Thrombocytes are important players in hemostasis. There is still much to be explored regarding the molecular basis of the thrombocyte function. In our previous microarray analysis data, we found IFT122 (an intraflagellar transport protein known to be involved in cilia formation) transcripts in zebrafish thrombocytes. Given recent discoveries of non-ciliary roles for IFTs, we examined the possibility that IFT122 affects thrombocyte function. We studied the role of IFT122 in thrombocyte function. We also found that IFT122 plays a central role in thrombocyte activation initiated by the agonists ADP, collagen, PAR-1 peptide and epinephrine. Although the receptors for ADP, PAR-1 peptide and epinephrine are present in the zebrafish genome, the collagen receptor GPVI was missing. In this study, we identified G6fL as a collagen receptor in zebrafish thrombocytes. Furthermore, IFT knockdown results in reduction in Wnt signaling. The Wnt signaling has been shown to be involved in megakaryocyte proliferation and proplatelets production. Therefore, defects in IFT could lead to thrombocytopenia. Splenectomy is performed in humans to treat such conditions. Therefore, in this study we developed a survival surgery protocol for splenectomy. We have shown that number of thrombocytes and their microparticles increase following splenectomy in zebrafish. Thus overall the studies on thrombocyte function in zebrafish could enhance fundamental knowledge on hemostasis and may provide future target candidates for therapies.

The new pavilion of entrance into the Zoo Dvůr Králové nad Labem is inspired by African wildlife – the dorsum of zebra. The building contains the basic functions like the entry including box office and turnstile and the exhibition of little animals makeing the pleasant feelings for the entrance into the Zoo. There is a restaurant, multifunction areas, sanitary facilities and a standalone exit object with a Zoo shop.

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Biological invasion has become a major threat to economy, ecology, global biodiversity and ecosystem function of aquatic ecosystems. The main aim of the thesis was to study the effects of the zebra mussel (Dreissena polymorpha), a versatile invasive species, on phytoplankton dynamics and ecosystem function of lakes. In a first attempt, I compared the density of Dreissena and the physicochemical data of ecosystems that it invaded among North American and European lakes to identify important factors in its invasion success. Secondly, I investigated the impact of zebra mussels on phytoplankton community composition in a natural lake. Thirdly, I evaluated whether zebra mussel feeding behavior were affected by the presence of predatory waterborne cues. Finally, I examined the effect of Dreissena on seston stoichiometry. A Generalized Additive Model revealed that a joint effect of surface area, mean depth, total phosphorus and calcium concentrations can explain the variability in Dreissena density. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics. Risk cues released by predators affected both feeding rate and prey selection of the mussels and had cascading indirect effects on phytoplankton biomass and community structure. I found that the flux in nutrients caused by differences in zebra mussel consumption lead to a variation in phytoplankton nutrient limitation. The flexibility of zebra mussel feeding behavior and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences. The results of this thesis contribute to the growing evidence that predators indirectly affect resource dynamics and food web structure through their non-lethal effects on consumers. The results suggested that zebra mussel can indirectly both reduce and increase the energy transfer efficiency from primary producers to upper trophic levels in the pelagic and benthic food webs, respectively.

