Biological Sciences - Theses, Dissertations, and other Required Graduate Degree Essays

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The effect of sulphate on selenium bioaccumulation in two freshwater primary producers and a primary consumer

Author: 
Date created: 
2014-12-16
Abstract: 

Site-specific conditions (e.g. presence of sulphate), may be linked to the variability in the uptake of selenium in organisms at the base of a food chain, potentially affecting the risk of adverse effects in higher trophic-level organisms. In this project, the effect of sulphate on selenate bioaccumulation in two primary producers (Lemna minor and Pseudokirchneriella subcapitata) and a primary consumer (Daphnia magna) was explored. When exposed to selenate, all three species exhibited a decrease in selenium tissue concentration with increasing sulphate. When D. magna were exposed to sulphate and dietary selenium, sulphate did not affect selenium tissue concentrations. The results were used to develop equations estimating selenium tissue concentrations when exposed to selenate and sulphate. The strong predictive ability of the equations suggests that selenate, sulphate, and dietary selenium (applicable to D. magna) are important for describing the relationship between selenate and selenium tissue concentrations.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Christopher Kennedy
Department: 
Science:
Thesis type: 
(Project) M.E.T.

Palynology and Paleoecology at Kilgii Gwaay Archaeological Site, Southern Haida Gwaii

Date created: 
2014-11-26
Abstract: 

Buried pond sediments at the Kilgii Gwaay archaeological site on Ellen Island in Gwaii Haanas National Park, were analyzed palynologically to produce a high-resolution record of postglacial vegetation during late glacial and early Holocene time. Seven AMS radiocarbon dates provide a sediment core chronology spanning the period 14,470-10,870 cal yr BP. Four biostratigraphic zones are defined, with a transition from early herb-shrub tundra (14,510 cal yr BP) to a Pinus-dominated forest 14,000 cal yr BP. Pinus is largely replaced by Picea 13,290 cal yr BP, followed by establishment of Tsuga heterophylla 12,420 cal yr BP. Changes in vegetation assemblages and stratigraphy may indicate cooling associated with the Younger Dryas event. Charcoal analysis reveal peak abundance during the known occupation of Kilgii Gwaay (10,700 cal yr BP). Charcoal extends below the known occupation horizon, indicating human presence as early as 11,500 cal yr BP, approximately 800 years earlier than previously documented.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Rolf Mathewes
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Web reduction behaviour and the chemical communication system of the western black widow, Latrodectus hesperus

Date created: 
2014-12-03
Abstract: 

In spiders, pheromones mediate intersexual attraction, courtship behaviour, and mate recognition. I studied the chemical communication system of the western black widow spider, Latrodectus hesperus. Females attract males to their webs with silk-borne sex pheromones. Contact with the silk elicits courtship behaviour by males. Often, the courting male engages in web reduction behaviour, during which he excises and bundles up sections of the web and wraps them with his own silk. Using analytical chemistry, and behavioural tests in both the laboratory and the field, I investigated (1) the molecular structure and function of the female’s contact sex pheromone, and (2) the function of web reduction behaviour. A silk-borne contact pheromone elicits web reduction behaviour, and a serine derivative similar to the pheromone of congeneric L. hasselti is one constituent of the multi-component pheromone. Web reduction decreases web attractiveness to rival males in the field, thereby limiting male-male competition.

Document type: 
Thesis
File(s): 
Video A1
Video B1
Senior supervisor: 
Gerhard Gries
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

An evaluative mode for assessing the fate and effects of contaminants in engineered wetlands

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2014-10-17
Abstract: 

To investigate the potential of engineered wetlands to remove contaminants from wastewaters, a steady-state and temporal multimedia model was developed for a free water surface design. The model estimates contaminant fate throughout wetland media, assesses the potential for bioaccumulation, and evaluates ecological risk using relevant toxicological endpoints (i.e. EC5). Illustrative examples for pyrene, arsenic, a naphthenic acid, and a chemical universe defined by a range of log KOW (-0.5 – 7.5) and log KOA (-4.5 – 11.5) were used to demonstrate the models applications. In these illustrative applications, the steady-state removal efficiencies of pyrene, arsenic, and the naphthenic acid from the wetland were 41%, 83%, and 31%, respectively. The most efficiently removed chemicals had a log KOW ≈ 6 and log KOA ≤ 2.5. Removal efficiency was lowest for substances showing reduced evapotranspiration flux. This study concluded that wetland treatment could be a feasible method of remediation for certain contaminants in wastewater.

