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PubMed2004

The metal-insulator phase transition in mixed potassium-rubidium electro-sodalites.

The collapse under pressure of the antiferromagnetic ground state of the potassium-rubidium electro-sodalite is studied using the linearized augmented plane wave with local orbitals method. Special considerations needed for setting up this basis for systems such as the electro-sodalites are discussed. It is demonstrated that the magnetism collapses at a unit-cell volume similar to potassium electro-sodalite and rubidium electro-sodalite. A critical pressure of 8 GPa is predicted. The mechanism behind the collapse is a mixing of the F-center states with the highly diffuse unoccupied p states of the alkali atoms.

Journal Article↗
PubMed2005

Absolute frequency measurement of rubidium 5S-7S two-photon transitions with a femtosecond laser comb.

The absolute frequencies of rubidium 5S-7S two-photon transitions at 760 nm are measured to an accuracy of 20 kHz with an optical frequency comb based on a mode-locked femtosecond Ti:sapphire laser. The rubidium 5S-7S two-photon transitions are potential candidates for frequency standards and serve as important optical frequency standards for telecommunication applications. The accuracy of the hyperfine constant of the 7S1/2 state is improved by a factor of 5 in comparison with previous results.

Journal Article↗
PubMed1999

[The Raman spectra of rubidium titanyl arsenate].

The Raman spectra of rubidium titanyl arsenate (RTA) single crystal with different geometric arrangements were obtained and compared with those of rubidium titanyl phosphate (RTP), potassium titanyl arsenate (KTA) and potassium titanyl phosphate (KTP) single crystals. The assignments of various vibration modes were made according to the experimental results. The strong Raman scattering intensity implies that RTA crystal possesses large nonlinear optical property and the strongest scattering is from the TiO6 octahedron. From the mode splitting of AsO4 tetrahedron, we conclude that the distortion of AsO4 in RTA is larger than that of PO4 in KTP.

English Abstract↗
PubMed2006

[Energy-pooling collisions of rubidium atoms: Rb (5P(J)) + Rb (5P(J))--> Rb (5S) + Rb (nl = 5D,7S)].

An experimental study of rubidium energy pooling collisions, Rb(5P(J)) + Rb(5P(J))-->Rb(nlJ') + Rb(5S), at thermal energies, was carried out in a cell. Atoms were excited to either the 5P 1/2 or 5P 3/2 state using a single-mode diode laser. The excited atom density and spatial distribution were mapped by monitoring the absorption of a counter-propagating single-mode diode laser beam, tuned to either 5P 1/2-->5D 3/2 or 5P 3/2-->7S 1/2 transition, which could be translated parallel to the pump beam. The excited atom densities were combined with the measured fluorescence ratios to determine cross sections for the rubidium energy pooling process. For 5P 3/2 excitation the cross sections for nlJ' being 5D 5/2, 5D 3/2, and 7S 1/2 are (1.32+/-0.59) x 10(-14), (1.18+/-0.53) x 10(-14) and (3. 21+/-1. 44) x 10(-15) cm2, respectively. For 5P 1/2 excitation the cross sections for nlJ' being 5D 5/2 and 5D 3/2 are (6.57+/-2.96) x 10(-15), and (5.90+/-2.66) x 10(-15) cm2, respectively. The results were compared with those of other experiments.

English Abstract↗
PubMed1994

The role of -SH groups in methylmercuric chloride-induced D-aspartate and rubidium release from rat primary astrocyte cultures.

Methylmercuric chloride (MeHgCl) was shown to increase D-aspartate and rubidium (Rb; a marker for potassium) release from preloaded astrocytes in a dose- and time-dependent fashion. Two sulfhydryl (-SH) protecting agents: a cell membrane non-penetrating compound, reduced glutathione (GSH), and the membrane permeable dithiothreitol (DTT), were found to inhibit the stimulatory action of MeHgCl on the efflux of radiolabeled D-aspartate as well as Rb. MeHgCl-induced D-aspartate and Rb release was completely inhibited by the addition of 1 mM DTT or GSH during the actual 5 min perfusion period with MeHgCl (10 microM). However, when added after MeHgCl treatment, this inhibition could not be fully sustained by GSH, while DTT fully inhibited the MeHgCl-induced release of D-aspartate. Neither DTT or GSH alone had any effect on the rate of astrocytic D-aspartate release. Accordingly, it is postulated that the stimulatory effect exerted by MeHgCl on astrocytic D-aspartate release is associated with vulnerable -SH groups located within, but not on the surface of the cell membrane. Omission of Na+ from the perfusion solution did not accelerate MeHgCl-induced D-aspartate release, suggesting that reversal of the D-aspartate carrier cannot be invoked to explain MeHgCl-induced D-aspartate release. Omission of Ca2+ from the perfusion solution increased the time-dependent MeHgCl-induced D-aspartate release.

