Thesis (M.A. (Social Work)) -- Univesity of Limpopo, 2012 / Refer to document

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Cognitive control allows us to function in a world filled with constant stimulation. For example, the act of reading a book requires the ability to inhibit irrelevant information while focusing attention towards the letters on the page. Our cognitive control system regulates what information receives attention and what is denied resources. The goal of the current paper is to investigate the mechanisms underlying the activation and maintenance of the control system and how this process changes in healthy aging. First, the ability of younger and older adults to activate and maintain control in response to trial type manipulations is investigated. Second, improvements are made to recent experimental evidence suggesting younger adults are able to modulate performance based on specific stimulus history. Third, this work is extended to an older population suggesting the ability to modulate performance based on specific stimulus history is maintained in healthy aging. Finally, it is demonstrated that current theories of control fail to account for age-related differences in performance based on the comparison of trial type and specific stimulus manipulations.

Previous evidence has shown that older adults may have specific declines in prefrontal cortex (PFC)-mediated processes supported source memory retrieval, such as strategic retrieval and post-retrieval monitoring. This decline may manifest in the form of attenuated late-frontal ERP effects. Behavioral research suggests that explicitly integrating a target context, or source, with a stimulus during encoding will improve subsequent source memory performance for both younger and older adults. Explicit item-feature binding instructions during encoding may alleviate source memory impairments, in part, by reducing the need for strategic processing during episodic retrieval. The present ERP study investigated whether explicit direction of attention toward item-feature integration may reduce age-related deficits in source memory by alleviating the necessity of frontally-mediated strategic processing at retrieval. Results demonstrated that explicit direction of attention improved source memory accuracy for both young and older adults, but older adults benefited less than the young, indicating additional age-related deficits. ERPs revealed that explicit encoding support attenuated post-retrieval monitoring effects in the young. In the old, explicit encoding instruction resulted in earlier onset of early frontal effects, possibly related to familiarity. Results suggest explicit direction of attention toward item-source integration at encoding may improve source memory by alleviating the need for strategic retrieval, but age-related deficits persist.

Parkinson's disease (PD) is an age-related neurodegenerative disease characterized by the selective loss of dopaminergic neurons in the substantia nigra of the brain. The pathogenesis and etiology of PD are unclear. Mitochondrial dysfunction occurs in PD, causing a decrease in complex I activity in postmortem brain, and exacerbating reactive oxygen species production and ATP deficiency contributing to neuronal cell death. Mutation of leucine-rich-repeat kinase 2 (LRRK2) gene is the most common genetic factor identified in both familial and sporadic PD cases. Several mutations in LRRK2 have been linked to PD, in which R1441G is the second commonest mutation after G2019S. LRRK2 protein is ubiquitously expressed in human body, in which a portion is localized to the mitochondria. Mutations of LRRK2 directly or indirectly cause mitochondria dysfunction. Dysfunction of mitochondrial respiratory complexes has been described in skin fibroblasts and skeletal muscle of PD patients. Therefore, these clinically accessible tissues are good for monitoring disease progression. The objectives of this study were to investigate how LRRK2 R1441G mutation affects normal mitochondrial function, and whether this specific LRRK2 mutation potentiates age-dependent deterioration of mitochondrial function. To achieve these aims, colonies of skin fibroblast carrying LRRK2 R1441G mutation or wild-type LRRK2 were derived from a novel LRRK2 R1441G knock-in (KI) mouse model and its wild-type (WT) littermates. Skeletal muscles were dissected from the hind legs of WT and KI mice. The effects of aging and LRRK2 R1441G mutation on mitochondrial function were investigated in vitro using these derived skin fibroblast cultures, and ex vivo using skeletal muscle obtained from young (3-month-old) and aged (18-month-old) WT and KI mice. Reduction-oxidation activities of mitochondrial complex I and complex II in skin fibroblasts and skeletal muscle were measured spectrophotometrically. Intracellular ATP levels in skin fibroblasts were determined by bioluminescent assay. Phase-contrast microscopy showed that aging and LRRK2 R1441G mutation did not affect cell morphology of the derived skin fibroblast cultures. Complex I activity determined in skin fibroblasts and skeletal muscle derived from KI and their WT littermates revealed that, aging caused a significant increase in complex I activity in WT but not KI skin fibroblasts. Conversely, a significant decrease in complex I activity was observed in both WT and KI skeletal muscle, demonstrating an aging effect ex vivo. LRRK2 R1441G mutation did not affect complex I activity in WT and KI skin fibroblasts and skeletal muscle. Moreover, complex II activity in these two tissues was neither affected by aging nor R1441G LRRK2 mutation. Intracellular ATP levels in the skin fibroblast cultures were also unaltered by aging and LRRK2 R1441G mutation. In conclusion, my current findings indicated a significant aging effect on mitochondrial complex I activity ex vivo, supporting the role of age-dependent deterioration of complex I activity in mitochondrial dysfunction of PD. LRRK2 R1441G mutation did not affect complex I and II activities in both skin fibroblasts and skeletal muscle. Also, this mutation did not potentiate the age-dependent deterioration of complex I activities as observed in skin fibroblasts and skeletal muscle of the LRRK2 R1441G knock-in mice. / published_or_final_version / Medicine / Master / Master of Philosophy

