ABSTRACT It has been widely recognized that microRNAs are involved in nearly all cellular processes that have been investigated and contribute to a variety of diseases including cancer. Our prior studies demonstrated the depletion of one-carbon metabolism related B-vitamins, including folate, vitamin B2, B6 and B12, induced a genomic DNA hypomethylation and an elevation of the tumorigenic Wnt signaling in mouse colonic epithelium. The present study aimed to define whether microRNAs serve as mediators between these B-vitamins and the Wnt signaling, and thereby influence intestinal tumorigenesis. MicroRNA expression profiles were measured using miRNA microarray and real-time PCR on colonic epithelial cells from Apc1638N mice fed with diets deplete or sufficient in those B-vitamins. In silico bioinformatic analysis were performed to predict microRNA gene targets within the Wnt signaling cascade. Out of 609 microRNA examined, 18 microRNAs were found to be either significantly (p < 0.05) or mildly (p < 0.10) differentially expressed in the colonic epithelium of mice fed the depleted diet when compared to the counterpart. Bioinformatic prediction of microRNA gene targets identified 40 genes within the Wnt pathway to have homology with microRNA seed sequences within their 3’-UTR or protein coding sequence. Of the 6 genes tested for experimentally target validation, the expression of Sfrp1 was shown to be significantly inhibited (p < 0.05) whereas β-catenin was shown to be significantly elevated (p < 0.05) with alterations of others in a fashion indicating the activation of Wnt signaling. These findings indicate that microRNAs may constitute a mechanism by which one-carbon B-vitamin depletions regulate the Wnt signaling pathway and thereby inform intestinal tumorigenesis.

Avian leukosis virus (ALV)-induced osteopetrosis is a proliferative disorder of the bone affecting the growth and differentiation of osteoblasts. Osteopetrosis is a polyclonal disease in which cells of the bone contain, on average, multiple viral DNA copies. Osteopetrotic bone is also characterized by the accumulation of unintegrated viral DNA, suggesting an atypical life cycle of the virus in the infected osteoblasts. To better understand virus-host interactions in the induction of osteopetrosis by ALVs, infected chick osteoblast cultures and osteopetrotic bone were examined for aspects of the virus life cycle and effects of infection on osteoblast function. Levels of infection and virus expression were compared in cultured osteoblasts and osteopetrotic bone. Osteopetrotic bone contained higher levels of viral DNA and correspondingly higher levels of viral proteins than infected osteoblast cultures, suggesting a higher viral load in the diseased bone. A significant level of mature Gag protein was present in the bone, suggesting the accumulation of mature virus particles in the diseased bone. It is possible that the accumulation of virus could facilitate the high levels of infection observed in the diseased bone. The mechanism by which unintegrated viral DNA persisted in osteopetrotic bone was investigated by examining the susceptibility of infected osteoblasts to superinfection. The results indicated that, in culture, infected osteoblasts were able to establish interference to superinfection. This suggests that the persistence of unintegrated viral DNA in osteopetrotic bone may not result from the continuing infection of productively infected osteoblasts. The effect of virus infection on osteoblast function was examined in the diseased bone and in osteoblast cultures. In infected chickens, osteoblast activity, as evidenced by the expression of osteoblast phenotypic markers, was increased only in chickens developing severe osteopetrosis. In culture, virus infection had no apparent effect on either the proliferation or differentiation of osteoblasts. This indicates that infection was itself not sufficient to perturb osteoblast function. Furthermore, it suggested that additional components of the bone may be required for ALV infection to induce the abnormal activity of osteoblasts observed in osteopetrosis.

No description available.

No description available.

