MLH1-rheMac hereditary nonpolyposis colorectal cancer syndrome in rhesus macaques.

Over the past two decades, 33 cases of colonic adenocarcinomas have been diagnosed in rhesus macaques (Macaca mulatta) at the nonhuman primate colony of the Keeling Center for Comparative Medicine and Research at The University of Texas MD Anderson Cancer Center. The distinctive feature in these cases, based on PET/computed tomography (CT) imaging, was the presence of two or three tumor lesions in different locations, including proximal to the ileocecal juncture, proximal to the hepatic flexure, and/or in the sigmoid colon. These colon carcinoma lesions selectively accumulated [18F]fluorodeoxyglucose ([18F]FDG) and [18F]fluoroacetate ([18F]FACE) at high levels, reflecting elevated carbohydrate and fatty acid metabolism in these tumors. In contrast, the accumulation of [18F]fluorothymidine ([18F]FLT) was less significant, reflecting slow proliferative activity in these tumors. The diagnoses of colon carcinomas were confirmed by endoscopy. The expression of MLH1, MSH2, and MSH6 proteins and the degree of microsatellite instability (MSI) was assessed in colon carcinomas. The loss of MLH1 protein expression was observed in all tumors and was associated with a deletion mutation in the MLH1 promoter region and/or multiple single-nucleotide polymorphism (SNP) mutations in the MLH1 gene. All tumors exhibited various degrees of MSI. The pedigree analysis of this rhesus macaque population revealed several clusters of affected animals related to each other over several generations, suggesting an autosomal dominant transmission of susceptibility for colon cancer. The newly discovered hereditary nonpolyposis colorectal cancer syndrome in rhesus macaques, termed MLH1-rheMac, may serve as a model for development of novel approaches to diagnosis and therapy of Lynch syndrome in humans.

Comparison of Indoor Air Quality between 2 Ventilation Strategies in a Facility Housing Rhesus Macaques (Macaca mulatta).

Adequate indoor-air quality (IAQ)--defined by the temperature, relative humidity, and the levels of carbon dioxide, small particles, and total volatile organic compounds (TVOC)--is crucial in laboratory animal facilities. The ventilation standards for controlling these parameters are not well defined. This study assessed the effect of 2 ventilation strategies on IAQ in 2 rooms housing rhesus macaques (Macaca mulatta). We hypothesized that using a demand-controlled ventilation (DCV) system with a baseline ventilation rate of less than 3 fresh-air changes per hour (ACH) would maintain IAQ comparable to or better than the traditional constant flow rate (CFR) system at 12 fresh ACH. During a 60-d study period, each of the 2 rooms operated 30 d on DCV and 30 d on CFR ventilation. In both rooms, temperatures remained more consistently within the established setpoint during the DCV phase than during the CFR phase. Relative humidity did not differ significantly between rooms or strategies. CO2 was lower during the CFR phase than DCV phase. Small-particle and TVOC levels were lower during CFR in the larger (3060 ft(3)) room but not the smaller (2340 ft(3)) room. During the DCV phase, the larger room was at the baseline airflow rate over 99% of the time and the smaller room over 96% of the time. The DCV strategy resulted in a baseline airflow rate of less than 3 ACH, which in turn provided acceptable IAQ over 96% of the time; higher ventilation rates were warranted only during sanitation periods.

Dependence of DCE-MRI biomarker values on analysis algorithm.