Animals↗
PubMed1993

Effects of rubidium on responses to potassium channel openers in rat isolated aorta.

1. In a physiological salt solution (PSS) in which potassium (K) was replaced by rubidium (Rb), segments of rat aorta precontracted with 20 mM RbCl were fully relaxed by K-channel openers with an order of potency levcromakalim > cromakalim > aprikalim > RP 49356. These relaxations were inhibited by glibenclamide. 2. Segments of rat aorta bathed in normal PSS and precontracted with 20 mM KCl were also relaxed by these K-channel openers with an order of potency levcromakalim > cromakalim > aprikalim > RP 49356. These relaxations were glibenclamide-sensitive. However, the absolute potencies of the K-channel openers were approximately four times greater in normal PSS than in RbPSS. 3. In RbPSS, minoxidil sulphate relaxed segments of aorta precontracted with 20 mM RbCl by approximately 20% whereas in normal PSS it fully relaxed those contracted with 20 mM KCl. 4. In RbPSS, levcromakalim-induced relaxation of aortic segments precontracted with 20 mM RbCl was initially well-maintained but then faded by approximately 60% of the initial relaxation to a new, stable level. Subsequent exposure to RP 49356 or to higher concentrations of levcromakalim was without further relaxant effect. Similar changes were observed when RP 49356 was the initial relaxant and tissues were exposed to either RP 49356 or levcromakalim. In normal PSS, levcromakalim- or RP 49356-induced relaxation of contractions produced by 20 mM KCl was well-maintained. 5. In RbPSS, minoxidil sulphate-induced relaxation of aortic segments precontracted with 20 mM RbCl was well-maintained. Subsequent exposure to either levcromakalim or to RP 49356 produced further tissue relaxation. 6. In RbPSS, levcromakalim produced no detectable increase in either 86Rb- or 42K-efflux from rat aortic strips. In normal PSS, a significant increase in the exchange of both isotopes was detected.7. Levcromakalim hyperpolarized segments of rat aorta bathed both in normal PSS and after depolarization by the addition of 20 mM KCI. Exposure to RbPSS depolarized the tissue and under these conditions, levcromakalim had no effect on membrane potential.8. In Rb- and normal PSS, levcromakalim produced a similar degree of inhibition of the refilling of then or adrenaline-sensitive Ca store.9. It is concluded that millimolar concentrations of Rb inhibit the plasmalemmal ATP-sensitive K-channels (KATP) which are the target of the K-channel openers. The relaxant actions of the K-channel openers in both normal and Rb-PSS and the inhibition of these effects by glibenclamide may reflect a functional interaction between these agents at ATP-binding sites associated with both KATP and with intracellular structures including Ca stores.

Animals↗
PubMed1990

Measurement of Na-K-ATPase-mediated rubidium influx in single segments of rat nephron.

To determine the functioning rate of Na-K-ATPase in the rat nephron, a micromethod was developed to measure the rate of rubidium uptake in single nephron segments microdissected from collagenase-treated kidneys. Because the hydrolytic activity of Na-K-ATPase displayed the same apparent affinity for K and Rb ions, whereas the Vmax elicited by K was higher than that in the presence of Rb, experiments were performed in the presence of cold Rb plus 86Rb. Before the assay, tubules were preincubated for 10 min at 37 degrees C to restore the normal transmembrane cation gradients. 86Rb uptake was measured after washing out extracellular cations by rinsing the tubules in ice-cold choline chloride solution containing Ba2+. Rb uptake increased quasi-linearly as a function of incubation time up to 30 s in the thick ascending limb, 1 min in the proximal convoluted tubule, and 5 min in the collecting tubule, and reached an equilibrium after 5-30 min. The initial rates of Rb uptake increased in a saturable fashion as Rb concentration in the medium rose from 0.25 to 5 mM. In medullary thick ascending limb, the initial rate of Rb uptake was inhibited by greater than 90% by 2.5 mM ouabain and by 10(-5) M of the metabolic inhibitor carbonyl cyanide trifluoromethoxyphenylhydrazone. Correlation of Na-K-ATPase hydrolytic activity at Vmax and initial rates of ouabain-sensitive Rb uptake in the successive segments of nephron indicates that in intact cells the pump works at approximately 20-30% of its Vmax. Increasing intracellular Na concentration by tubule preincubation in a Rb- and K-free medium increased the initial rates of Rb intake up to the Vmax of the hydrolytic activity of the pump.

