Use of nested polymerase chain reaction (PCR) for detection of retroviruses from formalin-fixed, paraffin-embedded uveal melanomas in cats

Thirty-six formalin-fixed, paraffin-embedded enucleated globes from cats with a diagnosis of diffuse anterior uveal melanoma were obtained. Sections of tumor were excised, deparaffinized, and subjected to nested polymerase chain reaction (PCR) to identify proviral DNA sequences from the feline leukemia virus (FeLV)-feline sarcoma virus (FeSV; 36 eyes), and the feline immunodeficiency virus (FIV; 18 eyes). All samples tested were negative for FIV DNA. Three samples were positive for FeLV-FeSV DNA. This is the first reported evidence of a possible link between naturally occurring feline anterior uveal melanoma and the presence of FeLV-FeSV DNA.

Retinal degeneration in experimental scrapie after intraperitoneal or subcutaneous inoculation of hamsters

Hamsters injected intraperitoneally or subcutaneously with the scrapie agent developed photoreceptor degeneration. The degree of degeneration did not correlate well with infectivity titers of retinal tissue or stage of clinical encephalopathy, and was not as great as seen in intracerebrally injected animals. We conclude that retinal degeneration is universal in hamsters experimentally inoculated with the scrapie agent regardless of the route of inoculation.

Asymmetry of retinal lesions in experimental scrapie after intracerebral inoculation of hamsters

Hamsters injected into the right cerebral hemisphere with the scrapie agent developed retinal lesions to a greater extent in the contralateral than in the ipsilateral eye. This asymmetry was evident during the incubation period as well as during the clinical encephalopathy. The results explain much of the variation in the degree of retinal disease seen earlier at specific times after inoculation. Moreover, they strengthen the hypothesis that scrapie spreads via neurons.

Cyclic nucleotides in hamster retina

The concentrations of cyclic 3':5'-adenosine monophosphate (cyclic AMP) and cyclic 3':5'-guanosine monophosphate (cyclic GMP) were determined in white light- and dim red light-adapted golden Syrian hamster retinas. Retinas from animals in dim red light had cyclic AMP concentrations of 9.29 +/- 2.94 pmol/mg of protein and cyclic GMP concentrations of 110.62 +/- 32.98 pmol/mg of protein. After white light adaptation, retinal cyclic AMP and cyclic GMP concentrations were reduced to 74% and 45% of the previous values, respectively. In another experiment with white light-adapted animals, the sex or method of immobilization of the animals (cervical dislocation vs sodium pentobarbital) had no significant effect on cyclic nucleotide values.

Neural pathogenesis of experimental scrapie after intraocular inoculation of hamsters

Hamsters were inoculated intravitreally with the scrapie agent. All animals developed scrapie and retinal degeneration typical of scrapie. The retinal degeneration was greater in the inoculated eyes than in the uninoculated eyes. Replication of the scrapie agent was rapid in the inoculated eye. Infectivity then spread slowly down the ipsilateral optic nerve to the brain. The replication in the brain paralleled that in the retina of the uninoculated eye. The results support a neural spread of scrapie.

Pathogenesis of progressive rod-cone degeneration in miniature poodles

Visual cell pathologic changes and outer segment renewal were investigated in miniature poodles with progressive rod-cone degeneration. Early in this disease, visual cells in the posterior pole and equatorial regions show outer segment lamellar disorientation and vesicular profiles. Visual cells are normal in the periphery. Outer segment renewal determined after intravitreal injection of 3H-leucine was abnormally slower in affected animals than in controls. This renewal abnormality was similar in structurally normal and diseased photoreceptors, suggesting that the renewal defect is the earliest recognizable abnormality in the disease. The pigment epithelium was normal; the presence and density of pigment did not appear to affect the extent and severity of the disease or modify the abnormal renewal rate. As the disease progressed, photoreceptor outer segments were lost, and the remaining diminutive photoreceptors accumulated label in the inner segment and perinuclear zones. Sodium dodecyl sulfate gel electrophoresis of crude rod outer segment preparations showed no differences in opsin synthesis between normal and affected retinas early in the disease, but opsin synthesis decreased in the late stage of the disease.