Document type: 
Graduating extended essay / Research project
Senior supervisor: 
Frank Gobas
Department: 
Science:
Thesis type: 
(Project) M.E.T.

Downstream processing of a plant-made recombinant human therapeutic enzyme

Author: 
Date created: 
2014-07-25
Abstract: 

Mucopolysaccharidosis I is a lysosomal storage disease that is characterized by a deficiency of the lysosomal hydrolase alpha-L-iduronidase. Enzyme replacement therapy with purified, recombinant IDUA is one treatment option available for individuals that inherit this disease. The goal of my thesis was to engineer a transgenic line of Arabidopsis thaliana that could express, in the seed tissue, human iduronidase with a therapeutically acceptable N-glycan profile. Human iduronidase was expressed at 5.7% of total soluble protein (TSP) in the Arabidopsis cgl mutant line, which is deficient in N-acetylglucosamine transferase I, and at 1.5% of TSP in the Arabidopsis Golgi-Mannosidase I (GM-I) knockout line. The iduronidase purified from both lines was able to hydrolyze the fluorescent iduronide compound, 4-methylumbelliferyliduronide (4-MUI), at a rate comparable to that of iduronidase produced in Chinese Hamster Ovary cells, commercially available as Aldurazyme. Both plant-derived forms of iduronidase possessed primarily high-mannose N-glycans (at 95% for cgl-iduronidase and 100% for GM1-iduronidase); however, the dominant glycoform in the N-glycan profile of cgl-iduronidase was Man5GlcNAc2, whereas most of the N-glycans on GM1-iduronidase contained six to eight mannose sugars. Additionally, cgl-iduronidase contained a small percentage of complex glycans (and thus potentially immunogenic xylose and/or fucose sugars), which were not found on GM1-iduronidase. Surprisingly GM1-iduronidase did not contain an N-glycan at Asn336, which is normally present on the native human iduronidase and on the recombinant iduronidase of cgl Arabidopsis seeds and Chinese hamster ovary cells. Of importance to creating a product that is of therapeutic value, another goal was to determine whether the plant-produced iduronidase was amenable to in vitro phosphorylation to create the mannose-6-phosphate tag necessary for sequestration and lysosomal delivery in human cells. Both plant-derived forms of the enzymes were able to be phosphorylated in vitro by the UDP-GlcNAc:lysosomal enzyme (GlcNAc)-1-phosphotransferase at a rate similar to that of Aldurazyme.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Allison Kermode
Department: 
Science: Biological Sciences Department
Thesis type: 
(Thesis) M.Sc.

The Effects of Legacy and Emerging Persistent Organic Pollutants in Endocrine Signalling Pathways in Mammalian Cancer Cell Lines

Author: 
Date created: 
2014-08-14
Abstract: 

Despite its ban, DDT and DDE are still persistent in the environment. TBECH is a brominated flame retardant that has been detected in the biota. Here, we determined whether p,p’-DDT, p,p’-DDE and TBECH can negatively impact androgen receptor (AR)-regulated expression of prostate-specific antigen (PSA), prostate-specific membrane antigen (PSMA) and AR in human LNCaP cells. Real-time PCR, Western-blotting and COBAS PSA detection system were used to measure mRNA and protein levels. Chromatin-immunoprecipitation assay was used to determine AR-PSA promoter interaction. My results showed that p,p’-DDT and p,p’-DDE repressed R1881-inducible PSA mRNA and protein levels by blocking recruitment of AR to the PSA promoter. p,p’-DDT and p,p’-DDE can also significantly repress AR protein levels and relieve R1881-inducible PSMA repression. TBECH was found to repress R1881-inducible PSA protein levels. I conclude that men who have been exposed to either DDT or DDE may produce a false-negative PSA test when screening for prostate cancer.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Timothy Beischlag
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.

