Abstract  The metabolism of di-n-butylphthalate by a denitrifying strain of Pseudomonas pseudoalcaligenes B20b1 was studied under anaerobic conditions, with nitrate as the only electron acceptor. Thin-layer chromatography and mass spectral analysis of culture extracts (20 days at 30 degrees C) showed mono-n-butylphthalate and phthalic acid as the only products, suggesting that one butanol moiety served essentially as the carbon source for growth and denitrification. N(2) and N(2)O were detected by gas chromatography. In contrast to aerobic metabolism, phthalate was not degraded further if nitrate was the only electron acceptor.

Abstract  Di-n-butyl phthalate (DBP) is one of the most widely used phthalic acid esters (PAEs), which have shown increasing environmental concerns worldwide. A bacterial strain designated as QH-11, was isolated from activated sludge and found to be capable of utilizing DBP as carbon and energy sources for growth. 16S rRNA and gyrb gene sequence analysis revealed that strain QH-11 was most closely related to Gordonia sp. Kinetics studies of DBP degradation by the strain QH-11 revealed that DBP depletion curves fit with the modified Gompertz model (R(2)>0.98). Meanwhile, substrate utilization tests showed that strain QH-11 could utilize other common PAEs and also the main intermediate product phthalic acid (PA). A gene encoding the large subunit of the phthalate dioxygenase, which is responsible for PA degradation, was successfully detected in strain QH-11. Furthermore, the results of reverse transcription quantitative PCR demonstrate that mRNA expression level of phthalate dioxygenase increased significantly after strain QH-11 was induced by DBP and PA.

Abstract  Classification of the relationship between electronic structures and biological activities of endocrine disruptors (so-called environmental hormones) was attempted using the parameters of absolute hardness (eta), absolute electronegativity (chi), and global softness (S), approximately defined as eta=1/2(epsilonLUMO-epsilonHOMO), chi=-1/2(epsilonHOMO+ epsilonLUMO), and S=1/eta, respectively, based on the hardness concept. The strength of binding affinity and toxicity of the chemicals were approximately proportional to the absolute hardness, and laterally toxic chlorinated PCDDs, PCBs, and DDTs are classified as chemically soft. Here we found that the electronic structures of environmental hormones can be classified into four main groups: 17beta-estradiol type (group I), testosterone type (group II), thyroxine type (group III), and HCH (hexachlorocyclohexane) type (group IV). Therefore, if we can predict the coordinate (chi, eta) of the electronic structure of one chemical on the eta-chi activity diagram, we would be able to predict the receptor with which the chemicals (environmental hormones) interact. For instance, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) is classified in group II, therefore, it would bind with the thyroid receptor more than the estrogen receptor (group I). It appears that dibutyl phthalate would not interact with estrogen receptor because it does not belong to group I. In addition, the coordinates of these four groups do not complementarily overlap with the electronic structures of 20 natural amino acid residues. The eta-chi activity diagram is a new tool for the prediction of the toxicity and biological activity of environmental hormones.

Abstract  To better understand the molecular mechanisms of the pleiotropic responses induced by exposure to peroxisome proliferator chemicals (PPCs), we conducted a systematic search for genes whose mRNA levels are modulated by the PPC WY-14,643 (WY) in rat liver. The sequence of one up-regulated cDNA (2480 bp) was predicted to encode a protein of 735 aa with 82% identity to the porcine 17 beta-hydroxysteroid dehydrogenase type IV (HSD IV). Like the porcine enzyme, the rat HSD IV contains' a region homologous to yeast hydratase-dehydrogenase-epimerases and to sterol carrier proteins, indicating that the rat HSD IV has broad substrate specificity and contributes to cholesterol metabolism. The rat HSD IV was regulated by diverse PPCs via two distinct mechanisms. Induction of HSD IV and acyl-CoA oxidase (ACO) proteins in rat liver at different treatment times and concentrations of gemfibrozil and di-n-butyl phthalate were almost identical, indicating that HSD IV mRNA induction involves the peroxisome proliferator-activated receptor alpha, a regulator of ACO. In contrast, HSD IV protein levels were only weakly induced by WY, a strong inducer of ACO protein, even though the levels of HSD IV and ACO mRNA were strongly stimulated by WY and gemfibrozil. Thus, HSD IV protein levels were uniquely regulated pretranslationally by WY via a novel mechanism. Increased conversion of estradiol to the less-active estrone by HSD IV induction may explain how phthalate exposure leads to decreases in serum estradiol levels and suppression of ovulation.

Abstract  A laboratory-scale anaerobic-anoxic-oxic (AAO) system was established to investigate the fate of DnBP. A removal kinetic model including sorption and biodegradation was formulated, and kinetic parameters were evaluated with batch experiments under anaerobic, anoxic, oxic conditions. However, it is highly complex and is difficult to confirm the kinetic parameters using conventional mathematical modeling. To correlate the experimental data with available models or some modified empirical equations, an artificial neural network model based on multilayered partial recurrent back propagation (BP) algorithm was applied for the biodegradation of DnBP from the water quality characteristic parameters. Compared to the kinetic model, the performance of the network for modeling DnBP is found to be more impressive. The results showed that the biggest relative error of BP network prediction model was 9.95%, while the kinetic model was 14.52%, which illustrates BP model predicting effluent DnBP more accurately than kinetic model forecasting.

