Objective—To determine the effects of dexamethasone or synthetic ACTH administration on endogenous ACTH concentrations in healthy dogs. Animals—10 healthy neutered dogs. Procedures—Each dog received dexamethasone (0.01 mg/kg), synthetic ACTH (5 μg/kg), or saline (0.9% NaCl) solution (0.5 mL) IV at intervals of ≥ 30 days. Plasma endogenous ACTH concentrations were measured before (baseline; time 0) and 1, 8, 12, and 24 hours after drug administration; serum cortisol concentrations were measured before and 1 hour after synthetic ACTH and saline solution administration and 8 hours after dexamethasone administration. Results—Analysis of serum cortisol concentrations confirmed effects of drug administration. Dexamethasone significantly decreased the endogenous ACTH concentration from the baseline value at both 8 and 12 hours. Synthetic ACTH administration significantly decreased the endogenous ACTH concentration from the baseline value at 8 hours. Saline solution administration had no significant effect on endogenous ACTH concentration. Conclusions and Clinical Relevance—Dexamethasone and synthetic ACTH administered IV at doses used routinely during testing for hyperadrenocorticism caused significant but transient reductions of endogenous ACTH concentrations in healthy dogs. Thus, a 2-hour washout period following ACTH stimulation testing before collection of samples for measurement of the endogenous ACTH concentration may be insufficient. Although this effect has not been verified in dogs with hyperadrenocorticism, these data suggested that samples for measurement of endogenous ACTH concentrations should be obtained before or > 8 hours after initiation of an ACTH stimulation test or before or > 12 hours after the start of a low-dose dexamethasone suppression test.

Objective-To compare pathological changes and viral antigen distribution in tissues of calves with and without preexisting subclinical bovine viral diarrhea virus (BVDV) infection following challenge with bovine herpesvirus-1 (BHV-1). Animals-24 Friesian calves. Procedures-12 calves were inoculated intranasally with noncytopathic BVDV-1a; 12 days later, 10 of these calves were challenged intranasally with BHV-1 subtype 1. Two calves were euthanized before and 1, 2, 4, 7, or 14 days after BHV-1 inoculation. Another 10 calves were inoculated intranasally with BHV-1 only and euthanized 1, 2, 4, 7, or 14 days later. Two calves were inoculated intranasally with virus-free tissue culture fluid and euthanized as negative controls. Pathological changes and viral antigen distribution in various tissue samples from calves with and without BVDV infection (all of which had been experimentally inoculated with BHV-1) were compared. Results-Following BHV-1 challenge, calves with preexisting subclinical BVDV infection had earlier development of more severe inflammatory processes and, consequently, more severe tissue lesions (limited to lymphoid tissues and respiratory and digestive tracts) and greater dissemination of BHV-1, compared with calves without preexisting BVDV infection. Moreover, coinfected calves had an intense lymphoid depletion in the Peyer patches of the ileum as well as the persistence of BVDV in target organs and the reappearance of digestive tract changes during disease progression. Conclusions and Clinical Relevance-In calves, preexisting infection with BVDV facilitated the establishment of BHV-1 infection, just as the presence of BHV-1 favors BVDV persistence, thereby synergistically potentiating effects of both viruses and increasing the severity of the resultant clinical signs.

Objective-To compare presumed fatty acid content in natural diets of feral domestic cats (inferred from body fat polyunsatrated fatty acids content) with polyunsaturated fatty acid content of commercial feline extruded diets. Sample-Subcutaneous and intra-abdominal adipose tissue samples (approx 1 g) from previously frozen cadavers of 7 adult feral domestic cats trapped in habitats remote from human activity and triplicate samples (200 g each) of 7 commercial extruded diets representing 68% of market share obtained from retail stores. Procedures-Lipid, triacylglycerol, and phospholipid fractions in adipose tissue samples and ether extracts of diet samples were determined by gas chromatography of methyl esters. Triacylglycerol and phospholipid fractions in the adipose tissue were isolated by thin-layer chromatography. Diet samples were also analyzed for proximate contents. Results-For the adipose tissue samples, with few exceptions, fatty acids fractions varied only moderately with lipid fraction and site from which tissue samples were obtained. Linoleic, α-linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic acid fractions were 15.0% to 28.2%, 4.5% to 18.7%, 0.9% to 5.0%, < 0.1% to 0.2%, and 0.6% to 1.7%, respectively. As inferred from the adipose findings, dietary fractions of docosahexaenoic and α-linolenic acid were significantly greater than those in the commercial feline diets, but those for linoleic and eicosapentaenoic acids were not significantly different. Conclusions and Clinical Relevance-The fatty acid content of commercial extruded feline diets differed from the inferred content of natural feral cat diets, in which dietary n-3 and possibly n-6 polyunsaturated fatty acids were more abundant. The impact of this difference on the health of pet cats is not known.

