The varroa mite is a primary driver behind periodical losses of honey bee colonies. The mite requires bees for food and reproduction and, in turn, elicits physiological deficiencies and diseases that compromise bee colony health. The mite nervous system is a target site for existing acaricides. These acaricides not only have adverse health effects on bees, but resistance limits their use to reduce mites and diseases in bee colonies. Voltage-gated chloride channels are involved in the maintenance of nerve and muscle excitability in arthropod pests, which suggests that these channels might be exploited as targets for acaricides. Apistan® (the pyrethroid tau-fluvalinate), Checkmite+® (the organophosphate coumaphos), and Apivar® (the formamidine amitraz) are control products for mite management. The effectiveness of these chemistries has diminished as a result of the increasing incidence resistance in mite populations. I report a toxicological analysis of stilbene products against acaricide-susceptible and -resistant mites. My results find a significant increase in metabolic detoxification enzyme activities in acaricide-resistant mites compared to susceptible mites. Acetylcholinesterase of coumaphos-resistant mites was significantly less sensitive to the toxic coumaphos metabolite compared to susceptible mites, which suggests target-site insensitivity as a mechanism of acaricide resistance. The stilbene product DIDS had significantly higher field efficacy to acaricide-resistant mites compared to Apistan®- and CheckMite+®. These data suggest that DIDS, and other stilbene products, might serve as candidate chemistries to continue field efficacy testing of alternative acaricides for Apistan® and CheckMite+® resistant mites. / Master of Science in Life Sciences

For the modelling of chemistry we use undirected, labelled graphs as explicit models of molecules and graph transformation rules for modelling generalised chemical reactions. This is used to define artificial chemistries on the level of individual bonds and atoms, where formal graph grammars implicitly represent large spaces of chemical compounds. We use a graph rewriting formalism, rooted in category theory, called the Double Pushout approach, which directly expresses the transition state of chemical reactions. Using concurrency theory for transformation rules, we define algorithms for the composition of rewrite rules in a chemically intuitive manner that enable automatic abstraction of the level of detail in chemical pathways. Based on this rule composition we define an algorithmic framework for generation of vast reaction networks for specific spaces of a given chemistry, while still maintaining the level of detail of the model down to the atomic level. The framework also allows for computation with graphs and graph grammars, which is utilised to model non-trivial chemical systems. The graph generation relies on graph isomorphism testing, and we review the general individualisation-refinement paradigm used in the state-of-the-art algorithms for graph canonicalisation, isomorphism testing, and automorphism discovery. We present a model for chemical pathways based on a generalisation of network flows from ordinary directed graphs to directed hypergraphs. The model allows for reasoning about the flow of individual molecules in general pathways, and the introduction of chemically motivated routing constraints. It further provides the foundation for defining specialised pathway motifs, which is illustrated by defining necessary topological constraints for both catalytic and autocatalytic pathways. We also prove that central types of pathway questions are NP-complete, even for restricted classes of reaction networks. The complete pathway model, including constraints for catalytic and autocatalytic pathways, is implemented using integer linear programming. This implementation is used in a tree search method to enumerate both optimal and near-optimal pathway solutions. The formal methods are applied to multiple chemical systems: the enzyme catalysed beta-lactamase reaction, variations of the glycolysis pathway, and the formose process. In each of these systems we use rule composition to abstract pathways and calculate traces for isotope labelled carbon atoms. The pathway model is used to automatically enumerate alternative non-oxidative glycolysis pathways, and enumerate thousands of candidates for autocatalytic pathways in the formose process.

This thesis takes EV from the late 90’s as a baseline, assess the capability of today’s EV technology, and establishes its near-term and long-term prospects. Simulations are performed to evaluate EVs with different combinations of new electric machines and battery chemistries. Cost assessment is also presented to address the major challenge of EV commercialization. This assessment is based on two popular vehicle classes: subcompact and mid-size. Fuel, electricity and battery costs are taken into consideration for this study. Despite remaining challenges and concerns, this study shows that with production level increases and battery price-drops, full function EVs could dominate the market in the longer term. The modeling shows that from a technical and performance standpoint both range and recharge times already fall into a window of practicality, with few if any compromises relative to conventional vehicles. Electric vehicles are the most sustainable alternative personal transportation technology available to-date. With continuing breakthroughs, minimal change to the power grid, and optimal GHG reductions, emerging electric vehicle performance is unexpectedly high.

