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1
Danielsson, Marie. „Chemical defence in Norway spruce“. Doctoral thesis, KTH, Organisk kemi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-31133.
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Norway spruce (Picea abies) responds to stress by biosynthesis of chemical substances, which can deter invading insects or pathogens. Some of these substances are volatile and can be emitted to the surroundings while others are accumulated within the tree. Information about the susceptibility of individual plants to infestation, their volatile emissions and chemical defence is of interest, for example, in selecting plants for tree breeding programs. The first part of this research focused on volatiles emitted by Norway spruce plants. Collection of headspace volatiles by SPME and subsequent separation and identification with GC-MS was used to investigate Norway spruce plants of different ages and stress conditions as well as trapping semiochemicals like nepetalactone emitted by the spruce shoot aphids. It was even possible to analyse the emission of single needles in vivo and obtain spatial localisation of the stress reaction to methyl jasmonate or spruce spinning mites. Seedlings of different ages showed differences in chemical composition of emitted volatiles, with the pine weevil repellent, (4S)-(-)-limonene, one of the main compounds. Wounded phloem of conventional plants emitted high amounts of monoterpenes while the phloem of mini plants emitted (3Z)-hexenal and (3Z)-hexen-1-ol. In addition, a method to separate and identify the four diastereomers of nepetalactone by GC-MS and characteristic m/z-fragments was accomplished. The second part of the research deals with the chemical response of Norway spruce roots to inoculation with Heterobasidion annosum. Terpene concentrations increased after inoculation or wounding but the composition was mainly associated with clone identity and not to susceptibility or treatment. In contrast, inoculation with H. annosum induced a treatment-specific alteration of phenol composition. The constitutive phenol composition differed between more and less susceptible clones. The phenols astringin and astringin dimers (piceasides) as well as the terpene α-longipinene may be suitable markers of low susceptibility for P. abies to Heterobasidion.QC 20110314
2
Hsieh, Ji-Fan (Sarah). „Molecular and Chemical Mechanisms of Defence against Myrtle Rust in Australian Myrtaceae“. Phd thesis, Canberra, ACT : The Australian National University, 2018. http://hdl.handle.net/1885/143530.
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Increased human disturbance to forest ecosystems has exacerbated
the spread of fungal pathogens to non-native environments. Rust
pathogens (Pucciniales) can spread long distances by human
activity and wind dispersal, and can cause severe disease
outbreaks in cereal crops and in forest trees. The exotic fungus
Austropuccinia psidii (myrtle rust) arrived in Australia in 2010
and most species of native Myrtaceae including Eucalyptus and
Melaleuca are susceptible to infection to various degrees. Plants
infected by A. psidii can suffer from crown loss and eventual
mortality, which can be detrimental to ecosystems as well as to
many rural industries that produce essential oils and flavourings
from species of Myrtaceae. Within-species variation in resistance
to A. psidii has been discovered in many native species. However,
the molecular and chemical mechanisms of resistance to A. psidii
infection in these species are largely unknown. Finding the
molecular and chemical basis of resistance against A. psidii is
therefore an essential part of ensuring that future plantations
and re-afforestation programs are resistant to this pathogen.
This thesis therefore aims to elucidate the molecular and
chemical mechanisms of resistance to A. psidii in Myrtaceae in
Australia, with the goal of obtaining a comprehensive view of
potential mechanisms involved in defence to identify candidate
genes that may be implemented into resistance breeding. After
first screening multiple species of Myrtaceae, I selected
Melaleuca alternifolia (tea tree) and M. quinquenervia (broadleaf
paperbark) for detailed molecular study because they showed
varying disease symptoms from resistance to susceptibility among
individuals, and were economically and ecologically important and
amenable to molecular studies. I used a variety of experimental
approaches, including RNA-Seq, qRT-PCR, GC-MS, and functional
characterisation through heterologous gene expression in E. coli
to apply an integrated analysis that examined both molecular and
chemical aspects of plant defence. I constructed the
transcriptomes of M. alternifolia and M. quinquenervia de novo
and investigated differential gene expressions between resistant
and susceptible plants. I showed that resistant M. alternifolia
and M. quinquenervia over-express genes which may be contribute
to defence against to A. psidii infection, and have found and
functionally characterised new terpene synthase genes that showed
induction in response to infection by A. psidii in M.
quinquenervia.
3
Knapp, Jennifer J. „Chemical aspects of communication and defence in leaf-cutting ants“. Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295675.
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4
Law-Brown, Janette. „Chemical defence in the red-billed wood hoopoe : phoeniculus purpureus“. Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/6119.
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Red-billed Woodhoopoes, Phoeniculus purpureus, produce a pungent smelling secretion from their uropygial gland. Previous researchers have noted this odour and there has been much speculation on its function. This encouraged me to undertake this study to determine the origin of the odour and the role that the secretion plays. The chemical analysis of this secretion shows that it consists of 17 compounds including acids, aldehydes, lactones and other miscellaneous compounds. Cultures of the secretion showed the presence of a symbiotic bacterium resident within the gland. Antibiotic treatment of the gland suggested that this bacterium was instrumental in the synthesis of the secretion of P. purpureus. This bacterium has not previously been identified and has been proposed as 'Enterococcus phoeniculicola' (GenBank accession number: AYO28437). The secretion was synthesized and the responses of a range of 13 pathogenic and one parasitic bacteria were tested against it and its individual constituent compounds. The synthetic secretion and seven of its constituent compounds inhibited the growth of these bacteria. However, exposing feather mites resident upon the birds to the synthetic secretion did not illicit any significant response from these mites. Wanless (1998) showed that the synthetic secretion causes an averse reaction in cats. In this study I was able to identify indole, phenol and propionaldehyde as being responsible for eliciting this reaction in cats. A similar averse reaction is shown by Rock Monitor Lizards, Varanus albigularis, upon encountering mice tainted with the synthetic secretion. This is the first demonstration of a symbiotic relationship between birds and bacteria in which the modification of the birds' uropygial oils affords the birds some protection against pathogens and preators.
5
Thornton, Robert. „The effect of the aircrew chemical defence assembly on thermal strain“. Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/27005.
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6
Paul, Nicholas Andrew School of Biological Earth & Environmental Sciences UNSW. „The ecology of chemical defence in a filamentous marine red alga“. Awarded by:University of New South Wales. School of Biological, Earth and Environmental Sciences, 2006. http://handle.unsw.edu.au/1959.4/24304.
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I investigated the ecological functions of halogenated secondary metabolites from the red alga Asparagopsis armata, their localisation in specialised cells and also their cost of production. A. armata produces large amounts of halogenated metabolites ( < 20 ??g / mg dry weight) that are sequestered in gland cells, as was demonstrated with light, epifluorescence and transmission electron microscopy. Cellular structures were identified that likely assist the release of metabolites from the gland cells to the algal surface. The halogenated metabolites of A. armata have multiple ecological roles, functioning as both inhibitors of bacterial fouling and as herbivore deterrents. Their activity against bacteria and herbivores was measured by a novel test in which the metabolites were manipulated in A. armata by omitting bromide ions from the culture media. This technique prevented the production of halogenated metabolites, but did not impact on other aspects of algal biology. Algae lacking halogenated metabolites (bromide [-] algae) had higher densities of epiphytic bacteria than those that continued to produce metabolites (bromide [+] algae). Bioassays with pure compounds against individual bacterial isolates further supported an inhibitory role for the halogenated metabolites against epiphytic bacteria, and also indicated an affect on bacterial community structure as well as abundance. Bromide (+) A. armata produced halogenated metabolites that also deterred feeding by two herbivores (an amphipod and an abalone), but not a third (an opisthobranch mollusc). A novel outcome from these feeding assays was the demonstration of a relationship between herbivore size and consumption of the chemically defended A. armata by the abalone Haliotis rubra. In addition to the fitness benefits gained from chemical defence, there were also costs for allocating resources to secondary metabolites. These costs were only detected under limiting light resources, consistent with predictions of the plant defence models. The integration of chemical analyses and cellular measures of chemical defence proved essential in elucidating resource allocation to chemical defence in the filamentous stage of A. armata. This thesis highlights that the simple relationships between growth and defence in filamentous algae can provide an excellent model for studies of the ecology and evolution of chemical defences in marine algae.
