Field and laboratory studies of the etiology of liver neoplasms in marine fish from Puget Sound

Influence of demographics, exposure, and habitat use in an urban, coastal river on tumor prevalence in a demersal fish

Neoplasia and associated tissue biomarkers in benthic fishes are commonly used to characterize effects of contaminated sediments in aquatic ecosystems. However, these fish are often migratory or partially-migratory, and thus assessing the effect of location-specific contamination is challenging because the fish will have a complex exposure history. We determined liver and skin neoplasia prevalence for a benthic, partially-migratory fish, white sucker (Catostomus commersonii), and used carbon and nitrogen stable isotope ratios to determine the diet contribution associated with areas of contaminated sediments within the urbanized portion of the St. Louis River. We then tested which factors were significantly related to neoplasia prevalence, including age, sex, and the percent diet obtained from contaminated areas within the St. Louis River relative to Lake Superior, the reference area. Overall, the prevalence of contaminant-related internal and external tumors was low, <5%. For skin neoplasia prevalence, both sex and age were significant factors, whereas location-specific diet contribution based on stable isotope analysis was not a significant factor. For liver neoplasia prevalence, only age was a significant factor. Nevertheless, for all contaminants measured (polychlorinated biphenyls [PCBs], polychlorinated dibenzodioxins [PCDDs], and polychlorinated dibenzofurans [PCDFs]), there was a significant, negative correlation between liver tissue concentration and Lake Superior diet contribution, confirming that the St. Louis River is the primary source of contaminant exposure. The research highlights the complexity of exposure to location-specific contaminants and potentially infectious agents associated with neoplasia at urban, contaminated sites in the Great Lakes, and elsewhere. It also demonstrates the need to determine the full set of risk factors across life-stages, habitats, and biological endpoints.

Polycyclic aromatic hydrocarbons in bays of the Rio de Janeiro state coast, SE - Brazil: Effects on catfishes

The Brazilian coast of the Rio de Janeiro State has bays of great economic, ecological and social importance. However, these ecosystems have been suffering intense anthropogenic influence, mainly due to the contamination by polycyclic aromatic hydrocarbons (PAHs) from urban-industrial activities. Moreover, PAHs are organic pollutants of high toxicity and carcinogenicity causing global concern to human and environmental health. This study evaluated on catfish (Genidens genidens) a set of key parameters (sex, morphometric traits, condition factor (K), PAH metabolites in gallbladder, frequency of micronucleus (MN) and erythrocytic nuclear abnormalities (ENA) in blood. In addition we also evaluated histopathological hepatic effects, Ethoxyresorufin-O-deethylase (EROD) activity and Benzo(a)pyrene diol epoxide (BPDE)-DNA adducts) in liver samples, in order to indicate the fish health status and environmental pollution levels of three main Bays (Guanabara, Sepetiba and Ilha Grande) of the Rio de Janeiro State, in the Southeast of Brazil. In general, the worst physical and metabolic conditions in catfishes were evidenced in Guanabara Bay, possibly indicating the highest level of contamination by PAHs. Contrary evidence was observed in Ilha Grande Bay, showing lower biological changes in G. genidens. However in Sepetiba Bay, the influence of PAHs contamination showed the highest hepatic lesions in catfishes, prevailing foci of cellular alterations, megalocytic hepatosis and hydropic vacuolations. The employability of a set of biomarkers on catfish was efficient for screening pollution for PAHs in tropical environments. This reinforces the need for effective actions of monitoring and conservation strategies of bays of the Rio de Janeiro State (Brazil), in order to ensure quality and health to both human and environment.

Seasonal development of the coccidian parasite Goussia bayae and hepatobiliary histopathology in white perch Morone americana from Chesapeake Bay

The coccidium Goussia bayae infects the gallbladder and bile ducts of white perch Morone americana from Chesapeake Bay, USA. Seasonal changes in coccidian infections were analyzed from bile specimens of 1588 fish from the Choptank River during 2016-2018 using wet mount preparations with a Sedgwick-Rafter counting chamber. Histopathology of the gallbladder and liver was analyzed from a subset (n = 480) of these fish. Maximum parasite prevalence (100%) and intensities in the gallbladder occurred during the fish spawning season in March and April. Asynchronous coccidian development and prevalence of infections in fish increased gradually during autumn and winter, but coccidian intensity increased sharply 2-4 wk prior to the onset of fish spawning activity and decreased after spawning activity concluded. Sporulation was internal, and the gallbladder was the primary reservoir for oocysts. Two previously undescribed species of coccidia were observed in the intestine. Lesions in the gallbladder were rare and included cholecystitis and epithelial necrosis. Intrahepatic bile duct lesions were more common and included distension, cholangitis, epithelial erosion and necrosis, cholestasis, hyperplasia, and neoplasia. Cholangitis and necrosis of intrahepatic bile ducts were significantly associated with coccidial infections, while plasmodia of a myxosporean (spore morphology consistent with the genera Myxidium and Zschokella) were significantly associated with bile duct hyperplasia. Biliary neoplasia included cholangiomas (5% prevalence) and cholangiocarcinomas (1% prevalence). No association was detected between G. bayae and biliary neoplasms, but an association may exist between these lesions and the myxosporean plasmodia.

Cancer Prevalence and Etiology in Wild and Captive Animals

Neoplasia has been recorded in the vast majority of metazoans. The frequent occurrence of cancer in multicellular organisms suggests that neoplasia, similar to pathogens/parasites, may have a significant negative impact on host fitness in the wild. This is supported by the fact that wildlife cancers have recently been shown to result in significantly increased levels of mortality and concomitant reduction in fitness. By thorough searches of the available literature we provide a comprehensive and an updated list of cancer prevalence and etiology in the wild. We were, however, unable to find data on nontransmissible cancer prevalence in invertebrates and consequently this chapter focuses on cancer in wild vertebrates. Although single cases of cancer are frequently encountered in the wildlife, we were only able to retrieve robust data on cancer prevalence for 31 vertebrate species (12 fish, 3 amphibians, 2 reptiles, 2 birds, and 12 mammals). Cancer prevalence among these vertebrates ranged from as low as 0.2% observed in Canada geese (Branta canadensis) to more than 50% recorded in both Santa Catalina Island foxes (Urocyon littoralis catalinae) and Cape mountain zebras (Equus zebra zebra). The high prevalence recorded in some vertebrates strongly suggests that cancer in wildlife may indeed carry significant fitness costs. In spite of this, the low number of published comprehensive studies clearly shows that so far cancer in wildlife has received insufficient attention by biologists. We hope that this chapter will act as a catalyst for further studies focusing on the impact of cancer in wild animals. The chapter additionally compares cancer recorded in French zoological parks to those obtained at other zoological parks. Finally, we provide an updated list of cancer recorded as single cases in the wild, as well as in captive animals.

