Veterinary Pathology

The predominant acid mucopolysaccharides found in selected epithelial mammary tumors of dogs stained with alcian blue and were labile to hyaluronidase digestion. These histochemical characteristics identified them as hyaluronic acid, chondroitin-4- and chondroitin-6-sulfate. The intensity of the staining of these acid mucopolysaccharides varied in a transitionary process from a precartilaginous to a pseudocartilaginous intercellular matrix to mature hyaline cartilage.

The tumor acid mucopolysaccharides were indistinguishable from those associated with formation of cartilage in developing mammals; such cartilage is reported to be produced only by cells of mesodermal origin. There was no evidence to suggest transitional changes in myoepithelial cells, neoplastic epithelial cells or their components that could contribute to the formation of the acid mucopolysaccharides. It was concluded that the heterotopic tissues (cartilage, bone and fibrous connective tissue) in the epithelial mammary tumors were derived from cells of mesodermal orgin and formed the adjacent stroma in areas of neoplasia.

Cytopenia were recognized in three cats infected with feline leukemia virus. In one cat, marrow blast cells were increased in number, and a diagnosis of aleukemic leukemia was made. The disease progressed slowly for 31/2 months before terminating in acute myelomonocytic leukemia, recognized as a blast crisis in blood. In the other two cats, neutropenia and altered granulopoiesis in bone marrow preceded development of myeloid leukemia.

During a 2 1/2-year period 209 dogs with 218 malignant tumours were examined for skeletal metastases. There were 77 malignant tumours without visceral or skeletal metastases. Twenty-four (17%) of the 141 tumours with visceral metastases also had skeletal metastases. Ninety-eight of these tumours were of epithelial origin, and of these 21 (21.4%) had skeletal metastases. In 14 dogs, more than one bone had a metastatic tumour. The humerus, femur and vertebral column were most frequently involved. The lung was the most frequent site of metastatic tumours; then, in order, the liver, kidney and skeleton. The incidence of primary and secondary bone tumours was similar. Metastatic bone disease in the dog is far more common than is generally realized.

A 5-month-old minature Poodle dog had widespread cytoplasmic vacuolation of neurons in the central nervous system and foamy macrophages in the lung, spleen, renal lymph node, liver, adrenal gland and intestine. Concentric membranous cytoplasmic inclusions were seen in the neurons of the central nervous system by electron microscopy. There was no sphingomyelinase in the brain tissue. Sphingomyelin and cholesterol were increased in brain, kidney and liver. A diagnosis of Niemann-Pick Disease was based on absence of sphingomyelinase activity, as well as on histologic, histochemical and chemical findings.

Sudden unilateral blindness occurred in a 7-year-old grey gelding Quarterhorse. Ophthalmoscopy revealed a pigmented mass arising from the nasal ciliary body of the right eye and extending around the posterior surface of the lens, and there were pigmented particles in the vitreous. Examination of the enucleated globe showed a circumscribed, black, dense and symmetrically ovoid mass with sessile attachment to the nasal ciliary region and extension to posterior lens capsule, vitreous and along the vitreal face of the detached retina to the optic papilla. The mass was composed of heavily pigmented, plump, polyhedral cells that invaded the vitreous and the inner limiting membrane of peripapillary retina and optic papilla. It was considered to be a primary, malignant, intraocular melanoma arising from a large uveal nevus.

A feline pancreatic acinar cell carcinoma studied by light and electron microscopy was characterized by three growth patterns: acinar formation, colloid production and sheets of neoplastic cells. Ultrastructurally, the acinar origin of the tumor was determined by the presence of zymogen granules, some of which contained and released microfibrillar material.

Aortas of 334 sheep 6 months to 6 years old were stained with Sudan IV. Sudanophilic lesions resembling early fatty streaks of man were detected in 50% of these aortas. Metastatic calcification was seen in eight (2.3%) aortas.

