N J Walker

Summary

Affiliation: National Institutes of Health
Country: USA

Publications

  1. ncbi request reprint Unraveling the complexities of the mechanism of action of dioxins
    Nigel J Walker
    National Institute of Environmental Health Sciences, National Institutes of Health, PO Box 12233, MD EC 34, 111 T W Alexander Drive, Research Triangle Park, North Carolina 27709, USA
    Toxicol Sci 95:297-9. 2007
  2. pmc Absolute estimation of initial concentrations of amplicon in a real-time RT-PCR process
    Marjo V Smith
    Constella Group, Suite 200, 2605 Meridian Pky, Durham, NC, USA
    BMC Bioinformatics 8:409. 2007
  3. ncbi request reprint Tech.Sight. A technique whose time has come
    Nigel J Walker
    Environmental Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
    Science 296:557-9. 2002
  4. pmc A 21st century paradigm for evaluating the health hazards of nanoscale materials?
    Nigel J Walker
    National Toxicology Program, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
    Toxicol Sci 110:251-4. 2009
  5. pmc Comparison of chronic toxicity and carcinogenicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in 2-year bioassays in female Sprague-Dawley rats
    Nigel J Walker
    Environmental Toxicology Program, National Institute of Environmental Health Sciences, Natinal Institutes of Health, Research Triangle Park, NC 27709, USA
    Mol Nutr Food Res 50:934-44. 2006
  6. ncbi request reprint Real-time and quantitative PCR: applications to mechanism-based toxicology
    N J Walker
    Molecular Epidemiology and Dosimetry Section, Laboratory of Computational Biology and Risk Analysis, NIEHS, 111 Alexander Drive, PO Box 12233, MD D4 01, Research Triangle Park, NC 27709, USA
    J Biochem Mol Toxicol 15:121-7. 2001
  7. pmc Pulmonary lesions in female Harlan Sprague-Dawley rats following two-year oral treatment with dioxin-like compounds
    Nigel J Walker
    National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
    Toxicol Pathol 35:880-9. 2007
  8. ncbi request reprint Hepatocarcinogenesis in female Sprague-Dawley rats following discontinuous treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin
    N J Walker
    Environmental Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
    Toxicol Sci 54:330-7. 2000
  9. ncbi request reprint Characterization of the dose-response of CYP1B1, CYP1A1, and CYP1A2 in the liver of female Sprague-Dawley rats following chronic exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin
    N J Walker
    National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
    Toxicol Appl Pharmacol 154:279-86. 1999
  10. ncbi request reprint Differences in kinetics of induction and reversibility of TCDD-induced changes in cell proliferation and CYP1A1 expression in female Sprague-Dawley rat liver
    N J Walker
    Laboratory of Computational Biology and Risk Analysis, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
    Carcinogenesis 19:1427-35. 1998

Collaborators

Detail Information

Publications46

  1. ncbi request reprint Unraveling the complexities of the mechanism of action of dioxins
    Nigel J Walker
    National Institute of Environmental Health Sciences, National Institutes of Health, PO Box 12233, MD EC 34, 111 T W Alexander Drive, Research Triangle Park, North Carolina 27709, USA
    Toxicol Sci 95:297-9. 2007
  2. pmc Absolute estimation of initial concentrations of amplicon in a real-time RT-PCR process
    Marjo V Smith
    Constella Group, Suite 200, 2605 Meridian Pky, Durham, NC, USA
    BMC Bioinformatics 8:409. 2007
    ..The more elaborate mechanistic models require many more parameters than can be fit from a single amplification, while the empirical models provide little insight and are difficult to tailor to specific reactants...
  3. ncbi request reprint Tech.Sight. A technique whose time has come
    Nigel J Walker
    Environmental Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
    Science 296:557-9. 2002
  4. pmc A 21st century paradigm for evaluating the health hazards of nanoscale materials?
    Nigel J Walker
    National Toxicology Program, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
    Toxicol Sci 110:251-4. 2009
    ....
  5. pmc Comparison of chronic toxicity and carcinogenicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in 2-year bioassays in female Sprague-Dawley rats
    Nigel J Walker
    Environmental Toxicology Program, National Institute of Environmental Health Sciences, Natinal Institutes of Health, Research Triangle Park, NC 27709, USA
    Mol Nutr Food Res 50:934-44. 2006
    ..This may result from differences in the experimental protocols as well as divergence in the biological behavior of the different stocks of Sprague-Dawley rat strains used...
