No description available.

In the present study, the ease of rearing, short generation time and molecular research tools available for the zebrafish model (Danio rerio, Hamilton) were exploited to investigate transcriptional regulation in relation to feeding, photoperiod and experimental selection. Chapter 2 describes transcriptional regulation in fast skeletal muscle following fasting and a single satiating meal of bloodworms. Changes in transcript abundance were investigated in relation to the food content in the gut. Using qPCR, the transcription patterns of 16 genes comprising the insulin-like growth factor (IGF) system were characterized, and differential regulation between some of the paralogues was recorded. For example, feeding was associated with upregulation of igf1a and igf2b at 3 and 6h after the single-meal was offered, respectively, whereas igf1b was not detected in skeletal muscle. On the other hand, fasting triggered the upregulation of the igf1 receptors and igfbp1a/b, the only binding proteins whose transcription was responsive to a single-satiating meal. In addition to the investigation of the IGF-axis, an agnostic approach was used to discover other genes involved in transcriptional response to nutritional status, by employing a whole-genome microarray containing 44K probes. This resulted in the discovery of 147 genes in skeletal muscle that were differentially expressed between fasting and satiation. Ubiquitin-ligases involved in proteasome-mediated protein degradation, and antiproliferative and pro-apoptotic genes were among the genes upregulated during fasting, whereas satiation resulted in an upregulation of genes involved in protein synthesis and folding, and a gene highly correlated with growth in mice and fish, the enzyme ornithine decarboxylase 1. Zebrafish exhibit circadian rhythms of breeding, locomotor activity and feeding that are controlled by molecular clock mechanisms in central and peripheral organs. In chapter 3 the transcription of 17 known clock genes was investigated in skeletal muscle in relation to the photoperiod and food content in the gut. The hypothesis that myogenic regulatory factors and components of the IGF-pathway were clock-controlled was also tested. Positive (clock1 and bmal1 paralogues) and negative oscillators (cry1a and per genes) showed a strong circadian pattern in skeletal muscle in anti-phase with each other. MyoD was not clock-controlled in zebrafish in contrast to findings in mice, whereas myf6 showed a circadian pattern of expression in phase with clock and bmal. Similarly, the expression of two IGF binding proteins (igfbp3 and 5b) was circadian and in phase with the positive oscillators clock and bmal. It was also found that some paralogues responded differently to photoperiod. For example, clock1a was 3-fold more responsive than clock1b. Cry1b did not show a circadian pattern of expression. These patterns of expression provide evidence that the molecular clock mechanisms in skeletal muscle are synchronized with the molecular clock in central pacemaker organs such as eyes and the pineal gland. Using the short generation time of zebrafish the effects of selective breeding for body size at age were investigated and are described in chapter 4. Three rounds of artificial selection for small (S-lineage) and large body size (L-lineage) resulted in zebrafish populations whose average standard length were, respectively, 2% lower and 10% higher than an unselected control lineage (U-lineage). Fish from the L-lineage showed an increased egg production and bigger egg size with more yolk, possibly contributing to the larger body size observed in the early larval stage (6dpf) of fish from this lineage. Fish from S- and L-lineage exposed to fasting and refeeding showed very similar feed intake, providing evidence that experimental selection did not cause significant changes in appetite control. Investigation of the expression of the IGF-axis and nutritionally-response in skeletal muscle after fasting and refeeding revealed that the pattern of expression was not different between the selected lineages, but that a differential responsiveness was observed in a limited number of genes, providing evidence that experimental selection might have changed the way fish allocate the energy acquired through feeding. For example, a constitutive higher expression of igf1a was recorded in skeletal muscle of fish from the L-lineage whereas igfbp1a/b transcripts were higher in muscle of fish from the S-lineage. These findings demonstrate the rapid changes in growth and transcriptional response in skeletal muscle of zebrafish after only three rounds of selection. Furthermore, it provides evidences that differences in growth during embryonic and larval stages might be related to higher levels of energy deposited during oogenesis, whereas differences in adult fish were better explained by changes in energy allocation instead of energy acquisition. In chapter 5 the main findings made during this study and their impact on the literature are discussed.

