Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Use-dependent long-term plasticity in synaptic connections represents the cellular substrate for learning and memory. The hippocampus is the most thoroughly investigated brain area for long-term synaptic plasticity, long-term potentiation (LTP) and long-term depression (LTD) are both well characterized in glutamatergic excitatory connections between hippocampal principal cells in vitro and in vivo. An increasing number of studies based on acute brain slice preparations report LTP and LTD in excitatory synapses onto postsynaptic hippocampal GABAergic inhibitory interneurons. However, a systematic study of activity-induced long-term plasticity in excitatory synaptic connections to inhibitory GABAergic interneurons in vivo is missing. To determine whether LTP and LTD occur in excitatory synaptic connections to the hippocampal CA1 area GABAergic interneurons types in intact brain, I have used juxtacellular recording to measure synaptically evoked short-delay postsynaptic action potential probability in identified CA1 neurons in the urethane-anaesthetized rats. Plasticity in excitatory synaptic connections to CA1 cell types was measured as a change of afferent pathway stimulation-evoked postsynaptic spike probability and delay. In the study only experiments with monosynaptic-like short-delay (range 3-12 ms) postsynaptic spikes phase-locked to afferent stimulation were used. Afferent fibres were stimulated from the CA1 area of the hippocampus at the contralateral (left) side to avoid simultaneous monosynaptic activation of GABAergic fibres and to exclude antidromic spikes in recorded CA1 cells (in right hemisphere). Plasticity in pathways was tested using theta-burst high-frequency stimulation (TBS, 100 pulses), which is one of the most common synaptic plasticity induction protocols in acute brain slice studies. I discovered that TBS elicited permanent potentiation in single shock-evoked postsynaptic spike probability with shortening or no change in evoked spike latency in various postsynaptic neuron types including three identified pyramidal cells and parvalbumin-expressing (PV+) interneurons. Most fast-spiking PV+ cells showed LTP including an axo-axonic cell and one bistratified cell, whereas two identified basket cells exhibited LTD in similar experimental conditions. In addition, I discovered diverse plasticity in non-fast spiking interneurons, reporting LTP in an ivy cell, and LTD in three incompletely identified regular-spiking CA1 interneurons. I report that the underlying brain state, defined as theta oscillation (3-6 Hz) or non-theta in local field potential, failed to explain whether LTP, LTD or no plasticity was generated in interneurons. The results show that activity-induced potentiation and depression similar to LTP and LTD also occur in excitatory synaptic pathways to various CA1 interneurons types in vivo. I propose that long-term plasticity in excitatory connections to inhibitory interneurons may be take place in learning and memory processes in the hippocampus.

Master of Science / Department of Electrical and Computer Engineering / Punit Prakash / Microwave ablation is a minimally invasive therapeutic modality used for the treatment of cancer in various organs. In this procedure, microwave energy is sent through a thin antenna placed inside the tumor. The microwave energy radiated from the antenna generates heat which kills the tumor cells by necrosis. During multiple-applicator microwave ablation, geometric estimates of treatment outcome are typically obtained by assuming parallel insertion of the applicators. This assumption is based on the guidelines provided in the brochures of antenna manufacturing companies. This assumption is flawed because it is rare to insert the antennas in parallel configuration due to the flexible nature of the antennas and the presence of intervening organs. Furthermore, movement of patients during the treatment procedure alters the position of the antennas. In order to see the effect of non-parallel insertion of antennas, model-based treatment planning may be instructive. Treatment planning can also determine the changes needed to be made for prospective ablation therapy if the antennas are not positioned in their ideal parallel configuration. This thesis provides a detailed computational comparison of the skewed configurations of microwave antennas to their closest parallel configurations. The metric used for com-paring the similarity between the cases is Dice Similarity Coefficient (DSC). Experimental results to validate the computational data are also discussed. Computations were done by using realistic cases of antenna positions obtained from Rhode Island Hospital.

