During the past several years, concern has risen over potential pollution of waterways with estrogenic compounds, including steroidal hormones from human and animal sources. One potential source of steroid hormone contamination is through the incomplete removal of these compounds in wastewater treatment systems (WTS). To address this issue, laboratory mineralization assays using 14C-labeled estrogens and testosterone were performed with biosolids from four municipal treatment plants and one industrial system. The importance of adapted microbial populations in the removal of estrogen was shown by the dramatic differences in mineralization of 14C-17β-estradiol by biosolids from a municipal plant compared to that from the industrial plant, 84% versus 4%, respectively. Indeed, biosolids from all of the municipal plants mineralized 70−80% of added 14C-17β-estradiol to 14CO2 in 24 h. Removal of 14C-17β-estradiol from the aqueous phase by biodegradation and/or biosorption to cell matter was greater than 90%. A recombinant yeast estrogen assay (YES assay) also confirmed that biological estrogenic activity was removed from the biosolid samples to below the detection limit (1.56 nM). 14C-Testosterone was mineralized to 14CO2 in all four municipal biosolids in amounts ranging from 55% to 65%; moreover, total removal of 14C-testosterone from the aqueous phase was 95%. First-order rate constants k were obtained for the mineralization and removal from the aqueous phase of natural and a synthetic steroid hormone in biosolids from one WTP. In these biosolids, 14C-17β-estradiol and 14C-testosterone were rapidly mineralized to 14C-CO2 (k = 0.0042 ±0.0002 min-1 and 0.0152 ± 0.0021 min-1, respectively), whereas the mineralization of the synthetic estrogen 14C-17α-ethinylestradiol was 25−75-fold less (k = 0.0002 ± 0.0000 min-1). In addition, mineralization of 14C-ethinylestradiol did not reach completion in 24 h with only 40% mineralized to 14C-CO2. Approximately 20% of the 14C-ethinylestradiol remained in the aqueous phase and was biologically active as determined by the YES assay. Changes in temperature of approximately 15 °C had a statistically significant effect on the rate of mineralization and removal of 14C-17β-estradiol from the aqueous phase but not for 14C-testosterone or 14C-17α-ethinylestradiol. These results suggest that biosolids in municipal plants in this region have the capability to remove natural steroid hormones in their influents over a range of temperatures but may be less effective at removing the synthetic estrogen 17α-ethinylestradiol.

Toxicity data for the 50% growth inhibitory concentration against Tetrahymena pyriformis (log (IGC50-1)) for 42 alkyl- and halogen-substituted nitro- and dinitrobenzenes were obtained experimentally. Log (IGC50-1) along with the hydrophobicity, the logarithm of the 1-octanol/water partition coefficient (log Kow), and the molecular orbital properties, the lowest unoccupied molecular orbital energy (Elumo) and maximum acceptor superdelocalizability (Amax), were used to develop quantitative structure-activity relationships (QSARs). All the nitroaromatic compounds tested had toxicity in excess of baseline, nonpolar narcosis. The nitrobenzenes were thought to elicit their toxic response through multiple (and mixed) mechanisms. No high-quality relationship was observed between toxicity and hydrophobicity, or Elumo, individually. However, a strong relationship ¿log (IGC50-1) = 16.4(Amax) - 4.64; n = 42, r2 = 0.847, s = 0.279, F = 229¿ was obtained. In an effort to improve predictability, two-parameter QSAR, or response surface, analyses were performed. These analyses resulted in the following QSARs: ¿log (IGC50-1) = 0.206(log Kow) - 16.0(Amax) - 5.04; n = 42, r2 = 0.897, s = 0.229, F = 180¿ and ¿log (IGC50-1) = 0.467(log Kow) - 1.60(Elumo) - 2.55; n = 42, r2 = 0.881, s = 0.246, F = 154¿.