Contributions to the Molecular Biology of Kelp

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
1999
Abstract: 

Genetic relatedness between various kelp (Order Laminariales, Class Phaeophyceae, Division Heterokontophyta) taxa was investigated using DNA sequencing and PCR-typing. The rDNA ITS1 region of gametophytes generated by a naturally occurring apparent kelp hybrid of Macrocystis C. Agardh and Pelagophycus Areschoug were sequenced to determine parentage. All gametophytes examined had only Macrocystis rDNA suggesting either a non-hybrid, or more complicated hybridization than pure equal parental contribution occurred. Laboratory-generated intergeneric hybrids of Alaria Greville and Lessoniopsis Reinke were examined for parentage based on rDNA regions amplified using PCR. Both parental rDNA types were visible in one identified possible hybrid and non-hybrids were easily distinguished. Actin introns in both Alaria and Nereocystis Postels & Ruprecht were characterized and sequenced, representing the first actin intron sequences examined in the Heterokontophyta. The second actin intron fiom individuals of three Alaria species, spanning a geographic range of hundreds of kilometres, were sequenced to quantify variation and to examine individual relatedness for usage in studies of gene flow and population subdivision. Relatedness seemed to correlate with oceanographic distance but not with accepted species boundaries.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Louis D. Druehl
Department: 
Dept. of Biological Sciences - Simon Fraser University
Thesis type: 
(Thesis) Ph.D.

The evolution, ecology, and restoration of anadromy in rainbow trout/steelhead Oncorhynchus mykiss

Date created: 
2014-09-02
Abstract: 

Evolution can occur on ecologically relevant timescales, creating the potential for a bidirectional link between evolution and ecology. For example, migrating species provide important pulses of resources to recipient ecosystems, but are increasingly subject to intense selection due to ongoing global change. If heritable variation underlies migration, then contemporary evolution may increase non-migratory life histories, thereby increasing population persistence, but at the expense of important ecological processes. I examine contemporary evolution and its consequences of migration in an economically and ecologically important species, the resident and migratory ecotypes of the species Oncorhynchus mykiss. In Chapter 2, I show that a stream barrier has driven the evolutionary loss of the migratory ecotype in only ∼25 generations. I estimated the genetic contribution to variation in traits underlying the expression of migration and show that in the above-barrier population there has been a 30% decrease in expression of the migratory ecotype relative to the below-barrier population of origin. In Chapter 3, I examine the ecological consequences of this contemporary evolution. I show that the density decreases associated with loss of anadromy consistently had a greater effect on mesocosm ecosystems than the per-capita effects of the ecotypes. In Chapter 4, I use an analytical model to explore whether a population of O. mykiss would evolve toward greater residency in response to increased costs of migration. I find that evolution can rescue isolated populations; populations that persist are those that evolve in response to the changing selection regime on timescales that prevent population extinction. However, when conditions are restored to the pre-disturbance state, the rate of recovery of the migratory ecotype was unpredictable and generally slower than its loss. Finally, in Chapter 5 I review pathways for restoring the migratory ecotype, and how restoration of a life history may differ from restoring a species. Effective restoration of this life history will entail understanding the ecological and genetic mechanisms underpinning the expression of migratory behavior. Together, these chapters highlight that migratory barriers can drive contemporary evolution of the non-migratory ecotype that increases population persistence, but decreases their ecological impacts. More generally, this research highlights the importance of incorporating evolutionary perspectives in manage- ment, conservation, and restoration.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Jonathan Moore
Department: 
Science:
Thesis type: 
(Thesis) Ph.D.

