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  • Author or Editor: Bernhard M. Spiess x
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Abstract

Objective—To measure activities of NADPH-dependent reductases and sorbitol dehydrogenase in lenses from healthy dogs and cats.

Sample Population—Lenses from 37 dogs and 23 cats. All animals were healthy and had serum glucose concentrations within reference limits.

Procedure—Lenses were homogenized, and activities of NADPH-dependent reductases and sorbitol dehydrogenase were measured spectrophotometrically.

Results—Activities of NADPH-dependent reductases and sorbitol dehydrogenase were significantly lower in lenses from cats than in lenses from dogs. However, the ratio of NADPH-dependent reductases activity-to-sorbitol dehydrogenase activity was significantly higher in lenses from cats than in lenses from dogs.

Conclusions and Clinical Relevance—Results indicate that during periods of hyperglycemia, sorbitol would accumulate at a faster rate in the lenses of cats than in the lenses of dogs. Thus, the higher incidence of diabetic cataracts in dogs, compared with cats, is likely not attributable to a difference in the ratio of NADPH-dependent reductases activity-to-sorbitol dehydrogenase activity. (Am J Vet Res 2000;61: 1322–1324)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To assess the biological response to recombinant feline interferon-omega (rFeIFN-ω) following ocular or oral administration in cats via estimation of Mx protein expression in conjunctival cells (CCs) and WBCs.

Animals—10 specific pathogen–free cats.

Procedures—In multiple single-dose drug experiments, each cat received various concentrations of rFeIFN-ω administered topically into both eyes (50 to 10,000 U/eye) and orally (200 to 20,000 units). The same cats received saline (0.9% NaCl) solution topically and orally as control treatments. The CCs and WBCs were collected prior to treatment (day 0), on day 1, and every third or seventh day thereafter until samples yielded negative results for Mx protein. Samples were examined for Mx protein expression via immunohistochemistry and immunoblotting procedures involving murine anti-Mx protein monoclonal antibody M143.

Results—After topical application of 10,000 U of rFeIFN-ω/eye, CCs stained for Mx protein for a minimum of 7 days, whereas WBCs were positive for Mx protein for a minimum of 31 days. After topical application of lower concentrations, CCs did not express Mx protein, in contrast to WBCs, which stained for Mx protein at 1,000 units for at least 1 day. Following oral administration, Mx protein was expressed in WBCs at rFeIFN-ω concentrations as low as 200 units, whereas CCs did not stain for Mx protein at any concentration.

Conclusions and Clinical Relevance—Results indicate that Mx protein expression (a marker of the biological response to rFeIFN-ω) in CCs and WBCs of rFeIFN-ω–treated cats depends on the dose of rFeIFN-ω, site of administration, and cell type.

Full access
in American Journal of Veterinary Research

Abstract

Objective

To determine concentrations of dexamethasone in serum and urine of horses treated repeatedly with a topically administered ophthalmic dexamethasone preparation.

Animals

4 clinically normal horses (2 mares, 2 geldings).

Procedure

0.1% dexamethasone ophthalmic ointment was administered to the left eye of each horse every 5 to 9 hours for 8 consecutive days, yielding an estimated cumulative dexamethasone dose of 6.4 μg/kg of body weight. Serum and urine samples were obtained before the first dexamethasone treatment, on days 4 and 8 of treatment, and 24, 48, and 96 hours after cessation of treatment. To detect small concentrations of dexamethasone, serum and urine samples were analyzed by use of a competitive enzyme immunoassay.

Results

During the period of continued topical treatment, serum dexamethasone concentrations increased to between 0.10 and 0.49 ng/ml, then decreased below the limit of detection (0.06 ng/ml) within 24 hours after cessation of treatment. Dexamethasone also was detected in urine samples at concentrations of up to 0.98 ng/ml.

Conclusions

Repeated topical administration of dexamethasone ophthalmic ointment generated low, but detectable glucocorticoid concentrations in serum and urine.

Clinical Relevance

Because treatment of performance horses with dexamethasone is prohibited for most types of competitions and because enhanced glucocorticoid detection methods may result in positive test results, owners and trainers may wish to reconsider entering horses in competitions during periods of treatment with ophthalmic dexamethasone preparations. (Am J Vet Res 1999;60:571–576)

Free access
in American Journal of Veterinary Research

Summary

The pharmacokinetic properties of indomethacin and its effects on aqueous protein values were studied in 15 clinically normal Beagles. The dogs were treated every 6 hours with 1% indomethacin suspension in 1 eye, with the other eye serving as a control. After 24 hours, the dogs were anesthetized and samples of aqueous humor (ah) were drawn by aqueocentesis at 0, 15, 30, 60, and 90 minutes after initial paracentesis. Additional samples were drawn at the time of euthanasia, 180 (6 dogs) and 360 minutes (9 dogs) minutes after initial paracentesis. Blood samples were obtained at each treatment and at each aqueocentesis. The eyes were enucleated after dogs were euthanatized. Aqueous protein concentrations and indomethacin concentrations in ah, plasma, and different ocular tissues were determined.

Topical indomethacin administration had no effect on baseline protein concentrations of ah. It reduced protein concentrations in ah significantly at all times after initial aqueocentesis. This reduction was approximately 30%. Indomethacin in the ah is mostly protein-bound. Concentrations were 350 ng/ml in primary ah and 1,305 ng/ml in secondary ah, 90 minutes after initial aqueocentesis. Free-drug concentrations were relatively constant at about 220 ng/ml.

Indomethacin administered topically is readily absorbed by the ocular adnexae, reaching a steady-state concentration of 25 ng/ml in blood plasma 18 hours after the start of treatment. Plasma concentrations were 50 times lower than therapeutically effective concentrations. High indomethacin concentrations were found in the cornea only. Low concentrations were found in the iris and ciliary body, the lens, and in the choroid. On the basis of our findings, we conclude that topically administered indomethacin is effective in reducing protein concentrations in secondary ah and is rapidly eliminated from the eye.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To compare ultrasonographic and histologic examination findings for eyes of animals with ocular diseases.

Design—Retrospective case series.

Animals—116 eyes of 113 animals examined at 2 facilities.

Procedures—Diseased eyes of animals were examined by means of ultrasonography, removed via enucleation or exenteration, then histologically examined. Ultrasonographic images and histopathologic slides were evaluated, and diseases of eyes were identified with each of those methods and allocated to various categories. For each disease category, agreement between results of ultrasonography and those of histologic examination was assessed via determination of κ statistic values.

Results—Tests had good agreement for identification of iris or ciliary body neoplasia. Overall, intraocular neoplasia was not detected via ultrasonography for only 2 of 31 eyes with histologically detected neoplasia. Hemorrhagic or inflammatory changes were misinterpreted as neoplasia for 8 of 37 (22%) eyes. Tests had moderate to acceptable agreement for identification of retinal detachment. Retinal detachment was not detected by means of ultrasonography for 14 of 38 (37%) eyes with that diagnosis determined via histologic examination at one of the facilities (primarily in eyes with intraocular hemorrhage); however, retinal detachment was not identified via histologic examination for 6 of 38 (16%) eyes with that diagnosis determined via ultrasonography at the other facility.

Conclusions and Clinical Relevance—Agreement between tests evaluated in this study was clinically satisfactory for identification of intraocular neoplasia. Typically, diseases were misdiagnosed via ultrasonography for eyes with poor image contrast. Because determination of ultrasonographic diagnoses of retinal detachment and intraocular neoplasm may be of prognostic importance, performance of additional ultrasonographic techniques may be indicated.

Full access
in Journal of the American Veterinary Medical Association