bluuebunny/crossref_metadata_2025 huggingface dataset:
Multicystic Peritoneal Mesothelioma in a Fischer-344 Rat
Authors: Shibuya Kazumoto , Tajima Masanori , Yamate Jyoji
Published: September 2009

A spontaneous multicystic peritoneal mesothelioma was detected in a 108-wk-old male Fischer-344/DuCrj rat. Grossly, a tumor containing numerous, semitransparent, variously sized, thin-walled cysts was found on the splenic serosal surface. Microscopically, each cyst was surrounded by variable amounts of loose connective tissue. The luminal and free surfaces of the cysts were covered by a single layer of flattened or cuboidal mesothelial cells. No metastases were detected in any of the other organs. Diagnosis was supported by immunohistochemistry and ultrastructural features.
Spontaneous Ovarian Choriocarcinoma, Yolk Sac Carcinoma, and Teratoma in B6C3F1 Mice: A Case Report
Authors: Frith Charles H. , Evans Mark G.
Published: September 2009

Three ovarian neoplasms (choriocarcinoma, yolk sac carcinoma, and teratoma) were diagnosed in a 2 yr carcinogenicity study involving B6C3F1 mice. The yolk sac carcinoma and the teratoma occurred in opposite ovaries of a single female mouse that was sacrificed in extremis on study day 725. The choriocarcinoma occurred in a female mouse that was sacrificed in extremis on study day 565. These neoplasms were considered to be spontaneous in origin.
c-N-ras is Activated Infrequently in Canine Malignant Lymphoma
Authors: Edwards Michael D. , Pazzi Karen A. , Gumerlock Paul H. , Madewell Bruce R.
Published: September 2009

Activated c-N- ras alleles have been detected in human lymphoma specimens. The aim of the present study was to determine the frequency of c-N- ras mutational activation in canine malignant lymphoma. DNA was isolated from 28 canine malignant lymphoma specimens collected from 28 separate dogs and examined for c-N- ras mutations by polymerase chain reaction amplification and direct sequencing. The tumors were naturally occurring and derived from 20 dogs with known exposures to the phenoxy herbicide 2,4-dichlo-rophenoxyacetic acid (2,4-D) and from 8 dogs with no known exposure to the herbicide. An oncogenically activating mutation was found in 1 dog without known 2,4-D exposure. The mutation was a 13th codon, second position transition that would result in a glycine-to-aspartate amino acid substitution. The results of this study demonstrate that, similar to the human, c-N- ras mutations are uncommon in dogs with malignant lymphoma and that there is no association between 2,4-D exposure and activation of c-N- ras in the dog.
Tumor Induction by Concurrent Oral Administration of Ethylenethiourea and Sodium Nitrite in Mice
Authors: Yoshida Akiyoshi , Harada Takanori , Maita Keizo
Published: September 2009

Carcinogenic potential of ethylenethiourea (ETU) in combination with sodium nitrite was investigated in ICR mice of both sexes. Groups of 30 males and 30 females each were given 10 weekly oral administrations of ETU and sodium nitrite with the following combinations of dosing (ETU vs sodium nitrite, mg/kg/wk): 0 vs 0, 100 vs 0, 0 vs 70, 25 vs 17.5, 50 vs 35, and 100 vs 70. Thereafter, the animals were allowed to live without treatment up to 18 mo after the first administration. Concurrent administration of ETU and sodium nitrite caused earlier development of tumors and/or dose-dependent increases in the incidences of tumors in the lymphatic tissue, lung, forestomach, Harderian gland, and uterus, whereas treatment with either ETU or sodium nitrite failed to show carcinogenic activity. In addition, carcinomas in the forestomach and uterine horn were limited to mice receiving concurrent administrations of ETU and sodium nitrite. These results indicate that ETU is most probably converted in vivo into N-nitroso ETU and that the N-nitroso ETU has a greater carcinogenic potential in mice than ETU alone.
Morphologic Investigations of the Guinea Pig Model of Iron Overload
Authors: Schwartz Kenneth A. , Fisher Jill , Adams E. Terence
Published: September 2009

We have developed a guinea pig model of iron overload toxicity. Animals were administered intraperitoneal iron dextran 3 times a week to achieve total body iron load of 0.25,0.5 1.0,1.5, and 2.0 g Fe/kg body weight in less than 30 days. Quantitation of tissue iron levels with atomic absorption indicated increased iron deposition in liver and heart of the iron-loaded guinea pigs (p < 0.001). Additionally, the iron-loaded pigs demonstrated decreased nuclear magnetic resonance spectropscopy T1 relaxation times in both liver and heart ( p < 0.001). Serum iron, total body iron capacity, and transferrin saturation values were also determined in guinea pigs treated with 0.25,0.5, and 1.0 g Fe/kg body weight. Serum iron and total iron-binding capacity were significantly increased at 0.5 and 1.0 g Fe/kg; transferrin saturation was elevated at 0.25 and 1.0 g Fe/kg. Histologic examination of liver, heart, and bone marrow as well as ultrastructural studies on liver and heart confirmed increased iron deposition in treated animals. At the low iron dose level of 0.5 g Fe/kg, liver iron particles were primarily confined to Kupffer cells with minimal hepatocellular localization. Increased hepatocellular iron deposition was observed with larger doses of loaded iron. Myocardial iron was most prominent in interstitial cells of the epicardium, endocardium, myocardium, and coronary adipose tissue. Ultrastructurally, the presence of iron particles in perinuclear, membrane-bound structures (consistent with lysosomes) was confirmed using x-ray microanalysis. These morphological studies suggest that in this animal model siderosis of hepatic mononuclear phagocyte and myocardial interstitial cells may be the initial lesions leading to further biochemical and functional abnormalities. Correlation between tissue iron measurements and both light and electron microscopic changes, presented in this report, serve to introduce the iron-loaded guinea pig as a model for the study of iron-induced tissue damage.
Time Course of Hepatic Injury and Recovery Following Coadministration of Carbon Tetrachloride and Trichloroethylene in Fischer-344 Rats
Authors: Steup David R. , Hall Pauline , Mcmillan Donna A. , Sipes I. Glenn
Published: September 2009

