bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Carbon Dioxide Inhalation on Hematology, Coagulation, and Serum Clinical Chemistry Values in Rats
Authors: Walter Gail L.
Published: February 2008

Blood samples from adult male and female Charles River Cr1:CD® (SD) BR rats were collected at weekly intervals for 4 wk to evaluate the effects of inhalation of an anesthetic dose of carbon dioxide (CO2) or of a carbon dioxide-oxygen mixture (CO2/O2) on hematology, coagulation, and serum biochemistry values. During the first 3 wk of the study, rats were assigned to 1 of 3 groups and were bled from the orbital sinus once weekly. Prior to the blood collection, rats in group 1 were exposed to room air only, rats in group 2 received CO 2/O2 (approximately 66%:34% CO2:O2) by inhalation, and rats in group 3 received 100% CO2 by inhalation. In the rats exposed to CO2/O2 or CO2, leukocyte counts, lymphocyte counts, and glucose values were higher, and aspartate aminotransferase, creatine kinase, and calcium values were lower compared with those of rats exposed to room air only. Rats exposed to 100% CO2 had slightly (but statistically significant) lower mean corpuscular hemoglobin concentration when compared with rats exposed only to room air. During week 4, all rats were reassigned to 1 of 2 groups and were bled terminally via closed cardiac puncture following exposure to either CO2/O2 or CO 2. Increased lymphocyte counts (males only) and glucose and chloride concentrations were noted for rats exposed to CO2/O2 compared with those exposed to CO2. These alterations reiterate the importance of comparing clinical pathology values to those of concurrent control groups that have experienced blood collection under identical conditions in order to avoid potential errors in the interpretation of data.
Pathological Evaluation of the Effects of Intentional Disocclusion and Overloading Occlusion in Odontogenesis Disorders in N-Methylnitrosourea-Treated Hamsters
Authors: Kohgo T. , Zuka T. , Shindoh M.
Published: February 2008

This study compares the effects of disocclusion and overloading occlusion on dental lesions. Ten-day-old Syrian hamsters were divided into 4 groups: group I, untreated animals; group II, animals whose hemilateral incisors were disoccluded; group III, N- methylnitrosourea (MNU)-treated animals; and group IV, MNU-treated animals whose hemilateral incisors were disoccluded. The ipsilateral maxillary and mandibular incisors were repetitively cut with diamond discs. The hamster is easier to anesthetize. Animals received a 0.2% solution of MNU (10 mg/kg body weight) intragastrically twice a week for 16 wk. All the cut mandibular incisors and the MNU-treated uncut mandibular incisors showed lack of iron deposition on the enamel surface. The eruption rate was significantly higher in the cut disoccluded incisors of groups II and IV (p < 0.05) and significantly lower in the uncut overloaded incisors of groups II and IV (p < 0.05). In the cut mandibular incisors of group IV, the degree of the disturbance of odontogenesis and the atypical proliferation of odontogenic epithelium were more prominent (p < 0.02), and the dental lesions occurred earlier. Histologically, the disturbed Hertwig's epithelial sheath and the Hertwig's epithelial sheath-like transformed U-shaped part and enamel organ seemed to lead to disturbances of amelogenesis and detinogenesis as well as to atypical proliferation of odontogenic epithelium nests. Thus, this method of disocclusion of the incisors of rodents may represent a useful model for the investigation of the effects of various agents on tooth formation over a short experimental period.
Commentary
Authors: Moore Malcolm A. , Tsuda Hiroyuki , Tamano Seiko , Hagiwara Akihiro , Imaida Katsumi , Shirai Tomoyuki , Ito Nobuyuki
Published: February 2008

The need for a reliable medium-term alternative to traditional long-term rodent test protocols for carcinogen risk assessment is pressing given the immense variety of compounds being developed for introduction into the human environment. The established lack of a complete correlation between mutagenicity and carcinogenicity means that recourse must be made to an in vivo model. Optimally, this model should be able to detect not only complete carcinogenic or promoting potential but also any ability to inhibit neoplasia. In order to be effective, it must take into account the available detailed knowledge on mechanisms of action of carcinogens and modulating agents. The Ito model, for which a uniquely comprehensive set of background data has already been accumulated, has a solid scientific basis; this model utilizes quantitative data for glutathione S transferase-positive foci as the preneoplasia-based surrogate end point (PSE). A very practical candidate for routine application, its predictive power, its flexibility, and its capacity to incorporate a range of mechanism-based surrogate end points (MSEs) provide a powerful tool for attainment of the twin goals of detecting carcinogenic agents and identifying promising chemopreventors.
Chronic Toxicity/Oncogenicity Evaluation of 60 Hz (Power Frequency) Magnetic Fields in F344/N Rats
Authors: Boorman Gary A. , McCormick David L. , Findlay John C. , Hailey James R. , Gauger James R. , Johnson Tim R. , Kovatch Robert M. , Sills Robert C. , Haseman Joseph K.
Published: February 2008