In situ biomonitoring of caged, juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Lower Duwamish Waterway

Contaminated sediments may have wide-ranging impacts on human and ecological health. A series of in situ caged exposure studies using juvenile Chinook salmon was conducted in the Lower Duwamish Waterway (LDW). Chemical analysis of sediment, water, and fish tissue were completed. Additionally, in 2004, DNA adducts in hepatic and gill tissues were measured. Gills contained significantly higher DNA adducts at stations B2 and B4, prompting further analysis of gills in 2006 and 2007. Fluorescent aromatic compounds (FACs) in bile, and CYP1A1 in hepatic tissue were also measured during 2006 and 2007, respectively. FACs in field-caged fish were comparable or significantly higher than wild-caught fish LDW fish and significantly higher than lab fish after only 8-10 days, demonstrating the equivalency of exposure to that of migrating salmon. Furthermore, selected biomarkers appear to be capable of detecting spikes in contamination between sampling years, emphasizing the need for multiple year data collection.

Analytical methods for determining metabolites of polycyclic aromatic hydrocarbon (PAH) pollutants in fish bile: A review

The determination of polycyclic aromatic hydrocarbon (PAH) metabolites in bile can serve as a tool for assessing environmental PAH exposure in fish. Biliary PAH metabolite levels can be measured using several analytical methods, including simple fluorescence assays (fixed fluorescence detection or synchronous fluorescence spectrometry); high-performance liquid chromatography with fluorescence detection (HPLC-F); gas chromatography-mass spectrometry (GC-MS) after deconjugation, extraction and derivatization of the bile sample, and finally by advanced liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS) methods. The method alternatives are highly different both with regard to their analytical performance towards different PAH metabolite structures as well as in general technical demands and their suitability for different monitoring strategies. In the present review, the state-of-the-art for these different analytical methods is presented and the advantages and limitations of each approach as well as aspects related to analytical quality control and inter-laboratory comparability of data and availability of certified reference materials are discussed.

DNA damage as a biomarker for assessing the effects of suspended solids on the orange-spotted grouper, Epinephelus coioides

In Hong Kong, suspended solids (SS) introduced by dredging and mud disposal activities are a major cause of mass mortality in cage-cultured marine fish. We have used DNA damage in liver cells, as determined by the comet assay, to assess the impact of SS on the orange-spotted grouper Epinephelus coioides. Seabed sediments were collected from a heavily polluted site in Victoria Harbor and two less polluted sites in Port Shelter and Mirs Bay. Sediments from Victoria Harbor contained higher levels of copper (Cu) and polycyclic aromatic hydrocarbons (PAHs) than those from the other sites. In a 10-day experiment, SS from all three sites induced significant increase in comet tail length, but not in percentage (%) tail DNA. In a 20-day experiment, fish exposed to polluted SS from Victoria Harbor exhibited a significant increase in comet tail length after 5 days and % tail DNA after 10 days. After a 10-day recovery period, however, DNA damage was reduced as tail length and % tail DNA returned to control levels. These results suggest that DNA damage measured by the comet assay is a highly sensitive biomarker for assessing the genotoxic effects of SS to marine fish.

Biochemical changes in rockfish, Sebastes schlegeli, exposed to dispersed crude oil

This paper describes the response of the ovoviviparous rockfish, Sebastes schlegeli, to hydrocarbons in the water-accommodated fraction (WAF) of crude oil, in the presence or absence of oil dispersants. Concentrations of cytochrome P-450 1A (CYP1A) and levels of its catalytic activity ethoxyresorufin O-de-ethylase (EROD) in rockfish exposed to WAF at concentrations of 0.1% and 1% were significantly increased by the addition of a dispersant, Corexit 9500 after 48 h exposure. After 72 h exposure, the levels of CYP1A and EROD activity were significantly increased in 0.1% and 0.01% chemically enhanced WAF (CEWAF) (Corexit 9500 and Hiclean II dispersant). Bile samples from fish exposed to WAF alone had low concentrations of hydrocarbon metabolites, exemplified by 1-hydroxypyrene. After 72 h exposure, hydrocarbon metabolites in bile from fish exposed to WAF in the presence of either Corexit 9500 or Hiclean II were significantly higher compared with fish exposed to WAF alone or control fish. These experiments confirm that the use of oil dispersants will increase the exposure of ovoviviparous fish to hydrocarbons in oil.

Wildlife cancer: a conservation perspective

Until recently, cancer in wildlife was not considered to be a conservation concern. However, with the identification of Tasmanian devil facial tumour disease, sea turtle fibropapillomatosis and sea lion genital carcinoma, it has become apparent that neoplasia can be highly prevalent and have considerable effects on some species. It is also clear that anthropogenic activities contribute to the development of neoplasia in wildlife species, such as beluga whales and bottom-dwelling fish, making them sensitive sentinels of disturbed environments.

Biomarkers signal contaminant effects on the organs of English sole (Parophrys vetulus) from Puget Sound

Fish living in contaminated environments accumulate toxic chemicals in their tissues. Biomarkers are needed to identify the resulting health effects, particularly focusing on early changes at a subcellular level. We used a suite of complementary biomarkers to signal contaminant-induced changes in the DNA structure and cellular physiology of the livers and gills of English sole (Parophrys vetulus) . These sediment-dwelling fish were obtained from the industrialized lower Duwamish River (DR) in Seattle, Washington, and from Quartermaster Harbor (QMH) , a relatively clean reference site in south Puget Sound. Fourier transform-infrared (FT-IR) spectroscopy, liquid chromatography/mass spectrometry (LC/MS) , and gas chromatography/mass spectrometry (GC/MS) identified potentially deleterious alterations in the DNA structure of the DR fish livers and gills, compared with the QMH fish. Expression of CYP1A (a member of the cytochrome P450 multigene family of enzymes) signaled changes in the liver associated with the oxidation of organic xenobiotics, as previously found with the gill. The FT-IR models demonstrated that the liver DNA of the DR fish had a unique structure likely arising from exposure to environmental chemicals. Analysis by LC/MS and GC/MS showed higher concentrations of DNA base lesions in the liver DNA of the DR fish, suggesting that these base modifications contributed to this discrete DNA structure. A comparable analysis by LC/MS and GC/MS of base modifications provided similar results with the gill. The biomarkers described are highly promising for identifying contaminant-induced stresses in fish populations from polluted and reference sites and, in addition, for monitoring the progress of remedial actions.

Bioaccumulation and the effects of organochlorine pesticides, PAH and heavy metals in the Eel (Anguilla anguilla) at the Camargue Nature Reserve, France

Pesticides (organochlorines-OC), polycyclic aromatic hydrocarbons (PAH) and heavy metals are toxic to fish and may be taken in through gills, skin and contaminated foods. Here we measure concentrations of OC, PAH and heavy metals, and their effects in the eel Anguilla anguilla from three locations in the Camargue Reserve in southern France. The Camargue Biosphere Reserve is the largest coastal wetland in Western Europe, and A. anguilla is a common predator at the top of the food chain. Livers and spleens were analyzed for histopathological, chemical and organo-somatic (HSI and SSI) effects. Gill, liver and spleen samples were collected for histopathological studies. Livers and muscles were sampled for metabolic parameters and persistent organic pollutant analysis. Total lipids were estimated by spectrophotometry and lipid-free residues were used in protein and glycogen analysis. OC pesticides were extracted from lipids of muscles and livers, analyzed by gas chromatography, and PAH from bile were analyzed by fixed wavelength fluorescence spectrofluorimetry. Heavy metals were measured by inductively coupled plasma with optical or with mass spectrometers. High concentrations of contaminants were found in eel tissues. La Capelière had the greatest OC and PAH concentrations; unexpected lesions in gills, livers and spleens were more common at the other sites. Liver and spleen tumors and lipidosis in livers were associated with chronic, and gill lesions with acute exposure. High pesticide and PAH concentrations and lesions in eels from the Camargue reserve demonstrate the contamination of the area. A more complete study in the Camargue reserve is necessary to better understand the impact on wildlife and humans. Also, this study suggests that eel biology must be better understood before continued use of this species as a biomonitor of polluted areas.

