Veterinary Pathology

The ultrastructure of feline mammary hypertrophy was studied in a five-month-old female which had aborted recently, a ten-year-old female which was one month postestrus, and a four-year-old progestin-treated neutered male. Morphologic comparisons were made to normal mammary tissue from a one-year-old female cat. Hypertrophied mammary tissue had the same cell types and spatial relationships as did the normal gland. Major differences included a more highly developed duct system composed of metabolically active cells which often were arranged in multiple cell layers, and periductular stroma with increased fibroblasts and vascularization. Hypertrophied epithelial cells were characterized generally by smooth-contoured nuclear membranes, more evenly dispersed heterochromatin, prominent nucleoli, increased polyribosomes, and elongated mitochondria. Secretory activity was developed significantly only in the cat that had aborted recently. Modifications in myoepithelial cells included: more evenly dispersed nuclear heterochromatin, thicker bundles of cytoplasmic filaments, more straight plasma membranes along the basal lamina, and elongated hemidesmosomes. Multilayering of the basal lamina was accentuated. Stromal fibroblasts had nuclear heterochromatin distributed similarly to that of epithelial and myoepithelial cells, and increased rough endoplasmic reticulum. Myoepithelial cells did not contribute to the increased stromal cellularity. No significant ultrastructural differences were noted between mammary hypertrophy in young, old, and progestin-treated cats.

A paralytic disease in swine was observed on three farms located in the same geographical area of Georgia. Postmortem examinations revealed the paralysis to be related to spinal poliomalacia. Feed collected from two of the affected farms was used in a feeding study, and the paralytic condition was reproduced. In pigs from both the feeding trial and field cases, the poliomyelomalacia was characterized by focal, symmetrical lesions located in the cervical and lumbar intumescences. Selenium was detected in the feed at levels ranging from 19 to 24 ppm.

Spontaneous paratuberculosis was studied in free-ranging and captive bighorn sheep (Ovis canadensis), and Rocky Mountain goats (Oreamnos americanus). Lesions of paratuberculosis in these species resembled the disease in domestic sheep and goats. Mycobacterium paratuberculosis cultured from bighorn sheep was used to orally infect bighorn x mouflon (Ovis musimon) hybrid sheep, elk (Cervus elaphus nelsoni), mule deer (Odocoileus hemionus), and white-tailed deer (Odocoileus virginianus), Clinical paratuberculosis developed only in mule deer and was characterized by poor growth and diarrhea. Gross lesions were mild in all species. Enlargement of mesenteric lymph nodes was mild to moderate; the wall of the distal small intestine was affected minimally. Focal to diffuse infiltrates of epithelioid macrophages and giant cells occurred in the cortex of mesenteric lymph nodes, around mesenteric lymphatics, and in the intestinal mucosa. Extraintestinal lymph nodes, spleen, liver, and lung were involved in some animals; focal necrosis and mineralization was present in all species but was severe and widespread in the ceervids.

Nineteen spontaneous pancreatic islet cell tumors were studied in 26-month-old control Fischer 344 rats. Seventeen of 19 (89%) tumors demonstrated insulin reactivity using peroxidase-antiperoxidase immunocytochemistry. None of ten tumors had positive glucagon immunoreactivity. Immunocytochemical and ultrastructural observations suggested that spontaneous occurring islet cell tumors of F344 rats were composed exclusively of beta cells.

The histologic features of retinal dysplasia were studied in 26 English springer spaniel dogs of one day to four years of age. Dysplastic lesions in neonatal pups occurred predominantly in the peripapillary tapetal area of sensory retina. They consisted of complex linear folds and rosettes which were composed of hyperplastic neuroblasts. Dysplasia usually was not associated with incomplete differentiation of the outer neuroblastic layer. The outer limiting membrane was absent locally and numerous patent subretinal capillaries existed in the region of folds. The dysplastic features may be related to aberrant development of Muller cells and of retinal capillaries.

In adolescent dogs, dysplastic lesions were less complex and usually were not accompanied by aberrant capillaries. Focal or complete retinal separation was present in some adolescent dogs. In adult dogs, features of retinal atrophy were found within dysplastic areas. No significant histologic lesions were found in the extraocular tissues of 12 affected dogs which were surveyed extensively.

