3D-QSAR of fungal quorum-sensing inhibiting analogs of farnesol

Thirty-four analogs with variable antifungal activity were selected to develop models for establishing three-dimensional quantitative structure-activity relationships (3D-QSAR). Comparative molecular field analysis (CoMFA) and comparative similarity indices analyses (CoMSIA) were conducted on the group of analogs to determine the structural requirements for selectivity and potency in inhibiting biofilm formation and fungal growth. The best CoMFA model predicted a q² = 0.5 and an r² = 0.991, and revealed that electrostatic properties play a significant role in potency and selectivity. The best CoMSIA model combined electrostatics, hydrogen bond acceptor and donor, and hydrophobic fields with a q² = 0.664 r² = 0.952, S = 0.099, and F = 139.892. The analyses of the contour maps from both models provide significant insight into the structural necessities for a potent compound. Therefore, manipulating various chemical properties of the substituted groups on the farnesol chain can be used to enhance the fungicidal properties of the target compound.     

Three-dimensional quantitative structure activity relationships of quorum-sensing and biofilm inhibitors in gram-negative bacteria

Thirty N-acyl homoserine lactone (AHL) analogs with variable antibacterial activity and displaying inhibition of biofilm formation were selected to develop models for establishing three-dimensional quantitative structure-activity relationships (3D-QSAR). Comparative molecular field analysis (CoMFA) and comparative similarity indices analysis (CoMSIA) were carried out to determine the optimum structural requirements for selectivity and potency of quorum-sensing and bacterial biofilm inhibition. The best CoMFA model predicted a q² value of 0.519 and an r² value of 0.984 and revealed that electrostatic and steric properties play a significant role in potency and selectivity. The CoMSIA model predicted a q² value of 0.411 and an r² value of 0.938 based on a combination of steric, electrostatic, and hydrophobic effects. The analysis of the contour maps from each model provide insight into the structural requirements for increasing the activity of a compound. Consequently, manipulating the chemical and physical properties of substituted acyl groups on the homoserine lactone moiety can provide important information toward enhancing the antibacterial properties of the target chemical compound.     

Three-dimensional quantitative structure activity relationships of quorum-sensing and biofilm inhibitors in gram-negative bacteria

Thirty N-acyl homoserine lactone (AHL) analogs with variable antibacterial activity and displaying inhibition of biofilm formation were selected to develop models for establishing three-dimensional quantitative structure-activity relationships (3D-QSAR). Comparative molecular field analysis (CoMFA) and comparative similarity indices analysis (CoMSIA) were carried out to determine the optimum structural requirements for selectivity and potency of quorum-sensing and bacterial biofilm inhibition. The best CoMFA model predicted a q2 value of 0.519 and an r2 value of 0.984 and revealed that electrostatic and steric properties play a significant role in potency and selectivity. The CoMSIA model predicted a q2 value of 0.411 and an r2 value of 0.938 based on a combination of steric, electrostatic, and hydrophobic effects. The analysis of the contour maps from each model provide insight into the structural requirements for increasing the activity of a compound. Consequently, manipulating the chemical and physical properties of substituted acyl groups on the homoserine lactone moiety can provide important information toward enhancing the antibacterial properties of the target chemical compound.     

Tolerance of transgenic canola plants (Brassica napus) amended with plant growth-promoting bacteria to flooding stress at a metal-contaminated field site

The growth of transgenic canola (Brassica napus) expressing a gene for the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase was compared to non-transformed canola exposed to flooding and elevated soil Ni concentration, in situ. In addition, the ability of the plant growth-promoting bacterium Pseudomonas putida UW4, which also expresses ACC deaminase, to facilitate the growth of non-transformed and transgenic canola under the above mentioned conditions was examined. Transgenic canola and/or canola treated with P. putida UW4 had greater shoot biomass compared to non-transformed canola under low flood-stress conditions. Under high flood-stress conditions, shoot biomass was reduced and Ni accumulation was increased in all instances relative to low flood-stress conditions. This is the first field study to document the increase in plant tolerance utilizing transgenic plants and plant growth-promoting bacteria exposed to multiple stressors.     

