Veterinary Pathology

Anti-rat myoglobin (Mb) was prepared and used in the avidin-biotin-peroxidase complex (ABC) method on paraffin-embedded sections of nine soft tissue tumors (including two rhabdomyosarcomas) of rats. Distribution and nature of the reactive substance to Mb antiserum were compared to those of desmin antiserum. Rat Mb was isolated from the skeletal muscle; monospecificity of the rat antiserum was confirmed by the immunoblotting procedures. The Mb antiserum reacted specifically to normal and neoplastic striated muscle cells. Mb-staining reactions were present diffusely in the cytoplasm, while desmin-staining substances were localized at Z-bands or were diffuse in the cytoplasm as separated aggregates. Reaction to the Mb serum was also detected in cells of thick portions of Henle's loop and distal convoluted tubules.

Formalin-fixed histologic and acetone-fixed cytologic preparations from 87 surgically removed subcutaneous and soft tissue canine tumors were examined for immunoreactivity to cytokeratin. desmin. and vimentin. The avidin-biotin complex (ABC) technique demonstrated immunoreactivity in both preparations. but the intensity and specificity of the reactions were dependent on the primary' antibody. Polyclonal antibodies to cytokeratin were more consistent in immunoreactivity than were polyclonal desmin or vimentin antibodies. The monoclonal antibody proved more satisfactory for demonstrating vimentin than the polyclonal antibody. Greater dilutions of primary antibodies may be used on cytologic preparations than on histologic sections. Evaluation of cytologic preparations may be inconclusive due to background staining, scant cellularity, or poor cytoplasmic preservation.

Laboratory records and histologic material from 13 cases of naturally occurring, early- to late-term bovine abortion clue to Tritrichomonas foetus were examined. Placentitis was present in all placentas. Pyogranulomatous bronchopneumonia was in six of the 11 lungs which were examined. Trichomonad organisms were demonstrated within the placental stroma in all cases and free or phagocytized in pulmonary airways in seven cases.

Papillomaviruses, group-specific papillomavirus antigens, or extrachromosomal papillomavirus DNA were detected in cutaneous, mucocutaneous, and pulmonary tumors affecting a colony of European harvest mice (Micromys minutus). Skin lesions were classified as acanthomatous hyperplasia, epidermal inclusion cysts. squamous papillomas, inverted papillomas, trichoepitheliomas, and sebaceous carcinomas. Cutaneous horns (hyperkeratotic papillomas) were on mucocutaneous junctions of one animal. One mouse, with a cutaneous sebaceous carcinoma, had multiple pulmonary keratinaceous cysts. Papillomavirus antigens, detected by the avidin-biotin technique, were in 20 of 31 lesions tested. In contrast, by Southern blot hybridization all 28 lesions tested contained papillomavirus DNA. Papillomavirus DNA was demonstrated in two often benign cutaneous lesions by in situ hybridization.

Pulmonary lesions associated with Corynebacterium ovis were analyzed with an indirect immunoperoxidase staining technique using monoclonal antibodies. The predominant cells in abscess walls and surrounding lung parenchyma were large macrophages which expressed major histocompatibility complex (MHC) class II molecules on their surfaces. T lymphocytes were prominent in the same sites in the naturally occurring lesions, and SBU-T4-positivc (“helper/inducer”) cells were the major subset of lymphocytes (mean T4/T8 ratio = 3.5). B lymphocytes and granulocytes comprised minor populations of infiltrating cells. These results implicate activated macrophages and MHC class II-restricted T lymphocytes in the pathogenesis of established C. ovis infections in sheep.

Multiple outbreaks of acute severe fibrinopurulent lesions of the eyelids occurred in chickens and turkeys. Lesions began as tiny foci of epidermal necrosis and ulceration and spread to involve the entire eyelid. Scabs overlying the epidermis contained large gram-positive cocci; lesser numbers of small cocci and gram-negative bacilli were in more superficial areas. Staphylococcus hyicus was isolated from birds in all stages of the disease. Escherichia coli and Streptococcus sp. were isolated only during severe stages; no anaerobic bacterial pathogens were isolated. Vasculitis and perivascular lymphocytic infiltrates in deep layers of the dermis suggested that a staphylococcal toxin may have been involved. The disease was not reproduced by scarifying S. hyicus onto the eyelids or by intravenous inoculation of retro virus-infected chickens.

Fischer-344 rats were killed 1, 18, and 42 hr after a single 4-hr exposure to an atmosphere of 0, 116, or 615 mg m^-3 of hydrogen sulfide (H₂S). Lungs, fixed by the intratracheal route, were examined by light and electron microscopy. Histologic changes were transient and mainly present in rats exposed to 615 mg m^-3 H₂S. Lesions included severe but transitory pulmonary edema and fibrinocellular alveolitis which was restricted to the proximal alveolar region of the lung. Electron microscopically, ciliated bronchiolar cells were the only cells that developed necrosis; they were rapidly replaced by mitosis. Alveolar endothelium had cytoplasmic blebs, but alveolar epithelium had minor changes. No mast cell degranulation was detected in lungs with edema. A 4-hr exposure to 615 mg m^-3 is markedly edematogenic for the lung but only moderately cytotoxic for pulmonary cells.