Much work has been done to study the external stimulation of nervous tissue as well as the transmission of neural signals to electronics. Peter Fromherz was one of the pioneers in this area of electrophysiology, with a series of experiments in the 1990s that aimed to characterize and optimize the interface between neural tissue and transistors. In this thesis, Kurt Sjoberg and I interfaced a Retzius cell isolated from a Hirudo medicinalis ganglion with the insulated gate of a MOSFET. The goal was to see change in membrane potential that could be related Fromherz’s original 1991 work. Our experimental setup utilized a classic electrophysiology technique, the current clamp. After varying the amplitude of the stimulating current pulses injected via microelectrode and ensuring the tight seal of the neuronal membrane with the insulated transistor gate, we found evidence of transistor voltage change that was temporally consistent with the elicited action potential of the neuron.

In order to verify the research from this laboratory that sheep omasal epithelium contains mRNA encoding for a peptide transporter (s) and to determine di- to octapeptide transport capability, poly(A)+ RNA isolated from sheep omasal epithelium was injected into Xenopus laevis oocytes. Poly(A)+ RNA was functionally expressed in Xenopus oocytes 4 to 7 d post-injection. Peptide (5 di-, 10 tri-, 6 tetra-, 2 penta-, 1 hepta-, 1 septa-, 1 octapeptide) transport capability was measured by impaling oocytes with a microelectrode to monitor membrane potential (Vm). Oocytes were maintained in pH 5.5 buffer. Peptide transport was identified as being expressed when, in the presence of a buffered peptide substrate (1 mM), the oocyte membrane showed persistent depolarization (a more positive Vm). In the absence of peptide transport, the membrane became depolarized with the addition of buffered substrate, but rapidly repolarized to the resting potential. Peptide transport was expressed for some di-, tri-, and tetrapeptides. Measured depolarization ranged from 9.6 mV to 42.1 mV. Larger peptides were not transported by the oocytes. When transport expression was measured with the substrates in a pH 7.5 buffer, no transport occurred indicating that transport was dependent on a proton gradient. The data indicate that sheep omasal epithelium contains mRNA that code for a protein(s) capable of proton-dependent di-, tri-, and tetrapeptide transport. This provides further evidence that absorption of peptides from the ruminant stomach is possible. / Master of Science

Call number: LD2668 .T4 1978 P37 / Master of Science

published_or_final_version / Psychology / Doctoral / Doctor of Philosophy

published_or_final_version / Orthopaedic Surgery / Doctoral / Doctor of Philosophy

published_or_final_version / Physiology / Master / Master of Philosophy

published_or_final_version / abstract / Medicine / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Psychiatry / Doctoral / Doctor of Philosophy

Some patients suffer hearing loss in the early postoperative period following vestibular schwannoma (VS) excision despite having intact hearing immediately after surgery. As this phenomenon has rarely been documented or described, the putative mechanism remains vague. The objective of the current study was to document the patterns of change in behavioural and electrophysiological responses in patients following VS surgery to better describe the phenomenon of delayed hearing loss. In particular, we aimed to determine whether the impairment that eventually leads to delayed hearing loss is neural or cochlear in origin. Auditory function was monitored in six adult patients who underwent surgery at Christchurch Public Hospital for excision of unilateral vestibular schwannoma through the retrosigmoid approach. Patients were assessed pre- and postoperatively by puretone audiometry, speech audiometry, tympanometry, distortion product otoacoustic emissions (DPOAEs), and auditory brainstem response (ABR). When measurable hearing was demonstrated postoperatively, pure-tone audiometry, speech audiometry and ABR were assessed at 24 hour intervals following surgery. Transtympanic electrocochleography (ECochG) was carried out if wave I of the ABR was lost during the postoperative period. Postoperative monitoring revealed that 4 patients suffered permanent anacusis and the remaining 2 patients had permanent hearing preservation. There were no patients who experienced delayed hearing loss in the early postoperative period. A phenomenon similar to delayed hearing loss was observed in case 2 who demonstrated loss of ABR wave I on the 7th postoperative day. Postoperative ECochG recorded in this case showed an enhanced negative SP on the operated side. The findings of this study are discussed in detail with particular reference to the underlying pathophysiology.

No description available.