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PubMed2004

Dye adsorption by calcium chloride treated beech sawdust in batch and fixed-bed systems.

Batch and column kinetics of methylene blue and red basic 22 adsorption on CaCl(2) treated beech sawdust was investigated, using untreated beech sawdust as control, in order to explore its potential use as a low-cost adsorbent for wastewater dye removal. The adsorption capacity, estimated according to Freundlich's model, and the adsorption capacity coefficient values, determined using the Bohart and Adams' bed depth service model indicate that CaCl(2) treatment enhanced the adsorption properties of the original material.

Adsorption↗

PubMed1988

Effect of tetraphenylboron on the calcium-dependent ATPase activity of sarcoplasmic reticulum.

The apparent effect of tetraphenylboron on the Ca2+-dependent ATPase activity is rather complex being dependent of the physical state of the membrane. In leaky vesicles, tetraphenylboron decreases the affinity of the enzyme for Ca2+, and high concentrations (100 microM) inhibit the enzyme. These effects are mediated by the membrane structure. In native vesicles, tetraphenylboron induces an apparent stimulation of the maximum hydrolytic activity and a decrease of the Ca2+ gradient formed due to specific Ca2+ releasing activity of the mentioned drug.

Animals↗

PubMed2001

Direct visualization of sarcoplasmic reticulum regions discharging Ca(2+)sparks in vascular myocytes.

Localized Ca(2+)-release events, Ca(2+)sparks, have been suggested to be the 'elementary building blocks' of the calcium signalling system in all types of muscles. In striated muscles these occur at regular intervals along the fibre corresponding to the sarcomeric structures which do not exist in smooth muscle. We showed previously that in visceral and vascular myocytes Ca(2+)sparks occurred much more frequently at certain sites (frequent discharge sites [FDSs]). In this paper, we have related the position of FDSs to the distribution of the sarcoplasmic reticulum in the same living myocyte. The three-dimensional distribution of the SR in freshly isolated rabbit portal vein myocytes was visualized by means of high-resolution confocal imaging after staining with DiOC(6)and/or BODIPY TR-X ryanodine. Both fluorochromes revealed a similar staining pattern indicating a helical arrangement of well-developed superficial SR which occupied about 6% of the cell volume. Computing the frequency of spontaneous Ca(2+)sparks detected by means of fluo-4 fluorescence revealed that in about 70% of myocytes there was only one major FDS located on a prominent portion of superficial SR network usually within 1-2 microm of the nuclear envelope, although a few sparks occurred at other sites scattered generally in superficial locations throughout the cell. Polarized mitochondria were readily identified by accumulation of tetramethylrhodamine ethyl ester (TMRE). These were closely associated with the SR network in extra-nuclear regions. TMRE staining, however, failed to reveal any mitochondria near the FDS-related SR element. When observed, propagating [Ca(2+)](i)waves and associated myocyte contractions were initiated at FDSs. This study provide first insight into the three-dimensional arrangement of the SR in living smooth muscle cells and relates the peculiarity of the structural organization of the myocyte to the features of Ca(2+)signalling at subcellular level.

Aniline Compounds↗

PubMed1996

Postsynaptic levels of [Ca2+]i needed to trigger LTD and LTP.

Long-term potentiation (LTP) and long-term depression (LTD) in CA1 pyramidal neurons are both triggered by a postsynaptic rise in intracellular Ca2+ concentration ([Ca2+]i). We used photolysis of postsynaptic caged Ca2+ compounds to search for differential thresholds for activation of these processes. Long-lasting potentiation (LLP) resembling LTP, and long-lasting depression (LLD) resembling LTD, were evoked by [Ca2+]i elevations of comparable magnitude and duration in different cells. No distinctions in threshold for these processes were detectable. LLP was occluded by tetanically induced LTP and blocked by calmodulin inhibition, and LLD was occluded by electrically induced LTD and blocked by phosphatase inhibition.

Age Factors↗

PubMed1995

Immunological stimulation of single rat basophilic leukemia RBL-2H3 cells co-activates Ca(2+)-entry and K(+)-channels.