The effects of natural and anthropogenic disturbance in lotic ecosystems

Date created: 
2014-09-03
Abstract: 

The prevalence of large-scale anthropogenic and natural disturbance has increased in recent decades around the world. For example, over 50% of the world’s large rivers are currently dammed and the frequency of large wildfires has nearly quadrupled in western North America since the mid-1980s. Disturbances such as these are principal drivers of change in lotic ecosystems and we seek to improve our understanding of how they affect recipient ecosystems in the context of fisheries management and conservation. My thesis research combines empirical studies and modeling to improve our ability to predict and measure the effects of several major types of natural and anthropogenic disturbance in lotic ecosystems. In Chapter 1 I improved the accuracy of hydrodynamic habitat models for juvenile salmon by up to 10% by applying Akaike information criterion and model averaging. In Chapters 2 and 3 I applied multiple regression and bioenergetic models to illustrate how wildfire, by burning riparian vegetation, can elevate stream temperatures by up to 0.6°C adding ~5 kJ of metabolic costs to salmonids. As well, I found concentrations of food web resources such as nitrate and fine particulate organic matter increased in burned compared to unburned regions by 244% and 44%, respectively, and I found significantly greater seasonal changes in terrestrial and aquatic invertebrate abundance than changes attributable to wildfire. Despite similar regional invertebrate prey abundance, Bayesian stable isotope mixing models revealed seasonal and regional differences in salmonid diets, with higher trophic level prey contributing more to diets in the burned compared to a reference region. Lastly, in Chapter 4 I found that forest harvest and rising air temperatures are warming waters in the Fraser River basin at 0.07°C per decade on average by applying Spatial Stream Network models. In total, my thesis research builds on previous work and illuminates how disturbance can affect abiotic and biotic responses in lotic ecosystems at spatial scales ranging from less than 10 m2 to over 200,000 km2. Thus, results from my thesis research will aid fisheries management and conservation by improving our understanding of how natural and anthropogenic disturbance may alter streams and rivers in our future.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Jonathan W. Moore
Department: 
Science:
Thesis type: 
(Thesis) Ph.D.

The modulation of abcb4 and cyp3a65 gene expression and multidrug/multixenobiotic resistance (MDR/MXR) functional activity in the model teleost, Danio rerio (zebrafish)

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2014-08-28
Abstract: 

The multidrug/multixenobiotic resistance (MDR/MXR) mechanism is a cellular response involving the induction and coordinated action of the ATP-binding cassette (ABC) transporter, P-glycoprotein (P-gp), and the phase I metabolizing enzyme, cytochrome P450 3A (CYP3A), which confers protection against potentially cytotoxic exposures of various drugs and environmental contaminants. In mammals, ligand-mediated pregnane X receptor (PXR) transcriptional activity regulates the induction of P-gp and CYP3A but this mechanism is not well characterized in fish species. In this study, zebrafish treated with the Pxr (PXR) agonist PCN co-modulated P-gp (Abcb4) and CYP3A (Cyp3a65) mRNA expression and this co-modulation was associated with increased hepatic MDR/MXR functional activity in vivo. Consistent with a mammalian-like MDR/MXR mechanism regulated by PXR, zebrafish co-treated with PCN and the mammalian PXR antagonist, ketoconazole (KTC) attenuated the PCN-mediated modulation of hepatic abcb4 and cyp3a mRNA levels, as well as attenuated the PCN-mediated modulation of MDR/MXR functional activity. These results suggest abcb4 may be involved with the MDR/MXR response in the adult zebrafish liver, and that Pxr (PXR) may regulate this dynamic process. Finally, the lack of Cyp3c1 mRNA modulation by PCN suggests that Cyp3c1 and Cyp3a65 may be regulated by separate transcriptional pathways.

Document type: 
Graduating extended essay / Research project
File(s): 
Senior supervisor: 
Chris Kennedy
Department: 
Science: Biological Sciences Department
Thesis type: 
(Project) M.E.T.