This dissertation consists of three chapters. The first chapter titled ``U.S. Grass-fed Beef Price Premiums" examined monthly retail-level price premiums for grass-fed beef (relative to conventional grain-fed beef) in the U.S. from 2014 through 2021. We found that premiums were heterogeneous, with premium cuts (such as sirloin steak, tenderloin, ribeye, and filet mignon) enjoying the highest premiums. Premiums were not consistent with price levels, as the lowest premiums were observed for short ribs, skirt steak, and flank steak. Our findings suggest that grass-fed beef price premiums were negatively affected by the consumption of food away from home. Changes in income, increased information about taste, protein and minerals, fat, revocation of the USDA grass-fed certification program in 2016 and COVID-19 pandemic, also affected premiums for several individual cuts. Premiums were not sensitive to changes in information about climate change. The second chapter, ``Impact of Animal Disease Outbreaks on The U.S. Meat Demand'', examined the impact of the mad cow (BSE) and bird flu (AI) outbreaks on the demand for beef, pork, and broilers in the U.S from 1997 to 2019. Using time-varying elasticities obtained from a Rotterdam model with animal disease cases, we found that BSE outbreaks reduced beef consumption by 0.64 percent and increased pork consumption by 2.34 percent, on average. While BSE outbreaks reduced beef demand, these effects were short lived and did not extend beyond one quarter. On the other hand, broiler consumption decreased during the HPAI outbreaks while beef and broiler consumption increased after such outbreaks. Our time-varying cross-price elasticities indicated that substitution between beef and broilers and beef and pork strengthened after Quarter 4 of 2003. The third chapter is titled ``Impact of North American Mad Cow Disease Outbreaks on The U.S. Cattle Futures". Our study developed a distributional event response model (DERM) framework to show the duration and magnitude of market responses of the U.S. cattle futures market during episodes of mad cow disease (BSE) in North America between 2010 and 2019. Our results indicated that the 2017 U.S. BSE outbreak reduced the returns of live cattle futures. Additionally, the average duration of the BSE event response was about 8.5 days. / Doctor of Philosophy / This dissertation focused on the price analysis of the U.S. livestock market. The first chapter analysed the pattern of grass-fed beef price premiums measured as the difference between grass-fed beef price and conventional beef price. We mainly explored how the premiums were affected by consumers' income, food consumption away from home, and information on climate change, beef taste, and nutrition. We found that consumption of food away from home reduced the grass-fed beef price premiums. In addition, increased information about taste, protein and minerals, fat, and COVID-19 pandemic, could also affected the grass-fed premiums for several individual cuts. The second chapter explored how mad cow diseases and bird flu diseases affected the demand for beef, pork, and chicken. We particularly investigated how each disease outbreak affected the meat demand. My result showed that in the presence of mad cow diseases in the U.S., people bought more pork. This result that retailers should have higher pork demand when mad cow diseases are detected. The third chapter explored how mad cow diseases in North America affected the U.S. live cattle futures. We showed that the U.S. mad cow disease in 2017 reduced the returns of U.S. cattle futures and this impact lasted about 8.5 days. Simultaneously, we found that mad cow disease outbreaks in Canada did not significantly affect the U.S. cattle futures.

Streptococcus suis est un agent pathogène bactérien important qui affecte les porcelets post-sevrés et qui cause des septicémies, des méningites et des arthrites. L’infection se transmet principalement par voie respiratoire, cependant il existe une hypothèse que la voie intestinale pourrait aussi représenter une porte d’entrée pour le pathogène. Le déoxynivalénol (DON) est une mycotoxine soupçonnée depuis longtemps d’être un facteur prédisposant dans le développement de la maladie causée par S. suis, mais cela n’a encore jamais été étudié. L’objectif de cette étude est donc d’évaluer l’effet du DON sur les interactions de S. suis avec les cellules dendritiques (DCs) porcines, les macrophages alvéolaires porcins (PAMs) et les cellules épithéliales intestinales du porc (IPEC-J2). L’induction de médiateurs inflammatoires mesurée par RT-PCR ont révélé que le DON cause une diminution significative de l’expression des cytokines pro-inflammatoires (IL-6, IL-8, TNF-α) des DCs porcines et des PAMs favorisant ainsi un environnement immunosuppresseur. L’étude de l’expression du CMH-II par FACS a révélé que de faibles concentrations (≤ 1 μM) de DON augmentent significativement l’expression du CMH-II alors que de fortes concentrations (≥ 2 μM) causent plutôt une diminution significative de son expression influençant ainsi la mise en place de l’immunité adaptative. De plus, les tests de phagocytose ont révélé que de fortes concentrations (≥ 1 μM) de DON diminuent la capacité de phagocytose de S. suis par les PAMs favorisant ainsi la dissémination de la bactérie. Des tests d’adhésion et d’invasion ont révélé que le DON n’a pas d’impact sur l’adhésion de S. suis aux IPEC- J2 et que de fortes concentrations (≥ 4 μM) de DON favorisent l’invasion de S. suis dans ces cellules. Finalement, des tests ELISA ont montré que le DON (0,5, 1 et 4 μM) diminue significativement la production de cytokines pro-inflammatoires (IL-8) des IPEC-J2. / Streptococcus suis is an important bacterial pathogen that affects post-weaner piglets and causes septicemia, meningitis and arthritis. The infection is mainly transmitted by the respiratory route; however, there is a hypothesis that the intestinal tract could also represent an entry point for the pathogen. Deoxynivalenol (DON) is a mycotoxin that has long been suspected of being a predisposing factor in the development of disease caused by S. suis, but has never been studied. The objective of this study is therefore to evaluate the effect of DON on the interactions of S. suis with porcine dendritic cells (DCs), porcine alveolar macrophages (PAMs) and porcine intestinal epithelial cells (IPEC-J2). The induction of inflammatory mediators measured by RT-PCR revealed that DON causes a significant decrease in the expression of pro-inflammatory cytokines (IL-6, IL- 8, TNF-α) in porcine DCs and PAMs, thus promoting an immunosuppressive environment. The study of MHC-II expression by FACS revealed that low concentrations (≤ 1 μM) of DON significantly increase the expression of MHC-II while high concentrations (≥ 2 μM) rather cause a significant decrease in its expression, thus influencing the establishment of adaptive immunity. In addition, phagocytosis assays revealed that high concentrations (≥ 1 μM) of DON decrease the phagocytosis capacity of S. suis by PAMs, thus promoting the dissemination of the bacteria. Adhesion and invasion assays revealed that DON does not impact S. suis adhesion to IPEC-J2 and that high concentrations (≥ 4 μM) of DON promote S. suis invasion into IPEC-J2. Finally, ELISA have shown that DON (0,5, 1 et 4 μM) significantly reduce IPEC-J2’s production of pro-inflammatory cytokines (IL-8).