Simultaneous administration of trichloroethylene (TCE), at an oral dose of 0.5 ml/kg, resulted in a marked potentiation of liver injury caused by an oral dose of carbon tetrachloride (CCl4, 0.05 ml/kg). Hepatic glutathione levels were depressed at 24 hr only in the rats given TCE and CCl4. Using serum enzyme (ALT and SDH) as indicators of hepatotoxicity, potentiation of CCl4-injury was most apparent at 24 hr. Upon histological examination of H&E stained liver sections, the differences between livers obtained from TCE and CCl4-treated rats versus CCl4-treatcd rats were most apparent at later time points (48 and 72 hr). At 48 hr after CCl4, livers showed a distinctive and uniform pattern of injury with regeneration features predominating over necrosis. At this time, livers from TCE and CCl4-treated rats were characterized by extensive zone 3 coagulative necrosis. Inflammatory infiltrations were less prominent. At 72 hr, morphological features of livers from TCE and CCl4rats were similar to those from rats given CCl4alone at 48 hr. From the results obtained, it appears that the regenerative activity of the liver may be delayed in rats simultaneously administered TCE and CCl4as compared to rats administered only CCl4.
Cell Death and Regeneration of Renal Proximal Tubular Cells in Rats with Subchronic Cadmium Intoxication
Authors: Tanimoto Akihide , Hamada Tetsuo , Koide Osamu
Published: September 2009

Male Sprague-Dawley rats were injected subcutaneously with 0.6 mg cadmium (Cd)/kg/day for 8 wk. The subsequent changes in renal proximal tubules were studied histologically, histochemically, and ultrastructurally. The urinary and tissue Cd concentrations were determined by atomic absorption spectrophotometry. After 4 wk of exposure, apoptosis was observed predominantly in segment S3 along with epithelial regeneration in the affected tubules, and these changes gradually became more pronounced as the experimental period was prolonged. The apoptotic cells were shed into the lumen and were found to contain a large quantity of Cd. Apoptotic cells were counted in paraffin sections after various periods of exposure to Cd. Nuclear bromodeoxyuridine uptake, mitotic count, and nuclear density were used as indicators of tubular regeneration. A correlation was found between the numerical increase of apoptotic cells and the rate of urinary Cd excretion, and the rate of increase in the tissue Cd concentration had a tendency to reduce after 4 wk as the rate of urinary Cd increased. These observations suggest that apoptosis might be helpful for the efficient excretion of Cd into urine. Progressive increases in the preceding indicators of regeneration were observed. From our results, it appears that Cd-induced tubular damage, i.e., cell deletion due to apoptosis, is reversible as a result of marked epithelial regeneration. On the basis of these histological changes, the critical concentration of Cd required to produce renal tubular damage was estimated to be 600 μg/g dry tissue.
The High Incidence of Atrial Thrombosis in Mice Given Doxorubicin
Authors: Fujihira Shiro , Yamamoto Takao , Matsumoto Masahiro , Yoshizawa Katsuhiko , Oishi Yuji , Fujii Toshiyuki , Noguchi Hideyo , Mori Hiroshi
Published: September 2009

Doxorubicin (DX)-treated mice represent an animal model for studying new drugs for heart disease. Coincidentally, in the collection of damaged myocardial tissue, thrombosis was detected in the atrium. The incidence reached 75% in mice given 4 mg/kg DX iv 10 times. They were white thrombi consisting of the fibrin, platelets, and neutrophils. Cardiac muscle damage was more prominent in the atria than in the ventricles. Light microscopically, vacuolization and degeneration of atrial myocytes and interstitial inflammatory cell infiltration were observed. Electron microscopy revealed dilatation of the sarcoplasmic reticulum and an increase in number of normal and/or degenerate mitochondria. Inflammation extended from the cardiac muscle to the endocardium. The cause of atrial thrombosis in DX-treated mice is unknown but may relate to endocardial damage and changes of blood flow in the atrium secondary to cardiac muscle damage. DX-treated mice could serve as an experimental animal model for the evaluation of efficacy and toxicity of antithrombotic or antiplatelet drugs.
Effect of Alternate-Day Hydrocortisone Therapy on the Immunologically Immature Rat. III: Changes in T- and B-Cell Areas in Lymph Nodes
Authors: El Fouhil Ahmed F. I. , Iskander Fakhry A. , Turkall Rita M.
Published: September 2009

