Strain-specific variations in Fenestra LC uptake and signal duration were observed. At 7.5 ml/kg, this contrast agent is effective for imaging for 1 day, whereas at 15 ml/kg, it can be used up to 1 week. Fenestra LC does not appear to attenuate FDG uptake at 15 ml/kg for most tissues; therefore, it can be used in conjunction with microPET imaging studies.

Purpose-The ability to reproducibly and repeatedly image rodents in non-invasive imaging systems, such as small animal PET and CT, requires a reliable method for anesthetizing, positioning, and heating animals in a simple reproducible manner. In this paper we demonstrate that mice and rats can be reproducibly and repeatedly imaged using an imaging chamber designed to be rigidly mounted on multiple imaging systems.Procedures-Mouse and rat imaging chambers were made of acrylic plastic and aluminum. MicroCT scans were used to evaluate the positioning reproducibility of the chambers in multimodality and longitudinal imaging studies. The ability of the chambers to maintain mouse and rat body temperatures while anesthetized with gas anesthesia was also evaluated.Results-Both the mouse and rat imaging chambers were able to reproducibly position the animals in the imaging systems with a small degree of error. Placement of the mouse in the mouse imaging chamber resulted in a mean distance of 0.23 mm per reference point in multimodality studies, whereas for longitudinal studies the mean difference was 1.11 mm. The rat chamber resulted in a mean difference of 0.46 mm in multimodality studies, and a mean difference of 4.31 mm in longitudinal studies per reference point. The chambers maintained rodent body temperatures at the set point temperature of 38°C.Conclusions-The rodent imaging chambers were able to reproducibly position rodents in tomographs with a small degree of variability, and were compatible with routine use. The embedded anesthetic line and heating system was capable of maintaining the rodent's temperature and anesthetic state, thereby enhancing rodent health and improving data collection reliability.

Seven male Hartley guinea pigs, 3 to 18 months old, died or had to be euthanized because of nonspecific clinical signs unresponsive to supportive treatment. Gross necropsy and histopathology findings in all animals included severe soft tissue calcification affecting the myocardium, kidneys, and occasionally the liver.Keywords calcification, guinea pig, heart failure History and FindingsOver a period of 2 months, 7 out of 40 male Hartley guinea pigs (Crl:HA, Charles River Laboratories, Houston, TX) aged 3 to 18 months died or had to be euthanized. Six of the animals were used for noninvasive procedural training and 1 was experimentally injected intraperitoneally with ragweed pollen; all procedures were performed with IACUC approval at an AAALAC-accredited research facility. Clinical signs included dyspnea, bruxism, nasal discharge, stiff gait, lethargy, vocalization, rough haircoat, and reduced feed intake/anorexia. These signs varied among animals. Of 4 guinea pigs tested, 2 had hypercalcemia (12.0 and 12.5 mg/dl; reference, 9-11.3 mg/dl), and 4 had hyperphosphatemia (8.0, 8.3, 11.7, and 11.9 mg/dl; reference, 4.2-6.5 mg/dl). Gross necropsy findings included multifocal to diffuse white mineral deposits (mineralization) in cardiac muscle and renal cortices (Fig. 1). Quarterly colony health monitoring indicated animals were seropositive for parainfluenza virus type 3 and seronegative for Sendai virus, Mycoplasma pulmonis, lymphocytic choriomeningitis virus, Encephalitozoon cuniculi, simian virus 5, guinea pig adenovirus, and reovirus. Animals were provided with guinea pig chow and reverse osmosis purified water, corncob or aspen bedding material, and environmental enrichment device in conventional cages. Environmental conditions in housing rooms were 12:12-hour light:dark cycle, 40% to 80% relative humidity, and a temperature of 20 C to 24 C. All affected guinea pigs had multifocal to diffuse, moderate to severe biventricular cardiomyocyte mineralization with granulomatous inflammation, cardiomyocyte degeneration, and necrosis (Fig. 2) and mild to moderate multifocal renal predominantly cortical tubular mineralization (Fig. 3). Other variable findings included mild to moderate multifocal and chronic renal cortical infarcts, multifocal hepatocyte mineralization with or without lobular infarcts, and focal to multifocal arterial mineralization within organs. Von Kossa staining of hepatocytes demonstrated abundant mineral deposits (Fig. 4). One guinea pig had mild to moderate multifocal mineralization and foreign-body type inflammation of the lungs, adrenal glands, and pancreas. Another had mild multifocal alveolar histiocytosis with intrahistiocytic hemosiderin pigment (heart failure cells). Differential Diagnoses and Feed AnalysesThe differential diagnoses for metastatic calcification include dietary factors such as low-magnesium (Mg) and highphosphorus (P) diet and high calcium (Ca) and/or high vitamin D intake, inadvertent cholecalciferol rodenticide poisoning, and renal disease.Correspondence with feed ve...

No abstract