Identifikation und Beeinflussbarkeit supramolekularer Wechselwirkungen auf Quarzmikrowaagen

Die vorliegende Arbeit befasste sich mit der kompletten Bandbreite eines chemischen Sensors.rnIn einem ersten Schritt wurde die Desensibilisierung der Quarzmikrowaagen (QCM) gegenüber Störeinflüssen untersucht. Ausgehend von vorangegangenen Arbeiten konnte gezeigt werden, dass eine fluorige Modifikation der QCM-Elektroden die Affinität zu omnipräsenten Substanzen wie Wasser oder Alkanen stark herabsetzt. Neben der Desensibilisierung bewirkt die Schicht darüber hinaus vermutlich eine veränderte Ausrichtung der Affinitätsmaterialien auf der Oberfläche. Dies konnte durch die Anwendung auf einen TATP-Sensorsystem gezeigt werden.rnIm zweiten Teil der Arbeit wurden die vorherrschenden Arten supramolekularer Wechselwirkungen in Wirt-Gast-Systemen anhand gravimetrischer Messungen identifiziert. In Kooperation mit unterschiedlichen Forschergruppen konnte nachgewiesen werden, dass es möglich ist, diese Wechselwirkungen in einem gewissen Rahmen zu beeinflussen und damit die Sensorantworten zu steuern. Effekte wie die Hohlraumzugänglichkeit, die Hohlraumgröße sowie das chemische Milieu im Hohlraum wurden genauer untersucht.rnNeben dem Screening auf neue Affinitätsmaterialien konnten erste Erfolge bei der Übertragung der Erkenntnisse der letzten Jahre auf ein neues Sensorsystem erzielt werden. Zum Einsatz kam hierbei ein optisches Sensor-System basierend auf planaren Bragg-Gittern. Neben der Entwicklung einer geeigneten Messzelle wurde eine Beschichtung der Sensoren mit verschiedenen Cyclodextrin-Derivaten entwickelt.rnIm vierten Teil der Arbeit wurden Studien zur Synthese zweier Tetraphenylenderivate durchgeführt.rn

Maternal modulation of natal dispersal in a passerine bird: An adaptive strategy to cope with parasitism?

The decision of how far to disperse from the natal territory has profound and long-lasting consequences for young animals, yet the optimal dispersal behavior often depends on environmental factors that are difficult or impossible to assess by inexperienced juveniles. Natural selection thus favors mechanisms that allow the adaptive and flexible adjustment of the offspring's dispersal behavior by their parents via either paternal or maternal effects. Here we show that different dispersal strategies maximize the reproductive success of young great tits (Parus major) originating from a parasite-infested or a parasite-free nest and demonstrate that differential transfer of maternal yolk androgens in response to parasitism can result in a modification of the offspring's dispersal behavior that appears adaptive. It demonstrates that prenatal maternal effects are an important yet so far neglected determinant of natal dispersal and highlights the potential importance of maternal effects in mediating coevolutionary processes in host-parasite systems.

The Immune System of Spiders

Spiders, as all other arthropods, have an open circulatory system, and their body fluid, the hemolymph, freely moves between lymphatic vessels and the body cavities (see Wirkner and Huckstorf 2013). The hemolymph can be considered as a multifunctional organ, central for locomotion (Kropf 2013), respiration (Burmester 2013) and nutrition, and it amounts to approximately 20 % of a spider’s body weight. Any injury includes not only immediate hemolymph loss but also pathogen attacks and subsequent infections. Therefore spiders have to react to injuries in a combined manner to stop fluid loss and to defend against microbial invaders. This is achieved by an innate immune system which involves several host defence systems such as hemolymph coagulation and the production of a variety of defensive substances (Fukuzawa et al.2008). In spiders, the immune system is localised in hemocytes which are derived from the myocardium cells of the heart wall where they are produced as prohemocytes and from where they are released as different cell types into the hemolymph (Seitz 1972). They contribute to the defence against pathogens by phagocytosis, nodulation and encapsulation of invaders. The humoral response includes mechanisms which induce melanin production to destroy pathogens, a clotting cascade to stop hemolymph loss and the constitutive production of several types of antimicrobial peptides, which are stored in hemocyte granules and released into the hemolymph (Fukuzawa et al.2008) (Fig.7.1). The immune system of spiders is an innate immune system. It is hemolymph-based and characterised by a broad but not very particular specificity. Its advantage is a fast response within minutes to a few hours. This is in contrast to the adaptive immune system of vertebrates which can react to very specific pathogens, thus resulting in much more specific responses. Moreover, it creates an immunological memory during the lifetime of the species. The disadvantage is that it needs more time to react with antibody production, usually many hours to a few days, and needs to be built up during early ontogenesis.