Animals↗
PubMed2000

Na(+)-K(+)-ATPase-mediated basolateral rubidium uptake in the maturing rabbit cortical collecting duct.

Within the renal cortical collecting duct (CCD), transepithelial Na(+) absorption and K(+) secretion are linked to basolateral Na(+)-K(+)-ATPase activity. Our purpose was to examine the developmental changes in basolateral Na(+)-K(+)-ATPase-mediated (86)rubidium (Rb) uptake, its inhibitor sensitivity and relationship to pump hydrolytic activity and Na(+) transport. Multiple CCDs ( approximately 6 mm) from maturing rabbits were affixed to coverslips, preincubated at 37 degrees C for 10 min (+/-1-2.5 mM ouabain or 10 or 100 micro M Schering-28080, an inhibitor of H(+)-K(+)-ATPase), and then transferred to prewarmed incubation solution containing tracer amounts of (86)Rb (+/-inhibitors). After 1 min at 37 degrees C, tubular samples were rinsed and permeabilized and isotope counts were measured to calculate basolateral Rb uptake. Ouabain-inhibitable Rb uptake, an index of basolateral Na(+)-K(+) pump activity, increased approximately 3-fold during the 1st 8 wk of postnatal life (P < 0.03). The approximately 2-fold increase in absolute rate of Rb uptake between 1 and 6 wk (2.64 +/- 0.45 to 5.02 +/- 0.32 pmol. min(-1). mm(-1)) did not reach statistical significance. The rate of basolateral Rb uptake increased further after the 6th wk of life to 7.29 +/- 0.53 pmol. min(-1). mm(-1) in adult animals (P < 0.03 vs. 6 wk). Schering-28080 failed to inhibit Rb uptake, implying that functional H(+)-K(+)-ATPase is absent at the basolateral membrane. Na(+)-K(+)-ATPase hydrolytic activity, determined by using a microassay that measured inorganic phosphate release from [gamma-(32)P]ATP under maximum velocity (V(max)) conditions, also increased in the differentiating CCD (from 316.2 +/- 44.4 pmol. h(-1). mm(-1) at 2 wk to 555.9 +/- 105.1 at 4 wk to 789.7 +/- 145.0 at 6 wk; r = 1.0 by linear regression analysis; P < 0.005). The parallel approximately 2.5-fold increases in Na(+)-K(+)-ATPase activity and ouabain-sensitive Rb uptake between 2- and 6-wk postnatal age suggest that the developmental increase in basolateral transport capacity is due predominantly to an increase in enzyme abundance. The signals mediating the developmental increase in Na(+)-K(+)-ATPase activity in the CCD remain to be defined.

Algorithms↗
PubMed2001

7Li-NMR and FTIR studies of lithium, potassium, rubidium, and cesium complexes with ionophore lasalocid in solution.

Lasalocid metal salts were combined with 1 : 1 lithium and 2:2 potassium, rubidium, and cesium to form complexes. The nature of the lasolocid salt complexes was studied in a solid and chloroform by FTIR spectroscopy in the middle and far IR regions. The process of the complexation of lithium was also studied by (7)Li-NMR. In chloroform a 1 : 1 complex of lasalocid and Li(+) ions was formed. Continuous absorption was observed in the far FTIR spectrum of this complex. It indicated large Li(+) polarizability, which was due to fast fluctuations of the Li(+) ions in the multiminima potentials, in the monomeric structure. In the lasalocid salt with the other monovalent cations (K(+), Rb(+), Cs(+)) 2:2 complexes were formed in which the cations showed cation polarizability, which strongly depended on the mass and the radius of the cations.

Cesium↗
PubMed1981

Rubidium-86 uptake by red blood cells of breast cancer patients.

The red blood cell (RBC) uptake of rubidium-86 (Rb-86), a sensitive in vitro test of RBC membrane transport, was measured in 22 controls, 8 patients with benign breast lesions, and 30 stage I/II, 13 stage III/IV untreated breast cancers. Total Rb-86 transport was measured. Following ouabain block, passive transport was determined, allowing calculation of active Rb-86 uptake by difference. There was a significant decrease in total and passive uptake by RBCs from patients with breast cancer when compared to controls and those with benign lesions (total uptake 58.6 +/- 6.1% versus 63.6 +/- 3.9%, P less than 0.01; passive uptake 38.7 +/- 6.8% versus 42.7 +/- 4.6%, P less than 0.02). The Rb-86 uptake returned towards normal in successfully treated stages-II-to-IV patients. There were no correlations with the patient's age, hematocrit, or incubation hematocrit with RBC Rb-86 uptakes. Results from incubation in Krebs-Ringer solution were not consistent with a plasma blocking factor. The RBC potassium content was slightly increased in the cancer patients. This, along with decreased passive transport, eliminates the nonspecific malfunction of the Na-K-pump as an explanation, and suggests that the decreased uptake is a cancer-related phenomenon.

