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- Author or Editor: Juliet R. Gionfriddo x
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Objective—To determine whether glutamate contents are decreased in the ganglion cell layer (GCL) of retinas of DBA/2J mice with glaucoma, compared with unaffected control mice.
Sample Population—20 eyes from DBA/2J mice (9-week-old mice [n = 8] and 4- , 6- , and 12-month-old  mice) and 17 eyes from control CD-1 (7) and C57/BL6 (10) mice of similar age.
Procedure—After euthanasia, the eyes were rapidly dissected and fixed. Serial 0.5-μm sections were prepared from eyecups and stained with toluidine blue (to identify damaged cells) or immunogold (to localize glutamate). Microscopic images were captured digitally for comparison; immunostaining densities were assessed via special software.
Results—In the GCL of control mice, few cells appeared damaged; large amounts of glutamate were detected in 83 ± 8.3% of cells. In DBA/2J mice ≥ 9 weeks of age, damaged neurons were observed in retinal sections; the level of glutamate immunoreactivity was high in a few cells near areas of damage (13 ± 3.2%) and in many cells in less-damaged regions of the same sections (82 ± 4.2%). Many neurons with low amounts of glutamate in damaged regions did not appear damaged histologically.
Conclusions and Clinical Relevance—In retinas of young DBA/2J mice, damaged and undamaged GCL cells had decreased levels of immunostaining for glutamate, compared with less-damaged adjacent regions or retinas from control mice. The loss of neuronal glutamate in damaged retinal regions suggests that glutamate is contributing to early retinal damage prior to changes in intraocular pressure.
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 determine whether the tears of llamas, sheep, and cattle contain lysozyme and compare lysozyme concentrations in tears among these species.
Animals—40 llamas, 5 sheep, and 36 cattle.
Procedure—Electrophoresis, western blot immunoassay for lysozyme, a spectrophotometric assay to detect tear lysozyme by its ability to lyse a suspension of Micrococcus lysodeiticus, and a microtiter plate colorometric assay were performed.
Results—A 13.6-kd protein band was detected by use of electrophoresis and western blot immunoassay in llama and sheep tears but not cattle tears. Results of spectrophotometric assay suggested that llama and sheep tears had high concentrations of lysozyme, whereas cattle tears had low concentrations. Results of the microtiter plate colorometric assay suggested that llama tears had high concentrations of lysozyme, whereas concentrations in sheep and cattle tears were lower.
Conclusions and Clinical Relevance—Lysozyme concentrations in tears may vary among species and this variability may contribute to differing susceptibilities to ocular diseases such as infectious keratoconjunctivitis. (Am J Vet Res 2000;61:1294–1297)
Objective—To determine the frequency of canine and feline emergency visits with respect to the lunar cycle.
Design—Retrospective case series.
Animals—11,940 dogs and cats evaluated on an emergency basis during an 11-year period.
Procedures—Date of emergency visit, signalment, and chief complaint were retrieved from a medical records database. Emergency type was categorized as animal bite, cardiac arrest, epilepsy, ophthalmic, gastric dilatation-volvulus, trauma, multiple diseases, neoplasia, or toxicosis. The corresponding lunar phase was calculated and recorded as new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, or waning crescent. The effect of lunar phase on the frequency of emergency visits was evaluated by calculating relative risk.
Results—Of 11,940 cases, 9,407 were canine and 2,533 were feline. Relative risk calculations identified a significant increase in emergencies for dogs and cats on fuller moon days (waxing gibbous to waning gibbous), compared with all other days.
Conclusions and Clinical Relevance—Results suggested that more emergency room visits occurred on fuller moon days for dogs and cats. It is unlikely that an attending clinician would notice the fractional increase in visits (0.59 and 0.13 more canine and feline visits, respectively) observed in this study at a facility with a low caseload. If the study is repeated at a facility with a robust emergency caseload, these results may lead to reorganization of staffing on fuller moon dates. A prospective study evaluating these findings under conditions of high caseload is necessary to determine the clinical relevance.
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 analyze and compare contents of the preocular tear films of llamas and cattle.
Animals—40 llamas and 35 cattle.
Procedure—Tear pH was determined by use of a pH meter. Total protein concentration was determined by use of 2 microtiter methods. Tear proteins were separated by use of electrophoresis and molecular weights of bands were calculated. Western blot immunoassay was used to detect IgA, lactoferrin, transferrin, ceruloplasmin, α1-antitrypsin, α1-amylase, and α2-macroglobulin. Enzyme electrophoresis was used to detect proteases.
Results—The pH of llama and cattle tears were 8.05 ± 0.01 and 8.10 ± 0.01, respectively. For results of both methods, total protein concentration of llama tears was significantly greater than that of cattle tears. Molecular weights of tear protein bands were similar within and between the 2 species, although llama tears had a distinct 13.6-kd band that was not detected in cattle. Lactoferrin, IgA, transferrin, ceruloplasmin, α1-antitrypsin, α1-amylase, α2–macroglobulin, and proteases were detected in both species.
Conclusions and Clinical Relevance—Llama tears have significantly greater total protein concentration than cattle tears, whereas pH is similar between species. Because little variation was detected within species for the number and molecular weight of protein bands, pooling of tears for analysis is justified. Results suggest that lactoferrin, ceruloplasmin, transferrin, α1-antitrypsin, α2-macroglobulin, α1-amylase, and IgA are present in the tears of llamas and cattle. (Am J Vet Res 2000;61:1289–1293)