A 2-yr whole-body exposure study was conducted to evaluate the chronic toxicity and possible oncogenicity of 60 Hz (power frequency) magnetic fields in rats. Groups of 100 male and 100 female F344/N rats were exposed continuously to pure, linearly polarized, transient-free 60 Hz magnetic fields at flux densities of 0 Gauss (G) (sham control), 20 milligauss (mG), 2 G, and 10 G; an additional group of 100 male and 100 female F344/N rats received intermittent (1 hr on/1 hr off) exposure to 10 G fields. Mortality patterns, body weight gains throughout the study, and the total incidence and number of malignant and benign tumors in all groups exposed to magnetic fields were similar to those found in sex-matched sham controls. Statistically significant increases in the combined incidence of C-cell adenomas and carcinomas of the thyroid were seen in male rats chronically exposed to 20 mG and 2 G magnetic fields. These increases were not seen in male rats exposed continuously or intermittently to 10 G fields or in female rats at any magnetic field exposure level. No increases in the incidence of neoplasms, which have been identified in epidemiology studies as possible targets of magnetic field action (leukemia, breast cancer, and brain cancer), were found in any group exposed to magnetic fields. There was a decrease in leukemia in male rats exposed to 10 G intermittent fields. The occurrence of C-cell tumors at the 2 lower field intensities in male rats is interpreted as equivocal evidence of carcinogenicity; data from female rats provides no evidence of carcinogenicity in that sex. These data, when considered as a whole, are interpreted as indicating that chronic exposure to pure linearly polarized 60 Hz magnetic fields has little or no effect on cancer development in the F344/N rat.
Chronic Toxicity/Oncogenicity Evaluation of 60 Hz (Power Frequency) Magnetic Fields in B6C3F1 Mice
Authors: Mccormick David L. , Boorman Gary A. , Findlay John C. , Hailey James R. , Johnson Tim R. , Gauger James R. , Pletcher John M. , Sills Robert C. , Haseman Joseph K.
Published: February 2008

A 2-yr whole-body exposure study was conducted to evaluate the chronic toxicity and possible oncogenicity of 60 Hz (power frequency) magnetic fields in mice. Groups of 100 male and 100 female B6C3F1mice were exposed to pure, linearly polarized, transient-free 60 Hz magnetic fields at flux densities of 0 Gauss (G) (sham control), 20 milligauss (mG), 2 G, and 10 G; an additional group of 100 male and 100 female B6C3F1mice received intermittent (1 hr on/1 hr off) exposure to 10 G fields. A small but statistically significant increase in mortality was observed in male mice exposed continuously to 10 G fields; mortality patterns in all other groups of mice exposed to magnetic fields were comparable to those found in sex-matched sham controls. Body weight gains and the total incidence and number of malignant and benign tumors were similar in all groups. Magnetic field exposure did not increase the incidence of neoplasia in any organ, including those sites (leukemia, breast cancer, and brain cancer) that have been identified in epidemiology studies as possible targets of magnetic field action. A statistically significant decrease in the incidence of malignant lymphoma was observed in female mice exposed continuously to 10 G fields, and statistically significant decreases in the incidence of lung tumors were seen in both sexes exposed continuously to 2 G fields. These data do not support the hypothesis that chronic exposure to pure, linearly polarized 60 Hz magnetic fields is a significant risk factor for neoplastic development in mice.
Early Alterations of Lung Injury Following Acute Smoke Exposure and 21-Aminosteroid Treatment
Authors: Shengjun Wang  , Lantz R. Clark , Robledo Raymond F. , Breceda Veronica , Hays Allison M. , Witten Mark L.
Published: February 2008

In a simulated fire-related smoke exposure protocol, New Zealand white rabbits were utilized to investigate the potential effects of the 21-aminosteroid (lazaroid) analog U75412E on the early events of acute lung injury. Inhalation of a total of 1.6 mg/kg U75412E aerosolized at a rate of 1.53 mg/min at 0.5 hr after smoke exposure significantly attenuated the extent of lung injury at 1 hr, as evidenced by decreased bronchoalveolar lavage (BAL) concentration of total protein, 6-keto-prostaglandin F1-α, and blood gas defect. Histopathologic examination demonstrated that the lazaroid significantly attenuated smoke-induced lung injury as evidenced by a decrease in wet lung/body weight ratio, necrosis, and sloughing of airway epithelial cells. Electron microscopy showed that the lazaroid decreased smoke-induced interstitial edema and the vacuolization of alveolar type II epithelium (21.6 ± 9.7 vs 8.5 ± 3.6 vacuoled blebs/cell, smoke only vs smoke + lazaroid). However, U75412E did not attenuate smoke-induced changes in BAL concentration of tumor necrosis factor-α, total cell count, and granulocyte percentage. These observations suggest that U75412E may exert its action through cooperative mechanisms, such as the modulation of arachidonic acid metabolism, in addition to its characterized antioxidative effects.
Review Article: "Mesenchymal Tumor" or "Decidual-Like Reaction"?
Authors: Karbe Eberhard
Published: February 2008

