen
(2001)
Zusammenfassend konnte im Rahmen dieser Arbeit das Synthesepotential von Cyclohexadienen und Cyclohexenen deutlich erweitert werden. Die Darstellung der 1-Alkylcyclohexa-2,5-dien-1-carbonsäuren erfolgte mittels Birch-Reduktion in flüssigem Ammoniak und anschließender Umsetzung der intermediär entstehenden Dianionen mit Alkylhalogeniden. So konnte ausgehend von verschiedenen Benzoesäurederivaten eine Reihe interessanter Cyclohexadiene in sehr guten Ausbeuten synthetisiert werden. Erstmals gelangen säurekatalysierte Decarbonylierungen von Cyclohexadiencarbonsäuren, was die einfache Synthese substituierter Aromaten in ausgezeichneten Ausbeuten ermöglichte. In dieser Arbeit wird der Reaktionsmechanismus vorgestellt, welcher durch den Nachweis von Kohlenmonoxid in der Gasphase der Reaktionslösung durch IR-Spektroskopie untermauert wird. Bei der säurekatalysierten Umsetzung von 3-alkylsubstituierten Cyclohexadien-carbonsäuren entstanden neben den erwarteten Aromaten Lactone in ca. 50% Ausbeute. Schließlich zeigen die untersuchten Singulettsauerstoff-En-Reaktionen, der im ersten Teil dargestellten Cyclohexadiene und Lactone, durchweg hohe Regioselektivitäten und lieferten durch elektrostatische Wechselwirkungen und konformative Effekte zum Teil sehr gute Diastereoselektivitäten. Die auxiliarkontrollierte Photooxygenierungen von Cyclohexenon welches mit verschiedenen Weinsäureestern ketalisiert wurde, zeigten jedoch keine bevorzugte p-Facialität des Singulettsauerstoffs.
Inhalt: 1 Die öffentliche Diskussion: Blinde Flecken und „offene Selektivität“ 2 Die wissenschaftliche Übersetzung des Konzepts in Politikberatung 3 Nachhaltiger Umgang mit Natur – ein Problem technisch-ökonomischerInstrumente? 3.1 Natur als landschaftsökologisches System 3.2 Systemforschung – der „totale Zugriff“ 3.3 Naturraumpotenziale – unbestimmt bestimmte Bewertung von Natur 3.4 Ökonomische Naturbewertung – die „rohe Sprache des Geldes“ 3.5 Fazit 1: Leitplanken für eine ökologische Modernisierung derkapitalistischen Produktionsweise 4 Nachhaltiger Umgang mit Natur – eine Frage von Sinn und Moral? 4.1 Umweltgerechtes Verhalten – Natur als moralische Instanz 4.2 Wissenschaft – zukunftsfähig durch ein „neues Denken“? 4.3 Fazit 2: Leitbilder für einen ökologisch modernisierten Menschen 5 Abschließendes
Gemeinsame Gewerbegebiete durch interkommunale Kooperation : Grundlagen, Erfahrungen, Em,pfehlungen
(2001)
Schochat, A., Der Ursprung der jüdischen Aufklärung in Deutschland; Frankfurt, Campus-Verl., 2000
(2001)
Determination of phenolic compounds using recombinant tyrosinanse from Streptomyces antibioticus
(2001)
Rezensiertes Werk: Hohn, Uta: Stadtplanung in Japan : Geschichte, Recht, Praxis, Theorie / Uta Hohn. - Dortmund : Dortmunder Vertrieb für Bau- und Planungslit., 2000. - 616 S. : Abb., Risse, Pl., Tab., graph. Darst. Zugl.: Duisburg, Univ., Habil.-Schr., 1998 u.d.T.: Stadtplanung, Stadterneuerung und Stadtumbau in Japan ISBN 3-929797-67-4
In order to broaden our understanding of the eukaryotic CO2- concentrating mechanism the occurrence and localization of a thylakoid-asssocaate carbonic anhydrase (EC 4.2.1.1) were studied in the green algae Tetraedron on minimum and Chlamydomonas noctigama. Both algae induce a CO2-concentrating mechanism when grown under limiting CO2 conditions. Using mass- spectrometric measurements of O-18 exchange from doubly labelled CO2, the presence of a thylakoid-associated carbonic anhydrase was confirmed for both species. From purified thylakoid membranes, photosystem I (PSI), photosystem II (PSII) and the light-harvesting complex of the photosynthetic apparatus were isolated by mild detergent gel. The protein fractions were identified by 77 K fluorescence spectroscopy and immunological studies. A polypeptide was found to immunoreact with an antibody raised against thylakoid carbonic anhydrase (CAH3) from Chlamydomonas reinhardtii. It was found that this polypeptide was mainly associated with PSII, although a certain proportion was also connected to light harvesting complex II. This was confirmed by activity measurements of carbonic anhydrase in isolated bands extracted from the mild detergent gel. The thylakoid carbonic anhydrase isolated from T. minimum had an isoelectric point between 5.4 and 4.8. Together the results are consistent with the hypothesis that thylakoid carbonic anhydrase resides within the lumen where it is associated with the PSII complex.
