In JoVE (1)

Other Publications (8)

Articles by Nysia I. George in JoVE

 JoVE Neuroscience

A Visual Description of the Dissection of the Cerebral Surface Vasculature and Associated Meninges and the Choroid Plexus from Rat Brain

1Division of Neurotoxicology, National Center for Toxicological Research, 2Division of Personalized Nutrition and Medicine, National Center for Toxicological Research, 3Office of Planning, Finance, and Information Technology, National Center for Toxicological Research

JoVE 4285

Other articles by Nysia I. George on PubMed

Use of a Novel Genetic Mouse Model to Investigate the Role of Folate in Colitis-associated Colon Cancer

The Journal of Nutritional Biochemistry. Aug, 2009  |  Pubmed ID: 18926688

Inflammatory bowel disease (IBD) patients are at high risk for developing folate deficiency and colon cancer. Since it is difficult to study the subtle global and gene-specific epigenetic mechanisms involved in folate-mediated tumor initiation and promotion, we have generated genetically modified mouse models by targeting the reduced folate carrier (RFC1) and folate-binding protein (Folbp1) genes. The transgenic mice were fed semi-purified diets for 8 weeks containing either normal (2 mg) or deficient (0.1 mg folate/kg diet) levels of folate. Compound heterozygous mice (Folbp1(+/-); RFC1(+/-)) fed an adequate folate diet exhibited a reduction in plasma folate concentrations compared to heterozygous (Folbp1(+/-)) and littermate wild-type mice (P<.05). In contrast, no differences were observed in colonic mucosa. Consumption of a low folate diet significantly reduced (three- to fourfold) plasma and tissue folate levels in all animal models, although plasma homocysteine levels were not altered. In order to elucidate the relationship between folate status and inflammation-associated colon cancer, animals were injected with azoxymethane followed by dextran sodium sulphate treatment in the drinking water. Mice were fed a normal folate diet and were terminated 5 weeks after carcinogen injection. The number of high multiplicity aberrant crypt foci per centimeter of colon was significantly elevated (P<.05) in compound Folbp1(+/-); RFC1(+/-) (3.5+/-0.4) mice as compared to Folbp1(+/-) (1.9+/-0.3) and wild-type control mice (1.1+/-0.1). These data demonstrate that the ablation of two receptor/carrier-mediated pathways for folate transport increases the risk for developing inflammation-associated colon cancer.

Amphetamine and Environmentally Induced Hyperthermia Differentially Alter the Expression of Genes Regulating Vascular Tone and Angiogenesis in the Meninges and Associated Vasculature

Synapse (New York, N.Y.). Oct, 2009  |  Pubmed ID: 19582783

An amphetamine (AMPH) regimen that does not produce a prominent blood-brain barrier breakdown was shown to significantly alter the expression of genes regulating vascular tone, immune function, and angiogenesis in vasculature associated with arachnoid and pia membranes of the forebrain. Adult-male Sprague-Dawley rats were given either saline injections during environmentally-induced hyperthermia (EIH) or four doses of AMPH with 2 h between each dose (5, 7.5, 10, and 10 mg/kg d-AMPH, s.c.) that produced hyperthermia. Rats were sacrificed either 3 h or 1 day after dosing, and total RNA and protein was isolated from the meninges, arachnoid and pia membranes, and associated vasculature (MAV) that surround the forebrain. Vip, eNos, Drd1a, and Edn1 (genes regulating vascular tone) were increased by either EIH or AMPH to varying degrees in MAV, indicating that EIH and AMPH produce differential responses to enhance vasodilatation. AMPH, and EIH to a lesser extent, elicited a significant inflammatory response at 3 h as indicated by an increased MAV expression of cytokines Il1b, Il6, Ccl-2, Cxcl1, and Cxcl2. Also, genes related to heat shock/stress and disruption of vascular homeostasis such as Icam1 and Hsp72 were also observed. The increased expression of Ctgf and Timp1 and the decreased expression of Akt1, Anpep, and Mmp2 and Tek (genes involved in stimulating angiogenesis) from AMPH exposure suggest that angiogenesis was arrested or disrupted in MAV to a greater extent by AMPH compared to EIH. Alterations in vascular-related gene expression in the parietal cortex and striatum after AMPH were less in magnitude than in MAV, indicating less of a disruption of vascular homeostasis in these two regions. Changes in the levels of insulin-like growth factor binding proteins Igfbp1, 2, and 5 in MAV, compared to those in striatum and parietal cortex, imply an interaction between these regions to regulate the levels of insulin-like growth factor after AMPH damage. Thus, the vasculature and meninges surrounding the surface of the forebrain may be an important region in which AMPHs can disrupt vascular homeostasis.