Variaciones numéricas de Diaphorina citri Kuwayama (Sternorrhyncha: Psyllidae) y del Ectoparasitoide Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) en una plantación de naranjos de Entre Ríos, Argentina

Diaphorina citri es vector de la bacteria que produce la enfermedad HLB en cítricos, una de las más destructivas. En lotes comerciales de naranja dulce en Entre Ríos se analizó la abundancia espacio-temporal de adultos de D. citri y del ectoparasitoide Tamarixia radiata. Quincenalmente y durante tres años se colectaron adultos en 10 trampas cromotrópicas y los datos obtenidos fueron relacionados con el porcentaje medio de brotación de otra plantación. El número de D. citri/trampa/quincena se analizó mediante Kruskal-wallis y prueba de Mantel y la respuesta de agregación de T. radiata mediante correlación. Ambas poblaciones exhibieron la mayor abundancia el primer año: las frecuentes aplicaciones de abamectina en el segundo y tercero provocaron una marcada reducción. Espacialmente, la diferencia numérica de D. citri entre árboles no estuvo asociada a su cercanía pero la correlación entre ellos fue significativa. Temporalmente se evidenciaron cuatro picos de abundancia: tres asociados a brotación (invernal, primaveral y estival), y un cuarto no asociado a brotación. La mayor abundancia de T. radiata ocurrió en los árboles con mayor abundancia de D. citri y hubo una significativa correlación espacial entre ambas especies. El enrollamiento anti-horario del gráfico entre D. citri - T. radiata en árboles individuales sugiere una interacción huésped- parasitoide, estructurada como poblaciones locales.

Effect of Biodiversity Changes in Disease Risk: Exploring Disease Emergence in a Plant-Virus System

The effect of biodiversity on the ability of parasites to infect their host and cause disease (i.e. disease risk) is a major question in pathology, which is central to understand the emergence of infectious diseases, and to develop strategies for their management. Two hypotheses, which can be considered as extremes of a continuum, relate biodiversity to disease risk: One states that biodiversity is positively correlated with disease risk (Amplification Effect), and the second predicts a negative correlation between biodiversity and disease risk (Dilution Effect). Which of them applies better to different host-parasite systems is still a source of debate, due to limited experimental or empirical data. This is especially the case for viral diseases of plants. To address this subject, we have monitored for three years the prevalence of several viruses, and virus-associated symptoms, in populations of wild pepper (chiltepin) under different levels of human management. For each population, we also measured the habitat species diversity, host plant genetic diversity and host plant density. Results indicate that disease and infection risk increased with the level of human management, which was associated with decreased species diversity and host genetic diversity, and with increased host plant density. Importantly, species diversity of the habitat was the primary predictor of disease risk for wild chiltepin populations. This changed in managed populations where host genetic diversity was the primary predictor. Host density was generally a poorer predictor of disease and infection risk. These results support the dilution effect hypothesis, and underline the relevance of different ecological factors in determining disease/infection risk in host plant populations under different levels of anthropic influence. These results are relevant for managing plant diseases and for establishing conservation policies for endangered plant species.

