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Abstract

Objective—To compare the effects of 2 doses of cosyntropin (5 µg/kg vs 250 µg, IV) on serum concentrations of cortisol, sex hormones of adrenal origin, and adrenocortical steroid intermediates and determine the optimal sample collection time after adrenal stimulation with cosyntropin.

Animals—10 healthy, privately owned, neutered dogs.

Procedure—Dogs were randomly assigned to initially receive cosyntropin at 5 µg/kg or as a total dose of 250 µg, IV. Dogs received the alternate dose 1 to 2 weeks later. Serum was obtained from blood samples collected before (0 minutes) and 30, 60, 90, and 120 minutes after cosyntropin administration.

Results—Maximum stimulation of cortisol, androstenedione, progesterone, and 17-hydroxyprogesterone production was achieved at 60 minutes following IV administration of cosyntropin at 5 µg/kg or as a total dose of 250 µg. Serum estradiol concentration did not increase in response to either cosyntropin dose. For all hormones, no significant difference in serum hormone concentrations was found among sample collection times of 0, 30, 60, and 90 minutes when comparing the 2 doses of cosyntropin.

Conclusions and Clinical Relevance—Cosyntropin, when administered at 5 µg/kg, IV, effectively stimulated maximum production of cortisol, sex hormones of adrenal origin, and adrenocortical steroid intermediates at 1 hour after administration. (Am J Vet Res 2004;65:1631–1633)

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in American Journal of Veterinary Research

Abstract

Objective—To determine whether the stress of an ultrasonographic procedure would interfere with the suppressive effect of dexamethasone during a lowdose dexamethasone suppression test (LDDST) in healthy dogs.

Animals—6 clinically normal adult dogs.

Procedure—In phase 1, an LDDST was performed 5 times at weekly intervals in each dog. Serum samples were obtained 0, 2, 4, 6, and 8 hours after dexamethasone injection. A mock 20-minute abdominal ultrasonographic examination was performed on all dogs at each time point during the LDDST on weeks 2 through 5. In phase 2, serum cortisol concentrations were measured before and immediately after a 20-minute mock abdominal ultrasonographic examination, as described for phase 1.

Results—We did not detect significant differences after dexamethasone injection when comparing median cortisol concentrations for weeks 2 to 5 (mock ultrasonographic procedure) with median concentration for week 1 (no mock ultrasonographic procedure). For 5 of the 6 dogs, cortisol concentrations after dexamethasone injection decreased to < 35.9 nmol/L after each mock ultrasonographic procedure and remained low for the duration of the LDDST. In phase 2, all dogs had significant increases in cortisol concentrations immediately after the mock ultrasonographic procedure.

Conclusions and Clinical Relevance—A 20-minute mock abdominal ultrasonographic examination performed during LDDST did not alter results of the LDDST in most dogs. Cortisol concentrations measured immediately after a mock ultrasonographic examination were significantly increased. Ultrasonographic procedures should be performed a minimum of 2 hours before collection of samples that will be used to measure cortisol concentrations. ( Am J Vet Res 2004;65:267–270)

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in American Journal of Veterinary Research

Abstract

Objective—To evaluate effects of trimethoprim-sulfamethoxazole (T/SMX) on thyroid function in dogs.

Animals—6 healthy euthyroid dogs.

Procedure—Dogs were administered T/SMX (14.1 to 16 mg/kg, PO, q 12 h) for 3 weeks. Blood was collected weekly for 6 weeks for determination of total thyroxine (TT4), free thyroxine (fT4), and canine thyroid- stimulating hormone (cTSH) concentrations. Schirmer tear tests were performed weekly. Blood was collected for CBC prior to antimicrobial treatment and at 3 and 6 weeks.