For the modelling of chemistry we use undirected, labelled graphs as explicit models of molecules and graph transformation rules for modelling generalised chemical reactions. This is used to define artificial chemistries on the level of individual bonds and atoms, where formal graph grammars implicitly represent large spaces of chemical compounds. We use a graph rewriting formalism, rooted in category theory, called the Double Pushout approach, which directly expresses the transition state of chemical reactions. Using concurrency theory for transformation rules, we define algorithms for the composition of rewrite rules in a chemically intuitive manner that enable automatic abstraction of the level of detail in chemical pathways. Based on this rule composition we define an algorithmic framework for generation of vast reaction networks for specific spaces of a given chemistry, while still maintaining the level of detail of the model down to the atomic level. The framework also allows for computation with graphs and graph grammars, which is utilised to model non-trivial chemical systems. The graph generation relies on graph isomorphism testing, and we review the general individualisation-refinement paradigm used in the state-of-the-art algorithms for graph canonicalisation, isomorphism testing, and automorphism discovery. We present a model for chemical pathways based on a generalisation of network flows from ordinary directed graphs to directed hypergraphs. The model allows for reasoning about the flow of individual molecules in general pathways, and the introduction of chemically motivated routing constraints. It further provides the foundation for defining specialised pathway motifs, which is illustrated by defining necessary topological constraints for both catalytic and autocatalytic pathways. We also prove that central types of pathway questions are NP-complete, even for restricted classes of reaction networks. The complete pathway model, including constraints for catalytic and autocatalytic pathways, is implemented using integer linear programming. This implementation is used in a tree search method to enumerate both optimal and near-optimal pathway solutions. The formal methods are applied to multiple chemical systems: the enzyme catalysed beta-lactamase reaction, variations of the glycolysis pathway, and the formose process. In each of these systems we use rule composition to abstract pathways and calculate traces for isotope labelled carbon atoms. The pathway model is used to automatically enumerate alternative non-oxidative glycolysis pathways, and enumerate thousands of candidates for autocatalytic pathways in the formose process.

The near future will put a lot of demand on the increasing need for energy production and storage. Issues regarding the modern-day battery technology’s environmental benignity, safety and cost to sustain such demands thus serve as a huge bottleneck, necessitating the research into alternative electrochemical energy storage solutions. Conducting redox polymers are a class of materials which combines the concepts of conducting polymers and redox active molecules to work as fully organic electrode materials. In this work three conducting redox polymers based on 3,4-ethylenedioxythiopene and 3,4-propylenedioxythiopene (EPE) with hydroquinone, catechol and quinizarin pendant groups were investigated. The polymers were electrochemically characterized with regards to their ability to cycle protons (aqueous electrolyte) and cations (non-aqueous electrolyte), their kinetics and charge transport and as cathodes in a battery. In non-aqueous electrolyte, hydroquinone and catechol did not exhibit redox activity in a potential region where the backbone was conducting as they were not redoxmatched. Quinizarin showed redox-matching as concluded by in situ conductance and UV-vis measurements when cycling Na+, Li+, Ca2+ and Mg2+-ions in acetonitrile. Comparison of the kinetics revealed that the rate constant for Ca2+-ion cycling was several magnitudes larger than the rest, and galvanostatic charge/discharge showed that 90% of the polymer capacity was attainable at 5C. An EPE-Quinizarin cathode and metallic calcium anode coin cell assembly displayed output voltages of 2.4 V, and the presented material thus shows promising and exciting properties for future sustainable battery chemistries.