Abstract  Monolithic matrix-type transdermal drug delivery systems for carvedilol were prepared using a film casting technique involving hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), Eudragit RS 100 (ERS 100), and Eudragit RL 100 (ERL 100) as matrix-forming polymers. The prepared transdermal drug delivery systems were extensively evaluated for in vitro release, ex vivo permeation through rat abdominal skin, moisture absorption, moisture content, water vapor transmission, stability, and mechanical properties. Formulations F2, F3, and F5 were composed of a 4:1 ratio of HPMC, ERS 100; HPMC, HPC; and HPMC, ERL 100, respectively, whereas F4, F6, and F7 were composed of 3:0.5:0.5 of HPMC, ERS 100, HPC; HPMC, HPC, ERL 100; and HPMC, ERS 100, ERL 100. Formulation F1 was composed of HPMC polymer. All formulations carried 8% v/w of d-limonene as a penetration enhancer and 20% v/w of dibutylphthalate as a plasticizer. The physicochemical interaction between carvedilol and polymers were investigated by Fourier transform infrared spectroscopy and differential scanning calorimetry. Formulation F5 showed both maximum drug release (12.31 mg) and permeation (2987.67 microg/cm2) in 24 h, which differed significantly (P < 0.05) among all the formulations. Formulation F5 showed maximum flux (32.80 microg/h/cm2), which meets the flux requirements, and differed significantly (P < 0.05) among all the formulations with a permeation coefficient of 0.82 x 10(-2) cm/h. Fourier transform infrared spectroscopy and differential scanning calorimetry studies showed no evidence of interaction between the drug and polymers. The formulations mechanical properties, tensile strength and elastic modulus (5.89 kg/cm2 for formulation F5) reveal that they are strong but not brittle. A shelf life of 2 years was predicted for the transdermal drug delivery systems. Carvedilol monolithic matrix-type transdermal therapeutic systems could be prepared having both the required flux and suitable mechanical properties.

Abstract  OBJECTIVE: This study examined temporary restorative resins that use non-phthalate ester plasticizers.

METHODS: Three non-phthalate plasticizers were tested: tri-ethyl citrate (TEC), tri-butyl citrate (TBC), and di-butyl sebacate (DBS). The experimental resins were compared with resins that use a phthalate ester plasticizer (di-butyl phthalate, DBP) and commercial products (Dura Seal, Plast Seal, and Fit Seal). For the experimental resins, the ratio of plasticizer to PMMA/MMA resin was varied from 30 to 60% (wt). The mechanical properties of the experimental resins were evaluated using a modified diametral compressive strength and the resistance to explorer insertion.

RESULTS: The strengths of the experimental resins with plasticizer concentrations ranging from 40 to 50% (TEC, TBC, and DBP) or from 30 to 40% (DBS), by weight, were equivalent to the strengths of commercial temporary restorative resins. A similar tendency was seen for the resistance to explorer insertion.

CONCLUSIONS: The results suggest that new temporary restorative resins can be prepared by choosing the appropriate proportions of resin monomer and non-phthalate ester plasticizer.

Abstract  Simultaneous photocatalytic reduction of chromium(VI) to the less toxic Cr(III) and degradation of di-n-butyl phthalate (DBP) in aqueous TiO2, suspension under ultraviolet light irradiation was investigated. The batch experiments were carried out in a photoreactor equipped with 350 nm lamps. The system containing Cr(VI) and DBP showed the synergistic photocatalytic decontamination as DBP facilitated Cr(VI) reduction, whereas Cr(VI) accelerated DBP degradation. This study demonstrated for the first time that two important environmental pollutants Cr(VI) and DBP could be eliminated simultaneously using UV/TiO2 process. The intermediate products of DBP degradation were identified by gas chromatography-mass spectrometry, and the reaction mechanism was proposed.

Abstract  The construction and performance of plastic membrane (PME) oxytetracycline hydrochloride (OTC)-selective electrodes, based on three types of ion-pairs, OTC-tetraphenylborate (TPB), OTC-phosphotungstate (PT) and OTC-silicotungstate (SiT), as the electroactive substance in a plasticized PVC membrane with dibutylphthalate (DBP), were described. Furthermore, internal solid contact sensors (ISCS) OTC-selective sensors, based on a conducting polypyrrole (PPy) film immobilized on a platinum or glassy carbon electrode surface casted by a plasticized PVC membrane were constructed and evaluated. A novel optimization methodology in a numerical expression, comprehensive quality index (CQI) for a sensor, was used to optimize the composition of the membrane in the preparation of PME and screen the parameter of electropolymerization in the preparation of ISCS. Several PMEs and ISCSs were fully characterized and evaluated. An ISCS (Pt/PPy/PVC (OTC-TPB)) showed an excellent Nernstian response over the linear concentration range of 4.0 x 10(-7)-5.0 x 10(-2) M with the slope of 60.6 mV per decade (at 25 degrees C). The limit of detection was 1.0 x 10(-7) M of OTC (0.03 ppm). The response time was <25 s. The sensor was successfully used for the analysis of OTC in pharmaceutical formulation by using direct potentiometry.