Showing papers in "Toxicologic Pathology in 1998"
TL;DR: The data suggest that mortality resulting from brevetoxicosis may not necessarily be acute but may occur after chronic inhalation and/or ingestion, and suggests that brevet Toxicosis may initiate apoptosis and/ or the release of inflammatory mediators that culminate in fatal toxic shock.
Abstract: In 1996, at least 149 manatees (Trichechus manatus latirostris) died in an unprecedented epizootic along the southwest coast of Florida. At about the same time, a bloom of the brevetoxin-producing dinoflagellates, Gymnodinium breve, was present in the same area. Grossly, severe nasopharyngeal, pulmonary, hepatic, renal, and cerebral congestion was present in all cases. Nasopharyngeal and pulmonary edema and hemorrhage were also seen. Consistent microscopic lesions consisted of catarrhal rhinitis, pulmonary hemorrhage and edema, multiorgan hemosiderosis, and nonsuppurative leptomeningitis. Immunohistochemical staining using a polyclonal primary antibody to brevetoxin (GAB) showed intense positive staining of lymphocytes and macrophages in the lung, liver, and secondary lymphoid tissues. Additionally, lymphocytes and macrophages associated with the inflammatory lesions of the nasal mucosa and meninges were also positive for brevetoxin. These findings implicate brevetoxicosis as a component of and the likely primary etiology for the epizootic. The data suggest that mortality resulting from brevetoxicosis may not necessarily be acute but may occur after chronic inhalation and/or ingestion. Immunohistochemical staining with interleukin-1-beta-converting enzyme showed positive staining with a cellular tropism similar to GAB. This suggests that brevetoxicosis may initiate apoptosis and/or the release of inflammatory mediators that culminate in fatal toxic shock.
294 citations
TL;DR: Spontaneous neoplasm rates were determined for control Fischer 344 (F344) rats and B6C3F, mice from 2-yr rodent carcinogenicity studies carried out by the National Toxicology Program (NTP).
Abstract: ABSTRAC~ Spontaneous neoplasm rates were determined for control Fischer 344 (F344) rats and B6C3Fl mice from 2-yr rodent carcinogenicity studies carried out by the National Toxicology Program (NTP). The most frequently occurring neoplasms in untreated male F344 rats were testicular adenoma (89. I 56). mononuclear cell leukemia (50.5%), adrenal gland pheochromocytoma (3 1.9%). and pituitary gland neoplasms (30.4%). For untreated female F344 rats, the most frequently occurring neoplasms were pituitary gland neoplasms (54.2%). mammary gland fibrondenoma (41.2%). and mononuclear cell leukemia (28.1 8). The most frequently occurring neoplasms in untreated male B6C3Fl mice were liver adenomdcarcinoma (42.2%). lung adenomdcarcinoma (20.5%), and malignant lymphoma (8.3%). For untreated female B6C3F, mice, the most frequently occurring neoplasms were liver adcnomdcarcinomn (23.68). malignant lymphoma (20.9%). and pituitary gland adenomdcarcinoma (14.8%). The tumor rates observed in feeding study (untreated) and inhalation study (chamber) control rats were generally similar. The major exceptions were pituitary gland tumors and testicular adenoma in male F344 rats. The overall incidence of testicular adenoma was much lower in chamber controls (69.4%) than in feeding study controls (89.1%). whereas pituitary gland neoplasms showed the opposite trend (60.7% vs 30.4%). The most likely explanation for this difference is related to the individual housing of chamber controls and the group housing of feeding study controls. Differences in diagnostic criteria may influence reported tumor rates. To ensure consistency and comparability of tumor diagnosis from study to study, the NTP uses rigorous histopathology quality assurance and peer review procedures. Biological factors such as body weight may also affect tumor incidence. For example, increased body weights are associated with increased incidences of certain site-specific neoplasms, espccially pituitary gland and mammary gland neoplasms in rats and liver tumors in mice. The presence of Helicobacter hepporicrrs has been associated with an increased incidence of liver neoplasms in male B6C3FI mice. Other factors that may produce differences in control tumor rates from study to study include diet, environmental factors. genetic drift. study duration. and survival differences. The NTP database provides historical control data that may be useful jn the evaluation of possible chemically related changes in tumor incidence. However, it is essential that the study being evaluated be comparable to those in the NTP database with respect to those factors that are known to influence tumor occurrence.
271 citations
TL;DR: Evidence is provided that PPARα mediates the subacute-chronic toxicity of di(2-ethylhexyl)phthalate in liver, kidney, and testis and that DEHP can also act through PPAR α-independent pathways in mediating renal and testicular toxicity.
Abstract: The peroxisome proliferator-activated receptora (PPARα) is the mediator of the biological effects of peroxisome proliferators through control of gene transcription. To determine if the toxic effects of di(2-ethylhexyl)phthalate (DEHP) are mediated by PPARα, we examined its effect in PPARα-null mice. Male Sv/129 mice, PPARα-null (–/–) or wild-type (+/+) were fed ad libitum either a control diet or one containing 12,000 ppm DEHP for up to 24 wk. Significant body weight loss and high mortality was observed in (+/+) mice fed DEHP. By 16 wk, all DEHP-fed (+/+) mice had died of cystic renal tubular disease. In contrast, the (–/–) mice fed DEHP had no changes in body weight until later in the study nor increased mortality. Histologically, (+/+) mice fed DEHP had typical toxic lesions in liver, kidney, and testis while (–/–) mice fed DEHP had no toxic liver lesions but did show evidence of toxicity in kidney and testis after 4–8 wk of feeding, which progressed into moderate lesions by 24 wk. Analysis of hepatic a...
250 citations
TL;DR: Significant interspecies differences exist in the presence and distribution of COX isoforms, which may help explain the difference in species susceptibility to NSAID-related renal toxicity.
