The byssal adhesion mechanism of the biofouling species Dreissena polymorpha was investigated using a combination of studies on synthetic peptide mimics of tandem repeat sequences from byssal component Dreissena polymorpha foot protein 1 (Dpfp-1) and characterization of the regions of the byssus. A 20-residue fusion peptide incorporating two Dpfp-1 repeat sequences adopts a random coil and β-turn conformation in solution, and spontaneously forms a film at the solid-liquid interface in the presence of iron (III) cations. Infrared characterization of the byssus Amide I region showed that β-sheets dominate its secondary structure, although the proportion of different secondary structures varies between regions. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry of intact byssal regions identified previously unknown differences in the composition of byssal threads, plaques, and the adhesive interface, which are believed to correlate to the different roles of these components in the overall structure.

The byssal adhesion mechanism of the biofouling species Dreissena polymorpha was investigated using a combination of studies on synthetic peptide mimics of tandem repeat sequences from byssal component Dreissena polymorpha foot protein 1 (Dpfp-1) and characterization of the regions of the byssus. A 20-residue fusion peptide incorporating two Dpfp-1 repeat sequences adopts a random coil and β-turn conformation in solution, and spontaneously forms a film at the solid-liquid interface in the presence of iron (III) cations. Infrared characterization of the byssus Amide I region showed that β-sheets dominate its secondary structure, although the proportion of different secondary structures varies between regions. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry of intact byssal regions identified previously unknown differences in the composition of byssal threads, plaques, and the adhesive interface, which are believed to correlate to the different roles of these components in the overall structure.

In embryonic neurons, the intracellular chloride concentration is elevated, making GABA and glycine depolarizing. Later in development, coincident with neuronal maturation, the extruding potassium-chloride co-transporter KCC2 is expressed. It reverses the chloride gradient, rendering it hyperpolarizing. Early depolarization is assumed to play trophic roles during nervous system development. I thus decided to investigate the effects of the depolarizing chloride gradient on development in vivo in the zebrafish embryo. I first determined the temporal pattern of KCC2 expression in zebrafish and found it was absent in the embryo. I then over-expressed wild-type, gain-of-function and loss-of-function variants of human KCC2, using GFP-tagged constructs for detection purposes. Over-expression of functional hKCC2 perturbed the morphology and motor behaviours of the embryos. At the cellular level, KCC2 impaired axonal growth and affected the neuronal populations in the brain, hindbrain and spinal cord. This suggests the depolarizing effects of glycine are critical for neurogenesis.

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The Australian Zebra Finch (Taeniopygia guttata) is an important animal model for vertebrate development and behavior. New research initiatives in the fields of epigenetics rely heavily on injecting hormones and environmental toxins directly into the eggs of different bird species such as zebra finches and other passerine songbirds to replicate the effects maternal condition on offspring. However, the widely used method of egg-injections does not accurately replicate physiological conditions, as the injected substances remain concentrated at the injection site for extended periods and do not diffuse into the developing tissues. Therefore, we propose an alternative method to injection protocols that takes advantage of the porous nature of eggs. Corticosterone (CORT), a major vertebrate stress hormone, dissolved in ethyl alcohol was applied to the surface of zebra finch eggs daily. The effect of this treatment on decreasing hatching success shows that topical hormonal treatments are a viable alternative to egg injection.