Plusieurs espèces s’alimentant en groupe ont un comportement correspondant au jeu producteur-chapardeur (P-C). Même si à l’origine ce jeu ne prenait pas en compte plusieurs éléments susceptibles d’être présents dans un groupe social, certaines études récentes suggèrent que des facteurs, notamment le niveau de défense des ressources et les liens sociaux, pourraient affecter ses prédictions. Notre étude avait pour but d’étudier les effets de ces facteurs en exposant des groupes de diamants mandarins à quatre traitements expérimentaux faisant varier la taille du groupe et le degré d’attachement des oiseaux. Notre étude est la première à montrer que le niveau de défense des ressources a un réel effet sur les fréquences d’utilisation des tactiques producteur et chapardeur. De fait, contrairement à ce qui est prédit dans le jeu P-C original, nous avons trouvé que la fréquence des chapardeurs n’augmente pas avec la taille du groupe dans un contexte favorisant la défense des ressources. Par ailleurs, nous n’avons pas trouvé d’effet significatif du lien social sur les fréquences d’utilisation des tactiques. Cependant, nos résultats suggèrent que les liens de couple changent le comportement individuel des sujets en ce qui a trait au chapardage et à l’agressivité : bien que le résultat soit non significatif, les individus chapardent davantage leur partenaire social que les autres membres du groupe, mais avec une agressivité plus faible. Les résultats obtenus sont prometteurs et ouvrent la voie à de nombreuses autres études sur l’effet des liens sociaux et la défense des ressources chez les espèces grégaires. / Many species foraging in groups show behaviours in agreement with the producer-scrounger (PS) game. Originally, the PS game did not consider many elements likely to be found within feeding groups. However, recent studies suggest that some factors, namely resource defendability and social attachment, could indeed influence the predictions of the PS game. Thus, to investigate the effects of resource defendability and social bonds, we exposed flocks of zebra finches (Taeniopygia guttata), a monogamous species, to four different treatments intended to vary: (1) group size and, (2) degree of attachment among birds in a group. For the first time, we show that resource defendability has a true impact on the use of the two foraging tactics in the PS game. As a matter of fact, contrary to what is predicted in the original PS game, we found that the frequency of scrounger tactic did not increase with group size when tested in an economically defendable feeding context. On the other hand, even though pair bonding changed the individual scrounging and aggressive behaviours of the birds, we found no significant influence of this factor on the tactic use. Although the result was not significant, we found that scrounging was more frequent between social pairs than between experimental pairs, but individuals initiated aggressions towards their social partner with a lesser intensity. Thus, our results are promising and they call for many more studies on the effects of social bonds and resource defendability in gregarious species.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Le choix de partenaire est souvent considéré comme étant le résultat d’une simple interaction, mais, en nature, l’environnement social dans lequel les animaux communiquent correspond généralement à un réseau d’émetteurs et de récepteurs. La présence de congénères, de rivaux, et même de prédateurs durant le choix de partenaire peut avoir plusieurs répercussions sur ce choix. Être observé par une audience composée de congénères de même sexe peut pousser certaines espèces à modifier le niveau d’expression de leurs préférences, et même à modifier ces préférences pour réduire la compétition ou éviter d’être imitées. La préférence de plusieurs femelles diamant mandarin pour deux mâles a été mesurée en absence et en présence d’une audience femelle pour déterminer si la présence de rivales a des effets sur le choix de partenaire des femelles. De plus, afin de déterminer si ces effets varient en fonction de la qualité des femelles focales et audience, la condition de plusieurs femelles a été altérée en diminuant leur capacité à voler. Selon les résultats, les femelles diminuent leur niveau de sélectivité suite à l’ajout d’une audience femelle, et l’intensité des interactions mâle-femelle dépend de la condition des femelles focales. Les femelles ajustent leur comportement surtout pour éviter d’être imitées et non en fonction de leur condition. Cependant, ces deux mécanismes peuvent affecter les femelles simultanément. / Mate choice is often considered as the result of a simple interaction, but, in the wild, the social environment in which animals communicate generally corresponds to a network of several signallers and receivers. The presence of conspecifics, rivals, and even predators during mate choice can have many repercussions on that choice. Being observed by an audience of same-sex conspecifics can drive some species to alter the level of expression of their preferences, and even to modify those preferences to reduce competition or avoid being copied. The preference of several zebra finch females for two males was measured without and with a female audience to determine if the presence of an audience alters female mate choice. Moreover, to determine if these effects vary according to focal and audience females’ condition, the condition of several females was altered by diminishing their flying ability. According to the results, females lower their level of selectivity following the addition of an audience, and the intensity of male-female interactions depends on the focal females’ condition. Our findings suggest that females mainly adjust their behavior to avoid being copied and not according to their condition. However, these two mechanisms might have affected the females’ mating preferences simultaneously.