Abstract: Cyclooxygenase (COX) exists in 2 related but unique isoforms: one is constitutive (COX-1) and functions in normal cell physiology, and the other is inducible (COX-2) and is expressed in response to inflammatory stimuli. Nonsteroidal antiinflammatory drugs (NSAIDs) cause renal toxicity following inhibition of renal cyclooxygenases. Humans and animals exhibit differences in susceptibility to NSAID-related renal toxicity, which may be associated with differences in expression of 1 or both isoforms of COX in the kidney. In this study, we evaluated COX-1 and COX-2 expression in the kidneys of mixed-breed dogs, Sprague-Dawley rats, cynomolgus monkeys, and humans. In addition, the effect of volume depletion on renal COX expression was investigated in rats, dogs, and monkeys. COX expression was evaluated using 1 or more of the following procedures: reverse transcriptase polymerase chain reaction, in situ hybridization, and immunohistochemistry. We demonstrated that both COX isoforms are expressed in the kidneys of all species examined, with differences in the localization and level of basal expression. COX-1 is expressed at high levels in the collecting ducts and renal vasculature of all species and in a small number of papillary interstitial cells in rats, monkeys, and humans. Basal levels of COX-2 are present in the maculae densa, thick ascending limbs, and papillary interstitial cells in rats and dogs and in glomerular podocytes and small blood vessels in monkeys and humans. COX-2 expression is markedly increased in volume-depleted rats and dogs but not monkeys. These results indicate that significant interspecies differences exist in the presence and distribution of COX isoforms, which may help explain the difference in species susceptibility to NSAID-related renal toxicity.
209 citations
TL;DR: KBr03 was carcinogenic in rodents at water concentrations as low as 0.02 g/L (20 ppm; 1.5 mg/kg/day) and can be used to estimate the human health risk that would be associated with changing from chlorination to ozonation for disinfection of drinking water.
Abstract: Ozone has been proposed for water disinfection because it is more efficient than chlorine for killing microbes and rcsults in much lower levels of carcinogenic trihalomcthanes than does chlorination. Ozone leads to formation of hypobromous hcid in surface waters with high bromine content and forms brominated organic by-products and bromate. The carcinogenicity and chronic toxicity of potassium bromate (KBrO,) was studied in male B6C3F, mice and F344M rats to confirm and extcnd the results of previous work. Mice were treated with 0. 0.08, 0.4, or 0.8 g/L KBrO, in the drinking water for up to 100 wk, and rats werc provided with 0, 0.02, 0.1, 0.2. or 0.4 g/L KBrO,. Animals were euthanatized, necropsied, and subjected to a complete macroscopic examination. Selected tissues and gross lesions were processed by routine methods for light microscopic examination. The present study showed that KBrO, is carcinogenic in the rat kidney, thyroid, and mesothelium and is a renal carcinogen in the male mouse. KBrO, was carcinogenic in rodents at water concentrations as low as 0.02 g/L (20 ppm; 1.5 mglkglday). These data can be used to estimate the human health risk that would be associated with changing from chlorination to ozonation for disinfection of drinking water.
196 citations
TL;DR: Observations in rodents can assist in identifying possible mechanisms involved for these nongenotoxic chemicals and therefore can be important for a rational evaluation of human risk.
Abstract: Urinary bladder carcinogenesis in rodents bears numerous similarities to the diseases in humans In rats, the process progresses through the morphologic stages of simple hyperplasia, papillary and nodular hyperplasia, papilloma, noninvasive, and invasive carcinoma In mice, the pathogenesis can be similar or can follow a sequence of marked dysplasia with or without hyperplasia, leading to carcinoma in situ and ultimately to high-grade invasive carcinoma Although the papillary and nonpapillary diseases appear to be related in rodents and in humans, they are distinct morphologically, biologically, and molecularly Numerous classes of genotoxic chemicals have been identified as bladder carcinogens in rodents, and some of these have also been identified as carcinogenic in humans, most notably, aromatic amines, nitrosamines, and cyclophosphamide In contrast, nongenotoxic chemicals appear to be highly specific with respect to species, strain, diet, agent, dose, and mechanism For some, it is unclear whether the results at high doses in rodents can be extrapolated to low doses or to humans, eg, chemicals that cause bladder cancer only at high doses related to the formation of calculi Numerous observations in rodents can assist in identifying possible mechanisms involved for these nongenotoxic chemicals and therefore can be important for a rational evaluation of human risk
140 citations
TL;DR: The phagolysosomal nephropathy was detected in rats after acute exposure as well as in the surviving rats following 1 intraperitoneal injection of 500 mg/kg or intravenous injection of 100mg/kg, and may serve as a biological marker in toxicity screening tests for this class of compound.
Abstract: Polyalkylsulfonated C60, or FC4S, a highly water-soluble caged fullerene derivative, is believed to be a free radical remover or an antioxidant in biological systems. A 50 mg/ml aqueous solution was prepared as a master solution and administered to female Sprague-Dawley CD(Crl:CDR (SD)BR) rats in a single-dose acute toxicity study or a 12-day subacute toxicity study where rats were given the solution daily. In a study of the median lethal dose (LD50), no rats died after oral administration, and thus FC4S was considered to nontoxic if administered orally. In an LD50 intraperitoneal injection study, rats died within 30 hr after injection; the LD50 was determined to be approximately 600 mg per kilogram of body weight. Rats injected with the compound intraperitoneally or intravenously immediately eliminated the compound through the kidney; the kidney appeared to be the primary target organ. The compound induced a distinct lysosome-overload nephrosis, a phagolysosomal nephropathy characterized by a tinctorial ...
138 citations
TL;DR: The ubiquitous environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) is a member of a broad group of halogenated aromatic hydrocarbons (HAHs) that is known to induce a wide range of environmental effects as discussed by the authors.
