Search Results

You are looking at 1 - 10 of 41 items for

  • Author or Editor: Daniel Ward x
  • Refine by Access: All Content x
Clear All Modify Search
Author:

Abstract

Objective

To compare the relative efficacies of 4 topical nonsteroidal anti-inflammatory drugs at preventing blood-aqueous barrier (BAB) disruption in dogs.

Design

1 eye of each dog was treated with 1 % suspensions of diclofenac, flurbiprofen, suprofen, or tolmetin, or with control solution. After 4 applications of eyedrops at 10-minute intervals, BAB disruption was induced in the treated eye by anterior chamber paracentesis. The severity of BAB disruption was measured by anterior chamber fluorophotometry.

Animals

40 ocular-normal dogs.

Procedure

After pretreatment with eyedrops, rapid, 100-μl nonleaking anterior chamber paracentesis was performed in 1 eye of each dog to induce BAB disruption. 1 day after paracentesis, 1 ml of 10% fluorescein sodium was injected IV. The amount of fluorescein entering the anterior chamber of each eye was measured 30 to 60 minutes later by use of a computerized scanning fluorophotometer. The degree of BAB disruption was determined by comparing the amount of fluorescein entering the aqueous humor of the paracentesed eye with that of the nonparacentesed eye.

Results

At postparacentesis day 1, the order of statistically significant BAB-stabilizing efficacy among groups was: diclofenac > flurbiprofen > suprofen > tolmetin = control solution.

Conclusions

Topically applied 1% suspensions of diclofenac, flurbiprofen, and suprofen are effective at preventing BAB disruption after paracentesis in dogs, indicating their potential usefulness for treatment of prostaglandm-mediated ocular disease. 1 % tolmetin is no more effective than control solution. (Am J Vet Res 1996;57:875–878)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine tear volume, turnover rate, and flow rate in ophthalmologically normal horses by use of fluorophotometry.

Animals—12 mares free of ophthalmic disease.

Procedures—2 μL of 10% sodium fluorescein was instilled onto 1 eye of each horse, and tear samples were collected via microcapillary tubes from the inferonasal conjunctival culde-sac at 0, 2, 4, 6, 10, 15, and 20 minutes after instillation. Collected tear samples were then measured for fluorescein concentrations with a computerized scanning ocular fluorophotometer. A decay curve plot of concentration changes over time was used to determine tear flow rate and volume through 2 different mathematical treatments of the data (the including method and the excluding method).

Results—Fluorescein concentration in tears decreased in a first-order manner. The including method yielded a mean tear volume of 360.09 μL, a turnover rate of 12.22%/min, and a flow rate of 47.77 μL/min. The excluding method yielded values of 233.74 μL, 13.21%/min, and 33.62 μL/min, respectively. Mean ± SD correlation coefficients for the natural logarithm of the fluorescein concentration versus time were 0.93 ± 0.12 for the including method and 0.98 ± 0.03 for the excluding method.

Conclusions and Clinical Relevance—The excluding method yielded more accurate results. A tear flow rate of 33.62 μL/min and a tear volume of 233.74 μL imply a complete recycling of the tear volume in approximately 7 minutes and suggest that increased dosing regimens or constant infusion methods for topical administration of ophthalmic drugs may be indicated when treating horses for corneal disease in which high ocular surface concentrations are needed.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine aqueous humor flow rate (AHFR) in an avian species by use of anterior segment fluorophotometry.

Animals—9 healthy red-tailed hawks (Buteo jamaicensis; 4 males and 5 females) that ranged from 8 months to 8 years of age.

Procedures—A protocol was developed for fluorophotometric determination of AHFR. Topical administration of 10% fluorescein was used to load the corneas, and corneal and aqueous humor fluorescein concentrations were measured approximately 5, 6.5, and 8 hours later. Concentration-versus-time plots were generated, and slopes and cornea-to-aqueous humor concentration ratios from these plots were used to manually calculate flow rates.

Results—Mean ± SD AHFRs for the right eye, left eye, and both eyes were 3.17 ± 1.36 μL/min (range, 1.67 to 6.21 μL/min), 2.86 ± 0.88 μL/min (range, 2.04 to 4.30 μL/min), and 2.90 ± 0.90 μL/min (range, 1.67 to 4.42 μL/min), respectively. The AHFRs were similar for right and left eyes. These flow rates represented a mean aqueous humor transfer coefficient of 0.0082/min, which is similar to that of mammalian species.

Conclusions and Clinical Relevance—The AHFR in red-tailed hawks was similar to that of most mammalian species, and the fractional egress was almost identical to that of other species. This information will allow a greater understanding of aqueous humor flow in avian eyes, which is crucial when evaluating diseases that affect avian eyes as well as medications that alter aqueous humor flow.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine if clopidogrel enhanced the thrombolytic rate of tissue-plasminogen activator (t-PA) on an in vitro feline whole blood thrombosis model.