Das fakultativ intrazelluläre Bakterium Legionella pneumophila wurde erstmals 1977 als Erreger der Legionellose, einer schweren atypisch verlaufenden Pneumonie identifiziert. Es besitzt ein duales Wirtssystem und kann sich sowohl in aquatischen Habitaten in Protozoen als auch in phagozytierenden Humanzellen als Pathogen vermehren. Zur Analyse der komplexen Interaktion zwischen Pathogen und Wirtszelle wurde in dieser Arbeit ein GFP (Green Fluorescent Protein)-Reportersystem etabliert und erfolgreich eingesetzt. Es erlaubt ein in vivo Monitoring von Legionella Infektionen und ermöglicht die schnelle Quantifizierung bakterieller Invasion in Wirtszellen in Abhängigkeit von verschiedenen Faktoren. Zur Etablierung der GFP-vermittelten Fluoreszenz wurde eine transkriptionelle Fusion des gfpmut2-Gens mit dem Legionella spezifischen mip ("macrophage infectivity potentiator")-Promoter (Pmip) konstruiert. Zusätzlich wurde ein Vektor mit dem von Listeria stammenden sod ("super oxid dismutase")-Promoter eingesetzt. Mit diesen Vektoren transformierte Legionella-Stämme zeigten nach entsprechender Anregung eine starke Grünfluoreszenz und belegen somit erstmals die Funktionalität von GFP in Legionella. Durch den Einsatz von Fluoreszenzmikroskopie, Spektrofluorimetrie und Durchflusszytometrie (FACS-Analyse) wurden die Stämme hinsichtlich der Unterschiede in der Virulenz und der intrazellulären Vermehrung untersucht. Ergebnisse, die durch die zeitaufwendige Bestimmung von CFU-Werten ermittelt wurden, konnten verifiziert und damit die Validität des GFP-Reportersystems in Legionella bestätigt werden. Quantitative Analysen der mip-Promoteraktivität belegen die konstitutive Expression und zeigen, dass Unterschiede in der Virulenz nicht auf variierende mip-Promoteraktivität zurückzuführen sind. Darüber hinaus konnte der Einfluss verschiedener Phagozytose-Inhibitoren auf die Aufnahme von Legionellen in die Protozoenwirte Acanthamoeba castellanii und Hartmannella vermiformis mittels des GFP-Reportersystems quantifiziert und qualitativ bewertet werden. Durch die Verwendung des Inhibitors Cytochalasin D konnte ein Einfluss Mikrofilament-abhängiger Phagozytose auf die Aufnahme in H. vermiformis und A. castellanii ausgeschlossen werden. Wie in Inhibitionsstudien mit Cycloheximid und Methylamin bestätigt werden konnte, erfolgt die Phagozytose in H. vermiformis wahrscheinlich vorwiegend über Rezeptor-vermittelte-Endozytose. Dem Protozoenwirt A. castellanii stehen dagegen zusätzliche Möglichkeiten der bakteriellen Internalisierung zur Verfügung. Diese Ergebnisse bestätigen die postulierte Heterogenität der Aufnahme-Mechanismen innerhalb verschiedener Protozoenwirte. Nach erfolgter Phagozytose von L. pneumophila wird der endosomale Weg der Phagolysosom- Reifung blockiert, hierfür wird die Sekretion bislang unbekannter Effektoren verantwortlich gemacht. Durch die Konstruktion von C-terminalen Mip::GFP-Fusionsproteinen sollte die Detektion einer eventuellen Translokation des Mip-Proteins als Virulenzfaktor innerhalb der Wirtszelle ermöglicht werden. Die erzeugten Fusionsproteine waren wahrscheinlich aufgrund der homodimeren Mip-Struktur instabil und wurden nicht über die Cytoplasmamembran hinweg transportiert. Sie erwiesen sich daher als nicht geeignet, dieser Fragestellung weiter nachzugehen. Da die in vivo Funktion von PPIasen (Peptidyl-Prolyl-cis/trans-Isomerasen) wie dem Mip-Protein in Prokaryoten bis heute weitgehend unbekannt ist, sollte im zweiten Teil dieser Arbeit versucht werden, einen Interaktionspartner zu identifizieren und den Einfluss der Dimerisierung und der PPIase-Aktivität des Mip-Proteins auf die Virulenz von L. pneumophila zu untersuchen. Durch Quervernetzung-Experimente konnte ein putativer, prokaryotischer Interaktionspartner des Legionella Mip-Proteins detektiert werden. Die N-terminale Aminosäure-Sequenzierung