In pregnant Syrian hamsters (Mesocricetus auratus) used as an animal model for studying the migration of fetal trophoblasts and the associated changes in maternal blood vessels, intravascular trophoblasts migrated well beyond the blood vessels of the uterus and into the vessels of the mesometrium. They migrated beyond the decidua of the uterus, into the lumina of maternal uterine and mesometrial arteries, but not into veins. The arterial changes, which were often segmental, resembled those seen in the decidua and consisted of a replacement of normal smooth muscle cells by poorly differentiated stromal cells. Ultrastructurally, the trophoblasts were either above or below maternal endothelial cells. They occurred also as single or multiple layers within the lumina of arteries that lacked an endothelial lining. Apparent penetration of the elastic membrane by the fetal trophoblasts brought them into close apposition to maternal cells in the arterial wall. Histochemical studies showed heightened metabolic activity of the intravascular trophoblasts as suggested by strong histochemical reactions to nonspecific esterase, succinic dehydrogenase and the glycerophosphate dehydrogenase reactions. Thus, these metabolically active fetal trophoblasts actively migrate into the maternal arterial system, resulting in loss of endothelial cells and changes in the wall of the maternal arteries similar to those in the decidua at the uteroplacental junction.

Broth cultures of Treponema hyodysenteriae and colonic content from pigs with swine dysentery were tested for cytotoxicity in cell cultures, erythrocyte suspensions and in ligated segments of pig colon. Live cells of T. hyodysenteriae attached to the surface of cells in all cultures tested but did not penetrate them nor cause morphologic change detectable by light microscopy. Only live T. hyodysenteriae caused erythrolysis. Broth cultures or colonic content sterilized by filtration or by disruption with ultrasound had no visible effect on the cell cultures, erythrocyte suspensions or the mucosa of ligated colonic segments.

A single intraperitoneal dose of methyl(acetoxymethyl)nitrosamine (13 mg/kg body weight) given to 78 5-week-old male rats induced 25 mesotheliomas; two mesotheliomas were found in 67 control rats. All mesotheliomas arose from the peritesticular mesothelium and had a typical microscopic appearance of branching papillary fronds with a collagenous core covered by one or many layers of plump tumor cells. Cytoplasm of tumor cells contained material that reacted positively to a colloidal iron stain and was labile to hyaluronidase. In addition to frank mesotheliomas, 16 lesions, which we called atypical mesothelial proliferations. were found. These consisted of a single focus of plump mesothelial cells overlying an area of thick stroma. Often these foci included short, non-branched papillary projections above the surface of adjacent normal mesothelium. Twelve of the 16 lesions occurred in methyl(acetoxymethyl)nitrosamine-treated rats.

Pigs fed a ration, 25% of which was rice culture, of Aspergillus ochraceus lost weight or failed to gain and became depressed. Some pigs died and most developed subcutaneous edema, hydrothorax, hydroperitoneum, pulmonary atelectasis, edema of the mesentery and perirenal edema. Microscopic lesions in addition to edema were primarily renal and consisted of tubular degeneration and necrosis, hyaline tubular casts, interstitial fibrosis and tubular cell regeneration. The first change found after 3 days was cytoplasmic vacuolation of the convoluted and straight segments of the proximal tubules. Necrotic proximal tubules were found after 4 days and after 9 days degeneration and necrosis involved predominantly proximal tubular segments. Pigs fed a ration, 12.5% of which was rice culture, for 8 weeks did not develop perirenal edema but had firm kidneys. Extensive interstitial fibrosis of the cortical labyrinth was the principal change. Within the fibrous connective tissue, some tubules were necrotic and others were atrophied.

In rats with “stage S/E“ yellow fat disease an injection of colloidal carbon resulted in a marked reduction in the number of circulating platelets. The death rate of rats with experimental Listeria monocytogenes infection, the number of bacteria in their spleens and the decrease of bacteria in their spleens on the days after infection were the same in rats with yellow fat disease as in controls. The fact that the rats died during the first few days after infection also may indicate that their immunological resistance to L. monocytogenes was not altered by yellow fat disease.