Evaluation of chromosomal damage by flow cytometry in turbot (Scophthalmus maximus L.) exposed to fuel oil

Flatfishes, turbots (Scophthalmus maximus), were injected intraperitoneally with two doses of fuel oil number 2. Biliary metabolites were evaluated by fixed fluorescence to verify the efficiency of intoxication. Ethoxyresorufin-O-deethylase (EROD) activity was compared with chromosomal damage measured by flow cytometry. The analysis of biliary metabolites showed a good dose-response relation and constitutes a clear reference for the subsequent measurements. Comparing flow cytometry and EROD results, a shorter delay of response for EROD activity was obtained, but chromosomal damage was significant only after one week. The persistence of the EROD response was shorter, while the genotoxic signal still persisted after one month. The measurement of chromosomal damage allowed a good differentiation between the two tested doses. In the case of EROD activity, the results were less clear. The results suggest that within a few weeks after exposure to fuel oil number 2, the measurements of chromosomal damage by flow cytometry can be used to detect a dose-dependent genotoxic response in fish.

Resolving mechanisms of toxicity while pursuing ecotoxicological relevance?

In this age of modern biology, aquatic toxicological research has pursued mechanisms of action of toxicants. This has provided potential tools for ecotoxicologic investigations. However, problems of biocomplexity and issues at higher levels of biological organization remain a challenge. In the 1980s and 1990s and continuing to a lesser extent today, organisms residing in highly contaminated field sites or exposed in the laboratory to calibrated concentrations of individual compounds were carefully analyzed for their responses to priority pollutants. Correlation of biochemical and structural analyses in cultured cells and tissues, as well as the in vivo exposures led to the production and application of biomarkers of exposure and effect and to our awareness of genotoxicity and its chronic manifestations, such as neoplasms, in wild fishes. To gain acceptance of these findings in the greater environmental toxicology community, "validation of the model" versus other, better-established often rodent models, was necessary and became a major focus. Resultant biomarkers were applied to heavily contaminated and reference field sites as part of effects assessment and with investigations following large-scale disasters such as oil spills or industrial accidents. Over the past 15 years, in the laboratory, small aquarium fish models such as medaka (Oryzias latipes), zebrafish (Danio rerio), platyfish (Xiphophorus species), fathead minnow (Pimephales promelas), and sheepshead minnow (Cyprinodon variegatus) were increasingly used establishing mechanisms of toxicants. Today, the same organisms provide reliable information at higher levels of biological organization relevant to ecotoxicology. We review studies resolving mechanisms of toxicity and discuss ways to address biocomplexity, mixtures of contaminants, and the need to relate individual level responses to populations and communities.

The gender-specific risk to liver toxicity and cancer of flounder (Platichthys flesus (L.)) at the German Wadden Sea coast

Flatfish living in coastal areas are chronically exposed to a wide range of toxic and (pro)carcinogenic compounds derived from agriculture and industry. Flounder (Platichthys flesus (L.)) is the main target species for monitoring health effects of contamination in North Sea and Baltic Sea since the species is abundant, benthic, and inhabits shallow waters such as the Wadden Seas and estuaries along salinity gradients into fresh water. Chemical analysis in the same livers as investigated for histopathology in the present study showed positive correlation between accumulation of certain organochlorines in liver and the extend of liver injury. Toxipathic liver changes including neoplasms in female and male flounder were analysed by macroscopic and light microscopic diagnosis during a five-year survey on the basis of internationally accepted criteria agreed upon during the European BEQUALM intercalibration of liver histopathology of flatfish. Hepatocellular carcinogenesis of wild flounder principally showed sequential changes similar to experimental chemical carcinogenesis in other fish species and mammals. These ranged from early foci of altered hepatocytes (vacuolated/clear/eosinophilic, basophilic cells) and the development of adenomas. With progression to hepatocellular carcinomas, livers of wild flounder entered a multistage phase of carcinogenesis comprising of early foci, hepatocellular adenomas and carcinomas, as observed in human liver cancers. Female flounder had three-fold higher frequencies of macroscopically visible neoplasms than males of the same age classes. Histopathological diagnosis showed that hepatocellular alterations in male flounder never developed further than stages of basophilic foci and adenomas, and never into malignancies. In females, tumors of hepatocellular origin clearly dominated, occurred alone and together with cancers of bile duct epithelial cells and endothelial cells (cholangio-carcinomas, angiosarcomas). Because mutations of relevant genes could not be identified in the liver cancers that were analysed in the present study, we conclude that epigenetic events initiate carcinogenesis. Therefore, we conclude that mitogenic carcinogens found in the Elbe estuary play a dominant role for cancer development in this flounder population. Furthermore, the lower availability of reducing power (NADPH) needed for detoxification reactions in females compared to males, together with annual upregulation of the highly potent promotor 17-beta-estradiol during sexual maturation, promote progression of preneoplastic foci of initiated cells to malignant cancers in females.

Toxicopathic liver lesions in English sole and chemical contaminant exposure in Vancouver Harbour, Canada

The prevalence of toxicopathic liver lesions in English sole (Pleuronectes vetulus) was determined along a presumed gradient of chemical contamination in Vancouver Harbour, Canada. Fish were captured from five sites in or near Vancouver Harbour, British Columbia, Canada. No toxicopathic lesions were observed in fish examined at the reference site (Howe Sound outside Vancouver Harbour), or at the outer harbour site. In contrast, 20-23% of the fish from three sites located in the central harbour, Indian Arm and Port Moody Arm had one or more types of toxicopathic lesions. Likewise, aromatic hydrocarbon (AH) metabolites measured in bile exhibited a gradient in levels from lower concentrations at the reference site to significantly higher levels in fish from Indian Arm and Port Moody Arm harbour sites. The occurrence of toxicopathic liver lesions was statistically associated with concentrations of AHs measured in sediment and AH metabolite levels measured in bile.

Issues related to the use of fish models in toxicologic pathology: session introduction

Ready or not, fish models are "here to stay." No longer are fish confined to a few specialized laboratories, nor are they exclusively the purview of zoologists or environmental toxicologists. In fact, the institution that does not house at least 1 fish facility is probably not at the forefront of cutting edge research. In toxicologic pathology, fish models are increasingly being used to provide high animal numbers at relatively low cost in carcinogenicity testing and developmental research, and to provide mechanistic information on fundamental cellular processes. In this session, we attempt to provide some perspective for the pathologist that is faced with planning or performing experiments or testing protocols using fish models, or with reading or interpreting fish studies. First, we cover how to approach fish studies from the contract laboratory standpoint, including sectioning, quality control, and GLP considerations. Then, we discuss specifics on the use of the rainbow trout, zebrafish, and Japanese medaka models. The rainbow trout has a rich history in carcinogenicity and mechanistic cancer research. Similarly, the 2 workhorses in the small fish category, zebrafish and medaka, have found their way into many laboratories doing developmental biology and genomics research as well as carcinogenicity testing. Some fascinating genetically altered fish models have been developed with both of these species. This manuscript provides a session overview of the use of small fish models in toxicologic pathology, along with some historical perspective on how these models have played a role in the current state of the science.

