How estrogenic is nonylphenol? A transgenerational study using rainbow trout (Oncorhynchus mykiss) as a test organism

Concentration- and time-dependent effects of the synthetic estrogen, 17alpha-ethinylestradiol, on reproductive capabilities of the zebrafish, Danio rerio

Partial or full life-cycle tests are needed to assess the potential of endocrine-disrupting compounds (EDCs) to adversely affect development and reproduction of fish. Small fish species such as zebrafish, Danio rerio, are under consideration as model organisms for appropriate test protocols. The present study examines how reproductive effects resulting from exposure of zebrafish to the synthetic estrogen 17alpha-ethinylestradiol (EE2) vary with concentration (0.05 to 10 ng EE2 L(-1), nominal), and with timing/duration of exposure (partial life-cycle, full life-cycle, and two-generation exposure). Partial life-cycle exposure of the parental (F1) generation until completion of gonad differentiation (0-75 d postfertilization, dpf) impaired juvenile growth, time to sexual maturity, adult fecundity (egg production/female/day), and adult fertilization success at 1.1 ng EE2 L(-1) and higher. Lifelong exposure of the F1 generation until 177 dpf resulted in lowest observed effect concentrations (LOECs) for time to sexual maturity, fecundity, and fertilization success identical to those of the developmental test (0-75 dpf), but the slope of the concentration-response curve was steeper. Reproduction of zebrafish was completely inhibited at 9.3 ng EE2 L(-1), and this was essentially irreversible as a 3-mo depuration restored fertilization success to only a very low rate. Accordingly, elevated endogenous vitellogenin (VTG) synthesis and degenerative changes in gonad morphology persisted in depurated zebrafish. Full life-cycle exposure of the filial (F2) generation until 162 dpf impaired growth, delayed onset of spawning and reduced fecundity and fertilization success at 2.0 ng EE2 L(-1). In conclusion, results show that the impact of estrogenic agents on zebrafish sexual development and reproductive functions as well as the reversibility of effects, varies with exposure concentration (reversibility at < or = 1.1 ng EE2 L(-1) and irreversibility at 9.3 ng EE2 L(-1)), and between partial and full life-cycle exposure (exposure to 10 ng EE2 L(-1) during critical period exerted no permanent effect on sexual differentiation, but life-cycle exposure did).

Nonylphenol induces apoptosis of Jurkat cells by a caspase-8 dependent mechanism

Nonylphenol is the final biodegradation product of nonylphenol polyethoxylates, which are widely used surfactants in domestic and industrial products. Although nonylphenol is well known as an endocrine disrupting chemical, its effects on cell death and the mechanisms responsible for these apoptotic effects remain unclear. In the present study, Jurkat cells were treated with 0.1, 1 and 10 microM nonylphenol for 12 and 24 h, respectively. Cell viability was assessed with a Cell Counting Kit. The effects of nonylphenol on apoptosis of Jurkat cells were determined by DNA fragmentation (DNA ladder), Hoechst33258, PI and Annexin V FITC/PI double staining. Changes in mitochondrial membrane potential were detected with JC-1 fluorescence. In addition, enzyme activity of caspase-8 was evaluated by flow cytometry. The results demonstrated that nonylphenol inhibited the proliferation and induced loss of mitochondrial membrane potential, caspase-8 activation, internucleosomal DNA fragmentation. Furthermore, a caspase-8 inhibitor, IETD-fmk, blocked loss of mitochondrial membrane potential and apoptosis. These findings suggested that nonylphenol induced apoptosis of Jurkat cells by caspase-8 dependent mechanisms.