Abstract: The ubiquitous environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) is a member of a broad group of halogenated aromatic hydrocarbons (HAHs) that is known to induce a wide r...
133 citations
TL;DR: 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.
Abstract: 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 I1 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 cytochrorne(s) P450 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. epoxide hydrolases; renal prostaglandin H synthase; renal cysteine conjugate p-lyase; renal flavin monooxygenases h'eyr.ords. Renal cytochromes P-450; renal glutathione S-transferases; renal glucuronosyl transferases; renal sulfotransferases; renal
104 citations
TL;DR: The histopathologic nature of hydroquinone renal carcinogenesis suggests that an additional epigenetic pathway to renal tubule tumor formation in rats may be through chemical-mediated exacerbation of, and interaction with, the age-related spontaneous renal disease, chronic progressive nephropathy.
Abstract: Laboratory studies with classical renal carcinogens in the rat and mouse, as well as research investigation with some of the chemicals proving positive for the kidney in National Toxicology Program carcinogenicity bioassays, have demonstrated the existence of a range of diverse mechanisms underlying rodent kidney carcinogenesis. The classical carcinogens used as experimental models for studying renal tumor pathogenesis, such as the nitrosamines, are genotoxic and interact directly with DNA, forming DNA adducts with mutagenic potential. In contrast, potassium bromate and ferric nitrilotriacetate (Fe-NTA), also effective renal carcinogens, appear to cause indirect damage to DNA mediated by oxidative stress. A number of nongenotoxic chemicals are associated with epigenetic renal tumor induction in rodents, and the activity of these tends to involve prolonged stimulation of cell proliferation throughout the duration of exposure. This mode of action reflects a sustained regenerative response, either due to direct chemical toxicity to the tubule cells, as with chloroform, or to indirect cytotoxicity associated with lysosomal overload, as in alpha2u-globulin accumulation in male rats resulting from the administration of such chemicals as d-limonene and tetrachloroethylene. The histopathologic nature of hydroquinone renal carcinogenesis suggests that an additional epigenetic pathway to renal tubule tumor formation in rats may be through chemical-mediated exacerbation of, and interaction with, the age-related spontaneous renal disease, chronic progressive nephropathy. These various mechanistic pathways have implications for the nature of the induced cancer process with respect to tumor incidence, latency, malignancy, and sex predisposition.
98 citations
TL;DR: Characteristic features of metal nephrotoxicity are lesions that tend to predominate in specific regions of the nephron within specific cell types, which suggests that certain regions of this region are selectively sensitive to specific metals.
Abstract: The mechanisms by which metals induce renal injury are, in general, poorly understood. Characteristic features of metal nephrotoxicity are lesions that tend to predominate in specific regions of the nephron within specific cell types. This suggests that certain regions of the nephron are selectively sensitive to specific metals. Regional variability in sensitivity could result from the localization of molecular targets in certain cell populations and/or the localization of transport and binding ligands that deliver metals to targets within the nephron. Significant progress has been made in identifying various extracellular, membrane, and intracellular ligands that are important in the expression of the nephrotoxicity of metals. As an example, mercuric chloride induces a nephropathy that, at the lowest effective doses, is restricted primarily to the S3 segment of the proximal tubule, with involvement of the S2 and S1 segments at higher doses. This specificity appears to be derived, at least in part, from the distribution of enzymes and transport proteins important for the uptake of mercury into proximal tubule cells: apical gamma-glutamyltranspeptidase and the basolateral organic anion transport system. Regional distributions of transport mechanisms for binding proteins appear to be important in the expression of nephrotoxicity of metals. These and other new research developments are reviewed.
TL;DR: Data support the hypothesis that the increased incidence of liver neoplasms is associated with H. hepaticus and that hepatitis may be important in the pathogenesis and interpretation of carcinogenic effects in the liver of B6C3F1 mice may be confounded if there is H. liveraticus-associaled hepatitis.
Abstract: Male and female B6C3F, mice from 12 National Toxicology Program (NTP) 2-yr carcinogenesis studies were found to be infected with Helicobacrer hepaficirr. Many of the male mice from 9 of these studies had an associated hepatitis (affected studies). Helicobncrer hepnriciis has been reported to be associated with an increased incidence of hepatitis and hepatocellular neoplasms in the AlJCr male mouse. We attempted to determine if the data from the Helicobacrer-affected NTP B6C3F1 mouse studies were compromised and unsuitable for cancer hazard identification. The incidences of neoplasms of the liver (both hepatocellular and hemangiosarcoma) but not of other organs in control male B6C3F, mice \vere increased in affected studies as compared with control males from unaffected studies. The increased incidence of hepatocellular neoplasms was observed in those males exhibiting H. hepaficiis-associated hepatitis. Other observations further differentiated control male mice from affected and unaffected studies. H-ros codon 61 CAA to AAA mutations were less common in liver neoplasms from males from affected studies as compared with historical and study controls. In addition, increases in cell proliferation rates and apoptosis were observed in the livers of male mice with H. hepnriciis-associated hepatitis. These data support the hypothesis that the increased incidence of liver neoplasms is associated with H. hepaticits and that hepatitis may be important in the pathogenesis. Therefore, interpretation of carcinogenic effects in the liver of B6C3F, mice may be confounded if there is H. hepaticiir-associated hepatitis.
TL;DR: Smoke-induced epithelial hypertrophy, hyperplasia, and squamous metaplasia were reported in the conducting airways in most of the studies, along with increased numbers of intra-alveolar macrophages that were occasionally associated with alveolarmetaplasia.
