Spontaneous malignant myoid thymoma in an aged female Fischer 344 rat.

A whitish mass approximately 30 mm in diameter was noted in the anterior mediastinum of a 67-week-old female Fischer 344 rat. Histopathologically, two types of tumor cells were identified on the basis of morphologic features: epithelial tumor cells with a tubular or cord-like growth pattern and rhabdomyosarcomatous tumor cells characterized by the presence of cross-striations. Immunohistochemically, the epithelial tumor cells reacted positively for cytokeratin AE1/AE3, and some reacted positively for p63, which is expressed in normal thymic epithelial cells.

A spontaneous myoepithelial carcinoma in the mammary gland of an aged female ICR (CD-1) mouse.

We report a female Crlj:CD1(ICR) mouse with a spontaneous mammary gland tumor composed of biphasic tumor cells, i.e., epithelioid and spindle-shaped myoepithelial cells.

Spontaneous extraskeletal osteosarcoma with various histological growth patterns in the abdominal wall of an ICR mouse.

Extraskeletal osteosarcoma is extremely rare in mice. This case report demonstrates a spontaneous murine extraskeletal osteosarcoma that exhibited various histological growth patterns in an ICR mouse. At necropsy, the tumor mass was located in the abdominal wall and was 45 × 30 × 25 mm in size.

Poorly differentiated salivary gland carcinoma with prominent squamous metaplasia in a pregnant Wistar Hannover rat.

A subcutaneous pale brown-colored mass was observed macroscopically in the ventral neck of a 16-week-old Wistar rat on day 18 of gestation. The mass was well demarcated from the adjacent tissues with partial invasion into connective tissues. Necrosis and hemorrhage were evident throughout the mass.

Inhibition of lipopolysaccharide-induced liver injury in rats treated with a hepatic drug-metabolizing enzyme inducer p,p'-DDT.

Hepatocellular hypertrophy in association with drug-metabolizing enzyme induction is considered to be an adaptive change associated with drug metabolism. To improve our understanding of liver hypertrophy, we determined the effect of a single ip injection of either lipopolysaccharide (LPS) or vehicle in male F344 rats with hepatocellular hypertrophy induced by oral delivery of p,p'-DDT for 2 weeks. The rats were sacrificed 3h or 24h after LPS or vehicle injection.

Polygenic expression of teratozoospermia and normal fertility in B10.MOL-TEN1 mouse strain.

Subfertility and infertility are two major reproductive health problems in human and domestic animals. The contribution of the genotype to these conditions is poorly understood. To examine the genetic basis of male subfertility, we analyzed its relationship to sperm morphology in B10.

p,p'-DDT induces microcytic anemia in rats.

Emerging evidence suggests that chronic exposure to DDT and its derivatives is associated with a variety of human disorders such as anemia. The present study demonstrated that p,p'-DDT caused microcystic anemia in a dose-dependent manner (0, 5, 50, and 500 ppm) in the long-term study up to 2 years. To elucidate the mechanism(s) by which p,p'-DDT induces anemia, certain hematological parameters were assessed in rats fed specific doses of p,p'-DDT for 2 weeks, and the effect of lipopolysaccharide on anemia of inflammation was also examined in p,p'-DDT-treated rats.

Malignant peritoneal mesothelioma with a sarcomatoid growth pattern and signet-ring-like structure in a female f344 rat.

We report a biphasic malignant mesothelioma in an aged female F344/DuCrlCrlj rat. Macroscopically, multiple pale brown nodules were observed in the abdominal cavity with retention of bloody ascites. Histopathologically, the tumor cells spread over the peritoneum and formed masses on the surface and underlying adipose tissues.

Didecyldimethylammonium chloride induces pulmonary fibrosis in association with TGF-β signaling in mice.

Didecyldimethylammonium chloride (DDAC) is a representative dialkyl-quaternary ammonium compound that is used as a disinfectant against several pathogens and is also used in commercial, industrial, and residential settings. We previously investigated toxicity on air way system following single instillation of DDAC to the lungs in mice, and found that DDAC causes pulmonary injury, which is associated with altered antioxidant antimicrobial responses; the inflammatory phase is accompanied or followed by fibrotic response. The present study was conducted to monitor transforming growth factor-β (TGF-β) signaling in pulmonary fibrosis induced by DDAC.