ergab jedoch keinerlei Homologie zu bereits bekannten Legionella- oder anderen Proteinen. Es kann nicht ausgeschlossen werden, dass eine N-terminale Blockierung die Aufklärung der Sequenz ursächlich verhindert. Wie in früheren Arbeiten gezeigt wurde, ist die PPIase-Aktivität des Legionella Mip-Proteins für die Invasion und das intrazelluläre Überleben in Protozoen, Monozyten und der Makrophagen-ähnlichen Zelllinie U937 nicht notwendig. Ein weiteres Charakteristikum des Proteins ist seine homodimere Struktur und die Assoziation mit der äußeren Membran. In Kooperation mit der Arbeitsgruppe von Prof. Dr. G. Fischer in Halle konnte durch Deletion der N-terminalen Domäne (AS 4-79) ein verkürztes Dimer-defizientes Legionella Mip-Protein (L.p.FKBP-20-3, 80-213) erzeugt und biochemisch charakterisiert werden. Durch site-spezifische Mutagenese N-terminal lokalisierter Aminosäuren (K11A/D32A, Y16A/D32A und M38,42E) konnte deren Beteiligung an der Dimerisierung nachgewiesen werden. Zur Analyse des Einflusses der dimeren Ouartärstruktur auf die Pathogenität wurde ein mip-negativer Stamm mit dem nur noch als Monomer vorliegenden Mip-Protein (L.p.FKBP-20-3, 80-213) in cis komplementiert und die Expression sowie Integration in L. pneumophila PhilI JR32-2.4 verifiziert. Ergebnisse aus Infektionsstudien zeigten deutlich, dass die Dimerisierung des Legionella Mip-Proteins und nicht die Isomerase-Aktivität für die Infektion von monozellulären Systemen entscheidend ist. Im Gegensatz dazu konnte in Tierexprimenten (Meerschweinchen) die Beteiligung der Isomerase-Aktivität an der Pathogenität von L. pneumophila nachgewiesen werden. Der Verlust der Isomerase-Aktivität wirkt sich, verglichen mit dem monozellulären System (A. castellanii), im Tiermodel wesentlich dramatischer auf das intrazelluläre Überleben aus. Mit site-spezifisch verändertem Mip-Protein komplementierte Legionella-Stämme zeigten eine intrazelluläre Vermehrung in Abhängigkeit der gemessenen in vitro Isomerase-Restaktivität. Durch den Einsatz der dimerisierungsdefizienten Mip-Komplementante, L. pneumophila PhilI JR32-2.4, wurde die Notwendigkeit der Dimerisierung des Mip-Proteins auch im Tiermodell bestätigt. Durch die vorliegende Arbeit konnte gezeigt werden, dass die Funktion der Isomerase-Aktivität für die Infektion monozellulärer Systeme und höherer Organismen unterschiedlich ist. / The facultative intracellular bacterium Legionella pneumophila was first identified in 1977 as the etiologic agent of legionellosis, a severe and atypical pneumonia. It possesses a dual host system which allows the bacteria to replicate in protozoa in aquatic habitats as well as a pathogen in human phagocytic cells. In order to analyze the complex interaction of the bacterial pathogen and its host cells, in this thesis a new GFP reporter system was established and sussessfully evaluated. It is now possible to monitor a Legionella infection in vivo and to quantify bacterial invasion influenced by different factors in a more convenient way. To analyze GFP expression in Legionella a transcriptional fusion of the gfpmut2 gene with the Legionella-specific mip (macrophage infectivity potentiator) promoter was constructed. In addition, a vector habouring the sod (super oxid dimutase) promoter derived from Listeria monocytogenes was used. Following transformation into Legionella strains strong GFP-mediated fluorescence was detected confirming the functionality of GFP in Legionella for the first time. Using fluorescence microscopy, spectrofluorimetry and flow cytometry (FACS-analysis) the strains were examined regarding differences in virulence and intracellular replication. Re-confirming results from earlier studies obtained by using enumeration of CFU values showed the validity of the method. Quantification of the mip promoter activity revealed a constitutively