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in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine glycosaminoglycan (GAG) concentration and immunohistochemical staining characteristics of type-I, -II, and -X collagen from cartilage affected by osteochondritis dissecans (OCD) in dogs.

Animals—31 dogs with OCD and 11 clinically normal purpose-bred dogs.

Procedure—Cartilage samples were evaluated microscopically, and GAG content was determined. Immunohistochemical staining was performed for type-I, -II, and -X collagen. Sections were subjectively evaluated for location and intensity of staining.

Results—Cartilage affected by OCD had a variety of pathologic changes and significantly lower GAG concentrations than did normal cartilage. Normal cartilage had no detectable type-I collagen. For dogs < 9 months of age, cartilage affected by OCD had significantly more type-I collagen but significantly less type- X collagen than did control cartilage. For dogs > 12 months of age, cartilage affected by OCD contained significantly more type-I collagen than did control cartilage. There was a significant negative correlation between immunoreactivity of type-I collagen and that of type-II and -X collagen. A significant positive correlation was found between immunoreactivity of type-II and -X collagen.

Conclusions and Clinical Relevance—Cartilage affected by OCD contains less GAG, more type-I collagen, and less type-X collagen, compared with normal cartilage. A direct correlation between these changes and the etiopathogenesis of OCD was not established. (Am J Vet Res 2001;62:876–881)

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in American Journal of Veterinary Research

Summary

Ninety-five aborted bovine fetuses received from California dairies over a 4.5-year period had histologic lesions of focal encephalitis. Protozoa that reacted with Neospora caninum antiserum were detected in the brain of 88 of these fetuses and in the heart of 1 fetus. Sarcocystis spp schizonts were seen in the vascular endothelium of 1 fetus. It was concluded that a Neospora-like cyst-forming coccidian may be a major cause of abortion in California dairy cattle.

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in Journal of the American Veterinary Medical Association

Abstract

Case Description—A healthy 6-year-old 28.5-kg (62.7-lb) spayed female Boxer undergoing surgical repair of a ruptured cranial cruciate ligament was inadvertently administered an overdose of morphine (1.3 mg/kg [0.59 mg/lb]) via subarachnoid injection.

Clinical Findings—50 minutes after administration of the overdose, mild multifocal myoclonic contractions became apparent at the level of the tail; the contractions migrated cranially and progressively increased in intensity and frequency during completion of the surgery.

Treatment and Outcome—The myoclonic contractions were refractory to treatment with midazolam, naloxone, phenobarbital, and pentobarbital; only atracurium (0.1 mg/kg [0.045 mg/lb], IV) was effective in controlling the movements. The dog developed hypertension, dysphoria, hyperthermia, and hypercapnia. The dog remained anesthetized and ventilated mechanically; treatments included continuous rate IV infusions of propofol (1 mg/kg/h [0.45 mg/lb/h]), diazepam (0.25 mg/kg/h [0.11 mg/lb/h]), atracurium (0.1 to 0.3 mg/kg/h [0.045 to 0.14 mg/lb/h]), and naloxone (0.02 mg/kg/h [0.009 mg/lb/h]). Twenty-two hours after the overdose, the myoclonus was no longer present, and the dog was able to ventilate without mechanical assistance. The dog remained sedated until 60 hours after the overdose, at which time its mentation improved, including recognition of caregivers and response to voice commands. No neurologic abnormalities were detectable at discharge (approx 68 hours after the overdose) or at a recheck evaluation 1 week later.

Clinical Relevance—Although intrathecal administration of an overdose of morphine can be associated with major and potentially fatal complications, it is possible that affected dogs can completely recover with immediate treatment and extensive supportive care.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To assess IgE response and cytokine gene expressions in pulmonary lymph collected from bovine respiratory syncytial virus (BRSV)-infected calves after ovalbumin inhalation.

Animals—Thirteen 7- to 8-week-old calves.

Procedures—The efferent lymphatic duct of the caudal mediastinal lymph node of each calf was cannulated 3 or 4 days before experiment commencement. Calves were inoculated (day 0) with BRSV (n = 7) or BRSV-free tissue culture medium (mock exposure; 6) via aerosolization and exposed to aerosolized ovalbumin on days 1 through 6 and day 15. An efferent lymph sample was collected daily from each calf on days −1 through 16; CD4+ and CD8+ T lymphocyte subsets in lymph samples were enumerated with a fluorescence-activated cell scanner. Expressions of several cytokines by efferent lymphocytes and lymph ovalbumin-specific IgE concentration were measured. Each calf was euthanized on day 16 and then necropsied for evaluation of lungs.

Results—Mean fold increase in ovalbumin-specific IgE concentration was greater in BRSV-infected calves than in mock-infected calves. At various time points from days 4 through 10, percentages of T lymphocyte subsets and CD4+:CD8+ T lymphocyte ratios differed between BRSV-infected calves and day −1 values or from values in mock-infected calves. On days 3 through 5, IL-4 and IL-13 gene expressions in BRSV-infected calves were increased, compared with expressions in mock-infected calves. Lung lesions were consistent with antigen exposure.