Results—5 dogs had serum TT4 concentrations equal to or less than the lower reference limit, and 4 dogs had serum fT4 less than the lower reference limit after 3 weeks of T/SMX administration; cTSH concentrations were greater than the upper reference limit in 4 dogs. All dogs had TT4 and fT4 concentrations greater than the lower reference limit after T/SMX administration was discontinued for 1 week, and cTSH concentrations were less than reference range after T/SMX administration was discontinued for 2 weeks. Two dogs developed decreased tear production, which returned to normal after discontinuing administration.

Conclusions and Clinical Relevance—Results suggest that administration of T/SMX at a dosage of 14.1 to 16 mg/kg, PO, every 12 hours for 3 weeks caused decreased TT4 and fT4 concentrations and increased cTSH concentration, conditions that would be compatible with a diagnosis of hypothyroidism. Therefore, dogs should not have thyroid function evaluated while receiving this dosage of T/SMX for > 2 weeks. These results are in contrast to those of a previous study of trimethoprim- sulfadiazine. (Am J Vet Res 2005;66:256–259)

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in American Journal of Veterinary Research

Abstract

Objective—To determine the methicillin-resistant profile of staphylococcal isolates from the skin of dogs with pyoderma.

Animals—90 dogs with pyoderma.

Procedure—Staphylococci isolated from dogs with pyoderma were tested for susceptibility to methicillin by use of a standard disk diffusion test with oxacillin disks. The DNA extracted from the isolates was tested for the mecA gene that encodes the penicillinbinding protein 2a (PBP2a) by use of a polymerase chain reaction (PCR) assay. The expression of PBP2a was determined with a commercial latex agglutination assay. Species of staphylococcal isolates were identified by use of morphologic, biochemical, and enzymatic tests.

Results—Most of the isolated staphylococci were methicillin-susceptible, coagulase-positive Staphylococcus intermedius isolates. Whereas only 2 of 57 S intermedius isolates were resistant to methicillin, approximately half of the isolates had the mecA gene and produced PBP2a. Staphylococcus schleiferi was the second most common isolate. Widespread resistance to methicillin was found among S schleiferi isolates. More coagulase-negative S schleiferi isolates were identified with mecA gene-mediated resistance to methicillin, compared with coagulase-positive S schleiferi isolates.

Conclusions and Clinical Relevance—The latex agglutination assay for the detection of PBP2a expression coupled with the PCR assay for the mecA gene may provide new information about emerging antimicrobial resistance among staphylococcal isolates. (Am J Vet Res2004;65:1265–1268)

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in American Journal of Veterinary Research

Abstract

Objective—To characterize the L1 gene of papillomaviruses detected in epithelial lesions of cats and to determine the relationship between those L1 gene nucleotide sequences and known L1 gene sequences of human and feline papillomaviruses.

Sample Population—10 tissue samples of epithelial lesions from 8 cats.

Procedures—DNA was extracted from tissue samples. Primers were designed to amplify the L1 gene of papillomaviruses. Amplicons of DNA were sequenced; nucleotide sequences were compared with known L1 gene nucleotide sequences of papillomaviruses and used for phylogenetic analysis.

Results—Tissue samples were obtained from lesions (diagnosed as dysplasia [n = 1], squamous cell carcinoma in situ [3], or squamous cell carcinoma [6]) of the skin (9) and oral mucosa [1]. Two amplicons had 99% homology with the L1 gene nucleotide sequence of human papillomavirus type 38b subtype FA125. Another amplicon had 84% homology with the L1 gene nucleotide sequence of human papillomavirus type 80 and was considered to be a new type of papillomavirus. Phylogenetic tree analysis revealed that these 3 papillomaviruses were grouped into 2 clades that were not similar to the clades of Felis domesticus papillomavirus type 1 or F domesticus papillomavirus type 2 (FdPV2). The remaining 7 amplicons had 98% to 100% homology with the L1 gene nucleotide sequence of FdPV2. Phylogenetic tree analysis revealed that those 7 papillomaviruses were grouped nto a single clade with FdPV2.

Conclusions and Clinical Relevance—Results support the likelihood of transmission of papillomaviruses between humans and cats.

Full access
in American Journal of Veterinary Research