VictorJuiz/thesis huggingface dataset:
Towards an Understanding of Zebrafish Epiboly: The Characterization of the Epiboly Initiation Mutant Eomesodermin A

How cell movements are coordinated during morphogenesis is not well understood. We focus on epiboly, which describes the thinning and spreading of a multilayered cell sheet. The first phase of epiboly involves the doming of the yolk cell up into the overlying blastoderm. We previously showed that over-expression of a dominant– negative eomesodermin a construct inhibits doming. Here I report my analysis of embryos lacking both maternal and zygotic Eomesodermin A (MZeomesa). eomesafh105 mutant embryos (1) exhibit a doming delay, (2) have defective yolk cell microtubules, (3) have tightly packed deep cells with more bleb – like protrusions and (4) express early endoderm markers abnormally. Despite these phenotypes, the majority of MZeomesa embryos are able to complete epiboly and form endodermal derivatives. In both Xenopus and mice, Eomesodermin has also been implicated in the regulation of gastrulation movements and cell fate specification, suggesting a conserved role for Eomesodermin throughout vertebrate development.

Keywords: Zebrafish
Epiboly
Morphogenesis
Gastrulation
Eomesodermin A
T-box transcription factor
Endoderm
Microtubules
yolk cell
doming
Advisor: Bruce, Ashley
Supporting Canadian Caregivers: Current and Future Policy Directions

This thesis examines current Canadian social policies aimed at ameliorating the position of informal caregivers of terminally ill and elderly care recipients. Using an ethics of care theoretical approach, the thesis critically evaluates federal and provincial income tax regimes aimed at increasing the financial security of caregivers, and also looks at the shortcomings of the Compassionate Care Benefit offered through the federal Employment Insurance Act. The evaluation reveals that the benefit has a very low up-take compared with initial estimates, and offers some explanations for its low use. A review of the caregiver policies in three European countries provide additional background for the final chapter of the thesis, which offers concrete and incremental solutions to the problems with the current social policies in place. The aim of this thesis is not to suggest sweeping reforms, but to offer affordable, practical, and politically feasible solutions that can begin to make a difference in the lives of caregivers.

Keywords: Law
Informal Caregiving
Advisor: Nedelsky, Jennifer
Innovative Approaches for the Electrochemical Detection of Acetylcholinesterase Inhibitors

This document describes research conducted during 2009-2010 in the Kerman Group laboratory at the University of Toronto Scarborough to investigate the application of electrochemical techniques for the detection of acetylcholinesterase inhibitors in aqueous samples. Two main projects were completed and are discussed herein. The first project demonstrated that the new unmodified, nanostructured gold disposable electrochemical printed (DEP) chips produced by BioDevice Technology can compete with surface-modified electrode configurations to detect trace concentrations of insecticides. This was achieved through the measurement of acetylcholinesterase-catalyzed production of thiocholine after incubation of the enzyme with low concentrations of paraoxon (10 ppb) and carbofuran (8 ppb). The second project featured the novel application of a glassy carbon (GC) electrode to monitor the changes in availability of Thioflavin T (ThT) for oxidation at the electrode surface, which is non-linearly modulated by the presence of acetylcholinesterase and the enzyme’s pre-treatment with trace concentrations of paraoxon and carbachol.

Keywords: acetylcholinesterase
electrochemistry
Advisor: Kerman, Kagan
The Role of CtBP in Pituitary Tumorigenesis

C-terminal Binding Protein (CtBP) is a transcriptional co-repressor that plays an important role in mammalian development and tumorigenesis. CtBP is known to interact with Ikaros, an important transcriptional regulator in the pituitary; however CtBP itself has not been examined in this gland. I examined the role of CtBP in pituitary cell growth and survival. Compared to control pituitary GH4 cells, CtBP1-deficient cells exhibit reduced proliferation and de-regulation of genes involved in cell cycle and growth factor signaling. CtBP1-deficient cells were more susceptible to hypoxia-induced apoptosis and showed a reduction in hypoxia-induced Ikaros expression. Interactions between CtBP and Ikaros isoforms were demonstrated in pituitary tumor cell lines. CtBP and Ikaros also bound a common region of the previously characterized Ikaros target, the LDL-R promoter. These results identify oncogenic properties of CtBP1 in the pituitary and set the groundwork for future studies into regulatory roles of CtBP and Ikaros in the pituitary.

