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At least 199 records · Page 11Linked to original sources
PubMed2005

A novel assay of cell rubidium uptake using graphite furnace atomic absorption: application to rats on a magnesium-deficient diet.

The [Na,K]ATPase or sodium pump (SP) is a ubiquitous membrane cation transport system. Because of its potential participation in the pathophysiology of essential hypertension and cataract formation, the SP is under active investigation to detail its function and control. In this paper, we describe a novel, nonradioactive method of measuring SP ion transport activity in intact red blood cells (RBCs) using graphite furnace atomic absorption measurement of rubidium ion (Rb) uptake. This method provided sensitivity comparable to radioactive techniques, as assessed by experiments with human red blood cells (RBC) and ouabain, a known SP inhibitor, but this analytical approach eliminates the use of radioisotopes common to other Rb uptake assay methods. As a demonstration of its broader utility, the assay was used to assess the effects of dietary magnesium intake on SP-mediated ion transport in the RBCs of diet-controlled rats. Rats on 7 weeks of a magnesium-deficient (MgD) diet showed significant reductions in serum magnesium concentration, although levels remained in the lower region of the reference interval for healthy, magnesium replete animals. Red cell Rb uptake was significantly reduced in cells from the magnesium-restricted animals, demonstrating the sensitivity of Rb uptake to reduced magnesium intake, despite serum levels that fell within the reported normal range, and the utility of this Rb uptake assay in measuring physiological changes in SP function.

Animals↗
PubMed2006

Rubidium content in autopsy liver tissue samples from Greenlandic Inuit and Danes measured by X-ray fluorescence spectrometry.

BACKGROUND: The biological function of rubidium (Rb) is unknown, but this alkali metal probably has a normal biologic role. OBJECTIVE: To measure the content of Rb in liver tissue samples from Greenlandic Inuit using X-ray fluorescence spectrometry, and compare the results with those obtained in liver samples from ethnic Danes. STUDY DESIGN: Observational, descriptive survey on environmental pathology. METHODS: The setting was related to forensic medicine and hospitalised care in Nuuk, Ilulissat and Copenhagen. Normal liver tissue was obtained at autopsy from 50 Greenlandic Inuit (27 men) with a median age of 61 years (range 23-83) and from 42 Danes (31 men) with a median age of 38 years (range 16-83). RESULTS: Liver Rb content in Inuit was not significantly different compared with Danes. There was no significant gender difference in liver Rb content either in Inuit or in Danes. The content of Rb given as median (5-95 percentile) was 0.1837mmol/kg dry liver (0.1041-0.3147) in Inuit, and 0.1965mmol/kg dry liver (0.0799-0.2815) in Danes (p=0.6). There was an inverse correlation between liver Rb content and age in Inuit (r(s)=-0.45, p=0.002) but not in Danes. Median hepatic Rb index (Rb content in micromol/kg dry weight divided by age in years) in Inuit was 3.05 and in Danes 4.21 (p=0.02). The correlations between liver Rb and liver potassium content were: Inuit r(s)=0.28, p=0.07; Danes r(s)=0.25, p=0.08; combined series r(s)=0.34, p=0.01. CONCLUSIONS: Inuit have liver Rb levels, which are quite similar to the levels found in Danes. In Inuit, liver Rb content appears to decrease with age.

Adolescent↗
PubMedDate not supplied

Potential utility of rubidium 82 PET quantification in patients with 3-vessel coronary artery disease.

BACKGROUND: Standard perfusion imaging may underestimate the extent of disease in 3-vessel coronary atherosclerosis. This study determined whether positron emission tomography quantification of perfusion reserve by use of rubidium 82 net retention defined a greater extent of disease than the standard approach in patients with 3-vessel disease. METHODS AND RESULTS: Rb-82 net retention was quantified as an estimation of absolute perfusion at rest and with dipyridamole stress by use of dynamic positron emission tomography imaging. The percent of abnormal myocardial sectors, as compared with a normal database, for a standard and quantification approach was determined. Twenty-three patients were evaluated. Defect sizes were larger in patients with 3-vessel disease (n = 13) by use of quantification methods: 44% +/- 18% of the myocardial sectors were abnormal by use of the standard approach versus 69% +/- 24% of sectors when measured by quantification of the stress-rest perfusion difference (P =.008). In patients with single-vessel disease (n = 10), defect sizes were smaller with quantification methods. CONCLUSIONS: Quantification of Rb-82 net retention to measure the stress-rest perfusion difference in the myocardium defined a greater extent of disease than the standard approach in this group of patients with triple-vessel disease. More accurate measurement of the extent of coronary artery disease could facilitate better risk stratification and identify more high-risk patients in whom aggressive intervention is required.

