An ecotoxicological screening tool to prioritise acid mine drainage impacted streams for future restoration.

Streams impacted by acid mine drainage (AMD) typically present water exhibiting low pH and high metal concentrations. These factors result in the environmental degradation of watercourses. The objective of this study was to develop and evaluate an ecotoxicological screening tool (EST) to prioritise future remediation of streams impacted by AMD. The Bloubank stream drainage system in South Africa, served as study area for this purpose. In the initial EST development phase physicochemical variables were assessed while in the second phase, epilithic filamentous green algae biomass (chl-a mg m(-2)), diatoms and filamentous green algae community structures were employed as bioindicators as well as Daphnia magna toxicity assays. Using a weight of evidence approach, the first three sites receiving AMD were critically and seriously modified, followed by site 4 that was modified. Sites 1-3 with EST scores ≤70% were assessed as priority candidates for future restoration.

Spatially resolved measurements of laser filamentation in long scale length underdense plasmas with and without beam smoothing.

The onset of filamentation, following the interaction of a relatively long (τ(L)≃1 ns) and intense (I(L)≃5×10(14) W/cm(2)) laser pulse with a neopentane filled gas bag target, has been experimentally studied via the proton radiography technique, in conditions of direct relevance to the indirect drive inertial confinement fusion scheme. The density gradients associated with filamentation onset have been spatially resolved yielding direct and unambiguous evidence of filament formation and quantitative information about the filamentation mechanism in agreement with previous theoretical modelings. Experimental data confirm that, once spatially smoothed laser beams are used, filamentation is not a relevant phenomenon during the heating laser beams propagation through typical hohlraum gas fills.

Bioenergy from permanent grassland--a review: 2. Combustion.

The aim of this review is to summarize current knowledge on suitability and sustainability of grassland biomass for combustion. In the first section grassland management for solid biofuel as well as information on harvest, postharvest and firing technology are described. An extensive grassland management system with one late cut and low level of fertilization is favored for grass as a solid biofuel. The grass harvest usually involves drying in the field and clearing with conventional farm machinery. Pelleting or briquetting improves the biofuel quality. Grass combustion is possible as stand-alone biomass-firing or co-firing with other fuels. Firing herbaceous biomass requires various specific adaptations of the different combustion technologies. In the second section economic and environmental aspects are discussed. Costs for biomass supply mainly depend on yields and harvesting technologies, while combustion costs are influenced by the size and technical design of the plant. Market prices for grass and possible subsidies for land use are crucial for profitability. Regarding biogeochemical cycles a specific feature of combustion is the fact that none of the biomass carbon and nitrogen removed at harvest is available for return to the grassland. These exports can be compensated for by fixation from the air given legumes in the vegetation and sufficient biomass production. Greenhouse gas emissions can be considerably reduced by grass combustion. Solid biofuel production has a potential for predominantly positive impacts on biodiversity due to the extensive grassland management.

Bioenergy from permanent grassland--a review: 1. Biogas.

Grassland biomass is suitable in numerous ways for producing energy. It is well established as feedstock for biogas production. The aim of this review is to summarize current knowledge on suitability and sustainability of grassland biomass for anaerobic digestion. In the first section grassland management for biogas feedstock as well as specifics of harvest, postharvest and digestion technology are described. Methane yields from grass are influenced by many factors. While the effects of some parameters such as grass species, cutting period and management intensity can be regarded as well known, other parameters such as preservation and processing still need investigation. In the second section economic aspects and environmental impacts are discussed. Profitability can be achieved depending on grass silage supply costs and the concept of anaerobic digestion and energy use. Grassland biomass for biogas production competes with other feedstock and other forms of grassland use, in particular animal husbandry. In developed countries a growing production of milk and meat is achieved with decreasing ruminant numbers, resulting in an increasing amount of surplus grassland with a remarkable bioenergy potential. In emerging and developing countries a rapidly rising demand for and production of milk and meat induce growing pressure on grasslands, so that their use for animal feed presumably will take priority over use for bioenergy. Grasslands provide a variety of essential environmental benefits such as carbon storage, habitat function, preservation of ground and surface water quality. When producing biogas from grassland these benefits will remain or even grow, providing appropriate grassland management is implemented. In particular, greenhouse gas emissions can be considerably reduced.

