Immunomodulation in C57Bl/6 mice following consumption of halogenated aromatic hydrocarbon-contaminated coho salmon (Oncorhynchus kisutch) from Lake Ontario.

This report describes studies designed to assess the immunomodulatory effects associated with the consumption of coho salmon containing halogenated aromatic hydrocarbons (HAHs) and other compounds naturally bioaccumulated from Lake Ontario. Diets containing 33% coho salmon from Lake Ontario or the Pacific Ocean were fed to juvenile C57Bl/6 mice for 2-4 mo. Following 60 d, the mice that consumed Lake Ontario salmon had reduced IgM, IgG, and IgA plaque-forming cell responses to sheep erythrocytes. No changes were observed in total numbers of spleen lymphocytes, total T-lymphocytes or T-lymphocyte subsets as determined by flow cytometry. Cellular immunity, assessed by the cytotoxic T-lymphocyte response to allogeneic tumor target cells, was not altered following dietary exposure to Lake Ontario coho salmon for 4 mo. The observed humoral immunomodulation correlated with elevated PCB levels in the Lake Ontario salmon diets. The levels of pollutants such as mercury, tin compounds and other metals, PCDDs, and PCDFs were not examined.

Ultrastructure of the liver of Lake Erie coho salmon from post-hatching until spawning.

Hepatocytes were examined in coho salmon, Oncorhynchus kisutch, at several stages in their life cycles, using feral and laboratory-reared fish. Yolksac fry sampled before their first exogenous feed had low glycogen and lipid reserves in the hepatocytes and although 'light' cells were predominant, there was already evidence of a dimorphism in the electron density of hepatocytic cytoplasm. Within 1 day of the first exogenous feeding (a commercial salmonid starter diet) the hepatocytes in the fry contained extensive glycogen pools (up to 50% of the cell volume) and lipid droplets, often contained within the glycogen pools. This high glycogen and lipid condition was also evident in laboratory-reared male and female fish which had undergone smoltification. In sexually immature feral fish collected prior to the growth of their gonads, the hepatocytes were predominantly large 'light' cells. There was little glycogen in the hepatocytes of either males or females, lipid was abundant (particularly in females) as was ribosomal endoplasmic reticulum and smooth endoplasmic reticulum. In feral prespawning and spawning adults there was some loss of lipid and an apparent increase in the number of 'dark' hepatocytes. Treatment of fingerling fish with methyl testosterone resulted in a decrease of hepatocytic lipid content, whereas 17 beta-oestradiol stimulated an increase in hepatocytic lipid and ribosomal endoplasmic reticulum and a decrease in glycogen.

Toxic effects in C57B1/6 and DBA/2 mice following consumption of halogenated aromatic hydrocarbon-contaminated Great Lakes coho salmon (Oncorhynchus kisutch Walbaum).

Diets containing coho salmon (Oncorhynchus kisutch Walbaum) from the Pacific Ocean or from Lakes Erie, Michigan, and Ontario [containing a gradation from low to high of halogenated aromatic hydrocarbons, (HAHs)] were fed to C57B1/6 and DBA/2 mice. Following a 4-month dietary exposure to Lake Ontario salmon, both strains of mice demonstrated hepatomegaly. The ethoxyresorufin-O-deethylase (ERR) enzyme levels were elevated in livers of C57B1/6 mice fed diets of salmon from all of the Great Lakes studied, with exceptionally high levels detected in C57B1/6 mice fed Lake Ontario salmon. Induction of ERR enzyme levels was detected in DBA/2 mice only following dietary exposure to Lake Ontario salmon. Serum levels of L-thyroxine (T4) and triiodo-L-thryonine (T3) were suppressed in C57B1/6 mice following consumption of Lake Ontario coho salmon, but T3 and T4 levels remained unchanged in DBA/2 mice. In general, pathobiological effects correlated with both dietary HAH exposure level and Ah receptor status.

Relationship between anaphase aberrations and carcinogenicity in the trout embryo microinjection assay.

An increased incidence of anaphase aberrations was observed in the tissues of rainbow trout embryos (Salmo gairdneri) within 96 hours of exposure to mitomycin [(MM) CAS: 50-07-7; 50 and 100 ng/embryo] and aflatoxin B1 [(AFB1) CAS: 1162-65-8; 13 and 25 ng/embryo] with the use of the trout embryo microinjection assay. High numbers of anaphase aberrations in embryos exposed to MM were associated with low mitotic indices, cell pyknosis, and high embryo mortalities. When the anaphase aberration data for embryos exposed to AFB1 were compared to previously reported carcinogenesis data from the microinjection assay, the incidence of anaphase aberrations in embryos did not show the same quantitative variations as the incidence of hepatic carcinomas in adult trout. While anaphase aberrations may be an indicator of the clastogenic effects of chemicals on fish embryos, it is unlikely that these aberrations can be used as an early indicator of a carcinogenic response in the trout embryo assay.

Oil refinery effluents: evidence of cocarcinogenic activity in the trout embryo microinjection assay.

Extracts prepared from oil refinery effluents (soxhlet and XAD-2) were tested for carcinogenic potential by means of the rainbow trout (Salmo gairdneri) embryo-injection bioassay. No neoplasms were detected in fish given injections of refinery extracts alone (with and without exogenous rat S-9 activation). Refinery extracts coinjected with aflatoxin B1 induced elevated frequencies of hepatic neoplasms. This cocarcinogenic effect was most pronounced when aflatoxin B1 was preincubated with rat S-9 prior to injection. Effluent extracts coinjected with a direct-acting carcinogen [N-methyl-N'-nitro-N-nitrosoguanidine (CAS: 56-57-5)] did not increase the incidence of hepatic neoplasms (with and without exogenous S-9 activation).