Evaluation of Fecal MRNA Reproducibility Via a Marginal Transformed Mixture Modeling Approach

BMC Bioinformatics. 2010  |  Pubmed ID: 20055994

Developing and evaluating new technology that enables researchers to recover gene-expression levels of colonic cells from fecal samples could be key to a non-invasive screening tool for early detection of colon cancer. The current study, to the best of our knowledge, is the first to investigate and report the reproducibility of fecal microarray data. Using the intraclass correlation coefficient (ICC) as a measure of reproducibility and the preliminary analysis of fecal and mucosal data, we assessed the reliability of mixture density estimation and the reproducibility of fecal microarray data. Using Monte Carlo-based methods, we explored whether ICC values should be modeled as a beta-mixture or transformed first and fitted with a normal-mixture. We used outcomes from bootstrapped goodness-of-fit tests to determine which approach is less sensitive toward potential violation of distributional assumptions.

Endoplasmic Reticulum Stress Responses Differ in Meninges and Associated Vasculature, Striatum, and Parietal Cortex After a Neurotoxic Amphetamine Exposure

Synapse (New York, N.Y.). Aug, 2010  |  Pubmed ID: 20340164

Amphetamine (AMPH) is used to treat attention deficit and hyperactivity disorders, but it can produce neurotoxicity and adverse vascular effects at high doses. The endoplasmic reticulum (ER) stress response (ERSR) entails the unfolded protein response, which helps to avoid or minimize ER dysfunction. ERSR is often associated with toxicities resulting from the accumulation of unfolded or misfolded proteins and has been associated with methamphetamine toxicity in the striatum. The present study evaluates the effect of AMPH on several ERSR elements in meninges and associated vasculature (MAV), parietal cortex, and striatum. Adult, male Sprague-Dawley rats were exposed to saline, environmentally induced hyperthermia (EIH) or four consecutive doses of AMPH that produce hyperthermia. Expression changes (mRNA and protein levels) of key ERSR-related genes in MAV, striatum, and parietal cortex at 3 h or 1 day postdosing were monitored. AMPH increased the expression of some ERSR-related genes in all tissues. Atf4 (activating transcription factor 4, an indicator of Perk pathway activation), Hspa5/Grp78 (Glucose regulated protein 78, master regulator of ERSR), Pdia4 (protein disulfide isomerase, protein-folding enzyme), and Nfkb1 (nuclear factor of kappa b, ERSR sensor) mRNA increased significantly in MAV and parietal cortex 3 h after AMPH. In striatum, Atf4 and Hspa5/Grp78 mRNA significantly increased 3 h after AMPH, but Pdia4 and Nfkb11 did not. Thus, AMPH caused a robust activation of the Perk pathway in all tissues, but significant Ire1 pathway activation occurred only after AMPH treatment in the parietal cortex and striatum. Ddit3/Chop, a downstream effector of the ERSR pathway related to the neurotoxicity, was only increased in striatum and parietal cortex. Conversely, Pdia4, an enzyme protective in the ERSR, was only increased in MAV. The overall ERSR manifestation varied significantly between MAV, striatum, and parietal cortex after a neurotoxic exposure to AMPH.

A Comparison of Methylphenidate-, Amphetamine-, and Methamphetamine-induced Hyperthermia and Neurotoxicity in Male Sprague-Dawley Rats During the Waking (lights Off) Cycle