The histologic effects of the alternate-day hydrocortisone therapy (400 mg/M2 from day 7 to day 19 after birth) were studied on the mesenteric lymph nodes of immunologically immature rats. In rats sacrificed 2 days following the cessation of therapy, depletion of lymphocytes of the thymus-independent area was apparent. Smaller lymphocytes were more susceptible to the effect of hydrocortisone than larger ones. The absence of primary follicles, normally present at this age, suggested a possible retardation in development of the immune system. B lymphocytes appeared to be the target of the direct lymphocytolytic effect of hydrocortisone. In rats sacrificed 23 days following the treatment, immunological maturity was achieved, indicating the reversibility of the hydrocortisone effect.
A Quantitative Cytochemical Study on the Pathogenesis of Streptozotocin-Induced Epithelial Tumors in Rat Kidney
Authors: Chieco Pasquale , Venturini Anna P. , Barbanti Miriam , Romagnoli Eleonora
Published: September 2009

We investigated the development of early neoplastic lesions preceding the appearance of kidney epithelial tumors in rats treated with a single iv injection of 35 mg/kg of streptozotocin (STZ). Most of these lesions were associated with segments of atrophied and regenerative nephrons surrounded by a thick basal membrane that appear precociously in chronic progressive nephropathy. Cytochemical periodic acid-Schiff, Alcian blue, and colloidal iron reactions did not indicate an excessive storage of glycogen or acid mucopolysaccharides in early neoplastic lesions and tumors. Quantitative cytochemistry of mitochondrial succinate, α-glycerophosphate, and reduced nicotinamide adenine dinucleotide—dehydrogenases revealed a shift in metabolism toward glycolysis in atrophied and regenerative nephrons as well as in early neoplastic lesions and tumors. These correlative cytomorphological and cytochemical findings raise the possibility that changes associated with the initial stages of chronic progressive nephrosis may provide favorable conditions for the selective growth of STZ-initiated cells that generate focal collections of proliferating cells and then progress to tumor growth. Tumor prevalence was remarkably constant in animals sacrificed 33, 48, and 54 wk after treatment, suggesting that the prominent inflammatory and scarring reaction later developing in the course of progressive nephrosis might contribute to control the growth of STZ-induced cancer.
Modifying Effects of Chemicals on the Development of Liver Preneoplastic Placental Glutathione S-Transferase Positive Foci in Analbuminemic and Sprague-Dawley Rats
Authors: De Camargo Joãto Lauro V. , Tsuda Hiroyuki , Asamoto Makoto , Tagawa Yoshiaki , Wada Shigetsugu , Nagase Sumi , Ito Nobuyuki
Published: September 2009

Nagase analbuminemic rats (NARs) were compared to the Sprague-Dawley (SD) stock in a medium-term assay system for hepatocarcinogenesis regarding their susceptibilities to the influence of chemicals on the development of glutathione S-transferase, placental form, positive (GST-P+) foci. Two weeks after initiation with diethylnitrosamine (DEN), the animals were exposed alternatively to 0.06% 3'-methyl-4-dimethyl-aminoazobenzene(3'-Me-DAB), 50 ppm DEN, 0.25% ethionine, 1% clofibrate, and 1% butylated hydroxyanisole (BHA) for a 6-wk period. Adequate controls included groups only initiated with DEN or treated with each test compound alone. For evaluation of the modifying potential of the chemicals, indices were generated by using the mean values obtained for number and area of GST-P+ foci after each treatment. Comparison between these indices suggests that SD rats were relatively more sensitive than NARs to the modifying effects of complete carcinogens (3'-Me-DAB and DEN). The strains were similarly susceptible to the promoting influence of ethionine, a nongenotoxic carcinogen. The inhibitory influence of BHA was more intense in NARs, whereas in both strains clofibrate was associated to similarly reduced values for number and area of GST-P+ foci. The degree of susceptibility of each strain to the modifying influence of chemicals on foci development depended on the chemical agent investigated.
Insensitivity of the Chicken Embryo to the Ototoxicity of Aminoglycoside Antibiotics and a Loop Diuretic
Authors: Fikes James D. , Render James A. , Reed Willie M. , Bursian Steven , Poppenga Robert H. , Sleight Stuart D.
Published: September 2009

Guinea pigs are routinely used in the histological evaluation of the cochlea as a method of testing for ototoxicity, but the procedures are very time-consuming. Because the avian cochlea is easier to examine and newly hatched chicks are sensitive to the ototoxic effects of gentamicin, birds may be useful in testing for ototoxicity. The use of chicken embryos would be even better for testing, but whether or not chicken embryos are sensitive to ototoxicants is unknown. In an attempt to determine whether or not chicken embryos may be used instead of guinea pigs in screening tests for ototoxicity, aminoglycoside antibiotics and a loop diuretic, ethacrynic acid, were administered to chicken embryos. A maximum-tolerated dose of gentamicin, kanamycin, streptomycin, ethacrynic acid, or a combination of gentamicin and ethacrynic acid was administered to fertile eggs of White Leghorn chickens on incubation days 10–17. To compare the effect of route of exposure on ototoxicity, gentamicin was administered by injection into the allantoic space, yolk sac, and air cell as well as by submerging the egg in gentamicin solution. With the preferred air cell route the effects of the ototoxic drugs kanamycin, streptomycin, ethacrynic acid, and a combination of ethacrynic acid and gentamicin were compared. On incubation day 18, cochleas were removed from the chicken embryos. Serial sections of these avian cochleas were examined and hair cells were counted. No significant difference was seen between the number of hair cells in cochleas of control chicken embryos and those from chicken embryos treated with drugs. Therefore, the chicken embryo appears to be insensitive to the ototoxicity of aminoglycoside antibiotics and a loop diuretic.
Renal Papillary Necrosis and Urinary Protein Alterations Induced in Fischer-344 Rats by D-Ormaplatin
Authors: Kolaja Gerald J. , Packwood William H. , Bell Rosonald R. , Ratke Christine C. , Stout Cheryl L.
Published: September 2009