Animals—9 purpose-bred cats.

Procedure—Blood obtained from cats before (baseline) and after treatment with clopidogrel (75 mg, PO, q 24 h for 3 days) was anticoagulated with sodium citrate (9:1 volume-to-volume ratio) to which 1 µCi of I125- fibrinogen was added. Thrombi were formed by the addition of calcium chloride and bovine thrombin. Thrombi were placed into autologous plasma to which 0.1 mg of t-PA was added. Plasma samples were collected at different time points to determine the amount of released I125-fibrin split products. Thrombolytic rates were calculated by determining the time to 25%, 50%, and 75% thrombolysis (t25, t50, and t75, respectively). Confidence intervals for t25, t50, and t75 at baseline were compared with those after treatment.

Results—There were no significant differences in thrombolytic rates between values obtained at baseline and after clopidogrel treatment (t25, 18.0 vs 18.5 minutes; t50, 63.3 vs 65.6 minutes; and t75, 163.0 vs 170.1 minutes, respectively).

Conclusions and Clinical Relevance—Clopidogrel did not have an effect on the rate of thrombolysis of feline whole blood thrombi induced by t-PA in this in vitro model. (Am J Vet Res 2004;65:715–719)

Full access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine aqueous humor flow rate in clinically normal dogs, using fluorophotometry.

Animals—20 clinically normal Beagles.

Procedure—A study was performed on 5 dogs to establish an optimal protocol for fluorophotometric determination of aqueous humor flow rate. This protocol then was used to measure aqueous humor flow rate in 15 dogs. Corneas were loaded with fluorescein by topical application, and corneal and aqueous humor fluorescein concentrations were measured 5, 6.5, and 8 hours after application. Concentration-versus- time plots were generated, and slopes and ratios of the fluorescein concentration in the cornea and aqueous humor from these graphs were used to calculate flow rates. Calculations were performed by use of automated software provided with the fluorophotometer and by manual computation, and the 2 calculation methods were compared.

Results—The protocol established for the 5 dogs resulted in semilogarithmic and parallel decay of corneal and aqueous humor concentrations. Manually calculated mean ± SD aqueous humor flow rates for left, right, and both eyes were 5.58 ± 2.42, 4.86 ± 2.49, and 5.22 ± 1.87 μl/min, respectively, whereas corresponding flow rates calculated by use of the automated software were 4.54 ± 3.08, 4.54 ± 3.10, and 4.54 ± 2.57 μl/min, respectively. Values for the left eye were significantly different between the 2 computation methods.

Conclusions and Clinical Relevance—Aqueous humor flow rates can be determined in dogs, using fluorophotometry. This technique can be used to assess pathologic states and medical and surgical treatments that alter aqueous humor dynamics. (Am J Vet Res 2001;62:853–858)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate effects of topical application of a 2% solution of dorzolamide on intraocular pressure (IOP) and aqueous humor flow rate in clinically normal dogs.

Animals—15 Beagles.

Procedure—The IOP was measured in both eyes of all dogs for 3 days to determine baseline values. In a single-dose study, 50 μl of dorzolamide or control solution was applied in both eyes at 7:00 AM, and IOP was measured 7 times/d. In a multiple-dose study, dorzolamide or control solution was applied to both eyes 3 times/d for 6 days, and IOP was measured 4 times/d during treatment and for 5 days after cessation of treatment. Aqueous humor flow rate was measured for all dogs fluorophotometrically prior to treatment and during the multiple-dose study.

Results—In the single-dose study, dorzolamide significantly decreased IOP from 30 minutes to 6 hours after treatment. Mean decrease in IOP during this time span was 3.1 mm Hg (18.2%). Maximal decrease was detected 6 hours after treatment (3.8 mm Hg, 22.5%). In the multiple-dose study, dorzolamide decreased IOP at all time points, and maximal decrease was detected 3 hours after treatment (4.1 mm Hg, 24.3%). Mean aqueous humor flow rate decreased from 5.9 to 3.4 μl/min (43%) after treatment in the dorzolamide group.

Conclusions and Clinical Relevance—Topical application of a 2% solution of dorzolamide significantly decreases IOP and aqueous humor flow rate in clinically normal dogs. Therefore, topical administration of dorzolamide should be considered for the medical management of dogs with glaucoma. (Am J Vet Res 2001;62:859–863)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine effects of commonly used ophthalmic antibiotics on cellular morphologic characteristics and migration of canine corneal epithelium in cell culture.