7
Ohlsson, Åse. „Do plants change their defence strategy from a structural defence to a chemical one as a response to heavier herbivory?“ Thesis, Södertörn University College, School of Life Sciences, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-310.
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To the main part, this paper is the result of a literature survey and to the minor part of a field survey. The study is found on the question of, if and why unpalatable plant species invade heavily grassed rangelands and if plants change their defence strategy from a mechanical defence to a chemical defence if the herbivory pressure increase. I conclude that defended plants do invade heavily grassed rangelands if the rangelands lose essential recourses (often nutrients) and/or the defended plants are strongly avoided by mammalian herbivores. I also conclude that plants do go from a mechanical defence strategy to a chemical strategy if their environment loses essential recourses under a threshold. This firstly depends on that mechanical defended plants can not develop a complete defence if they suffer from a shortage in the nutrient supply, and secondly of that plants in resources rich environments often have lager possibilities of responding to herbivory with regrowth. They do not therefore have to defend them self as hard as plants in environments with low supply of recourses.
8
Foster, Rosie. „Plants signalling to herbivores : is there a link between chemical defence and visual cues?“ Thesis, University of Sussex, 2013. http://sro.sussex.ac.uk/id/eprint/45168/.
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The use of visual cues by insect herbivores is likely to be an important component of plant-herbivore interactions in the wild, yet has until recently received little attention from researchers. In the last decade, however, interest in this topic has intensified following Hamilton & Brown's (2001) autumn colouration hypothesis, which proposes that the intensity of colouration of trees at autumn time is a signal of their defensive commitment to potential herbivores. This idea remains controversial and to date robust empirical data linking colouration with chemical defence and herbivory have been lacking. This thesis begins with a meta-analysis, in which I synthesize and analyse previously published data to determine the evidence for the use of host plant colouration by herbivores. I then move to explore the relationship between chemical defences and colouration in a classic plant-herbivore system: the wild cabbage (Brassica oleracea) and its herbivores the cabbage white butterfly (Pieris rapae) and the cabbage aphid (Brevicoryne brassicae). Both species have colour vision, and I use spectral sensitivity data to model the colour of the host ‘through the eyes' of the herbivores. First, I present data from a field study of wild cabbage populations showing significant relationships between herbivory, plant colouration and levels of glucosinolates defensive compounds. These results suggest that plant colouration could be used by herbivores to gain information about plant chemical defence. I then show colouration has a fixed genetic component in a common garden experiment; a necessary requirement for evolution of a colour signal. I explore the use of colouration in host choice by herbivores in more detail in a series of behavioural experiments. I show that cabbage aphids do not use leaf brightness as a cue when selecting among plants, but they do respond to different leaf colours. I also show that cabbage white butterflies do not choose hosts based on particular colour cues, even though this colouration potentially provides important information about host defence levels, which are shown to impact upon offspring fitness. Together, these results provide a clear demonstration of a link between plant chemistry and colouration in the wild cabbage system. However, the data presented in this thesis indicate that the use of colouration as a guide to host defence is limited, and I conclude by discussing possible reasons why this might be the case.
9
Hedner, Erik. „Bioactive Compounds in the Chemical Defence of Marine Sponges : Structure-Activity Relationships and Pharmacological Targets“. Doctoral thesis, Uppsala University, Division of Pharmacognosy, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8218.
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Marine invertebrates, in particular sponges, represent a source of a wide range of secondary metabolites, many of which have been attributed various defensive capabilities against environmental stress factors. In this thesis sponge-derived low-molecular peptide-like compounds and associated analogs are investigated for bioactivity and pharmacological targets.
The compound bromobenzisoxazolone barettin (cyclo[(6-bromo-8-(6-bromo-benzioxazol -3(1H)-one)-8-hydroxy)tryptophan)]arginine) was isolated from the sponge Geodia barretti and its ability to inhibit larval settlement of the barnacle Balanus improvisus was determined. With an EC50 value of 15 nM, this compound’s antifouling effect was higher than those of the previously reported brominated dipeptides from Geodia barretti, i.e., barettin and 8,9-dihydrobarettin; moreover, this antifouling effect was demonstrated to be reversible. However, the compound lacked affinity for 5-HT1-7 receptors, whereas barettin possessed specific affinity to 5-HT2A, 5-HT2C and 5-HT4, while 8,9-dihydrobarettin interacted with 5-HT4. In an attempt to evaluate structure-activity relationships synthesized analogs with barettin and dipodazine scaffolds were investigated for antifouling activity. The analog benso[g]dipodazine, with an EC50 value of 34 nM, displayed the highest settlement inhibition.
The studies of the structure-activity relationships of sponge-derived compounds were extended to cover analogs of agelasines and agelasimines originally isolated from sponges of the genus Agelas. Synthesized (+)-agelasine D and two structurally close analogs were investigated for cytotoxic and antibacterial activity. The profound cytotoxicity and broad spectrum antibacterial activity found prompted a further investigation of structure-activity relationships in 42 agelasine and agelasimine analogs and several characteristics that increased bioactivity were identified.
In conclusion this work has produced new results regarding the potent bioactivity of compounds derived from the sponges Geodia barretti and Agelas spp. and increased SAR knowledge of the fouling inhibition, cytotoxicity and antimicrobial activity of these compounds.
10
Pöykkö, H. (Heikki). „Host range of lichenivorous moths with special reference to nutritional quality and chemical defence in lichens“. Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:951427959X.
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Abstract
Host use and range of herbivorous insects are determined by several factors, of which nutritional quality and secondary chemistry have been shown to play very important roles. For herbivores feeding on lichens these traits are assumed to be more critical than for species feeding on higher plants, since lichens are nutritionally poor and often contain high concentrations of secondary metabolites. I examined the role of lichens' nutritional quality and secondary chemicals on the performance of lichen-feeding Lepidopteran larvae. I also tested whether females of lichenivorous species preferably oviposit on host species of the highest nutritional quality for the growth of larvae.
Larvae of Eilema depressum performed best on Melanelia exasperata, which is of the highest nutritional quality, as indicated by the high N concentration and the absence of lichen secondary metabolites compared to the other lichens studied. Host nutritional quality did not promote the production of an additional generation. Larvae of E. depressum needed fewer instars and grew bigger on a high-quality diet than larvae reared on a diet of poorer quality. However, the main factor contributing to the wide variation in the number of larval instars was the question of whether or not larvae overwintered. Growth of Cleorodes lichenaria at the beginning of the larval period matched equally the nutritional quality of the hosts. However, the final larval period was shortest on Ramalina species, which was preferred by both females ovipositing their eggs and larvae searching for a host. In the field, larvae were found almost exclusively on Ramalina species.
Larvae of E. depressum were not able to survive on intact thalli of Vulpicida pinastri and Hypogymnia physodes, but after removal of lichen's secondary metabolites, larval survival remained equally high as on other lichens. Larvae also showed a clear preference towards thalli with lowered concentrations of secondary metabolites in Parmelia sulcata, V. pinastri and H. physodes. Parietin in Xanthoria parietina was the only secondary metabolite that had no impact on the survival or host selection of E. depressum larvae.
The present results show that the nutritional quality and some lichen secondary chemicals are important factors for the growth, survival and host selection of lichen-feeding Lepidopteran larvae. The preference-performance hypothesis is at least partly able to explain the host range of C. lichenaria, although it seems that there are also other factors, such as larval dispersal and host selection or top-down forces, that might contribute to host range of lichenivorous Lepidopteran larvae. Moreover, lichenivorous larvae seem to be partly responsible for their own host selection.
