Thesis (Ph. D.)--University of Wisconsin--Madison, 1951. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 68-69).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1953. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 70-74).

This study was concerned with the ultrastructural changes that occur in axons and glial cells during peripheral nerve regeneration in the cockroach <i>Periplaneta americana</i>. Metathoracic nerve 5 was cut and regeneration of the proximal stump was studied using electron microscopy. Nerve 5 was surrounded by an acellular layer, the neural lamella. Underneath this structure was a layer of glial cells which formed the perineurium. Lanthanum penetration stopped between the perineurial cell processes, revealing them to be the site of the blood-brain barrier (BBB). Underlying the perineurium were the axons, surrounded by the subperineurial glial cells. Extracellular matrix was present between subperineurial glial processes. After cutting nerve 5, the initial changes in the proximal stump were a result of the degeneration of sensory axons. Haemocytes accumulated outside the nerve and morphologically similar granule-containing (g-c) cells appeared inside the nerve. After the first week signs of regeneration were distinguishable. These included axonal sprouting, glial proliferation and extracellular matrix production. Many small axonal sprouts were formed by regrowing axons. These became grouped into bundles, surrounded by glial processes, as the nerve outgrowth elongated. Glial proliferation by cell division began after the first week, and reached a maximum rate between two and three weeks. It is possible that mitosis of glial cells may be triggered by contact with the sprouting axons. Freeze-fracture studies of the tip of the growing nerve showed that formation of gap and septate unctions took place between the glial cells. This junctional assembly was asynchronous. Reinnervation of the coxal muscles occurred 8 weeks after the nerve was cut. At this stage the nerve was composed of several axonal bundles, each containing large and small axons. The nerve did not completely resemble the control even after 16 to 20 weeks of regeneration. Lanthanum incubation showed that the tracer was again excluded by the perineurial cells, indicating that the BBB of the regrown nerve reappeared at 8 weeks. Glial repair was studied following selective glial disruption using localised application of ethidium bromide. This treatment killed the perineurial and subperineurial glial cells. The repair of the glial system involved the transitory appearance of g-c cells in the nerve. 11 days after ethidium bromide treatment, new glial cells were present and lanthanum was excluded by the perineurial cell layer. Preinjection of microspheres into the haemolymph, which were taken up by phagocytic haemocytes, reduced the numbers of g-c cells that appeared in the nerve after ethidium bromide treatment. This lengthened the time required for glial repair. Cell division of neuroglial cells was observed. Cells derived from haemocytes and glial cell division were probably involved in the replacement of the damaged glial cells after ethidium bromide treatment. This study shows that glial cells play an important role in peripheral nerve regeneration in insects, forming the environment through which the regenerating axons grow.

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Monitoring and controlling of insects are of great scientific and engineering interests based on the potential impacts on environments, search and rescue operations, and robotics design. This research focuses on studying insects’ locomotive behavior by employing noninvasive piezoelectric sensors and presenting a conceptual method of locomotion control. To do so, polyvinylidene fluoride thin sheets are used as bending sensors at the joints of a cockroach’s legs. Approaches include development of polymeric sensors; laboratory in vitro testing of sensors and cockroaches; and methodology to control them. This research successfully built an experimental foundation for sensor and roach testing and developed a methodology for roach locomotion control. This research links engineering and entomology potentially having impacts in the mentioned arenas. Testing showed that piezoelectric films, such as polyvinylidene fluoride (PVDF), can serve as motion sensors for the legs, providing frequency and range of motion of each of the roach’s legs. The film is thin enough to provide as little resistance to motion to prevent altering the roach’s natural walking patterns. Testing also showed that using the insect’s instinct to physically touch an unknown object can be used as a directional control method. By using this natural response, a device can be fit on the roach capable of guiding the roach in any direction desired. This thesis is organized to present a brief introduction on the history and need for biomimetic robots. This section is followed by the research objectives and an introduction to polyvinylidene fluoride and the piezoelectric properties that allow it to become a sensor. A brief description of the roach anatomy and physiology is presented that will provide baseline of information needed to proceed with the project. We finish with an explanation of the testing of sensors on the roach and a novel method to control the roach walking orientation.

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Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.