The relationship between type 1 Fc epsilon-receptor (Fc epsilon RI) mediated cell stimulation, Ca(2+)-signals and membrane currents was studied in rat mucosal mast cells, subline RBL-2H3 by combining patch-clamp, Fura-2, 45Ca(2+)-uptake and secretory response measurements. Cells were stimulated by Fc epsilon RI clustering either with IgE and antigen or by an IgE specific monoclonal antibody. Both stimuli induced a biphasic increase in the free intracellular Ca(2+)-concentration ([Ca2+]i). Fc epsilon RI clustering in Ca(2+)-free solution induces a transient increase in [Ca2+]i reflecting Ca2+ release from the Ins(1,4,5)P3 sensitive stores. Mn2+ applied to a nominally Ca(2+)-free solution, causes quenching of the Fura-2 emission during Fc epsilon RI clustering, indicating activation of a transmembrane pathway for the entry of extracellular calcium ions. Whole-cell current-voltage relationship of resting cells showed strong inward rectification. The inward current component at a potential of -100 mV is increased by 23 +/- 11% (n = 14) upon Fc epsilon RI clustering, whereas the outward component at +50 mV was enhanced by 45 +/- 6%. The Fc epsilon RI activated current was identified as due to K+ ions, because it reversed close to the K(+)-equilibrium potential, was blocked by Ba2+ or Cs+ containing or K(+)-free bath solutions. It was also inhibited by TEA and quinidine, while DIDS had no effect. Moreover, an inwardly rectifying K(+)-channel with a conductance of 28 pS was recorded in single channel measurements. The open probability of this channel increased by 39 +/- 16% (n = 8) upon Fc epsilon RI clustering. Superfusion of the cells with nominally K(+)-free solution also significantly inhibited both the Fc epsilon RI mediated 45Ca2+ uptake and the secretory response of the cells. We conclude that activation of K(+)-channels upon Fc epsilon RI clustering is functionally involved in the control and the maintenance of the secretory response of RBL-2H3 mast cells.

Animals↗

PubMed2006

Proposal of a sequential treatment methodology for the safe reuse of oil sludge-contaminated soil.

In this study sequential steps were used to treat and immobilize oil constituents of an oil sludge-contaminated soil. Initially, the contaminated soil was oxidized by a Fenton type reaction (13 wt% for H(2)O(2); 10mM for Fe(2+)). The oxidative treatment period of 80 h was carried out under three different pH conditions: 20 h at pH 6.5, 20 h at pH 4.5, and 40 h at pH 3.0. The oxidized contaminated sample (3 kg) was stabilized and solidified for 2h with clay (1 kg) and lime (2 kg). Finally, this mixture was solidified by sand (2 kg) and Portland cement (4 kg). In order to evaluate the efficiency of different processes to treat and immobilize oil contaminants of the oil sludge-contaminated soil, leachability and solubility tests were performed and extracts were analyzed according to the current Brazilian waste regulations. Results showed that the Fenton oxidative process was partially efficient in degrading the oil contaminants in the soil, since residual concentrations were found for the PAH and BTEX compounds. Leachability tests showed that clay-lime stabilization/solidification followed by Portland cement stabilization/solidification was efficient in immobilizing the recalcitrant and hazardous constituents of the contaminated soil. These two steps stabilization/solidification processes are necessary to enhance environmental protection (minimal leachability) and to render final product economically profitable. The treated waste is safe enough to be used on environmental applications, like roadbeds blocks.

Aluminum Silicates↗

PubMedDate not supplied

Rapid Ca(2+) signaling induced by Bisphenol A in cultured rat hippocampal neurons.

OBJECTIVES: Bisphenol A (BPA) is a typical endocrine disrupter. We investigated the mechanisms of rapid Ca(2+) signaling induced by a low dose BPA application in cultured hippocampal neurons. MATERIALS AND METHODS: The primary culture of hippocampal neurons were prepared from postnatal 3 to 5-day-old rats. Cells were loaded with Calcium Green-1 fluorophore. Ca(2+) imaging and analysis were performed by Argus system. RESULTS: The application of BPA at 10-100 nM induced a transient increase in the intracellular Ca(2+) of N-methyl-D-aspartate (NMDA)-responsive neurons. The Ca(2+) transient occurred within 30 sec after the BPA application. The proportion of BPA-responsive neurons was 9.6 % and 8.5 % of the total NMDA-responsive neurons, respectively, upon 10 nM and 100 nM BPA application. The pre-treatment of neurons with Ca(2+) channel blockers, thapsigargin and nifedipine, considerably decreased the proportion of BPA-responsive neurons to 0.7 % and 3.7%, respectively. The treatment of neurons with an antagonist of estrogen receptor, ICI 182,780, also significantly decreased the proportion of BPA-responsive neurons down to 1.1 %. CONCLUSION: These results suggest that a low dose BPA application rapidly drives the Ca(2+) signaling system via activation of non-genomic pathway including estrogen receptors.

