Efficiency and plant indication of nitrogen and phosphorus removal in constructed wetlands: A field-scale study in a frost-free area.

Frost-free areas have suitable climate for wetland plant growth and constructed wetlands (CW) technology. Information on the quantification of plant biomass and uptake efficiency in field-scale CWs is limited in these climates. The removal efficiency of total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), and total suspended solids (TSS) in wastewater from sewage plants, domestic sewage, and an industrial park in 15 rural and urban CWs in Guangdong Province, China, with an average temperature of 30 °C was evaluated. The effects of influent concentration, hydraulic load, the wastewater's physicochemical properties, operating conditions, and plant uptake were analysed. The mean removal rates were 40.0%, 45.2%, 41.1%, and 71.7% for TN, TP, COD, and TSS, respectively, which were higher than the removal load of the field-scale CWs in temperate regions. Removal loads of TN, TP, COD, and TSS were highest in CWs that have been operating for 5-6 years, treating wastewater volumes of over 1 m3/m2·d. The removal efficiency was mainly related to the inflow concentration and less affected by the type of CWs. Nutrient accumulation trends were primarily linked to influent concentrations (TN: r2 = 0.89, P = 0.007; TP: r2 = 0.96, P = 0.001) and plant biomass (TN: r2 = 0.96, P = 0.001; TP: r2 = 0.92, P = 0.004). Plant biomass contributed 2%-29% and 2%-70%, respectively, to removing N and P in CWs. The average uptake concentration of N and P in aboveground plant organs (15.66 ± 4.44 mg N/g, 2.15 ± 1.18 mg P/g) was generally higher than that of other temperate plants. A strong relationship between TN and TP in the biomass was also observed; however, the relationship is only restricted by the influent TP concentration. Arundo donax is well-adapted for nutrient accumulation and adaptation and is an ideal wetland plant to purify wastewater in frost-free climates.

Induction of cyp3a in primary cultures of human hepatocytes by ginkgolides a and B.

1. The present study was designed to determine the effects of ginkgolide A, ginkgolide B and quercetin on CYP3A protein expression and enzyme activity in primary cultures of human hepatocytes. 2. Hepatocytes were pretreated with ginkgolide A, ginkgolide B and quercetin (at 1, 3, 10 and 30 micromol/L) for 48 h and then exposed to testosterone (250 micromol/L) for 30 min. Rifampin (10 micromol/L) and phenobarbital (2 mmol/L) were used as positive controls. The CYP3A activity was measured by the amount of 6beta-hydroxytestosterone in the culture medium and CYP3A protein in hepatocyte lysate was semiquantified by immunoblotting. 3. Compared with the vehicle control, ginkgolides A and B, at 30 micromol/L, significantly induced CYP3A protein expression (2.1- and 2-fold, respectively; both P < 0.01) and markedly induced CYP3A-mediated testosterone 6beta-hydroxylation (2.5-fold each; P < 0.05 for ginkgolide A; P > 0.05 for ginkgolide B). Quercetin had no apparent induction. 4. Ginkgolide A and ginkgolide B can induce CYP3A protein expression and enzyme activity in primary cultures of human hepatocytes at higher doses.

Induction and inhibition of cytochromes P450 by the St. John's wort constituent hyperforin in human hepatocyte cultures.

St. John's wort extract (SJW) (Hypericum perforatum L.) is among the most commonly used herbal medications in the United States. The predominance of clinical reports indicates that SJW increases the activity of cytochrome P450 3A4 (CYP3A4) enzyme and reduces plasma concentrations of certain drugs. Although the inductive effect of SJW on CYP3A4 is clear, other reports indicate that SJW constituents may have, to a small degree, some enzyme inhibitory effects. Therefore, we sought to study the induction and inhibition effects of the constituents of SJW on CYP3A4 in the human hepatocyte model. Moreover, most research has focused on the induction of CYP3A4 by SJW with little attention paid to other prominent drug-metabolizing enzymes such as CYP1A2, CYP2C9, and CYP2D6. To examine the effects of SJW on CYP1A2, CYP2C9, CYP2D6, as well as CYP3A4, hepatocytes were exposed to hyperforin and hypericin, the primary constituents of SJW extract. Hepatocytes treated with hypericin or hyperforin were exposed to probe substrates to determine enzyme activity and protein and RNA harvested. Hyperforin treatment resulted in significant increases in mRNA, protein, and activity of CYP3A4 and CYP2C9, but had no effect on CYP1A2 or CYP2D6. Acute administration of hyperforin at 5 and 10 microM 1 h before and along with probe substrate inhibited CYP3A4 activity. Hypericin had no effect on any of the enzymes tested. These results demonstrate that with chronic exposure, the inductive effect of SJW on drug-metabolizing enzymes predominates, and human hepatocyte cultures are a versatile in vitro tool for screening the effect of herbal products on cytochrome P450 enzymes.

Evaluation of hepatotoxic potential of drugs by inhibition of bile-acid transport in cultured primary human hepatocytes and intact rats.

Inhibition of canalicular bile acid efflux by medications is associated with clinical liver toxicity, sometimes in the absence of major liver effects in experimental species. To predict the hepatotoxic potential of compounds in vitro and in vivo, we investigated the effect of clinical cholestatic agents on [3H]taurocholic acid transport in regular and collagen-sandwich cultured human hepatocytes. Hepatocytes established a well-developed canalicular network with bile acid accumulating in the canalicular lumen within 15 min of addition to cells. Removing Ca2+ and Mg2+ from the incubation buffer destroyed canalicular junctions, resulting in bile acid efflux into the incubation buffer. Canalicular transport was calculated based on the difference between the amount of bile acid effluxed into the Ca/Mg2+-free and regular buffers with linear efflux up to 10 min. Hepatocytes cultured in the nonsandwich configuration also transported taurocholic acid, but at 50% the rate in sandwiched cultures. Cyclosporin A, bosentan, CI-1034, glyburide, erythromycin estolate, and troleandomycin inhibited efflux in a concentration-dependent manner. In contrast, new generation macrolide antibiotics with lower incidence of clinical hepatotoxicity were much less potent inhibitors of efflux. An in vivo study was conducted whereby glyburide or CI-1034, administered iv to male rats, produced a 2.4-fold increase in rat total serum bile acids. A synergistic 6.8-fold increase in serum total bile acids was found when both drugs were delivered together. These results provide methods to evaluate inhibitory effects of potentially cholestatic compounds on bile-acid transport, and to rank compounds according to their hepatotoxic potential.