Posttranscriptional Gene Silencing in Transgenic Sugarcane. Dissection of Homology-Dependent Virus Resistance in a Monocot That Has a Complex Polyploid Genome1

RNA-mediated, posttranscriptional gene silencing has been determined as the molecular mechanism underlying transgenic virus resistance in many plant virus-dicot host plant systems. In this paper we show that transgenic virus resistance in sugarcane (Saccharum spp. hybrid) is based on posttranscriptional gene silencing. The resistance is derived from an untranslatable form of the sorghum mosaic potyvirus strain SCH coat protein (CP) gene. Transgenic sugarcane plants challenged with sorghum mosaic potyvirus strain SCH had phenotypes that ranged from fully susceptible to completely resistant, and a recovery phenotype was also observed. Clones derived from the same transformation event or obtained after vegetative propagation could display different levels of virus resistance, suggesting the involvement of a quantitative component in the resistance response. Most resistant plants displayed low or undetectable steady-state CP transgene mRNA levels, although nuclear transcription rates were high. Increased DNA methylation was observed in the transcribed region of the CP transgenes in most of these plants. Collectively, these characteristics indicate that an RNA-mediated, homology-dependent mechanism is at the base of the virus resistance. This work extends posttranscriptional gene silencing and homology-dependent virus resistance, so far observed only in dicots, to an agronomically important, polyploid monocot.

Long-circulating bacteriophage as antibacterial agents.

The increased prevalence of multidrug-resistant bacterial pathogens motivated us to attempt to enhance the therapeutic efficacy of bacteriophages. The therapeutic application of phages as antibacterial agents was impeded by several factors: (i) the failure to recognize the relatively narrow host range of phages; (ii) the presence of toxins in crude phage lysates; and (iii) a lack of appreciation for the capacity of mammalian host defense systems, particularly the organs of the reticuloendothelial system, to remove phage particles from the circulatory system. In our studies involving bacteremic mice, the problem of the narrow host range of phage was dealt with by using selected bacterial strains and virulent phage specific for them. Toxin levels were diminished by purifying phage preparations. To reduce phage elimination by the host defense system, we developed a serial-passage technique in mice to select for phage mutants able to remain in the circulatory system for longer periods of time. By this approach we isolated long-circulating mutants of Escherichia coli phage lambda and of Salmonella typhimurium phage P22. We demonstrated that the long-circulating lambda mutants also have greater capability as antibacterial agents than the corresponding parental strain in animals infected with lethal doses of bacteria. Comparison of the parental and mutant lambda capsid proteins revealed that the relevant mutation altered the major phage head protein E. The use of toxin-free, bacteria-specific phage strains, combined with the serial-passage technique, may provide insights for developing phage into therapeutically effective antibacterial agents.

Magnetism and photophysics in supramolecular transition-metal compounds

Based on a synthetic strategy, extended anionic, homo and bimetallic oxalato-bridged transition-metal compounds with two (2D) and three-dimensional (3D) connectivities can be synthesized and crystallized. Thereby, the choice of the templating counterions will determine the crystal chemistry. Since the oxalato bridge is a mediator for both antiferro and ferromagnetic interactions between similar and dissimilar metal ions, long-range magnetic ordering will occur. Examples of the determination of magnetic structures in 2D and 3D compounds by means of elastic neutron scattering methods will be discussed. In addition, due to the possibility of the variation of different metal ions in varying oxidation states, interesting photophysical processes can be observed within the extended three-dimensional host/guest systems.

Crystal Structures, Magnetic Structures and Photophysics in Supramolecular Transition-Metal Oxalate Compounds

Polymeric two- and three-dimensional, homo- and heterometallic oxalatebridged coordination compounds offer exciting opportunities, mainly in the fields of molecular magnetism and photophysics. Given that a large variety of magnetic phenomena have been reported so far from these molecular magnets, very limited experience is gained from elastic neutron scattering experiments. Therefore, with two examples, we will address the topic of the elucidation of magnetic structures by means of the neutron scattering technique. In addition, due to the possibility of the variation of different metal ions in varying oxidation states, interesting photophysical processes can be observed within the extended three-dimensional host/guest systems.

Living on the edge: parasite taxonomy in Australia

The way in which the huge Australian parasite fauna is described (discovery and naming) is the subject of this address. The approach to the task has never been well-organised so that a few groups of parasites are now relatively well-known because of the efforts of small groups of workers who have made sustained efforts in these groups, but equally some host-parasite systems have been almost completely ignored in that no worker has ever given them sustained attention. A high proportion of Australian parasites have been described by international workers; The sustaining of interest in a group of parasites over a long period is the key to real progress being made. The nature of the organisation of Australian science presently means that few positions are available for parasite taxonomists and funding for taxonomic research is scarce. Thus, parasite taxonomy (like the taxonomy of many groups of Australian plants and animals) can only be considered to be in crisis. (C) 2003 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

