Yiannis Kiparissis

Effects of the antiandrogens, vinclozolin and cyproterone acetate on gonadal development in the Japanese medaka (Oryzias latipes)

This study was focused on determining the effects of exposure to antiandrogens on the gonadal development of Japanese medaka (Oryzias latipes). Test compounds included the fungicide, vinclozolin and the clinical antiandrogen, cyproterone acetate. Newly hatched medaka were exposed to aqueous solutions of vinclozolin (2500 microg/l) and the vinclozolin fungicide formulation, Ronilan (1000 and 5000 microg/l) and cyproterone acetate (1 and 10 microg/l), for 3 months. Histological evaluation of the gonadal tissues of exposed fish indicated that the 5000 microg/l concentration of the vinclozolin formulation (Ronilan) induced a low incidence of intersex (i.e. testis-ova) and the 2500 microg/l concentration of vinclozolin-affected spermatogenesis in males. Also, the vinclozolin treatments induced moderate ovarian atresia. Cyproterone acetate also induced a low incidence of testis-ova, but in contrast to the vinclozolin treatment the amount of ovarian tissue in the testis-ova was equal to or greater than the amount of testicular tissue. In the cyproterone acetate treatments, both oogenesis and spermatogenesis were moderately inhibited at all test concentrations. The results of this study indicate that antiandrogens have the potential to alter testicular development and gametogenesis in fish. However, research is needed to determine the mechanisms by which antiandrogens affect fish.

Increased cellular apoptosis after chronic aqueous exposure to nonylphenol and quercetin in adult medaka (Oryzias latipes)

Increasing evidence suggests that sublethal effects of natural or xenobiotic chemicals in the environment may be mediated via the stimulation of apoptosis. To investigate whether apoptosis can be induced in fish by weakly estrogenic and androgenic chemicals, adult male Japanese medaka (Oryzias latipes) were exposed to 100 ppb of the estrogenic alkylphenol, 4-nonylphenol, and adult female medaka were exposed to 100 ppb of the aromatase-inhibiting bioflavonoid, quercetin, for 6 weeks. Exposure to nonylphenol and quercetin had no significant effect on the length, weight or condition factors compared to solvent (acetone) controls in male or female medaka. Apoptosis was evaluated in blinded histological sections of whole medaka using terminal dideoxynucleotidyl transferase dUTP nick end labeling (TUNEL) that labels nuclei of cells containing apoptotic (fragmented) DNA. There was a six-fold greater extent of apoptosis in spermatocytes, Sertoli cells and Leydig-homologue cells, but not in spermatids of testes from nonylphenol-exposed male medaka compared to testes of solvent controls. No significant differences in the extent of apoptosis were detected in intestine, liver or kidney from the same male fish. Quercetin-treated female medaka had a significantly increased number of atretic ovarian follicles, but no significant differences in the extent of apoptosis in intestine, liver or kidney. These results suggest that nonylphenol caused testicular degeneration via increased testicular cell apoptosis, while quercetin may be ovotoxic via increased follicular atresia.

Induction of hepatic EROD in fish exposed to leachates from wood pulp

Aqueous leachates from softwood and hardwood pulp collected from two different pulping stages in a kraft mill (i.e. pre- and post-oxygen delignification) were assessed for their ability to induce hepatic ethoxyresorufin-O-deethylase (EROD) in rainbow trout (Oncorhynchus mykiss). Immature rainbow trout were exposed to aqueous leachates from wood pulp for 21 days in a flow-through system. The leachates from softwood pulp collected at both pulping stages and leachates from pre-oxidation hardwood pulp elevated EROD activities 2.5 to 6-fold above reference fish, beginning at 7 days from the start of exposure. The EROD activity remained elevated in these treatments throughout exposure, but declined rapidly during a 14 day post-exposure period. Leachate from the softwood pulp appeared to be a more potent EROD inducer than leachate from hardwood pulp. The results of this study indicate that relatively hydrophilic chemicals capable of inducing MFOs in fish are present in wood pulp even before extensive mill processing.

Induction of hepatic ethoxyresorufin-O-deethylase (EROD) in rainbow trout (Oncorhynchus mykiss) exposed to 3,3′,4,4′-tetrachlorodiphenyl ether by intraperitoneal injection or gavage intubation

The induction of hepatic ethoxyresorufin-O-deethylase (EROD) was studied in rainbow trout (Oncorhynchus mykiss) exposed to 3,3′,4,4′-tetrachlorodiphenyl ether (3,3′,4,4′-TCDE) by two routes of administration. A single dose of 3.3 μmol Kg−1 of 3,3′,4,4′-TCDE was administered either by intraperitoneal (i.p.) injection or gavage intubation and fish were sampled over a duration of 24 d post-exposure. Gavage intubation of the test compound caused significantly higher induction of EROD enzyme activity than the controls at 3, 12 and 24 d post-exposure. However, the degree of EROD induction was weak at 2.9 ± 0.5, 2.9 f 0.4 and 3.4 ± 0.3-fold higher than activity in control fish, respectively. These levels of EROD induction are at least 10-fold lower than those in similar studies with comparable doses of 2,3,7,8-TCDD and 3,3′,4,4′-tetraCB. No significant EROD induction was observed in fish administered 3,3′,4,4′-TCDE by i.p. injection. The results of this study show that the routes of exposure can influence the degree of hepatic EROD induction.