11
Hochschorner, Elisabeth. „Assessment of tools for environmentally preferable procurement with a life cycle perspective : the case of acquisition in Swedish defence“. Licentiate thesis, Stockholm, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-331.
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12
A, Abdul Malik Shareen. „Defence on surface of Rhodophyta Halymenia floresii : metabolomic profile and interactions with its surface-associated bacteria“. Electronic Thesis or Diss., Lorient, 2020. http://www.theses.fr/2020LORIS598.
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Halymenia floresii, une Rhodophycée présente une surface remarquablement exempte d'épiphytes dans les conditions de l'Aquaculture MultiTrophique Intégrée (AMTI). Ce phénomène traduit la présence potentielle en surface de composés actifs allélopathiques. L'objectif de ce travail a été d'explorer les mécanismes de défense développés par H. floresii contre l'épibiose, de détecter et d'identifier les métabolites secondaires produits à la surface de l’algue et d'étudier les relations avec les bactéries épiphytes. Nous avons ainsi pu isoler la communauté épibactérienne de H. floresii cultivée dans des conditions contrôlées (AMTI) et non contrôlées (échantillons collectés in situ). Les épibactéries isolées ont été criblées in vitro pour analyser les signaux de détection de Quorum Sensing (QS). Les extraits produits en surface ont été analysés pour détecter toute interférence avec le Quorum Sensing. Les épibactéries pathogènes et non-pathogènes ont été différenciées par leur capacité à induire une maladie algale, le blanchiment. Vibrio owensii, ainsi que son signal C4-HSL QS, a été identifié comme pathogène opportuniste induisant un blanchiment. Les métabolites extraits de la surface et de cellules entières de H. floresii ont été analysés par LC-MS. Une base de données a été constituée à partir d’une analyse métabolomique non ciblée. Quarante et un métabolites actifs ont été identifiés, parmi lesquels les composés halogénés, des furanones et divers inhibiteurs étaient surreprésentés. Fait intéressant, les deux premières classes sont connues comme de puissants composés interférant avec le QS. La présence relativement élevée de métabolites allélopathiques à la surface de H. floresii soutient fortement l'hypothèse selon laquelle ils doivent être impliqués dans la protection de l'hôte. Des recherches supplémentaires seront nécessaires pour explorer l’ensemble des métabolites secondaires produits par H. floresii et leurs rôles chez l’algueThe surface of Halymenia floresii, a Mexican Rhodophyta, was observed to be remarkably free of epiphytes under Integrated MultiTrophic Aquaculture (IMTA) conditions. This suggests the presence of allelopathic active compounds released by this macroalgae. The aim of this work was to explore the defence mechanisms developed by H. floresii against surface epibiosis, to detect and identify the secondary metabolites produced at the surface of the algae, and to study its relation with surface associated bacteria. For the first time, we isolated the epibacterial community of H. floresii cultivated under controlled conditions (IMTA) and uncontrolled ones (beach-cast material collected in the area). The isolated epibacteria were screened in vitro to analyse Quorum Sensing (QS) signals, and others H. floresii surface extracts were assayed for any QS interference with them. We differentiated the epibacteria significant pathogens from the non- pathogens ones by their ability to induce bleaching, a well-known algal disease. Vibrio owensii was identified as an opportunistic pathogen inducing bleaching in H. floresii which was also associated to the presence of its C4-HSL QS signal. The surface and whole cell metabolites extracts from H. floresii specimens cultivated under controlled conditions were analysed by means of LC/MS. An untargeted metabolomic analysis of H. floresii was performed to provide a global metabolic profile as a first database. We identified ‘41’ active metabolites in H. floresii, among which halogenated compounds, furanones and various inhibitors were overrepresented. Interestingly, the first two classes are well known potent QS interfering compounds. The relatively higher occurrences of allelopathic metabolites at the surface of H. floresii strongly supports the hypothesis that they must be involved in the host protection. Further investigations are needed to explore the secondary metabolites of H. floresii et their role in the seaweed
13
Heckman, Melanie L. „A test of optimal defense theory vs. the growth-differentiation balance hypothesis as predictors of seaweed palatability and defenses“. Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42720.
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Because organisms have limited resources to allocate to multiple life history traits, the Optimal Defense Theory (ODT) and the Growth-Differentiation Balance Hypothesis (GDBH) were developed by terrestrial plant ecologists to predict intraindividual defense allocation based on the cost of defense and these life history trade-offs. However, these theories have garnered equivocal experimental support over the years and are rarely experimentally extended from predictions of plant physiology to the palatability of the tissues an herbivore experiences. We therefore examined tissue palatability, nutritional value, and defense mechanisms in multiple Dictyotalean seaweeds in two Caribbean locations, using two herbivores. Relative palatability of tissues varied greatly with algal species, grazer species, and location. Because older bases were not consistently defended, GDBH did not predict relative palatability. We could not reject ODT without intensive measures of tissue fitness value and herbivore risk, and this theory was therefore not useful in making broad predictions of tissue palatability. In testing the physiological predictions of these theories, we found the young, growing apices of these seaweeds to be generally more nutritionally valuable than the old, anchoring bases and found organic-rich apices to be more chemically deterrent, thus supporting ODT. However, the combined chemical, nutritional, and structural traits of these algae all influenced herbivore choice. As a result, these patterns of apical value and chemical defense reflected palatability of live tissues for only one of five algal species, which rendered ODT and GDBH poor predictors of relative palatability for most algae.
14
Joglekar, Shachi [Verfasser], Jane [Akademischer Betreuer] Parker, Ulf-Ingo [Akademischer Betreuer] Flügge und Renier van der [Akademischer Betreuer] Hoorn. „Dissection of EDS1-dependent and salicylic acid-independent defence signalling pathways in Arabidopsis thaliana: a chemical biology approach / Shachi Joglekar. Gutachter: Jane Parker ; Ulf-Ingo Flügge ; Renier van Der Hoorn“. Köln : Universitäts- und Stadtbibliothek Köln, 2014. http://d-nb.info/1079321594/34.
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15
Parshad, Henrik. „Design of poorly soluble drug salts : pharmaceutical chemical characterization of organic salts /“. [Cph.] : Department of Pharmaceutics, The Danish University of Pharmaceutical Sciences, 2003. http://www.dfh.dk/phd/defences/henrikparshad.htm.
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Rønsted, Nina. „Towards a natural classification of Plantago : chemical and molecular systematics /“. Cph. : Royal Danish School of Pharmacy, Department of Medicinal Chemistry, 2002. http://www.dfh.dk/phd/defences/Nina%20Ronsted.html.
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17
Petersson, Karsten. „Combined formulations based on prodrugs and in situ gelling systems : design and pharmaceutical chemical characterisation /“. [Cph.] : The Danish University of Pharmaceutical Sciences, Department of Pharmaceutics, 2004. http://www.dfh.dk/phd/defences/karstenpetersson.htm.
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18
Freeman, Christopher John. „Are chemical defenses allocated within sponges to defend regions most at risk to predator attack?“ Click here to access thesis, 2007. http://www.georgiasouthern.edu/etd/archive/spring2007/christopher_j_freeman/Freeman_Christopher_J_200701_MS.pdf.
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Thesis (M.S.)--Georgia Southern University, 2007."A thesis submitted to the Graduate Faculty of Georgia Southern University in partial fulfillment of the requirements for the degree Master of Science." Under the direction of Daniel F. Gleason. ETD. Electronic version approved: May 2007. Includes bibliographical references (p. 73-83) and appendices.
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McGinley, Susan. „Chemical Defenses in Herbs and Spices“. College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2007. http://hdl.handle.net/10150/622134.
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20
Skelhorn, John. „Avian chemical perception and the evolution of insect defences“. Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420011.
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21
Lin, Xiaonan. „Chemical and Cellular Defenses against Foreign Pathogens“. Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10354.