by Yan Hiu Mei, Carol. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 114-126). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgements --- p.iv / Table of Contents --- p.v / List of Tables --- p.viii / List of Figures --- p.ix / Abbreviations --- p.xii / Chapter CHAPTER 1 --- TRANSGENIC TECHNOLOGY --- p.1 / Chapter 1.1 --- Transgenesis in animals --- p.1 / Chapter 1.2 --- Transgenic fish in toxicology --- p.4 / Chapter 1.2.1 --- Aquatic metal toxicity --- p.4 / Chapter 1.2.2 --- Environmental monitoring of aquatic metal toxicity --- p.5 / Chapter 1.2.3 --- Biomarkers --- p.6 / Chapter 1.3 --- Transgenics in aquaculture --- p.9 / Chapter 1.3.1 --- Revolution is needed in aquaculture --- p.9 / Chapter 1.3.2 --- Aquaculture potential of tilapia in China --- p.10 / Chapter 1.3.3 --- Endocrinology for fish growth --- p.12 / Chapter 1.3.4 --- Growth promotion by exogenous growth hormone in tilapia --- p.14 / Chapter 1.3.5 --- Accelerated growth in transgenic fish --- p.15 / Chapter 1.4 --- General principle in transgenic fish production --- p.16 / Chapter 1.5 --- Project aim --- p.22 / Chapter CHAPTER 2 --- ISOLATION AND CHARACTERIZATION OF ZEBRAFISH METALLOTHIONEIN GENE PROMOTER --- p.23 / Chapter 2.1 --- Introduction --- p.23 / Chapter 2.1.1 --- Metallothionein --- p.23 / Chapter 2.1.2 --- Biological functions --- p.24 / Chapter 2.1.3 --- Metallothionein gene regulations --- p.25 / Chapter 2.1.4 --- Metallothionein as biomarker for metal pollution --- p.26 / Chapter 2.2 --- Materials and methods --- p.28 / Chapter 2.2.1 --- General molecular biology techniques --- p.28 / Chapter 2.2.2 --- Sequences of PCR primers used --- p.31 / Chapter 2.2.3 --- Cloning zebrafish MT gene 5-flanking region --- p.31 / Chapter 2.2.4 --- Cloning zebrafish MT gene --- p.32 / Chapter 2.2.5 --- Cloning full length zMT gene --- p.33 / Chapter 2.2.6 --- Cell culture --- p.35 / Chapter 2.2.7 --- Transient transfection assay --- p.37 / Chapter 2.2.8 --- Electrophoretic mobility shift assay --- p.39 / Chapter 2.3 --- Results --- p.42 / Chapter 2.3.1 --- Zebrafish metallothionein gene --- p.42 / Chapter 2.3.2 --- Deletion analysis of zMT promoter by transient transfection assay --- p.48 / Chapter 2.3.3 --- Functional characterization of zebrafish metallothionein promoter --- p.57 / Chapter 2.4 --- Discussions --- p.61 / Chapter 2.4.1 --- Zebrafish MT gene --- p.61 / Chapter 2.4.2 --- Functional characterization of zebrafish MT promoter --- p.61 / Chapter CHAPTER 3 --- PREPARATION OF GENE CONSTRUCTS FOR TRANSFER IN ZEBRAFISH --- p.65 / Chapter 3.1 --- Introduction --- p.65 / Chapter 3.1.1 --- Zebrafish as model in toxicological studies --- p.65 / Chapter 3.1.2 --- Reporter gene system --- p.66 / Chapter 3.1.3 --- Transgenic reporter fish --- p.68 / Chapter 3.1.4 --- Gene transfer by electroporation in zebrafish --- p.68 / Chapter 3.1.5 --- Objective --- p.69 / Chapter 3.2 --- Materials and methods --- p.70 / Chapter 3.2.1 --- Design of gene constructs for ectopic expression in zebrafish --- p.70 / Chapter 3.2.2 --- Testing electroporation conditions for zebrafish --- p.72 / Chapter 3.3 --- Results --- p.73 / Chapter 3.4 --- Discussions --- p.76 / Chapter 3.4.1 --- Engineering gene constructs --- p.76 / Chapter 3.4.2 --- Applications of transgenic zebrafish --- p.79 / Chapter CHAPTER 4 --- GENE TRANSFER EXPERIMENTS ON TILAPIA --- p.82 / Chapter 4.1 --- Introduction --- p.82 / Chapter 4.2 --- Materials and methods --- p.85 / Chapter 4.2.1 --- Isolation of O. aureus growth hormone --- p.85 / Chapter 4.2.2 --- Engineering gene constructs for ectopic expression in tilapia --- p.86 / Chapter 4.2.3 --- Gene transfer in tilapia --- p.87 / Chapter 4.2.4 --- Screening transgenic tilapia --- p.89 / Chapter 4.3 --- Results --- p.91 / Chapter 4.3.1 --- Tilapia growth hormone --- p.91 / Chapter 4.3.2 --- Gene constructs for ectopic expression in tilapia --- p.94 / Chapter 4.3.3 --- Testing electroporation conditions --- p.96 / Chapter 4.3.4 --- PCR screening for transgenic fish --- p.97 / Chapter 4.4 --- Discussions --- p.101 / Chapter 4.4.1 --- Tilapia growth hormone --- p.101 / Chapter 4.4.2 --- Electroporation experiments on of tilapia eggs --- p.101 / Chapter 4.4.3 --- Improvements on gene construct design for tilapia --- p.104 / Chapter 4.4.4 --- Ethical and safety considerations --- p.106 / Chapter CHAPTER 5 --- REFERENCES --- p.114 / APPENDIX --- p.127

No description available.