Mechanistic considerations in small fish carcinogenicity testing

Historically, small fish species have proven useful both as environmental sentinels and as versatile test animals in toxicity and carcinogenicity bioassays. They can be bred in large numbers, have low maintenance and bioassay costs, and have a low background incidence of tumors. However, more mechanistic information is needed to help validate the information garnered from these models and to keep pace with other more fully developed animal models. This paper focuses on mechanistic considerations when using small fish models for carcinogenicity testing. Several small aquarium fish species have proven useful. The Japanese medaka is perhaps the best characterized small fish model for carcinogenicity testing; however, the zebrafish is emerging as an important model because it is well characterized genetically. Both route and methodology of exposure may affect the outcome of the study. Most studies have been conducted by introducing the test compound into the ambient water, but dietary exposures and embryo microinjection have also been used. Other considerations in study design include use of an initiating carcinogen, such as diethlynitrosamine, and differences in xenobiotic metabolism, such as the fact that fish CYP2B is refractory to phenobarbital induction. The small size of these models has perhaps limited some types of mechanistic studies, such as formation and repair of DNA adducts in response to carcinogen exposure. However, improved analytical methods are allowing greater resolution and should be applied to small fish species. Slide-based methods such as immunohistochemistry are an important adjunct to routine histopathology and should be included in study design. However, there is a need for development of more species-specific antibodies for fish research. There is also a need for more fish-specific data on cytokines, serum biochemistry, and oncogenes to strengthen the use of these important test models.

Cytochrome P450 1A expression in midwater fishes: potential effects of chemical contaminants in remote oceanic zones

Cytochrome P450 1A (CYP1A) induction is a robust marker for exposure to polynuclear aromatic hydrocarbons and planar halogenated aromatic hydrocarbons that are aryl hydrocarbon receptor agonists. We examined CYP1A expression in mesopelagic fishes from the western North Atlantic. Individuals in 22 species were obtained from slope water and the Sargasso Sea in 1977, 1978, and 1993. Aryl hydrocarbon hydroxylase (AHH), a CYP1A activity, was detected in liver from all species in 1977/78. In some, including Gonostoma elongatum, AHH was inhibited by the CYP1A inhibitor alpha-naphthoflavone. CYP1A-dependent ethoxyresorufin O-deethylase (EROD) was detected in liver microsomes of all species in 1993; rates were highest in G. elongatum and Argyropelecus aculeatus. Immunoblot analysis with the CYP1A-specific monoclonal antibody 1-12-3 detected a single microsomal protein band in most 1993 samples; the highest content was in G. elongatum. Immunohistochemical analysis showed CYP1A staining in gill, heart, kidney, and/or liver of several species. Extracts of the 1993 G. elongatum and A. aculeatus, when applied to fish hepatoma cells (PLHC-1) in culture, elicited a significant induction of EROD in those cells. The capacity of the extracts to induce CYP1A correlated with the content of PCBs measured in the same fish (2-4.6 ng/g total body weight). Mesopelagic fish in the western North Atlantic, which experience no direct exposure to surface waters or sediments, are exposed chronically to inducers of CYP1A at levels that appear to be biochemically active in those fish.

Evidence of p53 mutation in an early stage of liver cancer in European flounder, Platichthys flesus (L.)

A number of flounders dwelling in highly contaminated coastal areas of Northern Europe develop liver tumours. In order to increase our understanding of the molecular pathogenesis of these sporadic tumours, we examined p53 mutations in eleven hyperplasia and six adenoma. p53 introns 4 to 8 were first sequenced to allow individual amplification of exons 5 to 8. DNA extracted from formalin-fixed livers was amplified and PCR products were directly sequenced. Two major results were obtained. (i) Flounders from different geographical areas displayed a high rate of sequence variation. Base substitutions were identified in both tumour and normal tissues and thus may be considered as polymorphic variations in individuals. (ii) One mutation was detected in two hyperplastic foci from the same flounder. This mutation was a T:A to A:T transversion at codon 147, resulting in the replacement of valine for glutamic acid. This residue took place in the L2 loop of the DNA binding surface. Its substitution by an hydrophilic and charged residue could thus impair p53 (protein) biological activity.

DNA adduct formation and persistence in liver and extrahepatic tissues of northern pike (Esox lucius) following oral exposure to benzo[a]pyrene, benzo[k]fluoranthene and 7H-dibenzo[c,g]carbazole

The formation and persistence of DNA adducts in liver, intestinal mucosa, gills and brain of juvenile northern pike (Esox lucius) following oral exposure to benzo[a]pyrene (BaP), benzo[k]fluoranthene (BkF) and 7H-dibenzo[c,g]carbazol (DBC) were analysed by 32P-postlabelling. The dosage was 25 micromol/kg body weight of each substance, administered on 5 occasions with an interval of 12-14 days. Sampling was carried out 9 days after the second treatment, and 9, 16, 33 and 78 days after the fifth treatment. Pikes were also fed with the substances singly for comparison of adduct patterns. A complex pattern of adducts was detected in all examined tissues from fish treated with the mixture. Total adduct levels were highest in intestine (347+/-17.4 nmol adducts/mol nucleotides, mean+/-SE), followed by liver (110+/-9.3), gills (69+/-6) and brain (14+/-4.2). In pike treated with BaP alone, one major adduct was detected in all examined tissues. This BaP-adduct made up approximately 50% of the total amount of adducts in the brain. Corresponding values in liver, intestine and gills were 23, 31 and 34%, respectively. One relatively weak BkF-adduct and at least 10 different DBC-adducts were detected in all analysed tissues. Total adduct level in the intestine declined to 29.4% of the maximum value 78 days after the last exposure, while there was no significant decline in adduct levels in liver, gills or brain. The results suggest that intestine is more susceptible to adduct formation than liver after oral exposure, and that adduct levels in the intestine represent ongoing or relatively recent exposure. DNA adducts in the other investigated tissues were much more persistent and may therefore accumulate during long-term exposure.