expression, this indicates that differences in Legionella virulene are not due to variations in mip promoter activity. Moreover, the influence of different phagocytosis inhibitors on Legionella uptake into the protozoan hosts Acanthamoeba castellanii and Hartmannella vermiformis using the GFP reporter system was examined. Application of cytochalasin D had no influence on bacterial uptake in A. castellanii and H. vermiformis suggesting in microfilament-independent mechanism. Phagocytosis in H. vermiformis is mainly accomplished using receptor-mediated phagocytosis as it was evident from inhibition studies with cycloheximide and methylamine. In contrast, phagocytosis in A. castellanii is mediated by other receptors or additional mechanisms are available. This results confirm the proposed heterogeneity of uptake mechanisms by different protozoan hosts. After L. pneumophila is phagocytosed the endosomal pathway of phagosome maturation is blocked, by means of secreted but as yet unidentified effector molecules. To study a putative protein translocation C-terminal Mip::GFP fusion proteins were constructed. The stability of the proteins was rather weak which is likely due to the dimeric conformational state of the Mip protein. In addition, transport over the cytoplasmic membran was not accomplished. Therefore the fusion proteins proved not to be useful for examine translocational events. Because of the unknown in vivo function of bacterial PPIases the focus in the the second part of this work was to identify a putative interaction partner of the Mip protein and to elucidate the influence of dimerization and PPIase activity on Legionella's virulence. Using cross linking experiments a putative interaction partner could be detected. N-terminal sequencing revealed no homology to already known Legionella or other proteins. N-terminal blockade of the putative partner molecule may be the cause that hampered sequence identification. It has been shown that the isomerase activity of the Legionella Mip protein is not necessary for invasion and intracellular survival in protozoan, monocytes and U937 macrophages. Additional features of the protein are its homodimeric conformational state and the assoziation with the outer membrane. In cooperation with the group of Prof. Dr. G. Fischer in Halle a N-terminal truncated (aa 4-79) dimerization-deficient Mip protein (L.p.FKBP25-20-3, 80-213) was constructed and biochemically characterized. Using site specific mutagenesis participation of the N-terminal located amino acids (K11A/D32A, Y16A/D32A und M38,42E) in the dimerization of the Mip protein was confirmed. To analyze the influence on pathogenicity of the dimeric state of the Mip protein a mip negative strain was complemented by providing the gene encoding the monomeric Mip (L.p.FKBP25-20-3, 80-213) in cis. The proper integration and protein expression was confirmed. The results demonstrate that the isomerase activity is dispensable for intracellular growth in protozoan hosts. Moreover, the results clearly demonstrated that dimerization and not the isomearse activity are essential for virulence of Legionella in a monocellular system. In contrast, it could be shown that the isomerase activity is necessary for full virulence in the animal model (guinea pigs). The loss of the isomerase avtivity have a more dramatic impact on the intracellular survival of Legionella compared to the monocellular system (A. castellanii). Moreover, Legionella strains replicated intracellulary dependent on their remaining in vitro isomerase activity. Using the monomeric Mip expressing strain L.p.JR32-2.4 it could be demonstrated that dimerization also plays a role in the animal model. This work provides evidence for a different role of the isomerase activity of the Mip protein in monocellular systems and during the infection of higher organisms.

