National Toxicology Program (NTP) pathologists are engaged in important initiatives that have significant global impact. These initiatives build on its leadership in pathology peer review and publications in the areas of toxicologic pathology, clinical pathology, and laboratory animal medicine. Over the past decade, NTP/National Institute of Environmental Health Sciences research initiatives have focused on cancer and noncancer hazard identification, with the goal of understanding cellular and molecular mechanisms of disease. New initiatives of significant global impact include the web-based nonneoplastic lesion atlas and an NTP partnership with international scientists to investigate molecular mechanisms at the whole genome level, which will be used to inform potential mechanisms of environmental exposures in human cancers. Also, we are dedicated to contributing to pathology and toxicology organizations through service on executive committees and editorial boards, participating in international projects and symposiums, and providing training for future leaders in toxicologic pathology. Herein, we provide highlights of our global contributions.

Tungsten is a naturally occurring, high-tensile strength element that has been used in a number of consumer products. Tungsten has been detected in soil, waterways, groundwater, and human tissue and body fluids. Elevated levels of tungsten in urine were reported for populations exposed to tungstate in drinking water in areas where natural tungsten formations were prevalent. Published reports indicated that sodium tungstate may modulate hematopoiesis, immune cell populations, and immune responses in rodent models. The objective of this study was to assess potential immunotoxicity of sodium tungstate dihydrate (STD), a drinking water contaminant. Female B6C3F1/N mice received 0-2000mg STD/L in their drinking water for 28 d, and were evaluated for effects on immune cell populations in spleen and bone marrow, and humoral-mediated, cell-mediated, and innate immunity. Three different parameters of cell-mediated immunity were similarly affected at 1000mg STD/L. T-cell proliferative responses against allogeneic leukocytes and anti-CD3 were decreased 32%, and 21%, respectively. Cytotoxic T-lymphocyte activity was decreased at all effector:target cell ratios examined. At 2000mg STD/L, the absolute numbers of CD3(+) T-cell progenitor cells in bone marrow were increased 86%, but the alterations in B-lymphocyte and other progenitor cells were not significant. There were no effects on bone marrow DNA synthesis or colony forming capabilities. STD-induced effects on humoral-mediated immunity, innate immunity, and splenocyte sub-populations were limited. Enhanced histopathology did not detect treatment-related lesions in any of the immune tissues. These data suggest exposure to STD in drinking water may adversely affect cell-mediated immunity.

Virginia cedarwood oil is widely used as a fragrance material in household and personal products and as a naturally derived pesticide alternative. Due to conflicting literature on dermal exposures in animals and humans, concern for safe levels of human exposure remains. The present study evaluated the toxicity of cedarwood oil applied dermally to F344/N rats and B6C3F1/N mice for 13 weeks. Groups of 10 male and female rats and mice received no treatment (untreated control) or were administered cedarwood oil in 95% aqueous ethanol dermally at concentrations ranging from 0% (vehicle control), 6.25%, 12.5%, 25%, 50%, and 100% (undiluted). Rats and mice developed extensive skin lesions at the site of application. Benchmark dose modeling (BMD) was performed for the significantly increased skin lesions observed in the rat, to provide perspective for risk assessment applications. Benchmark dose modeling levels (BMDL) of 0.65 to 2.1% and 1.2 to 4.4% (equivalent to 13 to 42 mg/kg and 24 to 48 mg/kg, respectively) cedarwood oil were calculated for the most sensitive endpoint of epidermal hyperplasia in female rats and chronic active inflammation in male rats, respectively. These BMDL levels coincide with reported use levels in cosmetics and pesticides, raising the concern for human exposure.

Cumene hydroperoxide (CHP) is a high production volume chemical that is used to generate phenol and acetone. Dermal exposure to CHP was hypothesized to result in systemic tissue toxicity, production of free radicals, and consequent decrease in plasma antioxidant levels. To evaluate the hypothesis and characterize the toxicity of CHP, male and female B6C3F1/N mice and F344/N rats were exposed to varying doses of CHP applied topically for 14 or 90 days. No significant changes in survival or body weight of mice and rats were observed following 14 days of exposure. However, 90 days of CHP exposure at the high dose (12 mg/kg) triggered a significant decrease (−15%) in the body weight of the male rat group only. Irritation of the skin was observed at the site of application and was characterized by inflammation and epidermal hyperplasia. In treated animals, histology of liver tissue, free radical generation, and antioxidant levels in blood plasma were not significantly changed as compared to the corresponding controls. Consistent with the lack of systemic damage, no increase in micronucleated erythrocytes was seen in peripheral blood. In conclusion, topical CHP application caused skin damage only at the application site and did not cause systemic tissue impairment.