Le développement de nouvelles technologies pour le transport aérien moins polluant est de plus en plus basé sur la simulation numérique, qui nécessite alors une description fiable de la chimie. Pour la plupart des carburants, la description de la combustion nécessite des mécanismes détaillés mais leur utilisation dans une simulation numérique de combustion turbulente est limitée par le coût calcul. Des mécanismes cinétiques réduits et des méthodes de tabulation ont été proposés pour surmonter ce problème. Ces descriptions chimiques simplifiées ayant été développées dans le cadre de configurations laminaires, cette thèse propose de les évaluer dans des configurations turbulentes: une DNS de flamme prémélangée méthane/air de type Bunsen et une LES d’un brûleur expérimental. Les mécanismes sont analysés en termes de structure de flamme, paramètres de flamme globaux, longuer de flamme, prediction des concentrations en espèces majoritaires et des émissions polluantes. Une méthodologie pour évaluer a priori la capacité d’un mécanisme à prédire correctement des phénomènes chimiques tridimensionnels est proposée en se basant sur les résultats de flammes laminaires monodimensionnelles non étirées et étirées. Il ressort que, d’une part, pour construire un mécanisme réduit, il est nécessaire de faire un compromis entre coût calcul, robustesse et qualité des résultats. D’autre part, la qualité des résultats de DNS et LES de configurations tridimensionnelles turbulentes peut être anticipée par une analyse du comportement des schémas réduits dans des configurations simplifiées de flammes monodimensionnelles laminaires non étirées et étirées. / A growing need for numerical simulations based on reliable chemistries has been observed in the last years in order to develop new technologies which could guarantee the reduction of the enviromental impact on air transport. The description of combustion requires the use of detailed kinetic mechanisms for most hydro-carbons. Their use in turbulent combustion simulation is still prohibitive because of their high computational cost. Reduced chemistries and tabulation methods have been proposed to over-come this problem. Since all these reductions have been developed for laminar configurations, this thesis proposes to evaluate their performances in simulations of turbulent configurations such as a DNS of a premixed Bunsen methane/air flame and a LES of an experimental PREC-CINSTA burner. The mechanisms are analysed in terms of flame structure, global burning parameters, flame length, prediction of major species concentrations and pollutant emissions. An a priori methodology based on one-dimensional unstrained and strained laminar flames to evaluate the mechanism capability to predict three-dimensional turbulent flame features is therefore proposed. On the one hand when building a new reduced scheme, its requirements should be fixed compromising the computational cost, the robustness of the chemical description and the desired quality of results. On the other hand, the quality of DNS or LES results in three-dimensional configurations could be anticipated testing the reduced mechanism on laminar one-dimensional premixed unstrained and strained flames.

Os neutrófilos desempenham um papel fundamental na defesa do organismo contra microrganismos invasores, através da fagocitose, da degranulação e da produção de espécies reativas de oxigênio (EROs), sendo que esta última é decorrente da ativação do metabolismo oxidativo dos neutrófilos. As EROs produzidas, tais como O2∙-, H2O2, HO∙, HOCl, 1O2 e NO, que são essenciais para matar os microrganismos fagocitados, podem também ser liberadas para o meio extracelular e causar lesões oxidativas aos tecidos do hospedeiro. Essas lesões têm sido implicadas na patogênese de doenças como aterosclerose, câncer, artrite reumatóide, pneumonia e enfisema pulmonar. Com o intuito de prevenir essas lesões oxidativas, tem-se investigado a atividade antioxidante de diversos compostos, especialmente os derivados de plantas. Neste trabalho foram avaliadas as atividades de oito cumarinas simples (compostos 1 a 8) sobre o metabolismo