Presence Of Lanthanum Research Articles

Electrokinetic behaviour of tin tailings slurries in solutions of lanthanum and thorium salts

The electrokinetic behaviour of clay particles in tin tailings slurries in the presence of lanthanum(III) and thorium(IV) salts were studied. The clay minerals in the two slurries chosen for this work were mainly kaolinite with some minor compositional variations. An interesting feature of the electrophoretic mobility-pH curves at fixed lanthanum(III) concentrations is the occurrence of two constant mobility regions, one in the acidic pH range and the other at alkaline pH. It is known that lanthanum(III) at different concentrations forms hydrolysed species of different charges with different pH. Thus at low lanthanum(III) concentrations, the concentration of hydrolysable species present was too low to cause any charge reversal and the clay particles remained negatively charged. The constant negative mobility was thus the result of a delicate balance between the charge behaviour of the clay particles and the adsorptivity of cationic hydrolysed mononuclear species with pH. In contrast, the effect of the clay surface on metal ion hydrolysis via surface nucleation was manifested in the formation of the insoluble hydroxide at a much lower pH compared with bulk solution hydrolysis. The interplay of this with the charge behaviour of the clay particles culminated in the second constant negative mobility region at alkaline pH. Results show that at fixed thorium(IV) concentrations, the higher the electrolyte concentration, the higher the pH at which charge reversal occurred. Adsorption of mononuclear hydrolysed species at low pH and ion concentration was sufficient to impart positive charges to the clay particles. The negative mobilities of the clay particles at different thorium(IV) concentrations all converged to about the same magnitude and remained constant above pH 7. The mobility of the clay particles results from a complex interplay of the hydrolysis of the cations under different conditions of concentration and pH, the charge behaviour of the clay particles as a function of pH and the presence of the clay surface itself.

Enhanced calcium influx by parathyroid hormone in identified Helisoma trivolvis snail neurons

The modulation of [Ca 2+] i by parathyroid hormone (PTH) has been extensively studied in vertebrates. The present study examined the effects of PTH on [Ca 2+] i in isolated invertebrate neurons B5 from buccal ganglia of the pond snail, Helisoma trivolvis, utilizing the Fura-2 fluorescence technique. Bovine PTH, bPTH-(1–84), induced a slow and sustained increase in [Ca 2+] i in neurons B5. In contrast, the elevation of extracellular K + concentration from 1.7 mM to 15 mM induced a rapid and transient increase in [Ca 2+] i. Simultaneous application of 15 mM KCl and bPTH-(1–84), or application of 15 mM KCl in the presence of bPTH-(1–84) additively increased [Ca 2+] i in neurons B5. An increase in [Ca 2+] i in neurons B5 was also induced by a PTH agonist [bPTH-(1–34)], but not by a PTH antagonist [bPTH-(3–34)]. The absence of calcium, or the presence of lanthanum (2 mM) or ω-conotoxin (10 μM), in the bath solution abolished the effect of bPTH-(1–84) on [Ca 2+] i. Furthermore, our results demonstrated that the effect of PTH on [Ca 2+] i in neurons B5 was not due to the hormonal modulation of voltage-dependent Na + or K + channels or a Na + Ca 2+ exchanger. The results from this study show that PTH can modulate [Ca 2+] i in an identified invertebrate neuron mainly by promoting extracellular calcium influx via the N-like voltage-dependent calcium channel.

A lanthanium(III) complex of a six-nitrogen donor macrocyclic ligand with aromatic sidechains: synthesis, crystal structure and spectra

Yellow crystals of formula [La(CH 3COO)(NCS) 2(C 26H 18N 6)] were synthesized by the condensation of 1,2-diaminobenzene and 2,6-pyridinedicarboxyaldehyde in the presence of lanthanum(III) acetate, followed by partial acetate-thiocyanate metathesis. The complex has been characterized by X-ray crystallography. The La III ion is 10-coordinate, being linked to the six nitrogen atoms of the macrocyclic ligand, to the nitrogen atoms of two isothiocyanates situated on opposite sides of the macrocycle and to a bidentate chelating acetate. The IR and NMR spectra ( 1H and 13C) of the complex were recorded and assigned.