Keywords: Pituitary
CtBP
Chromatin Remodeling
Ikaros
Advisor: Asa, Sylvia
Ezzat, Shereen
Defining the Mechanisms by which Palmitoylation Regulates the Localization and Function of RGS4

Regulator of G-protein signalling 4 (RGS4) modulates Gq and Gi signalling at the plasma membrane (PM). It has been demonstrated that the addition of palmitate to cysteine residues is an important regulator of RGS protein localization and function. The family of palmitate transferase enzymes shares a conserved Asp-His-His-Cys (DHHC) motif. We set out to establish the DHHC isoform(s) that affect RGS4 activity in HEK201 cells. Confocal microscopy revealed that overexpression of DHHCs 3 and 7 mobilized RGS4 to the Golgi. Knockdown of either DHHC3 or DHHC7 attenuated RGS4 inhibition of Gαq-coupled Ca2+ release and reduced RGS4 PM localization. Consistent with a role in promoting RGS4 lipid bilayer targeting, dominant negative mutants of the five most highly expressed DHHCs in HEK201 cells also diminished RGS4 PM association. Together, these data suggest that members of the mammalian DHHC family regulate RGS4 localization and function, likely through palmitoylation of its target cysteine residues.

Keywords: RGS4
localization
G protein
palmitoylation
plasma membrane
DHHC
Advisor: Heximer, Scott P.
The Tapestry of Colonial Communication: Colonizing Discourses in the Seoul Press

This thesis explores the coalescence of Japanese and Anglo-American colonial discourses in the Seoul Press. Between the Protectorate Treaty of 1905 and the Annexation Treaty of 1910, Korea was dominated not only territorially but also discursively. Under the guise of the “civilizing mission,” the Japanese Residency General sought to legitimize its colonial project in Korea. To accomplish its goals of silencing foreign opposition to Japanese colonialism and of dictating international opinion about Korea, the Residency General established an English language newspaper, the Seoul Press. In the pages of this daily paper, the views of Japanese colonial officials as well as Anglo-American observers found expression. Through an analysis of articles from the Seoul Press, this thesis will reveal the existence of a dual-layered gaze of colonialism, the rhetorical threads of which made up the tapestry of colonial communication.

Keywords: Colonialism
Korea
Discourse
Seoul Press
Advisor: Schmid, Andre
Alterations in Tgf-β Signaling Mediate the Biologic Behaviour of Osteosarcoma Cell Lines

Osteosarcoma is a mesenchymal tumour of bone common among children and young adults. Prognosis is poor if metastases are present at diagnosis. The transforming growth factor beta (TGF-β) signaling pathway plays a complex dual role in cancer. We hypothesized that alterations in the TGF-β signaling pathway are important in the tumorigenesis of osteosarcoma cell lines. Smad phosphorylation and nuclear localization, Smad4 expression, and TAZ expression were determined in the HOS osteosarcoma cell line and tumorigenic derivatives. Basal TGF-β activity and TAZ expression correlated with a tumorigenic phenotype in the KHOS cell lines as measured by Anchorage Independent Growth (AIG). In comparison, exogenous TGF-β suppressed AIG and acted as a tumour suppressor, while Smad4-deficient KHOS cells were resistant to the inhibitory TGF-β effect. In conclusion, basal TGF-β signaling and TAZ correlate with increased tumorigenic potential in osteosarcoma cell lines, whereas exogenous TGF-β acted as a tumour suppressor in a Smad4-dependent manner.

Keywords: Osteosarcoma
TGF-β
Advisor: Wunder, Jay
Synthetic Applications of N-H Aziridine Containing Compounds

Unprotected N-H aziridine aldehydes are surprisingly stable compounds which can undergo reactions in the absence of protecting groups. In total, three different transformations were explored during my Master’s thesis. The conversions include the dissociation of the aziridine aldehydes, which exist as dimers, and their subsequent re-dimerization in various solvents. The development of mixed aziridine aldehyde adducts and their attempted modifications will also be discussed. Finally, the discovery of N-H aziridine compounds containing a 1,3-dicarbonyl functionality will be discussed, as will their attempted transformations.