Stir-bar-sorptive extraction, with in-situ deconjugation, and thermal desorption with in-tube silylation, followed by gas chromatography-mass spectrometry for measurement of urinary 4-nonylphenol and 4-tert-octylphenol glucuronides

A novel method, stir-bar-sorptive extraction (SBSE), with in-situ deconjugation and thermal desorption (TD) with in-tube silylation, followed by gas chromatography-mass spectrometry (GC-MS), for determination of trace amounts of 4-nonylphenol glucuronide (NP-G) and 4-tert-octylphenol glucuronide (OP-G) in human urine, is described. The method involved correction by use of stable isotopically labeled internal standards 4-(1-methyl)octylphenol-d5 (NP-d) and deuterium 4-tert-octylphenol (OP-d). A human urine sample to which beta-glucuronidase had been added was extracted for 90 min at 37 degrees C using a stir bar coated with a 500-microm-thick layer of polydimethylsiloxane (PDMS). NP-G and OP-G were deconjugated, becoming free 4-nonylphenol (NP) and 4-tert-octylphenol (OP). The analytes were then extracted with the PDMS stir bar and the stir bar was subjected to TD with in-tube silylation; this was followed by GC-MS in selected-ion-monitoring (SIM) mode. To optimize the conditions for SBSE with in-situ deconjugation and to test recovery, NP-G and OP-G were synthesized by a biochemical technique in our laboratory. Average recoveries from human urine samples spiked with NP-G and OP-G were between 91.9 and 95.6% with correction using the added surrogate standards. Limits of detection were 0.11 ng mL-1 for NP and 0.01 ng mL-1 for OP. We also measured background levels of NP-G and OP-G in six urine samples from healthy volunteers. NP and OP were detected in the samples at concentrations of 0.62-1.95 ng mL-1 and <0.04-0.18 ng mL-1, respectively.

Biochemical effects of nonylphenol polyethoxylate adjuvant, Diquat herbicide and their mixture on the three-spined stickleback (Gasterosteus aculeatus L.)

This study examined the response of 7-ethoxyresorufine-O-deethylase, glutathione-S-transferase, glutathione peroxidase, glutathione content, level of thiobarbituric acid reactive compounds and circulating vitellogenin, in three-spined sticklebacks after 21 days of exposure to Diquat herbicide, commercial nonylphenol polyethoxylate adjuvant and mixture between Diquat and adjuvant. The results showed that adjuvant exerted more important oxidative effects than Diquat and that mixture effects were unlike to single additivity. This study argues for ecotoxicological risk assessment of adjuvants and mixtures of adjuvants and pesticides.

Amperometric immunosensor for nonylphenol determination based on peroxidase indicating reaction

Novel immunosensor for nonylphenol (NP) determination has been developed by immobilization of specific antibodies together with horseradish peroxidase on the surface of carbon screen-printed electrode. The signal of the immunosensor is generated by the involvement of NP accumulated in the peroxidase oxidation of mediator (Methylene Blue, hydroquinone or iodide). This results in the increase of the signal recorded by linear-sweep voltammetry. The sensitivity of the detection depends on the nature of mediator, its concentration and incubation period. Cross-selectivity of the response toward readily oxidized phenolic compounds has been determined. The immunosensor developed makes it possible to detect from 20 microgL(-1) to 44 mgL(-1) of NP with detection limit 10 microgL(-1) of NP.

Nonylphenol-induced oxidative stress and cytotoxicity in testicular Sertoli cells

Nonylphenol (NP) as an environment contaminant has been demonstrated to adversely affect male reproduction. The main objective of this study was to evaluate NP-induced oxidative stress and toxicity in testicular Sertoli cells. Sertoli cells were exposed to 10-40 microM NP for 24 h. Cell death and growth inhibition were observed by flow cytometric analysis and 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide (MTT) assay, while fluorescein diacetate (FDA) and propidium iodide (PI) staining was used to examine the morphological changes following NP exposure. Subsequently, we found that short-term treatment (2 h) of NP caused intracellular accumulation of reactive oxygen species (ROS), which was evaluated by loading of 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) without visible morphological changes. Loss of mitochondrial membrane potential (MMP) was detected following 12 and 24 h treatment of NP and assessment by Rhodamine 123 (Rh123) staining. In addition, incubation with NP for 12 h also increased lipid peroxidation of Sertoli cells. These results indicated that low micromolar concentrations of NP induce an adverse oxidative stress in rat Sertoli cells.