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Bacterial and viral infections affect billions of people each year. While bacterial infections are treated by the use of antibiotics, viral infections are eradicated by the immune system. This thesis comprises two parts. Part I presents the reconstitution of enzymes required for the synthesis of the minimal pharmacophore of moenomycin A (MmA), a molecule with antibacterial activity. Part II details single-particle electron microscopy studies of MDA5 alone and in complex with double-stranded RNA (dsRNA). MmA is a natural product antibiotic from Streptomyces ghanaensis that possesses remarkable potency against clinically relevant Gram-positive bacteria. MmA exerts its antibacterial activity by binding directly to peptidoglycan glycosyltransferases, enzymes involved in the synthesis of the glycan strands of peptidoglycan. The genes responsible for MmA biosynthesis have been identified, and a complete biosynthetic pathway has been proposed. Part I of this thesis describes the reconstitution of enzymes required for the synthesis of two trisaccharide scaffolds of MmA that retain antibacterial activity. It also describes the synthesis of unnatural phosphoglycerate lipid acceptors and UDP-amino sugars that can be used to probe the substrate tolerances of key glycosyltransferases in MmA biosynthesis. This work lays the foundation for the synthesis of unnatural MmA analogs that may possess better pharmacokinetic properties than the parent molecule. MDA5 is a helicase that detects viral dsRNA in the cytoplasm of vertebrate cells. Upon dsRNA recognition, MDA5 initiates a series of signal transduction events that activate the innate immune response. Part II of this thesis presents the structures of apo MDA5 protein and the MDA5-dsRNA complex obtained by using single-particle electron microscopy. Two-dimensional averages of apo MDA5 revealed that the protein is very flexible and can adopt multiple conformations. This finding suggests that MDA5 does not adopt an autorepressed conformation in the absence of viral dsRNA. When MDA5 is incubated with dsRNA, the protein assembles onto the dsRNA to form a linear oligomer. Two-dimensional averages and a three-dimensional reconstruction reveal the complex to consist of seven to eight stacked discs per strand of 112 base pair dsRNA. This work lays the foundation for further structural studies aimed at elucidating the mechanism by which MDA5 is activated.Chemistry and Chemical Biology
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Prusak, Anne C. „Activated and constitutive chemical defenses in freshwater plants“. Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131334/unrestricted/prusak%5Fanne%5Fc%5F200405%5Fms.pdf.
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Westley, Chantel Barbara, und chantel westley@flinders edu au. „The distribution, biosynthetic origin and functional significance of Tyrian purple precursors in the Australian muricid Dicathais orbita (Neogastropoda: Muricidae)“. Flinders University. Biological Sciences, 2008. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20090414.153942.
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Information on the biosynthetic origin and functional advantage of marine mollusc natural products is not only essential to our understanding of chemical ecology, but to the development and responsible production of therapeutic agents. As demonstrating in situ activity is methodologically hindered, functions inferred by in vitro activity have been assumed for many secondary metabolites. The anatomical and ontogenetic distribution of natural products can not only provide information on the biosynthesis and storage of metabolites, but identify selective pressures likely to affect survivorship at a specific life stage. Thus, dissection and chemical analysis of distinct tissues, in combination with histochemistry may offer a valuable approach.
Marine gastropods of the Muricidae are renowned for the ancient dye Tyrian purple, which evolves from choline esters of bromoindoxyl sulphate in the hypobranchial gland through a series of enzymatic and photo-oxidative reactions. Prochromogen hydrolysis by arylsulphatase liberates neuromuscular active choline esters and cytotoxic bromoindole precursors, which also occur in muricid egg masses. Although visual accounts of dye pigments in the muricid gonoduct suggest precursors may be incorporated into egg masses from a maternal source, their biosynthetic origin and the evolutionary significance of the hypobranchial gland is unknown. Thus, the Muricidae, and in particular Dicathais orbita upon which most previous research has been focused, is an ideal model for this novel approach to natural product research.
To confirm observations of dye pigments in muricid gonoducts and gain an understanding of their anatomical distribution, a liquid chromatography-mass spectrometry (LC-MS) method was developed to simultaneously quantify pigments, precursors and the prochromogen, tyrindoxyl sulfate. The prochromogen was not only detected in albumen and capsule gland extracts, but bioactive intermediates and the dye 6,6-dibromoindigo were also present in the latter. These findings provided preliminary evidence for the maternal provision of prochromogens in egg masses of D. orbita and identified regions within which to conduct histochemical investigations. Tyrindoxyl sulphate was also detected in male prostate gland extracts, along with the dibromoindigo isomer, 6,6-dibromoindirubin and its oxidative precursor, 6-bromoisatin. This not only implies physiological differences exist between male and female gonoducts, but that these secondary metabolites are not solely intended for egg masses and may hold significance throughout the life cycle.
Histomorphological inspection of the pallial gonoduct-hypobranchial gland complex was conducted over the annual cycle to determine a mechanism for precursor transfer between these structures. Although an anatomical connection was not detected, the secretions of two hypobranchial cell types thought to be involved in Tyrian purple synthesis were of remarkable biochemical similarity to those of various capsule and albumen gland lobes. Together these findings implied the potential for natural product synthesis within the pallial gonoduct of D. orbita.
To establish the role of these glandular lobes in the incorporation of intracapsular fluid and capsule laminae, identical histochemical techniques were applied to transverse capsule wall sections. Biochemical correlations not only provided a simple method of deciphering the complex process of encapsulation in neogastropods, but effectively identified the destination of gonoduct secretions in egg capsules of D. orbita. Comparisons of capsule and gonoduct biochemistry revealed that the intracapsular fluid and inner capsule wall are secreted by the posterior capsule gland lobe, the middle lamina by the lateral lobes and the outer layers by the dorsal lobe, albumen and pedal glands.
Investigation into the location of regulatory enzymes and precursors was conducted to establish the biosynthetic origin of Tyrian purple prochromogens and mechanisms governing bioactive precursor synthesis. Novel histochemical techniques for the localization of bromoperoxidase, the enzyme thought to facilitate prochromogen bromination, and tyrindoxyl sulphate were developed and applied to gonoduct, hypobranchial gland, and encapsulated larvae sections. Standard staining reactions for the indole precursor, tryptophan, and arylsulphatase were also applied. The histochemical approach adopted revealed that tyrindoxyl sulphate is de novo biosynthesized through the post-translational bromination of dietary derived tryptophan. Two biosynthetic sites were identified, one related to hypobranchial secondary metabolism and the second of significance to the presence of bioactive precursors in muricid egg masses.
Tryptophan is stored within secretory cells of the lateral hypobranchial epithelium and once exocytosed, is united with bromoperoxidase from supportive cells to form tyrindoxyl sulphate. Prochromogen synthesis also occurs in the subepithelial vascular sinus for storage and secretion by medial hypobranchial secretory cells. Bioactive precursor synthesis on the epithelial surface is regulated by the liberation of arylsulphatase from adjacent supportive cells. These findings not only provide evidence for de novo biosynthesis of Tyrian purple precursors, but are first account of natural product biosynthesis within the gastropod hypobranchial gland. Together these findings imply a naturally selected function for the synthesis of bioactive indoles in hypobranchial gland secretions of the Muricidae and Gastropoda.
Tyrindoxyl sulphate is also transported within the vascular sinus to lateral and dorsal capsule gland lobes where bromoperoxidase and arylsulphatase also occur. Arylsulphatase was also detected within the albumen gland, which along with the posterior capsule gland lobe, acts as a storage site for dietary tryptophan. Thus, tyrindoxyl sulphate and the constituents for prochromogen and precursor biosynthesis are introduced to intracapsular fluid and capsule laminae by the capsule gland. Histochemistry in combination with LC-MS revealed an identical biosynthetic profile within larval vitellus, which is elaborated during oogenesis and may also receive secretions from the albumen gland. Due to the absence of a hypobranchial gland in veligers, it appears that pelagic larvae rely on vitelline natural products until settlement and metamorphous. These findings together with the in situ antimicrobial activity of bromoindoles suggest Tyrian purple precursors are incorporated into muricid egg masses as a maternal investment in larval defence against pathogens.