BACKGROUND: Dynamic contrast-enhanced MRI (DCE-MRI) biomarkers have proven utility in tumors in evaluating microvascular perfusion and permeability, but it is unclear whether measurements made in different centers are comparable due to methodological differences. PURPOSE: To evaluate how commonly utilized analytical methods for DCE-MRI biomarkers affect both the absolute parameter values and repeatability. MATERIALS AND METHODS: DCE-MRI was performed on three consecutive days in twelve rats bearing C6 xenografts. Endothelial transfer constant (Ktrans), extracellular extravascular space volume fraction (ve), and contrast agent reflux rate constant (kep) measures were computed using: 2-parameter ("Tofts" or "standard Kety") vs. 3-parameter ("General Kinetic" or "extended Kety") compartmental models (including blood plasma volume fraction (vp) with 3-parameter models); individual- vs. population-based vascular input functions (VIFs); and pixel-by-pixel vs. whole tumor-ROI. Variability was evaluated by within-subject coefficient of variation (wCV) and variance components analyses. RESULTS: DCE-MRI absolute parameter values and wCVs varied widely by analytical method. Absolute parameter values ranged, as follows, median Ktrans, 0.09-0.18 min-1; kep, 0.51-0.92 min-1; ve, 0.17-0.23; and vp, 0.02-0.04. wCVs also varied widely by analytical method, as follows: mean Ktrans, 32.9-61.9%; kep, 11.6-41.9%; ve, 16.1-54.9%; and vp, 53.9-77.2%. Ktrans and kep values were lower with 3- than 2-parameter modeling (p<0.0001); kep and vp were lower with pixel- than whole-ROI analyses (p<0.0006). wCVs were significantly smaller for ve, and larger for kep, with individual- than population-based VIFs. CONCLUSIONS: DCE-MRI parameter values and repeatability can vary widely by analytical methodology. Absolute values of DCE-MRI biomarkers are unlikely to be comparable between different studies unless analyses are carefully standardized.

Reproducibility and comparison of DCE-MRI and DCE-CT perfusion parameters in a rat tumor model.

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and computed tomography (DCE-CT) provide independent measures of biomarkers related to tumor perfusion. We compared the reproducibilities and absolute values of DCE-MRI and DCE-CT biomarkers in the same tumors in an animal model, to investigate the physiologic validity of both approaches. DCE-MRI and DCE-CT were each performed sequentially on three consecutive days in each of twelve rats bearing C6 glioma xenografts. DCE-MRI yielded endothelial transfer constant (K(trans)), extracellular, extravascular space volume fraction (v(e)), and contrast agent reflux rate constant (k(ep)); and DCE-CT, blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability-surface area product (PS) using Tofts and deconvolution physiological models, with 6.6 and 0.4 seconds temporal resolutions, respectively. Variability in DCE-CT and DCE-MRI were evaluated by variance components analysis. Intra-rat coefficients of variation for DCE-CT parameters BF, BV, MTT and PS were 25%, 22%, 18% and 23%; and for DCE-MRI parameters K(trans), k(ep) and v(e) were 23%, 16% and 20%, respectively. Mean (±SD) BF, BV, MTT and PS were: 44.6 (±13.7) ml min(-1) 100 g(-1), 5.7 (±1.5) ml 100 g(-1), 10.8 (±2.3) seconds, and 14.6 (±4.7) ml min(-1) 100 g(-1), respectively. Mean (±SD) K(trans), k(ep) and v(e) were: 0.21 (±0.05) min(-1), 0.68 (±0.14) min(-1), and 0.29 (±0.06), respectively. Permeability estimates from DCE-MRI (K(trans)) were 44% higher than from DCE-CT (PS), despite application of appropriate corrections. DCE-MRI and DCE-CT biomarkers of tumor perfusion have similar reproducibilities suggesting that they may have comparable utility, but their derived parameter values are not equivalent.

Imaging long-term fate of intramyocardially implanted mesenchymal stem cells in a porcine myocardial infarction model.