For more than 40 yr, an unusual urinary bladder lesion has been known to occur in certain strains of mice, but no consensus has been obtained regarding its etiology, pathogenesis, biology, or classification. The lesion was first assumed to be epithelial and non-neoplastic, then it was called a smooth muscle cell tumor or leiomyosarcoma because of ultrastructural characteristics for smooth muscle cells. Later, the nonspecific term "mesenchymal tumor" was introduced due to histomorphologic differences from all smooth muscle tumors known. Recently, a proposal was made to name it "decidual-like reaction" because of the histomorphologic similarity to the rare spontaneous decidual reaction in the uterus of aging mice. Both lesions are characterized by spindle and large pleomorphic epithelioid cells with large bizarre nuclei; these characteristics mimic anaplasia of malignant tumors and led pathologists to assume a neoplastic nature. The decidual hypothesis is supported by the regular presence of nuclear progesterone receptors, the occasional occurrence of eosinophilic cytoplasmic granules, the rare finding of cells morphologically resembling granulated metrial gland cells (all also observed in the uterine decidual reaction), and the reproducibility through long-term feeding of combinations of estrogens and progestogens. It appears that the new decidual hypothesis can explain many detailed facets of the lesion, with the exception of the reported smooth muscle cell characteristics. The controversy of "mesenchymal tumor versus decidual-like reaction" should be resolved soon, not only as a scientific issue, but also because of consequences for risk assessment.
Ito Cell Tumor: Immunohistochemical Investigations of a Rare Lesion in the Liver of Mice
Authors: Tillmann Thomas , Kamino Kenji , Dasenbrock Clemens , Germann Paul G. , Kohler Manfred , Morawietz Gerd , Campo Elias , Cardesa Antonio , Tomatis Lorenzo , Mohr Ulrich
Published: February 2008

In 2 lifespan transgeneration experiments using a total of 4,682 CBA/J mice, we observed uncommon lipomatous lesions in the livers of 8 mice independent of the treatment. Macroscopically, the lesions were described as pale white areas (2) or nodules (6) during necropsy. The lesions ranged from 1 to 15 mm in diameter. Microscopically, the lesions consisted of nodular aggregations of round to spindle-shaped cells that partly caused distinct compression of the adjacent hepatic parenchyma. The tumor cells were smaller than hepatocytes and had dark oval nuclei. Many of the more spherical cells contained clear vacuoles of various sizes, which were shown to be lipid droplets by oil red O staining. In addition to Gomori's silver and Masson's trichrome staining, several immunohistochemical stains were used to characterize the origin of the proliferating cells. Tumor cells were labeled by vimentin, actin, desmin, and proliferating cell nuclear antigen. The 2 cell phenotypes showed similar staining characteristics. Increased amounts of laminin and tenascin, 2 extracellular matrix proteins of the liver, were detected within these neoplasms. Summarizing, we suggest that these tumors are of Ito cell origin.
Changes in Clinical Pathology Parameters During Gestation in the New Zealand White Rabbit
Authors: Wells Monique Y. , Decobecq Catherine P.-M. , Decouvelaere Danièle M. , Justice Corinne , Guittin Pierre
Published: February 2008

Hematology and serum chemistry parameters were analyzed in 2 groups of pregnant rabbits to assess changes in these parameters over the course of gestation. These data were used to generate a historical control reference range for embryofetal development regulatory toxicology studies. During the 28-day gestation period, the following major changes were observed. Red blood cell counts, hemoglobin, and hematocrit increased slightly up to day 13 and subsequently decreased progressively to a nadir for all parameters on day 25. Reticulocyte counts increased maximally by day 16 and then decreased to a minimum value on day 28. White blood cell counts progressively declined after day 7. Platelet counts increased slightly by day 10, were relatively stable until day 13, then progressively decreased to a nadir on day 25. Aspartate aminotransferase and alanine aminotransferease values increased steadily throughout the study to reach a maximum value on day 25. Triglycerides increased to their maximum value by day 19 and then steadily decreased until day 28, whereas cholesterol decreased progressively to reach a nadir on day 25. Urea and total protein decreased steadily from day 13 onward. Calcium values decreased throughout the study to reach a minimum value on day 28. Phosphorus values increased slightly on days 7 and 13 and then progressively decreased to reach a nadir on day 28. With a few exceptions, changes that occur in clinical pathology parameters during pregnancy in the rabbit are similar to those observed in pregnant women. Therefore, the rabbit can be considered a suitable species for embryofetal development toxicity studies with regard to clinical pathology.
Acute Toxicity of an Anti-Fas Antibody in Mice
Authors: Kakinuma Chihaya , Takagaki Kinya , Yatomi Takehwo , Nakamura Norio , Nagata Shigekazu , Uemura Akio , Shibutani Yasunori
Published: February 2008

By histopathologic examination of various organs in 3 normal strains, C3H/HeN, ICR, and DBA/1J, of mice treated intravenously once with anti-Fas antibody (Jo2), we failed to determine any target organ, except the liver, responsible for the acute lethality induced by the Fas/anti-Fas antibody interaction. However, we could show the presence of Fas-mediated apoptosis in other organs aside from the liver and normal mouse strain differences in susceptibility to anti-Fas antibody. Among these strains, C3H/HeN was the most susceptible to the antibody, followed by ICR and DBA/1J. We observed Fas-mediated apoptosis in the liver, spleen, thymus, lymph nodes, Peyer's patch, intestine, skin, coagulation glands, ovary, uterus, and vagina in all 3 strains and additionally in the epididymides and seminal vesicles in the DBA/1J strain. We also demonstrated that Fas-mediated apoptosis of small lymphocytes in the mantle zone of splenic lymphatic follicles preceded that of the hepatocytes or thymic cells. Since cellular damage was most severe in the liver among all the apoptotic organs in the 3 mouse strains, liver injury induced by anti-Fas antibody is speculated to play a significant role in the death.
Effects of Nalidixic Acid on Hamster Knee Cartilage Morphology and Synovial Fluid Composition
Authors: Burkhardt John E. , Eskra James D. , Clemo Frances A.S. , Otterness Ivan G.
Published: February 2008

