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We assessed the estrogen agonist activities of 21 parabens and their chlorinated derivatives by using yeast two-hybrid assays incorporating either the human or medaka (Oryzias latipes) estrogen receptor alpha (hERalpha and medERalpha, respectively), and by using hERalpha competitive enzyme-linked immunosorbent assay (ER-ELISA). In the two-hybrid assay with hERalpha, five parabens and three chlorinated derivatives exhibited estrogenic activity, and their relative activity (17beta-estradiol [E2] = 1) ranged from 2.0 x 10(-5) to 2.0 x 10(-4), with the highest activity observed in i-butylparaben. In the medERalpha assay, six parabens and six chlorinated derivatives exhibited estrogenic activity and their relative activity ranged from 2.7 x 10(-5) to 3.5 x 10(-3), with the highest activity observed in benzylparaben, its monochlorinated derivative, i-butylparaben, and n-butylparaben. Although medERalpha demonstrated an activity to E2 that was three times lower than that demonstrated by hERalpha, medERalpha has a higher sensitivity to parabens than hERa (1.3-8.9 times). Five parabens and two chlorinated derivatives exhibited a binding affinity to ERa in the ER-ELISA; of the parabens, i-butylparaben exhibited the strongest binding affinity. The yeast two-hybrid assay and the ER-ELISA also revealed that many of the assayed chlorinated parabens were much weaker than the parent compound. In addition, the results mainly showed that parabens with a bulk substituent (e.g., i-butyl and benzyl groups) had a higher activity than those with a sterically small substituent. It is considered that derivatization masks the apparent estrogenic activity of parabens, but the resulting chlorinated compounds may represent a potential hazard and therefore other toxicity tests should be performed to determine the toxicity of the chlorinated derivatives.

No abstract

We conducted feeding experiments on threadsail filefish Stephanolepis cirrhifer juveniles for 16 days to evaluate the efficacy of moon jellyfish Aurelia aurita as a prey item. Four treatments, each with 40 individuals, were prepared to compare fish growth performance. The treatments consisted of filefish that were starved (control) (S), fed only jellyfish (J), fed only krill (K), and fed both jellyfish and krill (JK). Fish in the S treatment exhibited a 50% mortality rate and reduced body weight, whereas the J treatment exhibited a zero mortality rate and increased body weight. Fish in the JK treatments showed a significantly faster growth than those in the K treatment. Filefish consumed as much as 24 and 13 times their own body weight in jellyfish per day in the J and JK treatments, respectively. This is the first report showing that growth can be sustained by feeding a marine fish only jellyfish, and indicates the potential of jellyfish as a fish prey in both nature and captivity.

Avian species have the possible risk of embryonic exposure to persistent, lipophilic environmental contaminants, such as dichlorodiphenyltrichloroethane (DDT), by transfer of chemicals accumulated in mother birds to eggs. To model developmental and reproductive disorders of wild birds living in contaminated areas, we exposed Japanese quails in ovo to o,p'-DDT prior to incubation. A positive estrogenic substance diethylstilbestrol (DES; 1 and 10 ng/g of egg) and o,p'-DDT (1-100 microg/g of egg) were injected into the yolk before incubation. Treatment with o,p'-DDT (10 or 100 microg/g) but not with DES significantly reduced the hatchability of eggs. After sexual maturation, o,p'-DDT affected eggshell formation in female quails but had little influence on laying; high doses of o,p'-DDT significantly reduced eggshell strength, shell weight, and shell thickness, and several females treated with 100 microg o,p'-DDT/g laid eggs lacking shells. Diethylstilbestrol decreased egg production itself but had little effect on the eggshell. Both o,p'-DDT and DES caused dose-dependent shortening of the left oviduct and abnormal development of the right oviduct in females, while testis asymmetry was observed in males treated with a high dose of DES. In the uterus of the oviduct, the mRNAs for calcium-regulating factors osteopontin and calbindin D28K were reduced by both treatments, particularly that with o,p'-DDT. The results indicated that transovarian exposure to o,p'-DDT could bring about population declines in avian species through loss of fecundity caused by depression of hatchability and dysfunction of the reproductive tract.

Organochlorine pesticide concentrations, particularly those of the DDT family and of toxaphene, were measured by gas chromatography in samples of liver and body fat taken from Australian freshwater crocodiles Crocodylus johnstoni at three locations along the Ord River in Western Australia. The three sampling sites were the irrigation area, downstream of the irrigation area, and well upstream of the irrigation area; the last site serving as the control. DDT and toxaphene were applied in large and known quantities to cotton grown in the Ord Irrigation Area from 1964 to 1974. Thus the residues in the crocodile tissues are representative of the situation almost thirty years after the use of DDT and toxaphene ceased in the area. Very high concentrations of p,p'-DDE and toxaphene were found in the lipid-rich tissues that were examined. Livers and body fat from estuarine crocodiles Crocodylus porosus from the downstream site were also analysed. As p,p'-DDE and toxaphene are both known to be disruptive of endocrine systems, a range of blood parameters, including estradiol and testesterone concentrations, were also measured for all the animals studied. The ovaries and testes of the freshwater crocodiles were also examined histologically. There were no obvious effects on blood chemistry or gonad histology of the large burden of pesticides and their metabolites carried by exposed animals, although the limited number of samples and the variability of the breeding state of the animals examined may have masked possible effects. The isolation of the area, the accurately known applications of DDT and toxaphene, and the simplicity of the drainage system make the lower Ord River a unique natural laboratory for studying the long term breakdown and effects of pesticides applied in a tropical environment.

To clarify breeding failure in avian species caused by the estrogenicity of chemicals, alterations in the reproductive systems of Japanese quail exposed in ovo to a xenoestrogen were investigated. An injection of diethylstilbestrol (DES) into the yolk before incubation decreased, after sexual maturation, egg-laying performance of female quails, which accompanied inducing abnormal development of the oviducts. All females treated with 50 ng DES/g of egg did not lay eggs, while 0.5-5 ng DES/g reduced egg weight and eggshell strength and thickness. In the uterus (shell gland), the mRNAs for calcium regulating factors, osteopontin and calbindin D28 K, were reduced dose-dependently by DES. Scanning electron microscopy showed that shell thinning was pronounced in the mammillary and cuticular layers of the eggshell, regions where osteopontin proteins are reportedly located. These indicate that transovarian exposure to xenoestrogens causes malformation and dysfunction of the oviducts, where calcium regulating molecules could play key roles in eggshell thinning.

The human thyroid receptor (hTR)-agonist activities of 796 compounds were evaluated using a yeast two-hybrid assay in this study. A total of 17 compounds exhibited agonist activity at tenfold the effective concentration (EC × 10 ) [0.0083 -7,500 nM]. Additionally, TRIAC, TETRAC, and GC-1, which exhibited 30 -200 times higher activities than T3 and T4, may cause thyroid-hormone receptors (TR) activity at extremely low concentrations in real environmental water. Moreover, 3-chloro-3',5,5'-triiodo-L-thyronine exhibited high TR-agonist activity for the first time. Chemicals with a structure equivalent to thyroid hormones exhibited TR-agonist activity regardless of the TR type. Information on hTR-agonist activity is important because previous studies, such as those involving EDSP21, have focused exclusively on rTR-agonist activity. Therefore, the knowledge gained from the present study will boost chemical regulation strategies benefiting human and wildlife.