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Summary

The temporal response of blood and serum proteins to chronic plasmapheresis was determined in 8 horses used in a commercial antibody enterprise. Plasmapheresis of between 4 and 11 L induced significant decreases in total protein, albumin, and IgG values. With the exception of a high hematocrit value for the first postplasmapheresis blood sample, there were no changes in erythrocyte or leukocyte measurements, and no changes in the proportions of serum protein in an electrophoretic profile. Regression equations generated for recovery of proteins after plasmapheresis indicated a return to preplasmapheresis values of total protein and albumin at approximately 1 month. Complications of repeated plasmapheresis were not detected when plasma extractions were done between 7 and 19 times at 30-day intervals.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the in vitro efficacy of an ophthalmic drug combination against common corneal pathogens of horses.

Sample Population—Representative isolates of 3 bacterial and 2 fungal corneal pathogens of horses.

Procedures—Pathogens were subjected to minimum inhibitory concentration (MIC) testing of a drug combination that consisted of equal volumes of natamycin 3.33%, tobramycin 0.3%, cefazolin 5.5%, and equine serum. Proteinase inhibitory activity of the drug combination was assessed by use of a fluorescence microplate assay with gelatin and collagen I as substrates. The MICs of the drug combination were compared with those for each of the component medications and antiproteinase activity of the drug combination was compared with that of serum by use of paired t tests and a 2-way ANOVA, respectively.

Results—The drug combination was at least as effective as each medication separately for inhibiting microbial growth of all pathogens tested and was significantly more effective against B-hemolytic Streptococcus spp, Aspergillus spp, and Fusarium spp than the relevant medications separately. Serum and the drug combination both had significant antigelatinase activity, and serum had significant anticollagenase activity. Antiproteinase activity of serum was a concentration-dependent event, which enabled serum to achieve significantly greater activity than the drug combination after 3.5 and 4 hours of intubation for the gelatin and collagen I assays, respectively.

Conclusions and Clinical Relevance—Drug combinations have the attractive potential of minimizing the time, stress, and fatigue associated with topical treatment regimens consisting of multiple drugs used separately for horses with keratitis.

Full access
in American Journal of Veterinary Research

SUMMARY

The pharmacokinetic properties of the fluoroquinolone antimicrobial enrofloxacina were studied in New Zealand White rabbits. Four rabbits were each given enrofloxacin as a single 5 mg/kg of body weight dosage by iv, sc, and oral routes over 4 weeks. Serum antimicrobial concentrations were determined for 24 hours after dosing. Compartmental modeling of the iv administration indicated that a 2-compartment open model best described the disposition of enrofloxacin in rabbits. Serum enrofloxacin concentrations after sc and oral dosing were best described by a 1- and 2-compartment model, respectively. Overall elimination half-lives for iv, sc, and oral routes of administration were 2.5, 1.71, and 2.41 hours, respectively. The half-life of absorption for oral dosing was 26 times the half-life of absorption after sc dosing (7.73 hours vs 0.3 hour). The observed time to maximal serum concentration was 0.9 hour after sc dosing and 2.3 hours after oral administration. The observed serum concentrations at these times were 2.07 and 0.452 μg/ml, respectively. Mean residence times were 1.55 hours for iv injections, 1.46 hours for sc dosing, and 8.46 hours for oral administration. Enrofloxacin was widely distributed in the rabbit as suggested by the volume of distribution value of 2.12 L/kg calculated from the iv study. The volume of distribution at steady-state was estimated at 0.93 L/kg. Compared with iv administration, bioavailability was 77% after sc dosing and 61% for gastrointestinal absorption. Estimates of predicted average steady-state serum concentrations were 0.359, 0.254, and 0.226 μg/ml for iv, sc, and oral administration, respectively. On the basis of maintaining enrofloxacin serum concentrations at 4 times the minimal inhibitory concentration90 for Pasteurella multocida, oral dosing resulted in the longest maximal time interval between doses of 15.4 hours vs 9.9 hours and 7.4 hours for iv and sc injections, respectively. Because enrofloxacin is widely dispersed in the rabbit's body, it is estimated from the data in this study that in vivo inhibitory concentrations of enrofloxacin for Pasteurella multocida may be maintained at oral dosage regimens equivalent to 5 mg/kg (q 12 h).

Free access
in American Journal of Veterinary Research

Abstract

Objective

To analyze the vitreal amino acid concentrations in dogs with breed-related primary glaucoma to determine whether excitotoxic amino acids associated with retinal ganglion cell death in other species were present in affected dogs.

Samples

11 normal control and 10 glaucomatous canine eyes.

