Comparison of hock- and footpad-injection as a prostate adenocarcinoma model in rats.

BACKGROUND: Objective of this study is a feasibility-test comparing hock- and footpad-injection in rats with inoculated MatLyLu - adenocarcinoma tumor model. This study compares the development of an adenocarcinoma model (MatLyLu) in 12 Copenhagen rats. Two groups (n = 6) of animals were inoculated with 1 × 106 MatLyLu tumor cells solved in 0.1 ml NaCl either by footpad or hock injection. All animals were examined before tumor inoculation and before euthanasia using a 3.0 Tesla MRI. Histological evaluation of all organs was performed post mortem. RESULTS: Both types of injection were able to induce the adenocarcinoma model using MatLyLu tumor cells. The primary tumor could be visualized in MRI and confirmed histologically. Comparing the risk of reflux and the maximum injection volume during injection, the hock injection was superior to the footpad injection (less reflux, less anatomical restrictions for larger volumes). The hock injection induces a faster tumor growth compared to the footpad injection. As consequence the maximum level of long term discomfort after hock injection was reached earlier, even if it grew on a not weight bearing structure. Early lymph node tumor metastasis could not be observed macroscopically nor detected histologically. Therefore the reproducibility of the MatLyLu tumor model is questionable. CONCLUSION: Hock injection is a feasible alternative technique compared with footpad-injection in rats. It provides a save and easy injection method for various early-terminated applications with the potential to increase animal welfare during tumor models in rats.

Assessment of Myocardial Perfusion at Rest and During Stress Using Dynamic First-Pass Contrast-Enhanced Magnetic Resonance Imaging in Healthy Dogs.

Objective: To assess the feasibility of myocardial perfusion analysis in healthy dogs using dynamic contrast-enhanced cardiac magnetic resonance (DCE-MR) imaging at rest and during simulated stress with two doses of adenosine. Animals: Ten healthy beagle dogs. Procedures: Dogs were anesthetized and positioned in dorsal recumbency in a 3.0 Tesla MR scanner. Electrocardiogram-triggered dynamic T1-weighted ultrafast gradient echo images of three slices in short-axis orientation of the heart were acquired during breath holds and the first pass of gadolinium contrast. Image acquisition was performed after 4 min infusion of 140 µg/kg/min and 280 µg/kg/min adenosine and, after a washout period, without adenosine, respectively. Images were processed by dividing each slice into 6 radial segments and perfusion analysis was performed from signal intensity-time data. Results: No differences in perfusion parameters were found between segments within any of the slices, but significant differences were found between slices for peak enhancement, accumulated enhancement, and the maximum upslope. In addition, significant differences were found within each slice between data at rest and during adenosine-induced stress for the relative and absolute maximum upslope, relative peak enhancement, time to peak, and accumulated enhancement although inter-individual variation was large and no difference was found between the two stress tests for some parameters. Conclusion and Clinical Relevance: Results of this study showed that rest and stress myocardial perfusion can be assessed using DCE-CMR in dogs using the methods described. Both, adenosine dose and slice appear to affect perfusion parameters in healthy dogs and individual response to adenosine was variable.