Skin and liver diseases induced in flounder (Platichthys flesus) after long-term exposure to contaminated sediments in large-scale mesocosms

Disease development in flounder (Platichthys flesus) was studied over a period of 3 years in three large mesocosms (40 m x 40 m x 3 m). Two of the mesocosms contained clean sand and the third, sharing a common water circulation with one of the clean-sand mesocosms, was stocked with contaminated dredged spoil. In this way, one of the clean-sand mesocosms was indirectly polluted via the water phase, and analysis of contaminant concentrations in sediments and flounder tissues showed that it had a status intermediate between the other two. Random samples of the flounder populations from the indirectly polluted and reference mesocosms were examined every 2 months for epidermal diseases (lymphocystis, skin ulcers, fin rot) and then released. In addition, every 6 months, random samples of fish from all three mesocosms were sacrificed for histological and chemical investigation. With regard to the development of epidermal disease, the results showed little difference between the reference mesocosm and the indirectly polluted mesocosm, with the exception that lymphocystis was significantly elevated in the indirectly polluted mesocosm. Although pollution may be a risk factor in the etiology of this disease, such a relationship would probably be obscured under field conditions due to variation arising from other factors. Histopathological analysis of the livers revealed in total four cases of hepatocellular adenoma (1.5% of sampled population) in fish from the polluted mesocosms, the first occurring after 2.5 years of exposure in fish from the indirectly polluted mesocosm. Furthermore, several other liver lesions, including foci of cellular alteration and hydropic vacuolated lesions, developed during the course of the experiment before tumor formation was apparent. Prevalences of these conditions were very much lower in the reference mesocosm than in the two polluted mesocosms. Densities of melanomacrophage centers in the liver showed a similar trend. The findings clearly indicate that long-term exposure to chemically contaminated dredged spoil can induce liver neoplasia and other liver lesions in flounder at contaminant levels comparable to those found in the natural environment.

Experimental chemical carcinogenesis in fish

Experimental carcinogenesis using fish species as alternative models is a dynamic field of research. The 1940's expansion of synthetic chemical producing industries coincided with a number of pollution-associated fish neoplasia epizootics, with polycyclic aromatic hydrocarbons as significant components of contaminated sediment in several cases. Epizootics of primarily liver and skin neoplasia in benthic species near coastal urban or industrial areas indicated the sensitivity of fish species to known mammalian carcinogens. Stressing a mechanistic approach, investigators have used data compiled from epizootics as the backbone of current research efforts to define carcinogenesis in fish species. With liver as the focus, patterns of neoplastic development similar to those seen in rodent bioassays have been induced in various fish species by genotoxic carcinogens. Similarities between fish and rodent models include chemical and species-specific responses to exposure and the development of predictable preneoplastic and neoplastic lesions. The expression of molecular molecules related to carcinogenesis is currently under investigation, which includes alterations in certain proteins, enzyme activity, and oncogene/tumor suppressor gene function. The potential for the application of research findings to both human and environmental health issues makes fish species attractive and valuable alternative models in carcinogenesis and toxicity research.

Exocrine pancreatic neoplasms in the mummichog (Fundulus heteroclitus) from a creosote-contaminated site

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.

Relationships between toxicopathic hepatic lesions and exposure to chemical contaminants in English sole (Pleuronectes vetulus), starry flounder (Platichthys stellatus), and white croaker (Genyonemus lineatus) from selected marine sites on the Pacific Coast, USA

Relationships between hepatic lesions and chemical contaminant concentrations in sediments, stomach contents, liver tissue, and bile were statistically evaluated in three species of bottomfish, English sole (Pleuronectes vetulus), starry flounder (Platichthys stellatus), and white croaker (Genyonemus lineatus), captured from 27 urban and nonurban sites on the Pacific Coast from Alaska to southern California. Lesions detected were neoplasms, preneoplastic foci of cellular alteration, nonneoplastic proliferative lesions, unique or specific degenerative/necrotic lesions, nonspecific degenerative/necrotic lesions, and hydropic vacuolation of biliary epithelial cells and hepatocytes. In general, lesion prevalences were significantly higher in all three species captured at chemically contaminated urban sites, and certain lesions had significantly higher relative risks of occurrence at urban sites in Puget Sound, San Francisco Bay, the vicinity of Los Angeles, and San Diego Bay. Concentrations of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, DDT and its derivatives, and chlordanes and dieldrin in sediment, stomach contents, liver, and fluorescent aromatic compounds in bile were significant risk factors for the occurrence of neoplastic, preneoplastic, nonneoplastic proliferative, and specific degenerative/necrotic lesions, as well as hydropic vacuolation. Fish age also had a significant influence on occurrence of several hepatic lesions, but gender was rarely a significant risk factor. These relationships provide strong evidence for the involvement of environmental contaminants in the etiology of hepatic lesions in several marine bottomfish species and clearly indicate the utility of these lesions as biomarkers of contaminant-induced effects in wild fish.

Identification of hydroxyl radical-induced lesions in DNA base structure: biomarkers with a putative link to cancer development

Hydroxyl radical-induced DNA base lesions of guanine and adenine were originally found in neoplastic and microscopically normal livers of fish exposed to environmental carcinogens. They were later identified in a mammalian tissue--the cancerous female breast. This evidence suggested that the base lesions are broadly present in the cancerous and microscopically normal tissues of a variety of eukaryotic organisms. The base lesion concentrations in both neoplastic tissues frequently exceeded 1 modified base in 1000 normal bases. By contrast, the base lesion:normal base ratios in healthy tissues were generally 10-100 times less. A greater variety of base lesions was found subsequently in the cancerous lung, brain, and other human tissues, although information relating to their biological significance is largely confined to the originally found purine derivatives. The biochemistry of the base lesions and the relationship of ring-opening (Fapy) derivatives to OH adducts in the DNA of normal and cancerous tissues is discussed with regard to the etiology of cancer and the potential use of the lesions as biomarkers for cancer risk assessment.

32P-postlabeling analysis of DNA adduct formation and persistence in English sole (Pleuronectes vetulus) exposed to benzo[a]pyrene and 7H-dibenzo[c,g]carbazole

The formation and persistence of benzo[a]pyrene (BaP)- and 7H-dibenzo[c,g]-carbazole (DBC)-DNA adducts in liver of English sole (Pleuronectes vetulus) were investigated. BaP is a putative hepatocarcinogen in English sole based on its ability to induce formation of preneoplastic foci, while DBC is a hepatocarcinogen in mammals but whose carcinogenicity in fish is not known. English sole liver was sampled from 2 h through 84 days after a single intermuscular injection of a BaP and DBC mixture (100 mumol of each/kg body wt.), and DNA adduct levels were measured by the nuclease P1 version of the 32P-postlabeling assay. The major BaP adducts detected were from binding of BaP-7,8-diol-9,10-epoxide to DNA, whereas multiple uncharacterized DBC-DNA adducts were detected. Total adduct levels for both BaP and DBC reached a maximum at 2 days post exposure. The levels of DBC-DNA adducts were greater than the levels of BaP adducts at all time points and increased more rapidly than did the levels of BaP-DNA adducts. The DBC to BaP adduct ratio was 33 +/- 8.8 at 2 h and declined to 4.2 +/- 0.48 by 12 h post exposure. From 2 to 28 days, the levels of both BaP and DBC adducts declined with apparent half-lives of 11 and 13 days, respectively. There was no apparent decline from 28 to 84 days in the levels of the remaining BaP or DBC adducts; these persistent adducts represented 32 and 36% of maximum levels, respectively. These results provide the first data on the kinetics of adduct formation and removal of a carcinogenic nitrogen-containing polycyclic aromatic compound in fish. The results showing greater binding and similar persistence of DBC-DNA adducts compared to BaP-DNA adducts suggest that DBC may be hepatotoxic and potentially carcinogenic in English sole. In a separate experiment, the effect of multiple doses of BaP (30 mumol/kg body wt.) on the levels of hepatic BaP-DNA adducts showed that adduct levels increased linearly (r = 0.815, P = 0.0007) with 5 successive doses administered at 2 day-intervals and sampled 2 days after the last dose. The persistence of both BaP-DNA and DBC-DNA adducts in liver, together with the increase in BaP-DNA adducts in English sole exposed to successive doses of BaP, suggest that hepatic xenobiotic-DNA adducts in English sole are molecular dosimeters of relatively longterm environmental exposure to genotoxic polycyclic aromatic compounds.