Alteration of steroid hormone balance in juvenile turbot (Psetta maxima) exposed to nonylphenol, bisphenol A, tetrabromodiphenyl ether 47, diallylphthalate, oil, and oil spiked with alkylphenols

In recent years, concern has been raised about the ability of some classes of environmental contaminants to disrupt the endocrine system of both humans and wildlife. In this study, juvenile turbots (Psetta maxima) were exposed under laboratory conditions to selected waterborne contaminants: oil, oil spiked with alkylphenols, bisphenol A, diallylphthalate, tetrabrominated diphenyl ether 47, and p-nonylphenol as a positive control for "estrogenic-type" effects. This work focused on sex steroids, because these hormones play a key role in the reproduction process. Analytical procedures, involving the off-line coupling of solid phase extraction and gas chromatography/mass spectrometry, were developed for the determination of 12 endogenous sex steroids levels in fish plasma, bile, and gonads. Because of the sexual immaturity of the fish used in this study, however, only six steroids could be detected in juvenile turbots. Bisphenol A and p-nonylphenol exhibited the highest potency towards steroids dynamics, lowering the ratio of androgens to estrogens in all three studied matrices. However, these two chemicals had different modes of action, because p-nonylphenol induced a decrease of androstenedione and 11-ketotestosterone levels, whereas bisphenol A exposure led to an elevation of estrone level. Overall, these two chemicals seemingly disrupted the activity of some steroidogenesis enzymes, leading to serious hormonal imbalance in juvenile turbot.

Zebrafish as a model for developmental neurotoxicity testing

BACKGROUND

To establish zebrafish as a developmental toxicity model, we used 7 well-characterized compounds to examine several parameters of neurotoxicity during development.

METHODS

Embryos were exposed by semistatic immersion from 6 hrs postfertilization (hpf). Teratogenicity was assessed using a modified method previously developed by Phylonix. Dying cells in the brain were assessed by acridine orange staining (these cells are likely to be apoptotic). Motor neurons were assessed by antiacetylated tubulin staining and catecholaminergic neurons were visualized by antityrosine hydroxylase staining.

RESULTS

Atrazine, dichlorodiphenyltrichloroethane (DDT), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were primarily teratogenic and not specifically neurotoxic. 2,4-dichlorophenoxyacetic acid (2,4-D), dieldrin, and nonylphenol showed specific neurotoxicity; dieldrin and nonylphenol were specifically toxic to catecholaminergic neurons. Malathion, although not teratogenic, showed some nonspecific toxicity.

CONCLUSIONS

Teratogenicity measured in 96-hpf zebrafish is predictive of mammalian teratogenicity and is useful in determining whether a compound causes specific neurotoxicity or general developmental toxicity. Induction of apoptosis or necrosis is an indicator of neurotoxicity. An effect on motor neurons in the caudal third of the embryo correlates with expected defects in motility. Overall, our results showed a strong correlation with mammalian data and suggest that zebrafish is a predictive animal model for neurotoxicity screening.

Seminiferous cord formation and germ-cell programming: epigenetic transgenerational actions of endocrine disruptors

The molecular and cellular control of embryonic testis development was investigated through an analysis of the embryonic testis transcriptome to identify potential regulatory factors for male sex determination and testis morphogenesis. One critical factor identified is neurotropin 3 (NT3). At the onset of male sex determination, Sertoli cells initiate differentiation and express NT3 to act as a chemotactic factor for mesonephros cells to migrate and associate with Sertoli-germ cell aggregates to promote cord formation. Promoter analysis suggests that NT3 may be an initial downstream gene to SRY and helps promote testis morphogenesis. Endocrine disruptors were used to potentially interfere with embryonic testis development and further investigate this biological process. The estrogenic pesticide methoxychlor and antiandrogenic fungicide vinclozolin were used. Previous studies have shown that methoxychlor and vinclozolin both interfere with embryonic testis cord formation and cause increased spermatogenic cell apoptosis in the adult testis. Interestingly, transient in vivo exposure to endocrine disruptors at the time of male sex determination caused a transgenerational phenotype (F1-F4) of spermatogenic cell apoptosis and subfertility. This apparent epigenetic mechanism involves altered DNA methylation and permanent re-programming of the male germ-line. A series of genes with altered DNA methylation and imprinting are being identified. Observations reviewed demonstrate that a transient embryonic in utero exposure to an endocrine disruptor influences the embryonic testis transcriptome and through epigenetic effects (e.g., DNA methylation) results in abnormal germ-cell differentiation that subsequently influences adult spermatogenic capacity and male fertility, and that this phenotype is transgenerational through the germ-line. The novel observations of transgenerational epigenetic endocrine disruptor actions on male reproduction critically impact the potential hazards of these compounds as environmental toxins. The literature reviewed provides insight into the molecular and cellular control of embryonic testis development, male sex determination, and the programming of the male germ-line.

