Environmental sciences : an international journal of environmental physiology and toxicology最新文献

A solid-phase extraction of ethynylestradiol (EE2) and its degradation intermediates and products by nitrifying activated sludge (NAS) was performed to measure estrogenic activity during the degradation by NAS. The yeast two-hybrid assay of the extract showed that NAS not only degraded EE2, but also removed the estrogenic activity originating from EE2, its degradation intermediates and products. This means that estrogenic activity decreases when EE2 concentrations are decreased by NAS. Although gas chromatography/mass spectrometer (GC/MS) analyses suggested the existence of nitrated EE2 as a degradation intermediate, its estrogenic activity was unmeasurable due to the lack of an authentic sample. However, on the basis of the dose-response relationship between EE2 concentration and estrogenic activity in the yeast two-hybrid assay, it was surmised that the estrogenic activity in the culture medium of NAS may have been produced mostly by the remaining EE2 and not by its degradation intermediates and products. The partial nucleotide sequence analyses of microorganisms in the consortiums acclimatized for EE2 and natural estrogens E2 and E1 enabled the identification of candidates that may be responsible for estrogen degradation by NAS.

Cytochrome P450 (CYP) genes, which make up a large gene superfamily, are known to play an important role in drug metabolism. The CYP1 family, one of the gene families of the CYP superfamily, has three subfamilies of genes whose sequences have been deposited in the GenBank/EMBL thus far: CYP1A, CYP1B, and CYP1C. Mammals as well as fish confront numerous foreign chemicals in the environment that may accumulate to toxic levels unless they are metabolized and eliminated by processes largely mediated by CYP enzymes. A new complementary DNA of the CYP1C subfamily encoding CYP1C2 was isolated from the carp liver after a single intraperitoneal injection of beta-napthoflavone (BNF). The full-length cDNA obtained contained a 5' noncoding region of 198 bp, an open reading frame of 1575 bp coding for 524 amino acids and a stop codon, and a 3' noncoding region of 531 bp. The predicted molecular weight of the protein was approximately 59.3 kDa. The amino acid sequence deduced from the carp CYP1C2 sequence showed a similarity of 76.6% with that deduced from our previously reported carp CYP1C1. It exhibited similarities of 77.3, 73.7, and 76.4% with those deduced from scup CYP1C2, scup CYP1C1, and Japanese eel CYP1C1 sequences, respectively. Carp CYP1C2 cDNA showed similarities with reported CYP1Bs of teleosts and mammals, namely, 47.6, 45.3, 45.7, 44.0, and 44.6% for carp, plaice, human, rat, and mouse CYP1B1s, respectively, while it exhibited a similarity of 49.0% with carp CYP1B2. The carp CYP1C2 sequence was aligned with the CYP1 sequences and has been deposited in the GenBank/EMBL data bank with the accession number AY437777. The phylogenetic tree constructed using fish and mammalian CYP1 sequences suggested a closer relationship of CYP1C with CYP1B than with CYP1A. The tree showed possibile existence of CYP1C subfamily genes in mammalian species. Northern blot analysis of the liver, intestines, kidneys, and gills revealed a distinct induced expression only in the kidneys, with no detectable constitutive expression in the other organs studied.

The presence of mercury in the environment is widespread and persistent, but the extent of exposure of Pakistanis to mercury is virtually unknown. We collected toenail and scalp hair samples from 158 subjects (83 males and 75 females) residing in Lahore and its suburbs. We also conducted a questionnaire survey and personal interviews to obtain information on demographic factors, lifestyles, and socioeconomic factors, among others. Mercury concentration in hair samples was measured by cold vapor atomic absorption spectrometry (CVAAS). In addition, the concentration of selenium in the toenail and hair samples was determined by inductively coupled plasma mass spectrometry (ICP-MS). The mean hair mercury concentration was 0.45 ppm (95% CI = 0.34-0.60) and did not show correlation with fish consumption, age, area of origin, or present residence. Mercury concentration was higher (p = 0.021) in females than in males, and was also higher in subjects with 11 or more years of education (p for trend = 0.013). There were 13 subjects with mercury concentration higher than 10 ppm. Most of them were young females and a few were middle-aged males. When the analysis was confined to subjects with mercury concentrations lower than 0.6 ppm, the amount of fish consumed showed correlation with hair mercury concentration with a marginal statistical significance (p = 0.065). The geometric means of selenium in hair and toenails were 0.87 and 1.01 ppm, respectively. Mercury and selenium concentrations in hair showed no correlation (correlation coefficient = 0.057, p = 0.478). This study shows that mercury exposure levels among residents in Lahore and its suburban areas are relatively low, except among outliers, wherein mercury exposure might be brought about by the use of mercury-containing soaps.

