4,282 research outputs found

    Investigating neural differentiation capacity in Alzheimer’s disease iPSC-derived neural stem cells

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    Neurodegeneration in Alzheimer’s disease (AD) may be exacerbated by dysregulated hippocampal neurogenesis. Neural stem cells (NSC) maintain adult neurogenesis and depletion of the NSC niche has been associated with age-related cognitive decline and dementia. We hypothesise that familial AD (FAD) mutations bias NSC toward premature neural specification, reducing the stem cell niche over time and accelerating disease progression. Somatic cells derived from patients with FAD (PSEN1 A246E and PSEN1 M146L heterozygous mutations) and healthy controls were reprogrammed to generate induced pluripotent stem cells (iPSC). Pluripotency for patient and control iPSC lines was confirmed, then cells were amplified and cryopreserved as stores. iPSC were subjected to neural specification to rosette-forming SOX2+/nestin+ NSCs for comparative evaluations between FAD and age-matched controls. FAD patient and control NSC were passaged under defined steady state culture conditions to assess stem cell maintenance using quantitative molecular markers (SOX2, nestin, NeuN, MAP2 and βIII-tubulin). We observed trends towards downregulated expression of the nestin coding gene NES (p=0.051) and upregulated expression of MAP2 (p=0.16) in PSEN1 NSC compared with control NSC, indicative of a premature differentiation phenotype induced by presence of the PSEN1 mutation. Cell cycle analysis of PSEN1 NSC showed that compared with controls, a greater number of PSEN1 NSC were retained in G0/G1 phase of the cell cycle (p=0.39), fewer progressed to S-phase (p=0.11) and fewer still reached G2 phase (p=0.23), suggesting cell cycle progression may be impaired in PSEN1 NSC. Nuclear DNA fragmentation was increased (p=0.10) in FAD NSC compared with controls, indicative of elevated cell death/apoptosis. Flow cytometry-based analysis of live, nestin+ NSC and NPC indicated increased apoptosis (p=0.14) in FAD NSC compared with controls, as well as increasing levels of apoptosis (p=0.33) in FAD NSC as they specified to neural progenitor cells. Global RNA sequencing was used to identify transcriptomic changes occurring during both disease and control neural specification. GO analysis of DEGs between PSEN1 and control NSC at P3 revealed significant upregulation (FDR<0.0000259) of 5 biological processes related to transcription and gene expression as well as significant upregulation (FDR<0.000000725) of 12 molecular functions related to DNA binding and transcription factor activity. These data suggest significant changes in gene expression were occurring in PSEN1 NSC at P3 compared with control NSC at the same stage in neural specification. The number of DEGs (p<0.05) between PSEN1 and control NSC at P3 was 9.92-fold higher than the number of DEGs between PSEN1 and control NSC at P2, suggesting transcriptomic differences between PSEN1 and control NSC become more pronounced as cells specify further down the neural lineage. Gene ontology (GO) analysis of differentially expressed genes (DEGs) specific to AD neural differentiation revealed significant dysregulation (FDR p<0.05) of genes related to neurogenesis, apoptosis, cell cycle, transcriptional control, and cell growth/maintenance as PSEN1 NSC matured from P2 to P3. The number of DEGs (p<0.05) in PSEN1 neural differentiation was 4.7-fold higher than the number of DEGs seen in control neural differentiation, indicating more transcriptional changes occurred in PSEN1 NSC than in controls at the same time point in neural specification. Dysregulation of Notch signalling was specific to PSEN1 neural differentiation and Notch related DEGs significantly upregulated (p<0.05) in PSEN1 NSC at P3 compared with P2 included NCOR2, JAG2, CHAC1 and RFNG. qPCR based validation displayed significant upregulation of RFNG (p=0.04) in PSEN1 NSC at P3 compared with PSEN1 NSC at P2, and indicated a trend towards upregulation of JAG2 expression, correlating with RNA sequencing data. Data generated in this study indicate that presence of the PSEN1 mutation significantly increases the number of transcriptional changes occurring during neural differentiation. It is plausible that transcriptional changes to Notch signalling cause dysregulated neural specification and increased apoptosis in PSEN1 NSC, ultimately resulting in depletion of the NSC niche

    Studying the interplay between ageing and Parkinson's disease using the zebrafish model

