Life Sciences Commons^™

Low Temperature Tolerance Of Adult Drosophila Suzukii (Diptera: Drosophilidae), Ruth Jakobs

Electronic Thesis and Dissertation Repository

The crop pest Drosophila suzukii, native to Southeast Asia, has been found in Ontario since 2010. This raises concern with respect to it establishing permanent populations, however, little is known about its cold tolerance. I investigated the low-temperature tolerance, including phenotypic plasticity, of D. suzukii. While acclimation increased cold tolerance, there was no evidence of short-term cold-hardening. Chill coma occurs at -1.2 °C, which will limit winter activity. Cold shock decreased the reproductive output of females, but this negative effect may be mitigated by re-mating. Drosophila suzukii is chill-susceptible and 80 % of the flies die after exposure …

Characterization Of Aldh Positive Cells In The Human Fetal Pancreas, Amanda Oakie

Electronic Thesis and Dissertation Repository

Aldehyde dehydrogenase (ALDH) is an enzyme that regulates differentiation during pancreatic development, but determining the role of ALDH during endocrine differentiation is not well defined. The purpose of this study was to characterize transcription factors (TFs) and putative stem cell surface markers in ALDHhi or ALDHlo populations of the human fetal pancreas (18-22 weeks of age), and examine their expansion and differentiation in vitro and in vivo. Cell surface marker analysis demonstrated high co-localization of the stem cell marker CD133 with ALDHhi cells. ALDHhi cells also contained higher expression of islet- associated TFs and insulin. Expansion of sorted ALDHhi cells …

A Rhog/Ilk/Elmo2/Rac1 Pathways Modulates Microtubule Stability, Bradley C. Jackson

Electronic Thesis and Dissertation Repository

Integrin-linked kinase (ILK) is a widely expressed scaffold protein important for cell adhesion, migration, and phagocytosis. ILK and its interacting partner, engulfment and cell motility protein 2 (ELMO2), may also modulate microtubule dynamics. Here, I show that sustained microtubule growth and acetylated tubulin levels are reduced in the absence of ILK and, conversely, that exogenous ILK exerts a stabilizing effect on microtubules. Further, exogenous ELMO2, ras homology growth related protein (RHOG) and ras-related C3 botulinum toxin substrate 1 (RAC1) stabilize microtubules in an ILK-dependent manner. Potential downstream effectors of the effect of ILK on microtubule stability include glycogen synthase kinase- …

Amyloid Β Peptides, Signalling And Trafficking Of The Α7 Nicotine Receptor, Kirk Young

Electronic Thesis and Dissertation Repository

The α7 nicotinic acetylcholine receptor (nAChR) is an ionotropic receptor for the neurotransmitter acetylcholine and its precursor, choline. Interestingly, α7 nAChR binds amyloid β 42 (Aβ42) peptide, which has a primary role in Alzheimer’s disease pathology. Aβ42 peptide forms aggregates and different structural forms elicit different physiological outcomes. Oligomeric, fibrillar and non-aggregated preparations of Aβ42 were characterized by atomic force microscopy. Immunoblotting of neuronal cells exposed to these preparations determined oligomeric aggregates of Aβ42 mediate ERK1/2 intracellular signalling through α7 nAChR. Cell surface ionotropic receptors are regulated through endocytosis to maintain the integrity of neurotransmission. Cellular pathways for endocytosis of …

Biosteel High Performance Sports Drink Improves Exercise Performance Following A Simulated Hockey Game, Kolten C. Abbott

Electronic Thesis and Dissertation Repository

INTRODUCTION: BioSteel High Performance Sports Drink (BioSteel) is one of the most popular sports supplements consumed by professional and amateur athletes. BioSteel Inc^® claims that consumption of BioSteel before and during exercise will result in “enhanced energy while delaying the onset of muscular and mental fatigue”. PURPOSE: Assess the efficacy of BioSteel supplementation on anaerobic and aerobic exercise performance as well as sport-specific cognition throughout exercise. METHODS: Eleven exercise-trained men completed a simulated hockey game on a cycle ergometer under two experimental conditions: BioSteel and isoenergetic placebo. Measures of exercise performance and cognition were assessed before, throughout and after …