Photoreceptor degeneration in a family of cats

Blindness developed at an early age in 2 generations of cats. Findings included abnormal pupillary responses to light, tapetal hyperreflectivity, retinal vascular attenuation, and virtually extinct electroretinograms. Histologic and ultrastructural abnormalities were found only in photoreceptors. There were poor inner and outer segment development and reduction in visual cell nuclei, with concomitant narrowing of the outer plexiform layer early in the postnatal period. Eventually, there was complete loss of the photoreceptor layer. The clinical and microscopic findings suggested this retinal disease may be a heritable rod-cone dysplasia.

Retinal degeneration during clinical scrapie encephalopathy in hamsters

Weanling hamsters were inoculated intracerebrally with brain suspensions from normal or scrapie-infected hamsters. A third group of uninoculated animal was fed cuprizone. Histologic and electron microscopic examination of the neural retinas and retinal pigment epithelium was done. At 50 days postinoculation, when scrapie-infected animals began to show clinical signs of encephalopathy, there was a variable degree of photoreceptor degeneration. By the time animals were moribund, at 74 days postinoculation, photoreceptor degeneration was severe, as demonstrated by loss of most outer and inner segments and cell bodies. The outer plexiform, inner nuclear, and inner plexiform layers were reduced in thickness. Some retinal pigment epithelial cells contained lipoidal inclusions. The neural retinas and retinal pigment epithelium of noninfected and cuprizone-treated animals were normal. We have previously shown that the scrapie agent accumulates in the retina; that together with our present work, we conclude that the scrapie agent is the cause of photoreceptor degeneration in experimentally inoculated hamsters.

Ocular lesions of blastomycosis in the dog

Twenty-one dogs with ocular disease and blastomycosis were studied clinically. The most common ocular lesion was uveitis. Other findings included retinal separation, panophthalmitis, and glaucoma. The results of the study indicated that when uveitis is found in dogs in central United States, east of the Mississippi River, blastomycosis should be a diagnostic consideration. When the uveitis was associated with lung, lymph node, skin, bone, or testicular lesions, the likelihood of blastomycosis was greater.

Photoreceptor degeneration preceding clinical scrapie encephalopathy in hamsters

Hamsters experimentally inoculated with scrapie had histologic and ultrastructural changes in their retinas before clinical signs of central nervous system disease became evident at 50 days postinoculation. The retinal changes were limited to the photoreceptors and began with degenerative changes in the inner segments as early as 8 days postinoculation. As the inner segment lesions became more prominent, associated degenerative changes within outer segments were seen (38 days postinoculation). An influx of macrophages was associated with increasing degenerative changes; these cells engulfed cellular debris did not appear to contribute directly to the degenerative process. Retinas having the greatest damage to the inner segment area also had moderate reduction in outer nuclear layer density and outer segment length, and in numbers of outer segments. All of the retinal changes described occurred almost exclusively in the central to mid-region of retina with relative sparing of peripheral retina.

Histology and fine structure of the hamster retinal pigment epithelium

The retinal pigment epithelium of normal adult golden Syrian hamsters was examined by light and electron microscopy, using conventional and enzyme histochemical techniques. Hamster retinal pigment epithelium was composed of a single layer of cuboidal cells that had marked infolding of the basal cell wall and numerous microvillous processes extending from the apical surface. Melanin content varied within each specimen and there appeared to be incomplete or aberrant development of many melanin granules. Many incompletely melanized granules showed acid phosphate activity. There were the usual cell organelles, and Golgi complexes. Large phagosomes increased in number in the morning hours. Autophagic vacuoles and small lipid droplets were commonly seen. Occasional basal bodies, cilia, and root filaments were found. In two specimens, a curious intranuclear paracrystalline structure was observed.

