• Influence of adolescent social instability stress on the intake of ethanol and sucrose in a rodent model

      de Lima Marcolin, Marina; Department of Biological Sciences
      Adolescence is a sensitive period in which the effects of stress and alcohol can have long-lasting impacts. Social instability stress in adolescent rats (SS; postnatal day 30-45, daily 1 hour isolation + new cage partner) alters behavioural responses to psychostimulants and increases anxiety-like behaviour, but differences in voluntary consumption of natural and drug rewards are unknown. The main goal of my thesis was to investigate the effects of adolescent social instability stress (SS) on immediate and long-lasting changes on reward-related behaviours in male rats using voluntary alcohol intake paradigms. Another goal was to investigate the influence of social context on the propensity to drink alcohol, as well as the influence of these factors on sucrose intake. In chapter 2, I found that adolescent SS increased alcohol intake irrespective of social context, and adolescents drank more alcohol than adults. The intake of sucrose was not altered by stress, except during context of competition. In chapter 3, I found that history of alcohol drinking reduced synaptic plasticity markers in the dorsal hippocampus and prefrontal cortex, and this reduction was sometimes further reduced by SS. The propensity to drink alcohol was found not to differ between SS and CTL rats in the first experiment, and reduced among SS rats in the second experiment. After nine days of alcohol absence, the propensity to drink alcohol was not increased by previous alcohol access, and SS increased intake only in alcohol-naïve rats. History of alcohol drinking reduced anxiety-like behaviours and blunted SS-induced reduction in social interactions. Both SS and alcohol decreased corticosterone levels at baseline and after fear recall without changing freezing behaviour. My findings indicate that using a model of mild social stressor can have great impact on adolescent rats, but moderate effects in adult rats. The behavioural changes caused by stress can be enhanced later in life by history of alcohol drinking, but that does not necessarily cause an increase in the propensity to drink during adulthood, as other studies have shown. Adolescent stressed rats drink more alcohol than other groups, but they don’t seem to continue drinking more when they reach adulthood. These results indicate that the effects of social instability stress are transient in regards to propensity to drink, and can be the basis for alterations caused by both alcohol and stress.
    • The Influence of Attentional Focus on the Self-Efficacy-Performance Relationship in a Continuous Running Task

      LaForge-MacKenzie, Kaitlyn; Applied Health Sciences Program (Brock University, 2015-02-04)
      The self-efficacy-performance relationship in continuous sport tasks has been shown to be significantly reciprocal yet unequal with stronger influences in the performance-to-self-efficacy pathway rather than self-efficacy-to-performance pathway (e.g., LaForge-MacKenzie & Sullivan, 2014b). Bandura (2012) suggested that sociocognitive variables may influence this relationship. Attention as a sociocognitve factor may bias the processing of performance and self-efficacy information (Bandura, 1982, 1997; Bandura & Jourden, 1991). As confidence and attention are important aspects of peak running performance (Brewer, Van Raalte, Linder, & VanRaalte, 1991), the primary purpose of the present study was to examine the self-efficacy-performance relationship under three conditions of attentional focus. The secondary purpose was to examine self-efficacy and performance as separate constructs under the same conditions of attention. Participants ran continuously for one kilometer in one of three randomly assigned attentional focus conditions: internal-focus (n = 51), external-focus (n = 50), and control (n = 49). Self-efficacy was assessed using a one-item measure every 200 meters. Path analyses examining the primary objective revealed significant self-efficacy-to-performance pathways in all conditions: external-focus (p < .05, βs ranging from -.17 to -.32), internal-focus (p < .05, βs ranging from -.26 to -.36), and control (p < .05, βs ranging from -.29 to -.42). Significant reciprocal relationships were absent in all conditions. ANOVAs examining the secondary objectives found significantly faster performance in the control condition at the start (F (2, 147) = 3.86, p < .05) and end of the task (F (2, 147) = 3.56, p < .05). Self-efficacy was significantly higher in the internal-focus condition at the end of the task (Self-Efficacy 4 (F (2, 147) = 3.21, p < .05) and Self-Efficacy 5 (F (2, 147) = 4.74, p < .05). In contrast to previous within-trial research (e.g., LaForge-MacKenzie & Sullivan, 2014b) self-efficacy-to-performance effects were more significant and robust than performance-to-self-efficacy effects. These results provided support for Bandura’s (2012) suggestion that sociocognitive factors may have the ability to alter the causal structure of the self-efficacy-performance relationship, proposing complexities in the self-efficacy-performance relationship (Sitzmann &Yeo, 2013). Results were discussed from both theoretical and applied perspectives.
    • The Influence of Cerebral Blood Flow and Carbon Dioxide on Neuromuscular Responses During Environmental Stress