Cadmium uptake byLupinus albus(L.): Cadmium excretion, a possible mechanism of cadmium tolerance

Abstract Cadmium (Cd) uptake by white lupin (Lupinus albus) was studied at low Cd concentrations (0.05nM to 5 μM) in hydroponic solution. Ten 12‐day old seedlings were pretreated in 0.5 mM CaCl2 solution in presence and absence of metabolic inhibitors (DCCD, DNP or NaN3). Cadmium solutions were labelled with carrier free 109CdCl2. Cadmium uptake was measured after a 2 h desorption in unlabelled CdCl2 solution. In the absence of any metabolic inhibitor and at 5 [μM Cd, roots absorbed 235.23 μg Cd/g root dry weight. Over the range of lnM to 5 μM Cd, exchangeable Cd represented approximately 5% of the absorbed fraction, and about 25 % of the total absorbed Cd was adsorbed to the root. Cadmium was passively absorbed to about 30% as observed in the presence of the inhibitor (DCCD). Ative absorption which represented 70% of Cd uptake involved H+‐ATPase carriers. Cadmium absorption was reduced to 30 and 20% in presence of lanthanum (La3+) and zinc (Zn2+), respectively which suggested that calcium (Ca), Cd, and Z...

Investigation of ion adsorption on silver sulfide, iodide and bromide precipitates by the radioactive tracer technique

The radioactive tracer method was used to investigate the adsorption of iodide and europium ions from aqueous solution on dried isoelectric precipitates of silver sulfide, silver iodide and silver bromide. The relationship between the amount of iodide ions adsorbed on Ag2S and the iodide ion and HNO3 concentrations in the solution was determined. It was shown that the iodide ions adsorbed on Ag2S could be desorbed with sulfide ions. Using Ag2S, AgI and AgBr precipitates, a relationship between the europium ion adsorption and Eu(NO3)3, H2S, NaI, NaBr and NaCl concentration in solution was established. The adsorption of europium ions was also assessed in respect to the presence of lanthanum and barium ions. For adsorption measurement iodide and europium ions were labeled with their radioactive isotopes and the amounts adsorbed were determined from the measured radioactivities of the precipitates after reaching the equilibrium between the solid phase and the solution.

Ouabain enhancement of compound 48/80 induced histamine secretion from rat peritoneal mast cells: dependence on extracellular sodium.

Purified populations of rat peritoneal mast cells were used to study the effect of ouabain on compound 48/80-induced histamine secretion and on 86Rb+ uptake. 86Rb+ was used as a tracer for extracellular K+. The calculated value of the ouabain-sensitive uptake of K+ and 86Rb+ was considered a measure of the Na(+)-K+ pump activity of the cells. Ouabain caused an immediate inhibition of the pump activity and a time-dependent increase in histamine secretion in the absence of extracellular calcium. No effect on the secretion was observed in the presence of calcium. The effect of ouabain on the secretion occurs in the presence of sodium but not when sodium was replaced by lithium. Preservation by ouabain of a high intracellular sodium content in sodium-loaded cells was associated with preservation of the secretory response in a calcium-free medium. In the presence of lanthanum in a calcium-free medium, the pump activity was inhibited and the enhancement by ouabain of the secretion of histamine was blocked. A less marked inhibition of the pump was found in a calcium-free medium containing magnesium. The inhibition exerted by magnesium was concentration-dependent (0-5 mM) as was the counteraction of magnesium of the enhancement of ouabain of the secretion of histamine. These observations indicate that the enhancement by ouabain of the secretory response of mast cells preincubated in a calcium-free medium is associated with accumulation of sodium inside the cell. In addition to a decreased rate of sodium-calcium exchange caused by a decreased inward directed sodium gradient, the mechanism by which ouabain enhances the secretory response is likely to involve an increased binding of calcium to membrane binding sites.

The template synthesis and characterization of new hexadentate N 4O 2 acyclic Schiff base complexes of lanthanum, praseodymium and neodymium nitrates

The partial Schiff base condensation reactions between 2,6-diacetylpyridine and 1,8-diaminonaphthalene in the presence of lanthanum(III), praseodymium(III) and neodymium(III) nitrates produced the new hexadentate N 4O 2-open chain complexes, which were characterized by IR, UV-vis, 1H NMR and MS data, in addition to elemental and thermogravimetric analyses.

Electric fields induce reversible changes in the surface to volume ratio of micropipette-aspirated erythrocytes

Micropipette-aspirated erythrocytes exhibit reversible changes in sphericity (surface-to-volume ratio) in response to applied electric fields. The potentials were applied between the shaft of the pipette and the bathing medium using Ag-AgCl electrodes and current clamping electronics. The change in surface-to-volume ratio is evidenced as a reversible change in the length of the cell projection in the pipette at constant aspiration pressure and changing voltage. The magnitude of the changes decreased in proportion to the inverse of the solute concentration indicating that the change in sphericity was due to a change in cell volume. Reversible changes in projection length equivalent to a 10% change in cell volume were observed to occur over times on the order of 10 s. The magnitude and time course of the effect were not affected by the removal of intracellular hemoglobin or inhibition of anion exchange. The effect was reduced by the presence of lanthanum and other multivalent cations in the suspending solution, suggesting that surface charge may play a role in mediating the effect.