Nonylphenol-induced thymocyte apoptosis is related to Fas/FasL pathway

Nonylphenol (NP) is the final biodegradation product of nonylphenol polyethoxylates, which are widely used as surfactants in domestic and industrial products. NP has been reported to have estrogenic activity and shown to have potential reproductive toxicity. However, its influence on immune system function remains unclear. In this study, to determine the immunological effects of NP, the effects of NP on apoptosis and Fas/FasL gene expression in rat thymocyte in vitro were investigated. Thymocytes were treated with NP 0.1, 1, and 10 ppm, respectively. Viable cell numbers were determined by MTT assay. Apoptotic cells were identified by DNA fragment analysis. A semi-quantitative reverse transcriptase-polymerase chain reaction method was used to analyze Fas and FasL mRNA levels. Fas and FasL protein expression was evaluated by flow cytometry. The results showed that NP decreased the cellularity; induced apoptotic death and enhanced the expression of Fas and FasL mRNA as well as proteins in thymocytes. These findings suggest that NP may induce apoptosis by altering the expression of Fas and FasL in thymocytes so as to affect the immune system function.

Stir bar sorptive extraction with in situ de-conjugation and thermal desorption gas chromatography-mass spectrometry for measurement of 4-nonylphenol glucuronide in human urine sample

4-Nonylphenol glucuronide (NP-G) in human urine samples was analyzed using stir bar sorptive extraction (SBSE) with in situ de-conjugation by beta-glucuronidase and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS). Distilled water (1 ml), 1.0 M ammonium acetate solution (100 microl) and beta-glucuronidase (10,000 units ml(-1), 10 microl) were added to human urine sample (1 ml), and extraction was commenced for 90 min at 37 degrees C while stirring at 250 rpm with a stir bar coated with a 500-microm-thick polydimethylsiloxane (PDMS) layer. Then, the stir bar was subjected to TD-GC-MS in the selected ion monitoring (SIM) mode. The calibration curve was made by SBSE method using 4-nonylphenol (NP) as the standard solution. The method showed good linearity and the correlation coefficients were 0.999 over the concentration range of 5-500 nM. Moreover, to optimize the conditions for SBSE with in situ de-conjugation and the recovery test, NP-G was synthesized by a biochemical technique in our laboratory. The limits of detection (S/N = 3) and quantitation (S/N > 10) for NP were 0.2 ng ml(-1) (1.0 nM) and 1.1 ng ml(-1) (5.0 nM), respectively. The average recoveries in the human urine samples (n = 6) spiked with NP-G at levels of 20 and 100 nM were 104.1 (R.S.D. 7.1%) and 100.6% (R.S.D. 9.2%), respectively, with correction using the added internal standard, 4-(1-methyl) octylphenol-d(5). The method enabled the precise determination of the standard and was applicable to the detection of trace amounts of NP-G in human urine samples.

Review of evidence: are endocrine-disrupting chemicals in the aquatic environment impacting fish populations?