Noise-induced dynamics of a prototypical bistable system with delayed feedback is studied theoretically and numerically. For small noise and magnitude of the feedback, the problem is reduced to the analysis of the two-state model with transition rates depending on the earlier state of the system. Analytical solutions for the autocorrelation function and the power spectrum have been found. The power spectrum has a peak at the frequency corresponding to the inverse delay time, whose amplitude has a maximum at a certain noise level, thus demonstrating coherence resonance. The linear response to the external periodic force also has maxima at the frequencies corresponding to the inverse delay time and its harmonics.
Distributed optimality
(2001)
In this thesis I propose a synthesis (Distributed Optimality, DO) between Optimality Theory (OT, Prince & Smolensky, 1993) and a morphological framework in a genuine derivational tradition, namely Distributed Morphology (DM) as developed by Halle & Marantz (1993). By carrying over the apparatus of OT to DM, phenomena which are captured in DM by language-specific rules or features of lexical entries, are given a more principled account in the terms of ranked universal constraints. On the other hand, also the DM part makes two contributions, namely strong locality and impoverishment. The first gives rise to a simple formal interpretation of DO, while the latter is shown to be indispensable in any theoretically satisfying account of agreement morphology. The empirical basis of the work is given by the complex agreement morphology of genetically different languages. Theoretical focus is mainly on two areas: First, so-called direction marking which is shown to be preferably treated in terms of constraints on feature realization. Second, the effects of precedence constraints which are claimed to regulate the status of agreement affixes as prefixes or suffixes and their respective order. A universal typology for the order of agreement categories by means of OT-constraints is proposed.
Breton and Irish, two Celtic and strongly endangered European minority languages, enjoy (or suffer) different fates of official recognition. While France does not officially recognise Breton as an independent language and has no even signed the European Charter of Minority Languages as most other EU countries did, Irish is by its constitution the first national language of the Republic of Ireland and therefore enjoys a very high official prestige. It is an obligatory subject in the schools and all EU documents need to be translated both into Irish and English. In spite of this difference of status and prestige, both languages have suffered, during the past 50 years, from a dramatic loss of speakers, as the young generation sees no need to preserve a regionalised minority heritage in a world of globalised communication and exchange. While both inherited languages were, traditionally and sociologically speaking, the medium of communication of the rural population, albeit with a long and venerable written tradition reaching back to the middle ages, the language of the future is that of the urban middle classes learnt as a second language (L2) und for all intents and purposes not used as a community language in the home. Middle class Breton and Irish are token languages, serving its users as identity markers in order to set themselves off from the English and French, most of whom only speak English and French and have no additional regional language. The linguistic gap between the inherited rural and the new urban varieties is great, so that older native rural speakers do not understand school Breton and school Irish. It is predictable that only the urban varieties will survive for still quite a while, whereas the rural varietes are unlikely to escape language death due to the ongoing change of living conditions in the rural areas and the absence of localised language engineering.
Transition to Coherence in Populations of Coupled Chaotic Oscillators: A Linear Response Approach
(2001)
We consider the collective dynamics in an ensemble of globally coupled chaotic maps. The transition to the coherent state with a macroscopic mean field is analyzed in the framework of the linear response theory. The linear response function for the chaotic system is obtained using the perturbation approach to the Frobenius-Perron operator. The transition point is defined from this function by virtue of the self-excitation condition for the feedback loop. Analytical results for the coupled Bernoulli maps are confirmed by the numerics.