Animals↗

PubMed2006

Methylmercury-induced toxicity is mediated by enhanced intracellular calcium through activation of phosphatidylcholine-specific phospholipase C.

Methylmercury (MeHg) is a ubiquitous environmental toxicant to which humans can be exposed by ingestion of contaminated food. MeHg has been suggested to exert its toxicity through its high reactivity to thiols, generation of arachidonic acid and reactive oxygen species (ROS), and elevation of free intracellular Ca(2+) levels ([Ca(2+)](i)). However, the precise mechanism has not been fully defined. Here we show that phosphatidylcholine-specific phospholipase C (PC-PLC) is a critical pathway for MeHg-induced toxicity in MDCK cells. D609, an inhibitor of PC-PLC, significantly reversed the toxicity in a time- and dose-dependent manner with concomitant inhibition of the diacylglycerol (DAG) generation and the phosphatidylcholine (PC)-breakdown. MeHg activated the group IV cytosolic phospholipase A(2) (cPLA(2)) and acidic form of sphingomyelinase (A-SMase) downstream of PC-PLC, but these enzymes as well as protein kinase C (PKC) were not linked to the toxicity by MeHg. Furthermore, MeHg produced ROS, which did not affect the toxicity. Addition of EGTA to culture media resulted in partial decrease of [Ca(2+)](i) and partially blocked the toxicity. In contrast, when the cells were treated with MeHg in the presence of Ca(2+) in the culture media, D609 completely prevented cell death with parallel decrease in [Ca(2+)](i). Our results demonstrated that MeHg-induced toxicity was linked to elevation of [Ca(2+)](i) through activation of PC-PLC, but not attributable to the signaling pathways such as cPLA(2), A-SMase, and PKC, or to the generation of ROS.

Animals↗

PubMed1993

Control of intracellular calcium by membrane potential in human melanoma cells.

The modulation of intracellular calcium ([Ca2+]i) by the membrane potential was investigated in human melanoma cells by combining the nystatin-perforated patch-clamp technique with Ca2+ measurements. Voltage steps to -100 mV induced a rise in [Ca2+]i and a creeping inward current. These effects were absent in Ca(2+)-free solution and could be blocked by Ni2+ or La3+. Voltage ramps revealed a close correlation between [Ca2+]i and voltage, with the strongest voltage dependence around the resting potential. Long-lasting tail currents, closely correlated with the rise in [Ca2+]i and a reversal potential close to the K+ equilibrium potential, occurred if the membrane potential was clamped back to 0 mV. They were absent if intracellular K+ was replaced by Cs+ and blocked by extracellular tetraethylammonium (5 mM), Ba2+ (1 mM), or a membrane-permeable adenosine 3',5'-cyclic monophosphate analogue. These observations are discussed in relation to cell proliferation. The enhanced expression of K+ channels during cell proliferation provides a positive-feedback mechanism resulting in long-term changes in [Ca2+]i required for the G1-S transition in the cell cycle.

Barium↗

PubMed1989

Examples of high-resolution electron microscopy (HREM) investigation of complex oxides related to perovskite.

The properties of oxides may be drastically influenced by their microstructures. Thus the knowledge of nonstoichiometric mechanisms is an essential tool for the conception of new inorganic compounds by solid-state chemist. Through three chosen examples of complex oxides with perovskite-related structure, these points are illustrated. The new families of phosphate tungsten bronzes, the antiferromagnetic AMn1-xFexO3-y, and the copper oxides LCuO3-x (L = Ba, Y, La) were studied by high-resolution electron microscopy (HREM) in order to analyze the mechanisms of nonstoichiometry, the defects of which can modify their physical properties (magnetism or electronic conductivity) and the factors that govern their stabilization.

Calcium↗

PubMed1990

Polarized 86Rb+ effluxes in primary cultures of rabbit kidney proximal cells: role of calcium and hypotonicity.