  6. ncbi request reprint Real-time and quantitative PCR: applications to mechanism-based toxicology
    N J Walker
    Molecular Epidemiology and Dosimetry Section, Laboratory of Computational Biology and Risk Analysis, NIEHS, 111 Alexander Drive, PO Box 12233, MD D4 01, Research Triangle Park, NC 27709, USA
    J Biochem Mol Toxicol 15:121-7. 2001
    ..The aim of this review is to provide the reader with an overview of this technology and to highlight specific applications of this technology to some key areas of molecular toxicology...
  7. pmc Pulmonary lesions in female Harlan Sprague-Dawley rats following two-year oral treatment with dioxin-like compounds
    Nigel J Walker
    National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
    Toxicol Pathol 35:880-9. 2007
    ..Potential mechanisms leading to altered differentiation and/or proliferation of bronchiolar and alveolar epithelia may be through CYP1A1 induction or disruption of retinoid metabolism...
  8. ncbi request reprint Hepatocarcinogenesis in female Sprague-Dawley rats following discontinuous treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin
    N J Walker
    Environmental Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
    Toxicol Sci 54:330-7. 2000
    ....
  9. ncbi request reprint Characterization of the dose-response of CYP1B1, CYP1A1, and CYP1A2 in the liver of female Sprague-Dawley rats following chronic exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin
    N J Walker
    National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
    Toxicol Appl Pharmacol 154:279-86. 1999
    ....
  10. ncbi request reprint Differences in kinetics of induction and reversibility of TCDD-induced changes in cell proliferation and CYP1A1 expression in female Sprague-Dawley rat liver
    N J Walker
    Laboratory of Computational Biology and Risk Analysis, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
    Carcinogenesis 19:1427-35. 1998
    ....
  11. pmc Dose-additive carcinogenicity of a defined mixture of "dioxin-like compounds"
    Nigel J Walker
    National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27705, USA
    Environ Health Perspect 113:43-8. 2005
    ..These data support the use of the TEF approach for dioxin cancer risk assessments...
  12. ncbi request reprint Physiological modeling of a proposed mechanism of enzyme induction by TCDD
    M C Kohn
    Laboratory of Computational Biology and Risk Analysis, National Institute of Environmental Health Sciences, PO Box 12233, Research Triangle Park, NC 27709, USA
    Toxicology 162:193-208. 2001
    ..Predicted induction at low doses was found to vary widely with the assumptions used in the construction of a model. More detailed descriptions of biological processes might provide more reliable predictions of enzyme induction...
  13. ncbi request reprint Regulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced tumor promotion by 17 beta-estradiol in female Sprague--Dawley rats
    M E Wyde
    National Institute of Environmental Health Sciences, Environmental Toxicology Program, Research Triangle Park, North Carolina 22709, USA
    Toxicol Appl Pharmacol 173:7-17. 2001
    ....
  14. ncbi request reprint Induction of hepatic 8-oxo-deoxyguanosine adducts by 2,3,7,8-tetrachlorodibenzo-p-dioxin in Sprague-Dawley rats is female-specific and estrogen-dependent
    M E Wyde
    National Institute of Environmental Health Sciences, Environmental Toxicology Program, Research Triangle Park, North Carolina 27709, USA
    Chem Res Toxicol 14:849-55. 2001
    ..These studies provide strong evidence that the induction of 8-oxo-dG by TCDD occurs via a chronic, sex-specific, estrogen-dependent mechanism...
  15. pmc Animal models of human response to dioxins
    J A Grassman
    Laboratory of Computational Biology and Risk Analysis, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
    Environ Health Perspect 106:761-75. 1998
    ..The information gained from animal models is important for developing mechanistic models of dioxin toxicity and critical for assessing the risks to human populations under different circumstances of exposure...
  16. ncbi request reprint Differential toxicogenomic responses to 2,3,7,8-tetrachlorodibenzo-p-dioxin in malignant and nonmalignant human airway epithelial cells
    Jeanelle M Martinez
    National Institute of Environmental Health Sciences, Rall Building 101, 111 Alexander Drive, Research Triangle Park, NC 27709, USA
    Toxicol Sci 69:409-23. 2002
    ..In addition, TCDD altered specific immunomodulatory genes in the HPL1A cells. These data show that TCDD alters multiple integrated networks of signaling pathways associated with pulmonary disease, particularly that of lung cancer...