Orientador: Roberto Sartori Filho / Banca: João Carlos Pinheiro Ferreira / Banca: Margot Alves Nunes Dode / Resumo: Objetivou-se com o presente estudo avaliar a criotorerância de mórulas e blastocistos produzidos in vivo de doadoras da raça Sindi e Nelore (Bos indicus) e Holandês Preto e Branco (HPB - Bos taurus). No Experimento 1, 24 fêmeas lactantes e não lactantes da raça Sindi foram superovuladas com 100 mg de FSH suíno com protocolos em que as duas últimas aplicações de FSH foram substituídas ou não por 300 UI de eCG. Sete dias após a indução da ovulação, os embriões foram colhidos e avaliados quanto ao estágio de desenvolvimento embrionário e grau de qualidade. Dois terços dos embriões foram destinados à criopreservação, dos quais metade foi congelada pelo método convencional, com curva de resfriamento de -0,5ºC/min e a outra metade foi vitrificada pela técnica de Cryotop. Em seguida, foram descongelados e transferidos para receptoras sincronizadas, de maneira contemporânea aos embriões frescos. No Experimento 2, 31 fêmeas da raça Nelore foram superovuladas com 133 mg de FSH suíno e os dois terços dos embriões colhidos foram criopreservados e transferidos semelhantemente ao Experimento 1. No Experimento 3, 67 vacas lactantes e novilhas da raça HPB foram superovuladas com 500 e 300 UI de FSH suíno, respectivamente, e após a colheita dos embriões foram adotados os mesmos procedimentos realizados nos Experimentos 1 e 2. Os resultados foram analisados por modelos lineares generalizados e estão apresentados na forma de média dos quadrados mínimos ± erro padrão. Nos Experimentos 1 e 2, os embriões transferidos a fresco apresentaram maior taxa de concepção aos 30 dias do que os vitrificados e congelados (54,8±7,4a, 17,7±7,3b e 19,5±6,6%b; respectivamente; P 0,0013) na raça Sindi (n=231 embriões) e (46,0±6,1a; 31,2±5,4b e 28,1±5,3%b; respectivamente, P 0,04) na raça Nelore (n=297 embriões). O estágio de desenvolvimento embrionário parece não... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this study was to evaluate the cryotolerance of morulae and blastocysts produced in vivo in Sindhi and Nelore (Bos indicus) and Holstein (Bos taurus) donnors. In Experiment 1, 24 lactating and non-lactating Sindhi donnors were superovulated with 100 mg porcine FSH with protocols in which the last two FSH treatments were replaced or not by 300 IU eCG. Embryos were collected 7 days after ovulation induction and embryo development and quality degree were accessed. Two thirds of the embryos were cryopreserved, by the conventional freezing or Cryotop method. After that, embryos were thawed and transferred to synchronized recipients, simultaneously to fresh embryos. In Experiment 2, 31 Nelore cows were superovulated with 133 mg porcine FSH and two thirds of the embryos were cryopreserved and transferred similarly to Experiment 1. In Experiment 3, 67 Holstein lactating dairy cows and heifers were superovulated with 500 and 300 IU pFSH, respectively, and the same procedures were performed as in Experiments 1 and 2. Results were analyzed using generalized linear models and are presented as least squares means ± standard error. In Experiments 1 and 2, fresh embryos had a higher conception rate at Day 30 than those vitrified and frozen (54.8±7.4a, 17.7±7.3b and 19.5±6.6%b; respectively; P 0.0013) in Sindhi donnors (n=231 embryos) and (46.0±6.1a; 31.2±5.4b and 28.1±5.3%b; respectively; P 0.04) in Nelore donors (n = 297 embryos). Embryo developmental stage seems to have not influenced conception rates of Zebu embryos, especially cryopreserved ones. Finnaly, in Experiment 3, conception rates of fresh and cryopreserved embryos were similar (37.4±12.3, 24.5±11.3 and 21.0±9.5%; respectively, P>0.15) and also no difference was detected for the cryotolerance of morulae versus blastocysts (P>0.10) / Mestre

O principal problema desta tese é a aplicação da teoria psicoacústica sobre percepção de dissonância em novas ferramentas de computação musical em tempo real. Os objetivos e contribuições incluem: Prover uma revisão critica do Estado da Arte em teoria psicoacústica de modelos de dissonância, projetar trabalhos futuros; Explorar um potencial criativo negligenciado de modelos psicoacústicos de dissonância em Eletrônica ao Vivo; Desenvolver novas ferramentas computacionais baseadas na teoria; Investigar o potencial e limitações da teoria e técnicas. Discutir sua pertinência e impacto; Tornar a teoria e técnicas mais acessíveis a músicos por meio deste texto e as ferramentas desenvolvidas. A percepção de Dissonância é um fenômeno complexo em que a abordagem psicoacústica cobre apenas uma porção. Além disso, ainda há muito debate na área da psicoacústica sobre o desenvolvimento de modelos de dissonância. Portanto, a tese apresenta uma revisão crítica do Estado da Arte da teoria psicoacústica, apontando pontos fracos e fortes do atual conhecimento, e futuros desenvolvimentos no campo. Um teste perceptivo também foi elaborado para gerar ponderações relevantes. Os modelos foram implementados em Pure Data, e uma série de patches foi desenvolvida para testar o potencial criativo em eletrônica ao vivo. Esse processo culminou em um sistema desenvolvido em Pure Data que agrega diversas das técnicas baseadas nos modelos psicoacústicos. Suas possibilidades