The toxicity of endocrine disrupters is involved in the activation of the aryl hydrocarbon receptor (AhR). We examined the toxicity of diesel exhaust particles (DEPs) using the Ah immunoassay (Ah-I) to study the inhibitory effects of various foods and polyphenols on DEP-induced AhR activation. The toxicity equivalent of DEP was 6,479 +/-58 ng dioxin toxicity equivalent/g (DEQ/g). The relationship between DEP dose and AhR activation was linear up to 27.8 microg/ml. Ginkgo biloba extract (GBE) had the strongest inhibitory effect on DEP-induced AhR activation. Quercetin, a major polyphenol in onions, and GBE showed a strong inhibitory effect. These results show that the DEP-induced AhR activation can be assessed using Ah-I and that the assay is suitable for determining the dioxin toxicity equivalent of DEP. In addition, Ah-I is also effective for screening food and its components that inhibit DEP-induced AhR activation.

The subacute toxicity of toluene-2,4-diamine (2,4-TDA) on marine fish was investigated in laboratory toxicity tests using red sea bream, Pagrus major. The fish were exposed to subacute concentrations of 2,4-TDA (measured concentrations: 0.0628, 0.234 and 0.878 mg/L) during the 14-day toxicity test and the effects on growth as well as on some biochemical parameters in the plasma, gills, liver and kidney structures were studied. The body weight and body length of the red sea bream exposed to the highest concentration were lower than those of the control. This study also showed a tendency towards decreases in three hematological parameters, i.e., the number of red blood cells, hemoglobin level and hematocrit, as well as blood chemical parameters in the plasma, i.e., the levels of total cholesterol, triglyceride, total protein and albumin, of fish exposed to the high concentrations. These findings were attributable to the reduced feeding of fish exposed to this concentration. In addition, cytoplasmic changes were observed in the cells of fish exposed to the highest concentration. It is suggested that the changes were caused by the decrease in feed efficiency derived from the exposure to 2,4-TDA.

Bundles of a strongly hydrophobic fibrous material (p-phenylene-2,6-benzobisoxazole; PBO; Zylon) were employed as an adsorbent for the removal of aqueous aromatic compounds, because the PBO fibers are too rigid to be woven and did not entrap suspended solids. The removal performance for nine kinds of polyaromatic hydrocarbons (PAHs) and di-(2-ethylhexyl) phthalate (DEHP) was evaluated. PAHs and DEHP at initial concentrations of 50 microg L(-1) were removed at 72.5-99.9% and ca. 95%, respectively, although the removal efficiencies were affected by the phase ratio (fiber weight/solution volume). The logarithm of the partition coefficient (log K) for planar PAHs was linearly correlated with the logarithm of the n-octanol/water partition coefficient (log P), but nonplanar PAHs, such as cis-stilbene, p-terphenyl, and o-terphenyl, showed significantly lower adsorption performance. The adsorbed PAHs were not desorbed effectively with CH3CN, CH2Cl2, and toluene. On the other hand, DEHP was effectively desorbed with methanol.