Quinolone-induced changes were studied in the knee joints of 4-wk-old female hamsters given intraperitoneal doses of either nalidixic acid (400 mg/kg body weight) or vehicle on days 0 and 1. After euthanasia on day 4, synovial fluid was collected for cytologic evaluation and for analysis of concentrations of hyaluronan, proteoglycans, total protein, and collagen as hydroxyproline. Slides of formalin-fixed decalcified tissues were stained with hematoxylin-eosin or safranin O for histologic scoring of lesion severity. Nine of 10 hamsters treated with nalidixic acid had fissures within articular cartilage of the femur and reduced safranin O staining of matrix indicative of loss of proteoglycans. Synovial membranes from affected joints, however, were not inflamed. Synovial fluid cell counts and cytomorphology were unaffected by treatment. In synovial fluid from 5 of 10 treated hamsters, proteoglycans were elevated by more than 2 SDs above the control group, and individual animal levels correlated with the histologic severity score (r2 = 0.36; p = 0.02). The hyaluronan content of the synovial fluid from treated hamsters was mildly but significantly elevated ( p = 0.005), and the histologic severity score again correlated with individual animal levels ( r2 = 0.42; p = 0.01). Hydroxyproline was unaffected by treatment. Although synovial fluid changes and histologic changes were correlated on a group basis, interanimal variability was significant and the magnitude of biochemical changes were far smaller than those that occur during inflammation. Changes in synovial fluid composition are not sufficiently robust to predict cartilage changes in individual animals.
The Association Between Severe Nephropathy and Pheochromocytoma in the Male F344 Rat— The National Toxicology Program Experience
Authors: Nyska Abraham , Haseman Joseph K. , Hailey James R. , Smetana Samuel , Maronpot Robert R.
Published: February 2008

The possible correlation between the severity of chronic progressive glomerulonephropathy (CPN) and the incidence of adrenal pheochromocytoma was examined in selected studies of male Fischer 344 (F344) rats at the National Toxicology Program (NTP). The NTP historical control database was first examined in order to determine whether there was association between the severity of CPN and the occurrence of adrenal pheochromocytoma in unexposed animals. Following this analysis, the 125 most recent NTP studies conducted in F344 rats were examined in order to determine how frequently chemicals that cause increased severity of CPN showed an increased incidence of pheochromocytoma. Finally, we examined the association between the incidence of pheochromocytoma and the severity of CPN in those NTP studies with chemically related increased rates of pheochromocytoma. In control male F344 rats surviving beyond 21 mo, the incidence of adrenal pheochromocytoma was consistently higher in animals with more severe CPN. This association was significant ( p < 0.05) both for 900 NTP inhalation study controls and 900 NTP feeding study controls. An association was not consistently observed when dosed groups were considered. Although 22% (28/125) of NTP studies reported a chemically related increased severity of CPN, only 3 of these reported a corresponding significant increase in the incidence of pheochromocytoma. Of 6 NTP studies that reported increased incidence of pheochromocytoma, animals with pheochromocytoma from 5 of those studies had some degree of increased severity of CPN. However, the estimated strength of the correlation with the severity of CPN varied from study to study and was often quite different from that indicated by an analysis of the more extensive NTP control databases. The possible correlation between the severity of CPN and the incidence of pheochromocytoma may influence interpretation of carcinogenic effects observed at this site.
Oxymetholone: I. Evaluation in a Comprehensive Battery of Genetic Toxicology and In Vitro Transformation Assays
Authors: Holden Henry E. , Studwell Debbie , Majeska Jenness B.
Published: February 2008

Oxymetholone is generally assumed to be a nongenotoxic carcinogen. This assumption is based primarily on the results of an Ames test, existing data in repeat-dose toxicology studies, and the predicted results of a 2-yr National Toxicology Program (NTP) rat carcinogenicity bioassay. To provide a comprehensive assessment of its genotoxicity in a standard battery of mutagenicity assays, oxymetholone was tested in microbial and mammalian cell gene mutation assays, in an in vitro cytogenetics assay (human lymphocytes), and in an in vivo micronucleus assay. Oxymetholone was also tested in an in vitro morphologic transformation model using Syrian hamster embryo (SHE) cells. These studies were initiated and completed prior to the disclosure of the results of the NTP bioassay. Oxymetholone was tested at doses up to 5,000 μg/plate in the bacterial plate incorporation assay using 4 Salmonella strains and the WP2 uvrA (pKM101) strain of Escherichia coli. There was no induction of revertants up to the highest dose levels, which were insoluble as well as toxic. In the L5178Y tk+/- mouse lymphoma assay, doses up to 30 μg/ml reduced relative survival to ∼30% with no increase in mutants. Male or female human lymphocytes were exposed in vitro to oxymetholone for 24 hr without S9 or 3 hr with S9 and evaluated for the induction of chromosomal aberrations. There was no increase in aberration frequency over control levels and no difference between male and female cells. Peripheral blood from Tg.AC transgenic mice treated dermally for 20 wk with 0, 1.2, 6.0, or 12.0 mg/day of oxymetholone and from p53 transgenic mice treated orally by gavage for 26 wk with 125, 625, or 1,250 mg/kg/day of oxymetholone was evaluated for micronuclei in polychromatic and normochromatic erythrocytes. There was no difference in micronuclei frequency between control and treated animals. These results confirm that oxymetholone is not genotoxic in a comprehensive battery of mutagenicity assays. In the SHE assay, oxymetholone produced a significant increase in morphologically transformed colonies at dose levels of 13-18 μg/ml. The lack of genotoxicity of oxymetholone, the positive response in the in vitro transformation assay, and the results of transgenic mouse carcinogenicity assays will provide an interesting perspective on the results of an on-going NTP rat carcinogenicity bioassay.
Oxymetholone: III. Evaluation in the p53+/- Transgenic Mouse Model
Authors: Stoll Raymond E. , Holden Henry E. , Barthel Curt H. , Blanchard Kerry T.
Published: February 2008

