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Abstract

Objective—To evaluate effects of imaging plane, flexion and extension, patient weight, and observer on computed tomographic (CT) image measurements of the area of the lumbosacral (L7-S1) intervertebral foramen (LSIF) in dogs.

Sample—12 dog cadavers (2 were excluded because of foraminal stenosis).

Procedures—In each cadaver, sagittal, sagittal oblique, transverse oblique, and double oblique CT images were obtained at 3 zones (entrance, middle, and exit zones) of the region of the lateral lumbar spinal canal that comprises the LSIF while the lumbosacral junction (LSJ) was positioned in flexion or extension. Barium-impregnated polymethylmethacrylate was used to fill the intervertebral foramina to aid boundary detection. Measurements of interest were obtained.

Results—Among the dog cadavers, there was large variability in LSIF cross-sectional areas (range, 0.12 to 0.44 cm2; SD, 0.1 cm2) and in foraminal angles required to obtain a double oblique plane in LSJ extension (SD, 8° to 9°). For LSIF area measurements in standard sagittal CT images, interobserver variability was 23% to 44% and intraobserver variability was 4% to 5%. Sagittal oblique images obtained during LSJ extension yielded smaller mean LSIF areas (0.30 cm2), compared with findings in sagittal images (0.37 to 0.52 cm2). The exit and middle zone areas were smaller than the entrance zone area in sagittal images obtained during LSJ extension.

Conclusions and Clinical Relevance—Repeated measurements of the LSIF area in images obtained during LSJ extension may be unreliable as a result of interobserver variability and the effects of dog positioning and CT slice orientation.

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in American Journal of Veterinary Research

Abstract

Objective—To determine expression of cyclooxygenase (COX) genes 1 and 2 (also called prostaglandin-endoperoxide synthases 1 and 2) and stability of housekeeping gene expression during low-flow ischemia and reperfusion in the jejunum of horses.

Animals—5 healthy adult horses.

Procedures—Horses were anesthetized, and two 30-cm segments of jejunum were surgically exteriorized. Blood flow was maintained at baseline (untreated) values in 1 (control) segment and was decreased to 20% of baseline (low-flow ischemia) for 75 minutes, followed by 75 minutes of reperfusion, in the other (experimental) segment. Biopsy samples were collected from experimental segments at baseline (T0), after 75 minutes of ischemia (T1), and after 75 minutes of reperfusion (T2); samples were collected from control segments at T0 and T2. Horses were euthanized 24 hours after induction of ischemia (T3), and additional samples were collected. Samples were evaluated histologically. Total RNA was extracted; expression of COX genes and stability of 8 housekeeping genes were determined via quantitative real-time PCR assays.

Results—COX-1 and COX-2 genes were constitutively expressed in baseline samples. Low-flow ischemia resulted in significant upregulation of COX-2 gene expression at each subsequent time point, compared with baseline values. The most stably expressed reference genes were β-actin and hypoxanthine phosphoribosyltransferase, whereas glyceraldehyde 3-phosphate dehydrogenase and β-2 microglobulin were the least stably expressed.

Conclusions and Clinical Relevance—Low-flow ischemia resulted in upregulation of COX-2 gene expression in the jejunum of horses. Housekeeping genes traditionally used as internal standards may not be stable in this tissue during arterial low-flow ischemia and reperfusion.

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in American Journal of Veterinary Research

Abstract

Objective—To evaluate canine histiocytic sarcoma cell lines and tumor samples for dysregulation of the Kit/stem-cell factor (SCF), Flt3/Flt3 ligand (Flt3L), and Met/hepatocyte growth factor (HGF) receptor tyrosine kinase signaling pathways, as these are known to contribute to the differentiation and survival of normal dendritic cells as well as malignant transformation of dendritic cells in mouse models.

Sample Population—4 histiocytic sarcoma tumor cell lines and 35 formalin-fixed histiocytic sarcoma specimens obtained from dogs.

Procedure—Histiocytic sarcoma cell lines were evaluated for expression of Kit/SCF, Flt3/Flt3L, and Met/HGF by use of reverse transcriptase-PCR procedures. Histiocytic sarcoma cell lines and tumor samples were evaluated for mutations in Kit, Flt3, and Met by use of PCR analysis of genomic DNA, followed by both sequencing and fluorescent PAGE for deletions or internal tandem duplications. The ability of the multitargeted split-kinase inhibitor SU11654 to block proliferation and induce apoptosis of histiocytic sarcoma cell lines was also evaluated.