Steroids are essential for successful reproduction in all vertebrate species. Over the last several decades, extensive research has indicated that exposure to various environmental pollutants can disrupt steroidogenesis and steroid signaling. Although steroidogenesis is regulated by the hypothalamic-pituitary axis, it is also modified by various paracrine and autocrine factors. Furthermore, the classical two-cell model of steroidogenesis in the developing ovarian follicle, involving the granulosa and theca cells in mammals, may not be universal. Instead, birds and probably reptiles use the two thecal compartments (theca interna and theca externa) as sites of steroid production. We have documented that embryonic or juvenile exposure to a complex mixture of contaminants from agricultural and storm water runoff leads to altered steroid hormone profiles in American alligators. Our observations suggest that alterations in plasma steroid hormone concentrations are due in part to altered gene expression, modified hepatic biotransformation and altered gonadal steroidogenesis. Future studies must examine the interplay between endocrine and paracrine regulation in the development and expression of gonadal steroidogenesis in individuals exposed to endocrine disrupting contaminants at various life stages if we are to fully understand potential detrimental outcomes.

Winter plants regrow after freeze-thawing in acidic meltwater from the acid-snow layer in early winter or early spring. In this study, the responses of cold-acclimated wheat seedlings to different light conditions during the regrowth period after simulated acid snow (SAS) stress were investigated. After freeze-thawing in sulfuric acid (SAS stress) of pH 2.0, dry weight and the maximal quantum yield of photosystem II (PSII) decreased more in mature leaves than in young leaves. In a subsequent regrowth period under light condition, dry weight, relative water content, and the maximal quantum yield of PSII were severely affected in mature leaves but were only slightly affected in SAS (pH 2.0)-stressed young leaves. The levels of membrane lipid peroxidation and hydrogen peroxide in mature leaves of SAS (pH 2.0)-stressed seedlings were significantly higher than those in young leaves during the regrowth period under light condition. The superoxide dismutase activity in young leaves was higher than that in mature leaves during the regrowth period. These results indicate that mature leaves of seedlings during the snow melt season are more sensitive than young leaves to photooxidative stress because of their low acid snow stress tolerance and low capacity for the detoxification of superoxide.

The precursor protein of egg yolk, vitellogenin (Vg), is cleaved into three major components (lipovitellin, phosvitin and beta'-component) at the time of incorporation by growing oocytes. We purified three yolk proteins (YP1, YP2 and YP3) from ovaries of the common carp (Cyprinus carpio) by a combined method of ammonium sulfate precipitation and column chromatography. Biochemical analyses of the purified proteins of this species suggest that YP1, YP2 and YP3 are lipovitellin, beta'-component and phosvitin, respectively. A specific antiserum against purified carp YP1 (lipovitellin) was used to develop a single radial immunodiffusion (SRID) technique and an enzyme-linked immunosorbent assay (ELISA) for carp Vg. By SRID and ELISA, we measured the circulating carp Vg level to be in the ranges of 12.5-400 microg/ml and 2.0-1000 ng/ml, respectively, which cover a wide range of Vg levels. From 1997-1998, male and female carp were captured at points of effluent discharge from a sewage treatment plant connected to the Tama River, where estrogenic compounds were later detected, and the presence of Vg in their circulation was examined. Vg was detected in both male and female carp at the mg/ml level, suggesting that estrogens such as estrone and estradiol were sufficiently high to induce Vg in male carp inhabiting this area. The result of this study supports the use of carp Vg as a biomarker of fish exposure to environmental estrogens.

Butylparaben and benzylparaben, used as preservatives mainly in cosmetic products, have recently been shown to be weakly estrogenic. Batch sunlight photolysis and river water biodegradation experiments were conducted to determine the persistence of these compounds in aquatic environments. As a result, benzylparaben was found to be moderately photodegradable whereas both n-butylparaben and i-butylparaben were highly stable against sunlight. Both benzylparaben and butylparabens were relatively biodegradable in the river water but the degradability was dependent on the sampling site and time. Batch sorption experiments were also conducted to determine the coefficients of sorption into river sediments and a model soil sample. The determined coefficients were slightly higher for benzylparaben than the two butylparabens and comparable to that of the natural estrogen 17beta-estradiol. The coefficients were also higher for sediment/soil with a higher organic content and the organic-carbon-based sorption coefficient (log K oc) shows a moderate linear correlation with the octanol-water partition coefficient (log K ow). These results suggest that hydrophobic interaction plays a predominant role in sorption at neutral pH.