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Browsing by Author "Foster, Michelle, committee member"

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    Double consciousness: the negotiation of the intersectionality of identities among academically successful Black women
    (Colorado State University. Libraries, 2014) Dickens, Danielle D., author; Chavez, Ernest, advisor; Stallones, Lorann, advisor; Foster, Michelle, committee member; Jennings, Louise, committee member
    Due to educational and professional obstacles, as well as the psychological tolls associated with racism and sexism, Black women may feel pressured to present a self to the world that is viewed as acceptable to others. Through identity negotiation, a conscious process of shifting one's worldview and/or cultural behaviors (Jackson, 2004), Black women may adopt multiple identities that appease both the White and Black community. The need to investigate the collective identities among Black women using a non-White ideology, such as Black feminist model, is critically needed. The purpose of this investigation was to understand the effect of the negotiation of race, class, and gender identities on Black women's self-perception, specifically as it relates to their participation in the workforce, and personal and professional relationships. Data were collected using semi-structured interviews and the sample consisted of ten academically successful Black women. To be eligible to participate in this study, co-researchers must have met the following criteria: 1) self-identify as a Black/African American woman, 2) recently obtained bachelor's degree in the past 5 years, 3) currently working in a predominantly White environment, and 4) living in a majority Black urban area. Data from the interviews were classified through identified themes, and interpretative phenomenological analysis. Themes constructed from the data include: a) the complexity of the intersectionalities of race, gender, and class identities, b) negotiation of identities in predominantly White social and work environments, c) negotiation of identities in a predominantly Black environments, d) triggers for the negotiations of race, class, and gender identities, and e) conflicted anxieties towards negotiating identities. The results of this study may be utilized to develop intervention programs that promote positive self-worth, and the development of academic and personal success among Black women aspiring to enter the evolving workforce.
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    Functional organization of a cortical-medullary neural circuit mediating organismal adaptation to stress
    (Colorado State University. Libraries, 2023) Pace, Sebastian A., author; Myers, Brent, advisor; Hentges, Shane, advisor; Tobet, Stuart, committee member; Foster, Michelle, committee member
    Hindbrain regions responsible for epinephrine and norepinephrine production are critical for orchestrating stress responses, maintaining physiological equilibrium and integrating afferent information. The nuclei central to hindbrain epinephrine and norepinephrine production, create a neural network that interfaces with forebrain and spinal cord regions, facilitating the integration of neuroendocrine and autonomic functions. Despite significant strides in our comprehension of stress response systems, questions concerning the roles of sex, stress history, and circuit mechanisms endure. In this study, we unveil and characterize a prefrontal-medullary circuit crucial for the suppression of stress responses. First, anterograde and retrograde tract-tracing studies demonstrated a stress-reactive vmPFC-RVLM circuit. Activation of this vmPFC-RVLM circuit mitigates glucocorticoid stress reactivity in both males and females, by targeting non-catecholaminergic neurons. Therefore, vmPFC-RVLM circuit activation may utilize local inhibitory neurons to limit catecholaminergic activation. To better understand how chronic stress affects the medulla, we explored the impact of chronic stress on signaling machinery and revealed elevated tyrosine hydroxylase (TH) levels in both male and female rats following chronic variable stress (CVS). To understand how CVS interacts with the vmPFC-RVLM circuit, we used an intersectional TeLC (Tetanus toxin - light chain) approach to disrupt the circuit and evaluate multiple stress response systems. In males, circuit disruption and CVS largely left behavioral and cardiovascular stress reactivity unaltered, however, some neuroendocrine endpoints were affected. Conversely, females exposed to circuit disruption and chronic stress exhibited heightened stress reactivity in glycemic, corticosterone, and arterial pressure responses, coupled with avoidant-like behaviors. These findings underscore the sex-specific necessity of the vmPFC-RVLM circuit in countering chronic stress-related outcomes, emphasizing a greater protective role in females relative to males. To gain deeper insights into the role of vmPFC inputs to the RVLM in females, we once again utilized a circuit-based TeLC approach, employing in situ hybridization (ISH) coupled with immunohistochemistry (IHC) to assess TH and phenylethanolamine N-methyltransferase (PNMT) transcript density across various VLM subregions. Notably, the TeLC-induced elevation of PNMT expression in females suggests that disrupting this circuit could potentially enhance epinephrine production by RVLM neurons, potentially intensifying stress reactivity post-CVS. This comprehensive study demonstrated the critical role of the vmPFC-RVLM circuit in modulating stress responses and revealing female-specific effects in mitigating physiological, behavioral, and transcriptional outcomes after chronic stress. These findings emphasize the significance of the vmPFC-RVLM circuit in managing stress reactivity in the context of chronic stress and identify the circuit as a potential candidate for reducing stress responding.