Two Japanese quail which were incapable of wing movement and three normal quail were examined by histological and ultrastructural methods. The diseased birds had glycogen deposits in their skeletal muscle, cardiac muscle, smooth muscle, and nerve cells of the brain and spinal cord. According to the distribution of the lesions and the characteristics of the deposited glycogen, the diseased birds had glycogenosis which was analogous to type II found in man. The usefulness of this disease as a model for glycogenosis in man is discussed.

Cytochemical reactions with a panel of special stains were explored in peripheral blood and lymph node cells of animals with the adult, calf, and thymic types of bovine lymphosarcoma as well as lymphosarcoma in sheep induced with the bovine leukosis virus. These results were compared with normal lymphoid cells. Cytochemical methods included Sudan black B. periodic acid-Schiff, acid phosphatase and three esterases. Cells from ovine lymphosarcomas and a thymic type of bovine lymphosarcoma were distinctively positive to the alpha naphthyl acetate esterase reaction. These cytochemical reactions which were obtained with standard cytochemical methods should aid in the characterization and classification of lymphoproliferative disorders in animals, especially when combined with immunologic surface markers.

Twenty-three mares were infected with contagious equine metritis organism by intrauterine inoculation, and necropsied after intervals of two to 116 days. Severe diffuse subacute salpingitis was seen in one mare, and mild multifocal subacute salpingitis was common. Severe diffuse endometritis and cervicitis initially were acute and became more severe, subacute and predominantly plasmacytic by 14 days, then declined but persisted as mild diffuse or multifocal inflammation for the rest of the experimental period. Vaginitis arose in parallel but resolved after 70 days. There were no lesions in the clitoral fossa or clitoral sinus.

The M5076 tumor, a reticulum cell sarcoma of histiocytic origin that arose spontaneously in the ovary of a C57BL/6 mouse, is highly invasive and metastatic. Regardless of the site of the primary tumor, this neoplasm rapidly and preferentially metastasizes to the liver and spleen, killing the host. Numerous other organs also are involved, including the lungs and bone marrow. This tendency to metastasize to osseous tissues appears to be a characteristic of the M5076 tumor that rarely is found with other rodent neoplasms. However, these extrahepatic foci are evident only microscopically and are seen relatively late in the progression of tumor growth. We describe the sequential gross and microscopic lesions that develop in syngeneic mice during the metastatic spread of the M5076 tumor. Since viable tumor cells form small tumor colonies in most organs, we suggest that the gross pattern of metastasis, with the apparent predilection for hepatic tissue, is caused by variations in tumor cell proliferation rather than by distinctive patterns of neoplastic cell spread and entrapment.

One hundred ninety-two male broiler chicks were dosed with monensin at concentrations of 0, 121, or 242 mg/kg feed throughout the normal growing period (50 days). Body weight gain and feed efficiency were determined weekly, and cardiac muscle was examined grossly and histologically at the end of the experiment. Livers also were weighed and examined grossly. Feed intake was determined daily, allowing continuous monitoring of drug intake. No depressing effects of the drug on growth rate and efficiency were observed until after four weeks, and then were evident only in the chicks receiving the 242 mg/kg diet. Subepicardial hemorrhage and congestion occurred in 40% of the hearts from the chickens fed the high monensin dose and were nonexistent in the other treatments. There appeared to be an inverse relationship between monensin dose and liver weight. The paralytic effects previously reported from acute dosing experiments were not observed. The results show that the heart and probably the liver are sensitive indicators of monensin toxicity and that the subchronic toxic dose is less than 18 mg/kg body weight per day.

The pathogenicity of the A4557-5 strain of infectious laryngotracheitis virus for eight-week-old chickens was investigated by acrosol route of infection; chickens were necropsied five days after infection. The virus caused mild catarrhal tracheitis, peribronchial lymphoid infiltration, and focal lymphocytic infiltration in the lung and focal lymphocytic infiltration in the air sacs of some chickens. Chickens infected with this virus developed low levels of humoral antibody and were resistant to intratracheal challenge with the virulent V154 strain. By comparison, aerosol infection with a similar dose of virulent V154 strain caused severe necrotizing laryngotracheitis with marked suppurative bronchopneumonia and airsacculitis.