David G Besselsen

David G Besselsen

Veterinary Specialist
Adjunct Associate Professor, Animal and Comparative Biomedical Sciences
Associate Research Scientist, BIO5 Institute
Member of the General Faculty
Member of the Graduate Faculty
Primary Department
Contact
(520) 626-6702

Research Interest

David Besselsen, DVM, PhD, is the Director of University Animal Care (UAC), the Attending Veterinarian. He is a board-certified veterinary specialist (Diplomate) in the American College of Laboratory Animal Medicine and the American College of Veterinary Pathology, and served as Interim Dean for the College of Veterinary Medicine from 2017-2019. In addition to his administrative and service responsibilities, Dr. Besselsen is actively engaged in research through the provision of comparative pathology support for rodent models and oversight of the gnotobiotic mouse service. He has directed UAC Pathology Services since his arrival in 1995 and has over 80 peer-reviewed publications. UAC Pathology Services provides diagnostic and comparative pathology support for the research animals and research animal facilities at the University of Arizona. Capabilities include hematology, blood chemistry, necropsy, histologic preparation and interpretation, and others.

Publications

Besselsen, D., Wagner, A. M., Loganbill, J. K., & Besselsen, D. G. (2004). Detection of lactate dehydrogenase-elevating virus by use of a fluorogenic nuclease reverse transcriptase-polymerase chain reaction assay. Comparative medicine, 54(3).

Lactate dehydrogenase-elevating virus (LDEV) induces persistent infections in laboratory mice, alters in vivo physiology, and is a common contaminant of biological materials such as transplantable tumor cell lines. The fluorogenic nuclease reverse transcriptase polymerase chain reaction (fnRT-PCR) assay combines RT-PCR analysis with an internal fluorogenic hybridization probe, thereby eliminating post-PCR processing and potentially enhancing specificity. An fnRT-PCR assay specific for LDEV was therefore developed by targeting primer and probe sequences to a unique region of the LDEV nucleocapsid (VP1) gene. Using the LDEV fnRT-PCR assay, we detected only LDEV and did not detect other RNA viruses that are capable of naturally infecting rodents. Using this assay, we detected as little as 10 fg of LDEV RNA; the assay was 10-fold less sensitive when directly compared with the mouse bioassay (measurement of serum LD after inoculation), without the problematic false-positive serum LD enzyme elevations associated with the mouse bioassay. Using the fnRT-PCR assay, we also were able to detect viral RNA in numerous tissues and in feces collected from experimentally inoculated C3H/HeN mice, but we did not detect any viral RNA in similar samples collected from age- and strain-matched mock-infected mice. Finally, using the fnRT-PCR assay, we were able to detect LDEV RNA in biological samples that had previously been determined to be contaminated with LDEV by use of the mouse bioassay and an RT-PCR assay at another laboratory. In conclusion, the LDEV fnRT-PCR assay is a potentially high-throughput diagnostic assay for detection of LDEV in mice and contaminated biological materials.

Flowers, M., Schroeder, J. A., Borowsky, A. D., Besselsen, D. G., Thomson, C. A., Pandey, R., & Thompson, P. A. (2010). Pilot study on the effects of dietary conjugated linoleic acid on tumorigenesis and gene expression in PyMT transgenic mice. Carcinogenesis, 31(9).

Conjugated linoleic acid (CLA) is a class of commercially available fatty acids that have been associated with anticancer properties in rodent models of chemical carcinogenesis. We conducted a pilot study to examine the antitumor effect of dietary CLA in a polyoma virus-middle T antigen (PyMT) mouse model of invasive breast cancer. Virgin 4-week-old PyMT mice were administered a mixed-isomer CLA diet (1% wt/wt) or control AIN-93G diet for 4 weeks (N = 6 and 5, respectively) and tumor burden was assessed at 8 weeks of age. Thoracic mammary glands were prepared as whole mounts with other glands being formalin fixed and paraffin embedded for histology and immunohistochemistry (IHC). Total RNA was prepared for microarray and real-time reverse transcription-polymerase chain reaction analysis. Western blots were performed for protein expression analysis. Tumor incidence was significantly increased in CLA-treated animals compared with controls (P = 0.009) and occurred with extensive lobular-alveolar expansion and loss of mammary adipose tissue. More than 100 genes were downregulated > or = 2-fold in the CLA-treated group compared with controls, including adipose-specific markers, as wells as cytoskeletal and adhesion-related genes. This was supported by dramatic decreases in the epithelial adherens E-cadherin and beta-catenin as demonstrated by IHC. Taken together, these results suggest that dietary CLA affects the mammary stromal environment, leading to tumor progression and cellular expansion in the PyMT mouse model. Further studies of the potential for cancer promotion are needed, especially because mixed-isomer CLA formulations are sold commercially as a nutritional supplement.