Aquatic toxicology: past, present, and prospects

Aquatic organisms have played important roles as early warning and monitoring systems for pollutant burdens in our environment. However, they have significant potential to do even more, just as they have in basic biology where preparations like the squid axon have been essential tools in establishing physiological and biochemical mechanisms. This review provides a brief summary of the history of aquatic toxicology, focusing on the nature of aquatic contaminants, the levels of contamination in our waters, and the origins of these agents. It considers the features of the aquatic environment that determine the availability of xenobiotics to aquatic life and the fate of foreign chemicals within the organism. Finally, toxic effects are considered with primary emphasis on the potential of aquatic models to facilitate identification of the underlying mechanisms of toxicity.

Aquatic pollution: effects on the health of fish and shellfish

As there is little evidence of pollution affecting the health of fish and shellfish on a global scale, this paper attempts to put into perspective the pollution/fish disease relationship by reviewing examples of studies and reports in the historic and current literature. Although there is no dispute that pollution can affect the aquatic organisms under laboratory conditions and may be responsible for the decline of populations of such animals in some inland waters and some estuaries, most of the evidence for pollution causing or increasing disease in fish in open waters is circumstantial. Historical data proves that almost all fish and shellfish diseases known today have been described since the end of the last century. However, it is also known that water pollution, especially in inland waters, has for the past 400-500 years been the result of urbanization and industrialization. This has resulted in some major rivers becoming devoid of or deficient in fish stocks. The concern that pollution may influence the health status of fish and shellfish stocks has increased over the past 20 years. Initial attention was paid to epidermal diseases, including fin-rot in demersal fish, and protozoan diseases in molluscs in the heavily polluted bays and estuaries in North America. As the interest in this subject spread, it became political, and often controversial, especially amongst the North Sea countries. The disagreements have largely been settled amongst scientists because international bodies, such as the International Council for Exploration of the Sea (ICES), established workshops to investigate sampling methods and disease-reporting techniques. Recommendations from those workshops have contributed to some form of standardization for field work and the subject, although largely subjective, has some objective approaches which are described. As there are variable, interacting biological and physical influences in the aquatic environment, it is difficult to establish the background prevalences of diseases in populations of fish and shellfish. Examples of the influences of climatic changes are presented, and these show that short-term catastrophes can be directly related. However, a more long-term problem is water acidification resulting largely from anthropogenic activities. In parts of Scandinavia this has, and is, leading to decimation of fish stocks in inland waters. In general, diseases in fish and shellfish are very localized, but there is concern amongst scientists that certain cancers, especially liver tumours, occurring in demersal fish inhabiting polluted estuarine and coastal waters, are related to the release of chemicals, e.g. hydrocarbons, pesticides and heavy metals.(ABSTRACT TRUNCATED AT 400 WORDS)

Carcinogen adducts as an indicator for the public health risks of consuming carcinogen-exposed fish and shellfish

A large variety of environmental carcinogens are metabolically activated to electrophilic metabolites that can bind to nucleic acids and protein, forming covalent adducts. The formation of DNA-carcinogen adducts is thought to be a necessary step in the action of most carcinogens. Recently, a variety of new fluorescence, immunochemical, and radioactive-postlabeling procedures have been developed that allow the sensitive measurement of DNA-carcinogen adducts in organisms exposed to environmental carcinogens. In some cases, similar procedures have been developed for protein-carcinogen adducts. In an organism with active metabolic systems for a given carcinogen, adducts are generally much longer lived than the carcinogens that formed them. Thus, the detection of DNA- or protein-carcinogen adducts in aquatic foodstuffs can act as an indicator of prior carcinogen exposure. The presence of DNA adducts would, in addition, suggest a mutagenic/carcinogenic risk to the aquatic organism itself. Vertebrate fish are characterized by high levels of carcinogen metabolism, low body burdens of carcinogen, the formation of carcinogen-macromolecule adducts, and the occurrence of pollution-related tumors. Shellfish, on the other hand, have low levels of carcinogen metabolism, high body burdens of carcinogen, and have little or no evidence of carcinogen-macromolecule adducts or tumors. The consumption of carcinogen adducts in aquatic foodstuffs is unlikely to represent a human health hazard. There are no metabolic pathways by which protein-carcinogen or DNA-carcinogen adducts could reform carcinogens. Incorporation via salvage pathways of preformed nucleoside-carcinogen adducts from foodstuffs into newly synthesized human DNA is theoretically possible.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between hepatic neoplasms and related lesions and exposure to toxic chemicals in marine fish from the U.S. West Coast

English sole (Parophrys vetulus) inhabiting polluted waterways and embayments of Puget Sound, Washington, are affected with a variety of multiple, co-occurring idiopathic hepatic lesions, including unique degenerative conditions, putatively preneoplastic foci of cellular alteration, and neoplasms. Results of a statistical analysis of the patterns of co-occurrence of these lesions in wild English sole are consistent with the concept that these lesions represent morphologically identifiable steps forming a sequence of progression ultimately leading to the development of hepatic neoplasms. This progressive sequence parallels the pattern identified in experimental models of chemically induced hepatocarcinogenesis in rodents. The rationale for the hypothesis that these lesions in wild English sole can be caused by exposure to certain hepatoxic and hepatocarcinogenic xenobiotic compounds in the marine environment is based on the demonstration of significant and consistent statistical associations between levels of aromatic hydrocarbons (AHs) in sediment and prevalences of these idiopathic liver lesions; a significant contribution by sediment AHs to the variability in hepatic neoplasm prevalence in a logistic regression model; significantly increased probabilities for several idiopathic lesions in sole from chemically contaminated sites in Puget Sound; significant correlations between uptake of polycyclic aromatic hydrocarbons, as measured by levels of fluorescent metabolites of aromatic compounds in bile of sole, and prevalences of several hepatic lesion types; and experimental induction of unique degenerative, proliferative, and putatively preneoplastic focal lesions in English sole injected with either benzo(a)pyrene or a polycyclic aromatic hydrocarbons (PAH) enriched fraction of an extract from a contaminated urban sediment from Puget Sound.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between hepatic neoplasms and related lesions and exposure to toxic chemicals in marine fish from the U.S. West Coast