Abstract: In this paper, I review the results of a representative selection of chronic inhalation studies with rats and mice exposed to mainstream cigarette smoke and describe the inhalation exposures and the histopathological changes reported by various authors. Many of the studies used nose-only exposure systems, whereas others simply used large whole-body chambers. Smoke-induced epithelial hypertrophy, hyperplasia, and squamous metaplasia were reported in the conducting airways in most of the studies, along with increased numbers of intra-alveolar macrophages that were occasionally associated with alveolar metaplasia. Lung adenomas and adenocarcinomas were reported in only a few of the studies. No statistically significant increase in the incidence of malignant lung tumors was seen in either species as a result of smoke exposure, a finding that does not agree with the results of epidemiological studies in humans. Possible reasons for this lack of correlation are given.
TL;DR: T-2 toxin induced-lesions in the hematopoietic tissues and in the lymphoid tissues were brought about by apoptosis of component cells, and it is believed that damage to thehematopOietic microenvironment may also play an indirect role in the induction of apoptosis in the bone marrow.
Abstract: We examined T-2 toxin-induced lesions in the bone marrow and splenic red pulp as many as 48 hr after oral inoculation with 10 mg/kg body weight of T-2 toxin in female ICR:CD-1 mice. Histopathologically, the bone marrow and splenic red pulp showed a significant hypocellularity. In the bone marrow, the number of myelocytes significantly decreased due to the loss of immature granulocytes, erythroblasts, and lymphocytes. The nuclei of the remaining cells showing pyknosis or karyorrhexis were positively stained by the TdT-mediated dUTP nick end labeling (TUNEL) method, and these TUNEL-positive cells showed ultrastructural characteristics of apoptosis. With agarose gel electrophoresis, DNA ladders were clearly detected in bone marrow samples. The number of TUNEL-positive cells in splenic red pulp increased earlier than it did in the splenic white pulp. Thus, T-2 toxin induced-lesions in the hematopoietic tissues and in the lymphoid tissues were brought about by apoptosis of component cells. We believe that damage to the hematopoietic microenvironment may also play an indirect role in the induction of apoptosis in the bone marrow.
TL;DR: The results suggest that the immunohistochemical localization of MCLR in centrilobular hepatocytes is closely associated with the onset of hemorrhage and apoptosis and is related to adduct formation.
Abstract: The relationship between the intralobular sites of hepatotoxic injury and the distribution of microcystin-LR (MCLR), an inhibitor of protein phosphatases 1 (PP1) and 2A (PP2A), was examined using a...
TL;DR: The relationship of time and dose to bromate-induced tumors in male Fischer 344 (F344) rats is investigated and some insight into the development of these tumors is provided to provide better understanding of KBrO3-induced cancer.
Abstract: Potassium bromate (KBrO 3) is a rodent carcinogen and a nephro- and neurotoxicant in humans. KBrO3 is used in cosmetics and food products and is a by-product of water disinfection by ozonization. KBrO3 is carcinogenic in the rat kidney, thyroid, and mesothelium and is a renal carcinogen in the male mouse. The present study was designed to investigate the relationship of time and dose to bromate-induced tumors in male Fischer 344 (F344) rats and to provide some insight into the development of these tumors. KBrO 3 was dissolved in drinking water at nominal concentrations of 0, 0.02, 0.1, 0.2, and 0.4 g/L and administered to male F344 rats as the sole water source for 12, 26, 52, 78, or 100 wk. Renal cell tumors were present after 52 wk of treatment only in the high-dose group. Mesotheliomas developed after 52 wk of treatment on the tunica vaginalis. Mesotheliomas were present at sites other than the testicle after 78 wk of treatment, indicating that their origin was the testicular tunic. Thyroid follicular ...
TL;DR: The results of the present histological study suggest that the lung, spleen and/or forestomach, where tumors are induced in rasH2 mice treated with known carcinogens, should be regarded as informative target organs in addition to the target organs reported in previous long-term carcinogenicity bioassays in rats and mice.
Abstract: ABSTRAC~ To validate the transgenic (Tg) mouse carrying a human prototype c-Ha-rus gene (rasH2 mouse) as a model for short or medium-term carcinogenicity testing, 6-mo carcinogenicity studies using more than 30 chemicals. including carcinogens and noncarcinogens. have been performed. The results obtaincd so far indicate that rasH2 mice are generally much more susceptible to both mutagenic and nonmutagenic carcinogens than are non-Tg mice, pointing to advantageous application for detection of carcinogenic potential. In this review, histopathological featurcs and diagnostic criteria for spontaneous and induced-tumors observed in our 6-mo carcinogenicity studies are described. Incidences of spontaneous tumors were generally low in rasH2 mice during the 6-mo studies, although values for lung adenomas and splenic hemangiosarcomas were higher than those in the control non-Tg mice. A few forestomach papillomas and skin papillomas were also observed in the control rasH2 mice. The target organs in rasH2 mice treated with known carcinogens were not always identical to those in the treated B6C3F, mice in 2-yr carcinogenicity bioassays, with forestomach squamous cell tumors, lung alveolar epithelial tumors and/or hemangiosarcomas in the spleen observed in addition to some but not all of the lesions in target organs observed in non-Tg mice in long-term carcinogenicity bioassays. The results of the present histological study suggest that the lung, spleen and/or forestomach, where tumors are induced in rasH2 mice treated with known carcinogens, should be regarded as informative target organs in addition to the target organs reported in previous long-term carcinogenicity bioassays in rats and mice. Human prototype c-Ha-ms transgenic mice; rasH2 mice; spontaneous tumors: induced tumors: 6-mo carcinogenicity
TL;DR: Nephrotoxicity has been reported in several species, and in rats and rabbits, the kidney appears to be the most sensitive target organ.
