Alternative sigma factors play a key role in the physiology of Bacillus anthracis by regulating the transcription of the appropriate genes required for adaptation and survival. Under specific conditions, alternative sigma factors activate transcription by binding to the promoter of the genes relevant to the condition and initiate synthesis of RNA. Here we report that the transcription of predicted sigI gene in B. anthracis, BAS3231, is induced by elevated temperatures and involved in the regulation of virulence gene expression. We show that BAS3231 is required for cell viability at elevated temperatures. We have also demonstrated that mutation in the BAS3231 gene results in a decrease in virulence gene expression. Our study provides new insight into the role of alternative sigma factors in B. anthracis.

Current knowledge indicates that nonthermal muscle metaboreflex activity plays a critical role in the modulation of skin vasodilation and sweating. However, the mechanisms of control have primarily been studied during isometric handgrip exercise in which muscle metaboreceptor activation is induced by a brief post-exercise ischemia of the upper limb. While the reflex increase in mean arterial pressure associated with this period of ischemia is consistent with the activation of muscle metaboreceptors, the change in baroreflex activity may in itself modulate the response. Thus, we sought to understand how these nonthermal stimuli interact in modulating the control of skin perfusion and sweating under conditions of elevated hyperthermia. Furthermore, we examined the mechanisms responsible for the maintenance of arterial blood pressure under varying levels of heat stress during isometric handgrip exercise. Our study findings indicate that the parallel activation of muscle metaboreceptors and baroreceptors during post-exercise ischemia causes divergent influences on the control of skin blood flow and sweating; and these nonthermal stimuli are dependent on the level of hyperthermia. Moreover, we report that heat stress reduces the increase in arterial blood pressure during isometric handgrip exercise and this attenuation is attributed to a blunted increase in peripheral resistance, since cardiac output increased to similar levels for all heat stress conditions. These results provide important insight and understanding into the role of muscle metabo- and baroreflex activity on the control of skin blood flow and sweating; along with further knowledge into the cardiovascular mechanisms responsible for the regulation of arterial blood pressure during hyperthermia.

The live export of cattle is an important industry for Australia. Concerns have arisen about animal welfare and in particular heat stress which may cause production losses and death. Cattle shipped live to the Middle East from a southern Australian winter can face continuous and prolonged periods of high heat and humidity as they cross the equator and arrive into a northern hemisphere summer, leading to heat stress and excessive heat load. Some live animal exporters treat heat stressed cattle with electrolyte supplements, but no scientific data exists as to whether this is beneficial to cattle in these unique environmental conditions. In response to industry’s concerns, the experiments described here monitored the physiological responses of Bos taurus and Bos indicus to conditions similar to those experienced by cattle being shipped from southern Australian to the Middle East. Initial experiments were conducted in climate controlled rooms at Murdoch University where intensive monitoring was possible. In the Bos taurus, increases in core body temperature, reductions in feed intake, and increased water intake were measured. There were also changes in blood gas variables consistent with the observed panting causing a compensated respiratory alkalosis. Following the heating period, there were decreases in blood and urinary pH. Bos indicus showed similar responses to the heat, but the changes were less pronounced at the temperatures tested. A pair feeding experiment was conducted to separate the effects of heat from the reductions in feed intake, and this indicated that the major measured effects were due to the responses to heat. On the basis of the measured responses, an electrolyte supplement was formulated and tested on Bos taurus, in the climate controlled rooms, and then on a commercial live export vessel. Results from these experiments indicated improved buffering capacity and a weight advantage for supplemented cattle, even in the absence of extreme heat stress. A final experiment investigated the effects of amount and quality of roughage in a pelleted feed on core and rumen temperature and feed intakes in Bos taurus subjected to hot environmental conditions in climate controlled rooms at Murdoch University. Both pelleted feeds had approximately the same metabolisable energy and crude protein but differed in content and type of roughage. There were no differences in feed intake, core temperature or rumen temperature between diets. This work has led to a greater understanding of the physiological responses of cattle to prolonged and continuous high heat and humidity, the requirements and effects of supplemental electrolytes in these conditions, and the effect of manipulating export diets. The demonstration of advantages in weight and buffering capacity with the electrolyte supplement highlights future areas of research to investigate electrolyte doses, route and types of supplementation, and dietary manipulation.

