The primary purpose of this investigation is not only to improve the present technique of culture of Mycobacterium tuberculosis, but also to make a comparative study of the media use, namely, Veterans Administration modification of Trudeau's medium, Lowenstein's egg medium, and that developed by the author, in order to find which, if any, of these will most easily and effectively meet the needs of the hospital laboratory.

Osteocytes are the most abundant bone cells, however, they are also the least understood. They sense mechanical stress within the bone matrix to control remodelling, but there is debate about the way that this occurs. The bone matrix experiences changes in electrical charge through stress generated potentials in the canaliculi, and piezoelectricity of the collagen-hydroxyapatite junctions. External electrical stimulation (ES) has been shown to increase bone formation, indicating that the cells involved in remodelling are electrically sensitive. However, the effects of ES on osteocytes specifically are under-researched. Before applying ES in vitro the electrical characteristics of the culture media need to be understood to see if it will negatively impact cells in culture. ES in culture media causes pH changes and gas formation as well as precipitate formation directly on the electrode surface. The resistance of the media increases rapidly upon application of the electrical stimulus and plateaus after 100 - 200 minutes. The pH gradient disperses around the same time frame, with most stimulating currents causing no permanent change to the media pH. Stimulation parameters that cause minimal side effects will be better for the health of cells in culture. This should also make it more clear which outcomes are a result of the electrical stimulation and which come from the electrochemical reactions that are present in the media due to the ES. / Thesis / Master of Applied Science (MASc) / Osteocytes are the least understood bone cells and the way that they communicate with the bone matrix and other cells is widely debated. It is assumed that osteocytes sense mechanical stresses within the bone matrix through electrical charges that develop in areas of increased strain. External electrical stimuli have been shown to increase bone formation indicating that the cells are electrically sensitive. The electrical sensitivity of the osteocytes specifically is under-researched causing a gap in knowledge of the behaviour of the cell in the remodelling process. To study the effects of electrical stimulation on osteocytes, an experimental apparatus must be designed to deliver stimulation to the cells in vitro and maintain a stable environment. A culture medium is needed to keep cells alive in vitro To do this, the electrical characteristics of the cell culture medium must be understood in attempts to maintain homeostatic conditions for the cells.

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A mechanistic model was developed, which described the growth of a bacterial colony on an agar medium. Diffusion of substrate (nutrients/oxygen) through the colony are considered. Rate of substrate use by the organisms is assumed to follow Michaelis-Menton kinetics for substrate concentrations between prescribed limits. Above and below the prescribed concentration limits, the substrate use rate is assumed constant and zero, respectively. Supply of substrate to the colony was assumed to be non-limiting. Under these conditions, the model predicted that diffusion of substrate through the colony will eventually control colony growth. It also described a slower eponential growth rate of the colony when the organisms utilized an alternate substrate for one that became deficient throughout a portion of the colony, and a constant linear growth rate when an alternate substrate was not utilized. Consistent with published literature, a mathematical description of substrate supply through the agar indicated that, under normal conditions, glucose supply through the agar to the colony would not be expected to limit colony growth before oxygen diffusion through the colony limited growth.

Azotobacter and various fungi were grown together in nitrogen-free media. Maximal fungal growth in the medium used was possible only at the expense of Azotobacter cells and growth was always accompanied by acid production. When the medium reached a pH of 2, the bacterial cells were aggregated on fungal hyphae and the culture fluid appeared to be free of Azotobacter. Aspergillus niger grew well at the expense of viable bacteria and other fungi grew well on heat-killed cells of A. vinelandii. Members of the genus Hormodendrum, although not causing significant decrease in pH, were also able to clear turbid cultures of Azotobacter. However, clearing, which involved the attachment of bacteria to fungal hyphae, was dependent on acid production by the fungi. Bacterial aggregation was followed by hyphal attachment, bacterial inactivation, and finally, bacterial cell lysis.

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Call number: LD2668 .T4 1965 V145 / Master of Science

Call number: LD2668 .T4 1979 A278 / Master of Science

Call number: LD2668 .T4 1979 F47 / Master of Science

Call number: LD2668 .T4 1979 R619 / Master of Science