About FDA

National Center for Toxicological Research (NCTR)

2013 Preceptors


Picture of Jeffrey W. Fisher, Ph.D.

Jeffrey W. Fisher, Ph.D.
Division of Biochemical Toxicology
National Center for Toxicological Research
3900 NCTR Road, Jefferson, AR 72079


  • Ph.D. Miami University, Oxford, OH, Zoology and Toxicology, 1987
  • M.S. Wright State University, Dayton, OH, Biology, 1979
  • B.S. University of Nebraska at Kearney, Kearney, NE, Biology, 1973
  • FDA Experience – 3 years

Research Interests:

  • Development and application of physiological models for chemical and drug toxicological assessments of dose-responses, exposure profiles, and risk assessment.
  • Development and application of biologically based models of the hypothalamic-pituitary-thyroid axis to evaluate hypothyroxinemia and hypothyroidism caused by chemical or drug exposure.

Proposed Regulatory Research Project for the FDA Commissioner's Fellow:

Bisphenol A is a food and environmental contaminant that has received much attention by federal agencies, including the FDA, states, advocacy organizations and other countries. NCTR scientists are conducting guideline toxicity studies, participating in a human clinical pharmacokinetic study, and serving on an FDA-wide BPA working group to review the literature on BPA and make recommendations to CFSAN.

Two confrontational issues with BPA are non-monotonic dose-response profiles in laboratory animals at low administered doses of BPA and the role of contamination in the measurement of BPA in animal and human biological samples. Physiological modeling, a mathematical tool to describe the dosimetry of chemicals or drugs in the body, is a very useful tool assist in the careful evaluation of dose response and expected exposure and pharmacokinetic behavior of BPA across species, particularly in the fetuses of pregnant women.

The FDA Fellow would develop rodent, non-human primate, and human pregnancy PBPK models for bisphenol-A under the guidance of Dr. Fisher. The PBPK model will be used to evaluate fetal exposure of bisphenol A across species, including human. Environmental and contaminated food BPA exposure scenarios will be simulated for use in on-going safely assessment efforts. The research would be published in the peer reviewed literature.

Applicant Requirements:

Previous experience preferred in pharmacokinetic analyses and physiologically based pharmacokinetic modeling. Curiosity about the use of computational tools and methods in toxicology is useful. Experience with Monte Carlo or other computation methods maybe helpful.

Selected Recent Publications:

Fisher, J.W., Gilbert, M., Crofton, K., McLanahan, E.D., and Li, S. 2013. Evaluation of Iodide Deficiency in the Lactating Rat and Pup using a Biologically Based Dose Response (BBDR) Model. Toxicol. Sci. doe:10.1093/toxsci/kfs336.

Patterson, T.A., Twaddle, N.C. Roegge, C.S., Callicott, R.J., Fisher, J.W. and Doerge, D.R. 2012. Concurrent Determination of Bisphenol A Pharmacokinetics in Maternal and Fetal Rhesus Monkeys. Toxicol. Appl. Pharmacol. Doi: 10.1016/j.taap.2012.12.006.

Fisher, J., Lumen, A., Latendresse, J. and D. Mattie. 2012. Extrapolation of Hypothalamic-Pituitary-Thyroid Axis Perturbations and Associated Toxicity in Rodents to Humans: Case Study with Perchlorate. J. Environ. Sci. and Health, Part C, 30, 81-105.

Fisher, J.W., Twaddle, N.C., Vanlandingham, M., and D.R. Doerge. 2011. Pharmacokinetic Modeling: Prediction and Evaluation of Route Dependent Dosimetry of Bisphenol A in Monkeys with Extrapolation to Humans. Toxicol. Appl. Pharmacol. 257, 122-136.


Picture of Sangeeta Khare, M.S., Ph.D.

Sangeeta Khare, M.S., Ph.D.
Division of Microbiology
National Center for Toxicological Research
3900 NCTR Road, Jefferson, AR 72079


  • Ph.D. – Microbiology and Immunology, All India Institute of Medical Sciences, New Delhi, India
  • Post-Doctoral Fellow – Immunology and Microbiology, University of Saskatoon, Canada
  • Academic Positions – Veterinary Pathobiology, Texas A&M University, USA
  • Adjunct Faculty – Veterinary Pathobiology, Texas A&M University, USA
  • FDA Experience – 3 years

Research Interests:

We are chronically exposed through dietary and environmental exposures to trace chemicals of modern society including prescription drugs, pesticides and herbicides, additives, and invading enteric pathogens. The goal of my research is to describe the complex relationships and health consequences of these trace exposures on the commensal bacteria populations of the gastrointestinal tract (GIT).

