Browsing by Author "Kubat, Elif."

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    Evaluation of the effect of aging on brain asymmetry with functional near infrared spectroscopy
    (Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2008., 2008.) Kubat, Elif.; Akın, Ata.
    Cognitive aging is a natural and lifelong process which may lead to the neurological diseases as dementia and Alzheimer’s. Investigation of the aging process on the cerebral hemodynamics of subjects would lead to the prevention of neurological diseases which are the last stages of cognitive aging process. The aim of this study was to investigate the prefrontal cortex (PFC) oxygenation increase as working memory load is increased, to determine the effect of cognitive aging on PFC hemoglobin oxygenation and to analyze the lateralization index of young and middle aged adults. The study included measurement of hemodynamic changes with Functional Near-Infrared Spectroscopy (fNIRS) during a mental arithmetic task. The study demonstrated that during the mental arithmetic study, prefrontal cortex (PFC) hemoglobin oxygenation increased with the increasing working memory load for both groups; there was no significant hemoglobin oxygenation difference between both groups; young subjects used right PFC regions, while the middle aged subjects used left PFC regions during the mental arithmetic task and lastly the lateralization index of two groups increased with the increasing memory load.|Keywords: Functional Near-Infrared Spectroscopy (fNIRS), local oxygen consumption, working memory, prefrontal cortex (PFC), mental arithmetic task (MA), lateralization index (LI).
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    SOD1 A4V mutation increases Nav1.3 channel excitability on xenopus laevis oocyte
    (Thesis (Ph.D.)-Bogazici University. Institute of Biomedical Engineering, 2016., 2016.) Kubat, Elif.; Ülgen, Yekta.; Akın, Ata.
    Amyotrophic lateral sclerosis (ALS) is a lethal, paralytic disease caused by degeneration of motor neurons in the spinal cord, brain stem and motor cortex. Mutations in the gene encoding copper/zinc superoxide dismutase (SOD1) are present in 20 % of familial ALS and 2 % of all ALS cases. The most common SOD1 gene mutation in North America is a missense mutation substituting valine for alanine (A4V). In this study, sodium channel currents in oocytes expressing either wild type or mutant (A4V) SOD1 protein were analyzed. In this study elicited on Xenopus Laevis oocyte, it is demonstrated that the A4V mutation confers a propensity to hyperexcitability on a voltage dependent sodium channel (Nav) mediated by heightened total Na+ conductance and a hyperpolarizing shift in the voltage dependence of Nav 1.3 activation. To estimate the impact of these channel effects on excitability in an intact neuron, these changes were simulated in the program NEURON; this shows that the changes induced by mutant SOD1 increase the spontaneous firing frequency of the simulated neuron. These findings are consistent with the view that excessive excitability of neurons is one component in the pathogenesis of this disease.|Keywords :Nav channel, amyotrophic lateral sclerosis, hyperexcitability, superoxide dismutase, oocyte