Thesis (M.Sc.(Hons.))--University of Wollongong, 2006. / Typescript. Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1984.

Thesis (M.S.)--University of Michigan, 1984.

Philosophiae Doctor - PhD (Biotechnology) / High temperature stress is synonymous with the attenuation of plant growth, metabolism and eventually death resulting in major loss of crop productivity worldwide. Part of the metabolic perturbations associated with heat stress leads to the excessive formation of reactive oxygen species (ROS), which have highly deleterious effects on cellular homeostasis. Naturally, through millions of years of evolution and adjustment, plants have developed antioxidant enzymes that neutralize harmful ROS species offering a protective role in the annulment of oxidative damage in response to high temperature. The aim of this study was to measure the activity of several antioxidant enzymes in response to heat stress in Zea mays.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第13852号 / 工博第2956号 / 新制||工||1436(附属図書館) / 26068 / UT51-2008-C768 / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 今中 忠行, 教授 青山 安宏, 教授 森 泰生 / 学位規則第4条第1項該当

Doctor of Philosophy / Department of Animal Sciences and Industry / Micheal J. Brouk / Four studies were conducted that focused either on silage quality parameters or heat abatement systems to improve cow comfort. Study 1 evaluated the effects of treating whole-plant corn at harvest with a dual-purpose commercial silage inoculant containing Lactobacillus buchneri and Lactococcus lactis O224 on fermentation and aerobic stability of corn silage through 32 d of ensiling. Inoculating silage to be fed after minimal storage time (≤ 32 d post-harvest) had no effect (P > 0.05) on the chemical composition, fermentation variables, aerobic stability or rise in temperature post-harvest. Study 2 was designed to develop a berry processing score (BPS) for sorghum silage as well as evaluate the change in starch digestibility as the level of berry processing increased. A method to evaluate the level of processing in sorghum silage was successfully developed by measuring the percent of starch passing through a 1.7 mm screen. This provides the industry with a standardized method to measure the level of processing in sorghum silage. As BPS increased from 26.28 to 55.05 ± 0.04%, 7-h in situ starch digestibility increased from 50.54 to 82.07 ± 4.94% for unprocessed and heavily processed sorghum silage, respectively (R² = 0.43). By processing sorghum silage during harvest and measuring the extent of processing, sorghum silage starch digestibility can be enhanced and may serve as a viable alternative to corn silage in the diet of lactating dairy cows in areas of the country where corn silage is a high-risk forage crop due to lack of water. Study 3 evaluated the effects of 2 heat stress abatement systems on barn temperature, micro-environmental temperature, core body temperature (CBT), respiration rate, rear udder temperature, and lying time in lactating dairy cows. The systems evaluated were: direct cooling via feedline soakers and fans, or evaporative cooling via a fan and fog system. The evaporative cooling system was effective (P = 0.04) in reducing respiration rates (52.0 vs. 57.9 ± 2.2 breaths per min; P < 0.01) and rear udder temperatures (33.2 vs. 34.5 ± 0.3ºC; P < 0.01), and increased daily lying time (11.8 vs. 10.8 ± 0.3 h/d; P < 0.01) due to differences in barn THI and airflow. No treatment differences (P = 0.79) were detected for CBT, likely due to cooler ambient conditions during the study. Study 4 assessed the effects of the same evaporative and direct cooling systems as in Study 2 but were applied in the holding area prior to afternoon milking, where effects on CBT and micro-environmental temperature in lactating dairy cows were measured in addition to water usage by each system. No significant differences (P > 0.05) between direct cooling and evaporative cooling were detected for micro-environmental THI. However, the evaporative cooling system reduced the consumption of water in the holding area while maintaining CBT < 39.0ºC. Future research should be conducted under greater ambient THI to determine if an evaporative cooling system is able to maintain CBT < 39.0ºC, while also comparing CBT and water usage to a soaker system in the holding area.