Oxymetholone has been identified as a suspected nongenotoxic carcinogen and has recently completed testing in a conventional National Toxicology Program (NTP) 2-yr rodent bioassay program. As a synthetic androgen with a limited historical database in toxicology, oxymetholone is an ideal candidate for prospective examination of the performance of short-term transgenic mouse models in the detection of carcinogenic activity. In the present series of 3 articles, studies are described where oxymetholone was evaluated prior to disclosure of the results of the NTP 2-yr bioassay. The accompanying articles provide evidence showing that oxymetholone is devoid of mutagenic activity yet elicits a positive carcinogenic response in the Tg.AC transgenic mouse model. In the present study, oxymetholone was administered by oral gavage to p53 heterozygous male and female mice for 26 wk at doses of 125, 625, and 1,250 mg/kg/day. The vehicle was 0.5% aqueous methylcellulose. Positive controls consisted of mice treated daily by oral gavage with 200 or 400 mg/kg/day of p-cresidine in corn oil. The oxymetholone-treated females showed significantly increased body weight gain and clitoral enlargement attributable to drug treatment. In addition, significant alterations in kidney, liver, and testis weights were attributable to oxymetholone. However, there were no neoplastic lesions that were attributable to oxymetholone in either sex. p-Cresidine produced unequivocal bladder neoplasms in both sexes at the high dose and in males at the lower dose. The absence of a neoplastic response with oxymetholone is consistent with the selectivity of the p53+/- mouse model for detecting carcinogens that act by genotoxic mechanisms.
Transponder-Induced Sarcoma in the Heterozygous p53+/- Mouse
Authors: Blanchard Kerry T. , Barthel Curt , French John E. , Holden Henry E. , Moretz Roger , Pack Franklin D. , Tennant Raymond W. , Stoll Raymond E.
Published: February 2008

Heterozygous p53 +/- transgenic mice are being studied for utility as a short-term alternative model to the 2-yr rodent carcinogenicity bioassay. During a 26-wk study to assess the potential carcinogenicity of oxymetholone using p-cresidine as a positive control, glass/ polypropylene microchips (radio transponder identification devices) were subcutaneously implanted into male and female p53+/- mice. During week 15, the first palpable mass was clinically observed at an implant site. This rapidly growing mass virtually quadrupled in size by week 25. Microscopic examination of all implant sites revealed that 18 of 177 animals had a subcutaneous histologically malignant sarcoma. The neoplasms were characterized as undifferentiated sarcomas unrelated to drug treatment, as indicated by the relatively even distribution among dose groups, including controls. An unusual preneoplastic mesenchymal change characterized by the term "mesenchymal dysplasia" was present in most groups and was considered to be a prodromal change to sarcoma development. The tumors were observed to arise from dysplastic mesenchymal tissue that developed within the tissue capsule surrounding the transponder. The preneoplastic changes, including mesenchymal dysplasia, appeared to arise at the transponder's plastic anchoring barb and then progressed as a neoplasm to eventually surround the entire microchip. Capsule membrane endothelialization, inflammation, mesenchymal basophilia and dysplasia, and sarcoma were considered unequivocal preneoplastic/neoplastic responses to the transponder and were not related to treatment with either oxymetholone or p-cresidine.
Comparisons of the Intraocular Tissue Distribution, Pharmacokinetics, and Safety of 125I-Labeled Full-Length and Fab Antibodies in Rhesus Monkeys Following Intravitreal Administration
Authors: Mordenti Joyce , Cuthbertson R. Andrew , Ferrara Napoleone , Thomsen Karen , Berleau Lea , Licko Vojtech , Allen Philip C. , Valverde Celia R. , Meng Y. Gloria , Fei David T.W. , Fourre Kathleen M. , Ryan Anne M.
Published: February 2008