The Role of Particular Pericycle Cells in Apoplastic Transport in Root Meristems of Barley

Summary Two apoplastic markers, lanthanum and Fluorescent Brightener 28, were used to trace an apoplastic pathway in the root apex of barley seedlings (Hordeum vulgare L. cv. California Mariout). Light and electron microscopy revealed that the markers accumulated in the walls of pericycle cells immediately external to each protophloem sieve element. The presence of lanthanum was confirmed by X-ray micro-analysis of fully-hydrated, bulk-frozen samples. These results suggest that the apoplastic pathway for ions and water moving between the cortex and stele in the meristematic region is largely confined to the walls of particular cells in the pericycle layer.

Conversion of carbon oxide(s) on carbon-supported, nickel—rare earth catalysts

The catalytic properties of carbon-supported nickel catalysts depend heavily on the presence of lanthanum or cerium promoters. After addition of these elements, the activity and the hydrocarbon selectivity in (CO, H 2) or (CO 2, H 2) reactions increase while the T.O.F. of benzene hydrogenation is much less modified. Adsorption measurements and analytical microscopy data indicate that: (i) the nickel dispersion is favoured, particularly with cerium addition; (ii) the rare-earth element is well distributed over the charcoal surface. The formation of specific active centers is therefore favoured at the metal-support interface, leading to important changes in carbon monoxide or carbon dioxide adsorption states and in hydrogenation.

The calmodulin-stimulated ATPase of maize coleoptiles forms a phosphorylated intermediate

The calmodulin-stimulated ATPase of maize coleoptiles is a 140,000 M r polypeptide. In the present study, formation of a phosphorylated intermediate by the enzyme is demonstrated. Phosphorylation is sensitive to chasing with unlabelled ATP and to hydroxylamine; lanthanum enhances its intensity while calmodulin enhances phosphorylation in the presence of lanthanum but not in its absence. Ethyleneglycol-bis-(β-aminoethyl ether) N,N,N′,N′-tetraacetic acid (EGTA) inhibits phosphorylation of the purified enzyme, but microsome preparations give a band of phosphorylation of 153,000 M r in its presence. This latter phosphorylated band was not abolished after a variety of permeabilising treatments in the presence of Triton X-100; phosphorylation of the enzyme was absent when sodium deoxycholate was used as the solubilising detergent. The identity of the 153,000 M r band is discussed.

The effect of salyrgan and lanthanum on the calcium-pump in the oyster Crassostrea virginica

1. 1. Lateral ciliary activity was studied in whole ctenidial preparations in the oyster, Crassostrea virginica. 2. 2. It has been previously demonstrated by the author that the lateral cilia are under the control of axons present in the branchial nerve and that serotonin (5-HT) is the released neurocilioexcitatory neurotransmitter. 3. 3. This study confirms the above findings and in addition demonstrates that perfusates containing salyrgan (calcium-ATPase poison) in the presence of external calcium, in the various test salinities, is cilioinhibitory. The latter effect was reduced in the presence of the calcium chelator, EGTA. 4. 4. The addition of lanthanum to the salyrgan perfusate enhances the cilioinhibitory response of the latter, presumably by binding in an irreversible manner to calcium channels within the lateral ciliated cell membrane. This functions to more effectively stop the calcium-pump. 5. 5. It is postulated that salyrgan brings about an increase in the intracellular calcium pool within the lateral ciliated cell by poisoning the calcium-pump. This is further exacerbated in the presence of lanthanum and in the absence of the neurocilioexcitatory transmitter in the cut branchial nerve preparations. The latter presumably functions as a calcium-pump activator.

Disruption of sustentacular (Sertoli) cell tight junctions and regression of spermatogenesis in vitamin-A-deficient rats.