      Hartley, Geoffrey L.; Applied Health Sciences Program
      Although reductions in cerebral blood flow (CBF) may be implicated in the development of central fatigue during environmental stress, the contribution from hypocapnia-induced reductions in CBF versus reductions in CBF per se has yet to be isolated. The current research program examined the influence of CBF, with and without consequent hypocapnia, on neuromuscular responses during hypoxia and passive heat stress. To this end, neuromuscular responses, as indicated by motor evoked potentials (MEP), maximal M-wave (Mmax) and cortical voluntary activation (cVA) of the flexor carpi radialis muscle during isometric wrist flexion, was assessed in three separate projects: 1) hypocapnia, independent of concomitant reductions in CBF; 2) altered CBF during severe hypoxia and; 3) thermal hyperpnea-mediated reductions in CBF, independent of hypocapnia. All projects employed a custom-built dynamic end-tidal forcing system to control end-tidal PCO2 (PETCO2), independent of the prevailing environmental conditions, and cyclooxygenase inhibition using indomethacin (Indomethacin, 1.2 mg·Kg-1) to selectively reduce CBF (estimated using transcranial Doppler ultrasound) without changes in PETCO2. A primary finding of the present research program is that the excitability of the corticospinal tract is inherently sensitive to changes in PaCO2, as demonstrated by a 12% increase in MEP amplitude in response to moderate hypocapnia. Conversely, CBF mediated reductions in cerebral O2 delivery appear to decrease corticospinal excitability, as indicated by a 51-64% and 4% decrease in MEP amplitude in response to hypoxia and passive heat stress, respectively. The collective evidence from this research program suggests that impaired voluntary activation is associated with reductions in CBF; however, it must be noted that changes in cVA were not linearly correlated with changes in CBF. Therefore, other factors independent of CBF, such as increased perception of effort, distress or discomfort, may have contributed to the reductions in cVA. Despite the functional association between reductions in CBF and hypocapnia, both variables have distinct and independent influence on the neuromuscular system. Therefore, future studies should control or acknowledge the separate mechanistic influence of these two factors.
    • Influence of upper limb ischaemia-reperfusion injury on the regulation of cutaneous blood flow during local thermal hyperaemia

      McGarr, Gregory Walter; Applied Health Sciences Program
      The present research was developed to investigate the effects of acute upper limb ischaemia- reperfusion (I-R) on neurovascular and endothelial control of the cutaneous micro-circulation in the forearm and finger by evaluating its influence on the magnitude and kinetics of the vasodilatory response to local skin heating. Study 1 investigated between-day reliability of the local heating response in non-glabrous and glabrous index finger skin. Study 2 investigated the effects of I-R on the local heating response in non-glabrous and glabrous skin of the index finger. Study 3 investigated within- and between-day reliability of the local heating response in non-glabrous forearm skin. Study 4 investigated the effects of I-R on the local heating response in non-glabrous forearm skin, as well as the contribution of sensory nerves in mediating the magnitude and kinetics of this response. When data were normalized for blood pressure and expressed as cutaneous vascular conductance (CVC) reliability was generally comparable across all skin sites. In non-glabrous skin reliability was superior when CVC was normalized to maximum heating. At all skin sites, normalizing CVC to baseline produced poor results. Vasodilatory onset time and time to initial peak during local heating produced moderate to good reliability for all skin sites in Studies 1 and 3. In the finger, I-R did not influence the magnitude of the local heating response for the initial peak or plateau phases in either skin type. However, I-R did cause a ~23% delay in vasodilatory onset time and a ~16% delay in time to initial peak in non-glabrous skin. In the forearm, I-R attenuated the initial peak and plateau phases by ~31% and ~34%, respectively. Vasodilatory onset time was also delayed by 34% post-ischaemia. The contribution of sensory nerves in mediating the initial peak and vasodilatory onset time were significantly reduced post-ischaemia, while sensory nerves did not influence the plateau. It is concluded that upper limb I-R impairs the local heating response in non-glabrous forearm and index finger skin. A combination of cutaneous sensory nerve impairment and reduced nitric oxide bioavailability appear to be responsible for attenuating the vasodilatory response to local skin heating under these conditions.
    • Informal Teacher Leaders: Secondary School Teachers’ Perceptions of How They Collaboratively Construct and Implement Classroom Assessment Policy and Practice

      Clarke, Kristen A; Department of Graduate and Undergraduate Studies in Education
      Secondary school teachers enact informal teacher leadership to move their instructional and assessment practices forward by leveraging existing structures and navigating micropolitical contexts. Leadership cannot be oversimplified as the work of an individual because of the complex and interwoven nature of schools and the current political climate of educational settings. Informal teacher leaders (ITLs) co-create roles based on needs that focus on supporting learning for students, for colleagues, and for themselves. This study used a constructivist lens and inquiry methodology to explore perceptions of informal secondary school teacher leaders as they collaboratively construct and implement classroom assessment policy and practice. The study highlights the perceived purpose and nature of informal teacher leadership; organizational factors and conditions that ITLs face when working collaboratively to improve assessment practices; and strategies that these teachers leverage to navigate changes in assessment practice and policy. (Note: a provincial review of assessment was conducted during completion of this dissertation.) This qualitative study explored informal teacher leadership and assessment practice and policy through semi-structured interviews, focus groups, document analysis, and memoing. The research encompassed 28 participants, 11 of whom are ITLs in a suburban school district in Ontario. Findings reveal how ITLs structure their roles to be responsive, reciprocal, reflective, and results oriented. Recommendations are provided to inform educators and policy developers at the provincial, district, and school level for both supporting informal teacher leadership and developing assessment literacy.
    • Infrared Spectroscopy of Ge:Mn Thick Films Prepared by Ion Implantation and Post-annealing