Since their accidental introduction into the Great Lakes in mid- to late-1980s, the freshwater zebra mussels, Dreissena polymorpha, have colonized most lakes and waterways across eastern North America. Their rapid spread is partly attributed to their ability to tenaciously attach to hard substrates via an adhesive apparatus called the byssus, resulting in serious environmental and economic impacts. A detailed ultrastructural study of the bysuss revealed a 10 nm adhesive layer at the attachment interface. Distributions of the main adhesive amino acid, 3,4-dihydroxyphenylalanine (DOPA), and its oxidizing (cross-linking) enzyme, catechol oxidase, were determined histochemically. It was found that, upon aging, DOPA levels remained high in the portion of the byssus closest to the interface, consistent with an adhesive role. In contrast, reduced levels of DOPA corresponded well with high levels of catechol oxidase in the load-bearing component of the byssus, presumably forming cross-links and increasing the cohesive strength.

Since their accidental introduction into the Great Lakes in mid- to late-1980s, the freshwater zebra mussels, Dreissena polymorpha, have colonized most lakes and waterways across eastern North America. Their rapid spread is partly attributed to their ability to tenaciously attach to hard substrates via an adhesive apparatus called the byssus, resulting in serious environmental and economic impacts. A detailed ultrastructural study of the bysuss revealed a 10 nm adhesive layer at the attachment interface. Distributions of the main adhesive amino acid, 3,4-dihydroxyphenylalanine (DOPA), and its oxidizing (cross-linking) enzyme, catechol oxidase, were determined histochemically. It was found that, upon aging, DOPA levels remained high in the portion of the byssus closest to the interface, consistent with an adhesive role. In contrast, reduced levels of DOPA corresponded well with high levels of catechol oxidase in the load-bearing component of the byssus, presumably forming cross-links and increasing the cohesive strength.

Le choix de partenaire est souvent considéré comme étant le résultat d’une simple interaction, mais, en nature, l’environnement social dans lequel les animaux communiquent correspond généralement à un réseau d’émetteurs et de récepteurs. La présence de congénères, de rivaux, et même de prédateurs durant le choix de partenaire peut avoir plusieurs répercussions sur ce choix. Être observé par une audience composée de congénères de même sexe peut pousser certaines espèces à modifier le niveau d’expression de leurs préférences, et même à modifier ces préférences pour réduire la compétition ou éviter d’être imitées. La préférence de plusieurs femelles diamant mandarin pour deux mâles a été mesurée en absence et en présence d’une audience femelle pour déterminer si la présence de rivales a des effets sur le choix de partenaire des femelles. De plus, afin de déterminer si ces effets varient en fonction de la qualité des femelles focales et audience, la condition de plusieurs femelles a été altérée en diminuant leur capacité à voler. Selon les résultats, les femelles diminuent leur niveau de sélectivité suite à l’ajout d’une audience femelle, et l’intensité des interactions mâle-femelle dépend de la condition des femelles focales. Les femelles ajustent leur comportement surtout pour éviter d’être imitées et non en fonction de leur condition. Cependant, ces deux mécanismes peuvent affecter les femelles simultanément. / Mate choice is often considered as the result of a simple interaction, but, in the wild, the social environment in which animals communicate generally corresponds to a network of several signallers and receivers. The presence of conspecifics, rivals, and even predators during mate choice can have many repercussions on that choice. Being observed by an audience of same-sex conspecifics can drive some species to alter the level of expression of their preferences, and even to modify those preferences to reduce competition or avoid being copied. The preference of several zebra finch females for two males was measured without and with a female audience to determine if the presence of an audience alters female mate choice. Moreover, to determine if these effects vary according to focal and audience females’ condition, the condition of several females was altered by diminishing their flying ability. According to the results, females lower their level of selectivity following the addition of an audience, and the intensity of male-female interactions depends on the focal females’ condition. Our findings suggest that females mainly adjust their behavior to avoid being copied and not according to their condition. However, these two mechanisms might have affected the females’ mating preferences simultaneously.