Subject of this work is the investigation of generic synchronization phenomena in interacting complex systems. These phenomena are observed, among all, in coupled deterministic chaotic systems. At very weak interactions between individual systems a transition to a weakly coherent behavior of the systems can take place. In coupled continuous time chaotic systems this transition manifests itself with the effect of phase synchronization, in coupled chaotic discrete time systems with the effect of non-vanishing macroscopic mean field. Transition to coherence in a chain of locally coupled oscillators described with phase equations is investigated with respect to the symmetries in the system. It is shown that the reversibility of the system caused by these symmetries results to non-trivial topological properties of trajectories so that the system constructed to be dissipative reveals in a whole parameter range quasi-Hamiltonian features, i.e. the phase volume is conserved on average and Lyapunov exponents come in symmetric pairs. Transition to coherence in an ensemble of globally coupled chaotic maps is described with the loss of stability of the disordered state. The method is to break the self-consistensy of the macroscopic field and to characterize the ensemble in analogy to an amplifier circuit with feedback with a complex linear transfer function. This theory is then generalized for several cases of theoretic interest.
Impacts of agricultural land use on the environment are various and do not contribute to modifications of the ecology of central European landscapes. They do not only cause a progressive reduction of the number of plant ans animal specis typical for central Europe. Ever since the increasing intensification of farming, from the application of large amounts of fertilizers and pesticides to the use of increasingly larger machinery and progressive specialization there has also been an increase of other, hitherto little noticed environmental impacts. Heavy machinery and cultivation during disadvantageous weather will provoke soil compaction. Unvarying crop rotation systems and plouging of terrain too steep for it will increase water erosion. Due to groundwater lowering former peat lands are increasingly prone to desiccation and thus extremely susceptible to wind erosion. High rates of fertilizer application contiuously increase the risk of nitrate eluviation into the groundwater. These hazards are explained and measures of reduction are shown. The latter are indeed compatible with the aims of intensive farming but with less negative consequences for the environment. Above all they make sure that future generations will be able to continue farming the agricultural lands of central Europe that have been under cultivation for thousands of years.
Alejandro de Humboldt se interesó mucho por el problema de comprender las manifestaciones del arte indígena de América. Basándose su visión del arte en la educación de la ilustración y del humanismo, Humboldt llegó a conclusiones que oscilan entre admiración de los monumentos como tales de la historia e ideas del desarrollo del arte humana desde formas primitivas comparables con las de ensayos de niños hasta formas más elaboradas y primorosas de los griegos antiguos. Superó sus prejuicios analizando detalles y aclarando que se tendría que reflexionar sobre las circunstancias sociales del desarrollo artístico y quedar abierto para una discusión acerca de lo que se observa e interpreta.
We analyse the X-ray light curves of compact objects using linear and nonlinear time series analysis methods. A Power Density Spectrum (PDS) describes the overall second order properties of the observed data well. To look beyond we propose the nonlinear Q-statistic to detect an asymmetry of the time series. This allows us to find relevant time scales. This method even grants a subclassification of the known states of X-ray sources.