  17. ncbi request reprint Gingival carcinogenicity in female Harlan Sprague-Dawley rats following two-year oral treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin and dioxin-like compounds
    Katsuhiko Yoshizawa
    Laboratory of Experimental Pathology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
    Toxicol Sci 83:64-77. 2005
    ..These results indicate that dioxin and DLCs target the gingiva of the oral cavity, in particular the junctional epithelium of molars...
  18. ncbi request reprint Isolation and characterization of a novel gene induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in rat liver
    O Selmin
    Laboratory of Computational Biology and Risk Analysis, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
    Carcinogenesis 17:2609-15. 1996
    ....
  19. ncbi request reprint Promotion of altered hepatic foci by 2,3,7,8-tetrachlorodibenzo-p-dioxin and 17beta-estradiol in male Sprague-Dawley rats
    Michael E Wyde
    National Institute of Environmental Health Sciences, Environmental Toxicology Program, 111 Alexander Drive, Building 101, Room D452, MD4 01, Research Triangle Park, North Carolina 27709, USA
    Toxicol Sci 68:295-303. 2002
    ..The weaker potency of tumor promotion and lack of induction of cell replication and DNA damage in male rats likely explain the female-specific hepatocarcinogenicity of TCDD in chronic bioassays...
  20. ncbi request reprint Olfactory epithelial metaplasia and hyperplasia in female Harlan Sprague-Dawley rats following chronic treatment with polychlorinated biphenyls
    Abraham Nyska
    Laboratory of Experimental Pathology National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709 9998, USA
    Toxicol Pathol 33:371-7. 2005
    ..Variable amounts of acute inflammatory exudate appeared within the lumen of the nasal cavity, overlying the affected epithelium. Occasionally, the inflammation eroded through the skull and into the adjacent olfactory bulbs...
  21. ncbi request reprint Incidences of selected lesions in control female Harlan Sprague-Dawley rats from two-year studies performed by the National Toxicology Program
    Amy E Brix
    Experimental Pathology Laboratories, PO Box 12766, Research Triangle Park, NC 27709, USA
    Toxicol Pathol 33:477-83. 2005
    ..2%). Squamous metaplasia is not a lesion commonly observed in NTP control Fischer rats. The Harlan SD rats had a very low incidence of mononuclear cell leukemia (0.5%), compared with an incidence of 24% in female Fischer rats...
  22. pmc Exocrine pancreatic pathology in female Harlan Sprague-Dawley rats after chronic treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin and dioxin-like compounds
    Abraham Nyska
    Laboratory of Experimental Pathology, National Institute of Environmental Health Sciences, National Institutes of Health DHHS, PO Box 12233, Research Triangle Park, NC 27709, USA
    Environ Health Perspect 112:903-9. 2004
    ..These results indicate that the pancreatic acini are target tissues for dioxin and certain dioxin-like compounds. Key words: carcinogenesis, dioxin, furans, inflammation, pancreas, polychlorinated biphenyls...
  23. ncbi request reprint Classification of proliferative hepatocellular lesions in harlan sprague-dawley rats chronically exposed to dioxin-like compounds
    James R Hailey
    National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
    Toxicol Pathol 33:165-74. 2005
    ..This paper describes the morphology of these lesions, as well as the diagnostic approach taken in this series of studies...
  24. ncbi request reprint EGR1 is a novel target for AhR agonists in human lung epithelial cells
    Jeanelle M Martinez
    Laboratory of Computational Biology and Risk Analysis, NIEHS, Research Triangle Park, North Carolina 27709, USA
    Toxicol Sci 82:429-35. 2004
    ..Increased expression of a transcription factor EGR1 with tumorigenic and other biological activities could contribute to the deleterious pulmonary effects of exposure to these environmental agents...
  25. ncbi request reprint Oral and dermal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces cutaneous papillomas and squamous cell carcinomas in female hemizygous Tg.AC transgenic mice
    Michael E Wyde
    National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
    Toxicol Sci 82:34-45. 2004
    ..Differences in response between the routes of exposure may reflect pharmacokinetic differences in the delivery of TCDD to the skin over the duration of the study...
