Specific aspects of the selective sequestration, excretion and tolerance of cardenolides in the large milkweed bug, Oncopeltus fasciatus have been studied using spectrophotometry assays, thin-layer chromatography, tracer studies, in vivo tolerance assays, and enzyme inhibition techniques. The cardenolide content of the dorsolateral space, gut, wings and fat body of Oncopeltus fasciatus was examined. The results indicate that the majority of cardenolides sequestered in the insect are concentrated in the dorsolateral space, which confirms the basic pattern of quantitative distribution of cardenolides in O. fasciatus determined in earlier work. Large amounts of cardenolides were not found in the gut, wings and fat body. The female fat body contained 4-5% of the total cardenolide content of the insect. The cardenolide content of male fat body, and gut and wings of both sexes was below the detection limit of the cardenolide assay. Thin-layer chromatography was used to determine the cardenolide array of various tissues and secretions of O. fasciatus reared on seeds of a single species of milkweed (A. speciosa) and adult extracts and dorsolateral space fluid of O. fasciatus reared on seeds of two species of milkweed with different cardenolide arrays (A. speciosa and A. syriaca). The results indicate that cardenolides are not sequestered in the insect simply on the basis of polarity and that metabolism and differential excretion of cardenolides are involved in the sequestration of cardenolides in O. fasciatus.. The similarities in the cardenolide profiles of O. fasciatus reared on different food sources, and tissues of O. fasciatus reared on a single food source indicates that there is regulation of the cardenolide array in O. fasciatus. An in vitro preparation of Malpighian tubules was used to investigate the excretion of the polar cardenolide, ouabain, in O. fasciatus. Both segments of the tubules were found to metabolize ouabain. The distal Segment (Segment II) secreted primary urine and ouabain. Secretion of ouabain by Segment II was not observed to occur against a concentration gradient and increased with increasing fluid secretion. The proximal segment (Segment I) reabsorbed fluid and ouabain but not metabolites of ouabain. Ouabain was reabsorbed against a strong concentration gradient (23-fold), was independent of fluid reabsorption, and increased with increasing fluid secretion by Segment II. In rapidly secreting Malpighian tubules (a situation of high cardenolide secretion by Segment II), the presence of Segment I reduced the excretion of ouabain by 84 - 93%, mainly by reducing ouabain concentration. It appears excretory loss of cardenolides can be reduced in O. fasciatus and thus may be a factor in the sequestration of cardenolides in this insect. O. fasciatus tolerated 1954x and 7288x, respectively, the LD₅₀ ouabain dose of Schistocerca gregaria and Periplaneta americana when ouabain was injected into the hemocoel of these insects. The maximum ouabain dose that could be injected into 0. fasciatus (200 nmoles) resulted in no mortality; this dose is higher than the lethal ouabain doses recorded for vertebrates and invertebrates. The ouabain concentration resulting in 50% inhibition (I₅₀) of Na,K-ATPase activity was determined in lyophilates of nervous tissue of 0. fasciatus and brain and recta of S. gregaria and were 2.0 x 10⁻⁴, 2.0 x 10⁻⁶, and 1.0 x 10⁻⁶ M, respectively. The I₅₀ value for ouabain inhibition of Na,K-ATPase activity in the nervous tissue of O. fasciatus is higher than the I₅₀ values for nervous tissue in most other insects as well as many other invertebrate and vertebrate tissues. Thus, the presence of ouabain resistant Na,K-ATPases appears to be a factor in the tolerance and sequestration of plant cardenolides in O. fasciatus. / Science, Faculty of / Zoology, Department of / Graduate

Vinigrol was isolated in 1987 from the fungal strain Virgaria nigra F-5408 by Hashimoto and co-workers. This compound was identified as having antihypertensive and platelet aggregation properties as well as being recognized as a tumor necrosis factor inhibitor. Aside from its interesting biological activities, vinigrol also possesses a unique structural motif consisting in a decahydro-1,5-butanonaphthalene core decorated with 8 contiguous stereocenters. Despite synthetic efforts by many research groups since its isolation, it wasn’t until 2009 that the first total synthesis of vinigrol was reported by Baran and co-workers. Herein is presented a formal synthesis of this highly compact molecule which relies upon a highly diastereoselective ketal Claisen rearrangement as the stereodefining step and an intramolecular Diels-Alder reaction to access the tricyclic structure of the molecule. (+)-Digitoxigenin is a cardiac glycoside used in the treatment of many ailments such as congestive heart failure. It is a member of the cardenolides, a sub-type of steroid containing certain structural differences such as cis A/B and C/D ring junctions, a tertiary hydroxyl group at C14 and a butenolide substituent at C17. Although a few syntheses of this class of compounds have been reported, general strategies to access their framework is scarce. Herein we report our studies towards the total synthesis of digitoxigenin which rely upon a cascading gold-catalyzed cycloisomerization (or enyne metathesis)/Diels-Alder reaction.