The results of this investigation clearly highlight the benefits of adopting a histochemical approach to natural product research. This novel alternative to radioisotopes and in situ demonstration of bioactivity, can not only aid in the elucidation of secondary metabolic pathways and chemically mediated interactions, but identify mechanisms of metabolite regulation and differentiate between biosynthetic and storage tissues. Apart from providing insight into the ecological significance of muricid secondary metabolites, the biosynthetic information provided is valuable to our understanding of chemical phylogeny and biosynthetic enzyme sequencing for the environmentally sound development of natural products as biomedical agents.
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Zhao, Tao. „Conifer chemical defense : Rugulation of bark beetle colonization and pheromone emission“. Doctoral thesis, KTH, Organisk kemi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33199.
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Terpenes and phenols are of importance in conifer defense against insects and pathogens. Knowledge about tree chemical defense is vital for developing practical methods to maintain healthy forests. With the aims of characterizing the defensive chemical induction in Norway spruce Picea abies and demonstrating its ecological function to spruce bark beetle Ips typographus, we measured the terpenoid and phenolic content in the bark of mature Norway spruce trees suffering windstorm, inoculated with Ceratocystis polonica, or treated with methyl jasmonate (MeJA), and investigated the colonization and pheromone emission of I. typographus. All three stressors altered the chemical profile in the bark of Norway spruce. Trees damaged by windstorm had lower proportions of (+)-3-carene and two unidentified stilbenes, and a higher taxifolin glycoside content than trees without apparent windstorm damage; C. polonica inoculation induced extremely strong quantitative terpene accumulation in the wound reaction zone, but only increased the levels of (+)-3-carene, sabinene and terpinolene in the bark near the reaction zone; MeJA treatment generally elicited quantitative terpene accumulation, but the induction differed extensively between individual trees. In addition, logs from MeJA-treated tree showed much stronger wounding response compared to control logs. The chemical profile of Norway spruce affected the colonization and pheromone emission of I. typographus. In response to fungal inoculation, terpene present in the reaction zone inhibited the colonization of I. typographus in a dose-dependent manner. Host defense elicited by MeJA treatment reduced emissions of 2-methyl-3-buten-2-ol and (S)-cis-verbenol, the two key aggregation pheromone components of I. typographus, and altered the ratio between the two components.QC 20110503
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Sadowski, Andre T. „Joint Program Executive Office for Chemical and Biological Defense collaboration study“. Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5789.
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Approved for public release; distribution is unlimited.The Joint Program Executive Office for Chemical Biological Defense (JPEO-CBD) is interested in how it can achieve a higher success rate of fielded items with its nine subordinate Program Management Offices. The Joint Science and Technology Office (JSTO) is the research, development, and technology organization that assesses all the new technologies that may eventually become fielded. The JPEO-CBD organization suspects that many of the research projects funded by JSTO are rarely fielded into actual Chemical Biological Defense (CBD) systems used by the end user. This study analyzes the results of a JPEO-CBD Questionnaire and compares those results to applicable JPEOCBD and JSTO technology statistics. The aim of this study is to analyze the quality of the agency relationships and how the relationships impact the probability of projects being fielded. This study shows a significant statistical relationship between the collaboration survey score of a JPM and its anticipated future transition to the warfighter. A similar result is true for the correlation between the historical percentage of technologies that transition to warfighter use and the JPM's collaboration survey score.
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Dewhirst, Sarah Yvonne. „Aspects of aphid chemical ecology : sex pheromones and induced plant defences“. Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/11485.
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Hartley, S. E. „Rapidly induced chemical changes in birch foliage : Their biochemical nature and impact on insect herbivores“. Thesis, University of York, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381348.
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28
Majorczyk, Alexis M. „Chemical Defense Mechanisms of Arabidopsis thaliana Against Insect Herbivory: The Role of Glucosinolate Hydrolysis Products“. Bowling Green, Ohio : Bowling Green State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1249513273.
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Goodman, Keri M. „Freshwater red algae use activated chemical defenses against herbivores“. Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41208.
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Chemically mediated interactions have important ecological and evolutionary effects on populations and communities. Despite recognition that herbivory can significantly affect the biomass and composition of freshwater macrophyte communities, there are few investigations of chemical defenses among freshwater vascular plants and mosses and none of freshwater red algae. This study compares the palatability of five species of freshwater red algae (Batrachospermum helminthosum, Boldia erythrosiphon, Kumanoa sp., Paralemanea annulata, and Tuomeya americana) that occur in the southeastern United States relative to two co-occurring macrophytes (the chemically defended aquatic moss Fontinalis novae-angliae and the broadly palatable green alga Cladophora glomerata). We assessed the potential role of structural, nutritional, and chemical traits in reducing macrophyte susceptibility to generalist crayfish grazers. Both native and non-native crayfish significantly preferred the green alga C. glomerata over four of the five species of red algae. B. erythrosiphon was palatable, while the cartilaginous structure of P. annulata reduced its susceptibility to grazing, and chemical defenses of B. helminthosum, Kumanoa sp., and T. americana rendered these species as unpalatable as the moss F. novae-angliae. Extracts from these latter species reduced feeding by ~30-60% relative to solvent controls if tissues were crushed (simulating herbivore damage) prior to extraction in organic solvents. However, if algae were first soaked in organic solvents that inhibit enzymatic activity and then crushed, crude extracts stimulated or had no effect on herbivory. B. helminthosum, Kumanoa sp., and T. americana all exhibited "activated" chemical defenses in which anti-herbivore compounds are produced rapidly upon herbivore attack via enzymatic processes. In an additional accept/reject behavioral assay, B. helminthosum extracts reduced the number of crayfish willing to feed by >90%.
Given that three of the five red algal taxa examined in this study yielded deterrent crude extracts, selection for defensive chemistry in freshwater rhodophytes appears to be substantial. Activated chemical defenses are thought to be an adaptation to reduce the resource allocation and ecological costs of defense. As such, activated chemical defenses may be favored in freshwater red algae, whose short-lived gametophytes must grow and reproduce rapidly. Roughly 20% of the known chemical defenses produced by marine algae are activated; further examination is needed to determine whether the frequency of activated chemistry is higher in freshwater red algae compared to their marine counterparts. Continued investigation of chemical defenses in freshwater red algae will contribute to among-system comparisons, providing new insights in the generality of plant-herbivore interactions and their evolution.
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Cabioch, Léa. „Chemical signaling and defense in brown algal kelps during interactions with herbivores“. Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066708/document.