Environmental toxicants are ubiquitous throughout the environment as a result of human activity. Among these toxicants, environmental estrogens are a category of particular concern due to their environmental prevalence and potency in altering reproductive traits. While many studies have addressed the detrimental effects of environmental estrogens on both aquatic and terrestrial organisms, few have analyzed the potential for these compounds to alter mitochondrial function. Mitochondria are the primary energy-generating system for all eukaryotic life, supporting all aspects of development, metabolism, and growth. Each cell within the body contains many mitochondria which in turn contain multiple copies of their own DNA genome, mitochondrial DNA (mtDNA). Mutations in mtDNA are responsible for a wide range of human diseases such as metabolic syndromes, cancers, and obesity. Among these mitochondrial diseases many are characterized by increased levels of heteroplasmy, multiple mitochondrial DNA haplotypes within an individual. Increased heteroplasmy can alter normal mitochondrial function and influence disease initiation and progression. To date, no studies have investigated the effects of synthetic estrogens on mitochondrial genome stability. Synthetic estrogens have the capacity to bind to estrogen receptors and initiate estrogenic responses through translocation into the mitochondrion. Despite our knowledge about the relationship of heteroplasmy and disease, we still do not have a complete grasp of the mechanisms of heteroplasmic induction. Here we report our analysis of the effects of 17α-ethynylestradiol (EE2) exposure in three studies to investigate its effect on mitochondrial genome stability. Data analysis reveals a statistically significant relationship between EE2 exposure and increased heteroplasmic frequency.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Un animal qui s’approvisionne en groupe peut rechercher soi-même sa nourriture (tactique producteur) ou tenter de se joindre à des parcelles déjà découvertes par un autre individu (tactique chapardeur). Bien que les modèles de jeu producteur-chapardeur partent du principe que les gains moyens à l’équilibre associés à chacune de ces tactiques sont égaux et ne dépendent pas des caractéristiques des individus, de plus en plus d’études démontrent que le gain de chaque tactique est influencé par certaines caractéristiques phénotypiques (agressivité, capacités d’apprentissage,…). Dans cette étude, nous nous intéressons aux effets de la testostérone sur le choix des tactiques d’approvisionnement chez les mâles de diamant mandarin (Taeniopygia guttata). La testostérone est connue pour influencer le développement du cerveau et l’agressivité, nous avons donc testé les effets d’une exposition prénatale à la testostérone ainsi que durant l’âge adulte sur le choix des tactiques d’approvisionnement lorsque la nourriture est cryptique ou défendable. Nous avons réalisé deux expériences : nous avons tout d’abord utilisé la longueur du tarse ainsi que la différence entre les longueurs des doigts 2 et 4 comme des indicateurs de l’exposition prénatale à la testostérone puis testé si ces différences morphologiques se traduisent par des différences dans le choix des tactiques dans une condition défendable et une condition cryptique. Nous avons trouvé que le choix des tactiques chez les diamants mandarins était limité par le phénotype. Une exposition précoce à la testostérone au cours du développement prénatal pourrait donc être la cause d’au moins une part de la variation observée dans le choix des tactiques d’approvisionnement. Ensuite, nous avons manipulé le taux de testostérone plasmatique chez des mâles adultes grâce à des implants hormonaux sous-cutanés puis comparé le comportement des individus lorsqu’ils portaient un implant hormonal et un implant contrôle et ce, dans chacune des deux conditions d’approvisionnement. Nous n’avons mis en évidence aucun effet du taux de testostérone plasmatique sur le choix des tactiques à l’âge adulte. Nos résultats sont en accord avec l’hypothèse que le choix des tactiques d’approvisionnement peut être influencé par les hormones. Notre conclusion est que les hormones stéroïdiennes peut affecter le choix des tactiques via l’existence d’effets maternels dans le jeu producteur-chapardeur. / An animal foraging in groups can search for its own food (producer tactic) or try to join food patches previously discovered by another group member (scrounger tactic). Although producer-scrounger game models assume that the payoffs associated with both tactic are equal at equilibrium and so do not depend on individual characteristics, there is recent evidence that tactic choice is constrained by certain phenotypical traits (aggressivity, learning abilities…). In this study, we examined the effect of testosterone on tactic use in male zebra finches (Taeniopygia guttata). Because testosterone is known to affect both brain development and aggressiveness, we tested whether differences in testosterone exposure either during development or in adulthood had an effect on producer-scrounger tactic use, when food was cryptic or defendable. First, we measured the tarsus length and the distance between the end of the fourth and the end of the second digit as proxies of prenatal exposure to testosterone, and tested whether they were correlated with foraging tactic use under both conditions. We found that tactic choice in zebra finches is phenotypically constrained. We suggest that early exposure to sex hormones during the embryonic period could be responsible for at least a part of the variation in tactic choice. Second, we manipulated the circulating level of testosterone in adult male zebra finches using subcutaneous testosterone implants, and compared the behavior of individuals when they had either a control implant or a testosterone implant. This time we found no effect of plasmatic level of testosterone on tactic choice. Our results are consistent with the hypothesis that tactic choice in zebra finches could be mediated by hormones. Our finding that steroid hormones can affect tactic use provides evidence for maternal effects in producer-scrounger games.