The long-term fate of stem cells after intramyocardial delivery is unknown. We used noninvasive, repetitive PET/CT imaging with [(18)F]FEAU to monitor the long-term (up to 5 months) spatial-temporal dynamics of MSCs retrovirally transduced with the sr39HSV1-tk gene (sr39HSV1-tk-MSC) and implanted intramyocardially in pigs with induced acute myocardial infarction. Repetitive [(18)F]FEAU PET/CT revealed a biphasic pattern of sr39HSV1-tk-MSC dynamics; cell proliferation peaked at 33-35 days after injection, in periinfarct regions and the major cardiac lymphatic vessels and lymph nodes. The sr39HSV1-tk-MSC-associated [(18)F]FEAU signals gradually decreased thereafter. Cardiac lymphography studies using PG-Gd-NIRF813 contrast for MRI and near-infrared fluorescence imaging showed rapid clearance of the contrast from the site of intramyocardial injection through the subepicardial lymphatic network into the lymphatic vessels and periaortic lymph nodes. Immunohistochemical analysis of cardiac tissue obtained at 35 and 150 days demonstrated several types of sr39HSV1-tk expressing cells, including fibro-myoblasts, lymphovascular cells, and microvascular and arterial endothelium. In summary, this study demonstrated the feasibility and sensitivity of [(18)F]FEAU PET/CT imaging for long-term, in-vivo monitoring (up to 5 months) of the fate of intramyocardially injected sr39HSV1-tk-MSC cells. Intramyocardially transplanted MSCs appear to integrate into the lymphatic endothelium and may help improve myocardial lymphatic system function after MI.

Whole-body biodistribution kinetics, metabolism, and radiation dosimetry estimates of 18F-PEG6-IPQA in nonhuman primates.

UNLABELLED: We recently developed the radiotracer 4-[(3-iodophenyl)amino]-7-(2-[2-{2-(2-[2-{2-((18)F-fluoroethoxy)-ethoxy}-ethoxy]-ethoxy)-ethoxy}-ethoxy]-quinazoline-6-yl-acrylamide) ((18)F-PEG(6)-IPQA) for noninvasive detection of active mutant epidermal growth factor receptor kinase-expressing non-small cell lung cancer xenografts in rodents. In this study, we determined the pharmacokinetics, biodistribution, metabolism, and radiation dosimetry of (18)F-PEG(6)-IPQA in nonhuman primates. METHODS: Six rhesus macaques were injected intravenously with 141 ± 59.2 MBq of (18)F-PEG(6)-IPQA, and dynamic PET/CT images covering the thoracoabdominal area were acquired for 30 min, followed by whole-body static images at 60, 90, 120, and 180 min. Blood samples were obtained from each animal at several time points after radiotracer administration. Radiolabeled metabolites in blood and urine were analyzed using high-performance liquid chromatography. The (18)F-PEG(6)-IPQA pharmacokinetic and radiation dosimetry estimates were determined using volume-of-interest analysis of PET/CT image datasets and blood and urine time-activity data. RESULTS: (18)F-PEG(6)-IPQA exhibited rapid redistribution and was excreted via the hepatobiliary and urinary systems. (18)F-PEG(6) was the major radioactive metabolite. The critical organ was the gallbladder, with an average radiation-absorbed dose of 0.394 mSv/MBq. The other key organs with high radiation doses were the kidneys (0.0830 mSv/MBq), upper large intestine wall (0.0267 mSv/MBq), small intestine (0.0816 mSv/MBq), and liver (0.0429 mSv/MBq). Lung tissue exhibited low uptake of (18)F-PEG(6)-IPQA due to the low affinity of this radiotracer to wild-type epidermal growth factor receptor kinase. The effective dose was 0.0165 mSv/MBq. No evidence of acute cardiotoxicity or of acute or delayed systemic toxicity was observed. On the basis of our estimates, diagnostic dosages of (18)F-PEG(6)-IPQA up to 128 MBq (3.47 mCi) per injection should be safe for administration in the initial cohort of human patients in phase I clinical PET studies. CONCLUSION: The whole-body and individual organ radiation dosimetry characteristics and pharmacologic safety of diagnostic dosages of (18)F-PEG(6)-IPQA in nonhuman primates indicate that this radiotracer should be acceptable for PET/CT studies in human patients.

Repetitive noninvasive monitoring of HSV1-tk-expressing T cells intravenously infused into nonhuman primates using positron emission tomography and computed tomography with 18F-FEAU.