Based on stable integration of recombinant DNA into a host genome, transgenic technology has become an important genetic engineering methodology. An organism whose genetic characteristics have been altered by the insertion of foreign DNA is supposed to exhibit a new phenotype associated with the function of the transgene. However, successful insertion may not be sufficient to achieve specific modification of function. In this study we describe a strain of transgenic mouse, G7-882, generated by incorporation into the mouse genome of human Ca-v 1.2 alpha(1C) cDNA deprived of 3'-UTR to exclude transcription. We found that, in response to chronic infusion of isoproterenol, G7-882 develops dilated cardiomyopathy, a misleading "transgenic artifact" compatible with the expected function of the incorporated "correct" transgene. Specifically, using magnetic resonance imaging (MRI), we found that chronic beta-adrenergic stimulation of G7-882 mice caused left ventricular hypertrophy and aggravated development of dilated cardiomyopathy, although no significant changes in the kinetics, density and voltage dependence of the calcium current were observed in G7-882 cardiomyocytes as compared to cells from wild type mice. This result illustrates the possibility that even when a functional transgene is expressed, an observed change in phenotype may be due to the artifact of "incidental incorporation" leading to misleading conclusions. To exclude this possibility and thus provide a robust tool for exploring biological function, the new transgenic phenotype must be replicated in several independently generated transgenic strains.

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally-accepted nomenclature for proliferative and non-proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in the respiratory tract of laboratory rats and mice, with color photomicrographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous developmental and aging lesions as well as lesions induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for respiratory tract lesions in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

One of the challenges for toxicologic pathologists is to translate the diverse range of morphologic changes that are observed in toxicity studies into a consistent and readily understood set of diagnostic terms to be tabulated and summarized in regulatory reports or peer-reviewed publications. Historically, there have been multiple efforts to provide uniform nomenclature for lesions observed in laboratory animals. These efforts began as early as 1973 and have culminated in various textbooks, workshop reports, and monographs. The efforts have typically focused on the rat and mouse and, in many cases, were limited to proliferative lesions. Many of the texts or documents that describe suggested nomenclature are either not widely available or are out of print. To address this issue, members of the major societies of toxicologic pathology (JSTP, BSTP, ESTP, and STP) have been engaged in an international collaborative effort to codify and publish uniform nomenclature for both proliferative and nonproliferative lesions in laboratory rodents. Several features unique to this effort include (1) a truly international scope, (2) implementation of an open comment period allowing a wide group of toxicologic pathologists the opportunity to provide input, and (3) availability in a Web-based format. The project goes under the acronym INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice). Project oversight is provided by the Global Editorial and Steering Committee (GESC), which consists of members from each of the major societies of toxicologic pathology. The most important components of the INHAND project are the Organ System Working Groups. Formation of these groups is coordinated by the GESC, and they consist of a global chairperson and members from each of the major societies of toxicologic pathology. The GESC actively seeks out organ system experts to serve on these groups. In addition, the GESC often accommodates requests from pathologists who volunteer for a specific organ working group. The Organ System Working Groups have the responsibility to prepare the nomenclature guidelines for both proliferative and nonproliferative lesions of rats and mice for their assigned organ system. In addition to lesions that occur spontaneously, the groups are asked to determine if there are common, xenobiotic-induced lesions for which standardized nomenclature might be needed. The working groups draw heavily from existing nomenclature documents, Web sites, and publications including prior work of the Registry of Industrial Toxicology Animal-Data (RITA) and the Standardized System of Nomenclature and Diagnostic Criteria (SSNDC). For each diagnostic entity, the working group selects a preferred diagnosis and acceptable alternative diagnoses, provides diagnostic criteria and differential diagnosis, and prepares representative photomicrographs. An important feature of the INHAND project is the access provided to the global open Registry Nomenclature Information System (goRENI; www.goreni.org) (Figure 1). Access is provided to all members of toxicologic pathology societies worldwide. Access is free but must be requested through the goRENI Web site (Figure 2). Once access is granted, pathologists can navigate by organ systems (Figure 3) and ultimately select a diagnosis they would like to view. Within the goRENI system, each diagnostic entity is referred to as a ‘‘manuscript.’’ An example is the written information, and photographic illustrations, provided for a bronchiolo-alveolar carcinoma as shown in Figure 4. Once an organ working group has prepared a draft document, the nomenclature is placed on the goRENI Web site for review and discussion. Members of the contributing STPs are notified of the dates of the review period through their respective societies. Following the designated comment period, the working group revises the nomenclature documents and, in consultation with the GESC, finalizes the nomenclature for that organ system. Finalized nomenclature will be available to toxicologic pathologists in two forms: (1) electronic access via the goRENI Web site and (2) print-based publication in the toxicologic pathology journals. Due to the substantial costs associated with print-based This is an opinion article submitted to the Regulatory Forum and does not constitute an official position of the Society of Toxicologic Pathology or the journal Toxicologic Pathology. The views expressed in this article are those of the authors and do not necessarily represent the policies, positions, or opinions of their respective agencies and organizations. Conflict of interest: The authors have not declared any conflict of interest.