PAH exposure in a Ghanaian population at high risk for aflatoxicosis.

It was postulated that a population in sub-Saharan Africa, known to be at high risk for aflatoxicosis due to frequent ingestion of aflatoxin (AF)-contaminated foods could also be exposed to polycyclic aromatic hydrocarbons (PAHs) from a variety of environmental sources. Previously, participants in this population were shown to be highly exposed to AFs, and this exposure was significantly reduced by intervention with NovaSil clay (NS). Objectives of this study were 1) to assess PAH exposure in participants from the AF study using urinary biomarker 1-hydroxypyrene (1-OHP); 2) examine the effect of NS clay and placebo (cellulose) treatment on 1-OHP levels; and 3) determine potential association(s) between AF and PAH exposures. A clinical trial was conducted in 177 Ghanaians who received either NS capsules as high dose or low dose, or placebo (cellulose) for a period of 3 months. At the start and end of the study, urine samples were analyzed for 1-OHP. Of the 279 total samples, 98.9% had detectable levels of 1-OHP. Median 1-OHP excretion in nonsmokers was 0.64 micromol/mol creatinine at baseline and 0.69 micromol/mol creatinine after 3 months. Samples collected at both time points did not show significant differences between placebo and NS-treated groups. There was no linear correlation between 1-OHP and AF-albumin adduct levels. Results show that this population is highly exposed to PAHs (and AFs), that NS and cellulose treatment had no statistically significant effect on 1-OHP levels, and that this urinary biomarker was not linearly related with AF exposure.

Molecular characterization of two superoxide dismutases from Hydra vulgaris.

Apparent full-length cDNA sequences coding for manganese superoxide dismutase (HvMnSOD) and extracellular superoxide dismutase (HvEC-SOD) were isolated from Hydra vulgaris in order to understand their expression and 3D structures; and explore their possibility of being used as for biomarkers for environmental stress and toxicity. The deduced HvMnSOD protein consists of 219 amino acids of which first 21 amino acids constitute a presumed mitochondria-targeting signal peptide whereas HvEC-SOD protein consists of 189 amino acids of which first 19 amino acids constitute a presumed signal peptide. Molecular model generated for HvMnSOD displayed the N-terminal long alpha antiparallel hairpin and the C-terminal mixed alpha/beta fold characteristic of MnSODs and that for HvEC-SOD displayed the characteristic CuZnSOD â-barrel fold. Hydrae subjected to thermal, starvation, metal and oxidative stress responded by regulating MnSOD and EC-SOD mRNA transcription. These results indicated that these genes are involved in the cellular stress response and (anti)oxidative processes triggered by stressor and contaminant exposure. Hence the expression of these SODs in hydra may have potential as molecular biomarkers for assessing stress, toxicity and pro-oxidant quality of chemicals and aquatic environmental quality.

Molecular characterization of phospholipid hydroperoxide glutathione peroxidases from Hydra vulgaris.

Apparent full-length cDNA sequences coding respectively for mitochondrial (HvGPx41) and nuclear (HvGPx42) phospholipid hydroperoxide glutathione peroxidase were isolated from Hydra vulgaris. The cDNA sequences share total identity in their 3'-end and differ in their 5'-end. The protein-coding regions of the HvGPx41 and HvGPx42 cDNA encode polypeptides of 190 and 168 amino acids, including a TGA-encoded selenocysteine, respectively. Phylogenetic analysis showed that the HvGPx41 and HvGPx42 are clustered together along with other phospholipid hydroperoxide glutathione peroxidases (PHGPx) from several organisms. A tertiary structure model generated for the H. vulgaris PHGPx displayed the thioredoxin fold. Hydrae exposed to starvation, metal and oxidative stress responded by regulating their PHGPx mRNA transcription. These results indicated that the PHGPx gene is affected by the cellular stress response and (anti)oxidative processes triggered by stressor and contaminant exposure. Hence the expression of PHGPx mRNA in hydra may have potential use as molecular biomarkers for assessing stress, toxicity and pro-oxidant quality of chemicals and aquatic environmental quality.

Prevention of zearalenone-induced hyperestrogenism in prepubertal mice.