Isolated proximal cells from rabbit kidney were seeded on collagen-coated permeable supports. After 8 days, the cultured cells became organized as a confluent monolayer. The proximal origin of the monolayer was confirmed by enzymatic, immunological, electrical and electron microscopical studies. The epithelia exhibited a morphological polarity that allowed for measurements of effluxes across the apical or the basolateral membranes. 86Rb was used as an isotopic tracer to indicate potassium movements. The 86Rb+ efflux across the basolateral face was 1.93-times that across the apical face, and both effluxes were pH dependent. Apical and basolateral 86Rb+ effluxes increased when the Ca2+ ionophore ionomycin (3 microM) was applied and when monolayers were exposed to a hypotonic medium. A pharmacological study revealed that BaCl2 (5 mM), tetraethylammonium (TEA, 20 mM) and Leiurus quinquestriatus hebraeus scorpion venom (from which charybdotoxin is extracted) abolished both ionomycin and hypotonically-stimulated effluxes, whereas apamin had no significant effect on the hypotonically-stimulated 86Rb+ efflux. This stimulated efflux was also abolished when monolayers were preincubated with pertussis toxin, but did not decrease in a Ca2(+)-free medium.

Animals↗

PubMed1975

[Cardiac side-effects of bencyclan].

Bencyclan (Fludilat), used therapeutically as a vasodilator drug, exerts a distinct negative inotropic and chronotropic action on myocardium, in contrast to papaverine. It prolongs the functional refractory period in the isolated heart preparation. In isolated myocardial mitochondria it decreases the velocity of oxidative phosphorylation and the rate of calcium uptake. These results indicate that heart function should be checked if bencyclan is applied at high dosage, especially if other cardio-depressive substances such as narcotics, antidepressive and antiarrhythmic agents as well as beta-adrenergic blockers are used at the same time. On the other hand, the results suggest that bencyclan should be tested for possible use in the treatment of ischaemic heart disease as well as ventricular and supraventricular tachycardia.

Adrenergic beta-Antagonists↗

PubMed1988

Analogs of the hormonal form of vitamin D and their possible use in leukemia.

We have concluded a large analog study that suggests that specific analogs of 1,25-(OH)2D3 can be prepared that have markedly enhanced activity in promoting differentiation of HL-60 promyelocytes to benign monocytes. We have observed that lengthening the side chain of 1,25-(OH)2D3 increases activity in HL-60 by 1 order of magnitude when the side chain is increased in length by 1 carbon. At the same time, the biological activity of these compounds in serum calcium elevation is either unchanged or diminished. Thus, lengthening the side chain may well provide a preferentially active form of vitamin D on the promyelocytes. Shortening the side chain has resulted a 10-fold loss of activity in HL-60 for each carbon removed. Furthermore, elimination of the 26- and 27-carbons decreases biological activity by 100-fold. If, however, the hydroxyl is left off the side chain and small hydrocarbon side chains of ethyl or isopropyl are substituted, very high activity in HL-60 is achieved without activity in mobilizing calcium in vivo. We, therefore, have compounds in hand which illustrate at least in vitro specific activity in HL-60.

Animals↗

PubMed1984

The behaviour of apatite-based ceramics in relation to the critical 1150 degrees-1250 degrees C temperature range.

Characterization of synthetic calcium phosphates is reported and compared with previous studies. Barium hydroxyapatite was also synthesized. Shrinkage on sintering, water absorption, tensile strength, porosity and X-ray diffraction patterns were studied. Hydroxyapatite and beta-tricalcium phosphate show compositional and mechanical property variation dependent on sintering temperatures. The property change on introduction of barium removes the practical value. X-ray diffraction analysis is considered essential before clinical use due to sensitivity of composition to sintering conditions.

Barium Compounds↗

PubMed1999

Alpha7 nicotinic receptor mediated protection against ethanol-induced cytotoxicity in PC12 cells.

Ethanol caused a concentration-dependent loss of PC12 cells over a 24 h interval, accompanied by an increase in intracellular calcium. The specific alpha7 nicotinic receptor partial agonist DMXB attenuated both of these ethanol-induced actions at a concentration (3 microM) found previously to protect against apoptotic and necrotic cell loss. The alpha7 nicotinic receptor antagonist methylylaconitine blocked the neuroprotective action of DMXB when applied with but not 30 min after the agonist. These results indicate that activation of alpha7 nicotinic receptors may be therapeutically useful in preventing ethanol-neurotoxicity.

Aniline Compounds↗

PubMed2004

Endothelin B receptor Ca2+ signaling in shark vascular smooth muscle: participation of inositol trisphosphate and ryanodine receptors.

