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

and some of the changes have clinically prognostic significance. Unfortunately, evaluating chromosomal changes in dogs isdifficult because they have an unusually high number of chromosomes that lack identifying characteristics. Also, studyingchromosomes harvested from tumours is technically more difficult than evaluating chromosomes from blood samples.Fortunately our lab has determined that chromosomal aberrations can be identified in peripheral lymphocytes in dogs withlymphoma. We are correlating the changes observed in the blood with those in the tumour. We are also developing probes tohelp us identify specific aberrations.Analysis of skin defects associated with an ENU induced mutation in the p53 binding protein p53bp1Beth Chaffee, XiaoQing Zhao, Maria Morasso, Rocky Tuan, Cecilia Lo.Laboratory of Developmental Biology, National Heart Lung and Blood Institute, National Institutes of Health,Bethesda, MDThe p53 cell signaling pathway plays a pivotal role in oncogenesis, and in modulating cellular response to genotoxicstress. The protein p53BP1 interacts with the DNA binding domain of p53 and enhances transcriptional activation. Micedeficient in p53BP1 are viable, but have retarded growth, exhibit immunodeficiencies, have hypersensitivity to ionizingradiation and are also prone to developing cancer. We recovered an N-ethyl-N-nitrosourea (ENU) induced point mutation inp53BP1 that causes a spectrum of defect phenotypes that show overlap with DiGeorge syndrome. Thus the mutants showcraniofacial defects and cardiac defects consisting of persistent truncus arteriosus. In addition, the mutants are growthretarded, exhibit eye defects, as well as thickened skin with fewer pigmented hair follicles. To examine the skin defectphenotype in this mutant mouse model, histological sections were generated from skin obtained over various areas of thebody. Analysis by hematoxylin and eosin staining showed a thickened epidermis. This was associated with an apparentexpansion of cells in the suprabasalar layers, and the abnormal retention of cells with nuclei into the stratum granulosum. Inaddition, the stratum basale, which is usually unilaminar, appear to be multilayered and disorganized. To further analyze theskin phenotype, immunohistochemistry and immunofluorescence were performed to examine the distribution of keratins 1, 5,and 6 and filaggrin. We are also examining the expression of activated p53, and using antibodies to phosphohistone H3 andactivated caspases to investigate proliferation and apoptosis in the skin in these p53BP1 mutants. These studies will helpelucidate the possible role of p53BP1 and the p53 cell signaling pathway in regulating the growth and differentiation of theepidermis.A Blinded Test of Accuracy of Diagnosis of Canine Lymphomas by Comparison of Direct Examination ofMicroscope Slides with that of Scanned ImagesMarcia Chien*, V.E. ValliCenter for Zoonoses Research, University of Illinois College of Veterinary MedicineIn animals and humans, there are 30 subtypes of B and T-cell lymphomas which differ markedly in their normalbiology, untreated survival and response to therapy. A generic diagnosis of “lymphosarcoma” is often made in animals basedon morphology and increasingly with phenotypic identification of cell lineage based on a widespread acceptance that B-celllymphomas had better survival upon treatment than T-cell lymphomas. It is now shown that high and low grade lymphomasare present in both B and T-cell types and that tumor grade is more significant than cell lineage. This indicates a specificdiagnosis of lymphoma subtype is essential to properly titer treatment to tumor characteristics and to provide more accurateprognostication to the owner. A specific diagnosis will assist oncologists to better treat canine lymphoma, plus allowcooperative oncology trials to compare the efficacies of treatment on a single subtype of lymphoma rather than disease stageor lineage where there is far more variability due to subtypes. Since the detection of tumor related genetic changes can bemore easily detected in a purebred dog than in the out bred human population, the study of molecular aspects of lymphoma indogs also has the potential to advance identification of tumor subtypes in humans.To assist veterinary pathologists to provide this level of diagnostic specificity, an international study is underway todetermine the accuracy and reproducibility of veterinary pathologists in applying a revised system of lymphomaclassification. The World Health Organization (WHO) system of classification of hematopoietic tumors in humanscategorizes tumors as diseases rather than cell types. A blinded substudy of 50 slides was conducted utilizing cases selectedfrom the major diagnostic trial representative of the spectrum of B and T-cell lymphoma subtypes by phenotype and tumorgrade. Current data suggests a high degree of accuracy of the revised WHO human lymphoma classification scheme on thediagnosis of canine lymphomas. Since pathology consultations frequently require the production of further microscopicslides to be sent to additional reviewers for interpretation, an added comparison of diagnostic accuracy of lymphoma byroutine examination of histological preparations with that of scanned images of the same cases will be initiated.95