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Primary rat Sertoli cells are widely used as a model for mechanistic and toxicological studies, since they are often the target of toxicants in vivo. However, their isolation from testicular homogenates is tedious and requires the regular use of numerous immature animals. It is therefore of great interest to have available established cell lines that are usable in vitro for unlimited periods and closely similar to native cells. To this end, we have established a line of Wistar rat Sertoli cells (SerW3) by immortalization of fresh primary cells with the T antigens of the Simian virus (SV40). When plated on Matrigel, this cell line presents many of the functional characteristics of Sertoli cells in vivo. In addition, they are sensitive to cisplatin and secrete transferrin, although they do not show a clear response to follicle-stimulating hormone. They also present many morphological similarities, including the presence of tight junctions which mimic the natural epithelial barrier. Like Sertoli cells in vivo, they show extensive phagocytic activity. Finally, they display all the characteristics of immortalized, but not transformed, cells, i.e., topo-inhibition and apoptosis at confluence or under serum deprivation.

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Cutaneous papillomavirus infection was diagnosed in a 6-year-old female Boxer dog that was under long-term corticosteroid therapy for atopic dermatitis. Multiple black, rounded papules were present on the ventral skin. Spontaneous regression occurred within 3 weeks after cessation of corticosteroids. Histologically, the lesions consisted of well-demarcated cup-shaped foci of epidermal endophytic hyperplasia with marked parakeratosis. In the upper stratum spinosum and in the stratum granulosum, solitary or small collections of enlarged keratinocytes were observed with basophilic intranuclear inclusion bodies and a single eosinophilic fibrillar cytoplasmic inclusion. Ultrastructurally, viruslike particles (40-45 nm in diameter) were observed within the nucleus, free or aggregated in crystalline arrays. Undulating fibrillar material, thought to be a modified keratin protein, was observed in the cytoplasmic inclusion. Immunohistochemistry, restriction enzyme analysis, and molecular hybridization experiments indicated that these distinctive clinical, histologic, and cytologic features were associated with a novel canine papillomavirus.

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Sixteen juvenile Beagle dogs originating from a single breeding colony and regularly vaccinated against Leptospira interrogans (serogroups Canicola and Icterohaemorrhagiae) developed a clinical syndrome characterized by retarded growth, weight loss and often ascites. Over a 10-month period, post-mortem examinations were performed on all affected dogs. Gross lesions were confined to the liver which was often firm, tan-coloured and mottled. Microscopically, hepatic lesions ranged from those of severe chronic hepatitis to mild diffuse hepatocellular vacuolation, with bile stasis, occasional scattered lymphocytic aggregates and haemosiderin granulomas. Special stains and electron microscopy revealed spirochaetes within bile canaliculi. The genus Leptospira was recognized by immunohistochemical methods in nine dogs. Leptospires were isolated from six dogs, but serological tests failed to detect significant titres of antibody to L. interrogans in these animals. A serological survey of 37 kennelmates demonstrated that 20 dogs had high titres of serogroup Australis leptospiral antibody, which could not have resulted from vaccination. These findings strongly suggest a connection between the presence of leptospires and the hepatic lesions.

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A raised, hairless cutaneous nodule was found incidentally at necropsy of a 24-month-old CD1 mouse. Histologically there was infiltration of the epidermis by a monomorphic population of moderate to large lymphocytoid cells. Many large cells had bizarre convolutions of the nuclear membrane and resembled the so-called Sézary or mycosis cells seen in epidermotropic T-cell proliferative disorders. The pattern of cutaneous involvement and the presence of the large cells with convoluted nuclei is characteristic of pagetoid reticulosis. No previous reports of such cutaneous lymphoid neoplasms in mice were found in an extensive literature search.

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Wheat-germ lectin peroxidase conjugate was used to stain the liver of normal rats and rats given alpha-naphthylisothiocyanate (ANIT). Changes in patterns in bile duct and canalicular staining were compatible with the hypothesis that cell damage caused by ANIT is essentially restricted to bile ducts.

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