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Call number: LD2668 .T4 1979 C73 / Master of Science

The internal organisation of bacteria is far more complex than originally thought. Many components of the cell have specific localisation patterns. Proteins are localised to many different regions of the cell by numerous mechanisms, and often their function depends on correct localisation. Bacterial and plasmid DNA are also highly organised and actively positioned. These tightly regulated positioning patterns ensure stable maintenance of genetic material. Members of the ParA/MinD family of ATPases are responsible for the segregation of a large number of bacterial chromosomes and plasmids. Recently members of this family have been shown to position and segregate protein complexes. One such complex is the cytoplasmic chemosensory cluster of Rhodobacter sphaeroides. This large complexes are segregated from a single cluster positioned at the mid-cell to two clusters at 1/4, 3/4 positions by the ParA homologue PpfA using the nucleoid as a scaffold. This ensures that each daughter cell inherits a cluster. This study sought to investigate this cytoplasmic chemosensory cluster, and its positioning and segregation by PpfA through the cell cycle. The use of fluorescence recovery after photobleaching revealed that like membrane bound chemoreceptor arrays the cytoplasmic cluster of R. sphaeroides is a highly stable complex. The difference seen between the cytoplasmic cluster and the data reported for the membrane bound cluster of Escherichia coli is probably due to the lack of membrane helping hold the array together. Investigation of the role of PpfA in segregation of the cytoplasmic cluster, using fluorescence imaging and single molecule tracking with a range of mutants through the cell cycle, suggest that it uses a mechanism unlike any reported for ParA homologues. Single molecule tracking of PpfA molecules shows that the chemoreceptor TlpT stabilises PpfA molecules resulting in slower diffusion of PpfA molecules at the cluster. The use of a ΔppfA mutant shows that PpfA restrains the movement of the cluster, together these results suggest a model in which TlpT stabilises PpfA’s interaction with the nucleoid and PpfA positions the cluster.

Typescript. / Digitized by Kansas Correctional Industries

Identifying the sensory systems animals employ to communicate chemically and the function of the chemical signals facilitates further understanding of chemical communication. Increased knowledge of how animals use the olfactory and vomeronasal systems in order to interpret the meaning of body odors will aid in developing a more detailed organization of chemosensory pathways. The message that each body odor contains can change from species to species. The purpose of this thesis was to study three previously untested body odors in house mice (M musculus) for their role in gender recognition of conspecifics. These odors are the anogenital (feces, urine, and preputial gland secretions), the Harderian gland (Harderian gland sebaceous secretion; gland located at inner comer of eye), and mouth/nose (saliva, mucus, and food). The amount of time in seconds and the number of sniffs were measured in an habituation paradigm which involved four trials per odor. The means of the amount of time spent sniffing and the number of sniffs per odor showed that the mice sniffed the novel odor the most, the non-novel an intermediate amount, and the control the least amount. The mice recognized the novel as foreign and the non-novel as familiar and the mice could not determine the gender of the odor-donor from any of the three odors.

Graduation date: 1994

Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisor: William B. Farquhar, Dept. of Health, Nutrition, & Exercise Sciences. Includes bibliographical references.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references (leaves 163-177).

Thesis (Ph.D.)--McMaster University, 2004. / Advisor: Colin A. Nurse. Includes bibliographical references ( leaves 181-207). Also available online.

The role of the carotid chemoreceptors in the hyperpnea of exercise was investigated. The activity of the sinus nerve of the cat was monitored while the blood supply to the carotid body was controlled independently of the systemic circulation. By this technique, fluctuations in the arterial blood gases during a short interval of exercise induced by electrical stimulation of hindlimb muscles were unable to affect the chemoreceptor activity. While minute ventilation increased by an average of 51%, chemoreccptor discharge was found to be unchanged in 12 experiments, 6 while perfusing with normoxic blood and 6 while perfusing with hypoxic blood. Thus, it must be concluded that alteration of carotid chemoreceptor sensitivity does not occur during artificially induced exercise in anesthetized cats. However, the difference in the time course of ventilation following the initiation of artificially induced exercise between cats and other species does not allow it to be ruled out in other species, including man. Indirect evidence is against such a role.