Abstract: Fumonisins are mycotoxins produced worldwide by Fusarium fungi, principally F. moniliforme. The fungus is present in virtually all harvested com, but the toxins produced are variable. The toxins, especially fumonisin B1, cause mild to fatal diseases in animals, with peculiar species specificity for the dominant signs of toxicity. The mechanism of toxicity is poorly understood, but it appears to be related to interference with sphingolipid biosynthesis in multiple organs. Whereas brain, lung, and liver are well-known target organs, toxic effects on the kidney are also widespread and have only recently begun to be characterized. Increased urine volume and decreased osmolality are early changes associated with the toxin, as are increased excretions of high-and low-molecular-weight proteins. Enzymuria in vivo, reduced ion transport in vitro, and elevation of free sphinganine in renal tissue and in urine are present. An increase in serum creatinine and blood urea nitrogen and histopathologic change in renal tu...
TL;DR: There is no current agreement regarding which enzyme assays are the most appropriate for routine use in safety assessment studies, and if one wishes to conduct special assessment of nephrotoxicity in dogs, evaluation of several enzymes at multiple time points is needed.
Abstract: Over the past 20 yr, increased attention has been directed toward evaluation of urinary enzymes as markers of nephrotoxicity in dogs because the technique is noninvasive and considered to be more sensitive than the more commonly used conventional tests of renal function. Urinary enzymes also have the potential of determining the primary site of renal damage because different sections of the nephron have a characteristic complement of enzymes. In dogs, increases in brush border enzymes, including gamma-glutamyl transferase and alkaline phosphatase, have been associated with renal proximal tubular damage, while increases in N-acetyl-beta-D-glucosaminidase have been observed in the early stage of renal papillary necrosis. Urinary enzymes have been particularly useful in detection of acute renal damage in dogs, specifically tubular damage: however, their corresponding value in providing information about chronic renal damage remains to be established. Although elevation of certain enzymes appears to be a relatively sensitive measure of nephrotoxicity in the dog, there is no current agreement regarding which enzyme assays are the most appropriate for routine use in safety assessment studies. In addition, elevation of a single enzyme is of limited diagnostic value in detection of renal damage because spurious increases in urinary enzymes sometimes occur in normal dogs. Therefore, if one wishes to conduct special assessment of nephrotoxicity in dogs, evaluation of several enzymes at multiple time points is needed to compensate for normal enzyme variation and to identify potential anatomic site selectivity of the toxin.
TL;DR: Results with this first set of 11 chemicals tested in genetically altered mice appear to support the premise advanced by Tennant et al that these models have the potential to serve as more rapid and less expensive test systems to identify carcinogens.
Abstract: ABSTRAC~ National Institute of Environmental Health Sciences researchers are exploring the utility of genetically altered mice to study mechanisms of carcinogenesis. Two of these mouse models, the Tg.AC (carrier of an activated mouse H-ms oncogene) and the p53+ (heterozygous for the wild-type tumor suppressor gene Trp53), have genetic alterations that appear to hasten their expression of chemically induced tumors. These 2 models have been proposed as a basis for new strategies for identifying chemical carcinogens and for assessing risk. The National Toxicology Program (NTP) is conducting a series of studies with these 2 genetically altered strains to further examine their strengths and weaknesses for identification of documented rodent and human carcinogens. In this first evaluation, candidates for study were drawn from the NTP historical database of 2-yr rodent carcinogenicity studies and the open literature (primarily for drugs). Results with this first set of 11 chemicals tested in genetically altered mice, compared with previous findings in the traditional 2-yr rodent assays and literature on human tumor findings, appear to support the premise advanced by Tennant et a1 that these models have the potential to serve as more rapid and less expensive test systems to identify carcinogens. Tg.AC mice; p53; carcinogenicity; toxicity; bioassay; National Toxicology Program; mutagenicity Keyc.ords.
TL;DR: There is still a need to understand better the primary mechanism and the secondary consequences of RPN so that the risk of chemical agents in use and novel molecules can be fully assessed.
Abstract: Analgesics and nonsteroidal anti-inflammatory drugs (NSAIDs) are well recognized as a major class of therapeutic agent that causes renal papillary necrosis (RPN). Over the last decade a broad spectrum of other therapeutic agents and many chemicals have also been reported that have the potential to cause this lesion in animals and man. There is consensus that RPN is the primary lesion that can progress to cortical degeneration; and it is only at this stage that the lesion is easily diagnosed. In the absence of sensitive and selective noninvasive biomarkers of RPN there is still no clear indication of which compound, under what circumstances, has the greatest potential to cause this lesion in man. Attempts to mimic RPN in rodents using analgesics and NSAIDs have not provided robust models of the lesion. Thus, much of the research has concentrated on those compounds that cause an acute or subacute RPN as the basis by which to study the pathogenesis of the lesion. Based on the mechanistic understanding gleaned from these model compounds it has been possible to transpose an understanding of the underlying processes to the analgesics and NSAIDs. The mechanism of RPN is still controversial. There are data that support microvascular changes and local ischemic injury as the underlying cause. Alternatively, several model papillotoxins, some analgesics, and NSAIDs target selectively for the medullary interstitial cells, which is the earliest reported aberration, after which there are a series of degenerative processes affecting other renal cell types. Many papillotoxins have the potential to undergo prostaglandin hydroperoxidase-mediated metabolic activation, specifically in the renal medullary interstitial cells. These reactive intermediates, in the presence of large quantities of polyunsaturated lipid droplets, result in localized and selective injury of the medullary interstitial cells. These highly differentiated cells do not repair, and it is generally accepted that continuing insult to these cells will result in their progressive erosion. The loss of these cells is thought to be central to the degenerative cascade that affects the cortex. There is still a need to understand better the primary mechanism and the secondary consequences of RPN so that the risk of chemical agents in use and novel molecules can be fully assessed.
TL;DR: FB induces early elevations in sphingolipids and hepatic injury, followed by alveolar endothelial damage, which may be the critical event in the pathogenesis of PE in pigs.