In this paper, evidence from the current literature is presented that addresses either of two questions: 1) do EDCs in the aquatic environment have the potential to impact the reproductive health and survival of various fish species, and 2) are EDCs in the aquatic environment actually impacting the reproductive health and sustainability of indigenous populations of fish? Overall, data from laboratory experiments support the hypothesis that EDCs in the aquatic environment can impact the reproductive health of various fish species, but evidence that EDCs in the aquatic environment are actually impacting the reproductive health and sustainability of indigenous fish populations is less convincing. The scarcity of evidence linking impacts of environmental EDCs with changes in reproductive success of indigenous fish populations may reflect a critical need for a dependable method or indicator to assess reproduction of fish in situ. In addition, more studies that investigate whether fish populations routinely exposed to EDCs in situ are experiencing changes in population structure are needed. Linking endocrine disruption and reproductive impairment with an ecologically relevant impact on the sustainability of real fish populations remains, with few exceptions, an open challenge.

The effect of 4-nonylphenol on semen quality, viability of gametes, fertilization success, and embryo and larvae survival in rainbow trout (Oncorhynchus mykiss)

The present study investigated in vivo and in vitro effects of environmental relevant concentrations of 4-nonylphenol (100-750 ng l(-1)) on the reproduction of rainbow trout (Oncorhynchus mykiss). To determine the effect of 4-nonylphenol on semen quality rainbow trout were exposed to three concentrations of 4-nonylphenol in a flow-through system during the spawning period (60 days). At an estimated 4-nonylphenol concentration of 750 ng l(-1) semen production was completely inhibited, at 280 and 130 ng l(-1) the semen production was significantly reduced in comparison to the control. Sperm density, sperm motility and sperm fertility were not affected. Also the development of embryos and larvae at the end of yolk sac stage was affected by 4-nonylphenol. At estimated 4-nonylphenol exposure levels of 280 and 750 ng l(-1) the percentage of eyed stage embryos was slightly but significantly lower (2-4%) than at 130 ng l(-1) 4-nonylphenol and in the control. At 4-nonylphenol concentrations of 750 ng l(-1) only 23.8 +/- 1.2% of the larvae survived to the end of the yolk sac stage, at 280 ng l(-1) 53.7 +/- 8.2%, at 130 ng l(-1) 73.8 +/- 1.5%, and in the control 70.9 +/- 1.8%. Sperm motility was not affected by 4-nonylphenol as sperm motility rate, swimming velocity, swimming pattern and motility duration were similar in water and in water containing of 100, 250, or 750 ng l(-1) 4-nonylphenol. Incubation of eggs in physiological saline solution containing of 100, 250, or 750 ng l(-1) 4-nonylphenol did not change their fertilizability in comparison to the control. Therefore, 4-nonylphenol did not affect the egg viability. Also the fertilization process (sperm egg contact) was not influenced by 4-nonylphenol as the fertilization rate (percentage of hatched larvae) was similar to the control when eggs were fertilized in water containing of 100, 250, or 750 ng l(-1) 4-nonylphenol.

The Chinese rare minnow (Gobiocypris rarus) as an in vivo model for endocrine disruption in freshwater teleosts: a full life-cycle test with diethylstilbestrol

Chinese rare minnow (Gobiocypris rarus), a freshwater teleost, was exposed to diethylstilbestrol (DES) at 0.05, 0.5, 1 and 5 microg/L from fertilized eggs for up to mature period under flow-through condition. Several endpoints that related to development, reproductive fitness and transgenerational effects were evaluated. It was found that body length and body weight were significantly reduced and vitellogenin (Vtg) levels were significantly increased for fish exposed to DES. Histological examination showed that the sex ratios of F0 fish skewed to female and about 2% of the fish exposed to 0.05 microg/L DES developed testes-ova. The reproductive success, as determined from data on egg production, was reduced in female fish exposed to 0.05, 0.5, 1 and 5 microg/L DES. The lowest-observed-effect concentrations (LOEC) for changes of sex ratios, reproductive success and histology alteration of F0 are 0.05 microg/L. In the offspring, transgenerational effects on egg hatching rate, egg fertilization and Vtg levels of juvenile individuals were not observed. However, survival of F1 generation fry significantly declined. The analysis of sex steroid levels revealed a significant decrease of testosterone (T) in the whole body homogenates (WBH) of male progeny and somewhat elevation of estradiol (E2) in the WBH of female offspring. These findings indicate that exposure to DES causes a variety of developmental, reproductive and transgenerational effects.