      Obied, Laila Hassan; Department of Physics
      An infrared transmission study of Ge:Mn systems is presented in this work. Various Ge:Mn samples have been prepared by both single (Mn2+ ion energy 4.76 MeV, dose 2x10^16 /cm^2) or multiple (dose 1x10^16 /cm^2) into high resistivity (100) Ge substrates. Both conventional and flash lamp annealing procedures have been used to prepare a set of samples that were characterized by X-ray Diffraction (XRD), Secondary Ion Mass Spectrometry (SIMS) and magnetometry as well as infrared transmission spectroscopy (60-8000 cm^-1). After implantation, the Ge:Mn layers are about 3 mm thick and amorphous as revealed by XRD. Samples conventionally annealed at temperatures below 250C maintained their amorphous structure. Samples annealed at temperature above 330C recrystallized into a polycrystalline structure. SIMS measurements show that the diffusion of Mn is greatly affected by the starting distribution and that diffusion is much higher in samples prepared with the lower total Mn dose. The presence of multiple magnetic phases in all the annealed samples was indicated by field and temperature dependent measurements of the total moment. Our diverse preparations suggest that the formation of secondary phases in Ge:Mn system in unavoidable. Magnetic measurements suggest that the maximum volume fraction of metallic Mn5Ge3 inclusions is of the order of 1x10^-3, much lower than the percolation threshold of metallic inclusions in an insulating matrix. Infrared transmission measurements on the same samples show the presence of a low frequency Drude like absorption with high hole concentration (p~10^ 18 /cm^3) which is greater than the critical density for metal-insulator (MI) transition in Ge. This observation suggests Mn has crystallized in substitutional sites to a far greater degree than was achieved with traditional equilibrium crystal growth. The MI transition has been investigated in the Ge:Mn system by studying the temperature dependent transmission between 4K and 300K and comparing to similar measurements on a sample of Ga-doped Ge with p = 1.5x10^16 /cm^3 which is on the insulating side of the MI transition. Finally, absorption was observed that may possibly be attributed to Mn5Ge3 inclusions in the Ge:Mn matrix.
    • INHUMAN TARGETS: Psychopathy, Dehumanization, and Sexist and Violent Attitudes Towards Women

      Methot-Jones, Tabitha; Department of Psychology
      The current work presents three studies that examined the role of dehumanization in the association between psychopathy and sexist and violent attitudes towards women. This program had two overarching goals in examining psychopathy, dehumanization, and sexist and violent attitudes towards women. The first goal was to examine whether an indirect association between psychopathy and negative attitudes towards women existed through dehumanization. The second goal was to explore if, by introducing information that humanizes women, levels of dehumanization could be mitigated for individuals high on psychopathic traits. Employing mixed samples for both studies (student and community), Study 1 (n = 514) and Study 2 (n = 202) provided evidence that psychopathy demonstrated an indirect relationship with sexist and violent attitudes towards women via dehumanization. Study 2 also expanded on Study 1 by including a behavioural measure of violent attitudes towards women. Finally, Study 3 (n = 206), again using a mixed sample, attempted to manipulate dehumanization to see if it, and the sexist and violent attitudes associated with it, would be mitigated. Unfortunately, the manipulation failed, but we were able to use the data from Study 3 to provide a replication of the results of Study 2. Across three studies results suggested that the path from psychopathy to negative attitudes towards women was at least partially (if not fully) indirect through dehumanization. This suggests that dehumanization may be an important mechanism to consider when examining the tendency of individuals high in psychopathic traits to engage in violence towards women. Furthermore, because psychopathic traits are associated with violence perpetrated against women, dehumanization could be an important construct to consider when examining potential avenues for clinical interventions. Even more broadly, dehumanization could be an important construct for mitigating the association between psychopathy and violence generally.
    • Institutional Dimensions of Professional Knowledge: Implications for School Administrators’ Constructions of Equitable Leadership Knowledge in Kenya and Canada