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    Parkinson’s disease (PD) is a neurodegenerative disorder characterised by the loss of dopaminergic neurons in the substantia nigra. Ageing is the major risk factor for developing PD but the interplay between ageing and PD remains elusive. To investigate the effect of ageing on PD-relevant pathological mechanisms, zebrafish mutant lines harbouring mutations in ageing-associated genes (klotho-/-, sirt1-/-, satb1a-/-, satb1b-/- and satb1a-/-;satb1b-/-) were generated, using CRISPR/Cas9 gene editing. Likewise, a chemical model for SIRT1 deficiency was utilised. klotho-/- zebrafish displayed an accelerated ageing phenotype at 3mpf and reduced survival to 6mpf. Dopaminergic neuron number, MPP+ susceptibility and microglial number were unaffected in klotho-/- larvae. NAD+ levels were decreased in 6mpf klotho-/- brains. However, ATP levels and DNA damage were unaffected. sirt1-/- zebrafish did not display a phenotype through adulthood. il-1β and il-6 were not upregulated in sirt1-/- larvae, and chemical inhibition of sirt1 did not increase microglial number. cdkn1a, il-1β and il-6 were not upregulated in satb1a-/- and satb1b-/- larvae. Dopaminergic neuron number and MPP+ susceptibility were unaffected in satb1a-/- larvae. However, satb1b-/- larvae demonstrated a moderate decrease in dopaminergic neuron number but equal susceptibility to MPP+ as satb1b+/+ larvae. Adult satb1a-/- but not adult satb1b-/- zebrafish were emaciated. satb1a-/-;satb1b-/- zebrafish did not display a phenotype through adulthood. Transgenic zebrafish expressing human wildtype α-Synuclein (Tg(eno2:hsa.SNCA-ires-EGFP)) were crossed with klotho-/- and sirt1-/- zebrafish, and treated with a sirt1-specific inhibitor. Neither genetic cross affected survival. The klotho mutation did not increase microglial number in Tg(eno2:hsa.SNCA-ires-EGFP) larvae. Likewise, sirt1 inhibition did not induce motor impairment or cell death in Tg(eno2:hsa.SNCA-ires-EGFP) larvae. In conclusion, the suitability of zebrafish for studying ageing remains elusive, as only 1 ageing-associated mutant line displayed accelerated ageing. However, zebrafish remain an effective model for studying PD-relevant pathological mechanisms due to the availability of CRISPR/Cas9 gene editing, neuropathological and neurobehavioral tools

    EVALUATION OF BORON SUPPLEMENTATION IN SWINE AND POULTRY

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    The objectives of this dissertation were to evaluate dietary boron (B) supplementation as sodium borate in various swine models and broiler chicks through a series of experiments. The initial experiment evaluated supplemental B (0, 25, 50, and 100 ppm B) on serum insulin, glucose, and clinical chemistry panel of growing pigs. Serum insulin/glucose ratio tended to decrease linearly with increasing supplemental B in a fasting state (P = 0.08). These findings were more noticeable (linear effect, P = 0.02) in a postprandial state (~ 50 minutes following a meal). A series of follow-up studies further evaluating B supplementation (0, 5, and 25 ppm B) in sows, piglets, and grower and market pigs were conducted. In multiparous sows, B supplementation tended to result in sows farrowing fewer piglets (quadratic, P = 0.08) yet piglet birth weight was increased quadratically (P ≤ 0.05) with increasing B supplementation. Furthermore, B supplementation to multiparous sows resulted in a quadratic decrease in late gestation (d 80-90 of gestation) fasting serum insulin/glucose ratio (P = 0.02) whereas, in a postprandial state, serum insulin/glucose ratio was linearly increased (P = 0.02) with increasing B supplementation. In the second study, piglets from sows supplemented with dietary B exhibited an increase in the Mg content of the femur (quadratic effect, P = 0.02) at weaning. In the third study, both grower (70 kg BW) and market pigs supplemented with B had a greater kidney ash percentage (linear effect, P = 0.03; linear tendency, P = 0.08, respectively) compared to that of the control. Furthermore, grower pigs exhibited a linear increase in Mg concentration for the 3rd and 4th metacarpals (P = 0.05) with increasing B supplementation. In the final swine study, evaluating B supplementation on the apparent total tract digestibility (ATTD) and retention of nutrients in growing pigs resulted in a linear increase in both Mg absorption and digestibility regarding increasing B supplementation (P = 0.01 and P = 0.04, respectively). Lastly, an experiment evaluating B supplementation (0, 1, 2, 5, 10, 25, and 50 ppm B) to a semi-purified diet fed to broiler chicks resulted in a linear tendency for increasing tibia ash percentage (P = 0.08) with increasing supplemental B. Additionally, there was a greater tibia Mg concentration of birds supplemented B compared to control birds (P \u3c 0.01). In summation, B supplementation appeared to affect insulin concentration in both grower pigs and sows. Furthermore, B improved Mg absorption and digestibility in growing barrows while also affecting Mg concentrations in the bones of broilers, weaning pigs, and grower pigs, all suggesting B may play a key role in Mg metabolism