Nanoelectroporation of biomembranes is an effect of high-voltage, nanosecond-duration electric pulses (nsEP). It occurs both in the plasma membrane and inside the cell, and nanoporated membranes are distinguished by ion-selective and potential-sensitive permeability. Here we report a novel phenomenon of bioeffects cancellation that puts nsEP cardinally apart from the conventional electroporation and electrostimulation by milli- and microsecond pulses. We compared the effects of 60- and 300-ns monopolar, nearly rectangular nsEP on intracellular Ca2+ mobilization and cell survival with those of bipolar 60 + 60 and 300 + 300 ns pulses. For diverse endpoints, exposure conditions, pulse numbers (1–60), and amplitudes (15–60 kV/cm), the addition of the second phase cancelled the effects of the first phase. The overall effect of bipolar pulses was profoundly reduced, despite delivering twofold more energy. Cancellation also took place when two phases were separated into two independent nsEP of opposite polarities; it gradually tapered out as the interval between two nsEP increased, but was still present even at a 10-μs interval. The phenomenon of cancellation is unique for nsEP and has not been predicted by the equivalent circuit, transport lattice, and molecular dynamics models of electroporation. The existing paradigms of membrane permeabilization by nsEP will need to be modified. Here we discuss the possible involvement of the assisted membrane discharge, two-step oxidation of membrane phospholipids, and reverse transmembrane ion transport mechanisms. Cancellation impacts nsEP applications in cancer therapy, electrostimulation, and biotechnology, and provides new insights into effects of more complex waveforms, including pulsed electromagnetic emissions.

High-amplitude electric pulses of nanosecond duration, also known as nanosecond pulsed electric field (nsPEF), are a novel modality with promising applications for cell stimulation and tissue ablation. However, key mechanisms responsible for the cytotoxicity of nsPEF have not been established. We show that the principal cause of cell death induced by 60- or 300-ns pulses in U937 cells is the loss of the plasma membrane integrity (“nanoelectroporation”), leading to water uptake, cell swelling, and eventual membrane rupture. Most of this early necrotic death occurs within 1–2 hr after nsPEF exposure. The uptake of water is driven by the presence of pore-impermeable solutes inside the cell, and can be counterbalanced by the presence of a pore-impermeable solute such as sucrose in the medium. Sucrose blocks swelling and prevents the early necrotic death; however the long-term cell survival (24 and 48 hr) does not significantly change. Cells protected with sucrose demonstrate higher incidence of the delayed death (6–24 hr post nsPEF). These cells are more often positive for the uptake of an early apoptotic marker dye YO-PRO-1 while remaining impermeable to propidium iodide. Instead of swelling, these cells often develop apoptotic fragmentation of the cytoplasm. Caspase 3/7 activity increases already in 1 hr after nsPEF and poly-ADP ribose polymerase (PARP) cleavage is detected in 2 hr. Staurosporin-treated positive control cells develop these apoptotic signs only in 3 and 4 hr, respectively. We conclude that nsPEF exposure triggers both necrotic and apoptotic pathways. The early necrotic death prevails under standard cell culture conditions, but cells rescued from the necrosis nonetheless die later on by apoptosis. The balance between the two modes of cell death can be controlled by enabling or blocking cell swelling.

Background-Nanosecond electric pulses (EP) disrupt cell membrane and organelles and cause cell death in a manner different from the conventional irreversible electroporation. We explored the cytotoxic effect of 10-ns EP (quantitation, mechanisms, efficiency, and specificity) in comparison with 300-ns, 1.8-and 9-μs EP.Methods-Effects in Jurkat and U937 cells were characterized by survival assays, DNA electrophoresis and flow cytometry.Results-10-ns EP caused apoptotic or necrotic death within 2-20 hrs. Survival (S, %) followed the absorbed dose (D, J/g) as: S=αD (−K) , where coefficients K and α determined the slope and the "shoulder" of the survival curve. K was similar in all groups, whereas α was cell type-and pulse duration-dependent. Long pulses caused immediate propidium uptake and phosphatidylserine (PS) externalization, whereas 10-ns pulses caused PS externalization only.Conclusions-1.8-and 9-μs EP cause cell death efficiently and indiscriminately (LD 50 1-3 J/g in both cell lines); 10-ns EP are less efficient, but very selective (LD 50 50-80 J/g for Jurkat and 400-500 J/g for U937); 300-ns EP show intermediate effects. Shorter EP open propidium-impermeable, small membrane pores ("nanopores"), triggering different cell death mechanisms.General significance-Nanosecond EP can selectively target certain cells in medical applications like tumor ablation.