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Les kelps sont des espèces clés dans les écosystèmes marins tempérés, elles vivent en milieu intertidal le long des côtes où elles sont souvent exposées à des herbivores. Comme la plupart des organismes sessiles, les kelps ont développé des stratégies de défense contre l’herbivorie. Chez la laminaire Laminaria digitata, l’élicitation par les oligoguluronates induit des régulations transcriptomiques et l’activation de voies métaboliques, menant à la production et la libération de métabolites dans l’environnement, tels que des aldéhydes. De plus, cette espèce d’algue brune a montré des réponses systémiques suite à une élicitation. Des composés solubles dans l’eau de mer environnant les forêts de laminaires peuvent aussi modifier leur physiologie en réponse à l’élicitation. Une telle signalisation chimique à distance lors des réponses de défense rappelle les phénomènes de protection systémique et de potentialisation chez les plantes. Dans les forêts de laminaires, celle-ci pourrait jouer un rôle écologique majeur dans la structuration des algues marines et des communautés d’herbivores. Dans le contexte des interactions kelp/herbivores, nous avons étudié les réponses de défense et les processus de signalisation chez deux espèces emblématiques de laminaires originaires des côtes atlantiques et du Pacifique Sud, impliquées dans des interactions spécialisées avec leurs herbivores, L. digitata en interaction avec Patella pellucida (Bretagne, France) et Lessonia spicata avec Scurria scurra (Chili). Des approches combinées de métabolomique et de bio-essais ont été réalisées pour élucider la nature de potentiels signaux chimiques et leurs rôles biologiques et écologiques dans la défense des algues face aux herbivores. Les résultats ont montré que, en réponse à un broutage, les kelps présentent des modifications métaboliques telles que l’induction de voies de biosynthèse des acides gras, des oxylipines et d’acides aminés, ainsi que des modifications transcriptomiques. De plus, nous avons constaté que les laminaires co-incubées avec des algues broutées présentaient des changements de leur endo-métabolome en comparaison à des algues broutées, et semblaient moins consommées lors d’un broutage ultérieur, suggérant une perception et une intégration des composés algaux induits par l’herbivorie par les algues voisines. Des études de terrain et en laboratoire ayant précédemment mis en évidence une libération massive d’aldéhydes dans l’air et l’eau de mer après des stress biotiques et abiotiques, nous avons exploré les rôles biologiques d’une signalisation de type aldéhyde dans les interactions kelp/herbivores. Nous avons montré que les aldéhydes pouvaient modifier le métabolisme d’une algue par l’activation du métabolisme des acides gras, et que l’application de 4-HHE sur L. digitata pouvait réduire significativement une consommation algale ultérieure par les herbivores. Ainsi, ces résultats participent à une meilleure compréhension des réponses de défense suite à un broutage chez les laminaires, et confortent l’existence d’une signalisation à distance dans les interactions avec les herbivores, qui impliquerait des composés de défense émis par les algues, dont les aldéhydesKelps are founding species of temperate marine ecosystems, they evolve in the intertidal coastal areas where they are often challenged by herbivores. As most of sessile organisms, kelps develop defensive strategies against herbivory. In the kelp Laminaria digitata, elicitation by oligoguluronates induced regulations of transcription and metabolic pathways, leading to production and release of metabolites, such as aldehydes, in the environment. Moreover, this kelp species feature systemic responses upon defense elicitation and waterborne compounds surrounding a kelp bed have shown to modify its defense physiology. Such distant chemical signaling during defense responses are reminiscent of systemy and priming mechanisms in plants. In marine kelp beds, it should have a major ecological role in structuring marine algal and herbivore communities. In the context of kelp/herbivore interactions, we investigated the defense responses and signaling processes in two emblematic kelp species from north Atlantic and South Pacific coasts, involved in specialized interactions with their herbivores, L. digitata in interaction with Patella pellucida (Brittany, France) and Lessonia spicata with Scurria scurra (Chile). Combined approaches of metabolomics and bio-assays were carried out to decipher the nature of the putative chemical cues, and their biological and ecological roles in algal defense against herbivores. Results showed that, in response to grazing, kelps featured metabolic modifications such as induction of fatty acids, oxylipins and amino acids biosynthetic pathways, as well as transcriptomic modifications. Moreover, we observed that kelps co-incubated with grazed algae exhibited endo-metabolome changes compared to grazed one, and seemed to be less consumed during a subsequent grazing, suggesting the perception and integration of herbivory-induced algal compounds in neighboring algae. As field and lab studies previously highlighted a strong release of aldehydes into the air and the seawater following biotic and abiotic stresses, we further explored the biological roles of aldehyde-based signaling in kelp/herbivore interactions. We found that aldehydes could modify algal metabolism, including the activation of fatty acid metabolism, and that the application of 4-HHE on L. digitata could significantly reduce later algal consumption by herbivores. Thus, these results contribute to a better understanding of defense responses following grazing in kelps, and revealed the occurrence of distance signaling during interaction with herbivores, which could involve algal emitted compounds, such as aldehydes
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Priestley, R. A. „Phytoalexin synthesis in aggregated suspension cultures of Phaseolus vulgaris“. Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382750.
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Labeyrie, Estelle. „Mate choice, predation and chemical defense in two species of alpine leaf-beetles“. Neuchâtel : [s.n.], 2000. http://doc.rero.ch/lm.php?url=1000,40,4,20051027085201-VY/1_these_LabeyrieE.pdf.
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Bruner, Laura. „The study of Arabidopsis thaliana trichomes for source of chemical defense against pathogens“. Connect to resource, 2009. http://hdl.handle.net/1811/36944.
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34
Kurr, Martyn. „Trade-offs in macroalgal chemical defences : battle of the sexes, invaders and consumers“. Thesis, Bangor University, 2015. https://research.bangor.ac.uk/portal/en/theses/tradeoffs-in-macroalgal-chemical-defencesbattle-of-the-sexesinvaders-and-consumers(17ed360c-7d4d-4e1a-9216-036f23ceaec4).html.
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Macroalgae are useful as model organisms because their simple physiology and modular growth allows their investments into growth, defence, and reproduction to be quantified. Ascophyllum nodosum is a dioecious perennial which responds clearly to environmental stressors, and Sargassum muticum is an invasive pseudo-annual which grows in discrete populations of known time-since-invasion. Two chapters investigate the occurrence of sexual dimorphism in A. nodosum under stress, and incorporate surveys, chemical analyses, and feeding trials to demonstrate that females invest more into sexual reproduction at sites where stressors impact juvenile mortality, and compensate by reducing investment into defence, leaving them more vulnerable to grazers. At sites where stressors impact mainly on adult mortality and performance with lower influence on juvenile mortality, limited sexual dimorphism is observed. Similar results have been demonstrated in terrestrial plants, but none have quantified responses to stress in such detail. The second two chapters test the Enemy Release Hypothesis, the Evolution of Increased Competitive Ability hypotheses, and the Biotic Resistance hypothesis using surveys, chemical analyses, and feeding trials with S. muticum and its associated grazers from populations established for different lengths of time, over 40 years. Grazers from older S. muticum were more likely to feed upon it in the laboratory, but surveys of chemical defences did not reflect any increased pressure over time in the field. Instead, S. muticum increased its defensive investment in the presence of a greater diversity of grazers, irrespective of the length of time those grazers had been exposed to it. Therefore although grazers can learn to consume S. muticum, they are still unlikely to do so in the field, such that many species must be present before at least some begin to impart top-down pressure upon it. Collectively these investigations demonstrate the high value of using macroalgae in wider ecology.
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Park, Young Chul. „Chemical Investigation of Three Antarctic Marine Sponges“. Scholar Commons, 2004. https://scholarcommons.usf.edu/etd/1190.
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This thesis describes the chemical investigation of three marine sponges from Antarctica and the total syntheses of natural products erebusinone (12) and its derivative, erebusinonamine (52). Investigation of the yellow Antarctic marine sponge Isodictya setifera resulted in the isolation of two secondary metabolites, purine analog (32) and 3-hydroxykynurenine (24). Chemical investigation of Isodictya setifera led to the isolation of six secondary metabolites which included 5-methyl-2-deoxycytidine (25), uridine (28), 2-deoxycytidine (31), homarine (37), hydroxyquinoline (33), 3-hydroxykynurenine (24). The latter two compounds were found to be intermediates of tryptophan catabolism in crustaceans. From the Antarctic marine sponge Isodictya antractica ceramide analog (39) was isolated and its chemical structure was assigned by a combination of spectroscopic and chemical analyses. Stereochemistry was determined by modified Mosher's method. Erebusinone (12), a yellow pigment isolated from the Antarctic marine sponge Isodictya erinacea has been implicated in molt inhibition and mortality against the Antarctic crustacean amphipod, Orchomene plebs, possibly serving as a precursor of a xanthurenic acid analog.