Aged↗
PubMed1977

Myocardial stress perfusion scintigraphy with rubidium-81 versus stress electrocardiography.

Fifty-six patients who subsequently underwent selective coronary angiography were studied noninvasively with relative myocardial perfusion scintigraphy with rubidium-81 and graded stress electrocardiography in an attempt to evaluate the ability of these tests to identify the presence of significant ischemia and, indirectly, coronary stenosis. Both the sensitivity (0.91) and specificity (0.91) of perfusion scintigraphy were impressive and better than the sensitivity (0.79) and specificity (0.64) of stress electrocardiography, the specificity of scintigraphy significantly so (P less than 0.05). Additionally, perfusion scintigraphy yielded excellent localizing information and was reliable even in the presence of drug effect, conduction abnormalities and nonspecific electrocardiographic abnormalities. Rare cases of triple vessel disease, prior myocardial infarction or single vessel disease with widespread collateral vessels were causes of scintigraphic misdiagnosis. Although ribidium-81 perfusion scintigraphy with the scintillation camera requires special collimation and significant quality control, it provides well resolved images and may prove particularly useful in facilitating quick successive multiple scintigraphic cardiac studies.

Angina Pectoris↗
PubMed1997

Incremental value of rubidium-82 positron emission tomography for prognostic assessment of known or suspected coronary artery disease.

Myocardial perfusion imaging using positron emission tomography (PET) may be more accurate for the diagnosis of coronary artery disease (CAD) than conventional imaging. The purpose of this study was to evaluate the prognostic implications of perfusion abnormalities in 685 patients (age 62 +/- 11 years, 199 women) studied by PET, and to assess the incremental value of these data in relation to prognostic implications of clinical and angiographic findings. Rubidium (Rb)-82 PET was performed before and after dipyridamole stress. Transient defects were detected in 227 patients (33%), and were moderate or greater in severity (> 15% of the left ventricle) in 84 (12%). Resting defects were present in 435 (64%) and were moderate or greater in severity in 216 (32%). The total extent of abnormally perfused myocardium was small (< 15% of the left ventricle) in 198 (29%), moderate in 216 (32%), and extensive in 105 (15%). Clinic review or standardized phone interview in 657 patients (96%) identified 151 cardiac events, including 81 cardiac deaths, 16 patients with myocardial infarction, 7 with unstable angina, and 47 with late revascularization (> 3 months after PET). Normal scans had a 90% event-free survival, compared with 87% in patients with small, 75% with moderate, and 76% with extensive defects (log rank chi-square 30, p <0.0001). Functional class, extent of CAD, and the presence and extent of perfusion defects (both at rest and during stress) were independent predictors of cardiac death and total cardiac events. In sequential Cox proportional-hazards models, the results of PET were incremental to those of clinical and angiographic evaluation. Thus, the presence and extent of damaged and jeopardized myocardium are independent and incremental predictors of outcome in patients undergoing Rb-82 PET.

Aged↗
PubMed2001

The Candida albicans Na(+)/H(+) antiporter exports potassium and rubidium.

The Candida albicans Cnh1p belongs to the family of Na(+)/H(+) antiporters (TC 2.A.36) but it transports besides toxic sodium and lithium also rubidium and potassium. Upon heterologous expression in a Saccharomyces cerevisiae salt-sensitive strain, the Cnh1p is targeted to the plasma membrane and its transport activity results in increased tolerance of cells to external alkali metal cations. The cation efflux activity of Cnh1p in S. cerevisiae depends on the gradient of protons across the plasma membrane, and a Cnh1p-mediated K(+) efflux is involved in a cell response to sudden rise of cytoplasmic pH.

Amino Acid Sequence↗
PubMed1986

Noninvasive assessment of coronary stenoses by myocardial perfusion imaging during pharmacologic coronary vasodilation. VIII. Clinical feasibility of positron cardiac imaging without a cyclotron using generator-produced rubidium-82.

