Psittacine beak and feather disease is characterised by loss of feathers, abnormally shaped feathers and overgrowth and irregularity of the surface of the beak. The disease occurs in a number of psittacine species including the Sulphur-crested Cockatoo, Lovebirds , Budgerigars and Galahs . The abnormal appearance of feathers and beak is due to a dystrophic process within the epidermis of the feather and beak. The process consists of epidermal cell necrosis, epidermal hyperplasia and hyperkeratosis. Many of the feather abnormalities are due to retention of a hyperkeratotic feather sheath. A characteristic microscopic finding is the presence of macrophages containing purple intracytoplasmic inclusions in affected epidermis and feather pulp. The inclusions consist of aggregates of particles 17 to 22 nm in diameter. Similar but smaller inclusions occur in epidermal cells. In addition, non-suppurative inflammation occurs in the feather pulp. The findings are suggestive of a viral infection.

Abstract. Four cases of chronic eosinophilic gastroenteritis in horses are described. The disease was manifested clinically by weight loss, malabsorption and diarrhea or soft, formless feces. A chronic inflammatory reaction, with diffuse and focal eosinophilic infiltrates, was present in the esophagus, stomach, small and large intestine, and mesenteric lymph nodes. The cause of the lesion was not determined but was thought to be due to an ingested allergen, as the lesion is indicative of an on-going, immediate hypersensitivity reaction. One horse had generalized acanthosis, hyperkeratosis, and ulcerative coronitis.Chronic enteric disease in the horse, characterized by weight loss with or without diarrhea, has been reported in several countries [3, 5, 15, 17, 211. The enteric lesion in these horses was a chronic granulomatous inflammation. This paper describes a chronic eosinophilic enteritis that is pathologically distinct from the previously described chronic enteritides of horses. Materials and MethodsFour young-adult horses with signs of weight loss, diarrhea, or both (table I) were presented to Murdoch University Veterinary Hospital over an 18-month period. The horses were unrelated and from different areas of Western Australia. Routine clinical, hematological, biochemical, and fecal examinations were done. Glucose absorption tests [20] were done on all horses and full-thickness intestinal biopsies were removed from two horses. The horses either died or were killed. At necropsy, tissues from all visceral organs and skin from horse 4 were fixed in 10% neutral buffered formalin, processed routinely in paraffin, and stained with hematoxylin and eosin (HE). Selected tissues also were stained with the periodic acid-Schiff technique, Gram-Twort, Ziehl-Neelsen, Warthin and Starry, Castaneda's, and toluidine blue stains.Several sections of duodenum, jejunum, ileum, cecum, colon, and mesenteric lymph nodes from two horses were fixed in 3% glutaraldehyde in 0.1 mol/l phosphate buffer at pH 7.4, were post-fixed in 1% osmium tetroxide in the same buffer and embedded in epon. Sections for light microscopy were cut 1-pm thick and stained with toluidine blue. Thin sections were cut from selected areas and stained with uranyl acetate and lead citrate for examination by electron microscopy.Intestinal contents, mesenteric lymph node, and liver from all horses were cultured aerobically on sheep blood agar and McConkey's agar. Intestinal mucosa and mesenteric lymph node from horse 4 were homogenized in normal saline following removal of surface contam-486

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Abstract. Three canine laryngeal tumors were diagnosed as oncocytomas by light microscopy, but were determined to be rhabdomyomas following ultrastructural and immunocytochemical examination. Tumors consisted of large eosinophilic cells interspersed with smaller dark cells. Large tumor cells had a granular, intensely eosinophilic cytoplasm. Scattered through the tumors were a few elongated cells with cytoplasmic cross striations and multiple nuclei. Tumor cells from all three dogs contained numerous mitochondria and bundles of myofibrils with electron-dense Z-lines typical of striated muscle cells. Intracellular myoglobin and desmin were detected in the tumors by immunocytochemistry. Comparisons are made with a previous report of canine laryngeal oncocytomas.Oncocytes are considered to be epithelial cells. They are found as single cells or small clusters of cells in a variety of organs, such as, thyroid (Hiirthle cells), parathyroid (oxyphil cells), pituitary, adrenal, salivary glands, larynx, trachea, bronchi, nasopharynx, tongue, and liver.1,6.11.14,16,21 0 ncocytes are intensely eosinophilic, are packed with mitochondria and have a concurrent reduction in other cellThe majority of reported oncocytomas are case studies in people.2. 6-8. 13.23 Three canine laryngeal oncocytomas have been described." Many of the clinical, macroscopic, microscopic, and ultrastructural characteristics of these canine oncocytoma~'~ are similar to the laryngeal tumors described in this study. We describe three canine laryngeal tumors that were originally diagnosed as oncocytomas by light microscopy, but were confirmed to be of striated muscle origin by electron microscopy and immunocytochemistry. Materials and MethodsFour la -yngsal tumors were examined from the three dogs studied. T h r x tumors were primary and one was a local recurrence. Tumors were placed in 10% buffered neutral formalin, embedded in paraffin, and stained with hematoxylin and eosin (HE), periodic acid-Schiff (PAS), PAS with diastase, and phosphotungstic acid-hematoxylin. Thin slices of tumor from dog 1 were transferred to Trump's'' fixative after several weeks in formalin. Tissues were then rinsed in phosphate buffer (pH 7.2), placed in 1 % osmium tetroxide, rinsed in distilled water, and dehydrated in ascending concentrations of ethanol. Tissues were embedded in Spurr's resin"; thick sections were stained with toluidine blue, and thin sections were stained with alcoholic uranyl acetate followed by lead citrate. Tissues for electron microscopy from dogs 2 and 3 were deparaffinized and then processed similarly for transmission electron microscopy. Previous diagnosis on the tumors from both of these dogs were o n c o~y t o m a .~,~ Immunocytochemistry for desmin and myoglobin was done on paraffin-embedded sections from all four tumors. Sections of skeletal muscle and liver were used as positive and negative controls. Briefly, deparaffinized sections were incubated in rabbit antiserum specific for myoglobin or desmin (Dako Corp., Santa Barbara, Calif.) overnight at...