Sample Population—Corneal epithelial cells harvested from corneas of 12 euthanatized dogs and propagated in cell culture.

Procedure—Cells were treated with various antibiotics after a defect was created in the monolayer. Cellular morphologic characteristics and closure of the defect were compared between antibiotic-treated and control cells.

Results—Cells treated with ciprofloxacin and cefazolin had the greatest degree of rounding, shrinkage, and detachment from plates. Cells treated with neomycin-polymyxin B-gramicidin and gentamicin sulfate had rounding and shrinkage but with less detachment. Cells treated with tobramycin and chloramphenicol grew similarly to control cells. On the basis of comparisons of defect circumference between control cells and cells exposed to antibiotics, tobramycin affected cellular migration the least.

Conclusion and Clinical Relevance—Effects of ciprofloxacin and cefazolin on morphologic characteristics of canine corneal epithelial cells in vitro should be taken into consideration before using these antibiotics for first-line of treatment for noninfected ulcers. Of the antibiotics tested that have a primarily gramnegative spectrum of coverage, gentamicin inhibited corneal epithelial cell migration and had greater cytopathologic effects than tobramycin did. For antibiotics with a gram-positive coverage, chloramphenicol had no cytopathologic effects on cells in comparison to cefazolin, which caused most of the cells to shrink and detach from the plate. Polymyxin B-neomycingramicidin was midrange in its effects on cellular morphologic characteristics and migration. (Am J Vet Res 2001;62:xxx–xxx)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare results of a nonradioactive colorimetric microplate assay with results of a traditional radioactive proliferation assay for determination of its use as a reliable and accurate alternative method for determination of proliferative activity of feline lymphocytes.

Sample Population—Blood samples from 10 clinically normal domestic shorthair cats.

Procedure—Double-density gradient separation was used to isolate mononuclear cells. Isolated cells were stimulated with various concentrations of concanavalin A (Con-A) and cultured for 72 hours. Lymphocyte proliferation was measured by radioactive ([3H]thymidine) and nonradioactive (colorimetric) techniques. Immunophenotypic analysis with felinespecific CD4+ and CD8+ monoclonal antibody was performed, using flow cytometry.

Results—Mononuclear cells were successfully isolated (97 to 99% purity and viability) from blood samples. A similar dose-dependent proliferative response to Con-A stimulation was measured with [3H]thymidine incorporation and the colorimetric assay. For both techniques, concentrations of 0.1 and 1.0 µg of Con-A/ml were submitogenic, and 100 µg/ml was toxic to cultured cells. For both techniques, maximal proliferation was observed with 5 µg of Con-A/ml.

Conclusion and Clinical Relevance—These results indicate that the nonradioactive colorimetric technique is a reliable and accurate method for measuring proliferative activity of feline lymphocytes. Clinically, this assay can be used as part of a screening process to determine immunocompetence of at-risk cats and to evaluate treatments for cats with immune-mediated or T-cell-dependent diseases. (Am J Vet Res 2001; 62:567–571)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effects of endotoxin administration on thyroid function test results and serum tumor necrosis factor-α (TNF-α) activity in healthy dogs.

Animals—6 healthy adult male dogs.

Procedures—Serum concentrations of thyroxine (T4), 3,5,3'-triiodothyronine (T3), 3,3'5'-triiodothyronine (rT3), free T4 (fT4), and endogenous canine thyroid stimulating hormone (TSH), and TNF-α activity were measured before (day–1; baseline), during (days 0 to 3), and after (days 4 to 24) IV administration of endotoxin every 12 hours for 84 hours.

Results—Compared with baseline values, serum T3 concentration decreased significantly, whereas rT3 concentration increased significantly 8 hours after initial endotoxin administration. Serum T4 concentration decreased significantly at 8 and 12 hours after initiating endotoxin administration. Serum T4 concentration returned to reference range limits, then decreased significantly on days 6 to 12 and 16 to 20. Serum fT4 concentration increased significantly at 12, 24, and 48 hours after cessation of endotoxin treatment, compared with baseline values. Serum rT3 concentration returned to reference range, then decreased significantly days 5 and 7 after stopping endotoxin treatment. Serum TNF-α activity was significantly increased only 4 hours after initial endotoxin treatment, compared with baseline activity.

Conclusions and Clinical Relevance—Endotoxin administration modeled alterations in thyroid function test results found in dogs with spontaneous nonthyroidal illness syndrome. A decrease in serum T4 and T3 concentrations and increase in serum rT3 concentration indicate impaired secretion and metabolism of thyroid hormones. The persistent decrease in serum T4 concentration indicates that caution should be used in interpreting serum T4 concentrations after resolution of an illness in dogs. (Am J Vet Res 2003;64:229–234)

Full access
in American Journal of Veterinary Research