Besselsen, D., Loganbill, J. K., Wagner, A. M., & Besselsen, D. G. (2005). Detection of Mycoplasma pulmonis by fluorogenic nuclease polymerase chain reaction analysis. Comparative medicine, 55(5).

Mycoplasma pulmonis induces persistent infections in laboratory mice and rats and can contaminate biological materials. We developed a fluorogenic nuclease polymerase chain reaction (fnPCR) assay to detect M. pulmonis specifically. Primer and probe sequences for the assay were targeted to 16S rRNA sequences specific to M. pulmonis. The assay consistently detected the equivalent of fewer than 10 copies of template DNA. When evaluated against a panel of 24 species of bacteria, the M. pulmonis assay detected only M. pulmonis isolates. Evaluation of 10-fold serial dilutions of cultured M. pulmonis showed that the M. pulmonis fnPCR assay and culture on Dutch agar had comparable sensitivity in detecting viable M. pulmonis organisms, whereas the mouse antibody production test displayed positive serologic results at dilutions higher than those in which viable organisms could be detected. Finally, the M. pulmonis fnPCR assay was able to detect M. pulmonis DNA in nasopharyngeal wash fluid and trachea, lung, and uterus tissue collected from mice naturally infected with M. pulmonis but did not detect the organism in similar samples collected from uninfected, negative control mice. The M. pulmonis fnPCR assay provides a high-throughput, PCR-based method to detect M. pulmonis in infected rodents and contaminated biological materials.

Thurston, R. D., Larmonier, C. B., Majewski, P. M., Ramalingam, R., Midura-Kiela, M., Laubitz, D., Vandewalle, A., Besselsen, D. G., Mühlbauer, M., Jobin, C., Kiela, P. R., & Ghishan, F. K. (2010). Tumor necrosis factor and interferon-gamma down-regulate Klotho in mice with colitis. Gastroenterology, 138(4).

Klotho (KL) is an anti-inflammatory protein that protects the endothelium from nitric oxide (NO)-induced dysfunction, reduces the expression of endothelial adhesion molecules, and potentially regulates T-cell functions. KL deficiency leads to premature senescence and impaired Ca2+/Pi homeostasis, which can lead to inflammatory bowel disease (IBD)-associated osteopenia/osteoporosis. We investigated the changes in renal expression of Kl as a consequence of colitis.

Fisher, C. D., Lickteig, A. J., Augustine, L. M., Oude Elferink, R. P., Besselsen, D. G., Erickson, R. P., & Cherrington, N. J. (2009). Experimental non-alcoholic fatty liver disease results in decreased hepatic uptake transporter expression and function in rats. European journal of pharmacology, 613(1-3), 119-27.
BIO5 Collaborators
David G Besselsen, Nathan J Cherrington

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of diagnoses ranging from simple fatty liver (SFL), to non-alcoholic steatohepatitis (NASH). This study aimed to determine the effect of moderate and severe NAFLD on hepatic transporter expression and function in vivo. Rats were fed a high-fat diet (SFL model) or a methionine-choline-deficient diet (NASH model) for eight weeks. Hepatic uptake transporter function was determined by bromosulfophthalein (BSP) disposition. Transporter expression was determined by branched DNA signal amplification assay and western blotting; inflammation was identified by immunostaining of liver slices for interleukin 1 beta (IL-1beta). MC- rats showed significant retention of BSP in the plasma when compared to control rats. Hepatic NTCP, OATP1a1, 1a4, 1b2 and 2b1; and OAT 2 and 3 mRNA levels were significantly decreased in high-fat and MC- diet rats when compared to control. Protein expression of OATP1a1 was significantly decreased in high-fat animals, while OATP1a1 and OATP1b2 expressions were significantly lower in MC- rats when compared to control. Liver tissue from high-fat and MC- rats stained positive for IL-1beta, a pro-inflammatory cytokine known to decrease expression of NTCP, OATP and OAT transporters, suggesting a plausible mechanism for the observed transporter alterations. These data suggest that different stages of NAFLD result in altered hepatic uptake transporter expression that can lead to a functional impairment of xenobiotic uptake from the blood. Furthermore, NAFLD may alter the plasma retention time of clinically relevant drugs that are reliant on these transporters and may increase the potential drug toxicity.