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    Predictors of learning outcomes among students in nutrition science courses at Colorado State University
    (Colorado State University. Libraries, 2018) Peth, James Anthony, author; Melby, Christopher, advisor; Balgopal, Meena, advisor; Foster, Michelle, committee member; Gentile, Christopher, committee member; Hickey, Matthew, committee member
    Overview This dissertation is a summary of exploratory research to assess predictors of learning outcomes (academic background, conceptions of subject, motivations for studying, and approaches to learning) among students taking two undergraduate nutrition science courses at CSU—Human Nutrition (Course 1) and Integrative Nutrition & Metabolism (Course 2). It was comprised of three studies. Introduction There is a global need for experts trained in nutrition with an integrationist approach to health sciences and equipped to understand complex issues in health and disease. Yet, many students in nutrition sciences courses are not learning at a mastery level and often lack the knowledge and ability to integrate what they have learned to apply it to more advanced courses and their careers. Key factors influencing a student's approach to learning and performance outcomes in a course include their academic background, motivations for learning the subject, conceptions of the subject, and approaches to learning. Pilot data from preliminary research performed during a course re-design project at Colorado State University (CSU) indicate many students begin nutrition science courses with inadequate prior knowledge from prerequisite courses, lack autonomous motivations, exhibit fragmented conceptions of the science of nutrition, and adopt surface, rather than deeper, more meaningful approaches to learning. Methods Exploratory mixed-methods research was performed to assess academic background, motivations for studying nutrition, conceptions of the discipline, and approaches to learning among students in Course 1 (Human Nutrition) and Course 2 (Integrative Nutrition & Metabolism). It was comprised of three studies. The first was an analysis of academic and demographic data for 1,739 students, who had completed Course 1 only (n=1,377) or both Course 1 and Course 2 (n=362) between 2010-2016, to identify and evaluate relationships with in-class exam performance. Studies 2-3 were analyses of semi-structured interviews with students who had completed Course 1 only (n=12) or both Course 1 and Course 2 (n=27) between 2012-2015. Each student reflected on their experiences before and after the course(s) they completed, including their motivations for studying nutrition, conceptions of nutrition as a discipline, and approaches to learning. Transcripts were inductively coded and discrete categories of motivations, conceptions, and approaches were developed using phenomenography. Transcripts were re-analyzed using focused coding, and each student was categorized for each domain. Statistical tests were conducted to evaluate the strength of relationships among academic background variables, motivations, conceptions, approaches, and learning outcomes. Results Pre-course GPA, grades in prerequisite courses, and scores on a prior knowledge test for Course 1 were positively correlated with in-class exam performance. Pre-course GPA was the best predictor for both courses, explaining 51.9% and 43.9% of the score variance in Course 1 and Course 2, respectively. Alone, demographic variables were poor predictors of performance. First-generation status was negatively correlated with performance. Among students interviewed, 100% indicated having an intrinsic interest in learning nutrition before Course 1. However, when taking upper-level nutrition science Courses 1 and 2, 100% suggested being driven to some extent by extrinsic rewards, and only 53.8% and 63% of students suggested having autonomous motivations for studying the specific material covered in Courses 1 and 2, respectively. At the start of Course 1, 87.2% of students had a fragmented conception of nutrition as a discipline; 76.9% adopted a surface approach to learning. Most (82.4%) of the students with a fragmented conception of nutrition science adopted a surface approach to learning. For Course 2, 52% began with a coherent conception of nutrition as a science, and most (81.5%) adopted a deep approach to learning in the course. Statistically significant relationships were identified among motivations, conceptions, and approaches to learning for Course 1. In both Course 1 and 2, coherent conceptions, autonomous motivations, and deep approaches were associated with significantly higher mean grades. Conclusions and Implications Previous academic achievement and prior knowledge provide students a critical foundation for success in upper-level courses in nutrition science. Students develop more coherent conceptions of nutrition as a science, autonomous motivations for learning nutrition, and deep approaches to learning nutrition as they progress through their courses, attempting to meet academic demands. These developmental changes are associated with positive learning outcomes. Efforts should be made to support and increase students' development of cognitive prerequisites, such as prior knowledge from foundational sciences, coherent conceptions of nutrition as a science, and autonomous motivations and deep approaches for learning nutrition earlier in their academic program.