oxidativo de neutrófilos de coelho estimulados com Zimosan opsonizado, empregando-se os ensaios de quimioluminescência (QL) dependente de lucigenina (QLluc) e de QL dependente de luminol (QLlum). A QLluc reflete a produção apenas de O2∙- , enquanto que a QLlum é resultante da oxidação do luminol pelas diversas EROs produzidas pelos neutrófilos estimulados. Assim, a inibição da QLluc e da QLlum será decorrente da redução da concentração das EROs responsáveis pela oxidação da lucigenina e do luminol no meio de reação, respectivamente. Foram avaliadas também a atividade dos antioxidantes a-tocoferol, butil-hidroxitolueno (BHT) e quercetina sobre a QLlum e a QLluc, e a toxicidade das cumarinas 1 a 8 e dos três antioxidantes citados sobre os neutrófilos de coelho. Determinou-se o coeficiente de partição e o volume molecular das cumarinas 1 a 8. Dentre os três antioxidantes, observou-se que a quercetina inibiu tanto a QLlum quanto a QLluc, e não foi tóxica para os neutrófilos, na concentração de 50 mmol/L. O a-tocoferol não inibiu a QLlum nem a QLluc, enquanto o BHT foi tóxico para os neutrófilos de coelho. Para as cumarinas simples, observou-se que: (1) a cumarina 1 não apresentou atividade inibitória sobre a QLluc e sobre a QLlum; (2) as cumarinas 3, 4, 5 e 6 tiveram atividades inibitórias sobre a QLluc semelhantes à da quecetina, que foram maiores que as das cumarinas 2, 7 e 8; (3) as atividades inibitórias das cumarinas 2 a 8 sobre a QLluc não estão relacionadas à lipofilicidade e ao volume molecular desses compostos, nem à toxicidade dos mesmos sobre os neutrófilos de coelho; (4) as cumarinas 3 e 4 provocaram aumento da QLlum medida, enquanto as demais não tiveram atividade neste sistema. / Neutrophils play a crucial role in the defense of the organism against invading microorganisms, thorough phagocytosis, degranulation and generation of reactive oxygen species (EROS). The last one is a consequence of activation of neutrophils\' oxidative metabolism. The produced EROs, such as O2∙-, H2O2, HOCl, HO∙, 1O2 and NO, which are essential for killing phagocyted microorganisms, may also be released to the extracellular milieu and inflict oxidative damage to host tissues. This damage has been implicated in the pathogenesis of diseases, such as arteriosclerosis, cancer, rheumatoid arthritis, pneumonia and lung emphysema. The antioxidant activity of many compounds, especially those obtained from plants, has been investigated with the aim of avoid such oxidative damage. In this work, we studied the activity of eight simple coumarins (compounds 1 to 8) on the oxidative metabolism of rabbit neutrophils upon stimulation by opsonized zymosan, using luminol- (QLlum) and lucigenin (QLluc)-enhanced chemiluminescence (QL) assays. QLluc reflects generation of O2∙- only, whereas QLlum is a result of luminol oxidation by the various EROs produced by the stimulated neutrophils. Inhibition of QLluc and of QLlum will be a consequence of the decrease of the concentration of that EROs which are involved in the oxidation of lucigenin and luminol, respectively, in the reaction medium. We also evaluated the activity of the antioxidants a-tocopherol, butyl-hydroxytoluene (BHT) and quercetin on QLlum and QLluc, and the toxicity of coumarins 1 to 8 and the three antioxidants on rabbit neutrophils. Partition coefficient and molecular volume values of coumarins 1 to 8 were determined. We observed that, among the three antioxidants, quercetin inhibited QLlum and QLluc, and was not toxic to the neutrophils at concentration of 50 mmol/L. BHT was toxic to the rabbit neutrophils whereas a-tocopherol did not inhibit QLlum nor QLluc. For the simple coumarins we observed that: (1) coumarin 1 did not inhibit QLlum nor QLluc; (2) coumarins 3, 4, 5 and 6 had inhibitory effects, which were similar to the quercetin and higher than coumarins 2, 7 and 8; (3) the inhibitory activities of coumarins 2 to 8 on QLluc were not related to the lipophilicity and to the molecular volume of these compounds, nor to their toxicity upon the rabbit neutrophils; (4) coumarins 3 and 4 increased the QLlum, whereas the others had no effect on this system.