Procedure

Amino acid analyses were performed by high-pressure liquid chromatography in masked manner.

Results

Eyes from dogs with primary glaucoma had significantly high vitreal glutamate concentration, compared with values for eyes of clinically normal control dogs. Mean (± SD) glutamate concentrations were 31.7 ± 12.4 and 6.9 ± 6.3 μM in glaucomatous and normal eyes, respectively (P < 0.0001). Eyes from dogs with glaucoma also had lower vitreal glycine (37.0 ± 17.0 vs 59.4 ± 28.2 μM; P < 0.043) and higher of vitreal tryptophan (39.0 ± 22.8 vs 17.5 ± 11.2 μM; P < 0.012) concentrations, compared with values for normal eyes.

Conclusion

Glutamate concentration potentially toxic to retinal ganglion cells is associated with the pathogenesis of primary glaucoma in dogs. Increased glutamate concentration provides evidence of an ischemic mechanism for retinal ganglion cell death and optic nerve atrophy in dogs with glaucoma.

Clinical Relevance

The emphasis on reduction and normalization of high intraocular pressure as the primary focus of treatment for glaucoma in dogs should be augmented by other therapeutic approaches. (Am J Vet Res 1997;58:864–867)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To describe antimicrobial susceptibility testing practices of veterinary diagnostic laboratories in the United States and evaluate the feasibility of collating this information for the purpose of monitoring antimicrobial resistance in bacterial isolates from animals.

Design—Cross-sectional study.

Procedures—A questionnaire was mailed to veterinary diagnostic laboratories throughout the United States to identify those laboratories that conduct susceptibility testing. Nonrespondent laboratories were followed up through telephone contact and additional mailings. Data were gathered regarding methods of susceptibility testing, standardization of methods, data management, and types of isolates tested.

Results—Eighty-six of 113 (76%) laboratories responded to the survey, and 64 of the 86 (74%) routinely performed susceptibility testing on bacterial isolates from animals. Thirty-four of the 36 (94%) laboratories accredited by the American Association of Veterinary Laboratory Diagnosticians responded to the survey. Laboratories reported testing > 160,000 bacterial isolates/y. Fifty-one (88%) laboratories reported using the Kirby-Bauer disk diffusion test to evaluate antimicrobial susceptibility; this accounted for 65% of the isolates tested. Most (87%) laboratories used the NCCLS (National Committee for Clinical Laboratory Standards) documents for test interpretation. Seventy-five percent of the laboratories performed susceptibility testing on bacterial isolates only when they were potential pathogens.

Conclusions—The veterinary diagnostic laboratories represent a comprehensive source of data that is not easily accessible in the United States. Variability in testing methods and data storage would present challenges for data aggregation, summary, and interpretation. (J Am Vet Med Assoc 2003;222:168–173)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To examine postoperative ocular hypertension (POH) and other variables as predictors of the risk of developing glaucoma after cataract surgery in dogs.

Design—Retrospective study.

Animals—220 dogs that had cataract surgery.

Procedure—Medical records of 220 dogs (346 eyes) that had extracapsular cataract removal or phacoemulsification of cataracts were reviewed. With respect to glaucoma development, 8 variables were analyzed, which included development of POH, breed, sex, age at time of surgery, eye (right vs left), phacoemulsification time, intraocular lens (IOL) placement (yes or no), and stage of cataract development. Eyes developed glaucoma within 6 or 12 months of surgery or did not have signs of glaucoma at least 6 or 12 months after cataract surgery.

Results—Of 346 eyes, 58 (16.8%) developed glaucoma after surgery. At 6 months, 32 of 206 (15.5%) eyes examined had glaucoma; at 12 months, 44 of 153 (28.8%) eyes examined had glaucoma. Median follow-up time was 5.8 months (range, 0.1 to 48 months). Mixed-breed dogs were at a significantly lower risk for glaucoma, compared with other breeds. Eyes with IOL placement were at a significantly lower risk for glaucoma, compared with eyes without IOL placement. Eyes with hypermature cataracts were at a significantly higher risk for glaucoma, compared with eyes with mature or immature cataracts.