The purpose of this study was to determine the clinical feasibility of diagnosing significant coronary artery disease by positron imaging of myocardial perfusion without a cyclotron, using generator-produced rubidium-82 (82Rb). Fifty patients underwent positron emission tomography of the entire heart using a multislice positron camera and intravenous 82Rb or nitrogen-13 ammonia (13NH3) before and after intravenous dipyridamole combined with handgrip stress. Images were read by two observers blinded as to clinical or arteriographic data. Automated quantitative coronary arteriography was obtained for the arteriographic determination of coronary flow reserve, previously demonstrated to be a single integrated measure of stenosis severity accounting for all its geometric dimensions of length, absolute diameter, percent narrowing and asymmetry by quantitative analysis of cine films. Significant coronary artery disease was defined as an arteriographically determined coronary flow reserve of less than 3.0 based on all stenosis dimensions. Any single geometric measure of stenosis severity alone was an inadequate reference standard for comparison with perfusion images. Sensitivity of identifying patients with coronary artery disease having an arteriographically determined coronary flow reserve of less than 3.0 was 95% by positron imaging with a specificity of 100%. The single case that was missed, studied with 13NH3, had a 43% diameter narrowing of a small ramus intermedius off the left coronary artery with no significant narrowing of the major coronary arteries. Positron emission tomography of myocardial perfusion before and after intravenous dipyridamole combined with handgrip stress utilizing generator-produced 82Rb provides sensitive and specific diagnosis of reduced coronary flow reserve due to coronary artery disease in humans.

Coronary Angiography↗
PubMed2002

Preferential uptake of zinc, manganese, and rubidium in rat brain tumor.

The search for radionuclides that can be an index of viability in proliferating cells is important for nuclear medicine diagnosis of brain tumors. On the basis of the finding that 65Zn is preferentially taken up in rat brain tumors, the uptake of various radionuclides was examined in rat brain tumor by using the multitracer technique. Male Fisher rats were intrahippocampally injected with C6 glioma cells. Fourteen days after implantation, the radioactive multitracer solution was injected into the tail vein of tumor-bearing rats. One hour after intravenous injection, the uptake of 65Zn, 83Rb and 54Mn was relatively high in C6 glioma of 15 radionuclides detected, and was much higher than in other brain regions and in the blood. It is likely that rubidium and manganese, in addition to zinc, are preferentially taken up by tumors in the brain.

Animals↗
PubMedDate not supplied

Experimental validation of a new coronary guide wire labeled with rubidium 81/krypton 81m for continuous assessment of myocardial blood flow.

BACKGROUND: The rubidium 81/krypton 81m method was suggested for assessment of myocardial blood flow (MBF) three decades ago. This study investigates the novel concept of using 81Rb-/81mKr-labeled coronary guide wires with wire-attached 81Rb activity and diffusable 81mKr gas for assessment of lesion-specific impairment of MBF by evaluation of the 81Rb/81mKr activity ratio. The feasibility of wire production is tested, and application of the method is investigated in the canine model. METHODS AND RESULTS: Conventional coronary guide wires for angioplasty (0.014 in) were labeled with radioactive 81Rb/81mKr by ion bombardment of the wire tip. A total of 16 of the 18 wires labeled in series showed successful 81Rb fixation in combination with free 81mKr gas diffusability during quality control measurements. The suitability of the wires to assess MBF in combination with an external gamma ray detector was investigated in open-chested dogs. Electromagnetic measurement of coronary blood flow (CBF) was used as reference, providing a signal that is directly linked to volumetric MBF. The 81Rb/81mKr ratio tracked changes in CBF reliably in all 6 dogs. The found linear dependence of measured 81Rb/81mKr count rates on measured CBF supports the modeling assumptions made to apply the theoretic basis of the 81Rb/81mKr technique to 81Rb-labeled coronary guide wires. CONCLUSION: 81Rb-/81mKr-labeled coronary guide wires provide a signal that indicates volumetric MBF directly. This unique capability may qualify the technique as a valuable tool for research purposes and as an attractive method for invasive cardiology at centers where the logistic arrangements for short-lived isotope supply are provided.

Animals↗
PubMed2003

Bis(calix[4]diquinone) receptors: cesium- and rubidium-selective redox-active ionophores.

A new class of redox-active ionophore comprised of two calix[4]diquinone moieties connected through either alkylene or pyridylene linkages has been developed. Spectroscopic and electrochemical investigations, X-ray crystal structure analyses, and molecular modeling studies show butylene- and propylene-linked members of this family of redox-active receptors exhibit remarkable selectivity preferences and substantial electrochemical recognition effects toward cesium and rubidium cations.