Os neutrófilos desempenham um papel fundamental na defesa do organismo contra microrganismos invasores, através da fagocitose, da degranulação e da produção de espécies reativas de oxigênio (EROs), sendo que esta última é decorrente da ativação do metabolismo oxidativo dos neutrófilos. As EROs produzidas, tais como O2∙-, H2O2, HO∙, HOCl, 1O2 e NO, que são essenciais para matar os microrganismos fagocitados, podem também ser liberadas para o meio extracelular e causar lesões oxidativas aos tecidos do hospedeiro. Essas lesões têm sido implicadas na patogênese de doenças como aterosclerose, câncer, artrite reumatóide, pneumonia e enfisema pulmonar. Com o intuito de prevenir essas lesões oxidativas, tem-se investigado a atividade antioxidante de diversos compostos, especialmente os derivados de plantas. Neste trabalho foram avaliadas as atividades de oito cumarinas simples (compostos 1 a 8) sobre o metabolismo oxidativo de neutrófilos de coelho estimulados com Zimosan opsonizado, empregando-se os ensaios de quimioluminescência (QL) dependente de lucigenina (QLluc) e de QL dependente de luminol (QLlum). A QLluc reflete a produção apenas de O2∙- , enquanto que a QLlum é resultante da oxidação do luminol pelas diversas EROs produzidas pelos neutrófilos estimulados. Assim, a inibição da QLluc e da QLlum será decorrente da redução da concentração das EROs responsáveis pela oxidação da lucigenina e do luminol no meio de reação, respectivamente. Foram avaliadas também a atividade dos antioxidantes a-tocoferol, butil-hidroxitolueno (BHT) e quercetina sobre a QLlum e a QLluc, e a toxicidade das cumarinas 1 a 8 e dos três antioxidantes citados sobre os neutrófilos de coelho. Determinou-se o coeficiente de partição e o volume molecular das cumarinas 1 a 8. Dentre os três antioxidantes, observou-se que a quercetina inibiu tanto a QLlum quanto a QLluc, e não foi tóxica para os neutrófilos, na concentração de 50 mmol/L. O a-tocoferol não inibiu a QLlum nem a QLluc, enquanto o BHT foi tóxico para os neutrófilos de coelho. Para as cumarinas simples, observou-se que: (1) a cumarina 1 não apresentou atividade inibitória sobre a QLluc e sobre a QLlum; (2) as cumarinas 3, 4, 5 e 6 tiveram atividades inibitórias sobre a QLluc semelhantes à da quecetina, que foram maiores que as das cumarinas 2, 7 e 8; (3) as atividades inibitórias das cumarinas 2 a 8 sobre a QLluc não estão relacionadas à lipofilicidade e ao volume molecular desses compostos, nem à toxicidade dos mesmos sobre os neutrófilos de coelho; (4) as cumarinas 3 e 4 provocaram aumento da QLlum medida, enquanto as demais não tiveram atividade neste sistema. / Neutrophils play a crucial role in the defense of the organism against invading microorganisms, thorough phagocytosis, degranulation and generation of reactive oxygen species (EROS). The last one is a consequence of activation of neutrophils\' oxidative metabolism. The produced EROs, such as O2∙-, H2O2, HOCl, HO∙, 1O2 and NO, which are essential for killing phagocyted microorganisms, may also be released to the extracellular milieu and inflict oxidative damage to host tissues. This damage has been implicated in the pathogenesis of diseases, such as arteriosclerosis, cancer, rheumatoid arthritis, pneumonia and lung emphysema. The antioxidant activity of many compounds, especially those obtained from plants, has been investigated with the aim of avoid such oxidative damage. In this work, we studied the activity of eight simple coumarins (compounds 1 to 8) on the oxidative metabolism of rabbit neutrophils upon stimulation by opsonized zymosan, using luminol- (QLlum) and lucigenin (QLluc)-enhanced chemiluminescence (QL) assays. QLluc reflects generation of O2∙- only, whereas QLlum is a result of luminol oxidation by the various EROs produced by the stimulated neutrophils. Inhibition of QLluc and of QLlum will be a consequence of the decrease of the concentration of that EROs which are involved in the oxidation of lucigenin and luminol, respectively, in the reaction medium. We also evaluated the activity of the antioxidants a-tocopherol, butyl-hydroxytoluene (BHT) and quercetin on QLlum and QLluc, and the toxicity of coumarins 1 to 8 and the three antioxidants on rabbit neutrophils. Partition coefficient and molecular volume values of coumarins 1 to 8 were determined. We observed that, among the three antioxidants, quercetin inhibited QLlum and QLluc, and was not toxic to the neutrophils at concentration of 50 mmol/L. BHT was toxic to the rabbit neutrophils whereas a-tocopherol did not inhibit QLlum nor QLluc. For the simple coumarins we observed that: (1) coumarin 1 did not inhibit QLlum nor QLluc; (2) coumarins 3, 4, 5 and 6 had inhibitory effects, which were similar to the quercetin and higher than coumarins 2, 7 and 8; (3) the inhibitory activities of coumarins 2 to 8 on QLluc were not related to the lipophilicity and to the molecular volume of these compounds, nor to their toxicity upon the rabbit neutrophils; (4) coumarins 3 and 4 increased the QLlum, whereas the others had no effect on this system.