Keywords: Aziridine
Aziridine Aldehyde
Advisor: Yudin, Andrei
Reproductive Ecology of Bird-pollinated Babiana (Iridaceae): Floral Variation, Mating Patterns and Genetic Diversity

Flowering plants possess striking variation in reproductive traits and mating patterns, even among closely related species. In this thesis, I investigate morphological variation, mating and genetic diversity of five taxa of bird-pollinated Babiana (Iridaceae), including two species with specialized bird perches. Field observations in 12 populations demonstrated that sunbirds were the primary pollinators. Babiana ringens exhibited correlated geographic variation in flower and perch size. Controlled field pollinations revealed self-compatibility and low pollen limitation in B. ringens subspecies, and self-incompatibility and chronic pollen limitation in B. hirsuta. Allozyme markers demonstrated moderate to high selfing rates among populations and considerable variation in levels of genetic diversity. In B. ringens there was a positive relation between the geographic and genetic distance of populations. The results of a manipulative field experiment indicated position-dependent herbivory on inflorescences of B. hirsuta and this could play a role in the evolution of specialized bird perches in Babiana.

Keywords: Reproductive ecology
Floral variation
Bird pollination
Mating systems
Cape flora
Babiana (Iridaceae)
Advisor: Barrett, Spencer C. H.
Wet and Dry Deposition of Water-soluble Inorganic Ions, in Particular Reactive Nitrogen Species, to Haliburton Forest

Open and throughfall precipitation samples were collected at Haliburton Forest for a total of nine events from July – November of 2009. The following species were analyzed quantitatively: NO3-, SO42-, Cl-, HCOO-, C2O42-, NH4+, Na+, K+, Ca2+, and Mg2+. Wet deposition inputs to the system were quantified and the sources of wet-deposited species were probed. The throughfall method was employed to quantify inputs to the forest floor and probe canopy-precipitation interactions. Leaf wash samples at three heights aided in the interpretation of throughfall data and allowed for an examination of vertical profiles of dry deposition to the canopy. Results suggest possible nitrate foliar leaching during the growing season, although this appears to cease during senescence. This finding supports previous evidence that Haliburton Forest has shifted from nitrogen-limitation toward nitrogen-saturation and estimated total atmospheric N inputs to the system are close to the proposed critical load of 10 kg N ha-1 yr-1.

Keywords: Nitrogen
Deposition
Nitrogen saturation
Precipitation chemistry
Forests
Haliburton
Advisor: Murphy, Jennifer
Cardiac Glycosides, a Novel Treatment for Neuroblastoma: Efficacy and Mechanism

In an attempt to identify agents that specifically target neuroblastoma (NB) tumour-initiating cells (TIC) we performed drug screens using libraries of bioactive compounds. Cardiac glycosides (CGs) were the largest class of drugs identified with antitumour activity. At high CG doses inhibitory effects on the Na+/K+-ATPase induce cardiotoxicity; therefore, CG analogues were designed in an attempt to separate the effects on NB cells from cardiotoxicity. We identified RIDK34 as our lead compound from a structure-activity-relationship analysis (IC50 8 nM). RIDK34 contains a unique oxime group and shows increasing potency against NB TICs. The Na+/K+-ATPase is a target for the apoptotic activity of digoxin and RIDK34, whereby a signaling cascade involving Src and ERK may induce apoptosis. Furthermore, we predict that signaling activation does not require inactivation of the Na+/K+-ATPase and subsequent deregulation of [Na+]i and [K+]I gradients. Thus CGs and particularly RIDK34 may be expected to display diminished cardiotoxicity and greater therapeutic potential.

Keywords: cardiac glycosides
neuroblastoma
tumour initiating cells
cancer stem cells
structure-Activity Relationship Analyses
Advisor: Irwin, Meredith
Mapping the Interactome of Saccharomyces cerevisiae ABC Transporters Pdr12p and Ste6p

The ATP binding cassette (ABC) transporters represent the largest family of transmembrane proteins and play important roles in human inherited disease such as the multi-organ disease cystic fibrosis and cholesterol transport disorder Tangier’s disease. These proteins are also implicated in conferring multidrug resistance, rendering many cancer therapies ineffective, as well as contributing to the pathogenicity of some organisms. The yeast ABC proteins, Pdr12p, a weak acid efflux pump, and Ste6p, the a-factor exporter, were screened for interacting partners using the integrated membrane yeast two-hybrid (iMYTH) system to gain further insight into their biological function. Two interactors were identified for Ste6p, however, the Pdr12p screen identified 13 novel interactions, most notable of which are three other ABC transporters, Pdr5p, Pdr10p and Pdr11p. Subsequent functional analysis of double deletion mutants supports a genetic interaction between Pdr12p and Pdr10p as the pdr12Δ pdr10Δ strain showed resistance to increasing concentrations of weak organic acids.