Vinigrol was isolated in 1987 from the fungal strain Virgaria nigra F-5408 by Hashimoto and co-workers. This compound was identified as having antihypertensive and platelet aggregation properties as well as being recognized as a tumor necrosis factor inhibitor. Aside from its interesting biological activities, vinigrol also possesses a unique structural motif consisting in a decahydro-1,5-butanonaphthalene core decorated with 8 contiguous stereocenters. Despite synthetic efforts by many research groups since its isolation, it wasn’t until 2009 that the first total synthesis of vinigrol was reported by Baran and co-workers. Herein is presented a formal synthesis of this highly compact molecule which relies upon a highly diastereoselective ketal Claisen rearrangement as the stereodefining step and an intramolecular Diels-Alder reaction to access the tricyclic structure of the molecule. (+)-Digitoxigenin is a cardiac glycoside used in the treatment of many ailments such as congestive heart failure. It is a member of the cardenolides, a sub-type of steroid containing certain structural differences such as cis A/B and C/D ring junctions, a tertiary hydroxyl group at C14 and a butenolide substituent at C17. Although a few syntheses of this class of compounds have been reported, general strategies to access their framework is scarce. Herein we report our studies towards the total synthesis of digitoxigenin which rely upon a cascading gold-catalyzed cycloisomerization (or enyne metathesis)/Diels-Alder reaction.

Vinigrol was isolated in 1987 from the fungal strain Virgaria nigra F-5408 by Hashimoto and co-workers. This compound was identified as having antihypertensive and platelet aggregation properties as well as being recognized as a tumor necrosis factor inhibitor. Aside from its interesting biological activities, vinigrol also possesses a unique structural motif consisting in a decahydro-1,5-butanonaphthalene core decorated with 8 contiguous stereocenters. Despite synthetic efforts by many research groups since its isolation, it wasn’t until 2009 that the first total synthesis of vinigrol was reported by Baran and co-workers. Herein is presented a formal synthesis of this highly compact molecule which relies upon a highly diastereoselective ketal Claisen rearrangement as the stereodefining step and an intramolecular Diels-Alder reaction to access the tricyclic structure of the molecule. (+)-Digitoxigenin is a cardiac glycoside used in the treatment of many ailments such as congestive heart failure. It is a member of the cardenolides, a sub-type of steroid containing certain structural differences such as cis A/B and C/D ring junctions, a tertiary hydroxyl group at C14 and a butenolide substituent at C17. Although a few syntheses of this class of compounds have been reported, general strategies to access their framework is scarce. Herein we report our studies towards the total synthesis of digitoxigenin which rely upon a cascading gold-catalyzed cycloisomerization (or enyne metathesis)/Diels-Alder reaction.