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The growing development of new technologies that look for the increase of the production and productivity generates several levels of environmental and social impact. In compensation, the exponential growth of the organics segment victuals comes happening by virtue of the consumers' growing concern with the quality of the victuals that consume. The objective of this work went evaluate the aspects of the production of organic vegetables in Sergipe, concerning the quality of the marketed products, processing alternatives and analysis of the sustainability of the organic system of production. The quality analysis of the organic products was accomplished by comparison with the same produced species in a conventional way, being accomplished physical-chemical analyses of the products that demonstrated that the organic victuals, in a general way, present little qualitative advantage when compared to the conventional ones. As an alternative for the aggregation of value, generation of income and minimization of the postharvest losses of the organic products, the minimum processing of the lettuce was accomplished (Lactuca sativa) organic and conventional, with modification of the atmosphere seeking the increase of the life of shelf of the product. Through physical-chemistries analyses, it was observed that organic lettuce minimally processed maintains for its more time nutritionals qualities when compared to the conventional lettuce, independent of the composition of the tested modified atmosphere. In the third stage of this work, were identified, in organic agroecossistemas of production, and with base in questionnaires applied to the organic producers of Sergipe, the indicators more adapted for the evaluation of the levels of ecological, agronomic, economic, partner-institutional sustainability and of alimentary safety that, it was shown important in the sense of generating subsidies for the taking of decisions, mainly of the public power, in the construction of actions gone back to the development of the organic agriculture in family farmers' areas. / O crescente desenvolvimento de novas tecnologias que buscam o aumento da produção e produtividade gera diversos níveis de impacto ambiental e social. Em contrapartida, o crescimento exponencial do segmento de alimentos orgânicos vem ocorrendo em virtude da crescente preocupação dos consumidores com a qualidade dos alimentos que consomem. O objetivo deste trabalho foi avaliar os aspectos da produção de hortaliças orgânicas em Sergipe, no tocante à qualidade dos produtos comercializados, alternativas de processamento e análise da sustentabilidade do sistema orgânico de produção. A análise da qualidade dos produtos orgânicos foi realizada por comparação com as mesmas espécies produzidas de forma convencional, sendo realizadas análises físicoquímicas dos produtos onde foi verificado que os alimentos orgânicos, de uma forma geral, apresentam pouca vantagem qualitativa quando comparados aos convencionais. Como uma alternativa para a agregação de valor, geração de renda e minimização das perdas pós-colheita dos produtos orgânicos, foi realizado o processamento mínimo da alface (Lactuca sativa), feita a comparação entre amostras produzidas em sistemas orgânico e convencional, com modificação da atmosfera visando o aumento da vida de prateleira do produto. Através de análises físico-químicas, observou-se que alface orgânica minimamente processada mantém por mais tempo suas qualidades nutricionais quando comparada à alface convencional, independente da composição da atmosfera modificada testada. Na terceira etapa deste trabalho, foram identificados, em agroecossistemas orgânicos de produção, e com base em questionários aplicados aos produtores orgânicos de Sergipe, os indicadores mais apropriados para a avaliação dos níveis de sustentabilidade ecológica, agronômica, econômica, sócio-institucional e de segurança alimentar que, mostrou-se importante no sentido de gerar subsídios para a tomada de decisões, principalmente do poder público, na construção de ações voltadas para o desenvolvimento da agricultura orgânica em áreas de agricultores familiares.