Struvite crystallisation and recovery using a stainless steel structure as a seed material.

A metallic system acting as a seed substrate has been designed and developed in order to assess its efficiency in recovering phosphorus as struvite. The device, consisting of two concentric stainless steel meshes, was immerged in the upper section of a pilot crystallisation reactor fed with synthetic liquors (MgCl(2) x 6H(2)O, NH(4)H(2)PO(4),) for 2h. Apart from soluble PO(4)-P removals which remained in the range 79-80% with or without application of the metallic system, it was found that under the specific operating conditions tested the meshes were capable of accumulating struvite at a rate of 7.6 gm(-2)h(-1), hence reducing significantly the amount of fine particles remaining in solution from 302.2 to 12 mg L(-1) when compared to trials without mesh.

Kinetics of struvite precipitation: effect of the magnesium dose on induction times and precipitation rates.

The presence of white deposits in specific areas of wastewater treatment plants is generally the consequence of the spontaneous formation of a mineral called struvite. Struvite forms when the levels of phosphate, ammonium and magnesium naturally available in wastewater effluents reach a minimum molar ratio 1:1:1 under specific conditions of pH, temperature and mixing energy. Originally regarded as a phenomenon to be controlled or eliminated, struvite has been lately identified as an alternative way of removing and recovering P from wastewater effluents and generating a product identified as an excellent base for the production of slow release fertilisers. Chemical and physical principles of struvite precipitation and the development of crystallisation technologies have been widely investigated. However, little interest has been given to kinetics of struvite precipitation. In the present work the kinetics of struvite formation have been investigated at both laboratory and pilot scale in synthetic solutions containing Mg(2+), NH4(+), and PO4(3-) ions in a molar ratio 1:2:2 at room temperature. These different tests have used pH measurements to assess the impact of water chemistry on induction times, and more precisely the influence of magnesium levels on kinetic rates. Experimental results and kinetic calculations revealed that the control of the magnesium dose initially present in solution is decisive of the speed at which struvite nucleates.

Impact of reactor operation on success of struvite precipitation from synthetic liquors.

A pilot scale reactor was designed and developed to study struvite crystallisation principles. The present work focuses on the possible impact of the reactor's operating parameters on struvite characteristics, and evaluates the performances of the process in removing phosphorus. Struvite precipitation from synthetic liquors was investigated under various situations including: pH, magnesium dosing, addition of foreign ions such as calcium and increasing retention time. Small variations of all these parameters were found to have significant effects on struvite crystal characteristics and/or production. For instance, an increase of pH from 10.0 to 10.5 favoured the formation of Mg3(PO4)2.22H2O rather than struvite. For molar ratios Ca:Mg above 1:1, calcium ions competed with magnesium to form an amorphous calcium phosphate, hence inhibiting struvite formation. With regards to crystal growth, the process showed some limitations. Indeed, large amounts of fines were produced, and crystal rarely grew over 100 microm under optimum conditions. Based on those observations, zeta-potential measurements of struvite crystals were investigated. Results revealed highly negative zeta-potential values for all experiments, indicating that this may be a limitation to struvite tendency for agglomeration.

Influence of straw types and nitrogen sources on mushroom composting emissions and compost productivity.