Abstract: The fumonisin (FB) mycotoxins induce liver injury in all species but induce fatal pulmonary edema (PE) only in pigs. They inhibit ceramide synthase in the sphingolipid biosynthetic pathway. To study the pathogenesis of PE, we examined the early events in the development of FB-induced PE and hepatotoxicity in pigs. Pigs were fed FB-contaminated culture material at 20 mg fumonsin B1 (FB1)/kg body weight/day. Groups of 4 pigs were to be euthanatized on 0, 1, 2, 3, 4, or 5 days after initial exposure to FB or when PE developed. Pigs developed PE beginning on day 3; none survived beyond day 4. Progressive elevations in hepatic parameters, including serum enzymes, bile acids, total bilirubin, and histologic changes, began on day 2. Early histologic changes in the lung (day 2) consisted of perivascular edema followed by interlobular and peribronchial edema. Ultrastructurally, alveolar endothelial cells contained unique accumulations of membranous material in the cytocavitary network beginning on day 2. Marked elevations in sphinganine, sphingosine, and their ratio began on day 1 for all tissues whether affected morphologically (lung, liver) or not (kidney, pancreas). The membranous material in endothelial cells may be accumulations of sphingoid bases with damage to the cytocavitary network. Thus, FB induces early elevations in sphingolipids and hepatic injury, followed by alveolar endothelial damage, which may be the critical event in the pathogenesis of PE in pigs.
TL;DR: The proliferative target organ effects observed in this set of studies are described and the tumor profile in the control groups of this data set is presented to provide a comprehensive toxicologic assessment.
Abstract: Recently, the use of selected genetically altered mouse models in the detection of carcinogens after short-term chemical exposures has been evaluated. Studies of several chemicals conducted by the National Toxicology Program in Tg.AC transgenic and heterozygous p53-deficient mice have been completed recently and represent a major contribution to this effort, as well as the largest accumulation to date of toxicologic pathology data in these 2 lines of mice. The purpose of this report is to describe the proliferative target organ effects observed in this set of studies, as well as to present the tumor profile in the control groups of this data set. These findings provide a comprehensive toxicologic assessment of these 2 genetically altered mouse strains, which are of emerging importance in toxicologic pathology.
TL;DR: The dog is a good model in which to evaluate the safety of GH secretagogues as well as compounds with GH-like activity, and there was no chronic hyperglycemia based on glycosylated hemoglobin levels.
Abstract: The purpose of this study was to evaluate the pharmacological and toxicological effects of exogenous GH administration in normal adult dogs. Because porcine GH (pGH) is structurally identical to canine GH, pGH was selected for a 14-wk study in dogs. Thirtytwo dogs (<2 yr) were randomized to 4 groups (4 dogslsexlgroup); 1 group was treated with the vehicle and 3 groups received pGH at 0.025. 0.1, or 1.0 IU/kg/day subcutaneously. Daily clinical signs and weekly body weights were recorded. Hematology, serum biochemistry, urinalyses, electrocardiograms, and ophthalmoscopic examinations were done. Serum GH, insulin-like growth factor-1 (IGF- I), insulin, thyroxine (T4), triiodothyronine (T3). and cortisol levels werc determined. Necropsies were performed, organs weighed, and tissues were fixed and processed for light microscopic examination. Porcine GH caused increased body weight gain (p 5 0.05) through the mid dose; the mean weight gains at study termination in mid- and high-dose groups were 2.8 kg and 4.7 kg. respectively, compared to 0.4 kg and 0.8 kg in control and low-dose groups, respectively. Dose-related increased weights of liver, kidney, thyroid, pituitary gland, skeletal muscle, and adrenal gland were noted. In pGH-treated dogs, increased skin thickness seen grossly correlated histologically with increased dermal collagen. There was no gross or histomorphological evidence of edema. There were dose-related increased serum IGF-1 levels (=2-10-fold; p 5 0.05) that correlated with the elevated serum GH levels in pGHtreated dogs. Also, increased serum insulin levels 0, 5 0.05) through the mid dose were seen throughout the study. In high-dose dogs. the insulin levels remained elevated over 24 hr postdose. The serum glucose levels in fasted dogs remained within the control range and there was no chronic hyperglycemia based on glycosylated hemoglobin levels. Renal glomerular changes, significant polyuria with decreas'ed urine specific gravity, and increased serum insulin levels suggested that the dogs had early insulin-resistant diabetes. There was minimal or no biologically significant effect of pGH on serum T3. T4, and cortisol levels in dogs. Other serum biochemical changes in pGH-treated dogs included decreased urea nitrogen and creatinine, and increased potassium, cholesterol, and triglycerides. Significant increases in serum calcium and phosphorous levels and alkaline phosphatase activity (bone isozyme) correlated with the histological changes in bone. In pGH-trcated dogs, there was a dose-related normochromic. normocytic, nonregenerative anemia. The changes described above, except for the anemia, are related to either anabolic or catabolic effects of high doses of GH. Based on this study, it is concluded that the dog is a good model in which to evaluate the safety of GH secretagogues as well as compounds with GH-like activity. Ke~~rords. Insulin-like growth factor-1 (IGF-I) levels; insulin levels: insulin resistance; body weight change; erythroid depletion; hepatic change; anabolic effects; catabolic effects
TL;DR: This work developed a transgenic mouse model for prostate cancer by targeting the expression of the simian virus 40 (SV40) early region to the mouse prostate epithelium using the 5‘ flanking region of the rat C3(1) gene, a gene which is very highly expressed in the rat ventral prostate.