Made available in DSpace on 2014-06-11T19:27:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-06-08Bitstream added on 2014-06-13T18:31:17Z : No. of bitstreams: 1 gamba_jp_me_.pdf: 1043148 bytes, checksum: b0a0191eb557834ac568021e9b13ad91 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O estresse calórico é o agente desencadeador de diversos distúrbios metabólicos em frangos de corte, entre eles o desequilíbrio ácido- base. Com a finalidade de evitar esses efeitos e melhorar o desempenho dos animais, faz-se necessário a utilização de níveis adequados de eletrólitos e, também, uma correta proporção entre esses na ração, obtendo assim uma formulação com um equilíbrio eletrolítico apropriado para os animais. Assim, o presente trabalho teve como objetivo avaliar o desempenho e a mortalidade de frangos de corte submetidos a diferentes balanços (Na++K+–Cl-)e relações eletrolíticas [(K++Cl-)/Na+] na dieta em condições de termoneutralidade e sobre estresse térmico. Para tanto um primeiro experimento foi realizado com um total de 1575 pintos de corte machos de 1-21, em condições termoneutras, em que os tratamentos consistiam de cinco dietas decorrentes de combinações BE/RE (150/3, 250/2, 250/3, 250/4 e 350/3). Foram avaliados os parâmetros peso corporal, consumo de ração e conversão alimentar, os quais se apresentaram sensíveis aos níveis de suplementação de BE e RE, enquadrados numa análise de superfície que permitiu melhor avaliação dos crescentes níveis de BE e relação estreita e larga do RE. Os resultados indicaram que o melhor desempenho foi obtido somente com as combinações simultâneas de eletrólitos para BE entre 251 e 255mEq/kg e RE entre 2,73:1 e 3,5:1. Em um segundo experimento, foram utilizados os mesmos animais, porém de 21-46 dias de idade, distribuídos em arranjo fatorial 5x3, totalizando 15 tratamentos. Os tratamentos consistiram das mesmas cinco dietas com diferentes combinações entre BE e RE, associado com a aplicação do estresse por calor, no 25° ou 35° dia de idade. Foi possível verificar que a formulação estratégica do correto equilíbrio de eletrólitos melhora o desempenho e é capaz de evitar o efeito do estresse / The heat stress is the causative agent of several metabolic disorders in broiler chickens, including the acid-base imbalance. In order to avoid these effects and improve animal performance, it is necessary to use adequate levels of electrolytes and also a correct proportion of these in the diet, thereby obtaining a formulation with an appropriate electrolyte balance for the animals. Thus, this study aimed to evaluate the performance and mortality of broilers submitted to different balances Na++K+–Cl-) and relations electrolyte [(K++Cl-)/Na+] in the diet at thermoneutrality and on thermal stress. Therefore, a first experiment was conducted with a total of 1575 male broiler chicks of 1-21 in thermoneutral conditions, in which treatments consisted of five diets resulting from combinations BE/RE (150/3, 250/2, 250/3, 250/4 and 350/3). The parameters evaluated were body weight, feed intake and feed conversion, which were susceptible to dietary supplementation of BE and RE, embedded in a surface analysis which allowed a better assessment of rising levels of BE and close and wide-RE. The results indicated that the best performance was obtained only with simultaneous combinations of electrolytes to between 251 and 255mEq/kg BE and RE and between 3,5:1-2,73:1. In a second experiment, we used the same animals, but in 21-46 days of age in a factorial arrangement 5x3, totaling 15 treatments. The treatments were the same five diets with different combinations of BE and RE, together with the application of heat stress on the 25th or 35th day of age. It was possible to verify that the correct formulation of the strategic balance of electrolytes improves performance and is able to avoid the effect of heat stress in broilers, whereas a diet with BE of 250 mEq/kg and RE 3 for better performance and a diet with BE of 350 mEq/kg and 3 RE aimed at survival of animals