Adoptive transfer of antigen-specific cytotoxic T lymphocytes (CTLs) has been successfully used to treat patients with different types of cancer. However, the long-term spatial-temporal dynamics of the distribution of systemically infused CTLs remains largely unknown. Noninvasive imaging of adoptively transferred CTLs using molecular-genetic reporter imaging with positron emission tomography and computed tomography (PET-CT) represents an innovative approach to understanding the long-term migratory patterns and therapeutic potential of adoptively transferred T cells. Here we report the application of repetitive PET-CT imaging with [18F]fluoro-5-ethyl-1-beta-D-arabinofuranosyluracil (18F-FEAU) in two nonhuman primates demonstrating that autologous polyclonal macaque T lymphocytes activated and transduced with a retroviral vector encoding for the sr39 mutant herpes simplex virus 1 thymidine kinase (sr39HSV1-tk) reporter gene can be detected after intravenous infusion in discrete lymphoid organs and in sites of inflammation. This study represents a proof of principle and supports the application of 18F-FEAU PET-CT imaging for monitoring the distribution of intravenously administered sr39HSV1-tk gene-transduced CTLs in humans.

Use of a portable thermal imaging unit as a rapid, quantitative method of evaluating inflammation and experimental arthritis.

INTRODUCTION: Thermal imaging has been utilized, both preclinically and clinically, as a tool for assessing inflammation and arthritis. However, previous studies have employed large, relatively immobile devises to obtain the thermal signature of the tissue of interest. The present study describes the characterization of a hand-held thermal imaging device in a preclinical model of general inflammation and a model of rheumatoid arthritis (RA). METHODS: A hand-held ThermoView Ti30 portable thermal imager was utilized to detect the temporal changes in thermal signatures in rat model of carrageenan-induced paw edema (CFE) and a model of collagen-induced arthritis (CIA). In both in vivo models, the kinetics of the thermal changes were correlated to footpad swelling. In addition, the CFE model was utilized to examine the ability of this technology to delineate pharmacodynamic changes in thermal signature in response to the non-steroidal anti-inflammatory drug indomethacin (10 mg/kg; p.o.). RESULTS: Thermal analysis of rat paws in the CFE model demonstrated a significant increase in the mean temperature difference between the inflamed and contralateral control paw by two hours post-carrageenan (8.3 +/-0.5 degrees F). Indomethacin significantly decreased the mean temperature difference in treated animals as compared to vehicle. In the rat CIA model, increases in footpad temperature, as determined by thermal imaging, were significantly elevated by Day 11 and remained elevated throughout the duration of the 28 day protocol. Thermal changes were also found to precede increases in footpad edema (swelling). DISCUSSION: The results of this study demonstrate that the hand-held thermal imaging technology represents a rapid, highly-reproducible method by which to quantitate the degree of inflammation in rat models of general inflammation and rheumatoid arthritis. The ability to detect pharmacodynamic responses in paw temperature suggests that this technology may be a useful tool for the development of pharmacologic interventions for the treatment inflammation-related pathologies.

Harderian gland adenectomy: a method to eliminate confounding radio-opacity in the assessment of rat brain metabolism by 18F-fluoro-2-deoxy-D-glucose positron emission tomography.

The 18F isotope of fluoro-2-deoxy-D-glucose (FDG) is a radiotracer commonly used in positron emission tomography (PET) for determining regional metabolic activity in the brain. However, in rats and many other species with nictitating membranes, harderian glands located just behind the eyes aggressively incorporate 18F-FDG to the extent that PET images of the brain become obscured. This radioactive spillover, or 'partial volume error,' combined with the limited spatial resolution of microPET scanners (1.5 to 2 mm) may markedly reduce the ability to quantify neuronal activity in frontal brain structures. Theoretically, surgical removal of the harderian glands before 18F-FDG injection would eliminate the confounding uptake of the radioactive tracer and thereby permit visualization of glucose metabolism in the frontal brain. We conducted a pilot study of unilateral harderian gland adenectomy, leaving the contralateral gland intact for comparison. At 1 wk after surgery, each rat was injected intravenously with 18F-FDG, and 40 min later underwent brain microPET for 20 min. Review of the resulting images showed that the frontal cortex on the surgical side was defined more clearly, with only background 18F-FDG accumulation in the surgical bed. Activity in the frontal cortex on the intact side was obscured by intense accumulation of 18F-FDG in the harderian gland. By reducing partial volume error, this simple surgical procedure may become a valuable tool for visualization of the frontal cortex of rat brain by 18F-FDG microPET imaging.

Development of a mouse model of induced Staphylococcus aureus infective endocarditis.

We developed a mouse model of Staphylococcus aureus infective endocarditis to evaluate the efficacy of experimental antibacterial compounds for this disease. Experimental infective endocarditis was produced in CD1 mice by intravenous challenge with approximately 6 log10 colony-forming units (CFU) of methicillin-sensitive (MSSA) SA-3529 or -resistant (MRSA) SA-2015 S. aureus 1 d after aortic valve trauma. Valve trauma was produced by introduction of an indwelling 32-gauge polyurethane catheter into the aortic valve via the left carotid artery. Histologic examination of MSSA- and MRSA-infected and catheterized aortic valve sections revealed neutrophilic inflammation and vegetative bacterial colonies encapsulated within fibrin along the aortic valves 1 d after infection. The MSSA or MRSA endocarditis was determined to be catheter-dependent based on catheterized mice exhibiting heart bacterial counts 4 orders of magnitude greater than those seen for noncatheterized mice. The model was validated by using a 3-d regimen of vancomycin at exposures comparable to human dosing (500 microg x h/ml). Vancomycin treatment produced statistically significant reductions of 3.4 and 3.1 log10 CFU/heart for MSSA and MRSA, respectively, relative to controls. This mouse model of endocarditis shows promise in evaluating the predictive efficacy of antibiotics for S. aureus infective endocarditis.

Dose-dependent neovascularization-promoting effect of adenovirus vector CI-1023 in a rat hindlimb ischaemic model.

CI-1023 (AdGVVEGF121.10) is a replication-deficient adenovirus vector (complete E1a-, partial E1b-, partial E3-) delivering human vascular endothelial growth factor-121 gene. Previous studies from this group have established that CI-1023 can successfully transfer human vascular endothelial growth factor-121 gene resulting in local tissue expression of vascular endothelial growth factor protein. The purpose of this study was to evaluate neovascularization-promoting potency and efficacy of CI-1023 in a wide dose range. In a rat hindlimb ischaemic model, we measured neovascularization-promoting effect of CI-1023 using three end-points: post mortem angiography, immuno-histochemistry and Laser Doppler scanning of tissue blood perfusion. Neovascularization-promoting activity of CI-1023 over the dose range of 4 x 10(6) pu-4 x 10(10) pu was evaluated. Our data demonstrated an obvious dose-dependent effect between 4 x 10(6) pu-4 x 10(8) pu. The neovascularizing effect is somewhat plateaued at the levels between 4 x 10(8) pu and 4 x 10(10) pu. We conclude CI-1023 is a potent neovascularization-promoting compound, with a dose-dependent effect between 4 x 10(6) pu-4 x 10(8) pu in the rat hindlimb ischaemic model.

Determination of Optimal Angles for Intraoral Occlusal Views for the Radiographic Imaging of Dental Structures in the Cynomolgus Monkey (Macaca fascicularis).

Highly detailed dental radiographs aid in obtaining an accurate diagnosis of common dental abnormalities. This paper compares three oblique angle intraoral occlusal views for the evaluation of the teeth of the maxillary and mandibular arcade of cynomolgus monkeys. The best views for isolating tooth structures of the canine, premolar, and molar teeth of the mandibular and maxillary arcades were obtained by directing the primary beam 608 relative to the hard palate in the transverse plane. The dorsoventral view allowed superior visualization of the maxillary incisor teeth, whereas the ventrodorsal view was best for evaluating the mandibular incisor teeth. Survey radiographs obtained by using these views, coupled with thorough dental examination, would aid the accurate diagnosis of dental abnormalities in cynomolgus monkeys.