D-ormaplatin (previously called tetraplatin) produced dose-related renal papillary necrosis when given intravenously to Fischer-344 rats at doses of 2, 4, and 9 mg/kg. The lesions were most severe at 4 days postdosing and had repaired by day 9 in the 2-and 4-mg/kg dose groups. Blood urea nitrogen and the N-acetyl-β-glucosaminidase (NAG): creatinine ratio were slightly elevated at day 4 while creatinine clearance was decreased. Body weight was reduced in a dose-related manner while kidney weights increased. Total protein excretion in male and female rats was elevated at day 4 postdosing. The evaluation of urinary proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed an increase, primarily in high molecular weight proteins at 4 days postdosing, indicating an increase in glomerular filtration of albumin and transferrin. The morphologic appearance of the glomeruli was normal by light microscopy. At day 4 postdosing, α1-microglobulin was elevated. This correlated with an increase in the NAG: creatinine ratio also seen at this time and the morphologic appearance of the kidney, indicating that the proximal tubules were affected but were not a major site of toxicity. Although the change in urinary proteins occurred at the same time as morphologic alterations in the renal papilla, these findings were not considered to be related. SDS-PAGE provided a useful method for detecting and localizing renal toxicity when used in conjunction with morphologic and clinical chemistry methods.
Aminoglycoside Antibiotics Alter the Paracellular Transport Properties of Cultured Human Proximal Tubule Cells
Authors: Todd John H. , Sens Donald A. , Hazen-Martin Debra J. , Sens Mary Ann
Published: September 2009

Cell cultures retaining properties of the human proximal tubule were utilized to determine whether or not the aminoglycoside antibiotics alter paracellular transport. The transepithelial resistance (RT) of the human proximal tubule (HPT) cell monolayers was determined by Ussing chamber analysis of cells grown on permeable supports. This analysis revealed that RTwas reduced as a result of aminoglycoside exposure and that the reduction corresponded to the known clinical nephrotoxicities of the aminoglycosides. Variation in the aminoglycoside concentration necessary to elicit this response was documented using 14 individual cell isolates. Ultrastructural analysis provided evidence indicating that the alterations in RTwere not associated with general damage to the HPT cells. An examination of the structure of the tight junctions by freeze-fracture analysis demonstrated only minimal alteration of the sealing strands as a result of aminoglycoside exposure. Consequently, the reductions in RTwere not directly associated with discernible tight junction structural alterations. Alteration in the paracellular route of transport, as indicated by altered RTvalues, was clearly documented as a result of aminoglycoside exposure. In addition, this alteration was accompanied by an increased density of intramembrane particles within the apical cell membrane.
The Application of Toxicokinetic Data to Dosage Selection in Toxicology Studies
Authors: Morgan D. Gwyn , Kelvin Alan S. , Kinter Lewis B. , Fish Colin J. , Kerns William D. , Rhodes Gerald
Published: September 2009

Appropriate dosage selection is a key element in the design of toxicology studies and, hence, is the first step in the process of evaluating the safety of a new chemical or pharmaceutical agent. This demands careful consideration of exposure to the drug or chemical under investigation in relation to the pharmacological or toxicological effects it evokes in an experimental animal. Toxicokinetic data provide this perspective, but they should not be considered exclusively of other data which reflect the specific activity, potency, or metabolism of the drug or chemical in each individual test species. It is equally inappropriate to base dosage selection in toxicology studies exclusively on functional or morphological endpoints that cause effects outside the range which can be accommodated by homeostatic mechanisms and repair processes. Finally, extrapolation of toxicokinetic data across species lines can lead to serious miscalculations with respect to both dosage selection and the process of risk assessment. In each case, decisions should be based on the integration of toxicokinetic data with other measures and endpoints of biological and toxicological effect.
Toxicokinetic and Mechanistic Considerations in the Interpretation of the Rodent Bioassay
Authors: MacDonald James S. , Lankas George R. , Morrissey Richard E.
Published: September 2009

When chemicals that are nongenotoxic in conventional assays produce increases in tumor incidence in rodents in chronic bioassays, the determination of the significance of these data for human safety is a challenging task. An important first step in this process is consideration of available data on the mechanism of action and biological properties of the chemical as well as pharmacokinetic and metabolism data in the species showing the response. In recent years, there has been an increase in the understanding of so-called “secondary mechanisms” of carcinogenesis (e.g., thyroid tumors in rats following exposure to enzyme inducers). Application of these data may assist in determination of human risk. There are 2 important questions that will be explored and developed: Are there biological effects produced in the test species that could explain the increase in tumor incidence, and will these effects be reproduced in humans? What is the exposure to the chemical that is associated with the increase in tumors, and how does this relate to exposure in humans?
Peer Review in Carcinogenicity Bioassays: Uses/Abuses
Authors: McConnell Ernest E. , Eustis Scot L.
Published: September 2009

