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Annual Meeting Information

Veterinary Student Poster Awards

Clinical Disease

Ryan P. Traslavina, Cornell University

EFFECTS OF PRE-ANALYTICAL HANDLING ON SERUM POTASSIUM LEVELS OF HEALTHY LABORATORY MICE.
Ryan P. Traslavina1, Edward King2, Andrew Loar2, Rodolfo Ricart-Arbona3, Felix Wolf3, and Suzana S. Couto3
1Cornell University College of Veterinary Medicine, Ithaca; 2ALX Laboratory, New York; and3Tri-institutional Laboratory of Comparative Pathology & Genetically Engineered Mouse Phenotyping Service, Memorial Sloan-Kettering Cancer Center, New York, NY

Unusually high serum potassium (K+) levels have been reported in healthy mice during routine diagnostic screenings by the Laboratory of Comparative Pathology at Memorial Sloan-Kettering Cancer Center and anecdotally at other institutions. Normal reference range for adult mice is cited as 8.0±0.85 mEq/L in the literature even though such high values are inconsistent with life for most species. The purpose of this study was to elucidate the source of these results in order to differentiate artifactually high serum K+ levels from true hyperkalemia in laboratory mice. Variables tested include site of collection, time allowed for clot formation before serum separation, time elapsed between collection and analysis of samples collected in a serum separator tube, and pre-collection method of anesthesia and/or euthanasia employed. Serum K+ was measured from a total of 75 female ten-week old C57BL/6 mice divided into groups of at least 5 mice per variable. Comparisons were made using the Wilcoxon Rank Sum Test. Animals were sacrificed by exsanguination immediately following terminal CO2 or Ketamine-Xylazine administration. Mice euthanized by CO2 had a significantly higher mean (antemortem) serum K+ (7.0±0.5mEq/L, p<0.0001), range serum K+ (6.0-8.1), and bicarbonate levels (22.4±1.5mEq/L, p=0.002) than Ketamine-Xylazine treated animals, which had a lower mean serum K+ (3.8±0.3mEq/L), range serum K+ (3.5-4.6) and mean bicarbonate levels (17.7±1.3mEq/L). CO2 euthanasia resulted in significantly lower blood pH (6.9 ±0.1, p=0.0001), higher pCO2 (153.3±38.8mmHg, p=0.0003) and lactate levels (3.9±0.9mmol/L, p=0.002) than Ketamine-Xylazine anesthesia followed by exsanguination (7.2±0.1, 61.6±14.8mmHg, and 2.1±0.8mmol/L, respectively). These results suggest that antemortem respiratory acidosis resulting from CO2 administration causes artifactual hyperkalemia in mice. Blood collection under Ketamine-Xylazine anesthesia is recommended to obtain accurate electrolyte values in mice.

Experimental Disease

Cynthia Willson, North Carolina State University

PROTEIN EXPRESSION CHANGES DURING BLADDER TUMOR DEVELOPMENT INDUCED BY O-NITROANISOLE IN F344 RATS.
Cynthia J. Willson 1, 2, Robert C. Sills2, Tiwanda Masinde2, Natasha Clayton2, and Mark F. Cesta2
1NC State University College of Veterinary Medicine, Raleigh, NC and 2Cellular and Molecular Pathology Branch, NIEHS, NIH, DHHS, Research Triangle Park, NC

Bladder cancer, the 5th most common cancer in humans, develops via two pathways, nonpapillary and papillary. The majority of bladder transitional cell carcinomas (TCCs) are believed to arise via the papillary pathway, from hyperplasia to papilloma and then to carcinoma. In TCCs of the urinary bladder, the putative proto-oncogene Cyclin D1 and differentiation markers Cytokeratin-20 (CK 20) and Uroplakin III (UP III) have been implicated in neoplastic growth or transformation. Using immunohistochemistry, protein expression and distribution patterns were evaluated for Cyclin D1, CK 20, and UP III in normal (n=6), hyperplastic (n=11), and neoplastic (n=7 papillomas, n=11 carcinomas) urinary bladder epithelium from male F344 rats. Samples were from rats that had been treated with o-nitroanisole, an intermediate in the preparation of o-anisidine and the manufacture of azo dyes, and from untreated rats. Cyclin D1 expression in normal bladders was weak and limited to basal epithelial cells. With progression from hyperplasias to papillomas to carcinomas, Cyclin D1 expression progressively increased in intensity, percentage of cells, and distribution. CK 20 expression occurred only in the superficial cell layer in normal bladder epithelium, and expression decreased as tumor development increased from hyperplasia to papilloma to carcinoma. UP III expression persisted in superficial cells but increased in intermediate cells with tumor development and progression, from 0% in normal bladders to 25% of hyperplasias, 50% of papillomas, and 91% of carcinomas. Changes in protein expression suggest increased possible oncogene activity and decreased differentiation and corresponded to tumor development along the papillary pathway of bladder carcinogenesis found in humans.

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