Characterization of the pattern of the nongenomic signaling pathway through which TCDD-induces early inflammatory responses in U937 human macrophages

2,3,7,8-Tetrachlorodibenzo(p)dioxin (TCDD) has been known to induce inflammatory signaling in a number of cell types and tissues. We found that in U937 macrophages TCDD causes rapid activation of cytosolic phospholipase A2 (cPLA2) within 30 min as judged by the increase in the serine 505 phosphorylated form of cPLA2 protein and the increased cellular release of free arachidonic acid. This initial action of TCDD is accompanied with the up-regulation of an important inflammation marker, COX-2 mRNA expression within 1 h, and by 3 h, several other markers become up-regulated. These effects appear to be dependent on the initial increase in the intracellular concentration of Ca²⁺, and activation of cPLA2 and COX-2. A comparative study among three different human cell lines showed that activation of COX-2 within 1 h of action of TCDD is a common feature exhibited by all cell lines. On the other hand, the U937 macrophage line appears to be unique among them with respect to its ability to activate TNF-α and IL-8 mRNA expressions, and not requiring Src kinase in propagating the initial signaling of cPLA2. Based on the rapidity of activation of cPLA2 and COX-2, which occurs within 1 h of cell exposure to TCDD, when no change in mRNA expression of CYP1A1 has been observed, it is apparent that this unique action of TCDD is carried out through a distinct “nongenomic” pathway which, is clearly discernable from the classical, “genomic” action pathway of the AhR by not requiring the participation of ARNT.     

Transfer of Sr into fish in Finnish lakes

The long-term behavior of ⁹⁰Sr was investigated from 1987 to 1997 in fifteen lakes in southern and central Finland following the 1986 Chernobyl accident. Both water and fish samples (perch, pike, vendace) were analyzed. ⁹⁰Sr stays long in the freshwater ecosystem; the observed half-lives during the study period were generally around 10 years in water and even longer in fish. One lake exhibited very different behavior for ⁹⁰Sr, with elevated levels in fish and water and very short observed half-life in fish, less than 2 years. Concentration factors of ⁹⁰Sr in fish (Bqkg⁻¹ f.w. in fish/Bqkg⁻¹ in water) among the studied lakes significantly correlated with both the Ca concentration and electrical conductivity of the water. More ⁹⁰Sr was transferred into fish in lakes with a low electrical conductivity and a low Ca concentration. Among other water parameters evaluated were pH, color, total nitrogen, and phosphorus.     

High affinity binding of 3H‐verapamil to rat brain synaptic membrane is antagonized by pyrethroid insecticides

Abstract

Deltamethrin is a powerful neuroactive agent causing increased neurotransmitter release at the synapse. To understand the cause for such an action of this pyrethroid insecticide, we have studied its binding characteristics to the calcium channel by utilizing ³H‐verapamil as a specific ligand. It was found that deltamethrin is capable of competing at the same binding site as ³H‐verapamil. Also, it was found that nonlabeled verapamil could reduce the binding of ³H‐deltamethrin (tested at 1 nM) to its binding site. The EC₅₀ value of verapamil to displace 50% of ³H‐deltamethrin was in the order of 0.3 μM, which coincides with the approximate K_D value for this ligand to bind with calcium channels in the rat brain synaptosomal plasma membranes.     

Characterization of a limestone in a batch fluidized bed reactor for sulfur retention under oxy-fuel operating conditions

CO₂ and SO₂ are some of the main polluting gases emitted into atmosphere in combustion processes using fossil fuel for energy production. The former is one of the major contributors to build-up the greenhouse effect implicated in global climate change and the latter produces acid rain. Oxy-fuel combustion is a technology, which consists in burning the fuel with a mix of pure O₂ and recirculated CO₂. With this technology the CO₂ concentration in the flue gas may be enriched up to 95%, becoming possible an easy CO₂ recovery. In addition, oxy-fuel combustion in fluidized beds allows in situ desulfurization of combustion gases by supplying calcium based sorbent.In this work, the effect of the principal operation variables affecting the sulfation reaction rate in fluidized bed reactors (temperature, CO₂ partial pressure, SO₂ concentration and particle size) under typical oxy-fuel combustion conditions have been analyzed in a batch fluidized bed reactor using a limestone as sorbent. It has been observed that sulfur retention can be carried out by direct sulfation of the CaCO₃ or by sulfation of the CaO (indirect sulfation) formed by CaCO₃ calcination. Direct sulfation and indirect sulfation operating conditions depended on the temperature and CO₂ partial pressure. The rate of direct sulfation rose with temperature and the rate of indirect sulfation for long reaction times decreased with temperature. An increase in the CO₂ partial pressure had a negative influence on the sulfation conversion reached by the limestone due to a higher temperature was needed to work in conditions of indirect sulfation. Thus, it is expected that the optimum temperature for sulfur retention in oxy-fuel combustion in fluidized bed reactors be about 925–950 °C. Sulfation reaction rate rose with decreasing sorbent particle size and increasing SO₂ concentration.     