No description available.

No description available.

Louping ill virus (LIV) is a tick borne disease that causes mortality in red grouse, an economically important game bird of British uplands. The aim of this thesis is to extend previously published models of LIV , to consider the potential impact of different management strategies. In addition a new route of infection and the seasonal biology of both grouse and ticks will be explored. Grouse chicks are known to eat ticks as part of their diet in the first three weeks of life which may contribute to virus persistence if chicks consume infected ticks. This novel route of infection is incorporated in to the model which predicts that ingestion increases the range of host densities for which the virus is able to persist. The ingestion of ticks by grouse also reduces the tick population so that for low host densities the ingestion of ticks by grouse reduces the tick population so virus cannot persist. The model is adapted to take account of the seasonal biology of grouse and ticks. Although the temporal predictions of the seasonal models show some differences the addition of seasonality does not alter the model predictions of when LIV is likely to persist at different grouse and deer densities. Consequently seasonality is felt to be unimportant when considering management strategies. The treatment of sheep with acaricide in an attempt to reduce the tick population on a grouse moor is currently being trialled in Scotland. We use a model to predict the likely effect of this strategy at different deer densities. The number of ticks found attached to sheep varies so we consider the effect of tick attachment rates as well as acaricide efficacy. Although we predict that acaricide treated sheep can reduce the tick population and therefore LIV in grouse in some circumstances the treatment is less effective in the presence of deer. Consequently we use a model to make theoretical predictions of the effectiveness of acaricide treated deer as a control strategy for reducing LIV in red grouse. The effect of culling deer on LIV in grouse is also modelled and contrasted with the effect of acaricide use. It is predicted that acaricide treatment of deer could be highly effective, particularly if the deer density is first reduced by culling. Finally we considered the direct treatment of red grouse with acaricide. Female grouse can be given an acaricidal leg band which protects her directly and indirectly protects her chicks as they acquire some acaricide whilst brooding. Trials have suggested this can reduce tick burdens for individuals. We use the model to determine the potential effect that treating individual broods may have on the whole grouse population. The model predictions suggest that unless acaricide efficacy on chicks is high and long lasting treating individual broods is unlikely to reduce LIV in the whole population but will still provide some benefit for the individuals. The effectiveness of treatment is reduced by higher deer densities. The success of the management strategies considered in this thesis appear to be restricted by the presence of deer. It may therefore be that a combination of treatments including the treatment of deer may be of the greatest benefit to the grouse population.

