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This study explores the meanings and understandings of home of seniors experiencing homelessness and the supports and services these individuals need in their homes as they age. Guided by interpretive social sciences and critical gerontology this study engaged with 7 homeless seniors living in a seniors’ shelter in the City of Toronto. Using arts-based research methodology, this study had 7 seniors make collages to represent their vision and understandings of ‘home’. In addition, participants were asked what specific support and services they would need in their homes in order to support their overall health and wellbeing. Based on individual art session recordings and collages, thematic analysis was used to identify key themes in order to understand what home means, and what supports and services are required for homeless seniors. For these participants home is a unique physical space with nuanced meanings and provides unique elements that a shelter cannot. In addition, these participants identified specific in-home and community supports they would require in their homes. / Thesis / Master of Social Work (MSW)

There is a saturable, dose-response relationship between the amount of protein ingested at a meal, the ensuing hyperaminoacidemia, and the subsequent skeletal muscle protein synthesis (MPS) response. Imposition of an external load, usually practiced as resistance exercise, on skeletal muscle is also a potent stimulus for increasing MPS and adds synergistically to the hyperaminoacidemia-induced rise in MPS. The current thesis examined the potential for meal-focused protein/leucine intake strategies, alone and in combination with resistance exercise, to augment MPS in older men. MPS was measured acutely (hours) using the continuous infusion of L-[ring-13C6]phenylalanine (Study 1) or over longer-term, integrated periods via ingestion of deuterated water (Study 2: 2-wk and Study 3: 3-d) while participants were free-living. In Studies 1 and 2 we examined whether a balanced versus a skewed pattern of protein intake across daily meals would enhance MPS during energy restriction (ER) in overweight/obese older men. Study 1 showed that a balanced consumption of protein during ER stimulated acute (%/h) myofibrillar protein synthesis (MyoPS) more effectively than a traditional, skewed distribution. Combining resistance training (RT) with a balanced protein intake pattern restored the lower acute rates of MyoPS during ER to the higher levels observed in energy balance. Study 2 showed no effect of daily protein intake pattern during ER on longer-term integrated MyoPS (%/d). However, the inclusion of RT during ER enhanced integrated MyoPS and the synthesis of numerous individual contractile, sarcoplasmic and mitochondrial skeletal muscle proteins with both protein intake patterns. Study 3 showed that leucine co-ingestion with daily meals enhanced integrated (%/d) MyoPS in healthy older men who were in energy balance and was equally effective among those consuming higher (1.2 g/kg/d) and lower (0.8 g/kg/d) protein intakes. Furthermore, the stimulatory effect of leucine co-ingestion on integrated MyoPS was further potentiated with the performance of resistance exercise. Collectively, these studies support the potential for per-meal recommendations, optimizing the protein dose consumed on a per-meal basis and leucine co-ingestion with meals, to augment MyoPS in older men, especially when combined with RT. These data have implications for recommendations to optimize MyoPS and possibly muscle mass in aging persons. / Thesis / Doctor of Philosophy (PhD)

Binocular rivalry allows for the unique examination of the neural processes associated with binocular vision by instigating a disruption of normal stereoscopic vision. Although binocular rivalry has been examined extensively in young adults, we know relatively little about its developmental trajectory across the human lifespan. This thesis provides a foundation for characterizing perceptual alternations during binocular rivalry in children and older adults, with a specific emphasis on expanding our understanding of binocular rivalry in older adults. From a theoretical perspective, my studies on aging and binocular rivalry have a specific significance, because unique changes that are known to occur with aging to certain neural mechanisms often associated with characteristics of perceptual alternations allows for the study of aging to serve as a test for many of the current models of binocular rivalry. Overall, my studies provide evidence for a significant transitional period in the binocular visual system at the age of 70 and older, and highlights the developmental trajectories of specific characteristics of binocular rivalry from childhood to senescence. / Thesis / Doctor of Philosophy (PhD)