The effects of different straw types and organic and inorganic nitrogen (N) sources on the chemical composition and odor concentration (OC) of mushroom composting emissions, compost parameters, and mushroom yield were examined using bench-scale and large-scale (windrows and aerated tunnels) composting systems. There were close correlations between the butanol or combined H(2)S+dimethyl sulfide (DMS) concentration and OC of air samples taken from different composting ingredients (r=0.83 and 0.76-0.87, P<0.01, for log(e)-transformed data). Differences in N availability, in terms of NH(3) and N losses during composting, were found between different N sources. Materials in which the N was less available (chipboard and digester wastes, cocoa shells, ammonium sulfate) produced lower mushroom yields than materials in which the N was more readily available (poultry manure, urea, brewers' grains, hop and molasses wastes, cocoa meal). Replacement of poultry manure with the other N sources at 50-100% or wheat straw with rape, bean, or linseed straw in aerated tunnel or windrow composts reduced the OC and emissions of odorous sulfur-containing compounds, but also reduced yield. Urea and cocoa meal may be suitable for "low odor" prewetting of straw, with addition of poultry manure immediately before aerated tunnel composting. Rape straw in compost reduces the formation of anaerobic zones and resulting odorous emissions, since it maintains its structure and porosity better than wheat straw.

Olfactory response to mushroom composting emissions as a function of chemical concentration.

Odor pollution is a major problem facing mushroom [Agaricus bisporus (Lange) Imbach] compost production. Techniques for quantifying mushroom composting odors are needed to assess the effectiveness of odor control measures. Odor samples were obtained in nalophane bags from 11 mushroom composting sites. Samples were collected 0.2 m downwind from the pre-wetting heaps (aerated or unaerated) of raw composting ingredients (wheat straw, poultry and horse manures, and gypsum) and subsequent Phase I composting windrows or aerated tunnels. The odor concentrations (OCs) of the samples were assessed using serial dilution olfactometry and the chemical composition of the samples was determined using gas chromatography-mass spectrometry (GC-MS), both 24 h after sampling. Gas detector tubes were used for on-site measurement of gaseous compounds. Odorants that exceeded their published olfactory detection thresholds by the greatest order of magnitude, in decreasing order, were: H2S, dimethyl sulfide (DMS), butanoic acid, methanethiol, and trimethylamine. Concentrations of NH3 were not significantly correlated with OC, and they were not significantly affected by the use of aeration. Aeration reduced the OC and the combined H2S + DMS concentrations by 87 and 92%, respectively. There was a very close correlation (r = 0.948, P < 0.001) between the OC of bag samples and the combined H2S + DMS concentrations, measured on-site with detector tubes. This relationship was unaffected by the NH3 concentration or the type of compost: aerated or unaerated, pre-wet or Phase I, poultry manure-based or horse and poultry manure-based compost. Prediction of the OC will enable rapid and low-cost identification of odor sources on mushroom composting sites.

Apoptosis induction in cancer cells by a novel analogue of 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylic acid lacking retinoid receptor transcriptional activation activity.

The retinoid 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylic acid (AHPN) is reported to have anticancer activity in vivo. Induction of cell cycle arrest and apoptosis in cancer cell lines refractory to standard retinoids suggests a retinoid-independent mechanism of action for AHPN. Conformational studies suggested that binding of AHPN does not induce an unusual conformation in retinoic acid receptor (RAR) gamma. The 3-chloro AHPN analogue MM11453 inhibited the growth of both retinoid-resistant (HL-60R leukemia, MDA-MB-231 breast, and H292 lung) and retinoid-sensitive (MCF-7 breast, LNCaP prostate, and H460 lung) cancer cell lines by inducing apoptosis at similar concentrations. Before apoptosis, MM11453 induced transcription factor TR3 expression and loss of mitochondrial membrane potential characteristic of apoptosis. MM11453 lacked the ability to significantly activate RARs and retinoid X receptor alpha to initiate (TREpal)(2)-tk-CAT reporter transcription. These results, differential proteolysis-sensitivity assays, and glutathione S-transferase-pulldown experiments demonstrate that, unlike AHPN or the natural or standard synthetic retinoids, MM11453 does not behave as a RAR or retinoid X receptor alpha transcriptional agonist. These studies strongly suggest that AHPN exerts its cell cycle arrest and apoptotic activity by a signaling pathway independent of retinoid receptor activation.

Additives to reduce ammonia and odor emissions from livestock wastes: a review.