Results—No mutations in Kit, Flt3, and Met were identified in any of the cell lines or tumor samples evaluated. Furthermore, SU11654 did not induce cellcycle arrest or apoptosis of histiocytic sarcoma lines, even at supratherapeutic doses.

Conclusions and Clinical Relevance—These data suggest that dysregulation of Kit/SCF, Flt3/Flt3L, and Met/HGF signaling pathways is unlikely to occur in histiocytic sarcomas of dogs and that inhibitors of the Kit, Flt3, and Met pathways are unlikely to provide clinical benefit to dogs with histiocytic sarcomas.

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in American Journal of Veterinary Research

Abstract

Objective—To determine the prevalence of activating internal tandem duplications (ITDs) in exons 11 and 12 of c-kit in mast cell tumors (MCTs) of dogs and to correlate these mutations with prognosis.

Sample Population—157 formalin-fixed, paraffinembedded MCTs from dogs in the pathology database of the Veterinary Medical Teaching Hospital at the University of California, Davis.

Procedure—Genomic DNA was isolated from tumor specimens and a polymerase chain reaction procedure was performed to determine whether there were ITDs in exons 11 and 12.

Results—We identified ITDs in 1 of 12 (8%) grade-I, 42 of 119 (35%) grade-II, and 9 of 26 (35%) grade-III tumors (overall prevalence, 52 of 157 [33%]). Logistic regression analysis revealed that the odds of grade-II and -III tumors possessing an ITD were approximately 5 times greater than that for grade-I tumors, although these odds did not differ significantly. Although MCTs possessing an ITD were twice as likely to recur after excision and twice as likely to result in metastasis as those without an ITD, these values also did not differ significantly.

Conclusions and Clinical Relevance—These results provide evidence that ITDs in c-kit occur frequently in MCTs of dogs. The high prevalence of c-kit activating mutations in MCTs of dogs combined with the relative abundance of mast cell disease in dogs provide an ideal naturally developing tumor in which to test the safety and efficacy of novel small-molecule kinase inhibitors such as imatinib mesylate. (Am J Vet Res 2002;63:1718–1723)

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in American Journal of Veterinary Research
History

A 12-year-old 443-kg (975-lb) Quarter Horse mare, intended to be used for barrel racing, was referred to the theriogenology service of the veterinary teaching hospital at the University of California-Davis for a reproductive examination to assess fetal viability. Fifteen days prior to admission for the reproductive examination, clinicians at the same veterinary teaching hospital had examined and treated a laceration and subsequent septic condition involving the right metacarpophalangeal joint of the horse. At the time of admission, a solution (1 g of amikacin in 40 mL of isotonic saline [0.9% NaCl] solution) was perfused into the distal aspect of

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in Journal of the American Veterinary Medical Association

Abstract

Case Description—A 7-year-old Golden Retriever was examined because of anorexia, lethargy, vomiting, and gradual weight loss.

Clinical Findings—Splenomegaly, pancytopenia, high serum calcium concentration, and high alkaline phosphatase activity were detected. Magnetic resonance imaging revealed an enlarged mesenteric lymph node and increased signals from the bone marrow of the ilium and vertebral bodies. Histologic examination and immunophenotyping of biopsy specimens confirmed a stage V (b) T-cell malignant lymphoma.

Treatment and Outcome—Clinical remission was attained by use of 2 chemotherapy cycles, followed by an allogeneic hematopoietic cell transplant performed at 18 weeks after diagnosis. A donor was identified by molecular dog leukocyte antigen typing methods. The patient was conditioned with 2 fractions of 4 Gy total body irradiation delivered 3 hours apart at 7 cGy/min, followed by an IV infusion of recombinant canine granulocyte colony-stimulating factor mobilized leukapheresis product and postgrafting immunosuppression with cyclosporine. Chimerism analyses revealed full donor engraftment that has been maintained for at least 58 weeks after transplant. Remission has been confirmed by normal results of serum thymidine kinase assays and the absence of peripheral blood clonal T-cell receptor gene rearrangements.

Clinical Relevance—Systemic chemotherapy induces remissions; however, most dogs succumb to disease recurrence because of multidrug resistance. Outcome of allogeneic hematopoietic cell transplantation in dogs can be excellent because of improved donor-recipient selection by use of molecular dog leukocyte antigen typing, compared with early attempts, and better prevention of graft versus host disease, better supportive care, and substitution of peripheral blood mononuclear cells for bone marrow.

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in Journal of the American Veterinary Medical Association