      Oyugi, Perez; Department of Graduate and Undergraduate Studies in Education
      This international comparative study employed a constructivist grounded theory approach to explore the influence of institutional factors on school administrators’ constructions of equitable leadership knowledge and practice in Kenya and Canada. Six principals and vice principals from Kisumu County, Kenya and 5 from Ontario, Canada participated in the study. An institutional theory lens is used to compare and illuminate the processes school administrators used to link institutional imperatives to equitable leadership knowledge and practice. First, the results indicate that equitable leadership is an emerging concept in Kenya among school principals. Second, the results confirm that equitable leadership knowledge and practice is nested within regulative, normative, and cognitive pillars that underlie educational institutions in Kenya and Canada. Third, results show that equitable leadership knowledge arose out of interactions between institutional actors and from institutional processes for sensemaking and for organizing knowledge in both countries. Fourth, a three-stage process theory—mimetic, normalizing, and transference stages—emerged from the data to connect equitable leadership knowledge to institutional obligations.
    • The interaction of sleep and hormones on emotion functioning

      Lustig, Kari; Department of Psychology
      Insufficient sleep has been associated with deficits in emotion processing; sleepy individuals show increased emotional reactivity and decreased emotion regulation. Individual differences that predict performance after sleep loss has remained largely elusive. Concentrations of cortisol, progesterone, and testosterone are candidate predictors for variability in performance following sleep loss. These hormones are associated with emotion functioning under well-rested conditions and show interactions with sleep and circadian rhythms. The central aim of this dissertation was to investigate the interaction of natural sleep and hormones on measures of emotion functioning. Study 1 examined the role of cortisol in the relationship between sleep (across the first three years of university), and self reported emotion functioning in undergraduate students. Poor sleep was associated with worse emotion regulation and reactivity, and greater concentrations of cortisol and cortisol/DHEA-S. Consistently poor sleepers over three years, who had high cortisol, experienced the greatest difficulties with emotion regulation. Study 2 investigated the association between sleep satisfaction and objective measures of sleep on self-reported emotional functioning in a group of children and adolescents. Importantly, in girls who were dissatisfied sleepers, being further though puberty was associated with the greatest difficulties with emotion regulation. Study 3 examined natural sleep, hormones, and menstrual phase on processing emotional stimuli. Participants completed sleep diaries and wore actigraphy watches for 3-weeks and completed measures of emotion perception on two occasions in the laboratory, in different menstrual phases for women. The study supported dynamic relationships between hormone concentrations and various measures of sleep duration and quality on the processing of emotion stimuli. Many relationships emerged for threatening emotions, indicating that high concentrations of testosterone, progesterone or cortisol, combined with poor sleep resulted in increased sensitivity towards threat detection. Together these studies provide evidence that hormones are an important factor in understanding the link between poor sleep and emotion functioning. Hormone concentration plays a role in understanding individual differences in response to sleep loss and can compound with sleep loss to result in worse emotional outcomes. Consideration of hormonal factors may help identify certain at-risk populations for sleep related deficits or timing of interventions.
    • Interactions and Population Dynamics Between Erwinia amylovora, Pantoea agglomerans, and their Bacteriophages for Effective Phage Therapy

      Gayder, Steven C; Centre for Biotechnology
      Fire blight is a globally devastating disease of apples, pears, and other rosaceous plants caused by the bacterial phytopathogen Erwinia amylovora. Our lab is developing a dual-action biological control product using the epiphytic bacterial antagonist Pantoea agglomerans and a cocktail of bacterial viruses called bacteriophages. P. agglomerans act as host cells for a cocktail of phages targeting E. amylovora in planta and also exclude the pathogen from the blossom pistil and hypanthia by natural antagonism and antibiotic production. The objective of this research is to understand the dynamics between the pathogen, the carrier, and their phages and use this information to develop an effective phage-carrier system for the control of E. amylovora. A novel DNA plasmid was created which allows simultaneous quantification of E. amylovora, P. agglomerans, and four Erwinia phage species using quantitative real-time PCR (qPCR). This plasmid standard-based qPCR was used to study the host range of 10 phages against a global collection of Erwinia strains (n=106) and potential carriers (n=30), and to study the population dynamics of Erwinia phages in different host and cocktail combinations in unprecedented detail. The host range on E. amylovora revealed global phage resistance is located largely in western North America, and this resistance is due in part to a greater effect of exopolysaccharide production by these hosts. Also three phages, ɸEa21-4, ɸEa46-1-A1, and φEa35-70, were chosen to investigate for potential biocontrol efficacy. Phage ɸEa35-70, while ineffective alone, synergized with both ɸEa21-4 and ɸEa46-1-A1 for enhanced reduction of E. amylovora growth over 24 h. The competition between ɸEa21-4 and ɸEa35-70 was exploited which maximized carrier survival and lead to the design of an effective phage-carrier combination which will be formulated and further investigated for the control of E. amylovora in planta. Finally, the quantitative host range data and host genomic sequences were used to identify 10 host genes that are potentially associated with phage infection using a novel, k-mer based, genome wide association study (GWAS). These genes are indicative of a potential phage receptor, two novel phage resistance mechanisms, and other metabolic and biological functions which may affect phage infection.
    • Intracellular antioxidant and DNA repair enzymes as correlates of stress resistance and longevity in vertebrates