Evaluation of wetland and tertiary wastewater treatments for estrogenicity using in vivo and in vitro assays

The effects of wetland wastewater treatment on estrogenic activity and estrogenic activity of water after tertiary treatment were evaluated using in vivo (rainbow trout vitellogenin [VTG] expression) and in vitro (yeast estrogen screening) assays. Juvenile rainbow trout exposed to tertiary-treated wastewater from the Green Acres Treatment Plant in Orange County Water District had increased plasma VTG levels compared with control fish. When trout were exposed to wastewater-dominated water before it entered into Prado Wetland (Riverside County, CA), VTG concentrations were increased above those of controls and were not significantly different from fish exposed to water exiting the wetland. VTG E2-equivalent concentrations (EEQs) of the water samples from the Green Acres Plant were 16.92 +/- 16.49 ng/L. Activity of water entering Prado Wetland was 29.80 +/- 28.41 ng/L EEQ, and water exiting was 24.34 +/- 23.17 ng/L EEQ. In vitro assays estimated that estrogenic activity of water from the Green Acres Plant was <1 ng/L EEQ, whereas water entering and exiting Prado Wetland had yeast estrogen screening EEQs of 2.57 and <1 ng/L, respectively. Our results suggest that environmental estrogens that are not potent estrogen-receptor ligands exist in wastewaters from the Green Acres Plant as well as water entering and exiting Prado Wetland. Wetland treatment did not remove environmental estrogens in the water. Our results also suggest that in vitro assays may underestimate estrogenic activity of sampled water.

Stir bar sorptive extraction and trace analysis of alkylphenols in water samples by thermal desorption with in tube silylation and gas chromatography–mass spectrometry

A novel method called thermal desorption (TD) with in tube silylation followed by gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of alkylphenols (APs) in river water samples, is described. APs are extracted from river water samples and concentrated by the stir bar sorptive extraction (SBSE) technique. The stir bar coated with polydimethylsiloxane (PDMS) is added to 2.0 ml water sample and stirring is carried out for 60 min at room temperature (25 degrees C) in the vial. Then, the PDMS stir bar is subjected to TD with in tube silylation followed by GC-MS. The detection limit is of the sub pg ml(-1) (ppt) level. The method shows good linearity and the correlation coefficients are higher than 0.99 for all analytes. The average recoveries of APs are higher than 90% (R.S.D.: 3.6-14.8%, n=6). This simple and sensitive analytical method may be used in the determination of trace amounts of APs in river water samples.

Long-term exposure to environmental concentrations of the pharmaceutical ethynylestradiol causes reproductive failure in fish

Heightened concern over endocrine-disrupting chemicals is driven by the hypothesis that they could reduce reproductive success and affect wildlife populations, but there is little evidence for this expectation. The pharmaceutical ethynylestradiol (EE2) is a potent endocrine modulator and is present in the aquatic environment at biologically active concentrations. To investigate impacts on reproductive success and mechanisms of disruption, we exposed breeding populations (n = 12) of zebrafish (Danio rerio) over multiple generations to environmentally relevant concentrations of EE2. Life-long exposure to 5 ng/L EE2 in the F1 generation caused a 56% reduction in fecundity and complete population failure with no fertilization. Conversely, the same level of exposure for up to 40 days in mature adults in the parental F0 generation had no impact on reproductive success. Infertility in the F1 generation after life-long exposure to 5 ng/L EE2 was due to disturbed sexual differentiation, with males having no functional testes and either undifferentiated or intersex gonads. These F1 males also showed a reduced vitellogenic response when compared with F0 males, indicating an acclimation to EE2 exposure. Depuration studies found only a partial recovery in reproductive capacity after 5 months. Significantly, even though the F1 males lacked functional testes, they showed male-pattern reproductive behavior, inducing the spawning act and competing with healthy males to disrupt fertilization. Endocrine disruption is therefore likely to affect breeding dynamics and reproductive success in group-spawning fish. Our findings raise major concerns about the population-level impacts for wildlife of long-term exposure to low concentrations of estrogenic endocrine disruptors.