“Truth is the essence of science,” and “peer review” is a key element in assuring the “truth.” Peer review is particularly important with regard to diagnostic pathology in bioassays used for regulatory purposes and approval of drugs and medical devices for at least 2 reasons: (a) If a study is designed correctly and conducted properly, the bottom-line results rely almost entirely on pathological interpretations, and (b) diagnostic pathology is a subjective science that relies on the training and experience of the pathologist and therefore is subject to individual bias. “Bias” can be introduced during the collection and preparation of pathological materials, use of inconsistent terminology during the pathology evaluation and interpretation of the results. Peer review can help in reducing this bias. However, peer review is also subject to bias by knowledge of treatment groups, selection of inappropriate slides for review, in the type of question asked of the reviewers, and in the selection of the reviewers. When done correctly, pathology peer review can be an effective and important part of a process to assure the results of a study, but when done improperly it can cloud the issue and have a negative impact on the credibility of the study.
Potential of Machine-Vision Light Microscopy in Toxicologic Pathology
Authors: Taylor D. Lansing , DeBiasio Robbin , LaRocca Greg , Pane David , Post Penny , Kolega John , Giuliano Ken , Burton Kevin , Gough Bert , Dow Alasdair , Yu Judy , Waggoner Alan S. , Farkas Daniel L.
Published: September 2009

Major developments in machine-vision light microscopy and in reagent chemistry have led to a renaissance and revolution in the use of the light microscope in biology, biotechnology, and medicine. The potential use of this technology in the field of toxicologic pathology is discussed. It is suggested that a combination of investigating living cells and tissues and fixed samples using the new technologies will lead to understanding mechanisms of toxicity. Examples of the use of the methods in basic cell biology and medicine are presented.
Causes of Death in Rodent Toxicity and Carcinogenicity Studies
Authors: Ettlin Robert A. , Stirnimann Peter , Prentice David E.
Published: September 2009

Peto test procedures for the statistical evaluation of carcinogenicity studies require that each tumor in an animal that died intercurrently (or was sacrificed in extremis) be classified as either fatal, probably fatal, incidental, or probably incidental. There is considerable controversy as to whether or not the cause of death can be established with accuracy in rodent studies. In the present article, the causes of death or ill-being as found in 10 consecutive carcinogenicity studies—5 studies with 2400 OFA (Sprague-Dawley-derived) and Wistar rats and 5 studies with 2400 OF1 and NMRI mice—were re-examined. A cause of death or moribund state had been established in more than 80% of the cases in rats and in more than 70% in mice. These causes were, in rats, mainly pituitary tumors, chronic progressive nephropathy (males), mammary gland tumors (females), and subcutaneous tumors (males); in mice, mainly hemolymphoreticular tumors, lung tumors, liver tumors (males), and glomerulonephropathy. The criteria used for determining the tumorous or non-tumorous lesions as the cause of death were based on in-life and pathological findings. The validity of such procedures, the possibility of improving criteria in the future, and the usefulness of establishing causes of death in safety assessment are discussed.
Neoplastic Lesions of Questionable Significance to Humans
Authors: Alison Roger H. , Capen Charles C. , Prentice David E.
Published: September 2009

Many compounds giving a positive result in animal carcinogenicity studies through mechanisms involving secondary carcinogenesis pose little or no risk to humans. This article provides an overview of current understanding, with particular reference to renal tumors in male rats with α2μ-globulin nephropathy, urinary bladder neoplasia in rodents, mesovarian leiomyomas induced in rats by β2-receptor stimulants, carcinoid tumors in the rodent stomach induced by prolonged suppression of acid secretion, thyroid follicular cell tumors in rodents, canine mammary neoplasia due to administration of progestagens, rodent mammary neoplasia induced by estrogens, uterine endometrial carcinomas of rats induced by dopamine agonists, Leydig cell tumors in the testis of rats, and ovarian tubulostromal adenomas in mice. A positive result on a rodent carcinogenicity study should not automatically preclude further development of a compound; future progress in this field should increase the accuracy of the rodent carcinogenicity study as a tool in human safety assessment.
Issues with Biotechnology Products in Toxicologic Pathology
Authors: Terrell Timothy G. , Green James D.
Published: September 2009

The emergence of the biotechnology industry and introduction of drugs derived from recombinant DNA technology has generated many new issues in approaches to preclinical safety evaluation and extrapolation of results to risk assessment in humans. Products or therapeutic approaches for consideration include hormones, growth factors, cytokines, monoclonal antibodies, vaccines, blood products, antisense, and gene therapy. In many instances the application of standard safety tests conventionally used for small molecules are of limited value or are inappropriate. Studies should be designed to answer specific scientific questions rather than simply to fulfill regulatory requirements. Special consideration must be given to study design and species selection in terms of biological activity and species specificity, implications of immunological responses in the animal studies, and effects of systemic administration of molecules at clinically relevant doses. A full understanding of the clinical relevance of toxicological and pathologic findings associated with administration of these molecules to laboratory animals requires definition of the pathogenic mechanism of lesion induction.
Risk Assessment Methodology: Maximum Tolerated Dose and Two-Stage Carcinogenesis Models
Authors: Goldstein Bernard D.
Published: September 2009

The Committee on Risk Assessment Methodology of the Board on Environmental Studies and Toxicology of the National Academy of Sciences has considered issues related to the use of the maximum tolerated dose (MTD) in carcinogenesis bioassays and of 2-stage models of carcinogenesis. In each case, the goal has been to consider whether sufficient information is available to lead to a change in current methodology used by regulatory agencies in assessing risk. The majority of the committee favored retention of the MTD but recommended that lower doses also be used for cancer bioassays and, if the results are positive, performance of additional mechanistic studies aimed at improved extrapolation to environmentally relevant concentrations. The minority recommended that additional preliminary studies be done in order to obtain information about the highest dose relevant to extrapolation to humans for use in the cancer bioassay. Two-stage carcinogenesis models were found to be an excellent approach to increase understanding but required an extensive toxicological data base beyond that available for most chemicals. These deliberations have highlighted the value of increased understanding of the basic mechanisms of action of potential cancer-causing chemicals in order to advance the methodology of risk assessment.
Intuitive Toxicology: Expert and Lay Judgments of Chemical Risks
Authors: Neil Nancy , Malmfors Torbjörn , Slovic Paul
Published: September 2009