    Designing carbon fibre-reinforced composites with improved structural retention on exposure to heat/fire

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    Carbon fibre-reinforced composites (CFRCs) are increasing in popularity due to their high strength-to-weight ratio and resistance to corrosion. However, when exposed to temperatures above 300°C, the polymer matrix within CFRCs decomposes and then starts burning, exposing carbon fibres to the surroundings. The residual carbon fibres being electrically conductive, may pose a hazard to the surrounding electronics. Moreover, at over 550°C the carbon fibres begin to oxidise. This can lead to fibre defibrillation which also poses significant harm to human health as broken fibres can be sharp enough to cut through human skin, and under 7µm these particles are considered respirable where on inhalation they can causes damage to the trachea and lungs. While considerable work has been carried out on assessing the effect of heat/fire on degradation of the composite resin (matrix) and CFRCs themselves, there are limited studies on identifying the damage to carbon fibres within CFRCs and the hazards posed by the exposed damaged carbon fibres. This study examined the damage caused by high temperatures, radiant heat and flames on carbon fibres and CFRCs, and the effects on their physical properties. A methodology was developed to study and quantify the structural damage to carbon fibres and CFRCs after exposure to a range of heat/fire conditions. These included thermogravimetric analysis (up to 900oC in nitrogen and air atmospheres), the tube furnace (450oC–900oC), cone calorimeter (35kWm-2 to 75kWm-2 ) and a propane burner (116kWm-2 ) to simulate jet fuel fire conditions. Residual fibres were removed from different parts of the CFRCs and the physical properties were studied, such as fibre diameter reduction, change in electrical conductivity and decrease in tensile strength. It was found that at heat fluxes ≥60kWm-2 oxidation of the carbon fibres occurred. After 10min exposure to the propane flame, fibres in direct contact with the flame showed signs of internal oxidation.The aim of this PhD project was to also improve the structural retention of CFRCs on exposure to heat/fire so that the structural integrity is maintained and the carbon fibres are not exposed to the environment. To address this, the following approaches were undertaken: • Modification of the resin by adding flame retardants and nanoparticles in order to reduce the flammability of CFRCs, improve the mechanical integrity of the char and its adherence to the fibre. Flame retardants included ammonium polyphosphate, resorcinol bis-(diphenyl phosphate), 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide, and the nano-additives, nano-clay, layered double hydroxide and carbon nano-tubes. Cone calorimeter testing at 75kWm-2 showed that the addition of 15wt% ammonium polyphosphate resulted in large char formation and adherence to fibres in the underlying plies, which resulted in less oxidation to these carbon fibres. The addition of layered double hydroxides and carbon nano-tubes on the other hand caused pitting on fibres. • Provide heat protection to carbon fibres within CFRCs by the inclusion of high performance fibrous veils/woven fabrics of aramid, basalt, E-glass, polyphenylene sulphide and Kevlar. The inclusion of the woven E-glass resulted in a notable reduction in the percentage of carbon fibre oxidised. However, the volatiles produced during the decomposition of Kevlar and PPS sensitised the carbon fibre to oxidation, causing it to occur more rapidly and at a lower temperature. • Using high temperature chemical coatings to individually coat carbon fibres prior to making the CFRCs. Ceramic compounds (silica, alumina and zirconia), chosen as coating materials because of their high thermal stability, were applied by different processes. The most promising coatings included alumina and silica formed via sol-gel process and polysiloxane deposited during plasma exposure. Tows coated in these chemicals underwent heat testing in a tube furnace where those coated with alumina maintained the largest fibre diameters. While polysiloxane coating provided oxidation protection up to 600°C, after which cracks in the coating were observed. This was attributed to the mechanical mismatch of the polysiloxane coating and the carbon fibre

    Endogenous measures for contextualising large-scale social phenomena: a corpus-based method for mediated public discourse