Thought to act as a 3-hydroxykynurenine 24 mimic, erebusinone (12) may be involved chemical defense. This appears to be the first example in the marine realm of an organism utilizing tryptophan catabolism to modulate molting as a defensive mechanism. To further investigate the bioactivity and ecological role of erebusinone (12), the synthesis of this pigment was carried out in an overall yield of 44% involving seven steps which were economical and convenient. Erebusinonamine (52) was also similarly synthesized in eight steps with an overall yield of 45%.
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Mlejnková, Petra. „Plán opatření pro případ vzniku mimořádné události v objektu výzkumného ústavu“. Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-232720.
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This work deals with the elaboration of an action plan in the case of emergency (e.g., fire, explosion, leakage of hazardous chemicals, etc.) in the manufacturing Company VUES Brno. The Action plan, which is designed on the initiative of the Department of Civil Defence - District Brno – north, will become a part of the response plan within this district. The thesis applies particular requisites of the emergency plan in terms of the district Brno - north. The main requisites include the warning responsible authorities, the residents informing, the guidelines for sheltering and evacuation of residents, and the organization of a medical support. The action plan (Particulars requisites) is accompanied by corresponding legislation. The danger zone was determined by the model release of hazardous substances used in threatening object using software ALOHA and TerEx. These programs evaluate the possible consequences of the accident according to physical and chemical properties of the substances based on the conservative projections. Results correspond to the worst possible consequences of the situation. In the case of manufacturing Company VUES Brno the highest risk was evaluated as a fire of flammable liquids. The danger zone was set at 100m in the surroundings. Particular steps for population protection are therefore planned for the distance 100 m from the object. The work also contains the graphical part of the map marked with the radius threat map of evacuation routes and map roadblocks. In order to improve the awareness of potential emergency for the population living nearby, a leaflet containing necessary information in the case of emergency was designed.
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Nusnbaum, Matthew. „Chemical Defenses of Aplysia Californica and Sensory Processing by Predatory Fishes“. Digital Archive @ GSU, 2011. http://digitalarchive.gsu.edu/neurosci_diss/2.
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In predator-prey interactions, prey species have complex defensive behaviors to protect themselves from predators. Chemical defenses are one tool that is employed to protect against predators, especially for slow-moving or otherwise susceptible prey. Many of these chemical defenses have been studied and the effective compounds identified, but few studies were performed on their mechanisms of detection.
In my research, I used the sea hare, Aplysia californica, as chemically defended prey. This slow moving mollusk is soft-bodied with no external shell, but it has adapted a number of defenses including chemical defenses. Ink is a sticky mixture of the products of the ink gland and the opaline gland which are mixed in the mantle cavity and released toward an attacker. I show that this ink secretion protects the sea hare from predation by a fish predator.
Because many deterrent compounds taste bitter, bitter taste receptors are thought to protect predators from ingesting harmful compounds in prey. Studies of deterrent taste detection have commonly utilized bitter compounds from human hedonics to study the responses in animals, such as fruit flies, fishes, rats, and monkeys. In my dissertation, I argue that the study of chemical defenses allows us to ask more questions about detection of relevant deterrents and interactions between predators and prey at the individual and population levels. My results show that diet-derived pigments in Aplysia ink, aplysioviolin and phycoerythrobilin, are strongly deterrent to fish predators. Electrophysiological analyses of the gustatory system show that these compounds are equipotent and cross-adapt each others’ responses completely. Aplysioviolin and phycoerythrobilin produced incomplete reciprocal cross-adaptation with amino acids and adapted bile salt responses but were not significantly adapted by these latter stimuli. These results showed multiple pathways that are sensitive to aplysioviolin and phycoerythrobilin, which may have different effects on the physiology and behavior of the predatory fish. My findings demonstrate the value to the fields of chemical ecology and chemosensory biology of studying sensory processing of relevant deterrent compounds. This work lays the foundation for how a diet-derived photopigment is adapted by a species to protect itself from predators by stimulating their chemosensory systems.
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Guan, Chi [Verfasser]. „Zostera marina and epibionts : the dynamics of chemical defenses / Chi Guan“. Kiel : Universitätsbibliothek Kiel, 2017. http://d-nb.info/1136319174/34.
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39
Foulks, Frederick Spencer. „An analysis of Doppelt's defense of Kuhnian relativism as applied to the chemical revolution“. Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30566.
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Doppelt defends the key elements of Kuhn's thesis that scientific revolutions occur when one paradigm is replaced by another and that crucial aspects of competing paradigms are incommensurable. He concedes the merits in the views of those positivist critics of Kuhn who contend that for paradigms to be comparable their proponents must be able to communicate with one another, to agree on a common core of meaning for basic concepts and to deal with shared data and problems. However, he maintains that in identifying the problems which are held to be of fundamental importance and in adopting the standards by which explanatory adequacy is to be evaluated, rival paradigms do not overlap sufficiently for them to have genuine commensurability. This leads Doppelt to accept Kuhn's version of epistemological relativism which maintains that the rationality of the acceptance of new paradigms by the scientific community, at least in the short-run, has an irreducible normative dimension that is strongly conditioned by subjective factors.
Doppelt also accepts Kuhn's views with respect to the loss of data, and the question of cumulative progress. The absence of paradigm-neutral external standards allegedly allows each paradigm to assign priority to its own internal standards, thus providing persuasive grounds for the incommensurability of competing paradigms and for epistemological relativism. Nevertheless, he acknowledges
that the validity of these arguments over the long term is a contingent issue which can only be resolved by a careful examination of the historical evidence.
A chemical revolution took place in the latter part of the eighteenth century when the oxygen theory replaced that based on hypothetical phlogiston. This transition is frequently cited as a typical example of a paradigm - one that illustrates Kuhn's claims for a shift in standards and a loss of data as central features of scientific revolutions. The phlogiston theory held that phlogiston was a normal constituent of air. It explained smelting as the transfer of phlogiston from the air (or from phlogiston-rich charcoal) to the earthy components of the ore, and held that the similar properties of the metallic products could be attributed to their phlogiston content. Combustion, including the
calcination of metals and the respiration of living organisms, was viewed as a process involving the release of phlogiston to the atmosphere. The development of improved techniques for collecting gases and for measuring their volume and weight lead to emphasis on precise quantitative methods for evaluating chemical data as distinct from those based on simple quantitative descriptive observations.
These developments soon posed difficulties for the phlogiston theory (eg.,the anomalous weight loss during combustion). Eventually, clarification of the composition of water and the use of the 'nitrous air1 test for the ability of a gas to support combustion and respiration (its
'goodness') led to the discovery of oxygen as a component of air and the demonstration that combustion involved combination with an exact quantity of this gas. Within a relatively short period of time, the oxygen theory gained general acceptance and the phlogiston theory was abandoned by most chemists.
A critical examination of the events which culminated in the chemical revolution fails to bear out the claim that it was accompanied by a significant loss of empirical data or that it did not represent genuine cumulative progress in scientific knowledge. Instead the history of this revolution indicates that paradigm-neutral external standards for evaluating explanatory adequacy (conservatism, modesty, simplicity, generality, internal and external coherence, refutability, precision, successful predictions) were available and played a crucial role in bringing about this transition. Accumulating evidential warrant played the
decisive role in the triumph of the oxygen theory.Arts, Faculty of
Philosophy, Department of
Graduate
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Odate, Shobu. „The role of vanadium as a chemical defense of the solitary tunicate, Phallusia nigra /“. Electronic version (PDF), 2003. http://dl.uncw.edu/etd/2003/odates/shobuodate.html.
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Malfoy, Jordan I. „Britain Can Take It: Civil Defense and Chemical Warfare in Great Britain, 1915-1945“. FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3639.