Maternal effects are the non-genetic contributions of mothers (or fathers) towards the phenotype of their offspring. Maternal effects are now well recognised as a facilitator for evolutionary change in offspring phenotypes and life history strategies which can have effects on population dynamics, population divergence and even speciation. Furthermore, maternal effects have been shown to have a heritable genetic basis and that they are genetically variable, which suggests that they contribute to maintaining phenotypic variation. Maternal effects may impede or accelerate responses to selection which has implications for adaptive evolution and making predictions about their evolutionary potential. The importance of their contribution to phenotypic variation and life history evolution has made maternal effects an important consideration in fields such as conservation and population biology, evolutionary ecology and evolutionary genetics. The aim of this thesis is to investigate if maternal effects can influence offspring life history traits and fitness parameters through maternal resources via the egg. Main questions that are asked include: can maternal effects help facilitate transition to a novel host-diet (Chapter 2); does maternal diet influence egg composition and, if so, does this have an effect on offspring life-history parameters (Chapter 3); is there a genetic basis to egg composition and is there potential for egg composition to evolve (Chapter 4); and are defensive compounds from the diet transferred into the eggs, if so, are these uni- or biparentally transferred and does this offer protection against predation (Chapter 5)? To address these questions we used a specialist insect herbivore, the large milkweed bug Oncopeltus fasciatus (Hemiptera: Lygaeidae). In the wild, O. fasciatus feed on plants from the genus Asclepias (Apocynacea). However, O. fasciatus can be reared successfully in laboratories on sunflower seeds Helianthus annus. For our experiments we used two populations of O. fasciatus, one population has been maintained on dry seeds of A. syriaca while the other population has been reared and maintained on sunflower seeds. The results of Chapter 2 were suggestive of a maternal host-diet effect on egg mass and hatching success, but we did not find evidence that maternal host-diet was significant in influencing a transition to a novel host. In Chapter 3 we found that there was variation in the free amino acid profiles of the eggs between our treatments suggesting that amino acid profiles may be influenced by maternal diet. The results of our multivariate selection analysis to examine linear and nonlinear (quadratic) relationships between maternal diet and the free amino acid profiles of the eggs suggest that there may be population-specific responses which can influence specific amino acid profiles in relation to hatchling mass. In Chapter 4 we used only the milkweed-adapted population to determine if there was a genetic basis to amino acid profiles in the eggs. We constructed a genetic variance-covariance (G) matrix to determine the strength and direction of the relationships between amino acids and to assess the potential for amino acid profiles to evolve. While we found genetic variation for amino acids, and that there was evidence for positive moderate to strong genetic correlations between many of them, we also found evidence for constraints for the potential for amino acid profiles to evolve as evidenced by the calculation of gmax (which represents the linear combination of components that has the highest genetic variance and which is the most accessible to evolution). In Chapter 5 we found maternal, but not paternal, transmission of cardenolides into the eggs. However, this did not confer protection of all eggs against predation from larvae of the green lacewing Chrysoperla carnea. Overall, results suggest that for our populations of O. fasciatus, maternal effects are significant in influencing early life history traits such as egg mass and hatchling mass. However, we did not find any significant effects on other offspring life history or fitness parameters that we measured. This may be surprising as positive, and negative, effects of non-genetic contributions of females (and males) to their offspring has been widely reported in many taxa. The patterns and implications of maternal resource allocation and their effects on offspring life history evolution are explored and discussed, as are the limitations of our experimental designs. I hope that this research can be used to stimulate further investigations into maternal effects and the relationships between host-plant, maternal allocation strategies and life history evolution.