Objectives: This study aimed to investigate whether new potential risk factors (cognition, frailty, falls, social isolation/loneliness, and osteosarcopenia), not included in traditional fracture risk prediction models, are associated with fracture risk in community-dwelling older adults. Methods: Participants aged 65 years or older from the Canadian Longitudinal Study on Aging (CLSA) who completed the 2015 baseline and 2018 follow-up assessments were included. The outcome was self-reported fractures in the 12 months prior to both baseline and a three-year follow-up. Baseline predictor variables included cognition variables (memory, executive function, and psychomotor speed), frailty (assessed using the Rockwood Frailty Index), falls (assessed as occurrence at the 12 months prior to baseline), social isolation/loneliness (assessed using the CLSA-Social Isolation Index), and osteosarcopenia defined as a combination of osteopenia/osteoporosis (bone mineral density femoral neck T-score <-1) and sarcopenia (grip strength <35.5 kg for males and <16kg for females, as well as gait speed <0.8 m/s for both sexes). Findings: When considering cognition, frailty, and falls simultaneously, the frailty index was independently associated with fracture risk [adjusted odd ratio (OR) 1.44, 95% confidence interval (CI) 1.11-1.52 per each standard deviation (SD) increment in the frailty index]. The Social Isolation Index was associated with fracture risk (adjusted OR 1.13, 95% CI 1.01-1.27); however, this association was dependent on an interaction with depressive symptoms. In males, osteosarcopenia was associated with a 2.6-fold higher fracture risk compared to those with normal bone density without sarcopenia (adjusted OR 2.60, 95% CI 1.14-5.91). Conclusion: Frailty, social isolation/loneliness, and osteosarcopenia are associated with fracture risk in Canadian community-dwelling older adults aged 65 years or older. These new risk factors may be used in the future to develop better fracture prediction assessments. / Thesis / Doctor of Philosophy (PhD) / Several fracture risk prediction models use various risk factors, such as bone density, to predict fracture risk. However, many factors are not considered in these models that may be related to fractures. We explored the associations between new potential risk factors including cognition, frailty, falls, social isolation/loneliness, and osteosarcopenia; and fracture risk. When considering cognition, frailty, and falls together, we found that only frailty was associated with fracture risk. Social isolation/loneliness was also associated with fracture risk, but it depended on individuals’ depressive symptoms. Only in males, osteosarcopenia was associated with higher fracture risk compared with those with normal bone density and without sarcopenia. Frailty, social isolation/loneliness, and osteosarcopenia are associated with fracture risk in community-dwelling adults aged 65 years or older.

Selenium (Se) is an essential trace element exerting its biological functions mainly through selenoproteins. Our lab has recently shown a paradoxical role of dietary Se at nutritional levels of intake in the delay of age-related degeneration while reducing longevity in mice carrying humanized telomeres. The first aim of this dissertation was to evaluate the effects of long-term dietary Se deficiency, aging, and sex on selenotranscriptome hierarchy in tissues. Four unique patterns in selenotranscriptomic changes were summarized. First, the responses of selenotranscriptomes to dietary Se deprivation and aging were sexually dimorphic. Second, a few selenoproteins responded to dietary Se deficiency and aging in parallel. Third, there were selenoproteins up-regulated by aging or dietary Se deprivation. Forth, some selenoproteins, especially those in testis, were upregulated by aging in mice on a Se-deficient diet. Selenoprotein H (SELH) is ranked low in selenoprotein hierarchy and its expression is tissue-specific and abundant during embryogenesis. SELH is a nucleolar DNA-binding protein with thioredoxin (Txn)-like fold and glutathione peroxidase activity. The known biological functions of SELH include redox regulation and suppression of cellular senescence and tumorigenesis. The second aim of this dissertation was to study the functional interactions of SELH with other selenoproteins and its protective effects against oxidative stress. A FLAG-tagged plasmid expressing wild-type SELH was constructed. Compared to standard cell culture conditions, additional sodium selenite (Na2SeO3) increased SELH expression at protein but not mRNA level when FLAG-SELH was overexpressed. In the absence of supplemental Na2SeO3, FLAG-SELH overexpression suppressed the expression of other selenoproteins such as glutathione peroxidase 1 (GPX1) and thioredoxin reductase 1 (TrxR1) at protein but not mRNA level. FLAG-SELH overexpression protected the cells against oxidative stress only when additional Na2SeO3 was added. Identification of FLAG-SELH-associated proteins confirmed its nucleolar location. Altogether, a distinctive set of selenoproteins is maintained under dietary Se deficiency in a tissue- and sex-specific manner during the aging process. While SELH is ranked low in selenoprotein hierarchy implying that it is dispensable, this nucleolar selenoprotein competes with other selenoproteins for Se and protects the cells against oxidative stress.

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