Die Ausstattung der gastrointestinalen Mukosa des Menschen und der Ratte mit Sulfotransferasen wurde mit Hilfe von Immunodetektion und Enzymaktivitätsmessungen untersucht. In Proben aus Colon und Rektum von 39 Personen wurden die Formen h1A1, h1A3 und h1B1 identifiziert, wobei in einer weiteren Probe, die als einzige von einem an Colitis Ulcerosa erkrankten Patienten stammte, keine Sulfotransferasen nachgewiesen werden konnten. Bei der Immunblot-Analyse war das Expressionsmuster der einzelnen Formen in allen Proben ähnlich. In wenigen Proben waren die relativen Signalintensitäten der h1A1 und der h1B1 um die Hälfte erniedrigt. Der Gehalt von SULT an zytosolischem Protein zeigte einen bis zu 8 - 10fachen Unterschied, er betrug jedoch bei zwei Dritteln der Proben zwischen 0,15 und 0,3 (h1A1 und h1A3) bzw. 0,6 und 0,8 Promille (h1B1). Die Variation konnte nicht auf Alter, Geschlecht oder Krankheitsbild der Patienten zurückgeführt werden. Auch der für die allelischen Varianten der h1A1 beschriebene Effekt auf die Enzymaktiviät bzw. Stabilität konnte in der Menge an immunreaktivem Protein nicht in diesem Ausmaß detektiert werden. Die Allelhäufigkeit von h1A1*R und h1A1*H war gegenüber der gesunden Bevölkerung nicht verändert. In den sieben Proben aus dem Dünndarm (Coecum, viermal Ileum, Jejunum) konnten zusätzlich die Formen h1E1 und h2A1 identifiziert werden. Ein möglicherweise der Form h1C1 entsprechendes Protein wurde im Magen detektiert. Im Vergleich zum Menschen war die Expression in der Ratte stärker auf die Leber konzentriert. Während beim Menschen in allen untersuchten Abschnitten Sulfotransferasen in Mengen detektiert wurden, die in zwei Fällen (h1B1 und h1A3) sogar den Gehalt in der Leber überstiegen, beschränkte sich die Expression in der Ratte auf im Vergleich zur Leber geringe Mengen im Magen und Dickdarm. Nachgewiesen wurden die r1B1, r1A1 sowie eine nicht identifizierte Form von 35kD, bei der es sich vermutlich um die r1C2 handelt. Im Vergleich zur Leber enthielt der Dickdarm der Ratte 20 - 30 % an r1B1 und 3 % an r1A1, während im Dickdarm des Menschen die 3 - 5fache Menge an h1B1 und 25 - 50 % an h1A1 gefunden wurden. Die nicht identifizierte Form verhielt sich wie die r1B1. Die für die Leber der Ratte bekannte geschlechtsabhängige Expression wurde im Gastrointestinaltrakt nicht beobachtet. Die Verteilung der Sulfotransferasen im Colon und Ileum des Menschen wurde immunhistochemisch untersucht; für die Gewebe der Ratte war die Spezifität der zur Verfügung stehenden Antiseren nicht ausreichend. Im Colon traten h1B1-spezifische Färbungen in den differenzierten Enterozyten am oberen Ende der Krypten auf, im Dünndarm wurden die Epithelzellen der Zotten gefärbt. Die Färbung konzentrierte sich auf das Zytoplasma. Eine ähnliche Verteilung zeigte sich für h1A1 und h1A3, außer daß zusätzlich eine intensive Färbung der Endothelzellen der Kapillaren in der Submukosa des Ileums auftrat. Im Dickdarm war dies nur bei den Kapillaren in den Lymphfollikeln zu erkennen. Die h2A1 war lediglich im Zytoplasma der Epithelzellen der Zotten des Ileums nachzuweisen, während im Colon keine Farbreaktion auftrat. Durch die Verwendung der rekombinanten Indikatorstämme TA1538-h1A1, -h1A3 und -h1B1 und des Ausgangsstammes Salmonella typhimurium TA1538 im Ames-Test wurde gezeigt, daß verschiedene benzylische und allylische Alkohole durch im humanen Colon exprimierte Sulfotransferasen zu Mutagenen aktiviert werden. In den meisten Fällen erwies sich eine der drei Sulfotransferasen als besonders effizient in der Bioaktivierung, während durch die anderen Formen kein oder nur ein schwacher Effekt verursacht wurde. Die Bioaktivierung von Promutagenen durch Sulfotransferasen im Colon muß im Zusammenhang mit der Lokalisation diskutiert werden. Die Zellen im Darm, in denen immunhistochemisch Sulfotransferasen detektiert wurden, haben mit Ausnahme des Endothels je nach Abschnitt eine Lebensdauer von maximal fünf Tagen und machen keine weiteren Zellteilungen mehr durch. Daher sind DNA-Schäden in diesen Zellen ein sehr geringes Risiko für den Organismus. Soweit die reaktiven Metabolite in diesen Zellen gefangen bleiben, kann die Bioaktivierung in diesen Zellen und die Bildung von Addukten als protektiv betrachten werden, da letztere nach wenigen Tagen mit den toten Zellen in das Darmlumen abgegeben werden. Für den Vergleich der Bioaktiverung von Promutagenen durch die Form 1B1 des Menschen und der Ratte wurden aus V79 Lungenfibroblasten des Chinesischen Hamsters abgeleitete Zellinien hergestellt, die je eine der beiden Formen stabil exprimieren. Damit standen 1B1-profiziente Indikatorzellen für den HPRT-Genmutationstest zur Verfügung, und die 1B1-abhängige Bioaktivierung konnte in einem System untersucht werden, die dem eukaryontischen Organismus näher steht als die für die Ames-Tests verwendeten Bakterien. So war z.B. die Sulfotransferase wie im Gewebe im Zytoplasma lokalisiert. Als Modellsubstanzen wurden hierbei die bereits in TA1538-h1B1 mutagen wirkenden