Mutations At The 46th Residue Change Properties Of Cx50 Gap Junction Channels, Xiaoling Tong

Electronic Thesis and Dissertation Repository

The interface of the first transmembrane domain and the first extracellular loop (TM1/E1 border) in several gap junction (GJ) channels is known to line a portion of the pore and plays an important role in determining GJ channel properties. By introduction of a charged residue into this domain of Cx50, the resultant mutant channels showed drastically altered unitary conductance (γ_j) and transjunctional voltage-dependent gating (V_j-gating). Specifically G46D and G46E increased the Cx50 γ_j from 201 to 256 and 293 pS, respectively and G46K channel showed a decreased γ_j of only 20 pS. Moreover, in …

The Implications Of Altered Cholinergic Signaling In Cardiac Health And Disease, Ashbeel Roy

Electronic Thesis and Dissertation Repository

­Cardiac remodeling and dysfunction occur prior to the onset of heart failure. Altered regulation of cardiac function by the autonomic nervous system has been implicated in the progression of heart disease. Both altered sympathetic and parasympathetic tone contribute to cardiac disease; however, the role of the parasympathetic nervous system, and specifically acetylcholine (ACh), in cardiac dysfunction has not been fully elucidated. In these studies, we sought to determine whether changes in neuronal and/or non-neuronal ACh release regulate cardiac activity and alter the progression of cardiac remodeling and dysfunction. A systemic decrease in the expression of the vesicular acetylcholine transporter …

Ilk Modulates Stress-Induced Apoptosis In Epidermal Keratinocytes, Michelle Im

Electronic Thesis and Dissertation Repository

Integrin-linked kinase (ILK) is a ubiquitous scaffold protein that mediates cellular responses to integrin stimulation by extracellular matrix proteins. Mice with inactivation of the Ilk gene in squamous epithelia display defects in skin regeneration after injury, failure to thrive, and perinatal death. ILK-deficient epidermis exhibits reduced adhesion to the basement membrane and impaired hair follicle morphogenesis. In culture, ILK-deficient keratinocytes fail to attach and spread efficiently, and demonstrate decreased survival. We now show that ILK-deficient keratinocytes exhibit lower proliferative capacity and increased apoptosis in the absence or presence of growth factors. This reduced viability appears to be independent of the …

Role Of C-Kit Receptor Tyrosine Kinase On Ins-1 Cell Vegf-A Expression In Vitro, Alexei Popell

Electronic Thesis and Dissertation Repository

Interactions between Stem Cell Factor (SCF) and c-Kit are critical in maintaining β-cell survival and function. VEGF-A, essential in facilitating islet vasculature formation, is secreted by β-cells. This work investigates the mechanisms by which c-Kit regulates VEGF-A production in β-cells, using a rat insulinoma (INS-1) cell line as an in vitro model. Cells were treated with recombinant hSCF or cultured with c-Kit (r) siRNA for 72 h. VEGF-A accumulation in the culture medium was measured by ELISA, while qRT-PCR, western blot, and immunofluorescence analyses were also performed. SCF augmented VEGF-A production in a time-dependent (p < 0.05 vs. control at 6 h and 24 h), and dose-dependent manner (p < 0.01 vs. control at 30-100 ng/mL). SCF stimulation increased phosphorylation of proteins along the PI3K/Akt/mTOR pathway (p < 0.05 vs. control groups), and decreased phosphorylation following siRNA treatment. Our results indicate that c-Kit exerts a regulatory effect on VEGF-A production in β-cells.