Keywords: MYTH
Yeast
ABC Transporters
Interactome
Advisor: Stagljar, Igor
Determining the In vivo Conformation of p53 Tumour Suppressor Protein

This work details the design and generation of a monomer specific p53 rabbit polyclonal antibody. The technique involved careful analysis of published Nuclear Magnetic Resonance(NMR)and X-Ray structures to select an epitope buried in the wildtype tetramer of p53,while exposed in the monomer. The antibody was validated with indirect Enzyme Linked Immunosorbant Assay(ELISA),competition ELISA and western blot. Following these experiments, the antibody, denoted as α-tet,was employed in immunofluorescence (IF) experiments of cancer cell lines DU145 (prostate carcinoma, p53 P223L and V274F) and A549 (lung carcinoma,p53 wildtype)to determine the localization of monomeric p53. Monomeric p53 was confined to the nucleolus of DU-145 cells. Additional staining of the Golgi apparatus in both cell lines was also observed. However, upon investigation of a p53 null cell line, SKOV-3,the Golgi staining was determined to be a result of cross reactivity with another protein. Nevertheless, the presence of nucleolar monomeric p53 in DU-145 cells indicates that monomerization of p53 does occur in this cell line.

Keywords: structural biology
p53
antibody
oncology
Advisor: Chakrabartty, Avijit
Effect of Stress on Nicotine Self-administration on Adolescent and Adult Rats

Initiation of smoking mainly occurs during adolescence. Adolescents experience more stressful life events; therefore, stress may be a factor that contributes to this high risk of smoking initiation. The current study examines the effects of three different stressors (yohimbine, intermittent footshock and social defeat) on nicotine self-administration (NSA) in adolescent and adult rats. The effects of yohimbine and footshock were examined after the establishment of NSA behavior, while the effect of social defeat was tested on the initiation of NSA behavior. Yohimbine increased NSA, but the other two stressors did not. The increase in NSA induced by yohimbine tended to be higher in adults than in adolescents. No marked age differences in response to the other two stressors were observed. These results suggest that stress increases NSA in a stressor-specific manner, and that adolescents do not show enhanced vulnerability to the effect of stress on NSA.

Keywords: nicotine
self-administration
stress
adolescent
yohimbine
footshock
social defeat
rats
Advisor: Le, Anh Dzung
The Contribution of Domain Satisfaction to Life Satisfaction: Convergent Validity of Importance Measures

Global life satisfaction is the evaluation of one’s life among important domains. Therefore, importance ratings should improve the relation between domain satisfaction and life satisfaction. However, this is not the case because studies have shown that importance ratings do not improve the model. This study examined the validity of importance and satisfaction measures using a multi-method approach. 316 participants were recruited in friendship pairs to fill out a series of questionnaires about themselves and their friend. Based on the self-informant agreement scores, there is some validity in importance and the satisfaction ratings. The importance measures for some domains also predicted people’s behavioural patterns. Indirect importance ratings were also extracted using regression and correlational analysis. In conclusion, there was also evidence for convergent validity of the direct and indirect importance measures. Therefore, people do think about the important domains to some extent when making a global life satisfaction judgment.

Keywords: Life Satisfaction
Well-being
Advisor: Schimmack, Ulrich
Regulation of AMPA Receptor Currents by Mitochondrial ATP Sensitive K+ Channels in Anoxic Turtle Neurons

Mammalian neurons rapidly undergo excitotoxic cell death during anoxia, while neurons from the anoxia-tolerant painted turtle can survive without oxygen for hours without apparent damage. An anoxia-mediated decrease in AMPA receptor currents are an important part of the turtle’s natural defence however the mechanism underlying it is unknown. Here I investigate a mechanism that involves activation of a mitochondrial KATP channel that subsequently signals a decrease in AMPAR currents. Whole-cell AMPAR currents were stable during normoxia, but anoxia or pharmacological activation of mKATP channels resulted in a 50% decrease in AMPAR currents. Conversely, mKATP antagonists blocked the anoxia-mediated decrease. Mitochondrial KCa channel modulators responded similarly. Blocking the Ca2+-uniporter also reduced normoxic AMPAR currents by 40%, and including BAPTA in the recording abolished the anoxia or agonist-mediated decrease. Therefore, the mKATP channel is involved in the anoxia-mediated down-regulation of AMPAR activity and is a common mechanism to reduce glutamatergic excitability.