Conclusions and Clinical Relevance—Multiple factors appear to contribute to the onset of glaucoma in dogs after cataract surgery. Complications prohibiting IOL placement during cataract surgery may lead to a high risk of glaucoma development. (J Am Vet Med Assoc 2000;216:1780–1786)

Full access
in Journal of the American Veterinary Medical Association

SUMMARY

Using an applanation tonometer, 5 replicate intraocular pressure (iop) measurements were obtained from each eye of 12 young, clinically normal, American alligators. Alligator length ranged from 46 to 117 cm, measured from snout to tail tip. All iop were recorded by a single observer at an ambient temperature of approximately 25 C, and ranged from 5 to 35 mm of Hg. Observer reliability was excellent (intraclass r = 0.93), and iop did not change over the ordered sequence of 5 replicate measurements/eye. Replicate iop measurements were, therefore, averaged in each eye for comparison between eyes of the same alligator. Left and right eye iop were highly correlated within individual alligators (r = 0.92), whereas the mean within-animal difference between left and right eye iop was not statistically significant (95% confidence interval [ci] for the left eye-right eye mean difference, −1.9 to 1.5 mm of Hg). Mean iop determined for 5 confirmed females and 3 confirmed males did not differ significantly between the sexes (95% ci for the male-female difference in means, −2.1 to 3.7 mm of Hg). Mean ± sem iop of 23.7 + 2.1 mm of Hg determined for 4 alligators < 50 cm long was significantly (P = 0.009) greater than mean iop of 11.6 + 0.5 mm of Hg determined for 8 alligators > 50 cm long (95% ci for the difference in means, 8.5 to 15.7 mm of Hg). In young alligators, the relation between body length and iop appears to be nonlinear, possibly with a negative exponent.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To examine in vitro effects of various antiproteolytic compounds on activity of matrix metalloproteinase (MMP)-2 and -9 in the tear film of horses with active corneal ulcers.

Sample Population—Samples of tear film obtained from the eyes of 34 horses with active ulcerative keratitis.

Procedure—Horses were sedated, and tear samples were collected from the lower fornix of 34 ulcerated eyes by use of capillary tubes. The protease inhibitors 0.2% EDTA, 0.1% doxycycline, 10% N-acetylcysteine (NAC), 0.1% solution of a modified dipeptide that contains hydroxamic acid (ie, ilomostat), 0.1% α1-proteinase inhibitor (PI), 0.5% α1-PI, and 100% fresh equine serum (ES) were used to treat pooled samples. Amount of latent and active MMP-2 and -9 was measured by optical density scanning of gelatin zymograms of treated and untreated tear samples.

Results—Pooled tear samples obtained from ulcerated eyes contained the latent and active forms of MMP-2 and -9. Compared with MMP activity in untreated samples, total MMP activity (sum of all bands detected) observed on the gelatin zymogram gels was reduced by 99.4% by EDTA, 96.3% by doxycycline, 98.8% by NAC, 98.9% by ilomostat, 52.4% by 0.1% α1-PI, 93.6% by 0.5% α1-PI, and 90.0% by ES.

Conclusions and Clinical Relevance—We documented that EDTA, doxycycline, NAC, ilomostat, α1- PI, and ES inhibited MMP activity in vitro. Because these compounds use different mechanisms to inhibit various families of proteases in the tear film of horses, a combination of these protease inhibitors may be beneficial for treatment of corneal ulcers in horses. (Am J Vet Res 2003;64:1081–1087)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To characterize in vitro coagulation status in a cohort of dogs with extrahepatic biliary tract obstruction (EHBO) and to evaluate these patients for hypercoagulability by means of thromboelastography.

Design—Prospective cohort study.

Animals—10 dogs with EHBO and 19 healthy control dogs.

Procedures—Partial or complete EHBO was confirmed via exploratory celiotomy. Venous blood samples were collected for evaluation of prothrombin time (PT) and activated partial thromboplastin time (APTT); fibrinogen and D-dimer concentrations; protein C and antithrombin activities; and factor VII, VIII, and XI coagulant activities in plasma as well as thromboelastography in whole blood. Thromboelastography variables were measured from the thromboelastography tracing, and a coagulation index was calculated. Thromboelastography results were compared with those of healthy control dogs previously evaluated by the same laboratory.

Results—Hypercoagulability was diagnosed in all dogs with EHBO on the basis of a high coagulation index. Thromboelastography variables, including maximal amplitude, α-angle, and coagulation index, were significantly higher, and K (clot formation time) and R (reaction time) were significantly lower in these dogs than in control dogs. All dogs with EHBO had PT and APTT within respective reference ranges. Plasma D-dimer and fibrinogen concentrations were above reference ranges in 8 and 7 dogs, respectively, and protein C and antithrombin activities were below reference ranges in 3 and 1 dogs, respectively.

Conclusions and Clinical Relevance—In vitro hypercoagulability was commonly detected in dogs with naturally occurring EHBO. The traditional view of EHBO as a disease that causes hypocoagulability may need to be reconsidered.

Full access
in Journal of the American Veterinary Medical Association