Objective: To determine the antinociceptive and sedative effects of tramadol in Hispaniolan Amazon parrots (Amazona ventralis) following IV administration. Animals: 11 healthy Hispaniolan Amazon parrots of unknown sex. Procedures: Tramadol hydrochloride (5 mg/kg, IV) and an equivalent volume (≤ 0.34 mL) of saline (0.9% NaCl) solution were administered to parrots in a complete crossover study design. Foot withdrawal response to a thermal stimulus was determined 30 to 60 minutes before (baseline) and 15, 30, 60, 120, and 240 minutes after treatment administration; agitation-sedation scores were determined for parrots at each of those times. Results: The estimated mean changes in temperature from the baseline value that elicited a foot withdrawal response were 1.65° and −1.08°C after administration of tramadol and saline solution, respectively. Temperatures at which a foot withdrawal response was elicited were significantly higher than baseline values at all 5 evaluation times after administration of tramadol and were significantly lower than baseline values at 30, 120, and 240 minutes after administration of saline solution. No sedation, agitation, or other adverse effects were observed in any of the parrots after administration of tramadol. Conclusions and Clinical Relevance: Tramadol hydrochloride (5 mg/kg, IV) significantly increased the thermal nociception threshold for Hispaniolan Amazon parrots in the present study. Sedation and adverse effects were not observed. These results are consistent with results of other studies in which the antinociceptive effects of tramadol after oral administration to parrots were determined.

Objective: To measure platelet membrane–derived microparticle (PMP) content and thrombin-generating capacity of canine plasma subjected to specific processing and storage conditions. Animals: 31 clinically normal dogs (19 males and 12 females). Procedures: Citrate-anticoagulated blood samples obtained from each dog were centrifuged at 2,500 × g to isolate platelet-poor plasma (PPP), then PPP was centrifuged at 21,000 × g to isolate microparticle-free plasma (MPF) and microparticle-enriched plasma (MPEP). Whole blood and paired samples of fresh and frozen-thawed PPP, MPF, and MPEP were dual labeled for flow cytometric detection of membrane CD61 (constitutive platelet antigen) and annexin V (indicating phosphatidylserine externalization). Platelets and PMPs were enumerated with fluorescent, size-calibrated beads. Thrombin generation in fresh and frozen-thawed PPP, MPF, and MPEP was measured via kinetic fluorometric assays configured with low tissue factor and low phospholipid concentrations. Results: Initial centrifugation yielded PPP with < 0.5% the platelets of whole blood, with median counts of 413 PMPs/μL for males and 711 PMPs/μL for females. Sequential centrifugation resulted in a 10-fold concentration of PMPs in MPEP and virtually depleted PMPs from MPF. Thrombin generation depended on PMP content, with median endogenous thrombin potential of 0, 893, and 3,650 nmol•min for MPF, PPP, and MPEP, respectively. Freeze-thaw cycling caused significant increases in PMP counts and phosphatidylserine externalization. Conclusions and Clinical Relevance: Canine PMPs were major determinants of thrombin-generating capacity; preanalytic variables influenced plasma PMP content. Processing conditions described here may provide a basis for characterization of PMPs in clinical studies of thrombosis in dogs.

Objective: To compare acoustic startle reflexes (ASRs) of healthy cats and cats with interstitial cystitis (IC). Animals: 28 healthy cats (11 males and 17 females) and 20 cats with IC (13 males and 7 females). Procedures: To evaluate the effect of neutering on ASRs, ASRs in neutered and unneutered healthy cats were measured. To evaluate the effect of housing facility acclimation on ASRs in cats with IC, ASRs were measured in cats with IC within 1 month after arrival at the housing facility and again 2 to 3 months after arrival. To evaluate the effect of the environment on ASRs, ASRs were evaluated in all cats with and without IC after acclimation but before and then after environmental enrichment. Results: Neutering led to a significant decrease in overall ASR in the healthy cats. Habituation to the housing facility resulted in a significant decrease in overall ASR of female but not male cats with IC. Environmental enrichment led to a significant decrease in ASR in cats with IC but not in healthy cats. Conclusions and Clinical Relevance: The magnitude of the ASR appeared to be sensitive to environmental conditions and affected by sex, both in healthy cats and cats with IC. It was also higher in cats with IC versus healthy cats, except when cats were housed in a highly enriched environment. Impact for Human Medicine: Treatment approaches that include reduction of a patient's perception of environmental unpredictability may benefit humans with IC.

