Obesity and its co-morbidities are among the leading health problems facing the developed world. Multiple genetic and environmental factors are known to have a significant impact on obesity development, however, heterogeneity of adipose tissue also contributes to obesity and its complications. Regional variation in adipose tissue has been associated with disease risks. For example, accumulation of visceral white adipose tissue (VAT), when compared to accumulation of subcutaneous white adipose tissue (SAT), is associated with an increased risk of diabetes and metabolic syndrome. Accumulation of brown adipose tissue (BAT), when compared to accumulation of white adipose tissue (WAT), on the other hand, is associated with lower BMI and higher insulin sensitivity. The goal of our project is to identify molecular targets that can be used as diagnostics, prognostics, or for reprogramming adipose tissue to a healthier phenotype (e.g. reprogramming VAT to SAT or WAT to BAT). To this end, we used three approaches. First, we used metabolic modeling to compare brown and white adipocyte metabolic profiles to predict and experimentally validate flux differences in the metabolic networks. Through this, we predicted and discovered a difference in urea secretion between these two classes of adipocytes. Second, we conducted transcriptome analysis of preadipocytes derived from SAT and VAT to identify several differentially expressed genes. Among them, we focused on Membrane Metallo-Endopeptidase (MME/Neprilysin) and showed experimentally that MME regulated the inflammatory response and insulin signaling in white preadipocytes by differentially affecting the insulin receptor (IR) subunits by increasing IRα but not IRβ. Finally, we used single-cell transcriptomics in differentiating human white preadipocytes derived from a single adipose depot to identify two subpopulations populations and a novel gene cluster of zinc finger proteins involved in white preadipocyte differentiation. The results presented here identify several key targets underlying the molecular and metabolic heterogeneity of adipose tissue.

Glycogen is the primary glucose storage mechanism in in living systems and plays a central role in systemic glucose homeostasis. The study of muscle glycogen concentrations in vivo still largely relies on tissue sampling methods via needle biopsy. However, muscle biopsies are invasive and limit the frequency of measurements and the number of sites that can be assessed. Non-invasive methods for quantifying glycogen in vivo are therefore desirable in order to understand the pathophysiology of common diseases with dysregulated glycogen metabolism such as obesity, insulin resistance, and diabetes, as well as glycogen metabolism in sports physiology. Chemical Exchange Saturation Transfer (CEST) MRI has emerged as a non-invasive contrast enhancement technique that enables detection of molecules, like glycogen, whose concentrations are too low to impact the contrast of standard MR imaging. CEST imaging is performed by selectively saturating hydrogen nuclei of the metabolites that are in chemical exchange with those of water molecules and detecting a reduction in MRI signal in the water pool resulting from continuous chemical exchange. However, CEST signal can easily be compromised by artifacts. Since CEST is based on chemical shift, it is very sensitive to field inhomogeneity which may arise from poor initial shimming, subject respiration, heating of shim iron, mechanical vibrations or subject motion. This is a particular problem for molecules that resonate close to water, such as - OH protons in glycogen, where small variations in chemical shift cause misinterpretation of CEST data. The purpose of this thesis was to optimize the CEST MRI sequence for glycogen detection and implement a real-time simultaneous motion and shim correction and measurement method. First, analytical solution of the Bloch-McConnell equations was used to find optimal continuous wave RF pulse parameters for glycogen detection, and results were validated on a phantom with varying glycogen concentrations and in vivo on human calf muscle. Next, the CEST sequence was modified with double volumetric navigators (DvNavs) to measure pose changes and update field of view and zero- and first-order shim parameters. Finally, the impact of B0 field fluctuations on the scan-rescan reproducibility of CEST was evaluated in vivo in 9 volunteers across 10 different scans. Simulation results showed an optimal RF saturation power of 1.5µT and duration of 1s for glycoCEST. These parameters were validated experimentally in vivo and the ability to detect varying glycogen concentrations was demonstrated in a phantom. Phantom data showed that the DvNav-CEST sequence accurately estimates system frequency and linear shim gradient changes due to motion and corrects resulting image distortions. In addition, DvNav-CEST was shown to yield improved CEST quantification in vivo in the presence of motion and motion-induced field inhomogeneity. B0 field fluctuations were found to lower the reproducibility of CEST measures: the mean coefficient of variation (CoV) for repeated scans was 83.70 ± 70.79 % without shim correction. However, the DvNav-CEST sequence was able to measure and correct B0 variations, reducing the CoV to 2.6 ± 1.37 %. The study confirms the possibility of detecting glycogen using CEST MRI at 3 T and shows the potential of the real-time shim and motion navigated CEST sequence for producing repeatable results in vivo by reducing the effect of B0 field fluctuations.