Keywords: Anoxia-tolerance
Ischemia
mitochondria
AMPA receptor
Chrysemys picta
mKATP channel
Advisor: Buck, Leslie
Intersexual Differences in the Strength of Selection on Condition in Drosophila melanogaster

Variation in condition can result from environmental heterogeneity or genetic variation affecting resource acquisition and processing ability. Although condition should be positively correlated with the fitness of both males and females, the strength of selection on condition may differ between the sexes due to differences in reproductive variance. Sexual selection on male condition has been proposed to reduce mutation load, but only if selection is greater on males than females. To investigate the strength of selection on condition, the quality of the larval environment was used to manipulate the condition of Drosophila melanogaster. Additionally, selection was measured when the availability of key resources for females (live yeast) and males (access to females) were altered. Overall, selection was found to be stronger on males than females. However, selection on males weakened under a female-biased sex ratio, whereas selection on females was not significantly affected by the abundance of live yeast.

Keywords: Evolutionary genetics
Drosophila melanogaster
Sexual selection
Condition
Intersexual differences
Advisor: Agrawal, Aneil
Legal Liability of U.S. Credit Rating Agencies under Section 11 of the Securities Act: The Long and Winding Road toward Accountability

This paper argues that credit ratings have contributed to the current financial crisis. In United States, the previous “reputational model” as well as the current proposals aimed at reducing reliance on rating agencies, enhancing competition and increasing transparency is not sufficient to improve the integrity of rating agencies. This paper suggests that imposing stricter liability on rating agencies is necessary. The proposal to eliminate the exemption of NRSROs under Section 11 of the Securities Act is necessary but not sufficient for holding rating agencies accountable. The first amendment defense always shields rating agencies from legal liability, while the absence of a common standard make it hard to impose liability for negligent ratings. Finally, this paper suggests that the courts should not award the rating agencies First Amendment protection and consider the distinguished characteristics of rating agencies, when examining the professional liability of the agencies.

Keywords: credit rating agency
liability
Advisor: Betty, Ho
Scale-up of Extrusion Foaming Process for Manufacture of Polystyrene Foams Using Carbon Dioxide

An initial evaluation of the scalability of extrusion foaming technology is conducted in this thesis. Both lab- and pilot-scale foam extrusion systems along with annular dies and flat dies were used to investigate the effects of extrusion system scale on the foam expansion. The effects of the processing conditions including die temperature and blowing agent content on the volume expansion of extruded polystyrene foams blown with carbon dioxide are presented. A systematic comparison of the effects of extrusion system scale on the expansion behavior of polystyrene foams blown with carbon dioxide at the consistent pressure-drop rate, demonstrated that the scale of the foam extrusion system does not affect the principles of the foaming process, and the effects of extrusion system size on the scale-up of foam techniques, such as shear rate and temperature uniformity, could be suppressed by tailoring the processing conditions and experimental parameters.

Keywords: scale-up
extrusion foaming
Advisor: Park, Chul B.
Deficiency in MBD2 is Sufficient to Cause Behavioral Impairments in Mice

Methyl-CpG-binding proteins (MeCP2, MBD1-MBD3) recruit transcriptional co-repressor molecules to methylated regions and silence transcription. The role of MBD2 in regulating brain function and behavior remains largely unexamined. To begin elucidating whether MBD2 influences neural function, I assessed the behavioral performance of Mbd2 null mice, compared their hippocampal electroencephalographic activity during exploration, and performed protein and mRNA expression assessments. The results indicate that mutant mice display a heightened anxiety-like behavior, diminished explorative activity and reduced sociability compared to wild-type mice. However, these behavioral differences were not paralleled by neurophysiological impairments. Mutant hippocampal and cortical samples display significantly elevated MeCP2 mRNA levels. Yet, MeCP2 protein expression did not mirror the mRNA profile and instead was significantly reduced. Glucocorticoid Receptor mRNA levels were significantly reduced in the hippocampus and cortex regions of Mbd2 null brains. The loss of MBD2 is sufficient to induce behavioral impairments in mice without introducing gross deficits in hippocampal neurophysiology.

Keywords: MBD2
behavioral impairments
MeCP2
EEG
Advisor: Eubanks, James