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At least 631 records · Page 35Linked to original sources
PubMed1985

The effects of cesium chloride on insulin release, ionic fluxes and membrane potential in pancreatic B-cells.

Cs+ decreases K+ permeability in nerve and muscle cells. Its effects on the pancreatic B-cell function were studied with mouse islets. In the presence of 3 mM glucose, Cs+ substitution for K+ steadily inhibited 86Rb+ efflux and hyperpolarized the B-cell membrane. Addition of Cs+ to a K+-medium also inhibited 86Rb+ efflux, but depolarized the B-cell membrane. None of these changes altered insulin release. Substitution of Cs+ for K+ in a medium containing 10 mM glucose caused a Ca2+-dependent stimulation of insulin release and 45Ca2+ efflux, produced an initial fall and a secondary rise in 86Rb+ efflux and augmented the electrical activity in B-cells. Reintroduction of K+ to the medium was followed by a marked and transient inhibition of insulin release, that was blocked by ouabain and accompanied by an inhibition of 45Ca2+ and 86Rb+ efflux and by a hyperpolarization of the B-cell membrane. Addition of Cs+ to a K+ medium containing 10 mM glucose stimulated insulin release, 45Ca2+ efflux and 86Rb+ efflux. It also increased the electrical activity in B-cells. In the absence of Ca2+, however, Cs+ addition decreased the rate of 86Rb+ efflux. The effects of Cs+ on the B-cell function may be explained by its ability to decrease K+ permeability of the plasma membrane, by its inability to activate the sodium pump, and by a third unidentified effect likely brought about by the accumulation of intracellular Cs+.

Animals↗
PubMed1991

The effects of lithium, rubidium, cesium and magnesium ions on the close packing of persistence-length DNA fragments.

By application of scaled particle theory to persistence-length DNA fragments in sedimentation-equilibrium at speeds high enough to maintain close packing, the range of interhelical electrostatic repulsion was evaluated with LiCl, RbCl, CsCl, and MgCl2 as supporting electrolytes. Analysis of the data in terms of the Zimm cluster function confirmed that the net interaction between helices is purely repulsive in all cases. At constant ionic strength the electrostatic radius of the rod-like DNA decreases as the counterion changes from Li+ to Rb+ to Cs+. In contrast to univalent counterions, electrostatic radius increases with Mg2+ concentration, except at very low (mM) MgCl2 concentrations. All solutions undergo a reversible transition to a turbid, optically anisotropic phase at a slightly salt-dependent, critical DNA concentration, as observed previously for NaDNA.

Animals↗
PubMed1994

Developmental toxicity of cesium in the mouse.

1. Maternal intake of 1 mEq CsCl in drinking water at conception until weaning the offspring mice resulted in certain maternal mediated neonatal and developmental toxicity. 2. Initial reduction in body and brain weights were determined in male offspring due to maternal exposure to Cs salt before they attained the control levels. 3. Offspring from both sexes showed increased spleen weight from control as a consequence of maternal exposure to Cs. This may precipitate delayed immunotoxicity. 4. Maternal Cs exposure did not alter litter size or specific activities of offspring heart lactate dehydrogenase isoenzymes from respective controls. 5. Maternal exposure to Cs altered specific activities of offspring liver alcohol- and aldehyde dehydrogenase during development compared to controls. 6. The results indicate neonatal and developmental toxicity of Cs as a function of maternal intake of CsCl during pregnancy and breast feeding.

Alcohol Dehydrogenase↗
PubMed1990

Applicator for use of cesium-137 miniaturized tube sources in the treatment of uterine cervix cancer.

A modified afterloading Kumar Cervical Applicator with a 3 mm diameter central tandem permits insertion of the afterloading tandem into the uterus without need of manual cervical dilatation. While general anesthesia is required for insertion of standard cervical applicators, this is eliminated because the central tandem is no larger than a uterine sound, and the tandem may be painlessly inserted into the uterus while the patient is awake.

Brachytherapy↗
PubMed2005

Sorption of Cesium on smectite-rich clays from the Bohemian Massif (Czech Republic) and their mixtures with sand.

Sorption is an important process for the transport of radionuclides through backfill materials in a radioactive waste underground repository. Within this study, sorption of Cs on selected Czech clay materials and their mixtures with sand was investigated by batch tests. The experiments were performed under oxic conditions at 25 degrees C. Synthetic groundwater as a liquid phase and unconditioned clays (as they were provided by their producer) were used to reach the natural conditions as close as possible. Distribution ratios (Rds) of Cs for all selected clays rise with increase of the clay fraction in clay/sand mixtures in agreement with previous works studying sorption behaviour of such mixtures. The rise of Rds is from 10(2) cm3 g(-1) for mixtures with 80% of sand to 10(3) cm3 g(-1) for pure clays. There are significant differences between natural and technologically modified clays.

Adsorption↗
PubMed2006

Immobilization of cesium and strontium radionuclides in zeolite-cement blends.