Previous methods for the control of zearalenone (ZEN)-induced hyperestrogenism in animals have proven largely ineffective. The main objective in this study was to identify an enterosorbent that decreases the dietary bioavailability, and subsequent estrogenic effects, of ZEN. Initial in vitro screenings in aqueous solution (4 microg ZEN/ml) indicated that an activated carbon (AC) was the most efficient sorbent (99%), followed by a combination of 2 parts AC plus 3 parts HEC (hectorite) (69%), cetylpyridinium-exchanged low-pH montmorillonite (CP-LPHM) clay (58%), hexadecyltrimethylammonium-exchanged low-pH montmorillonite (HDTMA-LPHM) clay (54%), and HEC alone (28%). Results from the adult hydra bioassay suggested that the addition of either AC or HEC effectively decreased the effects of ZEN on Hydra attenuata without toxicity, as was observed with the use of either CP-LPHM or HDTMA-LPHM. Based on these results, AC, HEC, and 2AC:3HEC were evaluated in prepubertal mice. At a dietary inclusion level of 0.8% (w/w), AC alone significantly protected mice against the estrogenic effects induced by 35 mg ZEN/kg feed. Inclusion of 1.2% HEC with the 0.8% AC showed no additional protection; whereas 1.2% HEC alone failed to decrease the estrogenic effects. Ground flaxseed (25% w/w) in the diet also elicited protection, but to a lesser extent. Preliminary studies suggested that three similar carbons failed to decrease ZEN bioavailability. These findings suggest that the AC used in this study may be efficacious as an enterosorbent in animals consuming ZEN-contaminated diets. However, further studies are needed to evaluate the binding specificity, as well as the safety of chronic exposure.

Matrix-immobilized organoclay for the sorption of polycyclic aromatic hydrocarbons and pentachlorophenol from groundwater.

Sorbent materials consisting of organoclay immobilized onto the surface of a solid support were evaluated for use in pentachlorophenol (PCP) and polycyclic aromatic hydrocarbon (PAH) remediation of groundwater at a creosote-contaminated Superfund site. Cetylpyridinium-exchanged low pH montmorillonite clay (CP-LPHM) was bonded to either sand (CP-LPHM/sand) or granular activated carbon (GAC) (CP-LPHM/GAC) using the free acid form of carboxymethylcellulose as an adhesive. Effluent from an oil-water separator was eluted through equal bed volumes of composite (4 g 3:2 CP-LPHM/GAC or 13 g CP-LPHM/sand), affinity-extracted, and quantitatively analyzed by GC/MS. PCP, naphthalene, fluorene, phenanthrene, pyrene, and total PAHs were initially reduced by both CP-LPHM/GAC (> or =99%, 61%, 99%, > or =99%, 97%, and 94%, respectively) and CP-LPHM/sand (90%, 70%, 94%, 95%, 93%, and 86%, respectively). Complete breakthrough of naphthalene occurred after approximately 15 h of elution through 3:2 CP-LPHM/GAC and 22 h through CP-LPHM/sand. PCP showed complete breakthrough following 18 h of elution through 3:2 CP-LPHM/GAC and 26 h through CP-LPHM/sand. However, 50% breakthrough was not attained for higher molecular weight PAHs, as fluoranthene, pyrene, benzo[a]anthracene, and chrysene continued to be greatly reduced with both 3:2 CP-LPHM/GAC (98%, 95%, 94%, and 95%, respectively) and CP-LPHM/sand (75%, 73%, 76%, and 78%, respectively) after 48 h of continuous elution. Results confirm prior studies, indicating that these organoclay-containing composites have a high capacity for contaminants found in wood preserving waste. Further, results suggest that the inclusion of CP-LPHM may be useful as part of an effective strategy for groundwater remediation of high concentrations of PCP and PAHs, in particular high molecular weight and carcinogenic PAHs.

Biodegradation of simple chemical mixtures in soil.

Exogenous microorganisms often are used to enhance bioremediation. This study compared the capabilities of two exogenous microbial cultures and an indigenous population to detoxify a Weswood silt loam soil amended with a simple chemical mixture. The first three treatments were unamended soils inoculated with either indigenous microorganisms, Pseudomonas aeruginosa, or Phanerochaete sordida. Three additional treatments consisted of soil amended with benzo[a]pyrene, pentachlorophenol, and 2,4,6-trinitrotoluene, which were inoculated with either indigenous microorganisms, P. aeruginosa, or P. sordida. Samples were collected from the soils at several time points from 0 through 540 or 720 d, sequentially extracted with methylene chloride and methanol, and analyzed for genotoxicity (using the Salmonella/microsome assay) and chemical degradation. Although the indigenous microorganisms were effective for removal of benzo[a]pyrene, the Pseudomonas bacteria exhibited slightly greater removal rates for 2,4,6,-trinitrotoluene. The fungal cultures were significantly more effective at degrading pentachlorophenol. The day 540 extracts from all model chemical-amended treatments were genotoxic. In most cases, the day 540 extracts were more genotoxic than the day 0 extracts. The results suggest that, under appropriate conditions, enriched cultures of microorganisms may have an increased capacity to degrade individual chemicals. However, the products of degradation in some cases might be more genotoxic than the parent compounds.

Toxicological evaluation and metal bioavailability in pregnant rats following exposure to clay minerals in the diet.