Induction of hyperchromic microcytic anaemia by repeated oral administration of methotrexate in rats.

Anaemia is a significant prognostic factor in cancer patients receiving anticancer drugs such as methotrexate (MTX). This study focuses on the effects of toxicological changes on the hematopoietic systems in male and female Wistar Hannover rats when MTX is orally administered at a dose of 0, 0.05, 0.

Proliferative and nonproliferative lesions of the rat and mouse male reproductive system.

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 nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature and differential diagnosis for classifying microscopic lesions observed in the male reproductive system of laboratory rats and mice, with color microphotographs illustrating examples of some lesions. The standardized nomenclature presented in this document is also available for society members electronically on the Internet (http://goreni.

The enhancing effect of the antioxidant N-acetylcysteine on urinary bladder injury induced by dimethylarsinic acid.

Dimethylarsinic acid (DMA(V)), the major excreted metabolite of inorganic arsenic, is carcinogenic to the rat urinary bladder. Oxidative stress has been proposed as one possible mechanism of DMA(V)-induced carcinogenesis. The authors determined whether the antioxidant N-acetylcysteine (NAC) modifies DMA(V)-induced urinary bladder injury in rats.

Altered pulmonary defense system in lung injury induced by didecyldimethylammonium chloride in mice.

Didecyldimethylammonium chloride (DDAC), a representative dialkyl-quaternary ammonium compound (QAC), could contaminate working atmospheres when used in disinfectant operation and adversely affect human health. Furthermore, the development of bacteria resistant to DDAC might become public health concern. We postulated that DDAC instillation in the lungs alters pulmonary antioxidant and antimicrobial responses and increases susceptibility to systemic administration of a bacterial component lipopolysaccharide (LPS).

Malignant Leydig cell tumor with spindle-shaped cells in a male CD-1 mouse.

Leydig cell tumors with spindle-shaped cells are very rare in humans and animals. We report that an 84-week-old male CD-1 mouse had a malignant Leydig cell tumor characterized by proliferation of oval to spindle-shaped cells with or without fat deposition, and with a storiform pattern. These cells were immunopositive for inhibin and S-100, and negative for the androgen receptor, thereby suggesting that they may have differentiated from Leydig cells.

Pulmonary injury and antioxidant response in mice exposed to arsenate and hexavalent chromium and their combination.

Chromated copper arsenate, which is used worldwide as a wood preservative, can adversely affect human health. Accumulating evidence suggests that chromium (Cr) and arsenic (As) can potentially disrupt the redox balance and cause respiratory diseases and cancer in humans. The present study was designed to determine the combined toxic effects of these metals in the lungs and to clarify the specific molecules that are stimulated by combined exposure to both metals.

Didecyldimethylammonium chloride induces pulmonary inflammation and fibrosis in mice.

Didecyldimethylammonium chloride (DDAC) is used worldwide as a germicide, in antiseptics, and as a wood preservative, and can cause adverse pulmonary disease in humans. However, the pulmonary toxicity of DDAC has not yet been thoroughly investigated. Mice were intratracheally instilled with DDAC to the lung and the bronchoalveolar lavage (BAL) fluid and lung tissues were collected to assess dose- and time-related pulmonary injury.

Malignant myopericytoma-like tumor in a Fischer rat.

Myopericytoma is a perivascular tumor that has been recently described in humans, but not in laboratory rodents. The authors encountered an intra-abdominal tumor resembling human malignant myopericytoma in a Fischer rat. Grossly, the tumor was found as two brown-colored masses located in the mesentery of rectum.

Establishment of a novel specific ELISA system for rat N- and C-ERC/mesothelin. Rat ERC/mesothelin in the body fluids of mice bearing mesothelioma.

Mesothelioma is a type of malignant tumor that most commonly arises from the pleural or peritoneal membrane and is usually associated with previous exposure to asbestos. In humans, ERC/mesothelin is expressed on the normal mesothelium and in some cancers such as mesothelioma or ovarian carcinoma. Recently, several enzyme-linked immunosorbent assay (ELISA) systems for ERC/mesothelin have been developed, the reported usefulness of which has been assessed and demonstrated as a diagnostic tool.