Niacin And Microvascular Endothelial Cell Response To Fatty Acid Excess And Hypoxia, Dominic Pang

Electronic Thesis and Dissertation Repository

Niacin can reduce vascular disease risk, but its mechanism of action is controversial, and may not be dependent on systemic lipid modifying effects. This thesis tested the hypothesis that niacin directly improves endothelial cell function under lipotoxic and low oxygen conditions, as seen in ischemic conditions during metabolic syndrome, and investigated the potential mechanism involved. Human microvascular endothelial cell (HMVEC) survival was reduced by exposure to excess fatty acids under both normoxic and low oxygen conditions. Angiogenic function, as determined by tube formation on Matrigel, was impaired during fatty acid overload under either normoxic or low oxygen conditions. These effects …

The Role Of C-Kit Receptor Tyrosine Kinase In Beta-Cell Proliferation, Function And Survival, Zhi Chao Feng

Electronic Thesis and Dissertation Repository

c-Kit, a receptor tyrosine kinase, interacts with Stem Cell Factor (SCF), mediating cell differentiation, function, and survival. c-Kit is critical for the development and maintenance of beta-cell function in both rodents and humans. The mutation of c-Kit at W locus (c-Kit^Wv/+) in mice results in an early onset of diabetes. However, the underlying mechanisms by which c-Kit deficiency leads to beta-cell failure are unknown. Therefore, studying SCF/c-Kit downstream signaling pathways is essential to understanding the precise mechanism by which c-Kit regulates beta-cell survival and function in vivo.

We identified that dysregulated Akt/Glycogen synthase kinase 3β (Gsk3β)/cyclin …

Characterization Of Blood-Derived Human Progenitor Cells For Vascular Regeneration, David Putman

Electronic Thesis and Dissertation Repository

Cardiovascular disease (CVD) remains a leading cause of premature death worldwide. Despite advances in treatment of ischemic diseases including myocardial infarction and peripheral arterial disease (PAD) there remains a need for effective revascularization therapies. Although early cell therapy trials investigated use of MNC from autologous bone marrow, emerging evidence indicates that purified progenitor cell populations are required to induce optimal vascular regeneration. In addition, autologous cells show reduced efficacy due to CVD-related progenitor dysfunction. This thesis presents preclinical studies characterizing several blood-derived cell types for the development of cellular therapies to treat PAD, focusing on the use of allogeneic umbilical …

Islet Regenerative Properties Of Ex Vivo Expanded Hematopoietic Progenitor Cells, Ayesh K. Seneviratne

Electronic Thesis and Dissertation Repository

Human umbilical cord blood (UCB) progenitor cells with high aldehyde dehydrogenase activity (ALDH^hi), can stimulate endogenous islet regeneration after transplantation into mice with steptozotocin (STZ)-induced diabetes. However, UCB ALDH^hi cell are extremely rare, and expansion will be required to develop cell-mediated strategies to treat patients with diabetes. To increase the number of progenitor cells available for clinical application, we expanded ALDH^hi UCB cells under clinically applicable, serum-free hematopoietic-restricted conditions. 6 day expansion resulted in a 15-fold increase in total cell number, and a 3-fold increase in the number of HPC retaining high ALDH (ALDH^hi HPC) …

Analysis Of The Vascular Phenotype Of The Ent1-Null Mouse, Keisha A. Best

Electronic Thesis and Dissertation Repository

Adenosine is important in the regulation of vascular tone and the Equilibrative Nucleoside Transporter 1 (ENT1) is a regulator of adenosine concentrations. Thus, changes in ENT1 expression and activity may alter vascular tone regulation. We therefore examined the cardiovascular phenotype of ENT1-null (ENT1^-/-) as compared to wild type mice (ENT1^+/+). Heart rates (HRs) and blood pressures (BPs) of ENT1^-/- and ENT1^+/+ littermate male mice were obtained while conscious and anaesthetized, and metabolic data were collected over a 24 hr period. Vascular reactivity was assessed in aortic ring segments obtained from 3 month old ENT1 …

Role Of Nitric Oxide In Embryonic Heart Development And Adult Aortic Valve Disease, Yin Liu

Electronic Thesis and Dissertation Repository

Congenital heart disease (CHD) is the most common birth defect in infants. Identifying factors that are critical to embryonic heart development or CHDs in general could further our understanding of the disease and may lead to new strategies of its prevention and treatment. Endothelial nitric oxide synthase (NOS3/eNOS) is known for many important biological functions including vasodilation, vascular homeostasis and angiogenesis. Previous studies have shown that deficiency in NOS3 results in congenital septal defects, cardiac hypertrophy and postnatal heart failure. In addition, NOS3 is pivotal to morphogenesis of aortic valve and myocardial capillary development. The aim of my thesis was …