Human beings have always been intuitive toxicologists, relying on their senses of sight, taste, and smell to detect harmful or unsafe food, water, and air. As we have come to recognize that our senses are not adequate to assess the dangers inherent in exposure to a chemical substance, we have created the sciences of toxicology and risk assessment to perform this function. Yet despite this great effort to overcome the limitations of intuitive toxicology, it has become evident that even our best scientific methods still depend heavily on extrapolations and judgments in order to infer human health risks from animal data. Many observers have acknowledged the inherent subjectivity in the assessment of chemical risks and have indicated a need to examine the subjective or intuitive elements of expert and lay risk judgments. Such an examination was begun by surveying members of the Society of Toxicology and the lay public about basic toxicological concepts, assumptions, and interpretations. The results demonstrated large differences between toxicologists and laypeople, as well as differences among toxicologists working in industry, academia, and government. In addition, toxicologists were found to be sharply divided in their opinions about the ability to predict a chemical's effect on human health on the basis of animal studies. These results place the problems of risk communication in a new light. Although the survey identifies misconceptions that experts should clarify for the public, it also suggests that controversies over chemical risks may be fueled as much by limitations of the science of risk assessment and disagreements among experts as by public misconceptions.
Legal Responsibilities of the Pathologist
Authors: Picut Catherine A. , Parker George A.
Published: September 2009

Pharmaceutical companies exist today in a hostile legal and regulatory environment. The threat of product liability in the pharmaceutical industry has risen to the point where it stifles research and development, especially for contraceptive and psychotropic drugs. Regulatory sanctions against the industry are more likely now than in the past since the Food and Drug Administration (FDA) has placed significant emphasis on regulatory inspection and enforcement. Industrial pathologists play a critical role in defending their company in product liability litigation and from regulatory sanctions. In-house and contract pathologists should be prepared to give expert testimony in court and ensure that an effective document retention policy is implemented. Pathologists should know the limits of the FDA's inspection authority and be aware of the “pitfalls” of the FDA's new Fraud Policy. In addition to keeping abreast of science, industrial pathologists today can best serve the pharmaceutical industry if they maintain an awareness of legal issues that pose a threat to the future success of the industry.
The Pathologist in Litigation: A Scientist's Perspective
Authors: Newberne James W.
Published: September 2009

Escalation of myriad litigious facets of our society can be found in almost any large city newspaper, especially in the United States, and, in particular, in the Yellow Pages of the telephone directory listing of personal injury (toxic tort) lawyers—many with full-page advertisements offering a cornucopia of services replete with free consultation and contingency “no-fee” offers if litigation proceedings are undertaken and fail to be financially productive. With such inducements, it is little wonder that such an environment essentially guarantees that many pathologists such as yourselves will be increasingly drawn into litigation at some stage in his/her career, especially in the area of product (toxic tort) liability.
Exocrine Pancreatic Neoplasms in the Mummichog (Fundulus heteroclitus) from a Creosote-Contaminated Site
Authors: Fournie John W. , Vogelbein Wolfgang K.
Published: September 2009

A high prevalence of exocrine pancreatic neoplasms occurred in mummichog, Fundulus heteroclitus, from a creosote-contaminated site in the Elizabeth River, Virginia. A total of 20 neoplasms were found in a group of about 1,300 fish obtained at this site over a 2-yr period. Of 240 fish collected during October 1991, 3.3% had pancreatic neoplasms. Adjusted total lesion prevalence for large adult fish (Size Class III: total length = 75–85 mm; Size Class IV: total length > 85 mm) was 6.7%. Pancreatic neoplasms were not observed in 234 fish collected at this site during May 1991, nor were they found in 420 fish obtained during fall 1991 from 1 uncontaminated and 6 moderately contaminated localities. Lesions involved both mesenteric and intrahepatic exocrine pancreas and ranged from well-differentiated acinar cell adenomas to poorly differentiated acinar cell carcinomas. One fish had an atypical acinar cell focus. All specimens with pancreatic neoplasms also had hepatocellular lesions. This epizootic of exocrine pancreatic neoplasia is the first to be reported in a wild fish population. Based on chemical characterization of the site and limited experimental data on chemically induced pancreatic carcinogenesis in other small fish species, the neoplasms were probably caused by exposure of the mummichog to chemical carcinogens in their environment.
Ultrastructure of Normal and Neoplastic Exocrine Pancreas in the Mummichog, Fundulus heteroclitus
Authors: Vogelbein Wolfgang K. , Fournie John W.
Published: September 2009

