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The synthesis and characterization of novel platinum(II) complexes containing bulky aromatic groups
Full text linkSix iminopyridine ligands were prepared from the condensation of 6-methyl-2-pyridinecarboxyaldehyde and the corresponding primary amines containing bulky cycloalkyl groups. Addition of these ligands to [PtCl2(coe)]2 (coe=cis-cyclooctene) gave the desired platinum(II) coordination complexes in moderate to high yields. All compounds were fully characterized using FT-IR and multinuclear NMR spectroscopy. Solid compounds were subjected to melting point analysis. Elemental analysis (EA) was performed on three of the platinum(II) complexes. Future work will involve completing elemental analysis studies and performing biological testing. X-ray diffraction studies must be performed to support the existing characterization data
Synthesis, reactivity and computational studies of redox-active indium thiolate complexes
Full text linkGreen Chemistry initiatives have recently been at the forefront of both industrial and academic communities in order to address fundamental scientific challenges of protecting human health and the environment. The Twelve Principles of Green Chemistry, of which catalysis is a primary tenet and the main motivation for this project, has led the path to reduce waste production in the chemical industry. The principle of catalysis states that catalytic reactions necessarily produce less waste than stoichiometric reactions. Traditionally, precious and toxic heavy transition metals such as platinum and palladium have been used as metal centres in catalysts because of their stability, favourable redox properties, and ease of characterization. These concerns prompted this research in finding more environmentally friendly alternatives as metal centres in catalysis, such as main group complexes. Indium is a heavy main group metal that is environmentally benign. It is most stable in the +3 oxidation state and, notably, does not possess other readily accessible oxidation states. To make indium complexes redox-active, so-called “non-innocent” redox-active ligands are being explored. The current work seeks to synthesize a series of redox-active indium catalysts with varied steric bulk about the indium centre and different redox-active ligands. The goals of this study are to first synthesize and structurally characterize organometallic indium compounds with the redox-active ligand 2-amninobenzenethiol, and then test the reactivity of indium complexes with dithiolate ligands using mild oxidizing agents. A third goal is to use DFT methods to rationalize the synthesized complexes in terms of structure, reactivity, bonding motifs, and in interpreting the experimental spectroscopic data
L-Phenylalanine differentially activates G protein-coupled receptor signalling pathways
Full text linkThe most abundant cell surface receptor in eukaryotes, G-protein coupled receptors (GPCRs) couple with heterotrimeric G proteins, utilizing active Gα and Gbg subunits, to initiate
distinct intracellular signaling pathways implicated in cell functions and physiological responses. Several GPCRs are validated therapeutic drug targets, while the majority of GPCRs represent
unexplored potential, with many studies aiming to define their signal transduction response, identify ligands, and determine their roles in diseases and disorders. Amino acids have become an
interest of studies aiming to elucidate their role as ligands, with previous findings demonstrating that L-phenylalanine activates 12 Class A GPCRs. The aim of this study was to characterize the signal transduction response in multiple established signaling pathways for the L-phenylalanine - responsive GPCRs. This was investigated utilizing mammalian cells expressing a target GPCR and luciferase reporter for one of the Ga12/13, Gaq/11, Gbg, Gai/o, and Gas signaling pathways. Cells were treated with either L-phenylalanine or a control vehicle prior to luciferase assay examinations of their response. L-phenylalanine differentially activated GPCR signaling pathways, in a manner that was receptor-dependent, to preferentially increase or decrease cellular responses. Moreover, this response was not always limited to one preferential pathway, and not all receptors previously identified to be activated by L-phenylalanine were observed to significantly signal through the examined pathways. Elucidation of L-phenylalanine’s role in the regulation of cellular communication and function must be explored through independent receptor characterization due to its promiscuous receptor-dependent activation of GPCRs
Better estimating the core mass of Jupiter
Full text linkThe mass of Jupiter’s core is currently estimated to be between 5 and 20E⊕, which leaves the core mass as a significant unknown quantity when examining the solar system. The two primary theories that address the formation of giant planets such as Jupiter, are Core Accretion (CA) and Disc Instability (DI). CA predicts that the core mass should be between 15 − 20E⊕, and DI predicts that the core mass should
be between 5 − 10E⊕. Since both predictions overlap with the current estimates, neither method can be confirmed as the one used to form Jupiter. Through Modules of Experiments in Stellar Astrophysics (MESA), a series of models of Jupiter was created with changes in their core mass in 0.5E⊕ intervals within the current estimate. Using GYRE, a stellar oscillation code, the model’s p-modes and g-modes