This paper reviews the use of additives to reduce odor and ammonia (NH3) emissions from livestock wastes. Reduction of NH3 volatilization has been shown to be possible, particularly with acidifying and adsorbent additives, and potential exists to develop further practical and cost-effective additives in this area. Masking, disinfecting, and oxidizing agents can provide short-term control of malodor, but as the capacity of these additives is finite, they require frequent reapplication. Microbial-based digestive additives may offer a solution to this problem as they are regenerative, but they appear to have been developed without a thorough understanding of microbiological processes occurring in livestock wastes. Currently, their use to reduce odor or NH3 emissions cannot be recommend. If the potential of these types of additives is to be realized, research needs to shift from simply evaluating these unknown products to investigating known strains of bacteria or enzymes with known modes of action. To protect the farmers' interest, standard independent test procedures are required to evaluate efficacy. Such tests should be simple and quantify the capacity of the additive to perform as claimed. The principle use of additives needs to be identified and addressed during their development. Producers may not use effective additives in one area if they further compound other problems that they perceived to be more important. There is the potential to use additives to treat other problems associated with livestock wastes, particularly to improve handling properties, reduce pollution potential to watercourses, and reduce pathogenic bacteria. Further work is required in these areas.

Retinoic acid (RA) receptor transcriptional activation correlates with inhibition of 12-O-tetradecanoylphorbol-13-acetate-induced ornithine decarboxylase (ODC) activity by retinoids: a potential role for trans-RA-induced ZBP-89 in ODC inhibition.

Evaluation of retinoic acid receptor (RAR) subtype-selective alpha and gamma agonists and antagonists and a retinoid X receptor (RXR) class-selective agonist for efficacy at inhibiting both induction of ornithine decarboxylase (ODC) by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse epidermis and rat tracheal epithelial cells and the appearance of papillomas in mouse epidermis treated in the 2-stage tumor initiation-promotion model indicated that (i) RXR class-selective transcriptional agonists, such as MM11246, were not involved in ODC inhibition; (ii) RAR-selective agonists that induce gene transcription from RA-responsive elements (RAREs) were active at low concentrations; (iii) RAR-selective antagonists that bind RARs and inhibit AP-1 activation on the collagenase promoter but do not activate RAREs to induce gene transcription were less effective inhibitors; and (iv) RARgamma-selective retinoid agonists were more effective inhibitors of TPA-induced ODC activity than RARalpha-selective agonists. These results suggest that RARE activation has a more important role in inhibition of ODC activity than RXR activation or AP-1 inhibition and that RARgamma-selective agonists would be the most useful inhibitors of epithelial cell proliferation induced by tumor promoters. The natural retinoid all-trans-RA induced expression of transcription factor ZBP-89, which represses activation of the GC box in the ODC promoter by the transcription factor Sp1.

Cytochrome c release and apoptosis induced by mitochondrial targeting of nuclear orphan receptor TR3.

TR3, an immediate-early response gene and an orphan member of the steroid-thyroid hormone-retinoid receptor superfamily of transcription factors, regulates apoptosis through an unknown mechanism. In response to apoptotic stimuli, TR3 translocates from the nucleus to mitochondria to induce cytochrome c release and apoptosis. Mitochondrial targeting of TR3, but not its DNA binding and transactivation, is essential for its proapoptotic effect. Our results reveal a mechanism by which a nuclear transcription factor translocates to mitochondria to initiate apoptosis.

sp2-bridged diaryl retinoids: effects of bridge-region substitution on retinoid X receptor (RXR) selectivity.

RXR class selectivity and RXR transcriptional activation activity compared to those for the retinoic acid receptor subtypes were enhanced on the 4-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenylethenyl)be nzoic acid scaffold and its 3-methyl analogue by replacing their 1,1-ethenyl bridge by a 1,1-(2-methylpropenyl) or cyclopropylidenylmethylene group.

4-[3-(5,6,7,8-Tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)phenyl]benzoic acid and heterocyclic-bridged analogues are novel retinoic acid receptor subtype and retinoid X receptor alpha agonists.