The relationship between the intactness of sustentacular (Sertoli) cell tight junctions and the status of spermatogenesis was examined in rats fed a vitamin-A-deficient diet after weaning (VAD rats). Both serum and testicular retinol concentrations of the VAD rats declined to a nadir by 80 days of age. At this time, it was observed that Sertoli cell tight junctions of the VAD animals were intact and complete spermatogenesis was maintained. Leakage in Sertoli cell tight junctions, as demonstrated by the presence of lanthanum in the adluminal compartment of the seminiferous epithelium, was first observed in 90-day-old VAD rats. Severe regression of spermatogenic cells was noted in 100-day or older VAD animals. These results suggest that severe germ cell loss observed during chronic vitamin A deficiency may result from abnormal intratubular environment due to the disruption of the blood-testis barrier.

Effect of histamine on cardiac sarcolemmal calcium binding as indicated by use of ionic lanthanum.

To determine whether the inotropic effect of histamine might be associated with enhanced calcium binding to the sarcolemmal-glycocalyx complex, the effect of histamine on lanthanum binding to the cell membrane in the presence of verapamil was assessed. Rabbit hearts were perfused firstly with histamine, secondly with histamine and verapamil, and subsequently with histamine in the presence of lanthanum and verapamil. Subsequent transmission electron microscopy showed the presence of bound lanthanum on both the cellular surface and cytoplasmic vesicles of most cardiac myocytes, which is in contrast to the absence of lanthanum binding that occurs in the presence of verapamil alone. Furthermore, this histamine mediated enhancement of lanthanum binding is not affected by the H1 antagonist diphenhydramine but is reduced by the H2 antagonist cimetidine. This visual evidence of an apparent enhancement of lanthanum binding under histamine and subsequent attenuation with cimetidine supports the hypothesis that histamine may exert its positive inotropic effect by causing increased calcium binding to the sarcolemmal-glycocalyx complex of cardiac muscle and that the effect is mediated at least in part by H2 receptors.

Histamine induced alteration of calcium binding to microvascular endothelium as indicated by use of ionic lanthanum.

To determine whether histamine's effect on microvascular permeability might be associated with altered calcium binding, the influence of histamine on lanthanum binding to vascular endothelium was assessed in the presence of verapamil. Isolated rabbit hearts were perfused firstly with histamine, secondly with histamine and verapamil, and subsequently with histamine in the presence of lanthanum and verapamil. Examination by transmission electron microscopy showed that 92% of microvessels examined contained bound lanthanum on plasma membranes, plasmalemmal vesicles, or endothelial clefts of vascular endothelium, or all three, in both atria and ventricles, which is in contrast to the low proportion (4%) of microvessels containing bound lanthanum found in the presence of verapamil alone. The enhancement of lanthanum binding was reduced by both H1 and H2 receptor antagonists. This evidence supports the hypothesis that the increase in vascular permeability with histamine may be associated with increased calcium binding to vascular endothelial membranes and that both H1 and H2 receptors play a part in this activity.

THE EFFECT OF ABSCISIC ACID ON CALCIUM‐MEDIATED REGULATION OF HETEROCYST FREQUENCY AND NITROGENASE ACTIVITY IN NOSTOC 6720

SummaryAbscisic acid (ABA) promoted a significant increase of the heterocyst frequency in cultures of Nostoc 6720. A significant interaction between ABA and the concentration of Ca2+ in the growth medium was detected. Studies using 45Ca2+ confirmed that the intracellular Ca2+ content was raised by 20% in the presence of 10−6 M ABA. Verapamil, a Ca2+ channel antagonist, inhibited the ABA‐induced increase in heterocyst frequency. Trifluoroperazine, a known inhibitor of Ca2+/protein binding, also inhibited the response to ABA.The characteristics of the response to ABA were similar to those of the Ca2+ ionophore, A23187. Both promote an increase in the total nitrogenase activity of the culture, which, it is suggested, may result from a Ca2+‐dependent protective mechanism similar to that proposed for Gleocapsa. A Ca2+‐dependent repression of dinitrogen fixation is suggested to account for the increased nitrogenase activity in cultures induced to form heterocysts in the presence of lanthanum or when the concentration of Ca2+ in the growth medium is less than 10−4 M.

Effect of rare earth cations on bactericidal activity of anionic surfactants

Rare earth metal cations are antibacterially synergistic with anionic surfactants, yielding mixtures that have bactericidal activity against a variety of gram-positive and gram-negative bacteria at minimum concentrations ranging from 16 to 125 μg/ml. Uptake of surfactant byEscherichia coli increases in the presence of lanthanum, suggesting that the role of rare earth metal cations is to reduce the net negative surface charge on the bacteria, thereby increasing the affinity between the negatively charged surfactant and the bacterial surface.