Removal of carbon nanotubes from aqueous environment with filter paper

The potential health and environmental hazards of carbon nanotubes (CNTs) have been a concerned issue. However, in contrast to the wide recognition of the toxicity of CNTs, little attention has been paid to the decontamination/remediation of CNT pollution. In this study, we report that CNTs can be removed from aqueous environment. In the presence of Ca²⁺, CNTs aggregate quickly to micron size and then enable easy and effective removal via normal filtration. After filtration, CNT suspension becomes colorless with the remnant CNT concentration less than 0.5 μg mL⁻¹, a safe dose based on the published data. The filtration approach also works well in the presence of typical surfactant and dissolved organic matter. The removal efficiency is Ca²⁺ concentration-dependent and regulated by the initial pH value and ionic strength. Our study is helpful for future decontamination of CNTs from aqueous environment.     

Synthesis of calcium phosphate hydrogel from waste incineration fly ash and its application to fuel cell

Waste incineration fly ash was successfully recycled to calcium phosphate hydrogel, a type of fast proton conductor. The crystallized hydrogel from incineration fly ash had a lower electric conductivity and a lower crystallinity than that from calcium carbonate reagent. However, the difference in electric conductivity between these crystallized hydrogels decreases with temperature. This was due to the presence of potassium in the incineration fly ash. The fuel cell with a membrane electrode assembly (MEA) using the calcium phosphate hydrogel membrane prepared from incineration fly ash was observed to generate electricity. The performance of this fuel cell was almost equal to that of a mixture of K₂CO₃ and CaCO₃ reagents; further, the performance of the former was superior to the fuel cell with a perfluorosulfonic polymer membrane at temperatures greater than approximately 85 °C.     

The effect of calcium and pH on nickel accumulation in and rhizotoxicity to pea (Pisum sativum L.) root-empirical relationships and modeling

The accumulation and rhizotoxicity of Ni to pea were investigated. Calcium, H, and Ni competed for root-binding sites with high pH and low Ca favoring more Ni accumulation. At low pH, Ca accumulation is the key factor determining root growth, while at medium to high pH, root elongation is more sensitive to Ni concentration. The tissue concentration of Ni and Ca ([Ni]t or [Ca]t, μmol g⁻¹ dry root) can be predicted from total dissolved Ni ([Ni]_T, μM), pH, and total dissolved Ca ([Ca]_T, mM) by two approaches. Approach 1 is the empirical equations [Ni]t = (0.361 pH-0.695[Ca]_T)*[Ni]_T and [Ca]t = 8.29 pH + 10.8 [Ca]_T. The second approach involves a two-step model. The surface-bound Ni and Ca are estimated from a surface adsorption model with binding constants derived from independent ion adsorption experiments. Then transfer functions are used to predict internal root Ni and Ca accumulation.     

Mechanochemical dechlorination of polyvinyl chloride with calcium sulfates

Polyvinyl chloride (PVC) was milled with hydrated or unhydrated calcium sulfates (CaSO₄·2H₂O or CaSO₄) in air by using a planetary mill to investigate mechanochemical dechlorination behavior. The milling process resulted in size reduction and in the breaking of bonds leading to mechanically induced solid state reaction, forming CaCl₂ and dechlorinated hydrocarbon with C=C double bonds in the product. Washing the milled mixtures with water at room temperature allowed removal of the chloride formed during milling, and more than 95% of the chlorine in PVC was removed from a mixture milled for 4 h. This process could offer a potential route for the handling and disposal of both PVC and gypsum wastes. H₂S gas was generated during milling; more H₂S was released from the unhydrated sample than from the hydrated sample.     

Fast and Living Ring-Opening Polymerization of l-Lactide Initiated with In-situ–Generated Calcium Alkoxides

The ring-opening polymerization of l-lactide with calcium alkoxides generated in-situ from bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] and 2-propanol are presented. The polymerization in THF at room temperature proceeds rapidly and in a living manner, giving poly(l-lactide)s of controlled molecular weight, low polydispersity, and tailored end-functionalities. Kinetic studies show the absence of an induction period and a pseudo-first order rate constant of 6.41 L mol^–1 min^–1, which is significantly higher than for related Y₅(-O)(O ⁱ Pr)_13– or aluminum alkoxide-initiated polymerizations. The initiation involves a two-step process: (1) alcoholysis of bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] to give the corresponding calcium alkoxide and (2) ring-opening of l-lactide via acyl-oxygen cleavage and insertion into the calcium-alkoxide bond. In the presence of excess alcohol, fast and reversible exchange between free alcohol molecules and coordinated alkoxide ligands takes place. This allows tuning of the poly(l-lactide) molecular weight over a wide range.     

Breeding performance of blue tits (Cyanistes caeruleus) and great tits (Parus major) in a heavy metal polluted area

We compared heavy metal levels, calcium levels, breeding parameters and condition of nestling and adult Cyanistes caeruleus and Parus major along a heavy metal pollution gradient. Both species started laying earlier and showed inferior nestling growth and smaller fledging probability in the polluted areas, which are phenologically advanced in spring due to sparse forests. The major inter-specific difference in the responses was that the clutch size and hatching success were decreased in the polluted area in P. major, but not in C. caeruleus. Heavy metal profiles in nestling feces were relatively similar in the two species, though Ni and Pb levels were higher in C. caeruleus than in P. major. However, the latter species showed markedly higher fecal calcium concentrations. Lower calcium levels and higher levels of some heavy metals in C. caeruleus suggest that in Ca-deficient environments this species might be more susceptible to negative pollution effects than P. major.