benzylischen Alkohole 6-Hydroxymethylbenzo[a]pyren und 4-Hydroxycyclopenta-[def]chrysen getestet. Da die Sensitivität einer Sulfotransferase-exprimierenden V79-Zellinie sowohl durch die Menge an Sulfotransferase als auch durch die Verfügbarkeit des Sulfodonors limitiert sein könnte, wurden die Mutagenitätsexperimente mit V79-r1B1-Zellinien durchgeführt, die sich in ihrer Enzymaktivität um das Zwanzigfache unterschieden: V79-r1B1/A und -/B. Eine starke Erhöhung der Mutantenfrequenz wurde nur in der hoch exprimierenden Zellinie V79-r1B1/A (1019 ± 224 pmol/mg/min) beobachtet, so daß eine gravierende Beeinträchtigung der Sensitivität durch einen Mangel an Kosubstrat ausgeschlossen wurde. In der niedriger exprimierenden Zellinie V79-r1B1/B (57 ± 9 pmol/mg/min) war nur mit 6-Hydroxymethylbenzo[a]pyren ein schwacher Anstieg der Mutantenfrequenz zu erkennen, der mit 0,3 µM bei einer in etwa 100fach höheren Konzentration begann als bei V79-r1B1/A. Die zytosolische Fraktion aus V79-r1B1/B-Zellen enthielt in etwa die dreifache Menge an r1B1-Protein wie die aus Colonmucosa der Ratte. Da zumindest für die humane Mukosa gezeigt wurde, daß die 1B1 nur im einschichtigen Epithel, nicht aber in allen Zellen der Mukosa exprimiert wird, repräsentiert die zytosolische Fraktion aus der Mukosa nur bedingt die Expression in den Epithelzellen und der Vergleich mit den V79-1B1-Zellen ist grob. Im Gegensatz zu V79-r1B1/B war die Zellinie V79-h1B1, die ebenfalls nur mit Darm und Leber vergleichbare Mengen an h1B1 exprimierte, in der Lage, beide benzylischen Alkohole zu aktivieren. Der Erhöhung der Mutantenfrequenz im Vergleich zur KontrollZellinie war ähnlich wie bei der stark exprimierenden Zellinie V79-r1B1/A, erforderte aber 10fach höhere Konzentrationen. Somit unterscheiden sich Mensch und Ratte nicht nur insgesamt in ihrer Ausstattung des Gastrointestinaltrakts mit Sulfotransferasen, auch bei Betrachtung einer einzelnen Form zeigten sich deutliche Unterschiede in der Aktivierung von zwei Promutagenen. Die Ratte ist daher ein ungeeignetes Modell, um die Rolle von Sulfotransferasen bei tumorinitiierenden Prozessen im Darm zu untersuchen. Dies unterstreicht die Bedeutung von rekombinanten in-vitro-Systemen für die Erfassung des humanen Metabolismus von Fremdstoffen. Insgesamt kennt man nur eine geringe Anzahl von Substanzen, die im Tierexperiment Colontumore erzeugen, und mit Ausnahme der heterozyklischen aromatischen Amine sind diese lediglich von experimenteller Bedeutung. Dies spricht für effiziente Schutzmechanismen der Darmmukosa gegenüber Mutagenen und läßt die Frage nach der hohen Inzidenz des Kolorektalkarzinoms offen.
With the new government, coming to power in 1998, a new emphasis on development cooperation as part of a global strategy for structural change was launched. Since then the federal minister for development cooperation – Heidemarie Wieczorek- Zeul – presented some interesting strategic papers under the label "aid as a global policy to overcome structural blockades to social progress and development". Special emphasis was put on the Program of Action for Poverty Reduction and on the strategy paper of a new Africa policy, but neither are concrete results yet in sight nor is an answer to the burning question of what to do with half of all African countries not having a long-term perspective for development at all (the "failing states" etc.). The article shows the great discrepancy between the impressive political rhetoric and the meager budget to cope with the many challenges of the poor developing countries in Africa. The new concept of the enlarged security intends to stabilize the structural conditions for social and economic development. In order to realize this aim, the article proposes a link between public expenditures on military measures for security and such on civil measures for structural security. Finally the article asks how development cooperation can influence the political attitudes of state and society in Africa in the direction of good governance and structural reforms.
Einleitung
(2001)
Christoph Heins Lektüren
(2001)
"Copernican" is the term the author is calling the turn in present Islamism. After a mostly failed fundamentalist reaction to a high-speed westernisation, there are current debates among Islamists to find an own identity - based on Islam and connected with Western values. Aim of these efforts is to link Islam with the contemporary realities in the Arabian world.