The ultrastructure of exocrine pancreatic neoplasms occurring in the mummichog, Fundulus heteroclitus, from a creosote-contaminated site in the Elizabeth River, Virginia, is described and related to nonneoplastic exocrine pancreas. Normal mummichog pancreas was an anastomosing tubular gland, with parenchymal cells organized as branched, anastomosing tubules around a central ductular system. The pancreatic ductular system consisted sequentially of terminal canalicular lumens lined by acinar cells, pancreatic preductules formed by an acinar and a centroductular cell, pancreatic ductules lined by 2 centroductular cells, and pancreatic ducts lined by cuboidal or columnar epithelial cells resting on a basal lamina and stromal sheath. Acinar cell adenomas retained the normal tubular organization and relationship between acinar and centroductular cells. Tumor cells exhibited nuclear pleomorphism but contained a full complement of normal zymogen granules and rough endoplasmic reticulum (RER). Some adenomas exhibited necrosis and cellular degeneration. Acinar cell carcinomas ranged from well to poorly differentiated. They exhibited loss of cell polarity, moderate to severe nuclear pleomorphism, extensive variation in size, shape, and number of zymogen granules, variability in RER content, and cellular degeneration. Acinar cell neoplasms in the mummichog were similar to those induced chemically in other fishes and certain mammals, suggesting that this fish population has been exposed to potent chemical carcinogens and that the species may be an effective indicator of polluted estuarine environments.
Tumor-Promoting Effects of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin and Phenobarbital in Initiated Weanling Sprague-Dawley Rats: A Quantitative, Phenotypic, and ras p21 Protein Study
Authors: Sills Robert C. , Goldsworthy Thomas L. , Sleight Stuart D.
Published: September 2009

In an initiation-promotion protocol, female weanling Sprague-Dawley rats were initiated with 10 mg/kg nitrosodiethylamine and promotion was started after 30 days. Promotion regimens were as follows: 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD; 150 ppt in diet) continuously until day 450; phenobarbital (PB; 500 ppm in diet) until day 170; PB until day 170, followed by TCDD until day 240; and PB until day 170, followed by a basal diet (BD) until day 240 and subsequently TCDD from days 240 to 450. TCDD fed to initiated rats had a promoting effect on the development of adenosine triphosphatase-negative altered hepatocellular foci (AHF). At 450 days, the volume fraction of liver occupied by AHF was increased in initiated rats given TCDD continuously and in those given PB followed by TCDD, whereas the mean volume of AHF was significantly larger in initiated rats given TCDD continuously. PB and TCDD promoted similar phenotypes of AHF as seen in hemotoxylin and eosin-stained sections, but the eosinophilic phenotype most closely correlated with the development of hepatocellular neoplasms. The protooncogene product ras p21 protein was present in the majority of PB- and TCDD-promoted AHF, hepatocellular adenomas, and hepatocellular carcinomas. Eosinophilic AHF and ras p21 protein expression most closely correlated with neoplastic development, suggesting that these cell populations, when promoted, may be at greater risks for developing into neoplasms.
Effect of Phenobarbital and Mirex Pretreatments on CCl4Autoprotection
Authors: Thakore Kashyap N. , Mehendale Harihara M.
Published: September 2009

Male Sprague-Dawley rats maintained on either normal diet (N) or on a diet containing phenobarbital (PB; 225 ppm) or mirex (M; 10 ppm) for 15 days received either com oil or 1 single administration of a protective dose of CCl4(0.3 ml/kg, po) on day 16. At 24, 48, 72, 96, or 144 hr after the protective dose, a high dose of CCl4(5 ml/kg, po) was administered to rats of all the groups, and they were observed for 14-day lethality. In a second experiment, in rats maintained on N, PB, or M diet, liver microsomal cytochromes P-450, aminopyrine demethylase, and aniline hydroxylase were measured at various time points after the administration of the protective dose of CCl4. Serum aspartate transaminase, alanine transaminase, and sorbitol dehydrogenase elevations and histopathological changes observed under a light microscope were used as toxic end points to assess hepatotoxicity. Autoprotection was 100% when the high dose was given at 24 hr after the protective dose in N rats, whereas it was only 55% in PB- or M-pretreated rats. For later time points of 48, 72, and 96 hr, autoprotection was only around 50% in N rats, whereas it was almost 100% in PB- and M-pretreated rats. When the high dose was administered at 144 hr after the protective dose, autoprotection further declined to 25% in N rats and to 75% in M-treated rats, but it remained at 100% in PB-treated rats. The liver microsomal cytochromes P-450, aminopyrine demethylase, and aniline hydroxylase were induced in rats after the dietary treatment with PB or M when compared to the rats on N diet. However, after administration of the protective dose of CCl4to these rats, these enzyme activities were decreased in all the groups at 24 hr after the protective dose, persisted at a low level even at the 72-hr time point, and then slowly recovered to normal by 120 hr. Liver injury was evident by serum enzyme elevations and histopathological changes in all the groups at 24 hr after the protective dose, but the injury was progressive in PB- and M-treated rats with maximum injury at 48 hr, injury in PB-treated rats being greater than that in M-treated rats. The livers recovered completely in all the groups by 120 hr as revealed by serum enzymes and liver histology. The levels of microsomal enzymes at various time points after the protective dose in N, PB, and M treatment groups correlate neither with liver toxicity nor with animal survival after the administration of the large dose of CCl4. Therefore, a postponement of the hepatocellular regeneration stimulated by the protective dose of CCl4caused by prior exposure to PB and M, as reported earlier, appears to play a role in the correspondingly postponed maximal expression of CCl4autoprotection. Furthermore, the prolongation of autoprotection by M and even greater effect by PB appears to be related to the greater stimulation of hepatocellular proliferation and augmented tissue repair processes attributable to the protective dose of CCl4reported previously.
The Effects of Overfeeding and Dietary Restriction on Sprague-Dawley Rat Survival and Early Pathology Biomarkers of Aging
Authors: Keenan Kevin P. , Smith Peter F. , Hertzog Phillip , Soper Keith , Ballam Gordon C. , Clark Robert L.
Published: September 2009

