2006 merck/merial - School of Veterinary Medicine - Louisiana State ...

has been isolated from all samples and standardized. Results from duplex quantitative PCR assay comparing MDV gB and aunique host chicken sequence are pending. Supported in part by the Witter Fellowship at MSU and NIHT-35RR017491.Inducing Transmissible Spongiform Encephalopathies in White-tailed Deer using Spiroplasma mirum.Hilari French 2 *, Sue Hagius 1 , Joel Walker 1 , Fred Enright 1 , Frank Bastian 1 , and Philip Elzer 1,2Department of Veterinary Science 1 , Louisiana State University Agricultural CenterSchool of Veterinary Medicine, Louisiana State University 2Current research on transmissible spongiform encephalopathies (TSE) has centered on the origin of the abnormalprion that causes the characteristic neurological defects in many different animal species. Research has revealed that anabnormal prion does not have to be present at all for TSE pathology to occur, and there is discussion that inoculation ofabnormal prions alone will not induce TSE infections. One bacterium, Spiroplasma mirum, has been found to be associatedwith TSE infections in various animal species. We hypothesize that neonatal white-tailed deer injected with S. mirum willdevelop the characteristic signs of chronic wasting disease (CWD), the cervid form of TSE. Neonates will be inoculated withpure cultures of S. mirum via intracranial injection into the right hemisphere between the fontanels using a 23-gauge needle.Animals will be euthanatized upon onset of clinical signs or at the termination of the study if no symptoms develop. Controlanimals inoculated with media alone will be sacrificed concurrently with the experimental animals.Three out of four deer inoculated intracranially with S. mirum in a previous study developed clinical signs, and allfour exhibited histological changes consistent with spongiform encephalopathies (vacuolar encephalopathy with prominentperineuronal vacuoles). Microglia proliferation was observed throughout the brain, but there was no evidence of anysignificant inflammation. The spongiform changes were most prevalent in the cerebellar tissue and brain stem which is wherethey are located in the naturally-occurring disease. Neonatal white-tailed deer appear to serve as a model for CWD in thatexperimental infection with S. mirum leads to the induction of clinical symptoms and histological findings of spongiformchange in the brain.Role of c-KIT in Gastrointestinal Stromal TumorsEmmalena Gregory-Bryson*, Elizabeth Bartlett, Schantel Hayes, Matti Kiupel, and Vilma Yuzbasiyan-GurkanCollege of Veterinary Medicine, Michigan State University, East Lansing, MI 48824Gastrointestinal stromal tumors (GIST) are the most common mesenchymal neoplasms in the GI tract of humansand have also been described in dogs. GISTs are a separate neoplastic entity from smooth muscle and neural tumors that arethought to originate from the interstitial cells of Cajal and typically express KIT (CD117), a tyrosine kinase receptor encodedby the proto-oncogene c-KIT. Little is known about the pathogenesis of these malignant neoplasms. The purpose of this studyis to evaluate the role of c-KIT in GISTs, specifically, investigating gain of function mutations in exon 11 of c-KIT, whichhave been implicated in many tumors, including canine mast cell tumors (MCT). Formalin-fixed, paraffin-embedded tissuesof 17 canine GISTs with confirmed positive KIT immunostaining were included in this study. Of these dogs, 71% werefemale and 29% were male and represented various dog breeds. These dogs ranged from 4 to 15 years old. Exon 11, codingfor the juxtamembrane domain of KIT, was amplified from neoplastic tissue. 14 of these cases yielded amplificationproducts, with 6 showing an aberrant banding pattern. Sequencing of 3 of the aberrant patterns identified in frame deletions.The analysis of the other aberrant bands is ongoing. The mutations include two different, but overlapping 6 base pairdeletions, which translate to a deletion of 2 amino acids in one case and an amino acid change and a deletion of 2 amino acidsin the other case. Interestingly, these deletion mutations are the same as those previously found in the juxtamembrane domainof c-KIT in MCTs in our laboratory. The expression of KIT and the presence of these mutations in c-KIT implicate KIT inthe pathogenesis of these tumors. While preliminary, our results indicate that mutations in KIT may be of prognosticsignificance and that targeting KIT may be a rational approach to treatment of these malignant neoplasms. Supported in partby grant number NIHT-35RR017491 to Michigan State University.Evaluation of the effects of endotoxin and Polymyxin B on longitudinal smooth muscle of equine jejunumin vitroShannon Guy*, Micah Bishop, Dehong Li, Erin Malone, and Robert WashabauGastrointestinal Physiology Laboratory, College of Veterinary Medicine, University of MinnesotaUp to forty percent of horses admitted to veterinary teaching hospitals for colic are in a state of endotoxicshock. The inflammatory cascade initiated by lipopolysaccharide (LPS) destroys the epithelial barrier in the gut, exposing therest of the body to the effects of endotoxemia. Within the GI tract, LPS induces production of inflammatory immunemediators that inhibit motility, thereby producing ileus. Indeed, in the presence of LPS, phenylephrine has been shown toelicit weaker than normal contractions in intestinal smooth muscle. Because of its ability to bind the Lipid A portion of theLPS molecule, treatment with Polymyxin B is an often an adjunct therapy for endotoxemia.This study is a pilot project whose objective is twofold. The first objective is to establish an in vitro model of LPSinducedileus. Our hypothesis is that in vitro administration of endotoxin (E. coli O55:B5) on jejunal smooth muscle strips98