Biosensing Techniques↗
PubMed2005

Threshold behavior in electron-transfer collisions between rubidium atoms and C2F5Cl or C2F5I molecules.

Rubidium atoms are accelerated in a high-temperature expansion of hydrogen to produce beams with energies high enough to observe collisional ionization with a cross beam. The speed of the atoms is directly measured by time-of-flight techniques, and the positive and negative ions produced are detected in separate mass spectrometers and detected in coincidence. Chloroperfluoroethane produces C(2)F(5)(-) and Cl(-) ions, whereas iodoperfluoroethane produces I(-), C(2)F(5)(-), and C(2)F(5)I(-) ions. When the measured speed distributions are used, the signal versus energy may be deconvolved to yield thresholds and electron affinities (EAs). The EA for C(2)F(5)I is measured to be 0.96 +/- 0.1 eV. Anomalously high EA values result for C(2)F(5) apparently because C(2)F(5)(-) is produced by parts per million concentrations of Rb(2).

Electron Transport↗
PubMed2006

Theoretical study of alkali cation-benzene complexes: potential energy surfaces and binding energies with improved results for rubidium and cesium.

High level ab initio quantum chemical calculations have been carried out on the binding of alkali metal to benzene with special attention to heavier metals for which the agreement between the most recent theoretical investigations and the experimental bond dissociation energies (BDEs) is not very good. We performed BSSE-corrected geometry optimizations employing the MP2 level of theory with large basis sets and a modified Stuttgart RSC 1997 basis set for rubidium and cesium and carried out single point energy calculations at the MP4 level, obtaining, also for the latter metals, BDE values in good agreement with the experimental results. Furthermore, in view of the development of empirical correction terms to force fields to describe cation-pi interactions, we evaluated the potential energy surface along the benzene symmetry axis and discussed the role of the BSSE correction on the accuracy of our results.

Algorithms↗
PubMed1997

Rubidium uptake and accumulation in peripheral myelinated internodal axons and Schwann cells.

To study mechanisms of K+ transport in peripheral nerve, uptake of rubidium (Rb+), a K+ tracer, was characterized in rat tibial nerve myelinated axons and glia. Isolated nerve segments were perfused with zero-K+ Ringer's solutions containing Rb+ (1-20 mM) and x-ray microanalysis was used to measure water content and concentrations of Rb, Na, K, and Cl in internodal axoplasm, mitochondria, and Schwann cell cytoplasm and myelin. Both axons and Schwann cells were capable of removing extracellular Rb+ (Rb+(o)) and exchanging it for internal K+. Uptake into axoplasm, Schwann cytoplasm, and myelin was a saturable process over the 1-10 mM Rb+(o) concentration range, although corresponding axoplasmic uptake rates were higher than respective glial velocities. Mitochondrial accumulation was a linear function of axoplasmic Rb+ concentrations, which suggests involvement of a nonenzymatic process. At 20 mM Rb+(o), a differential stimulatory response was observed; i.e., axoplasmic Rb+ uptake velocities increased more than fivefold relative to the 10 mM rate, and glial cytoplasmic uptake rose almost threefold. Finally, Rb+(o) uptake rate into axons and glia was completely inhibited by ouabain (2-4 mM) exposure or incubation at 4 degrees C. These results suggest that Rb+ uptake into peripheral nerve internodal axons and Schwann cells is mediated by Na+,K+-ATPase activity and implicate the presence of axonal- and glial-specific Na+ pump isozymes.

Analysis of Variance↗
PubMed1978

Promotion of radiation peroxidation in models of lipid membranes by caesium and rubidium counter-ions: micellar linoleic and linolenic acids.

Caesium and rubidium counter-ions increase peroxidation in irradiated micelles of linoleic (18 : 2) and linolenic (18 : 3) acids. The effect is specific to Cs+ and Rb+ in the alkali metal series. The effect is independent of the salts used (Cl-, NO3-, ClO4-) and, therefore, independent of the chaotropic nature, and reactivity with hydroxyl radicals of Cl-, NO3- and ClO4-. The promotion of peroxidation by Cs+ and Rb+ is interpreted in terms of their effect on fatty acid micelle structure. The dependence of radiation peroxidation on lipid structure in the micelles may be significant for studies of peroxidation in highly structured cell membranes.