Includes bibliographical references / Fetal alcohol spectrum disorders (FASD) describe the spectrum of cognitive, behavioural and neurological impairments associated with prenatal alcohol exposure (PAE). Diffusion tensor imaging (DTI) and resting-state functional MRI (rs-fMRI) were used to assess effects of PAE on microstructural integrities of cerebellar and cerebral white matters (WM) and on resting-state functional connectivity (RSFC) in gray matter (GM) in children with varying degrees of FASD severity (fetal alcohol syndrome (FAS) and partial FAS (PFAS)), as well as nonsyndromal heavily exposed (HE) children. Children with FAS revealed lower fractional anisotropy (FA) bilaterally in the superior peduncles. Mean diffusivity (MD) was higher in the left middle peduncle in children with FAS or PFAS (FAS/PFAS). Mediation of effects of PAE on eyeblink conditioning (EBC) provided statistical evidence that poorer microstructural integrity in these regions may play an important role in the EBC deficit observed in children with FASD. The FAS/PFAS children also revealed lower FA and/or higher MD in 7 cortical WM regions and lower RSFC in 5 GM regions within 5 networks. Four of the 7 WM and 3 of the 5 GM regions also showed alterations in HE children, providing evidence that alterations in nonsyndromal children are less extensive and that some regions appear to be relatively spared. Alterations in DTI parameters (FA and MD) were dose dependent in many, but not all, of the regions where group differences were detected, specifically in the left (L) and right (R) superior peduncles, L middle peduncle, L inferior longitudinal fasciculus, medial (M) splenium of the corpus callosum (CC), and M isthmus of the CC. The WM deficits were attributable to increased radial diffusivity (RD) rather than decreased axial diffusivity (AD), suggesting poorer axon packing density and/or myelination. Increasing alcohol exposure was associated with reduced fractional amplitude of low frequency fluctuations (fALFF), indicating changes in functional connectivity in the default mode, salience, and dorsal attention networks. The locations of the WM alterations found with DTI suggest that the compromised RSFC found in 3 of the 5 networks could be attributable to WM deficits in tracts providing intra-network connections.

The human cerebellar cortex is a highly foliated structure that supports both motor and complex cognitive functions in humans. Magnetic Resonance Imaging (MRI) is commonly used to explore structural alterations in patients with psychiatric and neurological diseases. The ability to detect regional structural differences in cerebellar lobules may provide valuable insights into disease biology, progression and response to treatment, but has been hampered by the lack of appropriate tools for performing automated structural cerebellar segmentation and morphometry. In this thesis, time intensive manual tracings by an expert neuroanatomist of 16 cerebellar regions on high-resolution T1-weighted MR images of 18 children aged 9-13 years were used to generate the Cape Town Pediatric Cerebellar Atlas (CAPCA18) in the age-appropriate National Institute of Health Pediatric Database (NIHPD) asymmetric template space. An automated pipeline was developed to process the MR images and generate lobule-wise segmentations, as well as a measure of the uncertainty of the label assignments. Validation in an independent group of children with ages similar to those of the children used in the construction of the atlas, yielded spatial overlaps with manual segmentations greater than 70% in all lobules, except lobules VIIb and X. Average spatial overlap of the whole cerebellar cortex was 86%, compared to 78% using the alternative Spatially Unbiased Infra-tentorial Template (SUIT), which was developed using adult images.