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    The role of fatty acids on endoplasmic reticulum proteostasis in non-alcoholic fatty liver disease
    (Colorado State University. Libraries, 2017) Estrada, Andrea Lee, author; Pagliassotti, Michael, advisor; Miller, Benjamin, committee member; Foster, Michelle, committee member; Frye, Melinda, committee member; Gentile, Christopher, committee member
    Non-alcoholic fatty liver disease (NAFLD) is currently a significant health concern in both adults and children. NAFLD is a disease characterized by accumulation of fat in the liver (steatosis) in the absence of chronic alcohol consumption. In some individuals, steatosis progresses to non-alcoholic steatohepatitis (NASH), which is characterized by steatosis, inflammation, apoptosis and fibrosis, and can ultimately lead to end-stage liver disease. The underlying causes of NAFLD are unclear, although recent evidence has implicated the endoplasmic reticulum (ER) in both the development of steatosis and progression to NASH. Disruption of ER homeostasis or "ER stress" has been observed in the livers and adipose tissue of humans with NAFLD and/or obesity. Downstream signaling events that arise from ER stress include lipid biogenesis, insulin resistance, inflammation, fibrosis and apoptosis, all of which are hallmark features of NAFLD and NASH. Elevated circulating free fatty acids are a characteristic feature of humans with NAFLD and are positively correlated with disease severity. Our laboratory has demonstrated that in rodents, selective elevation of circulating free fatty acids induces ER stress in liver and adipose tissue. In addition, ER stress is exacerbated when the composition of fatty acids includes levels of saturated fats comparable to what is encountered in the typical western diet. We, and others, have also demonstrated that saturated fatty acids provoke ER stress in cultured hepatocytes, pancreatic beta cells, and various other cell types. These data have led to the hypothesis that the composition of fatty acids presented to and stored within the liver is an important determinant of ER homeostasis. ER stress is characterized by an accumulation of unfolded proteins within the lumen of the ER. Therefore, the presence of ER stress in NAFLD implies that there is an imbalance between the protein load presented to the ER, and the ability of the ER to process, degrade and/or remove these proteins. The overall aim of this thesis was to examine how saturated fatty acids disrupt ER homeostasis in the liver. We explored in vivo hepatic protein synthesis in response to acute dietary intervention, namely using diets high saturated fat and sucrose, which promote hepatic steatosis and insulin resistance in rats. We utilized the saturated fat, palmitate in controlled delivery to H4IIE liver hepatocytes in order to assess protein synthesis and components of protein degradation. Lastly, we examined the roles of calcium homeostasis and protein palmitoylation in response to palmitate treatment in H4IIE liver hepatocytes. We found that diets high in saturated fat did not affect hepatic protein synthesis in rats. In agreement with this observation, H4IIE hepatocyte treatment with palmitate did not selectively stimulate cellular protein synthesis. Provision of palmitate increased protein ubiquitination, this result was observed independent of proteasome activity or total cellular protein degradation. Lastly, we found that palmitate-induced ER stress was characterized by a reduction in sarcoendoplasmic reticulum ATPase (SERCA) activity. Our data suggest that saturated fatty acid-induced ER stress is mediated via reduced SERCA activity, and subsequent disruption in protein handling.