<p>  </p> <p>Vector-borne diseases (VBDs) represent a significant health burden worldwide, threatening approximately 80% of the global population. Insecticide-based vector control is the most effective method to manage many VBDs, but its efficacy has been declining due to high levels of resistance in vector populations to the main insecticide classes which operate via limited modes of action. Therefore, the discovery of new chemistries from non-conventional chemical classes and with novel modes of action is a priority for the control of vectors and VBDs. Natural products (NPs) are diverse in chemical structures and, potentially, modes of action. They have been used as insecticides for many decades and have inspired the development of multiple synthetic insecticides, suggesting the discovery of novel NPs could lead to the development of highly effective insecticides. </p> <p><br></p> <p>In this thesis, I report two studies with a main goal to identify novel mosquito-active insecticide leads that operate via modes of action distinct from existing insecticides. First, I tested the hypothesis that new mosquito-active insecticide leads with novel chemical structures, possibly operating via novel modes of action, can be identified by high-content larval phenotypic screening against a natural product collection and using novel phenotypic endpoints in addition to mortality endpoints. Here, I performed a high-content larval phenotypic screen using first instar (L1) larvae of <em>Aedes aegypti</em> (Linnaeus, 1762) against 3,680 compounds from the AnalytiCon MEGx Natural Product Libraries and a screening platform developed by Murgia et al., (2022). Compounds were screened in a 384-well plate format using the Perkin Elmer Opera Phenix and larvae were scored for lethal and novel phenotypic endpoints. Screening revealed five chemistries that caused larval mortality, including rotenone and a new NP chemistry, NP-4. The identification of rotenone confirmed the ability of the screen to detect mosquito-active NP chemistries. NP-4 caused high levels of larval mortality in the screen, and toxicity was confirmed in a subsequent concentration-response assay against third instar (L3) larvae of <em>Ae. aegypti</em>. 140 chemistries that caused atypical larval phenotypes, including cuticular pigmentation and morphometric changes relative to negative controls, were also identified by the screen. Some of these chemistries may operate by disruption of pathways regulating melanization, growth and development, and novel targets in the insect nervous systems, thus representing potential leads for further insecticide toxicity and mode of action studies. To facilitate quantitative analyses of atypical phenotypes, an attempt was made to assess the morphometrics of the thorax in larvae exposed to test chemistry, relative to control larvae. However, assessment was limited by the number of larvae images of suitable quality for measurements. </p> <p><br></p> <p>In the second study, I tested the hypothesis that metergoline (Murgia et al., 2022) and NP-4 (this study), two chemistries identified by the HTP phenotypic screen described in this project, operate via disruption of targets in the insect nervous systems that are distinct from the current insecticidal modes of products used in mosquito control programs. Specifically, I explored the hypothesis that metergoline operates via one or more insect orthologs of the mammalian G protein-coupled serotonin and dopamine receptors. An electrophysiology study was performed using the suction electrode technique and ganglia of the German cockroach, <em>Blattella germanica </em>(Linnaeus, 1767). To facilitate the investigation of metergoline agonism/antagonism and disruption of invertebrate GPCR signaling, 5-hydroxytryptamine (5-HT; serotonin) was included as a chemical probe. Electrophysiological recordings showed 5-HT (10µM and 1mM) and metergoline (10µM) caused no significant neurological activity at the tested concentrations in comparison to the saline control. However, a consistent neuro-inhibitory trend was observed, suggesting possible agonism of a 5-HT1-like receptor ortholog and antagonism of a putative 5-HT7-like receptor ortholog in the cockroach, respectively.  NP-4 caused significant neuro-inhibition at the tested concentration of 20µM, in comparison to the negative saline control. Given the demonstration of rapid contact toxicity to <em>Ae. aegypti</em> larvae and neurological inhibition in <em>B. germanica</em>, we propose NP-4 may act at one or more conserved targets in the insect nervous systems, which remain to be elucidated. </p> <p><br></p> <p>The significance of the present study is three-fold. First, this study reports the first high-content phenotypic screen of mosquito larvae against a NP collection and identification of 145 mosquito-active chemistries associated with lethal and phenotypic endpoints. These data confirm that the screening platform provided an innovative and effective system to rapidly identify mosquito-active small molecules with potential novel modes of action. Second, metergoline and NP-4 represent potential novel chemical leads for the development of new insecticides that can be incorporated into vector control programs targeting insecticide-resistant populations. Lastly, the study describes the first electrophysiology study of 5-HT, metergoline, and NP-4 via the suction electrode technique in an insect system and contributes new knowledge to the study of the insect serotonergic system, which represents an expanding area of vector biology research given its roles in feeding regulation.  </p> <p><br></p> <p>Future studies resulting from this thesis might include: (1) development of a set of morphometric criteria for quantitative analyses of atypical larval phenotypes, (2) incorporation of new phenotypic endpoints to expand the capacity of the screen to identify novel mode of action chemistries for insecticide discovery, and (3) identification of chemistry candidates suitable for further development from the 140 chemistries associated with atypical larval phenotypes in the primary screen using chemo-informatic and toxicological studies. In addition, studies using reverse transcription-polymerase chain reaction (RT-PCR), cell-based expression systems, mutant/insecticide resistant strains, and patch clamp electrophysiology could be pursued to further investigate the molecular mode of action of metergoline and NP-4, and potential for vector control.</p>