Establishment of the enzyme-linked immunosorbent assay system to detect the amino terminal secretory form of rat Erc/Mesothelin.

By representational difference analysis, we previously identified the rat Erc (Expressed in renal carcinoma) gene that was more abundantly expressed in the renal carcinoma tissues of Eker rats than in the rat normal kidney. In this study, we raised antibodies against the amino-terminal portion of the rat Erc, and demonstrated the existence of a approximately 30-kDa secretory form in the supernatant of cultured cells derived from rat renal carcinoma. The enzyme-linked immunosorbent assay (ELISA) system using these antibodies detected high concentrations of this form in the sera of Eker rats bearing renal carcinomas, and in the sera of rats transplanted with mesothelioma cells.

Store-mediated calcium entry in pleural mesothelial cells.

Store-mediated Ca2+ entry is thought as the main pathway for Ca2+ influx in non-excitable cells. Although a role for the actin cytoskeleton in store-mediated Ca2+ entry has been proposed in some cell types, the role of actin cytoskeleton in store-mediated Ca2+ entry is still a controversy. To address this question, the effects of cytoskeletal modifiers on store-mediated Ca2+ entry in pleural mesothelial cells were examined.

Two-generation reproduction toxicity study in rats with 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (p,p'-DDT).

DDT, an organochlorine pesticide, has been cited as a representative chemical suspected of having endocrine disrupting effects. In this study, the potential endocrine disrupting activities of p,p'-DDT, a major component of DDT, were investigated in rats in a 2-generation reproduction toxicity study in accordance with the most current test guidelines of the Ministry of Agriculture, Forestry and Fisheries in Japan, Organization for Economic Cooperation and Development (OECD) and United States Environmental Protection Agency (USEPA) with some modifications and additions. p,p'-DDT was given to parental rats at dietary levels of 0, 5, 50 or 350 ppm.

Pathogenetic transition in the morphology of abnormal sperm in the testes and the caput, corpus, and cauda epididymides of male rats after treatment with 4,6-dinitro-o-cresol.

In order to elucidate the pathogenesis of tailless sperm, 4,6-dinitro-o-cresol (DNOC) was administered to Jcl:SD male rats at daily oral doses of 0, 10 or 15mg/kg for 5 days. Sperm were collected from the caput, corpus, and cauda epididymides on days 1, 7 and 14 after the last dosing (D1, D7 and D14, respectively), counted and examined morphologically by phase-contrast and scanning electron microscopy. The incidence of abnormal sperm was significantly increased in the DNOC 15mg/kg group.

A two-generation reproductive toxicity study of 2,4-dichlorophenol in rats.

A two-generation reproductive toxicity study was conducted with 2,4-dichlorophenol (2,4-DCP), an agent suspected of exerting endocrine disrupting effects. Wistar-Hannover rats, 24/sex/group, were given diet containing 2,4-DCP at dose levels of 0, 500, 2000 or 8000 ppm to examine the potential effects of the test substance on parental animals and their offspring over 2 successive generations. Neither clear systemic nor reproductive toxicity of 2,4-DCP was apparent in the 500 ppm group.

The effect of testosterone propionate supplement on testicular toxicity with thiamphenicol in male Sprague-Dawley rats.

Testosterone propionate (TP) was supplemented to male rats for assessment of its ameliorating effect on testicular toxicity with thiamphenicol (TAP). A total of 20 male Sprague-Dawley rats were treated orally with TAP at 200 mg/kg/day for up to 4 weeks. In addition, 5 male rats were allotted to the control group receiving vehicle only.

Pulmonary sequestration with ectopic pancreatic tissue in a Wistar Hannover GALAS rat.

A multicystic mass of the lung was found in a male 11-week-old Wistar Hannover GALAS rat. The cystic mass was located in the region of the right caudal lobe and had no direct communication with the tracheobranchial tree. Histologically, the pulmonary mass was composed of variably sized cysts containing mucinous material, cellular debris, erythrocytes, and inflammatory cells.