Trends in Pesticide Concentrations in Streamsof the Western United States, 1993‐20051

Johnson, Henry M., Joseph L. Domagalski, and Dina K. Saleh, 2010. Trends in Pesticide Concentrations in Streams of the Western United States, 1993‐2005. Journal of the American Water Resources Association (JAWRA) 00(0):1‐22. DOI: 10.1111/j.1752‐1688.2010.00507.x Abstract: Trends in pesticide concentrations for 15 streams in California, Oregon, Washington, and Idaho were determined for the organophosphate insecticides chlorpyrifos and diazinon and the herbicides atrazine, s‐ethyl diproplythiocarbamate (EPTC), metolachlor, simazine, and trifluralin. A parametric regression model was used to account for flow, seasonality, and antecedent hydrologic conditions and thereby estimate trends in pesticide concentrations in streams arising from changes in use amount and application method in their associated catchments. Decreasing trends most often were observed for diazinon, and reflect the shift to alternative pesticides by farmers, commercial applicators, and homeowners because of use restrictions and product cancelation. Consistent trends were observed for several herbicides, including upward trends in simazine at urban‐influenced sites from 2000 to 2005, and downward trends in atrazine and EPTC at agricultural sites from the mid‐1990s to 2005. The model provided additional information about pesticide occurrence and transport in the modeled streams. Two examples are presented and briefly discussed: (1) timing of peak concentrations for individual compounds varied greatly across this geographic gradient because of different application periods and the effects of local rain patterns, irrigation, and soil drainage and (2) reconstructions of continuous diazinon concentrations at sites in California are used to evaluate compliance with total maximum daily load targets.     

The importance of experience in the interpretation of conspecific chemical signals

Foraging bumblebees scent mark flowers with hydrocarbon secretions. Several studies have found these scent marks act as a repellent to bee foragers. This was thought to minimize the risk of visiting recently depleted flowers. Some studies, however, have found a reverse, attractive effect of scent marks left on flowers. Do bees mark flowers with different scents, or could the same scent be interpreted differently depending on the bees’ previous experience with reward levels in flowers? We use a simple experimental design to investigate if the scent marks can become attractive when bees forage on artificial flowers that remain rewarding upon the bees’ return after having depleted them. We contrast this with bees trained in the more natural scenario where revisits to recently emptied flowers are unrewarding. The bees’ association between scent mark and reward value was tested with flowers scent marked from the same source. We find that the bees’ experience with the level of reward determines how the scent mark is interpreted: the same scent can act as both an attractant and a repellent. How experience and learning influence the interpretation of the meaning of chemical signals deposited by animals for communication has rarely been investigated.     

The hydrogeochemistry of the Pleistocene aquifer in the Nile Delta area,Egypt

The Pleistocene aquifer represents the main aquifer underlying the Nile Delta area. This aquifer is directly affected by the surface water from the Nile branches. However, the study of the hydrogeochemistry of this aquifer indicates the possibility of classifying it into three hydrochemical zones from south to north. The groundwater chemistry of each zone is the resultant effect of the local factors controlling the development of groundwater quality.     

Experimental investigation on dish solar distiller with modified absorber and phase change material under various operating conditions

Environmental Science and Pollution Research - The shortage of potable water is a global problem. One of the techniques used to participate solving this problem is the solar distiller. The main...     

Histological and histochemical alterations induced by lead in the liver of the quail Coturnix coturnix

Adult males of the quail Coturnix coturnix were exposed to lead acetate trihydrate in drinking water (0.1, 0.25, 0.5, and 1% for one–six months) to investigate histological and histochemical alterations induced by lead intoxication in the liver. Chronic exposure to subtoxic concentrations of lead produced changes in hepatocytes, portal veins, Kupffer cells, and blood sinusoids. Alterations in hepatocytes mainly involved cytoplasmic vacuolation, necrosis, cytolysis, and glycogen accumulation. Kupffer cell hyperplasia, hemosiderosis, blood sinusoidal dilatation, portal vein congestion, and edema were also observed. No fibrosis or cirrhosis in the liver of any member of the dose groups over the entire period of the study was noted. The findings revealed that chronic exposure to lead produced mild histological and histochemical changes in the liver of the quail Coturnix coturnix.     

Ludwigia stolonifera for remediation of toxic metals from simulated wastewater

The present study investigated the phytoremediation of simulated wastewater, mimicking wastewater generated by industrial processes containing significant amounts of toxic heavy metal ions. The wetland plant Ludwigia stolonifera was used to study its efficiency in the removal of the three toxic metals Pb, Cd and Cr. Survivability of the plant has been studied in solutions at different concentrations of three metals separately or as a mixture, and the accumulation of these toxic metals for a prolonged period has been evaluated. The plant performed very successful in eliminating Cd, Cr and Pb as single metals of up to 65%, 97% and 99%, respectively, within four days. In addition, the trend of metal uptake revealed negligible dependence on different masses of plant and on various pH-values. L. stolonifera has high potential in eliminating various toxic pollutants from aquatic environments.