Unique calcium dependencies of the activating mechanism of the early and late aldosterone biosynthetic pathways in the rat

This study compared the extracellular calcium dependency and the enzymatic locus of that dependency for N6 O2'-dibutyryl cyclic AMP (dbcAMP)-, angiotensin II- and potassium-stimulated aldosterone secretion in dispersed rat glomerulosa cells. The need for extracellular calcium, calcium influx, and specifically for calcium influx through the calcium channel was examined. dbcAMP, angiotensin II and potassium, in the presence of calcium (3.5 mmol/l), significantly (P less than 0.01) increased aldosterone output by at least 1.5-fold. Yet in the absence of extracellular calcium or in the presence of lanthanum (an inhibitor of calcium influx by most mechanisms) all three stimuli failed to increase aldosterone secretion. Nifedipine, a dihydropyridine calcium channel antagonist, significantly (P less than 0.01) reduced angiotensin II- and potassium-stimulated aldosterone secretion, but had no effect on dbcAMP-stimulated aldosterone secretion (100 +/- 14 vs 105 +/- 19 pmol/10(6) cells). Likewise nitrendipine failed to inhibit ACTH-stimulated aldosterone secretion. Angiotension II and potassium activation of both the early aldosterone biosynthetic pathway (as reflected by pregnenolone production in the presence of cyanoketone) and also its late pathway (as reflected by the conversion of exogenous corticosterone to aldosterone in the presence of cyanoketone) were significantly (P less than 0.01) inhibited by lanthanum, nifedipine and by reducing the extracellular calcium concentration. However, with dbcAMP stimulation, none of these manipulations modified pregnenolone production. Late pathway activation by dbcAMP was inhibited by lanthanum and a reduction in extracellular calcium, but not by nifedipine. These observations suggest that: the extracellular calcium dependency of dbcAMP-, angiotensin II- and potassium-stimulated aldosterone secretion reflects a need for calcium influx; with dbcAMP stimulation, activation of the late pathway is dependent on calcium influx by a calcium channel-independent mechanism, whereas activation of the early pathway is not dependent on extracellular calcium or calcium influx and activation of both the early and late pathway by angiotensin II and potassium is dependent on calcium influx by a calcium channel-dependent mechanism. Therefore, we conclude that the mechanism of activation of the early aldosterone biosynthetic pathway by dbcAMP is different from angiotensin II or potassium and early pathway activation is distinct from that of late pathway activation with dbcAMP stimulation.

Effect of lanthanum on the no reduction over palladium catalysts

A palladium-lanthanum (Pd-La) catalyst was found to be more active for NO reduction than a palladium (Pd) catalyst under the reducing conditions found in engine exhaust gas. Both the Pd-La and Pd catalysts had same activities for the NO reduction with CO. However, in the presence of hydrocarbons, the NO reduction activity of a Pd-La catalyst was much better than that of a Pd catalyst. The NO reduction of the Pd catalyst was significantly inhibited by hydrocarbons. The behavior of the adsorbed hydrocarbons on the both catalysts were studied by means of the transient response method. The hydrocarbon was more strongly adsorbed on the Pd catalyst than on the Pd-La catalyst. Also, the partial oxidation activity of hydrocarbon for the Pd-La catalyst was much better than that for the Pd catalyst. The presence of lanthanum in the Pd-La catalyst perhaps weakens the adsorption strength of hydrocarbons.

Hyperthermia and cytotoxic drugs. Possible use of lanthanum as a potentiator of hyperthermia.

Recent studies indicate that differences in membrane fluidity may account for differences of thermal sensitivity. This possibility was studied by using lanthanum, a trivalent cation which is known to displace calcium in a number of biological systems, to modify the structural framework of cell membranes and consequently their biological properties. With Ehrlich ascites cells trypan blue exclusion uptake of 86Rb, 42K and 45Ca, indicate an increase of plasma cell permeability by La3+. The reduction of 86Rb and 42K uptake by tumour cells with La3+ appears to be independent of temperature. The increase of 45Ca2+ influx in the presence of lanthanum plus hyperthermia seems related to an important loss of cell viability. The enhancement of hyperthermia lethality by concentrations of lanthanum over 0.5 mM after 2 h at 44 degrees C has been demonstrated using HeLa S3 cells using a standard cloning technique. In vivo experiments have been performed on C3H mice bearing rhabdomyosarcoma using ultrasound heating at 44-46 degrees C. The results show a remarkable inhibition of tumour growth and a significant increase of the survival time after only one hyperthermia session of 30 min combined with one intratumoural injection of 1 mM lanthanum chloride.