English sole (Parophrys vetulus) inhabiting polluted waterways and embayments of Puget Sound, Washington, are affected with a variety of multiple, co-occurring idiopathic hepatic lesions, including unique degenerative conditions, putatively preneoplastic foci of cellular alteration, and neoplasms. Results of a statistical analysis of the patterns of co-occurrence of these lesions in wild English sole are consistent with the concept that these lesions represent morphologically identifiable steps forming a sequence of progression ultimately leading to the development of hepatic neoplasms. This progressive sequence parallels the pattern identified in experimental models of chemically induced hepatocarcinogenesis in rodents. The rationale for the hypothesis that these lesions in wild English sole can be caused by exposure to certain hepatoxic and hepatocarcinogenic xenobiotic compounds in the marine environment is based on the demonstration of significant and consistent statistical associations between levels of aromatic hydrocarbons (AHs) in sediment and prevalences of these idiopathic liver lesions; a significant contribution by sediment AHs to the variability in hepatic neoplasm prevalence in a logistic regression model; significantly increased probabilities for several idiopathic lesions in sole from chemically contaminated sites in Puget Sound; significant correlations between uptake of polycyclic aromatic hydrocarbons, as measured by levels of fluorescent metabolites of aromatic compounds in bile of sole, and prevalences of several hepatic lesion types; and experimental induction of unique degenerative, proliferative, and putatively preneoplastic focal lesions in English sole injected with either benzo(a)pyrene or a polycyclic aromatic hydrocarbons (PAH) enriched fraction of an extract from a contaminated urban sediment from Puget Sound.(ABSTRACT TRUNCATED AT 250 WORDS)

Carcinogenesis studies in rodents for evaluating risks associated with chemical carcinogens in aquatic food animals

Fish and shellfish caught in polluted waters contain potentially dangerous amounts of toxic and carcinogenic chemicals. Public concern was heightened when a large percentage of winter flounder taken from Boston Harbor was found to have visible cancer of the liver; winter flounder outside the estuary area had no liver lesions. Long-term chemical carcinogenesis studies could be easily and feasibly designed using laboratory rodents offered diets containing fish caught in polluted waters. Induced cancers in rodents would corroborate field observations in fish; positive results from these studies would provide further evidence about potential human health hazards from eating substantial amounts of chemically contaminated fish. Nonetheless, fish and aquatic organisms should be viewed as environmental biological monitors of pollution or of potential human health hazards, and authorities responsible for assuring clean and safe rivers, bodies of water, and biota should give more attention to these valid biological indicators or sentinels of environmental pollution. Consequently, fish and other sea creatures alone should serve as alarms regarding whether water areas constitute public health hazards.

Ultrastructure of hepatocellular neoplasms in aflatoxin B1 (AFB1)-initiated rainbow trout (Oncorhynchus mykiss)

The fine structure of hepatocellular neoplasms from aflatoxin B1 (AFB1)-initiated rainbow trout was studied by transmission electron microscopy. Large, usually uniform hepatic nuclei, large nucleoli, abundant, dilated rough-surfaced endoplasmic reticulum, and reduced glycogen storage were common findings in both hepatocellular adenomas and hepatocellular carcinomas. In addition, the presence of poorly developed microvilli in the space of Disse and in bile canaliculi, the occurrence of few or no bile preductule cells and a striking increase in the size and number of intercellular spaces characterized hepatocellular carcinomas. The three latter characteristics of hepatocellular carcinomas suggest loss of inter-relationships between hepatocytes and the microvascular system (sinusoids), between hepatocytes and the biliary system, and between individual hepatocytes, respectively. With respect to these parameters, adenomas were more similar to normal liver than to carcinomas.

4,6-Diamino-5-formamidopyrimidine, 8-hydroxyguanine and 8-hydroxyadenine in DNA from neoplastic liver of English sole exposed to carcinogens

Attack of the hydroxyl radical on the 8-carbon of guanine results in the formation of 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua). This modified nucleotide was recently found in neoplastic livers of wild English sole exposed to aromatic hydrocarbons (Malins et al., Carcinogenesis, 11, 1045-1047, 1990). Gas-chromatographic-mass spectrometric evidence reported here indicates that three other modified nucleotides are also present in the neoplastic liver: 4,6-diamino-5-formamidopyrimidine, 8-hydroxyguanine and 8-hydroxyadenine. These findings support the hypothesis that the purine nucleotides were modified by the hydroxyl radical and that these changes play a crucial role in tumor formation.

Consistent associations between hepatic lesions in English sole (Parophrys vetulus) and polycyclic aromatic hydrocarbons in bottom sediment

A consistent and statistically significant association between prevalence of hepatic neoplasms in free-living sole (Parophrys vetulus) and levels of anthropogenic polycyclic aromatic hydrocarbons in bottom sediment from sites of fish capture was documented in a series of studies conducted over a period of 7 years in Puget Sound, Washington. This result strengthens the evidence supporting a causal relationship between exposure to sediment-associated hydrocarbons and development of hepatic neoplasms in this bottom-dwelling marine fish species. Prevalences of two other distinct categories of idiopathic hepatic lesions-megalocytic hepatosis and steatosis/hemosiderosis-also showed consistent, statistically significant associations with polycylic aromatic hydrocarbon concentrations in bottom sediment, and association with prevalence of a third category (putatively preneoplastic foci of cellular alteration) approached statistical significance. On the basis of other studies, megalocytic hepatosis and foci of cellular alteration are both considered to be important precursor lesions in the stepwise histogenesis of hepatic neoplasms.

Implications of aquatic animal health for human health

Human health and aquatic animal health are organically related at three distinct interfaces. Aquatic animals serve as important contributors to the nutritional protein, lipid, and vitamin requirements of humans; as carriers and transmitters of many infectious and parasitic diseases to which humans are susceptible; and as indicators of toxic and carcinogenic substances that they can convey, in some part, from aquatic environments to man and other terrestrial animals. Transcending these relationships, but less visible and definable to many, is the role that aquatic animals play in the sustenance of our integrated planetary ecosystem. Up to the present, this ecosystem has been compatible with mankind's occupation of a niche within it at high but ultimately limited population levels. In the past century we have become clearly aware that human activities, particularly over-harvesting of aquatic animals together with chemical degradation of their habitats, can quite rapidly lead to perturbances that drastically shift aquatic ecosystems toward conditions of low productivity and impaired function as one of earth's vital organs. The negative values of aquatic animals as disease vectors are far outweighed by their positive values as nutritional sources and as sustainers of a relatively stable equilibrium in the global ecosystem. In the immediate future we can expect to see increased and improved monitoring of aquatic habitats to determine the extent to which aquatic animals cycle anthropogenic toxic and carcinogenic chemicals back to human consumers. In the long term, methods are particularly needed to assess the effects of these pollutants on reproductive success in aquatic communities and in human communities as well. As inputs of habitat-degrading substances change in quality and quantity, it becomes increasingly urgent to evaluate the consequences in advance, not in retrospect. A new, more realistic and comprehensive philosophy regarding aquatic environmental preservation and equally new and comprehensive technological advances reflective of this philosophy will be required. In the next century we will see a serious test of whether or not mankind has lost its ability to foresee and forestall the side effects of scientific and technological ingenuity.