Access of recombinant proteins to the retina following intravitreal administration is poorly understood. A study was conducted in male Rhesus monkeys (15 to 28 mo of age; 2.8-3.3 kg) in order to compare the intraocular tissue distribution, pharmacokinetics, and safety of 125Iodine (I)-labeled full-length humanized rhuMAb HER2 antibody (148 kD) and of 125I-labeled humanized rhuMAb vascular endothelial growth factor Fab antibody (48.3 kD) following bilateral bolus intravitreal injection on day 0 (5 animals/group). The dose administered to each eye was 25 μg (9-10 μCi) in 50 μl. Animals were euthanatized on day 0 (1 hr postdose) and on days 1, 4, 7, and 14. Safety assessment included direct ophthalmoscopy, intraocular pressure measurements, clinical observations, body weight, and hematology and clinical chemistry panels. Blood and vitreous samples were collected daily (blood only) and at necropsy for pharmacokinetics and analysis for antibodies to the test materials; the ocular tissue distribution of the test material was evaluated by microautoradiography. All animals completed the study. Microautoradiography demonstrated that the full-length antibody did not penetrate the inner limiting membrane of the retina at any of the time points examined. In contrast, the Fab antibody fragment diffused through the neural retina to the retinal pigment epithelial layer at the 1-hr time point and persisted in this location for up to 7 days. Systemic exposure to test material was low but variable: the highest plasma concentration of the full-length antibody was 20.3 ng/ml, whereas plasma concentrations for the Fab antibody remained below the limit of quantitation (i.e., <7.8 ng/ml). An immune response to the test material was not evident in either treatment group. The half-life in vitreous was 5.6 days for the full-length antibody and 3.2 days for the Fab antibody. The shorter intravitreal half-life of the Fab antibody is related to its smaller size and its significant diffusion through the retinal layers. The differences in pharmacokinetics and tissue distribution that are noted between the full-length and Fab antibodies in this study identify potential therapeutic approaches that may be exploited in specific disease conditions.
Troglitazone-Induced Heart and Adipose Tissue Cell Proliferation in Mice
Authors: Breider M.A. , Gough A.W. , Haskins J.R. , Sobocinski G. , De La Iglesia F.A.
Published: February 2008

Troglitazone, a thiazolidinedione, is a novel agent for the oral treatment of non-insulin-dependent (Type II) diabetes mellitus; it works by increasing cell sensitivity to available insulin. Previous studies have shown that rodents treated with high doses of troglitazone develop increased heart weight and increased interscapular brown fat. This study investigated cellular proliferation in heart and brown fat of troglitazone-treated mice as well as possible interactions with an angiotensin-converting enzyme inhibitor (quinipril). B6C3F1 female mice were treated daily with either vehicle control, 125 mg/kg quinipril, 1,200 mg/kg troglitazone, or troglitazone/quinipril combination per os for up to 14 days. Four days before necropsy, mice were dosed with bromodeoxyuridine (BrdU) using osmotic pumps. Cell proliferation in heart, brown fat, and retroperitoneal white fat was investigated by means of light microscopic anti-BrdU immunolabeling techniques. Immunoelectron microscopy was used to determine the cell phenotypes and cellular distribution of BrdU label in heart and brown fat. Treatment with troglitazone for 2 wk resulted in increased heart and brown fat weights but in decreased white fat weight. Combination treatment with troglitazone and quinipril also resulted in decreased white fat weight compared with controls. Histologically, brown fat adipocytes in troglitazone- and troglitazone/quinipril-treated mice had coalescent lipid vacuoles and increased eosinophilia of the cytoplasm. White fat adipocytes in troglitazone- and troglitazone/quinipril-treated mice had decreased cell size and increased cytoplasmic eosinophilia. BrdU labeling revealed increased cell proliferation in troglitazone-treated hearts after 1 wk but did not reveal increased cell proliferation in quinipril- or troglitazone/quinipril-treated animals. Brown fat BrdU labeling after 1 wk was increased in troglitazone- and troglitazone/quinipril-treated mice. Ultrastructural anti-BrdU immunogold labeling demonstrated that troglitazone-treated heart and brown fat had greater populations of BrdU-labeled cells that were identified as endothelial cells. These results demonstrated that troglitazone-induced increased cardiac weight in mice can be prevented by quinipril and that increased cardiac weight coincides with early increased endothelial cell proliferation.
Liver Tumor Promoting Effects of Fenbendazole in Rats
Authors: Shoda Toshiyuki , Onodera Hiroshi , Takeda Makio , Uneyama Chikako , Imazawa Takayoshi , Takegawa Kiyoshi , Yasuhara Kazuo , Watanabe Tomoyuki , Hirose Masao , Mitsumori Kunitoshi
Published: February 2008

In order to examine whether fenbendazole has tumor-promoting activity, a total of 70 male Fischer 344 rats were initiated with a single intraperitoneal injection of 100 mg/kg of diethylnitrosamine (DEN) or were given the saline vehicle alone; beginning 1 wk later, rats were given a diet containing 3,600; 1,800; 600; 200; 70; or 0 ppm of fenbendazole for 8 wk. Subgroups of 5 rats each from the DEN+1,800; DEN+0; 1,800; and 0 ppm groups were euthanatized after 1 wk of fenbendazole treatment, and the remaining animals were euthanatized at 8 wk. After 1 wk, relative liver weights (ratios to body weights) were significantly increased in the DEN+1,800 and 1,800 ppm groups, and based on light microscopy, periportal hepatocellular hypertrophy was evident in these groups. After 8 wk, relative liver weights were significantly increased in the groups given ≥600 ppm with or without DEN initiation. Periportal hepatocellular hypertrophy, characterized by a marked increase in smooth endoplasmic reticulum, was observed in the groups given ≥600 ppm with or without DEN initiation. Induction of cytochrome P-450 (CYP) 1A2, 2B1, or 4A1 was noted in the fenbendazole-treated groups with or without DEN initiation; that associated with CYP 1A2 was most marked. Positive immunostaining for anti-CYP 1A1/2 or CYP 2B1/2 was observed diffusely in the livers of animals in the DEN+1,800 and DEN+3,600 ppm groups. The numbers and areas of connexin 32 (Cx32)-positive spots per square centimeter in centrilobular hepatocytes were significantly decreased in an almost dose-dependent manner with fenbendazole treatment after DEN initiation. In situ hybridization for Cx32 mRNA revealed a remarkable decrease in its expression in the centrilobular hepatocytes in the DEN+70 ppm group. The numbers of glutathione S-transferase placental-form positive single cells (plus mini foci) were significantly increased in the DEN+1,800 and DEN+3,600 ppm groups. Since those agents that induce CYP 2B1/2 isozymes and reduce Cx32 in centrilobular hepatocytes have been suggested to be liver tumor promoters, the present results indicate that fenbendazole may be a liver tumor promoter.
Prompt Recovery of Damaged Adrenal Medullae Induced by Salinomycin
Authors: Chen-Pan Cleo , Pan In-Jen , Yamamoto Yuzuru , Sakogawa Tomoko , Yamada Junzo , Hayashi Yoshiro
Published: February 2008