Objective-To compare the efficacy of gamithromycin with that of tulathromycin for the treatment of undifferentiated bovine respiratory disease complex (BRDC) in feedlot calves. Animals-1,049 weaned crossbred beef calves. Procedures-At each of 6 feedlots, newly arrived calves with BRDC were administered a single dose of gamithromycin (6.0 mg/kg, SC; n = 523) or tulathromycin (2.5 mg/kg, SC; 526). Case-fatality and BRDC retreatment rates during the first 120 days after treatment, final body weight, and average daily gain (ADG), were compared between treatments. At 2 feedlots, calves were assigned clinical scores for 10 days after treatment to determine recovery rates for each treatment. Bioequivalence limits for gamithromycin and tulathromycin were calculated for outcomes for which there was no significant difference between treatments. Results-Mean BRDC retreatment rate (17.7%) for calves administered gamithromycin was greater than that (9.0%) for calves administered tulathromycin. Mean case-fatality rate, final body weight, ADG, and clinical score 10 days after treatment did not differ significantly between treatments. Limits for mean differences within which gamithromycin was bioequivalent to tulathromycin were +/- 2.4% for case-fatality rate, +/- 13 kg for final body weight, and +/- 0.1 kg/d for ADG. Conclusions and Clinical Relevance-Calves administered gamithromycin had a higher BRDC retreatment rate than did calves administered tulathromycin; otherwise, the clinical efficacy did not differ between the 2 treatments for the treatment of BRDC in feedlot calves.

Objective—To evaluate the accuracy of digitally scanned rhodanine-stained liver biopsy specimens for determination of hepatic copper concentration and compare results with qualitatively assigned histologic copper scores in dogs. Sample—353 liver biopsy specimens from dogs. Procedures—Specimens (n = 139) with quantified copper concentration ranging from 93 to 6,900 μg/g were allocated to group 1 (< 400 μg/g [37]), group 2 (401 to 1,000 μg/g [27]), group 3 (1,001 to 2,000 μg/g [34]), and group 4 (> 2,001 μg/g [41]); stained with rhodanine; and digitally scanned and analyzed with a proprietary positive pixel algorithm. Measured versus calculated copper concentrations were compared, and limits of agreement determined. Influence of nodular remodeling, fibrosis, or parenchymal loss on copper concentration was determined by digitally analyzing selected regions in 17 specimens. After method validation, 214 additional liver specimens underwent digital scanning for copper concentration determination. All sections (n = 353) were then independently scored by 2 naive evaluators with a qualitative scoring schema. Agreement between assigned scores and between assigned scores and tissue copper concentrations was determined. Results—Linear regression was used to develop a formula for calculating hepatic copper concentration ≥ 400 μg/g from scanned sections. Copper concentrations in unremodeled specimens were significantly higher than in remodeled specimens. Qualitative scores widely overlapped among quantitative copper concentration groups. Conclusions and Clinical Relevance—Calculated copper concentrations determined by means of digital scanning of rhodanine-stained liver sections were highly correlated with measured values and more accurate than qualitative copper scores, which should improve diagnostic usefulness of hepatic copper concentrations and assessments in sequential biopsy specimens.

Objective—To determine the association between urine osmolality and specific gravity (USG) in dogs and to evaluate the effect of commonly measured urine solutes on that association. Animals—60 dogs evaluated by an internal medicine service. Procedures—From each dog, urine was obtained by cystocentesis and USG was determined with a refractometer. The sample was divided, and one aliquot was sent to a diagnostic laboratory for urinalysis and the other was frozen at −80°C until osmolality was determined. Urine samples were thawed and osmolality was measured in duplicate with a freezing-point depression osmometer. The correlation between mean urine osmolality and USG was determined; the effect of pH, proteinuria, glucosuria, ketonuria, bilirubinuria, and hemoglobinuria on this relationship was investigated with multiple regression analysis. Results—The Pearson correlation coefficient between urine osmolality and USG was 0.87. The final multivariable regression model for urine osmolality included USG and the presence of ketones; ketonuria had a small negative association with urine osmolality. Conclusions and Clinical Relevance—Results indicated a strong linear correlation between osmolality and USG in urine samples obtained from dogs with various pathological conditions, and ketonuria had a small negative effect on that correlation.