Smith-Magenis Syndrome (SMS; OMIM #182290) is a multiple congenital abnormality and intellectual disability (ID) disorder caused by either an interstitial deletion of the 17p11.2 region containing the retinoic acid induced-1 (RAI1) gene or a mutation of the RAI1 gene. Individuals diagnosed with SMS typically present characteristics such as ID, self-injurious behavior, sleep disturbance, ocular and otolaryngological abnormalities, craniofacial and skeletal abnormalities, neurological and behavioral abnormalities, as well as other systemic defects and manifestations. Previous work by Vyas in 2009 showed temporal expression of rai1 in zebrafish embryos as early as 9 hpf. We hypothesize that there is maternal rai1 expression as early as zero hours post fertilization in wild type embryos. Using end-point PCR, we found that in fact there is maternal rai1 expression is detectable as early as 2 hours post fertilization (hpf) in wild type zebrafish embryos. Furthermore, we quantified rai1 expression using qPCR and found that rai1 expression declines significantly after 6 hpf. We hypothesize that a down regulation of rai1 or loss of rai1 will lead to morphological phenotypes, especially if that loss of rai1 function occurs during the earliest stages of zebrafish embryogenesis. Using a rai1morpholino oligonucleotide (MO), we found a loss of rai1 expression did not induce a morphological phenotype in in wild type embryos; furthermore, we also found that a loss of maternal rai1 expression did not induce a morphological phenotype as well. Utilizing a mutant rai1 zebrafish line, we found that both rai1 +/fh370 progeny nor rai1 fh370/fh370 progeny exhibited a morphological phenotype and that downstream targets such as bdnf were not affected by a reduction or complete loss of rai1. Prior research has shown that retinoic acid (RA) can induce rai1 expression. We hypothesize that RA can induce expression of rai1 during zebrafish embryogenesis. Using wild type fish and a rai1 in situ hybridization probe, we found that RA treatment at 25 hpf induced expression of rai1. The construction of a rai1 overexpression vector used for overexpression studies was started. Further development of GFP expression vector and zebrafish rai1 antibody are needed to determine if the morpholino is reducing rai1 protein expression.

A nutrição tem sido identificada como um fator chave que afeta diretamente o crescimento e o bom desempenho reprodutivo do animal quando utilizado como modelo experimental. Desta forma, é essencial uma dieta ideal acessível através da qual o zebrafish possa suprir todas suas necessidades nutricionais desde a fase larval até a sua fase adulta sem que haja necessidade de complementá-la com outros tipos de dietas, simplificando o cultivo destes animais. A dieta recomendada nos guidelines para a alimentação do Zebrafish criado em laboratório é composta por náuplios de Artemias (crustáceo rico em proteínas) em conjunto com uma ração seca rica em proteínas e sais minerais fundamentais para o bom desenvolvimento e reprodução desses animais. Este estudo teve como objetivo desenvolver e padronizar uma dieta ideal de alimentação simples, eficaz, saudável e de baixo custo a fim de obter o melhor desempenho possível nos experimentos desenvolvidos com o zebrafish. Foram utilizadas 4 diferentes modelos de dietas preparadas a partir de 3 formas de alimentação que consistiram em náuplios de Artemias, a ração padrão-ouro disponível no mercado europeu denominada Gemma Micro® desenvolvida pela Skretting e a ração elaborada para este estudo identificada como Ração Ideal. Os animais foram divididos em 4 grupos de acordo com a dieta recebida: Grupo1- alimentados com Ração Gemma(G), Grupo 2- alimentados com Ração Gemma + Artemia (G+A), Grupo 3- alimentados com Ração Ideal (I) e Grupo 4- alimentados com Ração Ideal+Artemia (I+A). Para avaliar o desempenho da Ração Ideal, foram analisados comparativamente entre os grupos os parâmetros de sobrevivência, crescimento, maturação sexual e fertilidade em duas gerações de animais (Geração 0 Geração 1). Após a análise e vários testes realizados dentro de um modelo de ração que se ajustasse ao perfil de referência, Gemma Micro® e que atendesse as necessidades do zebrafish passamos a dar início aos experimentos utilizando a ração que apresentou melhor desempenho que passou a ser denominada Ração Ideal. Em relação a sobrevivência dos animais, observamos que, na Geração 0 os animais dos grupos 3 e 4 apresentaram maiores taxas de sobrevivência em relação aos outros grupos, no entanto na geração 1 todos os grupos apresentaram taxas de sobrevivência semelhantes. Analisando o crescimento dos animais, na geração 0 os animais dos grupos 