Canine blastomycosis: a review of 47 clinical cases

In a limited retrospective survey, canine blastomycosis was found to be a disease affecting predominantly young, male dogs of the larger breeds. Clinical signs usually related to weight loss and to respiratory and ocular problems. The agar-gel immunodiffusion test was helpful in establishing a diagnosis. The diagnosis was confirmed by microscopic evaluation of aspiration or excision biopsies. Of 22 dogs treated with amphotericin B, 18 were clinically normal 6 months after initiation of therapy.

Replication of the scrapie agent in ocular neural tissues

Optic nerves and retinas removed from hamsters experimentally inoculated with the scrapie agent contain a high titer of infectivity. Ophthalmoscopic examination of these animals revealed gross lesions of retinopathy as early as 3 weeks before the onset of clinical signs of brain degeneration. These results suggest that the scrapie agent may spread centrifugally in nerve fibers after intracerebral inoculation and that the scrapie-associated retinopathy seen in hamsters is directly induced by the agent rather than the result of retrograde degeneration from central neural damage.

Prevalence of ocular disease in a colony of tamarins and marmosets

In a large tamarin and marmoset experimental colony, 526 animals were examined by biomicroscopy and ophthalmoscopy for the presence of ocular disease. In 109 animals, there were 147 abnormalities involving the eyelids, cornea, iris, lens, retina or optic nerve. Most abnormalities were unimportant in terms of ocular function, but a few did cause loss of vision and included diffuse, progressive retinal atrophy and a severely traumatized globe. The survey indicated that while usually minor, ocular disease in the tamarin and marmoset was widespread.

Ocular effects of scrapie agent in hamsters: preliminary observations

Scrapie is caused by one of a group of so-called slow viruses responsible for the subacute spongiform encephalopathies. In the present study, young hamsters were inoculated intracerebrally with hamster-adapted scrapie agent. At termination, all inoculated animals showed signs and central nervous system pathology compatible with scrapie infection. The eyes appeared well developed grossly, but histologically the retina and optic nerve were abnormal. There were varying degrees of thinning of the retina, with the photoreceptor layer being most severely affected. Although the ganglion cell layer was not much different from the controls, the optic nerve appeared more cellular than that of the controls.

Heterotransplantation of retinoblastoma into the athymic "nude" mouse

Fresh surgical specimens of retinoblastoma were successfully transplanted into the anterior chamber of the "nude" mouse (a homozygous mutant, nu/nu, with a severe defect in cellular immunity), filling the eyes but failing to grow subcutaneously. Retinoblastoma cells from an established cell line, Y-79,1 spread from the intraocular injection site to invade the orbit, optic nerve, and brain and formed large tumors when implanted subcutaneously. Tumor cells injected into the anterior chamber of immunologically normal litter-males (heterozygotes, nu/+) survived for varying periods in the anterior chamber but showed little growth.

Rod disc turnover in the dog

Tritiated l-leucine was injected intravitreally into normal adult dogs to study rod outer segment renewal. Eyes were removed at various times after injection and the retinas prepared for light microscope autoradiography. Rod outer segment disc turnover was found to be similar to other species, i.e., discs were produced at the base of the outer segments and migrated sclerad with time. The time for turnover averaged 6 days. Cone outer segments never showed banding of the labeled protein but rather a diffuse label such as reported in other species.

Protothecosis with ocular involvement in a dog

An 8 1/2-year-old Collie dog was referred for evaluation of chronic diarrhea as well as sudden blindness and leukokoria of the right eye. An organism morphologically similar to Prototheca sp was recovered from the subretinal fluid and was found at necropsy in the eyes, gastrointestinal tract, lungs, lymph nodes, kidneys, heart, abdominal fat, and omentum.

Exophthalmos secondary to zygomatic adenocarcinoma in a dog

An 8-year-old Labrador Retriever developed unilateral exophthalmos over a 1-year period. Contrast radiography, surgical exploration, and histologic examination revealed the cause to be an adenocarcinoma arising from the zygomatic salivary gland or duct.