were analyzed. Upon examination of p-modes, it was found that changes in the core had no significant effect on their oscillations per theoretical predictions. Several models exhibited irregular behaviours in their g-modes, showing higher than average percentage of frequencies with positive mode work and normalized growth rates (η). The physical characteristics of these irregular models were examined and found that the sound speed varied in regions less than 0.40 Jupiter radii. Additionally, period spacings of these models found the spacings to be regular and dips in the spacing, likely being caused by changes in the local molecular weight. Variations in regions of g-mode oscillations with core mass were found between 0.2 and 0.5 Jupiter radii, which further indicates that the core mass is affecting the g-mode oscillations and could be causing physical changes in the models. This research was not able to fully examine the exact differences in the interior structures that might be causing these irregular behaviours to occur but should be examined in the future. The results of this research remain inconclusive in determining better estimations for the core mass of Jupiter but can act as a foundation for future esearchers to continue
Investigating the developmental mechanisms responsible for within-plan variation in Halenia deflexa
Full text link(From "Introductory Remarks")
My honours research contributes to answering the large question, “Are the developmental mechanisms that result in variation in spur length among flowers within individuals of H. deflexa the same as those that produce variation in spur length among species within the genus Halenia?” This question is beyond the scope of a single honours project, so my objective was to address the first part of the question. I aimed
to describe the floral developmental adjustments responsible for the within-plant variation of nectar spur lengths in Halenia deflexa. Specifically, my goals were (1) to develop methods for clearing, staining, and imaging preserved H. deflexa floral tissue, and (2) to describe what cellular changes are causing these variations in nectar spur lengths, whether it’s due to the size, shape, or number of cells, or some
combination of factors.
Historically within-plant variation has been mostly seen as inconvenient, an
irrelevant detail obscuring the mean (Herrera 2009). Recently, however, within-plant
variation is increasingly being investigated as a possible target for selection. This
research could be the first step towards uncovering some important evolutionary
significance in an under-appreciated trait. If within-plant variation is indeed a blueprint
for diversification, then maybe it can give us a glimpse into the evolutionary trajectory of
plants
Cryopreservation of shortnose sturgeon (Acipenser brevirostrum) ovarian tissue
Full text linkThere are many factors that risk the survival of wild sturgeon populations; namely, illegal poaching for caviar and anthropogenic consequences such as habitat destruction. In fact, based on their classification by the IUCN, sturgeon are considered one of the most endangered vertebrate groups worldwide. Therefore, the need for a largescale conservation effort is growing. Cryopreservation is used as a method of preserving important genetic material for conservation purposes by storing biological samples at very low temperatures. Thus, the work presented here is aimed to optimize cryopreservation protocols with a focus on shortnose sturgeon (Acipenser brevirostrum) ovarian tissue. Shortnose sturgeon were specifically chosen as they are locally accessible, smaller in size than other sturgeon species, and have a lower endangerment status. I examined the effectiveness of three different cryoprotectants for their use in cryopreserving oogonial cells: dimethyl sulfoxide (DMSO), ethylene glycol (EG), and glycerol (GLY). Additionally, the antioxidant melatonin was also included at three different concentrations (0.01 mM, 0.1 mM, and 1 mM) in hopes of mitigating freezing injury and enhancing post-thaw cell viability which I assessed using a Luminescent ATP Determination kit. When comparing only the three cryoprotectants without any further supplementation, EG was found to be the least effective cryoprotectant, whereas DMSO was most effective in samples from fish #1 and GLY was most effective in samples from fish #2. However, post-thaw analysis following melatonin supplementation to the cryomedia revealed that there was no one treatment group that stood out from the rest. Alternatively, the four samples with the highest post-thaw ATP concentration all resulted in statistically equal values and were treated with either DMSO + 0.1 mM melatonin, EG + 0.01 mM melatonin, GLY + 0.01 mM melatonin, or GLY without any further supplementation. These results suggest that the addition of melatonin has a favourable effect on viability during the freezing. Overall, the work presented here represents an endeavour to conserve sturgeon populations by using cryopreservation to maintain the integrity and viability of genetic samples
An investigation into DNA damage response and repair genes in cancers of epithelial origin
Full text linkBiomarkers are extremely powerful tools in cancer research. The transition to cancer care under the precision medicine model will require the investigation of novel biomarkers that provide