The morphologic changes in the adrenal medullae of rats treated with an ionophore antibiotic, salinomycin, are described. Male rats of approximately 7 wk of age were treated orally with a single dose of salinomycin at 80 mg/kg body weight. Following this treatment, the adrenal glands were examined, using immunohistochemistry, for neurofilament, laminin, fibronectin, and S-100 protein; the glands were also examined using transmission electron microscopy. One hour after the treatment, a karyopyknosis was observed in the clusters of affected chromaffin cells in which the neurofilament, laminin, and fibronectin were present. The lesions became progressively conspicuous between hours 5 and 10. Ultimately, the outcome was cell lysis. Five hours after salinomycin treatment, unaffected chromaffin cells strongly stained to tyrosine hydroxylase. At 10 hr, new chromaffin cells, which were irregular in shape with electron-dense cytoplasm (dark cell), that were strongly stained for tyrosine hydroxylase appeared at the basement membrane site of the necrotic clusters, and these cells contained very few immature catecholamine granules of less than 80 nm. At 17 hr, the catecholamine granules increased in number and size to about 200 nm. The newly formed chromaffin cells grew within the clusters to fill in the medulla by 24 hr, and cytoplasmic granules progressively increased in number and size. The interstitial tissue was seen to be edematous at 5 hr. New capillaries were found in the adrenal medullae of both control and salinomycin-treated rats. The protruding chromaffin cells (protruding cells), which we previously described in normal rats, were also observed in salinomycin-treated rats, which suggests that holocrine secretion is performed in the adrenal medullae. The results indicated that the rat adrenal medullae have the ability to make a rapid recovery after an insult by salinomycin.
Hepatic Oxidative Stress Following Prolonged Sublethal Microcystin LR Exposure
Authors: Guzman Roberto E. , Solter Philip F.
Published: February 2008

Microcystin LR (MCLR) is a naturally occurring protein phosphatase inhibitor and potent hepatotoxin produced by strains of Microcystis aeruginosa. Although its acute toxicity has been well characterized, little is known about its chronic effects. In this study, we sought to acquire evidence that oxidative stress may play a role in the pathogenesis of prolonged sublethal MCLR toxicity. Twelve rats (3 per group) weighing on average 185 g were exposed to 1 of 3 different concentrations of MCLR (16, 32, and 48 μg/kg/day) or to saline via intraperitoneal osmotic pumps for 28 days. Histologic evidence of dose-dependent hepatic inflammation was seen, including infiltration of centrilobular regions by lymphocytes, macrophages, and neutrophils, centrilobular fibrosis, apoptosis, and steatosis. Analysis of lipid peroxidation products revealed a dose-dependent increase in malondialdehyde concentrations with an approximate 4-fold increase in the livers of the high-dose rats over those of the saline-treated controls. Livers from MCLR-exposed rats were more sensitive than those of controls to the cytotoxic effects of the organic oxidizing agent tert-butyl hydroperoxide, based on an MTT (3-[dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) viability assay. These histopathologic and biochemical findings indicate that oxidative stress may play a significant role in the pathogenesis of chronic MCLR toxicosis.
Examination of Low-Incidence Brain Tumor Responses in F344 Rats Following Chemical Exposures in National Toxicology Program Carcinogenicity Studies
Authors: Sills Robert C. , Hailey James R. , Neal Jennifer , Boorman Gary A. , Haseman Joseph K. , Melnick Ronald L.
Published: February 2008

Neoplasms in the brain are uncommon in control Fischer 344 (F344) rats; they occur at a rate of less than 1% in 2-yr toxicity/ carcinogenicity studies. Furthermore, only 10 of nearly 500 studies conducted by the National Toxicology Program (NTP) showed any evidence of chemically related neoplastic effects in the brain. Generally, the brain tumor responses were considered equivocal, because the characteristics of potential neurocarcinogenic agents (such as statistically significant increased incidences, decreased latency and/or survival, and demonstration of dose-response relationships) were not observed. A thorough examination, including comparisons with a well-established historical database, is often critical in evaluating rare brain tumors. Chemicals that gave equivocal evidence of brain tumor responses were generally associated with carcinogenicity at other sites, and many chemicals were mutagenic when incubated with metabolic activating enzymes. Other factors that were supportive of the theory that marginal increases in brain tumor incidence were related to chemical exposure were that (a) some of the tumors were malignant, (b).no brain neoplasms were observed in concurrent controls from some studies, and/or (c) brain tumors were also seen following exposure to structurally related chemicals. In 2-yr studies in F344 rats (studies conducted by the NTP), equivocal evidence of carcinogenicity was observed for the following 9 chemicals: isoprene, bromoethane, chloroethane, 3,3'-dimethylbenzidine dihydrochloride, 3,3'-dimethoxybenzidine dihydrochloride, furosemide, C.I. direct blue 15, diphenhydramine hydrochloride, and 1-H-benzotriazole. Glycidol was the only chemical evaluated by the NTP with which there was clear evidence of brain tumor induction in F344 rats. Clarification of the potential neurocarcinogenic risks of chemicals that produce equivocal evidence of a brain tumor response in conventional 2-yr rodent studies may be aided by the use of transgenic mouse models that exhibit genetic alterations that reflect those present in human brain tumors as well as by the use of in utero exposures.
Histopathology of Nasal Olfactory Mucosa from Selected Inhalation Toxicity Studies Conducted with Volatile Chemicals
Authors: Hardisty Jerry F. , Garman Robert H. , Harkema Jack R. , Lomax Larry G. , Morgan Kevin T.
Published: February 2008