Biacore biosensor immunoassay for 4-nonylphenols: assay optimization and applicability for shellfish analysis

A rapid Biacore biosensor immunoassay of 4-nonylphenols was developed. Two types of antibodies were used in the study: polyclonal antibodies with high cross-reactivity towards technical 4-nonylphenol and a monoclonal antibody very specific to 4-n-nonylphenol. 9-(p-Hydroxyphenyl)nonanoic acid was immobilized onto surface of a sensor chip. The best assay sensitivity was achieved using a flow rate of 50 microl min(-1) and injection time of 2 min. For the assay incorporating monoclonal antibodies a limit of detection 2 ng ml(-1) for 4-n-nonylphenol was achieved. With polyclonal antibodies one order lower sensitivity was observed for 4-nonylphenols. High background level of calibration curve for technical 4-nonylphenol was decreased by using IgG fraction of polyclonal antibodies in combination with lower amount of immobilised 9-(p-hydroxyphenyl)nonanoic acid. Sensitivity of the assay was improved by using a chip with a new derivative on a surface-N-aminobutyl [2-(4-hydroxyphenyl)ethylamine] (limit of detection--5 ng ml(-1)). Applicability of the developed assays to ecological monitoring was checked in experiments using shellfish samples. 4-n-Nonylphenol from spiked samples was extracted into hexane followed by clean-up on NH2 SPE columns. Calibration curves generated for cockles, mussels and oyster samples were identical (limit of detection about 10 ng g(-1)) whereas for scallop samples a slight decrease (about 5-10%) of absolute response was observed. In the assay using the monoclonal antibody specific to 4-n-nonylphenol 31 shellfish samples were found to be negative. Results obtained with polyclonal antibodies indicated that two scallop samples contained a quantity of 4-nonylphenols. The developed biosensor assay could be applied for shellfish analysis as a preliminary screening method.

Stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry for the measurement of 4-nonylphenol and 4-tert-octylphenol in human biological samples

Alkylphenols, 4-nonylphenol (NP) and 4-tert-octylphenol (OP), in human urine and plasma samples were analyzed using stir bar sorptive extraction (SBSE) in combination with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). The method involved correction by stable isotopically labeled surrogate standards, 4-(1-methyl)octylphenol-d5 (m-OP-d5) and deuterium 4-tert-octylphenol (OP-d). A biological sample was extracted for 60 min at room temperature (25 degrees C) using a stir bar coated with a 500 microm thick polydimethylsiloxane (PDMS) layer. Then, the stir bar was analyzed by TD-GC-MS in the selected ion monitoring (SIM) mode without any derivatization step. The average recoveries in human urine and plasma samples spiked with NP and OP at levels of 0.5 and 10 ng ml-1 were between 95.8 and 99.8% with correction using the added surrogate standards. The limits of quantitation were 0.2 ng ml-1 for NP and 0.02 ng ml-1 for OP. We measured the background levels of NP and OP in five human urine and three human plasma samples from healthy volunteers. NP and OP were not detected in all human urine samples (N.D. < 0.2 ng ml-1 for NP, and N.D. < 0.02 ng ml-1 for OP). However, 0.2-0.3 ng ml-1 for NP and 0.1-0.2 ng ml-1 for OP in human plasma samples were observed by this method.

Seasonal and spatial distribution of nonylphenol in Shihwa Lake, Korea

Alkylphenols (APs) have been known as endocrine disruptors and consequently received much environmental concern. This study focused on seasonal variation and spatial distribution of nonylphenol (NP) in various matrixes including dissolved water, particulates, surface sediment, sediment trap and sediment core taken from Shihwa Lake and its adjacent areas. A total of 11 phenolic compounds including nonylphenol, t-octylphenol (t-OP) and bisphenol A (BPA) were measured in February, June and October 2002. NP is the most abundant chemical among the phenolic compounds and its concentrations in dissolved water, particulates and surface sediments from Shihwa Lake were measured as 17.4-1533.1 ng/l, 4.3-831.2 ng/l and 10.4-5054.1 ng/g dw, respectively. NP concentration in dissolved water varied with seasons and generally showed a decreasing order of June > October > February, while the seasonal trend was hardly found in sediment. High levels of NP were measured in surrounding industrial complexes, the concentrations was decreased gradually with distance from the industrial areas. NP in core samples showed an increasing trend toward the core depth. There exists a reasonable correlation between NP in dissolved water and in particulates, whereas the correlation between NP in dissolved water and in sediments is not significant. APs concentrations in Shihwa Lake were comparable to other highly polluted areas of the world and their possible effects on various organisms in the lake are discussed.