Airborne infection control (AIC) measures are used extensively in healthcare settings to curtail the spread of airborne infectious diseases; these measures include administrative, architectural, engineering (e.g. ventilation) and personal protective interventions, serving either to reduce the concentration of airborne infectious particles or to protect individuals from direct exposure to airborne infection. Few such measures are applied in public congregate spaces outside of health facilities, such as those associated with public transport. Limited literature is available on existing AIC measures in the context of public transport modalities. This study explores the role of ventilation as an AIC measure in minibus taxis in Cape Town, South Africa, to determine its potential role in reducing airborne infectious disease transmission. The minibus taxi model chosen for the study was the Toyota Quantum Ses’fikile, which is commonly used in the Cape Town metropole. The Ses’fikile taxi has 6 windows, 2 at the front, 2 in line with the main passenger door and 2 towards the rear of the taxi. Ultrasonic anemometers were placed at key positions throughout the taxi-interior to measure and log airflow patterns, under different widow-open/close configurations and at different taxi speeds. To determine ventilation rates, the configurations were tested in an occupied taxi, with occupants comprising the driver, a researcher, and 14 volunteer participants. This study analysed TB transmission risk using the Issarow equation, a dose-response model. Airflows created by different window configurations produced patterns in airflow direction and velocity. A linear regression model fit to the ventilation data revealed that increasing taxi speed increased ventilation. Ventilation rates were found to depend on interior airflow as a result of the window configuration, as well as on the number of open windows, although the ventilation rate was not highest with the highest number of open windows. The best ventilation rates were found with four open windows, which included the front windows on both sides of the vehicle, and either the middle windows on both sides or the rear windows on both sides. The ventilation rates produced by these configurations at all tested taxi speeds (40 km/h, 80 km/h and 100 km/h) ranged from 108 to 316 L/s and exceeded the World Health Organization recommendation for new healthcare facilities, airborne precaution rooms, and general wards and outpatient departments. TB transmission probabilities in a taxi were dependent on ventilation, occupancy, number of infectors and duration of exposure. The risk of transmission was shown to increase substantially when ventilation rates fell below 50 L/s. In conclusion, minibus taxis were found to provide an effective range of ventilation rates that reduce the risk of TB transmission at varying speeds, however when natural ventilation is not used and with typical high occupancies, the risk posed to all occupants is high. Alternative AIC interventions may have to be considered.

Includes bibliography. Includes disk in pocket at back of book.

Includes abstract. Includes bibliographical references (p. 143-151).

Includes abstract. / Includes bibliographical references (leaves 108-118). / Fetal Alcohol Syndrome (FAS) is a clinical condition caused by excessive pre-natal alcohol exposure and is regarded as a leading identifiable and preventable cause of mental retardation in the Western world. The highest prevalence of FAS was reported in the wine-growing regions of South Africa but data for the rest of the country is not available. Required, therefore, are large-scale screening and surveillance programmes to be conducted in South Africa in order for the epidemiology of the disease to be understood. Efforts to this end have been stymied by the cost and labour-intensive nature of collecting the facial anthropometric data useful in FAS diagnosis. Stereo-photogrammetry provides a low cost, easy to use and non-invasive alternative to traditional facial anthropometry. The design and implementation of a landmark-based stereo-photogrammetry system to obtain 3D facial information for fetal alcohol syndrome diagnosis (FAS) is described. The system consists of three high resolution digital cameras resting on a purpose-built stand and a control frame which surrounds the subject's head during imaging. Reliability and assessments of accuracy for the stereo-photogrammetric tool are presented using 275 inter-landmark distance comparisons between the system and direct anthropometry using a doll. These showed the system to be highly reliable and precise.