Thesis (PhD (Molecular Biology and Human Genetics))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The growing global epidemic of human tuberculosis (TB) results in 8 million new cases of this disease and 2 million deaths annually. Control thereof will require greater insight into the biology of the causative organism, Mycobacterium tuberculosis, and into the pathogenesis of the disease. This will benefit the design of new vaccines and diagnostic assays which may reduce the degree of both disease transmission and progression. Animal models have played a vital role in the understanding of the aetiology, pathogenesis, and treatment of TB. Much of such insight has been obtained from experimental infection models, and the development of new vaccines, for example, is dependant on these. Nonetheless, studies utilising naturally occurring TB in animals, such as those which have investigated the use of interferon-gamma release assays (IGRA) for its diagnosis, have contributed substantially to the body of knowledge in this field. However, there are few such examples, and this study sought to identify and investigate naturally occuring animal TB in South Africa as an opportunity to gain further insight into this disease. During the course of this study, the dassie bacillus, a distinctly less virulent variant of M. tuberculosis, was isolated from a rock hyrax from the Western Cape Province of South Africa. This has provided new insight into the widespread occurrence of this organism in rock hyrax populations, and has given impetus to further exploring the nature of the difference in virulence between these pathogens. Also investigated was M. tuberculosis infection in dogs in contact with human TB patients. In so doing, the first reported case of canine TB in South Africa was described, v a novel canine IGRA was developed, and a high level of M. tuberculosis infection in these animals was identified. This supports human data reflecting high levels of transmission of this pathogen during the course of human disease. Additionally, the fact that infected companion animals may progress to disease and potentially act as a source of human infection was highlighted. However, an attempt to adapt a flow cytometric assay to study cell-mediated immune responses during canine TB revealed the limitations of such studies in species in which the immune system remains poorly characterised. The use of IGRAs to diagnose TB was further explored by adapting a human assay, the QuantiFERON-TB Gold (In-Tube Method), for use in non-human primates. These studies have shown that such an adaption allows for the sensitive detection of TB in baboons (Papio ursinus) and rhesus macaques (Macaca mulatta) and may be suitable for adaption for use in other species. However, they have also evidenced the limitation of this assay to specifically detect infection by M. tuberculosis. Finally, to contextualise the occurrence of the mycobacterial infections described above, and other similar examples, these have been reviewed as an opinion piece. Together, these investigations confirm that animal models will continue to make important contributions to the study of TB. More specifically, they highlight the opportunities that naturally occuring animal TB provides for the discovery of novel insights into this disease. / AFRIKAANSE OPSOMMING: Wêreldwye tuberkulose (TB) epidemie veroorsaak agt miljoen nuwe gevalle en twee miljoen sterftes jaarliks. Ingryping by die beheer hiervan vereis begrip van die biologie van die mikroörganisme Mycobacterium tuberculosis, die oorsaak van TB, asook van die patogenese van die siekte self. Hierdie kennis kan lei tot ontwerp van nuwe entstowwe en diagnostiese toetse wat gevolglik beide die oordrag- en vordering van die siekte mag bekamp. Dieremodelle speel lankal 'n rol in ons begrip van die etiologie-, patogenese- en behandeling van TB. Insig is grotendeels verkry vanaf eksperimentele infeksiemodelle, en ontwikkeling van entstowwe, onder andere, is afhanklik van soortgelyke modelle. Desnieteenstaande, studies wat natuurlike TB voorkoms in diere ondersoek, byvoorbeeld dié wat op die ontwikkeling van interferon-gamma vrystellingstoetse (IGVT) fokus, het merkwaardige bydrae gemaak tot kennis en begrip in hierdie studieveld. Daar is slegs enkele soortgelyke voorbeelde. Om hierdie rede is die huidige studie uitgevoer waarbinne natuulike diere-TB geïdentifiseer en ondersoek is in Suid-Afrika om verdere kennis en insig te win aangaande TB. Die "dassie bacillus", bekend om beduidend minder virulent te wees as M. tuberculosis, is tydens hierdie studie geïsoleer vanuit 'n klipdassie (Procavia capensis) in die Wes-Kaapse provinsie, Suid-Afrika. Insig in die wydverspreide voorkoms van hierdie organisme in klipdassie bevolkings is gevolglik verkry en verskaf momentum om die aard van verskil in virulensie tussen dié patogene te bestudeer. vii Voorts is M. tuberculosis infeksie bestudeer in honde wat in kontak is met menslike TB pasiënte en word die eerste geval van honde TB dus in Suid-Afrika beskryf. In hierdie groep diere, is 'n hoë vlak van M. tuberculosis infeksie geïdentifiseer deur gebruik te maak van 'n nuut ontwikkelde IGVT vir die diagnose van honde TB. Gevolglik ondersteun dié studie bevindinge van menslike studies wat toon dat besondere hoë vlakke van M. tuberculosis oordrag voorkom gedurende die verloop van die siekte. Verder toon die studie dat geïnfekteerde troeteldiere 'n bron van menslike infeksie kan wees. 'n Poging om 'n vloeisitometriese toets te ontwikkel om die aard van selgefundeerde immuunreaksies te bestudeer in honde met TB toon die beperkings van dergelike studies in spesies waarin die immuunsisteem gebrekkig gekarakteriseer is. Die gebruik van IGVT'e in die diagnose van TB is verder ondersoek deur 'n menslike toets (QuantiFERON-TB Gold, In-Tube Method) aan te pas vir die gebruik van nie-menslike primaat gevalle. Hierdie studies toon gevolglik dat so 'n aanpassing toepaslik is vir hoogs sensitiewe deteksie van TB in chacma bobbejane (Papio ursinus) en rhesus ape (Macaca mulatta), en mag ook aangepas word vir gebruik in ander spesies. Tog word die beperkings van hierdie toets om infeksie wat spesifiek deur M. tuberculosis veroorsaak uitgelig. Ter afsluiting word hierdie studie in konteks geplaas deur 'n oorsig te gee van bogenoemde- en soortgelyke gevalle van dierlike infeksie deur mikobakterieë in Suid-Afrika. Hierdie studies bevestig dat dieremodelle steeds belangrike toevoegings maak tydens die bestudering van TB en lig veral die moontlikhede uit dat bestudering van natuulike TB in diere kan lei tot die ontdekking van nuwe insigte ten opsigte van die siekte self.