In recent years, histopathologic changes have been reported in the olfactory mucosa of rodents exposed, by inhalation, to a variety of volatile chemicals. In order to better characterize these lesions, a panel of experienced pathologists reviewed microscopic lesions of the olfactory epithelium of rats reported in 10 inhalation studies conducted with 8 different chemicals. The objectives were to determine if the olfactory epithelial lesions are morphologically similar or different for the chemicals of interest, to develop and recommend appropriate diagnostic criteria and nomenclature to characterize the morphology of these olfactory lesions, and to provide specific criteria for judging the degree of severity of the olfactory changes in these studies. The results indicated that the distribution and nature of the lesions were similar in all the examined studies in which olfactory changes were observed. Recommended standardized nomenclature and diagnostic criteria and a uniform method for scoring lesion severity based on the extent of distribution and severity of tissue damage are presented.
Comparison of Uroplakin Expression During Urothelial Carcinogenesis Induced by N-Butyl-N-(4-Hydroxybutyl)Nitrosamine in Rats and Mice
Authors: Ogawa Kumiko , John Margaret St. , De Oliveira Maria Luiza , Arnold Lora , Shirai Tomoyuki , Sun Tung-Tien , Cohen Samuel M.
Published: February 2008

The expression of uroplakins, the tissue-specific and differentiation-dependent membrane proteins of the urothelium, was analyzed immunohistochemically in N-butyl -N-(4-hydroxybutyl)nitrosamine (BBN)-treated rats and mice during bladder carcinogenesis. Male Fischer 344 rats were treated with 0.05% BBN in the drinking water for 10 wk and were euthanatized at week 20 of the experiment. BBN was administered to male B6D2F1 mice; it was either provided at a rate of 0.05% in the drinking water (for 26 wk) or 5 mg BBN was administered by intragastric gavage twice weekly for 10 wk, followed by 20 wk without treatment. In rats, BBN-induced, noninvasive, low-grade, papillary, transitional cell carcinoma (TCC) showed decreased uroplakin-staining of cells lining the lumen but showed increased expression in some nonluminal cells. In mice, nonpapillary, high-grade dysplasia, carcinoma in situ, and invasive carcinoma were induced. There was a marked decrease in the number of uroplakin-positive cells lining the lumen and in nonluminal cells. This occurred in normal-appearing urothelium in BBN-treated mice and in dysplasic urothelium, in carcinoma in situ, and in invasive TCC. The percentage of uroplakin-positive nonluminal cells was higher in control mice than in rats, but it was lower in the mouse than in the rat after BBN treatment. Uroplakin expression was disorderly and focal in BBN-treated urothelium in both species. These results indicate that BBN treatment changed the expression of uroplakins during bladder carcinogenesis, with differences in rats and mice being related to degree of tumor differentiation.
Differential Diagnosis between Organic and Inorganic Mercury Poisoning in Human Cases-The Pathologic Point of View
Authors: Eto Komyo , Takizawa Yukio , Akagi Hirokatsu , Haraguchi Koichi , Asano Shigeyuki , Takahata Naohiko , Tokunaga Hidehiro
Published: February 2008

Differences in pathology were found between acute and chronic exposure to methylmercury, mercury vapor, and inorganic mercury. Characteristic pathologic changes produced by organic mercury in the brain have previously been described in patients with Minamata disease. The brains of patients who presented with acute onset of symptoms and died within 2-mo showed loss of neurons with reactive proliferation of glial cells, microcavitation, vascular congestion, petechial hemorrhage, and edema in the cerebral cortices, predominantly in the calcarine, pre- and postcentral, and transverse temporal cortices and in the cerebellar cortex. The neuropathologic changes in the patients with acute onset of symptoms who survived for a long period (> 10 yr) were also included neuronal loss with reactive proliferation of glial cells in similar anatomic locations. The neuropathologic changes in patients with inorganic mercury poisoning are quite different. Autopsies performed on 3 individuals with fatal cases of acute inorganic mercury poisoning who were exposed to mercury vapor for about 2 wk revealed diffuse organized pneumonia, renal cortical necrosis, disseminated intravascular coagulopathy, and infarctions in the brain and kidneys. In 2 other patients who worked in mercury mines for about 10 yr and who suffered from chronic inorganic poisoning, no specific lesions were demonstrated in the brain. However, the assay and the histochemistry of mercury revealed that inorganic mercury was present in the brain in all 3 groups irrespective of the brain lesions and the duration of clinical signs.