I have used several models (in vivo, ex vivo and in vitro) and innovative technologies (omics approach, massive parallel sequencing, nanotechnology and systems biology modeling) to define gastrointestinal responses and identify biomarkers for cytotoxicity due to acute and chronic exposure (with biosafety level 2 and biosafety level 3 pathogens).

My ongoing research defines comparative patho-genomics studies of host-pathogen interaction and influence of pathogen virulence factors on the invasion and persistence of invading microorganism and commensal bacterial population. Another aspect of my research is to assess the interaction of nanoparticles with GIT. The outcome of this research will have a direct impact on the discovery of biomarkers, improved food safety and personalized treatment

Proposed Regulatory Research Project for the FDA Commissioner's Fellow:

Prevention is a key aspect in the foundation of the FDA Food Safety Modernization Act (FMSA) of 2011. Hazard identification and hazard evaluation are new preventive control requirements under the FMSA. Utilization of new and emerging tools of hazard assessment of residues in consumed food products is recognized as a critical need in National and International regulatory agencies including WHO.

The maximum residue limit (MRL) and acceptable daily intake (ADI) of residues are estimated by evaluating short, medium and long term dosing studies, of residue in question, on animals of various ages for potential to form tumor, cause birth defects and effect on DNA. Furthermore, cardiovascular, respiratory, central nervous systems and intestinal microbiome are considered vital systems in assessing toxicity.

The guidelines for the MRL value differ greatly between countries. More recently, several regulatory agencies have revisited the regulations governing residues in food producing animals, and the GIT homeostasis has emerged and proposed as a new standard for testing residue toxicity.

The FDA Fellow research would focus on the safety of macrolide, tetracyclines and β-lactams drugs that are commonly used antibiotics in food producing animals (US-CFR Title 21, Part 556 for veterinary drug tolerances). These drugs have been associated with gastrointestinal upset and adverse effects related to enteric flora imbalance.

Homeostasis of GIT depends on the integrity of epithelial barrier and commensal bacteria population. We propose to develop in vitro assays to define MRL and assess the acute and chronic toxicokinetics of tested residues. The increase in the trans-epithelial resistance of polarized epithelial cells will be the end point of the toxicity study.

The omics approach will be used to discover the biomarkers that cause the changes in the permeability. The results of the proposed research will lead to enhanced product safety by assessing the gastrointestinal responses to residues of antibiotics and drugs. The developed in vitro assay may become a new tool to evaluate residue toxicity. The outcome of the proposed research will promote the effective translation of in vitro findings to the ex vivo and in vivo model.

The successful completion of project will establish science-based minimum standards for conducting hazard analysis and will be a step towards FDA readiness to evaluate innovative emerging technologies for improving product assessment and quality, as well as, modernize toxicology. I am highly committed to enhance professional growth and development by promoting awareness in regulatory sciences and compliance issues.

Towards this, before joining FDA, I established a graduate level course “Biosafety and Biosecurity”, at Texas A&M University and mentored several students, post-doctoral fellows and exchange faculty, and now I am extremely enthusiastic to continue the same at NCTR.

Applicant Requirements:

Applicant areas of knowledge should include cellular and molecular biology, toxicology, immunology and tissue culture. The ideal candidate will have a microbial physiology educational background and demonstrated interests related to these research areas coupled with commitment to enhance regulatory science by developing new assays for toxicological and hazard assessment.

Selected Recent Publications:

Shelman D, Gokulan K, Akiyama T, Khan A and Khare S. Identification of Cytolethal Distending Toxin in Non-Typhoidal Salmonella Serovar and its Molecular Mechanism during Macrophage Genotoxicity. Submitted to Journal of Innate Immunity 2013.

Shakir Z, Khan S, Sung K, Khare S, Khan A, et al. Molecular Characterization of Fluoroquinolone-Resistant Aeromonas spp. Isolated from Imported Shrimp. Applied and Environmental Microbiology. 2012;78(22):8137-41.

Khare S, Lawhon SD, Drake KL, Nunes JE, Figueiredo JF, et al. Systems Biology Analysis of Gene Expression during in Vivo Mycobacterium avium subsp. paratuberculosis Enteric Colonization Reveals Role for Immune Tolerance. PloS One 2012;7(8):e42127.

Lawhon SD, Khare S, Rossetti CA, Everts RE, Galindo CL, et al. Role of SPI-1 Secreted Effectors in Acute Bovine Response to Salmonella enterica Serovar Typhimurium: a Systems Biology Analysis Approach. PLoS One. 2011;6(11):e26869.

Adams LG, Khare S, Lawhon SD, Rossetti CA, Lewin HA, et al. Enhancing the Role of Veterinary Vaccines Reducing Zoonotic Diseases of Humans: Linking Systems Biology with Vaccine Development. Vaccine. 2011;29(41):7197-206.