Silicate clays are frequently added to animal feeds to bind and reduce the bioavailability of mycotoxins in the gastrointestinal tract. However, the bioavailability of trace metals in these clay feed additives has not been thoroughly investigated. Clays that act nonselectively may interact with nutrients, minerals, and other feedborne chemicals to pose significant hidden risks. In this study, a calcium montmorillonite clay (Novasil Plus, NSP) commonly used as an enterosorbent for aflatoxins and a sodium montmorillonite clay (Swy-2) (Source Clay Minerals Repository, Columbia, MO) were examined. Clays were supplemented in the balanced diet of Sprague-Dawley rats during pregnancy at a level of 2% (w/w). Evaluations of toxicity were performed on gestation d 16 and included maternal body weights, maternal feed intakes, litter weights, and embryonic resorptions. Liver, kidneys, tibia, brain, uterus, pooled placentas, and pooled embryonic mass were collected and weighed. Tissues were lyophilized and neutron activation analysis (NAA) was performed. Elements considered by NAA included Al, Ba, Br, Ca, Ce, Co, Cr, Cs, Cu, Dy, Eu, Fe, Hf, K, La, Lu, Mg, Mn, Na, Nd, Ni, Rb, S, Sb, Sc, Se, Sm, Sr, Ta, Tb, Te, Th, Ti, Tl, U, V, Yb, Zn, and Zr. Inductively coupled plasma-mass spectroscopy further confirmed that Al was below detection limits (<0.5 ppm) in the brain. Animals supplemented with either NSP or Swy-2 were similar to controls with respect to toxicity evaluations and metal analysis, with the exception of decreased brain Rb following clay supplementation. Overall, the results of this study suggest that neither NSP nor Swy-2, at relatively high dietary concentrations, influences mineral uptake or utilization in the pregnant rat.

Clay-based affinity probes for selective cleanup and determination of aflatoxin B1 using nanostructured montmorillonite on quartz.

A study was conducted to investigate the selective cleanup and determination of aflatoxin B1 (AfB1) from contaminated media. Composite adsorbents were formulated from calcium montmorillonite clay, which possesses a high affinity and enthalpy of adsorption for AfB1. Nanostructuring techniques were used to construct various formulations of the clay-based composite media. In AfB1 adsorption studies with prototypical affinity columns, these composites offered narrowly defined, reproducible capacity ranges. Composite recoveries of AfB1 from spiked grains exhibited linear trends that correlated well with the range of spike levels. Composite columns provided lower recoveries of AfB1 from naturally contaminated corn than did immunoaffinity columns; however, recoveries were consistent and purified extracts were free of interfering compounds, as determined by liquid chromatography with fluorescence detection.

Chronic toxicological evaluation of dietary NovaSil clay in Sprague-Dawley rats.

NovaSil (NS) clay, a common anti-caking agent in animal feeds, has been shown to sorb aflatoxins in the GI tract and diminish their bioavailability and adverse effects in short-term animal studies. Based on this evidence, it is hypothesized that clay-based enterosorption of aflatoxins may be a useful strategy for the prevention of aflatoxicosis in human populations. However, the potential toxicity of long-term dietary exposure to NS has not been determined. In this research, 5-6-week-old male and female Sprague-Dawley rats were fed rations containing 0, 0.25, 0.5, 1.0, or 2.0% (w/w) levels of NS for 28 weeks. Analysis of the NS showed negligible levels of dioxin and furan contaminants. Total feed consumption, cumulative feed consumption, body weight, total body weight gain, feed conversion efficiency, cumulative feed conversion efficiency, and relative organ weights were unaffected in either sex at the doses tested. No NS-dependent differences in relative organ weights or gross or histopathological changes were observed. Analysis of hematological parameters, clinical chemistry, and selected vitamin and mineral levels revealed isolated significant differences between some treatments and control groups (mean corpuscular hemoglobin, serum Ca, serum vitamin A, and serum Fe). However, the differences observed in each case were not dose-dependent. These results suggest that dietary inclusion of NS at levels as high as 2.0% (w/w) does not result in overt toxicity. These findings (as well as others) support the use of NS clay for dietary intervention studies in human populations at high risk for aflatoxicosis.

Organophosphate nerve agent toxicity in Hydra attenuata.

The toxicity for analogues of sarin (GB), soman (GD), and VX was evaluated using Hydra attenuata as a model organism. The organophosphate nerve agent analogue simulants used in this investigation included the following: isopropyl p-nitrophenyl methylphosphonate (for GB); pinacolyl p-nitrophenyl methylphosphonate (for GD); and diisopropyl S-(2-diisopropylaminoethyl)phosphorothioate, diethyl S-(2-diisopropylaminoethyl)phosphorothioate, and diethyl S-(2-trimethylaminoethyl)phosphorothioate (for VX). The toxicity of each organophosphate nerve agent was assessed quantitatively by measuring the minimal effective concentration within 92 h in H. attenuata. There is a positive correlation between the molecular hydrophobicity of the compound and its ability to cause toxicity. Results from this study indicate the potential for application of this assay in the field of organophosphate chemical warfare agent detection, as well as for the prediction of toxicity of structurally similar organophosphate compounds. The minimal effective concentration for two of the VX analogues was 2 orders of magnitude more toxic than the analogue for GD and 4 orders of magnitude more toxic than the analogue for GB.