Neurotoxicology and Teratology. Mar, 2012  |  Pubmed ID: 22289608

Previous studies focusing on amphetamine (AMPH), methamphetamine (METH) and methylphenidate (MPH) neurotoxicity have almost exclusively been conducted in rodents during the light cycle, which is when most rodents sleep. There are virtually no studies that have simultaneously compared the effects of these three stimulants on body temperature and also determined serum stimulant levels during exposure. The present study compared the effects of MPH, AMPH and METH treatment on body temperature and neurotoxicity during the waking (dark) cycle of the rat. This was done to more effectively replicate stimulant exposure in waking humans and to evaluate the relative risks of the three stimulants when taken inappropriately or non-therapeutically (e.g., abuse). Four subcutaneous injections (4×), at 2 h intervals, were used to administer each dose of the stimulants tested. Several equimolar doses for the three stimulants were chosen to produce plasma levels ranging from 3 times the highest therapeutic levels (no effect on body temperature) to those only attained by accidental overdose or intentional abuse in humans. Either 4×2.0 mg/kg AMPH or 4×2.2 mg/kg METH administered during the waking cycle resulted in peak serum levels of between 1.5 and 2.5 μM (4 to 5 times over maximum therapeutic levels of METH and AMPH) and produced lethal hyperthermia, 70% striatal dopamine depletions, and neurodegeneration in the cortex and thalamus. These results show that METH and AMPH are equipotent at producing lethal hyperthermia and neurotoxicity in laboratory animals during the wake cycle. Administration of either 4×2.2 or 4×3.3 mg/kg METH during the sleep cycle produced lower peak body temperatures, minimal dopamine depletions and little neurodegeneration. These findings indicate that administration of the stimulant during the waking cycle compared to sleep cycle may significantly increase the potency of amphetamines to produce hyperthermia, neurotoxicity and lethality. In contrast, body temperature during the waking cycle was only significantly elevated by MPH at 4×22 mg/kg, and the serum levels producing this effect were 2-fold (approximately 4.5 μM) greater on a molar basis than hyperthermic doses of AMPH and METH. Thus, AMPH and METH were equipotent on a mg/kg body weight basis at producing hyperthermia and neurotoxicity while MPH on a mg/kg body weight basis was approximately 10-fold less potent than AMPH and METH. However, the 10-fold lower potency was in large part due to lower plasma levels produced by MPH compared to either AMPH or METH.

Physiological Effects Following Administration of Citrus Aurantium for 28 Days in Rats

Toxicology and Applied Pharmacology. Jun, 2012  |  Pubmed ID: 22521485

Since ephedra-containing dietary supplements were banned from the US market, manufacturers changed their formulations by eliminating ephedra and replacing with other botanicals, including Citrus aurantium, or bitter orange. Bitter orange contains, among other compounds, synephrine, a chemical that is chemically similar to ephedrine. Since ephedrine may have cardiovascular effects, the goal of this study was to investigate the cardiovascular effects of various doses of bitter orange extract and pure synephrine in rats.

Model Uncertainty and Model Averaging in the Estimation of Infectious Doses for Microbial Pathogens

Risk Analysis : an Official Publication of the Society for Risk Analysis. Jun, 2012  |  Pubmed ID: 22681783

Food-borne infection is caused by intake of foods or beverages contaminated with microbial pathogens. Dose-response modeling is used to estimate exposure levels of pathogens associated with specific risks of infection or illness. When a single dose-response model is used and confidence limits on infectious doses are calculated, only data uncertainty is captured. We propose a method to estimate the lower confidence limit on an infectious dose by including model uncertainty and separating it from data uncertainty. The infectious dose is estimated by a weighted average of effective dose estimates from a set of dose-response models via a Kullback information criterion. The confidence interval for the infectious dose is constructed by the delta method, where data uncertainty is addressed by a bootstrap method. To evaluate the actual coverage probabilities of the lower confidence limit, a Monte Carlo simulation study is conducted under sublinear, linear, and superlinear dose-response shapes that can be commonly found in real data sets. Our model-averaging method achieves coverage close to nominal in almost all cases, thus providing a useful and efficient tool for accurate calculation of lower confidence limits on infectious doses.

Development of Doxorubicin-induced Chronic Cardiotoxicity in the B6C3F(1) Mouse Model

Toxicology and Applied Pharmacology. Nov, 2012  |  Pubmed ID: 23142469

Serum levels of cardiac troponins serve as biomarkers of myocardial injury. However, troponins are released into the serum only after damage to cardiac tissue has occurred. Here, we report development of a mouse model of doxorubicin (DOX)-induced chronic cardiotoxicity to aid in the identification of predictive biomarkers of early events of cardiac tissue injury. Male B6C3F(1) mice were administered intravenous DOX at 3mg/kg body weight, or an equivalent volume of saline, once a week for 4, 6, 8, 10, 12, and 14weeks, resulting in cumulative DOX doses of 12, 18, 24, 30, 36, and 42mg/kg, respectively. Mice were sacrificed a week following the last dose. A significant reduction in body weight gain was observed in mice following exposure to a weekly DOX dose for 1week and longer compared to saline-treated controls. DOX treatment also resulted in declines in red blood cell count, hemoglobin level, and hematocrit compared to saline-treated controls after the 2nd weekly dose until the 8th and 9th doses, followed by a modest recovery. All DOX-treated mice had significant elevations in cardiac troponin T concentrations in plasma compared to saline-treated controls, indicating cardiac tissue injury. Also, a dose-related increase in the severity of cardiac lesions was seen in mice exposed to 24mg/kg DOX and higher cumulative doses. Mice treated with cumulative DOX doses of 30mg/kg and higher showed a significant decline in heart rate, suggesting drug-induced cardiac dysfunction. Altogether, these findings demonstrate the development of DOX-induced chronic cardiotoxicity in B6C3F(1) mice.

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