2 e 4 apresentaram crescimento semelhante e foram maiores que os animais dos grupos 1 e 3. Na geração 1, os animais do grupo 2 foram os que mais cresceram e o grupo 4 cresceu mais em relação ao grupo 3. Todos os animais estavam maduros sexualmente aos 90dpf e quantidade de ovos viáveis foram maior nos grupos 1 e 2 em ambas as gerações. A Ração Ideal forneceu um aporte calórico suficiente e semelhante á ração Gemma para a sobrevivência dos animais nas fases iniciais do desenvolvimento, apresentando taxas de sobrevivência semelhantes entre os grupos. O acréscimo da artêmia á ração ideal foi fundamental para que o crescimento dos animais alimentados com essa ração demonstrassem um crescimento semelhante á ração referência, demonstrando a deficiência proteica da ração ideal. Todas as dietas promoveram maturidade sexual na faixa etária esperada (a partir de 90dpf) no entanto parece que a fertilidade foi maior nos grupos 1 e 2, possivelmente pelo maior aporte proteico que esses animais receberam. Este estudo conseguiu desenvolver e padronizar uma dieta ideal de alimentação, eficaz, saudável e de baixo custo semelhante ao padrão-ouro utilizado em laboratórios europeus e americanos que, após alguns ajustes em sua formulação poderá ser comercializada e utilizada pelos laboratórios de pesquisa ao redor do país / Nutrition has been identified as a key factor that directly affects the growth and good reproductive performance of the animal when used as an experimental model. In this way, an ideal diet should be accessible through which the zebrafish can meet all their nutritional needs from the larval phase to adulthood without any complement with other types of diets, simplifying the management of these animals. The diet recommended in the Zebrafish feeding guidelines is composed of Artemias nauplii (crustacean rich in proteins) together with a dry diet rich in proteins and minerals that are essential for the proper development and reproduction of these animals. This study aimed to develop and standardize an ideal diet for simple, effective, healthy and low-cost feeding in order to obtain the best possible performance in the experiments developed with zebrafish. Four different diets were prepared from 3 feeding forms consisting of Artemias nauplii, the gold-standard feed available in the Europe, the Gemma Micro® developed by Skretting and the dry feed elaborated in this study identified as Ideal . The animals were divided into 4 groups according to the diet received: Group 1 fed with Gemma (G), Group 2 fed with Gemma + Artemia (G + A), Group 3 fed with Ideal dry feed (I) and Group 4- fed with Ideal dry feed+ Artemia (I + A). To evaluate the performance of the Ideal dry feed, the parameters of survival, growth, sexual maturation and fertility in two generations of animals (Generation 0 Generation 1) were comparatively analyzed between the groups. After several tests performed within a feed model that fits the reference profile, Gemma Micro® and meets the zebrafish needs, we initiated the experiments using the feed that presented the best performance, named Ideal. Regarding the animals survival, we observed that in the Generation 0 animals of groups 3 and 4 presented higher survival rates in relation to the other groups, however in generation 1 all groups had similar survival rates. Analyzing the growth of the animals, in generation 0 the animals of groups 2 and 4 presented similar growth and were larger than the animals of groups 1 and 3. In generation 1, the animals of group 2 were the ones that were bigger than other ones. Animals of group 4 were bigger than group 3. All animals were sexually mature at 90dpf and fertility was evaluated by viable egg count. The number of viable egg were higher in groups 1 and 2 in both generations. The Ideal feed provided a sufficient caloric intake similar to the Gemma for the survival of the animals in the early stages of development, once survival rates were similar between the groups. Adding artemia to the ideal feed was fundamental for animal development, once the growth of the animals fed with ideal plus artemia demonstrated a similar growth to the reference feed, demonstrating the protein deficiency of the ideal feed. All diets promoted sexual maturity at the expected age range (from 90dpf), however it appears that fertility was higher in groups 1 and 2, possibly due to the higher protein intake of these animals. This study was able to develop and standardize an ideal, effective, healthy and low-cost diet similar to the gold standard feed used in laboratories around the world. After some adjustments in its formulation, the ideal feed should be marketed and used in the research laboratories in the country