Picture of Igor P. Pogribny, M.D., Ph.D.

Igor P. Pogribny, M.D., Ph.D.
Division of Biochemical Toxicology
National Center for Toxicological Research
Jefferson, AR 72079


  • M.D., Ivano-Frankivsk Medical University
  • Ph.D., Kyiv National Medical University
  • FDA Experience – 16 years

Picture of Frederick A. Beland, Ph.D.

Frederick A. Beland, Ph.D.
Division of Biochemical Toxicology
National Center for Toxicological Research
Jefferson, AR 72079


  • B.A., Colorado College
  • M.S., Montana State University
  • Ph.D., Montana State University
  • FDA Experience – 37 years

Research Interests:

Molecular toxicology, molecular carcinogenesis, genetics, and epigenetics.

Proposed Regulatory Research Project for the FDA Commissioner's Fellow:

Development of a novel in vitro epigenomic approach for the safety assessment of FDA-regulated products. The goal of this research project is to develop a novel predictive approach to improve safety assessments and enhance the efficiency of carcinogenicity testing of FDA-regulated products. The approach consists of incorporating epigenetic technologies into safety assessments of FDA-regulated products.

Evaluating the carcinogenic risk of chemicals has long been a challenge to regulatory agencies, including the FDA. Many industrial chemicals, food contaminants, and pharmaceutical compounds have not been adequately tested for carcinogenicity. For instance, it has been estimated that approximately 31% of marketed drugs have not been tested according to present carcinogenicity testing guidelines.

The recognition of a fundamental role of epigenetic alterations in toxicology suggests that epigenetic alterations may be used as biomarkers for evaluating the carcinogenic potential from exposure to both genotoxic and non-genotoxic agents.

This is of great importance, especially for non-genotoxic agents, since there are no reliable tests to evaluate their carcinogenic potential. Incorporating epigenetic biomarkers into the studies on cancer risk holds a number of advantages over traditionally used methods, including (i) early appearance; (ii) stability; (iii) target tissue-specificity; (iv) relatively low cost of the assays needed to detect these changes, (v) applicability to both genotoxic and non-genotoxic agents, and, more importantly, (vi) a greater number of detectable epigenetic changes as compared to the genetic alterations after exposure.

In our previous studies, we have demonstrated that various genotoxic (e.g., 2-acetylaminofluorene, 1,3-butadiene, and tamoxifen) and non-genotoxic (e.g., WY-14,643 and di-(2-ethyhexyl)phthalate) carcinogens induce epigenetic alterations in the target organs for carcinogenesis.

In this proposal we plan to develop an early screening model for determination of carcinogenicity of genotoxic and non-genotoxic pharmaceuticals and products regulated by the FDA. We hypothesize that pharmaceuticals with carcinogenic potential, contrary to pharmaceuticals without carcinogenic activity, will induce epigenetic abnormalities that can be easily detected.

To achieve this goal, we will expose HepaRG™ cells (Life Technologies, Grand Island, NY), which are metabolically complete human hepatic cells, to various regulated by FDA pharmaceutical products. Following exposure, control and exposed HepaRG™ cells will be analyzed for the presence of epigenetic aberrations, e.g., cytosine DNA methylation and histone histone modifications, gene expression changes, and microRNA alterations.

The incorporation of epigenetic technologies into safety assessments promises to enhance substantially the efficiency of carcinogenicity testing and increase the safety of FDA-regulated products.

Applicant Requirements:

Ph.D. in Chemistry, Biochemistry, Molecular Biology, or Toxicology

Selected Recent Publications:

Koturbash I, Beland F.A., Pogribny I.P. Role of microRNAs in the regulation of drug metabolizing and transporting genes and in the response to environmental toxicants. Expert Opinion on Drug Metabolism and Toxicology, 2012, 8: 597-606.

Tryndyak V., de Conti A., Kobets T., Kutanzi K., Koturbash I., Han T., Fuscoe J.C., Latendresse J.R., Melnyk S., Shymonyak S., Collins L., Ross S.A., Rusyn I., Beland F.A., Pogribny I.P. Inter-strain differences in the severity of liver injury induced by a choline- and folate-deficient diet in mice are associated with dysregulation of genes involved in lipid metabolism. The FASEB Journal, 2012, 26: 4592-4602.

Pogribny I.P., Rusyn I. Environmental toxicants, epigenetics, and cancer. Advances in Molecular Medicine and Biology, 2013, 754: 215-232.

Pogribny I.P., Beland F.A. DNA methylome alterations in chemical carcinogenesis. Cancer Letters, 2013, (in press).

Pogribny I.P., Rusyn I. Role of epigenetic alterations in the development and progression of human hepatocellular carcinoma. Cancer Letters, 2013, (in press).

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