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This study compared three indirect calorimetry determinations, as kcals/minute, over three consecutive days on 28 healthy, sedentary women of varying body composition. No significant within-individual variation for VO2, CO2, respiratory quotient (RQ), or Kcals/minute was found among the three days. A low coefficient of variation (3.4 +/- 3%) and a relatively small standard deviation in mean Kcals/day (1383 +/- 214) suggests possibly one or only a few measures are necessary for predicting resting metabolic rate (RMR) within a range applicable for clinical use. There were strong correlations of body weight and body composition variables (fat and LBM) with RMR. Knowing both LBM and fat mass increased the ability to predict RMR significantly over the prediction with either variable alone. The Harris Benedict equation over-predicted RMR by 11.1% compared to RMR measured by indirect calorimetry. When equations are based on body weight, rather than LBM, metabolic rate may be over-predicted in obese populations.

In this thesis, I have used a combination of computational models such as mean field and spikingnetwork simulations to study various sub-circuits of basal ganglia. I first studied the striatum(chapter 2), which is the input nucleus of basal ganglia. The two types of Medium SpinyNeurons (MSNs), D1 and D2-MSNs, together constitute 98% of the neurons in striatum. Thecomputational models so far have treated striatum as a homogenous unit and D1 and D2 MSNs asinterchangeable subpopulations. This implied that a bias in a Go/No-Go decision is enforced viaexternal agents to the striatum (eg. cortico-striatal weights), thereby assigning it a passive role.New data shows that there is an inherent asymmetry in striatal circuits. In this work, I showedthat striatum due to its asymmetric connectivity acts as a decision transition threshold devicefor the incoming cortical input. This has significant implications on the function of striatum asan active participant in influencing the bias towards a Go/No-Go decision. The striatal decisiontransition threshold also gives mechanistic explanations for phenomena such as L-Dopa InducedDyskinesia (LID), DBS-induced impulsivity, etc. In chapter 3, I extend the mean field model toinclude all the nuclei of basal ganglia to specifically study the role of two new subpopulationsfound in GPe (Globus Pallidus Externa). Recent work shows that GPe, also earlier consideredto be a homogenous nucleus, has at least two subpopulations which are dichotomous in theiractivity with respect to the cortical Slow Wave (SWA) and beta activity. Since the data for thesesubpopulations are missing, a parameter search was performed for effective connectivities usingGenetic Algorithms (GA) to fit the available experimental data. One major result of this studyis that there are various parameter combinations that meet the criteria and hence the presenceof functional homologs of the basal ganglia network for both pathological (PD) and healthynetworks is a possibility. Classifying all these homologous networks into clusters using somehigh level features of PD shows a large variance, hinting at the variance observed among the PDpatients as well as their response to the therapeutic measures. In chapter 4, I collaborated on aproject to model the role of STN and GPe burstiness for pathological beta oscillations as seenduring PD. During PD, the burstiness in the firing patterns of GPe and STN neurons are shownto increase. We found that in the baseline state, without any bursty neurons in GPe and STN,the GPe-STN network can transition to an oscillatory state through modulating the firing ratesof STN and GPe neurons. Whereas when GPe neurons are systematically replaced by burstyneurons, we found that increase in GPe burstiness enforces oscillations. An optimal % of burstyneurons in STN destroys oscillations in the GPe-STN network. Hence burstiness in STN mayserve as a compensatory mechanism to destroy oscillations. We also propose that bursting inGPe-STN could serve as a mechanism to initiate and kill oscillations on short time scales, asseen in the healthy state. The GPe-STN network however loses the ability to kill oscillations inthe pathological state. / <p>QC 20160509</p>

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The problem was to compare the motivational elements of basal reader stories of the past with those of the present. The purpose of the problem were 1) to determine the motivational content as represented by thema found in current basal reader stories and 2) to find differences, if any, between motivational content basal reader stories and findings of previous research.

Basal metabolic rate (BMR), an individual bird's minimum rate of energy expenditure, was followed in adult and juvenile captive Knot throughout their annual cycle, in conjunction with measurements of total body mass (BM) and body composition (lean mass and fat mass, as predicted using Total Body Electrical Conductivity). Adult captive Knot increased significantly in BM during spring, primarily due to fat deposition. Most juvenile Knot did not display fat deposition in their first spring in captivity. A seasonal peak in BMR, often double the seasonal minimum, occurred during spring but typically took place, on average, 5,11 and 4 days (respectively) after the seasonal peaks in BM, lean mass and fat mass. Little of the variation in BMR seen within or amongst captive Knot, irrespective of physiological state, was explained by variation in a single parameter (BM, lean mass or fat mass). As variation in BMR was not simply a consequence of variation in total lean mass, the average metabolic output per gram of the lean tissues must also have altered seasonally. During fat deposition in spring, Knot exhibited a significant increase in liver mass and a significant elevation (approximately 50% higher) in the activity of succinate dehydrogenase (SDH, an indicator of metabolic activity) in the small intestine. Such adaptations may have assisted an increase in fat deposition rate. SDH activity decreased by approximately 60% in the pectoral muscle of Knot during this period. Such a reduction in SDH may also aid fat deposition as it lowered an individual’s overall BMR. As Knot BM decreased after the spring peak, then BMR decreased in parallel with a decrease in SDH activity in their pectoral muscles. The spring peak in overall BMR may indicate an increase in the maximal sustainable metabolic rate (MMR) of an individual during migratory flight. If a relationship exists between BMR and MMR, then variation in metabolic activity rather than variation in the mass of various lean tissues (e.g. pectoral muscle) will increase metabolic scope without increasing the energetic costs of flight.

Iron is the most abundant trace metal in the brain and is essential for many biological processes, such as neurotransmitter synthesis and myelin formation. This thesis investigates small, multifocal hypointensities that are apparent on T2*- weighted (T2*w) MRI in the basal ganglia, where presumably most iron enters the brain via the blood-brain-barrier along the penetrating arteries. These basal ganglia T2*w hypointensities are believed to arise from iron-rich microvascular mineral deposits, which are frequently found in community-dwelling elderly subjects and are associated with age-related cognitive decline. This thesis documents the characteristic spatial distribution and morphology of basal ganglia T2*w hypointensities of 98 community-dwelling, elderly subjects in their seventies, as well as their imaging signatures on T1-weighted (T1w) and T2- weighted (T2w) MRI. A fully automated, novel method is introduced for the segmentation of basal ganglia T2*w hypointensities, which was developed to reduce the high intra- and inter-rater variability associated with current semi-automated segmentation methods and to facilitate the segmentation of these features in other single- and multi-centre studies. This thesis also presents a multi parametric quantitative MRI relaxometry methodology for conventional clinical MRI scanners that was developed and validated to improve the characterisation of brain iron. Lastly, this thesis describes the application of the developed methods in the segmentation of basal ganglia T2*w hypointensities of 243 community-dwelling participants of the Austrian Stroke Prevention Study Family (ASPS-Fam) and their analysis on R2* (=1/T2*) relaxation rate and Larmor frequency shift maps. This work confirms that basal ganglia T2*w hypointensities, especially in the globus pallidus, are potentially MRI markers of microvascular mineralization. Furthermore, the ASPS-Fam results show that basal ganglia mineral deposits mainly consist of paramagnetic particles, which presumably arise from an imbalance in the brain iron homeostasis. Hence, basal ganglia T2*w hypointensities are possibly an indicator of age-related microvascular dysfunction with iron accumulation, which might help to explain the variability of cognitive decline in normal ageing.