      Page, Melissa Maire; Department of Biological Sciences (Brock University, 2011-10-14)
      In animals, both stress resistance and longevity appear to be influenced by the insulin/insulin-like growth factor-l signaling (lIS) pathway, the basic organization of which is highly conserved from invertebrates to vertebrates. Reduced lIS or genetic disruption of the lIS pathway leads to the activation of forkhead box transcription factors, which is thought to upregulate the expression of genes involved in enhancing stress resistance, including perhaps key antioxidant enzymes as well as DNA repair enzymes. Enhanced antioxidant and DNA repair capacities may underlie the enhanced cellular stress resistance observed in long-lived animals, however little data is available that directly supports this idea. I used three. experimental approaches to test the association of intracellular antioxidant and DNA base excision repair (BER) capacities with stress resistance and longevity: (1) a comparison of multiple vertebrate endotherm species of varying body masses and longevities; (2) a comparison of long-lived Snell dwarf mice and their normallittermates; and (3) a comparison of hypometabolic animals undergoing hibernation or estivation with their active counterparts. The activities of the five major intracellular antioxidant enzymes as well as the two rate-limiting enzymes in the BER pathway, apurininc/apyrimidinic (AP) endonuclease and polymerase ~, were measured. These measurements were performed in one or more of the following: (1) cultured dermal fibroblasts; (2) brain tissue; (3) heart tissue; (4) liver tissue. My results indicate that antioxidant enzymes are not universally upregulated in association with enhanced stress resistance and longevity. I also did not find that BER enzyme activity was positively correlated with longevity, in an inter-species context, though there was evidence for enhanced BER in long-lived Snell dwarf mice. Thus, while there were instances in which enhanced antioxidant and BER enzyme activities were associated with increased stress resistance and/or longevity, this was not universally the case, indicating that other mechanisms must be involved. These results suggest the need to re-examine existing 'oxidative stress' hypotheses of longevity and probe further into the molecular physiology of longevity to discover its mechanistic basis.
    • Investigating a dynamic modular framework for subjective well-being

      Busseri, Michael A.; Department of Psychology (Brock University, 2009-01-28)
      According to Diener (1984), the three primary components of subjective well-being (SWB) are high life satisfaction (LS), frequent positive affect (P A), and infrequent negative affect (NA). The present dissertation extends previous research and theorizing on SWB by testing an innovative framework developed by Shmotkin (2005) in which SWB is conceptualized as an agentic process that promotes and maintains positive functioning. Two key components ofShmotkin's framework were explored in a longitudinal study of university students. In Part 1, SWB was examined as an integrated system of components organized within individuals. Using cluster analysis, five distinct configurations of LS, P A, and NA were identified at each wave. Individuals' SWB configurations were moderately stable over time, with the highest and lowest stabilities observed among participants characterized by "high SWB" and "low SWB" configurations, respectively. Changes in SWB configurations in the direction of a high SWB pattern, and stability among participants already characterized by high SWB, coincided with better than expected mental, physical, and interpersonal functioning over time. More positive levels of functioning and improvements in functioning over time discriminated among SWB configurations. However, prospective effects of SWB configurations on subsequent functioning were not observed. In Part 2, subjective temporal perspective "trajectories" were examined based on individuals' ratings of their past, present, and anticipated future LS. Upward subjective LS trajectories were normative at each wave. Cross-sectional analyses revealed consistent associations between upward subjective trajectories and lower levels of LS, as well as less positive mental, physical, and interpersonal functioning. Upward subjective LS trajectories were biased both with respect to underestimation of past LS and overestimation of future LS, demonstrating their illusional nature. Further, whereas more negative retrospective bias was associated with greater current distress and dysfunction, more positive prospective bias was associated with less positive functioning in the future. Prospective relations, however, were not consistently observed. Thus, steep upward subjective LS trajectory appeared to be a form of wishful-thinking, rather than an adaptive form of selfenhancement. Major limitations and important directions for future research are considered. Implications for Shmotkin's (2005) framework, and for research on SWB more generally, also are discussed
    • Investigating a Potential Function of Belief in a Just World: Providing Purpose in Life as a Pathway to Subjective Well-Being