individualized information about the genetic profiles of particular tumours within a given patient. This study sought to investigate DNA damage response and repair genes, which play an important role in maintaining the integrity of the genome, in cancers of epithelial origin. Given their important role, these genes are potential biomarkers that could indicate whether DNA damage is being repaired adequately; where both a lack of or an increase in response could result in cancer. To investigate their potential as biomarkers, two types of DNA damage-related genes were investigated in this study. First, the ability of the status of mismatch repair genes to be used with the status of MAPK pathway oncogenes, as combined biomarkers, to predict survival probability was examined retrospectively using a database from a rural population in New Brunswick, Canada. Both Kaplan-Meier survival analyses and Cox Proportional Hazards Regression analyses were performed. Next, the Translesion Synthesis E3 ubiquitin ligase, RAD18, was investigated as a potential biomarker in lung cancer. Immunohistochemistry was performed in autopsy samples from an individual donor, and a protocol for subsequent quantitative polymerase chain reaction was created using a control primer set with the experimental samples. The results found that combined mismatch repair gene and oncogene biomarkers were not as powerful as previously described, with other covariates such as biological sex having more predictive power. For RAD18, there did not appear to be a qualitative difference in the amount of RAD18 across tumour samples and normal lung tissue. Overall, further studies with larger sample sizes and quantitative methods will be needed to verify the findings from this study
The undermining effect of sucrose reinforcement on automatically-reinforced operant wheel-running study in rats
No full textThe undermining effect can be defined as a decrease in levels of intrinsic motivation for a behaviour as a consequence of the delivery and subsequent removal of a contingent extrinsically-motivating reward. A well-documented phenomenon in humans, the present study investigated the potential presence of an undermining effect of extrinsic sucrose reinforcement on intrinsically motivated (automatically-reinforced) operant wheel running in eight female Long-Evans rats. In each session, rats ran for 20 min prior to and following operant wheel running on a fixed interval (FI) 60-s schedule. Across three conditions, water, sucrose, and water were delivered as outcomes for operant wheel running on the FI 60-s schedule. No undermining effect was observed for wheel running on the FI 60-s schedule following the removal of sucrose; nor was there a decrease in running during the 20-min post-operant running period. However, wheel running during the 20 min period prior to operant running significantly decreased. Contrary to previous findings, this result suggests that an undermining effect can occur in rats. Explanations for the presence of this effect as well as suggestions for future research investigating this effect in non-human species are discussed
Relationships between plasma metabolites and mass gain in semipalmated sandpipers during migratory staging in the Northumberland Strait
Full text linkSemipalmated Sandpipers are long distance migrants that depend upon staging sites to build reserves during their fall migration to non-breeding sites. Eastern breeding Sandpipers use sites in Atlantic Canada, such as Petit-Cap, NB, to prepare for migration to South America. Rates of mass gain are an important metric used to predict migratory success and assess site quality, although this is difficult to obtain given that it requires the recapture of individual birds, which is not feasible at many staging sites. Plasma metabolites are a useful tool for indicating these metabolic changes in mass over time, but these relationships have not been examined in freeliving Semipalmated Sandpipers, despite their widespread use in the literature. At the study site, Petit-Cap, recaptures are possible, allowing us to test this relationship.
We examined plasma metabolites (plasma triglycerides, glycerol, and bhydroxybutyrate) in relation to changes in mass in recaptured Semipalmated Sandpipers at Petit-Cap, NB. We failed to detect relationships between plasma triglycerides and b-hydroxybutyrate and mass changes in recaptured Semipalmated Sandpipers, suggesting that inferences of mass changes through plasma metabolites
should not be integrated over long time intervals. We did find a significant positive relationship between glycerol and mass gain. As an extension of studying migratory refueling, we also assessed diets of the shorebirds while staging at this site. We found that bivalves were contributing largely to diets of both adult and juvenile Semipalmated Sandpipers, with no significant differences in diet breadth between the
two age classes.
While collecting data for this study, we encountered a storm midway through the staging season. This provided an opportunity to examine the effects of short-term weather events upon body condition and refueling in staging Semipalmated Sandpipers. We found significant impacts upon migratory refueling in both recaptured and non-recaptured Semipalmated Sandpipers following a storm. Recaptured birds, on
average, lost mass during the week following the storm. Similarly, non-recaptured birds had significantly lower size adjusted masses during versus before or after the week of the storm. These findings support previous research on the sensitivity of staging shorebirds to environmental fluctuations and highlight the importance of considering weather events a threat to migratory refueling.
We emphasize the need for further investigation into the relationships between plasma metabolites, diet, handling, and weather upon rates of migratory refueling in Semipalmated Sandpipers