Conclusions and Clinical Relevance—In response to the inhalation of aerosolized ovalbumin, BRSV infection in calves appeared to facilitate induction of a T helper 2 cell response and ovalbumin-specific IgE production.

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in American Journal of Veterinary Research

Abstract

Objective

A microbial receptor assay method (MRAM; Charm II test) for β-lactam antibiotics and a liquid chromatography (LC) method with a detection limit of 2 to 5 ppb were evaluated for detection of ampicillin or amoxicillin residues in milk samples from individuell cows.

Design

The MRAM was compared to the LC in 2 respects. Measured concentrations of drugs were compared, as well as the classification of samples relative to the FDA tolerance value of 10 ppb.

Animals

A total of 6 clinically normal lactating Holstein cows were used per drug.

Procedure

Ampicillin trihydrate or amoxicillin trihydrate was administered at an extra-label dosage of 22 mg/kg of body weight, IM, once to each of 6 cows/drug. Milk samples were collected at milkings prior to and for 156 hours after drug administration. Drug concentrations in milk samples from individual cows were determined by use of the MRAM and LC tests. Additionally, the classification of milk samples relative to the presence or absence of residues above the FDA tolerance value was determined. Pharmacokinetic analysis was performed on derived milk drug concentrations.

Results

Concentration of ampicillin in milk samples from all cows was < 10 ppb by the MRAM and LC methods by the fourth milking (48 hours) after treatment with ampicillin. Values were < 10 ppb by both methods for all cows treated with amoxicillin by the sixth milking (72 hours) after treatment. For individual milk samples, significant differences were found between test methods in the proportion of positive (failing) tests; the MRAM had a higher proportion of presumptive positives.

Conclusions

Even at an extra-label dosage of 22 mg/kg, IM, milk residues > 10 ppb (the FDA tolerance value) were not detected beyond the label milk withholding times for ampicillin (48 hours) and amoxicillin (96 hours). When used for testing milk of individual cows by the control point procedure, the MRAM had a tendency to give presumptive positive test results for milk samples containing < 10 ppb ampicillin or amoxicillin as determined by LC. (Am J Vet Res 1996;57:73-78)

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in American Journal of Veterinary Research

SUMMARY

Milk antimicrobial residues are a serious concern for the dairy industry. Residues of the tetracycline family of antimicrobials have been reported in market milk by investigators, using radioimmunoassay and microbial receptor technology (hereafter referred to as the Charm II test). In response to these reports, an investigation was conducted to determine the potential of 3 extra-label routes of oxytetracycline (otc) administration to cause milk residues above the Food and Drug Administration safe value of 30 parts per billion (ppb). Lactating Holstein cows were administered otc once by use of 1 of 3 routes: iv at 16.5 mg/kg of body weight (n = 6); im at 11 mg/kg (n = 6); and intrauterine (iu) at 2 g in 500 ml of saline solution/cow (n = 6). Duplicate milk samples were collected at the milking prior to drug administration and for the next 13 milkings at 12-hour intervals. Concentrations of otc in milk samples were analyzed by use of the Charm II test for tetracyclines (lmit of otc detection, approx 5 ppb) and were compared with concentrations determined by use of a high-performance lquid chromatography (hplc) method (lower lmit of otc quantitation, approx 2 ppb).

The potential for milk otc residues above the Food and Drug Administration safe value of 30 ppb after treatment was considerably greater for the iv and im routes, compared with the iu route. Mean peak otc concentrations in milk at the first milking after treatment for the hplc and Charm II tests were approximately 3,700 to 4,200 ppb for the iv route, 2,200 to 2,600 ppb for the im route, and 186 to 192 ppb for the iu route, respectively.

Pharmacokinetic analysis, based on milk otc concentrations, indicated that the area under the curve (auc) and milk maximal concentration (Cmax) differed significantly (P < 0.001) among routes of administration. The auc was similar for iv and im administrations; values for both were greater than the auc for iu administration. The Cmax was greatest for iv, intermediate for im, and least for iu administration. There were significant (P ≤ 0.01) differences in auc between assay methods (Charm II vs hplc) for the iv route. Concentrations of otc in milk determined by the Charm II test were often greater than those determined by hplc.

Administration of otc to lactating cows via these routes is extra-label drug use. Failure to withhold the product from early milkings of cows administered otc by the iv or im route should be considered a potential cause of otc residues in market milk. Milk from nearly all cows contained otc (< 30 ppb), the Food and Drug Administration safe level, by 120 hours after otc administration. Use of appropriate withholding times and antibiotic residue testing is indicated to avoid otc residues.

Free access
in American Journal of Veterinary Research