      Rubel, Alicia N.; Department of Psychology
      According to justice motive theory, individuals have a fundamental need to believe that the world is a just place where people get what they deserve, or to have belief in a just world (BJW; Lerner, 1977, 1980). There are several reasons why individuals need BJW that have been proposed in the extant literature (Dalbert, 1999, 2001; Hafer, 2000; Lerner, 1980; Lerner & Miller, 1978; Lipkus, Dalbert, & Siegler, 1996). In the current research, I examine two of these functions: to encourage investment in long-term goals (Callan, Shead, & Olson, 2009; Hafer, 2000; Hafer, Bègue, Choma, & Dempsey, 2005) and to reduce fear of death (Hirschberger, 2006; Pyszczynski, Greenberg, & Solomon, 1997). Moreover, I propose a new function of BJW—to provide individuals with a sense of purpose in life. Specifically, I argue that BJW provides a sense of purpose because, if individuals have BJW, then they can see the world as a place where their lives are both desirable and important. Further, having a sense of purpose in life should in turn improve subjective well-being (Ryff, 1989; Ryff & Keyes, 1995; Ryff, Lee, Essex, & Schmutte, 1994; Zika & Chamberlain, 1992). Therefore, purpose in life, or purpose anxiety, should mediate the association between BJW and well-being. I examined this proposal in four studies. For each study, I predicted that BJW would have an indirect association with positive affect, negative affect, and satisfaction with life, through purpose in life, or purpose anxiety, and that this association would be unique from those through other potential mediators in each model. My hypotheses were supported in each of the four studies. I discuss limitations, topics for future research, and implications for theory as well as reducing victim blame and supporting victims of trauma.
    • Investigating the bone-muscle interaction during growth and development in children

      Ludwa, Izabella A.; Applied Health Sciences Program
      The purpose of this dissertation was to assess functional changes in the muscle-bone unit during normal growth and maturation in peri-pubertal children, and determine if changes in muscle strength are directly related to changes in bone properties. The first part of this work was a systematic review of literature on the effect of physical activity on bone development in children. It was found the best time to see large improvements in bone properties may be during the peri-pubertal years. It was not clear the best type of activity, nor which loading characteristic, should be utilized. This led to the second part of this work, where a non weight-bearing bone, the radius, was investigated in order to separate the influence of muscle properties on bone from ground reaction forces. Children and adolescents (n=172), between the ages of 8-16 years, were examined over a 2-year period. Measurements of somatic maturity, anthropometry, grip strength, bone properties (reflected by speed of sound (SOS)), physical activity (accelerometery), nutrition (24-hour recall), and bone resorption (NTX) were taken. Materials and procedures were identical between studies allowing for both a cross-sectional and longitudinal examination of the muscle-bone unit. Cross-sectionally, results demonstrated relative grip strength, maturity, dietary calcium and NTX explained 21% of the variance in radial SOS (p<0.05). Calcium intake was found to be a significant predictor only after NTX was accounted for, suggesting its effects on the muscle-bone unit may be modulated through bone resorption. In boys, the primary explanatory variables of radial SOS was NTX, followed by grip strength and maturity; where as in girls, it was maturity and dietary calcium. Longitudinally, maturity was found to have indirect effects on radial SOS mediated by grip strength. The influence of maturity on grip strength was similar between sexes, with the effect of grip strength on radial SOS being significantly greater in girls than boys (14.26 vs. 6.60; p<0.05); implying female bones maybe more responsive to muscle forces. Together, these studies provide an overview of muscle-bone unit development during peri-pubertal maturation, demonstrating radial bone properties to be appropriately adapted to muscle function and force independent of physical activity.
    • Investigating the Cluster Chemistry of α-Methyl-2-pyridine methanol (mpmH) with Select 3d Ions

      Abbasi, Parisa; Department of Chemistry
      This thesis describes an investigation of the coordination chemistry of the potentially chiral bridging, chelating ligand, α-methyl-2-pyridinemethanol (mpmH) with select 3d ions for the discovery of polynuclear clusters with single molecule magnet (SMM) properties. Chapter 1 introduces the theory of molecular magnetism, SMMs and the concepts of chiral SMMs, magnetochiral dichroism and multiferroics. In Chapter 2, two NiII clusters, {Ni8} and {Ni18} prepared from rac-mpmH are reported. The {Ni8} cluster crystallizes in a trapezoidal prismatic topology and contains tetrazolate ligands that are formed via a metal-assisted click reaction. The molecular structure of the second {Ni18} cluster is highly disordered comprising of eight edge-sharing cubane subunits. Dc magnetic susceptibility measurements reveal dominant ferromagnetic interactions down to ~18 K, stabilizing spin states with large values, whereas at T < 18 K the antiferromagnetic contribution results in the population of smaller, but appreciable non-zero spin states. Ac magnetic susceptibility measurements confirm the presence of two relaxation processes at two temperature regimes that is extremely rare for a 3d-metal based SMM. The first at low temperature (5 K) is attributed to conventional SMM behavior with τ0 = 3.26 × 10-10 s and Ueff = 11 K. The origin of high temperature (15 K) relaxation process with a large Ueff = 381 K and τ0 = 2.7 × 10-15 s is less clear, but tentatively assigned to spin-glass properties. In Chapter 3, the synthesis and structure of a large mixed-valence [MnII2MnIII28MnIV] polynuclear cluster with a closed cage-like conformation is presented. Ac magnetic susceptibility measurements show the compound is an SMM with Ueff of 58 K, that is large for a 3d cluster, and a τ0 = 3 × 10−8 s. Chapter 4 describes the coordination chemistry of racemic and chiral-mpmH with CuII and FeIII, where the synthesis and magnetostructural properties of a chiral {Cu4} tetramer, a non-chiral 1-D chain, as well as a chiral {Fe6} and a non-chiral{Fe8} cluster are reported. Dc magnetic susceptibility measurements on all four complexes reveal the presence of dominant antiferromagnetic exchange interactions affording S = 0 spin ground states at low temperature that precludes the observation of any SMM behavior.
    • Investigating the Conditional Adaptiveness of Adolescents’ Aggression from an Evolutionary Perspective