incluem, por exemplo, encontrar intervalos consonantes de acordo com um espectro, ou alterar componentes espectrais para que estejam de acordo com uma escala musical ou afinação particular. Essas ferramentas foram empregadas em um duo de improvisação livre com o autor e um saxofonista. O autor também compôs uma peça orquestral que utilizou o sistema desenvolvido na parte de eletrônica ao vivo. / The problem of this research is to apply the state of the art in psychoacoustic theories about dissonance perception in the development of novel creative computer music tools for composition and live electronics. Goals and contributions include: To provide a critical review of the State of the Art in Psychoacoustic theory regarding dissonance modeling, project further work; To explore neglected creative potential of psychoacoustic dissonance models in Live Electronics; To develop novel computer music tools based on the theory; To investigate the potential and limitations of the theory and techniques; To discuss its creative musical impact and pertinence; To make the theory and techniques more accessible to musicians through the text and the free developed tools. The perception of Dissonance is a complex phenomenon in which the psychoacoustical approach covers just a portion thereof. Not only that, but psychoacoustic theory is still in debate about the development of dissonance models. Therefore, the thesis provides a critical review of the state of the art in psychoacoustic theory, pointing out weaknesses and strong points of the current knowledge, and future developments in the field. A perceptual test was also designed to generate data for relevant insights. Apart from the theoretical review, the models were implemented in Pure Data, and a series of patches was developed in order to test their creative potential in Live Electronics. This culminated in a system developed as a Pure Data Patch that aggregates several techniques based on the psychoacoustic models. Their possibilities include, for example, finding consonant intervals according to a spectrum, or altering spectral components so they are in accordance to musical intervals and particular tunings. These tools were used in a Free Improvisation duo with the author and a sax player, and the author also composed an orchestral piece that applied the developed system in the Live Electronics section.

During nervous system development, growing axons navigate towards their targets using signals from their environment. These signals may be biochemical or mechanical in nature; however, the role of mechanical cues in axon pathfinding in vivo, and the spatiotemporal dynamics of embryonic brain mechanics, are still largely uncharacterised. Here, I have identified a role for tissue mechanics in embryonic axon guidance in vivo, using retinal ganglion cell (RGC) axon outgrowth in the developing Xenopus laevis optic tract (OT) as a model system. Using atomic force microscopy (AFM) to map brain stiffness in vivo, I found that embryonic Xenopus brain tissue was mechanically heterogeneous at both early and later stages of OT outgrowth, i.e. just before RGC axons make a stereotypical turn in the mid-diencephalon, and when they reach their target, respectively. The final path of RGC axon turning followed a clear mechanical gradient: by the later stage, tissue rostral to the OT had become stiffer than tissue caudal to it. This mid-diencephalic stiffness gradient was an intrinsic property of the underlying brain tissue, and correlated with local cell body densities (with higher density rostral to the OT and lower density caudal to it). Crucially, inhibiting cell proliferation in vivo during OT outgrowth abolished the stiffness gradient and reduced OT turning at the later stage. Next, I developed a time-lapse AFM technique to track tissue stiffness and RGC axon behaviour simultaneously in vivo. Using this approach, I followed the evolution of the mid-diencephalic stiffness gradient during intermediate developmental stages, around the time when the OT’s caudal turn is initiated. The stiffness gradient was shallow pre-turn, but increased in magnitude during axon turning (mostly due to an increase in tissue stiffness rostral to the OT). This increase in stiffness gradient preceded the rise in OT turning angle, suggesting that the stiffness gradient is not caused by the invading axons. The observed rise in stiffness gradient correlated with stage-specific increases in local cell density, and was attenuated by blocking mitosis in vivo during time-lapse AFM measurements (which also reduced OT turning). As final confirmation that brain stiffness contributes to RGC axon pathfinding, I disrupted mechanical gradients by artificially stiffening brain tissue in vivo. Importantly, global stiffening via application of transglutaminase eliminated the mid-diencephalic stiffness gradient by increasing tissue stiffness caudal of the OT, and reduced the OT turning angle. Sustained mechanical compression of small areas using an AFM probe stiffened brain locally and repelled RGC axons, consistent with the way they turned away from rapidly stiffening tissue regions during time-lapse AFM experiments. Taken together, these results are consistent with a function for tissue mechanics in axon pathfinding in vivo.