Adolescent↗
PubMed1989

Rubidium transport in human erythrocyte suspensions monitored by 87Rb NMR with aqueous chemical shift reagents.

Dysprosium(III) triethylenetraamine-N,N,N',N",N"',N"'-hexaacetic acid (DyTTHA3-) was used as an aqueous chemical shift reagent in conjunction with high-resolution nuclear magnetic resonance (NMR) spectroscopy to monitor 87-rubidium (87Rb+) transport in human erythrocyte suspensions. NMR spectra demonstrated two resonances which were assigned to the intra- and extracellular compartments of the erythrocyte suspension. Uptake of 87Rb+ was shown to proceed via the [Na,K]-ATPase dependent pump as evidenced by the inhibition of uptake in the presence of ouabain. The steady state intra- to extracellular concentration ratio of 87Rb was 3.00 and 1.13 in the absence and presence of ouabain, respectively. The rate of uptake of 87Rb+ in the absence and presence of ouabain was found to be 1.3 and 0.5 mmol Rb+/L erythrocytes/h at 18 mM Rb+, respectively. Data are also presented which indicate that the intracellular component of 87Rb is less than 100% NMR visible.

Biological Transport↗
PubMed1994

Single-photon emission tomography studies of rubidium-81 in the detection of ischaemic heart disease, using a stress-reinjection protocol.

The present study was designed to determine the feasibility of using single-photon emission tomography (SPET) imaging with rubidium-81 (T1/2 = 4.54 h) to detect ischaemic heart disease, using a stress-reinjection protocol and a specially constructed 511-keV hexagonal hole collimator for a standard gamma camera. The diagnostic performance of 81Rb SPET in detecting coronary artery disease (CAD) was investigated in 52 patients with a high prevalence of CAD. Coronary arteriography was performed in 34 patients, 25 of whom were classified as having significant stenosis (> or = 50%). At peak exercise (Cornell protocol), 111-222 MBq 81Rb was injected i.v. for stress imaging, and after 3 h of rest, 74-111 MBq was reinjected for rest imaging. The displayed short- and long-axis slices and the polar map images were interpreted qualitatively. In comparison to coronary arteriography, which served as the gold standard, the performance of 81Rb SPET revealed a sensitivity of 95% for the detection of CAD. Images of diagnostic quality were obtained in all patients, these being comparable to thallium-201 SPET images. In conclusion, these results indicate that the described method can be routinely used for the positron emitter 81Rb with a conventional gamma camera and special shielding. 81Rb has the well-known advantages of a potassium analogue and 81Rb SPET permits better visualization, particularly of the posterior wall of the myocardium, due to the higher photon energy. Considering the typical dose of 201Tl used for SPET (74-148 MBq), a 81Rb SPET scan imposes a significantly lower radiation burden on the patient.

Adult↗
PubMed1978

In vitro labeling of platelets with stable rubidium compounds.

It is a common practice in diagnostic hematology to mark blood cells with radioactive tracers, such as 51Cr, 55Fe, 75Fe, etc., to determine their life-span and study their metabolism. A program has been started to verify the possibility of marking blood cells with stable indicators, assayed by radioisotope-induced X-ray fluorescence analysis. All elements may be considered as indicators aggregating to blood cells, and for in vivo measurements, which are not toxic in the quantities injected, calculated on the basis of the limit of detection of the technique. In this study platelets were marked with a very small quantity of stable compounds of rubidium, a potassium analog. Measurements were carried out in vitro on platelets of normal subjects and in vivo on platelets of rats and rabbits. Several survival curves were deduced and life-span values obtained in accord with previously reported values.

Animals↗
PubMed1985

Measurements of the rubidium isotopic activities and the elution parameters of 81mKr generators using a standardized 114mIn source.