      Lapierre, Kiana; Department of Psychology
      Growing evidence supports the evolutionary perspective characterizing aggression as a strategy to achieve proximate adaptive benefits which can indirectly and probabilistically contribute to ultimate evolutionary goals (survival and reproduction). However, aggression may only be adaptive under certain conditions. Therefore, this dissertation investigated various conditions that may affect the adaptiveness of adolescent aggression, namely aggression characteristics (aggressive form, function, and anonymity), target characteristics (power of victim relative to the perpetrator), and perpetrator characteristics (experience of victimization and gender). Study 1 used a person-oriented approach to investigate how proactive and reactive cyber aggression and concurrent experiences of cyber victimization were associated with evolutionarily relevant social advantages and disadvantages in a community sample. Study 2 examined differential associations between aggression involvement and evolutionarily relevant aggressive functions, considering variations in aggressive form, the target’s power relative to perpetrator, and the perpetrator’s gender in a school-based sample. Finally, in a school-based sample, Study 3 investigated (1) how the associations between anonymous perpetration and evolutionary functions of aggression varied by aggressive form and the perpetrator’s gender, (2) how the target’s power and the perpetrator’s gender related to adolescents’ use of anonymous perpetration in each aggressive form, and (3) differential associations between anonymous victimization and victims’ perceptions of harm as a function of aggressive form and gender of the victim. Results suggest that adolescents’ aggression was linked to evolutionarily relevant aggressive functions motivated by competitive (e.g., aggression deterrence, intrasexual competition), impression management (seeking status and mates), sadistic (enjoyment), and reactive (impulsive response to real/perceived threats) functions, and to social advantages (social dominance, dating behaviour) for aggressors who used reactive aggression less frequently. However, aggression involvement was differentially associated with evolutionary motives based on the form, function, or anonymity of aggression, target characteristics, and perpetrator characteristics. Moreover, aggression was associated with costs, especially for cyber aggressor-victims who frequently aggressed reactively, and for victims of anonymous aggression. Thus, adolescents’ aggression may be conditionally adaptive for a narrow range of functions, depending on the characteristics of the aggression, target, and perpetrator. By highlighting the conditional adaptiveness of adolescent aggression, this research may inform efforts to improve interventions addressing aggression.
    • Investigating the Effect of Cell Culture Compositions on Mitochondrial Metabolism, Dynamics, and Transcriptome and Proteome of cells

      Moradi, Fereshteh; Department of Biological Sciences
      The phytoestrogen Resveratrol (RES) is a natural polyphenol that has been detected in more than 70 plant species. RES has structural similarity to mammalian estrogens and can bind to estrogen receptors, eliciting genomic and non-genomic effects. Both RES and physiological estrogens like 17-β-estradiol (E2) have wide-ranging effects on mitochondria. In this thesis, I began by investigating RES’s effects on mitochondrial network dynamics (Chapter 2) and discovered a pro-fusion activity apparently mediated by the mitofusin enzyme Mfn2. RES stimulated mitochondrial network hyper-fusion morphology in all three cell lines investigated (C2C12 (mouse myoblast), PC3 (prostate cancer), and MEFs (mouse embryonic fibroblast)), but the effect was absent in Mfn2-null MEFs. As this work was being completed; several research groups introduced ‘physiologic cell culture media’ that are modeled on the human plasma metabolome. I co-authored a study (not in this thesis) demonstrating that RES’s effects on mitochondrial dynamics are dependent on cell culture conditions. To follow up on this, I investigated whether E2’s mitochondrial effects might also be dependent on the cell culture environment, and showed conclusively that this is indeed the case, using C2C12 cells as a model system (Chapter 3). These results and those published by others in 2017-2019 suggested that medium composition can profoundly affect cellular functions. In Chapter 4, I followed this up by studying how culture conditions affect mitochondrial bioenergetics and network morphology using four cancer cell lines and showed that this is a significant issue. Finally, to gain a more complete understanding of this phenomenon, I completed a full transcriptomic and proteomic analysis of media effects using MCF7 breast cancer cells as a model (Chapter 5). I showed that hundreds of transcripts and proteins are affected according to culture conditions. Taken together, the results presented in this thesis emphasize the significant extent to which the cell culture environment affects experimental outcomes, particularly with respect to mitochondrial bioenergetics and dynamics. This information contributes to the development of cell culture experiments providing results that can be translated in vivo.
    • Investigating the Emotional Impact of Narrative Dialogue on Struggling Readers’ Discovery of Learning Potential