Seasonal flux of nonylphenol in Han River, Korea

In order to understand the behavior of nonylphenol (NP) in Han River, water, suspended particle and sediment samples were analyzed during summer, autumn and winter. Concentrations of nonylphenol in water ranged from 23.2 to 187.6 ng/l, in suspended particle from 6.8 to 190.8 ng/l and in sediment from 25.4 to 932.0 ng/gdrywt. An increasing trend in the concentration is noticed in all matrices along down the river. In case of water and suspended particle, concentrations were higher in warmer season than in colder season. Percentage of nonylphenol in the suspended particle phase decreased from 67% to 28% with decreasing temperature in water. A reasonable correlation (R2 = 0.63) was obtained for water and suspended particle. The partition coefficient Log Kp is 4.8. No seasonal variation of the concentration in sediment is noticed in this study.

Differential gene expression analysis in fish exposed to endocrine disrupting compounds

This review discusses various methodologies that can be used to understand, at the gene level, the consequences to fish upon exposure to endocrine disrupting compounds (EDCs). Several approaches for measuring expression of gene transcripts are discussed, including directed approaches, such as Northern blotting and quantitative reverse transcriptase polymerase chain reaction (RT-PCR) as well as open-ended approaches, such as differential display RT-PCR, subtractive hybridizations, and gene arrays. Each of these systems has advantages and disadvantages, strengths and weaknesses. Conducting experiments with each of these methods provides important information about the molecular mechanisms that result from exposure to EDCs, information which can be used in risk assessment of polluted sites found in the environment.

Nonylphenol induces thymocyte apoptosis through Fas/FasL pathway by mimicking estrogen in vivo

Nonylphenol (NP) is the final biodegradation product of nonylphenol polyethoxylates, which are widely used surfactants in domestic and industrial products. Nonylphenol has been reported to have estrogenic activity and shown to have potential reproductive toxicity. However, its influence on immune system function remains unclear. In this study, we investigated the effects of nonylphenol on apoptosis and Fas/FasL gene expression in rat thymus. Nonylphenol were given orally by gavages at 125, 250, and 375mg/kg per day. Negative and positive controls were treated with the vehicle and E(2) 10ng/kg per day, respectively. Atrophy of thymus was determined by in situ morphological examination using hematoxylin and eosin staining. Apoptotic cells were identified by terminal deoxynucleotide transferase-mediated deoxy-UTP nick end labeling (TUNEL) assay. A semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method was used to analyze Fas and FasL mRNA levels. The results showed that both nonylphenol and E(2) increased the rates of apoptotic death; reduced the expression of Fas; enhanced the expression of FasL. These findings demonstrated that nonylphenol with estrogen-like activity might affect the regulation of the immune function through thymocyte apoptosis. This apoptosis was mediated by altering the expression of Fas and FasL mRNA.

Multihormonal control of vitellogenesis in lower vertebrates

The comparative approach on how and when vitellogenesis occurs in the diverse reproductive strategies displayed by aquatic and terrestrial lower vertebrates is presented in this chapter; moreover, attention has been paid to the multihormonal control of hepatic vitellogenin synthesis as it is related to seasonal changes and to vitellogenin use by growing oocytes. The hormonal mechanisms regulating vitellogenin synthesis are also considered, and the effects of environmental estrogens on the feminization process in wildlife and humans have been reported. It is then considered how fundamental nonmammalian models appear to be, for vitellogenesis research, addressed to clarifying the yolkless egg and the evolution of eutherian viviparity.