In mammals, endothelin receptors are sub-classified into ET(A) receptors (ET(A)R), which are purely constrictive in vascular smooth muscle (VSM), and ET(B)R, which may produce constriction in VSM or dilatation by stimulating the production of nitric oxide (NO) from endothelial cells. In contrast, previous studies suggested that shark VSM is stimulated exclusively by ET(B)R. The Ca(2+) signaling pathways utilized by shark VSM in response to stimulation by endothelin-1 (ET-1) have not previously been investigated. We measured cytosolic Ca(2+) concentration ([Ca(2+)](i)) in fura-2-loaded VSM of anterior mesenteric artery of Squalus acanthias and show that the ET(B)R agonists IRL 1620 and sarafotoxin S6c (SRX) increase [Ca(2+)](i) in VSM to the same extent as ET-1 and ET(B)R appears to be the only ETR subtype in sharks. To investigate the participation of the inositol trisphosphate (IP(3)) receptors (IP(3)R), we utilized two inhibitors of the mammalian IP(3)R, TMB-8 and 2-APB. In Ca(2+)-free Ringer, these agents inhibit the response to ET(B)R agonist stimulation by 71%. The ryanodine-sensitive receptor (RyR) may be activated by low concentrations of ryanodine, by abrupt local increases of [Ca(2+)](i), (calcium-induced calcium release) or by cyclic adeninediphosphate ribose (cADPR). We employed three inhibitors of activation of the RyR, Ruthenium Red, 8-Br cADPR and high concentrations of ryanodine; these agents blocked the [Ca(2+)](i) response to ET(B)R agonist stimulation by a mean of 39%. These data show for the first time that in VSM of the shark, ET(B)R activation stimulates both IP(3)R and RyR, and that cADPR is involved in RyR activation.

Analysis of Variance↗

PubMed2002

Immunotoxicity of soluble and insoluble salts of cadmium instilled intratracheally.

Rats were intratracheally (i.t.) exposed to 36.5 or 27.5 microg of cadmium (Cd) as soluble cadmium chloride (CdCl2) and insoluble cadmium oxide (CdO) salts. The retention of metal in lungs, liver and kidney was assessed by atomic adsorption spectrophotometer. The animals were intraperitoneally (i.p.) primed with sheep red blood cells (SRBC) and assessed for the number of antibody forming cells in lung associated lymph nodes (LALN) and spleen. Both the compounds had similar retention of metal in lungs but CdO induced more pulmonary inflammatory and degradative changes than CdCl2. The larger influx of polymorphonuclear cells (PMNs) following CdO exposure appears to be due to the absence of protection afforded by Cd induced metallothionein cytoplasmic protein while the Cd metallothionein complex formed in the case of CdCl2 is more protective. However both forms of Cd had similar local immunosuppressive potential but CdO had more prolonged suppressive effect.

Animals↗

PubMed2005

Stable isotope probing analysis of the influence of liming on root exudate utilization by soil microorganisms.

Rhizosphere microorganisms play an important role in soil carbon flow, through turnover of root exudates, but there is little information on which organisms are actively involved or on the influence of environmental conditions on active communities. In this study, a 13CO2 pulse labelling field experiment was performed in an upland grassland soil, followed by RNA-stable isotope probing (SIP) analysis, to determine the effect of liming on the structure of the rhizosphere microbial community metabolizing root exudates. The lower limit of detection for SIP was determined in soil samples inoculated with a range of concentrations of 13C-labelled Pseudomonas fluorescens and was found to lie between 10(5) and 10(6) cells per gram of soil. The technique was capable of detecting microbial communities actively assimilating root exudates derived from recent photo-assimilate in the field. Denaturing gradient gel electrophoresis (DGGE) profiles of bacteria, archaea and fungi derived from fractions obtained from caesium trifluoroacetate (CsTFA) density gradient ultracentrifugation indicated that active communities in limed soils were more complex than those in unlimed soils and were more active in utilization of recently exuded 13C compounds. In limed soils, the majority of the community detected by standard RNA-DGGE analysis appeared to be utilizing root exudates. In unlimed soils, DGGE profiles from 12C and 13C RNA fractions differed, suggesting that a proportion of the active community was utilizing other sources of organic carbon. These differences may reflect differences in the amount of root exudation under the different conditions.

Bacteria↗