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- Author or Editor: Cynthia C. Powell x
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Objective—To determine whether taurine and glutamate contents are reduced in damaged photoreceptors in dogs with primary glaucoma (PG) in a manner consistent with an ischemia-like release of both of these amino acids from damaged cells.
Sample Population—Retinas from 6 dogs with PG and 3 control dogs.
Procedure—Serial, semithin sections of each canine retina were stained with toluidine blue to identify damaged photoreceptors or via immunogold techniques to quantify taurine and glutamate content in retinal cells.
Results—Regions with a thin outer nuclear layer and pathologic nuclear changes in photoreceptors were evident in retinas of dogs with PG. The density of immunostaining for taurine in damaged photoreceptors was significantly reduced to (mean ± SEM) 37.5 ± 2.6% of the density in adjacent undamaged photoreceptors. Photoreceptors with decreased taurine immunostaining also had decreased glutamate immunostaining, consistent with ischemia-like release of both of these amino acids from damaged cells. Immunostaining for glutamate, but not taurine, was increased in presumptive radial glial cells (ie, Müller cells) in damaged regions, consistent with an ischemia-induced redistribution of amino acids in dogs with PG.
Conclusions and Clinical Relevance—Retinal damage in dogs with PG includes ischemia-like losses of taurine and glutamate from photoreceptors and accumulation of glutamate, but not taurine, in nearby Müller cells. These changes are consistent with glutamate release and depletion of intracellular taurine in damaged regions, perhaps contributing to progressive damage in these areas. (Am J Vet Res 2005;66:791–799)
Objective—To evaluate composition of aqueous humor obtained from normal eyes of llamas (Lama glama) and alpacas (Lama pacos).
Sample Population—Aqueous humor obtained from 10 male llamas and 10 male alpacas.
Procedure—All animals had normal eyes, as determined by ocular examination. Aqueous humor samples were obtained via paracentesis of the anterior chamber of animals that were heavily sedated. Chemical analysis included measurement of concentrations of sodium, potassium, magnesium, chloride, bicarbonate, phosphorus, and glucose as well as osmolality and pH.
Results—With the exception of potassium concentrations, values for aqueous humor composition did not differ significantly between llamas and alpacas. Mean ± SD values for llamas and alpacas, respectively, were: sodium, 154.7 ± 2.1 and 152.7 ± 2.1 mEq/L; potassium, 5.3 ± 0.4 and 4.6 ± 0.4 mEq/L; magnesium, 1.8 ± 0.1 and 1.7 ± 0.1 mg/dl; chloride, 130.0 ± 1.6 and 127.0 ± 3.3 mEq/L; bicarbonate, 19.2 ± 1.5 and 20.2 ± 2.3 mEq/L; phosphorous, 2.7 ± 0.3 and 2.5 ± 0.4 mg/dl; glucose, 80.3 ± 3.9 and 80.8 ± 7.3 mg/dl; total protein, 29.0 ± 8.6 and 31.5 ± 10.1 mg/dl; and osmolality, 305.8 ± 11.8 and 306.2 ± 4.9 mOsm. The pH ranged from 7.5 to 8.0 for both species. Potassium concentrations were significantly higher in llamas than alpacas.
Conclusions and Clinical Relevance—Except for potassium, composition of aqueous humor did not differ significantly between llamas and alpacas. Aqueous humor composition of llamas and alpacas is similar to that of other species that have been examined. (Am J Vet Res 2001;62:1060–1062)
Objective—To use PCR assays to determine the prevalence of feline herpesvirus 1 (FHV-1), Chlamydophila felis, and Mycoplasma spp DNA in conjunctival cells collected from cats with and without conjunctivitis; to compare results of conventional and real-time fluorogenic PCR assays for amplification of FHV-1 DNA; and to determine whether copy numbers of FHV-1 DNA are correlated with conjunctivitis.
Animals—55 cats with active conjunctivitis, 39 healthy cats that never had conjunctivitis, and 32 cats with a history of conjunctivitis that had been resolved for at least 3 months.
Procedures—Samples were obtained by rolling cotton-tipped applicators on the ventral conjunctiva of awake cats treated topically with proparacaine. The DNA was extracted from the swab specimens and assessed in PCR assays to detect DNA of FHV-1 (fluorogenic PCR assay and conventional PCR assay), Mycoplasma spp (conventional PCR assay), and C felis (conventional PCR assay).
