Veterinary Pathology

The first case of a uterine tumor in the New World primate Saguinus (Oedipomidus) oedipus is described. Histologically, the tumor was composed of telangiectatic vessels, proliferating smooth muscle, and an intervening dense collagenous matrix. These structures were considered to represent a hamartomatous growth of primoidial uterine elements.

A precise electron microscopical distinction between so-called mature and immature mast cell tumours is possible. In immature mast cell tumours, the neoplastic cells contain granules in various phases of development, well-developed ergastoplasm, many free ribosomes, extended Golgi apparatus, complex cytoplasmic membranes, and nuclei with folded nuclear membranes, hypertrophic nucleoli, and finely dispersed chromatin. In mature mast cell tumours, the neoplastic cells have scarce ergastoplasm, fewer free ribosomes, a small Golgi apparatus, some cytoplasmic protrusions, and nuclei with predominantly heterochromatin and only a few folds of the nuclear membrane; the cytoplasmic granules are electron-dense and amorphous or reticular or granular or contain membranous structures. The mature neoplastic cells resemble normal tissue mast cells. In the genesis of granules five phases of maturation can be distinguished. The release of substrate may result from dissolution of granules. In experimental degranulation the release of whole granules may be the immediate result of a relatively strong stress and interference with the cell structure. The intranuclear virus-like structures observed (a small virus containing DNA?) are discussed as a possible oncogenic agent.

A septicemia caused by a Haemophilus-like organism occurs singly and multiplicate in feedlot and pastured cattle and has been reproduced experimentally. Clinically the disease may be peracute and neurologic, acute and respiratory, subchronic to chronic and arthritic, or an amalgam. Grossly, lesions are widespread but most prevalent are multifocal hemorrhagic necrosis of the brain, meningitis, polyarthritis, polyserositis, and pseudomembranous or ulcerative laryngitis. Histologically, there are intense vasculitis, thrombosis, infarction, and a purulent exudate. The lesions of the experimental infection in cattle and mice resemble the natural ones.

A spontaneous outbreak of infection with C. kutscheri occurred in a commercial rat colony. Clinical signs were emaciation, hyperpnea, nasal and ocular encrustations, humping of the back, sluggishness, and roughness of the hair coat. Caseopurulent foci, 1 to 15 mm in diameter, occurred, primarily in the lungs and occasionally in the liver, kidneys, and subcutis. Corynebacterium kutscheri was consistently isolated from organs with lesions. Typical lesions were experimentally reproduced in some, but not all, rats inoculated by the intranasal, intraperitoneal, and oral routes with cultures of C. kutscheri.

Spontaneous development of tumors in 5086 Holtzman-source rats ranging in age from 1 to 18 months is reviewed. Overall incidence of tumors was 4.3% (8.2% for females, 2.3% for males). Statistical analysis of the data demonstrated that the potentiality for tumors was comparable to previously reported lifetime studies. Characteristics of development of tumors are given, and the more uncommon tumors are described briefly. The occurrence of tumors in young rats in this survey indicates the need for accumulating data on tumors in other than “old” rats as an aid in interpreting data obtained from toxicological studies.

The cutaneous lesions in 25 spontaneous cases of porcine exudative epidermitis (EE) were studied. During the first 4 days mild acanthosis, increase of cytoplasmic RNA, enlarged nucleoli, and intercellular oedema in the stratum spinosum with formation of vesicles occur. A PAS-positive, diastase-resistant material accumulates in the stratum intermedium. The keratohyaline granules disappear and parakeratotic horn containing abundant protein-bound SH-groups and lipids is produced.

Beyond 4 days duration acanthosis and the formation of parakeratotic horn with microabscesses are increased. During healing keratohyaline granules reappear and the formation of normal horn cells is resumed.

Acid phosphatase and succinic dehydrogenase are increased in the parakeratotic horn. Lactic acid dehydrogenase is increased in the transitional zone and alkaline phosphatase in the stratum basale.

The observations indicate inhibition in the stratum intermedium of the differentiation of epithelial cells to horny cells. The disease is believed to be of viral origin.

The nature and localization of the brown adipose in young calves, lambs, and in practically full-term foetuses of cows and sheep has been examined. It was found that brown adipose tissue could be composed of types of fat cells greatly differing mutually and that, in lambs, a greater variety of cell-types is to be found than in calves. These types of fat cells, or the types of adipose tissue consisting of them, may transmute into one another. As a rule, these transformations begin to take place in the adipose tissue of the thorax, the more peripheral adipose tissue gradually being involved.

Geotrichum candidum was isolated from lung and bronchial lymph node of a dog with signs of pulmonary disease and which had generalized mycotic lesions. Firm fleshy nodules were scattered throughout the lungs. The pulmonary lesions consisted of foci of coagulative necrosis encircled by an inflammatory infiltrate composed chiefly of alveolar macrophages. Histologic features of lesions in bronchial lymph nodes, kidneys, adrenals, and myocardium resembled those in the lungs, but foci of involvement were smaller. Tiny, well-defined granulomas occurred in liver, spleen, bone marrow, brain, and eye. Fungi were abundant in most lesions, particularly those in the lungs. The organisms, predominantly yeast-like, occurred both free and in the cytoplasm of macrophages and multinucleated giant cells.

Three cases of spontaneous cerebral tumors are reported in Wistar rats, 2 oligodendrogliomas and 1 malignant ganglioglioma or astrocytoma (grade 4).