Pathogenesis of skin and liver neoplasms in white suckers from industrially polluted areas in Lake Ontario

Increased prevalences of epidermal and hepatobiliary neoplasms in white suckers (Catostomu commersoni) and brown bullheads (Ictalurus nebulosus) in the Western region of Lake Ontario have been associated with industrial pollution, but the identity and causative role of environmental carcinogens have not yet been established. Most epidermal tumors of lip and body skin are benign focal proliferations that occur in fish from the polluted Hamilton region, and also in fish from less polluted sites in the Great Lakes. These skin tumors in white suckers do not have consistent alterations in cellular glutathione S-transferases (GST), suggesting that growth of skin tumors is not promoted by chemicals normally detoxified by GST. However, elevated levels of glutathione peroxidase (GPO) and glutathione reductase (GR) in skin papillomas are indicative of promotional peroxidative tissue injury, either caused directly by xenobiotics or indirectly by chemical-induced inflammation. Liver tumors in white suckers from Lake Ontario include preneoplastic, benign, and malignant populations of hepatocellular and biliary cells, all of which are more prevalent in fish from polluted sites. These liver tumors are consistently associated with chronic cholangiohepatitis and segmental cholangiofibrosis, but these conditions also occur in white suckers in non-industrial locations. Thus, the natural occurrence of biliary disease, not attributable to industrial pollution, may have some influence on the development of liver tumors. Some preneoplastic lesions and the majority of neoplastic hepatocellular and biliary lesions in white suckers have low levels of total GST, indicating that these liver neoplasms are not promoted by xenobiotics normally detoxified by hepatic GSTs.(ABSTRACT TRUNCATED AT 250 WORDS)

The ultrastructure and histology of cholangiocellular carcinomas in English sole (Parophrys vetulus) from Puget Sound, Washington

The ultrastructure and histology of cholangiocellular carcinomas from feral English sole (Parophyrs vetulus) living in polluted waterways of Puget Sound, WA. are described. Electron microscopy confirmed that biliary epithelial cells were the main proliferative cell type composing this variety of neoplasm. The arrangement of these cells varied from well-organized multiple bile duct-like structures to disorganized multilayered sheets of poorly differentiated biliary epithelial cells. A fibrous stroma consisting of multiple layers of collagen fibers and fibroblasts, with macrophages and various blood cell types scattered among these layers occurred between bile duct-like structures or aggregates of biliary epithelial cells. Hepatocytes were not apparent in these neoplasms except within small necrotic regions surrounded by neoplastic biliary epithelial cells. No virus-like particles were observed among the cases examined in this study.

The role of glutathione S-transferases in the hepatic metabolism of benzo[a]pyrene in white suckers (Catostomus commersoni) from polluted and reference sites in the Great Lakes

1. Orally administered 3H-benzo[a]pyrene (3H-BaP) was excreted in the bile of White Suckers predominantly as water soluble metabolites some of which were hydrolyzed by arylsulfatase or beta-glucuronidase. 2. Non-hydrolysible polar metabolites comprised a substantial proportion of biliary metabolites. 3. HPLC analysis revealed fluorescent and 3H-labelled peaks which co-eluted with standards of the glucuronide and sulfate conjugates of BaP. 4. The most polar peak co-chromatographed with a double-radiolabelled metabolite produced in vitro with 3H-BaP and 35S-glutathione. 5. Inhibition of epoxide hydrolase in vitro reduced all water soluble metabolites except the glutathione conjugate of BaP. 6. Glutathione conjugation represents a major hepatic detoxication pathway of BaP in White Suckers.

Initiation, promotion, and inhibition of carcinogenesis in rainbow trout

The identification of etiological agents in feral fish neoplasia epizootics has been hampered in part by the lack of suitable fish models, and complicated by the likely existence of environmental agents which can act to stimulate or reduce population responses to genotoxin insult. The response of fish to tumor inhibitors and promoters, and the underlying mechanisms of modulation, have been studied in the rainbow trout model. Dietary treatment of trout with the compounds indole-3-carbinol (I3C), beta-naphthoflavone (BNF), or the polychlorinated biphenyl (PCB) complex Aroclor 1254, before and during exposure to aflatoxin B1 (AFB1), was shown to reduce the final incidence of hepatocellular carcinoma after 12 months, compared to fish receiving AFB1 only. By contrast, treatment of trout with BNF or I3C following AFB1 initiation led to a significant enhancement of ultimate tumor response. Similarly, simultaneous treatment of trout with PCB and the carcinogen N-nitrosodiethylamine led to syncarcinogenic enhancement, rather than inhibition, of tumor response. Mechanisms of inhibition of AFB1 carcinogenesis by PCB, BNF, and I3C were investigated. PCB and BNF, but not I3C, are known to be strong inducers of trout cytochrome P448 and associated activities. Dietary induction by BNF or PCB was shown to be accompanied in isolated hepatocytes by considerably altered AFB1 metabolism, and by significantly reduced rates of DNA adduct formation for all three agents. All agents differentially altered in vivo AFB1 pharmacokinetics, enhanced bile elimination of AFB1 as the aflatoxicol-M1 glucuronide, and significantly reduced peak levels of liver DNA adduct formation. No effects were seen on repair of AFB1-DNA adducts, which was very slow in trout.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemical carcinogenesis in feral fish: uptake, activation, and detoxication of organic xenobiotics

The high prevalence of liver neoplasms in English sole (Parophrys vetulus) and substantially lower prevalence of neoplasms in a closely related species, starry flounder (Platichthys stellatus) captured from industrialized waterways, provide a unique opportunity to compare biochemical processes involved in chemical carcinogenesis in feral fish species. Because levels of aromatic hydrocarbons (AHs) in urban sediments are correlated with prevalences of liver neoplasms in English sole, we have initiated detailed studies to evaluate the effects of endogenous and exogenous factors on uptake, activation and detoxication of carcinogenic AHs, such as benzo[a]pyrene (BaP), using spectroscopic, chromatographic, and radiometric techniques. The results obtained thus far show that sole readily takes up AHs associated with sediment from urban areas and that the presence of other xenobiotics, such as PCBs, in sediment increases tissue concentrations of BaP metabolites. Extensive metabolism of BaP occurred whether sole was exposed to this AH via sediment, per os, or intraperitoneally. Substantial modification of hepatic DNA occurred and persisted for a period of 2-4 weeks after a single exposure to BaP. The level of covalent binding of BaP intermediates to hepatic DNA was 10-fold higher in juvenile than adult sole and 90-fold higher in juvenile sole than in Sprague-Dawley rat, a species which is resistant to BaP-induced hepatocarcinogenesis. The level of chemical modification of hepatic DNA in juvenile flounder was 2-4 fold lower than that for juvenile sole and concentration of BaP 7,8-diol glucuronide in bile of sole was significantly higher than that in flounder bile, although the rate of formation of BaP 7,8-diol by hepatic microsomes was comparable for both species. Moreover, liver microsomes from both species, in the presence of exogenous DNA, metabolized BaP into essentially a single adduct, identified as (+)anti-7,8-diol-9,10-epoxy-7,8,9,10-tetrahydroBaP-dG. These results, along with our findings that hepatic GST activity in flounder was two times higher than in sole, demonstrate that microsomal metabolism of BaP does not accurately reflect the differences in the ability of these fish to form BaP-DNA adducts in vivo and also suggest that detoxication of reactive intermediates is an important factor in determining the levels of DNA modification by AHs and resulting toxic effects in feral fish.