A method is described for measuring a number of parameters associated with an inorganic ion-exchange krypton generator. These are the activities of rubidium isotopes in inorganic ion-exchange krypton generators, the 81mKr extraction rate, the 81mKr activity delivered to patients during ventilation studies, the elution efficiency, and the radionuclide purity of the eluted gas. The method is based on the calibration of detectors, Ge(Li) and NaI(Tl), with a standardized 114mIn source at matching photon energies. The average activities present in our generators at the end of bombardment (EOB) were 14.6 +/- 3.8 mCi (81Rb), 6.2 +/- 1.6 mCi (82mRb) and 53 +/- 9.4 microCi (83Rb). The 81mKr extraction rate 2 h post-EOB was 10.2 +/- 2.3 mCi/min at an air flowrate of 1 l/min. The 81mKr activity delivered to patients during a ventilation study was 91 +/- 16 mCi. The elution efficiency of the generators averaged 50% +/- 7% at an air flowrate of 1 l/min. The eluted gas contained Rb radioisotopic impurities in trace quantities of approximately 0.06 microCi/l.

Humans↗
PubMed1993

Transcellular sodium transport and basolateral rubidium uptake in the isolated perfused cortical collecting duct.

The relation between transcellular Na+ absorption, intracellular Na+ concentration and Na+/K(+)-ATPase activity (the last estimated by the rubidium uptake across the basolateral cell membrane) was examined in the different cell types of the rabbit cortical collecting duct (CCD). Experiments were performed on isolated perfused CCD in which Na+ absorption was varied by perfusing the tubule with solutions containing different Na+ concentrations (nominally Na(+)-free, 30 mM and 144 mM). Experiments were terminated by shock-freezing the tubules during perfusion. Precisely 30 s before shock-freezing, the K+ in the bathing solution was exchanged for Rb+. Intracellular element concentrations, including Rb+, were determined in freeze-dried cryosections of the tubules using energy-dispersive X-ray analysis. Increasing Na+ concentration in the perfusion solution caused significant rises in intracellular Na+ concentration and Rb+ uptake of principal cells. Principal cell Na+ and Rb+ concentrations were 7.8 +/- 0.9 and 7.0 +/- 0.8 mmol/kg wet weight respectively, when the perfusion solution was Na(+)-free, 10.1 +/- 0.7 and 11.6 +/- 0.6 mmol/kg wet weight with 30 mM Na+ in the perfusion solution, and 14.5 +/- 1.5 and 14.9 +/- 0.9 mmol/kg wet weight with 144 mM Na+ in the perfusion solution. In contrast, a comparable relationship between lumen Na+ concentration, intracellular Na+ concentration and basolateral Rb+ uptake was not seen in intercalated cells. These results support the notion that principal, but not intercalated, cells are involved in transepithelial Na+ absorption. In addition, the data demonstrate that apical Na+ entry and basolateral Na+/K(+)-ATPase activity are closely coupled in principal cells of the rabbit CCD.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1975

The role of noradrenaline, dopamine and 5-hydroxytryptamine in the hyperactivity response resulting from the administration of tranylcypramine to rats pretreated with lithium or rubidium.

1. The administration of 15 mg/kg tranylcypromine sulphate (Tc) to rats which have been given lithium chloride (LiCl) in the diet (30 mmol/kg dry food) for 14 days produces hyperactivity within 4 hrs, and this lasts for at least 4 further hours. 2. If LiCl is replaced by rubidium chloride (RbCl) at the same dose, the hyperactivity following Tc is increased and it appears within 2 hrs. 3. 5-Hydroxytryptamine (5HT) accumulation after a monoamine oxidase inhibitor (Tc) is increased 46% and 85% respectively above control values by LiCl and RbCl administration. 4. The hyperactivity produced by the above combinations is inhibited by alpha-methyl-p-tyrosine (alphampt). The inhibition is more effective following LiCl than RbCl treatment. 5. After sodium chloride (NaCl) and LiCl treatment, but not after RbCl treatment, the combination of alphampt and Tc produced rat brain concentrations of dopamine (DA) significantly below control values. 6. The smaller increase of brain noradrenaline (NA) after Tc and RbCl suggests that a lower percentage of NA is being metabolised by MAO. The greater decrease of NA after giving alphampt to RbCl and LiCl treated rats suggests an increased "turnover" rate of Na. 7. The hyperactivity syndrome seen in rats after the administration of LiCl or RbCl and Tc is dependent upon both 5HT and dopamine mechanisms.

Animals↗
PubMed1979

Urinary dicarboxylic acids in patients receiving lithium or rubidium salts.

Lithium salts administered in therapeutic doses to four subjects who were kept on controlled diets increased up to fivefold the urinary output of some dicarboxylic acids. Some of the acids affected are intermediates in the tricarboxylic acid cycle, others are chemically similar but not directly related in metabolic terms. This is probably a direct effect on renal transport. Rubidium salts increased urinary 2-oxoglutarate output and blood 2-oxoglutarate levels, probably by some action on intermediary metabolism.

Bipolar Disorder↗