  26. pmc Gene interaction network suggests dioxin induces a significant linkage between aryl hydrocarbon receptor and retinoic acid receptor beta
    Hiroyoshi Toyoshiba
    Laboratory of Computational Biology and Risk Analysis, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
    Environ Health Perspect 112:1217-24. 2004
    ..Simulation studies demonstrated the method works well, even for small samples...
  27. ncbi request reprint Evaluation of toxic equivalency factors for induction of cytochromes P450 CYP1A1 and CYP1A2 enzyme activity by dioxin-like compounds
    Hiroyoshi Toyoshiba
    National Institute of Environmental Health Sciences, 27709, Durham, NC, USA
    Toxicol Appl Pharmacol 194:156-68. 2004
    ..These results indicate that for some biological responses, the use of a single relative potency factor (RPF) is not appropriate for the comparison of the dose response behavior of different dioxin-like congeners...
  28. ncbi request reprint The putative tumor suppressor Tsc-22 is downregulated early in chemically induced hepatocarcinogenesis and may be a suppressor of Gadd45b
    Mari Iida
    Laboratory of Molecular Carcinogenesis, Toxicology Operations Branch, Environmental Toxicology Program, National Institute of Environmental Health Sciences, National Institute of Health, Research Triangle Park, NC 27709, USA
    Toxicol Sci 99:43-50. 2007
    ..These data provide evidence that Tsc-22 is a suppressor of Gadd45b expression, which may contribute to an early antiapoptotic response...
  29. ncbi request reprint Mechanisms of exocrine pancreatic toxicity induced by oral treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin in female Harlan Sprague-Dawley Rats
    Katsuhiko Yoshizawa
    Laboratory of Experimental Pathology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
    Toxicol Sci 85:594-606. 2005
    ..Changes in the expression of CYP or CCKAR may have induced the acinar-cell tumors by initiating proliferation...
  30. ncbi request reprint Follicular epithelial cell hypertrophy induced by chronic oral administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin in female Harlan Sprague-Dawley rats
    Yoshiro Tani
    Laboratory of Experimental Pathology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
    Toxicol Pathol 32:41-9. 2004
    ..These results indicate that the follicular cell response was hypertrophic and reversible. This information should contribute to diagnosis of nonneoplastic thyroid follicular lesions in rats...
  31. ncbi request reprint Characterization of bronchiolar metaplasia of the alveolar epithelium in female Sprague-Dawley rats exposed to 3,3',4,4',5-pentachlorobiphenyl (PCB126)
    Amy E Brix
    Experimental Pathology Laboratories, Inc, Research Triangle Park, North Carolina 27709, USA
    Toxicol Pathol 32:333-7. 2004
    ....
  32. doi request reprint Predicting the hepatocarcinogenic potential of alkenylbenzene flavoring agents using toxicogenomics and machine learning
    Scott S Auerbach
    National Toxicology Program, National Institute of Environmental Health Sciences, NIH, RTP, NC 27709, USA
    Toxicol Appl Pharmacol 243:300-14. 2010
    ..Furthermore, we find that exposure duration is a critical variable in the success or failure of such an approach, particularly when evaluating chemicals with unknown carcinogenic potency...
  33. ncbi request reprint Drug-induced expression of nonsteroidal anti-inflammatory drug-activated gene/macrophage inhibitory cytokine-1/prostate-derived factor, a putative tumor suppressor, inhibits tumor growth
    Jeanelle M Martinez
    Laboratories of Molecular Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, USA
    J Pharmacol Exp Ther 318:899-906. 2006
    ..Drugs that target NAG-1 could lead to a unique strategy for the development of chemotherapeutic and chemopreventive agents...
  34. ncbi request reprint Effects of TCDD upon IkappaB and IKK subunits localized in microsomes by proteomics
    Maribel E Bruno
    Proteomics Group, National Center for Toxicogenomics, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
    Arch Biochem Biophys 406:153-64. 2002
    ..Overall, proteomic analysis indicated the presence of NF-kappaB pathway members in microsomes, selectively altered by dioxin, which may influence immune and inflammatory responses within the liver...