Cesium↗
PubMed1998

Activation of cAMP synthesis in rat brain cortical membranes by rubidium and cesium ions.

Rubidium and cesium chlorides accelerated cAMP synthesis in rat brain cortex membranes, while other alkali metal chlorides had no influence on the rate of this process. The effect was dose-dependent and yielded above 2-fold activation of adenylate cyclase. It has been shown that Rb+ and Cs+ influenced directly the catalytic subunit of the enzyme and did not substitute Mg2+ in formation of the metal-ATP complex in this reaction. The stimulatory effect of Rb+ was additive to the activation of adenylate cyclase by the half-maximal (0.3 microM) as well as by the saturating (10 microM) forskolin concentrations, pointing to the fact that these effectors activate different isoforms of the enzyme in rat brain cortex.

Animals↗
PubMed2004

Validation of an atomic absorption rubidium ion efflux assay for KCNQ/M-channels using the ion Channel Reader 8000.

M-channels (M-current), encoded by KCNQ2/3 K(+) channel genes, have emerged as novel drug targets for a number of neurological disorders. The lack of direct high throughput assays combined with the low throughput of conventional electrophysiology (EP) has impeded rapid screening and evaluation of K(+)-channel modulators. Development of a sensitive and efficient assay for the direct measurement of M-current activity is critical for identifying novel M-channel modulators and subsequent investigation of their therapeutic potential. Using a stable CHO cell line expressing rat KCNQ2/3 K(+) channels confirmed by EP, we have developed and validated a nonradioactive rubidium (Rb(+)) efflux assay in a 96-well plate format. The Rb(+) efflux assay directly measures the activity of functional channels by atomic absorption spectroscopy using the automated Ion Channel Reader (ICR) 8000. The stimulated Rb(+) efflux from KCNQ2/3-expressing cells was blocked by the channel blockers XE991 and linopirdine with IC(50) values of 0.15 microM and 1.3 microM, respectively. Twelve compounds identified as KCNQ2/3 openers were further assessed in this assay, and their EC(50) values were compared with those obtained with EP. A higher positive correlation coefficient between these two assays (r = 0.60) was observed than that between FlexStation membrane potential and EP assays (r = 0.23). To simplify the assay and increase the throughput, we demonstrate that EC(50) values obtained by measuring Rb(+) levels in the supernatant are as robust and consistent as those obtained from the ratio of Rb(+) in supernatant/lysate. By measuring the supernatant only, the throughput of ICR8000 in an eight-point titration is estimated to be 40 compounds per day, which is suitable for a secondary confirmation assay.

Animals↗
PubMed1976

Effect of lithium and rubidium on the sleeping time caused by various intravenous anaesthetics in the mouse.

The effects of acute and long-term lithium (LiCl) and rubidium chloride (RbCl) treatments on the sleeping time caused by intravenous thipentone, methohexitone, ketamine, propanidid. Althesin and diazepam were studied in white mice. The doses of the anasthetic agents were selected from the dose-response experiments. When given acutely, LiCl 5 m-equiv/kg prolonged significantly the sleeping time caused by both of the barbiturates, whereas RbCl given for 21 days in tap water shortened the sleeping time induced by methohexitone and ketamine. Both LiCl and RbCl, given acutely, enhanced the sleeping time caused by diazepam. The rectal temperatures were lower in the LiCl-treated mice than in the control and RbCl-treated mice.

Alfaxalone Alfadolone Mixture↗
PubMed1975

Trace element concentration in human brain. Activation analysis of cobalt, iron, rubidium, selenium, zinc, chromium, silver, cesium, antimony and scandium.

Up to 60 tissue samples were dissected from 13 human brains in defined regions and were analysed by means of neutron activation analysis for trace element concentration of cobalt, iron, rubidium, selesium, zinc, chromium, silver, cesium, antimony and scandium. It was shown that the variation in concentration of the non-essential elements in the different brain regions was greater than the corresponding variations in concentration of the essential elements. The mean values of Fe and Rb concentrations were higher in the basal ganglia than in the cortex areas. With increasing age the Fe concentration in the human brain was found to increase and that of Rb to decrease. Comparison of the trace element concentration in corresponding areas of the right and left hemispheres showed highly significant positive correlations for the essential elements. The concentration of each of the essential elements Fe, Rb and Zn was also found to differ significantly between defined functional regions. The characteristic distribution of essential trace elements in different areas is discussed in the light of known metabolic functions of these elements.

Adult↗