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dc.contributor.authorHudson, Neil Peter Hammertonen
dc.date.accessioned2018-05-14T10:13:34Z
dc.date.available2018-05-14T10:13:34Z
dc.date.issued2001
dc.identifier.urihttp://hdl.handle.net/1842/29810
dc.description.abstracten
dc.description.abstractGastrointestinal diseases, including obstructive and motility disorders such as grass sickness, are very common in the horse. Motility disorders may represent a dysfunction of the neural, muscular or pacemaker components (interstitial cells of Cajal, ICC) of bowel control. ICC are the c-Kit-immunoreactive cells responsible for the generation of pacemaker activity in gastrointestinal smooth muscle. Impairment of this ICC-mediated pacemaker action has been implicated in several motility disorders in humans and laboratory mammals. Equine dysautonomia (grass sickness) is a common, frequently fatal disease of horses characterised by dysfunction of the gastrointestinal tract. Neurons of the enteric nervous system (ENS) are primarily and most severely targeted by the putative neurotoxin causing the disease. The aims of this study were:en
dc.description.abstract• to characterise the morphology and neurochemical expression of the equine ENS using tissue culture and immunohistochemistry.en
dc.description.abstract• to study the distribution of the ICC in the intestine in normal and grass sicknessaffected horses.en
dc.description.abstract• to perform a detailed in vitro investigation of the electrical properties and control of smooth muscle in both the healthy and diseased intestine.en
dc.description.abstract• to test the hypothesis that impaired ICC-mediated control is responsible for intestinal dysfunction.en
dc.description.abstractFresh ileal samples were harvested from adult horses free from gastrointestinal disease euthanased on humane grounds. Small mammal (guinea pig and rat) systems were used for comparison and development of techniques. The tissues were microdissected to prepare wholemounts for immunohistochemistry and for either explant or dissociated culture systems of the ENS. Immunoreactivity was assessed using a standard indirect immunofluorescence technique. In the horse, explant culture systems were established using wholemounts of either the submucous plexus or the muscularis externa (including the myenteric plexus). Dissociated cell cultures could only be obtained from the submucous plexus. This was in contrast to small mammal models where enteric neurons were grown in both the myenteric and submucous systems. Culture systems were maintained for up to 5 days in the horse and 8 days in the guinea pig. Immunoreactivity for a neuronal marker {Pan-N) and for glial cell markers (GFAP and SI00) indicated the presence of both neurons and enteric glia in the tissue culture preparations. Further refinements to the techniques will be required before this in vitro model can be used for quantitative analysis.en
dc.description.abstractTo examine the ICC in the horse, samples were taken at multiple anatomicallydefined sites from stomach to small colon. After tissue fixation in 10% phosphatebuffered formalin, 10 pm cryostat sections were processed using standard immunohistochemical techniques and the avidin-biotin-peroxidase method. The primary antiserum used was an affinity-purified polyclonal antibody raised against the c-Kit protein. Specific immunoreactivity for c-Kit was detected in all sites and three types of immunoreactive cell were identified. These were spindle-shaped cells in the region of the myenteric plexus with occasional cellular processes extending into the longitudinal muscle, stellate- or bipolar-shaped cells in the circular muscle layer and round cells in the submucosa. The round cells were shown to be mast cells with the use of toluidine blue staining whereas the other c-Kit-immunoreactive cells did not exhibit metachromasia and were therefore classified as ICC. In the duodenum, jejunum and ileum, ICC were found predominantly in the region of the myenteric plexus and to a lesser extent in the circular muscle. In contrast, in the large intestine (large colon, caecum, small colon) most cells were seen throughout the circular muscle and very few ICC were seen in the myenteric plexus area. A semi¬ quantitative grading system was used to examine any differences in ICC in grass sickness-affected ileum and pelvic flexure sections compared to normal animals. In horses with grass sickness, ICC were significantly decreased in both the myenteric plexus and circular muscle regions of both ileum and pelvic flexure compared to normal animals. It is possible therefore that the decline in ICC may be in some way responsible for the development of intestinal dysmotility in grass sickness.en
dc.description.abstractNormal and diseased equine tissue from clinical cases and abattoir samples from pigs were collected and examined using in vitro microelectrode electrophysiological recordings from smooth muscle cells. Slow wave activity and spike potentials were recorded in normal equine and porcine ileal preparations. The slow wave activity was preserved in the presence of tetrodotoxin. A waxing and waning pattern of the slow wave activity was noted. Nifedipine abolished the spiking contractile activity of the smooth muscle but did not abolish the slow waves. The majority of ileal preparations from grass sickness-affected horses exhibited prominent slow wave activity with reduced slow wave frequency and increased duration suggesting that, although the neural elements are destroyed, the ICC-mediated pacemaker function remains intact.en
dc.description.abstractThis work will increase understanding of gastrointestinal dysmotility and information on the role of ICC will also offer benefits in potential developments in pharmacological therapy.en
dc.publisherThe University of Edinburghen
dc.relation.ispartofAnnexe Thesis Digitisation Project 2018 Block 18en
dc.relation.isreferencedbyAlready catalogueden
dc.titleThe enteric nervous system and interstitial cells of cajal of the horseen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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