Aromatic retinoids having a meta-substituted aromatic ring bridge, such as 4-[3-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)phenyl]benzo ic acid and its 3,5-diaryl-substituted 4,5-dihydroisoxazole analogue, function as retinoid receptor panagonists by activating both retinoic acid and retinoid X receptors to induce gene transcription, and thereby provide novel scaffolds for retinoid drug development. Both classes of these ligand-inducible transcription factors are involved in mediating the inhibitory effects of retinoids on cancer cell growth.

Identification of a unique binding protein specific for a novel retinoid inducing cellular apoptosis.

The retinoid 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylic acid (AHPN, CD437) induces apoptosis in a variety of cell types, many of which are cancer cells that resist the antiproliferative and/or differentiating effects of retinoids. While the retinoids exert their effects by binding to the retinoic acid nuclear receptors (RARs) or retinoid X receptors (RXRs), AHPN (CD437) binds to another protein with different ligand specificity. In nuclear extracts from HL-60R cells the binding of AHPN (CD437) was only minimally competed by either retinoic acid (tRA)or 9-cis-retinoic acid (9-cis-RA), the natural ligands for the RARs and RXRs, respectively. Moreover, AHPN (CD437) was unable to compete with either tRA or 9-cis-RA for binding to endogenous retinoid receptors in nuclear extracts from the MDA-MB-468 breast carcinoma cell line. Size exclusion chromatography revealed AHPN binding to a 95 kDa protein(s) which is neither an RAR or RXR. Our results suggest that apoptosis induction by AHPN (CD437) may occur through interaction with another protein and is independent of the RAR/RXR-signaling pathways.

Antioxidant activity of michellamine alkaloids.

The alkaloids michellamines A, B, and C are natural products isolated from a Central African tropical plant Ancistrocladus korupensis. We have investigated the radical scavenging ability of these compounds. The alkaloids inhibited the azo-induced oxidation of beta-phycoerythrin with IC50 values in the 0.5- to 0.8-microM range. Michellamine B also protected rat liver mitochondria against lipid peroxidation induced by adenosine diphosphate and Fe2+. The alkaloids were more potent antioxidants in these assays than several compounds being considered clinically as chemoprevention agents.

Kinetic and thermodynamic analysis of 9-cis-retinoic acid binding to retinoid X receptor alpha.

The interaction of retinoid X receptor alpha with 9-cis-retinoic acid was studied using stopped-flow fluorescence spectroscopy. Transient kinetic analyses of this interaction suggest a two-step binding mechanism involving a rapid, enthalpically driven pre-equilibrium followed by a slower, entropically driven reaction that may arise from a conformational change within the ligand binding domain of the receptor. The assignment of this kinetic mechanism was supported by agreement between the overall equilibrium constant, Kov, derived from kinetic studies with that determined by equilibrium fluorescence titrations. Although these analyses do not preclude ligand-induced alteration in the oligomerization state of the receptor in solution, the simplest model that can be applied to these data involves the stoichiometric interaction of 9-cis-retinoic acid with retinoid X receptor alpha monomers.

Michellamine alkaloids inhibit protein kinase C.

Michellamines A, B, and C have shown antiviral activity against HIV-1 and HIV-2 in cell culture. They act in a complex manner by at least two reported antiviral mechanisms, inhibition of HIV reverse transcriptase and inhibition of HIV-induced cellular fusion. On the basis of their structural similarity to other protein kinase C (PKC) inhibitors, we have investigated another possible mechanism-inhibition of PKC. The michellamines were found to inhibit rat brain PKC with IC50 values in the 15-35 microM range. Michellamine B was a noncompetitive PKC inhibitor with respect to ATP with a Ki value of 4-6 microM, whereas mixed-type inhibition was observed when the peptide concentration was varied. Michellamine B inhibited the kinase domain of PKC similarly. These results indicate that the michellamines bind to the PKC kinase domain and not its regulatory domain. Molecular modeling showed that all three michellamines can bind in the active site cleft of the PKC kinase domain, to block both the ATP and the peptide substrate subsites.