Zeolites are preferred ion exchange materials for the removal of radioisotopes from aqueous nuclear wastes because of their selectivity, radiation and temperature stability, and good compatibility with the cement matrix. Loaded materials, which are not regenerated, are preferably embedded in a solid matrix prior to ultimate storage in a repository. The aim of the present study is to investigate the possibility of solidifying exhausted synthetic zeolite A, loaded with (137)Cs and/or (90)Sr radionuclides, in Ordinary Portland Cement (OPC). Several factors affecting the characteristics of the final solidified waste product towards safe disposal such as mechanical strength and leaching behavior of the radionuclides have been studied. A simplified mathematical model based on diffusion mechanism for cylindrical geometry waste matrix has been simulated to predict the release rates of the investigated radionuclides from cement matrix. The predicted values are discussed in relation to experimentally observed leach rates to confirm the proposed mechanism in the model. The obtained results showed that the presence of zeolite A in the final cemented wastes improve the mechanical characteristics of the solidified cement matrix (mechanical strength and setting times) towards the safety requirements and reduce considerably the radionuclides leach rates.

Cesium Radioisotopes↗
PubMed2006

Equilibrium isotherm modeling of cesium adsorption onto magnetic materials.

The present work investigates the adsorptive interactions of Cs ions with natural magnetite and synthesized iron ferrite in aqueous medium. The applied adsorbents were characterized by FTIR and DTA/TGA analyses. Batch adsorption studies were performed to evaluate the influences of various experimental parameters like initial pH, contact time and initial concentration on the removal of Cs. The adsorption is strongly dependent on pH of the medium where the removal efficiency increases as the pH turns to alkaline range. The process was very fast initially and maximum adsorption was attained within 60 min of contact. The adsorption process follows a pseudo-second order kinetics with rate constant amounted to 76.83 x 10(4) and 18.75 x 10(4)g mg(-1)h(-1) with ferrite and magnetite. The presence of interfering cations seriously decreases the extent of Cs adsorption. The equilibrium data of Cs adsorption on both adsorbents were analyzed using the Freundlich, Langmuir, Temkin, Dubinin-Radushkevich and Redlich-Peterson isotherm models. The different isotherms constants were determined from the linearzed form of their equations and used to characterize Cs distribution on adsorbent surfaces and provide adopted information about the affinity of the adsorbents towards Cs ions. The values of Langmuir separation factor indicate a favorable Cs adsorption. The apparent free energies from the Dubinin-Radushkevich are 32.29 and 27.51 kJ mol(-1) for Cs adsorption onto iron ferrite and magnetite, respectively.

Adsorption↗
PubMed2006

Sorption of cesium, cobalt and europium on low-rank coal and chitosan.

Potential low-cost sorbents of metals based on combined action of coal and chitosan have been investigated. Sorption of Cs, Co and Eu on oxidized coals in mixture with chitosan was studied as function of pH ( approximately 3-6) in batch experiments using radiotracer method. An improved sorption efficiency of the coal sorbents at neutral pH was obtained in mixture with chitosan, namely for oxihumolite at sorption of Eu and Co. Chitosan prevented deterioration of the sorption ability of coal with pH increase probably via retaining the soluble complexes with humic substances leached from coal by formation of an insoluble complex. The effect of chitosan addition was negligible or reverse in case of lignite upon acidification, where the interaction takes place preferentially on the coal surface and may restrict availability of the binding sites for metal ions.

Adsorption↗
PubMed1986

Different behavior of the octadeoxynucleotides d(A-T)4 and d(T-A)4 at high concentrations of cesium fluoride.

High CsF concentrations induce a zig-zag double helix, which we call X-DNA, in poly d(A-T) and also in the octadeoxynucleotide d(T-A)4 while d(A-T)4 remains fixed in a B-DNA form. Intermolecular contacts promote the B-X isomerization of the former oligonucleotide but induce aggregation of the latter. This indicates that there is an intramolecular factor, presumably base stacking in the T-A steps, stabilizing the X-DNA conformation.

Cesium↗
PubMed1965

Zone centrifugation in a cesium chloride density gradient caused by temperature change.

In this communication is described a new technique for the determination of sedimentation coefficients of macromolecules banded in equilibrium density gradients. Initially, the macromolecules are banded in the analytical ultracentrifuge at a low temperature of about 5 degrees C. After equilibrium has been obtained, the temperature is increased to 25 degrees C. The equilibrium band will now sediment to a new equilibrium position in the ultracentrifuge cell: (a) By following the position of the migrating band as a function of time, sedimentation coefficients may be determined. (b) If several species having different sedimentation coefficients are present in the original band, then during the course of the migration the band may split into several new bands which eventually reunite at the final equilibrium position. (c) If different chemical species of macromolecules such as nucleic acids and carbohydrates are present, in general they will exhibit different temperature density relationships, and can move different distances and directions in response to temperature change.

Carbohydrates↗
PubMed1969

Cesium chloride density gradient study of some modifications induced by ultraviolet radiation on the denatured DNA molecule of phage T2.

The behaviour of the modifications due to ultraviolet (UV) radiation on denatured phagic DNA has been investigated by looking at the changes of density in CsCl gradient, after irradiation with increasing doses of monochromatic light. The spectral range studied is 2300-2900 A, with a wavelength resolution Deltalambda = +/-20 A. The observed effect is a gradual shift toward higher densities as the UV absorbed dose increases. The experimental results show an exponential law and the analysis of the action spectra indicates that thymine is the main factor responsible for the observed effect. An evaluation of the quantum yield for the thymine-dimers formation gives a constant value of (18 +/- 3) x 10(-3) quanta(-1).

Bacteriophages↗