Abstract: BACKGROUND Prostate and mammary cancers are the most common malignant diseases in the Western world and have increased dramatically during the past decade (23). Both cancers are now the second leading cause of cancer deaths in men and women in the United States and their incidences continue to rise. According to recent estimates (23), approximately 317,000 men will be diagnosed with prostate cancer and 41,000 will die of the disease in the United States this year. For women, the cumulative lifetime risk of developing breast cancer is 12%, whereas the lifetime mortality risk has been estimated to be 3.5% (1 1). Despite this serious situation, the etiologies and risk factors for cancer in these organs have remained largely unknown. Some hereditary factors appear to be involved, but other unknown genetic alterations and environmental and life-style factors appear to be the most important causative factors. Although transgenic models for mammary cancer have been developed, no transgenic animal for prostate cancer has been available until recently. Several useful animal models for prostate cancer have been developed using chemical carcinogens (2, 30), but these models are labor intensive and generally require tumor promotion with pharmacologic doses of steroid hormone. Therefore, we developed a transgenic mouse model for prostate cancer by targeting the expression of the simian virus 40 (SV40) early region to the mouse prostate epithelium using the 5‘ flanking region of the rat C3(1) gene, a gene which is very highly expressed in the rat ventral prostate (20). This was the first reported transgenic model for prostate cancer. Other transgenic mouse models for prostate cancer have also been developed (Table I; see Ref. #7 for review). In addition to the development of prostate cancers, aged male C3( l)/TAg transgenic mice develop tumors of the urethral, bulbourethral, and salivary ‘glands, whereas 100% of female transgenic mice develop mammary adenocarcinomas.
TL;DR: An inventory of complex CK expression patterns provides the basis for investigating test substance-related effects in inhalation toxicology, e.g., cigarette smoke-induced changes.
Abstract: Cytokeratin (CK) polypeptides constitute the intermediate filament cytoskeleton of epithelial cells. The patterns of CK expression can be regarded as specific markers for the epithelial differentiation status. Our objective was to map the cell type-specific CK expression patterns at all representative sites of the respiratory tract of untreated rats to use as a base for the detection of inhalation exposure-related differentiation changes. Using routine paraffin-embedded sections and a panel of well-characterized monoclonal antibodies for immunohistochemistry, we obtained CK staining patterns as follows. Nasal cavity: respiratory epithelium CK18, CK19 (basal, ciliated, nonciliated cells), CK14, and/or CK15 (basal and nonciliated cells); olfactory epithelium CK18 (basal, mid, apical zones and Bowman's glands), CK14, and CK15 (basal zone); squamous epithelium of ventral meatus CK14, CK15 (basal and suprabasal cells), CK1, 10/11, and CK13 (suprabasal cells); glands and columnar epithelia of vomeronasal organ and nasolacrimal duct CK7 and CK13 in addition to respiratory epithelial CK pattern. Trachea: similar to nasal respiratory epithelium with pronounced CK15 and additional CK7. Larynx: CK14, CK15 (basal, ciliated, nonciliated cells), CK8, CK18, CK19 (not in basal cells), CK4, and CK13 (cuboidal and squamoid cells of ventral half). Lung: bronchial epithelium CK14 and CK15 (basal cells only); bronchial and alveolar epithelium CK7, CK8, CK18, and CK19; bronchiolar epithelium similar but less CK8 and no CK7; pleural mesothelium CK7, CK8, and CK19. This inventory of complex CK expression patterns provides the basis for investigating test substance-related effects in inhalation toxicology, e.g., cigarette smoke-induced changes.
TL;DR: A slight to moderate decrease in both isoforms was observed in essentially normal renal papillary cells within 2 hr, that was followed by an increase in COX-2 immunoreactivity in the renal papilla, macula densa, and thick ascending limbs (both 10-and 75-mg/kg animals).
Abstract: hSTRACT Inhibition of renal vasodilatory prostaglandins (PGs) and secondary ischemia due to inhibition of cyclooxygenase (COX) activity has been suggested as a possible mechanism for development of analgesic-related renal papillary necrosis (RPN) in rats. Recently, it has been shown that COX exists in two related but unique isoforms, COX-1 and COX-2. It is unclear what potential roles these isoforms play in the maintenance of blood flow in the renal papilla or genesis of RPN. We evaluated the effect of 2 papillotoxic agents, including a nonsteroidal anti-inflammatory drug, indomethacin, and a chemical agent, 2-bromoethanamine hydrobromide (2BEA), on COX-I and COX-2 in the renal papilla as a means of assessing what changes occur in the expression of these isoforms during the development of RPN. Female Wistar rats ==10-17 wk old were treated with either indomethacin (75 mglkg. singIe dose, or 10 mglkglday for 5 days) or 2-BEA (100 mg/kg/day for 4 days) to create lesions of RPN. In this study, a single 75-mg/kg dose of indomethacin did not cause light microscopic changes of RPN. However, RPN was observed in animals administered indomethacin at 10 mg/kg/day for 1 wk or 2-BEA for 5 days. The immunohistochemical analyses of kidneys showed that both COX-I and COX2 were present in the renal papilla of control rats. In animals treated with indomethacin (75 mglkg), a slight to moderate decrease in both isoforms was observed in essentially normal renal papillary cells within 2 hr, that was followed by an increase in COX-2 immunoreactivity in the renal papilla, macula densa, and thick ascending limbs (both 10- and 75-mgkg animals). This COX-2 immunoreactivity was greatest in animals with concomitant indomethacin-induced gastrointestinal injury, suggesting a possible role of inflammatory cytokines in COX-2 induction. No changes in the expression of COX isoforms in the intact papilla occurred as a result of 2-BEA; however, cells undergoing degeneration and necrosis lost immunoreactivity to both COX isoforms. The possible mechanism that leads to an initial decrease in COX immunoreactivity in indomethacin-treated animals is not known; however, a reversible ultrastructural change in the papillary cells cannot be ruled out. This decrease in COX isoforms in the renal papilla may contribute to the development of RPN through the loss of vasodilatory PGs. Cyclooxygenase-1 ; cyclooxygenase-2; prostaglandin H synthase; nonsteroidal anti-inflammatory drugs; kidney; indomethacin; 2-bromoethanamine hydrobromide Keyrords.