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    The roles of iron, the infrapatellar fat pad, and dietary factors in the Hartley guinea pig model of spontaneous osteoarthritis
    (Colorado State University. Libraries, 2018) Radakovich, Lauren, author; Santangelo, Kelly, advisor; Olver, Christine, committee member; MacNeill, Amy, committee member; Foster, Michelle, committee member; Pagliassotti, Michael, committee member
    Osteoarthritis (OA) is the most prevalent musculoskeletal disorder across the world, affecting close to 300 million people. The disease manifests as degeneration and loss of articular cartilage, synovial hyperplasia, formation of osteophytes, subchondral bone remodeling, and joint space narrowing. These changes result in decreased range of motion as well as painful mobility in affected individuals. The knee joint is the most commonly afflicted joint. Osteoarthritic changes may develop secondary to a localized injury, referred to as post-traumatic OA. Degenerative changes can also develop without an inciting cause, which is referred to as spontaneous, or primary OA. Spontaneous OA is an insidious disease that is associated with aging, and, more recently, with obesity. The mechanisms contributing to disease development are not yet fully characterized, which has impeded implementation of successful treatment options. Currently, there are no treatments that are able to restore degraded cartilage. Thus, most patients with symptomatic knee OA undergo costly total knee joint replacement surgeries. The aims of this dissertation were to explore the roles that aging-associated iron accumulation, the infrapatellar fat pad, and calorie restriction with various diets may play in OA development. These studies were performed in the Hartley guinea pig, one of the only small animal models of spontaneous OA. One study was performed in Strain 13 guinea pigs, a strain that is OA-resistant. Iron is an element that acts as a double-edged sword. It is essential for oxidative phosphorylation and heme synthesis, yet its redox potential means it has the capacity to incite oxidant damage when present in excess. As there is no direct excretion mechanism for iron, it tends to accumulate slowly within tissues over time. This cellular iron accrual has been implicated in many degenerative diseases associated with aging, but its potential role in spontaneous OA has not been well-studied. In our first studies, we demonstrated that systemic iron levels have an influence on OA. We were able to induce bony and cartilage lesions in OA-resistant Strain 13 guinea pigs by systemic administration of iron dextran. Immunohistochemistry (IHC) indicated higher levels of lipid peroxidation in cartilage, menisci, the infrapatellar fat pad (IFP), and synovium in the iron overload animals. Special stains revealed that iron content was significantly higher in the IFP in these animals, which we propose serves as a local depot of oxidant damage to the knee joint. In a parallel study, we fed OA-prone Hartley guinea pigs an iron deficient diet to determine if reducing systemic iron levels may have a protective effect on the knee joint. Cartilage lesions were significantly lower in the iron deficient diet group compared to controls. Likewise, IHC for lipid peroxidation revealed less oxidant damage in the iron deficient pigs. However, no differences were noted in knee joint iron content, so the exact mechanisms for the lessened OA remain unclear. Because the iron overload study pointed to the IFP as a potential iron depot, we wanted to further characterize how this adipose tissue contributes to overall knee joint homeostasis. First, we demonstrated that quantitative iron content in the IFP was increased in aged, osteoarthritic guinea pigs compared to young, healthy animals. Gene expression data collected suggested that dysregulated iron trafficking, particularly increased expression of ZIP14 – which has been linked to pathologic iron uptake in other conditions – may be contributing to this aging-associated increase of iron in the IFP. Because of our suspicion that the IFP may be inciting local oxidant damage to the knee, we surgically removed it from a set of young Hartley guinea pigs. An identical sham procedure was performed in the contralateral limb. Four months post-surgery, animals were collected to evaluate OA in both limbs. Both cartilage and bony OA scores were markedly decreased in the IFP removal limb compared to the sham surgery limb. It is possible that removal of the IFP removed a source of local inflammatory mediators and iron, which resulted in lessened OA. As the IFP was replaced by a thick band of fibrous connective tissue, increased joint stability was also considered a contributing factor. Future studies will more closely examined contributions of biomechanical factors that may be at play. Finally, we aimed to determine how dietary manipulations may influence early OA, as previous studies suggest that calorie restriction may improve end-stage OA. Additionally, many studies have shown high fat diet (HFD)-induced obesity plays a role in OA development due to the inflammatory nature of excess adipose tissue. In our study, we demonstrated that calorie restriction with a low fat regular chow diet, but not a calorie restricted HFD, delayed onset of OA in Hartley guinea pigs. In fact, the HFD group had higher levels of systemic inflammation than the restricted regular chow group. The HFD group had similar levels of inflammation and OA scores as obese animals. Thus, we concluded that the pro-inflammatory nature of a HFD supersedes any positive effects of calorie restriction in the onset of spontaneous OA.