The Role Of Integrins In Support Of Pancreatic Function, Survival And Maturation, Matthew Riopel

Electronic Thesis and Dissertation Repository

The pancreas is a glandular organ composed of endocrine and exocrine compartments. Integrins are cell adhesion molecules that connect cells to the extracellular matrix (ECM). Integrins modulate a variety of cellular effects, yet their mechanism of action in the developed pancreas is not well understood. Fibrin is a provisional ECM protein that contains ligands for integrin receptors. Fibrin is capable of supporting islet health, but it is unclear how fibrin exerts its effects. The objective of this thesis is to understand the role of integrin receptors on in vivo pancreatic cell function, survival, and proliferation. In addition, this thesis investigates …

Quantifying The Effect Of Age And Contraction Mode On The Force-Velocity-Power Relationship In The Knee Extensors, Justin R. Paturel

Electronic Thesis and Dissertation Repository

PURPOSE: To assess and compare the force-velocity-power relationship (F-V-P) using isotonic and isokinetic knee extensions in 11 younger (19-30y) and 11 older (69-81y) men. METHODS: The construction of the F-V-P curves were attained with each participant performing maximal, explosive knee extensions at 8 different loads (isotonic) and 8 different velocities (isokinetic) on a Cybex HUMAC NORM dynamometer. Maximal voluntary contraction (MVC or P_o), maximal shortening velocity (V_max), maximum power, optimal torque (P_opt) and velocity (V_opt) were assessed and compared. RESULTS: The older men were 43% weaker, 18% slower and ~54% less powerful …

The Effects Of Ocean Acidification And Eutrophication On The Growth, Lipid Composition And Toxicity Of The Marine Raphidophyte Heterosigma Akashiwo., Julia Rose Matheson

Electronic Thesis and Dissertation Repository

Anthropogenic forcing, such as ocean acidification caused by rising carbon dioxide emissions, and eutrophication due to increased nutrient loadings in run-off, are causing major changes to the biogeochemistry of the oceans. As a consequence, coastal phytoplankton are susceptible to altered biogeochemical environments. This study examined the effect of a lower pH and increased levels of nutrients on the common coastal harmful alga, Heterosigma akashiwo. Growth rates, maximal cell yields, neutral lipid accumulation and toxicity of cells grown under various pH and nutrients regimes were measured. H. akashiwo growth was near maximal when grown at lower pH levels. There was …

Sex Hormones And Sympathetic Nerve Activity, Charlotte W. Usselman

Electronic Thesis and Dissertation Repository

The purpose of this thesis was to test the hypothesis that changes in circulating sex hormone levels are associated with changes in muscle sympathetic nerve activity. The hypothesis was tested through the comparison of low- (early follicular [EF]) and high-hormone (midluteal [ML]) phases of the menstrual cycle and of hormonal contraceptive use (low hormone [LH] versus high hormone [HH]). The microneurography technique was used to compare both the frequency and size of bursts in muscle sympathetic nerve activity (MSNA) at baseline and during two sympatho-excitatory maneuvers: baroreceptor unloading elicited through lower body negative pressure, and chemoreflex stimulation elicited through a …

Functional Anatomy Of The Anconeus: Muscle Architecture And Motor Unit Number Estimation, Daniel E. Stevens

Electronic Thesis and Dissertation Repository

Exploring muscle architecture in vivo and estimating the number of MUs in the human anconeus muscle have important implications related to the neuromuscular function of this muscle as a model for study in health and disease. The two studies presented in this thesis investigate the functional anatomy of the anconeus in 10 healthy young men (25±3y).

Ultrasound imaging has facilitated the measure of the architectural variables, fascicle length (L_F) and pennation angle (PA), in many human skeletal muscles in vivo. However, the functional anatomy of the anconeus has been investigated mainly from cadavers exclusively. Thus, the purpose …