Les intoxications ayant pour cause la prise de toxiques végétaux sont relativement fréquentes. Ces intoxications font suites à une ingestion accidentelle ou volontaire (aliments contaminés, préparations à but « thérapeutique », acte suicidaire, .). Le nombre de ces intoxications est sous-estimé car les signes cliniques sont souvent non spécifiques et les médecins méconnaissent la dangerosité des composés présents et l'incidence des intoxications par les plantes. La sous-estimation du nombre d'intoxications est également liée au manque de méthodes analytiques développées spécifiquement pour la détermination de ces toxines. Enfin de nombreuses molécules restent, à l'heure actuelle, indétectables avec les outils analytiques disponibles. L'objectif de cette thèse était de mettre en lumière l'implication des plantes en toxicologie médico- légale et de proposer des méthodes analytiques pour des composés qui, jusqu'alors, n'étaient pas disponibles. Nous avons développé un screening en CLHP-SM/SM et en CLHP-HRSM/SM pour l'analyse du plus grand nombre de phytotoxines simultanément dans des prélèvements biologiques. Ces méthodes ont été éprouvées par plusieurs cas réels d'intoxication. Nous avons développé la première méthode d'analyse toxicologique de l'hypoglycine A, de l'atractyloside et du carboxyatractyloside applicable en médecine légale. Nous avons enfin approfondi la connaissance des principes toxiques du faux manguier. L'ensemble de ce travail confirme l'importance de l'analyse toxicologique des phytotoxines en médecine légale. Les travaux réalisés ont permis d'approfondir les connaissances sur les toxiques végétaux et de combler certaines lacunes analytiques / Plant poisonings are relatively common. They are caused by accidental or voluntary ingestion (contaminated food, "therapeutic" preparations, suicide attempts.). The number of such poisonings is underestimated, since the clinical signs are often non- specific and doctors are unaware of the incidence of plant poisonings or of the dangerous nature of the compounds present. The lack of analytical methods developed specifically to determine these toxins is another factor in the underestimation of the number of plant poisonings. Furthermore, many molecules are still undetectable with the analytical tools currently available. The aim of this thesis was to highlight the part played by plants in forensic toxicology, and to propose analytical methods for compounds, which up to now had not been available. We have developed a screening method in HPLC-MS/MS and HPLC-HRMS/MS for analysing the highest number of phytotoxins simultaneously in biological samples. The methods were tested on several real poisoning cases. We developed the first toxicological analysis method applicable in forensic medicine for hypoglycin A, atractyloside and carboxyatractyloside. We then deepened our knowledge of the toxic principles of the sea mango. This work, as a whole, confirms the importance of toxicological analysis of phytotoxins in forensic medicine. The work carried out enabled us to improve our knowledge of plant poisons and to fill some analytical gaps

La pompe à sodium, la Na+/K+-ATPase, est un échangeur ionique transmembranaire impliqué dans le maintien de l’homéostasie ionique. Elle est principalement constituée de deux sous-unités, la sous-unité alpha, qui correspond au site catalytique de la pompe, et la sous-unité beta qui régule son activité. <p>La sous-unité alpha de la pompe à sodium possède un site de fixation pour les stéroïdes cardiotoniques, molécules bien connues pour leur utilisation dans le traitement des décompensations cardiaques sévères et des arythmies auriculaires. Les stéroïdes cardiotoniques peuvent être subdivisés en deux groupes, les cardénolides et les bufadiénolides.<p>Diverses études épidémiologiques ont mis en évidence l’activité anticancéreuse des stéroïdes cardiotoniques. En effet, lorsque l’on compare le risque de développement d’un cancer, la mortalité liée au cancer ainsi que le taux de récidive d’un cancer du sein ou d’un cancer prostatique chez les patients traités par de la digoxine dans le cadre de leur traitement cardiaque et les patients non traités, on observe un réel bénéfice des stéroïdes cardiotoniques.<p>Il a déjà été démontré que la pompe à sodium, en plus de sa fonction d’échangeur ionique, possède un rôle central dans de nombreux mécanismes de signalisation cellulaire, impliquant notamment les processus de migration, d’invasion et de mort cellulaire. <p>De plus, de nombreux cancers au pronostic sombre présentent des altérations dans l’expression des sous-unités alpha de la pompe à sodium. C’est le cas par exemple des cancers pulmonaires non à petites cellules (NSCLC), des gliomes, des mélanomes et des cancers rénaux qui surexpriment la sous-unité & / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished