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Jefferson City, AR, United States

Mattes W.,PharmPoint Consulting | Davis K.,Toxicologic Pathology Associates | Fabian E.,BASF | Greenhaw J.,National Center for Toxicological Research (NCTR) | And 12 more authors.
Toxicology Letters | Year: 2014

While conventional parameters used to detect hepatotoxicity in drug safety assessment studies are generally informative, the need remains for parameters that can detect the potential for hepatotoxicity at lower doses and/or at earlier time points. Previous work has shown that metabolite profiling (metabonomics/metabolomics) can detect signals of potential hepatotoxicity in rats treated with doxorubicin at doses that do not elicit hepatotoxicity as monitored with conventional parameters. The current study extended this observation to the question of whether such signals could be detected in rats treated with compounds that can elicit hepatotoxicity in humans (i.e., drug-induced liver injury, DILI) but have not been reported to do so in rats. Nine compounds were selected on the basis of their known DILI potential, with six other compounds chosen as negative for DILI potential. A database of rat plasma metabolite profiles, MetaMap®Tox (developed by metanomics GmbH and BASF SE) was used for both metabolite profiles and mode of action (MoA) metabolite signatures for a number of known toxicities. Eight of the nine compounds with DILI potential elicited metabolite profiles that matched with MoA patterns of various rat liver toxicities, including cholestasis, oxidative stress, acetaminophen-type toxicity and peroxisome proliferation. By contrast, only one of the six non-DILI compounds showed a weak match with rat liver toxicity. These results suggest that metabolite profiling may indeed have promise to detect signals of hepatotoxicity in rats treated with compounds having DILI potential. © 2014 Elsevier Ireland Ltd. Source

Pandiri A.R.,National Health Research Institute | Pandiri A.R.,Experimental Pathology Laboratories Inc. | Sills R.C.,National Health Research Institute | Hoenerhoff M.J.,National Health Research Institute | And 9 more authors.
Toxicologic Pathology | Year: 2011

Aloe vera is one of the most commonly used botanicals for various prophylactic and therapeutic purposes. Recently, NTP/NCTR has demonstrated a dose-dependent increase in large intestinal tumors in F344 rats chronically exposed to Aloe barbadensis Miller (Aloe vera) non-decolorized whole leaf extract (AVNWLE) in drinking water. The morphological and molecular pathways of AVNWLE-induced large intestinal tumors in the F344 rats were compared to human colorectal cancer (hCRC) literature. Defined histological criteria were used to compare AVNWLE-induced large intestinal tumors with hCRC. The commonly mutated genes (Kras, Ctnnb1, and Tp53) and altered signaling pathways (MAPK, WNT, and TGF-β) important in hCRC were evaluated within AVNWLE-induced large intestinal tumors. Histological evaluation of the large intestinal tumors indicated eight of twelve adenomas (Ads) and four of twelve carcinomas (Cas). Mutation analysis of eight Ads and four Cas identified point mutations in exons 1 and 2 of the Kras gene (two of eight Ads, two of four Cas), and in exon 2 of the Ctnnb1 gene (three of eight Ads, one of four Cas). No Tp53 (exons 5-8) mutations were found in Ads or Cas. Molecular pathways important in hCRC such as MAPK, WNT, and TGF-β signaling were also altered in AVNWLE-induced Ads and Cas. In conclusion, the AVNWLE-induced large intestinal tumors in F344 rats share several similarities with hCRC at the morphological and molecular levels. © Society of Toxicologic Pathology 2011. Source

Liu F.,U.S. Food and Drug Administration | Rainosek S.W.,University of Arkansas for Medical Sciences | Sadovova N.,Toxicologic Pathology Associates | Fogle C.M.,U.S. Food and Drug Administration | And 5 more authors.
NeuroToxicology | Year: 2014

Propofol is a widely used general anesthetic. A growing body of data suggests that perinatal exposure to general anesthetics can result in long-term deleterious effects on brain function. In the developing brain there is evidence that general anesthetics can cause cell death, synaptic remodeling, and altered brain cell morphology. Acetyl- l-carnitine (l-Ca), an anti-oxidant dietary supplement, has been reported to prevent neuronal damage from a variety of causes. To evaluate the ability of l-Ca to protect against propofol-induced neuronal toxicity, neural stem cells were isolated from gestational day 14 rat fetuses and on the eighth day in culture were exposed for 24. h to propofol at 10, 50, 100, 300 and 600. μM, with or without l-Ca (10. μM). Markers of cellular proliferation, mitochondrial health, cell death/damage and oxidative damage were monitored to determine: (1) the effects of propofol on neural stem cell proliferation; (2) the nature of propofol-induced neurotoxicity; (3) the degree of protection afforded by l-Ca; and (4) to provide information regarding possible mechanisms underlying protection. After propofol exposure at a clinically relevant concentration (50. μM), the number of dividing cells was significantly decreased, oxidative DNA damage was increased and a significant dose-dependent reduction in mitochondrial function/health was observed. No significant effect on lactase dehydrogenase (LDH) release was observed at propofol concentrations up to 100. μM. The oxidative damage at 50. μM propofol was blocked by l-Ca. Thus, clinically relevant concentrations of propofol induce dose-dependent adverse effects on rat embryonic neural stem cells by slowing or stopping cell division/proliferation and causing cellular damage. Elevated levels of 8-oxoguanine suggest enhanced oxidative damage [reactive oxygen species (ROS) generation] and l-Ca effectively blocks at least some of the toxicity of propofol, presumably by scavenging oxidative species and/or reducing their production. © 2014. Source

Zhang X.,U.S. Food and Drug Administration | Paule M.G.,U.S. Food and Drug Administration | Newport G.D.,U.S. Food and Drug Administration | Sadovova N.,Toxicologic Pathology Associates | And 6 more authors.
Journal of Neural Transmission | Year: 2011

Recent reports indicate that 6-12 h of ketamine anesthesia can trigger neuronal apoptosis in postnatal day (PND) 7 rats. In vitro, ex vivo, and confocal fluorescent imaging studies suggest that dansyl compounds can accumulate within the cytoplasm of the apoptotic cell. High-resolution positron emission tomography (microPET) imaging has been proposed as a minimally invasive method for detecting apoptosis in the rat brain. Compared with [ 18F]-labeled annexin V, which binds to externalized phosphatidylserine (PS) on the outer membrane of apoptotic cells, intracellular uptake of the dansylhydrazone of p-fluorobenzaldehyde (DFNSH) may lead to improved target-to-background contrast ratios. In this study, the effect of ketamine on the uptake and retention of [18F]-DFNSH in the rat brain was investigated using microPET imaging. On PND 7, rat pups in the experimental group were exposed, at 2-h intervals, to six subcutaneous injections of ketamine (20 mg/kg) and control rat pups received six injections of saline. On PND 35, [18F]-DFNSH (37 MBq) was injected into the tail vein of rats and microPET images were obtained over 2 h following the injection. Radiolabeled tracer accumulation in the region of interest (ROI) in the frontal cortex was converted into standard uptake values (SUVs). The radiotracer was quickly distributed into the brains of both ketamine- and saline-treated rats. Compared with the control group, the uptake of [18F]-DFNSH was significantly increased in the ROI, frontal cortex area of ketamine-treated rats. In addition, the wash-out duration of the tracer was prolonged in the ketamine-treated animals. This study demonstrates that microPET imaging is capable of distinguishing differences in retention of [18F]-DFNSH in ROI and suggests that this compound may serve as a minimally invasive biomarker of neuronal apoptosis in rodents. © Springer-Verlag 2010. Source

Gamboa da Costa G.,National Center for Toxicological Research (NCTR) | Jacob C.C.,National Center for Toxicological Research (NCTR) | Von Tungeln L.S.,National Center for Toxicological Research (NCTR) | Hasbrouck N.R.,Center for Veterinary Medicine | And 4 more authors.
Toxicology and Applied Pharmacology | Year: 2012

The adulteration of pet food with melamine and derivatives, including cyanuric acid, has been implicated in the kidney failure and death of cats and dogs in the USA and other countries. In a previous 7-day dietary study in F344 rats, we established a no-observed-adverse-effect level (NOAEL) for a co-exposure to melamine and cyanuric acid of 8.6. mg/kg bw/day of each compound, and a benchmark dose lower confidence limit (BMDL) of 8.4-10.9. mg/kg bw/day of each compound. To ascertain the role played by the duration of exposure, we treated F344 rats for 28. days. Groups of male and female rats were fed diet containing 0 (control), 30, 60, 120, 180, 240, or 360. ppm of both melamine and cyanuric acid. The lowest dose that produced histopathological alterations in the kidney was 120. ppm, versus 229. ppm in the 7-day study. Wet-mount analysis of kidney sections demonstrated the formation of melamine cyanurate spherulites in one male and two female rats at the 60. ppm dose and in one female rat at the 30. ppm dose, establishing a NOAEL of 2.1. mg/kg bw/day for males and <. 2.6. mg/kg bw/day for females, and BMDL values as low as 1.6. mg/kg bw/day for both sexes. These data demonstrate that the length of exposure is an important component in the threshold of toxicity from a co-exposure to these compounds and suggest that the current risk assessments based on exposures to melamine alone may not reflect sufficiently the risk of a co-exposure to melamine and cyanuric acid. © 2012. Source

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