Plasma cortisol and sex steroid levels in Great Lakes coho salmon (Oncorhynchus kisutch Walbaum) in relation to fecundity and egg survival.

Plasma 11-ketotestosterone and cortisol levels in spawning male and female coho salmon (Oncorhynchus kisutch Walbaum) collected from a Lake Erie (Pennsylvania) stock were significantly lower (P less than 0.01) than in stocks of coho salmon at a comparable stage of sexual development collected from Lakes Ontario (two stocks) or Michigan. Plasma testosterone levels in female coho salmon from Lake Erie were significantly lower (P less than 0.01) than in females from Lake Ontario or Lake Michigan stocks. There were no significant differences in plasma testosterone levels in the males, or 17 beta-estradiol levels in male or female salmon of the four stocks sampled from the three study lakes. This apparent dysfunction in androgen and cortisol secretion in the Lake Erie stock is correlated with and may account for the low fecundity and poor expression of secondary sexual characteristics in that stock.

Microinjection of carcinogens into rainbow trout embryos: an in vivo carcinogenesis assay.

Liver tumors were induced in rainbow trout (Salmo gairdneri) 1 year after carcinogens were microinjected into embryos. Neoplasms were induced by a single injection of 13 and 25 ng per egg of aflatoxin B1 (CAS: 1162-65-8), 500 ng per egg of 7,12-dimethylbenz[a]anthracene (CAS: 57-97-6), and 250 ng per egg of 2-anthramine (CAS: 613-13-8). Over 70% of [3H]benzo[a]-pyrene (CAS: 50-32-8) injected into eggs was retained in hatched embryos, 120 hours postinjection. Exogenous activation of test compounds with the use of rat liver microsome preparation (S-9) increased the incidence of liver tumors in fish given injections of 25 ng aflatoxin B1. The amount of chemical required for the embryo injection assay was comparable to that required for the Ames bacterial mutagenesis assay.

Bioaccumulation of organochlorines by yearling coho salmon (Oncorhynchus kisutch walbaum) fed diets containing Great Lakes' coho salmon, and the pathophysiological responses of the recipients.

1. Yearling coho salmon were fed diets containing the flesh of sexually mature adult coho salmon from Lakes Ontario, Erie and Michigan; Pacific Ocean coho salmon and a commercial trout chow were used to prepare control diets. The fish were fed the experimental diets for 27 weeks. Samples were taken of fed fish and fish fed for 27 weeks and then food deprived for 4 weeks. 2. Total accumulated organochlorine in the recipient was directly proportional to dietary total organochlorine levels, although there were considerable interlake differences in the degree of clearance of specific organochlorine compounds. 3. There was evidence of changes in thyroid physiology, hematocrit, liver structure and inter-renal gland activity in recipients fed the Great Lakes' coho salmon, apparently correlated with organochlorine bioaccumulation.

Quantitative interlake comparison of thyroid pathology in Great Lakes coho (Oncorhynchus kisutch) and chinook (Oncorhynchus tschawytscha) salmon.

Coho salmon (Oncorhynchus kisutch) and chinook salmon (Oncorhynchus tshawytscha) from Lakes Ontario, Michigan, Erie, or Huron were found to suffer epizootics of thyroid hyperplasia and goiters which appeared to have an environmental etiology. There were 13-fold differences in goiter prevalence within the Great Lakes, and the differences in goiter frequency were correlated with the degree of thyroid hyperplasia. A means of assessing the degree of thyroid hyperplasia (thyroid index) is described, and the derived index was used to facilitate statistical interlake and interspecies comparisons. Despite the hyperplastic (or goitered) condition in all prespawning or spawning Great Lakes salmon, serum thyroid hormone levels were generally higher than in prespawning coho salmon from the Fraser River, British Columbia, indicating that the Great Lakes fish were not necessarily hypothyroid. The hyperplastic lesions appear to undergo progressive changes: (a) large follicles, partly colloid depleted, surrounded by cuboidal epithelial cells; (b) small follicles, largely colloid depleted, surrounded by columnar epithelial cells (in this form, the follicles commonly assume a trabeculate arrangement); (c) "microfollicles" with greatly enlarged columnar epithelial cells encompassing very small follicles; (d) apparently afollicular lesions with little or no colloid in evidence. There was some evidence of benign invasiveness, although the lesions generally resembled simple hyperplastic parenchymatous goiters seen in humans.

Structure of normal testis and testicular tumors in cyprinids from Lake Ontario.

Two types of testicular tumor were evident in cyprinid fishes collected from Lake Ontario. Both types of tumors appeared to be of Sertoli cell origin. One contained predominantly Sertoli cells with little or no lipid content and germinal cells in only small numbers. The second contained large numbers of spermatogonia together with Sertoli cells that contained large amounts of lipid and smooth endoplasmic reticulum. Small, apparently inactive Leydig cells were present in both types of tumors and also in testes of fish not bearing gonadal tumors.

Increasing frequency of thyroid goiters in Coho salmon (Oncorhynchus kisutch) in the Great Lakes.

Coho salmon collected during the 1976 spawning runs from Lakes Michigan, Ontario, and Erie had overt goiter frequencies of 6.3, 47.6, and 79.5%, respectively. These represent significant increases over the frequencies observed in previous years. Epizootiological data suggest that environmental goitrogens (possibly pollutants) may be involved in the etiology of the thyroid disorder.