Two groups of neuropeptides (secretin and gonadotropin-releasing hormone groups, GnRH) and their receptors are of considerable interest because they are highly conserved in structure during evolution and have important physiological effects. To study the role of these neuropeptides during development, the zebrafish was selected initially as a model because the embryo is transparent and accessible for genetic manipulation. Later, a mouse model was added to evaluate the effects of permanent gene loss. The purpose of this thesis was to 1) characterize the structure and function of several peptides and receptors within the secretin group that had not been previously identified for zebrafish, 2) examine brain development in zebrafish after gene knock down of an important peptide in each of the secretin and GnRH groups, 3) identify the pattern and location of expression of the GnRH receptors in zebrafish embryos, and 4) study the functional importance of the GnRH receptor in a mouse line deficient in the receptor. The secretin superfamily of hormones includes 10 structure-related polypeptides in mammals, but fewer in zebrafish. In this thesis it was discovered that within the secretin group, zebrafish have two peptides, peptide histidine-isoleucine (PHI) and vasoactive intestinal polypeptide (VIP), in addition to two receptors, PHI receptor and growth hormone-releasing hormone-like peptide (GHRH-LP) receptor that were not previously identified. After isolation of the cDNA for each, the signaling pathways were characterized in vitro by transfection of the receptors into COS cells. The PHI-R was activated by PHI but not by VIP or pituitary adenylate cyclase-activating polypeptide (PACAP). The GHRH-LP receptor was activated by GHRH-LP 1 and GHRH but not by GHRH-LP2. A novel observation was that the PAC, receptor is activated by both PACAP and VIP, whereas the PAC, receptor is usually specific to PACAP. Also novel was evidence that a VPAC2 receptor in zebrafish was structurally and functionally a PHI receptor. In examining the role of PACAP in early brain development in zebrafish, morpholinos were used to knockdown PACAP1 and PACAP2 in the zygote. The study revealed that loss of PACAP leads to change in the expression of brain markers. GnRH and its receptors (GnRH-R) are key regulators of reproduction and sexual behaviour. In zebrafish, morpholino-induced knock down of GnRH revealed that GnRH is critical in eye and brain development by affecting transcription factors and/or secreted factors: pax2.1, fgf8, pax6.1 and mab. Further, the GnRH receptor was expressed at 24h post fertilization showing that GnRH and its receptor could influence early development. To determine whether the GnRH receptor is critical at all stages of reproduction, a mouse line was created in which the GnRH receptor was disrupted using the gene trap method. This model has a similar phenotype to the clinical syndrome of hypogonadotropic hypogonadism. In mice, GnRH receptor disruption results in small sexual organs, low gonadotropin and steroid hormone levels, failure of sexual maturation, and lack of reproduction. Also, the GnRH receptor may be important in the fetal testis. This thesis provides evidence that 1) in evolution the PAC, receptor may have responded to both PACAP and VIP in fish, 2) zebrafish have a PHI receptor rather than a VPAC2 receptor, 3) PACAP and GnRH peptides have a fundamental role in early brain development, 4) the GnRH receptor is not only important in reproduction but unexpectedly, in zebrafish embryos is localized in hindbrain motor neurons and fibers, which are involved normally in movement and escape, and 5) GnRH receptor-disrupted mice should be a valuable model for understanding reproduction and clinical approaches to hypogonadotropic hypogonadism.

Degradation of water quality, introduction of dreissenid mussels (notably <i>Dreissena polymorpha</i>) and depletion of oxygen concentrations in the hypolimnion in Lake Simcoe, Ontario prompted a study of phytoplankton primary production to inform efforts to improve the lake conditions. The characterization of algal production is critical since, as primary producers, their biomass is positively correlated with production at higher trophic levels in pelagic food webs and oxygen levels. This study was conducted from August 2010 to August 2011, including the winter season (Dec-Mar). Temporally, the lake displayed a unimodal pattern with late summer to fall production maxima. For all seasons considered, the pelagic daily areal primary production (P_int) was lower in the nearshore than offshore, consistent with the nearshore shunt hypothesis that mussels should be able to deplete phytoplankton more effectively in the nearshore. The sensitivity analysis revealed that chl a and the photosynthetic parameter P^B_max were the most influential variables for explaining such spatial differences. The size distribution of chl a and production varied where both netplankton (>20µm) and nanoplankton (2-20µm) were greatest in fall and picoplankton (<2µm) was highest in summer and early fall. A large chl a peak of nanoplankton was also found in late-winter (Mar) at offshore stations. The seasonal areal primary production (SAPP; May-Oct) and chl a:TP were significantly lower nearshore than offshore, consistent with grazing impacts from the large nearshore dreissenid mussel community. The lake as a whole is quite productive comparable to other large lakes with comparable total P concentrations and dreissenid mussel populations. The latter part of the study showed that the deep chlorophyll layer (DCL) was not as frequent as expected and was detected only 28% of time during late-spring to summer when the lake was thermally stratified (Aug-Sept 2010 and May-Aug 2011). The percent dissolved oxygen (%) did not show any indications of elevated primary production in the DCL although the production estimates suggested that there is a substantial (an average of 55%) amount of primary production occurring below thermocline when a DCL exists. Whether or not the DCL has potential to nourish the benthic filterers (dreissenids) and has ecological significance in the lake remains unclear. Overall, the factors that control phytoplankton primary production in Lake Simcoe seem to operate somewhat differently from other large lakes and further investigation is needed to elucidate them. The analysis of primary production and biomass has improved knowledge of non-summer production and can provide guidance to site-specific P and oxygen remediation.

Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 70-82). Also available for download via the World Wide Web; free to University of Oregon users.