      Moukperian, Sharon; Department of Graduate and Undergraduate Studies in Education
      I investigated the cognitive, emotional and embodied responses to reading of four children/youth who experienced struggles with reading using phenomenology of embodiment (Husserl, 1913/2012; Taipale, 2014) as a theoretical framework and taking the role of an interpretive phenomenological approach (IPA) researcher (Smith & Osborne, 2007; Van Manen, 1997). Narrative theory (Bal, 2009; Chase, 2005; Clandinin & Connelly, 2000; Denison, 2016; White, 2007) supported the primary methodological and research approach complemented by the use of arts-based inquiry (Campbell, 1949/2008; Doherty, 1990; Gladwin, 2014; O’Donoghue, 2006) to probe stories about how participants thought and felt about their reading struggles and through dialogue individual learning strengths were discovered. The narrative approach provided an opportunity to ask how emotions and embodiment played a role in the reading process. I explored children and youths’ embodied experiences through narratives around reading and reading challenges, as they experienced reading difficulties and discovered learning strength during interview conversations about a reading challenge. Life narratives can change as emotions are evoked and described (Angus & Greenberg, 2011; White, 2007, 2011). As a listener, questioner, and recorder of these stories, I was not neutral and my own reflexivity played a role in the data collection [i.e., I was aware that I needed to evaluate my relationship with my participants because I had an influence on them by the observations and dialogues we had (Goldstein, 2017)]. This research focused on: (a) the emotional impact of reading deficits and children/youths’ discovery of cognitive learning strengths; (b) the influence of emotions on the children/youths’ and parents’ perceptions of the struggling reader lived experience; and (c) children/youths’ awareness of their own emotional experiences and cognitive processes when reading leading to connections between the embodied reaction and cognitive processes signaling that this phenomenon related to realizing a learning strength. Implications for future research involve exploring further the dialogic approach to discovering learning strengths and how to apply them to reading challenges that trigger a visceral emotional response. This research contributes to a theory that emotional meta-awareness maybe necessary to guide metacognitive reading strategies. There is a connection between embodied-emotional responses, reading challenges, and the discovery of learning strengths. Metacognitive awareness is heightened by being able to interpret the visceral emotional responses possibly leading children/youth to be aware when they have a learning strength that they can apply independently by listening to their body while completing a challenging reading task.
    • Investigating the Impact of Lessons Based on Marzanoʼs Theory of Learning on Student Attitude, Engagement, and Achievement in Grade 10 Academic Mathematics

      IRVINE, JEFF; Department of Graduate and Undergraduate Studies in Education
      Motivation is an important construct in education, both for its links to student learning and in its own right as a factor in student development. The relationship between motivation and student learning is particularly important in mathematics since numerous studies have demonstrated that motivation in mathematics is linked to student achievement, and that student achievement and student attitudes toward mathematics are reciprocally related. This study investigated the impact of an instructional intervention that specifically addressed two dimensions of motivation: engagement and student attitudes. Based on Marzano’s (1998, 2007) New Taxonomy of Educational Objectives©, a unit of study in Grade 10 Academic Mathematics was developed that utilized targeted activities and complete lessons to positively influence student engagement and attitudes. This mixed methods study used pre–post comparisons as well as treatment-control comparisons of 70 students in 3 classes of Grade 10 mathematics to investigate the impact of the instructional intervention on student engagement, attitude, and achievement in order to determine whether such an intervention could function as an exemplar for development of similar interventions that positively impacted student learning. The results of the study showed statistically significant changes in student engagement and student attitudes, but not for student achievement. Implications of these results pointed to directions for future research in this area.
    • Investigating the Relationships Between Teacher Identity Norms and Collaboration

      Weston, Deborah PA; Department of Graduate and Undergraduate Studies in Education
      The purpose of this study was to investigate how teacher identity norms relate to teacher collaboration among the practices of elementary teachers in Ontario. Using quantitative research methods, the data indicated two clusters of teacher identity norms. The norm cluster of innovation, interdependence, and cooperation showed positive correlations with collaboration and the norm cluster of conservatism, individualism, and competition showed negative correlations with collaboration. The two clusters of norms also correlated with each other. The data showed that teachers highly valued collaboration as part of their teaching practice but did not always experience it in their school setting. The analysis suggested that if schools reinforce norms of innovation, interdependence, and cooperation, collaboration will be nurtured. Further, the data showed that if norms of conservatism, individualism, and competition are continued in school cultures, then collaboration will not be sustained. As a broad educational reform agenda, teacher collaboration is used (a) to support school cultures, (b) to change teaching practices, and (c) to implement policy-based initiatives. This research is expected to benefit teachers in its capacity to inform policy makers concerning the highly complex nature of teacher collaboration and some of the factors that impact it. With an understanding of the relationships between teacher identity norms and collaboration, it may be possible for policy makers to provide appropriate support structures that reinforce collaboration in teachers' practices as well as predict potential levels of collaboration within school cultures.