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Background: The ICD controls the heart rhythm and reacts to serious heart rhythm abnormalities and trigger, if necessary, a defibrillation to restore the heart to normal rhythm. Living with an ICD can provide major changes in everyday life. Nurse´s important role regards to provide relevant patient education to include promoting the health and quality of life (QOL) for these individuals. Purpose: To describe QOL for people living with an ICD, from a gender and age perspective, and to examine the included articles selection strategy and research group. Method: The result of this descriptive literature review compiled from eleven quantitative scientific articles, sought in PubMed and Scopus. Main Results: Women reported lower QOL then men linked to impaired mental, physical and social function. Also a greater concern and anxiety were found in women. Mental illness affected mainly young people, who also experienced a lower acceptance to the device than older ICD- receivers. Older people reported less concern that the ICD would deliver a shock. However, a reduced QOL related to higher incidence of physical impairment, were noticed in the elderly ICD- receivers compared to the younger. Four articles specified their selection strategy. All reported the number of participants and how many were men and women. The age range of participants was specified in five articles. Conclusion: Impacts on QOL could be discerned to different gender and ages. These findings confirmed the need for health professionals to access more holistic patient- education programs that focus not only on the technical aspects of living with an ICD but more on the individual impact. / Bakgrund: En ICD kontrollerar hjärtrytmen, reagerar på allvarliga hjärtrytmrubbningar och utlöser vid behov en defibrillering för att återställa normal hjärtrytm. Att leva med en ICD kan innebära stora omställningar i det vardagliga livet. Sjuksköterskan har en betydande roll i omvårdnaden kring dessa personer där bland annat relevant patientutbildning är viktig för att främja personers hälsa och livskvalitet. Syfte: Syftet med denna litteraturstudie var att beskriva livskvaliteten hos personer som lever med en implanterbar defibrillator (ICD), ur ett köns- och åldersperspektiv, samt att granska de inkluderade artiklarnas urvalsstrategi och undersökningsgrupp. Metod: Denna beskrivande litteraturstudies resultat sammanställdes utifrån elva granskade artiklar av kvantitativ ansats, eftersökta i databaserna PubMed och Scopus. Huvudresultat: Kvinnor rapporterade lägre livskvalitet än männen kopplat till nedsatt mental, fysisk och social funktion. Även en ökad oro och ångest förekom hos kvinnor. Psykisk ohälsa utvecklades främst hos yngre, vilka också upplevde lägre acceptans till enheten än äldre ICD- bärare vilket påverkade livskvaliteten. Äldre personer rapporterade mindre oro över att ICD:n skulle defibrillera. Dock sågs en nedsatt livskvalitet relaterat till högre förekomst av fysisk nedsättning i större grad hos äldre än yngre ICD- bärare. Fyra av resultatartiklarna angav använd urvalsstrategi. Samtliga redogjorde för antalet deltagare och hur många som var män respektive kvinnor. Åldersspannet mellan deltagarna angavs i fem artiklar. Slutsats: Olika inverkan på livskvaliteten kunde skönjas både mellan kön och olika åldrar. Dessa fynd bekräftade behovet av att sjukvårdspersonal behöver få tillgång till mer holistiska patientutbildningsprogram som inte enbart fokuserar på de tekniska aspekterna av att leva med en ICD.

The effects of exogenous estrogen administration on aspects of memory and cognition in women were examined in two studies. In Study 1, women receiving estrogen replacement therapy were compared to untreated women on four measures of verbal memory. Those receiving estrogen had significantly better scores on a measure of delayed memory for propositional material. In Study 2, women in the early stages of Alzheimer's Disease (AD) were administered either estrogen or placebo on a double-blind basis for six months. Women given estrogen showed improvement on a measure of verbal memory and spatial attention compared to the placebo controls. The combined results of these studies provide evidence that estrogen enhances aspects of verbal memory in both healthy postmenopausal women and in postmenopausal women in the early stages of AD as measured by neuropsychological tests. These effects might be mediated by actions of estrogen on neuronal morphology and physiology in brain areas important for memory and cognition.

Differences in fatty acid distributions in adipose tissue and fatty acid synthetase levels in the liver were determined in Strain A/ST mice of different ages and diets. Since fatty acids have been found to be influential in many disease processes such as heart disease and cancer, which become more prevalent with increasing age, it is important to understand the processes of fat metabolism and changes that occur during the life-stage of senescence. Fatty acid distributions were determined by gas liquid chromatography and fatty acid synthetase (FAS) activities by spectrophotometry.The data from FAS analyses indicated that the mice fed the highfat palmitic acid and low-fat corn oil diets were similar to previous research. The mice fed the stearic acid diets had FAS activity that was affected in a very different manner than other high-fat diets.The results of this study also indicated that aging does not significantly effect the distribution of fatty acids in the adipose tissue of experimental mice. Weight gain in the middle age mice appears to be the result of an increase in all types of fatty acids and not just increased storage of one or a few types. / Department of Biology