Includes bibliographical references. / Impairment in classical eyeblink conditioning (EBC) has previously been reported in children with fetal alcohol spectrum disorders (FASD) (Jacobson et al., 2008). The deep cerebellar nuclei and cerebellar cortex are critical elements of the cerebellar-brainstem circuitry that mediates EBC (Green et al., 2002a; Yeo and Hardiman, 1992; Perret et al., 1993). In this study, we used magnetic resonance spectroscopy (MRS) and functional MRI (fMRI) to assess the effects of prenatal alcohol exposure on brain metabolism in the cerebellar deep nuclei and brain function in the cerebellar cortex, respectively. We found that higher levels of prenatal alcohol exposure were associated with lower levels of both N-Acetylaspartate (NAA) and choline-containing metabolites, and with higher levels of glutamate plus glutamine (Glx), suggesting a disruption of the glutamate-glutamine cycling involved in glutamatergic excitatory neurotransmission. Since the interpositus nucleus is one of the most crucial structures in the acquisition of the EBC response, abnormal metabolism in this region could be responsible for altered synaptic plasticity in children with FASD. Of the four cerebellar regions that were identified as being activated more by control children during rhythmic vs. non-rhythmic finger tapping, smaller differences in BOLD (blood oxygenation level dependent) activation were observed in children with FASD in two, namely vermis IV-V and right Crus I. Increasing levels of prenatal alcohol exposure were, however, associated with smaller differences in activation in all four regions, all of which have previously been linked to timed responses. In the paced/unpaced finger tapping fMRI study, we found four regions where increased BOLD activation during unpaced tapping compared to rest was associated with improved ability to maintain rhythm as evidenced by lower intertapping variability - right VIIIa and b, left VIIIa and right VI. These regions have previously been implicated in motor control with additional evidence of timing in lobule VI. In three of the regions, all except right VIIIa, increasing alcohol exposure was related to smaller increases in activation during unpaced tapping, with the strongest relations seen in the dosage dependent variable. Interestingly, the location of the activation in right VI is similar to a region that has been implicated in studies of EBC (Blaxton et al., 1996; Cheng et al., 2008). Our results point to altered metabolic levels in the deep nuclei and reduced functioning of several cerebellar cortical regions in children with FASD, highlighting the extensive damage caused by prenatal alcohol exposure. Although we did not find associations of EBC performance with either metabolite levels or activity in these regions, suggesting that damage to these areas are not primarily responsible for the observed EBC deficit, the extent of this damage could play a role in the impaired EBC performance seen in these children.

Includes bibliographical references. / Bone mineral density (BMD) is an indicator of bone strength. While femoral and spinal BMDs are traditionally used in the management of osteoporosis, BMD at peripheral sites such as the hand has been shown to be useful in evaluating fracture risk for axial sites. These peripheral locations have been suggested as alternatives to the traditional sites for BMD measurement. Dual-energy X-ray absorptiometry (DXA) is the gold standard for measuring BMD due to low radiation dose, high accuracy and proven ability to evaluate fracture risk. Computed digital absorptiometry (CDA) has also been shown to be very effective at measuring the bone mass in hand bones using an aluminium step wedge as a calibration reference. In this project, the aim was to develop algorithm s for accurate measurement of BMD in hand bones on a slot - scanning digital radiography system. The project assess e d the feasibility of measuring bone mineral mass in hand bones using CDA on the current system. Images for CDA - based measurement were acquired using the default settings on the system for a medium sized patient. A method for automatic processing of the hand images to detect the aluminium step wedge, included in the scan for calibration, was developed and the calibration accuracy of the step wedge was evaluated. The CDA method was used for computation of bone mass with units of equivalent aluminium thickness (mmA1). The precision of the method was determined by taking three measurements in each of 1 6 volunteering subjects and computing the root - mean - square coefficient of variation (CV) of the measurements. The utility of the method was assessed by taking measurements of excised bones and assessing the correlation between the measured bone mass and ash weight obtained by incinerating the bones. The project also assessed the feasibility of implementing a DXA technique using two detectors in a slot-scanning digital radiography system to acquire dual-energy X-ray images for measuring areal and volumetric BMD of the middle phalanx of the middle finger. The dual-energy images were captured in two consecutive scans. The first scan captured the low- energy image using the detector in its normal set-up. The second scan captured the high- energy image with the detector modified to include an additional scintillator to simulate the presence of a second detector that would capture the low-energy image in a two-detector system. Scan parameters for acquisition of the dual-energy images were chosen to optimise spectral separation, entrance dose and image quality. Simulations were carried out to evaluate the spectral separation of the low- and high-energy spectra.