Results—Overall prevalence rates of FHV-1, C felis, and Mycoplasma spp as assessed by the conventional PCR assays were 6.7%, 3.2%, and 9.6%, respectively. Percentage concordance between conventional PCR and fluorogenic PCR assays for FHV-1 was 92.5%. There were no significant differences among the 3 groups of cats for the mean copy number of FHV-1 divided by the copy number of glyceraldehyde-3-phosphate dehydrogenase.
Conclusions and Clinical Relevance—Mycoplasma spp were the most prevalent organism detected and was associated with conjunctivitis. This study could not confirm that there are increased copy numbers of FHV-1 DNA in cats with conjunctivitis, compared with the copy numbers for cats without conjunctivitis.
Objective—To determine whether retinal damage in dogs with primary glaucoma (PG) is consistent with ischemia-induced glutamate toxicosis.
Sample Population—Retinal tissue sections from 25 dogs with PG and 12 normotensive control dogs.
Procedure—Retinal sections from control and glaucomatous dogs were stained for morphometric and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) analyses to determine whether retinal damage was consistent with glutamate toxicosis. Immunohistochemical analysis was performed to detect ischemia-like loss of glutamate from neurons in damaged areas.
Results—In severely damaged glaucomatous retinas, all neurosensory layers had focal regions that were thin or disrupted. There was less thinning of the outer nuclear layer (ONL) and inner nuclear layer (INL) in moderately damaged retinas than in severely damaged retinas. Acute signs of damage in the INL included cells with dark, condensed chromatin and lightly stained cytoplasm interspersed with a few TUNELpositive cells, which was consistent with glutamate toxicosis. Glutamate immunoreactivity was reduced in thin areas and in damaged cells of the INL and ONL, which was consistent with glutamate release in damaged areas. Glutamate immunoreactivity was increased in putative Müller cells in damaged areas, which also was consistent with glutamate release.
Conclusions and Clinical Relevance—Retinal damage in dogs with PG differs in intensity in focal areas. Damage in affected regions resembles damage induced by glutamate. Glutamate is lost from damaged neurons and accumulates in Müller cells, which is consistent with increased glutamate release contributing to the damage. Glutamate antagonists may protect INL cells in dogs with glaucoma. (Am J Vet Res 2004;65:776–786)
Objective—To F whether vessels in the ocular fundus changed over the lifetime of Beagles and whether any changes were substantial enough to likely preclude positive identification of individual dogs by use of their retinal vascular patterns.
Procedures—Fundic photographs of both eyes of 18 Beagles taken at 1 or 3, 5, and 7 or 9 years of age were digitalized. Photographs were analyzed by use of 2 software programs. One was used to determine vessel numbers and widths and the other to determine the locations of the 3 largest vessels. Measurements were compared over time periods in the life of each dog. Only observations made at baseline (1 or 3 years of age) and again at 5 and 9 years of age were included in the statistical analysis, as these points were common to all dogs.
Results—No significant changes in numbers or locations of the blood vessels were detected over time. Widths of the vessels decreased significantly as the dogs aged.
Conclusions and Clinical Relevance—The ocular fundus of Beagles changed over each dog's lifetime in that the retinal blood vessels became smaller but did not change in number or location. Results suggest that digitalized retinal images can likely be used to identify dogs over their lifetimes.
Objective—To evaluate the efficacy of twice-daily ophthalmic application of 0.5% cidofovir solution in cats with experimentally induced primary ocular feline herpesvirus-1 (FHV-1) infection.
Animals—Twelve 6-month-old sexually intact male cats.
Procedures—Cats were randomly assigned to either a treatment or control group. Ocular infection with FHV-1 was induced (day 0) in all cats via inoculation of both eyes with 104 plaque-forming units of a plaque-purified FHV-1 field strain. Twice daily for 10 days beginning on day 4 after virus inoculation, the treatment group received 1 drop of 0.5% cidofovir in 1% carboxymethylcellulose in both eyes, and the control group received 1 drop of 1% carboxymethylcellulose in both eyes. A standardized scoring method was used to evaluate clinical signs of FHV-1 infection in each cat once daily for 24 days. The amount of ocular viral shedding was assessed by use of a quantitative real-time PCR procedure every 3 days during the study period. Clinical scores and viral quantification were averaged over the pretreatment (days 0 to 3), treatment (days 4 to 14), and posttreatment (days 15 to 24) periods for each cat.
Results—During the treatment period, clinical scores and amount of viral ocular shedding were significantly lower in the treatment group, compared with findings in the control group.
Conclusions and Clinical Relevance—Twice-daily application of 0.5% cidofovir solution in both eyes significantly decreased the amount of viral shedding and the severity of clinical disease in cats with experimentally induced ocular FHV-1 infection.