Edward A. Mahaffey

Cytologie Differentiation of Benign from Malignant Canine Mammary Tumors

Cytologic and histologic examination of 91 canine mammary masses was performed by two cytologists and two histopathologists. Ten important cytologic criteria of malignancy for canine mammary tumors were identified. A cytologic grading system for differentiation of benign from malignant mammary tumors was proposed using these criteria. With this system, approximately one fourth of the malignant mammary tumors were given a concordant cytologic diagnosis. Approximately one-half of the benign masses were given a concordant cytologic diagnosis by the two cytologists. One-half of all the tumors examined were given inconclusive cytologic diagnoses by both cytologists. The cytologic identification of spindle cells did not differentiate complex and mixed mammary tumors from simple tumors. Only five of the animals studied died of mammary cancer, precluding a critical analysis of the cytologic criteria for prediction of cancer mortality.

Immunohistochemical Demonstration of Desmin in Canine Smooth Muscle Tumors

Sections of formalin-fixed, paraffin-embedded canine leiomyomas, leiomyosarcomas, or fibrosarcomas were examined by immunohistochemical methods for the presence of desmin. Twenty-two leiomyomas and leiomyosarcomas were stained using the avidin-biotin complex technique, and 14 samples demonstrated positive staining for desmin. The eight negative results obtained may reflect differences in fixation or the affinity of the primary antibody for the tissues examined. Desmin was specific for myogenic tissues. Five canine fibrosarcomas examined immunohistochemically were all negative for desmin staining. The results indicate that desmin is a useful marker for immunohistochemical identification of canine leiomyomas and leiomyosarcomas.

Detection of equine and bovine T- and B-lymphocytes in formalin-fixed paraffin-embedded tissues

Formalin-fixed paraffin-embedded sections of equine and bovine lymph nodes, spleen, thymus, and Peyers patches were incubated with monoclonal antibodies to B-lymphocyte markers BLA.36, B29, and mb-1 and T-lymphocyte markers CD3 and CD5. The monoclonal antibody BLA.36 reacted with 80-90% of lymphocytes in the germinal centers and mantle zones of follicles in lymph nodes, spleen, and Peyers patches. In addition, 90% of lymphocytes in the marginal zone of the spleen, and variable numbers of lymphocytes within lymph node medullary cords were immunopositive for BLA.36. Antibodies to B29 and mb-1 produced similar staining patterns as BLA.36 with fewer positive cells in the germinal centers and medullary cords. BLA.36, B29, and mb-1 reacted with 30-50% of lymphocytes in the medulla of the thymus and with 5-10% of lymphocytes in the cortex. CD3 and CD5 reacted with 90% of lymphocytes in the paracortex and parafollicular zones of lymph nodes, spleen, and Peyers patches; 40-50% of lymphocytes in the medullary cords of lymph nodes, and scattered positive cells within follicles. Anti-CD3 antibody reacted with 95% of lymphocytes in the splenic red pulp, but antibodies directed against CD5 reacted only faintly with approximately 5-10% of lymphocytes in the red pulp. CD3 and CD5 reacted with 50-60% of cells in the medulla of the thymus and with 40-80% of lymphocytes in the thymic cortex. The biochemical characterization of the antibodies by Western blotting against lysates of equine and bovine peripheral blood mononuclear cells confirmed that antibodies to BLA.36, mb-1, B29, CD3, and CD5 detected molecules of the same approximate molecular mass as found on lymphoid cells of human beings and rats.

Septicemia in vaccinated and nonvaccinated turkeys inoculated with Pasteurella multocida serotype A:3,4.

Sixty-four, 10-week-old turkeys were inoculated with a highly virulent field isolate (86–1913) of Pasteurella multocida serotype A:3,4 by an oculo-nasal-oral route. Inoculated turkeys were examined at 4, 8, 16, 20, and 24 hours post-inoculation for bacteremia and histologic lesions. Bacteremia was detected in one of six turkeys 8 hours after inoculation and in four of six turkey poults at 16 hours post-inoculation. Pasteurella multocida was isolated from the spleens of two turkeys at 8 hours and from the spleens of all six poults 16 hours after inoculation. Peak concentrations of P. multocida reached 10° colony forming units per ml of blood. At 4 to 8 hours post-inoculation, isolate 86–1913 produced a fibrinopurulent bronchopneumonia followed by severe pulmonary necrosis, pleuritis, vasculitis; and, at 16 to 24 hours post-inoculation numerous extracellular bacteria were observed. Hepatic lesions included focal heterophil aggregates 8 hours after inoculation; these progressed to hepatic necrosis. Numerous extracellular bacteria within sinusoids were present 16 to 24 hours after inoculation. At 16 to 24 hours post-inoculation, there was degeneration of periarteriolar reticular cells in the spleen; these cells progressed to coalescing coagulative splenic necrosis with extracellular bacterial colonies. A second group of 41, 10–week-old turkeys, previously vaccinated with the Clemson University strain of P. multocida serotype A:3,4, were challenged with isolate 86-1913. When compared to the nonvaccinated group, vaccination with the Clemson University strain resulted in significantly fewer vaccinated turkeys with bacteremia. Although histologic lesion scores were not significantly different for vaccinated and nonvaccinated turkeys, the vaccinated turkeys had a significantly lower mortality rate. These findings suggest that respiratory infection of susceptible turkeys with virulent P. multocida serotype A:3,4 is followed by septicemic disease characterized by progressive bacteremia with massive tissue necrosis and extracellular bacterial replication in vascular and tissue spaces. In addition, vaccination may reduce mortality rates by lowering the incidence of bacteremia.