Mammals and fish rely on hormones to regulate blood glucose levels. The two major glucose regulating hormones are insulin and glucagon. Literature on mammalian insulin and glucagon is quite extensive, however, there is limited information on how these hormones regulate blood glucose levels in fish. The material available for fish mostly pertains to changes in glucose concentration and gene expression of enzymes, but there is no information on the direct influence they have on glucose kinetics. Therefore, the main goal of my thesis is to measure the change in hepatic glucose production and glucose disposal when rainbow trout are administered insulin or glucagon. The beginning of my research focused on insulin. I hypothesized that rainbow trout respond to insulin by decreasing hepatic glucose production and increase glucose disposal, just like mammals. To test this, I infused insulin for 4 hours at 1.5 g insulin kg 1 min-1. I measured glucose disposal (Rd glucose), hepatic glucose production (Ra glucose), and blood glucose concentration. Following insulin administration the glucose fluxes decreased steadily (Rd glucose -37% and Ra glucose -43%). The decline in blood glucose levels follows the difference between Rd and Ra. These results explain why rainbow trout are unable to clear a glucose load to the same degree as mammals. The second major glucose hormone (glucagon) is what interested me for the second part of the research. The limited information on fish glucagon is even less than that of fish insulin. I speculated that trout respond to glucagon the same way mammals do (increase hepatic glucose production and show no affect on glucose disposal). To study the effects of glucagon on glucose fluxes, I tracked the changes in Ra and Rd glucose. The results showed glucose fluxes showed no siginificant difference from baseline in the first few hours, then steadily decreasing until the final time point reached values below baseline. Therefore, these experiments revealed that glucagon follows a similar pattern of effects in trout as mammals. However, the strength of the response to glucagon is different between trout and mammals. This thesis is the first to investigate the effects of insulin and glucagon on glucose kinetics in rainbow trout. I have concluded that rainbow trout have different responses to insulin and glucagon when compared to mammals. Furthermore, fish showing limited glucoregulatory capacity can be partially explained by their responses to insulin and glucagon.

Efficient delivery into cells is essential for many applications. However, cellular access of “cell-impermeable” molecules, such as drugs, sensors, proteins and oligonucleotides, can often be severely limited due to the plasma membrane which protects cells from unregulated influx of hydrophilic materials. In order to solve this issue, several physical techniques and bio-chemical products are today available. One of them is called peptoids (N-alkylglycines). These compounds are peptidomimetics which are resistant to enzymatic degradation, non-immunogenic and are readily prepared by an Fmoc chemical approach. Peptoids based on the "TAT"-peptide (RKKRRQRRR) offer rapid cellular uptake/delivery and low cytotoxicity. In this thesis, based on previous works using fluorescein-cationic peptoids, various fluorescent N-substitued glycines (lysine-like) were prepared by the monomer method followed by solid-phase synthesis. Their cellular uptakes in vitro into several cell lines (such as HeLa, B16F10, HEK293T and primary immune cells) were examined via flow cytometry and microscopy. The cellular delivery of small molecules mediated by the 9mer polymer achieved an efficient and rapid penetration. These results open up a vast number of applications for delivery of macromolecules using nonalysine-like peptoid. In order to demonstrate this ability, the nonalysinelike carrier was used to deliver various biopolymer molecules such as peptides, GFP protein and DNA (in collaboration with Dr. Stefano Caserta). In addition, thanks to the non-cytotoxicity of this cellular transpoter (MTT assays); experiments were carried out in vivo in mice using peptoids labelled near-infrared dyes. The first results have shown that the peptoid is not toxic for the mouse and does not block cell movements. These results allowed the use of 9mer-peptoid as a cellular tracking agent. Based on the development on antimicrobial peptides, the polylysine-like peptoid was also tested as an antibiotic. Recent experiments carried out in collaboration with Dr. Kevin Dhaliwal have revealed a new antimicrobial property of the peptoids. In vitro and in vivo studies have been carried out using both gram positive and negative bacteria. These results present a promising alternative to conventional antibiotics and antimicrobial peptides (AMPs).

Tese de mestrado integrado. Engenharia Informática e Computação. Faculdade de Engenharia. Universidade do Porto. 2013