A significant correlation exists between average daily food consumption and 2-yr survival in control ad libitum (AL)–fed Sprague-Dawley (SD) rats. SD rats were fed Purina Rodent Chow 5002 or a modified chow, 5002–9, with lower protein, fat, metabolizable energy and increased fiber AL or by dietary restriction (DR) to 65% of the AL amount by measurement or time (6.5 hr). At 52 wk, food consumption and key pathology biomarkers correlated with 106-wk survival. The modified chow, 5002–9 fed AL, did not significantly improve survival. SD rats fed either diet AL consumed the greatest amount of feed and kcal/rat but consumed the same amount of feed per gram body weight as DR-fed rats. At 52 wk, AL rats fed either diet had the same brain weights as DR rats, but the AL-fed rats had greater body weight and body fat content and increased heart, lung, kidney, liver, adrenal, thyroid, and pituitary weights as well as an increased incidence and severity of degenerative and/or proliferative lesions in these organs. This study demonstrates that overfeeding best correlates with low 2-yr survival in SD rats and that simple DR by caloric restriction modifies key pathology biomarkers in the pituitary, mammary gland, kidney, and heart of SD rats at 52 wk that are predictive of 106-wk survival.
Alterations in Glomerular Anionic Sites in Canine Anti-Glomerular Basement Membrane Nephritis with Onset of Severe Proteinuria
Authors: Sugimoto Jiro , Wasaki Masahiko , Shirota Kinji , Nomura Yasuo
Published: September 2009

Rabbit anti-glomerular basement membrane serum (AGBM) or normal rabbit serum (NRS) were given intravenously (2 ml/kg body weight) to 8 male beagle dogs. Light and transmission electron microscopy and immunofluorescence were performed on the kidneys on day 7 postinjection. Alterations of anionic sites (ASs) of glomerular basement membrane (GBM) in peripheral, proximal, and paramesangial portions were studied quantitatively by electron microscopy using polyethyleneimine (PEI; molecular weight = 1,800) as a cationic probe. Severe or mild proteinuria developed on day 1 and continued until day 6 postinjection. On day 7 after AGBM injection, the number of PEI granules per 1,000 nm length of the lamina rara externa of GBM in all portions was significantly less than that in NRS-treated dogs (10.48 ± 1.78 versus 14.19 ± 2.35 granules per 1,000 nm of GBM in peripheral portion, 10.81 ± 1.91 versus 14.97 ± 1.35 granules per 1,000 nm of GBM in proximal portion, 8.44 ± 1.76 vs 13.43 ± 2.10 granules per 1,000 nm of GBM in paramesangial portion; p < 0.001). These results indicate that a reduction glomerular AS occurs in AGBM-treated dogs in association with severe or mild proteinuria and alterations in glomerular ASs might play an important role in the pathogenesis of proteinuria in the canine anti-GBM nephritis in addition to morphological changes.
Normal Ultrastructure of the Kidney and Lower Urinary Tract
Authors: Verlander Jill W.
Published: September 2009

The mammalian urinary tract includes the kidneys, ureters, urinary bladder, and urethra. The renal parenchyma is composed of the glomeruli and a heterogeneous array of tubule segments that are specialized in both function and structure and are arranged in a specific spatial distribution. The ultrastructure of the glomeruli and renal tubule cpithelia have been well characterized and the relationship between the cellular structure and the function of the various components of the kidney have been the subject of intense study by many investigators. The lower urinary tract, the ureters, urinary bladder, and urethra, which are histologically similar throughout, are composed of a mucosal layer lined by transitional epithelium, a tunica muscularis, and a tunica serosa or adventitia. The present manuscript reviews the normal ultrastructural morphology of the kidney and the lower urinary tract. The normal ultrastructure is illustrated using transmission electron microscopy of normal rat kidney and urinary bladder preserved by in vivo perfusion with glutaraldehyde fixative and processed in epoxy resin.
Xenobiotic Metabolizing Enzymes of the Kidney
Authors: Lock Edward A. , Reed Celia J.
Published: September 2009

The kidney possesses most of the common xenobiotic metabolizing enzymes, and is thus able to make an important contribution to the body's metabolism of drugs and foreign compounds. An overview of the renal localization, catalytic activity, developmental regulation, induction, and sex and species differences for the key enzymes involved in phase I and phase II of xenobiotic metabolism is presented. In general, the catalytic activities of the various renal enzymes are lower than those of the liver, although there are exceptions, such as the enzymes involved in the processing of glutathione conjugates to their mercapturic acids. Xenobiotic metabolizing enzymes are not evenly distributed along the nephron; cytochromes P-450 and those enzymes involved in the conjugation of glutathione, glucuronic acid, or sulfate are primarily localized in the proximal tubules. However, some isozymes of cytochrome(s) P-450 and glutathione S-transferases are selectively localized in cells of the thick ascending limb and distal tubules, whereas prostaglandin H synthase is concentrated in the collecting ducts in the medulla. Thus, the proximal tubule, the principal site of xenobiotic biotransformation, is particularly susceptible to chemical insult, and the localization of prostaglandin synthase in the inner medulla and papilla may be a contributary factor to the toxicity produced by chemicals in this part of the nephron. Many of the enzymes discussed, in addition to metabolizing foreign compounds, have important endogenous functions in the kidney, such as the regulation of salt and water balance and the synthesis of vitamin D.