Presence of a novel small RNA-containing virus in a laboratory culture of the endoparasitic wasp Venturia canescens (Hymenoptera : Ichneumonidae)

Parasitoid wasps use a variety of mechanisms to alter their host's physiology to the benefit of the developing endoparasite inside the host larva. Association of certain wasps with viruses and virus-like particles (VLPs) that contribute to their success in parasitism is one of the fascinating evolutionary adaptations conferring active or passive protection for the endoparasite from the host immune system. Venturia canescens has been shown to produce VLPs that provide protection for the developing parasitoid egg inside the host, Ephestia kuehniella. Here, we report on the presence of a novel small RNA-containing virus from V. canescens, designated as VcSRV, occurring in the ovaries of the wasp. The virus particles are found together with VcVLPs in the lumen of the calyx region of the ovaries and are injected together with the egg and VcVLPs into E kuehniella larvae where they enter hemocytes. Alignment of the RNA-dependent RNA polymerase gene of VcSRV indicates that the virus most likely belongs to the recently described genus Iflavirus. (c) 2004 Elsevier Ltd. All rights reserved.

Proteins in the saliva of the Ixodida (ticks): Pharmacological features and biological significance

The saliva of ticks (Suborder Ixodida) is critical to their survival as parasites. A tick bite should result in strong responses from the host defence systems (haemostatic, immune and inflammatory) but tick saliva appears to have evolved to counter these responses. We review current knowledge of tick saliva components, with emphasis on those molecules confirmed to be present in the secreted saliva but including some that have only been confirmed to be present in salivary glands. About 50 tick saliva proteins that are well described in the literature are discussed. These saliva components include enzymes, enzyme inhibitors, amine-binding proteins and cytokine homologues that act as anti-haemostatic, anti-inflammatory or immuno-modulatory agents. Sequence comparisons are illustrated. The importance of tick saliva and the significance of the findings to date are also discussed. (C) 2006 Elsevier Ltd. All rights reserved.

Estudos bioecológicos da mosca mineira Liriomyza (diptera: agromyzidae) e dos seus parasitóides, em culturas protegidas, no Algarve

Tese de dout. em Ciências Agrárias, especialidade Protecção de Plantas, Faculdade de Engenharia e Recursos Naturais, Univ. do Algarve, 2001

Host preference and host suitability in an egg-pupal fruit fly parasitoid, Fopius arisanus (Sonan) (Hym., Braconidae)

The relative oviposition rate of the parasitoid Fopius arisanus (Sonan) was investigated across three frugivorous tephritid species, Bactrocera tryoni Froggart, Bactrocera jarvisi (Tryon) and Bactrocera cucumis French. Choice and no-choice tests were both used. The suitability of these three species for sustaining larval development and survival to the adult stage was also assessed. Fopius arisanus parasitized all three tephritid species. regardless of the method of exposure, but showed stronger preference for B. tryoni and B. jarvisi over B. cucumis. Superparasitism was extremely rare. Successful development of F. arisanus varied across host species. Bactrocera tryoni yielded significantly more parasitoids than B. jarvisi, but no wasps emerged from B. cucumis puparia. Tests were set up in replicated trials. but results were not homogeneous across trials. We discuss the host relationships of F. arisanus with reference to this variation and in relation to host suitability for larval development.

Hymenoepimecis neotropica (Brues & Richardson) (Hymenoptera, Ichneumonidae, Pimplinae) parasitoid of Araneus omnicolor (Keyserling) (Araneae, Araneidae): first host record and new occurrence to Brazil

Hymenoepimecis neotropica (Brues & Richardson) (Hymenoptera, Ichneumonidae, Pimplinae) parasitoid of Araneus omnicolor (Keyserling) (Araneae, Araneidae): first host record and new occurrence to Brazil. The species of the genus Hymenoepimecis occur only in Neotropical region, being recognized for using as their hosts spiders which build orbicular webs. That wasp was described occurring only in the Guyana. This work expands the geographical distribution of the species to Brazil and records the spider Araneus omnicolor (Araneae, Araneidae) as its host. Furthermore, it provides information about the natural history of this interaction.