TL;DR: The Tg.AC transgenic mouse skin paint assay is one of the short-term carcinogenesis models that has been proposed as a replacement for 1 species in the conventional 2-yr bioassay required for safety testing of pharmaceuticals and it should be possible to selectively enrich the T.AC mouse colony to consist exclusively of responders and to guard against further genetic instability.
Abstract: The Tg.AC transgenic mouse skin paint assay is one of the short-term carcinogenesis models that has been proposed as a replacement for 1 species in the conventional 2-yr bioassay required for safety testing of pharmaceuticals. In our initial efforts to evaluate the sensitivity and specificity of this model for human pharmaceuticals, 61% of the hemizygous Tg.AC mice in the positive control groups were refractory to treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA). Tg.AC mice are reported to carry ≤10 copies of a transgcne consisting of a ζ-globin promoter fused to the v-Ha-ras structural gene with a terminal simian virus 40 (SV40) polyaden-ylation signal. Southern blot hybridization of genomic DNA from 66 tail biopsies using a ζ-globin probe revealed that all of the hemizygous Tg.AC mice screened contained approximately 40 copies of the transgene and that mice unresponsive to TPA had lost a 2-kb BamHI fragment containing ζ-gIobin promoter sequence. By systematic screening of Tg.AC breeder mice for...
TL;DR: The Alternatives to Carcinogenicity Testing Technical Committee was formed under the auspices of the International Life Sciences Institute (ILSI) Health and Environmental Sciences Institute to assist in the further evaluation of these new experimental approaches for carcinogenicity testing.
Abstract: The current approach for carcinogenicity testing usually incorporates a genetic toxicity screen, 14and 90day subchronic toxicity studies in rats and mice, toxicokinetic and disposition studies, and 2-yr chronic bioassays in rats and mice. The 2-yr bioassays are both time and resource intensive, and questions have been raised regarding the relevance of some of the carcinogenic responses in rodents for human risk assessment. At the 1996 meeting of the International Conference on Harmonization (ICH) Expert Working Group on Safety, the international pharmaceutical and regulatory communities acknowledged the limited utility of certain aspects of conventional rodent studies and proposed a new scheme for carcinogenicity testing for pharmaceuticals (Fed. Reg. 61: 43298-43300). The proposed strategy incorporates a conventional bioassay in a single rodent species and the option to conduct a shortor medium-term in vivo assay with a tumor end point in place of the second species bioassay. The available alternative models include initiation-promotion assays, newborn rodent assays, and several transgenic mouse assays that have recently been developed. The willingness of the regulatory authorities to accept data from these new experimental approaches as part of the safety assessment process for pharmaceuticals has stimulated international interest in gaining experience and a greater understanding of the strengths and limitations of the specific models. These new methods have not been fully characterized, and the scientific community is considering their most appropriate application(s). The Alternatives to Carcinogenicity Testing Technical Committee was formed under the auspices of the International Life Sciences Institute (ILSI) Health and Environmental Sciences Institute to assist in the further evaluation of these new experimental approaches for carcinogenicity testing. Through the efforts of this committee, which is composed of interested scientists from industry, government, and academia, an international collaborative research program was established. The goals of this research program, currently being conducted in more than 45 laboratories in the United States, Europe, and Japan, are: to expand the data base on several of these new test methods; to enhance the understanding of the specific responses of each model to compounds representing a range of chemical and pharmaceuticalltherapeutic classes, including various modes of toxic and carcinogenic action; to evaluate potential criteria that should be considered in the selection of one model over another for a particular
TL;DR: By defining initial area and depth of injury associated with an ocular irritant, it may be possible to predict the subsequent response and final outcome and is applicable to the development of mechanistically based in vitro assays.
Abstract: The pathology of surfactant-induced ocular irritation, especially in the context of accidental human exposures and animal tests used to assess a surfactant's potential ocular irritation, is not well understood. The purpose of this study was to characterize the microscopic changes in rats at 3 hr and on days 1, 2, 3, 4, 7, 14, and 35 following treatment with anionic, cationic, and nonionic surfactants of differing irritancy. The right eye of each rat was treated by placing 10 microliters of a surfactant directly on the cornea. Untreated left eyes served as the controls. At each time point, eyes and eyelids were macroscopically examined and collected for microscopic examination. Macroscopically, the differing levels of irritation were characterized by differences in incidence and magnitude of scores, reflecting involvement of the cornea, conjunctiva, and iris, as well as by the incidence of neovascularization and time to recovery. Microscopically, differences in the area and depth of injury paralleled the differences seen grossly and the relative irritancy of the various surfactants. All surfactants affected the corneal and conjunctival epithelium. All surfactants, except the slightly irritating anionic surfactant, caused corneal stromal changes, with this involvement being proportional to their overall level of irritation. Corneal endothelial cell effects principally occurred with only the severely irritating cationic surfactant. Over time, responses to surfactants of differing irritancy were qualitatively and quantitatively different, and these differences correlated with the extent of initial injury. Qualitative differences in response included presence of keratocyte regeneration, corneal neovascularization, and conjunctivalization of the corneal epithelium with all of the surfactants except the slight irritant. Quantitative differences in response occurred in the extent of epithelial regeneration, edema, and inflammation for surfactants of slight to severe irritancy, and with neovascularization, keratocyte regeneration, and conjunctivalization for surfactants of mild to severe irritancy. These results suggest that by defining initial area and depth of injury associated with an ocular irritant, it may be possible to predict the subsequent response and final outcome. Such an approach would be applicable to the development of mechanistically based in vitro assays.