It was hypothesized in previous studies that the Exxon Valdez oil spill in Prince William Sound, Alaska, induced heritable mutations and resulted in mortality of pink salmon (Oncorhynchus gorbuscha) embryos. In one of these studies, laboratory exposure of pink salmon embryos to crude oil resulted in apparent mutation-induction in exon 1 and exon 2 of the K-ras oncogene, but no fish from the area impacted by the oil spill were analyzed. We assessed K-ras exon 1 and exon 2 DNA sequences in pink salmon from five streams that were oiled and five streams that were not oiled by the Exxon Valdez oil spill in Prince William Sound, and two streams with natural oil seeps and one stream without seeps on the Alaska Peninsula. Of the 79 fish analyzed for exon 1 and the 89 fish analyzed for exon 2, none had the nucleotide substitutions representing the mutations induced in the laboratory study. Other variable nucleotides occurred in similar proportions in oiled and non-oiled streams and probably represent natural allelic variation. These data do not support the hypothesis that heritable mutations in the K-ras gene were induced by the Exxon Valdez oil spill or oil seeps.
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"When spilt, for instance due to shipwrecking, these products can induce modifications in the marine environment causing disruption at the ecosystem level. For example, in situ contact with field and high concentrations of PAHs could induce external abnormalities (Pollino and Holdway, 2002), somatic mutations (Cronin et al., 2002; Roy et al., 1999) and immunodepression (Holladay et al., 1998) in fish. Many studies have therefore focused on the immune systems of fish whose some compounds are often used as biomarkers of xenobiotic effects. "
[Show abstract][Hide abstract] ABSTRACT: The in vitro effects of polycyclic aromatic hydrocarbons (PAHs) on two plasmatic immune parameters, lysozyme concentration and haemolytic alternative complement activity, of the European sea bass, Dicentrarchus labrax, were tested using field (10(-7) and 10(-9) mg mL(-1)) and high concentrations (10(-3) and 10(-5) mg mL(-1)) observed during oil spills. Peripheral blood from 105 fish was collected, centrifuged at 1200 g, for 10 min, at 4 degrees C and three plasma pools, each of 35 fish, were constituted. Two oils (heavy fuel oil and light cycle oil) and 16 pure PAHs, selected on the basis of the American Environmental Protection Agency list (US EPA), were tested in vitro on the two humoral immune parameters. Only three pure PAHs (anthracene, chrysene and dibenz[a,h]anthracene) modulated lysozyme concentration. Acenaphthene, acenaphthylene, anthracene, benzo[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, pyrene and light cycle oil modified the haemolytic alternative complement activity after 4h of incubation. This study investigates the direct effects of several PAHs on fish humoral immune functions and describes the haemolytic complement activity of fish as suitable biomarkers of oil pollution.
Full-text · Article · Mar 2009 · Toxicology in Vitro
"Regarding direct and/or indirect involvement of EDCs in carcinogenesis , there were some examples in Winter flounder (Pleuronectes americanus) exposed to polycyclic aromatic hydrocarbons (PAHs) (Wirgin et al., 1989), tomcod (Microgadus tomcod) exposed to polychlorinated biphenyls (PCBs) (McMahon et al., 1990), and dragonets (Callionymus lyra) exposed to PAH and PCB (Vincent et al., 1998). However, Cronin et al. (2002) found that the heavy oil-derived EDC could not induce heritable mutations in Ki-ras as shown for example in the Exxon Valdez oil spill. This suggests that the effect of chemicals on ras genes in fish and its role in carcinogenesis upon EDC exposure still remain uncertain (Lee et al., 2008c). "
[Show abstract][Hide abstract] ABSTRACT: The hermaphroditic fish Krytolebias marmoratus is a potential fish model for study of tumour development. Recently, sequences and expression of some oncogenes and tumor suppressor gene have been studied in K. marmoratus. To get a better understanding of oncogene expression at different development stage, and in different tissues three R-ras genes were cloned and fully sequenced. Expression of these R-ras genes (R-ras1, R-ras2, R-ras3) was also studied in fish exposed to endocrine-disrupting chemicals (EDCs). Liver showed the highest level of expression compared to other tissues, even though each R-ras gene showed different expression patterns in tissues. Interestingly, in secondary male (ovary atresia stage), expression levels of three R-ras genes was lower compared to hermaphrodites. At different developmental stages, R-ras2 gene showed most pronounced expression at early embryogenesis but at stage 5 (hatchling stage) and juvenile stage, R-ras3 gene showed the highest expression. After the juvenile stage, R-ras1 gene was upregulated compared to other R-ras genes, which showed the highest expression at the hermaphroditic stage. When fish were exposed to 17-beta-estradiol (E2), a natural estrogen and tamoxifen, a nonsteroidal estrogen antagonist and three EDCs viz., 4-n-nonylphenol (NP), bisphenol A (BPA), and 4-tert-octylphenol (OP), all the three R-ras genes were induced, except in the fish exposed to tamoxifen. These results suggest that EDCs modulate the expression of R-ras genes and thus affect subsequent signal transduction and tumor development.
Full-text · Article · Nov 2008 · Comparative Biochemistry and Physiology Part C Toxicology & Pharmacology
"Recently, ras mutation analysis has been performed in pink salmon (Oncorhynchus gorbuscha) embryos (Cronin et al., 2002) to confirm the earlier observation of Roy et al. (1999) who had reported Ki-ras mutations in pink salmon embryos exposed to weathered Prudhoe Bay oil samples. However, study of Cronin et al. (2002) in field samples revealed that heritable mutations in Ki-ras are not induced by Exxon Valdez oil spill or oil seeps. This suggests that effect of chemicals on ras genes in fish still remains uncertain. "
[Show abstract][Hide abstract] ABSTRACT: Kryptolebias marmoratus is the only known internally self-fertilizing vertebrate. It shows high susceptibility to many chemical carcinogens and has been proposed as a potential cancer model species alternative to mammals. Since use of this fish species is expected to rise in cancer research, regulation of oncogenes from K. marmoratus needs proper understanding. We cloned and deduced full-length sequence of cDNA of N-ras oncogene from K. marmoratus. Study of expression profile of N-ras by using quantitative real-time RT-PCR revealed that brain had the highest level of expression compared to other tissues. Some embryonic stages showed more N-ras expression than juveniles and adults. Exposure to two environmental endocrine disrupting chemicals (EDCs), bisphenol A (BPA) and 4-nonylphenyl (NP) caused up-regulation of N-ras in gonad, intestine and liver of hermaphrodite K. marmoratus. It is suggested that K. marmoratus may be a suitable model species for oncogene expression studies. The observed EDC-induced expression of N-ras supports the assumption that EDC exposure may predispose the host to the risk of environmental carcinogenesis.
Full-text · Article · May 2008 · Comparative Biochemistry and Physiology Part C Toxicology & Pharmacology