  35. ncbi request reprint Area under the curve as a dose metric for promotional responses following 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure
    Amy H Kim
    University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
    Toxicol Appl Pharmacol 191:12-21. 2003
    ..74 versus 0.20%, respectively. These findings suggest that the peak magnitude of TCDD in liver rather than AUC may play a significant role in the induction of complex biological responses by TCDD...
  36. ncbi request reprint Increase in cardiovascular pathology in female Sprague-Dawley rats following chronic treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin and 3,3',4,4',5-pentachlorobiphenyl
    Micheal P Jokinen
    Pathology Associates, Durham, NC, USA
    Cardiovasc Toxicol 3:299-310. 2003
    ..The authors' investigations indicate that the rat cardiovascular system is a target for dioxin toxicity, which increases the incidence of spontaneous cardiomyopathy and arteritis...
  37. pmc Accumulation of M1dG DNA adducts after chronic exposure to PCBs, but not from acute exposure to polychlorinated aromatic hydrocarbons
    Yo Chan Jeong
    Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, NC 27599, USA
    Free Radic Biol Med 45:585-91. 2008
    ..In summary, the results from the present study support the hypothesis that oxidative DNA damage plays a key role in toxicity and carcinogenicity following long-term PCB exposure...
  38. pmc Respiratory tract lesions in noninhalation studies
    Donald M Sells
    Battelle Columbus Laboratories, Columbus, OH 43201, USA
    Toxicol Pathol 35:170-7. 2007
    ..The presence of respiratory tract lesions in noninhalation studies emphasizes the need for a thorough examination of the respiratory tract including nasal passages, regardless of the route of administration...
  39. pmc A critical comparison of murine pathology and epidemiological data of TCDD, PCB126, and PeCDF
    Katsuhiko Yoshizawa
    Toxicologic Pathology, Drug Safety Research Laboratories, Astellas Pharma Inc, Yodogawa, Osaka, Japan
    Toxicol Pathol 35:865-79. 2007
    ....
  40. pmc Subchronic exposure to TCDD, PeCDF, PCB126, and PCB153: effect on hepatic gene expression
    Chad M Vezina
    University of Wisconsin Madison, School of Pharmacy, Madison, Wisconsin, USA
    Environ Health Perspect 112:1636-44. 2004
    ..Together, these findings may help to elucidate some of the fundamental features of dioxin toxicity and may further clarify the biologic role of the AhR signaling pathway...
  41. ncbi request reprint Development of a refined database of mammalian relative potency estimates for dioxin-like compounds
    Laurie C Haws
    ChemRisk, 8024 Mesa Dr, 126, Austin, Texas 78731, USA
    Toxicol Sci 89:4-30. 2006
    ....
  42. pmc Migration of intradermally injected quantum dots to sentinel organs in mice
    Neera V Gopee
    National Center for Toxicological Research, U S Food and Drug Administration, Jefferson, Arkansas 72079, USA
    Toxicol Sci 98:249-57. 2007
    ....
  43. pmc Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin) enhances triggered afterdepolarizations in rat ventricular myocytes
    An Xie
    Department of Basic Pharmaceutical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC, USA
    Cardiovasc Toxicol 6:99-110. 2006
    ..These effects may lead to clinically relevant ventricular arrhythmia especially when susceptible individuals are under elevated sympathetic stress or suffering from other myocardiopathies coincided with Ca2+-overload...
  44. ncbi request reprint Impact of physiologically based pharmacokinetic modeling on benchmark dose calculations for TCDD-induced biochemical responses
    Amy H Kim
    Curriculum in Toxicology, University of North Carolina at Chapel Hill, 509 Mary Ellen Jones Building, CB 7270, 27599, USA
    Regul Toxicol Pharmacol 36:287-96. 2002
    ..BB(01) and BB(10) values from both methods were within two orders of magnitude of current human general population exposure to all dioxin-like compounds...
  45. ncbi request reprint Safe handling of nanotechnology
    Andrew D Maynard
    Woodrow Wilson International Center for Scholars, USA
    Nature 444:267-9. 2006
  46. ncbi request reprint Research strategies for safety evaluation of nanomaterials, part II: toxicological and safety evaluation of nanomaterials, current challenges and data needs
    Michael P Holsapple
    ILSI Health and Environmental Sciences Institute, One Thomas Circle, NW, 9th Floor, Washington, District of Columbia 20005, USA
    Toxicol Sci 88:12-7. 2005
    ....