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This dissertation argues that the origins of civil defense are to be found in pre-World War II Britain and that a driving force of this early civil defense scheme was fear of poison gas. Later iterations of civil defense, such as the Cold War system in America, built on already existing regimes that had proven their worth during WWII. This dissertation demonstrates not only that WWII civil defense served as a blueprint for later civil defense schemes, but also that poison gas anxiety served as a particular tool for the implementation and success of civil defense. The dissertation is organized thematically, exploring the role of civilians and volunteers in the civil defense scheme, as well as demonstrating the vital importance of physical manifestations of civil defense, such as gas masks and air raid shelters, in ensuring the success of the scheme.
By the start of World War II, many civilians had already been training in civil defense procedures for several years, learning how to put out fires, recognize bombs, warn against gas, decontaminate buildings, rescue survivors, and perform first aid. The British government had come to the conclusion, long before the threat became realized, that the civilian population was a likely target for air attacks and that measures were required to protect them. World War I (WWI) saw the first aerial attacks targeted specifically at civilians, suggesting a future where such attacks would occur more frequently and deliberately. Poison gas, used in WWI, seemed a particularly horrifying threat that presented significant problems. Civil defense was born out of this need to protect the civil population from attack by bombs or poison gas. For the next five years of war civil defense worked to maintain British morale and to protect civilian lives. This was the first real scheme of civil defense, instituted by the British government specifically for the protection of its civilian population.
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Lane, Amy L. „Marine natural products as antimicrobial chemical defenses and sources of potential drugs“. Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26556.
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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.Committee Chair: Kubanek, Julia; Committee Member: Fernandez, Facundo M.; Committee Member: Harvey, Stephen C.; Committee Member: Hay, Mark E.; Committee Member: Hud, Nicholas V. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Dumdei, Eric J. „Rearranged spongian diterpenoids from the nudibranch Chromodoris cavae that may serve as a chemical defense“. Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27420.
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Nudibranchs of the genus Chromodoris are known to selectively sequester sponge metabolites which have novel structures and often serve as deterrents to predation. Spectroscopic and X-ray diffraction studies on a biologically active metabolite from Chromodoris cavae have led to the discovery of a diterpenoid, chromodorolide A (100), with a new carbon skeleton.[See Thesis for Diagram]Science, Faculty of
Chemistry, Department of
Graduate
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Cardoso, Márcio Zikán. „The evolutionary and ecological consequences of pollen feeding in Heliconius butterflies : resource acquisition, chemical defense and mating /“. Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Kojima, Yosuke. „Active foraging for toxic prey and chemical protection of offspring by females of Rhabdophis tigrinus“. 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188515.
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Vogelhut, Jonas. „Revolutionizing the United States Army's chemical defense through the acquisition of software and software-intensive systems“. Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA370708.
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Thesis (M.S. in Management) Naval Postgraduate School, September 1999."September 1999". Thesis advisor(s): Mark E. Nissen, David F. Matthews. Includes bibliographical references (p. 89-96). Also Available online.
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Uzarski, Joshua Robert. „Reflection Absorption Infrared Spectroscopic Studies of Surface Chemistry Relevant to Chemical and Biological Warfare Agent Defense“. Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26107.
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Reflection absorption infrared spectroscopy was used as the primary analysis technique to study the interfacial chemistry of surfaces relevant to chemical and biological warfare agent defense. Many strategies utilized by the military to detect and decompose chemical and biological warfare agents involve their interaction with surfaces. However, much of the chemistry that occurs at the interface between the agents and surfaces of interest remains unknown. The surface chemistry plays an important role in efficacy of both detection and decontamination technology, and by obtaining a deeper understanding of that chemistry, researchers might be able to develop more sensitive detection devices and more effective decontamination strategies. Our efforts have focused on three different areas of surface chemistry relevant to chemical and biological warfare agent defense:
1) The development of a surface synthesis strategy to create and control the structure of antibacterial self-assembled monolayers (SAMs). Our work demonstrated a successful strategy for creating SAMs that contain long-chain quaternary ammonium groups, which were synthesized and subsequently characterized using RAIRS and X-ray photoelectron spectroscopy (XPS).
2) The determination of the surface conformation, orientation, and relative surface density of immobilized antimicrobial peptides. Our results revealed that the peptides consisted of tilted (50-60°), α-helices on the surface, regardless of solution conditions.
3) The design and construction of a new ultrahigh vacuum surface science instrument that allows for the study of gas-surface reactions with up to three gases simultaneously.
4) The study of the adsorption of chemical warfare agent simulants to silica nanoparticulate films. Our work demonstrated that the adsorbate structure was dependent on the number of hydrogen-bonding groups, and the adsorption consists of a pressure-dependent two part mechanism.
The results presented here will help increase the understanding of the surface chemistry of three interfaces relevant to chemical and biological defense. Future researchers may apply the new information to develop more effective detection and decontamination strategies for chemical and biological warfare agents.Ph. D.
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Davidson, Seana Kelyn. „Biology of the bryostatins in the marine bryozoan Bugula neritina : symbiosis, cryptic speciation and chemical defense /“. Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p3035405.
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Sarmiento, Leslie Vanesa. „Inducible chemical defenses in temperate reef sponges of the South Atlanitic Bight, U.S.A“. Click here to access dissertation, 2008. http://www.georgiasouthern.edu/etd/archive/spring2008/leslie_v_bates/Sarmiento_Leslie_V_200801_MS.pdf.
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Thesis (M.A.)--Georgia Southern University, 2008."A dissertation submitted to the Graduate Faculty of Georgia Southern University in partial fulfillment of the requirements for the degree Master of Arts." Under the direction of Joe Pellergino. ETD. Electronic version approved: May 2008. Includes bibliographical references (p. 83-86) and appendices.
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Nowotny, Maria Materials Science & Engineering Faculty of Science UNSW. „Defect disorder, semiconducting properties and chemical diffusion of titanium dioxide single crystal“. Awarded by:University of New South Wales. School of Materials Science and Engineering, 2006. http://handle.unsw.edu.au/1959.4/27223.
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Semiconducting properties and related defect disorder for well defined TiO2 single crystal were studies. Semiconducting properties have been determined using simultaneous measurements of two independent electrical properties, including electrical conductivity, ??, and thermoelectric power, S, at elevated temperatures (1073-1323 K) in the gas phase of controlled oxygen activity (10-10 Pa < p(O2) < 75 kPa). Measurements of s and S were conducted (i) in the gas/solid equilibrium and (ii) during equilibration. Oxygen vacancies have been identified as the predominant defects in TiO2 over a wide range of p(O2). Individual conductivity components related to electrons, electron holes and ions, were determined from the obtained ?? data. The effect of p(O2) on these individual components was considered in the form of a diagram. This work led to the discovery of the formation and diffusion of Ti vacancies. However, the obtained diffusion data indicate that, in the temperature ranges commonly used in studies of semiconducting properties (1000-1400K), the Ti vacancies concentration is quenched and may thus be assumed constant. In addition it was shown that Ti vacancies in appreciable concentrations form only during prolonged oxidation. It was determined that the discrepancies in the reported n-p transition point are related to the concentration and spectrum of impurities as well as the concentration of Ti vacancies. It has been shown that the n-p transition point in high-purity TiO2 is determined by the Ti vacancy concentration. A well defined chemical diffusion coefficient, Dchem, was determined using kinetic data obtained during equilibration. A complex relationship between p(O2) and Dchem was observed. These data showed a good agreement between the obtained diffusion data and defect disorder. Examination of the determined equilibration kinetics, led to the discovery of two kinetic regimes, the result of the transport of defects at different mobilities. The determined data are considered well defined due to the following reasons: 1. The studied specimen was of exceptionally high purity and free of grain boundaries (single crystal) 2. The specimen was studied in the gas phase of controlled and well defined oxygen activity which was continuously monitored. 3. Whenever the experimental data were measured in equilibrium, the gas/solid equilibrium has been verified experimentally. 4. A good agreement between the two, self-confirmatory, electrical properties, including ?? and S has been determined simultaneously and independently. The defect disorder model derived in the present work may be used for tailoring controlled semiconducting properties through the selection of annealing conditions involving the temperature and oxygen activity.