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    This work presents an interdisciplinary methodology for developing endogenous measures of group membership through analysis of pervasive linguistic patterns in public discourse. Focusing on political discourse, this work critiques the conventional approach to the study of political participation, which is premised on decontextualised, exogenous measures to characterise groups. Considering the theoretical and empirical weaknesses of decontextualised approaches to large-scale social phenomena, this work suggests that contextualisation using endogenous measures might provide a complementary perspective to mitigate such weaknesses. This work develops a sociomaterial perspective on political participation in mediated discourse as affiliatory action performed through language. While the affiliatory function of language is often performed consciously (such as statements of identity), this work is concerned with unconscious features (such as patterns in lexis and grammar). This work argues that pervasive patterns in such features that emerge through socialisation are resistant to change and manipulation, and thus might serve as endogenous measures of sociopolitical contexts, and thus of groups. In terms of method, the work takes a corpus-based approach to the analysis of data from the Twitter messaging service whereby patterns in users’ speech are examined statistically in order to trace potential community membership. The method is applied in the US state of Michigan during the second half of 2018—6 November having been the date of midterm (i.e. non-Presidential) elections in the United States. The corpus is assembled from the original posts of 5,889 users, who are nominally geolocalised to 417 municipalities. These users are clustered according to pervasive language features. Comparing the linguistic clusters according to the municipalities they represent finds that there are regular sociodemographic differentials across clusters. This is understood as an indication of social structure, suggesting that endogenous measures derived from pervasive patterns in language may indeed offer a complementary, contextualised perspective on large-scale social phenomena

    Sensing the Interactions of Ionizing Radiation in a Semiconductor Substrate using Carbon Nanotubes

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    The production and collection of charge carriers or photons in a bulk medium is the basis behind the detection of ionizing radiation. This core operating principle has imposed the requirements of acceptable detection efficiency and complete energy deposition which in turn set volume and atomic number restrictions on these bulk mediums. As a result, the application of nanomaterials in radiation detection is often hindered by their nanoscale dimensions material composition. This work investigates the use of vertically aligned carbon nanotubes (CNTs) as a sensing volume for ionizing radiation. Specifically, CNTs are integrated into a global gate field effect transistor geometry where the gate voltage controls the conductance of the device by modulating the Schottky barrier between the CNT channel and the source and drain electrodes. Similar to a p-channel metal-oxide-semiconductor field effect transistor (MOSFET), the conductance of the CNT-based detector increases at negative gate voltages. In the presence of diagnostic range x-rays, the current flowing through the device increases from the baseline noticeably due to the radiation induced electron-hole pairs adding to the electric field felt by the CNT/electrode interface. Despite the scale of the device, it is sensitive to x-rays of varying energy and flux. The device also demonstrates considerable inherent photoconductive properties which can be utilized to complement the detection efficiency of ionizing radiation or for new photodetection applications entirely. This novel device demonstrates the promise of integrating nanostructured materials into traditional semiconductor substrates for radiation detection.Ph.D

    Measurement of the Environmental Impact of Materials

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    Throughout their life cycles—from production, usage, through to disposal—materials and products interact with the environment (water, soil, and air). At the same time, they are exposed to environmental influences and, through their emissions, have an impact on the environment, people, and health. Accelerated experimental testing processes can be used to predict the long-term environmental consequences of innovative products before these actually enter the environment. We are living in a material world. Building materials, geosynthetics, wooden toys, soil, nanomaterials, composites, wastes and more are research subjects examined by the authors of this book. The interactions of materials with the environment are manifold. Therefore, it is important to assess the environmental impact of these interactions. Some answers to how this task can be achieved are given in this Special Issue

    Palaeoenvironmental research at Hawelti–Melazo (Tigray, northern Ethiopia) – insights from sedimentological and geomorphological analyses

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    The sites of Hawelti–Melazo in the Tigray region of the northern Ethiopian Highlands is an archaeological hotspot related to the D'mt kingdom (ca. 800–400 BCE). The existence of several monumental buildings, which have been excavated since the 1950s, underline the importance of this area in the Ethio-Sabaean period. We investigated the geomorphological and geological characteristics of the site and its surroundings and carried out sedimentological analyses, as well as direct (luminescence) and indirect (radiocarbon) sediment dating, to reconstruct the palaeoenvironmental conditions, which we integrated into the wider context of Tigray. Luminescence dating of feldspar grains from the May Agazin catchment indicate enhanced fluvial activity in the late Pleistocene, likely connected to the re-occurring monsoon after the Last Glacial Maximum (LGM). The abundance of trap basalt on the Melazo plateau, which provides the basis for the development of fertile soils, and the presumably higher groundwater level during the Ethio-Sabaean Period, provided favourable settlement conditions. The peninsula-like shape of the Melazo plateau was easily accessible only from the east and northeast, while relatively steep scarps enclose the other edges of the plateau. This adds a possible natural protective function to this site.</p
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